JPH10340010A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transfer a toner image well in either case of both-side image formation and surface image formation by changing the value of a transfer current or the value of a transfer voltage for transferring the toner image in the case of the surface image formation and in the case of the both-side image formation. SOLUTION: In the case of image formation, the value of an optimum transfer current in the case of a both-side image formation mode is larger than that in the case of a surface image formation mode. It is because the toner image of a back surface image exists between the back surface of a recording paper P and a toner image receiving body 14a in the case of the both-side image formation mode, so that a transfer electric field is weakened. Consequently, the transfer current value to a transfer device 14c obtained when the toner image of the surface image carried on a photoreceptor drum 10 is transferred to the surface of the paper P is changed between in the case of the both-side image formation mode and in the case of the surface image formation mode. That is, the transfer current value IA2 in the case of the both-side image formation mode is set larger than the transfer current value IA1 in the case of the surface image formation mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine in which a charging means, an image exposing means and a developing means are arranged around an image carrier to transfer and fix a toner image formed on the image carrier onto a transfer material. And an electrophotographic image forming apparatus such as a printer, a facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, in double-sided image formation, an image on one side formed on an image carrier is transferred and fixed on a transfer material, and this is temporarily stored in a double-sided reversing paper feeder, and the image is formed again. A method has been adopted in which a transfer material is fed from a double-sided reversing sheet feeding device in synchronization with an image formed on a carrier, and an image on the other surface is transferred and fixed on the transfer material.

In this double-sided image forming apparatus, as described above,
The transfer of the transfer material, such as feeding to the two-sided reversing paper feeder or passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low, which causes a jam or the like. In contrast, JP-B-49-37538 and JP-B-54-28
740, JP-A-1-44457 and JP-A-4-44.
JP-A-214576 and the like propose a method in which a toner image is formed on both surfaces of a transfer material and then fixed once. There has been proposed a method of forming a two-sided color image by arranging image forming means including a body, a charging means, an image exposing means, a developing means and the like in parallel on a plurality of toner image receiving bodies.

[0004]

However, Japanese Patent Application Laid-Open Nos. Hei 1-44457 and Hei 4-214576 mentioned above.
In the double-sided color image formation proposed in Japanese Patent Application Laid-Open Publication No. H08-27, the transferability of the transfer material is improved, but the color toner images are superimposed one by one on the toner image receiver, so that color misregistration, toner scattering and rubbing, etc. Image degradation easily occurs.

Therefore, the present inventors arranged a plurality of image forming means including a charging means, an image exposing means, a developing means and the like around the first image bearing means (photosensitive drum), and provided on the photosensitive drum. After the formed superimposed color toner image is once transferred to the second image carrying means (toner image receiver) by the first transfer means, the superimposed color toner image is formed again on the photosensitive drum. The transfer material supplied at the same timing as the toner image on the photosensitive drum and the toner image on the toner image receiver is charged by the transfer material charging means, attracted to the toner image receiver, and transported on the toner image receiver. The toner image on the photosensitive drum was transferred as a front image by a first transfer unit, and the toner image on the toner image receiver was transferred as a back image by a second transfer unit on both sides of the transfer material to be formed. An image forming apparatus for separating a transfer material from a toner image receiving body by a transfer material separating unit and fixing a toner image on the transfer material by a fixing unit to form a two-sided color image; Formation (when forming images on both sides of the transfer material), single-sided image formation with only the front image (when performing image formation only on the front side of the transfer material), and single-sided image formation with only the back side image (images only on the back side of the transfer material) Etc.) are being considered.

However, when an image is formed on both surfaces of a transfer material and when an image is formed only on the surface of the transfer material, the toner image of the surface image on the photosensitive drum is transferred to the surface of the transfer material. If the transfer current or the transfer voltage of the transfer unit 1 is the same, the transfer from the photosensitive drum to the surface of the transfer material is affected by the presence or absence of the toner image on the toner image receiver, and the toner of the surface image This causes a problem that the image is not always transferred well on the transfer material.

Similarly, when an image is formed on both surfaces of the transfer material and when an image is formed only on the back surface of the transfer material, the toner image of the back surface image on the toner image receiver is transferred to the back surface of the transfer material. If the transfer current or the transfer voltage of the second transfer means is the same, the transfer from the toner image receiver to the back surface of the transfer material is affected by the presence or absence of the toner image on the transfer material surface, and the toner of the back surface image is affected. There is a problem that the image is not always transferred well on the transfer material.

Further, when an image is formed on both surfaces of a transfer material, a transfer current or a transfer voltage of a first transfer means for transferring a toner image of a back surface image formed on a photosensitive drum to a toner image receiver. Is equal to the value of the transfer current or the transfer voltage of the first transfer means when the toner image of the surface image on the photosensitive drum is transferred to the surface of the transfer material, the transfer is performed depending on the presence or absence of the transfer material. Since the electric field is formed differently, the transferability is affected, and the transfer of the toner image formed on the photosensitive drum to the toner image receiver or the surface of the transfer material is not always performed well. Is generated.

Further, when the image is formed only on the front surface of the transfer material, and when the image is formed only on both surfaces or the back surface of the transfer material, the transfer material is charged in the supply portion of the transfer material to the toner image receiving member. If the charging current or the charging voltage of the transfer material charging means to be attracted to the toner image receiving member is the same,
The presence or absence of the toner image on the toner image receiver affects the adhesion between the transfer material and the toner image receiver, and the transfer of the transfer material by the toner image receiver is not performed well. There is a problem that the toner image is disturbed and the image is disturbed.

Further, when the image is formed only on the front surface of the transfer material and when the image is formed only on the back surface or both surfaces of the transfer material, the transfer material is separated from the toner image receiving member at the separation portion of the transfer material. If the charge-removing current or the charge-removing voltage of the transfer material separating means for separating is the same, the charge accumulated on the transfer material differs depending on the presence or absence of the toner image on the front surface or the back surface of the transfer material. As a result, there arises a problem that the separation is not performed well.

Further, the transfer of the toner image to the toner image receiving member or the transfer material, and the charging or separation of the transfer material may be caused by a change in the type of the transfer material or environmental conditions, or a change or deterioration of the toner image receiver due to repeated use. There is a problem that it is not performed well.

The present invention solves the above-mentioned problems, and can be used for forming an image on both surfaces of a transfer material, for forming an image only on the front surface of the transfer material, and for forming an image only on the back surface of the transfer material. It is another object of the present invention to provide an image forming apparatus in which the transfer of a toner image to a toner image receiving body or a transfer material is favorably performed, and the transfer and transfer of the transfer material are also favorably performed.

Further, the transfer of the toner image to the toner image receiving member or the transfer material, and the charging or separation of the transfer material may be caused by a change in the type of the transfer material or environmental conditions or a change or deterioration of the toner image receiving member due to repeated use. It is an object of the present invention to provide an image forming apparatus in which the image quality is improved.

[0014]

An object of the present invention is to provide a first image carrying means for carrying a toner image formed by a toner image forming means, and a transfer of the toner image carried by the first image carrying means. A second image carrying means for carrying the transferred toner image on the surface again, and transferring the toner image carried on the first image carrying means to the surface of the second image carrying means and the transfer material. A first transfer unit, a second transfer unit for transferring the toner image carried by the second image holding unit to the back surface of the transfer material, and a fixing unit for fixing the toner image transferred to the transfer material The image forming apparatus having an image forming apparatus having: Transfer current or transfer voltage of the transfer means It is achieved by an image forming apparatus, characterized by further (first invention).

Further, the above object is to provide a first image carrying means for carrying a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again; and a toner image carried on the first image carrying means. Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And an image forming apparatus having fixing means for fixing the toner image transferred to the transfer material, when performing image formation only on the back surface of the transfer material, and when performing image formation on both surfaces of the transfer material. Thus, an image forming apparatus is characterized in that the value of the transfer current or the transfer voltage of the second transfer means for transferring the toner image to the back surface of the transfer material is changed (second invention).

The above object is also achieved by a first image carrying means for carrying a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again; and a toner image carried on the first image carrying means. Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And an image forming apparatus having a fixing unit for fixing the toner image transferred to the transfer material, when forming an image on both surfaces of the transfer material, a back side image carried by the first image carrying unit. A transfer current or a transfer voltage value of the first transfer means for transferring the toner image to the second image carrying means, and a toner image of a surface image carried by the first image carrying means to the transfer material. The transfer current of the first transfer means for transferring to the surface of It is achieved by an image forming apparatus characterized by changing the value of the transfer voltage (third invention).

The above object is also achieved by a first image carrying means for carrying a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again; and a toner image carried on the first image carrying means. Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And a fixing unit for fixing the toner image transferred to the transfer material, when an image is formed only on the surface of the transfer material, when an image is formed on both surfaces of the transfer material, or When an image is formed only on the back surface of the transfer material, the value of the charging current or the charging voltage of the transfer material charging unit that charges the transfer material in the supply unit of the transfer material to the second image bearing unit Image forming characterized by changing It is achieved by location (fourth invention).

The above object is also achieved by a first image holding means for holding a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again; and a toner image carried on the first image carrying means. Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And an image forming apparatus having a fixing unit for fixing the toner image transferred to the transfer material, when an image is formed only on the front surface of the transfer material and when an image is formed only on the back surface of the transfer material. Alternatively, when an image is formed on both surfaces of the transfer material, the value of the static elimination current or the static elimination voltage of the transfer material separating unit that separates the transfer material in the separation unit of the transfer material from the second image bearing unit Image shape characterized by changing It is achieved by a device (a fifth aspect of).

The above object is also achieved by a first image holding means for holding a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again, and a toner image carried on the first image carrying means Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And an image forming apparatus having a fixing unit for fixing the toner image transferred to the transfer material, wherein when performing image formation on both surfaces of the transfer material, the image forming apparatus according to the type of the transfer material or environmental conditions, The value of the charging current or the charging voltage of the transfer material charging means for charging the transfer material in the supply section of the transfer material to the second image bearing means, and the toner image carried on the first image bearing means are The first transfer to be transferred to a second image bearing unit; A transfer current or a transfer voltage value of a step, a transfer current or a transfer voltage value of the first transfer means for transferring the toner image carried by the first image carrying means onto a surface of the transfer material, A transfer current or a transfer voltage value of the second transfer means for transferring the toner image carried by the image carrying means to the back surface of the transfer material, and a separation portion of the transfer material from the second image carrying means. This is achieved by an image forming apparatus characterized in that at least two sets of values of the static elimination current or the static elimination voltage of the transfer material separating means for separating the transfer material are changed in conjunction with each other (sixth embodiment). invention).

The above object is also achieved by a first image carrying means for carrying a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again, and a toner image carried on the first image carrying means Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And a fixing unit for fixing the toner image transferred to the transfer material, when performing image formation only on the surface of the transfer material, according to the type of the transfer material or environmental conditions, In the supply section of the transfer material to the second image carrying means, the value of the charging current or the charging voltage of the transfer material charging means for charging the transfer material, and the toner image carried on the first image carrying means. The first transfer for transferring to the surface of the transfer material At least one of a value of a transfer current or a transfer voltage of a step, and a value of a charge elimination current or a charge elimination voltage of a transfer material separating unit that separates the transfer material in a separation unit of the transfer material from the second image bearing unit This is achieved by an image forming apparatus characterized in that two sets of values are changed in conjunction with each other (a seventh invention).

The above object is also achieved by a first image holding means for holding a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again; and a toner image carried on the first image carrying means. Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And a fixing unit for fixing the toner image transferred to the transfer material, when forming an image only on the back surface of the transfer material, according to the type of the transfer material or environmental conditions, The value of the charging current or the charging voltage of the transfer material charging means for charging the transfer material in the supply section of the transfer material to the second image bearing means, and the toner image carried on the first image bearing means. The first image transferring to the second image bearing means; The value of the transfer current or the transfer voltage of the transfer means, the value of the transfer current or the transfer voltage of the second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material, the transfer And changing at least two sets of values of the static elimination current or the static elimination voltage of the transfer material separating means for separating the transfer material in the separation section of the material from the second image bearing means. This is achieved by an image forming apparatus according to the present invention (eighth invention).

Further, the above object is to provide a first image carrying means for carrying a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again, and a toner image carried on the first image carrying means Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And a fixing unit for fixing the toner image transferred to the transfer material, wherein a voltage is applied to the transfer material to detect a value of an energizing current at that time or to apply a current to the transfer material. And a transfer material resistance / capacity detecting means for detecting the resistance, capacity or resistance and capacity of the transfer material by detecting the value of the applied voltage at that time. According to the detection result of the transfer material, The value of the charging current or the charging voltage of the transfer material charging means for charging the transfer material in the supply section to the second image bearing means, and the toner image carried by the first image bearing means are transferred to the transfer material. The value of the transfer current or the transfer voltage of the first transfer means for transferring to the front surface, and the transfer current of the second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material Alternatively, the value of the transfer voltage or the value of the static elimination current or the static elimination voltage of the transfer material separating unit that separates the transfer material in the separation unit of the transfer material from the second image bearing unit is changed. This is achieved by an image forming apparatus characterized by the above feature (ninth invention).

The above object is also achieved by a first image carrying means for carrying a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again; and a toner image carried on the first image carrying means. Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And a fixing unit for fixing the toner image transferred to the transfer material, wherein a voltage is applied to the transfer material to detect a value of an energizing current at that time or to apply a current to the transfer material. Then, by detecting the value of the applied voltage at that time, the transfer material resistance / capacity detecting means for detecting the resistance, the capacity or the resistance and the capacity of the transfer material together, and orthogonal to the transport direction of the transfer material Transfer material width detecting means for detecting the width in the direction And charging the transfer material in a supply section of the transfer material to the second image bearing means in accordance with a detection result by the transfer material resistance / capacity detection means and a detection result by the transfer material width detection means. And the transfer current or transfer voltage of the first transfer means for transferring the toner image carried by the first image carrying means to the surface of the transfer material. A value, a value of a transfer current or a transfer voltage of the second transfer means for transferring the toner image carried by the second image bearing means to the back surface of the transfer material, a value of the second image bearing means of the transfer material The image forming apparatus according to the tenth aspect of the present invention is characterized in that any one of a static elimination current and a static elimination voltage of a transfer material separating unit that separates the transfer material in a separation unit from the image forming apparatus is changed (tenth aspect of the invention). ).

The above object is also achieved by a first image holding means for holding a toner image formed by a toner image forming means,
A second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface again; and a toner image carried on the first image carrying means. Transfer means for transferring the toner image carried on the second image bearing means and the surface of the transfer material, and second transfer means for transferring the toner image carried on the second image bearing means to the back surface of the transfer material And a fixing unit for fixing the toner image transferred to the transfer material, wherein a voltage is applied to the second image bearing unit to detect a value of a current flowing at that time, or the second The second image bearing means for detecting the resistance, the capacitance or the resistance and the capacitance of the second image bearing means by applying a current to the image bearing means and detecting the value of the applied voltage at that time. Resistance / capacitance detection means, and the second image carrier means A value of a transfer current or a transfer voltage of the first transfer means for transferring the toner image carried on the first image bearing means to the second image bearing means in accordance with a detection result by the capacity detecting means; A value of a transfer current or a transfer voltage of the first transfer means for transferring the toner image carried by the first image carrying means onto the surface of the transfer material;
A transfer current or a transfer voltage value of the second transfer means for transferring the toner image carried by the image bearing means to the back surface of the transfer material, and a separation portion of the transfer material from the second image bearing means. This is achieved by an image forming apparatus characterized in that any one of a value of a static elimination current or a static elimination voltage of a transfer material separating means for separating the transfer material is changed (first example).
1 invention).

[0025]

Embodiments of the present invention will be described below. The description in this section does not limit the technical scope of the claims and the meaning of the terms. The assertive description below shows the best mode, and limits the meaning of the terms and the technical scope of the present invention. It does not do. In the following description of the embodiment, the surface of the transfer material facing the image carrier in the transfer area is the surface, and the surface of the other side of the transfer material, that is, the transfer material on the side facing the second image bearing means. The surface is called the back surface, the image transferred to the front surface of the transfer material is called the front image, and the image transferred to the other surface of the transfer material is called the back image. In the following description, the value of the charging current or charging voltage of the transfer material charging unit, the value of the transfer current or transfer voltage of the first transfer unit, and the value of the transfer current or transfer voltage of the second transfer unit are increased. In this case, it means that the absolute value of each current or voltage is increased, and when the value of the static elimination current or the static elimination voltage of the transfer material separating unit is increased,
It simply means increasing the AC current or AC voltage. However, when the charge removing current or the charge removing voltage of the transfer material separating means includes a DC component, this also means that the absolute value of the current or voltage of the DC component is increased.

Embodiment 1 An image forming process and each mechanism of an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing a first embodiment of the image forming apparatus of the present invention, and FIG.
FIG. 3 is a diagram showing a toner image formation state and supply of a transfer material when images are formed on both surfaces of a transfer material by the image forming apparatus according to the present invention. FIG. 3A and 3B are diagrams illustrating a toner image forming state and supply and discharge of a transfer material when performing image formation only on the front surface or the back surface. FIG. 3A is a diagram illustrating front surface image formation, and FIG. FIG. 5 is a diagram illustrating backside image formation.

Photosensitive drum 10 as first image bearing means
Is formed by forming a photosensitive layer such as a transparent conductive layer, an a-Si layer, or an organic photosensitive layer (OPC) on the outer periphery of a cylindrical substrate formed of, for example, a transparent member made of optical glass or transparent acrylic resin. And is rotated clockwise as indicated by the arrow in FIG. 1 in a grounded state.

Scorotron charger 1 as charging means
1. An exposure unit 12 as an image exposure unit and a developing unit 13 as a developing unit are used in an image forming process of each color of yellow (Y), magenta (M), cyan (C) and black (K). In the present embodiment, Y, M, C, and K are arranged in this order with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG.

The scorotron charger 11 as a charging means for each color is maintained at a predetermined potential with respect to the corona discharge electrode 11a composed of a sawtooth electrode or a wire electrode and the above-mentioned organic photosensitive layer of the photosensitive drum 10. The photoconductive drum 10 is mounted in a direction perpendicular to the direction in which the photoconductive drum 10 moves. The scorotron charger 11 performs corona discharge of the same polarity as the toner (in this embodiment, negative charge), and applies a uniform potential to the photosensitive drum 10.

The exposure unit 12 as an image exposing means for each color is arranged such that the exposure position on the photosensitive drum 10 is on the downstream side in the rotation direction of the photosensitive drum 10 with respect to the scorotron charger 11 for each color. , Are arranged inside the photosensitive drum 10.

The exposure units 12 for each color are respectively
LED (light emitting diode) as light emitting element of image exposure light
A linear exposure element 12a in which a plurality of elements 121 are arranged in an array parallel to the axis of the photosensitive drum 10 and a selfoc lens 12b as an equal-magnification imaging element are provided as an exposure unit in which a holder (not shown) is attached. Be composed. The exposure unit 12 for each color is attached to the holding member 20 together with the uniform exposure unit 12c and the simultaneous transfer exposure unit 12d, and the holding unit 20 is fixed to the apparatus main body. The unit 12c and the simultaneous transfer exposure unit 12d are integrally housed inside the base of the photosensitive drum 10. As the exposure element, a linear element in which a plurality of light emitting elements such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array is used. The exposure unit 12 performs image exposure on the photosensitive drum 10 based on image data of each color read by a separate image reading device and stored in a memory, and forms a latent image on the photosensitive drum 10. The emission wavelength of the light emitting element used in this embodiment is usually Y, M,
A range of 680 to 900 nm, which has a high transmittance of the C toner, is preferable, but a shorter wavelength which does not have sufficient transparency for the color toner since image exposure is performed from the back surface may be used.

The developing device 13 as a developing means for each color includes
For example, each has a thickness of 0.5 mm to 1 mm and an outer diameter of 15 to
25 mm cylindrical developing sleeve 131 which is a developer carrier made of a non-magnetic stainless steel or aluminum material
And a developing casing 138, and Y, M, C
And one-component or two-component developer K. The developing sleeve 131 is provided with a gap of a predetermined value, for example, 100 μm, from the photosensitive drum 10 by an abutting roller (not shown).
The photosensitive drum 10 is rotated in the forward direction with respect to the rotation direction of the photoconductor drum 10 and has the same polarity as the developing bias with respect to the developing sleeve 131 (minus polarity in the present embodiment). By applying a DC voltage or a superimposed voltage of DC and AC, reversal development is performed in a non-contact state with respect to the exposed portion of the photosensitive drum 10. At this time, the precision of the development interval needs to be about 20 μm or less in order to prevent image unevenness.

The toner image receiving member 14a as the second image bearing means is an endless belt stretched between the driving roller 14d and the driven roller 14e and provided in contact with the photosensitive drum 10. A toner filming preventing layer having a thickness of 5 μm to 50 mm on the outside of a semiconductive rubber belt base made of silicon rubber or urethane rubber having a thickness of 0.5 to 2.0 mm and a volume resistivity of 10 ⁸ to 10 ¹⁴ Ω · cm.
It has a two-layer structure with a μm semiconductive fluorine coating. Instead of rubber belt base, thickness 0.1 ~
Use of semi-conductive polyester, polystyrene, polyethylene, polyethylene terephthalate, polyimide, modified polyimide, ETFE (ethylene-tetrafluoroethylene copolymer) or the like having a thickness of 0.5 mm and a volume resistivity of 10 ⁸ to 10 ¹⁴ Ω · cm. Can also.

Paper charger 150 as transfer material charging means
Represents the toner image receiving member 14a with the support shaft 152 as a rotation fulcrum.
And a charging brush capable of contacting and releasing the contact, and is disposed to face a grounded driven roller 14e which stretches the toner image receiver 14a. The paper charger 150 is brought into contact with the toner image receiving body 14a via the recording paper P as the recording paper P as the transfer material passes, and immediately before or simultaneously with the passage of the rear end of the recording paper P. The contact is released from the recording paper P from 14a. When the recording paper P passes through the paper charger 150, the recording paper P is charged by applying a DC voltage having the same polarity as the toner to the paper charger 150, and the recording paper P is attracted to the toner image receiver 14a. The sheet is fed to the transfer area 14b. By charging the paper with the same polarity as the toner, the toner image on the toner image receiver 14a or the toner image on the photosensitive drum 10 and the recording paper P are prevented from attracting to each other, and the toner image is prevented from being disturbed. ing. In addition, as the transfer material charging unit, a conductive roller, a conductive film, or the like that can be brought into contact with and released from the toner image receiver 14a can be used.

The transfer device 14c as the first transfer means includes:
Polarity opposite to toner (positive polarity in this embodiment)
Is applied to the photosensitive drum 10 via the toner image receiver 14a. The transfer device 14c charges the back surface of the toner image receiving member 14a to the opposite polarity to the toner, thereby causing the photosensitive drum 1 to charge.
0, a transfer area 14b is formed, the toner image of the back side image on the photosensitive drum 10 is transferred to the toner image receiver 14a, and the toner image of the front side image on the photosensitive drum 10 is Transfer to the surface.

Back transfer device 14g as second transfer means
Is a corotron charger to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied, and the toner image receiver 14 faces the drive roller 14d which is grounded.
a is disposed on the front side of the recording paper P conveyed on the recording paper P. The back transfer unit 14g charges the surface of the recording paper P to the opposite polarity to the toner, and transfers the toner image of the back image on the toner image receiver 14a to the back of the recording paper P.

The paper separating AC static eliminator 14h as a transfer material separating means is a corotron charger to which an AC voltage or a superimposed voltage of AC and DC is applied, and is opposed to the grounded drive roller 14d. It is arranged on the front side of the recording paper P conveyed on 14a. Paper separation AC neutralizer 14
h removes the charge of the recording sheet P from the toner image receiving member 14a at a portion where the recording sheet P separates from the toner image receiving member 14a, and separates the recording sheet P from the toner image receiving member 14a.

A fixing device 17 as a fixing means includes a fixing roller 17a having a heater inside and a pressure roller 1a.
7b, which is a heat roller fixing device, which heats and pressures the recording paper P, which is separated from the toner image receiving body 14a and has toner images on both sides, by nipping and conveying the recording paper P between the fixing roller 17a and the pressure roller 17b. To fix the toner image on the recording paper P.

The photosensitive drum 10 is rotated clockwise as indicated by an arrow in FIG. 1 by starting a photosensitive member drive motor (not shown) at the start of image recording, and the photosensitive member is charged by the charging action of a yellow (Y) scorotron charger 11. The application of the potential to the drum 10 is started.

As an original image, an image read by an image pickup device of an image reading apparatus separate from the present apparatus or an image edited by a computer is used for Y, M, C, and K.
Is temporarily stored in a memory as image data for each color.

After the photosensitive drum 10 is applied with a potential,
The first color signal, that is, Y
Exposure scanning by an electric signal corresponding to the image data is started, and an electrostatic latent image corresponding to the Y image of the original image is formed on the surface of the photosensitive drum 10.

The Y electrostatic latent image formed on the photosensitive drum 10 is reversely developed in a non-contact state by the Y developing unit 13 to form a yellow (Y) toner image on the photosensitive drum 10. Is done.

Next, the photosensitive drum 10 is placed on the magenta (M) scorotron charger 11 from above the Y toner image.
A potential is given by the charging action of the M exposure unit 1
Exposure using an electrical signal corresponding to the second color signal, that is, the M image data, is performed by 2, and an M electrostatic latent image is formed. The M electrostatic latent image is reversely developed in a non-contact state by the M developing unit 13, and a magenta (M) toner image is formed on the yellow (Y) toner image.

By the same process, the scorotron charger 11 for cyan (C), the exposure unit 12 for C and
The cyan (C) toner image corresponding to the third color signal is further produced by the developing device 13 of the third color, and the scorotron charger 11 of black (K), the exposure unit 12 of the K and the developing device 13 of the fourth color produce the fourth color. A black (K) toner image corresponding to the signal is sequentially superimposed and formed, and a superposed color toner image of Y, M, C and K is formed on the peripheral surface within one rotation of the photosensitive drum 10. (Toner image forming means).

The exposure of the organic photosensitive layer of the photosensitive drum 10 by the Y, M, C, and K exposure units 12 is performed from the inside of the drum through the above-described transparent substrate. Exposure of the image corresponding to the color signal is also performed without being affected by the previously formed toner image, and an electrostatic latent image equivalent to the image corresponding to the first color signal can be formed. .

By the above-described image forming process, a superimposed color toner image serving as a back image is formed on the photosensitive drum 10 as the first image carrying means. The images are collectively transferred onto a toner image receiving body 14a as a carrying means. At this time, for example, uniform exposure may be performed by the simultaneous transfer exposure device 12d using a light emitting diode so that good transfer is performed.

After the toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the photosensitive drum AC static eliminator 16, the toner is transferred to a cleaning device 19 as cleaning means for the photosensitive drum 10, The toner is cleaned by a cleaning blade 19a made of a rubber material in contact with the drum 10, and collected by a screw 19b in a not-shown waste toner container. Also, the photosensitive drum 10
Is removed by, for example, exposure by the uniform exposure device 12c before charging using a light emitting diode, and the history of the photosensitive drum 10 in the previous image formation is eliminated.

After the superimposed color toner image serving as the back surface image is formed on the photosensitive drum 10 as described above, the superimposed color toner image serving as the front surface image is continuously formed in the same manner as the above-described color image forming process. An image is formed on photoconductor drum 10. It is necessary to change the image data so that the front surface image formed on the photosensitive drum 10 is a mirror image of the back surface image formed earlier.

The paper feed cassette 1 serving as a transfer material storage means
5, the recording paper P, which is the transfer material,
As shown in FIG. 2, the toner image is sent to the timing roller 15b, and the driving of the timing roller 15b causes the color toner image of the front surface image carried on the photosensitive drum 10 and the back surface carried by the toner image receiver 14a, as shown in FIG. The color toner image of the image is synchronized with the recording paper P and fed to the paper charger 150.

The paper charger 150 is brought into contact with the recording paper P as it passes, and charges the recording paper P. The recording paper P is attracted to the toner image receiver 14a via the color toner image of the back surface image carried on the toner image receiver 14a,
The toner image is transferred to the transfer area 14b as the toner image receiver 14a moves.

In the transfer area 14b, the color toner image of the surface image on the photosensitive drum 10 is collectively transferred to the surface of the recording paper P by the transfer device 14c as the first transfer means. At this time, the color toner image of the back side image carried on the toner image receiver 14a is not transferred to the recording paper P but exists on the toner image receiver 14a. The transfer device 14c
The transfer simultaneous exposure unit 12 using, for example, a light emitting diode, provided inside the photosensitive drum 10 in opposition to the transfer unit 14c so that good transfer is performed at the time of transfer.
The uniform exposure may be performed by d.

The recording paper P on which the color toner image has been transferred to the front surface is then conveyed to a back transfer device 14g as a second transfer means, and the back image transfer device 14g causes the toner image receiving member 1 to be transferred.
The color toner of the back surface image carried on 4a is collectively transferred to the back surface of the recording paper P.

The recording paper P on which the color toner images have been transferred on both sides as described above is a paper separation A for transfer material separation.
C The charge is removed by the charge remover 14h, and the toner image receiver 14a
Separated from

The recording paper P separated from the toner image receiving body 14a is conveyed to a fixing device 17 as fixing means, and
After the toner adhered to the front and back surfaces is fixed by heat and pressure, the toner is discharged to a tray outside the apparatus via a paper discharge roller 18.

The toner remaining on the toner image receiving member 14a after transferring the toner image of the back side image onto the recording paper P is provided to face the driven roller 14e, and the toner image receiving member 14a The toner image receiving member is cleaned by a toner image receiving member cleaning device 140 which is a cleaning unit and includes a toner image receiving member cleaning blade 141 as a blade member capable of contacting and releasing the contact. Incidentally, the toner image receiving body cleaning blade 14
The contact release and contact of 1 are performed by turning on / off a contact release solenoid (not shown).

The toner remaining on the photosensitive drum 10 after transferring the toner image of the front surface image onto the recording paper P is subjected to static elimination by the photosensitive drum AC static eliminator 16 in the same manner as in the case of the back surface image formation. The residual toner is removed by the photosensitive drum cleaning device 19, and the peripheral surface of the photosensitive drum 10 is discharged by the exposure by the uniform exposure device 12c before charging, so that the history of the photosensitive drum 10 in the previous image formation is eliminated. Then, the process enters the next image forming cycle.

In the above-described image forming apparatus, the color image is superimposed on the recording paper P to form a color image on both sides by transferring the superimposed color toner images collectively as described above. It is possible to form a favorable double-sided color image with less occurrence of misalignment, toner scattering and rubbing, and less image deterioration.

In the above description, an image is formed on both sides of the recording paper P. However, it goes without saying that an image can be formed only on the front surface or the back surface of the recording paper P.

When an image is formed only on the surface of the transfer material, the recording paper P is transferred so as to synchronize with the color toner image of the surface image formed on the photosensitive drum 10 as shown in FIG. The recording paper P is fed to the area 14b, the toner image of the surface image is collectively transferred to the surface of the recording paper P by the transfer device 14c, and the recording paper P on which the toner image is formed is separated from the paper separation A.
C The charge is removed by the charge remover 14h, and the toner image receiver 14a is removed.
After being separated from the sheet, the sheet is conveyed to a fixing device 17 as a fixing unit, is reversed in a discharge path to a sheet discharge roller 18, is aligned with the toner image surface as a lower surface, and is discharged to a tray outside the device. .

When an image is to be formed only on the back surface of the transfer material, as shown in FIG. 3B, the color toner image of the back surface image formed on the photosensitive drum 10 is temporarily received by the transfer device 14c. The recording paper P is fed to the transfer area 14b so as to synchronize with the color toner image of the back side image transferred onto the toner image receiving body 14a at a time, and is transferred by the back side transfer unit 14g. The recording sheet P on which the toner image of the back side image is collectively transferred to the back side of the recording sheet P and the toner image is formed on the back side is removed by the paper separating AC neutralizer 14h and separated from the toner image receiving body 14a. rear,
The sheet is conveyed to the fixing device 17 as a fixing unit, is conveyed substantially horizontally by switching the discharge path by a discharge path switching member (not shown), is aligned with the toner image surface as an upper surface, and is transferred to a tray (not shown) outside the apparatus. Is discharged.

In this apparatus, as shown in FIG. 1, for example, a humidity detecting sensor 160 for detecting the humidity inside the apparatus is used as a sensor for measuring the environmental conditions inside the apparatus. , The charging condition by the paper charger 150, the transfer condition by the transfer device 14c and the back surface transfer device 14g, the charge elimination condition by the paper separation AC eliminator 14h, and the like can be controlled according to the detection result of the sensor. . In addition, a temperature sensor or the like may be provided as a sensor for measuring environmental conditions in the machine.

Next, in the first embodiment of the present invention, the transfer current of the first transfer means, the transfer current of the second transfer means,
The control of the charging current of the transfer material charging unit and the charge removal current of the transfer material separating unit will be described with reference to FIGS. FIG.
FIG. 4 is a block diagram illustrating control of a transfer current of a first transfer unit, a transfer current of a second transfer unit, a charging current of a transfer material charging unit, and a charge removal current of a transfer material separation unit in the first embodiment; 5A and 5B are diagrams showing transfer characteristics when forming an image only on the front surface or the back surface of the transfer material or on both surfaces of the transfer material. FIG. 5A shows the first image bearing in double-sided image formation and front surface image formation. FIG. 5B is a diagram illustrating transfer characteristics when a toner image of a front surface image carried on the transfer unit is transferred to the front surface of a transfer material by a first transfer unit. FIG. 5C is a diagram illustrating transfer characteristics when a toner image of a back surface image carried on the second image carrying unit is transferred to the back surface of the transfer material by the second transfer unit. FIG. Carried on the first image carrying means at FIG. 6 is a diagram illustrating transfer characteristics when the toner image of the back image and the toner image of the front image are transferred to the second image holding unit or the surface of the transfer material by the first transfer unit. FIG. 6A is a diagram showing a state of charging of the transfer material when the material is supplied to the second image carrying means and a state of being attracted to the second image carrying means, and FIG. FIG. 6B is a diagram illustrating a state during double-sided image formation and a state during backside image formation.

In FIG. 4, reference numeral 10 denotes a photosensitive drum serving as a first image holding means, 14a denotes a toner image receiving body serving as a second image holding means, 150 denotes a paper charger serving as a transfer material charging means, and 14c denotes a paper charger. A transfer device as a first transfer device, a back surface transfer device 14g as a second transfer device, a paper separation AC static eliminator 14h as a transfer material separating device, and E1 supplies a charging current to the paper charger 150. DC constant current power supply,
E2 is a DC constant current power supply for supplying a transfer current to the transfer device 14c, E3 is a DC constant current power supply for supplying a transfer current to the back surface transfer device 14g, and E4 is a paper separation AC static eliminator 14
h is an AC constant current power supply for supplying a static elimination current.

In this apparatus, an image forming mode is selected from a double-sided image forming mode, a front side image forming mode, and a back side image forming mode by an operation unit (not shown), and each image is formed. At this time, the optimum current value based on the image forming mode, which is obtained by an experiment in advance according to the selected image forming mode and is stored in the ROM or RAM as the storage means, is read from the ROM or RAM through the control unit. The transfer current value by the DC constant current power supply E2 of the transfer device 14c, the transfer current value by the DC constant current power supply E3 of the back transfer device 14g, and the DC constant current power supply E1 of the paper charger 150
, And the static elimination current value by the AC constant current power supply E4 of the paper separating AC static eliminator 14h is corrected.

FIG. 5 (A) shows a normal temperature and a normal humidity (20 ± 5 ° C., 4 ° C.).
(5 ± 10%) when using plain paper having a paper thickness of 45 to 55 kg / m ² under the environmental condition, the toner image of the surface image carried on the photosensitive drum 10 as the first transfer means. 7A and 7B are diagrams showing transfer characteristics when transferring to the surface of the recording paper P by the transfer device 14c of FIG. 7A, wherein FIG.

The optimum transfer current value in the double-sided image forming mode is larger than the optimum transfer current value in the front-side image forming mode. It is considered that this is because the transfer electric field is weakened due to the existence of the toner image of the back image between the body 14a.

In order to obtain good transferability in both the double-sided image forming mode and the front-side image forming mode,
It is necessary to set the transfer current value IA2 in the double-sided image forming mode to be larger than the transfer current value IA1 in the front-side image forming mode.
In both the double-sided image forming mode and the front-side image forming mode, the toner image of the surface image carried on the photosensitive drum 10 is applied to the surface of the recording paper P so that A1 is 0.2 to 0.6 mA. The transfer current value to the transfer device 14c at the time of transfer is changed.

FIG. 5 (B) shows a normal temperature and normal humidity (20 ± 5 ° C., 4 ° C.).
(5 ± 10%) when using plain paper having a paper thickness of 45 to 55 kg / m ² under the environmental conditions, the second transfer unit transfers the toner image of the back surface image carried on the toner image receiver 14a. 7A and 7B are diagrams illustrating transfer characteristics when transferring to the back side of the recording paper P by the back side transfer unit 14g, where FIG. 7A illustrates a back side image forming mode, and FIG.

The optimum transfer current value in the double-sided image forming mode is larger than the optimum transfer current value in the back-side image forming mode. It is considered that the transfer electric field is weakened by the presence of the toner image.

In order to obtain good transferability in both the double-sided image forming mode and the rear-side image forming mode,
It is necessary to set the transfer current value IB2 in the double-sided image forming mode to be larger than the transfer current value IB1 in the back side image forming mode.
The toner image of the back side image carried on the toner image receiving body 14a in the double-sided image forming mode and the back side image forming mode is set so that B1 becomes 0.2 to 0.5 mA. The transfer current value to the back side transfer device 14g when transferring to the back side is changed.

FIG. 5C shows a normal temperature and normal humidity (20 ± 5 ° C., 4 ° C.).
When the double-sided image forming mode is selected using plain paper having a paper thickness of 45 to 55 kg / m ² under an environmental condition of (5 ± 10%), the toner image of the rear surface image Each of the toner images of the surface image is transferred to a toner image receiver 14a by a transfer device 14c as a first transfer unit.
6A and 6B are diagrams illustrating transfer characteristics when transferring to the front surface of the recording paper P, and FIG. 7A illustrates the time when the back surface image is transferred to the toner image receiver 14a. (B) shows the time when the front surface image is transferred to the front surface of the recording paper P.

The optimum transfer current value at the time of transferring the front image is larger than the optimum transfer current value at the time of transferring the back image. This is because the transfer current between the photosensitive drum 10 and the toner image receiver 14a is changed at the time of transferring the front image. It is considered that this is because the transfer electric field is weakened due to the presence of the recording paper P and the toner image of the back surface image.

In order to obtain good transferability both at the time of transferring the front surface image and at the time of transferring the back surface image, the transfer current value IC2 at the time of transferring the front image is changed to the transfer current value I at the time of transferring the back image.
It is necessary to set it larger than C1, for example, 0.4 to 0.8 mA for IC2 and 0.2 to 0.6 mA for IC1.
The toner image of the back side image and the toner image of the front side image carried on the photoreceptor drum 10 at the time of the back side image transfer and the front side image transfer, respectively, so as to be mA. The transfer current value to the transfer device 14c when transferring to the surface of the image is changed.

Further, room temperature and normal humidity (20 ± 5 ° C., 45 ± 10
%) When using plain paper having a paper thickness of 45 to 55 kg / m ² under the environmental conditions of
The charging characteristics when the recording paper P is charged by 50 and the toner is attracted to the toner image receiving member 14a are experimentally determined. The optimum charging current value in the back surface image forming mode or the duplex image forming mode is larger than that in the front surface image forming mode. It is confirmed that the optimal charging current value in the backside image forming mode is slightly larger than the optimal charging current value in the backside image forming mode and the optimum charging current value in the backside image forming mode. Was. This is because, as shown in FIG. 6, in the back image forming mode or the duplex image forming mode, the toner image of the back image having the same polarity as the charging polarity of the recording paper P by the paper charger 150 is provided on the toner image receiving member 14a. This is considered to be due to the fact that the toner image attracts the recording paper P to the toner image receiver 14a due to the influence of the toner image. The difference between the back image forming mode and the two-side image forming mode is that the first transfer unit is used to transfer the toner image of the front surface image on the photosensitive drum 10 to the surface of the recording paper P in the two-side image forming mode. It is considered that the application of the transfer unit 14c increases the adhesion between the recording paper P and the toner image receiving body 14a, whereas the transfer unit 14c is inoperative and has no adhesion effect in the backside image forming mode. .

In order to obtain good charging / adsorbing property in any of the front side image mode, the back side image mode, and the both side image forming mode, the charging current value in the both side image forming mode must be changed in the front side image forming mode. It is necessary to set the charging current value in the backside image forming mode to be larger or equal to the charging current value in the double-sided image forming mode while making the charging current value larger than the charging current value. At the time of the front image forming mode, at the time of the both-side image forming mode, and at the time of the back image forming mode, the charging current value in the double-sided image forming mode is −70 μA, and the charging current value in the back-side image forming mode is −75 μA. In each of the cases, when the recording paper P is charged by the paper charger 150 and attracted to the toner image receiver 14a, To change the Denden current value.

Further, at room temperature and normal humidity (20 ± 5 ° C., 45 ± 10
%) When using plain paper having a paper thickness of 45 to 55 kg / m ² under the environmental conditions of
The recording paper P is discharged by the discharger 14h, and the toner image receiver 1 is discharged.
When the static elimination characteristics at the time of separation from 4a were determined by experiments, the optimal static current value in the double-sided image forming mode or the reverse image forming mode was larger than the optimal charging current value in the front surface image forming mode. In addition, it was confirmed that the optimum static elimination current value in the double-sided image forming mode was slightly larger in the double-sided image forming mode and in the rear side image forming mode. This is because in the double-sided image forming mode or the back side image forming mode, the transfer of the toner image of the back side image by the back side transfer unit 14g is performed immediately before the discharging of the recording paper P by the paper separation AC neutralizer 14h. It is considered that the adsorption between the image receiving member 14a and the recording paper P is strengthened, and a larger static elimination current is required. Further, the difference between the two-sided image forming mode and the backside image forming mode is that in the two-sided image forming mode, it is necessary to remove the toner image existing on the surface of the recording paper P, so that a larger discharging current is required. It is considered something.

In order to obtain good separability in any of the front image mode, the back image mode, and the double-side image forming mode, the static elimination current value in the back image forming mode is determined by changing the static elimination current value in the front image forming mode. It is necessary to set the static elimination current value in the double-sided image forming mode to be greater than or equal to the static elimination current value in the back side image forming mode. 7kV _PP , 150μA AC component +
A DC component of 500 V is superimposed, a discharge current value of 5 to 7 kV _PP in the backside image forming mode, a DC component of -500 V is superimposed on an AC component of 200 μA, and a discharge current value of 5 to 7 kV in the double-sided image formation mode. _{In each of} the front image forming mode, the back image forming mode, and the double-sided image forming mode, the paper separating AC neutralizer 1 is provided so that the DC component of -500 V is superimposed on the AC component of _PP , 220 μA.
In step 4h, the value of the charge elimination current to the paper separation AC charge eliminator 14h when the recording paper P is discharged and separated from the toner image receiver 14a is changed.

Next, the transfer current of the first transfer means, the transfer current of the second transfer means, the charge current of the transfer material charging means, and the transfer current of the transfer material separating means with respect to variations in the type of transfer material and environmental conditions of the present invention. Correction control of transfer current of static elimination current
This will be described with reference to FIG. 11 and FIG. FIG. 7 is a diagram illustrating the transfer when the toner image of the back side image carried on the first image carrying unit is transferred to the second image carrying unit by the first transfer unit in the duplex image forming mode and the back image forming mode. 8A and 8B are diagrams showing the characteristics, and FIG. 8A is a diagram showing the transfer characteristics in the double-sided image forming mode. FIG. 8A shows the toner image of the surface image carried on the first image carrying means. FIG. 8B is a diagram showing a transfer characteristic when transferring to the front surface of a transfer material by the transfer means. FIG. 8B is a view showing the toner image of the back surface image carried on the second image carrying means. FIG. 9 is a diagram showing a transfer characteristic when the toner image is transferred to the back surface of the transfer material according to the first embodiment. FIG. 9 shows the toner image of the front image carried on the first image carrier in the front image forming mode.
FIG. 10 is a diagram showing a transfer characteristic when transferring to the front surface of a transfer material by the transfer means. FIG. 10 is a view showing the toner image of the back side image carried on the second image carrying means in the back side image forming mode. FIG. 11 is a diagram showing a transfer characteristic when a transfer is performed on the back surface of the transfer material by the transfer means. FIG. 11 shows a transfer current of the first transfer means, a transfer current of the second transfer means, FIG. 4 is a schematic diagram for correcting and controlling the charging current of the charging unit and the transfer current of the discharging current of the transfer material separating unit in conjunction with each other.

In FIG. 4, reference numeral 10 denotes a photosensitive drum serving as a first image holding means; 14a, a toner image receiving body as a second image holding means; 150, a paper charger as a transfer material charging means; A transfer device as a first transfer device, a back surface transfer device 14g as a second transfer device, a paper separation AC static eliminator 14h as a transfer material separating device, and E1 supplies a charging current to the paper charger 150. DC constant current power supply,
E2 is a DC constant current power supply for supplying a transfer current to the transfer device 14c, E3 is a DC constant current power supply for supplying a transfer current to the back surface transfer device 14g, and E4 is a paper separation AC static eliminator 14
h is an AC constant current power supply for supplying a static elimination current.
Reference numeral 160 denotes a humidity detection sensor as environmental condition detecting means in the apparatus, and the paper charger 150 is also used as a transfer material thickness detecting means as a transfer material type detecting means.

In this apparatus, as described with reference to FIG. 1, the humidity detection sensor 160 for detecting the humidity inside the apparatus is used as a sensor (environmental condition detecting means) for detecting the environmental conditions inside the apparatus. It is provided at a position close to the image receiving body 14a, and performs humidity detection. In addition, a temperature sensor or the like may be provided as the environmental condition detecting means, and the temperature detection and the like may be performed together.

As a means for detecting the type of transfer material (transfer material type detection means), for example, a thickness detection means for the recording paper P is provided. In this apparatus, a paper charger 150 is also provided as a transfer material thickness detecting means, and when the recording paper P is fed to the toner image receiving body 14a, an energization current value at a leading end portion of the recording paper P is detected. Thus, the thickness of the recording paper P is detected.

When an image forming mode is selected from an operation unit (not shown) and each image is formed, the selected image forming mode and a humidity detection signal or a transfer signal from the above-mentioned humidity detecting sensor or transfer material thickness detecting means are transferred. According to the material thickness detection signal, it is obtained by an experiment in advance, and RO as storage means is used.
M, the optimum current value based on the image forming mode, humidity condition, paper thickness condition, etc. stored in the RAM
The transfer current value read from the OM or the RAM and transferred by the DC constant current power supply E2 of the transfer device 14c, the transfer current value by the DC constant current power supply E3 of the back transfer device 14g, and the charging by the DC constant current power supply E1 of the paper charger 150. The correction of the current value and the static elimination current value by the AC constant current power supply E4 of the paper separating AC static eliminator 14h is performed.

FIG. 7 shows a transfer device 1 as a first transfer means for transferring a toner image of a back surface image carried on a photosensitive drum 10 in a double-sided image forming mode and a back side image forming mode.
FIG. 4C is a diagram showing the transfer characteristics when the toner image is transferred to the toner image receiving member 14a according to FIG. 4C.
(° C, 45 ± 10%) environment, and (b)
Is under a high humidity environment with a humidity of 60 to 80%. The optimum transfer current value at normal temperature and normal humidity is IC1, but when the humidity becomes high, that is, 60 to 80%, the transfer rate decreases. For this reason, when it is determined that the humidity is high based on the humidity detection signal from the humidity detection sensor 160, the ROM, R
Optimum transfer current value IC1 at high humidity stored in AM
1 is read, and correction control of the transfer current value to the transfer device 14c is performed.

FIG. 8A shows a case where the toner image of the front surface image carried on the photosensitive drum 10 is transferred to the surface of the recording paper P by the transfer device 14c as the first transfer means in the double-sided image forming mode. FIG. 4 is a diagram showing the transfer characteristics of
(A) is a case where plain paper having a paper thickness of 45 to 55 kg / m ² is used under the normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%) environment. This is a case where a cardboard having a high humidity of 〜80% and a paper thickness of 60 to 75 kg / m ² is used. The optimum transfer current value when plain paper is used in a normal temperature and normal humidity environment is IA2, but transfer is performed when thick paper having a paper thickness of 60 to 75 kg / m ² is used in a high humidity environment where the humidity is 60 to 80%. The rate drops. Therefore, the humidity detection sensor 1
When it is determined that the paper is high-humidity and thick paper based on the humidity detection signal by the control unit 60 and the transfer-material thickness detection signal by the transfer-material-thickness detecting means, the optimal transfer current at the time of high-humidity and thick paper stored in the ROM and RAM in advance. Read the value IA21,
The correction control of the transfer current value to the transfer device 14c is performed. The correction control when both the type of transfer material and the environmental condition change may be individually corrected according to the type of transfer material and the environmental condition.

FIG. 8B shows the transfer of the toner image of the back side image carried on the toner image receiving body 14a to the back side of the recording paper P by the back side transfer unit 14g as the second transfer means in the both side image forming mode. FIG. 6A is a diagram showing transfer characteristics when the above-mentioned process is performed.
%) When plain paper having a paper thickness of 45 to 55 kg / m ² is used in an environment, and (b) shows a case where the humidity is 60 to 80% and the paper thickness is 60 to 75 kg / m ² . This is when thick paper is used. The optimum transfer current value when plain paper is used in a normal temperature and normal humidity environment is IB2, but the humidity is 60 to 80%.
When a thick paper having a paper thickness of 60 to 75 kg / m ² is used in a high humidity environment, the transfer rate is reduced. Therefore, in the same manner as the above-described correction control, the optimum transfer current value IB at the time of high humidity and thick paper is used.
21 is read, and correction control of the transfer current value to the back transfer device 14g is performed.

FIG. 9 shows the transfer characteristics when the toner image of the surface image carried on the photosensitive drum 10 is transferred to the surface of the recording paper P by the transfer device 14c as the first transfer means in the surface image forming mode. (A) is a graph showing 4 × in the normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%) environment.
(B) shows the case where the plain paper having a paper thickness of 5 to 55 kg / m ² is used.
This is when thick paper having a paper thickness of 5 kg / m ² is used.
The optimum transfer current value when plain paper is used in a normal temperature and normal humidity environment is IA1, but transfer is performed when thick paper having a paper thickness of 60 to 75 kg / m ² is used in a high humidity environment of 60 to 80% humidity. The rate drops. For this reason, in the same manner as the above-described correction control, the optimal transfer current value IA11 for high humidity and thick paper is read, and the correction control of the transfer current value to the transfer device 14c is performed.

FIG. 10 shows a state in which the toner image of the back side image carried on the toner image receiver 14a is transferred to the back side of the recording paper P by the back side transfer unit 14g as the second transfer means in the back side image forming mode. FIG. 5A is a diagram showing transfer characteristics, and FIG. 6A shows the normal temperature and normal humidity (20 ± 5 ° C.,
%) When plain paper having a paper thickness of 45 to 55 kg / m ² is used in an environment, and (b) shows a case where the humidity is 60 to 80% and the paper thickness is 60 to 75 kg / m ² . This is when thick paper is used. The optimum transfer current value when plain paper is used in a normal temperature and normal humidity environment is IB1, but the humidity is 60 to 80%.
When a thick paper having a paper thickness of 60 to 75 kg / m ² is used in a high humidity environment, the transfer rate is reduced. Therefore, in the same manner as the above-described correction control, the optimum transfer current value IB at the time of high humidity and thick paper is used.
11 is read out, and correction control of the transfer current value to the back side transfer unit 14g is performed.

As described above, in any of the two-sided image forming mode, the front-side image forming mode, and the back-side image forming mode, good transfer is obtained even if there is a difference in the type of transfer material or a change in environmental conditions. Done in

In the same manner as described above, the correction control of the charging current value to the paper charger 150 as the transfer material charging means is performed.

For example, in the double-sided image forming mode, 45 to 5% under normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%) environment.
When using plain paper having a paper thickness of 5 kg / m ² , the charging current value to the paper charger 150 is set to −70 μA as described above. 7
When using a thick paper having a paper thickness of 5 kg / m ² , the optimum charging current value at the time of high humidity at the time of thick paper is read and set to −80 μA.

Further, for example, in the surface image forming mode, under a normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%) environment,
When using plain paper having a paper thickness of 5 to 55 kg / m ² , the charging current value to the paper charger 150 is set to −50 μm as described above.
A, but in a high humidity environment of 60-80% humidity, 6
When thick paper having a paper thickness of 0 to 75 kg / m ² is used, the optimal charging current value for thick paper at high humidity is read out and set to −60 μA.

Further, for example, in the back side image forming mode, the temperature is 4 ° C. under normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%).
When using plain paper having a paper thickness of 5 to 55 kg / m ² , as described above, the charging current value to the paper charger 150 is set to −75 μm.
A, but in a high humidity environment of 60-80% humidity, 6
When using thick paper having a paper thickness of 0 to 75 kg / m ² , the optimal charging current value for thick paper at high humidity is read and set to −85 μA.

As described above, in any of the two-sided image forming mode, the front-side image forming mode, and the back-side image forming mode, even if there is a difference in the type of the transfer material or a change in environmental conditions, the transfer material can be used. Charging and adsorption are performed well.

Further, in the same manner as described above, the correction control of the static elimination current value to the paper separating AC static eliminator 14h as the transfer material separating means is performed.

For example, in the double-sided image forming mode, 45 to 5 under normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%) environment
When using plain paper having a paper thickness of 5 kg / m ² , as described above, the discharge current value to the paper separation AC neutralizer 14 h is set to 5 to 7.
kV _PP, but set to a value obtained by superimposing a DC component of -500V to the AC component of 220Myuei, if the humidity is used 60~75kg / m ² of the sheet thickness of the cardboard under 60-80% of high humidity environment, Reads the optimal static elimination current value for thick paper at high humidity,
5-7 kV _PP , a value obtained by superimposing a DC component of −600 V on an AC component of 240 μA.

Further, for example, in the surface image forming mode, under a normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%) environment,
When using plain paper having a paper thickness of 5 to 55 kg / m ² , as described above, the discharging current value to the paper separating AC neutralizer 14 h is 5 to 7 kV _PP , and a DC component of +500 V is superimposed on an AC component of 150 μA. Set the value, but the humidity is 60-80
% Of thick paper having a thickness of 60 to 75 kg / m ² in a high humidity environment, the optimum static elimination current value at the time of high humidity and thick paper is read out, and +60 kV _PP , 180 μA of the AC component is added.
It is set to a value in which a DC component of 0 V is superimposed.

Further, for example, in the back side image forming mode, the temperature is 4 ° C. under normal temperature and normal humidity (20 ± 5 ° C., 45 ± 10%).
When using plain paper having a paper thickness of 5 to 55 kg / m ² , as described above, the discharging current value to the paper separating AC neutralizer 14 h is 5 to 7 kV _PP , and a DC component of −500 V is superimposed on an AC component of 200 μA. The humidity is set to 60-80.
% In a high-humidity environment of 60% to 75 kg / m ² , the optimum static elimination current value of the cardboard at the time of high humidity is read out at 5 to 7 kV _PP and an AC component of 220 μA.
It is set to a value in which a DC component of 0 V is superimposed.

As described above, in any of the two-sided image forming mode, the front side image forming mode, and the back side image forming mode, even if there is a difference in the type of the transfer material or a change in the environmental conditions, the transfer material can be used. Good separation is achieved.

In the present invention, each mode of the double-sided image forming mode, the front side image forming mode, and the back side image forming mode described with reference to FIGS. A transfer device 1 as a first transfer unit when transferring the toner image of the back surface image carried on the photosensitive drum 10 to the toner image receiving member 14a
The transfer current value of the transfer device 14c as a first transfer unit when correcting the transfer current value of 4c and transferring the toner image of the surface image carried on the photosensitive drum 10 to the surface of the recording paper P Correction of the transfer current value of the backside transfer unit 14g as a second transfer unit when transferring the toner image of the backside image carried on the toner image receiver 14a to the backside of the recording paper P, The correction of the charging current value to the paper charger 150 as a transfer material charging unit when the recording paper P is supplied to the toner image receiver 14a, and the separation of the recording paper P from the toner image receiver 14a. Paper separation AC static eliminator 1 as transfer material separating means
At least two sets of correction of the static elimination current value to 4h are performed in conjunction with each other.

That is, in the double-sided image forming mode, the transfer current value of the transfer device 14c as the first transfer means for transferring the back surface image on the photosensitive drum 10 to the toner image receiving member 14a, and the transfer current value on the photosensitive drum 10 The transfer current value of the transfer device 14c as the first transfer means for transferring the front surface image to the front surface of the recording paper P, and the back surface image on the toner image receiver 14a are recorded on the recording paper P.
Transfer device 1 as second transfer means for transferring to the back surface of
At least two sets of a transfer current value of 4 g, a charging current value to the paper charger 150 as a transfer material charging unit, and a charge removal current value to the paper separating AC neutralizer 14 h as a transfer material separating unit. In the front image forming mode, the transfer current value of the transfer device 14c as a first transfer unit for transferring the front image on the photosensitive drum 10 to the surface of the recording paper P, and the transfer material charging unit At least two values of the charging current value to the paper charger 150 as the charging device and the discharging current value to the paper separating AC discharging device 14h as the transfer material separating means are changed in conjunction with each other, and the back side image forming mode is changed. Sometimes, the transfer current value of the transfer device 14c as the first transfer means for transferring the back surface image on the photosensitive drum 10 to the toner image receiver 14a or the back surface image on the toner image receiver 14a is recorded on the back surface of the recording paper P. Transfer to the second Reverse side transfer device 14g as shooting means
Transfer current value, and a paper charger 15 as a transfer material charging unit.
Charge current value to 0 or paper separation A as transfer material separation means
At least two sets of values of the static elimination current value to the static eliminator 14h are changed in conjunction with each other.

By performing the correction in conjunction with each other, the transfer current value of the transfer device 14c as the first transfer device and the transfer current value of the back surface transfer device 14g as the second transfer device are complicatedly entangled in the image forming mode. The value, the charging current value of the paper charger 150 as the transfer material charging means, and the charge removal current value of the paper separation AC charge remover 14h as the transfer material separation means can be set to optimal conditions. When performing each correction independently, since the optimal setting range of each current value has a maximum value, there are cases where the current value is too large or the increase of the current value is too small. As a result, it is not always possible to set optimal conditions, and correction control becomes very complicated.

For example, as shown in FIG. 11, in the double-sided image forming mode, the toner image of the back side image carried on the photosensitive drum 10 is changed according to the variation due to the type of transfer material and environmental conditions. When the transfer current value to the transfer device 14c as the first transfer means for transferring the image to the body 14a is corrected, the toner image of the surface image carried on the photosensitive drum 10 is transferred to the surface of the recording paper P. Correction of a transfer current value to a transfer unit 14c as a first transfer unit, and a second transfer unit for transferring a toner image of a back surface image carried on the toner image receiver 14a to the back surface of the recording paper P. Correction of the transfer current value to the back side transfer device 14g as the
To correct the charging current value to the paper charger 150 as a transfer material charging unit when supplying the toner image to the toner image receiver 14a, and as a transfer material separating unit when separating the recording paper P from the toner image receiver 14a. Correction of the static elimination current value to the paper separation AC static eliminator 14h is performed in conjunction with the correction.

That is, in the double-sided image forming mode, when the transfer current value of the transfer device 14c as the first transfer means for transferring the back surface image on the photosensitive drum 10 to the toner image receiving member 14a is increased, The transfer current value of the transfer device 14c as the first transfer device for transferring the front surface image on the drum 10 to the surface of the recording paper P and the transfer current value of the back transfer device 14g as the second transfer device are also increased. When the transfer current value of the transfer device 14c for transferring the surface image on the photosensitive drum 10 to the front surface of the recording paper P is increased, the transfer current value of the back transfer device 14g or the paper separation AC as transfer material separating means is increased. The static elimination current value of the static eliminator 14h is also increased. Further, when the transfer current value of the back transfer device 14g is increased, the charge removal current value of the paper separation AC charge remover 14h is also increased. Furthermore, when the charging current value of the paper charger 150 as the transfer material charging means is increased, the transfer current value of the transfer device 14c for transferring the surface image on the photosensitive drum 10 to the surface of the recording paper P and the back surface transfer. Transfer current value of paper separator 14g and paper separation AC neutralizer 1
The static elimination current value of 4h is also increased.

In the surface image forming mode, when the transfer current value of the transfer unit 14c for transferring the surface image on the photosensitive drum 10 to the surface of the recording paper P is increased, the discharge current of the paper separation AC neutralizer 14h is increased. The value is also increased, and the paper charger 1
When the charging current value of 50 is increased, the photosensitive drum 1
Transfer device 14 for transferring the surface image on the recording paper P to the surface of the recording paper P
The transfer current value of c and the discharge current value of the paper separation AC discharger 14h are also increased.

Further, in the backside image forming mode, when the transfer current value of the transfer unit 14c for transferring the backside image on the photosensitive drum 10 to the toner image receiver 14a is increased,
When the transfer current value of the back transfer device 14g is also increased and the transfer current value of the back transfer device 14g is increased, the charge removal current value of the paper separation AC charge remover 14h is also increased, and the charging current value of the paper charger 150 is increased. Then, the transfer current value of the back transfer device 14g and the charge removal current value of the paper separation AC charge remover 14h are also increased.

As described above, the transfer current value of the first transfer unit, the transfer current value of the second transfer unit, the charge current value of the transfer material charging unit, and the charge removal current value of the transfer material separation unit are corrected in conjunction with each other. By controlling, even if there is a difference in the type of transfer material or a change in environmental conditions, the transfer and transfer of the toner image can be performed in any of the two-sided image forming mode, the front side image forming mode, and the back side image forming mode. The charging and adsorption of the material and the separation of the transfer material are performed favorably.

In the above description, the transfer current value of the first transfer means, the transfer current value of the second transfer means, the charge current value of the transfer material charging means, the transfer current value of the transfer material, Correction control of the static elimination current value of the separation unit was performed, but the transfer voltage value of the first transfer unit, the transfer voltage value of the second transfer unit, and the charge voltage value of the transfer material charging unit were used using a constant voltage power supply. And
Of course, the correction control of the static elimination voltage value of the transfer material separating means may be performed.

Embodiment 2 FIGS. 12 and 13 show an image forming process and each mechanism of an image forming apparatus according to a second embodiment of the present invention.
This will be described with reference to FIG. FIG. 12 is a sectional configuration diagram of an image forming apparatus according to a second embodiment of the present invention, and FIG. 13 is a timing chart of an image forming process according to the second embodiment. In the present embodiment, a monochrome image is formed instead of the color image of the first embodiment, and a member having the same function and structure as described in the image forming apparatus of the first embodiment is used. Have the same numbers.

The image forming apparatus of the present embodiment uses the charging means and the first transfer means of the image forming apparatus of the first embodiment with a change.

As the charging means, a roller charger 110 as a contact charging member is used instead of the above-mentioned scorotron charger 11, and an AC voltage (AC voltage) is superimposed on a DC voltage (DC voltage) on the roller charger 110. The photosensitive drum 10 is charged by applying the charging bias thus applied.

As the first transfer means, a transfer roller 14j, which is a contact transfer member, is used instead of the transfer device 14c formed of the corona discharger described above, and the transfer roller 14j is connected to the photosensitive member via the toner image receiver 14a. A nip (transfer area) T is formed by bringing the transfer roller 14j into contact with the drum 10, and a transfer bias (DC voltage) having the opposite polarity (positive polarity in this embodiment) to the toner is applied to the transfer roller 14j. A transfer electric field is formed, and the toner image on the photosensitive drum 10 is transferred onto the surface of the toner image receiver 14a and the surface of the recording paper P.

As in the first embodiment, as a sensor for measuring the environmental conditions inside the apparatus, for example, a humidity detection sensor 160 for detecting the humidity inside the apparatus is located close to the photosensitive drum 10 and the toner image receiver 14a. Position.
A temperature sensor or the like may be provided as a sensor for measuring the environmental conditions in the machine.

The image forming process of the image forming apparatus according to the second embodiment will be described below.

Photosensitive drum 1 as first image bearing means
Numeral 0 indicates that a photosensitive layer such as a-Si (amorphous silicon) or an organic photoreceptor (OPC) is formed on the outer periphery of a substrate formed of, for example, a cylindrical aluminum member. Circumferential speed 280mm / s
It is rotated at the speed of ec.

A roller charger 110 as a charging means is
It is a charging member that comes into contact with the photoconductor drum 10, and a charging action (the negative polarity in the present embodiment) of the toner applied to the roller charger 110 causes the photoconductor layer of the photoconductor drum 10 to perform a charging operation ( In this embodiment, negative charging is performed, and a uniform potential is applied to the photosensitive drum 10.

Exposure unit 120 as image exposure means
Denotes a semiconductor laser as a light emitting element (not shown), a rotary polygon mirror 120b for rotating and scanning a laser beam emitted from the semiconductor laser, an fθ lens 120c, and a reflection mirror 120.
d, the laser light emitted from the semiconductor laser is rotationally scanned by the rotating polygon mirror 120b, and is passed through the fθ lens 120c and the reflecting mirror 120d. Image exposure to form a latent image. The image data needs to be changed so that the image data corresponding to the front image and the image data corresponding to the back image are mirror images of each other.

The developing device 13 as a developing means contains, for example, a one-component or two-component developer of black (K) and is kept at a predetermined gap from the photosensitive drum 10 by an abutting roller (not shown). Sagged, for example, 0.5-1 mm thick,
A developing sleeve 131 which is a cylindrical nonmagnetic stainless steel or aluminum developer carrier having an outer diameter of 15 to 25 mm is provided. The developing sleeve 131 has the same polarity as toner (minus polarity in the present embodiment). By applying a developing bias consisting of the DC voltage of the above, reverse development is performed, and the latent image on the photosensitive drum 10 is developed. As a developing bias, a DC voltage (DC voltage) is converted to an AC voltage (A
C voltage) may be used.

In this embodiment, the roller chargers 11 are sequentially arranged from the upstream side in the moving direction of the photosensitive drum 10.
0, an exposure unit 120 and a developing device 13 are arranged, and the photosensitive drum 10 is rotated clockwise by an unillustrated photosensitive member drive motor at the start of image recording, and the roller charger 110 is operated at the same time. Then, the application of the potential to the photosensitive drum 10 is started. The photosensitive drum 10 to which the potential has been applied is then subjected to image exposure by a laser beam by the exposure unit 120, and the photosensitive drum 1
0, an electrostatic latent image is formed. The electrostatic latent image is then reversely developed by the developing device 13 to form a toner image on the photosensitive drum 10 (toner image forming means).

By the above-described image forming process, a toner image serving as a back surface image is formed on the photosensitive drum 10 as the first image carrying means, and the toner image has a polarity opposite to that of the toner in the transfer area T (this embodiment). The transfer roller 14j, which is a first transfer unit to which a DC voltage having a positive polarity (in the embodiment, a positive polarity) is applied, is transferred onto a toner image receiver 14a as a second image carrying unit.

The toner image receiving member 14a as a second image bearing means is stretched between a driving roller 14d, a driven roller 14e and a tension roller 14i.
Endless belt provided in contact with
On the outside of a semiconductive modified polyimide belt substrate having a thickness of 0 to 500 μm and a volume resistivity of 10 ¹⁰ to 10 ¹⁴ Ω · cm, preferably as a toner filming preventing layer, a thickness of 5 to 50 μm.
The film belt has a two-layer structure with a semiconductive fluorine coating of m. In place of the modified polyimide substrate, a thickness of 100 to 500 μm and a volume resistivity of 1
0 ¹⁰ to 10 ¹⁴ Ω · cm semiconductive polyester, polystyrene, polyethylene, polyethylene terephthalate, ETFE (ethylene tetrafluoroethylene copolymer), etc. film, thickness 0.5 to 2.0 mm, volume resistivity A semiconductive urethane rubber or silicon rubber of 10 ¹⁰ to 10 ¹⁴ Ω · cm can be used as the base.

The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by a photosensitive drum AC static eliminator 16 and then enters a cleaning device 19 as a photosensitive drum cleaning unit, or to a photosensitive drum cleaning unit. Photoreceptor drum cleaning blade 1 made of rubber material in contact with
It is cleaned by 9a and collected by a screw 19b into a not-shown waste toner container.

After the toner image serving as the back side image is formed on the toner image receiving member 14a serving as the second image carrying means as described above, the photosensitive material serving as the first image carrying means from which the residual toner has been removed. The formation of a toner image as a surface image on the body drum 10 is subsequently started.

The recording paper P, which is a transfer material, is sent out from the paper feed cassette 15 as the transfer material storage means by the timing roller 15b via the feed roller 15a. At this time, the toner image of the back surface image formed on the toner image receiver 14a, the toner image of the front surface image formed on the photosensitive drum 10, and the recording paper P are synchronized in the transfer area 14b. Thus, the timing of the front surface image formation and the timing of feeding the recording paper P are matched.

The recording paper P sent out at the timing by the timing roller 15b is charged with a brush-like paper as a transfer material charging means to which a DC voltage of the same polarity as the toner (in this embodiment, a negative polarity) is applied. Vessel 1
The paper is charged to the same polarity as the toner by 50, and is attracted to the toner image receiver 14a.

Paper charger 150 as transfer material charging means
Represents the toner image receiving member 14a with the support shaft 152 as a rotation fulcrum.
Is a conductive brush capable of contacting and releasing contact, and is provided to face the driven roller 14e that is grounded. The paper charger 150 is brought into contact only when the recording paper P is being fed, a DC voltage having the same polarity as that of the toner is applied, and the paper charger 150 comes into contact immediately before or simultaneously with the passage of the rear end of the recording paper P. Is released and separated from the recording paper P, and the applied voltage is cut off.

The paper charging by the paper charger 150 has the same polarity as the toner, and prevents the toner from being attracted to the toner image on the toner image receiving member 14a or the toner image on the photosensitive drum 10 to prevent the toner image from being disturbed. Preventing. Further, as the transfer material charging means, it is also possible to use a conductive roller capable of contacting and releasing contact with the toner image receiver 14a and applying a DC voltage having the same polarity as the toner.

The recording paper P attracted to the toner image receiving member 14a by the paper charger 150 is fed to the transfer area T, where the toner has the opposite polarity (positive polarity in this embodiment) to the toner. The toner image of the surface image on the photosensitive drum 10 is transferred to the surface (upper surface side) of the recording paper P by the transfer roller 14j as the first transfer unit to which the voltage is applied. The toner image of the back side image on the toner image receiver 14a is not transferred to the recording paper P but exists on the toner image receiver 14a.

Recording paper P on which the toner image of the surface image has been transferred
Is transported to the second transfer area along with the movement of the toner image receiver 14a while being attracted to the toner image receiver 14a. In the second transfer area, a rear transfer unit 14g as a second transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied, and is disposed opposite to the grounded drive roller 14d. The toner image receiver 1
The toner image of the back surface image on 4a is transferred to the back surface (lower surface side) of the recording paper P.

The recording paper P on which the toner images have been transferred on both sides as described above is placed opposite to the grounded drive roller 14d, and the transfer material separation to which the AC voltage or the superimposed voltage of AC and DC is applied. Separation AC static eliminator 14
The charge is removed by h, and the toner image is separated from the toner image receiver 14a.

The recording paper P separated from the toner image receiving body 14a receives two rollers 17a and 1 having a heater therein.
7b, the toner is conveyed to a fixing device 17 as a fixing means, and the toner adhered to the front surface and the back surface is fixed by heat and pressure, and then discharged to a tray outside the device via a paper discharge roller 18.

The toner remaining on the toner image receiving member 14a after transferring the toner image of the back side image onto the recording paper P is provided to face the driven roller 14e, and the toner image receiving member 14a Cleaning device 1 as a second image carrier cleaning means, having a blade member 141 capable of contacting and releasing contact with the toner image receiver.
The cleaning is performed by 40. The contact release and contact of the blade member 141 are performed by turning on / off a contact release solenoid (not shown).

The toner remaining on the photosensitive drum 10 after transferring the toner image of the front surface image to the recording paper P is subjected to static elimination by the photosensitive drum AC static eliminator 16 in the same manner as in the case of the back surface image formation. The residual toner is removed by the cleaning device 19 and the next image forming cycle is started.

In the above-described image forming apparatus, an image is formed on both sides of the recording paper P as described above. However, as described with reference to FIG. Of course, an image can be formed only on the back surface.

FIG. 13 is a timing chart of the image forming process according to the present embodiment, which is for forming one A-3 size double-sided image. In the drawing, laser output 1 indicates laser exposure scanning from the exposure unit 120 to the photosensitive drum 10 during backside image formation, and laser output 2 indicates laser exposure from the exposure unit 120 to the photosensitive drum 10 during front side image formation. It shows scanning. Further, the transfer roller high voltage output 1 is used for transferring the back side image on the photosensitive drum 10 to the toner image receiving body 14a.
The transfer high voltage output 2 is used to transfer a surface image on the photosensitive drum 10 to the surface of the recording paper P.
6 shows the application of a transfer voltage to j. The high voltage output of the backside transfer unit 14 is used to transfer the toner image of the backside image on the toner image receiver 14a to the backside of the recording paper P.
g indicates a transfer voltage application, and the paper charger high voltage output indicates a charge voltage application to the paper charger 150 when the recording paper P is charged and attracted to the toner image receiver 14a. The high voltage output of the separation AC static eliminator indicates the application of a static elimination voltage to the paper separation AC static eliminator 14h when the recording paper P is separated from the toner image receiver 14a.

In this embodiment, the transfer roller 1
4j, the transfer voltage to the back transfer device 14g, the charging voltage to the paper charger 150, and the paper separation AC.
The static elimination voltage is applied to the static eliminator 14h using a constant voltage power supply, and the transfer voltage of the transfer roller 14j,
g transfer voltage, paper charger 150 charging voltage and paper separation A
The static elimination voltage of the C static eliminator 14h is controlled. In the present embodiment, the transfer current of the transfer roller 14j and the back surface transfer unit 14g are also used in the same manner as in the first embodiment, using a constant current power supply.
Transfer current, charging current of paper charger 150 and paper separation AC
It goes without saying that the static elimination current of the static eliminator 14h may be controlled.

Next, the transfer voltage of the first transfer means, the transfer voltage of the second transfer means, the charge voltage of the transfer material charging means, and the transfer material separation in accordance with the result of detection by the transfer material resistance / capacity detecting means. The control of the static elimination voltage of the means will be described with reference to FIG. 14 and FIG. FIG. 14 shows the transfer material resistance
FIG. 4 is a block diagram showing control of a transfer voltage of a first transfer unit, a transfer voltage of a second transfer unit, a charging voltage of a transfer material charging unit, and a charge removal voltage of a transfer material separation unit according to a detection result by a capacity detection unit; It is.

In this apparatus, by applying a voltage to the transfer material and detecting the value of the applied current at that time or by applying a current to the transfer material and detecting the value of the applied voltage at that time, the resistance of the transfer material is detected. As the transfer material resistance / capacity detecting means for detecting both the capacity or the resistance and the capacity, the paper charger 150 as the transfer material charging means is also used. The transfer material resistance / capacity detection by the paper charger 150 is performed, for example, as shown in FIG. 13, when the recording paper P as a transfer material is charged by the paper charger 150, for example, between 1 and 5 mm. The detection is performed by detecting the value of the current flowing from the DC constant voltage power supply E11 in step (1), and a transfer material resistance / capacity detection signal is input to the control unit.

The resistance and capacity of the transfer material vary depending on the thickness and material of the transfer material, environmental conditions in the machine, and the like. However, when the width of the transfer material changes, the resistance and capacity of the transfer material itself change. However, the width of the contact between the paper charger 150 and the toner image receiver 14a at both ends of the transfer material changes, so that the transfer material resistance / capacity detection signal from the paper charger 150 changes. Become. For this reason, in the present apparatus, a transfer material size detection member (not shown) is provided as a means for detecting the width of the transfer material in the transport direction (transfer material width detection means), for example, in the paper supply cassette 15 serving as the transfer material storage means. A transfer material width detection signal is input to the control unit from a transfer material size detection member as the transfer material width detection means.

When an image forming mode is selected from an operation unit (not shown) and each image is formed, according to the selected image forming mode and the above-described transfer material resistance / capacity detection signal and transfer material width detection signal. The optimum current value based on the image forming mode, the change in the resistance / capacity of the transfer material, etc., which is obtained in advance by experiment and is stored in the ROM or RAM as the storage means, is read out from the ROM or RAM through the control unit. Transfer voltage value of the transfer roller 14j by the DC constant voltage power supply E21, and the back side transfer device 14 by the DC constant voltage power supply E31.
The correction of the transfer voltage value of g, the charging voltage value of the paper charger 150 by the DC constant voltage power source E11, and the static elimination voltage value of the paper separating AC static eliminator 14h by the AC constant voltage power source E41 are performed. In the above description, since the paper charger 150 is also used as the paper charger transfer material resistance / capacity detecting means, the charging voltage value of the paper charger 150 as the transfer material charging means is corrected by the transfer material. Is corrected from the middle after the leading end portion has passed.

As described above, even when the resistance and capacity of the transfer material change due to the thickness and material of the transfer material or the environmental conditions in the machine, the transfer of the toner image, the charging and adsorption of the transfer material, and the separation of the transfer material are performed well. Done.

Next, the transfer voltage of the first transfer means, the transfer voltage of the second transfer means, and the charging voltage of the transfer material charging means according to the result of detection by the resistance / capacity detection means of the second image carrying means. The control of the charge removal voltage of the transfer material separating means will be described with reference to FIGS. 15 to 17 and FIG. FIG.
5 is a current control circuit block diagram showing an example in which the transfer material charging means is used as the second image carrying means resistance / capacity detecting means, and FIG. 16 is a circuit diagram showing the first transferring means as the second image carrying means. FIG. 17 is a circuit block diagram of current control showing an example of use as a resistance / capacity detecting means. FIG. 17 shows an example in which a second image carrying means cleaning means is used as a second image carrying means resistance / capacity detecting means. It is a circuit block diagram of a current control.

FIG. 15 shows a toner image receiver resistance / capacitance detection signal from the paper charger 150 which also uses the paper charger 150 as the transfer material charging means as the second image carrier resistance / capacity detecting means. The transfer voltage value of the transfer roller 14j as the first transfer means for transferring the back surface image on the photosensitive drum 10 to the toner image receiving member 14a, and the recording of the front surface image on the photosensitive drum 10 as a transfer material The transfer voltage value of the transfer roller 14j as the first transfer means for transferring the image to the front surface of the paper P, and the back side image on the toner image receiver 14a are recorded on the recording paper P.
Transfer device 1 as a second transfer means for transferring to the back surface of
FIG. 9 is a block diagram when controlling a transfer voltage value of 4 g and a charge removal voltage value of a paper separation AC charge remover 14 h as a transfer material separating unit when the recording paper P is separated from the toner image receiver 14 a.

As shown in FIG. 13, for example, as shown in FIG. 13, when the recording paper P as a transfer material does not pass over the toner image receiver 14a, the paper charger 150 detects the toner image receiver resistance / capacity. This is performed by applying a voltage to the toner image receiving member 14a and detecting the value of a current supplied from the DC constant voltage power supply E11.
The capacitance detection signal is input to the control unit.

When an image forming mode is selected by an operation unit (not shown) and each image is formed, an experiment is performed in advance in accordance with the selected image forming mode and the above-described toner image receiver resistance / capacity detection signal. ROM as a storage means, an image forming mode stored in the RAM,
The optimal current value based on the change in the resistance / capacity of the toner image receiver is read from the ROM or RAM through the control unit,
The transfer voltage value of the transfer roller 14j by the DC constant voltage power supply E21, the transfer voltage value of the backside transfer unit 14g by the DC constant voltage power supply E31, and the static elimination voltage value of the paper separation AC static eliminator 14h by the AC constant voltage power supply E41 are corrected. .

FIG. 16 shows the resistance of the second image bearing means.
A transfer roller 14j as a first transfer means is also used as a capacity detection means, and the photosensitive drum 1 is used in accordance with a toner image receiver resistance / capacity detection signal from the transfer roller 14j.
0 to transfer the back side image on the toner image receiver 14a.
The transfer voltage value of the transfer roller 14j as the transfer means, and the surface image on the photosensitive drum 10 is used as the transfer material for the recording paper
Roller 1 as First Transfer Means for Transferring to Surface of Sheet
4j, the transfer voltage value of the backside transfer unit 14g as a second transfer means for transferring the backside image on the toner image receiver 14a to the backside of the recording paper P, and the recording paper P from the toner image receiver 14a. FIG. 9 is a block diagram when controlling a static elimination voltage value of a paper separation AC static eliminator 14h as a transfer material separating unit at the time of separation.

The transfer roller 14j detects the resistance and capacity of the toner image receiver by applying a voltage to the transfer roller 14j before transferring the toner image onto the photosensitive drum 10 onto the toner image receiver 14a or the recording paper P. The detection is performed by detecting the value of a current supplied from the constant voltage power supply E21, and a toner image receiver resistance / capacity detection signal is input to the control unit.

When an image forming mode is selected by an operation unit (not shown) and the respective images are formed, the optimum current value is read out in the same manner as described above, and the transfer voltage of the transfer roller 14j by the DC constant voltage power supply E21. Value, DC constant voltage power supply E
The correction of the transfer voltage value of the backside transfer device 14g by 31 and the charge removal voltage value of the paper separation AC charge remover 14h by the AC constant voltage power supply E41 are performed.

FIG. 17 shows a toner image receiver cleaning device 140 as a second image carrying cleaning means.
Image receiving member cleaning blade 14 provided in the printer
1 is capable of applying a voltage, and a toner image receiving member cleaning blade 14 is used as a second image carrying means resistance / capacity detecting means.
1 and a transfer roller 14j as a first transfer means for transferring the back surface image on the photosensitive drum 10 to the toner image receiver 14a in response to the toner image receiver resistance / capacity detection signal from the blade 141. Transfer voltage value, photosensitive drum 1
The transfer voltage value of the transfer roller 14j as the first transfer means for transferring the front surface image on the recording paper P to the front surface of the recording paper P as the transfer material, and the rear surface image on the toner image receiver 14a is transferred to the rear surface of the recording paper P Back transfer device 14 as second transfer means
FIG. 9 is a block diagram when controlling a transfer voltage value of g and a charge removal voltage value of a paper separation AC charge remover 14h as a transfer material separating unit when the recording paper P is separated from the toner image receiver 14a.

Toner image receiver cleaning blade 14
1, the toner image receiver cleaning blade 141 is applied to the toner image receiver 14a before the toner image on the photosensitive drum 10 is transferred to the toner image receiver 14a or the recording paper P. The DC constant voltage power supply E5
The detection is performed by detecting the value of the supplied current from the printer, and the resistance / capacitance detection signal of the toner image receiver is input to the control unit.

When an image forming mode is selected by an operation unit (not shown) and each image is formed, the optimum current value is read out in the same manner as described above, and the transfer voltage of the transfer roller 14j by the DC constant voltage power supply E21 is set. Value, DC constant voltage power supply E
The correction of the transfer voltage value of the backside transfer device 14g by 31 and the charge removal voltage value of the paper separation AC charge remover 14h by the AC constant voltage power supply E41 are performed.

As described above, even if the resistance and capacity of the second image carrier change due to deterioration due to repeated use of the second image carrier or environmental conditions in the apparatus, transfer of the toner image and separation of the transfer material can be performed. Well done.

In the above embodiment, the transfer material resistance
The capacity detection means or the second transfer means resistance / capacity detection means is provided also as a process member such as a transfer material charging means. However, the present invention is not limited to this, and the transfer material having the same function as described above is provided. It is a matter of course that the present invention includes an apparatus in which the resistance / capacitance detection means or the second transfer means resistance / capacity detection means is independently provided.

[0153]

According to the first or second aspect, the transfer of the toner image of the front surface image is favorably performed during both the double-sided image formation and the rear-side image formation.

According to the third or fourth aspect, the transfer of the toner image of the back side image is favorably performed in both the double-sided image formation and the back side image formation.

According to the fifth or sixth aspect, at the time of forming a double-sided image, both the transfer of the toner image of the back side image and the transfer of the toner image of the front side image on the first image carrying means are performed favorably.

According to the seventh or eighth aspect, the charging of the transfer material is favorably performed at the time of both-side image formation, front-side image formation, and back-side image formation.

According to the ninth or tenth aspect, the transfer material can be satisfactorily separated at the time of both-side image formation, front-side image formation, and back-side image formation.

According to the eleventh to nineteenth aspects, when forming a double-sided image, the transfer of the toner image, the charging of the transfer material, and the separation of the transfer material are excellent even if there is a difference in the type of transfer material or a change in environmental conditions. Done in

According to the twentieth to twenty-third aspects, even when there is a difference in the type of transfer material or a change in environmental conditions during surface image formation, transfer of a toner image, charging of the transfer material, and separation of the transfer material are satisfactory. Done in

According to the twenty-fourth to twenty-eighth aspects, even when there is a difference in the type of transfer material or a change in environmental conditions during the formation of the back surface image, the transfer of the toner image, the charging of the transfer material, and the separation of the transfer material are satisfactory. Done in

According to claim 29 or 30, even if the resistance and capacity of the transfer material change due to the thickness and material of the transfer material or the environmental conditions in the machine, the transfer of the toner image and the charging and transfer of the transfer material are performed. Good separation of the material is achieved.

According to the thirty-first or thirty-second aspect, even if the resistance / capacity of the second image carrier changes due to deterioration due to repeated use of the second image carrier or environmental conditions in the machine, etc.
Transfer of the toner image and separation of the transfer material are performed favorably.

According to Claims 33 to 36, the second image bearing means resistance / capacity detecting means detects the change or deterioration of the second image bearing means due to a change in the type of transfer material or environmental conditions or repeated use. Even if there is, the transfer of the toner image, the charging of the transfer material, and the separation of the transfer material during the formation of the one-sided image of the front image, the formation of the one-sided image of the back image, or the formation of the two-sided image are performed well.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a color image forming apparatus showing a first embodiment of the image forming apparatus of the present invention.

FIG. 2 is a diagram illustrating a state of forming a toner image and supply of a transfer material when images are formed on both surfaces of a transfer material by an image forming apparatus according to the present invention.

FIG. 3 is a diagram illustrating a toner image forming state and supply and discharge of a transfer material when an image is formed only on the front surface or the back surface of the transfer material by the image forming apparatus according to the present invention.

FIG. 4 is a block diagram illustrating control of a transfer current of a first transfer unit, a transfer current of a second transfer unit, a charging current of a transfer material charging unit, and a charge removal current of a transfer material separation unit in the first embodiment. is there.

FIG. 5 is a diagram illustrating transfer characteristics when an image is formed only on the front surface or the back surface of the transfer material or on both surfaces of the transfer material.

FIG. 6 is a diagram illustrating a state of charging of the transfer material and adsorption of the transfer material to the second image holding means when the transfer material is supplied to the second image holding means.

FIG. 7 is a diagram illustrating transfer when a toner image of a back side image carried on a first image carrying unit is transferred to a second image carrying unit by a first transfer unit in a duplex image forming mode and a back image forming mode; It is a figure showing a characteristic.

FIG. 8 is a diagram illustrating transfer characteristics in a double-sided image forming mode.

FIG. 9 is a diagram illustrating transfer characteristics when a toner image of a surface image carried on a first image carrying unit is transferred to a surface of a transfer material by a first transfer unit in a surface image forming mode.

FIG. 10 is a diagram illustrating transfer characteristics when a toner image of a back image carried on a second image carrying unit is transferred to the back surface of a transfer material by a second transfer unit in a back image forming mode.

FIG. 11 is a diagram illustrating a transfer current of a transfer current of a first transfer unit, a transfer current of a second transfer unit, a charging current of a transfer material charging unit, and a transfer current of a charge removing current of a transfer material separation unit in a duplex image forming mode; It is a schematic diagram which controls.

FIG. 12 is a cross-sectional configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 13 is a timing chart of an image forming process according to the second embodiment.

FIG. 14 shows a transfer voltage of a first transfer unit, a transfer voltage of a second transfer unit, a charging voltage of a transfer material charging unit, and a transfer voltage of a transfer material separating unit according to a detection result by a transfer material resistance / capacity detecting unit. It is a block diagram which shows control of a static elimination voltage.

FIG. 15 is a circuit block diagram of current control showing an example in which a transfer material charging unit is used as a second image carrying unit resistance / capacitance detecting unit.

FIG. 16 is a circuit block diagram of current control showing an example in which the first transfer unit is used as a second image carrying unit resistance / capacitance detection unit.

FIG. 17 is a current control circuit block diagram showing an example in which the second image carrying means cleaning means is used as the second image carrying means resistance / capacity detecting means.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure unit 13 developing device 14a toner image receiver 14c transfer device 14g backside transfer device 14h paper separation AC neutralizer 14j transfer roller 17 fixing device 140 toner image receiver cleaning device 141 toner image receiver Cleaning blade 150 Paper charger 160 Humidity detection sensor E1, E2, E3 DC constant current power supply E4 AC constant current power supply E5, E11, E21, E31 DC constant voltage power supply E41 AC constant voltage power supply P Recording paper

Claims (36)

[Claims] A first image carrying means for carrying the toner image formed by the toner image forming means; and a toner image carried by the first image carrying means is transferred. A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. An image forming apparatus having a fixing unit for fixing a toner image transferred onto a transfer material, wherein the image transfer is performed when image formation is performed only on the surface of the transfer material and when image formation is performed on both surfaces of the transfer material. An image forming apparatus, wherein a value of a transfer current or a transfer voltage of the first transfer means for transferring a toner image to a surface of a material is changed. 2. The method according to claim 1, wherein an absolute value of a transfer current or a transfer voltage of the first transfer unit when forming an image on both surfaces of the transfer material is determined by the first value when forming an image only on the surface of the transfer material. 2. The image forming apparatus according to claim 1, wherein the transfer current or the transfer voltage of the transfer unit is larger than an absolute value of the transfer current. 3. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred. A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. An image forming apparatus having a fixing unit for fixing a toner image transferred to a transfer material, wherein an image is formed only on the back surface of the transfer material and an image is formed on both surfaces of the transfer material. An image forming apparatus, wherein a value of a transfer current or a transfer voltage of the second transfer means for transferring a toner image to a back surface of a material is changed. 4. The method according to claim 1, wherein an absolute value of a transfer current or a transfer voltage of the second transfer unit when performing image formation on both surfaces of the transfer material is determined by using the second value when performing image formation only on the back surface of the transfer material. 4. The image forming apparatus according to claim 3, wherein the transfer current or the transfer voltage of the transfer unit is larger than an absolute value of the transfer current. 5. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried on the first image carrying means is transferred, and the transferred toner image is A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. An image forming apparatus having a fixing unit for fixing a toner image transferred to a material, wherein when forming an image on both surfaces of the transfer material, a toner image of a back surface image carried by the first image carrying unit is formed. The value of the transfer current or the transfer voltage of the first transfer means for transferring to the second image bearing means and the toner image of the surface image carried by the first image bearing means are transferred to the surface of the transfer material An image forming apparatus which changes a value of a transfer current or a transfer voltage of the first transfer unit. 6. An absolute value of a transfer current or a transfer voltage of the first transfer means for transferring the toner image of the front surface image onto the front surface of the transfer material, and a transfer of the toner image of the back surface image to the second transfer portion.
6. The image forming apparatus according to claim 5, wherein the transfer current or the transfer voltage of the first transfer unit for transferring the image to the image bearing unit is larger than an absolute value of the transfer voltage. 7. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried on the first image carrying means is transferred, and the transferred toner image is A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. An image forming apparatus having a fixing unit for fixing a toner image transferred to a transfer material, when an image is formed only on the surface of the transfer material, and when an image is formed on both surfaces of the transfer material, or when the transfer material is Changing the value of the charging current or the charging voltage of the transfer material charging unit that charges the transfer material in the supply unit of the transfer material to the second image holding unit when performing image formation only on the back surface An image forming apparatus comprising: 8. The transfer material charging means when the image formation is performed only on the surface of the transfer material, and the absolute value of the charging current or the charging voltage of the transfer material charging means when performing image formation on both surfaces of the transfer material is determined. The absolute value of the charging current or the charging voltage of the transfer material charging unit when forming an image only on the back surface of the transfer material is set to be larger than the absolute value of the charging current or the charging voltage of the transfer material. 8. The image forming apparatus according to claim 7, wherein the charging current or the charging voltage of the transfer material charging unit at the time of image formation is set to be larger or equal to the absolute value. 9. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred, and the transferred toner image is A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. A fixing unit for fixing a toner image transferred to a transfer material, wherein an image is formed only on the front surface of the transfer material, and an image is formed only on the back surface of the transfer material, or the transfer material Changing the value of the static elimination current or the static elimination voltage of the transfer material separating means for separating the transfer material from the second image bearing means in the portion where the transfer material is separated from the second image bearing means. An image forming apparatus comprising: 10. The transfer material separation means when the image formation is performed only on the front surface of the transfer material, and the value of the static elimination current or the charge elimination voltage of the transfer material separation unit when performing the image formation only on the back surface of the transfer material. The value of the charge elimination current or voltage of the transfer material separating means when forming an image on both surfaces of the transfer material is set to be larger than the value of the charge elimination current or the charge elimination voltage of the transfer member. The image forming apparatus according to claim 9, wherein the value of the charge elimination current or the charge elimination voltage of the transfer material separating unit is set to be greater than or equal to the value of the charge elimination current. 11. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred. A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. An image forming apparatus having a fixing unit for fixing a toner image transferred to a transfer material, wherein when performing image formation on both surfaces of the transfer material, depending on a type of the transfer material or environmental conditions, A charging current or a charging voltage value of a transfer material charging unit for charging the transfer material in a supply unit to the second image holding unit;
A value of a transfer current or a transfer voltage of the first transfer means for transferring the image to the image carrying means; and a first transfer means for transferring the toner image carried by the first image carrying means to the surface of the transfer material. The value of the transfer current or the transfer voltage of the transfer material, the value of the transfer current or the transfer voltage of the second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material, At least two sets of values of a static elimination current or a static elimination voltage of a transfer material separating unit that separates the transfer material in a separation unit from the second image bearing unit are changed in conjunction with each other. Image forming apparatus. 12. When the transfer current or transfer voltage of the first transfer means for transferring the toner image carried on the first image carrying means to the second image carrying means is increased, 12. The transfer device according to claim 11, wherein an absolute value of a transfer current or a transfer voltage of the first transfer unit that transfers the toner image carried on the first image carrying unit to a surface of the transfer material is also increased. Image forming apparatus. 13. When the transfer current or transfer voltage of the first transfer means for transferring the toner image carried on the first image bearing means to the second image bearing means is increased, 12. The image forming apparatus according to claim 11, wherein an absolute value of a transfer current or a transfer voltage of the second transfer unit is also increased. 14. When the transfer current or transfer voltage of the first transfer means for transferring the toner image carried on the first image carrying means to the surface of the transfer material is increased, The image forming apparatus according to claim 11, wherein an absolute value of a transfer current or a transfer voltage of the second transfer unit is also increased. 15. When the transfer current or the transfer voltage of the first transfer means for transferring the toner image carried on the first image carrying means to the surface of the transfer material is increased, the transfer is performed. 12. The image forming apparatus according to claim 11, wherein the value of the charge elimination current or the charge elimination voltage of the material separating means is also increased. 16. The method according to claim 11, wherein when the absolute value of the transfer current or the transfer voltage of the second transfer unit is increased, the value of the static elimination current or the static elimination voltage of the transfer material separating unit is also increased. An image forming apparatus according to claim 1. 17. The method according to claim 17, wherein when the absolute value of the charging current or the charging voltage of the transfer material charging unit is increased, the first image transferring unit transfers the toner image carried on the first image bearing unit to the surface of the transfer material. 12. The image forming apparatus according to claim 11, wherein an absolute value of a transfer current or a transfer voltage of the transfer unit is increased. 18. The method according to claim 18, wherein when the absolute value of the charging current or the charging voltage of the transfer material charging unit is increased, the absolute value of the transfer current or the transfer voltage of the second transfer unit is also increased. 12. The image forming apparatus according to item 11. 19. The method according to claim 11, wherein when the absolute value of the charging current or the charging voltage of the transfer material charging unit is increased, the value of the static elimination current or the static elimination voltage of the transfer material separating unit is also increased. The image forming apparatus as described in the above. 20. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred. A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. An image forming apparatus having a fixing unit for fixing the toner image transferred to the transfer material, wherein an image is formed only on the surface of the transfer material, A charging current or a charging voltage value of a transfer material charging unit for charging the transfer material in a supply unit to the second image holding unit; a toner image carried on the first image holding unit; A value of a transfer current or a transfer voltage of the first transfer unit for transferring to the surface, or a charge elimination current of a transfer material separating unit that separates the transfer material at a portion where the transfer material is separated from the second image bearing unit. Value of static elimination voltage Image forming apparatus and changes in conjunction with two sets of values even without. 21. The method according to claim 20, wherein when the absolute value of the transfer current or the transfer voltage of the first transfer unit is increased, the value of the static elimination current or the static elimination voltage of the transfer material separating unit is also increased. An image forming apparatus according to claim 1. 22. The method according to claim 22, wherein when the absolute value of the charging current or the charging voltage of the transfer material charging unit is increased, the absolute value of the transfer current or the transfer voltage of the first transfer unit is also increased. 20. The image forming apparatus according to 20. 23. The method according to claim 20, wherein when the absolute value of the charging current or the charging voltage of the transfer material charging unit is increased, the value of the static elimination current or the static elimination voltage of the transfer material separating unit is also increased. The image forming apparatus as described in the above. 24. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried on the first image carrying means is transferred, and the transferred toner image is copied. A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. An image forming apparatus having a fixing unit for fixing the toner image transferred to the transfer material, wherein when forming an image only on the back surface of the transfer material, depending on the type of the transfer material or environmental conditions, The value of the charging current or the charging voltage of the transfer material charging means for charging the transfer material in the supply section to the second image bearing means, and the toner image carried on the first image bearing means is transferred to the second image bearing means.
A value of a transfer current or a transfer voltage of the first transfer means for transferring the image to the image carrying means; and a second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material. At least two of the transfer current or the transfer voltage value of the transfer material separating unit that separates the transfer material from the transfer unit at the separation unit of the transfer material from the second image bearing unit. An image forming apparatus, wherein a set value is changed in conjunction with each other. 25. The method according to claim 25, wherein when the absolute value of the transfer current or the transfer voltage of the first transfer unit is increased, the absolute value of the transfer current or the transfer voltage of the second transfer unit is also increased. Item 25. The image forming apparatus according to Item 24. 26. The method according to claim 24, wherein when the absolute value of the transfer current or the transfer voltage of the second transfer means is increased, the value of the static elimination current or the static elimination voltage of the transfer material separating means is also increased. An image forming apparatus according to claim 1. 27. The method according to claim 27, wherein when the absolute value of the charging current or the charging voltage of the transfer material charging unit is increased, the absolute value of the transfer current or the transfer voltage of the second transfer unit is also increased. 25. The image forming apparatus according to 24. 28. The method according to claim 24, wherein when the absolute value of the charging current or the charging voltage of the transfer material charging unit is increased, the value of the static elimination current or the static elimination voltage of the transfer material separating unit is also increased. The image forming apparatus as described in the above. 29. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred, and the transferred toner image is A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. A fixing unit for fixing the toner image transferred to the transfer material, wherein a voltage is applied to the transfer material to detect a value of an energizing current at that time, or a current is applied to the transfer material, A transfer material resistance / capacity detecting means for detecting the resistance, capacity or resistance and capacity of the transfer material by detecting the value of the applied voltage of the transfer material; Accordingly, a value of a charging current or a charging voltage of a transfer material charging unit for charging the transfer material in a supply unit of the transfer material to the second image holding unit, Transfer the toner image to the transfer material A value of a transfer current or a transfer voltage of the first transfer means for transferring to a surface; a transfer current of the second transfer means for transferring a toner image carried by the second image carrying means to a back surface of the transfer material. Alternatively, the value of the transfer voltage or the value of the charge elimination current or the charge elimination voltage of the transfer material separating unit that separates the transfer material in the separation unit of the transfer material from the second image bearing unit is changed. An image forming apparatus comprising: 30. The transfer material charging means as the transfer material resistance / capacity detection means.
10. The image forming apparatus according to 9. 31. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred, and the transferred toner image is copied. A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. A fixing unit for fixing the toner image transferred to the transfer material, wherein a voltage is applied to the transfer material to detect a value of an energizing current at that time, or a current is applied to the transfer material, Transfer material resistance / capacity detecting means for detecting the resistance of the transfer material, the capacitance or the resistance and the capacitance together by detecting the value of the applied voltage of A transfer material width detecting means for detecting the transfer material, and detecting the transfer material according to the detection result by the transfer material resistance / capacitance detecting means and the detection result by the transfer material width detecting means; Transfer in the supply section of The value of the charging current or the charging voltage of the transfer material charging means for performing the charging of the transfer material, or the transfer current or the transfer of the first transfer means for transferring the toner image carried by the first image carrying means onto the surface of the transfer material. A voltage value; a transfer current or a transfer voltage value of the second transfer means for transferring the toner image carried on the second image carrying means to the back surface of the transfer material; and the second image of the transfer material. An image forming apparatus, wherein a value of a static elimination current or a static elimination voltage of a transfer material separating unit that separates the transfer material in a separation unit from a supporting unit is changed. 32. The transfer material charging means as the transfer material resistance / capacity detection means.
2. The image forming apparatus according to 1. 33. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred, and the transferred toner image is copied. A second image carrying means carried on the surface again, and a toner image carried on the first image carrying means,
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. A fixing unit for fixing a toner image transferred to a material, wherein a voltage is applied to the second image bearing unit to detect a value of an energizing current at that time, or the second image bearing unit By passing a current through and detecting the value of the applied voltage at that time,
A resistance / capacitance detection means for detecting the resistance and capacitance of the second image bearing means or a combination of the resistance and the capacitance is provided. The detection result by the resistance / capacity detection means for the second image bearing means is provided. The toner image carried on the first image carrying means is transferred to the second
A value of a transfer current or a transfer voltage of the first transfer means for transferring the image to the image carrying means; and a first transfer means for transferring the toner image carried by the first image carrying means to the surface of the transfer material. The value of the transfer current or the transfer voltage of the transfer material, the value of the transfer current or the transfer voltage of the second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material, An image forming apparatus, wherein a value of a static elimination current or a static elimination voltage of a transfer material separating unit that separates the transfer material in a separation unit from the second image bearing unit is changed. 34. A transfer material charging means for charging the transfer material in a supply section of the transfer material to the second image bearing means as the second image holding means resistance / capacity detecting means. The image forming apparatus according to claim 33, wherein: 35. The first transfer means includes a roller member which is in contact with the second image bearing means and is capable of applying a voltage. The first transfer means serves as a resistance / capacity detecting means for the second image bearing means. 34. The image forming apparatus according to claim 33, wherein means is used. 36. A second image bearing means cleaning means for abutting on said second image bearing means to clean toner on said second image bearing means, capable of applying a voltage, wherein said second image bearing means is capable of applying a voltage. The image forming apparatus according to claim 33, wherein the second image carrier cleaning unit is used as the resistance / capacity detection unit.