JPH0619332A - Image forming device - Google Patents

Abstract

PURPOSE:To realize an image forming device in which a soft, low-pressure uniformly-contacting conductive member is used for stably obtaining a high- quality image. CONSTITUTION:The electric field forming means of a transfer means which transfers a toner image on a photosensitive drum 3 (image carrier) onto a transfer material with electric field is constituted of a conductive nonwoven fabric 21 which comes in contact with the back surface of the transfer material at least at the time of transfer. Since the conductive nonwoven fabric 21 keeps a soft, low-pressure and tight contact state with a transfer material/transfer drum 9, the high-quality image without the striped unevenness of the gradation of the image, the omission of discharge pattern, the striped unevenness of color, and color slurring is stably obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an image forming apparatus, and more particularly to a toner image on an image carrier formed by an electrophotographic system or an electrostatic recording system, which is carried on a transfer carrier member. The present invention relates to an image forming apparatus that obtains an image by applying a transfer electric field to the transferred transfer material and transferring the transfer material. As such an image forming apparatus, there are an electrophotographic copying apparatus, a printer, and various other recording devices.

[0002]

2. Description of the Related Art Conventionally, for example, various image forming apparatuses have been proposed, and FIG. 19 shows a typical multicolor electrophotographic copying apparatus equipped with a developing apparatus called a so-called rotary developing apparatus.

The multicolor electrophotographic copying machine shown in FIG. 19 has a photosensitive drum 3 which is an image carrier rotatably driven in the direction of the arrow shown in the figure, and an image forming means is arranged around the photosensitive drum 3. ing. The image forming means may be any means, but in this embodiment, the photosensitive drum 3 is irradiated with a primary charger 4 for uniformly charging the photosensitive drum 3 and a color-separated optical image or an optical image corresponding thereto. An exposure unit 8 having an electrostatic latent image formed thereon, such as a laser beam exposure device, and a rotary developing apparatus 1 having the electrostatic latent image on the photosensitive drum 3 as a visible image.
Etc.

The rotary developing device 1 includes four developing devices 4 for separately storing four color developers of yellow color developer, magenta color developer, cyan color developer and black color developer.
Y, 4M, 4C, 4BK and these four developing devices 4Y, 4
It is composed of a substantially cylindrical housing that holds M, 4C and 4BK and that is rotatably supported. Then, this rotary developing device 1 is provided with a desired developing device (4
(Y, 4M, 4C, 4BK) is conveyed to a position opposed to the outer peripheral surface of the photosensitive drum 3, and the electrostatic latent image on the photosensitive drum 3 is developed to enable full-color development for four colors. .

On the other hand, the visible toner image on the photosensitive drum 3 is transferred onto the transfer material P carried by the transfer device 9.
Is transcribed to. In this embodiment, the transfer device 9 is composed of a transfer drum that is rotatably supported, and the transfer drum 9 includes cylinders 9a and 9b arranged at both ends and both cylinders, as shown in FIG. The cylinder 9a, 9b has a connecting portion 9c for connecting the transfer material carrying member 93. As the transfer material carrying member 93, a film-shaped dielectric sheet such as polyethylene terephthalate or polyvinylidene fluoride resin film is usually used. A transfer material gripper 7 that holds the transfer material P fed from the paper feeding device is provided in the connecting portion 9c.

Inside the transfer drum 9 and outside, a transfer discharger 10, an inner charge-eliminating discharger 13 and outer charge-eliminating dischargers 11 and 14 which constitute charge-eliminating means are respectively arranged.

The process of forming a full-color image by the multicolor electrophotographic copying apparatus having the above-described structure will be briefly described below.

When the photosensitive drum 3 is uniformly charged by the primary charger 4 and the optical image E corresponding to the image information is irradiated onto the photosensitive drum 3 by the exposing means 8, the photosensitive drum 3 is electrostatically charged. A latent image is formed. The electrostatic latent image is formed on the rotary developing device 1
In, the toner is visualized as a toner image by the toner having a resin-based material and having an average particle diameter of 8 to 10 μm.

On the other hand, the transfer material P is sent to the transfer drum 9 through the paper feed guide 18 in synchronization with the image by the registration roller 6, and the tip of the transfer material P is gripped by the gripper 7 or the like.
The transfer drum 9 is conveyed in the direction of the arrow in the figure.

Next, the dielectric sheet 9 which is the transfer material carrying member of the transfer drum 9 in the area in contact with the photosensitive drum 3.
The toner image on the photosensitive drum 3 is transferred onto the transfer material P by being subjected to corona discharge having a polarity opposite to that of the toner by the transfer discharger 10 from the back surface of 3.

The transfer material P is separated from the transfer drum 9 by the action of the separating claw 15 while receiving the charge removal by the charge removing dischargers 11, 13, 14 after undergoing the required number of transfer steps.
The toner is conveyed to the fixing device 17 by the conveying belt 16, the toner image is fixed by the fixing device 17 by heat, and then the toner image is discharged to the outside of the apparatus.

On the other hand, the photosensitive drum 3 is subjected to the image forming process again after the residual toner on the surface is cleaned by the cleaning device 12.

The surface of the dielectric sheet 93 of the transfer drum 9 is also cleaned by the action of the cleaning device 5 such as a fur brush and the like, and is then subjected to the image forming process again.

[0014]

However, in the above-mentioned conventional example, since the discharger is used to perform the transfer,
It had the following drawbacks.

That is, it is usually necessary to apply a high voltage of 6 to 8 KV to the wire of the discharger, and only a part of the corona current flows toward the photosensitive drum, and the other part is to the shield of the discharger which is grounded. Therefore, a current larger than the transfer corona current that actually contributes to the transfer is required. Therefore, a power source having a large voltage and current capacity is required, and a high withstand voltage is required from the viewpoint of insulating the wiring, which leads to an increase in size of the device and an increase in cost.

Further, since the discharger is used, corona discharge is generated and ozone is generated, and the generated ozone adversely affects the photosensitive drum and the human body.

The applicant of the present invention has proposed a solution to the above problems in Japanese Patent Application Nos. 2-29896 and 2-29898. In these proposals, the problem is solved by using a conductive metal sheet or a conductive roller provided at the tip of an elastic synthetic resin sheet as a contact conductive member instead of a corona charger as a transfer electric field forming means, Since the contact injection current contributes to the transfer material adsorption current and the toner transfer current efficiently, unlike the corona charger, ozone-less high-potential, low-current high-efficiency transfer is realized.

However, since the contact conductive member used in the above proposal is a linear line contact member having a sheet shape, a blade shape, or a roller shape, the contact state with the transfer dielectric sheet or the transfer material is macro. However, when viewed in the longitudinal direction of the photosensitive drum, it is quite microscopically locally non-uniform.

Therefore, when the voltage applied to the contact conductive member is low, the transfer injection current is insufficient at a place where the contact state is weak and a difference in transfer efficiency occurs, so that the transfer material is transferred to the transfer material. Streaky light and dark stripes having different toner concentrations occur in parallel with the traveling direction.

On the contrary, when the applied voltage is high, the contact state is weak and a gap discharge is generated where there is a microscopic gap between the transfer dielectric sheet and the contact conductive member. Similarly, there are problems such as dark and light uneven streaks and discharge pattern missing, which causes a problem that the appropriate application condition is narrow.

Further, even under the proper application conditions, the difference in the contact conditions results in a difference in transfer efficiency, which is at an allowable level such that slight unevenness in density occurs in monocolor, but multicolor toners are transferred onto the transfer material. When used in a multi-color image forming apparatus that multiple-transfers images, there arises a problem that the slight unevenness in light and shade is remarkably embodied as uneven streaks.

When the contact pressure between the transfer dielectric sheet or the transfer material and the contact conductive member is increased for the purpose of eliminating the difference in the contact conditions, the contact conductive member has a shorter useful life and must be replaced frequently. It becomes necessary to raise the cost. In particular, in the case of a multicolor image forming apparatus, the durability life of the dielectric sheet is shortened, which further increases the cost.

If the contact pressure is high, the dynamic frictional force with the transfer dielectric sheet increases, and the load on the transfer dielectric sheet increases, so that the transfer dielectric sheet is displaced or distorted.
Since the transferred transfer material is displaced or distorted, it is not a problem in mono color, but when used in a multi-color image forming apparatus that multi-transfers multi-color toner images onto the transfer material, the image color There arises a problem that misalignment, color unevenness and the like occur.

The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of stably obtaining a high quality image.

[0025]

In order to achieve the above object, a first invention is an image carrier on which a developed image is formed, and a transfer means for transferring the developed image on the image carrier onto a transfer material by an electric field. In the image forming apparatus having the above-mentioned, the electric field forming means for generating the electric field has at least a conductive member which is in direct or indirect contact with the back surface of the transfer material at the time of transfer, and the conductive member is composed of fine fibers. It is characterized in that it is made of a conductive non-woven fabric which is formed by bonding the above to each other to form a web.

According to a second aspect of the invention, an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and the transfer material carrier, and a conveying means for conveying the transfer material to the image carrier. In the image forming apparatus having the above, a transfer material charging unit for charging the transfer material before the transfer material contacts the transfer material carrier is provided.

A third aspect of the present invention is an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and the transfer material carrier, and a carrying means for carrying the transfer material to the image carrier. In an image forming apparatus having a transfer material, a charging means for charging the transfer material before the transfer material contacts the transfer material carrier, a charge amount control means for controlling the charge amount of the transfer material charging means, and a charge amount of the transfer material. And a control means for controlling the charge amount control means according to the measurement result of the transfer material charge amount measuring means.

In a fourth aspect of the invention, an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and the transfer material carrier, and a conveying means for conveying the transfer material to the image carrier. In the image forming apparatus including the transfer material, a transfer material charging unit that charges the transfer material before the transfer material comes into contact with the transfer material carrier is provided, and the charge amount at the leading end portion and / or the trailing end portion of the transfer material is set to other areas. It is characterized by being different from the charge amount.

According to a fifth aspect of the invention, an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and the transfer material carrier, and a conveying means for conveying the transfer material to the image carrier. And a transfer material charging unit that charges the transfer material before the transfer material comes into contact with the transfer material carrier.
A control means for controlling the transfer material charging means according to the characteristics of the transfer material is provided.

According to a sixth aspect of the invention, an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and the transfer material carrier, and a transport means for transporting the transfer material to the image carrier. And a transfer material charging unit that charges the transfer material before the transfer material comes into contact with the transfer material carrier.
It is characterized in that an environment measuring means for measuring an environment in the vicinity of the transfer material and a control means for controlling the transfer material charging means according to a measurement result by the environment measuring means are provided.

[0031]

According to the first aspect of the invention, it is possible to uniformly maintain a soft, low pressure and close contact state between the conductive member made of a conductive non-woven fabric and the back surface of the transfer material / transfer material carrier.
It is possible to stably obtain a high-quality image free from image shading unevenness, discharge pattern missing, tint unevenness, color shift, and the like.

According to the second to sixth aspects of the invention, since it is not necessary to provide an independent suction assisting means on the transfer material carrier, a stable and sufficiently strong electrostatic attraction force of the transfer material can be obtained with a simple structure. Sufficiently good transferability can be secured and a high quality image can be stably obtained.

[0033]

【Example】

[First Invention] An embodiment of the first invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a block diagram of a transfer portion of an image forming apparatus according to the present invention.

The present invention can be implemented in a multicolor electrophotographic copying machine having the rotary developing apparatus 1 described above with reference to FIG. Therefore, the image forming apparatus according to the present exemplary embodiment is similar to that illustrated in FIG.
The multicolor electrophotographic copying machine shown in FIG. 9 is embodied in a multicolor electrophotographic copying machine in which only the transfer electric field forming means is modified.
Further, the image forming apparatus according to the present embodiment is provided with the transfer drum 9 shown in FIG. 1, and its configuration and action are as described above. Therefore, the description of the overall structure and operation of the multicolor electrophotographic copying apparatus and the transfer drum 9 will be omitted except for the electric field forming means.

In FIG. 1, the inside of the dielectric sheet 93 of the photosensitive drum 3 which is an image carrier and the dielectric sheet 93 of the transfer drum 9 which is a transfer material carrying member is in contact with a conductive material which is an electric field generating means. The non-woven fabric 21 is in contact. A bias power source 30 that gives a transfer electric field is connected to the conductive nonwoven fabric 21.

In this embodiment, as the conductive nonwoven fabric 21, a bundle of acrylic ultrafine fibers (diameter of about 5 μm) is processed and a cloth-shaped nonwoven fabric is dyed with carbon to be conductive (volume resistivity 10 ⁴ Ω.multidot. cm) was used. In addition, non-woven fabric made of resin, such as nylon, polyester, rayon, etc., that has been subjected to metal plating, or a mixture of resin and conductive fine powder such as carbon or metal powder, or a composite that has been processed into a non-woven fabric. Further, it is possible to use a non-woven fabric obtained by processing an ultrafine carbon fiber or the like, which is obtained by carbonizing a resin fiber or the like to give conductivity.

As the material of the conductive non-woven fabric 21, a material having a volume resistivity of 10 ¹⁰ Ω · cm or less can be used, and a material having a volume resistivity of 10 ⁸ Ω · cm or less is preferable.

As for the arrangement of the conductive non-woven fabric 21, the conductive non-woven fabric 21 is a dielectric sheet 9 which is a transfer material carrier.
3 extends from the introduction side to the downstream side in the moving direction, and further, a position at which the transfer material held on the dielectric sheet 93 has finished contacting the photosensitive drum 3, or a position at which contact is started, or as close as possible. The position corresponding to the position
At this position, the surface of the conductive nonwoven fabric 21 is covered with the dielectric sheet 93.
Are pressed and brought into contact with each other.

Since the conductive fine fibers are very densely and softly present on the surface of the conductive non-woven fabric 21, the dielectric sheet 93 and the conductive non-woven fabric 21 are in contact with each other. Unlike the conventional direct contact using an elastic sheet-shaped, blade-shaped, or roller-shaped contact conductive member, a uniform and soft contact state can be achieved without increasing the contact pressure.

Further, in this embodiment, the conductive non-woven fabric 21 is adhesively fixed on the support member 22 made of mylar, as shown in FIG. With this configuration, when the conductive nonwoven fabric 21 is worn and deteriorated, it is possible to easily replace only the conductive nonwoven fabric 21, so that the replacement cost can be reduced.

According to this embodiment, a two-component developer of magenta, cyan, yellow and black (volume average particle size 8 μm)
Was used to transfer a four-color image.

The transfer current and voltage of the four-color image formed by the above developer are shown in the table below.

[0044]

[Table 1] (All images were transferred with a toner amount of 8.0 mg / cm ^2. ) The images obtained in this way are free from dark and light streaks, discharge pattern missing, tint streaks, and color shifts, and have high transfer efficiency. there were.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, a conductive non-woven fabric roller 23 is used instead of the fixed conductive non-woven fabric 21 in the first embodiment.
Are using.

As the conductive non-woven fabric roller 23, a metal round bar having a diameter of 8 mm and the conductive non-woven fabric used in the first embodiment wound and adhered (volume resistivity 10).
¹⁰ Ω · cm) was used. The conductive non-woven fabric roller 23
A volume resistivity of 10 ¹⁰ Ω · cm or less can be used, and preferably 10 ⁸ Ω · cm or less.

The conductive non-woven fabric roller 23 is arranged as follows.
It is desirable that the transfer material held on the dielectric sheet 93 comes into contact with the photosensitive drum 3 and a position at which the transfer material starts to come into contact, or a position as close as possible, and the conductive non-woven fabric roller 23 having elasticity is the dielectric sheet. It is configured to press 93 against. The conductive non-woven fabric roller 23 may be driven at the same speed as the moving dielectric sheet 93, or may be rotationally driven with a peripheral speed difference.

Also in this embodiment, by using the conductive non-woven fabric roller 23 as the transfer electric field forming means, the same effect as that of the first embodiment can be obtained, and the same experiment is carried out. As a result, good images were obtained under each environment without image distortion such as image unevenness, uneven streaks, discharge pattern missing, tint streaks, unevenness, color misregistration, scattering, and missing transfer at the leading edge of the image. Further, it was possible to improve friction durability as compared with the first embodiment.

<Third Embodiment> FIG. 3 shows a third embodiment.

In this embodiment, a winding mechanism 25 for the electrically conductive non-woven fabric is provided, and every time the regular number of sheets is acquired (for example, 10).
It is possible to use a good portion of the non-woven fabric by winding a fixed amount (for example, 3 mm) per 100 sheets, and to prevent transfer defects due to abrasion deterioration of the conductive non-woven fabric and transfer defects due to dust contamination. .

<Fourth Embodiment> This embodiment is an example in which the present invention is applied to a normal monochrome copying machine when the transfer electric field means is brought into direct contact with the transfer material. At this time,
As shown in FIG. 4, for example, a conductive non-woven fabric roller 23 'similar to that of the second embodiment is used, and this can also be used as a transfer material conveying means. [Second Invention] An embodiment of the second invention will be described below with reference to the accompanying drawings.

<First Embodiment> Image carrier 3 and transfer drum 9
Transfer material P passes between the transfer sheets 93 of
FIG.
Shown in.

The feature of the present invention is that the paper guide 35,
This is because a transfer material transfer means for charging the transfer material P is provided in the conveyance path such as the registration rollers 36.

FIG. 5 shows, as an example of a transfer material charging means for charging the transfer material P, a corona discharger 33 to which a high voltage is applied by a high voltage power supply 31 and a ground which opposes the corona discharger 33 via the transfer material P. The charging means constituted by the counter electrode 34 is shown.

The timing of corona discharge is a predetermined time after the transfer material P is started to be fed by the registration roller 36, immediately before the front end of the transfer material P rushes into the corona discharger 33, and the rear end of the transfer material P is corona discharger 33. Until just after taking off.

The corona discharge current is the strength of the electric field from the surface of the transfer sheet 93 toward the surface of the photosensitive drum 3 during transfer attraction.
The surface potential of the transfer sheet 93 is + although it depends on the orientation.
When the surface potential of the photosensitive drum 3 is 5 KV and the surface potential of the photosensitive drum 3 is −700 V, an electric field is formed from the transfer sheet 93 toward the photosensitive drum 3, so that the transfer material P is electrostatically attracted to the transfer sheet 93. Approximately −200 μA from the corona discharger to increase the force (depending on the shape of the discharger, −8 kv
The surface of the transfer material P is negatively charged by applying a constant current corona current of about (1).

By the above action, the transfer sheet 9 of the transfer material P
It was possible to increase the adsorption force to 3.

The transfer material charging means for charging the transfer material P is not limited to this embodiment. Alternatively, a conductive brush may be brought into contact and a negative voltage may be applied from a power source to be negatively charged. Also, contact the conductive roller,
A negative voltage may be applied from a power source so as to be negatively charged.

In the present embodiment, the case where the electric field at the transfer attracting portion is directed from the transfer sheet 93 to the photosensitive drum 3 is shown.
Although the transfer material P is negatively charged in the transport path, in the case of an apparatus in which the electric field is directed from the photosensitive drum 3 to the transfer sheet 93, the transfer material P is positively charged in the transport path.

It is desirable that the time from when the transfer material P passes through the charging means to reach the transfer attracting portion is set as short as possible in order to reduce the decay of the charges.

Further, there is an action (for example, a grounded conductive member is brought into contact) of decaying the charge of the transfer material P in the path after the transfer material P has passed through the charging means and before reaching the transfer attracting portion. Not desirable.

<Second Embodiment> The present invention is also effective when a contact type charger 10 'such as a conductive brush or a conductive fur brush shown in FIG. 6 is used as an adsorption and transfer discharger.

In particular, in this case, as compared with the corona discharger 10 shown in FIG.
That is, since the sway of the electric field forming region can be suppressed to be small, the sway of the time from the transfer material charging unit to the transfer attracting portion can be suppressed to be small, and the amount of the increase in the electrostatic attraction force can be suppressed to be small. There is an advantage.

<Third Embodiment> In the first embodiment, the timing at which the transfer material charging means is operated is set from immediately before the leading edge of the transfer material P enters the charging means to when the trailing edge of the transfer material P is charged by the charging means. Although the process is performed immediately after the removal, the present invention is not limited to this.

The transfer material charging means may be always operated, and in this case, there is an advantage that the ON / OFF control system can be omitted. [Third Invention] An embodiment of the third invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 7 shows a cross section of the timing at which the transfer material P passes between the photosensitive drum 3 and the transfer sheet 93 and is attracted to the transfer sheet 93.

The feature of the present invention is that the paper guide 35,
The charging means for the transfer material P is provided in the conveying path constituted by the registration rollers 36 and the like, and the transfer material charging means is a surface electrometer 26 which is an example of the transfer material charge amount measuring means.
The charge amount is controlled according to the measurement result of

FIG. 7 shows, as an example of means for charging the transfer material P, a corona discharger 33 to which a high voltage is applied by a high-voltage power supply 31 and a grounded counter-measure against the corona charger 33 via the transfer material P. The charging means constituted by the electrodes 34 is shown.

The timing of corona discharge is a predetermined time after the transfer material P is started to be fed by the registration roller 36, immediately before the front end of the transfer material P rushes into the corona discharger 33, and the rear end of the transfer material P is corona discharger 33. Until just after taking off.

Below, the surface potential of the transfer sheet 93 is +5 KV and the surface potential of the photosensitive drum 3 is −700 V during transfer and adsorption.
Is shown. In this case, it is desirable that the surface potential of the transfer material P before entering the transfer attracting portion is controlled to be about -500V. Control target potential is -500 ± 50
An example of V is shown below.

In actual control, for example, the transfer material P is idly fed to control the charge amount. First, when the transfer material P is conveyed, for example, a constant current corona discharge of −200 μA is performed to measure the surface potential. If the potential is lower than the target potential, the current is increased, and if the potential is higher than the target potential, the current is decreased. This operation is repeated until the target potential range is reached. Although it is desirable that the above control be completed while one transfer material P is being conveyed, if this is not possible, the next transfer material P is conveyed and control is continued.

The timing for performing the above control is as follows.
If the amount of charged charge fluctuates even with a constant corona discharge current,
If the decay of the charge within a certain period of time until it reaches the transfer attracting part is fluctuating, or if there is a possibility, that is, if the moisture absorption amount of the transfer material is fluctuating, the resistance, or the capacity is fluctuating. , When the transfer material P has changed. Incidentally, in order to output a timing signal for performing control, a type detecting means of the transfer material P and / or a moisture absorption amount measuring means of the transfer material and / or an environment detecting means are provided, and a control ON signal is output when there is a change of a predetermined value or more. Is output.

Alternatively, the control is performed every time before the fixing unit warms up when the power is turned on. The initial corona constant current of −200 μA is not limited to this. If the device is provided with a means for storing the corona current value that has reached the target range last time, the number of repetitions can be reduced by setting the stored corona current value as the initial value.

The means for charging the transfer material P is not limited to this embodiment. For example, a conductive brush may be contacted and a negative voltage may be applied from a power source to be negatively charged. Alternatively, a conductive roller may be contacted and a negative voltage may be applied from a power source to be negatively charged.

Further, in the present embodiment, the case where the electric field at the transfer attracting portion is transferred from the transfer sheet 93 to the photosensitive drum 3 and the transfer material P is negatively charged in the conveying path has been described.
In the case of an apparatus in which the electric field is directed from the photosensitive drum 3 to the transfer sheet 93, the transfer material P may be positively charged in the transport path.

The time from when the transfer material P passes through the charging means to when it reaches the transfer attracting portion is preferably set as short as possible in order to reduce the decay of charges. In addition, there is no action (for example, contacting a grounded conductive member) of decaying charges in the path from when the transfer material P passes through the charging means to when it reaches the transfer attracting portion. desirable.

In this embodiment, the surface potential meter 26 for measuring the surface potential of the transfer material P is used as the charge amount measuring means of the transfer material P.
However, the present invention is not limited to this. A contact electrode such as a conductive brush may be provided on the transfer material P, and an ammeter may be arranged between the electrode and the ground to measure the induced current with the ammeter.

By the way, the control means of the charging means is, for example, means for performing D / A exchange of the output of the measuring means and controlling the high voltage output current value by illuminating the table in the microcomputer.

Further, in the present embodiment, the measuring means is arranged immediately before the transfer attracting portion, but the installation position is not limited to this. An electrometer may be arranged and controlled so as to measure the surface potential of the transfer material immediately after adsorption. In this case,
Since the transfer material is carried on the transfer material carrying member, there is an advantage that the distance between the electrometer and the transfer material does not fluctuate, and the surface potential measurement accuracy, that is, the control accuracy increases.

<Second Embodiment> In the case where a contact type charger 10 'such as a conductive brush or a conductive fur brush shown in FIG. 8 is used instead of the suction and transfer discharge device 10 shown in FIG. The present invention is effective.

In particular, in the above case, as compared with the corona discharger 10 shown in FIG. 7, the fluctuation of the charging area due to the spread of the air discharge,
That is, since the sway of the electric field forming region can be suppressed to be small, the sway of the time from the transfer material charging unit to the transfer attracting portion can be suppressed to be small, and the amount of the increase in the electrostatic attraction force can be suppressed to be small. You get the advantage that you can.

<Third Embodiment> In the first embodiment, the timing at which the transfer material charging means is operated is from immediately before the front end of the transfer material enters the charging means to immediately after the rear end of the transfer material degreases the charging means. However, the present invention is not limited to this, and the copying material charging means may be constantly operated, and in this case, there is an advantage that the ON / OFF control system can be omitted. [Fourth Invention] An embodiment of the fourth invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIGS. 9 to 11 are cross-sectional views of the timing at which the transfer material P passes between the photosensitive drum 3 and the transfer sheet 93 and the transfer material P is attracted to the transfer sheet 9. .

The feature of the present invention is that the paper guide 35,
The transfer material charging means is provided in the conveying path constituted by the registration rollers 36 and the like, and the charge amount of the leading end portion and / or the trailing end portion of the transfer material P is made to be different from other areas.

9 to 11, as an example of means for charging the transfer material P, a corona discharger 33 to which a high voltage is applied by a high voltage power source 31 is opposed to the corona discharger 33 with the transfer material P sandwiched therebetween. The means for charging by the grounded counter electrode 34 is shown.

The corona discharge current is the strength of the electric field from the surface of the transfer sheet 93 toward the surface of the photosensitive drum 3 during transfer attraction.
The surface potential of the transfer sheet 93 is +5 KV and the surface potential of the photosensitive drum 3 is −70 when the transfer attracts, though it depends on the direction.
When charged to 0V, the transfer sheet 93
Since an electric field is formed from the transfer material P toward the photosensitive drum 3, the front end portion of the transfer material P (area 1 of FIG. 12 showing the transfer material P) is
In order to increase the force of electrostatic attraction to the transfer sheet 93, a constant current corona current of about −200 μA (depending on the shape of the discharge device, about −8 KV) is applied to the surface of the transfer material P from the corona discharger 33. Charge negatively.

The timing immediately after the front end of the transfer material P has passed the transfer attracting portion is shown at 9. Here, since the transfer material P is made to follow the cylindrical transfer drum 9, the transfer material P is f _A force acting from the transfer drum 9 indicated by 2a works. On the other hand, since the electrostatic attraction force f ₂ b stronger than f ₂ a is obtained by the above operation, the tip of the transfer material P does not float.

FIG. 10 shows the timing when the central portion (area 2 in FIG. 12) of the transfer material P has passed the transfer attracting portion. Since the force f ₂ b due to the stiffness of the transfer material P becomes small,
The required electrostatic attraction force may be small. In this embodiment, the transfer material charging means is turned off to obtain the electrostatic attraction force f ₁ b.

FIG. 11 shows the timing at which the rear end of the transfer material P passes through the transfer attracting portion. Here, the force f ₂ c due to the stiffness becomes large as in the case of the front end, so that the transfer material is charged. The means is turned on to prevent the transfer material P from floating from the transfer drum 9 by the strong electrostatic attraction force f ₁ c.

Areas 1 and 3 of the transfer material P are areas 10 mm from the front and rear ends, respectively. Charged OF in area 2
By setting to F, it was possible to save unnecessary power consumption.

The means for charging the transfer material P is not limited to this embodiment. For example, a conductive brush may be contacted and a negative voltage may be applied from a power source to be negatively charged. Alternatively, a conductive roller may be contacted and a negative voltage may be applied from a power source to be negatively charged.

In this embodiment, the case where the electric field at the transfer attracting portion is transferred from the transfer sheet to the photosensitive drum 3 and the transfer material P is negatively charged in the conveying path has been described, but the electric field is transferred from the photosensitive drum 3. In the case of a device that faces the sheet, the transfer material P may be positively charged in the transport path.

Furthermore, it is desirable that the time from when the transfer material P passes through the charging means to when it reaches the transfer attracting portion is set as short as possible in order to reduce the decay of charges. In addition, it is desirable that there is no action (for example, contacting a grounded conductive member) in the path from the transfer material P passing through the charging means to the transfer attracting portion.

<Second Embodiment> A contact type charger 10 'such as a conductive brush or a conductive fur brush shown in FIG. 13 is used in place of the attraction and transfer discharger 10 shown in FIGS. In this case, the present invention is effective.

In particular, in the above-mentioned case, as compared with the corona discharger 10 shown in FIGS. 9 to 11, the fluctuation of the charging area due to the spread of the aerial discharge, that is, the fluctuation of the electric field forming area can be suppressed to be small. There is an advantage that the fluctuation of the time from the material charging means to the transfer attracting portion can be suppressed to be small, and the fluctuation due to the increase of the electrostatic attracting force can be suppressed to be small.

<Third Embodiment> In the first embodiment, both the front end and the rear end of the transfer material P are -200 μm in the area of 10 mm.
Although the example of A constant-current charging is shown, the present invention is not limited to this.

If the transfer material P has a low elasticity, the area may be reduced or the charging current may be reduced. Further, in the case of a transfer material of a type in which charges are easily swept to the rear end portion (transfer material having low surface resistance), the charge amount at the rear end portion is weakened or the charging means is turned off.

As described above, in order to change the charging area according to the transfer material P, the transfer material type detecting means 27 and the charging means controlling means 28 as shown in FIGS. 9 to 11 are provided.

<Fourth Embodiment> The present invention can also be applied to the charging of the transfer material P in which areas 1 and 3 shown in FIG. 12 are non-image areas. In this case, it is possible to eliminate the concern that the transfer image may be disturbed by the charging of the transfer material P. [Fifth Invention] An embodiment of the fifth invention will be described below with reference to the accompanying drawings.

<First Embodiment> The transfer material 9 passes between the photosensitive drum 3 and the transfer sheet 93, and the transfer material P becomes the transfer sheet 9.
FIG. 14 shows a cross-sectional view of the timing of adsorption to No. 3.

The feature of the present invention is that the paper guide 35,
The transfer material charging means is provided in the conveyance path constituted by the registration rollers 36 and the like, and the charging means controls the charge amount according to the judgment result by the transfer material characteristic judging means 29.

FIG. 14 shows, as an example of means for charging the transfer material P, a corona discharger 33 to which a high voltage is applied by a high-voltage power supply 31 and a grounded counter-measure against the corona discharger 33 via the transfer material P. A charging means composed of electrodes 34 is shown.

The corona discharge timing is a predetermined time after the transfer material P is started to be fed by the registration roller 36, and immediately before the leading end of the transfer material P enters the corona discharger 33.
This is until immediately after the trailing edge of the transfer material P is removed from the corona discharger 33.

The corona discharge current varies depending on the strength and direction of the electric field from the surface of the transfer sheet 93 toward the surface of the photosensitive drum 3 during transfer attraction, but the surface potential of the transfer sheet 93 is +5.
When the surface potential of the photosensitive drum 3 is KV and is charged to −700 V, an electric field is formed from the transfer sheet 93 toward the photosensitive drum 3, so that the transfer material P is electrostatically adsorbed to the transfer sheet 93. In order to increase the force, when the transfer material P is determined to be 80 g / m ² by the transfer material characteristic determination means 29, the corona discharger 33 outputs −200 μm.
The surface of the transfer material P is negatively charged by passing a constant current corona current of about A (about -8 kv depending on the shape of the discharge device).

As a result, the attraction force of the transfer material P to the transfer sheet 93 can be increased by the above action. The means for charging the transfer material P is not limited to this embodiment. For example, a conductive brush may be contacted and a negative voltage may be applied from a power source to be negatively charged.
Alternatively, a conductive roller may be contacted and a negative voltage may be applied from a power source to be negatively charged.

Further, in this embodiment, the case where the electric field at the transfer attracting portion is directed from the transfer sheet 93 to the photosensitive drum 3 and the transfer material P is negatively charged in the conveying path has been described.
In the case of an apparatus in which the electric field is directed from the photosensitive drum 3 to the transfer sheet 93, the transfer material P may be positively charged in the transport path.

The time from when the transfer material P passes through the charging means to when it reaches the transfer attracting portion is preferably set as short as possible in order to reduce the decay of charges. Further, there is no action (for example, contacting a grounded conductive member) of decaying the charge of the transfer material P on the path from the transfer material P passing through the charging means to the transfer attracting portion. Not desirable.

When the transfer material characteristic determining means 29 determines that the transfer material P is a transparency sheet (hereinafter abbreviated as trapene), the corona discharger 33 supplies a constant corona current of −400 μA. Is flowed to negatively charge the surface of the transfer material P, and when it is determined that the paper is 105 g / m ² , the corona discharger 33 outputs −300.
A constant current of μA is passed to negatively charge the surface of the transfer material P.

LED as an example of transfer material type determination means
By providing a paper trapen judgment means for judging by the reflected light detection output in which the photodiode is set, the above-mentioned judgment of the paper and the trapene can be performed.
Further, the registration roller 36 is provided with a registration roller separation distance (a minute interval between the upper and lower registration rollers 36) measuring means.
The density of the transfer material P can be determined by measuring the thickness of the transfer material P when the transfer material P rushes into the registration roller 36.

The transfer material type determining means is not limited to the above. Further, a user or a service person may be provided with a means for inputting the transfer material characteristic, and the output of the corona charger 33 may be controlled according to the input result. Alternatively, the output control of the corona charger 33 according to the size of the transfer material by the output from the transfer material size detection means (the smaller the transfer material is, the stronger the transfer material is, the more the corona current flows). You may do it.

Further, the transfer material P is temporarily stopped by the registration roller 36 to form a loop, and the pressure measuring means is brought into contact with the transfer material P at the loop portion, and the stiffness of the transfer material P is judged from the pressure measurement result. Corona charger 33 according to the judgment result
May be controlled. In this case, if the transfer material P has a strong elasticity, a higher output is supplied.

Further, the transfer material characteristic determining means compares the weight of the transfer material, which has been input to the apparatus in advance, with the weight of the transfer material at the time of drying, and the water absorption amount of the transfer material is calculated based on the comparison. The resistance decrease (that is, the degree of decay) may be estimated and the output of the corona charger 33 may be controlled accordingly (transfer material resistance value measurement (estimation) control).

In the case of 80 g / m ² paper in this embodiment, −
Although corona discharge was performed at a constant current of 200 μA, the current value is not limited to this. The optimum current value varies depending on the device configuration, process speed, and the like. The set value is determined by an experiment for each transfer material depending on the device.

<Embodiment 2> Even when a contact type charger 10 'such as a conductive brush or a conductive fur brush shown in FIG. 15 is used in place of the suction and transfer discharger 10 shown in FIG. The invention is effective.

In particular, in this case, the deflection of the charging area due to the spread of the air discharge, that is, the deflection of the electric field forming area can be suppressed to a small level as compared with the corona discharger 10 shown in FIG. This has the advantage that the fluctuation of the time to reach the adsorption unit can be suppressed to a small level, and the increase in the electrostatic adsorption force can be suppressed to a small level.

<Third Embodiment> In the first embodiment, the timing at which the transfer material charging means is operated is from immediately before the front end of the transfer material P enters the charging means and the rear end of the transfer material P is at the charging means. Although the process is performed immediately after the removal, the present invention is not limited to this.

The transfer material charging means may be operated at all times, and in this case, there is an advantage of omitting the ON / OFF control system. [Sixth Invention] An embodiment of the sixth invention will be described below with reference to the accompanying drawings.

<First Embodiment> The transfer material 9 passes between the photosensitive drum 3 and the transfer sheet 93, and the transfer material P is transferred.
FIG. 16 shows a cross section of the timing of adsorption to No. 3.

A feature of the present invention is to have a means for charging the transfer material P whose charge amount is controlled according to the measurement result by the transfer material near environment measuring means 30.

FIG. 16 shows, as an example of means for charging the transfer material P, a corona discharger 33 to which a high voltage is applied by a high voltage power supply 31 and a ground which opposes the corona discharger 33 via the transfer material P. A charging means composed of a counter electrode 34 and a counter electrode 34 is shown.

The timing of corona discharge is a predetermined time after the transfer material P is started to be fed by the registration roller 36, immediately before the front end of the transfer material P rushes into the corona discharger 33, and the rear end of the transfer material P is corona discharger. It is until immediately after 33 is taken out.

The corona discharge current varies depending on the strength and direction of the electric field from the surface of the transfer sheet 93 to the surface of the photosensitive drum 3 during transfer attraction, and the measurement result by the transfer material vicinity environment measuring means 30, but the surface potential of the transfer sheet 93 is +5 KV. When the surface potential of the photosensitive drum 3 is charged to −700 V, an electric field is formed from the transfer sheet 93 toward the photosensitive drum 3, so that the transfer material P is electrostatically attracted to the transfer sheet 93. Temperature of 23 ℃, humidity of 60% to increase
If the environment is determined to be, the corona discharger 23
-200 μA (depending on the shape of the discharger, but -8k
The surface of the transfer material P is negatively charged by applying a constant corona current of about V). Under this environment, the current of the adsorption transfer discharger 10 is +200 μA.

Thus, by the above-mentioned action, the attraction of the transfer material P to the transfer sheet 93 can be increased.

The means for charging the transfer material P is not limited to the above. For example, a conductive brush may be contacted and a negative voltage may be applied from a power source to be negatively charged. Alternatively, a conductive roller may be contacted and a negative voltage may be applied from a power source to be negatively charged.

In the above embodiment, the electric field at the transfer attracting portion is directed from the transfer sheet 93 to the photosensitive drum 3 and the transfer material P is negatively charged in the conveying path. In the case of an apparatus in which the transfer sheet 93 goes from the transfer sheet 93 to the transfer sheet 93, the transfer material P may be positively charged in the transport path.

By the way, it is desirable that the time from when the transfer material P passes through the charging means to when it reaches the transfer attracting portion is set as short as possible in order to reduce the decay of charges. Further, there is no action (for example, contacting a grounded conductive member) of decaying the charge of the transfer material P on the path from the transfer material P passing through the charging means to the transfer attracting portion. Not desirable.

Further, the environment measuring means 30 is operated at 23.degree.
When the humidity is higher than 0%, for example, 23 ° C. and 80%, the applicant can obtain a good transfer property.
As previously filed in 6320, adsorption transfer discharger 1
The zero current is controlled to be low (for example, +50 μA). In this environment, a sufficient electrostatic attraction force cannot be obtained with the above current, so it is necessary to increase the amount of charging the transfer material P by the corona discharger 33.

Further, when the humidity becomes high, the amount of charge decay during the time until the transfer material P reaches the transfer attracting portion from the corona discharger 33 increases, so it is necessary to further increase the amount of charge on the transfer material P. is there.

Further, the amount of moisture absorbed by the transfer material P (that is, the resistance of the transfer material P) is estimated from the detection output of the environment sensor arranged near the cassette, which is the place where the transfer material is left unattended. Estimate the amount of decay and transfer material P
Control the amount of charging. Note that when the humidity is high, the resistance becomes low and the amount of decay of the charge increases, so the amount of charging the transfer material P is increased.

In addition to the above controls, when the environmental sensors arranged near the transfer material leaving place, near the corona discharger 33, and near the adsorption transfer unit detect that the temperature is 23 ° C. and the humidity is 80%, it is Increase the current of the corona discharger 33, -4
A sufficiently strong electrostatic adsorption force could be obtained by applying 00 μA.

FIG. 17 shows an example of the output table of the discharger 10 when the humidity changes at 23 ° C. As shown in the figure, the same output is produced when the absolute water content is the same. To do so.

In the present embodiment, when the environment changes from the temperature of 23 ° C. and the humidity of 60% to the temperature of 23 ° C. and the humidity of 80%, the output of the corona discharger 33, which is the transfer material charger, is changed to −.
Although the value is changed from 200 μA to −400 μA, the values are not limited to these values, and the device configuration,
This optimum value varies depending on the process speed and the like. In practice, the setting value is determined by conducting an experiment for each environment according to the device. In addition, how to control the corona discharger 33 by weighting is determined by an experiment when the detection outputs of the environmental sensors arranged near the transfer material cassette, the corona discharger 33, and the suction transfer unit are different. .

<Second Embodiment> In the case where a contact type charger 10 'such as a conductive brush or a conductive fur brush shown in FIG. 18 is used instead of the suction and transfer discharger 10 shown in FIG. The present invention is effective.

In particular, in this case, the deflection of the charging area due to the spread of the air discharge, that is, the deflection of the electric field forming area can be suppressed to a smaller level than that of the corona discharger 10 shown in FIG. There is an advantage that the fluctuation of the time to reach the adsorption portion can be suppressed to a small value, and the increase of the electrostatic adsorption force can be suppressed to a small value.

<Third Embodiment> In the first embodiment, the timing at which the transfer material charging means is operated is from immediately before the front end of the transfer material P enters the charging means and the rear end of the transfer material P is at the charging means. However, the present invention is not limited to this.

The transfer material charging means may be always operated, and in this case, there is an advantage that the ON / OFF control system can be omitted.

[0138]

As is apparent from the above description, according to the first aspect of the present invention, the conductive member made of the conductive non-woven fabric and the transfer material / the back surface of the transfer material carrying member are in soft, low pressure and in close contact with each other. Therefore, it is possible to stably obtain a high-quality image free from image dark and light unevenness, discharge pattern missing, tint unevenness, color misregistration, and the like.

Further, according to the second to sixth inventions, since it is not necessary to provide an independent suction assisting means on the transfer material carrier, a stable and sufficiently strong electrostatic attraction force of the transfer material can be obtained with a simple structure. Sufficiently good transferability can be secured and a high quality image can be stably obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a transfer unit of an image forming apparatus according to a first embodiment of the first invention.

FIG. 2 is a sectional view showing a configuration of a transfer portion of an image forming apparatus according to a second embodiment of the first invention.

FIG. 3 is a cross-sectional view showing a configuration of a transfer portion of an image forming apparatus according to a third embodiment of the first invention.

FIG. 4 is a sectional view showing a configuration of a transfer portion of an image forming apparatus according to a fourth embodiment of the first invention.

FIG. 5 is a sectional view showing a configuration of a transfer portion of the image forming apparatus according to the first embodiment of the second invention.

FIG. 6 is a sectional view of a transfer portion showing a second embodiment of the second invention.

FIG. 7 is a sectional view showing a configuration of a transfer portion of the image forming apparatus according to the first embodiment of the third invention.

FIG. 8 is a sectional view of a transfer portion showing a second embodiment of the third invention.

FIG. 9 is a cross-sectional view showing a configuration of a transfer portion of the image forming apparatus according to the first embodiment of the fourth invention.

FIG. 10 is a sectional view showing a configuration of a transfer portion of the image forming apparatus according to the first embodiment of the fourth invention.

FIG. 11 is a cross-sectional view showing a configuration of a transfer portion of the image forming apparatus according to the first embodiment of the fourth invention.

FIG. 12 is a diagram showing a region of a transfer material.

FIG. 13 is a sectional view of a transfer portion showing a second embodiment of the fourth invention.

FIG. 14 is a sectional view showing a configuration of a transfer portion of the image forming apparatus according to the first embodiment of the fifth invention.

FIG. 15 is a sectional view of a transfer portion showing a second embodiment of the fifth invention.

FIG. 16 is a sectional view showing a configuration of a transfer portion of the image forming apparatus according to the first embodiment of the sixth invention.

FIG. 17 is a diagram showing an example of a control table (a diagram showing changes in discharger output with respect to changes in humidity).

FIG. 18 is a sectional view of a transfer portion showing a second embodiment of the sixth invention.

FIG. 19 is a sectional view of a multicolor electrophotographic copying machine.

FIG. 20 is a perspective view in which a part of the transfer drum is cut away.

[Explanation of symbols]

 3 Photosensitive Drum (Image Carrier) 9 Transfer Drum (Transfer Material Carrier) 26 Surface Potential Meter (Transfer Material Charge Amount Measuring Means) 27 Transfer Material Type Detecting Means 28 Charging Means Controlling Means 29 Transfer Material Characteristic Determining Means 30 Environment Measuring Means 33 Corona Discharger 34 Counter Electrode 93 Transfer Sheet P Transfer Material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruhiko Moriguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (8)

[Claims] 1. An image forming apparatus having an image carrier on which a developed image is formed and a transfer unit for transferring the developed image on the image carrier onto a transfer material by an electric field, the electric field forming unit generating the electric field. Has a conductive member that comes into direct or indirect contact with the back surface of the transfer material at least at the time of transfer, and the conductive member is composed of a conductive non-woven fabric formed by combining fine fibers to form a web. An image forming apparatus characterized by the above. 2. An image having an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and a transfer material carrier, and a transport means for transporting the transfer material to the image carrier. An image forming apparatus, comprising a transfer material charging unit that charges the transfer material before the transfer material contacts the transfer material carrier. 3. An image having an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and the transfer material carrier, and a transporting means for transporting the transfer material to the image carrier. In the forming apparatus, a charging unit that charges the transfer medium before the transfer medium comes into contact with the transfer medium carrier, a charge amount control unit that controls the charge amount of the transfer medium charging unit, and a charge amount of the transfer medium are measured. An image forming apparatus comprising: a transfer material charge amount measuring means; and a control means for controlling the charge amount control means according to a measurement result of the transfer material charge amount measuring means. 4. An image having an image carrier on which a developed image is formed, an electric field forming unit provided between the image carrier and the transfer material carrier, and a transport unit for transporting the transfer material to the image carrier. In the forming apparatus, a transfer material charging unit that charges the transfer material before the transfer material contacts the transfer material carrier is provided, and the charge amount of the leading end portion and / or the rear end portion of the transfer material is set as the charge amount of other areas. An image forming apparatus characterized by differentiating. 5. The image forming apparatus according to claim 4, wherein a detection unit for detecting the type of the transfer material is provided, and the charged area of the transfer material is changed according to the detection result of the detection unit. 6. An image having an image carrier on which a developed image is formed, an electric field forming unit provided between the image carrier and the transfer material carrier, and a transport unit for transporting the transfer material to the image carrier. The forming apparatus is provided with a transfer material charging unit that charges the transfer material before the transfer material contacts the transfer material carrier, and a control unit that controls the transfer material charging unit according to the characteristics of the transfer material. Image forming apparatus. 7. An image having an image carrier on which a developed image is formed, an electric field forming means provided between the image carrier and a transfer material carrier, and a transporting means for transporting the transfer material to the image carrier. In the forming apparatus, a transfer material charging means for charging the transfer material before the transfer material contacts the transfer material carrier, an environment measuring means for measuring an environment in the vicinity of the transfer material, and a measurement result by the environment measuring means. An image forming apparatus comprising a control means for controlling the transfer material charging means. 8. The environment measuring means is arranged at a place where the transfer material is left and / or near the transfer material charging means and / or the electric field forming means. Image forming apparatus.