JPH06348152A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] The recording material 14 is fed to the transfer portion N between the image carrier 1 and the transfer means 12 in contact with the image carrier 1 so as to be formed and carried on the image carrier 1. In the image forming apparatus of the type that transfers a transferred image onto a recording material, the recording material 1 fed
Even if 4 is thick and strong, the image should be transferred without omission in the transfer. [Structure] In order to receive a recording material 14 fed from a paper feeding portion side and guide it to a transfer portion, tip portions 16a and 17a are provided in a predetermined manner with the surface of the image carrier 1 in the vicinity of the recording material inlet side of the transfer portion N. Recording material guide member 1 disposed facing each other with a gap between them
6. The recording material guide member is provided with 6 and 17, and a part or all of the recording material guide member is movable.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a transfer type electrophotographic apparatus.
The present invention relates to an image forming apparatus such as an electrostatic recording device.

More specifically, the recording material is fed to the transfer portion (contact nip portion between the image carrier and the transfer means) between the image carrier and the transfer means in contact with the image carrier so that the recording material is transferred onto the image carrier. The present invention relates to an image forming apparatus of a type in which a transferable image (toner image) formed and carried is transferred onto a recording material.

[0003]

2. Description of the Related Art Conventionally, in a transfer type image forming apparatus,
Toner as a transferable image corresponding to desired image information, which is formed and carried on an image carrier such as a photoconductor, a dielectric or a magnetic body by an appropriate image forming process such as electrophotography, electrostatic recording, magnetic recording, etc. As a transfer means for transferring an image onto a recording material (transfer material, printing paper, printing paper, etc.), a non-contact transfer device using a corona charger has been widely used.

This is because a corona charger is disposed on the image carrier so as to be opposed to each other in a non-contact manner, a recording material is fed between the image carrier and the corona charger, and the back surface of the recording material is fed. Further, a corona discharge charge having a predetermined polarity for transfer is applied by a corona charger to electrically attract and transfer the formed and carried toner image on the image carrier to the surface of the recording material.

However, this transfer means has to apply a considerably high voltage to the corona charger in order to generate corona discharge, which requires a high voltage power source, and ozone is generated due to the corona discharge. Have problems such as.

For this reason, in recent years, an image forming apparatus has been developed which uses a contact charging type transfer means which only needs to apply a relatively low voltage.

In this system, a charging member such as a conductive roller or a conductive brush is provided in contact with an image carrier as a transfer member, and a recording material is fed to a transfer portion which is a contact nip portion between the two, and the recording material is recorded. By applying a bias voltage to the transfer member, which is in contact with the back surface of the material, to a predetermined polarity for transfer (contact charging), the formed toner image on the image carrier is transferred onto the surface of the recording material. It is the one that is electrically attracted and transferred.

In such a contact charging type transfer means, the voltage applied to the transfer member may be a relatively low voltage and the current may be relatively small, so that the power source can be made compact and lightweight.
It has the advantages of cost reduction and low ozone generation.

[0009]

However, like the image forming apparatus using the above-mentioned contact charging type transfer means,
In the case of a contact transfer type image forming apparatus in which a transfer member is brought into contact with the image carrier, and the recording material is fed to the transfer portion which is the contact nip portion to transfer the toner image on the image carrier side to the recording material side. However, a so-called “transfer dropout” phenomenon in which the central portion of a character or an image is not transferred easily occurs.

This void in transfer mainly occurs when transferring to a recording material having a large thickness and a strong strain.

This is because at the transfer portion, the developer (toner) is sandwiched between the recording material and the image bearing member and pressed against the transfer member and the recording material, so that the developers cohere with each other due to physical force. It seems that the reason is.

This void in transfer can be reduced by lowering the pressure applied to the transfer member, but in the case of using a recording material having a strong stiffness, the recording material promotes agglomeration of the developer, resulting in the void in transfer. .

When the recording material is soft, the pressure applied to the image carrier is low, so that voids in transfer do not occur.

Therefore, the present invention is directed to an image forming apparatus of this type so that even if the recording material to be fed has a large thickness and a strong strain, the image can be transferred without omission of transfer. And

[0015]

The present invention is an image forming apparatus having the following configuration.

(1) A recording material is fed to a transfer portion between an image carrier and a transfer means in contact therewith, and a transferable image formed and carried on the image carrier is transferred onto the recording material. In an image forming apparatus of the transfer type, in order to receive the recording material fed from the paper feeding section side and guide it to the transfer section, the front end portion of the transfer section is fixed to the surface of the image carrier near the recording material inlet side. A recording material guide member arranged facing each other with a gap of
An image forming apparatus, wherein a part or all of the recording material guide member is movable. (2) A method of feeding a recording material to a transfer portion between an image carrier and a transfer unit in contact therewith, and transferring a transferable image formed and carried on the image carrier onto the recording material. In this image forming apparatus, in order to receive the recording material fed from the paper feeding section side and guide it to the transfer section, the front end portion of the transfer section near the recording material inlet side is provided with a predetermined gap from the surface of the image carrier. The recording material guide member is provided so as to be opposed to the recording material, and the recording material has a relatively small thickness depending on the thickness of the recording material. An image forming apparatus comprising means for moving a recording guide member so as to enter the upstream side of the contact nip portion.

(3) The variable range of the entry position of the recording material to the contact nip between the image carrier and the transfer means is from the position of the nip to a position upstream of the drum and where the transfer electric field does not substantially reach. The image forming apparatus according to (1) or (2), characterized in that

(4) The transfer means is a contact charging type transfer means for contacting with the back surface of the recording material to be fed so as to impart an electric charge for transfer, (1) or (2) The image forming apparatus described.

(5) The image according to (1) or (2), wherein the transferable image on the image carrier is a developed visible image of the electrostatic latent image formed on the image carrier. Forming equipment.

(6) A recording material thickness detecting means fed to the transfer portion is provided, and the movable recording material guide member is operated according to the detected thickness information of the recording material. The image forming apparatus as described in (1) or (2) above.

(7) A manual feed tray is provided, and the movable recording material guide member is operated in conjunction with the movement operation of the movable paper feed guide of the manual feed tray (1) or The image forming apparatus according to (2).

[0022]

When a recording material having a large thickness is fed, part or all of the recording material guiding member is moved or displaced in a direction in which the pressing force of the recording material on the image carrier is suppressed. This prevents the occurrence of voids in the transfer due to the aggregation of the developer.

[0023]

【Example】

<Embodiment 1> (FIGS. 1 and 2) (1) Example of image forming apparatus FIG. 1 is a schematic view of an image forming apparatus of an embodiment. The image forming apparatus of this example is a transfer type laser printer or copying machine using an electrophotographic process.

Reference numeral 1 denotes a drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member, which is adhered to a conductive base layer 1b made of aluminum, iron or the like and an outer peripheral surface thereof. For example, a photoconductive layer 1a made of an organic photoconductor is used as a basic constituent layer, and is rotationally driven at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow around a spindle 1d. The conductive base layer 1b is grounded.

The photosensitive drum 1 is uniformly charged with a predetermined polarity and potential by the primary charging device 2 in the course of its rotation.

The primary charging device 2 of this example is a contact charging roller, and is a conductive roller 2c such as a metal roller which is a core metal, a conductive layer 2b formed on the outer peripheral surface thereof, and a resistance layer formed on the outer peripheral surface thereof. 2a ₁ and 2a ₂ , both end portions of the conductor roller 2c are rotatably supported by bearing members (not shown) and arranged in parallel with the photosensitive drum 1, and a spring (not shown) or the like is pressed. The photosensitive drum 1 is pressed against the photosensitive drum 1 with a predetermined pressing force by means, and is driven to rotate as the photosensitive drum 1 rotates.

Then, the electric contactor 3a is attached to the conductor roller 2c.
By applying a predetermined bias voltage (DC voltage or oscillating voltage) from the power source 3 via the, the peripheral surface of the rotary photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a contact charging method.

Then, the charged surface is subjected to image exposure processing of the target image information by the image exposure means 10 such as a laser scanner and slit exposure means, and an electrostatic latent image of the target image information is formed on the surface of the photosensitive drum 1. It is formed.

The electrostatic latent image is developed by a developer (toner) carried in a thin layer on the developing sleeve 11a of the developing device 11 to form a visible image (toner image).

At the transfer portion N, which is the contact nip portion between the photosensitive drum 1 and the transfer member 12 brought into contact with the toner image, the toner image is fed to the transfer portion N from the paper feeding portion side at a predetermined timing. The recording material 14 thus transferred is sequentially transferred.

The transfer member 12 of this example is a contact charging transfer roller, and is a conductor roller 12a such as a metal roller serving as a core metal.
And a cylindrical conductive layer 12b formed on the outer peripheral surface thereof, and both ends of the conductive roller 12a are rotatably supported by bearing members (not shown) so as to be arranged in parallel with the photosensitive drum 1. , Is pressed against the photosensitive drum 1 by a pressing means such as a spring (not shown), and is rotated by the rotation of the photosensitive drum 1. A contact nip portion between the photosensitive drum 1 and the transfer roller 12 is a transfer portion N.

The recording material 14 is fed to the transfer portion N and is nipped and conveyed. When the leading end of the recording material 14 enters the transfer portion N, a predetermined transfer bias voltage is applied from the power source 4 to the conductor roller 12a, and the back surface of the recording material in contact with the transfer roller 12 has a polarity opposite to that of the toner. The toner image on the photosensitive drum 1 is transferred to the recording material surface by being charged by the contact charging method.

The recording material 14 which has received the transfer of the toner image through the transfer portion N is separated from the surface of the photosensitive drum 1 and sent to an image fixing means (not shown) so that the transferred toner image is transferred onto the recording material 14. It is fixed as a permanently fixed image on the sheet, and is ejected outside the machine as a print or copy.

On the other hand, the surface of the photosensitive drum after passing through the transfer portion is cleaned by removing residual developer and other adhering substances by a cleaner 13, and further, a static eliminator (static erasing lamp).
It is neutralized by 15 and initialized, and is repeatedly used for image formation.

Gears and the like may be attached to the contact charging type charging roller 2 and the transfer roller 12, respectively, and they may be forcibly driven by a driving means such as a motor. Further, the member is not limited to the roller type, but may be a member having another form such as a brush type or a blade type.

A recording material 14 is introduced into the apparatus one by one from a paper feeding portion such as a paper feeding cassette or a manual feeding tray (not shown), and the paper feeding roller 20 → conveying rollers 21a and 21b → upper and lower recording material guides. The sheet is fed to the transfer portion N via a path between the members 16 and 17 (hereinafter, referred to as transfer upper and lower guides).

The transfer upper and lower guides 16 and 17 are arranged at a higher position than the transfer portion N, with their front ends facing the surface of the photosensitive drum 1 with a predetermined gap in the vicinity of the recording material inlet side of the transfer portion N. The recording material 14 fed through the upper and lower guides 16 and 17 hits the tip of the recording material 14 at the photosensitive drum surface position on the upstream side of the transfer portion N in the rotational direction of the photosensitive drum. Rotating photoconductor drum 1
Is contacted with the surface of the photoconductor drum to enter the transfer portion N, and the transfer portion N is nipped and conveyed to receive the transfer of the toner image.

By thus advancing the recording material 14 into the transfer portion N, the recording material 14 is transferred to the transfer portion N where the leading end of the recording material 14 is a contact nip portion between the photosensitive drum 1 and the transfer roller 12.
The toner is prevented from being scattered to the non-image portion due to the electric field in the gap between the photoconductor drum 1 and the recording material 14, which is observed when the toner is directly fed to the sheet and is fed.

(2) Upper and lower transfer guides 16 and 17 In this embodiment, the upper transfer guide 16 of the upper and lower transfer guides 16 and 17 is fixed (fixed), but the lower transfer guide 17 is used.
Is driven by a driving means 22 such as a motor, and is shown in FIG.
As shown in FIG. 2B, the first switching position, in which the front end portion 17a substantially coincides with the front end portion 16a of the fixed upper transfer guide 16 as shown in FIG. The front end portion 17 a of the transfer upper guide 16 is
It is a movable guide that is slidable in the front-rear direction substantially parallel to the upper transfer guide 16 at a second switching position that is retracted from the photosensitive drum 1 by a predetermined distance from a.

Reference numerals 18a and 18b denote electrode roller pairs as recording material thickness detecting portions (paper thickness detecting means) arranged in a recording material passage (sheet path) between the paper feed roller 20 and the conveying rollers 21a and 21b. When the fed recording material 14 passes between the pair of rollers 18a and 18b, the electrostatic capacity or resistance value of the recording material 14 is measured, and this is used as information of the thickness of the recording material by the control unit. 19 is transmitted.

The control section 19 controls the driving means 22 in accordance with the thickness information so that the movable lower transfer guide 17 is moved to the above first position.
The switch position is moved to the second switch position or the second switch position.

If the fed recording material 14 has a small thickness of a predetermined thickness or less, the paper thickness detecting means 18a, 18b
2 is detected, the lower transfer guide 17 is shown in FIG.
The recording material 14 is held at the first switching position, and the recording material 14 contacts the contact nip portion (transfer portion) N between the photosensitive drum 1 and the transfer roller 2.
The toner is prevented from being scattered to the non-image portion by the electric field in the gap between the photoconductor 1 and the recording material 14, and the recording material 14 is fed to the transfer portion N. When the recording material 14 is a soft material having a predetermined thickness or less, since the pressure applied to the photosensitive drum 1 is low as described above, voids in transfer do not substantially occur.

On the other hand, when it is detected that the fed recording material 14 is thicker than the predetermined thickness (strong), the lower transfer guide 17 is moved to the second position shown in FIG. 2, the distance between the lower transfer guide 17 and the photosensitive drum 1 is increased, and the amount of deflection against the strength of the recording material 14 is small. This is smaller than in the case of feeding, and the pressing force of the recording material 14 on the photosensitive drum 1 due to the flexural reaction force is suppressed.

That is, since the pressure applied to the photosensitive drum 1 by the strain of the recording material having a large thickness is suppressed, it is possible to prevent the occurrence of voids in the transfer due to the aggregation of the developer (toner).

<Second Embodiment> (FIG. 3) The basic structure is the same as that of the first embodiment.

In this embodiment, the lower transfer guide 17 is set to be substantially parallel to the fixed upper transfer guide 16 as shown by the chain double-dashed line about the hinge shaft 17b on the rear end side. This is a movable guide that is rotatable and movable between a rotation position and a second switching rotation position in which the tip side is lowered and rotated diagonally downward to the left as shown by the solid line.

If the fed recording material 14 has a small thickness of a predetermined thickness or less, the paper thickness detecting means 18a, 18b
When detected by, the transfer lower guide 17 is switched and held at the first switching rotational position shown by the chain double-dashed line.

When it is detected that the fed recording material 14 is thicker than a predetermined thickness, the recording material 14 is switched and held in the second diagonally downward downward switching rotary position shown by the solid line, and the embodiment is carried out. As in the case of No. 1, the pressure applied to the photosensitive drum 1 due to the strain of the recording material having a large thickness is suppressed, so that it is possible to prevent the occurrence of voids in the transfer due to the aggregation of the developer.

<Third Embodiment> (FIGS. 4 and 5) The basic structure is the same as that of the first embodiment.

In this embodiment, the transfer upper / lower guide 16
Although all 17 are fixed guides, the transfer lower guide 17 has a width d smaller than that of the transfer upper guide 16, and the front end portion 17a of the guide 17 is fixed to the transfer upper guide 16.
It is arranged so as to be retracted from the photoconductor drum 1 by a predetermined distance with respect to the front end portion 16a.

A shutter plate 23 for covering the lower transfer guide 17 is provided. The shutter plate 23 has its width D substantially matched with the upper transfer guide 16, and its tip portion 23a is substantially matched with the leading end portion 16a of the upper transfer guide 16, and is divided into two parts, left and right, as shown in FIG. As shown in (a), there is a first switching state in which the lower transfer guide 17 is covered and closed, and in a second switching position where the lower transfer guide 17 is exposed by exposing the lower transfer guide 17 as shown in (b). It is opened and closed.

If the fed recording material 14 has a small thickness of a predetermined thickness or less, the paper thickness detecting means 18a, 18b
5A, the shutter plate 23 is switched and held in the first switching state in which the transfer lower guide 17 is covered and closed as shown in FIG. 5A, and the recording material 14 has a large width D. The shutter plate 23 passes over the shutter plate 23 as a transfer lower guide.

When the fed recording material 14 is detected to be thicker than a predetermined thickness, the shutter plate 23 is pulled leftward and rightward as shown in FIG. The lower guide 17 is held in the exposed second switching state, and the recording material 14 passes over the transfer lower guide 17 having a narrow width d, so that the recording material having a large thickness is recorded as in the first embodiment. Since the pressure applied to the photoconductor drum 1 by the straining of the material is suppressed, it is possible to prevent the occurrence of voids in the transfer due to the aggregation of the developer.

<Embodiment 4> (FIG. 6) In this embodiment, in Embodiment 3, an elastic thin plate 24 is provided along the length at the tip portion 17a of the lower transfer guide 17.

When the fed recording material 14 is thicker than a predetermined thickness and has a strong strain, when the recording material 14 passes through the lower transfer guide 17, the elastic thin plate 24 at the front end scrapes the recording material 14. Pushed down by.

As a result, similarly to the case of the first embodiment, the pressure applied to the photosensitive drum 1 by the strain of the recording material having a large thickness is suppressed, so that it is possible to prevent the occurrence of the void in the transfer due to the aggregation of the developer. Become.

In general, the recording material 14 having a large thickness and a strong strain is mainly supplied from the manual feed tray 25 to the apparatus.

Therefore, in this embodiment, the left and right shutter plates 2 are
The shutter plate 2 is moved to the left and right by interlocking with the left and right movable paper feed guides (side guides) 25a, 25a of the manual feed tray 25 in conjunction with the paper width adjusting movement operation.
3.23 is opened by the width of the recording material that is manually fed.

This structure prevents the elastic thin film 24 from becoming settled when a large amount of recording material supplied from the paper feeding cassette side passes through the lower transfer guide 17.

The above structure does not require the paper thickness detecting means 18a and 18b as in the case of the above-mentioned first to third embodiments, and the structure is simple.

<Fifth Embodiment> (FIG. 7) The basic structure is the same as that of the first embodiment.

In the present embodiment, the transfer upper and lower guides 16
The first switching position in which the end portions 16a and 17a are close to the photoconductor drum 1 in a predetermined manner as shown by the two-dot chain line in FIG. 7 and the photoconductor drum 1 as shown by the solid line
Is a movable guide that is slidable in the front-rear direction to a second switching position that is retracted by a predetermined distance.

If the fed recording material 14 has a small thickness of a predetermined thickness or less, the paper thickness detecting means 18a, 18b
When detected by, the transfer upper and lower guides 16 and 17 are switched and held at the first switching position indicated by the chain double-dashed line.

When it is detected that the fed recording material 14 is thicker than a predetermined thickness, the transfer vertical guides 16 and 17 are switched and held at the second switching position shown by the solid line. Thus, as in the first embodiment, the distance between the lower transfer guide 17 and the photosensitive drum 1 becomes long, the pressing force to the photosensitive drum 1 due to the strain of the recording material 14 having a large thickness is suppressed, and the developer agglomerates. It is possible to prevent the occurrence of voids in the transfer.

<Sixth Embodiment> (FIG. 8) The basic structure is the same as that of the first embodiment.

In this embodiment, the transfer up / down guide 16
17 is integrated into a hinge shaft 16b on the rear end side of the guide.
17b as a center, and a first rotation angle position of a substantially horizontal rotation angle posture as shown by a chain double-dashed line in FIG. 8 and a rotation angle posture in which the tip end side is slanted downward leftward as shown by a solid line. The second guide is a movable guide that can be rotated to the second rotation angle position.

If the fed recording material 14 has a small thickness of a predetermined thickness or less, the paper thickness detecting means 18a, 18b
When detected by, the transfer upper and lower guides 16 and 17 are switched and held at the first rotation angle position indicated by the chain double-dashed line.

When the fed recording material 14 is detected to be thicker than a predetermined thickness, the transfer upper and lower guides 16 and 17 are switched and held at the second rotation angle position shown by the solid line. As in the first embodiment, the pressure applied to the photosensitive drum 1 due to the strain of the recording material 14 having a large thickness is suppressed, and the occurrence of voids in the transfer due to the aggregation of the developer can be prevented.

[0069]

As described above, according to the present invention, the transfer member is brought into contact with the image bearing member, and the recording material is fed to the contact nip portion (transfer portion) of both members, and the recording material is fed from the image bearing member side. Regarding an image forming apparatus of the type that transfers an image to the recording material side, even if the recording material to be fed has a large thickness and is strong, it is possible to perform image transfer without omission in the transfer. The purpose of the period is often achieved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an example of an image forming apparatus.

2A and 2B are views showing a state in which a movable lower transfer guide is switched and held at a first and a second switching position, respectively.

FIG. 3 is a main part diagram of an apparatus according to a second embodiment.

FIG. 4 is a main part diagram of an apparatus according to a third embodiment.

5A is a plan view when a cover shutter plate for a transfer lower guide is closed, and FIG. 5B is a plan view when the cover shutter plate is open.

FIG. 6 is a plan view of the main part of the device according to the fourth embodiment.

FIG. 7 is a main part diagram of an apparatus according to a fifth embodiment.

FIG. 8 is a main part diagram of an apparatus according to a sixth embodiment.

[Explanation of symbols]

 1 image carrier (electrophotographic photosensitive drum) 2 primary charging device (contact charging roller) 3.4 bias applying power supply 10 image exposure means 11 developing device 12 transfer member (contact charging transfer roller) 13 cleaner 14 recording material 15 removal Electric appliances 16/17 Recording material guide member (transfer vertical guide) 18a / 18b Recording material thickness detecting means 19 Control section 20 Paper feeding roller 21a / 21b Conveying roller 22 Driving means 23 Shutter plate 24 Elastic thin plate 25 Manual feed tray 25a / 25b Paper feed guide (side guide)

Claims (7)

[Claims] 1. A recording material is fed to a transfer portion between an image carrier and a transfer means in contact with the image carrier to transfer a transferable image formed and carried on the image carrier onto the recording material. In this type of image forming apparatus, in order to receive the recording material fed from the paper feeding section side and guide it to the transfer section, the front end portion of the transfer section near the recording material inlet side and the surface of the image carrier are set to a predetermined position. An image forming apparatus, comprising: a recording material guide member disposed so as to face each other with a gap, and a part or all of the recording material guide member is movable. 2. A recording material is fed to a transfer portion between an image carrier and a transfer means in contact with the image carrier to transfer a transferable image formed and carried on the image carrier onto the recording material. In this type of image forming apparatus, in order to receive the recording material fed from the paper feeding section side and guide it to the transfer section, the front end portion of the transfer section near the recording material inlet side and the surface of the image carrier are set to a predetermined position. The recording material guide member is provided so as to face each other with a gap, and for a recording material having a relatively small thickness depending on the thickness of the recording material, the recording material is an image carrier and a transfer unit. An image forming apparatus, comprising means for moving a recording guide member so as to enter the upstream side of a contact nip portion with the recording guide member. 3. The variable range of the entry position of the recording material to the contact nip portion between the image carrier and the transfer means is from the position of the nip portion to the upstream side of the drum and a position where the transfer electric field does not substantially reach. The image forming apparatus according to claim 1, wherein the image forming apparatus is an area. 4. The transfer device according to claim 1 or 2, wherein the transfer device is a contact charging type transfer device which comes into contact with the back surface of the recording material to be fed and applies a transfer charge. Image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the transferable image on the image carrier is a developed visible image of an electrostatic latent image formed on the image carrier. 6. A recording medium thickness detecting means for feeding a recording medium fed to a transfer portion is provided, and a movable recording medium guiding member is operated according to the detected thickness information of the recording medium. The image forming apparatus according to claim 1 or 2, which is characterized in that. 7. A manual feed tray is provided, and a movable recording material guide member is operated in association with a moving operation of a movable paper feed guide of the manual feed tray. 2. The image forming apparatus according to item 2.