JP2000112319A - Process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a fluctuation in the surface direction of a belt-type image carrier at a position where it is opposed to a developing means and to improve the image quality by making the rotational load torque of a roller member on the upstream side larger than that of a roller member on the downstream side. SOLUTION: The rotational load torque of a 1st turning roller 2 functioning as the roller member disposed on the upstream side in the rotating direction of a belt photoreceptor 10 is made larger than that of a 2nd turning roller 3 functioning as the roller member disposed on the downstream side. Namely, resultant force F1 applied by the rotation of the photoreceptor 10 on the roller 2 is made stronger than the resultant force F2 applied by the rotation of the photoreceptor 10 on the roller 3 disposed on the downstream side. Thus, when the photoreceptor 10 is driven in the case of forming an image, the photoreceptor 10 is tensioned and the fluctuation in the surface direction of the photoreceptor 10 at a developing position by a developing device 13 and a scanning position by an exposure optical system 12 is restrained and the high-quality image can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms an image on a belt-shaped image carrier by arranging a charging means, a scanning means and a developing means around a belt-shaped image carrier such as a copying machine, a printer, a facsimile or the like. The present invention relates to an electrophotographic image forming apparatus and a process cartridge that is detachable from the image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a charging means, a scanning means and a developing means are arranged around a photosensitive drum (image carrier) or a belt photosensitive body (belt-shaped image carrier). Then, a toner image is formed on a photoreceptor drum or a belt photoreceptor, transferred to a recording paper (transfer material) and fixed. The belt photoreceptor is designed to be compact because its shape can be freely selected, and the belt photoreceptor is stretched between a plurality of rollers (roller members) for the purpose of ensuring separation of the recording paper after transfer. For example, Japanese Patent Application No. Hei. No. and so on.

[0003]

However, in the process cartridge and the image forming apparatus proposed above, the belt-shaped image carrier is stretched by a plurality of roller members.
Since the belt-like image carrier is configured to be tensioned by the tension roller, it is necessary to increase the load of the tension roller in order to sufficiently and uniformly apply the tension. In such a configuration, if the belt tension is increased, the tension is always applied to the belt-shaped image carrier other than during image formation, so that cracks and bending habits due to stress on the belt-shaped image carrier may occur. Further, there arises a problem that the belt-shaped image carrier is deteriorated and its life is shortened, such as occurrence of permanent elongation of the belt. In addition, since the tension is applied to all the roller members on which the belt-shaped image carrier is stretched, the load on each part is increased, and there is a problem that the torque is increased as a whole system.

Further, in the case of stretching using only a plurality of roller members, the belt-shaped image carrier fluctuates in the surface direction at a position facing the developing means provided to face the belt-shaped image carrier during driving, and image quality is deteriorated. The problem of degradation occurs.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and suppresses variations in the surface direction of the belt-shaped image carrier at the position facing the developing means during driving, thereby enabling high-quality image formation. It is an object of the present invention to provide a process cartridge and an image forming apparatus having a long-life belt-shaped image carrier by preventing the occurrence of deterioration such as bending habit or permanent elongation due to stress on the image.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an endless belt-shaped image carrier that is driven and rotated, a plurality of roller members that stretch the belt-shaped image carrier, and a rotatable support for the roller members. And a developing member disposed outside the belt-shaped image carrier when the device is mounted on the image forming apparatus. The rotational load torque of the roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier is greater than the rotational load torque of the roller member disposed on the downstream side with respect to the position of the developing means opposed to the belt-shaped image carrier. The first aspect of the present invention is achieved by a process cartridge.

Another object of the present invention is to provide an endless belt-shaped image carrier that is driven and rotated, a plurality of roller members that stretch the belt-shaped image carrier, and a bearing member that rotatably supports the roller members. And a developing means disposed outside the belt-shaped image carrier in opposition to the belt-shaped image carrier, wherein the developing means is provided at a position facing the developing means with the belt-shaped image carrier. On the other hand, the image forming apparatus is characterized in that the rotational load torque of the roller member disposed on the upstream side in the rotational direction of the belt-shaped image carrier is larger than the rotational load torque of the roller member disposed on the downstream side. (Second invention).

[0008]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.

The structure of a process cartridge according to the present invention and the image forming process and each mechanism of an embodiment of an image forming apparatus having the process cartridge will be described with reference to FIGS. FIG. 1 is a sectional view of a color image forming apparatus showing an embodiment of an image forming apparatus having a process cartridge according to the present invention, and FIG. 2 is a detachable view of the process cartridge from the image forming apparatus. 3 is a configuration diagram of the process cartridge, and FIG. 4 is a diagram illustrating each configuration for applying tension to a surface of the belt-shaped image carrier facing the developing unit.

According to FIG. 1 or FIG. 2, a belt photoreceptor 10, which is a belt-shaped image carrier, is stretched around a driving roller 1, a first rotating roller 2, and a second rotating roller 3 as roller members. The endless flexible photoreceptor belt is tensioned by the action of the tension roller 4 and locally abuts against backup members 41 and 42 provided on the inner peripheral surface, as shown by arrows in FIG. Rotate clockwise. The belt photoreceptor 10 is provided with a thin metal film such as tin oxide, lead oxide, or indium oxide as a conductive layer on a flexible substrate such as polyester, polyimide, or polyethylene terephthalate, and is coated with various organic photosensitive layers (OPC) on the upper surface thereof. And the conductive layer is grounded. The belt photoconductor 10 used in the present embodiment is 80
OP based on polyethylene terephthalate having a thickness of μm
C is applied, and is molded with high accuracy so as to have a uniform thickness of 100 μm.

The belt photoreceptor 10 is provided with a cleaning device 19 as a belt-shaped image carrier cleaning means described later.
And the waste toner collecting container 190 and the resin casing 140
And is configured as a process cartridge 300.

A scorotron charger 11 as a charging unit, an exposure optical system 12 as a scanning unit, and a developing unit 13 as a developing unit, which will be described below, are respectively yellow (Y), magenta (M), and cyan (C). And black (K)
Are used for the image forming process of each color, and in the present embodiment, the belt photoconductor 1
0, Y, M, C, and K are arranged in this order with respect to the rotation direction of the belt photoconductor 10 indicated by the arrow in FIG.

A scorotron charger 11 as a charging means for each color is opposed to and close to the belt photoreceptor 10 in a direction orthogonal to the moving direction of the belt photoreceptor 10 as an image forming body (perpendicular direction in FIG. 1). A control grid (without a sign) maintained at a predetermined potential with respect to the aforementioned organic photosensitive layer of the belt photoreceptor 10 and a corona discharge electrode (without a sign), for example, a saw-tooth electrode, The charging action (minus charging in the present embodiment) is performed by corona discharge having the same polarity, and the belt photoconductor 10 is charged.
To give a uniform potential. As a corona discharge electrode,
In addition, a wire electrode or a needle electrode can be used.

An exposure optical system 12 serving as a scanning means for each color.
Scans (exposes) a laser beam emitted by a semiconductor laser with a polygon mirror rotated by a drive motor, scans (exposes) scanning light (exposure light) on the belt photoreceptor 10 via an fθ lens, and forms a latent image. Perform formation. This scanning light is performed by subjecting image signals of respective colors read by a separate image reading device to image processing and inputting them to the exposure optical system 12 as electric signals.

The exposure optical system 12 for each color scans the belt photoreceptor 10 between the scorotron charger 11 and the developing unit 13 by scanning the belt photoreceptor 10 with scanning light. It is arranged outside the photoconductor 10 away from the photoconductor 10.

A developing device 13 as a developing means for each color includes
Inside yellow (Y), magenta (M), cyan (C)
Alternatively, a two-component (or one-component) developer of black (K) is accommodated, and the belt surface is arranged on one side of the vertically arranged belt photoconductor 10 at right angles to the moving direction of the belt photoconductor 10. The developer is a cylindrical developer carrier formed of a non-magnetic stainless steel or aluminum material having a thickness of, for example, 0.5 mm to 1 mm and an outer diameter of 15 to 25 mm, respectively. A sleeve 131 is provided.

In the developing area, the developing sleeve 131 is kept out of contact with the belt photoreceptor 10 with a predetermined gap, for example, 100 μm to 1000 μm, by abutting rollers (not shown). And a DC voltage of the same polarity as the toner (in this embodiment, a negative polarity) or a voltage that superimposes the AC voltage AC on the DC voltage is applied to the developing sleeve 131 as a developing bias. As a result, non-contact reversal development is performed on the exposed portion of the belt photoconductor 10. At this time, the precision of the development interval needs to be about 20 μm or less in order to prevent image unevenness.

To the developing unit 13 for each of the colors Y, M, C and K, a developer for replenishing each of the colors Y, M, C and K supplies toner corresponding to Y, M, C and K. It is supplied from the tank 24.

As described above, the developing unit 13 transfers the electrostatic latent image formed on the belt photoreceptor 10 formed by the charging by the scorotron charger 11 and the scanning light by the exposure optical system 12 to the belt photoreceptor in a non-contact state. The reversal development is performed with toner having the same polarity as the charge polarity of No. 10 (in this embodiment, the belt photoconductor is negatively charged, and the toner has negative polarity).

At the start of image recording, the drive motor rotates and the belt photoreceptor 10 rotates clockwise via the drive roller 1, and the Y-scorotron charger 11 charges the belt photoreceptor 10 to the belt photoreceptor 10. The application of the potential is started. After a potential is applied to the belt photoreceptor 10, scanning exposure is started in the Y exposure optical system 12 by an electric signal corresponding to a first color signal, that is, an image signal of yellow (Y), and rotation of the belt (sub-scanning) is performed. ), An electrostatic latent image corresponding to the yellow (Y) image of the developed image is formed on the photosensitive layer on the surface. This latent image is reversely developed in a state where the yellow (Y) developer adhered and conveyed onto the developing sleeve 131 by the Y developing device 13 in a non-contact state, and the belt photoreceptor 1
Yellow (Y) on the belt photoreceptor 10 according to the rotation of 0
Is formed.

Next, the belt photoreceptor 10 places an M scorotron charger 11 on the yellow (Y) toner image.
A potential is applied by the charging action of the M exposure optical system 12
The second color signal, that is, the scanning exposure by the electric signal corresponding to the image data of magenta (M) is performed, and the non-contact reversal development by the M developing unit 13 causes the yellow (Y) toner image to A magenta (M) toner image is formed to overlap.

By the same process, the cyan (C) toner image corresponding to the third color signal is further processed by the C scorotron charger 11, the exposure optical system 12, and the developing device 13, and the K scorotron charger 11 , Exposure optical system 1
A black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed by the second and developing units 13, and a color toner image is formed on the peripheral surface within one rotation of the belt photoconductor 10. You.

The color toner image formed on the peripheral surface of the belt photoreceptor 10 is charged by the scorotron charger 11A so that the potential of the adhered toner is made uniform, and then the charge is removed by the pre-transfer exposure unit 16a.

On the other hand, the recording paper P as the transfer material is sent out from one of the paper feed cassettes 15A and 15B as the transfer material storage means by the corresponding feed rollers 15a and 15b, and is conveyed to the timing roller 15c.

The recording paper P is fed to the transfer area in synchronization with the color toner image carried on the belt photoreceptor 10 by driving the timing roller 15c, and is driven in the transfer area. A transfer roller 16b as a transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied opposite to the lower portion of the driving roller 1 for transfer, and the peripheral surface of the belt photoreceptor 10 Are collectively transferred to the recording paper P.

The recording paper P to which the toner image has been transferred is separated from the peripheral surface of the belt photoreceptor 10 along the curvature of the driving roller 1 and then conveyed to the fixing device 17 where a heater (not shown) is provided. ) And the pressure roller 1
7b, the toner adhered to the recording paper P is fixed by applying heat and pressure to the recording paper P.
18b, and sent by the paper discharge roller 18, and the process cartridge 300 provided on the upper portion.
The recording paper P is discharged to the discharge tray 20 which also serves as an opening / closing lid for taking out the toner with the toner image surface on the recording paper P facing down.

The toner remaining on the peripheral surface of the belt photoreceptor 10 after the transfer is transferred to the surface of the belt photoreceptor 10 by a cleaning blade 19a which is a cleaning member provided in a cleaning device 19 as a belt-shaped image carrier cleaning means. The rubbing is performed, the residual toner is removed and cleaned, and the formation of the toner image of the next original image is continued, or
Alternatively, stop temporarily and wait. The waste toner removed from the belt photoreceptor 10 by the cleaning blade 19a is collected from the cleaning device 19 to a waste toner collection container 190 through, for example, a conveying screw (not shown). When the formation of the toner image of the next original image is subsequently performed, the belt photoreceptor 1
Exposure is performed on the surface of the photosensitive member 0 to remove the previous history.

Further, as shown in FIG.
The process cartridge 300 having an opening 0 opens and closes the above-described paper discharge tray 20 at the upper part of the image forming apparatus 100, and uses the holes 40a and 40b provided in the front side plate 40A and the rear side plate 40B constituting the process cartridge 300 as a handle. It is detachable, and maintenance and replacement of the belt photoreceptor 10, the cleaning device 19, the waste toner collecting container 190, etc., and replacement of the process cartridge 300 are performed. At this time, the developing device 1 for each color described with reference to FIG.
3 is a lever (not shown) associated with the opening of the paper discharge tray 20, for example.
The belt is retracted from the surface of the photoconductor 10 by the operation of the cam or the like. When the sheet discharge tray 20 is closed, an abutment roller (not shown) is brought into contact with the surface of the belt photoreceptor 10 by the operation of the lever, the cam, and the like, and the developing device 13 is positioned.

According to FIG. 3, integrally with the rear side plate 40B,
The support rods 1a, 2a, and 3a as bearing members that support the roller member on the rear side plate 40B.
Are provided to form the resin casing 140. A plurality of sets of backup members 41 and 42, which will be described in detail with reference to FIG. Support shafts 1a, 2a,
The driving roller 1, the first rotating roller 2, and the second rotating roller 3 are fitted into 3a, respectively. Backup member 4
An endless belt photoreceptor 10 is stretched around a driving roller 1, a first rotating roller 2, and a second rotating roller 3 and includes a support 40 on which the first and second members 42 are provided. Belt photoconductor 1 is pressed by tension roller 4
0 is nervous. Thereby, the backup member 41,
The inner peripheral surface of the belt photoreceptor 10 abuts locally on 42. Cleaning device 19 and waste toner collecting container 190
Is attached to the resin casing 140, the support shafts 1a,
The front side plate 40A (not shown in FIG. 4) shown in FIG. 2 is symmetrical to the rear side plate 40B with the support members 40 provided with the backup members 41 and 42 and the backup members 41 and 42 interposed therebetween. The process cartridge 300 is configured by being attached to the resin casing 140.

As shown in FIG. 4, a backup member 41 provided inside the belt photoreceptor 10 faces the developing sleeve 131 of the developing unit 13 for each of the colors Y, M, C, and K and faces the developing means. In the position (development position), the tip radius is 1.5
A semi-cylindrical tip portion 41a of mm is provided, and is provided on the back surface of the belt photoconductor 10 so as to abut in a direction orthogonal to the rotation direction of the belt photoconductor 10. In addition, a rotation of the surface of the belt photoreceptor 10 is provided at a back surface of a scanning unit facing position (scanning position) where exposure scanning is performed on the photosensitive layer of the belt photoreceptor 10 by the Y, M, C, and K exposure optical systems 12. A semi-cylindrical tip portion 42a having a small radius of 1.5 mm and having a tip radius of 1.5 mm is orthogonal to the rotation direction of the belt photoreceptor 10 in order to prevent vibration or fluctuation occurring therein. The belt photoreceptor 10, which is provided so as to abut each other in the direction, and stretched between the first and second rotating rollers 2, 3, has a constant tension applied to the belt by a tension roller 4 on one side. On the other side on which image formation is performed, the backup members 41 and 42 for Y, M, C and K are brought into contact with the back surface of the belt photoreceptor 10 at eight positions, and have a large winding angle. Constant speed Belt-shaped photoreceptor 10 is constant speed in a clockwise direction by a drive roller 1 rotating I.

As described above, the belt photoreceptor 10 is tensioned by the tension roller 4 having a smaller pressing force than the conventional one, but when the belt photoreceptor 10 is stopped, the tension of the belt photoreceptor 10 by the tension roller 4 is made as small as possible. Then, when the belt photoreceptor 10 rotates, the tension between the first rotation roller 2 and the second rotation roller 3 is increased, and the backup members 41 and 42 at the developing position and the scanning position are securely connected. The rotation load torque of the first rotating roller 2 as a roller member disposed on the upstream side in the rotation direction of the belt photoconductor 10 is reduced so as to make contact with the belt photoconductor 10 and suppress fluctuation in the surface direction of the belt photoconductor 10. The belt photosensitive member 1 is set to be larger than the rotational load torque of the second rotating roller 3 as a roller member disposed on the side of the belt photosensitive member 1.
0 at the developing position and the scanning position.
In the plane direction is suppressed. That is, the first rotating roller 2
The resultant force F1 applied by the rotation of the belt photoreceptor 10 at
A fluctuation in the surface direction of the belt photoreceptor 10 at the developing position and the scanning position of the belt photoreceptor 10 when the resultant force is greater than the resultant force F2 applied by the rotation of the belt photoreceptor 10 by the second rotating roller 3 disposed on the downstream side Suppress. Specifically, the following configuration is used.

As a first configuration, a sliding bearing by the support shaft 2a is used as a bearing member of the first rotating roller 2 disposed on the upstream side in the rotation direction of the belt photoreceptor 10, and a bearing member is mounted on the support shaft 3a. The second downstream side of the belt photoreceptor 10 in the rotation direction via a bearing B1 which is a rolling bearing
And the load torque of the bearing member of the first rotating roller 2 due to the sliding bearing is made larger than the load torque of the bearing member of the second rotating roller 3 due to the rolling bearing. The rotation load torque of the rotation roller 2 is set to be larger than the rotation load torque of the second rotation roller 3.

As a second configuration, the contact angle α between the first rotating roller 2 disposed on the upstream side in the rotation direction of the belt photoreceptor 10 and the belt photoreceptor 10 is disposed on the downstream side. 2
The rotation load torque of the first rotation roller 2 is larger than the rotation load torque of the second rotation roller 3 assuming that the rotation angle of the rotation roller 3 with the belt photoreceptor 10 is larger. The contact angle α of the belt photoreceptor 10 with the first rotating roller 2 is 12
It is preferably about 0 to 180 °.

A third configuration is a cleaning member that cleans the belt photoconductor 10 with the belt photoconductor 10 interposed between the first rotating roller 2 disposed on the upstream side in the rotation direction of the belt photoconductor 10. Cleaning blade 19
a, a rotational load is applied only to the first rotating roller 2, and the first rotating roller 2 is disposed upstream of the belt photoreceptor 10 in the rotation direction.
The rotation load torque of the rotation roller 2 is set to be larger than the rotation load torque of the second rotation roller 3 disposed on the downstream side. The contact pressure of the cleaning blade 19a to the belt photoreceptor 10 is preferably about 10 to 20 g / cm in relation to the cleaning property.

As a fourth configuration, a brake member that slides on and contacts the first rotating roller 2 with the first rotating roller 2 disposed on the upstream side in the rotation direction of the belt photosensitive member 10 with the belt photosensitive member 10 interposed therebetween. BK, and the rotational load torque of the first rotating roller 2 disposed on the upstream side in the rotation direction of the belt photoconductor 10 is larger than the rotational load torque of the second rotating roller 3 disposed on the downstream side. I do. The brake member BK may be provided inside the belt photoconductor 10, and the first rotating roller 2 may be slidably contacted directly.

By using one or a combination of the above configurations, the belt photoconductor 10 is tensioned when the belt photoconductor 10 is driven during image formation, and the developing position of the developing unit 13 and the exposure optical system The fluctuation in the surface direction of the belt photoconductor 10 at the scanning position of the system 12 is suppressed, so that high-quality image formation is possible, and the belt photoconductor 10 is tensioned only at the time of driving. Thus, the process cartridge 300 and the image forming apparatus 100 having the long-life belt photoreceptor 10 can be prevented from being caused by deterioration, bending habit or permanent elongation. Further, an increase in the torque of the entire drive system of the belt photoconductor 10 is prevented.

[0037]

According to the first to sixth aspects, the belt-shaped image carrier is tensioned at the time of driving during image formation, and the fluctuation in the surface direction of the belt-shaped image carrier at the position facing the developing means is suppressed. While high quality image formation is possible, the belt-shaped image carrier is tensioned only at the time of driving, so that deterioration due to stress on the belt-shaped image carrier and deterioration such as bending habit or permanent elongation are prevented, A process cartridge having a long-life belt-shaped image carrier is provided. Also,
The torque increase of the whole system is prevented.

According to the seventh to twelfth aspects, the belt-shaped image carrier is tensioned at the time of driving at the time of image formation, and the fluctuation in the surface direction of the belt-shaped image carrier at the position opposed to the developing means is suppressed, and high image quality is achieved. And the belt-shaped image carrier is tensioned only at the time of driving, so that deterioration due to stress on the belt-shaped image carrier, deterioration such as bending habit or permanent elongation is prevented, and long life is achieved. An image forming apparatus having the belt-shaped image carrier is provided. In addition, an increase in torque of the entire system is prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus having a process cartridge according to the present invention.

FIG. 2 is a detachable view of the process cartridge from the image forming apparatus.

FIG. 3 is a configuration diagram of a process cartridge.

FIG. 4 is a diagram showing each configuration for applying tension to a surface of the belt-shaped image carrier facing a developing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive roller 1a, 2a, 3a Support shaft 2 1st rotation roller 3 2nd rotation roller 4 Tension roller 10 Belt photoreceptor 11 Scorotron charger 12 Exposure optical system 13 Developing device 19 Cleaning device 19a Cleaning blade 100 Image Forming device 300 Process cartridge B1 Bearing BK Brake member

Claims (12)

[Claims] An endless belt-shaped image carrier that is driven and rotated; a plurality of roller members that stretch the belt-shaped image carrier; and a bearing member that rotatably supports the roller members. In a process cartridge in which a developing unit is disposed outside the belt-shaped image carrier when facing the belt-shaped image carrier when installed in the image forming apparatus, a developing unit of the developing unit with the belt-shaped image carrier A process cartridge wherein the rotational load torque of a roller member disposed on the upstream side in the rotational direction of the belt-shaped image carrier is larger than the rotational load torque of the roller member disposed on the downstream side with respect to the facing position. . 2. The belt according to claim 1, wherein a load torque of a bearing member of a roller member disposed on an upstream side in a rotation direction of the belt-shaped image carrier is larger than a load torque of a bearing member of a roller member disposed on a downstream side. 2. The process cartridge according to claim 1, wherein the rotational load torque of a roller member disposed on the upstream side in the rotational direction of the image carrier is larger than the rotational load torque of the roller member disposed on the downstream side. 3. The belt-shaped image bearing member, wherein a bearing member of a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier is a sliding bearing, and a bearing member of a roller member disposed on the downstream side is a rolling bearing. The load torque of a bearing member of a roller member disposed on the upstream side in the rotation direction of the carrier is set to be larger than a load torque of a bearing member of a roller member disposed on the downstream side. Process cartridge. 4. The belt-shaped image carrier of a roller member disposed on the downstream side with a contact angle of a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier with the belt-shaped image carrier. The rotation load torque of the roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier is larger than the rotation load torque of the roller member disposed on the downstream side as the contact angle with the roller. The process cartridge according to claim 1, wherein: 5. A cleaning device for cleaning the belt-shaped image carrier with the belt-shaped image carrier interposed between a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier. 2. The process cartridge according to claim 1, wherein the rotational load torque of a roller member disposed on the upstream side in the rotational direction of the image carrier is larger than the rotational load torque of the roller member disposed on the downstream side. 6. A belt member, which is disposed on the upstream side in the rotation direction of the belt-shaped image carrier and which comes into contact with a brake member sandwiching the belt-shaped image carrier or directly in sliding contact with the roller member, 2. The process cartridge according to claim 1, wherein the rotational load torque of a roller member disposed on the upstream side in the rotation direction of the image carrier is larger than the rotational load torque of the roller member disposed on the downstream side. 7. An endless belt-shaped image carrier that is driven and rotated; a plurality of roller members that stretch the belt-shaped image carrier; a bearing member that rotatably supports the roller member; A developing unit disposed outside the belt-shaped image carrier in opposition to the image carrier, wherein the developing unit is arranged so that the developing unit faces the developing unit with the belt-shaped image carrier. An image forming apparatus, wherein the rotational load torque of a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier is larger than the rotational load torque of the roller member disposed on the downstream side. 8. The belt according to claim 1, wherein a load torque of a bearing member of a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier is larger than a load torque of a bearing member of the roller member disposed on the downstream side. 8. The image forming apparatus according to claim 7, wherein the rotational load torque of a roller member disposed on the upstream side in the rotational direction of the image carrier is larger than the rotational load torque of the roller member disposed on the downstream side. . 9. The belt-shaped image bearing member, wherein a bearing member of a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier is a sliding bearing, and a bearing member of a roller member disposed on the downstream side is a rolling bearing. The load torque of a bearing member of a roller member disposed on the upstream side in the rotation direction of the carrier is set to be larger than a load torque of a bearing member of a roller member disposed on the downstream side. Image forming device. 10. The belt-shaped image carrier of a roller member disposed downstream of a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier with a contact angle with the belt-shaped image carrier. The rotation load torque of the roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier is larger than the rotation load torque of the roller member disposed on the downstream side as the contact angle with the roller. The image forming apparatus according to claim 7. 11. A cleaning device for cleaning the belt-shaped image carrier with the belt-shaped image carrier interposed therebetween, the roller being disposed upstream of the belt-shaped image carrier in the rotation direction. 8. The image forming apparatus according to claim 7, wherein the rotational load torque of a roller member disposed on the upstream side in the rotational direction of the image carrier is larger than the rotational load torque of the roller member disposed on the downstream side. . 12. The belt-shaped image carrier is sandwiched by a roller member disposed on the upstream side in the rotation direction of the belt-shaped image carrier, or a brake member that slides directly on the roller member is brought into contact with the roller member. 8. The image forming apparatus according to claim 7, wherein the rotational load torque of a roller member disposed on the upstream side in the rotation direction of the image carrier is larger than the rotational load torque of the roller member disposed on the downstream side.