JP2003140474A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the transportability of recoding paper and to prevent a discharge pattern and faulty transfer or the like from occurring when transferred. SOLUTION: This image forming apparatus 100 is equipped with an intermediate transfer belt 51 freely movably laid in a tensioned condition across a driving roller 55, a secondary transfer roller 56 and a tension roller 58 or the like, and secondary transfer parts 56 and 57 transferring a toner image formed on the belt 51 to the recording paper P. Then, the roller 58 is a tension roller for adjusting tensile force by which appropriate tensile force is applied to the belt 51. Even when the tensile force applied to the belt 51 is changed by imparting biasing force to the roller 58 nearly in parallel with the extension line of the belt 51 linking the roller 58 and the transfer parts 56 and 57 by a spring 90, an angle formed by the extension line and the extension line of a transport guide 84 for guiding the recording paper P is made nearly constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to an image forming apparatus which has stable paper transportability and has no discharge pattern or transfer failure during transfer.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system, a method has been proposed in which a toner image formed on a photoconductor is transferred to a recording material (sheet) to obtain an image.

An image forming method in a color image forming apparatus using the multiplex intermediate transfer system will be described below with reference to FIG.

In the figure, the process units are Y,
Four of them are provided corresponding to each color of M, C and K, and the primary charging devices 2a to 2 are provided around the photosensitive drums 1a to 1d.
d, exposure devices 3a to 3d, developing devices 4a to 4d, and four process units including a cleaner are provided. Photosensitive drum 1a formed by each process unit
The images on .about.1d are sequentially transferred by the primary transfer rollers 53a.about.53d onto the intermediate transfer belt 51 which moves and passes adjacent to the photosensitive drums 1a.about.1d.
The image transferred onto the secondary transfer roller 56, 57
In the above, it is configured to be transferred to a recording material such as paper.
6a to 6d are photosensitive drum cleaners, 55 is an intermediate transfer belt drive roller, 58 is a tension roller, and 60 is a tension roller.
Is an intermediate transfer belt cleaner.

Specifically, after the photosensitive drums 1a to 1d are uniformly charged by the primary charging devices 2a to 2d, exposure is performed by the exposure devices 3a to 3c according to an image signal, whereby the photosensitive drums 1a to 1d are exposed. An electrostatic latent image is formed on the drums 1a to 1d. After that, the toner images are developed by the developing devices 4a to 4d, and the toner images on the photosensitive drums 1a to 1d are
A transfer bias is applied to the transfer rollers 53a to 53d from a transfer high-voltage power supply (not shown), so that the transfer rollers 53a to 53d are sequentially transferred to the intermediate transfer belt 51.

The transfer residual toner remaining on the photosensitive drums 1a to 1d is collected by the photosensitive drum cleaners 6a to 6d. The images that have been sequentially transferred from the respective photosensitive drums 1a to 1d onto the intermediate transfer belt 51 in the above-described manner are fed by applying a secondary transfer bias between the secondary transfer rollers 56 and 57. It is transferred to the recording material P that has been conveyed.

The secondary transfer residual toner remaining on the intermediate transfer belt is collected by the intermediate transfer belt cleaner 60. The toner image on the recording material P is fixed by the fixing device 7 to obtain a full-color image.

[0008]

In the above structure, the intermediate transfer belt 51 is stretched around the drive roller 55, the tension roller 58, the secondary transfer roller 56, and the intermediate transfer belt cleaner opposing roller 59, and at the same time, the tension roller is also stretched. It is always urged in one direction by 58.

However, in the conventional image forming apparatus, as shown in FIG. 7, the biasing direction of the tension roller 58 to the intermediate transfer belt 51 is set substantially perpendicular to the intermediate transfer belt 51. It was For this reason,
When the circumference of the intermediate transfer belt 51 changes, the position of the tension roller 58 fluctuates, so that the tension angle of the intermediate transfer belt 51 between the secondary transfer roller 56 and the tension roller 58 changes.

Then, the transport guide 8 for transporting the recording material P
4 and the intermediate transfer belt 51 change in angle, the intermediate transfer belt 51 and the recording material P fed and conveyed.
When the angle becomes large, there is a problem that image defects such as scattering of character images occur in the vicinity of the secondary transfer portion.

On the other hand, as shown in FIG. 8, if a roller 80 is arranged along the intermediate transfer belt 51 immediately upstream of the secondary transfer portion so that the angle of the intermediate transfer belt 51 does not change, The problem is solved. However, in this case, it is necessary to dispose the roller 80 newly, which increases the cost, which is not preferable.

Further, in the structure in which the intermediate transfer belt 51 is supported by two supporting rollers, the degree of freedom in the shape and arrangement of the belt is lowered, which is not preferable. For example, with respect to the intermediate transfer belt 51, the photosensitive drums 1 arranged around it.
In order to increase the degree of freedom in the arrangement, such as paper feeding and paper ejection to the secondary transfer unit, and the arrangement of the intermediate transfer belt cleaner and the patch sensor on the intermediate transfer belt, three or more support rollers should be provided. preferable.

Incidentally, for example, Japanese Unexamined Patent Publication No. 2000-330395.
In Japanese Patent Laid-Open Publication No. 2003-242242, an image forming apparatus is disclosed which regulates the direction of tension applied to the intermediate transfer belt.
In this conventional example, the relationship between the tension direction to the intermediate transfer belt and the tension direction of a member such as a cleaner contacting the intermediate transfer belt is defined, which is different from the object and configuration of the present invention.

Also, for example, Japanese Patent Laid-Open No. 2000-137386.
In the publication, there is disclosed an image forming apparatus provided with a pressing member that bends the intermediate transfer belt inwardly from a common tangent line on the outside connecting the secondary transfer roller and the nearest support roller on the downstream side. Although disclosed, this prior art example also differs from the gist and configuration of the present invention.

The present invention has been made to solve the above problems, and an object of the present invention is to stabilize the transportability of a recording material and prevent discharge patterns and transfer defects during transfer. It is to provide an image forming apparatus capable of performing

[0016]

To achieve the above object, the invention according to claim 1 is a belt-shaped image carrier movably stretched around a plurality of rotary supports, and the belt-shaped image carrier. In an image forming apparatus including a transfer unit that transfers a toner image formed on an image carrier onto a recording material, at least one of the plurality of rotary supports is disposed adjacent to the transfer unit. And a rotary support for tension adjustment for applying an appropriate tension to the belt-shaped image carrier, and the rotary support for tension adjustment includes the rotary support for tension adjustment and the transfer section. And a biasing means for moving the belt-shaped image carrier substantially parallel to the extension line of the belt-shaped image carrier, and guides the extension line and the recording material even when the tension of the belt-shaped image carrier changes. The angle formed by the extension line of the guide member is almost constant. To.

The invention according to claim 2 is characterized in that the rotary support for adjusting the tension and the guide member for guiding the recording material are arranged so as to be integrally interlockable with each other.

The invention according to claim 3 is characterized in that the belt-shaped image carrier is an intermediate transfer member.

The invention according to claim 4 is characterized in that the belt-shaped image carrier is a photoconductor.

According to a fifth aspect of the present invention, the toner image formed on the image carrier is transferred to an intermediate transfer belt stretched over a plurality of rotary supports, and a primary transfer section, and the intermediate transfer belt. In an image forming apparatus including a secondary transfer unit that transfers the upper toner image onto a recording material, at least one of the plurality of rotary supports is disposed adjacent to the primary transfer unit, and A rotary support for tension adjustment for applying an appropriate tension to the intermediate transfer belt, the rotary support for tension adjustment connecting the rotary support for tension adjustment to the primary transfer portion. The tension adjusting rotary support moves substantially parallel to the extension line even when the tension of the intermediate transfer belt changes, having a biasing means for moving the extension substantially parallel to the extension line of the intermediate transfer belt. The feature is that

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 schematically shows an image forming apparatus according to the present invention. The image forming apparatus 100 is a full-color electrophotographic image forming apparatus that has four photosensitive drums 1a to 1d and uses an intermediate transfer member.
Around the photosensitive drums 1a to 1d, charging rollers 2a to 2 are provided.
d, process units Pa and P having exposure devices 3a to 3d, developing devices 4a to 4d, cleaners 6a to 6d, etc.
b, Pc, and Pd are provided. Images of each color of yellow, magenta, cyan, and black are formed by the process units Pa to Pd, and the photosensitive drums 1a to 1d are rotatable in the directions of the arrows in the figure.

The images formed on the photosensitive drums 1a to 1d are the primary transfer rollers 53a, 53b, 53c and 53d.
In the first transfer portion having the photosensitive drums 1a to 1d
Are sequentially transferred onto an intermediate transfer belt (belt-shaped image carrier) 51 that moves and passes adjacent to the intermediate transfer belt 51.
The image transferred onto the secondary transfer roller 56, 57
In the second transfer portion having the structure, the image is transferred to a recording material such as paper.

The above-mentioned process units will be described below with reference to FIG.
Since a to Pd have the same configuration, the process unit Pa will be described here.

The process unit Pa includes a photosensitive drum 1a which is rotatably supported by an apparatus main body (not shown). The photosensitive drum 1a is formed of a conductive base 11 such as aluminum and the outer periphery thereof. It is a cylindrical electrophotographic photoreceptor having the photoconductive layer 12 as a basic configuration. The support shaft 13 is provided at the center thereof, and the support shaft 13 is rotationally driven in the direction of arrow R1 by a drive means (not shown).

A charging roller 2 is provided above the photosensitive drum 1a.
The charging roller 2a is arranged in contact with the surface of the photosensitive drum 1a to uniformly charge the surface to a predetermined polarity and potential, and is configured in a roller shape. The charging roller 2a has a conductive cored bar 21 arranged at the center.
And a low-resistance conductive layer 22 and a medium-resistance conductive layer 23 formed on the outer periphery of the photosensitive drum 1a, and both ends of the cored bar 21 in the longitudinal direction are rotatably supported by bearing members (not shown). Are arranged substantially parallel to.

The bearing member of the cored bar 21 is urged toward the center of the photosensitive drum 1a by a pressing means (not shown), whereby the charging roller 2a is moved to the photosensitive drum 1a.
It is pressed against the surface with a certain pressing force. The charging roller 2a is driven to rotate in the arrow R2 direction as the photosensitive drum 1a rotates in the arrow R1 direction. A bias voltage is applied to the charging roller 2a by the power supply 24, and as a result,
The surface of the photosensitive drum 1a is uniformly contact-charged.

An exposure device 3a is arranged downstream of the charging roller 2a along the rotation direction of the photosensitive drum 1a.
The exposure device 3a exposes the photosensitive drum 1a by scanning while turning on / off a laser beam based on image information, for example, and forms an electrostatic latent image according to the image information.

Further, the developing device 4a arranged on the downstream side of the exposure device 3a includes a developing container 41 containing a two-component developer.
The developing sleeve 42 is rotatably installed in the opening of the container 41 facing the photosensitive drum 1a. In the developing sleeve 42, a magnet roller 43 for carrying a developer on the developing sleeve 42 is fixedly arranged so as not to rotate with respect to the rotation of the developing sleeve 42. A regulating blade 44 that regulates the developer carried on the developing sleeve 42 to form a thin developer layer is installed below the developing sleeve 42 in the developing container 41. Further, a developing chamber 45 and a stirring chamber 46 which are partitioned are provided in the developing container 41, and a replenishing chamber 47 containing replenishment toner is provided above the partitioned developing chamber 45 and the stirring chamber 46.

When the developer formed on the thin developer layer is conveyed to the developing area opposite to the photosensitive drum 1a, the magnetic force of the main developing pole located in the developing area of the magnet roller 43 causes the ears to stand. Then, a magnetic brush of the developer is formed. By rubbing the surface of the photosensitive drum 1a with this magnetic brush and applying a developing bias voltage to the developing sleeve 42 by the power source 48, the toner adhering to the carrier forming the brush of the magnetic brush is electrostatically latent. A toner image is formed on the photosensitive drum 1a by adhering to the exposed portion of the image and developing.

Below the photosensitive drum 1a on the downstream side of the developing device 4a, the transfer roller 5 is sandwiched with the intermediate transfer belt 51 interposed therebetween.
3a is provided. The transfer roller 53a includes a cored bar 531 that is grounded, and a conductive layer 532 that is formed in a cylindrical shape on the outer peripheral surface thereof. Further, both ends of the transfer roller 53a in the longitudinal direction are urged toward the center of the photosensitive drum 1a by pressing members such as springs (not shown).

As a result, the conductive layer 5 of the transfer roller 53a is
32 is pressed against the surface of the photosensitive drum 1a via the intermediate transfer belt 51 with a predetermined pressing force, and a transfer nip portion is formed between the photosensitive drum 1a and the transfer roller 53a. The intermediate transfer belt 51 is sandwiched in the transfer nip portion, and the toner negatively charged due to the potential difference between the surface of the photosensitive drum 1a and the transfer roller 53a is not transferred to the photosensitive drum 1a.
The image is transferred from the surface a to the surface of the intermediate transfer belt 51.

After the image is transferred, the cleaner 6a removes the adhering substances such as residual toner from the photosensitive drum 1a. The cleaner 6a has a cleaner blade 61 and a conveying screw 62, and the cleaner blade 62 is brought into contact with the photosensitive drum 1a at a predetermined angle and pressure by a pressing means (not shown). The residual toner and the like are collected. The collected residual toner and the like are conveyed and discharged by the conveying screw 62.

Next, referring to FIG. 1, each photosensitive drum 1a
The intermediate transfer unit 5 is arranged below the to 1d. The intermediate transfer unit 5 includes an intermediate transfer belt 51.
And transfer rollers 53a to 53d, an intermediate transfer belt drive roller 55, secondary transfer rollers 56 and 57, a tension roller 58, and an intermediate transfer belt cleaner 60.

The intermediate transfer belt 51 is made of a dielectric resin, but in this embodiment, the volume resistivity is 10 ⁹ Ω.
-Cm (using a probe conforming to JIS-K6911, applied voltage 100V, applied time 60sec, 23 ° C 60% R
H), and a PI resin having a thickness t = 90 μm was adopted.

The transfer roller 53a is composed of a core metal having a diameter of 8 mm and a conductive urethane sponge layer having a thickness of 4 mm. The resistance value of the transfer roller 53a is applied to a grounded opposing roller with a load of 500 g. Press to 50mm / se
The value was about 10 ⁵ Ω (23 ° C. 60% RH), which was obtained from the relationship of the currents measured by applying a voltage of 100 V to the core metal while rotating at a peripheral speed of c.

The toner images of the respective colors formed on the photosensitive drums 1a to 1d are sequentially transferred onto the intermediate transfer belt 51 as described above, and then conveyed to the secondary transfer portion as the belt rotates. On the other hand, by this time, the paper cassette 8
The recording material P taken out from the pickup roller 81
The toner is supplied to the conveying rollers 82 and 83 via the conveying roller 84, is further conveyed leftward along the conveying guide 84, and is conveyed to the left side by the secondary transfer bias applied between the secondary transfer rollers 56 and 57 in the secondary transfer portion. The image is transferred onto the recording material P. The transfer residual toner and the like on the intermediate transfer belt 51 are removed and collected by the intermediate transfer belt cleaner 60.

The fixing device 7 has a fixing roller 71 rotatably arranged and a pressure roller 72 which rotates while being in pressure contact with the fixing roller 71. A heater 73 such as a halogen lamp is provided inside the fixing roller 71, and the temperature of the surface of the fixing roller 71 is adjusted by controlling the voltage to the heater 73.
In this state, when the recording material is conveyed, the fixing roller 71 and the pressure roller 72 rotate at a constant speed, and when the recording material P passes between the fixing roller 71 and the pressure roller 72, the recording material P comes from both front and back surfaces. It is pressurized and heated at a substantially constant pressure and temperature. As a result, the unfixed toner image on the surface of the recording material is melted and fixed, and a full-color image is formed on the recording material P.

In this embodiment, the intermediate transfer unit 5
The tension roller (rotation support for tension adjustment) 58 arranged inside is a hollow aluminum tube having a diameter of 16 mm and a thickness of 1 t, and the tension roller 58 is formed by an elastic force of a spring (biasing means) 90. It is biased in one direction. That is, the tension roller 58 is the secondary transfer roller 56.
The intermediate transfer belt 51 is urged in a direction substantially parallel to the intermediate transfer belt 51 (direction indicated by an arrow in FIG. 1) extending over the tension roller 58 to urge the intermediate transfer belt 51.

With this configuration, even when the circumferential length of the intermediate transfer belt 51 is slightly deviated from the standard value and the position of the tension roller 58 is changed, the intermediate transfer belt 51 straddling the secondary transfer roller 56 and the tension roller 58 is formed. The tension angle does not change. Therefore, the angle formed by the intermediate transfer belt 51 and the conveyance guide 84 is also constant, and therefore the angle between the recording material P and the intermediate transfer belt 51 does not change. As a result, it is possible to prevent abnormal discharge that occurs due to an increase in the angle between the intermediate transfer belt 51 and the recording material P immediately before the secondary transfer rollers 56 and 57, and suppress abnormal images such as scattering. .

[Second Embodiment] FIG. 3 schematically shows an image forming apparatus according to a second embodiment. In the present embodiment, the tension roller 58 causes the recording material P conveyance guide 84.
It is configured to work with. The configuration and operation of the other parts are the same as those in the first embodiment,
Detailed description is omitted.

In the figure, the tension roller 58 is urged by the elastic force of the spring 90 in a direction substantially perpendicular to the intermediate transfer belt 51 spanning the secondary transfer roller 56 and the tension roller 58 (direction of arrow in FIG. 3), Thereby, the intermediate transfer belt 51 is biased in the same direction. Further, the support member that rotatably supports the tension roller 58 and the transport guide 84 that transports the recording material P to the secondary transfer portion are integrally configured to be interlockable.

Therefore, even when the tension of the intermediate transfer belt 51 fluctuates and the position of the tension roller 58 changes, the tension direction of the intermediate transfer belt 51 and the conveying direction of the recording material P supplied to the secondary transfer portion. The angle between and can be kept constant. Therefore, just before the secondary transfer portions 56 and 57,
The angle between the intermediate transfer belt 51 and the recording material P does not become too large, and abnormal images such as scattering can be suppressed.

[Third Embodiment] FIG. 4 schematically shows an image forming apparatus according to a fourth embodiment. The image forming apparatus of the present embodiment is a full-color electrophotographic image forming apparatus that has one photosensitive drum 1 and uses an intermediate transfer belt 51.

In the figure, the photosensitive drum 1 serving as a latent image carrier.
The charging device 2, the exposure device 3, and the developing devices 4a-4
A process unit having d, a cleaner 6 and the like is provided, and an intermediate transfer belt 51 is provided adjacent to the photosensitive drum 1. This intermediate transfer belt 51 is
It is supported by three support rollers, a drive roller 55, a secondary transfer roller 56, and a tension roller 58. The configuration and operation of the process unit section are the same as those in the first embodiment, so detailed description will be omitted.

To form an image, four color toner images are formed on the intermediate transfer belt 51. First, 1
A toner image of a color is formed on the photosensitive drum 1 by the developing device 4a and transferred onto the intermediate transfer belt 51. 1
After the next transfer, the cleaner 6 removes adhered substances such as residual toner from the photosensitive drum 1. Subsequently, when the rotating body that houses the developing unit rotates and the developing device 4b that develops the toner of the second color comes to the side opposite to the photosensitive drum 1, the image of the second color is similarly formed on the photosensitive drum 1. . On the other hand,
After the image of the first color is formed on the intermediate transfer belt 51,
The same portion is again positioned on the opposite side of the photosensitive drum 1 by the rotation, and the image of the second color is transferred from the photosensitive drum 1.
During this time, the secondary transfer roller 57 is separated from the intermediate transfer belt 51 and does not disturb the toner image on the intermediate transfer belt 51.

After that, when the images of the third and fourth colors are developed on the photosensitive drum 1 and transferred onto the intermediate transfer belt 51, the secondary transfer roller 57 contacts the intermediate transfer belt 51 at the secondary transfer portion. . On the other hand, the recording material P taken out from the paper feed cassette 8 is supplied to the conveyance rollers 82 and 83 via the pickup roller 81, and is further conveyed to the conveyance guide 8.
4 is conveyed to the left. Then, the recording material P passes between the secondary transfer rollers 56 and 57, and the above-mentioned toner image is transferred onto the recording material P by the secondary transfer bias applied between these. The transfer residual toner and the like on the intermediate transfer belt 51 are removed and collected by the intermediate transfer belt cleaner 60.

After that, when the recording material P passes between the fixing roller 71 and the pressure roller 72 in the fixing device 7, the recording material P is pressed and heated from both front and back surfaces to form an unfixed toner image on the surface of the recording material. It is fused and fixed, and a full-color image is formed on the recording material P.

In the present embodiment, the tension roller 58 causes the secondary transfer roller 56 to move by the elastic force of the spring 90.
Is urged in a direction substantially parallel to the intermediate transfer belt 51 spanning the tension roller 58 (the direction of the arrow in FIG. 4), thereby urging the intermediate transfer belt 51 in the same direction.

With this configuration, even when the position of the tension roller 58 changes due to the change of the length of the intermediate transfer belt 51, the tension angle of the intermediate transfer belt 51 spanning the secondary transfer roller 56 and the tension roller 58 is maintained. There is no change and the separation condition of the recording material P separated from the secondary transfer portion can be always kept constant. For this reason, it is possible to suppress the separation failure or the like that tends to occur when the angle between the intermediate transfer belt 51 and the recording material P becomes small.

[Fourth Embodiment] FIG. 5 schematically shows an image forming apparatus according to a fourth embodiment. The image forming apparatus of the present embodiment is a full-color electrophotographic image forming apparatus that has one photosensitive drum 1 and uses an intermediate transfer belt 51.

In the present embodiment, the intermediate transfer belt 51
Is a drive roller 55, a secondary transfer roller 56, an intermediate transfer belt cleaner facing roller 59, a tension roller 58.
It is supported by four support rollers. The configuration and operation of these are similar to those of the above-described embodiment, and therefore detailed description thereof is omitted.

In the figure, the elastic force of the spring 90 in the direction of the arrow A causes the cam 91 having the fulcrum 91a as its fulcrum.
The tension roller 58 is biased in a direction substantially parallel to the photosensitive drum 1 and the intermediate transfer belt 51 spanning the tension roller 58 (the direction of arrow B in FIG. 5), thereby biasing the intermediate transfer belt 51 in the same direction. ing.

With this configuration, even if the position of the tension roller 58 changes, the tension angle of the intermediate transfer belt 51 spanning the photosensitive drum 1 and the tension roller 58 does not change, and the tension roller 58 and the primary transfer portion are not changed. It is possible to always keep the tension angle of the extension line of the intermediate transfer belt 51 that connects the two. Therefore, immediately before the nip portion of the primary transfer portion, it is possible to prevent an unstable state such as occurrence of an abnormal image such as scattering due to discharge between the photosensitive drum 1 and the intermediate transfer belt 51. You can

In the above-described embodiment, the belt-shaped image carrier is the intermediate transfer belt 51, but the image carrier is rotatably stretched on three or more supporting rollers. As long as it is a belt-like material, it may be a photoreceptor that is directly subjected to charging-exposure-development.
Further, as the tension roller 58 for adjusting the tension of the intermediate transfer belt 51, the one which urges the endless intermediate transfer belt 51 from the inside has been described, but as shown in FIG. Tension roller 5
8 may be arranged, and the tension roller 58 may urge the intermediate transfer belt 51 from the outside.

[0056]

As described above, according to the present invention, even when the tension of the belt-shaped image carrier changes, an extension line of the belt-shaped image carrier which connects the tension adjusting rotary support and the transfer portion. Since the angle formed by the extension line of the guide member that guides the recording material is substantially constant, it is possible to stabilize the transportability of the recording material and prevent discharge patterns and transfer defects during transfer. You can

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic configuration diagram of the above process unit.

FIG. 3 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 4 is a schematic configuration diagram of an image forming apparatus according to a third embodiment.

FIG. 5 is a schematic configuration diagram of an image forming apparatus according to a fourth embodiment.

FIG. 6 is a schematic configuration diagram of an image forming apparatus of a modified example of the present embodiment.

FIG. 7 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 8 is a schematic configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

1a, 1b, 1c, 1d Photosensitive drum 2a, 2b, 2c, 2d charging roller 3a, 3b, 3c, 3d exposure apparatus 4a, 4b, 4c, 4d Developing device 5 Intermediate transfer unit 6a, 6b, 6c, 6d cleaner 7 Fixing device 51 Intermediate transfer belt (belt-shaped image carrier) 53a to 53d Primary transfer roller 55 Drive roller (rotary support) 56 Secondary transfer roller (rotary support) 57 Secondary transfer roller 58 Tension roller (rotary support for tension adjustment) 59 Intermediate transfer belt cleaner Opposing roller 84 Transport guide (guide member) 90 spring (biasing means) 100 image forming apparatus P recording material

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H035 CB06 CF01 CG03                 2H200 FA04 FA17 GA12 GA17 GA23                       GA24 GA47 HA02 HB12 HB22                       HB43 JA02 JA25 JB12 JB17                       JC03 JC07 JC16 LA17 MA04                       MB04

Claims (5)

[Claims] 1. A belt-shaped image carrier movably stretched around a plurality of rotary supports, and a transfer section for transferring a toner image formed on the belt-shaped image carrier onto a recording material. In the image forming apparatus including :, at least one of the plurality of rotary supports is disposed adjacent to the transfer section, and is for tension adjustment for applying an appropriate tension to the belt-shaped image carrier. A biasing member that is a rotation support and that moves the tension adjustment rotation support substantially parallel to an extension line of the belt-shaped image carrier that connects the tension adjustment rotation support and the transfer portion. And a substantially constant angle formed between the extension line and the extension line of the guide member that guides the recording material even when the tension of the belt-shaped image carrier changes. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the tension adjusting rotary support and the guide member for guiding the recording material are integrally and interlockably arranged. 3. The image forming apparatus according to claim 1, wherein the belt-shaped image carrier is an intermediate transfer member. 4. The image forming apparatus according to claim 1, wherein the belt-shaped image carrier is a photoconductor. 5. A primary transfer portion for transferring a toner image formed on an image carrier to an intermediate transfer belt stretched over a plurality of rotary supports, and a toner image on the intermediate transfer belt is recorded. An image forming apparatus comprising: a secondary transfer unit for transferring onto a material; at least one of the plurality of rotary supports is disposed adjacent to the primary transfer unit, and is suitable for the intermediate transfer belt. Which is a rotary support for tension adjustment for applying various tensions, and an extension line of the intermediate transfer belt which connects the rotary support for tension adjustment to the rotary support for tension adjustment and the primary transfer portion. And a biasing means for moving the tension transfer roller substantially parallel to the extension line, and the tension adjusting rotary support moves substantially parallel to the extension line even when the tension of the intermediate transfer belt changes. A characteristic image forming apparatus.