JP2012242554A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in which: when supporting means is mistakenly pressed in a direction in which a contact part of the supporting means of a steering roller in a halting state is separated from a cam, the cam receives an impact when the contact part of the supporting means returns in a direction to abut against the cam.SOLUTION: A regulation part is provided in an area not used for image formation by a cam to regulate the movement of a contact part in a direction to be separated from the cam.

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic system or an electrostatic recording system.

  In order to cope with various recording materials, a transfer unit for transferring a toner image formed on an image carrier such as a photosensitive drum to an intermediate transfer member and then transferring the toner image formed on the intermediate transfer member to the recording material is provided. The image forming apparatus is employed.

  Patent Document 1 describes a configuration in which a roller that stretches the intermediate transfer belt is provided with a steering mechanism that steers the intermediate transfer belt in order to prevent the running intermediate transfer belt from moving in the width direction. . In Patent Document 1, as a steering mechanism, a support unit that includes a contact portion and rotatably supports an end portion of the steering roller, and contacts the contact portion provided in the support means to rotate the support means. The structure which provided the cam for this and the drive source which drives a cam is described. In order to improve the workability of replacement of the intermediate transfer belt, the support means is stabilized by the weight of the steering roller being applied in the direction in which the cam and the contact portion of the support means come into contact with each other.

JP-A-2005-292480

  However, in such a configuration, the support means stops with the cam pushed in by the weight of the steering roller. For this reason, if the support means is accidentally pushed away from the cam when the intermediate transfer belt is replaced, the cam or drive source will return when the abutment portion of the support means returns to the direction in which it abuts away from the cam. There is a risk of shock. That is, it is desirable to restrict the movement of the support means in the direction away from the cam at the position where the support means has pushed the cam and stopped by the weight of the steering roller.

  The present invention for solving the above-described problems includes a movable belt member, a tension member that stretches the belt member, and a steering roller that stretches the belt member and steers the belt member in the width direction. And a support means for rotatably supporting the steering roller, an area used for image formation, and an area not used for image formation, and a cam rotatable to rotate the support means, In an image forming apparatus comprising an abutting portion provided on the support means and contacting the cam, and a drive source for driving rotation of the cam, the image forming apparatus is provided in an area not used for image formation of the cam. It has a restricting part that restricts the contact part from moving in a direction away from the cam.

  According to the present invention, even if the support means is pushed in the direction in which the contact portion of the steering roller support means in a stopped state is separated from the cam, the cam is returned when the contact means of the support means comes into contact with the cam. It can relieve shock.

1 is a front longitudinal sectional view showing a schematic configuration of an image forming apparatus using an intermediate transfer belt to which the present invention can be applied. It is a perspective view which shows the structure of a steering mechanism and a cancellation | release mechanism. It is a front view which shows the structure of a steering mechanism and a cancellation | release mechanism. It is a top view which shows the structure of the front side of a steering mechanism and a cancellation | release mechanism. It is a top view which shows the structure of the rear side of a steering mechanism and a cancellation | release mechanism. FIG. 6 is a diagram for explaining a pressure state of an intermediate transfer belt by a steering roller. FIG. 6 is a diagram for explaining a pressure release state of an intermediate transfer belt by a steering roller. It is a figure explaining the state where a cam follower is located in the bottom dead center of a cam. FIG. 6 is a top view illustrating a state in which the intermediate transfer belt unit is pulled out from the image forming apparatus main body. FIG. 6 is a left view for explaining a state when the intermediate transfer belt is replaced. FIG. 6 is a right view for explaining a state when the intermediate transfer belt is replaced.

[Overall Configuration and Operation of Image Forming Apparatus]
An embodiment of the conveying means according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a schematic configuration diagram of an image forming apparatus using the present embodiment.
This sheet conveying apparatus is an electrophotographic full color sheet conveying apparatus, and has a digital color image reader unit R in the upper part and a digital color image printer part P in the lower part.

  In the reader unit R, reference numeral 31 denotes an original platen glass, and 32 denotes an original pressing plate that can be opened and closed with respect to the glass 31. A color original O is placed on the glass 31 with the image surface facing downward according to a predetermined placement standard, and the original pressure plate 32 is placed thereon to set the original O.

The document pressing plate 32 may be an automatic document feeder (ADF, RDF) so that a sheet document is automatically fed onto the glass 31.
A moving optical system 33 is driven to move along the lower surface of the glass 31. The moving optical system 33 optically scans the downward image surface of the document O on the glass 31. The original scanning light is imaged on a CCD 34, which is a photoelectric conversion element (solid-state imaging element), and is color-separated and read with three primary colors of RGB (red, green, and blue).

The read RGB signals are input to an image processing unit (not shown in the figure).
The printer unit P is an electrophotographic image forming mechanism having one drum, a rotary development configuration, and an intermediate transfer configuration.

The outline of the operation of the printer unit P is as follows.
A laser scanner 2 forms an electrostatic latent image on an electrophotographic photosensitive drum (hereinafter referred to as a photosensitive drum) 1 as an image carrier based on an image signal.

  The electrostatic latent image formed on the photosensitive drum is developed by a plurality of developing devices. The developing device contains a developer of a desired color, and includes a replenishment pipe 400 for replenishing toner as a developer as needed from a toner cartridge section (not shown in the figure), and is disposed inside the development rotary. The

  The toner image of each color on the photosensitive drum 1 is further primary transferred for each color on the intermediate transfer belt 51 to form a toner image of an unfixed necessary color on the intermediate transfer belt 51. Thereafter, the toner image is secondarily transferred onto the recording material S in a lump and then fixed to output a full-color image formed product.

This will be described in more detail below.
A photosensitive drum 1 as an image carrier for carrying a toner image is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined speed, and its surface is uniformly charged to a predetermined polarity and potential by a charger 2 as a charging means. The The charged surface is subjected to laser scanning exposure by a laser scanner 3 as exposure means.

  The laser scanner 3 includes a laser output unit, a polygon mirror, an imaging lens, a folding mirror, and the like, and outputs a laser beam (optical signal) modulated in accordance with an image information signal input from the image processing unit 35. Then, the charged surface of the rotating photosensitive drum 1 is scanned and exposed. As a result, an electrostatic latent image corresponding to the scanning exposure pattern is formed on the surface of the photosensitive drum 1.

  In addition to the image information read from the reader unit R, the image information signal may be synthesized and formed from image information transmitted from an external device such as a personal computer.

The electrostatic latent image is developed as a toner image by the rotary developing device 4.
The rotary developing device 4 includes a rotary 41 and a plurality of developing devices 4 each containing a color developer (toner).

  When the rotary 41 is rotated at a predetermined control timing by a predetermined angle in the direction of the arrow in the drawing, each developing device is switched to a developing position facing the photosensitive drum 1 and arranged. At the developing position, the distance (SD distance) between the photosensitive drum 1 and the developing sleeve on the developing device side is kept within a predetermined range.

  The intermediate transfer belt 51 to which the toner image is transferred is an endless belt made of a dielectric material having flexibility, and is suspended and stretched between a plurality of rollers 5a to 5g as stretch members. The outer surface of the intermediate transfer belt 51 contacts the photosensitive drum 1 between the rollers 5b and 5c to form a primary transfer nip T1.

In the primary transfer nip T 1, a primary transfer roller 6 is disposed on the opposite side of the belt 5 from the photosensitive drum 1 side and is in contact with the inner surface of the intermediate transfer belt 51.
A primary transfer voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 6 at a predetermined control timing. The intermediate transfer belt 51 is configured as a belt member that can move in the clockwise direction indicated by an arrow at substantially the same speed as the rotational speed of the photosensitive drum 1 with the roller 5a as a driving roller, for example.

First, a toner image of the first color is formed on the photosensitive drum 1 by the above-described image forming process of charging / exposure / development. Then, the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 51 at the primary transfer nip portion T1.
The primary transfer residual toner that is not transferred to the intermediate transfer belt 51 and remains on the surface of the photosensitive drum 1 is removed from the surface of the photosensitive drum by the drum cleaning device 7. The photosensitive drum 1 cleaned by the cleaning device 7 is repeatedly used for image formation.

  The same image forming process as described above is repeated as necessary for the second to Nth colors. As a result, an unfixed toner image is formed and synthesized on the intermediate transfer belt 51 by sequentially superimposing and transferring the toner images of the development colors.

  On the other hand, the sheet feeding roller 11 of the sheet feeding section selected in advance among the plurality of sheet feeding sections of the first to third sheet feeding cassettes 81 to 83 is driven at a predetermined control timing. As a result, one sheet of the recording material S accommodated in the sheet feeding unit is separated and sent out, and is sent from the sheet path 13 to the registration roller pair 14.

  The pair of registration rollers 14 controls the skew correction of the recording material S and the timing of the secondary transfer of the toner image from the intermediate transfer belt 51 to the recording material S, and the recording material fed from the paper feeding unit side. The tip of S is received and stopped once.

  Reference numeral 15 denotes a secondary transfer roller. The secondary transfer roller 15 faces the roller 5g (opposing roller) among the plurality of rollers 5a to 5g that urge the intermediate transfer belt 51. The secondary transfer roller 15 is pressed into a first state in which the belt 5 is pressed against the opposing roller 5g with a predetermined pressure and a second state separated from the outer surface of the intermediate transfer belt 51 (not shown in the drawing). Switching is performed by the control mechanism, and the detachment control is performed.

  The secondary transfer roller 15 is always switched and held in the second state separated from the outer surface of the intermediate transfer belt 51. By switching to the first state, a secondary transfer nip portion T2 is formed between the outer surface of the intermediate transfer belt 51.

  The secondary transfer roller 15 is switched to the first state at a predetermined control timing. In addition, the recording material S that has been temporarily stopped at the position of the registration roller pair 14 is re-fed from the registration roller pair 14 at a predetermined control timing, and is switched to the first state and the intermediate transfer belt 15. 51 is introduced into the secondary transfer nip T2 between the first and second transfer nips 51.

  The recording material S is nipped and conveyed through the secondary transfer nip portion T2. In the meantime, a predetermined secondary transfer voltage is applied to the secondary transfer roller 15, and a toner image composed of a plurality of colors on the intermediate transfer belt 51 is electrostatically collectively transferred onto the recording material S. An unfixed toner image is formed (transferred) on.

  The secondary transfer residual toner not transferred to the recording material S and remaining on the intermediate transfer belt 51 is removed from the surface of the intermediate transfer belt by the belt cleaning device 16. The intermediate transfer belt 51 cleaned by the cleaning device 16 is repeatedly used for image formation.

  The cleaning device 16 is always held in a state of being separated from the outer surface of the intermediate transfer belt 51. When the secondary transfer of the toner image from the intermediate transfer belt 51 to the recording material S is performed at the secondary transfer nip portion T2, the toner image is switched to a state in contact with the outer surface of the intermediate transfer belt 51 at a predetermined control timing.

  The recording material S that has exited the secondary transfer nip T2 is separated from the surface of the intermediate transfer belt 51 and conveyed to the fixing device 18 by the conveying belt unit 17, and the unfixed toner image is transferred onto the recording material S by heat and pressure. It is fused to form a fixed image. The recording material S exiting the fixing device 18 is discharged onto the paper discharge tray 20 through the sheet conveyance path 19.

[Configuration of intermediate transfer unit]
Next, the configuration of the intermediate transfer belt unit 50 including the intermediate transfer belt 51 of the present embodiment will be described in detail.

  The intermediate transfer belt 51 may move in the width direction orthogonal to the moving direction during movement. Therefore, in the present embodiment, a steering roller 5d for steering the intermediate transfer belt in the width direction is provided in order to suppress a shift in the width direction of the intermediate transfer belt. The configuration of the intermediate transfer unit of this embodiment will be described with reference to FIGS.

  Reference numeral 5d denotes a steering roller that stretches the intermediate transfer belt and steers the intermediate transfer belt in the width direction. Reference numerals 115 and 125 denote bearing holders that rotatably support the shaft of the steering roller 5d at front and rear ends in the width direction of the steering roller 5d.

  The front bearing holder 115 is configured to be slidable by being fixed to a slide 113 that can slide on the front slide rail 116. Similarly, the rear bearing holder 125 is configured to be slidable by being fixed to the slide 123 slidable on the rear slide rail 116.

  The front slide rail 116 is fixed to a steering arm 101 provided on the front side as shown in FIG. As shown in FIG. 5, the rear slide rail 126 is fixed to a rear plate 132 that forms the housing of the intermediate transfer belt unit 50. That is, the front slider 113 is configured to be slidable on the steering arm 101, and the rear slider 123 is configured to be slidable on the rear plate 132.

  The front slider 113 is urged in the direction of arrow G by a spring 114 applied to the steering arm 101, and the rear slider 123 is urged in the direction of arrow G by a spring 124 applied to the rear plate 132. That is, the steering roller 5 d functions as a tension roller that applies tension to the inner peripheral surface of the intermediate transfer belt 51.

  The steering arm 101 is configured to be rotatable around a rotation shaft 112. The rotating cam 103 is a rotatable cam for rotating the steering roller 5d. A cam follower 102 is provided on the steering arm 101 and serves as an abutting portion that abuts on the rotating cam 103. The cam follower 102 is disposed on the opposite side of the rotating shaft 112 from the side on which the steering roller 5d is disposed. Reference numeral 104 denotes a steering motor as a drive source for driving the cam 103. That is, the bearing holder 115, the slider 113, the slide rail 116, the steering arm 101, and the like are configured as support means for rotatably supporting the steering roller 5d.

(Intermediate transfer belt offset correction by steering)
When the rotating cam 103 rotates in the direction of arrow A in FIG. 3, the side of the steering arm 101 on which the cam follower 102 is provided rotates in the direction of arrow C about the rotating shaft 112. As a result, the side of the steering arm on which the steering roller 5d is provided rotates in the direction of arrow E, so that the intermediate transfer belt 51 moves to the back side. On the contrary, when the rotating cam 103 rotates in the direction of arrow B, the side of the steering arm 101 on which the cam follower 102 is provided rotates in the direction of arrow D about the rotating shaft 112. As a result, the intermediate transfer belt 51 moves forward as the steering roller 5d side rotates in the direction of arrow F.

  Incidentally, a home position flag 105 is provided on the output shaft of the steering motor 104 opposite to the side on which the rotating cam 103 is provided. The phase of the rotation cam 103 can be detected by detecting the phase of the home position flag 105 with the home position sensor 106.

  In the present embodiment, a belt edge detection sensor not explicitly shown in the drawing detects the position of the edge portion in the width direction of the intermediate transfer belt 51. The steering motor 104 rotates based on the position information detected on the basis of the detected position information, and the deviation of the intermediate transfer belt 51 is corrected by changing the alignment of the steering roller 5d.

(Configuration to release tension)
By the way, when ensuring the workability of replacing the intermediate transfer belt 51, it is desirable to lower the tension of the intermediate transfer belt 51. A release mechanism for releasing the tension of the intermediate transfer belt 51 in the present embodiment will be described with reference to FIGS.

  The rotation shaft 112 is rotatably supported between the front side plate 131 and the rear side plate 132, and supports the steering arm 101 on the outside of the front side plate 131 so as to be rotatable. A release cam 111 is fixed to the front end portion of the rotating shaft 112, and a release cam 121 is fixed to the rear end portion. By rotating a lever 111c provided on the release cam 111, the release cam 111 is rotated integrally. It is configured to be movable.

6 and 7 are sectional views for explaining the operation of the release cam 111. FIG. 6 shows a pressurized state and FIG. 7 shows a released state.
In the released state of FIG. 7, the top dead center 111 a of the release cam 111 hits the follower surface 113 a of the slider 113, and the slider 113 is moved in the direction of arrow H against the spring 114. As a result, the bearing holder 115 moves in the direction of the arrow H, and the tension of the intermediate transfer belt 51 is released. At this time, the release cam 121 on the back side is also rotated in conjunction with the rotation shaft 112 and operates in the same manner as the release cam 111.

  When removing the intermediate transfer belt 51 by periodic replacement or the like, the release cam 111 is rotated to the position described above to release the tension, and the intermediate transfer belt 51 is slid in the axial direction and removed from the unit. Here, the projected area of the front side plate 131 is smaller than the cross-sectional area of the intermediate transfer belt 51, and the intermediate transfer belt 51 can be pulled out to the front side.

  On the other hand, when the release 111 is rotated clockwise, the phase hitting the follower surface 113a of the slider 113 gradually shifts from the top dead center 111a to the bottom dead center 111b. Accordingly, the slider 113 is pulled by the spring 114 and moves in the direction of arrow G, and tension is gradually applied to the intermediate transfer belt 51. When the phase of the bottom dead center 111b is reached, a desired tension is applied, and the state shown in FIG. 6 is reached, and the image forming operation described above is performed. In practice, the amount of movement of the steering roller 5d in the direction of the arrow G is regulated by the length of the intermediate transfer belt 51, and the bottom dead center 111b does not hit the follower surface 113a but has a clearance W. Tension is applied.

[Cam control section]
Next, a characteristic configuration of the present embodiment will be described.
FIG. 8 is an enlarged view of the installation portion of the rotating cam 103. In the present embodiment, a cam profile for contacting the cam follower 102 is formed on the rotating cam 103.

  The cam profile of the rotating cam 103 is provided with a neutral point 103b where the alignment of the steering roller 5d does not change. During a normal image forming operation, a range in which the phase around the rotation axis 112 is about ± 5 deg around the neutral point 103b is used. That is, this range functions as an area used for image formation of the rotating cam 103. As a result, the deviation of the running intermediate transfer belt 51 in the width direction is suppressed during the image forming operation.

  Further, the cam profile of the rotating cam 103 is from the rotating shaft 1041 from the top dead center 103a where the distance from the rotating shaft is maximum to the bottom dead center 103c where the distance from the rotating shaft is minimum. The distance is monotonously decreased. That is, the top dead center 103a is the maximum portion where the radius of the cam centering on the rotation axis is maximum, and the bottom dead center 103c is the minimum portion where the radius of the cam centering on the rotation axis is minimum. In addition, the weight of the steering roller 5 d is configured to be applied in a direction in which the cam follower 102 abuts against the rotating cam 103. As a result, the rotational moment that rotates the rotating cam 103 acts in the direction of arrow A due to the weight of the steering roller 5d. As a result, if the supply of driving force to the rotating cam 103 of the steering motor 104 is stopped when the image forming apparatus main body is on standby or turned off, the rotating cam 103 is directed in the direction of arrow A and the cam follower 102 is directed toward the bottom dead center 103c. It rotates automatically.

  In the present embodiment, as shown in FIG. 8, when the cam follower 102 comes into contact with the bottom dead center 103c of the rotating cam 103, the rotation restricting portion 103e is controlled in order to restrict the cam follower 102 from further rotating in the A direction. (Second restriction part) is provided. The rotation restricting portion 103e has a shape that fits with a half of the circumference of the cam follower 102 in a state where the cam follower 102 is in contact with the bottom dead center 103c of the rotation cam 103. Since the bottom dead center 103c and the rotation restricting portion 103e of the rotation cam 103 are formed in an area not used for cam profile image formation, the rotation of the cam follower automatically stops in an area not used for image formation.

  Furthermore, in this embodiment, when the cam follower 102 comes into contact with the bottom dead center 103c of the rotating cam 103, a separation restricting portion 103d (first restricting portion) for restricting the cam follower 102 from moving in a direction away from the rotating cam. ) Is provided. L1 indicates a straight line connecting the center of the rotating shaft 1041 of the rotating cam 102 and the bottom dead center 103c. Since the direction in which the cam follower 102 in contact with the bottom dead center 103c is separated from the rotating cam is the direction L1, the separation regulating portion 103d is positioned on the straight line L1 in the direction from the rotary shaft 1041 toward the bottom dead center 103c. It is provided at a position further advanced than the dead center 103c.

  The reason for providing the separation restricting portion 103d will be described. If the steering arm 101 is accidentally pushed when the intermediate transfer belt is replaced, the cam follower 102 of the steering roller 5 d may be separated from the rotating cam 103. Then, when the cam follower 102 returns to the abutting direction after being momentarily separated from the rotating cam 103, there is a risk of shocking the rotating cam or the drive source. That is, it is desirable to restrict the cam follower of the steering arm from moving in a direction away from the cam at a position where the cam follower pushes the cam and stops due to its own weight.

  Furthermore, in the present embodiment, the separation restricting portion is arranged so that the cam follower 102 contacts the separation restricting portion 103d on L1 in a state where the cam follower 103 reaches the bottom dead center and the turning is restricted by the turning restricting portion 103e. An interval between 103d and bottom dead center 103c is set. As a result, the cam follower 103d in a stopped state is effectively prevented from separating.

  In the present embodiment, when the cam follower 102 reaches the bottom deadline 103c, it is configured to contact the separation regulating portion 103d on the straight line L1, but this is not intended to be limited to this configuration. A slight gap (clearance) may be provided between the cam follower 102 and the separation restricting portion 103a in a state where the cam follower 102 has reached the bottom dead center 103c. In that case, the size of the gap needs to be smaller than the movable range of the rotational movement of the steering arm 101.

  In the present embodiment, the rotation cam 103 automatically moves to the bottom dead center 103c when the driving of the steering roller 104 is stopped, but is not intended to be limited to this embodiment. When the cam profile of the rotating cam 103 is gentle, the cam follower 102 may not be positioned at the bottom dead center 103 c of the rotating cam 103 even if the steering motor 104 is turned off. In this case, the phase of the home position flag 105 is detected by the home position sensor 106 after receiving a signal from the user to enter the standby of the image forming apparatus or to turn off the power. In addition, it is possible to add a sequence in which the rotating cam 103 is rotated to the position of the bottom dead center 103c and then the standby or power-off state is set.

(Replacing the intermediate transfer belt 51)
FIG. 9 is a top view showing a state in which the intermediate transfer belt unit 50 is pulled out from the image forming apparatus main body. When the intermediate transfer belt 51 is replaced, the lever 111c provided on the release cam 111 is pulled in the direction indicated by the arrow J in FIG. 9 from the state of being installed in the image forming apparatus main body (the broken line portion in FIG. 9). It can be pulled out from the forming apparatus main body. At this time, the slide rail left 107e and right 107f installed in the image forming apparatus main body extend in the front direction in FIG. 9, and the intermediate transfer belt frame front 107a, left 107b and right fixed to the slide rail left 107e and right 107f. 107c and back 107d are both pulled out. The intermediate transfer belt unit 50 is pulled out together with the intermediate transfer belt frames (107a, 107b, 107c, 107d). At this time, the release cam 111 is supported on the front side 107a of the intermediate transfer belt frame on the front side. On the other hand, the intermediate transfer belt unit rotation shaft left 109a is supported on the intermediate transfer belt frame left 107b and the intermediate transfer belt unit rotation shaft right 109b is rotatably supported on the intermediate transfer belt frame right. Further, a fixed shaft 108 for fixing the intermediate transfer belt unit after an operation of flipping up an intermediate transfer belt unit 50 described later is mounted on the right intermediate transfer belt frame 107c.

  FIG. 10 is a left side view showing a state after the intermediate transfer belt unit 50 is pulled out from the image forming apparatus main body and the intermediate transfer belt 51 is flipped up to replace the intermediate transfer belt 51. FIG. 11 is a right side view. It is. From the broken line portion in FIG. 10, the lever 111c provided on the release cam 111 is held and pulled in the direction of arrow K in the drawing. By doing so, the intermediate transfer belt unit 50 can be flipped up with the intermediate transfer belt unit rotation shaft left 109a and the intermediate transfer belt unit rotation shaft right 109b as rotation centers. After the intermediate transfer belt unit 50 is flipped up, the fixed shaft 108 is detached from the intermediate transfer belt frame right 107 while holding the lever 111c, and installed on the fixed shaft fixing portions 1071 and 1072 provided in the intermediate transfer belt frame back 107d. To do. The intermediate transfer belt unit 50 is self-supporting when the fixed shaft 108 supports the rear plate 132.

  The intermediate transfer belt 51 can be pulled out in the direction indicated by the arrow N in FIGS. 10 and 11 by performing the above-described intermediate transfer belt tension releasing operation while the intermediate transfer belt unit 50 is standing independently. 10 and 11, even if an external force is applied to the steering roller 5 d or the like when the intermediate transfer belt 51 is replaced in the self-supporting state of the intermediate transfer belt unit 50 shown in FIGS. 10 and 11, the steering arm 101 does not rotate. It is possible to prevent damage and improve serviceability.

  In the above-described embodiment, the intermediate transfer belt unit 50 has been described as an example. However, the same configuration can be applied to the photosensitive belt, the transfer belt, and the fixing belt body, and in this case, the same effect can be obtained. Can be played.

51 Intermediate transfer belt 5d Steering roller 101 Steering arm 102 Cam follower 103 Rotating cam 104 Steering motor 105 Home position flag 108 Fixed shaft 109a, 109b Intermediate transfer belt unit rotating shaft 111, 121 Release cam 112 Rotating shaft 114, 124 Spring ( (Biasing member)
115,125 Bearing holder (slide member)
131 Front plate 132 Rear plate

Claims (6)

A movable belt member;
A tension member that stretches the belt member;
A steering roller that stretches the belt member and steers the belt member in the width direction;
Support means for rotatably supporting the steering roller;
A cam that includes a region that is used for image formation and a region that is not used for image formation, and is rotatable to rotate the support means;
A contact portion provided on the support means and contacting the cam;
An image forming apparatus comprising a drive source for driving rotation of the cam;
An image forming apparatus comprising: a restricting portion that is provided in an area not used for image formation of the cam and restricts the contact portion from moving in a direction away from the cam.   The image forming apparatus according to claim 1, wherein a minimum portion having a minimum radius around the rotation axis of the cam is provided in an area not used for image formation of the cam.   3. The image formation according to claim 2, wherein a radius around the rotation axis of the cam monotonously decreases from an area used for image formation of the cam to an area not used for image formation of the cam. apparatus.   2. The control unit according to claim 1, further comprising a control unit configured to control the driving source so as to move the contact portion from an area used for image formation of the cam to an area not used for image formation of the cam. Image forming apparatus. The restriction part is a first restriction part,
4. A second restricting portion that is provided in an area not used for image formation of the cam and that restricts rotation of the cam in contact with the contact portion. An image forming apparatus described in any one of the above. The first restricting portion is configured so that the abutting portion also contacts the first restricting portion in a state where the abutting portion is in contact with the second restricting portion of the cam. The image forming apparatus according to claim 4, wherein:

Images