JP5509172B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus in which a fixing unit having a fixing roller is detachably attached to an apparatus main body, and in particular, to a first position at which driving force from the apparatus main body can be transmitted to the fixing roller and the fixing roller. The present invention relates to an image forming apparatus in which the fixing unit is provided so as to be insertable / removable between a second position where transmission of the driving force is blocked.

  2. Description of the Related Art Conventionally, a fixing unit is provided in an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multi-function machine equipped with these functions. The fixing unit includes a fixing roller having a built-in heater, and a pressure roller pressed against the fixing roller. The fixing roller is rotatably supported by the fixing unit, and a driving force is transmitted from the apparatus main body in a state where the fixing roller is mounted on the apparatus main body. As a result, the fixing roller rotates in one direction. When the transfer paper passes between the fixing roller and the pressure roller, the toner on the transfer paper is melted by the fixing roller heated to a high temperature by a heater, and the toner is fixed on the transfer paper.

  As shown in the schematic diagram of FIG. 11, this type of image forming apparatus is provided with a drive transmission mechanism 100 that transmits a driving force to the fixing roller 120 of the fixing unit. In the drive transmission mechanism 100, the driven transmission unit 101 provided in the fixing unit and the drive transmission unit 111 provided in the apparatus main body are connected to each other in a state where the fixing unit is mounted on the apparatus main body. A driving force is transmitted from the transmission unit 111 to the driven transmission unit 101. Specifically, the drive joint 105 is rotatably provided on the support shaft 103 provided on the frame 102 of the driven transmission portion 101, and the drive joint is connected to the support shaft 113 provided on the frame 112 of the drive transmission portion 111. 115 is rotatably provided, and when a driving force is input to the transmission gear 114 integral with the driving joint 115, the fixing roller 120 is passed through the driving joint 115, the driving joint 105, the intermediate gear 104, and the driving gear 119. Driving force is transmitted. Although not a transmission mechanism for driving the fixing roller, Patent Documents 1 to 5 disclose various transmission mechanisms for transmitting a driving force to each rotating body.

JP 2007-72158 A JP 2006-171631 A JP-A-10-69157 JP 2003-28241 A JP 2002-82506 A

  However, in the conventional drive transmission mechanism 100 shown in FIG. 11, if the fixing roller 120 suddenly stops when a jam occurs in the fixing unit, an excessive load is applied to the intermediate gear 104, and the intermediate load is caused by the load. Stress concentrates on the base portion 106 of the support shaft 103 of the gear 104 and the drive joint 105, and the base portion 106 of the support shaft 103 may be cracked, or the support shaft 103 may be broken in some cases.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus capable of preventing cracks and breakage of a support shaft of a driven transmission portion of a fixing unit.

  The present invention includes a fixing roller rotatably supported, and a first position where a driving force from the apparatus main body can be transmitted to the fixing roller and a second position where transmission of the driving force to the fixing roller is blocked. A fixing unit provided in the apparatus main body so as to be able to be inserted into and removed from the position; and a driving force transmitted from the apparatus main body at the first position in the insertion direction of the fixing unit. An image forming apparatus comprising: a driven transmission unit configured to transmit to the driven unit; and a drive transmission unit provided to face the back of the fixing unit in the apparatus main body and transmit the driving force to the driven transmission unit. It is configured as. The drive transmission unit includes a first support shaft extending in a removal direction of the fixing unit, a first drive joint rotatably provided on the first support shaft, and the removal from the tip of the first support shaft. And a protruding portion protruding in the direction. The driven transmission portion is provided on a second support shaft extending in the insertion direction from the inner portion of the fixing unit and rotatably on the second support shaft, and is connected to the first drive joint in the axial direction. A second driving joint that receives a driving force in the direction of shaft rotation from the first driving joint, and a tip of the second support shaft, and the protrusion is inserted when the fixing unit is inserted into the first position. Possible insertion holes.

  With this configuration, when the fixing unit is inserted to the first position of the apparatus main body, the protruding portion of the first support shaft is inserted into the insertion hole of the second support shaft. Accordingly, the base side of the second support shaft is supported by the fixing unit, while the distal end side of the second support shaft is supported by the protruding portion of the first support shaft. Thereby, the crack and breakage of the second spindle of the fixing unit are prevented. In addition, misalignment of the shaft center at the connecting portion between the first drive joint of the drive transmission unit and the second drive joint of the driven transmission unit is also prevented.

  The image forming apparatus of the present invention further includes guide ribs provided at the back of the fixing unit. The guide rib is formed in an arc shape centered on the second support shaft.

  Thereby, since the outer peripheral surface of the second drive joint is reinforced by the guide rib, cracks and breakage of the base portion of the second support shaft are prevented.

  In the second drive joint, the intermediate gear is formed on an outer peripheral surface centering on the second support shaft. The intermediate gear is meshed with an upper portion of a drive gear provided on the fixing roller. In this case, it is preferable that the guide rib is disposed on the upstream side in the rotation direction of the intermediate gear from the meshing point of the intermediate gear and the drive gear.

  Thus, in the configuration in which the intermediate gear is disposed above the drive gear, when the fixing roller suddenly stops due to a jam or the like, the intermediate gear tends to move along the outer periphery of the drive gear. That is, the intermediate gear tends to go from the meshing point of the intermediate gear and the drive gear to the upstream side in the rotation direction of the second support shaft. For this reason, the second support shaft receives a load that is tilted toward the upstream side from the intermediate gear. In order to suppress this load from being applied to the second support shaft, the guide rib is disposed on the upstream side in the rotational direction of the second support shaft from the meshing point. Thereby, the load by the said intermediate gear is applied to a guide rib, As a result, the crack and breakage of the said 2nd spindle are prevented.

  The image forming apparatus of the present invention further includes a plurality of reinforcing ribs provided at the back of the fixing unit. The reinforcing ribs are provided radially outward from the outer peripheral surface of the guide rib in the normal direction.

  Thereby, since the guide rib is reinforced, the guide rib can receive a larger load from the intermediate gear.

  It is preferable that a peripheral edge portion of the insertion hole is formed in a tapered shape.

  Thereby, since the protrusion part of the said 1st spindle is easily guided by the said insertion hole, the said drive transmission part and the said driven transmission part are connected easily.

  The fixing unit has a frame having a uniform thickness formed by injection molding a synthetic resin material. The second support shaft is formed integrally with the frame and has an outer diameter larger than the uniform thickness. In this case, it is preferable that the insertion hole of the second support shaft is formed by stealing the second support shaft so as to have the uniform thickness. The present invention is suitable for such a configuration.

  According to the image forming apparatus of the present invention, it is possible to prevent the shaft of the driven transmission portion of the fixing unit from being cracked or broken.

1 is a perspective view showing an external configuration of an image forming apparatus 10 according to an embodiment of the present invention. FIG. 3 is a perspective view showing an external configuration of a fixing unit 18. FIG. 3 is an exploded perspective view showing a driven transmission unit 40 of the fixing unit 18. FIG. 3 is an enlarged perspective view showing a rear portion of the fixing unit 18. The schematic diagram which shows the periphery mechanism of the drive gear 48 and the intermediate | middle gear 49. FIG. FIG. 4 is a partial perspective view showing a configuration of a drive unit 60. FIG. 6 is a partially enlarged perspective view showing a configuration of a joint 69 of the drive unit 60. The fragmentary sectional view which shows the cross-section of the cut surface VIII-VIII in FIG. The partial expansion perspective view which shows the structure of the modification 1 of this invention. The partial expansion perspective view which shows the structure of the modification 2 of this invention. Sectional drawing which shows the structure of the conventional drive transmission mechanism typically.

  A copying machine 10 (an example of an image forming apparatus of the present invention) according to an embodiment of the present invention will be described below with reference to the drawings as appropriate. The embodiment described below is merely an example embodying the present invention, and the embodiment of the present invention can be changed as appropriate without departing from the scope of the present invention. In the following description, the vertical direction 7 is defined with reference to the state where the copying machine 10 is installed (the state shown in FIG. 1), and the side on which the operation display unit 17 is provided is the front side (front side). ), The front-rear direction 8 is defined, and the left-right direction 9 is defined when the copying machine 10 is viewed from the front side (front side).

  First, a schematic configuration of the copying machine 10 will be described with reference to FIG. As shown in FIG. 1, a copying machine 10 transfers a read original image onto a recording sheet, and is provided with a scanner 12 for reading the original image on the upper portion and an electrophotographic image forming portion on the lower portion. A unit 14 (corresponding to the apparatus main body of the present invention) is provided. In FIG. 1, the document cover of the scanner 12 is not shown.

  The image forming unit 14 forms a monochrome image or a color image on recording paper based on the image data read by the scanner 12, and mainly includes a paper feed tray 16 capable of holding the recording paper, and a paper feed tray 16 A transfer device (not shown) for transferring the toner image to the recording paper fed from the printer, a fixing unit 18 (an example of the fixing unit of the present invention) for fixing the toner image transferred to the recording paper to the recording paper, and an operation The display unit 17 and a drive unit 60 (an example of the drive transmission unit of the present invention, see FIG. 6) are provided. These components are arranged inside a casing 20 that constitutes a housing of the image forming unit 14. Between the upper part of the casing 20 and the scanner 12, a paper discharge space 21 whose front is open is defined. A paper discharge tray 23 divides the lower surface of the paper discharge space 21. The recording paper fed from the paper feed tray 16 is moved upward along a conveyance path (not shown) defined on the left side in the casing 20, and a toner image is transferred onto the recording paper in the moving process. The toner image transferred to the recording paper is fixed on the recording paper by being heated and melted when passing through the fixing unit 18. The recording paper that has passed through the fixing unit 18 is discharged into the paper discharge space 21 and held on the paper discharge tray 23.

  As shown in FIG. 1, the fixing unit 14 is provided on the left side of the upper portion of the casing 20. The fixing unit 14 is supported so as to be slidable in the front-rear direction 8 so that it can be inserted into and removed from the casing 20. Specifically, the fixing unit 14 includes a mounting position (corresponding to the first position of the present invention) mounted in the rear rear part of the casing 20 and a withdrawal that is pulled forward from the casing 20 as shown in FIG. It is slidably supported between positions (corresponding to the second position of the present invention). In this embodiment, when the fixing unit 14 is disposed at the mounting position, a driving force can be transmitted from the driving unit 60 (see FIG. 6) in the image forming unit 14 to the fixing unit 14. Further, when the fixing unit 14 is pulled forward from the mounting position and is not mounted, transmission of the driving force from the driving unit 60 is interrupted.

  Hereinafter, the configuration of the fixing unit 14 and the drive unit 60 will be described in detail with reference to FIGS. 2 to 5. In each figure, the posture of the fixing unit 14 when attached to the casing 20 is shown. For convenience of explanation, the vertical direction in the attached posture is the vertical direction 7, and the insertion / removal direction with respect to the casing 20 is the front-rear direction. The direction is 8 and the horizontal direction is 9 in the left-right direction. FIG. 5 is a schematic view of the peripheral mechanism of the drive gear 48 and the intermediate gear 49 when viewed from the rear.

  As shown in FIG. 2, the fixing unit 14 has a long shape in the front-rear direction 8, and is supported by a frame 34 extending in the front-rear direction 8 and side frames 35, 36 at both ends in the longitudinal direction of the frame 34. The fixing roller 38 (see FIG. 3) and a pressure roller (not shown) are provided. The fixing roller 38 is rotatably supported by the side frames 35 and 36. The frame 34 is a synthetic resin product formed by pouring molten synthetic resin into a mold and performing injection molding (injection molding). In general, a dissolved synthetic resin shrinks when cooled and hardened. Therefore, the frame 34 is formed to have an equal thickness so that the so-called “sink” does not occur in the frame 34 due to the contraction. Note that “sink” refers to defects such as dents, depressions, and distortion caused by shrinkage differences caused by uneven thickness in synthetic resin products.

  In the fixing unit 18, the surface temperature of the fixing roller 38 is heated to about 250 ° C. in order to melt the toner. Therefore, in the present embodiment, as the material of the frame 34 of the fixing unit 18, among thermoplastic synthetic resins, PET resin (polyethylene terephthalate) excellent in heat resistance and strength or a synthetic resin mainly composed of a PET resin is used. It has been. Of course, the frame 34 may be formed of a synthetic resin other than the PET resin as long as it can withstand the high temperature environment of the fixing unit 18.

  As shown in FIG. 2, the driven transmission connected to the drive unit 60 of the image forming unit 14 is connected to the back side of the fixing unit 14, specifically, to the side frame 35 on the rear side of the frame 34. A portion 40 (an example of a driven transmission portion of the present invention) is provided. The driven transmission unit 40 transmits the driving force from the driving unit 60 to the fixing roller 38.

  As shown in FIG. 3, the driven transmission portion 40 includes a support shaft 41 (an example of a second support shaft of the present invention) that protrudes rearward from the side frame 35 and a joint that is rotatably provided on the support shaft 41. 42 (an example of the second drive joint of the present invention). A plurality of reinforcing ribs 51 (see FIG. 4) are provided at the connection portion between the base portion 44 of the support shaft 41 and the side frame 35 along the outer peripheral surface of the base portion 44. The support shaft 41 is configured integrally with the frame 34 and is formed integrally with the frame 34 by injection molding. Therefore, the support shaft 34 is formed of the same material as the frame 34, that is, PET resin.

  The joint 42 is a portion that receives a driving force from the driving unit 60, and therefore, a strong rotational load is applied to the joint 42. Therefore, the outer diameter of the support shaft 41 is designed to be large enough to withstand the rotational load, and is at least larger than the thickness of the frame 34. On the other hand, since the support shaft 41 is integrated with the frame 34, if the outer diameter of the support shaft 41 is larger than the thickness of the frame 34, “sink” is likely to occur on the support shaft 41. Therefore, so-called meat stealing is performed on the support shaft 41. Specifically, the core portion of the support shaft 41 is deeply dug along the axial direction from the center of the distal end portion (rear end portion) 45 of the support shaft 41. As a result, a cylindrical hole 43 (an example of the insertion hole of the present invention) extending from the distal end portion 45 along the support shaft 41 is formed in the shaft core portion of the support shaft 41. The hole 43 extends from the distal end portion 45 of the support shaft 41 to the vicinity of the base portion 44 of the support shaft 41 located on the side frame 35 side. The thickness of the hole 43 and the outer peripheral wall of the support shaft 41 (the thickness of the support shaft 41) is the same size as the thickness of the frame 34 by performing the above-described wall stealing on the support shaft 41. This meat theft prevents the “sink” that occurs when a thicker part of the frame 34 is cooled and hardened after the injection molding.

  When the driven transmission unit 40 and the drive unit 60 are connected to each other, the protrusion 43 (see FIG. 7) of the drive unit 60 is inserted into the hole 43. At this time, a tapered portion 55 (see FIG. 4) formed in a tapered shape is provided at the peripheral portion of the opening on the rear side of the hole 43 so that the protruding portion 62 is smoothly inserted. The tapered portion 55 is formed by tapering the peripheral edge portion of the hole 43 from the distal end portion 45 of the support shaft 41 toward the front. Thereby, the protrusion 62 is smoothly inserted into the hole 43 so as to be guided by the tapered portion.

  The joint 42 includes a coupled portion 46 that is coupled to a drive unit 60 (see FIG. 6), which will be described later, and an intermediate gear 49 that meshes with a drive gear 48 that is provided coaxially with the fixing roller 38. The intermediate gear 49 is composed of a plurality of teeth integrally formed on the outer peripheral surface centering on the axis of the joint 42. A shaft hole 47 that can be inserted into the support shaft 41 is formed at the center of the joint 42. The joint 42 is mounted in the direction of the arrow in FIG. 3, and the support shaft 41 is passed through the shaft hole 47, so that the joint 42 is rotatably supported by the support shaft 41. With the joint 42 supported by the support shaft 41, the intermediate gear 49 is meshed with the drive gear 48.

  The intermediate gear 49 is disposed above the drive gear 48 of the fixing roller 38. That is, with the joint 42 attached to the support shaft 41, the intermediate gear 49 is disposed above the drive gear 48, and the lower portion of the intermediate gear 49 and the upper portion of the drive gear 48 are engaged. In this embodiment, the fixing roller 38 rotates in the direction of the arrow 26 shown in FIG. 4 (counterclockwise direction when viewed from the rear) in order to fix the toner while conveying the recording paper upward in the image forming unit 14. Is done. Therefore, a driving force for rotating the joint 42 in the direction of the arrow 27 opposite to the arrow 26 (clockwise direction when viewed from the rear) is transmitted to the joint 42.

  As shown in FIG. 4, guide ribs 53 are formed on the rear side surface of the side frame 35. The guide rib 53 is formed integrally with the side frame 35. The guide rib 53 protrudes rearward from the side frame 35. The guide rib 53 is formed in an arc shape centered on the axis of the support shaft 41. Specifically, when the joint 42 is attached to the support shaft 41, the same curvature as that of the outer peripheral surface of the intermediate gear 49 does not interfere with the outer peripheral surface of the intermediate gear 49 of the joint 42 and is along the outer peripheral surface. The arc shape is formed.

  As shown in FIG. 5, the guide rib 53 is disposed on the upstream side in the rotational direction 26 of the joint 42 from the meshing point 57 between the intermediate gear 49 and the drive gear 48. In other words, the guide rib 53 is disposed on the upstream side in the rotational direction 26 as viewed from the meshing point 57 with respect to the line segment connecting the support shaft 41 and the meshing point 57. Therefore, if the recording paper is jammed by the fixing unit 18 and an excessive load is applied to the fixing roller 38 and the fixing roller 38 stops, the intermediate gear 49 rotates around the drive gear 48 from the meshing point 57. Even if an attempt is made to move upstream in the direction 27, the movement is blocked by the guide rib 53. As a result, the support shaft 41 is prevented from being tilted and broken due to excessive movement of the intermediate gear 49. The side frame 35 is provided with a plurality of reinforcing ribs 54 that are provided radially outward from the outer peripheral surface of the guide rib 53 in the normal direction. Thereby, even if the intermediate gear 49 strongly presses against the guide rib 53, the movement of the intermediate gear 49 can be reliably prevented.

  Hereinafter, the configuration of the drive unit 60 provided in the image forming unit 14 will be described in detail with reference to FIGS. 6 to 8. The drive unit 60 is provided in the rear rear part of the casing 20 so as to face the side frame 35 of the fixing unit 18. As shown in FIG. 6, the drive unit 60 includes a front support plate 63 disposed on the front side, a rear support plate 64 disposed on the rear side, a motor 66 that is a drive source of the fixing roller 38, and a plurality of drive units 60. , A joint 69 (an example of the first drive joint of the present invention) connected to the gear train 67, and a support shaft 75 that supports the joint 69 (an example of the first support shaft of the present invention). And. The motor 66 is attached to the rear support plate 64. An output gear (not shown) of the motor 66 is engaged with a gear train 67 including a plurality of gears rotatably supported between the front support rate 63 and the rear support plate 64.

  As shown in FIG. 8, a support shaft 75 is fixed to the front support plate 63 and the rear support plate 64. The support shaft 75 extends in a direction in which the fixing unit 18 is removed from the casing 20. Specifically, the support shaft 75 is bridged to the front support plate 63 and the rear support plate 64 so that the axial direction thereof coincides with the front-rear direction 8 and is coaxial with the support shaft 41 of the fixing unit 18. It is attached to be. A joint 69 is rotatably supported on the support shaft 75.

  As shown in FIG. 7, the joint 69 includes a connecting portion 71 that is connected to the joint 42 of the driven transmission portion 40, and an intermediate gear 73 that is meshed with the gear train 67. The intermediate gear 73 is composed of a plurality of teeth integrally formed on the outer peripheral surface centering on the axis of the joint 69. A shaft hole 77 that can be inserted into the support shaft 75 is formed at the center of the joint 69. Since the support shaft 75 is passed through the shaft hole 77 of the joint 69, the joint 69 is rotatably supported by the support shaft 75. With the joint 69 supported by the support shaft 75, the intermediate gear 73 is engaged with the gear train 67. Thus, when the motor 66 is driven, the driving force of the motor 66 is transmitted to the joint 42 of the fixing unit 18 through the gear train 67, the intermediate gear 73, and the connecting portion 71.

  A pin-like protrusion 62 (an example of the protrusion of the present invention) protruding rearward from the center of the tip 79 is formed at the tip (back end) 79 of the support shaft 75. As for the protrusion part 62, the trunk | drum is formed in the column shape, and the front-end | tip part is formed in the taper shape. The protrusion 62 is formed in a size that can be inserted into the hole 43 on the fixing unit 18 side. In the present embodiment, the hole 43 and the protruding portion 62 are formed in a size such that the gap fits.

  Since the copying machine 10 of the present embodiment is configured as described above, when the fixing unit 18 is inserted into the casing 20 of the image forming unit 14 and disposed at the mounting position, the hole of the support shaft 41 of the fixing unit 18 is formed. A protrusion 62 is inserted into 43. Accordingly, the base portion 44 of the support shaft 41 is supported by the side frame 35, while the tip portion 45 of the support shaft 41 is supported by the protruding portion 62 of the support shaft 75. As a result, the support shaft 41 of the fixing unit 18 is supported by both the base portion 44 and the tip portion 45, and even if an excessive rotational load is applied to the fixing roller 38, cracking or breakage of the support shaft 41 is prevented. Is done.

  In the above-described embodiment, the case where the hole 43 of the support shaft 41 is formed in a cylindrical shape and the protruding portion 62 of the support shaft 75 is formed in a columnar shape is illustrated. For example, as shown in FIG. A hole 43A (see FIG. 9A) formed in a triangular cylindrical shape is formed in the support shaft 41, and a triangular prism-shaped protrusion 62A (see FIG. 9B) is provided in the support shaft 75, so that the hole 43A It is also possible to adopt a configuration in which the projecting portion 62A can be inserted. As shown in FIG. 10, a hole 43 </ b> B (see FIG. 10A) formed in a rectangular tube shape is formed in the support shaft 41, and a quadrangular columnar protrusion 62 </ b> B (FIG. It is also possible to employ a configuration in which the protrusion 62B can be inserted into the hole 43B.

  The present invention can be used in an image forming apparatus in which a fixing unit having a fixing roller is detachably attached to the apparatus main body.

10: copier 12: scanner 14: image forming unit 18: fixing unit 20: casing 34: frame 35: side frame 38: fixing roller 40: driven transmission unit 41: support shaft 42: joint 43: hole 48: driving gear 49: Intermediate gear 51: Reinforcing rib 55: Tapered portion 57: Engagement point 60: Drive unit 62: Protruding portion 66: Motor 67: Gear train 69: Joint 70: Connecting portion 73: Intermediate gear

Claims (6)

Between a first position having a fixing roller rotatably supported and capable of transmitting a driving force from the apparatus main body to the fixing roller and a second position where transmission of the driving force to the fixing roller is interrupted A fixing unit provided in the apparatus main body so that it can be inserted and removed at
A driven transmission unit that is provided at a depth in the insertion direction of the fixing unit and that transmits a driving force transmitted from the apparatus main body to the fixing roller at the first position;
A drive transmission unit provided in the apparatus main body so as to be opposed to a back part of the fixing unit, and transmitting the driving force to the driven transmission unit;
The drive transmission unit is
A first support shaft extending in the removal direction of the fixing unit;
A first drive joint rotatably provided on the first support shaft;
A protrusion protruding from the tip of the first spindle in the removal direction,
The driven transmission unit is
A second spindle extending in the insertion direction from the back of the fixing unit;
A second drive joint which is rotatably provided on the second support shaft and receives a driving force in the axial rotation direction from the first drive joint by being axially connected to the first drive joint;
An image forming apparatus, comprising: an insertion hole provided at a tip of the second support shaft and into which the protrusion can be inserted when the fixing unit is inserted into the first position.   The image forming apparatus according to claim 1, further comprising an arcuate guide rib provided at a back portion of the fixing unit and having the second support shaft as a center. The second drive joint has an intermediate gear formed on an outer peripheral surface centered on the second support shaft,
The intermediate gear is meshed with an upper portion of a drive gear provided on the fixing roller,
The image forming apparatus according to claim 2, wherein the guide rib is disposed on an upstream side in a rotation direction of the intermediate gear from a meshing point between the intermediate gear and the drive gear.   4. The image forming apparatus according to claim 2, further comprising a plurality of reinforcing ribs provided in a back portion of the fixing unit and radially provided outward from the outer peripheral surface of the guide rib in the normal line direction.   The image forming apparatus according to claim 1, wherein a peripheral edge portion of the insertion hole is formed in a tapered shape. The fixing unit has a uniform thickness frame formed by injection molding a synthetic resin material,
The second support shaft is formed integrally with the frame and has an outer diameter larger than the uniform thickness.
The image forming apparatus according to claim 1, wherein the insertion hole of the second support shaft is formed by stealing the second support shaft so as to have the uniform thickness.