JP6643010B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus that forms an image using an electrophotographic method.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus, or a composite image forming apparatus that integrally combines them has an image forming unit such as an image carrier, an intermediate transfer body, and a developing device. . Some of these image forming units are detachable from the image forming apparatus main body.

  In such a configuration, the drive from the drive motor, which is the drive source of the image forming unit, is transmitted via the connecting means that can be connected and separated when the image forming unit is attached and detached. Therefore, high positional accuracy is required between the connecting means and the image forming unit.

  If the positional accuracy between the connecting means and the image forming unit is not sufficient, positional fluctuations occur due to rotational fluctuations and vibrations of the image carrier and the intermediate transfer body. As a result, there is a possibility that an image defect such as occurrence of periodic band-like shading unevenness called banding and deviation of an image writing position may occur.

  It is necessary to increase the positional accuracy between the connecting means and the image forming unit. For this purpose, for example, in Patent Literature 1, one end of a positioning member provided in a drive unit is connected to a drive support member that is arranged to face a support member provided in the image forming apparatus main body at a predetermined interval. I have. Further, there has been proposed a configuration in which the other end of the positioning member protrudes through a support member provided in the image forming apparatus main body, and is fitted to the image forming unit for positioning.

JP 2005-43387 A

  In the method of supporting the drive unit as in Patent Document 1, the material of the drive support member is not specified. Therefore, when a highly flexible resin member is used for the purpose of weight reduction and miniaturization, it is difficult to guarantee positional accuracy by thermal deformation.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing image defects such as banding and image writing position shift.

A typical configuration of the image forming apparatus according to the present invention for achieving the above object is an image forming apparatus , which includes a frame of the image forming apparatus, a rotatable photosensitive member, and a driving force applied to the photosensitive member. anda drive transmission device for transmitting the drive transmission device includes a drive shaft which rotates to transmit the driving force to the photosensitive member, a metal frame which is fixed to a frame of the image forming apparatus, wherein A first support member through which the drive shaft is inserted through a metal frame to support the drive shaft; and a resin frame having a larger linear expansion coefficient than the metal frame of the first support member , and a rotational axis direction of the drive shaft. It said first support member has a a second support member for supporting the drive shaft is inserted through the drive shaft to the resin frame at a position away from the portion for supporting the drive shaft in the resin frame Provided on the resin frame screw holes and the second support member bis is fastened to secure the second support member with respect to the frame of the image forming apparatus, the drive of the resin frame and the screw hole axis, characterized in that it comprises a and an opening formed between the insertion has been inserted portion.

  According to the present invention, it is possible to suppress image defects such as banding and image writing position shift.

FIG. 1 is an explanatory cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. (A) is a perspective explanatory view of the engagement state between the drive transmission device and the photosensitive drum as viewed from the front side. (B) is a perspective explanatory view of the engagement state between the drive transmission device and the photosensitive drum as viewed from the back side. It is a front explanatory view showing the composition of the drive transmission device of a 1st embodiment. FIG. 3 is an explanatory front view showing a configuration of a gear train of the drive transmission device. It is a perspective explanatory view showing fall of a drive shaft in a comparative example in which an opening is not formed around a fastening part of a resin frame. (A) is a figure which shows the structure of the opening formed around the fastening part of the resin frame. FIG. 4B is a diagram illustrating an effect of absorbing thermal deformation by an opening formed around a fastening portion of the resin frame. It is a front explanatory view showing the composition of the drive transmission device of a 2nd embodiment. It is a front explanatory view showing the composition of the drive transmission device of a 3rd embodiment. It is front explanatory drawing which shows the structure of the drive transmission device of 4th Embodiment.

  An embodiment of the image forming apparatus according to the present invention will be specifically described with reference to the drawings.

  First, the configuration of an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS. The dimensions, materials, relative positions, and the like of the components of the image forming apparatus 1 described below are not intended to limit the scope of the present invention to them unless otherwise specified. . Also, in each figure, the components denoted by the same reference numerals have the same configuration or operation, and redundant description thereof will be omitted as appropriate.

<Image forming apparatus>
FIG. 1 is an explanatory cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. The image forming apparatus 1 shown in FIG. 1 is an example of a full-color image forming apparatus including a multifunction peripheral having a copy function, a printer function, and a facsimile function.

  In FIG. 1, an image forming apparatus 1 is a plurality of (four in the present embodiment) image forming units which are detachably attached to the main body of the image forming apparatus 1 (the main body of the image forming apparatus), and The photosensitive drum 2 includes a drum-shaped electrophotographic photosensitive member.

  The photosensitive drums 2Y, 2M, 2C, and 2Bk of the present embodiment respectively share a yellow Y component, a magenta M component, a cyan C component, and a black Bk component from the left side in FIG. For convenience of description, the photosensitive drums 2Y, 2M, 2C, and 2Bk may be simply described using the photosensitive drum 2 as a representative. The same applies to other image forming process means.

  The photosensitive drums 2 of the respective colors are driven at a predetermined process speed (264 mm / sec in the present embodiment) in a counterclockwise direction in FIG. 1 by a drum drive unit 3 serving as a drive transmission device shown in FIGS. 2 (a) and 2 (b). It is driven to rotate.

  Around the photosensitive drums 2, a charging roller 29 serving as a charging unit for uniformly charging the surface of the photosensitive drum 2 is provided. Further, the surface of the photosensitive drum 2 uniformly charged by the charging roller 29 is irradiated with a laser beam 4a based on image information to form an image exposure unit for forming an electrostatic latent image on the surface of the photosensitive drum 2. A laser scanner 4 is provided.

  Further, there is provided a developing device 5 or the like which is a developing unit for attaching toner to the electrostatic latent image formed on the surface of the photosensitive drum 2 and developing it as a developer image (toner image).

  An intermediate transfer belt 10 serving as an intermediate transfer member is provided facing the surface of each photosensitive drum 2. The intermediate transfer belt 10 is stretched by a drive roller 6, a tension roller 9 and a secondary transfer inner roller 8 so as to be rotatable in the direction of arrow a in FIG.

  On the inner peripheral surface side of the intermediate transfer belt 10, primary transfer rollers 7 serving as primary transfer means facing the surface of each photosensitive drum 2 via the intermediate transfer belt 10 are provided, respectively.

  The intermediate transfer belt 11, the driving roller 6, the tension roller 9, the secondary transfer inner roller 8, and the primary transfer roller 7 constitute an intermediate transfer device 11.

  The drive roller 6 is driven to rotate by a motor (not shown) serving as a drive source. As a result, the intermediate transfer belt 10 is driven to rotate so that the peripheral speed of the outer peripheral surface is substantially equal to the process speed of each photosensitive drum 2.

  Each primary transfer roller 7 is pressed against the surface of each photosensitive drum 2 via the intermediate transfer belt 10. Each primary transfer roller 7 sequentially primary-transfers and superimposes the toner image formed on the surface of each photosensitive drum 2 onto the outer peripheral surface of the intermediate transfer belt 10 rotating in the direction of arrow a in FIG. As a result, a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 10.

  On the other hand, the recording materials S stacked in the feeding cassette 13 are sequentially fed out from the uppermost recording material S by the feeding roller 30, and are separated and fed one by one in cooperation with a separating unit (not shown). Thereafter, the leading end abuts on the registration roller 33 which has been conveyed along the conveyance path 32 by the conveyance roller 31 and stopped once, and the skew is corrected by the stiffness of the recording material S. Thereafter, the recording material S is nipped and conveyed by the registration roller 33 and conveyed at a predetermined timing to a secondary transfer nip formed by the outer peripheral surface of the intermediate transfer belt 10 and the outer secondary transfer roller 12.

  A secondary transfer outer roller 12 which is a secondary transfer unit and serves as a secondary transfer rotating member is disposed opposite to the secondary transfer inner roller 8 via an intermediate transfer belt 10.

  The recording material S conveyed to the secondary transfer nip portion between the secondary transfer outer roller 12 and the secondary transfer inner roller 8 via the intermediate transfer belt 10 is applied to the recording material S on the outer peripheral surface of the intermediate transfer belt 10. The transferred full-color toner image is secondarily transferred.

  In the secondary transfer nip portion, the toner image on the outer peripheral surface of the intermediate transfer belt 10 is secondarily transferred to the recording material S by the operation of the secondary transfer outer roller 12. The toner image secondary-transferred onto the recording material S is heated and pressurized while being nipped and conveyed by a fixing roller and a pressure roller provided in a fixing device 14 serving as a fixing unit, and is thermally fixed and then discharged. It is discharged onto the tray 15.

<Drive transmission device>
Next, the configuration of the drum drive unit 3 serving as the drive transmission device of the present embodiment will be described with reference to FIGS. FIG. 2A is a perspective view illustrating the engagement state between the drum drive unit 3 and the photosensitive drum 2 as viewed from the front side. FIG. 2B is a perspective explanatory view of the engagement state between the drum drive unit 3 and the photosensitive drum 2 as viewed from the rear side.

  FIG. 3 is an explanatory front view showing the configuration of the drum drive unit 3 of the present embodiment. FIG. 4 is an explanatory front view showing the configuration of the gear train of the drum drive unit 3.

  The drum drive unit 3 of the present embodiment integrally rotates the photosensitive drums 2Y, 2M, and 2C shown in FIGS. 2A and 2B by a motor 16a serving as a drive source. Further, the photosensitive drum 2Bk is independently driven to rotate by a motor 16b serving as a drive source.

  In many cases, a direct current (DC) brushless motor is used for the motors 16a and 16b, and the rotation speed is generally about 2000 rpm (rotation per minute) to 3000 rpm from the viewpoint of efficiency.

  The photosensitive drum 2 is driven to rotate at a predetermined process speed. For this purpose, as shown in FIG. 4, a drive gear 16G provided coaxially with the respective drive shafts of the motors 16a and 16b is considered. Further, drum gears 17Y, 17M, 17C, and 17Bk provided coaxially with the rotation axis of each photosensitive drum 2 are considered. The rotational speed transmitted from each of the motors 16a and 16b is reduced by these gear ratios.

As shown in FIG. 4, the drive gear 16Ga provided coaxially with the drive shaft of the motor 16a that rotationally drives the photosensitive drums 2Y, 2M, 2C is as follows. The driving gear 16Ga is disposed between any two of the drum gears 17Y, 17M, 17C provided coaxially with the rotation axes of the photosensitive drums 2Y, 2M, 2C of each color. The remaining one of the drum gears 17Y, 17M, and 17C is transmitted by an idler gear 18.

  In the present embodiment shown in FIG. 4, an example is shown in which a drive gear 16Ga is arranged and meshed between the drum gears 17M and 17C, and the drum gear 17Y is meshed with the drum gear 17M via the idler gear 18. Thus, the photosensitive drums 2Y, 2M, 2C can be rotated at the same speed in the same direction via the drive gear 16Ga, the drum gears 17M, 17C, the idler gear 18, and the drum gear 17Y by the rotation of the motor 16a.

  A drive gear 16Gb provided coaxially with a drive shaft of a motor 16b that rotates the photosensitive drum 2Bk is meshed with a drum gear 17Bk provided coaxially with the rotation shaft of the photosensitive drum 2Bk. The rotation of the motor 16b allows the photosensitive drum 2Bk to rotate independently via the drive gear 16Gb and the drum gear 17Bk, or to rotate at the same speed in the same direction as each of the photosensitive drums 2Y, 2M, 2C.

  A drive shaft 19 shown in FIG. 3 is connected to each drum gear 17. The rotational driving force transmitted from each of the motors 16 a and 16 b to each of the drum gears 17 is engaged with each of the photosensitive drums 2 by a coupling member 20 provided at the end of the drive shaft 19 so as to be able to be transmitted to each of the photosensitive drums 2.

  A drive shaft 19 provided on the drum drive unit 3 serving as a drive transmission device is connected to each photosensitive drum 2 serving as an image forming unit via a coupling member 20 to transmit rotational drive.

  As shown in FIG. 3, a fitting hole 21 is formed at the tip of the drive shaft 19. A part of the photosensitive drum 2 fits into the fitting hole 21. Thereby, the photosensitive drum 2 is positioned with respect to the image forming apparatus 1 main body. That is, the photosensitive drum 2 serving as an image forming unit is positioned by fitting with the drive shaft 19.

  The drum gear 17 shown in FIG. 4 is arranged in a drive box 22 shown in FIG. The drive box 22 includes two frames: a sheet metal frame 23 serving as a first support member having a different linear expansion coefficient, and a resin frame 24 serving as a second support member having a larger linear expansion coefficient than the sheet metal frame 23. I have. The coefficient of linear expansion refers to the ratio between the initial size of each frame and the amount of displacement due to thermal expansion at a temperature of 1 ° C.

  In the present embodiment, as shown in FIG. 3, the drive box 22 has a sheet metal frame 23 made of an iron-based material and serving as a first support member. Further, a resin frame 24 serving as a second support member having a larger linear expansion coefficient than the sheet metal frame 23 is provided. The resin frame 24 is made of a polymer alloy of ABS resin (a copolymer synthetic resin of acrylonitrile, butadiene, and styrene) and polycarbonate.

  The two sheet metal frames 23 having different coefficients of linear expansion and the resin frame 24 are fastened to each other at the fastening portions 25 serving as connecting portions of the support members at a plurality of locations. Thereby, the drive box 22 is formed in a box shape.

<Tightening part of support member>
The fastening portions 25 serving as fastening portions of the support members are arranged at substantially equal intervals with respect to the four drive shafts 19 shown in FIG. The drive shaft 19 connected to each drum gear 17 shown in FIG. 4 includes a sheet metal frame 23 serving as a first support member and a resin frame 24 serving as a second support member having a larger linear expansion coefficient than the sheet metal frame 23. Is fitted and held. Thus, the drive shaft 19 is rotatably supported by the drive box 22.

<Main body fastening part>
Next, the configuration of the fastening portion 26 serving as a body fastening portion between the main body of the image forming apparatus 1 and the drive box 22 will be described with reference to FIG. The drive box 22 shown in FIG. 3 has a main body that is fastened and fixed to the frame of the main body of the image forming apparatus 1 at a plurality of positions of a sheet metal frame 23 serving as a first support member and a resin frame 24 serving as a second support member. It has fastening portions 26F and 26M serving as fastening portions.

  The fastening portion 26F serving as the first body fastening portion illustrated in FIG. 3 fastens and fixes the sheet metal frame 23 to the frame of the image forming apparatus 1 body. The fastening portion 26M serving as the second body fastening portion fastens and fixes the resin frame 24 to the frame of the image forming apparatus 1 body. At least one of the fastening portions 26F and 26M is arranged to face the drive shaft 19.

  In the present embodiment, the drive box 22 is fixed to the main body of the image forming apparatus 1 by fastening the fastening portions 26 with screws (not shown) or the like. The drum drive unit 3 serving as the drive transmission device is fastened and fixed to the frame of the image forming apparatus 1 main body by the fastening portion 26F serving as the first main body fastening portion of the sheet metal frame 23 serving as the first support member.

  In the present embodiment, as shown in FIG. 3, the fastening portion 26F of the sheet metal frame 23 and the fastening portion 26M of the resin frame 24 are arranged on the opposite side with respect to the drive shaft 19. The fastening portion 26M serving as the second body fastening portion of the resin frame 24 serving as the second support member is as follows.

  As shown in FIGS. 6A and 6B, an arc-shaped opening 27 of about 135 ° (1/4 turn or more) around the fastening portion 26M is formed at the outer peripheral portion of the fastening portion 26M. (Drive shaft side) (upward in FIGS. 6A and 6B). The fastening portion 26M fastens and fixes the frame of the image forming apparatus 1 body and the resin frame 24 at a portion of the resin frame 24 other than the arc-shaped opening 27.

<Effect of opening>
Next, the effect of the opening 27 formed around the fastening portion 26M of the resin frame 24 will be described with reference to FIGS. FIG. 5 is a perspective explanatory view showing the fall of the drive shaft 19 in the comparative example in which the opening 27 is not formed around the fastening portion 26M of the resin frame 24. FIG. 6 is a diagram illustrating the effect of the opening 27 formed around the fastening portion 26M of the resin frame 24.

  Usually, the dimensions of the resin member are measured under the measurement environment temperature condition after being left at a measurement environment temperature for a certain period of time. That is, the positional accuracy is guaranteed only within the measurement environment temperature. However, the actual use environment temperature of the image forming apparatus 1 is often different from the measurement environment temperature of the resin member. Therefore, the resin member repeatedly undergoes thermal deformation such as thermal expansion and contraction according to its linear expansion coefficient.

  Usually, thermal deformation of the resin member occurs uniformly within the resin member. Therefore, if the resin member is in a natural state (unsupported state), the adverse effect on the positional accuracy due to thermal deformation is small. However, in a fixed support state in which one end of the resin member is fixed, thermal deformation to the side to which the resin member is fixed is restricted. Therefore, thermal deformation of the resin member occurs only on the non-fixed side. This makes it difficult to ensure the positional accuracy of the resin member.

  In the present embodiment, the drum drive unit 3 is heated by heat generated from the motors 16a and 16b, the fixing device 14, and the like. Thereby, the temperature of the resin frame 24 rises to about 50 ° C. Therefore, in the fixed support state in which the resin frame 24 is fastened to the main body of the image forming apparatus 1, in the comparative example in which the opening 27 is not formed around the fastening portion 26M of the resin frame 24 as shown in FIG. The drive shaft 19 falls down in the directions of arrows d, e, f, and g.

  When the drive shaft 19 is tilted in the directions of arrows d, e, f, and g in FIG. The meshing state of is deteriorated.

  As a result, the photosensitive drum 2 undergoes position fluctuation due to rotation fluctuation and vibration. As a result, image defects such as band-like shading unevenness called banding and deviation of an image writing position occur.

  Further, in the present embodiment, the photosensitive drum 2 is positioned by the drive shaft 19. Therefore, if the drive shaft 19 falls in the directions of arrows d, e, f, and g in FIG. 5, the rotating shaft of the photosensitive drum 2 also falls. This increases the possibility of various image defects.

  In order to solve these problems, in the present embodiment, as shown in FIGS. 3 and 6A and 6B, an opening 27 is provided around the fastening portion 26M of the resin frame 24. Thus, as shown in FIG. 6B, most of the thermal deformation of the resin frame 24 heated by the heat generated from the motors 16a and 16b, the fixing device 14, and the like occurs in the opening 27 serving as the open end. For this reason, the thermal deformation of the resin frame 24 is absorbed by the open end of the opening 27, so that the fall of the drive shaft 19 can be reduced.

  In the present embodiment, as shown in FIGS. 3 and 6A and 6B, the opening 27 is provided around the fastening portion 26M of the resin frame 24. As a comparative example, a case where the opening 27 is not provided around the fastening portion 26M of the resin frame 24 as shown in FIG. 5 is considered. Comparing the inclination amount of the drive shaft 19 in both cases, the embodiment shown in FIGS. 3 and 6A and 6B shows that the inclination amount of the drive shaft 19 is 43 compared to the comparative example shown in FIG. % Could be reduced.

  In the present embodiment, an example of the resin frame 24 has been described as a drive support member that constitutes the drive box 22 of the drum drive unit 3 serving as a drive transmission device. The fall of the drive shaft 19 due to the deformation can be reduced.

  Thereby, it is possible to suppress image defects such as banding and a shift of an image writing position caused by the fall of the drive shaft 19, and the configuration of the drive box 22 serving as a drive support member is flexible and a high-quality image forming apparatus 1 is provided. Can be provided.

  Next, a configuration of an image forming apparatus including a drive transmission device according to a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment have the same reference numerals or the same reference numerals, even if the reference numerals are different.

  FIG. 7 is an explanatory front view showing the configuration of the drum drive unit 3 of the present embodiment. The drum drive unit 3 of the present embodiment is different from the configuration of the drum drive unit 3 of the first embodiment in the support structure of the drive box 22 and the drive shaft 19.

  The drive box 22 of the present embodiment has an auxiliary sheet metal 28 serving as a third support member made of the same material as the sheet metal frame 23 serving as the first support member. The auxiliary sheet metal 28 serving as the third support member is fastened and fixed to the sheet metal frame 23 serving as the first support member and the resin frame 24 serving as the second support member having a larger linear expansion coefficient than the auxiliary sheet metal 28 serving as the third support member. ing.

  The drive shaft 19 is fitted and held by a sheet metal frame 23 serving as a first support member and an auxiliary sheet metal 28 serving as a third support member having the same linear expansion coefficient as the sheet metal frame 23. Thus, the drum gear 17 is rotatably supported.

  The sheet metal frame 23 and the auxiliary sheet metal 28 of the present embodiment are integrally formed. Thereby, the positional accuracy of the drive shaft 19 can be increased as compared with the configuration of the first embodiment.

  Further, the auxiliary sheet metal 28 is thermally deformed integrally with the resin frame 24. In the present embodiment, an opening 27 of １ ／ or more turns is provided on the drive shaft 19 side in the outer peripheral portion of the fastening portion 26M serving as the second main body fastening portion of the resin frame 24 serving as the second support member.

  As a result, much of the thermal deformation of the resin frame 24 heated by the heat generated from the motors 16a and 16b, the fixing device 14, and the like occurs in the opening 27 serving as the open end, as in the first embodiment. For this reason, the fall of the drive shaft 19 can be reduced. Other configurations are the same as those of the first embodiment, and the same effects can be obtained.

  Next, a configuration of an image forming apparatus according to a third embodiment of the present invention will be described with reference to FIG. In addition, the same components as those in the above-described embodiments are denoted by the same reference numerals or the same reference numerals even if the reference numerals are different, and the description is omitted.

  FIG. 8 is an explanatory front view showing the configuration of the drum drive unit 3 of the present embodiment. In this embodiment, as compared with the configuration of the drum drive unit 3 of the first embodiment, the configuration of the drive box 22 and the fastening portion 26 serving as a main body fastening portion between the drive box 22 and the main body of the image forming apparatus 1 are different. different.

  As shown in FIG. 8, the drive box 22 of the present embodiment is configured such that a sheet metal frame 23 serving as a first support member having a different linear expansion coefficient and a resin frame 24 serving as a second support member are fastened to a plurality of support members. It is fastened and fixed at a fastening portion 25 serving as a portion. Thereby, the drive box 22 is formed in a box shape.

  As shown in FIG. 8, the sheet metal frame 23 serving as the first support member is fastened and fixed to the frame of the image forming apparatus 1 main body by a plurality of fastening portions 26F serving as first body fastening portions provided on the sheet metal frame 23. ing.

  The thermal deformation of the sheet metal frame 23 serving as the first support member having a different linear expansion coefficient and the resin frame 24 serving as the second support member forming the drive box 22 is performed by the drive shaft 19 and the fastening portion serving as the fastening portion of the support member. It is proportional to the length up to 25 (length between subjects). Therefore, if the fastening portions 25 between the sheet metal frame 23 and the resin frame 24 are not equidistant from the drive shaft 19, the drive shaft 19 may fall due to thermal deformation.

  Therefore, in the present embodiment, the fall of the drive shaft 19 due to a difference in thermal deformation caused by the distance from the plurality of fastening portions 25 to the drive shaft 19 is suppressed. For this purpose, a fastening portion 25 serving as a fastening portion of the support member of the resin frame 24 serving as the second support member is as follows.

  At the outer peripheral portion of the fastening portion 25, an arc-shaped opening 27 of about 135 ° (1/4 turn or more) is provided toward the drive shaft 19 side (upward in FIG. 8) around the fastening portion 25. Have been. The fastening portion 25 fastens and fixes the sheet metal frame 23 and the resin frame 24 at a portion of the resin frame 24 other than the arc-shaped opening 27.

  As a result, much of the thermal deformation of the resin frame 24 heated by the heat generated from the motors 16a and 16b, the fixing device 14, and the like occurs in the opening 27 serving as the open end, as in the first embodiment.

  Thereby, the fall of the drive shaft 19 due to a difference in thermal expansion caused by a difference in the distance from the fastening portion 25 serving as the fastening portion of the support member between the sheet metal frame 23 and the resin frame 24 to the drive shaft 19 can be suppressed. Other configurations are configured in the same manner as the above embodiments, and the same effects can be obtained.

  Next, a configuration of an image forming apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. In addition, the same components as those in the above-described embodiments are denoted by the same reference numerals or the same reference numerals even if the reference numerals are different, and the description is omitted.

  FIG. 9 is an explanatory front view showing the configuration of the drum drive unit 3 of the present embodiment. In the present embodiment, the configuration for supporting the drive box 22 and the drive shaft 19 is different from the configuration of the drum drive unit 3 of the third embodiment.

  The drive box 22 includes a sheet metal frame 23 serving as a first support member and a third support member having the same material as the sheet metal frame 23 and having the same thermal expansion coefficient as described in the second embodiment shown in FIG. Auxiliary metal plate 28. The auxiliary sheet metal 28 serving as the third support member is fastened and fixed to the sheet metal frame 23 serving as the first support member and the resin frame 24 serving as the second support member having a larger thermal expansion coefficient than the auxiliary sheet metal 28 serving as the third support member. ing.

  The drive shaft 19 is fitted and held by a sheet metal frame 23 serving as a first support member and an auxiliary sheet metal 28 serving as a third support member having the same thermal expansion coefficient as the sheet metal frame 23. Thus, the drum gear 17 is rotatably supported.

  The sheet metal frame 23 and the auxiliary sheet metal 28 are integrally formed. Thereby, the positional accuracy of the drive shaft 19 can be improved as compared with the configuration of the drum drive unit 3 of the third embodiment.

  Further, the auxiliary sheet metal 28 is thermally deformed integrally with the resin frame 24. The sheet metal frame 23 serving as a first support member and the resin frame 24 serving as a second support member are fastened and fixed by a fastening portion 25 serving as a fastening portion of the support member.

  The fastening portion 25 serving as a fastening portion of the support member of the resin frame 24 serving as the second support member has an arc shape of about 135 ° (1/4 turn or more) around the fastening portion 25 around the fastening portion 25. Opening 27 is provided toward the drive shaft 19 side (upward in FIG. 9). The fastening portion 25 serving as a fastening portion of the support member fastens and fixes the sheet metal frame 23 and the resin frame 24 at a portion of the resin frame 24 other than the arc-shaped opening 27.

  As a result, most of the thermal deformation of the resin frame 24 heated by the heat generated from the motors 16a and 16b, the fixing device 14, and the like occurs in the opening 27 serving as the open end. This makes it possible to prevent the drive shaft 19 from falling due to a difference in thermal expansion caused by a difference in the distance between the drive portion 19 and the fastening portion 25 between the sheet metal frame 23 and the resin frame 24 which are fastening portions of the support member.

  In the configuration in which the drive box 22 supports the drive shaft 19, it is possible to reduce the inclination of the drive shaft 19 due to thermal deformation, regardless of the material of the members forming the drive box 22. Other configurations are configured in the same manner as the above embodiments, and the same effects can be obtained.

1. Image Forming Apparatus 2, 2Y, 2M, 2C, 2Bk ... Photosensitive Drum (Image Forming Means; Image Carrier)
19: drive shaft 23: sheet metal frame (first support member)
24 resin frame (second support member)
26, 26F, 26M ... fastening part (main body fastening part)
26F: Fastening portion (first body fastening portion) between sheet metal frame 23 and the frame of image forming apparatus 1 main body
26M: fastening portion between resin frame 24 and frame of image forming apparatus 1 main body (second main body fastening portion)
27 ... Opening

Claims (6)

An image forming apparatus,
A frame of the image forming apparatus ;
A rotatable photoconductor ,
A drive transmission device for transmitting a drive force to the photoconductor ,
Has,
The drive transmission device,
A drive shaft which rotates to transmit the driving force to the photosensitive member,
A first support member including a metal frame fixed to a frame of the image forming apparatus, wherein the drive shaft is inserted through the metal frame to support the drive shaft ,
A resin frame having a larger linear expansion coefficient than the metal frame of the first support member, wherein the first support member is spaced apart from a portion supporting the drive shaft in a rotational axis direction of the drive shaft. A second support member through which the drive shaft is inserted to support the drive shaft ,
Has ,
The resin frame ,
A screw hole in which a screw is fastened to fix the second support member to the frame of the image forming apparatus is provided in the resin frame of the second support member , and the screw hole and the driving in the resin frame are provided. an opening axis is formed between the insertion has been inserted portion,
An image forming apparatus comprising: a. The image forming apparatus according to claim 1, wherein the opening is formed in a range from 90 ° to 135 ° around the screw hole . The resin frame before Symbol second support member, wherein characterized by further comprising, it a second screw hole which screw is tightened to secure said first supporting member and the second supporting member The image forming apparatus according to claim 1 or 2 . Before SL drive shaft, an image forming apparatus according to any one of claims 1 to 3 wherein the coupling portion for coupling the photosensitive member is provided, it is characterized. The photoconductor is a first photoconductor,
The drive shaft is a first drive shaft,
A second photoconductor on which a toner image of a different color from the first photoconductor is formed ,
A second drive shaft for transmitting a drive force to the second photoconductor ,
Has ,
5. The device according to claim 1, wherein the second drive shaft is inserted into and supported by the metal frame of the first support member and the resin frame of the second support member . 6. 2. The image forming apparatus according to claim 1. The drive transmission device ,
And the first motor,
A first gear that transmits a driving force from the first motor to the first drive shaft ,
A second motor different from the first motor ,
A second gear that transmits a driving force from the second motor to the second drive shaft ,
The a, image forming apparatus according to claim 5, characterized in that.

Images