Image forming apparatus

Abstract

The present application provides an image forming apparatus capable of realizing miniaturization and low cost of a driving force transmission mechanism for transmitting driving force of a motor. The image forming apparatus is provided with: a first developing gear train having a gear directly engaged with a developing drive gear driven by a motor, capable of transmitting driving force from the motor to a developing roller; a second developing gear train having a gear directly engaged with the developing drive gear, capable of transmitting driving force from the motor to the developing roller; a first processing gear train having a gear directly engaged with a processing drive gear driven by the motor, capable of transmitting driving force from the motor to a photosensitive drum; and a second processing gear train having a gear directly engaged with the processing drive gear, capable of transmitting driving force from the motor to the photosensitive drum.

Description

TECHNICAL FIELD

[0001] The present application relates to an image forming apparatus provided with a plurality of photosensitive drums and a plurality of developing rollers provided corresponding to each of the photosensitive drums. BACKGROUND

[0002] Conventionally, as an image forming apparatus, there is known an image forming apparatus provided with a first gear train that transmits driving force from a developing motor to three developing rollers corresponding to yellow, magenta, and cyan, and a second gear train different from the first gear train that transmits driving force from the developing motor to one developing roller corresponding to black (Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2016-224418

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in the existing structure, torque acting on a gear that constitutes the first gear train that transmits driving force from the developing motor to the three developing rollers, particularly, a stage gear located upstream of the first gear train, is large, and thus the teeth of the stage gear can be deformed. If the teeth of the gear are deformed, the transmission performance of the driving force deteriorates, and thus, as a countermeasure, for example, it is considered to thicken the tooth width of the gear to reduce the load per unit width. However, in this case, the size of the gear becomes large, or the cost of the gear becomes high, which leads to a large size or a high cost of a driving force transmission mechanism for transmitting the driving force of the motor. SUMMARY OF THE INVENTION

[0008] Therefore, an object of the present application is to provide an image forming apparatus that can achieve a small size and a low cost of a driving force transmission mechanism for transmitting the driving force of a motor.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] In order to achieve the above object, the image forming apparatus of the present application is provided with a first photosensitive drum, a second photosensitive drum, a third photosensitive drum, a fourth photosensitive drum, a first developing roller that supplies toner to the first photosensitive drum, a second developing roller that supplies toner to the second photosensitive drum, a third developing roller that supplies toner to the third photosensitive drum, a fourth developing roller that supplies toner to the fourth photosensitive drum, a developing driving gear, a developing motor that drives the developing driving gear, a first developing gear train, a second developing gear train, a processing driving gear, a processing motor that drives the processing driving gear, a first processing gear train, and a second processing gear train.

[0011] The first developing gear train has a first gear directly engaged with the developing drive gear and is capable of transmitting the driving force from the developing motor to the first developing roller and the second developing roller.

[0012] The second developing gear train is provided independently of the first developing gear train, has a second gear directly engaged with the developing drive gear, and is capable of transmitting the driving force from the developing motor to the third developing roller and the fourth developing roller.

[0013] The first processing gear train has a third gear directly engaged with the processing drive gear and is capable of transmitting the driving force from the processing motor to the first photosensitive drum and the second photosensitive drum.

[0014] The second processing gear train is provided independently of the first processing gear train, has a fourth gear directly engaged with the processing drive gear, and is capable of transmitting the driving force from the processing motor to the third photosensitive drum and the fourth photosensitive drum.

[0015] According to such a structure, it is possible to suppress the torque applied to the first gear, the second gear, the third gear, and the fourth gear from becoming large, and thus it is possible to suppress deformation of the gear teeth without thickening the tooth widths of these gears. In addition, it is possible to make the torques applied to the first developing gear train and the second developing gear train substantially equal, and thus it is possible to share at least a part of the gears (parts) between the first developing gear train and the second developing gear train. Likewise, it is possible to make the torques applied to the first processing gear train and the second processing gear train substantially equal, and thus it is possible to share at least a part of the gears (parts) between the first processing gear train and the second processing gear train. Thus, it is possible to achieve miniaturization and low cost of the driving force transmission mechanism for transmitting the driving force of the motor to the developing roller and the photosensitive drum. In addition, it is possible to achieve sharing of parts, and thus it is possible to suppress uneven rotation of the gears constituting the gear trains and to stably drive the developing roller and the photosensitive drum.

[0016] In the image forming apparatus described above, a structure can be employed in which the first developing gear train has a first clutch that is switchable between a transmission state in which a driving force input to the first gear is transmitted to the first developing roller and a cutoff state in which the driving force input to the first gear is not transmitted to the first developing roller, and a second clutch that is switchable between a transmission state in which a driving force input to the first gear is transmitted to the second developing roller and a cutoff state in which the driving force input to the first gear is not transmitted to the second developing roller, the second developing gear train has a third clutch that is switchable between a transmission state in which a driving force input to the second gear is transmitted to the third developing roller and a cutoff state in which the driving force input to the second gear is not transmitted to the third developing roller, and a fourth clutch that is switchable between a transmission state in which a driving force input to the second gear is transmitted to the fourth developing roller and a cutoff state in which the driving force input to the second gear is not transmitted to the fourth developing roller.

[0017] Thus, by switching the clutches between the transmission state and the cutoff state, the corresponding developing rollers can be caused to rotate or stop.

[0018] The image forming apparatus described above can employ a structure that includes a belt that is configured to be in contact with the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum, and a belt gear train that has a fifth gear that directly engages with a gear that constitutes the first process gear train or a gear that constitutes the second process gear train, and that is capable of transmitting a driving force from a process motor to the belt.

[0019] Thus, the plurality of photosensitive drums and the belt that is configured to be in contact with the plurality of photosensitive drums can be driven by a common motor, so the photosensitive drums and the belt can be stably driven. In addition, in a case where the fifth gear is engaged with a gear that constitutes a process gear train of the first process gear train and the second process gear train that is disposed in the vicinity of the belt gear train, and a driving force is input to the belt gear train, the number of gears can be reduced, so downsizing and cost reduction of a driving force transmission mechanism can be achieved. In addition, by reducing the number of gears, a loss of driving force can be reduced.

[0020] In addition, the image forming apparatus described above can employ a structure that includes a belt that is configured to be in contact with the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum, and a belt gear train that has a sixth gear that directly engages with a process driving gear, and that is capable of transmitting a driving force from a process motor to the belt.

[0021] Thus, the plurality of photosensitive drums and the belt configured to be in contact with the plurality of photosensitive drums can be driven by the common motor, and thus the photosensitive drums and the belt can be stably driven. In addition, the belt gear train is provided independently of the processing gear train, and thus the torque applied to the processing gear train can be prevented from becoming large.

[0022] The above-described image forming apparatus can employ a structure including a cleaning roller that comes into contact with the belt to recover the adherent attached to the belt, and a cleaning gear train that has a seventh gear directly engaged with a gear provided to an output shaft of the processing motor and that is capable of transmitting a driving force from the processing motor to the cleaning roller.

[0023] Thus, the photosensitive drum, the belt, and the cleaning roller can be driven by the common motor, and thus the photosensitive drum, the belt, and the cleaning roller can be stably driven. In addition, the cleaning gear train is provided independently of the processing gear train, and thus the torque applied to the processing gear train can be prevented from becoming large.

[0024] In addition, the above-described image forming apparatus can employ a structure including a cleaning roller that comes into contact with the belt to recover the adherent attached to the belt, and a cleaning gear train that has an eighth gear directly engaged with the processing driving gear and that is capable of transmitting a driving force from the processing motor to the cleaning roller.

[0025] Thus, the photosensitive drum, the belt, and the cleaning roller can be driven by the common motor, and thus the photosensitive drum, the belt, and the cleaning roller can be stably driven. In addition, the cleaning gear train is provided independently of the processing gear train, and thus the torque applied to the processing gear train can be prevented from becoming large.

[0026] In the above-described image forming apparatus, a first developing gear train can have a first output gear that outputs a driving force input to a first gear to a first developing roller and a second output gear that outputs a driving force input to the first gear to a second developing roller, a second developing gear train can have a third output gear that outputs a driving force input to a second gear to a third developing roller, and the number of gears interposed between the first gear and the first output gear, the number of gears interposed between the first gear and the second output gear, and the number of gears interposed between the second gear and the third output gear can be the same number.

[0027] Thus, rotation unevenness of the gears that transmit the driving force to the first developing roller, the second developing roller, and the third developing roller can be prevented, and the first developing roller, the second developing roller, and the third developing roller can be stably driven.

[0028] In the image forming apparatus described above, the following structure can be employed. The second developing gear train has a fourth output gear that outputs the driving force input to the second gear to the fourth developing roller, and the number of gears interposed between the second gear and the fourth output gear is greater than the number of gears interposed between the second gear and the third output gear.

[0029] Thus, the freedom of arrangement of the developing driving gear and the developing motor can be improved, and thus the freedom of design of the image forming apparatus can be improved.

[0030] In the image forming apparatus described above, the following structure can be employed. The process driving gear is a gear that directly engages with a gear provided to an output shaft of the process motor.

[0031] Thus, compared with a case where other gears are interposed between the process driving gear and the gear provided to the output shaft of the process motor, the number of gears can be reduced, and thus the driving force transmission mechanism can be downsized and reduced in cost. In addition, by reducing the number of gears, the loss of driving force can be reduced.

[0032] In the image forming apparatus described above, the following structure can be employed. The process driving gear is a gear provided to an output shaft of the process motor.

[0033] Thus, the number of gears can be reduced, and thus the driving force transmission mechanism can be downsized and reduced in cost. In addition, by reducing the number of gears, the loss of driving force can be reduced.

[0034] In the image forming apparatus described above, the following structure can be employed. The developing driving gear is a gear provided to an output shaft of the developing motor.

[0035] Thus, the number of gears can be reduced, and thus the driving force transmission mechanism can be downsized and reduced in cost. In addition, by reducing the number of gears, the loss of driving force can be reduced.

[0036] Effects of the Invention

[0037] According to the present application, downsizing and reduction in cost of a driving force transmission mechanism for transmitting driving force of a motor to a developing roller and a photosensitive drum can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a diagram showing the structure of an image forming apparatus of an embodiment.

[0039] Figure 2 is a diagram showing the structure of a driving force transmission mechanism of an embodiment.

[0040] Figure 3is a perspective view of the developing motor, a developing gear train of the first drive force transmission mechanism, the processing motor, and a second drive force transmission mechanism viewed from the upper right.

[0041] Figure 4 is a view of the developing motor, the developing gear train of the first drive force transmission mechanism, the processing motor, and the second drive force transmission mechanism viewed from the right side.

[0042] Figure 5 is a perspective view of the developing motor, the first drive force transmission mechanism, and the moving mechanism viewed from the upper right.

[0043] Figure 6 is a view of the developing motor, the first drive force transmission mechanism, and the moving mechanism viewed from the right side.

[0044] Figure 7 is a perspective view (a) and a side view (b) showing the cam, the cam follower, the clutch, and the restriction member when the developing roller is located at the contact position.

[0045] Figure 8 is a view (a), (b) of the structure of the developing cartridge viewed from above.

[0046] Figure 9 is an exploded perspective view (a) of the clutch viewed from the sun gear side and an exploded perspective view (b) viewed from the carrier side.

[0047] Figure 10 is a perspective view (a) and a side view (b) showing the cam, the cam follower, the clutch, and the restriction member when the developing roller is located at the separation position.

[0048] Figure 11 is a view showing the structure of the drive force transmission mechanism of the first modification example.

[0049] Figure 12 is a view showing the structure of the drive force transmission mechanism of the second modification example.

[0050] Explanation of symbols

[0051] 1 image forming apparatus

[0052] 3D developing motor

[0053] 3P processing motor

[0054] 50Y Y photosensitive drum

[0055] 50M M photosensitive drum

[0056] 50C C photosensitive drum

[0057] 50K K photosensitive drum

[0058] 61Y developing roller

[0059] 61M M developing roller

[0060] 61C C developing roller

[0061] 61K K developing roller

[0062] 100G developing drive gear

[0063] 100A first developing gear train

[0064] 100B second developing gear train

[0065] 110A idling gear

[0066] 110B idling gear

[0067] 200G processing drive gear

[0068] 200A first processing gear train

[0069] 200B second processing gear train

[0070] 211A idling gear

[0071] 211B idling gear DETAILED DESCRIPTION

[0072] As shown in FIG. 1, the image forming apparatus 1 of the embodiment is a color printer, and includes a housing 10, a sheet supply portion 20, an image forming portion 30, a belt cleaning device 90, and a control portion 2. In addition, in the present embodiment, the left side of the image forming apparatus 1 is set as the front, the right side is set as the rear, the upper side is set as the upper side, and the lower side is set as the lower side. In addition, the paper face of the image forming apparatus 1 is set as the right side, and the back of the paper face is set as the left side. Figure 1 Figure 1 Figure 1

[0073] The sheet supply portion 20 includes a sheet tray 21 on which a sheet S is placed, and a supply mechanism 22. The sheet tray 21 is disposed below the image forming portion 30, and can be pulled out to the front side from the housing 10 to be removed. The supply mechanism 22 includes a paper feed roller 23, a separation roller 24, a separation pad 25, a conveyance roller 26, and a registration roller 27. The sheet S is a medium on which an image can be formed by the image forming apparatus 1, and includes ordinary paper, an envelope, a postcard, thin paper, thick paper, glossy paper, a resin sheet, a sticker, and the like.

[0074] The sheet S accommodated in the sheet tray 21 is separated one by one between the separation roller 24 and the separation pad 25 after being fed by the paper feed roller 23, and is conveyed toward the registration roller 27 by the conveyance roller 26. Then, the position of the leading end of the sheet S is regulated by the registration roller 27 in a rotation-stopped state, and the sheet S is supplied to the image forming portion 30 by the rotation of the registration roller 27.​​​

[0075] The image forming section 30 is provided with an exposure device 40, a plurality of photosensitive drums 50, a plurality of developing cartridges 60, a conveyance device 70, and a fixing device 80.

[0076] The exposure device 40 is provided with a laser diode, a deflector, a lens, and a mirror, which are not shown. The exposure device 40 is configured to emit a plurality of light beams, which are indicated by single-dot chain lines, to expose the plurality of photosensitive drums 50, and to expose the surface of each photosensitive drum 50.

[0077] The plurality of photosensitive drums 50 includes a Y photosensitive drum 50Y corresponding to yellow, an M photosensitive drum 50M corresponding to magenta, a C photosensitive drum 50C corresponding to cyan, and a K photosensitive drum 50K corresponding to black. In the present embodiment, the Y photosensitive drum 50Y corresponds to a "first photosensitive drum", the M photosensitive drum 50M corresponds to a "second photosensitive drum", the C photosensitive drum 50C corresponds to a "third photosensitive drum", and the K photosensitive drum 50K corresponds to a "fourth photosensitive drum". Further, in the present specification and the drawings, in the case where the colors are distinguished in the description of the components provided corresponding to the respective colors, the symbols are assigned Y, M, C, and K, and in the case where the colors are not distinguished, the symbols are not assigned Y, M, C, and K.

[0078] The developing cartridges 60 are provided one by one corresponding to each of the plurality of photosensitive drums 50. The plurality of developing cartridges 60 includes a Y developing cartridge 60Y having a Y developing roller 61Y that supplies toner to the Y photosensitive drum 50Y, an M developing cartridge 60M having an M developing roller 61M that supplies toner to the M photosensitive drum 50M, a C developing cartridge 60C having a C developing roller 61C that supplies toner to the C photosensitive drum 50C, and a K developing cartridge 60K having a K developing roller 61K that supplies toner to the K photosensitive drum 50K.

[0079] Each developing cartridge 60 is movable between a position where the developing roller 61 is located at a contact position in contact with the corresponding photosensitive drum 50 (refer to a solid line) and a position where the developing roller 61 is located at a separation position separated from the corresponding photosensitive drum 50 (refer to a broken line). In the present embodiment, the Y developing roller 61Y corresponds to a "first developing roller", the M developing roller 61M corresponds to a "second developing roller", the C developing roller 61C corresponds to a "third developing roller", and the K developing roller 61K corresponds to a "fourth developing roller".

[0080] The plurality of photosensitive drums 50 is supported by a support member 55 so as to be rotatable. The support member 55 is provided with a charger 52 configured to charge the photosensitive drum 50, which is disposed corresponding to each photosensitive drum 50. The support member 55 is detachable with respect to the housing 10 from an opening formed by opening a front cover 11 of the housing 10. In addition, the support member 55 supports the plurality of developing cartridges 60 so as to be detachable.

[0081] A conveyor 70 is disposed between the sheet tray 21 and the plurality of photosensitive drums 50. The conveyor 70 includes a drive roller 71, a driven roller 72, an annular belt, i.e., a conveyor belt 73, and four transfer rollers 74. The conveyor belt 73 is configured to be stretched between the drive roller 71 and the driven roller 72, with its outer surface in contact with each photosensitive drum 50 (50Y, 50M, 50C, 50K). Each transfer roller 74 is disposed on the inner side of the conveyor belt 73 such that it clamps the conveyor belt 73 between each transfer roller 74 and each photosensitive drum 50.

[0082] The fuser 80 is located behind the plurality of photosensitive drums 50 and the transport device 70. The fuser 80 includes a heating roller 81 and a pressure roller 82 disposed opposite to the heating roller 81. A transport roller 15 and a discharge roller 16 are provided on the downstream side of the fuser 80 in the transport direction of the sheet S.

[0083] In the image forming unit 30, the surface of the photosensitive drum 50 is uniformly charged by the charger 52 and then exposed by a light beam irradiated from the exposure device 40. This forms an electrostatic latent image based on image data on the photosensitive drum 50. Meanwhile, toner stored in the developing cartridge 60 is carried on the surface of the developing roller 61 and supplied from the developing roller 61 at the contact position to the electrostatic latent image formed on the photosensitive drum 50. This forms a toner image on the photosensitive drum 50.

[0084] The sheet S, supplied to the conveyor belt 73, is conveyed along the conveyor belt 73 and passes between the photosensitive drum 50 and the transfer roller 74, thereby transferring the toner image formed on the photosensitive drum 50 to the sheet S. Furthermore, since the sheet S passes between the heating roller 81 and the pressure roller 82, the toner image is thermally fixed onto the sheet S. Then, the sheet S is discharged onto the paper discharge tray 13 by the conveyor roller 15 and the discharge roller 16.

[0085] A cleaning device 90 is disposed between the sheet tray 21 and the conveyor belt 73. The cleaning device 90 includes a cleaning roller 91, a recovery roller 92, a scraper 93, a storage section 94, and a back support roller 95 that clamps the conveyor belt 73 between the cleaning roller 91 and the back support roller 95. The cleaning roller 91 is configured to contact the conveyor belt 73 and recover pigments, paper dust, and other adhering substances attached to the conveyor belt 73.

[0086] In the cleaning device 90, the residue adhering to the conveyor belt 73 is recovered by the cleaning roller 91. Then, the residue adhering to the cleaning roller 91 is scraped off and recovered by the recovery roller 92, and the residue adhering to the recovery roller 92 is scraped off by the scraper 93 and stored in the storage section 94.

[0087] like Figure 2 As shown, the image forming apparatus 1 also includes a developing motor 3D, a processing motor 3P, a YMC moving mechanism 5A, a K moving mechanism 5K, a first driving force transmission mechanism 100, and a second driving force transmission mechanism 200.

[0088] The developing motor 3D is a driving source that drives the developing rollers 61, the cams 150 (150Y, 150M, 150C, 150K) of the moving mechanisms 5A, 5K by driving the developing drive gear 100G.

[0089] The processing motor 3P is a driving source that drives the photosensitive drum 50, the conveyance belt 73 by driving the processing drive gear 200G. In addition, the processing motor 3P is also a driving source that drives the cleaning roller 91.

[0090] The YMC moving mechanism 5A is configured to move the Y developing roller 61Y, the M developing roller 61M, and the C developing roller 61C between the contact position and the separation position, and includes the Y cam 150Y, the M cam 150M, and the C cam 150C. The K moving mechanism 5K is configured to move the K developing roller 61K between the contact position and the separation position, and includes the K cam 150K.

[0091] The first drive force transmission mechanism 100 is configured to be able to transmit the driving force from the developing motor 3D to the developing rollers 61, the cams 150. The first drive force transmission mechanism 100 has the developing drive gear 100G, the first developing gear train 100A, the second developing gear train 100B, the first control gear train 100C, and the second control gear train 100D. In addition, in Figure 2 In the drawing, the developing gear trains 100A, 100B are indicated by thick solid lines, and the control gear trains 100C, 100D are indicated by thick broken lines.

[0092] The first developing gear train 100A is a gear train that is able to transmit the driving force from the developing motor 3D to the Y developing roller 61Y and the M developing roller 61M, and the second developing gear train 100B is a gear train that is able to transmit the driving force from the developing motor 3D to the C developing roller 61C and the K developing roller 61K. The first developing gear train 100A and the second developing gear train 100B are independently provided.

[0093] The first control gear train 100C is a gear train that is able to transmit the driving force from the developing motor 3D to the cams 150Y, 150M, 150C, and the second control gear train 100D is a gear train that is able to transmit the driving force from the developing motor 3D to the K cam 150K. The first control gear train 100C and the second control gear train 100D are independently provided. In addition, the first control gear train 100C is provided to branch from the first developing gear train 100A, and the second control gear train 100D is independently provided with the first developing gear train 100A and the second developing gear train 100B.

[0094] The second drive force transmission mechanism 200 is configured to transmit the drive force from the process motor 3P to the photosensitive drums 50, the conveyance belt 73, and the cleaning roller 91. The second drive force transmission mechanism 200 includes a process drive gear 200G, a first process gear train 200A, a second process gear train 200B, a belt gear train 200C, and a cleaning gear train 200D. In addition, in Figure 2 , the process gear trains 200A and 200B and the cleaning gear train 200D are indicated by thick solid lines, and the belt gear train 200C is indicated by a thick broken line.

[0095] The first process gear train 200A is a gear train that is capable of transmitting the drive force from the process motor 3P to the Y photosensitive drum 50Y and the M photosensitive drum 50M, and the second process gear train 200B is a gear train that is capable of transmitting the drive force from the process motor 3P to the C photosensitive drum 50C and the K photosensitive drum 50K. The first process gear train 200A and the second process gear train 200B are independently provided.

[0096] The belt gear train 200C is a gear train that is capable of transmitting the drive force from the process motor 3P to the conveyance belt 73. The belt gear train 200C is provided to branch from the second process gear train 200B.

[0097] The cleaning gear train 200D is a gear train that is capable of transmitting the drive force from the process motor 3P to the cleaning roller 91. The cleaning gear train 200D is independently provided from the first process gear train 200A, the second process gear train 200B, and the belt gear train 200C.

[0098] Next, the detailed structures of the first drive force transmission mechanism 100 and the moving mechanisms 5A and 5K will be described. In Figure 3 and Figure 4 , the developing gear trains 100A and 100B are mainly indicated, and in Figure 5 and Figure 6 , the control gear trains 100C and 100D and the moving mechanisms 5A and 5K disposed on the right side of the developing gear trains 100A and 100B are mainly indicated. In addition, in Figure 4 and Figure 6 , the meshing of the respective gears constituting the gear trains with each other is indicated by thick solid lines.

[0099] As shown in Figure 3 and Figure 4 , the developing drive gear 100G is a gear provided to the output shaft 3A of the developing motor 3D. The developing drive gear 100G rotates integrally with the output shaft 3A by the drive of the developing motor 3D.

[0100] The first developing gear train 100A has an idle gear 110A, 113A, 115Y, 115M, a Y clutch 120Y, an M clutch 120M, a Y coupling gear 117Y, and an M coupling gear 117M. In the present embodiment, the idle gear 110A corresponds to the "first gear", the Y clutch 120Y corresponds to the "first clutch", the M clutch 120M corresponds to the "second clutch", the Y coupling gear 117Y corresponds to the "first output gear", and the M coupling gear 117M corresponds to the "second output gear".

[0101] The idle gear 110A is a gear directly engaged with the developing drive gear 100G, and is disposed on the front side of the developing drive gear 100G.

[0102] The idle gear 113A is disposed on the lower side of the idle gear 110A, and is directly engaged with the idle gear 110A.

[0103] The idle gear 115Y is disposed on the front side of the idle gear 113A, and is directly engaged with the idle gear 113A.

[0104] The Y clutch 120Y is disposed on the lower side of the idle gear 115Y, and is directly engaged with the idle gear 115Y. Further, the structure of the clutch 120 (120Y, 120M, 120C, 120K) will be described later.

[0105] The Y coupling gear 117Y is a gear that outputs the driving force input from the developing motor 3D to the Y developing roller 61Y via the idle gears 110A, 113A, 115Y, and the Y clutch 120Y. The Y coupling gear 117Y is disposed on the front side of the Y clutch 120Y, and is directly engaged with the Y clutch 120Y. The driving force from the developing motor 3D is transmitted to the Y coupling gear 117Y via the idle gears 110A, 113A, 115Y, and the Y clutch 120Y.

[0106] The idle gear 115M is disposed on the rear side of the idle gear 113A, and is directly engaged with the idle gear 113A.

[0107] The M clutch 120M is disposed on the lower side of the idle gear 115M, and is directly engaged with the idle gear 115M.

[0108] The M coupling gear 117M is a gear that outputs the driving force input from the developing motor 3D to the M developing roller 61M via the idle gears 110A, 113A, 115M, and the M clutch 120M. The M coupling gear 117M is disposed on the front side of the M clutch 120M, and is directly engaged with the M clutch 120M. The driving force from the developing motor 3D is transmitted to the M coupling gear 117M via the idle gears 110A, 113A, 115M, and the M clutch 120M.

[0109] The Y coupling gear 117Y and the M coupling gear 117M are disposed at the most downstream of the first developing gear train 100A in the transmission direction of the driving force of the first developing gear train 100A.

[0110] The second developing gear train 100B has an idling gear 110B, 113B, 115C, 113C, 115K, a C clutch 120C, a K clutch 120K, a C coupling gear 117C, and a K coupling gear 117K. In the present embodiment, the idling gear 110B corresponds to the "second gear", the C clutch 120C corresponds to the "third clutch", the K clutch 120K corresponds to the "fourth clutch", the C coupling gear 117C corresponds to the "third output gear", and the K coupling gear 117K corresponds to the "fourth output gear".

[0111] The idling gear 110B is a gear that directly engages with the developing drive gear 100G and is disposed at the rear side of the developing drive gear 100G.

[0112] The idling gear 113B is disposed at the lower side of the idling gear 110B and directly engages with the idling gear 110B.

[0113] The idling gear 115C is disposed at the rear side of the idling gear 113B and directly engages with the idling gear 113B.

[0114] The C clutch 120C is disposed at the lower side of the idling gear 115C and directly engages with the idling gear 115C.

[0115] The C coupling gear 117C is a gear that outputs the driving force input from the developing motor 3D to the idling gear 110B to the C developing roller 61C. The C coupling gear 117C is disposed at the front side of the C clutch 120C and directly engages with the C clutch 120C. The driving force from the developing motor 3D is transmitted to the C coupling gear 117C via the idling gears 110B, 113B, 115C, and the C clutch 120C.

[0116] The idling gear 113C is disposed at the rear side of the idling gear 115C and directly engages with the idling gear 115C.

[0117] The idling gear 115K is disposed at the rear side of the idling gear 113C and directly engages with the idling gear 113C.

[0118] The K clutch 120K is disposed at the lower side of the idling gear 115K and directly engages with the idling gear 115K.

[0119] The K coupling gear 117K is a gear that outputs the driving force input from the developing motor 3D to the idling gear 110B toward the K developing roller 61K. The K coupling gear 117K is disposed on the front side of the K clutch 120K and directly engages with the K clutch 120K. The driving force from the developing motor 3D is transmitted to the K coupling gear 117K via the idling gears 110B, 113B, 115C, 113C, 115K, and the K clutch 120K.

[0120] The C coupling gear 117C and the K coupling gear 117K are disposed at the most downstream of the second developing gear train 100B in the direction of transmission of the driving force of the second developing gear train 100B.

[0121] Each coupling gear 117 has a coupling shaft 119 that rotates coaxially and integrally. The coupling shaft 119 is movable in the axial direction of the developing roller 61 in linkage with the opening and closing of the front cover 11 (refer to Figure 1 ) and engages with a not-shown coupler of the developing cartridge 60 if the front cover 11 is closed. If the coupling gear 117 rotates in a state where the coupling shaft 119 engages with the coupler of the developing cartridge 60, the driving force from the developing motor 3D is transmitted to the developing roller 61 and the developing roller 61 rotates.

[0122] In the developing gear trains 100A, 100B, the gears interposed between the idling gear 110A and the Y coupling gear 117Y are the idling gears 113A, 115Y, and the Y clutch 120Y, and the number thereof is three. Also, the gears interposed between the idling gear 110A and the M coupling gear 117M are the idling gears 113A, 115M, and the M clutch 120M, and the number thereof is three. Also, the gears interposed between the idling gear 110B and the C coupling gear 117C are the idling gears 113B, 115C, and the C clutch 120C, and the number thereof is three.

[0123] That is, the number of gears interposed between the idling gear 110A and the Y coupling gear 117Y for color, the number of gears interposed between the idling gear 110A and the M coupling gear 117M for color, and the number of gears interposed between the idling gear 110B and the C coupling gear 117C for color are the same number.

[0124] On the other hand, in the second developing gear train 100B, the gears interposed between the idling gear 110B and the K coupling gear 117K are the idling gears 113B, 115C, 113C, 115K, and the K clutch 120K, and the number thereof is five. That is, the number of gears interposed between the idling gear 110B and the K coupling gear 117K for monochrome is larger than the number of gears interposed between the idling gear 110B and the C coupling gear 117C for color. Further, the number of gears interposed between the idling gear 110B and the K coupling gear 117K for monochrome is larger than the number of gears interposed between the idling gears 110A, 110B and the coupling gears 117Y, 117M, 117C for color.

[0125] As shown in FIG. 1, the first control gear train 100C has the idling gears 131A, 131B, the YMC electromagnetic clutch 140A, the idling gears 133A, 134A, the Y cam 150Y (gear portion 150G), the idling gear 135, the M cam 150M (gear portion 150G), the idling gear 136, and the C cam 150C (gear portion 150G). Figure 5 Figure 6 As shown in FIG. 1, the first control gear train 100C has the idling gears 131A, 131B, the YMC electromagnetic clutch 140A, the idling gears 133A, 134A, the Y cam 150Y (gear portion 150G), the idling gear 135, the M cam 150M (gear portion 150G), the idling gear 136, and the C cam 150C (gear portion 150G).

[0126] The YMC electromagnetic clutch 140A has a large-diameter gear 140L and a small-diameter gear 140S, the large-diameter gear 140L directly engages with the idling gear 131B, and the small-diameter gear 140S directly engages with the idling gear 133A.

[0127] The driving force from the developing motor 3D is transmitted to the Y cam 150Y via the idling gears 110A, 131A, 131B, the YMC electromagnetic clutch 140A, the idling gears 133A, 134A. The driving force is transmitted from the Y cam 150Y to the M cam 150M via the idling gear 135. The driving force is transmitted from the M cam 150M to the C cam 150C via the idling gear 136.

[0128] The second control gear train 100D has the idling gears 132A, 132B, 132C, 132D, the K electromagnetic clutch 140K, and the idling gears 133B, 134B.

[0129] The K electromagnetic clutch 140K has a large-diameter gear 140L and a small-diameter gear 140S, the large-diameter gear 140L directly engages with the idling gear 132D, and the small-diameter gear 140S directly engages with the idling gear 133B.

[0130] The driving force from the developing motor 3D is transmitted to the K cam 150K via the idling gears 132A to 132D, the K electromagnetic clutch 140K, the idling gears 133B, 134B.

[0131] ​Electromagnetic clutches 140A and 140K switch the rotation and stop of the corresponding cam 150 by switching the transmission and disengagement of driving force. Specifically, when electromagnetic clutches 140A and 140K are energized, they become engaged, causing the large-diameter gear 140L and the small-diameter gear 140S to rotate together. This transmits driving force, causing the corresponding cam 150 to rotate. Conversely, when electromagnetic clutches 140A and 140K are de-energized, they become disengaged, causing the large-diameter gear 140L to idle relative to the loaded small-diameter gear 140S, while the small-diameter gear 140S does not rotate. This disengages the driving force, stopping the corresponding cam 150. The engagement and disengagement of electromagnetic clutches 140A and 140K are controlled independently by the control unit 2.

[0132] The YMC moving mechanism 5A includes cams 150Y, 150M, and 150C, and multiple cam followers 170 corresponding to each cam 150. The K moving mechanism 5K includes a K cam 150K and cam followers 170 corresponding to the K cam 150K.

[0133] The cam 150 is a component that moves the corresponding developing roller 61 between a contact position and a separation position by rotating it. For example... Figure 7 As shown, each cam 150 has a circular plate portion 151, a gear portion 150G formed on the outer periphery of the circular plate portion 151, a first cam portion 152, and a second cam portion 153.

[0134] The first cam portion 152 is the part that moves the developing roller 61 between a contact position and a separation position, and protrudes axially from the side of the circular plate portion 151 toward the developing roller 61. The first cam portion 152 has a cam surface 152F on its axial end face. The cam surface 152F has a first holding surface F1, a second holding surface F2, a first guide surface F3, and a second guide surface F4.

[0135] The first holding surface F1 is the surface that holds the cam follower 170 in the standby position (described later), and the second holding surface F2 is the surface that holds the cam follower 170 in the protruding position (described later). Figure 7 In the diagram, the dotted shading given to the first cam portion 152 represents the second retaining surface F2. The first guide surface F3 is a surface that connects the first retaining surface F1 and the second retaining surface F2 and is inclined relative to the first retaining surface F1. The second guide surface F4 is a surface that connects the second retaining surface F2 and the first retaining surface F1 and is inclined relative to the first retaining surface F1.

[0136] The second cam portion 153 is the part that cooperates with the limiting member 160 (described later) to switch the state of the clutch 120. It protrudes axially from the side of the circular plate portion 151 opposite to the side where the first cam portion 152 is located toward the developing roller 61. When viewed axially, the second cam portion 153 extends in a generally arcuate shape.

[0137] The cam follower 170 has a sliding shaft portion 171, a contact portion 172, and a spring hooking portion 174.

[0138] The sliding shaft portion 171 is supported by a support shaft 179 (refer to Figure 8 (b) of the housing 10 so as to be slidable in the axial direction of the developing roller 61. Thus, the cam follower 170 is slidable in the axial direction of the developing roller 61

[0139] The contact portion 172 is a portion that is in contact with the cam surface 152F of the first cam portion 152, and extends from the sliding shaft portion 171. The cam follower 170 is slidable between a projected position shown in (b) and a standby position shown in (a), the projected position being a position at which the contact portion 172 is in contact with the second holding surface F2 so that the developing roller 61 is located at the separated position, and the standby position being a position at which the contact portion 172 is in contact with the first holding surface Fl so that the developing roller 61 is located at the contact position. Figure 8 Figure 8 The contact portion 172 is a portion that is in contact with the cam surface 152F of the first cam portion 152, and extends from the sliding shaft portion 171. The cam follower 170 is slidable between a projected position shown in (b) and a standby position shown in (a), the projected position being a position at which the contact portion 172 is in contact with the second holding surface F2 so that the developing roller 61 is located at the separated position, and the standby position being a position at which the contact portion 172 is in contact with the first holding surface Fl so that the developing roller 61 is located at the contact position.

[0140] Returning to Figure 7 The spring hooking portion 174 is a portion to which one end of a spring 176 is hooked, and extends from the sliding shaft portion 171 in a direction different from the contact portion 172. The spring 176 is a tension spring, and the other end thereof is hooked to an unillustrated spring hooking portion provided at a position lower than the spring hooking portion 174 and to the left of the housing 10. The spring 176 exerts a force on the cam follower 170 from the projected position toward the standby position.

[0141] As shown in Figure 8 , the developing cartridge 60 is supported by a support member 55 so as to be movable in the front-rear direction. The support member 55 has an abutting portion 55A and a pressing member 55B. The abutting portion 55A is a portion to which a later-described sliding member 66 is abutted, and is constituted by a roller that is rotatable about an axis in the up-down direction. The pressing member 55B is urged toward the rear by a spring 55C, and presses the developing cartridge 60 if the developing cartridge 60 is attached to the support member 55, so that the developing roller 61 is moved to the contact position in contact with the corresponding photosensitive drum 50.

[0142] The developing cartridge 60 has a casing 65 that accommodates toner, and a sliding member 66. The sliding member 66 is a member that is slidable in the axial direction of the developing roller 61 with respect to the casing 65, and is slidable in the axial direction by being pressed by the cam follower 170. The sliding member 66 has a shaft 66A that is supported by the casing 65 so as to be slidable, a first abutting member 66B provided at one end of the shaft 66A, and a second abutting member 66C provided at the other end of the shaft 66A.

[0143] ​The first abutting member 66B has a pressing surface 66D and an inclined surface 66E inclined with respect to the axial direction, and the second abutting member 66C has an inclined surface 66F inclined in the same way as the inclined surface 66E. The pressing surface 66D is pressed by the cam follower 170. In a case where the sliding member 66 is pressed by the cam follower 170, the inclined surfaces 66E, 66F are abutted by the abutting portion 55A to apply a force to the developing cartridge 60 in a direction orthogonal to the axial direction, and the developing roller 61 is moved to a separation position separated from the corresponding photosensitive drum 50. A spring 67 that applies a force to the sliding member 66 to the left is arranged between the first abutting member 66B and the housing 65.

[0144] As Figure 9 indicated, the clutch 120 (120Y, 120M, 120C, 120K) is a member capable of switching between a transmission state in which a driving force input to the idling gear 110A, 110B (refer to Figure 4 ) is transmitted to the corresponding developing roller 61 and a cut-off state in which the driving force input to the idling gear 110A, 110B is not transmitted to the corresponding developing roller 61. The clutch 120 is formed of a planetary gear mechanism. Specifically, the clutch 120 has a sun gear 121 that can rotate about one shaft, a ring gear 122 and a carrier 123, and a planetary gear 124 supported by the carrier 123.

[0145] The sun gear 121 has a gear portion 121A, a rotation plate 121B that rotates integrally with the gear portion 121A, and a pawl portion 121C provided to an outer periphery of the rotation plate 121B.

[0146] The ring gear 122 has an internal gear 122A provided to an inner periphery surface, and an input gear 122B provided to an outer periphery surface. The input gear 122B directly engages with the idling gear 115 (115Y, 115M, 115C, 115K) (refer to Figure 4 ).

[0147] The carrier 123 has four shaft portions 123A that support the planetary gear 124 so as to be rotatable, and an output gear 123B provided to an outer periphery surface. The output gear 123B directly engages with the coupling gear 117 (117Y, 117M, 117C, 117K) (refer to Figure 4 ).

[0148] Four planetary gears 124 are provided, and each of the planetary gears 124 is supported so as to be rotatable by the shaft portion 123A of the carrier 123. The planetary gear 124 engages with the gear portion 121A of the sun gear 121, and engages with the internal gear 122A of the ring gear 122.

[0149] In a state where the rotation of the sun gear 121 is restricted, the clutch 120 is in a transmission state where the driving force input to the input gear 122B is transmitted to the output gear 123B. On the other hand, in a state where the sun gear 121 is able to rotate, the clutch 120 is in a cut-off state where the driving force input to the input gear 122B is not transmitted to the output gear 123B. In a case where the clutch 120 is in the cut-off state and the driving force is input to the input gear 122B in a state where a load is applied to the output gear 123B, the output gear 123B does not rotate, and the sun gear 121 idles.

[0150] As shown in FIG. 1, the first driving force transmission mechanism 100 further includes a plurality of clutches 120. The clutches 120 are provided corresponding to the respective sun gears 121. The clutches 120 are each a dog clutch. Figure 7 As shown in FIG. 1, the first driving force transmission mechanism 100 further includes a plurality of clutches 120. The clutches 120 are provided corresponding to the respective sun gears 121. The clutches 120 are each a dog clutch.

[0151] The rotation support portion 162A is supported by a not-shown support shaft of the housing 10 so as to be able to turn.

[0152] The tip end of the second arm 162C extends toward the outer peripheral surface of the sun gear 121. A spring hooking portion 162E is provided to the second arm 162C, and one end of a spring 169 is hooked to the spring hooking portion 162E. The spring 169 is a tension spring, and the other end is hooked to a not-shown spring hooking portion provided to the housing 10 at a position further forward than the spring hooking portion 162E. Thus, the spring 169 exerts a force on the restriction member 160 in the clockwise direction of the drawing from a disengagement position to an engagement position, which will be described later.

[0153] The restriction member 160 is able to swing between an engagement position where the tip end of the second arm 162C engages with the claw portion 121C of the sun gear 121 to restrict the rotation of the sun gear 121, and a disengagement position where the tip end of the second arm 162C disengages from the claw portion 121C to not restrict the rotation of the sun gear 121. Figure 10

[0154] In addition, the tip end portion of the first arm 161C of the restriction member 160 is able to contact the second cam portion 153. In a case where the tip end portion of the first arm 161C is separated from the second cam portion 153, the restriction member 160 is located at the engagement position due to the force of the spring 169, and in a case where the tip end portion of the first arm 161C contacts the second cam portion 153 (see FIG. 6), the restriction member 160 swings against the force of the spring 169 and is located at the disengagement position. Figure 10

[0155] ​​The second cam portion 153 is configured such that, before the developing roller 61, moving from the separation position toward the contact position, contacts the corresponding photosensitive drum 50, the limiting member 160 is in the engaged position and the clutch 120 is in the transmission state; after the developing roller 61, moving from the contact position toward the separation position, separates from the photosensitive drum 50, the limiting member 160 is in the disengaged position and the clutch 120 is in the disengaged state. Thus, the developing roller 61 rotates when in the contact position and stops when in the separation position.

[0156] The control unit 2 is a device that controls the operation of the image forming apparatus 1. The control unit 2 includes a CPU, ROM, RAM, input / output unit, etc., and performs various processes by executing pre-stored programs. The control unit 2 controls the operation of the cam 150 by controlling the drive of the developing motor 3D or by controlling the engagement and disengagement of the electromagnetic clutches 140A and 140K, thereby controlling the drive and stop of the developing roller 61 and the contact and separation of the developing roller 61 relative to the corresponding photosensitive drum 50.

[0157] Here, an example of the processing of control unit 2 will be explained.

[0158] In the image forming apparatus 1, in the standby state before image forming is performed, all the developing rollers 61 are in the separated position. At this time, as... Figure 10 As shown, the cam follower 170 is located at a protruding position where the contact portion 172 contacts the second retaining surface F2 of the cam 150.

[0159] When an image is formed by inputting a printing task, the control unit 2 drives the developing motor 3D and, depending on the color of the toner used for image formation, engages the YMC electromagnetic clutches 140A and K electromagnetic clutches 140K, causing the cam 150 to rotate clockwise around the image. As a result, the contact portion 172 of the cam follower 170 is guided from the second holding surface F2 to the second guide surface F4, where it slides and contacts the second guide surface F4. Figure 7 As shown, it contacts the first retaining surface F1. Therefore, the cam follower 170 is pulled away by the force of the spring 176 from... Figure 8 The prominent position shown in (b) is towards Figure 8 The developing roller 61 moves from the separation position to the contact position as shown in (a). After the developing roller 61 moves to the contact position, the control unit 2 disengages the YMC electromagnetic clutch 140A and the K electromagnetic clutch 140K, thereby stopping the cam 150.

[0160] When development based on the developing roller 61 is completed, the control unit 2 engages the YMC electromagnetic clutch 140A and the K electromagnetic clutch 140K, causing the cam 150 to rotate... Figure 7The contact portion 172 is then rotated clockwise again. As a result, the contact portion 172 is guided from the first holding surface F1 to the first guiding surface F3, where it slides in contact with the first guiding surface F3, and... Figure 10 As shown, it contacts the second retaining surface F2. Therefore, the cam follower 170 moves from... Figure 8 The standby position shown in (a) is towards Figure 8 As shown in (b), the developing roller 61 slides from the contact position to the separation position. After the developing roller 61 moves to the separation position, the control unit 2 disengages the YMC electromagnetic clutch 140A and the K electromagnetic clutch 140K, thereby stopping the cam 150.

[0161] Next, the detailed structure of the second driving force transmission mechanism 200 will be described.

[0162] like Figure 3 and Figure 4 As shown, the processing drive gear 200G is a gear that directly meshes with the motor gear 3G. The motor gear 3G is a gear located on the output shaft 3B of the processing motor 3P.

[0163] The first processing gear system 200A includes idle speed gears 211A and 213A, a Y-drum gear 250Y, and an M-drum gear 250M. In this embodiment, the idle speed gear 211A is equivalent to the "third gear".

[0164] The idle speed gear 211A is a gear that directly meshes with the processing drive gear 200G and is located on the front side of the processing drive gear 200G.

[0165] The idle speed gear 213A is located on the upper front oblique side of the idle speed gear 211A and directly meshes with the idle speed gear 211A.

[0166] Y-drum gear 250Y is a gear that is coaxial with and rotates integrally with Y-photosensitive drum 50Y. Y-drum gear 250Y is located on the front side of idle speed gear 213A and meshes directly with idle speed gear 213A.

[0167] M drum gear 250M is a gear that is coaxial with and rotates integrally with M photosensitive drum 50M. M drum gear 250M is located on the rear side of idle speed gear 213A and meshes directly with idle speed gear 213A.

[0168] The driving force from the processing motor 3P is transmitted to the Y drum gear 250Y and the M drum gear 250M via the processing drive gear 200G, idle gears 211A and 213A.

[0169] The second processing gear system 200B includes: idle speed gears 211B and 213B, C drum gear 250C, and K drum gear 250K. In this embodiment, the idle speed gear 211B is equivalent to the "fourth gear".

[0170] The idling gear 211B is a gear directly engaged with the process drive gear 200G, and is disposed on the rear side of the process drive gear 200G.

[0171] The idling gear 213B is disposed on the upper side of the rear side of the idling gear 211B, and is directly engaged with the idling gear 211B.

[0172] The C-drum gear 250C is a gear coaxial with and integral with the C photosensitive drum 50C. The C-drum gear 250C is disposed on the front side of the idling gear 213B, and is directly engaged with the idling gear 213B.

[0173] The K-drum gear 250K is a gear coaxial with and integral with the K photosensitive drum 50K. The K-drum gear 250K is disposed on the rear side of the idling gear 213B, and is directly engaged with the idling gear 213B.

[0174] The driving force from the process motor 3P is transmitted to the C-drum gear 250C and the K-drum gear 250K via the process drive gear 200G, the idling gears 211B, 213B.

[0175] The geared train 200C has idling gears 215A, 215B, 215C, and a drive roller gear 271. In the present embodiment, the idling gear 215A corresponds to the "fifth gear".

[0176] The idling gear 215A is a gear directly engaged with the idling gear 213B that constitutes the second process geared train 200B, and is disposed on the lower side of the idling gear 213B. The idling gear 213B is a gear that constitutes the second process geared train 200B disposed in the vicinity of the geared train 200C, among the first process geared train 200A and the second process geared train 200B.

[0177] The idling gear 215B is disposed on the rear side of the idling gear 215A, and is directly engaged with the idling gear 215A.

[0178] The idling gear 215C is disposed on the rear side of the idling gear 215B, and is directly engaged with the idling gear 215B.

[0179] The drive roller gear 271 is a gear coaxial with and integral with the drive roller 71 that drives the conveyance belt 73, and is directly engaged with the idling gear 215C. The driving force from the process motor 3P is transmitted to the drive roller gear 271 via the process drive gear 200G, the idling gears 211B, 213B, 215A, 215B, 215C.

[0180] The cleaning gear train 200D has an idling gear 217A, 217B, 217C, a clutch mechanism 220, an idling gear 231A, 231B, a recovery roller gear 292, and a cleaning roller gear 291. In the present embodiment, the idling gear 217A corresponds to the "seventh gear".

[0181] The idling gear 217A is a gear that directly engages with the motor gear 3G and is disposed on the lower side of the motor gear 3G. Further, the idling gear 217A is disposed on the substantially opposite side to the processing drive gear 200G with the motor gear 3G interposed therebetween. The idling gear 217A has a large-diameter gear 217L and a small-diameter gear 217S.

[0182] The idling gear 217B is disposed on the front side of the idling gear 217A and directly engages with the large-diameter gear 217L of the idling gear 217A.

[0183] The idling gear 217C is disposed on the obliquely lower front side of the idling gear 217A and directly engages with the small-diameter gear 217S of the idling gear 217A.

[0184] The idling gear 217B is a gear having a smaller diameter than the idling gear 217C. If the idling gear 217A rotates, the idling gear 217B rotates at a faster speed than the idling gear 217C.

[0185] The clutch mechanism 220 is disposed on the front side of the idling gears 217B, 217C. The clutch mechanism 220 has an electromagnetic clutch 221, a one-way clutch 222, an output shaft 223, and an output gear 224 provided to the output shaft 223. The electromagnetic clutch 221 and the one-way clutch 222 are coaxially disposed. The electromagnetic clutch 221 has an input gear 221A that directly engages with the idling gear 217B, and the one-way clutch 222 has an input gear 222A that directly engages with the idling gear 217C.

[0186] In a case where the electromagnetic clutch 221 is energized to be on, the clutch mechanism 220 transmits the driving force input to the input gear 221A of the electromagnetic clutch 221 to the output shaft 223 and does not transmit the driving force input to the input gear 222A of the one-way clutch 222 to the output shaft 223. In addition, in a case where the electromagnetic clutch 221 is not energized to be off, the clutch mechanism 220 does not transmit the driving force input to the input gear 221A of the electromagnetic clutch 221 to the output shaft 223 and transmits the driving force input to the input gear 222A of the one-way clutch 222 to the output shaft 223.

[0187] The idling gear 231A is disposed on the upper side of the output gear 224 and directly engages with the output gear 224. Further, the output gear 224, the idling gears 231A, 231B, the recovery roller gear 292, and the cleaning roller gear 291 are disposed on the right side (the paper front side) of the processing gear train 200A, 200B. Figure 4

[0188] The idling gear 231B is disposed on the obliquely front upper side of the idling gear 231A and directly engages with the idling gear 231A.

[0189] The recovery roller gear 292 is a gear that is coaxial with and integrally rotates with the recovery roller 92. The recovery roller gear 292 is disposed on the front side of the idling gear 231B and directly engages with the idling gear 231B.

[0190] The cleaning roller gear 291 is a gear that is coaxial with and integrally rotates with the cleaning roller 91. The cleaning roller gear 291 is disposed on the front side of the recovery roller gear 292 and directly engages with the recovery roller gear 292.

[0191] In the case where the electromagnetic clutch 221 is engaged, the driving force from the processing motor 3P is transmitted to the cleaning roller gear 291 via the idling gears 217A, 217B, the clutch mechanism 220 (the electromagnetic clutch 221), the idling gears 231A, 231B, and the recovery roller gear 292. In addition, in the case where the electromagnetic clutch 221 is disengaged, the driving force from the processing motor 3P is transmitted to the cleaning roller gear 291 via the idling gears 217A, 217C, the clutch mechanism 220 (the one-way clutch 222), the idling gears 231A, 231B, and the recovery roller gear 292.

[0192] That is, in the case where the electromagnetic clutch 221 is engaged, the driving force from the processing motor 3P is transmitted to the cleaning roller gear 291 via the idling gear 217B and the electromagnetic clutch 221, and in the case where the electromagnetic clutch 221 is disengaged, the driving force from the processing motor 3P is transmitted to the cleaning roller gear 291 via the idling gear 217C and the one-way clutch 222. In the case where the electromagnetic clutch 221 is engaged, the cleaning roller gear 291 (the cleaning roller 91) rotates at a faster speed than in the case where the electromagnetic clutch 221 is disengaged.

[0193] ​According to the present embodiment described above, the first developing gear train 100A is able to transmit the driving force from the developing motor 3D to the two developing rollers 61Y, 61M, and the second developing gear train 100B is also able to transmit the driving force from the developing motor 3D to the same two developing rollers 61C, 61K, so it is possible to suppress the torque applied to the idling gears 110A, 110B from becoming large, for example, compared to a structure in which one developing gear train is able to transmit the driving force to three of the four developing rollers. Also, the same applies to the process gear trains 200A, 200B, so it is possible to suppress the torque applied to the idling gears 211A, 211B from becoming large. Thus, it is possible to suppress deformation of the gear teeth without thickening the tooth width of the idling gears 110A, 110B, 211A, 211B.

[0194] Also, it is possible to make the torque applied to the first developing gear train 100A and the second developing gear train 100B approximately equal, so it is possible to share at least a part of the gears (parts) between the first developing gear train 100A and the second developing gear train 100B. For example, it is possible to share the idling gear 110A and the idling gear 110B, or to share the idling gear 113A and the idling gear 113B, or to share the idling gear 115. Also, it is possible to make the torque applied to the first process gear train 200A and the second process gear train 200B approximately equal, so it is possible to share at least a part of the gears (parts) between the first process gear train 200A and the second process gear train 200B. For example, it is possible to share the idling gear 211A and the idling gear 211B, or to share the idling gear 213A and the idling gear 213B.

[0195] Furthermore, according to the above, it is possible to achieve miniaturization and low cost of the driving force transmission mechanism 100, 200 for transmitting the driving force of the motors 3D, 3P to the developing rollers 61, the photosensitive drum 50. Also, it is possible to achieve sharing of parts, so it is possible to suppress uneven rotation of the gears that make up the gear trains 100A, 100B, 200A, 200B, and it is possible to stably drive the developing rollers 61, the photosensitive drum 50.

[0196] Also, the first developing gear train 100A has the clutches 120Y, 120M, and the second developing gear train 100B has the clutches 120C, 120K, so by switching the clutches 120 between the transmission state and the cut-off state, it is possible to make the corresponding developing rollers 61 rotate or stop. Thus, for example, it is possible to switch between a color printing mode in which a plurality of developing rollers 61Y, 61M, 61C, 61K are used to form an image on the sheet S and a monochrome printing mode in which only one developing roller 61 (the K developing roller 61K) is used to form an image on the sheet S.

[0197] Further, the belt gear train 200C is provided to branch from the second process gear train 200B, is able to transmit the driving force from the process motor 3P to the conveyance belt 73, and thus is able to drive the plurality of photosensitive drums 50 and the conveyance belt 73 configured to contact the plurality of photosensitive drums 50 by the common motor (process motor 3P). Thereby, the photosensitive drums 50 and the conveyance belt 73 are able to be stably driven.

[0198] Further, the idling gear 215A of the belt gear train 200C is caused to mesh with the idling gear 213B constituting the second process gear train 200B disposed in the vicinity of the belt gear train 200C, and the driving force is input to the belt gear train 200C, and thus the number of gears is able to be reduced. Thereby, the second driving force transmission mechanism 200 is able to be downsized and reduced in cost. Further, by reducing the number of gears, friction acting on a shaft possessed by the gears, friction acting between gears and a shaft supporting the gears, friction acting between teeth of meshed gears, and the like are able to be reduced, and thus the loss of driving force is able to be reduced.

[0199] Further, the cleaning gear train 200D is provided, has an idling gear 217A directly meshing with the motor gear 3G, is able to transmit the driving force from the process motor 3P to the cleaning roller 91, and thus is able to drive the photosensitive drum 50, the conveyance belt 73, and the cleaning roller 91 by the common motor (process motor 3P). Thereby, the photosensitive drum 50, the conveyance belt 73, and the cleaning roller 91 are able to be stably driven. Further, the cleaning gear train 200D is provided independently of the process gear trains 200A and 200B, and thus the torque applied to the process gear trains 200A and 200B is able to be suppressed from becoming large.

[0200] Further, the number of gears interposed between the idling gear 110A and the Y coupling gear 117Y, the number of gears interposed between the idling gear 110A and the M coupling gear 117M, and the number of gears interposed between the idling gear 110B and the C coupling gear 117C are the same number, and thus the rotation unevenness of the gears that transmit the driving force to the developing rollers 61Y, 61M, and 61C is able to be suppressed, and the developing rollers 61Y, 61M, and 61C are able to be stably driven. Thereby, for example, in a case where the developing rollers 61Y, 61M, and 61C are used to form an image on the sheet S, color shift in which the position where a toner image is generated is shifted is able to be suppressed.

[0201] Further, the number of gears between the idling gear 110B and the K coupling gear 117K is larger than the number of gears between the idling gears 110A, 110B and the coupling gears 117Y, 117M, 117C, and thus, compared to a case where, for example, the number of gears between the idling gears 110A, 110B and each of the coupling gears 117Y, 117M, 117C, 117K is the same, the degree of freedom of the arrangement of the developing drive gear 100G and the developing motor 3D can be increased. Thus, the degree of freedom of the design of the image forming apparatus 1 can be increased.

[0202] Further, the process drive gear 200G is a gear directly engaged with the motor gear 3G, and thus, compared to a case where there is another gear between the process drive gear and a gear provided to the output shaft of the process motor, the number of gears can be reduced. Thus, the second drive force transmission mechanism 200 can be downsized and reduced in cost. Further, by reducing the number of gears, the loss of drive force can be reduced.

[0203] Further, the developing drive gear 100G is a gear provided to the output shaft 3A of the developing motor 3D, and thus, compared to a case where there is another gear between the developing drive gear and a gear provided to the output shaft of the developing motor, the number of gears can be reduced. Thus, the first drive force transmission mechanism 100 can be downsized and reduced in cost. Further, by reducing the number of gears, the loss of drive force can be reduced.

[0204] The above describes the embodiments, but the present application is not limited to the above-described embodiments, and can be implemented as appropriately modified as exemplified below. Further, in the following description, the same reference signs are attached to the same structural elements as those described above, and the description thereof is omitted.

[0205] In the above-described embodiments, the first control gear train 100C for color of the YMC moving mechanism 5A to which the drive force from the developing motor 3D is transmitted is provided to branch from the first developing gear train 100A, and the second control gear train 100D for monochrome of the K moving mechanism 5K to which the drive force from the developing motor 3D is transmitted is provided independently of the first developing gear train 100A and the second developing gear train 100B, but is not limited thereto. For example, the first control gear train for color can be provided independently of the first developing gear train and the second developing gear train, and the second control gear train for monochrome can be provided to branch from the second developing gear train. Further, both the first control gear train and the second control gear train can be provided independently of the first developing gear train and the second developing gear train.

[0206] Also, in the above embodiment, the idler gear 215A serving as the fifth gear possessed by the belt gear train 200C is a gear directly engaged with the idler gear 213B constituting the second process gear train 200B, but is not limited thereto. For example, the fifth gear can also be a gear directly engaged with a gear constituting the first process gear train. Further, the gear directly engaged with the fifth gear can also be an arbitrary gear as long as it is a gear constituting the first process gear train or a gear constituting the second process gear train.

[0207] Also, in the above embodiment, the belt gear train 200C is provided to branch from the second process gear train 200B, but is not limited thereto. For example, as shown in FIG. 9, the belt gear train 200C can be provided independently of the first process gear train 200A, the second process gear train 200B, and the cleaning gear train 200D, and have an idler gear 216A serving as a sixth gear directly engaged with the process drive gear 200G. Figure 11

[0208] According to such a configuration, the plurality of photosensitive drums 50 and the conveyance belt 73 configured to be in contact with the plurality of photosensitive drums 50 can also be driven by the common motor (process motor 3P), and thus the photosensitive drums 50 and the conveyance belt 73 can be stably driven. Also, the belt gear train 200C is provided independently of the process gear trains 200A, 200B, and thus the torque applied to the process gear trains 200A, 200B can be suppressed from becoming large.

[0209] Also, in the above embodiment, the cleaning gear train 200D has the idler gear 217A directly engaged with the motor gear 3G, and the driving force from the process motor 3P is directly input from the motor gear 3G, but is not limited thereto. For example, as shown in FIG. 10, the cleaning gear train 200D can have an idler gear 218A serving as an eighth gear directly engaged with the process drive gear 200G, and the driving force from the process motor 3P can be input from the motor gear 3G via the process drive gear 200G. Figure 11

[0210] According to such a configuration, the photosensitive drum 50, the conveyance belt 73, and the cleaning roller 91 can also be driven by the common motor (process motor 3P), and thus the photosensitive drum 50, the conveyance belt 73, and the cleaning roller 91 can be stably driven. Also, the cleaning gear train 200D is provided independently of the process gear trains 200A, 200B, and thus the torque applied to the process gear trains 200A, 200B can be suppressed from becoming large.

[0211] ​​Further, in the above embodiment, the cleaning gear train 200D is provided independently of the first and second process gear trains 200A and 200B, but is not limited thereto. For example, the cleaning gear train can be provided to branch from the first process gear train or the second process gear train.

[0212] Further, in the above embodiment, the process drive gear 200G is a gear directly engaged with the motor gear 3G, but is not limited thereto. For example, as shown in FIG. 9, the process drive gear 200G can be a gear provided to an output shaft of the process motor 3P. Figure 12 According to such a configuration, the number of gears can be reduced, and thus the second drive force transmission mechanism 200 can be downsized and reduced in cost. Further, by reducing the number of gears, the loss of drive force can be reduced.

[0213] Further, the process drive gear can be a gear engaged with a gear provided to an output shaft of the process motor via one or more idle gears.

[0214] Further, in the above embodiment, the developing drive gear 100G is a gear provided to an output shaft 3A of the developing motor 3D, but is not limited thereto. For example, the developing drive gear can be a gear directly engaged with a gear provided to an output shaft of the developing motor, or can be a gear engaged with a gear provided to an output shaft of the developing motor via one or more idle gears.

[0215] Further, in the above embodiment, the number of gears between the idle gear 110B and the K coupling gear 117K for monochrome is greater than the number of gears between the idle gear 110B and the C coupling gear 117C for color in the second developing gear train 100B, but is not limited thereto, and for example, the numbers can be the same.

[0216] Further, in the above embodiment, the clutch 120 having a planetary gear mechanism is exemplified as the first clutch, the second clutch, the third clutch, and the fourth clutch, but is not limited thereto, and for example, can be an electromagnetic clutch. Further, the image forming apparatus can be configured such that the developing gear train does not have a clutch.

[0217] Further, in the above embodiment, the conveyance belt 73 is exemplified as the endless belt, but is not limited thereto, and for example, can be an intermediate transfer belt. Further, in the above embodiment, the conveyance belt 73 is driven by the process motor 3P that drives the photosensitive drum 50, but is not limited thereto, and for example, the conveyance belt 73 can be driven by a motor other than the process motor, such as a dedicated motor for driving the belt.

[0218] Furthermore, in the above embodiment, the cleaning roller 91 is driven by the processing motor 3P that drives the photosensitive drum 50, but it is not limited to this. The cleaning roller 91 can also be driven by a motor other than the processing motor, such as a dedicated motor for driving the cleaning roller. In addition, the image forming apparatus may also have a structure that does not include a cleaning roller.

[0219] Furthermore, the structure of the moving mechanisms 5A and 5K described in the above embodiment is one example. For example, the moving mechanism may also be a structure with a linearly driven cam instead of a rotating cam 150. In addition, in the above embodiment, the developing roller 61 moves between the contact position and the separation position, and therefore moves back and forth, but is not limited to this; for example, it may also move up and down.

[0220] Furthermore, in the above embodiment, the first developing gear system 100A can transmit the driving force from the developing motor 3D to the two developing rollers 61Y and 61M, and the second developing gear system 100B can transmit the driving force from the developing motor 3D to the two developing rollers 61C and 61K, but it is not limited to this. For example, the first developing gear system can transmit the driving force from the developing motor to three or more developing rollers, and the second developing gear system can transmit the driving force from the developing motor to the same number of developing rollers as the developing rollers that receive the driving force from the developing motor via the first developing gear system. The same applies to the first processing gear system and the second processing gear system.

[0221] In addition, the image forming apparatus is not limited to printers, but can also be copiers, multifunction printers, etc.

[0222] Furthermore, the elements described in the above-described embodiments and variations can be implemented in appropriate combinations.

Claims

1. An image forming apparatus characterized by comprising: Possessing: a first photosensitive drum; a second photosensitive drum; a third photosensitive drum; a fourth photosensitive drum; a first developing roller that supplies toner to the first photosensitive drum; a second developing roller that supplies toner to the second photosensitive drum; a third developing roller that supplies toner to the third photosensitive drum; a fourth developing roller that supplies toner to the fourth photosensitive drum; a developing drive gear; a developing motor that drives the developing drive gear; a first developing gear train that has a first gear that directly engages with the developing drive gear and that is capable of transmitting driving force from the developing motor to the first developing roller and the second developing roller; a second developing gear train that is provided independently of the first developing gear train, has a second gear that directly engages with the developing drive gear, and that is capable of transmitting driving force from the developing motor to the third developing roller and the fourth developing roller; a process drive gear; a process motor that drives the process drive gear; a first process gear train that has a third gear that directly engages with the process drive gear and that is capable of transmitting driving force from the process motor to the first photosensitive drum and the second photosensitive drum; a second process gear train that is provided independently of the first process gear train, has a fourth gear that directly engages with the process drive gear, and that is capable of transmitting driving force from the process motor to the third photosensitive drum and the fourth photosensitive drum; a belt that is configured to come into contact with the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum; a belt gear train that has a fifth gear that directly engages with a gear that constitutes the first process gear train or a gear that constitutes the second process gear train and that is capable of transmitting driving force from the process motor to the belt; a cleaning roller that recovers adherents adhering to the belt while coming into contact with the belt; and a cleaning gear train that has a seventh gear that directly engages with a gear provided to an output shaft of the process motor and that is capable of transmitting driving force from the process motor to the cleaning roller. Possessing:

2. An image forming apparatus characterized by comprising: a first photosensitive drum; a second photosensitive drum; a third photosensitive drum; a fourth photosensitive drum; a first developing roller that supplies toner to the first photosensitive drum; a second developing roller that supplies toner to the second photosensitive drum; a third developing roller that supplies toner to the third photosensitive drum; a fourth developing roller that supplies toner to the fourth photosensitive drum; a developing drive gear; a developing motor that drives the developing drive gear; a first developing gear train that has a first gear that directly engages with the developing drive gear and that is capable of transmitting driving force from the developing motor to the first developing roller and the second developing roller; ​ a second developing gear train, which is provided independently of the first developing gear train, has a second gear directly engaged with the developing drive gear, and is capable of transmitting driving force from the developing motor to the third developing roller and the fourth developing roller; a process drive gear; a process motor, which drives the process drive gear; a first process gear train, which has a third gear directly engaged with the process drive gear, and is capable of transmitting driving force from the process motor to the first photosensitive drum and the second photosensitive drum; a second process gear train, which is provided independently of the first process gear train, has a fourth gear directly engaged with the process drive gear, and is capable of transmitting driving force from the process motor to the third photosensitive drum and the fourth photosensitive drum; a belt, which is configured to be in contact with the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum; a belt gear train, which has a fifth gear directly engaged with a gear constituting the first process gear train or a gear constituting the second process gear train, and is capable of transmitting driving force from the process motor to the belt; a cleaning roller, which is in contact with the belt to recover an adherent adhering to the belt; and a cleaning gear train, which has an eighth gear directly engaged with the process drive gear, and is capable of transmitting driving force from the process motor to the cleaning roller. provided with:

3. An image forming apparatus characterized by comprising: a first photosensitive drum; a second photosensitive drum; a third photosensitive drum; a fourth photosensitive drum; a first developing roller, which supplies toner to the first photosensitive drum; a second developing roller, which supplies toner to the second photosensitive drum; a third developing roller, which supplies toner to the third photosensitive drum; a fourth developing roller, which supplies toner to the fourth photosensitive drum; a developing drive gear; a developing motor, which drives the developing drive gear; a first developing gear train, which has a first gear directly engaged with the developing drive gear, and is capable of transmitting driving force from the developing motor to the first developing roller and the second developing roller; a second developing gear train, which is provided independently of the first developing gear train, has a second gear directly engaged with the developing drive gear, and is capable of transmitting driving force from the developing motor to the third developing roller and the fourth developing roller; a process drive gear; a process motor, which drives the process drive gear; a first process gear train, which has a third gear directly engaged with the process drive gear, and is capable of transmitting driving force from the process motor to the first photosensitive drum and the second photosensitive drum; ​ a second process gear train, which is provided independently of the first process gear train, has a fourth gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the third photosensitive drum and the fourth photosensitive drum; a ring-shaped belt configured to contact the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum; a belt gear train having a sixth gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the belt; a cleaning roller that recovers adherents adhering to the belt while contacting the belt; and a cleaning gear train having a seventh gear that directly engages with a gear provided to an output shaft of the process motor, and is capable of transmitting driving force from the process motor to the cleaning roller.

4. An image forming apparatus characterized by comprising: provided with: a first photosensitive drum; a second photosensitive drum; a third photosensitive drum; a fourth photosensitive drum; a first developing roller that supplies toner to the first photosensitive drum; a second developing roller that supplies toner to the second photosensitive drum; a third developing roller that supplies toner to the third photosensitive drum; a fourth developing roller that supplies toner to the fourth photosensitive drum; a developing drive gear; a developing motor that drives the developing drive gear; a first developing gear train having a first gear that directly engages with the developing drive gear, and is capable of transmitting driving force from the developing motor to the first developing roller and the second developing roller; a second developing gear train, which is provided independently of the first developing gear train, has a second gear that directly engages with the developing drive gear, and is capable of transmitting driving force from the developing motor to the third developing roller and the fourth developing roller; a process drive gear; a process motor that drives the process drive gear; a first process gear train having a third gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the first photosensitive drum and the second photosensitive drum; a second process gear train, which is provided independently of the first process gear train, has a fourth gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the third photosensitive drum and the fourth photosensitive drum; a ring-shaped belt configured to contact the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum; a belt gear train having a sixth gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the belt; a cleaning roller that recovers adherents adhering to the belt while contacting the belt; and a cleaning gear train having a seventh gear that directly engages with a gear provided to an output shaft of the process motor, and is capable of transmitting driving force from the process motor to the cleaning roller. provided with: a first photosensitive drum; a second photosensitive drum; a third photosensitive drum; a fourth photosensitive drum; a first developing roller that supplies toner to the first photosensitive drum; a second developing roller that supplies toner to the second photosensitive drum; a third developing roller that supplies toner to the third photosensitive drum; a fourth developing roller that supplies toner to the fourth photosensitive drum; a developing drive gear; a developing motor that drives the developing drive gear; a first developing gear train having a first gear that directly engages with the developing drive gear, and is capable of transmitting driving force from the developing motor to the first developing roller and the second developing roller; a second developing gear train, which is provided independently of the first developing gear train, has a second gear that directly engages with the developing drive gear, and is capable of transmitting driving force from the developing motor to the third developing roller and the fourth developing roller; a process drive gear; a process motor that drives the process drive gear; a first process gear train having a third gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the first photosensitive drum and the second photosensitive drum; a second process gear train, which is provided independently of the first process gear train, has a fourth gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the third photosensitive drum and the fourth photosensitive drum; a ring-shaped belt configured to contact the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum; a belt gear train having a sixth gear that directly engages with the process drive gear, and is capable of transmitting driving force from the process motor to the belt; a cleaning roller that recovers adherents adhering to the belt while contacting the belt; and a cleaning gear train having a seventh gear that directly engages with a gear provided to an output shaft of the process motor, and is capable of transmitting driving force from the process motor to the cleaning roller.

5. The image forming apparatus according to any one of claims 1 to 4, characterized in that the first developing gear train has: a first clutch that is switchable between a transmission state in which a driving force input to the first gear is transmitted to the first developing roller and a cutoff state in which the driving force input to the first gear is not transmitted to the first developing roller; and a second clutch that is switchable between a transmission state in which a driving force input to the first gear is transmitted to the second developing roller and a cutoff state in which the driving force input to the first gear is not transmitted to the second developing roller, the second developing gear train has: a third clutch that is switchable between a transmission state in which a driving force input to the second gear is transmitted to the third developing roller and a cutoff state in which the driving force input to the second gear is not transmitted to the third developing roller; and a fourth clutch that is switchable between a transmission state in which a driving force input to the second gear is transmitted to the fourth developing roller and a cutoff state in which the driving force input to the second gear is not transmitted to the fourth developing roller.

6. The image forming apparatus according to any one of claims 1 to 4, characterized in that the first developing gear train has: a first output gear that outputs a driving force input to the first gear to the first developing roller; and a second output gear that outputs a driving force input to the first gear to the second developing roller, the second developing gear train has a third output gear that outputs a driving force input to the second gear to the third developing roller, the number of gears interposed between the first gear and the first output gear, the number of gears interposed between the first gear and the second output gear, and the number of gears interposed between the second gear and the third output gear are the same number.

7. The image forming apparatus according to claim 6, characterized in that the second developing gear train has a fourth output gear that outputs a driving force input to the second gear to the fourth developing roller, the number of gears interposed between the second gear and the fourth output gear is more than the number of gears interposed between the second gear and the third output gear.

8. The image forming apparatus according to any one of claims 1 to 4, characterized in that the process driving gear is a gear that directly engages with a gear provided to an output shaft of the process motor.

9. The image forming apparatus according to any one of claims 1 to 4, characterized in that the process driving gear is a gear provided to an output shaft of the process motor.

10. The image forming apparatus according to any one of claims 1 to 4, characterized in that the developing driving gear is a gear provided to an output shaft of the developing motor. ​ ​ ​

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