JP4900581B2 - DRIVE DEVICE, OFFSET DISCHARGE DEVICE, AND IMAGE FORMING DEVICE - Google Patents

Description

  The present invention relates to a drive device, an offset paper discharge device having the drive device, and an image forming apparatus having the drive transmission device.

  In this type of image forming apparatus, a driving device that transmits the driving force of a driving source to a movable member at a predetermined timing is used. For example, the clutch includes a locking portion provided in the circumferential direction of the clutch and a solenoid including an actuator that can be moved toward and away from the locking portion. A pair of engaging claws that are alternately connectable and disengageable are provided, and a predetermined amount of rotation of the clutch is set by engaging one of the engaging claws with the engaging portion according to the excitation state of the solenoid. Known (for example, Patent Document 1). Further, for example, there is a known one having a chipped gear having a plurality of engaging portions to which a solenoid flapper is hooked, and controlling the rotational position of the chipped gear by energizing the solenoid for a certain time (for example, Patent Documents). 2).

JP 2001-304296 A JP 2005-227315 A

  However, in the invention described in Patent Document 1, since the clutch is provided with a plurality of locking portions, it does not rotate beyond the locking portion or get over the locking portion due to the length of the energization time of the solenoid. was there. Further, in the invention described in Patent Document 2, since the plurality of locking portions are provided on the chipped gear, the springs that rotate (until they mesh) the chipped gears correspond to the stop positions at a plurality of positions. It was difficult. As described above, when a plurality of engaging portions are provided in the clutch or the chipped gear, and a plurality of operations are performed, it is difficult to increase the speed and the operation becomes unstable.

  An object of the present invention is to provide a driving device that solves the above-described conventional problems and realizes a stable operation, and an offset paper discharge device and an image forming apparatus having the driving device.

  In order to achieve the above object, a first feature of the present invention is a tooth missing gear having a tooth missing portion lacking a part of a tooth, and rotationally driven to transmit a driving force to the tooth missing gear. A driving gear and a driven portion driven by the driving force transmitted from the driving gear via the tooth-missing gear, and each time the driving gear and the tooth-missing portion face each other, the driven portion is at least There are two different operating states in the drive. Therefore, reliable and stable operation of the driven portion is realized.

  Preferably, rotation of the toothless gear is locked at a position where the toothless portion is opposed to the drive gear, and by releasing the lock, the toothless gear is rotated and meshed with the drive gear. With actuating means for matching. Therefore, every time the drive gear and the tooth missing portion face each other, the tooth missing gear is reliably locked.

  Preferably, it has a detecting means for detecting an operating state of the driven portion. Therefore, the operating state of the driven unit can be grasped from the outside.

  Preferably, the driven portion has a driven gear, and the driven gear has a cam portion for giving a periodic motion.

  Preferably, the driven portion has a coupling having at least two gears, and the cam portion performs connection or disconnection of power between the at least two gears.

  According to a second aspect of the present invention, a tooth missing gear having a tooth missing portion lacking a part of a tooth, a driving gear that is rotationally driven to transmit a driving force to the tooth missing gear, and the tooth missing A driven portion driven by a driving force transmitted from the drive gear via a gear, and the driven portion is in at least two different operating states each time the drive gear and the tooth missing portion face each other. It is in an offset paper discharge device having a drive device.

  According to a third aspect of the present invention, there is provided a tooth missing gear having a tooth missing portion lacking a part of a tooth, a drive gear that is rotationally driven to transmit a driving force to the tooth missing gear, and the tooth missing tooth. A driven portion driven by a driving force transmitted from the drive gear via a gear, and the driven portion is in at least two different operating states each time the drive gear and the tooth missing portion face each other. An image having a driving device, at least one developing unit, and a driving source provided the same as or different from the driving device, wherein the driving device is incorporated in a gear train between the driving source and the developing unit. In the forming device.

  Preferably, the driving device releases transmission of power to at least one of the developing units.

  According to the present invention, since the driven portion is in at least two different operating states each time the drive gear and the tooth missing portion face each other, a reliable and stable operation of the driven portion can be realized.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus 10 according to the first embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12. A paper feeding device 14 is disposed below the image forming apparatus main body 12, and a paper discharge unit 16 is disposed above the image forming apparatus main body 12. Is formed.

  The paper feed unit 14 has a paper feed cassette 18, and a large number of sheets are stacked on the paper feed cassette 18. A paper feed roll 20 that comes into contact with the stacked paper is disposed at one upper end of the paper feed cassette 18, and a separating roll 22 is provided to face the paper feed roll 20. The uppermost sheet in the sheet feeding cassette 18 is picked up by the sheet feeding roll 20, and the sheet is rolled and conveyed by the cooperation of the sheet feeding roll 20 and the separating roll 22.

  The sheet conveyed from the sheet feeding cassette 18 is temporarily stopped by a registration roller 24, and discharged at a predetermined timing between a photosensitive unit 26 and a belt unit 28, which will be described later, and through a fixing device 30 by a discharge roller 32. 16 is discharged.

  In the image forming apparatus main body 12, a photosensitive unit 26, a belt unit 28, a power supply unit 34, and a control unit 36 are disposed as image forming means. In the photoconductor unit 26, for example, four photoconductors 40 are rotatably supported by the photoconductor unit main body 38. Around each photoconductor 40, a charging device 42 as a charging unit provided with a charging roll for uniformly charging the photoconductor 40, and an electrostatic latent image written on each photoconductor 40 with a developer (toner) A developing device 44 as a developing means that develops and visualizes the toner, a neutralizing device 46 that neutralizes the photoconductor 40 after transfer, and a toner removing device 48 that removes residual toner on the surface of the photoconductor 40 after transfer. Have. The photoconductor unit 26 includes four photoconductors 40, a charging device 42, a developing device 44, a charge removal device 46, and a toner removal device 48, and is detachable from the image forming apparatus main body 12. .

  The power supply unit 34 is disposed on the upper part of the image forming apparatus main body 12 and supplies power to the paper feeding device 14, the belt unit 28, the charging device 42, the developing device 44, and the like described above.

  The four toner boxes 50 are connected to the back side of the photoconductor unit 26. Each toner box 50 is for magenta, yellow, cyan, and black, and a toner supply unit 52 and a toner recovery unit 54 are integrated. The toner supply unit 52 is connected to the developing device 44 to supply the toner of each color to the developing device 44, and the toner recovery unit 54 is connected to the toner removing device 48 to recover the toner of each color.

  Each of the optical writing devices 56 is composed of a laser exposure device, and is arranged on the back side of the photoconductor unit 26 at a position corresponding to each photoconductor 40, and irradiates the uniformly charged photoconductor 40 with a laser. Thus, a latent image is formed.

  The belt unit 28 is on the front side of the photoconductor unit 26 and is arranged in the vertical direction so as to face the photoconductor unit 26. The belt unit 28 is formed in a belt shape, and a conveyance belt 60 that conveys a sheet on which a toner image formed by the developer 44 is transferred is supported on two support rolls 58 provided in the vertical direction. Further, a transfer roll 62 is provided so as to face each photoconductor 40 with the conveyance belt 60 interposed therebetween.

  The cleaning device 64 is disposed on the front side of the belt unit 28 so as to face the belt unit 28. The cleaning device 65 includes a cleaning device main body 66, a cleaning blade 68 as a cleaning member, a collection container 70, and a charge removal film 72, and removes deposits such as toner and paper dust on the surface of the conveyor belt 60. It is like that.

  A user interface (UI) device 73 is provided integrally with the image forming apparatus main body 12 or via a network, and is electrically connected to the control unit 36. The UI device 73 is provided with a display panel 73a and an input button 73b as display means for selecting and displaying processing contents of the image forming apparatus 10.

  Therefore, each photoconductor 40 is uniformly charged by the charging device 42, a latent image is formed by the optical writing device 56, and the latent image is visualized by toner by the developing device 44. The toner images formed on the respective photoconductors 40 are transferred onto the conveyed paper by the transfer roller 62 of the belt unit 28 in order from below, and are fixed on the paper by the fixing device 30.

Details of the developing device 44 and the drive transmission device 76 are shown in FIGS.
As shown in FIG. 2, the developing device 44 is for yellow (Y), magenta (M), cyan (C) and black (K) in order from the upstream direction (downward), and development for developing toner of each color. Rolls 74Y, 74M, 74C, and 74K are provided. These developing rolls 74Y, 74M, 74C, and 74K are driven by a driving force of a driving source 82a via a driving device 86 and a drive transmission device 76 described later.

  As shown in FIG. 3, the drive transmission device 76 is provided in the image forming apparatus main body 12 and has a plurality of gears. More specifically, the drive transmission device 76 includes a drive source 82a, first transmission gears 78a, 78b, 78c, second transmission gears 80a, 80b, 80c, 80d, and third transmission gears 82b, 82c, 82d. , Development drive transmission gears 84a, 84b, 84c, and 84d, and an input gear 108 and an output gear 110 of a drive device 86 to be described later.

  The developing roll 74K is driven from the driving source 82a via the third transmission gears 82b, 82c, 82d and the developing driving gear 84d. When the driving force is transmitted from the driving source 82a to the second transmission gear 80d and the first transmission gear 78c, and the driving force is transmitted from the input gear 108 to the output gear 110, the first transmission gears 78a and 78b. The developing rolls 74Y, 74M, and 74C are driven through the second transmission gears 80a, 80b, and 80c and the developing drive gears 84a, 84b, and 84c.

Details of the drive 86 are shown in FIGS.
As shown in FIGS. 4 and 5, the driving device 86 has a driving device main body 88 and is provided in the image forming apparatus main body 12. The driving device main body 88 is provided with a toothless gear 90, a driving gear 92, and a driven portion 93 that is driven by the driving force transmitted from the driving gear 92 via the toothless gear 90. The driven portion 93 is provided with a driven gear 94, a solenoid 96, a coupling 98, and a detection device 100.

  The tooth missing gear 90 is rotatably provided in the driving device main body 88, and a tooth portion 90a in which a plurality of teeth are formed at a predetermined pitch on the outer periphery and a tooth is not provided in part (tooth teeth). A missing tooth portion 90b, which is partially missing, is formed. Further, the tooth missing gear 90 is formed integrally with the tooth missing gear 90 with a cylindrical boss portion 104 protruding in the axial direction (tooth width direction). The boss portion 104 is formed with a sliding surface 104 a on which a movable piece 116 of a solenoid 96 described later slides, and a gear portion 104 b that meshes with the driven gear 94. A part of the sliding surface 104a is provided with a locking part 104c. When the locking part 104c and the movable piece 116 of the solenoid 96 are engaged, the rotation of the tooth missing gear 90 is restricted. It is like that.

  A drive gear 92 that is connected to a drive source (not shown) such as a motor and that is rotationally driven to transmit power to the tooth missing gear 90 is disposed in the vicinity of the tooth missing gear 90. The drive gear 92 is rotatably provided on the drive device main body 88 and is disposed at a position where the drive gear 92 meshes with the tooth portion 90 a of the tooth missing gear 90. When the drive 92 and the tooth missing portion 90 b of the tooth missing gear 90 face each other, the drive gear 92 idles so that the power from the tooth missing gear 90 is not transmitted to the tooth missing gear 90.

  The driven gear 94 is rotatably provided in the drive device main body 88 and is disposed at a position where the driven gear 94 meshes with the gear portion 104b. A light shielding member 105 is formed on one side surface of the driven gear 94, and a cam 106 is formed integrally with the driven gear 94 on the other side surface. The light blocking member 105 rotates integrally with the driven gear 94 and blocks the optical signal of the detection device 100 at a predetermined timing. The cam 106 is formed integrally with the driven gear 94 on a substantially half circumference (about 180 °) portion of the side surface of the driven gear 94, and is provided so as to contact the slide member 112 of the coupling 98. The cam 106 is rotated integrally with the driven gear 94 to give a periodic motion to the slide member 112. The gear ratio between the driven gear 94 and the gear portion 104b of the tooth missing gear 90 is 1: 2, and when the tooth missing gear 90 rotates once, the driven gear 94 rotates halfway.

  The coupling 98 is rotatably provided on a rotation support shaft 102 formed in the drive device main body 88, and includes an input gear 108, an output gear 110, and a slide member 112. As described above, the input gear 108 is disposed at a position that meshes with the first transmission gear 78c. Further, the input gear 108 has an engaging portion 108 a that engages with the engaged portion 112 a of the slide member 112.

  The slide member 112 is provided so as to be slidable in the axial direction with respect to the rotation support shaft 102, and an engaged portion 112 a that engages with the engaging portion 108 a of the input gear 108 is formed at the distal end portion. The slide member 112 supports the output gear 110 so as to rotate integrally with the output gear 110 and is slidable with respect to the output gear 110. As described above, the output gear 110 is disposed at a position that meshes with the first transmission gears 78a and 78b.

  The output gear 110 is slidably supported by the slide member 112 and rotates together with the slide member 112. The coil spring 114 is provided between the drive device main body 88 and the slide member 112, and biases the slide member 112 in the direction of the input gear 108. In this way, the coupling 98 performs connection or disconnection of power between the input gear 108 and the output gear 110.

  The solenoid 96 is disposed in the vicinity of the tooth missing gear 90 and includes a movable piece 116 and a coil spring 117. The movable piece 116 is formed with a locking claw 116a whose tip is bent in an L shape. The coil spring 117 urges the locking claw 116 a of the movable piece 116 toward the sliding surface 104 a of the tooth missing gear 90. The locking claw 116 is configured to regulate the rotation of the tooth missing gear 90 by engaging with the locking portion 104 c of the tooth missing gear 90.

  The detection device 100 includes, for example, a photosensor, and includes a light emitting unit 100a that outputs an optical signal and a light receiving member 100b that receives the optical signal output from the light emitting unit 100a. The detection device 100 is configured to detect the position of the light shielding member 105 of the driven gear 94. That is, when the light path of the optical signal output from the light emitting unit 100a to the light receiving unit 100b is blocked by the light blocking member 105 by the light blocking member 105, the detection device 100 sends a signal indicating that the optical signal has been blocked to the control unit 36. In response to this, it is designed to output. Thus, the detection apparatus 100 is used as a detection unit that detects the operation state of the driven unit 93.

  One end of the biasing spring 118 is locked to the spring hooking portion 90 c of the tooth missing gear 90, and the other end is locked to the drive device main body 88 so that a predetermined biasing force is applied to the tooth missing gear 90. It has become. More specifically, the biasing spring 118 applies a biasing force for rotating the tooth missing gear 90 until the tooth portion 90a of the tooth missing gear 90 and the drive gear 92 are engaged with each other. . The biasing spring 118 and the above-described solenoid 96 lock the rotation of the tooth missing gear 90 at a position where the tooth missing portion 90b faces the drive gear 92, and release the lock to remove the tooth missing gear 90. An actuating means that rotates and meshes with the drive gear 92 is configured.

Next, the operation of the drive device 86 in the embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 6 and 8A, when the driven portion 93 of the driving device 86 is in the first operation state, the power between the input gear 108 and the output gear 110 is connected. Yes. More specifically, the portion of the side surface of the driven gear 94 where the cam 106 is not formed and the slide member 112 of the coupling 98 come into contact with each other, and the engaging portion 108 a of the input gear 108 and the slide member are urged by the biasing force of the coil spring 114. 112 is engaged with the engaged portion 112a. Therefore, the input gear 108 and the output gear 110 are rotated by the driving force transmitted from the first transmission gear 78c. Accordingly, the output gear 110 operates the developing rolls 74Y, 74M, and 74C via the first transmission gears 78a and 78b, the second transmission gears 80a to 80c, and the development driving gears 84a to 84d. Thus, when the driven portion 93 of the driving device 86 is in the first operating state, the developing rolls 74Y, 74M, 74C, and 74K are operated.

  Further, when the driven portion 93 of the driving device 86 is in the first operation state, the locking claw 116a of the movable piece 116 is locked to the locking portion 104c of the tooth missing gear 90, whereby the tooth missing gear 90 is rotated. The tooth missing gear 90 is held at the operation start position. In this operation start position, the tooth missing portion 90b of the tooth missing gear 90 and the drive gear 92 are in a position facing each other. Therefore, the drive gear 92 idles and no driving force is transmitted to the tooth missing gear 90.

  When the driven portion 93 of the driving device 86 is in the first operating state, the light shielding portion 105 of the driven gear 94 blocks the optical path of the optical signal output from the light emitting portion 100a of the detecting device 100 toward the light receiving portion 100b. It has become a state. At this time, the detection apparatus 100 outputs a signal indicating that the optical signal has been blocked to the control unit 36. The control unit 36 receives the signal from the detection device 100 and determines that the driving device 86 is in the first operation state, that is, the developing rolls 74Y, 74M, 74C, and 74K are operating.

  Subsequently, when the solenoid 96 is energized (on), a magnetic attractive force acts on the movable piece 116, and the movable piece 116 is pulled against the urging force of the coil spring 117. As a result, the engagement between the locking portion 104 c of the tooth missing gear 90 and the locking claw 116 a of the movable piece 116 is released, and the tooth missing gear 90 is rotated by the biasing force of the biasing spring 118. When the tooth missing gear 90 further rotates and the drive gear 92 and the tooth portion 90a of the tooth missing gear 90 mesh with each other, the tooth missing gear 90 is rotated by the power of the drive gear 92.

  During the rotation of the tooth missing gear 90, the locking claw 116 a of the movable piece 116 slides on the sliding surface 104 a of the tooth missing gear 90. When the tooth missing gear 90 rotates approximately once, the tooth missing portion 90b again faces the meshing position with the drive gear 92, and the tooth missing gear 90 and the drive gear 92 are disengaged. When the toothless gear 90 and the drive gear 92 are disengaged, the locking portion 104 of the toothless gear 90 abuts against the locking claw 116a of the movable piece 116, and the rotation of the toothless gear 90 is restricted by the movable piece 116. . As a result, the tooth missing gear 90 is again held at the operation start position, and the driven portion 93 of the drive device 86 enters a second operation state described later.

  As shown in FIGS. 7 and 8B, when the driven portion 93 of the driving device 86 is in the second operation state, the power connection between the input gear 108 and the output gear 110 is released. It has become. More specifically, as compared with the first operation state, the driven gear 94 is rotated by about 180 °, and the cam 106 of the driven gear 94 resists the biasing force of the coil spring 114 and the sliding member of the coupling 98. 112 is pressed, and the slide member 112 is slid in the direction opposite to the input gear 108. As a result, the engagement between the engaging portion 108a of the input gear 108 and the engaged portion 112a of the slide member 112 is released. Accordingly, only the input gear 108 is rotated by the driving force transmitted from the first transmission gear 78c, the transmission of the driving force from the input gear 108 to the output gear 110 is released, and the developing rolls 74Y, 74M, and 74C are operated. Stopped. On the other hand, the developing roller 74K continues to operate by the driving force of the driving source 82a. Thus, when the driven portion 93 of the driving device 86 is in the second operation state, the developing roll 74K is activated, and the operations of the developing rolls 74Y, 74M, and 74C are stopped. In this manner, the drive device 86 switches the transmission of the driving force to the developing rolls 74Y, 74M, 74C, and 74K by switching the operation state of the driven portion 93.

  As described above, according to the drive device 86 of the present invention, every time the drive gear 92 and the tooth missing portion 90b of the tooth missing gear 90 face each other, that is, the engagement portion 104c of the tooth missing gear 90 and the movable piece 116 are engaged. Each time the pawl 116a is engaged, the driven portion 93 enters at least two different operation states (first operation state or second operation state). Therefore, the driving device 86 realizes a reliable and stable operation of the driven portion 93. Further, by switching the operating state of the driven portion 93, the driving force switching operation to each of the developing rolls 74Y, 74M, 74C, and 74K is performed reliably and stably.

  The toner in the developing device 44 has a property that the deterioration is accelerated as the toner is agitated by a toner feed screw (not shown). Therefore, for a user who outputs a large amount of K (black), a full color image is displayed. Although not recorded, there is a problem that the toner deterioration of each color of YMC is promoted, and an image defect or toner scattering due to the deteriorated toner occurs. On the other hand, according to the drive device 86 of the present invention, in the case of K (black) monochrome output, the driven portion 93 is set to the second operation state, and the operation of the developing rolls 74Y, 74M, and 74C can be stopped. Therefore, it is possible to suppress the deterioration of the YMC colors and the occurrence of image defects and toner scattering due to the deteriorated toner.

Next, a second embodiment of the present invention will be described with reference to FIG.
The drive device 86 according to the second embodiment of the present invention is used in the offset paper discharge device 120. The offset paper discharge device 120 includes a drive device 86 and an offset mechanism 122. The offset mechanism 122 includes a slide member 124, and the slide member 124 is provided with a paper guide 126 that guides the side surface of the discharged paper 128.

  As shown in FIG. 9A, when the driven portion 93 of the driving device 86 is in the first operating state, the portion of the driven gear 94 where the cam 106 is not formed contacts the offset member 124 of the coupling 98. It has become a state. At this time, the paper 128 is discharged to a predetermined position along the paper guide 126.

  As shown in FIG. 9B, when the driven portion 93 of the driving device 86 is in the second operation state, the driven gear 94 is approximately 180 ° compared to the first operation state. The cam 106 of the driven gear 94 slides and moves the slide member 124 of the coupling 98 against the biasing force of the coil spring 114. As a result, the paper guide 126 moves by a predetermined amount in a direction perpendicular to the conveyance direction of the paper 128 as compared with the first operation state. Accordingly, the paper 128 moves with the movement of the paper guide 126, and is discharged with a predetermined offset compared to the first operation state.

Thus, according to the offset paper discharge device 120 of the present embodiment, every time the drive gear 92 and the tooth missing portion 90b of the tooth missing gear 90 face each other, that is, the locking portion 104c of the tooth missing gear 90 and the movable piece 116. Each time the engaging claw 116a is engaged, the driven portion 93 enters at least two different operating states (first operating state or second operating state). Therefore, the offset paper discharge device 120 realizes reliable and stable offset paper discharge by the offset mechanism 122.
In the description of the second embodiment of the present invention, the same parts as those in the first embodiment of the present invention are designated by the same reference numerals and omitted.

1 is a side view showing an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a side view for explaining the periphery of the photosensitive unit of the image forming apparatus according to the first embodiment of the present invention. It is a schematic diagram explaining the drive transmission device which has the drive device which concerns on the 1st Embodiment of this invention. It is a side view explaining the drive device concerning a 1st embodiment of the present invention. It is a front view explaining the drive device concerning a 1st embodiment of the present invention. It is a perspective view explaining the 1st operation state of the follower concerning a 1st embodiment of the present invention. It is a perspective view explaining the 2nd operation state of the driven part concerning a 1st embodiment of the present invention. The operation state of the driven part which concerns on the 1st Embodiment of this invention is shown, (a) is a 1st operation state, (b) is a front view explaining a 2nd operation state. The operation | movement of the offset paper discharge apparatus which concerns on the 2nd Embodiment of this invention is shown, (a) 1st operation state, (b) is a front view explaining 2nd operation state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 44 Developing device 74Y, 74M, 74C, 74K Developing roll 76 Drive transmission device 86 Drive device 90 Tooth missing gear 90b Tooth missing portion 92 Drive gear 93 Followed portion 94 Followed gear 96 Solenoid 98 Coupling 100 Detection device 106 Cam 120 Offset paper discharge device

Claims (6)

A tooth missing gear having a tooth missing part lacking a part of the tooth;
A drive gear that rotates to transmit drive force to the toothless gear;
A driven portion driven by the driving force transmitted from the driving gear via the tooth-missing gear,
The driven portion includes at least two gears that rotate on the same axis, an engaged portion that transmits power between the two gears , a coupling having an engaging portion that engages with the engaged portion , and the cup and a cam portion providing a periodic movement to the ring,
Whenever the drive gear and the tooth missing portion face each other, at least one of the engaged portion and the engaging portion of the coupling is moved by the rotation of the cam portion to connect the power between the at least two gears. Or the drive device characterized by performing connection cancellation | release.   Actuating means for locking the rotation of the tooth missing gear at a position where the tooth missing portion is opposed to the drive gear, and rotating the tooth missing gear to engage with the drive gear by releasing the lock. The drive device according to claim 1, wherein the drive device is provided.   The driving apparatus according to claim 1, further comprising a detecting unit that detects an operation state of the driven unit. A tooth missing gear having a tooth missing portion in which a part of teeth is missing, a drive gear that rotates to transmit a driving force to the tooth missing gear, and a drive transmitted from the drive gear via the tooth missing gear A driven portion driven by force, and the driven portion engages with at least two gears rotating on the same axis, an engaged portion transmitting power between the two gears , and the engaged portion. coupling having an engaging portion, each having a cam portion providing a periodic movement in the coupling, and the drive gear and the toothless portion is opposed, the coupling by the rotation of the cam portion An offset paper discharge device comprising: a driving device that moves or releases the power between the at least two gears by moving at least one of the engaged portion and the engaging portion . A tooth missing gear having a tooth missing portion in which a part of teeth is missing, a drive gear that rotates to transmit a driving force to the tooth missing gear, and a drive transmitted from the drive gear via the tooth missing gear A driven portion driven by force, and the driven portion engages with at least two gears rotating on the same axis, an engaged portion transmitting power between the two gears , and the engaged portion. coupling having an engaging portion, each having a cam portion providing a periodic movement in the coupling, and the drive gear and the toothless portion is opposed, the coupling by the rotation of the cam portion A driving device for moving or releasing the power between the at least two gears by moving at least one of the engaged portion and the engaging portion, at least one developing unit, and the same or different from the driving device. A drive source, Serial image forming apparatus, wherein said that the drive device is incorporated in the gear train between the drive source and the developing means.   The image forming apparatus according to claim 5, wherein the driving device releases transmission of power to at least one of the developing units.

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