Oldham coupling and image forming apparatus

Abstract

To provide an Oldham coupling that has play in a rotation direction and can transmit a driving force.SOLUTION: In an Oldham coupling 1 having a development drive gear 99 being a first hub, a drive coupling 89 being a second hub, and an intermediate member 3 transmitting a driving force between the development drive gear 99 and the drive coupling 89, the development drive gear 99 has a projection 99a fitted to a concave part 3a of the intermediate member 3 and transmitting the driving force between the intermediate member 3 and the projection, and when seen from a rotation axis direction of the Oldham coupling 1, a projection 89a has a substantially diamond shape.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to an Oldham coupling that transmits drive from a drive source to a unit to be driven, and to an image forming apparatus equipped with the same. [Background technology]

[0002] Conventionally, a configuration has been used in which drive is transmitted from a motor to each unit to be driven by a drive train using gears, etc. For example, Patent Document 1 describes a configuration in which one motor is used to rotate both a photosensitive drum and a developing sleeve provided in a developing unit.

[0003] Furthermore, Patent Document 1 describes a configuration for selectively rotating a photosensitive drum and a developing sleeve, which are multiple drive targets. The configuration in Patent Document 1 includes a power transmission mechanism that transmits drive force from a drive source to the drive targets, the developing sleeve and the photosensitive drum, and a drive train that is provided with a coupling having a predetermined rotational angle of play. This configuration makes it possible to selectively transmit drive force to the drive targets when the motor is rotated forward or reverse. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-234643 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, in a power transmission mechanism that transmits driving force from a drive source to a unit to be driven, a configuration is conceivable in which the unit to be driven is attached to or detached from a device equipped with a drive source. In this case, the rotation axis of the drive source and the rotation axis of the detached unit are likely to be misaligned.

[0006] In a configuration in which the rotation axes of the two rotating shafts are likely to be misaligned, an Oldham coupling may be provided to enable transmission of driving force even when the rotation axes of the two rotating shafts are misaligned.

[0007] Generally, an Oldham coupling includes a first hub, a second hub, and an intermediate member that transmits driving force between the first and second hubs. However, if an Oldham coupling configuration like the coupling shape in Patent Document 1 is applied to selectively transmit driving force to a driven object when the motor is rotated forward or reverse, there is a risk that the driving force will not be transmitted.

[0008] That is, in the two couplings described in Patent Document 1, the shape of one is considered to be the first hub, and the shape of the other is considered to be the intermediate member. In this case, because the intermediate member cannot move radially relative to the first hub, there is a risk that driving force will not be transmitted if the rotational axes of the first rotating shaft on the drive source side and the second rotating shaft on the unit to be driven are misaligned. In other words, if a configuration with play in the rotational direction as in Patent Document 1 is applied, driving force will not be transmitted when the rotational axes of the two rotating shafts are misaligned, and the coupling will no longer function as an Oldham coupling.

[0009] In view of the current situation, the present invention has an object to provide an Oldham coupling that is capable of transmitting driving force even when configured with play in the rotational direction. [Means for solving the problem]

[0010] A representative configuration of an Oldham coupling according to the present invention for achieving the above object is an Oldham coupling having a first hub, a second hub, and an intermediate member for transmitting a driving force between the first hub and the second hub, wherein one of the intermediate member and the first hub has a first recess formed on an end surface of the Oldham coupling in the rotational axis direction, recessed in the rotational axis direction, and extending in a first direction perpendicular to the rotational axis direction, the first recess having a first inner wall on one side in a second direction perpendicular to the rotational axis direction and the first direction, and a second inner wall provided on the other side in the second direction and extending parallel to the first inner wall, the other of the intermediate member and the first hub having a first protruding portion protruding in the rotational axis direction, fitted into the first recess, and transmitting a driving force between the intermediate member and the first hub, the first protruding portion being configured such that the Oldham coupling is a first coupling having a first recess formed on an end surface of the Oldham coupling in the rotational axis direction, recessed in the rotational axis direction, and extending in a first direction perpendicular to the rotational axis direction, the first recess having a first inner wall on one side in a second direction perpendicular to the rotational axis direction and the first direction, the second inner wall being provided on the other side in the second direction and extending parallel to the first inner wall, a first edge portion that contacts the first inner wall when the Oldham coupling rotates in a rotational direction, a second edge portion that contacts the second inner wall when the Oldham coupling rotates in the first rotational direction, a third edge portion that contacts the first inner wall when the Oldham coupling rotates in a second rotational direction opposite to the first rotational direction, and a fourth edge portion that contacts the second inner wall when the Oldham coupling rotates in the second rotational direction opposite to the first rotational direction, wherein when the first edge portion contacts the first inner wall and the second edge portion contacts the second inner wall, the third edge portion is spaced apart from the first inner wall and the fourth edge portion is spaced apart from the second inner wall, and when the third edge portion contacts the first inner wall and the fourth edge portion contacts the second inner wall, the first edge portion is spaced apart from the first inner wall and the second edge portion is spaced apart from the second inner wall, Motorwhen the Oldham coupling rotates in conjunction with the rotation of the motor in the second rotation direction, a portion of the first edge farthest from a first center of rotation that is the center of rotation of the first hub in the first direction is located closer to the second inner wall than the first center of rotation, and a portion of the second edge farthest from the first center of rotation in the first direction is located closer to the first inner wall than the first center of rotation in the second direction; when the Oldham coupling rotates in conjunction with the rotation of the motor in the first rotation direction, a portion of the third edge farthest from the first center of rotation in the first direction is located closer to the second inner wall than the first center of rotation, and a portion of the fourth edge farthest from the first center of rotation in the first direction is located closer to the first inner wall than the first center of rotation in the second direction. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an Oldham coupling that has play in the rotational direction and is capable of transmitting driving force. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Figure 2] FIG. 2 is a perspective view of the process cartridge. [Figure 3] FIG. 2 is a cross-sectional view of the process cartridge. [Figure 4] FIG. 2 is a perspective view of the drum unit. [Figure 5] 4(a) to 4(d) are cross-sectional views of the drum unit. [Figure 6] FIG. [Figure 7] (a) and (b) are front and rear views of the drive unit. [Figure 8] FIG. 4 is a diagram showing gears of a drive unit. [Figure 9]1A and 1B are diagrams showing the configurations of a drive coupling, a drum coupling, and a development coupling. [Figure 10] FIG. 2 is an exploded perspective view of the Oldham coupling. [Figure 11] FIG. 2 is an exploded perspective view of the Oldham coupling. [Figure 12] 10A and 10B are diagrams showing the mating portion of the development drive gear, intermediate member, and drive coupling of the Oldham coupling. [Figure 13] 6 is a timing chart showing the operation timing of each member after the image forming operation is completed. [Figure 14] FIG. 2 is an exploded perspective view of the Oldham coupling. [Figure 15] FIG. 2 is an exploded perspective view of the Oldham coupling. [Figure 16] 10A and 10B are diagrams showing the mating portion of the development drive gear, intermediate member, and drive coupling of the Oldham coupling. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) <Image forming device> The overall configuration of an image forming apparatus equipped with an Oldham coupling according to the present invention will be described below with reference to the drawings, along with its operation during image formation. Note that the dimensions, materials, shapes, relative positions, etc. of the components described below are not intended to limit the scope of the present invention unless otherwise specified.

[0014] The image forming apparatus A according to this embodiment is an intermediate tandem type image forming apparatus that transfers four colors of toner (yellow Y, magenta M, cyan C, and black K) as developers onto an intermediate transfer belt, and then transfers the image onto a sheet to form an image. Note that in the following description, although components that use the above-mentioned respective colors of toner are given the suffixes Y, M, C, and K, the configurations and operations of the components are essentially the same except for the color of the toner used, and therefore the suffixes will be omitted as appropriate unless a distinction is required.

[0015] Fig. 1 is a schematic cross-sectional view of an image forming apparatus A. As shown in Fig. 1, the image forming apparatus A includes an image forming unit 61 that forms an image on a sheet S. The image forming unit 61 includes process cartridges 65 (65Y, 65M, 65C, 65K), a laser scanner unit 28, primary transfer rollers 31 (31Y, 31M, 31C, 31K), an intermediate transfer belt 30, a secondary transfer roller 51, and a secondary transfer opposing roller 52.

[0016] Each process cartridge 65 (image forming unit) is configured to be detachably attached to the image forming apparatus A. Each process cartridge 65 includes a photosensitive drum 26 (26Y, 26M, 26C, 26K) as a photosensitive member, and a charging roller 27 (27Y, 27M, 27C, 27K). Each process cartridge 65 also includes a developing unit 29 (29Y, 29M, 29C, 29K) having a developing sleeve 71 (71Y, 71M, 71C, 71K) as a developer carrier, and a cleaning blade 45 (45Y, 45M, 45C, 45K).

[0017] Next, the image forming operation will be described. First, when a control unit (not shown) receives an image formation job signal, a sheet S stored in a sheet cassette 22 is conveyed to a registration roller 24 by a feed roller 66. Thereafter, the registration roller 24 conveys the sheet S to a secondary transfer unit formed by a secondary transfer roller 51 and a secondary transfer counter roller 52 at a predetermined timing.

[0018] Meanwhile, in the image forming unit 61, the surface of the photosensitive drum 26Y is first charged by the charging roller 27Y. Then, the laser scanner unit 28 irradiates the surface of the photosensitive drum 26Y with laser light in accordance with image data input from an external device (not shown). As a result, an electrostatic latent image in accordance with the image data is formed on the surface of the photosensitive drum 26Y.

[0019] Next, a developing sleeve 71Y of the developing unit 29Y deposits yellow toner onto the electrostatic latent image formed on the surface of the photosensitive drum 26Y, forming a yellow toner image on the surface of the photosensitive drum 26Y. The toner image formed on the surface of the photosensitive drum 26Y is primarily transferred to the intermediate transfer belt 30 by applying a bias to the primary transfer roller 31Y. Thereafter, the toner remaining on the surface of the photosensitive drum 26Y is scraped off by a cleaning blade 45Y. The cleaning blade 45Y abuts against the surface of the photosensitive drum 26Y in a direction counter to the rotation direction of the photosensitive drum 26Y during image formation.

[0020] By a similar process, magenta, cyan, and black toner images are formed on the photosensitive drums 26M, 26C, and 26K. Then, by applying a bias to the primary transfer rollers 31M, 31C, and 31K, these toner images are transferred and superimposed on the yellow toner image on the intermediate transfer belt 30. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 30. After that, any toner remaining on the surfaces of the photosensitive drums 26M, 26C, and 26K is scraped off by cleaning blades 45M, 45C, and 45K.

[0021] The intermediate transfer belt 30 moves in a circular motion following the rotation of the secondary transfer opposing roller 52. As the intermediate transfer belt 30 carrying the full-color toner image moves, the toner image is sent to the secondary transfer section. Then, at the secondary transfer section, a bias is applied to the secondary transfer roller 51, so that the toner image on the intermediate transfer belt 30 is transferred to the sheet S.

[0022] Next, the sheet S onto which the toner image has been transferred is conveyed to a fixing unit 36, where it is subjected to a heat and pressure treatment, thereby fixing the toner image on the sheet S to the sheet S. Thereafter, the sheet S onto which the toner image has been fixed is discharged to a discharge unit 40 by a discharge roller 38.

[0023] <Process cartridge> Next, the structure of the process cartridge 65 will be described.

[0024] Fig. 2 is a perspective view of the process cartridge 65. Fig. 3 is a cross-sectional view of the process cartridge 65. As shown in Figs. 2 and 3, the process cartridge 65 is made up of a drum unit 42 and a developing unit 29.

[0025] First, the configuration of the drum unit 42 will be described. Fig. 4 is a perspective view of the drum unit 42. Figs. 5(a) to 5(d) are cross-sectional views of the photosensitive drum 26 and its surroundings in the drum unit 42. Figs. 5(a) to 5(d) show how the charging roller 27 separates from the photosensitive drum 26. As shown in Fig. 4 and Figs. 5(a) to 5(d), the drum unit 42 has the photosensitive drum 26, the charging roller 27, and a cleaning blade 45 (Fig. 3), and these members are held together by the drum container 11.

[0026] The drum container 11 rotatably holds the photosensitive drum 26. A drum coupling 13 that receives a driving force from a drive unit 90 (FIG. 7), which will be described later, is provided integrally with the photosensitive drum 26 at one end of the drum container 11 in the direction of the rotation axis of the photosensitive drum 26. The drum coupling 13 is disposed on the rear side of the image forming apparatus A in the drum container 11. Furthermore, flange gears 14 are provided integrally with the photosensitive drum 26 at both ends of the photosensitive drum 26 in the direction of the rotation axis.

[0027] The drum container 11 is also provided with a collection section 16 (FIG. 3) that collects toner removed from the surface of the photosensitive drum 26 by the cleaning blade 45. A transport screw 17 is provided inside the collection section 16 to transport the toner in the collection section 16 to the outside of the drum unit 42. The transport screw 17 rotates by receiving a driving force from the flange gear 14 via an idler gear 67, thereby transporting the toner. The toner transported to the outside of the drum unit 42 by the transport screw 17 is collected in a container (not shown) provided in the image forming apparatus A.

[0028] The drum container 11 is also provided with a bearing 19 that rotatably holds the charging roller 27. The bearing 19 is held in the drum container 11 so as to be slidable in a direction approaching or moving away from the photosensitive drum 26, and is biased toward the photosensitive drum 26 by a spring 12. This biasing force causes the charging roller 27 to come into pressure contact with the photosensitive drum 26 and to rotate in response to the rotation of the photosensitive drum 26.

[0029] One-way clutches 21 are provided on both ends of the charging roller 27. When torque is applied to the one-way clutch 21 in the direction opposite to the rotation direction of the charging roller 27 during image formation, the one-way clutch 21 enters a locked state and rotates integrally with the charging roller 27. When torque equal to or greater than a predetermined torque (idling torque) in the same direction as the rotation direction of the charging roller 27 during image formation is applied to the one-way clutch 21, the locked state is released and the one-way clutch 21 rotates idly without transmitting driving force between the charging roller 27. In this embodiment, the one-way clutch 21 is configured using a latch pawl and a rack.

[0030] Additionally, a spacing member 32 having gear portions 32a that mesh with flange gears 14 provided on both ends of the photosensitive drum 26 is provided on the outer periphery of the one-way clutch 21. The spacing member 32 and the one-way clutch 21 always rotate integrally, regardless of the rotation direction. In other words, when the charging roller 27 rotates in the direction opposite to the rotation direction during image formation in response to the rotation of the photosensitive drum 26, the one-way clutch 21 and spacing member 32 rotate in conjunction with this. The spacing member 32 separates the charging roller 27 from the photosensitive drum 26 by the operation described below, in order to prevent the charging roller 27 from being deformed due to the charging roller 27 being in pressure contact with the photosensitive drum 26 for a long period of time, which could adversely affect image quality.

[0031] That is, as shown in FIG. 5A, while the image forming apparatus A is performing an image formation operation, the gear portion 32a of the spacing member 32 and the flange gear 14 are separated and not engaged. When a predetermined time (eight hours in this embodiment) has elapsed since the image forming apparatus A finished its image formation operation, the photosensitive drum 26 is rotated in the direction opposite to the rotation direction during image formation. This causes the charging roller 27 to rotate in the direction opposite to the rotation direction during image formation, driven by the rotation of the photosensitive drum 26, and the one-way clutch 21 and spacing member 32 also rotate. As shown in FIG. 5B, when the spacing member 32 rotates, the gear portion 32a of the spacing member 32 engages with the flange gear 14. In this embodiment, the one-way clutch 21 enters a locked state when the charging roller 27 rotates 54 degrees. As a result, the gear portion 32a of the spacing member 32, which rotates integrally with the one-way clutch 21, engages with the flange gear 14. Until the gear portion 32a of the spacing member 32 meshes with the flange gear 14, the charging roller 27 rotates at a diameter ratio to the photosensitive drum 26. In this embodiment, the diameter of the photosensitive drum 26 is φ30 mm, and the diameter of the charging roller 27 is φ14 mm, so the amount of rotation of the photosensitive drum 26 is 25.2 degrees.

[0032] 5(c), when the photosensitive drum 26 and the charge roller 27 continue to rotate in the direction opposite to the rotation direction during image formation, the one-way clutch 21 and the spacing member 32 also rotate further. As the spacing member 32 rotates further, a force acts on the charge roller 27 in a direction separating it from the photosensitive drum 26 due to the shape of the spacing member 32, and this force causes the charge roller 27 to separate from the photosensitive drum 26 against the biasing force of the spring 12. In this embodiment, when the gear portion 32a of the spacing member 32 meshes with the flange gear 14 and the charge roller 27 rotates another 45 degrees, the charge roller 27 separates from the photosensitive drum 26. After the gear portion 32a of the spacing member 32 meshes with the flange gear 14, the charge roller 27 rotates at the gear ratio between the gear portion 32a of the spacing member 32 and the flange gear 14. In this embodiment, the amount of separation between the photosensitive drum 26 and the charging roller 27 is 1 mm, and therefore the amount of rotation of the photosensitive drum 26 is 24 degrees. Note that, when the next image is formed, the photosensitive drum 26 rotates in the rotation direction during image formation, and the charging roller 27 that has been separated from the photosensitive drum 26 performs an operation opposite to the above-described separation operation, thereby contacting the photosensitive drum 26 again.

[0033] 5(d), if the photosensitive drum 26 continues to rotate in the direction opposite to the rotation direction during image formation after the charging roller 27 has separated from the photosensitive drum 26, the spacing member 32 may come into contact with the drum container 11, resulting in malfunction. In this embodiment, if the charging roller 27 and the photosensitive drum 26 rotate an additional 45 degrees (24 degrees in terms of the amount of rotation of the photosensitive drum 26) after they have separated, the spacing member 32 will come into contact with the drum container 11. Therefore, in this embodiment, in order to prevent contact between the spacing member 32 and the drum container 11 while separating the charging roller 27 from the photosensitive drum 26, the amount of rotation of the photosensitive drum 26 in the direction opposite to the rotation direction during image formation is set to 49.2 degrees to 73.2 degrees.

[0034] Next, the configuration of the developing unit 29 will be described. Figure 6 is a perspective view of the developing unit 29. In Figure 6, a part of the developing container 70 is cut away to illustrate the internal configuration of the developing unit 29. As shown in Figure 6, the developing unit 29 includes a developing sleeve 71, a developing blade 72, and conveying screws 73 and 74, and these members are integrally held by the developing container 70.

[0035] The developing container 70 has an opening at a portion facing the photosensitive drum 26, and the developing sleeve 71 is disposed so that a portion of the developing sleeve 71 is exposed through this opening. The developing sleeve 71 is disposed facing the photosensitive drum 26 with a predetermined gap (240 μm in this embodiment) between them. A developing coupling 75 is provided at one end of the developing sleeve 71 in the direction of its rotation axis, and receives a driving force from a drive unit 90 (FIG. 7), which will be described later. The developing sleeve 71 rotates by receiving a driving force transmitted from the drive unit 90 via the developing coupling 75.

[0036] The developing coupling 75 is held by the developing container 70 at one end side in the rotational axis direction of the developing sleeve 71 in the developing container 70, at a position on the rear side of the image forming apparatus A. A D-cut shaped engaging portion (not shown) that engages with the developing coupling 75 is formed on the rotation shaft of the developing sleeve 71, thereby causing the developing sleeve 71 to rotate integrally with the developing coupling 75. A sleeve gear 81 is provided on one end side of the developing sleeve 71 in the developing container 70. The sleeve gear 81 is connected to the rotation shaft of the developing sleeve 71 by a parallel pin (not shown), and rotates integrally with the developing sleeve 71.

[0037] The developing sleeve 71 also contains a non-rotating magnet roller 76 (FIG. 3) with multiple magnetic poles. As shown in FIG. 3, the magnet roller 76 has a developing pole S1 in a developing region facing the photosensitive drum 26. The magnet roller 76 also has a transport pole N1, a scraping pole N2, a draw-up pole S2, and a cutting pole N3, located downstream of the developing pole S1 in the direction of rotation of the developing sleeve 71 during image formation. The center positions of these magnetic poles are 60 degrees for the transport pole N1, 180 degrees for the scraping pole N2, 230 degrees for the draw-up pole S2, and 290 degrees for the cutting pole N3, relative to the direction of rotation of the developing sleeve 71 during image formation (counterclockwise in FIG. 3), assuming that the developing pole S1 is at 0 degrees. The magnet roller 76 uses the magnetic force of each magnetic pole to support and transport toner to the developing region during image formation.

[0038] That is, the magnet roller 76 first draws up the toner contained in the developer container 70 with the draw-up pole S2 and causes the toner to be carried on the developing sleeve 71. Next, the toner carried on the developing sleeve 71 is made into brush-like spikes by the cutting pole N3. The made-up spikes are then transported to the development area by the rotation of the developing sleeve 71 and moved onto the photosensitive drum 26 by the developing pole S1. Thereafter, the toner remaining on the developing sleeve 71 gradually rises toward the center position between the transport pole N1 and the stripping pole N2 due to the repulsive magnetic field formed by the transport pole N1 and the stripping pole N2, and is finally stripped off from the developing sleeve 71.

[0039] A developing blade 72 is provided near the developing sleeve 71 with a predetermined distance between it and the developing sleeve 71. The developing blade 72 comes into contact with the toner carried on the developing sleeve 71 to form a toner layer of a predetermined thickness. Specifically, as the developing sleeve 71 rotates, the toner carried on the developing sleeve 71 and made to stand up by the cutting pole N3 passes between the tip of the developing blade 72 and the surface of the developing sleeve 71, thereby regulating the amount of toner and forming a toner layer. A scooping sheet 77 is attached to the developing blade 72 on the side opposite to the side where the developing sleeve 71 is disposed, to prevent toner from scattering outside the developing container 70.

[0040] The interior of the developing container 70 is divided into a developing chamber 79 and an agitating chamber 80 by a partition wall 78 extending in the direction of the rotation axis of the developing sleeve 71. Communication portions (not shown) that connect the developing chamber 79 and the agitating chamber 80 are provided at both longitudinal ends of the partition wall 78.

[0041] The developing chamber 79 and the stirring chamber 80 are provided with conveying screws 73 and 74, which rotate to convey toner by means of spiral blades. The conveying screws 73 and 74 convey toner in the longitudinal direction of the partition wall 78 and in opposite directions to each other. The conveying screws 73 and 74 are rotated by a driving force transmitted from a sleeve gear 81 that is provided integrally with the developing sleeve 71. When the conveying screws 73 and 74 rotate, toner circulates between the developing chamber 79 and the stirring chamber 80 via a communication portion (not shown).

[0042] Furthermore, with each image formation operation, toner accumulates in the space enclosed by the developing sleeve 71, developing blade 72, and scooping sheet 77 in the developing container 70. If the amount of accumulated toner becomes excessive, the accumulated toner may invade the development area and cause image defects known as blotches. To prevent this, the developing sleeve 71 rotates in the opposite direction to the rotation direction during image formation during non-image formation periods after a predetermined number of image formation operations. This moves the toner accumulated in the space enclosed by the developing sleeve 71, scooping sheet 77, and developing blade 72 toward the agitation chamber 80. Specifically, the toner raised by the repulsive magnetic field formed by the transport pole N1 and the scraping pole N2 passes through the space enclosed by the developing sleeve 71, scooping sheet 77, and developing blade 72 as the developing sleeve 71 rotates, and pushes the toner accumulated in this space back toward the agitation chamber 80. In this embodiment, the developing sleeve 71 rotates in the opposite direction every time 500 images are formed on A4 paper.

[0043] If the amount of rotation of the developing sleeve 71 in the direction opposite to the rotation direction during image formation is large, the toner picked up by the pick-up pole S2 will not pass through the developing blade 72 and a large amount of toner will be transported to the development area. This could cause the toner to scatter outside the developing container 70. Therefore, in order to prevent the toner from scattering outside, the amount of rotation of the developing sleeve 71 in the direction opposite to the rotation direction during image formation is set to the angle from the transport pole N1 to the scraping pole N2. That is, in this embodiment, the angle around the rotation axis of the developing sleeve 71 is set to between 60 degrees and 180 degrees.

[0044] <Drive unit> Next, the configuration of the drive unit 90 that drives the process cartridge 65 will be described.

[0045] Fig. 7(a) is a front view of the drive unit 90. Fig. 7(b) is a rear view of the drive unit 90. Fig. 8 is a diagram showing gears included in the drive unit 90. As shown in Figs. 7(a), 7(b), and 8, the drive unit 90 includes a box-shaped drive frame 91 formed by a rear frame 91a and a front frame 91b.

[0046] A motor 92a serving as a drive source for the photosensitive drums 26Y, 26M, and 26C and the developing sleeves 71Y, 71M, and 71C, and a motor 92b serving as a drive source for the photosensitive drum 26K and the developing sleeve 71K are fixed to the drive frame 91. In this embodiment, the motors 92a and 92b are DC brushless motors.

[0047] A pinion gear 93a is attached to the shaft of the motor 92a. A drum reduction gear 94a1 meshes with the pinion gear 93a, and drum reduction gear 94a1 meshes with drum drive gears 95M and 95C. Furthermore, a drum reduction gear 94a2 meshes with the drum drive gears 95M and 95Y. Due to the gear ratio of this gear train, the rotational speed of the drum drive gears 95Y, 95M, and 95C is reduced relative to the rotational speed of the motor 92a.

[0048] A pinion gear 93b is attached to the shaft of the motor 92b. The pinion gear 93b is engaged with a drum reduction gear 94b, which is in turn engaged with a drum drive gear 95K. Due to the gear ratio of this gear train, the rotational speed of the drum drive gear 95K is reduced relative to the rotational speed of the motor 92b.

[0049] Furthermore, drive couplings 96Y, 96M, 96C, and 96K that engage with the drum couplings 13 provided in the process cartridges 65Y, 65M, 65C, and 65K are provided coaxially with the drum drive gears 95Y, 95M, 95C, and 95K. As shown in Figure 9(a), a play α in the rotational direction is provided between the drive coupling 96 and the drum coupling 13 for each color. In this embodiment, the play α is set to an angle of 34 degrees around the rotation axis of the photosensitive drum 26.

[0050] With this configuration, the driving force of the motor 92a is transmitted to the drum coupling 13 via the pinion gear 93a, drum reduction gears 94a1 and 94a2, drum drive gears 95Y, 95M, and 95C, and drive couplings 96Y, 96M, and 96C, thereby rotating the photosensitive drums 26Y, 26M, and 26C. Meanwhile, the driving force of the motor 92b is transmitted to the drum coupling 13 via the pinion gear 93b, drum reduction gear 94b, drum drive gear 95K, and drive coupling 96K, thereby rotating the photosensitive drum 26K.

[0051] A development reduction gear 97a meshes with the pinion gear 93a. A plurality of idler gears 98a to 98g are provided to form a gear train with the development reduction gear 97a. The idler gears 98a, 98d, and 98g mesh with development drive gears 99Y, 99M, and 99C, respectively. Due to the gear ratio of this gear train, the rotational speed of the development sleeves 71Y, 71M, and 71C is reduced relative to the rotational speed of the motor 92a to 198% of the rotational speed of the photosensitive drums 26Y, 26M, and 26C.

[0052] The pinion gear 93b is in mesh with a development drive gear 99K via a gear train formed by a drum reduction gear 94b, an idler gear 98h, a development reduction gear 97b, and an idler gear 98i. Due to the gear ratio of this gear train, the rotation speed of the development sleeve 71K is reduced relative to the rotation speed of the motor 92b so as to be 198% of the rotation speed of the photosensitive drum 26K.

[0053] The rotational shafts (not shown) of the development drive gears 99Y, 99M, 99C, and 99K are connected to the rotational shafts 100Y, 100M, 100C, and 100K of the development couplings 75 provided in the process cartridges 65Y, 65M, 65C, and 65K shown in FIG. 7A via the Oldham couplings 1 (FIG. 10), which will be described later. The development couplings 75 are engaged with the drive couplings 89Y, 89M, 89C, and 89K, which form part of the Oldham couplings 1. As shown in FIG. 9B, the development couplings 75 have three protrusions, and the drive couplings 89 have three mating grooves into which the three protrusions of the drive couplings 75 are respectively fitted. Having three or more protrusions of one coupling and three or more mating grooves of the other coupling ensures stable drive transmission. A rotational play β is provided between the mating grooves of the drive couplings 89 for each color and the protrusions of the development couplings 75. In this embodiment, the play β is set to an angle of 30 degrees around the rotation axis of the developing sleeve 71.

[0054] With this configuration, the driving force of the motor 92a is transmitted to the developing coupling 75 via the pinion gear 93a, the developing reduction gear 97a, the idler gears 98a to 98g, the developing drive gears 99Y, 99M, and 99C, and the drive couplings 89Y, 89M, and 89C. This causes the developing sleeves 71Y, 71M, and 71C to rotate. Similarly, the driving force of the motor 92b is transmitted to the developing coupling 75 via the pinion gear 93b, the developing reduction gear 97a, the idler gears 98h and 98i, the developing drive gear 99K, and the drive coupling 89K. This causes the developing sleeve 71K to rotate.

[0055] As described above, in this embodiment, the rotation speed of the developing sleeve 71 for each color is 198% of the rotation speed of the photosensitive drum 26 for that color. Furthermore, in this embodiment, the diameter of the photosensitive drum 26 is φ30 mm, and the diameter of the developing sleeve 71 is φ18 mm. Therefore, the difference in gear ratio between the photosensitive drum 26 and the developing sleeve 71 is 3.3 times. In other words, when the photosensitive drum 26 makes one rotation, the developing sleeve 71 makes 3.3 rotations.

[0056] <Oldham Coupling> Next, the configuration of the Oldham coupling 1 will be described.

[0057] Fig. 10 is an exploded perspective view of the Oldham coupling 1 as seen from the front side of the image forming apparatus A. Fig. 11 is an exploded perspective view of the Oldham coupling 1 as seen from the rear side of the image forming apparatus A. Fig. 12(a) is a diagram showing the fitting portion between the development drive gear 99 of the Oldham coupling 1 and the intermediate member 3. Fig. 12(b) is a diagram showing the fitting portion between the drive coupling 89 of the Oldham coupling 1 and the intermediate member 3.

[0058] 10 and 11, the Oldham coupling 1 is made up of a developing device drive gear 99 (first hub), a drive coupling 89 (second hub), and an intermediate member 3 that transmits driving force between the developing device drive gear 99 and the drive coupling 89. The Oldham coupling 1 is rotatably held inside a coupling holder 2 provided on the front frame 91b.

[0059] In the direction of arrow X, which is the rotational axis direction of the Oldham coupling 1, a recess 3a (first recess) with a rectangular cross section is formed on one end face of the intermediate member 3. The recess 3a is recessed in the direction of arrow X and extends in the direction of arrow Y (first direction) perpendicular to the direction of arrow X. In addition, in the direction of arrow X, a recess 3b (second recess) with a rectangular cross section is formed on the other end face of the intermediate member 3. The recess 3b is recessed in the direction of arrow X and extends in the direction of arrow Z (second direction) perpendicular to the directions of arrow X and arrow Y. The recesses 3a and 3b have the same shape except that they extend in directions perpendicular to each other. The rotational axis direction of the Oldham coupling 1 is the same as the rotational axis direction of the development drive gear 99, the rotational axis direction of the drive coupling 89, and the rotational axis direction of the intermediate member 3.

[0060] Furthermore, in the rotational axis direction (arrow X direction) of the Oldham coupling 1, a convex portion 99a (first protrusion) that protrudes in the arrow X direction and fits into the recessed portion 3a of the intermediate member 3 is formed at one end of the development drive gear 99. Furthermore, in the rotational axis direction of the Oldham coupling 1, a convex portion 89a (second protrusion) that protrudes in the arrow X direction and fits into the recessed portion 3b of the intermediate member 3 is formed at one end of the drive coupling 89.

[0061] When the driving force of the motor 92a or 92b rotates the developing drive gear 99, the convex portion 99a of the developing drive gear 99 slides relatively inside the recessed portion 3a while contacting the inner wall of the recessed portion 3a, thereby transmitting the driving force to the intermediate member 3, and the intermediate member 3 rotates. When the intermediate member 3 rotates, the convex portion 89a of the drive coupling 89 slides relatively inside the recessed portion 3b while contacting the inner wall of the recessed portion 3a, thereby transmitting the driving force to the drive coupling 89, and the drive coupling 89 rotates. In this way, even if the rotation axis (not shown) of the developing drive gear 99 and the rotation axis of the rotation shaft 100 of the developing coupling 75 are misaligned, the driving force of the motor 92a or 92b is stably transmitted to the rotation shaft 100 of the developing coupling 75 via the Oldham coupling 1.

[0062] 12(a), the protrusion 99a has an edge 99a1 (first edge) that comes into contact with one inner wall 3a1 (first inner wall) in the width direction of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R1 (first rotation direction). The protrusion 99a also has an edge 99a2 (second edge) that comes into contact with the other inner wall 3a2 (second inner wall) in the width direction of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R1. The protrusion 99a also has an edge 99a3 (third edge) that comes into contact with the inner wall 3a1 of the recess 3a and an edge 99a4 (fourth edge) that comes into contact with the inner wall 3a2 when the Oldham coupling 1 rotates in the direction of arrow R2 (second rotation direction). The edges 99a1 to 99a4 are in surface contact with the inner wall 3a1 or 3a2 of the recess 3a via surfaces extending in the directions of arrow Y and arrow X. The width direction of the recess 3a is the direction of arrow Z, which is perpendicular to the direction of arrow Y in which the recess 3a extends and is the same direction as the direction in which the recess 3b extends.

[0063] When the Oldham coupling 1 rotates in the direction of arrow R2, the portion of the edge 99a1 farthest from the rotation center CT1 (first rotation center) of the development drive gear 99 in the direction of arrow Y is located closer to the inner wall 3a2 in the direction of arrow Z than the rotation center CT1. When the Oldham coupling 1 rotates in the direction of arrow R2, the portion of the edge 99a2 farthest from the rotation center CT1 in the direction of arrow Y is located closer to the inner wall 3a1 in the direction of arrow Z than the rotation center CT1. When the Oldham coupling 1 rotates in the direction of arrow R1, the portion of the edge 99a3 farthest from the rotation center CT1 in the direction of arrow Y is located closer to the inner wall 3a2 in the direction of arrow Z than the rotation center CT1. When the Oldham coupling 1 rotates in the direction of arrow R1, the portion of the edge 99a4 farthest from the rotation center CT1 in the direction of arrow Y is located closer to the inner wall 3a1 in the direction of arrow Z than the rotation center CT1.

[0064] Furthermore, when viewed from the rotational axis direction of the Oldham coupling 1, the convex portion 99a has a shape that is formed as a substantial rhombus by an imaginary line H1 connecting the edge portion 99a1, the edge portion 99a2, the edge portion 99a3, and the edge portion 99a4. Specifically, when a corner is formed by an imaginary line extending the edge portion 99a1 and the edge portion 99a4, the angle of the corner is 45 degrees, and when a corner is formed by an imaginary line extending the edge portion 99a2 and the edge portion 99a3, a rhombus is formed with the angle of the corner being 45 degrees. Note that the substantial rhombus shape may have the above-described corners or may have the above-described corners chamfered.

[0065] With this configuration, when the Oldham coupling 1 rotates in the direction of arrow R2, a play γ1 is created between the edge 99a1 and the inner wall 3a1 of the recess 3a, and between the edge 99a2 and the inner wall 3a2 of the recess 3a. When the Oldham coupling 1 rotates in the direction of arrow R1, a similar play γ1 is created between the edge 99a3 and the inner wall 3a1 of the recess 3a, and between the edge 99a4 and the inner wall 3a2 of the recess 3a.

[0066] 12(b), the convex portion 89b has the same shape as the convex portion 99a. That is, the convex portion 89a has an edge portion 89a1 (fifth edge portion) that contacts one inner wall 3b1 (third inner wall) in the width direction of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of the arrow R1. The convex portion 89a also has an edge portion 89a2 (sixth edge portion) that contacts the other inner wall 3b2 (fourth inner wall) in the width direction of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of the arrow R1. The convex portion 89a also has an edge portion 89a3 (seventh edge portion) that contacts the inner wall 3b1 of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of the arrow R2, and an edge portion 89a4 (eighth edge portion) that contacts the inner wall 3b2. The edges 89a1 to 89a4 are in surface contact with the inner wall 3b1 or 3b2 of the recess 3b via surfaces extending in the directions of arrow Z and arrow X. The width direction of the recess 3b is the direction of arrow Y, which is perpendicular to the direction of arrow Z in which the recess 3b extends and is the same direction as the direction in which the recess 3a extends.

[0067] When the Oldham coupling 1 rotates in the direction of arrow R2, the portion of edge 89a1 farthest from the rotation center CT2 (second rotation center) of the drive coupling 89 in the direction of arrow Z is located closer to the inner wall 3b2 in the direction of arrow Y than the rotation center CT2. When the Oldham coupling 1 rotates in the direction of arrow R2, the portion of edge 89a2 farthest from the rotation center CT2 in the direction of arrow Z is located closer to the inner wall 3b1 in the direction of arrow Y than the rotation center CT2. When the Oldham coupling 1 rotates in the direction of arrow R1, the portion of edge 99a3 farthest from the rotation center CT2 in the direction of arrow Z is located closer to the inner wall 3b2 in the direction of arrow Y than the rotation center CT2. When the Oldham coupling 1 rotates in the direction of arrow R1, the portion of edge 89a4 farthest from the rotation center CT2 in the direction of arrow Z is located closer to the inner wall 3b1 in the direction of arrow Y than the rotation center CT2.

[0068] Furthermore, when viewed from the direction of the rotation axis of the Oldham coupling 1, the convex portion 89a has a shape that is formed as a substantial rhombus by an imaginary line H2 connecting the edge portions 89a1, 89a2, 89a3, and 89a4. Specifically, when a corner is formed by an imaginary line extending from the edge portions 89a1 and 89a4, the angle of the corner is 45 degrees, and when a corner is formed by an imaginary line extending from the edge portions 89a2 and 89a3, a rhombus is formed with the angle of the corner being 45 degrees. Note that the substantial rhombus shape may have the above-described corners, or the above-described corners may be chamfered as in this embodiment.

[0069] With this configuration, when the Oldham coupling 1 rotates in the direction of arrow R2, a play γ2 is created between the edge 89a1 and the inner wall 3b1 of the recessed portion 3b, and between the edge 89a2 and the inner wall 3b2 of the recessed portion 3b. When the Oldham coupling 1 rotates in the direction of arrow R1, a similar play γ2 is created between the edge 89a3 and the inner wall 3b1 of the recessed portion 3b, and between the edge 89a4 and the inner wall 3b2 of the recessed portion 3b.

[0070] As described above, according to the configuration of this embodiment, in the Oldham coupling 1, a driving force can be transmitted while providing a rotational play γ1 between the development drive gear 99 and the intermediate member 3 and a rotational play γ2 between the drive coupling 89 and the intermediate member 3. Furthermore, the edge portions 99a1 to 99a4 are in surface contact with the inner wall 3a1 or the inner wall 3a2 of the recessed portion 3a, and the edge portions 89a1 to 89a4 are in surface contact with the inner wall 3b1 or the inner wall 3b2 of the recessed portion 3b, so that the strength of the convex portions 99a, 89a when transmitting the driving force can be ensured and deformation can be suppressed.

[0071] Furthermore, by providing play in the rotational direction between the development drive gear 99 and the intermediate member 3, and between the drive coupling 89 and the intermediate member 3, as in this embodiment, it is possible to suppress a decrease in the strength of the coupling itself compared to when the play β (FIG. 9(b)) provided between the protrusion of the development coupling 75 and the fitting groove of the drive coupling 89 is increased. Also, by increasing the play β, it is possible to suppress a situation in which stable drive transmission becomes impossible.

[0072] For example, if the length of the engagement groove of the drive coupling 89 in the rotational direction is increased to increase the play β, the strength of the drive coupling 89 itself may be reduced, potentially preventing stable drive transmission. Furthermore, if the length of the engagement groove of the drive coupling 89 in the rotational direction is increased, depending on the size of the drive coupling 89, it may not be possible to provide three engagement grooves. If only two engagement grooves are provided, the development coupling 75 will also have two protrusions, and the driving force will be transmitted by the engagement of the two protrusions with the two engagement grooves. In this case, if the engagement force between any of the protrusions and the engagement groove is weak, stable drive transmission will be impossible. Furthermore, if the length of the protrusion of the development coupling 75 in the rotational direction is shortened to increase the play β, the strength of the protrusion of the development coupling 75 will be reduced by shortening the length in the rotational direction, potentially causing damage during drive transmission.

[0073] In this embodiment, instead of increasing the play β between the development coupling 75 and the drive coupling 89, which are separated when the unit is attached or detached, a configuration is adopted in which play is provided between the development drive gear 99 of the Oldham coupling and the intermediate member 3, and / or between the drive coupling 89 and the intermediate member 3. This enables stable drive transmission and makes it possible to selectively transmit drive force to the driven object when the motor is rotated forward or reverse. Furthermore, despite the configuration having play in the rotational direction, drive force can be transmitted even when the rotation axes of the two rotation shafts are misaligned.

[0074] <Operation timing when the motor rotates in reverse> Next, the operation timing when the photosensitive drum 26, the developing sleeve 71, and the charging roller 27 rotate in the direction opposite to the rotation direction during image formation will be described.

[0075] 13 is a timing chart showing the operation timing when the photosensitive drum 26, developing sleeve 71, and charging roller 27 rotate in the direction opposite to the rotation direction during image formation, from a state in which drive by the motors 92a and 92b has stopped. Here, when the image formation operation is completed, these members stop in a state in which the play α between the drive coupling 96 and the drum coupling 13, the play β between the drive coupling 89 and the developing coupling 75, and the play γ1 and γ2 of the Oldham coupling 1 are secured. The play γ1 is the play provided in the rotational direction between the developing drive gear 99 and the intermediate member 3 in the Oldham coupling 1. The play γ2 is the play provided in the rotational direction between the drive coupling 89 and the intermediate member 3 in the Oldham coupling 1.

[0076] From this stopped state, the motors 92a and 92b start to rotate in the direction opposite to the direction of rotation during image formation. When the motors 92a and 92b start to rotate, the drum drive gear 95 and the development drive gear 99 also start to rotate (timing T1).

[0077] Next, at timing T2, the rotation of the development drive gear 99 reduces the play γ1 of the Oldham coupling 1, and the intermediate member 3 starts to rotate. After that, at timing T3, the rotation of the intermediate member 3 reduces the play γ2 of the Oldham coupling 1, and the drive coupling 89 starts to rotate.

[0078] Next, at timing T4, the rotation of the drum drive gear 95 eliminates the play α, the drum coupling 13 starts to rotate, and accordingly the photosensitive drum 26 starts to rotate. After that, at timing T5, the rotation of the drive coupling 89 eliminates the play β, the development coupling 75 starts to rotate, and accordingly the development sleeve 71 starts to rotate.

[0079] Next, at time T6, the gear portion 32a of the spacing member 32 meshes with the flange gear 14 as the photosensitive drum 26 rotates, and the charging roller 27 begins to separate from the photosensitive drum 26. Then, at time T7, the charging roller 27 separates to a predetermined position, completing the separation. Thereafter, at time T8, the developing sleeve 71 rotates to a predetermined rotation angle, and the driving of the motors 92a and 92b is stopped.

[0080] In this way, by providing the Oldham coupling 1 of this embodiment, the rotation of the developing sleeve 71 in the opposite direction due to the rotational drive of the motors 92a, 92b in the direction opposite to the rotational direction during image formation and the separation operation of the charging roller 27 from the photosensitive drum 26 can be performed at different times. In other words, when the motor is rotated in the direction opposite to the rotational direction during image formation, only the developing sleeve 71 can be rotated in the direction opposite to the rotational direction during image formation without separating the charging roller 27 from the photosensitive drum 26.

[0081] This makes it possible to prevent defects caused by the simultaneous separation of the charge roller 27 and reverse rotation of the developing sleeve 71. For example, when an image forming apparatus continuously forms images on recording materials, the reverse rotation of the developing sleeve 71 is performed every time 500 sheets of A4 paper are image-formed. However, because image formation is continuously performed, the separation of the charge roller 27 from the photosensitive drum 26 is unnecessary. Therefore, by providing the Oldham coupling 1 of this embodiment, it is possible to rotate only the developing sleeve 71 in the direction opposite to the rotation direction during image formation without separating the charge roller 27 from the photosensitive drum 26, thereby preventing unnecessary separation of the charge roller 27.

[0082] Furthermore, by providing the Oldham coupling 1 of this embodiment, it is possible to prevent malfunctions caused by the spacing member 32 and the developing sleeve 71 rotating in the same reverse direction during reverse rotation of the motor, which is the opposite direction to the rotation direction during image formation. For example, by starting the spacing operation of the charge roller 27 at the same timing as the developing sleeve 71 and ending the rotation of the spacing member 32 in accordance with the end of the reverse rotation of the developing sleeve 71, it is possible to prevent malfunctions caused by the spacing member 32 coming into contact with the drum container 11. Furthermore, by starting the spacing operation of the charge roller 27 at the same timing as the developing sleeve 71 and ending the reverse rotation of the developing sleeve 71 in accordance with the end of the spacing operation of the charge roller 27, it is possible to prevent an insufficient amount of toner accumulated in the space surrounded by the developing sleeve 71, the scoop sheet 77, and the developing blade 72 being pushed back into the stirring chamber 80.

[0083] (Second embodiment) Next, a second embodiment of the Oldham coupling according to the present invention will be described with reference to the drawings. Portions that overlap with the first embodiment will be given the same reference numerals and will not be described again.

[0084] The configuration of the Oldham coupling 1 according to this embodiment is different from the configuration of the first embodiment in the shapes of the convex portion 99a of the development drive gear 99 and the convex portion 89a of the drive coupling 89. The other configurations, including the overall configuration of the image forming apparatus A, are the same as those of the first embodiment.

[0085] Fig. 14 is a perspective view of the Oldham coupling 1 according to this embodiment, as seen from the front side of the image forming apparatus A. Fig. 15 is a perspective view of the Oldham coupling 1 according to this embodiment, as seen from the rear side of the image forming apparatus A. Fig. 16(a) is a diagram showing a fitting portion between the development drive gear 99 of the Oldham coupling 1 and the intermediate member 3. Fig. 16(b) is a diagram showing a fitting portion between the drive coupling 89 of the Oldham coupling 1 and the intermediate member 3.

[0086] 14 and 15, the protrusion 99a of the development drive gear 99 according to this embodiment is made up of a cylindrical portion 99x1 and cylindrical portions 99x2 and 99x3 that have smaller diameters than the cylindrical portion 99x1. The cylindrical portions 99x2 and 99x3 have the same shape, and the distance between them and the cylindrical portion 99x1 is also set to be the same.

[0087] The protrusion 89a of the drive coupling 89 is made up of a cylindrical portion 89x1 and cylindrical portions 89x2 and 89x3 that are smaller in diameter than the cylindrical portion 89x1. The cylindrical portions 89x2 and 89x3 have the same shape, and the distance between them and the cylindrical portion 89x1 is also set to be the same.

[0088] When the driving force of the motor 92a or 92b rotates the developing drive gear 99, the convex portion 99a of the developing drive gear 99 slides relatively inside the recessed portion 3a while contacting the inner wall of the recessed portion 3a, thereby transmitting the driving force to the intermediate member 3, and the intermediate member 3 rotates. When the intermediate member 3 rotates, the convex portion 89a of the drive coupling 89 slides relatively inside the recessed portion 3b while contacting the inner wall of the recessed portion 3a, thereby transmitting the driving force to the drive coupling 89, and the drive coupling 89 rotates. In this way, even if the rotation axis (not shown) of the developing drive gear 99 and the rotation axis of the rotation shaft 100 of the developing coupling 75 are misaligned, the driving force of the motor 92a or 92b is stably transmitted to the rotation shaft 100 of the developing coupling 75 via the Oldham coupling 1.

[0089] 16(a), the cylindrical portion 99x1 has an edge 99x1a (first edge) that contacts one inner wall 3a1 (first inner wall) in the width direction of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R1 (first rotation direction), and an edge 99x1b (second edge) that contacts the other inner wall 3a2 (second inner wall) in the width direction of the recess 3a. The cylindrical portion 99x2 has an edge 99x2a (first edge) that contacts the inner wall 3a1 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R1. The cylindrical portion 99x3 has an edge 99x3a (second edge) that contacts the inner wall 3a2 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R1. These edges 99x1a, 99x1b, 99x2a, and 99x3a are in line contact with the inner wall 3a1 or 3a2 of the recess 3a along a line extending in the direction of the rotation axis of the Oldham coupling 1.

[0090] The cylindrical portion 99x1 has an edge 99x1a (third edge) that comes into contact with the inner wall 3a1 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R2 (second rotation direction), and an edge 99x1b (fourth edge) that comes into contact with the inner wall 3a2. The cylindrical portion 99x3 has an edge 99x3b (third edge) that comes into contact with the inner wall 3a1 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R2. The cylindrical portion 99x2 has an edge 99x2b (fourth edge) that comes into contact with the inner wall 3a2 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R2. These edges 99x1a, 99x1b, 99x2b, and 99x3b come into line contact with the inner wall 3a1 or 3a2 of the recess 3a along a line extending in the rotational axis direction of the Oldham coupling 1.

[0091] When the Oldham coupling 1 rotates in the direction of arrow R2, an edge 99x2a of the cylindrical portion 99x2 is located in a position closer to the inner wall 3a2 in the direction of arrow Z than the rotation center CT1 (first rotation center) of the development drive gear 99. Of the edges that come into contact with the inner wall 3a1 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R1, the edge 99x2a of the cylindrical portion 99x2 is the part that is farthest from the rotation center CT1 of the development drive gear 99 in the direction of arrow Y.

[0092] Furthermore, when the Oldham coupling 1 rotates in the direction of arrow R2, an edge 99x3a of the cylindrical portion 99x3 is located in a position in the direction of arrow Z closer to the inner wall 3a1 than the rotation center CT1 of the development drive gear 99. Of the edge portions that come into contact with the inner wall 3a2 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R1, the edge 99x3a of the cylindrical portion 99x3 is the portion that is farthest from the rotation center CT1 of the development drive gear 99 in the direction of arrow Y.

[0093] Furthermore, when the Oldham coupling 1 rotates in the direction of arrow R1, an edge 99x2b of the cylindrical portion 99x2 is located in a position in the direction of arrow Z closer to the inner wall 3a1 than the rotation center CT1 of the development drive gear 99. Of the edges that come into contact with the inner wall 3a2 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R2, the edge 99x2b of the cylindrical portion 99x2 is the part that is farthest from the rotation center CT1 of the development drive gear 99 in the direction of arrow Y.

[0094] Furthermore, when the Oldham coupling 1 rotates in the direction of arrow R1, an edge 99x3b of the cylindrical portion 99x3 is located in a position in the direction of arrow Z closer to the inner wall 3a2 than the rotation center CT1 of the development drive gear 99. Of the edges that come into contact with the inner wall 3a1 of the recess 3a when the Oldham coupling 1 rotates in the direction of arrow R2, the edge 99x3b of the cylindrical portion 99x3 is the part that is farthest from the rotation center CT1 of the development drive gear 99 in the direction of arrow Y.

[0095] When viewed from the direction of the rotation axis of the Oldham coupling 1, the convex portion 99a has a shape that is formed into a substantial diamond by an imaginary line H3 connecting the edge portions 99x1a, 99x1b, 99x2a, 99x2b, 99x3a, and 99x3b. Specifically, when the imaginary line connecting the edge portion 99x1a and the edge portion 99x2a and the imaginary line connecting the edge portion 99x1b and the edge portion 99x2b are extended to form corners, the corner angles are 45 degrees. When the imaginary line connecting the edge portion 99x1a and the edge portion 99x3b and the imaginary line connecting the edge portion 99x1b and the edge portion 99x3a are extended to form corners, the corner angles are 45 degrees. The substantial diamond shape may have corners as described above, or may have chamfered corners as described above.

[0096] With this configuration, when the Oldham coupling 1 rotates in the direction of arrow R2, a play γ3 is created between the edge 99x2a and the inner wall 3a1 of the recess 3a, and between the edge 99x3a and the inner wall 3a2 of the recess 3a. When the Oldham coupling 1 rotates in the direction of arrow R1, a similar play γ3 is created between the edge 99x2b and the inner wall 3a2 of the recess 3a, and between the edge 99x3b and the inner wall 3a1 of the recess 3a.

[0097] 16(b), the cylindrical portion 89x1 has an edge 89x1a (fifth edge) that contacts one inner wall 3b1 (third inner wall) in the width direction of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of arrow R1, and an edge 89x1b (sixth edge) that contacts the other inner wall 3b2 (fourth inner wall). The cylindrical portion 89x2 has an edge 89x2a (fifth edge) that contacts the inner wall 3b1 of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of arrow R1. The cylindrical portion 89x3 has an edge 89x3a (sixth edge) that contacts the inner wall 3b2 of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of arrow R1. These edges 89x1a, 89x1b, 89x2a, and 89x3a come into line contact with the inner wall 3b1 or 3b2 of the recess 3b along a line extending in the direction of the rotation axis of the Oldham coupling 1.

[0098] The cylindrical portion 89x1 has an edge 89x1a (fifth edge) that comes into contact with the inner wall 3b1 of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of arrow R2, and an edge 89x1b (sixth edge) that comes into contact with the inner wall 3b2. The cylindrical portion 89x3 has an edge 89x3b (fifth edge) that comes into contact with the inner wall 3b1 of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of arrow R2. The cylindrical portion 89x2 has an edge 89x2b (sixth edge) that comes into contact with the inner wall 3b2 of the recessed portion 3b when the Oldham coupling 1 rotates in the direction of arrow R2. These edges 89x1a, 89x1b, 89x2b, and 89x3b come into line contact with the inner wall 3b1 or 3b2 of the recessed portion 3b along a line extending in the rotational axis direction of the Oldham coupling 1.

[0099] Here, when the Oldham coupling 1 rotates in the direction of arrow R2, an edge 89x2a of the cylindrical portion 89x2 is located at a position closer to the inner wall 3b2 in the direction of arrow Y than the center of rotation CT2 (second center of rotation) of the drive coupling 89. Of the edge portions that come into contact with the inner wall 3b1 of the recess 3b when the Oldham coupling 1 rotates in the direction of arrow R1, the edge 89x2a of the cylindrical portion 89x2 is the portion that is farthest from the center of rotation CT2 of the drive coupling 89 in the direction of arrow Z.

[0100] Furthermore, when the Oldham coupling 1 rotates in the direction of arrow R2, the edge 89x3a of the cylindrical portion 89x3 is located in a position closer to the inner wall 3b1 in the direction of arrow Y than the center of rotation CT2 of the drive coupling 89. Of the edge portions that come into contact with the inner wall 3b2 of the recess 3b when the Oldham coupling 1 rotates in the direction of arrow R1, the edge 89x3a of the cylindrical portion 89x3 is the portion that is farthest from the center of rotation CT2 of the drive coupling 89 in the direction of arrow Z.

[0101] Furthermore, when the Oldham coupling 1 rotates in the direction of arrow R1, the edge 89x2b of the cylindrical portion 89x2 is located in a position closer to the inner wall 3b1 in the direction of arrow Y than the center of rotation CT2 of the drive coupling 89. Of the edge portions that come into contact with the inner wall 3b2 of the recess 3b when the Oldham coupling 1 rotates in the direction of arrow R2, the edge 89x2b of the cylindrical portion 89x2 is the portion that is farthest from the center of rotation CT2 of the drive coupling 89 in the direction of arrow Z.

[0102] Furthermore, when the Oldham coupling 1 rotates in the direction of arrow R1, the edge 89x3b of the cylindrical portion 89x3 is located in a position closer to the inner wall 3b2 in the direction of arrow Y than the center of rotation CT2 of the drive coupling 89. Of the edge portions that come into contact with the inner wall 3b1 of the recess 3b when the Oldham coupling 1 rotates in the direction of arrow R2, the edge 89x3b of the cylindrical portion 89x3 is the portion that is farthest from the center of rotation CT2 of the drive coupling 89 in the direction of arrow Z.

[0103] When viewed from the direction of the rotation axis of the Oldham coupling 1, the convex portion 89a has a shape that is formed into a substantial diamond by an imaginary line H4 connecting the edge portions 89x1a, 89x1b, 89x2a, 89x2b, 89x3a, and 89x3b. Specifically, when the imaginary line connecting the edge portion 89x1a and the edge portion 89x2a and the imaginary line connecting the edge portion 89x1b and the edge portion 89x2b are extended to form corners, the corner angles are 45 degrees. When the imaginary line connecting the edge portion 89x1a and the edge portion 89x3b and the imaginary line connecting the edge portion 89x1b and the edge portion 89x3a are extended to form corners, the corner angles are 45 degrees. The substantial diamond shape may have corners as described above, or may have chamfered corners as described above.

[0104] With this configuration, when the Oldham coupling 1 rotates in the direction of arrow R2, a play γ4 is created between the edge 89x2a and the inner wall 3b1 of the recessed portion 3b, and between the edge 89x3a and the inner wall 3b2 of the recessed portion 3b. When the Oldham coupling 1 rotates in the direction of arrow R1, a similar play γ4 is created between the edge 89x2b and the inner wall 3b2 of the recessed portion 3b, and between the edge 89x3b and the inner wall 3b1 of the recessed portion 3b.

[0105] As described above, according to the configuration of this embodiment, in the Oldham coupling 1, a driving force can be transmitted while providing a rotational play γ3 between the development drive gear 99 and the intermediate member 3 and a rotational play γ4 between the drive coupling 89 and the intermediate member 3. In addition, it is possible to selectively transmit a driving force to a driven object when the motor is rotated forward or reverse, and it is also possible to transmit a driving force even when the rotational axes of the two rotation shafts are misaligned.

[0106] In the first and second embodiments, the drive unit 90 is described as being provided with the Oldham coupling 1 in the drive train that transmits the drive force to the developing sleeve 71, but the present invention is not limited to this. That is, the same effect as above can be obtained by providing the Oldham coupling 1 in another portion that transmits the drive force, such as in the drive train that transmits the drive force to the photosensitive drum 26.

[0107] Furthermore, in the first and second embodiments, the drive unit 90 is configured to rotate both the photosensitive drum 26 and the developing sleeve 71 in the direction opposite to the rotation direction during image formation, but it may also be configured to rotate only one of the photosensitive drum 26 or the developing sleeve 71 in the direction opposite to the rotation direction during image formation. In this case, the provision of the above-mentioned Oldham coupling 1 can increase the amount of rotation of either the photosensitive drum 26 or the developing sleeve 71 in the opposite direction. This makes it possible to selectively transmit driving force to the driven object when the motor is rotated forward or reverse, and also makes it possible to transmit driving force even when the rotation axes of the two rotation shafts are misaligned.

[0108] Furthermore, in devices other than image forming devices, the same effect as above can be obtained by providing the Oldham coupling 1 as a means for transmitting driving force from a drive source to a target unit.

[0109] Furthermore, in the first and second embodiments, the configuration in which both the convex portion 99a of the development drive gear 99 and the convex portion 89a of the drive coupling 89 in the Oldham coupling 1 are substantially diamond-shaped has been described, but the present invention is not limited to this. That is, either the convex portion 99a of the development drive gear 99 or the convex portion 89a of the drive coupling 89 may be formed in substantially the same rectangular shape as the concave portion 3a or the concave portion 3b of the intermediate member 3. That is, a configuration may be provided in which only either the play γ1 between the development drive gear 99 and the intermediate member 3 or the play γ2 between the drive coupling 89 and the intermediate member 3 is provided. Furthermore, the rotation angles of the play γ1 to γ4 are not limited to the angles described in the first and second embodiments, and can be set to any angle.

[0110] Furthermore, in the first and second embodiments, the configuration has been described in which the convex portions 99a, 89a are provided on the development drive gear 99 and the drive coupling 89 in the Oldham coupling 1, and the concave portions 3a, 3b are provided on the intermediate member 3, but the present invention is not limited to this. That is, even if convex portions corresponding to the convex portions 99a, 89a are provided on one end and the other end of the intermediate member 3 in the rotational axis direction of the Oldham coupling 1, and concave portions that fit into the convex portions of the intermediate member 3 are provided on the development drive gear 99 and the drive coupling 89, the same effects as those described above can be obtained. [Explanation of symbols]

[0111] 1...Oldham coupling 3...Intermediate member 3a...recess (first recess) 3b...recess (second recess) 26...Photosensitive drum (photoconductor) 65...Process cartridge (image forming unit) 71...Developing sleeve (developer carrier) 89...Drive coupling (second hub) 89a...convex portion (second protruding portion) 92a, 92b...Motor 99...Development drive gear (first hub) 99a...protrusion (first protrusion) A...Image forming device

Claims

1. An Oldham coupling having a first hub, a second hub, and an intermediate member that transmits driving force between the first hub and the second hub, one of the intermediate member and the first hub has a first recess formed on an end surface of the Oldham coupling in the rotational axis direction, recessed in the rotational axis direction, and extending in a first direction perpendicular to the rotational axis direction, the first recess having a first inner wall on one side in a second direction perpendicular to the rotational axis direction and the first direction, and a second inner wall provided on the other side in the second direction and extending parallel to the first inner wall, the other of the intermediate member and the first hub has a first protrusion that protrudes in the rotation axis direction, is fitted into the first recess, and transmits a driving force between the intermediate member and the first hub, The first protrusion is a first edge portion that comes into contact with the first inner wall when the Oldham coupling rotates in a first rotational direction; a second edge portion that contacts the second inner wall when the Oldham coupling rotates in a first rotational direction; a third edge portion that comes into contact with the first inner wall when the Oldham coupling rotates in a second rotational direction opposite to the first rotational direction; a fourth edge portion that contacts the second inner wall when the Oldham coupling rotates in a second rotational direction opposite to the first rotational direction, when the first edge contacts the first inner wall and the second edge contacts the second inner wall, the third edge is spaced apart from the first inner wall and the fourth edge is spaced apart from the second inner wall; when the third edge portion contacts the first inner wall and the fourth edge portion contacts the second inner wall, the first edge portion is spaced apart from the first inner wall and the second edge portion is spaced apart from the second inner wall; when the Oldham coupling rotates in conjunction with rotation of the motor in the second rotation direction, a portion of the first edge portion farthest from a first rotation center that is a rotation center of the first hub in the first direction is located at a position closer to the second inner wall than the first rotation center in the second direction, and a portion of the second edge portion farthest from the first rotation center in the first direction is located at a position closer to the first inner wall than the first rotation center in the second direction, 1. The Oldham coupling according to claim 1 , wherein, when the Oldham coupling rotates in conjunction with rotation of the motor in the first rotation direction, a portion of the third edge farthest from the first center of rotation in the first direction is located at a position closer to the second inner wall than the first center of rotation in the second direction, and a portion of the fourth edge farthest from the first center of rotation in the first direction is located at a position closer to the first inner wall than the first center of rotation in the second direction.

2. 2. The Oldham coupling according to claim 1, wherein the first protrusion has a shape that, when viewed from the direction of the rotation axis, is formed into a substantially rhombus shape by imaginary lines connecting the first edge portion, the second edge portion, the third edge portion, and the fourth edge portion.

3. 3. The Oldham coupling according to claim 1, wherein the first protruding portion has a first edge portion and a third edge portion that are in surface contact with the first inner wall via surfaces extending in the rotational axis direction and the first direction, and the second edge portion and the fourth edge portion that are in surface contact with the second inner wall via surfaces extending in the rotational axis direction and the first direction.

4. 3. The Oldham coupling according to claim 1, wherein the first edge portion and the third edge portion of the first protrusion are in line contact with the first inner wall along lines extending in the direction of the rotation axis, and the second edge portion and the fourth edge portion are in line contact with the second inner wall along lines extending in the direction of the rotation axis.

5. one of the intermediate member and the second hub has a second recess formed on an end surface in the rotational axis direction, recessed in the rotational axis direction, and extending in the second direction, the second recess having a third inner wall on one side in the first direction and a fourth inner wall provided on the other side in the first direction and extending parallel to the first inner wall, the other of the intermediate member and the second hub has a second protruding portion that protrudes in the rotation axis direction, is fitted into the second recess, and transmits a driving force between the intermediate member and the second hub, The second protrusion is a fifth edge portion that comes into contact with the third inner wall when the Oldham coupling rotates in accordance with the rotation of the motor in the first rotation direction; a sixth edge portion that comes into contact with the fourth inner wall when the Oldham coupling rotates in association with the rotation of the motor in the first rotational direction; a seventh edge portion that comes into contact with the third inner wall when the Oldham coupling rotates in association with the rotation of the motor in the second rotational direction; an eighth edge portion that comes into contact with the fourth inner wall when the Oldham coupling rotates in conjunction with the rotation of the motor in the second rotational direction, when the fifth edge portion contacts the third inner wall and the sixth edge portion contacts the fourth inner wall, the seventh edge portion is spaced apart from the third inner wall and the eighth edge portion is spaced apart from the fourth inner wall; when the seventh edge portion contacts the third inner wall and the eighth edge portion contacts the fourth inner wall, the fifth edge portion is spaced apart from the third inner wall and the eighth edge portion is spaced apart from the fourth inner wall; when the Oldham coupling rotates in conjunction with rotation of the motor in the second rotational direction, a portion of the fifth edge portion farthest from a second rotation center that is a rotation center of the second hub in the second direction is located at a position closer to the fourth inner wall than the second rotation center in the first direction, and a portion of the sixth edge portion farthest from the second rotation center in the second direction is located at a position closer to the third inner wall than the second rotation center in the first direction, 5. The Oldham coupling according to claim 1, wherein, when the Oldham coupling rotates in conjunction with rotation of the motor in the first rotation direction, a portion of the seventh edge farthest from the second center of rotation in the second direction is located at a position closer to the fourth inner wall than the second center of rotation in the first direction, and a portion of the eighth edge farthest from the second center of rotation in the second direction is located at a position closer to the third inner wall than the second center of rotation in the first direction.

6. 6. The Oldham coupling according to claim 5, wherein the second protruding portion has a shape that is substantially a rhombus formed by imaginary lines connecting the fifth edge portion, the sixth edge portion, the seventh edge portion, and the eighth edge portion when viewed from the direction of the rotation axis.

7. 7. The Oldham coupling according to claim 5, wherein the fifth edge portion and the seventh edge portion of the second protruding portion are in surface contact with the third inner wall via surfaces extending in the rotational axis direction and the second direction, and the sixth edge portion and the eighth edge portion are in surface contact with the fourth inner wall via surfaces extending in the rotational axis direction and the second direction.

8. 7. The Oldham coupling according to claim 5, wherein the fifth edge portion and the seventh edge portion of the second protruding portion are in line contact with the third inner wall along lines extending in the direction of the rotation axis, and the sixth edge portion and the eighth edge portion are in line contact with the fourth inner wall along lines extending in the direction of the rotation axis.

9. A motor; An Oldham coupling according to any one of claims 1 to 8; an image forming unit that is driven by the driving force of the motor transmitted via the Oldham coupling and forms an image on a sheet; An image forming apparatus comprising:

10. the image forming unit includes a photoreceptor and a developer carrier that carries a developer and causes the developer to adhere to a surface of the photoreceptor; 10. The image forming apparatus according to claim 9, wherein the developer carrier is rotated by a driving force of the motor transmitted via the Oldham coupling.

11. 11. The image forming apparatus according to claim 10, wherein the photosensitive member is rotated by the driving force of the motor.

12. 12. The image forming apparatus according to claim 9, wherein the image forming unit is configured to be detachable from the image forming apparatus.

Images