Image forming apparatus

Abstract

This provides a new configuration for driving units in an image forming apparatus. [Solution] An image forming apparatus comprising: a unit having a driven part; a drive source having a drive force and an output unit having an output unit having a drive force; a first drive transmission unit connected to the output unit and the unit; and a second drive transmission unit having a planetary gear mechanism and connected to the output unit, wherein the drive force transmission path includes a closed loop, and the closed loop includes the driven part, the output unit, the first drive transmission unit, and the second drive transmission unit.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus for forming an image on a recording material. [Background technology]

[0002] Patent Document 1 describes an image forming apparatus in which the photosensitive drum of a process cartridge is rotationally driven by the driving force of a motor located in the apparatus body, while receiving a braking force generated by a brake member located in the apparatus body. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-154313 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the image forming apparatus described in the above-mentioned document, the driving force of the motor was transmitted through a transmission path that sequentially passed through a drum drive coupling, a drum coupling, a brake engagement member, and a brake member, with the brake member as the terminal, forming a non-loop transmission path.

[0005] The present invention aims to provide a novel configuration for driving a unit in an image forming apparatus. [Means for solving the problem]

[0006] One aspect of the present invention is an image forming apparatus characterized by comprising: a unit having a driven part; a drive source having a drive force; an output unit having an output unit having the drive force; a first drive transmission unit connected to the output unit and the unit; and a second drive transmission unit having a planetary gear mechanism and connected to the output unit and the unit, wherein the transmission path of the drive force includes a closed loop, and the closed loop includes the driven part, the output unit, the first drive transmission unit, and the second drive transmission unit. [Effects of the Invention]

[0007] According to the present invention, a new configuration for driving a unit in an image forming apparatus can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing the cross-sectional configuration of the image forming apparatus according to Example 1. [Figure 2] A schematic diagram showing the door of the image forming apparatus according to Example 1 in the open position. [Figure 3] A perspective view of the cartridge according to Example 1. [Figure 4] An enlarged view showing a part of the cartridge according to Example 1. [Figure 5] Diagrams (a-c) illustrating the main drive train according to Example 1. [Figure 6] Exploded view (a, b) of the drive transmission unit according to Example 1. [Figure 7] A side view (a) and a cross-sectional view (b) of the drive transmission unit according to Example 1. [Figure 8] Perspective views (a-c) showing a part of the drive transmission unit according to Example 1. [Figure 9] Cross-sectional view of the drive transmission unit and drum coupling according to Example 1. [Figure 10] Figure (a) shows the engagement state of the drive transmission unit and drum coupling according to Example 1, and Figure (b) shows the engagement state of the drive transmission unit and drum coupling according to Example 2. [Figure 11]Figures (a, b) show the operation of the main drive train according to Example 1. [Figure 12] A cross-sectional view showing the operation of the main drive train according to Example 1. [Figure 13] Model diagrams of the main drive train according to Example 1(a), Reference Example 1(b), and Reference Example 2(c). [Figure 14] Figures (a, b) show the operation of the main drive train according to Example 2. [Figure 15] A cross-sectional view showing the operation of the main drive train according to Example 2. [Figure 16] Model diagram of the main drive train according to Example 2. [Figure 17] Schematic diagrams (a-d) of the main drive train according to Example 2. [Figure 18] Figures (a, b) show the operation of the main drive train according to Example 3. [Figure 19] A cross-sectional view showing the operation of the main drive train according to Example 3. [Figure 20] Model diagram of the main drive train according to Example 3. [Figure 21] Model diagram of the main drive train according to Example 4 (a) and schematic diagram of the planetary gear mechanism (b). [Figure 22] Figures (a, b) show the operation of the main drive train according to another embodiment. [Modes for carrying out the invention]

[0009] The embodiments relating to this disclosure will be described below with reference to the drawings.

[0010] Example 1 A printer 1 as an image forming apparatus according to one embodiment (Example 1) of the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing the overall cross-sectional configuration of the printer 1 according to this embodiment. Figure 2 is a schematic diagram showing the printer 1 with the door 20 open.

[0011] The printer 1 according to this embodiment is an electrophotographic color laser beam printer that forms an image on a sheet S. A variety of sheet materials of different sizes and materials can be used as the recording material (recording medium), such as plain paper and cardboard, sheet materials with surface treatments such as coated paper, specially shaped sheet materials such as envelopes and index paper, plastic film, and cloth.

[0012] The printer 1 comprises a main unit (housing) 1A, a scanner (exposure device) 2, a control unit 3, and a door (opening / closing member) 20 that can be opened and closed relative to the main unit 1A. Furthermore, the printer 1 comprises a sheet feeding unit 30, a transfer unit (transfer device) 40, a tray unit (moving unit, support unit) 50, and a fixing device 80. The portion including the main unit 1A and the door 20 can also be called the main frame 100. The main frame 100 includes the exterior of the printer 1.

[0013] The main unit 1A houses the scanner 2, control unit 3, sheet feeding unit 30, transfer unit 40, tray unit 50, and fixing device 80.

[0014] The sheet feeding unit 30 includes a loading tray 31 on which sheets S are loaded, and a feeding roller 32 as a feeding member for feeding the sheets S. The loading tray 31 is configured to be pulled out from the main body 1A of the device in the direction in which the door 20 is opened (to the right in Figure 1), thereby allowing for replenishment of sheets S.

[0015] The tray unit 50 includes a tray (support member, drawer) 51 and cartridges PY, PM, PC, and PK. The cartridges PY, PM, PC, and PK are removably mounted on the tray 51. In this embodiment, each of the cartridges PY, PM, PC, and PK is independently attachable to and detachable from the tray 51 relative to one another.

[0016] Cartridges PY, PM, PC, and PK each contain yellow (Y), magenta (M), cyan (C), and black (K) toner (developer), respectively. Cartridges PY, PM, PC, and PK have the same configuration except for the color of the toner they contain. Therefore, the configuration and operation of one of the cartridges PY, PM, PC, or PK may be described, while the others may be omitted. Also, when there is no need to distinguish between cartridges PY, PM, PC, and PK, they may simply be referred to as cartridge P. The tray unit 50 can be said to have multiple cartridges P and a tray 51 into which the multiple cartridges P are removably mounted.

[0017] Cartridge P is an example of a replacement unit that is removable (replaceable) attached to the main body 1A of the device. In this embodiment, cartridge P is part of the tray unit 50 and is removablely attached to the main body 1A of the device via the tray 51. However, cartridge P may be removablely attached to the main body 1A without going through the tray 51.

[0018] Alternatively, instead of cartridge P, a unit with equivalent functionality to cartridge P may be attached to the device body 1A in a manner that does not anticipate user attachment or removal (replacement). In other words, cartridge P is an example of a "unit" that is not necessarily removable from the device body 1A. In the case of cartridge P (a fixed process unit) that is fixed and cannot be removed from the device body 1A, toner may be supplied to the developing unit from outside the printer 1 using a supply container.

[0019] In this embodiment, the tray unit 50 has a plurality of photosensitive drums (image carriers) 6 and 1, a plurality of charging rollers 62 (charging members), and a plurality of developing rollers (developer carriers) 71. Specifically, the tray unit 50 of this embodiment has four photosensitive drums 61, four charging rollers 62, and four developing rollers 71. The rotational axis directions of the photosensitive drums 61, the developing rollers 71, and the charging rollers 62 are parallel. The photosensitive drums 61 are an example of a rotating member rotatably mounted on the cartridge P.

[0020] The part of the tray unit 50 that forms the black (K) image is called the black station (first station), and the photosensitive drum 61 of the first station is called the first photosensitive drum, the developing roller 71 is called the first developing roller, and the charging roller 62 is called the first charging roller. The part of the tray unit 50 that forms the cyan (C) image is called the cyan station (second station), and the photosensitive drum 61 of the second station is called the second photosensitive drum, the developing roller 71 is called the second developing roller, and the charging roller 62 is called the second charging roller. The part of the tray unit 50 that forms the magenta (M) image is called the magenta station (third station), and the photosensitive drum 61 of the third station is called the third photosensitive drum, the developing roller 71 is called the third developing roller, and the charging roller 62 is called the third charging roller. The part of the tray unit 50 that forms the yellow (Y) image is called the yellow station (fourth station), and the photosensitive drum 61 of the fourth station is called the fourth photosensitive drum, the developing roller 71 is called the fourth developing roller, and the charging roller 62 is called the fourth charging roller.

[0021] Cartridge PK is installed in the black station, cartridge PC in the cyan station, cartridge PM in the magenta station, and cartridge PY in the yellow station. In this embodiment, cartridge PK is referred to as the first cartridge, cartridge PC as the second cartridge, cartridge PM as the third cartridge, and cartridge PY as the fourth cartridge.

[0022] The numbers 1st, 2nd, 3rd, and 4th are used for explanatory purposes only. The photosensitive drum 61, charging roller 62, and developing roller 71 may be provided in either the cartridge P or the tray 51. In this embodiment, the cartridge P has the photosensitive drum 61, charging roller 62, and developing roller 71.

[0023] The transfer unit 40 includes a belt 41, a primary transfer roller 42, a cleaning unit 43, a drive roller 46 for driving the belt 41, and a tension roller 47. In this embodiment, the printer 1 is equipped with an optical sensor 44 for detecting the toner image transferred to the belt 41. In this embodiment, the belt 41 is positioned below the four photosensitive drums 61 and is in contact with the photosensitive drums 61 such that a primary transfer section is formed between the belt 41 and each of the photosensitive drums 61. The printer 1 also has a secondary transfer roller 45 that contacts the belt 41 so that a secondary transfer section is formed. The secondary transfer section is formed between the belt 41 and the secondary transfer roller 45. The rotational axis directions of the primary transfer roller 42, the drive roller 46, the tension roller 47, and the secondary transfer roller 45 are parallel. A pair of registration rollers 4 is positioned in front of the secondary transfer section.

[0024] The fixing device 80 has a fixing unit 81 and a switching guide 5. The fixing device 80 is housed inside the main body 1A. The fixing unit 81 is a thermal fixing unit that heats and pressurizes the image on the sheet S while transporting the sheet S during the image forming operation. In this embodiment, the fixing unit 81 includes a heating unit (heating roller) including a heater and a pressurizing unit (pressurizing roller).

[0025] [Image Formation Process] Using Figure 1, the image formation operation, which is a series of operations in which the printer 1 transports a sheet S and forms an image on the sheet S, will be explained. The control unit 3 of the printer 1 starts the image formation operation based on image information received from an external host device 900. The external host device 900 is, for example, a personal computer, an image reader, and a facsimile machine.

[0026] When the image forming operation starts, the rotational drive of each photosensitive drum 61 and belt 41 begins. A charging voltage is applied to each charging roller 62, and the surface of the corresponding photosensitive drum 61 is charged. Based on the image information, the scanner 2 is driven, and a laser is shone from the scanner 2 onto the photosensitive drum 61, exposing the surface of the photosensitive drum 61. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 61.

[0027] The developing roller 71 rotates while carrying toner. A developing voltage is applied to the developing roller 71. The electrostatic latent image formed on the photosensitive drum 61 is developed by the toner supplied from the developing roller 71, thereby forming a toner image on the surface of the photosensitive drum 61. When a full-color image is formed, toner images of each color are formed on the four photosensitive drums 61. In this embodiment, the developing roller 71 develops the electrostatic latent image while in contact with the photosensitive drum 61, but the developing roller 71 may develop the electrostatic latent image with a gap between the developing roller 71 and the photosensitive drum 61.

[0028] In this embodiment, the developing roller 71 is movable between a contact position in contact with the photosensitive drum 61 and a separated position away from the photosensitive drum 61. Specifically, a switching device provided in the main body 1A switches between the developing roller 71 being in the contact position and the developing roller 71 being in the separated position. This allows the developing roller 71 to be kept away from the photosensitive drum 61 when no image forming operation is being performed.

[0029] Furthermore, printer 1 can form monochrome images when the developing roller 71 and photosensitive drum 61 corresponding to cartridge PK are in contact, and when the developing roller 71 and photosensitive drum 61 corresponding to cartridges PY, PM, and PC are separated. In addition, printer 1 can form full-color images when the photosensitive drum 61 and belt 41 corresponding to cartridges PY, PM, PC, and PK are in contact.

[0030] The toner images formed on each photosensitive drum 61 are transferred onto the belt 41 by the primary transfer roller 42 in the primary transfer section and transported toward the secondary transfer section formed by the belt 41 and the secondary transfer roller 45.

[0031] Meanwhile, the main body 1A of the device has a transport path (first path, first transport path) 1c through which the sheet S heading toward the fuser 80 passes. The door 20 also has a double-sided transport path (second path, second transport path) 20a through which the sheet S that has passed through the fuser 80 passes. When the door 20 is closed, it covers the transport path 1c. When the door 20 is opened, the transport path 1c and the double-sided transport path 20a are exposed to the outside of the printer 1 (Figure 2).

[0032] In parallel with the formation of the toner image described above, in the sheet feeding unit 30, one sheet S is fed from the sheets S loaded on the loading tray 31 by the feeding roller 32 at a predetermined timing. The fed sheets S are transported through the transport path 1c toward the secondary transfer unit. In the secondary transfer unit, the toner image is transferred from the belt 41 to the sheets S. Toner that was not transferred to the sheets S is removed from the belt 41 by a cleaning blade (cleaning member) 43A provided in the cleaning unit 43.

[0033] The sheet S onto which the toner image has been transferred in the secondary transfer section is transported toward the fuser unit 80. In the fuser unit 80, the sheet S is heated and pressurized in the fuser section 81, and the toner image is fixed to the sheet S. The sheet S with the fixed toner image is transported toward the switching guide 5, which acts as a path switching section.

[0034] The switching guide 5 is movable between an discharge position that guides the sheet S, which has passed through the fixing unit 81, toward the discharge path 1d, and a reversal position that guides it toward the reversal path 1e. In the case of single-sided printing, in which an image is formed on one side of the sheet S, the sheet S is guided to the discharge path 1d by the switching guide 5 and discharged into the discharge tray 1f formed on the upper part of the main body 1A. On the other hand, in the case of double-sided printing, in which an image is formed on the first and second sides of the sheet S, the sheet S, which has an image formed on the first side by passing through the secondary transfer unit and fixing unit 81, is guided to the reversal path 1e by the switching guide 5. After the sheet S is guided into the reversal path 1e, the transport direction of the sheet S is reversed, and the sheet S is transported again toward the secondary transfer unit through the double-sided transport path 20a formed in the door 20. Then, the sheet S, which has an image formed on the second side by passing through the secondary transfer unit and fixing unit 81, is guided to the discharge path 1d by the switching guide 5 and discharged into the discharge tray 1f.

[0035] [cartridge] The configuration of cartridge P will be explained using Figures 3 and 4. Figure 3 is a perspective view showing the entire cartridge P. Figure 4 is a perspective view near the drum coupling 63. The direction of the rotation axis of the photosensitive drum 61 of cartridge P is called the longitudinal direction of cartridge P. In the following description, "photosensitive drum 61" refers to any one of the one or more (four in this embodiment) photosensitive drums 61 provided by printer 1.

[0036] As shown in Figure 3, the cartridge P consists of a drum unit 60 and a developing unit 70. A first side cover 66 and a second side cover 67 are fixed to both ends of the drum unit 60 in the longitudinal direction of the cartridge P, respectively. The developing unit is rotatably supported by the first side cover 66 and the second side cover 67.

[0037] The drum unit 60 consists of a photosensitive drum 61, a charging roller 62, a drum frame 65 which is the first frame, and the like. A drum coupling 63 and a drum flange 64 are fixed to the photosensitive drum 61. The drum coupling 63 is rotatably supported by the first side cover 66, and the drum flange 64 is rotatably supported by the second side cover 67. In addition, cleaning means (for example, a cleaning blade) for removing residual toner remaining on the surface of the photosensitive drum 61 may be provided in the drum unit 60. The drum unit 60 in this embodiment does not have cleaning means.

[0038] The developing unit 70 consists of a developing roller 71, a toner supply roller, a developing blade, a developing coupling 72, and a developing frame 73. The toner supply roller supplies toner from the toner storage space formed inside the developing frame 73 to the developing roller 71. The developing blade contacts the outer surface of the developing roller 71 with a predetermined contact pressure, regulating the thickness of the toner layer carried on the developing roller 71 and causing the toner to rub and become electrically charged. The developing coupling 72 is a drive input section in which the developing unit 70 receives driving force from the main body 1A of the device.

[0039] The drum coupling 63 engages with the drive transmission unit 200 of the device body 1A, which will be described later, and rotates in response to the driving force of the motor 301. In this embodiment, the drum coupling 63 is arranged coaxially with the photosensitive drum 61, but the drum coupling 63 may be a member that rotates around an axis different from the rotation axis of the photosensitive drum 61.

[0040] As shown in Figure 4, the drum coupling 63 has a circular hole 63a, a first force receiving portion 63b, and a second force receiving portion 63c. The circular hole 63a is configured to engage with the positioning boss 180i (Figure 6) of the drive transmission unit 200. The first force receiving portion 63b is configured to receive driving force from the drive transmission unit 200. The second force receiving portion 63c is configured to receive braking force from the drive transmission unit 200.

[0041] In this embodiment, the first force-receiving portion 63b and the second force-receiving portion 63c are both provided on projections 63p formed at the axial end of the drum coupling 63. The first force-receiving portion 63b is the surface of projection 63p facing upstream in the forward rotation direction A1, and the second force-receiving portion 63c is the surface of projection 63p facing downstream in the forward rotation direction A1.

[0042] Thus, the cartridge P has a driven part that is driven by the motor 301. The driven part includes a force receiving part that engages with a member constituting the main drive train 1D of the device body 1A and receives force from the main drive train 1D, and a driven object that is driven by the transmission of force through the force receiving part. In this embodiment, the force receiving part of the cartridge P is the first force receiving part 63b and the second force receiving part 63c of the drum coupling 63. In this embodiment, the driven object of the motor 301 in the cartridge P includes the photosensitive drum 61.

[0043] Note that the drive target of cartridge P may be a component other than the photosensitive drum 61.

[0044] The driven part of cartridge P includes a rotating member, and the rotation direction (first rotation direction) of the rotating member during image formation (when the image formation operation described above is performed) is defined as the forward rotation direction A1. In other words, the driven part of cartridge P includes a rotating member that rotates in the forward rotation direction A1 (first rotation direction) when the driven part of cartridge P is driven by the drive source (motor 301) of the device body 1A. The drum coupling 63 is an example of a rotating member, but the "rotating member" is not limited to the drum coupling 63, and may be, for example, a photosensitive drum 61.

[0045] In this embodiment, the cartridge P (replacement unit) receives a driving force (first force) acting on the drum coupling 63 (rotating member) in the forward rotation direction A1 (first rotation direction) from the first drive transmission unit 1D1 of the main drive train 1D, which will be described later. In addition, the cartridge P (replacement unit) in this embodiment receives a braking force (second force) acting on the drum coupling 63 (rotating member) in the opposite direction to the forward rotation direction A1 (second rotation direction) from the second drive transmission unit 1D2 of the main drive train 1D, which will be described later.

[0046] During image formation, the force (driving force, first force) received by the first force receiving part 63b from the first drive transmission part 1D1 of the main drive train 1D acts on the drum coupling 63 in the forward rotation direction A1. During image formation, the force (braking force, second force) received by the second force receiving part 63c from the second drive transmission part 1D2 of the main drive train 1D acts on the drum coupling 63 in the reverse direction (second rotation direction) opposite to the forward rotation direction A1. In other words, the cartridge P (replacement unit) of this embodiment has a first force receiving part 63b (first surface) that receives a driving force (first force) from the first drive transmission part 1D1, and a second force receiving part 63c (second surface) that receives a braking force (second force) from the second drive transmission part 1D2.

[0047] [Main unit drive row] Next, we will describe the main drive train 1D provided in the main body 1A of this embodiment. First, we will explain the overview of the main drive train 1D using Figure 13(a), and then we will mainly explain the configuration of the main drive train 1D in this embodiment using Figures 5(a) to 8(c).

[0048] (Overview of the main drive train) Figure 13(a) is a model diagram showing the drive transmission path from the motor 301 to the cartridge P in this embodiment. The main body 1A of the device in this embodiment has a main body drive train 1D as a drive unit (driving means) that drives the cartridge P etc. using the driving force of the motor 301. The motor 301 drives the cartridge P.

[0049] The main drive train 1D broadly includes a drive device 1Dd, a first drive transmission unit 1D1 (first drive transmission path), and a second drive transmission unit 1D2 (second drive transmission path). The drive device 1Dd includes a motor 301 as a drive source that generates driving force, and a branch gear 302 as an output unit that outputs the driving force of the motor 301. The first drive transmission unit 1D1 is connected to the branch gear 302 (output unit) and the cartridge P (replacement unit). The second drive transmission unit 1D2 includes a torque limiter 410 (allowance device, differential device) and is connected to the branch gear 302 (output unit) and the cartridge P (replacement unit).

[0050] The first drive transmission unit 1D1 and the second drive transmission unit 1D2 are connected to each other via the cartridge P. Therefore, the transmission path of the driving force of the motor 301 in the printer 1 of this embodiment includes a closed loop. This closed loop includes a branch gear 302 (output unit), the first drive transmission unit 1D1, the second drive transmission unit 1D2 which includes a torque limiter 410 (allowing device, differential device), and the drum coupling 63 of the cartridge P (driven unit).

[0051] The first drive transmission unit 1D1 and the second drive transmission unit 1D2 each connect the branch gear 302 (output unit) and the cartridge P in parallel. In other words, each of the first drive transmission unit 1D1 and the second drive transmission unit 1D2 has a member that engages with the branch gear 302 (output unit) (in this embodiment, the first drive gear 303 and the second drive gear 304). Furthermore, each of the first drive transmission unit 1D1 and the second drive transmission unit 1D2 has a member that engages with the cartridge P (in this embodiment, the main body coupling 180 and the engaging members (204, 208)). In this embodiment, the first drive gear 303 and the second drive gear 304 directly engage with the branch gear 302, and the main body coupling 180 and the engaging members (204, 208) directly engage with the drum coupling 63 (driven unit).

[0052] In this embodiment, the second drive transmission unit 1D2 can be divided into a motor-side transmission unit 1D2a (drive source-side transmission unit) and a cartridge-side transmission unit 1D2b (unit-side transmission unit), with the torque limiter 410 as the dividing line. The motor-side transmission unit 1D2a is connected to the branching gear 302 and the inner ring 410b of the torque limiter 410. The cartridge-side transmission unit 1D2b is connected to the outer ring 410a of the torque limiter 410 and the drum coupling 63 of the cartridge P.

[0053] Furthermore, the outer ring 410a may be connected to the motor-side transmission unit 1D2a and the inner ring 410b may be connected to the cartridge-side transmission unit 1D2b. In addition, the outer ring 410a, the inner ring 410b, or a member that rotates integrally with the outer ring 410a / inner ring 410b of the torque limiter 410 may be directly engaged with the driven part of the cartridge P without the need for other gears or the like.

[0054] In this embodiment, the first drive transmission unit 1D1 transmits force between the branch gear 302 and the drum coupling 63 (Figure 4) of the cartridge P, mainly transmitting the driving force of the motor 301 from the former to the latter. In this embodiment, the motor-side transmission unit 1D2a of the second drive transmission unit 1D2 transmits force between the branch gear 302 and the inner ring 410b of the torque limiter 410. Furthermore, the cartridge-side transmission unit 1D2b of the second drive transmission unit 1D2 transmits force between the outer ring 410a of the torque limiter 410 and the drum coupling 63 of the cartridge P.

[0055] The first drive transmission unit 1D1 and the second drive transmission unit 1D2 can transmit the driving force of the motor 301 to drive target units other than the cartridge P in the printer 1. In this embodiment, the motor-side transmission unit 1D2a of the second drive transmission unit 1D2 is connected to a load body 306 and can transmit the driving force of the motor 301 to the load body 306. An example of the load body 306 is a transport roller for transporting a sheet S (for example, a feed roller 32 or a pair of registration rollers 4).

[0056] (Configuration of the main drive train) The configuration of the main drive train 1D in this embodiment will be described. Figure 5(a) is a diagram showing the main drive train 1D, and is a diagram that combines a perspective view of a part of the main drive train 1D (drive transmission unit 200 and differential mechanism 400) viewed from the front side with a schematic diagram representing other elements of the main drive train 1D. Figure 5(b) is a perspective view of the drive transmission unit 200 and differential mechanism 400 viewed from the rear side. Figure 5(c) is an exploded perspective view of the differential mechanism 400. Figure 6(a) is an exploded perspective view of the drive transmission unit 200. Figure 6(b) is an exploded perspective view showing an enlarged part of the drive transmission unit 200. Figure 7(a) is a view of the drive transmission unit 200 and differential mechanism 400 viewed from the front side. Figure 7(b) is a cross-sectional development view of the drive transmission unit 200 and differential mechanism 400 at the cross-section indicated by line AA in Figure 7(a). Figure 8 is a perspective view of the main body side coupling 180.

[0057] As shown in Figure 5(a), the main drive train 1D includes a drive transmission unit 200, a gear train 300, and a differential mechanism 400.

[0058] As shown in Figures 5(a), 6(a)(b), and 7(b), the drive transmission unit 200 includes a main body coupling 180, a coupling gear 201, and a transmission shaft 209. The drive transmission unit 200 also includes a bearing member 202, a first engaging member 204, a force transmission member 207, a second engaging member 208, a coupling spring 210, a brake engaging spring 211, and a spring holding member 214.

[0059] As shown in Figures 5(a) to (c) and Figure 7(b), the differential mechanism 400 includes a torque limiter 410 having an outer ring 410a and an inner ring 410b. The differential mechanism 400 also includes a first differential gear 401, a second differential gear 402, an outer gear 403, a third differential gear 404, a fourth differential gear 405, a differential shaft 406, an engagement pin 407, and bearings 408 and 409.

[0060] As shown in Figure 5(a), the gear train 300 includes a branch gear 302, a first drive gear 303, a second drive gear 304, and a load gear 305. The gear train 300 also includes one or more gears (not shown) connecting the first drive gear 303 to the coupling gear 201 of the drive transmission unit 200, and one or more gears (not shown) connecting the load gear 305 to the fourth differential gear 405 of the differential mechanism 400. Furthermore, the gear train 300 may include one or more gears (not shown) connecting the second drive gear 304 to the load gear 305. In other words, the gears connected by the dashed line in Figure 5(a) may be connected via one or more gears.

[0061] The correspondence between the components of the drive transmission unit 200, the differential mechanism 400, and the gear train 300 and the motor-side transmission unit 1D2a and cartridge-side transmission unit 1D2b of the first drive transmission unit 1D1 and the second drive transmission unit 1D2 (Figure 13(a)) is as follows.

[0062] In this embodiment, the first drive transmission unit 1D1 includes a part of the gear train 300 (first drive gear 303) and a part of the drive transmission unit 200 (coupling gear 201 and main body side coupling 180). The first drive transmission unit 1D1 may include one or more gears connecting the first drive gear 303 and the coupling gear 201.

[0063] In this embodiment, the motor-side transmission section 1D2a of the second drive transmission section 1D2 includes a part of the gear train 300 (second drive gear 304 and load gear 305) and a part of the differential mechanism section 400 (third differential gear 404, fourth differential gear 405, and differential shaft 406). The motor-side transmission section 1D2a of the second drive transmission section 1D2 may include one or more gears connecting the second drive gear 304 and the load gear 305, and one or more gears connecting the load gear 305 and the fourth differential gear 405.

[0064] In this embodiment, the cartridge-side transmission section 1D2b of the second drive transmission section 1D2 includes a part of the differential mechanism section 400 (first differential gear 401, second differential gear 402, outer peripheral gear 403) and a part of the drive transmission unit 200 (transmission shaft 209, force transmission member 207, first engaging member 204, second engaging member 208).

[0065] (Details of the gear train) As shown in Figure 5(a), the branch gear 302 is connected to the motor 301 and rotates due to the driving force of the motor 301. The first drive gear 303 and the second drive gear 304 mesh with the branch gear 302, respectively. The first drive gear 303 is connected to the coupling gear 201 of the drive transmission unit 200 in a drive-transmission manner. The second drive gear 304 is connected to the fourth differential gear 405 of the differential mechanism 400 via the load gear 305 in a drive-transmission manner. The load gear 305 is connected to the load 306 in a drive-transmission manner.

[0066] (Details of the drive transmission unit) The drive transmission unit 200 is a unit that engages with the drum coupling 63 (Figure 4) of the cartridge P and transmits force from the device body 1A to the cartridge P. In this embodiment, the body-side coupling 180, the first engaging member 204, and the second engaging member 208 of the drive transmission unit 200 are each members that can engage with the drum coupling 63 of the cartridge P.

[0067] As shown in Figure 6(a), the main body coupling 180, the first engaging member 204, the second engaging member 208, the force transmission member 207, and the transmission shaft 209 are all rotatable members that can rotate around the axis M1. In this embodiment, the multiple members (main body coupling 180, engaging members (204, 208)) that engage with the driven portion of the cartridge P and transmit force to the cartridge P are arranged concentrically.

[0068] The axis M1 can be called the central axis of the drive transmission unit 200. When the drive transmission unit 200 is engaged with the drum coupling 63, the drum coupling 63 rotates around the axis M1 (Figure 4). On the other hand, the bearing member 202 is fixed to a frame member attached to the device body 1A. In this embodiment, when the cartridge P is mounted on the device body 1A, the axis M1 coincides with the rotation axis of the photosensitive drum 61.

[0069] The direction parallel to the axis M1, in which the main body coupling 180 is positioned relative to the drum coupling 63, is called the first axial direction M1A. The direction parallel to the axis M1, in which the drum coupling 63 is positioned relative to the main body coupling 180, is called the second axial direction M1B. When there is no particular distinction between the first axial direction M1A and the second axial direction M1B, they may simply be referred to as the axial direction.

[0070] As shown in Figures 6(a) and 8(a)-(c), the main body coupling 180 has a flange portion 180a, an engaging projection 180b, a cylindrical portion 180c, a force transmission surface 180d, a through hole 180f, and a positioning boss 180i. The main body coupling 180 is supported by a coupling gear 201 so as to be movable in the first axial direction M1A and the second axial direction M1B.

[0071] The cylindrical portion 180c is formed in a cylindrical shape centered on the axis M1. The flange portion 180a extends in a flange shape from the end of the cylindrical portion 180c in the first axial direction M1A. The engaging projection 180b protrudes further outward from the outer circumference of the flange portion 180a. The engaging projection 180b is the part that engages with the coupling gear 201. The force transmission surface 180d, the through hole 180f, and the positioning boss 180i will be described later.

[0072] The coupling gear 201 is rotatably supported by a bearing member 202. The gear portion (teeth) on the outer circumference of the coupling gear 201 meshes with a gear (not shown) connected to the first drive gear 303.

[0073] The coupling gear 201 has a fitting portion 201c and an engagement surface 201d. The fitting portion 201c is a substantially cylindrical wall portion through which the cylindrical portion 180c of the main body coupling 180 is inserted. The engagement surface 201d engages with the engagement projection 180b of the main body coupling 180. Due to the contact between the engagement surface 201d and the engagement projection 180b, the coupling gear 201 and the main body coupling 180 rotate integrally in the forward rotation direction A1. In other words, the driving force of the motor 301 is transmitted from the coupling gear 201 to the main body coupling 180 via the contact between the engagement surface 201d and the engagement projection 180b.

[0074] Inside the cylindrical portion 180c of the main body coupling 180, a force transmission member 207, a first engaging member 204, a second engaging member 208, a brake engaging spring 211, a coupling spring 210, and a spring holding member 214 are arranged.

[0075] The force transmission member 207 is connected to the first differential gear 401 of the differential mechanism 400 via the transmission shaft 209. The first engaging member 204 and the second engaging member 208 are configured to engage with the second force receiving portion 63c (Figure 4) of the drum coupling 63. The brake engagement spring 211 and the coupling spring 210 are arranged along the axis M1 and generate a biasing force in the direction of the axis M1 (axial direction). The spring holding member 214 holds the brake engagement spring 211 and the coupling spring 210.

[0076] Further explanation will be given regarding the components located inside the cylindrical portion 180c of the main body coupling 180.

[0077] As shown in Figure 6(b), the first engaging member 204 has a ring portion 204a, a coupling engaging portion 204b, a recess 204c, and a protrusion 204e. The ring portion 204a is formed in an annular shape with axis M1 as the center. The coupling engaging portion 204b is claw-shaped and protrudes from the ring portion 204a in the second axial direction M1B. The coupling engaging portion 204b is the part that engages with the second force receiving portion 63c of the drum coupling 63. In this embodiment, the coupling engaging portion 204b extends spirally toward the axial direction M1B in the opposite direction to the forward rotation direction A1. The recess 204c is a concave shape in which a part of the end face of the ring portion 204a in the second axial direction M1B is recessed toward the first axial direction M1A. The recess 204c is the part that engages with the protrusion 208c of the second engaging member 208. The protrusion 204e extends from the ring portion 204a toward the second axial direction M1B. The protrusion 204e is the portion that engages with the projection 207e of the force transmission member 207.

[0078] The second engaging member 208 has a ring portion 208a, a coupling engaging portion 208b, and a protrusion portion 208c. The ring portion 208a is formed in an annular shape with the axis M1 as the center. The coupling engaging portion 208b is claw-shaped and protrudes from the ring portion 208a in the second axial direction M1B. The coupling engaging portion 208b is the part that engages with the second force receiving portion 63c of the drum coupling 63. In this embodiment, the coupling engaging portion 208b extends spirally in the direction opposite to the forward rotation direction A1 toward the axial direction M1B.

[0079] The engagement of the convex portion 208c and the concave portion 204c restricts the relative rotation of the second engaging member 208 with respect to the first engaging member 204. In other words, the first engaging member 204 and the second engaging member 208 rotate integrally around the axis M1.

[0080] Furthermore, the biasing force of the brake engagement spring 211 presses the first engagement member 204 toward the second engagement member 208, causing the first engagement member 204 and the second engagement member 208 to move integrally in the axial direction. For this reason, the first engagement member 204 and the second engagement member 208 are sometimes collectively referred to as the engagement members (204, 208).

[0081] Furthermore, the first engaging member 204 can be described as an external engaging member positioned radially outward, and the second engaging member 208 as an internal engaging member positioned radially inward. The radial direction refers to the radial direction of a virtual circle centered on axis M1.

[0082] The force transmission member 207 has a flange portion 207a, a shaft portion 207b, a hole portion 207c, an end face 207d, a projection 207e, and a projection 207f. The flange portion 207a extends radially outward from the end of the shaft portion 207b in the second axial direction M1B, which extends in the axial direction. The projection 207e can engage with the convex portion 204e of the first engaging member 204.

[0083] The force transmission member 207 is positioned such that its flange portion 207a is located axially between the ring portion 204a of the first engaging member 204 and the ring portion 208a of the second engaging member 208 (Figure 7). Since the distance between the ring portions 204a and 208a in the axial direction is greater than the thickness of the flange portion 207a, a gap (backlash, clearance) is set between the ring portions 204a and 208a and the flange portion 207a. Due to this gap, the force transmission member 207 is axially movable relative to the engaging members (204 and 208).

[0084] Specifically, the engaging members (204, 208) are movable relative to the force transmission member 207 between an engaged position in which the projection 207e engages with the convex portion 204e of the first engaging member 204, and a disengaged position in which the projection 207e disengages from the convex portion 204e. When the engaging members (204, 208) are in the engaged position, the force transmission member 207 and the engaging members (204, 208) rotate integrally around the axis M1. When the engaging members (204, 208) are in the disengaged position, relative rotation of the force transmission member 207 and the engaging members (204, 208) is permitted.

[0085] The hole 207c of the force transmission member 207 is non-circular when viewed in the axial direction and is formed in the shaft portion 207b. The end of the transmission shaft 209 is inserted through the hole 207c (Figure 7). As a result, the force transmission member 207 and the transmission shaft 209 rotate integrally around the axis M1. A first differential gear 401 is attached to the transmission shaft 209. Therefore, the first differential gear 401 rotates integrally with the force transmission member 207.

[0086] The brake engagement spring 211 is a compression coil spring, which is positioned in a compressed state, sandwiched between the spring holding member 214 and the ring portion 204a of the first engagement member 204 in the axial direction. The brake engagement spring 211 provides an axial repulsive force (biasing force, elastic force) to both the spring holding member 214 and the ring portion 204a of the first engagement member 204.

[0087] The coupling spring 210 is a compression coil spring, and is positioned in a compressed state, sandwiched between the spring holding member 214 and the end face 207d of the force transmission member 207 in the first axial direction M1A. The coupling spring 210 provides a repulsive force (biasing force, elastic force) to both the spring holding member 214 and the force transmission member 207.

[0088] The spring retaining member 214 is a cylindrical member positioned on the outer circumference of the transmission shaft 209. The spring retaining member 214 abuts against the end face of the bearing member 202 in the second axial direction M1B due to the repulsive force of the two springs (210, 211).

[0089] The force transmission member 207 receives a repulsive force in the second axial direction M1B from the brake engagement spring 211 via the ring portion 204a of the first engagement member 204, and also receives a repulsive force in the second axial direction M1B directly from the coupling spring 210. Due to this force in the second axial direction M1B, the projection 207f at the end of the force transmission member 207 in the second axial direction M1B abuts against the abutment surface 180g of the main body coupling 180 (Figure 7).

[0090] Therefore, the main body coupling 180 is biased in the second axial direction M1B by the repulsive force of two springs (210, 211). Near the main body coupling 180, a restricting member is provided to restrict the movement of the main body coupling 180 in the second axial direction M1B (Figure 7). The restricting member is positioned so as to overlap with the flange portion 180a of the main body coupling 180 when viewed in the axial direction. The restricting member prevents the main body coupling 180 from falling off the coupling gear 201. The restricting member may be, for example, a member fixed to the coupling gear 201, or a member fixed to the frame of the device body 1A.

[0091] Furthermore, when the main body coupling 180 receives an external force in the first axial direction M1A, it can move in the first axial direction M1A while compressing the two springs (210, 211).

[0092] As shown in Figure 8(a), the main body coupling 180 has a force transmission surface 180d. In this embodiment, the force transmission surface 180d is a surface (drive transmission surface) that transmits the force (driving force) acting in the forward rotation direction A1 when the main body coupling 180 is engaged with the drum coupling 63.

[0093] The main body coupling 180 of this embodiment has two force transmission surfaces 180d positioned 180 degrees apart in the rotational direction around axis M1. Furthermore, the main body coupling 180 of this embodiment has two coupling engagement portions 204b and two coupling engagement portions 208b positioned 180 degrees apart in the rotational direction. In other words, the end face shape of the main body coupling 180 on the drum coupling 63 side (second axial direction M1B side) has rotational symmetry (point symmetry) around axis M1 when viewed in the axial direction.

[0094] At the end face of the main body coupling 180 in the second axial direction M1B, a through hole 180f is provided in the portion other than the force transmission surface 180d, extending axially. When viewed in the axial direction, the coupling engagement portions 204b and 208b of the engaging members (204 and 208) are exposed inside the through hole 180f.

[0095] Figure 8(b) shows the state in which the coupling engagement portions 204b and 208b of the first engaging member 204 and the second engaging member 208 are exposed. Figure 8(b) shows the state in which the coupling engagement portions 204b and 208b and the force transmission surface 180d are in a phase relationship that is close together in the forward rotation direction A1 of the drum coupling 63. The size of the through hole 180f is set to be wider than the width of the coupling engagement portions 204b and 208b in the circumferential direction. Therefore, as shown in Figure 8(c), the coupling engagement portions 204b and 208b can move within a certain range in the rotational direction within the main body coupling 180, and a gap G1 is created between the coupling engagement portions 204b and 208b and the force transmission surface 180d. When the cartridge P is installed, the projection 63p (Figure 4) of the drum coupling 63 is inserted into the gap G1.

[0096] (Details of the differential mechanism) As shown in Figure 7(b), the torque limiter 410 has an outer ring 410a and an inner ring 410b. Either the outer ring 410a or the inner ring 410b can be called the first rotating body, and the other of the outer ring 410a and the inner ring 410b can be called the second rotating body. In this embodiment, the outer ring 410a is described as an example of the first rotating body, and the inner ring 410b is described as an example of the second rotating body. The outer ring 410a is also called the housing that accommodates the inner ring 410b.

[0097] The outer ring 410a and the inner ring 410b are rotatable around a common axis of rotation, axis M2, and are rotatable relative to each other. Axis M2 is parallel to and away from the axis M1 of the drive transmission unit 200. In other words, the torque limiter 410 is positioned on axis M2, which is parallel to and away from the axis M1 of the main body coupling 180. However, the torque limiter 410 can also be positioned coaxially on the axis M1 common to the main body coupling 180. According to this embodiment, for example, by arranging the differential mechanism 400 (e.g., differential shaft 406) and the drive transmission unit 200 to overlap when viewed in a direction perpendicular to the direction of axis M1, space can be saved for the main body drive train 1D in the axial direction.

[0098] The torque limiter 410 is an example of a tolerance device that includes a first rotating body and a second rotating body, and is configured to allow the transmission of the driving force of the motor 301 between the first rotating body and the second rotating body, and to allow fluctuations in the ratio of the first angular velocity of the first rotating body to the second angular velocity of the second rotating body. The tolerance device allows a state in which the ratio of the first angular velocity of the first rotating body to the second angular velocity of the second rotating body is a first ratio, and a state in which it is a second ratio different from the first ratio. Note that the tolerance device only needs to have a configuration (function) that allows fluctuations in the ratio of the first angular velocity to the second angular velocity, and it is not necessary for the ratio of the first angular velocity to the second angular velocity to fluctuate when the drive source (motor 301) is rotating at a constant speed during image formation. Furthermore, unlike a mechanism in which two gears are simply arranged coaxially and no force (torque) is transmitted between the two gears, the tolerance device is capable of transmitting force (torque) between the first rotating body and the second rotating body.

[0099] Furthermore, the torque limiter 410 can be considered an example of a differential device that includes a first rotating body and a second rotating body and allows relative rotation (differential rotation) between the first and second rotating bodies. The differential device allows rotations of different angular velocities to be input to the first and second rotating bodies and absorbs the difference in angular velocity. In addition, the differential device can transmit force (torque) between the first and second rotating bodies while allowing relative rotation (differential rotation) between them.

[0100] The torque limiter 410 may be, for example, a dry friction plate type or a ball ratchet type. Furthermore, the torque limiter 410 is merely one example of a tolerance device or differential device, and other tolerance devices or differential devices may be used. For example, the tolerance device or differential device may be the planetary gear mechanism shown in Embodiment 4. Also, the tolerance device or differential device is not limited to one that generates a load by friction, but may be a rotary damper that generates a load by the viscosity of a fluid such as oil. A rotary damper has an inner ring (shaft) and an outer ring (housing), and allows relative rotation between the inner ring and the outer ring, and generates a load corresponding to the speed difference between the inner ring and the outer ring by the viscosity of the fluid sealed in the space between the inner ring and the outer ring. Thus, it can be said that the tolerance device or differential device has a functional part (absorption function part, tolerance function part) that absorbs speed differences or allows for speed ratio fluctuations. For example, in the torque limiter 410, the contact part between the outer ring 410a and the inner ring 410b can be said to correspond to the functional part.

[0101] As will be described later, in the printer 1 of this embodiment, when the driven part of the cartridge P is driven by the motor 301 of the device body 1A, the functional unit operates, and the tolerance device or differential device transmits the torque of the motor 301. In other words, when the driven part of the cartridge P is driven by the motor 301 of the device body 1A, the torque of the motor 301 is transmitted by the tolerance device or differential device while the functional unit absorbs the speed difference and allows for speed ratio fluctuations. The time when the driven part of the cartridge P is driven by the motor 301 of the device body 1A includes the time when the image is formed.

[0102] As shown in Figure 7(b), the outer ring 410a is provided with a protrusion 410d, and the outer gear 403 is provided with a hole 403h. Due to the engagement of the protrusion 410d and the hole 403h, the outer ring 410a rotates integrally with the outer gear 403 around the axis M2.

[0103] As shown in Figures 5(b)(c) and 7(b), the outer gear 403 meshes with the second differential gear 402. The second differential gear 402 meshes with the first differential gear 401. As previously mentioned, the first differential gear 401 is mounted on the transmission shaft 209. Furthermore, when the engaging members (204, 208) are in the engaged position, the transmission shaft 209 rotates integrally with the force transmission member 207 and the engaging members (204, 208). Therefore, the outer ring 410a of the torque limiter 410 is configured to rotate in conjunction with the rotation of the engaging members (204, 208) of the drive transmission unit 200.

[0104] As shown in Figure 7(b), the inner ring 410b is provided with a groove that engages with an engagement pin 407 inserted through the differential shaft 406. The engagement of the groove with the engagement pin 407 causes the inner ring 410b to rotate integrally with the differential shaft 406 around the axis M2. Furthermore, the engagement of the groove with the engagement pin 407 positions the torque limiter 410 in the direction of the axis M2.

[0105] The differential shaft 406 is supported by bearings 408 and 409 fixed to the frame of the device body 1A and rotates about axis M2. A third differential gear 404 is attached to the differential shaft 406. The third differential gear 404 meshes with the fourth differential gear 405. The fourth differential gear 405 is connected to the coupling gear 201 of the drive transmission unit 200 via a gear train 300 (Figure 5(a)). As described above, the coupling gear 201 rotates integrally with the body-side coupling 180 in the forward direction A1. Therefore, the inner ring 410b of the torque limiter 410 is configured to rotate in conjunction with the rotation of the body-side coupling 180 of the drive transmission unit 200.

[0106] The outer ring 410a and the inner ring 410b are engaged by friction. When the torque acting between the outer ring 410a and the inner ring 410b is less than a predetermined value, the outer ring 410a and the inner ring 410b rotate together. When a torque greater than or equal to the predetermined value acts between the outer ring 410a and the inner ring 410b, relative rotation of the outer ring 410a and the inner ring 410b occurs due to sliding of the friction surfaces. Therefore, the torque limiter 410 allows a difference to occur between the angular velocity of rotation input to the outer ring 410a and the angular velocity of rotation input to the inner ring 410b.

[0107] Furthermore, the torque limiter 410 generates a load when absorbing the difference in rotational speed input to the outer ring 410a and the inner ring 410b. In other words, when there is a difference in angular velocity between the outer ring 410a and the inner ring 410b, a torque in the direction of reducing the speed difference acts on each of the outer ring 410a and the inner ring 410b. In this embodiment, the load is generated by friction when the outer ring 410a and the inner ring 410b (first rotating body and second rotating body) rotate relative to each other. In this embodiment, the load generated by the torque limiter 410 acts on the drum coupling 63 as a braking force that restricts the preceding rotation of the drum coupling 63 relative to the coupling gear 201. The relationship between the torque limiter 410 and the braking force will be described later.

[0108] [Engagement of drum coupling] The engagement between the drive transmission unit 200 and the drum coupling 63 in this embodiment will be explained using Figures 9 and 10(a). Figure 9 is a cross-sectional view showing the state in which the drive transmission unit 200 and the drum coupling 63 are engaged (see line AA in Figure 7(a) for the cutting position). Figure 10(a) is an enlarged view of the cross-section of the engagement portion between the main body coupling 180 and the second engaging member 208 and the drum coupling 63. Note that in Figure 10(a), only the second engaging member 208 of the engaging members (204, 208) is shown. In the state in which the drive transmission unit 200 and the drum coupling 63 are engaged, the positional relationship of the first engaging member 204 with respect to the drum coupling 63 and the direction of force transmission are basically the same as the positional relationship and direction of force transmission of the second engaging member 208.

[0109] When the cartridge P is installed in a predetermined position within the main body 1A of the device, the drive transmission unit 200 and the drum coupling 63 engage, as shown in Figures 9 and 10(a). With the drive transmission unit 200 and the drum coupling 63 engaged, the circular hole 63a of the drum coupling 63 engages with the positioning boss 180i of the main body coupling 180 (Figure 9). The engagement of the circular hole 63a and the positioning boss 180i causes the rotation axis of the drum coupling 63 to coincide with the axis M1 of the drive transmission unit 200. In other words, the drum coupling 63 is aligned (positioned).

[0110] Furthermore, when the drive transmission unit 200 and the drum coupling 63 are engaged, the force transmission surface 180d of the main body coupling 180 comes into contact with the first force receiving portion 63b of the drum coupling 63 (Figure 10(a)). Also, when the drive transmission unit 200 and the drum coupling 63 are engaged, the coupling engagement portion 208b of the second engagement member 208 comes into contact with the second force receiving portion 63c of the drum coupling 63 (Figure 10(a)).

[0111] The main body coupling 180 is rotated in the forward direction A1 by drive transmission via the first drive transmission unit 1D1. When the drive transmission unit 200 and the drum coupling 63 are engaged, the drum coupling 63 is rotated in the forward direction A1 by pressing the first force receiving part 63b against the force transmission surface 180d. In other words, the force transmission surface 180d functions as a drive force application part that provides driving force to the drum coupling 63.

[0112] On the other hand, the second engaging member 208 is connected to the torque limiter 410 via the cartridge-side transmission part 1D2b of the second drive transmission part 1D2, and transmits the load generated by the torque limiter 410 to the drum coupling 63. When the drive transmission unit 200 and the drum coupling 63 are engaged, the drum coupling 63 receives a braking force in the opposite direction to the forward rotation direction A1 by having its second force receiving part 63c pressed by the coupling engaging part 208b.

[0113] Therefore, the drum coupling 63 is rotated in the forward direction A1 by the driving force received from the main body coupling 180 while receiving a braking force from the engaging members (204, 208). With this configuration, compared to the case where the drum coupling 63 does not receive a braking force, the pre-rotation (rapid rotation) of the drum coupling 63 relative to the main body coupling 180 can be suppressed. As a result, fluctuations in the rotational speed of the drum coupling 63 and the photosensitive drum 61 can be reduced.

[0114] The pre-rotation of the drum coupling 63 refers to the temporary rotation of the drum coupling 63 at a faster angular velocity than the main body coupling 180, causing the first force receiving part 63b to separate (lift) from the force transmission surface 180d. Pre-rotation of the drum coupling 63 may occur, for example, when an external force in the forward rotation direction A1 is applied to the photosensitive drum 61. If the pre-rotation of the drum coupling 63 is not restricted, the photosensitive drum 61 may become unstable during the image forming operation, potentially resulting in a decrease in image quality. Furthermore, the drum coupling 63 can stabilize the drive speed of other driven objects of the cartridge P besides the photosensitive drum 61 that are driven via the drum coupling 63.

[0115] According to this embodiment, by applying a braking force to the drum coupling 63 via the engaging members (204, 208), the preceding rotation of the drum coupling 63 can be restricted, and fluctuations in the rotational speed of the drum coupling 63 can be suppressed. This makes it possible to stabilize the drive speed of the driven object, such as the photosensitive drum 61 in the cartridge P, and, for example, prevent a decrease in image quality due to fluctuations in the rotational speed of the photosensitive drum 61.

[0116] [Operation of the main drive train] The operation of the main drive train 1D and the torque transmission flow will be explained using Figures 11(a)(b) and 12. Figure 11(a) is a schematic diagram showing the main drive train 1D when the drive force transmission path is not connected in a closed loop. Figure 11(b) is a diagram showing the main drive train 1D when it is connected in a closed loop. Figure 12 is a diagram showing the torque transmission flow in a cross-sectional unfolded view of the main drive train 1D when it is connected in a closed loop (see line AA in Figure 7(a) for the cutting position).

[0117] The "closed-loop connected state" of the main drive train 1D refers to a state in which the components constituting each drive transmission unit are connected such that force is transmitted in the direction indicated by the arrows in Figure 13(a), for example, between the first drive transmission unit 1D1 and the second drive transmission unit 1D2. The connection between the components of the main drive train 1D is, for example, the contact of the tooth surfaces of gears. The main drive train 1D is in a closed-loop connected state when, for example, the drum coupling 63 is steadily rotated by the driving force of the motor 301 during the execution of an image forming operation.

[0118] As shown in Figure 11(a), if there is a gap G between the tooth surfaces 402a and 403a of the second differential gear 402 and the outer gear 403, the main drive train 1D in this embodiment is not connected in a closed loop. When there is a gap G, torque is not transmitted from the second differential gear 402 to the outer gear 403. The state shown in Figure 11(a) appears, for example, immediately after the motor 301 is started.

[0119] In the state shown in Figure 11(a), the driving force is transmitted from the motor 301 to the branch gear 302, the first drive gear 303, the coupling gear 201, the main body coupling 180, and the drum coupling 63 in that order. Furthermore, the driving force is transmitted from the drum coupling 63 to the engaging members (204, 208), the transmission shaft 209, the first differential gear 401, and the second differential gear 402 in that order. As a result, the second differential gear 402 rotates at a peripheral speed V1. Peripheral speed V1 is the speed at which the teeth of the second differential gear 402 move along the pitch circle of the second differential gear 402. As will be explained below, peripheral speed V1 can also be said to be the peripheral speed of the second differential gear 402 and the outer peripheral gear 403 when the photosensitive drum 61 is driven at a steady state at the process speed (peripheral speed of the photosensitive drum 61 during image formation). Furthermore, the peripheral speed V1 is determined by the angular velocity of the output shaft of the motor 301, the speed transmission ratio of the transmission path from the motor 301 to the second differential gear 402, and the pitch circle radius of the second differential gear 402. This speed transmission ratio is the ratio of the rotation angle of the second differential gear 402 to the rotation angle of the motor 301 when the second differential gear 402 is being rotated by the motor 301.

[0120] In the state shown in Figure 11(a), the second differential gear 402 is not subjected to a load from the torque limiter 410. Therefore, the load from the torque limiter 410 is not transmitted from the second differential gear 402 to the engaging members (204, 208) by reversing the above drive transmission path, and no braking force is applied to the drum coupling 63 due to the load from the torque limiter 410. In other words, in the state shown in Figure 11(a), the preceding rotation of the drum coupling 63 is not restricted.

[0121] On the other hand, in the state shown in Figure 11(a), the driving force is transmitted from the motor 301 to the branch gear 302, the second drive gear 304, the load gear 305, the fourth differential gear 405, the third differential gear 404, the differential shaft 406, the torque limiter 410, and the outer gear 403 in that order. Also, in the state shown in Figure 11(a), the outer gear 403 is not subjected to a load from the second differential gear 402, so the torque limiter 410 does not slip, and the outer gear 403 and the differential shaft 406 rotate together at an angular velocity R2. The angular velocity R2 is determined by the angular velocity of the output shaft of the motor 301 and the speed transmission ratio of the transmission path from the motor 301 to the differential shaft 406. This speed transmission ratio is the ratio of the rotation angle of the differential shaft 406 to the rotation angle of the output shaft of the motor 301 when the differential shaft 406 is rotated by the motor 301.

[0122] Let V2 be the peripheral speed of the outer gear 403 when it rotates at the same angular velocity R2 as the differential shaft 406. Peripheral speed V2 is the speed at which the teeth of the outer gear 403 move along the pitch circle of the outer gear 403. Peripheral speed V2 is expressed as the product of the angular velocity R2 and the pitch circle radius of the outer gear 403.

[0123] Here, in the state shown in Figure 11(a), the peripheral speed V1 of the second differential gear 402 is faster than the peripheral speed V2 of the outer gear 403 (V1 > V2). Therefore, immediately after the motor 301 starts up, the state shown in Figure 11(a) is reached, and then the teeth of the second differential gear 402 catch up to the teeth of the outer gear 403.

[0124] As a result, as shown in Figure 11(b), the tooth surfaces 402a and 403a of the second differential gear 402 and the outer gear 403 come into contact. Torque is transmitted between the second differential gear 402 and the outer gear 403 through the contact of the tooth surfaces 402a and 403a. Therefore, when the tooth surfaces 402a and 403a are in contact, the main drive train 1D of this embodiment is connected in a closed loop, as shown in Figure 13(a).

[0125] As shown in Figure 11(b), when the teeth of the second differential gear 402 catch up with the teeth of the outer gear 403, the tooth surface 403a of the outer gear 403 is pressed against the tooth surface 402a of the second differential gear 402, causing the outer gear 403 to rotate at the same peripheral speed V1 as the second differential gear 402. Meanwhile, the differential shaft 406 continues to rotate at an angular velocity R2. The angular velocity R1 of the outer gear 403, which corresponds to peripheral speed V1, is faster than the angular velocity R2 of the differential shaft 406 (R1 > R2). In other words, the angular velocity R1 of the outer ring 410a, which rotates integrally with the outer gear 403, is faster than the angular velocity R2 of the inner ring 410b, which rotates integrally with the differential shaft 406.

[0126] In this configuration, when the main drive train 1D is connected in a closed loop, different angular velocities R1 and R2 are input to the outer ring 410a and inner ring 410b of the torque limiter 410, causing slippage of the torque limiter 410 (relative rotation of the outer ring 410a and inner ring 410b). The torque limiter 410 tolerates the input of different angular velocities R1 and R2 to the outer ring 410a and inner ring 410b and absorbs the difference in angular velocity.

[0127] In other words, the first drive transmission unit 1D1 and the second drive transmission unit 1D2 are configured such that there is a difference in the angular velocities R1 and R2 of the outer ring 410a (first rotating body) and the inner ring 410b (second rotating body) when the driven part of the cartridge P is driven by the motor 301. In this embodiment, when the driven part of the cartridge P is driven by the motor 301 (drive source), the angular velocity R1 (first angular velocity) of the outer ring 410a (first rotating body) is faster than the angular velocity R2 (second angular velocity) of the inner ring 410b (second rotating body).

[0128] Furthermore, the torque limiter 410 in this embodiment generates a load to apply a braking force to the drum coupling 63 when the outer ring 410a and the inner ring 410b rotate relative to each other. Specifically, in the state shown in Figure 11(b), the outer ring 410a rotates at a faster angular velocity R1 than the inner ring 410b, overcoming friction with the inner ring 410b. As a result, the outer ring 410a receives a load as frictional resistance in the opposite direction to its rotation. This load is transmitted from the outer peripheral gear 403, which is integrated with the outer ring 410a, to the engaging members (204, 208) via the second differential gear 402, the first differential gear 401, and the transmission shaft 209. Then, a torque (braking force) acting in the opposite direction to the forward rotation direction A1 is transmitted from the engaging members (204, 208) to the second force receiving portion 63c of the drum coupling 63 (Figure 10(a)). In other words, when the outer ring 410a (first rotating body) and the inner ring 410b (second rotating body) rotate relative to each other, at least a portion of the force that the outer ring 410a receives from the inner ring 410b is transmitted as a braking force (second force) to the driven part of the cartridge P by the cartridge-side transmission part 1D2b (unit-side transmission part).

[0129] In this configuration, when the main drive train 1D is connected in a closed loop, a braking force is applied to the drum coupling 63 by the load generated by the torque limiter 410. This restricts the preceding rotation of the drum coupling 63 and suppresses fluctuations in the rotational speed of the drum coupling 63.

[0130] On the other hand, in the state shown in Figure 11(b), the inner ring 410b is maintained at an angular velocity R2 slower than the outer ring 410a, resisting friction with the outer ring 410a. Therefore, the inner ring 410b receives a frictional force in the same direction as the rotation of the outer ring 410a. This frictional force can be considered part of the driving force generated by the motor 301. Furthermore, as shown in Figure 12, this frictional force is transmitted from the differential shaft 406, which is integrated with the inner ring 410b, to the load gear 305 via the third differential gear 404 and the fourth differential gear 405, and then further transmitted from the load gear 305 to the load 306. Also, as shown in Figure 11(b), for example, the meshing surfaces of the teeth of the third differential gear 404 and the teeth of the fourth differential gear 405 switch. In other words, the state changes from one in which the fourth differential gear 405 is pressing against the third differential gear 404 (Figure 11(a)) to one in which the third differential gear 404 is pressing against the fourth differential gear 405 (Figure 11(b)).

[0131] In this configuration, when the main drive train 1D is connected in a closed loop, the driving force corresponding to the load generated by the torque limiter 410 is transmitted from the motor 301 to the load body 306 via the drive transmission path (see Figure 12) through the torque limiter 410.

[0132] In this embodiment, the load for driving the load body 306 is the driving force corresponding to the load generated by the torque limiter 410 when the main drive train 1D is connected in a closed loop, and is greater than the driving force transmitted to the load body 306 via the torque limiter 410. Therefore, the deficit in the driving force required to drive the load body 306 is transmitted to the load body 306 via a path that does not go through the torque limiter 410 from the motor 301 (i.e., the path that goes through the branch gear 302, the second drive gear 304, and the load body gear 305 in Figure 5(a)). Thus, in this embodiment, the load body 306 is driven by the sum of the driving force transmitted via the path that goes through the torque limiter 410 and the driving force transmitted via the path that does not go through the torque limiter 410.

[0133] [Model of the main drive train] The torque transmission flow in the main drive train 1D of this embodiment will be explained using Figures 13(a) to 13(c).

[0134] Fig. 13(a) is a model diagram showing the main body drive train 1D of the present embodiment. Fig. 13(b) is a model diagram showing the main body drive train 1D' according to Reference Example 1. In Reference Example 1 of Fig. 13(b), the inner ring 410b of the torque limiter 410 is not connected to the motor side transmission part 1D2a of the second drive transmission part 1D2, and is fixedly non-rotatably attached to the frame 1Af of the apparatus main body 1A, which is different from the present embodiment. That is, in this reference example, the differential shaft 406 that supports the inner ring 410b is fixed to the frame 1Af, and the third differential gear 404 and the fourth differential gear 405 are omitted. Fig. 13(c) is a model diagram showing the main body drive train 1D″ of Reference Example 2 having a configuration in which the torque limiter 410 is further omitted from Reference Example 1. It is assumed that the other configurations of the main body drive trains 1D' of Reference Examples 1 and 2 and the cartridge P are common to the present embodiment.

[0135] In the description of Figs. 13(a) to (c), the torques (T L , T p , T TL , T IF , etc.) are all compared as values converted to torques on the rotation axis line of the motor 301. Also, in common to Figs. 13(a) to (c), the load required for driving the load body 306 is T L , and the load required for driving the cartridge P is T p .

[0136] First, Reference Example 2 shown in Fig. 13(c) will be described. In Reference Example 2, the load received by the main body side coupling 180 from the drum coupling 63 is defined as the coupling torque T IF ″. In Reference Example 2, since the drum coupling 63 is not connected to the torque limiter 410, the coupling torque T IF ″ is equal to the load T p of the cartridge P. T IF ″ = T p

[0137] In Reference Example 2, for example, T pWhen the force is relatively small, an external force applied to the photosensitive drum 61 causes the photosensitive drum 61 to rotate ahead of the other, making the rotational speed of the photosensitive drum 61 unstable. Also, the total load T applied to the motor 301 in Reference Example 2 M " is the load T of cartridge P p and load T of load body 306 L This will be the sum of the two. T M ″=T p +T L

[0138] Next, in Reference Example 1 shown in Figure 13(b), a torque limiter 410 is provided, so slippage occurs in the torque limiter 410 when the cartridge P is driven. Specifically, while the outer ring 410a of the torque limiter 410 rotates at the same angular velocity R1 as in this embodiment, the angular velocity of the inner ring 410b is 0. Therefore, when the torque limiter 410 is subjected to load T TL This generates load T TL The load T is transmitted from the outer ring 410a via the outer peripheral gear 403, the second differential gear 402, the first differential gear 401, and the transmission shaft 209, similar to this embodiment. Then, the load T is transmitted from the engaging members (204, 208) to the drum coupling 63 of the cartridge P. TL A braking force equivalent to this is applied.

[0139] In Reference Example 1, the main unit coupling 180 is connected to the original load T of cartridge P. p In addition, the drum coupling 63 rotates while receiving the braking force input to it as a load. The main body coupling 180 in Reference Example 1 receives the load from the drum coupling 63 as a coupling torque T IF Let's assume it's '. In the case of Reference Example 1, the coupling torque T IF ' is the load T of cartridge P. p The load T generated by the torque limiter 410 TL It is equal to the sum of [the numbers]. T IF ′=T p +T TL

[0140] As can be seen from the above equation, the load T generated by the torque limiter 410 TL In addition, T p Even if it is small, the coupling torque T acting between the main body coupling 180 and the drum coupling 63 IF The value of ' becomes less likely to fall below 0. In other words, even if an external force is applied to the photosensitive drum 61, the first force-receiving part 63b of the drum coupling 63 becomes less likely to separate from the force-transmission surface 180d of the main body coupling 180. Therefore, in Reference Example 1, the drum coupling 63 is less likely to rotate faster than the main body coupling 180 compared to Reference Example 2, and the photosensitive drum 61 is less likely to rotate ahead of the drum.

[0141] On the other hand, the total load T applied to motor 301 in Reference Example 1 M ' is the load T of cartridge P. p and load T of load body 306 L The load T generated by the torque limiter 410 TL This will be the sum of the two. T M ′=T p +T L +T TL

[0142] As described above, the load T applied to motor 301 in Reference Example 1 M ' represents the load T applied to motor 301 in Reference Example 2. M Larger than (T M ′>T M Therefore, in Reference Example 1, the torque limiter 410 can apply braking force to the drum coupling 63, while the load T generated by the torque limiter 410 TL This also increases the load on motor 301.

[0143] In contrast, in the main drive train 1D of this embodiment shown in Figure 13(a), the inner ring 410b of the torque limiter 410 is connected to the load body 306 via the motor-side transmission unit 1D2a of the second drive transmission unit 1D2.

[0144] Here, the load T required to drive the load body 306 is shown. LOf these, the portion borne by the drive transmission path that does not go through the torque limiter 410 from the motor 301 is T L ′ and the portion borne by the drive transmission path from motor 301 via torque limiter 410 is T TL Let's use '.

[0145] As shown in Figure 11(b), when the main drive train 1D is connected in a closed loop, the angular velocity R1 of the outer ring 410a is faster than the angular velocity R2 of the inner ring 410b, as described above, causing slippage of the torque limiter 410. The load generated by the torque limiter 410 due to the relative rotation of the outer ring 410a and the inner ring 410b is transmitted to the load body 306 as torque (driving force) in the direction that drives the load body 306 via the motor-side transmission unit 1D2a of the second drive transmission unit 1D2. The load T borne by the drive transmission path via the torque limiter 410 is... TL ′ is the load generated by the torque limiter 410 due to the relative rotation of the outer ring 410a and the inner ring 410b. That is, when the outer ring 410a (first rotating body) and the inner ring 410b (second rotating body) rotate relative to each other, at least a portion of the force that the inner ring 410b (second rotating body) receives from the outer ring 410a (first rotating body) is transmitted to the load body via the motor-side transmission unit 1D2a (drive source-side transmission unit). TL ′ can also be described as the driving force transmitted from the motor 301 to the load body 306 via the driven part of the cartridge P and the torque limiter 410.

[0146] The driving force (T) applied from the torque limiter 410 to the load body 306 TL ′) is a load (T) corresponding to the braking force input from the torque limiter 410 to the drum coupling 63 via the cartridge-side transmission unit 1D2b. TL ) may be a value smaller than ). This is because the load (frictional force) on the outer ring 410a and the load (frictional force) on the inner ring 410b on the rotation axis of the torque limiter 410 are of the same magnitude and are torques in opposite directions, TL ' and T TL This is because it is a value converted to torque along the rotation axis of motor 301.

[0147] Here, load T for driving load body 306 L This is the driving force (T) applied from the torque limiter 410 to the load body 306. TL It is larger than '). T TL ′ <T L

[0148] Therefore, the driving force transmitted from the motor 301 to the load body 306 via a drive transmission path that does not go through the torque limiter 410, and the driving force applied from the torque limiter 410 to the load body 306 (T TL The load body 306 is driven by both of the following: L , T TL ′、T L The relationship between ′ is as follows: T L ′=T L -T TL ′

[0149] In this embodiment as well, slippage occurs in the torque limiter 410 when the cartridge P is driven. Specifically, the outer ring 410a of the torque limiter 410 rotates at an angular velocity R1, while the inner ring 410b rotates at a slower angular velocity R2 than the outer ring 410a. Therefore, when the torque limiter 410 is subjected to load T TL This generates load T TL The load T is transmitted from the outer ring 410a via the outer gear 403, the second differential gear 402, the first differential gear 401, and the transmission shaft 209. Then, the engaging members (204, 208) transmit the load T to the drum coupling 63 of the cartridge P. TL A braking force equivalent to this is applied.

[0150] In this embodiment as well, similar to Reference Example 1, the main unit coupling 180 is connected to the original load T of the cartridge P. p In addition, the drum coupling 63 rotates while receiving the braking force input to it as a load. The main body coupling 180 in this embodiment receives the load from the drum coupling 63 and the coupling torque T IF Let's assume the linked torque T IFis the torque acting between the main body side coupling 180 and the drum coupling 63. In the case of the first embodiment, the coupling torque T IF is the load T of the cartridge P p and the load T generated by the torque limiter 410 TL is equal to the sum of. T IF = T p + T TL

[0151] As can be seen from the above equation, also in this embodiment, as in the reference example, the leading rotation of the drum coupling 63 with respect to the main body side coupling 180 is less likely to occur due to the load generated by the torque limiter 410.

[0152] Furthermore, in this embodiment, the total load T applied to the motor 301 M is the load T of the cartridge P p and the load T generated by the torque limiter 410 TL and a part (T L ′) of the load T of the load body L L L L of the load body 306, and the load T L ′) of the load body 306 is the load borne by the drive transmission path that does not pass through the torque limiter 410 from the motor 301 among the loads T L required for driving the load body 306. That is, the load T M applied to the motor 301 during image formation can be expressed as follows. T M = T p + T TL + T L ′

[0153] As described above, since there is a relationship of T L ′ = T L - T TL ′, the above equation can be rewritten as follows. T M = T p + T TL + T L - T TL ′ = Tp +T L +(T TL -T TL ′)

[0154] The above equation and the load T applied to motor 301 in Reference Example 1 M Comparing this with the formula ', the driving force (T) transmitted to the load body 306 via the torque limiter 410 is TL The load T applied to the motor 301 in this embodiment is due to the amount of ') M It can be seen that this is reduced.

[0155] (Advantages of this embodiment) As described above, this embodiment provides an image forming apparatus with a new configuration for driving the exchange unit.

[0156] For example, according to this embodiment, the driving force in the forward rotation direction A1 and the braking force in the opposite direction can be transmitted to the drum coupling 63 of the cartridge P via a closed-loop transmission path. This suppresses the preceding rotation of the drum coupling 63 and the photosensitive drum 61, and allows the cartridge P to be driven at a more stable driving speed. In particular, in this embodiment, the above advantages can be realized by a configuration in which the load generated by the torque limiter 410 (allowance device, differential device) is transmitted to the drum coupling 63 as a braking force in the opposite direction to the forward rotation direction A1.

[0157] Furthermore, according to this embodiment, since the load generated by the torque limiter 410 is used to drive the load body 306, the load on the motor 301 can be reduced. As a result, the lifespan of the motor 301 can be improved, heat generation can be reduced, and energy saving can be improved. In addition, since a small or low-power motor 301 can be used, for example, it is advantageous for miniaturizing the device and reducing costs.

[0158] The improvement in energy saving due to the reduction of the load on the motor 301 can also be explained from the perspective of energy consumption (dissipation) by the torque limiter 410. That is, the load generated by the torque limiter 410 (torque value of the torque limiter 410) is the same in Reference Example 1 and Example 1. However, in Reference Example 1, the entire amount of mechanical work (torque value × R1) done to rotate the outer ring 410a of the torque limiter 410 at angular velocity R1 against the frictional resistance with the inner ring 410b is dissipated as heat. On the other hand, in Example 1, the speed difference (R1-R2) between the outer ring 410a and the inner ring 410b is smaller than in Reference Example 1, so the mechanical work done to rotate the outer ring 410a against the frictional resistance with the inner ring 410b (torque value × (R1-R2)) is smaller than in Reference Example 1. Therefore, even if the load generated by the torque limiter 410 is the same, in Example 1, the amount of mechanical energy consumed (dissipated) as heat by the torque limiter 410 is less than in Reference Example 1. As a result, the energy efficiency (ratio of mechanical work to power consumption of motor 301) when viewed as the entire main drive train 1D can be improved, and energy saving is enhanced.

[0159] Furthermore, in this embodiment, since the speed difference between the outer ring 410a and the inner ring 410b of the torque limiter 410 is smaller compared to Reference Example 1, wear of the torque limiter 410 can be reduced, and the lifespan of the torque limiter 410 can be extended.

[0160] (modified version) In this embodiment, a configuration in which the load body 306 is connected to a part of the main drive train 1D (the motor-side transmission part 1D2a of the second drive transmission part 1D2) has been described. However, the main drive train 1D does not necessarily have to be connected to load bodies other than the cartridge P. Also, other load bodies other than the load body 306 may be connected to other parts of the main drive train 1D (for example, the first drive transmission part 1D1).

[0161] Furthermore, the direction of force transmission in the first drive transmission unit 1D1 and the second drive transmission unit 1D2 can be changed according to the specific configuration of the printer 1 (see also Examples 2 and 3).

[0162] Furthermore, although this embodiment uses a configuration without a cleaning means that contacts the photosensitive drum 61, a cleaning means may be provided on the cartridge P. The cleaning means is, for example, a blade member that slides against the photosensitive drum 61. If the load that the cleaning means places on the photosensitive drum 61 is relatively small, there is a possibility that the drum coupling 63 will rotate prematurely. With a configuration in this embodiment in which a braking force is applied to the drum coupling 63 by the load generated by the torque limiter 410, it is possible to prevent the drum coupling 63 from rotating prematurely even when the load that the cleaning means places on the photosensitive drum 61 is relatively small.

[0163] Furthermore, although the branch gear 302 is given as an example of an output section in this embodiment, the output section only needs to be configured to form part of a closed-loop transmission path and to output the driving force of the drive source. For example, when the first drive gear 303 and the second drive gear 304 of this embodiment are engaged with a pinion gear on the output shaft of the motor 301, this pinion gear functions as an output section.

[0164] Furthermore, in this embodiment, the load T of the load body 306 L This is the load T generated by the torque limiter 410. TL Although it was explained as being larger than, the relative magnitudes of the two can be reversed. That is, the load T of load body 306 L This is the load T generated by the torque limiter 410. TL Below (T L ≦T TL ) is also acceptable.

[0165] Example 2 Another embodiment of the present disclosure (Example 2) will be described using Figures 14(a) to 17(d). Hereinafter, elements with the same reference numerals as in Example 1 will have basically the same configuration and function as those described in Example 1 unless otherwise specified, and the differences from Example 1 will be described primarily.

[0166] In Example 1, an example was described in which the driving force is transmitted in the following order from the coupling gear 201 to the main body coupling 180, the drum coupling 63, and the first differential gear 401 (Figure 12). In this example, an example is described in which the driving force is transmitted in the following order from the first differential gear 401, the drum coupling 63, the main body coupling 180, and the coupling gear 201 (Figure 15).

[0167] In accordance with the transmission of driving force in the direction described above, the drive transmission unit 200 and drum coupling 63 in this embodiment have a mirror-symmetric configuration with respect to the drive transmission unit 200 and drum coupling 63 of Embodiment 1. That is, the shape of the drive transmission unit 200 in this embodiment when viewed in the direction of axis M1 may be the same as the shape of the drive transmission unit 200 in Embodiment 1 when viewed in the direction of axis M1, inverted with respect to a line passing through axis M1. Similarly, the shape of the drum coupling 63 in this embodiment when viewed in the direction of axis M1 may be the same as the shape of the drum coupling 63 in Embodiment 1 when viewed in the direction of axis M1, inverted with respect to a line passing through axis M1.

[0168] Specifically, the positional relationship between the force transmission surface 180d of the main body coupling 180, the coupling engagement portion 208b of the second engaging member 208, and the first force receiving portion 63b and the second force receiving portion 63c of the drum coupling 63 in this embodiment is as shown in Figure 10(b). The rotation direction of the drum coupling 63 during image formation is defined as the forward rotation direction A1. In this case, in Embodiment 1 (Figure 10(a)), the force transmission surface 180d, the first force receiving portion 63b, the second force receiving portion 63c, and the coupling engagement portion 208b are arranged in this order from upstream to downstream in the forward rotation direction A1. In contrast, in this embodiment (Figure 10(b)), the coupling engagement portion 208b, the second force receiving portion 63c, the first force receiving portion 63b, and the force transmission surface 180d are arranged in this order from upstream to downstream in the forward rotation direction A1.

[0169] [Operation of the main drive train] The operation of the main drive train 1D and the torque transmission flow according to Embodiment 2 will be explained using Figures 14(a) and 14(b). Figure 14(a) is a schematic diagram showing the main drive train 1D in a state where the drive force transmission path is not connected in a closed loop. Figure 14(b) is a diagram showing the main drive train 1D in a state where it is connected in a closed loop. Figure 15 is a diagram showing the torque transmission flow in a cross-sectional unfolded view of the main drive train 1D in a state where it is connected in a closed loop.

[0170] As shown in Figure 14(a), if there is a gap G between the tooth surfaces 402b and 403b of the second differential gear 402 and the outer gear 403, the main drive train 1D in this embodiment is not connected in a closed loop. When there is a gap G, torque is not transmitted from the outer gear 403 to the second differential gear 402. The state shown in Figure 14(a) appears, for example, immediately after the motor 301 is started.

[0171] In the state shown in Figure 14(a), the driving force is transmitted from the motor 301 to the branch gear 302, the first drive gear 303, the coupling gear 201, and the main body coupling 180 in that order, causing the main body coupling 180 to rotate in the forward direction A1. The forward direction A1 is the direction in which the force transmission surface 180d of the main body coupling 180 moves away from the first force receiving portion 63b of the drum coupling 63 (see Figure 10(b)). Furthermore, as will be explained below, in the state shown in Figure 14(a), no torque is transmitted from the torque limiter 410 to the drum coupling 63. Therefore, in the state shown in Figure 14(a), immediately after the motor 301 is started, the drum coupling 63 remains in place without rotating in the forward direction A1.

[0172] On the other hand, in the state shown in Figure 14(a), driving force is transmitted from the motor 301 to the branch gear 302, the second drive gear 304, the load gear 305, the fourth differential gear 405, the third differential gear 404, and the differential shaft 406, causing the differential shaft 406 to rotate at an angular velocity R4. In the state shown in Figure 14(a), the outer circumferential gear 403 is not subjected to a load from the second differential gear 402, so the torque limiter 410 does not slip, and the outer circumferential gear 403 and the differential shaft 406 rotate together at an angular velocity R4. The angular velocity R4 is determined by the angular velocity of the output shaft of the motor 301 and the speed transmission ratio of the transmission path from the motor 301 to the differential shaft 406. This speed transmission ratio is the ratio of the rotation angle of the differential shaft 406 to the rotation angle of the output shaft of the motor 301 when the differential shaft 406 is rotated by the motor 301.

[0173] Let V4 be the peripheral speed of the outer gear 403 when it rotates at the same angular velocity R4 as the differential shaft 406. Peripheral speed V4 is the speed at which the teeth of the outer gear 403 move along the pitch circle of the outer gear 403. Peripheral speed V4 is expressed as the product of the angular velocity R4 and the pitch circle radius of the outer gear 403.

[0174] In the state shown in Figure 14(a), the outer gear 403 rotates at a peripheral speed V4, while the second differential gear 402 remains stationary due to the presence of a gap G. The first differential gear 401, the transmission shaft 209, and the engaging members (204, 208) also remain stationary. Therefore, no torque in the forward rotation direction A1 is transmitted from the engaging members (204, 208) to the drum coupling 63. Consequently, the drum coupling 63 remains stationary without rotating in the forward rotation direction A1.

[0175] After a very short time has elapsed in the state shown in Figure 14(a), the tooth surface 403b of the outer gear 403 comes into contact with the tooth surface 402b of the second differential gear 402, as shown in Figure 14(b), and the second differential gear 402 begins to rotate at a peripheral speed V4. When the tooth surfaces 402b and 403b are in contact, it can be said that the main drive train 1D of this embodiment is connected in a closed loop, as shown in Figure 16.

[0176] As the second differential gear 402 rotates, the first differential gear 401, the transmission shaft 209, and the engaging members (204, 208) also begin to rotate. Then, torque (driving force) in the forward rotation direction A1 is transmitted from the engaging members (204, 208) to the drum coupling 63.

[0177] Here, the angular velocity of the engaging members (204, 208) corresponding to the peripheral speed V4 of the second differential gear 402 is faster than the angular velocity of the main body coupling 180 and the drum coupling 63 in the state shown in Figure 14(a). However, the main body coupling 180 is connected to the first drive gear 303 via the coupling gear 201, and the angular velocity of the first drive gear 303 is restricted by its meshing with the branch gear 302. Even when the branch gear 302 is pressed against the first drive gear 303 as the second differential gear 402 starts rotating at peripheral speed V4, the angular velocity of the branch gear 302 does not change. This is because the force with which the first drive gear 303 presses against the branch gear 302 is a portion of the force that the branch gear 302 outputs to the second drive gear 304, which returns to the branch gear 302 through a closed-loop transmission path. In other words, a portion of the force with which the branch gear 302 presses against the second drive gear 304 against the load in the transmission path from the second drive gear 304 onward (including the first drive gear 303) is returned from the first drive gear 303 to the branch gear 302. Therefore, the force with which the first drive gear 303 presses against the branch gear 302 never exceeds the load required to rotate the second drive gear 304, and the angular velocity of the branch gear 302 never increases.

[0178] Therefore, after the second differential gear 402 starts rotating, it temporarily rotates at the same peripheral speed V4 as the outer gear 403, and then is reduced to a peripheral speed V3 which is slower than peripheral speed V4 (V4 > V3). Peripheral speed V3 is the peripheral speed of the second differential gear 402 when the drum coupling 63 and the engaging members (204, 208) rotate at the same angular velocity as the main body coupling 180.

[0179] As shown in Figure 14(b), the reduction of the second differential gear 402 also reduces the outer circumferential gear 403 from peripheral speed V4 to peripheral speed V3. Meanwhile, the differential shaft 406 continues to rotate at the same angular velocity R4 as in Figure 14(a). The angular velocity R3 of the outer circumferential gear 403, which corresponds to peripheral speed V3, is slower than the angular velocity R4 of the differential shaft 406 (R4 > R3). In other words, the angular velocity R3 of the outer ring 410a of the torque limiter 410, which rotates integrally with the outer circumferential gear 403, is slower than the angular velocity R4 of the inner ring 410b of the torque limiter 410, which rotates integrally with the differential shaft 406.

[0180] Thus, when the main drive train 1D is connected in a closed loop, different angular velocities R3 and R4 are input to the outer ring 410a and inner ring 410b of the torque limiter 410, causing slippage of the torque limiter 410 (relative rotation of the outer ring 410a and inner ring 410b). In other words, in this embodiment as well, the torque limiter 410, acting as a tolerance device or differential device, tolerates the input of different angular velocities R3 and R4 to the outer ring 410a (first rotating body) and the inner ring 410b (second rotating body), and absorbs the difference in angular velocity.

[0181] In other words, the first drive transmission unit 1D1 and the second drive transmission unit 1D2 are configured such that there is a difference in the angular velocities R3 and R4 of the outer ring 410a (first rotating body) and the inner ring 410b (second rotating body) when the driven part of the cartridge P is driven by the motor 301. In this embodiment, the angular velocity R3 (first angular velocity) of the outer ring 410a (first rotating body) is slower than the angular velocity R4 (second angular velocity) of the inner ring 410b (second rotating body) when the driven part of the cartridge P is driven by the motor 301.

[0182] Furthermore, in the states shown in Figures 14(b) and 15, the drum coupling 63 receives a force (driving force, third force) in the forward rotation direction A1 from the engaging members (204, 208), while receiving a force (braking force, fourth force) in the opposite direction to the forward rotation direction A1 from the main body coupling 180. In other words, the force (braking force, fourth force) received by the first force receiving part 63b from the first drive transmission part 1D1 of the main body drive train 1D during image formation acts on the drum coupling 63 in the opposite direction to the forward rotation direction A1 (second rotation direction). The force (driving force, third force) received by the second force receiving part 63c from the second drive transmission part 1D2 of the main body drive train 1D acts on the drum coupling 63 in the forward rotation direction A1 (first rotation direction). In other words, the cartridge P (replacement unit) of this embodiment has a second force receiving part 63c (third surface) that receives a driving force (third force) from the second drive transmission part 1D2, and a first force receiving part 63b (fourth surface) that receives a braking force (fourth force) from the first drive transmission part 1D1.

[0183] Therefore, similar to Example 1, the preceding rotation of the drum coupling 63 can be restricted, and the cartridge P can be driven at a stable drive speed.

[0184] Incidentally, in the states shown in Figures 14(b) and 15, the drum coupling 63 rotates while pressing the main body coupling 180, which is rate-limited by the rotation of the branch gear 302, in the forward rotation direction A1. In other words, a portion of the force (driving force) that the engaging members (204, 208) exert on the drum coupling 63 in the forward rotation direction A1 is transmitted from the drum coupling 63 to the main body coupling 180. The magnitude of this force corresponds to the load generated by the torque limiter 410 minus the load required to drive the cartridge P.

[0185] Furthermore, in the states shown in Figures 14(b) and 15, the force transmitted from the drum coupling 63 to the main body coupling 180 is further transmitted from the main body coupling 180 to the branch gear 302 via the coupling gear 201 and the first drive gear 303. In other words, a portion of the braking force (third force) applied from the second drive transmission unit 1D2 to the driven part of the cartridge P is transmitted from the driven part to the branch gear 302 (output part) via the first drive transmission unit 1D1.

[0186] The direction of the force (torque) transmitted from the driven part of cartridge P to the branch gear 302 (output part) via the first drive transmission part 1D1 is the same as the direction of rotation of the branch gear 302 when the driven part of cartridge P is driven by the driving force of motor 301 (drive source). In other words, the force transmitted from the driven part of cartridge P to the branch gear 302 (output part) via the first drive transmission part 1D1 can assist the rotation of the branch gear 302 (output part).

[0187] [Model of the main drive train] The torque transmission flow in the main drive train 1D of Embodiment 2 will be explained using Figure 16. Figure 16 is a model diagram showing the main drive train 1D of this embodiment. All torques used in the explanation of Figure 16 will be compared as values ​​converted to the torque applied to the output shaft of the motor 301.

[0188] As shown in Figure 16, the torque transmitted from the motor 301 to the inner ring 410b of the torque limiter 410 via the motor-side transmission part 1D2a of the second drive transmission part 1D2 is T TL2 The torque transmitted from the outer ring 410a of the torque limiter 410 to the drum coupling 63 of the cartridge P via the cartridge-side transmission part 1D2b of the second drive transmission part 1D2 is T TL2 Let's use '.

[0189] As mentioned above, the angular velocity R3 of the outer ring 410a during image formation is slower than the angular velocity R4 of the inner ring 410b (R4 > R3), so slippage (relative rotation) occurs between the outer ring 410a and the inner ring 410b during image formation. Torque T TL2This corresponds to the torque required to rotate the inner ring 410b relative to the outer ring 410a, overcoming the friction between the outer ring 410a and the inner ring 410b. TL2 ′ corresponds to the torque applied to the outer ring 410a by friction between the outer ring 410a and the inner ring 410b. In this embodiment, when comparing the torque values ​​along the rotation axis of the motor 301, T TL2 ′ <T TL2 They are in a relationship.

[0190] In this embodiment, as in Embodiment 1, the drum coupling 63 receives torque (driving force, first force) in the forward rotation direction A1 from the main drive train 1D, and also receives torque (braking force, second force) in the opposite direction to the forward rotation direction A1 from the main drive train 1D. However, unlike Embodiment 1, the drum coupling 63 receives driving force from the engaging members (204, 208) of the second drive transmission unit 1D2 and braking force from the main body side coupling 180 of the first drive transmission unit 1D1 (see also Figure 10(b)).

[0191] The force that the main body coupling 180 receives from the drum coupling 63 in this embodiment is the coupling torque T. IF2 Let's assume that the load required to drive cartridge P is T. p As described above, the drum coupling 63 receives the torque T from the torque limiter 410 via the cartridge-side transmission unit 1D2b of the second drive transmission unit 1D2. TL2 ', therefore, the load T of cartridge P p It rotates in the forward direction A1 against resistance. The torque that the main body coupling 180 receives when the drum coupling 63 presses the main body coupling 180 in the forward direction A1 is equal to the torque T input to the drum coupling 63. TL2 ' Load T from cartridge P p It is equal to the result of subtracting [a certain value]. That is, the coupling torque T in this embodiment. IF2 The magnitude can be expressed by the following formula: T IF2 =T TL2 '-T p

[0192] From the above equation, the torque T transmitted from the torque limiter 410 to the drum coupling 63 is TL2 If ' is large, the load T of cartridge P p Even if it temporarily increases, the coupling torque T IF2 It can be seen that it does not fall below zero. For example, in the normal image forming operation of printer 1, load T p Assuming a range in which T fluctuates, p The linked torque T against the assumed upper limit IF2 The torque value of the torque limiter 410 is set so that the load T of cartridge P does not become a negative value. p Even if the vibration temporarily increases, the rotation of the drum coupling 63 can be made to lag behind the rotation of the main body coupling 180, thereby suppressing fluctuations in the rotation speed of the drum coupling 63.

[0193] Furthermore, according to the above equation, the load T of cartridge P p If it temporarily decreases, the coupling torque T IF2 As the size increases, it can be seen that the drum coupling 63 and the main body coupling 180 become less likely to separate. This will be explained later using Figures 17(a) to (d).

[0194] In this embodiment, the coupling torque T is input from the drum coupling 63 to the main body coupling 180. IF2 The current is returned to the branch gear 302 via the first drive transmission unit 1D1. The coupling torque T is applied to the branch gear 302. IF2 The direction in which it acts (the direction of rotation around the rotation axis of the branch gear 302) is the same as the direction of rotation of the branch gear 302 during image formation. Therefore, the coupling torque T returned to the branch gear 302 is the same. IF2 This assists the rotation of the branching gear 302 during image formation.

[0195] Specifically, the load required to drive the load body 306 is T L Let's assume that the total load on the motor 301 during image formation is T. M2 Let's assume that motor 301 controls load T LThe load body 306 is driven against this, and the torque T corresponds to the sliding resistance of the torque limiter 410. TL2 This causes the outer ring 410a of the torque limiter 410 to rotate against the force. Meanwhile, the coupling torque T is returned to the branch gear 302 via the first drive transmission unit 1D1. IF2 This is used to rotate the load body 306 and the outer ring 410a of the torque limiter 410. In other words, in this embodiment, the load T applied to the motor 301 during image formation M This can be expressed as follows: T M2 =T L +T TL2 -T IF2 =T L +T TL2 -(T TL2 '-T p ) =T p +T L +(T TL2 -T TL2 ′)

[0196] As described in Reference Example 1 of Example 1 (Figure 13(b)), in a configuration in which the inner ring 410b of the torque limiter 410 is fixed, the load T applied to the motor 301 during image formation M2 ' is the T of cartridge P p and load T of load body 306 L and torque T, which corresponds to the sliding resistance of the torque limiter 410. TL2 The sum is equal to (T M2 ′=T p +T L +T TL2 ).

[0197] T M2 and T M2 Comparing the two, according to this embodiment, the torque T transmitted from the torque limiter 410 to the drum coupling 63 via the cartridge-side transmission unit 1D2b of the second drive transmission unit 1D2 is TL2 This shows that the load on motor 301 can be reduced by the amount of '.

[0198] [Suppression of the photosensitive drum's pre-rotation] Using Figures 17(a) to (d), the behavior of the main drive train 1D when an external force in the forward rotation direction A1 is applied to the photosensitive drum 61 in this embodiment will be explained in comparison with the aforementioned Reference Example 2 (Figure 13(c)). Figures 17(a) to (d) show the photosensitive drum 61, belt 41, and a part of the main drive train 1D (coupling gear 201 and pre-stage gear 190) as viewed in the direction of the rotation axis of the photosensitive drum 61. Figure 17(a) shows the drive transmission during normal image formation in this embodiment. Figure 17(b) shows the case in this embodiment where the force in the forward rotation direction A1 transmitted from belt 41 to photosensitive drum 61 becomes stronger. Figure 17(c) shows the drive transmission during normal image formation in Reference Example 2. Figure 17(d) shows the case in Reference Example 2 where the force in the forward rotation direction A1 transmitted from belt 41 to photosensitive drum 61 becomes stronger.

[0199] As shown in Figure 17(a), the gear that is part of the first drive transmission unit 1D1 and meshes with the coupling gear 201 is designated as the pre-stage gear 190. In this embodiment, the drum coupling 63 receives a force (driving force) in the forward rotation direction A1 from the engaging members (204, 208), while receiving a force (braking force) in the opposite direction to the forward rotation direction A1 from the main body coupling 180. Therefore, during normal image formation, the main body coupling 180 is pressed by the drum coupling 63 in the forward rotation direction A1 and rotates. In addition, the coupling gear 201, which rotates integrally with the main body coupling 180, rotates in the forward rotation direction A1 while pressing the pre-stage gear 190.

[0200] In other words, in this embodiment, during normal image formation, the downstream tooth surface 201a of the coupling gear 201 in the forward rotation direction A1 comes into contact with the tooth surface 190a of the corresponding preceding gear 190. That is, when the driven part of the cartridge P is driven by the motor 301 (drive source), the tooth surface 201a (first tooth surface) of the coupling gear 201 (first gear) and the tooth surface 190a (second tooth surface) of the preceding gear 190 (second gear) come into contact.

[0201] On the one hand, in Reference Example 2 shown in FIG. 17(c), the drum coupling 63 receives a force (driving force) in the forward rotation direction A1 from the main body side coupling 180. Therefore, during normal image formation, the coupling gear 201 rotates in the forward rotation direction A1 by being pressed against the front stage gear 190. Further, the main body side coupling 180 that rotates integrally with the coupling gear 201 rotates in the forward rotation direction A1 while pressing the drum coupling 63.

[0202] That is, in the case of Reference Example 2, during normal image formation, the tooth surface 201b on the upstream side in the forward rotation direction A1 of the teeth of the coupling gear 201 abuts against the tooth surface 190b of the teeth of the corresponding front stage gear 190.

[0203] Here, in the present embodiment and Reference Example 2, it is assumed that the peripheral speed of the belt 41 during image formation is set to be higher than the peripheral speed of the photosensitive drum 61. Therefore, the photosensitive drum 61 receives a leading rotation force Fb which is a force in the forward rotation direction A1 from the belt 41.

[0204] In Reference Example 2, the main body side coupling 180 receives a force including the rotational load of the photosensitive drum 61 and the leading rotation force Fb from the drum coupling 63. When the leading rotation force Fb is smaller than the rotational load of the photosensitive drum 61, the photosensitive drum 61 rotates at a stable speed without the photosensitive drum 61 and the drum coupling 63 rotating at an angular velocity higher than that of the main body side coupling 180.

[0205] However, the magnitude of the leading rotation force Fb may vary due to, for example, the impact when the leading edge of the sheet contacts the belt 41 or the trailing edge of the sheet detaches from the belt 41. When the leading rotation force Fb temporarily becomes larger than the rotational load of the photosensitive drum 61, the photosensitive drum 61 and the drum coupling 63 rotate (lead rotation) at an angular velocity higher than that of the main body side coupling 180. Then, as shown in FIG. 17(d), the meshing surfaces of the coupling gear 201 and the front stage gear 190 are switched from the tooth surfaces 190b and 201b to the tooth surfaces 190a and 201a.

[0206] Then, when transitioning from the state in Figure 17(c) to the state in Figure 17(d), a state occurs in which neither of the tooth surfaces 201a, 201a of the coupling gear 201 is in contact with the tooth surfaces 190a, 190b of the preceding gear 190. In other words, in Reference Example 2, depending on the magnitude of the external force (Fb) in the forward rotation direction A1 applied to the photosensitive drum 61, the connection between the preceding gear 190 and the coupling gear 201 may be temporarily interrupted, causing the rotation of the photosensitive drum 61 to become unstable.

[0207] Furthermore, according to Reference Example 1 (Figure 13(b)), the drum coupling 63 receives a force (braking force) from the engaging members (204, 208) in the opposite direction to the forward rotation direction A1. Therefore, compared to Reference Example 2, it is less likely for the drum coupling 63 to rotate ahead of the drum coupling. However, even in Reference Example 1, if the leading rotational force Fb applied to the photosensitive drum 61 exceeds the sum of the rotational load of the photosensitive drum 61 and the braking force from the engaging members (204, 208), the drum coupling 63 may rotate ahead of the drum coupling.

[0208] In contrast, according to the configuration of this embodiment shown in Figure 17(a), even during normal image formation, the downstream tooth surface 201a of the teeth of the coupling gear 201 in the forward rotation direction A1 is in contact with the tooth surface 190a of the teeth of the preceding gear 190. Therefore, even if the preceding rotational force Fb applied to the photosensitive drum 61 temporarily increases, only the force acting between the tooth surfaces 190a and 201a increases, and the meshing surfaces do not switch from tooth surfaces 190a and 201a to tooth surfaces 190b and 201b. Rather, the aforementioned equation (T IF2 =T TL2 '-T p As can be seen from the above, the load T of cartridge P is due to the preceding rotational force Fb. p When it decreases, the coupling torque (T) acting between the main body coupling 180 and the drum coupling 63 decreases. IF2 ) will become larger.

[0209] In other words, suppose an external force is applied that attempts to rotate the drum coupling 63 (rotating member) in the forward direction A1 (first rotation direction) faster than the driving speed of the motor 301 (drive source). In this case, the first drive transmission unit 1D1 is configured such that contact is maintained between the tooth surface 201a (first tooth surface) of the teeth of the coupling gear 201 (first gear) and the tooth surface 190a (second tooth surface) of the teeth of the preceding gear 190 (second gear). Also in this case, the first drive transmission unit 1D1 is configured to withstand the force (T) acting between the fourth surface (first force receiving part 63b) of the cartridge P and the first drive transmission unit 1D1. IF2 ) is configured to become stronger in response to external forces.

[0210] Therefore, according to the configuration of this embodiment, even if the preceding rotational force Fb applied to the photosensitive drum 61 temporarily increases, the preceding rotation of the photosensitive drum 61 and the drum coupling 63 is suppressed, and the rotational speed of the photosensitive drum 61 can be made more stable.

[0211] In this explanation, the peripheral speed of the belt 41 during image formation is set to be faster than the peripheral speed of the photosensitive drum 61. However, the photosensitive drum 61 may also be subjected to an external force in the forward rotation direction A1 due to other causes. For example, in a direct transfer method in which the toner image is transferred directly from the photosensitive drum 61 to the sheet S without going through the belt 41 (intermediate transfer body), the photosensitive drum 61 may receive a leading rotational force Fb from the sheet S. Even in such cases, the configuration of this embodiment can suppress the leading rotation of the photosensitive drum 61 and the drum coupling 63, and make the rotational speed of the photosensitive drum 61 more stable.

[0212] (Advantages of this embodiment) As described above, this embodiment provides an image forming apparatus with a new configuration for driving the exchange unit.

[0213] For example, according to this embodiment, a driving force in the forward rotation direction A1 and a braking force in the opposite direction can be transmitted to the drum coupling 63 of the cartridge P via a closed-loop transmission path. This suppresses the preceding rotation of the drum coupling 63 and the photosensitive drum 61, allowing the cartridge P to be driven at a more stable speed. In particular, in this embodiment, the above advantages can be realized by a configuration in which the load generated by the torque limiter 410 (allowing device, differential device) is transmitted to the drum coupling 63 as a force (driving force) in the forward rotation direction A1.

[0214] Furthermore, according to this embodiment, a portion of the load generated by the torque limiter 410 is returned to the branch gear 302 (output section) via a closed-loop transmission path, thereby reducing the load on the motor 301. As a result, the lifespan of the motor 301 can be improved, heat generation can be reduced, and energy efficiency can be improved. In addition, since a small or low-power motor 301 can be used, for example, it is advantageous for miniaturizing the device and reducing costs.

[0215] Furthermore, according to this embodiment, as explained using Figures 17(a) to (d), even if the preceding rotational force Fb applied to the photosensitive drum 61 suddenly increases, fluctuations in the rotational speed of the photosensitive drum 61 can be suppressed.

[0216] Example 3 Another embodiment of this disclosure (Example 3) will be described with reference to Figures 18(a) to 20. Hereinafter, elements with the same reference numerals as in Example 1 will have basically the same configuration and function as those described in Example 1 unless otherwise specified, and the differences from Example 1 will be described primarily.

[0217] [Operation of the main drive train] The operation of the main drive train 1D and the torque transmission flow will be explained using Figures 18(a)(b) and 19. Figure 18(a) is a schematic diagram showing the main drive train 1D when the drive force transmission path is not connected in a closed loop. Figure 18(b) is a diagram showing the main drive train 1D when it is connected in a closed loop. Figure 19 is a diagram showing the torque transmission flow in a cross-sectional unfolded view of the main drive train 1D when it is connected in a closed loop.

[0218] The configuration of the main drive train 1D in this embodiment differs from that of the main drive train 1D in Embodiment 1 in that the speed settings of the second differential gear 402 and the outer peripheral gear 403, which will be described below, are different. In this embodiment, the coupling engagement portions 204b and 208b of the engaging members (204 and 208) are configured to be able to press the drum coupling 63 in the forward rotation direction A1. In this embodiment, the coupling engagement portion 208b is configured to be able to press the projection 63p (Figure 4) of the drum coupling 63 from the upstream side in the forward rotation direction A1. The other configurations of the main drive train 1D in this embodiment may be the same as in Embodiment 1.

[0219] As shown in Figure 18(a), if there is a gap G between the tooth surfaces 402b and 403b of the second differential gear 402 and the outer gear 403, the main drive train 1D in this embodiment is not connected in a closed loop. When there is a gap G, torque is not transmitted from the second differential gear 402 to the outer gear 403. The state shown in Figure 18(a) appears, for example, immediately after the motor 301 is started.

[0220] In the state shown in Figure 18(a), the driving force is transmitted from the motor 301 to the branch gear 302, the first drive gear 303, the coupling gear 201, the main body coupling 180, and the drum coupling 63 in that order. Furthermore, the driving force is transmitted from the drum coupling 63 to the engaging members (204, 208), the transmission shaft 209, the first differential gear 401, and the second differential gear 402 in that order. As a result, the second differential gear 402 rotates at a peripheral speed V5. Peripheral speed V5 is the speed at which the teeth of the second differential gear 402 move along the pitch circle of the second differential gear 402. Also, peripheral speed V5 is determined by the angular velocity of the output shaft of the motor 301, the speed transmission ratio of the transmission path from the motor 301 to the second differential gear 402, and the pitch circle radius of the second differential gear 402. This speed transmission ratio is the ratio of the rotation angle of the second differential gear 402 to the rotation angle of the motor 301 when the second differential gear 402 is being rotated by the motor 301.

[0221] On the other hand, in the state shown in Figure 18(a), the driving force is transmitted from the motor 301 to the branch gear 302, the second drive gear 304, the load gear 305, the fourth differential gear 405, the third differential gear 404, the differential shaft 406, the torque limiter 410, and the outer gear 403 in that order. Also, in the state shown in Figure 11(a), since the outer gear 403 is not subjected to a load from the second differential gear 402, the torque limiter 410 does not slip, and the outer gear 403 and the differential shaft 406 rotate together at an angular velocity R6. The angular velocity R6 is determined by the angular velocity of the output shaft of the motor 301 and the speed transmission ratio of the transmission path from the motor 301 to the differential shaft 406. This speed transmission ratio is the ratio of the rotation angle of the differential shaft 406 to the rotation angle of the output shaft of the motor 301 when the differential shaft 406 is rotated by the motor 301.

[0222] Let V6 be the peripheral speed of the outer gear 403 when it rotates at the same angular velocity R6 as the differential shaft 406. Peripheral speed V6 is the speed at which the teeth of the outer gear 403 move along the pitch circle of the outer gear 403. Peripheral speed V6 is expressed as the product of the angular velocity R6 and the pitch circle radius of the outer gear 403.

[0223] Here, the circumferential speed V5 of the second differential gear 402 in the state of FIG. 18(a) is slower than the circumferential speed V6 of the outer peripheral gear 403 (V5 < V6). That is, unlike in the first embodiment, the moving speed of the teeth of the outer peripheral gear 403 is faster than the moving speed of the teeth of the second differential gear 402. Therefore, after the state of FIG. 18(a) is reached immediately after the motor 301 is started, the teeth of the second differential gear 402 are chased by the teeth of the outer peripheral gear 403, so that the tooth surfaces 402b and 403b come into contact.

[0224] As a result, as shown in FIG. 18(b), the tooth surfaces 402b and 403b of the second differential gear 402 and the outer peripheral gear 403 come into contact. Due to the contact of the tooth surfaces 402b and 403b, torque transmission is performed between the second differential gear 402 and the outer peripheral gear 403. Therefore, when the tooth surfaces 402b and 403b are in contact, it can be said that the main body drive train 1D of this embodiment is in a state of being connected in a closed loop as shown in FIG. 20.

[0225] In the above description, it has been described that the second differential gear 402 rotates at the circumferential speed V5 in the state of FIG. 18(a), but it may also be configured that the second differential gear 402 remains stationary without rotating in the state of FIG. 18(a). That is, in the state of FIG. 18(a), the torque in the forward rotation direction A1 is not transmitted from the drum coupling 63 to the engaging members (204, 208), and the engaging members (204, 208), the transmission shaft 209, the first differential gear 401, and the second differential gear 402 may be stopped. Even in this case, since the circumferential speed V5 (= 0) of the second differential gear 402 in the state of FIG. 18(a) is slower than the circumferential speed V6 of the outer peripheral gear 403, the tooth surfaces 402b and 403b come into contact because the teeth of the second differential gear 402 are chased by the teeth of the outer peripheral gear 403.

[0226] As shown in Fig. 18(b), when the teeth of the outer peripheral gear 403 catch up with the teeth of the second differential gear 402, the outer peripheral gear 403 rotates at the same circumferential speed V5 as the second differential gear 402 due to the reaction force received by the tooth surface 403b of the outer peripheral gear 403 from the tooth surface 402b of the second differential gear 402. On the other hand, the differential shaft 406 continues to rotate at an angular velocity R6. The angular velocity R5 of the outer peripheral gear 403 corresponding to the circumferential speed V5 is slower than the angular velocity R6 of the differential shaft 406 (R5 < R6). That is, the angular velocity R5 of the outer ring 410a that rotates integrally with the outer peripheral gear 403 becomes slower than the angular velocity R6 of the inner ring 410b that rotates integrally with the differential shaft 406.

[0227] Thus, in the state where the main body drive train 1D is connected in a closed loop, different angular velocities R5 and R6 are input to the outer ring 410a and the inner ring 410b of the torque limiter 410, and slippage (relative rotation between the outer ring 410a and the inner ring 410b) of the torque limiter 410 occurs. The torque limiter 410 allows different angular velocities R5 and R6 to be input to the outer ring 410a and the inner ring 410b and absorbs the difference in angular velocity.

[0228] In the state of Fig. 18(b), as shown in Fig. 19, the torque corresponding to the load generated by the torque limiter 410 is transmitted from the outer peripheral gear 403 to the second differential gear 402, the first differential gear 401, the transmission shaft 209, and the engagement members (204, 208) in sequence. Then, the torque corresponding to the load generated by the torque limiter 410 is transmitted from the engagement members (204, 208) to the drum coupling 63.

[0229] The torque corresponding to the load generated by the torque limiter 410 transmitted from the engagement members (204, 208) to the drum coupling 63 is smaller than the load for driving the cartridge P. Therefore, the insufficient torque for driving the cartridge P is supplied from the main body side coupling 180 to the drum coupling 63. That is, the cartridge P receives a force (driving force) acting in the forward rotation direction A1 on the drum coupling 63 from both the main body side coupling 180 of the first drive transmission unit 1D1 and the engagement members (204, 208) of the second drive transmission unit 1D2.

[0230] [Model of the main body drive train] Using FIG. 20, the torque transmission flow in the main body drive train 1D of Example 3 will be described. FIG. 20 is a model diagram showing the main body drive train 1D of this example. All the torques used in the description of FIG. 20 are to be compared as values converted to the torque applied to the output shaft of the motor 301.

[0231] As shown in FIG. 20, let the torque transmitted from the motor 301 through the motor-side transmission part 1D2a of the second drive transmission part 1D2 to the inner ring 410b of the torque limiter 410 be T TL3 Let the torque transmitted from the outer ring 410a of the torque limiter 410 through the cartridge-side transmission part 1D2b of the second drive transmission part 1D2 to the drum coupling 63 of the cartridge P be T TL3 '.

[0232] As described above, since the angular velocity R5 of the outer ring 410a during image formation is slower than the angular velocity R6 of the inner ring 410b (R5 < R6), slippage (relative rotation) between the outer ring 410a and the inner ring 410b occurs during image formation. Torque T TL3 corresponds to the torque required to relatively rotate the inner ring 410b with respect to the outer ring 410a against the friction between the outer ring 410a and the inner ring 410b. Torque T TL3 ' corresponds to the torque applied to the outer ring 410a due to the friction between the outer ring 410a and the inner ring 410b. In this example, when comparing the torque values on the rotation axis line of the motor 301, T TL3 ' < T TL3 is in the relationship of.

[0233] In this example, the drum coupling 63 receives the torque (driving force, first force) in the forward rotation direction A1 from the first drive transmission part 1D1 and also receives the torque (driving force, second force) in the forward rotation direction A1 from the second drive transmission part 1D21. In other words, the replacement unit in this example receives the force acting in the first rotation direction on the rotating member of the replacement unit from both the first drive transmission part 1D1 and the second drive transmission part 1D2.

[0234] The force that the main body coupling 180 receives from the drum coupling 63 in this embodiment is the coupling torque T. IF3 Let's assume that the load required to drive cartridge P is T. p In this embodiment, the load T of cartridge P is p In contrast, the torque T transmitted from the torque limiter 410 to the drum coupling 63 TL3 The remaining torque is transmitted from the main body coupling 180 to the drum coupling 63. That is, the coupling torque T IF3 This can be expressed as follows: T IF3 =T p -T TL3 ′

[0235] According to the above equation, the load on the first drive transmission unit 1D1 can be reduced by the amount of driving force transmitted via the second drive transmission unit 1D2, which includes the torque limiter 410. In other words, in the case of reference example 2 (Figure 13(c)) which does not have the second drive transmission unit 1D2, the coupled torque T IF " is the load T of cartridge P p Equivalent to (T IF ″=T p Therefore, a load T is applied to the gears, etc., that constitute the first drive transmission unit 1D1. p This is applied. In contrast, the load on the gears etc. that constitute the first drive transmission unit 1D1 in this embodiment is T IF3 It is reduced to this extent.

[0236] According to this embodiment, for example, the load T of cartridge P p When the load is large or due to external force, T p Even if the force temporarily increases, it becomes less likely that a large load will be placed on the gears and other components constituting the first drive transmission unit 1D1, thus reducing the likelihood of deformation. For example, deformation of the gear teeth and deformation of the force transmission surface 180d of the main body coupling 180 become less likely. As a result, it is possible to suppress fluctuations in the rotational speed input to the drum coupling 63 via the first drive transmission unit 1D1 due to deformation of the components.

[0237] (Advantages of this embodiment) As described above, this embodiment provides an image forming apparatus with a new configuration for driving the exchange unit.

[0238] For example, according to this embodiment, a force (driving force) in the forward rotation direction A1 is transmitted to the drum coupling 63 of the cartridge P via multiple paths through a closed-loop transmission path. Since the load on the members constituting the transmission path is reduced, fluctuations in the driving speed caused by deformation of the members can be suppressed.

[0239] Example 4 Figure 21(a) is a model diagram of the main drive train 1D according to another embodiment (Example 4) of the present disclosure. Figure 21(b) is a schematic diagram of the planetary gear mechanism 500.

[0240] The planetary gear mechanism 500 is an example of a permissible device including a first rotating body and a second rotating body in a closed-loop transmission path. The planetary gear mechanism 500 has a first gear 500a, a second gear 500b, a third gear 500c, and a planetary gear 500p. The first gear 500a, the second gear 500b, and the third gear 500c are all rotatable around the orbital axis Ax of the planetary gear mechanism 500 and are rotatable relative to each other. The planetary gear 500p is rotatable around its axis of rotation which rotates around the orbital axis Ax.

[0241] As shown in Figure 21(b), the planetary gear mechanism 500 includes a sun gear 501, a ring gear 502, and a carrier 503 (planetary carrier). The sun gear 501 has an external gear 501a that is radially outward. The ring gear 502 is positioned on the outer circumference of the sun gear 501 and has an internal gear 502b that is radially inward. The carrier 503 rotatably supports the planetary gear 500p that meshes with the external gear 501a and the internal gear 502a.

[0242] In Figure 21(a), the first gear 500a (first rotating body) is one of the sun gear 501, the ring gear 502, and the carrier 503. The second gear 500b (second rotating body) is one of the two from the sun gear 501, the ring gear 502, and the carrier 503, excluding the first gear 500a (first rotating body). The third gear 500c (third rotating body) is the remaining one from the sun gear 501, the ring gear 502, and the carrier 503, excluding the first gear 500a (first rotating body) and the second gear 500b (second rotating body). In the planetary gear mechanism 500, the first gear 500a, the second gear 500b, the third gear 500c, and the planetary gear 500p can be said to correspond to the functional parts of the tolerance device or differential device.

[0243] The motor-side transmission unit 1D2a is connected to the first gear 500a of the planetary gear mechanism 500 and the branch gear 302 (output unit). The cartridge-side transmission unit 1D2b is connected to the second gear 500b of the planetary gear mechanism 500 and the drum coupling 63 (driven unit) of the cartridge P.

[0244] The first drive transmission unit 1D1 and the second drive transmission unit 1D2 are configured such that the angular velocity of rotation input to the third gear 500c and the angular velocity input to the first gear 500a are different when the drum coupling 63 is driven. The planetary gear mechanism 500 allows the sun gear 501, ring gear 502, and carrier 503 to rotate relative to each other due to the rotation of the planetary gear 500p. The planetary gear mechanism 500 is also capable of transmitting force (torque) between the first gear 500a and the second gear 500b. In other words, the planetary gear mechanism 500 is an example of a tolerance device (differential device) that is capable of transmitting driving force between the first rotating body and the second rotating body and is configured to tolerate fluctuations in the ratio of the first angular velocity of the first rotating body to the second angular velocity of the second rotating body.

[0245] Furthermore, in the example shown in Figure 21(a), the third gear 500c (third rotating body) is connected to the load body 306. In the planetary gear mechanism 500, if the angular velocities of two of the three rotating bodies (sun gear, ring gear, and carrier) that rotate around the orbital axis Ax are given, the angular velocity of the remaining element is determined. In this embodiment, the first gear 500a (first rotating body) and the second gear 500b (second rotating body) are connected to the branch gear 302 (output section) via a closed-loop transmission path. That is, the first gear 500a is connected to the branch gear 302 (output section) via the motor-side transmission section 1D2a. The second gear 500b is connected to the branch gear 302 via the cartridge-side transmission section 1D2b, the driven section of the cartridge P, and the first drive transmission section 1D1. Therefore, the angular velocities of the first gear 500a (first rotating body) and the second gear 500b (second rotating body) are determined according to the angular velocity of the branching gear 302 (output section) when driven by the motor 301, and further, the angular velocity of the third gear 500c (third rotating body) is determined.

[0246] With this configuration, the planetary gear mechanism 500 can absorb the difference in angular velocity input to each component via a closed-loop transmission path, and can also transmit the driving force of the motor 301 to the load body 306, which is the object to be driven other than the cartridge P.

[0247] Furthermore, at least a portion of the load that the third gear 500c receives from the load body 306 when the load body 306 is driven is transmitted from the third gear 500c to the second gear 500b in the planetary gear mechanism 500. In addition, this load is transmitted from the second gear 500b to the drum coupling 63 via the cartridge-side transmission unit 1D2b as a force (braking force) acting in the opposite direction to the forward rotation direction A1. In other words, at least a portion of the load of the load body 306 is transmitted to the cartridge P (unit) as a braking force (second force) via the third gear 500c (third rotating body), the second gear 500b (second rotating body), and the cartridge-side transmission unit 1D2b (unit-side transmission unit). With this configuration, similar to embodiments 1 and 2, the preceding rotation of the drum coupling 63 and the photosensitive drum 61 is suppressed, and the cartridge P can be driven at a more stable driving speed.

[0248] The planetary gear mechanism 500 can be positioned in the same location as the torque limiter 410 in Examples 1 to 3. For example, the planetary gear mechanism 500 can be positioned such that its orbital axis Ax is parallel to the axis M1 of the drive transmission unit 200 and passes through a position away from the axis M1 (see Figures 5(a) and 7(a)(b)). However, the orbital axis Ax of the planetary gear mechanism 500 can also be coaxial with the axis M1.

[0249] Furthermore, the connection relationships between the first gear 500a, the second gear 500b, and the third gear 500c, and the motor-side transmission unit 1D2a and cartridge-side transmission unit 1D2b of the second drive transmission unit 1D2, as well as the load body 306, are not limited to those described above. In other words, the combination of connections between the three rotating bodies of the planetary gear mechanism 500 (sun gear, ring gear, and carrier) and the motor-side transmission unit 1D2a, cartridge-side transmission unit 1D2b, and load body 306 can be changed.

[0250] For example, the first gear 500a may be connected to the motor-side transmission unit 1D2a, the third gear 500c to the cartridge-side transmission unit 1D2b, and the second gear 500b to the load unit 306. Alternatively, the second gear 500b may be connected to the motor-side transmission unit 1D2a, the first gear 500a to the cartridge-side transmission unit 1D2b, and the third gear 500c to the load unit 306. Alternatively, the second gear 500b may be connected to the motor-side transmission unit 1D2a, the third gear 500c to the cartridge-side transmission unit 1D2b, and the first gear 500a to the load unit 306. Alternatively, the third gear 500c may be connected to the motor-side transmission unit 1D2a, the second gear 500b to the cartridge-side transmission unit 1D2b, and the first gear 500a to the load unit 306. Alternatively, the third gear 500c may be connected to the motor-side transmission unit 1D2a, the first gear 500a may be connected to the cartridge-side transmission unit 1D2b, and the second gear 500b may be connected to the load unit 306.

[0251] (Advantages of this embodiment) As described above, this embodiment provides an image forming apparatus with a new configuration for driving the exchange unit.

[0252] As mentioned above, cartridge P is an example of a "unit" that is not necessarily removable from the main body 1A of the image forming apparatus. In other words, according to this embodiment, it is possible to provide an image forming apparatus with a new configuration for driving a unit in the image forming apparatus.

[0253] For example, according to this embodiment, a driving force in the forward rotation direction A1 and a braking force in the opposite direction can be transmitted to the drum coupling 63 of the cartridge P via a closed-loop transmission path. This suppresses the preceding rotation of the drum coupling 63 and the photosensitive drum 61, allowing the cartridge P to be driven at a more stable speed. In particular, in this embodiment, the above advantages can be realized by a configuration in which a portion of the load of the load body 306 is transmitted to the drum coupling 63 as a braking force (driving force) via the planetary gear mechanism 500.

[0254] Example 5 Figures 22(a) and 22(b) show a main drive train 1D according to yet another embodiment (Embodiment 5). This embodiment differs from Embodiment 1 in that the rotation direction of the inner ring 410b of the torque limiter 410, the third differential gear 404, the fourth differential gear 405, and the differential shaft 406 during image formation is in the opposite direction to Embodiment 1 (see Figures 11(a) and 11(b)).

[0255] Immediately after starting the motor 301, as shown in Figure 22(a), the second differential gear 402 rotates counterclockwise in the figure at a peripheral speed V1, and the outer gear 403 rotates clockwise in the figure at a peripheral speed V2'. The outer gear 403 and the outer ring 410a rotate together with the inner ring 410b and the differential shaft 406 at an angular velocity R1. As a result, as shown in Figure 22(b), the tooth surface 403a of the outer gear 403 and the tooth surface 402a of the second differential gear 402 come into contact.

[0256] When the tooth surface 403a of the outer gear 403 and the tooth surface 402a of the second differential gear 402 come into contact, the outer ring 410a of the torque limiter 410 rotates at a peripheral speed V1 against friction with the inner ring 410b. At this time, the outer ring 410a rotates in the opposite direction to the rotation direction of the inner ring 410b at an angular velocity R1 corresponding to the peripheral speed V1.

[0257] In the state shown in Figure 22(b), the load generated by the slippage of the torque limiter 410 is transmitted via the second differential gear 402, the first differential gear 401, the transmission shaft 209, and the engaging members (204, 208). The load generated by the slippage of the torque limiter 410 is then transmitted to the drum coupling 63 (driven part) as a force (braking force) in the opposite direction to the forward rotation direction A1.

[0258] In this configuration, when the main drive train 1D is connected in a closed loop, different angular velocities R1 and R2' are input to the outer ring 410a and inner ring 410b of the torque limiter 410, causing slippage of the torque limiter 410 (relative rotation of the outer ring 410a and inner ring 410b). In particular, in this embodiment, the rotation directions of the outer ring 410a and inner ring 410b are opposite to each other. The torque limiter 410 allows different angular velocities R1 and R2' to be input to the outer ring 410a and inner ring 410b and absorbs the difference in angular velocity. Furthermore, similar to Embodiment 1, the torque limiter 410 in this embodiment generates a load to apply a braking force to the drum coupling 63 due to the relative rotation of the outer ring 410a and inner ring 410b.

[0259] This configuration also provides the same advantages as in Example 1.

[0260] Other embodiments In the embodiments described above, the driving of the photosensitive drum 61 provided in the cartridge P was mainly explained as an example, but the application of the technology of this disclosure is not limited to the photosensitive drum 61 and cartridge P. The "exchange unit" is not limited to the cartridge P equipped with the photosensitive drum 61, but may be, for example, a transfer unit 40. The object to be driven is not limited to the photosensitive drum 61, but may be, for example, a drive roller 46 that rotates a belt 41.

[0261] Summary of this disclosure This disclosure includes at least the following: (Composition 1) A unit having a driven part, A drive device having a drive source that generates driving force and an output unit that outputs the driving force, The output unit and the first drive transmission unit connected to the unit, A second drive transmission unit, which includes a planetary gear mechanism and is connected to the output unit and the unit, It has, The driving force transmission path includes a closed loop, and the closed loop includes the driven unit, the output unit, the first drive transmission unit, and the second drive transmission unit. An image forming apparatus characterized by the following features. (Configuration 2) The second drive transmission unit includes a drive source side transmission unit connected to the output unit and a unit side transmission unit connected to the unit, The first drive transmission unit, the drive source side transmission unit, and the unit side transmission unit are configured such that when the driven unit is rotationally driven by the drive source, a difference is created between the angular velocity of the rotation input to the planetary gear mechanism via the drive source side transmission unit around the orbital axis of the planetary gear mechanism and the angular velocity of the rotation input to the planetary gear mechanism via the unit side transmission unit around the orbital axis. The image forming apparatus according to configuration 1, characterized in that it is a picture forming apparatus. (Composition 3) The planetary gear mechanism comprises a sun gear, a ring gear positioned on the outer circumference of the sun gear, planetary gears that mesh with the sun gear and the ring gear, and a carrier that supports the planetary gears. Any one of the sun gear, the ring gear, and the carrier is a first rotating body connected to the unit-side transmission section. One of the two remaining components from the sun gear, ring gear, and carrier (excluding the first rotating body) is a second rotating body connected to the drive source side transmission unit. The image forming apparatus according to configuration 2, characterized in that... (Composition 4) The third rotating body is one of the components obtained by removing the first and second rotating bodies from the sun gear, ring gear, and carrier. The load body further comprises a load body to which the driving force of the drive source is transmitted via the third rotating body, The image forming apparatus according to configuration 3, characterized in that it is a picture forming apparatus. (Composition 5) The load body is a conveyor roller for transporting recording material. The image forming apparatus according to configuration 4, characterized in that... (Composition 6) The driven portion includes a rotating member that is rotated in a first rotational direction by the drive source, The unit receives a first force from the first drive transmission unit acting on the rotating member in the first rotational direction and a second force from the second drive transmission unit acting on the rotating member in the second rotational direction opposite to the first rotational direction. The image forming apparatus according to configuration 5, characterized by the features described herein. (Composition 7) At least a portion of the load of the load body is transmitted to the unit as the second force via the third rotating body, the first rotating body, and the unit-side transmission unit. The image forming apparatus according to configuration 6, characterized by the features described therein. (Composition 8) The unit has a first surface that receives the first force from the first drive transmission unit and a second surface that receives the second force from the second drive transmission unit. The image forming apparatus according to configuration 6 or 7, characterized by the above. (Composition 9) The unit has a photosensitive drum, and the photosensitive drum is rotated by the driving force. An image forming apparatus according to any one of configurations 1 to 8 characterized by the above. [Explanation of symbols]

[0262] 1A…Main unit / 1D1…First drive transmission unit / 1D2…Second drive transmission unit / 1Dd…Drive unit / 63, 61…Driven parts (drum coupling, photosensitive drum) / 301…Drive source (motor) / 302…Output unit (branching gear) / 410…Allowance device, differential device (torque limiter) / 500…Allowance device, differential device (planetary gear mechanism) / P…Unit (cartridge)

Claims

1. A unit having a driven part, A drive device having a drive source that generates driving force and an output unit that outputs the driving force, The output unit and the first drive transmission unit connected to the unit, A second drive transmission unit, which includes a planetary gear mechanism and is connected to the output unit and the unit, It has, The driving force transmission path includes a closed loop, and the closed loop includes the driven unit, the output unit, the first drive transmission unit, and the second drive transmission unit. An image forming apparatus characterized by the following features.

2. The second drive transmission unit includes a drive source side transmission unit connected to the output unit and a unit side transmission unit connected to the unit, The first drive transmission unit, the drive source side transmission unit, and the unit side transmission unit are configured such that, when the driven unit is rotationally driven by the drive source, a difference is created between the angular velocity of the rotation input to the planetary gear mechanism via the drive source side transmission unit around the orbital axis of the planetary gear mechanism and the angular velocity of the rotation input to the planetary gear mechanism via the unit side transmission unit around the orbital axis. The image forming apparatus according to feature 1.

3. The planetary gear mechanism comprises a sun gear, a ring gear positioned on the outer circumference of the sun gear, planetary gears that mesh with the sun gear and the ring gear, and a carrier that supports the planetary gears. Any one of the sun gear, the ring gear, and the carrier is a first rotating body connected to the unit-side transmission section. One of the two remaining components from the sun gear, ring gear, and carrier (excluding the first rotating body) is a second rotating body connected to the drive source side transmission unit. The image forming apparatus according to feature 2.

4. The third rotating body is one of the components obtained by removing the first and second rotating bodies from the sun gear, ring gear, and carrier. The load body further comprises a load body to which the driving force of the drive source is transmitted via the third rotating body, The image forming apparatus according to feature 3.

5. The load body is a conveyor roller for transporting recording material. The image forming apparatus according to feature 4.

6. The driven portion includes a rotating member that is rotated in a first rotational direction by the drive source, The unit receives a first force from the first drive transmission unit acting on the rotating member in the first rotational direction and a second force from the second drive transmission unit acting on the rotating member in the second rotational direction opposite to the first rotational direction. The image forming apparatus according to feature 5.

7. At least a portion of the load of the load body is transmitted to the unit as the second force via the third rotating body, the first rotating body, and the unit-side transmission unit. The image forming apparatus according to feature 6.

8. The unit has a first surface that receives the first force from the first drive transmission unit and a second surface that receives the second force from the second drive transmission unit. The image forming apparatus according to feature 6.

9. The unit has a photosensitive drum, and the photosensitive drum is rotated by the driving force. The image forming apparatus according to any one of claims 1 to 8.

Images