Rotational force transmission device and image forming apparatus

Abstract

The present invention provides a rotational force transmission device and an image forming apparatus that, despite having a simple configuration, can effectively prevent a decrease in the driving capacity of the moving device when the moving member is kept in a rotational stop position. [Solution] The rotational force transmission device 200 comprises an input gear 210, a carrier 220, a moving member 310, a moving device 300, and an output gear 230. The engaging portion 221 has a biasing force generating portion (221a) that receives rotational force from the input gear 210 and biases the moving member 310 toward the rotation axis α when the moving member 310 is in a rotation stop position and the input gear 210 is rotating.

Description

Technical Field

[0001] The present disclosure relates to a rotational force transmission device and an image forming apparatus such as a copying machine, a multifunction peripheral, a printer, and a facsimile apparatus.

Background Art

[0002] 17 and 18 are exploded perspective views of an example of a conventional rotational force transmission device 200X viewed from the carrier 220X side and the input gear 210 side, respectively. FIG. 19 is a front view showing a state where the moving member 310X is located at the rotation allowable position P2 with respect to the carrier 220X by the moving device 300X in the conventional rotational force transmission device 200X. Further, FIG. 20 is a front view showing a state where the moving member 310X is located at the rotation stop position P1 with respect to the carrier 220X by the moving device 300X in the conventional rotational force transmission device 200X.

[0003] As shown in FIGS. 17 to 20, the conventional rotational force transmission device 200X includes an input gear 210, a carrier 220X, a moving member 310X, a moving device 300X, and an output gear 230.

[0004] The input gear 210 receives a rotational force F from a rotational drive unit (drive motor) not shown and rotates about the rotational axis α. The carrier 220X has engagement portions 221X to 221X. The carrier 220X receives the rotational force from the input gear 210 and rotates about the rotational axis α.

[0005] The moving member 310X has a contact portion 311X that contacts the engagement portion 221X in the carrier 220X so that the carrier 220X rotating in a predetermined rotation direction D stops. The moving member 310X is movable between a rotation allowable position P2 (see FIG. 19) and a rotation stop position P1 (see FIG. 20). The rotation allowable position P2 is a position that allows the rotation of the carrier 220X because the contact portion 311X does not contact the engagement portion 221X. The rotation stop position P1 is a position that stops the rotation of the carrier 220X when the contact portion 311X contacts the engagement portion 221X.

[0006] The moving device 300X drives the movement of the moving member 310X from the rotation-permitted position P2 to the rotation-stop position P1. The output gear 230 is made rotatable around the rotation axis α by receiving rotational force from the carrier 220X.

[0007] The carrier 220X rotates when the moving member 310X is positioned at the rotation-permissible position P2 by the moving device 300X while the input gear 210 is rotating, but does not transmit the rotational force F from the input gear 210 to the output gear 230, thereby preventing the output gear 230 from rotating. On the other hand, the carrier 220X stops rotating when the moving member 310X is positioned at the rotation-stop position P1 by the moving device 300X while the input gear 210 is rotating, but transmits the rotational force F from the input gear 210 to the output gear 230, causing the output gear 230 to rotate.

[0008] In this example, the input gear 210 has an input gear section 211 and a sun gear section 212. The input gear section 211 receives a rotational force F from a rotational drive section (not shown) and rotates around the rotation axis α. The sun gear section 212 has a smaller diameter than the input gear section 211 and rotates together with the input gear section 211 around the rotation axis α.

[0009] The carrier 220X is a rotating body rotatable around a rotation axis α, and has one or more (six in this example) engaging parts 221X~221X, multiple (three in this example) planetary gears 222~222, and multiple support shafts 223~223. The engaging parts 221X~221X are parts for stopping the rotation of the carrier 220X around the rotation axis α, and have wall portions along both the rotation axis direction W and the radial direction E centered on the rotation axis α of the carrier 220X.

[0010] The planetary gears 222-222 mesh with the sun gear section 212. Multiple support shafts 223-223 each rotatably support multiple planetary gears 222-222.

[0011] The output gear 230 has an internal tooth section 231 and an external tooth section 232. The internal tooth section 231 meshes with a plurality of planetary gears 222-222 on the inside in the radial direction E centered on the rotation axis α. The external tooth section 232 transmits rotational force F on the outside in the radial direction E.

[0012] The movable member 310X (carrier arm) is movable between a rotation stop position P1 in which it engages with the engaging portion 221X to rotate / stop the carrier 220X, and a rotation allowable position P2 in which it does not engage with the engaging portion 221X.

[0013] The moving device 300X (electromagnetic solenoid unit) has a biasing member 320, and when energized, it drives the moving member 310X to move from the rotation-permitted position P2 to the rotation-stop position P1 against the biasing force of the biasing member 320, and when not energized, the moving member 310X moves from the rotation-stop position P1 to the rotation-permitted position P2 by the biasing member 320.

[0014] The rotational force transmission device 200X transmits rotational force F to the output gear 230 when the moving device 300X is energized and the moving member 310X is in the rotation stop position P1, but does not transmit rotational force F to the output gear 230 when the moving device 300X is not energized and the moving member 310X is in the rotation allowable position P2. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] Japanese Patent Publication No. 2003-315899 [Overview of the project] [Problems that the invention aims to solve]

[0016] In such a conventional rotational force transmission device 200X, when transmitting rotational force F to the output gear 230, if the moving device 300X is not kept energized at all times, there is a risk that the moving member 310X will move from the rotation stop position P1 to the rotation allowable position P2, preventing the transmission of rotational force F to the output gear 230. Therefore, while transmitting rotational force F to the output gear 230, the moving device 300X must be kept energized at all times. However, if the time spent transmitting rotational force F to the output gear 230 is long, the moving device 300X (electromagnetic solenoid) will generate heat due to the energization, and if the temperature of the moving device 300X (electromagnetic solenoid) rises too high due to the generated heat, the holding force required to keep the moving member 310X at the rotation stop position P1 against the biasing force of the biasing member 320 will decrease, and there is a risk that it will move to the rotation stop position P1. In other words, even though the driving capacity of the moving device 300X decreases and it becomes necessary to stop the rotation of the carrier 220X, the moving member 310X may not be able to be positioned at the rotation stop position P1, and therefore the rotation of the carrier 220X may not be able to be stopped.

[0017] In this regard, Patent Document 1 (paragraph

[0013] , Figure 5) describes a configuration (configuration of a retractable ballpoint pen) in which, by pressing the stop shaft downward against the biasing force of the compression spring, the bent end of the connecting rod slides in the cam groove, and when the pressure on the stop shaft is released, it stops and the stop shaft is held in the lowered position, and after pressing the stop shaft downward again against the biasing force of the compression spring and then releasing the pressure, the bent end of the connecting rod moves in the upward direction indicated by the arrow and the stop shaft returns to its original position.

[0018] However, when the configuration described in Patent Document 1 is applied to the rotational force transmission device 200X, the movable member 310X can be held in the rotation stop position P1, and therefore, it is not necessary to constantly energize the moving device 300X. Although this effectively prevents a decrease in the driving capacity of the moving device 300X, the configuration of the movable member 310X becomes more complex.

[0019] Therefore, the present disclosure aims to provide a rotational force transmission device and an image forming apparatus that, despite having a simple configuration, can effectively prevent a decrease in the driving capacity of the moving device when the moving member is maintained in a rotation-stopped position. [Means for solving the problem]

[0020] To solve the aforementioned problems, the rotational force transmission device according to the present disclosure includes: an input gear that receives rotational force from a rotation drive unit and rotates around a rotation axis; a carrier having an engagement portion that receives rotational force from the input gear and rotates around the rotation axis; a movable member having a contact portion that can contact the engagement portion, and which is movable between a rotation stop position in which the contact portion contacts the engagement portion to stop the rotation of the carrier that rotates in a predetermined first rotation direction in response to rotational force from the input gear, and a rotation allowable position in which the contact portion is separated from the engagement portion and rotation of the carrier in the first rotation direction is permitted; and a drive for the movable member from the rotation allowable position to the rotation stop position. The present invention comprises a moving device and an output gear rotatable around the rotation axis, wherein the carrier does not transmit rotational force from the input gear to the output gear when the moving member is in the rotation-permitted position and rotating in the first rotation direction, and transmits rotational force from the input gear to the output gear when the moving member is in the rotation-stop position and the input gear is rotating in a direction that rotates the carrier in the first rotation direction, and the engaging portion has a biasing force generating portion that receives rotational force from the input gear and biases the moving member toward the rotation axis when the moving member is in the rotation-stop position and the input gear is rotating. Furthermore, the present invention comprises a rotational force transmission device. [Effects of the Invention]

[0021] According to this disclosure, even with a simple configuration, it is possible to effectively prevent a decrease in the driving capacity of the moving device when the moving member is kept in a rotation-stop position. [Brief explanation of the drawing]

[0022] [Figure 1] It is a cross-sectional view showing a schematic configuration of an image forming apparatus including a rotational force transmission device according to the present embodiment. [Figure 2] It is a cross-sectional view showing an image forming unit, a primary transfer belt device, and a secondary transfer device in the image forming apparatus shown in FIG. 1. [Figure 3] It is a perspective view seen from the front side of a gear train portion on the front side of a driving device that drives an image forming unit and a primary transfer belt device. [Figure 4] It is a perspective view showing the gear train portion on the front side of the driving device shown in FIG. 3 together with one developing device. [Figure 5] It is a front view showing a state in which the rotational force transmission device is on in a gear train portion on the back side from which the gear train on the front side of the driving device has been removed. [Figure 6] It is a front view showing a state in which the rotational force transmission device is off in a gear train portion on the back side from which the gear train on the front side of the driving device has been removed. [Figure 7] It is a perspective view showing a rotational force transmission device portion in the driving device shown in FIG. 5. [Figure 8] It is a perspective view showing a rotational force transmission device portion in the driving device shown in FIG. 6. [Figure 9] It is an exploded perspective view showing an input gear, a carrier, and an output gear in an example of the rotational force transmission device according to the present embodiment. [Figure 10] In FIG. 9, it is an exploded perspective view showing a state in which an output gear is attached to an input gear. [Figure 11] It is a front view showing a state in which a moving member is located at a rotation allowable position of a carrier by a moving device. [Figure 12] It is a front view showing one aspect of a state in which a moving member is located at a rotation stop position of a carrier by a moving device. [Figure 13] It is a front view showing another aspect of a state in which a moving member is located at a rotation stop position of a carrier by a moving device. [Figure 14] It is an enlarged front view showing a state in which an engaging portion and a contact portion of a carrier are in contact with each other. [Figure 15] This is a schematic block diagram showing the system configuration of the control unit in an image forming apparatus. [Figure 16] This is a timing chart illustrating an example of control for the control unit. [Figure 17] This is an exploded perspective view of an example of a conventional rotational force transmission device, seen from the carrier side. [Figure 18] This is an exploded perspective view of an example of a conventional rotational force transmission device, viewed from the input gear side. [Figure 19] This is a front view showing a conventional rotational force transmission device in which the moving member is positioned relative to the carrier at a rotationally permissible position by the moving device. [Figure 20] This is a front view showing a conventional rotational force transmission device in which the moving member is positioned at a rotational stop position relative to the carrier by the moving device. [Modes for carrying out the invention]

[0023] The embodiments of this disclosure will be described below with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0024] [Image forming apparatus] Figure 1 is a cross-sectional view showing the schematic configuration of the image forming apparatus 100 according to this embodiment. Figure 2 is a cross-sectional view showing the image forming unit 50, the primary transfer belt device 70, and the secondary transfer device 11 in the image forming apparatus 100 shown in Figure 1. In the figures, the width direction is X, the left side is X1, the right side is X2, the direction perpendicular to the width direction X is the depth direction Y, the front side is Y1, the back side is Y2, and the vertical direction perpendicular to the width direction X and the depth direction Y is Z, and will be described below.

[0025] The image forming apparatus 100 is a multifunction device having copying, scanning, facsimile, and printing functions, and transmits the image of the original document G read by the image reading device 102 to an external source. The image forming apparatus 100 also forms an image on a sheet P of paper or the like in color or monochrome from the image of the original document G read by the image reading device 102 or from an external source.

[0026] The image reading device 102 includes a document placement table 130a (document setting table) on which the document G is placed, and an image reading unit 130 that reads the document G placed on the document placement table 130a. The image reading unit 130 creates image data by moving the scanning optical system 130c in the scanning direction, thereby reading the image of the document G placed on the document placement table 130a with the document reading unit 130b.

[0027] The image reading device 102 further includes a document feeder 160. The document feeder 160 is supported above the image reading unit 130 so as to be openable and closable relative to the image reading unit 130. The document feeder 160 transports one or more documents G one by one to the image reading position 130d. The documents G sent to the image reading position 130d are read by the document reading unit 130b via the scanning optical system 130c which is stopped at the image reading position 130d, and image data is created. As described above, the image reading unit 130 generates image data by scanning the scanning optical system 130c and reading the documents G placed on the document tray 130a with the document reading unit 130b, or by reading the documents G transported by the document feeder 160 with the document reading unit 130b.

[0028] The image forming apparatus main unit 101 includes a light scanning device 1, developing devices 2y, 2m, 2c, 2k, photoreceptor drums 3y, 3m, 3c, 3k, drum cleaning devices 4y, 4m, 4c, 4k, chargers 5y, 5m, 5c, 5k, primary transfer belt device 70, secondary transfer device 11, fixing device 12, sheet transport path S, paper feed cassette 18, and sheet discharge trays 141 (141a, 141b).

[0029] The image forming apparatus 100 first transfers a toner image formed using multiple colors of toner onto a belt 71 (a primary transfer belt in this example), and then secondarily transfers the toner image transferred onto the belt 71 onto a sheet P.

[0030] In this embodiment, image data corresponding to color images using yellow (Y), magenta (M), and cyan (C), or monochrome images using a single color [e.g., black (K)], is handled. In the following description, yellow, magenta, cyan, and black will simply be referred to as Y, M, C, and K, respectively.

[0031] The image forming unit 50 of the image forming apparatus 100 includes developing devices 2y, 2m, 2c, 2k for forming four types of toner images, photoreceptor drums 3y, 3m, 3c, 3k, drum cleaning devices 4y, 4m, 4c, 4k, and chargers 5y, 5m, 5c, 5k, and is composed of four image stations Py, Pm, Pc, Pk, which correspond to Y, M, C, and K respectively.

[0032] The chargers 5y, 5m, 5c, and 5k uniformly charge the surfaces of the photoreceptor drums 3y, 3m, 3c, and 3k to a predetermined potential. The optical scanning device 1 exposes the surfaces of the photoreceptor drums 3y, 3m, 3c, and 3k, which are charged to the predetermined potential, to form an electrostatic latent image. The developing devices 2y, 2m, 2c, and 2k develop the electrostatic latent image on the surface of the photoreceptor drums 3y, 3m, 3c, and 3k with toners of each color to form a toner image on the surface of the photoreceptor drums 3y, 3m, 3c, and 3k. Therefore, the developing devices 2y, 2m, 2c, and 2k have developing rollers 21y, 21m, 21c, and 21k (see Figure 2) that supply toners of each color to the surface of the photoreceptor drums 3y, 3m, 3c, and 3k. The drum cleaning devices 4y, 4m, 4c, and 4k remove and recover residual toner remaining on the surface of the photoreceptor drums 3y, 3m, 3c, and 3k after the primary transfer described later. Through the series of operations described above, toner images of each color are formed on the surface of each photoreceptor drum 3y, 3m, 3c, and 3k.

[0033] The primary transfer belt device 70 comprises a belt 71, primary transfer rollers 6y, 6m, 6c, 6k, a plurality of belt tension rollers 72-72 (including a drive roller 721, a driven roller 722, and a tension roller 723), and a belt cleaning device 9. The belt 71 is stretched over the plurality of belt tension rollers 72-72, and when the drive roller 721, which is one of the belt tension rollers 72-72, is rotationally driven by the drive device 400 described later, it rotates in a predetermined rotational direction R. At this time, the driven roller 722 and the tension roller 723 rotate in conjunction with the belt 71. The primary transfer rollers 6y, 6m, 6c, 6k are provided on the inside of the belt 71 to bring the belt 71 into contact with the surface of the corresponding photoreceptor drums 3y, 3m, 3c, 3k. The toner images of each color formed on the surface of the photoreceptor drums 3y, 3m, 3c, and 3k are primary transferred to the belt 71 by the primary transfer rollers 6y, 6m, 6c, and 6k.

[0034] The secondary transfer device 11 has a secondary transfer roller 11a. The secondary transfer device 11 forms a transfer nip section TN (transfer nip region) between the secondary transfer roller 11a and the belt 71, and transports the sheet P that has been transported through the sheet transport path S by sandwiching it in the transfer nip section TN. As the sheet P passes through the transfer nip section TN, the toner image on the surface of the belt 71 is secondary transferred to the sheet P and it is transported to the fixing device 12. The belt cleaning device 9 removes and collects waste toner that remains on the surface of the belt 71 without being transferred to the sheet P.

[0035] The fixing device 12 is equipped with a fixing roller 31 and a pressure roller 32 that rotate with the sheet P in between. The fixing device 12 places the sheet P, on which the toner image has been transferred, between the fixing roller 31 and the pressure roller 32, heats and pressurizes it, and fixes the toner image to the sheet P.

[0036] The paper feed cassette 18 is for storing sheets P used for image formation and is located on the lower side of the optical scanning device 1. The sheets P are pulled out from the paper feed cassette 18 by the pickup roller 16 and transported to the sheet transport path S. The sheets P transported to the sheet transport path S pass through the secondary transfer device 11 and the fixing device 12, and are transported to the discharge rollers 17 (17a, 17b), and discharged to the sheet discharge trays 141 (141a, 141b) in the discharge section 140. The sheet transport path S is equipped with a transport roller 13, a registration roller 14, and discharge rollers 17 (17a, 17b). In this example, the discharge rollers 17 consist of two discharge rollers 17a and 17b located vertically, and the sheet discharge trays 141 consist of two sheet discharge trays 141a and 141b, corresponding to the two discharge rollers 17a and 17b, respectively. The transport rollers 13-13 facilitate the transport of the sheet P along the sheet transport path S. The register roller 14 temporarily stops the sheet P and aligns the leading edge of the sheet P. The register roller 14 then transports the temporarily stopped sheet P in sync with the timing of the toner image on the belt 71. As described above, the toner image on the belt 71 is secondarily transferred to the sheet P at the transfer nip TN between the belt 71 and the secondary transfer roller 11a.

[0037] Although Figure 1 shows only one paper feed cassette 18, the system is not limited to this configuration. Multiple paper feed cassettes 18 may be provided, each loaded with a different type of sheet P.

[0038] Furthermore, when image formation is to be performed on both the front and back surfaces of sheet P, the image forming apparatus 100 transports sheet P in the reverse direction from the upper discharge roller 17b to the sheet reversal path Sr. As sheet P is transported in the reverse direction, its front and back surfaces are reversed, and it is guided again to the register roller 14. Here, the image forming apparatus 100 forms an image on the back surface of sheet P guided to the register roller 14 in the same way as the front surface, and then transports it to the sheet discharge tray 141 (141a, 141b).

[0039] Figure 3 is a perspective view of the front gear train (410, 420, 430) portion of the drive unit 400 that drives the image forming unit 50 and the primary transfer belt device 70, viewed from the front. Figure 4 is a perspective view of the front gear train (410, 420, 430) portion of the drive unit 400 shown in Figure 3, together with a developing device 2y. Figures 5 and 6 are front views showing the rotational force transmission device 200 (clutch device) in the on and off states in the rear gear train (440, 450) portion of the drive unit 400, with the front gear train (410, 420, 430) removed. Figures 7 and 8 are perspective views showing a part of the drive unit 400 and a part of the rotational force transmission device 200 shown in Figures 5 and 6, respectively.

[0040] When forming a color image, the image forming apparatus 100 rotates the belt 71, the photoreceptor drums 3y, 3m, 3c, 3k, and the developing rollers 21y, 21m, 21c, 21k of the developing apparatus 2y, 2m, 2c, 2k (an example of a developer carrier). When forming a monochrome image, the belt 71, the photoreceptor drums 3y, 3m, 3c, 3k, and the developing roller 21k of the developing apparatus 2k are rotated, but the rotation of the developing rollers 21y, 21m, 21c of the developing apparatus 2y, 2m, 2c is stopped.

[0041] Next, the drive unit 400 that rotates the belt 71, the photoreceptor drums 3y, 3m, 3c, 3k, and the developing rollers 21y, 21m, 21c, 21k of the developing unit 2y, 2m, 2c, 2k will be described in detail.

[0042] The drive unit 400 comprises a rotary drive unit 401 (drive motor), a first gear train 410 (see Figure 3), a second gear train 420 (see Figure 3), a third gear train 430 (see Figure 3), a fourth gear train 440 (see Figure 5), and a fifth gear train 450 (see Figure 5). The rotary drive unit 401 and the first to fifth gear trains 410 to 450 are supported by the main frame FL and subframe FL1 (see Figures 3 and 4) of the image forming apparatus body 101. The subframe FL1 is attached to the main frame FL. Here, the coupling gears 2ay, 2am, 2ac, 2ak that transmit rotational force from the rotary drive unit 401 to the yellow, magenta, cyan, and black developing units 2y, 2m, 2c, 2k (and their developing rollers 21y, 21m, 21c, 21k), the fourth intermediate gear 414 and fifth intermediate gear 415 of the first gear row 410, and the fourth intermediate gear 424 and fifth intermediate gear 425 of the second gear row 420 are supported by the subframe FL1. Figures 5 and 6 show the first gear row 410 to the third gear row 430 and the subframe FL1 removed from the main frame FL.

[0043] As shown in Figures 3 and 4, the first gear train 410 includes a first intermediate gear 411 to a fifth intermediate gear 415, and transmits the rotational force F from the rotating shaft 401a of the rotary drive unit 401 to the first photoreceptor gear 3ay and the second photoreceptor gear 3am, respectively, which rotate the two photoreceptor drums 3y and 3m. The first intermediate gear 411 transmits the rotational force F from the rotating shaft 401a of the rotary drive unit 401 to the second intermediate gear 412. The second intermediate gear 412 transmits the rotational force F from the first intermediate gear 411 to the third intermediate gear 413. The third intermediate gear 413 transmits the rotational force F from the second intermediate gear 412 to the fourth intermediate gear 414 and the fifth intermediate gear 415, respectively. The fourth intermediate gear 414 and the fifth intermediate gear 415 transmit the rotational force F from the third intermediate gear 413 to the first photoreceptor gear 3ay and the second photoreceptor gear 3am, respectively. In this embodiment, the first photoreceptor gear 3ay is formed on the same axis as the fourth intermediate gear 414, and the second photoreceptor gear 3am is formed on the same axis as the fifth intermediate gear 415.

[0044] The second gear train 420 includes a first intermediate gear 421 to a fifth intermediate gear 425, and transmits the rotational force F from the rotating shaft 401a of the rotary drive unit 401 to the third photoreceptor gear 3ac and the fourth photoreceptor gear 3ak, respectively, which rotate the two photoreceptor drums 3c and 3k. The first intermediate gear 421 transmits the rotational force F from the rotating shaft 401a of the rotary drive unit 401 to the second intermediate gear 422. The second intermediate gear 422 transmits the rotational force F from the first intermediate gear 421 to the third intermediate gear 423. The third intermediate gear 423 transmits the rotational force F from the second intermediate gear 422 to the fourth intermediate gear 424 and the fifth intermediate gear 425, respectively. The fourth intermediate gear 424 and the fifth intermediate gear 425 transmit the rotational force F from the third intermediate gear 423 to the third photoreceptor gear 3ac and the fourth photoreceptor gear 3ak, respectively. In this embodiment, the third photoreceptor gear 3ac is formed on the same axis as the fourth intermediate gear 424, and the fourth photoreceptor gear 3ak is formed on the same axis as the fifth intermediate gear 425.

[0045] The third gear train 430 comprises a first intermediate gear 431 to a third intermediate gear 433, and transmits the rotational force F from the second intermediate gear 422 of the second gear train 420 to the roller gear 721a that rotates the drive roller 721. The first intermediate gear 431 transmits the rotational force F from the second intermediate gear 422 of the second gear train 420 to the second intermediate gear 432. The second intermediate gear 432 transmits the rotational force F from the first intermediate gear 431 to the third intermediate gear 433. The third intermediate gear 433 transmits the rotational force F from the second intermediate gear 432 to the roller gear 721a that rotates the drive roller 721. In this embodiment, the roller gear 721a is formed on the same axis as the third intermediate gear 433.

[0046] As shown in Figures 5 to 8, the fourth gear train 440 includes a first intermediate gear 441 to a fifth intermediate gear 445, and transmits the rotational force F from the rotating shaft 401a of the rotary drive unit 401 to a coupling gear 2ak that transmits to the black developing device 2k (and its developing roller 21k). The first intermediate gear 441 transmits the rotational force F from the rotating shaft 401a of the rotary drive unit 401 to the second intermediate gear 442. The second intermediate gear 442 transmits the rotational force F from the first intermediate gear 441 to the third intermediate gear 443. The third intermediate gear 443 transmits the rotational force F from the second intermediate gear 442 to the fourth intermediate gear 444. The fourth intermediate gear 444 transmits the rotational force F from the third intermediate gear 443 to the fifth intermediate gear 445. The fifth intermediate gear 445 transmits the rotational force F from the fourth intermediate gear 444 to the coupling gear 2ak, which transmits the rotational force F to the black developing device 2k. In this embodiment, the coupling gear 2ak is formed on the same axis as the fifth intermediate gear 445.

[0047] The fifth gear train 450 comprises a first intermediate gear 451, a rotational force transmission device 200, and gears 452 through 455, and transmits rotational force F from the first intermediate gear 441 of the fourth gear train 440 to coupling gears 2ac, 2am, and 2ay, respectively, which transmit to the cyan, magenta, and yellow developing units 2c, 2m, and 2y (and their developing rollers 21y, 21m, and 21c). The first intermediate gear 451 transmits rotational force F from the first intermediate gear 441 of the fourth gear train 440 to the input gear section 211 of the input gear 210 in the rotational force transmission device 200. The external teeth 232 (output gear section) of the output gear 230 in the rotational force transmission device 200 transmit to the second intermediate gear 452 and the third intermediate gear 453, respectively. The second intermediate gear 452 and the third intermediate gear 453 transmit power to coupling gears 2ac and 2am, respectively, which transmit power to the cyan and magenta developing units 2c and 2m (and their developing rollers 21c and 21m). The fourth intermediate gear 454 transmits the rotational force F from the third intermediate gear 453 to the fifth intermediate gear 455. The fifth intermediate gear 455 transmits the rotational force F from the fourth intermediate gear 454 to the coupling gear 2ay, which transmits power to the yellow developing unit 2y (and its developing roller 21y). In this embodiment, coupling gear 2ac is formed on the same axis as the second intermediate gear 452, coupling gear 2am is formed on the same axis as the third intermediate gear 453, and coupling gear 2ay is formed on the same axis as the fifth intermediate gear 455.

[0048] In the drive unit 400 described above, when the rotary drive unit 401 is rotated while the rotational force transmission device 200 is not operating (off state = non-operating state), the rotational force transmission device 200 does not transmit the rotational force F from the rotary drive unit 401 to the coupling gears 2ay, 2am, 2ac. Therefore, the developing rollers 21y, 21m, and 21c of the developing units 2y, 2m, and 2c, which develop with color toner respectively, remain stopped. On the other hand, the belt 71 and the developing roller 21k of the photoreceptor drums 3y, 3m, 3c, 3k and the developing unit 2k for monochrome photography rotate in response to the rotational force F from the rotary drive unit 401. As a result, the electrostatic latent image formed on the surface of the photoreceptor drum 3k can be developed by the developing roller 21k to form a monochrome image. At this time, since the developing rollers 21y, 21m, and 21c are stopped and not rotating, wear of the corresponding color toner due to rotation can be prevented. From this state, if the rotational force transmission device 200 is activated (on state = operating state), or if the rotational drive unit 401 is rotated while the rotational force transmission device 200 is activated, the rotational force transmission device 200 transmits the rotational force F from the rotational drive unit 401 to the coupling gears 2ay, 2am, 2ac, causing the developing rollers 21y, 21m, 21c of the color toner developing unit 2y, 2m, 2c to rotate. Here, the belt 71 and the developing roller 21k of the photoreceptor drums 3y, 3m, 3c, 3k and the monochrome developing unit 2k are rotating in response to the rotational force F from the rotational drive unit 401, so a color image can be formed by developing the electrostatic latent image formed on the surface of the photoreceptor drums 3y, 3m, 3c, 3k with the developing rollers 21y, 21m, 21c, 21k.

[0049] (Regarding this embodiment) Figure 9 is an exploded perspective view showing an input gear 210, carrier 220, and output gear 230 in an example of a rotational force transmission device 200 according to this embodiment. Figure 10 is an exploded perspective view showing the output gear 230 mounted on the input gear 210 in Figure 9.

[0050] Figure 11 is a front view showing the state in which the moving device 300 has positioned the moving member 310 at a rotation-permitted position P2 that allows the carrier 220 to rotate. Figures 12 and 13 show the state in which the moving device 300 has positioned the moving member 310 at a rotation-stop position P1 that stops the rotation of the carrier 220. In particular, Figure 12 shows the state just before the contact portion 311 of the moving member 310 contacts the engaging portion 221 of the rotating carrier 220, and Figure 13 is a front view showing the state after the contact portion 311 has contacted the engaging portion 221 (the state in which the rotation of the carrier 220 has stopped).

[0051] In the rotational force transmission device 200 according to this embodiment, the configuration is the same as the rotational force transmission device 200X shown in Figures 17 to 20, except for the configuration of the engaging portions 221-221 on the carrier 220 and the contact portion 311 on the movable member 310. Therefore, the configuration common to the rotational force transmission device 200X will be explained first, and the differences from the rotational force transmission device 200X will be explained in detail later.

[0052] As shown in Figures 7 to 13, the rotational force transmission device 200 according to this embodiment includes an input gear 210, a carrier 220, a moving member 310, and an output gear 230.

[0053] The input gear 210 has an input gear section 211 and a sun gear section 212. The input gear section 211 receives a rotational force F from the rotary drive unit 401 and rotates around the rotation axis α. The sun gear section 212 has a smaller outer diameter than the input gear section 211 and rotates together with the input gear section 211 around the rotation axis α. Specifically, the input gear 210 has the input gear section 211 integrally provided on the outer circumferential surface of a disc-shaped input gear body 213 centered on the rotation axis α. The input gear 210 also has the sun gear section 212 integrally provided on the side of the input gear body 213 on the carrier 220 and output gear 230 side. The input gear body 213 and the sun gear section 212 have a circular through hole 210a centered on the rotation axis α. Here, "hole" means a protruding "hole". The rotating shaft 201 is inserted through the through-hole 210a.

[0054] The carrier 220 is a rotating body having engaging parts 221-221 that receives a rotational force F from the input gear 210 and rotates around the rotation axis α. The carrier 220 has a disc-shaped carrier body 224 which is a rotating body that can rotate around the rotation axis α, a plurality of (three in this example) planetary gears 222-222, a plurality of support shafts 223-223 which each support the plurality of planetary gears 222-222, and one or more (nine in this example) engaging parts 221-221.

[0055] Here, the multiple support shafts 223-223 are integrally erected on the side surface of the disc-shaped carrier body 224 facing the input gear 210 and output gear 230, such that the rotation axes of each of the multiple support shafts 223-223 are parallel to the rotation axis α and are arranged at equal intervals around the rotation axis α. Each of the multiple support shafts 223-223 rotatably supports the planetary gears 222-222 (see Figures 17 and 18).

[0056] The planetary gears 222-222 are gears that mesh with the sun gear section 212 of the input gear 210 and the output gear 230, which will be explained in detail later. These gears transmit the rotational force F from the input gear 210 to the output gear 230 or to the carrier body 224 of the carrier 220. The mechanism for transmitting this rotational force F will be described later.

[0057] As shown in Figures 9 to 12, the engaging portion 221 is a part that stops the rotation of the carrier 220 (the disc-shaped carrier body 224) around the rotation axis α by contacting the contact portion 311 provided on the movable member 310, which will be described later. It is formed as a wall portion provided on the side of the carrier body 224 opposite to the side on which the multiple planetary gears 222~222 are provided, so as to be aligned with both the rotation axis direction W and the radial direction E centered on the rotation axis α. More specifically, a projection 225 is provided integrally on the side of the carrier body 224 opposite to the side on which the multiple planetary gears 222~222 are provided, having multiple V-shaped portions 225a~225a that are high in the radial direction E of the rotation axis α. Of the wall portions that make up the projection 225, the wall portion that is downstream with respect to a predetermined first rotation direction R1 in which the carrier body 224 rotates becomes the engaging portion 221. Furthermore, the carrier body 224 and the protruding portion 225 have a circular through-hole 220a centered on the rotation axis α, and the rotation shaft 201 is inserted through the through-hole 220a.

[0058] The output gear 230 is provided between the input gear 210 and the carrier 220 in the direction of the rotation axis W. The output gear 230 is a gear rotatable around the rotation axis α and has an output gear body 233 including a cylindrical portion in which an internal tooth portion (meshing gear portion) 231 and an external tooth portion 232 (output gear portion) are formed, and a disc portion extending radially along the rotation axis α in which a through hole 230a through which the sun gear portion 212 is inserted is formed. The internal tooth portion 231 is a gear that meshes with a plurality of planetary gears 222~222 and is provided on the inner surface (rotation axis α side) of the cylindrical portion of the output gear 230 in the radial direction E centered on the rotation axis α. The external tooth portion 232 is provided on the outer surface of the cylindrical portion in the radial direction E of the rotation axis α and transmits rotational force F. The through-hole 230a is provided in a disc portion connected to the input gear 210 side surface of the cylindrical portion where the internal teeth 231 and external teeth 232 are formed.

[0059] As shown in Figures 7 and 8, and Figures 11 to 13, the rotational force transmission device 200 according to this embodiment has a contact portion 311 that can contact the engaging portion 221 of the carrier 220, and for a carrier 220 that rotates in a predetermined first rotational direction R1 by receiving rotational force from the input gear 210, it comprises a movable member 310 that can move between a rotation stop position P1 in which the contact portion 311 contacts the engaging portion 221 to stop the rotation of the carrier 220 and a rotation allowable position P2 in which the contact portion 311 is separated from the engaging portion 221 and rotation of the carrier 220 in the first rotational direction R1, and a movable device 300 that moves the movable member 310 from the rotation allowable position to the rotation stop position.

[0060] The movable member 310 is capable of swinging between a rotation-stop position P1 (see Figure 13) where the contact portion 311 is locked to the engagement portion 221 of the carrier 220 and a rotation-permitted position P2 (see Figure 11) where the contact portion 311 is not locked to the engagement portion 221, and includes a swinging portion 310a that swings around a first swing axis β1 along the rotation axis α, a first arm portion 310b that extends radially from the swinging portion 310a in the direction of the first swing axis β1 and has a contact portion 311 at its tip, and a second arm portion 310c that extends radially from the swinging portion 310a in a direction different from the first arm portion 310b in the direction of the first swing axis β1 and has its tip connected to an electromagnetic solenoid and a biasing member 320 which will be described later. The first arm portion 310b is selectively movable between a rotation-stop position P1 in which the contact portion 311 (provided at the tip) engages with the engagement portion 221 of the carrier 220, and a rotation-permitted position P2 in which it is not engaged with the engagement portion 221 of the carrier 220, by the oscillation of the swinging portion 310a around the first oscillation axis β1.

[0061] The rotational force transmission device 200 has a moving device 300 that moves the movable member 310 from a rotation-permitted position P2 in which it is not engaged with the engaging portion 221 to a rotation-stopping position P1 in which it is engaged with the engaging portion 221, and the moving device 300 includes an electromagnetic solenoid 301.

[0062] The electromagnetic solenoid 301 comprises a main body 301a containing an electromagnet and a plunger (movable piece) 301b that moves in a predetermined direction when power is supplied to the electromagnet. The main body 301a of the electromagnetic solenoid 301 is fixed to the subframe FL1, and one end of the plunger 301b is connected to the tip of the second arm portion 310c. When the electromagnetic solenoid 301 is ON, it attracts the plunger 301b, and when it is OFF, it releases the attraction of the plunger 301b. Here, ON is the operating state in which power is supplied to the electromagnet of the electromagnetic solenoid 301 = power supply state, energized state. OFF is the non-operating state in which power is not supplied to the electromagnet of the electromagnetic solenoid 301 = non-power supply state, unenergized state.

[0063] The moving device 300 further includes a biasing member 320. One end 321 of the biasing member 320 is connected to the tip of the second arm portion 310c, and the other end 322 is connected to the subframe FL1. Therefore, the biasing member 320 provides a biasing force to the moving member 310 in the direction that moves it to the rotation-permissible position P2, and also provides a biasing force to the plunger 301b connected to the tip of the second arm portion 310c that moves it in the direction opposite to the attraction direction of the electromagnet.

[0064] Because the moving device 300 has the above configuration, when it is ON (power supplied, energized), the plunger 301b is attracted against the biasing force of the biasing member 320, causing the first arm portion 310b to swing around the first oscillation axis β1 and come into contact with (engage with) the engagement portion 221 on the carrier 220. In other words, when the moving device 300 is ON, it can move the moving member 310 from the rotation-permitted position P2 to the rotation-stopped position P1 against the biasing force of the biasing member 320. On the other hand, when the moving device 300 is OFF (no power supplied, not energized), the first arm portion 310b swings around the first oscillation axis β1 due to the biasing force of the biasing member 320 and moves to the rotation-permitted position P2.

[0065] Here, the mechanism for transmitting rotational force F from the rotational drive unit 401 in the rotational force transmission device 200 will be explained in detail.

[0066] When the rotary drive unit 401 is rotating and the moving device 300 is off (no power supply and no energization), that is, when the input gear 210 is receiving a rotational force F from the rotary drive unit 401 and rotating around the rotation axis α, and the moving device 300 is off and the moving member 310 is in the rotation-permissible position P2, the output gear 230 is receiving a rotational load from the developing devices 2y, 2m, 2c via the coupling gears 2ac, 2am, 2ay and is therefore stationary. At this time, the planetary gears 222~222 that mesh with the sun gear portion 212 of the input gear 210 and the internal teeth portion 231 of the output gear 230 attempt to rotate in response to the rotational force F from the input gear 210, but since the output gear 230 is stopped by the developing load, the carrier body 224 rotates in the opposite direction to the rotation direction of the input gear 210 via the multiple support shafts 223~223. In other words, since the rotational force F from the input gear 210 is not transmitted to the output gear 230, the output gear 230 remains stationary, and instead the carrier 220 rotates by receiving the rotational force F from the input gear 210 (see Figure 11).

[0067] Next, while the input gear 210 is rotating around the rotation axis α due to the rotational force F from the rotation drive unit 401, when the moving device 300 is turned on and the moving member 310 moves to the rotation stop position P1, the carrier 220, which was rotating due to the rotational force F from the input gear 210, stops rotating because the contact portion 311 is locked against the engagement portion 221 (Figure 13). At this time, the carrier 220 stops, but the input gear 210 and the sun gear section 212 are rotating, so the planetary gears 222~222 meshing with the sun gear section 212 transmit rotational force F to the output gear 230. In other words, when the rotation of the carrier 220 is restricted by the moving member 310, the rotational force F from the rotation drive unit 401 is transmitted to the internal teeth 231 of the output gear 230, causing the output gear 230 to rotate, and thus the developing rollers 21y, 21m, and 21c of the developing devices 2y, 2m, and 2c rotate.

[0068] As described above, when the input gear 210 is rotating, the moving device 300 is turned ON (energized), which moves the moving member 310 (the first arm portion 310b) to the rotation stop position P1, stopping the rotation of the carrier 220 around the rotation axis α. This allows the output gear 230 to rotate. On the other hand, when the moving device 300 is turned OFF (not energized) while the input gear 210 is rotating, the moving member 310 (the first arm portion 310b) is moved by the biasing member 320 to the rotation-permitted position P2, allowing the carrier 220 to rotate. As a result, the output gear 230 remains stationary under load from the developing devices 2c, 2m, and 2y, while the carrier 220 rotates instead.

[0069] In other words, when the movable member 310 is in the rotation-permissible position P2 and rotating in the first rotation direction R1, the carrier 220 does not transmit the rotational force F from the input gear 210 to the output gear 230, and when the movable member 310 is in the rotation-stop position P1 and the input gear 210 is rotating in a direction that rotates the carrier 220 in the first rotation direction R1, the carrier 220 transmits the rotational force F from the input gear 210 to the output gear 230.

[0070] Furthermore, the input gear 210 of the rotational force transmission device 200 has a sun gear section 212 that has a smaller outer diameter than the input gear 210 and rotates integrally with the input gear 210. The carrier 220 of the rotational force transmission device 200 has a plurality of planetary gears 222-222 that are rotatably supported on the carrier 220 and mesh with the sun gear section 212. In addition, the output gear 230 of the rotational force transmission device 200 has an internal tooth section 231 that meshes with the plurality of planetary gears 222-222.

[0071] As described above, the rotational force transmission device 200 transmits the rotational force F of the input gear 210 to the output gear 230 when the engaging portion 221 of the carrier 220 is in contact with the moving member 310 of the moving device 300, that is, when the moving member 310 is in the rotation stop position P1. When the contact between the engaging portion 221 of the carrier 220 and the moving member 310 of the moving device 300 is released, that is, when the moving member 310 is in the rotation allowable position P2, the rotational force F of the input gear 210 is not transmitted to the output gear 230.

[0072] As mentioned above, the carrier 220 rotates around the rotation axis α by receiving a rotational force F from the input gear 210, and the movable member 310 has a contact portion 311. The contact portion 311 can contact the engaging portion 221 on the carrier 220 so that the carrier 220, which is rotating in a predetermined first rotation direction R1, stops, and the movable member 310 is movable between a rotation-permitted position P2 (see Figure 11) and a rotation-stop position P1 (see Figures 12 and 13). The rotation-permitted position P2 is a position in which the rotation of the carrier 220 is permitted because the contact portion 311 does not contact the engaging portion 221. The rotation-stop position P1 is a position in which the rotation of the carrier 220 is stopped because the contact portion 311 contacts the engaging portion 221.

[0073] Here, the engaging portion 221 of the carrier 220 is shaped to receive a rotational force F from the input gear 210 when the carrier 220 rotates in the first rotational direction R1 while in contact with (engaged with) the contact portion 311 of the movable member 310, thereby generating a biasing force H (see Figure 13) that biases the contact portion 311 of the movable member 310 toward the rotation axis α. In other words, when the carrier 220, which is rotating in response to the rotational force F from the rotation drive unit 401, is stopped from rotating by the movable member 310, the engaging portion 311 of the movable member 310 is shaped to generate a biasing force H based on the reaction force acting on the contact portion 311 of the movable member 310. Note that the contact portion 311 of the movable member 310 may be shaped in any way as long as it can contact the engaging portion 221 of the carrier 220 rotating in the first rotational direction R1, stop the rotation of the carrier 220, and receive a biasing force H from the engaging portion 221 as a result of the carrier 220 stopping. In this example, the contact portion 311 is formed in a shape that corresponds to the shape of the engaging portion 221.

[0074] In this embodiment, the engaging portion 221 of the carrier 220 receives rotational force F from the input gear 210 via planetary gears 222-222, and when it is in contact (engaged) with the contact portion 311 of the moving member 310, it generates a biasing force H that biases the contact portion 311 toward the rotation axis α, based on the reaction force of the rotational force F. Therefore, after the moving member 310 is moved to the rotation stop position P1 and the contact portion 311 comes into contact with the engaging portion 221, as long as the rotation drive unit 401 is generating rotational force F, the moving device 300 does not need to be constantly energized, and the biasing force H prevents the moving member 310 from moving to the rotation-permitted position P2. In other words, the moving member 310 can be held at the rotation stop position P1. Consequently, since the moving device 300 does not need to be constantly energized (only momentarily), a decrease in the driving capacity of the moving device 300 (due to continuous energization) can be effectively prevented. Furthermore, since the engaging portion 221 is formed in a shape that generates a biasing force H, the movable member 310 can be made into a simple structure.

[0075] Thus, according to this embodiment, even though the movable member 310 has a simple configuration, when the movable member 310 is maintained at the rotation stop position P1, a decrease in the driving capacity of the moving device 300 can be effectively prevented.

[0076] <First Embodiment> In this embodiment, the engaging portion 221 of the carrier 220 has a first engaging surface 221a (an example of an engaging surface) (see Figure 13) that extends outward from the rotation axis α side toward the downstream side in the first rotation direction R1, intersecting the first rotation direction R1 when the engaging portion 221 is in contact with the contact portion 311 of the movable member 310 located at the rotation stop position P1.

[0077] Here, the first engagement surface 221a of the engagement portion 221 is configured to extend outward from the rotation axis α side toward the downstream side in the first rotation direction R1. In other words, the engagement portion 221 is inclined in the circumferential direction of the rotation axis α such that the distance from the rotation axis α increases as it moves toward the downstream side in the first rotation direction R1, and has a first engagement surface 221a (biasing force generating portion, engagement surface) facing toward the rotation axis α.

[0078] This configuration allows the carrier body 224 to generate a biasing force H that biases the movable member 310 (the contact portion 311) that abuts against the first engagement surface 221a toward the rotation axis α due to the rotational force F (and its reaction force) received from the input gear 210.

[0079] As described above, the engaging portion 221 has a biasing force generating portion (first engaging surface 221a) that receives the rotational force from the input gear 210 and biases the moving member 310 toward the rotation axis α when the moving member 310 is in the rotation stop position P1 and the input gear 210 is rotating due to the rotational force F.

[0080] As a result, even without maintaining the ON state of the moving device 300, the biasing force H generated at the first engagement surface 221a can reliably hold the moving member 310 in the rotation stop position P1.

[0081] <Second Embodiment> In this embodiment, as shown in Figure 13, when the engaging portion 221 of the carrier 220 is in contact with the contact portion 311 of the movable member 310 located at the rotation stop position P1, the virtual straight line γ passing through the first end 2211 and the second end 2212 of the first engaging surface 221a passes upstream of the rotation axis α in the first rotation direction R1 when viewed from the rotation axis direction W along the rotation axis α. Here, the first end 2211 is the end of the first engaging surface 221a opposite to the rotation axis α side. The second end 2212 is the end of the first engaging surface 221a on the rotation axis α side.

[0082] In other words, the first engagement surface 221a (engagement surface) has a first end 2211 which is the end that is farther from the axis of rotation α, and a second end 2212 which is the end that is closer to the axis of rotation. The virtual straight line γ passing through the first end 2211 and the second end 2212 passes upstream of the axis of rotation α in the first rotation direction R1 when viewed from the rotation axis direction W along the axis of rotation α.

[0083] Furthermore, the first engagement surface 221a (engagement surface) has a first end 2211 which is the end on the side farther from the axis of rotation α, and a second end 2212 which is the end on the side closer to the axis of rotation α. ​​The first end 2211 can also be said to be located downstream in the first rotation direction R1 with respect to a virtual straight line λ in the radial direction E passing through the second end 2212 and the axis of rotation α.

[0084] In this configuration, since the virtual straight line γ passes upstream of the rotation axis α in the first rotation direction R1, a biasing force H can be reliably generated that biases the contact portion 311 of the movable member 310 that abuts against the first engagement surface 221a toward the rotation axis α.

[0085] As a result, even without maintaining the ON state of the moving device 300, the biasing force H generated at the first engagement surface 221a can reliably hold the moving member 310 in the rotation stop position P1.

[0086] In this example, the first engagement surface 221a is a plane, and the virtual line γ lies along the first engagement surface 221a. The angle θ between the virtual line γ and the virtual reference line δ passing through the axis of rotation α and the second end 2212 is acute (for example, 45 degrees or less, preferably 30 degrees or less, 15 degrees in this example). The engagement portion 221 further has a second engagement surface 221b adjacent to the first engagement surface 221a on the inside in the radial direction E, extending downstream in the first rotation direction R1 from the second end 2212 of the first engagement surface 221a. The angle φ between the virtual line γ and the tangent line ε at the second end 2212 of the second engagement surface 221b is acute (for example, 45 degrees or more, preferably 60 degrees or more, 70 degrees in this example). Furthermore, the contact portion 311 has a contact surface 311a that contacts the first engagement surface 221a, and a projection 311c that extends outward in the radial direction E from the outer end 311b of the contact surface 311a in the radial direction E and protrudes upstream in the first rotation direction R1. This ensures that the movable member 310 is reliably maintained in the rotation stop position P1 while in contact with the contact portion 2213 of the second engagement surface 221b.

[0087] <Third Embodiment> As described above, the moving device 300 according to this embodiment includes a biasing member 320 (a coil spring in this example) and an electromagnetic solenoid 301. The biasing member 320 applies a biasing force to the moving member 310 that biases it toward the rotation-permissible position P2. When energized, the electromagnetic solenoid 301 moves the moving member 310 toward the rotation-stop position P1 against the biasing force of the biasing member 320.

[0088] In other words, the moving device 300 includes a biasing member 320 that applies a biasing force to the moving member 310 in a direction that biases it to move to a rotation-permitted position P2, and an electromagnetic solenoid 301 that has a plunger (movable piece) 301b that moves when energized, and moves the moving member 310 to a rotation-stop position P1 against the biasing force of the biasing member 320 by the movement of the plunger 301b.

[0089] In this configuration, when the rotation drive unit 401 is rotated in the opposite direction to the rotational force F, that is, when the carrier 220 is rotated in the second rotational direction R2 which is opposite to the first rotational direction R1, the biasing force of the biasing member 320 can reliably release the contact between the contact portion 311 of the moving member 310 and the engaging portion 221 of the carrier 220. Therefore, the moving member 310 can be reliably moved from the rotation stop position P1 to the rotation-allowed position P2.

[0090] By the way, in the conventional rotational force transmission device 200X shown in Figures 17 to 20, if the moving member 310X is to be kept at the rotation stop position P1 (see Figure 20), that is, if the developing devices 2y, 2m, and 2c are to be driven continuously, the electromagnetic solenoid 301 of the moving device 300 must be kept energized. Therefore, if the developing devices 2y, 2m, and 2c are driven for a long period of time, the electromagnetic solenoid 301 may overheat, reducing the attractive force, causing the moving member 310X to move to the rotation-permitted position P2, and potentially causing the driving of the developing devices 2y, 2m, and 2c to stop unexpectedly.

[0091] In this respect, in this embodiment, the engaging portion 221 of the carrier 220 generates a biasing force H that biases the contact portion 311 of the movable member 310 toward the rotation axis α. Therefore, even without constantly energizing the electromagnetic solenoid 301, the movable member 310 can be held in the rotation stop position P1 by the biasing force H. Accordingly, a decrease in the driving capacity of the moving device 300 can be effectively prevented.

[0092] <Fourth Embodiment> In this embodiment, the movable member 310 has a swinging portion 310a, a first arm portion 310b, and a second arm portion 310c. The swinging portion 310a is capable of swinging around a swing axis (first swing axis β1) along the rotation axis α. The first arm portion 310b extends from the swinging portion 310a toward the engagement portion 221 on the carrier 220 and has a contact portion 311 at its tip. The second arm portion 310c extends in a direction different from the direction extending from the swinging portion 310a to the first arm portion 310b and its tip is connected to the electromagnetic solenoid 301. In this example, the oscillation axis (β1) is located downstream of the virtual reference line δ in the first rotation direction R1, and the angle ω between the virtual line λ passing through the oscillation axis (β1) and the rotation axis α and the virtual line γ passing through the first end 2211 and the second end 2212 is acute (for example, 45 degrees or less, preferably 30 degrees or less, and 15 degrees in this example).

[0093] In other words, the movable member 310 includes a swinging part 310a that can swing around a swinging axis (first swinging axis β1) along the rotation axis α, a first arm part 310b that extends from the swinging part 310a in the radial direction of the swinging axis and has a contact part 311 at its tip, and a second arm part 310c that extends from the swinging part 310a in a radial direction of the swinging axis different from that of the first arm part 310b and has its tip connected to the movable piece of the electromagnetic solenoid 301 and the biasing member 320.

[0094] In this configuration, despite its simple structure consisting of a swinging part 310a, a first arm part 310b, and a second arm part 310c, the movable member 310 can be easily moved between the rotation-permitted position P2 and the rotation-stop position P1.

[0095] <Fifth Embodiment> Here, an example of a rotational force transmission device 200 having an engaging portion 221 having a different shape and a contact portion 311 that contacts this engaging portion 221 having a different shape will be described using Figure 14. Here, Figure 14 is an enlarged front view showing the state in which the engaging portion 221 and the contact portion 311 of the carrier 220 are in contact.

[0096] In this embodiment, as shown in Figure 14, the engaging portion 221 of the carrier 220 has a protruding portion 211c at its tip that protrudes downstream in the first rotation direction R1 (towards the contact portion 311 of the movable member 310). The contact portion 311 of the movable member 310 has a retracting portion 311d into which the protruding portion 211c engages. Examples of the shape of the protruding portion 211c include a convex rectangular shape, a convex arc shape, and a convex semicircular shape. Examples of the shape of the retracting portion 311d include shapes corresponding to the shape of the protruding portion 211c, such as a concave rectangular shape, a concave arc shape, and a concave semicircular shape. In this example, the protruding portion 211c is formed in a convex semicircular shape, and the retracting portion 311d is formed in a concave semicircular shape.

[0097] <Sixth Embodiment> Figure 15 is a schematic block diagram showing the system configuration of the control unit 110 in the image forming apparatus 100.

[0098] In this embodiment, the image forming apparatus 100 further comprises a control unit 110. The control unit 110 controls the entire image forming apparatus 100. As shown in Figure 15, the control unit 110 realizes various functions by reading and executing various programs stored in the storage unit 112 (for example, storage or ROM). The control unit 110 may be realized by one or more control devices / arithmetic units [CPU (Central Processing Unit), SoC (System on a Chip)]. Alternatively, the control unit 110 may be composed of one or more control circuits. The control unit 110 has a processing unit 111 consisting of a microcomputer such as a CPU, and a storage unit 112 including non-volatile memory such as ROM and volatile memory such as RAM. The control unit 110 controls the operation of various components by having the processing unit 111 load a control program pre-stored in the ROM of the storage unit 112 onto the RAM of the storage unit 112 and execute it.

[0099] The control unit 110 comprises a moving device control unit Q1, a rotary drive unit control unit Q2, and an image forming processing execution unit Q3. The moving device control unit Q1 controls the energizing timing of the moving device 300 (electromagnetic solenoid 301 in this example). The rotary drive unit control unit Q2 controls the driving timing of the rotary drive unit 401. The image forming processing execution unit Q3 executes image forming processing.

[0100] When the control unit 110 transmits the rotational force F of the input gear 210 to the output gear 230, it drives the rotation drive unit 401, then energizes (turns on) the moving device 300 to move the moving member 310 to the rotation stop position P1. After that, it maintains the drive to the rotation drive unit 401, and after a predetermined driving time has elapsed since the moving device 300 was energized, it de-energizes (turns off) the moving device 300, while maintaining the drive to the rotation drive unit 401. In other words, after the rotation drive unit 401 is driven, the control unit 110 de-energizes the moving device 300 after a predetermined driving time has elapsed since the moving device 300 was energized. Here, the "predetermined driving time" of the moving device 300 is the time required to move the moving member 310 from the rotation-permitted position P2 to the rotation stop position P1, or a time longer.

[0101] In this configuration, the control unit 110 energizes the moving device 300 to move the moving member 310 to the rotation stop position P1, and after a predetermined driving time has elapsed, it deenerges the moving device 300 and continues driving the rotation drive unit 401. Therefore, when the moving member 310 is maintained at the rotation stop position P1, the energized time of the moving device 300 can be shortened as much as possible, thereby suppressing a decrease in the driving capacity of the moving device 300.

[0102] <Seventh Embodiment> In this embodiment, when the control unit 110 stops transmitting rotational force F to the output gear 230, that is, when it stops driving the developing devices 2c, 2m, and 2y, it first stops driving the rotary drive unit 401, then rotates the rotary drive unit 401 in the direction opposite to the rotational force F to rotate the carrier 220 by a predetermined angle in the second rotation direction R2, which is opposite to the first rotation direction R1, and then stops the rotary drive unit 401. Here, the "predetermined rotation angle" of the carrier 220 refers to the rotation angle corresponding to the circumferential travel distance at which the contact portion 311 of the moving member 310 can release contact with the engaging portion 221 of the carrier 220.

[0103] In this configuration, the control unit 110 rotates (moves) the carrier 220 by a predetermined rotation angle in the second rotation direction R2, and then stops the rotation drive unit 401. This ensures that the contact between the contact portion 311 of the moving member 310 and the engaging portion 221 of the carrier 220 is reliably released by the biasing force of the biasing member 320. Therefore, the moving member 310 can be reliably moved from the rotation stop position P1 to the rotation allowable position P2.

[0104] [Timing Chart] Figure 16 is a timing chart illustrating the control by which the control unit 110 controls the rotary drive unit 401 and the moving device 300 to enter a rotational force transmission state in which the rotational force F of the rotary drive unit 401 is transmitted to the output gear 230, and then controls the rotary drive unit 401 to enter a rotational force non-transmission state in which the rotational force F of the rotary drive unit 401 is not transmitted to the output gear 230.

[0105] In Figure 16, t1 indicates the start timing of driving the rotary drive unit 401 in the first rotation direction R1, t2 / t3 indicate the start / end timing of power supply to the moving device 300, and t4 / t5 indicate the start / end timing of the image forming process. Furthermore, t6 indicates the stop timing of driving the rotary drive unit 401 in the first rotation direction R1 and the start timing of driving in the second rotation direction R2, and t7 indicates the stop timing of driving the rotary drive unit 401 in the second rotation direction R2.

[0106] By the way, as shown in Figures 19 and 20, in the conventional rotational force transmission device 200X, if the moving device 300 is not constantly energized in order to maintain the moving member 310X at the rotation stop position P1, the moving member 310X will move to the rotation-permitted position P2. Therefore, while the moving member 310X is positioned at the rotation stop position P1, the moving device 300 must be constantly energized, as shown by the dashed line τ in Figure 16. This reduces the driving capacity of the moving device 300, and even though it is necessary to stop the rotation of the carrier 220X, it may not be possible to position the moving member 310X at the rotation stop position P1, and thus the rotation of the carrier 220X cannot be stopped.

[0107] In this embodiment, the control unit 110 starts driving the rotary drive unit 401 in the first rotation direction R1 (t1), and energizes the moving device 300 after a predetermined first time T1 (t2-t1) has elapsed (t2). The energization of the moving device 300 by the control unit 110 is performed for a predetermined second time T2 (t3-t2), which includes the time required to move the moving member 310 to the rotation stop position P1. The control unit 110 then terminates the energization of the moving device 300 after the second time T2 has elapsed (t3). At this time, the biasing force H (see Figure 13) can prevent the moving member 310 from being positioned at the rotation-permitted position P2, that is, the moving member 310 can be held at the rotation stop position P1.

[0108] Next, the control unit 110 starts the image forming process (print job) (t4), and after the image forming process is completed (t5), it temporarily stops driving the rotary drive unit 401 in the first rotation direction R1 after a predetermined third time T3 (t6-t5) has elapsed (t6). Then, the control unit 110 drives the rotary drive unit 401 to start the input gear 210 rotating in the second rotation direction R2 (t6), and after a predetermined fourth time T4 (t7-t6) has elapsed, it stops driving the rotary drive unit 401 and stops driving the input gear 210 in the second rotation direction R2 (t7).

[0109] This ensures that the contact portion 311 of the movable member 310 is reliably released from contact with the engaging portion 221 of the carrier 220, and therefore the movable member 310 can be reliably moved from the rotation stop position P1 to the rotation allowable position P2.

[0110] As described above, the image forming apparatus 100 equipped with the rotational force transmission device 200 includes a control unit 110 that controls the energizing timing of the moving device 300 and the driving timing of the rotational drive unit 401. When the control unit 110 transmits the rotational force F from the input gear 210 to the output gear 230, it drives the rotational drive unit 401, energizes the moving device 300 to move the moving member 310 to the rotation stop position P1, and after a predetermined driving time (third time T3) has elapsed, it de-energizes the moving device 300 and continues driving the rotational drive unit.

[0111] As a result, even without maintaining the energized state (on state) of the moving device 300, the biasing force H generated at the first engagement surface 221a can reliably hold the moving member 310 in the rotation stop position P1.

[0112] Furthermore, when the control unit 110 stops transmitting rotational force F to the output gear 230, it controls the rotation drive unit 401 to rotate the carrier 220 by a predetermined rotational angle in a second rotational direction opposite to the first rotational direction, and then stops the rotation drive unit 401, thereby creating a state of no rotational force transmission where the output gear 230 does not rotate even if the rotation drive unit 401 is rotated.

[0113] This makes it easy to ensure that even when the rotary drive unit 401 is driven to form a monochrome image, the color developing units 2c, 2m, and 2y are not driven.

[0114] This disclosure is not limited to the embodiments described above, and can be implemented in a variety of other ways. Therefore, these embodiments are merely illustrative in all respects and should not be constrained. The scope of this disclosure is defined by the claims and is not restricted by the text of the specification. Furthermore, any variations or modifications falling within the equivalent scope of the claims are all within the scope of this disclosure. [Explanation of Symbols]

[0115] 100 Image forming apparatus 110 Control Unit 111 Processing Unit 112 Storage section 200 Rotational force transmission device 210 Input Gear 211 Input Gear Section 220 carriers 221 Engaging part 2211 First end 2212 Second end 2213 Contact part 221a First engagement surface (an example of an engagement surface) 221b Second engagement surface 230 Output Gear 300 Mobile devices 301 Electromagnetic Solenoid 301a Main Unit 301b Plunger (movable piece) 310 Movable member 310a Swivel part 310b First Arm Section 310c Second Arm Section 311 Contact part 320 Biasing member 400 Drive unit 401 Rotary drive unit 50 Image forming unit F Rotational force H biasing force P Sheet P1 Rotation stop position P2 Rotation tolerance position R1 First rotation direction R2 Second rotation direction T1 1st hour T2 2nd hour T3 3rd hour T4 4th hour W rotation axis direction X Width direction Y (depth direction) Z vertical direction α rotation axis β1 First oscillation axis (an example of an oscillation axis) β2 Second oscillation axis γ virtual line

Claims

1. An input gear that rotates around the axis of rotation by receiving rotational force from the rotary drive unit, A carrier having an engaging portion that receives rotational force from the input gear and rotates around the rotation axis, A movable member having a contact portion that can contact the engagement portion, and which is movable between a rotation stop position in which the contact portion contacts the engagement portion to stop the rotation of the carrier, and a rotation allowable position in which the contact portion is separated from the engagement portion to allow the carrier to rotate in the first rotation direction, with respect to the carrier which rotates in a predetermined first rotation direction by receiving a rotational force from the input gear, A moving device that drives the moving member from the rotation-permissible position to the rotation-stop position, An output gear that can rotate around the aforementioned axis of rotation, Equipped with, When the moving member is in the rotation-permissible position and rotating in the first rotational direction, the carrier does not transmit the rotational force from the input gear to the output gear. When the moving member is in the rotation stop position and the input gear is rotating in a direction that rotates the carrier in the first rotation direction, the rotational force from the input gear is transmitted to the output gear. The rotational force transmission device is characterized in that the engaging portion has a biasing force generating portion that receives rotational force from the input gear and biases the moving member toward the rotation axis when the moving member is in the rotation stop position and the input gear is rotating.

2. A rotational force transmission device according to claim 1, The rotational force transmission device is characterized in that the biasing force generating portion of the engaging portion is inclined in the circumferential direction of the rotation axis such that the distance from the central axis increases as it moves downstream in the first rotation direction, and has an engaging surface facing the rotation axis.

3. A rotational force transmission device according to claim 2, The engagement surface has a first end which is the end furthest from the axis of rotation, and a second end which is the end closest to the axis of rotation. A rotational force transmission device characterized in that a virtual straight line passing through the first end and the second end passes upstream of the rotation axis in the first rotational direction when viewed from the direction of the rotation axis along the rotation axis.

4. A rotational force transmission device according to claim 1, The moving device includes a biasing member that applies a biasing force to the moving member in a direction that moves the moving member to the rotationally permissible position, An electromagnetic solenoid having a movable piece that moves when energized, the movement of the movable piece moves the moving member against the biasing force of the biasing member to the rotation stop position, A rotational force transmission device characterized by having the following:

5. A rotational force transmission device according to claim 4, The rotational force transmission device is characterized in that the moving member comprises: a swinging part that can swing about a swinging axis along the rotation axis; a first arm part that extends from the swinging part in the radial direction of the swinging axis and has the contact part at its tip; and a second arm part that extends from the swinging part in a radial direction of the swinging axis different from that of the first arm part and has its tip connected to the movable piece of the electromagnetic solenoid and the biasing member.

6. A rotational force transmission device according to claim 1, The input gear has a sun gear section that has a smaller outer diameter than the input gear and rotates integrally with the input gear. The carrier has a plurality of planetary gears that are rotatably supported relative to the carrier and mesh with the sun gear section. The rotational force transmission device is characterized in that the output gear has internal teeth that mesh with the plurality of planetary gears.

7. An image forming apparatus comprising a rotational force transmission device according to any one of claims 1 to 6.

8. An image forming apparatus according to claim 7, The system further comprises a control unit that controls the energization timing of the moving device and the drive timing of the rotary drive unit, The image forming apparatus is characterized in that, when the control unit transmits rotational force from the input gear to the output gear, it drives the rotation drive unit, then energizes the moving device to move the moving member to the rotation stop position, de-energizes the moving device after a predetermined driving time has elapsed, and continues driving the rotation drive unit.

9. An image forming apparatus according to claim 8, The image forming apparatus is characterized in that, when the control unit stops transmitting rotational force to the output gear, it controls the rotation drive unit to rotate the carrier by a predetermined rotation angle in a second rotation direction opposite to the first rotation direction, and then stops the rotation drive unit, thereby creating a state of no rotational force transmission in which the output gear does not rotate even if the rotation drive unit is rotated.

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