Image forming device

Abstract

To provide an image forming apparatus that can arrange a cam and a cam follower in a compact manner, while achieving a function to retreat the cam follower.SOLUTION: An image forming apparatus comprises: a cam 150K; and a cam follower 170K that, with the rotation of the cam 150K, is slide-movable in a rotation axis direction of the cam 150K between a pressing position in contact with a cam surface 154 and a non-pressing position separated from the cam surface 154. The cam 150K has: a switching projection 156 that causes a switching lever 160 to swing between a transmission position where a driving force can be transmitted to a developing roller and a cut-off position where the driving force is not transmitted to the developing roller, and that is arranged on a surface on one side in the rotation axis direction of the cam 150K; and a first projection 157A that, when brought into contact with a linear motion plate 200 linearly moving forward from a first position to a second position, rotates the cam 150K to locate the cam follower 170K at the non-pressing position, and that is arranged on a surface on the other side in the rotation axis direction of the cam 150K.SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that includes a cam and a cam follower for moving a developing roller into and out of contact with a photosensitive drum. [Background technology]

[0002] Conventionally, an image forming apparatus has been known that includes a rotatable cam having a first cam portion and a second cam portion, a slide shaft portion that is slidable in the rotational axis direction of the cam, and a cam follower that extends from the slide shaft portion and has a contact portion that contacts the first cam portion (Patent Document 1). In this technology, the cam follower is slidable by the first cam portion of the rotating cam between a standby position where the developing roller is positioned to contact the photosensitive drum, and a protruding position where the cam follower presses against a developing cartridge having the developing roller to position the developing roller away from the photosensitive drum.

[0003] Also, with this technology, the image forming apparatus is provided with a clutch that can be switched between a transmission state in which the driving force from the motor is transmitted to the developing roller and a disconnection state in which the driving force is not transmitted to the developing roller, and a lever that swings while being guided by a second cam portion, and the clutch can be switched between the transmission state and the disconnection state by swinging the lever with the second cam portion of the rotating cam.Furthermore, with this technology, the image forming apparatus is provided with a release member that moves linearly in conjunction with the opening and closing of a cover that opens and closes an opening in a housing, and the linear movement of the release member causes a release engagement portion of the release member to come into contact with the arm of the cam follower, thereby rotating the cam follower and positioning the cam follower in a standby position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-015140 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in order to reduce the size of an image forming apparatus, it is desirable to have a configuration in which the cam and cam follower can be arranged compactly, while at the same time, it is desirable to realize a function for retracting the cam follower as necessary.

[0006] Therefore, an object of the present invention is to provide an image forming apparatus that can compactly arrange the cams and cam followers while realizing the function of retracting the cam followers. [Means for solving the problem]

[0007] An image forming apparatus having a first photosensitive drum, the image forming apparatus comprising: a first motor; a first developing cartridge having a first developing roller, the first developing cartridge being movable between a contact position where the first developing roller contacts the first photosensitive drum and a separation position where the first developing roller is separated from the first photosensitive drum; a first cam having a cam surface, the first cam rotating to move the first developing cartridge between the contact position and the separation position; a pressing position where the cam surface of the rotating first cam presses the first developing cartridge to position the first developing cartridge at the separation position; a first cam follower that is slidable in the direction of the rotation axis of the first cam between a first transmission position where the driving force from the first motor can be transmitted to the first developing roller and a first disconnection position where the driving force from the first motor is not transmitted to the first developing roller by rotation of the first cam; and a linear motion plate that moves linearly between the first position and the second position, and that comes into contact with the first cam when moving from the first position to the second position with the first cam follower in the pressing position, causing the first cam to rotate and position the first cam follower in the non-pressing position. The first cam has a switching protrusion that is capable of coming into contact with the switching lever and moves the switching lever between the first transmission position and the first disconnection position, the switching protrusion being arranged on one side surface of the first cam in the direction of the rotation axis, and a first protrusion that is capable of coming into contact with the linear plate and rotates the first cam when the linear plate comes into contact, the first protrusion being arranged on the other side surface of the first cam in the direction of the rotation axis.

[0008] According to this configuration, the first cam and the first cam follower can be arranged compactly while realizing the function of positioning the first cam follower in the non-pressing position.

[0009] The image forming apparatus may also include a housing having an opening, and a cover that is movable between a closed position that closes the opening and an open position that opens the opening, and the linear plate may be capable of linear movement between a first position, which is the position when the cover is in the closed position, and a second position, which is the position when the cover is in the open position, in conjunction with the movement of the cover between the closed position and the open position.

[0010] According to this, the first cam follower can be positioned in the non-pressing position by opening the cover, which makes it possible to prevent interference between the first developer cartridge and the first cam follower when installing or removing the first developer cartridge.

[0011] The cam surface may be disposed on one side of the first cam in the direction of the rotation axis.

[0012] This increases the degree of freedom in arranging the first protrusions on the surface opposite the cam surface, making it possible to prevent the first cam from becoming too large and to arrange the first cam and the linear motion plate in a compact manner.

[0013] In addition, the cam surface may have a retaining surface that retains the first cam follower in a pressing position, and the switching protrusion may be positioned so as to overlap with the retaining surface in a circumferential direction centered on the rotation axis of the first cam, when viewed from the direction of the rotation axis.

[0014] This allows the first cam and the first cam follower to have a compact configuration, which allows the first cam and the first cam follower to be arranged more compactly.

[0015] In addition, the first cam may have a disc portion, a gear portion formed on the outer periphery of the disc portion, and a flange portion formed on the outer periphery of the disc portion and located on one side of the gear portion in the direction of the rotation axis, and the switching protrusion may be arranged on the flange portion.

[0016] This allows the cam surface to be disposed close to the outer periphery of the disk portion, thereby ensuring the length of the cam surface in the rotation direction of the first cam while preventing the first cam from becoming too large.

[0017] The cam surface may be disposed on the surface of the first cam on the other side in the direction of the rotation axis.

[0018] This increases the degree of freedom in arranging the switching protrusion on the surface opposite the cam surface, making it possible to prevent the first cam from becoming too large and to arrange the first cam and the switching lever in a compact manner.

[0019] In addition, the cam surface may have a retaining surface that retains the first cam follower in a pressing position, and the first protrusion may be positioned at a position that overlaps with the retaining surface in a circumferential direction centered on the rotation axis of the first cam, when viewed from the rotation axis direction.

[0020] This allows the first cam and the first cam follower to have a compact configuration, which allows the first cam and the first cam follower to be arranged more compactly.

[0021] In addition, the first cam may have a disc portion, a gear portion formed on the outer periphery of the disc portion, and a flange portion formed on the outer periphery of the disc portion and located on the other side of the gear portion in the direction of the rotation axis, and the first protrusion may be arranged on the flange portion.

[0022] This allows the cam surface to be disposed close to the outer periphery of the disk portion, thereby ensuring the length of the cam surface in the rotation direction of the first cam while preventing the first cam from becoming too large.

[0023] The image forming apparatus may also be configured to include a second motor for rotating the first cam, the second motor being provided separately from the first motor.

[0024] This makes it possible to separately control the rotation and stopping of the first developing roller to which the driving force is transmitted from the first motor and the rotation and stopping of the first cam to which the driving force is transmitted from the second motor.

[0025] In addition, the linear plate may be configured to have a first contact piece that comes into contact with the first protrusion when the first cam follower is positioned in the pressing position and moves from the first position to the second position, and that, when coming into contact with the first protrusion, rotates the first cam and positions the first cam follower in the non-pressing position.

[0026] This allows the linear motion of the linear motion plate to be converted into the rotational motion of the first cam.

[0027] Furthermore, the first contact piece may be configured to retract and not rotate the first cam if it comes into contact with the first protrusion when the linear motion plate moves from the second position to the first position.

[0028] This makes it possible to prevent the position of the first cam follower from changing from the position before the linear motion plate moves when the linear motion plate moves from the second position to the first position.

[0029] In addition, the switching protrusion may be configured to move the switching lever to the first transmission position before the first developing cartridge moves to the contact position, and to move the switching lever to the first disconnection position after the first developing cartridge moves to the separated position.

[0030] According to this, the first developing roller can be rotated before it comes into contact with the first photosensitive drum, and can be stopped after it separates from the first photosensitive drum.

[0031] The image forming device may also include a planetary gear mechanism having an input element to which driving force from the first motor is input, an output element that outputs driving force toward the first developing roller, and a transmission element that can transmit driving force from the input element to the output element when rotation is restricted, but does not transmit driving force from the input element to the output element when rotation is not restricted, and the switching lever may be configured to restrict rotation of the transmission element when positioned in the first transmission position, and not restrict rotation of the transmission element when positioned in the first disconnection position.

[0032] The image forming apparatus may also be configured to include a control unit that rotates the first cam in a first rotational direction when the first developing cartridge is moved between the contact position and the separated position, and the linear plate may be configured to rotate the first cam in a second rotational direction opposite to the first rotational direction when moving from the first position to the second position with the first cam follower positioned in the pressing position, thereby positioning the first cam follower in the non-pressing position.

[0033] The switching lever may be pivotable around a pivot axis between a first transmission position and a first disconnection position, and the switching lever may include a first lever pivotable around the pivot axis and capable of contacting a switching protrusion, a second lever pivotable around the pivot axis and capable of engaging with a transmission element, a rotation regulating portion provided on the second lever that regulates rotation of the first lever in one direction relative to the second lever, and a first spring that urges the first lever to prevent it from rotating relative to the second lever when the rotation regulating portion provided on the second lever comes into contact with the first lever, and the image forming apparatus may further include a second spring that urges the second lever in a direction that urges it toward the transmission element, and when the second lever is engaged with the transmission element, the first cam rotates in a second rotation direction and the first lever is pressed by the switching protrusion, so that the first lever pivots relative to the second lever against the urging force of the first spring.

[0034] This prevents excessive force from being applied to the switching lever when the first cam rotates in the second rotation direction.

[0035] The image forming apparatus also includes a second photosensitive drum, a third photosensitive drum disposed downstream of the second photosensitive drum in the sheet transport direction, a fourth photosensitive drum disposed downstream of the third photosensitive drum in the transport direction, a second developing cartridge having a second developing roller movable between a contact position where the second developing roller contacts the second photosensitive drum and a separated position where the second developing roller is separated from the second photosensitive drum, and a third developing cartridge having a third developing roller movable between a contact position where the third developing roller contacts the third photosensitive drum and a separated position where the third developing roller is separated from the second photosensitive drum. a third developing cartridge movable between a contact position where the third developing roller is in contact with the fourth photosensitive drum and a separated position where the fourth developing roller is separated from the fourth photosensitive drum; a fourth developing cartridge having a fourth developing roller, movable between a contact position where the fourth developing roller is in contact with the fourth photosensitive drum and a separated position where the fourth developing roller is separated from the fourth photosensitive drum; a second cam having a cam surface, which rotates to move the second developing cartridge between the contact position and the separated position; and a third cam having a cam surface, which rotates in conjunction with the second cam, which rotates a third cam that moves the third developer cartridge between the contact position and the separated position by pressing the third cam; a fourth cam that has a cam surface and rotates in conjunction with the second cam and the third cam, and that moves the fourth developer cartridge between the contact position and the separated position by rotating; a second cam follower that is slidable in the direction of the rotation axis between a pressing position where the cam surface of the rotating second cam presses the second developer cartridge to position the second developer cartridge at the separated position and a non-pressing position where the second developer cartridge is positioned at the contact position; The configuration may include a third cam follower that can slide in the direction of the rotation axis between a pressing position where the cam surface of the cam presses the third developer cartridge to position the third developer cartridge at the separated position and a non-pressing position where the third developer cartridge is positioned at the contact position, and a fourth cam follower that can slide in the direction of the rotation axis between a pressing position where the cam surface of the rotating fourth cam presses the fourth developer cartridge to position the fourth developer cartridge at the separated position and a non-pressing position where the fourth developer cartridge is positioned at the contact position.

[0036] In addition, the linear plate may be configured such that when at least one of the second cam follower, the third cam follower, and the fourth cam follower is positioned in the pressing position, the linear plate rotates the second cam, the third cam, and the fourth cam to position the second cam follower, the third cam follower, and the fourth cam follower in the non-pressing position when moving from the first position to the second position.

[0037] According to this, the second cam follower, the third cam follower and the fourth cam follower can be positioned at the non-pressing position by the linear motion plate.

[0038] Furthermore, the second cam, the third cam and the fourth cam may be end face cams, and the cam surface of the second cam, the cam surface of the third cam and the cam surface of the fourth cam may be arranged so that the third cam follower starts to move from the non-pressing position towards the pressing position at a timing after the second cam follower has moved to the pressing position, the fourth cam follower starts to move from the non-pressing position towards the pressing position at a timing after the third cam follower has moved to the pressing position, and the second cam follower, the third cam follower and the fourth cam follower are simultaneously positioned at the pressing position.

[0039] This allows the timing at which force is applied to the cam follower to be shifted, thereby preventing the driving force for driving the cam from becoming too large.

[0040] Furthermore, one of the second cam, the third cam and the fourth cam may have a second protrusion protruding in the direction of the rotation axis, and the cam other than the cam having the second protrusion may have a third protrusion protruding in the direction of the rotation axis, and the linear plate may have a second contact piece that can come into contact with the second protrusion when moving from the first position to the second position when the cam follower corresponding to the cam having the second protrusion is positioned in the pressing position, the second contact piece rotating the second cam, the third cam and the fourth cam when coming into contact with the second protrusion, and a third contact piece that can come into contact with the third protrusion when moving from the first position to the second position, rotating the second cam, the third cam and the fourth cam when coming into contact with the third protrusion, and positioning the second cam follower, the third cam follower and the fourth cam follower at the non-pressing position, and the third contact piece may be arranged to come into contact with the third protrusion at a timing after the second contact piece comes into contact with the second protrusion when the linear plate moves from the first position to the second position.

[0041] This makes it possible to reliably rotate the second cam, which has a cam surface that is long in the rotation direction, and to reliably move the second cam follower from the pressing position to the non-pressing position.

[0042] In addition, the third contact piece may be arranged to come into contact with the third protrusion at a timing after the second contact piece moves away from the second protrusion when the linear motion plate moves from the first position to the second position.

[0043] This allows the linear motion plate and the cam to operate smoothly.

[0044] The image forming apparatus may also be configured to include a control unit that rotates the second cam, the third cam, and the fourth cam in a first rotational direction when moving the second developer cartridge, the third developer cartridge, and the fourth developer cartridge between the contact position and the separated position, and the linear plate may be configured to rotate the second cam, the third cam, and the fourth cam in a second rotational direction opposite to the first rotational direction when moving from the first position to the second position with at least the second cam follower positioned in the pressing position, thereby positioning the second cam follower, the third cam follower, and the fourth cam follower in the non-pressing position.

[0045] This allows the operating load of the linear motion plate to be reduced.

[0046] In addition, the cam surface of the second cam, the cam surface of the third cam, and the cam surface of the fourth cam may be arranged so that the timing when the second cam follower moves from the pressing position toward the non-pressing position, the timing when the third cam follower moves from the pressing position toward the non-pressing position, and the timing when the fourth cam follower moves from the pressing position toward the non-pressing position overlap with each other.

[0047] This allows the length of the cam surface in the rotation direction of the cam to be shortened, thereby reducing the rotation angle of the cam required to slide the cam follower between the non-pressing position and the pressing position, and also allowing the cam to be made smaller.

[0048] The image forming apparatus may also be configured to include a third motor for driving the second, third and fourth developing rollers, an input gear to which driving force from the third motor is input, an output gear that outputs driving force toward the second, third and fourth developing rollers, a movable gear that meshes with the input gear and is movable between a second transmission position in which it meshes with the output gear and a second disconnection position in which it does not mesh with the output gear, and a switching cam that rotates in conjunction with the second cam and moves the movable gear between the second transmission position and the second disconnection position by rotating.

[0049] This allows the developing roller to rotate when the developing cartridge is in the contact position, and to stop when the developing cartridge is in the separated position, thereby preventing the developing roller from rotating more than necessary.

[0050] In addition, the switching cam may be configured to move the moving gear to the second transmission position before the second developer cartridge moves to the contact position, and to move the moving gear to the second disconnection position after the fourth developer cartridge moves to the separated position.

[0051] This allows the second developing roller, the third developing roller, and the fourth developing roller to rotate before the second developing roller contacts the second photosensitive drum, and the second developing roller, the third developing roller, and the fourth developing roller to stop after the fourth developing roller separates from the fourth photosensitive drum. [Effects of the Invention]

[0052] According to the image forming apparatus described above, the first cam and the first cam follower can be arranged compactly while realizing the function of positioning the first cam follower at the non-pressing position. [Brief explanation of the drawings]

[0053] [Figure 1] FIG. 1 is a diagram illustrating an image forming apparatus according to a first embodiment. [Figure 2] 3A and 3B are diagrams illustrating a mechanism for transmitting a driving force to a photosensitive drum, a developing roller, and a cam. [Figure 3] FIG. 2 is a perspective view showing a cam, a cam follower, a second shaft, and a stopper. [Figure 4] 1A and 1B are diagrams illustrating a configuration for moving a developer cartridge, in which FIG. 1A shows the developer cartridge at a contact position and FIG. 1B shows the developer cartridge at a separated position. [Figure 5] 1A is a perspective view of a first cam as seen from the switching protrusion side, and FIG. 1B is a perspective view as seen from the first protrusion side. [Figure 6] 10A is a perspective view showing a first cam, a first cam follower, a switching lever, and a planetary gear mechanism when the first developing cartridge is in the contact position, and FIG. 10B is a side view thereof. [Figure 7]10A is a perspective view showing a first cam, a first cam follower, a switching lever, and a planetary gear mechanism when the first developing cartridge is in the separated position, and FIG. 10B is a side view thereof. [Figure 8] 10 is a timing chart illustrating the position of the cam follower (the position of the developing cartridge) and the driving state of the developing roller. [Figure 9] FIG. 10 is a side view showing the second cam, the third cam, and the fourth cam, and the second developing drive gear train when the movable gear is in the second transmission position. [Figure 10] FIG. 10 is a side view showing the second cam, the third cam, and the fourth cam, and the second developing drive gear train when the movable gear is at the second disconnection position. [Figure 11] 1A is an exploded perspective view of a planetary gear mechanism as seen from the transmission element side, and FIG. 1B is an exploded perspective view as seen from the output element side. [Figure 12] This is a side view showing the first cam, the switching lever, and the planetary gear mechanism, with (a) being a view after the first developing cartridge has moved to the separated position but before the first developing roller has stopped, and (b) being a view when the first developing roller has started to rotate but before the first developing cartridge has moved to the contact position. [Figure 13] 10 is a side view showing the second cam, the third cam, and the fourth cam, and the switch gear train when the movable gear is in the second transmission position. FIG. [Figure 14] 10 is a side view showing the second cam, the third cam, and the fourth cam, and the switching gear train when the movable gear is at the second disengagement position. FIG. [Figure 15] FIG. 4 is a side view showing the cam and the linear motion plate. [Figure 16] 10A and 10B are diagrams illustrating the operation of the contact piece when the contact piece comes into contact with the protrusion of the cam when the linear motion plate moves from the second position to the first position. [Figure 17] 4A and 4B are diagrams illustrating the action of the linear motion plate of the first embodiment. [Figure 18] 18(a) and 18(b) are diagrams continuing from FIG. 17, illustrating the action of the linear motion plate. [Figure 19] 18(a) and 18(b) illustrating the action of the linear motion plate. [Figure 20] 19(a) and 19(b) illustrating the action of the linear motion plate. [Figure 21] 10A and 10B are diagrams illustrating the action of the linear motion plate from the phase immediately after the second cam follower has moved to the non-pressing position. [Figure 22] 10A is a perspective view of a first cam, a first cam follower, a switching lever, and a planetary gear mechanism of a second embodiment, as seen from the switching protrusion side, and FIG. 10B is a perspective view of the first cam, a first cam follower, a switching lever, and a planetary gear mechanism of a second embodiment, as seen from the first protrusion side. [Figure 23] FIG. 1(a) is a side view of the first cam, first cam follower, switching lever, and planetary gear mechanism when the first developing cartridge is in the contact position, as viewed from the switching protrusion side, and FIG. 1(b) is a side view of the first cam, first cam follower, switching lever, and planetary gear mechanism when viewed from the first protrusion side. [Figure 24] FIG. 1A is a side view of the first cam, first cam follower, switching lever, and planetary gear mechanism when the first developing cartridge is in the separated position, as viewed from the switching protrusion side, and FIG. 1B is a side view of the first developing cartridge when viewed from the first protrusion side. [Figure 25] 1A is an exploded perspective view of the switching lever of the second embodiment, FIG. 1B is a diagram showing a state in which the rotation of the first lever is restricted by the rotation restricting portion, and FIG. 1C is a diagram showing a state in which the first lever is swung relative to the second lever. [Figure 26] 10A and 10B are diagrams illustrating the operation of the switching lever of the second embodiment. [Figure 27] 10A and 10B are perspective views showing the first cam and the first cam follower of the third embodiment, in which (a) shows the first cam follower in a non-pressing position, (b) shows the first cam follower in a pressing position, and (c) shows the first cam follower as seen from the first protrusion side. [Figure 28] 10A and 10B are diagrams illustrating the operation of the linear motion plate of the third embodiment. [Figure 29] 28(a) and 28(b) are diagrams illustrating the action of the linear motion plate. [Figure 30] 10(a) to 10(f) are diagrams illustrating a cam and a cam follower according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0054] Next, a first embodiment will be described. 1, image forming apparatus 1 is a color printer and includes a housing 10, a cover 11, a sheet supply unit 20, an image forming unit 30, and a control unit 2. In the embodiment, the left side of FIG. 1 is the front, the right side is the rear, the top and bottom are the top and bottom, and the front side of the paper in FIG. 1 is the right side and the back side of the paper is the left side.

[0055] Housing 10 has an opening 10A at the front. Cover 11 opens and closes opening 10A. Specifically, cover 11 is movable between a closed position where opening 10A is closed and an open position where opening 10A is opened. Specifically, cover 11 is rotatable between a closed position shown by a solid line and an open position shown by a virtual line.

[0056] The sheet supply unit 20 includes a sheet tray 21 on which the sheets S are set, and a supply mechanism 22. The supply mechanism 22 includes a pickup roller 23, a separation roller 24, a separation pad 25, a conveyance roller 26, and a registration roller 27. The sheets S in the sheet tray 21 are sent out by the pickup roller 23, then separated one by one between the separation roller 24 and the separation pad 25, and supplied to the image forming unit 30 by the conveyance roller 26 and the registration roller 27.

[0057] The image forming section 30 includes an exposure unit 40, a plurality of photosensitive drums 50, a plurality of developing cartridges 60, a transfer unit 70, and a fixing unit 80. The exposure unit 40 includes a light source, a deflector, a lens, a mirror, etc. (not shown). The exposure unit 40 emits a light beam (see the dashed line) to expose the surface of the photosensitive drum 50.

[0058] The photosensitive drums 50 include a first photosensitive drum 50K corresponding to black, a second photosensitive drum 50Y corresponding to yellow, a third photosensitive drum 50M corresponding to magenta, and a fourth photosensitive drum 50C corresponding to cyan. The third photosensitive drum 50M is disposed downstream of the second photosensitive drum 50Y in the conveying direction of the sheet S (hereinafter simply referred to as the "conveying direction"). The fourth photosensitive drum 50C is disposed downstream of the third photosensitive drum 50M in the conveying direction. The first photosensitive drum 50K is disposed downstream of the fourth photosensitive drum 50C in the conveying direction. That is, the second photosensitive drum 50Y, the third photosensitive drum 50M, the fourth photosensitive drum 50C, and the first photosensitive drum 50K are disposed in this order from the upstream side to the downstream side in the conveying direction.

[0059] In this specification and drawings, when describing components provided corresponding to each color by distinguishing between colors, the components are designated with the symbols Y, M, C, and K, and when describing components without distinguishing between colors, the components are not designated with the symbols Y, M, C, and K.

[0060] The developing cartridges 60 are provided corresponding to the respective photosensitive drums 50. In detail, the developing cartridges 60 include a first developing cartridge 60K having a first developing roller 61K that supplies toner to the first photosensitive drum 50K, a second developing cartridge 60Y having a second developing roller 61Y that supplies toner to the second photosensitive drum 50Y, a third developing cartridge 60M having a third developing roller 61M that supplies toner to the third photosensitive drum 50M, and a fourth developing cartridge 60C having a fourth developing roller 61C that supplies toner to the fourth photosensitive drum 50C.

[0061] The developing cartridge 60 is movable between a contact position shown by a solid line where the developing roller 61 contacts the corresponding photosensitive drum 50, and a separation position shown by a virtual line where the developing roller 61 is separated from the corresponding photosensitive drum 50.

[0062] Specifically, the first developing cartridge 60K is movable between a contact position where the first developing roller 61K is in contact with the first photosensitive drum 50K and a separated position where the first developing roller 61K is separated from the first photosensitive drum 50K. The second developing cartridge 60Y is movable between a contact position where the second developing roller 61Y is in contact with the second photosensitive drum 50Y and a separated position where the second developing roller 61Y is separated from the second photosensitive drum 50Y.

[0063] The third developing cartridge 60M is movable between a contact position where the third developing roller 61M contacts the third photosensitive drum 50M and a separated position where the third developing roller 61M is separated from the third photosensitive drum 50M. The fourth developing cartridge 60C is movable between a contact position where the fourth developing roller 61C contacts the fourth photosensitive drum 50C and a separated position where the fourth developing roller 61C is separated from the fourth photosensitive drum 50C.

[0064] The photosensitive drums 50 are rotatably supported in a drawer 55. A charger 52 for charging the photosensitive drum 50 is provided in the drawer 55 corresponding to each photosensitive drum 50. The drawer 55 detachably supports a plurality of developing cartridges 60. The drawer 55 is detachable from the housing 10 through an opening 10A that is exposed when the cover 11 is opened.

[0065] The transfer unit 70 includes a drive roller 71, a driven roller 72, an endless conveyor belt 73, and four transfer rollers 74. The conveyor belt 73 is stretched between the drive roller 71 and the driven roller 72, and its outer surface is in contact with each photosensitive drum 50. The transfer rollers 74 are disposed inside the conveyor belt 73, and sandwich the conveyor belt 73 between themselves and the corresponding photosensitive drum 50.

[0066] The fixing unit 80 includes a heating roller 81 and a pressure roller 82 disposed opposite the heating roller 81. Downstream of the fixing unit 80 in the conveying direction, a conveying roller 15 and a discharge roller 16 are provided.

[0067] In the image forming section 30, the surface of the photosensitive drum 50 is uniformly charged by the charger 52 and then exposed to a light beam emitted from the exposure unit 40. As a result, an electrostatic latent image based on image data is formed on the photosensitive drum 50. Furthermore, toner contained in the developer cartridge 60 is carried on the surface of the developer roller 61 and supplied from the developer roller 61, which is positioned at a contact position, to the electrostatic latent image formed on the photosensitive drum 50. As a result, a toner image is formed on the photosensitive drum 50.

[0068] The toner image formed on the photosensitive drum 50 is transferred onto the sheet S when the sheet S is fed onto the conveyor belt 73 and conveyed on the conveyor belt 73 and passes between the photosensitive drum 50 and the transfer roller 74. The toner image is then fixed onto the sheet S when the sheet S passes between the heating roller 81 and the pressure roller 82. Thereafter, the sheet S is discharged onto the discharge tray 13 by the conveyor roller 15 and the discharge roller 16.

[0069] As shown in FIG. 2, the image forming apparatus 1 further includes a first motor M1, a second motor M2, a third motor M3, a drum drive gear train 110, a first development drive gear train 120, a second development drive gear train 130, a cam drive gear train 140, a plurality of cams 150, a switching lever 160, and a plurality of cam followers 170.

[0070] The first motor M1 is a drive source that mainly drives the first developing roller 61K. The second motor M2 is a drive source that mainly rotates the cams 150, more specifically, the first cam 150K, the second cam 150Y, the third cam 150M, and the fourth cam 150C, which will be described later. The second motor M2 is provided separately from the first motor M1. The third motor M3 is a drive source that mainly drives the photosensitive drums 50 (50Y, 50M, 50C, 50K), the second developing roller 61Y, the third developing roller 61M, and the fourth developing roller 61C. The third motor M3 is a motor that drives the developing rollers 61Y, 61M, and 61C. The third motor M3 is provided separately from the first motor M1 and the second motor M2.

[0071] The drum drive gear train 110 is capable of transmitting the driving force of the third motor M3 to the four photosensitive drums 50 (50Y, 50M, 50C, 50K). The drum drive gear train 110 includes idle gears 111, 112A, 112B, a first drum gear 113K, a second drum gear 113Y, a third drum gear 113M, and a fourth drum gear 113C. The idle gear 111 is a two-stage gear including a large-diameter gear 111L that meshes with a gear MG provided on the output shaft of the third motor M3, and a small-diameter gear 111S that has fewer teeth than the large-diameter gear 111L.

[0072] The third drum gear 113M is a gear that rotates integrally with the third photosensitive drum 50M and meshes with the small diameter gear 111S of the idle gear 111. The idle gear 112A meshes with the third drum gear 113M. The second drum gear 113Y is a gear that rotates integrally with the second photosensitive drum 50Y and meshes with the idle gear 112A. The fourth drum gear 113C is a gear that rotates integrally with the fourth photosensitive drum 50C and meshes with the small diameter gear 111S of the idle gear 111. The idle gear 112B meshes with the fourth drum gear 113C. The first drum gear 113K is a gear that rotates integrally with the first photosensitive drum 50K and meshes with the idle gear 112B.

[0073] The first developing drive gear train 120 is capable of transmitting the driving force of the first motor M1 to the first developing cartridge 60K. The second developing drive gear train 130 is capable of transmitting the driving force of the third motor M3 to the second developing cartridge 60Y, the third developing cartridge 60M, and the fourth developing cartridge 60C.

[0074] The cam drive gear train 140 is capable of transmitting the driving force of the second motor M2 to the cam 150. The cam drive gear train 140 has a first cam drive gear train 140A that is capable of transmitting the driving force to the first cam 150K, and a second cam drive gear train 140B that is capable of transmitting the driving force to the second cam 150Y, the third cam 150M, and the fourth cam 150C.

[0075] The first cam drive gear train 140A includes a first electromagnetic clutch 141A. The first electromagnetic clutch 141A switches between transmitting and disconnecting the driving force, thereby switching between rotating and stopping the first cam 150K. For example, when the first electromagnetic clutch 141A is energized, it transmits the driving force, causing the first cam 150K to rotate. When the first electromagnetic clutch 141A is not energized, it disconnects the transmission of the driving force, causing the first cam 150K to stop. The control unit 2 (see FIG. 1) controls the first electromagnetic clutch 141A to switch between transmitting and disconnecting the driving force, thereby controlling the rotation and stopping of the first cam 150K.

[0076] The second cam drive gear train 140B includes a second electromagnetic clutch 141B. The second electromagnetic clutch 141B switches between transmitting and disconnecting the driving force, thereby switching between rotating and stopping the cams 150Y, 150M, and 150C. For example, when the second electromagnetic clutch 141B is energized, it transmits the driving force, causing the cams 150Y, 150M, and 150C to rotate. When the second electromagnetic clutch 141B is not energized, it disconnects the driving force, causing the cams 150Y, 150M, and 150C to stop. The control unit 2 controls the second electromagnetic clutch 141B to switch between transmitting and disconnecting the driving force, thereby controlling the rotation and stopping of the cams 150Y, 150M, and 150C.

[0077] The control unit 2 includes a CPU, a ROM, a RAM, an input / output unit, etc., and performs control by executing a pre-stored program. The control unit 2 controls the driving of the motors M1 to M3, and the operation of the cam 150 by controlling the electromagnetic clutches 141A and 141B, thereby controlling the driving and stopping of the developing roller 61 and the contact and separation of the developing roller 61 with the corresponding photosensitive drum 50.

[0078] As shown in FIG. 3, the cam 150 rotates to move the corresponding developer cartridge 60 between the contact position and the separated position. The cam 150 includes a first cam 150K, a second cam 150Y, a third cam 150M, and a fourth cam 150C. The first cam 150K rotates to move the first developer cartridge 60K between the contact position and the separated position. The second cam 150Y rotates to move the second developer cartridge 60Y between the contact position and the separated position. The third cam 150M rotates to move the third developer cartridge 60M between the contact position and the separated position. The fourth cam 150C rotates to move the fourth developer cartridge 60C between the contact position and the separated position.

[0079] The cam follower 170 is slidable in the direction of the rotation axis of the first cam 150K (corresponding to the direction in which the dashed line shown in FIG. 3 extends; hereinafter, simply referred to as the "rotation axis direction"). As the corresponding cam 150 rotates, the cam follower 170 slides in the direction of the rotation axis between a pressing position shown in FIG. 4(b) where it presses the corresponding developer cartridge 60 to position the developer cartridge 60 at the separated position, and a non-pressing position shown in FIG. 4(a) where it positions the corresponding developer cartridge 60 at the contact position.

[0080] As shown in FIGS. 4(a) and 4(b), the developer cartridge 60 is supported in the drawer 55 so as to be movable back and forth. The drawer 55 has a contact portion 55A and a pressing member 55B. The contact portion 55A is the portion that a slide member 66 (described later) contacts, and is made of a roller that can rotate around a vertical axis. The pressing member 55B is biased rearward by a spring 55C, and when the developer cartridge 60 is installed in the drawer 55, it presses the developer cartridge 60 to move it to a contact position where the developing roller 61 contacts the photosensitive drum 50.

[0081] The developer cartridge 60 has a case 65 that contains toner, and a slide member 66. The slide member 66 is slidable in the direction of the rotation axis relative to the case 65, and slides in the direction of the rotation axis when pressed by a cam follower 170. The slide member 66 has a shaft 66A slidably supported by the case 65, a first contact member 66B provided at one end of the shaft 66A, and a second contact member 66C provided at the other end of the shaft 66A.

[0082] The first contact member 66B has a pressing surface 66D and an inclined surface 66E inclined relative to the axial direction, and the second contact member 66C has an inclined surface 66F inclined similarly to the inclined surface 66E. The pressing surface 66D is pressed by the cam follower 170. When the slide member 66 is pressed by the cam follower 170, the inclined surfaces 66E and 66F come into contact with the contacted portion 55A and urge the developer cartridge 60 in a direction perpendicular to the rotational axis direction, moving the developer roller 61 to a spaced position where it is spaced from the photosensitive drum 50. A spring 67 is disposed between the first contact member 66B and the case 65 to urge the slide member 66 leftward.

[0083] Returning to FIG. 3, the cam followers 170 include a first cam follower 170K, a second cam follower 170Y, a third cam follower 170M, and a fourth cam follower 170C. The first cam follower 170K slides between a pressing position where it presses the first developer cartridge 60K to position the first developer cartridge 60K at the separated position and a non-pressing position where it positions the first developer cartridge 60K at the contact position due to the rotation of the first cam 150K. The first cam follower 170K slides in the rotation axis direction between the pressing position and the non-pressing position due to a cam surface 154 (described later) of the rotating first cam 150K.

[0084] The second cam follower 170Y slides between a pressing position where it presses the second developer cartridge 60Y to position the second developer cartridge 60Y at the separated position and a non-pressing position where it positions the second developer cartridge 60Y at the contact position due to the rotation of the second cam 150Y. The second cam follower 170Y slides in the rotation axis direction between the pressing position and the non-pressing position due to the cam surface 154 of the rotating second cam 150Y.

[0085] The third cam follower 170M slides between a pressing position where it presses the third developer cartridge 60M to position the third developer cartridge 60M at the separated position and a non-pressing position where it positions the third developer cartridge 60M at the contact position due to the rotation of the third cam 150M. The third cam follower 170M slides in the direction of the rotation axis between the pressing position and the non-pressing position due to the cam surface 154 of the rotating third cam 150M.

[0086] The fourth cam follower 170C slides between a pressing position where it presses the fourth developer cartridge 60C to position the fourth developer cartridge 60C in the separated position and a non-pressing position where it positions the fourth developer cartridge 60C in the contact position due to the rotation of the fourth cam 150C. The fourth cam follower 170C slides in the rotation axis direction between the pressing position and the non-pressing position due to the cam surface 154 of the rotating fourth cam 150C.

[0087] The cams 150 (first cam 150K, second cam 150Y, third cam 150M, and fourth cam 150C) are end face cams. Each cam 150 has a disk portion 151, a gear portion 152, and a cam portion 153. The disk portion 151 has a through-hole 151A at the center thereof that penetrates in the direction of the rotation axis.

[0088] The image forming apparatus 1 further includes four second shafts 159. The second shafts 159 rotatably support the corresponding cams 150 (first cam 150K, second cam 150Y, third cam 150M, and fourth cam 150C). The second shafts 159 are provided in the housing 10. The cams 150 are rotatably supported by the housing 10 by the through-holes 151A of the disk portions 151 engaging with the second shafts 159.

[0089] The gear portion 152 is formed on the outer periphery of the disk portion 151 . The cam portion 153 protrudes in the direction of the rotation axis from the side surface of the disk portion 151. The cam portion 153 has a cam surface 154 that moves the cam follower 170 between a pressing position and a non-pressing position, thereby moving the developer cartridge 60 between a separated position and a contact position. The cam surface 154 of each cam 150 (first cam 150K, second cam 150Y, third cam 150M, fourth cam 150C) has a first guide surface 154A, a holding surface 154B, and a second guide surface 154C, as shown in FIG. 5(a) representatively for the first cam 150K.

[0090] The first guide surface 154A moves the corresponding cam follower 170 from the non-pressing position to the pressing position when the cam 150 rotates in the first rotation direction R1. For example, the first guide surface 154A of the first cam 150K moves the first cam follower 170K from the non-pressing position to the pressing position when the first cam 150K rotates in the first rotation direction R1. The first guide surface 154A is inclined with respect to the rotation direction of the cam 150. The first guide surface 154A is inclined so as to move away from the disk portion 151 from the downstream end toward the upstream end in the first rotation direction R1.

[0091] The control unit 2 rotates the first cam 150K in the first rotation direction R1 when moving the first developer cartridge 60K between the contact position and the separated position. The control unit 2 also rotates the second cam 150Y, the third cam 150M, and the fourth cam 150C in the first rotation direction R1 when moving the second developer cartridge 60Y, the third developer cartridge 60M, and the fourth developer cartridge 60C between the contact position and the separated position (see FIG. 3).

[0092] The holding surface 154B holds the corresponding cam follower 170 in the pressing position. For example, the holding surface 154B of the first cam 150K holds the first cam follower 170K in the pressing position (see FIG. 7). The holding surface 154B is approximately parallel to the rotation direction of the cam 150. Note that in FIG. 6(b) and other figures to be referred to later, the holding surface 154B is indicated by dot hatching.

[0093] The second guide surface 154C moves the corresponding cam follower 170 from the pressing position to the non-pressing position when the cam 150 rotates in the first rotation direction R1. For example, the second guide surface 154C of the first cam 150K moves the first cam follower 170K from the pressing position to the non-pressing position when the first cam 150K rotates in the first rotation direction R1. The second guide surface 154C is inclined with respect to the rotation direction of the cam 150. The second guide surface 154C is inclined so as to approach the disc portion 151 from the downstream end toward the upstream end in the first rotation direction R1.

[0094] The angle of second guide surface 154C relative to the rotation direction of cam 150 is larger than the angle of first guide surface 154A relative to the rotation direction of cam 150. For example, the angle of second guide surface 154C relative to the rotation direction of first cam 150K is larger than the angle of first guide surface 154A relative to the rotation direction of first cam 150K. In other words, the gradient of second guide surface 154C is larger than the gradient of first guide surface 154A.

[0095] As shown in FIG. 6, the cam followers 170 (first cam follower 170K, second cam follower 170Y, third cam follower 170M, and fourth cam follower 170C) have a first shaft 171, a contact arm 172, and a restriction arm 173.

[0096] First shaft 171 is supported so as to be slidable in the direction of the rotation axis. More specifically, first shaft 171 has a cylindrical shape. First shaft 171 is engaged with second shaft 159 (see FIG. 3) extending in the direction of the rotation axis, and is thereby supported so as to be slidable in the direction of the rotation axis. This allows cam follower 170 to slide in the direction of the rotation axis between the non-pressing position shown in FIG. 6 and the pressing position shown in FIG. 7. Cam follower 170 is biased from the pressing position toward the non-pressing position by a spring (not shown).

[0097] As shown in FIG. 7, the contact arms 172 are portions that come into contact with the cam surfaces 154 of the corresponding cams 150 (first cam 150K, second cam 150Y, third cam 150M, and fourth cam 150C). The contact arms 172 extend from the first shaft 171 toward the outside in the radial direction of the first shaft 171. Note that in FIG. 7(b) and other figures, the contact arms 172 are indicated by dot hatching. When the dot-hatched contact arms 172 and the holding surface 154B overlap, the cam follower 170 is positioned in the pressing position, and the corresponding developer cartridge 60 is positioned in the separating position.

[0098] The restriction arm 173 is an arm separate from the contact arm 172, and extends from the first shaft 171 toward the outside in the radial direction of the first shaft 171. The restriction arm 173 extends from the first shaft 171 toward substantially the opposite side from the contact arm 172 when viewed from the rotation axis direction. As shown in FIG. 6( a), the restriction arm 173 is disposed at a position different from the contact arm 172 in the rotation axis direction so as not to come into contact with the cam portion 153 (cam surface 154). More specifically, when the cam follower 170 is in the non-pressing position, the restriction arm 173 is disposed at a position different from the cam portion 153 in the rotation axis direction. The cam portion 153 of the rotating cam 150 passes through a position between the disc portion 151 and the restriction arm 173 and does not come into contact with the restriction arm 173.

[0099] Image forming apparatus 1 further includes stoppers 179 that restrict rotation of cam followers 170 (first cam follower 170K, second cam follower 170Y, third cam follower 170M, and fourth cam follower 170C) around first shaft 171. Stoppers 179 are a pair of rod-shaped members, and are provided corresponding to each cam follower 170 (see FIG. 3). Stoppers 179 are provided on housing 10. Stoppers 179 are arranged to sandwich restriction arms 173 of the corresponding cam followers 170 from both sides in the circumferential direction of first shaft 171. This restricts rotation of cam followers 170 (first cam follower 170K, second cam follower 170Y, third cam follower 170M, and fourth cam follower 170C) around first shaft 171.

[0100] As shown in FIG. 2, the first shaft 171 of the cam follower 170 is disposed inside the outer periphery of the corresponding cam 150 when viewed from the rotational axis direction. Specifically, the first shaft 171 of the first cam follower 170K is disposed inside the outer periphery of the first cam 150K when viewed from the rotational axis direction. The first shaft 171 of the second cam follower 170Y is disposed inside the outer periphery of the second cam 150Y when viewed from the rotational axis direction. The first shaft 171 of the third cam follower 170M is disposed inside the outer periphery of the third cam 150M when viewed from the rotational axis direction. The first shaft 171 of the fourth cam follower 170C is disposed inside the outer periphery of the fourth cam 150C when viewed from the rotational axis direction.

[0101] In the image forming apparatus 1, all of the developer cartridges 60 are positioned at the separated positions when the image forming apparatus 1 is in a standby state before printing is performed. At this time, as shown in FIG. 7, the cam follower 170 is positioned at the pressing position where the contact arm 172 contacts the holding surface 154B of the cam 150.

[0102] When printing is performed, the control unit 2 places the first electromagnetic clutch 141A or the second electromagnetic clutch 141B in a transmission state depending on the color of toner used for printing, causing the cam 150 to rotate in the first rotation direction R1. As a result, the contact arm 172 of the cam follower 170 is guided from the holding surface 154B to the second guide surface 154C, slides on the second guide surface 154C, and disengages from the cam surface 154. As a result, the cam follower 170 slides from the pressing position to the non-pressing position shown in FIG. 6 due to the biasing force of the spring (not shown), and the corresponding developer cartridge 60 moves from the separated position to the contact position. Once the developer cartridge 60 moves to the contact position, the control unit 2 disengages the first electromagnetic clutch 141A or the second electromagnetic clutch 141B, causing the cam 150 to stop rotating.

[0103] When development by the developing roller 61 is completed, the control unit 2 puts the first electromagnetic clutch 141A and the second electromagnetic clutch 141B into a transmission state and rotates the cam 150 again in the first rotation direction R1. As a result, the contact arm 172 of the cam follower 170 contacts the first guide surface 154A of the cam surface 154, slides over the first guide surface 154A, and contacts the holding surface 154B. As a result, the cam follower 170 slides from the non-pressing position to the pressing position shown in FIG. 7, and the corresponding developing cartridge 60 moves from the contact position to the separated position. Once the developing cartridge 60 moves to the separated position, the control unit 2 puts the first electromagnetic clutch 141A and the second electromagnetic clutch 141B into a disengaged state and stops the rotation of the cam 150.

[0104] 8, the cam surface 154 of the second cam 150Y, the cam surface 154 of the third cam 150M, and the cam surface 154 of the fourth cam 150C are provided so that the third cam follower 170M starts to move from the non-pressing position toward the pressing position at timing t2 after timing t1 when the second cam follower 170Y moves to the pressing position. Also, the cam surface 154 of the second cam 150Y, the cam surface 154 of the third cam 150M, and the cam surface 154 of the fourth cam 150C are provided so that the fourth cam follower 170C starts to move from the non-pressing position toward the pressing position at timing t4 after timing t3 when the third cam follower 170M moves to the pressing position.

[0105] In addition, the cam surface 154 of the second cam 150Y, the cam surface 154 of the third cam 150M, and the cam surface 154 of the fourth cam 150C are arranged so that there are times t5 to t8 when the second cam follower 170Y, the third cam follower 170M, and the fourth cam follower 170C are simultaneously positioned in the pressing position.

[0106] In addition, the cam surface 154 of the second cam 150Y, the cam surface 154 of the third cam 150M, and the cam surface 154 of the fourth cam 150C are arranged so that the timing when the second cam follower 170Y moves from the pressing position toward the non-pressing position, the timing when the third cam follower 170M moves from the pressing position toward the non-pressing position, and the timing when the fourth cam follower 170C moves from the pressing position toward the non-pressing position overlap each other (t8 to t9).

[0107] 9, the third cam 150M rotates in conjunction with the second cam 150Y. Furthermore, the fourth cam 150C rotates in conjunction with the second cam 150Y and the third cam 150M. Specifically, the image forming apparatus 1 includes idle gears G1 and G2. The idle gear G1 meshes with the gear portion 152 of the second cam 150Y and the gear portion 152 of the third cam 150M, and the idle gear G2 meshes with the gear portion 152 of the third cam 150M and the gear portion 152 of the fourth cam 150C. As a result, when the driving force from the second motor M2 (see FIG. 2) is input to the second cam 150Y, the cams 150Y, 150M, and 150C rotate integrally in conjunction with one another.

[0108] The cams 150Y, 150M, and 150C have holding surfaces 154B that are longer in the rotation direction of the cam 150 in the order of the fourth cam 150C, the third cam 150M, and the second cam 150Y. The cams 150Y, 150M, and 150C have second guide surfaces 154C that are generally in phase with each other in the rotation direction of the cam 150, but have first guide surfaces 154A that are out of phase with each other in the rotation direction of the cam 150. Specifically, the first guide surface 154A of the third cam 150M is located upstream of the first guide surface 154A of the fourth cam 150C in the first rotation direction R1, and the first guide surface 154A of the second cam 150Y is located upstream of the first guide surface 154A of the third cam 150M in the first rotation direction R1.

[0109] As a result, when the cams 150Y, 150M, 150C rotate in the first rotation direction R1 from the state in which the cam followers 170Y, 170M, 170C are positioned in the non-pressing position shown in Figure 9, first, the second cam follower 170Y moves from the non-pressing position to the pressing position, causing the second developer cartridge 60Y to move from the contact position to the separated position, then the third cam follower 170M moves from the non-pressing position to the pressing position, causing the third developer cartridge 60M to move from the contact position to the separated position, and finally, the fourth cam follower 170C moves from the non-pressing position to the pressing position, causing the fourth developer cartridge 60C to move from the contact position to the separated position.

[0110] Furthermore, when the cams 150Y, 150M, and 150C rotate in the first rotation direction R1 from the state in which the cam followers 170Y, 170M, and 170C are positioned in the pressing position shown in Figure 10, the cam followers 170Y, 170M, and 170C move from the pressing position to the non-pressing position at approximately the same time, causing the developer cartridges 60Y, 60M, and 60C to move from the separated position to the contact position at approximately the same time.

[0111] Next, a mechanism for switching between transmitting and disconnecting the driving force to the first developing roller 61K will be described. As shown in FIG. 2, the first developing drive gear train 120 includes a planetary gear mechanism 180, an idle gear 122, and a first coupling gear 126K. 11, the planetary gear mechanism 180 has an input element 180A, an output element 180B, and a transfer element 180C. The input element 180A, the output element 180B, and the transfer element 180C are rotatable coaxially.

[0112] More specifically, planetary gear mechanism 180 has a sun gear 181, a ring gear 182, a carrier 183, and four planetary gears 184. Of input element 180A, output element 180B, and transfer element 180C, one has the sun gear 181, one other than the element having the sun gear 181 has the ring gear 182, and the remaining one has the carrier 183. In this embodiment, transfer element 180C has the sun gear 181, input element 180A has the ring gear 182, and output element 180B has the carrier 183.

[0113] The input element 180A is an element to which a driving force from the first motor M1 (see FIG. 2) is input. The input element 180A has a ring gear 182 and a first outer peripheral gear 185 formed on the outer periphery of the ring gear 182. The input element 180A inputs the driving force from the first motor M1 to the first outer peripheral gear 185.

[0114] The output element 180B is an element that outputs a driving force toward the first developing roller 61K. The output element 180B has a carrier 183 and a second outer peripheral gear 186 formed on the outer periphery of the carrier 183. The carrier 183 also has four shaft portions 183A that rotatably support planetary gears 184.

[0115] Transfer element 180C is an element configured to be able to transmit driving force from input element 180A to output element 180B when rotation is restricted, and not to transmit driving force from input element 180A to output element 180B when rotation is not restricted. Transfer element 180C has a sun gear 181, a rotating plate 187 that rotates integrally with sun gear 181, and claws 188 formed on the outer periphery of rotating plate 187.

[0116] The planetary gear 184 is rotatably supported by a shaft portion 183A of the carrier 183. The planetary gear 184 meshes with the sun gear 181 and also meshes with the ring gear 182.

[0117] When the rotation of the transfer element 180C is stopped, the planetary gear mechanism 180 is in a transfer state in which the driving force input to the first outer peripheral gear 185 can be transferred to the second outer peripheral gear 186. On the other hand, when the transfer element 180C is rotatable, the planetary gear mechanism 180 is in a disconnected state in which the driving force input to the first outer peripheral gear 185 cannot be transferred to the second outer peripheral gear 186. When the planetary gear mechanism 180 is in a disconnected state and a load is applied to the second outer peripheral gear 186, and a driving force is input to the first outer peripheral gear 185, the output element 180B does not rotate, and the transfer element 180C rotates freely.

[0118] Returning to FIG. 2, the idle gear 122 is a two-stage gear having a large diameter gear 122L that meshes with the second outer peripheral gear 186 of the planetary gear mechanism 180, and a small diameter gear 122S that has fewer teeth than the large diameter gear 122L. The first coupling gear 126K is a gear that outputs the driving force from the first motor M1 to the first developing cartridge 60K (first developing roller 61K), and meshes with the small diameter gear 122S of the idle gear 122.

[0119] As shown in FIG. 5(a), the first cam 150K further includes a flange portion 155 and a switching protrusion 156. The flange portion 155 is formed on the outer periphery of the disk portion 151. The flange portion 155 is located on one side of the gear portion 152 in the rotational axis direction. The flange portion 155 is provided so as to overlap with the gear portion 152 when viewed from the rotational axis direction. The flange portion 155 extends radially outward from the tips of the gear teeth of the gear portion 152.

[0120] The switching protrusion 156 is capable of coming into contact with the switching lever 160 (see FIG. 7) and moves the switching lever 160 between a first transmission position and a first disconnection position, which will be described later. The switching protrusion 156 is disposed on the flange portion 155. Specifically, the switching protrusion 156 protrudes from the flange portion 155 toward one side in the rotational axis direction. The switching protrusion 156 is disposed on a surface on one side in the rotational axis direction of the first cam 150K. In the first embodiment, the cam surface 154 (cam portion 153) is disposed on the same surface as the switching protrusion 156, i.e., on a surface on one side in the rotational axis direction of the first cam 150K.

[0121] 7(b), the switching protrusion 156 is disposed at a position overlapping with the holding surface 154B of the cam surface 154 in the circumferential direction centered on the rotation axis of the first cam 150K, as viewed from the rotation axis direction. More specifically, the switching protrusion 156 is disposed at a position overlapping with the upstream end of the holding surface 154B in the first rotation direction R1, in the circumferential direction of the first cam 150K. The switching protrusion 156 is provided to extend from the cam portion 153 toward the radially outer side of the first cam 150K.

[0122] 5(a), the length of the switching protrusion 156 in the rotational axis direction is shorter than the distance in the rotational axis direction from the flange portion 155 to the holding surface 154B. In other words, the switching protrusion 156 is located closer to the disk portion 151 in the rotational axis direction than the holding surface 154B.

[0123] 6(b), the switching lever 160 can be moved by rotation of the first cam 150K between a first transmission position where the driving force from the first motor M1 can be transmitted to the first developing roller 61K, and a first disconnection position where the driving force from the first motor M1 is not transmitted to the first developing roller 61K. The switching lever 160 has a rotation support portion 161, a first arm 162 extending from the rotation support portion 161, and a second arm 163 extending from the rotation support portion 161 in a direction different from that of the first arm 162.

[0124] The rotation support part 161 is rotatably supported by a shaft (not shown) provided on the housing 10. This allows the switching lever 160 to swing around the swing shaft 160A between a first transmission position shown in Fig. 6 and a first disconnection position shown in Fig. 7. The switching lever 160 is biased from the first disconnection position toward the first transmission position by a spring (not shown).

[0125] 6, when the switching lever 160 is located in the first transmission position, the tip of the second arm 163 engages with the claw portion 188 of the transmission element 180C to restrict the rotation of the transmission element 180C. As a result, the driving force input from the first motor M1 to the planetary gear mechanism 180 is transmitted to the first developing cartridge 60K via the idle gear 122 and the first coupling gear 126K, causing the first developing roller 61K to rotate.

[0126] 7, when the switching lever 160 is located at the first disconnection position, the tip of the second arm 163 disengages from the claw portion 188 of the transfer element 180C and does not restrict the rotation of the transfer element 180C. As a result, the driving force input from the first motor M1 to the planetary gear mechanism 180 is not transmitted to the first developing cartridge 60K, and the first developing roller 61K does not rotate.

[0127] The first arm 162 is capable of coming into contact with the switching protrusion 156 of the first cam 150K. As shown in Fig. 6, when the first arm 162 is no longer in contact with the switching protrusion 156, the switching lever 160 swings to the first transmission position due to the biasing force of a spring (not shown). Also, as shown in Fig. 7, when the first arm 162 comes into contact with the switching protrusion 156, the switching lever 160 swings to the first disconnection position against the biasing force of the spring (not shown).

[0128] The switching protrusion 156 positions the switching lever 160 in the first transmission position when the first developing cartridge 60K is in the contact position, and swings the switching lever 160 to the first disconnection position when the first developing cartridge 60K is in the separated position. As a result, the first developing roller 61K rotates when in contact with the first photosensitive drum 50K and stops when separated from the first photosensitive drum 50K.

[0129] 8, the switching protrusion 156 is provided to move the switching lever 160 to the first disconnection position to stop the first developing roller 61K at timing t12 after timing t11 when the first developing cartridge 60K moves to the separated position. The switching protrusion 156 is also provided to move the switching lever 160 to the first transmission position to rotate the first developing roller 61K at timing t13 before timing t14 when the first developing cartridge 60K moves to the contact position.

[0130] Specifically, as shown in Fig. 12(a), after the contact arm 172 of the first cam follower 170K is guided from the first guide surface 154A to the holding surface 154B and held by the holding surface 154B, the switching protrusion 156 comes into contact with the first arm 162 to swing the switching lever 160 from the first transmission position to the first disengagement position, as shown in Fig. 7(b). Also, as shown in Fig. 12(b), before the contact arm 172 of the first cam follower 170K is guided from the holding surface 154B to the second guide surface 154C, the switching protrusion 156 disengages from the first arm 162 to swing the switching lever 160 from the first disengagement position to the first transmission position.

[0131] Next, a mechanism for switching between transmitting and cutting off the driving force to the second developing roller 61Y, the third developing roller 61M, and the fourth developing roller 61C will be described. As shown in FIG. 9, the second development drive gear train 130 includes idle gears 131 and 132, an input gear 133, a moving gear 134, an output gear 135, a second coupling gear 136Y, a third coupling gear 136M, an idle gear 137, and a fourth coupling gear 136C.

[0132] The idle gear 131 is a two-stage gear having a large diameter gear 131L that meshes with a gear MG provided on the output shaft of the third motor M3, and a small diameter gear 131S (see FIG. 13) that has fewer teeth than the large diameter gear 131L. The idle gear 132 meshes with the small diameter gear 131S of the idle gear 131. The input gear 133 meshes with the idle gear 132. A driving force is input to the input gear 133 from the third motor M3 via the idle gears 131 and 132.

[0133] The movable gear 134 meshes with the input gear 133. The movable gear 134 is movable between a second transmission position, which is a transmission position indicated by a solid line, and a second disconnection position, which is a disconnection position indicated by a virtual line. More specifically, the movable gear 134 is rotatably supported by a bearing 134A (see FIG. 13), and the bearing 134A is supported by the housing 10 so as to be able to swing around the input gear 133. This allows the movable gear 134 to swing around the input gear 133 between the second transmission position and the second disconnection position. When the movable gear 134 is located at the second transmission position, it meshes with the large diameter gear 135L of the output gear 135, and when located at the second disconnection position, it does not mesh with the large diameter gear 135L of the output gear 135.

[0134] The output gear 135 is a gear that outputs driving force toward the second developing roller 61Y, the third developing roller 61M, and the fourth developing roller 61C. The output gear 135 is a two-stage gear that has a large diameter gear 135L that can mesh with the movable gear 134, and a small diameter gear 135S that has fewer teeth than the large diameter gear 135L.

[0135] The second coupling gear 136Y is a gear that outputs the driving force from the third motor M3 to the second developing cartridge 60Y (second developing roller 61Y), and is in mesh with the small diameter gear 135S of the output gear 135. The third coupling gear 136M is a gear that outputs the driving force from the third motor M3 to the third developing cartridge 60M (third developing roller 61M), and meshes with the small diameter gear 135S of the output gear 135.

[0136] The idle gear 137 meshes with the third coupling gear 136M. The fourth coupling gear 136C is a gear that outputs the driving force from the third motor M3 to the fourth developing cartridge 60C (fourth developing roller 61C), and is in mesh with an idle gear 137.

[0137] As shown in FIG. 13, the image forming apparatus 1 further includes a switching gear train 190. The switching gear train 190 moves the movable gear 134 between the second transmission position and the second disconnection position. The switching gear train 190 includes idle gears 191, 192, and 193, and a switching cam 194.

[0138] The idle gear 191 is a two-stage gear that has a large diameter gear 191L ​​that meshes with the gear portion 152 of the second cam 150Y, and a small diameter gear 191S that has fewer teeth than the large diameter gear 191L. The idle gear 192 meshes with the small diameter gear 191S of the idle gear 191. The idle gear 193 meshes with the idle gear 192 .

[0139] The switching cam 194 is a plate cam that rotates to move the moving gear 134 between the second transmission position and the second disconnection position. The switching cam 194 has a gear portion 194A and a cam portion 194B. The gear portion 194A meshes with the idle gear 193. This causes the switching cam 194 to rotate in conjunction with the second cam 150Y.

[0140] Cam portion 194B has a cam surface 195 on its outer periphery. Cam surface 195 has a first holding surface 195A, a switching surface 195B, and a second holding surface 195C. The first holding surface 195A positions the movable gear 134 at the second transmission position. When the movable gear 134 is at the second transmission position, the first holding surface 195A may be in contact with the bearing 134A or may be spaced apart from the bearing 134A.

[0141] The second holding surface 195C holds the moving gear 134 at the second disconnection position (see FIG. 14). The first holding surface 195A and the second holding surface 195C are arc-shaped surfaces centered on the rotation axis of the switching cam 194. The distance from the rotation axis of the switching cam 194 to the second holding surface 195C is greater than the distance from the rotation axis of the switching cam 194 to the first holding surface 195A.

[0142] The switching surface 195B moves the movable gear 134 from the second transmission position to the second disconnection position. The switching surface 195B is a linear surface that connects the upstream end of the first holding surface 195A and the downstream end of the second holding surface 195C in the rotation direction of the movable gear 134 (see the arrow).

[0143] The switching cam 194 rotates together with the cams 150Y, 150M, and 150C. When the switching cam 194 rotates counterclockwise in FIG. 13 while the movable gear 134 is in the second transmission position shown in FIG. 13, the switching surface 195B comes into contact with the bearing 134A, and the switching surface 195B moves the movable gear 134 toward the right in the figure. Then, as shown in FIG. 14, when the second holding surface 195C comes into contact with the bearing 134A, the movable gear 134 reaches the second disconnection position.

[0144] 14 when the movable gear 134 is located at the second disengagement position, the contact between the bearing 134A and the second holding surface 195C is released, and the bearing 134A faces the first holding surface 195A, and the movable gear 134 moves from the second disengagement position to the second transmission position by the force received from the input gear 133. Note that the movable gear 134 may be biased from the second disengagement position toward the second transmission position by, for example, a spring.

[0145] The switching cam 194 positions the movable gear 134 in the second transmission position when the developer cartridges 60Y, 60M, 60C are positioned in the contact position, and swings the movable gear 134 to the second disconnection position when the developer cartridges 60Y, 60M, 60C are positioned in the separated position. As a result, the developing rollers 61Y, 61M, 61C rotate when in contact with the corresponding photosensitive drums 50Y, 50M, 50C, and stop when separated from the corresponding photosensitive drums 50Y, 50M, 50C.

[0146] 8, the switching cam 194 is provided to move the moving gear 134 to the second disconnection position to stop the developing rollers 61Y, 61M, and 61C at timing t6 after timing t5 when the fourth developing cartridge 60C moves to the separated position. The switching cam 194 is also provided to move the moving gear 134 to the second transmission position to rotate the developing rollers 61Y, 61M, and 61C at timing t7 before timing t9 when the second developing cartridge 60Y moves to the contact position.

[0147] Next, a mechanism for forcibly moving the cam follower 170 to the non-pressing position and moving the developing cartridge 60 to the contact position when the cover 11 is opened will be described. 15, the image forming apparatus 1 further includes a linear motion plate 200. The first cam 150K has a first protrusion 157A, the second cam 150Y has a second protrusion 157B, and the fourth cam 150C has a third protrusion 157C.

[0148] The linear motion plate 200 moves linearly in a direction perpendicular to the direction of the rotation axis between a first position, which is the position when the cover 11 is in the closed position, and a second position (see FIG. 20(b)), which is the position when the cover 11 is in the open position, in conjunction with the movement of the cover 11 (see FIG. 1) between the closed position and the open position. Specifically, the linear motion plate 200 can move linearly in the front-to-rear direction, which is the direction in which the photosensitive drums 50 are lined up, between the first position and the second position in conjunction with the opening and closing operation of the cover 11. The second position is a position forward of the first position. The linear motion plate 200 moves forward from the first position to the second position when the cover 11 is opened, and moves rearward from the second position to the first position when the cover 11 is closed.

[0149] When linear motion plate 200 moves from the first position to the second position with first cam follower 170K in the pressing position, linear motion plate 200 comes into contact with first cam 150K to rotate first cam 150K and position first cam follower 170K in the non-pressing position. Furthermore, when linear motion plate 200 moves from the first position to the second position with at least one of second cam follower 170Y, third cam follower 170M, and fourth cam follower 170C in the pressing position, linear motion plate 200 rotates second cam 150Y, third cam 150M, and fourth cam 150C and position second cam follower 170Y, third cam follower 170M, and fourth cam follower 170C in the non-pressing position.

[0150] In the first embodiment, when the linear motion plate 200 moves from the first position to the second position with the first cam follower 170K in the pressing position, the linear motion plate 200 rotates the first cam 150K in a second rotational direction R2 opposite to the first rotational direction R1, thereby positioning the first cam follower 170K in the non-pressing position. Also, when the linear motion plate 200 moves from the first position to the second position with at least the second cam follower 170Y in the pressing position, the linear motion plate 200 rotates the second cam 150Y, the third cam 150M, and the fourth cam 150C in the second rotational direction R2 opposite to the first rotational direction R1, thereby positioning the second cam follower 170Y, the third cam follower 170M, and the fourth cam follower 170C in the non-pressing position.

[0151] The first protrusion 157A is capable of coming into contact with the linear motion plate 200, and rotates the first cam 150K when the linear motion plate 200 comes into contact with the first protrusion 157A while moving from the first position to the second position. The first protrusion 157A protrudes in the rotation axis direction from the side surface of the disc portion 151 of the first cam 150K. More specifically, the first protrusion 157A protrudes from the disc portion 151 in the rotation axis direction toward the side opposite to the side where the cam portion 153 and the switching protrusion 156 (see FIG. 5(a)) are arranged. The first protrusion 157A is arranged on the surface of the first cam 150K on the other side in the rotation axis direction. The first protrusion 157A has a cylindrical shape. In other words, the first protrusion 157A has a cylindrical surface that is capable of coming into contact with the first oscillating piece 220A of the linear motion plate 200.

[0152] The second protrusion 157B is capable of coming into contact with the linear motion plate 200, and when the linear motion plate 200 comes into contact with the second protrusion 157B as it moves from the first position to the second position, it rotates the second cam 150Y, the third cam 150M, and the fourth cam 150C. The second protrusion 157B protrudes from the side surface of the disc portion 151 of the second cam 150Y toward the other side in the rotation axis direction. The second protrusion 157B has a cylindrical shape. In other words, the second protrusion 157B has a cylindrical surface that is capable of coming into contact with the second oscillating piece 220B of the linear motion plate 200.

[0153] The third protrusion 157C is capable of coming into contact with the linear motion plate 200, and when the linear motion plate 200 moves from the first position to the second position and comes into contact with the third protrusion 157C, the third protrusion 157C rotates the second cam 150Y, the third cam 150M, and the fourth cam 150C. The third protrusion 157C protrudes from the side surface of the disc portion 151 of the fourth cam 150C toward the other side in the rotation axis direction. The third protrusion 157C has a cylindrical shape. In other words, the third protrusion 157C has a cylindrical surface that is capable of coming into contact with the first oscillatory piece 220A or the third oscillatory piece 220C of the linear motion plate 200.

[0154] 17(a), in the first embodiment, the first protrusion 157A is disposed at a position substantially opposite the cam surface 154 of the first cam 150K across the rotation axis of the first cam 150K, as viewed from the rotation axis direction. The second protrusion 157B is disposed at a position substantially opposite the cam surface 154 of the second cam 150Y across the rotation axis of the second cam 150Y, as viewed from the rotation axis direction. The third protrusion 157C is disposed at a position substantially overlapping with the upstream end of the holding surface 154B of the fourth cam 150C in the first rotation direction R1, as viewed from the rotation axis direction.

[0155] As shown in FIG. 15, the linear motion plate 200 has a linear motion plate body 210, a rocking piece 220, and three springs 230. The linear motion plate body 210 is supported by the housing 10 so as to move back and forth in conjunction with the opening and closing operation of the cover 11. The linear motion plate body 210 is connected to the cover 11 via a link (not shown).

[0156] The oscillating piece 220 is supported by the linear motion plate body 210 and moves back and forth together with the linear motion plate body 210. In the first embodiment, the oscillating piece 220 includes a first oscillating piece 220A serving as a first contact piece and a third contact piece, a second oscillating piece 220B serving as a second contact piece, and a third oscillating piece 220C. In the first embodiment, the first oscillating piece 220A serves as both the "first contact piece" and the "third contact piece."

[0157] When the linear moving plate 200 moves from the first position to the second position with the first cam follower 170K located at the pressing position, the first rocking piece 220A comes into contact with the first protrusion 157A of the first cam 150K. When the linear moving plate 200 moves from the first position to the second position, the first rocking piece 220A comes into contact with the first protrusion 157A, causing the first cam 150K to rotate and position the first cam follower 170K at the non-pressing position.

[0158] The first rocking piece 220A can come into contact with the third protrusion 157C of the fourth cam 150C when the linear moving plate 200 moves from the first position to the second position. If the first rocking piece 220A comes into contact with the third protrusion 157C when the linear moving plate 200 moves from the first position to the second position, the first rocking piece 220A rotates the second cam 150Y, the third cam 150M, and the fourth cam 150C, and positions the second cam follower 170Y, the third cam follower 170M, and the fourth cam follower 170C in the non-pressing position.

[0159] The second oscillating piece 220B can come into contact with the second protrusion 157B of the second cam 150Y when the linear moving plate 200 moves from the first position to the second position in a state where the second cam follower 170Y corresponding to the second cam 150Y having the second protrusion 157B is located in the pressing position. When the second oscillating piece 220B comes into contact with the second protrusion 157B when the linear moving plate 200 moves from the first position to the second position, the second oscillating piece 220B rotates the second cam 150Y, the third cam 150M, and the fourth cam 150C.

[0160] In the first embodiment, the first rocking piece 220A is provided so as to come into contact with the third protrusion 157C at a timing after the second rocking piece 220B comes into contact with the second protrusion 157B when the linear moving plate 200 moves from the first position to the second position. In more detail, the first rocking piece 220A is provided so as to come into contact with the third protrusion 157C at a timing after the second rocking piece 220B moves away from the second protrusion 157B when the linear moving plate 200 moves from the first position to the second position.

[0161] The third rocking piece 220C can come into contact with the third protrusion 157C of the fourth cam 150C when the linear moving plate 200 moves from the first position to the second position. If the third rocking piece 220C comes into contact with the third protrusion 157C when the linear moving plate 200 moves from the first position to the second position, the third rocking piece 220C rotates the second cam 150Y, the third cam 150M, and the fourth cam 150C, and positions the second cam follower 170Y at the non-pressing position.

[0162] The oscillating piece 220 is oscillatably supported by the linear motion plate body 210. More specifically, the oscillating piece 220 is oscillatably supported by a oscillating shaft 211 provided on the linear motion plate body 210. The oscillating piece 220 can oscillate between an active position indicated by a solid line and a retracted position indicated by a virtual line. The linear motion plate body 210 has a first oscillating restriction portion 212 and a second oscillating restriction portion 213 for defining the oscillating range of the oscillating piece 220. The oscillating piece 220 contacts the first oscillating restriction portion 212 when located in the active position, and contacts the second oscillating restriction portion 213 when located in the retracted position. Each oscillating piece 220 is biased from the retracted position toward the active position by a corresponding spring 230.

[0163] The oscillating piece 220 (first oscillating piece 220A, second oscillating piece 220B and third oscillating piece 220C) has a first contact surface 221 that is approximately perpendicular to the linear motion direction of the linear motion plate 200, and a second contact surface 222 that is inclined with respect to the linear motion direction of the linear motion plate 200.

[0164] The first contact surface 221 of the first rocking piece 220A comes into contact with the first protrusion 157A of the first cam 150K when the linear moving plate 200 moves from the first position to the second position with the first cam follower 170K in the pressing position. The first contact surface 221 of the first rocking piece 220A can come into contact with the third protrusion 157C of the fourth cam 150C when the linear moving plate 200 moves from the first position to the second position. The first contact surface 221 of the second rocking piece 220B can come into contact with the second protrusion 157B of the second cam 150Y when the linear moving plate 200 moves from the first position to the second position. The first contact surface 221 of the third rocking piece 220C can come into contact with the third protrusion 157C of the fourth cam 150C when the linear moving plate 200 moves from the first position to the second position.

[0165] The second contact surface 222 can come into contact with the first protrusion 157A, the second protrusion 157B, and the third protrusion 157C when the linear moving plate 200 moves from the second position to the first position, that is, when the cover 11 is closed. As shown in Fig. 16(a), for example, if the second contact surface 222 comes into contact with the first protrusion 157A when the linear moving plate 200 moves from the second position to the first position from front to rear, the first rocking piece 220A retracts from the operative position to the retracted position as shown in Fig. 16(b), thereby preventing the first cam 150K from rotating.

[0166] The same applies when the second contact surface 222 of the first rocking piece 220A comes into contact with the second protrusion 157B of the second cam 150Y or the third protrusion 157C of the fourth cam 150C. The same applies when the second contact surface 222 of the third rocking piece 220C comes into contact with the second protrusion 157B of the second cam 150Y or the third protrusion 157C of the fourth cam 150C. The same applies when the second contact surface 222 of the second rocking piece 220B comes into contact with the second protrusion 157B of the second cam 150Y.

[0167] Next, the function of the linear motion plate 200 will be described. In the image forming apparatus 1, all of the developer cartridges 60 are positioned at the separated position when the image forming apparatus 1 is in a standby state before printing is performed or after printing has been successfully completed. At this time, as shown in FIG. 17(a), the cam follower 170 is positioned at the pressing position where the contact arm 172 contacts the holding surface 154B of the corresponding cam 150. The contact arm 172 contacts the downstream end of the holding surface 154B in the first rotation direction R1. In this state, the first oscillating piece 220A of the linear motion plate 200 positioned at the first position can contact the first protrusion 157A of the first cam 150K, and the second oscillating piece 220B can contact the second protrusion 157B of the second cam 150Y.

[0168] 17(b), when the cover 11 is rotated from the closed position to the open position, the linear motion plate 200 moves forward from the first position to the second position in conjunction with this. As a result, the second oscillating piece 220B of the linear motion plate 200 first comes into contact with the second protrusion 157B of the second cam 150Y. As the linear motion plate 200 moves further forward, the second protrusion 157B is pushed by the second oscillating piece 220B, causing the second cam 150Y, the third cam 150M, and the fourth cam 150C to rotate in conjunction with each other in a second rotation direction R2, which is opposite to the first rotation direction R1.

[0169] As a result, the contact arms 172 of the cam followers 170Y, 170M, 170C come into sliding contact with the holding surfaces 154B of the corresponding cams 150Y, 150M, 150C toward the first guide surface 154A. Then, first, the contact arm 172 of the fourth cam follower 170C is guided from the holding surface 154B of the fourth cam 150C to the first guide surface 154A, and comes into sliding contact with the first guide surface 154A before disengaging from the cam surface 154. As a result, the fourth cam follower 170C slides from the pressing position to the non-pressing position, and the fourth developer cartridge 60C moves from the separated position to the contact position.

[0170] 18(a), when the second protrusion 157B is no longer pressed by the second swing piece 220B due to the movement of the linear motion plate 200 and the rotation of the cams 150Y, 150M, and 150C, the rotation of the cams 150Y, 150M, and 150C stops. At this time, the fourth cam follower 170C is in the non-pressing position, the third cam follower 170M has its contact arm 172 positioned on the first guide surface 154A of the third cam 150M, and the second cam follower 170Y has its contact arm 172 positioned on the holding surface 154B of the second cam 150Y, so is still in the pressing position.

[0171] When the second protrusion 157B is no longer pressed by the second oscillatory piece 220B, the first oscillatory piece 220A of the linear moving plate 200 comes into contact with the first protrusion 157A of the first cam 150K. As shown in Figure 18(b), when the linear moving plate 200 moves further forward, the first protrusion 157A is pressed by the first oscillatory piece 220A, causing the first cam 150K to rotate in a second rotation direction R2 that is opposite to the first rotation direction R1.

[0172] As a result, the contact arm 172 of the first cam follower 170K comes into sliding contact with the first guide surface 154A on the holding surface 154B of the first cam 150K. Then, the contact arm 172 of the first cam follower 170K is guided from the holding surface 154B of the first cam 150K to the first guide surface 154A, and comes into sliding contact with the first guide surface 154A, as shown in Figure 19(a). As a result, the first cam follower 170K slides from the pressing position to the non-pressing position, and the first developer cartridge 60K moves from the separated position to the contact position.

[0173] When the first protrusion 157A is no longer pressed by the first swinging piece 220A due to the movement of the linear motion plate 200 and the rotation of the first cam 150K, the rotation of the first cam 150K stops. At this time, the second swinging piece 220B is separated from the second protrusion 157B of the second cam 150Y.

[0174] 19(b), when the linear motion plate 200 moves further forward, the first oscillating piece 220A then comes into contact with the third protrusion 157C of the fourth cam 150C. When the linear motion plate 200 moves further forward, the third protrusion 157C is pushed by the first oscillating piece 220A, causing the cams 150Y, 150M, and 150C to rotate again in the second rotation direction R2.

[0175] As a result, first, the contact arm 172 of the third cam follower 170M slides on the first guide surface 154A of the third cam 150M and disengages from the cam surface 154. As a result, the third cam follower 170M slides from the pressing position to the non-pressing position, and the third developer cartridge 60M moves from the separated position to the contact position. Thereafter, the contact arm 172 of the second cam follower 170Y is guided from the holding surface 154B of the second cam 150Y to the first guide surface 154A, slides on the first guide surface 154A, and disengages from the cam surface 154, as shown in FIG. 20(a). As a result, the second cam follower 170Y slides from the pressing position to the non-pressing position, and the second developer cartridge 60Y moves from the separated position to the contact position.

[0176] 20(b), when the cover 11 is opened and positioned at the open position, the linear motion plate 200 is positioned at the second position. At this time, all of the cam followers 170 are positioned at the non-pressing position, and all of the developer cartridges 60 are positioned at the contact position.

[0177] As shown in Figure 21, if the image forming apparatus 1 stops during printing, for example, and the cams 150Y, 150M, and 150C stop at a phase immediately after the second cam follower 170Y slides to the non-pressing position, the third oscillating piece 220C of the linear motion plate 200, which is located in the first position, can come into contact with the third protrusion 157C of the fourth cam 150C.

[0178] In this state, when the cover 11 is opened and the linear motion plate 200 moves forward from the first position to the second position, the third swing piece 220C comes into contact with the third protrusion 157C, and the third protrusion 157C is pushed by the third swing piece 220C, causing the cams 150Y, 150M, and 150C to rotate in the second rotation direction R2. As a result, the contact arm 172 of the second cam follower 170Y is guided from the holding surface 154B of the second cam 150Y to the first guide surface 154A, sliding on the first guide surface 154A and disengaging from the cam surface 154. As a result, the second cam follower 170Y slides from the pressing position to the non-pressing position.

[0179] Next, the effects of the image forming apparatus 1 of the first embodiment will be described. Since the first shaft 171 of the first cam follower 170K is arranged inside the outer periphery of the first cam 150K when viewed from the direction of the rotation axis, the first cam 150K and the first cam follower 170K can be arranged compactly when viewed from the direction of the rotation axis.

[0180] Furthermore, since the first shaft 171 of the second cam follower 170Y is disposed inside the outer periphery of the second cam 150Y when viewed from the rotational axis direction, the second cam 150Y and the second cam follower 170Y can be disposed compactly when viewed from the rotational axis direction. Furthermore, since the first shaft 171 of the third cam follower 170M is disposed inside the outer periphery of the third cam 150M when viewed from the rotational axis direction, the third cam 150M and the third cam follower 170M can be disposed compactly when viewed from the rotational axis direction. Furthermore, since the first shaft 171 of the fourth cam follower 170C is disposed inside the outer periphery of the fourth cam 150C when viewed from the rotational axis direction, the fourth cam 150C and the fourth cam follower 170C can be disposed compactly when viewed from the rotational axis direction.

[0181] As a result, in a configuration including a plurality of cams 150 and a plurality of cam followers 170, the cams 150 and the cam followers 170 can be arranged compactly when viewed from the direction of the rotation axis.

[0182] Furthermore, since the first shaft 171 of the cam follower 170 is engaged with the second shaft 159 that rotatably supports the cam 150 and is capable of sliding movement, the cam 150 and the cam follower 170 having the contact arm 172 and the regulating arm 173 extending from the first shaft 171 can be arranged more compactly when viewed from the direction of the rotation axis.

[0183] Furthermore, since the rotation of the cam follower 170 around the first shaft 171 is restricted, the rotational movement of the cam 150 can be efficiently converted into the sliding movement of the cam follower 170.

[0184] Furthermore, the rotation of the cam follower 170 around the first shaft 171 can be reliably restricted by the stopper 179 that sandwiches the restriction arm 173 .

[0185] Furthermore, by opening the cover 11, the first cam follower 170K can be positioned in the non-pressing position by the linear motion plate 200. This makes it possible to prevent interference between the first developing cartridge 60K and the first cam follower 170K when attaching or detaching the first developing cartridge 60K.

[0186] Furthermore, by opening the cover 11, the second cam follower 170Y, the third cam follower 170M, and the fourth cam follower 170C can be positioned in the non-pressing position by the linear motion plate 200. This makes it possible to prevent interference between the developing cartridges 60Y, 60M, and 60C and the corresponding cam followers 170Y, 170M, and 170C when attaching or detaching the second developing cartridge 60Y, etc.

[0187] Furthermore, since the linear motion plate 200 has the swinging piece 220 that rotates the cam 150 when it comes into contact with the protrusions 157A, 157B, 157C of the cam 150, the linear motion of the linear motion plate 200 can be converted into the rotational motion of the cam 150.

[0188] Furthermore, since the oscillating piece 220 has the first contact surface 221, the oscillating piece 220 of the linear motion plate 200 moving from the first position to the second position can be reliably abutted against the protrusions 157A, 157B, 157C of the cam 150 while the cam 150 is positioned within a predetermined phase range.

[0189] Furthermore, when the linear motion plate 200 moves from the second position to the first position, it is possible to prevent the position of the cam follower 170 from changing from the position before the linear motion plate 200 moved. More specifically, if the swinging piece 220 comes into contact with the protrusions 157A, 157B, 157C when the cover 11 is closed, the swinging piece 220 retracts and does not rotate the cam 150, so it is possible to prevent the position of the corresponding cam follower 170 from changing from the position before the cover 11 was closed.

[0190] Furthermore, since the protrusions 157A, 157B, and 157C of the cam 150 have cylindrical surfaces that can come into contact with the oscillating piece 220, the protrusions 157A, 157B, and 157C can be kept in continuous contact with the oscillating piece 220 in the same contact state even when the cam 150 rotates. This allows the linear motion of the linear motion plate 200 to be efficiently converted into the rotational motion of the cam 150.

[0191] Furthermore, because the angle of second guide surface 154C with respect to the rotation direction of cam 150 is larger than the angle of first guide surface 154A, the length of cam surface 154 in the rotation direction of cam 150 can be shortened compared to when the angle of the second guide surface is substantially the same as the angle of the first guide surface. This makes it possible to reduce the rotation angle of cam 150 required to slide cam follower 170 between the non-pressing position and the pressing position. Also, cam 150 can be made smaller.

[0192] Furthermore, because the timing at which the cam followers 170Y, 170M, and 170C move from the non-pressing position to the pressing position is staggered, it is possible to stagger the timing at which force is applied to the cam followers 170Y, 170M, and 170C. This makes it possible to prevent the driving force for driving the cams 150Y, 150M, and 150C from becoming too large. Additionally, when the cam follower 170 moves from the non-pressing position to the pressing position where it presses the corresponding developer cartridge 60, a force is applied to the cam follower 170, making it difficult for the cam follower 170 to slide and for the corresponding cam 150 to rotate. If the timing at which the cam followers 170Y, 170M, and 170C move from the non-pressing position to the pressing position overlaps, a large driving force is required to drive the cams 150Y, 150M, and 150C. However, in the first embodiment, it is possible to prevent the driving force for driving the cams 150Y, 150M, and 150C from becoming too large.

[0193] Furthermore, when the linear plate 200 moves from the first position to the second position, the cams 150Y, 150M, and 150C are rotated by the second oscillating piece 220B, and then the cams 150Y, 150M, and 150C are further rotated by the first oscillating piece 220A, so that the second cam 150Y, which has a longer cam surface 154 in the rotation direction, can be rotated reliably, and the second cam follower 170Y can be moved reliably from the pressing position to the non-pressing position.

[0194] Furthermore, when the linear moving plate 200 moves from the first position to the second position, the first rocking piece 220A comes into contact with the third protrusion 157C of the fourth cam 150C at the timing after the second rocking piece 220B separates from the second protrusion 157B of the second cam 150Y, thereby enabling smooth operation of the linear moving plate 200 and the cams 150Y, 150M, and 150C. Additionally, if the first rocking piece 220A comes into contact with the third protrusion while the second rocking piece 220B is in contact with the second protrusion, friction generated by contact between the rocking piece 220 and the protrusion of the cam increases, which may interfere with the operation of the linear moving plate 200 and the cams 150Y, 150M, and 150C; however, in the first embodiment, such an increase in friction can be suppressed, enabling smooth operation of the linear moving plate 200 and the cams 150Y, 150M, and 150C.

[0195] Furthermore, when the linear moving plate 200 moves from the first position to the second position, the cam 150 is rotated in the second rotation direction R2, which is opposite to the first rotation direction R1 during normal control. This reduces the operating load of the linear moving plate 200. Specifically, if the cam 150 is rotated in the first rotation direction R1 when the linear moving plate moves from the first position to the second position, particularly from the phase immediately after the second cam follower 170Y slides to the non-pressing position (see FIG. 21), the cam followers 170M and 170C must be temporarily moved from the non-pressing position to the pressing position by the cam surface 154 before the second cam follower 170Y moves to the non-pressing position, which increases the operating load of the linear moving plate. In the first embodiment, since it is not necessary to temporarily move the cam followers 170M and 170C from the non-pressing position to the pressing position, the operating load of the linear moving plate 200 can be reduced. This reduces the operating load required when the user opens the cover 11.

[0196] Furthermore, because the timing at which the cam followers 170Y, 170M, and 170C move from the pressing position to the non-pressing position overlaps with one another, the length of the cam surface 154 in the rotation direction of the cams 150Y, 150M, and 150C can be shortened. This reduces the rotation angle of the cams 150Y, 150M, and 150C required to slide the cam followers 170Y, 170M, and 170C between the non-pressing position and the pressing position. Furthermore, the cams 150Y, 150M, and 150C can be made smaller.

[0197] Furthermore, the moving gear 134 and the switching cam 194 allow the developing rollers 61Y, 61M, and 61C to rotate when the developing cartridges 60Y, 60M, and 60C are in the contact position, and the developing rollers 61Y, 61M, and 61C to stop when the developing cartridges 60Y, 60M, and 60C are in the separated position. This prevents the developing rollers 61Y, 61M, and 61C from rotating more than necessary. This, for example, can prevent deterioration of the developing rollers 61Y, 61M, and 61C, toner, and the like.

[0198] Furthermore, because the first cam 150K has the cam surface 154, the switching protrusion 156 disposed on one surface in the rotational axis direction, and the first protrusion 157A disposed on the other surface in the rotational axis direction, it is possible to prevent the first cam 150K from becoming too large. Furthermore, the first cam 150K can be provided with the functions of sliding the first cam follower 170K between the pressing position and the non-pressing position, operating the switching lever 160, and positioning the first cam follower 170K at the non-pressing position via the linear motion plate 200. This eliminates the need for a portion of the first cam follower 170K that contacts the linear motion plate 200, eliminating the need to secure space for rotating this portion. This allows the first cam 150K and the first cam follower 170K to be compactly arranged while still achieving the function of positioning the first cam follower 170K at the non-pressing position.

[0199] Furthermore, since the cam surface 154 of the first cam 150K is disposed on one surface of the first cam 150K in the direction of the rotation axis, it is possible to increase the degree of freedom in the arrangement of the first protrusion 157A disposed on the surface opposite to the cam surface 154. This makes it possible to prevent the first cam 150K from becoming large, and to arrange the first cam 150K and the linear motion plate 200 in a compact manner.

[0200] Furthermore, because the switching protrusion 156 is positioned so as to overlap the holding surface 154B of the cam portion 153 in the circumferential direction around the rotation axis of the first cam 150K, the first cam 150K and the first cam follower 170K can be configured compactly. Furthermore, if the switching protrusion and the holding surface 154B were not positioned so as to overlap in the circumferential direction, the switching protrusion and the contact arm of the first cam follower 170K positioned in the non-pressing position would need to be offset in the rotation axis direction to prevent interference between the switching protrusion and the contact arm. In the first embodiment, because it is not necessary to offset the switching protrusion 156 and the contact arm 172 in the rotation axis direction, the first cam 150K and the first cam follower 170K can be configured compactly. This allows the first cam 150K and the first cam follower 170K to be arranged more compactly.

[0201] Furthermore, since the switching protrusion 156 is disposed on the flange portion 155, the cam surface 154 can be disposed near the outer periphery of the disk portion 151. This makes it possible to ensure the length of the cam surface 154 in the rotation direction of the first cam 150K while preventing the first cam 150K from becoming large.

[0202] Furthermore, since the first motor M1 and the second motor M2 are provided separately, it is possible to separately control the rotation and stopping of the first developing roller 61K to which the driving force is transmitted from the first motor M1 and the rotation and stopping of the first cam 150K to which the driving force is transmitted from the second motor M2. Furthermore, since the third motor M3 is provided separately from the second motor M2, it is possible to separately control the rotation and stopping of the developing rollers 61Y, 61M, and 61C to which the driving force is transmitted from the third motor M3 and the rotation and stopping of the cams 150Y, 150M, and 150C to which the driving force is transmitted from the second motor M2.

[0203] Furthermore, since the switching protrusion 156 is provided to move the switching lever 160 to the first transmission position at a timing before the first developing cartridge 60K moves to the contact position, the first developing roller 61K can be rotated before the first developing roller 61K comes into contact with the first photosensitive drum 50K. Furthermore, since the switching protrusion 156 is provided to move the switching lever 160 to the first disconnection position at a timing after the first developing cartridge 60K moves to the separated position, the first developing roller 61K can be stopped after it is separated from the first photosensitive drum 50K.

[0204] Furthermore, since the switching cam 194 is provided to move the moving gear 134 to the second transmission position at a timing before the second developing cartridge 60Y moves to the contact position, the developing rollers 61Y, 61M, and 61C can be rotated before the second developing roller 61Y contacts the second photosensitive drum 50Y. Furthermore, since the switching cam 194 is provided to move the moving gear 134 to the second disconnection position at a timing after the fourth developing cartridge 60C moves to the separated position, the developing rollers 61Y, 61M, and 61C can be stopped after the fourth developing roller 61C separates from the fourth photosensitive drum 50C.

[0205] This eliminates the constraint that, for example, the developing roller 61 and the photosensitive drum 50 start to rotate simultaneously after the developing roller 61 has been brought into contact with the photosensitive drum 50, and the developing roller 61 and the photosensitive drum 50 stop simultaneously before the developing roller 61 is separated from the photosensitive drum 50. Furthermore, for example, the timing of rotation and stopping of the photosensitive drum 50 can be set regardless of the timing of contact and separation of the developing roller 61.

[0206] Next, a second embodiment will be described. Note that the following will focus on differences from the previously described embodiment, and descriptions of the same points will be omitted as appropriate, for example, by assigning the same reference numerals to similar elements. As shown in FIG. 22, the first cam 150K of the second embodiment has a disk portion 151, a gear portion 152, a cam portion 253, a flange portion 255, a switching protrusion 256, and a first protrusion 257.

[0207] The switching protrusion 256 is capable of coming into contact with the switching lever 260 and moves the switching lever 260 between a first transmission position (see FIG. 23) and a first disconnection position (see FIG. 24). The switching protrusion 256 protrudes from the disc portion 151 toward one side in the rotational axis direction. The switching protrusion 256 is disposed on a surface of one side in the rotational axis direction of the first cam 150K.

[0208] The flange portion 255 is formed on the outer periphery of the disk portion 151. The flange portion 255 is located on the other side in the rotational axis direction of the gear portion 152. The flange portion 255 is provided so as to overlap with the gear portion 152 when viewed from the rotational axis direction. The flange portion 255 extends radially outward from the tips of the gear teeth of the gear portion 152.

[0209] The first protrusion 257 is capable of coming into contact with the linear motion plate 200, and rotates the first cam 150K when the linear motion plate 200 comes into contact with the first protrusion 257 while moving from the first position to the second position. The first protrusion 257 is disposed on the flange portion 255. More specifically, the first protrusion 257 protrudes from the flange portion 255 toward the other side in the rotation axis direction. The first protrusion 257 is disposed on the surface of the first cam 150K on the other side in the rotation axis direction.

[0210] The cam portion 253 protrudes from the disk portion 151 toward the other side in the rotational axis direction. The cam portion 253 has a cam surface 154. In the second embodiment, the cam surface 154 is arranged on the surface on the other side in the rotational axis direction of the first cam 150K. In the second embodiment, the cam surface 154 is arranged on the same surface as the first protrusion 257. As shown in FIG. 23(b), the first protrusion 257 is arranged at a position overlapping with the holding surface 154B of the cam surface 154 in the circumferential direction centered on the rotational axis of the first cam 150K, as viewed from the rotational axis direction. The first protrusion 257 and the cam portion 253 are connected by a rib 258 provided to extend from the cam portion 253 toward the radially outer side of the first cam 150K.

[0211] The switching lever 260 can swing around the swing shaft 260A between a first transmission position shown in Fig. 23 where the switching lever 260 engages with the claw portion 188 of the transmission element 180C to enable transmission of the driving force to the first developing roller 61K, and a first disconnection position shown in Fig. 24 where the switching lever 260 disengages from the claw portion 188 to disable transmission of the driving force to the first developing roller 61K. As shown in Fig. 25(a), the switching lever 260 has a first lever 261, a second lever 262, and a first spring 263.

[0212] The first lever 261 is swingable around the swing shaft 260A and is capable of coming into contact with the switching protrusion 256 of the first cam 150K. The first lever 261 has a first support portion 261A that is swingably supported around the swing shaft 260A on the housing 10, a first arm 261B that extends from the first support portion 261A, and a lever protrusion 261C that protrudes in the direction of the rotation axis. As shown in FIGS. 25(b) and (c), the first lever 261 is also swingable around the swing shaft 260A relative to the second lever 262.

[0213] The second lever 262 is swingable around the swing shaft 260A and is engageable with the transfer element 180C of the planetary gear mechanism 180. The second lever 262 has a second support portion 262A swingably supported around the swing shaft 260A on the housing 10, a second arm 262B extending from the second support portion 262A, a rotation restricting portion 262C, and a spring hook portion 262D. The tip portion of the second arm 262B extends toward the outer periphery of the transfer element 180C. The switching lever 260 restricts the rotation of the transfer element 180C when the tip portion of the second arm 262B engages with the claw portion 188 of the transfer element 180C. The rotation restricting portion 262C protrudes from the second support portion 262A toward the opposite side to the second arm 262B. The rotation restricting portion 262C restricts the rotation of the first lever 261 relative to the second lever 262 in one direction by contacting the lever protrusion 261C of the first lever 261.

[0214] First spring 263 biases first lever 261 so as not to rotate relative to second lever 262 when rotation restricting portion 262C provided on second lever 262 comes into contact with lever protrusion 261C of first lever 261. First spring 263 is, for example, a torsion spring.

[0215] As shown in FIG. 23(a), the image forming apparatus 1 further includes a second spring 269. The second spring 269 biases the switching lever 260 in a direction that causes the switching lever 260 to swing from the first disconnection position toward the first transmission position. Specifically, the second spring 269 biases the second lever 262 in a direction that causes the second lever 262 to swing toward the transmission element 180C. The second spring 269 is a tension coil spring, and one end of the second spring 269 is hooked to a spring hook 262D provided on the second lever 262, and the other end of the second spring 269 is hooked to a spring hook (not shown) provided on the housing 10 at a position rearward of the spring hook 262D. As a result, the second spring 269 biases the second lever 262 in a counterclockwise direction in FIG. 23(a).

[0216] 23, when the first developer cartridge 60K is located at the contact position, the first cam follower 170K is located at the non-pressing position where the contact arm 172 is disengaged from the cam surface 154. At this time, the switching protrusion 256 of the first cam 150K is separated from the first arm 261B of the switching lever 260, and the switching lever 260 is located at the first transmission position where the second arm 262B engages with the claw portion 188 of the transmission element 180C.

[0217] When the control unit 2 rotates the first cam 150K in the first rotation direction R1 from the state shown in Fig. 23, the contact arm 172 comes into contact with the first guide surface 154A of the cam surface 154, slides on the first guide surface 154A, and comes into contact with the holding surface 154B as shown in Fig. 24. This causes the first cam follower 170K to move from the non-pressing position to the pressing position, and the first developing cartridge 60K to move from the contact position to the separated position.

[0218] Furthermore, when the first cam follower 170K moves to the pressing position, the switching protrusion 256 of the first cam 150K comes into contact with the first arm 261B, and the switching lever 260 is pushed and moved by the switching protrusion 256, causing it to swing from the first transmitting position to the first disconnecting position. This causes the second arm 262B to disengage from the claw portion 188 of the transmitting element 180C. When the developing cartridge 60 moves to the separated position, the control unit 2 stops the rotation of the first cam 150K.

[0219] 24, when the control unit 2 rotates the first cam 150K in the first rotation direction R1, the contact arm 172 of the first cam follower 170K is guided from the holding surface 154B to the second guide surface 154C, slides on the second guide surface 154C, and disengages from the cam surface 154. As a result, the first cam follower 170K moves from the pressing position to the non-pressing position, and the first developing cartridge 60K moves from the separated position to the contact position.

[0220] Furthermore, when the first cam follower 170K moves to the non-pressing position, the switching protrusion 256 of the first cam 150K moves away from the first arm 261B, and the switching lever 260 swings from the first disconnection position to the first transmission position due to the biasing force of the second spring 269. This causes the second arm 262B to engage with the claw portion 188 of the transmission element 180C. When the developer cartridge 60 moves to the contact position, the control unit 2 stops the rotation of the first cam 150K.

[0221] As shown in Figure 26(a), when the linear plate 200 moves forward from the first position to the second position with the first cam follower 170K positioned in the pressing position, it rotates the first cam 150K in a second rotation direction R2 opposite to the first rotation direction R1, thereby positioning the first cam follower 170K in the non-pressing position.

[0222] More specifically, when the linear motion plate 200 moves forward from the first position to the second position with the contact arm 172 in contact with the holding surface 154B, the first swinging piece 220A comes into contact with the first protrusion 257. Then, the first protrusion 257 is pushed by the first swinging piece 220A, causing the first cam 150K to rotate in a second rotation direction R2 that is opposite to the first rotation direction R1. As a result, the contact arm 172 is guided from the holding surface 154B to the first guide surface 154A, slides on the first guide surface 154A, and disengages from the cam surface 154, causing the first cam follower 170K to slide from the pressing position to the non-pressing position.

[0223] When the first cam 150K rotates in the second rotation direction R2 while the second lever 262 of the switching lever 260 is engaged with the claw portion 188 of the transfer element 180C, the switching protrusion 256 comes into contact with the first lever 261, and the first lever 261 is pushed by the switching protrusion 256, as shown in FIG. 26(b). This causes the first lever 261 to swing relative to the second lever 262 against the biasing force of the first spring 263, as shown by the imaginary line. This prevents excessive force from being applied to the switching lever 260 when the first cam 150K rotates in the second rotation direction R2.

[0224] Furthermore, according to the second embodiment, the cam surface 154 of the first cam 150K is disposed on the surface on the other side in the rotational axis direction of the first cam 150K, which increases the degree of freedom in the arrangement of the switching protrusion 256 that is disposed on the surface on the opposite side of the cam surface 154. This makes it possible to prevent the first cam 150K from becoming larger, and to arrange the first cam 150K and the switching lever 260 in a compact manner.

[0225] Furthermore, because the first protrusion 257 is positioned so as to overlap the holding surface 154B of the cam portion 253 in the circumferential direction about the rotation axis of the first cam 150K, the first cam 150K and the first cam follower 170K can be configured compactly. Additionally, if the first protrusion and the holding surface 154B are not positioned so as to overlap in the circumferential direction, the first protrusion and the contact arm of the first cam follower 170K positioned in the non-pressing position must be positioned so as to be offset in the rotation axis direction so as not to interfere with each other. In the second embodiment, because the first protrusion 257 and the contact arm 172 do not need to be offset in the rotation axis direction, the first cam 150K and the first cam follower 170K can be configured compactly. This allows the first cam 150K and the first cam follower 170K to be arranged more compactly.

[0226] Furthermore, since the first protrusion 257 is disposed on the flange portion 255, the cam surface 154 can be disposed near the outer periphery of the disk portion 151. This makes it possible to ensure the length of the cam surface 154 in the rotation direction of the first cam 150K while preventing the first cam 150K from becoming large.

[0227] Next, a third embodiment will be described. In the third embodiment, illustration and description of a mechanism for switching between transmitting and cutting off the driving force to the developing roller 61 will be omitted. As shown in FIGS. 27(a) and 27(b), a cam 150 of the third embodiment has a disk portion 151, a gear portion 152, and a cam portion 153.

[0228] The cam follower 170 of the third embodiment has a first shaft 171 and a contact arm 272. The cam follower 170 of the third embodiment does not include a restricting arm. The contact arm 272 is a portion that contacts the cam surface 154 of the cam 150. The contact arm 272 extends from the first shaft 171 toward the outside in the radial direction of the first shaft 171. Note that in Figures 28 and 29, which will be referred to later, the holding surface 154B and the contact arm 272 are indicated by dot hatching.

[0229] Image forming apparatus 1 includes stoppers 279 that restrict rotation of cam follower 170 around first shaft 171. Stoppers 279 are a pair of rod-shaped members. Stoppers 279 are provided in housing 10. Stoppers 279 are arranged to sandwich contact arm 272 of cam follower 170 from both sides in the circumferential direction of first shaft 171. This restricts rotation of cam follower 170 around first shaft 171. In the third embodiment, stoppers 279 that sandwich contact arm 272 can reliably restrict rotation of cam follower 170 around first shaft 171.

[0230] 27(c), the first cam 150K has a first protrusion 257A. The first protrusion 257A can come into contact with the first oscillating piece 220A of the linear motion plate 200, and rotates the first cam 150K when the linear motion plate 200, which moves from the first position to the second position, comes into contact with the first protrusion 257A. The first protrusion 257A protrudes in the direction of the rotation axis from the side surface of the disc portion 151 of the first cam 150K.

[0231] 28(a), the second cam 150Y has a second protrusion 257B. The second protrusion 257B can come into contact with the second oscillating piece 220B of the linear motion plate 200, and rotates the cams 150Y, 150M, and 150C when the linear motion plate 200, which moves from the first position to the second position, comes into contact with the second protrusion 257B. The second protrusion 257B protrudes in the direction of the rotation axis from the side surface of the disc portion 151 of the second cam 150Y.

[0232] The fourth cam 150C has a third protrusion 257C. The third protrusion 257C can come into contact with the third oscillating piece 220C of the linear motion plate 200, and rotates the cams 150Y, 150M, and 150C when the linear motion plate 200 moves from the first position to the second position and makes contact with the third protrusion 257C. The third protrusion 257C protrudes from the side surface of the disc portion 151 of the fourth cam 150C in the direction of the rotation axis.

[0233] As an example, in the third embodiment, the first protrusion 257A is disposed at a position substantially opposite the cam surface 154 of the first cam 150K across the rotation axis of the first cam 150K when viewed from the rotation axis direction. The second protrusion 257B is disposed at a position substantially opposite the cam surface 154 of the second cam 150Y across the rotation axis of the second cam 150Y when viewed from the rotation axis direction. The third protrusion 257C is disposed at a position substantially opposite the cam surface 154 of the fourth cam 150C across the rotation axis of the fourth cam 150C when viewed from the rotation axis direction.

[0234] When the linear motion plate 200 of the third embodiment moves from the first position to the second position with the first cam follower 170K located in the pressing position, the linear motion plate 200 rotates the first cam 150K in the first rotation direction R1 to position the first cam follower 170K at the non-pressing position. Also, when the linear motion plate 200 of the third embodiment moves from the first position to the second position with at least the second cam follower 170Y located in the pressing position, the linear motion plate 200 rotates the cams 150Y, 150M, and 150C in the first rotation direction R1 to position the cam followers 170Y, 170M, and 170C at the non-pressing position.

[0235] The linear motion plate 200 has a linear motion plate body 210, a swinging piece 220, and a spring 230. In the third embodiment, the swinging piece 220 includes a first swinging piece 220A as a first contact piece, a second swinging piece 220B as a second contact piece, and a third swinging piece 220C as a third contact piece.

[0236] When the linear moving plate 200 moves from the first position to the second position with the first cam follower 170K located at the pressing position, the first rocking piece 220A comes into contact with the first protrusion 257A of the first cam 150K. When the linear moving plate 200 moves from the first position to the second position, the first rocking piece 220A comes into contact with the first protrusion 257A, causing the first cam 150K to rotate in the first rotation direction R1 and positioning the first cam follower 170K at the non-pressing position.

[0237] The second oscillating piece 220B can come into contact with the second protrusion 257B of the second cam 150Y when the linear motion plate 200 moves from the first position to the second position with the second cam follower 170Y located at the pressing position. When the second oscillating piece 220B comes into contact with the second protrusion 257B when the linear motion plate 200 moves from the first position to the second position, the second oscillating piece 220B rotates the cams 150Y, 150M, and 150C in the first rotation direction R1.

[0238] The third oscillating piece 220C can come into contact with the third protrusion 257C of the fourth cam 150C when the linear moving plate 200 moves from the first position to the second position. If the third oscillating piece 220C comes into contact with the third protrusion 257C when the linear moving plate 200 moves from the first position to the second position, the third oscillating piece 220C rotates the cams 150Y, 150M, and 150C in the first rotation direction R1, and positions the cam followers 170Y, 170M, and 170C in the non-pressing position.

[0239] Next, the function of the linear motion plate 200 will be described. As shown in Figure 28(a), in the phase immediately after the second cam follower 170Y slides to the non-pressing position, the second oscillating piece 220B of the linear motion plate 200 located in the first position can come into contact with the second protrusion 257B of the second cam 150Y.

[0240] 28(b), as the cover 11 is opened, the linear motion plate 200 moves forward from the first position to the second position. As a result, the second oscillating piece 220B comes into contact with the second protrusion 257B. As the linear motion plate 200 moves further forward, the second protrusion 257B is pushed by the second oscillating piece 220B, causing the cams 150Y, 150M, and 150C to rotate in the first rotation direction R1.

[0241] 29(a), the contact arm 272 of the second cam follower 170Y comes into sliding contact on the holding surface 154B of the second cam 150Y toward the second guide surface 154C. The contact arm 272 of the third cam follower 170M comes into contact with the first guide surface 154A of the third cam 150M and slides on the first guide surface 154A, then comes into contact with the holding surface 154B and slides on the holding surface 154B toward the second guide surface 154C. The contact arm 272 of the fourth cam follower 170C comes into contact with the first guide surface 154A of the fourth cam 150C and slides on the first guide surface 154A, then comes into contact with the holding surface 154B.

[0242] When the second protrusion 257B is no longer pressed by the second oscillatory piece 220B, the third oscillatory piece 220C now comes into contact with the third protrusion 257C of the fourth cam 150C. When the linear motion plate 200 moves further forward, the third protrusion 257C is pressed by the third oscillatory piece 220C, causing the cams 150Y, 150M, and 150C to rotate in the first rotation direction R1.

[0243] 29(b), the cam followers 170Y, 170M, 170C slide on the holding surfaces 154B of the cams 150Y, 150M, 150C corresponding to the contact arms 272 toward the second guide surfaces 154C, are guided from the holding surfaces 154B to the second guide surfaces 154C, and slide on the second guide surfaces 154C to disengage from the cam surfaces 154. As a result, the cam followers 170Y, 170M, 170C slide from the pressing positions to the non-pressing positions, and the developer cartridges 60Y, 60M, 60C move from the separated positions to the contact positions. When the cover 11 is opened, the linear motion plate 200 is positioned at the second position indicated by the imaginary lines.

[0244] 27(c), when the first rocking piece 220A comes into contact with the first protrusion 257A of the first cam 150K as the linear moving plate 200 moves from the first position to the second position, the first protrusion 257A is pushed by the first rocking piece 220A, causing the first cam 150K to rotate in the first rotation direction R1. As a result, the contact arm 272 of the first cam follower 170K slides on the holding surface 154B of the first cam 150K toward the second guide surface 154C, is guided from the holding surface 154B to the second guide surface 154C, and slides on the second guide surface 154C to disengage from the cam surface 154. As a result, the first cam follower 170K slides from the pressing position to the non-pressing position, and the first developer cartridge 60K moves from the separated position to the contact position.

[0245] Next, a fourth embodiment will be described. In the fourth embodiment, illustrations and descriptions of a mechanism for switching between transmitting and disconnecting the driving force to the developing roller 61 and a mechanism for moving the cam follower 170 to the non-pressing position when the cover 11 is opened will be omitted.

[0246] As shown in Fig. 30(a), the cam 150 of the fourth embodiment has a disk portion 151, a gear portion 152, and a cam portion 353. The cam follower 170 is slidable in the direction of the rotation axis by the rotation of the cam 150 between the pressing position shown in Fig. 30(a) and the non-pressing position shown in Fig. 30(e).

[0247] The cam portion 353 protrudes from the side surface of the disc portion 151 in the direction of the rotation axis. The cam portion 353 has a cam surface 354 that moves the cam follower 170 between a pressing position and a non-pressing position, thereby moving the developer cartridge 60 between a separated position and a contact position. The cam portion 353 has a first cam portion 353A and a second cam portion 353B. The second cam portion 353B has a shape that is point-symmetrical to the first cam portion 353A about the rotation axis of the cam 150.

[0248] Cam surface 354 has a first cam surface 354A provided on first cam portion 353A and a second cam surface 354B provided on second cam portion 353B. Second cam surface 354B has a shape that is point-symmetrical to first cam surface 354A about the rotation axis of cam 150. As shown in FIG. 30(b), first cam surface 354A and second cam surface 354B each have a first guide surface 154A that moves cam follower 170 from the non-pressing position to the pressing position, a holding surface 154B that holds cam follower 170 at the pressing position, and a second guide surface 154C that moves cam follower 170 from the pressing position to the non-pressing position.

[0249] As shown in FIG. 30( a ), the cam follower 170 has a first shaft 371 and a contact arm 372 . First shaft 371 is supported so as to be slidable in the direction of the rotation axis. More specifically, image forming apparatus 1 includes second shaft 359 that rotatably supports cam 150, and first shaft 171 is engaged with second shaft 359, thereby being supported so as to be slidable in the direction of the rotation axis. This allows cam follower 170 to slide in the direction of the rotation axis between a pressed position and a non-pressed position.

[0250] The contact arm 372 has a first contact arm 372A and a second contact arm 372B. The first contact arm 372A extends from the first shaft 371 in a direction perpendicular to the rotation axis direction. The first contact arm 372A can alternately contact the first cam surface 354A and the second cam surface 354B as the cam 150 rotates. The second contact arm 372B extends from the first shaft 371 in a direction perpendicular to the rotation axis direction. The second contact arm 372B extends from the first shaft 371 in the opposite direction to the first contact arm 372A. The second contact arm 372B can alternately contact the second cam surface 354B and the first cam surface 354A as the cam 150 rotates. In FIGS. 30(b), (d), and (f), the contact arms 372 (372A, 372B) and the holding surface 154B are hatched.

[0251] When cam 150 rotates in first rotation direction R1 from a state in which cam follower 170 is located in the pressing position shown in FIGS. 30(a) and (b), contact arm 372 (372A, 372B) is guided from holding surface 154B to second guide surface 154C and comes into sliding contact with second guide surface 154C, as shown in FIGS. 30(c) and (d). As a result, cam follower 170 slides from the pressing position toward the non-pressing position. Then, as shown in FIGS. 30(e) and (f), when contact arm 372 (372A, 372B) disengages from second guide surface 154C (cam surface 354), cam follower 170 is located in the non-pressing position.

[0252] When cam 150 rotates in first rotation direction R1 from a state in which cam follower 170 is located in the non-pressing position, contact arm 372 (372A, 372B) comes into contact with first guide surface 154A and slides on first guide surface 154A. As a result, cam follower 170 slides from the non-pressing position toward the pressing position. Then, when contact arm 372 (372A, 372B) comes into contact with holding surface 154B, cam follower 170 is located in the pressing position.

[0253] According to the cam 150 of the fourth embodiment, the load applied from the contact arm 372 (372A, 372B) to the cam surface 354 (354A, 354B) can be distributed and applied approximately uniformly. This makes it possible to suppress wear on the contact arm 372 and the cam surface 354, for example. Furthermore, since it is possible to suppress tilting of the cam 150 and the cam follower 170 with respect to the second shaft 359, it is possible to stably operate the cam 150 and the cam follower 170.

[0254] Although the embodiment has been described above, the image forming apparatus can be modified as appropriate as exemplified below.

[0255] In the above embodiment, the second cam 150Y has the second protrusions 157B, 257B, and the fourth cam 150C has the third protrusions 157C, 257C. However, it is sufficient that one of the second cam, the third cam, and the fourth cam has the second protrusion and the other cam has the third protrusion. For example, the third cam may have the third protrusion. Also, for example, the fourth cam may have the second protrusion and the second cam may have the third protrusion.

[0256] In the above embodiment, the mechanism for switching between transmitting and disconnecting the driving force to the developing rollers 61Y, 61M, and 61C is different from the mechanism for switching between transmitting and disconnecting the driving force to the first developing roller 61K, but they may be the same mechanism. For example, the image forming apparatus may be configured to include a switching lever and a planetary gear mechanism for each cam, and each cam may have a switching protrusion that moves the corresponding switching lever between the first transmission position and the first disconnection position.

[0257] The mechanism for switching between transmitting and disconnecting the driving force to the developing roller may include, for example, a motor for driving the developing roller and a clutch for switching between transmitting and disconnecting the driving force from the motor.Furthermore, a driving force transmission mechanism including such a motor and a clutch may be provided for each developing roller.

[0258] In the above embodiment, the first developing roller 61K is driven by the first motor M1, and the second, third, and fourth developing rollers 61Y, 61M, and 61C are driven by the third motor M3. However, for example, all four developing rollers may be driven by the same motor. In other words, the first and third motors may be the same motor. Even in this case, it is desirable that the motor for driving the developing rollers and the motor for driving the cam are different motors.

[0259] In the above embodiment, examples of a configuration for restricting the rotation of cam follower 170 around first shaft 171 include a configuration in which stopper 179 sandwiches restriction arm 173 of cam follower 170, and a configuration in which stopper 279 sandwiches contact arm 272 of cam follower 170. However, for example, if the cam is configured to rotate only in one direction, the rotation of the cam follower may be restricted by contacting a single rod-shaped member with the restriction arm or contact arm, rather than by a configuration in which a pair of rod-shaped members sandwich the restriction arm or contact arm. Also, for example, as shown in FIG. 30(b), the cross-sectional shape of the portion where first shaft 371 of cam follower 170 engages with shaft 359 that slidably supports first shaft 371 may be substantially rectangular to restrict the rotation of cam follower 170. The cross-sectional shape of the portion where the first shaft engages with the shaft that slidably supports the first shaft may be, for example, D-shaped or elliptical.

[0260] In the above embodiment, the angle of the second guide surface 154C relative to the rotation direction of the cam 150 is larger than the angle of the first guide surface 154A relative to the rotation direction of the cam 150, but for example, the angle of the second guide surface relative to the rotation direction of the cam may be the same as the angle of the first guide surface relative to the rotation direction of the cam.

[0261] In the above embodiment, the first protrusion 157A has a cylindrical shape with a cylindrical surface that can come into contact with the first rocking piece 220A, but the first protrusion may be, for example, ribbed, etc. The same applies to the second and third protrusions.

[0262] In the above embodiment, the timings at which cam followers 170Y, 170M, and 170C move from the non-pressing position to the pressing position are offset from one another, but for example, the timings at which they move from the non-pressing position to the pressing position may overlap. In this case, any one of the second cam, the third cam, and the fourth cam may have a protrusion, and the linear motion plate may come into contact with the protrusion when moving from the first position to the second position with the second cam follower, the third cam follower, and the fourth cam in a state where the second cam follower, the third cam follower, and the fourth cam follower are in the pressing position, thereby rotating the second cam, the third cam, and the fourth cam, and positioning the second cam follower, the third cam follower, and the fourth cam follower in the non-pressing position.

[0263] In the above embodiment, the timing at which the cam followers 170Y, 170M, and 170C move from the pressing position to the non-pressing position overlaps with each other, but for example, the timing at which the cam followers move from the pressing position to the non-pressing position may be in the order of the second cam follower, the third cam follower, and the fourth cam follower.

[0264] In the above embodiment, the first rocking piece 220A is provided to retract if it comes into contact with the first protrusion 157A when the linear motion plate 200 moves from the second position to the first position, but for example, the first rocking piece may be configured not to retract if it does not come into contact with the first protrusion when the linear motion plate moves from the second position to the first position. The same applies to the second rocking piece and the third rocking piece.

[0265] In the above embodiment, the linear motion plate 200 has the first oscillating piece 220A (first contact piece and third contact piece) that can come into contact with the first protrusion 157A, but for example, the part of the linear motion plate that can come into contact with the first protrusion may be integrally provided as a part of the linear motion plate. The same applies to the second contact piece.

[0266] In the above embodiment, as shown in Fig. 5(a), the cam surface 154 and the switching protrusion 156 are arranged on the same surface of the first cam 150K, and the switching protrusion 156 is arranged on the flange portion 155. However, for example, the switching protrusion may be arranged on the disk portion 151. Also, in the above embodiment, as shown in Fig. 22(b), the cam surface 154 and the first protrusion 257 are arranged on the same surface of the first cam 150K, and the first protrusion 257 is arranged on the flange portion 255. However, for example, the first protrusion may be arranged on the disk portion 151.

[0267] In the above embodiment, as shown in Fig. 7(b), the switching protrusion 156 is disposed at a position overlapping with the holding surface 154B in the circumferential direction centered on the rotation axis of the first cam 150K, but for example, the switching protrusion may be disposed at a position different from the holding surface 154B in the circumferential direction. Also, in the above embodiment, as shown in Fig. 23(b), the first protrusion 257 is disposed at a position overlapping with the holding surface 154B in the circumferential direction centered on the rotation axis of the first cam 150K, but for example, the first protrusion may be disposed at a position different from the holding surface 154B in the circumferential direction.

[0268] In the above embodiment, the first shaft 171 of the cam follower 170 is engaged with the second shaft 159 that rotatably supports the cam 150 and is capable of sliding movement, but for example, the shaft that supports the first shaft so that it is capable of sliding movement may be a shaft different from the second shaft.

[0269] In the above embodiment, the image forming apparatus 1 is a color printer equipped with multiple photosensitive drums 50, but the image forming apparatus may be, for example, a monochrome printer equipped with only a first photosensitive drum. Also, for example, the image forming apparatus may be a copier, a multifunction peripheral, or the like.

[0270] The elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0271] 1. Image forming device 50K 1st photosensitive drum 60K 1st Developer Cartridge 61K First developing roller 150K 1st cam 154 Cam surface 156 Switching protrusion 157A 1st protrusion 160 Switching Lever 170K 1st cam follower 200 Linear motion plate M1 First motor

Claims

1. An image forming apparatus including a first photosensitive drum, a first motor; a first developing cartridge having a first developing roller, the first developing cartridge being movable between a contact position where the first developing roller contacts the first photosensitive drum and a separation position where the first developing roller is separated from the first photosensitive drum; a first cam having a cam surface, the first cam rotating to move the first developing cartridge between the contact position and the separated position; a first cam follower that is slidable in a rotational axis direction of the first cam between a pressing position where the first developer cartridge is pressed by a cam surface of the rotating first cam to position the first developer cartridge at the separated position and a non-pressing position where the first developer cartridge is positioned at the contact position; a switching lever that is movable between a first transmission position where the driving force from the first motor can be transmitted to the first developing roller and a first disconnection position where the driving force from the first motor is not transmitted to the first developing roller by rotation of the first cam; a linear motion plate that moves linearly between a first position and a second position, and that comes into contact with the first cam when moving from the first position to the second position with the first cam follower located at the pressing position, causing the first cam to rotate and positioning the first cam follower at the non-pressing position; The first cam is a switching protrusion that is contactable with the switching lever and moves the switching lever between the first transmission position and the first disconnection position, the switching protrusion being arranged on a surface of one side in the rotational axis direction of the first cam; a first protrusion that is contactable with the linear motion plate and rotates the first cam when the linear motion plate comes into contact with the first cam, the first protrusion being disposed on a surface of the first cam on the other side in the rotation axis direction; An image forming apparatus comprising:

2. a housing having an opening; a cover that is movable between a closed position that closes the opening and an open position that opens the opening, 2. The image forming apparatus according to claim 1, wherein the linear motion plate is capable of linear motion between the first position, which is the position when the cover is in the closed position, and the second position, which is the position when the cover is in the open position, in conjunction with the movement of the cover between the closed position and the open position.

3. 3. The image forming apparatus according to claim 1, wherein the cam surface is disposed on one side of the first cam in the direction of the rotation axis.

4. the cam surface has a holding surface that holds the first cam follower in the pressing position, 4. The image forming apparatus according to claim 3, wherein the switching protrusion is disposed at a position overlapping the holding surface in a circumferential direction centered on the rotation axis of the first cam, as viewed from the rotation axis direction.

5. The first cam is A disk portion, a gear portion formed on the outer periphery of the disk portion; a flange portion formed on an outer periphery of the disk portion, the flange portion being located on one side of the gear portion in the direction of the rotation axis; and 5. The image forming apparatus according to claim 3, wherein the switching protrusion is disposed on the flange portion.

6. 3. The image forming apparatus according to claim 1, wherein the cam surface is disposed on a surface of the first cam on the other side in the direction of the rotation axis.

7. the cam surface has a holding surface that holds the first cam follower in the pressing position, 7. The image forming apparatus according to claim 6, wherein the first protrusion is arranged at a position overlapping the holding surface in a circumferential direction centered on the rotation axis of the first cam, when viewed from the rotation axis direction.

8. The first cam is A disk portion, a gear portion formed on the outer periphery of the disk portion; a flange portion formed on an outer periphery of the disk portion, the flange portion being located on the other side of the gear portion in the direction of the rotation axis; and 8. The image forming apparatus according to claim 6, wherein the first protrusion is disposed on the flange portion.

9. 9. The image forming apparatus according to claim 1, further comprising a second motor for rotating the first cam, the second motor being provided separately from the first motor.

10. 10. An image forming apparatus according to claim 1, wherein the linear plate has a first contact piece that comes into contact with the first protrusion when the linear plate moves from the first position to the second position while the first cam follower is positioned in the pressing position, and when the first contact piece comes into contact with the first protrusion, the first contact piece rotates the first cam to position the first cam follower in the non-pressing position.

11. 11. The image forming apparatus according to claim 10, wherein the first contact piece retracts to prevent the first cam from rotating when the linear plate comes into contact with the first protrusion when moving from the second position to the first position.

12. An image forming apparatus according to any one of claims 1 to 11, characterized in that the switching protrusion is configured to move the switching lever to the first transmission position before the first developer cartridge moves to the contact position, and to move the switching lever to the first disconnection position after the first developer cartridge moves to the separated position.

13. a planetary gear mechanism including an input element to which a driving force from the first motor is input, an output element that outputs the driving force toward the first developing roller, and a transmission element that can transmit the driving force from the input element to the output element when rotation is restricted and does not transmit the driving force from the input element to the output element when rotation is not restricted, 13. The image forming apparatus according to claim 1, wherein the switching lever restricts rotation of the transfer element when positioned at the first transfer position, and does not restrict rotation of the transfer element when positioned at the first disconnection position.

14. a control unit that rotates the first cam in a first rotation direction when the first developing cartridge is moved between the contact position and the separated position, 14. The image forming apparatus according to claim 13, wherein when the linear motion plate moves from the first position to the second position while the first cam follower is positioned at the pressing position, the linear motion plate rotates the first cam in a second rotation direction opposite to the first rotation direction, thereby positioning the first cam follower at the non-pressing position.

15. the switching lever is swingable around a swing shaft between the first transmitting position and the first disconnecting position, a first lever that is swingable around the swing shaft and that is capable of contacting the switching protrusion; a second lever pivotable about the pivot axis and engageable with the transmission element; a rotation restricting portion provided on the second lever that restricts rotation of the first lever relative to the second lever in one direction; a first spring that biases the first lever so as not to rotate relative to the second lever when the rotation restricting portion provided on the second lever comes into contact with the first lever; and the image forming apparatus further includes a second spring that biases the second lever in a direction that causes the second lever to swing toward the transmission element; 15. The image forming apparatus according to claim 14, wherein when the second lever is engaged with the transmission element, the first cam rotates in the second rotation direction and the first lever is pressed by the switching protrusion, the first lever swings relative to the second lever against the biasing force of the first spring.

16. A second photosensitive drum; a third photosensitive drum disposed downstream of the second photosensitive drum in the sheet conveying direction; a fourth photosensitive drum disposed downstream of the third photosensitive drum in the transport direction; a second developing cartridge having a second developing roller, the second developing cartridge being movable between a contact position where the second developing roller contacts the second photosensitive drum and a separation position where the second developing roller is separated from the second photosensitive drum; a third developing cartridge having a third developing roller, the third developing cartridge being movable between a contact position where the third developing roller contacts the third photosensitive drum and a separation position where the third developing roller is separated from the third photosensitive drum; a fourth developing cartridge having a fourth developing roller, the fourth developing cartridge being movable between a contact position where the fourth developing roller contacts the fourth photosensitive drum and a separation position where the fourth developing roller is separated from the fourth photosensitive drum; a second cam having a cam surface, the second cam rotating to move the second developing cartridge between the contact position and the separated position; a third cam having a cam surface and rotating in conjunction with the second cam, the third cam rotating to move the third developing cartridge between the contact position and the separated position; a fourth cam having a cam surface, rotating in conjunction with the second cam and the third cam, the fourth cam rotating to move the fourth developing cartridge between the contact position and the separated position; a second cam follower that is slidable in the direction of the rotation axis between a pressing position where the second developer cartridge is pressed by a cam surface of the rotating second cam to position the second developer cartridge at the separated position and a non-pressing position where the second developer cartridge is positioned at the contact position; a third cam follower that is slidable in the direction of the rotation axis between a pressing position where the third developer cartridge is pressed by a cam surface of the rotating third cam to position the third developer cartridge at the separated position and a non-pressing position where the third developer cartridge is positioned at the contact position; 3. The image forming apparatus according to claim 1, further comprising a fourth cam follower that is slidable in the direction of the rotation axis between a pressing position where the cam surface of the rotating fourth cam presses the fourth developer cartridge to position the fourth developer cartridge at the separated position, and a non-pressing position where the fourth developer cartridge is positioned at the contact position.

17. 17. The image forming apparatus according to claim 16, wherein when the linear motion plate moves from the first position to the second position with at least one of the second cam follower, the third cam follower, and the fourth cam follower positioned at the pressing position, the linear motion plate rotates the second cam, the third cam, and the fourth cam to position the second cam follower, the third cam, and the fourth cam follower at the non-pressing position.

18. the second cam, the third cam, and the fourth cam are end surface cams, The cam surface of the second cam, the cam surface of the third cam, and the cam surface of the fourth cam are the third cam follower starts to move from the non-pressing position toward the pressing position at a timing after the second cam follower has moved to the pressing position, the fourth cam follower starts to move from the non-pressing position toward the pressing position at a timing after the third cam follower has moved to the pressing position, the second cam follower, the third cam follower, and the fourth cam follower are simultaneously positioned at the pressing position; 18. The image forming apparatus according to claim 17, wherein the image forming apparatus is provided as follows.

19. one of the second cam, the third cam, and the fourth cam has a second protrusion protruding in the rotation axis direction, and the other cam other than the cam having the second protrusion has a third protrusion protruding in the rotation axis direction, The linear motion plate is a second contact piece that can come into contact with the second protrusion when the cam follower corresponding to the cam having the second protrusion moves from the first position to the second position in a state where the cam follower is located at the pressing position, and that rotates the second cam, the third cam, and the fourth cam when the second contact piece comes into contact with the second protrusion; a third contact piece that can come into contact with the third protrusion when moving from the first position to the second position, and that, when coming into contact with the third protrusion, rotates the second cam, the third cam, and the fourth cam, thereby positioning the second cam follower, the third cam follower, and the fourth cam follower at the non-pressing position; and The image forming apparatus according to claim 18, wherein the third contact piece is configured to contact the third protrusion at a timing after the second contact piece contacts the second protrusion when the linear motion plate moves from the first position to the second position.

20. 20. The image forming apparatus according to claim 19, wherein the third contact piece is configured to contact the third protrusion at a timing after the second contact piece separates from the second protrusion when the linear plate moves from the first position to the second position.

21. a control unit that rotates the second cam, the third cam, and the fourth cam in a first rotation direction when the second developer cartridge, the third developer cartridge, and the fourth developer cartridge are moved between the contact position and the separated position; 21. An image forming apparatus according to claim 18, wherein when the linear plate moves from the first position to the second position with at least the second cam follower positioned at the pressing position, the linear plate rotates the second cam, the third cam, and the fourth cam in a second rotational direction opposite to the first rotational direction, thereby positioning the second cam follower, the third cam follower, and the fourth cam follower at the non-pressing position.

22. 22. The image forming apparatus according to claim 18, wherein the cam surface of the second cam, the cam surface of the third cam, and the cam surface of the fourth cam are arranged so that the timing at which the second cam follower moves from the pressing position toward the non-pressing position, the timing at which the third cam follower moves from the pressing position toward the non-pressing position, and the timing at which the fourth cam follower moves from the pressing position toward the non-pressing position overlap with each other.

23. a third motor for driving the second developing roller, the third developing roller, and the fourth developing roller; an input gear to which driving force from the third motor is input; an output gear that outputs a driving force toward the second developing roller, the third developing roller, and the fourth developing roller; a movable gear that meshes with the input gear and is movable between a second transmission position where it meshes with the output gear and a second disconnection position where it does not mesh with the output gear; 23. The image forming apparatus according to claim 18, further comprising: a switching cam that rotates in conjunction with the second cam, and that rotates to move the moving gear between the second transmission position and the second disconnection position.

24. The image forming apparatus according to claim 23, wherein the switching cam is configured to move the movable gear to the second transmission position before the second developer cartridge moves to the contact position, and to move the movable gear to the second disconnection position after the fourth developer cartridge moves to the separated position.

Images