Image forming apparatus

Abstract

To reduce a force added to a rotary cam from a cam follower when the cam follower is held with the rotary cam at a pressing position.SOLUTION: A rotary cam (150) has a first part P1, a second part P2, and a third part P3. The first part P1 faces a cam follower 170 in a rotation axis direction when the cam follower 170 is located at a non-pressing position. The second part P2 holds the cam follower 170 at a pressing position. The second part P2 is positioned on one side of the rotation axis direction of the first part P1. The third part P3 is positioned on one side in the rotation axis direction of the second part P2. The third part P3 locates the cam follower 170 at a second pressing position. A developing roller moves from a contact position to a second separate position more remote from the contact position than the separate position and then moves to the separate position by the cam follower 170 contacting the third part P3 as the rotary cam rotates and contacting the second part P2.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] Conventionally, an image forming apparatus has been known that includes a cam follower for moving a developing roller relative to a photosensitive drum and a rotating cam that can rotate forward and backward for moving the cam follower (see Patent Document 1). The developing roller is movable between a contact position where it contacts the photosensitive drum and a separation position where it is separated from the photosensitive drum.

[0003] The cam follower is movable between a non-pressing position where the developing roller is positioned at the contact position and a pressing position where the developing roller is positioned at the separated position by pressing the developing cartridge. The rotating cam has a cam portion that protrudes toward the cam follower and moves the cam follower from the non-pressing position to the pressing position.

[0004] The cam portion has a holding surface that holds the cam follower in the pressing position. The holding surface is a plane that is perpendicular to the rotation axis of the rotating cam. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-124947 Summary of the Invention [Problem to be solved by the invention]

[0006] In the prior art, the cam follower is held by the holding surface immediately after the cam portion moves the cam follower from the non-pressing position to the pressing position, so a strong force is applied from the cam follower to the rotating cam when the holding surface is holding the cam follower. More specifically, when the cam portion presses the cam follower, the frictional force generated between the developer cartridge and other members is applied to the rotating cam via the cam follower, and this frictional force is applied to the rotating cam even when the holding surface is holding the cam follower.

[0007] Therefore, an object of the present disclosure is to reduce the force applied from the cam follower to the rotating cam when the rotating cam holds the cam follower in the pressing position. [Means for solving the problem]

[0008] In order to solve the above-described problems, the image forming apparatus of the present disclosure includes a motor, a photosensitive drum, a developing cartridge, a rotating cam, and a cam follower. The developer cartridge includes a developer roller. The developing roller is movable between a contact position where it contacts the photosensitive drum, a spaced position where it is spaced from the photosensitive drum, and a second spaced position that is farther from the contact position than the spaced position. The rotating cam rotates when driven by the motor. The cam follower moves in the direction of the rotation axis of the rotating cam in response to rotation of the rotating cam and is movable between a non-pressing position where the developing roller is positioned at the contact position, a pressing position where the developing cartridge is pressed to position the developing roller at the separated position, and a second pressing position where the developing cartridge is pressed to position the developing roller at the second separated position. The rotating cam has a first portion, a second portion, and a third portion. The first portion faces the cam follower in the direction of the rotation axis when the cam follower is in the non-pressing position. The second portion holds the cam follower in the pressing position and is located to one side of the first portion in the direction of the rotation axis. The third portion is located on one side of the second portion in the direction of the rotation axis, and the third portion positions the cam follower at the second pressing position. The developing roller moves from the contact position to the second separated position and then to the separated position when the cam follower comes into contact with the third portion due to rotation of the rotating cam and then comes into contact with the second portion.

[0009] By configuring the cam follower to contact the third portion and then the second portion, the developing roller moves from the contact position to the second separated position and then back to the separated position, so that the frictional force between the developing cartridge and other members acts in the opposite direction to the force applied from the cam follower to the rotating cam. Therefore, when the rotating cam holds the cam follower in the pressing position, the force applied from the cam follower to the rotating cam can be reduced.

[0010] The image forming apparatus may further include a drum frame. The drum frame is a frame on which a developing cartridge can be mounted and which holds a photosensitive drum. The developer cartridge may further include a developer frame, a spacing shaft, and a spring. The developer frame holds the developer roller. The separation shaft is held by the developing frame so as to be movable in the direction of the rotation axis. When pressed by the cam follower, the separation shaft comes into contact with the drum frame and moves together with the developing frame in a direction away from the photosensitive drum, thereby moving the developing roller from the contact position to the separation position. A spring biases the spacing shaft toward the cam follower.

[0011] By configuring the developing roller to move from the contact position to the separated position when the separating shaft pressed by the cam follower comes into contact with the drum frame, when the developing roller moves from the second separated position to the separated position, the frictional force between the separating shaft and the drum frame acts in the direction opposite to the force applied from the cam follower to the rotating cam. Therefore, when the rotating cam holds the cam follower in the pressing position, the force applied from the cam follower to the rotating cam can be reduced.

[0012] The rotating cam may have a first surface, a second surface, a third surface, a first inclined surface, and an inverse inclined surface. The first surface has a first portion. The second surface has a second portion. The third surface has a third portion and is located between the first surface and the second surface in the rotation direction of the rotating cam. The first inclined surface extends obliquely from the first surface toward one side of the rotation axis direction and is located between the first surface and the third surface in the rotation direction. The reverse inclined surface extends obliquely from the third surface toward the other side of the rotation axis direction and is located between the third surface and the second surface in the rotation direction.

[0013] By configuring the first surface, second surface, third surface, first inclined surface, and reverse inclined surface to be arranged in the order of first surface, first inclined surface, third surface, reverse inclined surface, and second surface in the direction of rotation, the cam follower can be moved from the non-pressing position to the pressing position via the second pressing position by simply rotating the rotating cam in one direction.

[0014] Furthermore, the first inclined surface may be connected to the first surface and the third surface, and the reverse inclined surface may be connected to the third surface and the second surface.

[0015] The rotating cam may further include a fourth surface and a second inclined surface. The fourth surface is located between the first surface and the third surface in the rotation axis direction. The fourth surface is located between the first surface and the third surface in the rotation direction. The fourth surface is connected to the first inclined surface. The second inclined surface extends obliquely from the fourth surface toward one side of the rotation axis direction and is connected to the fourth surface and the third surface.

[0016] The rotating cam may also have a first surface, a third inclined surface, and a fourth inclined surface. The first surface has a first portion. The third inclined surface extends obliquely from the first surface toward one side of the rotation axis direction. The fourth inclined surface extends obliquely from the third inclined surface toward one side of the rotation axis direction. The fourth inclined surface has a smaller inclination angle with respect to the first surface than the third inclined surface. The fourth inclined surface has a second portion and a third portion.

[0017] By configuring the rotating cam to have a first surface, a third inclined surface, and a fourth inclined surface, the rotating cam can be rotated in one direction to move the cam follower from the non-pressing position through the pressing position to the second pressing position, and then the rotating cam can be rotated in the other direction to move the cam follower from the second pressing position to the pressing position.

[0018] The rotating cam may also have a first surface, a fifth inclined surface, and a sixth inclined surface. The first surface has a first portion. The fifth inclined surface extends obliquely from the first surface toward one side of the rotation axis direction. The sixth inclined surface extends obliquely from the fifth inclined surface toward the other side of the rotation axis direction, and has a second portion and a third portion.

[0019] By configuring the rotating cam to have a first surface, a fifth inclined surface, and a sixth inclined surface, the cam follower can be moved from the non-pressing position to the pressing position via the second pressing position simply by rotating the rotating cam in one direction.

[0020] The drum frame may further include rollers that rotate in contact with the spaced shafts. The spacing shaft may further have an inclined surface that can contact the roller. The inclined surface is inclined with respect to the direction of the rotation axis. The separating shaft is movable between a roller non-contact position where the inclined surface does not contact the roller and a roller contact position where the inclined surface contacts the roller. When the separating shaft moves from the roller non-contact position to the roller contact position, it moves the developing frame away from the photosensitive drum to separate the developing roller from the photosensitive drum, and when the separating shaft moves from the roller contact position to the roller non-contact position, it moves the developing frame closer to the photosensitive drum to bring the developing roller into contact with the photosensitive drum.

[0021] The motor may be capable of rotating forward and backward, and the cam follower may have a contact portion that is capable of contacting the second portion and the third portion. When the motor rotates in the reverse direction while the contact portion is located at a reference position opposite the first portion in the rotation axis direction, the contact portion moves relative to the rotating cam from the reference position to the second portion via the third portion. When the motor rotates in the forward direction while the contact portion is located at the second portion, the contact portion moves from the second portion to the reference position via the third portion.

[0022] The motor may be capable of rotating forward and backward, and the cam follower may have a contact portion that is capable of contacting the second portion and the third portion. When the motor rotates in the reverse direction while the contact portion is located at a reference position opposite the first portion in the rotation axis direction, the contact portion moves from the reference position to the third portion via the second portion, and then moves relative to the rotating cam so as to return to the second portion when the motor rotates in the forward direction or is stopped. When the motor rotates in the forward direction while the contact portion is located at the second portion, the contact portion moves from the second portion to the reference position without passing through the third portion.

[0023] When the motor rotates forward with the contact portion positioned at the second portion, the contact portion is configured to move from the second portion to the reference position without passing through the third portion, thereby reducing the force applied to the rotating cam from the cam follower when the motor rotates forward. [Effects of the Invention]

[0024] When the rotating cam holds the cam follower in the pressing position, the force applied from the cam follower to the rotating cam can be reduced. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram illustrating an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an outline of a driving force transmission system of the image forming apparatus. [Figure 3] FIG. [Figure 4] FIG. 2 is a diagram showing a spacing cam, a cam follower, a shaft, and a stopper. [Figure 5] 1A and 1B are diagrams showing a configuration for moving a developer cartridge, in which the developer cartridge is positioned at a contact position (FIG. 1A) and at a separated position (FIG. 1B). [Figure 6] 1A is a perspective view showing a separation cam and a cam follower positioned in a non-pressing position, and FIG. 1B is a side view showing the separation cam and the cam follower positioned in a non-pressing position. [Figure 7] 1A is a perspective view showing a separation cam and a cam follower positioned at a pressing position, and FIG. 1B is a side view showing the separation cam and the cam follower positioned at a pressing position. [Figure 8] 1A and 1B are perspective views showing a gear cover. [Figure 9] 5A is a cross-sectional view showing a separation cam, a cam follower, a gear cover, and a spring, in which FIG. 5A shows the cam follower in a non-pressing position, and FIG. 5B shows the cam follower in a pressing position. [Figure 10] 10A and 10B are diagrams showing the relationship between the separating cam and the cam follower, etc., in which FIG. 10A shows a state in which the contact portion of the cam follower is positioned at a reference position, FIG. 10B shows a state in which the contact portion is in contact with the third portion, and FIG. 10C shows a state in which the contact portion is in contact with the second portion. [Figure 11] FIG. 10 is a view showing a separating cam according to a second embodiment. [Figure 12] FIG. 10 is a view showing a separating cam according to a third embodiment. [Figure 13] 10A and 10B are diagrams showing a separating cam according to a fourth embodiment, in which FIG. 10A shows a state in which the contact portion is positioned at a reference position, FIG. 10B shows a state in which the contact portion is in contact with the third portion, and FIG. 10C shows a state in which the contact portion is in contact with the second portion. DETAILED DESCRIPTION OF THE INVENTION

[0026] [First embodiment] Next, a first embodiment of the image forming apparatus will be described. As shown in FIG. 1, the image forming apparatus 1 is a color printer and includes a housing 10, a front cover 11, a sheet supply unit 20, an image forming unit 30, a second discharge roller 91 as a discharge roller, and a control unit 2. In this embodiment, the left side of FIG. 1 is the "front" and the right side of FIG. 1 is the "rear." The top of FIG. 1 is the "top" and the bottom of FIG. 1 is the "bottom." The front of the paper in FIG. 1 is the "right" and the back of the paper in FIG. 1 is the "left."

[0027] Housing 10 has an opening 10A at the front. Front cover 11 opens and closes opening 10A. Specifically, front cover 11 is rotatable relative to housing 10 between a closed position shown by solid lines and an open position shown by imaginary lines. The closed position is a position where opening 10A is closed, and the open position is a position where opening 10A is open.

[0028] The sheet supply unit 20 includes a sheet tray 21 and a sheet supply mechanism 22. Sheets S are set in the sheet tray 21. The sheet supply mechanism 22 is a mechanism that receives a driving force to supply the sheets S toward photosensitive drums 50 (50Y, 50M, 50C, 50K) of the image forming unit 30, which will be described later. The sheet supply mechanism 22 includes a pickup roller 23, a separation roller 24, a separation pad 25, a conveying roller 26, and a registration roller 27.

[0029] The sheet supply mechanism 22 feeds the sheet S from the sheet tray 21 using the pickup roller 23. Next, the sheet supply mechanism 22 separates the sheet S into a single sheet between the separation roller 24 and the separation pad 25. Thereafter, the sheet supply mechanism 22 supplies the sheet S toward the image forming unit 30 using the conveyance roller 26 and the registration roller 27.

[0030] The image forming section 30 includes an exposure unit 40, four photosensitive drums 50, four developing cartridges 60, a transfer unit 70, and a fixing unit 80. The exposure unit 40 includes, for example, a light source, a deflector, a lens, and a mirror. The exposure unit 40 emits a light beam indicated by a dashed line to expose the surface of the photosensitive drum 50.

[0031] The photosensitive drums 50 include a photosensitive drum 50Y corresponding to yellow, a photosensitive drum 50M corresponding to magenta, a photosensitive drum 50C corresponding to cyan, and a photosensitive drum 50K corresponding to black. The four photosensitive drums 50 are arranged in the order of photosensitive drum 50Y, photosensitive drum 50M, photosensitive drum 50C, and photosensitive drum 50K from upstream to downstream in the conveyance direction of the sheet S.

[0032] Specifically, the photosensitive drum 50Y is disposed upstream of the photosensitive drum 50M in the transport direction of the sheet S. The photosensitive drum 50M is disposed upstream of the photosensitive drum 50C in the transport direction of the sheet S. The photosensitive drum 50C is disposed upstream of the photosensitive drum 50K in the transport direction of the sheet S.

[0033] In this specification and drawings, for components corresponding to each color, when the colors are to be distinguished, Y, M, C, K are added to the symbols, and when the colors are not to be distinguished, Y, M, C, K are not added to the symbols.

[0034] The image forming apparatus 1 further includes a drawer 55. The drawer 55 is movable between an inner position and an outer position in the direction in which the photosensitive drums 50 are arranged, through an opening 10A of the housing 10 that is exposed by opening the front cover 11. The inner position is a position where the drawer 55 is housed within the housing 10, and the outer position is a position where at least a portion of the drawer 55 is exposed to the outside of the housing 10. In this embodiment, the outer position is a position where the drawer 55 is pulled out from the inner position to the front. In this embodiment, the drawer 55 is detachable from the housing 10.

[0035] The drawer 55 has a drum frame 55F. The drum frame 55F rotatably holds four photosensitive drums 50 (50Y, 50M, 50C, and 50K). The drum frame 55F also supports four chargers 52. The chargers 52 charge the surfaces of the corresponding photosensitive drums 50.

[0036] The developer cartridges 60 include a developer cartridge 60Y containing yellow toner, a developer cartridge 60M containing magenta toner, a developer cartridge 60C containing cyan toner, and a developer cartridge 60K containing black toner. The developer cartridge 60Y has a developer roller 61Y that supplies yellow toner to the photosensitive drum 50Y. The developer cartridge 60M has a developer roller 61M that supplies magenta toner to the photosensitive drum 50M. The developer cartridge 60C has a developer roller 61C that supplies cyan toner to the photosensitive drum 50C. The developer cartridge 60K has a developer roller 61K that supplies black toner to the photosensitive drum 50K.

[0037] The developing roller 61Y is movable relative to the photosensitive drum 50Y between a contact position where it contacts the photosensitive drum 50Y, a separation position where it is separated from the photosensitive drum 50Y, and a second separation position that is farther from the contact position than the separation position. In Fig. 1, the contact position is indicated by a solid line, the separation position is indicated by a two-dot chain line, and the second separation position is indicated by a dashed line.

[0038] The developing roller 61M is movable relative to the photosensitive drum 50M between a contact position where it contacts the photosensitive drum 50M, a separated position where it is separated from the photosensitive drum 50M, and a second separated position that is farther from the contact position than the separated position. The developing roller 61C is movable relative to the photosensitive drum 50C between a contact position where it contacts the photosensitive drum 50C, a separated position where it is separated from the photosensitive drum 50C, and a second separated position that is farther from the contact position than the separated position. The developing roller 61K is movable relative to the photosensitive drum 50K between a contact position where it contacts the photosensitive drum 50K, a separated position where it is separated from the photosensitive drum 50K, and a second separated position that is farther from the contact position than the separated position.

[0039] The drum frame 55F detachably supports the developer cartridges 60 (60Y, 60M, 60C, 60K). Each developer cartridge 60 can be replaced when the drawer 55 is in the outer position or when the drawer 55 is removed from the housing 10.

[0040] The developer cartridge 60 is supported by the drum frame 55F so as to be movable back and forth between a first position, a second position, and a third position. The first position is a position where the corresponding developer roller 61 is located at the contact position. The second position is a position where the corresponding developer roller 61 is located at the separated position. The third position is a position where the corresponding developer roller 61 is located at the second separated position.

[0041] Specifically, the developing cartridge 60Y is movable relative to the photosensitive drum 50Y between a first position in which the developing roller 61Y is positioned in a contact position, a second position in which the developing roller 61Y is positioned in a separated position, and a third position in which the developing roller 61Y is positioned in the second separated position. The developing cartridge 60M is movable relative to the photosensitive drum 50M between a first position in which the developing roller 61M is positioned in a contact position, a second position in which the developing roller 61M is positioned in a separated position, and a third position in which the developing roller 61M is positioned in the second separated position.

[0042] The developing cartridge 60C is movable relative to the photosensitive drum 50C between a first position in which the developing roller 61C is positioned in a contact position, a second position in which the developing roller 61C is positioned in a separated position, and a third position in which the developing roller 61C is positioned in the second separated position. The developing cartridge 60K is movable relative to the photosensitive drum 50K between a first position in which the developing roller 61K is positioned in a contact position, a second position in which the developing roller 61K is positioned in a separated position, and a third position in which the developing roller 61K is positioned in the second separated position.

[0043] 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 across the drive roller 71 and the driven roller 72, with its outer surface in contact with the four photosensitive drums 50. The transfer rollers 74 are disposed inside the conveyor belt 73, and sandwich the conveyor belt 73 between themselves and the corresponding photosensitive drums 50.

[0044] The fixing device 80 is a device that fixes the toner image transferred onto the sheet S to the sheet S. The fixing device 80 has a heating section 81, a pressure section 82, and a first discharge roller 83 as a discharge roller. The heating section 81 includes a heating roller 81A and a heater 81B. The heating roller 81A is a cylindrical roller made of metal. The heater 81B is a heater that heats the heating roller 81A and is arranged to pass inside the heating roller 81A.

[0045] The pressure applying unit 82 sandwiches the sheet S between itself and the heating unit 81. Specifically, the pressure applying unit 82 is a pressure roller that sandwiches the sheet S between itself and the heating roller 81A. The pressure roller is a roller with a core metal covered with a rubber layer. The fixing unit 80 receives a driving force to transport the sheet S between the heating roller 81A of the heating unit 81 and the pressure applying unit 82 (pressure roller). The fixing unit 80 also receives a driving force to transport the sheet S by the first discharge roller 83.

[0046] In the image forming unit 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. In this way, the image forming unit 30 forms an electrostatic latent image based on image data on the photosensitive drum 50. In addition, the image forming unit 30 supplies toner contained in the developer cartridge 60 to the photosensitive drum 50 from the developer roller 61 located at the contact position. In this way, the image forming unit 30 forms a toner image on the photosensitive drum 50.

[0047] The image forming unit 30 transfers the toner image formed on the photosensitive drum 50 onto the sheet S by transporting the sheet S supplied from the sheet supply unit 20 between the photosensitive drum 50 and the transfer roller 74. Thereafter, the image forming unit 30 fixes the toner image onto the sheet S by transporting the sheet S onto which the toner image has been transferred between the heating roller 81A and the pressure unit 82.

[0048] The first discharge roller 83 and the second discharge roller 91 receive a driving force to discharge the sheet S from between the heating unit 81 and the pressure unit 82 to the outside of the housing 10. Specifically, the first discharge roller 83 and the second discharge roller 91 discharge the sheet S on which the toner image has been fixed to the discharge tray 13.

[0049] As shown in FIG. 2, the image forming apparatus 1 further includes a main motor M1 as an example of a motor, a process motor M2, a separating mechanism 5, and a nip pressure adjusting mechanism 200.

[0050] The main motor M1 is a motor that drives the separation cam 150 of the separation mechanism 5, the fixing unit 80, the nip pressure adjustment mechanism 200, and the sheet supply mechanism 22. In other words, the separation cam 150 of the separation mechanism 5, the fixing unit 80, the nip pressure adjustment mechanism 200, and the sheet supply mechanism 22 receive driving force from the main motor M1. The main motor M1 is rotatable forward and reverse. The main motor M1 rotates forward when the sheet S is transported from the sheet tray 21 toward the discharge tray 13 to form an image on the sheet S.

[0051] The process motor M2 is a motor that drives the photosensitive drum 50, the developing roller 61, and the transfer unit 70. In other words, the photosensitive drum 50, the developing roller 61, and the transfer unit 70 receive a driving force from the process motor M2.

[0052] As shown in Figures 2 and 3, the image forming apparatus 1 further includes a developer separation gear train GT1, a fixing drive gear train GT2, a nip pressure adjustment gear train GT3, a sheet supply gear train GT4, a drum drive gear train GT5, a first developer drive gear train GT6, and a second developer drive gear train GT7.

[0053] The development separation gear train GT1 is a gear train that transmits the driving force of the main motor M1 to the separation cams 150 (150Y, 150M, 150C, 150K) of the separation mechanism 5. The development separation gear train GT1 has an electromagnetic clutch (not shown). When the control unit 2 connects the electromagnetic clutch, the driving force of the main motor M1 is transmitted to the separation cam 150. When the control unit 2 disconnects the electromagnetic clutch, the driving force of the main motor M1 is not transmitted to the separation cam 150.

[0054] The fixing drive gear train GT2 is a gear train that receives the driving force of the main motor M1 from the development separation gear train GT1 and transmits it to the fixing device 80. Specifically, the fixing drive gear train GT2 receives the driving force of the main motor M1 from the development separation gear train GT1 and transmits it to the heating roller 81A.

[0055] The nip pressure adjusting gear train GT3 is a gear train that receives the driving force of the main motor M1 from the development separation gear train GT1 and transmits it to the nip pressure adjusting cam 230 of the nip pressure adjusting mechanism 200. The sheet supply gear train GT4 is a gear train that transmits the driving force of the main motor M1 to the sheet supply mechanism 22.

[0056] The drum drive gear train GT5 is a gear train that transmits the driving force of the process motor M2 to the photosensitive drums 50 (50Y, 50M, 50C, 50K). The first developing drive gear train GT6 is a gear train that transmits the driving force of the process motor M2 to the developing rollers 61Y, 61M, and 61C. The second developing drive gear train GT7 is a gear train that transmits the driving force of the process motor M2 to the developing roller 61K. Specifically, the second developing drive gear train GT7 receives the driving force of the process motor M2 from the first developing drive gear train GT6 and transmits it to the developing roller 61K.

[0057] The separation mechanism 5 is a mechanism that receives a driving force from the main motor M1 to move the developing roller 61 between the contact position and the separation position. The separation mechanism 5 includes four separation cams 150 and four cam followers 170. The spacing cam 150 is an example of a rotating cam. The spacing cam 150 includes a spacing cam 150Y, a spacing cam 150M, a spacing cam 150C, and a spacing cam 150K.

[0058] The separation cam 150Y rotates by receiving a driving force from the main motor M1, and moves the developing roller 61Y between the contact position and the separation position. Specifically, the separation cam 150Y rotates to move the developing cartridge 60Y between the first position and the second position, thereby moving the developing roller 61Y between the contact position and the separation position. The separation cam 150M rotates by receiving a driving force from the main motor M1, and moves the developing roller 61M between the contact position and the separation position. Specifically, the separation cam 150M rotates to move the developing cartridge 60M between the first position and the second position, thereby moving the developing roller 61M between the contact position and the separation position.

[0059] The separation cam 150C rotates by receiving a driving force from the main motor M1, and moves the developing roller 61C between the contact position and the separation position. Specifically, the separation cam 150C rotates to move the developing cartridge 60C between the first position and the second position, thereby moving the developing roller 61C between the contact position and the separation position. The separation cam 150K rotates by receiving a driving force from the main motor M1, and moves the developing roller 61K between the contact position and the separation position. Specifically, the separation cam 150K rotates to move the developing cartridge 60K between the first position and the second position, thereby moving the developing roller 61K between the contact position and the separation position.

[0060] As shown in Fig. 4, the cam followers 170 include cam follower 170Y, cam follower 170M, cam follower 170C, and cam follower 170K. The cam followers 170 are slidable in the rotational axis direction of the separating cam 150 in response to the rotation of the separating cam 150. The rotational axis direction of the separating cam 150 corresponds to the direction in which the dashed dotted line shown in Fig. 4 extends. Hereinafter, the rotational axis direction of the separating cam 150 will also be simply referred to as the "rotational axis direction." The rotational axis direction is also the rotational axis direction of cam gears 115 (115Y, 115M, 115C, 115K) described below.

[0061] The cam follower 170Y is movable between a non-pressing position, a pressing position, and a second pressing position. The non-pressing position of the cam follower 170Y is a position where the developing roller 61Y is positioned at the contact position. The pressing position is a position where the cam follower 170Y presses the developing cartridge 60Y to position the developing roller 61Y at the separated position. The second pressing position is a position where the cam follower 170Y presses the developing cartridge 60Y to position the developing roller 61Y at the second separated position.

[0062] The cam follower 170M is movable between a non-pressing position, a pressing position, and a second pressing position. The non-pressing position of the cam follower 170M is a position where the developing roller 61M is positioned at the contact position. The pressing position is a position where the cam follower 170M presses the developing cartridge 60M to position the developing roller 61M at the separated position. The second pressing position is a position where the cam follower 170M presses the developing cartridge 60M to position the developing roller 61M at the second separated position.

[0063] The cam follower 170C is movable between a non-pressing position, a pressing position, and a second pressing position. The non-pressing position of the cam follower 170C is a position where the developing roller 61C is positioned at the contact position. The pressing position is a position where the cam follower 170C presses the developing cartridge 60C to position the developing roller 61C at the separated position. The second pressing position is a position where the cam follower 170C presses the developing cartridge 60C to position the developing roller 61C at the second separated position.

[0064] The cam follower 170K is movable between a non-pressing position, a pressing position, and a second pressing position. The non-pressing position of the cam follower 170K is a position where the developing roller 61K is positioned at the contact position. The pressing position is a position where the cam follower 170K presses the developing cartridge 60K to position the developing roller 61K at the separated position. The second pressing position is a position where the cam follower 170K presses the developing cartridge 60K to position the developing roller 61K at the second separated position.

[0065] As shown in FIG. 5(a), the drawer 55 has a roller 55A, a pressing member 55B, and a spring 55C. The roller 55A is the part that comes into contact with the separation shaft 66 (described later) and is rotatable around an axis that runs vertically. The roller 55A is rotatably supported by the drum frame 55F. The pressing member 55B is biased rearward by the spring 55C. When the developer cartridge 60 is attached to the drawer 55, the biasing force of the spring 55C causes the pressing member 55B to press the developer cartridge 60 rearward. This causes the developer cartridge 60 to move to a first position where the developing roller 61 comes into contact with the photosensitive drum 50.

[0066] The developer cartridge 60 includes a developer frame 65 , a spacer shaft 66 , and a spring 67 . The developing frame 65 holds the developing roller 61. The developing frame 65 contains toner.

[0067] The separation shaft 66 slides in the direction of the rotation axis when pressed by the cam follower 170. The separation shaft 66 has a shaft 66A, a first contact member 66B, and a second contact member 66C. The shaft 66A is held by the developing frame 65 so as to be able to slide in the direction of the rotation axis. The first contact member 66B is fixed to one end of the shaft 66A, and the second contact member 66C is fixed to the other end of the shaft 66A.

[0068] The first contact member 66B has a pressed surface 66D and an inclined surface 66E, and the second contact member 66C has an inclined surface 66F. The pressed surface 66D is a surface that is pressed by the cam follower 170. The inclined surfaces 66E, 66F are surfaces that are inclined with respect to the left-right direction (the direction of the rotation axis). The inclined surfaces 66E, 66F may be flat or curved. As shown in FIG. 5(b), when the separation shaft 66 is pressed by the cam follower 170, the inclined surfaces 66E, 66F come into contact with the roller 55A and move the developer cartridge 60 forward. As a result, the developer cartridge 60 moves to the second position or the third position where the developer roller 61 is separated from the photosensitive drum 50.

[0069] In other words, when pressed by the cam follower 170, the separating shaft 66 comes into contact with the roller 55A and moves together with the developing frame 65 in a direction away from the photosensitive drum 50, thereby moving the developing roller 61 from the contact position to the separating position or the second separating position. The separating shaft 66 is movable between a roller non-contact position where the inclined surfaces 66E, 66F do not contact the roller 55A and a roller contact position where the inclined surfaces 66E, 66F contact the roller 55A. When the separating shaft 66 moves from the roller non-contact position to the roller contact position, it moves the developing frame 65 away from the photosensitive drum 50, separating the developing roller 61 from the photosensitive drum 50. When the separating shaft 66 moves from the roller contact position to the roller non-contact position, it moves the developing frame 65 closer to the photosensitive drum 50, bringing the developing roller 61 into contact with the photosensitive drum 50.

[0070] The spring 67 is disposed between the first contact member 66B and the developing frame 65. The spring 67 biases the spacing shaft 66 toward the cam follower 170.

[0071] 4, the separation cam 150 is an end face cam. The separation cam 150 has a disk portion 151, a boss 152, and a cam portion 153. The boss 152 extends in the direction of the rotation axis from the center of the disk portion 151. The boss 152 has a cylindrical shape.

[0072] The image forming apparatus 1 further includes four shafts 159 and a metal plate 15 (see FIG. 3). The metal plate 15 is a member that rotatably supports the gears of each gear train. The shafts 159 are fixed to the metal plate 15. The separating cam 150 (cam gear 115) is rotatably supported by the metal plate 15 as a result of a boss 152 engaging with the shaft 159.

[0073] The cam portion 153 protrudes in the rotational axis direction from the disk portion 151. Specifically, the cam portion 153 protrudes toward one side in the rotational axis direction from the disk portion 151. The cam portion 153 protrudes in the rotational axis direction from the surface of the disk portion 151 opposite to the metal plate 15 (see FIG. 3) in the rotational axis direction.

[0074] 6, the separating cam 150 has a first surface F1, a second surface F2, a third surface F3, a first inclined surface F4, and a reverse inclined surface F5. Specifically, the disc portion 151 has a first surface F1. The cam portion 153 protrudes from the first surface F1. The cam portion 153 has a second surface F2, a third surface F3, the first inclined surface F4, and a reverse inclined surface F5.

[0075] The first surface F1, the second surface F2, and the third surface F3 are substantially parallel to a plane perpendicular to the rotation axis direction. The first inclined surface F4 and the reverse inclined surface F5 are inclined with respect to the rotation axis direction. The first inclined surface F4 and the reverse inclined surface F5 may be flat or curved.

[0076] The first surface F1 has a first portion P1, which faces the cam follower 170 in the direction of the rotation axis when the cam follower 170 is in the non-pressing position (see FIG. 10(a)).

[0077] The second surface F2 has a second portion P2. The second portion P2 holds the cam follower 170 in the pressing position (see FIGS. 7(a) and 10(c)). The second portion P2 is located to one side of the first portion P1 in the direction of the rotation axis.

[0078] The third surface F3 has a third portion P3. The third portion P3 is located on one side of the second portion P2 in the rotational axis direction. The third portion P3 positions the cam follower 170 at the second pressing position (see FIG. 10(b)). The third surface F3 is located between the first surface F1 and the second surface F2 in the rotational direction of the separating cam 150. The area of ​​the third surface F3 is smaller than the area of ​​the second surface F2.

[0079] The first inclined surface F4 is located between the first surface F1 and the third surface F3 in the rotational direction. The first inclined surface F4 extends obliquely from the first surface F1 toward one side of the rotational axis direction and is connected to the third surface F3. The first inclined surface F4 guides the cam follower 170 between the non-pressing position and the second pressing position.

[0080] The reverse inclined surface F5 is located between the third surface F3 and the second surface F2 in the rotational direction. The reverse inclined surface F5 extends obliquely from the third surface F3 toward the other side of the rotational axis direction and is connected to the second surface F2. The reverse inclined surface F5 guides the cam follower 170 between the second pressing position and the pressing position.

[0081] The cam follower 170 includes a slide shaft 171 , an arm 172 , a pin 173 , and a rib 174 .

[0082] The slide shaft 171 is slidable in the direction of the rotation axis. Specifically, the slide shaft 171 has a cylindrical shape. The slide shaft 171 is engaged with the boss 152 of the separating cam 150, thereby being slidable in the direction of the rotation axis relative to the boss 152.

[0083] The arm 172 extends from the slide shaft 171 in a direction perpendicular to the rotation axis direction. Specifically, the arm 172 extends from the slide shaft 171 toward the outside in the radial direction of the slide shaft 171. The arm 172 is plate-shaped.

[0084] The pin 173 extends from the arm 172 in the direction of the rotation axis. Specifically, the pin 173 extends from the end of the arm 172 farthest from the slide shaft 171 toward one side in the direction of the rotation axis. The pin 173 is cylindrical, and its tip has a convex curved surface. The tip of the pin 173 can come into contact with the developer cartridge 60. Specifically, the tip of the pin 173 can come into contact with the pressed surface 66D (see FIG. 5(b)) of the separation shaft 66 provided in the developer cartridge 60.

[0085] The rib 174 extends from the slide shaft 171 in a direction perpendicular to the rotation axis direction. Specifically, the rib 174 extends from the slide shaft 171 toward the outside in the radial direction of the slide shaft 171. The rib 174 extends in a direction different from the direction in which the arm 172 extends. In this embodiment, the rib 174 extends forward from the slide shaft 171, and the arm 172 extends diagonally downward and rearward from the slide shaft 171.

[0086] The image forming apparatus 1 further includes stoppers 530. Four sets of stoppers 530 are provided corresponding to the four cam followers 170 (see FIG. 4). The stoppers 530 restrict the rotation of the cam followers 170 around the rotation axis of the separation cam 150 (cam gear 115). Specifically, as shown in FIGS. 8(a) and 8(b), the image forming apparatus 1 includes a gear cover 500, and the gear cover 500 has stoppers 530.

[0087] The gear cover 500 is fixed to the metal plate 15 (see FIG. 3 ) to cover the separating cam 150 (cam gear 115) and the cam follower 170. The gear cover 500 has a cover wall 510. The cover wall 510 is a wall that covers the separating cam 150 and the cam follower 170, and faces the metal plate 15 in the direction of the rotation axis when the gear cover 500 is fixed to the metal plate 15.

[0088] The stoppers 530 extend in the rotation axis direction from the cover wall 510 toward the corresponding separating cams 150. The stoppers 530 are wall-shaped. The stoppers 530 sandwich the arms 172 of the cam followers 170 from both sides in the circumferential direction of the slide shaft 171 (see FIGS. 6 and 7). This restricts the rotation of the cam followers 170 around the bosses 152.

[0089] The cover wall 510 further has four insertion holes 520. As shown in Fig. 9, the insertion holes 520 are through holes through which the pins 173 of the cam followers 170 are inserted.

[0090] The image forming apparatus 1 further includes springs 430. Four springs 430 are provided corresponding to the four cam followers 170. The springs 430 bias the cam followers 170 from the pressed position shown in FIG. 9(b) toward the non-pressed position shown in FIG. 9(a). As an example, the springs 430 are compression coil springs. The springs 430 are located between the gear cover 500 and the slide shafts 171 of the cam followers 170. Specifically, the springs 430 are located between the cover wall 510 and the slide shafts 171.

[0091] The slide shaft 171 has a recess 171A. The recess 171A is an annular recess that opens toward the cover wall 510 in the direction of the rotation axis. At least one end of the spring 430 is disposed within the recess 171A. By providing the recess 171A, it is possible to prevent the spring 430 from shifting out of position.

[0092] The control unit 2 (see FIG. 1) is equipped with a CPU, ROM, RAM, and input / output circuits, and performs control by executing pre-stored programs. The control unit 2 controls the driving and stopping of the main motor M1 and the rotation direction of the output shaft of the main motor M1. The control unit 2 switches the transmission state of the driving force from the main motor M1 to the separation cam 150 by controlling the electromagnetic clutch of the development separation gear train GT1.

[0093] Next, the operation of each member for moving the developing roller 61 will be described with reference to Figures 6 and 10. Here, in Figure 10, for the sake of convenience, each surface (F1 to F5) aligned in the rotation direction of the separating cam 150 is shown expanded to line up in a straight line.

[0094] 6 and 10(a), when the developing roller 61 is in the contact position, the cam follower 170 is in the non-pressing position. The cam follower 170 has a contact portion TP that can come into contact with the second portion P2 and the third portion P3 of the separating cam 150. The contact portion TP is located at the tip of the arm 172. When the cam follower 170 is in the non-pressing position, the contact portion TP is located at a reference position facing the first portion P1 of the separating cam 150 with a gap in the rotational axis direction.

[0095] When the driving force of the main motor M1 rotating in the reverse direction is transmitted to the separating cam 150, the separating cam 150 rotates in the second rotation direction R2. When the separating cam 150 rotates in the second rotation direction R2 with the contact portion TP located at the reference position, the contact portion TP moves relatively to the separating cam 150 from the reference position to the second surface F2 (second portion P2) via the first inclined surface F4, the third surface F3 (third portion P3), and the reverse inclined surface F5, as shown in the order of FIGS. 10(a) to 10(c).

[0096] When the contact portion TP comes into contact with the first inclined surface F4, the first inclined surface F4 presses the contact portion TP in a direction away from the first surface F1, and the cam follower 170 moves from the non-pressing position toward the second pressing position. As a result, the cam follower 170 presses the separating shaft 66, and the separating shaft 66 moves in a direction away from the separating cam 150.

[0097] When the inclined surfaces 66E, 66F of the spacing shaft 66 come into contact with the roller 55A, the spacing shaft 66 moves together with the developer cartridge 60 in a direction away from the photosensitive drum 50. As a result, the developing roller 61 moves from the contact position toward the second spacing position. At this time, a first friction force FR1 acting in the direction opposite to the moving direction of the spacing shaft 66 is generated between the inclined surfaces 66E, 66F and the roller 55A. The first friction force FR1 has a force component in a direction from the spacing shaft 66 toward the cam follower 170.

[0098] When the contact portion TP comes into contact with the third surface F3, the cam follower 170 is positioned at the second pressing position, and the developing roller 61 is positioned at the second separating position. When the contact portion TP comes off the third surface F3 and comes into contact with the reverse inclined surface F5, the cam follower 170 moves from the second pressing position toward the pressing position, and the separating shaft 66 moves together with the developing cartridge 60 in a direction approaching the photosensitive drum 50. As a result, the developing roller 61 moves from the second separating position toward the separating position.

[0099] At this time, the separating shaft 66 moves in the direction of its rotation axis so as to approach the separating cam 150, and a second frictional force FR2 in a direction substantially opposite to the first frictional force FR1 acts between the inclined surfaces 66E, 66F and the roller 55A. When the contact portion TP comes into contact with the second surface F2, the cam follower 170 is positioned at the pressing position, and the developing roller 61 is positioned at the separating position.

[0100] In a state in which the cam follower 170 is held by the second surface F2, a second friction force FR2 directed in a direction away from the separating cam 150 acts on the separating shaft 66, thereby reducing the force applied from the cam follower 170 to the separating cam 150. More specifically, if the shape of the cam portion 153 were such that the protrusion having the third surface F3 and the reverse inclined surface F5 was removed from the cam portion 153 and the second surface F2 extended to the first inclined surface F4, and the cam follower 170 was designed to move only between the non-pressing position and the pressing position, the following problem would arise.

[0101] In a structure in which the cam follower 170 is moved only between the non-pressing position and the pressing position, when the contact portion TP comes off the first inclined surface F4 and comes into contact with the second surface F2, a frictional force in approximately the same direction as the first frictional force FR1 acts on the separating shaft 66. If the separating shaft 66 is held by the second surface F2 via the cam follower 170 in a state in which such a frictional force is acting, the force applied from the cam follower 170 to the separating cam 150 increases.

[0102] In this embodiment, the cam follower 170 is moved from the non-pressing position to a second pressing position that is farther from the non-pressing position than the pressing position, and then returned from the second pressing position to the pressing position, thereby switching the direction of the friction force applied to the separation shaft 66. Therefore, when the separation cam 150 holds the cam follower 170 in the pressing position, the force applied from the cam follower 170 to the separation cam 150 can be reduced.

[0103] 7, when the driving force of the main motor M1 rotating forward is transmitted to the separating cam 150 while the contact portion TP is located on the second surface F2 (second portion P2), the separating cam 150 rotates in the first rotation direction R1. When the separating cam 150 rotates in the first rotation direction R1, the contact portion TP moves relative to the separating cam 150 from the second surface F2 (second portion P2), via the reverse inclined surface F5, the third surface F3 (third portion P3), and the first inclined surface F4, to the reference position, as shown in the order of FIGS. 10(c) to 10(a).

[0104] As described above, according to this embodiment, the following effects can be obtained. As the separating cam 150 rotates in the second rotation direction R2, the cam follower 170 comes into contact with the third portion P3 and then with the second portion P2, causing the developing roller 61 to move from the contact position to the second separating position and then to the separating position, so that the frictional force between the separating shaft 66 and the roller 55A acts in the direction opposite to the direction of the force applied from the cam follower 170 to the separating cam 150. Therefore, when the separating cam 150 holds the cam follower 170 in the pressing position, the force applied from the cam follower 170 to the separating cam 150 can be reduced.

[0105] By configuring the first surface F1, the second surface F2, the third surface F3, the first inclined surface F4, and the reverse inclined surface F5 to be arranged in the order of first surface F1, first inclined surface F4, third surface F3, reverse inclined surface F5, and second surface F2 in the rotational direction, the cam follower 170 can be moved from the non-pressing position to the pressing position via the second pressing position by simply rotating the separating cam 150 in one direction.

[0106] [Second embodiment] Next, the second embodiment will be described in detail with reference to the drawings as appropriate. Note that since this embodiment is a modification of the shape of the cam portion 153 according to the first embodiment, components that are substantially the same as those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0107] As shown in FIG. 11, the separating cam 150 according to the second embodiment has a first surface F1, a second surface F2, a third surface F3, a first inclined surface F4, and a reverse inclined surface F5, which are substantially the same as those of the first embodiment, and further has a fourth surface F11 and a second inclined surface F12.

[0108] The fourth surface F11 is located between the first surface F1 and the third surface F3 in the rotational axis direction. The fourth surface F11 is located between the first surface F1 and the third surface F3 in the rotational direction. The fourth surface F11 is connected to the first inclined surface F4.

[0109] The second inclined surface F12 extends obliquely from the fourth surface F11 toward one side of the rotation axis direction. The second inclined surface F12 is connected to the fourth surface F11 and the third surface F3. The second inclined surface F12 may be a flat surface or a curved surface.

[0110] In the second embodiment, the relative movement of the cam follower 170 with respect to the separating cam 150 is the same as in the first embodiment. That is, in the second embodiment, when the separating cam 150 rotates in the second rotation direction R2 with the contact portion TP located at the reference position, the contact portion TP moves relative to the separating cam 150 from the reference position to the second portion P2 via the third portion P3. When the separating cam 150 rotates in the first rotation direction R1 with the contact portion TP in contact with the second portion P2, the contact portion TP moves from the second portion P2 to the reference position via the third portion P3. Therefore, the second embodiment can also achieve the same effects as the first embodiment.

[0111] [Third embodiment] Next, the third embodiment will be described in detail with reference to the drawings as appropriate. Note that since this embodiment is a modification of the shape of the cam portion 153 according to the first embodiment, components that are substantially the same as those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0112] As shown in FIG. 12, the separating cam 150 according to the third embodiment has a first surface F1 substantially similar to that of the first embodiment, and further has a fifth inclined surface F21 and a sixth inclined surface F22.

[0113] The fifth inclined surface F21 extends obliquely from the first surface F1 toward one side of the rotation axis direction. The sixth inclined surface F22 extends obliquely from the fifth inclined surface F21 toward the other side of the rotation axis direction. The sixth inclined surface F22 has a second portion P2 and a third portion P3. The fifth inclined surface F21 and the sixth inclined surface F22 may be flat or curved.

[0114] In the third embodiment, the relative movement of the cam follower 170 with respect to the separating cam 150 is the same as in the first embodiment. That is, in the third embodiment, when the separating cam 150 rotates in the second rotation direction R2 with the contact portion TP located at the reference position, the contact portion TP moves relative to the separating cam 150 from the reference position to the second portion P2 via the third portion P3. When the separating cam 150 rotates in the first rotation direction R1 with the contact portion TP in contact with the second portion P2, the contact portion TP moves from the second portion P2 to the reference position via the third portion P3. Therefore, the second embodiment can also achieve the same effects as the first embodiment.

[0115] [Fourth embodiment] Next, the fourth embodiment will be described in detail with reference to the drawings as appropriate. Note that since this embodiment is a modification of the shape of the cam portion 153 according to the first embodiment, components that are substantially the same as those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0116] As shown in FIG. 13, the separating cam 150 according to the fourth embodiment has a first surface F1 substantially similar to that of the first embodiment, and further has a third inclined surface F31 and a fourth inclined surface F32.

[0117] The third inclined surface F31 extends obliquely from the first surface F1 toward one side of the rotation axis direction. The fourth inclined surface F32 extends obliquely from the third inclined surface F31 toward one side of the rotation axis direction. The fourth inclined surface F32 has a smaller inclination angle with respect to the first surface F1 than the third inclined surface F31. The fourth inclined surface F32 has a second portion P2 and a third portion P3. The second portion P2 is located between the third inclined surface F31 and the third portion P3. The third inclined surface F31 and the fourth inclined surface F32 may be flat or curved.

[0118] In the fourth embodiment, when the main motor M1 rotates in the reverse direction and the separating cam 150 rotates in the second rotation direction R2 while the contact portion TP is located at the reference position, the contact portion TP moves from the reference position to the third portion P3 via the second portion P2, as shown in the order of Figures 13(a) and 13(b). Thereafter, the contact portion TP moves relative to the separating cam 150 so as to return to the second portion P2 as the main motor M1 rotates in the forward direction or stops, as shown in the order of Figures 13(b) and 13(c).

[0119] More specifically, if the frictional force between the separating cam 150 and the metal plate 15 is equal to or greater than a predetermined value and the separating cam 150 does not move due to the pressing force applied from the cam follower 170 to the fourth inclined surface F32 when the main motor M1 is stopped, a method of switching the rotation direction of the main motor M1 is used. With this method, after the contact part TP reaches the third part P3, the control unit 2 switches the rotation direction of the main motor M1, and when the main motor M1 rotates forward, the rotation direction of the separating cam 150 is switched to the first rotation direction R1, and the contact part TP moves relatively to the separating cam 150 from the third part P3 to the second part P2.

[0120] Furthermore, if the frictional force between the separating cam 150 and the metal plate 15 is smaller than a predetermined value and the separating cam 150 moves due to the pressing force applied from the cam follower 170 to the fourth inclined surface F32 when the main motor M1 is stopped, a method of stopping the main motor M1 can be used. Here, the separating cam 150 is engaged with an upstream gear to which driving force is transmitted from the main motor M1. Therefore, when the main motor M1 is stopped, the separating cam 150 that has rotated in the second rotation direction R2 can rotate in a direction in which backlash with the upstream gear is reduced, i.e., in the first rotation direction R1.

[0121] In this method, when the main motor M1 is stopped by the control unit 2 after the contact portion TP reaches the third portion P3, the separating cam 150 rotates in the first rotation direction R1 due to the force from the cam follower 170, and the contact portion TP moves relatively to the separating cam 150 from the third portion P3 to the second portion P2. The upstream gear may be configured so that the separating cam 150 contacts the upstream gear and stops rotating when the contact portion TP contacts the second portion P2. For example, the upstream gear may be biased against the metal plate 15 by a spring to increase the frictional force between the upstream gear and the metal plate 15.

[0122] Furthermore, in this method, when the control unit 2 rotates the main motor M1 in the forward direction while the contact portion TP is positioned at the second portion P2, the contact portion TP moves relative to the separating cam 150 from the second portion P2 to the reference position without passing through the third portion P3, as shown in the order of Figures 13(c) and (a).

[0123] When the main motor M1 rotates forward with the contact portion TP positioned at the second portion P2, the contact portion TP is configured to move from the second portion P2 to the reference position without passing through the third portion P3, thereby reducing the force applied from the cam follower 170 to the separation cam 150 when the main motor M1 rotates forward.

[0124] Although the image forming apparatus has been described above in accordance with the various embodiments, the image forming apparatus can be modified as appropriate as exemplified below.

[0125] In the embodiment described above, the separation cam 150 is configured to move the developing roller 61 from the separation position to the contact position when the main motor M1 rotates forward, and to move the developing roller 61 from the contact position to the separation position when the main motor M1 rotates reversely. However, for example, the separation cam may be configured to move the developing roller from the separation position to the contact position, or from the contact position to the separation position, when the main motor rotates in only one direction.

[0126] In the first to third embodiments, when the main motor rotates in only one direction, if the separating cam 150 rotates in the second rotation direction R2 with the contact portion TP in contact with the second portion P2, the contact portion TP moves from the second portion P2 to the reference position without passing through the third portion P3. Therefore, the first to third embodiments can achieve the same effect as the fourth embodiment.

[0127] In the above embodiment, the stopper 530 is wall-shaped, but the stopper may be rod-shaped, for example. Also, in the above embodiment, the stopper 530 is formed integrally with the cover wall 510, but the stopper may be a member fixed to the cover wall, for example.

[0128] Furthermore, for example, if the separating cam is configured to rotate in only one direction, the rotation of the cam follower may be restricted by having one stopper in contact with one side of the arm, rather than having a pair of stoppers sandwiching the arm.Furthermore, for example, without providing a stopper, the cross-sectional shape of the portion where the cam boss and the cam follower slide shaft engage may be triangular, rectangular, D-shaped, oval, or the like, to restrict the rotation of the cam follower.

[0129] In the above embodiment, the photosensitive drum 50 is rotatably supported in the drawer 55, but the photosensitive drum may be detachably attached to the drawer. Specifically, a drum cartridge having a photosensitive drum may be provided, and the drum cartridge may be detachably attached to the drawer. Alternatively, a cartridge having a photosensitive drum and a developing roller, in which the drum cartridge and the developing cartridge 60 of the above embodiment are integrated, may be provided, and the cartridge may be detachably attached to the drawer.

[0130] In the above embodiment, the image forming apparatus 1 is a color printer capable of forming color images, but the image forming apparatus may be, for example, a monochrome printer capable of forming only monochrome images. Also, for example, the image forming apparatus may be a copier or a multifunction peripheral.

[0131] The elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0132] 1. Image forming device 50 Photosensitive drum 60 Developer cartridge 61 Developing roller 150 Separation Cam 170 Cam follower M1 main motor P1 Part 1 P2 2nd part P3 3rd part

Claims

1. A motor; A photosensitive drum; a developing cartridge including a developing roller movable between a contact position in contact with the photosensitive drum, a spaced position away from the photosensitive drum, and a second spaced position farther from the contact position than the spaced position; a rotating cam that rotates by receiving the driving force of the motor; a cam follower that moves in a direction of a rotation axis of the rotating cam in response to rotation of the rotating cam, and is movable between a non-pressing position where the developing roller is positioned at the contact position, a pressing position where the developing cartridge is pressed to position the developing roller at the separated position, and a second pressing position where the developing cartridge is pressed to position the developing roller at the second separated position; The rotating cam is a first portion that faces the cam follower in the direction of the rotation axis when the cam follower is located at the non-pressing position; a second portion that holds the cam follower at the pressing position, the second portion being located on one side of the first portion in the direction of the rotation axis; a third portion located on one side of the second portion in the rotational axis direction, the third portion positioning the cam follower at the second pressing position, An image forming apparatus characterized in that the developing roller moves from the contact position to the second separation position and then to the separation position when the cam follower contacts the third portion due to rotation of the rotating cam and then contacts the second portion.

2. a drum frame into which the developing cartridge can be attached, the drum frame holding the photosensitive drum; The developing cartridge is a developing frame for holding the developing roller; a spacing shaft held by the developing frame so as to be movable in the direction of the rotation axis, the spacing shaft coming into contact with the drum frame when pressed by the cam follower, thereby moving together with the developing frame in a direction away from the photosensitive drum, thereby moving the developing roller from the contact position to the spacing position; 2. The image forming apparatus according to claim 1, further comprising: a spring that biases the separation shaft toward the cam follower.

3. The rotating cam is a first surface having the first portion; a second surface having the second portion; a third surface having the third portion and positioned between the first surface and the second surface in the rotation direction of the rotating cam; a first inclined surface extending obliquely from the first surface toward one side of the rotation axis direction, the first inclined surface being located between the first surface and the third surface in the rotation direction; 2. The image forming apparatus according to claim 1, further comprising: a reverse inclined surface extending obliquely from the third surface toward the other side of the rotation axis direction, the reverse inclined surface being positioned between the third surface and the second surface in the rotation direction.

4. the first inclined surface is connected to the first surface and the third surface; 4. The image forming apparatus according to claim 3, wherein the reverse inclined surface is connected to the third surface and the second surface.

5. The rotating cam is a fourth surface located between the first surface and the third surface in the rotation axis direction and between the first surface and the third surface in the rotation direction, the fourth surface being connected to the first inclined surface; 4. The image forming apparatus according to claim 3, further comprising: a second inclined surface extending obliquely from the fourth surface toward one side of the rotation axis direction, the second inclined surface being connected to the fourth surface and the third surface.

6. The rotating cam is a first surface having the first portion; a third inclined surface extending obliquely from the first surface toward one side of the rotation axis direction; 2. The image forming device according to claim 1, further comprising: a fourth inclined surface extending obliquely from the third inclined surface toward one side of the rotation axis direction, the fourth inclined surface having a smaller inclination angle with respect to the first surface than the third inclined surface, the fourth inclined surface having the second portion and the third portion.

7. The rotating cam is a first surface having the first portion; a fifth inclined surface extending obliquely from the first surface toward one side of the rotation axis direction; 2. The image forming apparatus according to claim 1, further comprising: a sixth inclined surface extending obliquely from the fifth inclined surface toward the other side of the rotation axis direction, the sixth inclined surface having the second portion and the third portion.

8. The drum frame further includes a roller that rotates in contact with the spacer shaft; The spaced shaft the roller is inclined relative to the rotation axis direction, and the inclined surface is inclined relative to the rotation axis direction, and the inclined surface is in contact with the roller, the inclined surface is movable between a roller non-contact position where it does not contact the roller and a roller contact position where it contacts the roller, 3. The image forming apparatus according to claim 2, wherein when the developing frame is moved from the roller non-contact position to the roller contact position, the developing roller is separated from the photosensitive drum by moving the developing frame away from the photosensitive drum, and when the developing frame is moved from the roller contact position to the roller non-contact position, the developing roller is brought into contact with the photosensitive drum by moving the developing frame closer to the photosensitive drum.

9. The motor is capable of rotating forward and reverse, the cam follower has a contact portion that can come into contact with the second portion and the third portion, The contact portion is When the motor rotates in the reverse direction while being positioned at a reference position opposite to the first portion in the rotation axis direction, the rotating cam moves from the reference position to the second portion via the third portion, relative to the rotating cam, 8. The image forming apparatus according to claim 3, wherein when the motor rotates forward while positioned at the second portion, the motor moves from the second portion to the reference position via the third portion.

10. The motor is capable of rotating forward and reverse, the cam follower has a contact portion that can come into contact with the second portion and the third portion, The contact portion is When the motor rotates in the reverse direction while positioned at a reference position opposite to the first portion in the rotation axis direction, the motor moves from the reference position to the third portion via the second portion, and then moves relative to the rotating cam so as to return to the second portion by forward rotation or stopping of the motor, 7. The image forming apparatus according to claim 6, wherein when the motor rotates forward while positioned at the second portion, the image forming apparatus moves from the second portion to the reference position without passing through the third portion.

Images