Image forming device

Abstract

To provide an image forming apparatus capable of accurately positioning a drum unit mounted on a housing in the right and left directions to prevent a shift after the mounting.SOLUTION: An image forming apparatus comprises: a drum unit 500 including a photosensitive drum and drawably mounted on a housing 10; a developer cartridge supported on the drum unit 500 at a position corresponding to each photosensitive drum; and the housing 10 including regulation parts 411 and 412. The regulation parts 411 and 412 control that the drum unit 500 moves even when an action member provided at a position corresponding to each developer cartridge of the housing 10 as a separation mechanism for moving a developing roller from a contact position to a separation position in the state of mounting the drum unit 500 on the housing 10 presses the developer cartridge from the side of a first side wall 910.SELECTED DRAWING: Figure 20

Description

[Technical Field]

[0001] The present invention relates to an electrophotographic image forming apparatus having a drum unit that is attached to a housing so as to be removable. [Background technology]

[0002] Conventionally, there has been known an image forming apparatus in which a drum unit including a photosensitive drum is attached to a housing so that it can be pulled out. For example, Patent Document 1 discloses a color printer in which a drum unit including multiple photosensitive drums arranged in tandem below an exposure device is configured to be pullable out from the housing together with a developing roller and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-211940 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, when a drum unit is attached to a housing, a shaft extending left and right on the housing is fitted into a notch on the rear end of the side wall of the drum unit to position the rear end of the drum unit in the front-to-back and up-to-down directions, and the end of the shaft extending left and right on the drum unit is abutted from above against a positioning member on the front end of the housing to position the front end of the drum unit in the up-to-down direction. Here, no consideration is given to positioning the drum unit left and right, i.e., the direction parallel to the rotation axis of the photosensitive drum (hereinafter simply referred to as the "axial direction").

[0005] Since misalignment of the drum unit relative to the housing in the left-right direction has a significant impact on the quality of images formed, it is desirable to accurately position the drum unit not only in the front-to-back and up-to-down directions but also in the left-to-right direction after installation to prevent misalignment after installation. [Means for solving the problem]

[0006] In a first aspect of the present invention, we propose an image forming apparatus including a housing, a drum unit, a first developing cartridge, a second developing cartridge, a first operating member, and a second operating member. The drum unit is retractably mounted in the housing. The drum unit has a first side wall and a second side wall spaced apart in a direction perpendicular to the retraction direction, and a first photosensitive drum and a second photosensitive drum spaced apart along the retraction direction between the first and second side walls. The first photosensitive drum and the second photosensitive drum are supported by the first and second side walls so as to be rotatable about axes perpendicular to the retraction direction. The first developing cartridge is supported by the drum unit at a position corresponding to the first photosensitive drum. The first developing cartridge has a first developing roller that can contact the first photosensitive drum and is movable between a contact position where the first developing roller contacts the first photosensitive drum and a separated position where the first developing roller is separated from the first photosensitive drum. The second developing cartridge is supported by the drum unit at a position corresponding to the second photosensitive drum. The second developer cartridge has a second developer roller that can contact the second photosensitive drum, and is movable between a contact position where the second developer roller contacts the second photosensitive drum and a separated position where the second developer roller is separated from the second photosensitive drum. The first acting member is provided in a position corresponding to the first developer cartridge in the housing and presses the first developer cartridge from the first side wall side to move the first developer roller from the contact position to the separated position. The second acting member is provided in a position corresponding to the second developer cartridge in the housing and presses the second developer cartridge from the first side wall side to move the second developer roller from the contact position to the separated position. The housing has a regulating portion that regulates movement of the drum unit caused by the first acting member pressing the first developer cartridge and / or the second acting member pressing the second developer cartridge when the drum unit is attached to the housing.

[0007] With this configuration, the first and second acting members restrict the axial movement of the drum unit caused by pressing the first and second developing cartridges, thereby suppressing axial positional deviation after installation.

[0008] The image forming apparatus may further include a first cam and a second cam, wherein the first acting member includes a first cam follower that is movable by the first cam between an operating position where it presses the first developer cartridge and a standby position where it does not press the first developer cartridge, and the second acting member includes a second cam follower that is movable by the second cam between an operating position where it presses the second developer cartridge and a standby position where it does not press the second developer cartridge. Here, the first cam and the second cam may be rotating cams or linearly moving cams.

[0009] In the image forming device described above, the housing may have a first side frame that covers the side of the first side wall opposite the second side wall in the axial direction of the first photosensitive drum and the second photosensitive drum when the drum unit is attached to the housing, and a second side frame that covers the side of the second side wall opposite the first side wall in the axial direction, and the regulating portion may include a first regulating portion and a second regulating portion provided on the first side frame at positions spaced apart from each other in the pull-out direction.

[0010] According to this configuration, the first regulating portion and the second regulating portion each regulate axial displacement at positions spaced apart from each other in the pulling-out direction, so that even if only one of the first acting member and the second acting member presses the first developing cartridge or the second developing cartridge in the axial direction, rotation of the drum unit around an axis perpendicular to the axial direction and the pulling-out direction can be effectively regulated without distorting the drum unit.

[0011] In an aspect including the first and second restricting portions, preferably, when the image forming apparatus is installed on an installation surface and the drum unit is attached to the housing, the height from the installation surface to the first and second restricting portions is the same as the height from the installation surface to the first and second acting members. In other words, by restricting the first and second restricting portions at the same height as the first and second acting members, it is possible to effectively restrict rotation around an axis perpendicular to the axial direction and the pull-out direction without distorting the drum unit.

[0012] In the aspect including the first and second restricting portions, the first restricting portion is preferably disposed at a position further back than the second restricting portion in the pull-out direction and closer to the second side frame than the second restricting portion in the axial direction. By disposing the first restricting portion and the second restricting portion in this manner, interference with the pull-out and installation of the drum unit can be suppressed even if they are disposed at the same height.

[0013] In various aspects including the first and second restricting portions, the housing may further include a positioning portion provided between the first and second restricting portions in the pull-out direction, and the first side wall may have a first abutment surface provided at a rear end in the pull-out direction and facing the second side wall in the axial direction, and a second abutment surface provided at a front end in the pull-out direction and facing the second side wall in the axial direction. When the drum unit is attached to the housing, the first restricting portion may abut against the first abutment surface, the second restricting portion may abut against the second abutment surface, and the positioning portion may abut against a side surface of the first side wall opposite the second side wall.

[0014] In this way, the regulating portion of the housing abuts against the abutment surface facing inward of the drum unit on both the front and back sides of the drum unit, and between them, the positioning portion of the housing abuts against the side surface facing outward of the drum unit, thereby ensuring that the first side wall is positioned and fixed in the axial direction.

[0015] The positioning portion may include a first protrusion provided at a position corresponding to the first working member in the drawing direction, and a second protrusion provided at a position corresponding to the second working member.

[0016] Furthermore, in an aspect including the first protrusion and the second protrusion, the image forming apparatus may further include a first electrode spring that is electrically connected to the first developer cartridge when the drum unit is attached to the housing and urges the drum unit from the second side frame toward the first side frame, and a second electrode spring that is electrically connected to the second developer cartridge when the drum unit is attached to the housing and urges the drum unit from the second side frame toward the first side frame. The first electrode spring and the first protrusion, and the second electrode spring and the second protrusion, may be provided at positions symmetrical with respect to an imaginary plane perpendicular to the axial direction.

[0017] With this configuration, the urging forces of the first electrode spring and the second electrode spring can be reliably received by the protrusions of the housing, so the drum unit can be more stably positioned and held on the housing.

[0018] In various embodiments in which the housing includes a first side frame and a second side frame, the housing may further have a connecting member connecting the rear ends of the first side frame and the second side frame in the pull-out direction, and when the drum unit is attached to the housing, the first side wall and the second side wall engage with the connecting member, thereby positioning the drum unit in the pull-out direction relative to the housing, and the regulating portion may regulate axial movement of the first side wall prior to the first side wall and the second side wall engaging with the connecting member when the drum unit is attached to the housing.

[0019] In this way, by positioning in the drawing direction after positioning in the axial direction, scraping or the like caused when the first side wall and the second side wall engage with the connecting member can be suppressed.

[0020] In various aspects in which the housing includes the first and second side frames, the image forming apparatus may further include an exposure device that exposes the first and second photosensitive drums, and the housing may further include a connecting plate that connects the first and second side frames, with the exposure device being fixed to the connecting plate. In this way, in an aspect in which the exposure device is fixed to the connecting plate of the housing, it is possible to suppress deviation of the exposure position on the photosensitive drum due to axial movement of the drum unit, thereby suppressing deterioration in the quality of the formed image.

[0021] We propose a second aspect of an image forming apparatus including a housing, a drum unit, a first developing cartridge, a second developing cartridge, a first acting member, and a second acting member. The housing has a first side frame. The drum unit is retractable in a first direction relative to the housing. The drum unit has a first side wall having a first opening and a second opening, a second side wall spaced apart from the first side wall in a second direction perpendicular to the first direction, a first photosensitive drum supported between the first and second side walls to be rotatable about a rotation axis parallel to the second direction, and a second photosensitive drum spaced apart from the first photosensitive drum in the first direction and supported to be rotatable about a rotation axis parallel to the second direction. The first side wall of the drum unit is supported by the first side frame so as to be movable along a first direction between a storage position where the first and second photosensitive drums are located inside the housing and a drawn-out position where the first and second photosensitive drums are located outside the housing. The first developer cartridge has a first developer roller and, when attached to the drum unit, is movable between a contact position where the first developer roller contacts the first photosensitive drum and a separated position where the first developer roller is separated from the first photosensitive drum. The second developer cartridge has a second developer roller and, when attached to the drum unit, is movable between a contact position where the second developer roller contacts the second photosensitive drum and a separated position where the second developer roller is separated from the second photosensitive drum. The first acting member is provided at a position corresponding to the first developer cartridge of the first side frame and passes through a first opening in the first side wall to press the first developer cartridge in the second direction to move the first developer roller from the contact position to the separated position. The second acting member is provided at a position corresponding to the second developer cartridge on the first side frame and passes through a second opening in the first side wall to press the second developer cartridge in a second direction, moving the second developer roller from the contact position to the separated position. The first side wall has a first engaging portion and a second engaging portion located at a position spaced apart from the first engaging portion in the first direction. The first side frame has a first regulating portion and a second regulating portion.When the drum unit is in the storage position, the first engagement portion engages with the first regulating portion and the second engagement portion engages with the second regulating portion, thereby regulating movement of the drum unit caused by the first acting member pressing the first developing cartridge and / or the second acting member pressing the second developing cartridge. When the drum unit is in the pulled-out position, the first engagement portion disengages from the first regulating portion and the second engagement portion disengages from the second regulating portion.

[0022] In this aspect, the first and second restricting portions engage with the first and second engaging portions, respectively, at positions spaced apart in the first direction, so that the drum unit can be positioned and fixed in place in the housing after installation so as not to move in the storage position. This makes it possible to prevent the first and second acting members from pressing the first and second developing cartridges against each other, thereby preventing the first and second photosensitive drums from shifting in position.

[0023] In the second aspect, when the image forming apparatus is installed on an installation surface and the drum unit is attached to the housing, the height from the installation surface to the first and second restricting portions is preferably the same as the height from the installation surface to the first and second acting members. By restricting the first and second restricting portions at the same height as the first and second acting members, rotation around an axis perpendicular to the first and second directions can be effectively restricted without distorting the drum unit. Furthermore, it is preferable that the first restricting portion be positioned farther from the second photosensitive drum in the first direction and farther from the first side frame in the second direction than the second restricting portion. This is because interference between the first engaging portion and the second restricting portion can be suppressed when the drum unit moves from the storage position to the extended position.

[0024] In a second aspect, when the housing further has a second side frame supporting the second side wall so as to be movable along a first direction between a storage position where the first photosensitive drum and the second photosensitive drum are located inside the housing and a pull-out position where the first photosensitive drum and the second photosensitive drum are located outside the housing, the housing may further include a first electrode spring that is electrically connected to the first developer cartridge when the drum unit is attached to the housing and urges the drum unit from the second side frame side toward the first side frame, and a second electrode spring that is electrically connected to the second developer cartridge when the drum unit is attached to the housing and urges the drum unit from the second side frame side toward the first side frame.

[0025] By configuring it in this manner, when the housing is in the storage position, the spring force of the first electrode spring and the second electrode spring acts in the opposite direction to the pressing direction (second direction) of the first acting member and the second acting member, so that the drum unit can be stably supported between the first side frame and the second side frame.

[0026] The housing may further include a second side frame supporting the second side wall, the second side frame being movable along a first direction between a storage position where the first photosensitive drum and the second photosensitive drum are located inside the housing and a pull-out position where the first photosensitive drum and the second photosensitive drum are located outside the housing, and a connecting member connecting the first side frame and the second side frame, the first side wall and the second side wall contacting the connecting member when the drum unit is in the storage position, thereby positioning the drum unit in the first direction relative to the housing; and when the drum unit moves from the pull-out position to the storage position, the first engagement portion engages with the first regulating portion, and the second engagement portion engages with the second regulating portion, thereby restricting movement of the drum unit in the second direction, and then the first side wall and the second side wall contacting the connecting member to restrict movement of the drum unit in the first direction.

[0027] With this configuration, the first and second regulating portions engage with the first and second engaging portions, respectively, at positions spaced apart in the first direction to regulate movement of the drum unit in the second direction, thereby enabling the drum unit to be accurately positioned in the second direction and effectively preventing misalignment of the first and second photosensitive drums caused by the first and second acting members pressing against the first and second developer cartridges. Furthermore, when the first and second side walls contact the connecting member, movement of the drum unit in the second direction is regulated, thereby preventing abrasion and the like caused by contact between the first and second side walls and the connecting member.

[0028] In a third aspect, we propose an image forming apparatus including a housing, a drum unit, a first side frame, a second side frame, and a connecting member. The drum unit is retractable from the housing in a first direction and includes a first side wall having a first engagement portion and a second engagement portion positioned away from the first engagement portion in the first direction, a second side wall spaced apart from the first side wall in a second direction perpendicular to the first direction, and a photosensitive drum supported between the first and second side walls for rotation about a rotation axis parallel to the second direction. The first side frame is provided inside the housing and supports the first side wall so that the photosensitive drum can move along the first direction between a storage position where the photosensitive drum is located inside the housing and a pulled-out position where the photosensitive drum is located outside the housing. The first side frame has a first restriction portion that engages with the first engagement portion when the drum unit is in the storage position and a second restriction portion that engages with the second engagement portion when the drum unit is in the storage position. The second side frame is provided inside the housing and is spaced apart from the first side frame in the second direction. The connecting member connects the first side frame and the second side frame, and when the drum unit is in the storage position, the first side wall and the second side wall contact the connecting member to determine the position of the drum unit in the first direction relative to the housing. When the drum unit moves from the pulled-out position to the storage position, the first engagement portion engages with the first regulating portion, and the second engagement portion engages with the second regulating portion to regulate movement of the drum unit in the second direction, and then the first side wall and the second side wall contact the connecting member to regulate movement of the drum unit in the first direction.

[0029] In the third aspect, the first and second restricting portions engage with the first and second engaging portions, respectively, at positions spaced apart in the first direction to restrict movement of the drum unit in the second direction relative to the housing, so that the installed drum unit can be precisely positioned in the storage position relative to the housing, particularly so as not to move in the second direction. Furthermore, when the first and second side walls engage with the connecting member during the process of installing the drum unit in the housing, movement of the drum unit in the second direction is restricted, so that accurate positioning in the first direction can be achieved without causing scraping or the like between the first and second side walls and the connecting member. [Effects of the Invention]

[0030] According to the present invention, the drum unit can be accurately positioned relative to the housing in the axial direction of the photosensitive drum (the second direction perpendicular to the pull-out direction), and misalignment after installation can be suppressed. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the arrangement of a housing, an exposure device, and a drum unit. [Figure 3] FIG. 4 is a perspective view showing a first side frame and a connecting pipe. [Figure 4] FIG. 1 is a perspective view of a support member, a cam, and a cam follower; [Figure 5] 1A is a perspective view of a developing cartridge, and FIG. 1B is a side view thereof. [Figure 6] 1A and 1B are schematic diagrams illustrating the sliding member, showing the periphery of the developing cartridge as viewed from above, with the cam follower positioned at a standby position (FIG. 1A) and at an operating position (FIG. 1B). [Figure 7] 10 is a diagram showing the inner surface (developer cartridge side) of the side wall of the support member. FIG. [Figure 8] FIG. 2 is a perspective view of the drive transmission mechanism as seen from the upper left. [Figure 9]FIG. 2 is a view of the drive transmission mechanism as seen from the left side along the axial direction. [Figure 10] FIG. 2 is a perspective view of the drive transmission mechanism as seen from the upper right. [Figure 11] FIG. 2 is a view of the drive transmission mechanism as seen from the right side along the axial direction. [Figure 12] 1A is an exploded perspective view of the clutch as seen from the sun gear side, and FIG. 1B is an exploded perspective view of the clutch as seen from the carrier side. [Figure 13] 10A is a view from the axial direction and FIG. 10B is a perspective view showing the separation mechanism, the lever, the clutch, and the coupling gear when the developing roller is in the contact position and the clutch is in the transmission state. [Figure 14] 14A and 14B are axial views and a perspective view, respectively, showing the separation mechanism, lever, clutch, and coupling gear when the cam rotates from the state shown in FIG. 13 and the developing roller corresponding to yellow is in the contact position to form an image. [Figure 15] 15A is a view from the axial direction and FIG. 15B is a perspective view showing the separation mechanism, lever, clutch, and coupling gear when the cam rotates from the state shown in FIG. 14, the developing roller is in the separated position, and the clutch is in the transmitted state. [Figure 16] 16A and 16B are a view from the axial direction and a perspective view, respectively, showing the separation mechanism, the lever, the clutch, and the coupling gear when the cam rotates from the state shown in FIG. 15, the developing roller is in the separated position, and the clutch is in the disengaged state. [Figure 17] 17A and 17B are axial views and a perspective view, respectively, showing the separation mechanism, lever, clutch, and coupling gear when the cam rotates from the state shown in FIG. 16 and the developing roller corresponding to yellow is paused just before it starts to move to the contact position. [Figure 18] FIG. 10 is a view showing the drum unit positioned at the storage position, as viewed from the axial direction. [Figure 19] 1A is an overall view showing an engaged state of a restricting portion provided on a first side frame, FIG. 1B is a partial enlarged view of the periphery of the first restricting portion, and FIG. 1C is a partial enlarged view of the periphery of a second restricting portion. [Figure 20]10A and 10B are diagrams illustrating the arrangement of a restricting portion and a positioning portion. [Figure 21] FIG. 1(a) shows the state before the drum unit engages with the regulating portion and engagement recess of the housing when installed, and FIG. 1(b) shows the state after engaging with the regulating portion and before engaging with the engagement recess. [Figure 22] 10A and 10B are diagrams illustrating the standby and operating movements of the cam follower when color printing is performed. [Figure 23] 23A to 23B are diagrams (a) to (b) following FIG. 22, illustrating the standby and operating movements of the cam follower when color printing is performed. DETAILED DESCRIPTION OF THE INVENTION

[0032] As shown in FIG. 1, an image forming apparatus 1 according to the embodiment is a color printer, and includes a housing 10, a sheet supply unit 20, an image forming unit 30, and a control unit 2 as main components.

[0033] The sheet supply unit 20 is located in the lower part of the housing 10 and includes a sheet tray 21 that stores sheets S and a supply mechanism 22 that supplies sheets S from the sheet tray 21 to the image forming unit 30. The sheet tray 21 is configured to be removable by pulling it out from the housing 10 to the left side in FIG. 1. The supply mechanism 22 is located in the front part of the housing 10 and includes a paper feed roller 23, a separation roller 24, a separation pad 25, and a registration roller 27. For convenience, in this specification, directions such as front and back will be described assuming that the left side of FIG. 1, where the sheet tray 21 is pulled out, is the front. That is, the left side of FIG. 1 is the front, the right side is the rear, and up and down are the same, with the front side of the page in FIG. 1 being the right and the back side being the left. The sheet S in this specification refers to a medium on which the image forming apparatus 1 can form an image, and includes plain paper, envelopes, postcards, thin paper, cardboard, glossy paper, plastic sheets, stickers, etc.

[0034] In the sheet supply unit 20, the sheets S in the sheet tray 21 are fed by a paper feed roller 23, and then the sheets S are separated one by one between a separation roller 24 and a separation pad 25. Thereafter, the leading edge position of the sheet S is regulated by the registration rollers 27, which are stopped from rotating, and then the registration rollers 27 rotate to supply the sheet S to the image forming unit 30. A paper feed sensor 28A that detects the passage of the sheet S is provided downstream of the separation roller 24 in the conveyance direction of the sheet S. A pre-registration sensor 28B that comes into contact with the sheet S and detects the passage of the sheet S is arranged upstream of the registration rollers 27 in the conveyance direction of the sheet S. A post-registration sensor 28C is arranged downstream of the registration rollers 27 in the conveyance direction of the sheet S.

[0035] The image forming section 30 includes an exposure device 40, a drum unit 500, a plurality of developing cartridges 60, a conveying device 70, and a fixing device 80.

[0036] The exposure device 40 includes a laser diode, a deflector, a lens, and a mirror (not shown). The exposure device 40 is configured to emit a plurality of laser beams that expose the plurality of photosensitive drums 50 and scan the surfaces of the photosensitive drums 50.

[0037] The drum unit 500 mainly includes a plurality of (four in this embodiment) photosensitive drums 50, a plurality of chargers 52 provided corresponding to each photosensitive drum 50, and a support member 90 (see FIG. 4). The drum unit 500 is attached to the housing 10 so as to be removable from an opening formed by opening the front cover 11 of the housing 10. Each photosensitive drum 50 is supported so as to be rotatable about an axis 50X perpendicular to the direction in which the drum unit 500 is removed.

[0038] The photosensitive drum 50 includes a first photosensitive drum 50Y corresponding to yellow, which is an example of a first color; a second photosensitive drum 50M corresponding to magenta, which is an example of a second color; a third photosensitive drum 50C corresponding to cyan, which is an example of a third color; and a fourth photosensitive drum 50K corresponding to black, which is an example of a fourth color. In this specification and drawings, components corresponding to yellow, magenta, cyan, and black are designated by Y, M, C, and K, respectively, when distinguishing between colors. On the other hand, when describing components without distinguishing between colors, the Y, M, C, and K symbols are not used, and the names "first," "second," etc. are omitted. In this embodiment, the first photosensitive drum 50Y is an example of a "first photosensitive drum," and the second photosensitive drum 50M, the third photosensitive drum 50C, and the fourth photosensitive drum 50K correspond to "second photosensitive drums" that are photosensitive drums provided separately from the "first photosensitive drum."

[0039] The developer cartridges 60 are supported by the drum unit 500 (specifically, a support member 90, which will be described later with reference to FIG. 4) at positions corresponding to the respective photosensitive drums 50. Specifically, the developer cartridges 60 include a first developer cartridge 60Y having a first developer roller 61Y that can come into contact with the first photosensitive drum 50Y, a second developer cartridge 60M having a second developer roller 61M that can come into contact with the second photosensitive drum 50M, a third developer cartridge 60C having a third developer roller 61C that can come into contact with the third photosensitive drum 50C, and a fourth developer cartridge 60K having a fourth developer roller 61K that can come into contact with the fourth photosensitive drum 50K.

[0040] In this embodiment, the first developing cartridge 60Y, the second developing cartridge 60M, the third developing cartridge 60C, and the fourth developing cartridge 60K are examples of the "first developing cartridge" and the "second developing cartridge" corresponding to the "first photosensitive drum" and the "second photosensitive drum," respectively. Also, the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C, and the fourth developing roller 61K are examples of the "first developing roller" and the "second developing roller" corresponding to the "first developing cartridge" and the "second developing cartridge," respectively.

[0041] The first developing roller 61Y, the second developing roller 61M, the third developing roller 61C, and the fourth developing roller 61K are arranged in this order from the upstream side to the downstream side in the moving direction of the sheet S.

[0042] 1, where the developing roller 61 is in contact with the corresponding photosensitive drum 50, and a position shown by an imaginary line in Fig. 1, where the developing roller 61 is in a separated position where the developing roller 61 is separated from the corresponding photosensitive drum 50. When the corresponding developing rollers 61M, 61C, 61K of the second developing cartridge 60M, the third developing cartridge 60C, and the fourth developing cartridge 60K are in the separated position, the second developing cartridge 60M, the third developing cartridge 60C, and the fourth developing cartridge 60K are positioned at positions shifted in a direction perpendicular to the rotation axis 61X of the developing roller 61, which is parallel to the rotation axis 50X of the photosensitive drum 50, compared to when they are in the contact position, and therefore overlap with the optical path of the laser light that exposes the adjacent photosensitive drum 50 on the upstream side in the movement direction of the sheet S. Specifically, when the second developing roller 61M is in the separated position, the second developing cartridge 60M overlaps with the optical path of the laser light that exposes the first photosensitive drum 50Y, when the third developing roller 61C is in the separated position, the third developing cartridge 60C overlaps with the optical path of the laser light that exposes the second photosensitive drum 50M, and when the fourth developing roller 61K is in the separated position, the fourth developing cartridge 60K overlaps with the optical path of the laser light that exposes the third photosensitive drum 50C.

[0043] 2, housing 10 has a first side frame 410 on the left side, a second side frame 420 on the right side, a connecting plate 430, a connecting pipe 440 as an example of a connecting member, and first and second restricting portions 411 and 412 as examples of restricting portions. If the direction in which drum unit 500 is pulled out (i.e., the direction from rear to front in FIG. 1) is defined as a first direction, second side frame 420 is disposed at a distance from first side frame 410 in a second direction (i.e., the direction from left to right in FIG. 2) that is perpendicular to the first direction. First restricting portion 411 and second restricting portion 412 are provided in first side frame 410 at positions spaced apart from each other in the first direction.

[0044] The connecting plate 430 is a member made of sheet metal that connects the upper parts of the first side frame 410 and the second side frame 420 , and the exposure device 40 is fixed to the upper surface of the connecting plate 430 .

[0045] The connecting pipe 440 connects the first side frame 410 and the second side frame 420 at a position corresponding to the engaging recess 930 on the rear side in the drawing direction of the drum unit 500 (see also FIGS. 3 and 18).

[0046] As shown in FIG. 4, the support member 90 of the drum unit 500 includes a first side wall 910 on the left side, a second side wall 920 on the right side, a connecting frame 92 connecting the front portions of the first side wall 910 and the second side wall 920, and a connecting frame 93 connecting the rear portions of the first side wall 910 and the second side wall 920.

[0047] The first side wall 910 and the second side wall 920 are spaced apart in a direction perpendicular to the drawing direction (first direction). In other words, the second side wall 920 is spaced apart from the first side wall 910 in the right direction (the second direction shown in FIG. 2). The engagement recesses 930 are provided at the rear ends of the first side wall 910 and the second side wall 920 in the drawing direction. The first side wall 910 has a first engagement portion 911 located above the engagement recess 930 and a second engagement portion 912 located away from the first engagement portion 911 in the first direction.

[0048] 2, when the drum unit 500 is attached to the housing 10, the first side frame 410 is disposed so as to cover the outside of the first side wall 910, i.e., the side surface opposite the second side wall 920, and the second side frame 420 is disposed so as to cover the outside of the second side wall 920, i.e., the side surface opposite the first side wall 910. When the drum unit 500 is attached, the first engagement portion 911 and the second engagement portion 912 engage with the first restriction portion 411 and the second restriction portion 412 provided on the first side frame 410 of the housing 10, respectively.

[0049] The support member 90 is provided with chargers 52 (see FIG. 1) that are arranged opposite each photosensitive drum 50 and charge the photosensitive drum 50. As shown in FIG. 4, the photosensitive drums 50 are arranged between a first side wall 910 and a second side wall 920 at intervals along the first direction and are supported by the first side wall 910 and the second side wall 920 so as to be rotatable about rotation axes 50X (see FIG. 1) that are parallel to the second direction. The support member 90 also detachably supports the first developer cartridge 60Y, the second developer cartridge 60M, the third developer cartridge 60C, and the fourth developer cartridge 60K. A handle 97 is provided on the front connecting frame 93 shown in FIG. 4. A user can grasp the handle 97, which is exposed through an opening formed by opening the front cover 11 (see FIG. 1) of the housing 10, to pull out and install the drum unit 500 relative to the housing 10.

[0050] The image forming device 1 has a separation mechanism 5 that moves the first developing cartridge 60Y, the second developing cartridge 60M, the third developing cartridge 60C and the fourth developing cartridge 60K to a contact position where each developing roller 61 contacts a corresponding photosensitive drum 50 among multiple photosensitive drums 50, and to a separation position where each developing roller 61 is separated from the corresponding photosensitive drum 50. The spacing mechanisms 5 are provided corresponding to the first color, the second color, the third color, and the fourth color, respectively.

[0051] Specifically, each spacing mechanism 5 includes a cam 150 (150Y, 150M, 150C, 150K) that rotates around an axis parallel to the rotation axis 61X (see FIG. 1) of the developing roller 61, and a cam follower 170 that presses against the developing cartridge 60 (60Y, 60M, 60C, 60K) to move the developing roller 61 (61Y, 61M, 61C, 61K) from the contact position to the spacing position. The spacing mechanism 5 is housed in an inner cover 460 of the first side frame 410 shown in FIG. 3, and the cam followers 170 are disposed at positions corresponding to the respective developing cartridges 60. The tips of the cam followers 170 protrude from holes 470 provided in the inner cover 460 and can enter the inside of the support member 90 through openings 914 in the first side wall 910 shown in FIG. 4. Here, the cam follower 170 exemplifies a "first acting member" and a "second acting member" corresponding to the "first developing cartridge" and the "second developing cartridge," respectively. The four cams 150 exemplify a "first cam" and a "second cam" corresponding to the "first acting member" and the "second acting member," respectively. The four openings 914 provided in the first side wall 910 exemplify a "first opening" and a "second opening" corresponding to the "first acting member" and the "second acting member," respectively.

[0052] The cam 150 is rotatable in the direction of the rotation axis of the developing roller 61 (hereinafter simply referred to as the "rotation axis direction"). ) has a first cam portion 152A that protrudes. The cam follower 170 is in contact with a cam surface 152F, which is the end face of the first cam portion 152A of the cam 150, and is movable between an operating position shown in FIG. 6(b) where the developing roller 61 is located at the separated position, and a standby position shown in FIG. 6(a) where the developing roller 61 is located at the contact position. The cam follower 170 is in contact with the first cam portion 152A of the cam 150, and slides in the direction of the rotation axis as the cam 150 rotates to be located at the operating position, and presses the developing cartridge 60 from the first side wall 910 side (through the opening 914 of the first side wall 910 shown in FIG. 4 in the second direction). In addition, the cam follower 170 is separated from the developing cartridge 60 at the standby position, and does not press the developing cartridge 60.

[0053] Returning to Figure 4, the cam 150 and the cam follower 170 are provided corresponding to each developing cartridge 60. The cam 150 and the cam follower 170 are disposed on the outer side in the left-right direction of the left first side wall 910. The detailed structures of the cam 150 and the cam follower 170 will be described later.

[0054] The support member 90 has contact portions 94, which come into contact with a slide member 64 (described later), provided on the upper portions of the first side wall 910 and the second side wall 920. The contact portions 94 are, for example, rollers that are rotatable around an axis along a third direction (vertical direction) that is perpendicular to both a first direction in which the photosensitive drums 50 are lined up and a second direction that is parallel to the axial direction of the photosensitive drums 50.

[0055] The support member 90 also includes a pressing member 95 provided in correspondence with each developer cartridge 60. The pressing member 95 is provided for each developer cartridge 60 at both axial ends of the photosensitive drum 50. The pressing member 95 is biased rearward by a spring 95A (see FIGS. 6(a) and 6(b)), and when the developer cartridge 60 is attached to the support member 90, the pressing member 95 presses the protrusion 63D of the developer cartridge 60 to bring the developing roller 61 into pressure contact with the corresponding photosensitive drum 50.

[0056] As shown in FIGS. 5(a) and 5(b), the developing cartridge 60 (60Y, 60M, 60C, 60K) includes a case 63 for accommodating toner, a slide member 64, and a coupling 65.

[0057] The case 63 has, on one side thereof, a first protruding portion 63A and a second protruding portion 63B as protruding portions that protrude in the direction of the rotation axis. The first protrusion 63A is disposed coaxially with the rotational axis 61X of the developing roller 61, and protrudes in the direction of the rotational axis. The second protrusion 63B is disposed at a predetermined distance from the first protrusion 63A. In this embodiment, the second protrusion 63B is disposed above the first protrusion 63A. The first protruding portion 63A and the second protruding portion 63B are both rollers that can rotate around an axis that is parallel to the direction of the rotation axis. Although not shown, the case 63 also has a first protrusion 63A and a second protrusion 63B on the other side surface at positions symmetrical to those on the one side surface.

[0058] Furthermore, the case 63 has a protrusion 63D on the upper part of the front surface that is pressed by the pressing member 95. The protrusions 63D are provided on both ends of the case 63 in the direction of the rotation axis.

[0059] The coupling 65 is engaged with a coupling shaft 119 (described later) and receives a rotational driving force from the coupling shaft 119.

[0060] The slide member 64 is a member that is slidable in the direction of the rotation axis relative to the case 63. The slide member 64 is pressed by the cam follower 170, thereby being slidable in the direction of the rotation axis.

[0061] 6(a) and 6(b), the slide member 64 includes a shaft 181, a first contact member 182, and a second contact member 183. The first contact member 182 is fixed to one end of the shaft 181, and the second contact member 183 is fixed to the other end of the shaft 181.

[0062] The shaft 181 is disposed through a hole formed in the case 63 and extending in the direction of the rotation axis, and is supported by the case 63 so as to be slidable.

[0063] The first contact member 182 has a pressing surface 182A which is an end surface in the direction of the rotation axis, and an inclined surface 182B which is inclined with respect to the direction of the rotation axis. The pressing surface 182A is a surface that is pressed by the cam follower 170. When the slide member 64 is pressed in the rotation axis direction by the cam follower 170, the inclined surface 182B comes into contact with the contact portion 94 of the support member 90, urging the developer cartridges 60 (60Y, 60M, 60C, 60K) in a direction parallel to the moving direction of the sheet S, thereby moving the developer cartridges 60 (see FIG. 6(b)). The inclined surface 182B is a surface facing diagonally rearward to the right, and is inclined so that the surface position shifts forward, that is, in the direction from the photosensitive drum 50 toward the corresponding developing roller 61, as it moves from its left end toward the right end connected to the shaft 181.

[0064] The second contact member 183 has an inclined surface 183B that is inclined similarly to the inclined surface 182B of the first contact member 182. When the slide member 64 is pressed in the rotation axis direction by the cam follower 170, the inclined surface 183B also comes into contact with the contacted portion 94 of the support member 90, and urges the developer cartridges 60 (60Y, 60M, 60C, 60K) in a direction parallel to the movement direction of the sheet S, thereby moving the developer cartridges 60 (see FIG. 6(b)).

[0065] A spring 184 that biases the slide member 64 toward one side in the rotation axis direction, in this case, toward the left, is disposed between the first abutment member 182 and the case 63. The spring 184 is a compression coil spring, and is disposed outside the shaft 181 so that the shaft 181 passes through the coil.

[0066] 7, the support member 90 has a first support surface 96A and a second support surface 96B on the inner surface of one side wall (first side wall 910). The first support surface 96A and the second support surface 96B support the first protrusion 63A and the second protrusion 63B from below, respectively, when the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C, and the fourth developing roller 61K move from the contact position to the separated position. The first support surface 96A and the second support surface 96B extend in the movement direction of the sheet S. The first support surface 96A is disposed so as to support the first protrusion 63A. The first support surface 96A serves both to guide the developing roller 61 when the developing cartridge 60 is attached to the support member 90 and to position the developing roller 61 in the up-down direction. The second support surface 96B is disposed above the first support surface 96A so as to support the second protrusion 63B. Although not shown, the support member 90 also has a first support surface 96A and a second support surface 96B on the inner surface of the other side wall (second side wall 920) that are symmetrical to the first side wall 910.

[0067] When the developing roller 61 is located at a contact position where it contacts the photosensitive drum 50, the first protrusion 63A is located toward the rear of the first support surface 96A, as in the first developing cartridge 60Y, the second developing cartridge 60M, and the third developing cartridge 60C in Fig. 7. On the other hand, when the developing roller 61 is located at a separated position where it is separated from the photosensitive drum 50, the first protrusion 63A is located toward the front of the first support surface 96A, as in the fourth developing cartridge 60K in Fig. 7. In this way, when the separation mechanism 5 moves the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C and the fourth developing roller 61K from the contact position to the separation position, the separation mechanism 5 moves the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C and the fourth developing roller 61K from the downstream side to the upstream side in the movement direction of the sheet S.

[0068] 13(a) and (b), the cam 150 has a disk portion 151, a gear portion 150G, an end face cam 152, and a clutch control cam 153. The cam 150 is a member that moves the corresponding developing roller 61 between a contact position and a separated position by rotating.

[0069] The disk portion 151 has a substantially disk shape and is rotatably supported by a support plate 102 (see FIG. 10). The gear portion 150G is formed on the outer periphery of the disk portion 151. The end surface cam 152 has a first cam portion 152A that is a portion that protrudes from the disk portion 151 and that constitutes the separating mechanism 5 for the developing roller 61. The end surface cam 152 has a cam surface 152F on its end surface in the rotational axis direction. The cam surface 152F has a first holding surface F1, a second holding surface F2, a first guide surface F3, and a second guide surface F4. The first holding surface F1 holds the cam follower 170 in the standby position. The second retaining surface F2 retains the cam follower 170 in the actuated position. The first guide surface F3 is a surface that connects the first holding surface F1 and the second holding surface F2 and is inclined relative to the first holding surface F1. The first guide surface F3 guides the cam follower 170 from the first holding surface F1 to the second holding surface F2 as the cam 150 rotates. The second guide surface F4 is a surface that connects the second holding surface F2 and the first holding surface F1 and is inclined with respect to the first holding surface F1. The second guide surface F4 guides the cam follower 170 from the second holding surface F2 to the first holding surface F1 as the cam 150 rotates.

[0070] The clutch control cam 153 cooperates with the lever 160 to switch between transmission and disconnection of the clutch 120. The clutch control cam 153 has a cylindrical base circular portion 153A and a second cam portion 153B that protrudes from the base circular portion 153A in the radial direction of the cam 150. The clutch control cam 153 is formed integrally with the disk portion 151. Therefore, the second cam portion 153B rotates together with the cam 150.

[0071] The cam follower 170 has a slide shaft portion 171 and a contact portion 172 . The slide shaft portion 171 is slidably supported on a shaft portion (not shown) fixed to the housing 10, and is slidable in the direction of the rotation axis. The slide shaft portion 171 is biased by a spring 173, which is a biasing member, in a direction in which the contact portion 172 contacts the cam surface 152F of the cam 150. As a result, the cam follower 170 is biased toward the standby position. The spring 173 is a tension coil spring, one end of which is hooked to the slide shaft portion 171 and the other end of which is hooked to a spring attachment portion (not shown) provided inside the housing 10 . The contact portion 172 is provided so as to extend from the slide shaft portion 171. An end face of the contact portion 172 in the rotation axis direction faces the cam surface 152F and is capable of coming into contact with the cam surface 152F.

[0072] As shown in FIG. 10, the cams 150Y, 150M, 150C, and 150K are all substantially the same in configuration except that the length of the first cam portion 152A of the cam 150 in the rotation direction of the cam 150 is longer than the others. Each of the cams 150C and 150K has a detection target portion 154 that protrudes in the axial direction from the disk portion 151 at a position closer to the center of rotation than the first cam portion 152A. The housing 10 is provided with separation sensors 4K and 4C corresponding to black and cyan. The separation sensors 4K, 4C are phase sensors that detect the phase of the cams 150C, 150K. The separation sensors 4K, 4C output a separation signal when the cams 150C, 150K are located within a predetermined phase range in which the third developing roller 61C and the fourth developing roller 61K are in the separated position, and do not output a separation signal when the cams 150C, 150K are not located within the predetermined phase range. In this embodiment, for convenience, the case where a separation signal is output is referred to as ON, and the case where a separation signal is not output is referred to as OFF. It does not matter which voltage is higher when a separation signal is output or not output.

[0073] The separation sensors 4K, 4C have a light-emitting element 4P that emits detection light and a light-receiving element 4R that can receive the detection light from the light-emitting element 4P. When the detection target 154 comes between the light-emitting element 4P and the light-receiving element 4R and blocks the detection light from the light-emitting element 4P, the separation sensors 4K, 4C output an ON signal to the control unit 2, and when the detection target 154 comes out of between the light-emitting element 4P and the light-receiving element 4R and the light-receiving element 4R receives the detection light from the light-emitting element 4P, the separation sensors 4K, 4C output an OFF signal to the control unit 2. Note that the cams 150Y, 150M are also provided with a shape similar to the detection target 154, but since no separation sensors are provided corresponding to the cams 150Y, 150M, these do not function as detection targets.

[0074] Returning to FIG. 1 , the conveying device 70 is provided between the sheet tray 21 and the photosensitive drums 50. The conveying device 70 includes a drive roller 71, a driven roller 72, a conveying belt 73 formed of an endless belt, and four transfer rollers 74. The conveying belt 73 is stretched between the drive roller 71 and the driven roller 72, and its outer surface is disposed facing each of the photosensitive drums 50. Each transfer roller 74 is disposed inside the conveying belt 73 so as to sandwich the conveying belt 73 between itself and each of the photosensitive drums 50. The conveying device 70 conveys the sheet S by moving the conveying belt 73 with the sheet S placed on the outer peripheral surface of the upper side, and at this time, transfers the toner images on the multiple photosensitive drums 50 onto the sheet S.

[0075] The fixing device 80 is provided behind the photosensitive drum 50 and the conveying device 70. The fixing device 80 includes a heating roller 81 and a pressure roller 82 disposed opposite the heating roller 81. A paper discharge sensor 28D that detects the passage of the sheet S is provided downstream of the fixing device 80 in the conveying direction of the sheet S. A conveying roller 15 is provided above the fixing device 80, and a discharge roller 16 is provided above the conveying roller 15.

[0076] In the image forming unit 30 configured as above, first, the surface of each photosensitive drum 50 is uniformly charged by the charger 52, and then exposed to light emitted from each exposure device 40. As a result, an electrostatic latent image based on image data is formed on each photosensitive drum 50.

[0077] The toner in the case 63 is carried on the surface of the developing roller 61, and when the developing roller 61 faces and contacts the photosensitive drum 50, the toner is supplied to the electrostatic latent image formed on the photosensitive drum 50. As a result, a toner image is formed on the photosensitive drum 50.

[0078] Next, the sheet S supplied onto the conveyor belt 73 passes between each photosensitive drum 50 and each transfer roller 74, whereby the toner images formed on each photosensitive drum 50 are transferred onto the sheet S. Then, the sheet S passes between the heating roller 81 and the pressure roller 82, whereby the toner images transferred onto the sheet S are thermally fixed to the sheet S.

[0079] The sheet S discharged from the fixing unit 80 is accumulated on a paper discharge tray 13 on the top surface of the housing 10 by a conveying roller 15 and a discharge roller 16.

[0080] Next, a configuration for driving and stopping the developing roller 61 and a configuration for moving the developing roller 61 so as to contact and separate from the photosensitive drum 50 will be described in detail. 8 and 9, the image forming apparatus 1 includes a motor 3 and a drive transmission mechanism 100 that transmits a drive force from the motor 3 to the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C, and the fourth developing roller 61K. The cam 150, which is part of the spacing mechanism 5, is mechanically connected to the drive transmission mechanism 100. The drive transmission mechanism 100 is configured not to transmit a drive force to the developing rollers 61 when the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C, and the fourth developing roller 61K are in the spacing position.

[0081] 9, the drive transmission mechanism 100 includes a drive transmission gear train 100D for transmitting the drive force of the motor 3 to the developing roller 61, and is mechanically connected to a drive control gear train 100C for controlling the transmission of the drive force of the drive transmission gear train 100D. In Figures 9 and 11, the meshing of the gears in the drive transmission gear train 100D is indicated by thick solid lines, and the meshing of the gears in the drive control gear train 100C is indicated by thick dashed lines.

[0082] The drive transmission gear train 100D includes two first idle gears 110 (110A, 110B), three second idle gears 113A, 113B, 113C, a third idle gear 115 (115Y, 115M, 115C, 115K), four clutches 120, and four coupling gears 117 (117Y, 117M, 117C, 117K). Each gear constituting the drive transmission gear train 100D is supported by a support plate 102 or a frame (not shown), and is rotatable around a rotation axis parallel to the axial direction of the photosensitive drum 50.

[0083] The motor 3 has an output shaft 3A that rotates and drives the motor 3. The output shaft 3A is provided with a gear (not shown).

[0084] As shown in FIG. 8, the first idle gear 110 is a two-stage gear including a large-diameter gear 110L and a small-diameter gear 110S having fewer teeth than the large-diameter gear 110L. The large-diameter gear 110L and the small-diameter gear 110S rotate integrally. The two first idle gears 110 include a first idle gear 110A disposed on the front side of the output shaft 3A and a first idle gear 110B disposed on the rear side of the output shaft 3A. The small-diameter gear 110S of each first idle gear 110 meshes with a gear on the output shaft 3A.

[0085] As shown in FIG. 9, the second idle gear 113A is in mesh with the small diameter gear 110S of one of the first idle gears 110 arranged on the front side. The second idle gear 113B is in mesh with the small diameter gear 110S of the other first idle gear 110 arranged on the rear side.

[0086] The third idle gears 115Y, 115M, 115C, and 115K are provided corresponding to the respective colors and are arranged in this order from front to rear. The third idle gears 115Y and 115M are each in mesh with the second idle gear 113A. The third idle gear 115C is in mesh with the second idle gear 113B. The third idle gear 115C and the third idle gear 115K are each meshed with the second idle gear 113C, so that the third idle gear 115K receives a driving force from the third idle gear 115C via the second idle gear 113C.

[0087] The four clutches 120 each have the same configuration. Each clutch 120 meshes with one of the third idle gears 115Y, 115M, 115C, and 115K to receive driving force from the third idle gear 115. The configuration of the clutches 120 will be described later.

[0088] Each coupling gear 117 is engaged with one of the clutches 120. Each coupling gear 117 has a coupling shaft 119 that is coaxial and rotates integrally with the coupling gears 117 (see FIG. 8). The coupling shaft 119 is configured to be movable axially in conjunction with the opening and closing of the front cover 11, and engages with the coupling 65 of the developing cartridge 60 (see FIG. 5(a)) when the front cover 11 is closed.

[0089] By means of this drive transmission gear train 100D, the driving force is transmitted from the motor 3 to the yellow coupling gear 117Y via the first idle gear 110A, the second idle gear 113A, the third idle gear 115Y and the clutch 120. Further, the driving force is transmitted from the motor 3 to the magenta coupling gear 117M via the first idle gear 110A, the second idle gear 113A, the third idle gear 115M and the clutch 120. Further, the driving force is transmitted from the motor 3 to the cyan coupling gear 117C via the first idle gear 110B, the second idle gear 113B, the third idle gear 115C and the clutch 120. Further, driving force is transmitted from the motor 3 to the black coupling gear 117K via the first idle gear 110B, the second idle gear 113B, the third idle gear 115C, the second idle gear 113C, the third idle gear 115K and the clutch 120.

[0090] 10 and 11, the drive control gear train 100C includes two fourth idle gears 131 (131A, 131B), two fifth idle gears 132 (132A, 132B), a YMC clutch 140A and a K clutch 140K which are examples of a switching mechanism, two sixth idle gears 133 (133A, 133B), a seventh idle gear 134, an eighth idle gear 135, a ninth idle gear 136, a tenth idle gear 137, and a cam 150 (150Y, 150M, 150C, 150K). Each gear constituting the drive control gear train 100C is supported by a support plate 102 or a frame (not shown) and is rotatable around a rotation axis parallel to the axial direction of the photosensitive drum 50.

[0091] The fourth idle gear 131 is a two-stage gear including a large diameter gear 131L and a small diameter gear 131S having fewer teeth than the large diameter gear 131L (see FIG. 10). The large diameter gear 131L and the small diameter gear 131S rotate integrally. The two fourth idle gears 131 include a fourth idle gear 131A disposed in front of the first idle gear 110A and a fourth idle gear 131B disposed behind the first idle gear 110B. The large diameter gear 131L of each fourth idle gear 131 meshes with the small diameter gear 110S of the first idle gear 110.

[0092] The two fifth idle gears 132 include a fifth idle gear 132A disposed in front of the fourth idle gear 131A and a fifth idle gear 132B disposed behind the fourth idle gear 131B. Each of the fifth idle gears 132A, 132B meshes with a small diameter gear 131S of the fourth idle gears 131A, 131B.

[0093] The YMC clutch 140A switches between transmitting and disconnecting the driving force of the drive control gear train 100C, which is a series that transmits driving force to the yellow, magenta, and cyan cams 150. In other words, the YMC clutch 140A can switch between rotating and stopping the cams 150Y, 150M, and 150C. The YMC clutch 140A includes a large-diameter gear 140L and a small-diameter gear 140S that has fewer teeth than the large-diameter gear 140L. The YMC clutch 140A is disposed in front of the fifth idle gear 132A, and the large-diameter gear 140L meshes with the fifth idle gear 132A. The YMC clutch 140A is, for example, an electromagnetic clutch, and when electricity is applied (ON), the large diameter gear 140L and the small diameter gear 140S rotate together, and when electricity is stopped (OFF), the large diameter gear 140L rotates freely and the small diameter gear 140S does not rotate.

[0094] The K-clutch 140K has the same configuration as the YMC clutch 140A. The K-clutch 140K switches between transmitting and disconnecting the driving force of the drive control gear train 100C that transmits driving force to the black cam 150. The K-clutch 140K includes a large-diameter gear 140L and a small-diameter gear 140S that has fewer teeth than the large-diameter gear 140L. The K-clutch 140K is disposed behind the fifth idle gear 132B, and the large-diameter gear 140L meshes with the fifth idle gear 132B.

[0095] The sixth idle gear 133 is a two-stage gear including a large-diameter gear 133L and a small-diameter gear 133S having fewer teeth than the large-diameter gear 133L (see FIG. 8). The large-diameter gear 133L and the small-diameter gear 133S rotate integrally. The two sixth idle gears 133 include a sixth idle gear 133A disposed in front of the YMC clutch 140A and a sixth idle gear 133B disposed in rear of the K clutch 140K. The large-diameter gear 133L of each sixth idle gear 133 is in mesh with the small-diameter gear 140S of the YMC clutch 140A or the K clutch 140K.

[0096] The seventh idle gear 134 is disposed between the sixth idle gear 133A and the cam 150Y. The seventh idle gear 134 meshes with a small diameter gear 133S (see FIG. 8) of the sixth idle gear 133A and a gear portion 150G of the cam 150Y.

[0097] The eighth idle gear 135 is disposed between the cam 150Y and the cam 150M. The eighth idle gear 135 is in mesh with a gear portion 150G of the cam 150Y and a gear portion 150G of the cam 150M.

[0098] The ninth idle gear 136 is disposed between the cam 150M and the cam 150C. The ninth idle gear 136 is in mesh with a gear portion 150G of the cam 150M and a gear portion 150G of the cam 150C.

[0099] The tenth idle gear 137 is disposed between the sixth idle gear 133B and the cam 150K. The tenth idle gear 137 meshes with the small diameter gear 133S (see FIG. 8) of the sixth idle gear 133B and the gear portion 150G of the cam 150Y.

[0100] With this drive control gear train 100C, the driving force is transmitted from the motor 3 to the yellow cam 150Y via the first idle gear 110A, the fourth idle gear 131A, the fifth idle gear 132A, the YMC clutch 140A, the sixth idle gear 133A and the seventh idle gear 134. Further, the driving force is transmitted to the magenta cam 150M from the yellow cam 150Y via the eighth idle gear 135. Further, the driving force is transmitted to the cyan cam 150C from the magenta cam 150M via the ninth idle gear 136. When the YMC clutch 140A is energized, the cams 150Y, 150M, and 150C rotate simultaneously, and when the YMC clutch 140A is de-energized, the cams 150Y, 150M, and 150C all stop.

[0101] On the other hand, the driving force is transmitted from the motor 3 to the black cam 150K via the first idle gear 110B, the fourth idle gear 131B, the fifth idle gear 132B, the K clutch 140K, the sixth idle gear 133B and the tenth idle gear 137. When the K-clutch 140K is energized, the cam 150K rotates, and when the K-clutch 140K is de-energized, the cam 150K stops.

[0102] Here, the configuration and function of the clutch 120 will be described. As shown in FIGS. 12(a) and 12(b), the clutch 120 includes a planetary gear mechanism. The clutch 120 is configured to be switchable between a transmission state in which the driving force from the motor 3 is transmitted to the developing roller 61 and a disconnection state in which the driving force from the motor 3 is not transmitted to the developing roller 61. Specifically, the clutch 120 is configured to include a sun gear 121, a ring gear 122, and a carrier 123, which are elements that can rotate around one axis, and a planetary gear 124 supported by the carrier 123.

[0103] Sun gear 121 has a disk portion 121B that rotates integrally with gear portion 121A, and a plurality of claw portions 121C provided on the outer periphery of disk portion 121B. Claw portions 121C have sharp tips that are inclined circumferentially toward one rotational direction. The ring gear 122 has an inner gear 122A provided on the inner circumferential surface and an input gear 122B provided on the outer circumferential surface.

[0104] The carrier 123 has four shaft portions 123A that rotatably support the planetary gear 124. The carrier 123 also has an output gear 123B provided on its outer circumferential surface.

[0105] There are four planetary gears 124, each rotatably supported on a shaft portion 123A of the carrier 123. The planetary gears 124 mesh with the gear portion 121A of the sun gear 121 and also mesh with the inner gear 122A of the ring gear 122.

[0106] The clutch 120 has an input gear 122B meshed with the third idle gear 115, and an output gear 123B meshed with the coupling gear 117 (see FIG. 8). When the sun gear 121 is stopped from rotating, a transmission state is established in which the driving force input to the input gear 122B can be transmitted to the output gear 123B. On the other hand, when the sun gear 121 is in a rotatable state, the driving force input to the input gear 122B cannot be transmitted to the output gear 123B, and the drive force is in a disconnected state. When a driving force is input to the input gear 122B while the clutch 120 is in a disengaged state and a load is applied to the output gear 123B, the output gear 123B does not rotate and the sun gear 121 rotates freely.

[0107] 11, the drive transmission mechanism 100 further includes a lever 160. The lever 160 is supported by a support shaft 102A fixed to the support plate 102 so as to be able to swing. By working in cooperation with the cam 150, the lever 160 engages with the sun gear 121, which is one of the elements of the planetary gear mechanism, the sun gear 121, the ring gear 122, and the carrier 123, to prevent the sun gear 121 from rotating, thereby placing the clutch 120 in a transmission state, and disengaging from the sun gear 121 to place the clutch 120 in a disconnected state.

[0108] Specifically, as shown in FIG. 13(a), lever 160 has a rotation support part 161, a first arm 162 extending from rotation support part 161, and a second arm 163 extending from rotation support part 161 in a direction different from that of first arm 162.

[0109] The rotation support portion 161 has a cylindrical shape, and the support shaft 102A of the support plate 102 is inserted inside the rotation support portion 161 and is supported by the support shaft 102A.

[0110] The tip of second arm 163 extends toward the outer peripheral surface of disc portion 121B of clutch 120. Lever 160 is biased by a torsion spring (not shown) so that the tip faces the outer peripheral surface of sun gear 121 (disc portion 121B). Second arm 163 has hook 163A at its tip. Hook 163A can engage with claw portion 121C on the outer peripheral surface of sun gear 121 to restrict the rotation of sun gear 121.

[0111] The tip end 162A of the first arm 162 of the lever 160 can come into contact with the second cam portion 153B. The lever 160 can move between an engaged position where the tip end 162A of the first arm 162 faces the base circle portion 153A and the hook 163A engages with the claw portion 121C of the clutch 120, and a disengaged position where the tip end 162A of the first arm 162 comes into contact with the second cam portion 153B and is pushed and moved, thereby disengaging the hook 163A from the claw portion 121C of the sun gear 121, which is one element of the planetary gear mechanism. When the lever 160 is located at the engaged position away from the second cam portion 153B, the clutch 120 is in a transmitted state, and when the lever 160 is located at the disengaged position in contact with the second cam portion 153B, the clutch 120 is in a disengaged state.

[0112] This operation will be described with reference to Figures 13 to 17. Note that the components shown in Figures 13 to 17 are components corresponding to yellow, but the basic operation is the same for the other colors, except that the phase of the cam 150 is different.

[0113] As shown in FIGS. 13(a) and 13(b), the tip portion 162A of the first arm 162 moves away from the second cam portion 153B and then faces the base circle portion 153A. Then, the hook 163A of the second arm 163 engages with the claw portion 121C of the sun gear 121 of the clutch 120, and the lever 160 is positioned in the engaged position. Since the rotation of the sun gear 121 is stopped by the lever 160, the clutch 120 enters a transmission state in which the output gear 123B rotates when the input gear 122B is rotated. This allows the driving force from the motor 3 to be transmitted to the developing roller 61, and when the motor 3 rotates, the developing roller 61 rotates via the drive transmission gear train 100D. Furthermore, the end face of the contact portion 172 of the cam follower 170 is positioned on the first holding surface F1 of the cam surface 152F. Therefore, the slide shaft portion 171 is spaced apart from the slide member 64 of the developer cartridge 60 (see FIG. 6(a)). Therefore, the developing roller 61 is located at the contact position.

[0114] 14(a) and (b), when the cam 150 rotates from the state shown in FIGS. 13(a) and (b), the contact portion 172 of the cam follower 170 slides on the first holding surface F1 and approaches the first guide surface F3. When stopping the yellow cam 150Y, among the four cams 150, with the developing roller 61 in the contact position, the cam is stopped at a position where the contact portion 172 comes into contact with the first guide surface F3, as shown in FIGS. 14(a) and (b).

[0115] When the developing roller 61 is separated from the photosensitive drum 50, the cam 150Y further rotates, and the contact portion 172 slides against the first guide surface F3 and is pushed by the first guide surface F3, so that the contact portion 172 comes into contact with the second holding surface F2, as shown in Figures 15(a) and 15(b). At this time, the slide shaft portion 171 pushes the slide member 64 of the developing cartridge 60 in the direction of the rotation axis. Then, the developing cartridge 60 is pushed forward by the reaction force of the support member 90 (see FIG. 6(b)). The developing roller 61 separates from the photosensitive drum 50 when the contact portion 172 is in a position close to the second holding surface F2 of the first guiding surface F3. When the contact portion 172 comes into contact with the second holding surface F2, the developing roller 61 is held in the separated position.

[0116] As shown in FIGS. 16(a) and 16(b), after the developing roller 61 is positioned at the separated position, the cam 150 further rotates, and the tip 162A of the first arm 162 of the lever 160 comes into contact with the second cam portion 153B. The lever 160 swings as the first arm 162 is pushed and moved by the second cam portion 153B, and the hook 163A disengages from the claw portion 121C of the sun gear 121 and is positioned at the disengaged position. Because the rotation of the sun gear 121 of the clutch 120 is no longer stopped by the lever 160, the output gear 123B enters a disconnected state in which it does not transmit driving force when the input gear 122B is rotated. As a result, driving force from the motor 3 cannot be transmitted to the developing roller 61. Even if the motor 3 rotates, the sun gear 121 simply rotates idly, and the developing roller 61 does not rotate.

[0117] When the developing roller 61 is to be positioned and maintained at the separated position, the cam 150 stops at a position where the lever 160 is in the disengaged position as shown in Figures 16(a) and 16(b). Of the four cams 150, when the yellow cam 150Y in particular is to be temporarily stopped with the developing roller 61 in the separated position, it is rotated further from the state shown in Figures 16(a) and 16(b). Then, as shown in Figures 17(a) and 17(b), the contact portion 172 is temporarily stopped at the end of the second holding surface F2 on the second guide surface F4 side (a position immediately before the contact portion 172 contacts the second guide surface F4).

[0118] When the developing roller 61 is moved from the separated position to the contact position, the cam 150 is rotated from the state shown in FIGS. 16(a) and 16(b) or 17(a) and 17(b). The contact portion 172 then slides along the second guide surface F4 and is positioned facing the first holding surface F1 as shown in FIG. 13. The sliding shaft portion 171 is then moved in the direction of the rotation axis by the biasing force of the spring 173 and moves away from the sliding member 64. The sliding member 64 returns to the position shown in FIG. 6(a), and the developing cartridge 60 returns to the position shown by the solid line in FIG. 1. This causes the developing roller 61 to come into contact with the photosensitive drum 50. The developing roller 61 comes into contact with the photosensitive drum 50 when the contact portion 172 passes a position on the second guide surface F4 close to the second holding surface F2 (see FIG. 17(b)).

[0119] As described above, when the lever 160 is positioned at the engagement position where it faces the base circle portion 153A and engages with the sun gear 121, the clutch 120 is put into the transmission state.

[0120] Next, a structure for positioning the drum unit 500 when it is attached to the housing 10 will be described in detail below. In the following description, the position of the drum unit 500 when it is attached to the housing 10 and all the photosensitive drums 50 are positioned in predetermined positions within the housing 10, and image formation processing is possible, as shown in Figure 18, will be referred to as the "storage position." When replacing the developer cartridge 60, for example, the user pulls out the drum unit 500 to the "pulled out position" where the photosensitive drums 50 and developer cartridges 60 are positioned outside the housing 10, and then performs the work.

[0121] 18, when the drum unit 500 is in the storage position, the first engagement portion 911 of the first side wall 910 engages with the first restriction portion 411 of the first side frame 410, and the second engagement portion 912 of the first side wall 910 engages with the second restriction portion 412 of the first side frame 410. When the drum unit 500 is in the pulled-out position, the first engagement portion 911 of the first side wall 910 is disengaged from the first restriction portion 411 of the first side frame 410, and the second engagement portion 912 of the first side wall 910 is disengaged from the second restriction portion 412 of the first side frame 410.

[0122] 3, the first restricting portion 411 is provided on the inside (the side opposite to the side facing the second side frame 420) of an inner cover 450 that constitutes a part of the first side frame 410, and is accessible from the front (the opening side where the front cover 11 of the housing 10 is provided) through an opening at the front end of the inner cover 450. The second restricting portion 412 is provided on the inside (the side opposite to the side facing the second side frame 420) of an inner cover 460 that constitutes a part of the first side frame 410, and is accessible from the front through an opening at the front end of the inner cover 460.

[0123] 18, when image forming apparatus 1 is placed on an installation surface FP such as a floor or a table, and drum unit 500 is attached to housing 10, the distance from installation surface FP to first restriction portion 411 and second restriction portion 412, i.e., height H of first restriction portion 411 and second restriction portion 412, is the same. In addition, the height of cam follower 170 is also the same (height H) as the heights of restriction portions 411, 412. As a result, first restriction portion 411, second restriction portion 412, and four cam followers 170 are on an imaginary plane PL1 that is parallel to installation surface FP.

[0124] As shown in Figure 19(a), the first regulating portion 411 is positioned further back than the second regulating portion 412 in the pull-out direction, and closer to the second side frame 420 than the second regulating portion 412 in the axial direction parallel to the rotation axis 50X of the photosensitive drum 50 (i.e., farther from the first side frame 410 in the second direction than the second regulating portion 412).

[0125] 19(b), the first engagement portion 911 is a protrusion that protrudes rearward and is provided at the rear end of the upper part of the first side wall 910. The first engagement portion 911 has a first abutment surface 211 that is provided at the far end in the drawing direction (first direction) and faces the second side wall 920 in the axial direction. In addition, an inclined surface 311 is provided at the connection portion between the rear end surface of the first engagement portion 911 and the first abutment surface 211.

[0126] 19(c), the second engagement portion 912 is a protruding portion that protrudes rearward and is provided at the front upper portion of the first side wall 910. The second engagement portion 912 has a second abutment surface 212 that is provided at the front end portion in the pulling-out direction (first direction) and faces the second side wall 920 in the axial direction. In addition, an inclined surface 312 is provided at the joint between the rear end surface of the second engagement portion 912 and the second abutment surface 212.

[0127] As shown in FIG. 3, four protrusions 415 as an example of a "positioning portion" are provided on the first side frame 410 of the housing 10 between the first restricting portion 411 and the second restricting portion 412 in the pull-out direction. Each protrusion 415 is formed in a truncated pyramid shape. In this embodiment, one protrusion 415 is disposed below the positions of the four holes 470, that is, at a position corresponding to each cam follower 170 in the pull-out direction. Here, the four protrusions 415 exemplify a "first protrusion" and a "second protrusion" corresponding to a "first acting member" and a "second acting member," respectively.

[0128] 4, four protrusions 915 are provided on the surface of the first side wall 910 of the drum unit 500 opposite to the second side wall 920. Each of the protrusions 915 is formed in a truncated pyramid shape.

[0129] As shown in FIG. 20, when the drum unit 500 is attached to the housing 10, the protrusion 915 is positioned so that its end surface 916 abuts against the end surface of the corresponding protrusion 415 of the first side frame 410.

[0130] Four electrode springs ES are provided on the second side frame 420. The four electrode springs ES are provided at positions symmetrical to the four protrusions 415 with respect to an imaginary plane PL2 perpendicular to the second direction (a direction parallel to the rotation axis 50X of the photosensitive drum 50 of the attached drum unit 500). In other words, the four protrusions 415 of the first side frame 410 are arranged so that the positions at which they abut against the end faces 916 of the four protrusions 915 of the first side wall 910 overlap with the four electrode springs ES when viewed from the second direction. When the drum unit 500 is attached to the housing 10, each electrode spring ES is electrically connected to the corresponding developer cartridge 60 via a terminal portion (not shown) provided on the second side wall 920 of the drum unit 500, and biases the drum unit 500 from the second side frame 420 toward the first side frame 410. The four electrode springs ES are examples of the "first electrode spring" and the "second electrode spring" corresponding to the "first developing cartridge" and the "second developing cartridge."

[0131] With the drum unit 500 attached to the housing 10, the first restricting portion 411 abuts against the first abutment surface 211, the second restricting portion 412 abuts against the second abutment surface 212, and the four protrusions 415 abut against end faces 916 of the four protrusions 915 on the first side wall 910 side (i.e., the side surface opposite to the second side wall 920). Therefore, movement of the drum unit 500 in the second direction (the direction from the first side wall 910 toward the second side wall 920 along the axial direction) is restricted by the restricting portions 411, 412 of the first side frame 410, and movement of the drum unit 500 in the direction opposite to the second direction is restricted by the protrusions 415 of the first side frame 410.

[0132] As shown in FIGS. 3 and 18 , the first side frame 410 is provided with a guide rail 480 that supports the first side wall 910 so that the drum unit 500 can move back and forth in the first direction between the storage position and the pulled-out position. The second side frame 420 is also provided with a similar guide rail 480 that supports the second side wall 920. When the drum unit 500 is pulled out or installed, rollers W provided on the first side wall 910 and the second side wall 920 roll on the guide rails 480 provided on the first side frame 410 and the second side frame 420. In this way, the movement of the drum unit 500 is guided by the guide rail 480. A recess 490 that is recessed downward at a slightly lower position is provided at the rear end of the guide rail 480.

[0133] Next, the process of attaching the drum unit 500 to the housing 10 will be described with reference to FIGS. 18 and 21. As shown in FIG. 21(a), while the drum unit 500 is being pushed from the pulled-out position toward the stored position, the rollers W of the drum unit 500 are supported by the guide rails 480 of the first side frame 410 and the second side frame 420 and move rearward. At this time, the first engagement portion 911 is separated from the first restriction portion 411 and is in a disengaged state, and the second engagement portion 912 is separated from the second restriction portion 412 and is in a disengaged state. In addition, the four protrusions 915 are also separated from the corresponding protrusions 415, and the engagement recesses 930 are also separated from the connecting pipe 440.

[0134] 21(a) toward the storage position, as shown in FIG. 21(b), the first restricting portion 411 comes into contact with the first contact surface 211 of the first engaging portion 911, and the second restricting portion 412 comes into contact with the second contact surface 212 of the second engaging portion 912. More specifically, the inclined surface 311 of the first engaging portion 911 and the inclined surface 312 of the second engaging portion 912 first come into contact with the corresponding first restricting portion 411 and second restricting portion 412, respectively, almost simultaneously. At this point, the roller W reaches the edge of the recess 490, and the first engaging portion 911 of the drum unit 500 engages with the first restricting portion 411, and the second engaging portion 912 engages with the second restricting portion 412. At this time, the first and second restricting portions 411 and 412 are already in contact with the first and second contact surfaces 211 and 212, respectively, and restrict movement of the drum unit 500 in the second direction. However, even in this state, the engaging recess 930 is still not in contact with the connecting pipe 440.

[0135] 21(b), when the drum unit 500 is further pushed toward the storage position, the roller W enters the recess 490, and the drum unit 500, assisted by its own weight in moving toward the storage position, moves diagonally downward and rearward. At this time, the first restricting portion 411 abuts against the first engaging portion 911, the second restricting portion 412 abuts against the second engaging portion 912, and the end face of the protrusion 415 abuts against the end face 916 of the corresponding protrusion 915, thereby determining the position in the left-right direction (the direction parallel to the rotation axis 50X of the photosensitive drum 50). Finally, as shown in FIG. 18, the roller W completely enters the recess 490, thereby determining the position in the up-down direction, and the engaging recess 930 engages (contacts) with the connecting pipe 440, thereby determining the position in the front-rear direction.

[0136] In the image forming apparatus 1 of this embodiment, as described above, the cam follower 170 provided at a position corresponding to the pressing surface 182A of the developing cartridge 60 on the first side frame 410 is configured to pass through the opening 914 in the first side wall 910 and press the corresponding developing cartridge 60 in the second direction (see Figure 18), thereby moving the developing roller 61 from the contact position to the separated position (see Figure 6).

[0137] Specifically, when performing color printing using the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C, and the fourth developing roller 61K, the image forming device 1 moves the first developing roller 61Y, the second developing roller 61M, the third developing roller 61C, and the fourth developing roller 61K to a contact position in accordance with the movement of the sheet S when transferring a toner image to the sheet S, and then moves them to a separated position after development of each photosensitive drum 50 is completed.

[0138] The pressing operation of cam follower 170 will be described below with reference to Figures 22 and 23. In Figures 22 and 23, the outline arrows indicate that pressing force is being generated by cam follower 170.

[0139] Before the sheet S reaches the first photosensitive drum 50Y on the most upstream side, all of the developing rollers 61 are in the separated position. All of the cam followers 170Y, 170M, 170C, and 170K are in the actuated position as shown in FIG. 22(a), and press the first developing cartridge 60Y, the second developing cartridge 60M, the third developing cartridge 60C, and the fourth developing cartridge 60K, respectively.

[0140] When the sheet S approaches the first photosensitive drum 50Y, the cam followers 170Y and 170M are moved to the standby positions as shown in FIG. 22(b) to position the first developing roller 61Y and the second developing roller 61M at the contact positions, but the cam followers 170C and 170K remain at the operating positions. At this time, the cam followers 170C and 170K press the third developing cartridge 60C and the fourth developing cartridge 60K, respectively, but the cam followers 170Y and 170M do not press the first developing cartridge 60Y or the second developing cartridge 60M.

[0141] When the sheet S approaches the second photosensitive drum 50M, the third developing cartridge 60C is moved to the standby position as shown in Figure 22(c) in order to position the third developing roller 61C at the contact position, and only the cam follower 170K remains at the operating position. At this time, the cam follower 170K presses the fourth developing cartridge 60K, and the cam followers 170Y, 170M, and 170C do not press the first developing cartridge 60Y, the second developing cartridge 60M, or the third developing cartridge 60C.

[0142] Then, when the sheet S approaches the third photosensitive drum 50C, the fourth developing cartridge 60K is moved to the standby position as shown in Figure 22(d) in order to position the fourth developing roller 61K at the contact position. Here, all of the cam followers 170Y, 170M, 170C, and 170K are positioned at the standby positions, and none of the first developing cartridge 60Y, second developing cartridge 60M, third developing cartridge 60C, and fourth developing cartridge 60K is pressed.

[0143] Then, when development of the first photosensitive drum 50Y by the first developing roller 61Y is completed, the first developing cartridge 60Y is moved to the separated position by moving the cam follower 170Y to the operating position as shown in Figure 23(a). At this time, the cam follower 170Y presses the first developing cartridge 60Y, and the cam followers 170M, 170C, and 170K do not press the second developing cartridge 60M, the third developing cartridge 60C, or the fourth developing cartridge 60K.

[0144] Then, when development of the second photosensitive drum 50M by the second developing roller 61M is completed, the second developing cartridge 60M is moved to the separated position by moving the cam follower 170M to the operating position as shown in Figure 23(b). At this time, the cam followers 170Y and 170M press against the first developing cartridge 60Y and the second developing cartridge 60M, respectively, while the cam followers 170C and 170K do not press against the third developing cartridge 60C or the fourth developing cartridge 60K.

[0145] Then, when development of the third photosensitive drum 50C by the third developing roller 61C is completed, the third developing cartridge 60C is moved to the separated position by moving the cam follower 170C to the operating position as shown in Figure 23(c). At this time, the cam followers 170Y, 170M, and 170C press against the first developing cartridge 60Y, the second developing cartridge 60M, and the third developing cartridge 60C, respectively, and the cam follower 170K does not press against the fourth developing cartridge 60K.

[0146] Then, when development of the fourth photosensitive drum 50K by the fourth developing roller 61K is completed, the fourth developing cartridge 60K is moved to the separated position by moving the cam follower 170K to the operating position as shown in Figure 23(d). At this time, all of the cam followers 170Y, 170M, 170C, and 170K are pressing against the first developing cartridge 60Y, the second developing cartridge 60M, the third developing cartridge 60C, and the fourth developing cartridge 60K, respectively.

[0147] Similarly, when monochrome printing is performed using only the fourth developing roller 61K, when the sheet S approaches the fourth photosensitive drum 50K from a state in which all the cam followers 170Y, 170M, 170C, and 170K are in the operating position as shown in Fig. 23(d), only the cam follower 170K is positioned in the standby position as shown in Fig. 23(c), thereby moving only the fourth developing roller 61K to the separated position. At this time, the cam followers 170Y, 170M, and 170C press against the first developing cartridge 60Y, the second developing cartridge 60M, and the third developing cartridge 60C, respectively, and the cam follower 170K does not press against the fourth developing cartridge 60K. Then, when development of the fourth photosensitive drum 50K by the fourth developing roller 61K is completed, all cam followers 170Y, 170M, 170C, 170K return to the state shown in Figure 23(d) in which they are pressing against the first developing cartridge 60Y, the second developing cartridge 60M, the third developing cartridge 60C, and the fourth developing cartridge 60K, respectively.

[0148] The effects of the image forming apparatus 1 described above will be described. By providing the housing 10 with restricting portions 411, 412 that restrict movement of the drum unit 500 in the direction from the first side wall side toward the second side wall side (second direction) along the rotation axis 50X of the photosensitive drum 50 while the drum unit 500 is attached to the housing 10, the drum unit 500 can be accurately positioned in the axial direction and fixed so as not to shift after attachment. Therefore, the photosensitive drum 50 can be accurately positioned with respect to the exposure device 40 fixed to the connecting plate 430 of the housing 10, and deviation of the exposure position that affects image quality can be suppressed.

[0149] In particular, even in the case where the cam follower 170 that moves the developing roller 61 from the contact position to the separated position is configured to press the developing cartridge 60 in the second direction, as in the above embodiment, it is possible to suppress deviation in the second direction due to the drum unit 500 on which the developing cartridge 60 is supported being urged in the second direction by the pressing force of the cam follower 170.

[0150] Furthermore, as in the above embodiment, when the image forming apparatus 1 is a color printer in which the drum unit 500 has multiple photosensitive drums 50, as explained with reference to Figures 22 and 23, multiple cam followers 170 lined up in the pull-out direction of the drum unit 500 press the developer cartridge 60 at different times, causing stress to distort or rotate the drum unit 500. However, by configuring the regulating portion to include a first regulating portion 411 and a second regulating portion 412 located at positions spaced apart in the pull-out direction (first direction), distortion and rotation of the drum unit 500 can be suppressed.

[0151] In addition, since the first regulating portion 411 and the second regulating portion 412 are positioned at the same height H as the cam follower 170 that presses the developing cartridge 60, axial misalignment can be suppressed without distorting the drum unit 500.

[0152] When the drum unit 500 is attached to the housing 10, the first regulating portion 411 abuts against the first abutment surface 211 facing the second side wall 920 in the axial direction of the first side wall 910 (first engagement portion 911), the second regulating portion 412 abuts against the second abutment surface 212 facing the second side wall 920 in the axial direction of the first side wall 910 (second engagement portion 912), and the protrusion 415 provided between the first regulating portion 411 and the second regulating portion 412 abuts against the side surface (end surface 916 of the protrusion 915) facing the opposite side of the first side wall 910 from the second side wall 920 in the axial direction, thereby clamping the first side wall 910 from both sides in the axial direction and securely positioning and fixing it.

[0153] With the drum unit 500 attached to the housing 10, the protrusion 415 is provided at a position corresponding to the electrode spring ES that urges the drum unit 500 toward the first side frame 410, so that the urging force of the electrode spring ES can be reliably received by the protrusion 415. Therefore, it is possible to prevent the position of the drum unit 500 from shifting in the direction toward the first side frame 410.

[0154] Since the first regulating portion 411 is positioned further back than the second regulating portion 412 in the pull-out direction and closer to the second side frame 420 than the second regulating portion 412 in the axial direction, the first engagement portion 911 does not interfere with the second regulating portion 412 while the drum unit 500 is guided by the guide rail 480 and pushed from the pull-out position toward the storage position, and the installation operation can be performed smoothly.

[0155] Furthermore, in the final stage of the process of attaching drum unit 500 to housing 10, axial positioning (regulation) is performed by first regulating portion 411, second regulating portion 412 and protrusion 415 prior to positioning in the pull-out direction by engagement between engaging recess 930 of first side wall 910 and second side wall 920 and connecting pipe 440. Therefore, scraping and the like caused by axial misalignment of drum unit 500 relative to housing 10 can be suppressed when engaging recess 930 with the connecting pipe and after engagement.

[0156] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be practiced by appropriately modifying them.

[0157] In the above embodiment, the cam follower 170 that can move between an operating position and a standby position by the rotation of the rotating cam 150 is exemplified as the first and second acting members, but the acting members may also be, for example, cam followers that can move between an operating position and a standby position by a linearly acting cam, or may have a structure in which the developing cartridge is pressed by a linearly acting motor such as a solenoid, or may consist of a cam that directly presses the developing cartridge.

[0158] In the above embodiment, the housing 10 has two restricting portions (first restricting portion 411 and second restricting portion 412) and a positioning portion (plurality of protrusions 415) provided between the first restricting portion 411 and the second restricting portion 412, but the number of restricting portions may be one, or may be three or more. In addition, the number and arrangement of the protrusions are not limited to the exemplified embodiment.

[0159] Furthermore, the position of the restricting portion on the housing is not limited to the position exemplified in the above embodiment. The restricting portion does not have to be located on the first side frame 410, but can also be located on the inside of the second side frame 420. In an embodiment in which two or more restricting portions are located, the height of each restricting portion does not have to be the same as the cam follower, and they may be positioned offset up or down. As long as the arrangement does not interfere with the installation of the drum unit 500, the first restricting portion on the rear side does not have to be located more inward (closer to the side frame on the opposite side) than the second restricting portion on the front side. By arranging the regulating portion in an appropriate position adjacent to the housed drum unit 500 inside the housing 10, it is possible to accurately position the drum unit 500 in the second direction and prevent misalignment during and after installation, as in the above embodiment. Also, depending on the arrangement of the regulating portion, the positioning portion may not be necessary.

[0160] For example, in the above embodiment, an image forming device 1 that prints color images using four colors of toner is exemplified, but it may also be a device that prints color images using three or five colors of toner, or a device that prints monochrome images.

[0161] The image forming apparatus may also be a multifunction machine or a copier. [Explanation of symbols]

[0162] 1. Image forming device 10. Cabinet 40 Exposure equipment 500 drum unit 50 Photosensitive drum 50X rotation axis 60 Developer cartridge 61 Developing roller 170 Cam follower 410 First side frame 411 First Regulatory Department 412 Second Regulatory Department 415 Protrusion 420 Second side frame 430 connecting plate 440 Connecting Pipe 480 guide rail 910 First side wall 911 First engagement part 912 Second engagement portion 914 Aperture 920 Second side wall ES electrode spring

Claims

1. The housing and a support member that is movable in a front-rear direction relative to the housing between a storage position located inside the housing and a drawn-out position drawn forward from the storage position; a first cartridge detachably supported by the support member, the first cartridge having a first developing roller rotatable about a rotation axis parallel to a left-right direction intersecting the front-rear direction and the direction of gravity while supported by the support member; Equipped with The housing includes: a first side frame located on the left side of the support member in the left-right direction; a second side frame located on the right side of the support member in the left-right direction; a connecting member that connects the first side frame and the second side frame and is engageable with the support member; an engagement surface facing left or right, the engagement surface being engageable with the support member when the support member moves from the extended position to the retracted position before the support member engages with the connecting member; a reciprocating member provided on the second side frame, the reciprocating member being capable of contacting the first cartridge by reciprocating in the left-right direction; An image forming apparatus characterized by:

2. 2. The image forming apparatus according to claim 1, wherein the engagement surface is disposed forward of the connecting member.

3. 2. The image forming apparatus according to claim 1, wherein the engaging surface faces leftward and is engageable with the support member from the right side.

4. 2. The image forming apparatus according to claim 1, wherein the connecting member is capable of engaging with the support member from behind.

5. 2. The image forming apparatus according to claim 1, wherein the connecting member is a cylindrical connecting pipe.

6. 6. The image forming apparatus according to claim 5, wherein the support member has a recess that can be engaged with the connecting member.

7. 7. The image forming apparatus according to claim 6, wherein the recessed portion determines the position of the support member relative to the housing by engaging with the connecting member when the support member is located at the storage position.

8. 2. The image forming apparatus according to claim 1, wherein, when the image forming apparatus is installed on an installation surface, a height from the installation surface to the engagement surface is higher than a height from the installation surface to the connecting member.

9. 2. The image forming apparatus according to claim 1, wherein the support member has a contact surface that can contact the engagement surface and is located to the left of the center of the support member in the left-right direction.

10. 2. The image forming apparatus according to claim 1, wherein when the support member moves from the extended position to the retracted position, the connecting member engages with the support member after the engaging surface engages with the support member, thereby restricting the movement of the support member in the forward and backward directions.

11. 2. The image forming apparatus according to claim 1, wherein the engagement surface is provided on the first side frame.

12. a first photosensitive drum rotatable about a rotation axis parallel to the left-right direction; 2. The image forming apparatus according to claim 1, wherein the first cartridge is 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.

13. 2. The image forming apparatus according to claim 1, further comprising a second cartridge removably supported on the support member, the second cartridge having a second developing roller that can rotate around a rotation axis parallel to the left-right direction while supported on the support member.

Images