Image forming apparatus

Abstract

To provide an image forming apparatus in which a drum cartridge can be easily attached to a main body casing.SOLUTION: An image forming apparatus includes a main body casing 2, a drum cartridge, and a developing cartridge. The main body casing 2 has a slot 22B extending in a first direction from an opening 22A toward an inside of the main body casing 2. The drum cartridge and the developing cartridge can be attached to the slot 22B through the opening in the first direction. The main body casing 2 includes a drum guide groove 24 extending in the first direction to guide movement of the drum cartridge. The drum cartridge includes a drum protrusion extending in the first direction to engage with the drum guide groove. The width of the drum guide groove 24 in the second direction decreases toward the inside of the main body casing 2 from the opening 22A. The width of the drum protrusion in the second direction decreases toward the inside of the main body casing 2 from the opening 22A in a state where the drum cartridge is attached to the slot 22B.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus including a drum cartridge and a developing cartridge that are detachable from a main body housing.

Background Art

[0002] Conventionally, an image forming apparatus in which a drum cartridge and a developing cartridge are individually detachable from a main body housing is known (see Patent Document 1). In this technology, the drum cartridge and the developing cartridge are detachable in the axial direction of the photosensitive drum. The main body housing has an opening that allows the drum cartridge and the developing cartridge to be inserted, and a slot where the drum cartridge and the developing cartridge are mounted. Further, the slot includes a guide portion that guides the drum cartridge during attachment and detachment, and a guide portion that guides the developing cartridge during attachment and detachment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration disclosed in Patent Document 1, since the drum cartridge and the developing cartridge are each mounted in the slot, compared with a configuration in which a process cartridge integrating the drum cartridge and the developing cartridge is mounted in the slot of the main body housing, the number of guide portions increases, and the width of each guide portion and the interval between adjacent guide portions become narrow. With such a configuration, it becomes difficult for the user to mount the drum cartridge and the developing cartridge in the slot of the main body housing.

[0005] Therefore, the present invention aims to provide an image forming apparatus that allows the drum cartridge to be easily mounted on the main body housing even when the width of the guide section is narrowed. [Means for solving the problem]

[0006] To solve the aforementioned problems, the image forming apparatus according to the present invention comprises: a main body housing having an opening, the main body housing having a slot extending in a first direction toward the interior of the main body housing; a drum cartridge having a photosensitive drum rotatable about a first axis extending in the first direction, the drum cartridge being mountable in the slot via the opening in the first direction; and a developing cartridge having a developing roller rotatable about a second axis extending in the first direction, the developing cartridge being mountable in the slot via the opening in the first direction. The developing cartridge is aligned with the drum cartridge in a second direction intersecting the first direction when the drum cartridge and the developing cartridge are mounted in the slot. The main housing has a drum guide groove or drum guide projection that extends in the first direction and guides the drum cartridge. The drum cartridge has a drum projection extending in the first direction and fitted into the drum guide groove, or a drum groove extending in the first direction into which the drum guide projection fits. If the main housing has the drum guide groove, the width of the drum guide groove in the second direction narrows as it moves from the opening towards the inside of the main housing, or the width of the drum projection in the second direction narrows as it moves from the opening towards the inside of the main housing when the drum cartridge is mounted in the slot. If the main housing has the drum guide projection, the width of the drum guide projection in the second direction increases as it moves from the opening towards the inside of the main housing, or the width of the drum groove in the second direction increases as it moves from the opening towards the inside of the main housing when the drum cartridge is mounted in the slot.

[0007] In this configuration, if the main housing has a drum guide groove, the drum cartridge has a drum projection that fits into the drum guide groove, and when the drum cartridge is installed in the slot, the width of the drum projection in the second direction is approximately equal to the minimum width of the drum guide groove in the second direction at the front end (the end away from the opening) in the installation direction. Furthermore, the width of the drum guide groove in the second direction narrows as it moves from the opening towards the inside of the main housing, or the width of the drum projection in the second direction narrows as it moves from the opening towards the inside of the main housing. Furthermore, if the main housing has a drum guide projection, the drum cartridge has a drum groove into which the drum guide projection fits, and when the drum cartridge is installed in the slot, the width of the drum groove in the second direction is approximately equal to the maximum width of the drum guide projection in the second direction at the leading edge in the installation direction. In addition, the width of the drum guide projection in the second direction widens as it moves from the opening towards the inside of the main housing, or the width of the drum groove in the second direction widens as it moves from the opening towards the inside of the main housing. Thus, when the width of the opening side of the drum guide groove is greater than the width of the front end of the drum projection in the mounting direction, the drum cartridge is easier to install into the slot. Similarly, when the width of the opening side of the drum guide projection is smaller than the width of the front end of the drum groove in the mounting direction, the drum cartridge is easier to install into the slot.

[0008] In the image forming apparatus described above, the main body housing has the drum guide groove, the drum cartridge has the drum projection, and the width of the drum guide groove in the second direction may narrow as it moves from the opening towards the inside of the main body housing. In this configuration, the width of the drum projection in the second direction may narrow as it moves from the opening towards the inside of the main body housing when the drum cartridge is mounted in the slot.

[0009] In the image forming apparatus described above, the drum guide groove may have a tapered shape. In this configuration, the drum projection may have a tapered shape.

[0010] According to this, having a tapered shape allows for smoother insertion of the drum cartridge into the slot.

[0011] In the image forming apparatus described above, the main housing may have a developing guide groove or a developing guide projection extending in the first direction for guiding the developing cartridge. Furthermore, the developing cartridge may have a developing projection extending in the first direction and fitting into the developing guide groove, or a developing groove extending in the first direction into which the developing guide projection fits. If the main housing has the development guide groove, the width of the development guide groove in the second direction narrows as it moves from the opening towards the inside of the main housing, or the width of the development projection in the second direction narrows as it moves from the opening towards the inside of the main housing when the development cartridge is installed in the slot. If the main housing has the development guide projection, the width of the development guide projection in the second direction increases as it moves from the opening towards the inside of the main housing, or the width of the development groove in the second direction increases as it moves from the opening towards the inside of the main housing when the development cartridge is installed in the slot.

[0012] In this configuration, if the main housing has a development guide groove, the drum cartridge has a development projection that fits into the development guide groove, and when the drum cartridge is installed in the slot, the width of the development projection in the second direction is approximately equal to the minimum width of the development guide groove in the second direction at the front end (the end away from the opening) in the installation direction. Furthermore, the width of the development guide groove in the second direction narrows as it moves from the opening towards the inside of the main housing, or the width of the development projection in the second direction narrows as it moves from the opening towards the inside of the main housing. Furthermore, if the main housing has a development guide projection, the development cartridge has a development groove into which the development guide projection fits, and when the development cartridge is installed in the slot, the width of the development groove in the second direction is approximately equal to the maximum width of the development guide projection in the second direction at the front end in the installation direction. In addition, the width of the development guide projection in the second direction widens as it moves from the opening towards the inside of the main housing, or the width of the development groove in the second direction widens as it moves from the opening towards the inside of the main housing. Thus, when the width of the opening side of the development guide groove is greater than the width of the leading edge of the development projection in the mounting direction, the development cartridge is easier to insert into the slot. Similarly, when the width of the opening side of the development guide projection is smaller than the width of the leading edge of the development groove in the mounting direction, the development cartridge is easier to insert into the slot.

[0013] In the image forming apparatus described above, the main housing has the development guide projection, the development cartridge has the development groove, and the width of the development guide projection in the second direction may increase as it moves from the opening towards the inside of the main housing. In this configuration, the width of the developing groove in the second direction may increase from the opening towards the inside of the main housing when the developing cartridge is installed in the slot.

[0014] In the above-described image forming apparatus, the developing guide protrusion may have a tapered shape. In this configuration, the developing groove may have a tapered shape.

[0015] According to this, by having a tapered shape, the mounting of the developing cartridge into the slot can be performed more smoothly.

[0016] The above-described image forming apparatus may include an intermediate transfer belt positioned above the drum cartridge and the developing cartridge in a state where the drum cartridge and the developing cartridge are mounted on the main body housing. The main body housing may have a drum guide surface for guiding the drum cartridge, which is a drum guide surface aligned with the drum guide groove or the drum guide protrusion in the second direction. The drum cartridge may have a drum contact surface that contacts the drum guide surface in a state where the drum cartridge is mounted in the slot. And the drum guide surface may be configured to approach the intermediate transfer belt as it goes from the opening into the interior of the main body housing.

[0017] According to this, since the distance between the drum guide surface and the intermediate transfer belt increases on the opening side of the main body housing, when mounting the drum cartridge into the slot, the drum cartridge can be inserted from a position where the photosensitive drum is unlikely to collide with the intermediate transfer belt.

[0018] In the above-described image forming apparatus, the drum contact surface may be configured to approach the intermediate transfer belt as it goes from the opening into the interior of the main body housing in a state where the drum cartridge is mounted in the slot.

[0019] In the above-described image forming apparatus, the main body housing may have a developing guide surface for guiding the developing cartridge, the developing guide surface being aligned with the developing guide groove or the developing guide protrusion in the second direction. The developing cartridge may have a developing contact surface that contacts the developing guide surface when the developing cartridge is mounted in the slot. And the developing guide surface may be configured to approach the intermediate transfer belt as it extends from the opening toward the inside of the main body housing.

[0020] According to this, since the distance between the developing guide surface and the intermediate transfer belt increases on the opening side of the main body housing, when mounting the developing cartridge in the slot, the developing cartridge can be inserted from a position where it is less likely to collide with the intermediate transfer belt.

[0021] In the above-described image forming apparatus, the developing contact surface may be configured to approach the intermediate transfer belt as it extends from the opening toward the inside of the main body housing when the developing cartridge is mounted in the main body housing.

[0022] In the above-described image forming apparatus, the developing cartridge may include a first developing cartridge that stores a developer of a first color and a second developing cartridge that stores a developer of a second color different from the first color. When the main body housing has the developing guide groove, the developing guide groove includes a first developing guide groove for guiding the first developing cartridge and a second developing guide groove for guiding the second developing cartridge, and the length of the first developing guide groove in the second direction may be different from the length of the second developing guide groove in the second direction. Also, when the main body housing has the developing guide protrusion, the developing guide protrusion includes a first developing guide protrusion for guiding the first developing cartridge and a second developing guide protrusion for guiding the second developing cartridge, and the length of the first developing guide protrusion in the second direction may be different from the length of the second developing guide protrusion in the second direction.

[0023] According to this design, the width of the development guide groove or development guide projection in the second direction differs to correspond to the different colors of the development cartridges, thus preventing incorrect insertion of the development cartridges.

[0024] In the image forming apparatus described above, the developing cartridge may include a first developing cartridge containing a first-color developer and a second developing cartridge containing a second-color developer different from the first color. The drum cartridge may include a first drum cartridge corresponding to the first developing cartridge and a second drum cartridge corresponding to the second developing cartridge. If the main housing has the drum guide groove, the drum guide groove includes a first drum guide groove for guiding the first drum cartridge and a second drum guide groove for guiding the second drum cartridge, and the length of the first drum guide groove in the second direction may be the same as the length of the second drum guide groove in the second direction. Furthermore, if the main housing has the drum guide projection, the drum guide projection includes a first drum guide projection that guides the first drum cartridge and a second drum guide projection that guides the second drum cartridge, and the length of the first drum guide projection in the second direction may be the same as the length of the second drum guide projection in the second direction.

[0025] According to this, a common drum cartridge can be used with multiple developing cartridges, thus reducing manufacturing costs.

[0026] In the image forming apparatus described above, the main body housing includes a cover that opens and closes the opening, and a side wall that is located away from the cover in the first direction when the cover is in the closed position, and the side wall may have a first projection or a first elongated hole, and a second projection or a second elongated hole. Furthermore, the drum cartridge may have a drum slot into which the first projection fits, or a drum projection into which the first projection fits, when the drum cartridge is mounted on the main body housing, and the developing cartridge may have a developing slot into which the second projection fits, or a developing projection into which the second projection fits, when the developing cartridge is mounted on the main body housing.

[0027] According to this, the drum cartridge and the developing cartridge can be brought into contact with and separated from the intermediate transfer belt.

[0028] In the image forming apparatus described above, the intermediate transfer belt may be positioned above the drum cartridge and the developing cartridge when the drum cartridge and the developing cartridge are mounted in the main housing. In this configuration, the paper discharge section may be located above the intermediate transfer belt. [Effects of the Invention]

[0029] According to the present invention, it is possible to provide an image forming apparatus in which the drum cartridge is easily mounted to the main body housing. [Brief explanation of the drawing]

[0030] [Figure 1] This is a cross-sectional view showing the schematic configuration of a color printer according to one embodiment of the present invention. [Figure 2] This is a perspective view showing the main unit with the cover open, and the drum cartridge and developer cartridge removed from their slots. [Figure 3] These are perspective views (a) of the drum cartridge, front views (b) of the drum cartridge, and bottom views (c) of the drum cartridge. [Figure 4] These are perspective views (a) of the developing cartridge, front views (b) of the developing cartridge, and bottom views (c) of the developing cartridge. [Figure 5]This is an explanatory diagram illustrating the relationship between the drum guide groove and development guide projection of the slot, the drum projection of the drum cartridge, and the development groove of the development cartridge. [Figure 6] This is an explanatory diagram showing how to insert the drum cartridge into the slot on the main unit's casing. [Figure 7] This is an explanatory diagram showing how to insert the developing cartridge into the slot on the main unit. [Figure 8] This is an explanatory diagram relating to a first modified example illustrating the relationship between the drum guide groove and the developing guide projection, and the drum projection and the developing groove. [Figure 9] These are explanatory diagrams illustrating the relationship between the drum guide groove and the developing guide projection, and the drum projection and the developing groove. They are explanatory diagram (a) relating to the second modification, explanatory diagram (b) relating to the third modification, and explanatory diagram (c) relating to the fourth modification. [Figure 10] These are explanatory diagrams illustrating the relationship between the drum guide groove and the developing guide projection, and the drum projection and the developing groove, and are explanatory diagram (a) relating to the fifth modified example and explanatory diagram (b) relating to the sixth modified example. [Modes for carrying out the invention]

[0031] Next, one embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, the overall configuration of a color printer 1 as an example of an image forming apparatus will be described first. In the following explanation, direction will be described using the directions shown in Figure 1. That is, the left side of Figure 1 will be referred to as "front," the right side as "back," the front of the page as "right," and the back of the page as "left." Also, the top and bottom of Figure 1 will be referred to as "top and bottom."

[0032] As shown in Figure 1, the color printer 1 comprises a main body casing 2, a paper feeding unit 3, an image forming unit 4, and a paper output unit 5. The paper feeding unit 3 supplies paper P to the image forming unit 4. The image forming unit 4 forms an image on the paper P. The paper output unit 5 ejects the paper P.

[0033] The paper feed unit 3 is located at the bottom of the main body housing 2. The paper feed unit 3 comprises a paper feed tray 31 and a paper feed mechanism 32. The paper feed tray 31 is detachable from the main body housing 2. The paper feed mechanism 32 transports paper P from the paper feed tray 31 to the image forming unit 4.

[0034] The image forming unit 4 comprises four drum cartridges 40, four developing cartridges 50, an exposure device SU, a transfer unit 60, and a fixing unit 70. The image forming unit 4 consists of four drum cartridges 40, four developing cartridges 50, an exposure device SU, and a transfer unit 60, all of which are arranged at an angle so that they are positioned downwards from the front to the rear of the main housing 2.

[0035] Each drum cartridge 40 has a photosensitive drum 41, a charger (not shown), and a drum frame PF. The photosensitive drum 41 is rotatable about a first axis X1 extending in a first direction. The four drum cartridges 40 are arranged in a second direction perpendicular to the first direction when mounted in the main housing 2. In this embodiment, the image forming unit 4 is equipped with four drum cartridges 40. The four drum cartridges 40 correspond to toners of black (K), yellow (Y), magenta (M), and cyan (C). The four drum cartridges 40 are arranged in the order of black (K), yellow (Y), magenta (M), and cyan (C) from upstream to downstream in the direction of movement of the intermediate transfer belt 63 (from the front to the back of the color printer 1) as the surfaces that contact each photosensitive drum 41 move. In the following explanation, when identifying drum cartridges 40 corresponding to toner colors, the symbols K, Y, M, and C will be added after the code 40, corresponding to black, yellow, magenta, and cyan, respectively.

[0036] Each developing cartridge 50 has a developing roller 51 and a developing frame DF. The developing frame DF contains the developer. The developing roller 51 is rotatable about a second axis X2 extending in a first direction. The four developing cartridges 50 are arranged in the second direction when mounted in the main housing 2. With the four drum cartridges 40 and the four developing cartridges 50 mounted in the main unit housing 2, each developing cartridge 50 is aligned with each drum cartridge 40 in a second direction. In this embodiment, the image forming unit 4 is equipped with four developing cartridges 50. The four developing cartridges 50 correspond to toners of black (K), yellow (Y), magenta (M), and cyan (C). The four developing cartridges 50 are arranged in the order of black (K), yellow (Y), magenta (M), and cyan (C) from upstream to downstream in the direction of movement of the intermediate transfer belt 63, where the surfaces in contact with each photosensitive drum 41 move. In the following explanation, when identifying the developer cartridge 50 corresponding to the toner color, the symbols K, Y, M, and C will be added after the code 50, corresponding to black, yellow, magenta, and cyan, respectively.

[0037] The exposure unit SU is located beneath each drum cartridge 40. The exposure unit SU emits laser light to each photosensitive drum 41.

[0038] The transfer unit 60 is located between the four photosensitive drums 41 and the output tray 21. The transfer unit 60 comprises a drive roller 61, a driven roller 62, an intermediate transfer belt 63, four primary transfer rollers 64, and a secondary transfer roller 65.

[0039] The intermediate transfer belt 63 is an endless belt. When the drum cartridge 40 and the developer cartridge 50 are mounted in the main body housing 2, the intermediate transfer belt 63 is positioned above the drum cartridge 40 and the developer cartridge 50.

[0040] The primary transfer roller 64 is located inside the intermediate transfer belt 63. The primary transfer roller 64 and the photosensitive drum 41 sandwich the intermediate transfer belt 63.

[0041] The secondary transfer roller 65 is located on the outside of the intermediate transfer belt 63. The secondary transfer roller 65 and the drive roller 61 sandwich the intermediate transfer belt 63.

[0042] The fixing unit 70 is located on the intermediate transfer belt 63. The fixing unit 70 comprises a heating roller 71 and a pressure roller 72. The pressure roller 72 is pressed against the heating roller 71.

[0043] The paper output unit 5 is located at the top of the main body housing 2. The paper output unit 5 is located above the intermediate transfer belt 63. The paper output unit 5 comprises an output roller 9 and an output tray 21. The output roller 9 transports the paper P toward the output tray 21.

[0044] In the color printer 1, the charger first charges the surface of the photosensitive drum 41. Then, the exposure unit SU exposes the surface of the photosensitive drum 41. As a result, an electrostatic latent image is formed on the photosensitive drum 41.

[0045] Next, the developing roller 51 supplies developer to the electrostatic latent image on the photosensitive drum 41. This forms a developer image on the photosensitive drum 41. Then, the developer image on the photosensitive drum 41 is transferred onto the intermediate transfer belt 63.

[0046] As the paper P passes between the intermediate transfer belt 63 and the secondary transfer roller 65, the developer image on the intermediate transfer belt 63 is transferred onto the paper P. The developer image on the paper P is then fixed by the fixing unit 70. The paper P is then discharged into the output tray 21 by the output roller 9.

[0047] As shown in Figure 2, the main housing 2 has an opening 22A, a slot 22B, and a cover C. The opening 22A allows each drum cartridge 40 and each developer cartridge 50 to pass through when inserting or removing the drum cartridge 40 and each developer cartridge 50.

[0048] Slot 22B extends in a first direction toward the interior of the main body housing 2 from the opening 22A. Slot 22B is a space for housing four drum cartridges 40 and four developer cartridges 50.

[0049] Cover C is a component for opening and closing the opening 22A. Cover C rotates around its lower end. Cover C is movable between an open position (shown in Figure 2) that opens the opening 22A and a closed position (not shown) that closes the opening 22A. Cover C has a first projection C1 that fits into the elongated drum hole 43 of each drum cartridge 40 (described later), and a second projection C2 that fits into the elongated developing hole 53 of each developing cartridge 50 (described later).

[0050] The main housing 2 has a first projection D1 and a second projection D2 on the inside of the side wall 2A. The first projection D1 fits into the drum slot 43 of each drum cartridge 40, which will be described later. The second projection D2 fits into the development slot 53 of each development cartridge 50, which will be described later. The side wall 2A is a side wall that is located away from the cover C in the first direction when the cover C is in the closed position. When the cover C is in the closed position, the first projection D1 and the second projection D2 face the first projection C1 and the second projection C2 of the cover C in the first direction. Furthermore, the main unit housing 2 is equipped with a cartridge guide section 2B at the bottom of slot 22B.

[0051] The cartridge guide section 2B has drum guide grooves 24 and development guide protrusions 26. The drum guide grooves 24 and development guide protrusions 26 are located on the upper surface of the cartridge guide section 2B. There are four drum guide grooves 24 and four development guide protrusions 26 arranged in the second direction (see also Figure 5). Furthermore, the cartridge guide section 2B has a through-hole (not shown) through which the laser light from the exposure apparatus SU passes. As shown in Figure 5, each drum guide groove 24 is a groove that extends in a first direction to guide the drum cartridge 40. The width of the drum guide groove 24 in the second direction narrows from the opening 22A toward the side wall 2A (i.e., the inside of the main housing 2). More specifically, the drum guide groove 24 has a tapered shape in which the opposing sides forming the groove are symmetrically and continuously inclined. The four drum guide grooves 24K, 24Y, 24M, and 24C have the same shape. Each developing guide projection 26 is a projection that extends in a first direction to guide the developing cartridge 50. The width of the developing guide projection 26 in a second direction widens from the opening 22A toward the side wall 2A (i.e., the inside of the main housing 2). More specifically, the developing guide projection 26 has a tapered shape in which the opposing sides forming the projection are symmetrically and continuously inclined. The four developing guide projections 26K, 26Y, 26M, and 26C have the same shape. Furthermore, as shown in Figure 2, the upper surface of the cartridge guide section 2B is inclined upward so as it moves from the opening 22A towards the side wall 2A (i.e., the inside of the main housing 2) and closer to the intermediate transfer belt 63.

[0052] As shown in Figure 5, the upper surface of the cartridge guide section 2B has a drum guide surface 25 and a development guide surface 27. The drum guide surfaces 25 are located on both sides of the drum guide groove 24. The drum guide surfaces 25 are surfaces for guiding the drum cartridge 40 and are aligned with the drum guide groove 24 in the second direction. As described above, the upper surface of the cartridge guide section 2B is inclined to approach the intermediate transfer belt 63. Therefore, the drum guide surface 25 is inclined to approach the intermediate transfer belt 63 as it moves from the opening 22A towards the inside of the main body housing 2. The development guide surface 27 is located on both sides of the development guide projection 26. The development guide surface 27 is a surface for guiding the development cartridge 50 and is aligned with the development guide projection 26 in the second direction. As described above, the upper surface of the cartridge guide section 2B is inclined to approach the intermediate transfer belt 63. Therefore, the developing guide surface 27 is inclined to approach the intermediate transfer belt 63 as it moves from the opening 22A towards the inside of the main housing 2. As shown in Figure 6, the bottom surface 24A of the drum guide groove 24 is parallel to the lower surface of the intermediate transfer belt 63. On the other hand, the drum guide surface 25 is inclined with respect to the lower surface of the intermediate transfer belt 63. Similarly, as shown in Figure 7, the upper surface 26A of the development guide projection 26 is parallel to the lower surface of the intermediate transfer belt 63. On the other hand, the development guide surface 27 is inclined with respect to the lower surface of the intermediate transfer belt 63.

[0053] The drum cartridge 40 and the developing cartridge 50 are each independently detachable from the main body 2 in a first direction. In detail, each drum cartridge 40 can be mounted in slot 22B via opening 22A in a first direction. Similarly, each developer cartridge 50 can be mounted in slot 22B via opening 22A in a first direction. The four drum cartridges 40 have the same structure. The four developing cartridges 50 have the same structure.

[0054] As shown in Figure 3, the drum frame PF of the drum cartridge 40, when the drum cartridge 40 is mounted in the slot 22B, has a first drum side wall PF1 and a second drum side wall PF2 that face each other in the first direction, a third drum side wall PF3 and a fourth drum side wall PF4 that correspond in the second direction, and a fifth drum side wall PF5 that forms the bottom surface. The first drum side wall PF1 is a side wall located close to the opening 22A when the drum cartridge 40 is installed in the slot 22B. The first drum side wall PF1 has a drum elongated hole 43 into which the first projection C1 of the cover C fits when the cover C is moved to the closed position. The second drum side wall PF2 is a side wall located far from the opening 22A when the drum cartridge 40 is mounted in the main housing 2. The second drum side wall PF2 has a drum slot into which the first projection D1 of the main housing 2 fits. This drum slot has the same shape as the drum slot 43 and is therefore not shown in the illustration. The first drum side wall PF1 and the second drum side wall PF2 rotatably support the photosensitive drum 41. The third drum side wall PF3 and the fourth drum side wall PF4 connect the first drum side wall PF1 and the second drum side wall PF2, respectively.

[0055] The fifth drum side wall PF5 connects the first drum side wall PF1, the second drum side wall PF2, the third drum side wall PF3, and the fourth drum side wall PF4. The fifth drum side wall PF5 has a drum contact surface 45 that contacts the drum guide surface 25 when the drum cartridge 40 is mounted in slot 22B. More specifically, when the drum cartridge 40 is mounted in slot 22B, the drum contact surface 45 is inclined to approach the intermediate transfer belt 63 as it moves from the opening 22A towards the inside of the main housing 2 (see Figure 6). The inclination angle of the drum contact surface 45 with respect to the first axis X1 of the photosensitive drum 41 is equal to the inclination angle of the drum guide surface 25 with respect to the lower surface of the intermediate transfer belt 63. Therefore, when the drum cartridge 40 is mounted in slot 22B, the drum guide surface 25 and the drum contact surface 45 are in contact, and the photosensitive drum 41 and the intermediate transfer belt 63 are parallel. Furthermore, the fifth drum side wall PF5 has a drum projection 46 that protrudes from the drum contact surface 45. The drum projection 46 extends in a first direction and fits into the drum guide groove 24. In the second direction, the width of the drum projection 46 narrows as it moves from the opening 22A towards the inside of the main housing 2 when the drum cartridge 40 is mounted in the slot 22B. More specifically, the drum projection 46 has a tapered shape in which the opposing sides forming the projection are symmetrically and continuously inclined. Both sides of the drum projection 46 contact the side walls of the drum guide groove 24 when the drum cartridge 40 is mounted in the slot 22B. As shown in Figure 3, the lower surface of the drum projection 46 is parallel to the first axis X1 of the photosensitive drum 41, whereas the drum contact surface 45 is inclined with respect to the first axis X1 of the photosensitive drum 41. More specifically, when the drum cartridge 40 is installed in the slot 22B, the drum contact surface 45 is inclined upward as it moves from the opening 22A towards the inside of the main body housing 2.

[0056] As shown in Figure 4, the developing frame DF of the developing cartridge 50 has, when the developing cartridge 50 is mounted in the slot 22B, a first developing side wall DF1 and a second developing side wall DF2 that face each other in the first direction, a third developing side wall DF3 and a fourth developing side wall DF4 that correspond in the second direction, and a fifth developing side wall DF5 that forms the bottom surface. The first developing side wall DF1 is a side wall located close to the opening 22A when the developing cartridge 50 is installed in the slot 22B. The first developing side wall DF1 has a developing elongated hole 53 into which the second projection C2 of the cover C fits when the cover C is moved to the closed position. The second developing side wall DF2 is a side wall located far from the opening 22A when the developing cartridge 50 is installed in slot 22B. The second developing side wall DF2 has a developing slot into which the second projection D2 of the main housing 2 fits. This developing slot has the same shape as the developing slot 53 and is therefore not shown in the illustration. The first developing side wall DF1 and the second developing side wall DF2 rotatably support the developing roller 51. The third developing side wall DF3 and the fourth developing side wall DF4 connect the first developing side wall DF1 and the second developing side wall DF2, respectively.

[0057] The fifth developing side wall DF5 connects the first developing side wall DF1, the second developing side wall DF2, the third developing side wall DF3, and the fourth developing side wall DF4. The fifth developing side wall DF5 has a developing contact surface 55 that contacts the developing guide surface 27 when the developing cartridge 50 is installed in the slot 22B. More specifically, when the developing cartridge 50 is installed in the main housing 2, the developing contact surface 55 is inclined to approach the intermediate transfer belt 63 as it moves from the opening 22A towards the inside of the main housing 2 (see Figure 7). The inclination angle of the developing contact surface 55 with respect to the second axis X2 of the developing roller 51 is equal to the inclination angle of the developing guide surface 27 with respect to the lower surface of the intermediate transfer belt 63. Therefore, when the developing cartridge 50 is installed in the slot 22B, the developing guide surface 27 and the developing contact surface 55 are in contact, and the developing roller 51 and the intermediate transfer belt 63 are parallel. Furthermore, the fifth developing side wall DF5 has a developing groove 56 on the developing contact surface 55. The developing groove 56 extends in a first direction and fits into the developing guide projection 26 when the developing cartridge 50 is installed in the slot 22B. The width of the developing groove 56 in the second direction widens from the opening 22A towards the inside of the main housing 2 when the developing cartridge 50 is installed in the slot 22B. More specifically, the developing groove 56 has a tapered shape in which the opposing sides forming the groove are symmetrically and continuously inclined. Both sides of the developing groove 56 contact the side walls of the developing guide projection 26 when the developing cartridge 50 is installed in the slot 22B. As shown in Figure 4, the upper surface of the developing groove 56 is parallel to the second axis X2 of the developing roller 51, while the developing contact surface 55 is inclined with respect to the second axis X2 of the developing roller 51. More specifically, when the developing cartridge 50 is installed in the slot 22B, the developing contact surface 55 is inclined upward as it moves from the opening 22A towards the inside of the main housing 2.

[0058] Next, with reference to Figures 6 and 7, the procedure for installing the drum cartridge 40 and the developing cartridge 50 into slot 22B of the main unit housing 2 will be described. As shown in Figures 2 and 6, when installing the drum cartridge 40 into slot 22B, the cover C is moved to the open position to expose the opening 22A and slot 22B. Then, after inserting the tip of the drum projection 46 into the drum guide groove 24 of the cartridge guide section 2B, the drum cartridge 40 is inserted in the first direction, thereby installing the drum cartridge 40 into the main body housing 2. At this time, the width of the drum guide groove 24 on the opening 22A side is greater than the width of the drum projection 46 on the mounting direction tip side, which makes it easier to install the drum cartridge 40 into slot 22B. When the tip of the drum projection 46 is inserted into the drum guide groove 24, the drum contact surface 45 comes into contact with the drum guide surface 25. Then, as the drum cartridge 40 is inserted in the first direction, the tip of the drum projection 46 is guided by the drum guide groove 24, which gradually narrows in width, and the drum cartridge 40 is mounted in the correct position inside the main body housing 2.

[0059] With this configuration, when the drum cartridge 40 is inserted into the drum guide groove 24 from the second drum side wall PF2 side, the narrower end of the drum projection 46 in the second direction is inserted first, and the wider end of the drum projection 46 is inserted last. On the other hand, the drum guide groove 24 into which the drum projection 46 is fitted is widest on the opening 22A side and narrowest on the side wall 2A side in the second direction. Therefore, the drum cartridge 40 is more easily mounted into the main body housing 2 due to the large dimensional difference at the inlet (opening 22A) side. Furthermore, since the distance between the drum guide surface 25 and the intermediate transfer belt 63 is increased on the entrance (opening 22A) side, when installing the drum cartridge 40, it is possible to suppress the contact between the photosensitive drum 41 and the intermediate transfer belt 63, which could damage the surface of the photosensitive drum 41. In other words, when installing the drum cartridge 40 into the slot 22B, the drum cartridge 40 can be inserted from a position where it is less likely to come into contact with the intermediate transfer belt 63.

[0060] As shown in Figures 2 and 7, when installing the developing cartridge 50 into slot 22B, the cover C is moved to the open position to expose the opening 22A and slot 22B. Then, after inserting the tip of the developing groove 56 into the developing guide projection 26 of the cartridge guide section 2B, the drum cartridge 40 is inserted in the first direction, thereby installing the developing cartridge 50 into the main body housing 2. At this time, the width of the developing guide projection 26 on the opening 22A side is smaller than the width of the developing groove 56 on the mounting direction tip side, making it easier to install the developing cartridge 50 into slot 22B. When the tip of the developing groove 56 is inserted into the developing guide projection 26, the developing contact surface 55 comes into contact with the developing guide surface 27. Then, as the developing cartridge 50 is inserted in the first direction, the tip of the developing groove 56 is guided by the developing guide projection 26, which gradually widens, and the developing cartridge 50 is installed in the correct position inside the main body housing 2.

[0061] With this configuration, when the developing cartridge 50 is inserted into the drum guide groove 24 from the second developing side wall DF2 side, the wider end of the developing groove 56 in the second direction is inserted first, and the narrower end of the developing groove 56 is inserted last. On the other hand, the developing guide projection 26 into which the developing groove 56 is fitted has the narrowest width on the opening 22A side and the widest width on the side wall 2A side in the second direction. Therefore, the developing cartridge 50 is easier to install into the main body housing 2 due to the large dimensional difference at the entrance (opening 22A) side. Furthermore, since the distance between the development guide surface 27 and the intermediate transfer belt 63 is increased on the inlet (opening 22A) side, when installing the development cartridge 50, it is possible to suppress contact between the development roller 51 and the intermediate transfer belt 63 and damage to the surface of the development roller 51. In other words, when installing the development cartridge 50 into the slot 22B, the development cartridge 50 can be inserted from a position where it is less likely to come into contact with the intermediate transfer belt 63.

[0062] When the drum cartridge 40 is inserted into slot 22B, the first projection D1 on the side wall 2A of the main housing 2 fits into the elongated drum hole in the second drum side wall PF2 of the drum cartridge 40. When the developing cartridge 50 is inserted into slot 22B, the second projection D2 on the side wall 2A of the main housing 2 fits into the elongated developing hole in the second developing side wall DF2 of the developing cartridge 50. Then, when the cover C is moved to the closed position, the first projection C1 of the cover C fits into the elongated drum hole 43 of the first drum side wall PF1 of the drum cartridge 40, and the second projection C2 of the cover C fits into the elongated developing hole 53 of the first developing side wall DF1 of the developing cartridge 50. In this state, when the drum pressing member 80 (see Figure 1) is raised, the drum cartridge 40 rises and the photosensitive drum 41 comes into contact with the intermediate transfer belt 63. Also, when the developing pressing member (not shown) is raised, the developing cartridge 50 rises and the developing roller 51 comes into contact with the photosensitive drum 41 at a predetermined position.

[0063] Based on the above, the following effects can be obtained in this embodiment. The width of the drum guide groove 24 on the opening 22A side is greater than the width of the drum projection 46 on the mounting direction end side, which makes it easier to mount the drum cartridge 40 into the slot 22B.

[0064] The drum guide groove 24 of the main housing 2 has a tapered shape, and the drum projection 46 of the corresponding drum cartridge 40 also has a tapered shape, which allows the drum cartridge 40 to be mounted into the slot 22B more smoothly.

[0065] The width of the opening side 22A of the development guide projection 26 is smaller than the width of the leading edge side in the mounting direction of the development groove 56, which makes it easier to install the development cartridge 50 into the slot 22B.

[0066] The development guide projection 26 of the main housing 2 has a tapered shape, and the development groove 56 of the corresponding development cartridge 50 also has a tapered shape, which allows the development cartridge 50 to be inserted into the slot 22B more smoothly.

[0067] Since the distance between the drum guide surface 25 and the intermediate transfer belt 63 is increased on the opening 22A side of the main housing 2, when the drum cartridge 40 is installed in the slot 22B, the drum cartridge 40 can be inserted from a position where the photosensitive drum 41 is less likely to come into contact with the intermediate transfer belt 63.

[0068] Since the distance between the development guide surface 27 and the intermediate transfer belt 63 is increased on the opening 22A side of the main housing 2, when installing the development cartridge 50 into the slot 22B, the development cartridge 50 can be inserted from a position where it is less likely to come into contact with the intermediate transfer belt 63.

[0069] The first projection D1 and the second projection D2 on the side wall 2A of the main housing 2 fit into the elongated drum hole of the drum cartridge 40 and the elongated developing hole of the developing cartridge 50, respectively, so that the drum cartridge 40 and the developing cartridge 50 can be brought into contact with and separated from the intermediate transfer belt 63.

[0070] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Specific configurations can be modified as appropriate without departing from the spirit of the present invention.

[0071] In the above embodiment, the drum guide groove 24 and the development guide projection 26 were located on the upper surface of the cartridge guide portion 2B, but the present invention is not limited to this configuration. For example, the main housing 2 may be configured to have a drum guide projection instead of a drum guide groove 24, and a development guide groove instead of a development guide projection 26. In this case, the drum cartridge 40 has a drum groove that extends in the first direction and into which the drum guide projection fits when the drum cartridge 40 is mounted in the slot 22B. Similarly, the development cartridge 50 has a development projection that extends in the first direction and fits into the development guide groove when the development cartridge 50 is mounted in the slot 22B. Furthermore, if the main housing 2 has drum guide protrusions, the width of the drum guide protrusions in the second direction increases as they move from the opening 22A towards the interior of the main housing 2. In the drum cartridge 40, the width of the drum groove in the second direction increases as it moves from the opening 22A towards the interior of the main housing 2 when the drum cartridge 40 is mounted in the slot 22B. Furthermore, if the main housing 2 has a development guide groove, the width of the development guide groove in the second direction narrows as it moves from the opening 22A towards the inside of the main housing 2. And, in the development cartridge 50, the width of the development projection in the second direction narrows as it moves from the opening 22A towards the inside of the main housing 2 when the development cartridge 50 is installed in the slot 22B.

[0072] Alternatively, the main housing 2 may have a drum guide groove and a developing guide groove, the drum cartridge 40 may have a drum projection, and the developing cartridge 50 may have a developing projection. Similarly, the main housing 2 may have drum guide protrusions and development guide protrusions, the drum cartridge 40 may have drum grooves, and the development cartridge 50 may have development grooves. Furthermore, the main housing 2 may be configured to have a drum guide groove and drum guide projection, and a development guide groove and development guide projection.

[0073] In the above embodiment, the drum guide surface 25 and the developing guide surface 27 on the upper surface of the cartridge guide section 2B were inclined to approach the intermediate transfer belt 63 as they moved from the opening 22A towards the inside of the main housing 2, but the present invention is not limited to this configuration. The drum guide surface 25 and the developing guide surface 27 can also be configured not to be inclined so as they move closer to the intermediate transfer belt 63 as they move from the opening 22A towards the inside of the main housing 2. For example, the drum guide surface 25 and the developing guide surface 27 can be configured to be parallel to the lower surface of the intermediate transfer belt 63. In this case, the drum contact surface 45 of the drum cartridge 40 will be parallel to the first axis X1 of the photosensitive drum 41, and the developing contact surface 55 of the developing cartridge 50 will be parallel to the second axis X2 of the developing roller 51.

[0074] In the above embodiment, the side wall 2A of the main housing 2 has a first projection D1 and a second projection D2, and the cover C has a first projection C1 and a second projection C2, but the present invention is not limited to such a configuration. For example, the side wall 2A of the main body housing 2 may have a first elongated hole instead of the first projection D1, and a second elongated hole instead of the second projection D2. In this case, the drum cartridge 40 has a drum projection that fits into the first elongated hole when the drum cartridge 40 is mounted on the main body housing 2. Similarly, the developing cartridge 50 has a developing projection that fits into the second elongated hole when the developing cartridge 50 is mounted on the main body housing 2. Similarly, in cover C, the first projection C1 and the first elongated hole, and the second projection C2 and the second elongated hole may be swapped. In this case, the drum cartridge 40 has drum projections, and the developing cartridge 50 has developing projections. Furthermore, different combinations can be used on the entrance (opening 22A) side and the back (side wall 2A) side.

[0075] In the above embodiment, the four drum guide grooves 24 of the main body housing 2 had the same shape, and the four developing guide protrusions 26 had the same shape. Furthermore, the four drum cartridges 40 and the four developing cartridges 50 each had the same shape. However, the present invention is not limited to this configuration. For example, the developing cartridge 50 may include four developing cartridges, each having a developing groove or developing projection of a different width. On the other hand, the drum cartridge 40 may include four drum cartridges, each having a drum projection or drum groove of the same width.

[0076] More specifically, as shown in the first modified example in Figure 8, the developing cartridge 50 includes four developing cartridges 50K, 50Y, 50M, and 50C. Of these, for example, the developing cartridge 50K for black is the first developing cartridge containing the developer for the first color. The other developing cartridges 50Y, 50M, and 50C are second developing cartridges containing the developer for a second color different from the first color. As shown in Figure 8, the width of the developing groove 56 of the developing cartridge 50K is wider than the width of the developing groove 56 of the developing cartridges 50Y, 50M, and 50C. More specifically, the width of the leading edge of the developing cartridge 50K in the mounting direction is wider than the width of the leading edge of the other developing cartridges 50Y, 50M, and 50C in the mounting direction. Note that the width of the developing groove 56 of the developing cartridges 50Y, 50M, and 50C may be configured differently for each toner color.

[0077] On the other hand, drum cartridge 40 includes four drum cartridges: 40K, 40Y, 40M, and 40C. Of these, drum cartridge 40K, which is for black film, is the first drum cartridge, corresponding to the first developer cartridge. The other drum cartridges, 40Y, 40M, and 40C, are second drum cartridges, corresponding to the second developer cartridge. Regardless of the toner color, the length (width) of the drum protrusion 46 of the drum cartridge 40 in the second direction is the same for all. Specifically, the width of the leading edge in the mounting direction of the developer cartridges 50K, 50Y, 50M, and 50C is the same for all.

[0078] The main housing 2 has a first drum guide groove 24K for guiding the black drum cartridge 40K, a second drum guide groove 24Y for guiding the yellow drum cartridge 40Y, a second drum guide groove 24M for guiding the magenta drum cartridge 40M, and a second drum guide groove 24C for guiding the cyan drum cartridge 40C on the upper surface of the cartridge guide section 2B. The length of the first drum guide groove 24K in the second direction is the same as the length of the second drum guide grooves 24Y, 24M, and 24C in the second direction. Specifically, the width of the first drum guide groove 24K and the second drum guide grooves 24Y, 24M, and 24C on the opening 22A side are all equal. Furthermore, the main housing 2 has a first development guide projection 26K for guiding the black development cartridge 50K, a second development guide projection 26Y for guiding the yellow development cartridge 50Y, a second development guide projection 26M for guiding the magenta development cartridge 50M, and a second development guide projection 26C for guiding the cyan development cartridge 50C on the upper surface of the cartridge guide section 2B. The widths of the first development guide projection 26K and the second development guide projections 26Y, 26M, and 26C differ to correspond to the width of the development groove 56 of each development cartridge 50. In other words, the length of the first development guide projection 26K in the second direction is different from the length of the second development guide projections 26Y, 26M, and 26C in the second direction. Specifically, the width of the first development guide projection 26K on the opening 22A side is wider than the width of the second development guide projections 26Y, 26M, and 26C on the opening 22A side.

[0079] According to the configuration of the first modified example described above, the width of the developing groove 56 in the second direction differs to correspond to the different colors of the developing cartridge 50, thus preventing incorrect insertion of the developing cartridge 50. Furthermore, since a common drum cartridge 40 can be used with multiple developing cartridges 50, manufacturing costs can be reduced.

[0080] In the configuration of the first modified example described above, the main body housing 2 may also be configured to have a first drum guide projection and a second drum guide projection instead of the first drum guide groove 24K and the second drum guide grooves 24Y, 24M, and 24C. Alternatively, the main body housing 2 may also be configured to have a first development guide groove and a second development guide groove instead of the first development guide projection 26K and the second development guide projections 26Y, 26M, and 26C. In this case, the first drum cartridge 40K, when mounted in slot 22B, has a first drum groove extending in a first direction into which a first drum guide projection fits, and the second drum cartridges 40Y, 40M, and 40C, when mounted in slot 22B, have a second drum groove extending in a first direction into which a second drum guide projection fits. Similarly, the first developing cartridge 50K has a first developing projection that extends in a first direction and fits into a first developing guide groove when mounted in slot 22B, and the second developing cartridges 50Y, 50M, and 50 have a second developing projection that extends in a first direction and fits into a second developing guide groove when mounted in slot 22B. Furthermore, the length of the first drum guide projection in the second direction is the same as the length of the second drum guide projection in the second direction. Also, the length of the first developing guide groove in the second direction is different from the length of the second developing guide groove in the second direction.

[0081] The second to sixth modified examples will be described below with reference to Figures 9 and 10. In the following description, components similar to those in the above embodiments will be denoted by the same reference numerals, and detailed descriptions will be omitted.

[0082] As shown in Figure 9(a), in the second modified configuration, the main body housing 2 has a drum guide groove 124 and a development guide projection 126 on the upper surface of the cartridge guide section 2B. In the second direction, the width of the drum guide groove 124 tapers from the opening 22A towards the side wall 2A, and then maintains a constant width thereafter. In the second direction, the width of the development guide projection 126 tapers from the opening 22A towards the side wall 2A, widening towards the interior of the main housing 2, and then maintaining a constant width. The drum cartridge 40 has drum protrusions 146 that correspond to the shape of the drum guide groove 124. The developing cartridge 50 has developing grooves 156 that correspond to the shape of the developing guide protrusions 126. Even with this configuration, the drum cartridge 40 and the developing cartridge 50 are more easily mounted into the main body housing 2 due to the large dimensional difference on the inlet (opening 22A) side.

[0083] As shown in Figure 9(b), in the third modified configuration, the main body housing 2 has the same drum guide groove 124 and developing guide projection 126 as in the second modified configuration. On the other hand, the drum projection 246 of the drum cartridge 40 has a constant width corresponding to the width of the straight portion of the drum guide groove 124. The developing groove 256 of the developing cartridge 50 has a constant width corresponding to the width of the straight portion of the developing guide projection 126. Even with this configuration, the drum cartridge 40 and the developing cartridge 50 are easier to install into the main unit housing 2 due to the large dimensional difference at the input side.

[0084] As shown in Figure 9(c), in the fourth modified configuration, the main body housing 2 has a drum guide groove 324 and a development guide projection 326 on the upper surface of the cartridge guide section 2B. In the second direction, the width of the drum guide groove 324 narrows in a stepped manner from the opening 22A to the side wall 2A, as it moves towards the interior of the main housing 2. In the second direction, the width of the development guide projection 326 widens in a stepped manner from the opening 22A to the side wall 2A, as it moves towards the inside of the main housing 2. The drum cartridge 40 has drum protrusions 346 that correspond to the shape of the drum guide groove 324. The developing cartridge 50 has developing grooves 356 that correspond to the shape of the developing guide protrusions 326. Even with this configuration, the drum cartridge 40 and the developing cartridge 50 are easier to install into the main unit housing 2 due to the large dimensional difference at the input side.

[0085] As shown in Figure 10(a), in the fifth modified configuration, the main body housing 2 has a drum guide groove 424 and a development guide projection 426 on the upper surface of the cartridge guide section 2B. In the second direction, the width of the drum guide groove 424 is constant from the opening 22A to the side wall 2A. Similarly, the width of the development guide projection 426 in the second direction is constant from the opening 22A to the side wall 2A. Furthermore, the drum cartridge 40 has a drum projection 446 in the second direction that has a constant width corresponding to the width of the drum guide groove 424 from the opening 22A to partway towards the side wall 2A, and thereafter narrows in a tapered manner as it approaches the side wall 2A. In the developing cartridge 50, the width of the developing groove 456 in the second direction is constant, corresponding to the width of the developing guide projection 426 from the opening 22A to partway towards the side wall 2A, and thereafter widens in a tapered manner towards the side wall 2A. Even with this configuration, the drum cartridge 40 and the developing cartridge 50 are easier to install into the main unit housing 2 due to the large dimensional difference at the input side.

[0086] As shown in Figure 10(b), in the sixth modified configuration, the main body housing 2 has a drum guide groove 524 and a development guide projection 526 on the upper surface of the cartridge guide section 2B. In the second direction, the width of the drum guide groove 524 tapers as it moves from the opening 22A and side wall 2A towards the inside of the main housing 2, and remains constant in the central part. On the other hand, the width of the development guide projection 526 in the second direction is constant from the opening 22A to the side wall 2A. Furthermore, the drum projection 546 of the drum cartridge 40 has a constant width from the opening 22A to the side wall 2A. The developing groove 556 of the developing cartridge 50 tapers inward from the opening 22A and side wall 2A towards the inside of the main housing 2, and the central part has a constant width corresponding to the width of the developing guide projection 526. Even with this configuration, the drum cartridge 40 and the developing cartridge 50 are easier to install into the main unit housing 2 due to the large dimensional difference at the input side.

[0087] In the above embodiments and their modifications, the present invention was applied to a color printer 1, but the present invention is not limited thereto, and may also be applied to other image forming devices, such as monochrome printers, copiers, and multifunction devices.

[0088] The elements described in the above embodiments and modifications may be implemented in any combination. [Explanation of symbols]

[0089] 1. Color printer 2 Main unit 22A opening 22B slot 24 drum guide grooves 26 Development guide protrusion 40 Drum Cartridges 41 Photosensitive drum 46 Drum protrusions 50 developing cartridges 51 Developing roller 56 Developing groove

Claims

1. A main body housing having an opening, the main body housing having a slot extending in a first direction toward the interior of the main body housing, the main body housing including the inner surface located at the innermost part of the slot, A drum cartridge having a photosensitive drum rotatable about an axis extending in a first direction, the drum cartridge being removablely insertable into the main body housing through the opening in the first direction, A developing cartridge having a developing roller, comprising a developing cartridge that can be removably inserted into the main body housing through the opening in the first direction, With the drum cartridge and the developing cartridge mounted in the main housing, the photosensitive drum and the developing roller are arranged side by side in a second direction intersecting the first direction. The image forming apparatus is characterized in that the main housing has a drum guide groove extending in the first direction for guiding the movement of the drum cartridge, the drum guide groove has a first inclined surface, and the first inclined surface is inclined in a direction away from the developing roller in the second direction as it moves from the opening toward the inner surface of the main housing.

2. The image forming apparatus according to Claim 1, wherein the drum cartridge has a second inclined surface in the portion that is guided by the drum guide groove, and the second inclined surface is inclined in a direction away from the developing roller in the second direction as it moves toward the interior of the main body housing when the drum cartridge is mounted in the main body housing.

3. The image forming apparatus according to claim 1 or 2, characterized in that the drum guide groove has a shape that narrows in width towards the inside of the main body housing.

4. The image forming apparatus according to any one of claims 1 to 3, characterized in that the drum guide groove has a surface that is connected to the first inclined surface and extends along the first direction, located inside the main housing, more than the first inclined surface.

5. The image forming apparatus according to any one of claims 1 to 4, characterized in that the drum guide groove has a first opposing surface facing the first inclined surface, and the first inclined surface and the first opposing surface have a tapered shape in which the distance between them decreases as they move toward the interior of the main housing.

6. The drum cartridge has a first drum side wall and a second drum side wall that faces the first drum side wall in the first direction when the drum cartridge is mounted in the main housing, wherein the second drum side wall is further from the opening than the first drum side wall. The image forming apparatus according to any one of claims 1 to 5, characterized in that the drum cartridge has a drum projection that fits into the drum guide groove, and the drum projection has a tapered shape that narrows from the first drum side wall toward the second drum side wall.

7. The developing cartridge has a first developing side wall and a second developing side wall that faces the first developing side wall in the first direction when the developing cartridge is mounted in the main housing, The inner surface of the main housing and the second developing side wall of the developing cartridge have a second hole. The image forming apparatus according to any one of claims 1 to 6, characterized in that the inner surface of the main housing and the other of the second developing side wall of the developing cartridge have a second projection that engages with the second hole when the developing cartridge is mounted in the main housing.

8. The second developing side wall of the developing cartridge has the second hole, The image forming apparatus according to claim 7, characterized in that the inner surface of the main housing has the second projection.

9. The main housing has a developing guide groove for guiding the movement of the developing cartridge, The image forming apparatus according to any one of claims 1 to 8, characterized in that the developing guide groove extends in the first direction.

10. The image forming apparatus according to claim 9, characterized in that the developing guide groove has a tapered shape.

11. The image forming apparatus according to any one of claims 1 to 10, characterized in that the drum cartridge can be removed separately from the developing cartridge.

12. The image forming apparatus according to any one of claims 1 to 11, further comprising an intermediate transfer belt located above the drum cartridge and the developing cartridge when the drum cartridge and the developing cartridge are mounted in the main housing.

13. The image forming apparatus according to claim 12, further comprising a paper discharge section including a paper discharge roller configured to transport a sheet, wherein the paper discharge section is located above the intermediate transfer belt.

Images