Image forming device

Abstract

To reduce operation required for attachment and detachment of a drum unit.SOLUTION: A printer comprises: a developing device that includes a developing roller; a drum unit that includes a photoreceptor drum arranged to have its outer peripheral surface opposite to the developing roller, and has a drum bearing 23 projecting in an axial direction of the photoreceptor drum; an inside plate 50 that is opposite to an end in the axial direction of the drum unit; a first notch part 51 that is provided at a mounting position of the drum unit on the inside plate 50 and opens upward; a hook 60 that can be oscillated in a direction intersecting the axial direction along the inside plate 50; and an urging member that urges the hook 60 in a direction to approach the first notch part 51. When the hook 60 is pushed back by the drum bearing 23 inserted into the first notch part 51 from above, and the drum bearing 23 reaches a bottom 51B of the first notch part 51, the hook 60 pushes the drum bearing 23 against the first notch part 51 at a load including a downward component.SELECTED DRAWING: Figure 11

Description

[Technical Field]

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

[0002] In electrophotographic image forming apparatuses, a drum unit having a photosensitive drum and a developing device are generally configured to be detachable. For example, Patent Document 1 describes a configuration in which a side plate of the image forming apparatus main body is provided with a positioning portion and a receiving portion, and a process cartridge is attached to the image forming apparatus main body by pressing a first protrusion on the positioning portion and a second protrusion on the receiving portion. Patent Document 2 describes a configuration in which both ends of the shaft of the photosensitive drum are engaged with rails on the printer main body, and the developer unit's mounting rib is mounted on the mounting surface of the printer main body from above, so that part or all of the load of the developer unit is received from below by the mounting surface, and the process unit is supported by the printer main body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-108173 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-151568 Summary of the Invention [Problem to be solved by the invention]

[0004] In the past, when the drum unit was installed after the developing device, the drum unit was fixed by operating a lever or the like, and a mechanism was required to prevent forgetting to operate the lever.

[0005] SUMMARY OF THE INVENTION In consideration of the above circumstances, an object of the present invention is to provide an image forming apparatus that can reduce the number of operations required for attaching and detaching a drum unit. [Means for solving the problem]

[0006] In order to solve the above problem, the image forming apparatus of the present invention comprises a developing device having a developing roller, a drum unit including a photosensitive drum arranged with its outer peripheral surfaces facing the developing roller and having a protrusion protruding in the axial direction of the photosensitive drum, a side plate facing the axial end of the drum unit, a notch that opens upward and is provided in the side plate at the mounting position of the drum unit, a rocking member that can rock along the side plate in a direction intersecting the axial direction, and a biasing member that biases the rocking member in a direction approaching the notch, and is characterized in that when the rocking member is pushed back by the protrusion inserted into the notch from above and the protrusion reaches the bottom of the notch, the rocking member presses the protrusion against the notch with a load that includes a downward component.

[0007] The cutout portion may have a pair of side portions facing each other, and when the protrusion portion reaches the bottom portion of the cutout portion, the oscillating member may be configured to press the protrusion portion against one of the pair of side portions and the bottom portion of the cutout portion.

[0008] The oscillating member may have a curved portion that bulges in an arc toward the notch, and a flat inclined portion connected to the lower end of the curved portion, and the protrusion inserted into the notch from above comes into contact with the curved portion, pushing back the oscillating member, and when the protrusion reaches the bottom of the notch, the inclined portion presses the protrusion against one of the pair of side portions and the bottom of the notch.

[0009] The developing device may be configured so that it is urged in a direction to bring the developing roller closer to the photosensitive drum, and when the protrusion reaches the bottom of the notch, the inclined portion applies a load to the protrusion in a direction intersecting the urging force of the developing device. [Effects of the Invention]

[0010] According to the present invention, the operations required for attaching and detaching the drum unit can be reduced. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a front view schematically illustrating the internal configuration of a printer according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of a drum unit and a developing device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a front view showing a state in which the developing device according to the embodiment of the present invention is located at a predetermined position during image formation. [Figure 4] FIG. 10 is a front view showing a state in which the developing device according to the embodiment of the present invention is positioned closer to the drum unit than a predetermined position. [Figure 5] FIG. 2 is a perspective view of a front portion of a drum unit of a main body housing according to an embodiment of the present invention. [Figure 6] FIG. 2 is a perspective view of a front portion of a drum unit of a main body housing according to an embodiment of the present invention. [Figure 7] FIG. 2 is a perspective view of a front portion of a drum unit of a main body housing according to an embodiment of the present invention. [Figure 8] 10A and 10B are front views showing the operation of a hook according to an embodiment of the present invention. [Figure 9] 10A and 10B are front views showing the operation of a hook according to an embodiment of the present invention. [Figure 10] 10A and 10B are front views showing the operation of a hook according to an embodiment of the present invention. [Figure 11] 10A and 10B are front views showing the operation of a hook according to an embodiment of the present invention. [Figure 12] 5A and 5B are front views showing the direction of loads acting on the respective parts of the drum unit according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] First, the overall configuration of the printer 1 (an example of an image forming apparatus) will be described. Figure 1 is a front view that schematically shows the internal configuration of the printer 1. In the following description, the front side of the paper in Figure 1 is the front side (front side) of the printer 1, and left and right directions are described based on the direction when the printer 1 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr represent top, bottom, left, right, front, and rear, respectively.

[0013] The printer 1 includes a rectangular parallelepiped main body housing 3 (an example of a main body). A paper feed cassette 4 that stores sheets S and a paper feed roller 5 that feeds sheets S from the paper feed cassette 4 to the right are provided at the bottom inside the main body housing 3. An imaging device 6 that forms a toner image using an electrophotographic method is provided above the paper feed cassette 4, and a fixing device 7 that fixes the toner image to the sheet S is provided above the fixing device 7. A paper discharge roller 8 that discharges the sheet S with the fixed toner image, and a paper discharge tray 9 on which the discharged sheets S are stacked are provided above the fixing device 7.

[0014] Inside the main body housing 3, there is provided a conveying path 10 that runs from the paper feed roller 5 through the image forming device 6 and the fixing device 7 to the paper discharge roller 8. The conveying path 10 is mainly formed of plate-like members that face each other with a gap therebetween to allow the sheet S to pass through, and conveying rollers 17 that sandwich and convey the sheet S are provided at multiple locations in the conveying direction Y. A registration roller 18 is provided upstream of the image forming device 6 in the conveying direction Y. To the right of the fixing device 7, there is provided a reversing conveying path 10R that branches off from the conveying path 10 downstream of the fixing device 7 in the conveying direction Y and merges with the conveying path 10 upstream of the registration roller 18 in the conveying direction Y.

[0015] The image forming device 6 includes a photosensitive drum 11 whose potential changes when exposed to light, a charging device 12 that charges the photosensitive drum 11, an exposure device 13 that emits laser light according to image data, a developing device 14 that supplies toner to the photosensitive drum 11, an intermediate transfer unit 15 that transfers the toner image from the photosensitive drum 11 to a sheet S, and a cleaning device 16 that removes toner remaining on the photosensitive drum 11.

[0016] The intermediate transfer unit 15 includes an endless intermediate transfer belt 15B wound around a drive roller 15D and a driven roller 15N, a primary transfer roller 151 that faces the inner circumferential surface of the intermediate transfer belt 15B at a position corresponding to the photosensitive drum 11 and generates a primary transfer bias, and a secondary transfer roller 152 that faces the outer circumferential surface of the intermediate transfer belt 15B at a position corresponding to the drive roller 15D and generates a secondary transfer bias. A toner container 20 that supplies toner to the developing device 14 is connected to the developing device 14.

[0017] The image forming device 6 includes four sets of photosensitive drums 11, charging devices 12, exposure devices 13, developing devices 14, primary transfer rollers 151, cleaning devices 16, and toner containers 20, and forms a color image by superimposing four color toner images on the intermediate transfer belt 15B. Note that the present invention may also be applied to an image forming device that forms a color image using toners of three or less colors or five or more colors.

[0018] The control unit 2 includes a calculation unit and a storage unit. The calculation unit is, for example, a CPU (Central Processing Unit). The storage unit includes storage media such as ROM (Read Only Memory), RAM (Random Access Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). The calculation unit performs various processes by reading and executing control programs stored in the storage unit. Note that the control unit 2 may be realized by only an integrated circuit without using software.

[0019] The basic image formation operation of the printer 1 is as follows: When a print job for single-sided printing is input to the printer 1 from an external computer or the like, the paper feed rollers 5 feed the sheet S from the paper feed cassette 4 to the transport path 10, the registration rollers 18, whose rotation has stopped, correct any skew in the sheet S, and the registration rollers 18 feed the sheet S to the image creating device 6 at a predetermined timing. In the image creating device 6, the charging device 12 charges the photosensitive drum 11 to a predetermined potential, the exposure device 13 writes a latent image on the photosensitive drum 11, the developing device 14 develops the latent image with toner supplied from the toner container 20 to form a toner image, the primary transfer roller 151 transfers the toner image to the intermediate transfer belt 15B, and the secondary transfer roller 152 transfers the toner image to the sheet S. Next, the fixing device 7 melts the toner image while nipping and transporting the sheet S, thereby fixing the toner image to the sheet S, and the sheet ejection rollers 8 eject the sheet S to the sheet ejection tray 9. The cleaning device 16 removes toner remaining on the photosensitive drum 11. In the case of double-sided printing, the sheet S with a toner image fixed on its first surface is sent into the conveying path 10 via the reverse conveying path 10R, where the toner image is transferred to the second surface.

[0020] Next, the drum unit 21 and the developing device 14 will be described in detail. Fig. 2 is a perspective view of the drum unit 21 and the developing device 14. Fig. 3 is a front view showing the developing device 14 positioned at a predetermined position during image formation. Fig. 4 is a front view showing the developing device 14 positioned closer to the drum unit 21 than the predetermined position.

[0021] [Drum unit] The drum unit 21 (see FIG. 2) integrates the photosensitive drum 11, charging device 12, and cleaning device 16 into a drum frame 22. The drum frame 22 is provided with a drum bearing 23 that supports the drum shaft (not shown) of the photosensitive drum 11. The drum bearing 23 protrudes from the outer surface of the drum frame 22 (an example of a protrusion). The paper discharge tray 9 is hingedly connected to the main body housing 3, and the drum unit 21 is attached to a predetermined position in the main body housing 3 from above with the paper discharge tray 9 open.

[0022] [Developing device] The developing device 14 includes a developer, a screw (not shown) that agitates the developer, a developing roller 31 that holds the developer, and a developing housing 32 that houses the developer, the screw, and the developing roller 31. The developer includes toner and magnetic carriers. The developing roller 31 includes a rotating sleeve with a magnet (not shown) inside the sleeve. The developing roller 31 attracts the developer by magnetic force and forms a magnetic brush on the surface of the sleeve. A portion of the developing roller 31 is exposed from the developing housing 32. Annular gap regulating members 31S with a diameter larger than that of the sleeve are provided at both ends of the developing roller 31. The gap regulating members 31S come into contact with the outer peripheral surface of the photosensitive drum 11, so that the outer peripheral surface of the sleeve and the outer peripheral surface of the photosensitive drum 11 face each other with a predetermined gap therebetween.

[0023] The support parts 41 face both front and rear ends of the developer housing 32 and support the developer housing 32 so that it can swing about a swing shaft 42 provided below the developer roller 31. The support parts 41 are connected to the developer housing 32 by the swing shaft 42, and are integrated with the developing device 14. The developing device 14 is detachable from the main housing 3 in the vertical direction, and the support parts 41 are fixed to the main housing 3.

[0024] The biasing portion 43 is, for example, a compression coil spring, and is provided in the main body housing 3 to bias the developing housing 32 toward the drum frame 22. Fig. 3 shows a predetermined position of the developing device 14 when the drum unit 21 is attached to the main body housing 3 (predetermined position during image formation). On the other hand, Fig. 4 shows a state before the drum unit 21 is attached to the main body housing 3, in which the developing device 14 is positioned closer to the drum unit 21 than the predetermined position.

[0025] Next, we will explain the structure for supporting the drum unit 21. Figures 5 to 7 are perspective views of the front portion of the drum unit 21 in the main body housing 3. Below, we will explain the front portion of the drum unit 21 in the main body housing 3, but because the rear portion is configured in the same way, we will not explain the rear portion here.

[0026] The printer 1 includes a developing device 14 having a developing roller 31, a photosensitive drum 11 arranged with the outer circumferential surfaces of the developing roller 31 facing each other, and a drum unit 21 having a drum bearing 23 (an example of a protrusion) protruding in the axial direction of the photosensitive drum 11, an inner plate 50 (an example of a side plate) facing the axial end of the drum unit 21, a first notch 51 (an example of a notch) that opens upward and is provided in the inner plate 50 at the mounting position of the drum unit 21, a hook 60 (an example of a swinging member) that can swing along the inner plate 50 in a direction intersecting the axial direction, and a biasing member 64 that biases the hook 60 in a direction approaching the first notch 51, and when the drum bearing 23 reaches the bottom 51B of the first notch 51, the hook 60 presses the drum bearing 23 against the first notch 51 with a load that includes a downward component.

[0027] The main body housing 3 is provided with an inner plate 50 (an example of a side plate) and an outer plate 55. The inner plate 50 is provided rearward of the outer plate 55, i.e., on the drum unit 21 side. The inner plate 50 has an upper portion 50T, a lower portion 50B below the upper portion 50T, and a middle portion 50M connecting the upper portion 50T and the lower portion 50B. The lower portion 50B is located rearward of the upper portion 50T (toward the drum unit 21), and the middle portion 50M is inclined so that its rear end is located lower than its front end. The inner plate 50 is provided with a first notch 51 and a second notch 52 that open upward. The first notch 51 and the second notch 52 extend at least from the middle portion 50M to a predetermined position on the lower portion 50B.

[0028] The front drum bearing 23 of the drum unit 21 is inserted into the first cutout 51. The first cutout 51 has side portions 51S facing each other laterally and a bottom portion 51B connecting the lower ends of the side portions 51S. The side portions 51S are approximately vertical, and the bottom portion 51B is approximately horizontal.

[0029] The front end of the cleaning device 16 of the drum unit 21 is inserted into the second cutout 52. The second cutout 52 has side portions 52S facing each other laterally and a semicircular bottom portion 52B connecting the lower ends of the side portions 52S. A joint portion 53 to which the front end of the cleaning device 16 is connected is provided in front of the bottom portion 52B. A hole 53H is provided in the vertical direction in the joint portion 53, and waste toner discharged from the cleaning device 16 is guided through the hole 53H to a waste toner container (not shown). A sealant 54 is provided around the hole 53H to seal the gap between the cleaning device 16 and the joint portion 53.

[0030] A hook 60 is provided in the space between the inner plate 50 and the outer plate 55 to the left of the first cutout 51. The hook 60 secures the drum bearing 23 inserted into the first cutout 51. The hook 60 is a member whose longitudinal direction is in the up-down direction, and its lower end is supported by the outer plate 55 via a swing shaft 61 whose axial direction is in the front-to-rear direction. The right side surface of the upper part of the hook 60 (the side surface on the first cutout 51 side) has a curved portion 62 that bulges out to the right in an arc shape, and a flat inclined portion 63 that is connected to the lower end of the curved portion 62. The inclined portion 63 is inclined so that its lower end is located to the left of its upper end.

[0031] The biasing member 64 is, for example, a compression coil spring, and biases the hook 60 to the right. The outer plate 55 is provided with a facing portion 55F that faces the left side surface of the upper part of the hook 60, and the biasing member 64 is provided between the left side surface of the hook 60 and the facing portion 55F.

[0032] Next, the operation of the above configuration will be described. Figures 8 to 11 are front views showing the operation of the hook 60. Here, the operation when the drum unit 21 is installed after the developing device 14 has been installed will be described. Before the drum unit 21 is installed, the upper end of the hook 60 is tilted toward the first notch 51 by the biasing member 64.

[0033] When a user holds the drum unit 21, aligns the drum bearing 23 with the upper end of the first notch 51, aligns the front end of the cleaning device 16 with the upper end of the second notch 52, and then lowers the drum unit 21, the drum bearing 23 first comes into contact with the upper end of the curved portion 62 of the hook 60 (see FIG. 8). As the drum unit 21 is lowered, the contact position between the drum bearing 23 and the curved portion 62 moves downward, and the hook 60 is pushed to the left (see FIG. 9). When the drum bearing 23 reaches the lower end of the curved portion 62, the hook 60 is pushed all the way to the left (see FIG. 10). When the drum unit 21 is further lowered, the drum bearing 23 comes into contact with the inclined portion 63 of the hook 60, and the hook 60 is pushed back to the right by the biasing member 64 (see FIG. 11).

[0034] At this time, the inclined portion 63 of the hook 60 comes into contact with the upper left portion of the outer circumferential surface of the drum bearing 23, and applies a load F1 in a downward and rightward direction to the drum bearing 23. The load F1 presses the drum bearing 23 against the right side portion 51S and bottom portion 51B of the first cutout portion 51. As a result, the drum bearing 23 is restrained at three points: the inclined portion 63 of the hook 60, and the right side portion 51S and bottom portion 51B of the first cutout portion 51, so that the drum bearing 23 is accurately positioned.

[0035] If a flat inclined portion were provided instead of the curved portion 62, the inclined portion would become closer to horizontal as the drum unit 21 is lowered, and the upward component of the force with which the hook 60 pushes back against the drum bearing 23 would increase. Therefore, the user would need to increase the force with which they push the drum unit 21.

[0036] In contrast, in this embodiment, the direction of the tangent to the curved portion 62 at the contact position between the drum bearing 23 and the curved portion 62 remains approximately constant during the process of lowering the drum unit 21. Therefore, when the drum unit 21 is lowered, the magnitude of the upward component of the force with which the hook 60 pushes back against the drum bearing 23 hardly changes, and the user can push the drum unit 21 with an approximately constant force.

[0037] Here, we consider the load acting on each part of the drum unit 21. Figure 12 is a front view showing the direction of the load acting on each part of the drum unit 21. Note that the arrows shown in the figure indicate only the direction of the load, and the length of the arrow does not indicate the magnitude of the load.

[0038] The drum drive gear 24 is engaged with a drum driven gear (not shown) provided on the drum shaft of the photosensitive drum 11. The drum drive gear 24 drives the photosensitive drum 11 by transmitting a driving force generated by a motor (not shown) to the drum driven gear.

[0039] As described above, the hook 60 applies a load F1 to the drum bearing 23. The biasing portion 43 of the developing device 14 applies a load F2 to the photosensitive drum 11 via the gap restricting member 31S. The joint portion 53 pushes the cleaning device 16 upward with a load F3 via the sealing material 54. The drum drive gear 24 applies a load F4 to the drum driven gear in the direction of the line of action. The line of action is a straight line that intersects with the common tangent to the pitch circle of the drum drive gear 24 and the pitch circle of the drum driven gear in a direction that forms a pressure angle.

[0040] Focusing on the load in the vertical direction, the load acting upward on the drum unit 21 is the sum of the upward component of load F2 and load F3. The load acting downward on the drum unit 21 is the sum of the downward component of load F1, the downward component of load F4, and gravity acting on the drum unit 21. If the downward load is greater than the upward load, the drum unit 21 is prevented from floating up.

[0041] The load F4 includes a downward component, in other words, the line of action between the drum drive gear 24 and the drum driven gear slopes downward to the left, which acts to pull the drum unit 21 downward. This action has the same effect as increasing the load F1, making it possible to use a low-cost biasing member 64.

[0042] On the other hand, when focusing on horizontal loads, the load acting to the right on the drum unit 21 is the sum of the rightward component of load F1 and the rightward component of load F2. The load acting to the left on the drum unit 21 is the leftward component of load F4. If the load acting to the right is greater than the load acting to the left, the drum bearing 23 is pressed against the right side portion 51S of the first cutout portion 51, and the drum unit 21 is accurately positioned in the horizontal direction.

[0043] The printer 1 according to the present embodiment described above includes the developing device 14 having the developing roller 31, the drum unit 21 including the photosensitive drum 11 arranged with the outer circumferential surfaces of the developing roller 31 and the photosensitive drum 11 facing each other, and having a drum bearing 23 (an example of a protrusion) protruding in the axial direction of the photosensitive drum 11, an inner plate 50 (an example of a side plate) facing the end of the drum unit 21 in the axial direction, and a first cutout 23 (an example of a side plate) that is open upward and provided at the mounting position of the drum unit 21 on the inner plate 50. The drum unit 21 includes a notch 51 (an example of a notch), a hook 60 (an example of a swinging member) that can swing along the inner plate 50 in a direction intersecting the axial direction, and a biasing member 64 that biases the hook 60 in a direction approaching the first notch 51. When the drum bearing 23 is inserted into the first notch 51 from above and the drum bearing 23 reaches the bottom 51B of the first notch 51, the hook 60 presses the drum bearing 23 against the first notch 51 with a load that includes a downward component. With this configuration, the drum unit 21 can be attached simply by pushing down the drum unit 21, and can be detached simply by pulling up the drum unit 21. This reduces the number of operations required to attach and detach the drum unit 21.

[0044] Furthermore, in the printer 1 according to this embodiment, the first cutout 51 has a pair of side portions 51S that face each other, and when the drum bearing 23 reaches the bottom portion 51B of the first cutout 51, the hook 60 presses the drum bearing 23 against one of the pair of side portions 51S and the bottom portion 51B of the first cutout 51, thereby enabling the drum unit 21 to be positioned accurately.

[0045] Furthermore, in the printer 1 according to this embodiment, the hook 60 has a curved portion 62 that bulges in an arc toward the first notch 51, and a flat inclined portion 63 that connects to the lower end of the curved portion 62. When the drum bearing 23 is inserted into the first notch 51 from above, it comes into contact with the curved portion 62, pushing back the hook 60. When the drum bearing 23 reaches the bottom 51B of the first notch 51, the inclined portion 63 presses the drum bearing 23 against one of the pair of side portions 51S of the first notch 51 and the bottom 51B, thereby suppressing fluctuations in the force that presses the drum unit 21.

[0046] Furthermore, in the printer 1 according to this embodiment, the developing device 14 is biased in a direction that brings the developing roller 31 closer to the photosensitive drum 11, and when the drum bearing 23 reaches the bottom 51B of the first cutout 51, the inclined portion 63 applies a load to the drum bearing 23 in a direction that intersects with the bias of the developing device 14. With this configuration, the load that the inclined portion 63 applies to the drum bearing 23 is less likely to be offset by the bias of the developing device 14, so the drum unit 21 can be securely fixed with a small load.

[0047] The above embodiment may be modified as follows.

[0048] In the above embodiment, an example has been shown in which the drum bearing 23 also serves as the protrusion, but the protrusion may be provided at a location separate from the drum bearing 23.

[0049] Instead of the inclined portion 63 of the hook 60, the curved portion 62 may be extended downward from the lower end of the curved portion 62 in the above embodiment. [Explanation of symbols]

[0050] 1. Printer (image forming device) 11 Photosensitive drum 14 Developing device 21 Drum unit 23 Drum bearing (protrusion) 31 Developing roller 50 Inner plate (side plate) 51 First notch (notch) 51S side 51B Bottom 60 Hook (swinging member) 62 Curved section 63 Slope 64 biasing member

Claims

1. a developing device including a developing roller; a drum unit including a photosensitive drum disposed so that the outer circumferential surfaces of the developing roller and the photosensitive drum face each other, the photosensitive drum having a protrusion protruding in an axial direction of the photosensitive drum; a side plate facing an end portion of the drum unit in the axial direction; a notch that opens upward and is provided in the side plate at a mounting position of the drum unit; a swinging member that is swingable along the side plate in a direction intersecting the axial direction; a first biasing member that biases the swinging member in a direction approaching the notch; a second biasing member that biases the developing device toward the drum unit, When the protrusion inserted into the notch from above pushes back the swinging member and the protrusion reaches the bottom of the notch, the swinging member is biased by a first biasing member to press the protrusion against the notch with a first load including a downward component, and a second biasing member applies a second load including an upward component to the photosensitive drum via the developing roller, 1. An image forming apparatus, wherein a downward load including at least a downward component of a first load and gravity acting on a drum unit is greater than an upward load including at least an upward component of a second load.

2. a joint portion that pushes the drum unit upward with a third load, 2. The image forming apparatus according to claim 1, wherein the upward load includes the third load.

3. a drum drive gear that drives the photosensitive drum with a fourth load including a downward component; 3. The image forming apparatus according to claim 1, wherein the downward load includes a downward component of the fourth load.

Images