Image forming device

Abstract

To provide a technique that can stabilize a contact state between a toner electrifying member and a photoconductor drum, and improve and maintain performance of the toner electrifying member to electrify a transfer residual toner.SOLUTION: An image forming apparatus comprises: a support member that rotatably supports an end of an image carrier in a longitudinal direction along an axis of rotation of the image carrier; and a brush that is in contact with the image carrier. The support member has a first contact surface and a second contact surface that are in contact with an outer peripheral surface of the end at different positions from each other on a cross section perpendicular to the rotation axis. The first contact surface and second contact surface are such that, with respect to a virtual surface including the rotation axis and intersecting the brush, tangent lines passing through contact points with the outer peripheral surface of the end on the cross section intersect each other in an area on the virtual surface on the side of the brush with respect to the rotation axis. In image forming operation, the image carrier rotates in contact with the contact member to come into contact with the first contact surface, the second contact surface, a third contact surface, and a fourth contact surface, and is rotatably supported.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that utilizes an electrophotographic recording method. [Background technology]

[0002] In image forming devices that use electrophotographic recording, such as laser printers, copiers, and facsimiles, the surface of an electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) is uniformly charged by a charging means, and the charged photosensitive drum surface is exposed by an exposure means to form an electrostatic latent image. This electrostatic latent image is then developed by a developing means to form a toner image using a developer (hereinafter referred to as a toner), and this toner image is transferred to a recording material by a transfer means. Thereafter, the toner image is fixed on the recording material by a fixing means, and the image is output.

[0003] Here, in order to reduce the size of image forming apparatuses, a method has been proposed in which residual toner on the photosensitive drum after transfer (hereinafter referred to as "transfer residual toner") is cleaned simultaneously with development using a simultaneous development cleaning device, without providing a dedicated image carrier cleaning device. In image forming apparatuses that employ a so-called cleanerless system, toner particles remaining on the photosensitive drum from the previous image formation are collected by the developing device and reused as developer, which is advantageous in terms of environmental protection by not generating waste toner.

[0004] On the other hand, problems such as poor charging due to transfer residual toner adhering to the charging means, and positive ghosts due to transfer residual toner not being collected by the simultaneous development and cleaning means have occurred. Therefore, Patent Document 1 discloses an example in which a toner (developer) charging member is provided to align the polarity of the transfer residual toner. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-183905 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if the contact pressure between the photosensitive drum and the toner charging member is low, the residual toner cannot be charged and adheres to the charging means, resulting in charging defects. Furthermore, if the contact pressure between the photosensitive drum and the toner charging member is high, the toner charging member deforms, resulting in uneven pressure distribution. Residual toner passes through locally low-pressure areas, resulting in vertical stripe-like charging defects. In other words, if the contact state between the toner charging member and the photosensitive drum is unstable, the charging of the residual toner is disrupted, which can result in fogging and vertical stripes. Furthermore, in configurations where the toner charging member is not pressed toward the photosensitive drum but is fixed, the occurrence of image defects such as the fogging and vertical stripes described above is more pronounced.

[0007] The present invention aims to provide a technology that can stabilize the contact state between a toner charging member and a photosensitive drum, improve the charging performance of the toner charging member against transfer residual toner, and maintain this performance. [Means for solving the problem]

[0008] In order to achieve the above object, an image forming apparatus according to the present invention comprises: an image carrier that is driven to rotate; a first charging means for charging the surface of the image carrier; Exposing the electrostatic latent image formed on the surface of the image carrier charged by the first charging means a developing means for supplying a developer to the developer portion to form a developer image; a transfer means for transferring a developer image from the image carrier to a transfer material; a second charging means for charging residual developer remaining on the image carrier without being transferred to a transfer material before the first charging means charges the image carrier, the second charging means having a brush that comes into contact with the surface of the image carrier at a contact portion; a first support member that rotatably supports one end of the image carrier in a longitudinal direction along a rotation axis of the image carrier; a second support member that rotatably supports the other end of the image carrier in the longitudinal direction; Equipped with At least one of the first charging means, the developing means, and the transfer means has a configuration in which it contacts the image carrier, and an image forming apparatus capable of performing an image forming operation of forming an image on a transfer material, the first support member has a first contact surface and a second contact surface that come into contact with the outer circumferential surface of the one end at different positions in a cross section perpendicular to the rotation axis of the image carrier; tangents of the first contact surface and the second contact surface passing through points of contact with the outer peripheral surface of the one end in the cross section intersect with an imaginary plane that includes the rotation axis and intersects with the contact portion, in a region of the imaginary plane that is closer to the brush than the rotation axis, the second support member has a third contact surface and a fourth contact surface that contact the outer circumferential surface of the other end at different positions in the cross section, tangents of the third contact surface and the fourth contact surface passing through points of contact with the outer peripheral surfaces of the other ends in the cross sections intersect with the imaginary plane in regions on the imaginary plane that are closer to the brush than the rotation axis, In the image forming operation, the image carrier is rotatably supported by contacting the first contact surface, the second contact surface, the third contact surface, and the fourth contact surface as a contact member included in at least one of the first charging means, the developing means, and the transfer means abuts against and rotates. [Effects of the Invention]

[0010] According to the present invention, the contact state between the toner charging member and the photosensitive drum is stabilized, and the transfer residual toner can be effectively and stably charged by the toner charging member. [Brief explanation of the drawings]

[0011] [Figure 1] Schematic cross-sectional view of an image forming apparatus according to a first embodiment. [Figure 2]Schematic diagram of a brush member in Example 1 [Figure 3] Schematic diagram of a photosensitive drum in Example 1 [Figure 4] Schematic cross-sectional view of a bearing member in Example 1 [Figure 5] 1 is a schematic cross-sectional view of a state in which a photosensitive drum shaft portion and a bearing member are fitted together and a brush member in Example 1. [Figure 6] Schematic diagram showing the relationship between the direction of resultant force F and the contact surface in Example 1. [Figure 7] Graph showing the amount of fluctuation of the photosensitive drum in Example 1 and a conventional configuration [Figure 8] 1 is a schematic cross-sectional view of an image forming apparatus according to a first modification of the first embodiment; [Figure 9] 1 is a schematic cross-sectional view of a state in which a photosensitive drum shaft portion and a bearing member are fitted together, and a brush member in a first modified example of the first embodiment; [Figure 10] 10 is a schematic cross-sectional view of a state in which a photosensitive drum shaft portion and a bearing member are fitted together in a second modified example of the first embodiment. [Figure 11] Schematic cross-sectional view of an image forming apparatus according to a second embodiment. [Figure 12] In the image forming apparatus of Example 2, the transfer roller separates from the photosensitive drum when the door is opened and closed. [Figure 13] Schematic cross-sectional view of an image forming apparatus as a comparative example in Example 2. [Figure 14] In an image forming apparatus that is a comparative example of Example 2, the transfer roller separates from the photosensitive drum when the door is opened and closed. [Figure 15] 10A and 10B are schematic cross-sectional views of the photosensitive drum shaft and the bearing member fitted together and the brush member when an image is formed and when the door is open in the second embodiment; [Figure 16] 10A and 10B are schematic cross-sectional views of the photosensitive drum shaft and the bearing member during image formation and when the door is open, and the brush member in a comparative example of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, with reference to the drawings, a detailed description will be given of an embodiment of the present invention. Note that the dimensions, materials, shapes, and relative positions of the components described in the embodiment may be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions. In other words, the scope of the present invention is not limited to the following embodiment.

[0013] Example 1 (Overall configuration of image forming apparatus) The overall configuration of the image forming apparatus A will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing the schematic configuration of the image forming apparatus A according to an embodiment of the present invention, and each component is shown in a simplified manner.

[0014] 1, 5, 6, 8 to 16 show the image forming conditions as the normally assumed installation conditions. The diagram shows the configuration when the device 1 is placed on a horizontal installation surface, with the left-right direction of the paper corresponding to the horizontal direction and the up-down direction of the paper corresponding to the up-down direction of the device (gravity direction, vertical direction).

[0015] The image forming apparatus A according to this embodiment includes a photosensitive drum 1, which is a photosensitive member, a charging device 2, an exposure device 3, a developing device 4, a transfer device 5, and a fixing device 6. The charging device 2 charges the surface of the photosensitive drum 1. The exposure device 3 forms an electrostatic latent image corresponding to image data on the charged photosensitive drum 1. The developing device 4 develops the electrostatic latent image formed on the surface of the photosensitive drum 1 with toner (developer) T. The transfer device 5 sandwiches a recording material R between itself and the photosensitive drum 1 and transfers the toner image onto the recording material R. The fixing device 6 heats and presses the recording material R to fix the toner image (developer image) onto the recording material R. The image forming apparatus A also includes a power supply (not shown) for applying a predetermined voltage to the charging device 2, the developing device 4, the transfer device 5, etc.

[0016] In the image forming apparatus A according to this embodiment, a part of the process means capable of performing the image forming operation is configured as a process cartridge that is detachably attached to the main body of the image forming apparatus A. The process cartridge is configured so that the developing device 4 as a developing unit, and the photosensitive drum 1, the charging device 2, and the toner charging device 8 (described later) as a photosensitive unit, can be attached to and detached from the main body of the image forming apparatus A either individually or as a whole.

[0017] The photosensitive drum 1 is an image carrier in which a negatively chargeable organic photosensitive material is molded on a cylindrical cylinder. The photosensitive drum 1 has a diameter of 24 mm and is driven to rotate in a predetermined direction (clockwise in the drawing) at a predetermined process speed by a motor. In this embodiment, the photosensitive drum 1 is driven to rotate at a process speed of 139 mm / sec.

[0018] The charging device 2 is a charging means in which the charging roller 2, to which a desired charging voltage is applied by a power source (not shown), contacts the rotating photosensitive drum 1 with a predetermined pressure, thereby uniformly charging the surface of the photosensitive drum 1 to a predetermined potential. In this embodiment, the photosensitive drum 1 is negatively charged by the charging roller 2. The potential charged by the charging device 2 is called the dark potential.

[0019] The exposure device 3 is an exposure means that performs exposure corresponding to image information input from an external device or a reading device. There are scanner units that scan the surface of the photosensitive drum 1 with a semiconductor laser, and LED exposure devices that have an LED array in which multiple LEDs are arranged along the longitudinal direction of the photosensitive drum 1. In this embodiment, a scanner unit was used. The potential that is attenuated to near the ground potential when the exposure device exposes the photosensitive drum surface at the dark potential is called the bright potential.

[0020] The developing device 4 is a developing means including a developing roller 41 as a developer carrier that carries developer, a developing container that forms the frame of the developing device 4, a supply roller 42 that can supply developer to the developing roller 41, and a developing blade 43 that regulates the amount of developer. The developing roller 41 and the supply roller 42 are rotatably supported by the developing container. The developing roller 41 is disposed at the opening of the developing container so as to face the photosensitive drum 1. The supply roller 42 rotatably contacts the developing roller 41, and the toner contained in the developing container as the developer is applied to the surface of the developing roller 41 by the supply roller 42. The developing blade 43 is an elastic member that is bent against its elasticity and is disposed in contact with the developing roller 41. The toner carried on the surface of the developing roller 41 by the developing blade 43 forms a predetermined layer thickness and is transported to a developing section that faces the photosensitive drum 1.

[0021] The developing device 4 of this embodiment uses a contact development method. That is, the toner layer carried on the developing roller 41 comes into contact with the photosensitive drum 1 in a developing section (developing area) where the photosensitive drum 1 and the developing roller 41 face each other. A developing voltage is applied to the developing roller 41 by a power source (not shown). Under the developing voltage, the toner carried on the developing roller 41 is transferred to the photosensitive drum 1. The electrostatic latent image is developed into a toner image by transferring the toner from the developing roller 41 to the drum surface according to the potential on the surface of the developing roller 41.

[0022] The toner used in the image forming apparatus A of this embodiment is, for example, a polymerized toner produced by a polymerization method, spherical with a particle size of 6 μm, and normally charged negatively. The toner used in the image forming apparatus A of this embodiment is a so-called non-magnetic one-component developer, which does not contain a magnetic component and is supported on the developing roller 41 mainly by intermolecular forces and electrostatic forces (image forces). In addition to toner particles, one-component developers may also contain additives (e.g., wax or silica particles) to adjust the fluidity and charging performance of the toner. Alternatively, a magnetic one-component developer containing a magnetic component or a two-component developer composed of non-magnetic toner and a magnetic carrier may be used. When a magnetic developer is used, a cylindrical developing sleeve with a magnet disposed inside is used as the developer carrier.

[0023] The transfer device 5 is a transfer means that transfers the toner image carried on the photosensitive drum 1 onto the recording material R by means of a transfer roller 5 as a transfer member to which a transfer voltage is applied from a power supply (not shown). The recording material R onto which the toner image has been transferred is conveyed to a fixing device 6.

[0024] The fixing device 6 is a fixing means of a thermal fixing type that fixes an image by heating and melting the toner on the recording material R. The fixing device 6 includes a fixing film, a fixing heater such as a ceramic heater that heats the fixing film, a thermistor that measures the temperature of the fixing heater, and a pressure roller that is pressed against the fixing film.

[0025] The recording material R that has passed through the fixing device 6 is discharged to the outside (outside the machine) of the image forming apparatus A by a pair of discharge rollers as a discharge means, and is loaded onto a discharge tray as a stacking section formed on the top of the printer body.

[0026] Here, the image formation process is the period during which an electrostatic image is formed on the photosensitive drum 1, the electrostatic image is developed (a toner image is formed), the toner image is transferred, the toner image is fixed, and the image formation time refers to this period. More specifically, the timing of the image formation time differs depending on the position where the electrostatic image is formed, the toner image is formed, the toner image is transferred to the transfer material (recording material, intermediate transfer body), and the toner image is fixed to the recording material. Therefore, the image formation operation may be defined as up to the transfer of the toner image, or up to the fixation of the toner image.

[0027] [Recovery of residual toner after transfer] This embodiment employs a cleanerless configuration in which residual toner remaining on the photosensitive drum 1 without being transferred to the recording material R is collected and reused in the developing device 4. That is, the developing device 4 simultaneously performs a developing operation in which toner is supplied to the exposed portion of the electrostatic latent image formed on the surface of the photosensitive drum 1 to form a toner image, and a cleaning operation in which residual toner (residual developer) from the non-exposed portion is collected. The residual toner is removed by the following process.

[0028] The image forming apparatus A according to this embodiment includes a toner charging device (developer charging device) 8 as a second charging means. The toner charging device 8 is disposed downstream of a transfer unit that faces the transfer device 5 and upstream of a charging unit that faces the charging device 2 in the rotation direction of the photosensitive drum 1. The toner charging device 8 includes a brush member 80 that serves as a toner charge control member that contacts the surface of the photosensitive drum 1, and is fixed to a frame 51.

[0029] In this embodiment, the normal charge polarity of the toner used in image formation is negative, but the transfer residual toner contains a mixture of positively charged toner and negatively charged toner that does not have sufficient charge. The transfer residual toner is re-transferred to negative polarity by the brush member 80. In this embodiment, the contact state between the photosensitive drum 1 and the brush member 80 is stabilized by a support and positioning configuration for the photosensitive drum 1, which will be described later, and the charging performance of the residual toner after transfer is improved.

[0030] The toner, which has been negatively charged again by the brush member 80, reaches the developing unit as the photosensitive drum 1 rotates. Meanwhile, the surface area of ​​the photosensitive drum 1 that has passed through the charging unit is exposed by the exposure device 3 with the toner still attached to the surface, and an electrostatic latent image is formed.

[0031] Here, the behavior of toner on the surface of the photosensitive drum 1 that has reached the developing unit will be described separately for the non-exposed and exposed areas of the photosensitive drum 1. The non-exposed area is an area where a potential that prevents toner from adhering is formed in the electrostatic latent image formed on the photosensitive drum 1 by exposure by the exposure device 3, while the exposed area is an area where a potential that allows toner to adhere is formed. The non-exposed area may be referred to as a non-developed area, non-image area, or non-printed area depending on the image formation process. Similarly, the exposed area may be referred to as a developed area, image area, or printed area depending on the image formation process. Note that, depending on the charging characteristics of the toner, the non-exposed area may be an area where toner adheres and the exposed area may be an area where toner does not adhere. In such cases, the names of the non-developed area, non-image area, or non-printed area and the developed area, image area, or printed area are reversed.

[0032] The toner adhering to the non-exposed portion of the photosensitive drum 1 is transferred to the developing roller 41 in the developing section due to the potential difference between the potential of the non-exposed portion of the photosensitive drum 1 (dark area potential) and the developing voltage, and is then collected in the developing container. This is because in this embodiment, the normal charging polarity of the toner is negative, and the developing voltage applied to the developing roller 41 is positive relative to the potential of the non-exposed portion. The toner collected in the developing container is stirred and dispersed with the toner in the developing container by the stirring member, and is carried by the developing roller 41 to be used again in the developing process.

[0033] On the other hand, the toner adhering to the exposed portion of the photosensitive drum 1 does not transfer from the photosensitive drum 1 to the developing roller 41 in the developing section, but remains on the drum surface. This is because in this embodiment, the normal charging polarity of the toner is negative, and the developing voltage applied to the developing roller 41 is negative relative to the potential of the exposed portion (light portion potential). The toner remaining on the drum surface is carried by the photosensitive drum 1 together with other toner transferred from the developing roller 41 to the exposed portion, and moves to the transfer section, where it is transferred to the recording material R.

[0034] In this way, the cleanerless configuration eliminates the need for installation space for a collection container to collect residual toner, etc., making it possible to further miniaturize the image forming device, and also reduces printing costs by reusing residual toner.

[0035] The configuration of the brush member of this embodiment will be described below with reference to Fig. 2. Fig. 2(a) is a diagram showing a cross section of the brush member 80 in a standalone state (not in contact with the photosensitive drum 1) taken along an imaginary plane perpendicular to the rotation axis of the photosensitive drum 1. Fig. 2(b) is a diagram showing the above cross section of the brush member 80 in a state in contact with the photosensitive drum 1.

[0036] As shown in FIG. 2(a), when the brush member 80 is in a standalone state (natural state), i.e., when no external force is being applied to bend the conductive threads 81, the distance from the base cloth 82 to the tip of the conductive thread 81 exposed therefrom is defined as L1. In this embodiment, L1 is 6.5 mm. The brush member 80 has the base cloth 82 fixed to a support member (not shown) installed at a predetermined position in the image forming apparatus A by a fixing means such as double-sided tape so that the tip of the conductive thread 81a contacts the photosensitive drum 1. In other words, the base cloth 82 is fixed so that when the brush member 80 and the photosensitive drum 1 are virtually overlapped without considering deformation in terms of the positional relationship seen in the direction of the rotation axis of the photosensitive drum 1, the tip of the conductive thread 81a is positioned so as to intrude into the photosensitive drum 1. In this embodiment, the clearance between the support member and the photosensitive drum 1 is The roller is fixed. And, let the shortest distance from the base fabric 82 of the brush member 80 fixed to the support member to the photosensitive drum 1 be L2. In this embodiment, the difference between L2 and L1 is defined as the amount of intrusion of the brush member 80 into the photosensitive drum 1. In this embodiment, the amount of intrusion of the brush member 80 into the photosensitive drum 1 is 1 mm. Therefore, the distance corresponding to L2 in this embodiment is 5.5 mm.

[0037] As shown in FIG. 2(b), since L2 < L1, in the usage state of the brush member 80, that is, when the brush member 80 is fixed to the image forming apparatus A and abuts on the surface of the photosensitive drum 1, the tip side of the conductive yarn 81a extending from the base fabric 82 bends toward the rotation direction of the photosensitive drum 1. A region on the tip side including the tip of the bent conductive yarn 11a contacts the circumferential surface of the photosensitive drum 1 to form a contact portion 81b.

[0038] Also, in this embodiment, as shown in FIG. 2(a), when the brush member 80 is in a single state, the length L3 of the brush member 80 in the circumferential direction (hereinafter referred to as the "short side direction") of the photosensitive drum 1 is 5 mm. Also, in this embodiment, the length of the brush member 80 in the longitudinal direction (the direction parallel to the rotation axis of the photosensitive drum 1) is 216 mm. Thereby, with respect to the rotation axis direction of the photosensitive drum 1, the brush member 80 can contact the entire area of the image forming region (the region where a toner image can be formed) on the photosensitive drum 1. Also, in this embodiment, the thickness of the conductive yarn 81 is 2 denier (representing the thickness of a yarn with a weight of 2 g for 9000 m), and the density is 280 kF / inch 2 (kF / inch 2 is a unit of the density of the brush and indicates the number of filaments per square inch).

[0039] The length of the brush member 80 in the short direction (the circumferential direction of the photosensitive drum 1, the direction parallel to the rotation direction) is preferably 3 mm or more from the viewpoint of long life. The length of the brush member 80 in the long direction can be changed appropriately depending on the maximum paper passing width of the image forming apparatus A (the maximum length of the image forming area in the direction of the rotation axis of the photosensitive drum 1). The thickness and density of the conductive threads 81 are 1 to 6 denier and 150 to 350 kF / inch, respectively, from the viewpoint of paper dust collection ability. 2 It is preferable that:

[0040] A predetermined brush voltage (brush bias) is applied to the brush member 80 by a power supply (not shown). In this embodiment, during image formation, a negative DC voltage is applied as the brush voltage to the brush member 80. In this embodiment, the brush voltage during image formation is, for example, −300 V.

[0041] Here, the contact state between the conductive threads 81a of the brush member 80 and the surface of the photosensitive drum 1 is contact between each of the multiple conductive threads 81a and the surface of the photosensitive drum 1, and from a microscopic perspective, there may be gap regions between adjacent conductive threads 81a that do not contact the surface of the photosensitive drum 1. In other words, strictly speaking, it is difficult to clearly define the contact portion 81b between the bundle of conductive threads 81a of the brush member 80 and the photosensitive drum 1 as a single region. Therefore, in this embodiment, a single region defined as follows is assumed to be the region corresponding to the contact portion 81b.

[0042] That is, it is assumed that an area of ​​the conductive thread 81a, whose length (L1): 6.5 mm corresponds to a penetration depth (L1-L2): 1 mm, contacts the circumferential surface of the photosensitive drum 1. Furthermore, it is assumed that the length (L3): 5 mm of the brush member 80 in the circumferential direction of the photosensitive drum is the length (width) of the bundle of conductive threads 81a in the same direction. It is also assumed that the conductive threads 81a, which contact the circumferential surface of the photosensitive drum 1 with a contact area of ​​1 mm, form a row over a range of 5 mm in the circumferential direction of the photosensitive drum, and that this row extends in the longitudinal direction of the circumferential surface of the photosensitive drum 1 over a range of 216 mm, which corresponds to the longitudinal width of the brush member 80. In this embodiment, one approximately rectangular area (1 mm x 5 mm x 216 mm) defined by the above dimensional relationship is the area corresponding to the contact portion 81b. The method for defining the contact area is not limited to the above method, and other methods may be used.

[0043] [Photosensitive drum support and positioning structure] If the penetration depth of the brush member 80 into the photosensitive drum 1 is small, the transfer residual toner cannot be charged and adheres to the charging means, resulting in charging defects. Also, if the penetration depth of the brush member 80 into the photosensitive drum 1 is large, the brush member deforms, resulting in uneven pressure distribution, and the transfer residual toner slips through areas with locally low pressure, resulting in vertical streaks in charging defects. In other words, in a configuration in which the brush member 80 is fixedly disposed, the support and positioning configuration for the photosensitive drum 1 is an important element in the cleaner-less configuration of this embodiment.

[0044] Here, we will explain the configuration for positioning and supporting the photosensitive drum 1 in this embodiment (configuration of the drum support device). Note that with regard to the shaft portion 71 and the bearing member 90, many parts use members with similar shapes and effects on the non-drive side and drive side of the photosensitive drum rotation shaft. When using these in the explanation, the same numbers will be used for both the non-drive side and the drive side, and the suffix a will be added to those indicating the non-drive side, and the suffix b will be added to those indicating the drive side. Furthermore, those without the suffix a or b will apply to both the non-drive side and the drive side.

[0045] As shown in FIGS. 3, 4, and 5, the photosensitive drum 1 has a cylinder 11 coated with a photosensitive layer and shafts 71 provided at one and the other longitudinal ends of the cylinder 11 for supporting the cylinder 11. That is, the shafts 71 are provided for supporting the photosensitive drum 1. More specifically, flanges 70 are fixed to both ends of the cylinder 11. Cylindrical shafts 71a, 71b with a diameter smaller than the outer diameter of the cylinder 11 protrude from a flange 70a at one end (non-drive side) and a flange 70b at the other end (drive side). A drum coupling 72 that engages with a main body coupling of the image forming apparatus main body is provided at the tip of the shaft 71b of the flange 70b at the other end (drive side). The entire axial area of ​​the shafts 71a and 71b of the photosensitive drum 1 is slidably supported by the inner surfaces of holes 91 (91a, 91b) (first hole, second hole) formed in a bearing member 90 (90a, 90b) serving as a support member. In a cartridge-type device such as the image forming apparatus A of this embodiment, the bearing member 90 is provided in the frame 51 of the cartridge, and in a device that is not a cartridge-type device, the bearing member 90 is provided in the frame of the image forming apparatus main body. This allows the photosensitive drum 1 to be rotatably supported with respect to the cartridge or the apparatus main body. Here, being slidable means that there is an appropriate clearance between the outer surface of the shafts and the inner surface of the holes, and that frictional impediments to sliding are sufficiently suppressed.

[0046] Furthermore, the bearing member 90a as a first support member supports one longitudinal end of the photosensitive drum 1. This bearing member 90a has a hole 91a as a first hole that rotatably supports the shaft portion 71a. Furthermore, the bearing member 90b as a second support member supports the other longitudinal end of the photosensitive drum 1. This bearing member 90b has a hole 92b as a second hole that rotatably supports the shaft portion 71b.

[0047] As described above, the photosensitive drum 1 is supported by having the shaft 71 rotatably inserted into the hole 91 of the bearing member 90. At this time, pressing forces are applied to the photosensitive drum 1 by a plurality of process means such as the charging roller 2, the developing roller 40, and the transfer roller 5. As a result, the photosensitive drum 1 (shaft 71) is pressed against one side of the inner surface of the hole 91. This positions the photosensitive drum 1 relative to the frame 51 that supports it.

[0048] Next, the positioning configuration will be described in detail. As mentioned above, the charging roller 2 and the like as a process means are in contact with the photosensitive drum 1 as a contact member with a predetermined elastic pressing force (elastic biasing force). The pressing force acting on the photosensitive drum 1 includes, for example, the pressing force due to the contact of the charging roller 2, the pressing force due to the contact of the developing roller 40, the friction force of the developing roller 40 against the rotating photosensitive drum 1, and the force coupled to the drum coupling 72 of the photosensitive drum 1 and applied to the photosensitive drum 1. These include the meshing force between a main body gear (not shown) provided in the main body A that transmits rotational force to a main body coupling (not shown) that transmits the rotational force, and a main body drive gear (not shown) that meshes with the main body gear to transmit the rotational force to the main body gear, the pressing force of the transfer roller 50, the weight of the photosensitive drum 1, and the frictional force of the conveyed recording medium R. The pressing force due to the contact of the developing roller 40 is related to the elastic force of the developing pressure spring, the meshing force with a developing drive gear (not shown) that meshes with a main body drive gear (not shown) provided in the apparatus main body A to transmit the rotational drive force to the developing roller 40, and the pressing force of the supply roller 43, etc.

[0049] In this embodiment, the resultant force F of the above forces is set to about 1000 to 5000 gf.

[0050] The hole 91 of the bearing member 90 that supports the shaft portion 71 will be described using Figures 4 and 5. Only one shaft portion side will be described, but the other shaft portion side is configured in the same way. Figure 4 is a schematic cross-sectional view (cross-section perpendicular to the rotation axis of the photosensitive drum 1) showing the general configuration of the bearing member 90. Figure 5(a) is a schematic cross-sectional view showing the fitted state of the photosensitive drum shaft portion 70a and the bearing member 90a on the non-drive side and the positional relationship with the brush member 80 when viewed in the direction of arrow A in Figure 3. Figure 5(b) is a schematic cross-sectional view showing the fitted state of the photosensitive drum shaft portion 70b and the bearing member 90b on the drive side and the positional relationship with the brush member 80 when viewed in the direction of arrow B in Figure 3. Below, subscripts will be omitted for configurations common to the drive side and non-drive side, and they will be described together. As shown in Figures 4 and 5, the shape of the hole 91 supporting the shaft portion 71 has two contact surfaces 92 (hereinafter referred to as tangents when describing the cross section) that contact the outer periphery of the shaft portion 71, a brush opposing surface 93 that is on the side of intersection X where tangents that pass through the contact points of each tangential surface 92 with the photosensitive drum 1 intersect when extended, and an arc-shaped escape surface 94 with an inner diameter (circular shape) that is larger than the outer diameter of the shaft portion 71 (circular shape in cross section in the axial direction).

[0051] As described above, a clearance is provided to allow the shaft portion 71 to fit into and rotate in the hole portion 91 in consideration of tolerances, and the inner diameter of the hole portion 91 is designed to be larger than the outer diameter of the shaft portion 71. That is, in a cross section perpendicular to the rotation axis of the photosensitive drum 1, the width between the intersection points of the imaginary line passing through the center of the arc of the arc-shaped relief surface 94 on the inner surface of the hole portion 91 facing the shaft portion 71 is larger than the diameter of the shaft portion 71 at any angle of the imaginary line.

[0052] In the cross-sectional arrangement perpendicular to the axis of the photosensitive drum 1 shown in Figures 4, 5, etc., the brush-opposing surface 93 of the inner surface of the bearing member 90 forming the hole 91 is a surface provided in the opposing portion of the bearing member 90 that faces the brush member 80 (Figure 2). In addition, in the cross-sectional arrangement, the contact surfaces 92 are arranged on one end side and the other end side of the brush-opposing surface 93. Furthermore, this brush-opposing surface 93 has a gap Z with the outer surface of the supporting shaft portion 71. The distance of the gap Z is such that the contact surfaces 92 will not come into contact with the shaft portion 71 at the contact portions 94 even if the bearing member 90 is deformed due to the abutment of the respective contact surfaces 92 with the shaft portion 71.

[0053] The shaft portion 71 is supported at two points P and Q in the cross section by contact with each contact surface 92. This allows the position of the photosensitive drum 1 relative to the bearing member 90 (frame body 51) to be determined with high precision.

[0054] That is, in this embodiment, the bearing member 90a as a first support member has a hole 91a as a first hole that supports one end in the longitudinal direction of the photosensitive drum 1. The inner surface (substantially the inner peripheral surface) of the bearing member 91a, which forms the hole 91a facing to surround the outer peripheral surface of the shaft portion 71a, has two contact surfaces 92-1a and 92-2a that contact the shaft portion 71a at points Pa and Qa, respectively. The charging roller 2, developing roller 40, transfer roller 50, etc. contact the outer peripheral surface of the photosensitive drum 1 at different angles, but by balancing the pressing forces of these, the bearing member 90a is in contact with only the two contact surfaces 92-1a and 92-2a. It is possible. Due to the balance of these pressing forces, the shaft portion 71a of the photosensitive drum 1 is rotatably supported by the hole portion 91 of the bearing member 90. However, contact by only the two contact surfaces is a contact form that is formed at least during image formation operation, and this does not apply when the balance of pressing forces changes, for example, when part of the member that presses the photosensitive drum 1 is removed during maintenance. In other words, the bearing member 90 has a form that surrounds the outer periphery of the shaft portion 71 to prevent the photosensitive drum 1 from falling off the cartridge or the main body of the apparatus, and it is possible that the relief surface 94 will support the shaft portion 71, for example.

[0055] The two contact surfaces 92-1a and 92-2a are in approximate line contact with the outer circumferential surface of the shaft portion 71a, and in the cross section, they are in approximate point contact as indicated by points Pa and Qa. The contact surface 92-1a, serving as a first inclined surface (abutment surface), is located on one side of an imaginary plane I that passes through the axis of the photosensitive drum 1 and the contact portion 81b of the brush member 80 (including the rotation axis of the photosensitive drum 1 and intersecting with the contact portion 81b of the brush member 80) in the cross section, and extends in a direction inclined relative to the imaginary plane I so as to contact the outer circumferential surface of the shaft portion 71a of the photosensitive drum 1. The contact surface 92-2a, serving as a second inclined surface (abutment surface), is located on the other side of the imaginary plane I in the cross section, and extends in a direction inclined relative to the imaginary plane I so as to contact the outer circumferential surface of the shaft portion 71a of the photosensitive drum 1. An intersection point Xa of the two contact surfaces 92-1a and 92-2a is on the imaginary plane.

[0056] Furthermore, the bearing member 90b as a second support member has a hole 91b as a second hole that supports the other longitudinal end of the photosensitive drum 1. Similar to the bearing member 90a, the inner surface (substantially the inner peripheral surface) of the bearing member 91b, which forms the hole 91b facing the outer peripheral surface of the shaft portion 71b so as to surround the outer peripheral surface of the shaft portion 71b, has two contact surfaces 92-1b and 92-2b that contact the shaft portion 71b at points Pb and Qb, respectively. The contact surface 92-1b as a third inclined surface (abutment surface) is located on one side of the imaginary plane I in the cross section and extends in a direction inclined with respect to the imaginary plane I so as to contact the outer peripheral surface of the shaft portion 71b of the photosensitive drum 1. The contact surface 92-2b as a fourth inclined surface (abutment surface) is located on the other side of the imaginary plane I in the cross section and extends in a direction inclined with respect to the imaginary plane I so as to contact the outer peripheral surface of the shaft portion 71b of the photosensitive drum 1.

[0057] 5(a), in this embodiment, the contact surface 92-1a as the first inclined surface (abutting surface) and the contact surface 92-2a as the second inclined surface (abutting surface) are disposed symmetrically with respect to an imaginary plane I that includes the rotation axis O of the photosensitive drum 1 and intersects with the toner charging device 8. In addition, as shown in FIG. 5(b), the contact surface 92-1b as the third inclined surface (abutting surface) and the contact surface 92-2b as the fourth inclined surface (abutting surface) are also disposed symmetrically with respect to the imaginary plane I.

[0058] FIG. 6 shows the relationship between contact and force at the first inclined surface (third inclined surface) and the second inclined surface (fourth inclined surface). While FIG. 6 illustrates the configuration of the non-drive side, the configuration of the drive side is similar (axially symmetrical) to the configuration of the drive side and is therefore not shown. The contact surface 92-1a as the first inclined surface contacts the outer circumferential surface of the shaft at point Pa, and the contact surface 92-2a as the second inclined surface contacts the outer circumferential surface of the shaft at point Qa. The force Fp received from the contact surface 92-1a at point Pa, the force Fq received from the contact surface 92-2a at point Qa, and the resultant force Fpq are balanced with the resultant force F of the process means. That is, the directions of action of the resultant forces Fpq and F are opposite to each other along the virtual plane I. Similarly, the resultant force of the forces received from the contact surface 92-1b as the third inclined surface and the contact surface 92-2b as the fourth inclined surface also balances with F. In this way, for example, the position of the photosensitive drum 1 relative to the bearing member 90 can be determined only by the forces applied to the photosensitive drum 1 from various process means, without providing additional pressing means (biasing means such as a spring) that presses the shaft portion 71 of the photosensitive drum 1. Therefore, the positional relationship between the photosensitive drum 1 and the brush member 80 can be stably maintained.

[0059] In this embodiment, the causes of the resultant force described above are merely examples, and the present invention is not limited to these. If there are other members pressing against the photosensitive drum 1, they should be taken into consideration.

[0060] Figures 7(a) and 7(b) show the effect of adopting the bearing configuration of this embodiment. Figures 7(a) and 7(b) are graphs with the amount of drum fluctuation on the vertical axis and time on the horizontal axis. The graphs also show the amount of drum fluctuation over one drum rotation cycle. As shown in Figure 7(a), with the bearing configuration of this embodiment, only the amount of runout due to the shape of the photosensitive drum unit itself is measured. In contrast, as shown in Figure 7(b), with the conventional bearing hole shape (round), more fluctuation than the amount of runout due to the shape of the photosensitive drum unit itself is measured. This indicates that the position of the photosensitive drum 1 fluctuates within the clearance with the bearing. From the above, a configuration that supports the photosensitive drum 1 at two points is effective in suppressing positional fluctuation of the photosensitive drum 1.

[0061] Furthermore, in this embodiment, a configuration in which shaft flanges at both ends of the photosensitive drum 1 are supported has been exemplified, but the same effect can be obtained, for example, with a configuration in which the outer diameter of the cylinder 1a is directly supported by a resin bearing. However, with the configuration of this embodiment, the outer diameter of the shaft 71 is smaller than the outer diameter of the cylinder 1a. Therefore, supporting the shaft as in this embodiment allows the photosensitive drum support device to be made more compact.

[0062] In addition, in this embodiment, a plurality of process means, such as the charging roller 2 and the developing roller 41, are configured to urge the photosensitive drum 1, but it is not necessary for all process means to urge the photosensitive drum 1. The support structure of the present invention can be adopted as long as at least one of the process means is configured to urge the photosensitive drum 1.

[0063] As described above, the photosensitive drum 1 is brought into contact with two non-parallel contact surfaces formed on the bearing member 90, thereby positioning the photosensitive drum 1, thereby suppressing positional fluctuations of the photosensitive drum 1. This makes it possible to improve image quality. Furthermore, by bringing the photosensitive drum 1 into contact by the pressing (biasing) of the process means, there is no need to provide a separate pressing means (biasing means), and the number of parts can be reduced. Furthermore, the cartridge, and ultimately the image forming apparatus, can be made smaller. Furthermore, a stable support structure for the photosensitive drum 1 can be realized at low cost.

[0064] In this embodiment, as shown in FIG. 1, the toner charging device 8 and charging roller 2 are in contact with the center of the photosensitive drum 1 from above, the transfer roller 5 from the right side, and the developing roller 41, which serves as a developing and cleaning means, from below. However, this arrangement is not limited to this. As an example, as shown in FIG. 8, a configuration is possible in which the arrangement of the components in contact with the photosensitive drum 1 is rotated around the central axis of the photosensitive drum 1 compared to the arrangement of the image forming apparatus in FIG. 1. Specifically, the toner charging device 8 is in contact with the left side of the photosensitive drum 1, the charging roller 2 from above, the transfer roller 5 from below, and the developing roller 41 from the right side of the photosensitive drum 1. The process means includes an abutting member that abuts the photosensitive drum 1 so that the force acting on the photosensitive drum 1 includes a vertically upward component, i.e., an abutting member that is arranged on the side opposite the brush member 80 across the photosensitive drum 1.

[0065] 9 also shows the positional relationship with the bearing member 90 as a positioning member not shown in FIG. 8. Note that while FIG. 9 shows the configuration on the non-drive side, the configuration on the drive side is configured similarly (axially symmetrical) to the configuration on the drive side, and is therefore not shown. Compared to FIG. 3 in the case of FIG. 1, the bearing member 90 is also configured to be rotated about the center of the photosensitive drum 1, and the resultant force of each process means acts in the same way on the contact surfaces 92-1 and 92-2, so that the configuration in FIG. 8 can also exhibit the effect of stabilizing the contact state between the brush member 80 and the photosensitive drum 1, just as in the case of FIG. 1. This can be done.

[0066] What has been described so far is a configuration in which a cylindrical member is abutted against two surfaces at one end of the photosensitive drum 1, so that the resultant force of the force received from those surfaces and the force received from process means other than the toner charging device is balanced, but other configurations are also possible.

[0067] In contrast to FIG. 6, FIG. 10 shows a configuration in which curved surfaces (first contact curved surface, second contact curved surface) 930, each having a radius of curvature larger than the radius (radius of curvature) of the cylindrical shaft portion 71 at each longitudinal end of the photosensitive drum 1, are in contact with the cylindrical shaft portion 71. The radius of curvature of the curved surfaces 930 is smaller than the radius of the outer circumferential surface of the cylinder 11 of the photosensitive drum 1. In this case, point contact occurs at point U. In this case, the force Fu acting at point U from the curved surface 930 and the resultant force F of the process means are balanced, stabilizing the position of the photosensitive drum 1. By arranging the toner charging device 8 (brush member 80) on the straight line connecting the center O and point U, it is possible to maintain a stable positional relationship between the toner charging device 8 and the photosensitive drum 1 even in this configuration.

[0068] <Example 2> The image forming apparatus according to the second embodiment of the present invention has a configuration that is more suitable for preventing toner scattering when applied to an operation other than image forming.

[0069] In the first embodiment, the toner charging device was disposed above and to the side of the photosensitive drum. However, considering that trapped toner is held by the brush member 80 of the toner charging device 8 within the contact nip with the photosensitive drum 1, it is more preferable to dispose the toner charging device above to reduce the risk of the toner falling in the direction of gravity. Therefore, in this embodiment, a case where the toner charge control member is disposed above will be described. Figure 11 shows a schematic configuration of an image forming apparatus according to this embodiment. In this embodiment, components similar to those in the first embodiment are designated by the same reference numerals and will not be described again.

[0070] During image formation, each process means, such as the charging roller 2, transfer roller 5, and developing roller 41, presses (biases) against the photosensitive drum 1, thereby accurately determining the position of the photosensitive drum 1 relative to the bearing member 90. Therefore, the positional relationship between the toner charging device 8 and the photosensitive drum 1 can also be determined accurately, making it easier to maintain favorable conditions for recharging the residual toner after transfer. On the other hand, it is conceivable that a different situation may occur during non-image formation than during image formation.

[0071] 12 shows, as an example, a case where door Z is opened, assuming a configuration in which transfer roller 5 is arranged on an openable door (opening / closing member) provided on the image forming apparatus main body in FIG. 1. If paper that has been passed through during printing becomes jammed inside the image forming apparatus main body, when a user opens door Z to clear the jam, transfer roller 5 arranged on door Z moves away from photosensitive drum 1.

[0072] On the other hand, as a comparative example, FIG. 13 shows a configuration in which the arrangement of the developing roller 41 and the transfer roller 5 is changed from that of FIG. 11, which shows the present embodiment. The contact positions of the developing roller 41 and the transfer roller 5 with respect to the photosensitive drum 1 are different from those in FIG. 11. The developing roller 41 contacts from the right side, and the transfer roller 5 contacts from below. Similarly, the transfer roller 5 is placed on an openable door Z, and FIG. 14 shows the state in which the door is open.

[0073] First, in the case of the image forming apparatus shown in FIG. 11, for the sake of explanation, the door Z is opened as shown in FIG. 12, and the transfer roller 5 is separated from the photosensitive drum 1. In addition, although the configuration of the non-drive side is illustrated in FIG. 15(a) and FIG. 15(b), the configuration of the drive side is also configured similarly (axially symmetrical) to the configuration of the drive side. Therefore, illustrations and explanations are omitted.

[0074] During image formation operation, as shown in Figure 15(a) and as explained in Example 1, the position of the photosensitive drum 1 is determined by the action of the resultant force F of the process means, whereby the surface 92-1a abuts against the shaft portion 71a of the photosensitive drum 1 at point Pa, and the surface 92-2a abuts against the shaft portion 71a of the photosensitive drum 1 at point Qa.

[0075] On the other hand, when the door Z is opened, although the pressure applied to the photosensitive drum 1 by the transfer roller 5 is lost, the force component in the direction of contact with the surfaces 92-1a and 92-2a due to the pressure of the developing roller 41 is not lost. Therefore, although the resultant force changes from that during image formation, the contact can be maintained at points Pa and Qa as shown in FIG. 15(b). Because the contact at points Pa and Qa itself does not change, the relative positional relationship between the photosensitive drum 1 and the toner charging device 8 (brush member 80) does not change. In other words, a stable contact state can be maintained.

[0076] Next, the image forming apparatus of Fig. 13 will be described using Fig. 16, which shows an excerpt of the photosensitive drum 1 and its surroundings when the door is opened as shown in Fig. 14. Note that Figs. 15(a) and 15(b) illustrate the configuration of the non-drive side, but the configuration of the drive side is configured similarly to the configuration of the drive side (axially symmetrical), and therefore will not be illustrated or described here.

[0077] During image formation operation, as shown in Figure 16(a), the position of the photosensitive drum 1 is determined by the action of the resultant force F of the process means, whereby the contact surface 92-1a abuts against the shaft portion of the photosensitive drum 1 at point Pa, and the contact surface 92-2a abuts against the shaft portion of the photosensitive drum 1 at point Qa.

[0078] On the other hand, when the door is opened, the force component in the direction of contact with surfaces 92-1a and 92-2a due to the pressure of transfer roller 5 is lost. On the other hand, the pressure from developing roller 41 acts in the direction of contact with surface 92-1a, and it is thought that, as an example, as shown in Figure 16(b), contact may occur at point Ra on surface 92-1a and point Sa on surface 94a.

[0079] When this contact occurs, the photosensitive drum 1 clearly moves as the transfer roller 5 separates, compared to the contact at points Pa and Qa. This causes the surface of the photosensitive drum to move relative to the brush, causing the relative positional relationship with the toner charging device 8 to change over time, significantly altering the stable state during image formation. This undesirable situation could result in toner trapped in the nip between the brush member 80 of the toner charging device 8 and the surface of the photosensitive drum 1 becoming exposed to the drum surface and potentially scattering within the main body. Therefore, when the brush member 80 of the toner charging device 8 is located above, it is not desirable to place a process unit with a large separation below the photosensitive drum 1. In other words, it is preferable to contact the developing roller 41 from below, without separation, as shown in Figure 12. More preferably, it is preferable to place the developing roller 41 facing the toner charging device 8 across the center of the photosensitive drum 1.

[0080] Here, when the brush member 80 of the toner charging device 8 is disposed above the photosensitive drum 1, the developing roller 41, which is a simultaneous developing and cleaning means, is configured to contact the photosensitive drum 1 from below as the process means that contacts the photosensitive drum 1, but this is not limiting. As long as there is no separation, the charging roller 2 or the transfer roller 5 may be configured to contact the photosensitive drum 1 from below.

[0081] On the other hand, when considering the electrophotographic process around the photosensitive drum 1, the process generally goes through the order of charging → exposure → development (simultaneous cleaning) → transfer. Therefore, if the brush member 80 of the toner charging device 8 is disposed above the photosensitive drum 1, the process immediately before or after that 1, in which the developing roller 41, which is a simultaneous developing and cleaning means, is brought into contact with the brush member 80 so as to face it rather than the transfer roller 5 and charging roller 2, which are the means for cleaning the photosensitive drum 1 simultaneously. Furthermore, since the general pressure is larger than that for charging and transfer, this is suitable as a process means for pressing the photosensitive drum 1 in the direction toward the brush member 80.

[0082] In the above embodiment, a direct transfer type image forming apparatus in which a toner image formed on the photosensitive drum 1 is directly transferred to a recording material as a transfer receiving material has been described, but the present invention can also be applied to an intermediate transfer type image forming apparatus in which the toner image on the photosensitive drum 1 is first primarily transferred to an intermediate transfer belt as an intermediate transfer body or a transfer receiving body, and then secondarily transferred from the intermediate transfer belt to the recording material. [Explanation of symbols]

[0083] 1...photosensitive drum, 2...charging roller, 3...exposure device, 4...developing device, 41...developing roller, 5...transfer roller, 70...shaft portion, 8...toner charging device, 80...brush member, 90...bearing member, 91...hole portion, 92...contact surface, 93...brush opposing surface, 94...flank surface, A...image forming apparatus

Claims

1. an image carrier that is driven to rotate; a first charging means for charging the surface of the image carrier; a developing means for supplying a developer to an exposed portion of the electrostatic latent image formed on the surface of the image carrier charged by the first charging means, thereby forming a developer image; a transfer means for transferring a developer image from the image carrier to a transfer material; a second charging means for charging residual developer remaining on the image carrier without being transferred to a transfer material before the first charging means charges the image carrier, the second charging means having a brush that comes into contact with the surface of the image carrier at a contact portion; a first support member that rotatably supports one end of the image carrier in a longitudinal direction along a rotation axis of the image carrier; a second support member that rotatably supports the other end of the image carrier in the longitudinal direction; Equipped with At least one of the first charging means, the developing means, and the transfer means has a configuration in which it contacts the image carrier, and an image forming apparatus capable of performing an image forming operation of forming an image on a transfer material, the first support member has a first contact surface and a second contact surface that come into contact with the outer circumferential surface of the one end at different positions in a cross section perpendicular to the rotation axis of the image carrier; tangents of the first contact surface and the second contact surface passing through points of contact with the outer peripheral surface of the one end in the cross section intersect with an imaginary plane that includes the rotation axis and intersects with the contact portion, in a region of the imaginary plane that is closer to the brush than the rotation axis, the second support member has a third contact surface and a fourth contact surface that contact the outer circumferential surface of the other end at different positions in the cross section, tangents of the third contact surface and the fourth contact surface passing through points of contact with the outer peripheral surfaces of the other ends in the cross sections intersect with the imaginary plane in regions on the imaginary plane that are closer to the brush than the rotation axis, In the image forming operation, the image carrier is supported rotatably by contacting the first contact surface, the second contact surface, the third contact surface, and the fourth contact surface as a contact member included in at least one of the first charging means, the developing means, and the transfer means contacts and rotates.

2. 2. The image forming apparatus according to claim 1, wherein, in the cross section, the direction of action of the resultant force of the forces acting on the image carrier from each of the first contact surface and the second contact surface, or the direction of action of the resultant force of the forces acting on the image carrier from each of the third contact surface and the fourth contact surface, is a direction opposite to the direction of action of the resultant force of the forces acting on the image carrier from the abutment member.

3. the tangent to the first contact surface and the tangent to the second contact surface have an intersection on the imaginary plane in the cross section, 3. The image forming apparatus according to claim 1, wherein the tangent to the third contact surface and the tangent to the fourth contact surface have an intersection on the virtual plane in the cross section.

4. the first contact surface and the second contact surface are surfaces extending in a direction inclined with respect to the virtual plane, 4. The image forming apparatus according to claim 1, wherein the third contact surface and the fourth contact surface are surfaces that extend in a direction inclined with respect to the virtual surface.

5. the first support member has a first hole portion that includes the first contact surface and the second contact surface and surrounds an outer circumferential surface of the one end; The image forming apparatus according to any one of claims 1 to 4, characterized in that the second support member has a second hole portion that includes the third contact surface and the fourth contact surface and surrounds the outer peripheral surface of the other end.

6. 2. The image forming apparatus according to claim 1, further comprising a frame that fixes and supports the first and second support members and at least the brush.

7. 2. The image forming apparatus according to claim 1, wherein the contact member is at least one of a charging member provided in the first charging means, a developer carrier provided in the developing means, and a transfer member provided in the transfer means.

8. The brush is disposed at a position vertically higher than the contact member, There are a plurality of the abutment members, 2. The image forming apparatus according to claim 1, wherein the plurality of contact members include a contact member that contacts the image carrier so that a force acting on the image carrier includes a vertically upward component.

Images