Processing unit and image forming apparatus

Abstract

A processing unit includes a rotatable image bearing member, a charging roller, a brush unit having a brush and a holding member, a regulating member, and a pressing member. The retaining component comprises a first stress part, a second stress part and a third stress part, the first stress part is configured to receive the force in the first direction from the pushing and pressing component, and the second stress part is configured to receive the force in the second direction from the control component; and the third stress part is configured to receive the force in the second direction from the brush base. The first force receiving portion, the second force receiving portion, and the third force receiving portion are provided on one end side with respect to a center of the holding member in a rotation axis direction of the charging roller, and are arranged in the order of the second force receiving portion, the first force receiving portion, and the third force receiving portion from the one end toward the center.

Description

Technical Field

[0001] This disclosure relates to a processing unit for an image forming apparatus and an image forming apparatus for forming an image on a recording material. Background Technology

[0002] Japanese Patent Application Publication No. 2019-32412 discloses a brush-type cleaning component installed in an image forming apparatus without a cleaner to remove toner adhering to the charging roller. Summary of the Invention

[0003] This disclosure provides a new technology relating to a processing unit and an image forming apparatus equipped with a brush that contacts a charging roller.

[0004] One aspect of this disclosure provides a processing unit comprising: a rotatable image carrier member; a charging roller configured to contact a surface of the image carrier member and configured to charge the surface; a brush unit including a brush and a retaining member, the brush including a plate-shaped brush base and bristles projecting from the brush base, the retaining member being configured to retain the brush base and movable such that the brush base moves toward and away from the charging roller; a control member configured to abut against the retaining member to control the position of the retaining member; and a pushing member configured to push the retaining member such that the bristles contact the surface of the charging roller and the retaining member abuts against the control member, wherein in a direction parallel to the thickness of the brush base and from the brush base toward the charging roller... In the case where the direction of the electric roller orientation is referred to as the first direction and the direction opposite to the first direction is referred to as the second direction, the retaining member includes a first force-receiving portion, a second force-receiving portion, and a third force-receiving portion. The first force-receiving portion is configured to receive a force from the pushing member in the first direction, the second force-receiving portion is configured to receive a force from the control member in the second direction, and the third force-receiving portion is configured to receive a force from the brush base in the second direction when the bristles receive a reaction force from the surface of the charging roller. The first force-receiving portion, the second force-receiving portion, and the third force-receiving portion are disposed at one end relative to the center of the retaining member in the direction of the rotation axis of the charging roller, and are arranged from one end toward the center in the order of the second force-receiving portion, the first force-receiving portion, and the third force-receiving portion.

[0005] The features of this disclosure will become clear from the following description of embodiments with reference to the accompanying drawings. The following description of the embodiments is given by way of example. Attached Figure Description

[0006] Figure 1AThis is a diagram showing the brush unit according to an embodiment, viewed along the short side.

[0007] Figure 1B yes Figure 1A A magnified view of a portion of it.

[0008] Figure 2A This is a schematic diagram of an image forming apparatus according to an embodiment.

[0009] Figure 2B This is a perspective view of an image forming apparatus according to an embodiment.

[0010] Figure 3 This is a perspective view of an image forming apparatus according to an embodiment.

[0011] Figure 4A This is a cross-sectional view of the processing unit according to an embodiment.

[0012] Figure 4B This is a schematic diagram showing the layout of the photosensitive drum and processing components.

[0013] Figure 5A This is a perspective view of the drum unit according to an embodiment.

[0014] Figure 5B and Figure 5C These are enlarged views of a portion of the drum unit.

[0015] Figure 6 This is a perspective view of a portion of the drum unit according to an embodiment.

[0016] Figure 7A This is a rear view of the drum unit according to an embodiment.

[0017] Figure 7B and Figure 7C These are cross-sectional views of the drum unit according to the embodiment.

[0018] Figures 7D to 7G These are side views of the drum unit according to the embodiment.

[0019] Figure 8A and Figure 8B These are perspective views of the photosensitive drum and charging roller according to the embodiment.

[0020] Figures 9A to 9E These are explanatory diagrams of the brush unit according to the embodiments.

[0021] Figure 10A and Figure 10B These are explanatory diagrams of the brush unit according to the embodiments.

[0022] Figure 11A and Figure 11B These are explanatory diagrams of the brush unit according to the embodiments.

[0023] Figure 12A This is a rear view of the drum unit according to an embodiment.

[0024] Figure 12B and Figure 12C These are cross-sectional views of the drum unit according to the embodiment.

[0025] Figures 12D to 12G These are magnified views of a portion of the cross-section.

[0026] Figure 13A This is a schematic diagram of a brush unit according to an embodiment.

[0027] Figure 13B This is a schematic diagram of the brush unit based on the comparative example. Detailed Implementation

[0028] Embodiments according to this disclosure will now be described with reference to the accompanying drawings.

[0029] Image forming equipment

[0030] Reference Figure 2A , Figure 2B and Figure 3 An image forming apparatus 1 according to an embodiment is described. Figure 2A This is a schematic diagram of the image forming apparatus 1 according to an embodiment. Figure 2B and Figure 3 These are perspective views of image forming device 1.

[0031] Image forming equipment generally refers to a device that forms an image on a recording material P through the image forming section of an electrophotographic system. Examples of image forming equipment include electrophotographic copiers, laser beam printers, light-emitting diode (LED) printers, and electrophotographic fax machines. The image forming equipment 1 in this embodiment is a monochrome laser beam printer that forms an image on the recording material P based on image information input from an external device. Examples of recording material P include various sheet materials of different materials. Examples of various sheet materials include paper sheets (e.g., ordinary paper sheets and thick paper), plastic films (e.g., sheets used in overhead projectors), irregularly shaped sheets (e.g., envelope and index paper sheets), and fabrics.

[0032] In the following description and figures, the direction of the rotation axis of the image-carrying member (photosensitive drum 21) included in the image forming apparatus 1 will be referred to as the X direction. The vertical direction (direction of gravity) when the image forming apparatus 1 is placed on a horizontal surface will be referred to as the Z direction. The direction intersecting both the X and Z directions will be referred to as the Y direction. The X, Y, and Z directions are preferably orthogonal to each other.

[0033] In this embodiment, the input connection portion 51a (described later) that receives the driving force of the drive source (motor) provided in the device body 1A is provided on one end side of the processing unit 20 in the X direction. Therefore, the end side in the X direction (the side indicated by the arrow X in the figure) can be referred to as the "drive side", and the other side in the X direction (the side opposite to the side indicated by the arrow X) can be referred to as the "non-drive side".

[0034] like Figure 2A , Figure 2B and Figure 3 As shown, the image forming apparatus 1 includes an apparatus body 1A, an image forming section 10, a fixing section 70, a pickup roller 65 serving as a feed section, and an discharge roller pair 80 serving as a discharge section. The image forming section 10 includes a processing unit 20 serving as a processing unit, a scanner unit 11 serving as an exposure unit, and a transfer roller 12 serving as a transfer unit.

[0035] The device body 1A is a housing (structure) including frame members (e.g., a metal plate frame constituting the frame members of the image forming apparatus 1) and cover members (constituting the outer surface of the image forming apparatus 1). The image forming section 10, the fixing section 70, the pickup roller 65, and the discharge roller pair 80 are housed or supported by the device body 1A.

[0036] Figure 4A This is a cross-sectional view of the processing unit 20. Figure 4B This is a schematic diagram of the photosensitive drum 21 and the processing components arranged around the photosensitive drum. The processing unit 20 of this embodiment includes a drum unit 25 having the photosensitive drum 21 and a developing unit 30 having a developing roller 31.

[0037] The drum unit 25 includes a photosensitive drum 21, a charging roller 22, a pre-exposure section 23, a paper scrap collecting brush 24 serving as a brush unit for the photosensitive drum 21, a brush unit 40 for the charging roller 22, and a drum frame member 26. The developing unit 30 includes a developing roller 31, a developing container 32, a supply roller 33, a stirring member 34, and a developing blade 35. When the brush unit 40 for the charging roller 22 is a first brush unit, the brush unit for the photosensitive drum 21 can be referred to as a second brush unit.

[0038] The photosensitive drum 21 serves as an image carrier member for carrying the latent image (electrostatic latent image) and the toner image (developer image). The photosensitive drum 21 is a cylindrical (drum-shaped) photosensitive member. In this embodiment, the photosensitive drum 21 includes a columnar substrate formed of aluminum and a photosensitive layer formed on the substrate by a negatively charged organic photoconductor. During image formation, the photosensitive drum 21 is rotated in a predetermined direction (processing speed) by a motor of the device body 1A at a predetermined peripheral speed (processing speed). Figure 4A and Figure 4B (In the direction indicated by arrow Q) it rotates.

[0039] like Figure 4B As shown, the position where the surface 21a of the photosensitive drum 21 is opposite to the charging roller 22 is called the charging portion Q1. The position where the surface 21a of the photosensitive drum 21 is irradiated by the laser from the scanner unit 11 is called the exposure portion Q2. The position where the surface 21a of the photosensitive drum 21 is opposite to the developing roller 31 is called the developing portion Q3. The position where the surface 21a of the photosensitive drum 21 is opposite to the transfer roller 12 is called the transfer portion Q4. The position where the surface 21a of the photosensitive drum 21 contacts the paper scrap collecting brush 24 is called the brush contact portion Q5. During the image formation process, the charging portion Q1, the exposure portion Q2, the developing portion Q3, the transfer portion Q4, and the brush contact portion Q5 are arranged in this order along the rotation direction (Q) of the photosensitive drum 21. That is, in this embodiment, the rotation direction of the photosensitive drum 21 during the image formation process is the rotation direction of a point on the surface 21a of the photosensitive drum 21, which sequentially passes through the charging portion Q1, the exposure portion Q2, the developing portion Q3, the transfer portion Q4, and the brush contact portion Q5.

[0040] The charging roller 22 is configured to contact the photosensitive drum 21. In this embodiment, the charging roller 22 can contact and separate from the photosensitive drum 21, and performs an image forming operation while in contact with the photosensitive drum 21. Figure 4A Rotate counterclockwise (in the middle).

[0041] The charging roller 22 charges the surface 21a of the photosensitive drum 21 by receiving an applied charging voltage from a charging power source provided in the device body 1A. In this embodiment, the photosensitive drum 21 is charged to a negative polarity by the charging roller 22.

[0042] The pre-exposure section 23 is positioned downstream of the brush contact section Q5 and upstream of the charging section Q1 in the rotation direction (Q) of the photosensitive drum 21. The pre-exposure section 23 removes the surface charge of the photosensitive drum 21 by irradiating the surface 21a of the photosensitive drum 21 with light, thereby enabling a more stable discharge at the charging section.

[0043] The paper scrap collecting brush 24 (a brush unit for the photosensitive drum 21) includes a brush portion 24a formed of a lint-like fabric and a support member that supports the brush portion 24a and is fixed to the drum frame member 26. The paper scrap collecting brush 24 blocks foreign objects, such as paper scraps, from adhering to the surface 21a of the photosensitive drum 21 at the brush contact portion Q5, and suppresses the occurrence of image defects caused by foreign objects. Simultaneously, the paper scrap collecting brush 24 allows toner adhering to the surface 21a of the photosensitive drum 21 to pass through the brush contact portion Q5.

[0044] The brush unit 40 for the charging roller 22 includes a brush 41 capable of contacting the surface 22a of the charging roller 22. The brush 41 can scrape off foreign matter, such as paper scraps or dust, adhering to the surface 22a of the charging roller 22. The detailed configuration and function of the brush unit 40 will be described later.

[0045] The scanner unit 11 exposes the photosensitive drum 21 by radiating a laser corresponding to the image information input from an external device onto the photosensitive drum 21 and scanning the surface 21a of the photosensitive drum 21 using a faceted mirror (scanning optical system). As a result of this exposure step, an electrostatic latent image corresponding to the image information is formed on the surface 21a of the photosensitive drum 21. It should be noted that the exposure unit is not limited to the scanner unit 11 that radiates a laser, and an LED exposure unit can be used, for example. An LED exposure unit is an exposure unit that includes an LED array in which multiple LEDs are arranged as light sources in the direction of the rotation axis of the photosensitive drum 21 (the main scanning direction in the exposure step).

[0046] The developing unit 30 includes a developing roller 31 serving as a developer carrier, a developing container 32 serving as a frame member of the developing unit 30, a supply roller 33 capable of supplying developer to the developing roller 31, a stirring member 34, and a developing blade 35. The developing roller 31, the supply roller 33, and the stirring member 34 are rotatably supported by the developing container 32. Furthermore, the developing roller 31 is positioned at the opening of the developing container 32 so as to face the photosensitive drum 21. The supply roller 33 is rotatably in contact with the developing roller 31, and toner stored in the developing container 32 as developer is supplied (applied) to the surface of the developing roller 31 by the supply roller 33. It should be noted that the supply roller 33 is not necessarily required as long as a configuration is adopted that allows sufficient supply of toner to the developing roller 31.

[0047] In this embodiment, the developing unit 30 employs a contact developing system. Specifically, the toner layer carried on the developing roller 31 contacts the surface 21a of the photosensitive drum 21 at the developing portion Q3 (developing area) where the photosensitive drum 21 and the developing roller 31 are opposite each other. A developing voltage is applied to the developing roller 31 from a developing power source. The toner carried on the developing roller 31 is transferred from the developing roller 31 to the surface 21a of the photosensitive drum 21 according to the potential distribution of the surface 21a, and thus an electrostatic latent image is developed into a toner image. It should be noted that in this embodiment, a reverse developing system is used. That is, a toner image is formed on the surface 21a of the photosensitive drum 21, which is charged during the charging step, due to the toner adhering to areas where the charge has been reduced by light irradiation during the exposure step.

[0048] In this embodiment, a toner with a particle size of approximately 6 μm and a negative normal polarity (normal charged polarity) is used. For example, a polymerized toner manufactured by a polymerization method is used as the toner in this embodiment. Furthermore, the toner in this embodiment does not contain magnetic components and is primarily supported on the developing roller 31 by intermolecular forces or electrostatic forces (mirror forces). It should be noted that a single-component developer containing magnetic components can be used. Additionally, there are cases where single-component developers contain additives (e.g., wax and fine silica particles) for adjusting the toner's flowability and charged properties. Alternatively, a two-component developer consisting of a non-magnetic toner and a magnetic carrier can be used as the developer. When using a magnetic developer, for example, a cylindrical sleeve with a magnet disposed on its inner circumference is used as the developer-carrying member (developing roller).

[0049] The developing container 32 serves as a toner storage section for storing toner (developer). A toner storage chamber 36 for storing toner is formed inside the developing container 32. A stirring member 34 is disposed inside the toner storage chamber 36. The stirring member 34 is rotated by a motor driven by the device body 1A, thereby stirring the toner in the developing container 32 and conveying the toner toward the developing roller 31 and the supply roller 33. In addition, the stirring member 34 circulates the toner that has passed through the developing section Q3 but was not used for development and was then stripped from the developing roller 31 in the developing container 32, thereby homogenizing the toner in the developing container 32. It should be noted that the stirring member 34 is not limited to a rotating form. For example, a oscillating stirring member can be used.

[0050] The developing blade 35 is disposed together with the developing roller 31 at the opening of the developing container 32. The developing blade 35 controls the amount of toner carried on the developing roller 31. That is, as the developing roller 31 rotates, the toner supplied to the surface of the developing roller 31 is controlled into a uniform thin layer as it passes through the portion of the developing roller 31 opposite to the developing blade 35. Furthermore, when passing through the portion between the developing roller 31 and the developing blade 35, the charge of the toner supplied to the surface of the developing roller 31 increases on the negative polarity side through triboelectric charging.

[0051] The developing unit 30 of this embodiment includes a shielding member 37 disposed above the developing blade 35. The shielding member 37 shields the opposing portions between the developing roller 31 and the developing blade 35, and between the photosensitive drum 21 and the developing roller 31, so that when the brush 41 scrapes away foreign matter attached to the charging roller 22, foreign matter will not enter these opposing portions. The shielding member 37 is disposed below the contact position between the brush 41 and the charging roller 22 and above the opposing portions between the developing roller 31 and the developing blade 35, and between the photosensitive drum 21 and the developing roller 31. The shielding member 37 is supported by the developing container 32 and extends from the upper surface portion of the developing container 32 to a position near the surface 21a of the photosensitive drum 21. Except for a small gap between the shielding member 37 and the surface 21a of the photosensitive drum 21, Figure 4A In the cross-section shown, the space between the drum unit 25 and the developing unit 30, as well as the space where the developing roller 31 is disposed, are substantially isolated from each other by the shielding member 37. The shielding member 37 may be a member fixed to the developing container 32 by screws, adhesives, etc., or it may be integrally formed with the resin member constituting the developing container 32.

[0052] The term "processing unit" is not limited to a processing unit that includes all the constituent elements of the processing unit 20 of this embodiment, and it is sufficient as long as the processing unit includes an image carrier member (photosensitive drum) and at least one processing member. A processing member is a component that acts on the image carrier member in electrophotographic processing to perform steps such as charging, exposure, development, transfer, and cleaning. For example, the drum unit 25 is an example of a processing unit when the developing unit 30 is configured to be attachable to and detachable from the drum unit, which includes the photosensitive drum 21 and the charging roller 22. The charging roller 22, the developing roller 31, and the brush unit (paper scrap collection brush 24) for the photosensitive drum 21 in this embodiment are examples of processing members.

[0053] Image forming operations

[0054] Next, the image forming operation of the image forming apparatus 1 will be described. The image forming operation is a series of operations in which the image forming apparatus 1 forms an image on the recording material P by using the processing unit 20 while the recording material P is being transferred one by one. When image information and an execution command for the image forming operation are received from an external device connected to the image forming apparatus 1, the controller of the image forming apparatus 1 starts the image forming operation.

[0055] When the image forming operation begins, in the image forming section 10, the photosensitive drum 21 is driven to rotate, and by applying a voltage to the charging roller 22, the surface 21a of the photosensitive drum 21 is uniformly charged to a predetermined polarity and predetermined potential at the charging section Q1. The scanner unit 11 radiates laser light toward the photosensitive drum 21 based on the input image information. Therefore, the surface 21a of the charged photosensitive drum 21 is exposed at the exposure section Q2, and an electrostatic latent image is formed on the surface 21a of the photosensitive drum 21. The developing roller 31 rotates while carrying toner as a developer, thereby supplying toner to the photosensitive drum 21 at the developing section Q3. Therefore, the electrostatic latent image is developed into a toner image (developer image).

[0056] In parallel with the operation of the image forming section 10, recording materials P are fed one by one from the recording material storage section (tray, cassette) located in the lower part of the device body 1A by the pickup roller 65. The timing of the feeding of the recording materials P is controlled so that the recording materials P enter the transfer section Q4 at the time when the toner image formed on the photosensitive drum 21 arrives at the transfer section Q4. Then, as the recording materials P pass through the transfer section Q4, the toner image is transferred from the photosensitive drum 21 to the recording materials P by applying voltage to the transfer roller 12.

[0057] The recording material P, having passed through the transfer section Q4, is conveyed to the fixing section 70 and undergoes image fixing processing. That is, while the recording material P is held and conveyed in the clamping portion of a pair of rotating members (e.g., a pair of fixing rollers), the fixing section 70 heats and pressurizes the toner image on the recording material P. The recording material P, having passed through the fixing section 70, is discharged from the outside of the device body 1A by the discharge roller pair 80 and stacked on the discharge tray 81, which serves as a stacking portion and is formed in the upper part of the device body 1A.

[0058] Here, the image forming apparatus 1 of this embodiment does not include a cleaning member for collecting (removing) toner (transfer residue toner) that has not been transferred to the recording material P (transfer target) at the transfer section Q4 from the photosensitive drum 21. In this embodiment, the transfer residue toner adhering to the surface area of ​​the photosensitive drum 21 and having passed through the transfer section Q4 passes through the brush contact section Q5 and the charging section Q1, and is then collected by the developing roller 31 at the developing section Q3. Such a system is referred to as a cleaner-free system or a simultaneous developing and cleaning system.

[0059] More specifically, at the brush contact portion Q5, the paper scrap collecting brush 24 blocks foreign matter (e.g., paper scraps) adhering from the recording material P to the photosensitive drum 21, but allows residual toner to pass through. Additionally, when the residual toner passes through the charging portion Q1, a charge of normal polarity is supplied to toner particles with a polarity opposite to the normal polarity and toner particles with a charge close to zero, thus increasing the charge on the residual toner.

[0060] The behavior of residual toner after development section Q3 varies depending on the area on the surface 21a of the photosensitive drum 21. Because a reverse development system is used in this embodiment, the surface potential (bright area potential) of the photosensitive drum 21 in the exposed area (bright area) at exposure section Q2 is on the abnormal polarity side relative to the potential of the developing roller 31 to which the developing voltage is applied. Therefore, the residual toner adhering to the bright area remains on the surface 21a of the photosensitive drum 21 at development section Q3 without being transferred to the developing roller 31, and together with the toner supplied from the developing roller 31, constitutes part of the toner image. In contrast, the surface potential (dark area potential) of the photosensitive drum 21 in the unexposed area (dark area) at exposure section Q2 is on the normal polarity side relative to the potential of the developing roller 31 to which the developing voltage is applied. Therefore, the residual toner adhering to the dark area is transferred to the developing roller 31 at development section Q3 and collected in the developing container 32. The residual toner collected in the developing container 32 is stirred together with the toner present in the developing container 32 and used again for developing in a homogenized state.

[0061] In a cleanerless system, foreign matter adhering to the photosensitive drum 21 in the transfer section Q4 is not removed by the cleaning member. Even if the foreign matter is blocked by the paper scrap collection brush 24 as in this embodiment, a portion of the foreign matter may still manage to pass through the paper scrap collection brush 24. Therefore, as described below, it is preferable to reduce the occurrence of image defects caused by foreign matter adhering to the charging roller 22 by using the brush unit 40 for the charging roller 22.

[0062] Toner replenishment and box replacement

[0063] The toner replenishment and cartridge replacement in the image forming apparatus 1 of this embodiment will be described. For example... Figure 2B and Figure 3 As shown, an openable and closable top cover 82 is provided on the upper portion of the device body 1A. At least a portion of the upper surface of the top cover 82 is formed as a discharge tray 81 serving as a stacking portion. An opening and closing member 83, which is openably and closably supported about a pivot axis 83a extending in the front-rear direction (Y direction) of the device, is attached to the top cover 82. In addition, an upwardly opening portion 82a is formed in the discharge tray 81 of the top cover 82.

[0064] like Figure 2Aand Figure 3 As shown, the image forming apparatus 1 includes an attachment portion 106 that can be attached to a toner packet 100 used as a replenishment container. The attachment portion 106 has an opening (toner inlet port) that communicates with the toner discharge port of the toner packet 100, and includes a baffle that allows the toner inlet port to be opened and closed. The attachment portion 106 may be part of the processing unit 20, or it may be fixed to the apparatus body 1A.

[0065] The opening / closing member 83 is configured to move between a closed position and an open position. In the closed position, the opening portion 82a is closed, preventing the toner cartridge 100 from attaching to the attachment portion 106, and in the open position, the opening portion 82a is opened, allowing the toner cartridge 100 to attach to the attachment portion 106. When the opening / closing member 83 is in the open position, the attachment portion 106 is exposed to the outside of the image forming apparatus 1 through the opening portion 82a. The opening / closing member 83 serves as part of the discharge tray 81 and can support the recording material P discharged onto the discharge tray 81. Furthermore, the recessed portion 82b provided in the top cover 82 allows the user to easily hook their fingers onto the opening / closing member 83.

[0066] It should be noted that in this embodiment, a direct replenishment system is employed, wherein the developing unit 30 in the image forming apparatus 1 can be replenished with toner from outside the image forming apparatus 1. That is, the user can replenish the toner to the developing unit 30 from the toner pack 100 attached to the attachment portion 106 while the processing unit 20, including the developing unit 30, is attached to the apparatus body 1A. When the toner pack 100 is attached to the attachment portion 106 of the image forming apparatus 1, at least a portion of the toner pack 100 is exposed to the outside of the image forming apparatus 1.

[0067] Compared to a system where the entire processing unit 20 is replaced (a cassette system), the direct replenishment system has the following advantages. First, when the remaining toner dosage in the processing unit 20 is small, there is no need to remove the processing unit 20 from the image forming apparatus 1 to replace it with a brand new cassette, thus improving availability. Furthermore, compared to replacing the entire processing unit 20, the developing container 32 can be replenished with toner at a lower cost. Additionally, in the direct replenishment system, since the various rollers and gears do not need to be replaced, costs are reduced compared to a system where only the developing unit 30 in the processing unit 20 is replaced (a cassette system).

[0068] In this embodiment, the processing unit 20 is configured as a processing box that can be attached to and detached from the device body 1A (capable of being attached to and separated from the device body 1A). The user can remove the processing unit 20 from the device body 1A and replace the processing unit 20 with a brand new one by opening the opening and closing mechanism provided on the device body 1A.

[0069] It should be noted that the configuration of the brush unit 40 described below can be applied to image forming apparatuses with processing cartridge systems or developing cartridge systems. Furthermore, the processing unit 20 is not limited to a cartridge that can be attached to and detached from the device body 1A, and can, for example, be fixed to the device body 1A in a manner that does not require replacement by the user. That is, the "processing unit" in this disclosure can be a processing unit that is shipped attached to the device body 1A at the time of manufacture of the image forming apparatus 1 and can be used without replacement until the image forming apparatus 1 expires.

[0070] Drum unit

[0071] Reference Figures 4A to 8B Describe the configuration of drum unit 25. Figure 5A This is a perspective view of drum unit 25. Figure 5B This is a perspective view of the end portion of the drum unit 25 on the non-driving side, viewed from the center side in the longitudinal direction. Additionally, Figure 5C This is a perspective view of the drive-side end portion of the drum unit 25, viewed from the center side in the longitudinal direction. Figure 6 This is a perspective view of the drum unit 25 (excluding the drum frame member 26, the drive side cover member 43, and the non-drive side cover member 44). Figure 7A This is a diagram (rear view) showing the drum unit 25 (excluding the drum frame member 26, drive side cover member 43, and non-drive side cover member 44) as viewed from the upstream side in the Y direction. Figure 7B and Figure 7C They are along Figure 7A The cross-sectional view of drum unit 25 taken by line CC. Figure 7D and Figure 7E They are along Figure 7A The side view of drum unit 25 viewed in the direction of arrow D. Figure 7F and Figure 7G They are along Figure 7A The side view of drum unit 25 viewed in the direction of arrow E. Figure 8A and Figure 8B These are schematic diagrams illustrating the contact and separation between the photosensitive drum 21 and the charging roller 22. Figure 7B , Figure 7D , Figure 7F and Figure 8BThe states of contact between the charging roller 22 and the photosensitive drum 21 are shown respectively, and Figure 7C , Figure 7E , Figure 7G and Figure 8A The charging roller 22 and the photosensitive drum 21 are shown in their separated states.

[0072] like Figure 4A and Figure 5A As shown, the drum unit 25 includes a photosensitive drum 21, a charging roller 22, a paper scrap collecting brush 24, a drum frame member 26, a drive side cover member 43, a non-drive side cover member 44, and a brush unit 40. Additionally, the drum unit 25 includes a drive side shaft receiver 45 and a non-drive side shaft receiver 46. Figure 5B and Figure 5C ), charging roller pressing components 48 and 49 ( Figure 7D and Figure 7F ), charging roller separation components 28 and 29 ( Figures 7D to 7G ) and charging roller electrical contact 47 ( Figure 6 ).

[0073] The drum unit 25 has an elongated shape extending along the rotation axis of the photosensitive drum 21. Similarly, the charging roller 22 has an elongated shape extending along the rotation axis of the photosensitive drum 21. Therefore, in the following description, in some cases, the direction parallel to the rotation axis 21X of the photosensitive drum 21 (X direction) may be referred to as the longitudinal direction of the drum unit 25, the longitudinal direction of the photosensitive drum 21, or the longitudinal direction of the charging roller 22.

[0074] like Figures 5A to 5C As shown, the drive-side cover member 43 is attached to one end (drive side) of the drum frame member 26 extending in the X direction, and the non-drive-side cover member 44 is attached to the other end (non-drive side) of the drum frame member 26. The drive-side cover member 43 and the non-drive-side cover member 44 are fixed to the drum frame member 26 by means such as screws or adhesive. The drive-side cover member 43 forms at least a portion of the end face of the drum unit 25 on one end (drive side), and the non-drive-side cover member 44 forms at least a portion of the end face of the drum unit 25 on the other end (non-drive side). The drum frame member 26, drive-side cover member 43, and non-drive-side cover member 44, connected together, constitute the frame member of the drum unit 25. Furthermore, the drum frame member 26, drive-side cover member 43, and non-drive-side cover member 44, connected together, together with the frame member of the developing unit 30, constitute the frame member of the processing unit 20.

[0075] The photosensitive drum 21 is composed of a drive side cover member 43 and a non-drive side cover member 44 surrounding a rotation axis 21X ( Figure 5A It can be rotatably supported.

[0076] like Figure 5Aand Figure 6 As shown, the drum drive member 51 is disposed on one end (drive side) of the photosensitive drum 21 in the longitudinal direction. In this embodiment, the drum drive member 51 rotates integrally with the outer peripheral portion of the photosensitive drum 21, which contacts the charging roller 22. The drum drive member 51 includes an input connection portion 51a serving as a drive input portion, which receives a driving force (rotational force) for rotating the photosensitive drum 21 from the device body 1A.

[0077] With the processing unit 20 attached to the device body 1A, the input connection portion 51a of the drum drive member 51 engages with the output connection portion of the device body 1A. Driving force is transmitted from the motor of the device body 1A to the photosensitive drum 21 via the engagement between the output connection portion and the input connection portion 51a, and thus the photosensitive drum 21 is rotated in a predetermined rotation direction (Q).

[0078] The charging roller 22 is rotatably supported by a drive-side shaft receiver 45 and a non-drive-side shaft receiver 46, which serve as shaft support members. It should be noted that, in the case where the drive-side shaft receiver 45 is the first shaft support member, the non-drive-side shaft receiver 46 can be referred to as the second shaft support member. The charging roller 22 is positioned about a rotation axis 22X that is substantially parallel to the rotation axis 21X of the photosensitive drum 21. Figure 6 Rotate.

[0079] The drive-side receiver 45 and the non-drive-side receiver 46 are supported by the drum frame member 26 in a manner that allows them to move relative to the drum frame member 26 in a direction intersecting the longitudinal direction of the photosensitive drum 21. The charging roller 22 can move in directions closer to and further away from the photosensitive drum 21, depending on the movement of the drive-side receiver 45 and the non-drive-side receiver 46. Figure 7B and Figure 7C Move along the arrows S and T.

[0080] Specifically, in this embodiment, the drive-side shaft receiver 45 and the non-drive-side shaft receiver 46 are configured to be sandwiched between two guides 26d disposed in the drum frame member 26. Figure 7B and Figure 7C Between ) . Although in Figure 7B and Figure 7C The diagram shows two guides 26d corresponding to the non-drive side shaft receiver 46, but two guides corresponding to the drive side shaft receiver 45 are provided in the drum frame member 26. Grooves 45g are formed in both the drive side shaft receiver 45 and the non-drive side shaft receiver 46 to engage with the guides 26d. Figure 6Two guides 26d extend in directions orthogonal to the longitudinal direction of the photosensitive drum 21 (arrows S and T). The driven side-axis receiver 45 and the non-driven side-axis receiver 46 can move in the extending direction of the two guides 26d.

[0081] Charging roller pressing members 48 and 49 are disposed on corresponding end sides of the charging roller 22 in the longitudinal direction. The driving-side charging roller pressing member 48 is disposed between the driving-side shaft receiver 45 and the drum frame member 26. Figure 7F and Figure 7G The charging roller pushing member 49 on the non-drive side is disposed between the non-drive side shaft receiver 46 and the drum frame member 26. Figure 7D and Figure 7E The charging roller pushing members 48 and 49 are in the direction that moves the charging roller 22 closer to the photosensitive drum 21. Figure 7B The arrow T) pushes the drive side shaft receiver 45 and the non-drive side shaft receiver 46.

[0082] like Figure 6 As shown, the drive input gear 22G is attached to the end portion of the charging roller 22 on the drive side. The drive input gear 22G engages with the gear portion of the drum drive member 51. Therefore, when the photosensitive drum 21 is driven rotatably, the charging roller 22 in this embodiment follows the rotation of the photosensitive drum 21 by the driving force transmitted to it via the drum drive member 51 and the drive input gear 22G. Figure 6 and Figures 7B to 7G Rotate on the arrow R in the diagram.

[0083] It should be noted that the charging roller 22 is not limited to a configuration in which it rotates by drive transmission via the drum drive member 51 and the drive input gear 22G, but can be configured to rotate, for example, by frictional force acting between the surface 21a of the photosensitive drum 21 and the surface 22a of the charging roller 22.

[0084] like Figure 4A As shown, the paper scrap collecting brush 24 is fixed to the drum frame member 26 to contact the photosensitive drum 21.

[0085] Separation of charging rollers

[0086] The configuration relating to the contact and separation of the charging roller 22 from the photosensitive drum 21 will be described. The image forming apparatus 1 of this embodiment includes a mechanism that enables the charging roller 22 to remain out of contact with the photosensitive drum 21 after the image forming apparatus 1 has been shipped and before the image forming apparatus 1 reaches the user.

[0087] Specifically, such as Figure 8AAs shown, charging roller separation members 28 and 29 are disposed at corresponding ends of the charging roller 22 in the longitudinal direction. One charging roller separation member 28 is disposed on the end portion of the charging roller 22 on the drive side, and the other charging roller separation member 29 is disposed on the end portion of the charging roller 22 on the non-drive side. The charging roller separation members 28 and 29 are rotatable about the rotation axis 22X of the charging roller 22 and are rotatable relative to the charging roller 22.

[0088] like Figure 8A and Figure 8B As shown, the charging roller separation components 28 and 29 respectively include abutment ribs 28a and 29a, force-bearing protrusions 28b and 29b, and rods 28c and 29c.

[0089] The abutment ribs 28a and 29a are formed to protrude further outward than the outer periphery of the charging roller 22. The abutment ribs 28a and 29a are able to abut against the surface 21a of the photosensitive drum 21 outside the area where the surface 22a of the charging roller 22 contacts the surface 21a of the photosensitive drum 21 in the longitudinal direction (X direction) of the charging roller 22. Figure 8A , Figure 7C , Figure 7E and Figure 7G As shown, when the abutting ribs 28a and 29a abut against the surface 21a of the photosensitive drum 21, a predetermined gap d1 is formed between the surface 22a of the charging roller 22 and the surface 21a of the photosensitive drum 21. Furthermore, the charging roller separating members 28 and 29 receive the pushing force of the charging roller pushing members 48 and 49. That is, as a result of the abutting ribs 28a and 29a abutting against the surface 21a of the photosensitive drum 21, the charging roller 22 overcomes the pushing force of the charging roller pushing members 48 and 49 and remains in a separated position (separated position) from the photosensitive drum 21.

[0090] like Figure 8A and Figure 8B As shown, force-bearing protrusions 28b and 29b are provided on corresponding end portions of the photosensitive drum 21 in the longitudinal direction. A protrusion 51b is formed on the drum drive member 51 provided on one end side of the photosensitive drum 21, capable of engaging with the force-bearing protrusion 28b on the drive side of the charging roller separation member 28. A drum flange 52 is provided on the other end side of the photosensitive drum 21, rotating integrally with the photosensitive drum 21. A protrusion 52b is formed on the drum flange 52, capable of engaging with the force-bearing protrusion 29b on the non-drive side of the charging roller separation member 29.

[0091] The force-bearing protrusion 28b of the charging roller separation member 28 and the protrusion 51b of the drum drive member 51 are located at the same position in the longitudinal direction (X direction) of the charging roller 22. The force-bearing protrusion 29b of the charging roller separation member 29 and the protrusion 52b of the drum flange 52 are located at the same position in the longitudinal direction (X direction) of the charging roller 22. In addition, the drum drive member 51 and the drum flange 52 of this embodiment include multiple pairs (specifically, four pairs) of protrusions 51b and 52b, each pair including a protrusion 51b and a protrusion 52b having the same rotational phase around the rotation axis 21X of the photosensitive drum 21.

[0092] After the image forming apparatus 1 is installed at the location where the user uses it, an operation is performed during the initialization operation of the image forming apparatus 1 to bring the charging roller 22 into contact with the photosensitive drum 21. Specifically, during the initialization operation, the photosensitive drum 21 is rotated in a predetermined rotation direction (Q) by the driving force of a motor from the apparatus body 1A. Figure 8B As shown, a pair of protrusions 51b and 52b of the drum drive member 51 and the drum flange 52, which rotate integrally with the photosensitive drum 21, abut and press against the force-bearing protrusion 28b or 29b of the charging roller separation member 28 or 29. As a result, the charging roller separation members 28 and 29 rotate in the direction indicated by arrow R.

[0093] The contact between the surface 21a of the photosensitive drum 21 and the abutment ribs 28a and 29a is canceled by rotating the charging roller separation members 28 and 29. Then, as Figure 7B , Figure 7D and Figure 7F As shown, the drive-side shaft receiver 45 and the non-drive-side shaft receiver 46 slide in the direction indicated by arrow T by the pushing force of the charging roller pushing members 48 and 49, and the charging roller 22 moves to the position where the charging roller 22 contacts the photosensitive drum 21 (contact position).

[0094] It should be noted that when the charging roller separation components 28 and 29 are connected to the drum unit 25, the charging roller separation components 28 and 29 are held at a predetermined phase in the separation position of the charging roller 22. Figure 8A The connection is made at the point where the charging roller separation components 28 and 29 are located. However, if the charging roller separation components 28 and 29 rotate from the predetermined phase for some reason, the operator can return the charging roller separation components 28 and 29 to the predetermined phase by grasping and manipulating the levers 28c and 29c of the charging roller separation components 28 and 29.

[0095] With the aforementioned mechanism, for example, during the period after the image forming apparatus 1 is shipped and before it reaches the user, the charging roller 22 can be separated from the photosensitive drum 21. Therefore, deformation of the charging roller 22 caused by prolonged contact with the photosensitive drum 21 while stationary can be suppressed, thus reducing the risk of image defects caused by deformation of the charging roller 22. Furthermore, the configuration where the charging roller 22 automatically contacts the photosensitive drum 21 according to its rotation after the image forming apparatus 1 arrives at the user can shorten the waiting time for the user to begin using the image forming apparatus 1.

[0096] Conductive path of charging roller

[0097] The configuration related to the conductive path of the charging roller 22 in the drum unit 25 will be described. For example... Figure 6 As shown, the charging roller electrical contact 47 is disposed on one end (drive side) of the drum unit 25 in the longitudinal direction (X direction) of the charging roller 22 and is electrically connected to the charging roller 22.

[0098] Specifically, the charging roller electrical contact 47 includes a first contact portion 47a capable of contacting the electrical contacts (body-side contact portion) of the device body 1A and a second contact portion 47b contacting one end of the driving-side charging roller pressing member 48. The charging roller pressing member 48 is, for example, a compression coil spring formed of metal wire and is conductive. The other end of the charging roller pressing member 48 contacts the driving-side shaft receiver 45. The driving-side shaft receiver 45 is, for example, formed of a resin material mixed with a conductive material such as carbon and is conductive. In addition, the driving-side shaft receiver 45 includes, for example, a conductive shaft portion (metal shaft) of the charging roller 22. Therefore, in this embodiment, the charging roller electrical contact 47 is electrically connected to the charging roller 22 via the charging roller pressing member 48 and the driving-side shaft receiver 45.

[0099] With the processing unit 20 attached to the device body 1A, the first contact portion 47a of the charging roller electrical contact 47 contacts the body-side contact portion of the device body 1A. The body-side contact portion is electrically connected to a charging power supply provided on a high-voltage board in the device body 1A. Therefore, the charging power supply can apply a charging voltage to the charging roller 22 via the body-side contact portion and the conductive path from the charging roller electrical contact 47 to the charging roller 22.

[0100] Brush unit

[0101] The brush unit 40 for the charging roller 22 will be described. The brush unit 40 includes a brush 41 having bristles 41a. Figure 4A The brush 41 is configured such that the bristles 41a contact the surface 22a of the charging roller 22. The brush 41 can scrape away foreign matter adhering to the surface 22a of the charging roller 22 using the bristles 41a.

[0102] When foreign matter such as dust adheres to the charging roller 22, charging failures may occur due to the foreign matter, resulting in image defects such as black spots. Specifically, the following situations may occur.

[0103] When using the image forming apparatus 1, foreign matter such as dust may adhere to the surface 22a of the charging roller 22. For example, if the image forming apparatus 1 is used in an environment with a large amount of dust floating in the air (outdoor or near-outdoor environment), dust is more likely to adhere to the charging roller 22. The entry path of the foreign matter is not limited to one type, and for example, it is conceivable that dust may adhere from the recording material P to the photosensitive drum 21 in the transfer section Q4 and then from the photosensitive drum 21 to the charging roller 22, and that dust may be drawn into the apparatus body 1A along with the outside air and reach the charging roller 22 with the airflow.

[0104] When foreign matter adheres to the surface 22a of the charging roller 22, image defects caused by charging malfunctions may occur. For example, if the charging roller 22 rotates while a foreign matter, such as dust, adheres to a certain position on the surface 22a of the charging roller 22, the foreign matter may become embedded in the surface 22a due to repeated passage through the charging section Q1. In this case, as a result of a point-like charging malfunction occurring at the location corresponding to the foreign matter, periodic point-like image defects may appear in the image output by the image forming operation at intervals corresponding to the circumference of the charging roller 22. Such image defects are also referred to as black spots.

[0105] As a result of providing the brush unit 40 for the charging roller 22, foreign matter adhering to the surface 22a of the charging roller 22 can be scraped off by the bristles 41a of the brush 41. As a result of the brush 41, foreign matter such as dust can be prevented from accumulating at the same location on the surface 22a of the charging roller 22, and thus image defects such as black spots caused by the adhesion of foreign matter are less likely to occur. Furthermore, even when the image forming apparatus 1 is used in an environment with a large amount of dust floating in the air, for example, high image quality can be maintained for a long time.

[0106] Reference Figure 9AThe details of brush unit 40 are described up to Figure 11. Brush 41 has an elongated shape extending along the longitudinal direction (X direction) of charging roller 22. In the following description, the longitudinal direction (X direction) of charging roller 22 may be referred to as the longitudinal direction of brush 41. The direction orthogonal to the longitudinal direction (X direction) of brush 41 and extending along the brush base of brush 41 (the W direction in the figure) may be referred to as the short side direction of brush 41. In addition, the direction orthogonal to both the longitudinal direction (X direction) and the short side direction (W direction) of brush 41 (the V direction in the figure) may be referred to as the height direction of brush 41. The V direction and the W direction are not necessarily consistent with the Y direction and Z direction described above.

[0107] Figure 9A This is a diagram of the brush unit 40 as viewed from the side opposite to the charging roller 22 in the height direction (V direction) of the brush 41. Figure 9B This is a diagram showing the short side direction (W direction) of brush unit 40. Figure 9C The brush unit 40 is shown as viewed from the charging roller 22 side in the height direction (V direction) of the brush 41. Figure 9D This is the perspective view of cell 40. Figure 9E This is a perspective view of the base 42. Figure 10A This is the perspective view of cell 40. Figure 10B This is an exploded view of the end portion of the brush unit 40 on the non-driving side. Figure 11 is a perspective view of the brush 41 and the brush contact 50.

[0108] like Figure 9D As shown in Figure 10, the brush unit 40 includes a brush 41, a brush base 42, a brush contact 50, and brush pushing members 53 and 54.

[0109] The brush 41 includes bristles 41a (brush hairs), a sheet-like bristle support portion 41b supporting the bristles 41a, and a plate-like backing member 41c supporting the bristle support portion 41b. The bristle support portion 41b and the backing member 41c constitute a plate-like brush base. The bristles 41a protrude from the brush base toward one side in the thickness direction of the brush base (the thickness direction of the backing member 41c).

[0110] The brush 41 of this embodiment is formed by attaching a pile fabric to a backing member 41c, for example, using an adhesive. The bristles 41a are, for example, conductive velvet formed from nylon fibers containing carbon as a conductive agent, and the bristle support portion 41b is a base fabric in which the conductive velvet is woven. The backing member 41c is, for example, a metal plate member. Alternatively, the brush 41 of this embodiment can also be described as consisting of a brush body including the bristles 41a and the bristle support portion 41b, and a support body (backing member 41c) supporting the brush body.

[0111] It should be noted that brush 41 is not limited to a brush formed by combining a pile fabric with a metal plate component. For example, brush 41 may include a resin brush base with multiple holes and bundles of bristles 41a implanted in the corresponding holes of the brush base. That is, the brush base of brush 41 is not limited to a brush base formed by combining a bristle support portion 41b (the portion that directly supports the bristles 41a) and a backing member 41c (the portion that supports the bristle support portion 41b), but may be an integrally molded part that supports the bristles 41a.

[0112] The brush base 42 is an example of a retaining member for holding the brush 41. The brush base 42 includes a main unit portion 42a that serves as a brush holding portion for holding the brush 41, and swing support portions 42n and 42r that serve as a supported portion supported by the drum frame member 26. In this embodiment, the main unit portion 42a holds the brush base (particularly the backing member 41c) of the brush 41. The swing support portions 42n and 42r swing integrally with the main unit portion 42a.

[0113] It should be noted that although this embodiment describes an example where the main unit portion 42a and the swing support portions 42n and 42r are integrally formed, the swing support portions 42n and 42r can be components separate from the main unit portion 42a and can be fixed to the main unit portion 42a by screws, adhesives, etc. Furthermore, as shown in the example of fixing the swing support portions 42n and 42r, which are components separate from the main unit portion 42a, to the main unit portion 42a, the "retaining member" is not necessarily composed of a single component.

[0114] The brush base 42 includes a drive-side position control portion 42j and non-drive-side position control portions 42k and 42m, serving as control portions (abutment portions) for controlling the position of the brush unit 40. The drive-side shaft receiver 45 and non-drive-side shaft receiver 46 correspondingly include abutment portions (45a, 46a, and 46b) that abut against the drive-side position control portion 42j and the non-drive-side control portions 42k and 42m, respectively. That is, in this embodiment, the drive-side shaft receiver 45 and non-drive-side shaft receiver 46 function as control members (positioning members) for controlling the position of the brush base 42 by abutting against the brush base 42 (holding member). When the drive-side position control portion 42j is the first control portion, the non-drive-side position control portions 42k and 42m can be referred to as the second control portion. The position control of the brush unit 40 will be described later.

[0115] The main unit portion 42a of the brush base 42 extends substantially the entire length of the area where the bristles 41a are disposed in the longitudinal direction (X direction) of the brush 41. The brush 41, the brush contact 50, and the brush pressing members 53 and 54 are disposed in the main unit portion 42a. The swing support portions 42n and 42r are disposed on the corresponding outer sides of the main unit portion 42a in the longitudinal direction (X direction) of the brush 41. One swing support portion 42n is disposed on the driving side, and the other swing support portion 42r is disposed on the non-driving side.

[0116] The brush base 42 is composed of drum frame component 26 ( Figure 5B , Figure 5C and Figure 6 The brush unit 40 is movably supported and can move in directions toward and away from the charging roller 22. That is, the brush unit 40 is movable, allowing the brush base 42 (brush holding portion) to move toward and away from the charging roller 22. Since the support holes 42p and 42s provided in the brush base 42 engage with the support shafts 26a and 26b provided in the drum frame member 26, the brush unit 40 of this embodiment is oscillating (rotatable) relative to the drum frame member 26. Furthermore, the brush unit 40 of this embodiment is pushed by brush pushing members 53 and 54 in directions that move the brush base (41b and 41c) and brush base 42 toward the charging roller 22.

[0117] The main unit portion 42a of the brush base 42 is provided with width control grooves 42g, 42h, and 42i for controlling the position of the brush 41 in the short side direction (W direction) of the brush 41. In the brush base 42 of this embodiment, the width control grooves 42g, 42h, and 42i are respectively provided at the drive-side end portion, center, and non-drive-side end portion of the main unit portion 42a in the longitudinal direction (X direction) of the brush 41. The number and arrangement of the width control grooves 42g, 42h, and 42i can be changed. The inner width of the width control grooves 42g, 42h, and 42i is set to be approximately equal to the width of the brush 41 in the short side direction (W direction) of the brush 41 (especially the width of the backing member 41c). Since the brush 41 engages with the width control grooves 42g, 42h, and 42i, the position of the brush 41 relative to the brush base 42 in the short side direction (W direction) is controlled (determined).

[0118] In addition, in this embodiment, the drum frame member 26 is provided with longitudinal control ribs 26c. Figure 5B Furthermore, the main unit portion 42a of the brush base 42 is provided with a longitudinal control groove 42f (see also...). Figure 10AThe longitudinal control rib 26c protrudes in the direction intersecting the longitudinal direction (X direction) of the brush 41. Since the longitudinal control rib 26c engages with the longitudinal control groove 42f, it controls (determines) the position of the brush unit 40 relative to the drum frame member 26 in the longitudinal direction (X direction) of the brush 41. It should be noted that the brush base 42 may be provided with a longitudinal control rib (protrusion) protruding in the direction intersecting the longitudinal direction (X direction), and the drum frame member 26 may be provided with a longitudinal control groove (recess) engaging with the longitudinal control rib.

[0119] like Figure 9E As shown, brush placement surfaces 42b and 42c are provided at corresponding end portions of the main unit portion 42a in the longitudinal direction (X direction) of the brush 41. Compared to the surface 42z between the brush placement surfaces 42b and 42c, the brush placement surfaces 42b and 42c protrude toward the brush 41 in the height direction (V direction) of the brush 41. The backing member 41c is fixed to the brush placement surfaces 42b and 42c by means such as bonding with an adhesive, thereby fixing the brush 41 to the brush base 42. With the brush 41 fixed to the brush placement surfaces 42b and 42c, the surface 42z between the brush placement surfaces 42b and 42c is substantially not in contact with the brush 41.

[0120] In other words, the main unit portion 42a (brush holding portion) includes opposing surfaces (42b, 42c, and 42z) opposite the backing member 41c (metal plate member) in the thickness direction of the brush base (41b and 41c) of the brush 41. The opposing surfaces include a brush placement surface 42b (first placement surface portion) and a brush placement surface 42c (second placement surface portion), one end portion of the metal plate member in the direction of the rotation axis (X direction) of the charging roller is fixed to the brush placement surface 42b, and the other end portion of the metal plate member in the direction of the rotation axis (X direction) of the charging roller is fixed to the brush placement surface 42c. Additionally, the opposing surfaces include a surface 42z (non-fixed portion), which is formed in the region between the first and second placement surface portions in the direction of the rotation axis (X direction) of the charging roller, and the metal plate member is not fixed to this surface 42z.

[0121] In this embodiment, the brush base 42 is a molded product (resin molded part) and may undergo slight deformation during molding. For example, the brush base 42 may warp, causing the central portion of the brush base 42 in the longitudinal direction (X direction) to protrude toward the brush 41 or toward the opposite side in the height direction (V direction). Additionally, the brush base 42 may twist, causing the orientations of the brush placement surfaces 42b and 42c to differ between one end and the other end in the longitudinal direction (X direction).

[0122] Therefore, by employing a configuration in which the brush 41 includes a backing member 41c made of metal and having high rigidity, and the respective end portions of the backing member 41c are fixed to the brush placement surfaces 42b and 42c of the brush base 42, deformation of the brush base 42 can be corrected. That is, warping and twisting of the brush base 42 can be corrected by mimicking the backing member 41c, which has a higher rigidity than the brush base 42. As a result, conditions such as shape errors of the brush base 42 that affect the position and shape of the brush 41 can be suppressed, and thus the bristles 41a can be in stable contact with the charging roller 22.

[0123] like Figure 9D and Figure 10A As shown, the swing support portions 42n and 42r (the first and second extension portions) of the brush base 42 extend (protrude) to one side relative to the main unit portion 42a in the short side direction (W direction) of the brush 41. Support holes 42p and 42s, serving as either hole portions or receiving portions, are formed at the distal ends of the swing support portions 42n and 42r, respectively. The drum frame member 26 is provided with support shafts 26a and 26b, which serve as shaft portions engaging with the hole portions (receiving portions). Figure 5B and Figure 5C As a result of the support holes 42p and 42s engaging with the support shafts 26a and 26b of the drum frame member 26 (receiving the support shafts 26a and 26b of the drum frame member 26), the brush unit 40 is pivotally supported relative to the drum frame member 26. Both support shafts 26a and 26b extend in the direction of the rotation axis of the charging roller 22 (the longitudinal direction of the brush 41, the X direction). An imaginary straight line passing through the center of the support shafts 26a and 26b is the pivot axis of the brush unit 40.

[0124] When the swing support portion 42n and the support shaft 26a on the drive side are respectively the first swing support portion and the first support portion, the swing support portion 42r and the support shaft 26b on the non-drive side can be referred to as the second swing support portion and the second support portion, respectively. Furthermore, when the support hole 42p and the support shaft 26a are respectively the first hole portion (first receiving portion) and the first shaft portion, the support hole 42s and the support shaft 26b can be referred to as the second hole portion (second receiving portion) and the second shaft portion, respectively. It should be noted that although in this embodiment the support shafts 26a and 26b (shaft portions) are provided in the drum frame member 26 and the support holes 42s and 42p (hole portions, receiving portions) are formed in the brush unit 40, the hole portion (receiving portion) can be formed in the drum frame member 26, and the shaft portion engaging with the hole portion (receiving portion) can be provided in the brush unit 40.

[0125] Furthermore, the swing support portions 42n and 42r are respectively provided with openings 42q and 42t, wherein support holes 42p and 42s open in a direction intersecting the swing axis of the brush unit 40. In other words, as a result of providing openings 42q and 42t, support holes 42p and 42s are both formed in an arc shape, wherein a portion of their circumference around the swing axis of the brush unit 40 is cut off. The opening direction V1 of the drive-side opening 42q is different from the opening direction V2 of the non-drive-side opening 42t. As a result of providing openings 42q and 42t, when the brush unit 40 is attached to the drum frame member 26, the support holes 42p and 42s can more easily engage with the support shafts 26a and 26b.

[0126] like Figure 10A and Figure 10B As shown, brush pushing members 53 and 54 are respectively attached to one end portion and the other end portion of the main unit portion 42a in the longitudinal direction (X direction) of the brush 41. Specifically, the first end 53a of the drive-side brush pushing member 53 is attached to the shaft portion 42d provided at one end portion of the main unit portion 42a. One end of the non-drive-side brush pushing member 54 is attached to the shaft portion 42e provided at the other end portion of the main unit portion 42a. Figure 9A ).

[0127] The brush contact 50 includes a first portion 50a having a hole portion that engages with the shaft portion 42d, and a second portion 50b extending from the first portion 50a along the longitudinal direction (X direction) of the brush 41. The brush contact 50 is formed, for example, by stamping and bending a sheet metal member.

[0128] The first portion 50a has a flat surface shape that is substantially perpendicular to the height direction (V direction) of the brush 41, and is supported in a state where it is sandwiched between the first end 53a of the brush pressing member 53 and the brush base 42 when its hole portion engages with the shaft portion 42d. The other end (second end 53b) of the brush pressing member 53 contacts the third contact portion 47c provided in the aforementioned charging roller electrical contact 47 (see also...). Figure 6 ).

[0129] like Figure 11A and Figure 11B As shown, a contact portion 50c is provided at the distal end of the second portion 50b of the brush contact 50, which contacts the side surface 41d of the backing member 41c of the brush 41 in the short side direction (W direction). The second portion 50b is provided with one or more bent portions 50b1 for reliably contacting the side surface 41d of the backing member 41c by utilizing the elasticity (spring characteristics) of the metal plate. The contact portion 50c makes pressure contact with the side surface 41d of the backing member 41c by the elasticity (spring characteristics) of the second portion 50b of the brush contact 50.

[0130] According to the above configuration, brush 41 is electrically connected to the body-side contact portion of the device body 1A via charging roller contact 47, brush pressing member 53, and brush contact 50. Furthermore, since brush 41 is electrically connected to charging roller 22 via brush contact 50, the potential of brush 41 is equal to the potential of charging roller 22. In other words, charging voltage is applied from the charging power supply of device body 1A to both brush 41 and charging roller 22 via brush contact 50.

[0131] Foreign matter adhering to the charging roller 22 can be charged. Therefore, when there is a potential difference between the brush 41 and the charging roller 22, foreign matter may electrostatically press against the charging roller 22 through the contact portion between the charging roller 22 and the brush 41, making it difficult for the brush 41 to scrape off the foreign matter. When the brush 41 and the charging roller 22 are at the same potential, foreign matter adhering to the surface 22a of the charging roller 22 can be easily scraped off by the brush 41, regardless of whether the foreign matter is charged or not.

[0132] It should be noted that if the charging roller 22 and brush 41 are electrically connected, similar advantages can be obtained regardless of the specific configuration of the conductive path. In this embodiment, an example has been described where the conductive path of the charging roller electrical contact 47, which is a contact member exposed to the outside of the processing unit 20, branches into a conductive path to the charging roller 22 and a conductive path to the brush 41. This configuration is not limited to this, and for example, a conductive path from the charging roller 22 to the brush 41 can be formed by providing conductive members such as wires in the swing support portion 42n and the main unit portion 42a, which electrically connect the drive side shaft receiver 45 and the backing member 41c of the brush 41 to each other. Alternatively, a similar conductive path can be formed by forming a portion of the swing support portion 42n and the main unit portion 42a with conductive resin.

[0133] Location control of brush units

[0134] Reference Figures 12A to 12G Describes the position control of brush unit 40. Figure 12A This is a diagram (rear view) showing the drum unit 25 as viewed from the upstream side in the Y direction. Figure 12B It is along Figure 12A The cross-sectional view of drum unit 25 taken by line GG in the image. Figure 12C It is along Figure 12A The sectional view of drum unit 25 taken by line FF. Figure 12D yes Figure 12B Enlarged view of part (the part where brush unit 40 abuts against non-drive side shaft receiver 46). Figure 12E yes Figure 12C Enlarged view of part (the part where brush unit 40 abuts against drive side shaft receiver 45). Figure 12FThis shows that brush unit 40 has been moved around support shafts 26a and 26b from... Figure 12D A diagram showing the state of rotation. Figure 12G yes Figure 12B Enlarged view of the part (near support axis 26b).

[0135] As described above, the brush unit 40 is movable relative to the charging roller 22. The brush base 42 (holding member) is movable in the direction of movement of the brush base (41b and 41c) of the brush 41 toward and away from the charging roller 22. Figure 12B and Figure 12C Since the support holes 42p and 42s engage with the support shafts 26a and 26b of the drum frame member 26, the brush base 42 of this embodiment can move (oscillate) relative to the charging roller 22 in the direction of rotation (arrow U) about the support shafts 26a and 26b.

[0136] Here, the "direction of movement" of the brush base 42 can be a direction that includes a component in the direction orthogonal to the tangent of the arc centered on the axis of rotation of the charging roller 22. For example, the "direction of movement" can be a linear direction intersecting the arc centered on the axis of rotation of the charging roller 22, or it can be a rotational direction about an axis parallel to and away from the axis of rotation of the charging roller 22. In addition, the "direction of movement" is not limited to a linear direction following a single straight line or a direction following a single arc, but can be a direction following a curve composed of multiple line segments and / or multiple curved portions. For example, when the brush base 42 moves while being guided by a guide shape such as a groove portion provided in the drum frame member 26, the "direction of movement" can be a direction following the guide shape.

[0137] In the rotational direction about the support shafts 26a and 26b, the brush unit 40 of this embodiment is pushed by the brush pushing members 53 and 54 in the direction indicated by arrow U in the figure. The position of the brush unit 40 in the rotational direction about the support shafts 26a and 26b is controlled (determined) by abutting against the drive-side shaft receiver 45 and the non-drive-side shaft receiver 46.

[0138] The support hole 42p and the support shaft 26a on one side (drive side) of the brush 41 in the longitudinal direction (X direction) mate with each other so that they can slide smoothly relative to each other. Figure 12B In other words, the inner diameter of the support hole 42p is set to be approximately equal to the outer diameter of the support shaft 26a, and the inner surface of the support hole 42p (the first hole portion) is slidably in contact with the outer surface of the support shaft 26a (the first shaft portion). In contrast, in the case of the support hole 42s and support shaft 26b on the other side (the non-driving side), a gap d2 is formed between the outer surface of the support shaft 26b and the inner surface of the support hole 42s, as shown... Figure 12GAs shown. In other words, the inner diameter of the support hole 42s (the second hole portion) is set to be larger than the outer diameter of the support shaft 26b (the second shaft portion), and the difference between the inner diameter of the support hole 42s and the outer diameter of the support shaft 26b is greater than the difference between the inner diameter of the support hole 42p and the outer diameter of the support shaft 26a. The effect of the gap d2 will be described later.

[0139] The position control of brush unit 40 will be described in more detail. At one end (drive side) of brush unit 40 in the longitudinal direction (X direction) of brush 41, a drive-side position control portion 42j located in the main unit portion 42a of brush base 42 abuts against the drive-side abutment portion 45a of drive-side shaft receiver 45, as shown below. Figure 12E As shown. The drive-side shaft receiver 45 can move relative to the drum frame member 26 in the directions (arrows S and T) where the charging roller 22 moves closer to and away from the photosensitive drum 21, but is positioned by the contact between the charging roller 22 and the photosensitive drum 21. Therefore, the oscillation of the brush base 42 in the direction of arrow U caused by the pushing force of the brush pushing members 53 and 54 is stopped by the abutment between the drive-side position control portion 42j and the drive-side abutment portion 45a. Furthermore, as described above, no gap is provided between the support hole 42s and the support shaft 26a. Therefore, on the drive side, the position of the brush unit 40 (position of the brush base 42) is determined based on the center of the support shaft 26a and the abutment position (impact position) between the drive-side position control portion 42j and the drive-side abutment portion 45a.

[0140] In contrast, on the other end of brush unit 40 (the non-driving side), such as Figure 12D As shown, the non-drive side position control portions 42k and 42m, located in the main unit portion 42a of the brush base 42, abut against the non-drive side abutment portions 46a and 46b of the non-drive side shaft receiver 46. The non-drive side shaft receiver 46 can move relative to the drum frame member 26 in the directions (arrows S and T) where the charging roller 22 moves closer to and away from the photosensitive drum 21, but is positioned by the contact between the charging roller 22 and the photosensitive drum 21. Therefore, the rotation of the brush unit 40 in the direction of arrow U caused by the pushing force of the brush pushing members 53 and 54 is stopped by the abutment between the non-drive side position control portions 42k and 42m and the non-drive side abutment portions 46a and 46b.

[0141] Here, on the other end (non-drive side) of the brush unit 40, two control surfaces (non-drive side position control portions 42k and 42m) facing different directions when viewed in the longitudinal direction (X direction) of the brush 41 are provided. When the non-drive side position control portion 42k is the first control surface, the non-drive side position control portion 42m can be referred to as the second control surface. The non-drive side position control portion 42k (first control surface) abuts against the non-drive side abutting portion 46a (first abutting portion) of the non-drive side shaft receiver 46, and the non-drive side position control portion 42m (second control surface) abuts against the non-drive side abutting portion 46b (second abutting portion) of the non-drive side shaft receiver 46. As a result, the position of the brush unit 40 (the position of the brush base 42) on the non-drive side can be determined with high precision in a direction orthogonal to the longitudinal direction (X direction) of the brush 41.

[0142] More specifically, in this embodiment, the position of the brush unit 40 is determined because the protruding shape of the non-drive side shaft receiver 46 fits into the recessed shape (groove shape) defined by the non-drive side position control portions 42k and 42m. In other words, the protruding shape of the non-drive side shaft receiver 46, including the non-drive side abutment portions 46a and 46b, fits into the bottom portion 42v having the recessed shape defined by the non-drive side position control portions 42k and 42m. As a result, the brush unit 40 is positioned in a direction orthogonal to the longitudinal direction (X direction) of the brush 41.

[0143] As a result of the gap d2 set between the support hole 42s and the support shaft 26b on the non-drive side ( Figure 12G The protruding shape of the non-drive side shaft receiver 46 can engage more reliably with the recessed shape formed by the non-drive side position control portions 42k and 42m. That is, even if the brush base 42 is slightly warped or twisted, the protruding shape of the non-drive side shaft receiver 46 can engage more reliably with the recessed shape of the brush base 42 because the support hole 42s is allowed to displace relative to the support shaft 26b through the gap d2.

[0144] Incidentally, during the rotation of brush unit 40 around support shafts 26a and 26b, only one of the non-drive side position control sections 42k and 42m... Figure 12F The situation shown, where the abutment is against the non-drive side abutment portion 46a or 46b, is possible. Figure 12F In the example, the non-drive side position control portion 42k and the non-drive side contact portion 46a abut against each other, while the non-drive side position control portion 42m and the non-drive side contact portion 46b do not contact each other.

[0145] However, the recessed shape defined by the non-drive side position control portions 42k and 42m is formed as an upstream recess in the rotational direction (arrow U) of the brush unit 40 rotating around the support shafts 26a and 26b according to the pushing force of the brush pushing members 53 and 54. Therefore, according to the oscillation of the brush unit 40 in the oscillation direction indicated by arrow U caused by the pushing force of the brush pushing members 53 and 54, the protrusion shape of the non-drive side shaft receiver 46 slides on the drive side position control portion 42k toward the bottom portion 42v of the recessed shape. As a result, even if temporarily taken Figure 12F As shown, this state was subsequently achieved where the protruding shape of the non-drive side shaft receiver 46 was in contact with both the non-drive side position control portions 42k and 42m while simultaneously fitting within the recessed shape, as shown. Figure 12D As shown.

[0146] As described above, the position of the brush base 42 is controlled by the contact between the control portions (drive-side position control portion 42j and non-drive-side position control portions 42k and 42m) of the brush base 42 (holding member) and the shaft support member (drive-side shaft receiver 45 and non-drive-side shaft receiver 46). Since the position of the brush base 42 is controlled by the contact between the position control portions and the shaft support member holding the charging roller 22, the brush 41 can contact the charging roller 22 with a more stable amount of interference.

[0147] The interference amount of brush 41 relative to charging roller 22 is the distance by which the distal end of brush bristles 41a is pushed into the virtual cylindrical surface of the actual surface 22a following charging roller 22, assuming the absence of charging roller 22. For example, in Figure 12B and 12C In the state of the charging roller 22, the difference between the sum of the outer diameter of the charging roller 22 and the protrusion of the bristles 41a relative to the brush base (41b and 41c) (bristle height of the brush) and the minimum distance from the rotation axis of the charging roller 22 to the brush base (41b and 41c) of the brush 41 is defined as the interference amount of the brush 41.

[0148] Due to dimensional tolerances of components, the amount of interference between the brush 41 and the charging roller 22 can vary between products or depend on its position in the longitudinal direction (X direction). In this case, there is a possibility that the function of the brush 41 in scraping away foreign matter attached to the surface 22a of the charging roller 22 may deteriorate, leading to image defects. However, according to this embodiment, the brush 41 can contact the charging roller 22 with a more stable amount of interference. As a result, it is easier to maintain the charging performance of the charging roller 22 for a longer period of time, thus reducing the possibility of image defects.

[0149] Furthermore, on the non-drive side, a configuration is adopted whereby a gap d2 is provided between the support hole 42s and the support shaft 26b, and the position of the brush unit 40 is controlled by the contact between the non-drive side position control portions 42k and 42m and the non-drive side contact portions 46a and 46b. As a result, for example, even if the drum frame member 26 twists between one end and the other end in the longitudinal direction (X direction) due to variations in component dimensional tolerances or assembly, the twisting of the brush unit 40 can be suppressed. Furthermore, variations in the amount of interference between the brush 41 and the charging roller 22 can be reduced.

[0150] On the driving side, the driving-side position control portion 42j and the driving-side abutment portion 45a preferably have a shape that makes point contact with each other. As a result, even if the surface of the driving-side position control portion 42j or the surface of the driving-side abutment portion 45a is tilted due to part shape errors, etc., the change in the abutment position (impact position) between the driving-side position control portion 42j and the driving-side abutment portion 45a can be suppressed. As a result, the change in the amount of interference between the brush 41 and the charging roller 22 can be further reduced. Specifically, in this embodiment, the driving-side abutment portion 45a has a flat surface shape that intersects the direction in which the brush 41 moves closer to and away from the charging roller 22 (the direction orthogonal to the brush support portion 41b), and the driving-side position control portion 42j has an approximately arcuate shape when viewed in the longitudinal direction (X direction).

[0151] For similar reasons, on the non-drive side, the non-drive side position control portion 42k and the non-drive side abutting portion 46a preferably have a shape in point contact with each other, and the non-drive side position control portion 42m and the non-drive side abutting portion 46b preferably have a shape in point contact with each other. In this embodiment, the non-drive side position control portions 42k and 42m each have a flat surface shape, and the non-drive side abutting portions 46a and 46b each have an approximately arcuate shape. Furthermore, the non-drive side position control portions 42k and 42m are approximately orthogonal to each other when viewed in the longitudinal direction (X direction).

[0152] In this embodiment, the torsion of the brush unit 40 (torsion of the brush base 42) is suppressed by utilizing the stiffness of the backing member 41c of the brush 41. In a configuration that accepts the torsion of the brush unit 40, if the brush base 42 only abuts against one of the drive-side shaft receiver 45 and the non-drive-side shaft receiver 46, the amount of interference of the brush 41 relative to the charging roller 22 will vary. To avoid this, increasing the pushing force of the brush pushing members 53 and 54 can be considered, but there is a risk that the contact pressure of the charging roller 22 on the photosensitive drum 21 will become uneven in the longitudinal direction (X direction). That is, there is a situation where the difference in pushing force between the driving-side and non-driving-side charging roller pushing members 48 and 49, and the difference in pushing force between the driving-side and non-driving-side brush pushing members 53 and 54, are combined, resulting in a variation in the contact pressure of the charging roller 22 on the photosensitive drum 21. Variations in the contact pressure of the charging roller 22 on the photosensitive drum 21 can lead to problems such as uneven potential of the photosensitive drum 21 and the resulting uneven image density, as well as bias wear of the photosensitive drum 21. Therefore, from the viewpoint of suppressing variations in the contact pressure of the charging roller 22 on the photosensitive drum 21, the pushing force of the brush pushing members 53 and 54 is preferably low.

[0153] According to this embodiment, since the torsion of the brush unit 40 (torsion of the brush base 42) is suppressed, the positional accuracy of the brush 41 relative to the charging roller 22 can be improved while reducing the pushing force of the brush pushing members 53 and 54.

[0154] Furthermore, in this embodiment, a configuration in which the charging roller 22 can move between a contact position and a separation position relative to the photosensitive drum 21 has been described. In this configuration, the position of the brush holding portion is controlled by abutting the control portion of the brush unit 40 against the shaft support member of the charging roller 22, thereby improving the positional accuracy of the brush holding portion relative to the charging roller 22 while employing a movable configuration of the charging roller 22.

[0155] According to this embodiment, due to the contact between the control section and the shaft support member, the brush unit 40 moves as the charging roller 22 moves between the contact position and the separation position. As a result, the charging roller 22 can contact and separate from the photosensitive drum 21 without being blocked by the brush unit 40.

[0156] Details of brush unit

[0157] Figure 1A This is a diagram showing the brush unit 40 as viewed in the short side direction W. Figure 1B yes Figure 1A An enlarged view of a portion (the end portion of brush unit 40 on the drive side).

[0158] In the following description, the direction parallel to the thickness direction of the plate-shaped brush base (41b and 41c) of brush 41 and oriented from the brush base (41b and 41c) toward the charging roller 22 is referred to as the first direction D1, and the direction opposite to the first direction D1 is referred to as the second direction D2.

[0159] like Figure 1A and Figure 1B As shown, the brush base 42 primarily receives forces (F1 to F6) from the brush pressing members 53 and 54, the drive-side shaft receiver 45, the non-drive-side shaft receiver 46, and the brush base (41b and 41c) of the brush 41. Specifically, the brush base 42 receives a force (pressing force F1) along the first direction D1 from the drive-side brush pressing member 53 and a force (pressing force F4) along the first direction D1 from the non-drive-side brush pressing member 54. Furthermore, the pressing forces F1 and F4 cause the control portions (42j, 42k, and 42m) of the brush base 42 to abut against the drive-side shaft receiver 45 and the non-drive-side shaft receiver 46, which serve as control members. As a result, the brush base 42 receives forces (resistance forces F2 and F5) along the second direction D2 from the drive-side shaft receiver 45 and the non-drive-side shaft receiver 46. Furthermore, the bristles 41a, which are pressed against the surface of the charging roller 22 by the pushing forces F1 and F4, receive a reaction force from the surface of the charging roller 22. As a result, the brush base 42 receives a force (brush reaction force F3 and F6) in the second direction D2 from the brush base (41b and 41c) of the brush 41.

[0160] The brush base 42 (holding member) includes a first force-bearing portion that receives the pushing force F1 from the brush pushing member 53 (pushing member, first pushing member), and a second force-bearing portion that receives the abutting reaction force F2 from the drive side shaft receiver 45 (control member, first control member). Additionally, the brush base 42 (holding member) includes a third force-bearing portion that receives the brush reaction force F3 from the brush base (41b and 41c) of the brush 41.

[0161] In this embodiment, the first force-bearing part is the first part 50a of the brush base 42 and the brush contact 50 located between the brush base 42 and the brush pushing member 53. Figure 10B The contact surface. It should be noted that the first force-bearing portion of the brush base 42 can directly receive the pushing force F1 from the brush pushing member 53 by abutting against it without passing through other members such as the brush electrical contact 50. In this embodiment, the second force-bearing portion is the drive-side position control portion 42j that abuts against the drive-side abutment portion 45a of the drive-side shaft receiver 45. In this embodiment, the third force-bearing portion is the brush placement surface 42b of the drive-side end portion of the backing member 41c that supports the brush 41.

[0162] Additionally, the brush base 42 (holding member) includes a fourth force-bearing portion that receives the pushing force F4 from the brush pushing member 54 (pushing member, second pushing member), and a fifth force-bearing portion that receives the abutting reaction force F5 from the non-drive side shaft receiver 46 (control member, second control member). Furthermore, the brush base 42 (holding member) includes a sixth force-bearing portion that receives the brush reaction force F6 from the brush base (41b and 41c) of the brush 41.

[0163] In this embodiment, the fourth force-bearing portion is the end portion of the brush base 42 that abuts against the brush pushing member 54 and faces the second direction D2. It should be noted that the fourth force-bearing portion of the brush base 42 can indirectly receive the pushing force F4 from the brush pushing member 54 via other members disposed between the fourth force-bearing portion and the brush pushing member 54. In this embodiment, the fifth force-bearing portion is the non-drive side position control portions 42k and 42m that abut against the non-drive side abutting portions 46a and 46b of the non-drive side shaft receiver 46. In this embodiment, the sixth force-bearing portion is the brush placement surface 42c of the end portion of the backing member 41c supporting the brush 41 on the non-drive side.

[0164] For ease of description, the points of application of the forces (F1 to F6) acting on the brush base 42 (holding member) will be referred to as points P1 to P6, respectively. Points P1 and P4 are the points of application of the pushing forces F1 and F4. Points P2 and P5 are the points of application of the abutting reaction forces F2 and F5. Points P3 and P6 are the points of application of the brush reaction forces F3 and F6. Points P1 to P6 can also be referred to as representative points of the first to sixth force-bearing parts, respectively. For example, since the brush base 42 in this embodiment receives the pushing force F1 via the first portion 50a of the brush contact 50, point P1 represents the center of the load distribution acting on the contact surface between the brush base 42 and the first portion 50a of the brush contact 50.

[0165] In this embodiment, points P1 and P4 approximately correspond to the shaft portions 42d and 42e of the brush base 42 that are attached to the brush pushing members 53 and 54, respectively. Figure 9A and Figure 10B Additionally, in this embodiment, points P2 and P5 correspond to the drive-side position control section 42j and the non-drive-side position control sections 42k and 42m, respectively. Furthermore, in this embodiment, points P3 and P6 correspond to the brush placement surfaces 42b and 42c, respectively.

[0166] On one end (driving side) of the brush base 42, the pushing force F1, the abutting reaction force F2, and the brush reaction force F3 satisfy the following relationship (1). On the other end (non-driving side) of the brush base 42, the pushing force F1, the abutting reaction force F2, and the brush reaction force F3 satisfy the following relationship (2).

[0167] F1 = F2 + F3 ... (1)

[0168] F4 = F5 + F6 ... (2)

[0169] Positional relationship between points of application

[0170] like Figure 1A and Figure 1B As shown, points P1 to P3 are positioned on the drive side (the same side as the end portion 421 of the drive side of the brush base 42) relative to the center 420 of the brush base 42 in the longitudinal direction (X direction) of the brush 41. Furthermore, points P1 to P3 are arranged in the order of points P2, P1, and P3 along the direction Xa from the end portion 421 of the drive side of the brush base 42 towards the center 420. In other words, the second force-bearing portion, the first force-bearing portion, and the third force-bearing portion are positioned on one end side relative to the center of the holding member in the direction of the rotation axis of the charging roller, and are arranged in this order along the direction from one end towards the center.

[0171] Reference Figure 13A and Figure 13B The diagram illustrates the advantages of this layout. Figure 13A This is a schematic diagram of the brush unit 40 according to this embodiment. Figure 13B This is a schematic diagram based on the brush unit 40' of the comparative example.

[0172] The brush unit 40' according to the comparative example differs from that of this embodiment in the positional relationship between point P1' where the brush base 42 receives the pushing force F1, point P2' where the brush base 42 receives the abutting reaction force F2, and point P3' where the brush base 42 receives the brush reaction force F3. In the comparative example, points P1' to P3' are arranged in the order of points P2', P3', and P1' along direction Xa from the end portion 421 on the drive side of the brush base 42 toward the center 420. Apart from this, the brush unit 40' is configured in the same manner as the brush unit 40 of this embodiment.

[0173] The torque of the force acting on the brush base 42 around point P2 or P2' will be considered. In this embodiment ( Figure 13A In the example (), the distance from point P2 to point P1 in the X direction will be represented by L1, and the distance from point P2 to point P3 in the X direction will be represented by L2. Figure 13B In the example (), the distance in the X direction from point P2' to point P3' will be represented by L2'. Figure 13B In the example, the distance from point P2' to point P1' in the X direction is the same as the value (L1) in this embodiment.

[0174] In this embodiment ( Figure 13AIn the equation, the torque M1 acting on the brush base 42 about point P2 is expressed by the following formula. It should be noted that it is assumed that... Figure 13A The clockwise direction is the direction in which the torque M1 is positive.

[0175] M1 = L1 × F1 - L2 × F3 ... (3)

[0176] Similarly, in the comparison examples ( Figure 13B In the equation, the torque M2 acting on the brush base 42 around point P2' is expressed by the following formula.

[0177] M2 = L1 × F1 - L2' × F3 ... (4)

[0178] like Figure 13A and Figure 13B As shown, the magnitude relationship between distances L1, L2, and L2' is represented by L2 > L1 > L2'. Furthermore, according to the formula (1) for expressing force balance, F1 > F3 holds true.

[0179] exist Figure 13A In the arrangement sequence shown in this embodiment (the order of points P2, P1, and P3 from the drive side toward the center side), comparing the first and second terms on the right side of formula (3), F3 < F1 and L2 > L1 holds true. Therefore, by appropriately determining the values ​​of L1, L2, F1, and F3, the torque M1 can be set to a value close to zero.

[0180] In contrast, Figure 13B In the case of the arrangement order shown in the comparison example (points P2', P3', and P1' from the drive side toward the center side), comparing the first and second terms on the right side of formula (4), F3 < F1 and L2' < L1 hold true. Therefore, the absolute value of the first term on the right side is always greater than the absolute value of the second term, and the value of torque M2 is always positive.

[0181] In other words, in the arrangement sequence of the comparative example, the component of the torque originating from the brush reaction force F3 (L2' × F3) cannot sufficiently counteract the component of the torque originating from the pushing force F1 (L1 × F1). As a result, a larger torque M2 may act on the brush base 42 around point P2'.

[0182] When the torque M2 acting on the brush base 42 is large, there is a possibility that the brush base 42 warps, causing the central portion of the brush base 42 in the longitudinal direction (X direction) to protrude more in the first direction D1 than its end portion in the longitudinal direction (X direction). If the amount of interference between the brush 41 and the surface of the charging roller 22 is uneven in the longitudinal direction (X direction) due to the aforementioned warping of the brush base 42, there is a possibility that the function of the brush 41 in scraping foreign objects may be degraded.

[0183] Specifically, for example, there is a possibility that the interference amount of brush 41 is too large at the center portion in the longitudinal direction (X direction), and there is a possibility that the interference amount of brush 41 is too small near the end portion in the longitudinal direction (X direction). When the interference amount of brush 41 is too large, especially when the density of brush bristles 41a is high or the brush bristles 41a are thick, the following inconveniences may occur. For example, there may be a situation where the portion of brush bristles 41a at the root side rather than at the distal end side contacts the surface of the charging roller 22, but the distal end of brush bristles 41a is separated from the surface of the charging roller 22. As a result, the ability to scrape foreign objects off the surface of the charging roller 22 by the stiffness (bending stress) of the brush bristles 41a in contact with foreign objects may deteriorate. Furthermore, as a result of the brush bristles 41a pressing forcefully against the surface of the charging roller 22, bristle bundle splitting (bristle splitting) may occur, and therefore, there may be areas where foreign objects are not scraped off and pass through the area of ​​brush 41. In contrast, if the interference of the bristles 41a is too small, there is a possibility that the ability of the bristles 41a to scrape foreign objects off the surface of the charging roller 22 may be degraded due to insufficient contact pressure between the bristles 41a and the surface of the charging roller 22.

[0184] In contrast, in the arrangement sequence of this embodiment, the component of the torque originating from the pushing force F1 (L1 × F1) can be sufficiently canceled out by the component of the torque originating from the brush reaction force F3 (L2 × F3). As a result, the torque M1 acting on the brush base 42 around point P2 can be suppressed to a smaller value, and the warping of the brush base 42 can be reduced. Furthermore, the amount of interference between the brush 41 and the surface of the charging roller 22 can be made more uniformly distributed in the longitudinal direction (X direction).

[0185] As described above, according to this embodiment, the brush 41 can contact the charging roller 22 with a more stable interference amount in the longitudinal direction (X direction) of the brush 41. In addition, the function of the brush 41 in scraping away foreign objects can be improved.

[0186] It should be noted that, in order to minimize the warping of the brush base 42, it is preferable that points P1 to P3, the pushing force F1, the abutment reaction force F2, and the brush reaction force F3 are set such that the value of the torque M1 calculated using formula (3) is 0 (N·mm). However, depending on the constraints of the component layout in the specific configuration of the brush unit 40, the value of the torque M1 does not have to be 0.

[0187] Furthermore, as long as the points P2, P1, and P3, which are the points of application of the force, are arranged in this order from one end of the brush base 42 (holding member) toward the center, the ranges of the first force-bearing portion, the second force-bearing portion, and the third force-bearing portion in the longitudinal direction (X direction) can overlap with each other. For example, the range of the contact surface in the brush base 42 that contacts the first portion 50a of the brush contact 50 (the range that receives the pushing force F1) and the range of the brush placement surface 42b (the range that receives the brush reaction force F3) can partially overlap with each other. Similarly, in this case, as long as point P3 is positioned relative to point P1 on the center side of the brush base 42, similar advantages as in this embodiment can be obtained.

[0188] Incidentally, although it has been referenced Figure 13A and Figure 13B Describes the center 420 relative to the brush base 42 ( Figure 1A The positional relationship of the force acting on the brush base 42 on one end side (driving side) is described, but a similar description can also be applied to the other end side (non-driving side).

[0189] That is, such as Figure 1A As shown, points P4 to P6 are positioned on the non-driving side (the same side as the end portion 422 of the non-driving side of the brush base 42) relative to the center 420 of the brush base 42 in the longitudinal direction (X direction) of the brush 41. Furthermore, points P4 to P6 are arranged in the order of points P5, P4, and P6 along the direction Xb from the end portion 422 of the non-driving side of the brush base 42 towards the center 420. In other words, the fifth force-bearing portion, the fourth force-bearing portion, and the sixth force-bearing portion are positioned on the other end side relative to the center of the holding member in the direction of the rotation axis of the charging roller, and are arranged in this order along the direction from one end towards the center.

[0190] According to this configuration, compared to the case where the arrangement order of this embodiment (the order of points P2, P1 and P3 from the drive side toward the center side) is used only on one end side in the longitudinal direction, the brush 41 can contact the charging roller 22 with a more stable amount of interference.

[0191] Modify Example

[0192] The control member used to control the position of the brush unit 40 in the above embodiments can be a member different from the shaft support member that rotatably supports the charging roller 22. For example, the position of the brush unit 40 can be controlled by abutting between, for example, the control portion (42j, 42k, and 42m) of the brush base 42 and a protrusion provided on the frame member (drum frame member 26, drive side cover member 43, and non-drive side cover member 44) of the drum unit 25.

[0193] Other embodiments

[0194] In the above embodiments, an image forming apparatus 1 in a direct transfer system was described as an example, wherein a toner image is transferred from an image carrier member (photosensitive drum 21) to a recording material P used as a transfer target. The configuration is not limited to this, and the technology of this disclosure can be applied to an image forming apparatus in an intermediate transfer system, wherein a toner image is transferred from the image carrier member (photosensitive drum 21) to an intermediate transfer member used as a transfer target in a single transfer, and then the toner image is transferred from the intermediate transfer member to the recording material P. Furthermore, the technology of this disclosure is not limited to monochrome image forming apparatuses, but can be applied to color image forming apparatuses using toners of multiple colors.

[0195] Although the image forming apparatus 1 including a cleaner-less processing unit 20 has been described in the above embodiments, the processing unit 20 may include a cleaning member such as a cleaning blade that collects (removes) residual toner from the photosensitive drum 21. In this case, there is a possibility that foreign matter passing through the cleaning member and reaching the charging section Q1, or foreign matter entering the image forming apparatus 1 with external air, may adhere to the charging roller 22. Therefore, even in a configuration where the processing unit 20 includes a cleaning member, the occurrence of image defects caused by foreign matter adhering to the charging roller 22 can be reduced by providing the brush unit 40 described in the embodiments.

[0196] Based on the technology of this disclosure described as an example in the above embodiments, a processing unit and an image forming apparatus capable of suppressing image defects caused by foreign matter adhering to the charging roller can be provided.

[0197] While this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the following claims should be interpreted in the broadest possible sense to include all such modifications and equivalent structures and functions.

Claims

1. A processing unit comprising: Rotatable image-carrying component; A charging roller, configured to contact the surface of the image carrier member and configured to charge the surface; A brush unit, the brush unit including a brush and a retaining member, the brush including a plate-shaped brush base and bristles protruding from the brush base, the retaining member being configured to retain the brush base and being movable such that the brush base moves toward and away from the charging roller; A control member configured to abut against the retaining member to control the position of the retaining member; as well as A pressing member configured to press the retaining member such that the bristles contact the surface of the charging roller and the retaining member abuts against the control member. In the case where the direction parallel to the thickness direction of the brush base and oriented from the brush base toward the charging roller is referred to as the first direction, and the direction opposite to the first direction is referred to as the second direction,... The retaining member includes a first force-receiving portion, a second force-receiving portion, and a third force-receiving portion. The first force-receiving portion is configured to receive a force from the pushing member in a first direction. The second force-receiving portion is configured to receive a force from the control member in a second direction. The third force-receiving portion is configured to receive a force from the brush base in the second direction when the bristles receive a reaction force from the surface of the charging roller. The first force-receiving part, the second force-receiving part, and the third force-receiving part are disposed at one end relative to the center of the holding member in the direction of the rotation axis of the charging roller, and are arranged from one end toward the center in the order of the second force-receiving part, the first force-receiving part, and the third force-receiving part.

2. The processing unit according to claim 1, Where the pushing member is referred to as the first pushing member and the control member is referred to as the first control member. The processing unit further includes: A second control member, disposed at one end relative to the center of the retaining member in the direction of the rotation axis and configured to abut against the retaining member to control the position of the retaining member; and A second pushing member is disposed at the other end relative to the center of the retaining member in the direction of the rotation axis and is configured to push the retaining member. The retaining member includes a fourth force-receiving portion, a fifth force-receiving portion, and a sixth force-receiving portion. The fourth force-receiving portion is configured to receive a force from the second pushing member in a first direction. The fifth force-receiving portion is configured to receive a force from the second control member in a second direction when the bristles receive a reaction force from the surface of the charging roller. The fourth force-bearing part, the fifth force-bearing part, and the sixth force-bearing part are arranged in the order of the fifth force-bearing part, the fourth force-bearing part, and the sixth force-bearing part in the direction from the other end toward the center.

3. The processing unit according to claim 2, The retaining member includes a surface opposite to the brush base in the thickness direction of the brush base. The opposing surfaces include a first placement surface portion, a second placement surface portion, and a non-fixed portion. One end portion of the brush base in the direction of the rotation axis is fixed to the first placement surface portion, and the other end portion of the brush base in the direction of the rotation axis is fixed to the second placement surface portion. The non-fixed portion is formed in the region between the first and second placement surface portions in the direction of the rotation axis, and the brush base is not fixed to the non-fixed portion. The third force-bearing part is the first placement surface part, and the sixth force-bearing part is the second placement surface part.

4. The processing unit according to claim 3, The brush base includes a sheet-like bristle support portion and a metal plate component. The bristle support portion is configured to support the bristles, and the metal plate component is configured to support the bristle support portion. The retaining member includes a brush retaining portion, which comprises a first placement surface portion and a second placement surface portion and is formed of a resin material.

5. The processing unit according to any one of claims 1 to 4, The control component is a shaft support component configured to rotatably support the end portion of the charging roller. The second force-bearing part is the abutting part, and the retaining member abuts against the shaft support member at the abutting part.

6. The processing unit according to any one of claims 1 to 4, further comprising: A frame member configured to support the brush unit. The retaining member is pivotally supported by the frame member.

7. The processing unit according to claim 6, The retaining member includes a brush retaining portion and a swinging support portion, the brush retaining portion being configured to retain the brush base, and the swinging support portion being coupled to the end portion of the brush retaining portion in the direction of the rotation axis. The frame member includes a support portion configured to support the swing support portion. One of the support portion and the swing support portion includes a shaft portion extending in the direction of the rotation axis, and The other of the support portion and the swing support portion includes a receiving portion configured to receive the shaft portion.

8. The processing unit according to any one of claims 1 to 4, In the case where the brush unit is referred to as the first brush unit. The processing unit includes a second brush unit configured to collect foreign matter attached to the image carrier member, and The second brush unit includes a brush configured to contact the surface of the image carrier member at a position downstream of the transfer portion and upstream of the charging portion in the rotational direction of the image carrier member during image formation. The transfer portion is the part where the image is transferred from the image carrier member to the transfer target, and the charging portion is the part of the image carrier member opposite to the charging roller.

9. The processing unit according to any one of claims 1 to 4, further comprising: The developing unit includes a toner storage section and a developing roller. The toner storage section is configured to store toner, and the developing roller is configured to carry toner for supplying toner to the image carrier member. The processing unit is configured to collect toner that has not been transferred from the image carrier to the transfer target into the toner storage section via the developing roller.

10. An image forming apparatus comprising: The processing unit according to any one of claims 1 to 9; as well as Equipment body, The image forming apparatus is configured to form an image on a recording material using the processing unit attached to the apparatus body.

Images