Process unit and image forming apparatus

Abstract

This suppresses image defects caused by foreign matter adhering to the electrostatic roller. [Solution] A process unit comprising a brush unit having a rotatable image carrier, a charging roller positioned to contact the surface of the image carrier and charge the surface, a bearing member that rotatably supports the charging roller, a brush including a base material and brush fibers protruding from the base material and in contact with the surface of the charging roller, and a holding member that holds the base material, wherein the holding member has a restricting portion that can contact the bearing member, and the position of the holding member is restricted by the contact between the restricting portion and the bearing member.

Description

Technical Field

[0001] The present invention relates to a process unit used in an image forming apparatus and an image forming apparatus that forms an image on a recording material.

Background Art

[0002] Patent Document 1 describes that in a cleanerless image forming apparatus, a brush-shaped cleaning member is arranged to remove toner adhering to a charging roller.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The cleaning member in the above document is mainly for removing toner adhering to the charging roller. However, when foreign matter such as dust adheres to the charging roller, charging failure due to the foreign matter may occur, and for example, image defects called black spots may occur.

[0005] An object of the present invention is to provide a process unit and an image forming apparatus capable of suppressing image defects caused by foreign matter adhering to a charging roller.

Means for Solving the Problems

[0006] One aspect of the present invention is a process unit comprising a brush unit having a rotatable image carrier, a charging roller positioned to contact the surface of the image carrier and to charge the surface, a bearing member that rotatably supports the charging roller, a brush including a base material and brush fibers protruding from the base material and in contact with the surface of the charging roller, and a holding member that holds the base material, wherein the holding member has a restricting portion that can contact the bearing member, and the position of the holding member is restricted by the contact between the restricting portion and the bearing member. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a process unit and an image forming apparatus that can suppress image defects caused by foreign matter adhering to the charging roller. [Brief explanation of the drawing]

[0008] [Figure 1] Rear view (a), cross-sectional views (b, c), and enlarged views of a portion of the cross-section (d-g) of the drum unit according to the embodiment. [Figure 2] A schematic diagram (a) and a perspective view (b) of an image forming apparatus according to an embodiment. [Figure 3] A perspective view of an image forming apparatus according to an embodiment. [Figure 4] (a) A cross-sectional view of the process unit according to the embodiment, and (b) a schematic diagram showing the arrangement of the photosensitive drum and process components. [Figure 5] A perspective view (a) of the drum unit according to the embodiment, and enlarged views (b, c) of a part of the drum unit. [Figure 6] A perspective view showing a part of a drum unit according to an embodiment. [Figure 7] Rear view (a), cross-sectional view (b, c), and side view (d-g) of the drum unit according to the embodiment. [Figure 8] Perspective views (a, b) of a photosensitive drum and a charging roller according to an embodiment. [Figure 9] Diagrams (a-e) illustrating the brush unit according to the embodiment. [Figure 10] Diagrams (a, b) illustrating the brush unit according to the embodiment. [Figure 11] Diagrams (a, b) illustrating the brush unit according to the embodiment. [Modes for carrying out the invention]

[0009] The embodiments relating to this disclosure will be described below with reference to the drawings.

[0010] (Image forming apparatus) An overview of the image forming apparatus 1 according to one embodiment will be described using Figures 2(a) and 2(b) and Figure 3. Figure 2(a) is a schematic diagram of the image forming apparatus 1 according to one embodiment. Figures 2(b) and 2(3) are perspective views of the image forming apparatus 1.

[0011] An image forming apparatus refers to a general apparatus that forms an image on a recording material P using an electrophotographic image forming unit. Examples of image forming apparatuses include electrophotographic copiers, laser beam printers, LED printers, and electrophotographic facsimile machines. The image forming apparatus 1 of this embodiment is a monochrome laser beam printer that forms an image on a recording material P based on image information input from an external device. The recording material P includes various sheet materials of different materials, such as plain paper and cardboard, plastic films such as overhead projector sheets, specially shaped sheets such as envelopes and index paper, and cloth.

[0012] In the following description and drawings, the direction of the rotation axis of the image carrier (photosensitive drum 21) of the image forming apparatus 1 is defined as the X direction. The vertical direction (direction of gravity) when the image forming apparatus 1 is installed on a horizontal plane is defined as the Z direction. The direction that intersects both the X and Z directions is defined as the Y direction. Preferably, the X, Y, and Z directions are orthogonal to each other.

[0013] In the present embodiment, an input coupling portion 51a (described later) that receives the driving force of a driving source (motor) disposed in the apparatus main body 1A is disposed on one end side in the X direction of the process unit 20. Therefore, one end side in the X direction (the side indicated by the arrow X in the figure) may be referred to as the "driving side", and the other end side in the X direction (the side opposite to the arrow X) may be referred to as the "non-driving side".

[0014] As shown in FIGS. 2(a), (b) and FIG. 3, the image forming apparatus 1 includes an apparatus main body 1A, an image forming unit 10, a fixing unit 70, a pickup roller 65 as a feeding unit, and a pair of discharge rollers 80 as a discharging unit. The image forming unit 10 includes a process unit 20 as a process unit, a scanner unit 11 as an exposure device, and a transfer roller 12 as a transfer unit.

[0015] The apparatus main body 1A is a housing (structural housing) including a frame member such as a sheet metal frame that constitutes the frame of the image forming apparatus 1, and a cover member that forms the outer appearance surface of the image forming apparatus 1. The image forming unit 10, the fixing unit 70, the pickup roller 65, and the pair of discharge rollers 80 are accommodated or supported by the apparatus main body 1A.

[0016] FIG. 4(a) is a cross-sectional view of the process unit 20. FIG. 4(b) is a schematic view of the photosensitive drum 21 and process members disposed around it. The process unit 20 of the present embodiment has a drum unit 25 including a photosensitive drum 21 and a developing unit 30 including a developing roller 31.

[0017] The drum unit 25 has a photosensitive drum 21, a charging roller 22, a pre-exposure unit 23, a paper powder recovery brush 24 which is a brush unit for the photosensitive drum 21, a brush unit 40 for the charging roller 22, and a drum frame 26. The developing unit 30 has 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 referred to as the first brush unit, the brush unit for the photosensitive drum 21 can be referred to as the second brush unit.

[0018] The photosensitive drum 21 functions as an image carrier that holds a latent image (electrostatic latent image) and a toner image (developer image). The photosensitive drum 21 is a photoreceptor molded into a cylindrical (drum) shape. The photosensitive drum 21 of this embodiment has a cylindrical base made of aluminum and a photosensitive layer formed on the base of a negatively charged organic photoreceptor. The photosensitive drum 21 is rotated by the motor of the apparatus body 1A at a predetermined circumferential speed (process speed) in a predetermined rotational direction (direction indicated by arrow Q in Figures 4(a) and 4(b)) during image formation.

[0019] As shown in Figure 4(b), the charging section Q1 is defined as the position where the surface 21a of the photosensitive drum 21 and the charging roller 22 face each other. The exposure section Q2 is defined as the position where the laser light from the scanner unit 11 is irradiated onto the surface 21a of the photosensitive drum 21. The developing section Q3 is defined as the position where the surface 21a of the photosensitive drum 21 and the developing roller 31 face each other. The transfer section Q4 is defined as the position where the surface 21a of the photosensitive drum 21 and the transfer roller 12 face each other. The brush contact section Q5 is defined as the position where the surface 21a of the photosensitive drum 21 and the paper dust collection brush 24 come into contact. The charging section Q1, exposure section Q2, developing section Q3, transfer section Q4, and brush contact section Q5 are arranged in this order in the rotation direction (Q) of the photosensitive drum 21 during image formation. In other words, in this embodiment, the rotation direction of the photosensitive drum 21 during image formation is such that a point on the surface 21a of the photosensitive drum 21 passes through the charging section Q1, the exposure section Q2, the developing section Q3, the transfer section Q4, and the brush contact section Q5 in that order.

[0020] The charging roller 22 is positioned to contact the photosensitive drum 21. In this embodiment, the charging roller 22 can contact and separate from the photosensitive drum 21, and the image forming operation is performed with the charging roller 22 in contact with the photosensitive drum 21. The charging roller 22 is rotatable in a direction that follows the photosensitive drum 21 (counterclockwise in Figure 4(a)).

[0021] The charging roller 22 charges the surface 21a of the photosensitive drum 21 by applying a charging voltage from a charging power supply provided in the main body 1A of the device. In this embodiment, the photosensitive drum 21 is negatively charged by the charging roller 22.

[0022] 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 irradiates light onto the surface 21a of the photosensitive drum 21 to remove surface charge in order to generate a stable discharge in the charging section.

[0023] The paper dust collection brush 24 (brush unit for the photosensitive drum 21) has a brush portion 24a made of pile fabric or the like, and a support member that supports the brush portion 24a and is fixed to the drum frame 26. The paper dust collection brush 24 blocks foreign matter such as paper dust adhering to the surface 21a of the photosensitive drum 21 at the brush contact portion Q5, thereby suppressing the occurrence of image defects caused by foreign matter. On the other hand, the paper dust collection brush 24 allows toner adhering to the surface 21a of the photosensitive drum 21 to pass through the brush contact portion Q5.

[0024] The brush unit 40 for the electrostatic roller 22 has a brush 41 that can come into contact with the surface 22a of the electrostatic roller 22. The brush 41 can scrape off foreign matter such as paper dust and sand that has adhered to the surface 22a of the electrostatic roller 22. The detailed configuration and operation of the brush unit 40 will be described later.

[0025] The scanner unit 11 irradiates the photosensitive drum 21 with laser light corresponding to image information input from an external device, and exposes the photosensitive drum 21 by scanning the surface 21a of the photosensitive drum 21 using a polygon mirror (scanning optical system). This exposure process forms an electrostatic latent image on the surface 21a of the photosensitive drum 21 corresponding to the image information. Note that the exposure device is not limited to the scanner unit 11 that emits laser light, but may also be an LED exposure device, for example. An LED exposure device is an exposure device that uses an LED array, in which multiple LEDs are arranged along the rotation axis direction of the photosensitive drum 21 (the main scanning direction in the exposure process), as a light source.

[0026] The developing unit 30 includes a developing roller 31 as a developer carrier for holding the developer, a developing container 32 which forms the frame of the developing unit 30, a supply roller 33 capable of supplying developer to the developing roller 31, an agitator 34, and a developing blade 35. The developing roller 31, the supply roller 33, and the agitator 34 are rotatably supported by the developing container 32. 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 in rotatable contact with the developing roller 31, and the toner, which is the developer contained in the developing container 32, is supplied (applied) to the surface of the developing roller 31 by the supply roller 33. Note that the supply roller 33 is not necessarily required if a configuration is in place that can supply sufficient toner to the developing roller 31.

[0027] The developing unit 30 of this embodiment uses a contact developing method. That is, the toner layer supported on the developing roller 31 comes into contact with the surface 21a of the photosensitive drum 21 in the developing section Q3 (developing area) where the photosensitive drum 21 and the developing roller 31 face each other. A developing voltage is applied to the developing roller 31 by a developing power supply. Under the developing voltage, the toner supported on the developing roller 31 is transferred from the developing roller 31 to the drum surface according to the potential distribution of the surface 21a of the photosensitive drum 21, thereby developing the electrostatic latent image into a toner image. In this embodiment, an inversion developing method is employed. That is, in the charging process, toner adheres to the area of ​​the surface 21a of the photosensitive drum 21 that has been charged, and in the exposure process, the amount of charge has decreased due to light irradiation, thereby forming a toner image.

[0028] Furthermore, in this embodiment, a toner with a particle size of approximately 6 μm and a normal polarity (normal charging polarity) of negative polarity is used. As an example, the toner used in this embodiment is a polymerized toner produced by a polymerization method. In addition, the toner in this embodiment does not contain magnetic components, and the toner is supported on the developing roller 31 mainly by intermolecular forces and electrostatic forces (mirror image forces), making it a so-called non-magnetic one-component developer. However, a one-component developer containing magnetic components may also be used. Furthermore, the one-component developer may contain additives (for example, wax or silica fine particles) to adjust the fluidity and charging performance of the toner in addition to toner particles. Alternatively, a two-component developer composed of a non-magnetic toner and a magnetic carrier may be used as the developer. When a magnetic developer is used, for example, a cylindrical sleeve with a magnet placed inside is used as the developer carrier (developing roller).

[0029] The developing container 32 functions as a toner storage section that houses toner (developer). Inside the developing container 32, a toner storage chamber 36 is formed for storing toner. The agitator 34 is positioned inside the toner storage chamber 36. The agitator 34 rotates, driven by the motor of the main body 1A, to agitate the toner in the developing container 32 and to transport the toner toward the developing roller 31 and the supply roller 33. The agitator 34 also passes through the developing section Q3 without being used for development, and then circulates the toner stripped from the developing roller 31 within the developing container 32, homogenizing the toner in the developing container 32. Note that the agitator 34 is not limited to a rotating form. For example, an oscillating agitator may be used.

[0030] The developing blade 35 is positioned at the opening of the developing container 32 together with the developing roller 31. The developing blade 35 regulates the amount of toner carried on the developing roller 31. In other words, the toner supplied to the surface of the developing roller 31 is uniformly thinned as it passes through the area opposite the developing blade 35 as the developing roller 31 rotates. In addition, as the toner supplied to the surface of the developing roller 31 passes through the area opposite the developing blade 35, its charge is increased to a negative polarity due to triboelectric charging.

[0031] The developing unit 30 of this embodiment includes a shielding member 37 positioned above the developing blade 35. The shielding member 37 shields the area between the developing roller 31 and the developing blade 35, and between the photosensitive drum 21 and the developing roller 31, to prevent foreign matter from entering when the brush 41 scrapes off foreign matter adhering to the aforementioned charging roller 22. The shielding member 37 is positioned below the contact position between the brush 41 and the charging roller 22, and above the area 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 of the developing container 32 to a position close to the surface 21a of the photosensitive drum 21. The shielding member 37 substantially isolates the space between the drum unit 25 and the developing unit 30 and the space where the developing roller 31 is located, in the cross-section shown in Figure 4(a), except for a small gap between the shielding member 37 and the surface 21a of the photosensitive drum 21. The shielding member 37 may be a member fixed to the developing container 32 with screws or adhesive, or it may be integrally formed with the resin member constituting the developing container 32.

[0032] The term "process unit" is not limited to one comprising all the components of the process unit 20 in this embodiment, but may include an image carrier (photosensitive drum) and at least one process component. A process component is a component that acts on the image carrier to perform processes such as charging, exposure, development, transfer, and cleaning in an electrophotographic process. For example, a drum unit 25, which includes a photosensitive drum 21 and a charging roller 22, is an example of a process unit when a developing unit 30 is detachably attached to the drum unit 25. The charging roller 22, developing roller 31, and brush unit (paper dust collection brush 24) for the photosensitive drum 21 in this embodiment are examples of process components.

[0033] (Image formation process) 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 transports recording material P one sheet at a time and forms an image on the recording material P using the process unit 20. When the image forming apparatus 1 receives image information and instructions to execute the image forming operation from an external device connected to it, the control unit of the image forming apparatus 1 starts the image forming operation.

[0034] When the image forming operation starts, the photosensitive drum 21 is rotated in the image forming unit 10, and the surface 21a of the photosensitive drum 21 is uniformly charged to a predetermined polarity and potential in the charging unit Q1 by applying voltage to the charging roller 22. The scanner unit 11 irradiates the photosensitive drum 21 with laser light based on the input image information. As a result, the charged surface 21a of the photosensitive drum 21 is exposed in the exposure unit Q2, and an electrostatic latent image is formed on the surface 21a of the photosensitive drum 21. The developing roller 31 carries toner as a developer and rotates, supplying it to the photosensitive drum 21 in the developing unit Q3. As a result, the electrostatic latent image is developed into a toner image (developer image).

[0035] In parallel with the operation of the image forming unit 10, one sheet of recording material P is fed at a time from the recording material storage unit (tray, cassette) located at the bottom of the main body 1A by the pickup roller 65. The feeding timing of the recording material P is controlled so that the recording material P enters the transfer unit Q4 at the same time that the toner image formed on the photosensitive drum 21 reaches the transfer unit Q4. As the recording material P passes through the transfer unit Q4, the toner image is transferred from the photosensitive drum 21 to the recording material P by applying voltage to the transfer roller 12.

[0036] The recording material P that has passed through the transfer section Q4 is transported to the fixing section 70, where it undergoes image fixing. Specifically, the fixing section 70 heats and pressurizes the toner image on the recording material P while transporting it by gripping it with the nip portions of a pair of rotating bodies such as a fixing roller pair. The recording material P that has passed through the fixing section 70 is discharged to the outside of the device body 1A by a pair of discharge rollers 80 and loaded onto a discharge tray 81, which is a loading section formed on the upper part of the device body 1A.

[0037] In this embodiment, the image forming apparatus 1 does not include a cleaning member for recovering (removing) toner that was not transferred to the recording material P (transfer target) in the transfer section Q4 (transfer residue toner) from the photosensitive drum 21. In this embodiment, the transfer residue toner adhering to the surface area on the photosensitive drum 21 that has passed through the transfer section Q4 is recovered by the developing roller 31 in the developing section Q3 after passing through the brush contact section Q5 and the charging section Q1. This type of method is called a cleanerless method or a developing and cleaning method.

[0038] More specifically, the paper dust collection brush 24 blocks foreign matter such as paper dust adhering to the photosensitive drum 21 from the recording material P at the brush contact area Q5, while allowing the transfer residue toner to pass through. Furthermore, as the transfer residue toner passes through the charging area Q1, the toner particles charged with the opposite polarity to the normal polarity and toner particles with a charge amount close to zero are supplied with the normal polarity charge, thereby increasing the charge amount of the transfer residue toner.

[0039] Subsequently, the behavior of the residual toner as it passes through the developing unit Q3 differs depending on the region on the surface 21a of the photosensitive drum 21. In this embodiment, since an inversion development method is employed, the surface potential (bright area potential) of the photosensitive drum 21 in the region exposed in the exposure unit Q2 (bright area region) is on the non-normal polarity side with respect 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 without being transferred to the developing roller 31 in the developing unit Q3, and becomes part of the toner image together with the toner supplied from the developing roller 31. On the other hand, the surface potential (dark area potential) of the photosensitive drum 21 in the region not exposed in the exposure unit Q2 (dark area region) is on the normal polarity side with respect 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 in the developing unit Q3 and collected in the developing container 32. The transfer residue toner collected in the developing container 32 is mixed with the toner already present in the developing container 32 to become uniform, and then used again for developing.

[0040] In the 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 paper dust collection brush 24 blocks the foreign matter as in this embodiment, some of the foreign matter may slip through the paper dust collection brush 24. Therefore, as described below, it is preferable to use a brush unit 40 for the charging roller 22 to reduce the occurrence of image defects caused by the adhesion of foreign matter to the charging roller 22.

[0041] (Toner replenishment and cartridge replacement) This section describes toner replenishment and cartridge replacement in the image forming apparatus 1 of this embodiment. As shown in Figures 2(b) and 3, a top cover 82 that can be opened and closed is provided on the upper part of the apparatus body 1A. At least a portion of the upper surface of the top cover 82 is formed as an output tray 81 for loading. An opening / closing member 83 is attached to the top cover 82, which is supported so as to be openable and closable around a pivot axis 83a that extends in the front-rear direction (Y direction) of the apparatus. In addition, an opening 82a that opens upward is formed in the output tray 81 of the top cover 82.

[0042] As shown in Figures 2(a) and 3, the image forming apparatus 1 is provided with a mounting section 106 on which a toner pack 100, which serves as a replenishment container, can be attached. The mounting section 106 has an opening (toner receiving port) that can communicate with the toner discharge port of the toner pack 100, and a shutter that can open and close the toner receiving port. The mounting section 106 may be part of the process unit 20, or it may be fixed to the apparatus body 1A.

[0043] The opening / closing member 83 is configured to move between a closed position, which closes the opening 82a to prevent the toner pack 100 from being mounted on the mounting section 106, and an open position, which opens the opening 82a to allow the toner pack 100 to be mounted on the mounting section 106. When the opening / closing member 83 is in the open position, the mounting section 106 is exposed to the outside of the image forming apparatus 1 through the opening 82a. In the closed position, the opening / closing member 83 functions as part of the discharge tray 81 and can support the recording material P discharged into the discharge tray 81. In addition, a groove 82b provided in the top cover 82 allows the user to easily place their fingers on the opening / closing member 83.

[0044] In this embodiment, a direct replenishment method is employed that allows toner to be supplied to the developing unit 30 inside the image forming apparatus 1 from outside the image forming apparatus 1. In other words, the user can replenish toner to the developing unit 30 from the toner pack 100 mounted on the mounting section 106 while the process unit 20, including the developing unit 30, is mounted on the apparatus body 1A. With the toner pack 100 mounted on the mounting section 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.

[0045] The direct replenishment method has the following advantages compared to the method of replacing the entire process unit 20 (process cartridge method). First, it improves usability because it eliminates the need to remove the process unit 20 from the image forming apparatus 1 and replace it with a new process cartridge when the toner level in the process unit 20 becomes low. Also, it is cheaper to replenish the toner in the developing container 32 than to replace the entire process unit 20. Furthermore, the direct replenishment method reduces costs because it does not require the replacement of various rollers, gears, etc., compared to the method of replacing only the developing unit 30 of the process unit 20 (developing cartridge method).

[0046] In this embodiment, the process unit 20 is configured as a process cartridge that can be attached to and detached from the main body 1A of the device. The user can remove the process unit 20 from the main body 1A by opening an opening / closing member provided on the main body 1A and replace it with a new process unit 20.

[0047] The configuration of the brush unit 40 described below may also be applied to image forming apparatuses using process cartridges or developing cartridges. Furthermore, the process unit 20 is not limited to a cartridge that can be attached to or detached from the apparatus body 1A, but may be fixed to the apparatus body 1A in a manner that does not anticipate replacement by the user. In other words, the "process unit" in this disclosure may be shipped attached to the apparatus body 1A during the manufacture of the image forming apparatus 1 and can be used without replacement until, for example, the image forming apparatus 1 reaches the end of its lifespan.

[0048] (Drum unit) The configuration of the drum unit 25 will be explained using Figures 4(a) to 8(b). Figure 5(a) is a perspective view of the drum unit 25. Figure 5(b) is a perspective view of the non-driven end of the drum unit 25 as seen from the center of the drum unit 25 in the longitudinal direction. Figure 5(c) is a perspective view of the driven end of the drum unit 25 as seen from the center of the drum unit 25 in the longitudinal direction. Figure 6 is a perspective view of the drum unit 25 (excluding the drum frame 26, the driven-side cover member 43, and the non-driven-side cover member 44). Figure 7(a) is a rear view of the drum unit 25 (excluding the driven-side cover member 43 and the non-driven-side cover member 44) as seen from the upstream side in the Y direction. Figures 7(b) and 7(c) are cross-sectional views of the drum unit 25 along the CC line in Figure 7(a). Figures 7(d) and 7(e) are side views of the drum unit 25 as seen in the direction of arrow D in Figure 7(a). Figures 7(f) and 7(g) are side views of the drum unit 25 as seen in the direction of arrow E in Figure 7(a). Figures 8(a) and 8(b) are schematic diagrams illustrating the contact and separation of the photosensitive drum 21 and the charging roller 22. Figures 7(b), 7(d), 7(f) and 8(b) show the state in which the charging roller 22 is in contact with the photosensitive drum 21, while Figures 7(c), 7(e), 7(g) and 8(a) show the state in which the charging roller 22 is separated from the photosensitive drum 21.

[0049] As shown in Figures 4(a) and 5(a), the drum unit 25 includes a photosensitive drum 21, a charging roller 22, a paper dust collection brush 24, a drum frame 26, a drive-side cover member 43, a non-drive-side cover member 44, and a brush unit 40. The drum unit 25 also includes a drive-side bearing 45 and a non-drive-side bearing 46 (Figures 5(b) and 5(c)), charging roller biasing members 48 and 49 (Figures 7(d) and 7(f)), charging roller separation members 28 and 29 (Figures 7(d) to 7(g)), and a charging roller electrical contact 47 (Figure 6).

[0050] The drum unit 25 extends in a long, slender shape along the rotation axis of the photosensitive drum 21. Similarly, the charging roller 22 extends in a long, slender shape along the rotation axis of the photosensitive drum 21. Therefore, in the following description, the direction parallel to the rotation axis 21X of the photosensitive drum 21 (the 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.

[0051] As shown in Figures 5(a) to 5(c), a drive-side cover member 43 is attached to one end (drive side) of the drum frame 26 extending in the X direction, and a non-drive-side cover member 44 is attached to the other end (non-drive side) of the drum frame 26. The drive-side cover member 43 and the non-drive-side cover member 44 are fixed to the drum frame 26 by screwing or adhesive. The drive-side cover member 43 forms at least a part of the end face of one end (drive side) of the drum unit 25, and the non-drive-side cover member 44 forms at least a part of the end face of the other end (non-drive side) of the drum unit 25. The drum frame 26, drive-side cover member 43, and non-drive-side cover member 44, which are connected to each other, constitute the frame of the drum unit 25. Furthermore, the drum frame 26, drive-side cover member 43, and non-drive-side cover member 44, which are connected to each other, together with the frame of the developing unit 30, constitute the frame of the process unit 20.

[0052] The photosensitive drum 21 is rotatably supported around the rotation axis 21X (Figure 5(a)) by the drive-side cover member 43 and the non-drive-side cover member 44.

[0053] As shown in Figures 5(a) and 6, a drum drive member 51 is provided on one longitudinal end (drive side) of the photosensitive drum 21. In this embodiment, the drum drive member 51 rotates integrally with the outer circumference of the photosensitive drum 21 that contacts the charging roller 22. The drum drive member 51 has an input coupling part 51a which serves as a drive input part that receives a driving force (rotational force) from the main body 1A to rotate the photosensitive drum 21.

[0054] With the process unit 20 mounted on the apparatus body 1A, the input coupling portion 51a of the drum drive member 51 engages with the output coupling portion of the apparatus body 1A. Through the engagement of the output coupling portion and the input coupling portion 51a, driving force is transmitted from the motor of the apparatus body 1A to the photosensitive drum 21, causing the photosensitive drum 21 to rotate in a predetermined rotational direction (Q).

[0055] The charging roller 22 is rotatably supported by a drive-side bearing 45 and a non-drive-side bearing 46 of a bearing member. When the drive-side bearing 45 is referred to as the first bearing member, the non-drive-side bearing 46 can be referred to as the second bearing member. The charging roller 22 rotates around a rotation axis 22X (Figure 6) which is substantially parallel to the rotation axis 21X of the photosensitive drum 21.

[0056] The drive-side bearing 45 and the non-drive-side bearing 46 are supported on the drum frame 26 in such a manner that they are movable relative to the drum frame 26 in a direction intersecting the longitudinal direction of the photosensitive drum 21. As the drive-side bearing 45 and the non-drive-side bearing 46 move, the charging roller 22 is movable in directions toward and toward the photosensitive drum 21 (arrows S and T in Figures 7(b) and 7(c)).

[0057] Specifically, the drive-side bearing 45 and the non-drive-side bearing 46 in this embodiment are positioned between two guides 26d (Figures 7(b) and 7(c)) provided on the drum frame 26. Figures 7(b) and 7(c) show two guides 26d corresponding to the non-drive-side bearing 46, but the drum frame 26 is provided with two guides corresponding to the drive-side bearing 45. The drive-side bearing 45 and the non-drive-side bearing 46 have grooves 45g (Figure 6) formed therein that engage with the guides 26d. The two guides 26d extend in directions perpendicular to the longitudinal direction of the photosensitive drum 21 (arrows S and T). The drive-side bearing 45 and the non-drive-side bearing 46 are movable along the extending direction of the two guides 26d.

[0058] The charging roller biasing members 48 and 49 are arranged on both longitudinal ends of the charging roller 22. The charging roller biasing member 48 on the driving side is arranged between the driving-side bearing 45 and the drum frame body 26 (Figs. 7(f)(g)). The charging roller biasing member 49 on the non-driving side is arranged between the non-driving-side bearing 46 and the drum frame body 26 (Figs. 7(d)(e)). The charging roller biasing members 48 and 49 bias the driving-side bearing 45 and the non-driving-side bearing 46 in the direction in which the charging roller 22 approaches the photosensitive drum 21 (arrow T in Fig. 7(b)).

[0059] As shown in Fig. 6, a driving input gear 22G is attached to the driving-side end of the charging roller 22. The driving input gear 22G meshes with the gear portion of the drum driving member 51 described above. Therefore, the charging roller 22 of the present embodiment rotates in the direction of being carried around by the photosensitive drum 21 by the driving force transmitted through the drum driving member 51 and the driving input gear 22G when the photosensitive drum 21 is rotationally driven (arrow R in Figs. 6 and 7(b)-(g)).

[0060] Note that the charging roller 22 is not limited to the configuration of rotating by drive transmission through the drum driving member 51 and the driving input gear 22G, and may be configured to rotate by the frictional force acting between the surfaces 21a and 22a of the photosensitive drum 21 and the charging roller 22, for example.

[0061] As shown in Fig. 4(a), the paper powder collecting brush 24 is fixed to the drum frame body 26 so as to contact the photosensitive drum 21.

[0062] (Separation of the charging roller) The configuration regarding the contact and separation of the charging roller 22 with respect to the photosensitive drum 21 will be described. The image forming apparatus 1 of the present embodiment includes a mechanism capable of separating the charging roller 22 from the photosensitive drum 21 from when the image forming apparatus 1 is shipped from the apparatus main body 1A until it reaches the user's hands.

[0063] Specifically, as shown in Figure 8(a), the charging roller separation members 28 and 29 are provided at both longitudinal ends of the charging roller 22. One charging roller separation member 28 is positioned at the drive-side end of the charging roller 22, and the other charging roller separation member 29 is positioned at the non-drive-side end of the charging roller 22. The charging roller separation members 28 and 29 are rotatable around the rotation axis 22X of the charging roller 22 and are rotatable relative to the charging roller 22.

[0064] As shown in Figures 8(a) and 8(b), each of the charging roller separating members 28 and 29 has contact ribs 28a and 29a, force receiving protrusions 28b and 29b, and levers 28c and 29c.

[0065] The contact ribs 28a and 29a are formed to protrude outward beyond the outer diameter of the charging roller 22. The contact ribs 28a and 29a are capable of contacting 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. As shown in Figures 8(a) and 7(c), 7(e), and 7(g), when the contact ribs 28a and 29a are in contact with 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. In addition, the charging roller separation members 28 and 29 receive the biasing force of the charging roller biasing members 48 and 49. In other words, the contact ribs 28a and 29a come into contact with the surface 21a of the photosensitive drum 21, so that the charging roller 22 is held in a position separated from the photosensitive drum 21 (separated position) against the biasing force of the charging roller biasing members 48 and 49.

[0066] As shown in Figures 8(a) and 8(b), the force-receiving protrusions 28b and 29b are located at both longitudinal ends of the photosensitive drum 21. The drum drive member 51, located at one end of the photosensitive drum 21, has a protrusion 51b that can engage with the force-receiving protrusion 28b of the drive-side charging roller separation member 28. The other end of the photosensitive drum 21 has a drum flange 52 that rotates integrally with the photosensitive drum 21. The drum flange 52 has a protrusion 52b that can engage with the force-receiving protrusion 29b of the non-drive-side charging roller separation member 29.

[0067] The force-receiving projection 28b of the charging roller separation member 28 and the projection 51b of the drum drive member 51 are positioned at the same location in the longitudinal direction (X direction) of the charging roller 22. The force-receiving projection 29a of the charging roller separation member 29 and the projection 52b of the drum flange 52 are positioned at the same location in the longitudinal direction (X direction) of the charging roller 22. Furthermore, the drum drive member 51 and the drum flange 52 in this embodiment have multiple sets (specifically, four sets) of projections 51b and 52b, with each set consisting of one projection 51b and one projection 52b having equal rotational phases with respect to the rotation axis 21X of the photosensitive drum 21.

[0068] After the image forming apparatus 1 is installed at the user's location, during the initialization process of the image forming apparatus 1, the charging roller 22 is brought into contact with the photosensitive drum 21. Specifically, during the initialization process, the photosensitive drum 21 is rotated in a predetermined rotational direction (Q) by the driving force from the motor of the apparatus body 1A. Then, as shown in Figure 8(b), the protrusions 51b and 52b of either the drum drive member 51 or the drum flange 52, which rotate integrally with the photosensitive drum 21, come into contact with and press against the force-receiving protrusions 28b and 29b of the charging roller separation members 28 and 29. As a result, the charging roller separation members 28 and 29 rotate in the direction indicated by the arrow R.

[0069] The rotation of the charging roller separation members 28 and 29 releases the contact between the contact ribs 28a and 29a and the surface 21a of the photosensitive drum 21. Then, as shown in Figures 7(b), (d), and (f), the biasing force of the charging roller biasing members 48 and 49 causes the drive-side bearing 45 and the non-drive-side bearing 46 to slide in the direction indicated by arrow T, moving the charging roller 22 to a position where it contacts the photosensitive drum 21 (contact position).

[0070] When the charging roller separation members 28 and 29 are assembled to the drum unit 25, they are assembled in a predetermined phase (FIG. 8(a)) that holds the charging roller 22 in the separated position. However, if the charging roller separation members 28 and 29 rotate from the predetermined phase for some reason, the operator can return the charging roller separation members 28 and 29 to the predetermined phase by gripping and operating the levers 28c and 29c of the charging roller separation members 28 and 29.

[0071] With the mechanism described above, for example, the charging roller 22 can be separated from the photosensitive drum 21 until the image forming apparatus 1 reaches the user after being shipped. Therefore, deformation of the charging roller 22 due to the charging roller 22 being pressed against the photosensitive drum 21 for a long period of time in a stopped state can be suppressed, and the risk of image defects caused by deformation of the charging roller 22 can be reduced. Also, after the image forming apparatus 1 reaches the user, the charging roller 22 automatically contacts the photosensitive drum 21 as the photosensitive drum 21 rotates, so that the waiting time until the user starts using the image forming apparatus 1 can be shortened.

[0072] (Conduction path of charging roller) The configuration regarding the conduction path of the charging roller 22 in the drum unit 25 will be described. As shown in FIG. 6, the charging roller electrical contact 47 is disposed on one end side (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.

[0073] Specifically, the charging roller electrical contact 47 has a first contact portion 47a that can contact the electrical contact (body-side contact portion) of the device body 1A, and a second contact portion 47b that contacts one end of the driving-side charging roller biasing member 48. The charging roller biasing member 48 is, for example, a compression coil spring made of metal wire and is conductive. The other end of the charging roller biasing member 48 is in contact with the driving-side bearing 45. The driving-side bearing 45 is made of a resin material mixed with a conductive material such as carbon and is conductive. The driving-side bearing 45 also holds, for example, the conductive shaft portion (metal shaft) of the charging roller 22. Therefore, the charging roller electrical contact 47 of this embodiment is electrically connected to the charging roller 22 via the charging roller biasing member 48 and the driving-side bearing 45.

[0074] With the process unit 20 mounted on the main body 1A, the first contact portion 47a of the charging roller electrical contact 47 contacts the main body side contact portion of the main body 1A. The main body side contact portion is electrically connected to a charging power supply on a high-voltage substrate located on the main body 1A. Therefore, the charging voltage from the charging power supply can be applied to the charging roller 22 via the main body side contact portion and the conductive path from the charging roller electrical contact 47 to the charging roller 22.

[0075] (Brush unit) A brush unit 40 for the electrostatic roller 22 will now be described. The brush unit 40 has a brush 41 (Figure 4(a)) equipped with brush fibers 41a, and is configured so that the brush fibers 41a come into contact with the surface 22a of the electrostatic roller 22. The brush 41 can scrape off foreign matter adhering to the surface 22a of the electrostatic roller 22 with the brush fibers 41a.

[0076] While the image forming apparatus 1 is in use, foreign matter such as sand and 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 airborne sand and dust (outdoors or a similar environment), sand and dust are more likely to adhere to the charging roller 22. There is not just one path for foreign matter to enter; for example, in the transfer section Q4, it may adhere from the recording material P to the photosensitive drum 21 and then from the photosensitive drum 21 to the charging roller 22, or it may be taken into the apparatus body 1A along with the outside air and carried by the airflow to reach the charging roller 22.

[0077] If foreign matter adheres to the surface 22a of the charging roller 22, image defects may occur due to charging failure. For example, if foreign matter such as sand and dust adheres to a certain location on the surface 22a of the charging roller 22, and the rotation of the charging roller 22 causes the foreign matter to repeatedly pass through the charging section Q1, the foreign matter may become embedded in the surface 22a. In this case, a point-like charging defect occurs at the location corresponding to the foreign matter, and as a result, periodic point-like image defects may occur 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 called black spots.

[0078] By arranging 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 brush fibers 41a of the brush 41. The brush 41 prevents foreign matter such as sand and dust from remaining in a specific location on the surface 22a of the charging roller 22, making it less likely for image defects such as black spots caused by the adhesion of foreign matter to occur. Furthermore, even when the image forming apparatus 1 is used in an environment with a large amount of airborne sand and dust, for example, it becomes possible to maintain high image quality over a long period of time.

[0079] The brush unit 40 will be explained in detail using Figures 9(a) to 11. The brush 41 extends in a long, narrow shape along the longitudinal direction (X direction) of the charging roller 22. In the following explanation, the longitudinal direction (X direction) of the charging roller 22 may be referred to as the longitudinal direction of the brush 41. The direction perpendicular to the longitudinal direction (X direction) of the brush 41 and along the base material of the brush 41 (W direction in the figure) may be referred to as the short direction of the brush 41. In addition, the direction perpendicular to both the longitudinal direction (X direction) and the short direction (W direction) of the brush 41 (V direction in the figure) may be referred to as the height direction of the brush 41. The V and W directions do not necessarily coincide with the Y and Z directions mentioned above.

[0080] Figure 9(a) is a view of the brush unit 40 from the opposite side of the charging roller 22 in the height direction (V direction) of the brush 41. Figure 9(b) is a view of the brush unit 40 in the short direction (W direction). Figure 9(c) is a view of the brush unit 40 from the side of the charging roller 22 in the height direction (V direction) of the brush 41. Figure 9(d) is a perspective view of the brush unit 40. Figure 9(e) is a perspective view of the brush base 42. Figure 10(a) is a perspective view of the brush unit 40. Figure 10(b) is an exploded view of the non-driven end of the brush unit 40. Figure 11 is a perspective view showing the brush 41 and the brush electrical contact 50.

[0081] As shown in Figures 9(d) and 10, the brush unit 40 includes a brush 41, a brush base 42, a brush electrical contact 50, and brush biasing members 53 and 54.

[0082] The brush 41 comprises brush fibers 41a (brush bristles), a sheet-like base 41b that supports the brush fibers 41a, and a plate-like support member 41c that supports the base 41b. The base 41b and the support member 41c constitute a plate-like base material. The brush fibers 41a protrude from the base material to one side in the thickness direction of the base material (the thickness direction of the support member 41c).

[0083] The brush 41 of this embodiment is formed by attaching a pile fabric to a support member 41c using, for example, an adhesive. The brush fibers 41a are, for example, conductive yarn piles made of nylon fibers containing carbon as a conductive agent, and the base 41b is a base fabric into which the conductive yarn piles are woven. The support member 41c is, for example, a sheet metal member. Alternatively, the brush 41 of this embodiment can also be said to consist of a brush body including the brush fibers 41a and the base 41b, and a support (support member 41c) that supports the brush body.

[0084] Furthermore, the brush 41 is not limited to a combination of pile fabric and sheet metal member. For example, the brush 41 may have a resin base material with a plurality of holes formed therein, and bundles of brush fibers 41a implanted in each of the holes of the base material. In other words, the base material of the brush 41 is not limited to a combination of a base 41b (a part that directly supports the brush fibers 41a) and a support member 41c (a part that supports the base 41b), but may also be an integrally molded part that supports the brush fibers 41a.

[0085] The brush base 42 is an example of a holding member for holding the brush 41. The brush base 42 includes a main unit portion 42a as a brush holding portion for holding the brush 41, and swinging support portions 42n and 42r as supported portions supported by the drum frame 26. In this embodiment, the main unit portion 42a holds the base material (particularly the support member 41c) of the brush 41. The swinging support portions 42n and 42r swing integrally with the main unit portion 42a.

[0086] In this embodiment, an example is described in which the main unit portion 42a and the swing support portions 42n and 42r are integrally formed. However, the swing support portions 42n and 42r may be separate components from the main unit portion 42a and fixed to the main unit portion 42a with screws or adhesive. Furthermore, the "holding member" does not necessarily have to be composed of a single component, as in the example in which the swing support portions 42n and 42r, which are separate components from the main unit portion 42a, are fixed to the main unit portion 42a.

[0087] The brush base 42 has a drive-side position restricting portion 42j and non-drive-side position restricting portions 42k and 42m, which serve as restricting portions (contact portions) for restricting the position of the brush unit 40. The drive-side bearing 45 and non-drive-side bearing 46 have contact portions (45a, 46a, and 46b) that contact the drive-side position restricting portion 42j and non-drive-side position restricting portions 42k and 42m, respectively, as will be described later. In other words, the drive-side bearing 45 and non-drive-side bearing 46 in this embodiment function as restricting members (positioning members) that restrict the position of the brush base 42 by contacting the brush base 42 (holding member). When the drive-side position restricting portion 42j is called the first restricting portion, the non-drive-side position restricting portions 42k and 42m can be called the second restricting portion. The position restriction of the brush unit 40 will be described later.

[0088] The main unit portion 42a of the brush base 42 extends along the longitudinal direction (X direction) of the brush 41, over substantially the entire length of the region where the brush fibers 41a are arranged. The brush 41, brush electrical contacts 50, and brush biasing members 53 and 54 are arranged in the main unit portion 42a. The oscillating support portions 42n and 42r are arranged on both outer sides of the main unit portion 42a in the longitudinal direction (X direction) of the brush 41. One oscillating support portion 42n is located on the driving side, and the other oscillating support portion 42r is located on the non-driving side.

[0089] The brush base 42 is movably supported by the drum frame 26 (Figures 5(b)(c) and 6) and is movable in a direction toward and toward the charging roller 22. In other words, the brush unit 40 is movable so that the brush base 42 (brush holding part) moves toward and toward the charging roller 22. In this embodiment, the brush unit 40 is swingable (rotatable) relative to the drum frame 26 by the engagement of support holes 42p and 42s provided in the brush base 42 with support shafts 26a and 26b provided in the drum frame 26. In addition, in this embodiment, the brush unit 40 is biased by brush biasing members 53 and 54 so that the base material of the brush 41 (41b, 41c) and the brush base 42 move toward the charging roller 22.

[0090] The main unit portion 42a of the brush base 42 is provided with width regulating grooves 42g, 42h, and 42i for regulating the position of the brush 41 in the short direction (W direction) of the brush 41. In this embodiment, the brush base 42 is provided with width regulating grooves 42g, 42h, and 42i at three locations on the main unit portion 42a in the longitudinal direction (X direction) of the brush 41: the drive side end, the center, and the non-drive side end. The number and arrangement of the width regulating grooves 42g, 42h, and 42i may be changed. The inner width of the width regulating grooves 42g, 42h, and 42i is set to be approximately equal to the width of the brush 41 in the short direction (W direction) of the brush 41 (in particular, the width of the support member 41c). When the brush 41 engages with the width regulating grooves 42g, 42h, and 42i, the position of the brush 41 relative to the brush base 42 in the short direction (W direction) is regulated (positioned).

[0091] Furthermore, in this embodiment, the drum frame 26 is provided with a longitudinal regulating rib 26c (Figure 5(b)), and the main unit portion 42a of the brush base 42 is provided with a longitudinal regulating groove 42f (see also Figure 10(a)). The longitudinal regulating rib 26c protrudes in a direction intersecting the longitudinal direction (X direction) of the brush 41. By engaging the longitudinal regulating rib 26c with the longitudinal regulating groove 42f, the position of the brush unit 40 relative to the drum frame 26 is regulated (positioned) in the longitudinal direction (X direction) of the brush 41. Alternatively, the brush base 42 may be provided with a longitudinal regulating rib (convex portion) that protrudes in a direction intersecting the longitudinal direction (X direction), and the drum frame 26 may be provided with a longitudinal regulating groove (recess) that engages with this longitudinal regulating rib.

[0092] As shown in Figure 9(e), brush seating surfaces 42b and 42c are provided at both ends of the main unit portion 42a in the longitudinal direction (X direction) of the brush 41. The brush seating surfaces 42b and 42c protrude toward the brush 41 in the height direction (V direction) of the brush 41 compared to the surface 42z between the brush seating surfaces 42b and 42c. The brush 41 is fixed to the brush base 42 by a support member 41c being bonded to the brush seating surfaces 42b and 42c by an adhesive or other method. When the brush 41 is fixed to the brush seating surfaces 42b and 42c, the surface 42z between the brush seating surfaces 42b and 42c on the main unit portion 42a does not basically come into contact with the brush 41.

[0093] In other words, the main unit portion 42a (brush holding portion) has opposing surfaces (42b, 42c, 42z) that face the support member 41c (sheet metal member) in the thickness direction of the base material (41b, 41c) of the brush 41. The opposing surfaces include a brush seating surface 42b (first seating surface portion) to which one end of the sheet metal member is fixed in the rotation axis direction (X direction) of the charging roller, and a brush seating surface 42c (second seating surface portion) to which the other end of the sheet metal member is fixed in the rotation axis direction (X direction) of the charging roller. The opposing surfaces also include a surface 42z (unfixed portion) formed in the region between the first seating surface portion and the second seating surface portion in the rotation axis direction (X direction) of the charging roller, to which the sheet metal member is not fixed.

[0094] In this embodiment, the brush base 42 is a molded product (resin molded part), and some deformation may occur during molding. For example, the brush base 42 may warp, such that the central part of the brush base 42 in the longitudinal direction (X direction) protrudes towards the brush 41 side or the opposite side in the height direction (V direction). In addition, the brush base 42 may twist, such that the orientation of the brush seating surfaces 42b and 42c differs between one end and the other end in the longitudinal direction (X direction).

[0095] Therefore, by having a highly rigid metal support member 41c in the brush 41, and by having both ends of the support member 41c fixed to the brush seating surfaces 42b and 42c of the brush base 42, deformation of the brush base 42 can be corrected. In other words, the warping and twisting of the brush base 42 can be corrected by making it conform to the support member 41c, which is more rigid than the brush base 42. This suppresses the influence of shape errors in the brush base 42 on the position and shape of the brush 41, and allows the brush fibers 41a to make stable contact with the charging roller 22.

[0096] As shown in Figures 9(d) and 10(a), the oscillating support portions 42n and 42r of the brush base 42 extend (project) to one side in the short direction (W direction) of the brush 41 relative to the main unit portion 42a. Support holes 42p and 42s are formed at the tips of the oscillating support portions 42n and 42r. The drum frame 26 is provided with support shafts 26a and 26b (Figures 5(b) and 5(c)) which engage with the holes. The brush unit 40 is supported so as to be oscillating relative to the drum frame 26 by the engagement of the support holes 42p and 42s with the support shafts 26a and 26b of the drum frame 26, respectively. 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). The imaginary straight line passing through the centers of the support shafts 26a and 26b is the oscillating axis of the brush unit 40.

[0097] When the drive-side oscillating support portion 42n and support shaft 26a are referred to as the first oscillating support portion and the first support portion, respectively, the non-drive-side oscillating support portion 42r and support shaft 26b can be referred to as the second oscillating support portion and the second support portion, respectively. Also, when the support hole 42p and support shaft 26a are referred to as the first hole portion and the first shaft portion, respectively, the support hole 42s and support shaft 26b can be referred to as the second hole portion and the second shaft portion, respectively. In this embodiment, the support shafts 26a and 26b (shaft portions) are arranged in the drum frame 26 and the support holes 42s and 42p (hole portions) are formed in the brush unit 40, but it is also possible to form the holes in the drum frame 26 and arrange the shaft portions that engage with the holes in the brush unit 40.

[0098] Furthermore, the oscillating support parts 42n and 42r are provided with openings 42q and 42t, where support holes 42p and 42s open in a direction intersecting the oscillating axis of the brush unit 40. In other words, the support holes 42p and 42s are formed as an arc shape with a portion of the circumference around the oscillating axis of the brush unit 40 cut out by the provision of openings 42q and 42t. The opening direction V1 of the drive-side opening 42q and the opening direction V2 of the non-drive-side opening 42t are different from each other. By providing openings 42q and 42t, the support holes 42p and 42s can be more easily engaged with the support shafts 26a and 26b when attaching the brush unit 40 to the drum frame 26.

[0099] As shown in Figures 10(a) and 10(b), the brush biasing members 53 and 54 are attached to one end and the other end 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 biasing member 53 is attached to the shaft portion 42d provided at one end of the main unit portion 42a. One end of the non-drive-side brush biasing member 54 is attached to the shaft portion 42e (Figure 9(a)) provided at the other end of the main unit portion 42a.

[0100] The brush electrical contact 50 has a first portion 50a with a hole formed therein that engages with the shaft portion 42d, and a second portion 50b extending from the first portion 50a in the longitudinal direction (X direction) of the brush 41. The brush electrical contact 50 is formed, for example, by punching and bending a single sheet metal member.

[0101] The first part 50a is planar in shape, substantially perpendicular to the height direction (V direction) of the brush 41, and its hole engages with the shaft portion 42d. It is supported by being sandwiched between the first end 53a of the brush biasing member 53 and the brush base 42. The other end (second end 53b) of the brush biasing member 53 is in contact with the third contact portion 47c provided on the aforementioned electrostatic roller electrical contact 47 (see also Figure 6).

[0102] As shown in Figures 11(a) and 11(b), the tip of the second portion 50b of the brush electrical contact 50 is provided with a contact portion 50c that abuts against the side surface 41d of the support member 41c of the brush 41 in the short direction (W direction). The second portion 50b is provided with one or more bent portions 50b1 that utilize the elasticity (springiness) of the sheet metal to more reliably bring the contact portion 50c into contact with the side surface 41d of the support member 41c. The contact portion 50c is pressed against the side surface 41d of the support member 41c by the elasticity (springiness) of the second portion 50b of the brush electrical contact 50.

[0103] With the above configuration, the brush 41 is electrically connected to the main body side contact portion of the device body 1A via the charging roller electrical contact 47, the brush biasing member 53, and the brush electrical contact 50. Furthermore, since the brush 41 is electrically connected to the charging roller 22 via the brush electrical contact 50, the potential of the brush 41 is equal to that of the charging roller 22. In other words, a charging voltage is applied to both the brush 41 and the charging roller 22 via the brush electrical contact 50 from the charging power supply of the device body 1A.

[0104] Foreign matter adhering to the charged roller 22 may be electrically charged. Therefore, if there is a potential difference between the brush 41 and the charged roller 22, the foreign matter may be electrostatically pressed against the charged roller 22 as it passes through the contact area between the charged roller 22 and the brush 41, making it difficult for the brush 41 to scrape off the foreign matter. If the brush 41 and the charged roller 22 are at the same potential, the brush 41 will be able to easily scrape off foreign matter adhering to the surface 22a of the charged roller 22, regardless of whether the foreign matter is charged or not.

[0105] Furthermore, if the charging roller 22 and the brush 41 are electrically connected, the same advantages can be obtained regardless of the specific configuration of the conductive path. In this embodiment, an example has been described in which the conductive path from the charging roller electrical contact 47, which is a contact member exposed to the outside of the process unit 20, to the charging roller 22 and the conductive path to the brush 41 are branched. However, this is not the only example; for example, a conductive path from the charging roller 22 to the brush 41 may be configured by arranging conductive members such as wires that electrically connect the drive-side bearing 45 and the support member 41c of the brush 41 in the oscillating support part 42n and the main unit part 42a. Alternatively, a similar conductive path may be configured by forming a part of the oscillating support part 42n and the main unit part 42a from conductive resin.

[0106] (Brush unit position restriction) The positional control of the brush unit 40 will be explained using Figures 1(a) to 1(g). Figure 1(a) is a view of the drum unit 25 from the upstream side in the Y direction (rear view). Figure 1(b) is a cross-sectional view of the drum unit 25 along the GG line in Figure 1(a). Figure 1(c) is a cross-sectional view of the drum unit 25 along the FF line in Figure 1(a). Figure 1(d) is an enlarged view of a part of Figure 1(b) (the area where the brush unit 40 and the non-drive side bearing 46 are in contact). Figure 1(e) is an enlarged view of a part of Figure 1(c) (the area where the brush unit 40 and the drive side bearing 45 are in contact). Figure 1(f) shows the state in which the brush unit 40 has rotated around the support shafts 26a and 26b from the state in Figure 1(d). Figure 1(g) is an enlarged view of a part of Figure 1(b) (near the support shaft 26b).

[0107] As described above, the brush unit 40 is movable relative to the charging roller 22. The brush base 42 (holding member) is configured to be movable in the direction of movement in which the base material (41b, 41c) of the brush 41 moves toward and away from the charging roller 22 (Figure 1(b)(c)). In this embodiment, the brush base 42 is movable (oscillated) relative to the charging roller 22 in the direction of movement with respect to the rotational direction (arrow U) around the support shafts 26a, 26b, by which the support holes 42p, 42s engage with the support shafts 26a, 26b of the drum frame 26, respectively.

[0108] Here, the "direction of movement" of the brush base 42 is any direction that has a component perpendicular to the tangent to the arc centered on the rotation axis of the charging roller 22. For example, the "direction of movement" may be a linear direction intersecting the arc centered on the rotation axis of the charging roller 22, or a rotational direction around an axis parallel to the rotation axis of the charging roller 22 and spaced apart from the rotation axis of the charging roller 22. Furthermore, the "direction of movement" is not limited to a linear direction along a single straight line or a direction along a single arc, but may also be a direction along a curve formed by combining multiple line segments and / or multiple curved sections. For example, when the brush base 42 moves while being guided by a guide shape such as a groove provided in the drum frame 26, the "direction of movement" may be a direction along the guide shape.

[0109] In this embodiment, the brush unit 40 is biased by brush biasing members 53 and 54 in the direction indicated by arrow U in the figure in the rotational direction around the support shafts 26a and 26b. The brush unit 40 is positioned (contains) its position in the rotational direction around the support shafts 26a and 26b by contacting the drive-side bearing 45 and the non-drive-side bearing 46.

[0110] In the longitudinal direction (X direction) of the brush 41, the support hole 42p on one side (the drive side) and the support shaft 26a are fitted together so that they can slide smoothly (Figure 1(b)). 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 (first hole portion) is in slidable contact with the outer surface of the support shaft 26a (first shaft portion). In contrast, on the other side (the non-drive 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 in Figure 1(g). In other words, the inner diameter of the support hole 42s (second hole portion) is set to be larger than the outer diameter of the support shaft 26b (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 function of the gap d2 will be described later.

[0111] Let's explain the position restriction of the brush unit 40 in more detail. At one end (drive side) of the brush unit 40 in the longitudinal direction (X direction) of the brush 41, as shown in Figure 1(e), the drive side position restricting portion 42j provided on the main unit portion 42a of the brush base 42 contacts the drive side contact portion 45a of the drive side bearing 45. As mentioned above, the drive side bearing 45 is movable relative to the drum frame 26 in the direction in which the charging roller 22 approaches and moves away from the photosensitive drum 21 (arrows S, T), but is positioned by the contact between the charging roller 22 and the photosensitive drum 21. Therefore, the contact between the drive side position restricting portion 42j and the drive side contact portion 45a stops the swinging of the brush base 42 in the direction of arrow U due to the biasing force of the brush biasing members 53 and 54. As mentioned above, there is no gap in the engagement between the support hole 42s and the support shaft 26a. Therefore, on the drive side, the position of the brush unit 40 (the position of the brush base 42) is determined based on the center of the support shaft 26a and the contact position of the drive side position regulating part 42j and the drive side contact part 45a.

[0112] On the other hand, at the other end (non-driven side) of the brush unit 40, as shown in Figure 1(d), the non-driven side position restricting parts 42k and 42m provided on the main unit portion 42a of the brush base 42 come into contact with the non-driven side contact parts 46a and 46b of the non-driven side bearing 46. As mentioned above, the non-driven side bearing 46 is movable relative to the drum frame 26 in the direction in which the charging roller 22 approaches and moves away from the photosensitive drum 21 (arrows S and T), but is positioned by the contact between the charging roller 22 and the photosensitive drum 21. Therefore, the contact between the non-driven side position restricting parts 42k and 42m and the non-driven side contact parts 46a and 46b stops the rotation of the brush unit 40 in the direction of arrow U due to the biasing force of the brush biasing members 53 and 54.

[0113] Here, the other end (non-driven side) of the brush unit 40 is provided with two restricting surfaces (non-driven side position restricting sections 42k and 42m) that face in different directions when viewed in the longitudinal direction (X direction) of the brush 41. When the non-driven side position restricting section 42k is called the first restricting surface, the non-driven side position restricting section 42m can be called the second restricting surface. The non-driven side position restricting section 42k (first restricting surface) contacts the non-driven side contact section 46a (first contact section) of the non-driven side bearing 46, and the non-driven side position restricting section 42m (second restricting surface) contacts the non-driven side contact section 46b (second contact section) of the non-driven side bearing 46. This makes it possible to accurately determine the position of the brush unit 40 (position of the brush base 42) on the non-driven side in a direction perpendicular to the longitudinal direction (X direction) of the brush 41.

[0114] More specifically, in this embodiment, the position of the brush unit 40 is determined by the convex shape of the non-drive side bearing 46 fitting into the concave shape (groove shape) formed by the non-drive side position restricting portions 42k and 42m. In other words, the convex shape of the non-drive side bearing 46, including the non-drive side contact portions 46a and 46b, fits into the bottom portion 42v of the concave shape formed by the non-drive side position restricting portions 42k and 42m. This positions the brush unit 40 in a direction perpendicular to the longitudinal direction (X direction) of the brush 41.

[0115] The gap d2 between the non-driven support hole 42s and the support shaft 26b (Figure 1(g)) allows the convex shape of the non-driven bearing 46 to engage more reliably with the concave shape formed by the non-driven position restricting parts 42k and 42m. In other words, even if the brush base 42 has some warping or twisting, the gap d2 allows for displacement of the support hole 42s relative to the support shaft 26b, thus allowing the convex shape of the non-driven bearing 46 to engage more reliably with the concave shape of the brush base 42.

[0116] Incidentally, as the brush unit 40 rotates around the support shafts 26a and 26b, there may be cases where only one of the non-driven side position restricting parts 42k and 42m comes into contact with the non-driven side contact part 46a or 46b, as shown in Figure 1(f). In the example in Figure 1(f), the non-driven side position restricting part 42k and the non-driven side contact part 46a are in contact, while the non-driven side position restricting part 42m and the non-driven side contact part 46b are not in contact.

[0117] However, the concave shape formed by the non-drive side position restricting portions 42k and 42m is formed to be concave toward the upstream side in the rotational direction (arrow U) in which the brush unit 40 rotates around the support shafts 26a and 26b according to the biasing force of the brush biasing members 53 and 54. Therefore, as the brush unit 40 swings in the swinging direction indicated by arrow U according to the biasing force of the brush biasing members 53 and 54, the convex shape of the non-drive side bearing 46 slides over the non-drive side position restricting portion 42k toward the bottom 42v of the concave shape. As a result, even if the situation temporarily becomes as shown in Figure 1(f), thereafter, as shown in Figure 1(d), the convex shape of the non-drive side bearing 46 is in contact with both the non-drive side position restricting portions 42k and 42m and engages with the concave shape.

[0118] As explained above, the position of the brush base 42 is restricted when the restricting portion (drive-side position restricting portion 42j, non-drive-side position restricting portion 42k, 42m) of the brush base 42 (holding member) comes into contact with the bearing member (drive-side bearing 45, non-drive-side bearing 46). Since the position of the brush base 42 is restricted by the contact between the bearing member holding the charging roller 22 and the restricting portion, the brush 41 can come into contact with the charging roller 22 with a more stable penetration amount.

[0119] The amount of penetration of the brush 41 into the charging roller 22 refers to the distance that the tip of the brush fiber 41a, assuming the charging roller 22 is not present, penetrates inward relative to the virtual cylindrical surface along the actual surface 22a of the charging roller 22. For example, the amount of penetration of the brush 41 is defined as the difference between the sum of the outer diameter of the charging roller 22 and the amount of protrusion of the brush fiber 41a into the base material (41b, 41c) (brush bristle length), and the shortest distance from the rotation axis of the charging roller 22 to the base material (41b, 41c) of the brush 41 in the state shown in Figures 1(b) and (c).

[0120] The amount of penetration of the brush 41 into the charging roller 22 may vary from product to product due to dimensional tolerances of the parts, etc., and may also vary depending on the position in the longitudinal direction (X direction). In such cases, the function of the brush 41 in scraping off foreign matter adhering to the surface 22a of the charging roller 22 may be reduced, potentially causing image defects. In contrast, according to this embodiment, the brush 41 can be made to contact the charging roller 22 with a more stable amount of penetration. As a result, it becomes easier to maintain the charging performance of the charging roller 22 over a long period of time, and the possibility of image defects can be reduced.

[0121] Furthermore, on the non-driven side, a gap d2 is provided between the support hole 42s and the support shaft 26b, and the position of the brush unit 40 is restricted by the contact between the non-driven side position restricting parts 42k, 42m and the non-driven side contact parts 46a, 46b. As a result, even if the drum frame 26 is twisted at one end and the other end in the longitudinal direction (X direction) due to dimensional tolerances of the parts or variations during assembly, twisting of the brush unit 40 can be suppressed. This also reduces variations in the amount of penetration of the brush 41 into the charging roller 22.

[0122] On the drive side, it is preferable that the drive side position restricting portion 42j and the drive side contact portion 45a have a shape that allows for point contact. This makes it possible to suppress changes in the contact position between the drive side position restricting portion 42j and the drive side contact portion 45a, even if there is an inclination on the surface of the drive side position restricting portion 42j or the surface of the drive side contact portion 45a due to shape errors of the parts, etc. As a result, variations in the amount of penetration of the brush 41 into the charging roller 22 can be further reduced. Specifically, in this embodiment, the drive side contact portion 45a is planar in shape that intersects with the direction in which the brush 41 approaches and moves away from the charging roller 22 (the direction perpendicular to the base portion 41b), and the drive side position restricting portion 42j has a substantially arc shape when viewed in the longitudinal direction (X direction).

[0123] For similar reasons, on the non-driven side, it is preferable that the non-driven side position restricting portion 42k and the non-driven side contact portion 46a are in point contact, and it is preferable that the non-driven side position restricting portion 42m and the non-driven side contact portion 46b are in point contact. In this embodiment, the non-driven side position restricting portions 42k and 42m are planar, and the non-driven side contact portions 46a and 46b are substantially arc-shaped. Furthermore, the non-driven side position restricting portions 42k and 42m are substantially orthogonal to each other when viewed in the longitudinal direction (X direction).

[0124] In this embodiment, the rigidity of the support member 41c of the brush 41 is used to suppress twisting of the brush unit 40 (twisting of the brush base 42). If the configuration allows twisting of the brush unit 40, and the brush base 42 only contacts one of the drive-side bearing 45 and the non-drive-side bearing 46, then variations in the amount of penetration of the brush 41 into the charging roller 22 will occur. To avoid this, it is conceivable to increase the biasing force of the brush biasing members 53 and 54, but this raises concerns that the contact pressure of the charging roller 22 against the photosensitive drum 21 will become uneven in the longitudinal direction (X direction). In other words, the difference in biasing force between the drive-side and non-drive-side charging roller biasing members 48 and 49 and the difference in biasing force between the drive-side and non-drive-side brush biasing members 53 and 54 are superimposed, which may cause variations in the contact pressure of the charging roller 22 against the photosensitive drum 21. Variations in the contact pressure of the charging roller 22 against the photosensitive drum 21 can cause problems such as uneven potential of the photosensitive drum 21, resulting in uneven image density, and uneven wear of the photosensitive drum 21. Therefore, from the viewpoint of suppressing variations in the contact pressure of the charging roller 22 against the photosensitive drum 21, it is preferable that the biasing force of the brush biasing members 53 and 54 be small.

[0125] According to this embodiment, since twisting of the brush unit 40 (twisting of the brush base 42) is suppressed, the biasing force of the brush biasing members 53 and 54 can be reduced while improving the positional accuracy of the brush 41 relative to the charging roller 22.

[0126] Furthermore, in this embodiment, it has been explained that the charging roller 22 is movable between a contact position and a separation position relative to the photosensitive drum 21. In this configuration, by bringing the restricting portion of the brush unit 40 into contact with the bearing member of the charging roller 22 and restricting the position of the brush holding portion, it is possible to improve the positional accuracy of the brush holding portion relative to the charging roller 22, even though the charging roller 22 is movable.

[0127] According to this embodiment, the brush unit 40 moves in conjunction with the movement of the charging roller 22 between the contact position and the separated position due to the contact between the regulating portion and the bearing member. This allows the charging roller 22 to contact and separate from the photosensitive drum 21 without being obstructed by the brush unit 40.

[0128] (modified version) In the embodiment described above, the position of the brush 41 relative to the charging roller 22 is restricted by the brush base 42 of the brush unit 40 contacting the drive-side bearing 45 and the non-drive-side bearing 46. However, the configuration is not limited to this, and for example, the position of the brush 41 relative to the charging roller 22 may be restricted by the support member 41c of the brush 41 contacting the drive-side bearing 45 and the non-drive-side bearing 46.

[0129] Furthermore, in the above-described embodiment, a configuration was shown in which the brush base 42 (holding member) can swing in a rotational direction about the support shafts 26a and 26b (arrow U and its opposite direction in Figure 1(b), etc.). However, even if the brush unit 40 is not provided with a configuration intended to move the brush base 42 in a specific direction, the same advantages as in the embodiment may be obtained by the contact between the restricting portion of the holding member and the bearing member.

[0130] For example, the brush base 42 may be movable due to the presence of play in the engagement portion between the drum frame 26 and the brush base 42. Also, for example, if an elongated hole is provided in the drum frame 26 to absorb shape errors of a part, and a cylindrical shaft portion provided on the brush base 42 is engaged with the elongated hole, the brush base 42 becomes movable along the long axis of the elongated hole. In other words, regardless of the reason for the movement of the brush base 42 (holding member), the brush base 42 may be movable in a direction having a component perpendicular to the tangent to the arc centered on the rotation axis of the charging roller 22. In such cases, the position of the holding member can be restricted by the contact between the restricting portion of the holding member and the bearing member holding the charging roller, thereby allowing the brush to contact the charging roller with a more stable amount of penetration. In other words, the technology of this disclosure can be applied even when the holding member is not configured to move in the direction in which the substrate held by the holding member moves toward and away from the charging roller.

[0131] (Other embodiments) In the embodiments described above, an image forming apparatus 1 using a direct transfer method was illustrated, in which a toner image is transferred from an image carrier (photosensitive drum 21) to a recording material P, which is the transfer target. However, the technology of this disclosure may also be applied to an image forming apparatus using an intermediate transfer method, in which a toner image is first transferred from the image carrier (photosensitive drum 21) to an intermediate transfer target, and then the toner image is transferred from the intermediate transfer target to the recording material P. Furthermore, the technology of this disclosure is not limited to monochrome image forming apparatuses, but may also be applied to color image forming apparatuses that use multiple colors of toner.

[0132] In the above-described embodiment, the image forming apparatus 1 including the cleanerless process unit 20 has been described. However, the process unit 20 may have a cleaning member such as a cleaning blade that collects (removes) residual toner from the photosensitive drum 21. Even in this case, there is a possibility that foreign matter that passes through the cleaning member and reaches the charging unit Q1 or foreign matter contained in the outside air taken into the image forming apparatus 1 adheres to the charging roller 22. Therefore, even in a configuration where the process unit 20 has a cleaning member, by arranging the brush unit 40 described in the embodiment, it is possible to reduce the occurrence of image defects caused by the adhesion of foreign matter to the charging roller 22.

[0133] Summary of the Present Disclosure The present disclosure includes at least the following contents. (Configuration 1) A rotatable image carrier, A charging roller arranged to contact the surface of the image carrier and charge the surface, A bearing member that rotatably supports the charging roller, A brush unit having a brush including a base material and brush fibers protruding from the base material and contacting the surface of the charging roller, and a holding member that holds the base material, Comprising, The holding member has a regulating portion that can contact the bearing member, and is configured such that the position of the holding member is regulated by the contact between the regulating portion and the bearing member. A process unit characterized by the above. (Configuration 2) The holding member is configured such that the base material held by the holding member moves in a moving direction in which the base material approaches and separates from the charging roller. The process unit according to Configuration 1, characterized by the above. (Configuration 3) Further comprising a frame body that supports the image carrier, The holding member is swingably supported by the frame body, [[ID=3 six]]The swing of the holding member is regulated by the contact between the regulating portion and the bearing member. The process unit according to Configuration 2, characterized by the above. (Configuration 4) Further comprising a biasing member for biasing the holding member in a direction in which the base material held by the holding member approaches the charging roller in the moving direction. The regulating portion is pressed against the bearing member by the biasing force of the biasing member. The process unit according to Configuration 3, characterized by the above. (Configuration 5) The base material has a base portion that supports the brush fibers and a sheet metal member to which the base portion is fixed. The holding member is formed of a resin material and has a brush holding portion that holds the sheet metal member. The process unit according to Configuration 3 or 4, characterized by the above. (Configuration 6) The brush holding portion has a facing surface that faces the sheet metal member in the thickness direction of the base material. The facing surface includes a first seating surface to which one end portion of the sheet metal member in the rotation axis direction of the charging roller is fixed, a second seating surface to which the other end portion of the sheet metal member in the rotation axis direction is fixed, and a non-fixed portion that is formed in a region between the first seating surface and the second seating surface in the rotation axis direction and to which the sheet metal member is not fixed. The process unit according to Configuration 5, characterized by the above. (Configuration 7) The frame body has a support portion. The holding member has a swing support portion that is swingably supported by the support portion. Either one of the support portion and the swing support portion has a shaft portion that extends in the rotation axis direction of the charging roller. The other of the support portion and the swing support portion has a hole portion that engages with the shaft portion. The process unit according to any one of Configurations 3 to 6, characterized by the above. (Configuration 8) The regulation part and the bearing member are respectively a first regulation part and a first bearing member arranged on one end side of the charging roller in the rotational axis direction of the charging roller. The apparatus further includes a second bearing member that is arranged on the other end side of the charging roller in the rotational axis direction and rotatably supports the charging roller. The holding member has a second regulation part that can contact the second bearing member, and the position of the holding member on the other end side in the rotational axis direction is regulated by the contact between the second regulation part and the second bearing member. The process unit according to any one of Configurations 1 to 7, characterized in that. (Configuration 9) The apparatus further includes a frame body that supports the image carrier. The holding member includes a first swing support part provided on the one end side of the holding member in the rotational axis direction, and a second swing support part provided on the other end side of the holding member in the rotational axis direction. The frame body has a first support part that swingably supports the first swing support part, and a second support part that swingably supports the second swing support part. The process unit according to Configuration 8, characterized in that. (Configuration 10) Either one of the first support part and the first swing support part has a first shaft part extending in the rotational axis direction, and the other of the first support part and the first swing support part has a first hole part engaged with the first shaft part. Either one of the second support part and the second swing support part has a second shaft part extending in the rotational axis direction, and the other of the second support part and the second swing support part has a second hole part engaged with the second shaft part. The inner diameter of the second hole part is larger than the outer diameter of the second shaft part, and the difference between the inner diameter of the second hole part and the outer diameter of the second shaft part is larger than the difference between the inner diameter of the first hole part and the outer diameter of the first shaft part. The process unit according to Configuration 9, characterized in that. (Configuration 11) The second regulation part includes a first regulation surface and a second regulation surface that face different directions when viewed in the rotational axis direction. The second bearing member includes a first contact portion that contacts the first regulating surface and a second contact portion that contacts the second regulating surface. The process unit according to Configuration 10, characterized in that. (Configuration 12) The process unit further includes a biasing member for biasing the holding member in a direction approaching the charging roller. The first regulating surface and the second regulating surface form a concave shape that is recessed toward the upstream side in the direction in which the holding member swings according to the biasing force of the biasing member. The first contact portion and the second contact portion are convex shapes provided on the second bearing member and are part of a convex shape that fits into the concave shape. The process unit according to Configuration 11, characterized in that. (Configuration 13) The process unit further includes a frame body that supports the image carrier. The bearing member is movable with respect to the frame body so as to move between a contact position where the charging roller contacts the image carrier and a separation position where the charging roller is separated from the image carrier. The process unit according to any one of Configurations 1 to 12, characterized in that. (Configuration 14) In conjunction with the movement of the charging roller between the contact position and the separation position, the holding member moves in a state where the regulating portion and the bearing member are in contact with each other. The process unit according to Configuration 13, characterized in that. (Configuration 15) When the brush unit is a first brush unit, In the rotational direction of the image carrier during image formation, there is a brush that contacts the surface of the image carrier downstream of the transfer portion where an image is transferred from the image carrier to the transfer medium and upstream of the charging portion where the image carrier faces the charging roller, and the process unit further includes a second brush unit that collects foreign matter adhering to the image carrier. The process unit according to any one of Configurations 1 to 14, characterized in that. (Configuration 16) The developing unit further comprises a toner storage section for storing toner and a developing roller for carrying the toner and supplying it to the image carrier, The toner that was not transferred from the image carrier to the transfer target is collected in the toner storage section by the developing roller. A process unit according to any one of configurations 1 to 15, characterized by the features described above. (Composition 17) A process unit described in any one of configurations 1 to 16, The main body of the device, The process unit, which is mounted on the main body of the apparatus, is used to form an image on the recording material. An image forming apparatus characterized by the following features. [Explanation of symbols]

[0134] 20…Process unit / 21…Image carrier (photosensitive drum) / 22…Charging roller / 26…Frame / 41…Brush / 41a…Brush fibers / 41b, 41c…Substrate (base, support member) / 42…Holding member (brush base) / 42a…Brush holding part (main unit part) / 42j, 42k, 42m…Restricting part (drive side position restricting part, non-drive side position restricting part) / 42n, 42r…Oscillating support part / 45, 46…Bearing member (drive side bearing, non-drive side bearing)

Claims

1. A rotatable image carrier, A charging roller is positioned to contact the surface of the image carrier and charge the surface, A bearing member that rotatably supports the aforementioned charging roller, A brush unit comprising a base material, a brush including brush fibers protruding from the base material and in contact with the surface of the charging roller, and a holding member for holding the base material, Equipped with, The retaining member has a restricting portion that can contact the bearing member, and is configured such that the position of the retaining member is restricted by the contact between the restricting portion and the bearing member. A process unit characterized by the following features.

2. The holding member is configured to move in a direction in which the substrate held by the holding member moves toward and away from the charging roller. The process unit according to feature 1.

3. The frame further comprises the image carrier, The holding member is supported by the frame so as to be able to swing, The swinging of the retaining member is restricted by the contact between the restricting portion and the bearing member. The process unit according to feature 2.

4. The system further comprises a biasing member for biasing the holding member in the direction of movement in which the substrate held by the holding member approaches the charging roller, The biasing force of the biasing member causes the restricting portion to be pressed against the bearing member. The process unit according to feature 3.

5. The substrate has a base portion that supports the brush fibers and a sheet metal member to which the base portion is fixed. The holding member is made of a resin material and has a brush holding portion for holding the sheet metal member. The process unit according to feature 3.

6. The brush holding portion has a facing surface that faces the sheet metal member in the thickness direction of the base material, The opposing surface includes a first seating surface portion to which one end of the sheet metal member in the direction of the rotation axis of the charging roller is fixed, a second seating surface portion to which the other end of the sheet metal member in the direction of the rotation axis is fixed, and an unfixed portion formed in the region between the first seating surface and the second seating surface in the direction of the rotation axis, to which the sheet metal member is not fixed. The process unit according to feature 5.

7. The aforementioned frame has a support portion, The holding member has a swingable support portion that is swingably supported by the support portion, Either the support portion or the swinging support portion has a shaft portion that extends in the direction of the rotation axis of the charging roller. The other of the support portion and the swing support portion has a hole that engages with the shaft portion. The process unit according to feature 3.

8. The regulating portion and the bearing member are, respectively, a first regulating portion and a first bearing member, which are positioned on one end side of the charging roller in the direction of the rotation axis of the charging roller. The system further comprises a second bearing member positioned on the other end side of the charging roller in the direction of the rotation axis, which rotatably supports the charging roller. The retaining member has a second restricting portion that can contact the second bearing member, and the position of the retaining member at the other end is restricted in the direction of the rotation axis by the contact between the second restricting portion and the second bearing member. The process unit according to feature 1.

9. The frame further comprises the image carrier, The holding member includes a first swing support portion provided on one end of the holding member in the direction of the rotation axis, and a second swing support portion provided on the other end of the holding member in the direction of the rotation axis. The frame comprises a first support portion that pivotably supports the first pivoting support portion, and a second support portion that pivotably supports the second pivoting support portion. The process unit according to feature 8.

10. Either the first support portion or the first swing support portion has a first shaft portion extending in the direction of the rotation axis, and the other of the first support portion and the first swing support portion has a first hole portion that engages with the first shaft portion. Either the second support portion or the second swing support portion has a second shaft portion extending in the direction of the rotation axis, and the other of the second support portion and the second swing support portion has a second hole portion that engages with the second shaft portion. The inner diameter of the second hole is larger than the outer diameter of the second shaft, and the difference between the inner diameter of the second hole and the outer diameter of the second shaft is larger than the difference between the inner diameter of the first hole and the outer diameter of the first shaft. The process unit according to feature 9.

11. The second restricting portion includes a first restricting surface and a second restricting surface that are oriented in different directions from each other when viewed in the direction of the rotation axis, The second bearing member includes a first contact portion that contacts the first regulating surface and a second contact portion that contacts the second regulating surface. The process unit according to feature 10.

12. The holding member is further provided with a biasing member for biasing it toward the charging roller, The first and second restricting surfaces have a concave shape that is recessed toward the upstream side in the direction in which the holding member swings according to the biasing force of the biasing member. The first contact portion and the second contact portion are convex shapes provided on the second bearing member and are part of the convex shape that fits into the concave shape. The process unit according to feature 11.

13. The frame further comprises the image carrier, The bearing member is movable relative to the frame so that the charging roller moves between a contact position in which it contacts the image carrier and a separation position in which it moves away from the image carrier. The process unit according to feature 1.

14. The holding member moves in conjunction with the movement of the charging roller between the contact position and the separated position, while the regulating portion and the bearing member are in contact. The process unit according to feature 13.

15. When the brush unit is designated as the first brush unit, The image carrier is further provided with a second brush unit that has a brush that contacts the surface of the image carrier downstream of the transfer section where the image is transferred from the image carrier to the transfer target and upstream of the charging section where the image carrier faces the charging roller, in the rotation direction of the image carrier during image formation, and which collects foreign matter adhering to the image carrier. The process unit according to feature 1.

16. The developing unit further comprises a toner storage section for storing toner and a developing roller for carrying the toner and supplying it to the image carrier, The toner that was not transferred from the image carrier to the transfer target is collected in the toner storage section by the developing roller. The process unit according to feature 1.

17. A process unit according to any one of claims 1 to 16, The main body of the device, The process unit, which is mounted on the main body of the apparatus, is used to form an image on the recording material. An image forming apparatus characterized by the following:

Images