Charging device and image forming apparatus

Abstract

To provide an electrifying device that can reduce the load torque of a motor for moving a plurality of cleaning members that individually clean a plurality of grids.SOLUTION: An electrifying device 50 comprises: a carriage 60 that integrally holds a cleaning brush 62 that cleans a grid 56 and a cleaning brush 63 that cleans a grid 57; and a screw member 61 that moves the carriage 60 along the direction of the axis of rotation of a photoconductor drum 1. The slide resistance between the cleaning brush 62 and the grid 56 is configured to be larger than the slide resistance between the cleaning brush 63 and the grid 57. In a direction orthogonal to the direction of the axis of rotation of the photoconductor drum 1, the distance between the cleaning brush 62 and the screw member 61 is shorter than the distance between the cleaning brush 63 and the screw member 61.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a charging device that charges a photoconductor and an electrophotographic image forming apparatus that includes the charging device. [Background technology]

[0002] When forming an image with an electrophotographic image forming apparatus, a photoconductor, the surface of which is uniformly charged by a charging device, is first exposed to light according to image data to form an electrostatic latent image. Next, a toner image is formed by attaching toner to the electrostatic latent image by a developing device. After that, the toner image is transferred to a sheet to form an image.

[0003] A charging device that uses corona discharge to charge a photoconductor has been known in the past. This corona charging type charging device generates ions by corona discharge between a grid, which is a metal plate with multiple openings, and a discharge wire, and charges the photoconductor with these ions.

[0004] When corona discharge occurs between the discharge wire and the grid, discharge products such as ozone and ammonium nitrate, which is generated by combining ozone with nitrogen and moisture in the air, are generated. If these discharge products adhere to the grid, the grid may be oxidized and rusted, which may deteriorate the charging performance of the photoconductor.

[0005] In response to this, Patent Document 1 describes a configuration in which discharge products adhering to a grid are removed by a cleaning member having a brush portion that enters inside a plurality of openings in the grid. The configuration in Patent Document 1 includes a carriage that holds the cleaning member and a screw member having a spiral groove into which the carriage fits, and the carriage moves in the direction of the rotation axis of the photosensitive member as the screw member rotates by the driving force of a motor, causing the cleaning member and the grid to slide and remove the discharge products adhering to the grid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-45800 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to improve the charging performance of the photoconductor, it is preferable to arrange the discharge electrodes and grids in a shape that follows the curvature of the photoconductor as closely as possible. A possible configuration for achieving this is to provide multiple discharge electrodes and grids along the curvature of the photoconductor in the rotation direction of the photoconductor.

[0008] When multiple grids are provided, multiple cleaning members and a mechanism for moving the multiple cleaning members are required to clean each grid. In a configuration similar to that of Patent Document 1, in which multiple cleaning members are integrally held by a carriage and the multiple cleaning members are moved via the carriage by rotating a screw member, the following problem may arise. That is, since there is sliding resistance such as frictional force between the cleaning members and the grid, when multiple cleaning members are moved by the driving force of a motor, the load torque applied to the motor driving the screw member is larger than in a configuration in which a single cleaning member is moved.

[0009] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a charging device capable of reducing the load torque of a motor for moving a plurality of cleaning members which respectively clean a plurality of grids. [Means for solving the problem]

[0010] A representative configuration of a charging device according to the present invention for achieving the above object includes a charging device for charging a photoconductor, the charging device including a first discharge wire, a first grid arranged between the first discharge wire and the photoconductor, the first grid having a plurality of openings, and charging the photoconductor by generating a discharge between the first discharge wire and the first grid, a first cleaning member having a first brush portion that enters inside the plurality of openings of the first grid and sliding against the first grid to clean the first grid, a second discharge wire, the second grid arranged between the second discharge wire and the photoconductor, the second grid having a plurality of openings, and charging the photoconductor by generating a discharge between the second discharge wire and the second grid, and a second cleaning member having a second brush portion that enters inside the plurality of openings of the second grid and sliding against the second grid to clean the second grid, the cleaning device further comprising: a holding member which holds the first cleaning member and the second cleaning member integrally; and a rotating member which supports the holding member and rotates by receiving driving force from a motor to move the holding member along the rotational axis direction of the photosensitive body, the holding member moving along the rotational axis direction to cause the first cleaning member to slide against the first grid and the second cleaning member to slide against the second grid, wherein the sliding resistance between the first cleaning member and the first grid is greater than the sliding resistance between the second cleaning member and the second grid, and the first cleaning member and the second cleaning member are arranged so that the distance between the first cleaning member and the rotating member is shorter than the distance between the second cleaning member and the rotating member in a direction perpendicular to the rotational axis direction. Effect of the Invention

[0011] According to the present invention, in a charging device, it is possible to reduce the load torque of a motor for moving a plurality of cleaning members that respectively clean a plurality of grids. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a schematic cross-sectional view of a charging device. [Figure 4] FIG. 2 is a schematic diagram of a grid. [Diagram 5] FIG. 2 is a schematic cross-sectional view of a charging device. [Figure 6] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <Image forming device> Hereinafter, the overall configuration of an image forming apparatus equipped with a charging device according to one embodiment of the present invention will be described together with the operation during image formation with reference to the drawings. Note that the dimensions, materials, shapes, relative positions, etc. of the components described below are not intended to limit the scope of the present invention, unless otherwise specified.

[0014] Image forming apparatus A is an intermediate tandem type image forming apparatus that transfers four colors of toner, yellow Y, magenta M, cyan C, and black K, onto an intermediate transfer belt, and then transfers the image onto a sheet to form an image. Note that in the following description, although the components that use the above-mentioned toners of each color are given the suffixes Y, M, C, and K, the configurations and operations of the components are essentially the same except for the color of the toner used, and therefore the suffixes will be omitted as appropriate unless a distinction is required.

[0015] Fig. 1 is a schematic cross-sectional view of an image forming apparatus A. As shown in Fig. 1, the image forming apparatus A includes an image forming section 10 that forms a toner image and transfers it to a sheet. The image forming section 10 includes photosensitive drums 1 (1Y, 1M, 1C, 1K) as photosensitive members, and charging devices 50 (50Y, 50M, 50C, 50K). The image forming section 10 also includes a laser scanner unit 3, developing devices 4 (4Y, 4M, 4C, 4K), primary transfer rollers 5 (5Y, 5M, 5C, 5K), an intermediate transfer belt 6, a secondary transfer roller 9, and a secondary transfer opposing roller 8.

[0016] A reader 20 for reading an image of an original is provided above the image forming unit 10. The reader 20 has a document table glass 21 and a scanner unit 22. The scanner unit 22 optically reads an image of an original placed on the document table glass 21.

[0017] Next, a description will be given of the image forming operation of the image forming apparatus A. First, when an image formation job signal is input to a control unit (not shown), a sheet S stored in a sheet cassette 11 is conveyed to a registration roller 16 by a feed roller 12 and conveyance rollers 13, 14, and 15. The registration roller 16 conveys the sheet S to a secondary transfer unit formed by a secondary transfer roller 9 and a secondary transfer opposing roller 8 at a predetermined timing.

[0018] Meanwhile, in the image forming unit 10, the surface of the photosensitive drum 1Y is first uniformly charged by the charging device 50Y. After that, the laser scanner unit 3 irradiates the surface of the photosensitive drum 1Y with laser light in accordance with the image data of the document read by the reader 20, and forms an electrostatic latent image on the surface of the photosensitive drum 1Y. Next, the developing device 4Y causes yellow toner to adhere to the electrostatic latent image formed on the surface of the photosensitive drum 1Y, forming a yellow toner image on the surface of the photosensitive drum 1Y. The toner image formed on the surface of the photosensitive drum 1Y is primarily transferred to the intermediate transfer belt 6 by applying a voltage to the primary transfer roller 5Y.

[0019] Through a similar process, the surfaces of the photosensitive drums 1M, 1C, and 1K are also irradiated with laser light from the laser scanner unit 3 in accordance with image data, and magenta, cyan, and black toner images are formed. Then, by applying a voltage to the primary transfer rollers 5M, 5C, and 5K, these toner images are transferred and superimposed on the yellow toner image on the intermediate transfer belt 6. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 6.

[0020] Thereafter, the intermediate transfer belt 6 rotates, whereby the full-color toner image is sent to a secondary transfer section. Then, in the secondary transfer section, a voltage is applied to a secondary transfer roller 9, whereby the full-color toner image on the intermediate transfer belt 6 is transferred to the sheet S.

[0021] Next, the sheet S onto which the toner image has been transferred is subjected to a heat and pressure treatment in a fixing device 17, whereby the toner image on the sheet S is fixed to the sheet S. Thereafter, the sheet S onto which the toner image has been fixed is discharged onto a discharge tray 19 by a discharge roller 18.

[0022] <Charging device> Next, the configuration of the charging device 50 will be described.

[0023] Fig. 2 is a schematic perspective view of the charging device 50. Fig. 3 is a schematic cross-sectional view of the charging device 50 taken along the V1-V1 cross section shown in Fig. 2.

[0024] As shown in FIGS. 2 and 3, the charging device 50 includes a front block 51 and a rear block 52 made of an insulating material, four shield plates 53a to 53d, discharge wires 54 and 55, and grids 56 and 57.

[0025] The discharge wires 54 and 55 are tensioned by a support member (not shown) between the front block 51 and the rear block 52. The grid 56 (first grid) is disposed between the photosensitive drum 1 and the discharge wire 54 (first discharge wire) so as to follow the curvature of the photosensitive drum 1. The grid 57 (second grid) is disposed between the photosensitive drum 1 and the discharge wire 55 (second discharge wire) so as to follow the curvature of the photosensitive drum 1. The discharge wire 54 and the grid 56 are disposed downstream of the discharge wire 55 and the grid 57 in the rotation direction of the photosensitive drum 1 during image formation (the direction of the arrow R shown in FIG. 3).

[0026] Shield plates 53a and 53b are disposed so as to surround the discharge wire 54 and the grid 56, and define a charged area on the photosensitive drum 1 that is charged by the discharge wire 54 and the grid 56. Shield plates 53c and 53d are disposed so as to surround the discharge wire 55 and the grid 57, and define a charged area on the photosensitive drum 1 that is charged by the discharge wire 55 and the grid 57. In order to electrically separate these two charged areas from each other, a partition plate (not shown) made of an insulating material is provided between shield plates 53b and 53c.

[0027] During image formation, a high voltage is applied to the discharge wires 54, 55, the grids 56, 57, and the shield plates 53a to 53d from a high voltage power supply (not shown) via contacts of the rear block 52. In this embodiment, a voltage of about -7 kV is applied to the discharge wires 54, 55, about -1 kV to the grids 56, 57, and about -1 kV to the shield plates 53a to 53d.

[0028] When a voltage is applied to the discharge wires 54 and 55, the grids 56 and 57, and the shield plates 53a to 53d, a corona discharge is generated between the discharge wire 54 and the grid 56, and between the discharge wire 55 and the grid 57. The surface of the photosensitive drum 1 is charged by ions generated by this corona discharge.

[0029] Here, the closer the distance between the grids 56, 57 and the surface of the photosensitive drum 1, the more effective it is at uniformly charging the surface of the photosensitive drum 1. In this embodiment, the shortest distance between the grid 56 and the photosensitive drum 1 and the shortest distance between the grid 57 and the photosensitive drum 1 are set to 1.3±0.3 mm. In addition, the shortest distance between the grid 56 and the discharge wire 54 and the shortest distance between the grid 57 and the discharge wire 55 are set to 8 mm.

[0030] <Grid> Next, the configuration of the grids 56 and 57 will be described.

[0031] Fig. 4 is a schematic diagram of the grid 56. As shown in Fig. 4, the grid 56 is a member in which a plate portion 56b, an opening 56c, a beam portion 56d, and a frame portion 56e are formed on a base material 56a of a thin metal plate having a thickness of 1 mm or less by etching.

[0032] In this embodiment, the base material 56a is a metal plate made of austenitic stainless steel (SUS304) and having a thickness of about 0.1 mm. The base material 56a may be made of martensitic stainless steel, ferritic stainless steel, or the like.

[0033] A plurality of plate portions 56b and openings 56c are provided, and these are alternately formed in a mesh shape. The opening width L1 of the openings 56c is set to 0.3±0.03 mm. The opening angle θ of the openings 56c with respect to a virtual line parallel to the rotation axis of the photosensitive drum 1 is set to 45±1°. The width L2 of the plate portions 56b is set to 0.07±0.03 mm. The shape of the openings 56c is not limited to a mesh shape, and may be, for example, a honeycomb shape.

[0034] In order to prevent the grid 56 from bending, beams 56d are provided at equal intervals in the center of the base material 56a, and frame portions 56e are provided at the ends of the base material 56a. The width L3 of the beams 56d is set to 0.1±0.03 mm. The interval L4 between the beams 56d is set to 6.9±0.1 mm. The width L5 of the frame portions 56e is set to 1.5±0.1 mm.

[0035] Except for the points described below, the shape of the grid 57 and the manufacturing method thereof are the same as those of the grid 56. That is, the grid 57 is a member in which a plate portion (not shown), an opening portion (not shown), a beam portion (not shown), and a frame portion (not shown) are formed by etching a base material (not shown) made of a thin metal plate having a thickness of 1 mm or less.

[0036] The difference between the grid 57 and the grid 56 is the opening width of the openings (not shown) of the grid 57, which corresponds to the opening width L1 of the openings 56c of the grid 56. The opening width of the openings (not shown) of the grid 57 is larger than the opening width L1 of the openings 56c of the grid 56, and is set to 0.8±0.03 mm in this embodiment. Accordingly, the opening area of ​​each of the plurality of openings 56c of the grid 56 is smaller than the opening area of ​​each of the plurality of openings of the grid 57.

[0037] This is due to the following reason. That is, the larger the opening area of ​​the opening 56c of the grid 56 and the opening (not shown) of the grid 57, the easier it is for ions to flow toward the photosensitive drum 1, and the better the charging efficiency of the surface of the photosensitive drum 1. On the other hand, the smaller the opening area, the easier it is for the flow of ions to be rectified, and charging unevenness is less likely to occur on the surface of the photosensitive drum 1. Therefore, the above opening area of ​​the grid 57 located on the upstream side in the rotation direction of the photosensitive drum 1 is increased to improve the charging efficiency of the photosensitive drum 1, and the above opening area of ​​the grid 56 located on the downstream side is decreased to suppress charging unevenness of the photosensitive drum 1. This achieves both improvement of the charging efficiency of the photosensitive drum 1 and suppression of charging unevenness.

[0038] <Cleaning brush> During the corona discharge of the charging device 50 described above, discharge products such as ozone and ammonium nitrate, which is generated by combining ozone with nitrogen and moisture in the air, are generated. If these discharge products adhere to the grids 56, 57, the grids 56, 57 may be oxidized and rusted, which may deteriorate the charging performance of the photosensitive drum 1. Therefore, the charging device 50 is provided with cleaning brushes 62, 63 for cleaning the grids 56, 57. The configuration of the cleaning brushes 62, 63 will be described below.

[0039] Fig. 5 is a schematic cross-sectional view of the charging device 50 taken along the V2-V2 cross section shown in Fig. 2. Fig. 6 is a schematic perspective view of the periphery of cleaning brushes 62, 63 in the charging device 50. As shown in Figs. 5 and 6, the charging device 50 includes a cleaning brush 62 (first cleaning member) for cleaning the grid 56 and a cleaning brush 63 (second cleaning member) for cleaning the grid 57.

[0040] The cleaning brush 62 is composed of a brush portion 62a (first brush portion) made of flame-retardant resin fibers, and a holder portion 62b having a base fabric into which the brush portion 62a is woven (FIG. 4). The holder portion 62b is disposed on the opposite side of the grid 56 from the photosensitive drum 1, that is, on the side where the discharge wire 54 is located. The fibers of the brush portion 62a enter each of the multiple openings 56c of the grid 56 in the direction from the discharge wire 54 toward the photosensitive drum 1.

[0041] The cleaning brush 63 is a member having the same shape and manufacturing method as the cleaning brush 62. That is, the cleaning brush 63 includes a brush part (second brush part) (not shown) made of fibers that enter each of the multiple openings (not shown) of the grid 57, and a holder part (not shown) having a base fabric into which the fibers of the brush part are woven.

[0042] In this embodiment, the overall shape of the base fabric of the cleaning brushes 62, 63 is a rectangle of 21 mm x 5 mm. The fibers of the cleaning brushes 62, 63 are made of acrylic, with a fineness of 11 decitex, a free length of 3.0 mm, and a density of 60,000 fibers / inch. 2 The material, fineness, free length, etc. of the fibers of the cleaning brushes 62, 63 are not limited to those described above, and fibers made of, for example, nylon, polyvinyl chloride (PVC), or polyphenylene sulfide resin (PPS) may also be used.

[0043] The cleaning brushes 62, 63 are integrally held by a carriage 60 (holding member). The carriage 60 is supported by being fitted into a spiral groove (not shown) formed in a screw member 61 (rotating member). The screw member 61 rotates by receiving a driving force from a motor (not shown). The screw member 61 is also arranged so that its rotation axis direction is approximately parallel to the rotation axis direction of the photosensitive drum 1. The term "approximately parallel" as used here includes a configuration in which the rotation axis of the screw member 61 and the rotation axis of the photosensitive drum are completely parallel, as well as a configuration in which they are misaligned within a tolerance range.

[0044] When the screw member 61 rotates, the carriage 60 moves along the rotation axis direction of the photosensitive drum 1, and accordingly, the cleaning brushes 62, 63 held by the carriage 60 also move along the rotation axis direction of the photosensitive drum 1. In other words, the carriage 60 and the screw member 61 are moving parts that move the cleaning brushes 62, 63. As the cleaning brushes 62, 63 move, the brush portion 62a of the cleaning brush 62 slides against the grid 56, and the brush portion (not shown) of the cleaning brush 63 slides against the grid 57. As a result, the cleaning brush 62 removes discharge products adhering to the grid 56, and the cleaning brush 63 removes discharge products adhering to the grid 57.

[0045] As described above, the opening width L1 of the opening 56c of the grid 56 is configured to be smaller than the opening width of the opening (not shown) of the grid 57. Therefore, the reaction force and friction force that the cleaning brush 62 receives from the grid 56 are greater than the reaction force and friction force that the cleaning brush 63 receives from the grid 57. Accordingly, the sliding resistance between the cleaning brush 62 and the grid 56 is greater than the sliding resistance between the cleaning brush 63 and the grid 57.

[0046] For this reason, when the carriage 60 is moved in the direction of the arrow G shown in Fig. 6, the force F1 generated by the sliding resistance between the cleaning brush 62 and the grid 56 is greater than the force F2 generated by the sliding resistance between the cleaning brush 63 and the grid 57. The directions of the arrows F1 and F2 shown in Fig. 6 indicate the directions of the forces F1 and F2 generated by the sliding resistance.

[0047] These forces F1 and F2 are moments acting on the carriage 60 around the engagement portion with the screw member 61, generating a moment W in the rotation direction of the screw member 61 and in a direction intersecting the rotation axis direction. The moment W is calculated from the following formula 1, where D1 is the distance between the cleaning brush 62 and the screw member 61 and D2 is the distance between the cleaning brush 62 and the screw member 61 in a direction perpendicular to the rotation axis direction of the photosensitive drum 1 (the direction of the arrow X shown in FIG. 6). This moment W generates resistance when the carriage 60 moves along the rotation axis direction of the photosensitive drum 1. This resistance increases the load torque of a motor (not shown) that drives the screw member 61.

[0048] (Formula 1) W = F1 x D1 + F2 x D2

[0049] In order to clean the grids 56 and 57, the charging device 50 reciprocates the cleaning brushes 62 and 63 by rotating a motor (not shown) in the forward and reverse directions. When the motor is rotated in the reverse direction from the state shown in FIG. 6 to move the carriage 60 in the direction opposite to the direction of the arrow G, a moment in the opposite direction to the moment W acts on the carriage 60. This moment in the opposite direction generates resistance when the carriage 60 moves along the rotation axis direction of the photosensitive drum 1. This resistance increases the load torque of the motor (not shown) that drives the screw member 61.

[0050] Therefore, as in the configuration of this embodiment, the cleaning brushes 62 and 63 are arranged so that the distance between the cleaning brush 62 and the screw member 61 is shorter than the distance between the cleaning brush 63 and the screw member 61 in the direction perpendicular to the rotation axis direction of the photosensitive drum 1. As a result, in the above formula 1, D1 becomes smaller and D2 becomes larger. Also, as described above, F1>F2. Therefore, the value of the moment W can be made smaller compared to a configuration in which the positional relationship between the cleaning brush 62 and the cleaning brush 63 is opposite. Therefore, the load torque of the motor (not shown) that drives the screw member 61 can be reduced.

[0051] In this embodiment, the relationship in magnitude of the sliding resistance between the cleaning brushes 62, 63 and the grids 56, 57 is due to the opening area of ​​the openings of the grids 56, 57, but it can also be caused by the following factors: The cleaning ability of the cleaning brushes 62, 63 differs depending on the fineness and density of the fibers, the amount of penetration of the fibers into the openings of the grids 56, 57, etc., and if these are made different between the grids 56 and 57, the above-mentioned relationship in magnitude of the sliding resistance will arise.

[0052] Specifically, when the fiber fineness of the cleaning brushes 62, 63 is large, the sliding resistance is larger than when the fiber fineness is small. Also, when the fiber density of the cleaning brushes 62, 63 is large, the sliding resistance is larger than when the fiber density is small. Also, when the free length of the fibers of the cleaning brushes 62, 63 is long and the amount of penetration into the openings of the grids 56, 57 is large, the sliding resistance is larger than when the free length of the fibers of the cleaning brushes 62, 63 is short and the amount of penetration into the openings of the grids 56, 57 is small.

[0053] The degree of adhesion of the discharge products to the grids 56, 57 may change depending on the relative positions of the various components, etc. For this reason, it is possible to consider a configuration in which the cleaning ability is changed by changing the fineness and density of the fibers of the cleaning brushes 62, 63 and the amount of penetration of the fibers into the openings of the grids 56, 57 according to the degree of adhesion of the discharge products.

[0054] Therefore, the positional relationship between the cleaning brushes 62, 63 is regulated as in the configuration of this embodiment according to the sliding resistance that changes with the fineness and density of the fibers of the cleaning brushes 62, 63 and the amount of penetration of the fibers into the openings of the grids 56, 57. That is, in the direction perpendicular to the rotational axis direction of the photosensitive drum 1, the cleaning brush 62, 63 having a higher sliding resistance is disposed closer to the screw member 61 than the cleaning brush having a lower sliding resistance. This makes it possible to reduce the load torque of the motor (not shown) that drives the screw member 61 by the same mechanism as above.

[0055] The opening area of ​​the grids 56 and 57, the fiber fineness and density of the cleaning brushes 62 and 63, and the amount of fiber penetration into the openings of the grids 56 and 57 change from the initial state before use due to wear and the like that accompanies use of the charging device 50. The description of this embodiment focuses on the opening area of ​​the grids 56 and 57, the fiber fineness and density of the cleaning brushes 62 and 63, and the amount of fiber penetration into the openings of the grids 56 and 57 in the initial state. In other words, even if these change with use of the charging device 50 and the magnitude relationship between the sliding resistance between the cleaning brush 62 and the grid 56 and the sliding resistance between the cleaning brush 63 and the grid 57 changes from the initial state, it is sufficient that the relationship between the sliding resistances and the positional relationship between the cleaning brushes 62 and 63 and the screw member 61 in the initial state are as described above. [Explanation of symbols]

[0056] 1...Photosensitive drum (photoconductor) 50...Charging device 54...Discharge wire (first discharge wire) 55...Discharge wire (second discharge wire) 56...Grid (first grid) 57...Grid (second grid) 60...Carriage (holding member, moving part) 61...Screw member (rotating member, moving part) 62...Cleaning brush (first cleaning member) 63...Cleaning brush (second cleaning member) A: Image forming device

Claims

1. In a charging device for charging a photoconductor, A first discharge wire; a first grid disposed between the first discharge wire and the photoconductor, the first grid having a plurality of openings, and configured to generate a discharge between the first discharge wire and the first grid to charge the photoconductor; a first cleaning member having a first brush portion that enters inside the plurality of openings of the first grid and slides against the first grid to clean the first grid; A second discharge wire; a second grid disposed between the second discharge wire and the photoconductor, the second grid having a plurality of openings, and configured to generate a discharge between the second discharge wire and the photoconductor to charge the photoconductor; a second cleaning member having a second brush portion that enters inside the plurality of openings of the second grid and slides against the second grid to clean the second grid; a moving section including a holding member that integrally holds the first cleaning member and the second cleaning member, and a rotating member that supports the holding member and rotates by receiving a driving force of a motor to move the holding member along a rotation axis direction of the photosensitive body, the moving section causing the first cleaning member to slide against the first grid and causing the second cleaning member to slide against the second grid as the holding member moves along the rotation axis direction; Equipped with a sliding resistance between the first cleaning member and the first grid is greater than a sliding resistance between the second cleaning member and the second grid, a charging device characterized in that the first cleaning member and the second cleaning member are arranged such that a distance between the first cleaning member and the rotating member is shorter than a distance between the second cleaning member and the rotating member in a direction perpendicular to the rotation axis direction.

2. 2. The charging device according to claim 1, wherein an opening area of ​​each of the plurality of openings in the first grid is smaller than an opening area of ​​each of the plurality of openings in the second grid.

3. 3. The charging device according to claim 2, wherein the first grid is disposed downstream of the second grid in the direction of rotation of the photoconductor.

4. 2. The charging device according to claim 1, wherein the fineness of the first brush portion is greater than that of the second brush portion.

5. 2. The charging device according to claim 1, wherein the density of the first brush portion is greater than the density of the second brush portion.

6. 2. The charging device according to claim 1, wherein an amount of penetration of the first grid of the first brush portion into the plurality of openings is greater than an amount of penetration of the second grid of the second brush portion into the plurality of openings.

7. 7. The charging device according to claim 1, wherein the rotating member has a spiral groove into which the holding member is fitted.

8. 8. An image forming apparatus which forms an electrostatic latent image by irradiating a photoconductor having a charged surface with light and develops the electrostatic latent image to form an image, comprising the charging device according to claim 1 as a charging device for charging the surface of the photoconductor.

Images