Charging device

Abstract

The amount of cleaning material that penetrates the grid electrode is stabilized when the cleaning material is brought into contact with the grid electrode. [Solution] The invention is characterized by comprising: a housing having an opening formed on the surface facing the photoreceptor; a discharge electrode disposed inside the housing to which a voltage is applied; a control electrode disposed between the photoreceptor and the discharge electrode to control the amount of charge on the surface of the photoreceptor; a cleaning member disposed on the discharge electrode side of the control electrode and sliding against the control electrode to clean the control voltage by moving along the control electrode; a support member that supports the cleaning member in a state in which the control electrode is movable in the direction facing the photoreceptor; and a biasing member that presses the cleaning member in the direction of the control electrode.

Description

Technical Field

[0001] The present invention relates to a charging device suitable for use in an image forming apparatus such as a printer, a copier, a facsimile machine, or a multifunction peripheral using an electrophotographic method.

Background Art

[0002] In an image forming apparatus using an electrophotographic method, a corona charger is used as a charging device to uniformly charge the surface of a photosensitive drum to a predetermined polarity and potential. The corona charger is disposed opposite the photosensitive drum in a non-contact manner, and the photosensitive drum is charged by charged particles (corona ions) generated by the corona discharger. As the corona charger, a scorotron type is known. The scorotron type corona charger has a discharge electrode that generates charged particles and charges the surface of the photosensitive drum, and a control electrode that controls the amount of charge on the surface of the photosensitive drum. As an example, a wire-shaped one (referred to as a discharge wire) is used for the discharge electrode, and a plate member having a large number of through holes formed in a mesh shape (referred to as a grid electrode) is used for the control electrode.

[0003] In the case of the scorotron method, discharge products generated together with charged particles during corona discharge, or deposits such as toner and external additives of toner are likely to adhere to the grid electrode. The deposits adhering to the grid electrode can oxidize the grid electrode and cause rust. When rust occurs on the grid electrode, it becomes difficult to uniformly charge the photosensitive drum to a predetermined potential, and charge unevenness is likely to occur. Therefore, in order to remove the deposits adhering to the grid electrode, a charging device provided with a cleaning brush that slides on the surface of the grid electrode and cleans the grid electrode has been proposed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] Patent Document 1 describes a configuration in which, when a cleaning member is brought into contact with the grid electrode, the amount of penetration into the grid electrode is controlled by the shape of the cleaning member, thereby enabling optimal cleaning of the grid electrode. Specifically, the cleaning force on the sides of the through-hole is enhanced by allowing the cleaning member to penetrate sufficiently not only the grid electrode surface on the charging wire side but also the sides of the through-hole in the opening. This is because sufficient penetration of the cleaning member into the through-hole is expected to improve the cleaning force. As a result, when the sides of the through-hole are also thoroughly cleaned, compared to when only the grid electrode surface on the charging wire side is cleaned, the decrease in chargeability due to contamination of the grid electrode is reduced, and image defects are less likely to occur.

[0006] However, with continuous use of the cleaning material, there is a concern that wear on the cleaning material will reduce the amount of material that penetrates, leading to a decrease in the cleaning rate of the grid electrodes and, consequently, a decrease in the electrostatic charge due to contamination of the grid electrodes. In addition, variations in shape during manufacturing may cause instability in the amount of material that penetrates, even without continuous use.

[0007] On the other hand, increasing the amount of cleaning material that penetrates the surface accelerates wear on the cleaning material, leading to an increase in the rate of decrease in penetration per unit time.

[0008] The present invention has been made in view of the above-mentioned problems. The object of the present invention is to provide a charging device that can stabilize the amount of penetration of a cleaning member when the cleaning member is brought into contact with the grid electrode. [Means for solving the problem]

[0009] To achieve the above objective, a charging device according to one aspect of the present invention has the following configuration. Specifically, it comprises a housing having an opening formed on the surface facing a photoreceptor, a discharge electrode disposed within the housing to which a voltage is applied, a control electrode disposed between the photoreceptor and the discharge electrode to control the amount of charge on the surface of the photoreceptor, a cleaning member disposed on the discharge electrode side of the control electrode and sliding with the control electrode by moving along the control electrode to clean the control voltage, a support member that supports the cleaning member in a state in which the control electrode is movable in the direction facing the photoreceptor, and a biasing member that presses the cleaning member in the direction of the control electrode. [Effects of the Invention]

[0010] According to the present invention, the amount of penetration of the cleaning member when the cleaning member is brought into contact with the grid electrode can be stabilized. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of an image forming apparatus according to the first embodiment. [Figure 2] This is a schematic perspective view of the primary charger according to the first embodiment. [Figure 3] This is a schematic perspective view of the primary charger according to the first embodiment. [Figure 4] This is a schematic cross-sectional view of a primary charger according to the first embodiment. [Figure 5] This is a schematic diagram of a grid electrode according to the first embodiment. [Figure 6] This is a schematic diagram of a cleaning member according to the first embodiment. [Figure 7] This figure shows the relationship between the amount of intrusion and the cleaning rate. [Figure 8] This is a schematic perspective view of the cleaning member according to the first embodiment. [Figure 9] This is a schematic diagram of a cleaning member according to the first embodiment. [Figure 10] This diagram shows the relationship between load and penetration amount. [Figure 11]It is a diagram showing the relationship between the number of cleaning times and the intrusion amount. [Figure 12] It is a schematic perspective view of the cleaning member according to the first embodiment. [Figure 13] It is a schematic perspective view of the cleaning member at the standby position according to the first embodiment.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention according to the claims, and not all combinations of the features described in the present embodiment are essential for the solution means of the present invention. The present invention can be implemented in various applications such as a copying machine, a printer, a facsimile, and a multifunction device having a plurality of these functions.

[0013] <First Embodiment> [Image Forming Apparatus] FIG. 1 shows a full-color image forming apparatus according to the present embodiment. The image forming apparatus 1000 includes an image reading device 100 and an image forming apparatus main body 200. The image reading device 100 reads a document placed on the document table glass 101. The light irradiated from the light source 102 is reflected by the document and imaged on the CCD sensor 104 through an optical system member 103 such as a lens. Such an optical unit scans in the direction of the arrow to convert the document into an electric signal data sequence for each line.

[0014] The image signal obtained by the CCD sensor 104 is sent to the image forming apparatus main body 200, and image processing is performed by the control unit 105 in accordance with each image forming unit described below. Further, the control unit 105 can also receive an external input from a print server or the like as an image signal.

[0015] The image forming apparatus main body 200 includes a plurality of image forming units Pa, Pb, Pc, and Pd. In each image forming unit, image formation is performed based on the above-described image signal. That is, the image signal is converted into a laser beam PWM (pulse width modulation controlled) by the control unit 105. 201 is a laser scanner as an exposure device, and scans a laser beam corresponding to the image signal. Then, the photoconductors 202a to 202d as image carriers of each image forming unit Pa to Pd are irradiated with the laser beam.

[0016] Note that Pa is a yellow (Y) image forming unit, Pb is a magenta (M) image forming unit, Pc is a cyan (C) image forming unit, and Pd is a black (Bk) image forming unit, which form images of their corresponding colors respectively. Since the image forming units Pa to Pd are substantially the same, the details of the Y image forming unit Pa will be described below, and the descriptions of the other image forming units will be omitted.

[0017] In the Y image forming unit Pa, 202a is a photoconductor, and as described below, a toner image is formed on the surface based on the image signal. 203a is a primary charger, which charges the surface of the photoconductor 202a to a predetermined potential to prepare for electrostatic latent image formation. An electrostatic latent image is formed on the surface of the photoconductor 202a charged to a predetermined potential by the laser beam from the laser scanner 201. 204a is a developing device, which develops the electrostatic latent image on the photoconductor 202a to form a toner image. 205a is a transfer roller, which discharges from the back of the intermediate transfer belt 206 and applies a primary transfer bias of the opposite polarity to the toner, and transfers the toner image on the photoconductor 202a onto the intermediate transfer belt 206. After the transfer, the surface of the photoconductor 202a is cleaned by the cleaner 207a.

[0018] Also, the toner image on the intermediate transfer belt 206 is conveyed to the next image forming unit, and in the order of Y, M, C, Bk, the toner images of each color formed in each image forming unit are sequentially transferred, and a four-color image is formed on its surface.

[0019] After the paper is fed in the paper feeding unit 216, it waits in the registration unit 210. The control unit 105 then controls the timing to align the toner image on the intermediate transfer belt with the position of the paper, and the paper is transported from the registration unit. In the secondary transfer unit, which consists of secondary transfer roller pairs 208 and 209, a secondary transfer electric field with the opposite polarity to the toner image on the intermediate transfer belt 206 is applied, and the toner is transferred to the paper. After that, the toner image on the paper is fixed to the paper by the fixing device 211, which acts as a heating device, and the paper is discharged after passing through the fixing device 211.

[0020] In the case of a double-sided printing job, once the transfer and fixing of the toner on the first image forming surface (1st surface) is complete, the paper is reversed by passing through a reversal transport path 215 located inside the image forming apparatus after fixing. Subsequently, the transfer and fixing of the toner on the second image forming surface (2nd surface), cooling, and other processes are completed, and the paper is discharged from the machine.

[0021] [Primary charger] Figure 2 is a schematic perspective view of the primary charger 203 according to the present invention. Note that the numbering a, b, c, and d have been omitted, and this configuration can be applied to any image forming unit.

[0022] As shown in Figure 2, the primary charger 203, positioned above the photoreceptor 202, has a housing composed of a front block 219 and a rear block 220 made of insulating material, and an upstream shield plate 221 and a downstream shield plate 222 that restrict the charging area. The housing has an opening formed on the surface facing the photoreceptor 202. A charging wire 223 (discharge electrode) is stretched between the front block 219 and the rear block 220 (inside the housing), and a discharge area is formed using the upstream shield plate 221 and the downstream shield plate 222, the charging wire 223, and the grid electrode 224.

[0023] The charging wire 223, grid electrode 224, and each shielding plate are configured to receive voltage from the contact points of the rear block 220. In this embodiment, a DC voltage is applied to the charging wire 223, grid electrode 224, and each shielding plate, respectively, to discharge from the charging wire 223 to the photoreceptor 202.

[0024] [Cleaning method] Figure 3 shows a schematic diagram of the primary charger 203 as seen from the photoreceptor 202, and Figure 4 shows a schematic cross-sectional view of the primary charger 203 as seen from the side.

[0025] As shown in Figures 3 and 4, the primary charger 203 is equipped with a cleaning pad 228 as a means of cleaning the charging wire 223 and a cleaning member 250 as a means of cleaning the grid electrode 224. The cleaning member 250 is positioned on the charging wire 223 side of the grid electrode 224 (the discharge electrode side of the control electrode). The cleaning pad 228 and the cleaning member 250 are held by a support member 226, and the support member 226 is connected to a lead screw 227, making it movable in the longitudinal direction. That is, the support member 226 supports the cleaning pad 228 in a state where it can move in the direction in which the grid electrode 224 faces the photoreceptor 202. At that time, the respective cleaning members slide against the charging wire 223 and the grid electrode 224, removing attached toner, external additives, discharge products, airborne particles from the surrounding environment, etc., and performing cleaning.

[0026] [Grid electrode opening] Figure 5 is a schematic diagram of the grid electrode 224 as seen from the photoreceptor 202, showing the cleaning member 250 in contact with the grid electrode 224. The grid electrode 224 is positioned between the photoreceptor 202 and the charging wire 223 to control the amount of charge on the surface of the photoreceptor 202.

[0027] As shown in Figure 5, the grid electrode 224 has a mesh-like opening, with multiple through holes arranged in the longitudinal direction of the grid electrode 224. The area ratio of the openings to the surface area of ​​the grid electrode 224 excluding the ends is approximately 2:8. In addition, a beam B is provided along the longitudinal direction to suppress deflection of the opening mesh portion. Cleaning is performed by sliding the cleaning member 250 against the grid electrode 224.

[0028] Figure 6 is a schematic diagram of the vicinity of the cleaning member 250 shown in Figure 4. In Figure 6a, for illustrative purposes, all brush portions 251 are shown penetrating the opening of the grid electrode 224, but in reality, as shown in Figure 6b, there are also brush portions 251 that bend and flex without penetrating. The cleaning member 250 consists of brush portions 251 and a holding portion 252 to which the brush portions 251 are fixed. When cleaning the grid electrode 224, it is important to ensure that the brush portions 251 are in sufficient contact with the surface W of the grid electrode 224 on the side of the charged wire 223 and the side S of the through-hole of the grid electrode 224. When cleaning the surface W of the grid electrode 224, it is necessary to bring the brush portions 251 into contact with the surface W, and when cleaning the side S, it is necessary to penetrate the grid electrode 224 with the brush portions 251. The parameter at this time is defined as the penetration amount, and the setting of the penetration amount, which is important for cleaning the grid electrode 224, will be described in detail below.

[0029] [Intrusion amount] Regarding the material of the brush section 251, this device uses an acrylic bristle brush. In cleaning with a bristle brush, the aforementioned penetration amount is important. As shown in Figure 6, the penetration amount ΔX is the length to which the brush section 251 penetrates the grid electrode 224.

[0030] The reason why the penetration amount ΔX is important will be explained using Figure 6b. Figure 6b shows the cleaning member 250 moving along the grid electrode 224. During cleaning, it receives a reaction force from the grid electrode 224, and as shown in the figure, there is a part that bends. The bent part is mainly responsible for cleaning the surface W, while the part that does not bend and protrudes from the grid electrode 224 is mainly responsible for cleaning the side surface S. In cleaning using a bristle brush, if the penetration amount ΔX is appropriate, both the surface W and the side surface S can be cleaned effectively.

[0031] Figure 7 shows the relationship between the amount of intrusion ΔX and the cleaning rate when using a bristle brush. The cleaning rate represents how much of the dirt attached to the grid electrode 224 was removed. The charging current before cleaning of the grid electrode 224 coated with Si particles is defined as 0%, and the charging current of the grid electrode 224 without Si particles is defined as 100%. Based on this definition, the results of measuring the charging current after cleaning when the amount of intrusion ΔX was varied are shown.

[0032] When the penetration amount ΔX is appropriate, both the surface W and the side surface S can be cleaned effectively as described above. However, the penetration amount ΔX changes depending on factors such as the length of the brush portion 251, the distance between the cleaning member 250 and the grid electrode 224, the rigidity of the bristles, and the positional relationship with adjacent fibers. If the penetration amount ΔX is low, the amount of deflection is small and the bristle brush cannot penetrate the holes sufficiently, resulting in insufficient cleaning of the surface W and side surface S and a low cleaning rate. On the other hand, if the penetration amount ΔX is large, the amount of deflection of the brush portion 251 increases, reducing the portion that protrudes from the grid electrode 224, resulting in insufficient cleaning of the side surface S and a low cleaning rate. Thus, controlling the penetration amount ΔX is important when cleaning with a bristle brush.

[0033] The setting of the penetration amount in the conventional configuration will be explained using Figure 6. The penetration amount ΔX is determined by the total length L of the brush portion and the distance D between the holding portion 252 and the grid electrode 224. In the conventional configuration, the positions of the holding portion 252 and the grid electrode 224 are fixed, so the distance D is constant. On the other hand, when cleaning is performed repeatedly, wear occurs in the brush portion 251 due to sliding with the grid electrode 224, and the total length L of the brush portion decreases. As a result, the penetration amount ΔX also decreases. As shown in Figure 7, when the penetration amount ΔX decreases, the cleaning rate decreases, making it difficult to use the cleaning member 250 and the grid electrode 224 for a long period of time. On the other hand, even if the total length L of the brush portion is increased in advance to increase the penetration amount ΔX, a decrease in the cleaning rate due to the bending of the bristles of the brush portion 251 and an increase in the rate of decrease in the total length L of the brush portion due to increased sliding resistance are expected, so the effect on extending the lifespan is small. For this reason, when the brush portion 251 wears down and the total length L of the brush portion decreases, the parts are replaced before the cleaning rate decreases to prevent a decrease in electrostatic charge.

[0034] Furthermore, the total length L and distance D of the brush section fluctuate due to variations in the dimensions of each component. As a result, the penetration depth ΔX also fluctuates, making it difficult to achieve the desired penetration depth ΔX.

[0035] Thus, with conventional configurations, it was difficult to keep the intrusion amount ΔX constant over a long period of time.

[0036] [Features of the present invention] The configuration of the present invention will be explained with reference to Figure 8. Figure 8 is a perspective view of the cleaning member 250 that contacts the grid electrode 224. Figure 8a shows the brush portion 251 in a new state with no wear and a sufficient total length L of the brush portion, while Figure 8b shows the state where the brush portion 251 is worn and the total length L of the brush portion has decreased. The cleaning member 250 is pressed toward the grid electrode 224 by a biasing member 253 and is held in a movable state by a support member 226 in the direction in which the grid electrode 224 faces the photoreceptor 202.

[0037] Figure 9 is a schematic diagram of the cleaning member 250 near the grid electrode 224, viewed from the side of the primary charger 203. The penetration amount ΔX is determined by the load F. The position of the holding portion 252 of the cleaning member 250 is determined when the load F received from the biasing member 253 and the reaction force received from the grid electrode 224 are in equilibrium, and the penetration amount ΔX is determined. In this configuration as well, the relationship between the penetration amount ΔX and the cleaning rate shown in Figure 7 holds true, and the grid electrode 224 can be adequately cleaned by controlling the penetration amount ΔX to adequately clean both the surface W and the side surface S.

[0038] Figure 10 shows the relationship between load F and penetration depth ΔX. The brush portion 251 was fixed to the measuring block, and the holding portion 252 was pressed with a measuring probe. The load F was measured by changing the position of the holding portion 252, i.e., the penetration depth ΔX. Assuming the measuring block is a grid electrode 224 without an opening, the surface area ratio of this block to that of the grid electrode 224 used in this device is 10:2, and the load F is calculated using this ratio.

[0039] Two effects of this configuration can be cited: stabilization and extended lifespan. First, let's discuss stabilization against dimensional variations. As shown in Figure 8, this configuration uses a compression coil spring as the biasing member 253. In this case, the load F is calculated from the spring constant k and the displacement x. Compared to leaf springs and resin springs, compression coil springs can be manufactured with stable wire diameter and shape, allowing for a low and constant spring constant k. Therefore, the load F can be stabilized against changes in the displacement x. In this configuration, the load F is set to 1.8 N, indicated by P in Figures 7 and 10. Since two biasing members 253 are used, if the load of one biasing member 253 is 0.9 N, the spring constant k is 0.09 N / mm and the displacement x is 10.2 mm. When using the biasing member 253 under these conditions, even if the displacement x decreases by 0.5 mm due to changes in the deflection amount of the brush part 251 caused by an increase or decrease in the total length L of the brush part, or due to dimensional variations of the parts, the load F decreases by only 0.09 N. At this time, the penetration amount ΔX decreases by 0.2 mm, which is slightly below Q in the figure, but the cleaning efficiency does not decrease. On the other hand, in the conventional configuration, a decrease in the displacement x directly leads to a decrease in the penetration amount ΔX, so as shown by R in the figure, the penetration amount ΔX becomes 0.5 mm, and the cleaning efficiency decreases. As a result, by using this configuration, the decrease in the penetration amount ΔX can be suppressed by about 60% compared to the conventional configuration. Thus, by applying this configuration, the effects of changes in the deflection amount of the brush part 251 caused by an increase or decrease in the total length L of the brush part, or due to dimensional variations of the parts, can be suppressed, and the penetration amount ΔX can be stabilized.

[0040] Next, let's discuss the second effect, which is extended lifespan. In this configuration, even if the penetration amount ΔX is stabilized due to the shape variation mentioned in the first effect, if cleaning is performed continuously, the overall length L of the brush portion will decrease due to wear of the brush portion 251. At this time, as shown in Figure 8b, since the holding portion 252 is movable relative to the support member 226, the cleaning member 250 approaches the grid electrode 224, and the position of the holding portion 252 is determined at the point where the forces are balanced, thereby suppressing the decrease in the penetration amount ΔX.

[0041] Figure 11 shows the relationship between the number of cleaning cycles and the amount of intrusion ΔX. The cleaning member 250 cleans the grid electrode 224 by moving back and forth from one end to the other, and the number of times it moves back and forth is defined as the number of cleaning cycles. In the figure, T represents the current configuration, and U represents the result of the conventional configuration. U is measured data, with the vertical axis converted to the amount of intrusion, and T is a value calculated based on the data of U. In the conventional configuration, replacement was performed after about 700 to 800 cleaning cycles, and the amount of intrusion ΔX at that time was about 0.6 to 0.7. On the other hand, as shown by T in the figure, in this configuration, the decrease in the amount of intrusion ΔX can be suppressed, so that the amount of intrusion ΔX becomes about 0.7 after 1500 cleaning cycles, and the grid electrode 224 can be suitably cleaned for more than twice as long. In this way, even if the total length L of the brush part decreases, the amount of intrusion ΔX is stabilized, and the grid electrode 224 can be suitably cleaned for a long period of time.

[0042] When the grid electrode 224 is pressed against the brush portion 251, it receives a force that moves it closer to the photoreceptor 202. Because the grid electrode 224, held by the front block 219 and rear block 220, has a large longitudinal dimension, it is particularly prone to bending in the central part, and the distance to the photoreceptor 202 tends to decrease. When the grid electrode 224 comes into close proximity with the photoreceptor 202, there is a concern that it may come into contact and damage the photoreceptor 202. Therefore, a holding portion H as shown in Figure 8 is provided to prevent bending of the grid electrode 224 while cleaning is performed.

[0043] For effective cleaning, it is desirable that the load F applied by the cleaning member 250 to the grid electrode 224 be as uniform as possible within the pressing surface of the holding part 252. If there is an imbalance in the load F, the amount of penetration ΔX may increase or decrease locally, potentially leading to inadequate cleaning. For example, if the biasing member 253 is placed in one location, the amount of penetration ΔX at the pressing position will be large, and the amount of penetration ΔX will decrease as it moves away from the pressing position. Therefore, in order to press the cleaning member 250 uniformly, the biasing members 253 are placed in two locations as shown in Figure 8, making the load F as uniform as possible within the pressing surface. In addition, the outer diameter of the coil of the biasing member 253 is set to 5.5 mm, and the pressing surface of the holding part 252 is biased broadly to ensure uniformity.

[0044] Furthermore, when positioning the biasing member 253 near voltage-applying components such as the charged wire 223, it is important to ensure an appropriate insulation distance between the components. Voltage is applied to the charged wire 223, the grid electrode 224, and each shield plate, forming a discharge region. If the biasing member 253 is close to the charged wire 223, discharge will occur, leading to short circuits or deterioration of the chargeability. Therefore, as shown in Figure 12, by providing a partition wall V in the support member 226, an insulation distance between the biasing member 253 and the voltage-applying components can be ensured. In addition, when not cleaning, the effects can be reduced by positioning the support member 226, including the biasing member 253, outside the discharge region.

[0045] Furthermore, by using the configuration of the present invention, the amount of wear on the brush portion 251 is reduced compared to conventional methods, and it can withstand continuous use. However, if the wear on the brush portion 251 progresses significantly, the cleaning member 250 will need to be replaced. When replacing the cleaning member 250, there is a possibility that the biasing member 253 may fall off if it is not held in place, raising concerns about ease of replacement. Therefore, it is desirable that the biasing member 253 be held in place by the support member 226 by press-fitting or wall installation.

[0046] The standby position when not cleaning will be explained using Figures 13a and 13b. Figure 13a shows the cleaning member 250 just before moving to the standby position, and Figure 13b shows the cleaning member 250 when it is in the standby position.

[0047] During cleaning, the pressed grid electrode 224 deforms and approaches the photoreceptor 202. When the grid electrode 224 is close to the photoreceptor 202 during image formation, it significantly affects the electrostatic properties. Therefore, it is desirable that the brush portion 251 does not press against the grid electrode 224 when not cleaning. Also, considering the effect on electrostatic properties, it is necessary to move the cleaning member 250 outside the discharge area when not cleaning. In the following, the area outside the discharge area will be referred to as the standby position.

[0048] As shown in Figure 13a, a guide section G is provided inside the housing, which has an opening formed on the surface facing the photoreceptor 202. The guide section G provided in the front block 219 has a slope at an angle of 45° that guides the holding section 252, and smoothly moves the cleaning member 250 to the standby position. The guide section G is set so that even if the holding section 252 comes close to the grid electrode 224 due to wear of the brush section 251, the lowest point of the slope is set to be at least 1 mm lower than the holding section 252 so that it can be guided to the standby position. Subsequently, as shown in Figure 13b, when the cleaning member 250 approaches the standby position, the holding section 252 moves along the guide section, and the cleaning member 250 retracts in the direction away from the grid electrode 224. That is, the cleaning member 250 can be separated from the grid electrode 224 by the guide section G. As a result, during image formation, the brush portion 251 does not come into contact with the grid electrode 224, preventing the grid electrode 224 from coming into close contact with the photoreceptor 202, and thus not affecting the chargeability.

[0049] As described above, according to the first embodiment, the amount of penetration of the cleaning member 250 when the cleaning member 250 is brought into contact with the grid electrode 224 can be stabilized. [Explanation of symbols]

[0050] 1000 Image forming apparatus 203 Primary Charger 219 Previous block 220 Rear block 221 Upstream shield plate 222 Downstream shield plate 223 Electrostatic wire 224 grid electrodes 226 Support member 250 Cleaning parts 251 Brush part 252 Holding part 253 Biasing member

Claims

1. A housing with an opening formed on the surface facing the photoreceptor, Discharge electrodes, which are arranged inside the housing and to which voltage is applied, A control electrode is disposed between the photoreceptor and the discharge electrode to control the amount of charge on the surface of the photoreceptor, A cleaning member is positioned on the discharge electrode side of the control electrode and moves along the control electrode to slide against the control electrode and clean the control electrode. A support member that supports the cleaning member in such a state that the control electrode is movable in the direction facing the photoreceptor, A biasing member that presses the cleaning member in the direction of the control electrode, A charging device characterized by being equipped with the following features.

2. The housing is provided with a guide section, The cleaning member can be separated from the control electrode by the guide portion. The charging device according to feature 1.

3. The biasing member is a coil spring. The charging device according to feature 1.

4. The cleaning member is a bristle brush. The charging device according to feature 1.

Images