JP2019045801A - Charging device - Google Patents

Abstract

To provide a charging device capable of cleaning both surfaces of a wire surface and a drum surface of a grid electrode and, in particular, capable of maintaining a removable capability of deposits attached on the drum surface for a relatively long period.SOLUTION: A cleaning member 250 includes: a wire surface cleaning brush 500 and a drum surface cleaning brush 600 for cleaning a top surface and a rear surface of a grid electrode 206, respectively. The drum surface cleaning brush 600 has a main body 601 and a slide brush 602. The main body 601 has flexibility in a direction toward the drum surface of the grid electrode 206. The slide brush 602 is provided on a main body 601, and is brought into contact with the grid electrode 206 by the main body 601. In this way, the slid brush 602 is provided on the main body 601 having flexibility, and the slide brush 602 is compressed on the grid electrode 206 side by the main body 601 so that even if a free length of the slide brush 602 is reduced, the deposits can be favorably cleaned.SELECTED DRAWING: Figure 4

Description

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

  In an image forming apparatus using an electrophotographic method, a corona charger is used as a charging device in order to uniformly charge the surface of a photosensitive drum to a predetermined polarity and potential. The corona charger is disposed in non-contacting manner on the photosensitive drum, and the photosensitive drum is charged by charged particles (corona ions) generated by a corona discharger. As a 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. The discharge electrode is a wire (called a discharge wire), and the control electrode is a plate-like member having a large number of holes formed in a mesh by etching (called a grid electrode) Used.

  In the case of the scorotron system, discharge products generated together with the charged particles during corona discharge, or toners and extraneous substances such as external additives of toners tend to adhere to the grid electrodes. The deposit attached to the grid electrode can oxidize the grid electrode to cause rust. If rusting occurs on the grid electrode, it becomes difficult to uniformly charge the photosensitive drum to a predetermined potential, and charging unevenness tends to occur. Then, in order to remove the deposit | attachment adhering to a grid electrode, the charging device provided with the cleaning member which slides on a grid electrode and cleans a grid electrode is proposed (patent document 1).

JP, 2013-186269, A

  The apparatus described in the above-mentioned Patent Document 1 can clean both surfaces of the grid electrode on the side facing the discharge wire (referred to as a wire surface) and the surface on the side facing the photosensitive drum (referred to as a drum surface) It has a cleaning member. When the grid electrode is cleaned, the drum surface cleaning pad for cleaning the drum surface is pressed against the grid electrode by the movable holding member. In this way, even if the drum surface cleaning pad wears due to repeated cleaning operations, the ability to remove the deposits (cleaning power) can be maintained, and the drum surface cleaning pad replacement cycle can be made as long as possible. However, when the grid electrode is not cleaned, it is necessary to retract the drum surface cleaning pad to the standby position by the movable holding member, and in order to secure the arrangement space of the movable holding member and the retraction space of the drum surface cleaning pad It is easy to enlarge, which is contrary to the recent demand for miniaturization. In addition, since the movable holding member is provided, the cost tends to be high. Therefore, there has been a demand for an apparatus having a simple configuration that can clean both the wire surface and the drum surface of the grid electrode, and can maintain the removal of deposits on the drum surface for a relatively long time. Things have not been proposed.

  The present invention has been made in view of the above problems, and it is possible to clean both the wire surface and the drum surface of the grid electrode, and in particular, a charging device having a simple configuration, capable of maintaining the removing ability of the deposit on the drum surface relatively long. The purpose is to provide

  In the charging device according to the present invention, a housing is disposed facing the surface of the photosensitive member, and a housing having an opening formed in a surface facing the photosensitive member, and the housing is disposed in the housing. A discharge electrode which is charged, a control electrode which is disposed between the photosensitive member and the discharge electrode and which controls the amount of charge on the surface of the photosensitive member, and slides on a first surface of the control electrode facing the discharge electrode A first cleaning member for cleaning the first surface, a main body having flexibility in a direction toward the second surface of the control electrode facing the photosensitive member, and the main body provided with the first cleaning member; A second cleaning member having a sliding portion sliding on two surfaces to clean the second surface, and moving means for moving the second cleaning member with respect to the control electrode. I assume.

  According to the present invention, with regard to the second cleaning member for cleaning the second surface facing the photosensitive member of the control electrode, the simple configuration in which the sliding portion sliding on the second surface is provided in the flexible main body portion Thus, the removing ability of the deposit on the second surface by the second cleaning member can be maintained relatively long.

FIG. 1 is a schematic view showing the configuration of an image forming apparatus to which the charging device of the present embodiment can be applied. FIG. 2 is a schematic view showing an image forming unit. FIG. 1 is an external perspective view showing a charging device of the present embodiment. FIG. 2 is a cross-sectional view showing the charging device of the present embodiment. The schematic diagram explaining a grid electrode. It is a side view showing a charging device of this embodiment, and (a) shows a state in which the shutter is open and (b) shows a state in which the shutter is closed. The control block diagram of the movement control system of a cleaning member. It is a partially expanded perspective view which shows a drawing-in member, (a) is after drawing in a grid electrode, (b) shows after drawing in a grid electrode. It is a figure explaining the cleaning range of a grid electrode, and (a) shows a charging device, (b) shows electrification current distribution which flows into a photosensitive drum. It is a figure which shows a wire surface cleaning brush, (a) is the bottom view seen from the grid electrode side, (b) is a side view. The schematic diagram explaining the intrusion amount of a wire surface cleaning brush. The schematic diagram explaining the protrusion amount of a wire surface cleaning brush. The schematic diagram explaining cleaning of the grid electrode by a wire surface cleaning brush. It is a figure explaining the cleaning aspect of the grid electrode by a wire surface cleaning brush and a drum surface cleaning brush, (a) shows the time of going-forward, (b) shows the time of returning. The partially expanded perspective view which shows the charging device of other embodiment which has arrange | positioned the drum surface cleaning brush in the shutter.

<Image forming apparatus>
The schematic configuration of the image forming apparatus of the present embodiment will be described with reference to FIGS. 1 and 2. FIG. The image forming apparatus 100 of the present embodiment is an electrophotographic tandem full-color printer. The image forming apparatus 100 includes first, second, third, and fourth image forming units PY, PM, PC, and PK that form yellow, magenta, cyan, and black images, respectively. Image forming apparatus 100 records a toner image as a recording material according to an image signal from an original reading apparatus (not shown) connected to apparatus main body 100A or an external device such as a personal computer connected communicably to apparatus main body 100A. To form. Examples of the recording material include sheet materials such as paper, plastic film and cloth.

  As shown in FIG. 1, the image forming portions PY, PM, PC, and PK are arranged side by side along the moving direction of the intermediate transfer belt 8. The intermediate transfer belt 8 is stretched around a plurality of rollers and configured to travel in the direction of the arrow R2. Then, the intermediate transfer belt 8 carries and conveys the primarily transferred toner image as described later. A secondary transfer roller 10 is disposed at a position facing the roller 9 for stretching the intermediate transfer belt 8 with the intermediate transfer belt 8 interposed therebetween, and a secondary transfer for transferring the toner image on the intermediate transfer belt 8 to the recording material It constitutes part T2. A fixing device 11 is disposed downstream of the secondary transfer portion T2 in the recording material conveyance direction.

  Below the image forming apparatus 100, a cassette 12 containing a recording material is disposed. The recording material is conveyed from the cassette 12 toward the registration roller 14 by the conveyance roller 13. Thereafter, the registration roller 14 is rotated in synchronization with the toner image on the intermediate transfer belt 8, whereby the recording material is conveyed to the secondary transfer portion T2.

  The four image forming units PY, PM, PC, and PK provided in the image forming apparatus 100 have substantially the same configuration except that the developing color is different. Therefore, the image forming unit PK will be described as a representative here, and the description of the other image forming units will be omitted.

  As shown in FIG. 2, in the image forming unit PK, a cylindrical photosensitive drum 1 is disposed as a photosensitive member. The photosensitive drum 1 is rotationally driven in the arrow R1 direction. A charging device 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and a cleaning device 6 are disposed around the photosensitive drum 1.

  A process of forming, for example, a full color image of four colors by the image forming apparatus 100 having the above-described configuration will be described. First, when the image forming operation is started, the surface of the rotating photosensitive drum 1 (the surface of the photosensitive member) is uniformly charged by the charging device 2. The charging device 2 irradiates the charged particles associated with the corona discharge to charge the photosensitive drum 1 to a uniform negative dark potential. Details of the charging device 2 of the present embodiment will be described later. Next, the photosensitive drum 1 is scan-exposed by the laser beam L corresponding to the image signal emitted from the exposure device 3. Thereby, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum. The electrostatic latent image on the photosensitive drum is visualized by the toner contained in the developing device 4 and becomes a visible image.

  The toner image formed on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 8 at a primary transfer portion T1 configured between the intermediate transfer belt 8 and a primary transfer roller 5 disposed therebetween. At this time, a primary transfer bias is applied to the primary transfer roller 5. The toner and the like remaining on the surface of the photosensitive drum 1 after the primary transfer are removed by the cleaning device 6.

  Such an operation is sequentially performed in each of the yellow, magenta, cyan, and black image forming units, and four color toner images are superimposed on the intermediate transfer belt 8. Thereafter, the recording material accommodated in the cassette 12 is conveyed to the secondary transfer portion T2 in synchronization with the formation timing of the toner image. Then, by applying a secondary transfer bias to the secondary transfer roller 10, the four color toner images on the intermediate transfer belt 8 are collectively secondarily transferred onto the recording material.

  Next, the recording material is conveyed to the fixing device 11. The fixing device 11 heats and presses the recording material to be conveyed. As a result, the toner on the recording material is melted and mixed, and fixed to the recording material as a full color image. Thereafter, the recording material is discharged to the discharge tray 15. Thus, a series of image forming processes are completed.

<Charging device>
The configuration of the charging device 2 of the present embodiment will be described with reference to FIGS. 3 to 5. The charging device 2 of the present embodiment is a scorotron type corona charging device, and FIG. 3 shows the charging device 2 viewed from the photosensitive drum side. The charging device 2 is provided so as to be insertable into and removable from the main assembly 100A (see FIG. 1) of the image forming apparatus 100, and faces the photosensitive drum 1 along the rotational axis direction (longitudinal direction) of the photosensitive drum 1 as shown in FIG. Placed in the 3, for convenience of illustration, illustration of the cleaning member 250 mentioned later is abbreviate | omitted, and illustration of the shutter 210 mentioned later is abbreviate | omitted in FIG.

  As shown in FIG. 3, the charging device 2 includes a pair of shield electrodes 203, a front block 201 disposed on the front side of the charging device 2 insertion direction (arrow X direction in the drawing), and the charging device 2 insertion direction. And a back block 202 disposed on the back side of The shield electrodes 203 are formed in a plate shape using stainless steel (SUS), and are arranged to face each other at a predetermined interval (for example, 30 mm) in the width direction (short direction) intersecting the rotation axis direction of the photosensitive drum 1. ing. The shield electrode 203, the front block 201, and the back block 202 form a housing 90 having an open U-shaped cross section. The front block 201 and the back block 202 stretch a discharge wire 205 (see FIG. 4) described later in the rotational axis direction of the photosensitive drum 1 and hold a grid electrode 206.

<Discharge wire>
As shown in FIG. 4, the charging device 2 has a discharge wire 205 as a discharge electrode and a grid electrode 206 as a control electrode. The discharge wire 205 is disposed inside the pair of shield electrodes 203 (within the housing). The discharge wire 205 generates a corona discharge when a charging voltage is applied from a high voltage power supply (not shown). For example, stainless steel, nickel, molybdenum, tungsten or the like is used as the discharge wire 205, and these are formed in a wire shape. As the diameter of the discharge wire 205 becomes smaller, it becomes easier to cut due to the collision of ions generated with the discharge. On the other hand, as the diameter of the discharge wire 205 increases, the charging voltage needs to be higher to generate a stable corona discharge. However, if the charging voltage is too high, ozone is likely to be generated with the discharge. In view of the above point, the discharge wire 205 is preferably formed to have a diameter of 40 μm to 100 μm.

<Grid electrode>
The grid electrode 206 is provided between the photosensitive drum 1 and the discharge wire 205 at the opening 90 a of the housing 90 so as to be close to the surface of the photosensitive drum 1. The grid electrode 206 can control the amount of current flowing to the photosensitive drum side as a high voltage is applied from a high voltage power supply (not shown). Thereby, the charge amount of the surface of the photosensitive drum 1 is controlled. When the grid electrode 206 is closer to the photosensitive drum surface, the effect of uniformly charging the photosensitive drum surface can be enhanced. In the present embodiment, the closest contact distance (GD gap) between the grid electrode 206 and the photosensitive drum 1 is set to “1.3 ± 0.3 mm”. The closest distance between the grid electrode 206 and the discharge wire 205 was set to 8 mm.

  The grid electrode 206 is a so-called etching grid having a mesh-like portion in which a large number of through holes are formed by etching the base 206c of a thin plate-like metal flat plate (thin plate) having a thickness of 1 mm or less. It is. In the present embodiment, a thin plate of about 0.1 mm in thickness made of austenitic stainless steel (SUS 304) is used as the base material 206c. In addition, martensitic stainless steel or ferritic stainless steel may be used as the base material 206c.

  The shape of the grid electrode 206 will be described with reference to FIG. In FIG. 5, in order to describe the shape of the grid electrode 206, symbols “a to f” are attached for convenience. The remaining portion of the base 206c (see FIG. 4) other than the through hole 206a has a width “0” so that the through hole 206a has an opening width of “0.3 ± 0.03 mm” (see a symbol a in FIG. 5). It is formed so as to be “.07 ± 0.03 mm” (see a symbol b in FIG. 5). Further, the through hole 206a is formed at an angle “45 ± 1 °” (see a symbol c in FIG. 5) with respect to an imaginary line extending in the longitudinal direction. As the area ratio between the portion of the through hole 206a and the remaining portion other than the through hole 206a is larger, the effect of uniformly charging the surface of the photosensitive drum 1 is higher. In the width direction of the grid electrode 206, a width of "0.1. ± .0.03 mm" (see e in FIG. 5) at intervals of "6.9. ± .0.1 mm" for preventing deflection (FIG. 5). A beam 206b (see symbol d)) is provided in the longitudinal direction. In addition, it is preferable to leave the base material 206c at a width of about 1.5 ± 0.1 mm at both end portions in the width direction of the grid electrode 206 (refer to the symbol f in FIG. 5). Further, the grid electrode 206 is not limited to being formed in a mesh shape, and may be formed, for example, in a honeycomb shape.

  A surface treatment (so-called coating) is applied to the surface of the grid electrode 206 for the purpose of improving corrosion resistance, and a protective layer having an antirust effect is formed. For example, a protective layer of tetrahedral amorphous carbon (ta-C), which is a material chemically inert to the discharge products generated by corona discharge, is formed. ta-C is superior to other materials in inertness to air and water at normal temperature, corrosion resistance, low abrasion resistance, self-lubricity, high hardness and surface smoothness. Further, ta-C is less likely to cause chemical adsorption and oxidation reaction, and is further less likely to cause partial deterioration due to the occurrence of wear and damage. Therefore, it is suitable for use in the protective layer of the grid electrode surface.

<Shutter>
Further, as shown in FIG. 3, the charging device 2 has a shutter 210 which can move between the grid electrode 206 and the photosensitive drum 1. The shutter 210 moves in the longitudinal direction between the grid electrode 206 and the photosensitive drum 1, and an open position where the opening 90a (see FIG. 4) of the housing 90 is opened and a closed position where the opening 90a is shielded. It is provided movably. The shutter 210 is formed into a thin sheet having a thickness of about 100 μm using a soft flexible non-woven fabric such as rayon fiber, for example. Of course, the present invention is not limited to this, and the shutter 210 may be formed using a knitted nylon fiber, a film of urethane, polyester or the like if it can be formed into a thin sheet. The shutter 210 is formed such that its length in the width direction (short direction) is wider than the distance between the pair of shield electrodes 203 so as to cover the opening 90 a of the housing 90.

  As shown in FIGS. 6A and 6B, the shutter 210 has one end in the longitudinal direction connected to the winding mechanism 211 and is moved in the longitudinal direction by the winding mechanism 211. The winding mechanism 211 winds and stores the shutter 210 in a roll shape. As shown in FIG. 6A, when the shutters 210 are all in the position (open position) taken up by the winding mechanism 211, the opening 90a (see FIG. 4) of the housing 90 is opened. is there. On the other hand, as shown in FIG. 6B, when all the shutters 210 are in the position (closed position) pulled out from the winding mechanism 211, the opening 90a of the housing 90 is in the shielded state. That is, the shutter 210 is moved to one end side (right side of FIG. 6B) of the photosensitive drum 1 to block the opening 90a of the housing 90, and the other end side (left side of FIG. 6A) Is moved to open the opening 90 a of the housing 90.

  The winding mechanism 211 is held by the front block 201 together with a holding case 214 holding the winding mechanism 211. A guide roller for guiding the shutter 210 so that the shutter 210 does not interfere with the drawing operation of the shutter 210 because the shutter 210 abuts on the edge of the grid electrode 206, the holding portion 207, the knob 208, etc. 215 are arranged. Here, the holding portion 207 (209) is disposed in the front block 201 and the back block 202 respectively to hold the grid electrode 206, and the knob 208 holds the grid electrode 206 according to the operation by the user. It is for removing from.

  The other end of the shutter 210 opposite to the winding mechanism 211 is held by a plate spring 212. The leaf spring 212 can bias the shutter 210 toward the grid electrode, and can keep the shutter 210 in an arched state in the closed position. The shutter 210 is maintained in a closed position so that the vicinity of the center in the width direction (short direction) is convex toward the grid electrode side, thereby making it difficult for the discharge product to leak out of the housing.

  A plate spring 212 holding the shutter 210 is connected to the carriage 213. The carriage 213 is driven by the rotation of the drive screw 217. The drive screw 217 is rotationally driven by the motor M. As the carriage 213 moves toward the closed position, the shutter 210 is pulled out of the winding mechanism 211. Conversely, as the carriage 213 moves toward the open position, the shutter 210 is rewound by the winding mechanism 211. The plate spring 212 is formed of, for example, a metal having a thickness of 0.10 mm, and although thin, the strength to endure holding the shutter 210 is secured.

<Optical sensor>
The charging device 2 has a first optical sensor PS1 and a second optical sensor PS2 to detect whether the shutter 210 is in the open or closed position. The optical sensors PS1 and PS2 detect the position of the shutter 210, specifically, detect whether the shutter 210 is in a state (open position) taken up by the take-up mechanism 211 or not (closed position). In the case of the present embodiment, the optical sensors PS1 and PS2 are disposed at two positions above the axis of the drive screw 217 so that predetermined signals can be output respectively when the shutter 210 is in the open position and in the closed position. There is.

  As the optical sensors PS1 and PS2, for example, it is preferable to use a photo-interrupter type sensor in which a light emitting unit for emitting light and a light receiving unit for receiving light emitted from the light emitting unit are disposed opposite to each other. In the case of a photo interrupter type sensor, a shielding member 220 is provided on the carriage 213. The shielding member 220 is moved in response to the movement of the carriage 213, that is, the shutter 210. When the shielding member 220 is in the shielding position where the optical sensors PS1 and PS2 are shielded, the optical sensors PS1 and PS2 output a predetermined signal (here, a signal corresponding to the amount of light). On the contrary, when the shielding member 220 is in the non-shielding position which does not shield the optical sensors PS1 and PS2, the optical sensors PS1 and PS2 do not output a predetermined signal. In the present embodiment, as shown in FIG. 6A, when a predetermined signal is output from the optical sensor PS1 disposed closer to the winding mechanism 211, the shutter 210 is in the open position. On the other hand, as shown in FIG. 6B, when a predetermined signal is output from the optical sensor PS2 disposed far from the winding mechanism 211, the shutter 210 is in the closed position.

<Cleaning pad and cleaning member>
Furthermore, the charging device 2 has a cleaning pad 216 for cleaning the discharge wire 205 and a cleaning member 250 for cleaning the grid electrode 206. In the case of the present embodiment, the cleaning pad 216 and the cleaning member 250 are held by the carriage 213. Therefore, the cleaning pad 216 and the cleaning member 250 are reciprocated in the longitudinal direction in accordance with the movement of the shutter 210 between the open position and the closed position according to the drive of the motor M. The cleaning pad 216 is formed, for example, using a sponge, and cleans the discharge wire 205 by reciprocating the discharge wire 205 in a state of sandwiching the discharge wire 205 from above and below in the direction of gravity. The detailed configuration of the cleaning member 250 will be described later.

  Here, movement control of the cleaning member 250 will be described. In the case of the present embodiment, as described above, since the cleaning member 250 is reciprocated in accordance with the movement of the shutter 210, the cleaning member 250 is moved substantially according to the movement control of the shutter 210. The shutter 210 is moved under the control of the control unit 300 (see FIG. 1). A control block of a movement control system of the cleaning member 250 (substantially the shutter 210) in the control unit 300 is shown in FIG. As shown in FIG. 7, the control unit 300 is connected to a memory 301, a motor M, optical sensors PS1, PS2, and the like. Although various devices such as a motor and a power source for operating the image forming apparatus 100 are connected to the control unit 300 in addition to those illustrated, the illustration and the description thereof are omitted because they are not the purpose of the invention.

  The control unit 300 performs various controls of the image forming apparatus 100 such as an image forming operation, and includes a CPU (Central Processing Unit) whose illustration is omitted. The control unit 300 is connected to a memory 301 such as a ROM or RAM as a storage unit or a hard disk drive. The memory 301 stores various programs, data, and the like for controlling the image forming apparatus 100. The control unit 300 may execute the image forming job stored in the memory 301 to operate the image forming apparatus 100 to form an image. In the case of the present embodiment, the control unit 300 can execute cleaning control for operating the cleaning member 250 to clean the grid electrode 206. The memory 301 may temporarily store operation processing results accompanying the execution of various control programs.

  In the case of the present embodiment, the control unit 300 performs cleaning control to clean the grid electrode 206 every time the cumulative number of recording materials counted by the counter 302 reaches a predetermined number of image formations (for example, 6000). At this time, the control unit 300 controls the motor M as a drive unit, and moves the cleaning member 250 by operating the shutter 210 via the drive screw 217 and the carriage 213 described above. The movement of the cleaning member 250 relative to the grid electrode 206 is detected by the optical sensors PS1 and PS2. The control unit 300 can acquire signals output from the optical sensors PS1 and PS2. During movement control of the cleaning member 250, the control unit 300 controls the motor M to perform the outward movement until the predetermined signal is output from the optical sensor PS2, and when the predetermined signal is output from the optical sensor PS2, the return movement is performed. The motor M is reversely controlled to perform. The control unit 300 performs control to close the shutter 210 when an elapsed time from the end of the image formation job after execution of the image formation job is over a predetermined time (for example, 2 hours), and enters the sleep mode. When starting the image forming job from the sleep mode, the control unit 300 performs control to open the shutter 210 and then starts image forming.

  Further, in the case of the present embodiment, in order to cause the cleaning member 250 to clean the grid electrode 206, the grid electrode 206 is moved (drawn) from the photosensitive drum side to the discharge wire side before the start of the movement control of the cleaning member 250. That is, before cleaning, the grid electrode 206 stands by at a standby position where it does not contact the cleaning member 250 on the photosensitive drum side. When the grid electrode 206 is cleaned, it is moved between the standby position and the cleaning position in contact with the cleaning member 250 by the drawing members 252 (see FIG. 5) disposed at both ends of the carriage 213 in the lateral direction. It is cleaned by the cleaning member 250.

<Drawing-in member>
The pull-in member 252 will be described with reference to FIGS. 8 (a) and 8 (b). 8A and 8B show the charging device 2 viewed from the photosensitive drum side, and the upper side of the drawing is the gravity direction. As shown in FIGS. 8A and 8B, the drawing-in member 252 is provided so as to project inward from the carriage 213 more than the shield electrode 203. The pull-in member 252 is extended in the moving direction of the carriage 213, and has a tapered portion 252a and a rubbing portion 252b. The tapered portion 252a is an inclined surface formed to approach the photosensitive drum side as it proceeds in the insertion direction of the charging device 2 (the arrow X direction in the drawing). On the other hand, the rubbing portion 252b is a horizontal surface formed closer to the front block 201 than the tapered portion 252a.

  As shown in FIG. 8A, the pull-in member 252 moves in the arrow X direction in the drawing in response to the carriage 213 moving in the direction of the closed position. In response to the movement of the drawing member 252, the grid electrode 206 is moved along the tapered portion 252a toward the photosensitive drum so as to be pushed up to the side opposite to the direction of gravity (the upper side in the drawing). The grid electrode 206 pushed up against the gravity by the tapered portion 252a locally deforms. Then, as shown in FIG. 8B, the grid electrode 206 receives a force F that is displaced to the discharge wire side (the lower side in the drawing) by the rubbing portion 252b when moving to the rubbing portion 252b, and is displaced. It is held. That is, in response to the movement of the carriage 213, the grid electrode 206 is pressed from the photosensitive drum side to the discharge wire side. As described above, since the cleaning member 250 is held by the carriage 213, the cleaning member 250 moves in the same manner as the carriage 213 moves. At this time, the cleaning member 250 is moved in contact with the grid electrode 206 pressed from the photosensitive drum side to the discharge wire side to clean the grid electrode 206.

  As described above, since the drawing-in member 252 is moved by rubbing with the grid electrode 206, the grid electrode 206 may be locally worn as the number of times of cleaning by the cleaning member 250 increases. In the above-mentioned FIG. 5, the location of the grid electrode 206 worn away by rubbing with the lead-in member 252 is shown. A point g of the grid electrode 206 shown in FIG. 5 is a place where the lead-in member 252 rubs. The portion h of the grid electrode 206 is a portion which does not rub against the lead-in member 252. As shown in FIG. 5, the lead-in member 252 is provided so as not to contact the mesh portion of the grid electrode 206. This is because the remaining portion of the base material 206c (see FIG. 4) other than the through holes 206a in the mesh portion is thin and can be cut when it is rubbed by the drawing member 252.

Next, the cleaning range of the grid electrode 206 by the cleaning member 250 will be described with reference to FIG. The symbol "G" described in FIG. 9A indicates the distance between the discharge wire 205 and the shield electrode 203, and the symbol "H" indicates the distance between the discharge wire 205 and the grid electrode 206. Further, a code “R” described in FIG. 9B indicates a range in which a current having a half value or more flows with respect to the peak value of the charging current (Id) flowing to the photosensitive drum side. Further, a symbol “P” indicates the center in the width direction of the grid electrode 206. Here, a range indicated by a symbol “R” indicates a range of ± (R / 2) with respect to a straight line connecting the discharge wire 205 and the center “O” of the photosensitive drum 1. The range indicated by the symbol “R” is a range determined by Equation 1 shown below.
R ² = G ² + H ² ··· Formula 1

  Then, as shown in FIG. 9B, the peak value of the charging current (Id) flowing to the photosensitive drum 1 becomes the largest immediately under the discharge wire 205 (P). In the case of the present embodiment, the cleaning range of the grid electrode 206 by the cleaning member 250 is, as shown in the above equation 1, the square sum average of the interval "G" of the shield electrode 203 and the interval "H" of the grid electrode 206. It is set. This is because the deposit tends to adhere to the grid electrode 206 as the charging current (Id) flowing to the photosensitive drum side is larger. When the discharge wire 205 is disposed offset to one of the shield electrodes 203, the distance between the discharge wire 205 and the shield electrode 203 having a smaller distance from the discharge wire 205 is calculated as the above-mentioned distance "G". Is desirable.

  The configuration of the cleaning member 250 will be described in detail. As shown in FIG. 4, the cleaning member 250 of the present embodiment has a wire surface cleaning brush 500 as a first cleaning member and a drum surface cleaning brush 600 as a second cleaning member. The wire surface cleaning brush 500 and the drum surface cleaning brush 600 respectively clean the front and back surfaces of the grid electrode 206. That is, the wire surface cleaning brush 500 slides on the surface (referred to as the first surface, the wire surface) of the grid electrode 206 facing the discharge wire 205 to clean the wire surface. On the other hand, the drum surface cleaning brush 600 slides on the surface (referred to as a second surface, drum surface) of the grid electrode 206 facing the photosensitive drum 1 to clean the drum surface.

<Wire surface cleaning brush>
First, the wire surface cleaning brush 500 will be described with reference to FIGS. As shown in FIGS. 10 (a) and 10 (b), the wire surface cleaning brush 500 is a resin brush treated with flame retardancy and woven into a base fabric, and comprises a brush portion 501 and a base fabric portion 502. It is done. The brush portion 501 has a free length "L10" and is formed to cover the region (see FIG. 9B) indicated by the above-mentioned reference character "R" in the width direction of the grid electrode 206. In the case of this embodiment, the brush portion 501 is woven such that an acrylic pile having a thickness of 11 dtex is density of 60,000 pieces / inch ² and the free length “L10” is 3.0 mm. Was used. The brush unit 501 may use a resin brush such as nylon (registered trademark), polyvinyl chloride (PVC), or polyphenylene sulfide resin (PPS). The size of the wire surface cleaning brush 500 is, for example, 21 mm in the width direction and 5 mm in the longitudinal direction. The brush unit 501 is formed such that a margin indicated by a symbol “Δg” is, for example, 1 mm.

  As shown in FIG. 11, in the case of the present embodiment, the penetration amount (ΔX in the figure) of the brush portion 501 to the grid electrode 206 in the stationary state where the wire surface cleaning brush 500 is not sliding on the grid electrode 206 is, for example It is set to 0.8 mm.

  As shown in FIG. 12, when the wire surface cleaning brush 500 moves in the longitudinal direction and slides on the grid electrode 206, the brush portion 501 cleans the wire surface of the grid electrode 206, and cleans the through hole 206a. It divides into what to do. The “bending amount” of the grid electrode 206 described in FIG. 12 indicates the amount by which the brush portion 501 cleaning the wire surface presses the grid electrode 206. In the case of the present embodiment, the amount of deflection of the grid electrode 206 is suppressed to about 0.1 mm. Also, in the operating state in which the wire surface cleaning brush 500 slides on the grid electrode 206, the amount of protrusion (ΔL in the figure) of the brush portion 501 with respect to the grid electrode 206 is set to, for example, 0.4 to 0.6 mm. . The “protrusion amount ΔL” is a length of the brush portion 501 cleaning the through hole 206 a protruding from the grid electrode 206 toward the photosensitive drum.

  FIG. 13 shows how the brush portion 501 with the free length “L10” contacts and cleans the through hole 206a. The cleaning force of the through hole 206a by the brush unit 501 is proportional to the distance the brush unit 501 moves in contact with the through hole 206a. From this, if the “protrusion amount ΔL” (see FIG. 12) is increased, the contact movement distance between the brush portion 501 and the through hole 206a can be increased, so the cleaning power of the through hole 206a by the brush portion 501 is increased. Can. Further, the value of the “protrusion amount ΔL” is determined by the free length “L10” of the brush portion 501 and the intrusion amount (ΔX in FIG. 11) to the grid electrode 206 of the brush portion 501. In the present embodiment, the protrusion amount in the cleaning range (R region in FIG. 9B) of the grid electrode 206 is 0.4 to 0.6 mm as described above, and the protrusion amounts at both ends in the width direction other than that are 0 to It was 0.2 mm. That is, the cleaning power of the R region in which the adhering matter easily adheres is made higher than that in the width direction both ends where the adhering matter hardly adheres. In order to do so, it is preferable that the free length “L10” of the brush unit 501 and the penetration amount (ΔX in FIG. 11) of the brush unit 501 into the grid electrode 206 be set.

  Here, in order to clean both the wire surface of the grid electrode 206 and the through holes 206a, the protrusion amount ΔL (see FIG. 12) needs to be 0 mm or more. More preferably, in consideration of the plate thickness and deflection amount of the grid electrode 206, it is desirable to set the protrusion amount ΔL to 0.1 mm or more. Further, it is desirable to set the protrusion amount ΔL equal to the length J in the longitudinal direction of the through hole 206a shown in FIG. For example, when the formation angle of the through hole 206a is 45 degrees and the length J in the longitudinal direction of the through hole 206a is 0.3 mm, the protrusion amount ΔL is set to 0.4 mm or more. The upper limit of the protrusion amount ΔL is smaller than the interval (GD gap) between the grid electrode 206 and the photosensitive drum 1 so that the behavior of the brush portion 501 does not fluctuate due to contact with the photosensitive drum 1 when cleaning the grid electrode 206. It is desirable to do. By doing as described above, it is possible to preferably clean both the wire surface of the grid electrode 206 and the through hole 206 a while suppressing the amount of bending of the grid electrode 206.

<Drum surface cleaning brush>
Next, the drum surface cleaning brush 600 will be described. As shown in FIG. 4, the drum surface cleaning brush 600 has a main body portion 601 and a sliding brush portion 602 as a sliding portion. The main body portion 601 is a leaf spring formed of, for example, stainless steel (SUS) having a thickness of 100 μm, and has flexibility in the direction toward the drum surface of the grid electrode 206. The sliding brush portion 602 is provided on the main body portion 601, for example, using a flocked sheet on which a flame retardant treated resin brush with a free length of 1.5 mm is flocked. The sliding brush portion 602 is formed so as to be in contact with the grid electrode 206 in the R region (a predetermined region including the area immediately below the discharge wire 205) shown in FIG. 9B. The sliding brush portion 602 is in contact with the grid electrode 206 by the main body portion 601. The sliding brush portion 602 may be made of acrylic, nylon (registered trademark), PVC (polyvinyl chloride), PPS (polyphenylene sulfide resin) or the like subjected to a flame retardant treatment. The sliding brush portion 602 is not limited to a brush, and may be a sponge, a rubber, or a resin sheet.

  The inventors changed the contact area ratio of the drum surface to the wire surface with respect to the grid electrode 206 and experimented, and the relationship of "contact area ratio of drum surface (S2)> contact area ratio of wire surface (S1)" It was found that the grid electrode 206 was cleaned well. In the present embodiment, the contact area ratio (S2) of the drum surface cleaning brush 600 to the grid electrode 206 is larger than the contact area ratio (S1) of the wire surface cleaning brush 500 to the grid electrode 206. That is, in the case of the present embodiment, the wire surface cleaning brush 500 is used for the cleaning member for cleaning the wire surface, since it is required to remove (remove) the deposit adhering to the wire surface as the main purpose. It is done. However, in this case, the deposit attached to the wire surface may not be removed, and may be moved to the drum surface side through the through hole 206a. Therefore, in addition to removing the deposits attached to the drum surface, the cleaning member for cleaning the drum surface is at a position where the deposits transferred from the wire surface to the drum surface can be removed by the wire surface cleaning brush 500. It is required to move. Therefore, as the cleaning member for cleaning the drum surface, the electrostatically flocked drum surface cleaning brush 600, or a sponge, high density rubber, or the like is used. Therefore, the contact area ratio between the drum surface and the wire surface with respect to the grid electrode 206 is larger for the cleaning member cleaning the drum surface than for the cleaning member cleaning the wire surface. In addition, a contact area ratio prepares the transparent glass plate which imitated the grid shape at the time of cleaning, and applies the cleaning member which cleans a wire surface by the above-mentioned intrusion amount, and the cleaning member which cleans a drum surface to a transparent glass plate. The contact area is a contact area per unit area calculated by photographing the contact state with a camera.

  Further, in the present embodiment, the penetration amount of the drum surface cleaning brush 600 (more specifically, the sliding brush portion 602) to the grid electrode 206 is set to 0.3 mm. This is smaller than the penetration amount “0.8 mm” of the wire surface cleaning brush 500 (specifically, the brush portion 501) to the grid electrode 206. The inventors experimented by changing the penetration amount of the drum surface cleaning brush 600 and the wire surface cleaning brush 500 in the range of 0.05 to 3.0 mm. From the experimental results, it was found that the grid electrode 206 was cleaned well when the relationship of “invasion amount of wire surface cleaning brush 500 (L1)> invasion amount of drum surface cleaning brush 600 (L2)” was satisfied. Therefore, in the present embodiment, as described above, the intrusion amount of the wire surface cleaning brush 500 is set to 0.8 mm, and the intrusion amount of the drum surface cleaning brush 600 is set to 0.3 mm.

  However, since the sliding brush portion 602 of the drum surface cleaning brush 600 is worn by repeatedly performing the cleaning operation, the free length of the sliding brush portion 602 is reduced. If so, it becomes difficult to maintain the relationship between the contact area ratio and the amount of intrusion described above. Therefore, as described above, the sliding brush portion 602 is provided on the flexible main body portion 601, and the sliding brush portion 602 is pressed against the drum surface side of the grid electrode 206, whereby the sliding brush portion 602 is formed. Even if the free length is reduced, the deposit can be cleaned well.

  Furthermore, in the present embodiment, the wire surface cleaning brush 500 and the drum surface cleaning brush 600 are provided on the cleaning member 250 so as to slide relative to the grid electrode 206 at different positions in the longitudinal direction. That is, at the time of the cleaning operation of the cleaning member 250, the sliding brush portion 602 of the drum surface cleaning brush 600 is different from the sliding position of the wire surface by the brush portion 501 of the wire surface cleaning brush 500 in the moving direction. It is made to slide on the drum surface. By doing this, the cleaning property of the deposit adhering to the grid electrode 206 is enhanced. This point will be described with reference to FIGS. 14 (a) and 14 (b).

  FIG. 14A shows a cleaning mode of the grid electrode 206 by the wire surface cleaning brush 500 and the drum surface cleaning brush 600 when the shutter 210 moves from the open position to the closed position. As shown in FIG. 14A, during the forward pass, the sliding brush portion 602 of the drum surface cleaning brush 600 is located upstream of the sliding position of the grid electrode 206 by the brush portion 501 of the wire surface cleaning brush 500. Slide on the grid electrode 206. In other words, the brush portion 501 of the wire surface cleaning brush 500 cleans the grid electrode 206 earlier than the sliding brush portion 602 of the drum surface cleaning brush 600. In this case, the brush unit 501 moves the deposit attached to the wire surface to the drum surface side through the through hole 206a (see FIG. 11). Thereafter, the sliding brush unit 602 cleans the deposit moved to the drum surface side together with the deposit originally adhering to the drum surface. At this time, the deposit is made to fall on the shutter 210 so that the deposit does not fall on the photosensitive drum and adhere. As described above, by cleaning the wire surface having a relatively large amount of deposits first and then cleaning the drum surface, the cleaning property of the deposits adhering to the grid electrode 206 is enhanced.

  FIG. 14B shows a cleaning mode of the grid electrode 206 by the wire surface cleaning brush 500 and the drum surface cleaning brush 600 when the shutter 210 moves from the closed position to the open position. As shown in FIG. 14B, during the return path, the sliding brush portion 602 of the drum surface cleaning brush 600 is located downstream of the sliding position of the grid electrode 206 by the brush portion 501 of the wire surface cleaning brush 500 in the moving direction. Slide on the grid electrode 206. Although the grid electrode 206 is in a substantially cleaned state at the time of the above-described forward movement, if slight deposits remain, the sliding brush portion 602 of the drum surface cleaning brush 600 cleans the grid electrode 206 first. In this case, the sliding brush portion 602 moves the deposit attached to the drum surface to the wire surface side through the through hole 206a (see FIG. 11). Thereafter, the brush unit 501 cleans the extraneous matter moved to the wire surface side. In this case, deposits can fall on the photosensitive drum, but most deposits are cleaned when going forward, in which case very few deposits fall on the photosensitive drum, and many of them are rotating. Since it is made to flow by the air flow of the drum 1, it does not easily adhere to the photosensitive drum 1.

  As described above, in the present embodiment, the wire surface cleaning brush 500 can clean the wire surface, and the drum surface cleaning brush 600 can clean both surfaces of the grid electrode 206 on the drum surface. With respect to the drum surface cleaning brush 600, the sliding brush portion 602 is provided in the flexible main body portion 601, and the sliding brush portion 602 is pressed against the drum surface side of the grid electrode 206. With a simple configuration capable of cleaning both sides of the grid electrode 206 while preventing the upsizing of such a device, even if the sliding brush portion 602 wears, the ability to remove deposits on the drum surface is maintained relatively long. Can.

Other Embodiments
Although the wire surface cleaning brush 500 and the drum surface cleaning brush 600 are integrally provided as the cleaning member 250 in the above-described embodiment, the drum surface cleaning brush 600 is not limited to this. It may be arranged. The charging device 2 in such a case is shown in FIG. The cleaning member 250 shown in FIG. 15 is different from that in FIG. 8 in that the drum surface cleaning brush 600 is disposed on the shutter 210, and the other configuration and operation are the same as in the above embodiment. Are given the same reference numerals and explanation thereof is omitted.

  As shown in FIG. 15, in the present embodiment, a drum surface is obtained by affixing the sliding brush portion 602 described above to the plate spring 212 using the plate spring 212 holding the other end of the shutter 210 as the main body portion. The cleaning brush 600 is disposed on the shutter 210. In such a case, the sliding brush portion 602 of the drum surface cleaning brush 600 can be firmly slid on the grid electrode 206 while the shutter 210 is not in contact with the photosensitive drum 1. Further, since the plate spring 212 is also used as the main body, cost increase due to the addition of parts can be prevented.

Reference Signs List 1 photosensitive member (photosensitive drum) 2 charging device 90 housing 205 discharge electrode (discharge wire) 206 control electrode (grid electrode) 210 shutter 500 first cleaning member (wire surface) Cleaning brush) 600: second cleaning member (drum surface cleaning brush) 601: main body portion 602: sliding portion (sliding brush portion) M: moving means (motor)

Claims (6)

A housing disposed facing the surface of the photosensitive member and having an opening formed on the surface facing the photosensitive member;
A discharge electrode disposed in the housing and charging the surface of the photosensitive member;
A control electrode disposed between the photosensitive member and the discharge electrode to control the amount of charge on the surface of the photosensitive member;
A first cleaning member sliding on a first surface of the control electrode facing the discharge electrode to clean the first surface;
A main body having flexibility in a direction toward the second surface of the control electrode facing the photosensitive member, and a slide provided on the main body and sliding on the second surface to clean the second surface A second cleaning member having a moving part;
Moving means for moving the second cleaning member relative to the control electrode;
A charging device characterized by The first cleaning member and the second cleaning member have a contact area ratio per unit area to the first surface of the first cleaning member S1, and the contact per unit area to the second surface of the second cleaning member When the area ratio is S2,
Satisfy the relationship S2> S1,
The charging device according to claim 1, When the first cleaning member and the second cleaning member set the amount of intrusion of the first cleaning member to the control electrode as L1, and the amount of intrusion of the second cleaning member to the control electrode as L2,
Satisfy the relationship of L1> L2,
The charging device according to claim 1 or 2, characterized in that: It has a shutter movable to an open position where the opening is opened and a closed position where the opening is shielded,
In the second cleaning member, when the shutter is moved from the open position to the closed position, the sliding portion is upstream of the sliding position of the control electrode by the first cleaning member in the moving direction. Slide on the control electrode,
The charging device according to any one of claims 1 to 3, characterized in that: The shutter, the first cleaning member and the second cleaning member are moved together by the moving means.
The charging device according to claim 4, The second cleaning member is disposed on the shutter.
The moving means moves the second cleaning member by moving the shutter.
The charging device according to claim 4 or 5, characterized in that:

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