JP2008032854A - Charging device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately move a cleaning member back and forth, between both ends of an electrode together with a support by simple control, without the occurrence of cleaning defects and damages to the device in spite of the occurrence of a change in the amount of adhesion of dust on the electrode. <P>SOLUTION: The charger 1 is equipped with the support 4 and a conveyance screw 6. The support 4 is equipped with a projection member 4D formed with a projection 4E. The projection 4E fits into a root part 6D of the conveyance screw 6, in a radial direction from above and is made to climb over the crest part 6C by the elastic deformation of the projection member 4D. The support 4 is moved backwards and forwards, along the X-axis by the forward rotation and backward rotation of the conveyance screw 6. The projection 4E is made to abut against the crest part 6C, in such a manner that the distance L1, at the forward movement from the fulcrum 4F of the support 4 up to the abutting position with the crest part 6C, is shorter than the distance L2 at the time of the backward movement. Even if the conveyance screw 6 rotates intermittenly forward after the support 4 reaches the terminal of the forward movement, large deformation force will not act on the projection member 4D. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging device that discharges during electrophotographic image forming processing, and an image forming apparatus including the charging device.

  Some image forming apparatuses that perform electrophotographic image forming processing use a non-contact type charging device. The non-contact charging device discharges from an electrode to which a high voltage power source is applied. In a charging device using a charger wire having a diameter of 10 to 150 μm as an electrode, ozone is generated from the charger wire during discharge due to application of a high-voltage power source, thereby polluting the environment. For this reason, some charging devices use needle electrodes that generate a small amount of ozone when a high-voltage power supply is applied.

  The surrounding dust is adsorbed to the portion of the charging device where the high-voltage electric field is generated. If this is left unattended, proper discharge from the electrodes cannot be performed.

  Some conventional charging devices include a pair of pad members that are opposed to each other with the needles of the needle electrodes movably along the arrangement direction of the plurality of needles (see, for example, Patent Document 1). In this configuration, the pad member is moved along the arrangement direction of the plurality of needles. The pad member sequentially contacts the surfaces of the plurality of needles and removes dust attached to the needles.

  In a conventional charging device, a cleaning member such as a pad member is moved manually. For this reason, the electrode may not be cleaned at an appropriate timing according to the state of dust adhesion to the electrode.

  Therefore, it is conceivable to automatically move the cleaning member along the longitudinal direction of the electrode at a predetermined timing using a conveying screw. The conveying screw is rotatably supported by the charging device in parallel with the electrode. In the charging device, a moving body that supports the cleaning member is disposed so as to be movable along the longitudinal direction of the electrode without rotating to the charging device. A moving body is screwed into the conveying screw, and rotation in both forward and reverse directions is supplied from a motor.

The cleaning member reciprocates along the longitudinal direction of the electrode together with the moving body by the rotation of the conveying screw. When cleaning the electrode, the conveying screw is rotated forward to move the cleaning member forward from the first end portion of the electrode toward the second end portion. When the cleaning member reaches the second end, the conveying screw is reversed to move the cleaning member back from the second end toward the first end. When the cleaning member returns to the first end, the rotation of the conveying screw is stopped.
JP 11-338265 A

  In order to clean the entire area in the longitudinal direction of the electrode, it is necessary to reliably move the cleaning member to the second end during the forward movement. In order to prevent the discharge from the electrodes from being hindered during the image forming process, it is necessary to reliably return the cleaning member to the first end during the backward movement.

  The charging device is disposed in the image forming apparatus in the vicinity of the photosensitive member together with the developing device and the cleaner. When a female screw portion through which the conveying screw passes is formed in the moving body, and a sensor for detecting the cleaning member is disposed at both the first end portion and the second end portion of the electrode, the image forming apparatus is increased in size.

  For this reason, it is conceivable that the forward rotation time and the reverse rotation time of the conveying screw for reciprocating the cleaning member are controlled so that the sensor is not required and the image forming apparatus is not enlarged.

  However, the load acting on the cleaning member changes according to the dust adhesion state of the electrode, and the moving distance of the cleaning member within a certain time varies. If the conveying screw is rotated forward for a certain period of time, if a large amount of dust adheres to the electrode, the resistance acting on the moving cleaning member increases, and the cleaning member does not reach the second end. . In addition, when almost no dust adheres to the electrode, the resistance acting on the moving cleaning member becomes too small, and the conveying screw continues to rotate forward even after the cleaning member reaches the second end. The conveying screw, moving body and motor are damaged.

  The object of the present invention is to accurately reciprocate the cleaning member together with the support body between the both ends of the electrode by simple control without causing poor cleaning or damage to the apparatus even if the amount of dust attached to the electrode changes. Another object of the present invention is to provide a conveying screw mechanism, a charging device, and an image forming apparatus that can perform the above operation.

  The charging device of the present invention includes an electrode, a cleaning member, a conveying screw, a motor, a support, and a protruding member. The cleaning member contacts the linear electrode. The conveying screw is disposed parallel to the longitudinal direction of the electrode and is rotatably supported. The motor rotates the conveying screw in both forward and reverse directions. The support member holds the cleaning member and is reciprocally movable and non-rotatable from the first end portion to the second end portion of the electrode. The protruding member includes a protrusion that extends from the support and is fitted in the trough portion of the male screw of the conveying screw in the radial direction of the conveying screw. The protruding member has a distance between a contact position where the protrusion is in contact with the threaded portion of the male screw and a fulcrum of elastic deformation in a direction in which the protrusion is removed from the valley as a first distance when the support is moved forward. Sometimes the second distance is different from the first distance. The first distance and the second distance are set based on the moment acting on the fulcrum during elastic deformation.

  When the motor rotates the conveying screw in the forward direction, the position where the protrusion abuts in the valley of the male screw of the conveying screw moves from the first end side to the second end side of the electrode, and the support body Move forward. When the motor reverses the conveying screw, the position where the protrusion abuts in the valley of the male screw of the conveying screw moves from the second end side to the first end side of the electrode, and the support is restored. Move.

  When the rotation of the conveying screw is continued after the support body reaches the second end portion that is the end position in the forward movement direction or the first end portion that is the end position in the backward movement direction, the protrusion is elastic of the protrusion member. Due to the deformation, it is displaced in the direction over the threaded part of the male screw. At this time, the moment acting on the fulcrum of the protrusion member changes according to the distance from the fulcrum to the contact position between the protrusion and the peak. This distance is different between when the support is moved forward and when the support is moved backward because the peak portion is inclined with respect to an axis orthogonal to the longitudinal direction of the conveying screw and the protrusion has a partial spherical shape. After the support member reaches either the first end or the second end, the conveying screw continues to rotate, and a large moment acts on the fulcrum of the protrusion member even when the protrusion gets over the peak. Therefore, the protruding member etc. will not be damaged. For this reason, it is not necessary to accurately control the amount of rotation of the conveying screw during either the forward movement or the backward movement of the support member.

  For example, the first distance is shorter than the second distance. Even if the protrusion repeatedly climbs over the ridges by the rotation of the conveying screw after the support member reaches the second end, a large moment does not act on the fulcrum, causing damage to the protrusion member, etc. Absent. When the support is moved forward, it is not necessary to accurately control the rotation amount of the conveying screw.

  Further, a sensor for detecting the support at the first end is further provided, and the rotation of the conveying screw is stopped when the sensor detects the support during the backward movement of the support. If the protrusion repeatedly climbs over the peak by continuously rotating the conveying screw after the support reaches the first end, a large moment acts on the fulcrum, and the protrusion member or the like is likely to be damaged. However, when the support reaches the first end, the rotation of the conveying screw is stopped based on the detection result of the sensor, and the conveying screw does not over-rotate.

  During the forward movement of the support, the conveying screw is rotated forward for a predetermined time set in advance. For the predetermined time, for example, when the contact resistance acting on the cleaning member from the electrode is the largest, a time longer than the time required for the cleaning member to move forward from the first end to the second end is set. Even when a large amount of dust adheres to the electrode, the support reliably reaches the second end during the forward movement, and there is no need to provide a sensor for detecting the support at the second end.

  As the electrode, for example, a needle electrode in which a plurality of needles are arranged in one direction is used. In this case, the cleaning member is a rotating body that is held by the support so that the distal ends of the plurality of needles are sequentially buried from the surface to the inside during movement, and then exposed from the inside.

  According to this invention, when the support body reaches either the first end or the second end, the protruding member deforms relatively easily even if the conveying screw over-rotates, and the conveying screw Even if the amount of rotation is not accurately controlled, poor cleaning and damage to the apparatus will not occur. This simplifies the rotation control of the conveying screw and prevents the apparatus from becoming large.

  For example, if the distance between the abutting position and the fulcrum when the support is moved forward is longer than the distance between the abutting position and the fulcrum when the support is moved backward, the conveying screw is formed at the second end. The protrusion member can be deformed relatively easily even if it over-rotates. During the forward movement of the support, cleaning failure and damage to the apparatus do not occur even if the rotation amount of the conveying screw is not accurately controlled.

  Further, when the support body reaches the first end portion, the rotation of the conveying screw is stopped based on the detection result of the sensor, so that the cleaning is poor even after the support body reaches the first end portion when the support body returns. Or damage to the equipment.

  At the time of forward movement of the support, the support screw can be surely reached at the second end during forward movement by rotating the conveying screw forward for a predetermined time set in advance, and for detecting the support There is no need to provide a sensor at the second end.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 to which a charging device according to an embodiment of the present invention is applied. The image forming apparatus 100 has a copier mode, a printer mode, and a FAX mode as image forming modes for forming an image on a sheet (including a recording medium such as OHP). Each mode is selected by a user, and duplex printing is performed. Is possible.

  The image forming apparatus 100 includes a document reading unit 10, a paper feeding unit 20, an image forming unit 30, a paper discharge unit 40, an operation panel unit (not shown), and the like. The document reading unit 10 is disposed on the upper part of the apparatus main body, and includes a platen glass 11, a document placing tray 12, a scanner optical system 13, and the like. The scanner optical system 13 includes a light source 14, reflection mirrors 15 </ b> A to 15 </ b> C, an optical lens 16, and a CCD (Charge Coupled Device) 17. The light source 14 irradiates light on a document placed on the platen glass 11 or a document transported on the document transport path R from the document placing tray 12. The reflection mirrors 15 </ b> A to 15 </ b> C reflect the reflected light from the document and guide it to the optical lens 16. The optical lens 16 focuses the reflected light guided by the reflection mirrors 15 </ b> A to 15 </ b> C on the CCD 17. The CCD 17 outputs an electrical signal corresponding to the reflected light.

  The paper feed unit 20 is disposed at the lower part of the apparatus main body and includes a paper feed tray 21 and a pickup roller 22. The paper feed tray 21 stores paper to be fed to the paper transport path S1 during image formation. The pickup roller 22 rotates and feeds the paper placed on the paper feed tray 21 to the paper transport path S1.

  The image forming unit 30 is disposed below the document reading unit 10 and includes a laser scanning unit (hereinafter referred to as LSU) 37, a photosensitive drum 31, and a fixing device 36. Around the photosensitive drum 31, a charger 1, a developing unit 33, a transfer unit 34, and a cleaner unit 35 are arranged in this order along the direction of the arrow shown in FIG. .

  The paper discharge unit 40 is disposed above the paper feed tray 21 and includes a paper discharge roller 41 and a paper discharge tray 42. The paper discharge roller 41 discharges the paper transported on the paper transport path S <b> 1 to the paper discharge tray 42. The paper discharge roller 41 is capable of reversible rotation. When image formation is performed on both sides of the paper, the paper is discharged in a state where the paper on the front surface that has been transported on the paper transport path S1 is sandwiched. The paper rotates in the direction opposite to the rotation direction discharged to the paper tray 42 and is conveyed to the paper conveyance path S2. As a result, the back surface of the sheet faces the photosensitive drum 31, and the toner image is transferred to the back surface. The paper discharge tray 42 stacks and stores the paper discharged from the paper discharge rollers 41.

  When a start key provided on the operation panel unit is pressed, the image forming apparatus 100 rotates the pickup roller 22 to feed a sheet to the sheet conveyance path S1. The fed paper is conveyed to a registration roller 51 provided on the paper conveyance path S1.

  The registration roller 51 stops rotating when the leading edge of the sheet arrives. The registration roller 51 starts to rotate at a timing when the leading edge of the sheet coincides with the leading edge of the toner image formed on the photosensitive drum 31 between the photosensitive drum 31 and the transfer unit 34.

  The image data read by the document reading unit 10 is subjected to image processing under the conditions input from the operation panel unit, and then transmitted to the LSU 37 as print data. The LSU 37 irradiates the surface of the photosensitive drum 31 charged to a predetermined potential by the charger 1 with a laser beam based on the image data through a polygon mirror and various lenses (not shown) to form an electrostatic latent image. To do. The charger 1 is a charging device of the present invention. Thereafter, the toner adhering to the surface of the magnet roller 33A provided in the developing unit 33 is attracted and adhered to the surface of the photoconductive drum 31 according to the potential gap on the surface of the photoconductive drum 31, and electrostatic The latent image is visualized as a toner image.

  The toner image on the surface of the photosensitive drum 31 is transferred to the surface of the paper by the transfer unit 34. The charging device of the present invention can also be used for the transfer device 34. The toner remaining on the surface of the photosensitive drum 31 after the transfer process is collected by the cleaner unit 35.

  The paper that has completed the transfer process is heated and pressurized by passing through the fixing device 36, and after the toner image is melted and fixed on the paper, it is guided to the paper discharge unit 40.

  2A and 2B are a front sectional view of the charger 1 and a side view of the main part. The charger 1 includes a needle electrode 2, a holder 3, a support 4, a cleaning roller 5, a transport screw 6, and a case 7. The charger 1 is disposed above the photosensitive drum 31.

  The needle electrode 2 is made of a thin strip-shaped metal material, and a plurality of needles 2A extend downward from the lower end portion at regular intervals over the entire length. The plurality of needles 2 </ b> A are arranged along the X axis parallel to the length direction of the needle electrode 2. The charger 1 is arranged with the longitudinal direction of the needle electrode 2 parallel to the axial direction of the photosensitive drum 31. Therefore, the X axis is parallel to the rotation axis of the photosensitive drum 31. The length of the needle electrode 2 is longer than the axial length of the peripheral surface of the photosensitive drum 31.

  The holder 3 is made of an insulating material such as resin, and includes a holding portion 3A and a terminal portion 3B. The holding unit 3 </ b> A holds the needle electrode 2. The length of the holding portion 3 </ b> A is longer than the arrangement range of the plurality of needles 2 </ b> A in the needle electrode 2. 3 A of holding | maintenance parts exhibit a fixed cross-sectional shape shown by hatching in FIG. 2 (A) within the plane orthogonal to the X-axis. The terminal portion 3B houses a terminal (not shown). The terminal connects a high voltage power source (not shown) and the rear end of the needle electrode 2. The rear end portion of the needle electrode 2 corresponds to the second end portion of the present invention.

  The support 4 has an open bottom surface and is attached to the outside of the holding portion 3A from above. Projections 4A and 4B are formed on the inner surface of the support 4. The support 4 sandwiches the holding portion 3A in the vertical direction between the inner upper surface and the protrusions 4A and 4B, and sandwiches the holding portion 3A in the left-right direction on the inner side surface. Therefore, the support 4 is restricted from moving including rotation in a plane orthogonal to the X axis.

  The cleaning roller 5 is a cleaning member of the present invention, and is rotatably supported by the lower end portion of the support 4. As an example, the cleaning roller 5 is an elastic body containing an abrasive. The hardness of the abrasive is set lower than the material of the needle electrode 2 and higher than dust such as toner. From the peripheral surface of the cleaning roller 5, the tip of the needle 2A is buried inside.

  As the elastic body constituting the cleaning roller 5, a suitable material is experimentally selected from known rubber materials and resin materials on the condition that the needle 2A is elastically deformed without being easily cut by the insertion and removal of the needle 2A. Can be selected. The abrasive can be appropriately selected from known materials and used on the condition that toner and dust can be removed from the surface of the needle 2A without damaging the surface of the needle 2A. It can be included.

  The conveying screw 6 is pivotally supported by the bearing portion 3 </ b> C of the holder 3 at the back end 6 </ b> B. The conveying screw 6 passes through the hole 4 </ b> C of the support 4.

  A protruding member 4D extends from the upper surface of the support 4 in the horizontal direction. The protruding member 4D is a plate-like body that can be elastically deformed, such as resin, and includes a protrusion 4E. The protrusion 4 </ b> E is fitted in the trough portion of the male screw of the conveying screw 6 in the radial direction of the conveying screw 6.

  The case 7 is attached to the outside of the support 4 over the entire length of the holder 3. Case 7 shields needle electrode 2.

  When a high-voltage power supply is applied to the needle electrode 2 via the terminal housed in the terminal portion 3B, the applied electric field concentrates at the tip of each of the plurality of needles 2A of the needle electrode 2, and from each of the plurality of needles 2A Electric discharge is generated on the surface of the photosensitive drum 31. By this discharge, the surface of the photosensitive drum 31 is charged to a predetermined potential.

  The holding portion 3A has a constant cross-sectional shape orthogonal to the X axis at least within the arrangement range of the plurality of needles 2A. The support 4 is attached to the outside of the holding portion 3A and is restricted from moving including rotation in a plane perpendicular to the X axis. When the conveying screw 6 rotates, the support 4 is guided by the holding portion 3A and is reciprocally movable along the X axis within at least the arrangement range of the plurality of needles 2A. When the transport screw 6 rotates, the support 4 moves along the X axis by the contact of the protrusion 4E with the threaded portion of the male screw of the transport screw 6.

  In addition, the support body 4 as a moving body, the conveyance screw 6, and the protrusion member 4D constitute the conveyance screw mechanism of the present invention.

  FIG. 3 is a diagram illustrating a cleaning operation of the cleaning roller 5. The tip of the needle 2A is buried in the peripheral surface of the cleaning roller 5 that is rotatably supported by the support 4. When the support body 4 moves along the X axis, the cleaning roller 5 also moves with the support body 4. At this time, each of the plurality of needles 2 </ b> A is sequentially buried in the peripheral surface of the cleaning roller 5. The cleaning roller 5 moves along the X axis while rotating due to the resistance acting on the peripheral surface from the plurality of needles 2A.

  The cleaning roller 5 is disposed between the needle electrode 2 and the peripheral surface of the photosensitive drum 31. The diameter of the cleaning roller 5 is made as large as possible without contacting the peripheral surface of the photosensitive drum 31. When the cleaning roller 5 moves to the X axis, the tip of at least one needle 2 </ b> A is always buried in the peripheral surface of the cleaning roller 5. For this reason, the cleaning roller 2 rotates reliably when moving to the X-axis, and damage to the peripheral surface of the cleaning roller 5 due to the tip of the needle 2A and deformation of the needle 2A due to the peripheral surface of the cleaning roller 5 Minimized.

  The support position of the cleaning roller 5 on the support body 4 is set so that the tip portion having a length of about 0.5 mm from the tip of the needle 2 </ b> A is buried in the peripheral surface of the cleaning roller 5. When the cleaning roller 5 moves along with the support body 4 along the X axis, the tip of the needle 2A gradually immerses from the tip into the cleaning roller 5 and then is gradually pulled out. During this time, the entire surface of the tip of the needle 2A comes into contact with the elastic body constituting the cleaning roller 5, and is polished by the abrasive contained in the elastic body. Since the cleaning roller 5 rotates while the plurality of needles 2 </ b> A are sequentially inserted and removed, at least the adjacent needles 2 </ b> A are embedded at different positions on the circumferential surface of the cleaning roller 5. Thereby, the entire surface of the tip of the needle 2A is reliably cleaned.

  FIG. 4 is a side view of the charger 1. The charger 1 includes a conveying screw 6 on the upper surface side. The conveying screw 6 has a length comparable to the substantially entire length of the holder 3. An end 6 </ b> B on the back side of the conveying screw 6 is fixed to the bearing 3 </ b> C of the holder 3.

  A mounting portion 9 is formed at the front end portion of the needle electrode 2 mounted on the holder 3. The front end portion of the needle electrode 2 corresponds to the first end portion of the present invention. The mounting portion 9 has substantially the same outer shape as the terminal portion 3B. The mounting portion 9 includes a bearing portion 9A, a motor 8, and a sensor 9B. The bearing portion 9 </ b> A is formed on the upper surface of the mounting portion 9, and supports the end portion 6 </ b> A on the front surface side of the conveying screw 6. The motor 8 is held on the upper surface of the mounting portion 9 and supplies rotation in both forward and reverse directions to the conveying screw 6. The sensor 9B is held on the lower surface of the mounting portion 9 and detects the support 4.

  The motor 8 is driven in the forward rotation direction or the reverse rotation direction based on drive data output from the control unit of the image forming apparatus 100 or the control unit provided in the charger 1.

  In a state where the charger 1 is mounted in the image forming apparatus 100, the terminal portion 3 </ b> A and the mounting portion 9 are located in a range outside the image forming region W on the surface of the photosensitive drum 31. In a state where cleaning is not performed, the support 4 is positioned on the front end side of the needle electrode 2 at a standby position set within a range outside the image forming area W on the surface of the photosensitive drum 31. For this reason, the support 4, the end support 3 </ b> A, the bearing body 8, and the mounting portion 9 do not become an obstacle to image formation on the surface of the photosensitive drum 31.

  When cleaning the needle electrode 2, first, the motor 8 rotates the conveying screw 6 forward for a predetermined time. The support 4 moves forward along the X axis from the front end portion of the needle electrode 2 toward the rear end portion. The contact resistance acting on the cleaning member 5 from the needle electrode 2 changes depending on the state of dust adhesion on the needle 2A, and the moving speed of the support 4 changes according to the contact resistance acting on the cleaning member 5 from the needle electrode 2. At a predetermined time, a time longer than the time required for the support 4 to move forward from the front end portion to the rear end portion of the needle electrode 2 when the contact resistance acting on the cleaning member 5 from the needle electrode 2 is the largest is set. Yes. Therefore, the support 4 reliably reaches the rear end portion of the needle electrode 2 regardless of the state of dust adhesion on the needle 2A.

  When a predetermined time has elapsed from the start of forward rotation of the motor 8, the motor 8 reverses the conveying screw 6 until the sensor 9 </ b> B detects the support 4. The support 4 moves forward along the X axis from the front end portion to the rear end portion of the needle electrode 2 and is returned to the standby position.

  The support body 4 is guided by the support portion 3A of the holder 3 and reciprocates along the X axis. The cleaning roller 5 supported by the support body 4 rotates, and the plurality of needles 2A of the needle electrode 2 are sequentially surfaced on the surface. I will be buried in.

  When the tip portions of the plurality of needles 2A of the needle electrode 2 are sequentially inserted into and removed from the cleaning roller 5, the entire surface of the tip portion of each needle 2A comes into contact with the cleaning roller 5, and deformation of the needle 2A and adhesion of fibers The entire surface of the distal end portion of the needle 2A is surely cleaned without causing the.

  The cleaning roller 5 does not necessarily have to be used as the cleaning member, and any rotary body that is rotatably supported by the support body 4 may be used.

  FIG. 5 is a plan view of a main part of the charger 1, and shows a contact state of the protrusion 4 </ b> E with the male thread crest 6 </ b> C of the conveying screw 6. On the protruding member 4 </ b> D extending from the upper surface of the support body 4, a protrusion 4 </ b> E is formed that fits into the valley 6 </ b> D of the male screw of the conveying screw 6 in the radial direction from above. The protrusion 4E has a partial spherical shape, and a backlash is formed between the two ridges 6C sandwiching the valley 6D.

  When the support 4 moves forward in the direction of the arrow X1 due to backlash between the protrusion 4E and the two ridges 6C, the protrusion 4E is formed of the male screw of the conveying screw 6 as shown in FIG. Contact the back of the mountain. When the support body 4 moves backward in the direction of the arrow X2, the protrusion 4E comes into contact with the front surface of the threaded portion of the male screw of the conveying screw 6, as shown in FIG.

  The ridge 6C is inclined with respect to the movement directions X1 and X2 of the support, and the surface with which the protrusion E contacts the ridge 6C changes depending on whether the support 4 moves forward or backward. For this reason, the contact position of the protrusion 4E at the peak portion 6C in the direction along the Y axis perpendicular to the moving direction of the support 4 is different between the forward movement and the backward movement of the support 4.

  If the forward rotation or reverse rotation of the conveying screw 6 is continued after the support body 4 reaches the end in the forward movement direction or the backward movement direction, the protrusion 4E is displaced upward by elastic deformation of the protrusion member 4D, and the peak portion 6C. Is inserted into the adjacent valley 6D. At this time, the elastic deformation of the projecting member 4D occurs from a fulcrum 4F that is a fixed position of the projecting member 4D on the upper surface of the support 4 as a starting point.

  Since the contact position of the protrusion 4E at the peak portion 6C is different between the forward movement and the backward movement of the support body 4, the distance during the forward movement from the fulcrum 4F to the contact position of the protrusion 4E at the peak portion 6C. (This is the first distance of the present invention.) It differs between L1 and the distance during backward movement (also the second distance) L2.

  The distance L1 from the fulcrum 4F when the support 4 moves forward to the contact position of the protrusion 4E at the peak 6C is the contact position of the protrusion 4E at the peak 6C from the support 4F when the support 4 moves backward. Is shorter than the distance L2.

When the rotation of the conveying screw 6 is continued after the support body 4 reaches the end in the forward movement direction and the backward movement direction, the force FA acting on the protrusion 4E from the peak portion 6C of the conveying screw 6 is It is the same for forward movement and backward movement. At this time, a moment obtained by multiplying the component force F1 of the force FA in the axial direction of the conveying screw 6 by the distance L1 and the distance L2 acts on the fulcrum 4F of the protrusion member 4D. Therefore, the moment acting on the fulcrum 4F is larger during the backward movement than during the forward movement. For this reason, the deformation force acting on the projection member 4D is stronger during the backward movement than during the forward movement, and the projection member 4D is more easily damaged during the backward movement than during the forward movement of the support body 4.

  During the forward movement of the support 4, the conveying screw 6 rotates forward over a sufficiently long predetermined time. For this reason, the support body 4 does not move backward without reaching the rear end portion of the needle electrode 2 and does not stop without reaching the front end portion of the needle electrode 2. However, even after the support body 4 reaches the rear end portion of the needle electrode 2, there is a possibility that the conveying screw 6 continues to rotate forward and the protrusion 4E repeatedly gets over the peak portion 6C. However, since the deformation force acting on the projection member 4D is relatively small when the support body 4 moves forward, the projection member 4D, the projection 4E, and the conveying screw 6 are damaged even if the projection 4E repeatedly climbs over the mountain portion 6C. And overload does not act on the motor 8.

  When the support body 4 moves backward, the sensor 9B detects the support body 4 when the support body 4 reaches the front end portion of the needle electrode 2, which is the terminal, and the reverse rotation of the conveying screw 6 is stopped based on this detection signal. The When the conveying screw 6 continues to rotate after the supporting member 4 reaches the end when the supporting member 4 moves backward, a relatively large deformation force acts on the protruding member 4D. However, when the supporting member 4 moves forward, the supporting member 4 After reaching the end, the conveying screw 6 does not continue to rotate. For this reason, the protruding member 4D, the protruding 4E, and the conveying screw 6 are not damaged or an overload is applied to the motor 8 even when the support body 4 is moved backward.

  In this way, considering the magnitude of the deformation force acting on the protruding member 4D when the rotation of the conveying screw 6 is continued after the support body 4 reaches the end, the forward movement and the backward movement of the support body 4 are considered. The surface with which the protrusion 4E of the peak portion 6C contacts is determined. Without detecting that the support 4 has reached the rear end of the needle electrode 2 during the forward movement of the support 4, the support 4 can be securely moved by the control that always rotates the motor 8 forward over a predetermined time. 2 can be moved to the rear end. There is no need to provide a sensor for detecting the support 4 at the rear end portion of the needle electrode 2, the apparatus can be prevented from being enlarged, and the drive control of the motor 8 can be simplified. Thus, even if the amount of dust adhering to the needle electrode 2 changes, the cleaning member 5 can be accurately moved between the both ends of the needle electrode 2 together with the support 4 by simple control without causing poor cleaning or damage to the apparatus. It can be reciprocated.

  Note that when the motor 8 is attached to the image forming apparatus 100 and the charger 1 is attached to the image forming apparatus 100, the back end of the conveying screw 6 is mechanically connected to the rotating shaft of the motor 8. You can also. The motor 8 is driven when the power to the image forming apparatus 100 is turned on, when cleaning is performed when a predetermined number of image forming processes are completed, or when an operation unit is instructed to perform a cleaning operation.

  The charger 1 may include an electrode other than the needle electrode 2, for example, a wire electrode. The cleaning member 5 does not need to be a rotating body, and may be a pad member that sandwiches the electrode.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 to which a charging device according to an embodiment of the present invention is applied. FIG. 2 is a front sectional view of the charger 1 and a side view of the main part. It is a figure which shows the cleaning operation | movement of the cleaning roller. 2 is a side view of the charger 1. FIG. FIG. 3 is a plan view of a main part of the charger 1 and shows a contact state of a protrusion 4E with a male thread crest 6C of the conveying screw 6 when the support body 4 moves forward and backward.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charger 2 Needle electrode 3 Holder 3A Holding part 4 Support body 4D Protrusion member 4E Protrusion 4F A fulcrum 5 Cleaning roller 6 Conveying screw 31 Photosensitive drum 100 Image forming apparatus

Claims (8)

A linear electrode;
A cleaning member in contact with the electrode;
A conveying screw arranged in parallel to the longitudinal direction of the electrode and supported rotatably;
A motor for rotating the conveying screw in both forward and reverse directions;
A support for holding the cleaning member, wherein the support is reciprocally movable and non-rotatable from a first end to a second end of the electrode;
A protrusion member provided with a protrusion that extends from the support and is fitted in a radial direction of the conveying screw into a trough portion of the male screw of the conveying screw;
A distance between a contact position at which the protrusion abuts against a crest of the male screw and a fulcrum of elastic deformation of the protrusion member in a direction in which the protrusion is removed from the trough, and from the first end A first distance during forward movement of the support toward the second end, and a second distance during backward movement of the support from the second end toward the first end. Is set based on the moment acting on the fulcrum during the elastic deformation.   The charging device according to claim 1, wherein the first distance is shorter than the second distance. A sensor for detecting the support at the first end;
The charging device according to claim 2, wherein the rotation of the conveying screw is stopped when the sensor detects the support during the backward movement of the support.   The charging device according to any one of claims 1 to 3, wherein when the support is moved forward, the conveying screw is rotated forward for a predetermined time.   The predetermined time is a time longer than the time required for the cleaning member to move forward from the first end to the second end when the contact resistance acting on the cleaning member from the electrode is the largest. The charging device according to claim 1.   The electrode is a needle electrode in which a plurality of needles are arranged in one direction, and the cleaning member is exposed from the inside after the respective tip portions of the plurality of needles are sequentially buried from the surface to the inside during movement. The charging device according to claim 1, wherein the charging device is a rotating body held on the surface.   An image forming apparatus, comprising: the charging device according to claim 1; and a photoconductor with the electrode facing the surface, and performing an electrophotographic image forming process.   The image forming apparatus according to claim 8, wherein the charging device is accommodated with the first end portion of the electrode facing the front side.

Images