JP2012185299A - Charging device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging device that charges an outer peripheral surface of a cylindrical body to be charged uniformly and rapidly, and cleans a grid electrode plate using a cleaning member having a configuration to cover both ends of the grid electrode plate.SOLUTION: A cam mechanism 108 is provided for, when charging a photoreceptor 62 using a grid electrode plate 104, bringing both ends 104G of the grid electrode plate 104 close to an outer peripheral surface of the photoreceptor 62, and, when cleaning the grid electrode plate 104 using a cleaning member, separating the both ends 104G of the grid electrode plate 104 from the outer peripheral surface of the photoreceptor 62.

Description

  The present invention relates to a charging device and an image forming apparatus.

  Patent Document 1 discloses a scorotron that can separate a cleaning member from a grid electrode without providing a complicated separation mechanism, and can ensure the uniformity of charging by the grid electrode even when used for a longer period of time than before. A charging device is disclosed.

JP 2010-85944 A

  The present invention can charge the outer peripheral surface of a cylindrical object to be charged uniformly and at high speed, and can also clean the grid electrode plate using a cleaning member configured to hold both ends of the grid electrode plate. An object is to provide an apparatus.

  The charging device according to claim 1 of the present invention has a long plate shape, and is disposed outside the cylindrical body to be charged so that the longitudinal direction is parallel to the cylindrical axis direction of the body to be charged. A grid electrode plate for charging the object to be charged is fixed at a fixed relative distance between the center part in the hand direction and the object to be charged, and both end parts along the longitudinal direction of the grid electrode plate are held from both ends. A cleaning member that is movable along the longitudinal direction of the grid electrode plate and that cleans the surface of the grid electrode plate opposite to the surface facing the object to be charged, and the positions of the both end portions, A switching mechanism that switches between a position in which both ends are moved away from the outer peripheral surface of the member to be charged and a position in which both ends are brought close to the outer peripheral surface of the member to be charged. When cleaning with the cleaning member , While switching the position of the both ends to a position away from the outer peripheral surface of the charged body, when charging the charged body by the grid electrode plate, the position of the both ends approaches the outer peripheral surface of the charged body. It is characterized by switching to the position to be made.

  The charging device according to a second aspect of the present invention is the charging device according to the first aspect, wherein the switching mechanism moves the positions of the both end portions away from the outer peripheral surface of the body to be charged when the switching mechanism is not in contact with the both end portions. On the other hand, a cam mechanism is provided that switches the positions of the both end portions to a position to approach the outer peripheral surface of the charged body when contacting the both end portions.

  The charging device according to a third aspect of the present invention is the charging device according to the first aspect, wherein the switching mechanism is separated from the both end portions when energized, and the positions of the both end portions are arranged on the outer peripheral surface of the object to be charged. The electromagnetic solenoid includes an electromagnetic solenoid that contacts the both end portions when not energized and switches the positions of the both end portions closer to the outer peripheral surface of the member to be charged.

  A charging device according to a fourth aspect of the present invention is the charging device according to the second or third aspect, wherein the switching mechanism has rigidity and is attached to the both end portions along the longitudinal direction of the grid electrode plate. The auxiliary member is provided, and the positions of the both end portions are switched to a position to approach the outer peripheral surface of the charged body through the auxiliary member.

  The charging device according to a fifth aspect of the present invention is the charging device according to the first aspect, wherein the switching mechanism is displaceably attached to the cleaning member, and the positions of the both end portions are set when the both end portions are not contacted. A pressing member that switches the position of the both end portions to a position that approaches the outer peripheral surface of the member to be charged when contacting the both end portions while switching to a position away from the outer peripheral surface of the member to be charged, and the cleaning member With the movement of the grid electrode plate in the longitudinal direction, the guide member that guides the displacement of the pressing member relative to the cleaning member, and when the guide member cleans the grid electrode plate by the cleaning member, While the pressing member is displaced in a direction not to contact the both end portions, when the object to be charged is charged by the grid electrode plate, the pressing member is brought into contact with the both end portions. Wherein the displacing in that direction.

  The charging device according to a sixth aspect of the present invention is the charging device according to any one of the first to fifth aspects, wherein the grid electrode plate grips both ends in the longitudinal direction and a central portion in the lateral direction. And being fixed while being pulled in the longitudinal direction.

  A charging device according to a seventh aspect of the present invention is the charging device according to any one of the first to sixth aspects, wherein the grid electrode plate is formed along the longitudinal direction and arranged in the short direction. It is characterized by having a slit.

  The charging device according to an eighth aspect of the present invention is the charging device according to any one of the seventh aspect, wherein the grid electrode plate has a rib formed so as to cross the slit in the lateral direction. It is characterized by that.

  According to a ninth aspect of the present invention, there is provided an image forming apparatus comprising: the charged body charged by the charging apparatus according to any one of the first to eighth aspects; an exposure apparatus that forms an electrostatic latent image on the charged body; And a developing device that develops the electrostatic latent image formed on the body with toner, and a transfer device that transfers the toner image formed on the charged body to a transfer material.

  According to the charging device of the first aspect of the present invention, the outer peripheral surface of the cylindrical body to be charged is compared with the case where the body to be charged is charged in a state where both ends of the grid electrode plate are not brought close to the body to be charged. The grid electrode plate can be cleaned using a cleaning member configured to hold both ends of the grid electrode plate uniformly and at high speed.

  According to the charging device of the second aspect of the present invention, the positions of both ends of the grid electrode plate are switched by a simple mechanism as compared with the separation mechanism that separates the grid electrode plate from the object to be charged as a whole. be able to.

  According to the charging device of the third aspect of the present invention, the positions of both ends of the grid electrode plate are switched by a simple mechanism as compared with the separation mechanism that separates the grid electrode plate from the charged body as a whole. be able to.

  According to the charging device of the fourth aspect of the present invention, it is possible to surely switch the position of both end portions to the position where the auxiliary member is brought closer to the outer peripheral surface of the charged body as compared with the case where the auxiliary member is not provided at both end portions. .

  According to the charging device of the fifth aspect of the present invention, the positions of both ends of the grid electrode plate are switched by a simple mechanism as compared with the separation mechanism that separates the grid electrode plate from the charged body as a whole. be able to.

  According to the charging device of the sixth aspect of the present invention, it is possible to suppress the occurrence of bending in the longitudinal direction of the grid electrode plate and to extend the grid electrode plate along the outer peripheral surface of the member to be charged in the short direction. Can be curved.

  According to the charging device of the seventh aspect of the present invention, compared to the case where the slit along the longitudinal direction is not formed in the grid electrode plate, both ends of the grid electrode plate can be easily approached to the object to be charged. , You can keep away.

  According to the charging device of the present invention, the rigidity of the grid electrode plate can be improved as compared with the case where the grid electrode plate is not provided with a rib that crosses the slit in the short direction.

  According to the image forming apparatus of the ninth aspect of the present invention, it is possible to provide an image forming apparatus having a higher image quality than the image forming apparatus having no charging device according to the first to eighth aspects.

1 is an overall view of an image forming apparatus according to an embodiment of the present invention. It is a block diagram of the image forming unit shown in FIG. FIG. 3 is a configuration diagram of the charging unit shown in FIG. 2 and including a cam mechanism as a switching mechanism. FIG. 4 is a plan view of the grid electrode plate shown in FIG. 3. It is a perspective view which shows the state at the time of cleaning of the cleaning mechanism which concerns on 1st Embodiment. It is sectional drawing of the cleaning mechanism which concerns on 1st Embodiment. It is a perspective view which shows the state at the time of the charging of the cleaning mechanism which concerns on 1st Embodiment (at the time of non-cleaning). It is a block diagram of the same charging unit as FIG. 3 provided with the electromagnetic solenoid as a switching mechanism. It is the same perspective view as FIG. 7 which shows the form which added the metal rod to the cam mechanism as a switching mechanism. It is a perspective view which shows the state at the time of the cleaning of the cleaning mechanism which concerns on 2nd Embodiment. It is a perspective view which shows the state at the time of the charging of the cleaning mechanism which concerns on 2nd Embodiment (at the time of non-cleaning). It is a side view which shows the state at the time of cleaning of the cleaning mechanism which concerns on 2nd Embodiment. It is a side view which shows the state at the time of the charging of the cleaning mechanism which concerns on 2nd Embodiment (at the time of non-cleaning). It is sectional drawing which shows the state at the time of the cleaning of the cleaning mechanism which concerns on 2nd Embodiment. It is sectional drawing which shows the state at the time of the charging of the cleaning mechanism which concerns on 2nd Embodiment (at the time of non-cleaning). It is a top view which shows the structure of the shield member which concerns on the cleaning mechanism which concerns on 2nd Embodiment. It is a block diagram which shows the cleaning member of the structure which does not hold the both ends of a grid electrode plate as a comparative example.

  Embodiments of a charging device and an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

(overall structure)
FIG. 1 shows an image forming apparatus 10 as an example of the embodiment. The image forming apparatus 10 is supplied from the sheet storage unit 12 in which the recording sheet P is stored and the sheet storage unit 12 provided on the sheet storage unit 12 from the lower side to the upper side in the vertical direction (arrow V direction). The image forming unit 14 that forms an image on the recording paper P to be formed, the document reading unit 16 that is provided on the image forming unit 14 to read the read document G, and each unit of the image forming apparatus 10 that is provided in the image forming unit 14 And a control unit 20 that controls the operation of the above. In the following description, the vertical direction of the apparatus main body 10A of the image forming apparatus 10 is referred to as an arrow V direction, the left / right (horizontal) direction as an arrow H direction, and the depth (horizontal) direction as an arrow D direction. The surface and side of the image forming apparatus 10 in the direction of the arrow D may be referred to as “front”, “back”, “front side”, and “back side”.

  The paper storage unit 12 is provided with a first storage unit 22, a second storage unit 24, and a third storage unit 26 that store recording paper P having different sizes as an example of a recording medium. The first storage unit 22, the second storage unit 24, and the third storage unit 26 are provided with a delivery roll 32 that sends the stored recording paper P to a conveyance path 28 provided in the image forming apparatus 10. A pair of transport rolls 34 and transport rolls 36 that transport the recording paper P one by one are provided on the transport path 28 downstream of the feed roll 32. An alignment roll 38 that stops the recording paper P at one end and feeds it to a secondary transfer position (described later) at a predetermined timing downstream of the conveyance roll 36 in the conveyance direction of the recording paper P in the conveyance path 28. Is provided.

  The upstream portion of the conveyance path 28 is provided in a straight line from the left side of the sheet storage unit 12 to the lower left side of the image forming unit 14 in the arrow V direction when the image forming apparatus 10 is viewed from the front. The downstream portion of the conveyance path 28 is provided from the lower left portion of the image forming portion 14 to the paper discharge portion 15 provided on the right side surface of the image forming portion 14. Further, a double-sided conveyance path 29 through which the recording paper P is conveyed and reversed in order to form an image on both sides of the recording paper P is connected to the conveyance path 28.

  The double-sided conveyance path 29 includes a first switching member 31 that switches between the conveyance path 28 and the double-sided conveyance path 29 from the lower right side of the image forming unit 14 to the right side of the sheet storage unit 12 in a front view of the image forming apparatus 10. A reversing unit 33 linearly provided in the arrow -V direction (downward direction in the figure) and the rear end of the recording paper P conveyed to the reversing unit 33 enter and are conveyed in the arrow H direction (left direction in the figure). And a second switching member 35 that performs switching between the reversing unit 33 and the conveying unit 37. The reversing unit 33 is provided with a pair of conveying rolls 42 at intervals, and the conveying unit 37 is provided with a pair of conveying rolls 44 at intervals.

  The first switching member 31 is a triangular prism-shaped member, and the leading end portion is moved to either the transport path 28 or the double-side transport path 29 by a driving unit (not shown) so as to switch the transport direction of the recording paper P. It has become. Similarly, the second switching member 35 is a triangular prism-shaped member when viewed from the front, and the leading end is moved to either the reversing unit 33 or the conveyance unit 37 by a driving unit (not shown), so that the recording paper P is conveyed. The direction is changed. The downstream end of the transport unit 37 is connected to the front side of the transport roll 36 in the upstream portion of the transport path 28 by a guide member (not shown). Further, a foldable manual sheet feeding unit 46 is provided on the left side surface of the image forming unit 14 and is connected from the manual sheet feeding unit 46 to a position in front of the alignment roll 38 in the conveyance path 28. .

  The document reading unit 16 includes a document transport device 52 that automatically transports the read document G one by one, a platen glass 54 that is disposed below the document transport device 52 and on which one read document G is placed, and a document transport device. An original reading device 56 that reads the read original G conveyed by 52 or the read original G placed on the platen glass 54 is provided.

  The document conveying device 52 has an automatic conveyance path 55 in which a plurality of pairs of conveyance rolls 53 are arranged. A part of the automatic conveyance path 55 is arranged so that the read original G passes over the platen glass 54. Yes. The original reading device 56 reads the read original G conveyed by the original conveying device 52 while being stationary at the left end of the platen glass 54, or is read on the platen glass 54 while moving in the arrow H direction. G is read.

  On the other hand, the image forming unit 14 is provided with a photosensitive body 62 as an example of a cylindrical body to be charged in the center of the apparatus main body 10A. The photoconductor 62 is rotated in the direction of the arrow + R (clockwise direction in the drawing) by a driving unit (not shown) and holds an electrostatic latent image formed by light irradiation. A charging unit 100 as an example of a scorotron charging device that charges the surface of the photoconductor 62 is provided above the photoconductor 62 and at a position facing the outer peripheral surface of the photoconductor 62. Details of the charging unit 100 will be described later.

  As shown in FIG. 2, an exposure device 66 is provided at a position downstream of the charging unit 100 in the rotation direction of the photoconductor 62 and facing the outer peripheral surface of the photoconductor 62. The exposure device 66 is configured by an LED (Light Emitting Diode), and irradiates (exposes) light to the outer peripheral surface of the photosensitive member 62 charged by the charging unit 100 based on an image signal corresponding to each toner color. An electrostatic latent image is formed. The exposure device 66 is not limited to the LED system, and may be one that scans laser light with a polygon mirror, for example.

  The electrostatic latent image formed on the outer peripheral surface of the photoconductor 62 is developed with toner of a predetermined color on the downstream side of the portion irradiated with the exposure light of the exposure device 66 in the rotation direction of the photoconductor 62. A rotation switching type developing device 70 is provided for visualization.

  An intermediate transfer belt 68 to which a toner image formed on the outer peripheral surface of the photoconductor 62 is transferred is provided downstream of the developing device 70 in the rotation direction of the photoconductor 62 and below the photoconductor 62. Yes. The intermediate transfer belt 68 is endless, and is driven by being in contact with a drive roll 61 that is rotationally driven by the control unit 20, a tension applying roll 63 for applying tension to the intermediate transfer belt 68, and the back surface of the intermediate transfer belt 68. It is wound around a plurality of rotating transport rolls 65 and an auxiliary roll 69 that rotates in contact with the back surface of the intermediate transfer belt 68 at a secondary transfer position described later. The intermediate transfer belt 68 rotates in the direction of the arrow -R (the counterclockwise direction in the drawing) as the driving roll 61 rotates.

  A primary transfer roll 67 as an example of a transfer device that primarily transfers the toner image formed on the outer peripheral surface of the photoconductor 62 to the intermediate transfer belt 68 on the opposite side of the photoconductor 62 with the intermediate transfer belt 68 interposed therebetween. Is provided. The primary transfer roll 67 is in contact with the back surface of the intermediate transfer belt 68 at a position away from the position where the photoconductor 62 and the intermediate transfer belt 68 are in contact with the downstream side in the moving direction of the intermediate transfer belt 68. The primary transfer roll 67 is primarily energized from a power source (not shown) to primarily transfer the toner image on the photoreceptor 62 to the intermediate transfer belt 68 by a potential difference from the grounded photoreceptor 62.

  Further, on the opposite side of the auxiliary roll 69 across the intermediate transfer belt 68, a secondary transfer roll 71 for secondary transfer of the toner image primarily transferred onto the intermediate transfer belt 68 onto the recording paper P is provided. Between the secondary transfer roll 71 and the auxiliary roll 69 is a secondary transfer position (position Q in FIG. 2) for transferring the toner image onto the recording paper P. The secondary transfer roll 71 is in contact with the surface of the intermediate transfer belt 68. When the secondary transfer roll 71 is energized from a power source (not shown), the toner image on the intermediate transfer belt 68 is secondarily transferred onto the recording paper P by a potential difference from the auxiliary roll 69 that is grounded. Yes.

  A cleaning device 85 that collects residual toner after the secondary transfer of the intermediate transfer belt 68 is provided on the opposite side of the drive roll 61 with the intermediate transfer belt 68 interposed therebetween. Further, a predetermined reference on the intermediate transfer belt 68 is detected by detecting a mark (not shown) on the surface of the intermediate transfer belt 68 at a position facing the tension applying roll 63 around the intermediate transfer belt 68. A position detection sensor 83 is provided for detecting a position and outputting a position detection signal that serves as a reference for the start timing of the image forming process.

  A cleaning device 73 is provided on the downstream side of the primary transfer roller 67 in the rotation direction of the photoconductor 62 to clean residual toner or the like remaining on the surface of the photoconductor 62 without being primarily transferred to the intermediate transfer belt 68. . The cleaning device 73 is configured to collect residual toner and the like with a cleaning blade 87 and a brush roll 89 (see FIG. 2) that are in contact with the surface of the photoreceptor 62.

  Further, on the upstream side of the cleaning device 73 in the rotation direction of the photosensitive member 62 (downstream side of the primary transfer roll 67), a static eliminator 86 that performs static elimination by irradiating the outer peripheral surface of the photosensitive member 62 with light (see FIG. 2). ) Is provided. The neutralization device 86 reduces the adhesive force due to static electricity by irradiating the outer peripheral surface of the photoconductor 62 with light before collecting the residual toner by the cleaning device 73, thereby increasing the recovery rate of the residual toner. Is. Further, on the downstream side of the cleaning device 73 and the upstream side of the charging unit 100, a static elimination lamp 75, which is a static elimination means after collecting residual toner or the like, is provided.

  The secondary transfer position of the toner image by the secondary transfer roll 71 is set in the middle of the transport path 28 described above, and the secondary transfer roll 71 in the transport direction of the recording paper P in the transport path 28 (shown by the arrow A). On the further downstream side, a fixing device 80 for fixing the toner image on the recording paper P on which the toner image is transferred by the secondary transfer roll 71 is provided.

  The fixing device 80 is disposed on the toner image surface side (upper side) of the recording paper P, and has a heating roll 82 having a heat source that generates heat when energized, and the recording paper P disposed on the lower side of the heating roll 82 and the outer periphery of the heating roll 82. And a pressure roll 84 that pressurizes the surface. A transport roll 39 that transports the recording paper P toward the paper discharge unit 15 or the reversing unit 33 is provided downstream of the fixing device 80 in the transport direction of the recording paper P in the transport path 28.

  On the other hand, below the document reading device 56 and above the developing device 70, yellow (Y), magenta (M), cyan (C), black (K), first special color (E), and second special color. Toner cartridges 78 </ b> Y, 78 </ b> M, 78 </ b> C, 78 </ b> K, 78 </ b> E, and 78 </ b> F that store the respective color (F) toners are provided so as to be replaceable along the arrow H direction. The first special color E and the second special color F are selected from special colors (including transparent) other than yellow, magenta, cyan, and black, or are not selected.

  In the developing device 70, when the first special color E and the second special color F are selected, image formation is performed in six colors Y, M, C, K, E, and F, and the first special color E and When the second special color F is not selected, image formation with four colors Y, M, C, and K is performed. In this embodiment, as an example, a case where image formation is performed with four colors Y, M, C, and K and the first special color E and the second special color F are unused will be described. As an example, image formation may be performed with five colors using four colors Y, M, C, and K and the first special color E or the second special color F.

  As shown in FIG. 2, the developing device 70 includes yellow (Y), magenta (M), cyan (C), black (K), first special color (E), and second special color (F) toners. Developing units 72Y, 72M, 72C, 72K, 72E, and 72F corresponding to the colors are arranged side by side in the circumferential direction (counterclockwise in this order) and are rotated by a motor (not shown) that is a rotating means. By rotating the central angle by 60 °, the developing devices 72Y, 72M, 72C, 72K, 72E, and 72F for performing the development processing are switched so as to face the outer peripheral surface of the photoconductor 62. Since the developing units 72Y, 72M, 72C, 72K, 72E, and 72F have the same configuration, the developing unit 72Y will be described here, and the other developing units 72M, 72C, 72K, 72E, and 72F will be described. Is omitted.

  The developing device 72Y includes a case member 76 serving as a main body, and includes toner and a carrier that are supplied into the case member 76 from a toner cartridge 78Y (see FIG. 1) via a toner supply path (not shown). A developer (not shown) is filled. The case member 76 is formed with a rectangular opening 76 </ b> A facing the outer peripheral surface of the photoconductor 62, and the developing roll whose outer peripheral surface faces the outer peripheral surface of the photoconductor 62 is formed in the opening 76 </ b> A. 74 is provided. Further, a plate-like regulating member 79 for regulating the layer thickness of the developer is provided along the longitudinal direction of the opening 76A at a portion near the opening 76A in the case member 76.

  The developing roller 74 includes a cylindrical developing sleeve 74A that is rotatably provided, and a magnetic member 74B that includes a plurality of magnetic poles fixed inside the developing sleeve 74A. The developing sleeve 74A rotates. Thus, the developer (carrier) magnetic brush is formed, and the layer thickness is regulated by the regulating member 79, whereby the developer layer is formed on the outer peripheral surface of the developing sleeve 74A. The developer layer on the outer peripheral surface of the developing sleeve 74A is conveyed to a position facing the photoconductor 62, and a toner corresponding to a latent image (electrostatic latent image) formed on the outer peripheral surface of the photoconductor 62 is attached. To develop.

  In addition, in the case member 76, two conveyance rollers 77 formed in a spiral shape are arranged in parallel so as to be rotatable, and the case member 76 is filled by rotating the two conveyance rollers 77. The developer is circulated and conveyed in the axial direction of the developing roll 74 (longitudinal direction of the developing device 72Y). The six developing rolls 74 provided in each of the developing units 72Y, 72M, 72C, 72K, 72E, and 72F are arranged in the circumferential direction so that the distance from the adjacent developing roll 74 is a central angle of 60 °. Then, by switching the developing device 72, the next developing roll 74 is opposed to the outer peripheral surface of the photosensitive member 62.

  Next, an image forming process in the image forming apparatus 10 will be described.

  As shown in FIG. 1, when the image forming apparatus 10 is operated, yellow (Y), magenta (M), cyan (C), black (K), the first special color is supplied from an image processing apparatus (not shown) or from the outside. (E) The image data of each color of the second special color (F) is sequentially output to the exposure device 66. At this time, as an example, the developing device 70 is rotated and held so that the developing device 72 </ b> Y (see FIG. 2) faces the outer peripheral surface of the photoreceptor 62.

  Subsequently, in the charging unit 100, a potential difference is generated between the charging unit 100 and the grounded photosensitive member 62, whereby corona discharge is performed, and the photosensitive member 62 is charged.

  Subsequently, the light emitted from the exposure device 66 according to the image data exposes the outer peripheral surface (surface) of the photosensitive member 62 charged by the charging unit 100, and the surface of the photosensitive member 62 is converted into yellow image data. A corresponding electrostatic latent image is formed. Further, the electrostatic latent image formed on the surface of the photoreceptor 62 is developed as a yellow toner image by the developing device 72Y. Then, the yellow toner image on the surface of the photoconductor 62 is transferred to the intermediate transfer belt 68 by the primary transfer roll 67.

  Subsequently, as shown in FIG. 2, the developing device 70 is rotated 60 ° in the direction of the arrow + R, and the developing device 72 </ b> M faces the surface of the photoconductor 62. Then, charging, exposure, and development processes are performed, and the magenta toner image on the surface of the photoreceptor 62 is transferred onto the yellow toner image on the intermediate transfer belt 68 by the primary transfer roll 67. Similarly, toner images of cyan (C), black (K), and the first special color (E) and the second special color (F) are sequentially transferred onto the intermediate transfer belt 68 in accordance with the color setting. The

  On the other hand, as shown in FIG. 1, the recording paper P sent out from the paper storage unit 12 and conveyed through the conveyance path 28 is subjected to multiple transfer and timing of each toner image onto the intermediate transfer belt 68 by the alignment roll 38. Are transferred to the secondary transfer position (position Q in FIG. 2). The toner image that has been multiplex-transferred onto the intermediate transfer belt 68 is secondarily transferred by the secondary transfer roll 71 onto the recording paper P that has been transported to the secondary transfer position.

  Subsequently, the recording paper P to which the toner image has been transferred is conveyed toward the fixing device 80 in the direction of arrow A (right direction in the drawing). In the fixing device 80, the toner image is fixed on the recording paper P by being heated and pressed by the heating roll 82 and the pressure roll 84. Furthermore, the recording paper P on which the toner image is fixed is discharged to the paper discharge unit 15 as an example.

  When images are formed on both sides of the recording paper P, the image is fixed on the surface by the fixing device 80, and then the recording paper P is fed along the arrow -V direction to the reversing unit 33 and along the arrow + V direction. The leading edge and the trailing edge of the recording paper P are switched. Then, the recording paper P is conveyed in the direction of arrow B (left direction in the drawing) by the double-sided conveyance path 29 and further fed into the conveyance path 28 to perform image formation and fixing on the back surface of the recording paper P.

(Charging unit configuration)
Next, the charging unit 100 will be described.

  As shown in FIG. 3, the charging unit 100 includes a shield member 105 having a U-shaped HV surface (cross section). The shield member 105 has an upper wall 105U and a side wall 105S connected to the upper wall 105U and extending downward. The inside of the shield member 105 is partitioned into a small chamber 106A and a small chamber 106B by a partition plate 103 that is arranged upright with the arrow + D direction as the longitudinal direction. In the arrow + R direction, the small chamber 106A is disposed on the upstream side, and the small chamber 106B is disposed on the downstream side. Further, the opening 105 </ b> A of the shield member 105 is disposed to face the outer peripheral surface of the photoconductor 62.

  A charge wire 102A is erected in the small chamber 106A with the arrow + D direction as the major axis direction, and similarly, a charge wire 102B is erected in the small chamber 106B with the arrow + D direction as the major axis direction. A grid electrode plate 104 having an area corresponding to the opening 105 </ b> A is provided below the shield member 105.

  In the charging unit 100, the charge wires 102 </ b> A and 102 </ b> B are energized to generate a corona discharge by applying a potential difference between the grounded photoconductor 62 and the charge wires 102 </ b> A and 102 </ b> B and the outer peripheral surface of the photoconductor 62. By applying a voltage to the grid electrode plate 104 disposed therebetween, the photoconductor 62 is uniformly charged at a constant potential by the grid electrode plate 104.

  The grid electrode plate 104 is made of a metal material and has a long plate shape that is long in the direction of arrow D as shown in FIG. The end region 104A on both sides in the longitudinal direction of the grid electrode plate 104 is formed narrower than the central region 104B. The grid electrode plate 104 is fixed to a case member (not shown) of the charging unit 100 so as to be gripped at both ends in the longitudinal direction and the central portion 104C in the lateral direction and pulled in the longitudinal direction. By fixing the grid electrode plate 104 while pulling in the longitudinal direction, the grid electrode plate 104 is prevented from bending in the longitudinal direction.

  In the central region 104B of the grid electrode plate 104, a plurality of slits 104D (seven in FIG. 4) formed along the longitudinal direction are arranged in the short direction (arrow H direction), and adjacent slits 104D are arranged. A long rib 104E is formed between them. Further, short ribs 104F that connect adjacent long ribs 104E so as to cross the slit 104D are formed. In this way, the central region 104B of the grid electrode plate 104 has an amid-like rib structure, so that the uniform chargeability of the photoconductor 62 is improved as compared with, for example, a turtle shell-like rib structure. As described above, when both end portions 104G along the longitudinal direction of the grid electrode plate 104 are pressed, the grid electrode plate 104 is easily bent in the short direction. On the other hand, since the short rib 104F is formed, the grid electrode plate 104 is secured with rigidity enough to return from the curved state to the flat state when the pressure on both end portions 104G is released. Yes. Further, the grid electrode plate 104 is curved along the outer peripheral surface of the photoreceptor 62 in the short direction by pressing the both end portions 104G after fixing the center portion 104C of the grid electrode plate 104 so as to be pulled in the longitudinal direction. It has come to be.

  As shown in FIG. 3, the grid electrode plate 104 is disposed so that the longitudinal direction thereof is parallel to the cylindrical axis direction of the photoconductor 62. Further, the relative distance between the center portion 104C and the photosensitive member 62 in the short direction of the grid electrode plate 104 is always fixed. That is, the charging unit 100 does not have a retract mechanism for separating the grid electrode plate 104 from the photosensitive member 62 as a whole.

  Instead, a plurality of cam mechanisms 108 (two shown in FIG. 3) are provided between the shield member 105 and the grid electrode plate 104 as an example of a switching mechanism. When the cam 108A of the cam mechanism 108 is rotated to a position where it comes into contact with both end portions 104G of the grid electrode plate 104, the both end portions 104G are pressed to a position approaching the surface of the photoconductor 62, and the grid electrode plate 104 is pressed. It is set as the curve state which follows the outer peripheral surface of this. On the other hand, when the cam 108A of the cam mechanism 108 is rotated to a position where it does not contact the both end portions 104G of the grid electrode plate 104, the grid electrode plate 104 returns to a flat state due to rigidity.

  By switching the grid electrode plate 104 from the flat state to the curved state by the cam mechanism 108, the surface of the photoconductor 62 is made faster and more uniform than when the photoconductor 62 is charged with the grid electrode plate 104 in the flat state. To be charged.

  On the other hand, it is necessary to clean the grid electrode plate 104 in order to prevent the charging performance from being deteriorated due to adhesion of dust such as discharge products to the grid electrode plate 104. In order to ensure the cleaning performance, a cleaning member 112 (see FIGS. 5 and 6) configured to hold both ends 104G of the grid electrode plate 104 from both ends is used. In order to clean the grid electrode plate 104 with the cleaning member 112 configured to hold the grid electrode plate 104, a space for the cleaning member 112 to hold both ends of the grid electrode plate 104 is defined as the outer peripheral surface of the photoreceptor 62 and the grid electrode plate 104. Therefore, it is necessary to make the grid electrode plate 104 flat by the cam mechanism 108, that is, to place both end portions 104 </ b> G of the grid electrode plate 104 away from the photoconductor 62.

  Therefore, in the charging unit 100 including the cleaning mechanism according to the first embodiment described below, a cam mechanism 108 is provided as a switching mechanism for switching the grid electrode plate 104 between a curved state and a flat state.

(Configuration of the cleaning mechanism according to the first embodiment)
A cleaning mechanism 110 according to the first embodiment having a cleaning member 112 configured to hold both end portions 104G of the grid electrode plate 104 from both end sides will be described.

  As shown in FIGS. 5 and 6, the cleaning mechanism 110 has both ends along the longitudinal direction of the grid electrode plate 104 in the grid electrode plate 104 in which the cam 108 </ b> A is rotated to a position away from the grid electrode plate 104 to be in a flat state. A cleaning member 112 configured to hold the portion 104G from both ends, a ball screw 114 disposed along the arrow D direction above the grid electrode plate 104, and a connection member 116 connecting the ball screw 114 and the cleaning member 112. have.

  The cleaning member 112 is attached to the upper wall 112U, the side wall 112S extending downward at both ends of the upper wall 112U, the lower wall 112L connected to the lower end of the side wall 112S and folded back inside, and the inner surface of the upper wall 112U. And a brush member 112A. In the cleaning member 112, the grid electrode plate 104 is sandwiched between the upper surface of the lower wall 112L and the lower surface of the brush member 112A.

  An insertion hole 120 for inserting the ball screw 114 is provided in the upper part of the connection member 116, and the connection member 116 rotates the cleaning member 112 of the grid electrode plate 104 by rotating the ball screw 114 by a driving device (not shown). Move along the longitudinal direction (arrow D direction). That is, the cleaning member 112 is reciprocated by forward and reverse rotation of the ball screw 114. Thereby, the upper surface of the grid electrode plate 104 (the surface opposite to the lower surface facing the photoconductor) is cleaned by the brush member 112A of the cleaning member 112. An opening 122 is formed in the central portion of the connection member 116 to allow the above-described charge wires 102A and 102B and the partition plate 103 to pass therethrough (in FIG. 5, for convenience of explanation, the charge wires 102A and 102B and the partition plate 103 are formed. And are omitted).

  As shown in FIG. 7, when the grid electrode plate 104 is curved by the cam mechanism 108 (when the photosensitive member 62 is charged), the cleaning member 112 is retracted to the end region 104A of the grid electrode plate 104. The cleaning member 112 does not sandwich the both end portions 104G of the grid electrode plate 104. In FIG. 7, the cleaning member 112 is retracted to the end region 104A on the upper side of the grid electrode plate 104, but may be retracted to the end region 104A on the lower side of the paper.

  Thus, the grid electrode plate 104 is curved along the outer peripheral surface of the photoconductor 62 in order to charge the surface of the photoconductor 62 at high speed and uniformly when the photoconductor 62 is charged. When cleaning the grid electrode plate 104, the cleaning member 112 is brought into a flat state so that both end portions 104G of the grid electrode plate 104 are held. As shown in FIG. 6, the cam 108 </ b> A is rotated to a position where it can pass through the cleaning member 112 when the grid electrode plate 104 is not pressed.

  As shown in FIG. 8, an electromagnetic solenoid 109 may be used in place of the cam mechanism 108 as a switching mechanism for switching the grid electrode plate 104 between a curved state and a flat state. Specifically, an electromagnetic solenoid 109 having a movable rod 109C that is extended by a compression spring 109B inside the case 109A when no power is supplied, and the extended movable rod 109C is brought into contact with both end portions 104G of the grid electrode plate 104. Thus, both end portions 104G of the grid electrode plate 104 are brought close to the outer peripheral surface of the photoconductor 62, and the grid electrode plate 104 is brought into a curved state. When energized, the movable rod 109C is retracted inside the case 109A against the compression spring 109B, and the movable rod 109C and the both end portions 104G of the grid electrode plate 104 are not brought into contact with each other. Return to the flat state. The movable rod 109C is retracted to a position where it can pass through the cleaning member 112 when the grid electrode plate 104 is not pressed.

  Further, as shown in FIG. 9, after attaching a metal rod 124 as an example of an auxiliary member made of, for example, a metal material having rigidity to both ends 104G of the grid electrode plate 104, the cam mechanism 108 (or alternatively, through the metal rod 124). The both ends 104G of the grid electrode plate 104 may be pressed by the electromagnetic solenoid 109). By pressing the both end portions 104G of the grid electrode plate 104 via the rigid metal rod 124, the entire both end portions 104G of the grid electrode plate 104 can be reliably brought closer to the outer peripheral surface of the photoreceptor 62. .

(Configuration of the cleaning mechanism according to the second embodiment)
FIGS. 10-15 is a figure explaining the cleaning mechanism 210 about 2nd Embodiment of the charging device which concerns on this invention.

  The cleaning mechanism 210 is of a type that is manually operated by an operator. The cleaning mechanism 210 includes a cleaning member 212 configured to hold both end portions 104G of the grid electrode plate 104 in a flat state, a first pressing block 214 as an example of a pressing member connected to the cleaning member 212, and one end side It has a long operating rod 216 to which the first pressing block 214 is attached, and a second pressing block 218 as an example of a pressing member attached to the other end side of the operating rod 216.

  As with the cleaning member 112 shown in the first embodiment, the cleaning member 212 is connected to the upper wall 212U, the side wall 212S extending downward at both ends of the upper wall 212U, and the lower end of the side wall 212S and folded back inward. It has a lower wall 212L and a brush member 212A attached to the inner surface of the upper wall 212U. In the cleaning member 212, the grid electrode plate 104 is sandwiched between the upper surface of the lower wall 212L and the lower surface of the brush member 212A.

  Two protrusions 220 protruding upward are formed on the outer surface of the upper wall 212U of the cleaning member 212, and the two protrusions 220 are two engagement holes 222 provided in the first pressing block 214. By being engaged (see FIG. 12), the cleaning member 212 and the first pressing block 214 are connected to be displaceable in the vertical direction (arrow V direction). Guide protrusions 224 that protrude outward are formed on the outer surfaces of both side walls 212 </ b> S of the cleaning member 212.

  The first pressing block 214 has an L shape when viewed from the direction of the arrow H, and one end of the operation rod 216 is connected and fixed to the upper surface 214U. Engagement holes 222 corresponding to the two protrusions 220 of the cleaning member 212 described above are provided on the lower surface 214L1 of the first pressing block 214 facing the cleaning member 212.

  As shown in FIGS. 14 and 15, the lower surface 214 </ b> L <b> 2 at the position facing the grid electrode plate 104 of the first pressing block 214 is a curved surface that curves upwardly when viewed from the direction of arrow D. Yes. Guide protrusions 226 that protrude outward are formed on both side surfaces of the first pressing block 214. Two positioning protrusions 228 projecting outward are formed on the back surface of the first pressing block 214. An opening 230 is formed in the central portion of the first pressing block 214 for passing the charge wires 102A and 102B and the partition plate 103 (for convenience of explanation, the charge wires 102A and 102A in FIGS. 10 to 13). 102B and the partition plate 103 are omitted).

  The second pressing block 218 provided on the other end side of the operation rod 216 has a rectangular parallelepiped shape, and is connected and fixed to the operation rod 216 at the upper surface 218U. Similarly to the lower surface 214L2 of the first pressing block 214, the lower surface 218L of the second pressing block 218 is also a curved surface that curves in a convex shape when viewed from the arrow D direction. Guide protrusions 232 that protrude outward are formed on both side surfaces of the second pressing block 218. Two positioning protrusions 234 projecting outward are formed on the back surface of the second pressing block 218. In addition, an opening 236 for allowing the charge wires 102 </ b> A and 102 </ b> B and the partition plate 103 to pass through is formed at the center of the second pressing block 218.

  A first positioning block 238 is provided behind the first pressing block 214. The first positioning block 238 has a rectangular parallelepiped shape, and is connected and fixed to the inner wall surface of the shield member 105, for example. Two positioning holes 240 corresponding to the two positioning protrusions 228 of the first pressing block 214 are formed on the surface of the first positioning block 238 facing the first pressing block 214.

  A second positioning block 242 is provided behind the second pressing block 218. The second positioning block 242 has a rectangular parallelepiped shape, and is connected and fixed to the inner wall surface of the shield member 105, for example. Two positioning holes 244 corresponding to the two positioning protrusions 234 of the second pressing block 218 are formed on the surface of the second positioning block 242 facing the second pressing block 218.

  As shown in FIG. 16, the cleaning member guide groove 246 for guiding the movement of the cleaning member 212 by inserting the guide protrusion 224 of the cleaning member 212 and the first pressing block, respectively, on both side walls 105 </ b> S of the shield member 105. The first pressing block guide groove 248 as an example of a guide member that guides the movement of the first pressing block 214 by inserting the guiding protrusion 226 of 214 and the guiding protrusion 232 of the second pressing block 218 are inserted and inserted. A second pressing block guide groove 250 as an example of a guide member that guides the movement of the two pressing blocks 218 is formed.

  The cleaning member guide groove 246 is formed linearly along the arrow D direction. The cleaning member 212 is guided by the cleaning member guide groove 246 and is linearly moved along the arrow D direction.

  Most of the first pressing block guide grooves 248 extend along the direction of the arrow D, but the back is once bent downward and then bent along the direction of the arrow D to end. The first pressing block 214 is guided by the first pressing block guide groove 248 and moved in the direction of the arrow D, and is displaced downward in the back.

  The second pressing block guide groove 250 extends along the direction of arrow D, but the back side is once bent downward and then bent along the direction of arrow D to finish. The front side extends to the edge of the shield member 105 and opens. The second pressing block 218 is guided by the second pressing block guide groove 250 and is moved along the direction of the arrow D, and is displaced downward in the back.

  As shown in FIGS. 10, 12, and 14, when the operator operates the operation rod 216 in the direction of arrow D with the grip 252 provided on the operation rod 216, the first pressing block 214 and the second pressing block The blocks 218 are guided by the first pressing block guide groove 248 and the second pressing block guide groove 250, respectively, and move along the arrow D direction. Since the cleaning member 212 is also connected to the first pressing block 214 by the two protrusions 220, the cleaning member 212 moves along the direction of arrow D as the operation rod 216 is operated. At this time, the cleaning member 212 holds both end portions 104G of the grid electrode plate 104, and the upper surface of the grid electrode plate 104 is cleaned by the brush member 212A of the cleaning member 212.

  As shown in FIGS. 11, 13, and 15, when the operation rod 216 is operated to be moved to a position where the cleaning member 212 is retracted to the end region 104 </ b> A on the back side of the grid electrode plate 104, The cleaning member 212 is in a state where the both end portions 104G of the grid electrode plate 104 are not sandwiched, and the first pressing block 214 is a position where the both end portions 104G of the grid electrode plate 104 are pressed by the guide of the first pressing block guide groove 248. Is moved down. Then, the positioning protrusion 228 of the first pressing block 214 is inserted into the positioning hole 240 of the first positioning block 238, and the positioning of the first pressing block 214 with respect to the grid electrode plate 104 is performed. Similarly to the first pressing block 214, the second pressing block 218 is also moved downward to a position where the both end portions 104G of the grid electrode plate 104 are pressed by the guidance of the second pressing block guide groove 250. Then, the positioning protrusion 234 of the second pressing block 218 is inserted into the positioning hole 244 of the second positioning block 242 so that the second pressing block 218 is positioned with respect to the grid electrode plate 104.

  That is, when the operating rod 216 is operated so as to be inserted inward by the operator, both end portions 104G of the grid electrode plate 104 are pressed by the lower surfaces 214L2 and 218L having the curved shapes of the first pressing block 214 and the second pressing block 218. Then, the grid electrode plate 104 is switched from the flat state to the curved state. On the contrary, when the operation rod 216 is operated in the pulling direction by the operator, the grid electrode plate 104 is released from being pressed by the first pressing block 214 and the second pressing block 218 and switched from the curved state to the flat state.

  As described above, the cleaning mechanism 210 cleans the grid electrode plate 104 while cleaning the grid electrode plate 104 by the cleaning member 212 while holding the both end portions 104G of the grid electrode plate 104 after making the grid electrode plate 104 flat. When not, the cleaning member 212 is retracted to the end region 104A of the grid electrode plate 104, and the grid electrode plate 104 is curved in order to improve the charging performance of the photoconductor 62. In the cleaning mechanism 210 according to the second embodiment, the first pressing block 214, the second pressing block 218, the first pressing block guide groove 248, and the second pressing block guide groove 250 make the grid electrode plate 104 flat and curved. A switching mechanism for switching to a state is configured.

(Evaluation of charging performance)
When the grid electrode plate 104 is cleaned with the cleaning members 112 and 212 configured to hold both ends 104G of the grid electrode plate 104 and the cleaning member 300 configured to not hold both ends of the grid electrode plate illustrated in FIG. 17 as a comparative example The charging performance of the photosensitive member 62 by the charging unit 100 will be described.

  As charging performance, 30% half-tone images are printed (temperature 28 degrees, humidity 85%, 100 prints per print job, grid electrode plate 104 is cleaned every 2000 prints) Evaluation was performed depending on whether or not the above occurred.

  When the grid electrode plate 104 is cleaned with the cleaning member 300 shown in FIG. 17 as a comparative example, streaks are generated in the halftone from the 10,000th sheet. However, the grid electrodes are cleaned with the cleaning members 112 and 212 according to this embodiment. When the plate 104 was cleaned, no streaking occurred in the halftone even after the 10,000th sheet.

  In the cleaning mechanism 110 according to the first embodiment, the cleaning member 112 is moved by the driving device. However, the cleaning member 112 may be manually moved. On the contrary, in the cleaning mechanism 210 of the second embodiment, the cleaning member 212 is moved manually, but may be configured to be moved by a driving device.

10 Image Forming Device 62 Photoconductor (Example of Charged Body)
66 Exposure device 67 Primary transfer roll (an example of a transfer device)
68 Intermediate transfer belt 70 Developing device 71 Secondary transfer roll 100 Charging unit (an example of charging device)
102A Charge wire 102B Charge wire 103 Partition plate 104 Grid electrode plate 104A End region 104B Center region 104C Center portion 104D Slit 104E Long rib 104F Short rib 104G Both ends 105 Shield member 108 Cam mechanism (an example of a switching mechanism)
109 Electromagnetic solenoid (example of switching mechanism)
110 Cleaning mechanism 112 Cleaning member 112A Brush member 124 Metal rod (an example of an auxiliary member)
210 Cleaning mechanism 212 Cleaning member 212A Brush member 214 First pressing block (an example of a pressing member)
216 Operation rod 218 Second pressing block (an example of a pressing member)
220 Protruding portion 222 Engaging hole 224 Guide protrusion 226 Guide protrusion 232 Guide protrusion 246 Cleaning member guide groove 248 First pressing block guide groove (an example of a guide member)
250 second pressing block guide groove (an example of a guide member)

Claims (9)

It has a long plate shape and is arranged so that the longitudinal direction is parallel to the cylindrical axis direction of the charged body outside the cylindrical charged body, and the central portion in the short direction and the charged body A grid electrode plate for charging the object to be charged;
Holding both end portions along the longitudinal direction of the grid electrode plate from both end sides, the grid electrode plate is movable along the longitudinal direction of the grid electrode plate, and is opposite to the surface of the grid electrode plate facing the object to be charged. A cleaning member for cleaning the surface;
A switching mechanism for switching the positions of the both end portions between a position for moving the both end portions away from the outer peripheral surface of the member to be charged and a position for bringing the both end portions closer to the outer peripheral surface of the member to be charged;
Have
When the grid electrode plate is cleaned by the cleaning member, the switching mechanism switches the positions of the both ends to a position away from the outer peripheral surface of the charged body, while charging the charged body by the grid electrode plate. And a charging device that switches the positions of the both end portions to a position to approach the outer peripheral surface of the member to be charged.   The switching mechanism switches the positions of the both ends to a position away from the outer peripheral surface of the charged body when the both ends are not touched, while the positions of the both ends are switched to the charged position when contacting the both ends. The charging device according to claim 1, further comprising a cam mechanism that switches to a position to approach the outer peripheral surface of the body.   The switching mechanism is separated from the both ends when energized, and switches the positions of the both ends to a position away from the outer peripheral surface of the charged body, while contacting the both ends when de-energized, The charging device according to claim 1, further comprising an electromagnetic solenoid that switches a position of each of the both end portions to a position that approaches the outer peripheral surface of the member to be charged.   The switching mechanism includes an auxiliary member having rigidity and attached to the both end portions along the longitudinal direction of the grid electrode plate, and the positions of the both end portions approach the outer peripheral surface of the charged body through the auxiliary member. The charging device according to claim 2, wherein the charging device is switched to a position to be operated. The switching mechanism is
While being displaceably attached to the cleaning member, the position of the both end portions is switched to a position away from the outer peripheral surface of the charged body when the both end portions are not in contact with each other. A pressing member that switches the position to a position that approaches the outer peripheral surface of the charged body;
As the cleaning member moves in the longitudinal direction of the grid electrode plate, a guide member that guides displacement of the pressing member relative to the cleaning member;
Have
When the grid electrode plate is cleaned by the cleaning member, the guide member displaces the pressing member in a direction not to contact the both end portions, while the grid electrode plate charges the object to be charged. The charging device according to claim 1, wherein the member is displaced in a direction in which the member is brought into contact with the both end portions.   6. The charging device according to claim 1, wherein the grid electrode plate is gripped at both ends in the longitudinal direction and a central portion in the lateral direction, and is fixed while being pulled in the longitudinal direction.   The charging device according to claim 1, wherein the grid electrode plate has a plurality of slits formed along the longitudinal direction and arranged in the lateral direction.   The charging device according to claim 7, wherein the grid electrode plate has a rib formed so as to cross the slit in the short direction. The charged object charged by the charging device according to claim 1,
An exposure apparatus that forms an electrostatic latent image on the object to be charged;
A developing device for developing the electrostatic latent image formed on the member to be charged with toner;
A transfer device for transferring a toner image formed on the member to be charged to a transfer material;
An image forming apparatus.

Images