JP6041718B2 - Charging device and image forming apparatus - Google Patents

Description

  The present invention relates to a charging device provided in an image forming apparatus that performs electrophotographic image formation, and an image forming apparatus including the charging device.

  An image forming apparatus that performs electrophotographic image formation includes a charging device that charges a surface of a photoreceptor before an exposure process to a uniform potential. The charging device holds the discharge member with a uniform distance from the surface of the photoreceptor. In recent years, saw blade-shaped discharge members are frequently used in place of tungsten wires as discharge members (see, for example, Patent Document 1). The saw blade-shaped discharge member has no fear of disconnection during cleaning unlike a wire.

  A cleaning roller having elasticity such as rubber is used for cleaning the saw blade-shaped discharge member. By moving the cleaning roller along the longitudinal direction of the saw blade-like discharge member, the cleaning roller rotates while the plurality of tip portions of the discharge member are sequentially inserted and removed from the cleaning roller, and dust is discharged from the tip portion of the discharge member. Is removed. In order to clean the sawtooth discharge member so that the surface of the photoreceptor can be properly charged, it is necessary to immerse the tip of the discharge electrode into the cleaning roller by about 1 mm.

JP 2007-256672 A

  However, in the conventional charging device, all of the plurality of pointed ends of the saw blade-like discharge member are set at a constant height, so that the pointed ends located at both ends of the discharge member are not rotated. When immersing, the deformation may be caused by the action of a large load from the cleaning roller. On the other hand, the pointed portion located at the intermediate portion in the longitudinal direction of the discharge member is immersed in the cleaning roller that is rotating by contact with the pointed portion, so that a large load does not act from the cleaning roller and the deformation is not caused. It does not occur.

  When a part of the pointed portion of the saw blade-like discharge member is deformed, the discharge distance between the surface of the photoconductor changes and the photoconductor surface cannot be charged to a uniform potential. Such a problem also occurs in a charging device that cleans a sawtooth discharge member using a non-rotating cleaning member such as a non-rotating cleaning pad.

  It is an object of the present invention to prevent a large load from acting on a sharp end located at the end in the longitudinal direction among a plurality of sharp ends of a saw blade-like discharge member, and to generate charging unevenness due to deformation of the sharp end. It is an object of the present invention to provide a charging device capable of preventing the above-described problem and an image forming apparatus including the charging device.

  The charging device of the present invention includes a discharge member, a cleaning member, and a relaxation means. The discharge member has a thin strip shape having a predetermined length, and is provided with a plurality of sawtooth-shaped tip portions protruding along the longitudinal direction. The cleaning member moves along the longitudinal direction of the discharge member so that the plurality of tip portions are sequentially immersed and detached. The relaxation means relaxes the component force in the longitudinal direction of the force acting from the cleaning member on the tip portion located at the end portion in the longitudinal direction of the discharge member and the component force in the normal direction of the side surface of the discharge member.

  When the movement is started along the longitudinal direction of the discharge member, first, the tip end portion located at the end portion of the contact member is immersed in the cleaning member. At this time, from the cleaning member in a state where the component force in the longitudinal direction of the discharge member and the component force in the normal direction of the side surface of the discharge member are relaxed by the relaxing means at the pointed portion located at the end of the discharge member. Force acts. A large load that causes deformation does not act from the cleaning roller on the tip portion located at the end portion in the longitudinal direction among the plurality of tip portions of the discharge member.

  In this configuration, the mitigating means can make the amount of immersion of the tip end portion positioned at the end portion of the discharge member relative to the cleaning member smaller than the amount of immersion of the tip end portion positioned at the intermediate portion of the discharge member.

  For example, with respect to the direction perpendicular to the longitudinal direction and the normal direction of the side surface of the discharge member, the relaxing means is such that the position of the cleaning member is separated from the discharge member on the end side of the discharge member rather than the intermediate portion of the discharge member. can do.

  The mitigating means can also be realized by making the protruding amount of the tip end portion positioned at the end portion of the discharge member smaller than the protruding amount of the tip end portion positioned at the intermediate portion of the discharge member.

  According to the present invention, a large load from the cleaning member can be prevented from acting on the tip portion located at the end portion in the longitudinal direction among the plurality of tip portions of the saw blade-shaped discharge member. Generation of uneven charging can be prevented.

1 is a front view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. (A) And (B) is side sectional drawing of the charging device which concerns on 1st Embodiment of this invention, and the front view of the principal part. It is a front view of the principal part at the time of cleaning of the charging device. (A) And (B) is side sectional drawing of the charging device which concerns on 2nd Embodiment of this invention, and the front view of the principal part. It is a front view of the principal part at the time of cleaning of the charging device. (A) And (B) is side sectional drawing of the charging device which concerns on 3rd Embodiment of this invention, and the front view of the principal part.

  FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus 100 to which a charging device 1 according to an embodiment of the present invention is applied. The image forming apparatus 100 forms an electrophotographic image on a sheet (including a recording medium such as an OHP).

  As an example, the image forming apparatus 100 includes a document reading unit 10, a paper feeding unit 20, an image forming unit 30, and a paper discharge unit 40. The document reading unit 10 reads an image from a document placed on the platen glass 11 or a document transported in the document transport path R from the document placing tray 12. The paper feed unit 20 is disposed at the lower part of the apparatus main body, and feeds the papers placed on the paper feed tray 21 one by one toward the image forming unit 30.

  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, the charging device 1, the developing device 33, the transfer device 34, and the cleaner unit 35 are arranged in this order along the direction of the arrow shown in FIG. .

  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 forms an electrostatic latent image by irradiating the surface of the photosensitive drum 31 charged to a predetermined potential by the charger 32 with laser light based on the image data. The electrostatic latent image is visualized into a toner image by the toner supplied from the developing device 33.

  The toner image is transferred from the surface of the photosensitive drum 31 to the surface of the paper by the transfer device 34. The sheet that has completed the transfer process is heated and pressed by the fixing device 36, and after the toner image is melted and fixed, it is discharged to the discharge tray 42 of the discharge unit 40.

  As shown in FIGS. 2A and 2B, the charging device 1 according to the first embodiment includes a sawtooth electrode 2 as a discharge member, a holder 3, a support body 4, a cleaning roller 5, and an operation shaft 6. The case 7 is provided.

  The saw-toothed electrode 2 is made of a thin band-shaped metal material such as SUS, and a plurality of pointed portions 2A protrude downward from the lower end portion at regular intervals over the entire length. The plurality of pointed portions 2 </ b> A are formed along the arrangement direction X parallel to the longitudinal direction of the saw-toothed electrode 2. The charging device 1 is arranged with the longitudinal direction of the sawtooth electrode 2 parallel to the axial direction of the photosensitive drum 31. Therefore, the arrangement direction X is parallel to the rotation axis of the photosensitive drum 31. The length of the saw-tooth electrode 2 is slightly 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 sawtooth electrode 2. The length of the holding portion 3 </ b> A is longer than the arrangement range of the plurality of tip portions 2 </ b> A in the sawtooth 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 arrangement direction X. The terminal portion 3B houses a terminal (not shown). The terminal connects a high voltage power source (not shown) and the sawtooth electrode 2.

  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 arrangement direction X.

  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 made of an elastic body such as chlorosulfonated polyethylene.

  As an elastic body constituting the cleaning roller 5, a suitable material was tested from known rubber materials and resin materials on the condition that the elastic body is elastically deformed without being easily cut by the insertion and removal of the tip 2 </ b> A. Can be selected. Also, an abrasive appropriately selected from known materials on the condition that the toner and dust can be removed from the surface of the tip 2A without damaging the surface of the tip 2A may be contained in the elastic body by a known method. it can.

  The operation shaft 6 has an end on the back side fixed to the inside of the hole 4 </ b> C of the support 4. The operation shaft 6 has a front side end (not shown) protruding from the front surface of the holder 3.

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

  When a high voltage power source is applied to the sawtooth 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 tip portions 2A of the sawtooth electrode 2, and this portion It becomes easy to generate discharge. As a result, a discharge is generated on the surface of the photosensitive drum 31 from each of the plurality of tip portions 2A. 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 arrangement direction X within at least the arrangement range of the plurality of pointed portions 2A. The support 4 is attached to the outside of the holding portion 3 </ b> A and is restricted from moving including rotation in a plane orthogonal to the arrangement direction X. Accordingly, the support body 4 is guided by the holding portion 3A and is reciprocally movable in the arrangement direction X within an arrangement range of at least the plurality of tip portions 2A.

  When cleaning the sawtooth electrode 2, the support 4 is moved along the longitudinal direction of the sawtooth electrode 2 via the operation shaft 6. Along with this, the cleaning roller 5 reciprocates between the outermost points 2A positioned at the outermost sides at both ends in the longitudinal direction of the saw-tooth electrode 2, and a plurality of cleaning rollers 5 are provided inside from the peripheral surface of the cleaning roller 5. The pointed portion 2A is sequentially immersed and detached.

  As shown in FIG. 3, among the plurality of pointed portions 2A of the sawtooth-shaped electrode 2, the pointed portions 2A 'located at both ends in the longitudinal direction of the sawtooth-shaped electrode 2 are used as relaxation means of the present invention in the longitudinal direction. The amount of protrusion is made smaller than that of the other tip portion 2A located in the intermediate portion. For example, the protruding amount of the tip 2a 'located at both ends is made smaller by the length L = 0.5mm than the protruding amount H = 1.5mm of the tip 2A positioned in the middle. For this reason, when the tip 2 </ b> A located at the intermediate portion is immersed in the cleaning roller 5 at a depth D = 0.6 mm, the tip 2 </ b> A ′ is immersed in the cleaning roller 5 by 0.1 mm.

  Since the cleaning roller 5 is not supplied with a rotational force, immediately after the start of the cleaning of the sawtooth electrode 2, the cleaning roller 5 comes into contact with the tip 2A 'in a state of not rotating. Even in this case, the tip 2 </ b> A ′ is only slightly immersed in the cleaning roller 5 and does not receive an excessive load from the cleaning roller 5. The component force in the longitudinal direction (arrow X direction) of the saw-tooth electrode 2 of the force acting on the tip 2A ′ from the cleaning roller 5 and the normal direction of the side surface of the saw-tooth electrode 2 (shown in FIG. 2A) The component force in the direction of arrow Y) is relaxed, and the tip 2A ′ is not deformed.

  As a result, it is possible to discharge the photosensitive drum 31 in a uniform state from all of the plurality of tip portions 2A of the sawtooth electrode 2.

  As shown in FIGS. 4A and 4B, the charging device 1 'according to the second embodiment of the present invention is a guide 3C that protrudes downward from a part of the holding portion 3A as a relaxation means of the present invention. It has. Other configurations are the same as those of the charging device 1. The guide 3 </ b> C is formed so as to move the cleaning roller 5 downward at the positions of the tip portions 2 </ b> A ′ at both ends of the saw-tooth electrode 2.

  As shown in FIG. 5, the guide 3 </ b> C has a length M = higher than the height of the cleaning roller 5 at a position facing the intermediate point 2 </ b> A due to elastic deformation of the support 4 that supports the cleaning roller 5, for example. The cleaning roller 5 is moved downward by 0.5 mm. For this reason, when the tip 2 </ b> A located at the intermediate portion is immersed in the cleaning roller 5 at a depth D = 0.6 mm, the tip 2 </ b> A ′ is immersed in the cleaning roller 5 by 0.1 mm.

  Also with this configuration, the tip 2A 'can be slightly immersed in the cleaning roller 5, and an excessive load can be prevented from acting on the tip 2A' from the cleaning roller 5. The component force in the longitudinal direction (arrow X direction) of the saw-tooth electrode 2 of the force acting on the tip 2A ′ from the cleaning roller 5 and the normal direction of the side surface of the saw-tooth electrode 2 (shown in FIG. 2A) The component force in the direction of arrow Y) is relaxed, and the tip 2A ′ is not deformed.

  The configuration of the first and second embodiments of the present invention can be similarly applied to a charging device including a cleaning member that does not rotate, such as a cleaning pad, instead of the cleaning roller 5.

  As shown in FIGS. 6A and 6B, the charging device 1 ″ according to the third embodiment of the present invention includes a pinion gear 5A in the cleaning roller 5 and a holding portion as a relaxation means of the present invention. The rack gear 3D protrudes downward from a part of 3A, and the other configuration is the same as that of the charging device 1. The rack gear 3D has a point A ′ in the longitudinal direction at least at both ends of the sawtooth electrode 2. The cleaning roller 5 meshes with the pinion gear 5A.

  With this configuration, immediately after the cleaning of the sawtooth electrode 2 is started, the cleaning roller 5 can be brought into contact with the tip 2A ′ in a rotated state, and the cleaning roller 5 in a non-rotating state can be brought into contact with the tip 2A ′. The acting force can be reduced. The component force in the longitudinal direction (arrow X direction) of the sawtooth electrode 2 of the force acting on the pointed end 2A ′ from the cleaning roller 5 and the normal direction of the side surface of the sawtooth electrode 2 (shown in FIG. 6A) The component force in the direction of arrow Y) is relaxed, and the tip 2A ′ is not deformed.

  In addition, another charging device can be formed by appropriately combining the configurations included in the first to third embodiments.

  The present invention is also applied to a charging device provided with a conversion mechanism such as a ball screw for converting the motor and the rotation of the motor into the moving force in the longitudinal direction of the saw-tooth electrode 2 and automatically moving the support 4. Can be applied.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Charging device 2 Saw-tooth electrode 2A, 2A 'Pointed part 3C Guide 3D Rack gear 5 Cleaning roller 5A Pinion gear 10 Image forming apparatus

Claims (4)

A discharge member having a thin strip shape of a predetermined length and having a plurality of sawtooth-shaped tips protruding along the longitudinal direction;
A cleaning member that moves along the longitudinal direction of the discharge member so that the plurality of tip portions are sequentially immersed and detached, and
A charging device comprising: relaxation means for reducing a dip amount of a tip portion located at an end portion of the discharge member with respect to the cleaning member to be smaller than a dip amount of a tip portion located at an intermediate portion of the discharge member . The relaxation means is configured to separate the position of the cleaning member from the discharge member on the end side of the discharge member with respect to the direction orthogonal to the longitudinal direction and the normal direction of the side surface of the discharge member. The charging device according to claim 1 , wherein Examples relieving means, the charging device according to claim 1, smaller than the projection amount of the tip portion located a projection amount of the tip portion located at an end portion of the discharge member in the middle portion of the discharge member. Image forming apparatus that performs image formation processing of an electrophotographic system via the photoreceptor is charged by a charging device according to any one of claims 1 to 3.

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