JP4696676B2 - Corona discharge device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a corona discharge device, particularly a corona discharge device for applying a predetermined charge to an electrophotographic photosensitive member, a process cartridge including the corona discharge device, and the corona discharge device or the process cartridge. The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

  In general, in an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic method, an electrophotographic photosensitive member is uniformly charged by a charging device so as to have a predetermined charge, and image data is transferred onto the photosensitive member. Is exposed to form an electrostatic latent image, and the latent image is developed and transferred to obtain an image.

  Conventionally, a corona discharge device has been used as a charging device, and a device provided with an electrode plate in which a plurality of pointed discharge electrodes are arranged in a row has an advantage of less ozone generation than a wire type device. Has been put to practical use.

  However, when this type of electrode plate is repeatedly discharged, silicon oxide or the like adheres to the pointed discharge electrodes and grows, forming discharge products called so-called needles, and the pointed protrusions are formed by the scattered toner. As a result, the image-like discharge electrode and the grid electrode are fouled, and there is a problem in that image noise is caused by charging failure due to uneven discharge.

  Therefore, in Patent Document 1, the electrode plate is sandwiched from both sides by a pair of rotatable cleaning rollers and moved along the electrode plate so that the spine-shaped discharge electrode is cleaned while being rubbed by the rotating peripheral surface. A cleaning means is disclosed.

  However, this cleaning roller can clean the discharge electrodes, but it is difficult to clean even the grid electrodes. If it is attempted to clean the grid electrode with this cleaning roller, the rotating end face rubs against the grid electrode, so that the cleaning roller may involve and damage the grid electrode.

  Patent Document 2 discloses a cleaning unit that simultaneously cleans the discharge wire and the grid electrode with the hair. However, this hair for cleaning corresponds to a wire electrode, and when used for an electrode plate having a pointed discharge electrode, there is a problem that the pointed discharge electrode is deformed during cleaning. ing.

Patent Document 3 discloses a cleaning means for sliding and sliding a pad made of an elastic material to the inside of a discharge wire and a grid electrode. However, this cleaning pad also corresponds to a wire electrode, and the contact location of the pad with respect to the electrode is always the same, so that a desired cleaning effect cannot always be expected.
JP 7-43990 A JP 7-36259 A JP 2002-72620 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a corona discharge device, a process cartridge, and an image forming apparatus capable of effectively cleaning an electrode plate and a grid electrode and preventing the occurrence of image noise and maintaining the best performance for a long period of time. There is to do.

In order to achieve the above object, the present invention includes an electrode plate in which a plurality of pointed discharge electrodes are arranged in a line, a grid electrode provided in a discharge opening, and an electrode plate and a cleaning member for the grid electrode. In the corona discharge device,
The cleaning member includes a rotation axis in a direction orthogonal to the longitudinal direction of the electrode plate, and a pair of rollers that can be driven to rotate about the rotation axis.
The pair of rollers is installed with the electrode plate interposed therebetween, and has a rotating end surface that contacts the electrode plate and a rotating peripheral surface that contacts the inner side of the grid electrode, and rotates with the electrode plate interposed therebetween. and by moving along the longitudinal direction of the electrode plate, together with the rotating end face to clean both sides of the electrode plate, said rotating peripheral surface to clean the inside of the grid electrode,
It is characterized by.

In the corona discharge device according to the present invention, by a pair of rollers move along the longitudinal direction of the rotation and the electrode plate, together with the rotating end face is cleaned by rubbing the surfaces of the electrode plates, rotating circumferential surface grid Clean the inside of the electrode by rubbing. The cleaning member is always in contact with the electrode plate and the grid electrode, so that the cleaning effect is good, the occurrence of image noise is prevented, and the corona discharge device can be maintained in the best condition for a long time. Further, since the rotating peripheral surface of the cleaning member comes into contact with the grid electrode, there is no possibility that the cleaning member entrains the grid electrode.

  A process cartridge according to the present invention includes the corona discharge device. An image forming apparatus according to the present invention includes the corona discharge device or the process cartridge.

  Hereinafter, embodiments of a corona discharge device, a process cartridge, and an image forming apparatus according to the present invention will be described with reference to the accompanying drawings.

(Schematic configuration of image forming apparatus)
FIG. 1 shows a schematic configuration of an electrophotographic printer as an image forming apparatus. A corona discharge device 10, a laser scanning device 31, a developing device 32, and a transfer device are arranged around the photosensitive drum 1 along a rotation direction indicated by an arrow A. A roller 33, a cleaning device 34, and an eraser lamp 35 are disposed.

  First, a predetermined charge is uniformly applied to the photosensitive drum 1 by the corona discharge device 10, and a laser modulated based on the image data is scanned from the laser scanning device 31 to form an electrostatic latent image. The electrostatic latent image is developed (visualized) with toner by the developing device 32 and transferred onto the sheet S conveyed between the photosensitive drum 1 and the transfer roller 33. Thereafter, the sheet S is conveyed to the fixing device 36, where the toner is heated and fixed.

  The photosensitive drum 1 continues to rotate in the direction of arrow A even after transfer, and residual toner is removed by the cleaning device 34 and residual charge is removed by the eraser lamp 35.

  The detailed configuration and operation of these image forming elements and the image forming process are well known, and detailed description thereof is omitted.

(Corona discharge device)
As schematically shown in FIG. 1, the corona discharge device 10 is provided with an electrode plate 13 in a stabilizing plate 11 in which a grid electrode 12 is provided in a discharge opening. As shown in FIG. 3, the electrode plate 13 has a large number of pointed discharge electrodes 13a arranged in a line. The thickness of the electrode plate 13 is 30 to 80 μm, the angle between the two sides forming the apex of the discharge electrode 13a is 5 to 30 °, the height is 1 to 3 mm, and the pitch is 1 to 3 mm.

  A voltage of −6 to −7 kV (900 μA) is applied to the electrode plate 13, and corona discharge is generated from the pointed discharge electrode 13 a toward the photosensitive drum 1. A voltage of −300 to −900 V is applied to the grid electrode 12 to adjust the charging potential of the photosensitive drum 1 to a desired value.

(Cleaning member)
As shown in FIGS. 2 and 3, the cleaning member provided in the corona discharge device 10 is a cleaning roller 21 fixed to a shaft 22. The roller 21 is made of a rubber material, a resin material, or a metal material. Epoxy, polyimide, and the like can be preferably used. The cleaning roller 21 may be a felt material or may contain abrasive particles.

  The cleaning roller 21 is installed so that it can be rotationally driven with the shaft 22 as a fulcrum in a state where a pair of the rollers sandwich the electrode plate 13, and can reciprocate in the directions of arrows B and B ′ along the electrode plate 13. ing. The cleaning roller 21 has a rotating end surface 21 a in contact with each surface of the electrode plate 13 and a rotating peripheral surface 21 b in contact with the inner surface of the grid electrode 12.

  The rotation / movement mechanism will be described. The shaft 22 passes through the elongated hole 11a (see FIG. 2) of the stabilizing plate 11, and is rotatably held by the bracket 25. A screw shaft 27 is screwed into a screw hole 26a of a nut member 26 attached to the bottom surface of the bracket 25, and the screw shaft 27 is rotated forward and backward by a motor (not shown), whereby the cleaning roller 21 is integrated with the bracket 25. In particular, it moves along the electrode plate 13 in the directions of arrows B and B ′.

  A pinion 18 is fixed to each end of the shaft 22, and the pinion 18 meshes with a rack 19 installed in the longitudinal direction of the electrode plate 13. Therefore, as the cleaning roller 21 and the bracket 25 move in the directions of arrows B and B ′ based on the rotation of the screw shaft 27, the pinion 18 rotates integrally with the shaft 22, and the cleaning roller 21 also integrally moves. Rotate. The rotation direction of the cleaning roller 21 is the direction of the arrow C when moving in the direction of the arrow B, and the direction opposite to the arrow C when moving in the direction of the arrow B ′.

  In the above configuration, the cleaning roller 21 rotates and moves along the electrode plate 13 based on forward and reverse rotation of the screw shaft 27, and the rotating end surface 21a slides on each surface of the electrode plate 13 to form a pointed protrusion. The discharge product and toner adhering to the discharge electrode 13a are removed. At the same time, the rotating peripheral surface 21b of the cleaning roller 21 is rubbed inside the grid electrode 12 to remove the attached toner. As a result, the generation of image noise is prevented and the charging performance can be maintained in the best state for a long time.

  By the way, in order to improve the cleaning efficiency by the cleaning roller 21, it is only necessary to increase the peripheral speed of the cleaning roller 21, and it is preferable that the pinion 18 has a smaller diameter.

  The cleaning operation is incorporated in the control program of the image forming apparatus so as to be automatically executed every time a predetermined discharge time elapses (every time the predetermined number of printed sheets is converted into the number of printed sheets). The cleaning operation may be controlled when necessary.

  Various means can be adopted as means for moving / rotating the cleaning roller 21. For example, the bracket 25 may be moved by a wire. Alternatively, the bracket 25 may be manually moved. In this case, the user performs the cleaning process at an arbitrary timing.

(Other drive modes of cleaning roller)
The cleaning operation by the cleaning roller 21 is reciprocated along the same route. In this case, a gap 21 ′ (see FIG. 2) is generated in the rollers 21, 21, so that a cleaning residue with respect to the grid electrode 12 occurs.

  Therefore, when moving in the direction of arrow B, as shown in FIG. 4 (A), the cleaning roller 21 is moved slightly to the left, and when moving in the direction of arrow B ′, as shown in FIG. 4 (B). The cleaning roller 21 may be moved slightly to the right side. Thereby, the remaining cleaning due to the gap 21 'can be eliminated.

  Such a cleaning operation can be performed by appropriately installing a guide member using the fact that the electrode plate 13 is extremely thin and easily bent.

(Other examples)
The corona discharge device, the process cartridge, and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

  For example, the pointed discharge electrode 13a is not limited to a triangular shape, and may be a conical shape or a pin shape, for example. The corona discharge device 10 may be configured to be detachable from the image forming apparatus by itself, or may be configured to be detachable from the image forming apparatus as a process cartridge including the photosensitive drum 1 and the developing device 32. May be. Further, the photosensitive drum 1 is not necessarily required as a member to be charged by the corona discharge device 10.

It is a schematic block diagram which shows an example of the image forming apparatus provided with the corona discharge apparatus which concerns on this invention. It is a cross-sectional view showing the corona discharge device. The said corona discharge apparatus is shown, (A) is a side view, (C) is a center longitudinal cross-sectional view. (A), (B) is a cross-sectional view which shows the other drive form of the cleaning roller in the said corona discharge device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 10 ... Corona discharge device 12 ... Grid electrode 13 ... Electrode plate 13a ... Point-like discharge electrode 18 ... Pinion 19 ... Rack 21 ... Cleaning roller 22 ... Shaft 25 ... Bracket 26 ... Nut member 27 ... Screw shaft

Claims (5)

In a corona discharge device comprising an electrode plate in which a plurality of pointed discharge electrodes are arranged in a row, a grid electrode provided in a discharge opening, and a cleaning member for the electrode plate and the grid electrode,
The cleaning member includes a rotation axis in a direction orthogonal to the longitudinal direction of the electrode plate, and a pair of rollers that can be driven to rotate about the rotation axis.
The pair of rollers is installed with the electrode plate interposed therebetween, and has a rotating end surface that contacts the electrode plate and a rotating peripheral surface that contacts the inner side of the grid electrode, and rotates with the electrode plate interposed therebetween. and by moving along the longitudinal direction of the electrode plate, together with the rotating end face to clean both sides of the electrode plate, said rotating peripheral surface to clean the inside of the grid electrode,
A corona discharge device.   The corona discharge device according to claim 1, wherein the cleaning member is made of a rubber material, a resin material, or a metal material. The pair of rollers is further movable in a direction perpendicular to the longitudinal direction of the electrode plate,
By moving the pair of rollers in a direction perpendicular to the longitudinal direction, the path of movement along the longitudinal direction of the electrode plate is changed, and cleaning remaining due to the gap between the pair of rollers inside the grid electrode is removed. Cleaning,
The corona discharge device according to claim 1 or 2, characterized by the above. A process cartridge comprising the corona discharge device according to any one of claims 1 to 3 . An image forming apparatus comprising the process cartridge according to the corona discharge device or claim 4 according to any one of claims 1 to 3.

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