JP4715297B2 - 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 sawtooth discharge electrodes are arranged in a line has an advantage of less ozone generation than a wire type device. It has been put into practical use.

  However, when this type of electrode plate repeatedly discharges, silicon oxide or the like adheres to the sawtooth discharge electrode and grows, and a discharge product called a so-called needle is formed at the tip of the sawtooth discharge electrode. There has been a problem that image noise is caused by charging failure due to uneven discharge.

  Therefore, conventionally, as shown in FIG. 8A, an electrode plate 50 provided with a plurality of sawtooth discharge electrodes 52 on a base 51 is sandwiched by a rectangular parallelepiped cleaning member 53 made of an elastic material. Is reciprocated along the electrode plate 50 to remove discharge products.

  However, in this type of cleaning means, the tip portion of the sawtooth discharge electrode 52 is deformed as shown in FIG. 8B due to the resistance generated when the electrode plate 50 is rubbed and cleaned by the movement of the cleaning member 53. Had problems.

  Therefore, in Patent Document 1, when a cleaning member made of an elastic material sandwiching an electrode plate reciprocates in the longitudinal direction of the electrode plate and moves up and down in the apex direction of the sawtooth electrode, the cleaning member is brought into contact with the sawtooth electrode. A corona discharger is disclosed that moves away from the sawtooth electrode when moving up and down in a direction away from the apex.

However, this corona discharger requires not only a mechanism for moving the cleaning member in parallel but also a mechanism for moving it up and down, and has a problem that the configuration is complicated and expensive.
JP-A-8-190255

  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 that have a simple and inexpensive configuration and that do not cause deformation of the sawtooth discharge electrode, as well as effective removal of discharge products. Is to provide.

  In order to achieve the above object, a first invention is a corona discharge device having an electrode plate in which a plurality of sawtooth discharge electrodes are arranged in a row on a long base portion, in a state in which the electrode plate is in pressure contact with both surfaces. A planar cleaning member provided, and a moving means for moving the cleaning member in the longitudinal direction of the electrode plate, the leading end surface of the cleaning member in the moving direction from the base of the electrode plate to the sawtooth discharge electrode It is characterized in that it is tilted backward with respect to the moving direction toward the tip.

  In the corona discharge device according to the first aspect of the present invention, the front end surface in the moving direction of the planar cleaning member provided in pressure contact with both surfaces of the electrode plate is directed from the base of the electrode plate toward the front end of the sawtooth discharge electrode. Since it is tilted backward with respect to the moving direction, when the cleaning member moves, a frictional force is applied to the sawtooth discharge electrode from the base toward the tip, which occurs at the tip of the sawtooth discharge electrode. Resistance is reduced.

  According to the corona discharge device according to the first invention, since the planar cleaning member pressed against both surfaces of the electrode plate is used, the discharge product can be effectively removed, and the mechanism for the vertical movement is It is not necessary, and a simple and inexpensive configuration can be obtained. In addition, since the resistance force generated at the tip portion of the sawtooth discharge electrode during cleaning is reduced, deformation (bending or damage) of the tip portion can be prevented.

  The second invention is a corona discharge device having an electrode plate in which a plurality of sawtooth discharge electrodes are arranged in a row on a long base portion, and is a planar shape provided in pressure contact with both surfaces of the electrode plate. A cleaning member, and a moving means for moving the cleaning member in the longitudinal direction of the electrode plate, wherein α is an angle formed by the extending direction of the base portion of the electrode plate and the front end surface of the cleaning member in the moving direction. The angle formed by the extending direction of the base of the plate and the side facing the tip surface of the cleaning member forming the angle α out of the two sides forming the apex of the sawtooth discharge electrode is β, and the apex of the sawtooth discharge electrode Where β> α and β−α> θ / 2.

  According to the corona discharge device according to the second aspect of the invention, by satisfying the conditional expressions (β> α and β−α> θ / 2), the cleaning member moves with respect to the sawtooth discharge electrode. As a result, a rubbing force is applied from the base portion toward the tip, and the resistance force generated at the tip portion of the sawtooth discharge electrode is reduced. As a result, deformation (bending or damage) of the tip portion can be prevented. . Further, as in the case of the corona discharge device according to the first aspect of the invention, the discharge product can be effectively removed, and a simple and inexpensive configuration can be obtained.

  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, see FIG. 1)
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 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, see FIGS. 1 to 3)
As shown schematically in FIG. 1, the corona discharge device 10 is provided with an electrode plate 13 in a stabilizing plate 11 having a mesh 12 in an opening. As shown in FIG. 2, the electrode plate 13 includes a long base portion 14 in which a large number of sawtooth discharge electrodes 15 are 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 15 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 sawtooth discharge electrode 15 toward the photosensitive drum 1. A voltage of −300 to −900 V is applied to the mesh 12 to adjust the charging potential of the photosensitive drum 1 to a desired value.

In addition, the electrode plate 13 is provided with a pair of cleaning members 20 and 20 (see FIG. 3) made of a sheet-like elastic material while being pressed against both surfaces thereof. As the cleaning member 20, for example, a urethane foam material or a felt material having an elastic modulus of 1.0 × 10 ⁻² Pa or less is used, and the electrode plate 13 is sandwiched with a predetermined pressure contact force held by the housing 25. ing. The pressure contact force of the cleaning member 20 to the electrode plate 13 is preferably 10 to 20 gf / cm ^2, but is not limited to this value.

  In order to obtain a preferable pressure contact force, a spring force or the like may be applied to the cleaning member 20. Further, as the cleaning member 20, various materials other than the urethane foam material and felt material can be widely used, and those containing abrasive fine particles may be used.

  As shown in FIG. 3, the housing 25 has a screw hole 26 or a nut member (not shown). A screw shaft 27 is screwed into the screw hole 26 or the nut member, and the screw shaft 27 is attached by a motor (not shown). By rotationally driving in the forward and reverse directions, the cleaning member 20 moves along the longitudinal direction of the electrode plate 13, cleans the electrode plate 13, and removes the discharge product attached to the sawtooth discharge electrode 15.

  Various means can be adopted as means for moving the cleaning member 20, and for example, the housing 25 may be moved by a wire. Further, the housing 25 may be engaged with a guide rail or the like in order to guide the movement of the cleaning member 20.

(Refer to the first example of the cleaning member, FIG. 4)
FIG. 4 shows an elevational shape of the cleaning member 20A as the first example. The cleaning member 20 </ b> A has a trapezoidal elevation, and the movement direction tip surfaces 21 a and 21 b are inclined backward from the base 14 toward the tip of the sawtooth discharge electrode 15 with respect to the movement directions B and B ′. The tip surface 21a is a tip surface corresponding to the movement direction B, and the tip surface 21b is a tip surface corresponding to the movement direction B ′.

  The cleaning product 20 </ b> A reciprocates from one end of the electrode plate 13 to the other end while sandwiching the electrode plate 13, thereby removing discharge products attached to the discharge electrode 15. In this case, the moving direction front end surfaces 21 a and 21 b of the planar cleaning member 20 </ b> A provided in pressure contact with both surfaces of the electrode plate 13 move from the base portion 14 of the electrode plate 13 toward the front end of the sawtooth discharge electrode 15. Since it is tilted backward with respect to the directions B and B ′, when the cleaning member 20A moves, a sliding force is applied to the sawtooth discharge electrode 15 from the base portion 14 toward the distal end, so that the sawtooth discharge is performed. The resistance force generated at the tip portion of the electrode 15 is reduced. Therefore, deformation (bending or damage) of the tip portion of the sawtooth discharge electrode 15 can be prevented, and a high-quality image free from discharge unevenness (image noise) can be obtained.

  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.

(Refer to the second example of the cleaning member, FIG. 5)
FIG. 5 shows an elevational shape of the cleaning member 20B as the second example. This cleaning member 20B is obtained by tilting the upper part of the moving direction front end faces 21a, 21b (the part corresponding to the front end part of the sawtooth discharge electrode 15).

  Even in the cleaning member 20B, the same effect as the cleaning member 20A shown as the first example is obtained.

(Refer to the third example of the cleaning member, FIG. 6)
FIG. 6 shows an elevational shape of the cleaning member 20C as the third example. In the cleaning member 20C, the front end surfaces 21a and 21b in the moving direction are arcuate surfaces, and the rearward inclination of the front end surfaces 21a and 21b is set to be large from the base portion 14 of the electrode plate 13 toward the front end of the sawtooth discharge electrode 15. .

  Even in this cleaning member 20C, the same effect as the cleaning member 20A shown as the first example is obtained.

(See fourth example of cleaning member, FIG. 7)
Here, as shown in FIG. 7, a cleaning member 20D as a fourth example corresponding to the electrode plate 13 in which the extending direction of the tip of the sawtooth discharge electrode 15 is not perpendicular to the extending direction of the base portion 14 will be described.

  In the cleaning member 20D, the angles formed by the extending direction of the base portion 14 of the electrode plate 13 and the front end surfaces 21a and 21b in the moving direction of the cleaning member 20D are α1 and α2, and the extending direction of the base portion 14 and the sawtooth discharge electrode 15 are formed. The two sides forming the apex of the sawtooth discharge electrode 15 are the angles formed by the sides facing the tip surfaces 21a and 21b of the cleaning member 20D forming the angles α1 and α2 among the two sides forming the apex of Is θ, β1> α1, β1-α1> θ / 2, β2> α2, and β2-α2> θ / 2.

  Also in this cleaning member 20D, by satisfying the above conditional expression, when the cleaning member 20D moves in the directions of arrows B and B ′, a sliding force is applied to the sawtooth discharge electrode 15 from the base portion 14 toward the distal end. It will be added and has the same effect as the cleaning members 20A to 20C. The conditional expression is valid also in the first to third examples.

(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 sawtooth discharge electrode 15 is not limited to a triangular shape, and may be a conical 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 the perspective view which notched a part which shows the said corona discharge device. It is sectional drawing of the said corona discharge apparatus. It is a front view which shows the 1st example of the cleaning member provided in the said corona discharge apparatus. It is a front view which shows the 2nd example of the cleaning member provided in the said corona discharge apparatus. It is a front view which shows the 3rd example of the cleaning member provided in the said corona discharge apparatus. It is a front view which shows the 4th example of the cleaning member provided in the said corona discharge apparatus. (A) is a front view which shows the conventional cleaning member, (B) is a front view which shows a deformation | transformation of a sawtooth discharge electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 10 ... Corona discharge device 13 ... Electrode plate 14 ... Base 15 ... Sawtooth-shaped discharge electrode 20 (20A-20D) ... Cleaning member 21a, 21b ... Front end surface

Claims (5)

In a corona discharge device having an electrode plate in which a plurality of sawtooth discharge electrodes are arranged in a row on a long base,
A planar cleaning member provided in pressure contact with both surfaces of the electrode plate, and a moving means for moving the cleaning member in the longitudinal direction of the electrode plate,
The front end surface of the cleaning member in the moving direction is inclined backward with respect to the moving direction from the base of the electrode plate toward the front end of the sawtooth discharge electrode;
A corona discharge device.   2. The corona discharge device according to claim 1, wherein a rearward inclination of the front end surface in the moving direction of the cleaning member is set to be large from a base portion of the electrode plate toward a front end of the sawtooth discharge electrode. In a corona discharge device having an electrode plate in which a plurality of sawtooth discharge electrodes are arranged in a row on a long base,
A planar cleaning member provided in pressure contact with both surfaces of the electrode plate, and a moving means for moving the cleaning member in the longitudinal direction of the electrode plate,
The angle formed between the extending direction of the base portion of the electrode plate and the front end surface of the cleaning member in the moving direction is α, and the extending direction of the base portion of the electrode plate and the two sides forming the apex of the sawtooth discharge electrode are When β is an angle formed by a side facing the tip surface of the cleaning member forming an angle α and β is an angle formed by two sides forming the apex of the sawtooth discharge electrode, β−α and β−α > Θ / 2,
A corona discharge device.   A process cartridge comprising the corona discharge device according to any one of claims 1 to 3. An image forming apparatus comprising the corona discharge device according to claim 1 or the process cartridge according to claim 4.

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