JP4735048B2 - 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 an ozone generator that has an electrode plate with a plurality of pointed discharge electrodes arranged in a row on a long base rather than a wire type It has been put into practical use as having the advantage of a small amount.

  However, when this type of electrode plate is repeatedly discharged, silicon oxide or the like adheres to the pointed discharge electrode and grows, forming a discharge product called a so-called needle, and also due to scattered toner and dust. Since the pointed discharge electrode is soiled, there is a problem in that image noise is generated due to charging failure due to uneven discharge.

  Therefore, Patent Document 1 discloses a cleaning means in which a pair of cleaning rollers are rotatably provided on both sides of an electrode plate so that the electrode plate is sandwiched and moved along the electrode plate. However, since the electrode plate is composed of an elastic base and a bend-protruding discharge electrode that is easily bent, it is difficult to adjust the pressure contact force or friction force to the electrode plate with a single cleaning roller. If it is strong, the pointed discharge electrode is deformed. Accordingly, the pressure contact force / friction force is inevitably set to be weak, and the discharge product can be removed, but the effect of removing deposits such as toner and dust is insufficient.

  Further, Patent Document 2 discloses that a pin-like discharge electrode is sandwiched between a pair of brushes or flocked members and cleaned by moving the brush or flocked member along the electrode plate. However, this provides a sufficient cleaning effect, but causes a problem that the lateral stress acting on the cuspid discharge electrode is increased and the discharge electrode is bent.

Furthermore, Patent Documents 3 and 4 disclose cleaning means in which an electrode cleaner is moved while being positioned by a guide member so that an excessive force does not act on the pointed discharge electrode. However, this cleaning means has a complicated structure, a large number of parts, and the positional accuracy is not always accurate.
JP 7-43990 A Japanese Patent Laid-Open No. 9-190051 JP-A-6-83167 JP-A-6-161219

  Accordingly, an object of the present invention is to provide a corona discharge device and a process cartridge that have a simple and inexpensive configuration and that do not cause deformation of the pointed discharge electrodes, as well as effective removal of discharge products and toner. And providing an image forming apparatus.

In order to achieve the above object, the present invention provides a corona discharge device having an electrode plate in which a plurality of pointed discharge electrodes are arranged in a row on a long base, and is rubbed against at least one surface of the electrode plate. The cleaning member comprises a first portion that rubs against the base and a second portion that rubs against the pointed discharge electrode, and the hardness of the second portion is smaller than the hardness of the first portion. Ku, first and second portions are integrally held side by side in a direction along and said at least one surface in a direction perpendicular to the longitudinal direction of the electrode plate and the first portion The second portion is rubbed simultaneously with the cuspid discharge electrode at the base .

  In the corona discharge device according to the present invention, the first portion of the cleaning member is hard and rubs against the base of the electrode plate, thereby restricting the pressure with which the second portion rubs the pointed discharge electrode. And since the 2nd part which rubs against a cuspid-shaped discharge electrode is soft, deposits, such as a discharge product and a toner, can be removed effectively, without changing a cuspid-shaped discharge electrode. In addition, the cleaning member may have a simple and inexpensive configuration in which the electrode plate is rubbed with a roller shape or a block shape.

  In the corona discharge device according to the present invention, the cleaning member may be made of a different material between the first part and the second part, or different in friction resistance between the first part and the second part of the cleaning member. Also good. It is the second part that contributes to cleaning of the deposits substantially by the cleaning member, and the material of the second part and the material that exhibits a favorable cleaning effect without deforming the pointed discharge electrode due to frictional resistance. Or friction resistance.

  Further, the cleaning member may be a roller capable of rubbing the surface of the electrode plate. In this case, the outer diameter of the second portion is preferably larger than the outer diameter of the first portion. The first portion having a relatively high hardness can be rubbed against the base of the electrode plate to function as a position restricting member, and the pressure at which the second portion rubs against the pointed discharge electrode can be maintained constant.

  Alternatively, the cleaning member may be composed of a plurality of block members so as to be movable in the longitudinal direction of the electrode plate, and the second portion may be divided into a plurality of small blocks in the movement direction. In this case, the material or hardness may be different for each small block. For each small block of the second portion, it is possible to obtain a material or hardness that is preferable for removing discharge products or deposits such as toner.

  Furthermore, it is preferable that a pair of the cleaning members is provided on both surfaces of the electrode plate. It can be effectively cleaned from both sides of the electrode plate.

  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.

(See schematic configuration of image forming apparatus, FIG. 1 and FIG. 2)
FIG. 1 shows a schematic configuration of an electrophotographic color printer 10 as an image forming apparatus, which is configured to synthesize four color images by a so-called tandem method. FIG. 2 shows details of the image forming unit.

  Briefly, four process cartridges 20 including a photosensitive drum 25, a developing device 26, a residual toner cleaning device 27, a corona discharge device 28, a residual charge eraser lamp 29, and the like are provided at a substantially central portion of the apparatus main body 11. Are juxtaposed directly below the transfer belt 35. The transfer belt 35 is rotationally driven in the direction of arrow a, and the process cartridge 20 is installed along the rotational direction to form yellow, magenta, cyan, and black images. Further, an exposure device 30 for exposing an image on each photosensitive drum 25 is installed below each photosensitive drum 25.

  Each photosensitive drum 25 is rotationally driven in a clockwise direction indicated by an arrow b. First, a predetermined charge is uniformly applied by the corona discharge device 28, and the exposure device 30 scans light modulated based on image data. To form an electrostatic latent image. The electrostatic latent image is developed (visualized) with toner by the developing device 26 and is primarily transferred to the transfer belt 35. The photosensitive drum 25 continues to rotate after the primary transfer, and residual toner is removed by the cleaning device 27 and residual charges are removed by the eraser lamp 29.

  The transfer belt 35 is rotationally driven in the direction of arrow a by the support rollers 36 and 37 and the tension roller 38, and a secondary transfer roller 39 is disposed at a portion (secondary transfer portion) facing the support roller 36 with the transfer belt 35 interposed therebetween. Has been. Further, a primary transfer roller 32 is disposed inside the transfer belt 35 at a position (primary transfer portion) that faces each photosensitive drum 25.

  In the lower part of the apparatus main body 11, an automatic paper feeding unit 40 that feeds stacked sheets one by one is installed. A fixing device 45 is installed immediately above the secondary transfer portion.

  The toner images formed on the respective photoconductive drums 25 are successively primary-transferred sequentially onto a transfer belt 35 that is rotationally driven in the direction of arrow a, where four color images are combined. On the other hand, the sheets are fed one by one from the automatic sheet feeding unit 40 and are sandwiched between the transfer belt 35 and the transfer roller 39 by the secondary transfer unit, and the composite image is secondarily transferred. Thereafter, the sheet is conveyed to the fixing unit 45 where the toner is heated and fixed, and is discharged onto the tray 12.

  A cleaning device 33 for removing residual toner on the belt 35 and a waste toner collection box 34 are installed on the left side of the transfer belt 35. The toner removed from the photosensitive drum 25 by the cleaning device 27 of each process cartridge 20 is also collected in this box 34 through a conveyance path (not shown).

(Corona discharge device, see FIGS. 2 and 3)
As schematically shown in FIG. 2, the corona discharge device 28 is provided with an electrode plate 60 in a stabilizing plate 51 in which a grid electrode 55 is provided in an opening. As shown in FIG. 3, the electrode plate 60 has a long base 61 and a large number of pointed discharge electrodes 62 arranged in a row. The thickness of the electrode plate 60 is 30 to 80 μm, the angle between the two sides forming the apex of the discharge electrode 62 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 60, and corona discharge is generated from the pointed discharge electrode 62 toward the photosensitive drum 25. Further, a voltage of −300 to −900 V is applied to the grid electrode 55 to adjust the charging potential of the photosensitive drum 25 to a desired value.

(See first example of cleaning member, FIGS. 3 to 7)
Here, the configuration and operation of the cleaning member 70 as the first example will be described with reference to FIGS. As shown in FIGS. 5 and 6, the cleaning member 70 is composed of a pair of cleaning rollers 71 installed so as to sandwich both surfaces of the electrode plate 60, and an elastic roller material 72 provided on the upper portion of the rollers 71. Yes. As shown in FIG. 6, the cleaning roller 71 includes a lower large-diameter portion 71a and an upper small-diameter portion 71b, and the elastic roller material 72 is bonded to the small-diameter portion 71b.

  The large diameter portion 71 a of the cleaning roller 71 corresponds to a first portion that rubs against the base portion 61 of the electrode plate 60, and the elastic roller material 72 corresponds to a second portion that rubs against the pointed discharge electrode 62. FIG. 3 shows a positional relationship in which the large diameter portion 71 a rubs against the base portion 61, and a positional relationship in which the elastic roller material 72 rubs against the pointed discharge electrode 62.

  The cleaning roller 71 is made of a metal material, a resin material, a rubber material, or the like, which is a relatively hard material. The elastic roller material 72 is made of a single material such as polyurethane foam or felt, or a composite material thereof, which is a material having a relatively low hardness. The elastic roller material 72 is set to have a slightly larger outer diameter than the large diameter portion 71 a of the cleaning roller 71.

  As shown in FIGS. 6 and 7, the cleaning roller 71 is rotatably attached to a support shaft 85 of a frame-shaped holder 80 made of a resin molded product. Referring to FIG. 6 showing the unfolded state, the holder 80 includes an L-shaped segment 80a and rectangular parallelepiped segments 80b and 80c. After attaching the cleaning member 70 to the support shaft 85, the holder 80 bends the connecting portions 80d and 80e to engage the lock hole portion 81 of the segment 80c with the lock claw 82 of the segment 80a, and to form the hole portion 83. It is assembled by engaging with the upper part of the support shaft 85 (see FIG. 7).

  The holder 80 has a nut portion 86 formed with a screw hole 86a on the bottom surface, and a screw shaft 87 is screwed into the screw hole 86a, and the screw shaft 87 is driven to rotate forward and backward by a motor (not shown). As a result, the cleaning roller 71 moves along with the holder 80 along the longitudinal direction of the electrode plate 60. Further, the holder 80 is guided in the moving direction by the root portion of the nut portion 86 engaging with the groove portion 51a of the stabilizing plate 51 (see FIGS. 4 and 5).

  During the movement, the large diameter portion 71a of the cleaning roller 71 slides on the base portion 61 of the electrode plate 60 and is driven to rotate by the frictional force, and the elastic roller material 72 also rubs the pointed discharge electrode 62 in synchronization. Rotate while. Based on this rotation, the elastic roller material 72 removes discharge products, toner, and dust adhering to the pointed discharge electrode 62.

  Various means can be adopted as means for moving the holder 80 (cleaning roller 71). For example, the holder 80 may be moved by a wire. Or you may comprise so that it may move manually.

  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 prints is reached in terms of the number of prints). The cleaning operation may be controlled when necessary.

  During the cleaning, the large-diameter portion 71a having a relatively large hardness slides on the base portion 61 of the electrode plate 60 to function as a position regulating member, and the outer peripheral portion of the elastic roller material 72 having a relatively small hardness is a pointed protrusion. The pressure for rubbing against the discharge electrode 62 is kept constant. Thereby, deformation and breakage of the cuspid discharge electrode 62 are prevented in advance, and a desired cleaning effect can be obtained. Further, when the outer diameter of the elastic roller material 72 is large, the rotational peripheral speed of the outer peripheral surface is also increased, and the cleaning effect is improved.

  The material and hardness of the cleaning roller 71 need to be selected so that the large-diameter portion 71 a can rotate by sliding against the base portion 61. Usually, since the electrode plate 60 is made of slippery stainless steel, it is desirable that the cleaning roller 71 has a large frictional resistance (such as roughening the surface of the large diameter portion 71a) from the viewpoint of preventing poor rotation. On the other hand, the material, hardness, and frictional resistance of the elastic roller material 72 can prevent deformation and breakage of the pointed discharge electrode 62, and reliably remove deposits such as discharge products and toner. You need to choose from.

  The frictional resistance of the elastic roller material 72 does not need to be so large in order to remove discharge products, but needs to have a certain size in order to remove deposits such as toner. However, the large diameter portion 71a of the cleaning roller 71 does not need to be as large as the frictional resistance required for driven rotation.

  In order to obtain a preferable pressure contact force, the cleaning member 70 may be pressed against the electrode plate 60 by applying a spring force or the like. In addition to the urethane foam material and felt material, various materials can be widely used as the elastic roller material 72, and the elastic roller material 72 may contain abrasive fine particles.

  In the first example, if the lock hole 81 is detached from the lock claw 82 and the holder 80 is disassembled, the cleaning member 70 can be easily replaced, and the life cycle cost can be reduced.

(Refer to the second example of the cleaning member, FIGS. 8 to 10)
Next, the configuration and operation of the cleaning member 90 as the second example will be described with reference to FIGS. The cleaning member 90 is made of a block material. As shown in FIG. 8, both surfaces of the first members 91 and 91 and the pointed discharge electrodes 62 capable of sliding on both surfaces of the base 61 of the electrode plate 60 are rubbed. It is comprised by the 2nd member 95 (95a, 95b, 95c) which can rub. The second member 95 is fixed to the recesses 92 of the first member 91 facing each other by bonding.

  FIG. 9 shows a positional relationship in which the first member 91 rubs against the base 61, and a positional relationship in which the second member 95 rubs against the pointed discharge electrode 62. The first member 91 is attached to a holder (not shown), and the holder 95 reciprocates along the electrode plate 60 using a motor or a screw shaft 87 as shown in the first example. The pointed discharge electrode 62 is cleaned while being rubbed.

  Various characteristics such as hardness and material of the first member 91 and the second member 95 are the same as the relationship between the large diameter portion 71a of the cleaning roller 71 and the elastic roller material 72 shown in the first example. Accordingly, also in the second example, as in the first example, the first member 91 having a relatively high hardness functions as a position regulating member for the second member 95, and the second member 95 having a relatively low hardness is provided. The pressure for rubbing against the pointed discharge electrode 62 is kept constant. Thereby, deformation and breakage of the cuspid discharge electrode 62 are prevented in advance, and a desired cleaning effect can be obtained.

  In the second example, a resin molded product can be suitably used for the first member 91, and it is preferable that the frictional resistance is small in relation to the base 61. For the second member 95, the same material as in the first example can be used. In particular, in the second example, the hardness is varied for each member 95a, 95b, 95c divided in the moving direction. That is, in terms of hardness, the member 95a is the smallest, the member 95c is the largest, and the member 95b is an intermediate value thereof. The hardness of each member 95a, 95b, 95c is adapted to the discharge product, toner, dust and the like to be removed. The discharge product can be removed even if the material is not so hard, and deposits such as toner and dust can be effectively removed by using a material having a certain degree of hardness.

  In addition, the members 95a, 95b, and 95c may have different materials as well as hardness. For example, a felt material may be used for the members 95a and 95c, and a urethane foam material may be used for the member 95b. Of course, the number of divisions of the second member 95 is arbitrary.

(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 62 is not limited to a triangular shape, and may be a conical shape or a pin shape, for example. Further, the corona discharge device 28 may be in a form that can be detachably attached to the image forming apparatus by itself, or as the process cartridge 20 including the photosensitive drum 25 and the developing device 26 as shown in the above-described embodiment. The image forming apparatus may be configured to be detachable. In this case, the type of image forming element included in the process cartridge 20 is arbitrary. Further, the photosensitive drum 25 is not necessarily required as a member to be charged by the corona discharge device 28.

  In the above-described embodiment, the pair of cleaning members 70 and 90 are arranged on both surfaces of the electrode plate 60. However, only one of the surfaces may be rubbed.

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. 2 is a cross-sectional view illustrating an image forming unit of the image forming apparatus. FIG. It is explanatory drawing which shows the positional relationship of the electrode plate of a corona discharge device, and the 1st example of a cleaning member. It is sectional drawing which shows the corona discharge device which provided the 1st example of the cleaning member. It is sectional drawing which shows the 1st example of the cleaning member. It is a perspective view which shows the state which expand | deployed the holder in the 1st example of the cleaning member. It is a perspective view which shows the state which assembled the said holder. It is a disassembled perspective view which shows the 2nd example of the cleaning member. It is explanatory drawing which shows the positional relationship of the electrode plate of a corona discharge device, and the 2nd example of the cleaning member. The 2nd example of the cleaning member is shown, (A) is a top view and (B) is a sectional view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electrophotographic color printer 25 ... Photosensitive drum 28 ... Corona discharge device 60 ... Electrode plate 61 ... Base part 62 ... Point-like discharge electrode 70 ... Cleaning member 71 ... Cleaning roller 71a ... Large diameter part 72 ... Elastic roller material 90 ... Cleaning member 91 ... first member 95 (95a, 95b, 95c) ... second member

Claims (8)

In a corona discharge device having an electrode plate in which a plurality of pointed discharge electrodes are arranged in a row on a long base,
A cleaning member that rubs against at least one surface of the electrode plate, the cleaning member including a first portion that rubs against the base portion and a second portion that rubs against the pointed discharge electrode; the hardness of the part is rather smaller than the hardness of the first portion,
The first portion and the second portion are integrally held side by side in a direction perpendicular to the longitudinal direction of the electrode plate and along the at least one surface, and the first portion is the base portion In addition, the second portion is rubbed simultaneously with the pointed discharge electrode,
A corona discharge device.   The corona discharge device according to claim 1, wherein the first portion and the second portion of the cleaning member are made of different materials.   The corona discharge device according to claim 1, wherein the first portion and the second portion of the cleaning member have different frictional resistance.   The said cleaning member is a roller which can rub the surface of the said electrode plate, The outer diameter of a 2nd part is large with respect to the outer diameter of a 1st part, The Claim 2, Claim 2 or Claim characterized by the above-mentioned. 3. The corona discharge device according to 3.   The cleaning member is composed of a plurality of block materials, and is movable in the longitudinal direction of the electrode plate. The second portion is divided into a plurality of small blocks in the moving direction, and the material or hardness is different for each small block. The corona discharge device according to claim 1.   The corona discharge device according to any one of claims 1 to 5, wherein a pair of the cleaning members are provided on both surfaces of the electrode plate.   A process cartridge comprising the corona discharge device according to any one of claims 1 to 6.   An image forming apparatus comprising the corona discharge device according to claim 1 or the process cartridge according to claim 7.

Images