JP2006301484A - Discharging device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharging device capable of preventing a voltage applied to a discharge electrode from rising to prevent, for example, charging efficiency of a photoreceptor drum from decreasing, and an image forming apparatus equipped with the same. <P>SOLUTION: A conductive projection portion 36 is provided on the surface of a grid electrode 37 on the side of a discharge wire 33, so a non-uniform electric field is produced in the discharge space between the discharge wire 33 and grid electrode 37 and then even when the discharge wire 33 and grid electrode 37 are contaminated, the electric field concentrates on nearby the projection portion 36 to become intense. Consequently, electrons 38, negative ions or positive ions are strongly attracted to the surface of the grid electrode 37 on the side of the discharge wire 33 to make small a voltage applied to the discharge wire 33. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention particularly relates to a discharge device having a discharge electrode and a counter electrode, and an image forming apparatus including the discharge device.

In a conventional image forming apparatus, a corona charger provided with a discharge wire (discharge electrode) for corona discharge on the surface of a photosensitive drum, a counter electrode (grid electrode) disposed in the vicinity of the corona charger, The one with is known.
JP-A-8-160712 JP 2001-307859 A JP-A-11-295965 Japanese Patent Laid-Open No. 7-20682 JP-A-8-286469 JP 2002-221848 A

  By the way, when the photosensitive drum is charged by the corona charger, silica or toner may adhere to the discharge electrode or grid electrode and be contaminated. In particular, when constant current control is performed, these contaminations become a factor for increasing the voltage applied to the discharge electrode. Specifically, when the constant current is controlled to be −300 μA, it is necessary to apply a voltage of −5 kV to the discharge electrode. However, when the discharge electrode is contaminated, the constant current control of −300 μA is realized. Therefore, it is necessary to apply a voltage of −6 kV to −7 kV to the discharge electrode. On the other hand, when the constant voltage control is performed, a phenomenon such as a decrease in inflow voltage with respect to the discharge electrode occurs, and there is a problem that the charging efficiency of the photosensitive drum is deteriorated.

  Accordingly, in consideration of the above circumstances, the present invention provides a discharge device capable of preventing an increase in applied voltage to the discharge electrode, for example, preventing a reduction in charging efficiency of the photosensitive drum, and an image forming apparatus including the discharge device. The purpose is to provide.

  The invention according to claim 1 is a discharge device having a first electrode that generates electrons, negative ions, or positive ions when a voltage is applied thereto, and a second electrode that attracts the electrons, negative ions, or positive ions. And the electroconductive protrusion part is provided in the surface at the side of the 1st electrode of the said 2nd electrode, It is characterized by the above-mentioned.

  According to the first aspect of the present invention, since the conductive protrusion is provided on the surface of the second electrode on the first electrode side, the gap between the first electrode and the second electrode is provided. Even when the discharge space becomes an unequal electric field and the first electrode and the second electrode are contaminated, the electric field concentrates near the protrusion and becomes stronger. Thereby, electrons, negative ions, or positive ions are strongly attracted to the surface on the first electrode side of the second electrode, and the voltage applied to the first electrode can be reduced.

  According to a second aspect of the present invention, in the discharge device according to the first aspect, the protrusion is formed in a fluff shape.

  According to the invention described in claim 2, since the protrusion is formed in a fluff shape, the electric field can be effectively concentrated in the vicinity of the protrusion, and a large electric field can be generated in the vicinity of the protrusion. it can.

  According to a third aspect of the present invention, in the discharge device according to the first or second aspect, the protrusion is configured by attaching a carbon fiber or a carbon sheet to a surface on the first electrode side of the second electrode. It is characterized by being.

  According to the third aspect of the present invention, the projecting portion is configured by attaching a carbon fiber or a carbon sheet to the surface of the second electrode on the first electrode side. It can be used as it is. As a result, the manufacturing cost can be reduced.

  According to a fourth aspect of the present invention, in the discharge device according to the first or second aspect, the protrusion is formed by roughening a surface on the first electrode side of the second electrode. It is characterized by.

  According to the invention described in claim 4, the protrusion is formed by roughening the surface of the second electrode on the first electrode side, whereby the first electrode side of the second electrode is formed. Protrusions can be easily formed on the surface.

  The invention according to claim 5 has a member to be charged which is charged by the electrons, negative ions or positive ions generated from the first electrode, and according to any one of claims 1 to 4. A discharge device is used as a charger.

  According to the invention described in claim 5, by using the discharge device according to any one of claims 1 to 4 as the charger in the image forming apparatus, the electric field concentrates on the second electrode and becomes stronger. The voltage applied to the first electrode can be reduced. Thereby, even when the first electrode and the second electrode are contaminated, it is possible to prevent the charging efficiency of the member to be charged from decreasing.

  According to the present invention, an increase in the voltage applied to the discharge electrode can be prevented, and for example, a reduction in charging efficiency of the photosensitive drum can be prevented.

  Next, a discharge device and an image forming apparatus including the same according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the charger used in the image forming apparatus will be described as an example of the discharge device. However, the discharge device of the present invention is not limited to the charger used in the image forming apparatus, and for example, an air cleaner or the like. It is applied to the general discharge device used in the above.

  First, an outline of the image forming apparatus 1 included in a copying machine, a facsimile machine, or the like will be described.

  As shown in FIG. 1, the image forming apparatus 1 is disposed above the paper feed cassette 5, and a paper discharge tray 6 is formed above the image forming apparatus 1. Inside the image forming apparatus 1, there are formed a main transport path 11 for transporting the recording paper fed from the paper feed cassette 5 to the paper discharge tray 6, and a reversing path 12 for inverting the back side of the recording paper. ing. The reverse path 12 is arranged outside the main transport path 11 and is configured to branch and merge with the main transport path 11. In the image forming apparatus 1, a developing unit 2, a photosensitive drum unit 3, and a fixing unit 4 are arranged along the main conveyance path 11 toward the downstream side (upward).

  The photosensitive drum unit 3 includes a photosensitive drum (charged member) 31 having a photoconductive film on its outer peripheral surface as a photosensitive member, and a grid electrode 37 (for applying a predetermined negative or positive charge to the surface of the photosensitive drum 31). 1 includes a second electrode (not shown), a charger (discharge device) 32 that charges the outer peripheral surface of the photosensitive drum 31, and the like, and a discharge wire 33 (shown in FIG. 1) provided in the charger 32. When a high voltage is applied to the first electrode), corona discharge is generated, and negative or positive charges are uniformly applied to the outer peripheral surface of the photosensitive drum 31 by corona discharge.

  An exposure unit (not shown) is disposed obliquely above the photosensitive drum 31. The exposure unit is composed of a laser scanner unit or the like, and is arranged on the outer peripheral surface of the photosensitive drum 31 charged by the charger 32. Based on the input image information, the exposure light beam 50 is irradiated, the negative or positive charge of the portion irradiated with the exposure light beam 50 is erased, and the electrostatic surface corresponding to the image information is applied to the outer peripheral surface of the photosensitive drum 31. A latent image is formed.

  The developing unit 2 includes a supply roller 21 and a developing roller 22. The supply roller 21 supplies toner to the developing roller 22 while charging the toner negatively or positively from the toner case 20 containing the toner, and the developing roller 22 supplies the toner to the photosensitive drum 31 on which the electrostatic latent image is formed. The toner is attached only to the portion where the negative charge on the photosensitive drum 31 is erased by electrostatic force.

  A transfer roller 61 is disposed across the main conveyance path 11 so as to be in contact with the outer peripheral surface of the photosensitive drum 31. As a result, the recording paper is fed into the nip portion between the photosensitive drum 31 and the transfer roller 61, and a bias voltage is applied to the transfer roller 61 from the back side of the recording paper that is in close contact with the photosensitive drum 31, thereby negative or positive. The charged toner is transferred from the photosensitive drum 31 to the recording paper.

  The fixing device unit 4 includes a heat roller 41 and a press roller 42 that is disposed so as to sandwich the main transport path 11 so as to be in pressure contact with the outer peripheral surface of the heat roller 41. As a result, the recording paper is fed into the nip portion between the heat roller 41 and the press roller 42, and the recording paper after transfer is heated and pressed by the heat roller 41 and the press roller 42 to fix the toner image on the recording paper. Like that.

  As described above, the image information is formed on the recording paper fed from the paper feed cassette 5, fixed by the fixing unit 4, and then discharged to the paper discharge tray 6. .

  Next, the photosensitive drum unit 3 will be described.

  As shown in FIG. 1, a photosensitive drum 31 is arranged at the lower part (side part on the transfer roller 61 side) of the photosensitive drum unit 3, and a charger 32 is arranged at the upper part. The photosensitive drum 31 and the charger 32 are housed in the frame 30.

  An opening is formed in the lower part of the frame 30 (side part on the transfer roller 61 side), and the photosensitive drum 31 is rotatably supported by the frame 30. Further, a part of the outer peripheral surface of the photosensitive drum 31 is exposed from the opening, and the exposure unit exposes the exposure light beam 50 toward the outer peripheral surface of the photosensitive drum 31 exposed from the opening. It is comprised so that it may irradiate.

As shown in FIG. 2, the charger 32 includes a discharge wire (first electrode) 33 that performs corona discharge on the surface of the photosensitive drum 31. A grid electrode (second electrode) 37 and the photosensitive drum 31 are located below the discharge wire 33. The grid electrode 37 and the photosensitive drum 31 are provided over the entire extending direction of the discharge wire 33. The grid electrode 37 is formed in a mesh shape having an opening and a non-opening. The discharge wire 33 and the grid electrode 37 are accommodated in the shield case 35. When a negative high voltage is applied to the discharge wire 33, the surrounding air is ionized and electrons 38 or negative ions (for example, CO ₃ ⁻ , CO ₃ ⁻ (H ₂ O), O ⁻ , O ₃ ⁻ ) are used. Are generated, and the electrons 38 or negative ions are attracted to the grid electrode 37. As shown in FIG. 4, when a positive high voltage is applied to the discharge wire 33, the surrounding air is ionized and positive ions (for example, (H ₂ O) _n H ⁺ , H ⁺ , (H ₂₎ O) _n NO ⁺ ) 39 is generated, and the positive ions 39 are attracted to the grid electrode 37.

  Here, as shown in FIG. 2, a plurality of fluffy and conductive protrusions 36 are provided on the surface of the grid electrode 37 on the discharge wire 33 side. The protrusion 36 is configured by attaching a carbon fiber or a carbon sheet to the surface of the grid electrode 37 on the discharge wire 33 side.

  Further, the protrusion 36 is not limited to the case where the carbon fiber or the carbon sheet is attached to the surface of the grid electrode 37 on the discharge wire 33 side, and as shown in FIG. The surface of the 37 on the discharge wire 33 side may be formed by roughing (for example, blasting).

  Next, the operation of the discharge device according to the embodiment of the present invention and the image forming apparatus including the discharge device will be described.

  As shown in FIG. 2 and FIG. 3, since a plurality of conductive protrusions 36 are provided on the surface of the grid electrode 37 on the discharge wire 33 side, a discharge space between the discharge wire 33 and the grid electrode 37 is created. Even when the electric field becomes unequal and the discharge wire 33 and the grid electrode 37 are contaminated, the electric field concentrates in the vicinity of the protrusion 36 and becomes stronger. Thereby, electrons 38, negative ions, or positive ions are strongly attracted to the surface of the grid electrode 37 on the discharge wire 33 side, and the voltage applied to the discharge wire 33 can be reduced. As a result, even when the discharge wire 33 and the grid electrode 37 are contaminated, it is possible to prevent the charging efficiency of the photosensitive drum 31 from being lowered.

  In particular, as shown in FIG. 2, since the protrusion 36 is formed in a fluff shape, the electric field can be effectively concentrated in the vicinity of the protrusion 36, and a large electric field is generated in the vicinity of the protrusion 36. Can be made.

  Further, the carbon fiber or the carbon sheet is attached to the surface of the grid electrode 37 on the discharge wire 33 side to form the protrusion 36, so that the existing conductive member can be used as it is. As a result, the manufacturing cost can be reduced.

  Further, as shown in FIG. 3, the surface of the grid electrode 37 on the discharge wire 33 side is roughened to form the protrusion 36 so that the protrusion 36 can be easily formed on the surface of the grid electrode 37 on the discharge wire 33 side. Can be formed.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a charger used in an image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram of the modification of the charger used for the image forming apparatus which concerns on one Embodiment of this invention. It is a schematic block diagram of the modification of the charger used for the image forming apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

1 Image forming apparatus 31 Photosensitive drum (charged member)
32 Charger (discharge device)
33 Discharge wire (first electrode)
36 Projection 37 Grid electrode (second electrode)
38 electrons

Claims (5)

A discharge device having a first electrode that generates electrons, negative ions, or positive ions when a voltage is applied thereto, and a second electrode that attracts the electrons, negative ions, or positive ions,
A discharge device, wherein a conductive protrusion is provided on a surface of the second electrode on the first electrode side.   The discharge device according to claim 1, wherein the protrusion is formed in a fluff shape.   The discharge device according to claim 1, wherein the protrusion is configured by attaching a carbon fiber or a carbon sheet to a surface of the second electrode on the first electrode side.   The discharge device according to claim 1, wherein the protrusion is formed by roughening a surface of the second electrode on the first electrode side. A member to be charged which is charged by the electrons, negative ions or positive ions generated from the first electrode;
An image forming apparatus using the discharge device according to claim 1 as a charger.

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