JP2012078668A - Discharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharger capable of preventing troubles due to dropping of deposits, such as discharge products and scattered materials, onto a surface of a processing object.SOLUTION: A discharger 2 for discharging a processing object 1 located below to electrify or remove electricity from a surface of the processing object is configured to include: a discharge electrode 10 having an axial line; a shield 12 which has an inner surface 12b1 facing the discharge electrode 10 and an opposite outer surface 12b2 and includes a side plate 12b extending approximately in parallel with the axial line; a grid electrode 11 disposed between the discharge electrode 10 and the surface of the processing object; and a dropping object reception part 30 of planar shape which is disposed between the side plate 12b and the surface of the processing object 1 and is continuous from the inner surface 12b1 side to the outer surface 12b2 side of the side plate 12b in a direction approximately orthogonal to the axial line.

Description

  The present invention relates to a discharge device used in an electrophotographic apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile machine.

  In an image forming apparatus using an electrophotographic system, an electrostatic latent image is formed on the surface of the photoconductor by charging the surface of the electrophotographic photoconductor (photoconductor) and then exposing according to image information. As a method for charging the surface of the photoreceptor, a method using a corona charger as a discharge device is widely used.

  The corona charger has a configuration in which discharge lines (discharge electrodes) are stretched between blocks that are holding members provided at both ends of a shield (shield case) that is a support housing that is open on one side. The shield is typically made of stainless steel (hereinafter also referred to as “SUS”). Further, the discharge wire is made of a wire material such as tungsten. When charging the charged surface of a charged member such as a photoconductor using a corona charger, the opening of the shield is opposed to the charged surface and a discharge current is supplied to the discharge line to corona discharge. To generate a charge on the surface of the surface to be charged.

  The charged potential of the surface to be charged is controlled by providing a grid (grid electrode) between the discharge line and the surface to be charged and adjusting the amount of charge applied to the surface to be charged by the grid bias applied to the grid. . As the grid, a wire-shaped grid mainly formed of the same kind of material as the discharge line or SUS or a porous plate-shaped grid in which a large number of holes are formed by etching or the like are known.

  Contaminants such as toner are likely to adhere to the wire-shaped grid, and the function of controlling the charged potential of the charged surface becomes insufficient due to the adhesion of the contaminated material, and the charged potential of the charged surface becomes uneven. There is a case.

  The plate-shaped grid has a relatively large area compared to the wire-shaped grid, so that the charged potential of the surface to be charged can be controlled within an appropriate range. Little decrease in potential controllability. Further, a plate-like grid formed of SUS has high durability, does not deform even when used for a long time, and changes in controllability of the charged potential accompanying deformation are very small. Therefore, the porous plate-like grid as described above is suitable for controlling the charged potential of the surface to be charged to be substantially constant over a long period of time.

  By the way, when the corona charger is used in a high-temperature and high-humidity environment, uneven charging on the surface to be charged may occur in the longitudinal direction of the corona charger, which may cause image defects such as density spots. The cause is considered as follows. That is, an insulating metal oxide is generated as a discharge product on the surface of the grid by a chemical reaction with a discharge product generated by corona discharge. Due to the partial insulation of the grid by the discharge product, the amount of charge injected into the grid decreases, the charge in the direction of the surface to be charged increases, and as a result, the charged potential becomes uneven. A plate-like grid having a mesh-like opening is known. In such a plate-shaped grid, charging unevenness may occur due to a discharge product or the like closing a mesh-shaped opening. Such discharge products are generated not only in the grid but also in other members in the corona charger. In general, SUS is a material exhibiting excellent corrosion resistance in a normal atmospheric environment as compared with other metals, but the above-mentioned problems may occur particularly when used as a member of a discharge device. .

  Further, in the apparatus main body of the image forming apparatus, scattered matter (dust) such as toner, external additives, and paper dust is scattered, and the scattered matter adheres electrostatically to members in the corona charger. , May physically adhere. Such adhesion of scattered matter may cause problems due to the above-described charging unevenness.

  It has been proposed that a cleaning member is disposed in the corona charger to clean the deposits such as discharge products and scattered matter as described above. Japanese Patent Application Laid-Open No. H10-228707 discloses cleaning the deposits attached to the discharge lines with a cleaning member. Japanese Patent Application Laid-Open No. H10-228707 discloses cleaning the deposits attached to the grid with a cleaning member. Japanese Patent Application Laid-Open No. H10-228561 discloses that the adhering matter adhering to the shield is cleaned with a cleaning member.

JP 2004-085814 A JP 2005-338797 A JP 2003-295585 A

  However, the adhering matter adhering to the member in the corona charger may not be collected by the cleaning member and may fall onto the surface of the photosensitive member that is the surface to be charged as a processing target, for example. As a result, the fallen deposits are taken into the developing device, and if the deposits are toner, they may be mixed, and if they are foreign, they may cause clogging in the gap between the developer carrying member and the photosensitive member. For this reason, the fall of the adhering matter may be a cause of an image defect, and thus a decrease in the operating rate of the image forming apparatus due to parts replacement and an increase in the cost required for service.

  Further, the fallen deposits are exposed to corona discharge during image formation, so that discharge products are deposited. For this reason, for example, when this deposit falls on the surface of the photoconductor, it may affect the formation of a latent image on the photoconductor, which may cause an image flow.

  Accordingly, an object of the present invention is to provide a discharge device capable of preventing problems caused by deposits such as discharge products and scattered objects falling on the surface of the object to be treated.

  The above object is achieved by the discharge device according to the present invention. In summary, the present invention relates to a discharge device that discharges a processing target located below and charges or discharges the surface of the processing target, a discharge electrode having an axis, an inner surface facing the discharge electrode, and A shield having a side plate having an outer surface on the opposite side and extending substantially parallel to the axis, a grid electrode disposed between the discharge electrode and the surface of the processing target, the side plate and the processing target And a flat fallen object receiving portion that is continuous from the inner surface side to the outer surface side of the side plate in a direction substantially orthogonal to the axis. .

  ADVANTAGE OF THE INVENTION According to this invention, the malfunction by deposits, such as a discharge product and a scattered matter, falling on the surface of a process target can be prevented.

1 is a schematic cross-sectional view of a main part of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic perspective view of a charger according to an embodiment of the present invention. It is a schematic plan view of the grid with which the charger which concerns on one Example of this invention is provided. It is a schematic perspective view for demonstrating the cleaning member with which the charger which concerns on one Example of this invention is provided. It is a schematic perspective view for demonstrating the other example of the cleaning member applicable to the charger which concerns on one Example of this invention. FIG. 5 is a schematic diagram for explaining an arrangement relationship between a shield and a grid of a charger according to an embodiment of the present invention. It is a graph which shows the relationship between (DELTA) d1 (= Wg-Ws) and the fall amount of the standardized deposit | attachment. It is a schematic perspective view which shows the shield and shielding member of the charger which concern on the other Example of this invention. It is a schematic diagram for demonstrating the arrangement | positioning relationship between the shield and shielding member which concern on the other Example of this invention. It is a graph which shows the relationship between (DELTA) d2 (= Wb-Ws) and the fall amount of the deposit | attachment normalized.

  Hereinafter, the discharge device according to the present invention will be described in more detail with reference to the drawings.

Example 1
1. Image Forming Apparatus First, the overall configuration and operation of an embodiment of an electrophotographic image forming apparatus provided with a discharge device according to the present invention will be described.

  FIG. 1 shows a schematic configuration of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 includes a drum-type electrophotographic photosensitive member (photosensitive member) as an image carrier, that is, a photosensitive drum 1, which is rotationally driven in the direction of arrow R1 (counterclockwise). The following means are arranged around the photosensitive drum 1. First, a charger (corona charger) 2 which is a discharging device as a charging means. Next, an exposure apparatus (laser beam scanner) 3 as an exposure means (information writing means). Next, there is a developing device 4 as a developing unit. Next, there is a transfer device 5 as a transfer means. Next, there is a cleaning device 7 as a cleaning means.

  At the time of image formation, the surface of the rotating photosensitive drum 1 is charged to a constant potential by the charger 2. Thereafter, the surface of the charged photosensitive drum 1 is exposed by the exposure device 3 according to the image information. As a result, an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is developed as a toner image (developer image) with the developer toner attached by the developing device 4. The toner image formed on the photosensitive drum 1 is primarily transferred in the transfer device 5 by the primary transfer roller 5a as the primary transfer member onto the intermediate transfer belt 5b as the transfer target.

  Thereafter, the toner image on the intermediate transfer belt 5b is secondarily transferred onto a transfer material such as recording paper by a secondary transfer roller (not shown) as a secondary transfer member. Thereafter, the transfer material is heated and pressurized by a heating and pressure type fixing device (not shown) as a fixing means, and the toner image is fixed thereon.

  On the other hand, toner remaining on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 5b (transfer residual toner) is removed from the surface of the photosensitive drum 1 by the cleaning device 7 and collected. The cleaning device 7 scrapes off the toner from the surface of the photosensitive drum 1 by the cleaning blade 7a and the fur brush 7b disposed in contact with the photosensitive drum 1, and collects the toner in the collection container 7c. In addition, a charge pre-exposure unit 8 as a first pre-exposure unit and a second pre-exposure are disposed around the photosensitive drum 1 as a charge eliminating unit for eliminating a potential remaining on the surface of the photosensitive drum 1. A pre-cleaning exposure unit 9 as means is provided.

2. Photosensitive Drum The image forming apparatus 100 includes a drum-type electrophotographic photosensitive member (photosensitive member) that can rotate as an image carrier, that is, a photosensitive drum 1. The photosensitive drum 1 is a member to be charged as a processing target by the charger 2. This photosensitive drum 1 has a photosensitive layer formed of OPC (organic optical semiconductor) having negative charging characteristics. The photosensitive drum 1 has a diameter of 84 mm, and is driven to rotate in the direction of the arrow R <b> 1 at a process speed (circumferential speed) of 285 mm / sec around the center support shaft.

3. Charger (non-contact charging device)
The image forming apparatus 100 includes a charger (corona charger) 2 serving as a charging unit as a discharge device that discharges a processing target positioned below in the direction of gravity and charges or discharges the surface of the processing target. FIG. 2 shows the external appearance of the charger 2. The charger 2 is disposed to face the photosensitive drum 1 along the longitudinal direction (rotational axis direction) of the photosensitive drum 1 and charges the surface of the photosensitive drum 1 by discharging.

  The charger 2 includes a shield (shield case) 12 that is a support housing that performs an electrical shield action (blocking action). The shield 12 is electrically grounded. The shield 12 has two side plates 12b, 12b extending in parallel with each other along the longitudinal direction of the photosensitive drum 1, and a top plate 12c connecting the upper ends of the side plates 12b, 12b. . As a result, one surface of the shield 12 facing the photosensitive drum 1 is opened, and a cross section viewed in the longitudinal direction of the charger 2 (parallel to the rotational axis direction of the photosensitive drum 1) is substantially U-shaped. That is, the side of the shield 12 facing the photosensitive drum 1 has a length in the longitudinal direction of the charger 2 and a width in the short direction of the charger 2 (a direction substantially perpendicular to the rotational axis direction of the photosensitive drum 1). A rectangular opening 12a is formed. If desired, the top plate 12c may not be provided. Blocks 17 and 17 that are holding members for holding the side plates 12 b and 12 b, the top plate 12 c and the like are coupled to both ends of the shield 12 in the longitudinal direction of the charger 2, and are integrated with the shield 12. The side plates 12b and 12b and the top plate 12c of the shield 12 are made of a metal such as aluminum or stainless steel (SUS) (SUS in this embodiment), and the blocks 17 and 17 are electrically insulating materials such as resin (this embodiment). In this case, the resin is formed. Further, the charger 2 has a discharge wire 10 that is a discharge line (discharge electrode) having an axis in the internal space of the shield 12. The discharge wire 10 is stretched between the two blocks 17 so that the axis thereof is substantially parallel to the longitudinal direction of the charger 2 (that is, the axial direction of the photosensitive drum 1). Further, the charger 2 has a plate-like grid (grid electrode) 11 serving as a control electrode, which is positioned in the opening 12 a facing the photosensitive drum 1 of the shield 12. A first charging power source (not shown) is connected to the discharge wire 10, and a DC voltage is applied when the photosensitive drum 1 is charged. When the first charging power source applies a voltage to the discharge wire 10, corona discharge is generated in the discharge wire 10. The grid 11 is connected to a second charging power source (not shown), and a DC voltage is applied when the photosensitive drum 1 is charged. This is for stabilizing the amount of ions from the discharge wire 10 toward the photosensitive drum 1, and as a result, the photosensitive drum 1 can be charged to a desired potential.

  More specifically, the discharge wire 10 is connected to a first charging power source that is an external power source. A DC voltage having a predetermined polarity (negative polarity in this embodiment) and value is applied from the first charging power source to the discharge wire 10 to generate a corona discharge to charge the surface of the photosensitive drum 1. As a material of the discharge wire 10, a metal such as stainless steel, nickel, molybdenum, tungsten, or the like can be preferably used. In this example, tungsten, which is very stable among metals, was used as the material of the discharge wire 10. By using tungsten as the material of the discharge wire 10, stable corona discharge can be performed even under severe conditions of heating. Further, by using tungsten as the material of the discharge wire 10, the charger 2 can be used stably over a long period of time. The discharge wire 10 is held at a constant tension by the blocks 17 and 17 integrated with the support housing 12. Electrical insulation between the discharge wire 10 and the shield 12 is maintained by the blocks 17 and 17 formed of an electrically insulating material. The diameter of the discharge wire 10 is preferably 40 μm to 100 μm. If the diameter of the discharge wire 10 is too small, it may be cut by collision of ions due to discharge. Conversely, if the diameter of the discharge wire 10 is too large, the voltage applied to the discharge wire 10 necessary to obtain a stable corona discharge will be high. If the voltage applied to the discharge wire 10 is high, ozone is likely to be generated, and the cost of the power source is likely to increase. In this embodiment, the diameter of the discharge wire 10 is 60 μm.

  In addition, a constant voltage power source is connected to the grid 11 as a second charging power source which is an external power source. By controlling the bias applied to the grid 11 from the second charging power source, the amount of charge generated by corona discharge in the charging wire 10 and applied to the photosensitive drum 1 is adjusted to control the charging potential on the surface of the photosensitive drum 1. To do. In the present embodiment, the grid 11 is a porous (porous shape) plate-like grid in which a plurality of holes penetrating the side facing the photosensitive drum 1 and the side facing the discharge wire 10 are formed. . This plate-like grid 11 was produced by forming a large number of openings in a thin stainless steel plate by etching.

  More specifically, in this embodiment, as shown in FIG. 3, the grid 11 passes through a flat plate-like grid body (plate body) 11 a having a thickness of about 0.1 mm to 0.5 mm. A plurality of mesh-shaped through holes 11b are formed. The grid body 11 a has a length Lg in the longitudinal direction of the charger 2 and a width Wg in the short direction of the charger 2. In addition, the through hole 11b is formed in a region (hereinafter referred to as “longitudinal length lg (<Lg) in the longitudinal direction of the charger 2) and width wg (<Wg) in the short direction of the charger 2 at a substantially central portion of the grid body 11a. This is referred to as a “through-hole region”). That is, the grid 11 has the through-hole area | region 11c and the edge area | region surrounding the circumference | surroundings of the through-hole area | region 11c. This edge region includes edge regions 11d and 11d adjacent to both ends of the through-hole region 11c in the short direction of the charger 2, and edge regions 11e and 11e adjacent to both ends of the through-hole region 11c in the longitudinal direction of the charger 2. It consists of. The grid 11 is attached to the shield 12 so as to be positioned at the opening 12 a of the shield 12, and is disposed close to the outer peripheral surface of the photosensitive drum 1. More specifically, the grid 11 is fixed to the blocks 17 and 17 so that the through-hole region 11 c is accommodated in the opening 12 a of the shield 12. In this embodiment, the plate-like grid 11 is used. However, the present invention is not limited to this. For example, a wire-shaped grid may be used.

  In this embodiment, the charger 2 removes deposits attached to the discharge wires 10, the grid 11 and the shield 12, that is, discharge products generated by corona discharge, or scattered matter such as toner, external additives or paper dust. A cleaning member for cleaning is provided. This cleaning member will be described later.

4). Exposure Device The image forming apparatus 100 has an exposure device (laser beam scanner) 3 as exposure means (information writing means) for forming an electrostatic latent image on the surface of the charged photosensitive drum 1. In this embodiment, a laser beam scanner using a semiconductor laser is used as the exposure apparatus 3, but the present invention is not limited to this, and an exposure system using LEDs, for example, may be adopted.

5. Developing Device The image forming apparatus 100 includes a developing device 4 as a developing unit. The developing device 4 supplies developer toner to the electrostatic latent image on the photosensitive drum 1 and visualizes it as a toner image. In this embodiment, the developing device 4 is a two-component magnetic brush developing type. In this embodiment, the developing device 4 has the same charging polarity (negative polarity in this embodiment) as that of the photosensitive drum 1 in the exposed portion of the photosensitive drum 1 that has been uniformly charged. The electrostatic latent image is developed by a reversal development method in which a polar charged toner is attached.

More specifically, the developing device 4 includes a developing container 4a and a developing sleeve 4b as a developer carrying member rotatably attached to the developing container 4a. The developer container 4a contains a two-component developer in which mainly nonmagnetic toner particles (toner) and magnetic carrier particles (carrier) are mixed as a developer. As is generally done in the art, an external additive such as an inorganic fine powder may be added to the toner in order to adjust the fluidity and chargeability of the toner. In this example, the volume resistivity of the carrier was about 5 × 10 ⁸ Ω · cm, and the average particle size was 35 μm. The toner is triboelectrically charged to a negative polarity by rubbing with the carrier. The developing sleeve 4b is disposed to face the photosensitive drum 1 in a state where the closest distance (SD gap) to the photosensitive drum 1 is maintained at about 250 μm. A facing portion between the photosensitive drum 1 and the developing sleeve 4b is a developing portion. The developing sleeve 4b is rotationally driven so that the moving directions of the surfaces of the photosensitive drum 1 and the developing sleeve 4b in the developing unit are opposite to each other. That is, the developing sleeve 4b is rotationally driven in the forward direction with respect to the rotation of the photosensitive drum 1 in the arrow R1 direction. Inside the developing sleeve 4b, a magnet roller is provided as a magnetic field generating means. Due to the magnetic force, the two-component developer is transported to the developing unit as the developing sleeve 4b rotates. In the developing section, the two-component developer forms a magnetic brush layer that stands up from the surface of the developing sleeve 4b. The layer of the magnetic brush is arranged as a thin layer having a predetermined thickness by a developer coating blade (not shown). A predetermined developing bias is applied to the developing sleeve 4b from a developing power source. In this embodiment, the developing bias applied to the developing sleeve 4b is an oscillating voltage in which a direct current (Vdc) and an alternating voltage (Vac) are superimposed, the direct voltage is −650V, and the alternating voltage is Vpp1800V. By the electric field formed between the photosensitive drum 1 and the developing sleeve 4b by this developing bias, the toner in the two-component developer is selectively applied to the photosensitive drum 1 corresponding to the electrostatic latent image on the photosensitive drum 1. To be attached to. As a result, the electrostatic latent image is developed as a toner image. In this embodiment, the toner charge amount of the toner image formed on the photosensitive drum 1 was about −30 μC / g. The two-component developer on the developing sleeve 4b that has passed through the developing portion is returned to the developer reservoir in the developing container 4a as the developing sleeve 4b rotates.

6). Transfer Device The image forming apparatus 100 includes a transfer unit 5 serving as an intermediate transfer unit. The transfer device 5 includes an intermediate transfer belt 5b which is an endless belt-like intermediate transfer member. The primary transfer roller 5a as a primary transfer member is disposed on the inner peripheral surface side of the intermediate transfer belt 5b, and is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force via the intermediate transfer belt 5b. ing. A nip portion (contact region) between the photosensitive drum 1 and the intermediate transfer belt 5b becomes a transfer portion T where the toner image is transferred from the photosensitive drum 1 to the intermediate transfer belt 5b. The intermediate transfer belt 5b is nipped and conveyed between the photosensitive drum 1 and the primary transfer roller 5a. The primary transfer roller 5a receives a primary transfer bias, which is a DC voltage having a polarity (positive in this embodiment) opposite to the normal charging polarity of the toner (negative in this embodiment) from the primary transfer power source. Applied. In this embodiment, in particular, a primary transfer bias of +2.0 kV is applied. As a result, the toner image on the photosensitive drum 1 is electrostatically transferred to the surface of the intermediate transfer belt 5b.

  Although detailed description is omitted in this specification, as is well known to those skilled in the art, the toner image transferred onto the intermediate transfer belt 5b is then separately conveyed in a secondary transfer portion (not shown). It is transferred to the transfer material that has been used.

7). Cleaning Device The image forming apparatus 100 includes a cleaning device 7 as a cleaning unit that cleans the surface of the photosensitive drum 1 after the primary transfer process. The cleaning device 7 includes a cleaning blade 7a and a fur brush 7b as cleaning members, and a collected toner container 7c that stores toner removed from the photosensitive drum 1 by the cleaning blade 7a and the fur brush 7b. In the present embodiment, the cleaning blade 7 a is a plate-like member formed of urethane rubber, which is an elastic material, extends along the longitudinal direction of the photosensitive drum 1, and has a predetermined pressing force on the surface of the photosensitive drum 1. It is in pressure contact. Further, in this embodiment, the fur brush 7 b has a plurality of brush portions implanted on a rotation shaft extending along the longitudinal direction of the photosensitive drum 1, and the brush portions are in contact with the surface of the photosensitive drum 1. And rotated. The toner remaining on the photosensitive drum 1 after the primary transfer step is first removed from the surface of the photosensitive drum 1 by the fur brush 7b and collected in the collected toner container 7c. The toner that has not been collected by the fur brush 7b is removed from the surface of the photosensitive drum 1 by the cleaning blade 7a and collected in the collected toner container 7c.

8). Neutralizing Unit The image forming apparatus 100 serves as a neutralizing unit as a pre-charging exposure unit (pre-exposure lamp) 8 as a first pre-exposure unit and a pre-cleaning exposure unit (pre-cleaning exposure lamp) as a second pre-exposure unit. 9. By these two pre-exposure means, the potential of the surface of the photosensitive drum 1 after the primary transfer process is reset, thereby preventing the occurrence of ghost. In the present embodiment, as the pre-charge exposure device 8 and the pre-cleaning exposure device 9, LED chips (light emitting portions) manufactured by Stanley having a central wavelength of 660 nm were processed into an array. The pre-charging exposure unit 8 and the pre-cleaning exposure unit 9 constitute a charge eliminating unit (surface potential reset unit) that removes (resets) at least part of the surface potential of the photosensitive drum 1. The pre-charge exposure device 8 and the pre-clean exposure device 9 are connected to a pre-charge exposure device drive circuit and a pre-clean exposure device drive circuit as drive control units, respectively. Each of the pre-charge exposure device drive circuit and the pre-clean exposure device drive circuit is controlled by the information integrated circuit as the control means, such as the ON / OFF timing of light irradiation and the output value (light quantity).

9. Fixing Device The image forming apparatus 100 includes a heating and pressing type fixing device (not shown) as fixing means for fixing the toner image transferred to the transfer material on a transfer material in a secondary transfer unit (not shown). . In this embodiment, the fixing device is of a heat roller type, and the transfer material is conveyed while being heated and pressed in a nip portion (contact region) formed by a heating roller and a pressure roller pressed against the heating roller. The toner image is fixed on the transfer material. The transfer material that has undergone the toner image fixing process is output from the image forming apparatus 100 as an image formed product (print, copy).

10. Discharge Wire Cleaning Member As shown in FIG. 4, the charger 2 includes a discharge wire cleaning member 14 for cleaning deposits adhering to the discharge wire 10. The discharge wire cleaning member 14 is held by the support 13. In this embodiment, the discharge wire cleaning member 14 is composed of two rectangular pads that are pressed against each other while being held by the support 13 and sandwich the discharge wire 10 therebetween. The discharge wire cleaning member 14 moves while being pressed against the discharge wire 10 to clean the discharge wire 10. However, the shape of the discharge wire cleaning member 14 is not limited thereto. In the present embodiment, each pad of the discharge wire cleaning member 14 is provided with a rubber layer on the surface layer that contacts the discharge wire 10 with sponge as a base material, and the surface layer is coated with alumina as abrasive particles, A resin-bound one was used.

  When the support 13 is moved in the longitudinal direction of the charger 2 by a moving mechanism (described later), the discharge wire cleaning member 14 rubs the discharge wire 10 and wipes off the adhering matter attached thereto. The cleaning operation of the discharge wire 10 by the movement of the discharge wire cleaning member 14 is performed when the image forming apparatus 100 is turned on or whenever a certain number of images are formed.

11. 4. Cleaning member for shield As shown in FIG. 4, the charger 2 includes a shield 12, and more specifically, cleaning for shielding for cleaning deposits adhering to the inner surface of the side plates 12b, 12b facing the discharge wire 10. A member 15 is provided. The shield cleaning member 15 is held by the support 13. In this embodiment, the shield cleaning member 15 is composed of a rectangular pad held by the support 13 while being compressed between the support 13 and the shield 12. The shield cleaning member 15 moves while being pressed against the shield 12 to clean the shield 12. In this embodiment, the shield cleaning member 15 is a member in which an acrylic brush is woven into a base fabric. However, the material constituting the shielding cleaning member 15 is not limited to this, and nylon, PVC, PPS, or the like may be used. The shield cleaning member 15 is not limited to a flocking member, and may be an elastic member such as felt or sponge, or a sheet coated with an abrasive such as alumina or silicon carbide. If the mechanical resistance at the time of contact with the shield 12 does not cause inconvenience in cleaning the shield 12, any cleaning member can be used.

  The shield cleaning member 15 rubs the inner surfaces of the side plates 12b and 12b of the shield 12 facing the discharge wires 10 when the support 13 is moved in the longitudinal direction of the charger 2 by a moving mechanism (described later). Wipe off any deposits that have adhered to it. The cleaning operation of the shield 12 by the movement of the shield cleaning member 15 is performed when the image forming apparatus 100 is turned on or each time a certain number of images are formed.

12 Grid Cleaning Member As shown in FIG. 4, the charger 2 includes a grid cleaning member 16 for cleaning the deposit attached to the grid 11, more specifically, the surface facing the discharge wire 10. Have. The grid cleaning member 16 is held by the support 13. In the present embodiment, the grid cleaning member 16 is configured by a rectangular pad that is held between the support 13 and the grid 11 and held by the support 13 in a compressed state. The grid cleaning member 16 moves while being pressed against the grid 11 to clean the grid 11. In this embodiment, the grid cleaning member 16 is a member in which an acrylic brush is woven into a base fabric. However, the material constituting the grid cleaning member 16 is not limited to this, and nylon, PVC, PPS, or the like may be used. The grid cleaning member 16 is not limited to a flocking member, and may be an elastic member such as felt or sponge, or a sheet coated with an abrasive such as alumina or silicon carbide. An arbitrary cleaning member can be used as long as the mechanical resistance at the time of contact with the grid 11 does not cause inconvenience in cleaning the grid 11.

  The grid cleaning member 16 is adhered to the grid 11 by sliding the surface of the grid 11 facing the discharge wire 10 when the support 13 is moved in the longitudinal direction of the charger 2 by a moving mechanism (described later). Wipe off any deposits. The cleaning operation of the grid 11 by the movement of the grid cleaning member 16 is performed when the image forming apparatus 100 is turned on or each time a certain number of images are formed.

  In this embodiment, in addition to the shield cleaning member 15, a grid cleaning member 16 is provided. Thereby, the deposit | attachment adhering in the charger 2 can be cleaned more favorably. However, the grid cleaning member 16 may be omitted if desired.

  In this embodiment, the charger 2 includes a screw shaft 20 as a drive shaft and a motor (not shown) as a drive source that rotationally drives the screw shaft 20 as a moving mechanism. The screw shaft 20 has a spiral groove formed on the circumferential surface in the longitudinal direction, and the spiral groove is screwed into a drive engagement portion 13 a provided on the support 13. Accordingly, when the screw shaft 20 is rotated forward by the motor, the support 13 is moved in one direction, and when the screw shaft 20 is reversed by the motor, the support 13 is moved in the reverse direction. As described above, when the support 13 reciprocates, the cleaning operation by the discharge wire cleaning member 14, the shield cleaning member 15, and the grid cleaning member 16 held on the support 13 can be executed. In the present embodiment, the discharge wire cleaning member 14, the shield cleaning member 15, and the grid cleaning member 16 are held by the same support 13 and are driven in synchronization by the same moving mechanism.

  For example, as shown in FIG. 5, during the cleaning operation of the charger 2, after the shield cleaning member 15 starts moving in one moving direction, the grid cleaning member 16 starts moving in the same direction. You may be able to do that. Thereby, the deposits that have fallen without being completely collected by the shielding cleaning member 15 can be cleaned again by the grid cleaning member 16. Therefore, the cleaning function can be exhibited more effectively. For example, in this case, the shield cleaning member 15 and the grid cleaning member 16 can be moved by separate moving mechanisms. In order to clean the deposits that have dropped during cleaning by the shield cleaning member 15 with the grid cleaning member 16, the grid cleaning member 16 does not overtake the shield cleaning member 15 in the traveling direction of the cleaning member during cleaning. You can do it. In the example shown in FIG. 5, the discharge wire cleaning member 14 and the grid cleaning member 16 are supported by the same support 13, and the shield cleaning members 15 and 15 for cleaning the side plates 12 b and 12 b are individually provided. It is supported by the support 13.

13. Falling Object Receiving Unit FIG. 6 schematically shows the positional relationship between the charger 2 and the grid 11 in the short direction of the charger 2.

  In the present embodiment, the charger 2 is disposed between the side plate 12b of the shield 12 and the surface of the photosensitive drum 1, and from the inner surface 12b1 side facing the discharge wire 10 of the side plate 12b in the lateral direction of the charger 2. It has a flat fallen object receiving portion 30 that continues to the outer surface 12b2 side on the opposite side. More specifically, in the present embodiment, the fallen object receiving portion 30 is a flat plate extending inwardly of the side plate 12b of the shield 12 (inside the internal space of the shield 12) in the short direction of the charger 2. Inner extension 31. Further, in this embodiment, the fallen object receiving portion 30 has a flat plate-like outer extension portion 32 extending outward from the side plate 12 b of the shield 12 in the short direction of the charger 2. The inner extension portion 31 and the outer extension portion 32 are continuous on the same plane by a connection portion 33 corresponding to the thickness of the side plate 12b. In this embodiment, the fallen object receiving portion 30 is provided between each of the two side plates 12 b and 12 b and the surface of the photosensitive drum 1.

  In particular, in this embodiment, the fallen object receiving portion 30 including the inner extension portion 31, the outer extension portion 32, and the connection portion 33 is a flat plate adjacent to the through hole region 11 c of the grid 11 in the short direction of the charger 2. The edge region 11d has a shape.

  In the present embodiment, in consideration of the influence on the charging control, the inner extension portion 31 extends in a length of 1 ± 0.5 mm inside the side plate 12 b of the shield 12 in the short direction of the charger 2. To do. Further, in the present embodiment, the outer extension portion 32 extends to the outside of the side plate 12 b of the shield 12 with a length of 2 ± 0.5 mm in the short direction of the charger 2. Note that the distance between the grid 11 side end of the side plate 12 of the shield 12 and the grid 11 is 1.0 mm to 3.0 mm for the purpose of preventing high-pressure leakage due to creeping discharge.

  By providing the inner extension portion 31, deposits that have not been collected by the shield cleaning member 15 are deposited on the inner extension portion 31 near the shield cleaning member 15, that is, immediately below the shield 12. In the present embodiment, the deposits deposited on the inner extension 31 are cleaned by the grid cleaning member 16. Accordingly, it is possible to prevent the deposits from dropping from the shield 12 onto the surface of the photosensitive drum 1.

  Further, by providing the outer extension 32, the deposits from the through-hole region 11 c and the inner extension 31 move in the short direction of the charger 2 due to the lateral running of the deposits when cleaning the shield 12 and the grid 11. Thus, leakage from the grid 11 can be prevented.

  In the corona charger 2, ozone generated by corona discharge is processed by discharging it to the outside air through an ozone filter using an air flow. According to the present embodiment, the fallen object receiving portion 30 is formed integrally with the plate-like grid 11, so that there is little vortex generation in airflow control during image formation, and efficient supply / exhaust control can be maintained. . Therefore, the occurrence of charged spots due to the generation of non-uniform flow velocity distribution does not occur.

  In addition, according to the present embodiment, the fallen object receiving portion 30 is formed as a part of the grid 11, so that it is not necessary to provide a separate member, and a simple configuration can be achieved.

  As described above, in this embodiment, the fallen object receiving portion 30 is provided with a flat plate-like inner extension portion 31. According to such a structure, the deposit | attachment which fell from the shield 12 can be received more favorably by the inner side extension part 31. FIG. However, in the present embodiment, the falling object receiving portion 30 is formed as a portion of the grid 11. In this case, the portion of the grid body 11a that shields between the photosensitive drum 1 and the discharge wire 10 (wire, grill, etc.) other than the through hole 12b in the through hole region 11c is also dropped from the shield 12. You can receive a kimono. The deposits accumulated in this portion also move in the short direction of the charger 2 due to the lateral running at the time of cleaning the shield 12 and the grid 11, but the outer extension 32 is continuously provided in this portion. Falling is prevented. In this case, a planar fallen object receiving portion in which the portion of the grid body 11a other than the through hole 12b in the through hole region 11c is continuous with the outer surface side portion of the side plate 12b of the planar fallen object receiving portion 30. A portion on the inner surface side of 30 side plates 12b is formed.

  Thus, in this embodiment, the maximum width of the shield 12 in the short direction of the charger 2 (hereinafter also referred to as “shield width”) Ws and the maximum width of the grid 11 in the short direction of the charger 2 (hereinafter referred to as “shield width”). Also referred to as “grid width.”) Wg satisfies the relationship Ws <Wg. In the present embodiment, the shield width Ws is a distance between the outer surfaces 12b2 of the two side plates 12b of the shield 12. In the present embodiment, the width wg of the through-hole region 11c of the grid 11 in the short direction of the charger 2 is smaller than the width of the opening 12a of the shield 12 in the same direction.

  Here, the relationship between the shield width Ws and the grid width Wg will be further described. FIG. 7 shows the relationship between the difference Δd1 = Wg−Ws between the shield width Ws and the grid width Wg, and the value obtained by standardizing the amount of deposits dropped during cleaning. 7 that the amount of deposits falling on the photosensitive drum 1 is clearly reduced when Δd1> 0. Preferably, Δd1 is 1 mm or more, more preferably 2 mm or more. In addition, since it is not preferable that the charger 2 becomes larger than necessary, Δd1 is usually 5 mm or less, preferably 4 mm or less. In addition, it is preferable that the outer extension 32 extends to the outside of the two side plates 12b and 12b of the shield 12 with the same length, so that the fallen object can be satisfactorily dropped below any of the side plates 12b and 12b. Can receive.

  In addition, the development condition during image formation and the occurrence of image flow were confirmed by changing the condition of Δd1. Here, the development failure refers to a streak-like image in which the toner is not developed at a position to be developed on the image and is whitened in the output image. Here, the image flow refers to an image defect due to a latent image blur on an image after leaving it for 3 nights after passing 10,000 sheets in a high temperature and high humidity (30 ° C., 80%) environment. The results are shown in Table 1.

  From Table 1, it can be seen that the image quality can be satisfactorily maintained by setting Ws <Wg.

  As described above, according to the present embodiment, it is possible to prevent problems caused by deposits such as discharge products and scattered matters falling on the surface to be charged.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Accordingly, elements having the same functions or configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 8, in this embodiment, a shielding member 18 is disposed on substantially the same plane as the grid 11. More specifically, in this embodiment, the shielding member 18 has a through-hole in the grid 11 so as to penetrate the flat plate-shaped shielding member body (plate body) 18a having a thickness of about 0.1 mm to 0.5 mm. A through hole 18b is formed in a portion corresponding to the region 11c. The shielding member 18 has a length Lb in the longitudinal direction of the charger 2 (parallel to the rotation axis direction of the photosensitive drum 1), and a width in the short direction of the charger 2 (a direction substantially orthogonal to the rotation axis direction of the photosensitive drum 1). Wb. Further, the through long hole 18b is formed at a substantially central portion of the shielding member body 18a with a length lb (<Lb) in the longitudinal direction of the charger 2 and a width wb (<Wb) in the short direction of the charger 2. ing. That is, the shielding member 18 has a through long hole 18b and an edge region surrounding the through long hole 18b. This edge region includes edge regions 18c and 18c adjacent to both ends of the through-hole 18b in the short direction of the charger 2, and 18d and 18d adjacent to both ends of the through-hole 18b in the longitudinal direction of the charger 2. Composed. The shielding member 18 is fixed to the blocks 17 and 17 so that the through-hole 18b fits inside the opening 12a of the shield 12 on the substantially same plane as the grid 11 between the shield 12 and the grid 11. Yes.

  FIG. 9 schematically shows the arrangement relationship between the charger 2 and the shielding member 18 in the short direction of the charger 2.

  In the present embodiment, as in the first embodiment, the charger 2 is disposed between the side plate 12 b of the shield 12 and the surface of the photosensitive drum 1, and faces the discharge wire 10 of the side plate 12 b in the short direction of the charger 2. The flat fallen object receiving portion 30 is continuous from the inner surface side to the outer surface side opposite to the inner surface side. More specifically, in the present embodiment, the fallen object receiving portion 30 is a flat plate extending inwardly of the side plate 12b of the shield 12 (inside the internal space of the shield 12) in the short direction of the charger 2. Inner extension 31. Further, in this embodiment, the fallen object receiving portion 30 has a flat plate-like outer extension portion 32 extending outward from the side plate 12 b of the shield 12 in the short direction of the charger 2. The inner extension portion 31 and the outer extension portion 32 are continuous on the same plane by a connection portion 33 corresponding to the thickness of the side plate 12b. In this embodiment, the fallen object receiving portion 30 is provided between each of the two side plates 12 b and 12 b and the surface of the photosensitive drum 1.

  In particular, in this embodiment, the fallen object receiving portion 30 including the inner extension portion 31, the outer extension portion 32, and the connection portion 33 is a flat surface adjacent to the through long hole 18 b of the shielding member 18 in the short direction of the charger 2. It is formed by a plate-like edge region 18c. Since the inner extension portion 31 of the shielding member 18 is a portion in contact with the grid cleaning member 16, the grid cleaning member 16 can be used for cleaning.

  In the present embodiment, in consideration of the influence on the charging control, the inner extension portion 31 extends to the inside of the side plate 12b of the shield 12 with a length of 3 ± 0.5 mm in the short direction of the charger 2. To do. Further, in the present embodiment, the outer extension portion 32 extends to the outside of the side plate 12 b of the shield 12 with a length of 2 ± 0.5 mm in the short direction of the charger 2.

  By providing the inner extension portion 31, deposits that have not been collected by the shield cleaning member 15 are deposited on the inner extension portion 31 near the shield cleaning member 15, that is, immediately below the shield 12. In the present embodiment, the deposits deposited on the inner extension 31 are cleaned by the grid cleaning member 16. Accordingly, it is possible to prevent the deposits from dropping from the shield 12 onto the surface of the photosensitive drum 1.

  Further, by providing the outer extension 32, the deposit from the inner extension 31 moves in the short direction of the charger 2 due to the lateral running of the deposit during the cleaning of the shield 12 and the grid 11, and the grid 11. Can be prevented from leaking.

  Further, by arranging the shielding member 18 on substantially the same plane as the grid 11, turbulence caused by vortex flow is prevented between the shielding member 18 and the grid 11 in air flow control during image formation. Efficient supply / exhaust control can be maintained. Thereby, the scattered deposits can be prevented from adhering to the grid 11 again.

  In this embodiment, as the material of the shielding member 18, a thin plate stainless steel, which easily attaches the deposit by frictional charging, is used. As the material of the shielding member 17, it is possible to use a substance that is positively charged by friction such as glass, mica, or steel, or a substance that is negatively charged by friction such as Teflon (registered trademark), PVC, PPS, or PMMA. it can. A substance that is charged to a different polarity with respect to the deposit is preferred.

  As described above, in this embodiment, the maximum width (shield width) Ws of the shield 12 in the short direction of the charger 2 and the maximum width of the shielding member 18 in the short direction of the charger 2 (hereinafter referred to as “shielding member width”). Wb satisfies the relationship Ws <Wb. In the present embodiment, the width wb of the through long hole 18b of the shielding member 18 in the short direction of the charger 2 is smaller than the width of the opening 12b of the shield 12 in the same direction.

  Here, the relationship between the shield width Ws and the shielding member width Wb will be further described. FIG. 10 shows the relationship between the difference Δd2 = Wb−Ws between the shield width Ws and the shield member width Wb, and the value obtained by standardizing the amount of deposits dropped during cleaning. From FIG. 10, it can be seen that the amount of deposits falling on the photosensitive drum 1 is clearly reduced when Δd2> 0. Preferably, Δd2 is 1 mm or more, more preferably 2 mm or more. In addition, since it is not preferable that the charger 2 is unnecessarily large, Δd2 is usually 5 mm or less, preferably 4 mm or less. In addition, it is preferable that the outer extension 32 extends to the outside of the two side plates 12b and 12b of the shield 12 with the same length, so that the fallen object can be satisfactorily dropped below any of the side plates 12b and 12b. Can receive.

  Further, development defects during image formation and occurrence of image flow were confirmed by changing the condition of Δd2. Here, the development failure refers to a streak-like image in which the toner is not developed at a position to be developed on the image and is whitened in the output image. Here, the image flow refers to an image defect due to a latent image blur on an image after leaving it for 3 nights after passing 10,000 sheets in a high temperature and high humidity (30 ° C., 80%) environment. The results are shown in Table 2.

  From Table 2, it can be seen that the image quality can be maintained satisfactorily by setting Ws <Wb.

  As described above, the same effect as that of the first embodiment can be obtained also by providing the shielding member 18 at a predetermined position substantially on the same plane as the grid 11 as in the present embodiment.

  As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned Example.

  For example, in the above-described embodiments, the present invention is applied to a charger that charges a photoreceptor as a discharge device. However, the present invention is not limited to this. In an electrophotographic image forming apparatus, in addition to a charger for charging a photoreceptor, a discharge device for charging or neutralizing a processing target is used. For example, there is a corona discharger as a pre-transfer charging means for increasing the charge polarity of a charged toner image (toner) on a photoreceptor. There is also a corona discharger as transfer means for transferring the toner image on the photosensitive member to a transfer material. There is also a corona discharger as a separating means for discharging the transfer material onto which the toner image has been transferred and separating it from the surface of the photoreceptor. There is also a corona discharger as a charge eliminating means for discharging the surface of the photoreceptor after the transfer process. Even in these other discharge devices, when the deposits are likely to fall on the surface to be treated, the present invention is applied in the same manner to add discharge products and scattered materials. It is possible to prevent problems caused by the kimono falling on the surface to be treated.

1 Photosensitive drum (image carrier)
2 Charger (discharge device)
10 Discharge wire (discharge electrode)
11 Grid (grid electrode)
12 Shield 14 Wire Cleaning Member 15 Shield Cleaning Member 16 Grid Cleaning Member 17 Block 18 Shield Member 30 Falling Object Receiving Portion

Claims (6)

In a discharge device that discharges a processing target located below and charges or neutralizes the surface of the processing target,
A discharge electrode having an axis;
A shield provided with a side plate having an inner surface facing the discharge electrode and an outer surface opposite to the inner surface and extending substantially parallel to the axis;
A grid electrode disposed between the discharge electrode and the surface to be treated;
A planar fallen object receiving portion that is disposed between the side plate and the surface of the processing target and is continuous from the inner surface side to the outer surface side of the side plate in a direction substantially orthogonal to the axis.
A discharge device comprising:   The shield includes the two side plates so as to face each other with the discharge electrode interposed therebetween, and the falling object receiving portion is provided between each of the two side plates and the surface of the processing target. The discharge device according to claim 1, wherein:   The grid electrode has a flat plate-shaped grid body, and a through-hole formed in a region of the grid body facing the discharge electrode, and the falling object receiving portion is the grid of the grid The discharge device according to claim 1, wherein the discharge device is configured by the grid body around a region where a through hole is formed.   4. The discharge device according to claim 1, further comprising a shield cleaning member that presses against the inner surface of the side plate while moving to clean the inner surface. 5.   The discharge device according to claim 4, further comprising a grid cleaning member that presses against the grid electrode while moving to clean the grid electrode.   6. The movement of the grid cleaning member in the same direction is started after the movement of the shield cleaning member in one direction is started during the cleaning operation of the discharge device. Discharge device.

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