JP4413755B2 - Corona discharge device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a corona discharge device including needle-like electrodes and an image forming apparatus including the corona discharge device.

  In an image forming apparatus for forming an electrophotographic image such as a copying machine, an electrostatic latent image is formed on the surface of an electrophotographic photosensitive member whose surface is uniformly charged by exposure, and the electrostatic latent image is visualized by development. Further, the visualized image is transferred to a recording paper and fixed to obtain a recorded image. Some image forming apparatuses use a corona discharge device (also referred to as a main charger) in order to uniformly charge the electrophotographic photosensitive member before exposure.

  Conventionally, for example, a tungsten discharge wire having a diameter of 80 to 90 μm has been used for a discharge electrode of a corona discharge device. Since the discharge device using this discharge wire requires a large current to ensure charging uniformity, a large amount of ozone is generated at the time of discharge, and the electrophotographic photosensitive member and corona are used due to the strong oxidizing power of ozone. There was a problem that the discharge device itself deteriorated.

  As one method for solving such a problem, there is a method in which the electrode shape of the corona discharge device is formed in a needle shape instead of a wire (see Patent Document 1). In the corona discharge device using the needle-like electrode, the current value for obtaining the same output is reduced to about 1/4 compared to the case of using the wire electrode, and the ozone generation amount is about 1/4. To decrease. However, when a needle-like electrode is used, a phenomenon occurs in which silicone oil (which is used in the fixing portion for preventing high-temperature offset in the fixing portion) adheres to the electrode tip portion as the discharge is repeated. As the amount of silicone oil adhering to the tip of the electrode increases, the discharge becomes unstable, and if the corona discharge device is used for charging the electrophotographic photosensitive member in a state where the discharge is unstable, it is formed. This causes a defect that image unevenness such as streak is formed on the image.

As a method for solving the problem of adhesion of silicone oil in the needle electrode as described above, for example, there is a method disclosed in Patent Document 2 or Patent Document 3. Patent Document 2 discloses a method of removing dirt by rotating and moving a sponge roller against a needle electrode. Patent Document 3 discloses a method of removing dirt by sandwiching a needle electrode from both sides with a cleaning member composed of a pair of rollers that are rotatably supported, and moving the cleaning member relative to the needle electrode. ing.
Japanese Patent Laid-Open No. 1-312563 (Publication date: December 18, 1989) Japanese Utility Model Publication No. 2-75658 (publication date: June 11, 1990) Japanese Patent No. 3259515 (publication date February 14, 1995)

  However, the methods of Patent Documents 2 and 3 have the following problems. That is, in the method disclosed in Patent Document 2, the sponge roller is caught by the tip of the needle-like electrode and is damaged, and the sponge piece torn at the time of damage adheres to the tip of the needle-like electrode and destabilizes the discharge. There is a problem that the tip of the needle electrode is deformed by the force applied when the sponge roller rotates.

  In the method disclosed in Patent Document 3, the needle electrode is sandwiched and cleaned by a pair of rollers, so that the roller electrode does not sufficiently contact the tip of the needle electrode and the tip of the needle electrode is sufficient. It can happen that it is not cleaned. Furthermore, since a pressing mechanism for sandwiching the needle electrode from both sides is required, there is a problem that the apparatus becomes complicated.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is to provide a simple structure, sufficient cleaning without damaging the needle-like electrode, and corona discharge that enables stable discharge to be continued. An apparatus and an image forming apparatus including the same are provided.

  In order to solve the above problems, a corona discharge device according to the present invention is provided with a plate-like electrode having a plurality of sharp protrusions and a movable relative to the electrode, and the electrode is rubbed during movement. A cleaning member that cleans the surface of the electrode, and the cleaning member has a substantially L-shaped cross section including a first flat surface portion and a second flat surface portion. The flat surface portion is an attachment portion to the support member, and is disposed in parallel to the direction in which the cleaning member moves and is perpendicular to the flat surface of the electrode, and the second flat plate The portion is a cleaning portion of the electrode, and extends from the first flat portion toward the electrode, and is arranged perpendicular to the direction in which the cleaning member moves.

  According to the above configuration, the cleaning member that is provided so as to be relatively movable with respect to the electrode having the sharp protrusion, and that cleans the surface of the electrode by rubbing the electrode during movement, when rubbing the electrode, Since it is pressed and can be sufficiently brought into contact with the protruding portion of the electrode while being appropriately elastically deformed, dirt can be sufficiently removed without deforming and damaging the tip of the protruding portion of the electrode.

  In particular, by providing the cleaning member in the shape described above, when elastic deformation occurs in the cleaning member, the bending that occurs in the first flat surface portion is rubbed against the electrode to clean the electrode. It has the effect of pulling the flat part upward. For this reason, in the said cleaning member, the 2nd plane part of the cleaning member can be slidably moved with respect to the said electrode from the generation | occurrence | production initial stage of the bending, setting the pressing force with respect to the said electrode small (above-mentioned A high cleaning effect can be obtained while suppressing damage to the tip of the sharp projection of the electrode.

  By cleaning the electrode using such a cleaning member, the sharp projections of the electrode can be kept clean, so that it is possible to prevent the occurrence of discharge unevenness and the occurrence of image defects due to discharge unevenness. Can be prevented.

  In the corona discharge device, the cleaning member is formed by bending a metal plate having a thickness of 20 to 40 μm into an L-shaped cross section.

  According to the above configuration, by forming the cleaning member with a plate-shaped metal material having a thickness in a suitable range, the cleaning member is pressed against the electrode with an optimum force, and the most important needle tip for corona discharge is obtained. Cleans reliably and does not deform the needle tip. Moreover, since the surface hardness of the cleaning member is hard, the cleaning member is not shaved and the needle tip is not soiled.

  Further, in the corona discharge device, the cleaning member is characterized in that the rigidity of the second flat plate portion is set larger than the rigidity of the first flat surface portion.

  According to the above configuration, since the rigidity of the second plane portion is set to be larger than the rigidity of the first plane portion, the second plane portion is less likely to bend, and the elastic deformation of the cleaning member is mainly performed. Occurs as a deflection of the first flat surface portion. For this reason, in the electrode cleaning operation by the cleaning member, the action of pulling up the second planar portion upward from the initial stage of occurrence of the bending is increased, and the cleaning effect on the electrode can be further improved.

  Moreover, in the said corona discharge apparatus, the amount of biting of the sharp protrusion part with respect to the said cleaning member is 0.2-0.8 mm, It is characterized by the above-mentioned.

  According to said structure, since the amount of biting of the sharp protrusion part with respect to a cleaning member is set to an appropriate range, it becomes possible to clean efficiently, without changing the front-end | tip part of the protrusion part of an electrode. When the amount of biting is small, cleaning is insufficient, and when the amount of biting is large, the wear life of the cleaning member is shortened. This reliably removes the dirt on the protruding portion of the electrode and further improves the discharge stability.

  In the corona discharge device, the cleaning member is made of stainless steel.

  According to said structure, the durability of an apparatus is improved by using the stainless steel which has the outstanding intensity | strength and moderate elasticity for the said cleaning member, and is hard to oxidize also in the ozone atmosphere which generate | occur | produces by discharge. can do.

  Further, in the corona discharge device, the cleaning member uses a cleaning member having a substantially L-shaped cross section as a first cleaning member, and is further formed by a single flat plate member. It has the 2nd cleaning member which has these.

  According to said structure, the stain | pollution | contamination adhering to a needle-like electrode is scraped off by the 2nd cleaning member, or it makes it the state which is easy to disperse | distribute from a needle-like electrode. In this state, a high cleaning effect can be obtained by using the first cleaning member that easily moves slidably with respect to the needle-like electrode.

  An image forming apparatus according to the present invention includes any one of the corona discharge devices described above as a charger.

  According to the above configuration, since the image forming apparatus includes the corona discharge device having excellent discharge stability as the charger, the image forming apparatus can stably form an image having good image quality without streak stains and image unevenness due to discharge unevenness. be able to.

  As described above, the corona discharge device according to the present invention is provided with a plate-like electrode having a plurality of sharp protrusions and a movable relative to the electrode, and by rubbing the electrode during movement. A cleaning member that cleans the surface of the electrode, the cleaning member having a first flat surface portion and a second flat surface portion, having a substantially L-shaped cross section, and the first flat surface portion. Is a mounting part to the support member, is arranged parallel to the direction in which the cleaning member moves and is perpendicular to the flat plate surface of the electrode, and the second flat plate portion is This is a cleaning part of the electrode, and extends from the first flat part toward the electrode, and is arranged perpendicular to the direction in which the cleaning member moves.

  Therefore, when the electrode is scratched, the cleaning member is sufficiently pressed and elastically deformed so that it can sufficiently come into contact with the protruding portion of the electrode. Can be removed sufficiently.

  In particular, when elastic deformation occurs in the cleaning member, the bending that occurs in the first flat portion acts to rub against the electrode and pull up the second flat portion that cleans the electrode. For this reason, in the said cleaning member, the 2nd plane part of the cleaning member can be slidably moved with respect to the said electrode from the generation | occurrence | production initial stage of the bending, setting the pressing force with respect to the said electrode small (above-mentioned There is an effect that a high cleaning effect can be obtained while suppressing damage to the tip of the sharp projection of the electrode.

  In addition, an image forming apparatus provided with the corona discharge device as a charger has an effect that there is no streak stain or image unevenness due to discharge unevenness, and an image with good image quality can be stably formed.

  An embodiment of the present invention will be described below with reference to FIGS. First, a schematic configuration of the image forming apparatus according to the present embodiment will be described with reference to FIG.

  FIG. 2 shows a copying machine 2 which is one of image forming apparatuses. The copying machine 2 includes a document feeding unit 3, an image reading unit 4, a paper feeding unit 5, an image forming unit 6, and a fixing unit 7.

  The document feeder 3 places a double-sided automatic document feeder 8 (abbreviated as RADF: Reversing Automatic Document Feeder) for feeding a document to be copied and a document fed from the RADF 8 at a predetermined position. A document table 9 and a document receiving tray 10 are included. The RADF 8 has a predetermined positional relationship with the document table 9 and is supported in an openable / closable state. The RADF 8 feeds the original so that one side of the original is placed at a predetermined position of the original table 9 and opposed to the image reading unit 4, and the image reading on one side is completed. Then, the document is reversely transferred so that the other surface is placed at a predetermined position on the document table 9 and opposed to the image reading unit 4, and when the image reading on the other surface is completed, the document is removed. The document is discharged to the document receiving tray 10. Such document feeding and front / back reversing operations are controlled in relation to the overall operation of the copying machine 2. When only one side of the original is copied, the reverse transfer of the original is not executed.

  The image reading unit 4 is disposed below the document table 9, performs an operation of reading an image of the document fed to the document table 9 by the RADF 8, and reciprocally moves in parallel along the lower surface of the document table 9. Second scanning units 11 and 12, an optical lens 13, and a CCD (Charge Coupled Device) line sensor 14 that is a photoelectric conversion element are included.

  The first scanning unit 11 includes an exposure lamp 15 that exposes the surface of a document image to be read and a first mirror 16 that deflects a reflected light image from the document in a predetermined direction, and is constant with respect to the lower surface of the document table 9. While reciprocating at a predetermined scanning speed. The second scanning unit 12 includes second and third mirrors 17 and 18 that further deflect the reflected light image deflected by the first mirror 16 of the first scanning unit 11 in a predetermined direction. And reciprocally move in parallel along the lower surface of the document table 9 while maintaining a constant speed relationship.

  The optical lens 13 reduces the reflected light image deflected by the third mirror 18 of the second scanning unit 12 and forms an image at a predetermined position of the CCD line sensor 14. The CCD line sensor 14 is a three-line color CCD that can read a black-and-white image or a color image and output line data that is color-separated into red (R), green (G), and blue (B) color components. The reflected light image formed by the optical lens 13 is photoelectrically converted in sequence to output an electrical signal. Document image information output as an electrical signal from the CCD line sensor 14 is input to the image forming unit 6.

  The paper feeding unit 5 is disposed at the lowermost part of the copier 2 and has a paper tray 19 on which recording paper P as a recording medium is stacked and separated, and a separation roller that separates and feeds the recording paper P in the paper tray 19 one by one. 20 and a paper feed roller 21, and supplies the recording paper P as a recording medium to the image forming unit 6. The recording paper P separated and supplied one by one from the paper supply unit 5 is transported to the front of the image forming unit 6 by transport rollers 22 provided in various transport paths of the recording paper P, and is provided in front of the image forming unit 6. The sheet feeding timing is controlled by the pair of registration rollers 23 and is supplied to the image forming unit 6.

  The image forming unit 6 is disposed between the image reading unit 4 and the paper feeding unit 5, and includes a laser beam scanner unit 24, an image forming station 25, and a transfer conveyance belt mechanism 26. The transfer / conveying belt mechanism 26 is disposed below the image forming unit 6, and has a driving roller 27, a driven roller 28, an endless belt 29 stretched between the driving roller 27 and the driven roller 28, and a surface of the endless belt 29. An adsorption charger 30 for charging and adsorbing the recording paper P and a static eliminator 31 for separating the recording paper P adsorbed on the endless belt 29 are provided.

  The endless belt 29 is driven in the direction of the arrow 32 by rotation around the axis of the drive roller 27. The recording paper P supplied with timing control by the registration roller 23 is electrostatically attracted to the surface-charged endless belt 29 by the suction charger 30 and conveyed in the direction of the arrow 32 described above. An image is transferred to the recording paper P in the process of being conveyed in the direction of the arrow 32 by the endless belt 29, and the recording paper P on which the image has been transferred is peeled off from the endless belt 29 by the static eliminator 31 and is transferred to the fixing unit 7. It is conveyed. Paper feed timing control by the registration roller 23 is detected by a sensor (not shown) provided in the transport path of the recording paper P in the transport direction, and is executed according to the detection output of the sensor.

  Since the copying machine 2 is a color copying machine, four sets of the laser beam scanner unit 24 and the image forming station 25 are provided corresponding to each color of black, cyan, magenta, and yellow. Each of the laser beam scanner units 24 and the image forming station 25 has a pixel signal corresponding to a black component image of the image original information that the color of toner used for development is different from black, cyan, magenta, and yellow. Since the pixel signal corresponding to the cyan color component image, the pixel signal corresponding to the magenta color component image, and the pixel signal corresponding to the yellow color component image are the same, the configuration is the same. The unit 24 and the image forming station 25 will be described as representative examples, and the description of the other will be omitted. When the laser beam scanner unit 24 and the image forming station 25 corresponding to each color are individually shown, alphabetic suffixes: b (black), c (cyan), m (magenta), y (yellow) This is indicated with

  FIG. 3 is an enlarged view showing the configuration of the black image forming laser beam scanner unit 24b and the image forming station 25b. The laser beam scanner unit 24b deflects a laser beam from the semiconductor laser element (not shown) that emits dot light modulated according to image document information input from the image reading unit 4 and a laser beam from the semiconductor laser element in the main scanning direction. A polygon mirror 33b, an fθ lens 34b, 35b for imaging a laser beam deflected by the polygon mirror 33b on the surface of an electrophotographic photoreceptor 40b (hereinafter simply referred to as a photoreceptor), and reflection mirrors 36b, 37b, 38b; Is provided. The laser beam reflected by the reflecting mirror 38b exposes the surface of the photoreceptor 40b of the image forming station 25b, and forms an electrostatic latent image.

  The image forming station 25b is exposed with a photosensitive member 40b that is rotatably supported in the direction of the arrow F around the axis 39b, and the following equipment arranged along the circumferential surface of the photosensitive member 40b, that is, the laser beam described above. The electrostatic latent image formed on the surface of the photosensitive member 40b by developing the charger 41b for uniformly charging the surface of the photosensitive member 40b and the exposure of the laser beam output from the laser beam scanner unit 24b is developed. A developing device 42b for visualizing the image, a transfer discharge device 43b for transferring the developed image, which is provided opposite to the photoreceptor 40b via the endless belt 29, onto the recording paper P on the endless belt 29, and an electrostatic latent image. And a cleaning unit 44b that removes and collects toner remaining on the surface of the photoreceptor 40b after the developing process. The charger 41b, the developing unit 42b, the transfer discharger 43b, and the cleaning unit 44b are provided in this order from the upstream side to the downstream side in the rotation direction indicated by the arrow F.

  The corona discharge device 1 of the present invention is used for the charger 41b. The charger 41b uniformly charges the surface of the photoreceptor 40b by discharging. The surface of the uniformly charged photoreceptor 40b is exposed by the laser beam from the laser beam scanner unit 24b corresponding to the image document information, and the charged amount of the exposed portion and the charged amount of the unexposed portion are changed. Differences occur and an electrostatic latent image is formed.

  The developing device 42b can freely rotate a developing roller 45b provided to face the photoreceptor 40b, a developer conveying roller 46b that supplies a developer containing toner to the developing roller 45b, a developing roller 45b, and a developer conveying roller 46b. And a casing 47b for accommodating the developer in the internal space. The developer is supplied from the developing roller 45b of the developing device 42b to the surface of the photoreceptor 40b on which the electrostatic latent image is formed, whereby the electrostatic latent image is developed and visualized. The visualized image is transferred to the recording paper P on the endless belt 29 by the transfer discharger 43b as described above.

  Returning to FIG. 2 again, the recording paper P on which the black image is transferred is conveyed in the direction of the arrow 32 while being adsorbed by the endless belt 29, and is provided in the following order from the upstream side to the downstream side in the conveyance direction. The cyan, magenta, and yellow laser beam scanner units 24c, 24m, and 24y and the image forming stations 25c, 25m, and 25y are converted into the above-described black image. In the same manner as in, the images are sequentially transferred. In this way, a full color image is formed on the recording paper P. The recording paper P on which the full-color image is formed is peeled off from the endless belt 29 by the static eliminator 31 and fed to the fixing unit 7.

  The fixing unit 7 includes a heating roller 48 that includes a heating unit (not shown), and a pressure roller 49 that is provided to face the heating roller 48 and that is pressed by the heating roller 48 to form a so-called nip portion 50. The recording paper P supplied to the fixing unit 7 is heated and pressurized when passing through the nip part 50, and the developer on the recording paper P is fixed to form a robust image.

  When the recording paper P fixed by the fixing unit 7 forms an image only on one surface, or when the image is formed on the other surface after being reversed after forming the image on one surface, the switching gate 51 operates. The paper is fed upward, and is further discharged to a paper discharge tray 53 by a discharge roller 52. When an image is formed on one surface of the recording paper P and then further on the other surface, the recording paper P is fed downward by the operation of the switching gate 51, and the switchback transport path 54. Then, the image is reversed and then conveyed again to the image forming unit 6. An image is formed on the recording paper P fed to the image forming unit 6 in the same manner as described above.

  Next, the corona discharge device 1 provided as the charger 41 of the copying machine 2 will be described with reference to FIGS. 1, 4, and 5.

  The corona discharge device 1 has a plate-like electrode 61 (hereinafter referred to as a needle-like electrode) having a plurality of sharp projections 68, a holding member 62 that holds the needle-like electrode 61, and the needle-like electrode 61. A cleaning member 63 that cleans the surface of the needle electrode 61 by rubbing the needle electrode 61 during the movement, a support member 64 that supports the cleaning member 63, a cleaning member 63, and a support member. The structure includes a moving member 65 for moving the member 64, and a shield case 66 that houses the needle-like electrode 61, the holding member 62, the cleaning member 63, and the support member 64. The corona discharge device 1 is disposed along the longitudinal direction of the photoconductor 40 in the copying machine 2 while facing the photoconductor 40.

  The needle electrode 61 is a thin plate member made of, for example, stainless steel, and is formed so as to protrude in the short direction from one end surface constituting a flat plate portion 67 extending in one direction and a side extending in the longitudinal direction of the flat plate portion 67. It is comprised by the sharp-shaped projection part 68 made. Exemplifying the dimensions of the needle electrode 61, the length L2 in the short direction of the flat plate portion 67 is preferably about 10 mm, the length L3 in the protruding direction of the protruding portion 68 is preferably about 2 mm, and the tip of the protruding portion 68 Is preferably about 40 μm, and the pitch TP on which the protrusions 68 are formed is preferably about 2 mm.

  The holding member 62 that holds the needle-like electrode 61 is a member that extends in one direction as in the needle-like electrode 61 and has a reverse T-shaped cross section orthogonal to the longitudinal direction, and is made of, for example, resin. The needle electrode 61 is screwed by a screw member 69 to one side surface of the protruding portion of the holding member 62 in the vicinity of both ends in the longitudinal direction. A voltage of about 5 kV is applied to the needle-like electrode 61 for corona discharge during operation so as to charge the photosensitive member 40 described above.

  The cleaning member 63 has a shape obtained by bending a flat plate into an L shape, that is, a shape having a flat plate portion 63A and a flat plate portion 63B, and is made of a metal material having a thickness t of 20 to 40 μm.

  The attachment form of the cleaning member 63 to the support member 64 is, for example, as follows. That is, the support member 64 includes a first support portion 64A and a second support portion 64B, and the second support portion 64B functions to connect the first support portion 64A and the cleaning member 63. . Specifically, the second support portion 64B is a member having a substantially L-shaped cross section having two plane portions, and one plane portion is a mounting surface to the first support portion 64A, and the other The flat surface portion is an attachment surface to the cleaning member 63.

  In the cleaning member 63, the flat plate portion 63 </ b> A is an attachment portion to the second support portion 64 </ b> B, and the flat plate portion 63 </ b> B is a cleaning portion of the needle electrode 61. That is, the flat surface portion 63A is disposed parallel to the direction in which the cleaning member 63 moves (the line direction connecting the tips of the protrusions 68 of the needle electrode 61) and perpendicular to the flat plate surface of the needle electrode 61. The flat plate portion 63B is bent from the flat surface portion 63A toward the needle electrode 61 and is disposed perpendicular to the direction in which the cleaning member 63 moves.

  As a metal material of the cleaning member 63, phosphor bronze, ordinary steel, stainless steel, or the like can be used. However, since the cleaning member 63 is used in an ozone atmosphere generated by corona discharge, it is most preferably stainless steel from the viewpoint of a durable life in consideration of oxidation resistance. Examples of stainless steel include SUS304, which is an austenitic stainless steel defined in Japanese Industrial Standards (JIS) G4305, and SUS430, which is a ferritic stainless steel, but are not limited thereto. Stainless steel may be used.

  Regardless of which stainless steel is used as the cleaning member 63, it is desirable that the hardness of the stainless steel is 115 or more on the Rockwell hardness M scale defined in the American Society for Testing and Materials (ASTM) standard D785. This is because if the Rockwell hardness is less than 115, the hardness is too soft, so that when the contact is made against the needle-like electrode 61 and rubbed, the cleaning member is undesirably deformed and a cleaning effect cannot be obtained. Even though the hardness of the cleaning members 63a and 63b is high, there is no particular problem in function, so there is no need to set an upper limit. However, the upper limit value of Rockwell hardness M scale defined in ASTM standard D785 is 130. Therefore, if an upper limit is provided, it will be 130.

  Next, the reason for limiting the range of the thickness t of the cleaning member 63 will be described. When the thickness t is less than 20 μm, the deformation when contacting the needle electrode 61 is easy, but the pressing force against the needle electrode 61 obtained as a reaction force accompanying the deformation becomes weak. The adhered dirt cannot be removed sufficiently. Further, if the thickness t exceeds 40 μm, the dirt adhering to the needle electrode 61 can be sufficiently removed, but the rigidity increases and the pressing force against the needle electrode 61 becomes too strong. There is a risk that the tip of the projection 68 will be deformed and damaged. As a result, if the thickness t is out of the proper range, image unevenness due to defective charging may occur, which is not preferable.

  In addition, the width w of the flat portion 63B that is a portion that contacts the needle electrode 61, that is, the cleaning member 63 in the direction perpendicular to the direction in which the cleaning member 63 moves and in the direction perpendicular to the direction in which the flat portion 63B extends. The dimension w is formed to be 3.5 mm or more.

  If the width dimension w is less than 3.5 mm, the value per unit area of the force generated when the needle-like electrode 61 is pressed and deformed increases, so that fatigue failure due to repeated deformation is likely to occur, and the durability life is reduced. . By setting the width dimension w to 3.5 mm or more, the value per unit area of the force described above can be reduced and the durability life against repeated deformation can be increased. However, if the width is excessively wide, the rigidity becomes too strong. In order to increase the size of the apparatus, the upper limit is preferably set to about 10 mm.

  Furthermore, the relative arrangement of the cleaning member 63 and the needle electrode 61 will be described. The cleaning member 63 and the needle electrode 61 are preferably arranged so that the amount of biting d of the protrusion 68 of the needle electrode 61 with respect to the flat portion 63B of the cleaning member 63 is 0.2 to 0.8 mm. . Here, the amount of biting “d” is a state in which the cleaning member 63 and the protrusion 68 are projected on a virtual plane perpendicular to the direction in which the cleaning member 63 moves relative to the needle electrode 61. And the protruding portion 68 is an amount defined as a length overlapping in the extending direction of the protruding portion 68.

  When the biting amount d is less than 0.2 mm, the pressing force against the needle electrode 61 obtained as a reaction force accompanying the deformation of the cleaning member 63 becomes weak, so that the dirt adhering to the needle electrode 61 can be sufficiently removed. Can not. If the bite amount d exceeds 0.8 mm, the dirt adhering to the needle electrode 61 can be sufficiently removed, but the pressing force on the needle electrode 61 obtained as a reaction force accompanying the deformation of the cleaning member 63 is strong. Since it becomes too much, there is a possibility that the tip of the projection 68 of the needle electrode 61 is deformed and damaged. As a result, if the biting amount d is out of the proper range, image unevenness due to defective charging may occur, which is not preferable.

  The shield case 66 is made of, for example, stainless steel, and is a container-like member having an external shape of a rectangular parallelepiped and having an internal space and having an opening on one surface facing the above-described photoreceptor 40. The shield case 66 extends long in the same direction as the needle electrode 61 and has a substantially U-shaped cross section in a direction orthogonal to the longitudinal direction. The holding member 62 described above is attached to the bottom surface 71 of the shield case 66. The end of the columnar portion of the support member 64 is slidably inserted into a groove 73 formed by the inner surface 72 of the shield case 66 and the holding member 62.

  A through hole 74 is formed in the columnar portion of the first support portion 64A in parallel with the extending direction of the needle electrode 61, and a moving member 65 is provided through the through hole 74. Since the moving member 65 is fixed to the first support portion 64A at a portion inserted through the through-hole 74, by pulling the moving member 65 in the extending direction of the needle electrode 61, the support member 64 is It slides with respect to the groove part 73 and is guided by the groove part 73 and can move in the direction in which the needle electrode 61 extends. That is, since the cleaning member 63 supported by the support member 64 moves in the direction in which the needle electrode 61 extends, the flat portion 63B of the cleaning member 63 is abutted against the needle electrode 61 and rubbed as described above. Can do.

  The moving member 65 is a thread-like or wire-like member, extends outward from the shield case 66 through a hole or gap formed in the shield case 66, and is a pulley provided on the outer surface of the shield case 66 or the machine body of the copying machine 2. The ends are suspended via 75a and 75b (see FIG. 4). The ends of the pulleys 75a and 75b and the moving member 65 are omitted in FIGS. The end of the moving member 65 is extended to the outside of the copying machine 2 so that the corona discharge device 1 is not removed from the copying machine 2 and the copying machine 2 is not opened. It is preferable to enable cleaning.

  When the cleaning member 63 is brought into contact with the needle electrode 61 and cleaned by pulling the moving member 65, the pressing force of the cleaning member 63 against the needle electrode 61 is 10 gf or more and 30 gf or less. To be adjusted. This adjustment of the pressing force can be performed as follows, for example.

  A force applied to the cleaning member 63 by preparing a weight with various weights and connecting the weight of each weight to one end of the moving member 65 and connecting a spring balance or the like to the cleaning member 63 Measure. A weight having this force in the range of 10 gf to 30 gf is selected in advance, and when the needle electrode 61 is cleaned, the weight selected in advance is suspended from the end of the moving member 65 to obtain a desired weight. It can be cleaned with a pressing force. Further, an electric motor whose rotational torque has been adjusted in advance may be connected to the end of the moving member 65 to obtain a desired pressing force.

  The reason why the pressing force is limited to 10 gf or more and 30 gf or less is as follows. If the pressing force is less than 10 gf, the deposits on the needle electrode 61 cannot be sufficiently removed. If the pressing force exceeds 30 gf, the tip of the protrusion 68 of the needle electrode 61 is deformed and damaged.

  Subsequently, the cleaning operation of the needle-like electrode 61 by the corona discharge device 1 having the above configuration will be described with reference to FIGS.

  FIG. 6A shows an initial state where the flat surface portion 63 </ b> B of the cleaning member 63 comes into contact with one protrusion 68 having the needle-like electrode 61. Then, the cleaning member 63 further moves from this state, and the state shown in FIGS. 6B to 6C is obtained. In the state of FIG. 6B and FIG. 6C, the cleaning member 63 is bent at both the flat portions 63A and 63B, and the flat portion 63B of the cleaning member 63 moves upward. By rubbing the protrusion 68 of the needle electrode 61, the needle electrode 61 is cleaned.

  Here, the reason why the cleaning member 63 according to the present embodiment has the L-shaped cross section as described above is as follows. For comparison, FIGS. 7A to 7C show a cleaning operation in the case where the cleaning member is formed by a single flat plate member.

  In the cleaning operation shown in FIGS. 7A to 7C, if the cleaning member continues to move in contact with the needle-like electrode, the cleaning member bends. However, at the initial stage of the occurrence of the deflection (the state in FIG. 7B), the deflection does not cause the cleaning member to slide relative to the needle electrode (the cleaning member is moved along the needle electrode). Therefore, the cleaning effect is not so high.

  Therefore, in the configuration shown in FIGS. 7A to 7C, in order to improve the cleaning effect of the cleaning member, the waist of the cleaning member must be strengthened and the pressing force must be increased. Increases damage to the tip of the needle electrode protrusion. In particular, in the later stage of the occurrence of the bending (the state shown in FIG. 7C), the cleaning member that is greatly bent rubs in a state where the tip of the protruding portion of the needle electrode is pressed from above. There is a problem that wear at the tip of the part is promoted.

  On the other hand, in the cleaning operation shown in FIGS. 6A to 6C, when the cleaning member 63 continues to move while being in contact with the needle-like electrode 61, both the flat portions 63 </ b> A and 63 </ b> B of the cleaning member 63 are used. Deflection occurs. At this time, the flexure generated in the flat portion 63A acts to scrape the needle electrode 61 and pull up the flat portion 63B for cleaning the needle electrode 61 upward. For this reason, in the cleaning member 63 having an L-shaped cross section according to the present embodiment, the cleaning member 63 is slidable with respect to the needle-like electrode 61 from the initial stage of occurrence of the bending (the state of FIG. 6B). Therefore, a high cleaning effect can be obtained.

  Further, in the cleaning member 63 according to the present embodiment, the cleaning member 63 is reinforced by moving the cleaning member 63 slidably with respect to the needle-like electrode 61. There is no need to increase the pressing force. That is, since the pressing force on the needle electrode 61 can be set small, damage to the tip of the protrusion 68 of the needle electrode 61 can be suppressed. If damage to the needle electrode 61 can be reduced in this way, the maintenance cycle in the corona discharge device 1 can be lengthened.

  Moreover, in FIG. 8 (a)-(c), the cleaning operation | movement in the corona discharge apparatus which is a modification of embodiment of this invention is shown. 8A to 8C, in the cleaning member 63, the plate thickness of the flat portion 63B is larger than the plate thickness of the flat portion 63A. It is different from the example shown in.

  In this example, since the plate thickness of the flat portion 63B is increased, it is difficult for the flat portion 63B to bend. That is, the reason why the plate thickness of the flat portion 63B is larger than the plate thickness of the flat portion 63A is to set the rigidity of the flat portion 63B to be larger than the rigidity of the flat portion 63A. Therefore, when the cleaning member 63 continues to move while being in contact with the needle-like electrode 61, the bending of the cleaning member 63 occurs mainly at the flat surface portion 63A. For this reason, in the cleaning member 63 shown in FIGS. 8A to 8C, the action of pulling the flat portion 63 </ b> B upward from the initial stage of occurrence of the bending (state of FIG. 8B) becomes large, and the needle electrode 61. The cleaning effect can be further improved.

  Moreover, it is good also as a structure as shown in FIG. 9 as a further modification of the corona discharge apparatus which concerns on this invention. In the corona discharge device shown in FIG. 9, the support member 64 is formed not only by the cleaning member 63 having an L-shaped cross section but also by a single flat plate member (that is, having an I-shaped cross section). A member 76 is attached. The cleaning member 63 and the cleaning member 76 are attached so that the cleaning member 76 is on the front side when the support member 64 is moved. Further, the cleaning operation by the cleaning member 76 is an operation as shown in FIGS. 7A to 7C, and the cleaning operation by the cleaning member 63 is an operation as shown in FIGS. 6A to 6C. .

  As described above, the cleaning effect of the cleaning member 76 having the I-shaped section alone is not so high. Therefore, in the corona discharge device shown in FIG. 9, the cleaning member 63 having the L-shaped section is combined with this. Thus, dirt (toner, oil, paper dust) and the like that were difficult to remove with the cleaning member 76 can be completely removed.

  In the cleaning operation in this case, first, the cleaning member 76 scrapes off the dirt adhering to the needle electrode 61 or makes the needle electrode 61 easily dispersible. In this state, by using the cleaning member 63 that is slidably moved relative to the needle electrode 61, a high cleaning effect can be obtained.

  As described above, the present embodiment exemplifies a copying machine as an image forming apparatus, but the present invention is not limited to this, and a laser that forms an image according to image information given from a computer or the like. It may be a printer or the like.

  Further, as in the above example, the present invention is not limited to the configuration in which the laser beam scanner unit scans the laser beam and exposes the photosensitive member. Instead of the laser beam scanner unit, a light emitting diode (LED) array and an imaging lens are used. You may use the LED head which consists of these as a writing optical system. The LED head is smaller in size than the laser beam scanner unit, and has no moving parts and is silent. Therefore, the LED head is suitably used for an image forming apparatus such as a tandem digital color copying machine that requires a plurality of optical writing units. be able to.

1, showing an embodiment of the present invention, is a perspective view showing a schematic configuration of a corona discharge device. FIG. It is sectional drawing which shows schematic structure of an image forming apparatus provided with the said corona discharge apparatus. It is sectional drawing which shows the structure of the laser beam scanner unit for image formation, and an image formation station. It is a front view of the said corona discharge apparatus. It is a side view of the said corona discharge apparatus. 6A to 6C are diagrams illustrating a cleaning operation of the cleaning member in the corona discharge device. FIGS. 7A to 7C are diagrams showing a cleaning operation of the cleaning member in the corona discharge device shown for comparison. FIGS. 8A to 8C are diagrams illustrating the cleaning operation of the cleaning member in the modified example of the corona discharge device. It is a perspective view which shows the modification in embodiment of this invention, and shows schematic structure of a corona discharge apparatus.

Explanation of symbols

1 Corona discharge device 2 Copying machine (image forming device)
3 Document Feeding Unit 4 Image Reading Unit 5 Paper Feeding Unit 6 Image Forming Unit 7 Fixing Unit 61 Needle-shaped Electrode (Electrode)
62 Holding member 63 Cleaning member (first cleaning member)
63A 1st plane part 63B 2nd plane part 64 Support member 65 Member 66 for movement Shield case 68 Projection part (sharp projection part)
76 Cleaning member (second cleaning member)

Claims (7)

A comb- like electrode having a plurality of sharp protrusions;
A cleaning member provided so as to be movable relative to the electrode, and cleaning the surface of the electrode by rubbing the electrode during movement;
The cleaning member is
Having a substantially L-shaped cross section with a first planar portion and a second planar portion;
The first flat surface portion is attached to the support member at an L-shaped end , and is disposed parallel to the direction in which the cleaning member moves and perpendicular to the flat plate surface of the electrode. And
The second plane portion is a cleaning portion of the electrode, extends from the first plane portion to the electrode side, and is disposed perpendicular to the direction in which the cleaning member moves ,
When the cleaning member cleans the electrode, the cleaning member is parallel to the direction in which the comb teeth are arranged relative to the electrode in a state where the second flat surface portion is in contact with the sharp projection of the electrode. The first flat surface portion is bent by being moved, and the second flat surface portion is lifted along the sharp protrusion portion by the bending, and rubs the sharp protrusion portion. Corona discharge device.   The corona discharge device according to claim 1, wherein the cleaning member is formed by bending a metal plate having a thickness of 20 to 40 μm into an L-shaped cross section. 2. The corona discharge device according to claim 1, wherein the cleaning member has a rigidity of the second flat surface portion set to be larger than a rigidity of the first flat surface portion.   The corona discharge device according to claim 1, wherein the amount of biting of the sharp protrusion with respect to the cleaning member is 0.2 to 0.8 mm.   The corona discharge device according to claim 1, wherein the cleaning member is made of stainless steel. The cleaning member uses a cleaning member having a substantially L-shaped cross section as a first cleaning member,
The corona discharge device according to claim 1, further comprising a second cleaning member having an I-shaped cross section formed by a single flat plate member.   An image forming apparatus comprising the corona discharge device according to claim 1 as a charger.

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