JP2010002624A - Charging apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging means where the applied voltage to be required is made lower than a discharging apparatus using discharge wire, and further, the variation of the applied current made to flow into each discharge electrode is suppressed, so as to reduce the unevenness in charging on an image carrier. <P>SOLUTION: In a charging apparatus provided with a charging means comprising a plurality of discharge electrodes and a single electrode holding member holding the plurality of discharge electrodes, the plurality of discharge electrodes are arranged at intervals each other in the longitudinal direction of the single electrode holding member, wiring for respectively applying a discharge bias to the plurality of discharge electrodes is connected to the positions corresponding to the plurality of discharge electrodes in a longitudinal direction of the single electrode holding member, respectively, the single electrode holding member is provided with: conducting regions where the plurality of discharge electrodes and the wiring corresponding to the plurality of discharge electrodes are electrically connected; and resisting regions having resistance higher than that of the conducting regions, and the resisting regions are provided between the adjoining plurality of discharge electrodes, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging device, and an image forming apparatus such as an electrophotographic copying apparatus, a facsimile, a printer, a plotter, a multifunction peripheral, and a printing apparatus provided with the charging device.

  2. Description of the Related Art Conventionally, in an electrophotographic or electrostatic recording type image forming apparatus, a charging device having a non-contact type discharge electrode as a charging means for an image carrier such as an electrophotographic photosensitive member and an electrostatic recording dielectric (hereinafter referred to as non-contact charging) A device using a device) is known. There are various non-contact charging devices. One example is a corona charging device. In the corona charging device, a wire-like discharge electrode (hereinafter referred to as a discharge wire) is disposed in a non-contact manner facing an image carrier, and a high voltage (for example, 5 to 8 kV) is applied to the discharge wire to discharge. The image carrier is charged by generating a gas discharge around the wire. The corona charging device charges a discharge target by discharging the discharge target in a state where a discharge wire which is a thin wire is exposed.

  When the discharge object is an image carrier of an image forming apparatus, the image carrier uniformly charged by the non-contact charging device is subjected to image exposure, and an electrostatic latent image corresponding to the image is formed on the image carrier. It is formed. The electrostatic latent image is developed by a developing device provided opposite to the image carrier to be converted into a toner image and finally transferred onto a transfer sheet. After the transfer, the surface of the image bearing member is cleaned of residual toner by a cleaning device, discharged by a discharging lamp, and then charged again, and the image forming process described above is repeated.

  Since the non-contact charging device used in the image forming apparatus as described above can charge the discharge target without mechanical contact, the discharge target is not damaged at the time of charging. Foreign matter such as untransferred toner and paper dust hardly adheres to the charging device.

  However, in the case of a charging device using a discharge wire, it is necessary to apply a very high voltage to the discharge wire as described above in order to charge the image carrier. When such a high voltage is applied to the charging device to cause discharge, discharge products such as ozone are generated. Therefore, it is desired to reduce the voltage applied to the charging device.

Patent Document 1 discloses a charging device in which a plurality of comb-like discharge electrodes are arranged at equal intervals along the longitudinal direction of the charging device, and a sharp tooth tip is fixed toward the image carrier side. In such a configuration, the required applied voltage can be lowered as compared with a charging device using a discharge wire, so that the generation of discharge products such as ozone can be reduced. Patent Document 2 discloses a charging device in which a plurality of comb-like discharge electrodes are connected to a single electrode, thereby reducing the number of components and enabling stable discharge.
JP 2006-84951 A Japanese Patent Application Laid-Open No. 07-64375

  However, in the charging devices as in Patent Documents 1 and 2, the applied current flowing into each discharge electrode may vary depending on the difference in the resistance between each discharge electrode and the image carrier. As a result, discharge unevenness occurs in the longitudinal direction of the charging device, and charging unevenness on the image carrier may occur.

  The present invention has been made in view of the above background, and lowers the required applied voltage as compared with a charging device using a discharge wire, and suppresses variations in applied current flowing into each discharge electrode, so that the image on the image carrier. An object of the present invention is to provide a charging means for reducing the uneven charging.

  In a charging device including a charging unit having a plurality of discharge electrodes and a single electrode holding member that holds the plurality of discharge electrodes, the plurality of discharge electrodes are spaced from each other in the longitudinal direction of the single electrode holding member. The wiring for applying the charging bias to each of the plurality of discharge electrodes is connected to positions corresponding to the plurality of discharge electrodes in the longitudinal direction of the single electrode holding member, and the single electrode holding member is A plurality of discharge electrodes and wiring regions corresponding to the plurality of discharge electrodes are electrically connected to each other, and a resistance region having a higher resistance than the conduction region, and the resistance region includes a plurality of adjacent discharge electrodes. It is preferable to provide them respectively.

  Furthermore, it is preferable to provide a gap for separating a part between the conductive regions in each of the resistance regions. A resistance element having a higher resistance than the conduction region may be provided in the gap. The length L2 of the gap in the direction from the wiring connection point to the discharge electrode corresponding to the wiring connection point corresponds to the wiring connection point and the wiring connection point provided in the longitudinal direction of the single electrode holding member, respectively. It is preferable to have a length equal to or longer than the shortest distance L1 from the discharge electrode. It is preferable that the shortest distance L1 is substantially the same between the conductive regions.

  It is preferable that the electric resistance values of the resistance regions respectively provided between the plurality of adjacent discharge electrodes are substantially the same. In the single electrode holding member, it is preferable that the conduction region is formed of a conductive member and the resistance region is formed of a high resistance member having a resistance higher than that of the conductive member. The single electrode holding member electrically supports the discharge electrode and electrically connects the insulating support having a higher resistance than the discharge electrode and the wiring formed on the surface of the insulating support and the discharge electrode corresponding to the wiring. It is preferable that the conductive film has an area in the resistance region smaller than an area in the conduction region. The wiring connected to the conduction region may be plate-shaped.

  The plurality of discharge electrodes are preferably provided independently, and are preferably detachable independently from each other with respect to a single electrode holding member. The plurality of discharge electrodes may have a pin shape, a sawtooth shape, or a brush shape. The discharge electrode may be attached to the single electrode holding member by providing a hole on each surface of the single electrode holding member facing the surface to be charged in each conduction region and inserting one end side of the discharge electrode into the hole. The both side surfaces of the plurality of sawtooth discharge electrodes may be fixed by being sandwiched by a single electrode holding member.

  An image carrier that carries a latent image, a charging device that charges the surface of the image carrier, a latent image forming unit that forms a latent image on the charged surface of the image carrier, and a developing unit that develops the latent image It is preferable that the image carrier and the charging device can be integrally attached to and detached from the image forming apparatus. An image carrier that carries a latent image, a charging device that charges the surface of the latent image carrier, a latent image forming unit that forms a latent image on the charged surface of the image carrier, and a developing unit that develops the latent image In the image forming apparatus including the above, it is preferable to use the charging device described above as the charging device.

  According to the present invention, by appropriately supplying the applied current supplied from each wiring to the corresponding discharge electrode, discharge unevenness in the longitudinal direction of the charging means can be suppressed, and the image carrier can be uniformly charged. Is possible.

  Hereinafter, an embodiment in which the present invention is applied to an image forming apparatus will be described. FIG. 1 shows a schematic configuration of an image forming apparatus 100 provided with a charging device 12 of the present invention. Around the photosensitive member as the image carrier 10, a charging device 12, an exposure device 14, a developing device 16, a transfer device 18, a fixing device 20, a charge eliminating device 22, and a cleaning device 24 are disposed. The charging device 12 uniformly charges the image carrier 10. The exposure device 14 irradiates the image carrier with beam light based on the image information to form an electrostatic latent image on the image carrier 10. The developing device 16 develops the electrostatic latent image by attaching a developer such as toner to the image carrier 10 in accordance with the electrostatic latent image on the image carrier 10. The developing device 16 includes a developing roller 17 that is rotationally driven. The electrostatic latent image on the image carrier 10 is visualized by a developer such as toner carried on the peripheral surface of the developing roller 17. The transfer device 18 transfers the developer on the image carrier 10 onto the recording medium 300. The fixing device 20 fixes the developer attached on the recording medium 300 onto the recording medium 300 by the action of heat and pressure. The static eliminator 22 removes the charge remaining on the image carrier 10 after the transfer, and sets the surface potential on the image carrier 10 to an initial state. The cleaning device 24 cleans the image carrier 10 by removing paper dust, transfer residual developer, and the like attached to the image carrier 10 after transfer.

  Next, the operation of the image forming apparatus 100 having the above configuration will be described. In FIG. 1, the image carrier 10 is uniformly charged by the charging device 12 while being rotated in the clockwise direction indicated by the arrow, and then the exposure device 14 irradiates the image carrier 10 with beam light based on the image information. Thus, an electrostatic latent image is formed on the image carrier 10. This electrostatic latent image is developed by the developing device 16, and a toner image as a visible image is formed on the image carrier 10.

  The image carrier 10 of this example has a conductive base member 11 formed in a drum shape and a latent image holding layer 13 provided on the outer peripheral surface of the base member 11, and the latent image holding layer 13 is charged. An electrostatic latent image is formed by being charged by the device 12. The latent image holding layer 13 includes, for example, a photosensitive layer or a protective layer laminated on the surface of the photosensitive layer and the photosensitive layer. Further, as the image carrier 10, an endless belt-like image carrier 10 wound around a plurality of rollers and driven to rotate can be used instead of the drum-like photosensitive member. When the endless belt-shaped image carrier 10 is used, a latent image holding layer 13 made of, for example, a photosensitive layer is provided on the base member 11 made of an endless belt.

  The visible image formed with the developer on the image carrier 10 is transferred to the recording medium 300 by the transfer device 18, and the recording medium 300 to which the visible image is transferred is further conveyed and passed through the fixing device 20. The visible image on the recording medium 300 is fixed on the recording medium 300 by the action of heat and pressure applied to the recording medium 300 by the fixing device 20. The recording medium 300 that has passed through the fixing device 20 is discharged to the paper discharge unit 21.

  In the image forming apparatus 100 shown in FIG. 1, the image carrier 10, the charging device 12, the developing device 16, and the cleaning device 24 can be configured as a process cartridge integrally assembled. Further, the process cartridge may be configured by adding an element other than the above-described elements to the above-described process cartridge, for example, the static eliminator 22, or the process cartridge may be configured by only a part of the above-described elements. . For example, the process cartridge may include only the charging device 12 and the image carrier 10 charged by the charging device 12. The above process cartridge can be detachably mounted on the image forming apparatus 100 main body. In the above embodiment, the electrophotographic process in the monochrome machine has been described. However, in the color machine, image formation is performed by the same process.

  FIG. 2 is a diagram illustrating a configuration including the charging device 12 around the image carrier 10 in the image forming apparatus 100.

  The charging device 12 includes a discharge electrode 26 and an electrode holding member 28 that holds the discharge electrode 26. The discharge electrode 26 and the electrode holding member 28 are accommodated in a case 40 having an opening 37. The electrode holding member 28 is fixed to the inner wall of the case 40 by an insulating fixing member 42. The case 40 is disposed in the image forming apparatus 100 so that the opening 37 faces the surface of the image carrier 10, and the discharge-side tip portion 26 a of the discharge electrode 26 in the case 40 is interposed via the opening 37. It is arranged toward the image carrier 10 which is a charged body. The opening 37 of the case 40 has a grid electrode 34 having a plurality of slits 35. A power source 44 is connected to the grid electrode 34, and a predetermined bias is applied from the power source 44 to the grid electrode 34 during image formation.

  The electrode holding member 28 is formed so as to hold the discharge electrode 26 from one end to the other end in the axial direction of the shaft 302 of the image carrier 10. In the present embodiment, the discharge-side distal end portion 26a of the discharge electrode 26 has a thin pin shape, and a plurality of discharge electrodes 26 are arranged on the electrode holding member 28 from one end to the other end in the axial direction of the image carrier 10 at a predetermined interval. Established. The rear end portion 26 b of the discharge electrode 26 is held by the electrode holding member 28, and a plurality of the rear end portions 26 b are arranged at predetermined intervals in the longitudinal direction of the electrode holding member 28. In the present embodiment, the discharge electrodes 26 can be arranged at intervals of 2 to 8 [mm] in the longitudinal direction of the electrode holding member 28.

  In an example of this embodiment, as shown in FIG. 2, the distance X from the tip 26a of the discharge electrode 26 to the grid electrode 34 is set to 4 [mm]. Further, the distance Y from the grid electrode 34 to the surface of the image carrier 10 is set to 2 [mm]. The discharge electrode 26 is connected to a power source 46 through an electrode holding member 28 and a wiring 32, and a charging bias of 2 to 6 kV in absolute value is applied. In this case, a bias having the same polarity as the charging bias is set to an absolute value of 600 to 1000 V and applied to the grid electrode 34. A power source 46 and a power source 44 are connected to the electrode holding member 28 and the case 40, respectively. The charging bias applied from the power source 46 to the discharge electrode 26 has a larger absolute value than the bias applied from the power source 44 to the grid electrode 34, and the charging bias applied from the power source 46 to the discharge electrode 26 is the image carrier. The bias has the same polarity as the charging potential of 10. As a result, a discharge occurs between the leading end portion 26a of the discharge electrode 26 and the image carrier 10 via the grid electrode 34, and the image carrier 10 can be uniformly charged to a predetermined polarity. In this embodiment, the image carrier 10 is charged to a negative polarity. Note that the values of the distances X and Y and the value of the charging bias are not limited to the above values, and may be set to other numerical values.

  FIG. 3 shows an example of a cross section in the longitudinal direction of the charging device 12 of the present invention. The charging device 12 includes a plurality of discharge electrodes 26 and a single electrode holding member 28 that holds the plurality of discharge electrodes 26. The plurality of discharge electrodes 26 are spaced apart from each other in the longitudinal direction of the single electrode holding member 28. Wirings 32 for applying the charging bias to the plurality of discharge electrodes 26 are respectively connected to connection points 32 a provided at positions corresponding to the plurality of discharge electrodes 26 in the longitudinal direction of the single electrode holding member 28. . The single electrode holding member 28 includes a plurality of discharge electrodes 26 and a conductive region 29 in which wirings 32 corresponding to the plurality of discharge electrodes 26 are electrically connected, and a resistance region 31 having a higher resistance than the conductive region 29. Is provided. The resistance region 31 is provided between a plurality of adjacent discharge electrodes 26.

  The charging device 12 illustrated in FIG. 3 includes a gap 33 that separates a part between the conductive regions 29 in each of the resistance regions 31. For example, the resistance region 31 can be formed by forming the gap 33 in the electrode holding member 28 as shown in FIG. A plurality of the gaps 33 are provided in the longitudinal direction of the electrode holding member 28 and are alternately formed with the conduction regions 29 having the discharge electrodes 26. Further, the wiring 32 is connected to a conduction region 29 having each discharge electrode 26 in order to supply a charging bias supplied from a power source 46 to each discharge electrode 26. As described above, by providing the resistance regions 31 between the plurality of conductive regions 29 in the longitudinal direction of the electrode holding member 28, the applied current supplied from the wiring 32 corresponding to each discharge electrode 26 is applied to the corresponding discharge electrode 26. Can be prevented from flowing into the discharge electrode 26 adjacent to. In other words, it is possible to prevent an applied current supplied from the wiring 32 connected to each conduction region 29 from flowing into the discharge electrode 26 in the adjacent conduction region 29. In this way, by appropriately feeding the applied current supplied from each wiring 32 to the corresponding discharge electrode 26, discharge unevenness in the longitudinal direction of the charging means can be suppressed, and the image carrier 10 can be uniformly charged. Is possible.

  Further, as shown in FIG. 3B, a resistance element 50 having a resistance higher than that of the conduction region 29 can be inserted into the gap 33 in FIG. By providing the resistance element 50 in the resistance region 31, the insulation between the conduction regions 29 can be further improved, and the image carrier 10 can be more uniformly charged. As the resistance element 50, materials such as glass and resin can be used. In this case, it is preferable that the electric resistance values of the resistance regions 31 provided between the plurality of adjacent discharge electrodes 26 are substantially the same.

  Further, the shortest distance L1 between the connection point 32a of the wiring 32 provided in the longitudinal direction of the single electrode holding member 28 and the rear end portion 26b of the discharge electrode 26 corresponding to the connection point 32a of the wiring 32 is each conduction region. 29 is preferably substantially the same. Further, as shown in FIG. 3, the length L2 of the gap 33 in the direction from the connection point 32a of the wiring 32 to the discharge electrode 26 corresponding to the connection point 32a of the wiring 32 is the same as the connection point 32a of the wiring 32. It is preferable to have a length equal to or longer than the shortest distance L1 from the rear end portion 26b of the discharge electrode 26. In this way, since the gap 33 exists in the shortest path between the connection point 32a of the wiring 32 corresponding to the discharge electrode 26 in a certain conduction region 29 and the discharge electrode 26 in the adjacent conduction region 29, each wiring The applied current from 32 can be prevented from flowing into the discharge electrode 26 in the adjacent conduction region 29.

  FIG. 4 shows an equivalent circuit for explaining the principle of the charging device 12 of the present invention. 4, the conduction region 29a corresponds to the conduction region 29 in FIG. The resistance region 31a corresponds to the resistance region 31 in FIG. The conduction regions 29 a and the resistance regions 31 a are alternately provided in the longitudinal direction of the electrode holding member 28. The resistance regions 31a are respectively provided between the conductive regions 29a, and electrically connect the conductive regions 29a with resistors 52 having a resistance value R. The wirings 32 for supplying the charging bias supplied from the power supply 46 to each conduction region 29a are connected to the connection point 32a of each conduction region 29a. The conduction region 29a has a resistance value r. The resistance region 31a has a resistance value R. Since the resistance value R and the resistance value r have a relationship of R> r, it is possible to prevent the applied current supplied from each wiring 32 from flowing into the discharge electrode 26 in the adjacent conduction region 29a. Further, by setting the resistance value R and the resistance value r to be in a relationship of R> r, the discharge unevenness generated when the space resistance Rg between each discharge electrode 26 and the image carrier 10 is different in each discharge electrode 26. Can be reduced.

  FIG. 5 shows another embodiment of the charging device 12 of the present invention. The wirings 32 that supply the charging bias supplied from the power supply 46 to each conduction region 29 are connected to the connection point 32 a of each conduction region 29. In the electrode holding member 28, the conductive region 29 is formed of a conductive member 52 </ b> A, and the resistance region 31 is formed of a high resistance member 52 </ b> B having a higher resistance than the conductive member 52 </ b> A that forms the conductive region 29. In the electrode holding member 28, conductive members 52A and high resistance members 52B are alternately arranged. The single electrode holding member 28 can be formed by integrally forming the conductive member 52A and the high resistance member 52B by two-color molding. As a material of the conductive member 52A, a microfiber (filler) such as stainless steel or carbon can be added to a base material made of polycarbonate (PC) or the like. As a material of the high resistance member 52B, a base material made of polycarbonate (PC) or the like can be used as it is. The conductive member 52A and the high resistance member 52B may be fixed with an insulating adhesive. Thus, since the electrode holding member 28 of this embodiment can form the member which forms the conduction | electrical_connection area | region 29, and the member which forms the resistance area | region 31 as the single electrode holding member 28, from each wiring 32, it can be formed. The applied current can be prevented from flowing into the discharge electrode 26 in the adjacent conduction region 29.

  6 (A) to 6 (C) show still another embodiment of the charging device 12 of the present invention. The electrode holding member 28 is formed on the surface of the insulating support 39 that supports the discharge electrode 26 and has a higher resistance than the discharge electrode 26, and the connection points 32 a of the plurality of wirings 32. The conductive film 41 electrically connects the discharge electrodes 26 respectively corresponding to the connection points 32 a of the wiring 32, and the conductive film 41 has a larger area in the resistance region 31 than an area in the conductive region 29. It is formed to be smaller.

  6B and 6C show a cross section in a direction perpendicular to the longitudinal direction of the electrode holding member 28 in a state where the conductive film 41 is provided on the insulating support 39. As shown in FIGS. 6B and 6C, the conductive film 41 can be provided on the peripheral surface of the insulating support 39. In order to contact the conductive film 41 and the discharge electrode 26, an insertion hole 66 is provided in the bottom surface of the insulating support 39, and the conductive film 41 is inserted into the insertion hole 66 together with the discharge electrode 26 to be in contact with each other. Can do. The conductive film 41 and the insulating support 39 are preferably fixed with an insulating adhesive. As a material of the insulating support 39, a resin can be used. As a material of the conductive film 41, a microfiber (filler) such as stainless steel or carbon can be added to a base material made of polycarbonate (PC) or the like. 6A to 6C can prevent the applied current from each wiring 32 from flowing into the discharge electrode 26 in the adjacent conduction region 29. FIG. Furthermore, since the connection location of the wiring 32 can be set in consideration of the space around the electrode holding member 28, the degree of freedom of the installation location of the charging device 12 in the image forming apparatus 10 or the process cartridge can be increased. For example, as shown in FIG. 6B, the conductive film 41 is provided from the bottom surface of the insulating support 39 provided with the discharge electrode 26 to the side surface of the insulating support 39, and the wiring 32 is provided on the insulating support 39. You may connect to the conductive film 41 provided on the side surface. Further, as shown in FIG. 6C, the conductive film 41 is placed on the top surface of the insulating support 39 from the bottom surface of the insulating support 39 provided with the discharge electrode 26 via the side surface of the insulating support 39. The wiring 32 may be connected to the conductive film 41 provided on the top surface of the insulating support 39.

  7 and 8 show still another embodiment of the charging device 12 of the present invention. The electrode holding member 28 in the charging device 12 illustrated in FIG. 7A includes an insulating substrate 49 and a conductive substrate 51. A plurality of protruding portions 59 are provided on the conductive substrate 51 at a predetermined interval, and the protruding portions 59 correspond to the conductive region 29 described above. Discharge electrodes 26 are provided at positions corresponding to the respective conductive regions 29 at the lower end of the conductive substrate 51. An insulating substrate 49 is disposed above the conductive substrate 51, and the insulating substrate 49 is provided at a position corresponding to each protrusion 59, and a plurality of hole portions 55 that engage with each protrusion 59 are provided. The insulating substrate 49 and the conductive substrate 51 can be integrated by fitting the protrusions 59 of the conductive substrate 51 and the holes 55 of the insulating substrate 49 corresponding to the protrusions 59. In order to make the resistance characteristics of the plurality of protrusions 59 the same, the shapes of the plurality of protrusions 59 are preferably the same.

  A single plate-like wiring 53 provided along the longitudinal direction of the electrode holding member 28 can be used as a connection member for supplying the charging bias supplied from the power supply 46 to each conduction region 29. The plate-like wiring 53 has a plurality of wiring contact portions 32 b that come into contact with each of the protruding portions 59. The height of each protrusion 59 of the conductive substrate 51 is formed to be higher than the height of the hole 55 of the insulating substrate 49. Therefore, when the protrusions 59 of the conductive substrate 51 and the holes 55 of the insulating substrate 49 corresponding to the protrusions 59 are fitted together, the protrusions 59 of the conductive substrate 51 become holes of the insulating substrate 49. It protrudes from the portion 55 and can come into contact with the wiring contact portion 32 b of the plate-like wiring 53. As a material of the plate-like wiring 53, a sheet metal such as SUS (stainless steel) can be used. The plate-like wiring 53 is disposed on the insulating substrate 49. In this case, if a single plate-like wiring 53 is to be brought into contact with each protrusion 59 at the same time, if there is a difference in the height of each protrusion 59, the protrusion that does not come into contact with the protrusion 59 that contacts the plate-like wiring 53. May cause a contact failure. However, since the wiring contact portion 32b of the plate-like wiring 53 of the present application serves as a spring, the wiring contact portion 32b of the plate-like wiring 53 absorbs the difference in height of each protruding portion 59, and each protruding portion. The upper surface of 59 can be pressed into contact with all the protruding portions 59 with certainty.

  FIG. 7B shows a cross section of the plate-like wiring 53 shown in FIG. A convex portion 60 can be further provided on the upper surface of the protruding portion 59 so as to be in contact with the wiring contact portion 32 b of the plate-like wiring 53. By providing the convex portion 60, the protruding portion 59 can be brought into pressure contact with the wiring contact portion 32 b of the plate-like wiring 53 more reliably. Further, if the convex portion 60 is formed so that the convex portion 60 and the wiring contact portion 32b are in point contact, more stable contact can be obtained. When the protrusion 60 is provided on the upper surface of the protrusion 59, at least the protrusion 60 may be provided so as to protrude from the hole 55 without the protrusion 59 itself protruding from the hole 55. As shown in FIG. 8A, the protrusion 59 itself is protruded from the hole 55 without contacting the wiring contact portion 32b of the plate-like wiring 53 without providing the protrusion 60 on the upper surface of the protrusion 59. You can also. At this time, the plate-like wiring 53 and the protrusion 59 are preferably fixed with solder or a conductive adhesive 61. Further, the insulation between the conductive substrate 51 other than the contact points and the plate-like wiring 53 is maintained by, for example, subjecting the peripheral surface other than the contact point between the protruding portion 59 of the conductive substrate 51 and the plate-like wiring 53 to the insulating surface. If possible, the insulating substrate 49 may not be provided.

  FIG. 8B shows a cross section of the electrode holding member 28 in which the spring portion 62 is provided on the upper surface of the protruding portion 59 of the conductive substrate 51. By providing the cavity 64 in each protrusion 59, the spring part 62 can be formed around the protrusion 60 provided on the upper surface of the protrusion 59. When the plate-shaped wiring 53 is brought into contact with the tip of the convex portion 60 that is the contact point of the protruding portion 59, if the height of the convex portion 60 on each protruding portion 59 varies, it contacts the plate-shaped wiring 53. The convex part 60 which does not contact with the convex part 60 arises, and a bad contact may be caused. Therefore, in the embodiment of FIG. 8B, by providing the spring portion 62 around the convex portion 60, the convex portion 60 that is relatively higher than the other convex portions 60 comes into contact with the plate-like wiring 53. Due to the action of the spring, it sinks downward, and the other protrusion 60 can be brought into contact with the plate-like wiring 53 with certainty. The plate-like wiring 53 may be provided with the wiring contact portion 32b as shown in FIG. 7A, but a flat plate-like wiring without the wiring contact portion 32b can also be used.

  FIG. 9 shows various embodiments of the discharge electrode 26 used in the charging device 12. As the shape of the discharge electrode 26, for example, a pin-like electrode shown in FIG. 9A, a saw-tooth electrode shown in FIG. 9B, a brush-like electrode shown in FIG. 9C, and FIG. The cylindrical electrode shown can be used. The tip of the pin-shaped electrode shown in FIG. 9A is formed in a conical shape, and tungsten, SUS (stainless steel), or the like can be used as the material. As the sawtooth electrode shown in FIG. 9B, a plate-like material formed in a triangular or trapezoidal shape is used, and SUS (stainless steel) can be used as the material. The brush-like electrode shown in FIG. 9C is formed by bundling a plurality of conductive fibers, and the material is carbon fiber (carbon), conductive acrylic fiber (SA-7), or copper sulfide mixed fiber (Thunderron). ) Etc. can be used. It is desirable to use a brush-like electrode having a diameter φ of 0.1 to 100 [μm] on the tip side of the conductive fiber. More desirably, 0.1 to 10 [μm] is suitable. A plurality of such conductive fibers can be bundled to form a brush-like electrode. As the columnar electrode, a conductive material made of a wire having a diameter of about 5 to 60 μm can be used. In particular, in the case of a pin-shaped electrode or a sawtooth electrode, it is preferable that the discharge-side tip portion 26a is thinner than the other end side. The shape of the rear end portion 26b opposite to the discharge-side front end portion 26a of the pin-like electrode or the sawtooth electrode is not particularly limited, and is formed in a shape that can be held by the electrode holding member 28 and is formed in the conduction region 29. What is necessary is just to be formed in the shape which can be contacted.

  10 and 11 show the configuration of the discharge electrode 26 and the electrode holding member 28 when the sawtooth electrode shown in FIG. 9B is used as the discharge electrode 26. An electrode holding portion 48 that holds the discharge electrode 26 is provided at the end of the electrode holding member 28 on the image carrier 10 side in the conduction region 29.

  The electrode holding portion 48 is provided with gripping portions 54 for holding the discharge electrode 26 at positions corresponding to both sides of the discharge electrode 26. The grip portion 54 is formed with an inclined surface 57 that can be guided when the discharge electrode 26 is fitted. With the inclined surface 57, the discharge electrode 26 can be guided into the holding portion 54 of the electrode holding portion 48. Further, the discharge electrode 26 can be locked in the grip portion 54 by pushing the discharge electrode 26 into the inclined surface 57 of the grip portion 54. Further, an engagement protrusion 56 is provided on the electrode holding portion 48. The sawtooth electrode used as the discharge electrode 26 is provided with an engagement hole 58 that engages with the engagement protrusion 56. The discharge electrode 26 is positioned by the engaging protrusion 56 together with the grip portion 54 and fixed to the electrode holding portion 48 of the electrode holding member 28.

  If a contact failure occurs between the discharge electrode 26 and the electrode holding part 48 due to, for example, a gap between the discharge electrode 26 and the electrode holding part 48, the charging bias may not be properly applied to the discharge electrode 26. Therefore, the discharge electrode 26 needs to be fixed without generating a gap between the discharge electrode 26 and the electrode holding portion 48. Therefore, the rear end portion 26 b of the discharge electrode 26, that is, the end portion on the opposite side to the discharge-side front end portion 26 a is in contact with the discharge electrode contact portion 29 a that is a contact portion with the discharge electrode 26 in the conduction region 29. It is preferable. The engagement protrusion 56 determines the degree of contact between the rear end portion 26 b of the discharge electrode 26 and the discharge electrode contact portion 29 a of the conduction region 29. In other words, the engagement protrusion 56 has a positioning function in the direction in which the rear end portion 26 b of the discharge electrode 26 contacts or leaves the discharge electrode contact portion 29 a of the conduction region 29. Therefore, in order to appropriately apply the charging bias to the discharge electrode 26, the engagement protrusion 56 and the engagement hole 58 are provided so that the rear end portion 26b of the discharge electrode 26 and the discharge electrode contact portion 29a of the conduction region 29 are in close contact with each other. It is good to arrange each.

  As shown in FIGS. 9 to 11, the plurality of discharge electrodes 26 are provided independently of each other and can be independently attached to and detached from the single electrode holding member 28. Therefore, even when wear or contact failure occurs in any one of the discharge electrodes 26 over time and proper discharge cannot be performed, only the discharge electrode 26 can be replaced. There is no need to replace it. As another embodiment for holding the discharge electrode 26 when a sawtooth electrode is used, both side surfaces of the electrode may be sandwiched and fixed by a single electrode holding member.

  FIG. 12 shows an embodiment of the charging device 12 when the brush electrode shown in FIG. 9C is used as the discharge electrode 26. FIG. 10A shows the longitudinal side surface of the charging device 12. FIG. 10B shows a plan view of the charging device 12 when the charging device 12 is viewed from the discharge-side tip portion 26 a side of the brush-like discharge electrode 26. When the brush-like discharge electrode 26 is used, a plurality of insertion holes 66 are provided at the end of the conductive region 29 of the electrode holding member 28 on the image carrier 10 side in consideration of the diameter of the brush-like discharge electrode 26. The rear end portion 26 b of the brush-like discharge electrode 26 is inserted into the insertion hole 66 and disposed. At this time, a conductive adhesive may be applied to the insertion hole 66 to fix the rear end portion 26 b of the brush-like discharge electrode 26 and the insertion hole 66. Further, when the electrode shown in FIG. 9A, FIG. 9B, or FIG. 9D is used as the discharge electrode 26, the discharge electrode 26 can be attached to the electrode holding member 28 by the same method.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

1 is a schematic configuration diagram of an image forming apparatus including a charging device of the present invention. FIG. 2 is a diagram illustrating a configuration including a charging device around a photosensitive member in an image forming apparatus. It is a figure which shows an example of the cross section in the longitudinal direction of the charging device 12 of this invention. It is a figure which shows the equivalent circuit for demonstrating the principle of the charging device 12 of this invention. It is a figure which shows other embodiment of the charging device 12 of this invention. It is a figure which shows other embodiment of the charging device 12 of this invention. It is a figure which shows other embodiment of the charging device 12 of this invention. It is a figure which shows other embodiment of the charging device 12 of this invention. FIG. 6 is a diagram illustrating various embodiments of the discharge electrode 26 of the charging device 12. It is a figure which shows the method of attaching the discharge electrode 26 to the electrode holding member 28 at the time of using a sawtooth electrode. It is a figure which shows the state which attached the discharge electrode 26 at the time of using a sawtooth electrode to the electrode holding member 28. FIG. FIG. 3 is a diagram illustrating an embodiment of the charging device 12 using a brush-like electrode as the discharge electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image carrier 12 Charging apparatus 14 Exposure apparatus 16 Development apparatus 18 Transfer apparatus 20 Fixing apparatus 22 Static elimination apparatus 24 Cleaning apparatus 26 Discharge electrode 28 Electrode holding member 32 Wiring 34 Grid electrode 35 Slit 40 Case 42 Fixing member 44 and 46 Power supply 48 Electrode Holding part 50 Resistance element 52 Resistance 53 Plate-like wiring 54 Grip part 56 Engagement protrusion 57 Inclined surface 58 Engagement hole part

Claims (15)

In a charging device including a charging unit having a plurality of discharge electrodes and a single electrode holding member that holds the plurality of discharge electrodes,
The plurality of discharge electrodes are spaced apart from each other in the longitudinal direction of the single electrode holding member, and wiring for applying a charging bias to each of the plurality of discharge electrodes is provided on the single electrode holding member. Each connected to a position corresponding to the plurality of discharge electrodes in the longitudinal direction;
The single electrode holding member includes a conduction region in which the plurality of discharge electrodes and the wiring corresponding to the plurality of discharge electrodes are electrically connected, and a resistance region having a higher resistance than the conduction region. ,
The charging device according to claim 1, wherein the resistance region is provided between the plurality of adjacent discharge electrodes. The charging device according to claim 1,
A charging device, wherein each of the resistance regions is provided with a gap for separating a part between the conductive regions. The charging device according to claim 2,
A charging device, wherein a resistance element having a higher resistance than the conduction region is provided in the gap. The charging device according to claim 2 or 3,
The length L2 of the gap in the direction from the connection point of the wiring toward the discharge electrode corresponding to the connection point of the wiring is the connection point of the wiring provided in the longitudinal direction of the single electrode holding member. A charging device having a length equal to or longer than a shortest distance L1 from the discharge electrode corresponding to a connection point of the wiring. The charging device according to claim 4,
The charging device, wherein the shortest distance L1 is substantially the same between the conductive regions. The charging device according to any one of claims 1 to 3,
The charging device according to claim 1, wherein electrical resistance values of the resistance regions respectively provided between the plurality of adjacent discharge electrodes are substantially the same. The charging device according to claim 1,
The charging device according to claim 1, wherein the single electrode holding member includes the conductive region formed of a conductive member, and the resistance region formed of a high resistance member having a resistance higher than that of the conductive member. The single electrode holding member is formed on the surface of the insulating support that supports the discharge electrode and has a higher resistance than the discharge electrode, and corresponds to the wiring and the wiring. A conductive film that electrically connects the discharge electrode,
The charging device according to claim 1, wherein the conductive film has an area in the resistance region smaller than an area in the conduction region. The charging device according to any one of claims 1 to 8,
The charging device, wherein the wiring connected to the conduction region is plate-shaped. The charging device according to any one of claims 1 to 9,
The charging device according to claim 1, wherein the plurality of discharge electrodes are provided independently, and can be independently attached to and detached from the single electrode holding member. The charging device according to any one of claims 1 to 10,
The charging device according to claim 1, wherein the plurality of discharge electrodes have a pin shape, a sawtooth shape, or a brush shape. The charging device according to claim 11, wherein
A hole is provided in a surface of the single electrode holding member facing the surface to be charged in each conduction region, and one end of the discharge electrode is inserted into the hole to hold the discharge electrode. A charging device which is attached to a member. The charging device according to claim 11, wherein
A charging device, wherein both side surfaces of the plurality of sawtooth discharge electrodes are fixed by being sandwiched between the single electrode holding members. An image carrier that carries a latent image, a charging device that charges the surface of the image carrier, a latent image forming unit that forms a latent image on the charged surface of the image carrier, and develops the latent image The charging device according to claim 1, wherein the charging device is used in an image forming apparatus including a developing unit.
A charging device, wherein the image carrier and the charging device can be integrally attached to and detached from the image forming device. An image carrier that carries a latent image, a charging device that charges the surface of the latent image carrier, a latent image forming unit that forms a latent image on the charged surface of the image carrier, and developing the latent image An image forming apparatus comprising:
An image forming apparatus using the charging device according to claim 1 as the charging device.

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