JP5651802B2 - Charging device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a charging device that applies a charge to a photoconductor used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and an image forming apparatus including the charging device.

  Conventionally, when an electrostatic latent image is formed on a photoconductor as an image carrier, an image forming apparatus needs to charge the photoconductor to a predetermined potential in advance. As a charging device for charging the surface of the photoreceptor, a conductive roller having an elastic layer to which a voltage is applied on the surface, a charging member having a conductive shaft portion penetrating the shaft center of the conductive roller, and both ends of the shaft portion 2. Description of the Related Art A contact-type charging device is known that includes a bearing portion that rotatably supports a shaft and a power supply member that is in contact with one end side of the shaft portion and applies a voltage to a conductive roller. In the contact-type charging device, electric charges are given to the photoconductor by rotating each other with the charging member in contact with the photoconductor.

  In this charging device, when rust is generated in the sliding portion between the shaft portion and the bearing portion or in the contact portion between the shaft portion and the power supply member, rotation failure or power supply failure may occur, which may cause charging failure. For example, the toner image transferred to the paper is heated to fix it, and the moisture contained in the paper is evaporated in the apparatus by this heat, and the humidity in the apparatus is increased, or the charging member is kept under high humidity. When exposed for a period of time, moisture may permeate into the conductive roller. The conductive roller is often made of a special material containing a strong acidic substance, for example, soaked water pushes out the strong acidic substance contained in the conductive roller from the conductive roller, and the strong acidic substance is formed on the surface of the shaft portion. May adhere. When strong acidic substances adhere to the shaft, rust is generated at the contact portion of the shaft with the conductive roller, and contact between the contact portion with the conductive roller and the sliding portion of the shaft portion of the bearing or the power supply member of the shaft portion It was difficult to prevent rust from moving to the part.

  Therefore, related techniques for suppressing charging failure due to rust are conventionally known. For example, the charging member described in Patent Document 1 has a conductive roller and a shaft portion inserted into the conductive roller, and a rust preventive agent is applied to a portion of the shaft portion facing both ends of the conductive roller. . With this configuration, the rust generated at the portion of the shaft portion that comes into contact with the conductive roller is difficult to shift to the sliding portion with the bearing portion or the contact portion with the power supply member by the rust inhibitor.

JP 2002-156810 A (paragraph [0025], FIG. 4)

  However, in the charging member described in Patent Document 1, rust is generated on the surface of the shaft portion that contacts the conductive roller, and rust does not occur uniformly on the surface of the shaft portion that contacts the conductive roller. Therefore, the electrical resistance increases due to the rust on the shaft portion, and the electrical resistance varies between the rusted portion and the rust-free portion. There is a problem that the generated charge becomes unstable and it is difficult to uniformly charge the photosensitive member.

  The present invention has been made in order to solve the above-described problems, and provides a charging device that suppresses poor charging of a photoreceptor due to rust of a shaft portion made of a metal material, and an image forming apparatus including the charging device. For the purpose.

In order to achieve the above object, a first invention is a contact charging type charging device that contacts the surface of a photoconductor to charge the photoconductor and carries the electrostatic latent image on the photoconductor,
A first area portion provided in contact with the photoconductor and facing an image forming area of the photoconductor, and provided at an end portion in a longitudinal direction of the first area portion and outside the image forming area of the photoconductor. A conductive roller that has a second region portion facing to supply electric charge to the photoreceptor;
A shaft made of a metal material, to which a voltage is applied from a power source,
A portion corresponding to the first and second region portions of the outer peripheral surface of the shaft portion is formed with a plating region portion plated with a metal having a smaller ionization tendency than the shaft portion, and the second region portion includes The corresponding portion is characterized in that a non-plated region portion that is not partially plated is formed.

  According to 1st invention, the axial part which consists of metal materials is coat | covered by the plating process with the metal whose ionization tendency is smaller than an axial part, and corrosion of an axial part is prevented. Also, for example, if moisture enters the roller and rust is likely to occur on the surface of the shaft, rust is concentrated on the non-plated region formed in the portion corresponding to the second region of the shaft. Therefore, the occurrence of rust is suppressed at the portion corresponding to the first region portion of the shaft portion. For this reason, in the first region portion of the shaft portion facing the image forming region of the member to be charged, the generation of rust is suppressed, so that the roller is uniformly applied by the power source through the shaft portion, and The charged body is uniformly charged.

1 is a diagram schematically illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. Sectional drawing which shows the charging member used for the image forming apparatus which concerns on embodiment FIG. 3 is a plan view showing a charging member used in the image forming apparatus according to the embodiment.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Further, the use of the invention and the terms shown here are not limited thereto.

  FIG. 1 is a diagram schematically illustrating a configuration of an image forming apparatus including a charging device according to an embodiment of the present invention. The image forming apparatus 1 is a tandem type color printer, and the rotatable photoreceptors 11a to 11d use an organic photoreceptor (OPC photoreceptor) as a photosensitive material for forming a photosensitive layer, and are magenta, cyan, and yellow. , And black. The photoconductors 11a to 11d may be amorphous silicon photoconductors. Developing devices 2a to 2d, an exposure unit 12, charging devices 13a to 13d, and cleaning devices 14a to 14d are disposed around the photoreceptors 11a to 11d.

  The developing devices 2a to 2d are arranged to face the right sides of the photoconductors 11a to 11d, respectively, and supply toner to the photoconductors 11a to 11d. The charging devices 13a to 13d are arranged on the upstream side of the developing devices 2a to 2d with respect to the rotation direction of the photoconductors 11a to 11d and facing the surfaces of the photoconductors 11a to 11d, and charge the surfaces of the photoconductors 11a to 11d. Let

  The exposure unit 12 scans and exposes each of the photoconductors 11a to 11d based on image data such as characters and pictures input to an image input unit (not shown) from a personal computer or the like. The developing device 2a ~ 2d below. The exposure unit 12 is provided with a laser light source and a polygon mirror, and a reflection mirror and a lens are provided corresponding to each of the photoconductors 11a to 11d. Laser light emitted from the laser light source is applied to the surfaces of the photoconductors 11a to 11d from the downstream side in the photoconductor rotation direction of the charging devices 13a to 13d via the polygon mirror, the reflection mirror, and the lens. Electrostatic latent images are formed on the surfaces of the photoreceptors 11a to 11d by the irradiated laser light, and the electrostatic latent images are developed into toner images by the developing devices 2a to 2d.

  The endless intermediate transfer belt 17 is stretched around the tension roller 6, the driving roller 25, and the driven roller 27. The driving roller 25 is driven to rotate by a motor (not shown), and the intermediate transfer belt 17 is driven to circulate by the rotation of the driving roller 25.

  The photoreceptors 11a to 11d are arranged below the intermediate transfer belt 17 so as to be in contact with the intermediate transfer belt 17 along the conveying direction (arrow direction in FIG. 1). Primary transfer rollers 26a to 26d having shaft portions and rollers are opposed to the respective photoconductors 11a to 11d with the intermediate transfer belt 17 interposed therebetween, and press contact with the intermediate transfer belt 17 to form a primary transfer portion. In the primary transfer portion, the toner images on the photoreceptors 11a to 11d are sequentially transferred to the intermediate transfer belt 17 at a predetermined timing as the intermediate transfer belt 17 rotates by the primary transfer rollers 26a to 26d to which a transfer bias is applied. Is done. As a result, a toner image is formed on the surface of the intermediate transfer belt 17 by superimposing four color toner images of magenta, cyan, yellow, and black.

  The secondary transfer roller 34 faces the driving roller 25 with the intermediate transfer belt 17 interposed therebetween, and presses against the intermediate transfer belt 17 to form a secondary transfer portion. In the secondary transfer portion, the toner image on the surface of the intermediate transfer belt 17 is transferred onto the paper P by the secondary transfer roller 34 to which a transfer bias is applied. After the transfer, the belt cleaning device 31 cleans the toner remaining on the intermediate transfer belt 17.

  A paper feed cassette 32 that stores paper P is disposed below the image forming apparatus 1, and a stack tray 35 that supplies manually fed paper is disposed to the right of the paper feed cassette 32. On the left side of the paper feed cassette 32, a first paper transport path 33 for transporting the paper P sent from the paper feed cassette 32 to the secondary transfer portion of the intermediate transfer belt 17 is disposed. Further, on the left side of the stack tray 35, a second paper transport path 36 for transporting paper fed from the stack tray 35 to the secondary transfer unit is disposed. Further, on the upper left side of the image forming apparatus 1, a fixing unit 18 that performs a fixing process on the paper P on which the toner image is formed, and a third unit that conveys the paper P on which the fixing process has been performed to the paper discharge unit 37. A paper transport path 39 is provided.

  The paper feed cassette 32 is a sheet P that can be replenished by being pulled out of the apparatus (the front side of the paper surface in FIG. 1). Each is sent out to the first paper transport path 33 side.

  The first paper transport path 33 and the second paper transport path 36 merge before the registration roller pair 33c, and the registration roller pair 33c takes the timing of the image forming operation and the paper feeding operation in the intermediate transfer belt 17. Thus, the sheet P is conveyed to the secondary transfer unit. The sheet P conveyed to the secondary transfer unit is secondarily transferred with the toner image on the intermediate transfer belt 17 by the secondary transfer roller 34 to which a transfer bias is applied, and is conveyed to the fixing unit 18.

  The fixing unit 18 includes a fixing belt heated by a heater or the like, a fixing roller in contact with the fixing belt, a pressure roller disposed in pressure contact with the fixing roller across the fixing belt, and the toner image is transferred. The fixing process is performed by heating and pressurizing the sheet P. After the toner image is fixed on the sheet P by the fixing unit 18, the toner image is reversed by the fourth sheet conveyance path 40 as necessary, and the toner image is secondarily transferred to the back surface of the sheet by the secondary transfer roller 34. The fixing unit 18 performs fixing processing. The sheet on which the toner image is fixed passes through the third sheet conveyance path 39 and is discharged to the sheet discharge unit 37 by the discharge roller pair 19a.

  2 and 3 are diagrams showing the configuration of the charging device used in the image forming apparatus 1, FIG. 2 is a sectional view of the charging device, and FIG. 3 is a plan view of the charging device. In the following description, the configuration and operation of the charging device 13a corresponding to the photoconductor 11a shown in FIG. 1 will be described. However, the configuration and operation of the charging devices 13b to 13d are the same as those of the charging device 13a. Explanation is omitted, and reference numerals a to d indicating the charging device and the photosensitive member of each color are omitted, and reference numerals a to d are given when necessary.

  As shown in FIG. 2, the charging device 13 uses a contact charging method in which a charging member 41 as a charge supply member comes into contact with the surface of the photosensitive member 11 as a member to be charged to charge the photosensitive member 11.

  The charging member 41 is provided in contact with the surface of the photoconductor 11, a conductive roller 42 that supplies electric charge to the photoconductor 11, a shaft portion 43 that is integrally inserted in the conductive roller 42, and a surface of the shaft portion 43. And a plating region portion Ma to be used.

Conductive roller 42 is made of, for example, those having elasticity in such hydrin which contain additives chlorine, by a biasing member 45 such as a compression coil spring disposed in pressure contact with the photosensitive member 11, also the transfer means 10 ⁷ It consists of a rubber roller with excellent conductivity that is Ωcm or less. Accordingly, the conductive roller 42 is driven to rotate as the photoconductor 11 rotates, and a predetermined voltage is applied from the power source 46 described later via the shaft portion 43 to charge the entire circumference of the photoconductor 11.

  The shaft portion 43 is made of a conductive material, for example, a rust material such as a SUM material is easily generated, but a relatively inexpensive iron material is used, and power is supplied from one end portion in the axial direction by a power source 46. The shaft portion 43 is press-fitted into the hollow portion of the conductive roller 42 and is configured integrally with the conductive roller 42. By applying a voltage to the conductive roller 42 via the shaft portion 43, the surface of the photoconductor 11 in contact with the conductive roller 42 is charged. The conductive roller 42 may be integrally formed with the shaft portion 43, or the conductive roller 42 and the shaft portion 43 may be fixed with a conductive adhesive.

  The plating region portion Ma is plated with a metal having a smaller ionization tendency than the shaft portion 43, thereby preventing the shaft portion 43 from being corroded. For example, when the shaft portion 43 is made of an iron material such as a SUM material, the plating region portion Ma is plated with a metal having a smaller ionization tendency than iron, for example, electroless nickel plating, silver plating, copper plating, tin plating, or the like. . Nickel plating is excellent in terms of prevention of corrosion of the shaft portion 43, conductivity of the plating region portion Ma, cost of the plating material, and the like, and it is preferable to apply nickel plating to the plating region portion Ma.

  As shown in FIG. 3, the surface of the shaft portion 43 is plated. Specifically, the conductive roller 42 is fixed to the shaft portion 43, bearing portions (not shown) are disposed at both ends of the conductive roller 42, and a power source 46 (FIG. 2) is provided at one end portion of the shaft portion 43. Connection line (not shown) from (see) is arranged in contact. Further, the conductive roller 42 forms an image on the first region La facing the region where the photoconductor 11 (see FIG. 2) forms an image and the photoconductor 11 provided at both ends in the longitudinal direction of the first region La. And a second region portion Lb facing outside the region. A plated region portion Ma is formed in a portion corresponding to the first region portion La and the second region portion Lb on the surface of the shaft portion 43, a sliding portion with the bearing portion, and a connection portion of the power source 46. .

  On the other hand, in a portion corresponding to the second region portion Lb on the surface of the shaft portion 43, a non-plated region portion Mb that is not partially subjected to plating is formed. The non-plated region portion Mb is formed over the entire circumference of the shaft portion 43 with a relatively small width, for example, 0.5 mm, in the axial direction of the shaft portion 43. In the non-plating region portion Mb, the surface of the shaft portion 43 (background of the shaft portion material) and the surface of the conductive roller 42 to be fixed face each other.

  With the above configuration, the humidity in the image forming apparatus 1 becomes high, or the charging member 41 is exposed to high humidity for a long period of time, so that moisture penetrates into the conductive roller 42 and rust is generated on the surface of the shaft portion 43. If it becomes easy to do, rust will be concentrated on the non-plated region portion Mb formed in the portion corresponding to the second region portion Lb of the shaft portion 43, corresponding to the first region portion La of the shaft portion 43. The occurrence of rust is suppressed at the portion where the rusting occurs. For this reason, in the first area La facing the image forming area of the photoconductor 11, the conductive roller 42 is uniformly applied by the power source 46 via the shaft 43 without being affected by rust, and the photosensitive area 11 is exposed to light. The image forming area of the body 11 can be uniformly charged.

  In the plating process having the non-plating region portion Mb, the plating mask liquid is applied to the portion of the shaft portion 43 corresponding to the non-plating region portion Mb (masking treatment), and then the shaft portion 43 is immersed in the plating solution tank. Done. Alternatively, the non-plated region portion Mb may be formed by stripping a predetermined portion of the surface of the shaft portion 43 with a marking needle or the like after the plating treatment of the shaft portion 43. The non-plating region Mb may be provided in one second region Lb instead of the configuration provided in the second region Lb on both sides of the shaft 43, or on the entire circumference of the surface of the shaft 43. Instead of providing the non-plating region portion Mb, the non-plating region portion Mb may be partially provided in the circumferential direction of the shaft portion 43, such as a semicircular portion of the shaft portion 43.

  In the above embodiment, an example in which the member to be charged is applied to the photosensitive member 11 and the charge supply member is applied to the charging member 41 has been described. However, the present invention is not limited thereto, and the charge supply member may be an intermediate transfer belt. 17 is composed of a primary transfer roller 26 (transfer roller) that is pressed against the photoconductor 11 across 17 and transfers a toner image carried on the photoconductor 11 onto the intermediate transfer belt 17 by applying a voltage. The member to be charged may be constituted by the intermediate transfer belt 17. In this case, in the first area La facing the image forming area of the intermediate transfer belt 17, the occurrence of rust is suppressed, and the roller of the primary transfer roller 26 is uniformly applied by the power source via the shaft section. The image forming area of the intermediate transfer belt 17 can be uniformly charged.

  Further, the charge supply member may be constituted by a secondary transfer roller 34 (transfer roller) that transfers a toner image carried on the intermediate transfer belt 17 to a sheet P as a recording medium by applying a voltage. Good. In addition, the charge supply member is pressed against the photoconductor across the conveyance belt carrying the paper, and a voltage is applied to transfer the toner image formed on the photoconductor to the paper on the conveyance belt. You may comprise. Further, the charge supply member is a transfer roller that is pressed against the photoconductor to form a nip portion and is applied with a voltage to transfer a toner image carried on the photoconductor onto a sheet conveyed to the nip portion. There may be. In these cases, the same effects as those of the above embodiment can be obtained.

  Hereinafter, Examples 1 and 2 and Comparative Examples 1 and 2 that further embody the embodiment of the present invention will be described. In addition, this invention is not limited only to a following example.

  Using Examples 1 and 2 in which the shaft portion 43 of the charging member 41 is provided with the non-plated region portion Mb and Comparative Examples 1 and 2 in which the shaft portion 43 is not provided with the non-plated region portion Mb, Test 1 and Test 2 Went. In Test 1, the number of rust generated on the shaft portion 43 was evaluated, and in Test 2, the number of rust generated on the shaft portion 43 and the quality of the images were evaluated.

The conductive roller 42 of the charging member 41 used in Test 1 and Test 2 is made of hydrin rubber containing a chlorine-based additive having a transfer means of 10 ⁶ Ωm, the shaft portion 43 is made of a SUM22 drawing material, and the surface of the shaft portion 43 Was subjected to electroless nickel plating having a thickness of 3 to 6 μm.

  In Test 1, Example 1 and Comparative Example 1 use the one in which the conductive roller 42 is integrally molded and fixed to the shaft portion 43, while Example 2 and Comparative Example 2 use the conductive roller 42 and the shaft portion, respectively. What fixed 43 by the hydrophobic adhesive was used. In Example 1 and Example 2, the non-plating area | region Mb over the perimeter of 0.5 mm in width is formed in the shaft part 43 surface corresponding to the 2nd area | region part Lb of both ends, on the other hand, Comparative Example 1 And in the comparative example 2, the non-plating area | region part Mb is not formed.

  After each charging member 41 was immersed in 4% salt water for 3 hours, the conductive roller 42 was removed from the charging member 41, and the number of rusts in the first region La on the surface of the shaft portion 43 was visually measured. The results are shown in Table 1.

  As shown in Table 1, in Comparative Examples 1 and 2, a lot of rust was generated in the first region La on the surface of the shaft portion 43. In Examples 1 and 2, rust was generated in the non-plated region Mb, but no rust was generated in the first region La on the surface of the shaft 43, and good results were obtained.

  In Test 2, as in Test 1, Example 1 and Comparative Example 1 used the one in which the conductive roller 42 was integrally molded and fixed to the shaft portion 43, while Example 2 and Comparative Example 2 were respectively The conductive roller 42 and the shaft 43 were fixed with a hydrophobic adhesive. In Example 1 and Example 2, a non-plated region part Mb having a width of 0.5 mm is formed on the surface of the shaft part 43 corresponding to the second region part Lb, while Comparative Example 1 and Comparative Example 2 are used. Then, the non-plating area | region part Mb is not formed.

  Each of the charging members 41 is left in an environment of 50 ° C. and 90% temperature and humidity for 14 hours, and further energized for 7 days at an AC voltage of 1000 V at 10 kHz. The quality was evaluated. After the image evaluation, the conductive roller 42 was removed from the charging member 41, and the number of rust in the first region La on the surface of the shaft portion 43 was visually measured. The results are shown in Table 2.

  As shown in Table 2, in Comparative Examples 1 and 2, rust was generated in the first region La on the surface of the shaft portion 43. In Examples 1 and 2, rust was generated in the non-plated region Mb, but no rust was generated in the first region La on the surface of the shaft 43, and good results were obtained. Further, in Comparative Examples 1 and 2, since the electric resistance unevenness occurs in the charging member 41 due to the rust generated in the first region La, and the photoconductor 11 is not uniformly charged, a pattern image is formed on the gray background image. A defect occurred. In Examples 1 and 2, good images were obtained.

  The present invention can be used for a charge supply member that applies a charge to a member to be charged used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and an image forming apparatus including the charge supplying member.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11a-11d, 11 Photoconductor (charged body)
13a to 13d, 13 Charging device 17 Intermediate transfer belt (charged body)
26a to 26d, 26 Primary transfer roller (charge supply member)
41 Charging member (charge supply member)
42 Conductive roller 43 Shaft portion 45 Energizing member 46 Power supply La First region portion Lb Second region portion Ma Plated region portion Mb Non-plated region portion

Claims (10)

A charging device of a contact charging system that contacts the surface of the photoconductor to charge the photoconductor and carries an electrostatic latent image on the photoconductor;
A first area portion provided in contact with the photoconductor and facing an image forming area of the photoconductor, and provided at an end portion in a longitudinal direction of the first area portion and outside the image forming area of the photoconductor. A conductive roller that has a second region portion facing to supply electric charge to the photoreceptor;
A shaft made of a metal material, to which a voltage is applied from a power source,
A portion corresponding to the first and second region portions of the outer peripheral surface of the shaft portion is formed with a plating region portion plated with a metal having a smaller ionization tendency than the shaft portion, and the second region portion includes A charging device, wherein a corresponding portion is formed with a non-plated region portion that is not partially plated.   The charging device according to claim 1, wherein the non-plated region portion is formed with a predetermined width on the entire circumference of the shaft portion.   The charging device according to claim 1, wherein the non-plated region portion is formed with a predetermined width at least in a circumferential portion of the shaft portion.   The charging device according to claim 1, wherein the conductive roller is integrally formed with the shaft portion and fixed to the shaft portion.   The charging device according to any one of claims 1 to 3, wherein the conductive roller and the shaft portion are fixed with a hydrophobic adhesive.   6. The charging according to claim 1, further comprising: an urging member that presses the conductive roller against the photosensitive member; and a power source that supplies power to the shaft portion from one end in the axial direction. apparatus.   7. The non-plated region portion is formed by performing a masking process on the surface of the shaft portion and then plating the entire surface of the shaft portion. The charging device according to any one of the above.   The charging device according to claim 1, wherein the non-plated region portion is formed by partially peeling the plating after the entire surface of the shaft portion is plated. The conductive roller is made of a rubber material, and the shaft portion is made of an iron material,
The charging device according to claim 1, wherein nickel is plated on the plating region.   An image forming apparatus comprising the charging device according to claim 1.

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