JP2011027793A - Charging device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging device configured to suppress abnormal image quality caused by defective power feed and poor rotation, using a simple configuration. <P>SOLUTION: The charging device includes a charging roll, having a conductive core and a cylindrical charging layer formed on the conductive core, and if a bearing part which supports each end of the conductive core with at least two tangents and which has an opening and is provided with tangents between the conductive core and the bearing part, closest to the opening, is denoted as A and B, respectively, and if the distance connecting between the tangent A and the tangent B along the circumferential surface of the conductive core, one that is farther from the opening is denoted as L1, and the distance connecting between the tangent A and the tangent B along the inner peripheral surface of the bearing part is denoted as L2, the relation L2/L1>1.1 is holds. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a charging device, a process cartridge, and an image forming apparatus.

  In an image forming apparatus using an electrophotographic method, first, an electric charge is formed on the surface of an electrophotographic photosensitive member (hereinafter sometimes simply referred to as “photosensitive member”) which is an image holding member, and an image is formed. After forming an electrostatic latent image with a laser beam or the like whose signal is modulated, the electrostatic latent image is developed with charged toner to form a visualized toner image. A desired image can be obtained by electrostatically transferring the toner image to a transfer medium such as a recording sheet via an intermediate transfer body or fixing the toner image on the transfer medium.

  In recent years, in an electrophotographic image forming apparatus, a charging roll is frequently used as a charging member for charging the surface of a photosensitive member as a member to be charged. The charging roll comes into contact with the surface of the photoconductor in a state where a voltage is applied, and discharges in a minute gap with the photoconductor to charge the surface of the photoconductor. As this charging roll, a roller having a charging layer comprising a semiconductive rubber or the like on a conductive core is generally used. The charging roll is generally supported by a bearing portion made of conductive resin or the like, and a voltage is applied to the charging roll through the bearing portion made of conductive resin or the like to apply a voltage to the conductive core of the charging roll. Is done.

  For example, in Patent Documents 1 to 3, in order to perform stable power supply to the charging roll, not only the power supply from the bearing unit, but also the end surface of the conductive core different from the contact surface between the conductive core and the bearing unit In addition, a method of applying a voltage to the charging roll from a position different from the bearing portion has been proposed.

  Further, in Patent Document 4, a shaft of a conductive bearing is provided for the purpose of providing a charging device that prevents a charging failure due to a conduction failure due to intrusion of foreign matters such as toner over time and is not subject to space restrictions. There has been proposed a charging application device in which a plurality of protrusions are formed at intervals along the circumferential direction on an inner surface that supports the portion, and the shaft portion is rotatably supported by the plurality of protrusions.

JP-A-5-303263 Japanese Patent Laid-Open No. 9-211928 JP-A-10-207185 JP 2003-84543 A

  SUMMARY OF THE INVENTION An object of the present invention is to obtain a charging device, a process cartridge, and an image forming apparatus that have a simple configuration and suppress the occurrence of image quality abnormality due to power feeding failure and rotation failure.

  The above object is achieved by the present invention described below. That is, the invention according to claim 1 includes a charging roll having a conductive core and a cylindrical charging layer formed on the conductive core, and at least two tangents at both ends of the conductive core. And a bearing portion having an opening, and tangent lines between the conductive core and the bearing closest to the opening are A and B, respectively, along the circumferential surface of the conductive core. When connecting the tangent line A and the tangent line B, L1 is the distance far from the opening, and L2 is the distance between the tangent line A and the tangent line B along the inner peripheral surface of the bearing. > 1.1 charging device.

  According to a second aspect of the present invention, there is provided a gap portion between the conductive core body on the side far from the opening and the bearing portion, and the gap portion is filled with conductive grease. The charging device described.

  According to a third aspect of the present invention, there is provided a process cartridge comprising the image carrier and the charging device according to the first or second aspect.

  According to a fourth aspect of the present invention, there is provided an image carrier, the charging device according to the first or second aspect, a latent image forming unit that forms a latent image on the surface of the image carrier, and a surface of the image carrier. An image forming apparatus comprising: a toner image forming unit that forms a toner image by developing the formed latent image with toner; and a transfer unit that transfers the toner image formed on the surface of the image holding member to a transfer target. It is.

  According to claim 1 of the present invention, the bearing portion supports both ends of the conductive core body by at least two tangent lines, respectively, and has a simple configuration and poor power supply as compared with the case where L2 / L1> 1.1 is not satisfied. And a charging device that suppresses the occurrence of image quality anomalies due to poor rotation.

  According to the second aspect of the present invention, there is provided a charging device that further suppresses the occurrence of an image quality abnormality due to power feeding failure and rotation failure as compared with the case where the gap is not filled with conductive grease.

  According to claim 3 of the present invention, the bearing portion in the charging device supports both ends of the conductive core body by at least two tangent lines, respectively, and has a simple configuration as compared with the case where L2 / L1> 1.1 is not satisfied. The present invention provides a process cartridge that suppresses the occurrence of image quality abnormalities caused by power feeding failure and rotation failure.

  According to claim 4 of the present invention, the bearing portion in the charging device supports both ends of the conductive core body by at least two tangent lines, respectively, and has a simple configuration as compared with the case where L2 / L1> 1.1 is not satisfied. An image forming apparatus that suppresses occurrence of an image quality abnormality due to power feeding failure and rotation failure is provided.

1A is a schematic configuration diagram illustrating an example of an image forming apparatus including a charging device according to an embodiment of the present invention. FIG. 4B is an enlarged view of the periphery of the charging device and the photoconductor in the image forming apparatus including the charging device according to the embodiment of the present invention. It is a schematic sectional drawing which shows an example of a structure of the bearing part in the charging device which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the other example of a structure of the bearing part in the charging device which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the other example of a structure of the bearing part in the charging device which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the other example of a structure of the bearing part in the charging device which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the other example of a structure of the bearing part in the charging device which concerns on embodiment of this invention. It is a schematic structure figure showing an example of a process cartridge concerning an embodiment of the present invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. It is a schematic sectional drawing which shows an example of a structure of the bearing part in the conventional charging device. It is a schematic sectional drawing which shows the other example of a structure of the bearing part in the conventional charging device.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Charging device>
FIG. 1A is a schematic configuration diagram illustrating an example of an image forming apparatus including a charging device according to an embodiment of the present invention, and FIG. 1B illustrates the periphery of the charging device and the photosensitive member that is an image holding member. FIG. The charging device 1 includes a charging roll 10 that is a rotating cylindrical charging member, and a charging roll cleaner 12 that is a charging member cleaning member for cleaning the surface of the charging roll 10. The charging roll 10 includes a conductive core and a cylindrical charging layer formed on the outer periphery of the conductive core. In addition, a voltage is applied to the charging roll 10 by a high voltage power source (not shown).

  As shown in FIG. 1, the charging roll 10 is disposed so as to come into contact with the photosensitive member 26 when the charging device 1 is installed in the image forming apparatus 5. The conductive core of the charging roll 10 is rotatably supported by the bearing unit 14 at both ends. The charging roll 10 is pressed against the photosensitive member 26 by pressing the bearing portion 14 with an elastic body 20 such as a spring. A charging roll cleaner 12 is rotatably provided on the side of the charging roll 10 opposite to the photosensitive member 26.

  The photosensitive member 26 as an image holding member is driven to rotate in the direction of arrow X by a motor (not shown), and the charging roller 10 is driven to rotate in the direction of arrow Y by the rotation of the photosensitive member 26. The charging roll 10 charges the surface of the photoreceptor 26 while rotating in contact with the rotationally driven photoreceptor 26. Further, the charging roll cleaner 12 is driven to rotate following the charging roll 10. The charging roll 10 and the charging roll cleaner 12 may be driven by the photoreceptor 26 and the charging roll 10, respectively, or may be driven separately.

  FIG. 2 is a schematic configuration diagram illustrating an example of the bearing portion 14 in the charging device 1 according to the present embodiment. FIG. 3 is a schematic configuration diagram illustrating another example of the bearing portion 14 in the charging device 1 according to the present embodiment. The charging roll 10 includes a conductive core body 16 and a cylindrical charging layer 18 formed on the conductive core body 16. The bearing portion 14 supports both ends of the conductive core 16 at the same location on the inner peripheral surface of the bearing portion 14 by at least two tangent lines (extending in the direction perpendicular to the drawing), and has an opening 22. The tangents between the conductive core 16 and the bearing 14 that are closest to the opening 22 are A and B, respectively, and the tangent A and the tangent B are connected at the shortest distance along the peripheral surface of the conductive core 16. L2 / L1> 1.1 where L1 is a distance on the side far from 22 and L2 is a distance connecting the tangent line A and the tangent line B along the inner peripheral surface of the bearing portion 14 at the shortest distance. Further, in order not to hinder the rotation of the charging roll 10, the diameter D1 of the conductive core 16 and the width (minimum width) W1 of the bearing portion 14 have a relationship of W1> D1.

  When the bearing portion having an opening that supports the conductive core of the charging roll that rotates in contact with the photosensitive member in contact with the photosensitive member has, for example, a U shape shown in FIG. 9 or a C shape shown in FIG. In order not to inhibit the rotation of the charging roll 100, the width W1 of the bearing portion 104 is slightly larger than the diameter D1 of the conductive core 106 of the charging roll 100. In this case, when the charging roll 100 is pressed against the photoconductor 108, the tangent line between the conductive core 106 and the bearing unit 104 becomes one tangent at a position opposite to the position where the photoconductor 108 and the charging roll 100 are in contact with each other. . If foreign matter such as an insulating material or a high resistance material adhering to the conductive core body 106 or foreign matter mixed from the outside enters the tangent line (contact portion between the conductive core body 106 and the bearing portion 104), the bearing portion 104. Contact failure occurs between the bearing core 104 and the charging roll 100 is not supplied with power, or the supplied voltage may be reduced, so that the discharge from the charging roll 100 to the photoreceptor 108 is also reduced. As a result, an image quality abnormality may occur. Further, foreign matters such as toner and carrier are mixed into this contact portion, so that there is no gap between the bearing portion 104 and the conductive core 106, and as a result, the rotation of the charging roll 100 is hindered. In this case, the charging roll 100 may not discharge stably to the photoconductor 108, and an image quality abnormality may occur. In particular, when a resin bearing is used, this rotation failure tends to occur because the gap becomes small under a low temperature environment or the like due to a difference in linear expansion coefficient from the conductive core 106. Conversely, if the gap is increased, the positioning of the charging roll 100 becomes unstable, and an electrostatic memory may be generated between the photosensitive member 108 due to vibration during transportation or the like.

  As described above, the present inventors support the power supply with a simple configuration by supporting the both ends of the conductive core body 16 at least at two tangent lines and satisfying L2 / L1> 1.1 as described above. It has been found that the occurrence of image quality anomalies due to defects and rotation failures is suppressed. For example, in FIGS. 3 and 4, even when a foreign matter or the like is mixed into one contact portion between the bearing portion 14 and the conductive core body 16 and a power feeding failure occurs, the contact portion is secured in another place and power is supplied. Therefore, power supply failure hardly occurs over a long period of time. Further, since L2 / L1> 1.1, the gap portion 24 is formed, and even when foreign matter or the like is mixed into the bearing portion 14 from the outside, the gap portion 24 is collected, so that the bearing portion 14 and the conductive core are collected. There is almost no foreign matter or the like remaining between the body 16 and the charging roll 10 is stably rotated. Further, as compared with the case where the conductive core is supported by the protrusion, the conductive core is supported by the line of the bearing portion width instead of the point contact, so that power feeding is performed more stably.

  Although L2 / L1> 1.1, it is preferable that L2 / L1> 1.2. When L2 / L1 ≦ 1.1, the two tangent lines of the conductive core 16 and the bearing portion 14 are close to each other, so that the risk of straddling the two tangent lines at the same time when a relatively large foreign object is mixed increases.

  The diameter D1 of the conductive core 16 and the width W1 of the bearing portion 14 are in a relationship of W1> D1, for example, W1 / D1 is in the range of not less than 1.001 and not more than 1.02.

  In the example of FIGS. 3 and 4, the tangent line between the inner peripheral surface of the bearing portion 14 and the conductive core body 16 is two, but there may be two or more, and there is no particular limitation.

  Further, as shown in FIGS. 3 and 4, it is preferable that the gap portion 24 between the conductive core body 16 and the bearing portion 14 on the side far from the opening portion 22 is filled with grease. Moreover, it is preferable that the conductive grease is filled in at least the gap portion 24 on the side where power is supplied from the machine body among both ends of the conductive core body 16. When the gap 24 is filled with grease and the gap 24 on the side fed from the machine body is filled with conductive grease, stable power feeding and prevention of rotation failure are achieved. Further, the gap portion 24 secures a grease reservoir, and it is possible to prevent the grease from being cut off during use. In order to prevent leakage of grease from the gap 24, a partition member 23 such as a partition plate may be provided.

  For example, in FIGS. 2 and 3, even when foreign matter or the like is mixed in the contact portion between the bearing portion 14 and the conductive core body 16, the contact portion is secured in another place and the conductive grease is stably supplied. Therefore, power supply failure and rotation failure hardly occur over a long period of time. By simultaneously preventing power feeding failure and rotation failure with a simple configuration, power feeding failure and rotation failure of the charging roll can be suppressed without incurring costs. Further, even when foreign matter or the like is mixed into the bearing portion 14 from the outside, the foreign matter is hardly collected between the bearing portion 14 and the conductive core body 16 because it is collected in the gap portion 24, and the charging roll 10 Stable rotation is maintained.

  Grease is an oil mainly containing a thickener that imparts viscosity, and conductive grease is an oil containing a thickener and a conductivity-imparting additive, and is generally semi-solid. In addition, the grease and the conductive grease may contain an antioxidant, a corrosion inhibitor, a rust inhibitor, and the like. Examples of the conductive grease include FROIL HPG-D-2 manufactured by Kanto Kasei, KS660 manufactured by Shin-Etsu Silicon Co., Ltd., and the like.

  The filling amount of grease or conductive grease in the gap portion 24 is not particularly limited as long as the charging roller 10 is filled to such an extent that stable rotation is maintained. In addition, grease or conductive grease may be refilled in gaps in the charging device and the process cartridge after use to restore the function.

  The shape of the bearing portion 14 is not particularly limited as long as the above conditions are satisfied. In addition to the shapes shown in FIGS. 2 and 3, for example, the shapes shown in FIGS. 4 and 5 may be mentioned, but the shape is not limited thereto.

  Examples of the material of the bearing portion 14 include a resin such as polyacetal resin, polycarbonate resin, acrylonitrile / butadiene / styrene copolymer resin (ABS resin), and the like. Includes a conductive resin such as a conductive polyacetal resin, carbon black, and the like. According to the charging device according to the present embodiment, even if the material of the bearing portion 14 is a resin such as polyacetal resin, rotation failure in a low temperature environment is suppressed.

  The shape of the bearing portion that supports the core of the charging roll cleaner 12 that is a charging member cleaning member is also the same as the shape of the bearing portion 14 that supports the conductive core of the charging roll 10. The roll cleaner 12 is also rotated stably. That is, the charging device according to the present embodiment is, for example, as shown in FIG. 6, a charging roll that is a charging member cleaning member that further includes a core body 30 and a cylindrical elastic layer formed on the core body 30. The core body 30 is provided with the cleaner 12 and the bearing section 28 that supports both ends of the core body 30 at the same location on the inner peripheral surface of the bearing section with at least two tangent lines and has the opening section 32. And tangent lines of the bearing portion 28 are respectively A ′ and B ′, the tangent lines A ′ and the tangent line B ′ are connected at the shortest distance along the peripheral surface of the core body 30, and the distance on the side far from the opening 32 is M1 When a distance obtained by connecting the tangent line A ′ and the tangent line B ′ along the inner peripheral surface of the bearing portion 28 with the shortest distance is M2, it is preferable that M2 / M1> 1.1. Further, it is preferable that a gap portion 34 is provided between the core body 30 on the side farther from the opening portion 32 and the bearing portion 28 and the gap portion 34 is filled with grease. Moreover, it is preferable that at least one gap portion 34 of both ends of the core body 30 is filled with grease.

  The charging device according to the present embodiment stably supplies power to the charging roll without sacrificing an increase in the number of parts and space, and the rotation of the charging roll and the charging roll cleaner is stably performed.

[Charging roll]
The charging roll 10 will be described.

  In the charging roll 10, a conductive elastic layer, a surface layer, and the like are sequentially formed as a charging layer 18 on a conductive core 16.

  The diameter of the charging roll 10 is preferably φ8 mm to φ15 mm, more preferably φ9 mm to φ14 mm, and the thickness of the charging layer 18 is preferably 1.5 mm to 4 mm. When the diameter exceeds 15 mm, the number of times of contact with the external additive per place on the peripheral surface is reduced, and the number of discharges is reduced, which is disadvantageous from the viewpoint of miniaturization although it is excellent in long-term stability against dirt and charging performance. There is. If the diameter is less than 8 mm, the image forming apparatus is reduced in size, which is advantageous. However, the number of times of contact with the external additive per location on the peripheral surface is increased, and the number of discharges is increased. It may be disadvantageous.

  The charging roll 10 is not limited to the following configuration as long as it has a predetermined charging performance.

  As the material of the conductive core 16, free-cutting steel, stainless steel or the like is used, and the material and the surface treatment method are appropriately selected according to the application such as slidability, and the material having no conductivity is plated. For example, the conductive treatment may be performed by general processing.

  The conductive elastic layer constituting the charging layer 18 of the charging roll 10 is, for example, an elastic material such as rubber having elasticity, a conductive material such as carbon black or ionic conductive material that adjusts the resistance of the conductive elastic layer, and as necessary. Materials that can be usually added to rubber, such as softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, anti-aging agents, and fillers such as silica and calcium carbonate, may be added. The conductive elastic layer is formed by covering the peripheral surface of the conductive core 16 with a mixture obtained by adding a material usually added to rubber. As a conductive agent for the purpose of adjusting the resistance value, a material in which a material that conducts electricity using at least one of electrons and ions as a charge carrier, such as carbon black or an ionic conductive agent blended in a matrix material, is dispersed. It may be used. The elastic material may be a foam.

  The elastic material constituting the conductive elastic layer is formed, for example, by dispersing a conductive agent in a rubber material. Rubber materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide. -Allyl glycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber, natural rubber and the like, and blended rubbers thereof. Among these, silicone rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, acrylonitrile-butadiene copolymer rubber, and blended rubbers thereof are preferably used. These rubber materials may be foamed or non-foamed.

  As the conductive agent, an electronic conductive agent or an ionic conductive agent is used. Examples of electronic conductive agents include carbon blacks such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, stainless steel; tin oxide, indium oxide, titanium oxide And various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution; those obtained by conducting the surface of an insulating material; Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium, alkaline earth metal perchlorates and chlorates, etc. Is mentioned.

  These conductive agents may be used alone or in combination of two or more. Further, the amount of addition is not particularly limited, but in the case of the electronic conductive agent, it is preferably in the range of 1 part by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber material. In the case of an agent, it is preferably in the range of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the rubber material.

  A surface layer may be formed on the surface of the charging roll 10 in order to prevent contamination by foreign matters such as toner. As the material for the surface layer, any of resin, rubber and the like may be used, and there is no particular limitation. As resin and rubber, polyester, polyimide, copolymer nylon, silicone resin, acrylic resin, polyvinyl butyral, ethylenetetrafluoroethylene copolymer, melamine resin, fluororubber, epoxy resin, polycarbonate, polyvinyl alcohol, cellulose, polyvinylidene chloride , Polyvinyl chloride, polyethylene, ethylene vinyl acetate copolymer and the like.

  Of these, polyvinylidene fluoride, a tetrafluoroethylene copolymer, polyester, polyimide, and copolymer nylon are preferably used from the viewpoint of preventing contamination by an external additive. The copolymer nylon includes one or more of 610 nylon, 11 nylon, and 12 nylon as polymerized units, and other polymer units contained in the copolymer include 6 nylon, 66 nylon and the like. Here, the proportion of polymer units such as 610 nylon, 11 nylon, and 12 nylon contained in the copolymer is preferably 10% by mass or more in total by mass ratio. When the polymerized unit is 10% by mass or more, it has excellent liquid preparation properties and film formability during coating of the surface layer, and particularly less wear of the resin layer and adhesion of foreign matter to the resin layer during repeated use, and durability of the roll It tends to be excellent in properties and changes in properties due to the environment.

  The polymer materials (resins) may be used alone or in combination of two or more. Further, the number average molecular weight of the polymer material is preferably in the range of 1,000 or more and 100,000 or less, and more preferably in the range of 10,000 or more and 50,000 or less.

  The surface layer may contain a conductive material to adjust the resistance value. The conductive material preferably has a particle size of 3 μm or less.

  In addition, as a conductive agent for adjusting the resistance value, at least one of electrons and ions such as carbon black, conductive metal oxide particles, or ionic conductive agent blended in the matrix material is used as a charge carrier. A material in which a material that conducts electricity is dispersed may be used.

  Specifically, carbon black as a conductive agent includes “Special Black 350”, “Special Black 100”, “Special Black 250”, “Special Black 5”, “Special Black 4” manufactured by Degussa, "Special Black 4A", "Special Black 550", "Special Black 6", "Color Black FW200", "Color Black FW2", "Color Black FW2V", "MONARCH1000" manufactured by Cabot, Cabot “MONARCH1300” manufactured by the company, “MONARCH1400” manufactured by Cabot, “MOGUL-L”, “REGAL400R”, and the like.

  The carbon black preferably has a pH of 4.0 or less. Compared to general carbon black, it has good dispersibility in the resin composition due to the effect of oxygen-containing functional groups present on the surface. By adding carbon black with pH 4.0 or lower, charging uniformity is improved. In addition, the resistance value tends to vary less.

  The conductive metal oxide particles, which are conductive particles for adjusting the resistance value, are conductive materials such as tin oxide, tin oxide doped with antimony, zinc oxide, anatase titanium oxide, and indium tin oxide (ITO). As long as it is a conductive agent using electrons as charge carriers, any particle may be used, and there is no particular limitation. These may be used alone or in combination of two or more. In addition, any particle size may be used as long as the effect of the present embodiment is not hindered, but from the viewpoint of resistance value adjustment and strength, etc., preferably tin oxide, antimony-doped tin oxide, anatase-type titanium oxide More preferred are tin oxide and tin oxide doped with antimony.

  By performing resistance control with such a conductive material, the resistance value of the surface layer does not change depending on environmental conditions, and stable characteristics can be obtained.

  Furthermore, it is preferable that the surface layer is made of a fluorine-based or silicone-based resin, and particularly includes a fluorine-modified acrylate polymer. Moreover, you may add particle | grains in a surface layer. As a result, the surface layer becomes hydrophobic and acts to prevent the foreign matter from adhering to the charging roll 10. In addition, insulating particles such as alumina and silica are added to give unevenness to the surface of the charging roll 10, thereby reducing the burden at the time of rubbing against the photosensitive member 26, so that the charging roll 10 and the photosensitive member 26 are mutually connected. The wear resistance may be improved.

[Charging member cleaning member]
The shape of the charging member cleaning member according to the present embodiment is not particularly limited, and examples thereof include a roll shape and a pad shape. Among these, a roll shape (so-called cleaning roll) is preferable. The following description will be made on the assumption that the charging member cleaning member is a cleaning roll. Of course, the constituent material of each layer included in the charging member cleaning member can be similarly used for the charging member cleaning members of other shapes.

  A charging roll cleaner 12 which is a charging member cleaning member for contacting the charging roll 10 to clean the surface of the charging roll 10 includes a core body and a cylindrical elastic layer formed on the outer periphery of the core body. The structure of the charging member cleaning member is not particularly limited as long as it has a function of cleaning a charging member such as a charging roll.

  Examples of the material used for the core of the roll-shaped charging roll cleaner 12 include metals such as free-cutting steel and stainless steel, and resins such as polyacetal (POM). It is preferable to appropriately select the material of the core, the surface treatment method and the like according to the use such as slidability. In particular, in the case of a metal, it is preferable to perform plating treatment from the viewpoint of rust prevention or the like. Further, in the case of a material such as a resin that does not have conductivity, it may be processed by a general process such as a plating process, and may be used as it is.

  The configuration of the elastic layer on the core may be a single layer or a stacked configuration of two or more layers. The elastic layer may include a foam, or may have a two-layer structure including a solid layer and a foam layer. By configuring the elastic layer so that the charging member can be cleaned, a function as a cleaning roll can be obtained.

  Materials constituting the elastic layer include foamable resins such as polyurethane, polyethylene, polyamide, or polypropylene, or silicone rubber, fluorine rubber, urethane rubber, ethylene-propylene-diene rubber (EPDM), nitrile rubber (NBR), chloroprene. Using a material formed by mixing one or more rubber materials such as rubber (CR), chlorinated polyisoprene rubber, isoprene rubber, acrylonitrile-butadiene rubber, styrene-butadiene rubber, hydrogenated polybutadiene rubber and butyl rubber. Also good. If necessary, auxiliary agents such as foaming aids, foam stabilizers, catalysts, curing agents, plasticizers, and vulcanization accelerators may be added to these.

  In order to avoid scratching the surface of the charging member due to rubbing as much as possible, and to prevent tearing and breakage as much as possible over a long period of time, it is preferable to use foamed polyurethane that is resistant to tearing and pulling. Although it does not restrict | limit especially as a polyurethane, For example, polyols, such as polyester polyol, polyether polyol, and acrylic polyol, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4-diphenylmethane diisocyanate , Tolidine diisocyanate, 1,6-hexamethylene diisocyanate, and the like obtained by reaction with isocyanate. Further, a chain extender such as 1,4-butanediol or trimethylolpropane may be mixed. Foaming may be performed using a foaming agent such as water, azodicarbonamide, azo compounds such as azobisisobutyronitrile. Furthermore, you may add auxiliary agents, such as a foaming aid, a foam stabilizer, a catalyst, as needed.

<Process cartridge>
A process cartridge according to this embodiment includes an image carrier and the charging device that charges the surface of the image carrier. The process cartridge according to this embodiment includes a latent image forming unit that forms a latent image on the surface of the charged image carrier, and a toner that develops the latent image formed on the surface of the image carrier with toner as necessary. A toner image forming unit that forms an image, a transfer unit that transfers a toner image formed on the surface of the image carrier to a transfer target, and an image carrier cleaning unit that cleans the surface of the image carrier after the transfer. You may provide at least 1 type selected from the group. In the process cartridge according to this embodiment, the charging device and the photosensitive member are integrally formed into a cartridge that can be attached to and detached from the main body of the image forming apparatus.

  A schematic configuration of an example of the process cartridge according to the embodiment of the present invention is shown in FIG. 7, and the configuration will be described. The process cartridge 3 includes a photosensitive member (electrophotographic photosensitive member) 26 as an image holding member on which an electrostatic latent image is formed, a charging roll 10 that is a cylindrical charging member that contacts and charges the surface of the photosensitive member 26, and A charging roll cleaner 12 as a charging member cleaning member for cleaning the surface of the charging roll 10, and a toner image forming means for forming a toner image by attaching toner to an electrostatic latent image formed on the surface of the photoreceptor 26. And a developing blade 52 as an image carrier, and a cleaning blade 56 as an image carrier cleaning means that contacts the surface of the photosensitive member 26 and cleans toner remaining on the photosensitive member 26 after transfer, are integrally supported. It is detachable from the forming apparatus. When mounted on the image forming apparatus, an exposure device 58 as a latent image forming unit that forms an electrostatic latent image on the surface of the photosensitive member 26 around the photosensitive member 26 by the charging roll 10, laser light, or reflected light of the document. The developing roll 52, the transfer roll 54 as a transfer means for transferring the toner image on the surface of the photosensitive member 26 to the recording paper 62 as the transfer target, and the cleaning blade 56 are arranged in this order. As described above, in the charging device, the bearing portion supports both ends of the conductive core body with at least two tangent lines, and L2 / L1> 1.1. In FIG. 7, functional units normally required in other electrophotographic processes are not shown.

  The operation of the process cartridge 3 according to this embodiment will be described.

  First, the surface of the photoconductor 26 is charged to a high potential by supplying a voltage to the charging roll 10 in contact with the surface of the photoconductor 26 via a bearing member 14 from a high voltage power source (not shown). At this time, the photosensitive member 26 and the charging roll 10 rotate in the directions of the arrows in FIG. After charging, when image light (exposure) 60 corresponding to image information is irradiated onto the surface of the photosensitive member 26 by the exposure device 58, the potential of the irradiated portion decreases. Since the image light 60 has a light amount distribution corresponding to the black / white of the image, a potential distribution corresponding to the recorded image, that is, an electrostatic latent image is formed on the surface of the photoconductor 26 by the irradiation of the image light 60. When the portion where the electrostatic latent image is formed passes through the developing roll 52, toner adheres according to the level of the potential, and a toner image in which the electrostatic latent image is visualized is formed. The recording paper 62 is conveyed to a portion where the toner image is formed by a resist roll (not shown) at a predetermined timing, and overlaps the toner image on the surface of the photoreceptor 26. After the toner image is transferred to the recording paper 62 by the transfer roll 54, the recording paper 62 is separated from the photoreceptor 26. The separated recording paper 62 is transported through a transport path, fixed by heating and pressure by a fixing unit (not shown) as fixing means, and then discharged outside the apparatus.

  A charging roll cleaner 12 is installed on the charging roll 10 provided in the process cartridge 3. The charging roll cleaner 12 is disposed so as to be in contact with the surface of the charging roll 10, and by contacting the peripheral surface of the charging roll 10, deposits such as toner and toner external additives on the surface of the charging roll 10 are cleaned. .

  The photoreceptor 26 has a function of forming at least an electrostatic latent image (electrostatic charge image). In the electrophotographic photosensitive member, an undercoat layer, a charge generation layer containing a charge generation material, and a charge transport layer containing a charge transport material are formed in this order on the outer peripheral surface of a cylindrical conductive substrate as necessary. It is a thing. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. A single-layer type photoreceptor included in the above layer may be used, and a laminated photoreceptor is preferable. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

  The exposure device 58 is not particularly limited. For example, a laser optical system that exposes a light source such as semiconductor laser light, LED light, or liquid crystal shutter light on the surface of the photosensitive member 26 in a desired image-like manner, and optical such as an LED array. System equipment.

  The developing means has a function of developing the electrostatic latent image formed on the photoreceptor 26 with a one-component developer or a two-component developer containing an electrostatic charge image developing toner to form a toner image. Such a developing device is not particularly limited as long as it has the above-described function, and may be appropriately selected according to the purpose. Even a system in which the toner layer is in contact with the photosensitive member 26, a system in which the toner layer is not in contact is used. It may be a thing. For example, as shown in FIG. 7, a developer having a function of attaching toner for developing an electrostatic image to the photoreceptor 26 using the developing roll 52, or a development having a function of attaching the toner to the photoreceptor 26 using a brush or the like. And a known developing device.

  The transfer unit may be a type that directly transfers to paper or the like, or a type that transfers via an intermediate transfer member. For example, a transfer roll 54 and a transfer roll pressing device (not shown) using a conductive or semiconductive roll that directly transfers through a recording sheet 62 as shown in FIG. 7 may be used. Further, a recording sheet 62 may be used in which a charge having a polarity opposite to that of the toner is applied to the recording sheet 62 from the back side (the side opposite to the photoreceptor) of the recording sheet 62 and the toner image is transferred to the recording sheet 62 by electrostatic force. The transfer roll 54 may be arbitrarily set depending on the width of the image area to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is preferably used as the transfer roll 54 for cost reduction.

  The fixing unit as the fixing unit is not particularly limited as long as the toner image transferred onto the recording paper 62 is fixed by heating, pressing, or heating and pressing.

  Examples of the recording paper 62 that is a transfer target to which the toner image is transferred include plain paper, OHP sheet, and the like used in electrophotographic copying machines and printers. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the transfer material is as smooth as possible. For example, coated paper whose surface of plain paper is coated with resin, art paper for printing, etc. Preferably used.

  The process cartridge may have a communication mechanism for storing cartridge information.

  The process cartridge is not limited to one that forms a single color image, but may be one that forms a plurality of color images (for example, a two-color image, a three-color image, or a full color).

<Image forming apparatus>
The image forming apparatus according to the present embodiment includes an image carrier, the charging device that charges the surface of the image carrier, a latent image forming unit that forms a latent image on the surface of the image carrier, and the surface of the image carrier. A toner image forming unit that forms a toner image by developing the latent image formed on the toner, and a transfer unit that transfers the toner image formed on the surface of the image holding member to the transfer target. The image forming apparatus according to the present exemplary embodiment may include an image carrier cleaning unit that cleans the surface of the image carrier after the transfer, if necessary. The image forming apparatus according to the present embodiment may use the process cartridge.

  FIG. 8 shows a tandem full-color image forming apparatus 5 as an example of the image forming apparatus according to the present embodiment. Inside the image forming apparatus 5, an image forming unit (corresponding to a process cartridge) having a photoreceptor 26, a charging device including the charging roll 10, and the like is yellow (64Y), magenta (64M), cyan (64C), And for each color of black (64K). As the photoconductor 26, for example, a conductive cylinder whose surface is coated with a photoconductor layer including an organic photoconductor is used, and is rotated by a motor (not shown) at a process speed of, for example, about 150 mm / sec.

  The surface of the photosensitive member 26 is charged to a predetermined potential by the charging roll 10 disposed in contact with the photosensitive member 26, and then subjected to image exposure with a laser beam or the like emitted from the exposure device 58. An electrostatic latent image corresponding to the information is formed.

  The electrostatic latent image formed on the photosensitive member 26 is developed by developing units 66Y, 66M, 66C, and 66K for the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). A toner image of a predetermined color is obtained.

  For example, when a full-color image is formed, charging, exposure, and development processes are performed on the surface of each color photoconductor 26 in yellow (Y), magenta (M), cyan (C), and black (K). A toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the surface of the photoreceptor 26 of each color.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photoconductor 26 are sequentially applied to the recording paper 62 held on the paper transport belt 68. After the transfer, the recording paper 62 onto which the toner image has been transferred is conveyed to the fixing device 70 and is heated and pressurized by the fixing device 70 to fix the toner image on the recording paper 62. Thereafter, in the case of single-sided printing, the recording paper 62 on which the toner image is fixed is discharged as it is onto a discharge tray 74 provided on the upper portion of the image forming apparatus 5 by a discharge roll 72.

  On the other hand, in the case of double-sided printing, the recording paper 62 having the toner image fixed on the first surface (front surface) by the fixing device 70 is not directly discharged onto the discharge tray 74 by the discharge roll 72, With the rear end portion of the recording paper 62 held between the two, the discharge roll 72 is reversed, the conveyance path of the recording paper 62 is switched to the double-sided paper conveyance path 76, and the double-sided paper conveyance path 76 is arranged. With the conveying roll 78 provided, the recording sheet 62 is reversed and conveyed again to the transfer position of the sheet conveying belt 68, and the toner image is transferred to the second surface (back surface) of the recording sheet 62. Then, the toner image on the second surface (back surface) of the recording paper 62 is fixed by the fixing device 70, and the recording paper 62 is discharged onto the discharge tray 74.

  Note that the surface of the photoconductor 26 after the toner image transfer process is completed is made up of residual toner, paper dust, and the like by a cleaning blade 56 disposed obliquely above the photoconductor 26 every time the photoconductor 26 rotates once. Is removed, and is prepared for the next image forming step.

  A charging roll cleaner 12 is installed on the charging roll 10 provided in the image forming apparatus 5. The charging roll cleaner 12 is disposed so as to be in contact with the surface of the charging roll 10, and by contacting the peripheral surface of the charging roll 10, deposits such as toner and toner external additives on the surface of the charging roll 10 are cleaned. . Further, as described above, in the charging device, the bearing portion supports both ends of the conductive core body by at least two tangent lines, and L2 / L1> 1.1.

  The configurations other than the charging device of the image forming apparatus according to the present embodiment are not limited thereto, and conventionally known configurations may be applied as the respective configurations of the electrophotographic image forming apparatus. That is, the configuration other than the above-described charging device, for example, a latent image forming unit, a toner image forming unit, a transfer unit, an image carrier cleaning unit, a neutralizing unit, a paper feeding unit, a conveying unit, an image control unit, etc. A conventionally well-known thing is employ | adopted suitably. These configurations are not particularly limited in the present embodiment.

  Further, the image forming apparatus according to the present embodiment is not limited to the above-described configuration, and for configurations other than the charging device, for example, an image forming device having only one photoconductor, and a toner image held on the image holding member in the middle. Conventionally known devices such as a color image forming apparatus that sequentially repeats primary transfer onto a transfer body are appropriately employed. These configurations are not particularly limited in the present embodiment.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Example 1>
A bearing portion having a cross-sectional shape shown in FIG. 2 and attachable to a process cartridge of an image forming apparatus (manufactured by Fuji Xerox, DocuPrint C2100) was produced by cutting. Conductive polyacetal resin (POM) was used for the bearing portion on the charging roll power supply side, and polyacetal resin (POM) was used for the non-power supply side. L1 and L2 shown in FIG. 2 of the bearing portion are 1.5π mm and 6 mm, respectively, the angle θ is 90 degrees, and the width W1 is 6.1 mm. In this case, the conductive core of the charging roll comes into contact with the bearing portion at two tangent lines, and L2 / L1 = 1.27. The charging roll used in DocuPrint C2100 (the diameter D1 of the conductive core is 6.0 mm) is used, and an insulating adhesive is used for the conductive core on the power feeding side of the charging roll for this verification. (Cemedine Co., Ltd., Cemedine C) having a thickness of about 50 μm was prepared and assembled to the process cartridge of DocuPrint C2100 together with the above-mentioned bearing portion. In order to clarify the effect of this test, no conductive grease or the like was applied to the bearing portion on the power feeding side. As a result of printing 8,000 sheets using this process cartridge and confirming the image quality, no abnormality in image quality that seems to be caused by power feeding failure and rotation failure was confirmed.

<Example 2>
The bearing part produced in Example 1 is used as it is, and conductive grease (FROIL HPG-D-2 manufactured by Kanto Kasei Co., Ltd.) is filled in the gap part shown in FIG. 2 of the bearing part supplied with power from the machine body. Applied. In order to confirm the effect on the power supply and rotation against the contamination of foreign matter from the outside, in order to make the toner, which is a typical foreign matter in the machine, easily float, the external power supply is applied to the normal voltage applied to the charging roll. A voltage lower by 50 V was supplied, the charging potential of the photoconductor was intentionally lowered, and fogging was likely to occur in terms of image quality. Furthermore, the gap between the bearing portion and the conductive core caused by the difference in coefficient of linear expansion between the bearing portion and the conductive core of the charging roll is 8,000 sheets in an environment of 10 ° C./15% RH, which is a stress condition. A printing test was conducted. When this image quality was confirmed, no image quality anomaly that was attributed to power feeding failure and rotation failure of the charging roll was confirmed.

<Example 3>
A bearing portion having a cross-sectional shape shown in FIG. 3 and attachable to a process cartridge of an image forming apparatus (manufactured by Fuji Xerox, DocuPrint C2100) was manufactured by cutting. Conductive polyacetal resin (POM) was used for the bearing portion on the charging roll power supply side, and polyacetal resin (POM) was used for the non-power supply side. L1 and L2 shown in FIG. 3 of the bearing portion were 2π mm and 6√3 mm, the angle θ was 60 degrees, and the width W1 was 6.1 mm. In this case, the conductive core of the charging roll comes into contact with the bearing portion at two tangents, and L2 / L1 = 1.65. The charging roll used in DocuPrint C2100 (the diameter D1 of the conductive core is 6.0 mm) is used, and an insulating adhesive is used for the conductive core on the power feeding side of the charging roll for this verification. (Cemedine Co., Ltd., Cemedine C) having a thickness of about 50 μm was prepared and assembled to the process cartridge of DocuPrint C2100 together with the above-mentioned bearing portion. In order to clarify the effect of this test, no conductive grease or the like was applied to the bearing portion on the power feeding side. As a result of printing 8,000 sheets using this process cartridge and confirming the image quality, no abnormality in image quality that seems to be caused by power feeding failure and rotation failure was confirmed.

<Example 4>
The bearing part produced in Example 3 is used as it is, and conductive grease (FROIL HPG-D-2 manufactured by Kanto Kasei Co., Ltd.) is filled in the gap part shown in FIG. 3 of the bearing part supplied with power from the machine body. Applied. In order to confirm the effect on the power supply and rotation against the contamination of foreign matter from the outside, in order to make the toner, which is a typical foreign matter in the machine, easily float, the external power supply is applied to the normal voltage applied to the charging roll. A voltage lower by 50 V was supplied, the charging potential of the photoconductor was intentionally lowered, and fogging was likely to occur in terms of image quality. Furthermore, the gap between the bearing portion and the conductive core caused by the difference in coefficient of linear expansion between the bearing portion and the conductive core of the charging roll is 8,000 sheets in an environment of 10 ° C./15% RH, which is a stress condition. A printing test was conducted. When this image quality was confirmed, no image quality anomaly that was attributed to power feeding failure and rotation failure of the charging roll was confirmed.

<Comparative Example 1>
A bearing portion having a cross-sectional shape shown in FIG. 2 and attachable to a process cartridge of an image forming apparatus (manufactured by Fuji Xerox, DocuPrint C2100) was produced by cutting. Conductive polyacetal resin (POM) was used for the bearing portion on the charging roll power supply side, and polyacetal resin (POM) was used for the non-power supply side. L1 and L2 shown in FIG. 2 of the bearing portion are π mm and 6 / √3 mm, the angle θ is 120 degrees, and the width W1 is 6.1 mm. In this case, the conductive core of the charging roll comes into contact with the bearing portion at two tangents, and L2 / L1 = 1.1. The charging roll used in DocuPrint C2100 (the diameter D1 of the conductive core is 6.0 mm) is used, and an insulating adhesive is used for the conductive core on the power feeding side of the charging roll for this verification. (Cemedine Co., Ltd., Cemedine C) having a thickness of about 50 μm was prepared and assembled to the process cartridge of DocuPrint C2100 together with the above-mentioned bearing portion. In order to clarify the effect of this test, no conductive grease or the like was applied to the bearing portion on the power feeding side. As a result of printing 8,000 sheets using this process cartridge and confirming the image quality, a streak-like image quality abnormality of the charging roll pitch, which seems to be caused by power feeding failure and rotation failure, was confirmed.

<Comparative Example 2>
A bearing portion having a U-shaped cross-sectional shape shown in FIG. 9 and attachable to a process cartridge of an image forming apparatus (manufactured by Fuji Xerox, DocuPrint C2100) was manufactured by cutting. Conductive polyacetal resin (POM) was used for the bearing portion on the charging roll power supply side, and polyacetal resin (POM) was used for the non-power supply side. The width W1 shown in FIG. 9 of the bearing portion was set to 6.1 mm. In this case, the conductive core of the charging roll comes into contact with the bearing portion with one tangent. The charging roll used is DocuPrint C2100 (the diameter D1 of the conductive core is 6.0 mm), and for this verification, an insulating adhesive ( A product obtained by attaching Cemedine C) manufactured by Cemedine Co., Ltd. to a thickness of about 50 μm was prepared and assembled to the process cartridge of DocuPrint C2100 together with the above-described bearing portion. In order to clarify the effect of this test, no conductive grease or the like was applied to the bearing portion on the power feeding side. As a result of printing 8,000 sheets using this process cartridge and confirming the image quality, a streak-like image quality abnormality of the charging roll pitch, which seems to be caused by power feeding failure and rotation failure, was confirmed.

  As in the first to fourth embodiments, the bearing portion supports both ends of the conductive core with at least two tangent lines, and L2 / L1> 1.1, so that power supply failure and rotation failure are achieved with a simple configuration. The occurrence of image quality anomalies that may be caused by In addition, as in Examples 2 and 4, by filling conductive grease in at least one of the gaps, the occurrence of an image quality abnormality that seems to be caused by power feeding failure and rotation failure was further suppressed.

  DESCRIPTION OF SYMBOLS 1 Charging device, 3 Process cartridge, 5 Image forming apparatus, 10,100 Charging roll, 12 Charging roll cleaner, 14, 28,104 Bearing part, 16,106 Conductive core body, 18 Charging layer, 20 Elastic body, 22, 32 opening portion, 23 partition member, 24, 34 gap portion, 26, 108 photoconductor, 30 core body, 52 developing roll, 54 transfer roll, 56 cleaning blade, 58 exposure device, 60 image light, 62 recording paper, 64Y, 64M, 64C, 64K image forming unit, 66Y, 66M, 66C, 66K developing device, 68 paper transport belt, 70 fixing device, 72 discharge roll, 74 discharge tray, 76 paper transport path, 78 transport roll.

Claims (4)

A charging roll having a conductive core and a cylindrical charging layer formed on the conductive core;
A bearing part that supports both ends of the conductive core with at least two tangent lines, and has an opening;
With
The tangent lines between the conductive core closest to the opening and the bearing are A and B, respectively. The tangent A and the tangent B are connected along the peripheral surface of the conductive core, and are far from the opening. A charging device characterized in that L2 / L1> 1.1 where L1 is a distance on the side and L2 is a distance connecting tangent line A and tangent line B along the inner peripheral surface of the bearing portion.   The conductive grease is filled in at least one of the gaps, and a gap is provided between the conductive core on the side far from the opening and the bearing. Charging device.   A process cartridge comprising an image carrier and the charging device according to claim 1.   An image carrier, a charging device according to claim 1, latent image forming means for forming a latent image on the surface of the image carrier, and a latent image formed on the surface of the image carrier with toner. An image forming apparatus comprising: a toner image forming unit that forms a toner image by development; and a transfer unit that transfers a toner image formed on the surface of the image holding member to a transfer target.

Images