JP5327570B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of maintaining favorably image quality over a long period, by cleaning respectively both a charging member of a charging means and a gap holding member thereof at respective proper conditions. <P>SOLUTION: This image forming apparatus is provided with a photoreceptor 40, and a charging device 70 for charging uniformly the photoreceptor 40, and the charging device 70 comprises: a charging roller 77 including the charging member 82 for charging the photoreceptor 40, a support body 81 for supporting the charging member 82, and the gap holding member 83 abutting to the photoreceptor 40 and for holding a gap between the photoreceptor 40 and the charging member 82; a charging part cleaning roller 84 for cleaning the charging member 82; and a gap holding part cleaning roller 86 for cleaning the gap holding member 83. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus that employs an electrophotographic system such as a copying machine, a facsimile machine, or a printer.

  In an image forming apparatus employing an electrophotographic system, as a charging unit for uniformly charging an image carrier, a charging member for charging the image carrier, and a contact between the image carrier and the charging member in contact with the image carrier. A non-contact charging device including a gap holding member for holding a gap therebetween is known. In this non-contact charging device, since the charging member is not rubbed against the image carrier, contamination of the charging member can be greatly reduced. However, since the AC bias is superimposed and applied to the charging member for the purpose of uniformly charging the image carrier, the toner on the image carrier, the toner external additive, and the lubrication are slightly applied even when arranged in a non-contact manner. Dirt such as an agent adheres to the charging member. Further, when dirt is attached to the gap holding member, the charging gap widens and density unevenness occurs due to abnormal discharge. In order to maintain the charging performance of the charging device for a long period of time, it is known to provide a cleaning member for cleaning the charging member and the gap holding member. Since the structure is simple, it is generally performed that the cleaning member is always brought into contact with the charging member or the gap holding member (for example, Patent Document 1).

Japanese Patent No. 3723069

  However, when the cleaning member is always brought into contact with the charging member, the dirt on the surface of the charging member can be removed initially, but the dirt accumulated on the cleaning member is charged when used for a long time. It will be rubbed against the member. For this reason, the charging member is contaminated or the cleaning member itself deteriorates, so that the cleaning performance cannot be maintained, and the image quality cannot be maintained satisfactorily for a long time. Regarding the cleaning property of the charging member, it is considered that it is preferable to provide a contact / separation mechanism for bringing the cleaning member into and out of contact with the charging member to intermittently clean the charging member.

  On the other hand, when the cleaning member is intermittently brought into contact with the gap holding member, toner or the like is likely to accumulate in the gap holding member while the gap holding member and the cleaning member are separated from each other. While the gap holding member and the cleaning member are separated from each other, the toner slightly leaked from the end of the cleaning member installed on the image carrier or the toner slightly scattered from the developing unit adheres to the gap holding member. It is thought that it will end. The toner adhered to the gap holding member is fixed to the gap holding member by being crushed between the gap holding member and the image carrier. For this reason, when the cleaning member is intermittently brought into contact with the gap holding member, the charging gap is widened, and abnormal images such as density unevenness due to abnormal discharge tend to occur. Regarding the cleaning performance of the gap holding member, it is considered that the cleaning member is always in contact with the gap holding member.

  The present invention has been made in view of the above circumstances. The object is to provide an image forming apparatus capable of maintaining good image quality over a long period of time by cleaning both the charging member and the gap holding member of the charging unit under appropriate conditions. It is.

In order to achieve the above object, an invention according to claim 1 is an image forming apparatus comprising: an image carrier on which at least an electrostatic latent image is formed; and a charging device that uniformly charges the image carrier. The apparatus has a charging member that charges the image carrier, a support that supports the charging member, and a width that is in contact with the image carrier and maintains a gap between the image carrier and the charging member. Charging means comprising gap holding members provided on both outer sides of the charging member in the direction, a charging member cleaning means for cleaning the charging member, and a gap holding member cleaning means for cleaning the gap holding member, The charging member cleaning unit and the gap holding member cleaning unit perform cleaning while rotating, and the gap holding unit. Use cleaning means, such that the rotation axis is the rotation axis and substantially coaxially of the cleaning means for the charging member, corresponding to the both outer side of the gap holding member sandwiching the cleaning means for the charging member in the width direction together are a pair arranged so as, respective supports cleaning means for the pair of gap holding member is formed in a hollow shape, the support portion in the width direction both end portions of the charging member cleaning means of the gap holding member for the cleaning means located in the hollow support body, and the charging member cleaning means is movable within the hollow of the support so as to be separable with respect to the charging member, the charging member cleaning means regardless of and away state to said charging member, always in the gap holding member for the cleaning means is in said gap retaining member It is characterized in that it has configured to.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the gap holding member cleaning means is disposed above the gap holding member .
Invention 請 Motomeko 3, in the image forming apparatus according to claim 1 or 2, the charging means, the support is made of a conductive metal core made the charging member a conductive resin material, the gap holding The member is made of an insulating resin material.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect , a charging bias in which an AC bias is superimposed on a DC bias is applied to the charging unit.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first, second, third, or fourth aspect , the image carrier is made of an organic photoreceptor, and has a protective layer on the surface.
According to a sixth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, or fifth aspect , the image forming apparatus further comprises a lubricant supply unit that supplies a lubricant to the image carrier. .
According to a seventh aspect of the present invention, in the process cartridge used in the image forming apparatus of the first, second, fourth, fifth, or sixth aspect , at least the image carrier and a charging device that uniformly charges the image carrier. The image forming apparatus main body is configured to be integrated and easily detachable.
In these inventions, the cleaning means for cleaning both the charging member and the gap holding member of the charging means is constituted by a separate member. Therefore, both the charging member and the gap holding member can be cleaned under appropriate conditions.

  According to the present invention, there is an excellent effect that it is possible to provide an image forming apparatus capable of cleaning both the charging member and the gap holding member of the charging unit under appropriate conditions.

  Hereinafter, an embodiment in which the present invention is applied to a tandem intermediate transfer type full-color copying machine as an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram showing the internal configuration of the full-color copying machine. As shown in FIG. 1, the full-color copying machine includes an apparatus main body 100, a paper feed table 200 on which the apparatus main body 100 is mounted, a scanner 300 attached on the apparatus main body 100, and an automatic document feeder (ADF) 400 attached on the scanner 300. Etc. At the center of the apparatus main body 100, there is provided a tandem image forming unit 20 in which four image forming units 18Y, C, M, and Bk that form toner images of different colors of yellow, cyan, magenta, and black are arranged side by side. ing. Each image forming unit 18Y, C, M, Bk of the tandem image forming unit 20 has a charging device, a developing device 60Y, C, M, Bk, around the photoconductors 40Y, C, M, Bk, which are image carriers. A photoconductor cleaning device, a static eliminator, and the like are provided.

  An exposure device 21 is provided above the tandem image forming unit 20. The exposure device 21 has four laser diode (LD) light sources prepared for each color, a pair of polygon scanners composed of a six-surface polygon mirror and a polygon motor, and an fθ lens arranged in the optical path of each light source. The lens is composed of a lens or a mirror such as a long WTL. In this exposure device 21, the laser light emitted from the LD according to the image information of each color is deflected and scanned by the polygon scanner and irradiated to the photoreceptors 40Y, C, M, and Bk of each color.

  Below the tandem image forming unit 20, an endless belt-shaped intermediate transfer belt 10 is installed. In the illustrated example, the intermediate transfer belt 10 can be wound around three support rollers 14, 15, 16 and rotated clockwise in the figure, and the support roller 14 is a drive roller that drives the intermediate transfer belt 10 to rotate. Further, at a position facing the photoconductors 40Y, C, M, and Bk with the intermediate transfer belt 10 interposed therebetween, primary transfer is performed as a primary transfer unit that transfers a toner image from the photoconductor 40 of each color to the intermediate transfer belt 10. Rollers 62Y, C, M, and Bk are provided. An intermediate transfer belt cleaning device 17 for removing residual toner remaining on the intermediate transfer belt 10 after image transfer is provided on the downstream side of the third support roller 16 in the moving direction of the intermediate transfer belt. As the intermediate transfer belt 10, a resin material such as polyvinylidene fluoride, polyimide, polycarbonate, polyethylene terephthalate or the like can be molded into a seamless belt and used. These materials can be used as they are, or the resistance can be adjusted with a conductive material such as carbon black. Further, using these resins as a base layer, a surface layer may be formed by a method such as spraying or dipping to form a laminated structure.

  A secondary transfer device 22 is provided below the intermediate transfer belt 10. In the illustrated example, the secondary transfer device is configured by spanning a secondary transfer belt 24 that is an endless belt between two rollers 23 and is pressed against the third support roller 16 via the intermediate transfer belt 10. Then, the image on the intermediate transfer belt 10 is transferred to a transfer material. As the secondary transfer belt 24, the same material as that of the intermediate transfer belt can be used. A fixing device 25 for fixing the image on the transfer material is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt. The secondary transfer device 22 described above is also provided with a sheet transport function for transporting the transfer material after image transfer to the fixing device 25. Of course, a transfer roller or a transfer charger may be disposed as the secondary transfer device 22, and in such a case, it is necessary to provide this transfer material conveying function separately. In the illustrated example, a transfer material is reversely discharged below the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming unit 20 described above, or transferred to form images on both sides of the transfer material. A reversing device 28 for reversing and refeeding the material is provided.

  When performing a copying operation using this full-color copying machine, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, the automatic document feeder 400 is closed, and the document is pressed. When a start switch of an operation unit (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is placed on the other contact glass 32. When set, the scanner 300 is immediately driven to travel on the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34, and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read. Thereafter, when the mode setting is set in the operation unit or the automatic mode selection is set in the operation unit, the image forming operation is started in the full color mode or the monochrome mode according to the reading result of the original.

  When the full color mode is selected on the operation unit, the photoconductors 40Y, 40C, 40M, and 40B rotate in the counterclockwise direction in FIG. Then, the surfaces of the photoreceptors 40Y, 40C, 40M, and 40k are uniformly charged by the charging device. The photoconductors 40Y, C, M, and Bk are respectively irradiated with laser beams corresponding to the images of the respective colors from the exposure device 21, and latent images corresponding to the image data of the respective colors are formed. Each latent image is developed with toner of each color by the developing devices 60Y, 60C, 60M, and Bk of each color as the photoreceptors 40Y, 40C, 40M, and Bk rotate. The developed toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 10 along with the conveyance of the intermediate transfer belt 10 to form a full color image on the intermediate transfer belt 10. The photoconductors 40Y, 40C, 40M, 40Bk after the transfer are subjected to light neutralization by a neutralization lamp, and residual toner is removed by a cleaning unit.

  On the other hand, in the paper feed table 200, one of the paper feed rollers 42 is selectively rotated, the transfer material is sent out from one of the paper feed cassettes 44 provided in multiple stages to the paper feed table 43, and separated one by one by the separation roller 45. Then, the sheet is put into the sheet feeding path 46, conveyed by the conveying roller 47, guided to the sheet feeding path 48 in the main body, and abutted against the registration roller 49 and stopped. Alternatively, the transfer roller 50 is rotated to feed the transfer material on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped. Then, the registration roller 49 is rotated in synchronization with the full-color image on the intermediate transfer belt 10, the transfer material is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. The toner image is transferred onto the transfer material. The transfer material on which the toner image has been transferred is conveyed by the secondary transfer device 22 and sent to the fixing device 25, and is fixed to the transfer material by applying heat and pressure by the fixing device 25. The paper is switched and discharged by a discharge roller 56 and stacked on a discharge tray 57. Alternatively, the sheet is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and re-fed to the secondary transfer position 22, and an image is recorded on the back side. To be discharged. Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated. After the predetermined number of images have been formed, the post-image forming process is performed, and then the rotation of the photoconductors 40Y, C, M, and Bk is stopped. In the post-image processing, the photosensitive member 40 is rotated one or more times with the charging bias and transfer bias turned off, and at that time, the charge on the surface of the photosensitive member 40 is discharged by the discharging means, and the photosensitive member 40 is left discharged. This prevents the photoreceptor 40 from deteriorating.

  On the other hand, when the monochrome mode is selected on the operation unit, the support roller 15 moves downward to separate the intermediate transfer belt 10 from the photoreceptors 40Y, 40C, and 40M. Only the photoconductor 40Bk rotates counterclockwise in FIG. 1, the surface of the photoconductor 40Bk is uniformly charged by the charging device, a laser beam corresponding to the image of Bk is irradiated, a latent image is formed, and Bk A toner image is developed with the toner. This toner image is transferred onto the intermediate transfer belt 10. At this time, the three color photoconductors 40Y, 40C, 40M other than Bk and the developing devices 60Y, 60C, 60M are stopped, and unnecessary wear of the photoconductor and the developer is prevented. On the other hand, the transfer material fed from the paper feed cassette 44 is conveyed by the registration roller 49 at a timing that coincides with the toner image formed on the intermediate transfer belt 10, and the toner image on the intermediate transfer belt 10 is secondary. Transfer is performed by the transfer device 22. The transfer material onto which the toner image has been transferred is fixed by the fixing device 25 as in the case of a full-color image, and is processed through a paper discharge system corresponding to a designated mode. Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

  Next, the configuration of the image forming unit 18 will be described in detail. Since the image forming units 18Y, 18C, 18M, and 18K have the same configuration except that the toner colors used in the developing devices 60Y, 60C, 60M, and Bk are different, the following description is omitted. FIG. 2 is a schematic configuration diagram showing an internal configuration of the image forming unit. As shown in FIG. 2, a charging device 70 that uniformly charges the photoconductor 40, a potential sensor 71 that detects the potential of the photoconductor 40, and the photoconductor 40 are formed around the photoconductor 40 that is an image carrier. And a developing device 60 for developing the electrostatic latent image. Further, around the photosensitive member 40, a neutralizing lamp 72 for neutralizing the surface of the photosensitive member 40 after the toner image is transferred, two brush rollers 73, 74 as a cleaning device for cleaning the transfer residual toner, A cleaning blade 75 made of polyurethane rubber or the like is disposed. The case of the image forming unit 18 is provided with an opening for allowing the exposure light 76 from the exposure device 21 to pass therethrough. The toner scraped off from the photoreceptor 40 by the brush rollers 73 and 74 and the cleaning blade 75 is collected by a toner transport coil 79 and transported to a waste toner storage unit (not shown).

  A solid lubricant 78 is in contact with the brush roller 74 in FIG. 2, and also has a function as a lubricant supply member to the photoreceptor. By supplying a lubricant to the photoconductor, the wear of the photoconductor can be reduced and the cleaning property can be improved. Examples of solid lubricants include zinc stearate, barium stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, magnesium stearate, zinc oleate, oleic acid Fatty acid metal salts such as cobalt, magnesium oleate, and zinc palmitate, natural waxes such as carnauba wax, and fluorine-based resins such as polytetrafluoroethylene can be used.

  The image forming unit 18 shown in FIG. 2 is configured to clean the photoreceptor 40 that has been neutralized by the neutralizing lamp 72 after transfer, but is configured to neutralize the photoreceptor that has been cleaned after transfer. Also good. In the image forming unit 18 shown in FIG. 2, the lubricant 78 is disposed on the brush roller 74 serving as a cleaning unit. In this configuration, the lubricant 78 is supplied depending on the amount of toner input to the brush roller 74. There was a drawback of being easily affected. This is because the lubricant supply means is provided in the cleaning means of the photoconductor 40, so that the amount of toner input to the cleaning (transfer residual toner or reverse rotation by the toner image formed upstream in the full-color image forming apparatus). This is because the supply efficiency of the lubricant is affected when the transfer toner) fluctuates. Therefore, the lubricant supply means may be disposed downstream of the cleaning means in the moving direction of the photoconductor. FIG. 3 is a schematic configuration diagram showing an internal configuration of an image forming unit according to another embodiment different from that in FIG. As shown in FIG. 3, a brush roller 74 and a lubricant 78 that are lubricant supply means may be arranged downstream of the brush roller 75 and the cleaning blade 75 in the photosensitive member moving direction. Accordingly, the lubricant can be stably supplied to the photoconductor 40 even if the input amount of the transfer residual toner or the reverse transfer toner changes depending on the image area to be formed. In FIG. 3, the same members as those shown in FIG.

  As shown in FIGS. 2 and 3, the developing device 60 employs a two-component developing method, and the developing device 60 contains a two-component developer composed of toner and carrier. The developing device 60 detects the toner concentration of the developer in the developing device 60, the developing roller 61 disposed opposite to the photoreceptor 40, the two screws 62 and 63 that convey and stir the developer in the developing device 60, and the developing device 60. A toner density sensor 64 and the like are provided. The developing roller 61 includes an outer rotatable sleeve and a magnet fixed on the inner side, and carries toner to be supplied to the photoreceptor 40. The two-component developer in the developing device 60 is conveyed and circulated while being agitated by the two screws 62 and 63, and is supplied to the developing roller 61. The developer supplied to the developing roller 61 is regulated to an appropriate amount by the doctor blade 65 along with the rotation of the developing roller 61, and then transferred to the photoreceptor 40 by the developing bias voltage applied to the developing roller 61. The electrostatic latent image on 40 is visualized. After the visualization, the developer remaining on the developing roller 61 leaves the developing sleeve 65 where there is no magnetic force. When the toner concentration in the developing device 60 becomes light by this repetition, it is detected by the toner concentration sensor 71 and a necessary amount of toner is supplied by a toner supply device (not shown).

The toner used in the present embodiment is composed of a binder resin, a colorant, and a charge control agent as main components, and other additives are added as necessary. Specific examples of the binder resin include polystyrene, styrene-acrylic acid ester copolymer, polyester resin, and the like. As the colorant (for example, yellow, magenta, cyan and black) used for the toner, those known for toner can be used. The amount of the coloring material is suitably 0.1 to 15 parts by weight with respect to 100 parts by weight of the binder resin.
Specific examples of the charge control agent include a nigrosine dye, a chromium-containing complex, a quaternary ammonium salt, and the like, which are properly used depending on the polarity of the toner particles. The amount of the charge control agent is 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.
In addition, it is advantageous to add a fluidity imparting agent to the toner particles. Examples of the fluidity-imparting agent include fine particles of metal oxides such as silica, titania and alumina, and those obtained by surface-treating these fine particles with a silane coupling agent, titanate coupling agent, etc., polystyrene, polymethyl methacrylate, polyvinylidene fluoride. Polymer fine particles such as are used. These fluidity imparting agents have a particle size in the range of 0.01 to 3 μm. The addition amount of these fluidity-imparting agents is preferably in the range of 0.1 to 7.0 parts by weight with respect to 100 parts by weight of the toner particles.

  As a method for producing the toner for the two-component developer used in the present embodiment, it can be produced by various known methods or a combination thereof. For example, in the kneading and pulverization method, a binder resin, a colorant such as carbon black, and the necessary additives are dry-mixed, heated and melt-kneaded with an extruder or two-roll, three-roll, etc., and after cooling and solidification Then, the toner is pulverized by a pulverizer such as a jet mill and classified by an airflow classifier. In addition, a toner can be directly produced from a monomer, a colorant, and an additive by suspension polymerization or non-aqueous dispersion polymerization.

The carrier for the two-component developer used in the present embodiment is made of the core material itself or is provided with a coating layer on the core material. For example, the core material of the resin-coated carrier that can be used in the present embodiment is ferrite or magnetite. An appropriate particle size of the core material is about 20 to 60 μm.
Examples of the material used for forming the carrier coating layer include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinyl ether substituted with a fluorine atom, and vinyl ketone substituted with a fluorine atom. As a method for forming the coating layer, a resin may be applied to the surface of the carrier core material particles by a spraying method, a dipping method, or the like, as in the conventional case.

As an example of the photoreceptor 40 used in the present embodiment, a stacked organic photoreceptor including a charge generation layer and a charge transport layer, which are photosensitive layers formed on a conductive support, can be cited.
Conductive support, shows the following conductive volume resistivity 81 ⁰ [Omega] cm, for example, aluminum, nickel, chromium, nichrome, copper, silver, gold, metals such as platinum, tin oxide, metal oxides such as indium oxide The film is formed by vapor deposition or sputtering, film- or cylindrical plastic, paper-coated, pipes such as aluminum, aluminum alloy, nickel, and stainless steel are subjected to surface treatment by cutting, superfinishing, polishing, or the like.

The charge generation layer is a layer mainly composed of a charge generation material. The film thickness of the charge generation layer is usually 0.01 to 5 μm, preferably 0.1 to 2 μm. As the charge generation material, an inorganic or organic material is used, and typical examples include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squarics. Examples include acid dyes, phthalocyanine pigments, naphthalocyanine pigments, azulenium salt dyes, selenium, selenium-tellurium alloys, selenium-arsenic alloys, and amorphous silicon. These charge generation materials may be used alone or in combination of two or more.
The charge generation layer is obtained by dispersing the charge generation material together with a binder resin, using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, 2-butanone, dichloroethane, or the like by a ball mill, attritor, sand mill, etc., and applying a dispersion. Can be formed.
The charge generation layer can be applied by dip coating, spray coating, bead coating, or the like.
Examples of the binder resin used as appropriate include resins such as polyamide, polyurethane, polyester, epoxy, polyketone, polycarbonate, silicone, acrylic, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polyacryl, and polyamide. The amount of the binder resin is suitably 0 to 2 parts with respect to 1 part of the charge generating material on a weight basis.
The charge generation layer can also be formed by a known vacuum thin film manufacturing method.

  The charge transport layer can be formed by dissolving or dispersing a charge transport material and a binder resin in a suitable solvent, and applying and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added as needed. The thickness of the charge transport layer may be appropriately selected in accordance with desired photoreceptor characteristics within a range of 10 to 40 μm. In the present embodiment, the amount of the charge transport material contained in the photosensitive layer is preferably 30% by weight or more of the charge transport layer. If it is less than 30% by weight, a sufficient light decay time in a high-speed electrophotographic process cannot be obtained in pulsed light exposure in laser writing on a photoreceptor, which is not preferable.

Among the charge transport materials, low molecular charge transport materials include electron transport materials and hole transport materials. Examples of the electron transport material include chloroanil, bromanyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide. These electron transport materials may be used alone or as a mixture of two or more.
Examples of hole transport materials include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane. , Styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These hole transport materials may be used alone or as a mixture of two or more.

  As the binder resin used for the charge transport layer together with the charge transport material, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride- Vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy, polycarbonate, cellulose acetate, ethyl cellulose, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic, silicone, epoxy, melamine, urethane, phenol, alkyd, etc. A thermoplastic or thermosetting resin is mentioned. Examples of the solvent include tetrahydrofuran, dioxane, toluene, 2-butanone, monochlorobenzene, dichloroethane, methylene chloride and the like.

Examples of the plasticizer that is optionally added to the charge transport layer include dibutyl phthalate, dioctyl phthalate, and other general-purpose plasticizers. The amount used is 0 to 30% based on the weight of the binder resin. The degree is appropriate.
Leveling agents added to the charge transport layer as desired include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in the side chain. About 0 to 1% is appropriate for the binder resin on the basis.

In the photoreceptor used in the exemplary embodiment, an undercoat layer can be formed between the conductive support and the photosensitive layer. In general, the undercoat layer is mainly composed of a resin. However, considering that the photosensitive layer is applied using a solvent, the resin is a resin having high resistance to general organic solvents. Is desirable. Such resins include water-soluble resins such as polyvinyl alcohol, casein, sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine, alkyd-melamine, epoxy, etc., three-dimensional Examples thereof include a curable resin that forms a network structure.
Further, fine powder of metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide may be added to the undercoat layer in order to prevent moire and reduce residual potential. This undercoat layer can be formed by using an appropriate solvent and coating method as in the case of the photosensitive layer.
Furthermore, it is also useful to use a metal oxide layer formed by, for example, a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like as the undercoat layer. In addition, the undercoat layer which the _Al 2 _{O 3} was formed by those anodized, organic matter such as polyparaxylylene _{(parylene), SiO, SnO 2, TiO} 2, ITO, Ce0 2 , etc. inorganic It is also effective to form the film by a vacuum thin film manufacturing method. The thickness of the undercoat layer is suitably from 0 to 5 μm.

In the photoreceptor 40 used in the present embodiment, a protective layer can be formed on the photosensitive layer. By providing a protective layer on the surface of the photoconductor 40, wear of the photoconductor 40 can be reduced even when an AC bias is superimposed on the charging roller, as will be described later, and the life of the photoconductor 40 can be extended. . This protective layer has a structure in which metal oxide fine particles such as alumina, silica, titanium oxide, tin oxide, zirconium oxide, and indium oxide are added to the binder resin for the purpose of improving wear resistance. Binder resins include styrene-acrylonitrile copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, olefin-vinyl monomer copolymer, chlorinated polyether, allyl, phenol, polyacetal, polyamide, polyamide Imide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethine, polyethylene terephthalate, polyimide, acrylic, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polyurethane, polyvinyl chloride, polyvinylidene chloride And resins such as epoxy.
The amount of metal oxide fine particles added to the protective layer is usually 5 to 30% on a weight basis. If the amount of the metal oxide fine particles is less than 5%, the wear is large and the effect of improving the wear resistance is small and the durability is inferior. If it exceeds 30%, the bright portion potential is significantly increased during exposure, and the sensitivity is lowered. Is not desirable because it cannot be ignored. As a method for forming the protective layer, a normal coating method such as a spray method is employed. The thickness of the protective layer is 1 to 10 μm, preferably about 3 to 8 μm. If the protective layer is too thin, the durability will be poor, and if the protective layer is too thick, not only will the productivity at the time of photoconductor production decrease, but the residual potential will increase significantly over time. . The particle size of the metal oxide particles added to the protective layer is suitably 0.1 to 0.8 μm. When the particle size of the metal oxide fine particles is too large, the unevenness on the surface of the protective layer becomes large and the cleaning property is deteriorated, and the exposure light is easily scattered by the protective layer, so that the resolution is lowered and the image quality is inferior. If the particle size of the metal oxide fine particles is too small, the wear resistance is poor.
Further, a dispersion aid can be added to the protective layer in order to improve the dispersibility of the metal oxide fine particles in the base resin. As the added dispersion aid, those used in paints and the like can be used as appropriate, and the amount thereof is usually 0.5 to 4%, preferably 1 to 2 with respect to the amount of metal oxide fine particles contained on a weight basis. %.
Further, by adding a charge transport material to the protective layer, the movement of charges in the protective layer can be promoted. As the charge transport material added to the protective layer, the same material as the charge transport layer can be used.

  Further, the photoreceptor 40 used in the present embodiment has an antioxidant, a plasticizer, an ultraviolet absorber, and leveling for each layer for the purpose of improving the environmental resistance, in order to prevent a decrease in sensitivity and an increase in residual potential. An agent or the like can be added. The configuration of the protective layer that can be used in this embodiment is not limited to the type in which metal oxide particles are dispersed, and the protective layer is formed by using a light or thermosetting resin material. You can also.

Next, the configuration of the charging device 70 that is a feature of the present invention will be described. In this embodiment, a non-contact charging roller 77 is employed. FIG. 4 is a configuration diagram showing the configuration of the charging roller used in this embodiment. As shown in FIG. 4, the charging roller 77 includes a cored bar 81 as a conductive support, a charging member 82 formed around the cored bar 81, and a gap holding member formed at both ends of the charging member 82. 83. A gap is formed between the charging member 82 of the charging roller 77 and the photosensitive member 40 by contacting the gap holding member 83 outside the image area of the photosensitive member 40. In the charging roller 77, the gear attached to the end of the core 81 engages with the gear formed on the photosensitive member flange. When the photosensitive member 40 is rotated by the photosensitive member driving motor, the charging roller 77 is driven at a linear velocity substantially equal to that of the photosensitive member 40. Rotate around. Since the photosensitive member 40 and the charging member 82 of the charging roller 77 do not come into contact with each other, even when a hard resin material is used as the charging member 82 of the photosensitive member 40 and the charging roller 77, the photosensitive layer in the image area may be damaged. Never do. If the charging gap between the photosensitive member 40 and the charging roller 77 is too wide, abnormal discharge occurs and charging cannot be performed uniformly. Therefore, the maximum charging gap needs to be suppressed to about 100 μm or less. When using the charging device 70 having a charging gap between the photosensitive member 40 and the charging roller 77, it is desirable to superimpose an AC voltage on a DC voltage as a charging bias. Even if the photoconductor 40 and the charging roller 77 are arranged in a non-contact manner, the photoconductor 40 can be uniformly charged.

  Here, a metal such as stainless steel is used for the cored bar 81 of the charging roller 77. If the mandrel 81 is too thin, the influence of the deflection when the charging member 82 is cut or when the photosensitive member 40 is pressed cannot be ignored, and the required gap accuracy is difficult to obtain. Further, when the cored bar 81 is too thick, there is a problem that the charging roller 77 becomes large and the mass becomes heavy. Therefore, the diameter of the cored bar 81 is preferably about 6 to 10 mm.

The charging member 82 of the charging roller 77 is preferably made of a material having a volume resistance of 10 ⁴ to 10 ⁹ Ωcm, particularly a resin material. If the resistance is too low, charging bias leaks easily when there is a defect such as a pinhole in the photoconductor 40. If the resistance is too high, the discharge is not sufficiently generated and a uniform charging potential cannot be obtained. A desired volume resistance can be obtained by blending a conductive material with a resin as a base material. As the base resin, resins such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, and polycarbonate can be used. Since these base resins have good moldability, they can be easily molded.
The conductive material is preferably an ion conductive material such as a polymer compound having a quaternary ammonium base. Examples of polyolefins having a quaternary ammonium base include polyethylene, polypropylene, polybutene, polyisoprene, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene- Polyolefins such as propylene copolymer and ethylene-hexene copolymer. In the present embodiment, the polyolefin having a quaternary ammonium base is exemplified, but a polymer compound other than the polyolefin having a quaternary ammonium base may be used.
The ion conductive material is uniformly blended with the base resin by using a means such as a biaxial kneader or a kneader. The blended material can be easily molded into a roller shape by injection molding or extrusion molding on the core metal. The blending amount of the ion conductive material and the base resin is desirably 30 to 80 parts by weight of the ion conductive material with respect to 100 parts by weight of the base resin. The thickness of the charging member 82 of the charging roller 77 is preferably 0.5 to 3 mm. If the charging member 82 is too thin, molding is difficult and there is a problem in terms of strength. If the charging member 82 is too thick, the charging roller 77 is increased in size and the actual resistance of the charging member 82 is increased, so that charging efficiency is lowered.

The gap holding member 83 of the charging roller 77 is formed by forming the charging member 82, and then pressing and bonding the gap holding member 83 previously formed on both ends of the charging member 82, or by using both of them together. It is fixed to. In this way, after the charging member 82 and the gap holding member 83 are integrated, the phase of the flare between the charging member 82 and the gap holding member 83 is adjusted by adjusting the outer diameter of the charging roller 77 by performing processing such as cutting or grinding. And the fluctuation of the charging gap can be reduced.
As the material of the gap holding member 83, a resin such as polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-butadiene-styrene copolymer, and polycarbonate can be used in the same manner as the base material of the charging member 82. However, since the gap holding member 83 is brought into contact with the photosensitive layer, it is desirable to use a grade having a lower hardness than the charging member 82 in order to prevent the photosensitive layer from being damaged. In addition, as a resin material having excellent slidability and hardly damaging the photosensitive layer, polyacetal, ethylene-ethyl acrylate copolymer, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoro A resin such as a propylene copolymer can also be used.
Further, the charging member 82 and the gap holding member 83 can be formed with a thickness of about several tens of μm by coating or the like on which the toner or the like hardly adheres.

  The resin material used for the charging member 82 and the gap holding member 83 of the charging roller 77 described above can be processed with high accuracy because it is easy to process and the hardness variation due to the environment is small. Therefore, it is possible to stably form a minute charging gap between the photoconductor 40 and the charging roller 77.

  The charging roller 77 is provided with a charging member cleaning unit for cleaning the charging member 82 and a gap holding member cleaning unit for cleaning the gap holding member 83. A variety of materials such as sponges and brushes can be used as the charging member cleaning means and the gap holding member cleaning means. In this case, the toner or the like accumulated on the contact surface is easily attached to the charging member 82 or the gap holding member 63. Therefore, it is preferable that the charging member cleaning member and the gap holding member cleaning unit rotate in association with the charging member 82 and the gap holding member 83 in a roller shape.

  The charging unit cleaning roller that is the charging member cleaning unit and the gap holding unit cleaning roller that is the gap holding member cleaning unit according to the present embodiment are configured as follows. FIG. 5 is a cross-sectional view illustrating configurations of the charging unit cleaning roller and the gap holding unit cleaning roller. FIG. 6 is a configuration diagram illustrating positions of the charging unit cleaning roller and the gap cleaning roller. FIG. 7 is a partially enlarged perspective view showing the configuration of the charging unit cleaning roller. As shown in FIGS. 5 and 6, a charging unit cleaning roller 84 and a gap holding unit cleaning roller 87 are disposed around the charging roller 77. Here, the positional relationship between the charging unit cleaning roller 84 and the gap holding unit cleaning roller 87 may be either upstream or downstream in the movement direction of the charging roller 77.

  The charging unit cleaning roller 84 includes a cored bar 85 and a charging unit cleaning member 86 formed around the cored bar 85. The charging unit cleaning member 86 is opposed to the charging member 82 of the charging roller 77. Is configured to be able to contact and separate. Since an AC bias is superimposed and applied to the charging roller 77 as a charging bias, dirt on the image carrier is electrostatically attracted to the charging member. It also works to pull back the image carrier to static electricity. For this reason, it has been found that the charging member cleaning member 86 does not always need to contact the charging member 82. When the charging member cleaning member is kept in contact with the charging member at all times, the surface of the charging member can be removed initially. Will rub. As a result, the charging member is contaminated, or the cleaning member itself is deteriorated, so that the cleaning performance cannot be maintained. Therefore, the charging unit cleaning roller 84 is configured such that the charging unit cleaning member 86 can come into contact with and separate from the charging member 82 of the charging roller 77 by a contact / separation mechanism described later.

  As shown in FIG. 5, the charging unit cleaning member 86 of the charging unit cleaning roller 84 may be formed to have a width (length in the axial direction) that can clean the charging member 82 of the charging roller 77. The gap holding member 83 may also be formed with a width that can be cleaned. Further, a melamine resin foam (porous material) may be used for the charging portion cleaning member 86 of the charging portion cleaning roller 84. Melamine resin foam is superior in strength to other porous materials, and since there are many spaces in the foam, it is possible to retain a large amount of dirt such as toner and maintain cleaning performance over a long period of time. be able to. In order to prevent the dirt removed from the charging member 82 from rubbing against the charging member 82 and causing the dirt to adhere to the charging member 82, the charging unit cleaning roller 84 is connected to the charging member (charging roller) 82. Rather than abutting with a speed difference, the abutting while rotating at a constant speed with the charging member 82 is less likely to rub off dirt.

The gap holding portion cleaning roller 87 includes a cored bar 88 and a gap holding unit cleaning member 89 formed around the cored bar 88, and the gap holding unit cleaning member 89 serves as the gap holding member 83 of the charging roller 77. It is comprised so that it may always contact | abut. The gap holding portion cleaning member 89 of the gap holding portion cleaning roller 87 is formed with a width (length in the axial direction) that allows the gap holding member 83 to be cleaned. In the gap holding part cleaning roller 87, since the gap holding part cleaning member 89 is always in contact with the gap holding member 83, a large amount of toner does not adhere to the gap holding member 83, and the charging gap is maintained over a long period of time. Can be maintained. When the gap holding member cleaning member 89 is intermittently brought into contact with the gap holding member 83, the gap holding member 83 and the gap holding portion can be selected even if a material that does not easily adhere toner is selected as the gap holding member 83. While the cleaning member 89 is separated, toner that slightly leaks from the end of the cleaning blade installed on the photoconductor 40 or toner that slightly scatters from the developing device tends to accumulate on the gap holding member 83. . As a result, the toner is crushed between the photoconductor 40 and the gap holding member 83 and the toners are easily fixed to each other, so that the charging gap is widened, and abnormal images such as density unevenness due to abnormal discharge are easily generated.
As for the gap holding portion cleaning member 89, melamine resin foam can be used similarly to the charging portion cleaning member 86, and a different material may be used. In addition, the gap holding unit cleaning roller 87 is in contact with the gap holding member (charging roller) 83 with a speed difference, and the contact with the gap holding member 83 while rotating at a constant speed rubs dirt. Is unlikely to occur.

  In this manner, the charging unit cleaning roller 84 is intermittently brought into contact with the charging member 82 of the charging roller 77, so that the amount of dirt that reattaches to the charging member 82 is reduced, and good cleaning performance is maintained over a long period of time. be able to. Also. Compared to the case of constant contact, the amount of dirt accumulated on the charging unit cleaning roller 77 is reduced, and the charging unit cleaning roller 77 is less likely to be deteriorated and the life is extended. On the other hand, since the gap holding portion cleaning roller 87 is always in contact with the gap holding member 83, a large amount of toner does not adhere to the gap holding member 83, and the charging gap can be maintained for a long time. it can.

  Next, a configuration for causing the charging unit cleaning roller 84 to contact and separate will be described. FIG. 8 is a configuration diagram illustrating an example of a configuration in which the charging unit cleaning roller is moved toward and away from the charging unit. As shown in FIG. 8, both end portions of the cored bar 85 of the charging roller 77 are supported by the charging frame 101, and the gap holding member 83 abuts outside the image forming area of the photoreceptor 40 to form a desired charging gap. Be able to. Further, both end portions of the cored bar 85 of the charging unit cleaning roller 84 are supported by an arm 103 (partially indicated by a dotted line) supported by the charging frame 101 and capable of rotating about a fulcrum 102. By pushing down the protruding portion 104 of the arm 103 from the position shown in FIG. 8 by a solenoid (not shown) installed on the apparatus main body 100 side, the charging portion cleaning member 86 abuts against the charging member 82 of the charging roller 77 and rotates around. The charging member 82 is cleaned. On the other hand, when the pressure from the solenoid is released in the direction of the arrow in the figure, the charging unit cleaning roller 84 separates the charging unit cleaning member 86 from the charging member 82 of the charging roller 77. If the contact / separation operation of the charging unit cleaning flora 84 is performed during image formation, vibration due to the operation of the solenoid may be transmitted to the writing unit or the like, and the image may be disturbed. Therefore, the cleaning operation of the charging member 82 is performed during the image formation operation. It is necessary to carry out other than. If this cleaning operation is executed frequently, the waiting time of the user will increase, so it is preferable to reduce the frequency of execution of the cleaning operation as much as possible. In this embodiment, since the contamination of the charging roller 77 can be reduced by disposing the charging member 82 of the charging roller 77 in a non-contact manner with respect to the photoreceptor 40, the cleaning execution interval of the charging member 82 can be set long. This makes it possible to reduce the waiting time of the user.

  Further, the contamination of the charging member 82 of the charging roller 77 is also affected by usage conditions such as the usage environment, the number of sheets used, and the image area. Therefore, the execution interval of the cleaning operation of the charging member 82 is changed according to the usage conditions. It is preferable. Specifically, when the usage environment is a low-temperature and low-humidity environment, the charging member 82 itself or the resistance of dirt attached to the charging member 82 is increased, and charging failure is likely to occur. Further, as the number of phases used increases, deterioration of the photoreceptor cleaning means (wear of the cleaning blade 75, etc.) proceeds, so that the toner passing through the photoreceptor cleaning means increases and the charging member 82 is likely to become dirty. Further, even when a large number of images with a large image area are output, the toner input to the photoconductor cleaning means increases, so that the charging member 82 is easily contaminated. Therefore, when used in such a situation, it is desirable to increase the execution frequency of the charging operation of the charging member 82.

Next, another embodiment in which the arrangement of the charging unit cleaning roller and the gap holding unit cleaning roller is changed will be described. 7 and 8, the cored bar (rotating shaft) 85 of the charging unit cleaning roller 84 and the cored bar (rotating shaft) 88 of the gap holding unit cleaning roller 87 are located at different positions on the charging roller 77. Has been placed. On the other hand, the charging member cleaning means and the gap holding member cleaning means may be arranged integrally so that their rotational axes are substantially coaxial. FIG. 9 is a configuration diagram showing the configuration of this charging device integrated cleaning roller. FIG. 10A is a configuration diagram showing a state of the integrated cleaning roller when the charging unit cleaning member is in contact with the photosensitive member. FIG. 10B is a configuration diagram showing the state of the integrated cleaning roller when the charging unit cleaning member is separated from the photoreceptor.

As shown in FIGS. 9 and 10, the integrated cleaning roller 90 includes a charging portion cleaning member 91 formed to have a width capable of cleaning the charging member 82 of the charging roller 77, a core material 92 that supports the charging portion cleaning member 91, and a gap. The gap holding portion cleaning member 93 is formed to have a width capable of cleaning the holding member 83 and a hollow core member 94 that supports the gap holding portion cleaning member 93. Then, at a predetermined timing, as shown in FIG. 10A, the charging unit cleaning member 91 indicated by a dotted line in the drawing contacts the charging member 82, and the gap holding unit cleaning member 93 contacts the gap holding member 83. Further, normally, as shown in FIG. 10B, the charging portion cleaning member 91 indicated by the dotted line in the drawing is separated from the charging member 82, and the gap holding portion cleaning portion 93 is in contact with the gap holding member 83. Here, the inner diameter of the hollow core 94 of the gap holding part cleaning member 93, the outer diameter of the cored bar 92 of the charging part cleaning member 91 at the gap holding part cleaning member mounting position, and the outer diameter of the charging part cleaning member 91 Therefore, it is necessary to set an appropriate relationship with the stroke amount of the contact / separation operation of the charging unit cleaning member 91. By setting these conditions in an appropriate relationship, the gap holding member cleaning member 93 can always be in contact with the gap holding member 83 regardless of the contact / separation state of the charging unit cleaning member 91 with the charging member 82. At this time, the integrated cleaning roller 90 may be disposed above the charging roller 77. Thus, regardless of the contact / separation state of the charging unit cleaning member 91, the gap holding member 83 can be cleaned by always contacting the gap holding member cleaning member 93 with the gap holding member 83 by the action of gravity.

  As described above, the integrated cleaning roller 90 intermittently contacts the charging unit cleaning member 91 with the charging member 82 of the charging roller 77, so that the amount of toner or the like that accumulates on the charging unit cleaning member 91 compared to the case of constant contact. Can be reduced. Further, the charging unit cleaning member 91 is not easily deteriorated, and the life of the integrated cleaning roller 90 is extended. On the other hand, since the gap holding member 93 is always in contact with the gap holding member 83, a large amount of toner does not adhere to the gap holding member 83, and good image quality can be maintained over a long period of time. Can do. Furthermore, since the core material 92 of the charging unit cleaning member 91 and the hollow core material 94 of the gap holding member 93 are arranged substantially coaxially, space saving is possible.

Next, results of experiments using the charging devices shown in the comparative example and the example will be described.
[Comparative Example 1]
First, as a charging roller, a resin charging roller shown in FIG. 4 was prepared. Further, as a charging roller cleaning means, a cleaning roller provided with a cleaning member made of a melamine resin foam formed to have a width capable of cleaning the charging member and the gap holding member was prepared. The cleaning roller cleans the charging member and the gap holding member while always rotating with the charging roller.
Next, the charging device including these charging roller and cleaning roller was mounted on an experimental machine modified from Ricoh's full-color copier Imagio Neo 600. Then, after conducting a 150,000 sheet passing test in a normal temperature and humidity environment under the condition that the image area of each color is 5% and 5 sheets of A4 size transfer paper is passed per job, the temperature is 10% 15%. The images were checked in a low temperature and low humidity environment.
In the normal temperature and humidity environment, no abnormal image was generated due to the charging roller in any of the four image forming units. However, at 10 ° C. and 15%, the vertical stripe-like density unevenness was observed in the four image forming units in the halftone image. Occurred in. When the charging roller was observed, streaky stains that appeared to be toner, toner external additives, lubricants, and the like adhered to the charging member corresponding to the density unevenness. From the comparison with Comparative Example 3 to be described later, it is considered that the dirt adhered to the surface of the charging member is due to the dirt collected on the cleaning roller being reattached when the cleaning roller is in constant contact. It is considered that the charging member of the charging roller is not necessarily required to always contact the cleaning member. Even if there is no problem in the normal temperature and normal humidity environment, the problem due to the contamination of the charging roller 77 in the environment of 10 ° C. and 15% becomes apparent because the contamination adhered to the charging member 82 itself or the surface of the charging member 82 in the low temperature and low humidity environment. This is considered to be because the resistance of the substrate increases and discharge becomes difficult to occur.

[Comparative Example 2]
The paper passing test was performed under the same conditions as in Comparative Example 1 except that the cleaning roller used in Comparative Example 1 was able to be brought into contact with and separated from both the charging member and the gap holding member of the charging roller by the mechanism shown in FIG. went. Normally, the cleaning roller was separated from the charging roller, and the cleaning operation was performed by rotating the photosensitive member and the charging roller with the cleaning roller in contact with the charging roller for 10 seconds after every 2500 sheets after the job.
When the paper passing test was performed in a room temperature and humidity environment with the above configuration, up to 100,000 sheets, two image forming units generated a point-like abnormal image at the charging roller pitch at the edge of the image. When the charging roller is checked, in the image forming unit in which an abnormal image is generated, a lump of toner adheres to the gap holding member, so that the charging gap widens and an abnormal image is generated. Toner that slightly leaks from the edge of the cleaning blade that cleans the photoconductor or toner that slightly scatters from the developing unit or the like gradually accumulates in the gap holding member and is crushed between the gap holding member and the photoconductor. It is thought that it was fixed. Toner leakage from the edge of the cleaning blade and slight toner scattering from the developing device also occurred in Comparative Example 1. In Comparative Example 1, since the cleaning roller was always in contact with the gap holding member, toner fixing It is thought that it was removed from the gap holding member without reaching.

[Comparative Example 3]
As a charging means for cleaning the charging roller, a cleaning roller provided with a cleaning member made of a melamine resin foam formed with a width capable of cleaning only the gap holding member was prepared. The cleaning roller cleans the gap holding member while always rotating with the gap holding member. The charging member of the charging roller is not cleaned at all, and only the toner adhering to the gap holding member is removed. A paper passing test was performed under the same conditions as in Comparative Example 1 except that this cleaning roller was used.
After conducting a paper passing test up to 150,000 sheets with the above configuration, images were confirmed in a low-temperature and low-humidity environment at 10 ° C. and 15%. There was no occurrence, but at 10 ° C. and 15%, the four image forming units had halftone images and spotted density unevenness at the charging roller pitch. When the charging roller was observed, the deposit on the charging roller was uneven depending on the location, corresponding to the spotted density unevenness. Since the charging member is not cleaned, the amount of the deposit is partially uneven, which is considered to be manifested as density unevenness in the low temperature and low humidity environment where the resistance of the charging roller itself and the deposit increases.

[Example 1]
A sheet passing test was performed under the same conditions as in Comparative Example 1 except that the charging unit cleaning roller and the gap holding unit cleaning roller shown in FIGS. 5 and 6 were used as the charging roller cleaning means. As described above, the charging unit cleaning roller is normally separated from the charging member of the charging roller, and the charging unit cleaning roller is in contact with the charging member for 10 seconds after every 2500 sheets after the job. The charging roller is rotated to perform a cleaning operation. On the other hand, the gap holding unit cleaning roller always performs contact with the gap holding member to perform the cleaning operation.
After carrying out a paper passing test of 200,000 sheets in a normal temperature and humidity environment with the above configuration, an image check was performed in a low temperature and low humidity environment of 10 ° C. and 15%. No abnormal image was generated due to toner adhesion to the gap holding member. Further, when the surface of the charging member of the charging roller was observed, no dirt was adhered as in Comparative Examples 1 and 3. From these results, the charging member of the charging roller is intermittently cleaned by the charging unit cleaning roller, and the gap holding member is constantly cleaned by the gap holding unit cleaning roller. It can be seen that both abnormal images can be effectively prevented.

[Example 2]
A paper passing test was performed under the same conditions as in Example 1 except that the integrated cleaning roller shown in FIGS. 9 and 10 was used as the charging roller cleaning means. As described above, the gap holding member cleaning member can always be brought into contact with the gap holding member regardless of the contact / separation state of the charging unit cleaning member.
After carrying out a paper passing test of 200,000 sheets in a normal temperature and humidity environment with the above configuration, an image check was performed in a low temperature and low humidity environment of 10 ° C. and 15%. No abnormal image was generated due to toner fixing to the gap holding member. From these results, the charging member can be intermittently cleaned by the charging unit cleaning member, and the gap holding member can be constantly cleaned by the gap holding unit cleaning member. It can be seen that both images can be effectively prevented. In addition, since the cleaning roller including the charging unit cleaning member and the gap holding unit cleaning member is configured as an integrated cleaning roller, the image forming apparatus can be downsized as compared with the first exemplary embodiment.

As described above, in the image forming apparatus according to the present embodiment, the charging unit cleaning roller 84 serving as the charging member cleaning unit and the gap holding member cleaning unit are used as the cleaning unit for the charging member 82 and the gap holding member 83, respectively. A gap holding unit cleaning roller 87 is provided. Therefore, both the charging member 82 and the gap holding member 83 can be cleaned under appropriate conditions, and the image quality can be maintained satisfactorily for a long time.
In the image forming apparatus according to the present embodiment, the charging unit cleaning roller 84 is configured to be able to contact and separate from the charging member 82. For this reason, as compared with the case where the charging unit cleaning roller is always in contact with the charging member, the amount of dirt that adheres again to the charging unit 82 of the charging roller 77 is reduced, and good cleaning performance can be maintained. In addition, the amount of toner or the like that accumulates on the charging unit cleaning roller 84 is reduced as compared with the case where the charging unit is always in contact with the charging unit cleaning roller 84, and the charging unit cleaning roller 84 is less likely to be deteriorated and the service life is extended. On the other hand, the gap holding portion cleaning roller 89 is configured to always contact the gap holding member 83. For this reason, the toner does not easily accumulate in the gap holding member 83 and it is easy to maintain the charging gap.
In the image forming apparatus according to this embodiment, the charging unit cleaning roller 84 and the gap holding unit cleaning roller 87 perform cleaning while rotating with respect to the charging member 82 and the gap holding unit 83. Therefore, dirt such as toner on the surfaces of the cleaning rollers 84 and 87 is hardly rubbed against the charging member 82 and the gap holding member 83 as compared with the fixed cleaning means, and it becomes easy to maintain good cleaning performance for a long time.
In the image forming apparatus according to the present embodiment, the integrated cleaning roller 90 forms the core member 94 of the gap holding unit cleaning member 93 in a hollow shape, and the core member 92 of the charging unit cleaning member 91 as the hollow core. It is arranged in the material 94. The gap holding cleaning member 93 is always in contact with the gap holding member 83 regardless of whether the charging unit cleaning member 91 is in contact with or separated from the charging member 82. Therefore, the integrated cleaning roller 90 can save space even when the charging unit cleaning member 91 and the gap holding unit cleaning member 93 are configured as separate members as the cleaning unit of the charging unit.
In the image forming apparatus according to the present embodiment, the integrated cleaning roller 90 is disposed above the charging roller 77. Therefore, regardless of the contact / separation state of the charging unit cleaning member 91, cleaning can be performed while the gap holding unit cleaning member 93 rotates along with the gap holding member 83 by the action of gravity.
Further, in the image forming apparatus according to the present embodiment, resin materials are used for the charging unit cleaning members 86 and 91 and the gap holding unit cleaning members 89 and 93. Since the resin material has a small hardness variation due to the environment and can be processed with high accuracy, a minute charging gap can be stably formed.
Further, according to the image forming apparatus according to the present embodiment, the photoconductor as the image carrier is composed of the organic photoconductor 40 and has a protective layer on the surface. Therefore, even when an AC bias is superimposed on the charging roller 77, the wear of the photoconductor 40 can be reduced at a low cost, and the life of the photoconductor 40 can be extended.
Further, according to the image forming apparatus according to the present embodiment, the brush roller 74 and the lubricant 78 which are lubricant supply means for supplying the photoconductor 40 with the lubricant are provided, so that the wear of the photoconductor 40 is reduced. In addition, the cleaning property can be improved.
Further, the process cartridge according to the present embodiment has a configuration in which the positional relationship between the photoconductor 40 and the charging device 70 is determined in the process cartridge. Therefore, even if the charging unit cleaning members 86 and 91 have a complicated structure such as a contact / separation mechanism, even if it is necessary to maintain a highly accurate charging gap, adjustment by a service engineer is necessary. Instead, the user can easily replace it.

1 is a schematic configuration diagram showing an internal configuration of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram showing an internal configuration of an image forming unit of the image forming apparatus. FIG. 5 is a schematic configuration diagram showing an internal configuration of an image forming unit according to another embodiment. FIG. 3 is a configuration diagram illustrating a configuration of a charging roller used in the image forming unit. Sectional drawing which shows the structure of a charging part cleaning roller and a gap holding part cleaning roller. The block diagram explaining the position of a charging part cleaning roller and a gap holding | maintenance part cleaning roller. FIG. 4 is a partially enlarged perspective view illustrating a configuration of a charging unit cleaning roller. FIG. 3 is a configuration diagram illustrating an example of a configuration for causing a charging unit cleaning roller to contact and separate. FIG. 3 is a configuration diagram illustrating a configuration of an integrated cleaning roller for a charging device. FIG. 4A is a configuration diagram illustrating a state of an integrated cleaning roller when a charging unit cleaning member is in contact with a photosensitive member. FIG. 6B is a configuration diagram illustrating a state of the integrated cleaning roller when the charging unit cleaning member is separated from the photoreceptor.

Explanation of symbols

40 Photoconductor 77 Charging Roller 82 Charging Member 83 Gap Holding Member 84 Charging Portion Cleaning Roller 86 Charging Portion Cleaning Member 87 Gap Holding Portion Cleaning Roller 89 Gap Holding Portion Cleaning Member 90 Integrated Cleaning Roller 91 Charging Portion Cleaning Member 92 Core Material 93 Gap Holding member cleaning member 94 Hollow core material

Claims (7)

In an image forming apparatus comprising at least an image carrier on which an electrostatic latent image is formed, and a charging device that uniformly charges the image carrier.
The charging device holds a gap between the charging member that charges the image carrier, a support that supports the charging member, and the image carrier that is in contact with the charging member. Therefore, a charging unit comprising gap holding members provided on both outer sides of the charging member in the width direction, a charging member cleaning unit for cleaning the charging member, and a gap holding member cleaning for cleaning the gap holding member Means and
The charging member cleaning means and the gap holding member cleaning means perform cleaning while rotating,
The gap holding member cleaning means includes the gap holding members on both outer sides of the charging member cleaning means in the width direction so that the rotation axis is substantially coaxial with the rotation axis of the charging member cleaning means. together are a pair arranged so as to correspond to each pair of respective supports cleaning means for the gap holding member is formed in a hollow shape, the supporting part is the gap holding member in the width direction both end portions of the charging member cleaning means located in the hollow support body of the use cleaning means and the charging member cleaning means is movable within the hollow of the support so as to be separable with respect to the charging member, the charging member regardless of and away state to said charging member use a cleaning means, said gap holding member cleaning means the gap An image forming apparatus characterized by being configured to abut constantly holding member. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the gap holding member cleaning means is disposed above the gap holding member . The image forming apparatus 請 Motomeko 1 or 2,
The image forming apparatus according to claim 1, wherein the charging means includes the support made of a conductive metal core, the charging member made of a conductive resin material, and the gap holding member made of an insulating resin material. The image forming apparatus according to claim 1, 2 or 3 .
An image forming apparatus, wherein a charging bias in which an AC bias is superimposed on a DC bias is applied to the charging unit. The image forming apparatus according to claim 1, 2, 3, or 4 .
The image forming apparatus according to claim 1, wherein the image carrier is made of an organic photoreceptor and has a protective layer on the surface. The image forming apparatus according to claim 1, 2, 3, 4 or 5 .
An image forming apparatus comprising: a lubricant supply means for supplying a lubricant to the image carrier. The process cartridge used in the image forming apparatus according to claim 1, 2, 4, 5, or 6 .
A process cartridge, wherein at least an image carrier and a charging device for uniformly charging the image carrier are configured to be easily and detachable integrally with the image forming apparatus main body.

Images