JP4978064B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer that employs an electrophotographic method, and in particular, a plurality of charging rolls that charge the surface of an image carrier such as a photoconductor and the surfaces of the plurality of charging rolls The present invention relates to an image forming apparatus including a cleaning member.

  Conventionally, as a charging device for an image forming apparatus such as a copying machine or a printer adopting an electrophotographic method, a device using a corona discharge phenomenon such as a scorotron charger has been widely used, but a charging device using a corona discharge phenomenon is used. In this case, the generation of ozone and nitrogen oxides that have a negative effect on the human body and the global environment is a problem. In contrast, the contact charging method in which a conductive charging roll or the like is in direct contact with the photosensitive member to charge the photosensitive member generates less ozone and nitrogen oxides and has good power efficiency. It has become mainstream.

In such a contact charging method, dirt such as toner and external additives is likely to adhere to the charging roll. Therefore, a flexible film-like member that can be flexibly deformed is brought into surface contact with the charging roll, and the charging roll rotates flexibly. A device that cleans the surface of a charging roll while sliding a member has been proposed. In addition, there has been proposed a cleaning apparatus that improves the cleaning performance by providing a driving unit that reciprocates the flexible member in the axial direction of the charging roll (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-288150

  Recently, an image forming apparatus that performs charging by bringing a plurality of charging rolls into contact with the surface of a photosensitive member has been adopted in order to cope with a higher speed. In such an image forming apparatus, when the above-described cleaning device is provided for cleaning a plurality of charging rolls, if the cleaning device is provided for each charging roll, the image forming apparatus becomes large, and There is a disadvantage that it becomes expensive.

  The present invention has been made in view of the above problems, and provides an image forming apparatus capable of cleaning the surfaces of a plurality of charging rolls, downsizing the entire apparatus, and being configured at low cost. Objective.

In order to solve the above-described problems, an image forming apparatus according to the first aspect of the present invention includes an image carrier that is rotationally driven, and rotates in contact with the surface of the image carrier. a plurality of charging roll for charging, the arranged plurality of such contact with the surface of the charging roller, have a, and one sheet-like cleaning member for cleaning the surface of said plurality of charging roll, the cleaning member It is characterized by being sandwiched between the plurality of charging rolls .

  According to the first aspect of the present invention, a plurality of charging rolls rotating in contact with the surface of the image carrier are provided, and the surface of the image carrier is charged by the plurality of charging rolls. Further, one sheet-like cleaning member is provided so as to come into contact with the surfaces of the plurality of charging rolls, and the surfaces of the plurality of charging rolls are cleaned by this cleaning member. Since one sheet-like cleaning member is brought into contact with a plurality of charging rolls in this way, the image forming apparatus can be downsized as compared with the case where a cleaning device is provided for each of the plurality of charging rolls, and It can be configured at low cost.

Further, since one sheet-like cleaning member is sandwiched between a plurality of charging rolls, the image forming apparatus can be reduced in size and can be configured at low cost. In addition, since a cleaning member is provided between the plurality of charging rolls, even when the output value is high or when the polarity is changed, the predetermined distance is set so that the plurality of charging rolls are not affected (interfered with each other). Need not be provided. For this reason, it is possible to reduce the distance between the charging rolls, and it is possible to further reduce the size of the image forming apparatus.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the friction coefficient of the contact surface of the cleaning member in contact with the charging roll on the upstream side in the rotation direction of the image carrier is μ1, and the rotation direction. When the friction coefficient of the contact surface of the cleaning member in contact with the charging roll on the downstream side is μ2, μ1 <μ2.

According to the second aspect of the present invention, the friction coefficient μ1 of the contact surface of the cleaning member in contact with the charging roll on the upstream side in the rotation direction of the image carrier and the cleaning member in contact with the charging roll on the downstream side in the rotation direction. The relationship with the friction coefficient μ2 of the contact surface is set to μ1 <μ2. As a result, when the plurality of charging rolls rotate in the moving direction of the image carrier, the force that brings the cleaning member closer to the image carrier becomes stronger than the force that separates the cleaning member from the image carrier, and the cleaning member is rotated by the rotation of the plurality of charging rolls. It is suppressed from turning up. For this reason, it becomes possible to clean stably.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the surface roughness of the contact surface of the cleaning member that is in contact with the charging roll on the upstream side in the rotation direction of the image carrier. Ra1 <Ra2 where Ra1 is the surface roughness of the contact surface of the cleaning member that contacts the charging roll on the downstream side in the rotational direction.

According to the third aspect of the present invention, the surface roughness of the contact surface of the cleaning member that contacts the charging roll on the upstream side in the rotation direction of the image carrier is in contact with Ra1 and the charging roll on the downstream side in the rotation direction. The relationship between the surface roughness of the contact surface of the cleaning member and Ra2 is set to Ra1 <Ra2. As a result, when the plurality of charging rolls rotate in the moving direction of the image carrier, the force that brings the cleaning member closer to the image carrier becomes stronger than the force that separates the cleaning member from the image carrier, and the cleaning member is rotated by the rotation of the plurality of charging rolls. It is suppressed from turning up. For this reason, it becomes possible to clean stably.

According to a fourth aspect of the present invention, there is provided an image carrier that is rotationally driven , a plurality of charging rolls that rotate in contact with the surface of the image carrier and charge the image carrier, and a plurality of the charging rolls. A cleaning member disposed in contact with the surface and cleaning the surfaces of the plurality of charging rolls, the cleaning member being stretched over the plurality of charging rolls, and the cleaning member Is configured such that one end is a fixed end and the other end is a free end, and pressure increasing means for increasing the contact pressure with the charging roll is provided on the free end side .

According to the fourth aspect of the present invention, the plurality of charging rolls rotating in contact with the surface of the image carrier are provided, and the surface of the image carrier is charged by the plurality of charging rolls. Further, one sheet-like cleaning member is provided so as to come into contact with the surfaces of the plurality of charging rolls, and the surfaces of the plurality of charging rolls are cleaned by this cleaning member. At that time, since one sheet-shaped cleaning member is spread over a plurality of charging rolls, the image forming apparatus can be downsized as compared with the case where a cleaning device is provided for each of the plurality of charging rolls. And it can be configured at low cost.

Further, the cleaning member has one end fixed and the other end free, and the free end side is provided with pressure increasing means for increasing the contact pressure with the charging roll. Insufficient contact pressure with is suppressed.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect , the pressure increasing means is a backing member attached to the back side of the free end of the cleaning member. .

According to the fifth aspect of the present invention, since the backing member is attached to the back side of the free end of the cleaning member, the free end side of the cleaning member and the charging roll are in stable contact, and the contact pressure is The shortage is suppressed.

  According to the present invention, an image forming apparatus can be downsized and inexpensively configured by bringing one sheet-like cleaning member into contact with the surfaces of a plurality of charging rolls.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an image forming apparatus 100 according to the first embodiment of the present invention.

  The image forming apparatus 100 performs image processing based on color image information sent from an image data input device such as a personal computer (not shown), and forms a color image on a recording sheet P by an electrophotographic method.

  The image forming apparatus 100 includes image forming units 10Y, 10M, 10C, and 10K that form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K). In the following, when it is necessary to distinguish YMCK, description will be made by adding any of Y, M, C, and K after the reference. When YMCK does not need to be distinguished, Y, M, C, K is omitted.

  The image forming units 10Y, 10M, 10C, and 10K are arranged so that the image forming units 10Y, 10M, 10C, and 10K move in the traveling direction of the endless intermediate transfer belt 30 that is stretched by the backup roll 34 and the plurality of stretch rolls 32. They are arranged in series in the order of 10K. Further, the intermediate transfer belt 30 is provided with primary transfer rolls 16Y, which are arranged to face the photosensitive drums 12Y, 12M, 12C, and 12K as image carriers of the image forming units 10Y, 10M, 10C, and 10K, respectively. It is inserted between 16M, 16C and 16K.

  Next, the configuration of each of the image forming units 10Y, 10M, 10C, and 10K and the image forming operation will be described using the image forming unit 10Y that forms a yellow toner image as a representative.

  A plurality of (two in this embodiment) charging rolls 23Y and 24Y are arranged in contact with the surface of the photosensitive drum 12Y, and the surface of the photosensitive drum 12Y is uniform by the plurality of charging rolls 23Y and 24Y. Is charged. Next, image exposure corresponding to the yellow image is performed by the exposure device 14Y, and an electrostatic latent image corresponding to the yellow image is formed on the surface of the photosensitive drum 12Y.

  The electrostatic latent image corresponding to the yellow image is developed by the toner carried on the developing roll 18Y to which the developing bias of the developing device 15Y is applied, and becomes a yellow toner image. The yellow toner image is primarily transferred onto the intermediate transfer belt 30 by the pressing force of the primary transfer roll 16Y and the electrostatic attraction force by the transfer bias applied to the primary transfer roll 16Y.

  In this primary transfer, the entire yellow toner image is not transferred to the intermediate transfer belt 30, and a part of the yellow toner image remains on the photosensitive drum 12Y as transfer residual yellow toner. Further, an external additive of toner is also attached to the surface of the photosensitive drum 12Y. After the primary transfer, the photosensitive drum 12Y passes through a position facing the cleaning device 20Y, and transfer residual toner and the like on the surface of the photosensitive drum 12Y are removed. Thereafter, the surface of the photosensitive drum 12Y is charged again by the charging rolls 23Y and 24Y for the next image forming cycle.

  As shown in FIG. 1, in the image forming apparatus 100, the image forming process similar to the above is performed at each image forming unit 10Y at a timing in consideration of the relative position difference between the image forming units 10Y, 10M, 10C, and 10K. , 10M, 10C, and 10K, and Y, M, C, and K color toner images are sequentially superimposed on the intermediate transfer belt 30 to form a multiple toner image.

  Then, electrostatic attraction of the secondary transfer roll 36 to which the transfer bias is applied to the recording paper P conveyed to the secondary transfer position where the intermediate transfer belt 30 and the secondary transfer roll 36 face each other at a predetermined timing. The multiple toner images are collectively transferred from the intermediate transfer belt 30 to the recording paper P by the force.

  The recording paper P to which the multiple toner images have been transferred is separated from the intermediate transfer belt 30, and then conveyed to the fixing device 31, where it is fixed to the recording paper P by heat and pressure, thereby forming a full color image.

  The transfer residual toner on the intermediate transfer belt 30 that has not been transferred to the recording paper P is collected by the intermediate transfer belt cleaner 33.

As shown in FIG. 2, a plurality of (two in this embodiment) charging rolls 23 and 24 are disposed above the photosensitive drum 12 so as to be in contact with the photosensitive drum 12. The charging roll 23 has a conductive layer 23B formed around a conductive shaft 23A. Similarly, the charging roll 24 has a charging layer 24B formed around a conductive shaft 24A. A predetermined high voltage is applied to the shafts 23A and 24A from a power source (not shown). By charging the photosensitive drum 12 using the two charging rolls 23 and 24, the image forming apparatus 100 can be increased in speed.
A motor (not shown) is connected to the support shaft 12A of the photosensitive drum 12, and the photosensitive drum 12 is driven to rotate clockwise (in the direction of arrow 2) in FIG. Further, following the rotation of the photosensitive drum 12, the charging roll 23 rotates in the direction of arrow 4 and the charging roll 24 rotates in the direction of arrow 6.

  Between the charging roll 23 and the charging roll 24, a cleaning member 50 including a sheet member 54 that contacts the surfaces of the charging rolls 23 and 24 is provided. In the cleaning member 50, a support body 52 is supported by a frame (not shown) above the charging rolls 23 and 24, and a sheet member 54 is fixed to the support body 52. In other words, by sandwiching the sheet member 54 between the charging roll 23 and the charging roll 24, the charging roll 23 and the charging roll 24 are cleaned by one cleaning member 50.

The volume resistance of the sheet member 54 is set to 10 ¹⁴ Ω · cm or more. That is, the sheet member 54 only needs to have an insulating property of 10 ¹⁴ Ω · cm or more. For the sheet member 54, for example, a resin sheet is used. For example, polyimide, polyethylene terephthalate (PET) or the like is used as the resin sheet.

  As shown in FIG. 3, the sheet member 54 has a friction coefficient μ1 of the contact surface S1 with the charging roll 23 on the upstream side in the rotation direction of the photosensitive drum 12 and a contact surface with the charging roll 24 on the downstream side in the rotation direction. When the friction coefficient of S2 is μ2, μ1 <μ2 is set. The friction coefficient μ1 is set to 0.3 to 0.4, for example, and the friction coefficient μ2 is set to 0.6 to 0.8, for example.

  Here, the friction coefficient of the sheet member 54 can be measured using a static friction coefficient meter (friction coefficient measuring instrument HEIDON-14, manufactured by HEIDON). The static friction coefficient meter shown in FIG. 9 includes a steel ball (diameter 3 mm) 303, a zero-point adjusting balance 304, a load cell 305, and a load (100 g) 306. Specifically, a subject 301 having a film thickness of 20 μm is produced using the sheet member 54, and this is set on a fixed base 302. The subject 301 is moved at a moving speed of 0.1 cm under a load of 100 g. The coefficient of friction was measured by moving in the horizontal direction at / sec.

  Next, details of the charging rolls 23 and 24 will be described. Since the charging rolls 23 and 24 are the same member, the charging roll 23 will be described as a representative.

  The charging roll 23 is obtained by sequentially forming a conductive elastic layer and a surface layer as a charging layer 23B on a conductive shaft 23A.

  The diameter of the charging roll 23 is φ7 mm to φ15 mm, more preferably φ8 mm to φ14 mm, and the thickness of the charging layer 23B is preferably 2 mm to 4 mm. If the diameter is 15 mm or more, the number of times of contact with the external additive per location on the peripheral surface is reduced, and the number of discharges is reduced. This is disadvantageous from the viewpoint of miniaturization, although it has excellent long-term stability against dirt and charging performance. . If the diameter is 7 mm or less, the image forming apparatus 100 can be downsized, which is advantageous. However, the number of times of contact with the external additive per peripheral surface increases and the number of discharges increases, which is disadvantageous for long-term stability. It becomes.

  Needless to say, the charging roll 23 is not limited to the following configuration as long as it has a predetermined charging performance.

  As the material of the shaft 23A, free-cutting steel, stainless steel, or the like is used, and the material and surface treatment method are appropriately selected according to the use such as slidability, and plating material is generally used for materials that are not conductive. It may be processed by an appropriate process and a conductive process may be performed.

  The conductive elastic layer constituting the charging layer 23B of the charging roll 23 is, for example, an elastic material such as rubber having elasticity, a conductive material such as carbon black or ionic conductive material for adjusting the resistance of the conductive elastic layer, or the like. Accordingly, 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. It is formed by coating the peripheral surface of the conductive shaft 23 </ b> A with a mixture in which materials usually added to rubber are added. As a conductive agent for the purpose of adjusting the resistance value, a material in which a material that conducts electricity using electrons and / or ions as a charge carrier, such as carbon black or an ionic conductive agent blended in a matrix material, is used. it can. 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, and stainless steel; tin oxide, indium oxide, titanium oxide Examples thereof include fine powders such as various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution; Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; perchlorates and chlorates of alkaline earth metals Can be mentioned.

  The surface layer constituting the charging layer 23B is formed for the purpose of preventing contamination by foreign matters such as toner, and as the material of the surface layer, any of resin, rubber, etc. may be used. It is not limited. Polyester, polyimide, copolymer nylon, silicone resin, acrylic resin, polyvinyl butyral, ethylene tetrafluoroethylene copolymer, melamine resin, fluoro rubber, epoxy resin, polycarbonate, polyvinyl alcohol, cellulose, polyvinylidene chloride, polyvinyl chloride, polyethylene And ethylene vinyl acetate copolymer. Of these, polyvinylidene fluoride, a tetrafluoroethylene copolymer, polyester, polyimide, and copolymer nylon are preferably used from the viewpoint of contamination of the external additive.

  The surface layer can 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 the purpose of adjusting the resistance value, it electrically conducts electrons and / or ions as charge carriers, such as carbon black, conductive metal oxide particles, or ionic conductive agent blended in the matrix material. What disperse | distributed material etc. can be used.

  In addition, a fluorine-based or silicone-based resin is used for the surface layer. In particular, it is preferably composed of a fluorine-modified acrylate polymer. Further, fine particles may be added to the surface layer. As a result, the surface layer becomes hydrophobic and acts to prevent the adhesion of foreign matter to the charging roll 23. In addition, insulating particles such as alumina and silica are added to give irregularities to the surface of the charging roll 23, thereby reducing the burden at the time of rubbing against the photosensitive drum 12, and the charging roll 23 and the photosensitive drum. It is also possible to improve the mutual wear resistance.

  Next, the operation of the image forming apparatus 100 will be described.

  Between the charging rolls 23 and 24, a sheet member 54 is disposed as a cleaning member 50 so as to contact the charging rolls 23 and 24. The sheet member 54 serves as a toner external additive on the surface of the charging rolls 23 and 24. The toner external additive moves when touched (the position of the toner external additive is changed). As a result, the toner external additive is prevented from sticking to the surfaces of the charging rolls 23 and 24, and the toner external additive easily returns to the surface of the photosensitive drum 12. For this reason, the contamination of the charging rolls 23 and 24 is suppressed, and the occurrence of image quality deterioration can be prevented.

In addition, since one sheet member 54 is disposed between the two charging rolls 23 and 24, the image forming apparatus 100 can be downsized and manufactured at low cost. Further, since the volume resistance of the sheet member 54 is set to 10 ¹⁴ Ω · cm or more, there is no influence between the charging rolls 23 and 24 even when the output value is high or when the polarity is changed. It is not necessary to provide a predetermined distance so as not to interfere with each other. That is, the distance between the charging rolls 23 and 24 can be reduced, and the image forming apparatus 100 can be further downsized.

  Further, as shown in FIG. 3, the sheet member 54 has a friction coefficient μ1 of the contact surface S1 with the charging roll 23 on the upstream side in the rotation direction of the photosensitive drum 12, and the charging roll 24 on the downstream side in the rotation direction. When the friction coefficient of the contact surface S2 is μ2, μ1 <μ2 is set. As a result, when the charging rolls 23 and 24 rotate, the force F2 that brings the sheet member 54 closer to the photosensitive drum 12 becomes stronger than the force F1 that moves the sheet member 54 away from the photosensitive drum 12, and the sheet member 54 Turning up by rotation is suppressed. For this reason, the charging rolls 23 and 24 can be stably cleaned, and the occurrence of defective cleaning is suppressed.

  Next, an image forming apparatus according to a second embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 4, in this image forming apparatus, the cleaning member 60 for cleaning the charging rolls 23 and 24 includes a sheet member 64 in which two sheets 64A and 64B having different surface roughnesses are bonded together. The sheet member 64 has Ra1 as the surface roughness of the sheet 64A, that is, the surface roughness of the contact surface S1 with the charging roll 23 on the upstream side in the rotation direction of the photosensitive drum 12, and the surface roughness of the sheet 64B, that is, the rotation direction. When the surface roughness of the contact surface S2 with the charging roll 24 on the downstream side is Ra2, Ra1 <Ra2. In the present embodiment, the two sheets 64A and 64B are used, but sheets having different roughness on the front and back sides may be used.

  Here, the surface roughness is a centerline average surface roughness and is a surface roughness defined in JIS B0601 (2001). The surface roughness Ra1 is set to 0.05 to 0.1 μm, for example, and the surface roughness Ra2 is set to 0.4 to 0.5 μm, for example.

  The centerline average surface roughness Ra can be measured by using a surface roughness measuring instrument or the like. In the present invention, however, a contact surface roughness measuring device (23 ° C, 55RH%) Surfcom 1400D, manufactured by Tokyo Seimitsu Co., Ltd.) was used. When measuring the surface of the sheet member 64, the measurement distance is set to 4.0 mm, and the tip of the contact needle is diamond (2 μmR, 90 ° cone). Was determined as the centerline average surface roughness Ra.

  In such an image forming apparatus, by providing the sheet member 64 between the charging rolls 23 and 24, the force F2 for bringing the sheet member 64 closer to the photosensitive drum 12 becomes stronger than the force F1 for separating the sheet member 64 from the photosensitive drum 12. For this reason, it is possible to suppress the sheet member 64 from being turned up by the rotation of the charging rolls 23 and 24, and to perform stable cleaning.

  Next, an image forming apparatus according to a third embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st and 2nd embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 5, in this image forming apparatus, the interval between the charging rolls 23 and 24 is set wide, and the cleaning member 70 is arranged at a position opposite to the photosensitive drum 12 with respect to the charging rolls 23 and 24. It is installed. The cleaning member 70 is provided with a support 72 on the upstream side in the rotation direction of the photosensitive drum 12. One end of a sheet member 74 is attached to the back side of the support 72, and the other end of the sheet member 74 is attached. The portion is a free end, and is disposed downstream of the photosensitive drum 12 in the rotation direction. The free end side of the sheet member 74 is stretched over the charging rolls 23 and 24 and is in contact with the surfaces of the charging rolls 23 and 24. The charging rolls 23 and 24 are arranged at a predetermined distance so as not to influence each other (so as not to interfere with each other) when the output value is high or when the polarity is changed.

  In such an image forming apparatus, since one sheet member 74 is brought into contact with the surfaces of the two charging rolls 23 and 24, the image forming apparatus can be compared with a case where a cleaning device is provided for each of the charging rolls 23 and 24. Can be reduced in size and can be manufactured at low cost.

  Next, an image forming apparatus according to a fourth embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st-3rd embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 6, in this image forming apparatus, the charging rolls 23 and 24 are arranged at a predetermined interval, and the cleaning member is located at a position opposite to the photosensitive drum 12 with respect to the charging rolls 23 and 24. 80 is arranged. In the cleaning member 80, one end of a sheet member 74 is attached to the back side of the support 72, and a backing sheet 82 is attached to the free end of the other end of the sheet member 74.

  In such an image forming apparatus, since the backing sheet 82 is adhered to the free end side of the sheet member 74, the contact pressure between the free end side of the sheet member 74 and the charging roll 24 in contact therewith is increased. Can do. For this reason, insufficient contact pressure between the free end side of the sheet member 74 and the charging roll 24 is suppressed, and the charging rolls 23 and 24 can be cleaned stably.

  In this embodiment, the backing sheet 82 is attached to the free end side of the sheet member 74, but the thickness of the free end side of the sheet member 74 may be increased. Further, the pressing member may be brought into contact with the charging roll 24 side from the back side of the sheet member 74.

  Next, an image forming apparatus according to a fifth embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st-4th embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 7, in this image forming apparatus, the charging rolls 23 and 24 are arranged at a predetermined interval, and the charging rolls 23 and 24 are charged at positions opposite to the photosensitive drum 12. A cover-like cleaning member 90 is disposed so as to cover the back side and the side portions of the rolls 23 and 24. The cleaning member 90 is composed of a single sheet member, and both ends thereof are bent to form cleaning units 91A and 91B. The cleaning unit 91A contacts the surface of the charging roll 23, and the cleaning unit 91B is in contact with the charging roll 24. In contact with the surface.

  Since such a cleaning member 90 is arranged so as to cover the back side and the side part of the charging rolls 23 and 24, a toner cloud is generated when the cleaning parts 91A and 91B come into contact with the charging rolls 23 and 24. Even in this case, the toner can be prevented from leaking out of the cleaning member 90. For this reason, it is possible to reduce the occurrence of image quality degradation due to the toner cloud.

  Next, an image forming apparatus according to a sixth embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st-5th embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 8, in this image forming apparatus, the charging rolls 23 and 24 are disposed close to each other, and the charging rolls 23 and 24 are disposed at positions opposite to the photosensitive drums 12 with respect to the charging rolls 23 and 24. A cover-like cleaning member 110 is disposed so as to cover the back side and the side portion of 24. The cleaning member 110 is disposed so as to cover the back side and the side portions of the charging rolls 23 and 24 by bending both ends of one sheet member 112. A sheet member 54 is attached to an upper portion of the sheet member 112, and the sheet member 54 is sandwiched between the charging rolls 23 and 24 and is in contact with the surfaces of the charging rolls 23 and 24. That is, this embodiment has a configuration in which the first embodiment (see FIG. 2) and the fifth embodiment (see FIG. 7) are combined.

  In such a cleaning member 110, by providing the sheet member 54 disposed between the charging rolls 23 and 24, even when the output value is high or when the polarity is changed, the charging members 23 and 24 are mutually connected. It is not necessary to provide a predetermined distance for preventing the influence, and the charging rolls 23 and 24 can be arranged close to each other. Therefore, the image forming apparatus can be further reduced in size, and the cover-like sheet member 112 can suppress contamination of the charging rolls 23 and 24 by the toner cloud.

  In addition, although this embodiment is the structure which combined 1st Embodiment and 5th Embodiment, 1st Embodiment (refer FIG. 2) and 3rd Embodiment (refer FIG. 5) or 4th Embodiment besides this. You may combine a form (refer FIG. 6). By providing the sheet member 54 between the charging rolls 23 and 24, the charging rolls 23 and 24 can be arranged close to each other. For this reason, the image forming apparatus can be further downsized.

  The image forming apparatus 100 shown in FIG. 1 has a configuration in which image forming units 10Y, 10M, 10C, and 10K of yellow, magenta, cyan, and black are arranged in parallel along the moving direction of the intermediate transfer belt 30. The configuration is not limited to this. For example, the present invention can be applied to a cleaning member that cleans a plurality of charging rolls even in a configuration in which a toner image is formed on a photosensitive drum repeatedly by using a rotary developing device for four cycles. .

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a configuration diagram showing a plurality of charging rolls and cleaning members used in the image forming apparatus shown in FIG. 1. FIG. 2 is a configuration diagram showing a plurality of charging rolls used in the image forming apparatus shown in FIG. 1 and the vicinity of the cleaning member. FIG. 6 is a configuration diagram showing a plurality of charging rolls used in an image forming apparatus according to a second embodiment of the present invention and the vicinity of the cleaning member. It is a block diagram which shows the some charging roll used for the image forming apparatus which concerns on 3rd Embodiment of this invention, and its cleaning member vicinity. FIG. 10 is a configuration diagram showing a plurality of charging rolls used in an image forming apparatus according to a fourth embodiment of the present invention and the vicinity of a cleaning member thereof. It is a block diagram which shows the some charging roll used for the image forming apparatus which concerns on 5th Embodiment of this invention, and its cleaning member vicinity. It is a block diagram which shows the some charging roll used for the image forming apparatus which concerns on 6th Embodiment of this invention, and its cleaning member vicinity. It is a block diagram which shows the static friction coefficient meter which measures the friction coefficient of the sheet | seat member which comprises a cleaning member.

Explanation of symbols

10Y, 10M, 10C, 10K Image forming units 12Y, 12M, 12C, 12K Photosensitive drum 23 Charging roll 23A Shaft 23B Charging layer 24 Charging roll 24A Shaft 24B Charging layer 50 Cleaning member 52 Support 54 Sheet member 60 Cleaning member 64 Sheet Member 64A Sheet 64B Sheet 70 Cleaning member 72 Support body 74 Sheet member 80 Cleaning member 82 Backing sheet (backing member)
90 Cleaning member 91A Cleaning unit 91B Cleaning unit 100 Image forming apparatus 110 Cleaning member 112 Sheet member

Claims (5)

A rotationally driven image carrier;
A plurality of charging rolls rotating in contact with the surface of the image carrier and charging the image carrier;
A sheet-like cleaning member disposed so as to be in contact with the surfaces of the plurality of charging rolls and cleaning the surfaces of the plurality of charging rolls;
I have a,
An image forming apparatus, wherein the cleaning member is sandwiched between the plurality of charging rolls . The friction coefficient of the contact surface of the cleaning member in contact with the charging roll on the upstream side in the rotation direction of the image carrier is μ1, and the friction coefficient of the contact surface of the cleaning member in contact with the charging roll on the downstream side in the rotation direction is μ2. When
μ1 <μ2
The image forming apparatus according to claim 1, characterized in that a. Surface roughness of the contact surface of the cleaning member in contact with the charging roll with a surface roughness of the contact surface of the cleaning member in contact with the charging roller in the rotational direction upstream of the image bearing member Ra1, downstream in the rotation direction Is Ra2 ,
Ra1 <Ra2
The image forming apparatus according to claim 1 or claim 2, characterized in that a. A rotationally driven image carrier;
A plurality of charging rolls rotating in contact with the surface of the image carrier and charging the image carrier;
A sheet-like cleaning member disposed so as to be in contact with the surfaces of the plurality of charging rolls and cleaning the surfaces of the plurality of charging rolls;
Have
The cleaning member is stretched over the plurality of charging rolls,
The cleaning member is configured to have one end as a fixed end and the other end as a free end,
An image forming apparatus comprising pressure increasing means for increasing a contact pressure with the charging roll on the free end side . The image forming apparatus according to claim 4 , wherein the pressure increasing unit is a backing member attached to a back side of the free end of the cleaning member .

Images