JP2007108794A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus where the transfer rate of toner on an intermediate transfer member is improved to restrain the occurrence of an image with transfer central blanking, and the positional deviation of the intermediate transfer member is prevented. <P>SOLUTION: The image forming apparatus 20 includes a plurality of image forming means having a photoreceptor 40 on which an electrostatic latent image is carried, and equipped with a primary transfer means 62 transferring a toner image on the photoreceptor 40 to the intermediate transfer member 10 and a secondary transfer means 22 transferring the toner image transferred to the intermediate transfer member 10 to transfer material P. The primary transfer means 62 has: the intermediate transfer member 10 having at least the layer of an elastic body 12; a cleaning means 17 cleaning the intermediate transfer member 10; and a supply means 50 supplying lubricant 50b to the intermediate transfer member 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an image forming apparatus, a facsimile machine, and a printer. Specifically, the image forming apparatus includes a photoconductor and an intermediate transfer body, and further forms an image using an intermediate transfer body having an elastic layer. It relates to the device.

  Conventionally, a latent image formed on a latent image carrier (hereinafter referred to as “photosensitive member”) is visualized with toner, and an image on this photosensitive member (hereinafter referred to as “toner image”) is intermediate. In the color image forming apparatus, a color image is formed by superimposing the toner images of the respective colors on the intermediate transfer body, and the color image on the intermediate transfer body is secondarily formed on the transfer material. There are known ones that transfer and fix and obtain a color image on a transfer material.

  By the way, in an image forming apparatus using an intermediate transfer method, a plurality of photoconductors are arranged in parallel, and a developing device is provided for each photoconductor, thereby forming a single color toner image on each photoconductor, and a single color toner. An image employing a so-called tandem system is known in which an image is sequentially primary transferred onto an intermediate transfer member as an intermediate transfer member and superimposed to obtain a color image on the intermediate transfer member. With the tandem system, the intermediate transfer body is made into a belt shape, so that the degree of freedom in design layout is higher than when it is made into a drum shape, and at least the volume of the drum size is reduced. Therefore, a belt is often used for the intermediate transfer member in order to reduce the size and cost of the image forming apparatus. Such an image forming apparatus uses an intermediate transfer member to transfer color due to color misregistration at the time of image superposition or differences in the characteristics of the transfer material, compared to the case where an image is directly transferred from a photosensitive member to a transfer material. Since it has the advantage that problems such as defects can be improved, it is effective particularly when forming color images and is widely used.

  On the other hand, as a secondary transfer method for secondary transfer from the intermediate transfer member to a transfer material such as transfer paper, a bias roller or the like is disposed below the photosensitive member. However, in the case of a configuration in which the intermediate transfer member is pressed by a bias roller or the like, strong pressurization is locally applied at the secondary transfer portion, so that there may occur a transfer omission where the central portion of characters or the like is not transferred. Furthermore, in particular, for color images, transfer materials that are various papers such as thick paper, thin paper, and Japanese paper are often used. Therefore, conventionally, intermediate transfer members such as fluororesin, polycarbonate resin, and polyimide resin have high hardness and do not deform according to the toner layer. . In particular, there is a demand for forming full-color images on various types of paper, such as Japanese paper or paper with intentional unevenness, and as a result, paper with poor smoothness is likely to generate a gap between the toner during transfer. Since transfer unevenness is likely to occur in the halftone part and the solid part, increasing the transfer pressure to improve the adhesion will increase the aggregation of the toner layer, which will promote the transfer of characters in the middle, The amount of toner remaining on the intermediate transfer member may also increase.

  Further, in the cleaning device for the intermediate transfer member, when the cleaning blade of the cleaning device is separated from the intermediate transfer member when the image forming apparatus is stopped, the load of the cleaning blade that has been elastically deformed during the cleaning operation is eliminated. When returning to the state, the position of contact with the intermediate transfer member is slightly shifted, and the toner cleaned by the cleaning blade remains linearly on the intermediate transfer member. In this case, linear stains were generated.

  Accordingly, the present invention has been made in view of the above-described problems, and the problem thereof is an image in which occurrence of character transfer omission is suppressed without imposing excessive stress on the toner on the intermediate transfer member during transfer. Is to provide an image forming apparatus capable of obtaining the above. Furthermore, the problem is to provide an image forming apparatus in which linear stains do not occur on the image even if there is a positional shift caused by the separation of the cleaning blade when the intermediate transfer member stops.

  In order to achieve the above object, the invention described in claim 1 is directed to a latent image carrier that carries an electrostatic latent image, a charging means that carries the surface of the latent image carrier, and a toner image obtained by developing the latent image. A plurality of image forming means having a developing means for forming a toner image, a primary transfer means for transferring the toner image on the latent image carrier to the intermediate transfer member, and a toner image transferred to the intermediate transfer member to the transfer material In the image forming apparatus including the secondary transfer unit, the primary transfer unit includes an intermediate transfer member having at least an elastic layer, a cleaning unit that cleans the intermediate transfer member, and a supply unit that supplies a lubricant to the intermediate transfer member. An image forming apparatus. According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the intermediate transfer member is an image forming apparatus in which an elastic layer has a thickness of 0.07 to 0.3 mm. A third aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein the supply means is a rotating brush. According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the supply means includes an adjusting means for adjusting a contact state between the brush and the lubricant.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, the image forming apparatus is provided with a scattering prevention member for preventing the lubricant supplied to the downstream side from scattering to the supply unit. The image forming apparatus. A sixth aspect of the present invention is the image forming apparatus according to the fifth aspect, wherein the scattering prevention member also serves as a cleaning blade provided in a cleaning unit. A seventh aspect of the present invention is the image forming apparatus according to any one of the first to sixth aspects, wherein the charging means is a charging roller that charges the latent image carrier with a rotating roller. . According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the supply means for supplying the lubricant is substantially at the same time as the separation from the intermediate transfer body, and the charging means is separated from the image carrier. Device.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the supply means for supplying a lubricant separates the image forming apparatus from the intermediate transfer member, and the cleaning is further performed. An image forming apparatus for separating blades. According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the image forming apparatus includes a separating unit that separates a supply unit that supplies a lubricant and a cleaning blade at the same time. . The invention described in claim 11 is the image forming apparatus according to claim 10, wherein the separating means is a cam. According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, when the image forming operation of the image forming apparatus is stopped, the cleaning blade is separated from the intermediate transfer member, and the intermediate transfer member. Is an image forming apparatus that is rotated reversely and stopped.

  As described above, according to the image forming apparatus of the present invention, it is possible to provide an image forming apparatus capable of improving the transfer rate of the toner on the intermediate transfer member and suppressing the occurrence of an image such as a transfer omission. . Further, it is possible to provide an image forming apparatus that can prevent the positional displacement of the intermediate transfer member and prevent the occurrence of linear stains on the image and obtain a high-quality image.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described based on a tandem color image forming apparatus. FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus includes a scanner unit 300, an image forming unit 100, a paper feeding unit 200, and an automatic document feeder (ADF) 400 mounted on the scanner unit 300 from above. The image forming apparatus 20 also includes a control unit (not shown) that controls the operation of each device.

  In order to obtain a color image with this image forming apparatus, a document is set on the document table 30 of the document transport unit 400, or the document transport unit 400 is opened and a document is set on the contact glass 32 of the scanner unit 300, The document feeder 400 is closed and the document is pressed. When a start switch (not shown) is pressed, the original is conveyed onto the contact glass 32 when the original is set on the original conveying unit 400, and immediately after the original is set on the other contact glass 32, the scanner The unit 300 is 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. It puts in the reading sensor 36 and reads image information.

  When the image information is received from the scanner unit, the above-described laser writing or development process is performed to form toner images on the photosensitive drums 40Bk, 40Y, 40M, and 40C, and the size corresponding to the image information. In order to feed the transfer material P, one of the four feed rollers is operated. Along with this, one of the support rollers 14, 15, and 16 is rotationally driven by a drive motor (not shown), the other two support rollers are driven to rotate, and the intermediate transfer member 10 is rotated and conveyed.

  FIG. 2 is a schematic diagram illustrating a configuration around an intermediate transfer member in an image forming apparatus according to an embodiment of the present invention. At the same time, the photosensitive drums 40Bk, 40Y, 40M, and 40C are rotated by the individual image forming units 18 to form black, yellow, magenta, and cyan single-color images on the photosensitive drums 40Bk, 40Y, 40M, and 40C, respectively. Form. Then, along with the conveyance of the intermediate transfer member 10, the single color images are sequentially transferred to form a composite color image on the intermediate transfer member 10. On the other hand, one of the paper feed rollers 42 of the paper feed unit 200 is selectively rotated, the transfer material P is fed out from one of the paper feed cassettes 44, separated one by one by the separation port roller 45, and fed to the paper feed path 46. The transfer material P is guided to the paper feed path 48 in the image forming unit 100 by the conveyance roller 47, and the transfer material P is abutted against the registration roller 49 and stopped. Alternatively, the transfer roller P is rotated to feed the transfer material P 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 time with the composite color image on the intermediate transfer body 10, and the transfer paper P is placed in the secondary transfer nip portion where the intermediate transfer body 10 and the secondary transfer roller 23 are in contact with each other. The color image is secondarily transferred by the influence of the electric field for transfer and contact pressure formed in the nip, and the color image is recorded on the transfer paper P. After the image transfer, the transfer paper P is fed to the fixing device 25 by the conveying belt 24 of the secondary transfer means, and the toner image is fixed by the fixing device 25 by applying pressure and heat by the pressure porter 27. The paper is discharged onto the paper discharge tray 57 by the discharge port roller 56.

  A secondary transfer unit 22 is provided on the opposite side of the intermediate transfer body 10 from the tandem image forming apparatus 20. This secondary transfer means 22 is arranged by stretching a secondary transfer body 24 between two rollers 23 and pressing it against the third support roller 16 via the intermediate transfer body 10, and a secondary transfer nip portion. And the color toner image on the intermediate transfer member 10 is secondarily transferred onto the transfer paper. After the secondary transfer, the intermediate transfer body 10 is cleaned by an intermediate transfer body cleaning means 17 (hereinafter, simply referred to as “cleaning means”) to remove residual toner remaining on the intermediate transfer body 10 after image transfer, and thereby tandem. In preparation for another image formation by the image forming apparatus 20.

  The cleaning means 17 is provided with a cleaning blade 17a as a cleaning member. The cleaning blade 17a uses elastic rubber. As the elastic rubber, urethane resin and isoprene rubber are preferable. The contact method may be either a counter method or a trail method. The abutting position is preferably a position where the supporting roller is stretched. This is to prevent the intermediate transfer body 10 from being deformed due to contact with pressure. In this way, the toner on the intermediate transfer member 10 is removed by the cleaning blade 17a, but the scraped toner is collected in a tank (not shown).

  FIG. 3 is a longitudinal sectional view of an example of an intermediate transfer member used in the image forming apparatus of the present invention. The intermediate transfer member 10 used in the image forming apparatus 20 of the present invention includes at least a base layer 11, an elastic layer 12, and a surface coat layer 13. The intermediate transfer body 10 is provided with an elastic layer having low hardness so that it can be deformed with respect to the toner layer and the paper having poor smoothness at the transfer nip portion. Since the surface of the intermediate transfer body 10 can be deformed following local unevenness, it is possible to obtain a good adhesion without excessively increasing the transfer pressure with respect to the toner layer, and to prevent the transfer of characters from being lost. In addition, it is possible to obtain a transfer image excellent in uniformity without causing unevenness of transfer in a solid portion or the like even on paper having poor smoothness. Examples of the material used for the elastic layer 12 include elastic members such as elastic material rubber and elastomer, and specifically, butyl rubber, fluorine-based rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene rubber, natural rubber. , Isoprene rubber, styrene-butadiene rubber, butadiene rubber, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, polysulfide rubber, polynorbornene rubber, thermoplastic elastomer (for example, polystyrene, polyolefin, One kind or two or more kinds selected from the group consisting of polyvinyl chloride, polyurethane, polyamide, polyurea, polyester, and fluororesin) can be used. However, it is not limited to the said material.

  The thickness of the elastic layer 12 is preferably in the range of 0.07 to 0.3 mm, although it depends on the hardness and the layer configuration. If it is as thick as 0.3 mm or more, it will be bent by the pressing force of the cleaning blade, or the cleaning blade will be pushed into the intermediate transfer member 10 to prevent the intermediate transfer member 10 from moving smoothly. On the other hand, if it is as thin as 0.07 mm or less, the pressure on the toner on the intermediate transfer body 10 is increased at the secondary transfer nip portion, the transfer is liable to occur, and the toner transfer rate is lowered.

  The hardness of the elastic layer 12 is preferably 10 ≦ HS ≦ 65 (JIS-A). Although the optimum hardness differs depending on the layer thickness of the intermediate transfer body 10, if the hardness is lower than 10 ° JIS-A, transfer deficiency tends to occur. On the other hand, when the hardness is higher than 65 ° JIS-A, it is difficult to stretch the roller, and since it is stretched by long-term stretching, there is no durability and early replacement is necessary.

  In addition, the base layer 11 of the intermediate transfer member 10 is made of a resin with little elongation. Specifically, the material used for the base layer 11 includes polycarbonate, fluorine resin (ETFE, PVDF, etc.), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer. Polymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate) Copolymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer) , Styrene-phenyl methacrylate copolymer, etc.), Styrene resins (monopolymer or copolymer containing styrene or a styrene-substituted product), methyl methacrylate resin, methacrylic acid such as tylene-α-chloroacrylic acid methyl copolymer and styrene-acrylonitrile-acrylic acid ester copolymer Acid butyl resin, ethyl acrylate resin, butyl acrylate resin, modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, chloride Pinyl-vinyl acetate copolymer, rosin modified maleic resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silico Down resin, ketone resin, ethylene - can be used ethyl acrylate copolymer, xylene resin and polyvinyl butyral resin, polyamide resin, one kind or two kinds or more selected from the group consisting of modified polyphenylene oxide resin. However, it is not limited to the said material.

  Further, a method of forming a core layer made of a material that prevents elongation, such as canvas, on a rubber material having a large elongation on the base layer 11 and forming the elastic layer 12 thereon can be used. As a material for preventing elongation used for the core layer at this time, for example, natural fibers such as cotton and silk, polyester fibers, nylon fibers, acrylic fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, One kind selected from the group consisting of synthetic fibers such as polyvinylidene chloride fibers, polyurethane fibers, polyacetal fibers, polyfluoroethylene fibers and phenol fibers, inorganic fibers such as carbon fibers and glass fibers, and metal fibers such as iron fibers and copper fibers Alternatively, two or more types can be used and those in the form of yarn or woven fabric can be used. Of course, the material is not limited to the above. The above-described yarn may be twisted in any manner, such as one or a plurality of filaments twisted, one-twisted yarn, various twisted yarns, double yarn, or the like. Further, for example, fibers of a material selected from the above material group may be blended. Of course, the yarn can be used after being subjected to an appropriate conductive treatment. On the other hand, the woven fabric can be any woven fabric, such as knitted fabric, and of course, a woven fabric that has been woven can be used and can be subjected to a conductive treatment.

  Further, the coating layer 13 on the surface of the intermediate transfer body 10 is for coating the surface of the elastic layer 12 with, for example, a fluororesin or the like, and is composed of a layer having good smoothness. The material used for the coating layer is not particularly limited, but generally, a material that increases the secondary transferability by reducing the amount of toner adhering to the surface of the intermediate transfer member 10 is used. For example, one or more types of polyurethane, polyester, epoxy resin, etc., or materials that reduce surface energy and increase lubricity, such as fluorine fats, fluorine compounds, fluorocarbons, titanium oxide, silicon carbide, etc. Can be used by dispersing one type or two or more types or changing the particle size as required. Further, it is also possible to use a material such as a fluorine-based rubber material in which a heat treatment is performed to form a fluorine layer on the surface and the surface energy is reduced.

  If necessary, the base layer 11, the elastic layer 12 or the coat layer 13 is, for example, carbon black, graphite, metal powder such as aluminum or nickel, tin oxide, titanium oxide, antimony oxide, Conductive metal oxides such as indium oxide, potassium titanate, antimony oxide-tin oxide composite oxide (ATO), and indium oxide-tin oxide composite oxide (ITO) can be used. Here, the conductive metal oxide may be coated with insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate. However, it is not limited to the said material.

  Further, in the image forming apparatus of the present invention, a supply unit 50 for supplying the lubricant 50b to the intermediate transfer member 10 is provided. FIG. 4 is an enlarged schematic configuration diagram illustrating another example of the supply unit 50 for supplying the lubricant 50b used in the image forming apparatus of the present invention. The supply means 50 is in contact with the intermediate transfer member 10 and supplies a solid lubricant 50b to the intermediate transfer member 10, and a spring 50c that supports the lubricant 50b so as to contact the brush 50a with a predetermined pressure. The cover 50e supports the spring 50c. When the brush 50a rotates, the lubricant 50b pressed by the spring 50c is scraped off, and the lubricant 50b adheres to the surface of the brush 50a. The lubricant 50b adhering to the brush 50a is supplied to the surface of the intermediate transfer member 10 when the brush 50a contacts the intermediate transfer member 10. Furthermore, a means for adjusting the contact state between the brush 50a and the lubricant 50b can be provided. By applying the spring 50c pressing the lubricant 50b, the lubricant 50b is brought into contact with the brush 50a with a constant stress. Further, the separation unit 50d can be applied to the cover 50e that houses the spring 50c, and the separation unit 50d can be adjusted by moving the separation unit 50d according to the number of image formations or the driving time of the image forming apparatus 20, for example.

  Further, in the image forming apparatus 20 of the present invention, the anti-scattering member 17a is provided on the downstream side of the supply means 50 that supplies the lubricant 50b. Lubricant 50b supply means 50 scrapes the lubricant 50b with a rotating brush 50a into small particles and shares them with the intermediate transfer body 10, but the lubricant does not adhere to the intermediate transfer body 10 due to the small particles. The agent 50b is scattered. Therefore, as shown in FIG. 4, the scattering prevention member 17 a for the lubricant 50 b is provided on the downstream side of the supply unit 50, so that it can be prevented from diffusing inside the image forming apparatus 20.

  Further, it is preferable that the scattering prevention member 17 a is also used by using the cleaning blade 17 a of the cleaning device 17. The number of parts can be reduced, the design can be facilitated, and the cost can be reduced. Further, the lubricant 50b that has been dammed by colliding with the cleaning blade 17a, which is an anti-scattering member, and adhered to the intermediate transfer member 10, is cleaved with, for example, zinc stearate by the force with which the cleaning blade 17a etc. Then, a thin film is formed on the intermediate transfer body 10, and, for example, PTFE particles are firmly attached to the coat layer 13 on the surface of the intermediate transfer body 10 having the elastic layer 11, and the surface of the intermediate transfer body 10 is uneven. By providing both, it is possible to reduce the adhesion between the toner and the intermediate transfer member 10 and to suppress the occurrence of image defects such as transfer loss and to increase the transfer rate.

  The lubricant 50b to be supplied is not particularly limited, and materials having various lubricating actions can be used. For example, various fluorine-containing resins such as PTFE and PVDF, silicone resins, polyolefin resins, paraffin wax, fatty acid metal salts such as stearic acid, lauric acid, and palmitic acid, and lubricating solids such as graphite and molybdenum disulfide are used. Can do. Among these, the fatty acid metal salt is preferably a stearic acid metal salt, and the resin fine powder is preferably a fluororesin.

  The stearic acid metal salt is a compound such as stearic acid and zinc, aluminum, barium, magnesium, iron or the like. Many of these compounds are cleaved and cleave when applied with pressure to form a thin film. For example, a thin film is formed on the surface of the applied intermediate transfer body 10, and the surface of the intermediate transfer body 10 and the toner Decrease the adhesive strength. Of these, zinc stearate which is particularly soft and has high cleavage properties is particularly preferred. In addition, fluororesins can be used as lubricants because of low surface friction coefficient due to low intermolecular cohesive energy, structurally smooth molecular chain surfaces, and relaxation of frictional resistance by orientation. . A fluororesin is a synthetic polymer containing fluorine atoms in the molecule, and is usually polytetrafluoroethylene (tetrafluoroethylene resin: abbreviated PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (tetrafluoroethylene). Ethylene / perfluoroalkoxyethylene copolymer resin: abbreviated PFA), tetrafluoroethylene-hexafluoropropylene copolymer (tetrafluoroethylene / hexafluoropropylene copolymer resin: abbreviated FEP), tetrafluoroethylene-ethylene copolymer Copolymer (tetrafluoroethylene / ethylene copolymer resin: E / TFE), polyvinylidene fluoride (vinylidene fluoride resin: PVDF), polychlorotrifluoroethylene (ethylene trifluoride chloroethylene resin: abbreviation PCTFE), chlorotrifluoro Ethylene-ethylene Polymer (ethylene trifluoride chloride / ethylene copolymer resin: abbreviation E / CTFE), tetrafluoroethylene-perfluorodimethyldioxole copolymer resin (abbreviation TFE / PDD), polyvinyl fluoride (vinyl fluoride resin: Nine types of PVF). As a result, the toner image transferred to the intermediate transfer body 10 has a low adhesive force between the intermediate transfer body 10 and the toner image because the lubricant 50b is applied to the surface of the intermediate transfer body 10 in advance. Occurrence of image defects such as transfer omission can be suppressed.

The charging unit 19 used in the image forming apparatus 20 of the present invention is preferably a roller system. A voltage is applied to the charging roller 19 serving as a charging unit from a power source (not shown). The voltage is constant current control for supplying a constant current to the charging roller 19. The charging member has an ion conductive rubber layer formed on a stainless steel core. The resistance of the rubber layer is about 10 ⁴ Ω to 10 ⁸ Ω as a resistance value. The rubber hardness of the roller is 40 ° or more, preferably 70 ° or more, according to JIS-A. Moreover, what has electroconductivity other than rubber | gum may be sufficient and an elastomer, resin, etc. are mention | raise | lifted. These also desirably have a hardness corresponding to the rubber hardness. When the resin is used, since the material does not have elasticity, it is easy to maintain the gap accurately, that is, there is an advantage that a difference in gap is not easily generated between the photosensitive member and the photosensitive member in the axial direction. On the surface layer, a surface layer having a resistance value of about 10 ¹⁰ Ω is formed. This is to prevent a phenomenon in which current flows in a concentrated manner when there is a low resistance portion such as a pinhole in the photoconductor 40. By providing this surface layer, current concentration in the pinhole is reduced. It is preventing. The resistance value of the surface layer may be 10 ¹⁰ Ω or more.

  Further, in the image forming apparatus 20 of the present invention, the rotating charging roller 19 is separated from the intermediate transfer body 10 at the same time as the supply means 50 for supplying the lubricant 50b is separated from the intermediate transfer body 10 (not shown). 1 separation means. Almost simultaneously with the release of the contact of the brush 50a supplying the lubricant 50b with the intermediate transfer member 10, the charging roller 19 has a charging roller separating means for separating the charging roller 19 from the photosensitive member 40. 19 to the lubricant 50b is prevented. As the charging roller separating means, a charging device including a charging roller and a bearing can be separated by lifting with a solenoid, a cam or the like. The charging roller separation means is not particularly limited, but a solenoid is preferable. In this case, it is preferable to separate the charging roller 19 including a bearing that supports the shaft, and the power source and the charging roller 19 are preferably connected by a brush contact.

  The lubricant 50b adhering to the intermediate transfer member 10 is in direct contact with the photosensitive member 40 at the primary transfer nip portion. At this time, the lubricant 50b of the intermediate transfer member 10 moves to the photosensitive member 40 due to a printing stress due to a difference in pressing force or rotation speed of the transfer roller 62 or the like. The amount to be transferred is small, and the photosensitive member 40 is provided with the photosensitive member cleaning device 63 and therefore does not accumulate. However, the lubricant moves to the charging roller 19 that is in contact with or close to the photoreceptor 40 by the same mechanism. As described above, since the charging roller 19 is not so large as to provide a cleaning member such as a cleaning blade, it is difficult to provide a cleaning device, and the charging roller 19 has a lubricant applied nonuniformly on the surface of the charging roller. Then, the charged potential on the surface of the photoconductor 40 becomes uneven charging, and when an image is formed as it is, an image having unevenness in the halftone portion of the transfer material is obtained.

  In particular, in the tandem type color image forming apparatus, since the intermediate transfer body 10 sequentially contacts the photoconductor 40, the amount of lubricant transferred to the photoconductor 40 that contacts first is large, but the photoconductor that contacts last. The amount of transition to 40 is reduced. For this reason, the amount of transfer to the charging roller 19 that is in contact with or close to each other is different, the occurrence of unevenness of the image in the halftone portion is different for each color image forming unit, and the reproducibility of the intermediate color of the color image becomes impossible. Therefore, by separating the charging roller 19, it is possible to prevent the lubricant 50b from being transferred to the charging roller 19, and to obtain an image having no unevenness and good halftone reproducibility.

  Further, the image forming apparatus 20 of the present invention includes a second separating unit 50d that separates the cleaning blade 17a from the intermediate transfer body 10. Separation can be achieved by lifting with a solenoid, a cam or the like, and the means 50d for separation is not particularly limited. If the cleaning blade 17a is kept in contact, the elastic cleaning blade 17a is deformed while being stressed. Since the cleaning blade 17a is deformed and does not easily return to the original state after a long contact, the contact pressure may be reduced and a cleaning failure may occur. In addition, since the intermediate transfer member 10 has the elastic layer 12, when the operation of the image forming apparatus 20 is stopped, the elastic layer 12 of the intermediate transfer member 10 remains in the state where the cleaning blade 17 a applies pressure to the intermediate transfer member 10. Since it is difficult to return to its original state due to deformation, it becomes indented, the transfer failure of the toner image from the photoconductor 40, and the cleaning blade 17a is caught during continuous image formation, giving an impact to the intermediate transfer body 10, and its rotation The speed may change suddenly. For this reason, the cleaning blade 17a may be turned up or shattered. For this reason, the cleaning blade 17a is separated from the intermediate transfer member 10 by the separating means 50d, and the cleaning blade 17a and the like are suppressed to prevent the occurrence of defective cleaning. At this time, it is preferable to separate the cleaning blade 17a almost simultaneously with the separation of the brush 50a for supplying the lubricant 50b from the intermediate transfer member 10. The cleaning blade 17a is separated first to prevent the lubricant 50b from being scattered and contaminated in the image forming apparatus 20.

  The image forming apparatus 20 of the present invention reverses the intermediate transfer body 10 when the contact of the cleaning blade 17a with the intermediate transfer body 10 is released and separated when the image forming operation of the image forming apparatus 20 is stopped. Rotate to stop. FIG. 5 is a diagram for explaining the prevention of image smearing by rotating the intermediate transfer member in the reverse direction in the image forming apparatus of the present invention. This is because when the cleaning blade 17a of the cleaning unit 17 is separated from the intermediate transfer body 10 when the image forming apparatus 20 is stopped, the cleaning blade 17a that has been elastically deformed during the cleaning operation is no longer loaded, so that the original state is obtained. Returning, when the next image forming operation starts again, the contact position before the separation is slightly displaced from the contact position before the separation, and the position where the contact with the intermediate transfer body slightly shifts. 10, the toner cleaned by the cleaning blade 17a remains in a linear shape, and a linear stain is generated on an image to be formed next. FIG. 5A is a view for explaining a situation in which linear residual toner is generated by an elastic cleaning blade. Therefore, as shown in FIG. 5B, in the image forming apparatus 20, when the intermediate transfer member 10 is stopped and the cleaning blade 17a is separated from the intermediate transfer member 10, the intermediate transfer member 10 is slightly rotated in the reverse direction. Thus, the linear toner remaining on the intermediate transfer body 10 is returned to the upstream side in the circumferential direction of the cleaning blade 17a, thereby preventing the occurrence of linear contamination on the transfer material during the next image formation. .

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating a configuration around an intermediate transfer member in an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an intermediate transfer member used in an image forming apparatus that is an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of an intermediate transfer member cleaning device and a lubricant supply unit in an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a diagram for explaining prevention of image smearing by reversely rotating an intermediate transfer member in the image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intermediate transfer body 17 Cleaning means 17a Cleaning blade 18 Image forming unit 19 Charging means 20 Tandem type image forming apparatus 22 Secondary transfer means 24 Secondary transfer body 25 Fixing apparatus 40 Photoconductor 42 Paper feed roller 50 Supply means 50a Brush 50b Lubrication Agent 50c Spring 50d Separation means 50e Cover 61 Development unit 62 Primary transfer means 63 Photoconductor cleaning means 77 Metal electric field roller 100 Image forming part 200 Paper feed part 300 Scanner part 400 Document conveying part P Transfer material

Claims (12)

A plurality of image forming means having a latent image carrier for carrying an electrostatic latent image, a charging means for carrying the surface of the latent image carrier, and a developing means for developing the latent image to form a toner image; In an image forming apparatus comprising: a primary transfer unit that transfers a toner image on a carrier to an intermediate transfer member; and a secondary transfer unit that transfers a toner image transferred to the intermediate transfer member to a transfer material.
The primary transfer unit includes an intermediate transfer member having at least an elastic layer, a cleaning unit that cleans the intermediate transfer member, and a supply unit that supplies a lubricant to the intermediate transfer member. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the intermediate transfer member has an elastic layer having a thickness of 0.07 to 0.3 mm. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the supply unit is a rotating brush. The image forming apparatus according to claim 3.
The image forming apparatus, wherein the supply unit includes an adjustment unit that adjusts a contact state between the brush and the lubricant. The image forming apparatus according to claim 3 or 4,
In the image forming apparatus, an anti-scattering member for preventing the lubricant supplied downstream from being supplied to the supply unit is provided. The image forming apparatus according to claim 5.
The image forming apparatus, wherein the scattering prevention member also serves as a cleaning blade provided in a cleaning unit. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the charging unit is a charging roller that charges the latent image carrier with a rotating roller. The image forming apparatus according to claim 7.
An image forming apparatus, characterized in that the charging means is separated from the image carrier at the same time as the supply means for supplying the lubricant is substantially separated from the intermediate transfer member. The image forming apparatus according to claim 1,
In the image forming apparatus, the supply means for supplying the lubricant is separated from the intermediate transfer member, and the cleaning blade is further separated. The image forming apparatus according to claim 9.
The image forming apparatus includes a separation unit that simultaneously separates a supply unit that supplies a lubricant and a cleaning blade. The image forming apparatus according to claim 10.
The image forming apparatus, wherein the second separation unit is a cam. The image forming apparatus according to claim 1,
When the image forming operation of the image forming apparatus is stopped, the cleaning blade is separated from the intermediate transfer member, and the intermediate transfer member is reversely rotated to stop.