JP2005338351A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve transfer and cleaning properties without collapse/void of toner images, such as character and lines. <P>SOLUTION: The image forming apparatus has an intermediate transfer member having an elastic layer, a transfer means for forming a transfer nip with the intermediate transfer member and transferring the toner image onto the intermediate transfer member, a heating means for heating an intermediate transfer belt, a cooling means for cooling the same, and a cleaning means for cleaning the belt by abutting on the cooling means. The heating means is arranged upstream of the transfer nip and the cooling means is arranged upstream of the cleaning means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer, and more specifically, an image for transferring a toner image formed on an image bearing member such as a photosensitive drum to a transfer material such as paper via an intermediate transfer belt. The present invention relates to an improvement of a forming apparatus.

  As a conventional image forming apparatus, for example, a developing device for each color component of black (Bk), yellow (Y), magenta (M) and cyan (C) is provided around an image carrier such as a photosensitive drum, A transfer drum is disposed opposite to the image carrier, and a sheet as a transfer material is previously held on the transfer drum, and toner of each color component formed on the image carrier every rotation of the image carrier. An image in which an image is sequentially electrostatically transferred onto a sheet is known. However, due to factors such as the thickness and surface characteristics of the paper, the holding of the paper on the transfer drum becomes unstable, and the color image formed on the paper is disturbed.

  As means for solving such a problem, an image forming apparatus using an intermediate transfer member is already known. For example, a developing device for each color component of black (Bk), yellow (Y), magenta (M), and cyan (C) is provided around an image carrier such as a photosensitive drum, and For example, a belt-like intermediate transfer member (intermediate transfer belt) is arranged opposite to each other, and an unfixed toner image of each color component formed on the image carrier for each rotation of the image carrier is sequentially electrostatically applied to the intermediate transfer belt. The four-color full-color image superimposed on the intermediate transfer belt is electrostatically secondarily transferred onto a sheet as a transfer material to form a full-color image on the sheet. According to this type, since the four-color toner images that have already been multiplex-transferred onto the intermediate transfer belt are collectively transferred to the transfer material, the above-mentioned unstable factors can be eliminated, and the image at the time of multiplex transfer can be eliminated. Can be effectively prevented from occurring.

  However, the above-described image forming apparatus has a problem that the toner image on the intermediate transfer belt collapses after the primary transfer, and in particular, when the toner image is a line, a blurred line image occurs.

  In addition to the above-described image forming apparatus, for example, a plurality of image forming units are arranged in parallel, and an intermediate transfer belt that moves along the arrangement direction of the image forming units is disposed, and each image is arranged. Each color component formed by the forming unit, for example, black, cyan, magenta, and yellow images are sequentially electrostatically transferred to the intermediate transfer belt in sequence, and then the four-color full-color image on the intermediate transfer belt is transferred to a sheet as a transfer material. This also occurs in a tandem type image forming apparatus in which four-color full-color images are formed on a sheet by electrostatic secondary transfer (collective transfer).

  This problem has mainly occurred at the primary transfer nip portion formed by pressurizing from the back surface of the intermediate transfer belt by the primary transfer roller disposed at a position facing the photosensitive drum via the intermediate transfer belt. Conventionally, the surface layer of the photosensitive drum has a resin layer, and a resin such as polyimide or polycarbonate is also used for the intermediate transfer belt. When the toner image formed of powder passes through the primary transfer nip with such a configuration, the surface layer of the photosensitive drum and the intermediate transfer belt are resin, so that they are not easily deformed locally along the toner image. Stress concentrates on a high portion of the toner image layer existing at the interface between the photosensitive drum and the intermediate transfer belt in the transfer nip portion. In particular, when the toner image is a line, the area of the toner image that contacts the photosensitive drum and the intermediate transfer belt is small, and the local deformation along the toner image on the surface of the photosensitive drum and the intermediate transfer belt in the surrounding area is small, so further stress is applied. Become focused. In such a state, the toner image is destroyed so as to reduce the height of the toner layer, and the contact area between the photosensitive drum and the intermediate transfer belt is widened to reduce the stress concentration on the toner image. The phenomenon that became an image occurred.

Therefore, an elastic layer such as styrene-butadiene rubber, butadiene rubber, silicone rubber, urethane rubber, epichlorohydrin rubber, etc. is provided on the intermediate transfer belt, and a toner image is interposed between the image and the toner layer in the primary transfer nip. Even in this case, the elastic layer of the intermediate transfer belt is deformed according to the toner image, so that stress concentration applied to the toner image is alleviated and the toner image is prevented from collapsing.
JP2001-075376 JP2002-091179

  However, the toner on the intermediate transfer belt remaining after the secondary transfer to the transfer material is rubbed against an elastic blade made of polyurethane or the like while the residual toner on the intermediate transfer belt is damped by the elastic blade and cleaned. In this case, the elastic layer of the intermediate transfer belt at a location where a large amount of toner is locally present at the contact portion is deformed, and there is a problem that the toner cannot pass through the elastic blade contact portion and cannot be cleaned. . Further, when the amount of toner intervening in the contact portion increases, the deformation of the elastic layer of the intermediate belt increases, and the elastic blade and the intermediate transfer belt do not slide smoothly, and the elastic blade is swollen. Therefore, if the hardness of the elastic layer is increased so that the toner does not slip through and is not easily deformed, local deformation of the elastic layer of the intermediate transfer belt is less likely to occur at the primary transfer nip portion, and the stress applied to the toner image There is a problem that the concentration becomes large and as a result, the toner image is broken.

  According to the first aspect of the present invention, there is provided an image carrier that carries and conveys a toner image, an intermediate having an elastic layer, and the image carrier that is disposed so as to face the intermediate member through the intermediate. Primary transfer means for sequentially transferring the toner image on the image carrier onto the intermediate body by applying a charge having a polarity opposite to that of the toner, and transporting by applying a charge having a polarity opposite to that of the toner to the back surface of the transfer material In an image forming apparatus having a secondary transfer unit that collectively transfers the toner image on the intermediate body to the transfer material, and a cleaning member that is in contact with the intermediate body for cleaning, in the conveying direction of the intermediate body A heating unit that heats the intermediate body upstream of the primary transfer unit and a cooling unit that cools the intermediate body upstream of the cleaning member.

  The invention according to claim 2 relates to claim 1, wherein the intermediate body has a resin layer.

  The invention according to claim 3 relates to claims 1 and 2, characterized in that the heating means heats from the back surface of the intermediate body.

  The invention according to a fourth aspect relates to the first, second, and third aspects, wherein the cooling means cools from the back surface of the intermediate body.

  The invention according to claim 5 relates to claims 1, 2, 3, and 4, and is a second heating means for heating the intermediate body from the back surface of the intermediate body upstream of the secondary transfer means in the transport direction of the intermediate body. It is characterized by having.

  As described above, the intermediate body having the elastic layer is heated before passing through the transfer nip, and the intermediate body is cooled by contacting the intermediate body with a cleaning blade or the like and cleaning the intermediate body. The toner image did not collapse at the transfer nip, and the intermediate was well cleaned.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

  FIG. 1 shows a schematic configuration of a color image forming apparatus to which the present invention is applied. In the figure, reference numeral 1 denotes a photosensitive drum (latent image carrier), and the surface thereof is a known device such as a charging device 2 and an exposure device 3 that performs exposure based on image information as it rotates in the direction of arrow A. An electrostatic latent image corresponding to the image information is formed by the electrophotographic process. A developing unit 8 including developing units 4 to 7 corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk) is disposed around the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is developed by one of the developing devices to form a toner image. In this embodiment, the photosensitive drum 1 is configured to be negatively charged, and development is performed by a reversal development method. Therefore, all the toners used are of a negatively charged type.

  Reference numeral 9 denotes an intermediate transfer belt disposed so as to be in contact with the surface of the photosensitive drum 1, and is stretched around a plurality of stretching rollers 10 to 14 so as to rotate in the direction of arrow B. It has become. In the present embodiment, the stretching rollers 10 and 11 are disposed in the vicinity of the primary transfer position, and are used as a metal driven roller used for forming a flat primary transfer surface of the intermediate transfer belt 9, and the stretching roller 12 is an intermediate transfer. The tension roller 14 and the tension roller 14 that control the tension of the belt 9 to be constant are the driving roller of the intermediate transfer belt 9, and the tension roller 13 is a counter roller for secondary transfer.

  The rubber, elastomer, and resin used for the elastic layer and coating layer of the intermediate transfer belt 9 of the present embodiment include, for example, styrene-butadiene rubber, high styrene rubber, butadiene rubber, isoprene as the elastomer and rubber. Examples thereof include rubber, ethylene-propylene copolymer, nitrile butadiene rubber, chloroprene rubber, butyl rubber, silicone rubber, fluorine rubber, nitrile rubber, urethane rubber, acrylic rubber, epichlorohydrin rubber, and norbornene rubber. Resins include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene. -Acrylate ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer) Polymers), styrene-methacrylic acid ester copolymers (styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-phenyl methacrylate copolymers, etc.), styrene-α-chloroacrylic acid Methyl copolymer, styrene-acrylonitrile-acrylic Styrene resins (monopolymers or copolymers containing styrene or styrene-substituted products), vinyl chloride resins, styrene-vinyl acetate copolymers, rosin-modified maleic resins, phenol resins, polyesters Resins, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resins, polyurethane resins, silicone resins, ketone resins, ethylene-ethyl acrylate copolymers, xylene resins and polyvinyl butyral resins.

  The thickness of the elastic layer is preferably 0.5 mm to 1 mm. The film thickness of the coating layer is preferably a thin layer for transmitting the flexibility of the lower elastic layer to the surface of the photosensitive drum 1, and is preferably 20 μm to 100 μm.

  In addition, conductivity can be realized by incorporating an elastic layer having a DBP oil absorption amount of 50 cc / 100 g or more and 500 cc / 100 g or less, and the conductive filler of the oil absorption amount is mainly conductive. Since it is carbon and it is difficult to achieve medium conductivity as described above, a surface layer in which conductive metal oxide is dispersed thereon is realized by mixing in a large amount to realize stable conductivity with low resistance. By providing, a stable medium resistance can be realized.

  In addition, when a conductive metal oxide is contained in the elastic layer, it is possible to realize a medium resistance stably as in the case of the surface layer, and therefore it becomes easier to control the conductivity by combining with the surface layer. .

  At the primary transfer position of the intermediate transfer belt 9 facing the photosensitive drum 1, a primary transfer roller 15 is disposed on the back surface side of the intermediate transfer belt 9. The toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 9 by applying a positive polarity primary transfer bias of reverse polarity. Reference numeral 19 denotes a drum cleaner that removes toner remaining on the photosensitive drum 1 after the primary transfer.

  In the present embodiment, the secondary transfer roller 16 disposed in pressure contact with the toner image carrying surface side of the intermediate transfer belt 9 is disposed at the secondary transfer position of the intermediate transfer belt 9 facing the conveyance path of the transfer material 20. A grounded stretching roller 13 that is disposed on the back side of the intermediate transfer belt 9 and serves as a counter electrode of the secondary transfer roller 16 is provided. A secondary transfer bias having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 16. Further, a cleaning blade 21 for removing toner remaining on the intermediate transfer belt 9 after the secondary transfer is provided on the downstream side of the secondary transfer position. The secondary transfer roller 16 and the cleaning blade 21 are arranged so as to be able to come into contact with and separate from the intermediate transfer belt 9, and when a color image of a plurality of colors is formed, the toner image before the final color is formed. Is separated from the intermediate transfer belt 9 until it passes through the secondary transfer roller 16 and the cleaning blade 21.

  The cleaning blade 21 used in the embodiment of the present invention uses an elastic body such as urethane rubber or silicon rubber, and is supported by a support sheet metal (not shown) so as to be disposed opposite the stretching roller 14 via the intermediate transfer belt 9. The pressure contact force when attached and abutted against the intermediate transfer belt 9 is 25 g / cm.

  Further, in the present embodiment, after the positioning is temporarily stopped by the registration roller 17, the transfer material 20 is sent to the secondary transfer position at a predetermined timing, and the transfer material 20 after the secondary transfer is further transferred. The toner image is conveyed to a fixing device (not shown) by a conveying member (not shown), and the toner image is melted and fixed on the transfer material.

  Next, an image forming process of the image forming apparatus according to the present embodiment will be described. First, an electrostatic latent image is written on the photosensitive drum 1 and developed by a developing device corresponding to the electrostatic latent image. For example, if the electrostatic latent image written on the photosensitive drum 1 corresponds to the yellow image information, the electrostatic latent image is developed by the developing device 4 containing yellow toner and is exposed to light. A yellow toner image is formed on the body drum 1. The toner image formed on the photosensitive drum 1 is transferred from the photosensitive drum 1 to the surface of the intermediate transfer belt 9 at a primary transfer position where the photosensitive drum 1 and the intermediate transfer belt 9 are in contact with each other. On the other hand, the toner remaining on the photosensitive drum 11 after the primary transfer is removed by the drum cleaner 19.

  At this time, when forming a single color image, the toner image primary-transferred to the intermediate transfer belt 9 is immediately secondary-transferred to the transfer material 20, but a color image in which a plurality of color toner images are superimposed is formed. In this case, the toner image formation on the photosensitive drum 1 and the primary transfer process of the toner image are repeated for the number of colors. For example, when a full color image is formed by superimposing four color toner images, yellow, magenta, cyan, and black toner images are formed on the photosensitive drum 1 for each rotation. Sequentially transferred to the intermediate transfer belt 9 sequentially. On the other hand, the intermediate transfer belt 9 is rotated at the same cycle as the photosensitive drum 1 while carrying the toner image first transferred first, and magenta, cyan, and black toners are rotated on the intermediate transfer belt 9 for each rotation. The image is transferred.

  The toner image primarily transferred to the intermediate transfer belt 9 in this way is conveyed to the secondary transfer position as the intermediate transfer belt 9 rotates. On the other hand, the transfer material 20 is supplied to the secondary transfer position by the registration roller 17 at a predetermined timing, and the secondary transfer roller 16 sandwiches the transfer material 20 with respect to the stretching roller 13. Then, at the secondary transfer position, the toner image carried on the intermediate transfer belt 9 is transferred to the transfer material 20 at the secondary transfer position by the action of the transfer electric field formed between the secondary transfer roll 16 and the stretching roller 13. Electrostatic transfer. Thereafter, the transfer material 20 is conveyed to a fixing device (not shown) through a conveyance member (not shown), and the toner image of the transfer material 20 is fixed. On the other hand, the image bearing of the intermediate transfer belt 9 that has passed the secondary transfer position. The surface side is cleaned by the cleaning blade 21.

  Example 1 relates to Embodiment 1 of the invention. A heating unit that heats the intermediate transfer member 9 upstream of the primary transfer roller 9 and a cooling unit that cools the intermediate transfer belt 9 upstream of the cleaning blade 21 will be described.

  Reference numeral 23 in FIG. 1 denotes a heating means. The heating means is a heat roller 23 having a heat source such as a halogen lamp inside, and is provided inside the intermediate transfer belt 9 so as to be driven and rotated by the intermediate transfer belt 9. Due to the contact heat transfer between the heat roller 23 and the intermediate transfer belt 9, the back surface of the intermediate transfer member is heated. It is desirable to use a metal material such as aluminum or copper having good thermal conductivity for the heat roller. Thereby, the contact heat transfer from the heat roller 23 to the elastic layer of the intermediate transfer belt 9 can be improved, and the flexibility of the elastic layer can be increased by being heated. The output of the halogen lamp is adjusted in advance so that there is no problem in the flexibility of the elastic layer of the intermediate transfer belt 9.

  When the intermediate transfer belt 9 passes through the primary transfer nip portion in this state, even if a toner image is interposed in the primary transfer nip portion, stress is concentrated on the toner image due to the flexibility of the elastic layer of the intermediate transfer belt 9. The toner image can be prevented from being destroyed.

  Reference numeral 24 in FIG. 1 denotes a cooling means. The cooling means 24 is a metal roller or pipe that is driven to rotate on the inner surface of the intermediate transfer belt 9, thereby removing heat on the surface of the intermediate transfer member. Further, the cooling effect of the intermediate transfer belt can be further enhanced by providing fins with pleats inside the cooling metal roller or pipe and flowing a fluid such as air or water inside the pipe.

  As a result, the elastic layer of the intermediate transfer belt 9 that has been heated upstream of the primary transfer roller 15 and has increased flexibility becomes less flexible. In this state, the contact portion between the cleaning blade 21 and the intermediate transfer belt 9 , The deformation response of the elastic layer of the intermediate transfer belt 9 due to the stress is poor even if the cleaning blade 21 is stressed, and the surface layer of the intermediate transfer belt 9 due to the intervention of the toner in the contact portion is not good. There is little deformation of the elastic layer, and toner does not slip through the contact portion. Further, since the elastic layer of the intermediate belt 9 is hardly deformed, the cleaning blade 21 and the intermediate transfer belt 9 can be slid smoothly, so that the cleaning blade 21 does not bend.

  Example 2 relates to Embodiment 1 of the invention. The heating means for heating the intermediate transfer member 9 upstream of the primary transfer roller 15 and the cooling means for cooling the intermediate transfer belt 9 upstream of the cleaning blade 21 are the same as in the first embodiment. In the second embodiment, a heating unit for heating from the back surface of the intermediate transfer belt 9 is added upstream of the secondary transfer unit, and the heating unit will be described.

  When the secondary transfer roller 16 abuts on the intermediate transfer belt 9 for secondary transfer, the elastic layer of the intermediate transfer belt 9 is usually sufficiently softened by the heating means of the first embodiment. Since the intermediate transfer belt 9 may be air-cooled by the air in the machine before the secondary transfer due to fluctuations and its flexibility may not be obtained, in this embodiment, heat similar to that of the heat roller 23 used in Embodiment 1 is used. The roller 25 is arranged upstream of the secondary transfer roller 16 as shown in FIG. 2 to increase the flexibility of the elastic layer of the intermediate transfer belt 9 at the time of secondary transfer, and the toner image is destroyed at the secondary transfer nip at the time of secondary transfer. Was prevented.

<Embodiment 2 of the Invention>
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

  FIG. 3 shows a schematic configuration of a color image forming apparatus to which the present invention is applied. In the figure, reference numerals 1a, 1b, 1c, and 1d denote photosensitive drums (latent image carriers), and charging devices 2a, 2b, 2c, and 2d, image information are provided on the surface of the photosensitive drum as it rotates in the direction of arrow A. An electrostatic latent image corresponding to the image information is formed by a known electrophotographic process such as exposure devices 3a, 3b, 3c, 3d that perform exposure based on the above. Further, yellow (Y) around the photosensitive drum 1a, magenta (M) around 1b, cyan (C) around 1c, and black (Bk) around 1d. 7 is arranged, and the electrostatic latent image formed on each photosensitive drum 1 is developed by each developing device to form a toner image. In this embodiment, the photosensitive drum 1 is configured to be negatively charged, and development is performed by a reversal development method. Therefore, all the toners used are of a negatively charged type.

  Reference numeral 9 denotes an intermediate transfer belt disposed so as to be in contact with the surface of the photosensitive drum 1, which is stretched around a plurality of stretching rollers 11, 13, and 14 and rotates in the direction of arrow B. It is like that. In this embodiment, the tension roller 14 is a tension roller that controls the tension of the intermediate transfer belt 9 to be constant, the tension roller 11 is a driving roller for the intermediate transfer belt 9, and the tension roller 13 is for secondary transfer. The opposite roller.

  The rubber, elastomer, and resin used for the elastic layer and coating layer of the intermediate transfer belt 9 of the present embodiment include, for example, styrene-butadiene rubber, high styrene rubber, butadiene rubber, isoprene as the elastomer and rubber. Examples thereof include rubber, ethylene-propylene copolymer, nitrile butadiene rubber, chloroprene rubber, butyl rubber, silicone rubber, fluorine rubber, nitrile rubber, urethane rubber, acrylic rubber, epichlorohydrin rubber, and norbornene rubber. Resins include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene. -Acrylate ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer) Polymer), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-chloroacrylic acid Methyl copolymer, styrene-acrylonitrile-acrylic Styrene resins (monopolymers or copolymers containing styrene or styrene-substituted products), vinyl chloride resins, styrene-vinyl acetate copolymers, rosin-modified maleic resins, phenol resins, polyesters Resins, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resins, polyurethane resins, silicone resins, ketone resins, ethylene-ethyl acrylate copolymers, xylene resins, and polyvinyl butyral resins.

  The thickness of the elastic layer is preferably 0.5 mm to 1 mm. The film thickness of the coating layer is preferably a thin layer for transmitting the flexibility of the lower elastic layer to the surface of the photosensitive drum 1, and is preferably 20 μm to 100 μm.

  In addition, conductivity can be realized by incorporating an elastic layer having a DBP oil absorption amount of 50 cc / 100 g or more and 500 cc / 100 g or less, and the conductive filler of the oil absorption amount is mainly conductive. Since it is carbon and it is difficult to achieve medium conductivity as described above, a surface layer in which conductive metal oxide is dispersed thereon is realized by mixing in a large amount to realize stable conductivity with low resistance. By providing, a stable medium resistance can be realized.

  In addition, when a conductive metal oxide is contained in the elastic layer, it is possible to realize a medium resistance stably as in the case of the surface layer, and therefore it becomes easier to control the conductivity by combining with the surface layer. .

  Primary transfer rollers 15a, 15b, 15c, and 15d are disposed on the back surface side of the intermediate transfer belt 9 at the primary transfer positions of the intermediate transfer belt 9 facing the respective photosensitive drums 1a, 1b, 1c, and 1d. The toner image on the photosensitive drums 1 a, 1 b, 1 c, and 1 d is transferred onto the intermediate transfer belt 9 by applying a positive primary transfer bias having a polarity opposite to the charging polarity of the toner to the primary transfer roller 15. Next is to be transferred. Reference numeral 19 denotes a drum cleaner that removes toner remaining on the photosensitive drum 1 after the primary transfer.

  In the present embodiment, the secondary transfer roller 16 disposed in pressure contact with the toner image carrying surface side of the intermediate transfer belt 9 is disposed at the secondary transfer position of the intermediate transfer belt 9 facing the conveyance path of the transfer material 20. A grounded stretching roller 13 that is disposed on the back side of the intermediate transfer belt 9 and serves as a counter electrode of the secondary transfer roller 16 is provided. A secondary transfer bias having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 16. Further, a cleaning blade 21 for removing toner remaining on the intermediate transfer belt 9 after the secondary transfer is provided on the downstream side of the secondary transfer position. The secondary transfer roller 16 and the cleaning blade 21 are always in contact with the intermediate transfer belt 9.

  The cleaning blade 21 used in the embodiment of the present invention uses an elastic body such as urethane rubber or silicon rubber, and is supported by a support sheet metal (not shown) so as to be disposed opposite the stretching roller 14 via the intermediate transfer belt 9. The pressure contact force when attached and abutted against the intermediate transfer belt 9 is 25 g / cm.

  Further, in the present embodiment, after the positioning is temporarily stopped by the registration roller 17, the transfer material 20 is sent to the secondary transfer position at a predetermined timing, and the transfer material 20 after the secondary transfer is further transferred. The toner image is conveyed to a fixing device (not shown) by a conveying member (not shown), and the toner image is melted and fixed on the transfer material.

  Next, an image forming process of the image forming apparatus according to the present embodiment will be described. First, an electrostatic latent image is written on the photosensitive drum 1a, and a yellow toner image is formed on the photosensitive drum 1a by the developing device 4. The toner image formed on the photosensitive drum 1 is transferred from the photosensitive drum 1a to the surface of the intermediate transfer belt 9 at a primary transfer position where the photosensitive drum 1a and the intermediate transfer belt 9 are in contact with each other. On the other hand, the toner remaining on the photosensitive drum 1a after the primary transfer is removed by the drum cleaner 19a.

  At this time, when a single color image is formed, the toner image primarily transferred to the intermediate transfer belt 9 passes through the primary transfer nip where the photosensitive drums 1 b, 1 c, and 1 d are in contact with the intermediate transfer belt 9, and is transferred to the transfer material 20. Secondary transfer. When a color image is formed by superimposing a plurality of color toner images, the photosensitive drum 1b and the photosensitive drum 1b are synchronized so as to overlap the yellow toner image primarily transferred from the photosensitive drum 1a onto the intermediate transfer belt 9. A toner image of each color is formed on 1c and 1d, and is primarily transferred onto the intermediate transfer belt 9.

  The toner image primarily transferred to the intermediate transfer belt 9 in this way is conveyed to the secondary transfer position as the intermediate transfer belt 9 rotates. On the other hand, the transfer material 20 is supplied to the secondary transfer position by the registration roller 17 at a predetermined timing, and the secondary transfer roller 16 sandwiches the transfer material 20 with respect to the stretching roller 13. Then, at the secondary transfer position, the toner image carried on the intermediate transfer belt 9 is transferred to the transfer material 20 at the secondary transfer position by the action of the transfer electric field formed between the secondary transfer roll 16 and the stretching roller 13. Electrostatic transfer. Thereafter, the transfer material 20 is conveyed to a fixing device (not shown) through a conveyance member (not shown), and the toner image of the transfer material 20 is fixed. On the other hand, the image bearing of the intermediate transfer belt 9 that has passed the secondary transfer position. The surface side is cleaned by the cleaning blade 21.

  The heating means for heating the intermediate transfer member 9 upstream of the primary transfer roller 15 and the cooling means for cooling the intermediate transfer belt 9 upstream of the cleaning blade 21 will be described.

  Reference numerals 23a, 23b, 24c, and 25d in FIG. 3 are heating means. In this embodiment, the heating means is provided on all the upstream sides of the primary transfer rollers 15a, 15b, 15c, and 15d. The heating means is a heat roller 23 having a heat source such as a halogen lamp inside, and is provided inside the intermediate transfer belt 9 so as to be driven and rotated by the intermediate transfer belt 9. Due to the contact heat transfer between the heat roller 23 and the intermediate transfer belt 9, the back surface of the intermediate transfer member is heated. It is desirable to use a metal material such as aluminum or copper having good thermal conductivity for the heat roller. Thereby, the contact heat transfer from the heat roller 23 to the elastic layer of the intermediate transfer belt 9 can be improved, and the flexibility of the elastic layer can be increased by being heated. The output of the halogen lamp is adjusted in advance so that there is no problem in the flexibility of the elastic layer of the intermediate transfer belt 9.

  When the intermediate transfer belt 9 passes through the primary transfer nip portion in this state, even if a toner image is interposed in the primary transfer nip portion, stress is concentrated on the toner image due to the flexibility of the elastic layer of the intermediate transfer belt 9. The toner image can be prevented from being destroyed.

  Reference numeral 24 in FIG. 3 denotes a cooling means. The cooling means 24 is a metal roller or pipe that is driven to rotate on the inner surface of the intermediate transfer belt 9, thereby removing heat on the surface of the intermediate transfer member. Further, the cooling effect of the intermediate transfer belt can be further enhanced by providing fins with pleats inside the cooling metal roller or pipe and flowing a fluid such as air or water inside the pipe.

  As a result, the elastic layer of the intermediate transfer belt 9 that has been heated upstream of the primary transfer roller 15 and has increased flexibility becomes less flexible. In this state, the contact portion between the cleaning blade 21 and the intermediate transfer belt 9 , The deformation response of the elastic layer of the intermediate transfer belt 9 due to the stress is poor even if stress is applied by the pressure of the cleaning blade 21, and the surface layer of the intermediate transfer belt 9 due to the intervention of the toner in the contact portion is not good. There is little deformation of the elastic layer, and toner does not slip through the contact portion. Further, since the elastic layer of the intermediate belt 9 is not easily deformed, the cleaning blade 21 and the intermediate transfer belt 9 can be slid smoothly, so that the cleaning blade 21 does not bend.

  Example 4 relates to the second embodiment of the invention. The heating means for heating the intermediate transfer member 9 upstream of the primary transfer roller 15 and the cooling means for cooling the intermediate transfer belt 9 upstream of the cleaning blade 21 are the same as in the first embodiment. In the fourth embodiment, a heating unit 25 for heating from the back surface of the intermediate transfer belt 9 is added upstream of the secondary transfer unit, and the heating unit will be described.

  When the secondary transfer roller 16 abuts on the intermediate transfer belt 9 for secondary transfer, the elastic layer of the intermediate transfer belt 9 is usually sufficiently softened by the heating means of the first embodiment. Since the intermediate transfer belt 9 may be air-cooled by the air in the machine before the secondary transfer due to fluctuations and its flexibility may not be obtained, in this embodiment, heat similar to that of the heat roller 23 used in Embodiment 1 is used. The roller 25 is arranged upstream of the secondary transfer roller 16 as shown in FIG. 4 to increase the flexibility of the elastic layer of the intermediate transfer belt 9 at the time of secondary transfer, and the toner image is destroyed at the secondary transfer nip at the time of secondary transfer. Was prevented.

1 is a diagram for explaining Embodiment 1 and Example 1 of the present invention. FIG. FIG. 6 is a diagram illustrating Example 2. It is a figure explaining Embodiment 2 and Example 3 of this invention. FIG. 10 is a diagram for explaining a fourth embodiment.

Claims (5)

An image carrier that carries and conveys a toner image, an intermediate body having an elastic layer, and is placed opposite to the image carrier through the intermediate body to give an electric charge having a polarity opposite to that of the toner to the back surface of the intermediate body Thus, a primary transfer means for sequentially transferring a toner image on the image carrier onto the intermediate body, and a surface on the intermediate body that has been conveyed by applying a charge having a polarity opposite to that of the toner to the back surface of the transfer material. In an image forming apparatus having a secondary transfer unit that collectively transfers a toner image to the transfer material, and a cleaning member that contacts and cleans the intermediate body,
An image forming apparatus comprising: a heating unit that heats the intermediate body upstream of the primary transfer unit in the conveyance direction of the intermediate body; and a cooling unit that cools the intermediate body upstream of the cleaning member.   2. The image forming apparatus according to claim 1, wherein the intermediate has a resin layer.   The image forming apparatus according to claim 1, wherein the heating unit heats from the back surface of the intermediate body.   The image forming apparatus according to claim 1, wherein the cooling unit cools from the back surface of the intermediate body.   5. The second heating unit that heats the intermediate body from the back surface of the intermediate body upstream of the secondary transfer unit in the transport direction of the intermediate body. Image forming apparatus.

Images