JP2007328275A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus where a toner image on an intermediate transfer body is properly transferred to a recording body. <P>SOLUTION: The surface layer of a backup roller 16, abutting against a secondary transfer roller 23 via an intermediate transfer belt 10, is formed of an elastic layer 16-b. Thus, even when deflection to make the nip pressure of a secondary transfer nip part uneven is caused on the secondary transfer roller 23, the backup roller 16 is pressed by the secondary transfer roller 23 via the intermediate transfer belt 10 so as to be elastically deformed, according to the deflection of the secondary transfer roller 23. Accordingly, since the abutting state, between the secondary transfer roller 23 and the backup roller 16, is uniformized via the intermediate transfer belt in the secondary transfer nip part, the nip pressure of the secondary transfer nip part becomes uniform, and the toner image on the intermediate transfer belt 10 is properly transferred onto the recording medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to an image forming apparatus that transfers a toner image from an intermediate transfer member onto a recording member.

In the image forming apparatus described in Patent Document 1, a plurality of toner images formed on an image carrier are primarily transferred onto an intermediate transfer belt sequentially by a primary transfer roller at a primary transfer unit, and then the intermediate transfer belt. The toner image on the transfer belt is secondarily transferred onto the recording medium by a secondary transfer roller at a time at the secondary transfer portion. Among these, in the secondary transfer portion, the intermediate transfer belt is sandwiched between the secondary transfer roller and a backup roller facing the secondary transfer roller via the intermediate transfer belt, and the secondary transfer roller and the intermediate transfer belt A secondary transfer nip portion is formed between the two. Here, the formation of the secondary transfer nip portion will be described in detail. A pressing member provided in the apparatus main body presses both ends in the longitudinal direction of the secondary transfer roller toward the intermediate transfer belt, thereby Contact with the intermediate transfer belt. Further, when the secondary transfer roller presses the backup roller via the intermediate transfer belt, a secondary transfer nip portion is formed on the contact surface between the secondary transfer roller and the intermediate transfer belt. Note that the pressure applied to the secondary transfer nip at this time is defined as the nip pressure.
Further, a transfer bias is applied to the secondary transfer roller by a bias applying unit, thereby forming a transfer electric field in the secondary transfer nip portion. Then, the toner image on the intermediate transfer belt is transferred onto the recording medium by the transfer electric field and the nip pressure described above.

JP 2004-133284 A

  However, since the pressing member presses both ends in the longitudinal direction of the secondary transfer roller toward the intermediate transfer belt, the nip pressure at the center in the longitudinal direction of the secondary transfer nip portion is applied to the secondary transfer roller. Deflection occurs to be smaller than the nip pressure at both ends in the longitudinal direction of the transfer nip portion. As a result, the nip pressure at the secondary transfer nip becomes non-uniform, which causes a problem that the toner image on the intermediate transfer belt cannot be transferred onto the recording medium.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of satisfactorily transferring a toner image on an intermediate transfer member onto a recording member.

In order to achieve the above object, an invention according to claim 1 is directed to an image carrier that carries an image developed with a developer, an intermediate transfer member supported by a plurality of rollers, and the image on the image carrier. A primary transfer roller that transfers the image onto the intermediate transfer member, a secondary transfer roller that transfers the image transferred onto the intermediate transfer member onto the recording member, and the secondary transfer via the intermediate transfer member. In an image forming apparatus including a backup roller in contact with the roller, the surface layer of the backup roller is formed of an elastic layer.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the backup roller has a cored bar and an Asker C hardness formed on the outer peripheral surface of the cored bar in a range of 20 ° to 60 °. And an elastic member.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the backup roller is made of a foamed rubber member.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the secondary transfer roller can be brought into contact with or separated from the intermediate transfer member.
The invention of claim 5 is the image forming apparatus of claim 1, 2, 3 or 4, further comprising a cleaning means for cleaning the secondary transfer roller in contact with the secondary transfer roller, The secondary transfer roller has an Asker C hardness of 70 ° or more, and a friction coefficient between the cleaning means and the outer peripheral surface of the secondary transfer roller is 0.3 or less.

  In the present invention, the surface layer of the backup roller that contacts the secondary transfer roller via the intermediate transfer member is formed of an elastic layer. In the secondary transfer portion, a pressing member provided in the apparatus main body presses the secondary transfer roller toward the intermediate transfer member, whereby a secondary transfer nip portion is formed. At this time, even if the secondary transfer roller bends so that the nip pressure at the secondary transfer nip portion is not uniform, the backup roller is pressed by the secondary transfer roller via the intermediate transfer member. The backup roller can be elastically deformed in accordance with the bending of the secondary transfer roller. As a result, the contact state between the secondary transfer roller and the backup roller is made more uniform at the secondary transfer nip portion via the intermediate transfer member than when the surface layer of the secondary transfer roller is formed of a rigid layer. Therefore, it is possible to prevent the nip pressure at the secondary transfer nip portion from becoming uneven.

  As described above, according to the present invention, since the nip pressure at the secondary transfer nip portion is uniform, the toner image on the intermediate transfer member can be excellently transferred onto the recording member.

Hereinafter, an embodiment in which the present invention is applied to a copying machine will be described with reference to the drawings.
FIG. 2 shows a tandem indirect transfer type copying machine according to an embodiment of the present invention. The copying machine main body 100 is provided with an endless belt-like intermediate transfer belt 10 in the center. The intermediate transfer belt 10 is wound around three support rollers 14, 15, 16 and can be rotated and conveyed clockwise in the figure.
In the present embodiment, an intermediate transfer belt cleaning device 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer is provided on the left side of the roller 16 among the three rollers 14, 15, and 16. It has been. On the intermediate transfer belt 10 stretched between the first support roller 14 and the second support roller 15, four image formations of black, yellow, magenta, and cyan are formed along the conveyance direction. Means 18 are arranged side by side, and these image forming units 18 constitute a tandem image forming apparatus 20. An exposure device 21 is further provided on the tandem image forming apparatus 20.
On the other hand, a secondary transfer roller 23 is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming apparatus 20. The secondary transfer roller 23 is provided with a cleaning blade 22 and is driven at the same linear speed as the intermediate transfer belt 10 by a drive motor (not shown) so as to be pressed against the backup roller 16 via the intermediate transfer belt 10. The image on the intermediate transfer belt 10 is transferred to a sheet. A sheet conveying belt 23 is disposed beside the secondary transfer roller 23 and conveys the sheet to the fixing device 25. A fixing device 25 that fixes a transferred image on a sheet is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt.
In the present embodiment, sheet inversion is performed below the secondary transfer device 22 and the fixing device 25 to invert the sheet so as to record images on both sides of the sheet in parallel with the tandem image forming apparatus 20 described above. A device 28 is provided.

Next, image formation by the color copying machine having the above configuration will be described. When making a copy using the color copying machine having the above-described configuration, first, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it.
Next, when a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is conveyed by the automatic document feeder 400 and moved onto the contact glass 32, and then the scanner 300 is driven. The first traveling body 33 and the second traveling body 34 travel. On the other hand, when the document is set on the contact glass 32, the scanner 300 is immediately driven, and the first traveling body 33 and the second traveling body 34 travel. At this time, 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. The reflected light is further reflected by the mirror of the second traveling body 34 and enters the reading sensor 36 through the imaging lens 35. Thereby, the content of the original is read.
When the start switch is pressed as described above, one of the support rollers 14, 15, and 16 is rotationally driven by a drive motor (not shown), and the other two support rollers are driven to rotate, so that the intermediate transfer belt 10 is rotated. It is rotated and conveyed. At the same time, the photoconductors 40 are rotated by the individual image forming means 18, and black, yellow, magenta, and cyan single-color images are formed on the photoconductors 40 by the developing devices 70. Then, along with the conveyance of the intermediate transfer belt 10, these single color images are sequentially transferred to the intermediate transfer belt 10, and a composite color image is formed on the intermediate transfer belt 10.

Further, when the start switch is pressed as described above, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and a sheet is fed from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. It is paid out. The fed sheets are separated one by one by the separation roller 45, introduced into the paper feed path 46, transported by the transport roller 47, guided to the paper feed path 48 in the copying machine main body 100, and then registered. The roller 49 is abutted and stopped. When the manual feed tray 51 is used, the paper feed roller 50 is rotated to feed out the sheets on the manual feed tray 51, and the fed sheets are separated one by one by the separation roller 52 and then manually fed. The paper is introduced into the paper path 53 and is similarly stopped against the registration roller 49.
Thereafter, the registration roller 49 is rotated in time with the composite color image on the intermediate transfer belt 10, and the sheet is fed between the intermediate transfer belt 10 and the secondary transfer roller 23. A color image is recorded on the sheet by the transfer by the secondary transfer roller 23.

  The sheet after the image transfer is transported by the paper transport device 29 and sent to the fixing device 25. After the transfer image is fixed by applying heat and pressure in the fixing device 25, the switching claw 55 is switched. The paper is discharged by a discharge roller 56 and stacked on a paper discharge tray 57. On the other hand, in the case of double-sided copying, a sheet with an image transferred on one side is introduced into the sheet reversing device 28 by the switching of the switching claw 55 and reversed, and then guided again to the transfer position, and the image is recorded on the back side. Thereafter, the paper is discharged onto a paper discharge tray 57 by a discharge roller 56.

On the other hand, the residual toner remaining on the intermediate transfer belt 10 after the image transfer is removed from the intermediate transfer belt 10 after the image transfer by the intermediate transfer belt cleaning device 17, so that the tandem image forming device 20 prepares for the image formation again.
Further, since the secondary transfer roller 23 is in contact with the intermediate transfer belt 10, the background stain toner and the process pattern on the intermediate transfer belt 10 are transferred between portions where the sheet such as transfer paper is not placed or between the sheets. Since the secondary transfer roller 23 is soiled, the toner on the secondary transfer roller 23 is always removed by the secondary transfer cleaning blade 22 to prevent the back surface of the sheet from being soiled.

The detailed configuration of the secondary transfer unit used in this embodiment is shown in FIGS.
In FIG. 1, a backup roller 16 is disposed via an intermediate transfer belt 10 that carries a primarily transferred toner image, and this backup roller 16 supports the intermediate transfer belt 10 from the back surface. The backup roller 16 is connected to a power source 71 that applies a transfer voltage. The secondary transfer nip portion is formed such that the secondary transfer roller 23 comes into contact with the intermediate transfer belt 10 and presses against the backup roller 16, and the secondary transfer nip portion between the intermediate transfer belt 10 and the secondary transfer roller 23 is formed. When the sheet passes, a transfer voltage is applied to transfer the toner image on the intermediate transfer belt 10 to the sheet.

  The secondary transfer roller 23 includes a cylindrical metal core 23-a made of metal, an elastic layer 23-b formed on the outer peripheral surface of the metal core 23-a, and an outer peripheral surface of the elastic layer 23-b. The resin layer 23-c is formed. As described above, by providing the elastic layer 23-b, the sheet holding force at the secondary transfer nip portion is increased. For this reason, there is an advantage that the sheet can be more stably transported without being affected by the back tension of the paper feed and the transport resistance generated when the sheet such as a postcard or cardboard is rubbed against the sheet transport path.

  In addition, although it does not specifically limit as a metal which comprises the metal core 23-a, For example, stainless steel, aluminum, etc. are used. In addition, a rubber member is generally used as the rubber layer for the elastic layer 23-b formed on the outer peripheral surface of the core metal 23-a. Since this elastic layer 23-b is required to have an elastic function in order to secure a secondary transfer nip portion between the secondary transfer roller 23 and the intermediate transfer belt 10, the Asker C hardness of the elastic layer 23-b is 85 ° or less is desirable.

However, as described above, since the secondary transfer roller 23 uses the cleaning blade 22 as a cleaning means for the secondary transfer roller 23 in order to clean a pattern between sheets, the elastic layer 23-b. Is too soft, the contact state of the cleaning blade 22 becomes unstable and an appropriate cleaning angle cannot be obtained. Therefore, as the hardness of the elastic layer 23-b, the Asker C hardness is desirably 70 ° or more. Further, since the secondary transfer roller 23 is an insulator and cannot perform the function of transferring a toner image to a sheet, it is necessary to be a rubber member provided with a conductive function. Therefore, in this embodiment, the elastic layer 23-b is formed of epichlorohydrin rubber having an Asker C hardness of 75 °.
Note that as the rubber member imparted with a conductive function, EPDM or silicon rubber in which carbon is dispersed, NBR having an ion conductive function, urethane rubber, or the like may be used.
Further, since many rubber members have high chemical affinity for the toner and a large friction coefficient, the functions necessary for the outermost surface layer in contact with the cleaning blade 22 include a low friction coefficient, toner release Therefore, the resistance is adjusted by adding a resistance control material to the fluororesin resin, and the friction coefficient is set to 0.3 or less.

  As shown in FIG. 3, the secondary transfer roller 23 is supported by a support plate 25 via bearings 11 at both ends, and is rotated by a drive gear 12 from a body drive means (not shown). The support plate 25 is rotatable about the fulcrum shaft 24 shown in FIG. 1, and the support plate 25 is rotated in the direction of arrow H when the contact / separation cam 7 is rotated. Thus, the intermediate transfer belt 10 and the secondary transfer roller 23 can be brought into contact with and separated from each other. Further, by pressing the support plate 25 with the spring 14, the secondary transfer roller 23 presses the intermediate transfer belt 10 with an appropriate pressing force, and the secondary transfer nip is interposed between the intermediate transfer belt 10 and the secondary transfer roller 23. Forming part.

  In order to transfer the toner image onto the sheet, a transfer bias is applied to the secondary transfer roller 23 before the leading edge of the sheet enters the secondary transfer nip portion. By this application, a charge having a polarity opposite to that of the toner is applied on the secondary transfer roller 23, and a transfer electric field is formed in the secondary transfer nip portion. The toner image on the intermediate transfer belt 10 is transferred to the sheet by the action of the transfer electric field and nip pressure. Accordingly, it is necessary to make the transfer electric field and the nip pressure appropriate on the secondary transfer nip portion.

As the secondary transfer roller 23, a roller having an outer diameter of φ30 mm or less is often used in order to improve sheet separation. This is because, when the outer diameter of the secondary transfer roller 23 becomes φ30 or more, curvature separation cannot be performed, and the sheet that has passed through the secondary transfer nip portion is wound around the secondary transfer roller 23.
The secondary transfer roller 23 of this embodiment is provided with epichlorohydrin rubber as an elastic layer on a core metal 23-a φ14 mm, a fluororesin coating is formed on the outermost layer, the outer diameter is φ24 mm, and the length in the longitudinal direction is Although it is a 330 mm two-layer roller, since the core metal 23-a has a small diameter, it is easy to bend by applying pressure to both ends.

  In particular, in order to stabilize the contact state of the cleaning blade 22 as in the present embodiment, when the secondary transfer roller 23 having a relatively high hardness is used, the secondary transfer nip is deformed by the deflection of the secondary transfer roller 23. The difference in the nip pressure becomes large between the central portion in the longitudinal direction of the secondary transfer roller 23 and both ends. If the nip pressure at the central portion is low, an image of a portion where the toner overlaps such as a solid image cannot be transferred to the sheet, and the central portion becomes an image having a low toner density. For this reason, in order to obtain the nip pressure required for the central portion, a considerable pressure is required by the pressurizing means, so that the nip pressure at the both end portions becomes excessive. Accordingly, the force for rubbing the toner with a mechanical force due to the pressure is larger than the force for electrostatically moving the toner from the intermediate transfer belt 10 side to the sheet side, and the graininess of the image quality is deteriorated. In particular, the line image comes out in the case of sheets such as thick paper and OHP. As another problem, when the nip pressure at the end increases, cracks are likely to occur in the surface layer (resin layer) of the secondary transfer roller 23. Further, since cracks are formed in the surface layer of the secondary transfer roller 23, there is a problem that toner enters the surface layer and causes a back-stained image.

Due to the problems described above, in a copying machine configured such that the secondary transfer roller 23 is pressed against the intermediate transfer belt 10, the secondary transfer roller 23 has a central portion in the longitudinal direction and portions near both ends. It is necessary to eliminate the change in the nip pressure.
Therefore, in the present embodiment, as the backup roller 16 that faces the secondary transfer roller 23 through the intermediate transfer belt 10 and supports the intermediate transfer belt 10 from the back surface, the core metal 16-a and the core metal 16-a are used. The roller which consists of two layers which provided the elastic layer 16-b formed with the elastic material in the outer peripheral surface of is used. Thereby, the amount of elastic deformation of the partial elastic layer 16-b of the backup roller 16 is increased by the nip pressure, and the bending of the secondary transfer roller 23 can be absorbed.

Next, backup rollers 16 having different Asker C hardnesses were prepared and introduced into the copying machine of FIG. 2, and the results of checking the nip width N and the density comparison between the edge and the center of the solid image are shown in Table 1. Show.

From Table 1, if the Asker C hardness of the backup roller 16 is 60 ° or less, the nip pressure becomes uniform, and it is possible to eliminate the density difference between the central portion and the end portion in the longitudinal direction of the secondary transfer nip portion in the solid image. It becomes. If the nip width N is the same, it can be said that the nip pressure is the same, so the uniformity of the nip pressure is determined by the nip width N.
Further, as a material constituting the elastic layer of the backup roller 16, it is necessary to reduce the hardness of the rubber material. For that purpose, there is a method of blending a rubber member with a low molecular component such as a plasticizer, but the blended low molecular component exudes from the roller surface and becomes a contaminant, contaminates the intermediate transfer belt 10 and affects the image quality. For this purpose, the rubber member is made of a foamed rubber member such as EPDM foamed rubber or foamed urethane rubber having a foamed rubber member.
In this embodiment, since the backup roller 16 is also an insulator and cannot perform the function of transferring the toner image to the sheet, the backup roller 16 is made of foamed urethane rubber of Asker C 40 ° provided with a conductive function.
As described above, when the Asker hardness is 60 ° or less, it is possible to prevent the nip pressure at the central portion in the longitudinal direction of the secondary transfer nip portion from being lowered, and to make the nip width N and the nip pressure uniform. can do. Therefore, an image without unevenness can be formed. In addition, since it is disadvantageous in cost to manufacture a roller having an Asker hardness of 20 ° or less, the Asker C hardness is desirably 20 ° or more and 60 ° or less as the hardness of the backup roller 16.

  When the backup roller 16 having such a relatively soft hardness is brought into contact with and pressed against the secondary transfer roller 23 for a long time, the elastic layer of the backup roller 16 becomes partially concave due to permanent distortion, and banding. An abnormal image such as an image is generated. Therefore, in order to prevent such an abnormal image, the secondary transfer roller 23 and the intermediate transfer belt 10 are brought into contact with and separated from each other except during image formation, and the secondary transfer roller 23 and the intermediate transfer belt 23 are separated from each other. It is configured to wait.

As described above, according to the present embodiment, the photosensitive member 40 that is an image carrier that supports an image developed with the developer, the intermediate transfer belt 10 that is an intermediate transfer member supported by a plurality of rollers, and the photosensitive member 40. A primary transfer roller 62 for transferring the upper image onto the intermediate transfer belt 10, a secondary transfer roller 23 for transferring the image transferred onto the intermediate transfer belt 10 onto a recording medium, and the intermediate transfer belt 10. In the copying machine, which is an image forming apparatus provided with the backup roller 16 in contact with the secondary transfer roller 23, the surface layer of the backup roller 16 is formed of an elastic layer 16-b. Thus, even if the support plate 25 presses both ends in the longitudinal direction of the secondary transfer roller 23 via the bearing 11 and the secondary transfer roller 23 is bent, the backup roller 16 via the intermediate transfer belt 10. Can elastically deform in accordance with the bending of the secondary transfer roller 23. Therefore, it is possible to suppress the nip width N at the center portion in the longitudinal direction of the secondary transfer roller 23 in the secondary transfer nip portion from being smaller than the nip width N at both ends in the longitudinal direction of the secondary transfer roller 23. Therefore, since the nip width N of the secondary transfer nip portion becomes uniform, the toner image on the intermediate transfer belt 10 can be satisfactorily transferred onto the sheet.
Further, according to the present embodiment, the backup roller 16 includes a cored bar 16-a and an elastic member having an Asker C hardness in a range of 20 ° to 60 ° on the elastic layer 16-b of the cored bar 16-a. It consists of Thereby, the amount of elastic deformation of the elastic layer 16-b due to the nip pressure is increased, and it is possible to perform an elastic deformation that matches the bending of the secondary transfer roller. Accordingly, it is possible to further suppress a decrease in the nip pressure at the center portion in the longitudinal direction of the secondary transfer nip portion. Accordingly, the nip pressure at the secondary transfer nip portion becomes uniform, and the toner density difference between the central portion and the end portion in the longitudinal direction of the secondary transfer nip portion of the toner image transferred onto the sheet can be eliminated.
Moreover, according to this embodiment, the backup roller 16 consists of a foamed rubber member. The rubber member constituting the elastic layer 16-b of the backup roller 16 needs to have a low hardness in order to obtain good elasticity. As a method for reducing the hardness of the rubber member, there is generally a method of blending a rubber member with a low molecular component such as a plasticizer. However, when a rubber member containing a low molecular component plasticizer is used for the backup roller, the low molecular component plasticizer oozes out from the surface of the backup roller 16 to contaminate the intermediate transfer belt 10 and affect the image quality. Therefore, as a rubber member that can be reduced in hardness without blending a plasticizer of a low molecular component, EPDM foamed rubber or foamed urethane rubber, which is a foamed rubber member using a rubber member as a foam, is used. Accordingly, contaminants such as a low molecular component plasticizer do not ooze out from the surface of the backup roller 16, and the intermediate transfer belt 10 is not contaminated, so that it is possible to suppress adverse effects on image quality.
Further, according to the present embodiment, the secondary transfer roller 23 can contact and separate from the intermediate transfer belt 10. If the intermediate transfer belt 10 and the secondary transfer roller 23 come into contact with each other and the secondary transfer roller 23 presses the backup roller 16 via the intermediate transfer belt 10 and is left for a long time, the elastic layer 16 of the backup roller 16 -B becomes partly dented due to permanent distortion, and an abnormal image such as a banding image is generated. Therefore, in order to prevent such an abnormal image, the secondary transfer roller 23 and the intermediate transfer belt 10 can be separated from each other except during image formation. As a result, the secondary transfer roller 23 and the backup roller 16 are allowed to stand for a long time via the intermediate transfer belt 10, thereby preventing permanent deformation of the elastic layer 16-b of the backup roller 16. .
Further, according to the present embodiment, the cleaning blade 22 which is a cleaning unit that contacts the secondary transfer roller 23 and cleans the secondary transfer roller 23 is provided, and the hardness of the secondary transfer roller 23 is Asker C. The hardness is 70 ° or more, and the friction coefficient between the clean blade 22 and the outer peripheral surface of the secondary transfer roller 23 is 0.3 or less. As a result, the hardness of the secondary transfer roller 23 is not too soft, so that even if the cleaning blade 22 is used as a cleaning means for the secondary transfer roller 23, the cleaning blade 22 does not bite into the secondary transfer roller 23 for cleaning. A suitable cleaning angle can be obtained. Further, since the friction coefficient of the outer peripheral surface of the secondary transfer roller 23 is small, the cleaning blade 22 is not caught in the secondary transfer roller 23. Therefore, it is possible to obtain a high cleaning property of the secondary transfer roller 23 even when the cleaning blade 22 is used.

FIG. 3 is a schematic cross-sectional configuration diagram of a secondary transfer portion that is a characteristic portion of the embodiment. 1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 3 is a schematic configuration diagram of a secondary transfer unit that is a feature of the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belt 16 Backup roller 16-a Core metal 16-b Elastic layer 22 Cleaning blade 23 Secondary transfer roller 23-a Core metal 23-b Elastic layer 23-c Resin layer 25 Support plate

Claims (5)

An image carrier for carrying an image developed with a developer;
An intermediate transfer member supported by a plurality of rollers;
A primary transfer roller for transferring the image on the image carrier onto the intermediate transfer member;
A secondary transfer roller for transferring the image transferred onto the intermediate transfer member onto a recording member;
In an image forming apparatus comprising a backup roller that contacts the secondary transfer roller via the intermediate transfer member,
An image forming apparatus, wherein a surface layer of the backup roller is formed of an elastic layer. The image forming apparatus according to claim 1.
The backup roller is composed of a cored bar and an elastic member having an Asker C hardness of 20 ° or more and 60 ° or less formed on the outer peripheral surface of the cored bar. . The image forming apparatus according to claim 1 or 2,
The backup roller is made of a foam rubber member. The image forming apparatus according to claim 1, 2 or 3.
The image forming apparatus, wherein the secondary transfer roller is capable of contacting and separating from the intermediate transfer member. The image forming apparatus according to claim 1, 2, 3, or 4.
Cleaning means for cleaning the secondary transfer roller in contact with the secondary transfer roller;
An image forming apparatus, wherein the secondary transfer roller has an Asker C hardness of 70 ° or more, and a friction coefficient between the cleaning means and the outer peripheral surface of the secondary transfer roller is 0.3 or less.

Images