JP5273500B2 - Transfer device, transfer unit, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device, a transfer unit, and an image forming device, capable of minimizing disturbance of image caused by electric discharge generated between a belt and a transfer roll. <P>SOLUTION: The image forming device 10 comprises the transfer device 50, the transfer device 50 includes a transfer roll 86, and an endless sheet 84 disposed around the transfer roll 86, the endless sheet 84 having an inner circumferential length larger than the outer circumferential length of the transfer roll 86, and being conductive and flexible. The transfer roll 86 is in contact with an intermediate transfer belt 14 through the endless sheet 84 at a second position P which is located on the downstream side in the moving direction of the intermediate transfer belt 14 over a first position P1 where a photoreceptor 52 contacts with the intermediate transfer belt 14. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a transfer device, a transfer unit, and an image forming apparatus.

  In the transfer device for electrostatically transferring the toner image electrostatically supported on the toner image carrier to the material to be transferred by a transfer roller that sandwiches the material to be transferred together with the toner image carrier. The roller has a cylindrical elastic roller having at least an outer peripheral surface that is conductive and elastic, and an inner peripheral surface longer than the outer peripheral surface of the elastic roller, and the outer peripheral surface has releasability and smoothness with respect to toner. There is known a transfer device that includes a cylindrical body in which an elastic roller is inserted into an internal space (see Patent Document 1).

JP-A-6-67554

  An object of the present invention is to provide a transfer device, a transfer unit, and an image forming apparatus that can reduce image disturbance caused by electric discharge generated between a belt and a transfer roll.

The present invention according to claim 1 has a transfer roll to which a bias is applied by bias applying means, an inner peripheral length larger than the outer peripheral length of the transfer roll, is electrically conductive, and has flexibility. And an endless sheet disposed around the transfer roll, and the transfer roll has a second position downstream of the belt in the moving direction of the belt with respect to the first position where the image carrier contacts the belt. The endless sheet contacts the belt via the endless sheet, and the endless sheet contacts the surface of the belt opposite to the surface on which the image carrier is in contact, and electrostatically contacts the belt. The transfer device is attracted and disposed downstream of the first position in the movement direction of the belt .

According to a second aspect of the present invention, when the radius of the endless sheet is R, the radius of the transfer roll is r, and the distance between the first position and the second position is L, (2πR− 2. The transfer device according to claim 1 , wherein [pi] r) / 2 <L.

According the present invention according to claim 3, wherein as endless sheet is disposed in the downstream side in the movement direction of the belt than the first position, further comprising a regulating member for regulating a position of said endless sheet The transfer device according to Item 1 .

According to a fourth aspect of the present invention, there is provided a transfer for transferring a developer image held by a moving belt and an image holding member contacting the belt at a first position to the belt or a recording medium conveyed by the belt. A transfer unit main body mounted with the belt and the transfer device and detachable in the main body of the image forming apparatus, the transfer device including a transfer roll to which a bias is applied by a bias applying unit , An endless sheet having an inner peripheral length larger than the outer peripheral length of the transfer roll, conductive and flexible, and disposed around the transfer roll, and the transfer roll is , in a second position of the downstream side in the movement direction of the belt than the first position where the image holding member comes into contact with the belt, in contact with the belt through the endless sheet, the endless sheet, In front of the belt In contact with the side surface and the opposite side of the surface which contacts the image carrier, electrostatically attracted to the belt, the transfer unit disposed in the downstream side in the movement direction of the belt than the first position is there.

According to the fifth aspect of the present invention, the moving belt, the image holding member contacting the belt at the first position, and the developer image held by the image holding member are conveyed by the belt or the belt. A transfer device for transferring to a recording medium, the transfer device having a transfer roll to which a bias is applied by a bias applying means, an inner peripheral length larger than the outer peripheral length of the transfer roll, And an endless sheet disposed around the transfer roll, wherein the transfer roll is more than the first position where the image carrier contacts the belt. At a second position downstream in the moving direction of the belt, the belt contacts the belt via the endless sheet, and the endless sheet is placed on a surface opposite to the surface of the belt on which the image carrier contacts. Contact and electrostatically attracted to the belt An image forming device which is arranged in the downstream side in the movement direction of the belt than the first position.

  According to the present invention, it is possible to provide a transfer device, a transfer unit, and an image forming apparatus capable of making it difficult to cause image disturbance caused by electric discharge generated between a belt and a transfer roll.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus 10 according to a first embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, and a transfer unit 15 including an intermediate transfer belt 14 used as a belt in the image forming apparatus main body 12 and, for example, four image forming units 16Y, 16M, and 16C. , 16B.

  The image forming units 16Y, 16M, 16C, and 16B have image forming units 48Y, 48M, 48C, and 48B, respectively, and the image forming units 48Y, 48M, 48C, and 48B are attached to and detached from the image forming apparatus main body 12, respectively. For example, after being moved downward with respect to the intermediate transfer belt 14, it can be pulled out in the front direction in FIG.

  The image forming units 48Y, 48M, 48C, and 48B are arranged in parallel from the upper right to the lower left in FIG. 1, and the image forming apparatus 10 is a so-called tandem system. Each of the image forming units 48Y, 48M, 48C, and 48B includes photoconductors 52Y, 52M, 52C, and 52B that are used as image carriers, and the photoconductors 52Y, 52M, 52C, and 52B are the first ones of the intermediate transfer belt 14. The surface 14a used as the first surface can be contacted at the first positions P1, P1, P1, and P1.

  Of the image forming units 48Y, 48M, 48C, and 48B, the image forming units 48Y, 48M, and 48C are movable left and right within the image forming apparatus main body 12 as indicated by arrows in FIG. 1 between the position where the photoconductors 52Y, 52M, and 52C contact the surface 14a of the intermediate transfer belt 14 and the position separated from the surface 14a of the intermediate transfer belt 14 moved to the right side from the position shown in FIG. Can move. In the case of forming a color image, the image forming units 48Y, 48M, and 48C move to the left, and the photoconductors 52Y, 52M, and 52C are in contact with the surface 14a of the intermediate transfer belt 14 in the same manner as the photoconductor 52B. The yellow toner image, magenta toner image, cyan toner image, and black toner image respectively formed on the photoreceptors 52Y, 52M, 52C, and 52B are transferred to the surface 14a of the intermediate transfer belt 14.

  On the other hand, when forming a black monochrome image, the image forming units 48Y, 48M, and 48C move to the right side, and the photoconductors 52Y, 52M, and 52C are separated from the surface 14a of the intermediate transfer belt 14, and the photoconductors. Only the black toner image formed on 52B is transferred to the surface 14a of the intermediate transfer belt 14. The image forming units 48Y, 48M, and 48C are moved by controlling a moving mechanism (not shown) by a control mechanism (not shown).

  A paper supply device 18 is provided below the image forming apparatus main body 12. The paper supply device 18 is used as a recording medium. For example, a paper supply cassette 20 on which paper made of plain paper or the like is stacked, a pickup roll 22 that pulls out the paper stacked on the paper supply cassette 20, and a paper is sent out while being rolled up. It has a feed roll 24 and a retard roll 26. The paper supply cassette 20 is detachably provided with respect to the image forming apparatus main body 12 so that it can be pulled out, for example, in the front direction in the figure, and stores paper such as plain paper and OHP sheets.

  Near one end of the image forming apparatus main body 12 (near the left end in the figure), a paper supply path 28 is provided along a substantially vertical direction. A transport roll 29, a registration roll 30, a secondary transfer roll 32, a fixing device 34 and a discharge roll 36 are provided around the paper supply path 28 along the paper supply path 28. The registration roll 30 temporarily stops the paper sent to the paper supply path 28 and sends it to the secondary transfer roll 32 in time. The fixing device 34 includes a heating roll 34a and a pressure roll 34b, and fixes the toner image on the paper by applying heat and pressure to the paper passing between the heating roll 34a and the pressure roll 34b.

  A discharge tray section 38 is provided on the upper part of the image forming apparatus main body 12. The paper on which the toner image is fixed to the discharge tray portion 38 is discharged by the discharge roll 36 described above and is stacked on the discharge tray portion 38. Accordingly, the sheets in the sheet supply cassette 20 are sequentially discharged to the discharge tray unit 38 through a C-shaped path.

  For example, four toner bottles 40Y, 40M, 40C, and 40B used as developer storage means are provided on the other end side (right end side in FIG. 1) of the image forming apparatus main body 12. The toner bottle 40Y contains yellow toner, the toner bottle 40M contains magenta toner, the toner bottle 40C contains cyan toner, and the toner bottle 40B contains black toner. The toner bottle 40Y is supplied to the image forming unit 16Y, the toner bottle 40M is supplied to the image forming unit 16M, the toner bottle 40C is supplied to the image forming unit 16C, and the toner bottle 40B is supplied to the image forming unit 16B by supply pipes (pipes). The toner is supplied via a non-illustrated).

  The transfer unit 15 can be attached to and detached from the image forming apparatus main body 12, and can be pulled out in the front direction in FIG. 1, for example. Further, the transfer unit 15 includes the intermediate transfer belt 14 as described above, and support rollers 41, 42, and 43 used as support members that rotatably support the intermediate transfer belt 14. The support rolls 41, 42, and 43 support the intermediate transfer belt 14 so that the intermediate transfer belt 14 can be rotationally driven from the back surface 14 b used as the second surface of the intermediate transfer belt 14. At least one of the support rolls 41, 42, 43 is used as a drive roll that transmits drive to the intermediate transfer belt 14. For example, when the support roll 41 is used as a drive roll, drive is transmitted from the support roll 41 to the intermediate transfer belt 14.

  At least one of the support rolls 41, 42, and 43 is used as a tension roll that applies tension to the intermediate transfer belt 14. For example, when the support roll 43 is used as a tension roll, an elastic body 46 used as an urging member is connected to the support roll 43, and tension is applied to the intermediate transfer belt 14 by the elastic body 46. The intermediate transfer belt 14 is driven and transmitted in a tensioned state, and is driven to rotate in the direction of the arrow shown in FIG.

  Further, the transfer unit 15 includes transfer devices 50, 50, 50, 50 that transfer the developer images held by the photoreceptors 52 Y, 50 M, 50 C, 50 B to the surface 14 a of the intermediate transfer belt 14. . Each of the transfer devices 50 is disposed on the back surface 14 b side of the intermediate transfer belt 14 so as to face the image forming units 48, 48, 48, 48 via the intermediate transfer belt 14.

  Further, the transfer unit 15 includes a cleaning device 44 used as a cleaning unit that cleans the surface 14 a of the intermediate transfer belt 14. The cleaning device 44 has a cleaning member 45 made of, for example, a blade that comes into contact with the intermediate transfer belt 14 while being backed up by the support roll 43, and the surface of the intermediate transfer belt 14 is cleaned by being scraped off by the cleaning member 45. To do.

The secondary transfer roll 32 is unitized as a secondary transfer unit 33. The secondary transfer unit can be attached to and detached from the image forming apparatus main body 12, and can be pulled out in the front direction in FIG. 1, for example.

  FIG. 2 shows details of the image forming unit 16 and the transfer device 50. The image forming units 16Y, 16M, 16C, and 16B have the same configuration although the colors of the developers to be used are different, and therefore will be collectively described as the image forming unit 16. Further, the four transfer devices 50 have the same configuration. As described above, the image forming unit 16 includes the image forming unit 48 and the photoconductor 52, and includes a charging device 54 including, for example, a roll for charging the photoconductor 52, and an LED (light emitting diode), for example. A light emitting diode), an exposure device 56 that forms a latent image on the photoconductor 52, a developing device 58 that develops the latent image on the photoconductor 52 formed by the exposure device 56 with toner, and a photoconductor 52 after transfer. And a cleaning device 60 for cleaning the toner remaining on the top.

  The image forming unit 48 is configured by combining a detachable photosensitive unit 62 and a developing unit 64. In the photosensitive unit 62, a photosensitive body 52, a charging device 54, an exposure device 56, and a cleaning device 60 are housed in a first housing 66. In the developing unit 64, the developing device 58 is accommodated in the second housing 68. The first housing 66 and the second housing 68 are detachably coupled to form the image forming unit 48.

  Bearings 53 that rotatably support the photoconductor 52 are mounted at both ends in the longitudinal direction of the photoconductor 52. A part of the bearing 53 is exposed from the first casing 66 and the second casing 68 together with a part of the photosensitive member 52.

  The developing device 58 is, for example, a two-component system, and toner and carrier are used for development. The toner and the carrier are stirred by the augers 70 and 72 and supplied to the developing roll 74. In the developing roll 74, a magnetic brush is formed by a carrier, the toner attached to the carrier is conveyed by the magnetic brush, and the latent image on the photosensitive member 52 is developed by the toner. As in this embodiment, in the two-component developing device 58, the developing roll 74 is disposed above the augers 70 and 72, so that the toner and carrier are prevented from accumulating, and the toner and carrier are evenly distributed. The development performance can be maintained. The developing device 58 is supplied with toner from the toner bottle 40 described above.

  The cleaning device 60 includes a toner scraping unit 76 made of, for example, a blade, and a collecting unit 78 that collects the toner scraped off by the toner scraping unit 76.

  The transfer device 50 includes a transfer roll 86 and an endless sheet 84 disposed around the transfer roll 86. The transfer roll 86 is connected to a transfer bias applying device 88 that applies a transfer bias.

  The endless sheet 84 is made of a flexible semiconductive film-shaped member, has a circumferential surface that can be moved endlessly, has a cylindrical shape so as to have a hollow portion 84 a, and is formed on the intermediate transfer belt 14. The back surface 14b is in contact with the second position P2 located downstream of the first position in the moving direction of the intermediate transfer belt 14. The inner peripheral length of the endless sheet 84 is longer than the outer peripheral length of the transfer roll 86, and is movable so as to rotate in the circumferential direction so as to rotate with the rotation of the intermediate transfer belt 14.

As the material of the endless sheet 84, for example, polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride having a thickness of about 30 to 200 μm can be used. Further, as the material of the endless sheet 84, a material in which conductive particles such as carbon black are mixed in a film such as polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, and polyvinylidene fluoride may be used. Moreover, as a material used for the endless sheet | seat 84, the thing whose volume resistivity exists in the range of ¹⁰ < ³ > -10 < ¹⁰ > (omega | ohm) * cm is used, for example. Moreover, as a material used for the endless sheet | seat 84, the thing whose tensile elastic modulus exists in the range of 10-280Kg / mm < ² > is used, for example.

  The transfer roll 86 is inserted into the hollow portion 84 a of the endless sheet 84 and is in contact with the back surface 14 b of the intermediate transfer belt 14 via the endless sheet 84 at the second position P <b> 2.

  Further, at least a peripheral surface portion of the transfer roll 86 is made of a conductive material, and as a specific material, for example, a metal such as aluminum or SUS is used. As a material of the transfer roll 86, for example, a conductive polymer material may be used instead of metal.

  FIG. 3 shows the transfer unit 15. The transfer unit 15 has a transfer unit main body 92. The transfer unit main body 92 has side plates on the front side and the rear side in FIG. 3, for example, and is configured such that these side plates are connected. The transfer unit main body 92 includes the intermediate transfer described above. The belt 14, the transfer devices 50, 50, 50, 50 and the support rolls 41, 42, 43 are mounted, and together with these members, the image forming apparatus main body 12 (see FIG. 1) can be detachably attached. . The cleaning device 44 (see FIG. 1) may be attached to the transfer unit main body 92, and the transfer unit main body 92 and the cleaning device 44 may be integrally attached to and detached from the image forming apparatus main body 12.

  In the image forming apparatus 10 configured as described above, when a color image is formed, the surfaces of the photoreceptors 52Y, 52M, 52C, and 52B are uniformly charged by the charging device 54, and are uniformly charged. The latent images are written on the surfaces of the photoreceptors 52Y, 52M, 52C, and 52B by the exposure device 56, respectively, and these latent images are developed by the developing device 58, respectively, on the surfaces of the photoreceptors 52Y, 52M, 52C, and 52B. , A yellow developer image, a magenta developer image, a cyan developer image, and a black developer image are formed, and these developer images are respectively transferred to the surface 14 a of the intermediate transfer belt 14 by the transfer device 50. The intermediate transfer belt 14 is superposed on the surface 14a. Then, the developer image superimposed on the surface 14 a of the intermediate transfer belt 14 is transferred onto the sheet by the secondary transfer roll 32, and the developer image transferred onto the sheet is fixed onto the sheet by the fixing device 34. . Then, the sheet on which the toner image is fixed is discharged to the discharge tray portion 38 by the discharge roll 36.

  When a developer image is transferred from each photoconductor 52 to the intermediate transfer belt 14, a transfer bias is applied by a transfer bias applying device 88. If, for example, a transfer roll made of rubber or the like is used as the transfer roll 86 and the endless sheet 84 is not provided, the contact state between the transfer roll 86 and the back surface 14b of the intermediate transfer belt 14 may become unstable. is there. In particular, when the rotational speed of the intermediate transfer belt 14 is high, the transfer roll 86 and the intermediate transfer belt 14 are likely to be separated due to vibration, for example, and the developer image on the intermediate transfer belt 14 is caused by this separation. May not be transferred well.

  In contrast, in this embodiment, the flexible endless sheet 84 is electrostatically attracted to the intermediate transfer belt 14 and deformed so as to adhere to the back surface of the intermediate transfer belt 14. For this reason, the width (nip width) in which the back surface 14b of the intermediate transfer belt 14 and the endless sheet 84 are in contact with each other is increased, and the area in which the intermediate transfer belt 14 and the endless sheet 84 are in contact is increased. For example, even if the intermediate transfer belt 14 is locally moved in a direction away from the endless sheet 84 due to vibration, the flexible endless sheet 84 is electrostatically attracted to the intermediate transfer belt 14. The intermediate transfer belt 14 is deformed following the deformation of the intermediate transfer belt 14. For this reason, the intermediate transfer belt 14 and the endless sheet 84 are not easily separated.

  The transfer roll 86 is in contact with the back surface 14 b of the intermediate transfer belt 14 so as to sandwich the endless sheet 84 with the intermediate transfer belt 14 via the endless sheet 84. Therefore, compared with the case where the endless sheet 84 is pressed against the intermediate transfer belt 14 only by the elasticity of the endless sheet 84, the contact pressure between the endless sheet 84 and the intermediate transfer belt 14 is less likely to be separated. Transfer defects caused by

  Further, since the transfer roll 86 is in contact with the back surface 14b of the intermediate transfer belt 14 so as to sandwich the endless sheet 84 with the intermediate transfer belt 14 via the endless sheet 84, the intermediate transfer belt. 14 is pushed into the photoreceptor 52 side, and the intermediate transfer belt 14 and the photoreceptor 52 are compared with the case where the endless sheet 84 is pressed against the intermediate transfer belt 14 only by the elasticity of the endless sheet 84. The contact pressure increases. For this reason, poor transfer due to insufficient contact pressure between the intermediate transfer belt 14 and the photoreceptor 52 is unlikely to occur.

  FIG. 4 shows how the endless sheet 84 is deformed. In a state where no image is formed, that is, in a state where the intermediate transfer belt 14 is stopped and no transfer voltage is applied, the endless sheet 84 is not deformed as shown in FIG. In addition, it has a substantially cylindrical shape with a substantially circular cross section. In this state, the radius of the endless sheet 84 is R, and the radius of the transfer roll 86 is r.

  In a state where an image is formed, that is, in a state where the intermediate transfer belt 14 is rotationally driven and a transfer bias is applied, as shown in FIG. 4B, the endless sheet 84 is transferred to the intermediate transfer belt. 14 is electrostatically attracted to 14 and is attracted to the intermediate transfer belt 14 so that the portion attracted to the intermediate transfer belt 14 moves downstream in the moving direction of the intermediate transfer belt 14 along with the movement of the intermediate transfer belt 14. Transforms into For this reason, the intermediate transfer belt 14 and the photosensitive member 52 are in contact with each other, and the downstream side in the moving direction of the intermediate transfer belt 14 from the first position P1 where the transfer from the photosensitive member 52 to the sheet is performed. In this state, the endless sheet 84 is disposed. For this reason, a transfer electric field is hardly generated upstream from the first position P1, and the developer formed on the photoconductor 52 is scattered by the transfer electric field generated upstream from the first position P1 and adheres to the sheet. It is difficult for image quality degradation to occur.

  In contrast, even if the transfer roll 86 is arranged so as to contact the intermediate transfer belt 14 at the first position P1 and the endless sheet 84 is not provided, or even if the endless sheet 84 is provided, the endless sheet is provided. When at least a part of 84 is located upstream from the first position P1, the transfer electric field is likely to flow around upstream from the first position P1. For this reason, the developer formed on the photosensitive member 52 is scattered by the transferred transfer electric field and easily adheres to the paper, and the image quality of the image formed on the paper is likely to deteriorate.

  Further, in this embodiment, even if the endless sheet 84 is deformed toward the downstream side in the moving direction of the intermediate transfer belt 14 as shown in FIG. The distance L between the first position P1 and the second position P2 and the radius R of the endless sheet 84 (see FIG. 5) so that the end 84b is positioned downstream of the first position P1. 4 (a)), and the radius r of the transfer roll 86 (see FIG. 4 (a)) is determined.

  FIG. 5 shows a state where the endless sheet 84 is deformed upstream in the moving direction of the intermediate transfer belt 14 as shown in FIG. Here, the peripheral length l1 of the endless sheet 84 is 2πR since the radius of the endless sheet 84 before deformation is R. Further, the length l2 of the portion wound around the transfer roll 86 corresponding to the downstream portion of the endless sheet 84 is half the circumference of the transfer roll 86, and the radius of the transfer roll 86 is r. 2πr / 2. For this reason, half the length l3 of the portion of the endless sheet 84 that protrudes downstream from the transfer roll 86 is the length represented by the equation (1).

l3 = (2πR−πr) / 2 (Formula 1)

  And in order for the end 84b of the endless sheet 84 to be in a state of being located downstream of the first position P1, it is sufficient that at least l3 is shorter than L (see FIG. 4C). That is, the relationship between the radius R, the radius r, and the distance L may be determined so as to satisfy the relationship represented by (Expression 2).

l3 <L (Formula 2)

  Therefore, in this embodiment, the radius R and the radius are set so as to satisfy the relationship expressed by (Equation 3) so that the end portion 84b of the endless sheet 84 is positioned downstream of the first position P1. The relationship between r and distance L is defined.

(2πR−πr) / 2 <L (Formula 3)

  FIG. 6 is an enlarged view of the endless sheet 84 used in the second embodiment of the present invention and the periphery of the endless sheet 84. In the first embodiment described above, the transfer roll 86 is inserted into the hollow portion 84 a of the endless sheet 84. In contrast, in the second embodiment, a regulating member 96 that regulates the position of the endless sheet 84 is inserted into the hollow portion 84 a together with the transfer roll 86.

  The regulating member 96 has, for example, a substantially cylindrical shape, and is disposed downstream of the transfer roll 86 in the movement direction of the intermediate transfer belt 14, and the endless sheet 84 is disposed downstream of the first position P1. The position of the endless sheet 84 is regulated so as to be in the state of being. That is, the restricting member 96 restricts the position of the endless sheet 84 so that the upstream end 84b of the endless sheet 84 is positioned downstream of the first position P1.

  The endless sheet 84 moves in the circumferential direction so as to rotate along with the intermediate transfer belt 14 in a state where the endless sheet 84 is stretched between the transfer roll 86 and the regulating member 96. In addition, about the same part as 1st Embodiment, the same number is attached | subjected to FIG. 6, and description is abbreviate | omitted. Moreover, the structure of the part which is not shown by FIG. 6 is the same as 1st Embodiment.

  In the first and second embodiments described above, an intermediate transfer belt is used as a belt. However, a belt that conveys a recording medium made of plain paper, an OHP sheet, or the like is used as the belt. Even if it exists, this invention is applicable. That is, the present invention can be applied to a transfer device that performs transfer onto a transfer medium that is transported by a transport belt, a transfer unit that includes a transport belt that transports a transfer medium, and an image forming apparatus that includes a transport belt that transports a transfer medium. it can.

  As described above, the present invention can be applied to, for example, a transfer device, a transfer unit, and an image forming apparatus that transfer a developer held by a photoreceptor or the like to an intermediate transfer belt or the like.

1 is a front view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a front view showing a configuration of an image forming unit used in an image forming apparatus according to a first embodiment of the present invention. It is a front view which shows the transfer unit which concerns on the 1st Embodiment of this invention. It is explanatory drawing explaining the deformation | transformation of the endless sheet used for the image forming apparatus which concerns on the 1st Embodiment of this invention. It is explanatory drawing explaining the position where the endless sheet | seat used for the image forming apparatus which concerns on the 1st Embodiment of this invention is arrange | positioned. It is a front view which shows the structure of the endless sheet used for the image forming apparatus which concerns on the 2nd Embodiment of this invention, and an endless sheet periphery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming apparatus main body 14 Intermediate transfer belt 15 Transfer unit 50 Transfer apparatus 52 Photoconductor 84 Endless sheet 84a Hollow part 84b End part 86 Transfer roll 92 Transfer unit main body 96 Restriction member P1 First position P2 Second Position L Distance l1 Perimeter R Radius r Radius

Claims (5)

A transfer roll to which a bias is applied by a bias applying means ;
An endless sheet having an inner peripheral length larger than the outer peripheral length of the transfer roll, conductive and flexible, and disposed around the transfer roll;
Have
The transfer roll is in contact with the belt through the endless sheet at a second position downstream of the first position where the image carrier is in contact with the belt in the moving direction of the belt ,
The endless sheet is
Contacting the surface of the belt opposite to the surface on which the image carrier contacts;
Electrostatically attracted to the belt,
The transfer device, which is disposed downstream of the first position in the moving direction of the belt . When the radius of the endless sheet is R, the radius of the transfer roll is r, and the distance between the first position and the second position is L,
(2πR−πr) / 2 <L
The transfer device according to claim 1. The transfer device according to claim 1, further comprising a regulating member that regulates a position of the endless sheet such that the endless sheet is disposed downstream of the first position in the belt movement direction. A moving belt,
A transfer device for transferring a developer image held by an image holding member in contact with the belt at a first position to the belt or a recording medium conveyed by the belt;
A transfer unit body that is mounted with the belt and the transfer device and is detachable in the image forming apparatus body;
Have
The transfer device includes:
A transfer roll to which a bias is applied by a bias applying means ;
An endless sheet having an inner peripheral length larger than the outer peripheral length of the transfer roll, conductive and flexible, and disposed around the transfer roll;
Have
The transfer roll is in the second position in the downstream side in the movement direction of the belt than the first position where the image holding member comes into contact with the belt, in contact with the belt through the endless sheet,
The endless sheet is
Contacting the surface of the belt opposite to the surface on which the image carrier contacts;
Electrostatically attracted to the belt,
The transfer unit disposed on the downstream side in the moving direction of the belt with respect to the first position . A moving belt,
An image carrier that contacts the belt at a first position;
A transfer device for transferring the developer image held by the image carrier to the belt or a recording medium conveyed by the belt;
Have
The transfer device includes:
A transfer roll to which a bias is applied by a bias applying means ;
An endless sheet having an inner peripheral length larger than the outer peripheral length of the transfer roll, conductive and flexible, and disposed around the transfer roll;
Have
The transfer roll contacts the belt via the endless sheet at a second position downstream of the first position where the image carrier contacts the belt in the moving direction of the belt ,
The endless sheet is
Contacting the surface of the belt opposite to the surface on which the image carrier contacts;
Electrostatically attracted to the belt,
The image forming apparatus disposed on the downstream side in the moving direction of the belt with respect to the first position .

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