JP2012123413A - Transfer device and image forming apparatus with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device able to restrain change in toner transfer efficiency by restraining change in distance between the non-contact areas of an intermediate transfer belt, resulting from reciprocal displacement of a primary transfer roller.SOLUTION: Primary transfer rollers 12a to 12c are displaced between the position where an intermediate transfer belt 11 is brought into contact with photoreceptor drums 7a to 7c and the position where it is separated from them. An inter-center distance connecting the photoreceptors 7a to 7c in the position where the intermediate transfer belt 11 is in contact with the photoreceptor drums 7a to 7c and the primary transfer rollers 12a to 12c is set greater than the sum of the radii of the photoreceptors 7a to 7c and the radii of the primary transfer rollers 12a to 12c. An abutting part 25 provided on movable members 18a to 18c supporting the primary transfer rollers 12a to 12c is caused to abut on the target abutting face 26 of target abutting members 4A to 4C determined in positional relation with the photoreceptors 7a to 7c. Among displacements of the primary transfer rollers 12a to 12c, displacement in a direction orthogonal to the tension direction of the intermediate transfer belt 11 is restricted.

Description

  The present invention relates to a transfer provided with an intermediate transfer belt that is stretched around a plurality of photoreceptors in an arrangement direction and a primary transfer roller for transferring a toner image formed on the photoreceptor to the intermediate transfer belt. The present invention relates to an apparatus and an image forming apparatus provided with the apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus has an intermediate transfer belt that is stretched around an arrangement direction of a plurality of photosensitive members, and a primary transfer for transferring a toner image formed on the photosensitive member to the intermediate transfer belt. 2. Description of the Related Art A structure having a transfer device including a roller is known.

  The primary transfer roller is separated or approached between a position where the intermediate transfer belt is brought into contact with the photosensitive member and a position where the intermediate transfer belt is separated from the photosensitive member (for example, see Patent Document 1).

  Further, in the transfer device, the center-to-center distance connecting the central axis of the photosensitive member and the central axis of the primary transfer roller at the position where the intermediate transfer belt contacts the photosensitive member is the sum of the radius of the photosensitive member and the radius of the primary transfer roller. Some are set larger. This type of transfer device is called a so-called offset type transfer device.

  By the way, in this offset type transfer device, the primary transfer roller is structured to be displaced between a position where the intermediate transfer belt is brought into contact with the photosensitive member and a position where the intermediate transfer belt is separated from the photosensitive member. The non-contact distance of the intermediate transfer belt from the contact portion of the intermediate transfer belt that contacts the intermediate transfer belt to the contact portion of the intermediate transfer belt that contacts the primary transfer roller may vary each time the primary transfer roller is displaced.

  As a result, the energization resistance from the photoconductor to the primary transfer roller changes, and the toner transfer efficiency varies.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress variations in the non-contact distance of the intermediate transfer belt due to the reciprocating displacement of the primary transfer roller, and thus to transfer the toner. It is an object of the present invention to provide a transfer apparatus capable of suppressing fluctuations in efficiency and an image forming apparatus having a compact configuration using the transfer apparatus.

In order to achieve the above object, the transfer device according to claim 1, wherein an intermediate transfer belt that is stretched around a plurality of photoconductors and circulated, and a toner image formed on the photoconductor A primary transfer roller for transferring to the intermediate transfer belt, and the primary transfer roller is displaced between a position where the intermediate transfer belt is brought into contact with the photoconductor and a position where the intermediate transfer belt is separated from the photoconductor. The center-to-center distance connecting the central axis of the photosensitive member and the central axis of the primary transfer roller at a position where the intermediate transfer belt is brought into contact with the photosensitive member is a radius of the photosensitive member and a radius of the primary transfer roller. In what is set larger than the sum,
The primary transfer roller is rotatably supported by a movable member, and the movable member is provided with an abutting portion for defining the position of the primary transfer roller, and the abutting portion is configured to attach the intermediate transfer belt to the photoconductor. At the contacted position, it is abutted against an abutting member whose positional relationship is determined with respect to the photoconductor, and the abutting member abuts against the abutting portion of the positional deviation of the primary transfer roller and It has an abutting surface for restricting a positional deviation in a direction orthogonal to the stretching direction of the intermediate transfer belt.

  The transfer apparatus according to claim 2 is characterized in that the abutted surface is a plane parallel to the stretching direction of the intermediate transfer belt.

  The transfer device according to a third aspect is characterized in that the abutted member is constituted by a part of a case for housing the photoconductor.

  The transfer device according to a fourth aspect is characterized in that the abutted member is constituted by a part of a bearing member of the photoconductor.

  The transfer device according to claim 5, wherein a position where the intermediate transfer belt is brought into contact with the photosensitive member and a position where the intermediate transfer belt is separated from the photosensitive member are orthogonal to a stretching direction of the intermediate transfer belt. The movable member is configured to reciprocate the primary transfer roller between both positions.

  The transfer device according to claim 6, wherein the movable member draws an arc between a position where the intermediate transfer belt is brought into contact with the photoconductor and a position where the intermediate transfer belt is separated from the photoconductor drum. The primary transfer roller is configured to reciprocate.

  The transfer device according to a seventh aspect is characterized in that the abutting portion has an arc shape.

  The transfer device according to claim 8, wherein the movable member has an arm that rotates about a rotation shaft, and the primary transfer roller is between the abutting portion and the rotation shaft. Features.

  The transfer device according to claim 9, wherein the abutting portion is the photosensitive member at a position where the intermediate transfer belt is positioned below the photoconductor and the primary transfer roller contacts the intermediate transfer belt with the photoconductor. It is characterized by projecting upward from an intermediate transfer belt that contacts the body.

  An image forming apparatus according to a tenth aspect includes the transfer device according to any one of the first to ninth aspects.

  According to the first and second aspects of the present invention, the variation in the non-contact distance of the intermediate transfer belt due to the reciprocating displacement of the primary transfer roller is suppressed with a simple structure, and thus the variation in the toner transfer efficiency is reduced. Can be suppressed.

  According to the third and fourth aspects of the present invention, the positional deviation of the primary transfer roller can be detected by using a part of the case or the bearing of the photosensitive member whose positional relationship is directly determined with respect to the photosensitive member. Among them, the structure is configured to regulate the positional deviation in the direction orthogonal to the stretching direction of the intermediate transfer belt, so that the variation in the non-contact distance of the intermediate transfer belt due to the reciprocating displacement of the primary transfer roller is further increased. Can be small.

  According to the fifth aspect of the present invention, since the movable member is configured to reciprocate the primary transfer roller in a direction orthogonal to the stretching direction of the intermediate transfer belt, the reciprocation amount of the primary transfer roller can be reduced, and the thickness can be reduced. Compactness can be achieved. In addition, the intermediate transfer belt can be quickly brought into contact with and separated from the photosensitive member.

  According to the invention described in claim 6, since the primary transfer roller is reciprocated so that the movable member draws an arc, when the transfer device is pulled out from the image forming device in the stretching direction of the intermediate transfer belt, Even if force is applied to the primary transfer roller by the intermediate transfer belt when it is pulled out in the stretching direction, the primary transfer roller retracts with a small force, so that it is possible to prevent excessive force from being applied to the photoconductor. It is possible to reduce the occurrence of scratches on the photoreceptor when the transfer device is pulled out of the forming device.

  According to the seventh aspect of the invention, since the abutting portion is formed in an arc shape, the abutting portion can be brought into line contact with the abutted surface, and the intermediate transfer belt is caused by the reciprocal displacement of the primary transfer roller. The variation in the non-contact distance can be further reduced.

  According to the invention described in claim 8, the abutting portion of the movable member can be provided as far as possible from the photosensitive member, and the position where the intermediate transfer belt is brought into contact with the photosensitive member and the intermediate transfer belt from the photosensitive member. When the primary transfer roller is reciprocated between the position to be separated, the reciprocation displacement amount of the abutting portion can be made larger than the reciprocation displacement amount of the primary transfer roller. The distance between the intermediate transfer belts can be ensured, and the damage factors of the photoreceptor and the intermediate transfer belt can be reduced. Further, the variation in the non-contact distance of the intermediate transfer belt due to the reciprocal displacement of the primary transfer roller can be reduced as compared with the case where the abutting portion is provided at the same position as the primary transfer roller.

  According to the ninth aspect of the invention, in addition to the effect of the eighth aspect, in particular, it is possible to avoid the intermediate transfer belt from being damaged by the abutting member.

  According to the tenth aspect of the present invention, since the transfer device according to the first to ninth aspects is provided, stable image quality can be provided, and compactness, miniaturization, and cost reduction can be achieved. it can.

1 is a diagram illustrating an outline of an image forming apparatus including a transfer device according to the present invention. FIG. 4 is an explanatory diagram showing an enlarged portion of an intermediate transfer belt of a transfer apparatus according to the present invention, and is an explanatory diagram showing a state in which the intermediate transfer belt is in contact with each photoconductor. FIG. 4 is an explanatory diagram showing an enlarged portion of an intermediate transfer belt of a transfer apparatus according to the present invention, and is an explanatory diagram showing a state in which the intermediate transfer belt is separated from each photoconductor except for a black photoconductor. FIG. 3 is an explanatory diagram schematically showing a relationship among a primary transfer roller, a photoreceptor, and an intermediate transfer belt according to the present invention. FIG. 3 is a partially enlarged view showing a relationship among a primary transfer roller, an abutting portion, a photoreceptor, and a non-abutting surface according to the present invention. It is the elements on larger scale for demonstrating the effect | action of this invention. It is explanatory drawing which shows the modification of this invention, Comprising: It is a figure which shows the state which formed the to-be-abutted surface in the lower part of the bearing member. It is explanatory drawing which shows the modification of this invention, Comprising: It is a figure which shows the state which drives a primary transfer roller perpendicularly | vertically to an up-down direction.

Embodiments of a transfer apparatus according to the present invention and an image forming apparatus using the transfer apparatus will be described below with reference to the drawings.
FIG. 1 is an explanatory view showing an outline of an image forming apparatus provided with a transfer device according to the present invention. In FIG. 1, reference numeral 1 denotes a tandem type image forming apparatus main body. A paper feed tray 2 is provided at the lower part of the image forming apparatus main body 1, and an exposure device 3 is provided at the upper part of the image forming apparatus main body 1.

  A photosensitive member case 4 is provided between the paper feed tray 2 and the exposure device 3, and a unit type transfer device 5 is provided below the photosensitive member case 4.

  A bundle of transfer paper is set on the paper feed tray 2, and the exposure apparatus 3 is provided with an exposure optical system 6 that distributes illumination light to each photosensitive member described later. In FIG. 1, the exposure light source is not shown.

  In the photoconductor case 4, cylindrical photoconductors 7a to 7d are arranged in this order at predetermined intervals. Here, the photoreceptor 7a is for yellow, the photoreceptor 7b is for cyan, the photoreceptor 7c is for magenta, and the photoreceptor 7d is for black. In the photoreceptor case 4, yellow, cyan, magenta, and black process cartridges 8a to 8d are set corresponding to the photoreceptors 7a to 7d.

  Each of the photoconductors 7a to 7d is exposed by the exposure device 3 to form an electrostatic latent image. To each of the photoconductors 7a to 7d, toner is supplied from and attached to each of the process cartridges 8a to 8d, and each photoconductor 7a. A toner image (visible image) is formed on ˜7d.

  In the transfer device 5, a driving roller 9 and a tension roller 10 are provided with an interval in the arrangement direction of the photoreceptors 7a to 7d. An intermediate transfer belt 11 is provided between the driving roller 9 and the tension roller 10 so as to be stretched around the photoconductors 7a to 7d. The transfer device 5 is provided with primary transfer rollers 12a to 12d that are in contact with the intermediate transfer belt 11 so as to correspond to the photoreceptors 7a to 7d. The structure and operation of the primary transfer rollers 12a to 12d will be described later.

  A paper feed roller 13 is provided below the image forming apparatus main body 1 so as to face the paper feed tray 2. The transfer paper S is pulled out from the paper feed tray 2 by the paper feed roller 13.

  The image forming apparatus main body 1 is provided with a pair of registration rollers 14 in the direction of feeding the transfer paper S. A secondary transfer roller 15 facing the intermediate transfer belt 11 with the transfer paper S interposed therebetween is provided in the direction in which the transfer paper S is fed by the pair of registration rollers 14.

  A potential difference is given between the nips of the primary transfer rollers 12a to 12d and the photoreceptors 7a to 7d, and the toner formed on the photoreceptors 7a to 7d by the potential difference and the applied pressure using the primary transfer rollers 12a to 12d. The image is transferred on the intermediate transfer belt 11. The pair of registration rollers 14 are adjusted so that the leading edge of the transfer sheet S and the leading edge of the toner image coincide with each other at the position of the secondary transfer roller 15.

  Next, the toner image transferred to the intermediate transfer belt 11 is transferred to the transfer paper S by the secondary transfer roller 15.

  The image forming apparatus main body 1 is provided with a fixing device 16 ahead of the transfer sheet S on which the toner image is transferred. The toner adhering to the transfer paper S is pressurized and melted, and the toner image is fixed on the transfer paper S as an image.

  Subsequently, the transfer sheet S is conveyed from below to above by the paper feed roller 13, the pair of registration rollers 14, the driving roller 9, the secondary transfer roller 15, and the fixing device 16, and the image forming apparatus by the pair of discharge rollers 17. It is discharged to a discharge portion 17 ′ at the top of the main body 1.

  As shown in FIG. 2 in an enlarged manner, the transfer device 5 is provided with movable members 18a to 18d corresponding to the photoconductors 7a to 7d. The movable members 18a to 18d are supported on the fixed plate 19 so as to be swingable. Here, the movable members 18 a to 18 d are composed of a movable arm member 20. The movable arm member 20 is generally composed of a support arm 20a and a drive arm 20b. The movable arm member 20 is rotatable around a rotation shaft 20c. Each of the primary transfer rollers 12a to 12d is rotatably provided on the support arm 20a.

  As shown in FIG. 4, a pair of movable arm members 20 are provided at intervals in the axial direction of the photoconductors 7a to 7d (the width direction of the intermediate transfer belt 11), and the primary transfer rollers 12a to 12d are movable in pairs. It is stretched over the arm member 20.

  Here, the movable arm members 20 (18a to 18c) for yellow, cyan, and magenta colors are rotationally driven by, for example, a slide plate 21, as shown in FIG. In FIG. 5, the photoreceptor 7a and the movable member 18a corresponding to the photoreceptor 7a are shown partially enlarged.

  The slide plate 21 can be reciprocally displaced in the extending direction of the intermediate transfer belt 11. A locking pin 22 is provided on each drive arm 20b of the movable arm member 20 (18a to 18c) for yellow, cyan and magenta colors. The slide plate 21 is provided with corresponding locking pins 23 corresponding thereto. A biasing spring 24 is provided between each locking pin 22 and each locking pin 23.

  The primary transfer rollers 12a to 12c for color are displaced between a position where the intermediate transfer belt 11 is brought into contact with the photoconductors 7a to 7c and a position where the intermediate transfer belt 11 is separated from the photoconductors 7a to 7c. ing.

  Here, the transfer device 5 has a center-to-center distance connecting the central axis O1 of the photoconductors 7a to 7d and the central axis O2 of the primary transfer rollers 12a to 12c at a position where the intermediate transfer belt 11 contacts the photoconductors 7a to 7d. The so-called offset type is set to be larger than the sum of the radius R1 of the photoconductors 7a to 7c and the radius R2 of the primary transfer rollers 12a to 12c.

  The movable arm members 20 (18a to 18c) for yellow, cyan, and magenta colors are moved in the arrow A1 direction against the urging force of the urging spring 24 as shown in FIG. The primary transfer rollers 12a to 12c are rotated about the rotation shaft 20c in the direction of the arrow B1, and the intermediate transfer belts 12a to 12c are moved from the position where the intermediate transfer belt 11 shown in FIG. The movable arm member 20 (18a to 18c) for yellow, cyan and magenta colors is displaced while drawing an arc at a position separating the belt 11 from the photoreceptors 7a to 7c, as shown in FIG. When moved in the direction of the arrow A2, the primary transfer rollers 12a to 12c are rotated in the direction of the arrow B2 around the rotation shaft 20c by the urging force of the urging spring 24, and the primary transfer rollers 12a to 12c are moved to the intermediate transfer belt 11 shown in FIG. Is displaced with an arc to a position contacting the intermediate transfer belt 11 shown in FIG. 2 from the position to be separated from the photosensitive member 7 a to 7 c to photoreceptor 7 a to 7 c.

  Each support arm 20a of the movable arm member 20 (18a to 18c) for yellow, cyan, and magenta colors is provided with an abutting portion 25 that defines the positions of the primary transfer rollers 12a to 12c.

  Here, the lower part of the photoconductor case 4 is abutting members 4A to 4C whose positional relationships are determined with respect to the photoconductors 7a to 7c at the positions where the intermediate transfer belt 11 is in contact with the photoconductors 7a to 7c. The abutting members 4 </ b> A to 4 </ b> C have abutting surfaces 26 against which the abutting portions 25 abut at positions where the intermediate transfer belt 11 is brought into contact with the photoreceptors 7 a to 7 c.

  The abutting surface 26 is composed of a plane parallel to the stretching direction of the intermediate transfer belt 11. The abutting portion 25 has an arc shape as shown in an enlarged view in FIG. The primary transfer rollers 12a to 12c are positioned between the abutting portion 25 and the rotating shaft 20c. The abutting portion 25 is configured such that the primary transfer rollers 12a to 12c transfer the intermediate transfer belt 11 to the photoreceptors 7a to 7c. At the position of contact, it protrudes upward from the intermediate transfer belt 11 in contact with each of the photoconductors 7a to 7c.

  The abutted members 4 </ b> A to 4 </ b> C regulate the positional deviation in the direction perpendicular to the stretching direction of the intermediate transfer belt 11, among the positional deviations of the primary transfer rollers 12 a to 12 c. Have a role to play.

  Here, the primary transfer roller 12d is rotatably held at a position in contact with the photoconductor 7d with the intermediate transfer belt 11 interposed therebetween. The primary transfer roller 12d is used for black-and-white monochrome printing.

  With this configuration, it is possible to suppress the variation in the non-contact distance of the intermediate transfer belt 11 due to the reciprocal displacement of the primary transfer rollers 12a to 12c, and thus to suppress the variation in the toner transfer efficiency.

  FIG. 6 is a schematic diagram for explaining the variation in the distance between the contacts of the intermediate transfer belt 11 due to the reciprocal displacement of the primary transfer rollers 12a to 12c.

  That is, as shown in FIG. 6, due to the reciprocal displacement of the primary transfer rollers 12a to 12c, the primary transfer rollers 12a to 12c move in the vertical direction (a direction perpendicular to the stretching direction of the intermediate transfer belt 11). In the range F1, the non-contact of the intermediate transfer belt 11 from the contact portion g1 of the intermediate transfer belt 11 in contact with the photoreceptors 7a to 7c to the contact portion g2 of the intermediate transfer belt 11 in contact with the primary transfer rollers 12a to 12c. The inter-distance varies within a variation range from M1 to M2.

  Further, when the primary transfer rollers 12a to 12c vary in the left and right direction (stretching direction of the intermediate transfer belt 11) in the range F2 due to the reciprocal displacement of the primary transfer rollers 12a to 12c, the photosensitive members 7a to 7c are moved. The non-contact distance of the intermediate transfer belt 11 from the contact portion g1 of the intermediate transfer belt 11 in contact to the contact portion g2 of the intermediate transfer belt 11 in contact with the primary transfer rollers 12a to 12c varies within a variation range of M1 to M3.

  In FIG. 6, primary transfer rollers 12a to 12c indicated by solid lines indicate the reference positions of the variation ranges F1 and F2, and primary transfer rollers 12a to 12c indicated by broken lines are the upper limit position of the variation range F1 and the variation range F2. The primary transfer rollers 12a to 12c indicated by alternate long and short dash lines indicate a state at the reference position in the variation range F1 and the rightmost position in the variation range F2.

  Further, the non-contact distance M1 is an intermediate transfer that contacts the primary transfer rollers 12a to 12c from the contact portion g1 of the intermediate transfer belt 11 that contacts the photoreceptors 7a to 7c when the primary transfer rollers 12a to 12c are at the reference position. This means the length of the non-contact portion up to the contact portion g2 of the belt 11, and the non-contact distance M2 is when the primary transfer rollers 12a to 12c are at the upper limit position of the variation range F1 and at the reference position of the variation range F2. Means the length of the non-contact portion from the contact portion g1 of the intermediate transfer belt 11 in contact with the photoreceptors 7a to 7c to the contact portion g2 of the intermediate transfer belt 11 in contact with the primary transfer rollers 12a to 12c. The distance M3 is the intermediate transfer belt 11 in contact with the photoreceptors 7a to 7c when the primary transfer rollers 12a to 12c are at the reference position of the variation range F1 and the rightmost position of the variation range F2. It means the length of the non-contact portion from the contact portion g1 to the contact portion g2 of the intermediate transfer belt 11 to contact the primary transfer roller 12 a to 12 c.

  The variation Δ1 (Δ1 = M1−M2) in the non-contact distance of the intermediate transfer belt 11 in the vertical direction is larger than the variation Δ2 (Δ2 = M3−M1) in the distance between the contacts of the intermediate transfer belt 11 in the horizontal direction. This is because, as shown in FIG. 6, when the primary transfer rollers 12a to 12c are displaced in the vertical direction, the intermediate transfer belt 11 is wound around the outer peripheral surfaces of the photoreceptors 7a to 7c. A reference numeral 11 ′ is shown on the winding portion of the intermediate transfer belt 11.

  A predetermined potential is applied in advance to the photoconductors 7a to 7c, and toner is attached in accordance with exposure, and a potential difference V is generated between the photoconductors 7a to 7c and the primary transfer rollers 12a to 12c. When the length of the non-contact portion from the contact portion g1 of the intermediate transfer belt 11 in contact with 7a to 7c to the contact portion g2 of the intermediate transfer belt 11 in contact with the primary transfer rollers 12a to 12c is changed, the length of the non-contact portion is changed. Accordingly, the resistance corresponding to the length of the intermediate transfer belt 11 is changed, and the potential difference V is also changed, so that the transfer efficiency to the intermediate transfer belt 11 is changed.

Therefore, when the positional deviation in the vertical direction (direction orthogonal to the stretching direction of the intermediate transfer belt) of each primary transfer roller 12a to 12c due to the reciprocal displacement of each primary transfer roller 12a to 12c is regulated, Variations in the distance between the contacts of the intermediate transfer belt 11 can be suppressed.
(Modification 1)
In the embodiment, the lower part of the photoreceptor case 4 is used as the abutted members 4A to 4C. However, as shown in FIG. 7, the lower part 27a of the bearing member 27 of the photoreceptors 7a to 7c may be used. good. In FIG. 7, reference numeral 28 denotes a central axis of each of the photoconductors 7a to 7c, and 28 'denotes a gear. Here, each of the photoconductors 7a to 7c is rotated with respect to the central axis 28.
(Modification 2)
Here, as shown in FIG. 8, the movable members 18 a to 18 c include, for example, a vertical plate 30 that is biased upward by a spring 29. The vertical plate 30 is provided with a bearing plate 31 having an abutment portion 25 integrally therewith. Primary transfer rollers 12 a to 12 c are rotatably supported on the bearing plate 31.

  In the second modification, the position where the intermediate transfer belt 11 is brought into contact with the photoconductors 7 a to 7 c and the position where the intermediate transfer belt 11 is separated from the photoconductors 7 a to 7 c are orthogonal to the stretching direction of the intermediate transfer belt 11. When the vertical plate 30 is lowered, the primary transfer rollers 12a to 12c cause the intermediate transfer belt 11 to move from the position where the intermediate transfer belt 11 contacts the photoconductors 7a to 7c. When the vertical transfer plate 30 is moved up to the position where the intermediate transfer belt 11 is moved away from the photosensitive members 7a to 7c, the primary transfer rollers 12a to 12c move the intermediate transfer belt 11 away from the photosensitive members 7a to 7c. It is displaced to a position where it is brought into contact with ~ 7c.

4A to 4C: abutting members 7a to 7d ... photoconductor 11 ... intermediate transfer belts 12a to 12c ... primary transfer rollers 18a to 18c ... movable member 25 ... abutting portion 26 ... abutting surface

JP 2003-186313 A

In order to achieve the above object, the transfer device according to claim 1 is provided with an intermediate transfer belt supported by a plurality of rollers and stretched around an arrangement direction of the plurality of photosensitive members , and the plurality of the transfer devices. A plurality of primary transfer rollers for transferring the toner images formed on the photosensitive member to the intermediate transfer belt,
At least one primary transfer roller of the plurality of primary transfer rollers is displaced between a position where the intermediate transfer belt is brought into contact with the photoconductor and a position where the intermediate transfer belt is separated from the photoconductor.
The center-to-center distance connecting the central axis of the photoconductor and the central axis of the at least one primary transfer roller at a position where the intermediate transfer belt is in contact with the photoconductor is the radius of the photoconductor and the at least one primary transfer roller Is set to a predetermined distance larger than the sum of the radius of the intermediate transfer belt and the thickness of the intermediate transfer belt,
In addition, a region where the intermediate transfer belt is brought into contact with the at least one primary transfer roller is more than a first position where the intermediate transfer belt is projected to the back side of the belt among the regions where the intermediate transfer belt is brought into contact with the photosensitive member. The second position, which is the most protruding position on the belt front surface side, is the transfer device protruding on the front surface side of the intermediate transfer belt,
The at least one primary transfer roller is rotatably supported by a movable member, and the movable member is provided with an abutting portion that defines the position of the at least one primary transfer roller,
The abutting portion is a butted member whose positional relationship with respect to the photoconductor is determined at a position on the same side as the second position with respect to the traveling direction of the intermediate transfer belt. The abutting member regulates the amount of protrusion of the at least one primary transfer roller toward the front surface side of the intermediate transfer belt in a direction orthogonal to the stretching direction of the intermediate transfer belt. And an abutting surface that regulates movement of the at least one primary transfer roller in a direction in which the distance between the centers is smaller than the predetermined distance,
A rotating shaft provided at a position different from the plurality of rollers inside the rotation area of the intermediate transfer belt, and the movable member is rotatably supported by the rotating shaft;
The movable member has an arm rotated about the rotation axis, and the at least one primary transfer roller is located between the abutting portion and the rotation axis .

According to a second aspect of the present invention, the position where the intermediate transfer belt is brought into contact with the photoconductor and the position where the intermediate transfer belt is separated from the photoconductor are orthogonal to the stretching direction of the intermediate transfer belt. 2. The transfer device according to claim 1, wherein the movable member is configured to reciprocate the at least one primary transfer roller between both positions.

According to a third aspect of the present invention, the movable member has an arc drawn between a position where the intermediate transfer belt is brought into contact with the photoconductor and a position where the intermediate transfer belt is separated from the photoconductor. The transfer device according to claim 1, wherein the primary transfer roller is configured to reciprocate.

According to a fourth aspect of the present invention, the protruding amount of the at least one primary transfer roller is regulated by causing a planar shape and an arc shape to abut each other at a position where the abutting portion and the abutting surface are in contact with each other. The transfer device according to claim 1, wherein the transfer device is a transfer device.

According to a fifth aspect of the present invention, in any one of the first to third aspects, the abutted surface is a plane parallel to the stretching direction of the intermediate transfer belt. This is a transfer device.
According to a sixth aspect of the present invention, in any one of the first to third aspects, the portion of the abutting portion that is abutted against the abutted surface is a curved surface. The transfer device described.
The invention according to claim 7 is the image forming apparatus according to any one of claims 1 to 6.

The image forming apparatus according to claim 8, wherein a plurality of photoconductors on which toner images are formed;
  An intermediate transfer belt supported by a plurality of rollers and stretched in the arrangement direction of the plurality of photosensitive members;
  A plurality of primary transfer rollers for transferring toner images formed on the plurality of photosensitive members to the intermediate transfer belt, respectively.
  At least one primary transfer roller of the plurality of primary transfer rollers is displaced between a position where the intermediate transfer belt is brought into contact with the photoconductor and a position where the intermediate transfer belt is separated from the photoconductor.
  The center-to-center distance connecting the central axis of the photoconductor and the central axis of the at least one primary transfer roller at a position where the intermediate transfer belt is in contact with the photoconductor is the radius of the photoconductor and the at least one primary transfer roller. Is set to a predetermined distance larger than the sum of the radius of the intermediate transfer belt and the thickness of the intermediate transfer belt,
  In addition, a region where the intermediate transfer belt is brought into contact with the at least one primary transfer roller is more than a first position where the intermediate transfer belt is projected to the back side of the belt among the regions where the intermediate transfer belt is brought into contact with the photosensitive member. Among them, the second position, which is the position that protrudes most to the front side of the belt, is the image forming apparatus that protrudes to the front side of the intermediate transfer belt,
  A positional relationship is defined with respect to an abutting portion that displaces integrally with the at least one primary transfer roller and defines a position of the at least one primary transfer roller, and a region of the surface of the photoreceptor where a toner image is formed. Having a butted surface
  The abutting portion is abutted against the abutting surface at a position on the same side as the second position with respect to the traveling direction of the intermediate transfer belt, and the tension of the intermediate transfer belt is increased. The amount of protrusion of the at least one primary transfer roller toward the front surface side of the intermediate transfer belt in a direction perpendicular to the racking direction is regulated, and the distance between the centers becomes smaller than the predetermined distance. Restricting movement of the at least one primary transfer roller;
  A rotating shaft provided at a position different from the plurality of rollers inside the circumferential region of the intermediate transfer belt, wherein the at least one primary transfer roller and the abutting portion are centered on the rotating shaft; To rotate and move together
  The turning radius of the abutting portion about the turning shaft is larger than the turning radius of the at least one primary transfer roller around the turning shaft.
A ninth aspect of the present invention is the image forming apparatus according to the eighth aspect, wherein the abutting portion has a curved surface at a portion that abuts against the abutted surface.

The image forming apparatus according to claim 10, wherein a plurality of photoconductors on which toner images are formed;
  While being supported by a plurality of rollers including at least a drive roller and a tension roller, the first stretch region and the second stretch region are formed between the drive roller and the tension roller, An intermediate transfer belt facing the plurality of photoconductors in a first tension region;
  A plurality of primary transfer rollers for transferring a toner image formed on the plurality of photoconductors to the intermediate transfer belt by applying a potential difference to the plurality of photoconductors,
  At least one primary transfer roller of the plurality of primary transfer rollers is configured to release a position where the intermediate transfer belt is wound around and contacted with the photosensitive member, and winding between the intermediate transfer belt and the photosensitive member. A position where the intermediate transfer belt is separated from the photoconductor,
  A center-to-center distance connecting a central axis of the photosensitive member and a central axis of the at least one primary transfer roller at a position where the intermediate transfer belt is wound around and contacted with the photosensitive member is a radius of the photosensitive member and the at least one of the photosensitive members. An image forming apparatus set to a predetermined distance larger than the sum of the radius of the primary transfer roller and the thickness of the intermediate transfer belt,
  The at least one primary transfer roller is located at a position on the first stretching region on the tension roller side of a position where the photosensitive member and the intermediate transfer belt are in contact with each other in the stretching direction of the intermediate transfer belt. , Projecting toward the front surface side of the intermediate transfer belt and contacting the intermediate transfer belt,
  The at least one primary transfer roller is rotatably supported by a movable member, and the movable member is provided with an abutting portion that defines the position of the at least one primary transfer roller,
  The abutting portion is abutted against an abutting member whose positional relationship is determined with respect to the photoreceptor, and the abutting member is in the direction orthogonal to the stretching direction of the intermediate transfer belt. The amount of protrusion of the at least one primary transfer roller toward the front surface side of the intermediate transfer belt is regulated, and the at least one primary transfer roller moves in a direction in which the center-to-center distance is smaller than the predetermined distance. It has the butted surface which regulates.

The image forming apparatus according to claim 11, wherein a plurality of photoconductors on which toner images are formed;
  While being supported by a plurality of rollers including at least a driving roller and a tension roller, a first stretching region and a second stretching region are formed between the driving roller and the tension roller, and the first stretching region is formed. An intermediate transfer belt facing the plurality of photoconductors in one stretch region;
  A plurality of primary transfer rollers for transferring a toner image formed on the plurality of photoconductors to the intermediate transfer belt by applying a potential difference to the plurality of photoconductors,
  At least one primary transfer roller of the plurality of primary transfer rollers is configured to release a position where the intermediate transfer belt is wound around and contacted with the photosensitive member, and winding between the intermediate transfer belt and the photosensitive member. And a position for separating the intermediate transfer belt from the photoconductor,
  A center-to-center distance connecting a central axis of the photosensitive member and a central axis of the at least one primary transfer roller at a position where the intermediate transfer belt is wound around and contacted with the photosensitive member is a radius of the photosensitive member and the at least one of the photosensitive members. An image forming apparatus set to a predetermined distance larger than the sum of the radius of the primary transfer roller and the thickness of the intermediate transfer belt,
  The at least one primary transfer roller is located at a position on the first stretching region on the tension roller side of a position where the photosensitive member and the intermediate transfer belt are in contact with each other in the stretching direction of the intermediate transfer belt. , Projecting toward the front surface side of the intermediate transfer belt and contacting the intermediate transfer belt,
  A positional relationship is defined with respect to an abutting portion that displaces integrally with the at least one primary transfer roller and defines a position of the at least one primary transfer roller, and a region of the surface of the photoreceptor where a toner image is formed. Abutted surface, and
  The abutting portion regulates a protruding amount of the at least one primary transfer roller toward the front surface side of the intermediate transfer belt in a direction orthogonal to the stretching direction of the intermediate transfer belt, The movement of the at least one primary transfer roller in a direction in which the distance becomes smaller than the predetermined distance is restricted.

In a twelfth aspect of the present invention, a secondary transfer roller is provided so as to face the drive roller via the intermediate transfer belt,
  The image formation according to claim 10 or 11, wherein the toner image transferred onto the intermediate transfer belt is transferred onto a transfer sheet between the intermediate transfer belt and the secondary transfer roller. Device.
According to a thirteenth aspect of the present invention, the tension roller is provided on a side opposite to the driving roller across a position where the plurality of photosensitive members and the intermediate transfer belt face each other. 12. The image forming apparatus according to 12.
14. The image forming apparatus according to claim 14, wherein the intermediate transfer belt is supported by only the driving roller and the tension roller and is circulated. Device.

The invention according to claim 15 regulates the protrusion amount of the at least one primary transfer roller by causing a planar shape and an arc shape to abut each other at a position where the abutting portion and the abutted surface contact each other. 15. The image forming apparatus according to claim 10, wherein the image forming apparatus is an image forming apparatus.
According to a sixteenth aspect of the invention, in the image according to any one of the tenth to fourteenth aspects, the abutted surface is a plane parallel to the stretching direction of the intermediate transfer belt. Forming device.
The invention according to claim 17 is the invention according to any one of claims 10 to 14, characterized in that the abutting portion has a curved surface at a part that abuts against the abutted surface. An image forming apparatus.

According to the first to seventh aspects of the invention, the intermediate transfer belt is subjected to the primary transfer more than the first position that is the position that protrudes most toward the back side of the belt in the region where the intermediate transfer belt is brought into contact with the photosensitive member. In the configuration in which the second position, which is the position that protrudes most toward the front side of the belt in the region that contacts the roller, protrudes toward the front side of the intermediate transfer belt, the first transfer direction of the intermediate transfer belt At the same position as the second position when viewed from the position, it is abutted against the abutting member whose positional relationship is determined with respect to the photoconductor, and the abutting member is in the tension direction of the intermediate transfer belt. The amount of protrusion of the primary transfer roller to the front surface side of the intermediate transfer belt in the orthogonal direction is regulated, so that the amount of protrusion of the primary transfer roller relative to the primary intermediate transfer belt can be accurately determined. Belt position of the side of the primary transfer roller is provided as viewed from the body and determined accurately.
  This suppresses variations in the non-contact distance of the intermediate transfer belt from the contact portion of the intermediate transfer belt that contacts the photoconductor to the contact portion of the intermediate transfer belt that contacts the primary transfer roller, and thus changes in toner transfer efficiency. Can be suppressed.
  In particular, the abutting portion of the movable member can be provided as far as possible from the photosensitive member, and the primary transfer is performed between the position where the intermediate transfer belt is in contact with the photosensitive member and the position where the intermediate transfer belt is separated from the photosensitive member. When the roller is reciprocated, the amount of reciprocal displacement of the abutting portion can be made larger than the amount of reciprocal displacement of the primary transfer roller. Therefore, the distance between the abutted surface and the intermediate transfer belt is secured. It is possible to reduce damage factors of the photosensitive member and the intermediate transfer belt. Further, the variation in the non-contact distance of the intermediate transfer belt due to the reciprocal displacement of the primary transfer roller can be reduced as compared with the case where the abutting portion is provided at the same position as the primary transfer roller.

According to the invention described in claims 8 to 17, stable image quality can be provided, and compactness, miniaturization, and cost reduction can be achieved.

Claims (10)

An intermediate transfer belt that is stretched around a plurality of photoconductors in an arrangement direction, and a primary transfer roller that transfers a toner image formed on the photoconductor to the intermediate transfer belt. The roller is displaced between a position where the intermediate transfer belt is brought into contact with the photoconductor and a position where the intermediate transfer belt is separated from the photoconductor, and the photoconductor at a position where the intermediate transfer belt is brought into contact with the photoconductor. A center-to-center distance connecting the central axis of the primary transfer roller and the central axis of the primary transfer roller is set to be larger than the sum of the radius of the photoreceptor and the radius of the primary transfer roller,
The primary transfer roller is rotatably supported by a movable member, and the movable member is provided with an abutting portion that defines the position of the primary transfer roller.
The abutting portion is abutted against an abutting member whose positional relationship is defined with respect to the photoconductor at a position where the intermediate transfer belt is in contact with the photoconductor, and the abutting member is the primary member. The transfer roller has a butted surface that restricts a positional deviation in a direction perpendicular to the stretching direction of the intermediate transfer belt among the positional deviations of the transfer roller. apparatus.   The transfer apparatus according to claim 1, wherein the abutted surface is a plane parallel to a stretching direction of the intermediate transfer belt.   The transfer apparatus according to claim 2, wherein the abutted member is constituted by a part of a case that accommodates the photosensitive member.   The transfer apparatus according to claim 2, wherein the abutted member is constituted by a part of a bearing member of the photosensitive member.   The position where the intermediate transfer belt is brought into contact with the photoconductor and the position where the intermediate transfer belt is separated from the photoconductor are present in a direction perpendicular to the stretching direction of the intermediate transfer belt, and the movable member is The transfer device according to claim 2, wherein the primary transfer roller is configured to reciprocate between both positions.   The movable member is configured to reciprocate the primary transfer roller by drawing an arc between a position where the intermediate transfer belt is brought into contact with the photoconductor and a position where the intermediate transfer belt is separated from the photoconductor drum. The transfer device according to claim 2.   The transfer device according to claim 5, wherein the abutting portion has an arc shape.   The said movable member has an arm rotated centering on a rotating shaft, The said primary transfer roller is between the said abutting part and the said rotating shaft, The Claim 6 or Claim 7 characterized by the above-mentioned. The transfer apparatus according to 1.   The intermediate transfer belt is located below the photoconductor, and the abutting portion is located above the intermediate transfer belt in contact with the photoconductor at a position where the primary transfer roller contacts the intermediate transfer belt with the photoconductor. The transfer device according to claim 8, wherein the transfer device is located so as to protrude toward the front.   An image forming apparatus comprising the transfer device according to claim 1.