Transfer device, image forming device

Abstract

To provide a transfer device and an image formation apparatus which can suppress reduction in detection accuracy of an image in comparison to a case of detecting an image of a transfer belt of a curved portion wound around a roll in such a structure that the attitude of the transfer belt changes.SOLUTION: A transfer device comprises: an endless member; a primary transfer member which transfers an image of a plurality of image holding bodies to the endless member; a secondary transfer member which transfers the image to a recording medium; an application roll which is arranged on the downstream side of the primary transfer member and on the upstream side of the secondary transfer member and applies the tension to the endless member; an upstream roll which is arranged on the downstream side of the primary transfer member and on the upstream side of the application roll; a contact / separation member which moves at least a portion of the primary transfer member; a detection member which is opposed to the endless member of a portion between the application roll and the upstream roll and detects an image of the endless member; and a positioning mechanism which positions the detection member by changing the attitude of the detection member following the change in the attitude of the endless member.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a transfer device and an image forming apparatus. [Background technology]

[0002] The image forming apparatus described in Patent Document 1 has an image forming means that forms a toner image, a carrier medium that can carry a detection toner image formed by the image forming means, a holding means that holds and drives the carrier medium, a detection means that detects the detection toner image on the carrier medium, and a control means that controls image formation conditions based on detection information from the detection means, and has a positioning means that determines the detection position of the detection means provided on the holding means, and the detection means is positioned so as to detect the detection toner image on the carrier medium on the holding means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-29525 Summary of the Invention [Problem to be solved by the invention]

[0004] The transfer device includes a primary transfer member that transfers the image of each color onto an endless member, and a detection member that detects the image transferred onto the endless member. The detection member is disposed so as to face the belt surface of the endless member.

[0005] Here, there are modes in which the position of the primary transfer member is different, and the posture of the endless member changes. For this reason, a detection member may be positioned to face the portion of the endless member wound around the roll, based on the shaft of the roll around which the endless member is wound, and detect the image of the portion of the endless member wound around the roll.

[0006] However, since the endless member is curved at the portion wound around the roll, the accuracy of image detection decreases.

[0007] The object of the present disclosure is to prevent a decrease in image detection accuracy in a configuration in which the posture of the endless member changes, compared to when detecting an image of a curved portion of the endless member wound around a roll. [Means for solving the problem]

[0008] A transfer device according to a first aspect of the present disclosure includes a rotating endless member, primary transfer members arranged on opposite sides of a plurality of image carriers arranged in a rotating direction of the endless member, with the endless member sandwiched therebetween, and transferring an image held on the image carrier to the endless member, a secondary transfer member transferring the image transferred to the endless member to a recording medium, an application roll around which the endless member is wrapped, and arranged downstream of all of the primary transfer members and upstream of the secondary transfer members in the rotating direction, and biasing the endless member from an inner peripheral surface to apply tension to the endless member, and a tension roller around which the endless member is wrapped. the transfer roller is provided with an upstream roll disposed downstream of all the primary transfer members and upstream of the application roll in the rotation direction; a contact / separation member that moves at least some of the primary transfer members to contact or separate the endless member and the image carrier, thereby changing the posture of the endless member; a detection member that faces the endless member in a portion between the upstream roll and the application roll, and detects the image transferred to the endless member; and a positioning mechanism that changes the posture of the detection member in accordance with the change in posture of the endless member, thereby positioning the detection member with respect to the endless member.

[0009] A transfer device according to a second aspect of the present disclosure is characterized in that, in the transfer device described in the first aspect, the positioning mechanism comprises a long member stretched across the axis of the application roll and the axis of the upstream roll, and a support member that supports the detection member and whose posture changes in accordance with changes in the posture of the long member.

[0010] A transfer device according to a third aspect of the present disclosure is characterized in that, in the transfer device described in the second aspect, the long member has a disk portion centered on the axial center of the application roll, the support member has a contact portion that contacts the long member and another contact portion that contacts the circumferential surface of the disk portion from at least two directions, and is provided with a biasing member that biases the support member toward the long member.

[0011] A transfer device according to a fourth aspect of the present disclosure is characterized in that, in the transfer device described in the third aspect, the contact portion is formed with an arcuate surface that contacts the elongated member when viewed from the axial direction of the application roll.

[0012] A transfer device according to a fifth aspect of the present disclosure is characterized in that, in the transfer device described in the fourth aspect, the long member has a long surface that extends along a reference direction from the axial center of the application roll to the axial center of the upstream roll when viewed from the axial direction and faces the contact portion, and the arc surface is in contact with the long surface.

[0013] A transfer device according to a sixth aspect of the present disclosure is a transfer device according to any one of the third to fifth aspects, characterized in that, when viewed from the axial direction of the application roll, in a reference direction from the axial center of the application roll to the axial center of the upstream roll, the urging member urges the support member in a portion between the axial center of the application roll and a position where the contact portion contacts the elongated member.

[0014] A transfer device according to a seventh aspect of the present disclosure is characterized in that, in the transfer device described in the sixth aspect, the other contact portion contacts the circumferential surface at two points spaced apart in the circumferential direction, and when viewed from the axial direction, in the reference direction, the axial center of the application roll is located between the two points where the other contact portion contacts the circumferential surface.

[0015] An image forming apparatus according to an eighth aspect of the present disclosure includes an image forming unit that forms an image, and a transfer unit that transfers the image formed by the image forming unit onto a recording medium. Any one of the first to seventh aspects and the transfer device according to claim 1. [Effects of the Invention]

[0016] The transfer device according to the first aspect of the present disclosure, in a configuration in which the posture of the endless member changes, can suppress a decrease in image detection accuracy compared to when detecting an image of a curved portion of the endless member wound around a roll.

[0017] The transfer device according to the second aspect of the present disclosure can change the posture of the detection member without detecting a change in posture of the endless member.

[0018] The transfer device according to the third aspect of the present disclosure stabilizes the state in which the support member is in contact with the elongated member even when the posture of the elongated member changes, compared to when the support member is brought into contact with the elongated member by magnetic force.

[0019] The transfer device according to the fourth aspect of the present disclosure can prevent a decrease in the positioning accuracy of positioning the detection member on the endless member even when the posture of the long member changes, compared to when the portion of the contact section that comes into contact with the long member is rectangular.

[0020] The transfer device according to the fifth aspect of the present disclosure can suppress a decrease in positioning accuracy compared to when the surface with which the arcuate surface comes into contact is inclined with respect to the reference direction when viewed in the axial direction.

[0021] In the transfer device according to the sixth aspect of the present disclosure, the state in which the support member is in contact with the long member is stable even when the posture of the long member changes, compared to when the urging member urges the support member at a part other than between the axial center of the application roll and the position where the contact portion contacts the long member in the reference direction.

[0022] In the transfer device according to the seventh aspect of the present disclosure, the state in which the other contact portion is in contact with the peripheral surface is more stable than when the two points at which the other contact portion is in contact with the peripheral surface are located on one side of the axial center of the application roll in the reference direction.

[0023] The image forming apparatus according to the eighth aspect of the present disclosure, in a configuration in which the posture of the endless member changes, can suppress a decrease in the quality of the output image compared to a case in which the image forming apparatus is equipped with a transfer device that detects the image of the endless member in the portion wrapped around the roll. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] 1 is a configuration diagram illustrating a toner image forming unit of an image forming apparatus according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a front view of a transfer device according to an embodiment of the present disclosure, showing a color mode state; [Figure 4] FIG. 2 is a front view of a transfer device according to an embodiment of the present disclosure, showing a black mode state. [Figure 5] FIG. 2 is an enlarged front view of a transfer device according to an embodiment of the present disclosure, showing a color mode state. [Figure 6] FIG. 2 is an enlarged front view of a transfer device according to an embodiment of the present disclosure, showing the state in a black mode. [Figure 7] FIG. 2 is a perspective view of a transfer device according to an embodiment of the present disclosure, showing the periphery of a detection member; DETAILED DESCRIPTION OF THE INVENTION

[0025] An example of a transfer device and an image forming device according to an embodiment of the present disclosure will be described with reference to Figures 1 to 7. Note that arrow H shown in each figure indicates the vertical direction, i.e., the up-down direction of the device, arrow W indicates the horizontal direction, i.e., the width direction of the device, and arrow D indicates the horizontal direction, i.e., the depth direction of the device.

[0026] (Overall configuration of image forming apparatus 10) 1, the image forming apparatus 10 includes an image forming unit 12 that forms a toner image by electrophotography, and a conveying unit 14 that conveys a sheet material P as a recording medium along a conveying path 16. The image forming apparatus 10 also includes a storage member 18 that stores the sheet material P, and a control unit 28 that controls the entire apparatus.

[0027] In the image forming apparatus 10 configured as described above, the sheet material P stored in the storage member 18 is transported by the transport unit 14 along the transport path 16. Furthermore, a toner image formed by the image forming unit 12 is formed on the transported sheet material P, and the sheet material P with the toner image formed thereon is discharged to the outside of the apparatus main body 10a.

[0028] [Image forming unit 12] 1, the image forming unit 12 includes a plurality of toner image forming units 30 that respectively form toner images of each color, and a transfer unit 32 that transfers the toner images formed in the toner image forming units 30 onto a sheet member P. Furthermore, the image forming unit 12 includes a fixing device 34 that fixes the toner images transferred onto the sheet member P by the transfer units 32 onto the sheet member P.

[0029] -Toner image forming unit 30- A plurality of toner image forming units 30 are provided to form toner images for each color. In this embodiment, toner image forming units 30Y, 30M, 30C, and 30K are provided for a total of four colors: yellow (Y), magenta (M), cyan (C), and black (K). In the following description, when there is no need to distinguish between yellow (Y), magenta (M), cyan (C), and black (K), the Y, M, C, and K attached to the reference numerals will be omitted.

[0030] 2, each toner image forming unit 30 is equipped with a rotating cylindrical image carrier 40 and a charger 42 that charges the image carrier 40. The toner image forming unit 30 further includes an exposure device 44 that irradiates the charged image carrier 40 with exposure light to form an electrostatic latent image, and a developing device 46 that develops the electrostatic latent image into a toner image with developer Z containing toner. As a result, the toner image forming unit 30 for each color forms an image of each color using the toner of that color.

[0031] 1, the image carriers 40 of each color are in contact with a rotating transfer belt 50 (details will be described later). In the rotation direction of the transfer belt 50 (see the arrow in the figure), the toner image forming units 30 of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in this order from the upstream side.

[0032] -Transfer section 32- The transfer unit 32 has a function of transferring the toner image formed by the toner image forming unit 30 onto the sheet material P. The transfer unit 32 will be described in detail later.

[0033] -Fusing unit 34- 1, the fixing device 34 is disposed downstream of the transfer nip NT in the conveying direction of the sheet member P. The fixing device 34 applies heat and pressure to the toner image transferred to the sheet member P to fix it to the sheet member P.

[0034] [Transport unit 14] 1, the conveying unit 14 includes a feed roll 20 that feeds the sheet material P stored in the storage member 18 to the conveying path 16, and a prevention roll 22 that prevents double feeding of the sheet material P fed by the feed roll 20. The conveying unit 14 also includes an adjustment roll 24 that adjusts the timing at which the sheet material P is fed to the transfer nip NT, and a discharge roll 26 that discharges the sheet material P, on which the toner image has been fixed by the fixing device 34, to the outside of the apparatus main body 10a.

[0035] (Main part configuration) Next, a description will be given of the transfer unit 32. The transfer unit 32 is an example of a transfer device.

[0036] 3, the transfer unit 32 includes a transfer belt 50 and primary transfer rolls 52 that are arranged on the opposite side of the image carriers 40 of each color across the transfer belt 50 and that transfer the toner images formed on the image carriers 40 of each color to the transfer belt 50. The transfer unit 32 also includes a contact / separation member 60 that moves at least some of the multiple primary transfer rolls 52 to contact and separate the transfer belt 50 and the image carriers 40.

[0037] Furthermore, the transfer unit 32 includes a winding roll 56 around which the transfer belt 50 is wound, a driving roll 58 around which the transfer belt 50 is wound and which transmits a rotational force to the transfer belt 50, and a positioning roll 64 which positions the portion of the transfer belt 50 onto which the toner image is transferred. The transfer unit 32 also includes an applying unit 70 which applies tension to the transfer belt 50.

[0038] Furthermore, the transfer section 32 includes a detection member 82 that detects the image formed on the transfer belt 50, a holding member 84 that holds the detection member 82, and a positioning mechanism 86 that determines the position of the detection member 82 relative to the transfer belt 50.

[0039] The transfer unit 32 is also provided with a secondary transfer roll 54, which is disposed on the opposite side of the transfer belt 50 from the winding roll 56 and transfers the toner image transferred onto the transfer belt 50 onto the sheet material P. A transfer nip NT is formed between the secondary transfer roll 54 and the transfer belt 50 to transfer the toner image onto the sheet material P.

[0040] [Transfer belt 50, winding roll 56, driving roll 58] 3, the transfer belt 50 is endless and is disposed in such a position that one end (the left end in the drawing) in the device width direction is lower than the other end. The transfer belt 50 is an example of an endless member.

[0041] The winding roll 56 has an axial direction in the depth direction of the device, and one end portion of the transfer belt 50 in the device width direction is wound around the winding roll 56.

[0042] The drive roll 58 has an axial direction in the depth direction of the device, and the other end portion of the transfer belt 50 in the width direction of the device is wrapped around the drive roll 58.

[0043] In this configuration, the drive roll 58 rotates to which a drive force is transmitted from a drive source (not shown), causing the transfer belt 50 to rotate in the direction of the arrow in the figure (clockwise direction).

[0044] [Primary transfer roll 52, secondary transfer roll 54] As shown in FIG. 3 , the primary transfer roll 52 for each color is disposed downstream of the drive roll 58 and upstream of the winding roll 56 in the rotation direction of the transfer belt 50 (hereinafter referred to as the "belt rotation direction"). The primary transfer roll 52 for each color is in contact with the inner circumferential surface of the transfer belt 50 on the opposite side of the transfer belt 50 from the image carrier 40 for that color. The secondary transfer roll 54 is disposed on the opposite side of the transfer belt 50 from the winding roll 56. The primary transfer roll 52 is an example of a primary transfer member, and the secondary transfer roll 54 is an example of a secondary transfer member.

[0045] In this configuration, the primary transfer rolls 52 of each color transfer the toner images formed on the image carriers 40 of each color onto the transfer belt 50, with the transfer belt 50 sandwiched between the primary transfer rolls 52 and the image carriers 40 of each color. Furthermore, the secondary transfer rolls 54 transfer the toner images transferred onto the transfer belt 50 by the primary transfer rolls 52 onto the sheet member P being conveyed through the transfer nip NT.

[0046] [Applying unit 70, positioning roll 64] 3, the supply unit 70 is disposed in a portion surrounded by the transfer belt 50 and at one end side in the device width direction. As shown in FIG. 5, the supply unit 70 includes a supply roll 72 around which the transfer belt 50 is wound, a support member 74 that rotatably supports the supply roll 72, and a biasing member 76 that biases the supply roll 72 against the transfer belt 50 via the support member 74.

[0047] -Granting unit 70 granting role 72- The axial direction of the application roll 72 is the depth direction of the device, and as shown in Fig. 5, the application roll 72 is disposed downstream of the primary transfer roll 52K and upstream of the secondary transfer roll 54 in the belt rotation direction. In other words, the application roll 72 is disposed downstream of all the primary transfer rolls 52 and upstream of the secondary transfer roll 54 in the belt rotation direction. The application roll 72 is in contact with the inner circumferential surface of the transfer belt 50.

[0048] -Support member 74 of the application unit 70- The support members 74 are provided on both sides of the application roll 72 in the device depth direction. As shown in Fig. 5, the support members 74 have a main body portion 74a, a shaft portion 74b that forms the rotation shaft of the main body portion 74a, and a protrusion portion 74c that protrudes from the main body portion 74a.

[0049] The shaft portion 74b has its axial direction in the depth direction of the device and is disposed above the application roll 72 and on the other side in the width direction of the device. The main body portion 74a extends from the shaft portion 74b toward the application roll 72, and the application roll 72 is rotatably attached to the tip of the main body portion 74a. The protrusion 74c protrudes upward from the main body portion 74a.

[0050] - Urging member 76 of application unit 70 - The urging members 76 are compression coil springs, and are provided on both sides of the application roll 72 in the device depth direction. As shown in Fig. 5, the urging members 76 are disposed so as to extend in the direction in which the transfer belt 50 extends, as viewed from the device depth direction, and one end of the urging member 76 is attached to the protruding portion 74c, and the other end of the urging member 76 is attached to a holding portion 78 provided on a frame (not shown).

[0051] In this configuration, the urging member 76 is disposed in a compressed state between the protruding portion 74c and the holding portion 78, and urges the application roll 72, which is in contact with the inner circumferential surface of the transfer belt 50, against the transfer belt 50. In this way, tension is applied to the transfer belt 50. In other words, tension is applied to the transfer belt 50 by the application roll 72 urging the inner circumferential surface of the transfer belt 50 toward the outer circumferential surface of the transfer belt 50.

[0052] -Positioning Roll 64- The positioning rolls 64 have their axial direction in the device depth direction, and as shown in Fig. 3, a pair of positioning rolls 64 are provided in the belt rotation direction, with all of the primary transfer rolls 52 between them. Specifically, a positioning roll 64a is provided upstream of all of the primary transfer rolls 52 in the belt rotation direction, and a positioning roll 64b is provided downstream of all of the primary transfer rolls 52. The positioning roll 64b is an example of an upstream roll.

[0053] 5, the positioning roll 64b is disposed downstream of all the primary transfer rolls 52 and upstream of the application roll 72 in the belt rotation direction. The positioning roll 64b has a cylindrical portion 66a and a shaft portion 66b that is inserted into the cylindrical portion 66a and protrudes from both sides of the cylindrical portion 66a. The positioning roll 64b is rotatably supported by a support member 68 that is supported by a frame (not shown).

[0054] [Approaching and Separating Member 60] 3, the contacting / separating member 60 is disposed in a portion surrounded by the transfer belt 50. The contacting / separating member 60 is configured by combining known mechanisms, and moves the positioning roll 64a and at least some of the primary transfer rolls 52 among the plurality of primary transfer rolls 52 to contact and separate the transfer belt 50 and the image carrier 40. Note that contacting and separating means contacting and separating.

[0055] Here, the image forming device 10 is switched between a color mode in which toner image forming units 30Y, 30M, 30C, and 30K are used to form an image to be transferred to the sheet material P, and a black mode in which only toner image forming unit 30K is used to form an image to be transferred to the sheet material P.

[0056] In this configuration, when the user selects a color mode from an input screen (not shown), as shown in Fig. 3, the contact / separation member 60 positions the positioning roll 64a and the primary transfer roll 52 so that the transfer belt 50 is sandwiched between all of the primary transfer rolls 52 and all of the image carriers 40. Then, the tension applying roll 72 applies tension to the transfer belt 50 by urging the inner peripheral surface of the transfer belt 50 toward the outer peripheral surface of the transfer belt 50, as shown in Fig. 5.

[0057] On the other hand, when the user selects the black mode from an input screen (not shown), as shown in Fig. 4, the contact / separation member 60 positions the positioning roll 64a and the primary transfer roll 52 so that the transfer belt 50 is sandwiched only between the primary transfer roll 52 and the image carrier 40K. Here, the application roll 72 urges the inner peripheral surface of the transfer belt 50 toward the outer peripheral surface of the transfer belt 50 as shown in Fig. 5, so the application roll 72 rotates as shown in Fig. 6 and maintains the tension applied to the transfer belt 50. This causes the transfer belt 50 to separate from the image carriers 40Y, 40M, and 40C (see Fig. 4).

[0058] In this way, the transfer unit 32 switches between the color mode and the black mode. In order to maintain the tension applied to the transfer belt 50, the posture of the portion of the transfer belt 50 downstream of the drive roll 58 and upstream of the secondary transfer roll 54 in the belt rotation direction changes between the color mode and the black mode.

[0059] [Detection member 82, holding member 84] -Detection member 82- 5 and 7, the detection member 82 is an optical sensor and has a rectangular parallelepiped shape extending in the depth direction of the device, and faces the outer peripheral surface of the transfer belt 50 in a portion between the supply roll 72 and the positioning roll 64b. Specifically, the detection member 82 faces the transfer belt 50 in a thickness direction between a position where the transfer belt 50 is separated from the supply roll 72 (T01 shown in the figures) and a position where the transfer belt 50 is separated from the positioning roll 64b (T02 shown in the figures).

[0060] The pair of detecting members 82 are provided spaced apart in the width direction of the device, and as shown in FIG. 7, face the outer circumferential surface of the transfer belt 50 at the end side portion in the depth direction of the device.

[0061] In this configuration, the detection member 82 detects the image transferred to the transfer belt 50. Specifically, the detection member 82 detects the positional deviation of the image transferred to the transfer belt 50 and the density of the image.

[0062] -Holding member 84- 7, the holding member 84 has a rectangular parallelepiped shape extending in the device depth direction, and has through holes 84a that penetrate in the up-down direction. Specifically, the through holes 84a have a rectangular parallelepiped shape extending in the device depth direction, and are formed at each end portion of the holding member 84 in the device depth direction.

[0063] The detection member 82 is fitted into the through-hole 84a, so that the holding member 84 holds the detection member 82.

[0064] [Positioning mechanism 86, etc.] 5 and 7, the positioning mechanism 86 includes an elongated member 90 and a support member 102 that supports the detection member 82 via a holding member 84 and whose posture changes in accordance with a change in the posture of the elongated member 90. The transfer unit 32 also includes a biasing member 110 that applies pressure to the support member 102 against the elongated member 90.

[0065] -Long material 90- A pair of elongated members 90 are provided on both sides of the application roll 72 in the device depth direction, and as shown in FIGS. 5 and 7, are stretched over the axis of the application roll 72 and the axis of the positioning roll 64b.

[0066] Here, "stretched between the axis of the application roll 72 and the axis of the positioning roll 64b" means that the application roll 72 and the positioning roll 64b are connected so that their posture changes as the relative position between the axial center of the application roll 72 and the axial center of the positioning roll 64b changes.

[0067] The elongated member 90 includes a disk portion 92 centered on the axis of the application roll 72, and an elongated portion 94 extending from the disk portion 92 to the positioning roll 64b when viewed from the depth direction of the device.

[0068] The disk portion 92 has an outer diameter larger than that of the application roll 72, and is rotatably attached to the application roll 72. Furthermore, the disk portion 92 is formed with a peripheral surface 92a that faces radially outward.

[0069] When viewed from the depth direction of the device, the long portion 94 extends along a reference direction (arrow K shown in FIG. 5) from the axial center of the application roll 72 (S01 shown in FIG. 5) toward the axial center of the positioning roll 64b (S02 shown in FIG. 5).

[0070] The elongated portion 94 is a plate-shaped member whose thickness direction corresponds to the depth direction of the device, and has an elongated hole 94a formed therein that extends in the reference direction when viewed from the depth direction of the device. The shaft 66b of the positioning roll 64b is movably inserted into this elongated hole 94a. The elongated portion 94 is further formed with an elongated surface 94b that faces the support member 102 and extends along the reference direction.

[0071] -Support member 102- The support members 102 are provided as a pair on both sides of the transfer belt 50 in the depth direction of the device, and are attached to the side surfaces 84b of the holding member 84 as shown in FIGS.

[0072] The support member 102 is formed with a main body 104 to which the holding member 84 is attached, a contact portion 106 that extends from the main body 104 toward the long portion 94 and comes into contact with the long surface 94b, and a contact portion 108 that extends from the main body 104 toward the disk portion 92 and comes into contact with the circumferential surface 92a. The contact portion 108 is an example of another contact portion.

[0073] The contact portion 106 is rod-shaped and extends from the main body 104 toward the elongated portion 94, and an arc surface 106a that is arc-shaped when viewed from the depth direction of the device is formed at the tip of the contact portion 106. The arc surface 106a is in contact with the elongated surface 94b of the elongated member 90.

[0074] The contact portion 108 has one flat surface 108a and another flat surface 108b that contact the peripheral surface 92a when viewed from the depth direction of the device. When viewed from the depth direction of the device, the one flat surface 108a and the other flat surface 108b are arranged in a V-shape. The position of the one flat surface 108a that contacts the peripheral surface 92a and the position of the other flat surface 108b that contacts the peripheral surface 92a are spaced apart in the circumferential direction of the peripheral surface 92a. In this way, the contact portion 108 contacts the peripheral surface 92a of the disk portion 92 at two points from two different directions.

[0075] - Urging member 110 - 5 and 7, a pair of urging members 110 are provided at both ends of holding member 84 in the device depth direction. When viewed from the device depth direction, urging members 110 extend in the vertical direction, with one end of urging member 110 attached to the lower surface 84c of holding member 84 and the other end of urging member 110 attached to a holder 114 provided on a frame (not shown).

[0076] The urging member 110 urges the support member 102 at a position (T03 shown in FIG. 5) where the axial center S01 of the application roll 72 and the contact portion 106 contact the long surface 94b of the elongated member 90 in the reference direction (arrow K shown in FIG. 5) when viewed from the depth direction of the device. Specifically, the urging member 110 urges the support member 102 at a position T03 where the axial center S01 of the application roll 72 and the contact portion 106 contact the long surface 94b in the reference direction, toward the elongated member 90 via the holding member 84.

[0077] Furthermore, the axial center S01 of the application roll is located between the two points where the contact portion 108 contacts the circumferential surface 92a in the reference direction when viewed from the depth direction of the device.

[0078] (Function of main components) Next, the operation of the transfer unit 32 will be described. In the color mode shown in Figure 3, the contact / separation member 60 of the transfer section 32 positions the positioning roll 64a and the primary transfer roll 52 so that the transfer belt 50 is sandwiched between all of the primary transfer rolls 52 and all of the image carriers 40.

[0079] 5, the tension applying roll 72 applies tension to the transfer belt 50 by biasing the inner peripheral surface of the transfer belt 50 toward the outer peripheral surface of the transfer belt 50. As shown in FIG.

[0080] Furthermore, the biasing member 110 biases the support member 102, at a position T03 in the reference direction where the axial center S01 of the application roll 72 and the contact portion 106 contact the long surface 94b, toward the elongated member 90 via the holding member 84. As a result, the arcuate surface 106a of the contact portion 106 of the support member 102 contacts the long surface 94b of the elongated member 90. Furthermore, one flat surface 108a and the other flat surface 108b of the contact portion 108 of the support member 102 contact the circumferential surface 92a of the disk portion 92 of the elongated member 90.

[0081] As a result, the detection member 82 held by the holding member 84 is positioned on the transfer belt 50 via the elongated member 90 .

[0082] In contrast, in the black mode shown in Figure 4, the contact member 60 of the transfer section 32 positions the positioning roll 64a and the primary transfer roll 52 so that the transfer belt 50 is sandwiched between only the primary transfer roll 52 and the image carrier 40K.

[0083] 5 and 6, the application roll 72 rotates about the shaft 74b, maintaining the tension applied to the transfer belt 50. The rotational movement of the application roll 72 changes the posture of the transfer belt 50, and the transfer belt 50 separates from the image carriers 40Y, 40M, and 40C (see FIG. 4). Furthermore, as the posture of the transfer belt 50 changes, the posture of the elongated member 90 also changes.

[0084] Meanwhile, the biasing member 110 biases the support member 102, in the reference direction, at a position T03 where the axial center S01 of the application roll 72 and the contact portion 106 contact the long surface 94b, toward the elongated member 90 via the holding member 84. As a result, even if the posture of the elongated member 90 changes, contact between the arcuate surface 106a of the contact portion 106 of the support member 102 and the long surface 94b of the elongated member 90 is maintained. Also, contact between one flat surface 108a and the other flat surface 108b of the contact portion 108 of the support member 102 and the circumferential surface 92a of the disk portion 92 of the elongated member 90 is maintained.

[0085] In this way, the posture of the support member 102 changes in accordance with the change in the posture of the elongated member 90, and the detection member 82 attached to the support member 102 via the holding member 84 is positioned on the transfer belt 50 via the elongated member 90.

[0086] 5 and 6, the detection member 82 faces the transfer belt 50 in the thickness direction of the transfer belt 50 at a portion between position T01 where the transfer belt 50 separates from the application roll 72 and position T02 where the transfer belt 50 separates from the positioning roll 64b. In other words, the detection member 82 faces the planar portion of the transfer belt 50 in the thickness direction of the transfer belt 50.

[0087] (summary) As described above, the posture of the transfer belt 50 changes in the transfer unit 32. The positioning mechanism 86 changes the posture of the detection member 82 in accordance with the change in posture of the transfer belt 50, thereby positioning the detection member 82 on the transfer belt 50. The detection member 82 faces a flat portion of the transfer belt 50 and detects the image on this flat portion of the transfer belt 50. This prevents a decrease in image detection accuracy in a configuration in which the posture of the transfer belt 50 changes, compared to when detecting an image on a curved portion of the transfer belt wound around the application roll.

[0088] Furthermore, in the transfer unit 32, the detection member 82 faces the transfer belt 50 in the thickness direction of the transfer belt 50 at a portion between position T01 where the transfer belt 50 separates from the application roll 72 and position T02 where the transfer belt 50 separates from the positioning roll 64b. This makes it possible to reduce the size of the transfer unit 32 in the device width direction, for example, compared to a case where the detection member faces the transfer belt at a portion between the positioning roll 64b and the primary transfer roll 52K.

[0089] In the transfer unit 32, the positioning mechanism 86 includes a long member 90 whose posture changes in accordance with the posture of the transfer belt 50, and a support member 102 that supports the detection member 82 and whose posture changes in accordance with the posture of the long member 90. In this way, the posture of the detection member 82 changes without detecting the posture change of the transfer belt 50.

[0090] Furthermore, in the transfer unit 32, a biasing member 110 biases the support member 120 toward the elongated member 90. The contact portion 106 of the support member 102 contacts the elongated surface 94b of the elongated member 90, and the contact portion 108 of the support member 102 contacts the circumferential surface 92a of the disk portion 92 of the elongated member 90. This stabilizes the state in which the support member 102 is in contact with the elongated member 90, even if the posture of the elongated member 90 changes, compared to when the support member is brought into contact with the elongated member by magnetic force.

[0091] Furthermore, in the transfer unit 32, the contact portion 80 is formed with an arc surface 106a that comes into contact with the long surface 94b of the long member 90 when viewed from the depth direction of the device. This makes it possible to prevent a decrease in the positioning accuracy of the detection member 82 on the transfer belt 50 even when the posture of the long member 90 changes, compared to when the portion of the contact portion that comes into contact with the long member is rectangular.

[0092] Furthermore, in the transfer unit 32, the arc surface 106a of the contact portion 106 extends in the reference direction and is in contact with the long surface 94b facing the contact portion 106. Therefore, when viewed from the depth direction of the device, a decrease in positioning accuracy is suppressed compared to when the long surface is inclined with respect to the reference direction.

[0093] Furthermore, in the transfer unit 32, the biasing member 110 biases the support member 102 in a portion between the axial center S01 of the application roll 72 and a position T03 where the contact portion 106 contacts the elongated member 90 in the reference direction, via the holding member 84. This stabilizes the state in which the support member 102 is in contact with the elongated member 90 even when the posture of the elongated member 90 changes, compared to when a portion of the support member other than between the axial center S01 and the position T03 in the reference direction is biased.

[0094] Furthermore, in the transfer unit 32, the axial center S01 of the application roll 72 is located between two points at which the contact portion 108 contacts the circumferential surface 92a in the reference direction as viewed from the depth direction of the device. This stabilizes the state in which the contact portion 108 contacts the circumferential surface 92a compared to when, in the reference direction as viewed from the depth direction of the device, the two points at which the contact portion 108 contacts the circumferential surface 92a are located on one side of the axial center S01 of the application roll.

[0095] Furthermore, in the image forming device 10, in a configuration in which the posture of the transfer belt 50 changes, the deterioration of the quality of the output image is suppressed compared to a case in which a transfer unit is provided that detects the image of the transfer belt at the curved portion wrapped around the roll.

[0096] Although the present disclosure has been described in detail with respect to a specific embodiment, it will be apparent to those skilled in the art that the present disclosure is not limited to such an embodiment, and that various other embodiments of the present disclosure are possible within the scope of the present disclosure. For example, in the above embodiment, the biasing member 110 that biases the support member 102 against the elongated member 90 is a compression coil spring, but it may also be a tension coil spring, a torsion spring, or the like. In the case of a tension coil spring, one end of the coil may be located inside the transfer belt 50 when viewed from the depth direction of the device.

[0097] Furthermore, in the above embodiment, the elongated member 90 is rotatably supported by the application roll 72, but the elongated member 90 may be rotatably supported by the positioning roll 64b.

[0098] In the above embodiment, the color mode and the black mode are switched, but other modes may be used as long as the posture of the transfer belt 50 is changed.

[0099] Although not specifically mentioned in the above embodiment, the arcuate surface 106a formed on the contact portion 106 may be a convex curved surface, or a V-shape whose apex contacts the elongated surface 94b.

[0100] In the above embodiment, the contact portion 106 is formed with the arcuate surface 106a that comes into contact with the long surface 94b, but the arcuate surface may not be formed. In this case, the effect achieved by forming the arcuate surface is not achieved.

[0101] In the above embodiment, the long surface 94b extends in the reference direction, but the long surface may be inclined relative to the reference direction. In this case, the effect achieved by the long surface 94b extending in the reference direction is not achieved.

[0102] In the above embodiment, the posture of the support member 102 changes in accordance with the posture of the long member 90, but the posture of the support member may be changed in accordance with the posture of the transfer belt by bringing the support member into contact with the end of the transfer belt. In this case, the effect achieved by changing the posture of the support member 102 in accordance with the posture of the long member 90 is not achieved. [Explanation of symbols]

[0103] 10 Image forming device 30 Toner image forming unit (an example of an image forming unit) 32 Transfer unit (an example of a transfer device) 40 Image holder 50 Transfer belt (an example of an endless member) 52 Primary transfer roll (an example of a primary transfer member) 54 Secondary transfer roll (an example of a secondary transfer member) 60 Contact and separation member 64b Positioning roll (an example of an upstream roll) 72 Grant Roles 82 Detection member 86 Positioning mechanism 90 Long members 92 Disc Club 92a Circumferential surface 94 Long section 94b long surface 102 Support member 106 Contact part 106a Arc surface 108 Contact part (an example of another contact part) 110 biasing member

Claims

1. an endless member that rotates endlessly; primary transfer members, each disposed on an opposite side of the endless member with respect to a plurality of image carriers arranged in a circumferential direction of the endless member, for transferring an image held on the image carrier to the endless member; a secondary transfer member that transfers the image transferred to the endless member onto a recording medium; an applying roll around which the endless member is wound, the applying roll being disposed downstream of all of the primary transfer members and upstream of the secondary transfer members in the circumferential direction, and applying tension to the endless member by biasing the endless member from an inner peripheral surface thereof; an upstream roll around which the endless member is wound, the upstream roll being disposed downstream of all of the primary transfer members and upstream of the application roll in the circumferential direction; a contacting / separating member that moves at least some of the plurality of primary transfer members to contact and separate the endless member and the image carrier, thereby changing the attitude of the endless member; a detection member that faces the endless member in a portion between the upstream roll and the application roll and detects an image transferred to the endless member; a positioning mechanism that changes the posture of the detection member in accordance with a change in posture of the endless member to position the detection member on the endless member, and that includes: a long member stretched between a shaft of the application roll and a shaft of the upstream roll; and a support member that supports the detection member and whose posture changes in accordance with a change in posture of the long member, The elongated member has a disk portion formed thereon, the disk portion being centered on the axis of the application roll, the support member is formed with a contact portion that contacts the elongated member and another contact portion that contacts the circumferential surface of the disk portion from at least two directions, The transfer device includes a biasing member that biases the support member against the elongated member.

2. The contact portion has an arcuate surface that comes into contact with the elongated member when viewed in the axial direction of the application roll. The transfer device according to claim 1 .

3. the elongated member has a long surface that extends along a reference direction from an axial center of the application roll toward an axial center of the upstream roll when viewed from the axial direction and faces the contact portion, The arcuate surface is in contact with the elongated surface. The transfer device according to claim 2 .

4. When viewed from the axial direction of the application roll, in a reference direction from the axial center of the application roll toward the axial center of the upstream roll, the urging member urges the support member at a portion between the axial center of the application roll and a position where the contact portion contacts the elongated member. The transfer device according to any one of claims 1 to 3.

5. the other contact portion is in contact with the circumferential surface at two points spaced apart in the circumferential direction, When viewed from the axial direction, in the reference direction, the axial center of the application roll is located between two points where the other contact portion contacts the circumferential surface. The transfer device according to claim 4 .

6. an image forming unit that forms an image; a transfer device according to any one of claims 1 to 5, which transfers an image formed by the image forming unit onto a recording medium; An image forming apparatus comprising:

Images