Intermediate transfer unit and image forming apparatus

Abstract

To prevent a load in an axial direction acting on contact and separation roller support members and a movement in the axial direction of the contact and separation roller support members, and thereby prevent a shift in alignment between the left and right of a contact and separation roller.SOLUTION: An intermediate transfer unit comprises a contact and separation mechanism that, when a color image is output, moves a contact and separation roller to a contact position, brings a plurality of primary transfer rollers into contact with image carriers with an intermediate transfer body therebetween, and when a monochrome image is output, moves the contact and separation roller to a separation position, and separates the primary transfer rollers other than one of the plurality of primary transfer rollers from the intermediate transfer body and image carriers. The contact and separation mechanism has contact and separation roller support members that rotatably support both ends of a shaft of the contact and separation roller, an intermediate shaft that rotatably supports the contact and separation roller support members, frame members that support the intermediate shaft, and contact and separation roller pressing means that are each provided in the frame member and each press the contact and separation roller support member according to displacement of the contact and separation roller support member. The contact and separation roller pressing means urge the contact and separation roller to the center in the axial direction through the contact and separation roller support members.SELECTED DRAWING: Figure 11

Description

[Technical Field]

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

[0002] A tandem color image forming apparatus using an intermediate transfer method is known, which includes an intermediate transfer body, which is a belt member supported by multiple tension rollers, and multiple photosensitive bodies arranged in a row so as to contact and face the intermediate transfer body. In this apparatus, toner images of each color formed on each photosensitive body are transferred onto the endlessly moving intermediate transfer body in a superimposed manner (primary transfer), and the toner images on the intermediate transfer body are then transferred collectively onto a transfer material (secondary transfer), thereby forming a color image on the transfer material.

[0003] Such an image forming apparatus has a contact / separation mechanism that separates the color transfer rollers from the intermediate transfer body when outputting a monochrome image, and then, when outputting a color image, largely deflects the belt member with a contact / separation roller (backup roller) to bring the color transfer rollers into contact with the intermediate transfer body. This prevents unused photoconductors from coming into contact with the intermediate transfer body, thereby preventing unnecessary deterioration of them (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] The contact-separation roller receives a load (thrust load) in the axial direction due to the belt deviation caused by belt conveyance during color image output. The bearings (contact-separation roller support members) that support the contact-separation roller receive this load and are worn (wear), causing one side of the contact-separation roller support member to deviate from its specified position (target position), resulting in a problem of misalignment between the left and right contact-separation rollers.

[0005] In response to this, conventional intermediate transfer units including the above configuration have been devised to keep the belt misalignment within a target range by providing a belt misalignment adjustment roller (tension roller) (see, for example, Patent Document 2). However, the thrust load acting on the contact / separation roller varies depending on the machine, and wear occurs over time, which can lead to misalignment of the left and right contact / separation rollers.

[0006] If misalignment occurs between the left and right contact / separation rollers and the parallelism (parallelism in the axial direction) between the contact / separation rollers and the belt deviation adjustment roller located upstream of them deteriorates, the belt member may move outside the target range, which may lead to problems such as belt tearing.

[0007] Therefore, an object of the present invention is to provide an intermediate transfer unit that suppresses the axial load acting on the contact / separation roller support member and the axial movement of the contact / separation roller support member, thereby suppressing misalignment between the left and right contact / separation rollers. [Means for solving the problem]

[0008] The above problem is solved by a method for outputting a monochrome image, comprising: a plurality of image carriers that carry toner images; a rotatable belt-like intermediate transfer body; a plurality of primary transfer rollers that are arranged corresponding to the plurality of image carriers and that transfer the toner images from the plurality of image carriers to the intermediate transfer body; a method for outputting a monochrome image, wherein a contact / separation roller that contacts the intermediate transfer body is moved to a contact position, and the plurality of primary transfer rollers are brought into contact with the plurality of image carriers via the intermediate transfer body; and a method for outputting a monochrome image, wherein a contact / separation roller is moved to a separation position, and the other primary transfer rollers except one of the plurality of primary transfer rollers are brought into contact with the intermediate transfer body and the plurality of primary transfer rollers. The aforementioned problems are solved by an intermediate transfer unit including a contact / separation mechanism for separating the contact / separation roller from a number of image carriers, the contact / separation mechanism including a contact / separation roller support member for rotatably supporting both end shafts of the contact / separation roller, an intermediate shaft for rotatably supporting the contact / separation roller support member, a frame member for supporting the intermediate shaft, and a contact / separation roller pressing means provided on the frame member for pressing the contact / separation roller support member in accordance with displacement of the contact / separation roller support member, the contact / separation roller pressing means being configured to urge the contact / separation roller toward the center in the axial direction via the contact / separation roller support member. [Effects of the Invention]

[0009] In the intermediate transfer unit of the present invention, the contact / separation roller support member is pressed by the contact / separation roller pressing means provided on the frame member, thereby suppressing the axial load acting on the contact / separation roller support member and the axial movement of the contact / separation roller support member, and suppressing misalignment between the left and right contact / separation rollers. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of an intermediate transfer unit according to an embodiment of the present invention. [Figure 3] 3A and 3B are schematic diagrams illustrating the configuration of the intermediate transfer unit illustrated in FIG. 2 when a color image is output and when a monochrome image is output. [Figure 4]1A and 1B are schematic diagrams of the contact / separation mechanism as seen from the front, where (a) shows the state when a color image is output, and (b) shows the state when a monochrome image is output. [Figure 5] FIG. 2 is an enlarged schematic diagram showing a contact / separation mechanism around a contact / separation roller. [Figure 6] FIG. 6 is a cross-sectional view of the contact / separation mechanism of FIG. 5. [Figure 7] 3 is a schematic diagram illustrating a load acting on a contact / separation roller when a color image is output in the intermediate transfer unit illustrated in FIG. 2. FIG. [Figure 8] 1A and 1B are schematic diagrams of a contact / separation mechanism that is subjected to a thrust load, in which FIG. 1A shows a state in which one side of the roller is in contact with the other side, and FIG. 1B shows a state in which the contact / separation roller is displaced due to wear over time. [Figure 9] 10 is a schematic configuration diagram of a contact / separation mechanism seen from the front, in which left and right alignment deviations occur in the contact / separation rollers; FIG. [Figure 10] 10 is a schematic configuration diagram of the contact / separation mechanism shown in FIG. 9 as viewed from above. FIG. [Figure 11] FIG. 2 is a schematic diagram illustrating the configuration of an intermediate transfer unit according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. The image forming apparatus (color printer 1) uses an electrophotographic process and is a quadruple tandem intermediate transfer system that can selectively form color images or monochrome images using toner as developers of four colors: yellow, magenta, cyan, and black.

[0012] In the drawings, Y, M, C, and K are suffixes given to components related to the colors yellow, magenta, cyan, and black, and may be omitted.

[0013] The color printer 1 has a plurality of new toner storage sections (developer storage containers) 19, each containing four different color new toners, located at the top of the front side of the device body 2, which is the housing. Approximately in the center of the device body 2 are arranged four process cartridge units 3Y, 3M, 3C, and 3K, which serve as image forming sections that form single-color toner images from the four color toners, and an intermediate transfer unit 4 equipped with an intermediate transfer body (image carrier) onto which the toner images of each color are transferred. This intermediate transfer unit 4 is the transfer device (transfer unit) of the present invention.

[0014] The process cartridge units 3Y, 3M, 3C, and 3K are disposed below the intermediate transfer unit 4. An optical unit 5 serving as an exposure means is disposed below the process cartridge units 3Y, 3M, 3C, and 3K.

[0015] The process cartridge units 3Y, 3M, 3C, and 3K are equipped with drum-shaped photoreceptors 30Y, 30M, 30C, and 30K as image carriers on which electrostatic latent images are formed by being scanned with exposure light irradiated from the optical unit 5. The process cartridge units 3Y, 3M, 3C, and 3K are equipped with charging devices 31Y, 31M, 31C, and 31K, developing devices 32Y, 32M, 32C, and 32K, cleaning devices 33Y, 33M, 33C, and 33K, and well-known static eliminators, around the photoreceptors 30Y, 30M, 30C, and 30K.

[0016] The process cartridge units 3Y, 3M, 3C, and 3K are well-known devices that perform an electrophotographic process to form and carry single-color toner images on the photoreceptors 30Y, 30M, 30C, and 30K, respectively. In other words, the photoreceptors 30Y, 30M, 30C, and 30K are multiple image carriers that can carry toner images of each color.

[0017] The intermediate transfer unit 4 is configured such that a transfer belt 45, which is an endless belt member that serves as both an image carrier and an intermediate transfer member, is wound around a plurality of rotation support members, namely, rollers 41, 42, 43, and 44. The intermediate transfer unit 4 is configured such that the transfer belt 45 is rotated and conveyed counterclockwise in the drawing when the roller 44 is driven to rotate.

[0018] Within the inner loop of transfer belt 45, primary transfer rollers 6Y, 6M, 6C, and 6K are arranged as primary transfer members at positions facing photoreceptors 30Y, 30M, 30C, and 30K. Primary transfer rollers 6Y, 6M, 6C, and 6K press transfer belt 45 toward photoreceptors 30Y, 30M, 30C, and 30K, forming primary transfer sections 7Y, 7M, 7C, and 7K between photoreceptors 30Y, 30M, 30C, and 30K and transfer belt 45 for transferring the toner images on each photoreceptor to transfer belt 45. In other words, transfer belt 45 is a belt-like transfer member onto which the toner images are transferred.

[0019] Color printer 1 (intermediate transfer unit 4) is provided with a sensor facing member 46 arranged within the inner loop of transfer belt 45 to stabilize the position of the surface that serves as a detection surface for detecting the toner image on transfer belt 45. Also, it is provided with a pressing roller 47 as a pressing member that is arranged outside transfer belt 45, adjacent to toner image detection sensor 50, and is movable toward and away from the surface of transfer belt 45.

[0020] A transfer bias for primary transfer is supplied to primary transfer units 7Y, 7M, 7C, and 7K. A secondary transfer unit 8 is formed downstream of primary transfer units 7Y, 7M, 7C, and 7K in the belt conveyance direction. Secondary transfer unit 8 is formed between transfer belt 45 and a secondary transfer roller 9, which serves as a secondary transfer member and is disposed opposite roller 44 and in contact with transfer belt 45. A transfer bias for secondary transfer is supplied to secondary transfer unit 8.

[0021] A plurality of trays 10 containing recording materials P are provided below the optical unit 5. The recording materials P contained in the trays 10 are separated into individual sheets from the trays 10 by a group of rollers 11 that feeds and separates the sheets, and are transported toward the secondary transfer unit 8.

[0022] At the secondary transfer portion 8, the toner images transferred to the transfer belt 45 at the primary transfer portions 7Y, 7M, 7C, and 7K are transferred onto the recording material P. The recording material P onto which the toner images have been transferred is transported to a fixing device 12 that is arranged downstream of the secondary transfer portion 8 in the recording material transport direction.

[0023] The fixing device 12 applies heat and pressure to the recording material P to fix the toner image on the recording material P, and then conveys the recording material P toward the discharge outlet 13. The recording material P conveyed to the discharge outlet 13 is discharged by a pair of rollers 15 onto a discharge tray 14 formed on the top of the device main body 2 and stacked thereon.

[0024] After the transfer of the toner image has been completed, the transfer belt 45 is cleaned by the belt cleaning means 16, which sandwiches the transfer belt 45 between cleaning members such as blades and rollers, to remove any remaining toner and paper dust.

[0025] In the color printer 1 according to this embodiment, when the color of the image to be formed is full color, all of the photoconductors 30Y, 30M, 30C, and 30K are brought into contact with the image bearing surface (transfer surface) of the transfer belt 45 to transfer a color toner image (color mode). In addition, when the image is black only, the photoconductors 30Y, 30M, and 30C other than the black one are separated from the surface of the transfer belt 45, and only their surfaces are brought into contact with the photoconductor 30K to transfer a monochrome toner image (monochrome mode). In this way, these image modes are switchable.

[0026] Fig. 2 is a schematic diagram of an intermediate transfer unit according to one embodiment of the present invention, in which the same components as those in Fig. 1 are designated by the same reference numerals and detailed description thereof will be omitted.

[0027] Roller 44 is a drive roller and functions as a repulsive roller. Roller 41 is slidably supported by a side plate and is a tension roller (tensioning member) that applies tension to transfer belt 45 from the inside to the outside by spring 48 (stretching transfer belt 45). Roller 42 is a contact / separation roller that functions as a backup roller. And roller 43 constitutes an entrance roller for secondary transfer unit 8.

[0028] 2, the tension roller 41 is located upstream of the contact / separation roller 42. Alternatively, the tension roller 41 may be located downstream of the contact / separation roller 42.

[0029] Fig. 3 is a schematic diagram showing the state of the intermediate transfer unit shown in Fig. 2 when outputting a color image and when outputting a monochrome image. In Fig. 3, the roller group drawn with solid lines (tension roller 41, contact / separation roller 42, primary transfer rollers 6Y, 6M, 6C) is arranged when outputting a color image, and the same roller group drawn with dashed lines is arranged when outputting a monochrome image.

[0030] When outputting a color image, the intermediate transfer unit 4 according to this embodiment brings all of the primary transfer rollers 6Y, 6M, 6C, and 6K into contact with the rear surface of the transfer belt 45. That is, all of the photoconductors 30Y, 30M, 30C, and 30K are brought into contact with the surface of the transfer belt 45 that will become the image bearing surface (transfer surface), and a color toner image is transferred.

[0031] On the other hand, when outputting a monochrome image, the primary transfer rollers 6Y, 6M, and 6C other than black (K) are separated from the transfer belt 45. That is, only the photosensitive element 30K is brought into contact with the surface of the transfer belt 45 to transfer the monochrome toner image.

[0032] When switching from monochrome image output to color image output, the contact / separation roller 42 bends the transfer belt 45 and adjusts the position of the intermediate transfer belt 45 relative to the plurality of primary transfer rollers 6Y, 6M, and 6C.

[0033] Next, a contact / separation mechanism that moves the roller groups (contact / separation roller 42, primary transfer rollers 6Y, 6M, 6C) when outputting a color image and when outputting a monochrome image will be described.

[0034] 4 is a schematic diagram of the contact / separation mechanism as seen from the front, where (a) shows the state when a color image is output and (b) shows the state when a monochrome image is output. When a color image or monochrome image is output, the contact / separation mechanism 52 has the role of separating or contacting the contact / separation roller 42 with the slider 70 and separating or contacting the primary transfer rollers 6Y, 6M, and 6C with the transfer belt 45, thereby switching the trajectory of the transfer belt 45.

[0035] 4, the contact / separation mechanism 52 includes a frame member (not shown) that is a structural body, a slider 70 that is movably supported by the frame member, and a cam member 72 that drives the slider 70 in the horizontal direction. It also includes a contact / separation roller support member 54 that rotatably supports both end shafts of the contact / separation roller 42, and primary transfer roller support members 74Y, 74M, and 74C that rotatably support both end shafts of the primary transfer rollers 6Y, 6M, and 6C, respectively.

[0036] The cam member 72, the contact / separation roller support member 54, and the primary transfer roller support members 74Y, 74M, and 74C are rotatably supported by a frame member. The cam member 72 is rotationally driven by a drive device.

[0037] The slider 70 is moved and positioned at two predetermined positions by a cam member 72. Depending on the positions of the slider 70, the contact / separation roller 42 and the primary transfer rollers 6Y, 6M, and 6C are positioned at the output positions of a color or monochrome image.

[0038] When a color image is output (FIG. 4(a)), the slider 70 moves to the right in the figure, causing the abutting portion 70a of the slider 70 to come into contact with and press the positioning portion 54a of the contact / separation roller support member 54. The contact / separation roller support member 54 rotates counterclockwise, allowing the contact / separation roller 42 to significantly bend the transfer belt 45.

[0039] At the same time, the primary transfer rollers 6Y, 6M, and 6C are urged by the springs 76Y, 76M, and 76C, respectively, and come into contact with the transfer belt 45. This position of the contact / separation roller 42 is called the contact position.

[0040] On the other hand, when a monochrome image is output (FIG. 4(b)), the slider 70 moves leftward in the figure, causing the abutting portion 70a of the slider 70 to move away from the positioning portion 54a of the contact / separation roller support member 54. The contact / separation roller support member 54 rotates clockwise, moving the trajectory of the transfer belt 45 from the position (broken line) when a color image is output to the position (solid line) when a monochrome image is output.

[0041] At the same time, each of the primary transfer roller support members 74Y, 74M, and 74C rotates clockwise due to the pressure of the slider 70, and the primary transfer rollers 6Y, 6M, and 6C are separated from the transfer belt 45. This position of the contact / separation roller 42 is called the separation position.

[0042] FIG. 5 is an enlarged schematic diagram showing the contact / separation mechanism around the contact / separation roller, and FIG. 6 is a cross-sectional diagram of the same mechanism.

[0043] 5 and 6, the contact / separation mechanism 52 includes a contact / separation roller support member 54 that rotatably supports both end shafts of the contact / separation roller 42, an intermediate shaft 56 that rotatably supports the contact / separation roller support member 54, and a frame member 58 that supports the intermediate shaft 56. Also, as shown in FIG. 6, the contact / separation roller support member 54 has a positioning portion 54a that comes into contact with an abutment portion 70a of the slider 70.

[0044] 5, when the slider 70 (abutment portion 70a) urges the positioning portion 54a to the right in the figure, the contact / separation roller support member 54 rotates counterclockwise around the intermediate shaft 56, and the contact / separation roller 42 moves to the contact position. Therefore, the contact / separation roller 42 can significantly bend the transfer belt 45 (see FIG. 4(a)).

[0045] On the other hand, when the slider 70 releases the biasing force of the positioning portion 54a, the contact / separation roller support member 54 rotates clockwise around the intermediate shaft 56, and therefore the contact / separation roller 42 moves to the separation position (see FIG. 4(b)).

[0046] Next, the problem to be solved by the present invention will be described in detail.

[0047] Fig. 7 is a schematic diagram showing the load acting on the contact / separation roller when a color image is output in the intermediate transfer unit shown in Fig. 2. When a color image is output, the contact / separation roller 42 moves from the position shown by the dashed line to the position shown by the solid line, causing the transfer belt 45 to bend significantly, and therefore the load received from the transfer belt 45 also increases. Therefore, when the transfer belt 45 shifts to one side in the axial direction of the contact / separation roller 42 (belt shift), a thrust load (a force that moves the contact / separation roller 42 in the axial direction) acts on the contact / separation roller 42 in accordance with the shift.

[0048] FIG. 8 is a schematic diagram of the contact / separation mechanism under thrust load, where (a) shows a state where one-sided contact occurs, and (b) shows a state where the contact / separation roller has shifted in position due to wear over time.

[0049] When a thrust load acts on the contact / separation roller 42, the rotating shaft of the contact / separation roller 42 is pressed into the bearing portion of the contact / separation roller support member 54. This causes uneven contact between the rotating shaft of the contact / separation roller 42 and the bearing portion of the contact / separation roller support member 54 (area A surrounded by a dotted circle). Similarly, uneven contact occurs between the intermediate shaft 56 and the bearing portion of the contact / separation roller support member 54 that supports the intermediate shaft 56 (area B surrounded by a dotted circle).

[0050] As this uneven contact continues over time, wear (abrasion) progresses, and the contact / separation roller 42 moves from its initial position (target position) shown by the dashed line in FIG. 8(b) to a position deviated from the target position shown by the solid line, resulting in misalignment of the contact / separation roller 42 on the left and right.

[0051] 9 is a schematic diagram of the contact / separation mechanism as seen from the front, showing misalignment of the contact / separation roller 42. The contact / separation roller 42 has moved from its initial position (target position) indicated by the solid line to a position deviated from the target position indicated by the dashed line.

[0052] 10 is a schematic diagram of the contact / separation mechanism shown in FIG. 9, seen from above. The initial position (target position) of the contact / separation roller 42, indicated by the solid line, moves to the position indicated by the dashed line due to misalignment of one of the contact / separation rollers 42. In this case, the axial parallelism with the tension roller 41 deteriorates, and the transfer belt 45 moves outside the target range. In this case, an unexpected load acts on the transfer belt 45, which may, in the worst case, result in belt tearing.

[0053] Below, we will explain the intermediate transfer unit (contact / separation mechanism) that suppresses the axial load acting on the contact / separation roller support member 54 and the axial movement of the contact / separation roller support member 54, and suppresses left and right alignment deviation of the contact / separation roller 42.

[0054] Fig. 11 is a cross-sectional view of the structure of a contact / separation mechanism according to one embodiment of the present invention, in which the same components as those in Fig. 6 are given the same reference numerals and detailed description thereof will be omitted.

[0055] The contact / separation mechanism 52a of this embodiment is provided on the frame member 58 and has contact / separation roller pressing means 60 that presses the contact / separation roller support member 54 in response to displacement of the contact / separation roller support member 54. Specifically, the contact / separation roller pressing means 60 has one end that is provided on the frame member 58 and the other end that presses the contact / separation roller support member 54.

[0056] The contact / separation mechanism 52a of this embodiment has one end attached to a frame member 58 and the other end having contact / separation roller pressing means 60 that presses the contact / separation roller support member 54. This contact / separation roller pressing means 60 has a spring 62 that is an elastic member, and presses the contact / separation roller support member 54 when it receives a load from the contact / separation roller support member 54. In other words, the contact / separation roller pressing means 60 urges the contact / separation roller 42 toward its axial center via the contact / separation roller support member 54.

[0057] With this configuration, when (the rotation shaft of) the contact / separation roller 42 is pressed into the bearing portion of the contact / separation roller support member 54, causing the contact / separation roller support member 54 to move axially, the contact / separation roller pressing means 60 presses the contact / separation roller support member 54. In other words, the contact / separation roller pressing means 60 urges the contact / separation roller 42 toward its axial center via the contact / separation roller support member 54.

[0058] Therefore, misalignment between the left and right of the contact / separation roller 42 can be suppressed, and deterioration in parallelism between the contact / separation roller 42 and the tension roller 41 located upstream thereof can be suppressed.

[0059] Furthermore, even if the contact / separation roller support member 54 is scraped (worn) over time, the pressing force (urging force) of the contact / separation roller pressing means 60 can prevent misalignment of the contact / separation roller 42 from occurring between the left and right.

[0060] Furthermore, since the contact / separation roller pressing means 60 is provided (supported) on the frame member 58 that supports the intermediate shaft 56, uneven contact of the contact / separation roller support member 54 with the intermediate shaft 56 can also be prevented at the same time.

[0061] The contact / separation roller pressing means 60 has a spring 62 that generates a repulsive force (urging force) in proportion to the displacement, and therefore does not urge the contact / separation roller support member 54 unless the contact / separation roller 42 moves in the axial direction.

[0062] Furthermore, if the contact / separation roller pressing means 60 is disposed at both ends of the contact / separation roller 42, it is possible to deal with the deviation of the contact / separation roller 42 on either side, which is advantageous.

[0063] The present invention has been described in detail above using the embodiment. This embodiment is merely an example, and various modifications can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0064] 1 color printer 2. Device body 3C, 3K, 3M, 3Y process cartridge unit 4 Intermediate transfer unit 5 Optical unit 6C, 6K, 6M, 6Y Primary transfer roller 7C, 7K, 7M, 7Y Primary transfer section 8 Secondary transfer section 9 Secondary transfer roller 10 trays 11 Roller Group 12 Fixing device 13 Outlet 14 Output tray 15 Laura Vs. 16 Belt cleaning means 30C, 30K, 30M, 30Y photoconductor 31C, 31K, 31M, 31Y Charging device 32C, 32K, 32M, 32Y developing device 33C, 33K, 33M, 33Y cleaning device 41 Tension roller 42 Contact roller (backup roller) 43 Entrance Roller 44 Drive (repulsive) roller 45 Transfer belt 46 Sensor facing member 47 Pressing roller 48, 62, 76C, 76M, 76Y springs 50 Toner image detection sensor 52, 52a Approach / separation mechanism 54 Contact and separation roller support member 54a Positioning part 56 Intermediate shaft 58 Frame members 60 Contact and separation roller pressing means 70 slider 70a butt section 72 Cam member 74C, 74M, 74Y Primary transfer roller support member P recording material [Prior art documents] [Patent documents]

[0065] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-62642 [Patent Document 2] Japanese Patent Application Publication No. 2018-112623

Claims

1. a plurality of image carriers that carry toner images; a rotatable belt-like intermediate transfer body; a plurality of primary transfer rollers arranged corresponding to the plurality of image carriers, respectively, for transferring the toner image from the plurality of image carriers to the intermediate transfer member; When a color image is output, a contact roller in contact with the intermediate transfer body is moved to a contact position, and the plurality of primary transfer rollers are brought into contact with the plurality of image carriers via the intermediate transfer body, respectively; a contact / separation mechanism that moves the contact / separation roller to a separation position when outputting a monochrome image, and separates all but one of the plurality of primary transfer rollers from the intermediate transfer body and the plurality of image carriers; In an intermediate transfer unit comprising: The contact / separation mechanism includes: a contact / separation roller support member that rotatably supports both end shafts of the contact / separation roller; an intermediate shaft that rotatably supports the contact / separation roller support member; a frame member supporting the intermediate shaft; a contact / separation roller pressing means provided on the frame member for pressing the contact / separation roller support member in response to displacement of the contact / separation roller support member, The intermediate transfer unit is characterized in that the contact / separation roller pressing means urges the contact / separation roller toward the center in the axial direction via the contact / separation roller supporting member.

2. 2. The intermediate transfer unit according to claim 1, wherein the contact / separation roller pressing means are disposed at both ends of the contact / separation roller support member in the axial direction of the contact / separation roller.

3. The contact / separation roller pressing means has an elastic member, 3. The intermediate transfer unit according to claim 1, wherein one end of the elastic member is attached to the frame member, and the other end presses against the contact / separation roller support member.

4. 4. The intermediate transfer unit according to claim 1, further comprising a tension roller that applies tension to the intermediate transfer body, the tension roller being disposed upstream or downstream of the contact / separation roller.

5. An image forming apparatus comprising the intermediate transfer unit according to claim 1 .

Images