Image forming apparatus

Abstract

To provide an image forming apparatus capable of preventing an operation omission by a user.SOLUTION: An image forming apparatus comprises a plurality of photoconductor drums 3 and an intermediate transfer unit 6 that is attachable to and detachable from an apparatus body by being inserted and removed in an insertion / removal direction L. The intermediate transfer unit 6 includes an intermediate transfer belt 61, a color transfer roller 66 and a monochrome transfer roller 65 arranged along an inner circumference of the intermediate transfer belt 61, a lever 20 operated by a user, and a monochrome swing mechanism that swings the monochrome transfer roller 65. The monochrome swing mechanism switches the intermediate transfer belt 61 between a monochrome image forming state and a separated state when the lever 20 is operated. The apparatus body is provided with a restriction part 101 that restricts removal of the intermediate transfer unit 6 when in the monochrome image forming state.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus including an intermediate transfer unit that is detachable from the apparatus main body. [Background technology]

[0002] In an image forming apparatus having a plurality of photosensitive members (e.g., photosensitive drums) and an intermediate transfer belt, such as a tandem color (multicolor) image forming apparatus, the toner images formed on each photosensitive member are transferred (primary transfer) onto the rotating intermediate transfer belt in order from the upstream side to the downstream side. Also, in a color image forming apparatus, when forming a monochrome (single-color) image, only one photosensitive member is brought into contact with the intermediate transfer belt, and the other photosensitive members are separated from the intermediate transfer belt.

[0003] Incidentally, image forming devices employ a configuration having an internal device such as an intermediate transfer unit that combines some components including an intermediate transfer belt, and the internal device can be removed from the device body when maintenance work is performed on the internal device (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-167788 [Patent Document 2] Japanese Patent Publication No. 2020-101591 Summary of the Invention [Problem to be solved by the invention]

[0005] A conventional image forming apparatus includes a device housing, a plurality of photosensitive drums detachably arranged in parallel to the device housing, a transfer belt that is looped around a plurality of rollers and can change its belt position between a first position in which it contacts all of the photosensitive drums, a second position in which it contacts only one of the photosensitive drums, and a third position in which it is not in contact with any of the photosensitive drums, a belt displacement control mechanism that controls the change in belt position of the transfer belt, and a transfer belt unit that is detachably attached to the device housing, an opening / closing member that is provided in the device housing and opens and closes when the photosensitive drums are attached to or detached from the device housing, a lock lever that locks the opening / closing member, and a linkage mechanism that engages with the lock lever on one side and with the belt displacement control mechanism on the other side, and controls the belt displacement control mechanism to change the position of the transfer belt to the third position in conjunction with the release of the lock lever.

[0006] In addition, conventional image forming devices have a photosensitive member, a plurality of process units each including a charger and a developer for forming a toner image on the photosensitive member, a transfer unit including an endlessly wound transfer belt arranged to face the plurality of process units, a tension applying member that applies tension to the transfer belt, a position switching member that can contact and separate from the transfer belt to switch the position of the transfer belt relative to the photosensitive member, a support member that is provided near the end of the transfer belt along the longitudinal direction of the photosensitive member and can move in conjunction with the position switching member, an operating member for moving the position switching member, and a control unit that causes the support member to support the transfer belt when the position switching member is separated from the transfer belt in conjunction with the movement operation of the operating member.

[0007] The image forming device described above is provided with operating members and lock levers that are operated when separating the photosensitive element and the transfer belt, but if the transfer unit or the like is removed without operating these, there is a risk that the photosensitive element and the transfer belt will rub against each other, damaging both.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an image forming apparatus that can prevent a user from forgetting to operate the intermediate transfer unit by restricting removal of the intermediate transfer unit. [Means for solving the problem]

[0009] The image forming apparatus according to the present disclosure is an image forming apparatus comprising a plurality of photosensitive bodies, an apparatus main body, and an intermediate transfer unit that can be attached to and detached from the apparatus main body by inserting and removing it in an insertion / removal direction, wherein the intermediate transfer unit comprises an intermediate transfer belt stretched over a plurality of rollers, a color transfer roller and a monochrome transfer roller that are arranged along the inner circumference of the intermediate transfer belt and that, when oscillated, press the intermediate transfer belt to abut against the corresponding photosensitive bodies, a lever operated by a user, and a monochrome oscillating mechanism that oscillates the monochrome transfer roller, wherein the intermediate transfer belt is switchable between a color image forming state in which it abuts against all of the corresponding photosensitive bodies, a monochrome image forming state in which it abuts against the photosensitive bodies corresponding to the monochrome transfer rollers, and a separated state in which it is separated from all of the photosensitive bodies, and the monochrome oscillating mechanism switches between the monochrome image forming state and the separated state when the lever is operated, and wherein the apparatus main body is provided with a regulating section that regulates removal of the intermediate transfer unit when it is in the monochrome image forming state.

[0010] The image forming apparatus according to the present disclosure may be provided with a color oscillation mechanism that oscillates the color transfer roller, and the color oscillation mechanism may be configured to switch to the color image forming state when forming a color image, and to switch to the monochrome image forming state when the color image formation is completed.

[0011] In the image forming device according to the present disclosure, the monochrome oscillation mechanism may have a regulated portion that faces the regulating portion in the insertion / removal direction in the monochrome image forming state, and the regulated portion may be configured to move to a position that does not overlap with the regulating portion in the insertion / removal direction when transitioning from the monochrome image forming state to the separated state.

[0012] In the image forming apparatus according to the present disclosure, the intermediate transfer unit may have a pre-transfer roller arranged along the inner circumference of the intermediate transfer belt, and the monochrome oscillation mechanism may be configured to oscillate the pre-transfer roller in conjunction with the monochrome transfer roller.

[0013] In the image forming apparatus according to the present disclosure, the lever may be configured to be operated so as to move in the insertion / removal direction.

[0014] In the image forming device according to the present disclosure, the intermediate transfer unit is provided with an opening / closing cover that opens and closes the side of the device main body that faces the insertion / removal direction, and a locking portion that locks the lever to maintain the monochrome image forming state, and the lever may be configured to interfere with the opening / closing cover when it is closed and prevent the opening / closing cover from closing when it is not locked by the locking portion. [Effects of the Invention]

[0015] According to the present disclosure, since the monochrome transfer roller is operated by the user via the lever, the restriction portion restricts removal of the intermediate transfer unit, thereby preventing the user from forgetting to operate it. This prevents the intermediate transfer belt and the photosensitive member from being damaged when the intermediate transfer unit is removed while the intermediate transfer belt is still in contact with the photosensitive member. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a perspective view showing an intermediate transfer unit. [Figure 3] FIG. 2 is a schematic side view showing a structure in the vicinity of an intermediate transfer unit. [Figure 4] 4 is an enlarged top view showing the lever and its periphery in FIG. 3. FIG. [Figure 5] FIG. 2 is a schematic side view showing the structure in the vicinity of the intermediate transfer unit in a monochrome image forming state. [Figure 6]FIG. 10 is a schematic side view showing the structure in the vicinity of the intermediate transfer unit during transition from a monochrome image forming state to a separation state. [Figure 7] FIG. 4 is a schematic side view showing a structure in the vicinity of the intermediate transfer unit in a separated state. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

[0018] FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure.

[0019] The image forming device 100 is a multifunction device having a copy function, a scanner function, a facsimile function, and a printer function, and transmits an image of a document read by the image reading device 10 to an external device, and forms an image of a document read by the image reading device 10 or an image received from an external device in color or monochrome on a recording medium such as paper.

[0020] An original document table 11 is provided above the image reading device 10, and the image reading device 10 reads an original document placed on the original document table 11 and generates image data.

[0021] The image forming apparatus 100 is provided with an optical scanning device 1, a developing device 2, a photosensitive drum 3 (an example of a photosensitive body), a drum cleaning device 4, a charger 5, an intermediate transfer belt unit 6, a secondary transfer device 13, a fixing device 7, a paper feed tray 8, and a paper output tray 9.

[0022] Image forming apparatus 100 handles image data corresponding to color images using black (K), cyan (C), magenta (M), and yellow (Y), or monochrome images using a single color (e.g., black). Image forming apparatus 100 is provided with four developing devices 2, four photosensitive drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images, and four image stations Pa, Pb, Pc, and Pd are configured corresponding to black, cyan, magenta, and yellow, respectively.

[0023] The optical scanning device 1 exposes the surface of the photosensitive drum 3 to light to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photosensitive drum 3 to form a toner image on the surface of the photosensitive drum 3. The drum cleaning device 4 removes and collects residual toner on the surface of the photosensitive drum 3. The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. Through the series of operations described above, a toner image of each color is formed on the surface of each photosensitive drum 3.

[0024] The intermediate transfer unit 6 includes an endless intermediate transfer belt 61, an intermediate transfer drive roller 62, an intermediate transfer driven roller 63, a pre-transfer roller 64, and a plurality of intermediate transfer rollers (monochrome transfer roller 65 and color transfer roller 66). Details of the intermediate transfer unit 6 will be described later with reference to FIG. 2.

[0025] The intermediate transfer belt 61 is stretched around an intermediate transfer drive roller 62 and an intermediate transfer driven roller 63, and moves in a rotation direction M. In the image forming apparatus 100, the toner images of each color formed on the surface of each photosensitive drum 3 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 61.

[0026] The intermediate transfer rollers are provided at four locations along the inner circumference of the intermediate transfer belt 61 so as to form four types of toner images corresponding to each color. The intermediate transfer rollers press the intermediate transfer belt 61 against the photosensitive drum 3, and transfer the toner images of each color formed on the surface of the photosensitive drum 3 onto the intermediate transfer belt 61 as it moves around.

[0027] Of the four image stations Pa, Pb, Pc, and Pd described above, image station Pa is located closest to intermediate transfer drive roller 62 and corresponds to black. Of the four intermediate transfer rollers, monochrome transfer roller 65 corresponds to image station Pa, and three color transfer rollers 66 correspond to image stations Pb, Pc, and Pd. Pre-transfer roller 64 is located between monochrome transfer roller 65 and intermediate transfer drive roller 62, immediately adjacent to the intermediate transfer drive roller 62 on the upstream side.

[0028] The secondary transfer device 13 sandwiches and transports paper transported through the paper transport path R in a transfer nip portion between the secondary transfer roller 13a and the intermediate transfer belt 61. When the paper passes through the transfer nip portion, the toner image on the surface of the intermediate transfer belt 61 is transferred to the paper, and the paper is transported to the fixing device 7. The secondary transfer roller 13a is disposed so as to abut against a portion of the intermediate transfer belt 61 that is stretched between the pre-transfer roller 64 and the intermediate transfer drive roller 62.

[0029] The fixing device 7 includes a fixing belt 73 stretched between a fixing roller 71 and a heating roller 72, and a pressure roller 74 that presses the fixing roller 71 via the fixing belt 73. The heating roller 72 is equipped with a heat source and heats the fixing belt 73. The fixing device 7 sandwiches a sheet of paper onto which a toner image has been transferred in the nip portion between the fixing belt 73 and the pressure roller 74, and applies heat and pressure to fix the toner image to the sheet of paper.

[0030] The paper feed tray 8 is a tray for holding recording media (paper) used for image formation, and is provided below the optical scanning device 1. The paper is pulled out from the paper feed tray 8 and transported to the paper transport path R.

[0031] Conveyance rollers 14, registration rollers 15, post-fixing conveyance rollers 16, and discharge rollers 17 are arranged on the paper conveyance path R. Conveyance rollers 14 convey paper supplied from paper feed tray 8 to registration rollers 15. Registration rollers 15 are provided between paper feed tray 8 and secondary transfer device 13, and adjust the timing of paper conveyance so that the toner image is transferred to the paper by secondary transfer device 13. For example, registration rollers 15 wait (temporarily stop) while sandwiching the paper conveyed from paper feed tray 8, and then start conveying the paper at a constant speed in synchronization with secondary transfer device 13. After passing through secondary transfer device 13 and fixing device 7, the paper is conveyed by post-fixing conveyance rollers 16 to discharge rollers 17, and is discharged to paper output tray 9 by discharge rollers 17.

[0032] In the image forming apparatus 100, the intermediate transfer unit 6 can be freely attached and detached to and from the apparatus body by inserting and removing it in an insertion / removal direction L (left-right direction in FIG. 1). In the image forming apparatus 100, an opening / closing cover 110 is provided on the side (the right side in FIG. 1) that faces the intermediate transfer unit 6 attached to the apparatus body in the insertion / removal direction L. When attaching or removing the intermediate transfer unit 6, the opening / closing cover 110 is opened by the user. For the sake of explanation below, with regard to the insertion / removal direction L, the direction in which the intermediate transfer unit 6 attached to the apparatus body is pulled out (to the right in FIG. 1) may be referred to as the removal direction L1, and the direction in which the intermediate transfer unit 6 is inserted into the apparatus body from the outside (to the left in FIG. 1) may be referred to as the insertion direction L2.

[0033] 2 is a perspective view showing the intermediate transfer unit 6. In the following, the positional relationship of the intermediate transfer unit 6 will be described based on the state where it is attached to the apparatus main body.

[0034] The intermediate transfer unit 6 has a pair of unit frames 30 that support both end portions of the intermediate transfer drive roller 62 and the intermediate transfer driven roller 63. In the intermediate transfer unit 6, the intermediate transfer drive roller 62 is disposed at the end portion on the removal direction L1 side, and the intermediate transfer driven roller 63 is disposed at the end portion on the insertion direction L2 side. Note that the intermediate transfer unit 6 may be provided with rollers other than the intermediate transfer drive roller 62 and the intermediate transfer driven roller 63, and the other rollers may be supported by the unit frames 30.

[0035] A frame holding portion 31 is provided at the end of the unit frame 30 on the removal direction L1 side, and a lever 20 is attached to the frame holding portion 31. The lever 20 is operated by the user, and a detailed structure will be described later with reference to Figures 3 and 4. A lever 20 is provided on each of the pair of unit frames 30, but both have approximately the same structure and are operated in the same way, so below, the structure of one of the levers 20 will be described and a description of the other lever 20 will be omitted.

[0036] Fig. 3 is a schematic side view showing the structure in the vicinity of the intermediate transfer unit, and Fig. 4 is an enlarged top view showing the area around the lever in Fig. 3. Note that in Fig. 3 and Fig. 4, in consideration of ease of viewing the drawings, only a portion of the image forming apparatus 100 and the intermediate transfer unit 6 is shown, and portions other than the frame holding portion 31 of the unit frame 30 and portions other than the photosensitive drum 3 of the image station are omitted.

[0037] When attached to the apparatus main body, the intermediate transfer unit 6 is located above the four image stations Pa, Pb, Pc, and Pd, and the photosensitive drums 3 at the four image stations Pa, Pb, Pc, and Pd are located below the intermediate transfer belt 61. For ease of explanation, the surface of the intermediate transfer belt 61 that faces the photosensitive drums 3 may be referred to as the lower surface below.

[0038] The intermediate transfer unit 6 is provided with a color swinging mechanism 67 that swings the three color transfer rollers 66. When the color swinging mechanism 67 receives an instruction from the control unit of the image forming apparatus 100, it swings the color transfer rollers 66 downward. When the color transfer rollers 66 swing downward, the intermediate transfer belt 61 is pressed against the color transfer rollers 66, and the lower surface side is pushed downward and spread, and comes into contact with the three photosensitive drums 3 provided below the three color transfer rollers 66. When the intermediate transfer belt 61 receives an instruction from the control unit of the image forming apparatus 100, the color swinging mechanism 67 swings the color transfer rollers 66 upward, as shown in FIG. 5, which will be described later. The color swinging mechanism 67 may also be provided with a sensor that detects whether the color transfer rollers 66 are swinging upward or downward.

[0039] The intermediate transfer unit 6 is provided with a monochrome swinging mechanism that swings the monochrome transfer roller 65, and a lever 20 that is operated by the user to operate the monochrome swinging mechanism. The monochrome swinging mechanism is made up of a first swinging member 32, a second swinging member 33, and an interlocking member 34.

[0040] The first swinging member 32 is attached to the end of the rotation shaft of the intermediate transfer drive roller 62, and rotates around the rotation shaft of the intermediate transfer drive roller 62 as a fulcrum. The first swinging member 32 is not fixed to the rotation shaft of the intermediate transfer drive roller 62, and the first swinging member 32 does not rotate even when the intermediate transfer drive roller 62 rotates to move the intermediate transfer belt 61 in a circular motion. A swinging connection part 32a, to which the tip of the lever 20 is attached, is provided at the upper end of the first swinging member 32. A hole that penetrates the swinging connection part 32a in the insertion / removal direction L is formed, and the tip of the lever 20 (thin diameter part 21) is inserted so as to pass through the hole.

[0041] An end of the pre-transfer roller 64 is rotatably supported on the lower end side of the first swinging member 32. As shown in Fig. 7, which will be described later, when the first swinging member 32 rotates, the pre-transfer roller 64 swings up and down, and Fig. 3 shows a state in which the pre-transfer roller 64 swings downward. When the pre-transfer roller 64 swings downward, the intermediate transfer belt 61 is pressed by the pre-transfer roller 64, and the lower surface side is pushed out downward.

[0042] The lower end of the first swinging member 32 is a regulated portion 32b, and when the pre-transfer roller 64 is swung downward, the regulated portion 32b is adjacent to a regulating portion 101 provided on a part of the device body in the insertion / removal direction L. The rotation range of the first swinging member 32 is set to an extent that a small gap is generated between the regulated portion 32b and the regulating portion 101 when the pre-transfer roller 64 is swung downward.

[0043] The second swinging member 33 has a frame shaft support portion 33a pivotally supported by the unit frame 30, and rotates about the frame shaft support portion 33a. An end portion of the monochrome transfer roller 65 is rotatably supported on the lower end side of the second swinging member 33. As shown in FIG. 7 (described later), when the second swinging member 33 rotates, the monochrome transfer roller 65 swings up and down, and FIG. 3 shows the state in which the monochrome transfer roller 65 swings downward. When the monochrome transfer roller 65 swings downward, the intermediate transfer belt 61 is pressed by the monochrome transfer roller 65, and the lower surface side is pushed out downward and comes into contact with the photosensitive drum 3 provided below the monochrome transfer roller 65.

[0044] One end of an interlocking member 34 is attached to the upper end of the second swinging member 33, and the other end of the interlocking member 34 is attached to the first swinging member 32. When the first swinging member 32 rotates, the second swinging member 33 is pulled by the interlocking member 34 and rotates in conjunction with the first swinging member 32.

[0045] The second oscillating member 33 may be provided with a biasing member that biases the second oscillating member 33 in the opposite direction to the pulling direction of the interlocking member 34, and when no load is applied from the interlocking member 34, the biasing member may bias the monochrome transfer roller 65 to oscillate downward.

[0046] As described above, the monochrome oscillation mechanism is not limited to a configuration including a first oscillation member 32, a second oscillation member 33, and an interlocking member 34, but may be configured to oscillate both the pre-transfer roller 64 and the monochrome transfer roller 65 in the same direction.

[0047] As described above, the tip of the lever 20 on the insertion direction L2 side is attached to the swing connection part 32a. The tip side of the lever 20 in the insertion direction L2 is formed as a small diameter part 21 that is narrower than the hole provided in the swing connection part 32a, and a ring 21a with an outer diameter larger than the hole is fitted to the tip that protrudes further back than the swing connection part 32a. As shown in FIG. 6 (described later), when the lever 20 is pulled in the removal direction L1, the ring 21a gets caught on the swing connection part 32a. A large diameter part 22 that is thicker than the hole provided in the swing connection part 32a is provided on the insertion / removal direction L side of the small diameter part 21. When the lever 20 is pushed in the insertion direction L2, the large diameter part 22 gets caught on the swing connection part 32a.

[0048] In this embodiment, the length of the small diameter portion 21 in the insertion / removal direction L is longer than the swing connection portion 32a. In the state shown in FIG. 3, the large diameter portion 22 abuts against the swing connection portion 32a, and a gap (play) is provided between the swing connection portion 32a and the ring 21a. Then, as shown in FIG. 6 (described later), when the lever 20 is pulled slightly in the removal direction L1, the ring 21a abuts against the swing connection portion 32a, which acts to rotate the first swing member 32. In this configuration in which the lever 20 is attached with a gap provided relative to the first swing member 32, the rotation range of the first swing member 32 can be adjusted to differ depending on the operating distance of the lever 20.

[0049] Lever 20 has a cylindrical shaft extending in insertion / removal direction L, and the middle portion of the shaft (large diameter portion 22) is held by frame holding portion 31. Frame holding portion 31 is configured to lock lever 20 via pin 23 provided on lever 20, and when not locked by frame holding portion 31, lever 20 can be inserted and removed in insertion / removal direction L. Furthermore, lever 20 is held by frame holding portion 31 so as to rotate about its axis, and by rotating lever 20, it can be switched between a state locked by frame holding portion 31 (locked state) and a state not locked by frame holding portion 31 (released state).

[0050] Pin 23 is a protrusion that protrudes outward from the circumferential surface of the shaft. Frame holding portion 31 holds lever 20 so as to cover the circumferential surface of the shaft, and has a groove formed therein that opens at a portion corresponding to pin 23. The groove formed in frame holding portion 31 is made up of a first locking portion 31a (an example of a locking portion), a second locking portion 31b, and a slide portion 31c.

[0051] The sliding portion 31c extends in the insertion / removal direction L. The first locking portion 31a is connected to the end of the sliding portion 31c on the insertion direction L2 side and extends around the axis. The second locking portion 31b is connected to the end of the sliding portion 31c on the removal direction L1 side and extends around the axis. The width of the first locking portion 31a and the second locking portion 31b in the insertion / removal direction L is slightly wider than the pin 23. In other words, a bracket-shaped groove extending in the insertion / removal direction L is formed in the frame holding portion 31, and when the user operates the lever 20, the pin 23 moves within the groove. Figures 3 and 4 show a state in which the pin 23 is positioned within the first locking portion 31a and is locked by the first locking portion 31a.

[0052] As described above, the lever 20 is attached to the first swinging member 32, and when the first swinging member 32 rotates, the lever 20 is pushed by the swinging connection portion 32a, applying a force that moves the lever 20 in the insertion / removal direction L. Explaining this in more detail, the intermediate transfer belt 61 has elasticity that tends to maintain a constant circumferential length, and when it is pressed and spread by the pre-transfer roller 64 and the like, a reaction force that tries to push them back is generated. As a result, a force that moves the lever 20 in the removal direction L1 is applied to the lever 20 via the first swinging member 32. At this time, if the pin 23 is positioned within the first locking portion 31a or the second locking portion 31b, the pin 23 is caught, and the lever 20 will not move in the insertion / removal direction L.

[0053] When the pin 23 is engaged with the first engagement portion 31a, the rotation range of the first swing member 32 and the second swing member 33 and the operating distance of the lever 20 are set so that the pre-transfer roller 64 and the monochrome transfer roller 65 do not simply come into contact with the inner circumference of the intermediate transfer belt 61, but also apply a small load to press the intermediate transfer belt 61.

[0054] An interfered portion 24 that protrudes outward from the circumferential surface of the shaft is provided at the end of lever 20 on the removal direction L1 side. Interfered portion 24 is a handle that the user grips when operating the lever, and is a portion that interferes with cover interference portion 110a provided on opening / closing cover 110. The relationship between interfered portion 24 and cover interference portion 110a will be described later with reference to FIG. 6.

[0055] As described above, the image forming apparatus 100 is configured to swing the pre-transfer roller 64, the monochrome transfer roller 65, and the color transfer rollers 66 up and down to appropriately move the intermediate transfer belt 61 in contact with and away from the four photosensitive drums 3. In this way, the image forming apparatus 100 can form color (multicolor) images and monochrome (single-color) images by switching the positional relationship between the intermediate transfer belt 61 and the photosensitive drums 3. FIG. 3 shows a color image forming state in which the intermediate transfer belt 61 contacts all of the corresponding photosensitive drums 3, and in the color image forming state, color images are formed. In addition, the image forming apparatus 100 can be set to a monochrome image forming state in which the intermediate transfer belt 61 contacts the photosensitive drum 3 corresponding to the monochrome transfer roller 65, as shown in FIG. 5 (described later), and in the monochrome image forming state, monochrome images are formed. Furthermore, in the image forming apparatus 100, as shown in Figure 7 described later, a separated state is set in which the intermediate transfer belt 61 is separated from all of the photosensitive drums 3, and in the separated state, the intermediate transfer unit 6 is attached and detached.

[0056] FIG. 5 is a schematic side view showing the structure in the vicinity of the intermediate transfer unit in a monochrome image forming state.

[0057] 5 shows the intermediate transfer unit 6 that has transitioned from the color image forming state shown in FIG. 3 to the monochrome image forming state. As described above, the color swing mechanism 67 swings the color transfer rollers 66 upward in response to an instruction from the control unit of the image forming apparatus 100. The portions of the intermediate transfer belt 61 that were pressed against the color transfer rollers 66 rise up so as to separate from the three corresponding photosensitive drums 3. Note that the pre-transfer roller 64 and the monochrome transfer roller 65 remain in a downward swinging state, so the intermediate transfer belt 61 is in contact with the corresponding one of the photosensitive drums 3.

[0058] In the image forming apparatus 100, the color oscillation mechanism 67 is instructed to switch to a color image formation state when a color image is formed, and switch to a monochrome image formation state when the color image formation is completed. In this way, the color oscillation mechanism 67 controls the operation of the color transfer roller 66 so that the intermediate transfer belt 61 and the photosensitive drum 3 are brought into contact with each other in accordance with the image formation, and therefore, the intermediate transfer belt 61 is prevented from being left in contact with the corresponding photosensitive drum 3.

[0059] As shown in Figure 5, in the monochrome image formation state, the regulated portion 32b is adjacent to the regulating portion 101 in the insertion / removal direction L, so when an attempt is made to pull out the intermediate transfer unit 6 itself in the removal direction L1, the regulated portion 32b gets caught on the regulating portion 101, and removal of the intermediate transfer unit 6 is restricted.

[0060] FIG. 6 is a schematic side view showing the structure in the vicinity of the intermediate transfer unit during transition from the monochrome image forming state to the separation state.

[0061] FIG. 6 shows the intermediate transfer unit 6 in the process of transitioning from the monochrome image forming state shown in FIG. 5 to the separation state by operating the lever 20. When transitioning from the monochrome image forming state to the separation state, the user rotates the lever 20 around its axis, causing the pin 23 to move from the first locking portion 31a into the slide portion 31c, transitioning the lever 20 from the locked state to the released state. In the released state, the lever 20 can be pulled in the removal direction L1, causing the pin 23 to move toward the first locking portion 31a through the slide portion 31c. The width of the slide portion 31c around the axis is approximately the same as that of the pin 23, so that when the pin 23 is positioned within the slide portion 31c, the lever 20 cannot rotate around its axis.

[0062] FIG. 6 shows the open cover 110 in the process of being closed. The two-dot chain line (path KS) in the figure indicates part of the path of the cover interference portion 110a when the cover 110 is opened or closed. By rotating the lever 20, the interfered portion 24 changes the direction in which it protrudes from the shaft and overlaps the path KS of the cover interference portion 110a. Therefore, when the lever 20 is not engaged with the first locking portion 31a, it interferes with the cover 110 being closed and prevents the cover 110 from being closed. In this way, the lever 20 interferes with the cover 110, preventing the cover 110 from being closed if the lever 20 is not operated. In this embodiment, the lower end of the cover 110 is pivotally supported on the device body, and the path KS is shown accordingly. However, this is not limited to this. The positional relationship between the interfered portion 24 and the cover interference portion 110a may be adjusted depending on the opening and closing direction of the cover 110.

[0063] FIG. 7 is a schematic side view showing the structure in the vicinity of the intermediate transfer unit in the separated state.

[0064] FIG. 7 shows the intermediate transfer unit 6 in the separated state after further operation of the lever 20 from the state shown in FIG. 6 . To transition to the separated state, the user pulls the lever 20 in the removal direction L1 until the pin 23 reaches the second locking portion 31b. The swing connection portion 32a is pressed against the ring 21a, causing the first swing member 32 to rotate and the pre-transfer roller 64 to swing upward. The second swing member 33 also rotates in conjunction with the first swing member 32, causing the monochrome transfer roller 65 to swing upward. When the transition to the separated state occurs and the pre-transfer roller 64 and the monochrome transfer roller 65 swing upward, the portions of the intermediate transfer belt 61 that were pressed against the pre-transfer roller 64 and the monochrome transfer roller 65 lift off so as to separate from the corresponding photosensitive drums 3. As a result, the intermediate transfer belt 61 is separated from all of the photosensitive drums 3. In this way, the monochrome swinging mechanism swings the pre-transfer roller 64 in conjunction with the monochrome transfer roller 65, which reduces the user's effort when inserting and removing the intermediate transfer unit 6 and prevents the pre-transfer roller 64 from becoming an obstacle.

[0065] Thereafter, the user rotates the lever 20 about the axis to transition the lever 20 to the locked state again. As with the first locking portion 31a, when the pin 23 is locked by the second locking portion 31b, the lever 20 cannot move in the insertion / removal direction L, and the intermediate transfer unit 6 remains in the separated state.

[0066] When the state is shifted from the monochrome image forming state to the separated state, the first swinging member 32 rotates, and as a result, the regulated portion 32b moves to a position where it does not overlap with the regulating portion 101 in the insertion / removal direction L. In the state shown in FIG. 7, the regulated portion 32b is positioned slightly above the regulating portion 101. In this state, the regulated portion 32b does not come into contact with the regulating portion 101, so the intermediate transfer unit 6 can be pulled out in the removal direction L1.

[0067] As described above, in this embodiment, the user operates lever 20 to switch the monochrome swing mechanism between the monochrome image forming state and the separated state. Because the monochrome transfer roller 65 is thus operated by the user via lever 20, the regulating portion 101 restricts removal of the intermediate transfer unit 6, preventing the user from forgetting to operate it. This prevents the intermediate transfer belt 61 and the photosensitive drum 3 from being damaged when the intermediate transfer unit 6 is removed while the intermediate transfer belt 61 remains in contact with the photosensitive drum 3. Furthermore, the provision of regulated portion 32b in the monochrome swing mechanism prevents objects from coming into contact with the intermediate transfer belt 61 even when an attempt is made to remove the intermediate transfer unit 6 by mistake.

[0068] As described above, the lever 20 is operated to move in the insertion / removal direction L. In other words, the direction in which the lever 20 is operated is the same as the direction in which the intermediate transfer unit 6 is inserted or removed, so the user can touch the lever 20 and the intermediate transfer unit 6 without changing their position. Furthermore, after operating the lever 20 to change the state of the intermediate transfer belt 61, the user can grasp the lever 20 and pull out the intermediate transfer unit 6 from the main body of the device while maintaining the separated state.

[0069] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included. [Explanation of symbols]

[0070] 3 Photosensitive drum 6 Intermediate transfer unit 61 Intermediate transfer belt 64 Pre-transfer roller 65 Monochrome transfer roller 66 Color transfer roller 67 Collar swing mechanism 20 Lever 21 Thin diameter section 22 Large diameter part 23-pin 24 Interfered part 30 unit frame 31 Frame holder 31a 1st locking part 31b Second locking part 31c Slide 32 First swing member 32a Swing connection 32b Regulated part 33 Second swinging member 34 Interlocking members 100 Image forming device 101 Regulatory Department 110 Opening and closing cover 110a Cover interference part L Insertion / extraction direction L1 extraction direction L2 Insertion direction

Claims

1. An image forming apparatus including a plurality of photosensitive members, an apparatus main body, and an intermediate transfer unit that is detachable from the apparatus main body by inserting it in an inserting / removing direction, The intermediate transfer unit an intermediate transfer belt stretched over a plurality of rollers; a color transfer roller and a monochrome transfer roller disposed along the inner periphery of the intermediate transfer belt, and pressing the intermediate transfer belt against the corresponding photosensitive element when the color transfer roller and the monochrome transfer roller are oscillated; a lever operated by a user; a monochrome oscillation mechanism for oscillating the monochrome transfer roller, the intermediate transfer belt is switchable among a color image forming state in which it is in contact with all of the corresponding photosensitive members, a monochrome image forming state in which it is in contact with the photosensitive members corresponding to the monochrome transfer rollers, and a spaced state in which it is spaced from all of the photosensitive members, the monochrome swing mechanism switches between the monochrome image forming state and the separation state when the lever is operated, The apparatus main body is provided with a restricting portion that restricts removal of the intermediate transfer unit in the monochrome image forming state. An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, a color oscillation mechanism for oscillating the color transfer roller; The color oscillation mechanism is switched to the color image forming state when a color image is formed, and is switched to the monochrome image forming state when the color image formation is completed. An image forming apparatus comprising:

3. 2. The image forming apparatus according to claim 1, the monochrome swing mechanism has a regulated portion that faces the regulating portion in the insertion / removal direction in the monochrome image forming state, When the monochrome image forming state is changed to the separated state, the regulated portion moves to a position where it does not overlap with the regulating portion in the insertion / removal direction. An image forming apparatus comprising:

4. 2. The image forming apparatus according to claim 1, the intermediate transfer unit has a pre-transfer roller disposed along the inner periphery of the intermediate transfer belt, The monochrome swing mechanism swings the pre-transfer roller in conjunction with the monochrome transfer roller. An image forming apparatus comprising:

5. 2. The image forming apparatus according to claim 1, The lever is operated to move in the insertion / removal direction. An image forming apparatus comprising:

6. 2. The image forming apparatus according to claim 1, an opening / closing cover for opening and closing a side surface of the apparatus body that faces the intermediate transfer unit in the insertion / removal direction; a locking portion that locks the lever to maintain the monochrome image forming state, When the lever is not engaged with the engaging portion, it interferes with the opening / closing cover to prevent the opening / closing cover from being closed. An image forming apparatus comprising:

Images