Image forming apparatus

Abstract

The present invention provides an image forming apparatus that can change the position of all transfer rollers in conjunction with user operations. [Solution] The image forming apparatus comprises a plurality of photoreceptor drums 3 and an intermediate transfer unit 6 that can be attached to and detached from the apparatus body by inserting and removing it in the 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 the inner circumference of the intermediate transfer belt 61, a lever 20 operated by the user, a monochrome oscillation mechanism that oscillates the monochrome transfer roller 65, and a color oscillation mechanism 67 that oscillates the color transfer roller 66. When the lever 20 is operated in the monochrome image forming state, only the monochrome oscillation mechanism operates, and when the lever 20 is operated in the color image forming state, the monochrome oscillation mechanism and the color oscillation mechanism 67 operate to switch to a separated state.

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus including an intermediate transfer unit detachable from a main body of the apparatus.

Background Art

[0002] In an image forming apparatus having a plurality of photoreceptors (for example, a photoreceptor drum) and an intermediate transfer belt, such as a tandem type color (multi-color) image forming apparatus, toner images formed on each photoreceptor are transferred (primary transfer) in order from the upstream side to the downstream side onto the rotating intermediate transfer belt. Also, in a color image forming apparatus, when forming a monochrome (single-color) image, only one photoreceptor may be brought into contact with the intermediate transfer belt, and the other photoreceptors may be separated from the intermediate transfer belt. In such an image forming apparatus, the image quality may be different between monochrome image formation and color image formation, and countermeasures have been proposed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above-described transfer device includes a plurality of image carriers including a monochrome image carrier and a color image carrier, arranged such that the outer peripheral surface of an endless belt faces them, a plurality of transfer members arranged to face each of the plurality of image carriers with the endless belt interposed therebetween, and a transfer member moving mechanism that moves the transfer member between a pressing position for pressing the endless belt against the image carrier and a separating position for separating the endless belt from the image carrier, and the pressing position of the monochrome transfer member is made different so that the pressing amount of the endless belt is larger during monochrome image formation than during full-color image formation.

[0005] In the transfer device described above, a drive motor rotates a cam to automatically change the position of the transfer member. However, if, due to some malfunction, the transfer member remains pressed against the endless belt and the endless belt does not separate from the image carrier, there is a risk that the transfer device will not be able to be removed from the main unit for maintenance.

[0006] This disclosure is made to solve the above-mentioned problems and aims to provide an image forming apparatus that can change the position of all transfer rollers in conjunction with user operation. [Means for solving the problem]

[0007] The image forming apparatus according to this disclosure comprises a plurality of photoreceptors, an apparatus body, and an intermediate transfer unit that can be attached to and detached from the apparatus body by inserting and removing it in the 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 arranged along the inner circumference of the intermediate transfer belt and, when oscillating, pressing the intermediate transfer belt and bringing it into contact with the corresponding photoreceptor, a lever operated by the user, a monochrome oscillating mechanism that oscillates the monochrome transfer roller when the lever is operated, and a color oscillating mechanism that oscillates the color transfer roller, and the intermediate transfer unit The intermediate transfer unit is switchable between a color image forming state in which all transfer rollers are in contact with all corresponding photoreceptors, a monochrome image forming state in which the color transfer rollers are separated from the corresponding photoreceptors and the monochrome transfer rollers are in contact with the corresponding photoreceptors, and a separated state in which all transfer rollers are separated from all photoreceptors. When the lever is operated in the monochrome image forming state, only the monochrome oscillation mechanism operates to switch to the separated state, and when the lever is operated in the color image forming state, both the monochrome oscillation mechanism and the color oscillation mechanism operate to switch to the separated state. It is characterized by the following.

[0008] In the image forming apparatus according to this disclosure, the color oscillation mechanism may have a cam whose cam shaft is rotatably supported, the color transfer roller may oscillate so as to move away from the photoreceptor when the cam rotates, and the lever operated in the color image forming state may rotate the cam.

[0009] In the image forming apparatus according to this disclosure, the color oscillation mechanism may have a cam contact portion that contacts the outer circumferential surface of the cam, and a biasing member that biases the cam via the cam contact portion, wherein the biasing member rotates the cam and biases the color transfer roller in a direction that separates it from the photoreceptor.

[0010] In the image forming apparatus according to this disclosure, when the lever is operated in the color image forming state, the biasing force applied by the biasing member may be configured to increase the rotational force of the cam in response to the operation of the lever.

[0011] In the image forming apparatus according to this disclosure, the levers may be provided at both ends of the intermediate transfer belt in the direction of the rotation axis.

[0012] In the image forming apparatus according to this disclosure, the color oscillation mechanism may be configured to switch to the color image forming state when a color image is being formed, and to switch back to the monochrome image forming state when the color image forming is completed. [Effects of the Invention]

[0013] According to this disclosure, when the lever is operated to separate the monochrome transfer roller from the photoreceptor, the color transfer roller is also separated from the photoreceptor in conjunction. This prevents damage to the intermediate transfer belt and the photoreceptor by removing the intermediate transfer unit while the intermediate transfer belt is still in contact with the photoreceptor. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] It is a perspective view showing an intermediate transfer unit. [Figure 3] It is a schematic side view showing the structure near the intermediate transfer unit in the color image forming state. [Figure 4] It is a schematic side view showing the structure near the intermediate transfer unit in the monochrome image forming state. [Figure 5] It is a schematic side view showing the structure near the intermediate transfer unit in the separated state. [Figure 6] It is a schematic side view showing the structure near the cam in the color image forming state. [Figure 7] It is a schematic side view (part 1) showing the structure near the cam during the transition to the separated state. [Figure 8] It is a schematic side view (part 2) showing the structure near the cam during the transition to the separated state.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

[0016] FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present disclosure.

[0017] The image forming apparatus 100 is a multifunction device having a copying function, a scanner function, a facsimile function, and a printer function, and transmits the image of the document read by the image reading device 10 to the outside, or forms the image of the document read by the image reading device 10 or the image received from the outside on a recording medium such as paper in color or monochrome.

[0018] A document placing table 11 is provided above the image reading device 10, and the image reading device 10 reads the document placed on the document placing table 11 and generates image data.

[0019] 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 photoreceptor), a drum cleaning device 4, a charger 5, an intermediate transfer unit 6, a secondary transfer device 13, a fixing device 7, a paper feed tray 8, a paper discharge tray 9, and the like.

[0020] In the image forming apparatus 100, image data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (for example, black) is handled. The image forming apparatus 100 is provided with four each of a developing device 2, a photosensitive drum 3, a drum cleaning device 4, and a charger 5 for forming four types of toner images, and each is associated with black, cyan, magenta, and yellow, respectively, to constitute four image stations Pa, Pb, Pc, and Pd.

[0021] The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. The optical scanning device 1 exposes the surface of the photosensitive drum 3 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 recovers the residual toner on the surface of the photosensitive drum 3. By the above-described series of operations, toner images of each color are formed on the surface of each photosensitive drum 3.

[0022] The intermediate transfer unit 6 includes an endless intermediate transfer belt 61, an intermediate transfer driving roller 62, an intermediate transfer driven roller 63, a pre-transfer roller 64, and a plurality of intermediate transfer rollers (a monochrome transfer roller 65 and a color transfer roller 66). Details of the intermediate transfer unit 6 will be described later with reference to FIG. 2.

[0023] The intermediate transfer belt 61 is stretched between the intermediate transfer driving roller 62 and the intermediate transfer driven roller 63 and moves in a circumferential 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 overlapped to form a color toner image on the surface of the intermediate transfer belt 61.

[0024] The intermediate transfer rollers are positioned at four locations along the inner circumference of the intermediate transfer belt 61 to form four different toner images corresponding to each color. The intermediate transfer rollers press against the intermediate transfer belt 61 so that it comes into contact with the photoreceptor drum 3, thereby transferring the toner images of each color formed on the surface of the photoreceptor drum 3 to the circulating intermediate transfer belt 61.

[0025] Of the four image stations Pa, Pb, Pc, and Pd mentioned above, image station Pa is positioned closest to the intermediate transfer drive roller 62 and corresponds to black. Of the four intermediate transfer rollers, the monochrome transfer roller 65 corresponds to image station Pa, and the three color transfer rollers 66 correspond to image stations Pb, Pc, and Pd. The pre-transfer roller 64 is located between the monochrome transfer roller 65 and the intermediate transfer drive roller 62, and is positioned immediately upstream of the intermediate transfer drive roller 62.

[0026] The secondary transfer device 13 traps the paper that has been transported through the paper transport path R in the transfer nip between the secondary transfer roller 13a and the intermediate transfer belt 61. As the paper passes through the transfer nip, the toner image on the surface of the intermediate transfer belt 61 is transferred to the paper and it is then transported to the fuser device 7. The secondary transfer roller 13a is positioned to contact the portion of the intermediate transfer belt 61 that is stretched between the pre-transfer roller 64 and the intermediate transfer drive roller 62.

[0027] The fuser unit 7 includes a fuser belt 73 stretched over a fuser roller 71 and a heating roller 72, and a pressure roller 74 that presses the fuser roller 71 via the fuser belt 73. The heating roller 72 is equipped with a heat source and heats the fuser belt 73. The fuser unit 7 sandwiches the paper on which the toner image has been transferred between the fuser belt 73 and the pressure roller 74, heats and pressurizes it, and fixes the toner image to the paper.

[0028] The paper feed tray 8 is a tray for loading recording media (paper) used for image formation, and is located 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.

[0029] The paper transport path R includes a transport roller 14, a registration roller 15, a post-fixing transport roller 16, and an output roller 17. The transport roller 14 transports the paper supplied from the paper feed tray 8 to the registration roller 15. The registration roller 15 is located between the paper feed tray 8 and the secondary transfer device 13 and adjusts the timing of paper transport so that the toner image is transferred to the paper by the secondary transfer device 13. For example, the registration roller 15 holds the paper transported from the paper feed tray 8 and waits (stops temporarily), then starts transporting the paper at a constant speed in synchronization with the secondary transfer device 13. The paper, after passing through the secondary transfer device 13 and the fuser device 7, is transported by the post-fixing transport roller 16 to the output roller 17, and then output to the output tray 9 by the output roller 17.

[0030] In the image forming apparatus 100, the intermediate transfer unit 6 can be attached to and removed from the apparatus body by inserting and removing it in the insertion / removal direction L (left-right direction in Figure 1). The image forming apparatus 100 is provided with an opening / closing cover 110 on the side facing the intermediate transfer unit 6 attached to the apparatus body in the insertion / removal direction L (the right side in Figure 1). When attaching or removing the intermediate transfer unit 6, the user opens the opening / closing cover 110. For the purpose of explanation below, the direction in which the intermediate transfer unit 6 attached to the apparatus body is pulled out (right direction in Figure 1) will be called the removal direction L1, and the direction in which the intermediate transfer unit 6 is inserted into the apparatus body from the outside (left direction in Figure 1) will be called the insertion direction L2.

[0031] The image forming apparatus 100 is provided with a control unit that controls the entire system. The control unit realizes various functions by reading and executing various programs stored in the memory unit. The control unit may be realized by one or more control devices / arithmetic units, or by one or more control circuits.

[0032] Figure 2 is a perspective view showing the intermediate transfer unit. In the following description, the positional relationship of the intermediate transfer unit 6 will be explained based on its installation on the main body of the device.

[0033] The intermediate transfer unit 6 has a pair of unit frames 30 that support both ends 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 located at the end on the extraction direction L1 side, and the intermediate transfer driven roller 63 is located at the end on the insertion direction L2 side. In addition to the intermediate transfer drive roller 62 and the intermediate transfer driven roller 63, the intermediate transfer unit 6 may also be provided with other rollers, and the other rollers may be supported by the unit frames 30.

[0034] A frame holding portion 31 is provided at the end of the unit frame 30 on the side in the removal direction L1, and a lever 20 is attached to the frame holding portion 31. The lever 20 is the part operated by the user, and its detailed structure will be explained with reference to Figure 3, which will be described later. A lever 20 is provided on each of the pair of unit frames 30, but both have substantially the same structure and are operated in the same way, so below we will describe the structure of one lever 20 and omit the description of the other lever 20.

[0035] Figure 3 is a schematic side view showing the structure near the intermediate transfer unit in the color image formation state. Note that in Figure 3, for the sake of readability, only a portion of the intermediate transfer unit 6 is shown, and parts other than the unit frame 30 and the photoreceptor drum 3 of the image station are omitted.

[0036] When the intermediate transfer unit 6 is attached to the main body of the device, it is located above the four image stations Pa, Pb, Pc, and Pd, and the photoreceptor drums 3 at the four image stations Pa, Pb, Pc, and Pd are located below the intermediate transfer belt 61. For the purposes of this explanation, the side of the intermediate transfer belt 61 facing the photoreceptor drum 3 will be referred to as the bottom surface.

[0037] The intermediate transfer unit 6 is provided with a color oscillating mechanism 67 that oscillates three color transfer rollers 66. The color oscillating mechanism 67 includes a slide support portion 67a that slides in the insertion / removal direction L, a cam contact portion 67b provided at one end of the slide support portion 67a (the right end in Figure 3), an oscillating arm 67c that pivotally supports the end of the color transfer roller 66 at its tip, a biasing member 67d that biases the slide support portion 67a, and a cam 80 that contacts the cam contact portion 67b.

[0038] The slide support portion 67a is attached to the unit frame 30 so as to slide in the insertion / removal direction L. The cam contact portion 67b is provided at the end of the slide support portion 67a in the removal direction L1. The cam 80 is positioned so that its outer circumferential surface faces the cam contact portion 67b in the insertion / removal direction L.

[0039] The biasing member 67d is attached to the other end (left end in Figure 3) of the slide support portion 67a and biases the slide support portion 67a to slide in the extraction direction L1. In other words, the biasing member 67d biases the slide support portion 67a so as to press the cam contact portion 67b against the cam 80. The position in which the biasing member 67d is attached to the slide support portion 67a may be changed as appropriate, as long as the biasing direction of the biasing member 67d does not change.

[0040] The cam 80 is connected to a camshaft 81 by a drive source (not shown) and rotates around the axis of the camshaft 81. The cam 80 is egg-shaped, with an uneven distance from the camshaft 81 to its outer surface. The camshaft 81 is rotatably supported on the unit frame 30. As the cam 80 rotates, the portion of its outer surface that contacts the cam contact portion 67b changes. As a result, when the portion of the cam 80's outer surface furthest from the camshaft 81 contacts the cam contact portion 67b, the slide support portion 67a is pressed in the insertion direction L2 against the biasing force of the biasing member 67d, as shown in Figure 3. On the other hand, when the portion of the cam 80's outer surface closer to the camshaft 81 contacts the cam contact portion 67b, the slide support portion 67a is biased in the extraction direction L1 by the biasing force of the biasing member 67d, as shown in Figure 4, which will be described later.

[0041] The camshaft 81 is provided with a rotating projection 82 that protrudes toward the outer circumferential surface. The orientation of the rotating projection 82 and its relationship to other components will be explained later with reference to Figures 6 to 8.

[0042] Three oscillating arms 67c are provided, corresponding to the three color transfer rollers 66, and the base of each is attached to the slide support portion 67a. When the slide support portion 67a slides, the oscillating arms 67c oscillate to move the color transfer rollers 66 attached to their tips up and down. Specifically, when the slide support portion 67a moves in the removal direction L1, the oscillating arms 67c oscillate, causing the color transfer rollers 66 to move upward. On the other hand, when the slide support portion 67a moves in the insertion direction L2, the oscillating arms 67c oscillate, causing the color transfer rollers 66 to move downward. Figure 3 schematically shows the oscillating arms 67c, but is not limited to this, and the way the oscillating arms 67c are attached to the slide support portion 67a may be adjusted as appropriate. For example, the swing arm 67c may be provided with multiple pivot points supported by the slide support section 67a and the unit frame 30, and its tip may swing up and down in conjunction with the sliding movement of the slide support section 67a.

[0043] When the color oscillation mechanism 67 receives instructions from the control unit of the image forming apparatus 100, it rotates the cam 80 to move the color transfer roller 66 downward. As the color transfer roller 66 moves downward, the intermediate transfer belt 61 is pressed against the color transfer roller 66, causing its lower surface to spread downward and come into contact with the three photoreceptor drums 3 located below the three color transfer rollers 66. Also, when instructed by the control unit of the image forming apparatus 100, as shown in Figure 4 described later, the color oscillation mechanism 67 rotates the cam 80 to move the color transfer roller 66 upward. As described above, the biasing member 67d rotates the cam 80, biasing the color transfer roller 66 in a direction that separates it from the photoreceptor drums 3.

[0044] The intermediate transfer unit 6 is provided with a monochrome oscillation mechanism that oscillates the monochrome transfer roller 65, and a lever 20 that is operated by the user when operating the monochrome oscillation mechanism. The monochrome oscillation mechanism consists of a first oscillation member 32, a second oscillation member 33, and an interlocking member 34.

[0045] The first oscillating member 32 is attached to the end of the rotation axis of the intermediate transfer drive roller 62 and rotates with the rotation axis of the intermediate transfer drive roller 62 as the pivot point. The first oscillating member 32 is not fixed to the rotation axis of the intermediate transfer drive roller 62, and even when the intermediate transfer drive roller 62 rotates as the intermediate transfer belt 61 is moved in a circular motion, the first oscillating member 32 does not rotate. An oscillating connection portion 32a to which the tip of the lever 20 is attached is provided at the upper end of the first oscillating member 32. A hole is formed in the oscillating connection portion 32a that penetrates in the insertion / removal direction L, and the tip (small diameter portion 21) of the lever 20 is inserted so as to pass through this hole.

[0046] The end of the pre-transfer roller 64 is rotatably supported at the lower end of the first oscillating member 32. As shown in Figure 5, which will be described later, when the first oscillating member 32 rotates, the pre-transfer roller 64 oscillates up and down, and Figure 3 shows the state in which the pre-transfer roller 64 oscillates downward. When the pre-transfer roller 64 oscillates downward, the intermediate transfer belt 61 is pressed against the pre-transfer roller 64, and its lower surface is pushed outwards.

[0047] The second oscillating member 33 has a frame pivot 33a that is pivotally supported on the unit frame 30, and rotates around the frame pivot 33a as a fulcrum. The end of the monochrome transfer roller 65 is rotatably pivotally supported on the lower end of the second oscillating member 33. As shown in Figure 5, which will be described later, when the second oscillating member 33 rotates, the monochrome transfer roller 65 swings up and down, and Figure 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 against the monochrome transfer roller 65, and its lower surface is pushed downward and spread, coming into contact with the photoreceptor drum 3 located below the monochrome transfer roller 65.

[0048] One end of a linkage member 34 is attached to the upper end of the second oscillating member 33, and the other end of the linkage member 34 is attached to the first oscillating member 32. When the first oscillating member 32 rotates, the second oscillating member 33 is pulled by the linkage member 34 and rotates in conjunction with the first oscillating member 32.

[0049] The second oscillating member 33 may be fitted with a biasing member that biases it in the opposite direction to the pulling direction of the interlocking member 34, and when no load is applied from the interlocking member 34, it may be biased to cause the monochrome transfer roller 65 to oscillate downward.

[0050] As mentioned above, the mono-oscillation mechanism is not limited to a configuration comprising a first oscillating member 32, a second oscillating member 33, and an interlocking member 34; it is sufficient if the pre-transfer roller 64 and the mono-transfer roller 65 are oscillated together in the same direction.

[0051] As described above, the tip of the lever 20 on the insertion direction L2 side is attached to the oscillating connector 32a. The tip of the lever 20 in the insertion direction L2 is a narrow diameter portion 21 that is narrower than the hole provided in the oscillating connector 32a, and a ring 21a with an outer diameter larger than the hole is fitted to the tip that protrudes further inward than the oscillating connector 32a. As shown in Figure 5, which will be described later, when the lever 20 is pulled in the removal direction L1, the ring 21a catches on the oscillating connector 32a. On the removal direction L1 side of the narrow diameter portion 21, there is a wide diameter portion 22 that is wider than the hole provided in the oscillating connector 32a. When the lever 20 is pushed in the insertion direction L2, the wide diameter portion 22 catches on the oscillating connector 32a.

[0052] In this embodiment, the length of the small diameter portion 21 in the insertion / removal direction L is longer than that of the oscillating connection portion 32a. In the state shown in Figure 3, the large diameter portion 22 abuts against the oscillating connection portion 32a, and a gap (play) is provided between the oscillating connection portion 32a and the ring 21a. Then, as shown in Figure 5 which will be described later, when the lever 20 is pulled slightly in the removal direction L1, the ring 21a abuts against the oscillating connection portion 32a and acts to rotate the first oscillating member 32.

[0053] The lever 20 has a cylindrical shaft extending in the insertion / removal direction L, and the middle portion (large diameter portion 22) of the shaft is held by the frame holding portion 31. The lever 20 may be provided with a pin or the like (not shown) that locks into the frame holding portion 31. By locking the lever 20 via the pin or the like, the lever 20 may be held in either a pushed-in state (see Figure 3) or a pulled-out state (see Figure 5).

[0054] A release member 23 is provided above the cam 80, which interferes with the rotating projection 82. One end of a relay member 24 is attached to the end of the release member 23, and the other end of the relay member 24 is attached to the tip of the lever 20 on the insertion direction L2 side. When the lever 20 is pulled in the extraction direction L1, the release member 23 is pulled in the extraction direction L1 via the relay member 24. The operation when the relay member 24 is pulled will be explained later with reference to Figures 6 to 8.

[0055] As described above, the image forming apparatus 100 is configured to appropriately move the intermediate transfer belt 61 in contact with the four photoreceptor drums 3 by oscillating the pre-transfer roller 64, the monochrome transfer roller 65, and the color transfer roller 66 up and down. In this way, the image forming apparatus 100 can handle both color (multicolor) and monochrome (monochromatic) image formation by switching the positional relationship between the intermediate transfer belt 61 and the photoreceptor drums 3. Figure 3 shows the color image formation state in which the intermediate transfer belt 61 is in contact with all the corresponding photoreceptor drums 3, and in the color image formation state, color image formation is performed. In addition, as shown in Figure 4, which will be described later, the image forming apparatus 100 can be configured to have a monochrome image formation state in which the intermediate transfer belt 61 is in contact with the photoreceptor drum 3 corresponding to the monochrome transfer roller 65, and in the monochrome image formation state, monochrome image formation is performed. Furthermore, in the image forming apparatus 100, as shown in Figure 5 later, the intermediate transfer belt 61 is set to a separated state in which it is separated from all the photoreceptor drums 3, and in the separated state, the intermediate transfer unit 6 is attached and detached.

[0056] Figure 4 is a schematic side view showing the structure near the intermediate transfer unit in the monochrome image formation state.

[0057] Figure 4 shows the intermediate transfer unit 6 transitioning from the color image formation state shown in Figure 3 to the monochrome image formation state. As described above, the color oscillation mechanism 67 receives instructions from the control unit of the image forming apparatus 100 to rotate the cam 80, causing the color transfer roller 66 to oscillate upward. The portion of the intermediate transfer belt 61 that was pressed against the color transfer roller 66 lifts up so that it separates from the corresponding three photoreceptor drums 3. The pre-transfer roller 64 and the monochrome transfer roller 65 maintain their downward oscillation state, so the intermediate transfer belt 61 is in contact with the corresponding photoreceptor drum 3.

[0058] In the image forming apparatus 100, the color oscillation mechanism 67 is instructed to switch to a color image forming state when a color image is being formed, and to switch back to a monochrome image forming state when color image formation is complete. In this way, the operation of the color transfer roller 66 is controlled by the color oscillation mechanism 67 so that the intermediate transfer belt 61 and the photoreceptor drum 3 move away from each other according to the image formation, thus preventing the intermediate transfer belt 61 from being left in contact with the corresponding photoreceptor drum 3.

[0059] Figure 5 is a schematic side view showing the structure near the intermediate transfer unit in the separated state.

[0060] Figure 5 shows the intermediate transfer unit 6 after the lever 20 has been operated from the state shown in Figure 4 to the separated state. When transitioning to the separated state, the user pulls the lever 20 in the removal direction L1, causing the oscillating connection part 32a to be pressed against the ring 21a, the first oscillating member 32 to rotate, and the pre-transfer roller 64 to oscillate upward. In conjunction with the first oscillating member 32, the second oscillating member 33 also rotates, and the monochrome transfer roller 65 also oscillates upward. When the unit transitions to the separated state and the pre-transfer roller 64 and monochrome transfer roller 65 oscillate upward, the intermediate transfer belt 61 lifts up so that the parts that were pressed against the pre-transfer roller 64 and monochrome transfer roller 65 are separated from the corresponding photoreceptor drum 3. As a result, the intermediate transfer belt 61 is separated from all of the photoreceptor drum 3.

[0061] Incidentally, in the image forming apparatus 100, the color oscillation mechanism 67 switches between the color image forming state and the monochrome image forming state, and the switch from the monochrome image forming state to the separated state is performed by operating the lever 20. However, if, due to some malfunction, the switch from the color image forming state to the monochrome image forming state fails and the color transfer roller 66 remains oscillating downwards, the intermediate transfer unit 6 may be pulled out while the intermediate transfer belt 61 is still in contact with the photoreceptor drum 3.

[0062] In contrast, in this embodiment, when the lever 20 is operated in the color image formation state, the color oscillation mechanism 67 is forcibly activated to transition to the separated state. Next, the operation when the lever 20 is operated in the color image formation state will be described with reference to Figures 6 to 8.

[0063] Figure 6 is a schematic side view showing the structure near the cam in the color image formation state.

[0064] As shown in Figure 6, in the color image formation state, the rotating projection 82 extends upward from the camshaft 81. In Figure 6, the center line CL, which extends in the insertion / removal direction L and passes through the camshaft 81, is shown by a dashed line. In the color image formation state, the part of the outer surface of the cam 80 that is furthest from the camshaft 81 and coincides with the center line CL is in contact with the cam contact portion 67b.

[0065] The release member 23 is located above the cam 80, and a release projection 23a is provided at its tip on the insertion direction L2 side. The release member 23 is attached to the unit frame 30 and moves in the insertion / removal direction L in conjunction with the operation of the lever 20. The release projection 23a is the part that interferes with the rotating projection 82 in the color image forming state. When the lever 20 is pushed in, the release projection 23a is positioned further toward the insertion direction L2 than the rotating projection 82. In the color image forming state, the rotating projection 82 obstructs the path of the release projection 23a when the lever 20 is operated.

[0066] Furthermore, the positions of the cam 80 and the release member 23 are adjusted so that only the rotating projection 82 and the release projection 23a interfere with each other, and the other parts are positioned so that they do not come into contact.

[0067] Figure 7 is a schematic side view (part 1) showing the structure near the cam during the transition to the separated state.

[0068] Figure 7 shows the state in which the release member 23 is moved in the extraction direction L1 by operating the lever 20 from the state shown in Figure 6. When the release member 23 moves in the extraction direction L1, the release projection 23a contacts the rotation projection 82 and presses against it, causing the cam 80 to rotate in the rotation direction K (clockwise in Figure 7). As the cam 80 rotates, the portion of its outer surface slightly above the center line CL comes into contact with the cam contact portion 67b. Here, the cam contact portion 67b presses against the outer surface of the cam 80 at a position offset from the center line CL, and the biasing force applied by the biasing member 67d via the cam contact portion 67b acts to strengthen the rotational force on the cam 80. In this way, when the cam 80 rotates due to the operation of the lever 20, the biasing force of the biasing member 67d is applied, so the cam 80 can be reliably rotated even with a weak force.

[0069] Figure 8 is a schematic side view (part 2) showing the structure near the cam during the transition to the separated state.

[0070] Figure 8 shows the state in which the release member 23 has moved in the removal direction L1 by further operation of the lever 20 from the state shown in Figure 7. The release projection 23a has moved further in the removal direction L1 and passed over the cam shaft 81. The rotating projection 82 has changed direction as the cam 80 has rotated, so that it extends to the side of the cam shaft 81 (to the right in Figure 8). As a result, the rotating projection 82 has moved out of the path of the release projection 23a and is separated from the release projection 23a. Even in this state, it is in contact with and pressing against the outer surface of the cam 80 at a position offset from the center line CL, and the biasing force of the biasing member 67d acts to rotate the cam 80. The cam 80 rotates further from the state shown in Figure 8, and stops with the part of the outer surface of the cam 80 closest to the cam shaft 81 and overlapping with the center line CL in contact with the cam contact portion 67b.

[0071] As described above, the color oscillation mechanism 67 switches to a separated state when the lever 20 is operated in the color image formation state. In this way, when the lever 20 is operated to separate the monochrome transfer roller 65 from the photoreceptor drum 3, the color transfer roller 66 is also separated from the photoreceptor drum 3 in conjunction, so that the intermediate transfer unit 6 is removed while the intermediate transfer belt 61 is in contact with the photoreceptor drum 3, preventing damage to the intermediate transfer belt 61 and the photoreceptor drum 3. Furthermore, the function of oscillating the color transfer roller 66 can be realized with a simple structure using the cam 80. In addition, the lever 20 interfering with the cam 80 ensures that the color transfer roller 66 is reliably separated from the photoreceptor drum 3.

[0072] In this embodiment, the biasing member 67d is biased to transition to a separated state, so when a color image is not being formed, the color transfer roller 66 can maintain a separated state from the photoreceptor drum 3.

[0073] Furthermore, since the levers 20 are provided at both ends of the intermediate transfer belt 61 in the direction of the rotation axis, the intermediate transfer unit 6 can be stably supported by gripping the levers 20 at both ends when pulling out the intermediate transfer unit 6.

[0074] In this embodiment, a release member 23, a relay member 24, and a rotating projection 82 are provided as members that transmit the movement of the lever 20 to the cam 80. However, the embodiment is not limited to this, and other members may be used or the shape of the lever 20 may be changed to create a configuration in which the force used to operate the lever 20 is physically transmitted as a force that rotates the cam 80.

[0075] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of Symbols]

[0076] 3. Photoconductor drum 6. Intermediate Transfer Unit 61 Intermediate transfer belt 64 Pre-transfer roller 65 Monochrome Transfer Roller 66 Color Transfer Rollers 67 Color Oscillating Mechanism 67a Slide support section 67b Cam contact area 67c Swivel Arm 67d Biasing member 20 Lever 23 Release Member 24 Intermediate Members 30 Unit Frames 80 Cam 81 Camshaft 82 Rotating protrusions 100 Image forming apparatus L Insertion / extraction direction L1 extraction direction L2 Insertion direction

Claims

1. An image forming apparatus comprising a plurality of photoreceptors, a main body of the apparatus, and an intermediate transfer unit that can be attached to and detached from the main body of the apparatus by inserting and removing it in the insertion / removal direction, The aforementioned intermediate transfer unit is An intermediate transfer belt stretched across multiple rollers, A color transfer roller and a monochrome transfer roller are positioned along the inner circumference of the intermediate transfer belt and, when they oscillate, press against the intermediate transfer belt and bring it into contact with the corresponding photoreceptor. A lever operated by the user, When the lever is operated, a monochrome oscillation mechanism is provided to oscillate the monochrome transfer roller, It has a color oscillating mechanism that oscillates the color transfer roller, The intermediate transfer unit is switchable between a color image forming state in which all transfer rollers are in contact with all corresponding photoreceptors, a monochrome image forming state in which the color transfer rollers are separated from the corresponding photoreceptors and the monochrome transfer rollers are in contact with the corresponding photoreceptors, and a separated state in which all transfer rollers are separated from all photoreceptors. The intermediate transfer unit is configured such that when the lever is operated in the monochrome image forming state, only the monochrome oscillation mechanism operates to switch to the separated state, and when the lever is operated in the color image forming state, both the monochrome oscillation mechanism and the color oscillation mechanism operate to switch to the separated state. An image forming apparatus characterized by the following.

2. An image forming apparatus according to claim 1, The aforementioned collar swing mechanism has a cam whose cam shaft is rotatably supported, The color transfer roller oscillates so as to move away from the photoreceptor when the cam rotates. The lever operated in the color image forming state rotates the cam. An image forming apparatus characterized by the following.

3. An image forming apparatus according to claim 2, The aforementioned collar oscillating mechanism is, A cam contact portion that contacts the outer circumferential surface of the cam, It has a biasing member that biases the cam via the cam contact portion, The biasing member rotates the cam, thereby biasing the color transfer roller in a direction that separates it from the photoreceptor. An image forming apparatus characterized by the following.

4. An image forming apparatus according to claim 3, When the lever is operated in the color image forming state, the biasing force exerted by the biasing member increases the rotational force of the cam in response to the operation of the lever. An image forming apparatus characterized by the following.

5. An image forming apparatus according to claim 1, The levers are provided at both ends of the intermediate transfer belt in the direction of its rotation axis. An image forming apparatus characterized by the following.

6. An image forming apparatus according to claim 1, The color oscillation mechanism switches to the color image formation state when a color image is formed, and switches back to the monochrome image formation state when color image formation is complete. An image forming apparatus characterized by the following.

Images