Image forming apparatus

Abstract

To prevent creep deformation of members without providing a new configuration.SOLUTION: An image forming apparatus comprises: a plurality of image carriers; a transfer unit including an intermediate transfer belt, a plurality of transfer members that sandwich the intermediate transfer belt with the plurality of image carriers, urging means that urge the plurality of transfer members toward the plurality of image carriers with the intermediate transfer belt therebetween, and a frame that supports the intermediate transfer belt, the plurality of transfer members, and the urging means; and an apparatus body that supports the plurality of image carriers and the transfer unit. The apparatus body includes a support part that supports the transfer unit, and an urging force receiving part that is located at a position between the plurality of transfer members in the arrangement direction of the plurality of transfer members and can support the transfer unit.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer.

Background Art

[0002] As an electrophotographic image forming apparatus, a tandem type image forming apparatus is known in which a plurality of image forming units are arranged in the moving direction of a conveyance belt or an intermediate transfer belt. Each color image forming unit has a drum-shaped photoreceptor (hereinafter referred to as a photosensitive drum) as an image carrier. The toner images of each color carried on the photosensitive drums of each color are transferred to a transfer material such as paper or an OHP sheet conveyed by a transfer material conveyance belt, or after being once transferred to an intermediate transfer belt and then transferred to the transfer material, they are fixed to the transfer material by a fixing means.

[0003] In a configuration having such a belt, a tensioning mechanism for applying tension to the belt for stable driving and a pressing mechanism for biasing the photosensitive drum from inside the belt for toner image transfer are provided. Since there is a possibility that creep deformation of parts may occur during transportation or long-term storage at the user's site due to a mechanism for applying an urging force to such a belt unit (hereinafter referred to as a transfer unit), a countermeasure configuration has been provided.

[0004] For example, Patent Document 1 discloses a configuration for suppressing creep deformation of a member by configuring the tension applied to the belt to be releasable. More specifically, a separation member provided in the transfer unit is inserted into a bearing that supports a roller (tension roller) that applies tension to the belt. With this configuration, a configuration is provided for holding the tension roller at a position where the tension of the belt is relaxed against the urging force of a spring that applies tension to the belt.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in configurations that include a mechanism to release belt tension, as described in Patent Document 1, it is necessary to provide at least a new separating member. Therefore, there are concerns about increased costs due to the increased number of parts, and there is a risk that the separating operation may not be able to be performed in accordance with the timing of creep deformation during transportation or long-term storage, thus failing to achieve the desired effect.

[0007] Therefore, the object of the present invention is to provide an image forming apparatus that can stably suppress creep deformation in accordance with the creep deformation timing with a simple configuration, without having to newly provide a mechanism for releasing belt tension. [Means for solving the problem]

[0008] To achieve the above objective, the image forming apparatus of the present invention is Multiple image carriers, Intermediate transfer belt and Multiple transfer members that sandwich the intermediate transfer belt between the multiple image carriers, A biasing means for biasing each of the plurality of transfer members toward the plurality of image carriers via the intermediate transfer belt, The intermediate transfer belt, the plurality of transfer members, and the biasing means are supported by a frame. Mu and, A transfer unit including, The apparatus body supports the plurality of image carriers and the transfer unit, In an image forming apparatus comprising, The apparatus body includes a support portion for supporting the transfer unit and a biasing force receiving portion whose position in the direction of arrangement of the plurality of transfer members is located between the plurality of transfer members, and which is capable of supporting the transfer unit. It is characterized by the following: To achieve the above objective, the image forming apparatus of the present invention is Multiple image carriers, Intermediate transfer belt and Multiple transfer members that sandwich the intermediate transfer belt between the multiple image carriers, A biasing means for biasing each of the plurality of transfer members toward the plurality of image carriers via the intermediate transfer belt, The intermediate transfer belt, the plurality of transfer members, and the frame supporting the biasing means, A transfer unit including, The apparatus body supports the plurality of image carriers and the transfer unit, In an image forming apparatus comprising, The apparatus body includes a support portion for supporting the transfer unit, and a biasing force receiving portion whose position in the direction of alignment of the plurality of transfer members is located below the plurality of transfer members, and which is capable of supporting the transfer unit. It is characterized by the following: To achieve the above objective, the image forming apparatus of the present invention is Multiple image carriers, Intermediate transfer belt and Multiple transfer members that sandwich the intermediate transfer belt between the multiple image carriers, A biasing means for biasing each of the plurality of transfer members toward the plurality of image carriers via the intermediate transfer belt, The intermediate transfer belt, the plurality of transfer members, and the frame supporting the biasing means, A transfer unit including, The apparatus body supports the plurality of image carriers and the transfer unit, In an image forming apparatus comprising, The main body of the aforementioned device is A first support portion that supports one end of the intermediate transfer belt of the transfer unit, A second support portion that supports the other end of the intermediate transfer belt of the transfer unit, Between the first support portion and the second support portion, a biasing force receiving portion capable of supporting the transfer unit is provided, It is characterized by including. [Effects of the Invention]

[0009] According to the present invention, by supporting the transfer unit on the biasing force receiving portion provided in the apparatus main body of the image forming apparatus, it is possible to stably suppress the creep deformation of the transfer member.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic perspective view for explaining the external configuration of the image forming apparatus in Example 1. [Figure 2] It is a schematic cross-sectional view for explaining the internal configuration of the image forming apparatus in Example 1. [Figure 3] It is a schematic cross-sectional view for explaining the support configuration of the transfer means in Example 1. [Figure 4] It is a schematic cross-sectional view for explaining the support configuration of the transfer means in Example 1. [Figure 5] It is a schematic bottom view for explaining the support configuration of the transfer means in Example 1. [Figure 6] It is a schematic cross-sectional view for explaining the operation of the transfer means interlocked with the opening and closing operation of the door. [Figure 7] It is a schematic cross-sectional view for explaining the operation of the transfer means interlocked with the opening and closing operation of the door. [Figure 8] It is a schematic cross-sectional view for explaining the state when the transfer means is removed in Example 1. [Figure 9] It is a schematic cross-sectional view for explaining the support configuration of the transfer means in Example 2. [Figure 10] It is a schematic cross-sectional view for explaining the support configuration of the transfer means in Example 3. [Figure 11] It is a schematic cross-sectional view for explaining the support configuration of the transfer means in Example 4. [Figure 12] It is a schematic cross-sectional view for explaining the support configuration of the transfer means in Example 5.

Modes for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately modified depending on the configuration and various conditions of the apparatus to which the present invention is applied. Therefore, unless otherwise specifically stated, this is not intended to limit the scope of the present invention.

[0012] (Example 1) [Configuration of the image forming apparatus] Figure 1 is a schematic perspective view illustrating the external configuration of the image forming apparatus 1 of this embodiment, and Figure 2 is a schematic cross-sectional view showing the internal configuration of the image forming apparatus 1. The image forming apparatus 1 of this embodiment is a so-called tandem type image forming apparatus having multiple image forming units PY, PM, PC, and PK. The first image forming unit PY forms an image using yellow (Y) toner, the second image forming unit PM uses magenta (M) toner, the third image forming unit PC uses cyan (C) toner, and the fourth image forming unit PK uses black (Bk) toner to form an image.

[0013] Furthermore, the image forming apparatus 1 uses a process cartridge system, and the multiple image forming units PY, PM, PC, and PK are each configured as process cartridges (multiple cartridges) that are detachable from the apparatus body 2. Removal or installation of each process cartridge is performed with the opening / closing door 3 provided on the image forming apparatus 1 open. As shown in Figure 2, these four image forming units are arranged in a line at regular intervals, and the configuration of each image forming unit is substantially common in many ways, except for the color of the toner it contains. Therefore, in the following description, unless otherwise specified, the suffixes Y, M, C, and K indicating that an element is for one of the colors will be omitted, and the element will be described comprehensively.

[0014] Furthermore, in the following description, with respect to the image forming apparatus 1, the side with the opening / closing door 3 will be referred to as the front, and the side opposite the front will be referred to as the rear. Also, when viewing the image forming apparatus 1 from the front, the right side will be referred to as the drive side, and the left side as the non-drive side. In the drawings, the direction from the rear to the front of the apparatus body 2 will be defined as the X-axis direction, the direction from the non-drive side to the drive side will be defined as the Y-axis direction, and the direction from the bottom to the top of the apparatus body 2 will be defined as the Z-axis direction.

[0015] As shown in Figure 2, each image forming unit P is arranged horizontally with respect to the bottom surface of the main body 2 of the apparatus. The image forming unit P has an electrophotographic process mechanism, and rotational driving force is transmitted from a cartridge drive transmission unit (not shown) provided in the main body 2 of the apparatus. The image forming unit P comprises a plurality of photosensitive drums 40 (40Y, 40M, 40C, 40K) (a plurality of image carriers) as image carriers for holding toner images, a charging means (not shown), and a developing means (not shown).

[0016] Furthermore, above the image forming unit P in the Z-axis direction, an exposure means LS is provided, and the exposure means LS outputs laser light L in accordance with the image information received by a controller (not shown). The laser light L output from the exposure means LS passes through the exposure window of the image forming unit P and scans and exposes the surface of the photosensitive drum 40.

[0017] Furthermore, a transfer unit 11 is provided below the image forming section P in the Z-axis direction, serving as a transfer means. The transfer unit 11 includes an endless intermediate transfer belt 12 movable in the direction of arrow B in the figure, a primary transfer roller 16, a drive roller 13, a storage container 18, and also has a tension roller 17, an assist roller 15, and a recovery means 19. The drive roller 13 rotates upon receiving a driving force, moving the intermediate transfer belt 12 in the direction of arrow B in the figure, and tensions the intermediate transfer belt 12 together with the tension roller 17 and the assist roller 15. Details of the belt tensioning mechanism in the tension roller 17 will be described later. The recovery means 19 recovers the toner remaining on the intermediate transfer belt 12, and the toner recovered by the recovery means 19 is stored in the storage container 18, which is provided within the region formed by the inner circumferential surface of the intermediate transfer belt 12. In this configuration, the storage container 18 functions as the frame of the transfer unit 11.

[0018] Multiple primary transfer rollers 16 are provided and are transfer members for transferring the toner image supported on the photosensitive drum 40 from the photosensitive drum 40 to the intermediate transfer belt 12. As multiple transfer members, they are in contact with the inner circumferential surface of the intermediate transfer belt 12. Each primary transfer roller 16Y, 16M, 16C, and 16K is provided corresponding to each photosensitive drum 40Y, 40M, 40C, and 40K via the intermediate transfer belt 12. Each primary transfer roller 16 is provided extending in a direction perpendicular to the direction of arrow B in the figure, i.e., in the Y-axis direction, and is arranged in a manner that is spaced apart from each other in a direction substantially parallel to the X-axis. Each primary transfer roller 16 biases the intermediate transfer belt 12 toward each photosensitive drum 40, forming a primary transfer section where the photosensitive drum 40 and the intermediate transfer belt 12 are in contact. In this way, the intermediate transfer belt 12 is sandwiched between each photosensitive drum 40 and each primary transfer roller 16.

[0019] In this embodiment, as shown in Figure 2, each primary transfer roller 16 is positioned offset from the position of each primary transfer section where each photosensitive drum 40 and the intermediate transfer belt 12 come into contact. More specifically, with respect to the direction of movement of the intermediate transfer belt 12, each primary transfer roller 16 is positioned downstream of the position of each primary transfer section. Alternatively, each primary transfer roller 16 may be positioned upstream of the position of each primary transfer section.

[0020] The recovery means 19 comprises a frame 19a and a cleaning blade 19b (recovery member) provided inside the frame 19a and extending in the Y-axis direction. The cleaning blade 19b is positioned to contact the outer circumferential surface of the intermediate transfer belt 12 in a counter-direction opposite to the direction of movement of the intermediate transfer belt 12, and recovers the toner remaining on the intermediate transfer belt 12 into the frame 19a.

[0021] A secondary transfer roller 14 is positioned opposite the drive roller 13 (drive rotating body) via an intermediate transfer belt 12, and a secondary transfer section is formed at the position where the secondary transfer roller 14 and the intermediate transfer belt 12 come into contact. Furthermore, with respect to the transport direction of the transfer material S, a feeding means 50 is provided upstream of the secondary transfer section, which includes a paper feed cassette 51 for containing the transfer material S and a paper feed roller 52 for feeding the transfer material S from the paper feed cassette 51 toward the secondary transfer section.

[0022] With respect to the transport direction of the transfer material S, downstream of the secondary transfer section, there is a fixing means 21 for fixing a toner image onto the transfer material S, and a pair of discharge rollers 22 for discharging the transfer material S with the toner image fixed from the main body 2 of the device. The transfer material S discharged from the main body 2 by the pair of discharge rollers 22 is loaded onto the paper output tray 23.

[0023] [Image Formation Process] Next, the image forming operation of the image forming apparatus 1 in this embodiment will be described. When a control means such as a controller (not shown) receives an image signal, the image forming operation is started, and the photosensitive drum 40 and drive rollers 13, etc., start rotating at a predetermined peripheral speed (process speed) due to the driving force from a drive source (not shown).

[0024] The photosensitive drum 40 is uniformly charged on its surface by a charging means (not shown) to the same polarity as the normal charging polarity of the toner (negative polarity in this embodiment). Subsequently, an electrostatic latent image according to the image information is formed by irradiation with laser light L from an exposure means LS. Then, the electrostatic latent image formed on the photosensitive drum 40 is developed by the toner contained in a developing means (not shown), and a toner image corresponding to the image information is carried on the surface of the photosensitive drum 40. At this time, each photosensitive drum 40Y, 40M, 40C, and 40K is carried with a toner image corresponding to the image components of yellow, magenta, cyan, and black, respectively.

[0025] Subsequently, the toner images of each color carried on each photosensitive drum 40 reach each primary transfer section as each photosensitive drum 40 rotates. Then, when voltage is applied to each primary transfer roller 16 from a power supply (not shown), the toner images of each color carried on each photosensitive drum 40 are sequentially transferred onto the intermediate transfer belt 12 in each primary transfer section. As a result, four toner images corresponding to the desired color image are formed on the intermediate transfer belt 12.

[0026] Then, the four toner images supported on the intermediate transfer belt 12 reach the secondary transfer section as the intermediate transfer belt 12 moves, and are transferred all at once to the surface of the transfer material S, such as paper or an OHP sheet, as they pass through the secondary transfer section. At this time, a voltage with the opposite polarity to the normal charging polarity of the toner is applied to the secondary transfer roller 14 from a secondary transfer power supply (not shown).

[0027] The transfer material S, contained in the paper feed cassette 51, is fed from the paper feed cassette 51 by the paper feed roller 52 at a predetermined timing and transported toward the secondary transfer section. In the secondary transfer section, the transfer material S onto which the four-color toner images have been transferred is heated and pressurized in the fixing means 21, causing the four colors of toner to melt and mix, and then fixed to the transfer material S. After that, the transfer material S is discharged from the main body 2 by the discharge roller pair 22 and loaded onto the paper discharge tray 23, which serves as a loading section.

[0028] Toner remaining on the intermediate transfer belt 12 after secondary transfer (hereinafter referred to as residual toner) is removed from the surface of the intermediate transfer belt 12 by a recovery means 19 provided opposite the drive roller 13 via the intermediate transfer belt 12. In the image forming apparatus 1 of this embodiment, a full-color print image is formed by the above operation.

[0029] The image forming apparatus 1 of this embodiment is equipped with a controller (not shown) for controlling the operation of each part of the image forming apparatus, and a memory (not shown) as a storage means for storing various control information. The controller performs control related to the transport of the transfer material S, control related to the driving of the intermediate transfer belt 12 and each image forming unit P as a process cartridge, and control related to image formation.

[0030] [Support structure and creep prevention shape of the transfer means] Here, Figure 3 shows the support configuration of the transfer unit 11 (transfer means) in the image forming apparatus 1 (the intermediate transfer belt 12 is not shown in Figure 3). The drive roller bearing 13a, which is provided coaxially with the drive roller 13, is rotatably supported on the main body side plate 70. Specifically, the transfer unit 11 is inserted in the +X direction into the slit portion 70a provided in the main body side plate 70 and is held in place by the pressure of the secondary transfer roller 14 (not shown in Figure 3).

[0031] Furthermore, the process cartridge tray 80, which houses the process cartridge P, is inserted from the front of the main body. The process cartridge tray 80 is supported by the engagement of the tray slit 80b with the side plate pins 70b provided on the main body side plate 70 and the engagement of the tray pin 80a with the side plate slit 70c. The transfer unit 11, which is supported to be movable in the X-axis direction, is pressed in the +Z direction by the pressing portion 31a of the rail member 31 provided on the main body stay 90, which is fixedly held to the main body side plate 70. Then, it abuts against the tray contact portion 80c provided on the process cartridge tray 80, and its movement in the Z-axis direction is restricted. In this way, on the XZ plane, the transfer unit 11 is positioned on the main body side plate 70 via the process cartridge tray 80. This pressing portion 31a corresponds to a first support portion that supports the region on one end side of the intermediate transfer belt in the transfer unit 11 in the direction of alignment of the primary transfer rollers 16. Furthermore, the aforementioned drive roller bearing 13a corresponds to a second support portion that supports the region on the other end side of the intermediate transfer belt 12 in the transfer unit 11 in this embodiment, in the direction of alignment of the primary transfer rollers 16.

[0032] The following belt tensioning mechanism and toner image transfer mechanism are provided inside the housing container 18 of the transfer unit 11. More specifically, the tension roller 17 is pressed in the +X direction by the tension spring 171, and as a result, the housing container 18 receives a force in the direction of arrow C. Furthermore, the primary transfer spring 163, acting as a biasing means, causes the primary transfer roller 16 to press against the intermediate transfer belt 12 via the primary transfer bearing 162, so that the housing container 18 receives a force in the direction of arrow D from each primary transfer roller 16. Therefore, the housing container 18 receives a force in the -Z direction due to the resultant force of the forces in the directions of arrows C and D. When creep is reproduced by high-temperature storage while the transfer unit 11 is supported only by the lower contact portion 112 and the drive roller bearing 13a, the amount of deformation of the housing container 18 in the -Z direction is maximized directly below the primary transfer rollers 16M and 16C.

[0033] To suppress this creep, in the arrangement configuration viewed in the Y-axis direction as shown in Figure 3, it is desirable to provide a support structure for the containment container 18 directly below the section from the primary transfer roller 16M to 16C in the X-axis direction of the containment container 18. In this embodiment, a supported portion 18a is provided as part of the containment container 18, and a support portion 31b is provided as part of the rail member 31 of the device body. Since the rail member 31 is provided in contact with the main body stay 90, the deformation of the containment container 18, which also serves as the frame of the transfer unit 11 as described above, can be supported by the main body stay 90 through the supported portion 18a and the support portion 31b of the rail member 31. That is, this support portion 31b corresponds to a biasing force receiving portion that can support the transfer unit 11 (container container 18) between the pressing portion 31a, which is the first support portion, and the drive roller bearing 13a, which is the second support portion.

[0034] In this embodiment, the deformation of the transfer unit 11 (container 18) is suppressed by the support portion 31b. This eliminates the need for a new mechanism to suppress creep, and allows creep suppression using the supported portion 18a, which is part of the containment container 18, and the support portion 31b provided on the rail member 31. As mentioned above, the position where the support structure is provided is preferably directly below the section from primary transfer rollers 16M to 16C in the containment container 18 (a position that overlaps with the section from primary transfer rollers 16M to 16C in the positional relationship in the X-axis direction (the direction in which the primary transfer rollers 16 are aligned)). Alternatively, it is preferable to be directly below (downwards) either primary transfer roller 16M or 16C. This is because the amount of deformation due to creep is greatest directly below the primary transfer rollers 16M and 16C, at a location away from the pressing portion 31a that supports one end of the transfer unit 11 (container 18) and the drive roller bearing 13a that supports the other end in the X-axis direction. However, the support portion 31b is not limited to the section directly below the primary transfer rollers 16M to 16C in the containment container 18. It is also possible to obtain the same effect by providing the support portion 31b at any position in the section from the drive roller bearing 13a, which supports the transfer unit 11 in the X-axis direction, to the pressing portion 31a. That is, as shown in Figure 4 (the intermediate transfer belt 12 is not shown in Figure 4), the supported portion 18a and the support portion 31b The support portion 31b, which acts as a biasing force receiving portion, may be positioned such that its X-axis position is between the drive roller bearing 13a and the primary transfer roller 16Y. In addition, sufficient effect can sometimes be obtained by positioning the support portion 31b, which acts as a biasing force receiving portion, such that its X-axis position overlaps with at least the intermediate transfer belt 12. Furthermore, by providing the support portion 31b, it is also possible to configure the device without providing the pressing portion 31a, and to position the transfer unit 11 relative to the device body using the drive roller bearing 13a and the support portion 31b while suppressing deformation due to creep with the support portion 31b.

[0035] Here, from the viewpoint of creep suppression performance, it is desirable to restrict the position by bringing the supported part 18a and the support part 31b into contact, but it is also possible to leave a gap without contact. Leaving a gap will allow creep by the amount of the gap, but it is also possible to create a gap in the structure in order to suppress creep in the -Z direction thereafter. In other words, in the initial stages of use of the transfer unit 11, the supported part 18a and the support part 31b may be configured to be non-contact. Alternatively, it is also possible to configure the supported part 18a and the support part 31b to interfere with each other, and although the containment container 18 will be subjected to force in the +Z direction, this can be arbitrarily selected as long as it is acceptable in terms of the positional accuracy of the transfer unit 11.

[0036] In this embodiment, as described above, the remaining toner is collected by the recovery means 19 provided in the transfer unit 11, and this is also effective as a means to restrict displacement in the -Z direction due to the weight of the remaining toner. From the viewpoint of the weight of the remaining toner, it is desirable to provide a support structure directly below the section from the primary transfer roller 16M to 16C, which is close to the approximate center of the storage container 18 in the X-axis direction. By supporting the storage container 18, which is expected to deform due to the weight of the remaining toner, with the main body stay 90 via the supported part 18a and the support part 31b, there are fewer intervening parts and it is less affected by the precision of the parts, so it is easy to obtain a stable deformation suppression effect. Furthermore, even in a configuration in which the transfer unit 11 does not have a storage container 18, the creep suppression effect can be obtained by providing this configuration to the transfer unit 11.

[0037] Furthermore, this configuration also improves the freedom of material selection for the housing container 18, which also serves as the frame for the transfer unit 11. In other words, creep can be suppressed by adopting the above support configuration without the need to provide highly rigid resin materials or metal frames.

[0038] Here, Figure 5 shows a view of the transfer unit 11 from the bottom, and the supported portion 18a is provided outside the intermediate transfer belt 12 in the Y-axis direction on both the drive side and the non-drive side. The tension spring 171 and primary transfer spring 163 used in the belt tensioning mechanism and the pressing mechanism during toner image transfer within the transfer unit 11 are provided approximately outside the transfer unit 11 in the Y-axis direction. Therefore, it is desirable that the supported portion 18a, which is a creep suppression member, and the support portion 31b that supports the supported portion 18a are also provided approximately outside in the Y-axis direction, which is on the line of action of their biasing force.

[0039] [Insertion and removal (attachment / detachment) of the transfer means] As shown in Figures 6 and 7, the support portion 31b (biasing force receiving portion) for creep suppression is configured to contact and separate from the supported portion 18a in conjunction with the operation of the opening / closing door 3, which is the first opening / closing member. Figure 6 shows the operation of the transfer means in conjunction with the opening / closing door operation during long-term storage and image formation. In Figure 6, the opening / closing door 3 is closed, and the inside of the device body is not exposed (closed state). In this state, the transfer unit 11 is supported by the support portion 31b in the same way as the support configuration shown in Figure 3, and is in a position that allows creep suppression. At this time, the support portion 31b supports the transfer unit 11 in the support position. The rail member 31 that supports the housing container 18 of the transfer unit 11 is connected from the opening / closing door 3 via the first to third door links (32 to 34).

[0040] The details of the operation to open the opening / closing door 3 from the closed state of the image forming apparatus shown in Figure 6 are described below. The opening / closing door 3 is provided with a pivot center 3a, and the groove 3b engages with the boss 32b of the first door link 32. The first door link 32 rotates in the CW direction around the rotation center 32a, in conjunction with the opening direction E (CW direction) of the opening door 3. The boss 32c of the first door link 32 engages with the groove of the second door link 33, causing the second door link 33 to move linearly in approximately the +X direction. The boss 34b of the third door link 34 engages with the groove of the second door link 33, causing it to rotate in the CW direction around the rotation center 34a. Furthermore, the groove of the third door link 34 engages with the boss 31c of the rail member 31, causing the rail member 31 to move linearly in approximately the -X direction. As a result, the transfer unit 11 rotates in the CW direction around the drive roller bearing 13a.

[0041] As a result of the above operation, the image forming apparatus enters an open state (open state) with the opening / closing door 3 open, as shown in Figure 7, exposing the inside of the apparatus body. The support part 31b then retracts from the supported part 18a and moves to a position where it does not support the transfer unit 11 (retracted state), and the support part 31b moves to a non-supported position where it does not support the transfer unit 11. At this time, the pressing part 31a of the rail member 31 moves away from the lower contact part 112 of the transfer unit 11 by moving in the -X direction, and its position is restricted by a regulating member inside the rail member 31, and the transfer unit 11 is supported by the pressing part 31a. The support part 31b is at a distance from the housing container 18, and the supported part 18a is at a distance from the rail member 31, so there is no interference, and the transfer unit 11 can be directly and accurately supported by the aforementioned pressing part 31a. In this retracted state, the transfer unit 11 can be inserted into and removed from the main body of the device, and the ease of insertion and removal is improved by providing slopes in the +X and -X directions of the support portion 31b. Furthermore, the ease of assembly during insertion is further improved by providing a slope on the +X direction surface of the supported portion 18a.

[0042] In the main body of the device 2, as shown in Figure 8, opening the opening / closing door 3 causes the rail member 31 to retract (move), the support portion 31b moves to the aforementioned unsupported position, and the transfer unit 11 becomes unsupported. In this state, by opening the rear door 60, which is a second opening / closing member located at a different position from the opening / closing door 3, the transfer unit 11 can be pulled out in the -X direction toward the rear of the main body and removed from the main body of the device 2. Thus, the configuration of this embodiment can be said to have a creep suppression function while being easy to replace and insert / remove during assembly. On the other hand, after the transfer unit 11 is inserted into the main body of the device 2, the support portion 31b automatically moves to a support position, which is a position where creep can be suppressed, in conjunction with the closing operation of the opening / closing door 3, so that creep suppression can be achieved without additional operation. In this embodiment, the support portion 31b can be switched between the support position and the unsupported position in conjunction with the opening and closing operation of the opening / closing member, but a separate operation panel (operation unit) may be provided on the main body of the device, and the support position and unsupported position can be switched by operating the operation panel.

[0043] [Variations of creep prevention shapes] Next, other embodiments for enhancing the effects of the supported portion 18a and the support portion 31b in this embodiment will be described with reference to Figures 9 to 12. These configurations may be added to the configuration of Embodiment 1, or they may be used to replace the configuration of Embodiment 1.

[0044] (Example 2) This embodiment will be explained with reference to Figure 9. Figure 9(a) shows a diagram in which the shape of the support portion necessary for creep suppression is provided only on the support portion 31b of the rail member 31, and shows the state during storage and image formation. Even in this configuration, the force received by the transfer unit 11 can be received by the main body stay 90 through the support portion 31b of the rail member 31, thus having the effect of suppressing creep. As shown in Figure 9(b), when the opening / closing door 3 is opened, the image forming apparatus is opened, and the support portion 31b retracts from the support position and moves to the non-support position. At this time, the support portion 31b is inserted into the relief shape 18b (opening) provided in the storage container 18, so it does not interfere with the storage container 18. Therefore, the transfer unit 11 can be directly supported with high precision by the aforementioned pressing portion 31a. Furthermore, in this embodiment, there is no need to provide a protruding shape such as the supported portion 18a on the storage container 18. Moreover, in this embodiment, when the transfer unit 11 is pulled out... Furthermore, the shape of the support portion 31b is provided with an inclined surface that can slide against the edge of the relief shape 18b, thereby preventing snagging and further improving insertion and removal.

[0045] (Example 3) This embodiment will be explained with reference to Figure 10. Figure 10(a) shows a configuration in which a biasing member 35 is provided on the main body stay 90 as a creep suppression configuration. During storage and image formation, the biasing member 35 (receiving biasing member) that biases the support portion 31b, which is the biasing force receiving portion, contacts the storage container 18 from below in the Z-axis direction and biases it in the +Z direction. With this configuration, the transfer unit 11 resists the resultant force in the +Z direction against the force received by the tension spring 171 and the primary transfer spring 163, thereby suppressing creep deformation. In this embodiment, the storage container 18 is directly biased by the support portion 31b on which the biasing member 35 is provided. Therefore, it is not necessary to consider positional accuracy such as aligning the supported portion 18a on the Z-direction lower surface of the storage container 18 with the support portion 31b, and it is possible to apply a substantially constant biasing force in the +Z direction. Furthermore, as shown in Figure 10(b), when the image forming apparatus is in the open state and the transfer unit 11 is retracted from the apparatus body, the transfer unit 11 can be inserted and removed while compressing the biasing member 35. In this embodiment, the only creep-suppressing member provided is the biasing member 35. Therefore, as in Embodiments 1 and 2, the transfer unit 11 can be inserted and removed without providing a mechanism to switch the support portion 31b between a support position that supports the transfer unit 11 and a non-support position that does not support the transfer unit 11. In other words, the transfer unit 11 can be inserted and removed with a simpler configuration, and creep suppression is possible.

[0046] (Example 4) This embodiment will be explained with reference to Figure 11. Figure 11 shows that the biasing member 35 described in Figure 10 is provided on the rail member 31, and further, a guide portion 90a (restricting portion) is provided to restrict the movement of the biasing member 35 in the +Z direction when the image forming apparatus is in the open state and the transfer unit 11 is retracted from the apparatus body. During storage and image forming as shown in Figure 11(a), the biasing member 35 contacts the storage container 18 from below in the Z-axis direction, similar to Figure 10(a), and biases it in the +Z direction to suppress creep. Similar to Embodiment 3, since the storage container 18 is directly biased by the biasing member 35, it is possible to apply a substantially constant biasing force in the +Z direction regardless of the positional accuracy of the lower surface of the storage container 18 in the Z-axis direction. Also, as shown in Figure 11(b), when the image forming apparatus is in the open state and the transfer unit 11 is retracted from the apparatus body, the engaging portion 35a provided on the biasing member 35 is restricted by the guide portion 90a provided on the main body stay 90. In this configuration, the biasing member 35 moves in the -Z direction, creating a gap between the transfer unit 11 and the biasing member 35, resulting in non-contact with the lower surface of the containment container 18 in the Z direction. Thus, compared to Example 3, this configuration further improves the ease of insertion and removal of the transfer unit 11 by using the biasing member 35.

[0047] (Example 5) This embodiment will be explained with reference to Figure 12. Figure 12 shows a configuration in which the creep suppression member can select whether to support or not support the transfer unit 11 when the image forming apparatus is in the closed state. As shown in Figure 12(a), the support cam 182 (variable support cam) provided on the transfer unit 11 rotates in response to drive transmission from a coupling gear 181 connected to a drive source (not shown) on the main body side. In this configuration, drive transmission from the coupling gear is carried out by gear and belt drive, but the means are arbitrary, such as connecting everything with gears.

[0048] In this configuration, in modes where image formation is not occurring, such as during long-term storage or transportation, the tip 182a of the support cam 182 contacts the main body stay 90, as shown in Figure 12(a), and the transfer unit 11 is supported. The phase of the coupling gear 181, which is driven by the drive source, is then adjusted to a position that suppresses creep deformation of the transfer unit 11. Control (support phase).

[0049] On the other hand, during image formation, as shown in Figure 12(b), the support cam 182 rotates via the coupling gear in response to the drive input from the drive source (not shown) on the main body side. This results in a phase where the transfer unit 11 is not in contact with the main body stay 90 and is not supported by the support cam 182 (non-support phase). This configuration allows for avoidance of interference during image formation, even if the dimensional relationship of the transfer unit 11, which is positioned on the main body side plate 70 via the process cartridge tray 80, causes interference with the main body stay 90 when the support cam 182 makes contact. Therefore, the transfer unit 11 is not subjected to force in the +Z direction, preventing deformation and changes in the direction of play in supported parts such as the drive roller bearing 13a, which could affect image accuracy. Furthermore, as shown in Figure 12(c), when inserting or removing the transfer unit 11, the support cam 182 is set to the non-support phase, similar to during image formation, thus ensuring no impact on insertion or removal. [Explanation of Symbols]

[0050] 11: Transfer unit, 16: Primary transfer roller, 18: Storage container, 18a: Supported part, 31: Rail member, 31a: Pressing part, 31b: Support part, 40: Photosensitive drum, 90: Main body stay, 163: Primary transfer spring

Claims

1. A plurality of image carriers; An intermediate transfer belt; a plurality of transfer members that sandwich the intermediate transfer belt between the plurality of image carriers; a biasing means for biasing the plurality of transfer members toward the plurality of image carriers via the intermediate transfer belt; a frame supporting the intermediate transfer belt, the plurality of transfer members, and the biasing means; a transcription unit comprising an apparatus main body that supports the plurality of image carriers and the transfer unit; In an image forming apparatus comprising: The device main body includes a support portion that supports the transfer unit, and a biasing force receiving portion that is positioned between the plurality of transfer members in the arrangement direction of the plurality of transfer members and is capable of supporting the transfer unit. An image forming apparatus characterized by:

2. A plurality of image carriers; An intermediate transfer belt; a plurality of transfer members that sandwich the intermediate transfer belt between the plurality of image carriers; a biasing means for biasing the plurality of transfer members toward the plurality of image carriers via the intermediate transfer belt; a frame supporting the intermediate transfer belt, the plurality of transfer members, and the biasing means; a transcription unit comprising an apparatus main body that supports the plurality of image carriers and the transfer unit; In an image forming apparatus comprising: The device body includes a support portion that supports the transfer unit, and a biasing force receiving portion that is positioned below the plurality of transfer members in the arrangement direction of the plurality of transfer members and is capable of supporting the transfer unit. An image forming apparatus characterized by:

3. A plurality of image carriers; An intermediate transfer belt; a plurality of transfer members that sandwich the intermediate transfer belt between the plurality of image carriers; a biasing means for biasing the plurality of transfer members toward the plurality of image carriers via the intermediate transfer belt; a frame supporting the intermediate transfer belt, the plurality of transfer members, and the biasing means; a transcription unit comprising an apparatus main body that supports the plurality of image carriers and the transfer unit; In an image forming apparatus comprising: The device body includes: a first support portion that supports one end side of the intermediate transfer belt of the transfer unit; a second support portion that supports the other end side of the transfer unit with respect to the intermediate transfer belt; a biasing force receiving portion capable of supporting the transfer unit between the first support portion and the second support portion; 1. An image forming apparatus comprising:

4. the transfer member is a rotatable transfer roller; 4. The image forming apparatus according to claim 1, wherein the biasing force receiving portion is disposed so as to be able to support the frame outside the intermediate transfer belt in the axial direction of the transfer member.

5. The device body includes:

5. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to be movable between a support position where the transfer unit can be supported and a non-support position where the transfer unit is not supported.

6. The device body includes:

6. The image forming apparatus according to claim 5, further comprising an operation unit that moves the biasing force receiving portion between the supporting position and the non-supporting position.

7. The operation unit includes: an opening / closing member that can be switched between an open state in which the inside of the device main body is exposed and a closed state in which the inside of the device main body is not exposed, 7. The image forming apparatus according to claim 6, wherein the biasing force receiving portion is positioned at the support position when the opening / closing member is in the closed state, and the biasing force receiving portion is positioned at the non-support position when the opening / closing member is in the open state.

8. a plurality of cartridges each including the image carrier and detachably mountable to the main body of the apparatus; 8. The image forming apparatus according to claim 7, wherein the opening / closing member, in the open state, allows the plurality of cartridges to be attached to and detached from the main body of the apparatus.

9. The opening / closing member is a first opening / closing member, the device body further includes a second opening / closing member provided at a position different from that of the first opening / closing member and capable of switching between an open state in which the inside of the device body is exposed and a closed state in which the inside of the device body is not exposed, 9. The image forming apparatus according to claim 7, wherein when the first opening / closing member and the second opening / closing member are both in an open state, the transfer unit is detachable from the apparatus main body.

10. 10. The image forming apparatus according to claim 5, wherein the frame has an opening into which the urging force receiving portion in the non-support position is inserted at a position between the plurality of transfer members in the arrangement direction of the plurality of transfer members.

11. 11. The image forming apparatus according to claim 10, wherein the biasing force receiving portion has an inclined surface that slides against the edge of the opening to guide the transfer unit when the transfer unit is pulled out of the apparatus main body in the non-support position.

12. The device body includes:

10. The image forming apparatus according to claim 1, further comprising a receiving portion biasing member that biases the biasing force receiving portion toward the transfer unit, wherein the biasing force receiving portion receives a biasing force from the receiving portion biasing member when the transfer unit is in a support position where it can be supported.

13. The device body includes: a receiving portion biasing member that biases the biasing force receiving portion toward the transfer unit; 、 10. The image forming apparatus according to claim 5, further comprising a regulating portion that regulates the urging of the urging force receiving portion by the receiving portion urging member when the urging force receiving portion is in the non-support position.

14. In the closed state, The transfer unit comprises:

10. The image forming apparatus according to claim 7, further comprising a variable support cam that can assume a non-support phase in which it is not in contact with the device main body and a support phase in which it is in contact with the device main body and is supported by the device main body.

15. 15. The image forming apparatus according to claim 14, wherein the variable support cam is in the supporting phase when no image is formed, and in the non-supporting phase when an image is formed and when the transfer unit is removed from the apparatus main body.

16. 16. The image forming apparatus according to claim 1, wherein the biasing force receiving portion does not come into contact with the frame in an initial stage of use of the transfer unit.

Images