Image forming apparatus

Abstract

The present invention relates to an image forming apparatus (100) having an intermediate transfer body which can be easily inserted into and pulled out of an apparatus main body, and having a small size, low cost, difficult image density variation, and a long service life. The image forming apparatus (100) comprises: a plurality of frame members (49) for holding an image carrier (1); an intermediate transfer body (3) that secondarily transfers the toner image onto the recording medium (P); a plurality of primary transfer members (11) that primarily transfer the toner image onto the intermediate transfer body at the primary transfer section; a holding member (51, 81) that holds the primary transfer member; a plurality of pressing members (50, 80) for pressing the holding member; and a pressing member (57 or 58) that presses the image carrier against the intermediate transfer body frame (37) or the main body structure side plate (55), the holding member being brought into contact with the frame or the frame member to position the primary transfer member, one end side of the image carrier being pressed against the frame by the pressing member (57) to be positioned, and the other end side of the image carrier being pressed against the frame by the pressing member (57) to be positioned. The primary transfer member on one end side is positioned by pressing a holding member (81) against the frame (37) by means of a pressing member (80).

Description

Technical Field

[0001] The present invention relates to an image forming apparatus. Background Art

[0002] In a color printer, in order to extend the life of a photoreceptor, a primary transfer roller for colors other than black is generally separated from the photoreceptor in a monochrome mode. Patent document 1 discloses that a retaining member is provided on each of a primary transfer roller and a support roller, and the primary transfer roller and the support roller are separated from the photoreceptor by the rotation of a cam. The support roller is a roller for determining the shape of the belt so that the transfer nip of the most upstream primary transfer roller is in a target state.

[0003] However, in Patent Document 1, since the holding members are provided on the primary transfer roller and the backup roller, respectively, the distance between the primary transfer roller and the backup roller becomes longer, the size of the device increases, and the manufacturing cost of the device increases.

[0004] In Patent Document 2, the primary transfer rollers and support rollers of the colors (cyan, magenta, and yellow) are held by the same holding member, and when switching between the monochrome mode and the full-color mode, the holding member is moved as a whole to contact and separate from the primary transfer rollers. However, since the front and rear (left and right) ends of the primary transfer rollers and the support rollers of the colors must be held by the same holding member, the parts are enlarged, and the manufacturing cost of the device increases.

[0005] In order to make the transfer unit smaller and less expensive, Patent Document 3 discloses a mechanism for holding the primary transfer roller and the support roller by the same holding member and positioning the holding member by contacting the transfer frame. However, since the photosensitive body is not positioned relative to the transfer frame, when the holding member contacts the transfer frame, the position of the primary transfer roller relative to the photosensitive body is easily changed due to the accumulation of component tolerances. Therefore, image density deviation is easily generated left and right. In addition, since there is no mechanism for suppressing belt meandering, there is a problem that an expensive belt needs to be used or the belt life is short.

[0006] Therefore, an object of the present invention is to provide an image forming apparatus having an intermediate transfer body that can be easily inserted and removed from an apparatus main body, which is small and low-cost, is less likely to cause image density deviation, and has a long life.

[0007] [Patent Document 1] (Japanese) Patent Publication No. 2013-113907

[0008] [Patent Document 2] (Japanese) Patent Publication No. 2008-122596

[0009] [Patent Document 3] (Japanese) Patent Publication No. 2010-197774 Summary of the invention

[0010] The problem is solved by the following method: an image forming device, characterized in that it includes: a plurality of image carriers that carry colorant images; a plurality of frame members that hold the image carriers; an intermediate transfer body that is movable to transfer the colorant images transferred from the image carriers to a recording medium; a plurality of primary transfer members that transfer the colorant images from the image carriers to the intermediate transfer body at a primary transfer portion where the image carriers and the outer peripheral surfaces of the intermediate transfer body are in contact; a holding member that holds the primary transfer members; and an intermediate transfer body frame that holds the intermediate transfer body. The first transfer member is provided with an intermediate transfer body and the holding member is rotatably held; a plurality of pressure members that pressurize the holding member, and a pressing member that presses the image carrier onto the intermediate transfer body frame or the side plate of the main structure, and the first transfer member is positioned by causing the holding member to abut against the intermediate transfer body frame or the frame member, one end side of the image carrier is positioned by being pressed against the intermediate transfer body frame by the pressing member, and the first transfer member in the one end side is positioned by causing the holding member to abut against the intermediate transfer body frame by the pressure member.

[0011] The present invention can provide an image forming apparatus having an intermediate transfer body that can be easily inserted and removed from an apparatus main body, which is small and low-cost, is less likely to cause image density deviation, and has a long life. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 FIG. 1 is a diagram schematically showing an example of an image forming apparatus 100 configured as a printer.

[0013] Figure 2 FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

[0014] Figure 3 FIG. 1 is a schematic diagram showing the insertion and extraction directions of the intermediate transfer unit and the photosensitive unit into and out of the image forming apparatus.

[0015] Figure 4 The figure shows the intermediate transfer unit and the photosensitive unit on the inner side in the insertion and extraction direction.

[0016] Figure 5 Shown is a schematic diagram of the intermediate transfer unit and the photoreceptor unit on the front side of the insertion and extraction direction.

[0017] Figure 6 FIG. 1 is a schematic diagram showing the position of the primary transfer roller on the inner side in the insertion and extraction direction of the intermediate transfer unit.

[0018] Figure 7 FIG. 1 is a schematic diagram showing the position of the primary transfer roller on the front side in the insertion and extraction direction of the intermediate transfer unit.

[0019] Figure 8 Shown is a schematic diagram of a belt deviation correction mechanism for correcting the deviation of the belt.

[0020] Fig. 9 The figure shows a state where the tension roller is tilted by the belt deviation correction mechanism.

[0021] Fig.10 Shown is with Figure 8 The corresponding tension roller 5 (dashed line) and Fig. 9 Schematic representation of the corresponding position of the tensioning roller 5 (solid line). DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0023] Figure 1 FIG. 1 is a schematic diagram of an example of an image forming apparatus 100 configured as a printer. The image forming apparatus 100 shown here is provided with a plurality of photosensitive bodies (an example of an image carrier) arranged in its main body frame. In the example shown in the figure, the first to fourth photosensitive bodies 1a, 1b, 1c, and 1d (hereinafter, appropriately referred to as "photosensitive bodies 1" when the colors are not identified). A toner image of a different color is formed on each photosensitive body, and a toner image of a different color is formed on each photosensitive body. Figure 1 In the example shown, a black toner image, a magenta toner image, a cyan toner image, and a yellow toner image are formed on the photosensitive bodies 1a, 1b, 1c, and 1d, respectively. Figure 1 Although the photosensitive members 1a, 1b, 1c, and 1d shown in the figure are formed in a drum shape, an endless belt-shaped photosensitive member wound around a plurality of rollers and driven to rotate may be adopted.

[0024] An intermediate transfer belt 3 is disposed opposite to the first to fourth photosensitive bodies 1a, 1b, 1c, 1d, and is configured as an intermediate transfer body. Each of the photosensitive bodies 1a, 1b, 1c, 1d is in contact with the surface of the intermediate transfer belt 3. The intermediate transfer belt 3 transfers the toner image primarily transferred to the photosensitive bodies 1a, 1b, 1c, 1d to the recording medium P. The intermediate transfer belt 3 shown here is wound around a driving roller 4, a tension roller 5, and an inlet roller 7. One of these supporting rollers, for example, the supporting roller 4, is configured as a driving roller driven by a driving source (not shown). The intermediate transfer belt 3 is driven to rotate in the direction of arrow A by the driving of the roller. The intermediate transfer belt 3 may be a multi-layer structure or a single-layer structure. If it is a multi-layer structure, it is preferable that the base layer is made of, for example, a fluorine resin or PVDF sheet with a small stretch, or a polyimide resin, and the surface is covered with a coating layer with good flatness and smoothness such as a fluorine resin. In addition, if it is a single layer, materials such as PVDF, PC, and polyimide can be used.

[0025] The structures for forming toner images on the photoreceptors 1a, 1b, 1c, and 1d and for transferring the toner images to the intermediate transfer belt 3 are substantially the same, and only the colors of the toner images formed are different. Therefore, only the structure and function of forming a black toner image on the first photoreceptor 1a and transferring the toner image to the intermediate transfer belt 3 will be described. Figure 1 The photosensitive body 1a is rotated and driven in the counterclockwise direction as indicated by the arrow in the figure. At this time, light from the neutralization device (not shown) is irradiated onto the surface of the photosensitive body, and the surface potential of the photosensitive body 1a is initialized. The initialized photosensitive body surface is uniformly charged with a prescribed polarity, which is negative in this example, by the charging device 8. The light-modulated laser beam L emitted from the exposure device 9 is irradiated onto the charged surface, thereby forming an electrostatic latent image corresponding to the written information on the surface of the photosensitive body 1a. Figure 1 In the image forming apparatus 100 shown, the exposure device 9 composed of a laser writing device that emits a laser beam is used, but an exposure device having an LED array and an imaging unit may also be used.

[0026] When the electrostatic latent image formed on the photoreceptor 1a passes through the developing device 10, it is visualized as a black toner image. On the other hand, on the inner side of the intermediate transfer belt 3, primary transfer rollers 11a, 11b, 11c, and 11d (hereinafter, appropriately referred to as "primary transfer rollers 11" when the colors are not identified) are arranged as primary transfer components. The primary transfer rollers 11a, 11b, 11c, and 11d are arranged to sandwich the belt and are roughly opposite to the photoreceptor 1a. The primary transfer roller 11 abuts against the back side of the intermediate transfer belt 3 to ensure proper transfer clamping of the photoreceptor 1a and the intermediate transfer belt 3. The primary transfer roller 11 is made of metal and is therefore slightly offset relative to the photoreceptor 1 (indirect transfer method). In the present embodiment, the belt distance (offset) at which neither the photoreceptor 1 nor the primary transfer roller 11 contacts is 4 to 5 mm.

[0027] A transfer voltage having a polarity opposite to the toner charge polarity of the toner image formed on the photoreceptor 1a, which is positive in this example, is applied to the primary transfer roller 11. As a result, a transfer electric field is formed between the photoreceptor 1a and the intermediate transfer belt 3, and the toner image on the photoreceptor 1a is electrostatically transferred to the intermediate transfer belt 3 that is driven to rotate in synchronization with the photoreceptor 1a at the primary transfer portion where the photoreceptor 1a and the outer peripheral surface of the intermediate transfer belt 3 are in contact (primary transfer). The transfer residual toner attached to the surface of the photoreceptor 1a after the toner image is transferred to the intermediate transfer belt 3 is removed by the cleaning device 12, so that the surface of the photoreceptor 1a is cleaned.

[0028] In exactly the same manner, magenta toner images, cyan toner images and black toner images are formed on the second to fourth photoreceptors 1b, 1c, 1d, respectively, and the toner images of each color are electrostatically transferred in an overlapping manner in sequence to the intermediate transfer belt 3 to which the black toner image has been transferred.

[0029] At this time, there are two modes, that is, a full-color mode using four-color toner images and a black monochrome mode using only black monochrome. In the full-color mode, the intermediate transfer belt 3 and the photosensitive members 1 of the four colors are in contact, and the toners of the four colors are all transferred to the intermediate transfer belt 3. On the other hand, in the black monochrome mode, only the black photosensitive body 1a is in contact with the intermediate transfer belt 3, and only the black toner is transferred to the intermediate transfer belt 3. At this time, the intermediate transfer belt 3 and the magenta, cyan, and yellow photosensitive bodies 1b, 1c, and 1d are not in contact, and the primary transfer rollers 11b, 11c, and 11d are separated from the photosensitive bodies 1b, 1c, and 1d by the contact and separation mechanism 90 provided in the image forming apparatus 100.

[0030] On the other hand, Figure 1 As shown in the figure, a paper feed device 14 is arranged at the lower part of the main body of the device. The paper feed device 14 feeds a recording medium P, such as a transfer paper, in the direction of arrow B by the rotation of a paper feed roller 15. The fed recording medium P passes through a registration roller pair 16 and is conveyed to between a portion of the intermediate transfer belt 3 wound on the support roller 4 and a secondary transfer roller 17 facing the intermediate transfer belt 3 at a predetermined timing. At this time, a predetermined transfer voltage is applied to the secondary transfer roller 17, thereby causing the composite toner image on the intermediate transfer belt 3 to be secondarily transferred to the recording medium P.

[0031] The recording medium P to which the composite toner image is secondarily transferred is further transported upward and passes through the fixing device 18, at which time the toner image on the recording medium P is fixed by heat and pressure. The recording medium P after passing through the fixing device 18 is discharged to the outside of the image forming apparatus by means of a discharge roller pair 19 provided in the discharge section.

[0032] In addition, the transfer residual toner attached to the intermediate transfer belt 3 after the toner image is transferred is removed by the belt cleaning device 20. In the belt cleaning device 20 in this embodiment, a cleaning blade 21 in the shape of a blade made of urethane or the like is used, and the cleaning blade 21 is abutted in the opposite direction to the rotation direction of the intermediate transfer belt 3. However, those skilled in the art know that various suitable types of cleaning devices 20 can be used, for example, an electrostatic capacity type cleaning device can be used.

[0033] The transfer residual toner removed from the intermediate transfer belt 3 by the cleaning blade 21 is conveyed toward the rear side in the longitudinal direction through the waste toner coil in the cleaning box, and is conveyed toward the waste toner container through the waste toner path provided in the apparatus body.

[0034] Figure 1 FIG. 1 is an example of a schematic diagram of a power supply used in this embodiment.

[0035] The primary transfer bias power source 27BK, which is a primary transfer power source for applying a voltage to the primary transfer roller 11a, is connected to the detection unit 28 and the control unit 30. The detection unit 28 is connected to the primary transfer bias power source 27BK, the primary transfer roller 11a, and the control unit 30. Here, the detection unit 28 is connected only to the primary transfer roller 11a corresponding to the photosensitive body 1a of one color (black in this embodiment) among all the photosensitive bodies 1a, 1b, 1c, and 1d.

[0036] The detection section 28 is a primary transfer current detection section that detects the amount of current flowing through the primary transfer roller 11a when a bias is applied to the primary transfer roller 11a when the output of the primary transfer bias power supply 27BK is in a steady voltage control. The detection section 28 detects the output bias of the primary transfer bias power supply 27BK when the output of the primary transfer bias power supply 27BK is in a steady current control.

[0037] The other primary transfer rollers 11b, 11c, and 11d are powered by another primary transfer power source 29FC.

[0038] Therefore, the image forming apparatus 100 has a plurality of primary transfer power supplies 27BK, 29FC, one of which is connected to the primary transfer roller 11a corresponding to the photosensitive body 1a for the black toner image, and the detection unit 28 is also connected only to the primary transfer roller 11a corresponding to the photosensitive body 1a for the black toner image. Therefore, the image forming apparatus 100 only needs to have one detection unit 28, and the cost of the structure of the intermediate transfer body unit 60 and the resistance detection structure can be reduced. In addition, there is no need for control to change the target value of the transfer bias voltage every time the time or environment changes, and there is no need to drive the intermediate transfer device or the image carrier every time, so the life of the intermediate transfer body or the image carrier can be extended.

[0039] The control unit 30 is connected to the primary transfer bias power supply 27BK, the primary transfer power supply 29FC and the detection unit 28 , and determines the primary transfer voltage of the primary transfer roller 11 a corresponding to all colors based on the detection result of the detection unit 28 , that is, based on the current value X detected by the detection unit 28 .

[0040] Figure 2 FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention.

[0041] In the image forming apparatus 100 , the photoreceptors 1 a , 1 b , 1 c , and 1 d are held by photoreceptor frames 49 a , 49 b , 49 c , and 49 d (an example of a frame member). Figure 2 The photosensitive body 1d and the photosensitive body frame 49d on the front side of the device are representatively shown. Abutment members are provided at both ends of the length direction of the photosensitive bodies 1a, 1b, 1c, and 1d. Figure 2 In the embodiment, a contact member 48d is provided on the front side of the photosensitive body 1d in the insertion and extraction direction, and a contact member 53d is provided on the inner side of the photosensitive body 1d in the insertion and extraction direction. In addition, a photosensitive body frame 49d (an example of a frame member) is provided to hold the photosensitive body 1d, a photosensitive body pressing member 57d (an example of a pressing member) is provided on the front side of the photosensitive body frame 49d in the insertion and extraction direction, and a photosensitive body pressing member 58d (an example of a pressing member) is provided on the inner side of the photosensitive body frame 49d in the insertion and extraction direction. The contact members 48d and 53d are made to contact with the contacted members by these pressing members 57d and 58d to position the photosensitive bodies 1a, 1b, 1c, and 1d, but the contacted members contacted by these contact members 48d and 53d are different. That is, the abutment member 48d on the front side in the insertion and extraction direction abuts against the intermediate transfer body frame 37 or another member arranged on the intermediate transfer body frame 37 to be positioned, and the abutment member 53d on the inner side in the insertion and extraction direction abuts against the main structure side plate 55 or the main structure side plate retaining member 54d arranged on the main structure side plate 55 to be positioned.

[0042] Figure 3 FIG. 1 is a schematic diagram showing the insertion and extraction directions of the intermediate transfer unit and the photosensitive unit into and out of the image forming apparatus.

[0043] In the present embodiment, the intermediate transfer unit 60 and the photosensitive body units 70a, 70b, 70c, and 70d can be easily inserted and removed from the image forming apparatus 100 from the right side to the left side or from the left side to the right side when viewed from the front of the apparatus. The insertion and removal direction of the intermediate transfer unit 60 is parallel to the insertion and removal direction of the photosensitive body units 70a, 70b, 70c, and 70d. When the door of the image forming apparatus 100 is opened, the insertion and removal of the intermediate transfer unit 60 and the photosensitive body units 70a, 70b, 70c, and 70d are easy because the large opening 61 is opened. The intermediate transfer unit 60 has an intermediate transfer belt 3, a drive roller 4, a tension roller 5, an inlet roller 7, a belt cleaning device 20, four primary transfer rollers 11, etc. ( Figure 1 The photosensitive unit 70 includes four photosensitive bodies 1 and four charging devices 8 ( Figure 1 ).

[0044] Figure 4The figure shows the intermediate transfer unit and the photosensitive unit on the inner side of the insertion and extraction direction. Figure 5 Shown is a schematic diagram of the intermediate transfer unit and the photoreceptor unit on the front side of the insertion and extraction direction.

[0045] like Figure 4 As shown, on the inner side of the insertion and extraction direction, the photosensitive body abutting members 53a, 53b, 53c, 53d are abutted against the main body side plate retaining members 54a, 54b, 54c, 54d provided on the main body structure side plate 55 by the photosensitive body pressing members 58a, 58b, 58c, 58d as the first pressing members, so as to position the photosensitive bodies 1a, 1b, 1c, 1d respectively. Figure 5 As shown, on the front side in the insertion and extraction direction, the photosensitive body pressing parts 57a, 57b, 57c, 57d serving as the second pressing parts cause the photosensitive body abutting parts 48a, 48b, 48c, 48d to abut against the intermediate transfer body frame 37 or another part arranged on the intermediate transfer body frame 37, so as to position the photosensitive bodies 1a, 1b, 1c, 1d.

[0046] Next, refer to Figure 6 and Figure 7 Positioning of the primary transfer roller will be described.

[0047] Figure 6 FIG. 1 is a schematic diagram showing the position of the primary transfer roller on the inner side of the insertion and extraction direction of the intermediate transfer unit. Figure 7 FIG. 1 is a schematic diagram showing the position of the primary transfer roller on the front side in the insertion and extraction direction of the intermediate transfer unit.

[0048] exist Figure 6In the image forming device 100 shown, the first transfer rollers 11a, 11b, 11c, and 11d of each color are respectively held on the first transfer roller holding components 51a, 51b, 51c, and 51d (an example of a holding component), and the first pressurizing components 50a, 50b, 50c, and 50d for pressurizing the first transfer rollers 11a, 11b, 11c, and 11d are respectively arranged on the first transfer roller holding components 51a, 51b, 51c, and 51d. The primary transfer roller holding members 51a, 51b, 51c, 51d can rotate around the rotation shafts 52a, 52b, 52c, 52d by the pressure of the first pressure members 50a, 50b, 50c, 50d, and the abutment portions 56a, 56b, 56c, 56d formed at the lower portions of the primary transfer roller holding members 51a, 51b, 51c, 51d abut against the photosensitive body frames 49a, 49b, 49c, 49d. Thus, the primary transfer rollers 11a, 11b, 11c, 11d are positioned by causing the primary transfer roller holding members 51a, 51b, 51c, 51d to abut against the photosensitive body frames 49a, 49b, 49c, 49d, respectively. Thus, the change in the positional relationship of the primary transfer rollers 11a, 11b, 11c, 11d relative to the photosensitive bodies 1a, 1b, 1c, 1d is minimized, thereby suppressing uneven image density. In addition, the intermediate transfer unit 60 can be easily inserted and removed from the device body, thereby achieving miniaturization and cost reduction of the device. In addition, the intermediate transfer frame 37 holds the intermediate transfer belt 3 and rotatably holds the primary transfer roller holding members 51a, 51b, 51c, 51d.

[0049] Next, the positioning of the primary transfer roller on the front side in the insertion and extraction direction will be described.

[0050] exist Figure 7In the image forming device 100 shown, the first transfer rollers 11a, 11b, 11c, and 11d of each color are respectively held on the first transfer roller holding components 81a, 81b, 81c, and 81d (an example of a holding component) near the front side in the insertion and extraction direction, and the second pressing components 80a, 80b, 80c, and 80d for pressurizing the first transfer rollers 11a, 11b, 11c, and 11d are respectively arranged on the first transfer roller holding components 81a, 81b, 81c, and 81d. The primary transfer roller holding members 81a, 81b, 81c, 81d are rotatable about the rotation shafts 52a, 52b, 52c, 52d by the pressing force of the second pressing members 80a, 80b, 80c, 80d, and the abutting portions 86a, 86b, 86c, 86d formed at the lower portions of the primary transfer roller holding members 81a, 81b, 81c, 81d abut against the intermediate transfer body frame 37. Therefore, the primary transfer rollers 11a, 11b, 11c, 11d are positioned by the second pressing members 80a, 80b, 80c, 80d, respectively. The intermediate transfer body frame 37 holds the intermediate transfer belt 3 and rotatably holds the primary transfer roller holding members 81a, 81b, 81c, 81d.

[0051] As described above, since the positions of the photosensitive bodies 1a, 1b, 1c, 1d on the front side of the insertion and extraction direction are determined by causing the photosensitive body abutment members 48a, 48b, 48c, 48d to abut against the intermediate transfer body frame 37, even if the primary transfer rollers 11a, 11b, 11c, 11d are positioned by abutting against the intermediate transfer body frame 37, the positional variation of the primary transfer rollers 11a, 11b, 11c, 11d relative to the photosensitive bodies 1a, 1b, 1c, 1d does not become large. The small positional variation of the primary transfer rollers 11a, 11b, 11c, 11d relative to the photosensitive bodies 1a, 1b, 1c, 1d reduces the unevenness of the image density on the back side and the front side in the insertion and extraction direction, and a good image can be provided.

[0052] In summary, in the image forming apparatus 100, after the photoreceptors 1a, 1b, 1c, 1d are positioned with the intermediate transfer frame 37 by bringing one end of the photoreceptors 1a, 1b, 1c, 1d into contact with one end of the intermediate transfer frame 37 ( Figure 5 ), by making the primary transfer roller holding members 81a, 81b, 81c, 81d abut against the intermediate transfer body frame 37 ( Figure 7 ), the primary transfer rollers 11a, 11b, 11c, and 11d on the one end side can be positioned with high precision. In addition, since the intermediate transfer unit 60 can be attached and detached in the main scanning direction, the intermediate transfer unit 60 can be attached and detached from the device body.

[0053] In addition, in consideration of the ease of attachment and detachment of the intermediate transfer unit 60, the other ends of the photoreceptors 1a, 1b, 1c, and 1d are pressed and positioned by the main structure side plate 55 ( Figure 4 At this time, in order to determine the position of the primary transfer roller holding members 81a, 81b, 81c, 81d at the other end side, the primary transfer roller holding members 81a, 81b, 81c, 81d are brought into contact with the photosensitive body frames 49a, 49b, 49c, 49d ( Figure 6 ). Thus, the positions of the primary transfer rollers 11a, 11b, 11c, and 11d relative to the photosensitive members 1a, 1b, 1c, and 1d can be determined with high accuracy, and the variation in image density is reduced.

[0054] like Figure 6 and 7 As shown in FIG. 1 , the support roller 47 that rotates while in contact with the inner circumference of the intermediate transfer belt 3 is arranged upstream of the primary transfer rollers 11a, 11b, 11c, and 11d of each color. As a result, the shape of the transfer nip located at the most upstream position formed between the photosensitive body 1d and the intermediate transfer belt 3 can be formed as desired. In addition, the support roller 47 is formed by the primary transfer roller holding members 51d and 81d located at the most upstream position (yellow in this embodiment) in the rotation direction of the intermediate transfer belt 3 ( Figure 6 and Figure 7 ) to hold. The primary transfer roller holding members 51d and 81d are second holding members for holding the support roller 47. That is, the holding member for holding the primary transfer roller 11d at the most upstream among the plurality of primary transfer rollers 11a, 11b, 11c, and 11d and the second holding member for holding the support roller 47 are the same member. In addition, the support roller pressing member 72 (see Fig.10 ) and the first pressurizing member 50 ( Figure 6 ) and the second pressurizing member 80 ( Figure 7 ) are the same component. In addition, the other primary transfer rollers 11a, 11b, and 11c are provided at both ends ( Figure 6 and Figure 7 ) are held by respective primary transfer roller holding members 51a, 51b, 51c and 81a, 81b, 81c. In addition, in order to make the intermediate transfer belt 3 contact and separate with respect to the photosensitive body 1, a contact and separation mechanism 90 (see Fig.10 ). With these structures, compared with the case where the support roller 47 is provided alone, the image forming apparatus 100 can be miniaturized, and the manufacturing cost can be reduced and the device structure can be simplified.

[0055] In addition, in order to position the primary transfer roller 11 and the support roller 47, the second holding member that holds the support roller is positioned on the photosensitive body frames 49a, 49b, 49c, 49d ( Figure 6) or intermediate transfer body frame 37 ( Figure 7 )superior.

[0056] In addition, in the image forming apparatus 100, a belt deviation correction mechanism 150 is provided on the tension roller 5, which is a tiltable rotating body supporting the intermediate transfer belt 3 and located upstream of the support roller 47, and which corrects the deviation of the belt by tilting the tension roller 5. By providing the belt deviation correction mechanism 150, the durability of the intermediate transfer belt 3 against cracks can be improved, and the life of the belt can be extended.

[0057] Figure 8 Shown is a schematic diagram of a belt deviation correction mechanism for correcting the deviation of the belt.

[0058] The belt deviation correction mechanism 150 is a correction mechanism for correcting the deviation of the belt by tilting the tension roller 5. The belt deviation correction mechanism 150 is arranged at the axial end of the tension roller 5, and has a belt end detection component 130 and a belt position correction part 140. The belt end detection component 130 has a cylindrical shape and is arranged to be movable on the roller shaft 5a of the tension roller 5 in the roller shaft direction. The belt end detection component 130 has a plane portion 130a extending approximately perpendicularly to the roller shaft direction. The periphery of the plane portion 130a is formed in a circular shape, and the center of the circle is located on the axis of the tension roller 5. The function of the plane portion 130a is to serve as a belt abutment portion where the end of the intermediate transfer belt 3 (referred to as the belt end 3a) contacts when the intermediate transfer belt 3 moves outward in the roller shaft direction.

[0059] like Figure 8 As shown, the roller shaft 5a is arranged coaxially with the axis of the tension roller 5. The roller shaft 5a has a cylindrical shape with a smaller diameter than the tension roller 5, is integrally provided with the tension roller 5, and penetrates the belt end detection component 130, the shaft tilting component 128 of the belt position correction unit 140, and the tension roller support component 133.

[0060] When the belt end 3a hits the flat surface 130a of the belt end detection member 130, the belt end detection member 130 movably provided in the roller axis 5a direction moves in the axial direction of the tension roller 5 (referred to as the roller axis 5a direction).

[0061] The belt position correction unit 140 includes an axial tilting component 128, a guide component 135, a rotation support component 134, a tension roller support component 133, and a roller support spring 145. The axial tilting component 128 is arranged on the roller 5a in such a manner as to contact the belt end detection component 130 on the inner side in the direction of the roller 5a. When the belt end 3a collides with the belt end detection component 130 and the belt end detection component 130 moves axially outward, the axial tilting component 128 is pressed by the belt end detection component 130 and moves outward in the direction of the roller 5a. In addition, the axial tilting component 128 has an inclined surface 128a, which is a plane inclined relative to the surface of the belt 3, on the outer side in the direction of the roller 5a. As the axial tilting component 128 moves in the direction of the roller 5a, the inclined surface 128a also moves in the direction of the roller 5a.

[0062] Furthermore, if Figure 8 As shown in FIG. 1 , the guide member 135 is provided so as to contact the inclined surface 128a of the shaft tilting member 128. The guide member 135 is provided so as to contact the inclined surface 128a of the shaft tilting member 128 with the shaft displacement portion contact portion 135a as a part thereof. Even if the roller shaft 5a and the shaft tilting member 128 move, the guide member 135 is fixed and does not move. With such a configuration, when the shaft tilting member 128 moves outward in the direction of the roller shaft 5a, as shown in FIG. Fig. 9 As shown in FIG. 1 , the contact position between the shaft displacement portion abutting portion 135a and the inclined surface 128a is greater than Figure 8 The state is shifted upward, whereby the shaft inclination member 128 and the roller shaft 5a passing through the shaft inclination member 128 are inclined.

[0063] Fig.10 Shown is with Figure 8 The corresponding tension roller 5 (solid line) and Fig. 9 Schematic representation of the corresponding position of the tensioning roller 5 (dashed line). Fig.10 The schematic diagram shows the position of the primary transfer roller on the inner side of the insertion and extraction direction of the intermediate transfer unit. However, the front side of the insertion and extraction direction of the intermediate transfer unit is also similarly configured, and a support roller holding member, a support roller pressing member, etc. are provided.

[0064] The primary transfer roller 11d and the support roller 47 are held by a support roller holding member 71 as a second holding member, and the support roller holding member 71 is pressed by a support roller pressing member 72 as a third pressing member. Fig.10As shown by the solid and dotted lines, when the tension roller 5 and the roller shaft 5a are tilted, the angle at which the intermediate transfer belt 3 is wound around the support roller 47 changes. As a result, the force applied to the support roller holding member 71 also changes, and sometimes the position of the primary transfer roller 11d at the most upstream becomes unstable. Therefore, the pressing force of the support roller pressing member 72 is set so that when the intermediate transfer belt 3 is in contact with all the photosensitive bodies 1, regardless of the position of the tilted tension roller 5, the support roller holding member 71 located at the most upstream is in contact with the intermediate transfer body frame 37 (refer to Figure 7 ) or the photosensitive body frame 49d (refer to Figure 6 Thus, no matter where the tension roller 5 and the roller shaft 5a are located, the primary transfer roller 11d held by the support roller holding member 71 is always maintained at the same position, and a good image with little concentration deviation can be obtained.

[0065] Embodiments of the present invention are described below, for example.

[0066] (Method 1)

[0067] An image forming device, characterized in that it includes: a plurality of image bearing bodies that bear toner images; a plurality of frame members that hold the image bearing bodies; an intermediate transfer body that is movable so as to transfer the toner images primarily transferred from the image bearing bodies to a recording medium; a plurality of primary transfer members that primarily transfer the toner images from the image bearing bodies to the intermediate transfer body at primary transfer portions where the image bearing bodies and the outer peripheral surfaces of the intermediate transfer body are in contact; a holding member that holds the primary transfer members; an intermediate transfer body frame that holds the intermediate transfer body and The holding component is rotatably held; a plurality of pressure components that pressurize the holding component, and a pressing component that presses the image carrier onto the intermediate transfer body frame or the side plate of the main structure, and the first transfer component is positioned by causing the holding component to abut against the intermediate transfer body frame or the frame component, one end side of the image carrier is positioned by being pressed against the intermediate transfer body frame by the pressing component, and the first transfer component in the one end side is positioned by causing the pressure component to abut against the intermediate transfer body frame.

[0068] (Method 2)

[0069] The image forming apparatus according to method 1 is characterized in that the other end side of the image carrier is positioned by being pressed against the side plate of the main structure, and the primary transfer component at the other end side of the image carrier is positioned by causing the retaining component to abut against the frame component.

[0070] (Method 3)

[0071] The image forming device according to method 1 or 2 is characterized in that it includes: a supporting roller, which is arranged upstream of the multiple primary transfer components, contacts with the inner periphery of the intermediate transfer body and rotates; a second holding component, which holds the supporting roller; a third pressing component, which presses the second holding component; and a contact and separation mechanism, which makes the primary transfer components contact and separate so as to make the intermediate transfer body contact and separate with the image carrier, the holding component that holds the most upstream primary transfer component among the multiple primary transfer components and the second holding component are the same component, the third pressing component and the pressing component are the same component, and the other primary transfer components are held by the holding components respectively.

[0072] (Method 4)

[0073] The image forming apparatus according to method 3 is characterized by comprising: a tiltable rotating body which is located on the upstream side of the support roller and supports the intermediate transfer body, and a correction mechanism which corrects the deviation of the intermediate transfer body by tilting the rotating body.

[0074] (Method 5)

[0075] The image forming device according to method 3 is characterized in that: when the intermediate transfer body contacts all the image carriers, the pressure of the third pressure component at the most upstream is set so that no matter where the inclined belt supporting rotating body is located, the second retaining component at the most upstream collides with the frame component or the intermediate transfer body frame.

Claims

1. An image forming device, characterized in that include: a plurality of image bearing members that bear toner images; a plurality of frame members that hold the image bearing body; an intermediate transfer body that is movable to secondarily transfer the toner image primarily transferred from the image bearing body to a recording medium; a plurality of primary transfer members, which primarily transfer the toner image from the image bearing member to the intermediate transfer member at the primary transfer portion in contact with the outer peripheral surface of the image bearing member and the intermediate transfer member; a holding member that holds the primary transfer member; an intermediate transfer body frame that holds the intermediate transfer body and rotatably holds the holding member; a plurality of pressurizing members that pressurize the holding member, and a pressing member that presses the image carrier onto the intermediate transfer body frame or the main structure body side plate, The primary transfer member is positioned by causing the holding member to abut against the intermediate transfer body frame or the frame member. One end side of the image carrier is positioned by being pressed against the intermediate transfer body frame by the pressing member. The first transfer member on the one end side is positioned by the pressure member causing the holding member to abut against the intermediate transfer body frame.

2. The image forming device according to claim 1, wherein: The other end side of the image carrier is positioned by being pressed against the side plate of the main structure. The primary transfer member at the other end side of the image carrier is positioned by causing the holding member to abut against the frame member.

3. The image forming device according to claim 1 or 2, characterized in that include: a support roller disposed upstream of the plurality of primary transfer members, contacting the inner periphery of the intermediate transfer body and rotating; a second holding member that holds the support roller; a third pressurizing member that pressurizes the second holding member; and a contact and separation mechanism that brings the primary transfer member into contact with and separates from the image carrier so as to bring the intermediate transfer body into contact with and separate from the image carrier, the holding member that holds the most upstream primary transfer member among the plurality of primary transfer members and the second holding member are the same member, The third pressurizing member and the pressurizing member are the same member, The other primary transfer members are held by the holding members, respectively.

4. The image forming device according to claim 3, characterized in that include: a tiltable rotating body which is located on the upstream side of the support roller and supports the intermediate transfer body, and The correction mechanism corrects the deviation of the intermediate transfer body by tilting the rotating body.

5. The image forming apparatus according to claim 3, wherein: When the intermediate transfer body contacts all the image carriers, the pressure of the third pressure member at the most upstream position is set so that the second holding member at the most upstream position abuts against the frame member or the intermediate transfer body frame regardless of the position of the inclined rotating body.

Images