Sheet transport device and image forming apparatus

Abstract

To reduce misalignment of a roller for hanging a belt in a belt conveying unit which conveys a sheet by rotating the belt.SOLUTION: A sheet conveying device comprises: a device body; a belt conveying unit (80) which includes an endless belt part (82) and a plurality of rollers containing a first roller (101) and a second roller (102), to convey a sheet; and a first connection part, a second connection part and a third connection part (210, 211, 814). The belt conveying unit includes: a first bearing (201a); a second bearing (201b); a third bearing (202a); a fourth bearing (202b); and a support structure (81) containing a first support member (811), a second support member (812) and a third support member (813) bridging over the first support member and the second support member. The belt conveying unit is constituted by connecting the first support member to the device body by the first connection part and the second connection part, and by connecting the second support member to the device body by the third connection part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying apparatus that conveys sheets, and an image forming apparatus including the same. [Background Art]

[0002] Generally, image forming apparatuses such as copying machines and printers are known to include a belt conveying unit that conveys a sheet by rotating a belt stretched around a plurality of rollers to convey the sheet. As such a belt conveying unit, Patent Document 1 discloses a configuration in which a regulating member is provided on a roller that stretches the belt. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2006-65056 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] The regulating member of Patent Document 1 is provided with a taper formed such that the diameter decreases as approaching the belt, and this taper makes it possible to suppress movement of the belt in the axial direction of the roller. However, even when such a regulating member is provided, the frame of the belt conveying unit is twisted due to factors such as assembly of a support member that supports the belt conveying unit to the apparatus main body or impact during sheet conveyance, which causes alignment deviation of the rollers. The alignment deviation of the rollers has the problem of causing wear of the belt end portion during sheet conveyance, oblique traveling of the sheet, and the like.

[0005] The present invention has been made to solve the above problem, and an object of the present invention is to reduce alignment deviation of rollers stretching a belt in a belt conveying unit that conveys a sheet by rotating the belt. [Means for Solving the Problem]

[0006] One aspect of the present invention is a sheet conveying device comprising a device body and a belt conveying unit attachable to the device body, wherein the belt conveying unit comprises a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched by the plurality of rollers, the belt conveying unit being supported at two locations on one side of the device body by a first connecting portion and a second connecting portion, and at one location on the other side of the device body by a third connecting portion, the first connecting portion being in the state before the belt conveying unit is attached The belt conveying unit has The second connecting portion is formed by the fitting of a first protrusion and a first fitted portion that fits with the first protrusion, and the second connecting portion is formed in the state before the belt conveying unit is attached. The belt conveying unit has The sheet conveying device is characterized in that it is composed of a second protrusion and a second fitted portion that fits with the second protrusion, and the third connecting portion is composed of a fixing portion provided by the belt conveying unit and a support member provided by the device body, which are fastened together by a fastening member. [Effects of the Invention]

[0007] According to the present invention, in a belt conveying unit that conveys a sheet by rotating a belt, the misalignment of the rollers that tension the belt can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram of the printer in Example 1. [Figure 2] A perspective view of the belt conveying unit of Example 1. [Figure 3] A diagram showing the schematic internal configuration of the belt conveying unit in Example 1. [Figure 4] This diagram shows the belt conveying unit as viewed from the back of the main body of the device in Example 1, looking towards the door. [Figure 5] A diagram showing the connection structure between the main body of the device and the belt conveying unit in Example 1. [Figure 6] A diagram showing the connection structure between the main body of the device and the belt conveying unit in Example 1. [Figure 7] Model diagrams (A, B) show the belt conveying unit connected to the main body of the device as an example. [Figure 8] Model diagrams (A, B) showing the state in which the belt conveying unit is connected to the main body of the apparatus in Example 1. [Figure 9] This figure shows the belt conveying unit as viewed from the upstream side in the sheet conveying direction of Example 2. [Figure 10] This figure shows the belt conveying unit as viewed from the downstream side in the sheet conveying direction of Example 2. [Figure 11] A diagram showing the connection structure between the main body of the apparatus and the belt conveying unit in Example 2. [Figure 12] A diagram showing the connection structure between the main body of the apparatus and the belt conveying unit in Example 2. [Modes for carrying out the invention]

[0009] Hereinafter, exemplary embodiments for carrying out the present invention will be described with reference to the drawings. [Examples]

[0010] <Overall configuration of the image forming apparatus> Figure 1 is a schematic diagram of the printer 1 as a sheet transport device and image forming device of Embodiment 1. First, the configuration of the printer 1 will be described with reference to Figure 1. The printer 1 includes a feeding unit 10 for feeding sheets and a sheet transport unit 20 for transporting the sheets fed by the feeding unit 10. The printer 1 also includes an image forming unit 30 for forming a toner image to be fixed to the sheet, a secondary transfer unit 35 for transferring the toner image to the sheet, and a belt transport unit 80 for transporting the sheet on which the toner image has been transferred to the fixing unit 60. Furthermore, the printer 1 includes a sheet discharge unit 70 for transporting the sheet on which the toner image has been fixed by the fixing unit 60. The main body 2 of the printer 1 is provided with a door 2A that is configured to be openable and closable relative to the main body 2, and when the door 2A is open (open state), the user can access the transport surface 80A of the belt transport unit 80.

[0011] The feeding unit 10 is located at the bottom of the main body 2 of the printer 1. The feeding unit 10 includes sheet cassettes 11a and 11b, intermediate plates 12a and 12b that support and load sheets in the sheet cassettes 11a and 11b, and separation feeding units 13a and 13b that separate and feed the sheets loaded on the intermediate plates 12a and 12b one by one. The feeding unit 10 is configured such that the height of the uppermost sheet is maintained at a predetermined feeding position by raising and lowering the intermediate plates 12a and 12b. As for the method of feeding sheets in the feeding unit 10, Figure 1 shows an example using a friction separation method with rollers, but the sheet may also be fed using an air separation and adsorption method. Note that the separation feeding units 13a and 13b have similar configurations, so the configuration of the separation feeding unit 13a will be explained, and the configuration of the separation feeding unit 13b will be omitted. The separation and feeding section 13a includes a pickup roller 14a that can contact the uppermost sheet loaded on the sheet cassette 11a, a pair of separation rollers 15a located downstream of the pickup roller 14a in the sheet conveying direction, and a pair of pull-out rollers 16a. The separation roller pair 15a consists of a transport roller 15a1 that rotates in the same direction as the pickup roller 14a, and a separation roller 15a2 that is driven to rotate in the opposite direction to the sheet conveying direction or is fixed when sheets are fed in a double-feed configuration. When sheets are fed in a double-feed configuration, the sheets fed along with the uppermost sheet are separated from the uppermost sheet by a separation nip formed by the transport roller 15a1 and the separation roller 15a2. The pull-out roller pair 16a is located downstream of the separation roller pair 15a in the sheet conveying direction, and the sheets conveyed from the separation roller pair 15a are conveyed to the sheet conveying section 20.

[0012] The sheet conveying section 20 has a plurality of roller pairs, and a sheet fed from the feeding section 10 is sequentially transferred between the plurality of roller pairs provided in the sheet conveying section 20 and conveyed toward the secondary transfer section 35. Among the plurality of roller pairs of the sheet conveying section 20, the roller pair immediately before the secondary transfer section 35 in the sheet conveying direction is a registration roller pair 21. The registration roller pair 21 is configured to convey a sheet to the secondary transfer section 35 in synchronization with the image forming timing of the image forming section 30, and corrects skew of the sheet.

[0013] The image forming section 30 is a so-called tandem-type image forming means in which electrophotographic process cartridges PY, PM, PC, PK for forming yellow (Y), magenta (M), cyan (C) and black (K) toner images are arranged in series. The process cartridges PY, PM, PC, PK have a common configuration except that the toner colors are different. Therefore, the configuration of the process cartridge PY will be described as an example here, and descriptions of the configurations of the process cartridges PM, PC, and PK will be omitted. In FIG. 1, "Y", "M", "C", and "K" are added to the end of the reference numerals for the configuration of the process cartridge PY, the configuration of the process cartridge PM, the configuration of the process cartridge PC, and the configuration of the process cartridge PK, respectively. The process cartridge PY includes a photosensitive drum 32Y, an exposure device 40Y, a developing device 33Y, a primary transfer device 55Y, and a cleaner 34Y. The image forming section 30 includes an intermediate transfer belt 51 as an example of an image bearing member on which toner images visualized by the process cartridges PY, PM, PC, PK are carried. The intermediate transfer belt 51 is supported in a state stretched around a driving roller 52, a tension roller 53, and an inner transfer roller 54, and rotates in the direction of arrow T in FIG. 1 when driven by the driving roller 52.

[0014] The secondary transfer roller 56 is in pressure contact with the intermediate transfer belt 51 supported from the inner side of the intermediate transfer belt 51 by the inner transfer roller 54, and forms a secondary transfer nip N2 between itself and the intermediate transfer belt 51. The secondary transfer unit 35 is configured by the secondary transfer roller 56, the intermediate transfer belt 51, and the inner transfer roller 54. Residual toner, paper dust and the like remaining on the surface of the intermediate transfer belt 51 after passing through the secondary transfer nip N2 are removed by a cleaning device (not shown). The fixing unit 60 disposed downstream of the secondary transfer unit 35 in the sheet conveying direction is a fixing means that fixes the toner image onto the sheet by heat and pressure. The fixing unit 60 includes a heating roller 62 having a heater therein, and a counter roller 63 disposed to be able to abut against the heating roller 62 and forming a fixing nip N together with the heating roller 62.

[0015] Further, in the sheet conveying direction, a belt conveying unit 80 is disposed between the secondary transfer unit 35 and the fixing unit 60. The configuration of the belt conveying unit 80 will be described later.

[0016] The sheet discharge unit 70 includes a branch conveying unit 73 disposed between the fixing unit 60 and a pair of discharge rollers 71 in the sheet conveying direction, and a reverse conveying unit 74 that reversely conveys the sheet. The sheet discharge unit 70 also has a double-sided conveying path 75 that conveys the sheet reversed by the reverse conveying unit 74 and joins the sheet to the sheet conveying path of the sheet conveying unit 20.

[0017] Next, the process of forming an image on a sheet in printer 1 will be described. Based on the image forming job input to printer 1, first, the exposure unit 40Y exposes the photosensitive drum 32Y to form an electrostatic latent image on the surface of the photosensitive drum 32Y. The electrostatic latent image on the photosensitive drum 32Y is developed by the developing unit 33Y and made visible as a toner image. The toner image supported on the surface of photosensitive drum 1Y is sequentially transferred onto the intermediate transfer belt 51 by the primary transfer unit 55Y. The toner image transferred onto the intermediate transfer belt 51 is then transferred to the sheet S, which is held and transported by the secondary transfer nip section N2. The intermediate transfer belt 51 is driven by a drive roller 52 that rotates at a constant speed, and is rotated while maintaining a constant peripheral speed to achieve a constant transfer speed.

[0018] The registration roller 7 of the sheet transport unit 20 receives the sheet S while stopped rotating, and starts rotating in time with the toner image on the intermediate transfer belt 51, sending the sheet S toward the secondary transfer nip unit N2. In the secondary transfer nip unit N2, the toner image is transferred to the sheet. The sheet S, carrying the transferred toner image, is transported from the secondary transfer nip unit N2 toward the fuser unit 60 by the belt transport unit 80. In the fuser unit 60, the sheet S is held and transported by the fuser nip unit N, and heat and pressure are applied to the unfixed toner image to fix the toner image to the sheet. The sheet S sent out from the fuser unit 60 is discharged outside the printer 1 by the sheet discharge unit 70.

[0019] When forming an image on both sides of a sheet, the sheet fed from the fuser unit 60 is transported by the branch transport unit 73 to the inversion transport unit 74, and after being inverted by the inversion transport unit 74, it is transported to the double-sided transport path 75. The sheet is then transported again to the transport path of the sheet transport unit 20 via the double-sided transport path 75. For the sheet transported to the sheet transport unit 20, a toner image is formed on the second side (back side) of the sheet, just as on the first side (front side).

[0020] <Configuration of the belt conveying unit> Next, the configuration of the belt conveying unit 80 will be described with reference to Figures 1 to 3. Figure 2 is a perspective view of the belt conveying unit 80. Figure 3 is a diagram showing the schematic internal configuration of the belt conveying unit 80. As explained in Figure 1, the belt conveying unit 80 is positioned downstream of the image forming unit 30 and upstream of the fixing unit 60 in the sheet conveying direction, and conveys the sheet onto which the toner image has been transferred in the secondary transfer unit 35 to the fixing unit 60. As shown in Figure 1, a transfer exit guide 59, the belt conveying unit 80, and the fixing inlet guide 65 are provided between the secondary transfer unit 35 and the fixing unit 60 in the sheet conveying direction. The sheet conveyed from the secondary transfer unit 35 is conveyed to the belt conveying unit 80 via the transfer exit guide 59, and then conveyed from the belt conveying unit 80 to the fixing unit 60 via the fixing inlet guide 65. In this embodiment, the front direction of the main body in Figure 2 is on the side of the door 2A, and the rear direction of the main body is on the opposite side (rear side) from the door 2A.

[0021] As shown in Figure 2, the belt conveying unit 80 has a drive roller 101 composed of drive rollers 101a, 101b, 101c, and 101d, and a driven roller 102 composed of driven rollers 102a, 102b, 103c, and 104d. The drive roller 101 is the first roller in this embodiment, and the driven roller 102 is the second roller in this embodiment. The belt conveying unit 80 also has a frame 81 as a support structure in this embodiment, and an endless belt section 82 that is rotatably stretched by the drive roller 101, the driven roller 102, and shafts 103a and 104b. The belt section 82 is composed of breathable belt members 82a, 82b, 82c, and 82d that have a plurality of holes. The frame 81 has a front plate 811 and a rear plate 812 provided along the sheet conveying direction, and a bottom plate 813 that spans the front plate 811 and the rear plate 812.

[0022] Furthermore, the belt conveying unit 80 includes bearings 201a and 201b provided at the axial ends of the drive roller 101, and bearings 202a and 202b provided at the axial ends of the driven roller 102. Bearing 201a, as the first bearing in this embodiment, rotatably supports one axial end of the drive roller 101. Bearing 201b, as the second bearing in this embodiment, rotatably supports the other axial end of the drive roller 101. Bearing 202a, as the third bearing in this embodiment, rotatably supports one axial end of the driven roller 102. Bearing 202b, as the fourth bearing in this embodiment, rotatably supports the other axial end of the driven roller 102. Bearings 201a and 202a are supported by the front plate 811, and bearings 201b and 202b are also supported by the front plate 811 (see Figure 4). In this embodiment, the first support member is a front plate 811 capable of supporting bearings 201a and 202a, the second support member is a rear plate 812 capable of supporting bearings 201b and 202b, and the third support member is a bottom plate 813. Furthermore, as shown in Figure 3, the belt conveying unit 80 has suction fans 87a and 87b inside the belt members 82b and 82c. In the belt conveying unit 80, air is drawn from the outer surface to the inner surface of the belt section 82 by the driving of the suction fans 87a and 87b, making it possible to convey the sheet while pulling it towards the belt section 82.

[0023] <Connecting structure of belt conveying unit> Next, the connection structure between the device body 2 and the belt conveying unit 80 in this embodiment will be described with reference to Figures 2 to 6. Figure 4 shows the belt conveying unit 80 as viewed from the rear of the device body 2 toward the door 2A. Figure 5 shows the connection structure between the device body 2 and the belt conveying unit 80 as viewed from the door 2A side of the device body 2. Figure 6 shows the connection structure between the device body 2 and the belt conveying unit 80 as viewed from the rear of the device body 2. The belt conveying unit 80 is connected and supported to the device body 2 by a front support member 210, which is a plate-shaped member provided on the door 2A side of the device body 2, and a rear support member 220 provided on the rear side of the device body 2. Specifically, a fixing plate 814 fixed to the front plate 811 on the door 2A side of the device body 2 is fixed to the front support member 210 provided on the door 2A side of the device body 2 with fastening members 211 such as screws. In Figure 5, position P3 is shown as the position where the weight of the belt conveying unit 80 acts upon the fixing plate 814 and the front support member 210, fastened by the fastening member 211. In this embodiment, the first plate member is the fixing plate 814, and the second plate member is the front support member 210. Furthermore, the third connecting section in this embodiment is composed of the fixing plate 814, the front support member 210, and the fastening member 211.

[0024] Furthermore, at the rear of the main body 2 of the device, there are shaft members 815 and 816 fixed to the rear plate 812 by crimping or the like, and fitting portions 221 and 222 provided on the rear support member 220, which can be fitted with the shaft members 815 and 816, respectively. The belt conveying unit 80 is connected and supported to the main body 2 by the fitting of the shaft members 815 and 816 with the fitting portions 221 and 222, respectively. In Figure 6, the position where the weight of the belt conveying unit 80 acts when the shaft member 815 and the fitting portion 221 are fitted together is shown as position P4. Also in Figure 6, the position where the weight of the belt conveying unit 80 acts when the shaft member 816 and the fitting portion 222 are fitted together is shown as position P5. In this embodiment, the first protrusion is the shaft member 815, the second protrusion is the shaft member 816, the first recess is the fitted portion 221, and the second recess is the fitted portion 222. Furthermore, in this embodiment, the first connecting portion is composed of the shaft member 815 and the fitted portion 221 which fits into the shaft member 815, and the second connecting portion is composed of the shaft member 816 and the fitted portion 222 which fits into the shaft member 816. With this configuration, the center of gravity of the belt conveying unit 80 is located in the region formed by connecting the three points P3, P4, and P5 in the vertical direction.

[0025] When attaching the belt conveying unit 80 to the device body 2, first, the shaft members 815 and 816 are fitted into the fitting portions 221 and 222, respectively, located on one axial end of the drive roller 101, that is, on the rear side of the device body 2. Next, the fixing plate 814 is fixed to the front support member 210, which is located on the other axial end of the drive roller 101, that is, on the front side of the device body 2, using the fastening member 211. The fixing plate 814 is fixed to the front support member 210 by the fastening member 211, so that the shaft member 815 fitted into the fitting portion 221 and the shaft member 816 fitted into the fitting portion 222 cannot move in the fitting direction. In this embodiment, the belt conveying unit 80 is connected and supported to the device body 2 in this way. When removing the belt conveying unit 80 from the device body 2, the reverse procedure is performed with the door 2A open.

[0026] The rear support member 220 is provided with a guide portion 321 that guides the shaft member 815 to the entrance of the fitted portion 221, and a guide portion 322 that guides the shaft member 816 to the entrance of the fitted portion 222. In this embodiment, the guide portion 321, which serves as the first guide portion, forms a first guide path 221A that narrows from the top to the bottom in the vertical direction. The guide portion 322, which serves as the second guide portion in this embodiment, forms a second guide path 222A that narrows from the top to the bottom in the vertical direction. An example of the fitting direction in this embodiment is the direction in which the shaft members 815 and 816, guided by the first guide paths 221A and 222A, are inserted into the fitted portions 221 and 222. With this configuration, the belt conveying unit 80 can be moved from the top to the bottom in the vertical direction relative to the rear support member 220, making it possible to easily fit the shaft members 815 and 816 into the fitted portions 221 and 222.

[0027] Furthermore, in this embodiment, the fixing plate 814, the front support member 210, and the fastening member 211 are arranged on the side of the door 2A of the device body 2, which is easily accessible to the user. As a result, in this embodiment, the belt conveying unit 80 can be attached to and detached from the device body 2 simply by tightening or loosening the fastening member 211, thereby improving the work efficiency during maintenance. Note that the shaft members 815 and 816 may have shapes other than the cylindrical shape shown in Figure 4. In other words, the shaft members 815 and 816 and the fitted portions 221 and 222 may have interlocking concave and concave shapes.

[0028] <Features of 3-point connection> Next, with reference to Figures 7(A, B) and 8(A, B), the effects of the belt conveying unit 80 being connected and supported to the main body 2 in this embodiment will be explained. Figure 7(A) is a model diagram showing a state in which the belt conveying unit 80 is connected to the main body 2 at four points, P'1, P'2, P'4, and P'5, as a reference example. Figure 7(B) is a model diagram showing a state in which the configuration of Figure 7(A) is affected by tolerances of parts and impacts during sheet conveying. Figure 8(A) is a model diagram showing a state in which the belt conveying unit 80 is connected to the main body 2 at three points, P3, P4, and P5, as in this embodiment. Figure 8(B) is a model diagram showing a state in which the configuration of Figure 8(A) is affected by tolerances of parts and impacts during sheet conveying.

[0029] As shown in Figure 7(A), when the weight of the belt conveying unit 80 acts on the device body 2 at four points P'1, P'2, P'4, and P'5, the frame 81 is positioned along the plane formed by these four points. However, the plane formed by these four points becomes twisted due to tolerances of the components constituting each point and impacts during sheet conveying, as shown in Figure 7(B). As a result, the frame 81 becomes twisted with respect to the plane formed by the four points P'1, P'2, P'4, and P'5, causing misalignment between the drive roller 101 and the driven roller 102 supported by the frame 81. In this embodiment, the alignment between the drive roller 101 and the driven roller 102 refers to the relative positional relationship between the drive roller 101 and the driven roller 102. Furthermore, a state in which no alignment misalignment occurs refers to the positional relationship between the drive roller 101 and the driven roller 102 when the sheet conveying surface 80A formed by the belt section 82 is in a state where sheet slanting or buckling is unlikely to occur. A state in which misalignment occurs refers to the positional relationship between the drive roller 101 and the driven roller 102 when the sheet conveying surface 80A formed by the belt section 82 is in a state where sheet slanting or buckling is likely to occur.

[0030] If misalignment occurs between the drive roller 101 and the driven roller 102, a difference in tension will occur in the belt section 82 stretched by the drive roller 101 and the driven roller 102, causing the belt section 82 to move towards the weaker tension. Furthermore, the movement of the belt section 82 causes the sheet transported from the image forming section 30 to move diagonally in the same direction as the movement of the belt section 82 by the belt transport unit 80, resulting in wrinkles forming on the sheet when it enters the fixing section 60.

[0031] On the other hand, as shown in Figure 8(A), when the weight of the belt conveying unit 80 acts on the device body 2 at three points P3, P4, and P5, the frame 81 is positioned in a direction along the plane formed by these three points. The plane formed by these three points does not twist even when affected by tolerances of the parts placed at positions P3, P4, and P5 or impacts during sheet conveyance. As a result, the frame 81 is positioned in a direction along the plane formed by these three points, reducing misalignment between the drive roller 101 and the driven roller 102 supported by the frame 81. Therefore, in this embodiment, axial movement of the belt section 82 and diagonal movement of the sheet are less likely to occur compared to the reference example. Furthermore, in this embodiment, axial movement of the belt section 82 and diagonal movement of the sheet can be suppressed without providing a tapered restricting member on the roller that tensions the belt. Therefore, wear of the end of the belt section 82 due to the restricting member can be suppressed. [Examples]

[0032] Next, the configuration of Embodiment 2 of this disclosure will be described. In Embodiment 1, a configuration was described in which the belt conveying unit 80 is connected and supported to the device body 2 at both axial ends of the drive roller 101 and the driven roller 102. In this embodiment, a configuration will be described in which the belt conveying unit 80 is connected and supported to the device body 2 at the upstream and downstream ends in the sheet conveying direction. In the description of this embodiment, the same reference numerals are used for components that are the same as in Embodiment 1, and redundant explanations are omitted. Also, the schematic configuration of the printer 1 in Embodiment 2 is the same as in Figure 1, so its description is omitted.

[0033] The connection structure between the device body 2 and the belt conveying unit 80 in this embodiment will be described with reference to Figures 9 to 12. Figure 9 shows the belt conveying unit 80 as viewed from the upstream side in the sheet conveying direction. Figure 10 shows the device body 2 and the belt conveying unit 80 as viewed from the downstream side in the sheet conveying direction. Figure 11 shows the connection structure between the device body 2 and the belt conveying unit 80 as viewed from the upstream side in the sheet conveying direction. Figure 12 shows the connection structure between the device body 2 and the belt conveying unit 80 as viewed from the downstream side in the sheet conveying direction. The belt conveying unit 80 is connected and supported to the device body 2 by an upstream support member 230, which is a plate-shaped member provided on the upstream side in the sheet conveying direction of the device body 2, and a downstream support member 240 provided on the downstream side in the sheet conveying direction of the device body 2. Specifically, the upstream support member 230 is fixed to the bottom plate 813 by fastening members 213 such as screws at the other end of the bottom plate 813, that is, at the upstream end of the bottom plate 813 with respect to the sheet transport direction. The upstream support member 230 is positioned on the other end side in the sheet transport direction, that is, on the upstream side in the sheet transport direction relative to the belt transport unit 80. In Figure 11, the position where the bottom plate 813 and the upstream support member 230 are fixed by the fastening members 213 and the weight of the belt transport unit 80 acts upon them is shown as position P3. In this embodiment, the plate member is the upstream support member 230. Furthermore, the third connecting portion in this embodiment is composed of the fastening member 213 and the upstream support member 230 fixed to the bottom plate 813 by the fastening member 213.

[0034] Furthermore, on the downstream side of the device body 2 in the sheet conveying direction, there are shaft members 815 and 816 fixed to the bottom plate 813 by crimping or the like, and fitting portions 241 and 242 provided on the downstream support member 240, which can be fitted with the shaft members 815 and 816, respectively. The fitting portions 241 and 242 are each located on one end side in the sheet conveying direction, that is, on the downstream side in the sheet conveying direction with respect to the belt conveying unit 80. The belt conveying unit 80 is connected and supported to the device body 2 at one end of the bottom plate 813, that is, at the downstream end of the bottom plate 813 in the sheet conveying direction. In Figure 12, the position where the weight of the belt conveying unit 80 acts when the shaft member 815 and the fitting portion 241 are fitted together is shown as position P4. Furthermore, in Figure 12, the position where the shaft member 816 and the fitted portion 242 are fitted together and the weight of the belt conveying unit 80 acts upon them is shown as position P5. In this embodiment, the first convex portion is the shaft member 815, the second convex portion is the shaft member 816, the first recess is the fitted portion 241, and the second recess is the fitted portion 242. In this embodiment, the first connecting portion is composed of the shaft member 815 and the fitted portion 241 which is fitted to the shaft member 815, and the second connecting portion is composed of the shaft member 816 and the fitted portion 242 which is fitted to the shaft member 816. With this configuration, the center of gravity of the belt conveying unit 80 is located in the region formed by connecting the three points P3, P4, and P5 in the vertical direction.

[0035] When attaching the belt conveying unit 80 to the device body 2, first, the shaft members 815 and 816 are fitted into the fitting portions 241 and 242, respectively, located on the downstream side in the sheet conveying direction, that is, in front of the fixing portion 60, on the device body 2. Next, the upstream support member 230, which is provided on the upstream side in the sheet conveying direction on the device body 2, is fixed to the bottom plate 813 using the fastening member 213. As the upstream support member 230 is fixed to the bottom plate 813 by the fastening member 211, the shaft member 815 fitted into the fitting portion 241 and the shaft member 816 fitted into the fitting portion 242 become immobile in the fitting direction. In this embodiment, the belt conveying unit 80 is connected and supported to the device body 2 in this way. When removing the belt conveying unit 80 from the device body 2, the reverse procedure is performed.

[0036] The downstream support member 240 is provided with a guide portion 421 that guides the shaft member 815 to the entrance of the fitted portion 241, and a guide portion 422 that guides the shaft member 816 to the entrance of the fitted portion 242. In this embodiment, the guide portion 421, which serves as the first guide portion, forms a first guide path 241A that narrows from the top to the bottom in the vertical direction. The guide portion 422, which serves as the second guide portion in this embodiment, forms a second guide path 242A that narrows from the top to the bottom in the vertical direction. One example of the fitting direction in this embodiment is the direction in which the shaft members 815 and 816, guided by the first guide paths 241A and 242A, are inserted into the fitted portions 241 and 242. With this configuration, the belt conveying unit 80 can be moved from the top to the bottom in the vertical direction relative to the downstream support member 240, making it possible to easily fit the shaft members 815 and 816 into the fitted portions 241 and 242.

[0037] Furthermore, the upstream support member 230 is fixed to the bottom plate 813 by a fastening member 213 at the upstream end of the bottom plate 813 in the sheet conveying direction. As a result, in this embodiment, the belt conveying unit 80 can be attached to and detached from the device body 2 simply by tightening or loosening the fastening member 213, thereby improving the work efficiency during maintenance. Note that the shaft members 815 and 816 may have shapes other than the cylindrical shape shown in Figure 10. In other words, any concave and concave shape that allows the shaft members 815 and 816 and the fitted portions 241 and 242 to fit together is acceptable. In addition, in this embodiment, the belt conveying unit 80 is connected and supported to the device body 2 at two points (positions P4 and P5) on the downstream side in the sheet conveying direction. With this configuration, the inclination of the conveying surface 80A in the axial direction of the drive roller 101 is reduced, so that the sheet can be stably conveyed in the direction along the nip line formed by the heating roller 62 and the opposing roller 63 of the fixing section 60.

[0038] Furthermore, in this embodiment as well, similar to Embodiment 1, the frame 81 is positioned in a direction along the plane formed by the three points P3, P4, and P5, thereby reducing misalignment between the drive roller 101 and the driven roller 102 supported by the frame 81. Consequently, axial movement of the belt portion 82 and diagonal movement of the sheet are less likely to occur (see Figures 7(A, B) and 8(A, B)). Moreover, in this embodiment as well, axial movement of the belt portion 82 and diagonal movement of the sheet can be suppressed without providing a tapered restricting member on the roller that tensions the belt. As a result, wear of the end of the belt portion 82 due to the restricting member can be suppressed.

[0039] <Other examples> In Embodiment 1, the fixing plate 814, the front support member 210, and the fastening member 211 are arranged on the side of the door 2A of the device body 2, which is easily accessible to the user. However, the fixing plate 814, the front support member 210, and the fastening member 211 may also be arranged on the rear side of the device body 2. In this case, the fitted portions 221, 222 and the shaft members 815, 816 are arranged on the side of the door 2A of the device body 2. In Embodiment 2, the upstream support member 230 may be fixed to the bottom plate 813 with fastening members 213 such as screws at the downstream end of the bottom plate 813 in the direction of sheet transport. In this case, the fitted portions 241, 242 and the shaft members 815, 816 are arranged on the upstream side of the bottom plate 813 in the direction of sheet transport.

[0040] Furthermore, Figure 1 illustrates a printer 1 equipped with an electrophotographic image forming unit 30 as an example. However, the configuration of this embodiment can also be applied to a belt conveying unit mounted in an image forming apparatus that forms an image on a sheet using a coloring agent that hardens with ultraviolet light or the like. In Examples 1 and 2, the center of gravity of the belt conveying unit 80 was described as being in the region connecting positions P3, P4, and P5 in the vertical direction. However, the center of gravity of the belt conveying unit 80 does not need to be included in the region connecting positions P3, P4, and P5 in the vertical direction, as long as the belt conveying unit 80 can be stably connected to the apparatus body 2. [Explanation of Symbols]

[0041] 1 Printer (image forming apparatus) / 2 Main body of the apparatus / 2A Door / 30 Image forming section (image forming means) / 60 Fixing section (fixing means) / 80 Belt conveying unit / 80A Conveying surface / 81 Frame (support structure) / 82 Belt section / 101 Driven roller (first roller) / 102 Driven roller (second roller) / 201a Bearing (first bearing) / 201b Bearing (second bearing) / 202a Bearing (third bearing) / 202b Bearing (fourth bearing) / 210 Front support member (second plate member) / 211, 213 Fastening member / 220 Rear support member / 221 Fitted part (first recess) / 221A First guide path / 222 Fitted part (second recess) / 222A Second guide path / 230 Upstream support member (plate member) / 241 Fitting portion (first recess) / 241A First guide path / 242 Fitting portion (second recess) / 242A Second guide path / 321, 421 / First guide portion / 322, 422 Second guide portion / 811 Front plate (first support member) / 812 Rear plate (second support member) / 813 Bottom plate (third support member) / 814 Fixing plate (first plate member) / 815 Shaft member (first protrusion) / 816 Shaft member (second protrusion)

Claims

1. A sheet conveying device comprising a main body and a belt conveying unit that can be attached to the main body, The belt conveying unit comprises a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched by the plurality of rollers. The belt conveying unit is supported at two points on one side of the device body, by a first connecting portion and a second connecting portion, and at one point on the other side of the device body, by a third connecting portion. The first connecting portion is formed by the fitting of a first protrusion on the belt conveying unit and a first fitting portion that fits with the first protrusion, in the state before the belt conveying unit is attached. The second connecting portion is formed by the fitting of a second protrusion on the belt conveying unit and a second fitting portion that fits with the second protrusion, in the state before the belt conveying unit is attached. The third connecting portion is configured such that a fixing portion provided by the belt conveying unit and a support member provided by the main body of the device are fastened together by a fastening member. A sheet conveying device characterized by the following features.

2. The device body is equipped with a door on the front side of the device body that is configured to open and close, The first connecting portion and the second connecting portion are located on the rear side of the main body of the device. The third connecting portion is positioned on the front side of the main body of the device. The sheet conveying device according to feature 1.

3. The first connecting portion and the second connecting portion are arranged on one side in the sheet transport direction. The third connecting portion is positioned on the other side in the sheet transport direction. The sheet conveying device according to feature 1.

4. The fastening member is fastened from top to bottom. The sheet conveying device according to feature 1 or 3.

5. The belt conveying unit has a fan inside the endless belt, The fan draws air from the outer surface to the inner surface of the endless belt. A sheet conveying device according to any one of claims 1 to 4.

6. The sheet transport device has a guide path that guides the first protrusion to the first fitting portion. The aforementioned guide path narrows from the top vertically downwards. A sheet conveying device according to any one of claims 1 to 5.

7. By fixing the fixing portion and the support member with the fastening member, the first protrusion and the second protrusion become immovable in the fitting direction. A sheet conveying device according to any one of claims 1 to 6.

8. The fixing portion is positioned between the first protrusion and the second protrusion in the sheet transport direction. A sheet conveying device according to any one of claims 1 to 7.

9. The apparatus body comprises a transfer unit for transferring an image to a sheet, and a fixing unit for fixing the image transferred to the sheet by the transfer unit. The belt conveying unit is positioned between the transfer section and the fixing section in the sheet conveying direction. A sheet conveying device according to any one of claims 1 to 8.

10. The belt conveying unit has a plurality of the endless belts, A sheet conveying device according to any one of claims 1 to 9.

11. Image forming means for forming an image on a sheet, A sheet transport device according to any one of claims 1 to 10, comprising: An image forming apparatus characterized by the following features.

12. It includes a fixing means for fixing a toner image onto a sheet, The sheet transport device transports the sheet from the image forming means toward the fixing means. The image forming apparatus according to feature 11.

Images