Sheet conveying device, and image forming device

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 device that conveys a sheet, and an image forming apparatus including the same. [Background technology]

[0002] Generally, in image forming devices such as copiers and printers, there are known devices that include a belt conveying unit that conveys a sheet by rotating a belt that is stretched over a plurality of rollers. As such a belt conveying unit, Patent Document 1 discloses a configuration in which a regulating member is provided on the rollers that stretch the belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-65056 Summary of the Invention [Problem to be solved by the invention]

[0004] The regulating member in Patent Document 1 has a taper that reduces its diameter as it approaches the belt, which makes it possible to suppress belt movement in the axial direction of the roller. However, even with such a regulating member, the frame of the belt transport unit can twist due to the assembly of the support member that supports the belt transport unit to the device body or impacts during sheet transport, causing roller misalignment. Roller misalignment poses problems such as wear on the belt edge and skewed sheet movement during sheet transport.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to reduce misalignment of rollers that stretch a belt in a belt transport unit that rotates the belt to transport a sheet. [Means for solving the problem]

[0006] One aspect of the present invention is a sheet conveying device having an apparatus main body and a belt conveying unit that can be attached to the apparatus main body, wherein the belt conveying unit has a plurality of rollers, a frame that supports the plurality of rollers, and an endless belt that is rotatably stretched by the plurality of rollers, and the frame includes a first convex portion and a second convex portion arranged on the rear side and a fixed portion arranged on the front side, and the apparatus main body has a rear support member that includes a first fitted portion into which the first convex portion fits and a second fitted portion into which the second convex portion fits, and a front support member that supports the front side of the belt conveying unit, and the belt conveying unit is supported at two points on the rear side by the fitting of the first convex portion and the first fitted portion and the fitting of the second convex portion and the second fitted portion, and is supported at one point on the front side by fixing the fixed portion to the front support member with a fastening member. [Effects of the Invention]

[0007] According to the present invention, in a belt transport unit that rotates a belt to transport a sheet, it is possible to reduce misalignment of rollers that stretch the belt. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a printer according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a belt transport unit according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing a schematic configuration of the inside of a belt transport unit according to the first embodiment. [Figure 4] FIG. 2 is a view showing the belt transport unit when viewed from the back side of the apparatus main body of the first embodiment toward the door side. [Figure 5] FIG. 2 is a diagram showing a connection structure between the apparatus main body and the belt transport unit according to the first embodiment. [Figure 6] FIG. 2 is a diagram showing a connection structure between the apparatus main body and the belt transport unit according to the first embodiment. [Figure 7]10A and 10B are model diagrams showing a state in which a belt transport unit is connected to an apparatus main body as a reference example. [Figure 8] 3A and 3B are model diagrams showing a state in which a belt transport unit is connected to the apparatus main body of the first embodiment. [Figure 9] FIG. 10 is a diagram showing a belt conveying unit according to a second embodiment when viewed from the upstream side in the sheet conveying direction. [Figure 10] FIG. 10 is a diagram showing a belt conveying unit according to a second embodiment when viewed from the downstream side in the sheet conveying direction. [Figure 11] FIG. 10 is a diagram showing a connection structure between the apparatus main body and the belt transport unit according to the second embodiment. [Figure 12] FIG. 10 is a diagram showing a connection structure between the apparatus main body and the belt transport unit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. [Example]

[0010] <Overall configuration of image forming apparatus> FIG. 1 is a schematic diagram of a printer 1 serving as a sheet conveying device and an image forming apparatus according to a first embodiment. First, the configuration of the printer 1 will be described with reference to FIG. 1. The printer 1 includes a feeding unit 10 that feeds a sheet and a sheet conveying unit 20 that conveys the sheet fed by the feeding unit 10. The printer 1 also includes an image forming unit 30 that forms a toner image to be fixed on the sheet, a secondary transfer unit 35 that transfers the toner image to the sheet, and a belt conveying unit 80 that conveys the sheet on which the toner image has been transferred to a fixing unit 60. The printer 1 also includes a sheet discharge unit 70 that conveys the sheet on which the toner image has been fixed by the fixing unit 60. The device body 2 of the printer 1 is provided with a door 2A that can be opened and closed relative to the device body 2. With the door 2A open (in the open state), a user can access a conveying surface 80A of the belt conveying unit 80.

[0011] The feeding unit 10 is located at the bottom of the printer body 2 of the printer 1. The feeding unit 10 includes sheet cassettes 11a and 11b, middle plates 12a and 12b that support sheets stacked in the sheet cassettes 11a and 11b, and separation and feeding units 13a and 13b that separate and feed the sheets stacked on the middle plates 12a and 12b one by one. The feeding unit 10 is configured so that the height of the uppermost sheet is maintained at a predetermined feeding position by raising and lowering the middle plates 12a and 12b. While FIG. 1 shows an example of a friction separation system using rollers as a sheet feeding method in the feeding unit 10, sheets may also be fed using an air separation and suction system. Because the separation and feeding units 13a and 13b have similar configurations, the following describes the configuration of the separation and feeding unit 13a, and omits the description of the configuration of the separation and feeding unit 13b. The separation and feeding section 13a includes a pickup roller 14a that can contact the top sheet stacked in the sheet cassette 11a, a separation roller pair 15a located downstream of the pickup roller 14a in the sheet conveyance direction, and a pull-off roller pair 16a. The separation roller pair 15a is composed of a conveyance roller 15a1 that rotates in the same direction as the pickup roller 14a, and a separation roller 15a2 that is fixed or rotates in the opposite direction to the sheet conveyance direction when multiple sheets are fed. When multiple sheets are fed, a sheet that is fed along with the top sheet is separated from the top sheet by a separation nip formed by the conveyance roller 15a1 and the separation roller 15a2. The pull-off roller pair 16a is located downstream of the separation roller pair 15a in the sheet conveyance direction, and sheets conveyed from the separation roller pair 15a are conveyed to the sheet conveyance section 20.

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

[0013] The image forming unit 30 is a so-called tandem image forming unit in which electrophotographic process cartridges PY, PM, PC, and PK are arranged in series to form toner images of Y (yellow), M (magenta), C (cyan), and K (black). The process cartridges PY, PM, PC, and PK have the same configuration except for the toner colors they use. Therefore, the configuration of the process cartridge PY will be described as an example, and a description of the configurations of the process cartridges PM, PC, and PK will be omitted. Note that in FIG. 1, the configuration of the process cartridge PY is suffixed with "Y," the configuration of the process cartridge PM with "M," the configuration of the process cartridge PC with "C," and the configuration of the process cartridge PK with "K." 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 unit 30 includes an intermediate transfer belt 51, which is an example of an image carrier that carries a toner image visualized by the process cartridges PY, PM, PC, and PK. The intermediate transfer belt 51 is supported in a state in which it is stretched across a drive roller 52, a tension roller 53, and an inner transfer roller 54, and is rotated in the direction of arrow T in FIG. 1 by the drive of the drive roller 52.

[0014] The secondary transfer roller 56 presses against the intermediate transfer belt 51, which is supported from inside the intermediate transfer belt 51 by the inner transfer roller 54, forming a secondary transfer nip N2 between the intermediate transfer belt 51 and the secondary transfer roller 56. The secondary transfer roller 56, the intermediate transfer belt 51, and the inner transfer roller 54 form the secondary transfer unit 35. 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, which is located downstream of the secondary transfer unit 35 in the sheet conveyance direction, is a fixing unit that fixes the toner image to the sheet by heat and pressure. The fixing unit 60 includes a heating roller 62 equipped with an internal heater and an opposing roller 63 that is positioned so as to be able to abut against the heating roller 62 and forms the fixing nip N together with the heating roller 62.

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

[0016] The sheet discharge section 70 has a branch conveyance section 73 disposed between the fixing section 60 and the pair of discharge rollers 71 in the sheet conveyance direction, and a reversing conveyance section 74 that reverses and conveys the sheet. The sheet discharge section 70 also has a double-sided conveyance path 75 that conveys the sheet reversed by the reversing conveyance section 74 and merges it with the sheet conveyance path of the sheet conveyance section 20.

[0017] Next, a series of steps for forming an image on a sheet in the printer 1 will be described. Based on an image formation job input to the printer 1, the exposure device 40Y first exposes the photosensitive drum 32Y to light 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 device 33Y and visualized as a toner image. The toner image carried on the surface of the photosensitive drum 32Y is primarily transferred by the primary transfer device 55Y onto the intermediate transfer belt 51 in a sequentially overlapping manner. The toner image primarily transferred onto the intermediate transfer belt 51 is secondarily transferred onto the sheet S nipped and conveyed through the secondary transfer nip N2. The intermediate transfer belt 51 is rotationally driven by a drive roller 52 that rotates at a constant speed, and is rotated while its peripheral speed is maintained at a constant transfer speed.

[0018] The registration rollers 7 of the sheet conveying section 20 receive the sheet S while stopping their rotation, and start rotating in time with the toner image on the intermediate transfer belt 51, sending the sheet S toward the secondary transfer nip N2. The toner image is transferred to the sheet at the secondary transfer nip N2. The sheet S carrying the transferred toner image is then conveyed from the secondary transfer nip N2 by the belt conveying unit 80 toward the fixing section 60. At the fixing section 60, the sheet S is nipped and conveyed at the fixing nip 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 fixing section 60 is then discharged outside the printer 1 by the sheet discharge section 70.

[0019] When images are formed on both sides of a sheet, the conveying path of the sheet sent out from the fixing unit 60 is switched by the branch conveying unit 73 so that the sheet is conveyed toward the reversing conveying unit 74, and after being reversed by the reversing conveying unit 74, the sheet is conveyed toward the double-sided conveying path 75. Then, the sheet is conveyed again to the conveying path of the sheet conveying unit 20 via the double-sided conveying path 75. For the sheet conveyed to the sheet conveying unit 20, a toner image is formed on the second side (back side) of the sheet in the same way as on the first side (front side).

[0020] <Belt transport unit configuration> Next, the configuration of the belt transport unit 80 will be described with reference to FIGS. 1 to 3. FIG. 2 is a perspective view of the belt transport unit 80. FIG. 3 is a diagram showing a schematic internal configuration of the belt transport unit 80. As described with reference to FIG. 1, the belt transport unit 80 is disposed downstream of the image forming unit 30 and upstream of the fixing unit 60 in the sheet transport direction, and transports a sheet onto which a toner image has been transferred in the secondary transfer unit 35 to the fixing unit 60. As shown in FIG. 1, a transfer exit guide 59, the belt transport unit 80, and a fixing entrance guide 65 are provided between the secondary transfer unit 35 and the fixing unit 60 in the sheet transport direction. The sheet transported from the secondary transfer unit 35 is transported to the belt transport unit 80 via the transfer exit guide 59, and from the belt transport unit 80 to the fixing unit 60 via the fixing entrance guide 65. In this embodiment, the belt transport unit 80 is disposed such that the front side of the main body in FIG. 2 faces the door 2A, and the rear side of the main body faces the opposite side (rear side) from the door 2A.

[0021] As shown in FIG. 2, the belt conveying unit 80 includes 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 includes a frame 81 as a support structure in this embodiment, and an endless belt portion 82 rotatably stretched by the drive roller 101, the driven roller 102, and shafts 103a and 104b. The belt portion 82 is composed of breathable belt members 82a, 82b, 82c, and 82d having a plurality of holes. The frame 81 includes a front side plate 811 and a rear side plate 812 provided along the sheet conveying direction, and a bottom plate 813 stretched between the front side plate 811 and the rear side plate 812.

[0022] Furthermore, the belt conveying unit 80 has bearings 201a and 201b provided at axial ends of the drive roller 101 and bearings 202a and 202b provided at axial ends of the driven roller 102. The bearing 201a, which serves as a first bearing in this embodiment, rotatably supports one axial end of the drive roller 101. The bearing 201b, which serves as a second bearing in this embodiment, rotatably supports the other axial end of the drive roller 101. The bearing 202a, which serves as a third bearing in this embodiment, rotatably supports one axial end of the driven roller 102. The bearing 202b, which serves as a fourth bearing in this embodiment, rotatably supports the other axial end of the driven roller 102. The bearings 201a and 202a are supported by a front side plate 811, and the bearings 201b and 202b are supported by the front side plate 811 (see FIG. 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 Fig. 3, the belt conveying unit 80 has suction fans 87a and 87b on the inside of the belt members 82b and 82c. In the belt conveying unit 80, air is sucked from the outer surface of the belt portion 82 toward the inner surface by driving the suction fans 87a and 87b, making it possible to convey the sheet while pulling it toward the belt portion 82.

[0023] <Belt conveyor unit connection structure> Next, a connection structure between the device main body 2 and the belt conveying unit 80 in this embodiment will be described with reference to FIGS. 2 to 6. FIG. 4 is a diagram illustrating the belt conveying unit 80 when viewed from the rear of the device main body 2 toward the door 2A. FIG. 5 is a diagram illustrating the connection structure between the device main body 2 and the belt conveying unit 80 when viewed from the door 2A side of the device main body 2. FIG. 6 is a diagram illustrating the connection structure between the device main body 2 and the belt conveying unit 80 when viewed from the rear of the device main body 2. The belt conveying unit 80 is connected and supported to the device main body 2 by a front support member 210, which is a plate-like member provided on the door 2A side of the device main body 2, and a rear support member 220 provided on the rear side of the device main body 2. Specifically, a fixing plate 814 fixed to a front plate 811 on the door 2A side of the device main body 2 is fixed to the front support member 210 provided on the door 2A side of the device main body 2 with fastening members 211 such as screws. 5 shows the position where the weight of the belt transport unit 80 acts by fastening the fixed plate 814 and the front support member 210 with the fastening member 211 as position P3. In this embodiment, the first plate member is the fixed plate 814, and the second plate member is the front support member 210. In addition, the third connecting portion in this embodiment is made up of the fixed plate 814, the front support member 210, and the fastening member 211.

[0024] Further, at the rear side of the apparatus main body 2, there are provided shaft members 815 and 816 fixed to the rear side plate 812 by caulking or the like, and fitted portions 221 and 222 that are provided on the rear support member 220 and can be fitted with the shaft members 815 and 816, respectively. The shaft members 815 and 816 are fitted with the fitted portions 221 and 222, respectively, thereby connecting and supporting the belt conveying unit 80 to the apparatus main body 2. The position where the shaft member 815 is fitted with the fitted portion 221 and the weight of the belt conveying unit 80 acts is shown as position P4 in Fig. 6. The position where the shaft member 816 is fitted with the fitted portion 222 and the weight of the belt conveying unit 80 acts is shown as position P5 in Fig. 6. In this embodiment, the first convex portion is shaft member 815, the second convex portion is shaft member 816, the first recess is fitted portion 221, and the second recess is fitted portion 222. In addition, the first connecting portion in this embodiment is made up of shaft member 815 and fitted portion 221 fitted to shaft member 815, and the second connecting portion is made up of shaft member 816 and fitted portion 222 fitted to shaft member 816. With this configuration, the center of gravity of belt conveying unit 80 is located in an area formed by connecting three points, positions P3, P4, and P5, in the vertical direction.

[0025] When attaching the belt conveying unit 80 to the apparatus main body 2, first, the shaft members 815 and 816 are fitted to the fitting portions 221 and 222, respectively, located at one axial end of the drive roller 101, i.e., at the rear side of the apparatus main body 2. Next, the fastening member 211 is used to fasten the fixing plate 814 to the front support member 210, which is located at the other axial end of the drive roller 101, i.e., at the front side of the apparatus main body 2. By fastening the front support member 210 and the fixing plate 814 with the fastening member 211, the shaft member 815 fitted to the fitting portion 221 and the shaft member 816 fitted to the fitting portion 222 are immovable in the fitting direction. In this embodiment, the belt conveying unit 80 is connected and supported to the apparatus main body 2 in this manner. When removing the belt conveying unit 80 from the apparatus main 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. The guide portion 321, which serves as the first guide portion in this embodiment, forms a first guide path 221A that narrows from top to 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 top to 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 top to bottom in the vertical direction relative to the rear support member 220, allowing the shaft members 815 and 816 to be easily fitted into the fitted portions 221 and 222.

[0027] In this embodiment, the fixing plate 814, the front support member 210, and the fastening member 211 are disposed on the side of the door 2A of the apparatus main body 2, which is easily accessible to the user. As a result, in this embodiment, the belt transport unit 80 can be attached and detached from the apparatus main body 2 simply by fastening and loosening the fastening member 211, which improves the efficiency of maintenance work. The shaft members 815 and 816 may have a shape other than the cylindrical shape shown in Fig. 4. In other words, it is sufficient that the shaft members 815 and 816 and the fitted portions 221 and 222 have an uneven shape that allows them to be fitted together.

[0028] <Features of three-point linkage> Next, with reference to FIGS. 7A and 7B and 8A and 8B, the effect of connecting and supporting the belt transport unit 80 to the device main body 2 in this embodiment will be described. FIG. 7A is a model diagram showing a state in which the belt transport unit 80 is connected to the device main body 2 at four points, P'1, P'2, P'4, and P'5, as a reference example. FIG. 7B is a model diagram showing a state in which the configuration in FIG. 7A is affected by component tolerances, impacts during sheet transport, and the like. FIG. 8A is a model diagram showing a state in which the belt transport unit 80 is connected to the device main body 2 at three points, P3, P4, and P5, as this embodiment. FIG. 8B is a model diagram showing a state in which the configuration in FIG. 8A is affected by component tolerances, impacts during sheet transport, and the like.

[0029] As shown in FIG. 7A, when the weight of the belt transport unit 80 acts on the apparatus main body 2 at four points P'1, P'2, P'4, and P'5, the frame 81 is oriented along a plane formed by the four points P'1, P'2, P'4, and P'5. However, the plane formed by the four points becomes distorted as shown in FIG. 7B due to tolerances of the components constituting each point and shocks during sheet transport. As a result, the frame 81 becomes distorted relative 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, the state where no misalignment occurs refers to the positional relationship between the drive roller 101 and the driven roller 102 when the sheet is unlikely to skew, buckle, or the like on the sheet conveying surface 80A formed by the belt portion 82. The state where misalignment occurs refers to the positional relationship between the drive roller 101 and the driven roller 102 when the sheet is likely to skew, buckle, or the like on the sheet conveying surface 80A formed by the belt portion 82.

[0030] When misalignment occurs between the drive roller 101 and the driven roller 102, a difference occurs in the tension of the belt portion 82 stretched between the drive roller 101 and the driven roller 102, causing the belt portion 82 to move to the side with weaker tension. In addition, the movement of the belt portion 82 causes the sheet conveyed from the image forming unit 30 to run obliquely in the same direction as the movement direction of the belt portion 82 by the belt conveying unit 80, causing wrinkles to occur in the sheet when it enters the fixing unit 60.

[0031] On the other hand, as shown in FIG. 8A , when the weight of the belt transport unit 80 acts on the device main body 2 at three points P3, P4, and P5, the frame 81 is oriented along a plane formed by the three points P3, P4, and P5. The plane formed by the three points does not twist even when influenced by the tolerances of the components arranged at the three points P3, P4, and P5 or by impacts during sheet transport. As a result, the frame 81 is oriented along a 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. Therefore, in this embodiment, axial movement of the belt portion 82 and skewed running of the sheet are less likely to occur compared to the reference example. Furthermore, in this embodiment, axial movement of the belt portion 82 and skewed running of the sheet can be suppressed without providing a tapered regulating member for regulating belt movement on the roller that stretches the belt. Therefore, wear on the end of the belt portion 82 due to the regulating member can be suppressed. [Example]

[0032] Next, a configuration of Example 2 of the present disclosure will be described. In Example 1, a configuration in which the belt transport unit 80 is connected and supported to the device main body 2 at both ends in the axial direction of the drive roller 101 and the driven roller 102 has been described. In this example, a configuration in which the belt transport unit 80 is connected and supported to the device main body 2 at the upstream end and downstream end in the sheet transport direction will be described. In the description of this example, the same components as in Example 1 are given the same reference numerals, and redundant description will be omitted. In addition, the schematic configuration of the printer 1 of Example 2 is the same as that in FIG. 1, so description will be omitted.

[0033] The connection structure between the device main body 2 and the belt transport unit 80 in this embodiment will be described with reference to Figs. 9 to 12. Fig. 9 is a diagram showing the belt transport unit 80 as viewed from the upstream side in the sheet transport direction. Fig. 10 is a diagram showing the device main body 2 and the belt transport unit 80 as viewed from the downstream side in the sheet transport direction. Fig. 11 is a diagram showing the connection structure between the device main body 2 and the belt transport unit 80 as viewed from the upstream side in the sheet transport direction. Fig. 12 is a diagram showing the connection structure between the device main body 2 and the belt transport unit 80 as viewed from the downstream side in the sheet transport direction. The belt transport unit 80 is connected and supported to the device main body 2 by an upstream support member 230, which is a plate-shaped member provided on the upstream side of the device main body 2 in the sheet transport direction, and a downstream support member 240 provided on the downstream side of the device main body 2 in the sheet transport direction. Specifically, the upstream support member 230 is fixed to the bottom plate 813 with fastening members 213 such as screws at the other end of the bottom plate 813, i.e., at the upstream end of the bottom plate 813 in the sheet conveying direction. The upstream support member 230 is disposed on the other end side in the sheet conveying direction, i.e., on the upstream side in the sheet conveying direction relative to the belt conveying unit 80. The position where the bottom plate 813 and the upstream support member 230 are fixed by the fastening member 213 and where the weight of the belt conveying unit 80 acts is shown as position P3 in FIG. 11 . The plate member in this embodiment is the upstream support member 230. The third connecting portion in this embodiment is formed by the fastening member 213 and the upstream support member 230 fixed to the bottom plate 813 by the fastening member 213.

[0034] Further, on the downstream side of the apparatus main body 2 in the sheet conveying direction, there are provided shaft members 815 and 816 fixed to a bottom plate 813 by caulking or the like, and fitted portions 241 and 242 that are provided on a downstream support member 240 and can be fitted with the shaft members 815 and 816, respectively. The fitted portions 241 and 242 are each disposed at one end side in the sheet conveying direction, that is, downstream side in the sheet conveying direction with respect to the belt conveying unit 80. The shaft members 815 and 816 are fitted with the fitted portions 241 and 242, respectively, so that the belt conveying unit 80 is connected and supported to the apparatus main body 2 at one end of the bottom plate 813, that is, the downstream end of the bottom plate 813 in the sheet conveying direction. The position where the shaft member 815 is fitted with the fitted portion 241 and the weight of the belt conveying unit 80 acts is shown as position P4 in FIG. 12 . 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 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 made up of the shaft member 815 and the fitted portion 241 fitted to the shaft member 815, and the second connecting portion is made up of the shaft member 816 and the fitted portion 242 fitted to the shaft member 816. With this configuration, the center of gravity of the belt conveying unit 80 is located in an area formed by connecting the three points P3, P4, and P5 in the vertical direction.

[0035] When attaching the belt transport unit 80 to the apparatus main body 2, first, the shaft members 815 and 816 are fitted to the fitting portions 241 and 242, respectively, located on the downstream side of the apparatus main body 2 in the sheet transport direction, i.e., in front of the fixing unit 60. Next, the upstream support member 230, located on the upstream side of the apparatus main body 2 in the sheet transport direction, is fixed to the bottom plate 813 using the fastening member 213. By fixing the upstream support member 230 to the bottom plate 813 with the fastening member 211, the shaft member 815 fitted to the fitting portion 241 and the shaft member 816 fitted to the fitting portion 242 become immovable in the fitting direction. In this embodiment, the belt transport unit 80 is connected and supported to the apparatus main body 2 in this manner. When removing the belt transport unit 80 from the apparatus main 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. The guide portion 421, which serves as the first guide portion in this embodiment, forms a first guide path 241A that narrows from top to 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 top to 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 241A and 242A are inserted into the fitted portions 241 and 242. With this configuration, the belt conveying unit 80 can be moved from top to bottom in the vertical direction relative to the downstream support member 240, allowing the shaft members 815 and 816 to be easily fitted 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 conveyance direction. This allows the belt conveyance unit 80 to be attached and detached from the apparatus main body 2 simply by tightening and loosening the fastening member 213, thereby improving work efficiency during maintenance work. The shaft members 815 and 816 may have a shape other than the cylindrical shape shown in FIG. 10 . That is, any shape may be used as long as the shaft members 815 and 816 and the engagement portions 241 and 242 can be fitted to each other. Furthermore, in this embodiment, the belt conveyance unit 80 is connected and supported to the apparatus main body 2 at two points (positions P4 and P5) downstream in the sheet conveyance direction. This configuration reduces the inclination of the conveyance surface 80A in the axial direction of the drive roller 101, allowing the sheet to be stably conveyed in a direction along the nip line formed by the heating roller 62 and the counter roller 63 of the fixing unit 60.

[0038] Also in this embodiment, as in the first embodiment, the frame 81 is disposed 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. This reduces the likelihood of axial movement of the belt portion 82 or skew of the sheet (see FIGS. 7(A) and 7(B) and 8(A) and 8(B)). Furthermore, in this embodiment as well, it is possible to suppress axial movement of the belt portion 82 and skew of the sheet without providing a tapered regulating member for regulating belt movement on the roller that tensions the belt. This makes it possible to suppress wear of the end of the belt portion 82 due to the regulating member.

[0039] <Other Examples> In the first 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 apparatus 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 be arranged on the rear side of the apparatus body 2. In this case, the fitted portions 221 and 222 and the shaft members 815 and 816 are arranged on the side of the door 2A of the apparatus body 2. Also in the second embodiment, the upstream support member 230 may be arranged to 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 sheet conveyance direction. In this case, the fitted portions 241 and 242 and the shaft members 815 and 816 are arranged on the upstream side of the bottom plate 813 in the sheet conveyance direction.

[0040] 1 has been described using an example of a printer 1 equipped with an electrophotographic image forming unit 30. The configuration of this embodiment can also be applied to a belt transport unit mounted in an image forming apparatus that forms an image on a sheet using a colorant that hardens with ultraviolet light or the like. In addition, in the first and second embodiments, the center of gravity of the belt transport unit 80 is described as being located in the area connecting positions P3, P4, and P5 in the vertical direction. However, as long as the belt transport unit 80 can be stably connected to the apparatus main body 2, the center of gravity of the belt transport unit 80 does not have to be located in the area connecting positions P3, P4, and P5 in the vertical direction. [Explanation of symbols]

[0041] 1 Printer (image forming apparatus) / 2 Device body / 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 Drive 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 Back support member / 221 Fitting portion (first recess) / 221A First guide path / 222 Fitting portion (second recess) / 222A Second guide path / 230 Upstream support member (plate member) / 241 Mating portion (first recess) / 241A First guide path / 242 Mating portion (second recess) / 242A Second guide path / 321, 421 / First guide portion / 322, 422 Second guide portion / 811 Front side plate (first support member) / 812 Rear side plate (second support member) / 813 Bottom plate (third support member) / 814 Fixing plate (first plate member) / 815 Shaft member (first convex portion) / 816 Shaft member (second convex portion)

Claims

1. A sheet conveying device having a device main body and a belt conveying unit that can be attached to the device main body, the belt transport unit includes a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched and supported by the plurality of rollers; the frame includes a first protrusion and a second protrusion disposed on a rear side, and a fixing portion disposed on a front side, The device body includes: a rear support member including a first fitted portion into which the first protrusion is fitted and a second fitted portion into which the second protrusion is fitted; a front side support member that supports a front side of the belt transport unit, the belt transport unit is supported at two points on the rear side by the engagement between the first convex portion and the first engaged portion and the engagement between the second convex portion and the second engaged portion, and is supported at one point on the front side by the fastening of the fixing portion and the front-side support member by a fastening member; A sheet conveying device characterized by:

2. The device body includes a door configured to be openable and closable on the front side of the device body.

2. The sheet transport device according to claim 1.

3. the rear support member has a guide path that guides the first protrusion to the first fitted portion, The guideway narrows vertically from top to bottom.

3. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

4. By fixing the fixing portion and the front support member with the fastening member, the first convex portion and the second convex portion become immovable in the fitting direction.

4. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

5. the fixed portion is disposed between the first convex portion and the second convex portion in the sheet conveying direction.

5. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

6. the device body includes a transfer unit that transfers an image onto a sheet, and a fixing unit that fixes the image transferred onto the sheet by the transfer unit; the belt transport unit is disposed between the transfer unit and the fixing unit in the sheet transport direction; 6. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

7. The belt transport unit has a plurality of the endless belts.

7. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

8. A sheet conveying device having a device main body and a belt conveying unit that can be attached to the device main body, the belt transport unit includes a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched and supported by the plurality of rollers; the frame includes a first convex portion and a second convex portion disposed on one side in a sheet conveyance direction, and a fixing portion disposed on the other side; The device body includes: a one-side support member including a first fitted portion into which the first protrusion is fitted and a second fitted portion into which the second protrusion is fitted; an other-side support member that supports the other side of the belt transport unit, the belt transport unit is supported at two points on one side by the engagement between the first convex portion and the first engaged portion and the engagement between the second convex portion and the second engaged portion, and is supported at one point on the other side by the fastening of the fixing portion and the other-side support member by a fastening member; A sheet conveying device characterized by:

9. an image forming means for forming an image on a sheet; and the sheet conveying device according to any one of claims 1 to 8. An image forming apparatus characterized by:

10. a fixing means for fixing the toner image on the sheet, the sheet conveying device conveys the sheet from the image forming unit toward the fixing unit; 10. The image forming apparatus according to claim 9,

Images