JP7711287B2 - SHEET CONVEYING DEVICE AND IMAGE FORMING APPARATUS - Google Patents

Description

The present invention relates to a sheet conveying device that conveys a sheet, and an image forming apparatus equipped with the same.

Generally, image forming devices such as copiers and printers are known to have a belt transport unit that transports a sheet by rotating a belt stretched over multiple rollers. As an example of such a belt transport unit, Patent Document 1 discloses a configuration in which a regulating member is provided on the rollers that stretch the belt.

JP 2006-65056 A

The regulating member in Patent Document 1 is provided with a taper that is formed so that the diameter becomes smaller as it approaches the belt, and this taper makes it possible to suppress movement of the belt in the axial direction of the roller. However, even with such a regulating member, the frame of the belt conveying unit can twist and cause misalignment of the rollers due to the assembly of the support member that supports the belt conveying unit to the device main body and shocks during sheet conveyance. Misalignment of the rollers poses the problem of causing wear on the belt ends and slanting of the sheet during sheet conveyance.

The present invention has been made to solve the above problems, and aims to reduce misalignment of rollers that tension a belt in a belt conveying unit that rotates the belt to convey a sheet.

One aspect of the present invention is a sheet transport device having an apparatus main body and a belt transport unit that can be attached to the apparatus main body, wherein the belt transport unit has a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched by the plurality of rollers, the frame including a first convex portion and a second convex portion arranged on the rear side and a fixed portion arranged on the front side, the apparatus main body having a rear support member including a first engaged portion into which the first convex portion engages and a second engaged portion into which the second convex portion engages, and a front support member that supports the front side of the belt transport unit, wherein the belt transport unit is supported at two points on the rear side by the engagement of the first convex portion and the first engaged portion and the engagement of the second convex portion and the second engaged portion, and the front side is supported at one point by fixing the fixed portion to the front support member by a fastening member .

According to the present invention, in a belt conveying unit that rotates a belt to convey a sheet, it is possible to reduce misalignment of the rollers that tension the belt.

FIG. 1 is a schematic diagram of a printer according to a first embodiment. FIG. 2 is a perspective view of a belt transport unit according to the first embodiment. FIG. 2 is a diagram showing a schematic configuration of the inside of a belt transport unit according to the first embodiment. FIG. 4 is a diagram showing the belt transport unit when viewed from the rear side of the apparatus main body of the first embodiment toward the door side. FIG. 2 is a diagram showing a connection structure between the apparatus main body and the belt transport unit according to the first embodiment. FIG. 2 is a diagram showing a connection structure between the apparatus main body and the belt transport unit according to the first embodiment. 11A and 11B are model diagrams showing a state in which a belt transport unit is connected to an apparatus main body as a reference example. 4A and 4B are model diagrams showing a state in which a belt transport unit is connected to the apparatus main body of the first embodiment. FIG. 11 is a diagram showing a belt conveying unit according to a second embodiment when viewed from the upstream side in the sheet conveying direction. FIG. 11 is a diagram illustrating a belt conveying unit according to a second embodiment when viewed from the downstream side in the sheet conveying direction. FIG. 11 is a diagram showing a connection structure between an apparatus main body and a belt transport unit according to a second embodiment. FIG. 11 is a diagram showing a connection structure between an apparatus main body and a belt transport unit according to a second embodiment.

Below, an exemplary embodiment of the present invention will be described with reference to the drawings.

<Overall Configuration of Image Forming Apparatus>
FIG. 1 is a schematic diagram of a printer 1 as a sheet conveying device and an image forming device of the first embodiment. First, the configuration of the printer 1 will be described with reference to FIG. 1. The printer 1 includes a feeding section 10 that feeds a sheet, and a sheet conveying section 20 that conveys the sheet fed by the feeding section 10. The printer 1 also includes an image forming section 30 that forms a toner image to be fixed on the sheet, a secondary transfer section 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 the fixing section 60. The printer 1 also includes a sheet discharge section 70 that conveys the sheet on which the toner image has been fixed by the fixing section 60. The device main body 2 of the printer 1 is provided with a door 2A that is configured to be openable and closable relative to the device main body 2, and when the door 2A is open (open state), a user can access a conveying surface 80A of the belt conveying unit 80.

The feeding unit 10 is disposed at the bottom of the device body 2 of the printer 1. The feeding unit 10 has sheet cassettes 11a and 11b, middle plates 12a and 12b that support the 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 top sheet is maintained at a predetermined feeding position by raising and lowering the middle plates 12a and 12b. Although FIG. 1 shows an example of a friction separation method using rollers as a sheet feeding method in the feeding unit 10, the sheet may be fed by a separation and adsorption method using air. Since the separation and feeding units 13a and 13b have the same configuration, the configuration of the separation and feeding unit 13a will be described and the configuration of the separation and feeding unit 13b will be omitted. The separation and feeding section 13a has a pickup roller 14a that can contact the top sheet stacked in the sheet cassette 11a, a separation roller pair 15a provided downstream of the pickup roller 14a in the sheet conveying direction, and a pull-out roller pair 16a. The separation roller pair 15a is composed of a conveying 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 conveying direction when sheets are fed in a double-feed. When sheets are fed in a double-feed, the sheet fed along with the top sheet is separated from the top sheet by a separation nip formed by the conveying roller 15a1 and the separation roller 15a2. The pull-out roller pair 16a is provided downstream of the separation roller pair 15a in the sheet conveying direction, and the sheet conveyed from the separation roller pair 15a is conveyed to the sheet conveying section 20.

The sheet conveying section 20 has multiple roller pairs, and the sheet fed from the feeding section 10 is conveyed toward the secondary transfer section 35 by being passed sequentially through the multiple roller pairs provided in the sheet conveying section 20. Of the multiple roller pairs in the sheet conveying section 20, the roller pair immediately before 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 the skew of the sheet.

The image forming unit 30 is a so-called tandem type image forming means in which electrophotographic process cartridges PY, PM, PC, and PK that form toner images of Y (yellow), M (magenta), C (cyan), and K (black) are arranged in series. The process cartridges PY, PM, PC, and PK have a common configuration except for the toner colors. Therefore, the configuration of the process cartridge PY will be described as an example, and the configurations of the process cartridges PM, PC, and PK will be omitted. In FIG. 1, the configuration of the process cartridge PY is suffixed with "Y", the configuration of the process cartridge PM is suffixed with "M", the configuration of the process cartridge PC is suffixed with "C", and the configuration of the process cartridge PK is suffixed with "K". The process cartridge PY has 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 the toner images 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 the arrow T in FIG. 1 by the drive of the drive roller 52.

The secondary transfer roller 56 is pressed against the intermediate transfer belt 51 supported from the inside of the intermediate transfer belt 51 by the inner transfer roller 54 to form a secondary transfer nip portion 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 constitute the secondary transfer section 35. Residual toner and paper dust remaining on the surface of the intermediate transfer belt 51 after passing through the secondary transfer nip portion N2 are removed by a cleaning device (not shown). The fixing section 60, which is disposed downstream of the secondary transfer section 35 in the sheet conveying direction, is a fixing means that fixes the toner image to the sheet by heat and pressure. The fixing section 60 includes a heating roller 62 equipped with a heater inside, and an opposing roller 63 that is disposed so as to be able to come into contact with the heating roller 62 and forms the fixing nip portion N together with the heating roller 62.

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

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

Next, a series of steps for forming an image on a sheet in the printer 1 will be described. Based on an image forming 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 development device 33Y and visualized as a toner image. The toner image carried on the surface of the photosensitive drum 1Y is primarily transferred by the primary transfer device 55Y in a sequentially overlapping manner onto the intermediate transfer belt 51. The toner image primarily transferred onto the intermediate transfer belt 51 is secondarily transferred onto the sheet S nipped and conveyed to the secondary transfer nip portion N2. The intermediate transfer belt 51 is driven to rotate by the drive roller 52 that rotates at a constant speed, and is rotated in a state in which its peripheral speed is maintained at a constant transfer speed.

The registration roller 7 of the sheet conveying section 20 receives the sheet S while it is 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 section N2. The toner image is transferred to the sheet at the secondary transfer nip section N2. The sheet S carrying the transferred toner image is conveyed from the secondary transfer nip section N2 to the fixing section 60 by the belt conveying unit 80. At the fixing section 60, the sheet S is nipped and conveyed at the fixing nip section 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 discharged outside the printer 1 by the sheet discharge section 70.

When forming images 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, it is conveyed toward the double-sided conveying path 75. The sheet is then 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 manner as on the first side (front side).

<Configuration of Belt Conveyor Unit>
Next, the configuration of the belt conveying unit 80 will be described with reference to FIG. 1 to FIG. 3. FIG. 2 is a perspective view of the belt conveying unit 80. FIG. 3 is a diagram showing a schematic configuration inside the belt conveying unit 80. As described in FIG. 1, the belt conveying unit 80 is disposed downstream of the image forming unit 30 and upstream of the fixing unit 60 in the sheet conveying direction, and conveys 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, a belt conveying unit 80, and a fixing entrance guide 65 are provided between the secondary transfer unit 35 and the fixing unit 60 in the sheet conveying direction. Then, the sheet conveyed from the secondary transfer unit 35 is conveyed to the belt conveying unit 80 via the transfer exit guide 59, and is conveyed from the belt conveying unit 80 to the fixing unit 60 via the fixing entrance guide 65. In this embodiment, the belt conveying unit 80 is disposed on the door 2A side in the main body front direction in FIG. 2, and on the opposite side (rear side) to the door 2A in the main body rear direction.

2, the belt conveying unit 80 has a driving roller 101 composed of driving rollers 101a, 101b, 101c, and 101d, and a driven roller 102 composed of driven rollers 102a, 102b, 103c, and 104d. The driving 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 portion 82 rotatably stretched by the driving 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 has a front plate 811 and a rear plate 812 arranged along the sheet transport direction, and a bottom plate 813 that spans the front plate 811 and the rear plate 812.

Furthermore, the belt conveying unit 80 has bearings 201a and 201b provided at the axial ends of the driving roller 101, and bearings 202a and 202b provided at the axial ends of the driven roller 102. The bearing 201a as the first bearing in this embodiment rotatably supports one axial end of the driving roller 101. The bearing 201b as the second bearing in this embodiment rotatably supports the other axial end of the driving roller 101. The bearing 202a as the third bearing in this embodiment rotatably supports one axial end of the driven roller 102. The bearing 202b as the fourth bearing in this embodiment rotatably supports the other axial end of the driven roller 102. The bearings 201a and 202a are supported by the 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 to the inner surface by driving the suction fans 87a and 87b, making it possible to convey the sheet while pulling it to the belt portion 82.

<Connection structure of belt conveyor 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 Figs. 2 to 6. Fig. 4 is a diagram showing the belt conveying unit 80 when viewed from the rear side of the device body 2 toward the door 2A side. Fig. 5 is a diagram showing the connection structure between the device body 2 and the belt conveying unit 80 when viewed from the door 2A side of the device body 2. Fig. 6 is a diagram showing the connection structure between the device body 2 and the belt conveying unit 80 when viewed from the rear side 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 a front side 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 by a fastening member 211 such as a screw. 5 shows a position P3 at which 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. The first plate member in this embodiment is the fixed plate 814, and the second plate member is the front support member 210. The third connecting portion in this embodiment is composed of the fixed plate 814, the front support member 210, and the fastening member 211.

At the rear side of the device main body 2, shaft members 815 and 816 are fixed to the rear side plate 812 by rivets or the like, and fitted portions 221 and 222 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 into the fitted portions 221 and 222, respectively, so that the belt transport unit 80 is connected and supported to the device main body 2. The position where the shaft member 815 is fitted into the fitted portion 221 and the weight of the belt transport unit 80 acts is shown as position P4 in Figure 6. The position where the shaft member 816 is fitted into the fitted portion 222 and the weight of the belt transport unit 80 acts is shown as position P5 in Figure 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 this embodiment, the first connecting portion is composed of shaft member 815 and fitted portion 221 that is fitted to shaft member 815, and the second connecting portion is composed of shaft member 816 and fitted portion 222 that is fitted to shaft member 816. With this configuration, the center of gravity of belt conveying unit 80 is located in the area formed by connecting the three points P3, P4, and P5 in the vertical direction.

When attaching the belt conveying unit 80 to the device body 2, first, the shaft members 815 and 816 are fitted to the fitting parts 221 and 222 arranged at one end of the axial direction of the driving roller 101, that is, at the rear side of the device body 2. Next, the fixing plate 814 is fixed to the front support member 210 arranged at the other end of the axial direction of the driving roller 101, that is, at the front side of the device body 2, using the fastening member 211. By fixing the front support member 210 and the fixing plate 814 by the fastening member 211, the shaft member 815 fitted to the fitting part 221 and the shaft member 816 fitted to the fitting part 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.

The rear support member 220 is provided with a guide portion 321 that guides the shaft member 815 to the inlet of the fitted portion 221, and a guide portion 322 that guides the shaft member 816 to the inlet of the fitted portion 222. The guide portion 321 as the first guide portion in this embodiment forms a first guide path 221A that narrows from the top to the bottom in the vertical direction. The guide portion 322 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, 816 guided by the first guide paths 221A, 222A are inserted into the fitted portions 221, 222. With this configuration, it is possible to easily fit the shaft members 815, 816 into the fitted portions 221, 222 by moving the belt conveying unit 80 from the top to the bottom in the vertical direction relative to the rear support member 220.

In addition, 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 that is easily accessible to the user. As a result, in this embodiment, the belt transport unit 80 can be attached and detached from the device body 2 simply by tightening and loosening the fastening member 211, which makes it possible to improve work efficiency during maintenance work. Note that 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 mating portions 221 and 222 have an uneven shape that allows them to be mated with each other.

<Features of three-point linkage>
Next, with reference to Figs. 7(A, B) and 8(A, B), the effect of the belt conveying unit 80 being connected and supported to the device main body 2 in this embodiment will be described. Fig. 7(A) is a model diagram showing a state in which the belt conveying 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. 7(B) is a model diagram showing a state in which the configuration of Fig. 7(A) is affected by the tolerance of parts and impact during sheet conveyance. Fig. 8(A) is a model diagram showing a state in which the belt conveying unit 80 is connected to the device main body 2 at three points, P3, P4, and P5, as this embodiment. Fig. 8(B) is a model diagram showing a state in which the configuration of Fig. 8(A) is affected by the tolerance of parts and impact during sheet conveyance.

As shown in FIG. 7A, 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 arranged in a direction along the plane formed by the four points P'1, P'2, P'4, and P'5. However, the plane formed by the four points becomes twisted as shown in FIG. 7B due to the tolerance of the parts constituting each point and the impact during sheet conveyance. 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, and the alignment of the drive roller 101 and the driven roller 102 supported by the frame 81 occurs. In this embodiment, the alignment of 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 there is no misalignment refers to the positional relationship between the drive roller 101 and the driven roller 102 when the sheet is unlikely to skew or buckle on the sheet conveying surface 80A formed by the belt portion 82. A state in which there is a misalignment refers to the positional relationship between the drive roller 101 and the driven roller 102 when the sheet is likely to skew or buckle on the sheet conveying surface 80A formed by the belt portion 82.

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

On the other hand, as shown in FIG. 8A, when the weight of the belt conveying unit 80 acts on the device main body 2 at three points P3, P4, and P5, the frame 81 is arranged in a direction along the plane formed by the three points P3, P4, and P5. The plane formed by the three points is not twisted even if it is affected by the tolerance of the parts arranged at the positions P3, P4, and P5 or the impact during sheet conveyance. As a result, the frame 81 is arranged in a direction along the plane formed by the three points P3, P4, and P5, so that the alignment deviation between the drive roller 101 and the driven roller 102 supported by the frame 81 is reduced. Therefore, in this embodiment, the axial movement of the belt portion 82 and the skew of the sheet are less likely to occur compared to the reference example. Also, in this embodiment, the axial movement of the belt portion 82 and the skew of the sheet can be suppressed without providing a tapered regulating member for regulating the movement of the belt on the roller that stretches the belt. Therefore, it is possible to suppress wear of the end of the belt portion 82 caused by the regulating member.

Next, the 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 axial ends of the drive roller 101 and the driven roller 102 is 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 is described. In the description of this example, the same components as in Example 1 are given the same reference numerals, and duplicated descriptions will be omitted. In addition, the schematic configuration of the printer 1 in Example 2 is the same as that in FIG. 1, so description will be omitted.

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 is a diagram showing the belt conveying unit 80 when viewed from the upstream side of the sheet conveying direction. Figure 10 is a diagram showing the device body 2 and the belt conveying unit 80 when viewed from the downstream side of the sheet conveying direction. Figure 11 is a diagram showing the connection structure between the device body 2 and the belt conveying unit 80 when viewed from the upstream side of the sheet conveying direction. Figure 12 is a diagram showing the connection structure between the device body 2 and the belt conveying unit 80 when viewed from the downstream side of 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 of the sheet conveying direction in the device body 2, and a downstream support member 240 provided on the downstream side of the sheet conveying direction in the device body 2. Specifically, the upstream support member 230 is fixed to the bottom plate 813 by a fastening member 213 such as a screw at the other end of the bottom plate 813, that is, at the upstream end of the bottom plate 813 in the sheet conveying direction. The upstream support member 230 is disposed at the other end side of the sheet conveying direction, that is, upstream of the belt conveying unit 80 in the sheet conveying direction. The position where the bottom plate 813 and the upstream support member 230 are fixed by the fastening member 213 and 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 composed of the fastening member 213 and the upstream support member 230 fixed to the bottom plate 813 by the fastening member 213.

In addition, on the downstream side of the sheet conveying direction in the device main body 2, shaft members 815 and 816 fixed to the bottom plate 813 by rivets or the like, and engaged parts 241 and 242 that are provided on the downstream support member 240 and can be engaged with the shaft members 815 and 816, respectively, are provided. The engaged parts 241 and 242 are each disposed at one end side of the sheet conveying direction, that is, downstream side of the belt conveying unit 80 in the sheet conveying direction. The shaft members 815 and 816 are engaged with the engaged parts 241 and 242, respectively, so that the belt conveying unit 80 is connected and supported to the device 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 and the engaged part 241 are engaged and the weight of the belt conveying unit 80 acts is shown as position P4 in FIG. 12. In addition, 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 FIG. 12. 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 that is fitted to the shaft member 815, and the second connecting portion is composed of the shaft member 816 and the fitted portion 242 that is fitted to the shaft member 816. With this configuration, the center of gravity of the belt conveying unit 80 is located in the area formed by connecting the three points P3, P4, and P5 in the vertical direction.

When attaching the belt conveying unit 80 to the device body 2, first, the shaft members 815 and 816 are fitted to the fitting parts 241 and 242, which are located on the downstream side of the sheet conveying direction in the device body 2, that is, in front of the fixing unit 60. Next, the upstream support member 230, which is located on the upstream side of the sheet conveying direction in the device body 2, is fixed to the bottom plate 813 using the fastening member 213. By fixing the upstream support member 230 to the bottom plate 813 by the fastening member 211, the shaft member 815 fitted to the fitting part 241 and the shaft member 816 fitted to the fitting part 242 become immovable 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.

The downstream support member 240 is provided with a guide portion 421 that guides the shaft member 815 to the inlet of the fitted portion 241, and a guide portion 422 that guides the shaft member 816 to the inlet of the fitted portion 242. The guide portion 421 as the first guide portion in this embodiment forms a first guide path 241A that narrows from the top to the bottom in the vertical direction. The guide portion 422 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. 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, it is possible to easily fit the shaft members 815 and 816 into the fitted portions 241 and 242 by moving the belt conveying unit 80 from the top to the bottom in the vertical direction relative to the downstream support member 240.

The upstream support member 230 is fixed to the bottom plate 813 by the 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 and detached from the device main body 2 simply by tightening and loosening the fastening member 213, which makes it possible to improve the work efficiency during maintenance work. The shaft members 815 and 816 may have a shape other than the cylindrical shape shown in FIG. 10. In other words, it is sufficient that the shaft members 815 and 816 and the engagement parts 241 and 242 have an uneven shape that can be engaged with each other. In this embodiment, the belt conveying unit 80 is connected and supported to the device main 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 unit 60.

In this embodiment, as in the first embodiment, the frame 81 is arranged in a direction along the plane formed by the three points P3, P4, and P5, so that misalignment between the drive roller 101 and the driven roller 102 supported by the frame 81 is reduced. Therefore, the axial movement of the belt portion 82 and the skew of the sheet are less likely to occur (see Figures 7 (A, B) and 8 (A, B)). Furthermore, in this embodiment, too, the axial movement of the belt portion 82 and the skew of the sheet can be suppressed without providing a tapered regulating member that regulates the movement of the belt on the roller that tensions the belt. Therefore, it is possible to suppress wear of the end of the belt portion 82 caused by the regulating member.

<Other Examples>
In the first 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 device body 2 that is easily accessible to the user, but the fixing plate 814, the front support member 210, and the fastening member 211 may be disposed on the rear side of the device body 2. In this case, the fitted parts 221 and 222 and the shaft members 815 and 816 are disposed on the side of the door 2A of the device body 2. Also, in the second embodiment, the upstream support member 230 may be fixed to the bottom plate 813 by the fastening member 213 such as a screw at the downstream end of the bottom plate 813 in the sheet conveying direction. In this case, the fitted parts 241 and 242 and the shaft members 815 and 816 are disposed on the upstream side of the bottom plate 813 in the sheet conveying direction.

In addition, in FIG. 1, the printer 1 equipped with the electrophotographic image forming unit 30 is used as an example for explanation. In addition, the configuration of this embodiment can also be applied to a belt transport unit mounted in an image forming device 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 in the area connecting positions P3, P4, and P5 in the vertical direction. However, if the belt transport unit 80 can be stably connected to the device main body 2, the center of gravity of the belt transport unit 80 does not have to be included in the area connecting positions P3, P4, and P5 in the vertical direction.

1 Printer (image forming device) / 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 Fitted portion (first recess) / 221A First guide path / 222 Fitted portion (second recess) / 222A Second guide path / 230 Upstream support member (plate member) / 241 Fitted part (first recess) / 241A First guideway / 242 Fitted part (second recess) / 242A Second guideway / 321, 421 / First guideway / 322, 422 Second guideway / 811 Front side plate (first support member) / 812 Rear side plate (second support member) / 813 Bottom plate (third support member) / 814 Fixed plate (first plate member) / 815 Shaft member (first convex part) / 816 Shaft member (second convex part)

Claims (10)

A sheet conveying device having a device body and a belt conveying unit that can be attached to the device body,
the belt transport unit includes a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched around the plurality of rollers;
the frame includes a first protruding portion and a second protruding portion 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 for supporting a front side of the belt transport unit,
the belt transport unit is supported at two points on the rear side by the engagement of the first convex portion with the first engaged portion and the engagement of the second convex portion with the second engaged portion, and is supported at one point on the front side by fastening the fixing portion to the front side support member by a fastening member;
A sheet conveying device comprising: 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. 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. 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. the fixed portion is disposed between the first convex portion and the second convex portion in a sheet conveying direction.
5. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device. 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 a sheet transport direction;
6. The sheet transport device according to claim 1, wherein the sheet transport device is a sheet conveying device. The belt conveying 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. A sheet conveying device having a device body and a belt conveying unit that can be attached to the device body,
the belt transport unit includes a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched around the plurality of rollers;
the frame includes a first convex portion and a second convex portion disposed on one side in a sheet conveying direction, and a fixed 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;
and 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 fitting the first convex portion and the first fitted portion and fitting the second convex portion and the second fitted portion, and is supported at one point on the other side by fastening the fixing portion and the other side support member by a fastening member;
A sheet conveying device comprising: an image forming means for forming an image on a sheet;
The sheet conveying device according to claim 1 ,
1. An image forming apparatus comprising: A fixing means for fixing the toner image on the sheet,
the sheet conveying device conveys a sheet from the image forming unit to the fixing unit;
10. The image forming apparatus according to claim 9 ,