Sheet conveying 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 device for conveying a sheet and an image forming apparatus including the same.

Background Art

[0002] Generally, in an image forming apparatus such as a copying machine or a printer, in order to convey a sheet, there is known one including a belt conveying unit that rotates a belt stretched over 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 around which the belt is stretched.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The regulating member of Patent Document 1 is provided with a taper formed so that the diameter becomes smaller as it approaches the belt, and this taper makes it possible to suppress the movement of the belt in the axial direction of the roller. However, even when such a regulating member is provided, due to the assembly of the support member that supports the belt conveying unit with respect to the apparatus main body or the impact during sheet conveyance, etc., the frame of the belt conveying unit is twisted and the alignment of the rollers is displaced. The misalignment of the rollers has a problem of causing wear of the belt end portion and skew running of the sheet during sheet conveyance.

[0005] The present invention has been made to solve the above problems, and an object thereof is to reduce the alignment displacement of the rollers around which the belt is stretched in a belt conveying unit that rotates the belt to convey a sheet.

Means for Solving the Problems

[0006] This One aspect of the invention is , a mounting a placement body, and A sheet conveying device having a belt conveying unit attachable to the device main body, wherein the belt conveying unit includes a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched by the plurality of rollers. The frame includes a first convex portion and a second convex portion disposed on the back side, and a fixing portion disposed on the front side. The device main body includes a back side support member including a first fitting portion into which the first convex portion fits and a second fitting portion into which the second convex portion fits, and a front side support member that supports the front side of the belt conveying unit. The belt conveying unit is supported at two locations on the back side by the fitting of the first convex portion and the first fitting portion and the fitting of the second convex portion and the second fitting portion, and is supported at one location on the front side by fixing the fixing portion and the front side support member with a fastening member is characterized by is a sheet conveying device .

Advantages of the Invention

[0008] According to the present invention, in a belt conveyance unit that rotates a belt to convey a sheet, it is possible to reduce misalignment of rollers that stretch the belt.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0010] Hereinafter, exemplary embodiments for carrying out the present invention will be described with reference to the drawings.

Examples

[0011] <Overall Configuration of the Image Forming Apparatus> FIG. 1 is a schematic configuration diagram of the sheet conveyance apparatus of Example 1 and the printer 1 as an image forming apparatus. 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 conveyance unit 20 that conveys the sheet fed by the feeding unit 10. Further, the printer 1 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 conveyance unit 80 that conveys 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 that conveys the sheet on which the toner image has been fixed by the fixing unit 60. The apparatus main body 2 of the printer 1 is provided with a door 2A that is configured to be openable and closable with respect to the apparatus main body 2. In a state where the door 2A is open (open state), the user can access the conveyance surface 80A of the belt conveyance unit 80.

[0012] The feeding unit 10 is disposed at the lower part of the apparatus main body 2 of the printer 1. The feeding unit 10 includes sheet cassettes 11a and 11b, middle plates 12a and 12b for stacking and supporting sheets in the sheet cassettes 11a and 11b, and separating and feeding units 13a and 13b for separating and feeding the sheets stacked on the middle plates 12a and 12b one by one. The feeding unit 10 is configured such that the height of the uppermost sheet is held at a predetermined feeding position by the lifting of the middle plates 12a and 12b. As a method of feeding sheets in the feeding unit 10, although FIG. 1 shows an example using a friction separation method by rollers, the sheets may be fed by a separation and adsorption method by air. Since the separating and feeding units 13a and 13b have the same configuration, the configuration of the separating and feeding unit 13a will be described, and the description of the configuration of the separating and feeding unit 13b will be omitted. The separating and feeding unit 13a includes a pickup roller 14a that can contact the uppermost sheet stacked in the sheet cassette 11a, a pair of separating rollers 15a provided downstream of the pickup roller 14a in the sheet conveyance direction, and a pair of pulling rollers 16a. The pair of separating rollers 15a is composed of a conveyance roller 15a1 that rotates in the same direction as the pickup roller 14a and a separating roller 15a2 that is rotationally driven in the direction opposite to the sheet conveyance direction or fixed when the sheets are double-fed. When the sheets are double-fed, the sheets fed along with the uppermost sheet are separated from the uppermost sheet by a separation nip formed by the conveyance roller 15a1 and the separating roller 15a2. The pair of pulling rollers 16a is provided downstream of the pair of separating rollers 15a in the sheet conveyance direction, and the sheets conveyed from the pair of separating rollers 15a are conveyed to the sheet conveyance unit 20.

[0013] The sheet conveyance unit 20 has a plurality of roller pairs, and the sheet fed from the feeding unit 10 is sequentially transferred through the plurality of roller pairs provided in the sheet conveyance unit 20 and conveyed toward the secondary transfer unit 35. Among the plurality of roller pairs of the sheet conveyance unit 20, the roller pair immediately before the secondary transfer unit 35 in the sheet conveyance direction is the registration roller pair 21. The registration roller pair 21 is configured to convey the sheet to the secondary transfer unit 35 in synchronization with the image formation timing of the image forming unit 30 and correct the skew of the sheet.

[0014] The image forming unit 30 is a so-called tandem type image forming means in which electrophotographic process cartridges PY, PM, PC, and PK for forming 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 the same configuration except for the different toner colors. Therefore, here, the configuration of the process cartridge PY will be described as an example, and the description of the configurations of the process cartridges PM, PC, and PK will be omitted. In FIG. 1, "Y" is attached to the end of the reference numeral for the configuration of the process cartridge PY, "M" is attached to the end of the reference numeral for the configuration of the process cartridge PM, "C" is attached to the end of the reference numeral for the configuration of the process cartridge PC, and "K" is attached to the end of the reference numeral for the configuration of the process cartridge PK. 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 as an example of an image carrier on which the toner images visualized by the process cartridges PY, PM, PC, and PK are carried. The intermediate transfer belt 51 is supported in a state of being wound 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 by the driving of the driving roller 52.

[0015] The secondary transfer roller 56 presses against the intermediate transfer belt 51 supported from the inside of the intermediate transfer belt 51 by the inner transfer roller 54, and forms a secondary transfer nip portion N2 between the secondary transfer roller 56 and the intermediate transfer belt 51. The secondary transfer portion 35 is constituted by the secondary transfer roller 56, the intermediate transfer belt 51, and the inner transfer roller 54. Transfer residual toner, paper dust, etc. 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 portion 60 disposed downstream of the secondary transfer portion 35 in the sheet conveyance direction is a fixing means for fixing the toner image on the sheet by heat and pressure. The fixing portion 60 includes a heating roller 62 having a heater inside, and a counter roller 63 disposed so as to be able to contact the heating roller 62 and forming a fixing nip portion N together with the heating roller 62.

[0016] Also, in the sheet conveyance direction, a belt conveyance unit 80 is disposed between the secondary transfer portion 35 and the fixing portion 60. The configuration of the belt conveyance unit 80 will be described later.

[0017] The sheet discharge portion 70 includes a branch conveyance portion 73 disposed between the fixing portion 60 and the discharge roller pair 71 in the sheet conveyance direction, and a reverse conveyance portion 74 that reversely conveys the sheet. Further, the sheet discharge portion 70 has a duplex conveyance path 75 that conveys the sheet reversed by the reverse conveyance portion 74 and merges it into the sheet conveyance path of the sheet conveyance portion 20.

[0018] Next, a series of processes for forming an image on a sheet in the printer 1 will be described. Based on the image formation job input to the printer 1, first, the exposure device 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 device 33Y and visualized as a toner image. The toner image carried on the surface of the photosensitive drum 1Y is sequentially and repeatedly primary-transferred onto the intermediate transfer belt 51 by the primary transfer device 55Y. The toner image primary-transferred onto the intermediate transfer belt 51 is secondary-transferred onto the sheet S nipped and conveyed at the secondary transfer nip portion N2. The intermediate transfer belt 51 is rotationally driven by a driving roller 52 that rotates at a constant speed, and is rotated while being maintained in a state where its peripheral speed is a constant transfer speed.

[0019] The registration roller 7 of the sheet conveyance unit 20 receives the sheet S in a state where its rotation is stopped, starts rotating in synchronization with the toner image on the intermediate transfer belt 51, and sends out the sheet S toward the secondary transfer nip portion N2. The toner image is transferred onto the sheet at the secondary transfer nip portion N2. The sheet S carrying the transferred toner image is conveyed from the secondary transfer nip portion N2 toward the fixing unit 60 by the belt conveyance unit 80. In the fixing unit 60, the sheet S is nipped and conveyed at the fixing nip portion N, and heat and pressure are applied to the unfixed toner image to fix the toner image on the sheet. The sheet S sent out from the fixing unit 60 is discharged outside the printer 1 by the sheet discharge unit 70.

[0020] When forming images on both sides of the sheet, the conveyance path is switched so that the sheet sent out from the fixing unit 60 is conveyed toward the reverse conveyance unit 74 by the branch conveyance unit 73, reversed by the reverse conveyance unit 74, and then conveyed toward the duplex conveyance path 75. Then, the sheet is conveyed via the duplex conveyance path 75 and again to the conveyance path of the sheet conveyance unit 20. For the sheet conveyed to the sheet conveyance 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).

[0021] <Configuration of Belt Conveyance Unit> Next, the configuration of the belt conveyance unit 80 will be described with reference to FIGS. 1 to 3. FIG. 2 is a perspective view of the belt conveyance unit 80. FIG. 3 is a diagram showing a schematic configuration inside the belt conveyance unit 80. As described also in FIG. 1, the belt conveyance unit 80 is disposed downstream of the image forming unit 30 and upstream of the fixing unit 60 in the sheet conveyance 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 FIG. 1, between the secondary transfer unit 35 and the fixing unit 60 in the sheet conveyance direction, a transfer exit guide 59, a belt conveyance unit 80, and a fixing entrance guide 65 are provided. Then, the sheet conveyed from the secondary transfer unit 35 is conveyed to the belt conveyance unit 80 via the transfer exit guide 59, and is conveyed from the belt conveyance unit 80 to the fixing unit 60 via the fixing entrance guide 65. In the present embodiment, the front direction of the main body in FIG. 2 is disposed on the side of the door 2A, and the rear direction of the main body is disposed on the side opposite to the door 2A (the back side).

[0022] As shown in FIG. 2, the belt conveyance unit 80 includes 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 of the present embodiment, and the driven roller 102 is the second roller of the present embodiment. Further, the belt conveyance unit 80 includes a frame 81 as a support structure of the present 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 provided with a plurality of holes. The frame 81 has a front side plate 811 and a rear side plate 812 provided along the sheet conveyance direction, and a bottom plate 813 bridged between the front side plate 811 and the rear side plate 812.

[0023] Furthermore, the belt conveyance unit 80 includes 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 as the first bearing of this embodiment rotatably supports one axial end of the drive roller 101. The bearing 201b as the second bearing of this embodiment rotatably supports the other axial end of the drive roller 101. The bearing 202a as the third bearing of this embodiment rotatably supports one axial end of the driven roller 102. The bearing 202b as the fourth bearing of this embodiment rotatably supports the other axial end of the driven roller 102. The bearing 201a and the bearing 202a are supported by the front side plate 811, and the bearing 201b and the bearing 202b are also supported by the front side plate 811 (see FIG. 4). The front side plate 811, which is the first support member of this embodiment, can support the bearings 201a and 202a, the rear side plate 812, which is the second support member, can support the bearings 201b and 202b, and the bottom plate 813 is the third support member. Furthermore, as shown in FIG. 3, the belt conveyance unit 80 has suction fans 87a and 87b inside the belt members 82b and 82c. In the belt conveyance unit 80, air is sucked from the outer surface to the inner surface of the belt portion 82 by driving the suction fans 87a and 87b, and it is possible to convey the sheet while attracting the sheet to the belt portion 82.

[0024] <Connection Structure of Belt Conveyance Unit> Next, with reference to FIGS. 2 to 6, the connection structure between the apparatus main body 2 and the belt conveyance unit 80 in this embodiment will be described. FIG. 4 is a view showing the belt conveyance unit 80 when viewed from the back side of the apparatus main body 2 toward the door 2A side. FIG. 5 is a view showing the connection structure between the apparatus main body 2 and the belt conveyance unit 80 when viewed from the door 2A side of the apparatus main body 2. FIG. 6 is a view showing the connection structure between the apparatus main body 2 and the belt conveyance unit 80 when viewed from the back side of the apparatus main body 2. The belt conveyance unit 80 is connected and supported to the apparatus main body 2 by a front support member 210, which is a plate-like member provided on the door 2A side of the apparatus main body 2, and a rear support member 220 provided on the rear side of the apparatus main body 2. Specifically, a fixing plate 814 fixed to the front plate 811 on the door 2A side of the apparatus main body 2 is fixed to the front support member 210 provided on the door 2A side of the apparatus main body 2 with a fastening member 211 such as a screw. In FIG. 5, the position where the self-weight of the belt conveyance unit 80 acts is shown as position P3 by fastening the fixing plate 814 and the front support member 210 with 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. Further, the third connection portion of this embodiment is constituted by the fixing plate 814, the front support member 210, and the fastening member 211.

[0025] On the back 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 fitting portions 221 and 222 provided on the back side support member 220 and capable of fitting with the shaft members 815 and 816, respectively. The belt conveyance unit 80 is connected and supported to the apparatus main body 2 by fitting the shaft members 815 and 816 with the fitting portions 221 and 222, respectively. The position where the self-weight of the belt conveyance unit 80 acts when the shaft member 815 and the fitting portion 221 are fitted is shown as position P4 in FIG. 6. Also, the position where the self-weight of the belt conveyance unit 80 acts when the shaft member 816 and the fitting portion 222 are fitted is shown as position P5 in FIG. 6. In this embodiment, the first convex portion is the shaft member 815, the second convex portion is the shaft member 816, the first concave portion is the fitting portion 221, and the second concave portion is the fitting portion 222. Further, the first connecting portion of this embodiment is constituted by the shaft member 815 and the fitting portion 221 fitted to the shaft member 815, and the second connecting portion is constituted by the shaft member 816 and the fitting portion 222 fitted to the shaft member 816. With such a configuration, the center of gravity of the belt conveyance unit 80 is arranged in a region formed by connecting three points, positions P3, P4, and P5, in the vertical direction.

[0026] When attaching the belt conveyance unit 80 to the apparatus main body 2, first, the shaft members 815 and 816 are respectively fitted to the fitting portions 221 and 222 arranged on one end side in the axial direction of the drive roller 101, that is, on the back side of the apparatus main body 2. Next, the fixing plate 814 is fixed to the front side support member 210 provided on the other end side in the axial direction of the drive roller 101, that is, on the front side of the apparatus main body 2, using the fastening member 211. By fixing the front side 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 become immovable in the fitting direction. In this embodiment, in this way, the belt conveyance unit 80 is connected and supported to the apparatus main body 2. When removing the belt conveyance unit 80 from the apparatus main body 2, the reverse procedure is performed with the door 2A open.

[0027] Note that the back-side support member 220 is provided with a guide portion 321 that guides the shaft member 815 to the entrance of the fitting portion 221 and a guide portion 322 that guides the shaft member 816 to the entrance of the fitting portion 222. The guide portion 321 as the first guide portion of the present embodiment forms a first guide path 221A that becomes narrower from the upper side to the lower side in the vertical direction. Further, the guide portion 322 as the second guide portion of the present embodiment forms a second guide path 222A that becomes narrower from the upper side to the lower side in the vertical direction. An example of the fitting direction in the present 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 fitting portions 221 and 222. With such a configuration, it becomes possible to move the belt conveyance unit 80 downward from the upper side in the vertical direction with respect to the back-side support member 220 and easily fit the shaft members 815 and 816 to the fitting portions 221 and 222.

[0028] Also, in the present embodiment, a fixing plate 814, a front-side support member 210, and a fastening member 211 are arranged on the side of the door 2A of the apparatus main body 2 that is easily accessible to the user. Thereby, in the present embodiment, the belt conveyance unit 80 can be attached to and detached from the apparatus main body 2 only by performing the tightening and loosening operation of the fastening member 211, so that it becomes possible to improve the 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. That is, any uneven shape in which the shaft members 815 and 816 and the fitting portions 221 and 222 can be mutually fitted may be used.

[0029] <Features of three-point connection> Next, with reference to FIGS. 7(A, B) and 8(A, B), the effects when the belt conveyance unit 80 is connected and supported to the apparatus main body 2 in this embodiment will be described. FIG. 7(A) is a model diagram showing a state in which the belt conveyance unit 80 is connected to the apparatus 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 affected by component tolerances, impacts during sheet conveyance, etc. from the configuration of FIG. 7(A). FIG. 8(A) is a model diagram showing a state in which the belt conveyance unit 80 is connected to the apparatus main body 2 at three points P3, P4, and P5 as this embodiment. FIG. 8(B) is a model diagram showing a state affected by component tolerances, impacts during sheet conveyance, etc. from the configuration of FIG. 8(A).

[0030] As shown in FIG. 7(A), when the self-weight of the belt conveyance 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 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 is distorted as shown in FIG. 7(B) due to component tolerances of the components constituting each point, impacts during sheet conveyance, etc. As a result, the frame 81 is in a distorted state with respect to the plane formed by the four points P'1, P'2, P'4, and P'5, and misalignment occurs between the drive roller 101 and the driven roller 102 supported by the frame 81. The alignment between the drive roller 101 and the driven roller 102 in this embodiment refers to the relative positional relationship between the drive roller 101 and the driven roller 102. Also, the state where no misalignment has occurred refers to the positional relationship between the drive roller 101 and the driven roller 102 when, on the conveyance surface 80A of the sheet formed by the belt portion 82, it is difficult for the sheet to skew or buckle. The state where misalignment has occurred refers to the positional relationship between the drive roller 101 and the driven roller 102 when, on the conveyance surface 80A of the sheet formed by the belt portion 82, it is easy for the sheet to skew or buckle.

[0031] When an alignment deviation occurs between the driving roller 101 and the driven roller 102, a difference in the tension of the belt portion 82 stretched by the driving roller 101 and the driven roller 102 occurs, and the belt portion 82 moves toward the side with weaker tension. Further, due to the movement of the belt portion 82, the sheet conveyed from the image forming unit 30 obliquely runs 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 unit 60.

[0032] On the other hand, as shown in FIG. 8(A), when the self-weight of the belt conveying unit 80 acts on the apparatus 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 under the influence of the tolerances of the components arranged at the positions P3, P4, and P5 and the impact during sheet conveyance. As a result, since the frame 81 is arranged in a direction along the plane formed by the three points P3, P4, and P5, the alignment deviation between the driving roller 101 and the driven roller 102 supported by the frame 81 is reduced. Therefore, in the present embodiment, the axial movement of the belt portion 82 and the oblique running of the sheet are less likely to occur compared with the reference example. Further, in the present embodiment, even if a regulating member having a tapered shape for regulating the movement of the belt is not provided on the roller for stretching the belt, the occurrence of the axial movement of the belt portion 82 and the oblique running of the sheet can be suppressed. Therefore, it is possible to suppress the wear of the end portion of the belt portion 82 by the regulating member.

Embodiment

[0033] Next, the configuration of Embodiment 2 of the present disclosure will be described. In Embodiment 1, the configuration in which the belt conveying unit 80 is connected and supported to the apparatus main body 2 on both axial ends of the driving roller 101 and the driven roller 102 has been described. In the present embodiment, the configuration in which the belt conveying unit 80 is connected and supported to the apparatus main body 2 at the upstream end and the downstream end in the sheet conveyance direction will be described. In the description of the present embodiment, the same components as those in Embodiment 1 are denoted by the same reference numerals, and redundant descriptions are omitted. Further, since the schematic configuration of the printer 1 of Embodiment 2 is the same as that in FIG. 1, the description thereof is omitted.

[0034] With reference to FIGS. 9 to 12, the connection structure between the apparatus main body 2 and the belt conveyance unit 80 in this embodiment will be described. FIG. 9 is a view showing the belt conveyance unit 80 when viewed from the upstream side in the conveyance direction of the sheet. FIG. 10 is a view showing the apparatus main body 2 and the belt conveyance unit 80 when viewed from the downstream side in the conveyance direction of the sheet. FIG. 11 is a view showing the connection structure between the apparatus main body 2 and the belt conveyance unit 80 when viewed from the upstream side in the conveyance direction of the sheet. FIG. 12 is a view showing the connection structure between the apparatus main body 2 and the belt conveyance unit 80 when viewed from the downstream side in the conveyance direction of the sheet. The belt conveyance unit 80 is connected and supported to the apparatus main body 2 by an upstream side support member 230, which is a plate-like member provided on the upstream side in the conveyance direction of the sheet in the apparatus main body 2, and a downstream side support member 240 provided on the downstream side in the conveyance direction of the sheet in the apparatus main body 2. Specifically, at the other end of the bottom plate 813, that is, the upstream end of the bottom plate 813 with respect to the conveyance direction of the sheet, the upstream side support member 230 is fixed to the bottom plate 813 by a fastening member 213 such as a screw. The upstream side support member 230 is disposed on the other end side in the conveyance direction of the sheet, that is, on the upstream side in the conveyance direction of the sheet with respect to the belt conveyance unit 80. The position where the bottom plate 813 and the upstream side support member 230 are fixed by the fastening member 213 and the self-weight of the belt conveyance unit 80 acts is shown as position P3 in FIG. 11. The plate member in this embodiment is the upstream side support member 230. Further, the third connection portion in this embodiment is constituted by the fastening member 213 and the upstream side support member 230 fixed to the bottom plate 813 by the fastening member 213.

[0035] Also, on the downstream side in the sheet conveyance direction in the apparatus main body 2, there are provided shaft members 815 and 816 fixed to the bottom plate 813 by caulking or the like, and fitting portions 241 and 242 provided on the downstream side support member 240 and capable of fitting with the shaft members 815 and 816, respectively. The fitting portions 241 and 242 are respectively arranged on one end side in the sheet conveyance direction, that is, on the downstream side in the sheet conveyance direction with respect to the belt conveyance unit 80. Then, by fitting the shaft members 815 and 816 with the fitting portions 241 and 242, respectively, the belt conveyance unit 80 is connected and supported to the apparatus main body 2 at one end portion of the bottom plate 813, that is, at the downstream end of the bottom plate 813 in the sheet conveyance direction. The position where the weight of the belt conveyance unit 80 acts when the shaft member 815 and the fitting portion 241 are fitted is shown as position P4 in FIG. 12. Also, the position where the weight of the belt conveyance unit 80 acts when the shaft member 816 and the fitting portion 242 are fitted 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 concave portion is the fitting portion 241, and the second concave portion is the fitting portion 242. Further, the first connecting portion of this embodiment is constituted by the shaft member 815 and the fitting portion 241 fitted to the shaft member 815, and the second connecting portion is constituted by the shaft member 816 and the fitting portion 242 fitted to the shaft member 816. With such a configuration, the center of gravity of the belt conveyance unit 80 is arranged in a region formed by connecting the three points of positions P3, P4, and P5 in the vertical direction.

[0036] When attaching the belt conveyance unit 80 to the apparatus main body 2, first, in the apparatus main body 2, the shaft members 815 and 816 are respectively fitted into the fitting parts 241 and 242 disposed on the downstream side in the conveyance direction of the sheet, that is, in front of the fixing unit 60. Next, the upstream side support member 230 provided on the upstream side in the sheet conveyance direction in the apparatus main body 2 is fixed to the bottom plate 813 using the fastening member 213. When the upstream side support member 230 is fixed to the bottom plate 813 by the fastening member 211, the shaft member 815 fitted into the fitting part 241 and the shaft member 816 fitted into the fitting part 242 become immovable in the fitting direction. In this embodiment, the belt conveyance unit 80 is connected and supported to the apparatus main body 2 in this manner. When removing the belt conveyance unit 80 from the apparatus main body 2, the reverse procedure is performed.

[0037] Note that the downstream side support member 240 is provided with a guide part 421 for guiding the shaft member 815 to the entrance of the fitting part 241 and a guide part 422 for guiding the shaft member 816 to the entrance of the fitting part 242. The guide part 421 as the first guide part of this embodiment forms a first guide path 241A that becomes narrower from above in the vertical direction downward. Further, the guide part 422 as the second guide part of this embodiment forms a second guide path 242A that becomes narrower from above in the vertical direction downward. 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 path 241A and the second guide path 242A are inserted into the fitting parts 241 and 242. With such a configuration, it becomes possible to move the belt conveyance unit 80 downward from above in the vertical direction with respect to the downstream side support member 240 and easily fit the shaft members 815 and 816 to the fitting parts 241 and 242.

[0038] Further, 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. Thus, in this embodiment, by simply performing the tightening and loosening operation of the fastening member 213, the belt conveyance unit 80 can be attached to and detached from the apparatus main body 2, so that the work efficiency during maintenance work can be improved. Note that the shaft members 815 and 816 may have a shape other than the cylindrical shape shown in FIG. 10. That is, any concave and convex shape in which the shaft members 815 and 816 and the fitted portions 241 and 242 can be fitted to each other may be used. Also, 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) on the downstream side in the sheet conveyance direction. With such a configuration, the inclination of the conveyance 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 counter roller 63 of the fixing unit 60.

[0039] Also, in this embodiment as well, similar to the first embodiment, since the frame 81 is arranged in the direction along the plane formed by the three points of positions P3, P4, and P5, the alignment deviation 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 running of the sheet are less likely to occur (see FIGS. 7(A, B) and 8(A, B)). Further, also in this embodiment, even if a regulating member having a tapered shape for regulating the movement of the belt is not provided on the roller around which the belt is stretched, the occurrence of the axial movement of the belt portion 82 and the skew running of the sheet can be suppressed. Therefore, it is possible to suppress the wear of the end portion of the belt portion 82 due to the regulating member.

[0040] <Other Embodiments> 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 main body 2 that 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 back side of the apparatus main body 2. In this case, the fitting portions 221 and 222, and the shaft members 815 and 816 are arranged on the side of the door 2A of the apparatus main body 2. Also, in the second embodiment, the upstream support member 230 may be fixed to the bottom plate 813 with a fastening member 213 such as a screw at the downstream end of the sheet conveyance direction of the bottom plate 813. In this case, the fitting portions 241 and 242, and the shaft members 815 and 816 are arranged on the upstream side of the sheet conveyance direction of the bottom plate 813.

[0041] Also, in FIG. 1, the printer 1 including the electrophotographic image forming unit 30 has been described as an example. In addition to this, for example, the configuration of this embodiment can also be applied to a belt conveyance unit mounted on an image forming apparatus that forms an image on a sheet with a colorant that is cured by ultraviolet rays or the like. Also, in the first and second embodiments, the description has been made assuming that the center of gravity of the belt conveyance unit 80 is in the region connecting the positions P3, P4, and P5 in the vertical direction. However, if it is possible to stably connect the belt conveyance unit 80 to the apparatus main body 2, the center of gravity of the belt conveyance unit 80 does not have to be included in the region connecting the positions P3, P4, and P5 in the vertical direction.

Description of Reference Numerals

[0042] 1 Printer (Image Forming Apparatus) / 2 Apparatus Main Body / 2A Door / 30 Image Forming Unit (Image Forming Means) / 60 Fixing Unit (Fixing Means) / 80 Belt Conveying Unit / 80A Conveying Surface / 81 Frame (Support Structure) / 82 Belt Portion / 101 Driving 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 Side Support Member (Second Plate Member) / 211, 213 Fastening Member / 220 Rear Side Support Member / 221 Fitted Portion (First Concave Portion) / 221A First Guide Path / 222 Fitted Portion (Second Concave Portion) / 222A Second Guide Path / 230 Upstream Side Support Member (Plate Member) / 241 Fitted Portion (First Concave Portion) / 241A First Guide Path / 242 Fitted Portion (Second Concave Portion) / 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 Fixed 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 attachable to the device main body, wherein the belt conveying unit includes a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched by the plurality of rollers, the frame includes a first convex portion and a second convex portion disposed on the back side, and a fixing portion disposed on the front side, the device main body includes a back side support member including a first fitting portion into which the first convex portion fits and a second fitting portion into which the second convex portion fits, and a front side support member supporting the front side of the belt conveying unit, the belt conveying unit is supported at two locations on the back side by the fitting of the first convex portion and the first fitting portion and the fitting of the second convex portion and the second fitting portion, and is supported at one location on the front side by fixing the fixing portion and the front side support member with a fastening member, A sheet conveying device characterized by the above.

2. The device main body includes a door configured to be openable and closable on the front side of the device main body. The sheet conveying device according to claim 1, characterized by the above.

3. The back side support member has a guide path for guiding the first convex portion to the first fitting portion, and the guide path narrows from the upper side to the lower side in the vertical direction. The sheet conveying device according to claim 1 or 2, characterized by the above.

4. By fixing the fixing portion and the front side support member with the fastening member, the first convex portion and the second convex portion become immovable in the fitting direction. The sheet conveying device according to any one of claims 1 to 3, characterized by the above.

5. The fixing portion is disposed between the first convex portion and the second convex portion in the sheet conveying direction. The sheet conveying device according to any one of claims 1 to 4, characterized by the above.

6. The device main body has a transfer portion for transferring an image to a sheet, and a fixing portion for fixing the image transferred to the sheet by the transfer portion. The belt conveying unit is disposed between the transfer portion and the fixing portion in the sheet conveying direction. The sheet conveying device according to any one of claims 1 to 5, characterized by the above.

7. The belt conveying unit has a plurality of the endless belts. The sheet conveying device according to any one of claims 1 to 6, characterized by the above.

8. A sheet conveying device having a device main body and a belt conveying unit attachable to the device main body, wherein the belt conveying unit includes a plurality of rollers, a frame supporting the plurality of rollers, and an endless belt rotatably stretched by the plurality of rollers, the frame includes a first convex portion and a second convex portion disposed on one side in the sheet conveying direction and a fixing portion disposed on the other side, the device main body, one support member including a first fitting portion into which the first convex portion fits and a second fitting portion into which the second convex portion fits, and the other support member that supports the other side of the belt conveying unit, wherein one side of the belt conveying unit is supported at two locations by fitting of the first convex portion and the first fitting portion and fitting of the second convex portion and the second fitting portion, and the other side is supported at one location by fixing of the fixing portion and the other support member by a fastening member, characterized in that it is a sheet conveying device.

9. Image forming means for forming an image on a sheet, and the sheet conveying device according to any one of claims 1 to 8, characterized in that it is an image forming apparatus.

10. Fixing means for fixing a toner image on a sheet, and the sheet conveying device conveys the sheet from the image forming means toward the fixing means, characterized in that it is the image forming apparatus according to claim 9.

Images