Sheet conveying device and image forming apparatus

Abstract

To provide a sheet conveying device capable of miniaturizing the device and reducing the cost of the device.SOLUTION: A pressurizing mechanism 80, which is a pressing mechanism for pressing a driven roller 17b so that the contact pressure with a drive roller 17a becomes a predetermined contact pressure, is provided in a conveyance guide 90 as a guide member. The conveyance guide 90 is rotatably supported by a support shaft 42 supporting the driven roller 17b, and the center of rotation of the conveyance guide 90 is positioned coaxially with the center of rotation of the driven roller 17b. The conveying guide 90 slides in a direction orthogonal to the pressing direction of the driven roller 17b of the pressurizing mechanism 80 during rotation, and moves the driven roller 17b relatively to the driving roller 17a in a direction orthogonal to the pressing direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a sheet conveyance device and an image forming apparatus.

Background Art

[0002] Conventionally, there is known a sheet conveyance device including a driving roller that rotates drivenly, a driven roller that rotates following the driving roller, a guide member that is rotatable between a guide position for guiding a sheet that moves along a sheet conveyance path and an open position for opening the sheet conveyance path, and a pressing mechanism that presses the driven roller so that the contact pressure with the driving roller becomes a predetermined contact pressure, and conveying the sheet by the driving roller and the driven roller.

[0003] Patent Document 1 describes, as the above sheet conveyance device, a device that locks a guide member holding a driven roller at a guide position by a locking mechanism. By locking the guide member at the guide position by the locking mechanism, the driven roller contacts the driving roller with a predetermined pressing force. When the locking mechanism is released and the guide member is rotated from the guide position to the open position, the driven roller held by the guide member separates from the driving roller.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the configuration described in Patent Document 1 has problems of a large number of components, enlargement, and high cost.

Means for Solving the Problems

[0005] In order to solve the above-described problems, the present invention provides a sheet conveying apparatus that conveys a sheet by a driving roller that rotates and drives, a driven roller that rotates in accordance with the driving roller, a guide member that is rotatable between a guide position that guides a sheet moving along a sheet conveyance path and an open position that opens the sheet conveyance path, and a pressing mechanism that presses the driven roller so that a contact pressure with the driving roller becomes a predetermined contact pressure. In the sheet conveying apparatus, the pressing mechanism is provided on the guide member, a rotation center of the guide member is positioned coaxially with a rotation center of the driven roller, the driven roller interlocks with rotation of the guide member, and the driven roller relatively moves with respect to the driving roller in a direction orthogonal to a pressing direction of the driven roller by the pressing mechanism.

Advantages of the Invention

[0006] According to the present invention, it is possible to reduce the size and cost of the apparatus.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

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Figure 11

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Best Mode for Carrying Out the Invention

[0008] Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. Note that those skilled in the art can easily make changes and modifications to the present invention within the scope of the claims to form other embodiments, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode in this invention and does not limit the scope of the claims.

[0009] Hereinafter, as an image forming apparatus to which the present invention is applied, an electrophotographic printer (hereinafter simply referred to as a printer) that forms an image by an electrophotographic method will be described. FIG. 1 is a schematic configuration diagram showing a printer according to an embodiment. The printer shown in Fig. 1 is a monochrome printer. A process cartridge 1 as a detachable unit is detachably mounted on the apparatus main body 100. The process cartridge 1 includes a photosensitive drum 2 as an image carrier that carries an image on its surface, and a charging roller 3 as charging means for charging the surface of the photosensitive drum 2. Further, the process cartridge includes a developing device 4 as developing means for visualizing a latent image on the photosensitive drum 2, a cleaning blade 5 as cleaning means for cleaning the surface of the photosensitive drum 2, and the like. Also, an LED head array 6 as exposure means for exposing the surface is disposed around the photosensitive drum 2.

[0010] In addition, a toner cartridge 22 as a developer container is detachably provided in the process cartridge 1. The toner cartridge 22 has a developer storage portion 8 that stores toner, which is a developer to be supplied to the developing device 4. Further, the toner cartridge 22 of the present embodiment also integrally has a developer recovery portion 9 that recovers toner (waste toner) removed by the cleaning blade 5.

[0011] The printer also includes a transfer unit 10 that transfers an image to a sheet as a transfer material, a paper feeding device 11 that feeds the sheet, and a sheet conveying device 40 that conveys the sheet. The printer also includes a fixing device 12 that fixes the image transferred to the sheet, and a paper discharging device 13 that discharges the sheet outside the apparatus.

[0012] The transfer unit 10 includes a transfer roller 14 as a transfer member rotatably supported by a transfer frame 30. The transfer roller 14 is in contact with the photosensitive drum 2 in a state where the process cartridge 1 is mounted on the apparatus main body 100, and a transfer nip is formed at the contact portion between the two. Also, the transfer roller 14 is connected to a power source, and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied thereto.

[0013] The sheet feeding device 11 includes a sheet feeding cassette 15 that houses the sheet P, and a sheet feeding roller 16 that feeds the sheet P housed in the sheet feeding cassette 15. Further, on the downstream side in the sheet conveyance direction with respect to the sheet feeding roller 16, a pair of registration roller pairs 17 as timing rollers that measure the conveyance timing and convey the sheet to the secondary transfer nip are provided. Note that examples of the sheet P include thick paper, postcards, envelopes, plain paper, thin paper, coated paper (such as coated paper and art paper), tracing paper, OHP sheets, OHP films, and the like.

[0014] The fixing device 12 includes a fixing roller 18 and a pressure roller 19. The fixing roller 18 is heated by an infrared heater installed inside the fixing roller. The pressure roller 19 is pressed toward the fixing roller 18 and contacts the fixing roller 18, and a fixing nip is formed at the contact portion.

[0015] The sheet discharging device 13 includes a pair of sheet discharging rollers 20. The sheet discharged to the outside of the device by the sheet discharging rollers 20 is loaded onto a sheet discharging tray 21 formed by denting the upper surface of the device main body 100.

[0016] Next, with reference to FIG. 1, the basic operation of the printer according to the present embodiment will be described. When the image forming operation is started, the photoreceptor 2 of the process cartridge 1 is rotationally driven clockwise in FIG. 1, and the surface of the photoreceptor 2 is uniformly charged to a predetermined polarity by the charging roller 3. Based on the image information input from an external device, light is irradiated from the LED head array 6 onto the charged surface of the photoreceptor 2, and an electrostatic latent image is formed on the surface of the photoreceptor 2.

[0017] By supplying toner to the electrostatic latent image thus formed on the photoreceptor 2 by the developing device 4, the electrostatic latent image is visualized as a toner image (visible image).

[0018] When the image forming operation is started, the transfer roller 14 is rotationally driven, and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the transfer roller 14, thereby forming a transfer electric field between the transfer roller 14 and the photoreceptor 2.

[0019] At the lower part of the apparatus main body 100, the paper feed roller 16 starts rotational drive, and the sheet P is fed out from the paper feed cassette 15. The fed-out sheet P is temporarily stopped by the registration roller pair 17 of the sheet conveyance device 40.

[0020] Thereafter, the rotational drive of the registration roller pair 17 is started at a predetermined timing, and the sheet P is conveyed to the transfer nip in accordance with the timing when the toner image on the photoreceptor reaches the transfer nip. Then, by the transfer electric field, the toner image on the photoreceptor 2 is collectively transferred onto the sheet P serving as the transfer body. Also, the residual toner on the photoreceptor that could not be completely transferred to the sheet P is removed by the cleaning blade 5, and the removed toner is conveyed to and recovered by the developer recovery unit 9.

[0021] Thereafter, the sheet P onto which the toner image has been transferred is conveyed to the fixing device 12, and the toner image on the sheet P is fixed to the sheet P in the fixing device 12. Then, the sheet P is discharged outside the apparatus by a pair of paper discharge rollers 20 and stocked on the paper discharge tray 21.

[0022] FIG. 2 is a diagram showing a state in which the process cartridge 1 is taken out from the main body of the image forming apparatus. As shown in FIG. 2, an openable and closable cover 37 is provided on the side surface (right side surface in the figure) of the apparatus main body 100. By opening this cover 37, the process cartridge 1 is taken out from the apparatus main body through the opened opening.

[0023] Specifically, the cover 37 is opened, and the LED head array 6 is retracted to the retracted position shown by the solid line in the figure by the link mechanism. Thereby, it becomes possible to take out the process cartridge 1 from the apparatus main body while avoiding interference with the LED head array 6.

[0024] When the process cartridge 1 is removed from the apparatus main body, the conveyance guide 90, which is a guide member located in front of the resist roller pair 17, becomes rotatable. By moving the conveyance guide 90 from the guide position shown by the dashed line in FIG. 2 to the open position shown by the solid line, the sheet conveyance path is opened, and it becomes possible to remove jammed paper.

[0025] FIG. 3 is a perspective view showing the periphery of the resist roller pair 17 of the sheet conveyance device 40, and FIG. 4 is a top view looking down on the periphery of the resist roller pair 17. The resist roller pair 17 includes three drive rollers 17a provided at a predetermined interval in the axial direction, and three driven rollers 17b provided corresponding to each drive roller 17a. The three drive rollers 17a are attached to the drive shaft 41 so as to rotate integrally with the drive shaft 41.

[0026] On the other hand, the three driven rollers 17b are supported so as to be relatively rotatable with respect to the support shaft 42, and each driven roller 17b is pressed toward the drive roller 17a side by a pressurizing mechanism 80 which is a pressing mechanism. The three pressurizing mechanisms 80 provided corresponding to each driven roller 17b include a holder 82 and a pressurizing spring 81 which is a biasing means.

[0027] The drive shaft 41 is rotatably supported by a main body side plate 110 which is a main body structure via a bearing 43, and the support shaft 42 is fixedly provided to the main body side plate 110 so as not to rotate. A conveyance guide 90 is rotatably supported on the support shaft 42 via a bearing 93, and the conveyance guide 90 and the driven roller 17b are supported by the support shaft 42.

[0028] A drive gear 62 that meshes with a motor gear 61a of a conveyance motor 61 which is a drive source is attached to one end of the drive shaft 41 so as to rotate integrally with the drive shaft 41. Thereby, each drive roller 17a is rotationally driven by the driving force of the conveyance motor 61.

[0029] FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4. Support protrusions 82a are provided on both axial sides of the holder 82 of the pressing mechanism 80, and each support protrusion 82a is rotatably supported by a holder support hole 92 provided in the conveying guide 90. Further, the holder 82 has a pressing portion 82b that presses the flange portions 71 provided at both ends of the driven roller 17b. The pressing portion 82b is a semi-circular groove, into which the flange portion 71 is fitted to position the driven roller 17b in a direction (Y direction) orthogonal to the pressing direction (Z direction).

[0030] The pressing spring 81 is a coil spring, and one end of the pressing spring 81 is engaged with an engagement boss provided on the spring receiving portion 96 of the conveying guide 90. The pressing spring 81 is attached in a compressed state between the conveying guide 90 and the holder 82, and biases the central portion of the holder 82 in the direction of arrow F1 in FIG. 5. By this pressing spring 81, the holder 82 is biased to rotate counterclockwise in FIG. 5 with the support protrusion 82a as a fulcrum. As a result, the flange portion 71 of the driven roller 17b is pressed in the direction shown by arrow F2 in the figure by the pressing portion 82b of the holder 82. As a result, the driven roller 17b abuts against the driving roller 17a with a predetermined pressing force (contact pressure), a conveying nip is formed, and the driven roller 17b rotates well in synchronization with the driving roller 17a.

[0031] Further, by biasing the center of the holder 82 with the pressing spring 81, the flange portions 71 provided on both axial sides of the driven roller 17b can be evenly pressed, and the pressure distribution generated between the driving roller 17a and the driven roller 17b can be made uniform in the X direction. Thereby, skewing of the sheet and generation of wrinkles can be suppressed.

[0032] Conventionally, the fulcrum of the rotation of the conveyance guide 90 is at a position different from the center of the rotation axis of the driven roller 17b in the sheet conveyance direction (Y direction). In this case, the conveyance guide 90 rotates due to the reaction force of the drive roller 17a, and the driven roller 17b cannot be brought into contact with the drive roller 17a with a predetermined pressing force. Therefore, conventionally, the conveyance guide 90 is locked by a locking mechanism at the guide position so that the conveyance guide 90 does not rotate due to the reaction force of the drive roller 17a. In this way, conventionally, a locking mechanism is required, which increases the number of parts and leads to an increase in the size of the apparatus and an increase in the cost of the apparatus. Further, when rotating the conveyance guide 90 from the guide position to the open position for opening the sheet conveyance path, it is necessary to operate the locking mechanism to release the lock of the conveyance guide, which complicates the jam processing work.

[0033] In the present embodiment, the conveyance guide 90 is rotatably supported on the support shaft 42 on which the driven roller 17b is supported, and the rotation center of the conveyance guide 90 is made coaxial with the rotation center of the driven roller 17b. Thereby, the conveyance guide 90 does not rotate due to the reaction force of the drive roller 17a, and the pressing force (contact pressure) of the driven roller 17b against the drive roller 17a does not decrease. Therefore, even if the conveyance guide 90 is not locked at the guide position by the locking mechanism so as not to rotate, it does not occur that the sheet cannot be conveyed satisfactorily due to a decrease in the pressing force. Thereby, the locking mechanism can be made unnecessary, the number of parts can be reduced, and the size of the apparatus and the cost reduction of the apparatus can be achieved.

[0034] In the present embodiment, the reaction force of the drive roller 17a is received by the spring receiving portion 96 of the conveyance guide 90 via the pressing mechanism 80. In the present embodiment, the pressing mechanism 80 rotatably supports the holder 82 on the conveyance guide 90, and the biasing direction F1 of the pressing spring 81 is set to a direction orthogonal to the pressing direction F2. Thereby, the reaction force of the drive roller 17a received by the spring receiving portion 96 becomes a direction substantially orthogonal to the rotation direction. Thereby, it is possible to suppress the conveyance guide 90 from rotating from the guide position due to the reaction force of the drive roller 17a. Also, by setting the biasing direction of the compression spring 81 to a direction orthogonal to the pressing direction, it is possible to suppress the enlargement of the apparatus in the pressing direction (Z direction).

[0035] The force that rotates the conveyance guide 90 against the reaction force of the drive roller 17a is a vector component in a direction orthogonal to the line segment connecting the rotation center of the conveyance guide 90 and the contact portion between the compression spring 81 of the spring receiving portion 96. In the present embodiment, the fulcrum of the rotation of the conveyance guide 90 is on the driven roller side rather than the spring receiving portion 96 that receives the reaction force from the drive roller 17a. Further, the contact portion between the compression spring 81 of the spring receiving portion 96 that receives the reaction force from the drive roller is located above the conveyance guide 90 in the vertical direction (Z direction). Thereby, the force that rotates the conveyance guide 90 against the reaction force of the drive roller 17a (the vector component in the direction orthogonal to the line segment connecting the rotation center of the conveyance guide and the contact portion between the compression spring 81 of the spring receiving portion 96) becomes the direction to rotate the conveyance guide to the guide position. As a result, the reaction force of the drive roller 17a becomes a force that keeps the conveyance guide 90 at the guide position, and the conveyance guide can be favorably positioned at the guide position without a locking mechanism.

[0036] FIG. 6 is a cross-sectional view taken along line B-B of FIG. 4. As shown in FIG. 6, cam portions 91 that contact bearings 43, which are cam contact portions that receive the drive shaft 41, are provided at both axial ends of the conveyance guide 90 in accordance with the rotation of the conveyance guide 90 from the guide position to the open position where the sheet conveyance path is opened. Further, a fitting hole portion 98, which is a support hole for fitting a bearing 93 that receives a support shaft 42, which is a support portion of the conveyance guide 90, is a long hole that is long in the sheet conveyance direction (Y direction). Thereby, the conveyance guide 90 can slide in a direction orthogonal to the driven roller pressing direction of the pressing mechanism (which is also the sheet conveyance direction (Y direction)) within a predetermined range with respect to the support shaft 42.

[0037] On both side surfaces in the axial direction of the conveyance guide 90, positioning protrusions 95 are provided. When the conveyance guide 90 is positioned at the guide position, the positioning protrusions 95 are engaged with positioning grooves 111 provided on the main body side plate 110. Thereby, the conveyance guide 90 is positioned in the direction orthogonal to the pressing direction of the driven roller of the pressing mechanism (which is also the sheet conveyance direction (Y direction)) at the guide position. Therefore, when the sheet is being conveyed, it is possible to suppress the conveyance guide 90 from sliding in the direction orthogonal to the pressing direction (sheet conveyance direction (Y direction)), and thus the sheet can be conveyed smoothly.

[0038] FIG. 7 is a schematic view showing the periphery of the conveyance guide 90 of the image forming apparatus. As shown in FIG. 7, a pressing portion 9a for suppressing the rotation of the conveyance guide 90 is provided in the developer recovery portion 9. The sheet fed from the paper feeding device 11 has its conveyance direction changed from a substantially vertical direction to a substantially horizontal direction by the conveyance guide 90. Therefore, the tip of the sheet conveyed in the substantially vertical direction hits the side opposite to the fulcrum side of the rotation of the conveyance guide 90. In the present embodiment, since the conveyance guide 90 is pressed by the pressing portion 9a of the developer recovery portion 9, even if the tip of the sheet hits the conveyance guide 90 in the direction of rotating the conveyance guide 90, the conveyance guide 90 will not rotate, and the sheet can be guided smoothly.

[0039] In addition, when the rotation of the conveyance guide 90 when the tip of the sheet hits the conveyance guide 90 can be well suppressed by the reaction force of the drive roller 17a acting as a force to keep the conveyance guide 90 at the guide position, the pressing portion 9a of the developer recovery portion 9 is unnecessary. Also, as described above, even if the conveyance guide 90 rotates slightly, the pressing force of the driven roller 17b against the drive roller 17a does not fluctuate, and the sheet can be conveyed smoothly. Therefore, when the sheet can be conveyed smoothly to the nip portion of the resist roller pair 17 even if the conveyance guide 90 rotates slightly, the pressing portion 9a of the developer recovery portion 9 is unnecessary.

[0040] FIG. 8 is a perspective view showing a state in which the transport guide 90 is in an open position where the sheet transport path is opened, FIG. 9 is a cross-sectional view taken along line C-C of FIG. 8, and FIG. 10 is a cross-sectional view taken along line D-D of FIG. 8. When the process cartridge 1 is removed from the apparatus main body and the transport guide 90 is rotated from the guide position to the open position, the positioning projection 95 disengages from the positioning groove 111. As a result, the transport guide 90 can slide in a direction orthogonal to the pressing direction F3 in which the pressing portion 82b of the holder 82 presses the driven roller 17b. Further, when the transport guide 90 is rotated, the cam portion 91 of the transport guide 90 abuts against the bearing 43 that receives the drive shaft 41. Then, the transport guide 90 is pushed in by the bearing 43, and the transport guide 90 slides in a direction orthogonal to the pressing direction F3 (see arrow E in FIG. 10).

[0041] As shown in FIG. 9, since the pressing mechanism 80 is provided on the transport guide 90, the posture of the pressing mechanism 80 changes as the transport guide 90 rotates, and the pressing direction for pressing the driven roller 17b of the holder 82 changes. Specifically, the pressing direction when the transport guide 90 is in the guide position is vertically downward (a direction orthogonal to the sheet transport direction), but as the guide member rotates, as shown in FIG. 9, the pressing direction tilts with respect to the vertical direction. As a result, the direction orthogonal to the pressing direction F3 becomes a direction inclined with respect to the sheet transport direction (Y direction). Thus, the transport guide 90, which is pressed in by the bearing 43 when the cam portion 91 abuts against the bearing 43 that receives the drive shaft 41, slides obliquely upward. Due to the sliding of the transport guide 90, the holder 82 rotatably supported by the transport guide 90 slides in a direction orthogonal to the pressing direction F3 (obliquely upward) together with the transport guide 90. Therefore, the driven roller 17b positioned in a direction orthogonal to the pressing direction F3 by the pressing portion 82b of the holder 82 moves obliquely upward together with the transport guide 90. As a result, as shown in FIGS. 8 and 9, the driven roller 17b moves away from the drive roller 17a, and the sheet sandwiched between the resist roller pair 17 can be easily removed.

[0042] Thus, in this embodiment, as the conveyance guide 90 rotates to the open position, the driven roller 17b can be separated from the driving roller 17a. The jam processing operation in the configuration having the lock mechanism is as follows. That is, after removing the process cartridge 1 from the apparatus main body, the lock mechanism is operated to release the lock of the conveyance guide 90, and the conveyance guide 90 is rotated to the open position to separate the driven roller 17b from the driving roller 17a. On the other hand, in this embodiment, when the process cartridge 1 is removed from the apparatus main body, the conveyance guide is rotated to the open position to separate the driven roller from the driving roller. Thus, in this embodiment, the operation of operating the lock mechanism to release the lock of the conveyance guide is eliminated, and the jam processing operation can be simplified.

[0043] Further, when the driven roller 17b is separated from the driving roller 17a, as shown in FIG. 9, the driven roller 17b is a regulating portion, and by abutting against the support shaft 42 which is a through shaft, the rotation by the urging force of the pressing spring 81 of the holder 82 is regulated. By regulating the rotation of the holder 82 with the support shaft 42, when the conveyance guide 90 rotates from the open position to the guide position as described later, the driven roller 17b can be brought into contact with the driving roller 17a.

[0044] Note that, in the above description, the cam portion 91 abuts against the bearing 43 attached to the main body side plate 110 which is the main body structure, but a cam abutting portion that abuts against the cam portion 91 may be provided on the main body side plate 110.

[0045] When moving the conveyance guide 90 from the open position to the guide position, after the cam portion 91 separates from the bearing 43, the positioning projection 95 fits into the positioning groove 111. The groove width on the opening side of the positioning groove 111 is wider than the diameter of the positioning projection 95, and the positioning projection 95 can easily enter the positioning groove 111. When the positioning projection 95 enters the positioning groove 111, the conveyance guide 90 slides in a direction opposite to the direction of arrow E in FIG. 10 by the positioning groove 111.

[0046] In this embodiment, as described above, since the rotation of the holder 82 is restricted by the support shaft 42, the driven roller 17b can be brought into contact with the drive roller 17a by the reverse slide of the conveyance guide 90. Even after the driven roller 17b comes into contact with the drive roller 17a, the conveyance guide 90 slides in the reverse direction by the positioning groove 111. Then, against the biasing force of the compression spring 81, the driven roller 17b climbs up the outer peripheral surface of the drive roller 17a while the holder 82 rotates. When the positioning projection 95 abuts against the bottom of the positioning groove 111, the driven roller 17b abuts against the top of the drive roller 17a and abuts against the drive roller 17a with a desired pressing force (contact pressure). Also, the conveyance guide 90 is positioned in the sheet conveyance direction (a direction orthogonal to the pressing direction).

[0047] Next, a modification of this embodiment will be described.

[0048] [Modification 1] FIG. 11 is a perspective view of the sheet conveyance device 40A of Modification 1, and FIG. 12 is a plan view of the sheet conveyance device 40A of Modification 1. Further, FIG. 13(a) is a cross-sectional view taken along the line F-F of FIG. 12 in a state where the conveyance guide 90 is located at the guide position, and FIG. 13(b) is a cross-sectional view taken along the line F-F of FIG. 12 in a state where the conveyance guide 90 is located at the open position.

[0049] As shown in FIGS. 11 to 13, the sheet conveyance device 40A of this Modification 1 is provided with a positioning projection 112 on the main body side plate 110 and a positioning groove 97 on the conveyance guide 90. As shown in FIG. 13(a), when the conveyance guide 90 is located at the guide position, the positioning groove 97 of the conveyance guide 90 is engaged with the positioning projection 112 of the main body side plate 110. Thereby, the conveyance guide 90 is positioned in the sheet conveyance direction (a direction orthogonal to the direction in which the driven roller of the holder 82 is pressed, and also a direction orthogonal to the direction in which the driven roller presses the drive roller).

[0050] When the conveyance guide 90 is rotated from the guide position to the open position, the engagement between the positioning groove 97 of the conveyance guide 90 and the positioning projection 112 of the main body side plate 110 is disengaged, and the conveyance guide 90 becomes slidable. Then, in the same manner as described above, the conveyance guide 90 is slid by the cam portion 91, and the driven roller 17b is separated from the drive roller 17a.

[0051] Also in this Modification 1, the groove width on the opening side of the positioning groove 97 of the conveyance guide 90 is larger than the diameter of the positioning projection 112. Therefore, also in this Modification 1, when the conveyance guide 90 is rotated from the open position to the guide position, the positioning projection 112 of the main body side plate 110 can be easily inserted into the positioning groove 97.

[0052] [Modification 2] FIG. 14 is a perspective view of the sheet conveyance device 40B of Modification 2, and FIG. 15 is a plan view of the sheet conveyance device 40B of Modification 2. Further, FIG. 16 is a cross-sectional view taken along line G-G of FIG. 15 in a state where the conveyance guide 90 is located at the open position.

[0053] The sheet conveyance device 40B of this Modification 2 is provided with a shutter 50 which is a rotating member for correcting the skew of the sheet. Three shutter 50s are arranged alternately in the axial direction with the four driven rollers 17b. The shutter 50 is attached to the shutter shaft 52 so as to rotate integrally with the shutter shaft 52 which is a rotation shaft, and the driven roller 17b is supported by the shutter shaft 52 with a predetermined gap. Further, the conveyance guide 90 is rotatably supported by the shutter shaft 52 via a bearing 93. The shutter shaft 52 is rotatably supported by the main body side plate 110. The shutter 50 has contact portions 51 where the leading end of the sheet contacts at three positions in the rotation direction of the shutter 50.

[0054] A rotary cam 53 is attached to the motor-side end of the shutter shaft 52 so as to rotate integrally with the shutter shaft 52. As shown in FIG. 15, a cam follower 54 is in contact with the rotary cam 53, and the cam follower 54 is rotatably supported by an arm member 55. On the upstream side in the sheet conveyance direction of the main body side plate 110 on the motor side, there is an arm holder 113 that rotatably supports the arm member 55. One end of a cam spring 56 that biases the arm member 55 is attached to a surface of the arm holder 113 that is orthogonal to the sheet conveyance direction.

[0055] One of the three contact portions 51 of the shutter 50 is located at a standby position upstream of the conveyance nip of the resist roller pair 17 where the leading edge of the conveyed sheet abuts, in the sheet conveyance direction. At this time, the cam follower 54 is located in the groove portion of the rotary cam 53.

[0056] When the leading edge of the sheet abuts against the contact portion 51 located at the standby position, the leading edge of the sheet is stopped by the biasing force of the cam spring 56, the sheet bends, and the skew of the sheet is corrected. Then, when the sheet bends by a predetermined amount, the stiffness of the sheet becomes greater than the biasing force of the cam spring 56, and the shutter 50 rotates against the biasing force of the cam spring 56. When the shutter 50 rotates, the rotary cam 53 rotates, and while the arm member 55 rotates, the cam follower 54 of the arm member 55 climbs the inclined surface of the rotary cam 53. Then, when the cam follower 54 exceeds the apex of the rotary cam 53, the biasing force of the cam spring 56 switches from a force that hinders the rotation of the rotary cam 53 to a force that rotates the rotary cam 53. As a result, the shutter 50 rotates by the biasing force of the cam spring 56. Then, when the cam follower 54 is located in the groove portion of the rotary cam 53, the rotation of the shutter 50 stops, and the next contact portion 51 of the shutter 50 is located at the standby position.

[0057] Thus, in Modification 2, the shutter 50 is provided, and the skew correction of the sheet is performed by the shutter 50. As a result, it is not necessary to temporarily stop the resist roller pair 17 and abut the leading end of the sheet against the conveyance nip of the resist roller pair 17 for skew correction, and the resist roller pair 17 can be continuously rotated at a constant rotational speed.

[0058] Further, in this Modification 2, the driven roller 17b is supported by the shutter shaft 52. Therefore, as shown in FIG. 16, when the conveyance guide 90 is located at the open position and the driven roller 17b is separated from the driving roller 17a, the shutter shaft 52 restricts the rotation of the holder 82. Thus, similarly to the above, when the conveyance guide 90 rotates from the open position to the guide position, the driven roller 17b can be brought into contact with the driving roller 17a.

[0059] [Modification 3] FIG. 17 is a perspective view of the sheet conveyance device 40C of Modification 3, and FIG. 18 is a plan view of the sheet conveyance device 40C of Modification 3. Further, FIG. 19 is an enlarged view of the portion I circled in FIG. 17. Further, FIG. 20(a) is a cross-sectional view taken along the line H-H of FIG. 18 in a state where the conveyance guide 90 is located at the guide position, and FIG. 20(b) is a cross-sectional view taken along the line H-H of FIG. 18 in a state where the conveyance guide 90 is located at the open position.

[0060] The sheet conveyance device 40C of this Modification 3 eliminates the support shaft 42 and rotatably supports the driven roller 17b on the holder 82. Specifically, the pressing portion 82b of the holder 82 has a hole shape, and the flange portion 71 of the driven roller 17b is rotatably supported by the hole-shaped pressing portion 82b.

[0061] Further, the main body side plate 110 has a support protrusion portion 115 that rotatably supports the conveyance guide 90, and the support protrusion portion 115 is arranged coaxially with the rotation center axis of the driven roller 17b. Thereby, similarly to the embodiment, the fulcrum of the rotation of the conveyance guide 90 is located coaxially with the rotation center axis of the driven roller 17b, and the conveyance guide 90 does not rotate due to the reaction force of the driving roller 17a, and the pressing force of the driven roller 17b against the driving roller 17a does not decrease.

[0062] Further, a restricting portion 99 for restricting the rotation of the holder is provided on the conveyance guide 90. Thus, as shown in FIG. 20(b), when the conveyance guide 90 rotates to the open position and the driven roller 17b moves away from the driving roller 17a, the holder 82 abuts against the restricting portion 99 and its rotation is restricted. Accordingly, also in the third modification, when the conveyance guide 90 rotates to the guide position, the driven roller 17b can be brought into contact with the driving roller 17a.

[0063] As described above, the preferred embodiments of the present invention have been explained. However, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims, unless otherwise particularly limited in the above description.

[0064] In the above description, the present invention is applied to the resist roller pair 17, but the present invention can be applied to a conveyance roller pair for conveying a sheet. Further, in the above description, when the conveyance guide 90 is located at the open position, the driven roller 17b is separated from the driving roller 17a. However, the sliding amount of the conveyance guide by the cam portion 91 may be reduced so that the driven roller 17b is in contact with the driving roller 17a even when the conveyance guide 90 is located at the open position. Even with such a configuration, when the conveyance guide 90 slides during rotation from the guide position to the open position, the driven roller held by the conveyance guide moves in a direction orthogonal to the pressing direction of the driven roller of the holder relative to the driving roller. Accordingly, the contact position of the driven roller with the driving roller is changed to a position below the top of the driving roller. Thereby, the holder rotates, the compression spring extends, and the pressing force of the driven roller against the driving roller is reduced.

[0065] What has been described above is an example, and specific effects are achieved for each of the following aspects. (Aspect 1) A drive roller 17a that rotates for driving, a driven roller 17b that rotates following the drive roller 17a, a guide member such as a conveyance guide 90 that is rotatable between a guide position for guiding a sheet that moves along a sheet conveyance path and an open position for opening the sheet conveyance path, and a pressing mechanism such as a pressing mechanism 80 that presses the driven roller 17b so that the contact pressure between the drive roller 17a and the driven roller 17b becomes a predetermined contact pressure. In a sheet conveyance device that conveys a sheet by the drive roller 17a and the driven roller 17b, the pressing mechanism is provided on the guide member, the rotation center of the guide member is located coaxially with the rotation center of the driven roller 17b, and in conjunction with the rotation of the guide member, the driven roller 17b of the pressing mechanism moves relative to the drive roller 17a in a direction orthogonal to the pressing direction for pressing the driven roller 17b. Conventionally, a lock mechanism is provided so that a guide member such as a conveyance guide 90 does not rotate due to the reaction force of the drive roller 17a received by the driven roller 17b, and the contact pressure between the driven roller 17b and the drive roller 17a does not decrease, and the guide member is locked so as not to rotate at the guide position. Thus, conventionally, a lock mechanism is required, the number of parts increases, and the device becomes larger and more expensive. On the other hand, in aspect 1, the rotation center of the guide member is located coaxially with the rotation center of the driven roller 17b. Thereby, the guide member does not rotate due to the reaction force of the drive roller 17a received by the driven roller 17b, and the contact pressure between the driven roller 17b and the drive roller 17a does not decrease. Therefore, it is not necessary to lock the guide member at the guide position so that the guide member does not rotate with the lock mechanism. As a result, the number of parts can be reduced, and the size of the device can be reduced and the cost can be reduced. In Aspect 1, the driven roller 17b is configured to move relative to the driving roller 17a in a direction orthogonal to the pressing direction of the driven roller 17b by a pressing mechanism such as the pressing mechanism 80 in conjunction with the rotation of the guide member. When the guide member is in the guide position, the pressing direction of the driven roller 17b of the pressing mechanism is a direction orthogonal to the sheet conveyance direction. When the guide member rotates, the posture of the pressing mechanism provided on the guide member changes, and the pressing direction of the pressing mechanism tilts with respect to the pressing direction when the guide member is in the guide position. By configuring the driven roller 17b to move relative to the driving roller 17a in a direction orthogonal to the pressing direction when the guide member rotates, it becomes possible to move the driven roller 17b away from the driving roller 17a or move the driven roller 17b relative to the driving roller 17a in a direction in which the contact pressure between the driven roller 17b and the driving roller 17a is reduced. As a result, similar to the conventional case, as the guide member rotates from the guide position to the open position, the driven roller 17b can be separated from the driving roller 17a or the contact pressure between the driven roller 17b and the driving roller 17a can be reduced. Therefore, the jammed sheet can be easily removed.

[0066] (Aspect 2) In Aspect 1, the pressing portion 82b that presses the driven roller 17b of the pressing mechanism such as the pressing mechanism 80 positions the driven roller 17b in a direction orthogonal to the pressing direction, and the guide member is configured to be slidable within a predetermined range in a direction orthogonal to the pressing direction with respect to a support portion such as the support shaft 42 that rotatably supports the guide member. According to this, as described in the embodiment, when the guide member such as the conveyance guide 90 slides in a direction orthogonal to the pressing direction, the driven roller 17b slides in a direction orthogonal to the pressing direction together with the pressing mechanism provided on the guide member. Therefore, by sliding the guide member such as the conveyance guide 90 in a direction orthogonal to the pressing direction when the guide member rotates, the driven roller 17b can be moved relative to the driving roller 17a in a direction orthogonal to the pressing direction.

[0067] (Aspect 3) In Embodiment 2, the guide member of the conveyance guide 90 has a support hole such as a fitting hole 98 supported by a support portion that is the support shaft 42, and the support hole has an elongated hole shape that is long in a direction orthogonal to the pressing direction. According to this, as described in the embodiment, the guide member such as the conveyance guide 90 can be slid within a predetermined range in a direction orthogonal to the pressing direction with respect to the support portion such as the support shaft 42.

[0068] (Embodiment 4) In Embodiment 2 or 3, when the guide member such as the conveyance guide 90 is located at the guide position, it has positioning means (constituted by a positioning projection 95 and a positioning groove 111 in this embodiment) for positioning the guide member so that it cannot slide. According to this, as described in the embodiment, it is possible to prevent the guide member such as the conveyance guide 90 from sliding during sheet conveyance and reducing the contact pressure between the driven roller 17b and the driving roller 17a.

[0069] (Embodiment 5) In any one of Embodiments 2 to 4, when the guide member such as the conveyance guide 90 rotates, it has sliding means such as a cam portion 91 for sliding the guide member with respect to the support portion such as the support shaft 42. According to this, as described in the embodiment, in conjunction with the rotation of the guide member such as the conveyance guide 90, the driven roller 17b can be moved relative to the driving roller 17a in a direction orthogonal to the pressing direction.

[0070] (Embodiment 6) In Embodiment 5, the sliding means is a cam portion 91 provided on the guide member such as the conveyance guide 90. When the guide member is located at the guide position, the cam portion 91 is separated from a cam contact portion such as a bearing 43 with which the cam portion 91 of the main body structure such as the main body side plate 110 contacts, and when the guide member rotates, the cam portion 91 contacts the cam contact portion to slide the guide member with respect to the support portion such as the support shaft 42. According to this, as described in the embodiment, in conjunction with the rotation of a guide member such as the conveyance guide 90, the driven roller 17b can be moved relative to the drive roller 17a in a direction orthogonal to the pressing direction.

[0071] (Aspect 7) In any one of Aspects 1 to 6, a pressing mechanism such as the pressing mechanism 80 is rotatably supported by a guide member such as the conveyance guide 90, and has a holder 82 that positions the driven roller 17b at least in a direction orthogonal to the pressing direction and has a pressing portion 82b that presses the driven roller 17b, and a biasing means such as a pressing spring 81 that biases the holder 82 in the sheet conveyance direction. The biasing means biases the holder 82 in a direction orthogonal to the pressing direction. According to this, as described in the embodiment, compared with that which biases the holder in the pressing direction, an increase in size in the pressing direction can be suppressed. Further, the reaction force from the drive roller 17a becomes a direction orthogonal to the pressing direction and a direction orthogonal to the rotation direction of the guide member at the guide position. Thereby, rotation of the guide member due to the reaction force from the drive roller 17a can be suppressed. Furthermore, depending on the positional relationship between the center of rotation of the guide member and the location that receives the reaction force from the drive roller via the pressing mechanism of the guide member, a vector component that rotates the guide member to the guide position can be generated by the reaction force of the drive roller, and it becomes possible to keep the guide member at the guide position by the reaction force of the drive roller.

[0072] (Aspect 8) In Aspect 7, when the guide member such as the conveyance guide 90 is positioned at the open position, the driven roller 17b is separated from the drive roller 17a, and has a restricting portion that restricts the rotation of the holder 82 when the guide member is positioned at the open position. According to this, as described in the embodiment, when the guide member such as the conveyance guide 90 is located at the open position, the driven roller 17b is separated from the drive roller 17a, so that the rotation of the holder 82 by the biasing means such as the compression spring 81 is not restricted, and the holder 82 rotates greatly. In this state, when the guide member is rotated from the open position to the guide position, there is a possibility that the driven roller 17b may not contact the drive roller 17a. In Mode 8, when the guide member is located at the open position, the rotation of the holder 82 is restricted by the restricting portion, so that when the guide member such as the conveyance guide 90 is rotated from the open position to the guide position, the driven roller 17b can be brought into contact with the drive roller 17a.

[0073] (Mode 9) In Mode 8, the restricting portion is a penetrating shaft such as the support shaft 42 that penetrates the driven roller 17b. According to this, as described in the embodiment, the rotation of the holder 82 when the guide member is located at the open position can be restricted by the driven roller 17b abutting against the penetrating shaft such as the support shaft 42.

[0074] (Mode 10) In Mode 9, it has a contact portion where the leading end of the sheet contacts upstream of the conveyance nip formed by bringing the driven roller 17b into contact with the drive roller 17a in the sheet conveyance direction, and includes a rotating member such as the shutter 50 that rotates while correcting the skew of the sheet. The penetrating shaft is a rotating shaft such as the shutter shaft 52 to which the rotating member is fixed. According to this, as described in Modification 2, the rotation of the holder 82 when the guide member is located at the open position can be restricted by the driven roller 17b abutting against the rotating shaft such as the shutter shaft 52.

[0075] (Mode 11) An image forming apparatus including a sheet conveyance device that conveys a sheet and an image forming means that forms an image on the sheet conveyed from the sheet conveyance device, wherein any one of the sheet conveyance devices according to Modes 1 to 10 is used as the sheet conveyance device. According to this, cost reduction of the device can be achieved.

Explanation of Signs

[0076] 1: Process cartridge 9: Developer recovery unit 9a: Pressing part 17: Resist roller pair 17a: Driving roller 17b: Driven roller 37: Open / close cover 40: Sheet conveying device 41: Driving shaft 42: Support shaft 43: Bearing 50: Shutter 51: Contact part 52: Shutter shaft 53: Rotary cam 54: Cam follower 55: Arm member 56: Cam spring 61: Conveying motor 61a: Motor gear 62: Driving gear 71: Flange part 80: Pressing mechanism 81: Pressing spring 82: Holder 82a: Support protrusion 82b: Pressing part 90: Conveying guide 91: Cam part 92: Holder support hole 93: Bearing 95: Positioning protrusion 96: Spring receiving part 97: Positioning groove 98: Fitting hole part 99: Regulation part 110: Main body side plate 111: Positioning groove 112: Positioning protrusion 113: Arm holder 115: Support protrusion part F3: Pressing direction

Prior art documents

Patent documents

[0077]

Patent Document 1

Claims

1. A driving roller that rotates and drives, A driven roller that rotates following the driving roller, A guide member that is rotatable between a guide position for guiding a sheet moving along a sheet conveyance path and an open position for opening the sheet conveyance path, A pressing mechanism that presses the driven roller so that the contact pressure with the driving roller becomes a predetermined contact pressure, and In a sheet conveyance device that conveys a sheet by the driving roller and the driven roller, The pressing mechanism is provided on the guide member, The rotation center of the guide member is located coaxially with the rotation center of the driven roller, The driven roller moves relative to the driving roller in a direction orthogonal to the pressing direction of the driven roller by the pressing mechanism in conjunction with the rotation of the guide member. A sheet conveyance device characterized by this.

2. In the sheet conveyance device according to Claim 1, The pressing portion that presses the driven roller of the pressing mechanism positions the driven roller in a direction orthogonal to the pressing direction, The guide member is configured to be slidable within a predetermined range in a direction orthogonal to the pressing direction with respect to a support portion that rotatably supports the guide member. A sheet conveyance device characterized by this.

3. In the sheet conveyance device according to Claim 2, The guide member has a support hole supported by the support portion, The support hole has an elongated hole shape that is long in a direction orthogonal to the pressing direction. A sheet conveyance device characterized by this.

4. In the sheet conveyance device according to Claim 2, When the guide member is positioned at the guide position, it has positioning means for positioning the guide member so that it cannot slide. A sheet conveyance device characterized by this.

5. In the sheet conveyance device according to Claim 2, When the guide member rotates, it has sliding means for sliding the guide member with respect to the support portion. A sheet conveyance device characterized by this.

6. In the sheet conveyance device according to Claim 5, The sliding means is a cam portion provided on the guide member, When the guide member is positioned at the guide position, the cam portion of the guide member is separated from a cam contact portion where the cam portion of the main body structure contacts. When the guide member rotates, the cam portion contacts the cam contact portion and slides the guide member with respect to the support portion. A sheet conveyance device characterized by this.

7. In the sheet conveyance device according to Claim 1, The pressing mechanism is rotatably supported by the guide member, and has a holder having a pressing portion that positions the driven roller at least in a direction orthogonal to the pressing direction and presses the driven roller, and biasing means for biasing the holder in the sheet conveying direction. The biasing means biases the holder in a direction orthogonal to the pressing direction. A sheet conveying device characterized by this.

8. In the sheet conveying device according to claim 7, When the guide member is in the open position, the driven roller is separated from the driving roller. A sheet conveying device, characterized by having a restricting portion that restricts the rotation of the holder when the guide member is in the open position.

9. In the sheet conveying device according to claim 8, The restricting portion is a through shaft that passes through the driven roller. A sheet conveying device characterized by this.

10. In the sheet conveying device according to claim 9, It has a contact portion where the leading end of the sheet contacts upstream of the conveyance nip formed by bringing the driven roller into contact with the driving roller in the sheet conveyance direction, and includes a rotating member that rotates while correcting the skew of the sheet. The through shaft is a rotating shaft to which the rotating member is fixed. A sheet conveying device characterized by this.

11. An image forming apparatus including a sheet conveying device for conveying a sheet, and image forming means for forming an image on the sheet conveyed from the sheet conveying device. An image forming apparatus, characterized by using the sheet conveying device according to claim 1 as the sheet conveying device.

Images