Sheet conveying device

Abstract

To provide a sheet conveying device capable of accurately correcting skew of a sheet with a small-sized structure.SOLUTION: A sheet conveying device (12) comprises skew detection means (17) for detecting a skew amount with respective to a conveyance direction (F) of a conveyed sheet (S), and skew correction means (15) for correcting skew of the sheet. The skew correction means comprises guide members (30c, 32c, 28) that support the sheet in a width direction. The guide members are displaced so as to rotate an area in the width direction of the sheet supported by the guide members around a shaft line in parallel with the conveyance direction, according to the skew amount of the sheet.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a sheet transport device. [Background technology]

[0002] An image forming apparatus that forms images on sheet-like recording media (hereinafter referred to as paper) separates the paper sheets one by one and supplies them to an image forming unit, which then forms images on the paper sheets. The transport mechanism that transports paper sheets in the image forming apparatus includes a paper feed unit that transports paper sheets before image formation to the image forming unit. When an image formation start command is input to the image forming apparatus, the paper feed unit separates the paper sheets one by one using a separation transport unit, and transports each sheet sequentially to the image forming unit.

[0003] When paper is transported to the image forming unit by the paper feeding means, if the paper is transported in a skewed state that is inclined relative to the normal transport direction, problems such as a decrease in the quality of the image formed on the paper in the image forming unit (image misalignment on the paper, image protrusion from the paper, etc.) and poor paper transport occur. As a countermeasure, a skew correction transport unit is provided in the paper feeding means between the separation transport unit and the image forming unit, and the skew of the paper transported from the separation transport unit is corrected by the skew correction transport unit in accordance with the image formation timing before the paper is supplied to the image forming unit.

[0004] For example, the skew correction transport unit disclosed in Patent Document 1 has registration rollers that can be switched between a rotating state and a stopped state, and corrects skew by abutting the leading edge of the paper against the stopped registration roller to loosen the paper. The registration rollers are rotated at a predetermined timing, and the paper after skew correction is transported to the image forming unit.

[0005] Because registration rollers correct skewed paper by repeatedly rotating and stopping, physical factors such as the effects of rotational inertia make it difficult to meet the required operational performance when the number of times paper is transported per unit time increases. For example, if the registration rollers are repeatedly rotated and stopped at very short intervals, the registration rollers rotate and stop at times that deviate from the actual rotation and stop instructions input, resulting in poor positional accuracy of image formation on paper transported from the registration rollers to the image forming unit. For these reasons, a skew correction transport unit that repeats a rotation and stop cycle of the registration rollers has a limit to the operating speed at which it can ensure transport accuracy, and the skew correction transport unit has been a factor that limits the improvement of paper transport speed (the number of images formed per unit time).

[0006] To eliminate the bottleneck of the skew correction transport section in terms of paper transport speed, technologies have been proposed to increase the operation speed of the paper feed means. For example, in the invention described in Patent Document 2, a pair of transport rollers serving as a registration roller pair is configured so that the angle can be changed along the paper transport direction (thrust direction). Then, a sensor detects the amount of skew while the paper is being transported, and the angle of the pair of transport rollers is changed until the nip line of the pair of transport rollers is parallel to the leading edge of the paper. Once the paper is sandwiched between the pair of transport rollers, the angle of the pair of transport rollers is returned to a right angle with respect to the transport direction. This operation of the pair of transport rollers corrects the skew of the paper. An invention similar to Patent Document 2 is disclosed in Patent Document 3.

[0007] In the invention described in Patent Document 4, the skew of the paper is corrected by giving different rotation speeds to two transport rollers arranged parallel to the transport direction depending on the detected amount of skew of the paper. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 10-35910 [Patent Document 2] Japanese Patent Application Publication No. 6-234441 [Patent Document 3] Japanese Patent Application Publication No. 4-153149 [Patent Document 4] Japanese Patent Application Publication No. 4-144859 Summary of the Invention [Problem to be solved by the invention]

[0009] In a configuration in which the angle of a pair of conveying rollers is changed along the conveying direction of the paper to correct skew of the paper, as in Patent Document 2, a large space is required in the conveying direction to place the skew correction conveying unit, which lengthens the paper conveying path, resulting in an increase in the size of the image forming apparatus in the conveying direction.

[0010] In a configuration such as that described in Patent Document 4, in which two conveying rollers are made to have a speed difference to correct skewed paper, there is a risk that the speed difference between the two conveying rollers may cause distortion in the paper, and there is a problem in that it is difficult to perform appropriate operation control of the conveying rollers taking into account the rigidity of the paper, the friction coefficient of the conveying rollers, etc.

[0011] This problem exists not only in image forming devices that form images on paper, but also in various sheet conveying devices that convey sheet-like objects (hereinafter referred to as "sheets"). In other words, in conventional sheet conveying devices, when correcting skew of a sheet relative to the conveying direction, it has been difficult to improve the conveying speed without increasing the size of the conveying direction or causing sheet conveyance problems.

[0012] SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet transport device that has a small structure and is capable of correcting skewed sheets with high accuracy. [Means for solving the problem]

[0013] In one aspect, the present invention provides a sheet conveying device that includes a skew detection means for detecting the amount of skew of a sheet being conveyed relative to the conveying direction, and a skew correction means for correcting the skew of the sheet, wherein the skew correction means includes a guide member that supports the sheet along the width direction, and displaces the guide member so as to rotate the width direction area of ​​the sheet supported by the guide member around an axis parallel to the conveying direction in accordance with the amount of skew of the sheet detected by the skew detection means. [Effects of the Invention]

[0014] According to the above aspect, it is possible to obtain a sheet transport device that has a small structure and is capable of correcting skewed sheets with high precision. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a plan view of an image forming apparatus according to an embodiment; [Figure 2] FIG. 2 is a side view of the image forming apparatus. [Figure 3] FIG. 2 is a diagram illustrating a control system of the image forming apparatus. [Figure 4] FIG. 2 is a perspective view of a skew correction unit provided in the sheet conveying device of the image forming apparatus. [Figure 5] FIG. [Figure 6] FIG. 2 is a perspective view of a swing unit that constitutes a skew correction unit. [Figure 7] FIG. 10 is a side view of the skew correction unit in the reference state. [Figure 8] FIG. 10 is a front view of the skew correction unit in the reference state. [Figure 9] 10 is a side view showing a state in which a swing unit of the skew correction section is rotated in a first direction. FIG. [Figure 10] 10 is a front view showing a state in which a swing unit of the skew correction section is rotated in a first direction. FIG. [Figure 11] 10 is a side view showing a state in which the swing unit of the skew correction section is rotated in a second direction. FIG. [Figure 12]10 is a front view showing a state in which the swing unit of the skew correction section is rotated in a second direction. FIG. [Figure 13] 10A and 10B are diagrams illustrating skew correction of a sheet by a skew correction unit. [Figure 14] FIG. 10 is a perspective view showing a skew correction unit according to a different embodiment. [Figure 15] 10 is a side view showing a reference state of a skew correction unit of a different embodiment; FIG. [Figure 16] 10 is a side view showing a state in which a swing unit is rotated in a first direction in a skew correction section of a different embodiment. FIG. [Figure 17] 10 is a side view showing a state in which the swing unit is rotated in a second direction in a skew correction section of a different embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] 1 and 2 show a schematic structure of an image forming apparatus 1 according to an embodiment of the present invention. The X-axis, Y-axis, and Z-axis directions in the image forming apparatus 1 are perpendicular to one another. The Z-axis direction is the up-down direction, with the +Z direction side being the top and the -Z direction side being the bottom.

[0017] The image forming apparatus 1 is an apparatus that supplies a sheet S, which is a sheet-like image formation medium, to an image forming unit 10, and forms an image on the surface of the sheet S by the image forming unit 10. The image forming unit 10 is, for example, an inkjet print head that ejects ink onto the sheet S to perform printing.

[0018] 3 shows a control system of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 40, and operations such as conveying the sheet S and forming an image on the sheet S, which will be described below, are performed under the control of the control unit 40.

[0019] The image forming apparatus 1 includes a sheet conveying device 11 that conveys a sheet S. The width direction of the sheet S when conveyed by the sheet conveying device 11 is the X-axis direction. The sheet conveying device 11 conveys the sheet S from a paper feed unit 12 arranged on the -Y direction side of the image forming unit 10 toward a paper discharge unit 13 arranged on the +Y direction side of the image forming unit 10. In other words, the sheet conveying device 11 conveys the sheet S in a conveying direction F from the -Y direction side, which is the upstream side, toward the +Y direction side, which is the downstream side. The path along which the sheet S passes when conveyed by the sheet conveying device 11 is referred to as a conveying path T (see FIGS. 2 and 7).

[0020] The sheet conveying device 11 includes a paper feeding means for conveying the sheet S before image formation from the paper feeding section 12 to the image forming section 10, and a paper discharge means for conveying the sheet S after image formation from the image forming section 10 to the paper discharge section 13.

[0021] The paper feed unit 12 is configured with a paper feed tray or the like that can accommodate multiple sheets S stacked in the Z-axis direction. The paper feed means of the sheet conveying device 11 includes a separation conveying unit 14 that separates the sheets S stacked in the paper feed unit 12 one by one and advances them toward the image forming unit 10, and a skew correction unit 15 that corrects skew of the sheets S conveyed from the paper feed unit 12 toward the image forming unit 10.

[0022] The separating and conveying unit 14 includes a conveying roller 16. The conveying roller 16 is rotatably supported via a shaft member 16a extending in the X-axis direction, and is rotationally driven by a conveying motor 41 (see FIG. 3). The conveying roller 16 is brought into contact with the upper surface of the top sheet S stacked in the paper feed unit 12, and is rotated counterclockwise in FIG. 2, whereby the top sheet S is separated and moved in the conveying direction F.

[0023] The skew of the sheets S, which are conveyed one by one by the operation of the conveying rollers 16, is corrected by a skew correction unit 15, which is a skew correction means. Skew of the sheet S means that the sheet S advances with its orientation tilted relative to the conveying direction F when viewed from above as shown in FIG. 1. For example, when the sheet end Sa on the leading edge side of the conveying direction F is parallel to the X-axis direction (perpendicular to the Y-axis direction), the sheet S is not skewed. When the sheet end Sa is not parallel to the X-axis direction, the sheet S is in a skewed state.

[0024] The skew correction unit 15 is equipped with skew amount detection sensors 17, which are skew detection means. As shown in FIG. 1, the skew amount detection sensors 17 are provided at two locations spaced apart in the X-axis direction. As shown in FIG. 2, each skew amount detection sensor 17 is a photosensor having a light-emitting unit 17a and a light-receiving unit 17b that face each other across the conveyance path T in the Z-axis direction, and the light emitted by the light-emitting unit 17a is received by the light-receiving unit 17b. The passage of the sheet end Sa of the sheet S is detected when the light emitted by the light-emitting unit 17a is blocked by the sheet S.

[0025] When the sheet S is not skewed with respect to the conveying direction F, the detection timings of the two skew amount detection sensors 17 match. When the sheet S is skewed with respect to the conveying direction F, the detection timings of the two skew amount detection sensors 17 differ, and the control unit 40 calculates the skew amount of the sheet S based on the difference in detection timing. The skew amount of the sheet S calculated by the control unit 40 includes information on the direction in which the sheet end Sa is skewed with respect to the X-axis direction and information on the skew angle of the sheet end Sa with respect to the X-axis direction. When the skew amount detection sensor 17 detects that the sheet S is skewed, the control unit 40 causes the skew correction unit 15 to perform an operation to correct the skew. Details of skew correction by the skew correction unit 15 will be described later.

[0026] When the sheet S is conveyed to below the image forming unit 10 by the paper feeding means, the image forming unit 10 operates at a predetermined timing, and an image is formed on the sheet S by the image forming unit 10. Note that a lower conveying mechanism (not shown) that conveys the sheet S while suction-holding it may be provided at a position on the opposite side (-Z direction side) of the conveying path T from the image forming unit 10.

[0027] The sheet discharge means of the sheet conveying device 11 is disposed on the +Y direction side of the image forming unit 10 and includes a pair of conveying rollers 18 and 19 disposed on the -Z direction side and the +Z direction side of the conveying path T. The conveying rollers 18 and 19 are rotatably supported via shaft members 18a and 19a extending in the X-axis direction, respectively. The conveying roller 18 is driven to rotate by a conveying motor 42 (see FIG. 3). The shaft member 19a supporting the conveying roller 19 is supported movably in the Z-axis direction and is biased in a direction that brings the conveying roller 19 into contact with the conveying roller 18. By rotating the conveying roller 18 in the clockwise direction in FIG. 2 with the sheet S sandwiched between the conveying rollers 18 and 19, the sheet S after image formation moves in the conveying direction F and reaches the sheet discharge unit 13.

[0028] Next, the skew correction unit 15 will be described in detail. FIGS. 4 to 12 show the configuration and operation of the skew correction unit 15. The skew correction unit 15 includes a pair of conveyance rollers 20 and 21 arranged on the -Z and +Z sides of the conveyance path T. The conveyance rollers 20 and 21 are rotatably supported via shaft members 20a and 21a extending in the X-axis direction, respectively. The conveyance roller 20 is rotationally driven by a conveyance motor 43 (see FIG. 3). The shaft member 21a supporting the conveyance roller 21 is supported movably in the Z-axis direction and is biased in a direction that brings the conveyance roller 21 into contact with the conveyance roller 20. With the sheet S sandwiched between the conveyance rollers 20 and 21, the conveyance roller 20 is rotated clockwise in FIGS. 2 and 7 to move the sheet S in the conveyance direction F.

[0029] 4 and 5, a plurality of conveying rollers 20 and a plurality of conveying rollers 21 are arranged at predetermined intervals in the X-axis direction. The plurality of conveying rollers 20 and the plurality of conveying rollers 21 are arranged in the same region in the X-axis direction, and each conveying roller 20 and each conveying roller 21 form a pair to sandwich the sheet S.

[0030] A swinging unit 22 is provided on the +Y direction side of the conveying roller 20 and the conveying roller 21. As shown in Fig. 1 and Fig. 2, the swinging unit 22 is disposed on the +Y direction side of the skew amount detection sensor 17, and the skew of the sheet S detected by the skew amount detection sensor 17 can be corrected by the operation of the swinging unit 22.

[0031] As shown in FIG. 6, the swing unit 22 has a pair of side walls 23 spaced apart in the X-axis direction and a connecting portion 24 connecting the pair of side walls 23. The connecting portion 24 extends in the X-axis direction, and a rotation shaft 24a extending in the Y-axis direction is provided at approximately the center of the longitudinal direction of the connecting portion 24. The rotation shaft 24a is inserted into a shaft hole formed in a rotation support portion 25 (see FIGS. 4 and 5) that is fixedly supported inside the image forming apparatus 1. The swing unit 22 is supported rotatably about an axis (extending in the Y-axis direction) parallel to the conveyance direction F via the shaft hole of the rotation support portion 25 and the rotation shaft 24a. The rotation shaft 24a is provided across approximately the center of the first support shaft 26 in the longitudinal direction in a plan view.

[0032] The swing unit 22 further includes a first support shaft 26 and a second support shaft 27 that are substantially parallel to each other. The first support shaft 26 is disposed on the −Z direction side of the transport path T, and the second support shaft 27 is disposed on the +Z direction side of the transport path T. The first support shaft 26 and the second support shaft 27 are each a shaft with a circular cross section that extends in the X-axis direction, and both ends of each are supported by a pair of side walls 23.

[0033] A plurality of cylindrical guide rollers 28 are rotatably supported on the first support shaft 26. The plurality of guide rollers 28 are arranged at predetermined intervals in the axial direction of the first support shaft 26 (X-axis direction).

[0034] A plurality of lower guides 30 are supported on the shaft member 21a in addition to the above-mentioned transport rollers 20. The plurality of lower guides 30 are arranged at different positions in the X-axis direction, and are positioned between the plurality of transport rollers 20 in the X-axis direction (alternately with the plurality of transport rollers 20). As shown in Fig. 7, each lower guide 30 has a cylindrical portion 30b having an axial hole 30a at its center through which the shaft member 20a is inserted, and a guide arm 30c that protrudes in the +Y direction from the cylindrical portion 30b.

[0035] The shaft hole 30a is not fixed to the shaft member 20a in the rotational direction, and each of the multiple lower guides 30 is supported via the shaft hole 30a so as to be able to rotate independently relative to the shaft member 20a. The cylindrical portion 30b has a cylindrical shape with a diameter similar to that of the conveying roller 21. The guide arm 30c is disposed between the multiple guide rollers 28 in the X-axis direction, and the lower surface of the guide arm 30c near its tip is supported by the first support shaft 26 (see FIG. 7). A guide surface 30d is formed on the upper surface of the guide arm 30c, which has a mountain-shaped arc shape that convex toward the +Z direction when the guide arm 30c is supported by the first support shaft 26. The guide surface 30d has a shape that follows a portion of the outer circumferential surface of the guide roller 28.

[0036] A support shaft 31 extending in the X-axis direction is provided on the +Y-direction side of the swing unit 22. A plurality of upper guides 32 are supported on the support shaft 31 at predetermined intervals in the axial direction (X-axis direction). The plurality of upper guides 32 are arranged at approximately the same intervals and lengths in the X-axis direction as the plurality of lower guides 30. As shown in FIG. 7, each upper guide 32 has a cylindrical portion 32b having an axial hole 32a at its center through which the support shaft 31 is inserted, and a guide arm 32c protruding in the -Y direction from the cylindrical portion 32b.

[0037] The shaft hole 32a is not fixed in the rotational direction relative to the support shaft 31, and each of the multiple upper guides 32 is supported via the shaft hole 32a so as to be able to rotate individually relative to the support shaft 31. As shown in FIG. 7, the guide arm 32c has an elongated hole 32d whose longitudinal direction is oriented in the radial direction centered on the shaft hole 32a. The second support shaft 27 is inserted into the elongated hole 32d, and the guide arm 32c is supported via the second support shaft 27. A guide surface 32e is formed on the underside of the guide arm 32c. The guide surface 32e is an arc-shaped, valley-shaped surface that is concave toward the +Z direction when the guide arm 32c is supported by the second support shaft 27.

[0038] In the skew correction section 15, at the location of the swinging unit 22, the guide arms 30c of the multiple lower guides 30 arranged at intervals in the X-axis direction, which is the width direction of the sheet S, constitute a first guide member that supports the underside of the sheet S with their guide surfaces 30d. Furthermore, the guide arms 32c of the multiple upper guides 32 arranged at intervals in the X-axis direction constitute a second guide member that supports the upper side of the sheet S with their guide surfaces 32e. The guide surfaces 30d and 32e of the multiple guide arms 30c and the multiple guide arms 32c face each other in the Z-axis direction across the conveyance path T, and the sheet S passes between the guide surfaces 30d and 32e. Furthermore, the multiple guide rollers 28 arranged between the multiple guide arms 30c in the X-axis direction constitute an auxiliary guide member that, together with the guide arms 30c, supports the underside of the sheet S.

[0039] 7, the conveying path T of the sheet S moving in the conveying direction F in the skew correction unit 15 passes between the conveying rollers 20 and 21 located on the -Y direction side, passes through the support position of the guide members (guide arm 30c, guide arm 32c, guide roller 28) of the swinging unit 22, and follows the outer peripheral surface of the cylindrical portion 32b of the upper guide 32 on the +Y direction side. The support position of the sheet S in the guide members of the swinging unit 22 is located on the +Z direction side of the clamping position of the sheet S between the conveying rollers 20 and 21 and the support position of the sheet S by the cylindrical portion 32b of the upper guide 32. Therefore, at the location of the swinging unit 22, the sheet S is partially pushed up and protrudes in the +Z direction, forming a mountain-shaped slack portion Sb (see FIGS. 2, 7, and 13) that is slack in a direction perpendicular to the conveying direction F.

[0040] 7, on the +Y direction side of the swinging unit 22, there are provided a pair of conveying rollers 33 and 34 arranged on the -Z direction side and the +Z direction side of the conveying path T. The conveying rollers 33 and 34 are rotatably supported via shaft members 33a and 34a extending in the X-axis direction, respectively. The sheet S that has passed through the swinging unit 22 moves along the cylindrical portion 32b of the upper guide 32, and further passes between the conveying rollers 33 and 34 in the conveying direction F.

[0041] As shown in Fig. 4, the skew correction section 15 includes a motor unit 35 that applies a force to the oscillating unit 22 to rotate around the rotation shaft 24a. The motor unit 35 is provided adjacent to the side wall 23 on the +X direction side of the oscillating unit 22. When the motor included in the motor unit 35 is driven, the driving force is transmitted via a transmission mechanism (not shown), causing the position of the side wall 23 to change in the Z axis direction. This causes the oscillating unit 22 to rotate (oscillate) around the axis of the rotation shaft 24a. The rotation direction of the oscillating unit 22 changes by switching the drive direction of the motor of the motor unit 35, and the rotation angle of the oscillating unit 22 changes depending on the drive amount of the motor of the motor unit 35.

[0042] When the swinging unit 22 rotates around the rotation axis 24a, the angles of the first support shaft 26 and the second support shaft 27 with respect to the X-axis direction change along a plane perpendicular to the conveying direction F. FIGS. 7 and 8 show the skew correction unit 15 in a reference state in which the first support shaft 26 and the second support shaft 27 are parallel to the X-axis direction. FIGS. 9 and 10 show the skew correction unit 15 in a state in which the swinging unit 22 is rotated in a first direction in which the side wall 23 on the +X direction side is displaced toward the −Z direction and the side wall 23 on the −X direction side is displaced toward the +Z direction. FIGS. 11 and 12 show the skew correction unit 15 in a state in which the swinging unit 22 is rotated in a second direction in which the side wall 23 on the +X direction side is displaced toward the +Z direction and the side wall 23 on the −X direction side is displaced toward the −Z direction.

[0043] 9 to 12, when the angle of the first support shaft 26 with respect to the X-axis direction changes, the height positions in the Z-axis direction of the guide surfaces 30d of the guide arms 30c supported by the first support shaft 26 of the multiple lower guides 30 change in accordance with the first support shaft 26. Furthermore, when the angle of the first support shaft 26 with respect to the X-axis direction changes, the inclinations of the outer peripheral surfaces of the multiple guide rollers 28 supported by the first support shaft 26 (height positions in the Z-axis direction) change.

[0044] The height positions of the guide arms 30c of the multiple lower guides 30 are varied in stages in accordance with the inclination of the first support shaft 26, so that the guide surfaces 30d of the guide arms 30c that are positioned farther away from the rotation shaft 24a in the X-axis direction have a greater amount of displacement in the Z-axis direction. The height positions of the outer peripheral surfaces of the multiple guide rollers 28 are varied in stages in accordance with the inclination of the first support shaft 26, so that the outer peripheral surfaces of the guide rollers 28 that are positioned farther away from the rotation shaft 24a in the X-axis direction have a greater amount of displacement in the Z-axis direction. Therefore, when the swing unit 22 rotates, the inclination of the lower guide surface formed by the multiple guide surfaces 30d and the multiple guide rollers 28 changes.

[0045] 9 to 12, when the angle of second support shaft 27 changes, a force is transmitted to upper guide 32 via elongated hole 32d through which second support shaft 27 is inserted, and each of the multiple upper guides 32 changes the height position in the Z-axis direction of guide surface 32e of guide arm 32c in accordance with second support shaft 27. At this time, the position of second support shaft 27 in guide arm 32c changes in the longitudinal direction of elongated hole 32d, thereby absorbing differences in the inclination angles of each guide arm 32c and allowing the multiple upper guides 32 to operate smoothly.

[0046] The height positions of the guide arms 32c of the multiple upper guides 32 are varied in stages according to the inclination of the second support shaft 27, and the further away in the X-axis direction the guide surface 32e of the guide arm 32c is from the rotation shaft 24a, the greater the amount of displacement in the Z-axis direction. Therefore, when the swing unit 22 rotates, the inclination of the upper guide surface formed by the multiple guide surfaces 32e changes.

[0047] In this way, the skew correction unit 15 changes the inclination of the guide members (upper and lower guide surfaces) that support both sides of the sheet S in the X-axis direction by rotating the swing unit 22. The first support shaft 26 and the second support shaft 27 of the swing unit 22 extend from the axis of the rotation shaft 24a, which is the rotation center, on both sides in the X-axis direction, so that the displacement direction of the guide members in the Z-axis direction is opposite between the region on the +X-direction side and the region on the -X-direction side of the rotation shaft 24a. Furthermore, as the distance from the rotation shaft 24a in the X-axis direction increases, the amount of displacement of the guide members in the Z-axis direction when the swing unit 22 rotates increases. The sheet S is then displaced in accordance with the displacement of the guide members.

[0048] Specifically, in the region where the guide member of the swing unit 22 is displaced in the +Z direction, the guide arm 30c and the guide roller 28, which are guide members arranged on the -Z side of the conveying path T, push up the sheet S in the +Z direction, thereby displacing the sheet S in the +Z direction. In the region where the guide member of the swing unit 22 is displaced in the -Z direction, the guide arm 32c, which is a guide member arranged on the +Z side of the conveying path T, pushes down the sheet S in the -Z direction, thereby displacing the sheet S.

[0049] 7 and 8, the first support shaft 26 and the second support shaft 27 are not tilted with respect to the X-axis direction, and the height position of the guide member at the location of the swinging unit 22 is uniform throughout the X-axis direction. Therefore, the sheet S forms a slack portion Sb that is the same shape throughout the entire width direction, and moves along a conveyance path of the same length throughout the entire width direction. In this state, the skew correction unit 15 does not correct the skew of the sheet S, but conveys the sheet S in the conveyance direction F by a uniform conveyance amount throughout the entire width direction.

[0050] FIG. 13 shows a change in the conveyance path of the sheet S when the rocking unit 22 is displaced so as to rotate a region of the sheet S in the width direction (X-axis direction) around an axis parallel to the conveyance direction F. Line AA in FIG. 13 indicates a position in the width direction of the sheet S that corresponds to the rotation center of the rocking unit 22 (axis of the rotation shaft 24a). Line BB in FIG. 13 indicates a position in the width direction of the sheet S where the guide member of the rocking unit 22 is displaced in the +Z direction from the reference state, particularly a position close to one side edge of the sheet S where the amount of displacement in the +Z direction is greatest. Line CC in FIG. 13 indicates a position in the width direction of the sheet S where the guide member of the rocking unit 22 is displaced in the -Z direction from the reference state, particularly a position close to the other side edge of the sheet S where the amount of displacement in the -Z direction is greatest.

[0051] 13, in the region where the guide member of the swing unit 22 is displaced in the +Z direction (the position of line BB), the amount of slack in the slack portion Sb increases, and the transport path of the sheet S is longer than in the reference state. On the other hand, in the region where the guide member of the swing unit 22 is displaced in the -Z direction (the position of line CC), the amount of slack in the slack portion Sb decreases, and the transport path of the sheet S is shorter than in the reference state. The skew correction unit 15 corrects skew of the sheet S by utilizing such changes in the transport path length on both sides of the sheet S in the width direction.

[0052] For example, as shown in FIGS. 9 and 10 , when the swinging unit 22 is rotated in a first direction, the widthwise region of the sheet S supported by the guide member of the swinging unit 22 is rotated in the first direction around an axis parallel to the conveyance direction F, displacing the height of the −X-direction region toward the +Z direction and the height of the +X-direction region toward the −Z direction. As a result, a slack portion Sb is formed in the −X-direction region of the sheet S, which protrudes more in the +Z direction than in the reference state (see the position of line BB in FIG. 13 ), and the conveyance path of the sheet S becomes longer than in the reference state. In the +X-direction region of the sheet S, a slack portion Sb is formed, which protrudes less in the +Z direction than in the reference state (see the position of line CC in FIG. 13 ), and the conveyance path of the sheet S becomes shorter than in the reference state. As a result, the region of the sheet S on the −X-direction side, where the conveyance path is longer, reaches the image forming unit 10 later than the region on the +X-direction side, where the conveyance path is shorter.

[0053] As shown in FIGS. 11 and 12 , when the swinging unit 22 is rotated in the second direction, the widthwise region of the sheet S supported by the guide member of the swinging unit 22 is rotated in the second direction around an axis parallel to the conveyance direction F, displacing the height of the region on the +X direction side toward the +Z direction and the height of the region on the −X direction side toward the −Z direction. As a result, a slack portion Sb is formed in the region on the +X direction of the sheet S, which protrudes more in the +Z direction than in the reference state (see the position of line BB in FIG. 13 ), and the conveyance path of the sheet S becomes longer than in the reference state. In the region on the −X direction of the sheet S, a slack portion Sb is formed, which protrudes less in the +Z direction than in the reference state (see the position of line CC in FIG. 13 ), and the conveyance path of the sheet S becomes shorter than in the reference state. As a result, the region of the sheet S on the +X direction side, where the conveyance path is longer, reaches the image forming unit 10 later than the region on the −X direction side, where the conveyance path is shorter.

[0054] As described above, depending on the direction in which the swinging unit 22 is tilted with respect to the X-axis direction, it is possible to change the timing at which the region on the +X direction side and the region on the -X direction side of the sheet S reach the image forming unit 10. Therefore, when the sheet S is skewed, by having the swinging unit 22 perform an operation to displace the guide member toward the +Z direction for the region in the X-axis direction on the side where the position of the sheet end Sa is ahead in the conveying direction F, it is possible to reduce the degree of skew of the sheet S and make the orientation of the sheet end Sa after passing through the swinging unit 22 closer to parallel to the X-axis direction.

[0055] The greater the inclination of the swinging unit 22 with respect to the X-axis direction, the greater the difference in the length of the transport path between the area on the +X-direction side and the area on the -X-direction side of the swinging unit 22. Therefore, by appropriately adjusting the inclination angle of the swinging unit 22 according to the amount of skew of the sheet S, the orientation of the sheet end Sa can be made completely parallel to the X-axis direction, and the skew of the sheet S can be corrected.

[0056] When the sheet conveying device 11 conveys the sheet S, the control unit 40 detects whether the sheet S is skewed using the two skew amount detection sensors 17. If the sheet S is not skewed, the control unit 40 maintains the swinging unit 22 in the reference state (FIGS. 7 and 8).

[0057] When the sheet S is skewed, the control unit 40 calculates the amount of skew of the sheet S and, based on the amount of skew, determines the direction and amount of rotation of the swing unit 22 to correct the skew. The storage unit of the control unit 40 stores calculation data and table data for determining the direction and amount of rotation of the swing unit 22 based on the amount of skew detected by the skew amount detection sensor 17. The control unit 40 transmits a drive signal corresponding to the determined direction and amount of rotation of the swing unit 22 to the motor unit 35, and the motor unit 35, having received the drive signal, operates to swing the swing unit 22.

[0058] By performing the above control for each sheet S, the sheet conveying device 11 can correct the skew of the sheet S and convey it to the image forming unit 10.

[0059] Note that, as a result of rotating the swing unit 22, when the transport path of the sheet S becomes flat with no unevenness in the Z-axis direction at either the +X-direction end or the -X-direction end (a state in which the mountain-shaped slack portion Sb that existed in the reference state disappears), the difference in length between the transport path at both ends in the X-axis direction becomes maximum. This state corresponds to the maximum amount of skew that can be corrected by the skew correction unit 15. The longer the length of the slack portion Sb in the reference state of the skew correction unit 15, the greater the amount of skew that can be corrected. However, if the length of the slack portion Sb is made too long by the skew correction unit 15, bending, catching, or excessive load may occur during transport of the sheet S. Therefore, the slack portion Sb in the reference state is set within a range that achieves smooth transport of the sheet S.

[0060] As described above, in the sheet conveying device 11 of this embodiment, the skew correction unit 15, which is a skew correction means, is provided with guide members (guide arm 30c, guide arm 32c, guide roller 28) that support the sheet S along the width direction, and displaces the guide members so that the width direction area of ​​the sheet S supported by the guide members rotates around an axis parallel to the conveying direction F depending on the skew amount of the sheet S detected by the skew amount detection sensor 17.

[0061] As a result, the skew correction unit 15 can correct skew while continuously conveying the sheet S without temporarily stopping the conveyance of the sheet S. Therefore, compared to a configuration in which skew correction is performed by stopping the registration rollers, the conveyance speed per unit time can be improved, and efficient sheet conveyance can be achieved.

[0062] The skew correction unit 15 displaces the guide member along a plane perpendicular to the conveying direction F, so that it does not require a long space along the conveying direction F, and can be made compact in the Y-axis direction.

[0063] Furthermore, the skew correction unit 15 corrects skew by rotating the widthwise region of the sheet S supported by the guide member around an axis parallel to the conveying direction F. Therefore, compared to a skew correction structure that relatively changes the operating speeds of multiple conveying means arranged at different positions in the conveying direction F, distortion of the sheet S is less likely to occur, and the sheet S can be conveyed with high precision.

[0064] The skew correction unit 15 slackens the sheet S in a direction perpendicular to the conveying direction F and supports it with a guide member (forming slack portions Sb), and changes the length of the conveying path by relatively changing the amount of slack on both sides of the width of the sheet S through displacement of the guide member. As a result, even if one area on either side of the width of the sheet S is ahead in the conveying direction F, the skew can be corrected by switching the direction of rotation of the guide member. Furthermore, the conveying path of the sheet S in the skew correction unit 15 is formed by the gently curved slack portions Sb, allowing the sheet S to pass through the skew correction unit 15 smoothly without applying a large load to the sheet S.

[0065] The skew correction unit 15 is provided with a first support shaft 26 and a second support shaft 27, which are arranged on one side and the other side of the conveyance path T of the sheet S in a direction (Z-axis direction) perpendicular to the conveyance direction F of the sheet S, and which each extend in the width direction (X-axis direction) of the sheet S, and rotates the first support shaft 26 and the second support shaft 27 together around an axis parallel to the conveyance direction F according to the amount of skew of the sheet S. Then, both sides of the sheet S are supported by a guide arm 30c, which is a first guide member that operates in accordance with the first support shaft 26, and a guide arm 32c, which is a second guide member that operates in accordance with the second support shaft 27.

[0066] As a result, both sides of the sheet S can be supported by the guide members using a space-saving structure in which the guide arms 30c and 32c are concentrated near the first support shaft 26 and the second support shaft 27, which are arranged at a predetermined interval in the Z-axis direction. Furthermore, since the first support shaft 26 and the second support shaft 27 are rotated integrally as the swing unit 22, the guide arms 30c and 32c, which are arranged on both sides of the conveyance path T in the Z-axis direction, can be driven in conjunction with each other using a simple structure. Therefore, the operation of the first support shaft 26 and the second support shaft 27 can be transmitted to the sheet S via the guide arms 30c and 32c without delay, thereby achieving skew correction with excellent operational responsiveness.

[0067] The lower guide 30 having the guide arm 30c is supported via the shaft member 20a that supports the transport roller 20 disposed adjacent to the -Y direction side of the swing unit 22. In this way, the lower guide 30 is supported in a manner that straddles the shaft member 20a that supports the transport roller 20 and the first support shaft 26 that supports the guide arm 30c and the guide roller 28, so that the lower guide 30 can be provided in a structure that is highly space-efficient.

[0068] The upper guide 32 having the guide arm 32c is supported via a support shaft 31 disposed adjacent to the swinging unit 22 on the +Y direction side. As shown in FIG. 7, the cylindrical portion 32b of the upper guide 32 supported by the support shaft 31 has the function of guiding the conveyance of the sheet S after it has passed through the swinging unit 22. In other words, in the upper guide 32, not only the guide arm 32c but also the cylindrical portion 32b contributes to the formation of the conveyance path T for the sheet S, including the slack portion Sb. In this way, the upper guide 32 has a combined function provided by the cylindrical portion 32b and the guide arm 32c, so that the skew correction unit 15 can be efficiently configured with a small number of parts.

[0069] The skew correction unit 15 includes multiple guide arms 30c and multiple guide rollers 28 as guide members that support the underside (-Z direction side) of the sheet S. The multiple guide arms 30c are spaced apart in the width direction of the sheet S, and the multiple guide rollers 28 are arranged between the multiple guide arms 30c. By providing the multiple guide rollers 28 so as to fill the gaps between the multiple guide arms 30c in the width direction of the sheet S, the underside of the sheet S is supported over a wide range in the width direction, improving the stability of the sheet S and ensuring that the sheet S is displaced in the +Z axis direction during skew correction. The guide rollers 28 are supported by the first support shaft 26 together with the guide arms 30c, so that a dedicated drive source or the like is not required for operating the guide rollers 28, and the guide rollers 28 can be displaced together with the guide arms 30c with a simple structure.

[0070] Note that a guide roller similar to guide roller 28 may be provided as a guide member that supports the upper side (+Z direction side) of sheet S. Specifically, it is possible to provide a plurality of guide rollers that are rotatably supported via second support shaft 27 between a plurality of guide arms 32c that are spaced apart in the width direction of sheet S. Therefore, it is preferable that guide rollers (including guide roller 28) located between the plurality of guide arms 30c and the plurality of guide arms 32c in the width direction of sheet S are supported on at least one of first support shaft 26 and second support shaft 27 to complement either guide arm 30c or guide arm 32c.

[0071] The guide member for correcting skew is not limited to the configuration of the guide arm 30c, the guide arm 32c, and the guide roller 28 of the above embodiment. Figures 14 to 17 show a skew correction unit 50 of a different embodiment. Note that, although the configuration of the sheet conveying device other than the skew correction unit 50 is omitted in Figures 14 to 17, the configuration other than the skew correction unit 50 is assumed to be similar to that of the sheet conveying device 11 of the above embodiment.

[0072] The skew correction section 50 includes a lower guide unit 51 disposed on the -Z direction side and an upper guide unit 52 disposed on the +Z direction side. An endless (loop-shaped) first belt member 53 provided in the lower guide unit 51 and an endless second belt member 54 provided in the upper guide unit 52 constitute the guide members of the skew correction section 50. Note that the second belt member 54 is not shown in FIG. 14.

[0073] The lower guide unit 51 includes an upstream roller 55 disposed on the -Y direction side and a downstream roller 56 disposed on the +Y direction side. The upstream roller 55 and the downstream roller 56 are rotatably supported via shaft members 55a and 56a extending in the X-axis direction, respectively. At least one of the upstream roller 55 and the downstream roller 56 is driven to rotate by a conveyance motor (not shown). An endless first belt member 53 is stretched between the upstream roller 55 and the downstream roller 56. A rod-shaped tensioner 57 extending in the X-axis direction is disposed between the upstream roller 55 and the downstream roller 56. The tensioner 57 applies a predetermined tension to the first belt member 53 by pressing the first belt member 53 in the -Z direction.

[0074] The lower guide unit 51 further includes a swing unit 58. The swing unit 58 is disposed between the upstream roller 55 and the downstream roller 56 in the Y-axis direction, and a tensioner 57 is disposed on the −Z direction side of the swing unit 58.

[0075] 14, the swing unit 58 has a pair of side walls 59 spaced apart in the X-axis direction, and a connection portion 60 connecting the pair of side walls 59. The connection portion 60 extends in the X-axis direction, and a rotation shaft 60a extending in the Y-axis direction is provided at approximately the center of the longitudinal direction of the connection portion 60. The rotation shaft 60a is inserted into a shaft hole formed in a rotation support portion 61 that is fixedly supported. Both ends of a shaft member 62 extending parallel to the connection portion 60 are supported by the pair of side walls 59.

[0076] The shaft member 62 rotatably supports a plurality of guide rollers 63. The plurality of guide rollers 63 are arranged at predetermined intervals in the longitudinal direction (X-axis direction) of the shaft member 62. The outer circumferential surfaces of the plurality of guide rollers 63 contact the underside of the first belt member 53 along a linear region extending in the X-axis direction, at a position between the upstream roller 55 and the downstream roller 56 in the Y-axis direction.

[0077] The swinging unit 58 having a plurality of guide rollers 63 is supported rotatably about an axis (axis in the Y-axis direction) parallel to the conveying direction F via the shaft hole of the rotation support part 61 and the rotation shaft 60a. A motor unit (not shown) applies a force to the swinging unit 58 to rotate it about the rotation shaft 60a.

[0078] When the swinging unit 58 rotates around the rotation shaft 60a, the angle of the shaft member 62 with respect to the X-axis direction changes along a plane perpendicular to the conveying direction F. As the angle of the shaft member 62 changes, the inclination (height position in the Z-axis direction) of the outer circumferential surfaces of the plurality of guide rollers 63 supported by the shaft member 62 changes. As a result, the areas of the first belt member 53 supported on the outer circumferential surfaces of the plurality of guide rollers 63 are displaced along a plane perpendicular to the conveying direction F, changing the inclination with respect to the X-axis direction.

[0079] The upper guide unit 52 includes an upstream roller 65 disposed on the -Y direction side and a downstream roller 66 disposed on the +Y direction side. The upstream roller 65 and the downstream roller 66 are rotatably supported via shaft members 65a and 65a extending in the X-axis direction, respectively. At least one of the upstream roller 65 and the downstream roller 66 is driven to rotate by a conveyance motor (not shown). An endless second belt member 54 is stretched between the upstream roller 65 and the downstream roller 66. A rod-shaped tensioner 67 extending in the X-axis direction is disposed between the upstream roller 65 and the downstream roller 66. The tensioner 67 applies a predetermined tension to the second belt member 54 by pressing the second belt member 54 in the +Z direction.

[0080] 15 to 17, the conveying path T of the sheet S in the skew correction section 50 is formed in a portion where the first belt member 53 of the lower guide unit 51 and the second belt member 54 of the upper guide unit 52 face each other, and the first belt member 53 and the second belt member 54 have support surfaces in the facing portion that support the sheet S. Then, with the first belt member 53 as the lower guide member and the second belt member 54 as the upper guide member, a slack portion Sb is formed in the sheet S.

[0081] When the swinging unit 58 rotates around the rotation shaft 60a, the first belt member 53 and the second belt member 54 change the shape of their respective support surfaces that support the sheet S, and displace the supported widthwise region of the sheet S so as to rotate around an axis parallel to the conveyance direction F. Figures 15 to 17 show examples of displacement of the sheet S at the end of the skew correction unit 50 on the +X direction side.

[0082] 15, in the reference state of the swinging unit 58, the shaft member 62 is not tilted with respect to the X-axis direction, the entire widthwise area of ​​the sheet S forms a slack portion Sb of the same shape, and the entire widthwise area of ​​the sheet S moves along a conveying path of the same length. In this state, the skew correction unit 50 does not correct the skew of the sheet S, and conveys the entire widthwise area of ​​the sheet S in the conveying direction F by a uniform conveyance amount.

[0083] 16 shows the skew correction unit 50 in a state in which the swing unit 58 is rotated in a first direction in which the +X-direction end of the shaft member 62 is displaced toward the −Z direction and the −X-direction end of the shaft member 62 is displaced toward the +Z direction. When the swing unit 58 is rotated in the first direction, the first belt member 53, supported by the multiple guide rollers 63, displaces the height of the −X-direction region toward the +Z direction around the rotation shaft 60a in a plane perpendicular to the conveyance direction F, and displaces the height of the +X-direction region toward the −Z direction. The second belt member 54 of the upper guide unit 52 displaces following the displacement of the first belt member 53. As a result, a slack portion Sb is formed in the +X-direction region of the sheet S, which protrudes less in the +Z direction than in the reference state, and the conveyance path of the sheet S becomes shorter than in the reference state. Although not shown in Figure 16, in the area on the -X side of the sheet S, a slack portion Sb is formed that protrudes more in the +Z direction than in the reference state, and the transport path of the sheet S becomes longer than in the reference state.

[0084] 17 shows the skew correction unit 50 in a state in which the swing unit 58 is rotated in a second direction in which the +X-side end of the shaft member 62 is displaced in the +Z direction and the −X-side end of the shaft member 62 is displaced in the −Z direction. When the swing unit 58 is rotated in the second direction, the first belt member 53, supported by the multiple guide rollers 63, displaces the height of the +X-side region toward the +Z direction and the height of the −X-side region toward the −Z direction, centered around the rotation shaft 60a, in a plane perpendicular to the conveyance direction F. The second belt member 54 of the upper guide unit 52 displaces following the displacement of the first belt member 53. As a result, a slack portion Sb is formed in the +X-side region of the sheet S, which protrudes more in the +Z direction than in the reference state, and the conveyance path of the sheet S becomes shorter than in the reference state. Although not shown in Figure 17, in the area on the -X side of the sheet S, a slack portion Sb is formed that protrudes less in the +Z direction than in the reference state, and the transport path of the sheet S becomes longer than in the reference state.

[0085] As described above, the skew correction unit 50 includes the first belt member 53 and the second belt member 54, which are arranged on one side and the other side of the conveyance path T in a direction (Z-axis direction) perpendicular to the conveyance direction F of the sheet S, and which sandwich and support both sides of the sheet S. Then, by rotating the swinging unit 58 to change the support surface shapes of the first belt member 53 and the second belt member 54 according to the amount of skew of the sheet S, the relative lengths of the conveyance paths of the regions on the -X direction side and the +X direction side of the sheet S are changed, thereby correcting the skew of the sheet S.

[0086] The skew correction section 50 conveys the sheet S while clamping both sides of the sheet S between the first belt member 53 and the second belt member 54, which are guide members. This allows the sheet S to follow the displacement of the first belt member 53 and the second belt member 54 with excellent followability during skew correction, preventing the sheet S from shifting out of position and improving the accuracy of skew correction.

[0087] When the first belt member 53 in the lower guide unit 51 revolves between the upstream roller 55 and the downstream roller 56, the guide roller 63 rotates following the first belt member 53, thereby allowing the first belt member 53 to move smoothly, so it is preferable to displace the first belt member 53 via the guide roller 63 when correcting skew. However, it is also possible to displace the first belt member 53 by contacting a rod-shaped member such as the shaft member 62 without using the guide roller 63.

[0088] The above embodiments are examples of a sheet conveying device installed in an image forming apparatus. By applying the device to sheet conveyance in an image forming apparatus, it is possible to accurately correct sheet skew with a compact structure and improve the quality of the formed image. However, the sheet conveying device of the present invention can be applied to devices other than image forming apparatuses as long as it conveys sheets regardless of the type or purpose of the sheet. For example, the device can be applied to a processing device that performs processing such as cutting on sheets, in which the sheet is corrected for skew and conveyed to the position of a processing tool. If a sheet is conveyed in a skewed state relative to the processing tool, the processing position of the sheet by the processing tool will be misaligned with respect to the preset processing position. Therefore, the sheet conveying device of the present invention is useful for preventing sheet misalignment due to skew.

[0089] The skew detection unit that detects the amount of skew of the sheet relative to the conveying direction is not limited to a photosensor such as the skew amount detection sensor 17 in the above embodiment. For example, an ultrasonic sensor that detects the passage of a sheet by emitting ultrasonic waves and receiving reflected waves may be applied.

[0090] The present invention is not limited to the above-described embodiments, and can be embodied by modifying the components without departing from the spirit of the invention in the implementation stage. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiments. For example, all the components shown in the embodiments may be appropriately combined. Naturally, various modifications and applications are possible without departing from the spirit of the invention. Below, some of the inventions described in the specification of this application are additionally noted.

[0091] [Appendix 1] A sheet conveying device including a skew detection unit that detects an amount of skew of a conveyed sheet relative to a conveying direction, and a skew correction unit that corrects the skew of the sheet, The skew correction means is provided with a guide member that supports the sheet along the width direction, and is characterized in that the guide member is displaced so as to rotate the width direction area of ​​the sheet supported by the guide member around an axis parallel to the conveying direction in accordance with the amount of skew of the sheet detected by the skew detection means.

[0092] [Appendix 2] the guide member supports the sheet while slackening it in a direction perpendicular to the conveying direction, 2. The sheet conveying device according to claim 1, wherein the length of the conveying path is changed by relatively changing the amount of slack on both sides of the sheet in the width direction by displacing the guide member.

[0093] [Appendix 3] the skew correction means is provided with a first support shaft and a second support shaft, each of which is disposed on one side of a conveyance path of the sheet in a direction perpendicular to the conveyance direction of the sheet and extends in a width direction of the sheet, and rotates the first support shaft and the second support shaft integrally about an axis parallel to the conveyance direction according to an amount of skew of the sheet; The sheet conveying device described in Appendix 1 or 2, characterized in that the guide member comprises a first guide member that operates in accordance with the first support shaft and a second guide member that operates in accordance with the second support shaft, and the first guide member and the second guide member support both sides of the sheet.

[0094] [Appendix 4] a plurality of the first guide members and a plurality of the second guide members spaced apart in the width direction of the sheet; A sheet conveying device as described in Appendix 3, characterized in that at least one of the first support shaft and the second support shaft supports a plurality of rotatable rollers positioned between a plurality of the first guide members and a plurality of the second guide members in the width direction of the sheet.

[0095] [Appendix 5] the guide member includes a first belt member and a second belt member that are disposed on one side and the other side of a conveyance path of the sheet in a direction perpendicular to the conveyance direction of the sheet, and that sandwich and support both sides of the sheet; 3. The sheet conveying device according to claim 1, wherein the skew correction means changes the shape of the support surface of each of the first belt member and the second belt member according to the amount of skew of the sheet. [Explanation of symbols]

[0096] 1: Image forming device 10: Image forming unit 11: Sheet transport device 14: Separation and conveyance section 15: skew correction unit (skew correction means) 17: Skew amount detection sensor (skew detection means) 20: Transport roller 21: Transport roller 22: Swing unit 23: Side wall 24: Connection part 24a: Rotating axis 25: Rotation support part 26: 1st support shaft 27:Second support shaft 28: Guide roller (guide member) 30: Lower guide 30b: Cylindrical part 30c: Guide arm (guide member, first guide member) 30d: Guide surface 31: Support shaft 32: Upper guide 32b: Cylindrical part 32c: Guide arm (guide member, second guide member) 32d: Long hole 32e: Guide surface 35: Motor unit 40: Control section 50: Slant correction section 51: Lower guide unit 52: Upper guide unit 53: First belt member (guide member) 54: Second belt member (guide member) 58: Swing unit 59: Side wall 60: Connection part 60a: Rotating shaft 61: Rotation support part 62: Shaft member 63: Guide roller F: Transport direction S: Seat Sa: Sheet edge Sb: Loose part T: Transport route

Claims

1. A sheet conveying device including a skew detection unit that detects an amount of skew of a conveyed sheet relative to a conveying direction, and a skew correction unit that corrects the skew of the sheet, The skew correction means is provided with a guide member that supports the sheet along the width direction, and is characterized in that the guide member is displaced so as to rotate the width direction area of ​​the sheet supported by the guide member around an axis parallel to the conveying direction in accordance with the amount of skew of the sheet detected by the skew detection means.

2. the guide member supports the sheet while slackening it in a direction perpendicular to the conveying direction, 2. The sheet transport device according to claim 1, wherein the length of the transport path is changed by relatively changing the amount of slack on both sides of the sheet in the width direction by displacing the guide member.

3. the skew correction means includes a first support shaft and a second support shaft, each of which is disposed on one side of a conveyance path of the sheet in a direction perpendicular to the conveyance direction of the sheet and extends in a width direction of the sheet, and rotates the first support shaft and the second support shaft integrally about an axis parallel to the conveyance direction according to the amount of skew of the sheet; The sheet conveying device according to claim 1 or 2, characterized in that the guide member comprises a first guide member that operates in accordance with the first support shaft and a second guide member that operates in accordance with the second support shaft, and the first guide member and the second guide member support both sides of the sheet.

4. a plurality of the first guide members and a plurality of the second guide members spaced apart in the width direction of the sheet; 4. The sheet conveying device according to claim 3, wherein at least one of the first support shaft and the second support shaft supports a plurality of rotatable rollers positioned between the plurality of first guide members and the plurality of second guide members in the width direction of the sheet.

5. the guide member includes a first belt member and a second belt member that are disposed on one side and the other side of a conveyance path of the sheet in a direction perpendicular to the conveyance direction of the sheet, and that sandwich and support both sides of the sheet; 3. The sheet transport device according to claim 1, wherein the skew correction means changes the shapes of the support surfaces of the first belt member and the second belt member in accordance with the amount of skew of the sheet.

Images