Sheet processing device, image forming device, and image forming system

Abstract

To provide a sheet processing device capable of corresponding to various folding types with a simple constitution, and improving quality of folding processing.SOLUTION: A sheet processing device comprises: a conveying unit for conveying a sheet along a main conveyance path; a first folding roller and a second folding roller oppositely placed sandwiching the main conveyance path; a return conveyance path which branches from the main conveyance path at a branch position on the upstream side of the first folding roller, in a conveyance direction of the sheet, and has curvature which is merged into the main conveyance path at a confluent point on the upstream side in the conveyance direction from the branch position; and a third folding roller which is placed at a position opposite to the second folding roller so as to sandwich the return conveyance path. A conveyance amount of the sheet by the third folding roller which is an inner peripheral side roller of the return conveyance path, when conveying the sheet to the return conveyance path, is less than the conveyance amount of the sheet by the second folding roller which is an outer peripheral side roller of the return conveyance path.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a sheet processing apparatus, an image forming apparatus, and an image forming system. [Background technology]

[0002] There is known a sheet processing apparatus that performs a predetermined process on a sheet on which an image is formed by an image forming apparatus that forms an image on a sheet-like medium (hereinafter referred to as a "sheet"). Among conventionally known sheet processing apparatuses, there is known one that performs a "folding process" that folds a sheet on which an image is formed into a predetermined shape (for example, a Z-fold, an outer tri-fold, or a double fold).

[0003] There are also known sheet processing devices that can be installed inside the body of an image forming device. In an internal sheet processing device, a configuration has been disclosed in which a folding motor is controlled by feedback control using integral gain to improve the accuracy of the folding position, and the sheet is passed through a loop conveying path to enable folding in half (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] When a sheet is conveyed after a crease is formed using a loop conveying path having a curve, as in the case of the internal sheet processing device disclosed in Patent Document 1, the position of the crease is out of the nip between the conveying roller pair. If the sheet enters and passes through the nip with the crease out of the nip, an improper crease may be formed in a position different from the correct crease when, for example, folding in half.

[0005] That is, when a sheet with a crease is transported along a looped transport path having a curve, the transport distance (transport path length) differs depending on the portion of the sheet, and it is as if the relative lengths in the transport direction (sheet length) of the portions are different. In other words, when a sheet has a crease, the sheet is divided into a portion (piece) that is transported along a path corresponding to the inner circumference side of the looped transport path and a portion (piece) that is transported along a path corresponding to the outer circumference side of the looped transport path, when viewed along the crease.

[0006] In this case, the inner peripheral side of the sheet that has passed through the loop conveying path (the sheet conveyed with the fold at the leading edge) has a relatively shorter conveying distance than the outer peripheral side, so the sheet length becomes longer, and the leading edge in the conveying direction is not the fold but the part near the fold where the inner peripheral side is shifted downstream in the conveying direction from the outer peripheral side. In this way, if the sheet passes through the nip of the conveying roller pair in a state where the leading edge is a part that is not aligned with the fold, an incorrect fold will be formed in a part that is different from the part that was intended to be a valid fold.

[0007] Therefore, in sheet processing devices that perform folding processing using a loop conveying path, there is a problem that an improper fold is formed when the fold deviates from the nip position of the pair of conveying rollers used for conveying, resulting in so-called "box fold."

[0008] An object of the present invention is to provide a sheet processing apparatus that improves the quality of folding processing. [Means for solving the problem]

[0009] In order to solve the above technical problems, one aspect of the present invention comprises a conveying unit that conveys a sheet along a main conveying path, a first folding roller and a second folding roller arranged opposite each other on either side of the main conveying path, a return conveying path having a curvature that branches off from the main conveying path at a branching position upstream of the first folding roller in the conveying direction of the sheet and joins the main conveying path at a joining position upstream of the branching position in the conveying direction, and a third folding roller arranged at a position opposite the second folding roller so as to sandwich the return conveying path, and is characterized in that when the sheet is conveyed to the return conveying path, the amount of conveyance of the sheet by the third folding roller, which is an inner roller of the return conveying path, is less than the amount of conveyance of the sheet by the second folding roller, which is an outer roller of the return conveying path. Effect of the Invention

[0010] According to the present invention, the quality of the folding process can be improved. [Brief description of the drawings]

[0011] [Figure 1] 1 is an external view showing an example of an MFP as an embodiment of an image forming apparatus according to the present invention. [Diagram 2] FIG. 11 is an external view showing another example of an MFP as an embodiment of an image forming apparatus according to the present invention. [Diagram 3] FIG. 2 is a functional block diagram corresponding to an example of an MFP according to the present embodiment. [Figure 4] FIG. 11 is a functional block diagram corresponding to another example of the MFP according to the embodiment. [Diagram 5] 1 is a diagram showing an example of the configuration of an embodiment of a sheet processing apparatus according to the present invention; [Figure 6] FIG. 2 is a diagram showing a hardware configuration of the embodiment. [Figure 7] 11A and 11B are diagrams illustrating one process in a shift discharge mode performed by the binding processing device according to the embodiment. [Figure 8] 11A and 11B are diagrams illustrating one process in a shift discharge mode performed by the binding processing device according to the embodiment. [Figure 9]11A and 11B are diagrams illustrating one process in a shift discharge mode performed by the binding processing device according to the embodiment. [Figure 10] 11A and 11B are diagrams illustrating one process in a shift discharge mode performed by the binding processing device according to the embodiment. [Figure 11] 11A and 11B are diagrams illustrating a process in a binding discharge mode performed by the binding processing device according to the embodiment. [Figure 12] 11A and 11B are diagrams illustrating a process in a binding discharge mode performed by the binding processing device according to the embodiment. [Figure 13] 11A and 11B are diagrams illustrating a process in a binding discharge mode performed by the binding processing device according to the embodiment. [Figure 14] 11A and 11B are diagrams illustrating a process in a binding discharge mode performed by the binding processing device according to the embodiment. [Figure 15] 11A and 11B are diagrams illustrating a process in a binding discharge mode performed by the binding processing device according to the embodiment. [Figure 16] 11A and 11B are diagrams illustrating a process in a binding discharge mode performed by the binding processing device according to the embodiment. [Figure 17] 13A and 13B are diagrams illustrating another example of the configuration of the folding processing unit according to the embodiment. [Figure 18] 1A to 1C are diagrams illustrating a process of Z-folding performed by the binding device according to the embodiment. [Figure 19] 1A to 1C are diagrams illustrating a process of Z-folding performed by the binding device according to the embodiment. [Figure 20] 1A to 1C are diagrams illustrating a process of Z-folding performed by the binding device according to the embodiment. [Figure 21] 1A to 1C are diagrams illustrating a process of Z-folding performed by the binding device according to the embodiment. [Figure 22] 1A to 1C are diagrams illustrating a process of Z-folding performed by the binding device according to the embodiment. [Figure 23] 1A to 1C are diagrams illustrating a process of Z-folding performed by the binding device according to the embodiment. [Figure 24] 1A to 1C are diagrams illustrating a process of Z-folding performed by the binding device according to the embodiment. [Diagram 25] 10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Figure 26]10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Figure 27] 10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Figure 28] 10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Figure 29] 10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Diagram 30] 10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Diagram 31] 10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Diagram 32] 10A to 10C are diagrams illustrating one process of folding in half by the binding processing device according to the embodiment. [Diagram 33] 1A and 1B are diagrams for explaining problems with a conventional binding processing device. [Diagram 34] 1A and 1B are diagrams for explaining problems with a conventional binding processing device. [Diagram 35] 1A and 1B are diagrams for explaining problems with a conventional binding processing device. [Diagram 36] 11A and 11B are diagrams illustrating box creases that occur in a conventional binding processing device. [Figure 37] FIG. 13 is a diagram explaining the cause of box crease. [Figure 38] FIG. 13 is a diagram explaining the cause of box crease. [Figure 39] 1 is a diagram illustrating a first embodiment of a sheet processing apparatus according to the present invention. [Diagram 40] 1 is a diagram illustrating a first embodiment of a sheet processing apparatus according to the present invention. [Diagram 41] 1 is a diagram illustrating a first embodiment of a sheet processing apparatus according to the present invention. [Diagram 42] 5A to 5C are diagrams illustrating the effects of the first embodiment according to the present invention. [Diagram 43] 5A and 5B are diagrams illustrating a second embodiment of a sheet processing apparatus according to the present invention. [Diagram 44] 6A and 6B are diagrams illustrating a sheet processing apparatus according to a third embodiment of the present invention. [Diagram 45]13A and 13B are diagrams illustrating a fourth embodiment of a sheet processing apparatus according to the present invention. [Diagram 46] FIG. 13 is a diagram for explaining an example of the configuration of a fourth embodiment of a sheet processing apparatus according to the present invention. [Figure 47] FIG. 13 is a diagram for explaining an example of the configuration of a fourth embodiment of a sheet processing apparatus according to the present invention. [Figure 48] 13A to 13C are diagrams illustrating a sheet processing apparatus according to a fifth embodiment of the present invention. [Figure 49] 13A and 13B are diagrams for explaining a sixth embodiment of a sheet processing apparatus according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Embodiment of Image Forming Apparatus] First, an MFP1 as an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. Figs. 1 and 2 are external views of the MFP1 according to this embodiment. The MFP1 is a device that has an image forming function for forming an image on a sheet S as a sheet-like medium, and a post-processing function for performing a predetermined sheet process (post-processing) on ​​the sheet S on which the image has been recorded. Note that a specific example of the sheet S is assumed to be "paper" that is generally used for image formation (copying, printing, etc.).

[0013] 1, the MFP 1 mainly includes a device housing 301 and an image forming unit 300 inside the device housing 301. The device housing 301 is a box-shaped member having an internal space for accommodating the components of the MFP 1. The device housing 301 also has an internal space 302 that is accessible from outside the MFP 1. The internal space 302 is a portion that is exposed to the outside by cutting out an outer wall of the device housing 301, and is formed, for example, slightly above the center of the device housing 301 in the up-down direction.

[0014] In the internal space 302, as optional units that add optional functions, a folding processing unit 200 that enables folding processing and a binding processing unit 100 that enables binding processing to bind a plurality of sheets S can be attached. The folding processing unit 200 corresponds to an embodiment of the sheet processing device according to the present invention.

[0015] The image forming unit 300 discharges the sheet S picked up from the sheet storage tray and conveyed to the folding unit 200 and the binding unit 100. The image forming unit 300 may be of an inkjet type that forms an image using ink, or of an electrophotographic type that forms an image using toner. The configuration of the image forming unit 300 is already known, so a detailed description will be omitted.

[0016] The folding unit 200 is attached to an internal space 302 of the MFP 1 downstream of the image forming unit 300 and upstream of the binding unit 100 on a conveyance path (path indicated by a dashed arrow in FIG. 1) of the sheet S from the image forming unit 300 to the binding unit 100. That is, in the example of the MFP 1, the sheet S on which an image is formed by the image forming unit 300 is first handed over to the folding unit 200 where a predetermined folding process is performed, and then handed over to the binding unit 100 where a binding process described later is performed.

[0017] The folding processing unit 200 is configured to be detachable from the MFP 1. When the folding processing unit 200 is removed, the state shown in Fig. 2 is obtained. In this case, the sheet S on which an image is formed by the image forming section 300 is directly delivered to the binding processing unit 100 and subjected to binding processing. In addition, another processing unit that performs any processing on the sheet S may be attached to the position in the internal space 302 from which the folding processing unit 200 was removed.

[0018] [Control configuration of media processing device including image forming device] Next, the control configuration of the MFP 1 including the binding unit 100 will be described with reference to Fig. 3. Fig. 3 is a diagram illustrating an example of the control configuration of the MFP 1 in a state where the folding unit 200 is removed (see Fig. 2).

[0019] In FIG. 3, the transport path of the sheet S (flow of the sheet S) is indicated by dashed arrows, and the path of the communication signal (control signal) (signal flow) is indicated by solid arrows.

[0020] The MFP1 includes a display unit 303 for informing the user of the status of various devices and operation details, an operation unit 304 for the user to perform setting operations such as the mode and the number of copies, and a paper feed unit 305 for stocking sheets S and separating and feeding the sheets one by one. The MFP1 also includes an image creation unit 306 for forming a latent image on a photoconductor, both of which are not shown in Fig. 3, and transferring the image to the sheet S, and a fixing unit 307 for fixing the image transferred to the sheet S. The MFP1 also includes an image formation control unit 308 for controlling the operation of each of the above units.

[0021] In the embodiment of the media processing device, a binding processing unit 100 receives a processing instruction from an image formation control unit 308 of the MFP 1 via a communication line 309 to a binding processing control unit 102, and performs a specified process on a specified sheet S in a binding processing unit 101.

[0022] The image forming control units 308 and the binding process control units 102 connected to each other are connected by a communication line 309, enabling the exchange of information. This enables the exchange of information regarding the operation mode, the sheet size, timing, and the like, enabling the system to operate.

[0023] 4 is a diagram illustrating an example of the control configuration of the MFP 1 in a state in which the folding processing unit 200 is attached (see FIG. 1). In FIG. 4 as well, the transport path of the sheet S (flow of the sheet S) is indicated by a dashed arrow, and the path (flow of the signal) of the communication signal (control signal) is indicated by a solid arrow.

[0024] The MFP1 is similar in that it includes a display unit 303, an operation unit 304, and a paper feed unit 305. It also includes an image forming unit 306 and an image formation control unit 308.

[0025] In the binding processing unit 100 as an embodiment of the media processing device, a processing instruction is sent from the image formation control unit 308 of the MFP1 to the binding processing control unit 102 via a communication line 309, and the binding processing unit 101 performs a specified process on the specified sheets S. The binding processing unit 101 is notified of designation information on the process contents for the sheets S via the folding processing unit 201.

[0026] The image forming control units 308 and the binding process control units 102 connected to each other are connected by a communication line 309, enabling the exchange of information. This enables the exchange of information regarding the operation mode, the sheet size, timing, and the like, enabling the system to operate.

[0027] In the folding processing unit 200, a processing instruction is sent from the image formation control unit 308 of the MFP1 to the binding processing control unit 102 via a communication line 309, and an instruction is sent from the binding processing control unit 102 to the folding processing control unit 202 via a communication line 103. The folding processing control unit 202 controls the folding processing unit 201 to execute the instructed folding processing.

[0028] [Internal configuration of the folding unit 200 and the binding unit 100] 5 is a diagram showing the internal configuration of the folding processing unit 200 and the binding processing unit 100. The folding processing unit 200 and the binding processing unit 100 are each unitized, and an input / output interface for the sheet S can be connected to them. That is, the input interface IN of the folding processing unit 200 is configured to be connectable to the output interface of the image forming unit 300. Also, the input interface of the binding processing unit 100 is configured to be connectable to the output interface of the image forming unit 300 and the output interface OUT of the folding processing unit 200.

[0029] [Internal configuration of the folding unit 200] Folding unit 200 executes folding processing to fold sheet S, on which an image has been formed by image forming section 300, into a predetermined shape (for example, Z-fold, outward tri-fold, or double fold). As shown in Fig. 5, folding unit 200 includes folding unit housing 21, conveying roller pair 22 constituting a conveying section, first folding roller 23, second folding roller 24, third folding roller 25, and guide plate 26 as a guide member.

[0030] The folding unit housing 21 is box-shaped with an internal space for accommodating components of the folding processing unit 200. In addition, a main transport path Ph1 and a return transport path Ph2, which are spaces through which the sheet S passes, are formed in the internal space of the folding unit housing 21. The main transport path Ph1 is a transport path that runs from an input interface IN connected to the image forming section 300 to an output interface OUT connected to the binding processing unit 100. Hereinafter, the direction from the input interface IN toward the output interface OUT on the main transport path Ph1 will be referred to as the "transport direction."

[0031] The return transport path Ph2 is a loop-shaped transport path that branches off from the main transport path Ph1 at a branching position A and merges with the main transport path Ph1 at a merging position B. The merging position B is located upstream of the branching position A in the transport direction and upstream of the transport roller pair 22. The return transport path Ph2 corresponds to a curved transport path having a curvature that transports the sheet S from the branching position A toward the merging position B. The return transport path Ph2 has a gap (transport path gap g) through which the sheet S can pass. The wall surfaces that form this gap are composed of the wall surface on the inner periphery side and the wall surface on the outer periphery side of the curvature. In the following description, they may be referred to as the "inner periphery side wall surface" and the "outer periphery side wall surface" as appropriate.

[0032] The conveying roller pair 22 conveys the sheet S in the conveying direction along the main conveying path Ph1. The conveying roller pair 22 is composed of a drive roller 22a and a driven roller 22b that are disposed opposite each other across the main conveying path Ph1, upstream of the branching position A in the conveying direction and downstream of the joining position B in the conveying direction (i.e., between the branching position A and the joining position B).

[0033] The drive roller 22a and the driven roller 22b are rotatably supported by the folding unit housing 21. The drive roller 22a receives the driving force of the transport motor and rotates in a direction that transports the sheet S in the transport direction (clockwise when facing FIG. 5). The driven roller 22b is disposed opposite the drive roller 22a across the main transport path Ph1, and is driven by the rotation of the drive roller 22a. When the sheet S enters (is sandwiched in) the nip formed by the drive roller 22a and the driven roller 22b, the transport motor is driven to transport the sheet S in the transport direction along the main transport path Ph1.

[0034] The first folding roller 23 is rotatably supported by the folding unit housing 21 at a position facing the main transport path Ph1.

[0035] The second folding roller 24 is rotatably supported in the folding unit housing 21 at a position facing both the main conveying path Ph1 and the return conveying path Ph2 and forming a nip with the first folding roller 23.

[0036] Third folding roller 25 is rotatably supported by folding unit housing 21 at a position facing return conveyance path Ph2 and at a position where third folding roller 25 and second folding roller 24 form a paired nip.

[0037] That is, the first folding roller 23 and the second folding roller 24 are disposed opposite each other across the main conveying path Ph1, downstream in the conveying direction from the branching position A. Furthermore, the second folding roller 24 and the third folding roller 25 are disposed opposite each other across the return conveying path Ph2, between the branching position A and the merging position B.

[0038] The first folding roller 23 is provided with a first drive force transmission mechanism to which a drive force from a drive source that drives the second folding roller 24 is transmitted. The first folding roller 23 receives a drive force supplied by the drive source of the second folding roller 24 via the first drive force transmission mechanism and rotates forward and reverse. The forward rotation of the first folding roller 23 is a rotation in a direction to transport the sheet S on the main transport path Ph1 in the transport direction. The reverse rotation of the first folding roller 23 is a rotation in a direction opposite to the forward rotation.

[0039] The second folding roller 24 is provided with a second drive force transmission mechanism to which a drive force from a drive source is transmitted. The second folding roller 24 rotates forward and reverse by the drive force received from the second drive force transmission mechanism. The forward rotation of the second folding roller 24 is a rotation in a direction to transport the sheet S on the main transport path Ph1 in the transport direction and to transport the sheet S on the return transport path Ph2 from the junction position B toward the branch position A. The reverse rotation of the second folding roller 24 is a rotation in a direction opposite to the forward rotation.

[0040] In addition, the drive source of the second folding roller 24 enables forward rotation, which rotates the first folding roller 23 and the third folding roller 25 forward, and reverse rotation, which rotates the second folding roller 24 in the reverse direction, via a first drive force transmission mechanism that is connected to the second drive force transmission mechanism and the third drive force transmission mechanism.

[0041] The third folding roller 25 is provided with a third drive force transmission mechanism to which a drive force is transmitted from a drive source that drives the second folding roller 24. The third folding roller 25 receives a drive force supplied by a drive source of the second folding motor via the third drive force transmission mechanism, and rotates forward and reverse. The forward rotation of the third folding roller 25 is a rotation in a direction to convey the sheet S on the return conveying path Ph2 from the joining position B toward the branching position A. The reverse rotation of the third folding roller 25 is a rotation in a direction opposite to the forward rotation.

[0042] The guide plate 26 is rotatably supported by the folding unit housing 21 in the vicinity of the branching position A. The guide plate 26 switches between two positions: a "first position" when the sheet S is transported downstream from the junction position B through the branching position A, and a "second position" when the sheet S is transported from the junction position B and then transported from the branching position A toward the return transport path Ph2. The guide plate 26 is arranged in a rotatable state so as to be in either the first position or the second position.

[0043] The first position is a position of the guide plate 26 that allows the sheet S to be transported in the transport direction on the main transport path Ph1 and prevents the sheet S transported in the transport direction on the main transport path Ph1 from entering the return transport path Ph2 through the branch position A. On the other hand, the guide plate 26 in the first position allows the sheet S on the return transport path Ph2 to enter the main transport path Ph1 through the branch position A.

[0044] The second posture is a posture of the guide plate 26 that allows the sheet S to be transported from one of the main transport path Ph1 and the return transport path Ph2 to the other through the branch position A.

[0045] The binding processing unit 100 performs binding processing (post-processing) to bind and bind a plurality of sheets S (hereinafter referred to as a "sheet bundle Sb") on which images have been formed by the image forming section 300. Note that a bundle of a plurality of sheets S will hereinafter be referred to as a "sheet bundle Sb."

[0046] [Internal configuration of binding processing unit 100] In this embodiment, the binding processing unit 100 is described as an example of a post-processing unit that performs sheet processing other than folding, but a specific example of the post-processing unit (post-processing) is not limited to this. As shown in Fig. 5, the binding processing unit 100 includes a binding unit housing 31, a discharge tray 32, a plurality of conveying roller pairs (a pair of receiving conveying rollers 33, a pair of relay conveying rollers 34, a pair of shift conveying rollers 35 arranged in an internal tray 37, and a pair of discharge conveying rollers 36), an internal tray 37, a tapping roller 38, a return roller 39, end fences 40 (40L, 40R), side fences 41 (41L, 41R) (see Fig. 14(b)), and a binding processing unit 42.

[0047] The binding unit housing 31 is box-shaped with an internal space for accommodating components of the binding processing unit 100. A conveying path Ph3, which is a space through which the sheets S pass, is formed in the internal space of the binding unit housing 31. The discharge tray 32 is supported on the outer surface of the binding unit housing 31. The discharge tray 32 supports the sheets S or the sheet stack Sb conveyed by the receiving conveying roller pair 33, the relay conveying roller pair 34, the shift conveying roller pair 35, and the discharge conveying roller pair 36.

[0048] The receiving conveying roller pair 33, the relay conveying roller pair 34, the shift conveying roller pair 35, and the discharge conveying roller pair 36 are disposed at positions spaced apart from each other at a predetermined interval along the conveying path Ph3. That is, the sheet S received in the binding processing unit 100 is conveyed along the conveying path Ph3 by the receiving conveying roller pair 33, the relay conveying roller pair 34, the shift conveying roller pair 35, and the discharge conveying roller pair 36.

[0049] The basic configurations of the receiving conveying roller pair 33, the relay conveying roller pair 34, the shift conveying roller pair 35, and the discharge conveying roller pair 36 are the same as those of the conveying roller pair 22 of the folding processing unit 200. However, the discharge conveying roller pair 36 is composed of a discharge driving roller 36a and a discharge driven roller 36b that can be brought into contact with and separated from the discharge driving roller 36a. The shift conveying roller pair 35 may be configured to be slidable in the width direction in order to realize a sorting process in which the sheet S is shifted in the width direction and discharged to the discharge tray 32.

[0050] The internal tray 37 temporarily supports (stacks) a plurality of sheets S that are transported in sequence along the transport path Ph3. The tapping roller 38 is supported at the tip of a rotating arm above the internal tray 37. The tapping roller 38 supplies the sheet S sandwiched between the pair of discharge transport rollers 36 to the internal tray 37 as the rotating arm rotates. The return roller 39 rotates in contact with the upper surface of the sheet S supported by the internal tray 37, thereby guiding the sheet S toward the end fences 40 (40L, 40R).

[0051] The end fences 40 (40L, 40R) come into contact with the downstream end of the sheet S supported by the internal tray 37 in the conveying direction to align the position of the sheet S in the conveying direction. The side fences 41 (41L, 41R) come into contact with both ends of the sheet S supported by the internal tray 37 in the width direction to align the position of the sheet S in the width direction. The binding processing unit 42 performs a binding process to bind the sheet stack Sb supported by the internal tray 37. The binding process performed by the binding processing unit 42 may be a staple binding process in which a staple is inserted through the sheet stack Sb to bind the sheets, or a pressure binding process in which the sheet stack Sb is pressurized and deformed to bind the sheets. The binding processing unit 100 may include a staple binding processing unit that performs a staple binding process and a pressure binding processing unit that performs a pressure binding process, which are operable independently of each other at positions spaced apart in the width direction.

[0052] [MFP1 hardware configuration] Next, the hardware configuration of the binding processing unit 100 included in the MFP 1 will be described with reference to Fig. 6. Note that the description of the hardware configuration including the punching processing unit 400 will be omitted. As shown in Fig. 5, the binding processing unit 100 includes a CPU 110 as a controller, and is connected to a plurality of motors that serve as power sources for the operation of each mechanism via an I / F (interface) 120. The CPU 110 is a calculation means, and controls the operation of the entire binding processing unit 100.

[0053] The CPU 110 in the binding processing unit 100 is connected to the image formation control unit 308 of the MFP 1 via the I / F 120, and controls the binding processing unit 100 in response to a processing signal from the MFP 1. The binding processing unit 100 is also an optional device, and therefore has a detachable hardware configuration.

[0054] The I / F section that connects the image forming section 300 and the binding processing unit 100 is configured to be detachable in hardware, for example, by a relay connector or a drawer connector. The I / F section that connects the punching processing unit 400 and the image forming section 300 is also configured in the same way.

[0055] An encoder capable of detecting the drive amount of each motor in terms of the number of pulses is attached to a drive motor that drives a plurality of pairs of conveying rollers for performing the binding process in the binding process unit 100. Therefore, it is possible to drive and stop the pairs of conveying rollers at a position of a specific drive amount starting from a specific timing, and it is configured to realize control to convey the sheet S a specific amount in a specific direction.

[0056] In addition, the encoder pulses are measured based on the timing when the sensor on the conveying path is turned ON or OFF, and the drive amount of each motor can be calculated based on the encoder pulses. Then, the position of the edge of the conveyed sheet S can be detected based on the calculated drive amount.

[0057] As illustrated in FIG. 5, the binding processing control unit 102, which is the control unit of the binding processing unit 100, is connected to a CPU 110 via an I / F 120 with a conveying motor 151, a discharge motor 152, a staple movement motor 153, a conveying sensor 154, a discharge sensor 155, and a staple movement HP sensor 156.

[0058] In addition, a controller 202 of the folding unit 200 is connected to the CPU 110 via an I / F 121 to which a folding motor 162 , an entrance sensor 163 , and a folding sensor 164 are connected.

[0059] In addition, when a punch processing main unit that performs punching processing on sheet S is connected as an option, the control unit is connected to the CPU 110 via the I / F 122 with a punch motor 157, a punch movement motor 158, a pre-punch motor 159, a cover opening / closing sensor 160, and a punch unit HP sensor 161.

[0060] [First Operation Example of the Binding Processing Unit 100] Next, a description will be given of a first operation example in the binding processing unit 100. First, a description will be given of the movement of the sheet S when a shift discharge mode in which the sheet S is discharged while shifting it in the width direction of the conveying direction is executed in the binding processing unit 100, with reference to Figs. 7 to 10.

[0061] First, as shown in FIG. 7, the paper conveyed from the image forming section 300 is received in the binding processing unit 100 and conveyed by the receiving conveying roller pair 33 along the conveying path Ph3.

[0062] Next, as shown in Fig. 8(a), the discharge driven roller 36b of the discharge conveying roller pair 36 is positioned in a nip pressure release state, and conveyance is continued until the trailing end of the sheet S in the conveying direction passes through the relay conveying roller pair 34. Then, as shown in Fig. 8(b), the sheet S is conveyed while moving the shift conveying roller pair 35 in a direction perpendicular to the conveying direction of the sheet S (width direction), so that the sheet S can be conveyed while shifting in the width direction. In the example of Fig. 8(b), when viewed from the front of the binding processing unit 100 (Fig. 5), the sheet S is moved from the center of the conveying path Ph3 to the back side.

[0063] The shift conveying roller pair 35 is not limited to moving toward the rear as described above, but can also move in the opposite direction, from the center of the conveying path Ph3 in the binding processing unit 100 to the front. When multiple sheets S are continuously conveyed, the presence or absence of movement (shift) for each sheet and the movement direction may be switched. The movement direction may be switched for each sheet S constituting the sheet bundle Sb. The process of discharging the sheets to the discharge tray 32 after being moved (shifted) in the conveying direction by the shift conveying roller pair 35 may be referred to as a sorting process.

[0064] Next, at the timing when the shifting of the sheet S is completed, the discharge driven roller 36b of the discharge conveying roller pair 36 is moved to the nip position as shown in Fig. 8. Then, the sheet S is conveyed toward the discharge tray 32 by the discharge conveying roller pair 36.

[0065] Through the above series of operations, the sheet S is discharged onto the discharge tray 32, as illustrated in Fig. 10. In the above description, the sheet S is taken as an example of paper. However, as already described, the folding unit 200 may be present upstream of the binding unit 100. Therefore, the binding unit 100 can also transport and discharge the sheet S that has been folded in the folding unit 200 as described above.

[0066] [Second Operation Example of the Binding Processing Unit 100] Next, a description will be given of a second operation example of the binding processing unit 100. First, in the binding processing unit 100, a description will be given of the movement of the sheets S when a binding discharge mode is executed in which a plurality of sheets S are bound, the sheets are bound, and the sheet bundle Sb is discharged, with reference to FIGS.

[0067] As in the shift transport mode already described, first, as shown in FIG. 11, the paper transported from the image forming section 300 is received into the binding processing unit 100 and transported along the transport path Ph3 by the receiving transport roller pair 33.

[0068] 12, the discharge driven roller 36b of the discharge conveying roller pair 36 is positioned in a nip pressure release state, and the sheet S is conveyed toward the internal tray 37 without being shift-conveyed by the shift conveying roller pair 35.

[0069] 13, in a state where the sheet S is conveyed to the internal tray 37 by the shift conveying roller pair 35, the tapping roller 38 rotates to tap the sheet S from the conveying path Ph3 toward the internal tray 37, thereby moving the position of the sheet S. In addition, the operation of the tapping roller 38 causes the sheet S to be conveyed toward the end fence 40. This conveyance is called switchback conveyance.

[0070] 14(a), the sheet S is switchback-conveyed toward the end fence 40 by the action of the striking roller 38 and the return roller 39. After hitting the end fence 40, the sheet S is sandwiched between the side fences 41, so that the widthwise ends of the sheet S are aligned, as shown in FIG.

[0071] 11 to 14 are repeated, so that a predetermined number of sheets S are stacked on the internal tray 37. With the number of sheets S to form the sheet bundle Sb stacked, the binding processing unit 42 is driven to bind the sheet bundle Sb supported by the internal tray 37. Thereafter, as shown in FIG. 15, the binding processing unit 100 clamps the sheet bundle Sb between the discharge drive roller 36a and the discharge driven roller 36b. Then, the binding processing unit 100 discharges the sheet bundle Sb to the discharge tray 32 by rotating the discharge conveyor roller pair 36 and the return roller 39 forward.

[0072] Through the above series of operations, the sheet bundle Sb is discharged onto the discharge tray 32 as shown in Fig. 16. In the above description, the sheets S constituting the sheet bundle Sb are taken as paper sheets. However, as already described, a folding processing unit 200 may be present upstream of the binding processing unit 100. Therefore, the binding processing unit 100 can also form a sheet bundle Sb from the sheets S that have been folded in the folding processing unit 200, and transport and discharge the sheet bundle Sb as described above.

[0073] [Another example of the configuration of the folding processing unit 200] As illustrated in Fig. 5, the folding unit 200 is configured to perform folding processing using three folding rollers (first folding roller 23, second folding roller 24, and third folding roller 25), but may be configured to perform folding processing using four folding rollers (first folding roller 23, second folding roller 24, third folding roller 25, and fourth folding roller 29) as illustrated in Fig. 17. The following will be described based on the configuration illustrated in Fig. 5.

[0074] [First Operation Example of Folding Unit 200] Next, the flow of operations when performing "Z-folding" in the folding processing unit 200 will be described. First, as shown in Fig. 18, when the sheet S is transported from an upstream device (image forming section 300), the sheet S is received by the transport roller pair 22. Then, the sheet S is transported from the upstream side to the downstream side of the main transport path Ph1 by the transport roller pair 22, the first folding roller 23, and the second folding roller 24. At this time, the guide plate 26 is in a first position for guiding the sheet S to the nip between the first folding roller 23 and the second folding roller 24.

[0075] 19, the conveying roller pair 22 rotates forward to convey the sheet S upstream of the branch position A in the downstream direction, while the first folding roller 23 and the second folding roller 24 rotate in the reverse direction. As a result, the portion of the sheet S that has passed the nip between the first folding roller 23 and the second folding roller 24 on the downstream side is returned to the branch position A (upstream side). At this time, the guide plate 26 is in the second position. As a result, the bend of the sheet S is formed toward the nip between the second folding roller 24 and the third folding roller 25.

[0076] 20, the pair of conveying rollers 22 rotates forward, and both the portion of the sheet S that has passed the branch position A and the portion of the sheet S that has not passed the branch position A are guided to the nip between the second folding roller 24 and the third folding roller 25, and the first folding process is performed. At this time, the guide plate 26 remains in the second position. The second folding roller 24 and the third folding roller 25 are rollers used only for conveying the folded sheet S.

[0077] 21, the first folding roller 23 and the second folding roller 24 are rotated in the reverse direction, and the pair of conveying rollers 22 continues to rotate in the forward direction to convey the sheet S to the return conveying path Ph2 until the leading edge of the sheet S passes through the nip between the first folding roller 23 and the second folding roller 24. At this time, the guide plate 26 remains in the second position.

[0078] 22, the sheet S is no longer in the nip between the first folding roller 23 and the second folding roller 24, and the sheet S is conveyed downstream by the conveying roller pair 22. At this time, the guide plate 26 is returned to the first position, so that the portion of the sheet S upstream of the branch position A is directed toward the nip between the first folding roller 23 and the second folding roller 24.

[0079] 23, the sheet S continues to be conveyed in the normal direction to be conveyed in the normal direction toward the binding processing unit 100. At this time, the guide plate 26 returns to the position where the sheet S is guided to the nip between the first folding roller 23 and the second folding roller 24.

[0080] 24, the Z-folded sheet S is transported to a transport path Ph3 in the binding processing unit 100. At this time, the guide plate 26 is in a position to guide the sheet to the nip between the first folding roller 23 and the second folding roller 24. The subsequent operations and processing in the binding processing unit 100 are as already described.

[0081] [Second Operation Example of Folding Unit 200] Next, the flow of operations when "folding in two" is performed in the folding processing unit 200 will be described. First, as shown in Fig. 25, which is similar to Fig. 18, when the sheet S is transported from an upstream device (image forming section 300), the sheet S is received by the transport roller pair 22. Then, the sheet S is transported from the upstream side to the downstream side of the main transport path Ph1 by the transport roller pair 22, the first folding roller 23, and the second folding roller 24. At this time, the guide plate 26 is in a position to guide the sheet to the nip between the first folding roller 23 and the second folding roller 24.

[0082] 26, which is similar to FIG. 19, the first folding roller 23 and the second folding roller 24 are rotated in the reverse direction while the conveying roller pair 22 continues to rotate in the forward direction. Then, a flexure is formed in the sheet S between the conveying roller pair 22 and the first folding roller 23. At this time, the guide plate 26 is retracted and is in a position where the flexure of the sheet can be guided to the nip between the second folding roller 24 and the third folding roller 25.

[0083] Next, as shown in Fig. 27, which is similar to Fig. 19, the deflection of sheet S formed by the forward rotation of conveying roller pair 22 and the reverse rotation of first folding roller 23 and second folding roller 24 is guided to the nip between second folding roller 24 and third folding roller 25, and folding processing is performed. Guide plate 26 is kept in the second position. The fold formed at this time is referred to as "proper fold f".

[0084] 28, the sheet S folded by the forward rotation of the conveying roller pair 22 and the reverse rotation of the first folding roller 23 and the second folding roller 24 is conveyed in the return conveying path Ph2 toward the nip direction of the conveying roller pair 22. At this time, the guide plate 26 is kept in the second position.

[0085] 29, the sheet S is conveyed along the return conveying path Ph2 toward the nip of the conveying roller pair 22, and returned to the joining position B. At this time, the guide plate 26 is kept in the second posture.

[0086] 30, at the timing when the rear end of the sheet S leaves the nip between the second folding roller 24 and the third folding roller 25, the second folding roller 24 and the third folding roller 25 are returned from the reverse rotation to the forward rotation. Then, the guide plate 26 is returned from the second position to the first position. As a result, the sheet S conveyed by the conveying roller pair 22 (the sheet S that has been folded in half) is conveyed downstream in the conveying direction.

[0087] Subsequently, as shown in FIG. 31, the sheet S that has returned to the joining position B is received in the nip of the conveying roller pair 22 and conveyed toward the binding processing unit 100.

[0088] 32, the sheet S that has been folded in half is transported to a transport path Ph3 in the binding processing unit 100. At this time, the guide plate 26 is in a position to guide the sheet to the nip between the first folding roller 23 and the second folding roller 24. The subsequent operations and processing in the binding processing unit 100 are as already described.

[0089] [Additional explanation regarding the broken box] Next, a description will be given of "box fold" that can be prevented in the folding unit 200 according to this embodiment with reference to the drawings. An example will be taken of a case where "folding in two" is performed as in the series of folding processes shown in Figs. 25 to 32. In the folding unit 200, when the sheet S (which has been folded in two) passes through the return conveying path Ph2 and returns to the joining position B, and passes through the conveying roller pair 22, it is sufficient that the fold (legitimate fold f) is at the forefront when entering the nip of the conveying roller pair 22.

[0090] Fig. 33 illustrates a state in which a sheet S, which has been folded in half to form a proper fold f, is being conveyed along the return conveying path Ph2 having a curve. As shown in Fig. 33, the proper fold f of the sheet S conveyed along the return conveying path Ph2 starts to deviate from the leading edge in the conveying direction. This is because the relative conveying distances of one side and the other side of the sheet S separated by the proper fold f become different before returning to the joining position B due to the conveying path gap g and curvature of the return conveying path Ph2.

[0091] 34, the sheet S returns to the junction position B with the position of the proper fold f shifted from the leading edge in the conveying direction, and then the sheet S enters the nip of the conveying roller pair 22. In this case, the leading edge in the conveying direction is no longer the proper fold f, and the vicinity of the proper fold f becomes the leading edge in the conveying direction. Then, one side of the sheet S near the proper fold f enters the nip of the conveying roller pair 22 while remaining bulging in the nip direction.

[0092] As a result, as shown in FIG. 35, a crease is formed when a portion that is not a legitimate crease f passes through the nip of the conveying roller pair 22. The second crease formed in this manner is referred to as an "illegal crease fe." In this manner, an illegal crease fe that is different from the legitimate crease f that was originally intended to be formed is formed on one side of the sheet S, and the originally formed legitimate crease f and the illegal crease fe are formed adjacent to each other, resulting in a state in which a portion of the sheet S is folded twice. This type of folding state is referred to as a "box crease."

[0093] Figure 36 is an enlarged view of the folded box. A folded box occurs when only a valid fold line f should be formed, but an invalid fold line fe is formed in the vicinity of the valid fold line f.

[0094] It should be noted that the return transport path Ph2 illustrated in FIGS. 33 to 36 is expressed as an arc shape for the sake of simplicity.

[0095] 33 to 36, when the sheet S is conveyed along the return conveying path Ph2, the sheet S is conveyed along the inner periphery of the curvature of the return conveying path Ph2, and the sheet S is conveyed along the outer periphery of the curvature of the return conveying path Ph2. The inner portion is depicted with a solid line, and the outer portion is depicted with a dashed line.

[0096] When the folded sheet S is first conveyed along the return conveying path Ph2, the inner and outer pieces are in close contact with each other except for the vicinity of the proper fold f. Therefore, the difference in conveying distance due to the thickness (thickness dimension) of the sheet S has almost no effect. However, in the vicinity of the proper fold f, the inner and outer pieces are not in close contact with each other, so the difference in conveying distance between the inner and outer pieces has an effect. This is mainly because, as illustrated in FIG. 31 etc., the conveying distance of the inner piece is shorter than that of the outer piece, so the relative conveying direction length (length) of the sheet S is longer for the inner piece than for the outer piece. This results in the proper fold f facing the outer periphery of the return conveying path Ph2.

[0097] 34 follows the state shown in Fig. 33, and the sheet S enters the nip of the conveying roller pair 22 with the proper fold f facing outward. As a result, as shown in Fig. 35, an improper fold fe is formed at a position different from the position of the proper fold f formed by the second folding roller 24 and the third folding roller 25.

[0098] Fig. 34 is an enlarged view of the vicinity of proper fold f of sheet S after sheet S has passed through conveying roller pair 22 as shown in Fig. 33. As illustrated in Fig. 34, due to the influence of the curvature of return conveying path Ph2, a difference occurs in the conveying distance between the inner piece and the outer piece, and the inner piece becomes relatively longer than the outer piece, so that an improper fold fe is formed in addition to proper fold f, and the sheet is folded into a box shape. Box folding is a factor that reduces the quality of the folding process.

[0099] Here, we will explain the difference in the length of the return transport path Ph2 that causes the box to break. The following explanation is based on the difference in the apparent length in the transport direction (the length dimension of each piece of the sheet S) that occurs between the inner and outer pieces of the sheet S due to the difference in the transport path length. Hereinafter, the difference in the relative lengths between the pieces will be referred to as the "sheet length difference."

[0100] It should be noted that the return conveying path Ph2 already exemplified herein is in fact partially straight and is not formed solely of arcs, but since there is no curvature in the straight portions and no difference in sheet length occurs, this can be ignored in the consideration.

[0101] Assuming that a circle corresponds to the curvature of the arc portion of the return transport path Ph2, the radius of the imaginary circle is R [mm], and the arc of the return transport path Ph2 is 270°. The thickness (thickness dimension) of the sheet S is "sheet thickness t [mm]". The dimension of the path gap for the sheet S to pass through the return transport path Ph2 is "transport path gap g [mm]".

[0102] In this case, the difference in sheet length between the inner and outer sheets when conveyed through the return conveying path Ph2 is determined by "2πR×270 / 360-2π(Rt)×270 / 360", which can be simplified to "2πt×270 / 360".

[0103] If the sheet thickness t is 0.1 mm, the sheet length difference between the inner and outer pieces of the sheet S is approximately 0.4713. The larger the sheet thickness t, the larger the sheet length difference.

[0104] As shown in Fig. 36, based on the above, assuming that the return path Ph2 has an arc angle of 30° at R, the sheet length difference other than the contact part between the inner and outer pieces is defined as "2πg x 3 / 360". If the path gap g = 5 mm, the sheet length difference is approximately 2.62 mm. If the sheet length difference due to the sheet thickness t is added to this, a sheet length difference of approximately 3.1 mm occurs when the sheet S is transported along the return path Ph2 and returns to the joining position B. Note that the larger the value of the path gap g, the larger the sheet length difference.

[0105] As described above, when the return conveying path Ph2 is used to convey the sheet with the proper fold f formed by the second folding roller 24 and the third folding roller 25 at the front, the position of the proper fold f is shifted from the nip of the conveying roller pair 22 due to the influence of the curvature of the return conveying path Ph2. This shift is due to the influence of the sheet thickness t and the conveying path gap g, and is expected to be on the order of several mm.

[0106] As a result, the box crease described above occurs. Note that the values ​​used in the calculation of the sheet length difference above are hypothetical. In addition, since the return conveying path Ph2 has multiple curvatures, some variation is expected when the sheet length difference is calculated based on the above formula.

[0107] [First embodiment] Next, a first embodiment of a sheet processing apparatus according to the present invention will be described. Figures 39 to 41 are diagrams illustrating the configuration and operation of a folding processing unit 200 according to this embodiment. When third folding roller 25 is also driven to rotate by the driving source that rotates second folding roller 24 according to this embodiment, if the gears connecting them have the same number of teeth, second folding roller 24 and third folding roller 25 will rotate at the same speed.

[0108] In this embodiment, it is assumed that the second folding roller 24 and the third folding roller 25 rotate at the same speed. In this case, if the roller diameter of the second folding roller 24 as the outer peripheral roller is "Ra" and the roller diameter of the third folding roller 25 as the inner peripheral roller is "Rb", then if Ra=Rb, the conveyance amount of the outer piece conveyed by the second folding roller 24 and the inner piece conveyed by the third folding roller 25 will be the same. In this case, as already described, it is not possible to create a difference in conveyance amount that offsets the difference in sheet length when conveyed along the return conveyance path Ph2, and box folds will occur.

[0109] Therefore, in this embodiment, the roller diameter "Ra" of the second folding roller 24 is made larger than the roller diameter "Rb" of the third folding roller 25. In other words, the roller diameters of the second folding roller 24 and the third folding roller 25 are set so that the relationship is "Ra>Rb". This makes the amount of conveyance of the inner piece by the third folding roller 25 smaller than the amount of conveyance of the outer piece by the second folding roller 24. As a result, as illustrated in FIGS. 39 to 41, when the sheet S reaches the nip of the conveying roller pair 22, the nip position and the position of the proper fold f are aligned.

[0110] If the nip position and the position of the correct fold f are aligned, the sheet S (sheet S that has been folded) that has passed through the nip of the conveying roller pair 22 can be folded without causing box creases, as illustrated in Figure 42.

[0111] Assume that Ra=φ20 [mm] and Rb=φ19.8 [mm]. In this case, the circumferential length of the second folding roller 24 is “π×20=62.832 [mm]”. Also, the circumferential length of the third folding roller 25 is “π×19.8=62.204 [mm]”. The sheet length difference can be absorbed by the difference in circumferential length due to the difference in roller diameter. Since the conveyance amount per rotation is determined by the roller diameter, the roller diameters of the second folding roller 24 and the third folding roller 25 may be determined based on the conveyance amount (required conveyance amount) by the conveyance portion having the curvature of the return conveyance path Ph2.

[0112] In addition, when the sheet thickness t and the conveyance path gap g are large and the sheet length difference is large, the difference between "Ra", which is the roller diameter of the second folding roller 24, and "Rb", which is the roller diameter of the third folding roller 25, may be increased to increase the difference in the conveyance amounts of the respective sheets.

[0113] [Second Embodiment] Next, a second embodiment of the sheet processing apparatus according to the present invention will be described. FIG. 43 is a diagram for explaining the configuration and operation of the folding processing unit 200a according to the present embodiment. When the third folding roller 25 is also rotationally driven by a drive source that rotates the second folding roller 24 according to the present embodiment, if the diameters of the second folding roller 24 and the third folding roller 25 are the same size, there will be no difference in the conveyance amount.

[0114] Suppose the number of teeth of the second folding gear, which is a gear for transmitting the driving force from the drive source to the second folding roller 24, is "number G2", and the number of teeth of the third folding gear, which is a gear for transmitting the driving force to the third folding roller 25, is "G3". When gears with G2 = G3 are used, the conveyance amounts of the outer piece conveyed by the second folding roller 24 and the inner piece conveyed by the third folding roller 25 will be the same. In this case, as already explained, it is not possible to create a difference in the conveyance amount that cancels out the sheet length difference when conveyed through the reflux conveyance path Ph2, and box folding will occur.

[0115] Therefore, in the present embodiment, "G2", which is the number of teeth of the second folding gear that drives the second folding roller 24, is made smaller than "G3", which is the number of teeth of the third folding gear that drives the third folding roller 25. That is, the number of teeth of the gears that transmit the driving force to the second folding roller 24 and the third folding roller 25 is set so as to have the relationship of "G2 < G3".

[0116] As a result, the conveyance amount of the inner piece by the third folding roller 25 is made less than the conveyance amount of the outer piece by the second folding roller 24. As a result, as illustrated in FIG. 43, when the sheet S reaches the nip of the conveyance roller pair 22, the position of the nip and the position of the proper fold line f will match.

[0117] If the nip position and the position of the proper fold f are aligned, the sheet S that has passed through the nip of the conveying roller pair 22 (the sheet S that has been subjected to the folding process) will not be bent as shown in FIG.

[0118] Assume that Ra=φ20 [mm] and Rb=φ20 [mm]. Also, G2=60 and G3=61. The amount of transport of the outer piece per rotation by the second folding roller 24 is "π×20×60 / 60=62.832 [mm]". Also, the amount of transport of the inner piece per rotation by the third folding roller 25 is "π×20×60 / 61=61.802 [mm]". The difference in the transport amount due to the difference in the number of teeth can absorb the difference in sheet length.

[0119] Since the conveying amount per rotation is determined by the roller diameter, the reduction ratio can be determined based on the conveying amount (required conveying amount) by the conveying portion having a curvature of the return conveying path Ph2, by the number of gear teeth "G2" for rotating the second folding roller 24 and the number of gear teeth "G3" for rotating the third folding roller 25.

[0120] When the sheet thickness t and the conveying path gap g are large and the difference in sheet length is large, the difference between G2 and G3 (difference in the number of teeth) may be increased to increase the difference in the conveying amount.

[0121] [Third embodiment] Next, a second embodiment of the sheet processing apparatus according to the present invention will be described. Fig. 44 is a diagram illustrating the configuration and operation of a folding processing unit 200b according to this embodiment. The folding processing unit 200b includes a pair of intermediate conveying rollers (a first return intermediate conveying roller 27 and a second return intermediate conveying roller 28) on the return conveying path Ph2.

[0122] Return relay transport first roller 27 constituting the relay transport section is a roller for transporting sheet S, which has passed through the nip between second folding roller 24 and third folding roller 25, toward joining position B by the nip with return relay transport second roller 28, and has a peripheral surface formed of an elastic body such as rubber. Return relay transport first roller 27 receives driving force from a drive source via a gear and rotates in the forward or reverse direction.

[0123] Return relay transport second roller 28, which also constitutes the relay transport section, is a roller for transporting sheet S, which has passed through the nip between second folding roller 24 and third folding roller 25, toward joining position B by the nip with return relay transport first roller 27, and has a peripheral surface formed of an elastic body such as rubber. Return relay transport second roller 28 also receives a driving force from a driving source via a gear and rotates in the forward or reverse direction.

[0124] By applying the same design to return relay conveyance first roller 27 and return relay conveyance second roller 28 as to second folding roller 24 and third folding roller 25 according to the first embodiment, the sheet can be conveyed so as to absorb the difference in sheet length. In this case, the roller diameter or the number of gear teeth is set for return relay conveyance first roller 27 as for third folding roller 25. Also, the roller diameter or the number of gear teeth is set for return relay conveyance second roller 28 as for second folding roller 24.

[0125] [Fourth embodiment] As already described in the first to third embodiments, when a difference in roller diameter or rotation amount (reduction ratio) is used to absorb the difference in sheet length that occurs when a sheet S with a valid crease f formed thereon is transported through the return transport path Ph2, there may be a concern about wear between the rollers.

[0126] In other words, if the second folding roller 24 and the third folding roller 25 continue to rotate without nipping the sheet S, the rollers with different rotation speeds will constantly be in contact with each other and rotate, causing the roller surfaces to rub against each other, resulting in slight wear.

[0127] Therefore, as shown in FIG. 45, the folding processing unit 200c according to this embodiment is provided with a roller contact / separation mechanism 210 that combines a separation mechanism that separates the nips and a contact mechanism that brings the nips into contact when the sheet S is not being transported, taking into consideration the durability of the folding rollers.

[0128] 46 is a diagram for explaining the roller contact / separation mechanism 210 included in the folding processing unit 200c. As shown in FIG. 46, the roller contact / separation mechanism 210 includes a third folding roller bearing 419, a link 420, an eccentric cam 421, and a cam shaft 422.

[0129] Third folding roller bearing 419 is a bearing provided on the roller shaft of third folding roller 25. It slides idly on the roller shaft of third folding roller 25.

[0130] The link 420 is a link (connecting member) fitted to the third folding roller bearing 419 and the eccentric cam 421 so as to slide idly between them.

[0131] The eccentric cam 421 rotates to drive the link 420, and the eccentricity causes the third folding roller 25 to move away from the second folding roller 24.

[0132] The cam shaft 422 is a rotation shaft of the eccentric cam 421 .

[0133] As shown in Fig. 47(a), when roller contact / separation mechanism 210 rotates eccentric cam 421 around cam shaft 422, the eccentric cam pulls link 420 in the rotation direction as shown in Fig. 47(b). This operation of link 420 moves third folding roller 25 in a direction away from second folding roller 24.

[0134] The roller contact / separation mechanism 210 may be provided on either the return relay transport first roller 27 or the return relay transport second roller 28 described in the third embodiment.

[0135] [Fifth embodiment] Next, a fifth embodiment of the sheet processing apparatus according to the present invention will be described. Fig. 48 is a diagram illustrating the configuration and operation of a folding processing unit 200d according to this embodiment. The folding processing unit 200d includes a driving member that drives the first folding roller 23, the second folding roller 24, and the third folding roller 25 separately. This configuration realizes conveyance that can absorb differences in sheet length.

[0136] 48, folding processing unit 200e includes, in addition to folding processing unit 200 already described, a first folding drive gear 412a, a second folding drive gear 413a, and a third folding drive gear 414a as driving members. First folding drive gear 412a is a drive gear that transmits the drive source of first folding roller 23. Second folding drive gear 413a is a drive gear that transmits the drive source of second folding roller 24. Third folding drive gear 414a is a drive gear that transmits the drive source of third folding roller 25.

[0137] The folding unit 200 further includes a first idler gear 423 that connects the drive gears of the first folding roller 23 and the second folding roller 24 , and a second idler gear 424 that connects the drive gears of the first folding roller 23 and the second folding roller 24 .

[0138] The first folding roller 23 and the second folding roller 24 are connected by a drive gear and driven by a drive source DA. The first folding roller 23 and the second folding roller 24 need to be connected by gears so that their rotation directions are opposite to each other in order to transport the paper.

[0139] The third folding roller 25 is driven by a driving source DB, and the third folding roller 25 is driven by a different source of drive than the first folding roller 23 and the second folding roller 24 .

[0140] The second folding roller 24 and the third folding roller 25 also need to rotate in the opposite direction to transport the sheet S, and since they have separate drive sources, the rotation direction can be controlled by the drive source.

[0141] In the second and third embodiments, the second folding roller 24 and the third folding roller 25 are assumed to be driven in the same manner. Therefore, if a difference in the conveying amount is created by the roller diameter or reduction ratio, there is a concern that the rollers may rub against each other and wear out when rotating without nipping the sheet S.

[0142] In the folding processing unit 200d according to the fifth embodiment, the second folding roller 24 and the third folding roller 25 are driven separately, thereby making a difference in the transport amount when transporting the sheet S, and maintaining the same transport amount when not transporting the sheet S, thereby eliminating concerns about wear.

[0143] Here, second folding roller 24 is a driving source DA, and third folding roller 25 is a driving source DB. When conveying sheet S, the relationship between the rotation amount of driving source DA and the rotation amount of driving source DB is set to be rotation amount of driving source DA>rotation amount of driving source DB, thereby reducing the conveying distance of third folding roller 25 and making the nip position and the fold position match when the fold reaches the nip of conveying roller pair 22.

[0144] When the sheet S is not being transported, the rotation speed of the drive source DA is set to be equal to the rotation speed of the drive source DB, so that wear due to rubbing between the rollers does not occur. Alternatively, when the sheet S is not being transported, no current is passed through the drive source DB, so that the drive source DB becomes a driven roller, and wear can be prevented by rotating together with the drive source DA.

[0145] [Sixth embodiment] Next, a sixth embodiment of the sheet processing apparatus according to the present invention will be described. Fig. 49 is a diagram for explaining the configuration and operation of the folding processing unit 200e according to this embodiment. The folding rollers described in the first to fifth embodiments were assumed to be made of the same material, but the material of the third folding roller 25e according to this embodiment is made of a different material from that of the second folding roller 24, thereby providing a difference in slipperiness. This makes it possible to absorb differences in sheet length.

[0146] If the surface friction coefficient of the surface material of the second folding roller 24 is FA and the surface friction coefficient of the surface material of the third folding roller 25e is FB, when FA=FB, there is no difference in the conveying amount, so box folding occurs due to the difference in sheet length on the turning path. On the other hand, when FA>FB, the third folding roller 25e is more likely to slip because a higher surface friction coefficient makes it harder to slip and a lower surface friction coefficient makes it easier to slip. As a result, the actual conveying distance is reduced, so when the proper fold f reaches the nip of the conveying roller pair 22, the nip position and the fold position are made closer to each other. In this case, there is no difference in the amount of rotation of the rollers, so there is no wear, and no separation mechanism or separate drive is required.

[0147] In any of the first to sixth embodiments described above, when folding the sheet S using the return conveying path Ph2, the conveying amount of the sheet S by the rollers arranged on the inner circumference side and the rollers arranged on the outer circumference side of the curved conveying path is not set to the same amount but is adjustable. This makes it possible for the proper fold f formed by the folding process to be at the beginning of the conveying process with respect to the nip of the roller pair in the conveying path. This makes it possible to prevent box creases and improve the quality of the folding process.

[0148] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims.

[0149] The contents of the present invention are, for example, as follows. <1> a conveying section that conveys the sheet along a main conveying path; a first folding roller and a second folding roller disposed opposite each other across the main conveying path; a return conveying path having a curvature that branches off from the main conveying path at a branching position upstream of the first folding roller in a conveying direction of the sheet and joins the main conveying path at a joining position upstream of the branching position in the conveying direction; a third folding roller disposed at a position opposite to the second folding roller across the return conveying path; Equipped with when the sheet is conveyed to the return conveying path, a conveying amount of the sheet by the third folding roller, which is an inner peripheral side roller of the return conveying path, is smaller than a conveying amount of the sheet by the second folding roller, which is an outer peripheral side roller of the return conveying path. The sheet processing apparatus is characterized in that <2> a relay conveying section that conveys the sheet from the branching position toward the joining position in the return conveying path, a conveyance amount of the sheet by an inner roller located on an inner side of the return conveying path among the pair of relay conveying rollers included in the relay conveying section is smaller than a conveyance amount of the sheet by an outer roller located on an outer side of the return conveying path; The above <1> 2 is a sheet processing apparatus according to the first embodiment. <3> a conveyance amount by the inner peripheral side roller and a conveyance amount by the outer peripheral side roller are determined based on a path gap in the return conveyance path and a thickness dimension of the sheet. The above <1> or the above <2> 2 is a sheet processing apparatus according to the first embodiment. <4> The diameter of the inner roller is smaller than the diameter of the outer roller that is paired with the inner roller. The above <1> or the above <3> 13. The sheet processing apparatus according to claim 12, wherein the sheet is a sheet having a diameter of 100 mm or less. <5> the number of teeth of a gear constituting a driving member for rotating the inner peripheral roller or the diameter of the gear is larger than the number of teeth of a driving gear for rotating the outer peripheral roller or the diameter of the gear; The above <1> or the above <4> 13. The sheet processing apparatus according to claim 12, wherein the sheet is a sheet having a diameter of 100 mm or less. <6> The surface friction coefficient of the inner roller is lower than the surface friction coefficient of the outer roller that is paired with the inner roller. The above <1> or the above <5> 13. The sheet processing apparatus according to claim 12, wherein the sheet is a sheet having a diameter of 100 mm or less. <7> a roller contact / separation mechanism for relatively moving the inner roller and the paired outer roller closer to or farther apart from each other; The above <1> or the above <6> 13. The sheet processing apparatus according to claim 12, wherein the sheet is a sheet having a diameter of 100 mm or less. <8> the driving sources of the inner peripheral side roller and the outer peripheral side roller paired with the inner peripheral side roller are individual driving sources corresponding to each other, when the sheet passes through the nip between the inner roller and the outer roller, the rotation speed of the drive source of the inner roller is lower than the rotation speed of the drive source of the outer roller; when the sheet does not pass through the nip between the inner roller and the outer roller, the number of rotations of the drive source of the inner roller is equal to the number of rotations of the drive source of the outer roller; The above <1> or the above <7> 13. The sheet processing apparatus according to claim 12, wherein the sheet is a sheet having a diameter of 100 mm or less. <9> when the sheet does not pass through a nip between the inner peripheral roller and the outer peripheral roller, the rotation of the outer peripheral roller is caused to follow the rotation of the inner peripheral roller. The above <8> 2 is a sheet processing apparatus according to the first embodiment. <10> A housing and an image forming unit that is accommodated in the housing and forms an image on a sheet; a sheet on which an image is formed by the image forming unit, the sheet being detachably supported by the housing and performing a predetermined process; <1> or the above <9> a sheet processing apparatus according to any one of the preceding claims; The image forming apparatus is characterized by comprising: <11> a post-processing unit supported by the housing and configured to perform a predetermined post-processing on the sheet on which an image has been formed by the image forming unit, the sheet processing device is configured to be detachably attached to the housing at a position downstream of the image forming unit and upstream of the post-processing unit in a conveying path of the sheet from the image forming unit to the post-processing unit, The above-mentioned <10> The image forming apparatus according to claim 1, <12> The post-processing is a binding process for binding the plurality of sheets on which the images are formed by the image forming unit. <11> The image forming apparatus according to claim 1, <13> a controller capable of switching between a first control in which the sheet on which the image is formed by the image forming unit is folded by the sheet processing device and then delivered to the post-processing unit, and a second control in which the sheet is delivered to the post-processing unit without being folded by the sheet processing device; The above-mentioned <12> The image forming apparatus according to claim 1, <14> an image forming apparatus for forming an image on a sheet; The image forming apparatus connected to the <1> or the above <9> a sheet processing apparatus according to any one of the preceding claims; The image forming system includes: [Explanation of symbols]

[0150] 1:MFP 21: Folding unit housing 22: Transport roller pair 22a: Drive roller 22b: driven roller 23: First folding roller 24: Second folding roller 25: Third folding roller 25e: Third folding roller 26: Guide plate 27: First roller for return transfer 28: Return relay conveying second roller 29: Fourth folding roller 31: Unit housing 32: Output tray 33: Receiving conveying roller pair 34: Intermediate conveying roller pair 35: Shift conveying roller pair 36: Discharge conveying roller pair 36a: Discharge drive roller 36b: Discharge driven roller 42: Processing section 100: Binding processing unit 101: Binding processing section 102: Binding process control unit 103: Communication line 110: CPU 120: Interface 121: Interface 122: Interface 151: Transport motor 152: Discharge motor 153: Staple moving motor 154: Transport sensor 155: Discharge sensor 156: Staple movement HP sensor 162: Folding motor 163: Entrance sensor 164: Folding sensor 200: Folding unit 200a: Folding unit 200b: Folding unit 200c: Folding unit 200d: Folding unit 200e: Folding unit 201: Folding processing unit 202: Folding process control unit 210: Roller contact mechanism 300: Image forming unit 301: Equipment case 412a: First folding drive gear 413a: Second folding drive gear 414a: Third folding drive gear 419: Third folding roller bearing 420: Link 421: Eccentric cam 422: Camshaft 423: First idler gear 424: Second idler gear [Prior art documents] [Patent documents]

[0151] [Patent Document 1] JP 2017-210361 A

Claims

1. a conveying section that conveys the sheet along a main conveying path; a first folding roller and a second folding roller disposed opposite each other across the main conveying path; a return conveying path having a curvature that branches off from the main conveying path at a branching position upstream of the first folding roller in a conveying direction of the sheet and joins the main conveying path at a joining position upstream of the branching position in the conveying direction; a third folding roller disposed at a position opposite to the second folding roller across the return conveying path; Equipped with when the sheet is conveyed to the return conveying path, a conveying amount of the sheet by the third folding roller, which is an inner peripheral side roller of the return conveying path, is smaller than a conveying amount of the sheet by the second folding roller, which is an outer peripheral side roller of the return conveying path. A sheet processing apparatus comprising:

2. a relay conveying section that conveys the sheet from the branching position toward the joining position in the return conveying path, a conveyance amount of the sheet by an inner roller located on an inner side of the return conveying path among the pair of relay conveying rollers included in the relay conveying section is smaller than a conveyance amount of the sheet by an outer roller located on an outer side of the return conveying path; The sheet processing apparatus according to claim 1 .

3. a conveyance amount by the inner peripheral side roller and a conveyance amount by the outer peripheral side roller are determined based on a path gap in the return conveyance path and a thickness dimension of the sheet. The sheet processing apparatus according to claim 1 .

4. The diameter of the inner roller is smaller than the diameter of the outer roller that is paired with the inner roller. The sheet processing apparatus according to claim 1 .

5. the number of teeth or the diameter of a gear constituting a driving member that rotates the inner roller is larger than the number of teeth or the diameter of a driving gear that rotates the outer roller; The sheet processing apparatus according to claim 1 .

6. The surface friction coefficient of the inner roller is lower than the surface friction coefficient of the outer roller that is paired with the inner roller. The sheet processing apparatus according to claim 1 .

7. a roller contact / separation mechanism for relatively moving the inner roller and the paired outer roller closer to or farther apart from each other; The sheet processing apparatus according to claim 1 .

8. the driving sources of the inner peripheral side roller and the outer peripheral side roller paired with the inner peripheral side roller are individual driving sources corresponding to each other, when the sheet passes through the nip between the inner roller and the outer roller, the rotation speed of the drive source of the inner roller is lower than the rotation speed of the drive source of the outer roller; when the sheet does not pass through the nip between the inner roller and the outer roller, the number of rotations of the drive source of the inner roller is equal to the number of rotations of the drive source of the outer roller; The sheet processing apparatus according to claim 1 .

9. when the sheet does not pass through a nip between the inner peripheral roller and the outer peripheral roller, the rotation of the outer peripheral roller is caused to follow the rotation of the inner peripheral roller. The sheet processing apparatus according to claim 8 .

10. A housing and an image forming unit that is accommodated in the housing and forms an image on a sheet; the sheet processing apparatus according to claim 1 , which is detachably supported by the housing and performs a predetermined process on the sheet on which an image is formed by the image forming unit; An image forming apparatus comprising:

11. a post-processing unit supported by the housing and configured to perform a predetermined post-processing on the sheet on which an image has been formed by the image forming unit, the sheet processing device is configured to be detachably attached to the housing at a position downstream of the image forming unit and upstream of the post-processing unit in a conveying path of the sheet from the image forming unit to the post-processing unit, 11. The image forming apparatus according to claim 10.

12. 12. The image forming apparatus according to claim 11, wherein the post-processing is a binding process for bundling and binding the plurality of sheets on which the images have been formed by the image forming unit.

13. a controller capable of switching between a first control in which the sheet on which the image is formed by the image forming unit is folded by the sheet processing device and then delivered to the post-processing unit, and a second control in which the sheet is delivered to the post-processing unit without being folded by the sheet processing device; 13. The image forming apparatus according to claim 12.

14. an image forming apparatus for forming an image on a sheet; The sheet processing apparatus according to claim 1 , which is connected to the image forming apparatus; An image forming system comprising:

Images