Sheet processing device and image forming system

Abstract

To allow a deviation amount of sheets in the conveyance direction to be controlled when forming a sheet bundle by stacking a plurality of sheets conveyed to a loading part, so as to improve the productivity of a sheet processing device while maintaining the accuracy of sheet alignment processing.SOLUTION: In a post-processing device (sheet processing device), at a buffer part provided in a conveyance passage for conveying a sheet to a loading part, a sheet bundle is formed in which sheets conveyed in the conveyance passage are stacked by deviating the positions to the upstream side in the sheet conveyance direction sequentially, and the sheet bundle is conveyed to the loading part from the buffer part. The post-processing device performs alignment processing for aligning the positions of the sheets in the sheet conveyance direction with respect to the sheet bundle loaded at the loading part, and sheet processing is performed with respect to the sheet bundle on which the alignment processing has been performed. The post processing device controls the deviation amount of the position of the sheets when stacking the sheets sequentially at the buffer part, according to the size of the sheet conveyed in the conveyance passage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A post-processing device (sheet processing device) that performs predetermined post-processing (sheet processing) such as binding or sorting on sheets on which images have been formed by the image forming device may be optionally connected to the image forming device. The post-processing device may be configured to perform alignment processing to align the positions of multiple conveyed sheets before performing post-processing on the multiple sheets.

[0003] Patent Document 1 describes a technology for adjusting the amount of sheet shift based on the type or basis weight of sheets in a post-processing device that sends multiple sheets to a stacking section while shifting them in the conveying direction and aligning the multiple sheets in the stacking section, thereby enabling reliable alignment in the stacking section. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-208747 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, by feeding multiple sheets into the stacking unit (stacking unit) in a stacked state with the sheets shifted in the conveying direction, it becomes possible to more reliably align each sheet in the conveying direction in the stacking unit depending on the amount of sheet shift. However, while increasing the amount of sheet shift increases the accuracy of the alignment process in the stacking unit, it also increases the overall length of the sheet stack in the conveying direction, which increases the time required for the alignment process. This leads to a decrease in productivity of the post-processing device. On the other hand, if the amount of sheet shift is uniformly reduced, the time required for the alignment process is reduced, which improves the productivity of the post-processing device, but the accuracy of the alignment process may decrease.

[0006] Therefore, one aspect of the present invention provides a technology that can control the amount of sheet shift in the conveying direction when multiple sheets conveyed to a stacking section are stacked to generate a sheet bundle, so as to improve the productivity of a sheet processing device while maintaining the accuracy of sheet alignment processing. [Means for solving the problem]

[0007] A sheet processing apparatus according to one aspect of the present invention comprises a stacking section on which sheets to be processed are loaded, a buffer section provided on a transport path for transporting sheets to the stacking section, a control means for controlling the transport of sheets on the transport path so as to generate a stack of overlapping sheets by sequentially shifting the positions of sheets transported on the transport path upstream in the transport direction, and transporting the sheet stack from the buffer section to the stacking section, an alignment means for performing an alignment process to align the positions of sheets in the transport direction for the sheet stack loaded on the stacking section, and a processing means for performing sheet processing on the sheet stack after the alignment process, wherein the control means controls the amount of shift in the positions of sheets when overlapping them in order in the buffer section depending on the size of the sheets transported on the transport path. [Effects of the Invention]

[0008] According to the present invention, it is possible to control the amount of sheet shift in the conveying direction when multiple sheets conveyed to a stacking section are stacked to generate a sheet bundle, so as to improve the productivity of the sheet processing device while maintaining the accuracy of the sheet alignment process. [Brief explanation of the drawings]

[0009] [Figure 1] Cross-sectional view showing an example of the configuration of an image forming system [Figure 2] FIG. 10 is a perspective view showing a configuration example of a binding processing unit; [Figure 3] 10 is a cross-sectional view showing an example of the generation of a pile of sheets in a shingled state in the buffer section; [Figure 4] FIG. 10 is a diagram illustrating an example of vertical alignment of a sheet stack in a binding processing section. [Figure 5] Block diagram showing an example of the hardware configuration of an image forming system [Figure 6] Block diagram showing an example of the functional configuration of an image forming system [Figure 7] 1 is a flowchart showing a processing procedure for sheet transport control; [Figure 8] Flowchart showing the procedure of first sheet processing (S103) [Figure 9] Flowchart showing the procedure of second sheet processing (S104) (first embodiment) [Figure 10] 10 is a flowchart showing the procedure of second sheet processing (S104) (second embodiment); [Figure 11] 10 is a flowchart showing the procedure of the sheet stack shift process (S404) (second embodiment); DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] [First embodiment] <Image forming system> FIG. 1 is a cross-sectional view showing an example of the configuration of an electrophotographic image forming system according to an embodiment of the present disclosure. The image forming system 1S of this embodiment includes an image forming apparatus 1 that forms an image on a sheet, and a post-processing device 4 that is connected downstream of the image forming apparatus 1 in the sheet transport direction. The image forming system 1S further includes an image reading device 2 and a document feeding device 3 that are connected to the image forming apparatus 1. The image forming system 1S forms an image on a sheet that is a recording material, and performs post-processing (sheet processing) on ​​the sheet using the post-processing device 4 as needed. The post-processing device 4 is an example of a sheet processing device that performs predetermined sheet processing on the sheet. The configuration and operation of each device will be described below.

[0012] The document feeder 3 transports documents placed on a document tray 18 to the image reading units 16 and 19 of the image reading device 2. The image reading units 16 and 19 are image sensors that read images of the documents. The image reading unit 16 is configured to read an image of the first side of the document, and the image reading unit 19 is configured to read an image of the second side, which is the reverse side of the first side of the document. Using the image reading units 16 and 19, it is possible to read both sides of the document in one transport. The document whose image has been read by the image reading units 16 and 19 is discharged to the document discharge unit 20. In addition, the image reading device 2 can read images from stationary documents set on the document table glass (including documents that cannot be used with the document feeder 3, such as booklets) by reciprocating the image reading unit 16 using the drive device 17.

[0013] Image forming apparatus 1 includes image forming unit 1B of a direct transfer type, and forms images by an electrophotographic method. A controller (printer control unit 100 in FIG. 5) of image forming apparatus 1 controls the image forming operation of image forming unit 1B based on image data obtained by reading by image reading units 16 and 19, or image data received from an external device via a network.

[0014] The image forming unit 1B includes a cartridge 8 having a photosensitive drum 9, and a laser scanner unit 15 disposed above the cartridge 8. When performing an image forming operation, the image forming unit 1B charges the surface of the photosensitive drum 9 while rotating the photosensitive drum 9. The laser scanner unit 15 exposes the photosensitive drum 9 based on image data, thereby forming an electrostatic latent image on the drum surface of the photosensitive drum 9. The image forming unit 1B develops the electrostatic latent image carried on the photosensitive drum 9 into a toner image using charged toner particles. The toner image formed on the photosensitive drum 9 is transported to a transfer unit where the photosensitive drum 9 faces a transfer roller 10 as the photosensitive drum 9 rotates.

[0015] The image forming apparatus 1 includes a plurality of paper feed units 6, each of which feeds a sheet one by one to a conveyance path. The sheet fed from the paper feed unit 6 is transported along the conveyance path, and after skew correction by a registration roller 7, reaches a transfer unit. In the transfer unit, a toner image carried on a photosensitive drum 9 is transferred onto the sheet by a transfer roller 10. A fixing unit 11 is disposed downstream of the transfer unit in the sheet conveyance direction. The fixing unit 11 has a pair of rotating bodies that sandwich and convey the conveyed sheet, and a heating element such as a halogen lamp for heating the toner image on the sheet, and fixes the image by applying heat and pressure to the toner image on the sheet.

[0016] When the sheet on which the image has been formed in this manner is discharged outside the image forming apparatus 1, the sheet that has passed through the fixing unit 11 is conveyed to the post-processing device 4 via the conveying path 14. When double-sided printing is performed on the sheet, the sheet on which the image formation on the first side has been completed is passed through the fixing unit 11 and then handed over to the reversing rollers 12, which then perform a switchback conveyance. As a result, the sheet is conveyed again to the registration rollers 7 via the conveying path 13. Thereafter, when the sheet is conveyed to the transfer section, the image formed by the image forming section 1B is transferred to the second side of the sheet. After the image formation on the second side has been completed, the sheet passes through the fixing unit 11 and is conveyed to the post-processing device 4 via the conveying path 14.

[0017] The image forming unit 1B may be configured to form an image by an intermediate transfer method in which a toner image formed on a photosensitive member is transferred to a sheet via an intermediate transfer member. Alternatively, the image forming unit 1B may be configured to form an image by an inkjet method or an offset printing method.

[0018] <Post-treatment device> The post-processing device 4 has a binding processing unit 4A that performs binding processing as post-processing (sheet processing) for sheets. The post-processing device 4 performs binding processing on sheets conveyed from the image forming device 1 using the binding processing unit 4A, and discharges the bound sheets as a sheet bundle. The post-processing device 4 can also discharge sheets conveyed from the image forming device 1 without performing binding processing.

[0019] The post-processing device 4 has an receiving path 81, an internal discharge path 82, a first discharge path 83, and a second discharge path 84 as transport paths for transporting sheets. The post-processing device 4 has an upper discharge tray 25 and a lower discharge tray 37 as destinations for discharging sheets. The receiving path 81 is a transport path for transporting sheets received from the image forming device 1. The internal discharge path 82 is a transport path for transporting sheets toward the binding processing unit 4A. The first discharge path 83 is a transport path for discharging sheets to the upper discharge tray 25. The second discharge path 84 is a transport path for discharging sheets to the lower discharge tray 37.

[0020] In the receiving path 81, an inlet roller 21, an inlet sensor 27, and a pre-buffer roller 22 are arranged in this order in the sheet conveying direction. A reversing roller 24 is arranged in the first discharge path 83. In the inner discharge path 82, an inner discharge roller 26, an intermediate conveying roller 28, a kick-out roller 29, and an intermediate pre-stacking sensor 38 are arranged. A bundle discharge roller 36 is arranged in the second discharge path 84. The inlet sensor 27 and the intermediate pre-stacking sensor 38 both detect a sheet being conveyed at a predetermined detection position on the conveying path in the post-processing device 4. These sensors may be configured as optical sensors that use light to detect the presence or absence of a sheet at the detection position.

[0021] The following describes the path along which a sheet is transported in the post-processing device 4. A sheet discharged from the image forming device 1 through the transport path 14 is taken into the post-processing device 4 by the inlet rollers 21 and transported in the receiving path 81 toward the pre-buffer rollers 22. The sheet being transported in the receiving path 81 is detected by the inlet sensor 27 at a detection position between the inlet rollers 21 and the pre-buffer rollers 22. The pre-buffer rollers 22 transport the sheet transported by the inlet rollers 21 toward the first discharge path 83.

[0022] When the upper discharge tray 25 is specified as the discharge destination of the sheet, the reversing rollers 24 discharge the sheet, which has been guided to the first discharge path 83 by the pre-buffer rollers 22, onto the upper discharge tray 25. When the lower discharge tray 37 is specified as the discharge destination of the sheet, the reversing rollers 24 performs switchback transport of the sheet, which has been guided to the first discharge path 83 by the pre-buffer rollers 22, to guide the sheet to the internal discharge path 82. A check valve 23 is disposed upstream of the reversing rollers 24 in the sheet discharge direction to the upper discharge tray 25, at a branch point (switchback branch point) where the first discharge path 83 branches into the receiving path 81 and the internal discharge path 82. The check valve 23 has a function of preventing the sheet, which has been switchback transported by the reversing rollers 24, from flowing back into the receiving path 81.

[0023] The inner discharge rollers 26, intermediate conveyance rollers 28, and kick-out rollers 29 arranged in the inner discharge path 82 convey the sheets guided to the inner discharge path 82 by the reversing rollers 24 toward the binding processing section 4A while sequentially transferring the sheets. The sheet being conveyed in the inner discharge path 82 is detected by the intermediate pre-stacking sensor 38 at a detection position between the intermediate conveyance rollers 28 and the kick-out rollers 29.

[0024] The binding processing unit 4A has a stapler 51. The binding processing unit 4A aligns a plurality of sheets (a sheet stack) that have been transported through an internal discharge path 82 and stacked on an intermediate stacking unit, and then staples the plurality of sheets at predetermined positions using the stapler 51. The detailed configuration and operation of the binding processing unit 4A will be described later. The sheet stack stapled by the binding processing unit 4A is delivered to bundle discharge rollers 36 through a second discharge path 84 by the sliding movement of a bundle discharge guide 34, which is a first transport mechanism of the binding processing unit 4A. Thereafter, the sheet stack is discharged to a lower discharge tray 37 by bundle discharge rollers 36, which are a second transport mechanism of the binding processing unit 4A.

[0025] Both the upper discharge tray 25 and the lower discharge tray 37 are movable in the vertical direction relative to the housing of the post-processing device 4. The post-processing device 4 is equipped with sheet sensors that detect the positions (heights from the tray surfaces) of the upper surfaces of multiple sheets stacked on the upper discharge tray 25 and the lower discharge tray 37. Based on the detection results of the sheet sensors provided on the upper discharge tray 25, the upper discharge tray 25 is controlled to move up and down in the vertical direction (A1 direction or A2 direction) so as to keep the position of the upper surfaces of the sheets stacked on the upper discharge tray 25 constant. Furthermore, based on the detection results of the sheet sensors provided on the lower discharge tray 37, the discharge tray 37 is controlled to move up and down in the vertical direction (B1 direction or B2 direction) so as to keep the position of the upper surfaces of the sheets stacked on the lower discharge tray 37 constant. In this embodiment, the upper discharge tray 25 and the lower discharge tray 37 are controlled to move up and down by motor drive, but may also be controlled by a biasing mechanism such as a spring.

[0026] <Binding processing section> Next, the configuration and operation of the binding processing unit 4A will be described with reference to Fig. 2. Fig. 2(A) is a perspective view showing the binding processing unit 4A, and Fig. 2(B) is a perspective view showing the binding processing unit 4A in a state where some members (the intermediate upper guide 31) are open.

[0027] 2(A), 2(B) and 1, the binding processing section 4A includes a stapler 51, an upper intermediate guide 31, a lower intermediate guide 32, a vertical alignment reference plate 39, a vertical alignment roller 33, and a bundle discharge guide 34. The binding processing section 4A uses the stapler 51 to perform a binding process on sheets discharged from the internal discharge path 82 and stacked on the intermediate stacking section, thereby forming a bound sheet bundle.

[0028] The upper intermediate guide 31 and the lower intermediate guide 32 constitute an intermediate stacking section on which sheets to be processed are stacked. The lower intermediate guide 32 is a stacking section on which sheets discharged from the internal discharge path 82 by the kick-out roller 29 arranged at the most downstream position in the internal discharge path 82 are stacked. In this way, the intermediate stacking section is an example of a stacking section on which sheets to be processed (stitched) are stacked.

[0029] A bundle holding flag 30 is rotatably provided downstream of the kick-out roller 29 in the sheet conveyance direction. The lower surface of the bundle holding flag 30 holds down the trailing edge of a sheet (a preceding sheet) that has been previously discharged from the internal discharge path 82 to the intermediate stacking section. As a result, the leading edge of a sheet (a subsequent sheet) that is subsequently discharged by the kick-out roller 29 passes above the trailing edge of the preceding sheet. In this way, the bundle holding flag 30 has the function of preventing sheets from colliding with each other in the intermediate stacking section by moving downward the trailing edge of the sheet discharged from the internal discharge path 82 by the kick-out roller 29. The lower surface of the bundle holding flag 30 is provided within the range of the sheet width so that it can hold down both ends of the sheets in the sheet width direction in accordance with the size of sheets that can be processed in the binding processing section 4A.

[0030] The vertical alignment roller 33 is disposed above the intermediate lower guide 32. The vertical alignment roller 33 is molded from an elastic material such as synthetic rubber or elastomer resin, and has a roller portion 33a whose outer circumferential surface is adjusted to have a predetermined coefficient of friction. The roller portion 33a is supported by a shaft portion 33b rotatably supported on the intermediate upper guide 31. The roller portion 33a is driven to rotate intermittently by one rotation at a time by a drive transmission device including a gear portion 33c. The roller portion 33a, which is the outer circumferential portion of the vertical alignment roller 33, is non-circular when viewed from the axial direction of the shaft portion 33b. In a standby state before sheets are discharged to the intermediate stacking section, the vertical alignment roller 33 is held at a rotation angle such that the roller portion 33a is not exposed from the intermediate upper guide 31. During one rotation of the vertical alignment roller 33, the roller portion 33a is temporarily exposed from an opening 31a provided in the intermediate upper guide 31, contacting the upper surface of the sheet stacked on the intermediate lower guide 32 and applying a conveying force. The contact pressure of the longitudinal alignment roller 33 against the sheet is adjusted so that the longitudinal alignment roller 33 slips after the sheet hits the longitudinal alignment reference plate 39 .

[0031] The intermediate stacking section is provided with a flexible sheet support guide 56. The support guide 56 is disposed so as to abut against the intermediate lower guide 32, and applies a predetermined pressure to the upper surfaces of the sheets stacked in the intermediate stacking section.

[0032] The vertical alignment reference plate 39 is provided downstream of the vertical alignment roller 33 in the sheet discharge direction when the kick-out roller 29 discharges the sheet from the internal discharge path 82. The vertical alignment reference plate 39 has a reference wall 39a that protrudes upward from the upper surface of the intermediate lower guide 32 as a regulating member that abuts against the edge of the sheet. Two vertical alignment reference plates 39 are provided on both sides in the direction (sheet width direction) perpendicular to the sheet discharge direction.

[0033] Hereinafter, in the binding processing unit 4A, the direction in which the sheet discharged from the internal discharge path 82 by the kick-out roller 29 moves toward the vertical alignment reference plate 39 is referred to as the "vertical alignment direction X1." The vertical alignment direction X1 is a direction along the sheet conveyance direction in the internal discharge path 82, and is also a direction in which the vertical alignment roller 33 moves the sheet toward the vertical alignment reference plate 39. In addition, the direction opposite to the vertical alignment direction X1 (i.e., the direction in which the sheet bundle is discharged from the binding processing unit 4A) is referred to as the "bundle discharge direction X2."

[0034] The stapler 51 performs a binding process to bind a plurality of sheets stacked on the intermediate stacking section and aligned in the longitudinal alignment direction X1 and the sheet width direction at predetermined positions. The stapler 51 is provided on the same side as the lateral alignment reference plate 52 in the sheet width direction, and is provided to be movable in the longitudinal alignment direction X1 and the stack discharge direction X2. The intermediate lower guide 32 is large enough to accommodate legal-size sheets transported in the long-side feed direction (the transport direction in which the longitudinal alignment direction X1 is the long-side direction and the sheet width direction is the short-side direction). Therefore, the stapler 51 can perform not only corner binding, which binds the corners of the sheet stack stacked on the intermediate stacking section, but also long-side binding, which moves relative to the sheet stack to bind multiple positions along the long side of the sheet stack.

[0035] In the binding processing section 4A of this embodiment, the vertical alignment roller 33 and the vertical alignment reference plate 39 constitute an alignment processing section (alignment means) that performs an alignment process to align the position of sheets in the sheet conveyance direction for the sheet bundle loaded in the stacking section. The vertical alignment roller 33 is an example of an alignment roller that is rotated to move the sheets in the conveyance direction, and the vertical alignment reference plate 39 is an example of a first reference plate provided along the width direction perpendicular to the conveyance direction. The stapler 51 is an example of a processing means that performs sheet processing (binding process) on the sheet bundle that has been subjected to the alignment process.

[0036] <Processing for generating a pile of sheets> In the post-processing device 4 of this embodiment, to prevent subsequent sheets from being conveyed to the binding processing device 4A while the binding processing device 4A is performing the binding process, the post-processing device 4 makes subsequent sheets conveyed from the image forming device 1 wait in the inner discharge path 82 and the first discharge path 83 (buffer section). At this time, the post-processing device 4 makes the subsequent multiple sheets wait in a state where they are overlapped in order. The post-processing device 4 then conveys the sheet bundle, which is made up of multiple overlapping sheets, from the buffer section to the binding processing device 4A (intermediate stacking section). This makes it possible to continue image formation by the image forming device 1 while the binding processing device 4A is performing the binding process (post-processing by the post-processing device 4), preventing a decrease in productivity of the image forming system.

[0037] When stacking multiple sheets, the post-processing device 4 stacks the multiple sheets in a buffer unit while sequentially shifting the positions of the multiple sheets in the sheet conveyance direction, thereby generating a shingled sheet bundle. This allows the binding processing device 4A to perform vertical alignment on the stacked multiple sheets. The process of generating such a shingled sheet bundle will be described below with reference to FIG. 3.

[0038] The post-processing device 4 guides the sheet P1, which has been guided to the first discharge path 83, to the inner discharge path 82 by switchback conveyance by the reversing rollers 24, and stops the reversing rollers 24 and the inner discharge rollers 26 after the sheet P1 reaches the inner discharge rollers 26. This stops the sheet P1 at the position shown in Fig. 3(A). At this time, the post-processing device 4 separates the pair of rollers of the reversing rollers 24.

[0039] Thereafter, the trailing edge of sheet P2, which is conveyed after sheet P1, is detected by the inlet sensor 27. The post-processing device 4 brings the pair of reversing rollers 24 into contact after a predetermined time has elapsed from the timing at which the trailing edge of sheet P2 is detected by the inlet sensor 27 (FIG. 3B). Furthermore, the post-processing device 4 starts rotating the reversing rollers 24 and the inner discharge rollers 26 so that sheets P1 and P2 are conveyed toward the upper discharge tray 25.

[0040] Here, the above-mentioned predetermined time is a time that determines the amount of shift in the sheet conveyance direction when sheet P2 is superimposed on sheet P1. Increasing this time increases the amount of sheet shift, and shortening this time decreases the amount of sheet shift. As will be described later, the post-processing device 4 of this embodiment controls (sets) the amount of sheet shift according to the size of the sheets to be processed so as to improve the productivity of the post-processing device 4 while maintaining the accuracy of the sheet alignment process (ensuring the amount of shift required for vertical alignment).

[0041] 3(C), the post-processing device 4 rotates the reversing roller 24 and the inner discharge roller 26 so that the rotation directions of the reversing roller 24 and the inner discharge roller 26 are reversed at the timing when the rear end of the sheet P2 reaches the switchback branch point. As a result, the sheets P1 and P2 are guided to the inner discharge path 82 and transported in the direction of the binding processing unit 4A.

[0042] After sheet P2 guided to the internal discharge path 82 reaches the internal discharge rollers 26, the post-processing device 4 stops the reversing rollers 24 and the internal discharge rollers 26. This stops sheets P1 and P2 at the position shown in FIG. 3(D). The post-processing device 4 further separates the pair of rollers of the reversing rollers 24. At this time, the post-processing device 4 also separates the pair of rollers of the reversing rollers 24.

[0043] 3(D), a shingled sheet bundle consisting of two sheets is generated in the inner discharge path 82 and the first discharge path 83. Furthermore, by repeating the above-described process, it is possible to generate a shingled sheet bundle consisting of three or more sheets. In this way, the post-processing device 4 generates a sheet bundle (shingled sheet bundle) in the buffer section by shifting the sheets conveyed on the conveying path in order to the upstream side in the sheet conveying direction and overlapping them.

[0044] While the binding processing unit 4A is performing the binding process, the post-processing device 4 stores the subsequent multiple sheets transported from the image forming device 1 as the shingled sheet bundle thus generated in the inner discharge path 82 and the first discharge path 83. The post-processing device 4 uses the inner discharge path 82 and the first discharge path 83 as buffer units for storing the subsequent multiple sheets transported from the image forming device 1.

[0045] <Vertical alignment of sheet stack> 4 is a schematic diagram showing an example of vertical alignment of a sheet bundle consisting of three sheets in the intermediate stacking section. Here, vertical alignment is a process (alignment process) for aligning the positions of multiple sheets in the sheet conveyance direction. When the post-processing device 4 sends the shingled sheet bundle to the binding processing section 4A through the internal discharge path 82, it starts rotating the vertical alignment roller 33, thereby starting vertical alignment of the sheet bundle stacked in the intermediate stacking section in the binding processing section 4A.

[0046] 4(A) shows a state in which a shingled sheet stack discharged from the internal discharge path 82 is stacked on the intermediate stacking section. The intermediate stacking section is composed of an upper intermediate guide 31 and a lower intermediate guide 32. The intermediate stacking section is provided with a vertical alignment roller 33 and a vertical alignment reference plate 39 as members used for vertical alignment. The multiple sheets that make up the sheet stack are abutted against the vertical alignment reference plate 39 in order by the vertical alignment roller 33, thereby performing vertical alignment of the sheet stack (alignment processing in the sheet conveyance direction).

[0047] First, as shown in Fig. 4(B), the lowermost (bottom) sheet of the sheet stack stacked in the intermediate stacking section is abutted against the vertical alignment reference plate 39 by the vertical alignment roller 33. Next, as shown in Fig. 4(C), the second-lowest sheet of the sheet stack is abutted against the vertical alignment reference plate 39 by the vertical alignment roller 33. Furthermore, as shown in Fig. 4(D), the uppermost (top) sheet of the sheet stack is abutted against the vertical alignment reference plate 39 by the vertical alignment roller 33. This completes the vertical alignment of the sheet stack stacked in the intermediate stacking section.

[0048] In this embodiment, the post-processing device 4 generates a sheet bundle in the buffer unit by shifting the sheets conveyed on the conveyance path in order to the upstream side in the sheet conveyance direction and overlapping them, and sends the generated sheet bundle to the binding processing unit 4A (intermediate stacking unit). As a result, in the intermediate stacking unit, each sheet of the sheet bundle is abutted against the vertical alignment reference plate 39 by the vertical alignment roller 33, thereby performing vertical alignment on all sheets of the sheet bundle. In this way, the alignment processing unit, which is composed of the vertical alignment roller 33 and the vertical alignment reference plate 39, moves the sheets of the sheet bundle stacked in the intermediate stacking unit one by one from the bottom downstream in the sheet conveyance direction by the vertical alignment roller 33, and abuts the edge of each sheet against the vertical alignment reference plate 39. As a result, the alignment processing unit performs alignment processing (vertical alignment) on the sheet bundle in the sheet conveyance direction.

[0049] The amount of sheet shift when creating a shingled sheet stack in the buffer section is determined based on the distance L between the position where the longitudinal alignment roller 33 contacts the sheet and the position of the longitudinal alignment reference plate 39, the distance required for longitudinal alignment, and a distance that takes into account factors such as friction between sheets. When the size of the sheets to be processed is small (the surface area is small), the frictional force between the overlapping sheets is small, and the required longitudinal alignment capacity is low. In other words, even if the amount of shift between the overlapping sheets is small, the accuracy of the alignment process can be maintained. This allows the amount of sheet shift to be reduced.

[0050] Therefore, by setting the amount of sheet shift smaller as the size of the sheet conveyed on the conveying path becomes smaller, it is possible to shorten the time required for the alignment process while maintaining the accuracy of the sheet alignment process and improve the productivity of the sheet processing apparatus. For example, as follows, the amount of sheet shift is set so that the amount of shift when the size of the sheet to be processed conveyed on the conveying path is equal to or smaller than a threshold size is smaller than when the size is not equal to or smaller than the threshold size. For example, when L=20 [mm], ●If the sheet size is small (the length in the sheet transport direction is 210 mm or less and the width in the sheet width direction is 148 mm or less), the offset amount is set to 25 mm. ●If the sheet size is not small, set the offset amount to 30 mm.

[0051] In the above example, whether the sheet size is equal to or smaller than the threshold size is determined based on the length and width of the sheet to be processed, but the determination may also be made based on at least one of the length and width of the sheet. Also, although an example has been shown in which two levels of settings are provided for the amount of shifting the sheet position, three or more levels may also be provided, each corresponding to a different sheet size range.

[0052] <Configuration of image forming system> 5 is a block diagram showing an example of the hardware configuration of an image forming system 1S according to this embodiment. The image forming apparatus 1 includes a printer control unit 100, and the post-processing device 4 includes a finisher control unit 400. The printer control unit 100 and the finisher control unit 400 are connected to each other via a communication interface and cooperate to control the operation of the image forming system 1S.

[0053] The printer control unit 100 has a central processing unit (CPU) 101 and a memory 102. The CPU 101 reads and executes programs stored in the memory 102 to perform overall control of the image forming apparatus 1. For example, the CPU 101 executes a process of causing the image forming unit 1B to perform an image forming operation and a process of causing the image reading device 2 to perform a reading operation to acquire image data. The memory 102 includes a non-volatile storage medium such as a read-only memory (ROM) and a volatile storage medium such as a random access memory (RAM), and is used as a storage location for programs and data and as a workspace when the CPU 101 executes the programs. The memory 102 is an example of a non-transitory storage medium in which programs for controlling the image forming apparatus 1 are stored.

[0054] The printer control unit 100 is connected to external devices such as a personal computer (PC) and a portable information device via an external interface (I / F) 104. The printer control unit 100 receives various jobs, such as image formation jobs (print jobs), from the external devices via the external I / F 104. The printer control unit 100 is also connected to an operation display unit 103, which is a user interface for the image forming system 1S. The operation display unit 103 includes a display device, such as a liquid crystal panel, that presents information to the user, and an input device, such as physical buttons and a touch panel function unit of the liquid crystal panel, that accepts input operations by the user. The printer control unit 100 controls the display content of the display device and receives information input via the input device by communicating with the operation display unit 103.

[0055] The finisher control unit 400 has a CPU 401, a memory 402, and an input / output (I / O) port 403. The CPU 401 reads and executes programs stored in the memory 402, and performs overall control of the post-processing device 4. The memory 402 includes a non-volatile storage medium such as a ROM and a volatile storage medium such as a RAM, and is used as a storage location for programs and data, and as a workspace when the CPU 401 executes the programs. The memory 402 is an example of a non-transitory storage medium in which programs for controlling the post-processing device 4 are stored.

[0056] The functions of the printer control unit 100 and the finisher control unit 400 may be implemented on the control unit circuit as independent hardware such as an ASIC, or may be implemented by software as a functional unit of a program. Also, some or all of the functions of the finisher control unit 400 described below may be implemented as functions of the printer control unit 100.

[0057] The CPU 401 and the memory 402 are connected to an I / O port 403 via a bus 404. The I / O port 403 inputs and outputs control signals between the CPU 401 and the memory 402 and each device constituting the post-processing device 4. In addition to the entrance sensor 27 and the intermediate pre-stacking sensor 38, the I / O port 403 is connected to a plurality of motors (M1 to M14) that serve as drive sources for conveying sheets or drive sources for the binding processing unit 4A.

[0058] The inlet motor M1 rotates the inlet rollers 21. The pre-buffer motor M2 rotates the pre-buffer rollers 22. The first reverse motor M3 rotates the reverse rollers 24. The second reverse motor M4 brings the roller pair of the reverse rollers 24 into contact by rotating in a first direction (for example, a clockwise direction (CW direction)), and separates the roller pair of the reverse rollers 24 by rotating in a direction opposite to the first direction (a counterclockwise direction (CCW direction)). The third reverse motor M5 moves the roller pair of the reverse rollers 24 in a first direction (toward the front) of two directions perpendicular to the conveying direction by rotating in the CW direction, and moves them in the opposite direction to the first direction (toward the back) by rotating in the CCW direction.

[0059] The inner discharge motor M6 rotates the inner discharge roller 26. The kick-out motor M7 rotates the kick-out roller 29. The longitudinal alignment motor M8 supplies a driving force to intermittently operate the longitudinal alignment roller 33 one rotation at a time. The jogger drive motor M9 moves the lateral alignment jogger 58 in the sheet width direction. The stapler movement motor M10 moves the stapler 51 in the longitudinal alignment direction X1 and the stack discharge direction X2. The binding motor M11 causes the stapler 51 to perform an operation of stapling the sheet stack.

[0060] The guide drive motor M12 drives the guide drive unit 35 to slide the bundle discharge guide 34. The guide drive motor M12 moves the bundle discharge guide 34 in the longitudinal alignment direction X1 by rotational driving in the CW direction, and moves it in the bundle discharge direction X2 by rotational driving in the CCW direction. The first bundle discharge motor M13 rotates the bundle discharge rollers 36. The second bundle discharge motor M14 brings the roller pair of the bundle discharge rollers 36 into contact by rotational driving in the CW direction, and separates the roller pair of the bundle discharge rollers 36 by rotational driving in the CCW direction.

[0061] <Controller configuration> Fig. 6 is a block diagram showing an example of the functional configuration of the image forming system 1S according to this embodiment. Fig. 6 mainly shows functional blocks related to sheet conveyance control in the post-processing device 4 according to this embodiment, and omits functional blocks related to other functions.

[0062] The finisher control unit 400 has a conveyance control unit 410 and an information acquisition unit 412, and the conveyance control unit 410 includes a sheet stack control unit 411. The functions of the control units 410 to 412 are realized by the CPU 401 of the finisher control unit 400 (FIG. 5) executing a program read from the memory 402.

[0063] The conveyance control unit 410 controls sheet conveyance on the conveyance path in the post-processing device 4 by driving each of the motors M1 to M14 to be controlled based on information output from various sensors such as the entrance sensor 27 and the intermediate pre-stacking sensor 38. The sheet stack control unit 411 controls the generation of a shingled sheet stack in the buffer unit by driving the first reversing motor M3, the second reversing motor M4, and the internal discharge motor M6 based on information output from the entrance sensor 27 and the information acquisition unit 412. The information acquisition unit 412 acquires information (e.g., sheet size) set via the operation and display unit 103 via the printer control unit 100.

[0064] <Processing Procedure> 7, 8, and 9, a description will be given of sheet conveyance control executed by the conveyance control unit 410 (CPU 401) in the post-processing device 4 of this embodiment. Fig. 7 is a flowchart showing a processing procedure for sheet conveyance control. Fig. 8 is a flowchart showing a procedure for the first sheet processing in S103 of Fig. 7, and Fig. 9 is a flowchart showing a procedure for the second sheet processing in S104 of Fig. 7.

[0065] In the image forming system 1S, when execution of an image forming job including post-processing (sheet processing) by the post-processing device 4 is started, the conveyance control unit 410 of the finisher control unit 400 performs processing according to the procedure shown in Fig. 7 in accordance with instructions from the printer control unit 100. The following processing is performed each time a sheet on which an image has been formed is conveyed from the image forming device 1.

[0066] First, the conveyance control unit 410 (CPU 401) waits for the trailing edge of a sheet (hereinafter referred to as a "target sheet") that has been discharged from the image forming apparatus 1 through the conveyance path 14 and is to be processed by the post-processing apparatus 4 to be detected by the inlet sensor 27. In S101, when the trailing edge of the target sheet that has been conveyed from the image forming apparatus 1 is detected by the inlet sensor 27, the conveyance control unit 410 proceeds to S102.

[0067] In S102, the conveyance control unit 410 determines whether the target sheet whose trailing edge is detected by the inlet sensor 27 is the first sheet of the sheet bundle that is the processing unit in the post-processing (the sheet bundle to be bound in the binding process). If the target sheet is the first sheet of the sheet bundle, the conveyance control unit 410 proceeds to S103 and executes the first sheet process according to the procedure in FIG. 8. On the other hand, if the target sheet is not the first sheet of the sheet bundle (i.e., the second or subsequent sheet), the conveyance control unit 410 proceeds to S104 and executes the second sheet process according to the procedure in FIG. 9. When the process of S103 or S104 is completed, the conveyance control unit 410 ends the process according to the procedure in FIG. 7.

[0068] By executing the processes in S103 and S104, a shingled sheet bundle is generated in the buffer unit (the internal discharge path 82 and the first discharge path 83). Thereafter, the conveyance control unit 410 conveys the shingled sheet bundle generated in the buffer unit to the intermediate stacking unit via the internal discharge path 82, and performs alignment processing and post-processing (binding processing) on ​​the conveyed sheet bundle by the binding processing unit 4A in the intermediate stacking unit. The sheet bundle that has undergone binding processing is discharged to the lower discharge tray 37 via the second discharge path 84.

[0069] <First Sheet Processing (S103)> The first sheet processing (processing of the first sheet) in S103 is performed according to the procedure in Fig. 8. First, in S201, the conveyance control unit 410 (CPU 401) waits for the trailing end of the target sheet detected by the inlet sensor 27 in S101 to reach the switchback branch point. As described above, the switchback branch point is the position where the receiving path 81 and the inner discharge path 82 branch off from the first discharge path 83. When the trailing end of the target sheet reaches the switchback branch point, the conveyance control unit 410 proceeds to S202.

[0070] In S202, the conveyance control unit 410 switches (reverses) the rotation direction of the reversing roller 24, thereby sending the target sheet whose trailing end has reached the switchback branch point to the internal discharge path 82, and proceeds to S203. In S203, the conveyance control unit 410 waits for the target sheet (its leading end) sent to the internal discharge path 82 to reach the internal discharge roller 26, and proceeds to S204 when the target sheet reaches the internal discharge roller 26. In S204, the conveyance control unit 410 drives the second reversing motor M4 to separate the reversing roller 24.

[0071] Thereafter, in S205, the conveyance control unit 410 drives the inner discharge motor M6 to convey the target sheet a predetermined distance (10 mm in this embodiment) by the inner discharge rollers 26. After the target sheet has been conveyed the predetermined distance, in S206, the conveyance control unit 410 stops driving the first reversing motor M3 and the inner discharge motor M6, thereby stopping the reversing rollers 24 and the inner discharge rollers 26, and ends the processing according to the procedures in FIGS. 8 and 7. As a result, the first sheet of the sheet bundle that is the processing unit in post-processing (the sheet bundle to be bound in the binding process) stops in the inner discharge path 82 at a position (FIG. 3A) where the leading edge of the sheet has advanced a predetermined distance (10 mm) from the position of the inner discharge rollers 26.

[0072] The determination of the position of the target sheet in S201 and S203 and the determination of the conveying distance of the target sheet in S205 may be made based on the elapsed time based on the timing at which the trailing edge of the target sheet is detected by the inlet sensor 27. Alternatively, these determinations may be made based on the count value of the drive pulses of each motor.

[0073] <Second Sheet Processing (S104)> The second sheet processing (processing of the second and subsequent sheets) in S104 is performed according to the procedure in Fig. 9. First, in S301, the conveyance control unit 410 (CPU 401) determines whether the target sheet is a sheet of a size (small size) equal to or smaller than a predetermined threshold size. The conveyance control unit 410 acquires the sheet size set via the operation display unit 103 as the size of the target sheet using the information acquisition unit 412, and makes a determination based on the acquired size. Alternatively, the information acquisition unit 412 may acquire the size of the target sheet from the settings of the image formation job.

[0074] In this way, the conveyance control unit 410 determines whether the size of the target sheet is equal to or smaller than the threshold size based on the sheet size set by the user. The threshold size is predetermined to, for example, 210 mm in the sheet conveyance direction and 148 mm in the sheet width. If the conveyance control unit 410 determines that the target sheet is a small-sized sheet, the process proceeds to S302. If the conveyance control unit 410 determines that the target sheet is not a small-sized sheet, the process proceeds to S303.

[0075] The information acquisition unit 412 may acquire the size of the target sheet by measuring at least one of the length and width of the sheet being conveyed on the conveyance path. In this case, a sensor capable of detecting the size of the sheet being conveyed is disposed upstream of the buffer unit in the sheet conveyance direction. The information acquisition unit 412 uses the sensor disposed on the conveyance path to measure at least one of the length and width of the target sheet being conveyed on the conveyance path and acquires the measurement result. The conveyance control unit 410 determines whether the size of the target sheet is equal to or smaller than a threshold size based on the measurement result from the sensor.

[0076] In S302 and S303, the conveyance control unit 410 sets the conveyance start timing of the preceding sheet waiting at the position (buffer section) shown in FIG. 3A on the internal discharge path 82 and the first discharge path 83. Here, the conveyance start timing of the preceding sheet is the timing at which conveyance of the preceding sheet waiting in the buffer section toward the upper discharge tray 25 is started, based on the timing at which the trailing edge of the target sheet is detected by the inlet sensor 27. The preceding sheet is waiting at the position (buffer section) shown in FIG. 3A on the internal discharge path 82 and the first discharge path 83.

[0077] In S302, the conveyance control unit 410 sets the conveyance start timing of the preceding sheet so that the shift amount in the position in the conveyance direction when the target sheet is superimposed on the preceding sheet is a first shift amount (e.g., 25 mm). On the other hand, in S303, the conveyance control unit 410 sets the conveyance start timing of the preceding sheet so that the shift amount in the position in the conveyance direction when the target sheet is superimposed on the preceding sheet is a second shift amount (e.g., 30 mm) that is larger than the first shift amount.

[0078] When the setting in S302 or S303 is completed, in S304 the conveyance control unit 410 waits until the conveyance start timing of the preceding sheet is reached, and when the conveyance start timing of the preceding sheet is reached, the process proceeds to S305. In S305, the conveyance control unit 410 starts rotational driving of the reversing rollers 24 and the inner discharge rollers 26 so that the preceding sheet and the target sheet that is conveyed so as to overlap the preceding sheet are conveyed in the direction of the upper discharge tray 25. Furthermore, in S306, the conveyance control unit 410 brings the pair of rollers of the reversing rollers 24 into contact with each other, and the process proceeds to S307.

[0079] In S307, similar to S201, the conveyance control unit 410 waits for the trailing edge of the target sheet detected by the inlet sensor 27 in S101 to reach the switchback branch point. When the trailing edge of the target sheet reaches the switchback branch point (as shown in FIG. 3C), the conveyance control unit 410 proceeds to S307. In S308, similar to S202, the conveyance control unit 410 switches (reverses) the rotation direction of the reversing roller 24, thereby sending the target sheet whose trailing edge has reached the switchback branch point to the internal discharge path 82, and proceeds to S309.

[0080] In S309, the conveyance control unit 410 determines whether there are any subsequent sheets to be added to the shingled sheet bundle generated in the buffer unit (whether any sheets remain). If there are no subsequent sheets, the conveyance control unit 410 ends the processing according to the procedures in FIGS. 9 and 7. In this case, the shingled sheet bundle generated in the buffer unit is sent to the binding processing unit 4A (intermediate stacking unit) through the internal discharge path 82. In the binding processing unit 4A, the sheet bundle conveyed from the buffer unit is vertically aligned and then bound.

[0081] On the other hand, if there is a subsequent sheet, the conveyance control unit 410 proceeds from S309 to S310. In S310, similar to S203, the conveyance control unit 410 waits for (the leading edge of) the target sheet sent to the internal discharge path 82 to reach the internal discharge rollers 26, and proceeds to S311 when the target sheet reaches the internal discharge rollers 26. In S311, similar to S204, the conveyance control unit 410 separates the reversing rollers 24.

[0082] Thereafter, in S312, the conveyance control unit 410 conveys the target sheet a predetermined distance (10 mm in this embodiment) using the inner discharge rollers 26, as in S205. After conveying the target sheet the predetermined distance, in S313, the conveyance control unit 410 stops the reversing rollers 24 and the inner discharge rollers 26, as in S206, and ends the processing according to the procedures in FIGS. 9 and 7. As a result, the target sheet stops in the inner discharge path 82, stacked in a shingled state on the preceding sheet, with its leading edge positioned a predetermined distance (10 mm) from the position of the inner discharge rollers 26 (FIG. 3A). In this way, a sheet bundle in which one or more sheets, including the target sheet, are stacked in a shingled state on the first sheet stops at the position shown in FIG. 3D. In this case, by performing the processing according to the procedures in FIGS. 7 and 9, a subsequent sheet is further added to the shingled sheet bundle generated in the buffer unit.

[0083] The determination of the position of the target sheet in S304, S307, and S310 and the determination of the conveying distance of the target sheet in S312 may be made based on the elapsed time based on the timing at which the trailing edge of the target sheet is detected by the inlet sensor 27. Alternatively, these determinations may be made based on the count value of the drive pulses of each motor.

[0084] As described above, the post-processing device 4 of this embodiment includes a stacking unit (intermediate stacking unit) on which sheets to be processed are stacked, and a conveyance control unit 410. The conveyance control unit 410 generates a sheet bundle by shifting the positions of sheets conveyed on the conveyance path in order upstream in the sheet conveyance direction in a buffer unit provided on a conveyance path for conveying sheets to the stacking unit and overlapping them. The conveyance control unit 410 controls the conveyance of sheets on the conveyance path so that the sheet bundle is conveyed from the buffer unit to the stacking unit. The alignment processing unit performs an alignment process to align the positions of sheets in the sheet conveyance direction for the sheet bundle stacked on the stacking unit. The binding processing unit 4A performs sheet processing (binding process) on the sheet bundle that has been subjected to the alignment process. The conveyance control unit 410 controls the amount of shift in the positions of sheets when overlapping sheets in order in the buffer unit, depending on the size of the sheets conveyed on the conveyance path.

[0085] In this way, the post-processing device 4 of this embodiment controls the amount of shift in the sheet position when stacking sheets in the buffer unit to create a shingled sheet bundle, depending on the size of the sheets to be processed. This makes it possible to shorten the overall length of the shingled sheet bundle in the sheet transport direction to match the sheet size. As a result, it is possible to shorten the time required to transport a sheet bundle consisting of small-sized sheets to the binding processing device 4A (post-processing device), and it is also possible to shorten the time required to vertically align the sheet bundle. Therefore, according to this embodiment, it is possible to improve the productivity of the post-processing device 4 (sheet processing device) while maintaining the accuracy of the sheet alignment process (ensuring vertical alignment capability).

[0086] [Second embodiment] In the second embodiment, the intermediate stacking section of the post-processing device 4 performs not only vertical alignment but also horizontal alignment (alignment processing to align the position of the sheets in the sheet width direction perpendicular to the sheet transport direction) on the shingled sheet bundle transported from the buffer section and stacked therein. Furthermore, to prevent a decrease in the accuracy of horizontal alignment when the size of the sheets to be processed is small, a shift processing is performed in the buffer section to shift the position of the sheet bundle in the sheet width direction as necessary. Furthermore, the amount of shift of the sheets when generating the sheet bundle is controlled based on whether or not the shift processing is performed. The following mainly describes the parts that are different from the first embodiment, and a description of the parts that are common to the first embodiment will be omitted.

[0087] <Sheet stack shift processing> 2 and 3, a shift process will be described in which the reversing roller 24 is used to shift the shingled sheet bundle in the sheet width direction perpendicular to the sheet conveyance direction. After the sheet bundle is fed into the binding processing section 4A, the post-processing device 4 of this embodiment not only performs vertical alignment, but also performs horizontal alignment of the sheet bundle by moving the horizontal alignment jogger 58 shown in FIG. 2(B) in the sheet width direction. The horizontal alignment is a process (alignment process) for aligning the positions of multiple sheets in the sheet width direction.

[0088] In the binding processing section 4A of this embodiment, the lateral alignment jogger 58 and the lateral alignment reference plate 52 constitute an alignment processing section (alignment means) that performs an alignment process to align the positions of sheets in the sheet width direction perpendicular to the sheet conveyance direction for the sheet bundle stacked in the stacking section. The lateral alignment jogger 58 is an example of an alignment member provided along the sheet conveyance direction, and the lateral alignment reference plate 52 is an example of a second reference plate provided along the sheet conveyance direction. The alignment processing section, which is composed of the lateral alignment jogger 58 and the lateral alignment reference plate 52, performs an alignment process in the sheet width direction (lateral alignment) for the sheet bundle stacked in the intermediate stacking section. Specifically, the alignment processing section performs lateral alignment by moving the sheet bundle stacked in the intermediate stacking section in the sheet width direction using the lateral alignment jogger 58 (alignment member) so that the edge of the sheet bundle stacked in the sheet conveyance direction comes into contact with the lateral reference plate 52 and is aligned.

[0089] In lateral alignment in the binding processing unit 4A, the narrower the width of the sheets included in the sheet stack, the longer the distance between the edge of the sheet in the sheet width direction and the lateral alignment reference plate 52, and the greater the movement amount of the lateral alignment jogger 58 when lateral alignment is performed. Furthermore, the amount of movement of the sheet itself in the sheet width direction when lateral alignment is performed also increases. When the amount of movement of the sheet in the sheet width direction increases, a force that tends to rotate the sheet stack to be lateral aligned is generated due to friction between the sheet stack to be aligned and the intermediate lower guide 32 or sheets previously stacked on the intermediate lower guide 32. This leads to a decrease in the lateral alignment ability of the binding processing unit 4A (a decrease in the accuracy of the alignment process).

[0090] For this reason, when performing post-processing (binding) on ​​narrow sheets, the post-processing device 4 of this embodiment performs a shift process to shift the sheet bundle, which is located at the position shown in FIG. 3C in the buffer unit, in a direction perpendicular to the conveyance direction after generating a shingled sheet bundle. More specifically, the conveyance control unit 410 performs the shift process on the sheet bundle when the size of the sheets to be processed is equal to or smaller than a threshold size (for example, the sheet width is 148 mm or less). This shift process is performed by driving the third reversing motor M5 to move the pair of rollers of the reversing roller 24. Thus, the reversing roller 24 of this embodiment is an example of a shift means provided in the buffer unit that shifts the position of the sheet bundle generated in the buffer unit in the sheet width direction.

[0091] When the sheet bundle is transported to the binding processing unit 4A, the post-processing device 4 (conveyance control unit 410) performs a shift process on the shift bundle in a direction that shortens the distance between the edge of the sheets in the sheet width direction and the lateral alignment reference plate 52. That is, the post-processing device 4 (conveyance control unit 410) performs a shift process that shifts the position of the sheet bundle in the sheet width direction by the reversing roller 24 so that the amount of sheet movement in lateral alignment (alignment process in the sheet width direction by the alignment processing unit) is reduced. The sheet bundle that has undergone the shift process is transported from the buffer unit to the binding processing unit 4A through the internal discharge path 82.

[0092] In this way, by shifting the position of the sheet stack in the sheet width direction through the shift process using the reversing roller 24, the distance between the edge of the sheet and the lateral alignment reference plate 52 is shortened. As a result, even when lateral alignment is performed on a sheet stack that includes narrow sheets, the amount of sheet movement by the lateral alignment jogger 58 can be reduced, and it is possible to prevent a decrease in the lateral alignment ability of the binding processing unit 4A.

[0093] On the other hand, as described above, when the sheet stack is shifted using the reversing rollers 24 before being fed to the binding processing section 4A, it is necessary to avoid collision between the sheet stack being shifted and the subsequent sheets conveyed from the image forming apparatus 1. For this reason, it is necessary to increase the distance (paper spacing) between the sheets conveyed from the image forming apparatus 1, which may reduce the productivity of the image forming system 1S.

[0094] As described above, in the post-processing device 4 of this embodiment, even if the sheet spacing is increased as a result of the shift process, the shift amount of sheets when generating a shingled sheet bundle in the buffer unit is controlled to prevent a decrease in productivity of the post-processing device 4. Specifically, the conveyance control unit 410 sets the shift amount when the sheet bundle is shifted to be smaller than when the sheet bundle is not shifted. For example, the shift amount when the sheet bundle is not shifted is set to 30 mm, and the shift amount when the sheet bundle is shifted is set to 25 mm, which is 5 mm shorter than the shift amount when the sheet bundle is shifted. This setting shortens the overall length of the shingled sheet bundle transported from the buffer unit to the intermediate stacker, thereby reducing a decrease in productivity of the post-processing device 4 even if the sheet spacing is increased as a result of the shift process.

[0095] Furthermore, in the post-processing device 4 of this embodiment, the shift process of sheets is performed when the size of the sheets to be processed is equal to or smaller than a threshold size. Therefore, when the size of the sheets to be processed is equal to or smaller than the threshold size, the shift process is performed and control is performed to reduce the amount of shift of the sheets when generating a sheet bundle, as described above. Therefore, when the shift process is performed, it is possible to reduce a decrease in productivity of the post-processing device 4 while maintaining the accuracy of the alignment process in the sheet conveyance direction (ensuring vertical alignment capability), as in the first embodiment.

[0096] <Processing Procedure> 7, 8, 10, and 11, a description will be given of sheet conveyance control executed by the conveyance control unit 410 (CPU 401) in the post-processing device 4 of this embodiment. In this embodiment, the processes in FIGS. 7 and 8 are the same as those in the first embodiment. In S104 of FIG. 7, the conveyance control unit 410 performs processing according to the procedure in FIG. 10.

[0097] <Second Sheet Processing (S104)> The second sheet processing (processing of the second and subsequent sheets) in S104 is performed according to the procedure in Fig. 10. First, in S401, the conveyance control unit 410 (CPU 401) determines whether or not to perform the above-described shift processing of the sheet bundle in the buffer unit. In this embodiment, if the size of the target sheet is equal to or smaller than the threshold size, the conveyance control unit 410 determines to perform the shift processing of the sheet bundle, and proceeds to S302. On the other hand, if the conveyance control unit 410 determines not to perform the shift processing of the sheet bundle, the process proceeds to S303.

[0098] In S302 and S303, the conveyance control unit 410 sets the shift amount of the position in the conveyance direction when the target sheet is superimposed on the preceding sheet, as in the first embodiment. In S302, a first shift amount (e.g., 25 mm) is used, and in S303, a second shift amount (e.g., 30 mm) that is larger than the first shift amount is used.

[0099] The processes from S304 to S307 are the same as those in the first embodiment. In S307, when the trailing edge of the target sheet detected by the inlet sensor 27 in S101 reaches the switchback branch point, the conveyance control unit 410 advances the process to S402.

[0100] In S402, the conveyance control unit 410 determines whether or not there are any subsequent sheets to be added to the shingled sheet bundle generated in the buffer unit (whether or not there are any remaining sheets). If there are subsequent sheets, the conveyance control unit 410 proceeds to S308, and if there are no subsequent sheets, the conveyance control unit 410 proceeds to S403. In S403, similar to S401, the conveyance control unit 410 determines whether or not to perform the above-mentioned shift process of the sheet bundle in the buffer unit, and if not, proceeds to S308, and if shift process is to be performed, proceeds to S404. In S404, the conveyance control unit 410 performs the shift process of the sheet bundle in the buffer unit according to the procedure in FIG. 11.

[0101] On the other hand, if the process proceeds to S308, the transport control unit 410 performs the processes of S308 to S313, similar to the first embodiment.

[0102] <Shift processing (S410)> 11 is a flowchart showing the procedure for shifting a sheet bundle performed in S410 using the reversing rollers 24. When starting the shifting process, the conveyance control unit 410 waits in S501 for the first sheet (the bottom sheet) of the shingled sheet bundle generated in the buffer unit to pass the position of the inner discharge rollers 26 (between the pair of rollers). Note that the sheet bundle is in a state of being conveyed toward the upper discharge tray 25 due to the processes of S305 and S306. When the trailing edge of the first sheet of the sheet bundle being conveyed passes the position of the inner discharge rollers 26, the conveyance control unit 410 proceeds to the process of S502.

[0103] In S502, the conveyance control unit 410 stops the reversing rollers 24. At this time, since the entire sheet bundle has already passed through the inner discharge rollers 26, the sheet bundle stops in a state where it is sandwiched only by the roller pair of the reversing rollers 24.

[0104] Next, in S503, the conveyance control unit 410 drives the third reversing motor M5 for a predetermined time to shift the position of the reversing rollers 24 in the sheet width direction, thereby shifting the position of the shifted bundle. At this time, the conveyance control unit 410 shifts the shifted bundle in the sheet width direction in a direction that shortens the distance between the edge of the sheet and the lateral alignment reference plate 52 (for example, toward the front in FIG. 1). In this way, by shifting the position of the reversing rollers 24, the position of the sheet bundle held by the reversing rollers 24 is shifted in the sheet width direction. Depending on the shift amount (for example, 20 mm) of the reversing rollers 24 (sheet bundle), the movement distance of the sheet bundle in the sheet width direction when lateral alignment is performed in the binding processing unit 4A becomes shorter.

[0105] When the shift of the reversing rollers 24 is completed, the conveyance control unit 410 proceeds to S504. In S504, the conveyance control unit 410 starts driving the reversing rollers 24 and the inner discharge rollers 26 to rotate so that the sheet bundle is conveyed in the direction of the binding processing unit 4A, and proceeds to S505. In S505, the conveyance control unit 410 waits for the final sheet (topmost sheet) of the sheet bundle being conveyed to reach the inner discharge rollers 26, and when it reaches the inner discharge rollers 26, proceeds to S506.

[0106] In S506, the conveyance control unit 410 separates the reverse rollers 24. At this time, the final sheet of the sheet stack is being nipped and conveyed between the pair of inner discharge rollers 26. Therefore, even when the reverse rollers 24 are separated, the conveyance of the sheet stack continues.

[0107] Next, in S507, the conveyance control unit 410 drives the third reversing motor M5 for a predetermined time to return the position of the reversing roller 24, which was shifted in S503, to its original position, thereby shifting the position of the reversing roller 24 in the sheet width direction. After the shifting of the reversing roller 24 is completed, the conveyance control unit 410 proceeds to S508. In S508, the conveyance control unit 410 abuts the reversing roller 24 in preparation for the conveyance of the subsequent sheet from the image forming apparatus 1.

[0108] The determination of the sheet position in S501 and S505 may be made based on the elapsed time based on the timing at which the trailing edge of the target sheet is detected by the inlet sensor 27. Alternatively, the determination may be made based on the count value of the drive pulses of each motor.

[0109] 11, it is necessary to avoid collision between the sheet stack being shifted and the subsequent sheets conveyed from the image forming apparatus 1. For this reason, it is necessary to increase the distance (paper spacing) between the sheets conveyed from the image forming apparatus 1, which may reduce the productivity of the image forming system 1S.

[0110] In this embodiment, by performing the process according to the procedure in Fig. 10, when performing shift processing on a shift stack, the overall length in the conveyance direction of the shingled sheet stack generated in the buffer unit is shortened. This reduces a decrease in productivity of the post-processing device 4 even when the sheet spacing is increased as a result of performing shift processing. Furthermore, sheet shift processing is performed when the size of the sheets to be processed is equal to or smaller than a threshold size, and control is performed to reduce the amount of sheet shift when generating a sheet stack accordingly. Therefore, when performing shift processing, it is possible to reduce a decrease in productivity of the post-processing device 4 while maintaining the accuracy of alignment processing in the sheet conveyance direction (ensuring vertical alignment capability).

[0111] [Other embodiments] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0112] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0113] 1S: image forming system, 1: image forming device, 4: post-processing device, 4A: binding processing unit, 400: finisher control unit, 401: CPU, 410: transport control unit, 412: information acquisition unit, 24: reversing roller, 26: inner discharge roller, 81: receiving path, 82: inner discharge path, 83: first discharge path, 33: vertical alignment roller, 39: vertical alignment reference plate, 52: horizontal alignment reference plate, 58: horizontal alignment jogger (alignment member)

Claims

1. A sheet processing apparatus, a stacking section on which sheets to be processed are stacked; a control unit that controls conveyance of sheets on the conveyance path so that, in a buffer unit provided on a conveyance path for conveying sheets to the stacking unit, the sheets conveyed on the conveyance path are shifted in order upstream in a conveyance direction to form a sheet bundle that is superimposed on the sheets, and the sheet bundle is conveyed from the buffer unit to the stacking unit; an alignment unit that performs an alignment process to align the sheet position in the conveying direction with respect to the sheet bundle stacked on the stacking unit; a processing unit for performing sheet processing on the sheet bundle that has been subjected to the alignment processing, The control unit controls the amount of shift of the sheet positions when the sheets are stacked in order in the buffer unit in accordance with the size of the sheet transported on the transport path. A sheet processing apparatus characterized by:

2. The control unit reduces the shift amount as the size of the sheet transported on the transport path decreases.

2. The sheet processing apparatus according to claim 1, wherein the sheet processing apparatus is a sheet processing apparatus.

3. The control unit sets the shift amount to be smaller when the size of the sheet conveyed on the conveying path is equal to or smaller than a threshold size than when the size is not equal to or smaller than the threshold size.

3. The sheet processing apparatus according to claim 1, wherein the sheet processing apparatus is a sheet processing apparatus.

4. The control unit determines whether the size of the sheet transported on the transport path is equal to or smaller than the threshold size based on at least one of the length of the sheet transported on the transport path in the transport direction and the width of the sheet in the width direction perpendicular to the transport direction.

4. The sheet processing apparatus according to claim 3, wherein the sheet processing apparatus is a sheet processing apparatus.

5. The control unit determines whether the size of the sheet being conveyed through the conveying path is equal to or smaller than the threshold size based on the sheet size set by the user.

5. The sheet processing apparatus according to claim 3, wherein the sheet processing apparatus is a sheet processing apparatus.

6. a measuring unit that is provided upstream of the buffer unit in the conveying direction and that measures at least one of a length of the sheet conveyed on the conveying path in the conveying direction and a width of the sheet in a width direction perpendicular to the conveying direction, The control unit determines whether the size of the sheet being conveyed through the conveying path is equal to or smaller than the threshold size based on the measurement result by the measurement unit.

5. The sheet processing apparatus according to claim 3, wherein the sheet processing apparatus is a sheet processing apparatus.

7. The aligning unit includes an aligning roller that is driven to rotate and moves the sheets in the conveying direction, and a first reference plate that is provided along a width direction perpendicular to the conveying direction, and performs an aligning process on the sheet bundle in the conveying direction by moving the sheets of the sheet bundle stacked on the stacking unit one by one from the bottom downstream in the conveying direction by the aligning roller, and abutting an edge of each sheet against the first reference plate.

7. The sheet processing apparatus according to claim 1, wherein the sheet processing apparatus is a sheet processing apparatus.

8. The aligning unit further performs an alignment process for aligning the sheet position in the width direction perpendicular to the conveying direction with respect to the sheet bundle stacked on the stacking unit, the sheet processing apparatus further includes a shifting unit provided in the buffer unit and configured to shift a position of the sheet bundle generated in the buffer unit in the width direction; The control unit performs a shift process to shift the position of the sheet stack in the width direction by the shift unit so that the amount of movement of the sheets in the width direction alignment process by the alignment unit is reduced.

8. The sheet processing apparatus according to claim 1, wherein the sheet processing apparatus is a sheet processing apparatus.

9. The aligning unit includes an aligning member and a second reference plate provided along the conveying direction, and performs aligning processing on the sheet bundle in the width direction by moving the sheet bundle in the width direction with the aligning member so that an end of the sheet bundle stacked on the stacking unit along the conveying direction comes into contact with the second reference plate and is aligned.

9. The sheet processing apparatus according to claim 8, wherein the sheet processing apparatus is a sheet processing apparatus.

10. The control unit performs the shift process on the sheet stack when the size of the sheets conveyed on the conveying path is equal to or smaller than a threshold size.

10. The sheet processing apparatus according to claim 8, wherein the sheet processing apparatus is a sheet processing apparatus.

11. The control means sets the shift amount when the shift process is performed on the sheet bundle to be smaller than when the shift process is not performed on the sheet bundle. The sheet processing apparatus according to claim 10 .

12. The processing unit performs a binding process for binding the sheet bundle stacked on the stacking section as the sheet processing.

12. The sheet processing apparatus according to claim 1, wherein the sheet processing apparatus is a sheet processing apparatus.

13. an image forming device that forms an image on a sheet; a sheet processing apparatus according to claim 1 , the sheet processing apparatus being connected to a downstream side of the image forming apparatus in a sheet conveying direction and performing sheet processing on the sheet conveyed from the image forming apparatus through a conveying path; An image forming system comprising:

Images