Sheet post-processing device, and image forming system comprising image forming device and sheet post-processing device

Abstract

To maintain an alignment property of a sheet bundle by maintaining the alignment property of sheets constituting the sheet bundle subjected to post-processing at a processing tray, even when the sheets stacked at buffer means each have a different length from each other.SOLUTION: A sheet post-processing device includes: buffer means for successively receiving sheets conveyed and holding them in a state of being overlapped with each other; a processing tray on which the sheets fed via the buffer means are stacked; post-processing means by which the sheets stacked on the processing tray are subjected to predetermined post-processing; and a control part for controlling a deviation amount of a preceding sheet and a following sheet among the plurality of sheets stacked on the buffer means. Sheet information including a sheet length of a sheet conveyed by the buffer means is acquired, and a deviation amount of the following sheet with respect to a sheet that is not cut yet is increased in comparison with a predetermined deviation amount on the basis of the cut length of the sheet information when the preceding sheet held in a state of being overlapped on a buffer part is a sheet that is cut.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a sheet post-processing apparatus that receives an image-formed sheet and performs post-processing thereon. In particular, the present invention relates to a sheet post-processing apparatus (hereinafter simply referred to as a "post-processing apparatus" or a "finisher" in the present application) that receives an image-formed sheet cut in the vertical direction of the sheet conveyance direction and includes a buffer unit that holds the sheets in a stacked state.

Background Art

[0002] Conventionally, a sheet post-processing apparatus that performs post-processing on a stack of sheets discharged from an image forming apparatus such as a printer, a copier, or a facsimile on a processing tray has been widely known.

[0003] In such a sheet post-processing apparatus, during the post-processing of the image-formed sheets on the processing tray, in order to prevent the sheets constituting the next sheet stack from being discharged onto the sheet stack deposited on the processing tray, a buffer process is performed in which one or more sheets constituting the next stack of sheets are retained in a buffer path (buffer means) provided in the conveyance path and conveyed while being stacked. As a result, the image forming apparatus can discharge the image-formed sheets to the sheet post-processing apparatus side without widening the discharge interval between the last sheet of the sheet stack and the first sheet of the next sheet stack, enabling highly efficient post-processing.

[0004] As described above, in the buffer process of retaining one or more sheets constituting the next stack of sheets in a buffer path provided in the conveyance path, in order to ensure the alignment of the plurality of sheets stacked and conveyed to the processing tray with respect to the conveyance direction, when stacking subsequent sheets on the sheets retained in the buffer path, the downstream ends in the conveyance direction are shifted by a predetermined amount in the conveyance direction and stacked, thereby shifting the rear end side of the sheet on the upstream side in the conveyance direction by a predetermined amount. A technique has been proposed (see, for example, Patent Document 1).

[0005] By the way, there is also known a sheet cutting device that cuts a sheet discharged from an image forming apparatus in a direction orthogonal to the conveyance direction and cuts an edge portion of the generated sheet bundle.

[0006] In such an image forming apparatus, rather than forming an image on two sheets, by forming images of two sheets in parallel on one sheet of a larger size, there are advantages such as reducing the number of times of replenishing sheets in the paper feed tray.

[0007] Therefore, in order to perform image formation for a plurality of pages on a large-sized sheet, then cut the sheet in a subsequent process, and further perform post-processing such as stapling, a technique of discharging to a sheet post-processing device that performs predetermined post-processing on each of the cut sheets is known (for example, refer to Patent Document 2).

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, for example, when cutting a sheet on which images for two pages are formed on one large-sized sheet into two sheets with a sheet cutting device, if the cutting position of the sheet is shifted by 0.5 mm due to an error in the cutting operation as shown in FIG. 12(A-1), for example, the sheet P1 becomes 1.0 mm shorter than the sheet P2. Thereafter, when the cut sheet (for reference, P-1 in FIG. 12) is retained in the buffer means provided in the sheet conveyance path and the subsequent sheet (for reference, P-2 in FIG. 12) is stacked on the sheet P1, when stacking so that the downstream end in the conveyance direction of each sheet is shifted by a predetermined amount (X: 2.5 mm) in the conveyance direction, since the sheet lengths of the preceding sheet and the subsequent sheet are different, the shift amount at the upstream end in the conveyance direction becomes less than the required shift amount (for example, 2 mm) (Y: 1.5 mm).

[0009] As a result, when a sheet overlapping on the processing tray is conveyed, the switchback alignment of the sheet with respect to the conveyance direction cannot be correctly performed, and misalignment may occur within the sheet bundle when the binding process is performed on the processing tray, or there is a risk that some sheets do not reach the binding position and cannot be bound.

[0010] The present invention has been made in view of such problems of conventional sheet post-processing apparatuses, and in a sheet post-processing apparatus, even when the lengths of the sheets to be overlapped in the buffer means are different, an object is to improve the alignment of the sheets to be post-processed on the processing tray.

Means for Solving the Problems

[0011] In order to solve the above problems, the present invention provides a sheet post-processing apparatus that receives an image-formed sheet or an image-formed sheet cut in the vertical direction of the conveyance direction and performs post-processing, the buffer means for sequentially receiving the conveyed sheets and holding them in a stacked state of a plurality of sheets, a processing tray for stacking the sheets sent through the buffer means, post-processing means for performing predetermined post-processing on the sheets stacked on the processing tray, alignment means for abutting and aligning the leading end side of the sheets stacked on the processing tray, and a control unit for controlling the amount of displacement between the leading sheet and the subsequent sheet of the plurality of sheets stacked on the buffer means, the control unit acquires sheet information including the sheet length of the sheet conveyed to the buffer means, and based on the sheet length of the sheet information, when the leading sheet held in an overlapped state in the buffer unit is a cut sheet, controls to make the amount of displacement with the subsequent sheet larger (increase) than a predetermined amount of displacement for the uncut sheet.

[0012] Here, there is a sheet branching means for branching into a sheet branch path branched from a sheet conveyance path through which the imaged sheet is conveyed, and a buffer unit for retaining subsequent sheets in the sheet branch path so that no new subsequent sheet is sent onto the processing tray during the post-processing of the sheet in the post-processing means. The buffer means controls the amount of shift between the leading sheet and the subsequent sheet in the buffer unit.

[0013] And, as one of the controls of the shift amount, when the control unit controls the shift amount between the leading sheet and the subsequent sheet in the buffer means, the control unit performs this by changing the conveyance speed of the leading sheet or the subsequent sheet in the conveyance path.

[0014] Further, before overlapping the downstream ends in the conveyance direction of the leading sheet and the subsequent sheet retained in the buffer means after shifting them by a predetermined distance, when the sheet length acquired by the sheet length acquisition means is different from the length in the conveyance direction of the subsequent sheet, the control unit may control so as to overlap the downstream ends in the conveyance direction so that the rear ends in the conveyance direction of the leading sheet and the subsequent sheet are shifted by a predetermined distance.

Advantages of the Invention

[0015] According to the present invention, in the retention process of a plurality of sheets in the buffer unit of the sheet in the sheet post-processing apparatus, even if the lengths of the sheets to be overlapped are different, by overlapping so that the upstream end in the conveyance direction is shifted by a necessary amount set in advance in the conveyance direction, it is possible to prevent the alignment and consistency of the sheet bundle from being disturbed.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the details of the sheet post-processing device (this sheet post-processing layer) according to the present invention will be described in detail with reference to the drawings.

[0018] FIG. 1 shows an example of an embodiment of an image forming system including this sheet post-processing device. In the example shown in FIG. 1, the image forming system 1000 includes an image forming device 100, a document reading device 200 that reads a document image, an operation display device 600 that displays an operation screen, a cutting device 400 that cuts a sheet, and a sheet post-processing device (hereinafter, appropriately referred to as a "finisher" in the present application) 500 that performs post-processing on the sheet.

[0019] In addition to the embodiment example shown in FIG. 1, for example, a configuration in which a cutting device 400 for cutting a sheet and a sheet post-processing device are incorporated in the same housing, or a configuration in which buffer means is provided in the cutting device 400 is also included in the scope of this sheet post-processing.

[0020] The document reading device 200 includes a document feeding unit and a document reading unit. The document feeding unit feeds the documents set on the document tray 201 one by one in the left direction in FIG. 1, conveys them in the right direction through a curved path via the reading position on the platen glass 202, and discharges them onto the discharge tray 203. The document reading unit includes a scanner unit 204 provided at a position corresponding to the reading position, which is a predetermined position below the platen glass 202, and an image sensor 205. When the document passes through the reading position on the platen glass 202, the reading surface of the document is irradiated by the light source of the scanner unit 204, and the reflected light reaches the image sensor 205 through, for example, a mirror and a lens 206 and forms an image on the imaging surface of the image sensor 205.

[0021] The optically read image is converted into image data by the image sensor 205 and output. The image data output from the image sensor 205 is input as an image signal to the exposure device 103 of the image forming apparatus 100.

[0022] The image forming apparatus 100 includes an image forming unit and a paper feeding unit. The image forming unit mainly includes a photosensitive drum 101, a charger 102, an exposure unit 103, and a developing unit 104. The paper feeding unit includes paper feeding cassettes 111, 112, and a conveyance path 110 that extends from the paper feeding cassettes to a transfer unit 105 near the photosensitive drum 101 and a fixing unit 106 and then reaches a discharge roller 116. The paper feeding unit also includes a reversing path 119 that branches from the conveyance path 110 on the downstream side of the photosensitive drum 101, and a duplex conveyance path 120 that is connected to the reversing path 119 and has one end connected to the conveyance path 110 on the upstream side of the transfer unit 105. In the conveyance path 110, pickup rollers 127, 128 respectively arranged at the outlet portions of the paper feeding cassettes 111, 112, and paper feeding rollers 129, 130 for conveying the picked-up sheet to the transfer unit 105 are provided. In the conveyance path 110, a registration roller (hereinafter referred to as "registration roller") 114 arranged on the upstream side of the transfer unit 105 is also provided. In the conveyance path 110 on the downstream side of the fixing unit 106, a paper feeding roller 115, a flapper 118, and a discharge roller 116 are provided. The flapper 118 switches the conveyance direction of the sheet conveyed in the conveyance path 110 to the reversing path 119.

[0023] In the image forming apparatus 100 having such a configuration, the exposure unit 103 modulates and outputs laser light based on the image signal input from the document reading apparatus 200. The output laser light is irradiated onto the photosensitive drum 101 while being scanned by a polygon mirror 107. An electrostatic latent image corresponding to the scanned laser light is formed on the surface of the photosensitive drum 101 irradiated with the laser light. The electrostatic latent image on the photosensitive drum 101 is visualized by the developer supplied from the developing unit 104 to become a toner image.

[0024] On one hand, the sheet fed from the upper cassette 111 or the lower cassette 112 by the pickup roller 127 or 128 is conveyed by the paper feed rollers 129 and 130, and stops when its leading end reaches the registration roller 114 in a rotation - stopped state. Next, the registration roller 114 is driven at a predetermined timing, and conveys the sheet between the photosensitive drum 101 and the transfer unit 105 at a timing synchronized with the start of the irradiation of the laser beam. Then, the toner image formed on the photosensitive drum 101 by the transfer unit 105 is transferred onto the fed sheet. The sheet onto which the toner image has been transferred is conveyed to the downstream fixing unit 106, and the toner image is fixed to the sheet by heating and pressing the sheet by the fixing unit 106. The sheet onto which the toner image has been fixed is discharged from the image forming apparatus 100 via the flapper 118 and the discharge roller 116, and is discharged toward a cutting apparatus 400 described later.

[0025] Next, the configuration of the cutting apparatus 400 will be described. FIG. 2 is a diagram showing the schematic configuration of the cutting apparatus 400 in FIG. 1.

[0026] In FIG. 2, the cutting apparatus 400 is provided with a conveyance path for performing a cutting process on the sheet discharged from the image forming apparatus 100 and conveying it to the finisher 500 or the discharge tray 430. That is, the cutting apparatus 400 is provided with a conveyance path 420 for conveying the sheet received from the image forming apparatus 100 to the conveyance roller 403 on the upstream side of the flapper 416 via the cutter unit 415 as a cutting means. Subsequently, a discharge path 421 for conveying the sheet conveyed to the conveyance roller 403 to the finisher 500 and a discharge path 422 for conveying it to the discharge tray 430 are provided.

[0027] The conveyance path 420 is provided with conveyance rollers 401, 402, 403 and conveyance sensors 411, 412, and a cutter unit 415 is arranged between the conveyance rollers 402 and 403. A flapper 416 is arranged at the branch of the conveyance path 420, the discharge path 421, and the discharge path 422. The discharge path 421 is provided with a discharge roller 404 and a conveyance sensor 413. The discharge path 422 is provided with a discharge roller 405 and a conveyance sensor 414.

[0028] The cutter unit 415 sequentially takes in the sheets discharged from the image forming apparatus 100 and performs a cutting process on the taken-in sheets. As an example, the cutting process is carried out when the sheet information notified from the image forming apparatus 100 is set such that a plurality of pages of images are stored on one sheet and the page boundaries are cut to generate a plurality of valid sheets. This setting will be described later.

[0029] The sheets cut by the cutter unit 415 are discharged to the finisher 500 via the flapper 416 and the discharge roller 404, or to the discharge tray 430 via the flapper 416 and the discharge roller 405 according to the discharge destination set in the sheet information of each sheet notified from the image forming apparatus 100.

[0030] Next, the configuration of the finisher 500 will be described. FIG. 3 is a diagram showing the schematic configuration of the finisher 500 in FIG. 1.

[0031] In FIG. 3, the finisher 500 receives the sheets discharged from the cutting device 400, performs necessary processes, and discharges them outside the machine. As stacking means for stacking the discharged sheets, two upper and lower trays, an upper tray 536 and a lower tray 537, are provided.

[0032] The sheet discharged from the cutting device 400 is delivered to the inlet roller pair 502 of the finisher 500. At this time, the delivery timing of the sheet is also detected by the inlet sensor 501. The sheet conveyed by the inlet roller pair 502 is conveyed through the conveyance path 503 by the first conveyance roller pair 504, the second conveyance roller pair 505, and the third conveyance roller pair 510. The first, second, and third conveyance roller pairs 504, 505, and 510 are driven by a conveyance motor M701. Also, a pass sensor 590 is arranged between the first conveyance roller pair 504 and the second conveyance roller pair 505, and a pass sensor 506 is arranged between the second conveyance roller pair 505 and the third conveyance roller pair 510.

[0033] A buffer path switching flapper 507 is arranged between the third conveyance roller pair 510 and the second buffer roller pair 515 disposed downstream thereof. Also, downstream of the second buffer roller pair 515, an upper path switching flapper 518 as a switching means is arranged at a position where the conveyance path branches into an upper discharge path 517 (first conveyance path) and a lower discharge path 521 (second conveyance path). Comparing the path lengths, the lower discharge path 521 is longer than the upper discharge path 517.

[0034] The buffer path switching flapper 507 (hereinafter referred to as the buffer flapper 507) is driven by a buffer solenoid SL801 (see FIG. 6) to displace its flapper position. The upper path switching flapper 518 (hereinafter referred to as the upper path flapper 518) is driven by an upper discharge solenoid SL802 (see FIG. 6) to displace its flapper position.

[0035] In the claims of the present application, all mechanisms for guiding the sheet to the buffer path and retaining the sheet therein are included in the "buffer means".

[0036] The sheet conveyed by the second buffer roller pair 515 after passing through the buffer flapper 507 is detected by a buffer sensor 508 disposed downstream of the second buffer roller pair 515.

[0037] When the sheet is discharged onto the upper tray 536, the upper path flapper 518 is positioned at a position (a first position described later) that guides the sheet to the upper discharge path 517 connected to the upper tray 536. After the sheet is guided to the upper discharge path 517, it passes through the upper discharge sensor 509 and is discharged onto the upper tray 536 by the upper discharge roller pair 520. The upper discharge roller pair 520 is driven by a discharge motor M703.

[0038] When the sheet is not discharged onto the upper tray 536, the upper path flapper 518 is positioned at a position (a second position described later) that guides the sheet to the lower discharge path 521. The sheet conveyed by the second buffer roller pair 515 via the buffer flapper 507 is guided to the lower discharge path 521 and then sequentially passes through the conveyance path by the third buffer roller pair 522 and the first lower discharge roller pair 524. A lower path sensor 513 is arranged between the third buffer roller pair 522 and the first lower discharge roller pair 524.

[0039] A buffer path 540 is connected and provided near the buffer flapper 507 on the upstream side of the upper path flapper 518 in the conveyance path. In the sheet stacking process described later, a sheet whose leading end once enters the upper discharge path 517 or the lower discharge path 521 and whose trailing end passes over the buffer flapper 507 and is then reversely conveyed is received by the buffer path 540. The buffer flapper 507 switches between a position for conveying the sheet by the first, second, and third conveyance roller pairs 504, 505, 510 and a position for guiding the sheet to the buffer path 540.

[0040] A first buffer roller pair 512 is arranged in the buffer path 540. The first buffer roller pair 512, the second buffer roller pair 515, and the third buffer roller pair 522 are driven by a buffer motor M702. The sheet stacking process using the buffer path 540 will be described later.

[0041] The sheet conveyed to the first lower discharge roller pair 524 is conveyed to the bundle conveyance path 526. The plurality of sheets discharged to the processing tray 538 by the second lower discharge roller pair 528 are aligned on the processing tray 538. Thereafter, the aligned sheets are stapled by a stapler 532 as a post-processing unit if necessary, and then discharged to the lower tray 537 as a sheet bundle by the bundle discharge roller pair 530.

[0042] A pulse motor is used for the conveyance motor M701, the buffer motor M702, and the discharge motor M703, and the advance amount of each motor is controlled by the number of drive pulses.

[0043] Next, the control configuration of the entire image forming system including a controller that controls the entire image forming system 1000 will be described. FIG. 4 is a block diagram showing the control configuration of the image forming system of FIG. 1.

[0044] In FIG. 4, the image forming system 1000 has a controller CPU circuit section 900 as a control section. The controller CPU circuit section 900 incorporates a CPU 901, a ROM 902, and a RAM 903. The CPU 901 is a CPU that performs basic control of the entire image forming system 1000, and is connected to the ROM 902 in which a control program is written and the RAM 903 for performing processing by a data bus (not shown). The CPU 901 is communicably connected to each control section 911, 921, 922, 923, 904, 931, 941, 553, 971, and comprehensively controls these by the control program stored in the ROM 902. Examples of each control section include a document feeder control section 911, a document reading device control section 921, an image generation control section 922, an image signal control section 923, an external I / F 904, a printer control section 931, an operation display device control section 941, a finisher control section 553, and a cutting device control section 971. The RAM 903 temporarily holds control data and is used as a work area for arithmetic processing associated with control.

[0045] The original document feeding device control unit 911 drives and controls the document feeding unit of the document reading device 200 based on instructions from the controller CPU circuit unit 900. The document reading device control unit 921 performs drive control on the above-described scanner unit 204, image sensor 205, etc., and transfers the image signal output from the image sensor 205 to the image signal control unit 923. The image generation control unit 922 generates image data based on the digital image signal input from the computer 905 via the external I / F 904 and transfers it to the image signal control unit 923.

[0046] The image signal control unit 923 converts the analog image signal from the image sensor 205 into a digital signal, performs various processes on it, converts this digital signal into an image signal, and outputs it to the printer control unit 931. Also, the image signal control unit 923 performs various processes on the digital image signal input from the computer 905 via the external I / F 904, converts this digital image signal into an image (video) signal, and outputs it to the printer control unit 931. The processing operation by the image signal control unit 923 is controlled by the controller CPU circuit unit 900. The printer control unit 931 controls the image forming apparatus 100 based on the input image signal, and performs image formation and sheet conveyance.

[0047] Here, in the document reading device control unit 921 and the image generation control unit 922, when predetermined settings are made on the split mode setting screen described later, image data in which images for multiple pages or multiple jobs are stored for one sheet is generated.

[0048] The cutting device control unit 971 is mounted on the cutting device 400, and performs drive control of the entire cutting device 400 by exchanging information with the controller CPU circuit unit 900. The details of this control will be described later. The finisher control unit 553 is mounted on the finisher 500, and performs drive control of the entire finisher 500 by exchanging information with the controller CPU circuit unit 900.

[0049] The operation display device control unit 941 exchanges information with the operation display device 600 and the controller CPU circuit unit 900. The operation display device 600 has a plurality of keys for setting various functions related to image formation, a display unit for displaying information indicating the setting state, and the like. It outputs a key signal corresponding to the operation of each key to the controller CPU circuit unit 900, and displays corresponding information on the operation display device 600 based on a signal from the controller CPU circuit unit 900.

[0050] Here, the operation display device control unit 941 causes the display unit of the operation display device 600 to display a split mode setting screen for setting the method of face attachment for one sheet. Specifically, the operation display device control unit 941 causes the display unit of the operation display device 600 to display a screen as shown in FIG. 11, enabling settings for Nin1 printing in which image data of the same job is divided onto one sheet and reduced for face attachment, and print settings (hereinafter referred to as split sheet settings) in which image data of multiple jobs is divided onto one sheet and face-attached.

[0051] Next, the control configuration of the cutting device control unit 971 that drives and controls the cutting device 400 will be described. FIG. 5 is a block diagram showing the configuration of the cutting device control unit 971 in FIG. 4.

[0052] In FIG. 5, the cutting device control unit 971 is composed of a CPU 972, a ROM 973, a RAM 974, etc. The cutting device control unit 971 communicates with the controller CPU circuit unit 900 of the image forming apparatus 100 via a communication IC, and performs data exchange such as sheet information including job content and discharge destination, and delivery notification of sheets. The cutting device control unit 971 is also connected to an inlet conveyance motor M21, a cutting conveyance motor M22, a discharge conveyance motor M23, and conveyance sensors 411 to 414 for driving conveyance rollers for sheet conveyance. The cutting device control unit 971 is also connected to a cutting motor M24 and a solenoid SL3 for performing a cutting process on the conveyed sheet with a cutter unit 415. Then, based on an instruction from the controller CPU circuit unit 900, the cutting device control unit 971 executes various programs stored in the ROM 973 and controls the driving of the cutting device 400 by various motors and sensors provided in the cutting device 400. At this time, the cutting device control unit 971 outputs, for example, a drive signal to various motors and receives a detection signal from each sensor.

[0053] Here, in the setting of the above-described division mode shown in FIG. 11, the cutting device control unit 971 performs a cutting process on the boundary of the face-attached image data with the cutter unit 415 for a job in which a divided sheet is set, determines the discharge destination of the sheet based on the information of each cut sheet, and discharges it.

[0054] Next, the control configuration of the finisher 500 will be described. FIG. 6 is a block diagram showing the configuration of the finisher control unit 553 in FIG. 4.

[0055] In FIG. 6, the finisher control unit 553 is composed of a CPU 550, a ROM 551, a RAM 552, etc. The finisher control unit 553 communicates with the controller CPU circuit unit 900 provided in the image forming apparatus 100 via a communication IC, and performs data exchange such as job information and delivery notification of sheets.

[0056] The finisher control unit 553 detects the states of various sensors including the entrance sensor 501, the pass sensors 506 and 590, the buffer sensor 508, the lower pass sensor 513, the upper discharge sensor 509, and other sensors (not shown). The finisher control unit 553 performs drive control of various drive units including the conveyance motor M701, the buffer motor M702, the discharge motor M703, and other motors (not shown). These drive units further include a buffer solenoid SL801 (hereinafter referred to as buffer SL801) and an upper discharge solenoid SL802 (hereinafter referred to as upper discharge SL802). These various drive units and various rollers cooperate to function as a conveyance means for conveying the sheet.

[0057] Then, the finisher control unit 553 executes various programs stored in the ROM 551 based on instructions from the controller CPU circuit unit 900 to drive and control the finisher 500. At this time, the finisher control unit 553 outputs, for example, drive signals to various motors and receives detection signals from various sensors.

[0058] [Sheet stacking process] In FIGS. 7 to 8, the operation when the finisher 500 performs buffer processing on a plurality of sheets and discharges the sheets to the lower tray 537 (hereinafter referred to as lower discharge) or discharges the sheets to the upper tray 536 (hereinafter referred to as upper discharge) will be described.

[0059] FIGS. 7(a) to (e) are diagrams showing the flow when, as an example of a small size, two A4-sized sheets are buffer-processed and stacked and lower discharge is executed.

[0060] Here, in the initial state (off state) where the buffer flapper 507 does not receive driving force from the buffer SL801, it is in the "conveying position" (the position shown in FIG. 7(a)) where the sheet can be conveyed downstream by the first, second, and third conveying roller pairs 504, 505, and 510. When the buffer flapper 507 is driven by the turning on of the buffer SL801, it switches to the "buffer position" (the position shown in FIG. 7(c)) where it can guide the sheet to be reversely conveyed to the buffer path 540. In this case, the conveyance path from the buffer flapper 507 to the second buffer roller pair 515 communicates with the buffer path 540.

[0061] Also, in the initial state (off state) where the upper path flapper 518 does not receive driving force from the upper discharge SL802, the upper path flapper 518 is located at a position (the second position) where it can guide the sheet to the lower discharge path 521 (the position shown in FIG. 7(a)). When the upper path flapper 518 is driven by the turning on of the upper discharge SL802, it switches to a position (the first position) where it can guide the sheet to the upper discharge path 517 (the position shown in FIG. 8(a)).

[0062] In a job, it is specified whether post-processing is required for a plurality of sheets to be processed and the content of the post-processing to be performed, and it is also specified whether to discharge the sheet downward or upward. Immediately before the start of the job, the buffer flapper 507 and the upper path flapper 518 are in the initial state.

[0063] When the finisher 500 stacks two A4-sized sheets and performs downward discharge, first, the first sheet P1 is conveyed by the first conveying roller pair 504 and the second conveying roller pair 505 (FIG. 7(a)). When the sheet P1 passes through the buffer flapper 507 in the conveying position and passes through the second buffer roller pair 515, and the downstream end (sheet leading edge) of the sheet P1 in the sheet conveying direction reaches the buffer sensor 508, the buffer sensor 508 turns on (sheet present).

[0064] After the buffer sensor 508 is turned on and the sheet P1 is conveyed by a predetermined amount, the driving of the buffer motor M702 is stopped, and the buffer roller pairs 515 and 522 stop (FIG. 7(b)). Here, the above-mentioned predetermined amount is the conveyance amount for conveying the sheet P1 until the upstream end (the rear end of the sheet) of the sheet P1 in the sheet conveyance direction sufficiently passes the buffer flapper 507.

[0065] Next, when the buffer flapper 507 switches to the buffer position and the buffer motor M702 starts to reverse after a predetermined time has elapsed since it stopped, the sheet P1 is conveyed to the buffer path 540 and further conveyed by the first buffer roller pair 512. Then, after the buffer sensor 508 is turned off (no sheet) and the sheet P1 is conveyed by a predetermined amount, the driving by the buffer motor M702 stops. Then, the first buffer roller pair 512 stops, and the sheet P1 temporarily waits in a state of being clamped by the first buffer roller pair 512 (FIG. 7(c)).

[0066] When the first buffer roller pair 512 stops, the buffer flapper 507 switches to the conveyance position. Then, when the leading end of the second sheet P2 reaches the path sensor 506 and the path sensor 506 is turned on (sheet present), the buffer motor M702 operates after a predetermined time has elapsed from that point, the first buffer roller pair 512 that clamps the sheet P1 starts to rotate forward, and the sheets P1 and P2 are overlapped and conveyed downstream (FIG. 7(d)).

[0067] Next, the sheet bundle composed of the overlapped sheets P1 and P2 is conveyed by the second buffer roller pair 515. When the leading end of the sheet bundle reaches the buffer sensor 508, the buffer sensor 508 is turned on (sheet present). The sheet bundle is further conveyed downstream by the third buffer roller pair 522 and the first lower discharge roller pair 524 (FIG. 7(e)). The conveyed sheet bundle is loaded on the processing tray 538.

[0068] Thereafter, sheets P1 and P2 are aligned on the processing tray 538, stapled by the stapler 532 as necessary, and then discharged to the lower tray 537 by the bundle discharge roller pair 530.

[0069] For large-sized (e.g., A3 size) sheets, the sheet stacking process is also performed in the same manner, and the stacked sheets are discharged to the lower tray 537 via the processing tray 538.

[0070] In this way, the process of stacking multiple sheets in the buffer path 540 is the sheet stacking process (hereinafter referred to as the stacking process or buffer process). The finisher control unit 553 functions as a control unit that performs the stacking process by controlling the conveyance of the sheets in addition to controlling the switching operations of the upper path flapper 518 and the buffer flapper 507. In the stacking process, the leading edge of the sheet needs to enter the upper discharge path 517 or the lower discharge path 521 once, and in addition to the buffer path 540, the upper discharge path 517 or the lower discharge path 521 is used.

[0071] In the example of FIG. 7, when the finisher 500 executes lower discharge, in the stacking process, the lower discharge path 521 connected to the lower tray 537 is used. The upper path flapper 518 does not need to be switched before and after stacking. Therefore, from after the start of the job and before the start of sheet stacking to the end of the job, the upper path flapper 518 does not need to be driven and is always located at the second position, which is the initial position.

[0072] FIG. 8 is a diagram showing the flow when the finisher 500 performs buffer processing on two A4-size sheets as an example of a small size and executes upper discharge.

[0073] When the finisher 500 performs upper discharge, prior to sheet conveyance and the stacking process, the upper discharge SL802 is turned on and the upper path flapper 518 is switched to the first position (FIG. 8(a)). The first sheet P1 is conveyed by the first conveyance roller pair 504 and the second conveyance roller pair 505.

[0074] When the sheet P1 passes through the second buffer roller pair 515 via the buffer flapper 507 in the conveyance position and the leading end of the sheet P1 is detected by the buffer sensor 508, the buffer sensor 508 turns on (sheet present). Since the upper path flapper 518 is in the first position, the conveyed sheet P1 is guided to the upper discharge path 517.

[0075] When the sheet P1 has been conveyed a predetermined distance after the buffer sensor 508 turns on, the driving of the buffer motor M702 and the discharge motor M703 stops, so that the second buffer roller pair 515 and the upper discharge roller pair 520 stop (Fig. 8(b)). The predetermined distance is set so that when the sheet P1 stops in the state of Fig. 8(b), the leading end of the A4-size sheet does not protrude onto the upper tray 536.

[0076] Next, the buffer flapper 507 switches to the buffer position, and the buffer motor M702 and the discharge motor M703 reverse after a predetermined time has elapsed since they each stopped, starting the reverse rotation. Then, the sheet P1 is conveyed to the buffer path 540 and further conveyed by the first buffer roller pair 512. After that, when the sheet P1 has been conveyed a predetermined distance after the buffer sensor 508 turns off (no sheet), the driving by the buffer motor M702 stops. Then, the first buffer roller pair 512 stops, and the sheet P1 temporarily waits in a state of being sandwiched by the first buffer roller pair 512 (Fig. 8(c)).

[0077] When the first buffer roller pair 512 stops, the buffer flapper 507 switches to the conveyance position. Then, the path sensor 506 detects the leading end of the second sheet P2, and the path sensor 506 turns on (sheet present). When the sheet P2 is conveyed a predetermined distance from that point, the buffer motor M702 operates, so that the first buffer roller pair 512 sandwiching the sheet P1 starts to rotate forward, and the sheet P1 and the sheet P2 are overlapped and conveyed downstream (Fig. 8(d)).

[0078] A stack of sheets P1 and P2 is conveyed by the second buffer roller pair 515, and when the leading edge of the stack of sheets reaches the buffer sensor 508, the buffer sensor 508 turns on (sheet present). Since the upper path flapper 518 is still in the first position, the conveyed stack of sheets is guided to the upper discharge path 517. Then the stack of sheets is further conveyed downstream by the upper discharge roller pair 520 (Fig. 8(e)) and discharged to the upper tray 536.

[0079] [Printing process] Next, regarding the printing process executed by the image forming system 1000 in Fig. 1, for a job with the above-described split mode set, the sheets formed by the image forming apparatus 100 are delivered to the cutting apparatus 400, the sheets delivered by the cutting apparatus 400 are cut to generate a plurality of sheets, each cut sheet is discharged to the finisher 500, each sheet delivered by the finisher 500 is buffer-processed, and a series of operations until binding processing is performed and discharged at the processing tray 538 will be described using a flowchart.

[0080] Fig. 9 is a flowchart showing the procedure of the printing process. The printing process is realized by the CPU 901 of the controller CPU circuit section 900 in the image forming apparatus 100 reading and executing the program stored in the ROM 902 into the RAM 903 as necessary, the CPU 972 of the cutting apparatus control section 971 in the cutting apparatus 400 reading and executing the program stored in the ROM 973 into the RAM 974 as necessary, and the CPU 550 of the finisher control section 553 in the finisher 500 reading and executing the program stored in the ROM 551 into the RAM 552 as necessary.

[0081] In Fig. 9, when the printing process is started, the CPU 901 of the controller CPU circuit section 900 receives the input print job (step S101).

[0082] After receiving a print job, the CPU 901 performs imposition processing on the image data of two pages for one sheet (step S102).

[0083] When performing the imposition processing of the image data for one sheet, the CPU 901 forms the image data imposed in step S102 on one sheet by the transfer unit 105 and the fixing unit 106 as described above (step S103), and discharges the sheet on which the image is formed to the cutting device 400 (step S104).

[0084] When the cutting device 400 receives the discharged sheet, the CPU 972 of the cutting device control unit 971 cuts the boundary of the imposed image data with the cutter unit 415 (step S105).

[0085] When performing the cutting process by the cutter unit 415, the CPU 972 sequentially discharges the cut sheet to the finisher 500 (step S106).

[0086] When the finisher 500 receives the discharged sheet, the CPU 550 of the finisher control unit 553 determines whether buffer processing is necessary (step S107).

[0087] As a result of the determination in step S107, if it is determined that buffer processing is not necessary (''No'' in step S107), the CPU 550 discharges the sheet to the processing tray 538 without performing buffer processing (step S108) and proceeds to the next step.

[0088] Also, as a result of the determination in step S107, if it is determined that buffer processing is necessary (''Yes'' in step S107), the CPU 550 performs the buffer processing described below (step S109) and proceeds to the next step.

[0089] Next, the CPU 550 determines whether the sheet is the last sheet of the job (step S110).

[0090] If, as a result of the determination in step S110, it is determined that the sheet is not the final sheet ( "No" in step S110), the printing process is terminated.

[0091] If, as a result of the determination in step S110, it is determined that the sheet is the final sheet ( "Yes" in step S110), the CPU 550 performs stapling processing on the sheet bundle with the stapler 532 in the processing tray 538 as described above (step S111), then discharges the stapled sheet bundle to the lower tray 537 in a bundled manner (step S112), and terminates the printing process.

[0092] [Buffer Processing] Next, regarding the buffer processing executed by the finisher 500 in FIG. 1, a flowchart will be used to describe a series of operations from when each sheet transferred from the upstream device is buffer - processed and discharged in the finisher 500.

[0093] FIG. 10 is a flowchart showing the procedure of buffer processing. The buffer processing is realized in the finisher 500 when the CPU 550 of the finisher control unit 553 reads out the program stored in the ROM 551 to the RAM 552 and executes it as necessary.

[0094] In FIG. 10, when the buffer processing is started, the CPU 550 of the finisher control unit 553 determines whether the target sheet is the buffer head sheet (step S201).

[0095] Here, the buffer head sheet means a state where, as shown in the sheet P1 in FIG. 13(a), the buffer processing is to be performed with no sheet on the first buffer roller pair 512. Also, not being the buffer head sheet means a state where, as shown in the sheet P2 in FIG. 13(c), the buffer processing is to be performed with the sheet P1 waiting on the first buffer roller pair 512.

[0096] If, as a result of the determination in step S201, it is determined that the sheet is the leading sheet in the buffer (Yes in step S201), the CPU 550 detects the sheet length (step S202).

[0097] Here, detecting the sheet length means calculating, in a series of operations of transporting the sheet to the position of the sheet P1 shown in FIG. 13(b), the number of rotation steps of the transport motor M701 from when the downstream end of the sheet P1 in the transport direction is detected by the path sensor 590 until the upstream end in the transport direction is detected.

[0098] After detecting the sheet length in step S202, the CPU 550 transports the sheet to the buffer path 540 (step S203) and ends the buffer process.

[0099] Here, transporting to the buffer path 540 means waiting for the sheet at the first buffer roller pair 512 as shown in the sheet P1 in FIG. 13(c), and in step S203, the sheet is transported to this position and made to wait.

[0100] Next, the flow of the sheet until it is made to wait at the above-described first buffer roller pair 512 will be described with reference to FIGS. 13(a) to (c). The first sheet P1 is transported by the first transport roller pair 504 and the second transport roller pair 505 (FIG. 13(a)). The sheet P1 passes through the second buffer roller pair 515 via the buffer flapper 507 at the transport position, and when the downstream end (sheet leading end) of the sheet P1 in the sheet transport direction reaches the buffer sensor 508, the buffer sensor 508 turns on (sheet present).

[0101] When the driving of the buffer motor M702 stops after the sheet P1 has been transported a predetermined amount after the buffer sensor 508 turns on, the buffer roller pairs 515 and 522 stop (FIG. 13(b)). Here, the above-described predetermined amount is the transport amount for transporting the sheet P1 until the upstream end (sheet trailing end) of the sheet P1 in the sheet transport direction sufficiently passes through the buffer flapper 507.

[0102] Next, when the buffer flapper 507 switches to the buffer position and the buffer motor M702 starts to reverse after a predetermined time has elapsed since it stopped, the sheet P1 is conveyed to the buffer path 540 and further conveyed by the first buffer roller pair 512. Thereafter, when the buffer sensor 508 turns off (no sheet) and a predetermined amount of the sheet P1 has been conveyed, the driving by the buffer motor M702 stops. Then, the first buffer roller pair 512 stops, and the sheet P1 temporarily waits in a state of being sandwiched by the first buffer roller pair 512 (FIG. 13(c)).

[0103] In FIG. 10, if, as a result of the determination in step S201, it is determined that it is not the buffer leading sheet (''No'' in step S201), the CPU 550 stacks the subsequent sheet so that the downstream end in the conveyance direction is shifted by a predetermined amount in the conveyance direction on the sheet conveyed to the buffer path 540 in step S203 or on the topmost sheet of the sheet bundle conveyed to the buffer path 540 in step S210 described later (step S204).

[0104] Here, stacking the subsequent sheet so that the downstream end in the conveyance direction is shifted by a predetermined amount in the conveyance direction means, as shown in FIG. 13(d), stacking the subsequent sheet P2 on the sheet P1 waiting in the buffer path 540 so that the downstream end in the conveyance direction is shifted by a predetermined amount in the conveyance direction.

[0105] When the sheets are stacked in step S204 so that the downstream end in the conveyance direction is shifted by a predetermined amount in the conveyance direction, the CPU 550 detects the length of the subsequent sheet by the method described above (step S205).

[0106] When the length of the subsequent sheet is detected in step S205, the CPU 550 determines whether the length of the sheet or the topmost sheet of the sheet bundle waiting in the buffer path 540 differs from that of the subsequent sheet by 0.5 mm or more (step S206).

[0107] If, as a result of the determination in step S206, it is determined that the length of the subsequent sheet differs by 0.5 mm or more (”Yes” in step S206), the CPU 550 realigns the sheet waiting in the buffer path 540 or the top sheet of the sheet bundle so that the upstream end in the conveyance direction of the subsequent sheet is displaced by a predetermined amount in the conveyance direction (step S207).

[0108] Here, for example, when the sheet P2 waiting in the buffer path 540 is used as the subsequent sheet as shown in FIG. 12(A-1), the sheet lengths of the sheets P1 and P2 differ by 0.5 mm or more. When these sheets are overlapped so that the downstream end in the conveyance direction is displaced by a predetermined amount (X: 2.5 mm) in the conveyance direction in step S204 described above, as shown in FIG. 12(A-2), the downstream end in the conveyance direction overlaps in a state where it is displaced by a predetermined amount (X: 2.5 mm) in the conveyance direction. However, since the sheet lengths of the sheets P1 and P2 differ by 1.0 mm, the upstream end in the conveyance direction overlaps in a state where it is displaced by Y: 1.5 mm in the conveyance direction. Thus, if the amount of displacement of the upstream end in the conveyance direction decreases, the alignment of the sheet bundle conveyed to the processing tray 538 with respect to the conveyance direction cannot be performed correctly, and the alignment of the sheet bundle bound in the processing tray 538 is impaired.

[0109] Therefore, in step S207 described above, from the state shown in FIG. 12(A-2) to the state shown in FIG. 12(A-3), by realigning the sheets so that the upstream end in the conveyance direction is displaced by a predetermined amount (Y: 2.5 mm) in the conveyance direction, the upstream end in the conveyance direction is in a state where it is displaced by a predetermined amount (Y: 2.5 mm) in the conveyance direction, and it becomes possible to correctly perform the alignment of the sheet bundle conveyed to the processing tray 538 with respect to the conveyance direction.

[0110] In addition, as shown in Fig. 13(e), the means for re-aligning so that the upstream end in the conveyance direction is displaced by a predetermined amount in the conveyance direction is such that, until the downstream end in the conveyance direction of the stacked sheet bundle reaches the second buffer roller pair 515 from the position shown in Fig. 13(e), either one or both of the conveyance speeds of the first buffer roller pair 512 that conveys the sheet P1 and the third conveyance roller pair 510 that conveys the sheet P2 are changed, so that, as shown in Fig. 12(A-3), the upstream end in the conveyance direction is in a state of being displaced by a predetermined amount (Y: 2.5 mm) in the conveyance direction.

[0111] As a result of the determination in step S206, if it is determined that the length of the sheet waiting in the buffer path 540, or the top sheet of the sheet bundle and the subsequent sheet does not differ by 0.5 mm or more ( "No" in step S206), the CPU 550 proceeds to the process of step S208.

[0112] Next, the CPU 550 determines whether the stacked sheet is the buffer final sheet (step S208).

[0113] As a result of the determination in step S208, if it is determined that it is the buffer final sheet ( "Yes" in step S208), the CPU 550 discharges the sheet bundle to the processing tray 538 (step S209) and ends the buffer process.

[0114] Also, as a result of the determination in step S208, if it is determined that it is not the buffer final sheet ( "No" in step S208), the CPU 550 conveys the sheet bundle to the buffer path 540 (step S210) and ends the buffer process.

[0115] In the present embodiment, in step S204 of Fig. 10, an example was described in which a subsequent sheet is stacked on top of the sheet waiting in the buffer path 540 or on top of the top sheet of the sheet bundle so as to displace the downstream end in the conveyance direction by a predetermined amount in the conveyance direction, and then the sheet length of the subsequent sheet is detected in step S205. However, for example, when the sheet length is short, such as A5 size, there is a sheet for which the sheet length detection in step S205 is performed before the stacking process in step S204.

[0116] For such a sheet with a certain sheet length, as described above, after stacking subsequent sheets so that the downstream end in the conveyance direction is shifted by a predetermined amount in the conveyance direction on the sheet waiting in the buffer path 540 or on the topmost sheet of the sheet bundle, according to the detected sheet length, as shown in step S207, the upstream end in the conveyance direction may be re-stacked so as to be shifted by a predetermined amount in the conveyance direction, or according to the detected sheet length, the downstream end in the conveyance direction may be shifted in the conveyance direction and re-stacked so that the upstream end in the conveyance direction is shifted by a predetermined amount in the conveyance direction in the process of step S204.

[0117] In this embodiment, an example of an image forming system has been described in which the sheet on which an image is formed by the image forming apparatus 100 is delivered to the cutting apparatus 400, the delivered sheet is cut by the cutting apparatus 400 to generate a plurality of sheets, each of the cut sheets is discharged to the finisher 500, each of the sheets delivered to the finisher 500 is buffer-processed, and a binding process is performed and discharged at the processing tray 538. However, for example, the sheet on which an image is formed by the image forming apparatus 100 may be directly conveyed to the finisher 500, and a series of processes in the finisher 500 described above may be performed.

[0118] Also, in this embodiment, an example of an image forming system has been described in which the sheet on which an image is formed by the image forming apparatus 100 is delivered to the cutting apparatus 400, the delivered sheet is cut by the cutting apparatus 400 to generate a plurality of sheets, each of the cut sheets is discharged to the finisher 500, each of the sheets delivered to the finisher 500 is buffer-processed, and a binding process is performed and discharged at the processing tray 538. However, for example, the sheet processed in the previous process may be fed offline to the finisher 500, and a series of processes in the finisher 500 described above may be performed.

[0119] As described above, according to each of the above-described embodiments, in the buffer process, even if the lengths of the sheets to be stacked are different, by stacking them so that the upstream end in the conveyance direction is shifted by a predetermined amount in the conveyance direction, it is possible to prevent the deterioration of the alignment of the sheet bundle.

[0120] Note that the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the scope of the present invention. All technical matters included in the technical idea described in the claims are the subject of the present invention. The above embodiments are illustrative examples, and those skilled in the art can realize various alternative examples, modified examples, deformed examples, or improved examples from the content disclosed in this specification, and these are included in the technical scope described in the appended claims.

Claims

1. In a sheet post-processing apparatus that receives a sheet on which an image is formed or a sheet on which an image is formed and cut in the vertical direction in the conveyance direction, and performs post-processing, buffer means for sequentially receiving the conveyed sheets and holding them in a stacked state of a plurality of sheets; a processing tray for stacking the sheets sent through the buffer means; post-processing means for performing predetermined post-processing on the sheets stacked on the processing tray; alignment means for abutting and aligning the leading end side of the sheets stacked on the processing tray; a control unit for controlling the shift amount between a leading sheet and a trailing sheet of a plurality of sheets stacked on the buffer means; the control unit: acquires sheet information including the sheet length of the sheet conveyed to the buffer means; Based on the sheet length of the sheet information, when the leading sheet held in a stacked state in the buffer unit is a cut sheet, the shift amount between the trailing sheet and the uncut sheet is set to be larger than a predetermined shift amount for the uncut sheet. Control to make it, A sheet post-processing apparatus characterized by the above.

2. sheet branching means for branching into a sheet branch path branched from the sheet conveyance path through which the sheet on which an image is formed is conveyed; a buffer unit for retaining the subsequent sheets in the sheet branch path so that no new subsequent sheets are sent onto the processing tray during the post-processing of the sheets in the post-processing means; and The buffer means controls the shift amount between the leading sheet and the trailing sheet in the buffer unit. The sheet post-processing apparatus according to claim 1.

3. When the control unit controls the shift amount between the leading sheet and the trailing sheet in the buffer means, the control unit performs the control by changing the conveyance speed of the leading sheet or the trailing sheet in the sheet conveyance path. The sheet post-processing apparatus according to claim 1 or 2.

4. The control unit: Before overlapping the downstream ends in the conveyance direction of the leading sheet and the trailing sheet retained in the buffer means with a predetermined distance shifted, when the sheet length in the sheet information is different from the length in the conveyance direction of the trailing sheet, The sheet post-processing apparatus according to claim 1 or 2, wherein the downstream end in the conveyance direction is controlled to be overlapped so that the trailing ends in the conveyance direction of the leading sheet and the trailing sheet are shifted by a predetermined distance.

5. An image forming apparatus that forms an image on a sheet, The sheet post-processing apparatus according to any one of claims 1 to 4, An image forming system comprising the same.

6. An image forming apparatus, A cutting device that cuts a sheet sent from the image forming apparatus in a direction orthogonal to the sheet conveyance direction, A sheet post-processing apparatus that receives the sheet sent from the cutting device and performs post-processing, A control unit that controls the sheet post-processing apparatus, comprising: The sheet post-processing apparatus includes: Buffer means for sequentially receiving the conveyed sheets and holding them in a stacked state of a plurality of sheets; A processing tray on which the sheets sent via the buffer means are stacked; Post-processing means for performing predetermined post-processing on the sheets stacked on the processing tray; Alignment means for abutting and aligning the leading end side of the sheets stacked on the processing tray; and The control unit controls the shift amount between the leading sheet and the subsequent sheet among the plurality of sheets stacked on the buffer means, acquires sheet information including the sheet length of the sheet conveyed to the buffer means, and based on the sheet length of the sheet information, when the leading sheet held in a stacked state in the buffer unit is a cut sheet, controls the shift amount between the subsequent sheet and the uncut sheet to be larger than a predetermined shift amount for the uncut sheet. An image forming system characterized by the above.

Images