JP5921237B2 - Sheet stacking device - Google Patents

Description

  The present invention relates to a sheet processing apparatus having a function of aligning sheets.

  2. Description of the Related Art Conventionally, in an image forming system such as a printer, a copier, and a facsimile, a post-processing apparatus having a shift function for stacking on a discharge tray by changing the position in the direction orthogonal to the transport direction for each set number of sheets. Often provided.

  In the post-processing apparatus having a shift function, each of the sheet bundles sorted by the shift process is required to be accurately aligned on the discharge tray. Therefore, the post-processing apparatus having a high alignment function. Has been proposed.

  In Patent Document 1, a predetermined post-processing is performed on a sheet conveyed from an image forming apparatus, and the sheet is stacked on a sheet discharge tray. After that, the alignment plate installed above the discharge tray descends toward the stacking surface of the discharge tray and aligns the stacked sheets by moving the sheet so as to sandwich the sheet in the direction orthogonal to the conveyance direction. A post-processing device has been proposed.

JP 2009-286510 A

  However, Patent Document 1 has the following problems. FIG. 15 is a view of the stacking tray 701 viewed from the sheet discharging direction. In a print job in which sheets of different widths are mixed (hereinafter, different width mixed jobs), the alignment plate 711b is in contact with the upper surface of the already stacked sheets on the stacking tray 701 as shown in FIG. By moving to the alignment plate 711a side, the already stacked sheets are rubbed and the sheets are damaged. For this reason, it is not preferable to perform alignment with an alignment plate for a mixed width job. If the sheet is not aligned by the alignment plate, the sheet stacking position of the sheet discharged on the sheet discharge tray is as shown in FIG. 15B due to the skew amount, curl amount, electrostatic amount and air resistance when landing on the tray. And the stackability of the sheet bundle is deteriorated.

In order to solve the above-described problems, a sheet stacking apparatus according to the present invention includes, in a sheet stacking apparatus that performs sheet alignment, a transport unit that transports sheets, and a stack tray on which sheets transported by the transport unit are stacked. A pair of alignment members which are provided on the upper side of the stacking tray and are movable in a width direction orthogonal to the sheet conveying direction and can be moved up and down in a direction in which the sheets are stacked, and the pair of alignment members are stacked on the stacking tray. When aligning sheets stacked by offsetting them in the width direction on aligned sheets, the sheets are moved in the width direction so as to make contact with and separate from the side edges of the sheets to be aligned. Is moved up and down so that one of the pair of alignment members rides on the aligned sheet, and the other alignment member moves to the side edge of the offset and stacked sheets. Control means for controlling movement and raising / lowering of the pair of alignment members to perform alignment by moving in the width direction so as to perform contact and separation, and the control means is configured to control the alignment of the aligned sheets. When a sheet having a size smaller than the size of the sheet in the width direction is stacked on the sheet, the pair of alignment members is moved up and down so as to ride on the aligned sheet, Sheets are stacked in a state where each of the alignment members is moved to a position separated by a predetermined distance in the width direction from the side edges on both sides of the small size sheet, and the alignment is not performed on the small size sheet. the controls the movement and the lifting of the pair of alignment members, and further, the control means, the small size sheet is discharged is offset in the width direction, of the small size If one side end of the over bets are stacked so as to be located outside the sheets the matching, to control the movement and the lifting of the pair of aligning members to perform the alignment of the sheet of the small size It is characterized by that.

  According to the present invention, when a sheet having a size smaller than the width of the stacked sheet is stacked on the stacked sheet, the pair of alignment members are moved in the width direction from the position where the small size sheet should be aligned. Are moved to a position separated by a predetermined amount, and the alignment operation is not performed. This prevents the alignment member from rubbing the stacked sheets and prevents the alignment of newly stacked sheets from deteriorating. Further, when one side edge of a small size sheet is stacked so as to be positioned outside the aligned stacked sheet, the stackability can be improved by aligning the small size sheet. .

Sectional view showing configuration of image forming system Block diagram showing the configuration of the image forming system Illustration of operation display Sectional view showing the configuration of the finisher Block diagram showing the configuration of the finisher Illustration of alignment plate on finisher stacking tray Diagram showing raising and lowering of alignment plate Explanatory drawing of sheet conveyance in shift sort mode Illustration of the paper feed stage setting screen Illustration of the finish selection screen Illustration of mixed size selection screen Illustration of alignment operation Flow chart showing different width mixed loading determination processing Flow chart showing control of matching operation Explanatory drawing of alignment state and non-alignment state at the time of conventional mixed loading Illustration of alignment plate when mixed with different width

  Embodiments of the present invention will be described below with reference to the drawings.

(overall structure)
FIG. 1 is a configuration diagram showing a longitudinal sectional structure of a main part of the image forming system according to the first embodiment of the present invention. The image forming system includes an image forming apparatus 10 and a finisher 500 as a sheet stacking apparatus. The image forming apparatus 10 includes an image reader 200 that reads an image from a document and a printer 350 that forms the read image on a sheet.

  The document feeder 100 feeds documents set upward on the document tray 101 one by one in order from the first page, conveys them through a predetermined position on the platen glass 102, and then discharges a paper tray 112. To discharge. At this time, the scanner unit 104 is fixed at a predetermined reading position. When the original passes through the reading position, the original image is read by the scanner unit 104. When the document passes through the reading position, the document is irradiated with light from the lamp 103 of the scanner unit 104, and reflected light from the document is guided to the lens 108 via the mirrors 105, 106, and 107. The light that has passed through the lens 108 forms an image on the imaging surface of the image sensor 109, is converted into image data, and is output. Image data output from the image sensor 109 is input to the exposure unit 110 of the printer 350 as a video signal.

  The exposure unit 110 of the printer 350 modulates and outputs laser light based on the video signal input from the image reader 200. The laser beam is irradiated onto the photosensitive drum 111 while being scanned by a polygon mirror (not shown). An electrostatic latent image corresponding to the scanned laser beam is formed on the photosensitive drum 111. The electrostatic latent image on the photosensitive drum 111 is visualized as a developer image by the developer supplied from the developing device 113.

  A sheet fed from the upper cassette 114 or the lower cassette 115 provided in the printer 350 by the pickup rollers 127 and 128 is conveyed to the registration roller 126 by the sheet feeding roller 129 and the sheet feeding roller 130. When the leading edge of the sheet reaches the registration roller 126, the registration roller 126 is driven at a predetermined timing to convey the sheet between the photosensitive drum 111 and the transfer unit 116. The developer image formed on the photosensitive drum 111 is transferred by the transfer unit 116 onto the fed sheet. The sheet on which the developer image has been transferred is conveyed to the fixing unit 117, and the fixing unit 117 fixes the developer image on the sheet by heating and pressing the sheet. The sheet that has passed through the fixing unit 117 is discharged from the printer 350 to the outside of the image forming apparatus (finisher 500) through the flapper 121 and the discharge roller 118. When image formation is performed on both sides of the sheet, the sheet is conveyed to the duplex conveyance path 124 via the reverse path 122 and is conveyed again to the registration roller 126.

(Overall system block diagram)
Next, the configuration of the controller that controls the entire image forming system and the overall system block diagram will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration of a controller that controls the entire image forming system of FIG.

  As shown in FIG. 2, the controller includes a CPU circuit unit 900, and the CPU circuit unit 900 includes a CPU 901, a ROM 902, and a RAM 903. A CPU 901 is a CPU that performs basic control of the entire image type system. A ROM 902 in which a control program is written and a RAM 903 for processing are connected by an address bus and a data bus. The CPU 901 comprehensively controls each of the control units 911, 921, 922, 904, 931, 941, and 951 by a control program stored in the ROM 902. The RAM 903 temporarily stores control data and is used as a work area for arithmetic processing associated with control.

  The document feeder control unit 911 drives and controls the document feeder 100 based on an instruction from the CPU circuit unit 900. The image reader control unit 921 performs drive control on the scanner unit 104 and the image sensor 109 described above, and transfers the image signal output from the image sensor 109 to the image signal control unit 922. The image signal control unit 922 performs each process after converting the analog image signal from the image sensor 109 into a digital signal, converts the digital signal into a video signal, and outputs the video signal to the printer control unit 931. In addition, the digital image signal input from the computer 905 via the external I / F 904 is subjected to various processes, and the digital image signal is converted into a video signal and output to the printer control unit 931. The processing operation by the image signal control unit 922 is controlled by the CPU circuit unit 900. The printer control unit 931 controls the exposure unit 110 and the printer 350 based on the input video signal, and performs image formation and sheet conveyance. The finisher control unit 951 is mounted on the finisher 500, and performs drive control of the entire finisher by exchanging information with the CPU circuit unit 900. This control content will be described later. The operation display device controller 941 exchanges information between the operation display device 400 and the CPU circuit unit 900. The operation display device 400 includes a plurality of keys for setting various functions relating to image formation, a display unit for displaying information indicating a setting state, and the like. A key signal corresponding to the operation of each key is output to the CPU circuit unit 900 and corresponding information is displayed on the operation display device 400 based on the signal from the CPU circuit unit 900.

(Operation display device)
FIG. 3 is a diagram showing an operation display device 400 in the image forming apparatus of FIG. The operation display device 400 includes a start key 402 for starting an image forming operation, a stop key 403 for interrupting the image forming operation, ten keys 404 to 413 for setting numerical values, a clear key 415, a reset key 416, and the like. Is arranged. In addition, a display unit 420 having a touch panel formed thereon is arranged, and a soft key can be created on the screen.

  The image forming apparatus has various processing modes such as non-sort, sort, shift sort, and staple sort (binding mode) as post-processing modes. Such setting of the processing mode is performed by an input operation from the operation display device 400. For example, when setting the post-processing mode, when the “finishing” key 417 which is a soft key is selected on the initial screen shown in FIG. 3, a menu selection screen is displayed on the display unit 420, and this menu selection screen is used. The processing mode is set.

(Finisher)
FIG. 4 is a cross-sectional view showing the configuration of the finisher 500. The finisher 500 sequentially takes in the sheets discharged from the image forming apparatus 10, aligns a plurality of fetched sheets and bundles them into one bundle, and staples the staple end of the bundled sheet bundle with staples. Perform post-processing. The finisher 500 takes the sheet discharged from the image forming apparatus 10 into the conveyance path 520 by the conveyance roller pair 511. The sheet taken inside by the conveyance roller pair 511 is conveyed via the conveyance roller pairs 512, 513, and 514. On the conveyance path 520, conveyance sensors 570, 571, 572, and 573 are provided to detect the passage of sheets. The conveyance roller pair 512 is provided in the shift unit 580 together with the conveyance sensor 571. The shift unit 580 can move the sheet in the sheet width direction orthogonal to the conveyance direction by a shift motor M5 described later. By driving the shift motor M5 in a state where the conveyance roller pair 512 holds the sheet, the sheet can be offset (shifted) in the width direction while being conveyed. In the shift sort mode, the position of the sheet bundle is shifted in the width direction for each copy. The offset amount is 15 mm (front shift) on the front side with respect to the center position in the width direction, or 15 mm (back shift) on the back side. If there is no shift designation, the sheet is discharged to the same position as the previous shift. When the finisher 500 detects that the sheet has passed through the shift unit 580 by the input of the conveyance sensor 571, the finisher 500 drives the shift motor M5 to return the shift unit 580 to the center position.

  Between the conveying roller pair 513 and 514, a switching flapper 540 for guiding the sheet reversely conveyed by the conveying roller pair 514 to the buffer path 523 is disposed. The switching flapper 540 is driven by a solenoid SL1 described later. A switching flapper 541 for switching whether to transport to the upper discharge path 521 or the lower discharge path 522 is disposed between the transport roller pair 514 and 515. The switching flapper 541 is driven by a solenoid SL2 described later. When the switching flapper 541 is switched to the upper discharge path 521 side, the sheet is guided to the upper discharge path 521 by the conveyance roller pair 514 driven by the buffer motor M2, and the conveyance roller pair driven by the discharge motor M3. The sheet is discharged to the stacking tray 701 by 515. A conveyance sensor 574 is provided on the upper discharge path 521 to detect the passage of the sheet. When the switching flapper 541 is switched to the lower paper discharge path 522 side, the sheet is guided to the lower paper discharge path 522 by the conveyance roller pair 514 driven by the buffer motor M2. The sheet is further guided to the processing tray 630 by a pair of conveying rollers 517 and 518 driven by a paper discharge motor M3. Conveyance sensors 575 and 576 are provided on the lower discharge path 522 to detect the passage of the sheet.

  The sheet guided to the processing tray 630 is discharged onto the processing tray 630 or the stacking tray 700 according to the post-processing mode by the bundle discharge roller pair 680 driven by the bundle discharge motor M4.

  FIGS. 6A and 6B are views of the stacking trays 700 and 701 viewed from the discharge direction, respectively. On the upper side of the stacking trays 700 and 701, alignment plates 710 and 711 for aligning the misalignment in the width direction of the stacked sheets are arranged. The alignment plate 710 includes a pair of alignment plates 710a and 710b, and the alignment plate 711 includes a pair of alignment plates 711a and 711b. The alignment plates 711a and 711b are movable in the width direction by upper tray alignment motors M9 and M10, respectively, which will be described later, and align the sheets by making contact with and separating from the side edges of the stacked sheets. Similarly, the alignment plates 710a and 710b can be moved in the width direction by lower tray alignment motors M11 and M12, which will be described later.

  FIGS. 7A and 7B are views showing the position of the alignment plate 711. FIG. 7A shows the alignment position when the sheets are aligned, and FIG. 7B shows the retracted position. The alignment plate 711 moves up and down around the alignment plate shaft 713 between the alignment position and the retracted position. The alignment plate 710 moves in the same manner as the alignment plate 711. The alignment plates 710 and 711 can be moved up and down by driving an upper tray alignment plate lifting motor M13 and a lower tray alignment plate lifting motor M14, which will be described later. The alignment plate elevating HP sensors 714 and 715 detect the positions of the alignment plates 710 and 711, respectively.

  The stacking trays 700 and 701 can be moved up and down by tray lifting motors M15 and 16 described later. The paper surface detection sensors 720 and 721 detect the uppermost surface of the sheets on the stacking trays 700 and 701. The stacking trays 700 and 701 are controlled so that the uppermost surface of the sheet is at a fixed position by signals from the paper surface detection sensors 720 and 721, respectively.

(Finisher block diagram)
Next, the configuration of the finisher control unit 951 that drives and controls the finisher 500 will be described with reference to FIG. FIG. 5 is a block diagram showing a configuration of the finisher control unit 951 in FIG.

  As shown in FIG. 5, the finisher control unit 951 includes a CPU 952, a ROM 953, a RAM 954, and the like. The finisher control unit 951 communicates with the CPU circuit unit 900, exchanges data such as command transmission / reception, job information, and sheet delivery notification, and executes various programs stored in the ROM 953 to drive the finisher 500. Take control.

  Various input / outputs provided in the finisher 500 will be described. The finisher 500 includes an entrance motor M1, a buffer motor M2, a paper discharge motor M3, a shift motor M5, solenoids SL1 and SL2, and conveyance sensors 570 to 576 that drive the conveyance roller pairs 511 to 513 for conveying the sheet. Yes. Further, the finisher 500 as a means for driving various members of the processing tray 630, the bundle discharge motor M4 that drives the bundle discharge roller pair 680, the alignment motors M6 and M7 that drive the alignment member 641, and the swing guide are raised and lowered. A swing guide motor M8 for driving is provided. Further, the finisher 500 includes tray lifting motors M15 and M16 for moving the stacking trays 700 and 701 up and down, paper surface detection sensors 720 and 721, and alignment plate lifting HP sensors 714 and 715. The finisher 500 also includes upper tray alignment motors M9 and M10 for alignment operation on the stacking tray, lower tray alignment motors M11 and M12, M13 as an upper tray alignment plate elevating motor, and M14 as a lower tray alignment plate elevating motor. Yes.

(Description of sheet conveyance)
Next, the flow of sheets after receipt of sheets from the image forming apparatus until they are discharged to the stacking tray will be described with reference to FIGS. 3 and 8 to 10. When the “paper selection” key 418 is pressed on the initial screen shown in FIG. 3, a paper feed cassette selection screen as shown in FIG. 11 is displayed on the display unit 420. Here, the user selects a sheet to be used for the job. Here, the “A4” size is selected.

  When the user selects the “finishing” key 417 as a soft key on the initial screen shown in FIG. 3 on the operation display device 400 of the image forming apparatus 10, a finishing menu selection screen as shown in FIG. Is displayed. When the OK key is pressed while the “sort” key and the “shift” key are selected on the finishing menu selection screen shown in FIG. 10B, the shift sort mode is set. When the user designates the shift sort mode and submits a job, the CPU 901 of the CPU circuit unit 900 confirms that the shift sort mode is selected by the CPU 952 of the finisher control unit 951, as in the non-sort mode. Notice. The operation in the shift sort mode in which the number of sheets constituting one part (set) is three will be described below.

  When the sheet N is discharged from the image forming apparatus 10 to the finisher 500, the CPU 901 notifies the CPU 952 that the delivery of the sheet is started. Hereinafter, various input / output controls in the finisher 500 of the CPU 952 will be described.

  When the CPU 952 receives the notification of the start of sheet delivery, the CPU 952 drives the entrance motor M1, the buffer motor M2, and the paper discharge motor M3. As a result, as shown in FIG. 7, the conveyance roller pairs 511, 512, 513, 514, and 515 are rotationally driven, and the sheet N discharged from the image forming apparatus 10 is taken into the finisher 500 and conveyed. When the conveyance sensor 571 detects that the conveyance roller pair 512 pinches the sheet N, the CPU 952 drives the shift motor M5 to move the shift unit 580 to offset the sheet. If the shift information of the sheet notified from the CPU 901 is “front”, the sheet is offset to the front side 15 mm, and if it is “back”, the sheet is offset to the rear side 15 mm.

  The switching flapper 551 is rotationally driven by the solenoid SL1 to the illustrated position, and the sheet N is guided to the upper paper discharge path 521. When the conveyance sensor 574 detects passage of the trailing edge of the sheet N, the CPU 952 drives the sheet discharge motor M3 so that the conveyance roller pair 515 rotates at a speed suitable for stacking, and discharges the sheet N to the stacking tray 701. .

(Different width mixed setting)
Different width mixed loading in which a plurality of sheets having different widths are stacked on the stacking tray will be described. When the “paper selection” key 418 is pressed on the screen of FIG. 3, a transition is made to the paper feed stage selection screen shown in FIG. 9. Here, when the user selects the “automatic selection” key, an automatic paper selection mode in which a sheet having a size corresponding to the size of the document is automatically selected is set. Next, when the user presses the “applied mode” key 419 on the screen of FIG. 3, the screen transits to an application mode selection screen shown in FIG. Next, when the user presses the “mixed document size” key, the screen shifts to a mixed document size screen shown in FIG. Next, when the user selects the “different width” key and presses the OK button, the different width mixed loading mode is set. When the user depresses the start key 402 in this state, a plurality of originals stacked on the ADF 100 are fed one by one, and a paper feed stage that stores sheets according to the size of each original is automatically selected. Is sent. As a result, a plurality of sheets having different widths are stacked on the stacking tray.

  Also, not only copying original images but also receiving and printing data created by a computer, if pages with different image sizes are mixed, multiple sheets with different widths are stacked on the stacking tray. .

  Although the above-mentioned mixed loading with different widths is an example that occurs in one print job, the mixed loading with different widths that occurs in two consecutive print jobs will be described. When the user selects the “paper selection” key 418 on the screen shown in FIG. 3, the screen shifts to the paper feed stage selection screen shown in FIG. 9. Here, it is assumed that the user has selected the paper feed tray of “A4”. When image formation is executed in this state, A4 size sheets are stacked on the stacking tray.

  Next, it is assumed that the user selects the “paper selection” key 418 on the screen of FIG. 3 and selects the paper feed tray “B5” on the screen shown in FIG. When image formation is executed without changing the sheet discharge destination, a B5 size sheet is stacked on an A4 size sheet stacked on the stacking tray in the previous print job.

  Also, not only when copying original images, but also when receiving and printing computer-generated data, if the size of the sheets used in each print job is different, multiple sheets with different widths are stacked on the stacking tray. The

  Further, when the next print job is executed after executing one print job, the sheet of the next print job is discharged with a predetermined offset in the width direction with respect to the sheet discharged by the previous print job. The shift between jobs can also be set from the operation display device 400. Note that the shift between jobs is not an item set for each job, and is maintained until it is canceled once set regardless of the execution of the print job.

(Mixed loading determination process)
Next, processing for determining different width mixed loading will be described with reference to FIG. The flow in FIG. 13 is executed by the CPU 952. The different width mixed loading determination process is executed regardless of the finishing selection result in FIG. 10 and the presence / absence of the original mixed loading setting in FIG.

  The CPU 952 determines whether sheet information has been received from the image forming apparatus 10 (S1001). The sheet information includes the width W of the sheet N set by the image forming apparatus 10, the job head sheet flag, the job end sheet flag, the shift amount Z, the shift direction, and the discharge destination (upper tray and lower tray). The sheet N conveyed from the image forming apparatus 10 is referred to as a sheet N, and the sheet information of the sheets N and N−1 is updated every time the CPU 952 receives the sheet information. The width information of the sheet N and the sheet N-1 is initialized to (0) when the power is turned on.

  If the CPU 952 determines that sheet information has been received from the image forming apparatus 10, the CPU 952 determines whether the sheet N is the first sheet of the job (S1002). If the sheet N is the first sheet, the CPU 952 initializes the alignment disable flag to OFF and stores it in the RAM 954 (S1003). The unmatchable execution flag is a flag that is turned on when the job contents are mixedly loaded.

  Next, the CPU 952 determines whether the alignment impossibility flag is off (S1004). If the alignment impossibility flag is off, the CPU 952 determines whether or not the width information of the sheet N-1 is (0) (S1005). Note that the width information of the sheet N-1 is (0) because there is no width information of the sheet N-1, and therefore the sheet N is the first sheet of the first job after the image forming apparatus is turned on. Is shown. If the width information of the sheet N-1 is not (0), the CPU 952 determines whether the paper surface detection sensor (720 or 721) of the stacking tray designated as the sheet discharge destination is ON (S1006). When the paper surface detection sensor of the stack tray at the discharge destination is off, sheets are not stacked on the stack tray, so that the mixed loading state does not occur. If the paper surface detection of the stack tray of the discharge destination is ON, the sheets are stacked on the stack tray, so the sheet widths of the sheets N-1 and N are compared (S1007). When the CPU 952 determines that the width of the sheet N is different from the width of the sheet N-1, the CPU 952 determines that the sheet is mixedly loaded on the discharge tray. However, if the width of the sheet N is larger than the width of the sheet N-1, the alignment plate will not rub the sheet N-1 even if alignment with the sheet N is performed. Therefore, when the width of the sheet N is smaller than the width of the sheet N-1, the CPU 952 sets the alignment execution impossible flag to ON and stores it in the RAM 954 (S1008). When the width information of the sheet N-1 is (0), the mixed loading determination in S1007 is not performed, and therefore the alignment impossibility flag remains OFF.

  Next, the CPU 952 determines whether or not the sheet N is the final sheet of the job (S1009). If the sheet N is the last sheet, the CPU 952 ends the process of FIG. If the sheet N is not the final sheet, the CPU 952 receives the next sheet information (S1001).

  The process of the flowchart of FIG. 13 will be described using a specific example. It is assumed that the print job to be executed is the first job after the power is turned on, the first sheet of the job is an A4 size sheet, and the second sheet (final sheet) is an A4R size sheet, that is, size mixed loading is performed.

  The sheet information of the first sheet includes information on the sheet width 297 mm, the job head sheet flag ON, the job last sheet flag OFF, and the discharge destination stacking tray 701. Since the leading sheet flag is ON, the alignment impossibility flag is initialized to OFF in S1003. Since the alignment execution impossibility flag is OFF, it is determined No in S1004. Since the sheet N is the leading sheet, it is determined Yes in S1005, and the alignment impossibility flag remains OFF. Since the sheet N is not the final sheet, it is determined No in S1009, and the process returns to S1001.

  The sheet information of the second sheet includes information about a sheet width of 210 mm, a job head sheet flag OFF, and a job end sheet flag ON. When the sheet information of the second sheet is received, the sheet information is updated so that the first sheet is the sheet N-1 and the second sheet is the sheet N. Since the leading sheet flag is OFF for the second sheet N, it is determined No in S1002, and since the alignment impossible flag remains OFF, it is determined No in S1004. Since the sheet width information of the sheet N-1 (first sheet) is not (0), it is determined No in S1005, and since the sheet surface detection sensor 721 is turned on by discharging the sheet N-1, it is determined Yes in S1006. Since the widths of the sheet N-1 and the sheet N are different, it is determined No in S1007. In S1008, the alignment disabling flag is set to ON and stored in the RAM 954. Since the sheet N (second sheet) is the final sheet, it is determined Yes in S1009, and the process ends.

  As described above, when sheets of different sizes are mixedly loaded, the alignment execution impossible flag is turned ON.

(Alignment processing on the loading tray)
Next, alignment processing on the stacking tray 701 will be described with reference to FIGS. FIG. 12 is a view when the stacking tray 701 is viewed from the sheet discharge direction side. Here, a case where the shift direction is set on the front side (right side in FIG. 12) will be described as an example. The process of the flowchart of FIG. 14 is started when the CPU 952 receives the sheet information of the first sheet of the job.

  The CPU 952 determines whether the alignment completion flag for the sheet N-1 is ON (S2001). The alignment completion flag is a flag that is turned on when the alignment operation is completed and the alignment plate is stopped. If the alignment completion flag for the sheet N-1 is ON, the CPU 952 sets the alignment completion flag for the sheet N to OFF and stores it in the RAM 954 (S2002).

  Next, the CPU 952 determines whether or not the shift direction of the sheet N on the stacking tray is different from the shift direction of the sheet N-1 based on the shift direction information included in the sheet information (S2003). When the shift direction of the sheet N and the shift direction of the sheet N-1 are different, the CPU 952 drives the upper tray alignment plate elevating motor M13 to change the alignment plates 711 (711a, 711b) to FIGS. 7 (b) and 12 (a). ) To the retracted position (S2004).

When the alignment plate 711 is moved to the retracted position, the alignment plate elevating HP sensor 715 is turned on. The CPU 952 determines whether or not the alignment plate elevating HP sensor is turned on (S2005). Next, the CPU 952 drives the upper tray alignment motors M9 and M10 to move the alignment plate 711 to the alignment plate standby position in accordance with the shift amount and sheet width of the sheet N (S2006). The alignment plate standby position, as shown in FIG. 12 (b), from the standby position is the center position of the stacking tray 701 of one of the alignment plates 711b, subtracting the shift amount Z in length W / 2 of half the sheet width This is a position further away from the position of the distance X2 by a predetermined distance (retraction amount M). The standby position of the other alignment plate 711a is further away from the center position of the stacking tray 701 by a predetermined distance (retraction amount M) from the position from the distance X1 obtained by adding the shift amount Z to the half length W / 2 of the sheet width. Position.

  Thereafter, the CPU 952 drives the upper tray alignment plate elevating motor M13 to lower the alignment plate by a predetermined amount to the alignment position as shown in FIG. 12C (S2007). The CPU 952 determines whether or not the alignment disable flag for the sheet N is ON (S2008). If the size is not mixed, the alignment impossibility flag is turned OFF, and in that case, the CPU 952 determines whether a predetermined time has elapsed since the conveyance sensor 574 ON (S2009). This predetermined time is the time + α from when the conveyance sensor 574 detects a sheet until the sheet is discharged to the stacking tray 701. When the predetermined time has elapsed, the sheet is in a state as shown in FIG. When the predetermined time has elapsed, the CPU 952 aligns the upper tray so that the alignment plate 711a moves a predetermined distance (pushing amount 2M) toward the center of the stacking tray and the sheet N abuts against the alignment plate 711b as shown in FIG. The motor M9 is driven (S2010). When the shift amount Z is 15 mm and the pushing amount M is 5 mm, the offset amount of the sheet after the alignment operation is 10 mm.

  Thereafter, the CPU 952 drives the upper tray alignment motor M9 so that the alignment plate 711a is moved to the alignment standby position as shown in FIG. 12 (f) (S2011). Next, the CPU 952 sets the alignment completion flag of the sheet N to ON, stores it in the RAM 954 (S2012), and waits until the next sheet is conveyed to the stacking tray 701. Thereafter, the CPU 952 determines whether the sheet N is the final sheet (S1013), and repeats the processing from S2001 until the sheet N becomes the final sheet.

  On the other hand, if the alignment impossibility flag is ON (mixed size) in S2008, the process proceeds to S2012. That is, since the processing of S2010 and S2011 is skipped, the alignment plate 711 remains at the position shown in FIG. 12C, and alignment by the alignment plate 711 is not performed. However, the alignment plate 711 is in a position that is widened by the amount of pressing M on each side in the width direction with respect to the position where the sheets are to be aligned. During sheet discharge, the alignment plates 711a and 711b are fixed at this position. Accordingly, as shown in FIG. 16, the alignment plate 711 functions as a guide member, and the stacking variation is reduced as compared with the case where the alignment plate 711 is in the retracted position shown in FIG. 7B.

  As described above, even when sheets having different widths are mixedly loaded, it is possible to reduce the stacking variation in the width direction.

In steps S1007 and S1008 in FIG. 13, the alignment impossibility flag is turned on when the width of the sheet N is smaller than the width of the sheet N-1. However, even if the width of the sheet N is smaller than the width of the sheet N-1, the sheet N is discharged in the width direction and one side end of the sheet N is outside the side end of the sheet N-1. When the sheets are stacked so as to be positioned at the position N, the alignment plate does not rub the sheet N-1. Therefore, in this case, the matching execution disable flag may be turned off. For example, a case where a B5 size sheet (257 mm) is offset by 15 mm and stacked on a letter size sheet (279 mm) is applicable. This also applies to the case where an A4 size sheet (A4R: 210 mm) fed vertically is stacked with an offset of 10 mm on a letter size sheet (216 mm) fed vertically.

Claims (2)

In a sheet stacking device that aligns sheets,
Conveying means for conveying the sheet;
A stacking tray on which sheets conveyed by the conveying unit are stacked;
A pair of alignment members provided on the upper side of the stacking tray, movable in the width direction perpendicular to the sheet conveying direction and capable of moving up and down in the direction in which the sheets are stacked;
The pair of alignment members align the sheets by moving in the width direction so as to contact and separate the side edges of the sheets stacked on the stacking tray, and the width direction is placed on the aligned sheets. When aligning sheets that are stacked with an offset, the first alignment member is moved up and down so that one of the alignment members is placed on the aligned sheet, and the other alignment member is stacked with the offset. Control means for controlling movement and elevation of the pair of alignment members so as to perform alignment by moving in the width direction so as to contact and separate the side edges of the sheet;
Have
When the sheet having a size smaller than the size in the width direction of the sheet is stacked on the aligned sheet, at least one of the pair of alignment members is placed on the aligned sheet. The sheet is stacked in a state where the pair of alignment members are moved to a position separated by a predetermined distance in the width direction from the side edges on both sides of the small size sheet. Control the movement and elevation of the pair of alignment members so as not to align with the size sheet ,
Further, the control unit is configured to stack the small sized sheet so that the small size sheet is discharged in the width direction and one side end of the small sized sheet is positioned outside the aligned sheet. The sheet stacking apparatus controls movement and elevation of the pair of alignment members so as to align the small size sheets .   When the sheet having a size smaller than the size in the width direction of the sheet is stacked on the aligned sheet, the control unit moves the pair of alignment members while discharging the small size sheet. The sheet stacking apparatus according to claim 1, wherein the sheet stacking apparatus is fixed at a position separated by a predetermined distance.

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