JP2006076777A - Sheet handling device, paper folding method in sheet handling device, and image forming device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet handling device capable of easily indexing a fold position in accordance with paper folding conditions and preventing error of sheet size or error in conveyance from affecting the fold position. <P>SOLUTION: This sheet handling device is provided with a first conveyance means and a second conveyance means arranged across distance in a conveyance path of sheet, a paper folding roll means arranged between the first and second conveyance means, and a folding sheet conveyance path arranged by branching from the conveyance path and carrying out a folding sheet from the paper folding roll means to constitute the second conveyance means by a pair of rollers capable of rotating forward and reversely so as to invert and convey a sheet on the conveyance path. A first stopper means and a second stopper means are provided on the downstream side and the upstream side of the folding roll means in the conveyance path of the sheet, respectively. The first stopper means positions and regulates a tip side of sheet to lead a sheet payed out by the first conveyance means to the folding roll means, and the second stopper means positions and regulates a rear end side of sheet to lead a sheet inverted and conveyed by reverse rotation of the second conveyance means to the folding roll means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a sheet processing apparatus and a sheet processing apparatus for folding a sheet, which is formed and discharged from an image forming apparatus such as a copying machine or a printer, into two or three according to the subsequent bookbinding or filing state. The present invention relates to a paper folding method and an image forming apparatus using the same.

  In general, this type of sheet processing apparatus is used as an apparatus for folding a sheet discharged from a printing machine, a printer, or the like as a final process, or carrying it out to a post-processing apparatus such as binding in the next process after folding the paper. Many are connected to image forming devices such as printers, and are widely used as printing systems that consistently process everything from printing to bookbinding by folding the paper and then ejecting it directly or sending it to a post-processing device that performs binding such as stapling. Yes.

  Conventionally, this type of paper folding apparatus arranges a pair of pressure-contact rollers in a path for conveying a sheet and feeds the sheet into two by feeding the fold position of the sheet conveyed in the path between the pair of rollers. Further, the folded sheet is folded by a pair of rollers on the downstream side, and folded into three or four. When folding a sheet with such a pair of rollers, it is necessary to accurately determine the position of the fold, and when the fold position is incorrect, the folded edges of the sheets are aligned in order or when filing. I can not.

  In particular, when the sheet is folded in half compared to the case where the sheet is folded in two, if the fold position is incorrect, the edge of the sheet folded first may be rolled up during the second folding operation and folded into a folded ear shape. .

  For example, Japanese Patent Application Laid-Open No. 2004-99199 discloses a method of feeding a sheet trailing edge to a folding roll position in a state where the leading edge of the sheet fed into the conveying path is abutted against a stopper member and stopped at the leading edge. It is proposed in the gazette (patent document 1). In this document, a stopper piece whose position can be adjusted according to the sheet size is provided in the conveyance path, and a sheet is bent or a folding plate is entered in the conveyance path in a state where the leading end of the sheet is regulated to the stopper piece. The folding position is determined by guiding.

  Similarly, as a method for determining the folding position based on the leading edge of the sheet, Japanese Patent Application Laid-Open No. 2003-118932 (Patent Document 2) arranges a pair of rollers on the downstream side of the folding rolls arranged in the conveyance path. A method has been proposed in which a sheet is fed from a leading end of the sheet to a predetermined position (depending on the sheet size), and the roller is stopped at the predetermined position to guide the sheet to the folding roll.

  Patent Documents 1 and 2 each disclose a three-fold structure in which a sheet in which one end of a sheet is folded is guided from a folding roll to a carry-out path, and a second folding roll provided in the path is folded on the other end side of the sheet. Yes. Also when folding with the second folding roll, the one in Patent Document 1 determines the position of the fold by restricting the front end of the folded sheet against the stopper, and the one in Patent Document 2 determines the front end of the folded sheet as a pair. The crease position is determined by regulating with a nip roller.

  As described above, when the fold position is determined by a widely used folding roll, the fold position is assigned by restricting the front end of the sheet in the conveyance direction with a stopper or a nip roller. In other words, the position of the crease is determined by the stopper position in the path when using the stopper, and the position of the fold is determined by the feed amount of this roller when using the nip roller.

Further, Japanese Patent Application Laid-Open No. 7-69529 (Patent Document 3) proposes a method in which a fold position is determined by rotating conveyance rollers arranged upstream and downstream of a folding roll in opposite directions.
Also in this document, the position of the fold is determined by detecting the leading edge of the sheet with a sensor and reversing the sheet when the downstream conveying roller sends a predetermined amount of the sheet.
JP 2004-99199 A JP2003-118932A JP 7-69529 A

  As described above, when folding and folding a predetermined position of the sheet with the folding roll arranged in the conveyance path, the leading end side in the conveyance direction of the sheet is stopped with a stopper or a roller as disclosed in Patent Document 1 or 2 in the related art. There are the following inconveniences when the sheet is fed out in a restricted state and bent at the folding roll portion to determine the folding position.

  First, each sheet has an error in the length direction. For example, a JIS standard A4 size sheet has a variation in length within an allowable range such as 297 ± 2 mm in the length direction. Further, a positional deviation that restricts the sheet also occurs as a mechanism accuracy in the stopper member or roller pair that regulates the leading edge of the sheet. Further, even when the sheet is engulfed by the folding roller, the crease position is deviated by being biased to one of the rollers that the sheet is pressed against. If these positional deviations are always indexed with reference to the leading edge side of the sheet, the above-mentioned dimensional errors are always taken into account with reference to the leading edge, regardless of the folding procedure, when folding in three or more times. The folding position must be calculated, and its control becomes complicated. Furthermore, when folding the rear end side of a long sheet such as JIS A3 size paper in the conveyance direction, determining the folding position based on the leading end side has a large sheet conveyance error, and the optimum folding position considering these errors. The control mechanism for calculating and executing is also complicated.

  Similarly, as disclosed in Patent Document 3, the front end side and the rear end side of the sheet are simultaneously synchronized with each other by the same amount and fed in the opposite directions to the folding roll, thereby bending the sheet and folding the folding roll. Application is also complicated and it is difficult to accurately determine the position.

  The present invention makes it easy to index the crease position according to the paper folding conditions such as the sheet folding procedure, the sheet length size, etc., and the sheet size error or the conveyance error hardly affects the crease position. An object of the present invention is to provide a folding device and an image forming apparatus using the same.

The present invention adopts the following configuration in order to solve the above problems.
First and second conveying means arranged at a distance from the sheet conveying path, folding roll means arranged between the first and second conveying means, and branched from the conveying path. A folding sheet conveyance path for carrying out the folded sheet from the folding roll means, and the second conveyance means is configured to be able to reversely convey the sheet on the conveyance path with a pair of rollers capable of forward and reverse rotation. Further, the sheet conveying path is provided with a first stopper means on the downstream side of the folding roll means and a second stopper means on the upstream side, and the first stopper means regulates the positioning of the sheet leading end side. The sheet fed by the first conveying means is guided to the folding roll means, and the second stopper means regulates the positioning of the sheet rear end side and reversely conveys the sheet conveyed by reverse rotation of the second conveying means. It is comprised so that it may guide to the said folding roll means.

  The first stopper means is constituted by the pair of rollers capable of forward and reverse rotation, and the driving means of the roller pair includes control means for nipping and stopping a predetermined position of the sheet according to the sheet length, and the second The stopper means is a stopper member that protrudes into the conveyance path and restricts the rear end of the sheet that is reversed and conveyed by the reverse rotation of the second conveyance means. The stopper member is configured to allow the sheet conveyed by the first conveying means to pass and stop and abut the trailing edge of the sheet reversely conveyed by the reverse rotation of the second conveying means. . A second folding roll unit is disposed in the folded sheet conveyance path.

  An image forming unit for forming an image on the sheet, a paper folding unit for folding the sheet from the sheet discharge port of the image forming unit, and post-processing such as stapling and punching on the sheet from the discharge port of the paper folding unit. A post-processing unit for applying the sheet, and the paper folding unit conveys the sheet from the image forming unit. Further, in the paper folding unit, a stacker for storing the paper folded sheet and a sheet discharge path for conveying the paper folded sheet to the post-processing unit are connected to the folded sheet conveying path via a path switching unit.

  This is a method in which a sheet is sequentially folded by folding roll means arranged in a conveyance path, and the sheet is folded in a state where the sheet leading edge is regulated on the downstream side after passing through the folding roll means. A paper folding mode based on the leading edge for guiding and folding the paper, and a paper folding mode based on the trailing edge for guiding the sheet to the folding roll means and folding the paper with the rear end of the sheet positioned and regulated upstream of the folding roll means. Is provided.

  According to the present invention, when the sheet is folded by the folding roll means disposed in the sheet conveyance path, the first stopper means is provided on the downstream side of the folding roll means, and the second stopper means is provided on the upstream side. Since the stopper means of the sheet is guided to the folding roll means based on the sheet leading end side and the sheet trailing end side is referenced by the second stopper means, the sheet folding procedure, the sheet length size, etc. Depending on the folding conditions, it is possible to set whether the crease position is to be indexed based on the leading edge of the sheet or the trailing edge, so that an error in the sheet size or an error in the conveyance amount may affect the fold position. Few.

  The present invention will be described in detail below based on the preferred embodiments shown in the drawings. FIG. 1 shows an image forming apparatus using the sheet processing apparatus of the present invention, FIG. 2 is an explanatory diagram showing a paper folding procedure (paper folding mode) in the sheet processing apparatus, and FIG. 3 is an overall configuration diagram of the sheet processing apparatus Respectively.

  First, an overall system of an image forming apparatus using the present invention will be described. FIG. 1 illustrates an image forming unit 100, a sheet processing unit 200 (hereinafter referred to as a paper folding unit) for folding an image sheet carried out from the unit, and post-processing such as stapling on the sheet carried out from the paper folding unit 200. 2 shows an image forming apparatus A including a post-processing unit 300 that performs the processing. The image forming unit 100 has a built-in printing unit such as an inkjet, electrostatic drum, or offset drum, and is sent from a data forming unit such as a copying apparatus or a computer that prints an image read by the scanner unit 120 on a sheet by the printing unit. The printer is configured to print image data on a sheet by a printing unit.

  The paper folding unit 200 includes a paper folding mechanism that folds the sheets formed and sequentially conveyed by the image forming unit 100 into two or three folds, and binds the sheets after image processing or according to use conditions such as filing Paper folding process. The post-processing unit 300 is connected to the paper discharge port of the paper folding unit 200, receives a sheet after paper folding processing or a sheet that is not subjected to folding processing from the paper discharge port, and performs post-processing such as stapling and punching, The sheet is stored on the final delivery stacker.

  Various print processing systems as described above are widely known, and an example of an image forming unit and a post-processing unit will be described with reference to FIG. The illustrated image forming unit 100 shows the configuration of the copying machine, and includes a document feeding unit (ADF) 110 that feeds an original document, a scanner unit 120, and an image forming unit 130. Therefore, the document feeding unit 110 sequentially separates a series of documents placed on the stacker one by one and feeds them to the platen of the scanner unit 120. After the scanner unit 120 reads the document, the document is stored in the sheet discharge stacker. It is configured as a normal document feeder.

  The image data read by the scanner unit 120 is subjected to image processing and sent to the image forming unit 130. The image forming unit 130 irradiates and outputs laser light onto the photosensitive drum 140 in accordance with the received image signal. By this laser light irradiation, an electrostatic latent image is formed on the photosensitive drum 140. The electrostatic latent image is developed into a toner image by the developing device 141 and is transferred by the transfer charger 142 to a sheet such as paper fed from the paper feed cassette 150a or 150b. The paper PA onto which the toner image has been transferred is subjected to a fixing process by the fixing device 143. The fixed paper PA is discharged to a paper folding unit 200 connected by a main body discharge roller 160.

  At this time, discharge of the paper PA is detected by the main body discharge port sensor 161, and a main body discharge signal ES is transmitted from the main body CPU to the paper folding unit control unit 290 of the paper folding unit 200. The paper folding unit control unit 290 of the paper folding unit 200 takes the operation timing based on the main body paper discharge signal ES from the image forming unit 100, and uses the size signal DS and the folding mode signal FS for the sheet conveyed to the sheet carry-in port 210. Judge the processing.

  The paper PA taken in from the sheet carry-in roller 211 at the entrance of the paper folding unit 200 is routed by a carry-in gate 240 provided immediately after the sheet carry-in roller 211. When the folding process is not designated, the sheet folding unit 200 passes through the fourth conveyance path 253 formed by the pinch roller unit 230 formed by the pinch rollers 231 and 232 at the top of the sheet folding unit 200 and the sheet post-processing is performed. It is sent to a unit 300 (hereinafter referred to as a post-processing unit).

  When the folding process is designated, the sheet is transported to the first transport path 250 to be taken into the paper folding unit 200, and the information of the size signal SS and the folding mode signal FS is used to perform the 1/3 in-fold process and the 1 / 3Z-fold process. The folding process selected from either the process or the 1 / 4Z folding process is performed. At this time, when the 1/3 in-fold process is selected, the sheets are stored and stacked in the folded sheet storage box 280 in the paper folding unit 200. In the case of other folding processes, after the folding process, it passes through the third transport path 252 and joins the fourth transport path 253 and is sent to the post-processing unit 300 for further binding processing, punching processing, and the like.

  The post-processing unit 300 is installed by being connected to the carry-out port of the paper folding unit 200, and performs post-processing such as stapling, punching holes, and stamping the sheet from the paper folding unit 200. The structure is such that a sheet carry-in port is provided at the sheet carry-out port of the paper folding unit 200, and a post-processing mechanism (stepler) 304 for performing post-processing on the sheet is provided in a conveyance path 302 between the carry-in port and the sheet storage stacker 301. Deploy. The illustrated example illustrates the case where stapling is performed using a stapler as a post-processing mechanism. A staple tray 303 for stacking and holding sheets and a stapler 304 for performing staple binding on a sheet bundle stacked on the tray are arranged on the conveyance path 302.

  Various types of the stepper 304 are already known. Any of the present invention can be used, and a gluing device for gluing one side edge of the sheet instead of the stepper 304 also punches the sheet. A punching device or a stamping device that applies a predetermined marking to a sheet is also known, and these are incorporated into the conveyance path 302 according to the specifications of the post-processing unit 300. Incidentally, the reference numeral 305 in the figure denotes a second storage stacker that stores folded sheets via a paper discharge path 306 when there is no need to post-process the sheets from the paper folding unit 200.

  Next, the paper folding unit 200 will be described. First, in the image forming apparatus described with reference to FIG. 1, the forms of paper folding that are normally required are 1/2 fold, 1 / 3Z fold, 1/3 fold, and 1 / 4Z fold. Each form of the paper folding will be described.

(1/2 fold)
The sheet carried out from the image forming unit 100 is folded at a fold at a half position in the conveyance direction. In this way, a bag-bound document can be created by folding the center half position of the sheet, and stapling or glue-binding the folded end of the folded sheet. It is also used for organizing various documents, such as filing by punching a folded sheet. In this case, a half position of the sheet carried out from the image forming unit 100 is folded by a folding roll disposed in the conveyance path. Accordingly, the conveying path requires a pair of sheet folding rolls and a regulating means for determining the fold position based on the leading edge or the trailing edge of the sheet.

(Trifold in 1/3)
The front end side and the rear end side of the sheet are folded in the same direction at a position where the sheet is 1/3 in the conveyance direction length. As shown in FIG. 2A, the 1/3 position on the leading end side in the sheet conveyance direction is folded, and the 1/3 position on the trailing end side of the sheet is overlaid on the folded piece. The sheet folded in this way is suitable for use as a letter enclosed in an envelope. Therefore, it is necessary to arrange the first folding roll in the conveyance path, the folded sheet carry-out path for carrying out the sheet folded by the folding roll, and the second folding roll in the folded sheet carry-out path.

(1 / 3Z folding)
The leading end side and the trailing end side of the sheet are folded in the opposite direction to 1/3 of the sheet conveying direction length. As shown in FIG. 2B, the front end side 1/3 position and the rear end side 1/3 position in the sheet conveying direction are folded to the opposite sides. The sheet folded in this way is used, for example, enclosed in an envelope as a direct mail. Therefore, it is necessary to arrange the first folding roll on the upstream side and the second folding roll on the downstream side in the transport path.

(1 / 4Z folding)
As shown in FIG. 2C, the center of the sheet conveyance direction is folded in half at the 1/2 position, and then the piece folded in two is further folded in half on the opposite side at the 1/2 position. Sheets folded in this way are filing by sequentially stapling or punching a series of documents stacked one after another. As a result, large and small sizes, for example, A3 size documents can be aligned and bound to A4 size documents.

Next, a detailed description of the paper folding unit shown in FIG. 1 is shown in FIG.
The paper folding unit 200 includes a sheet carry-in port 210 for taking in the paper PA discharged from the image forming unit 100, a sheet carrying roller 211 for carrying the taken-in paper PA, and pinch rollers 231 and 232 at the entrance. There is a pinch roller unit 230 constituted by There is a carry-in gate 240 immediately after the pair of rollers on the sheet carry-in side, and the conveyance path is switched depending on whether or not folding processing is performed.

  When the folding process is not performed, the carry-in gate 240 is not switched and the paper PA is sent to the post-processing unit 300 through the horizontal fourth transport path 253 formed by the pinch roller unit 230 and the transport roller 211 facing the PA. Further, the pinch roller unit 230 has a hinge structure and can be opened and closed upward to cope with troubles such as a paper transport jam.

  When the folding process is selected, the carry-in gate solenoid SL1 is turned on and the carry-in gate 240 is switched, and the paper PA is conveyed to a sheet conveyance path 250 (hereinafter referred to as a first conveyance path) for performing the folding process. . On the first conveyance path 250 after passing through the carry-in gate 240, there is an entrance sensor SS1 that detects the carried-in paper PA. When the sheet is detected by the entrance sensor SS1, the folding drive motor M2 for performing the folding process starts to be driven. Downstream of the entrance sensor SS1, there is a roller pair of a carry-in roller 212 and a pinch roller 233 which are first transport means for taking the paper PA into the paper folding portion, and a path sensor for paper detection and paper jam detection before the roller pair. There is SS2. A sheet trailing edge stopper 242 (second stopper means), which will be described later, is provided downstream of the roller pair.

  Further, a first roll 214, a second roll 215, and a third roll 216 are disposed downstream of the first transport path 250, and between the first roll 214 and the second roll 215 and between the second roll 215 and the third roll 216. Are in pressure contact and have a space formed between the pressure contact rollers and the conveyance path. A fold 1 loop forming portion 255 is formed between the first conveying path 250 and the pressure contact rollers of the first roll 214 and the second roll 215, and a neutralizing brush 260 is installed in this portion corresponding to the leading portion of the paper folding portion. The static electricity on the paper surface that affects the charged paper folding generated on the main body is removed.

  Further, the folded sheet conveyance path 251 (hereinafter referred to as a second conveyance path), which is the opposite downstream conveyance path between the first roll 214 and the second roll 215, and the second roll 215 and the third roll 216 are in pressure contact with each other. A folded two-loop forming portion 256 is formed between the rollers. Further, on the downstream side of the folding 1 loop forming portion 255 of the first conveyance path 250, there is a roller pair of the registration SB roller 213 and the pinch roller SB234 which are the second conveyance means and the first stopper means, and immediately before the roller pair. Is provided with a pre-registration sensor SS3 and immediately after it is a post-registration sensor SS4, which performs registration and skew correction of the transport paper PA. Further, it is a conveyance path that has a folded one-sheet rear path 254 downstream thereof and stores the sheet when processing a long sheet in the conveyance direction.

  In the second transport path 251, the paper in a folded state is transported between the pressure rollers of the first roll 214 and the second roll 215, and a position variable described later is provided near the most downstream portion of the second transport path 215. A folding reference stopper 243 (abutting stopper member) which is an abutting stopper made of a lever member is disposed. This lever member has a pivot point on the curvature center side of the curved guide member, and is rotated by a predetermined angle by a stopper moving motor M4.

  Therefore, the position of the folding reference stopper 243 can be adjusted by the stopper moving motor M4 during the second transport pass. A sheet pressing guide 244 described later is provided on the second conveyance path 251 in the vicinity of the folding two-loop forming unit 256, and swings to prevent edge folding due to floating of the paper edge when folding the paper. Further, a folded sheet detection sensor SS5 is provided on the downstream side in the vicinity of the sheet pressing guide 244, and monitors a paper jam or the like when the paper is folded. The second transport path 251 is configured by a curved guide member that is curved as illustrated, and is configured by a plate-shaped member that is curved in a direction in which folded sheets are overlapped.

  The second paper fold is conveyed by nip conveyance between the pressure rollers of the second roll 215 and the third roll 216, and immediately after that, a fold portion is formed so as to make a crease with the roller pair of the discharge roller 217 and the discharge pinch roller 235. Pressurize and convey. After the folding process is completed, the sheet carry-out path 252 (hereinafter referred to as the third conveyance path) is transferred to the post-processing unit 300 by each roller pair of the conveyance rollers 218, 219, 220, 221, 222, and 223 and the conveyance pinch roller 236. Be transported.

  A storage gate 241 is provided immediately after the transport roller 218 on the third transport path 252, and a sheet that has been subjected to the inner folding process and the 1 / 3Z folding process is selectively placed in a folded sheet storage box 280 that is installed in the lower part thereof. Guide and stack. Further, the storage gate 241 has a folded portion discharge sensor SS6, and confirms that the storage gate 241 has passed through the storage gate 241 and has been transported and stored. A full detection sensor SS7 is provided in the upper part of the folded sheet storage box 280, and the storage fullness is detected via the folded sheet press flapper 282. Further, the folded sheet storage box 280 is detachable with a guide rail provided on the paper folding unit side. Further, a trapezoidal protrusion is provided at one end of the rack for rotating the folded sheet pressing flapper 282, and when the folded sheet storage box 280 is attached / detached, the folded sheet storage box 280 of the paper folding unit is attached to the end of the attaching / detaching opening. The folded sheet pressing flapper 282 is rotated and retracted into the folded sheet storage box 280 by applying the trapezoidal projection.

  Sheets subjected to folding processing other than the inner three-fold folding and the 1 / 3Z folding processing pass through the storage gate 241 and are conveyed by each pair of conveyance rollers and conveyance pinch rollers, and the sheet conveyance opposite to the pinch roller unit 230 is performed. It joins the horizontal fourth transport path 253 formed by the rollers 211 and is transported to the post-processing unit 300. Immediately after the merge point of the fourth conveyance path 253, there is a sheet discharge sensor SS8, which monitors the conveyance of the folded paper, and the paper folding device control unit 290 transmits a paper detection signal to the post-processing unit 300.

  A drawer upper rail 201 and a drawer lower rail 202 are installed at appropriate positions above and below the paper folding unit 200 so that a mechanism including a paper transport path can be pulled out for maintenance. A paper folding device control unit 290 including a driving power supply unit for the paper folding unit 200 is housed in the lowermost part of the paper folding unit 200. Furthermore, a caster that supports and moves the weight of the apparatus is attached to the lowermost part of the paper folding unit exterior.

<Description of stopper structure>
(Registration SB roller)
The registration SB roller 213 (tip regulating means) is independently driven by a registration motor M3 formed of a pulse motor, and is driven separately from the other transport rollers. A pinch roller 234 is pressed against the registration SB roller 213 and nips the sheet, but can be arbitrarily stopped by a registration motor M3. If the registration SB roller 213 is in a stopped state when the sheet is taken in and conveyed by the carry-in roller 212, the leading end of the sheet is stopped when it reaches the pressure contact line between the registration SB roller 213 and the pinch roller 234, and the registration SB The roller 213 functions as a paper stopper. Also, when the registration motor M3 stops while the pair of rollers of the registration SB roller 213 and the pinch roller 234 is conveying the sheet, the conveyance of the sheet stops at the nip point, and the registration SB roller 213 functions as a sheet stopper as described above. To do. At this time, by energizing the registration motor M3 which is a pulse motor, a reliable paper stopper can be obtained.

(Seat rear end stopper)
This will be described with reference to FIGS. FIG. 8B is a partial cross-sectional view of the sheet trailing edge stopper 242 provided in the first conveying path 250, and the sheet trailing edge stopper 242 is a swingable triangle having a rotation center on the upstream side outside the conveying path 250. A part of the path guide surface is cut out with a shaped lever so that it can be moved back and forth in the transport path. The sheet trailing edge stopper 242 is subjected to its own weight moment by the position of the center of gravity of the sheet trailing edge stopper 242 so as to be always located in the conveyance path. The position of the sheet trailing edge stopper 242 is on the downstream side of the carry-in roller 212. When the sheet is fed by the carry-in roller 212, the sheet leading edge advances along the lever slope of the sheet trailing edge stopper 242 while pushing the lever out of the path guide. . When the trailing edge of the sheet passes through the sheet trailing edge stopper 242, the sheet trailing edge stopper 242 returns to the conveyance path by its own weight moment. At this time, as shown in FIG. 8B, one side of the triangular sheet trailing edge stopper 242 is in a posture orthogonal to the conveyance direction of the conveyance path.

  Therefore, after the sheet trailing edge passes through the sheet trailing edge stopper 242, the sheet trailing edge stopper 242 functions as a sheet stopper when the registration SB roller 213 reversely rotates and conveys the sheet in the reverse direction. Further, the sheet rear end stopper 242 is unitized as shown in FIG. 8A, and is fixed to the path guide with a variable screw so that the stopper position can be adjusted.

(Fold standard stopper)
The function and configuration of the folding reference stopper will be described with reference to FIG.
In the folding process, the first folding process is performed by the first roll and the second roll, and the nip is conveyed to the second conveyance path 251 with the folded portion at the head for the second folding process. At this time, the folding reference stopper 243 variably disposed on the downstream side of the second conveyance path 251 hits the folding portion, prevents the conveyance of the sheet, and forms a loop in the folding 2 loop forming unit 256 to form the second roll and the second roll. Prompt the second folding process with three rolls. The function of the folding reference stopper 243 is to change the position and determine the second folding position, and to perform a plurality of foldings such as a three-fold inner folding process, a 1 / 3Z folding process, and a 1 / 4Z folding process. Is to enable the mode.

  As shown in FIG. 10, the folding reference stopper 243 is directly driven by a stopper moving motor M4 comprising a pulse motor, and the stopper position is a folding reference home detection sensor for detecting the rotation of the mask plate coaxially fixed to the motor shaft. The HS1 is arranged to determine the initial position, and the movement amount from the initial position is controlled by pulse counting.

<Sheet press guide>
This will be described with reference to FIGS.
FIG. 7A shows an entrance portion of the transport path on the folding roll side in the cross section of the second transport path 251. As shown in FIG. 7B, the sheet pressing guide 244 is rotatably supported by a support shaft fixed to one side of the second conveyance path guide 251. When the pressing solenoid SL4 is turned ON, the sheet pressing guide 244 is rotated. Return to the spring force with the presser foot OFF. The sheet presser guide 244 has a plurality of presser rollers that are rotatable in the paper transport direction, and reduces the transport resistance when the paper is pressed as much as possible.

  In addition, as shown in FIG. 7A, the sheet pressing guide 244 is normally at a position for guiding the first folded paper to the second transport path 251, and the first folding is performed when the second folding process is performed. The sheet pressing guide 244 reverses from the first roll side to the third roll side and presses the sheet in order to prevent the ear fold or the like from being caught due to the floating of the processed sheet end surface. The reversal timing is that the presser solenoid SL4 is actuated after a lapse of a predetermined time individually set by the folding mode from the time when the folded portion is detected by the folded sheet detection sensor SS5.

<Description of transport drive system>
FIG. 4 shows a conveyance drive system of the paper folding unit 200, which will be described below.
(Upper conveyance drive system)
The fourth conveyance path 253 that is the upper conveyance system is an independent conveyance system that bypasses the folding processing conveyance system of the paper folding unit when the folding processing is not designated. Sheet conveyance rollers 211 are arranged before and after the conveyance path, and are driven and transmitted by a timing belt by a single conveyance motor M1. However, the folding process is performed, and if there is further post-processing, the folding process is performed, and then the fourth transport path 253 is joined to the post-processing unit 300.

(Folding part conveyance drive system)
The folding part conveyance drive system is driven by a folding drive motor M2 which is a brushless motor except for a registration SB roller drive described later. The drive transmission is transmitted from a pulley P1 integrated with the M2 gear G7 fixed to the folding drive motor shaft to a third pulley P2 integrated with the third roll gear G6 via a timing belt, and the third roll gear G6 and the second roll gear. G5 and the first roll gear G4 and gear transmission are driven. The M2 gear G7 fixed to the folding drive motor shaft drives the carry-in roller 212 via the first gear G1, the second gear G2, and the third gear G3.

  The first transmission gear G8 is driven to transmit through the timing belt from the first pulley P3 integrated with the first roll gear G4 to the first transmission gear pulley P4 integrated with the first transmission gear G8 to reverse the rotation direction. To the second transmission gear G9 to drive the conveying roller 219 on which the second transmission gear G9 is coaxially fixed. A transport roller pulley P6 is coaxially fixed to the transport rollers 218, 219, 220, 221, 222, and 223 and the carry-out roller 217, and the transport roller 220 in the third transport path 252 is coaxially fixed to the transport roller 219. , 221, 222, and 223 are sequentially transmitted to the belt. Further, the belt branches from a conveyance roller pulley P6 coaxially fixed to the conveyance roller 219, and belt drive is transmitted to the carry-out roller 217 and the conveyance roller 218 sequentially.

(Registration SB roller drive system)
The registration SB roller drive transmission mechanism will be described with reference to FIGS. 10, 11A, and 11B.
As described above, the registration SB roller 213 is independently driven by the registration motor M3 for skew correction and folding processing of the conveyance paper, and is driven separately from the other conveyance rollers. Further, as shown in FIG. 11B, a saw-tooth pawl clutch mechanism is adopted for driving transmission from the registration motor M3 to the registration SB roller 213. One gear-integrated ratchet G10 of the pawl clutch is integrally fitted and positioned with respect to the resist SB roller shaft 261 integrally with the transmission gear directly connected to the resist motor M3, and the other shaft fixing ratchet G11 of the pawl clutch is The resist SB roller shaft 261 rotates integrally through a parallel pin, and an axial elongated hole for fitting the parallel pin is provided in the shaft fixing ratchet, thereby enabling the minimum axial movement necessary to disengage the mesh. . When the registration motor M3 is rotated forward and backward in this state, the clutch pawl shape is sawtooth, so that the drive can be transmitted in one direction as it is. However, in the opposite rotation, the axial force acts and the clutch pawl is released.

  For this reason, a pressing spring 263 is inserted into the registration SB roller shaft 261 in the direction in which the shaft fixing ratchet is engaged, and the spring is urged. Can be turned on and off. When the registration SB roller 213 mainly feeds the paper, the ratchet solenoid SL5 is turned on and the rear surface of the shaft fixing ratchet is engaged with the ratchet pressing lever 262.

  The functions of the registration SB roller 213 include: (1) a paper tip abutting roller function for skew correction, (2) a forward / reverse conveyance function at the time of three-fold folding within 1/3, and (3) at the time of 1 / 3Z folding processing And (4) a complete followability during fold roll nip conveyance (because it does not become a load on the fold roll).

  Since the above function has the function (4) in particular, the above mechanism is employed. That is, when the folding process is performed in a state where the sheet is nipped by the registration SB roller 213, in order for the folding function to be performed normally, after the sheet is delivered to the folding roll, the folding roll mainly becomes the registration SB roller 213. Needs to follow the sheet as it is conveyed by the folding roll. For this reason, as shown in the figure, a serrated pawl clutch mechanism is employed, and when the nip roll nip is conveyed with the sheet niped to the registration SB roller 213, the ratchet solenoid SL5 is turned off and the fold roll conveyance force causes the clutch to move. The engagement is released and the resist SB roller 213 is idled. In order to satisfy the function (4), the pressure contact of the pinch roller 234 on the other side of the registration SB roller 213 may be released without using a clutch, but it is only necessary to obtain certainty at the release timing or the like.

<Loading roller configuration>
The configuration of the carry-in roller will be described with reference to FIG.
There is a roller pair of a carry-in roller 212 and a pinch roller 233. The pinch roller 233 is rotatably supported by a pinch lever 264 that is swingably fitted and supported by a pinch shaft 267 fixed to an apparatus frame (not shown). The spring is in pressure contact with the carry-in roller 212. Particularly when registering the leading edge of the paper, the pressurizing solenoid is turned on, and the pinch roller 233 is pressed and pressed through the pressurizing arm 265 that is swingably fitted to the pinch shaft, thereby increasing the conveying force and the paper loop for registration. Enables the formation of

In addition, it is necessary to separate the pinch roller 233 from the carry-in roller 212 in order to make the paper free at the time of paper skew correction after registration and after the paper is transferred from the carry-in roller 212 to the folding roll.
For this reason, the separation solenoid SL2 is turned on, and the pinch lever is rotated in the direction in which the pinch roller 233 is separated by the separation arm 266 that is swingably fitted and supported by the separation arm shaft 269 fixed to the conveyance frame (not shown).

<Folded sheet storage box full detection mechanism>
The configuration of the full detection mechanism of the folded sheet storage box will be described with reference to FIG.
A folded sheet pressing flapper 282 is fixedly supported on a flapper shaft 283 that is rotatably fitted and supported on the upper part of the folded sheet storage box. A rack 286 is disposed on the rear side of the folded sheet storage box. When the rack 286 is moved, the flapper gear 284 fixed and supported by the parallel pin to the flapper shaft 283 is rotated via the pinion gear 287, and the folded sheet pressing flapper 282 is rotated. Rotates counterclockwise and comes into contact with the stack paper surface. The parallel pin grooves of the flapper gear 284 have a play in the rotation direction, and a flapper gear spring 285 is incorporated so as to absorb the play, thereby preventing the folded sheet pressing flapper 282 from being bent when contacting the stack sheet surface. .

  A flapper solenoid SL7 is disposed and fixed on a device frame (not shown) facing the rear side of the folded sheet storage box 280. When the flapper solenoid SL7 is turned on, the rack moves via the flapper SOL lever, and the folded sheet presser is moved by the above movement. The flapper 282 rotates to perform a full detection operation. A sensor mask plate 289 is fixed to the flapper shaft 283, and the full detection sensor SS7 is disposed opposite to the flapper shaft 283. When the full detection is performed, the full detection sensor is shielded from light. The sheet pressing flapper 282 is attached to the side for pressing the free end side of the sheet.

<Description of paper folding unit operation>
The operation of the paper folding unit will be described with reference to FIGS.
As a basic operation, for the paper output and discharged from the main body for which the paper folding process is designated, according to the designated folding mode, the above-described one-third in-fold, 1 / 3Z-fold, 1 / 4Z Perform the folding process.

(Initial operation)
When the main body power is turned on, the power supply on the paper folding unit side is also turned on, the state of actuators such as sensors and solenoids is compared with preset initial values, and communication is performed with the main body side to perform initial operation if necessary. Simultaneously with the above initial confirmation, the conveyance motor M1 and the folding drive motor M2 start to drive.

(Capture paper)
When a sheet is conveyed from the main body to the sheet carry-in entrance 210 of the paper folding unit 200, information on the paper discharge signal ES, the size signal DS, and the folding mode signal FS is sent from the main body CPU to the paper folding device control unit 290 of the paper folding unit. Entered. Based on this input information, the carry-in gate 240 immediately after the sheet carry-in entrance of the paper folding unit guides to the first conveyance path 250 into the paper folding unit.

(Paper registration processing)
The paper PA transported to the first transport path 250 is detected by the entrance sensor SS1 and the path sensor SS2, the transport state is monitored and further fed by the carry-in roller 212, and the leading edge of the paper is detected by the pre-registration sensor SS3. After the pre-registration sensor SS3 is turned ON, the carry-in roller 212 is further driven for a predetermined time in a state where the pre-registration sensor SS3 is abutted against the registration SB roller 213, thereby forming a paper loop in the conveyance path. At this time, the registration motor M3 is stationary in an excited state, and the ratchet solenoid SL5 of the clutch portion is turned on to fix and hold the registration SB roller.

  After the paper loop is formed, the pressure solenoid SL3 is turned off, the separation solenoid SL2 is turned on, and the pinch roller 233 facing the carry-in roller 212 is released from pressure contact, so that the paper PA is given a degree of freedom and faces the resist SB roller 213. The skew correction is performed with reference to the contact line of the pinch roller SB234, and the registration process is completed.

(Paper folding processing)
After the registration process, the process enters the paper folding process, but the process branches as follows based on the designated folding mode information.

[Third Folding Process in 1/3] Refer to FIG. 13 After the skew correction, the separation solenoid SL2 is turned OFF, the pinch roller 233 is pressed against the carry-in roller 212 again, and the registration motor M3 is driven forward to feed the paper PA. During this driving, the ratchet solenoid SL5 of the clutch portion is turned on to reliably transmit the drive. The registration motor M <b> 3 is pulse-counted by the pulse motor, and is driven and stopped until the sheet trailing edge passes through the sheet trailing edge stopper 242 in the downstream conveying path of the carry-in roller 212. The pulse amount corresponding to the trailing edge of the sheet passing through the sheet trailing edge stopper 242 is set according to the sheet size and folding mode, and the post-registration sensor SS4 performs pulse counting from the detection of the leading edge of the sheet.

  When the trailing edge of the sheet passes through the sheet trailing edge stopper 242, the registration motor M3 is driven in reverse while the ratchet solenoid SL5 remains on. The paper PA is reversely fed and the trailing edge hits the trailing edge stopper 242, and a paper loop is generated in the folding 1 loop forming unit 255. The sheet PA is nipped between the two folding rollers so as to follow the roller surfaces of the first roll 214 and the second roll 215.

  When carrying out the nip conveyance with these two folding rolls, after a predetermined time when the paper edge is detected again by the post-registration sensor SS4, the ratchet solenoid SL5 and the registration motor M3 are turned off and the registration SB roller 213 is driven to rotate more than necessary. I try not to stress it. For the same purpose, the pinch roller SB 234 as the counterpart of the registration SB roller 213 may be separated instead of turning off the drive transmission.

  As described above, the paper PA is transferred to the first roll 214 and the second roll 215, and the two folding rolls are nip-conveyed and the first folding process is performed between the folding rolls. In the folded state, the paper PA is fed with the paper folded portion at the head, detected by the folded sheet detection sensor SS5, and provided on the second conveyance path 251 downstream thereof and the folding reference stopper 243 set to move to a predetermined position. To form a paper loop in the folded two-loop forming portion 256.

  In particular, in the 1/3 inner fold process, when a paper loop is generated in the fold 2 loop forming section 256, the first folded paper end face comes to the paper loop side. Entrainment ear breakage is likely to occur. For this reason, in the 1/3 inner folding process, the folding sheet detection sensor SS5 detects and after a predetermined time has elapsed, the pressing solenoid SL4 is turned on to operate the sheet pressing guide 244 to hold the first folded sheet end surface. , Preventing the ears from being bent due to entanglement due to floating of the end face. Similarly to the first folding process, the paper PA is nipped between the folding rollers so as to follow the roller surfaces of the second roll 215 and the third roll 216, the second folding process is performed, and the paper is folded and carried out. The fold is pressed by the roller 217 and the folding process is completed within 1/3.

[1 / 3Z Folding Process] Refer to FIG. 14 The skew correction of the paper PA is performed in the same manner as the above-described three-folding process, the pinch roller 233 is again pressed against the carry-in roller 212, and the registration motor M3 is driven to rotate forward. Then, the sheet PA is conveyed by the registration SB roller 213. At this time, the conveyance amount is pulse-counted, and the registration motor M3 is stopped at the time when (1-3-α) equivalent of the paper length L in the conveyance direction of the paper PA is sent.

  While the ratchet solenoid SL5 remains ON, the registration motor M3 stops in an excited state, the sheet PA is nipped by the registration SB roller 213, the pressure solenoid SL3 is turned ON to increase the conveyance force, and the conveyance roller 212 further increases the sheet PA. When the sheet is conveyed, a sheet loop is generated in the folding 1 loop forming unit 255. The paper loop becomes larger and the paper PA is nipped between the two folding rolls so as to follow the roller surfaces of the first roll 214 and the second roll 215, and the first folding process is performed. At this time, the registration SB roller 213 is driven and rotated in the same manner as the inner three-fold process so as not to apply unnecessary stress to the sheet, and the pressure solenoid SL3 is also turned off on the carry-in roller 212 side.

  After the first folding process, the paper PA is fed with the paper folded portion at the head in the folded state in the same manner as the one-third in-three folding process, and is applied to the folding reference stopper 243 set to move to a predetermined position. In contact with each other, a paper loop is generated in the folded two-loop forming unit 256. At this time, the sheet end surface subjected to the first folding process is on the opposite side across the sheet loop and the sheet of the folding two-loop forming unit 256, so there is no fear of the sheet end surface being involved like the inner three-folding process. It is not necessary to press the sheet by operating the sheet pressing guide 244.

  Similarly to the first folding process, the paper PA is nipped between the folding rolls following the roller surfaces of the second roll 215 and the third roll 216, the second folding process is performed, and the carry-out roller is folded. The fold is pressed at 217 and the 1 / 3Z folding process is completed.

[1 / 4Z Folding Processing] See FIG. 15. After the skew correction, the separation solenoid SL2 is turned OFF, the pinch roller 233 is pressed against the carry-in roller 212 again, and the pressure solenoid SL3 is turned on to increase the carrying force of the carry-in roller 212. Transport paper PA. The registration motor M3 is stationary in an excited state, the ratchet solenoid SL5 is ON, and the registration SB roller 213 is held and fixed. The paper PA transported on the first transport path 250 by the carry-in roller 212 abuts on the stationary registration SB roller 213 to form a paper loop in the folded 1 loop forming unit 255. At this time, the pinch roller 233 to which the paper PA is transferred to the first roll 214 and the second roll 215 at the time when a predetermined time elapses from the re-pressing time point to the carry-in roller 212 so as not to apply unnecessary stress to the paper The registration SB roller 213 is driven and rotated in the same manner as the one-third inward folding process, and the pressure solenoid SL3 is also turned off on the carry-in roller 212 side.

  The paper loop becomes larger and the paper PA is nipped between the two folding rolls so as to follow the roller surfaces of the first roll 214 and the second roll 215, and the first folding process is performed. At this time, the conveyance path length to the nip point of the registration SB roller 213, the first roll 214, and the second roll 215 is equivalent to ¼ of the paper length L in the conveyance direction of the paper PA, and the paper length L of the paper PA. Can be folded at a portion corresponding to 1/4 of the above.

  At this time, the folding reference stopper 243 on the downstream second conveyance path 251 moves to a position corresponding to the 1 / 4Z folding process and comes into contact with the folded portion of the conveyed paper PA. Further, the paper PA nipped and conveyed between the two folding rolls forms a paper loop in the folding two-loop forming section 256, and the second folding 215 and the third roll 216 perform the second folding similarly to the first folding processing. Processing is performed. Further, the paper is folded and nipped by the carry-out roller 217, and the folded portion is pressurized, and the 1 / 4Z folding process is completed.

  The paper PA for which the folding process has been completed is transferred from the carry-out roller 217 to the conveyance roller 218 on the third conveyance path 252. A storage gate 241 is provided immediately after the transport roller 218, and selectively cuts the paper path after the paper folding process. When the 1 / 4Z folding process is selected, the storage gate 241 is not switched, and the sheet PA is transported on the third transport path 252 as it is and joined to the upper fourth transport path 253, and transported by the sheet discharge sensor SS8. Confirmed, the paper after the paper folding process is sent to the post-processing unit 300 together with the sheet discharge signal from the paper folding unit control unit 290, and the folding process is completed.

  In the case of the paper after the paper folding process excluding the 1 / 4Z folding process, the storage gate solenoid SL6 is turned ON, the storage gate 241 is switched to the folded sheet storage box side, the paper PA is confirmed by the folding portion discharge sensor SS6, and the folded sheet is stored. The folding process is completed by being stored in the box 280. The folded sheet storage box 280 has a full detection sensor SS7 to detect stack fullness.

1 is a cross-sectional view showing an embodiment of an image forming system according to the present invention. FIG. 5 is an explanatory diagram showing a paper folding procedure (paper folding mode) in the sheet processing apparatus, where (a) shows a 1/3 inner fold, (b) shows a 1 / 3Z fold, and (c) shows 1 / 4Z folding is shown. The whole block diagram of a paper folding unit. Explanatory drawing of the conveyance drive system of a paper folding unit. The block diagram of a carrying-in roller. 4A and 4B are perspective views of a sheet presser guide, where FIG. 5A is an explanatory diagram showing a presser solenoid being in an ON state, and FIG. It is sectional drawing of a sheet | seat pressing guide, (a) shows the time of insertion of a sheet | seat, (b) is explanatory drawing which shows the time of sheet | seat pressing. 4A and 4B are partial cross-sectional views of a sheet rear end stopper, in which FIG. 4A illustrates a state where the stopper is outside the conveyance path, and FIG. FIG. 6 is a diagram illustrating a relationship between a sheet rear end stopper and a carry-in roller. The block diagram of a fold reference | standard stopper. It is explanatory drawing of a resist SB roller drive transmission mechanism, (a) shows the state where the solenoid is OFF and the clutch is disengaged, (b) is the explanatory diagram of the state where the solenoid is ON and the clutch is engaged. Full detection mechanism for folded sheet storage box. Explanatory drawing which is an operation | movement flow of 1/3 inner folding, and shows a 1st folding form. Explanatory drawing which is an operation | movement flow of 1/3 inner folding, and shows a 1st folding form. Explanatory drawing which is an operation | movement flow of 1/3 inner folding, and shows a 1st folding form. Explanatory drawing which is an operation | movement flow of 1/3 inner folding, and shows a 1st folding form. Explanatory drawing which is an operation | movement flow of 1/3 inner folding, and shows a 2nd folding form. Explanatory drawing which is an operation | movement flow of 1/3 inner folding, and shows a 2nd folding form. Explanatory drawing which is an operation | movement flow of 1/3 folds inside, and shows the form of discharge to a storage box. Explanatory drawing which is an operation | movement flow of 1/3 folds inside, and shows the form of discharge to a storage box. Explanatory drawing which is a 1 / 3Z folding operation flow and shows a 1st folding form. Explanatory drawing which is a 1 / 3Z folding operation flow and shows a 1st folding form. Explanatory drawing which is a 1 / 3Z folding operation flow and shows a 1st folding form. Explanatory drawing which is a 1 / 3Z folding operation flow and shows a 1st folding form. Explanatory drawing which shows the operation | movement flow of 1 / 3Z folding, and shows a 2nd folding form. Explanatory drawing which shows the operation | movement flow of 1 / 3Z folding, and shows a 2nd folding form. Explanatory drawing which is an operation | movement flow of 1 / 3Z folding, and shows the form of discharge to a storage box. Explanatory drawing which is an operation | movement flow of 1 / 3Z folding, and shows the form of discharge to a storage box. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows a 1st folding form. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows a 1st folding form. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows a 1st folding form. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows a 1st folding form. Explanatory drawing which shows the operation | movement flow of 1 / 4Z folding and shows a 2nd folding form. Explanatory drawing which shows the operation | movement flow of 1 / 4Z folding and shows a 2nd folding form. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows the form of discharge to a post-processing unit. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows the form of discharge to a post-processing unit. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows the form of discharge to a post-processing unit. Explanatory drawing which is a 1 / 4Z folding operation | movement flow and shows the form of discharge to a post-processing unit.

Explanation of symbols

100 Image forming unit 200 Paper folding unit 213 Registration SB roller 214 First roll 215 Second roll 216 Third roll 230 Pinch roller unit 242 Sheet trailing edge stopper 243 Folding reference stopper 244 Sheet pressing guide 250 First conveyance path (sheet conveyance) Route)
251 Second transport path (folded sheet transport path)
252 Third conveyance path (sheet carry-out path)
253 Fourth transport pass 300 Post-processing unit

Claims (9)

First and second conveying means arranged at a distance in the sheet conveying path;
Folding roll means disposed between the first and second conveying means;
A folded sheet conveyance path that is arranged branched from the conveyance path and carries out the folded sheet from the folding roll means,
The second conveying means is configured to be able to reversely convey the sheet on the conveying path with a pair of rollers capable of forward and reverse rotation,
The sheet conveyance path is provided with a first stopper means on the downstream side of the folding roll means and a second stopper means on the upstream side,
The first stopper means regulates the leading end of the sheet and guides the sheet fed by the first conveying means to the folding roll means, and the second stopper means restricts the trailing end of the sheet and controls the position. A sheet processing apparatus configured to guide a sheet reversely conveyed by reverse rotation of the second conveying means to the folding roll means.   2. The first stopper means is composed of a pair of rollers capable of rotating forward and backward, and the driving means of the roller pair includes control means for nipping and stopping a predetermined position of the sheet according to the sheet length. The sheet processing apparatus according to 1.   The second stopper means includes a stopper member that protrudes into the conveyance path and restricts abutment of a rear end of the sheet that is reversed and conveyed by reverse rotation of the second conveyance means. The sheet processing apparatus according to 2.   The stopper member is configured to allow the sheet conveyed by the first conveying means to pass and stop and abut the trailing edge of the sheet reversely conveyed by the reverse rotation of the second conveying means. The sheet processing apparatus according to claim 3.   The sheet processing apparatus according to claim 1, wherein a second folding roll unit is disposed in the folded sheet conveyance path. An image forming unit for forming an image on a sheet;
A paper folding unit for folding the sheet from the sheet discharge port of the image forming unit;
A post-processing unit that performs post-processing such as stapling and punching on the sheet from the discharge port of the paper folding unit,
The paper folding unit includes a conveyance path for conveying a sheet from the image forming unit;
First and second conveying means arranged at a distance from the sheet conveying path;
Folding roll means disposed between the first and second conveying means;
A folded sheet conveyance path that is arranged branched from the conveyance path and carries out the folded sheet from the folding roll means,
The second conveying means is configured to be able to reversely convey the sheet on the conveying path with a pair of rollers capable of forward and reverse rotation,
The sheet conveyance path is provided with a first stopper means on the downstream side of the folding roll means and a second stopper means on the upstream side,
The first stopper means positions the sheet leading end side and guides the sheet fed by the first conveying means to the folding roll means.
The second stopper means is configured to restrict the positioning of the rear end side of the sheet and guide the sheet reversely conveyed by the reverse rotation of the second conveying means to the folding roll means. Forming equipment.   The paper folding unit is characterized in that a stacker for storing folded sheets and a sheet discharge path for conveying the folded sheets to the post-processing unit are connected to the folded sheet conveying path via a path switching means. The image forming apparatus according to claim 6. A method of sequentially folding sheets with folding roll means arranged in a conveyance path,
A paper folding mode based on the leading edge for guiding the sheet to the folding roll means and folding the paper in a state where the sheet leading edge is positioned and regulated on the downstream side after passing the folding roll means;
A rear end reference paper folding mode for guiding the sheet to the folding roll means and folding the paper in a state where the rear end of the sheet is regulated on the upstream side of the folding roll means;
A paper folding method in a sheet processing apparatus, wherein the leading edge reference paper folding mode and the trailing edge reference paper folding mode are selectively executed. In the paper folding mode based on the leading edge, paper folding is performed by the folding roll means by feeding the sheet by the conveying means arranged on the upstream side with the pair of rollers arranged in the conveying path being nipped. And
In the paper folding mode based on the trailing edge, paper folding is performed by the folding roll means by reversing and transporting the sheet while the roller pair is reversed and the trailing edge of the sheet is regulated by the stopper means arranged on the upstream side. The paper folding method in the sheet processing apparatus according to claim 8.

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