JP4938494B2 - Sheet folding apparatus, post-processing apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet folding apparatus that folds a sheet bundle, a post-processing apparatus using the same, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine using the same.

  In general, a post-processing device that is provided in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, and performs saddle stitching on a sheet output from an image forming unit of the image forming apparatus is known. Some of such post-processing apparatuses have a function of performing so-called half-folding processing so that a booklet can be formed by folding a saddle-stitched bundle, which is a sheet bundle that has been saddle-stitched, at a saddle-stitched portion.

  In this type of post-processing apparatus, it is known that a folding roller is used to fold a sheet bundle, and the sheet bundle is pushed between the nips of the folding roller by a folding blade to perform the sheet folding process. ing. Further, in the post-processing apparatus, it is also known that the additional folding is performed by moving the additional folding roller along the fold portion while pressing the additional folding roller against the fold portion of the sheet bundle subjected to the middle folding process by the folding roller. (For example, refer to Patent Document 1).

  In such a post-processing apparatus, when the saddle stitch bundle enters the nip portion of the folding roller depending on the paper type and image type during the middle folding process, the pressure applied by the folding roller is locally applied to the outside of the sheet bundle. For reasons such as working, only one sheet outside the sheet bundle may be torn and discharged. For this reason, the sheet bundle is folded by using the large-diameter folding roller and the smaller-diameter folding roller having a smaller diameter and the folding blade formed in a comb-teeth shape. A technique is known in which such a pressing force is dispersed so that a sheet bundle is not torn (for example, see Patent Document 2).

JP 2005-162345 A JP 2003-276937 A

  However, in the post-processing apparatus using the large-diameter folding roller, the small-diameter folding roller, and the comb-like folding blade, it is possible to prevent the sheet bundle from being broken, but the large-diameter folding roller and Since the small-diameter folding roller is coaxially continuous, no pressure is applied evenly when the sheet bundle is folded, so that wrinkles may occur. In addition, if the comb-like folding blade pushes the sheet bundle past the nip of the large diameter roller, it will cause resistance when transporting the sheet bundle, and there is a risk of image scraping, etc. There was a problem that the quality of the sheet bundle to be deteriorated.

  An object of the present invention is to provide a sheet folding apparatus, a post-processing apparatus, and an image forming apparatus that can prevent the sheet bundle from being torn while preventing the quality of the discharged sheet bundle from deteriorating.

In order to solve the above-mentioned problems, the invention described in claim 1 is a pair of main folding rollers for sandwiching a sheet bundle between the nip portions to fold the sheet bundle, and can be moved forward and backward with respect to the nip portions of these main folding rollers. In the sheet folding apparatus provided with the main folding blade, the sheet folding device is formed between the main folding roller and the main folding blade so as to be narrower than the minimum width of the sheet that can be passed, and the sheet bundle is formed in the nip portion. A pair of temporary folding rollers that sandwich and fold the sheet bundle are provided, and the main folding blade is provided so as to be able to advance to the front of the nip portion of the main folding roller, and when moving forward toward the main folding roller, interference is relief portion is formed to avoid, and, temporary folding rollers are held in a pressurized state when the folding blade to advance the temporary folding rollers, and then the folding blades of the nip portion of the folding rollers Sheet folding apparatus tentative folding rollers, characterized in <br/> releasing the pressurized state when moving forward.

The invention described in claim 2, in the invention described in claim 1, the relief portion of the folding blade, that the temporary folding blade to push the sheet bundle into the nip portion of the temporary folding rollers are provided Features.

The invention described in claim 3 is the invention described in claim 1 or 2 , wherein a plurality of temporary folding rollers are arranged coaxially within a range of a minimum width of a sheet that can be passed. Features.

The invention described in claim 4 is the invention described in any one of claims 1 to 3 , further comprising a single roller driving unit that drives the main folding roller and the temporary folding roller. And

The invention described in claim 5 is the invention described in any one of claims 1 to 3, wherein the main folding roller driving unit that drives the main folding roller and the temporary folding roller driving that drives the temporary folding roller. And a portion.

The invention described in claim 6 is the invention described in any one of claims 3 to 5 , wherein the main folding blade driving unit that drives the main folding blade and the temporary folding blade drive that drives the temporary folding blade. And a portion.

According to a seventh aspect of the present invention, the post-processing includes a binding processing unit that performs binding processing of a sheet bundle and the sheet folding device according to any one of the first to sixth aspects. Device.

According to an eighth aspect of the present invention, there is provided an image forming apparatus comprising: an image forming unit that forms an image on a sheet; and the post-processing apparatus according to the seventh aspect.

According to the present invention, the sheet bundle is folded in stages with the temporary folding roller and the main folding roller having a larger width than the sheet bundle, so that the load on the sheet bundle can be distributed and the sheet bundle can be broken. Can be prevented. In addition, since a relief portion is formed in the main folding blade and the temporary folding roller releases the pressure state when the main folding blade moves immediately before the nip portion of the main folding roller, a temporary folding roller is used. It is possible to prevent resistance from being applied to the conveyance. As a result, it is possible to suppress the occurrence of image shaving and the like and to prevent the quality of the discharged sheet bundle from being deteriorated.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. 1 is a schematic cross-sectional view of the image forming apparatus according to the first embodiment of the present invention, and FIG. 2 is a diagram schematically showing a middle folding section of the middle folding processing tray of FIG. 4 is a diagram for explaining the operation of the middle folding processing unit in FIG. 2, and FIG. 5 is a block diagram showing a control system of the middle folding processing unit.

  As shown in FIG. 1, the image forming apparatus PR has an image forming unit (not shown) that forms an image on a sheet (sheet), and a post-processing is performed on the sheet discharged from the image forming apparatus PD on its side. Is provided. The image forming unit includes a photosensitive drum that is an image carrier, a charging device that charges the outer periphery of the photosensitive drum, a writing device that forms an electrostatic latent image based on image information on the charged photosensitive drum, A developing device for supplying the electrostatic latent image on the photosensitive drum as a toner image by supplying toner, a transfer device for transferring the toner image on the photosensitive drum to the paper, a fixing device for fixing the toner image on the paper, and the like are provided. However, illustration and description thereof are omitted.

  In the present embodiment, the post-processing device PD forms a hole by the punch unit 100, a sheet alignment by the jogger fence 53 and the end face binding stapler S1, and an edge binding, a sheet by the jogger fence 53 and the saddle stitching stapler S2. Processing such as alignment + saddle stitching, paper sorting by the shift tray 202, and half-folding by a half-folding processing unit (a half-folding processing device) 20, which will be described later, can be performed. That is, the sheet discharged from the image forming apparatus PD passes through the conveyance path A having the punch unit 100 that performs punching processing on one sheet of paper, the conveyance path B that leads to the upper tray 201, and the conveyance path C that leads to the shift tray 202. Each of the branching claws 15 and the branching claws 16 distributes to a conveyance path D that leads to a staple processing tray (binding processing unit) F that performs alignment, staple binding, and the like.

  The sheet guided to the staple processing tray F through the conveyance paths A and D and aligned and stapled by the staple processing tray F is guided to the shift tray 202 by the branch guide plate 54 and the movable guide 55 which are deflection means. The paper is distributed to one of the conveyance path C and the middle folding processing tray G for folding. Further, the sheet that is folded in the middle folding processing tray G is guided to the saddle stitching tray 203 through the conveyance path H. Further, a branching claw 17 is disposed in the conveyance path D. After the trailing edge of the sheet conveyed by the conveyance roller 7 passes through this, at least the conveyance rollers 9 and 10 and the staple discharge roller 11 are conveyed. By rotating the roller 9 in the reverse direction, the trailing edge of the sheet is guided to the sheet accommodating portion E so that the sheet stays and can be conveyed while being overlapped with the next sheet. By repeating this operation, two or more sheets can be stacked and conveyed.

  In the conveyance path A, an inlet sensor 301 that detects a sheet received from the image forming apparatus PR via the inlet guide plate 3, and an inlet roller 1, a punch unit 100, a hopper 101, a conveyance roller 2, a branching claw 15, and a branch downstream thereof. The nail | claw 16 is arrange | positioned sequentially. When the solenoid is turned on, the branching claw 15 is rotated upward and the branching claw 16 is rotated downward, so that the paper is distributed to the conveyance path B, the conveyance path C, and the conveyance path D.

  When the sheet is guided to the conveyance path B, the branching claw 15 is in the state shown in FIG. 1 and the solenoid is OFF. When the sheet is guided to the conveyance path C, the branching claw 15 is turned upward by turning on the solenoid. When the sheet is guided to the conveyance path D, the branch claw 16 is turned upward by turning off the solenoid and the branch claw 15 is turned on by turning on the solenoid.

  The sheets guided to the processing tray F by the staple paper discharge roller 11 through the conveyance path D are sequentially stacked to form a sheet bundle (sheet bundle). In this case, alignment in the vertical direction (paper conveyance direction) is performed by the tapping roller 12 for each sheet, and alignment in the horizontal direction (paper width direction orthogonal to the sheet conveyance direction) is performed by the jogger fence 53. The end face stitching stapler S1 is driven by a staple signal from a control unit (not shown) between job breaks, that is, from the last sheet of the sheet bundle to the first sheet of the next sheet bundle, and the binding process is performed.

  The sheet bundle subjected to the binding process is sent to the shift paper discharge roller 6 by the discharge claw 52a provided on the discharge belt 52, and is discharged to the shift tray 202 set at the receiving position, or the discharge roller 56. And the conveying rollers 22 and 23 are conveyed to the paper folding stopper 24 of the middle folding processing tray G, are folded in half by the middle folding processing portion 20 of the middle folding processing tray G, and are discharged to the saddle stitching tray 203 by the paper discharge roller 26. It has come to be. In the figure, reference numeral 310 denotes a paper presence / absence sensor that detects the presence / absence of paper on the staple processing tray F, and reference numeral 311 denotes an HP sensor that detects the home position of the discharge claw 52a.

  As shown in FIGS. 2 and 5, the half-folding processing unit 20 is capable of moving forward and backward with respect to a pair of main folding rollers 25 that fold the paper bundle by sandwiching the paper bundle between the nip portions and the nip portion of the main folding roller 25. A main folding blade 28 provided, a pair of temporary folding rollers 30 formed between the main folding roller 25 and the main folding blade 28 so as to be narrower than the minimum width of paper that can be passed, and the temporary folding A temporary folding blade 29 provided so as to be movable forward and backward with respect to the nip portion of the roller 30 and a middle folding control unit 43 for controlling the middle folding processing unit 20 are provided.

  The temporary folding roller 30 is disposed in front of the main folding roller 25 (on the downstream side of the main folding roller 25) and is opposed to the central portion in the axial direction of the main folding roller 25, and is pushed by the main folding blade 28. A crease is formed at the center in the width direction of the sheet bundle. The temporary folding roller 30 and the main folding roller 25 are driven by the same drive source. That is, these rollers 25 and 30 are configured to be driven to rotate by transmitting the driving force from the roller driving unit 42 which is a single motor through the respective rotating shafts 25a and 30a. In the present embodiment, the driving force from the roller driving unit 42 is transmitted to the rotating shafts 25a and 30a by meshing of a gear (not shown), and the rollers 25 and 30 are the same by adjusting the gear ratio. It is designed to drive at linear speed.

  As shown in FIGS. 2 and 5, the main folding blade 28 includes a pair of pushing portions 28 a that push the both ends of the sheet bundle, a plate-like support member 28 b that supports the pushing portion 28 a, and the main folding blade 28. And a main folding blade drive unit 40 such as a motor that slides forward and backward in the direction toward the nip portion of the main folding roller 25 and in the opposite direction.

  The support member 28b of the main folding blade 28 is provided with a moving shaft 28c connected to the main folding blade driving unit 40, and the driving of the main folding blade driving unit 40 is transferred to the main folding blade 28 via the moving shaft 28c. As a result, the main folding blade 28 slides. Further, when the main folding blade 28 moves (advances) to a position in front of the nip portion of the main folding roller 25 at a position facing the temporary folding roller 30 in the support member 28b, interference with the temporary folding roller 30 is avoided. A plate-like notch 28 d is formed, and the width of the notch 28 d is slightly larger than the width of the temporary folding roller 30.

  Further, the pair of pushing portions 28 a are integrally provided at the tip of the support member 28 b so as to protrude toward the nip portion of the main folding roller 25. These pushing portions 28a are provided with an interval 28e slightly larger than the width of the temporary folding roller 30, and together with the notch portion 28b of the support member 28d, an escape portion 28f that avoids interference with the temporary folding roller 28. Is configured. Therefore, when the main folding blade 28 moves to the front of the nip portion of the main folding roller 25, the temporary folding roller 30 enters the escape portion 28f (see FIG. 4).

  A temporary folding blade 29 is disposed in the escape portion 28 f of the main folding blade 28. The temporary folding blade 29 includes a pressing portion 29a that pushes the central portion of the sheet bundle into the nip portion of the temporary folding roller 30, a support member 29b that supports the pressing portion 29a, and the temporary folding blade 29 that nips the temporary folding roller 30. And a temporary folding blade drive unit 41 that is slidably moved back and forth in the direction toward the portion and in the opposite direction.

  The support member 29b of the temporary folding blade 29 has a U-shaped cross section as shown in FIG. 2B, and the rear end portion 28g of the supporting member 28b of the main folding blade 28 is formed in the inner space S thereof. The central part of the can be inserted (see FIG. 4B). The support member 29b is provided with a moving shaft 29c connected to the temporary folding blade drive unit 41, and the driving of the temporary folding blade drive unit 41 is transmitted to the temporary folding blade 29 via the moving shaft 29c. The temporary folding blade 29 is slidably moved. Further, a pushing portion 29 a is integrally provided at the tip of the support member 29 b so as to protrude toward the nip portion of the temporary folding roller 30. The width of the pushing portion 29 a is substantially the same as the width of the temporary folding roller 30.

  The middle folding control unit 43 detects detection signals from the paper detection sensors 38 and 39 provided on the downstream side of the transport roller 23 and the main folding roller 25, the paper discharge sensor 37 provided on the downstream side of the paper discharge roller 26, and the like. Thus, the drive of the blade drive units 40 and 41 and the roller drive unit 42 is controlled. In the present embodiment, each of the folding rollers 25 and 30 is driven by a single drive unit 42, and therefore it is necessary to separately control the main folding roller 25 and the temporary folding roller 30 during the folding operation. Therefore, it is possible to prevent the control by the middle folding control unit 43 from being complicated, and the burden on the middle folding control unit 43 can be reduced.

  Next, the middle folding processing operation of the middle folding processing unit 20 will be described. In the initial state, the main folding blade 28 and the temporary folding blade 29 stand by at the positions shown in FIG. When the sheet detection sensor 38 or the like detects that the sheet bundle has been received by the sheet folding stopper 24 in this state, the center folding control unit 43 drives the blade driving units 40 and 41 simultaneously. As a result, as shown in FIG. 3, the blades 28 and 29 move together in the direction of the arrow a, and push the center of the sheet bundle across the width direction of the sheet bundle. At the same time, the middle folding control unit 43 drives the roller driving unit 42 to rotate the main folding roller 25 in the direction of arrow C and the temporary folding roller 30 in the direction of arrow b.

  When the blades 28 and 29 are moved to just before the nip portion of the temporary folding roller 30, the middle folding control unit 43 stops only the temporary folding blade driving unit 41. Therefore, the temporary folding blade 29 stops immediately before the nip portion of the temporary folding roller 30, and the main folding roller 25 further moves toward the nip portion of the main folding roller 25. By moving the blades 28 and 29 in this manner, the sheet bundle is first sandwiched between the nip portions of the temporary folding roller 30 and can be creased at the center in the width direction of the sheet bundle. At this time, the temporary folding blade 29 may be retracted to the initial position shown in FIG. 2, and in this case, the same effect is obtained.

  After that, as shown in FIG. 4, when the main folding blade 29 moves to just before the nip portion of the main folding roller 25, the middle folding control unit 43 also stops the main folding blade driving unit 40, thereby the main folding blade 29. Stops at this position. Then, the sheet bundle is pushed into the nip portion of the main folding roller 25 that rotates in the direction of arrow e by the main folding blade 29. As a result, the sheet bundle is sandwiched in the nip portion of the main folding roller 25 and the sheet bundle is folded, and the folded sheet bundle is discharged to the intermediate processing tray 203 by the discharge roller 26.

  According to this embodiment, the temporary folding roller 30 and the main folding roller 25 having a width wider than the temporary folding roller 30 are creased stepwise with respect to the sheet bundle, so that the load on the sheet bundle can be distributed. It is possible to prevent the bundle from being broken. Further, since the escape portion 28 f is formed in the main folding blade 28, the main folding blade 28 can be reliably moved to the front of the nip portion of the main folding roller 25. Therefore, the sheet bundle can be surely pushed into the temporary folding roller 30 and resistance to the conveyance of the sheet bundle by the temporary folding roller 30 when the sheet bundle is pushed in can be prevented. Therefore, it is possible to suppress the occurrence of image scraping and the like and to prevent the quality of the discharged sheet bundle from being deteriorated.

  Further, by driving the driving sources of the main folding blade 28 and the temporary folding blade 29 by different driving sources (the main folding blade driving unit 40 and the temporary folding blade driving unit 41), the temporary folding roller 30 The blades 28 and 29 are moved integrally to the front, and the whole width direction of the sheet bundle is pushed. From here onward, the paper bundle is pushed further downstream by the main folding blade 28, and the temporary folding blade 29 Fine drive control by the blades 28 and 29 can be performed such as waiting at the position as it is or returning to the initial position so as not to cause the bundle conveyance resistance.

  Next, a second embodiment of the present invention will be described. In the description, the same components as those described above are denoted by the same reference numerals to simplify the description. FIG. 6 is a diagram schematically showing a half-folding processing unit according to the second embodiment of the present invention, and FIGS. 7 and 8 are diagrams for explaining the operation of the middle-folding processing unit of FIG. FIG. 9 is a block diagram showing a control system of the middle folding processing unit of FIG.

  As shown in FIGS. 6 and 9, the center folding processing unit 21 according to the present embodiment includes a pair of main folding rollers 25 driven by a main folding roller driving unit 45 that is a motor, and a nip between the main folding rollers 25. A pair of temporary folding blades 31 that are formed so as to be capable of advancing and retreating with respect to the paper section, and between these regular folding rollers 25 and the regular folding blade 31 that are formed narrower than the minimum width of paper that can be passed. The roller 32 and the center folding control part 43 which controls the center folding processing part 21 are provided.

  The pair of temporary folding rollers 32 is provided in front of the main folding roller 25 and opposed to the central portion in the axial direction of the main folding roller 25, and is provided in two sets with a space therebetween. These temporary folding rollers 31 are supported by a single rotating shaft 32a within the range of the minimum width of paper that can be passed, and are not shown in the figure as indicated by an arrow g in FIG. 7B. Pressure is applied in a direction approaching each other by the pressurizing unit. These temporary folding rollers 32 are driven by a temporary folding driving unit 44 which is a motor different from the main folding roller driving unit 45 of the main folding roller 25. That is, the rollers 25 and 32 are individually controlled for rotation by separate drive units 44 and 45, respectively.

  The main folding blade 31 includes three pushing portions 31a for pushing the sheet bundle, a plate-like support member 31b for supporting the pushing portions 31a, the direction of the main folding blade 31 toward the nip portion of the main folding roller 25, and And a main folding blade drive unit 40 such as a motor that slides in the opposite direction.

  The support member 31b of the main folding blade 31 is provided with a moving shaft 31c connected to the main folding blade driving unit 40, and the driving of the main folding blade driving unit 40 is transferred to the main folding blade 31 via the moving shaft 31c. As a result, the main folding blade 31 slides. Further, in order to avoid interference with the temporary folding roller 32 when the main folding blade 31 moves to a position just before the nip portion of the main folding roller 25 at a position facing each temporary folding roller 32 in the support member 31b. The plate-like notch 31d is formed, and the width of the notch 31d is larger than the width of the opposing temporary folding roller 30.

  Further, the pushing portion 31 a is integrally provided at the tip of the support member 31 b so as to protrude toward the nip portion of the main folding roller 25. These pushing portions 31a are provided with an interval 31e larger than the width of the temporary folding roller 30, and together with the cutout portion 31d of the support member 31b, constitute an escape portion 31f that avoids interference with the temporary folding roller 32. is doing. Accordingly, when the main folding blade 31 moves to a position just before the nip portion of the main folding roller 25, the temporary folding roller 32 enters the escape portion 31f.

  Next, the middle folding processing operation of the middle folding processing unit 21 will be described. In the initial state, the main folding blade 31 stands by at the position shown in FIG. 6, and when the sheet bundle is received, the middle folding control unit 43 drives the main folding blade driving unit 40. As a result, as shown in FIG. 7, the main folding blade 31 moves in the direction of the arrow f and pushes the center of the sheet bundle across the width direction of the sheet bundle. At the same time, the middle folding control unit 43 presses the temporary folding roller 32 in the direction of arrow g by the pressure unit, and drives the temporary folding roller driving unit 44 to drive the temporary folding roller 32 in the direction of arrow h. . As a result, the sheet bundle is sandwiched between the temporary folding rollers 32.

  Thereafter, as shown in FIG. 8, the main folding blade 31 further moves in the direction of the arrow i and pushes the sheet bundle. While the main folding blade 31 moves to a position just before the nip portion of the main folding roller 25, the middle folding control unit 43 releases the pressure state of the temporary folding roller 32, whereby the temporary folding rollers 32 are separated from each other ( Move in the direction of arrow j). Note that the half-folding control unit 43 maintains the driving of the temporary folding roller driving unit 44 so as not to cause resistance of conveyance of the sheet bundle. Thereby, the temporary folding roller 32 is rotationally driven in the direction of the arrow i even after the pressure state is released to assist the conveyance of the sheet bundle.

  Further, the middle folding control unit 43 drives the main folding roller driving unit 42 while the main folding blade 31 moves to just before the nip portion of the main folding roller 25. As a result, the main folding roller 25 is driven to rotate in the direction of the arrow k, and the sheet bundle that has undergone the middle folding process is conveyed toward the paper discharge roller 26.

  According to the present embodiment, the same effects as the first embodiment can be obtained, and the plurality of temporary folding rollers 32 are provided within the minimum width of the sheet. Since a plurality of locations in the central portion are folded at the same time, even when the central portion of the paper bundle is difficult to be folded due to the stiffness, thickness, curl, etc. of the paper bundle, the paper bundle can be pushed in more reliably.

  In the present embodiment, the main folding roller 25 and the temporary folding roller 32 are driven and controlled by separate drive sources. For example, the linear speed of the temporary folding roller 32 is set to the line of the main folding roller 25 at the time of forward feeding. Each roller 25, for example, prevents the pulling of the bundle of sheets by making the linear speed of the main folding roller 25 faster than that of the temporary folding roller 32 at the time of reverse rotation of the roller at the time of additional folding or the like. It is possible to combine 32 operations in a complicated manner.

  Needless to say, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the scope of the invention. In the first embodiment described above, the provisional folding blade 29 is provided, but this may not be provided, and the middle folding process may be performed only by the main folding roller 28. Similarly, in the second embodiment, a temporary folding blade similar to that in the first embodiment may be provided in the escape portion 31f of the main folding blade 31.

1 is a schematic sectional view of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows roughly the middle folding process part of the middle folding process tray of FIG. It is a figure for demonstrating operation | movement of the middle folding process part of FIG. It is a figure for demonstrating operation | movement of the middle folding process part of FIG. FIG. 3 is a block diagram illustrating a control system of a folding processing unit in FIG. 2. It is a figure which shows schematically the folding process part which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating operation | movement of the middle folding process part of FIG. It is a figure for demonstrating operation | movement of the middle folding process part of FIG. FIG. 7 is a block diagram illustrating a control system of a middle folding processing unit in FIG. 6.

Explanation of symbols

20 Middle fold processing unit (sheet folding device)
25 Folding rollers 28, 31 Folding blades 28f, 31f Escape part 29 Temporary folding blades 30, 32 Temporary folding roller 40 Final folding blade drive part 41 Temporary folding blade drive part 42 Folding roller drive part 43 Middle folding processing control part 44 Temporary Folding roller driving unit 45 Folding roller driving unit F Stapling processing tray (binding processing unit)
PD Post-processing device PR Image forming device

Claims (8)

In a sheet folding apparatus comprising a pair of main folding rollers for sandwiching a sheet bundle in a nip portion and folding the sheet bundle, and a main folding blade provided so as to be movable forward and backward with respect to the nip portion of these main folding rollers.
Between the main folding roller and the main folding blade, a pair of temporary folding rollers that are formed narrower than the minimum width of a sheet that can be passed through and sandwich the sheet bundle in the nip portion to fold the sheet bundle,
The main folding blade is provided so as to be able to advance to the front of the nip portion of the main folding roller, and an escape portion is formed to avoid interference with the temporary folding roller when moving toward the main folding roller, and the main folding blade The temporary folding roller is held in a pressurized state when the roller advances to the temporary folding roller, and further, the temporary folding roller releases the pressurized state when the main folding blade moves immediately before the nip portion of the main folding roller <br / > A sheet folding apparatus characterized by that. Wherein the relief portion of the folding blade, the sheet folding apparatus according to claim 1, characterized in that temporary folding blade to push the sheet bundle into the nip portion of the temporary folding rollers are provided The sheet folding apparatus according to claim 1 or 2 , wherein a plurality of temporary folding rollers are coaxially arranged within a range of a minimum width of a sheet that can be passed. Sheet folding apparatus according to any one of claims 1 to 3, characterized in that it comprises a single roller drive unit for driving the present folding rollers and the temporary folding rollers. Wherein the present folding roller driving unit for driving this folding roller, according to any one of claims 1 to 3, characterized in that said and a tentative folding roller drive unit for driving the temporary folding rollers sheet Folding device. Sheet folding apparatus according to claim 3, characterized in that it comprises a present folding blade driving unit that drives the present folding blade, and a tentative folding blade driving unit for driving the temporary folding blade. A binding processing unit which performs binding processing of the sheet bundle, the post-processing apparatus characterized by comprising a sheet folding apparatus according to any one of claims 1 to 6. An image forming apparatus comprising: an image forming unit that forms an image on a sheet; and the post-processing device according to claim 7 .

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