SHEET FOLDER, POST-PROCESSING APPARATUS, IMAGE FORMING APPARATUS, AND IMAGE FORMING SYSTEM

Abstract

A sheet folder includes a conveyance roller pair, first, second and third folding rollers, a guide, and circuitry. The conveyance roller pair conveys a sheet in a conveyance direction at a first speed. The first folding roller is downstream from the conveyance roller pair. The second and third folding rollers are in contact with the first folding roller to form first and second nips, respectively, with the first folding roller, and rotate along with the first folding roller. The guide is between the conveyance roller pair and the first nip in the conveyance direction, and is changeable between first and second postures. The circuitry is to control the guide to guide the sheet to the first nip and change the posture to the second posture to fold the sheet into the second nip, and control the first folding roller to rotate at a second speed and folds the sheet.

Claims

1. A sheet folder comprising: a conveyance roller pair to convey a sheet in a conveyance direction at a first speed; a first folding roller downstream from the conveyance roller pair in the conveyance direction; a second folding roller in contact with the first folding roller to form a first nip with the first folding roller, the second folding roller to rotate along with the first folding roller; a third folding roller in contact with the first folding roller to form a second nip with the first folding roller, the third folding roller to rotate along with the first folding roller; a guide, between the conveyance roller pair and the first nip in the conveyance direction, the guide being changeable between: a first posture to guide the sheet from the conveyance roller pair to the first nip; and a second posture to guide the sheet from the conveyance roller pair to the second nip; and circuitry configured to: control the guide at the first posture to guide the sheet from the conveyance roller pair to the first nip; control the guide to change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet; and control the first folding roller to rotate at a second speed faster than the first speed of the conveyance roller pair while the second nip nips and folds the sheet.

2. The sheet folder according to claim 1, wherein the circuitry is further configured to: control the guide at the second posture to guide the sheet from the conveyance roller pair to the second nip; control the guide to change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.

3. The sheet folder according to claim 1, wherein the circuitry is further configured to: rotate the conveyance roller pair and the first folding roller in a forward direction while the first nip or the second nip nips and folds the sheet to convey the sheet in the conveyance direction; and rotate the conveyance roller pair and the first folding roller in a reverse direction opposite to the forward direction while the first nip or the second nip nips and folds the sheet.

4. The sheet folder according to claim 1, further comprising: a return conveyance path to convey the sheet, nipped between the first folding roller and the third folding roller, from the second nip to an upstream of the conveyance roller pair in the conveyance direction.

5. The sheet folder according to claim 4, wherein the second folding roller faces the first folding roller across a main conveyance path in the conveyance direction, the third folding roller faces the first folding roller across the return conveyance path branched from the main conveyance path at a branching portion upstream from the first nip in the conveyance direction, and the return conveyance path joins the main conveyance path at a joining portion upstream from the conveyance roller pair in the conveyance direction, and the circuitry is further configured to: control the conveyance roller pair to rotate in a forward direction to convey the sheet in the conveyance direction; control the first folding roller to rotate in a forward direction to: convey the sheet nipped by the first nip in the conveyance direction; and convey the sheet nipped by the second nip from the return conveyance path to the main conveyance path; and control the first folding roller to rotate in a reverse direction opposite to the forward direction to: convey the sheet nipped by the first nip in a direction opposite to the conveyance direction; and convey the sheet nipped by the second nip to the return conveyance path.

6. The sheet folder according to claim 5, wherein the circuitry is further configured to: change the guide to the first posture to rotate the conveyance roller pair and the first folding roller at conveyance speeds equal to each other in the forward direction, before a leading end of the sheet passes through the first nip and a folding position of the sheet reaches a given position; change the guide from the first posture to the second posture in response to arrival of the folding position of the sheet to the given position to rotate the first folding roller in the reverse direction until the folding position of the sheet passes through the second nip, to fold the sheet at the folding position; and rotate the conveyance roller pair in the forward direction while changing the guide from the second posture to the first posture and rotate the first folding roller in the forward direction at a conveyance speed faster than a conveyance speed of the conveyance roller pair, in response to passage of the folding position of the sheet through the second nip, to unfold a fold line of the sheet at the folding position and eject the sheet.

7. The sheet folder according to claim 6, wherein the circuitry is further configured to: fold the sheet at multiple folding positions including the folding position shifted in the conveyance direction; and unfold a fold line at each of the multiple folding positions and eject the sheet.

8. The sheet folder according to claim 5, wherein the circuitry is further configured to: change the guide to the second posture to rotate the conveyance roller pair in the forward direction and the first folding roller in the reverse direction, before a leading end of the sheet passes through the second nip and a folding position of the sheet reaches a given position; change the guide from the first posture to the second posture in response to arrival of the folding position of the sheet to the given position to rotate the first folding roller in the forward direction until the folding position of the sheet passes through the first nip, to fold the sheet at the folding position; rotate the conveyance roller pair in the forward direction while changing the guide from the first posture to the second posture until a given time elapses and rotate the first folding roller in the reverse direction at a conveyance speed faster than a conveyance speed of the conveyance roller pair, in response to passage of the folding position of the sheet through the first nip, to unfold a fold line of the sheet at the folding position and convey the sheet to the return conveyance path; and change the guide from the second posture to the first posture in response to elapse of the given time to rotate the conveyance roller pair and the first folding roller in the forward direction at conveyance speeds equal to each other, to eject the sheet.

9. The sheet folder according to claim 1, wherein multiple sheets including the sheet is sequentially conveyed from an image forming device, and the circuitry is further configured to: cause multiple sheets including the sheet to be sequentially conveyed; and shift respective folding positions of the multiple sheets in the conveyance direction of the sheet.

10. A post-processing apparatus comprising: the sheet folder according to claim 1; and a sheet binder to bundle multiple sheets including the sheet provided with a fold line folded by the sheet folder.

11. An image forming apparatus comprising: an image forming device to form an image on a sheet; and the sheet folder according to claim 1 to provide a fold line on the sheet on which the image is formed by the image forming device.

12. An image forming system comprising: an image forming apparatus to form an image on a sheet; a conveyance roller pair to convey a sheet in a conveyance direction of the sheet that has passed the image forming apparatus at a first speed; a first folding roller downstream from the conveyance roller pair in the conveyance direction; a second folding roller in contact with the first folding roller to form a first nip with the first folding roller, the second folding roller to rotate along with the first folding roller; a third folding roller in contact with the first folding roller to form a second nip with the first folding roller, the third folding roller to rotate along with the first folding roller; a guide between the conveyance roller pair and the first nip in the conveyance direction to change a posture between a first posture that guides the sheet to the first nip and a second posture that guides the sheet to the second nip; and circuitry configured to: control the guide at the first posture to guide the sheet from the conveyance roller pair to the first nip; control the guide to change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet; and control the first folding roller to rotate at a second speed faster than the first speed of the conveyance roller pair while the second nip nips and folds the sheet.

13. The image forming system according to claim 12, wherein the circuitry is further configured to: control the guide at the second posture to guide the sheet from the conveyance roller pair to the second nip; and control the guide to change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.

14. A sheet folder comprising: a conveyance roller pair to convey a sheet in a conveyance direction at a first speed; a first folding roller downstream from the conveyance roller pair in the conveyance direction; a second folding roller in contact with the first folding roller to form a first nip with the first folding roller, the second folding roller to rotate along with the first folding roller; a third folding roller in contact with the first folding roller to form a second nip with the first folding roller, the third folding roller to rotate along with the first folding roller; and a guide, downstream from the conveyance roller pair in the conveyance direction and having a first guide face facing a first face of the sheet and a second guide face facing a second face of the sheet, the guide being changeable between: a first posture to guide the sheet from the conveyance roller pair to the first nip; and a second posture that guides the sheet from the conveyance roller pair to the second nip, wherein the guide is configured to: guide the sheet at the first posture from the conveyance roller pair to the first nip, and change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet; or guide the sheet at the first posture from the conveyance roller pair to the second nip, and change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.

15. The sheet folder according to claim 14, wherein the first guide face and the second guide face have an interval having an upstream side greater than a downstream side in the conveyance direction.

16. An image forming apparatus comprising: an image forming device to form an image on a sheet; and the sheet folder according to claim 14 to provide a fold line on the sheet on which the image is formed by the image forming device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:

[0013] FIG. 1 is an external view of an image forming apparatus;

[0014] FIG. 2 is a diagram illustrating an internal configuration of a sheet folding unit and a sheet binding unit;

[0015] FIG. 3A is a diagram illustrating a configuration of a sheet folding unit when a guide plate is in a first posture;

[0016] FIG. 3B is a diagram illustrating a configuration of a sheet folding unit when a guide plate is at a second posture;

[0017] FIG. 4A is a perspective view of a guide plate;

[0018] FIG. 4B is a diagram illustrating a sheet folding unit as viewed from a thickness direction of the sheet on a main conveyance path;

[0019] FIG. 5A is a diagram illustrating a variation of a folding position;

[0020] FIG. 5B is a diagram illustrating another variation of a folding position;

[0021] FIG. 6 is a block diagram illustrating a hardware configuration of a sheet folding unit;

[0022] FIG. 7 is a flowchart of a process of a half-fold operation;

[0023] FIGS. 8A, 8B and 8C are diagrams illustrating a sheet folding unit in a half-fold operation;

[0024] FIGS. 9A, 9B, 9C and 9D are diagrams illustrating movement of a sheet in a sheet folding unit when changing a posture of a guide plate;

[0025] FIG. 10 is a flowchart of a process of a letter fold-in operation;

[0026] FIGS. 11A and 11B are diagrams illustrating a sheet folding unit in a letter fold-in operation;

[0027] FIG. 12 is a flowchart of a process of a letter fold-out operation;

[0028] FIGS. 13A, 13B and 13C are diagrams illustrating a sheet folding unit in a fold-out operation to fold out a binding position of a sheet;

[0029] FIGS. 14A, 14B and 14C are diagrams illustrating a sheet folding unit in a fold-in operation to fold in a binding position of a sheet;

[0030] FIGS. 15A, 15B, 15C and 15D are diagrams illustrating movement of a sheet in a sheet folding unit when changing a posture of a guide plate from a first posture to a second posture;

[0031] FIGS. 16A and 16B are diagrams illustrating a sheet binding unit from when a sheet is received to when the sheet reaches a conveyance roller pair;

[0032] FIGS. 17A and 17B are diagrams illustrating a sheet binding unit when ejecting a sheet to an ejection tray without performing a sheet binding operation on the sheet;

[0033] FIGS. 18A and 18B are diagrams illustrating a sheet binding unit that performs a sheet binding operation;

[0034] FIG. 19 is a diagram illustrating the sheet binding unit of FIG. 18B as viewed from a thickness direction of a sheet;

[0035] FIGS. 20A and 20B are diagrams illustrating a sheet binding unit when a sheet bundle subjected to a sheet binding operation is ejected to an ejection tray;

[0036] FIGS. 21A and 21B are diagrams illustrating another example in which a movable range of a guide plate is restricted;

[0037] FIGS. 22A and 22B are diagrams illustrating an internal structure of a punching unit;

[0038] FIG. 23 is a block diagram illustrating a hardware configuration of an image forming apparatus;

[0039] FIG. 24 is an external view of an image forming system; and

[0040] FIG. 25 is a block diagram illustrating a hardware configuration of an image forming system.

[0041] The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION

[0042] In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

[0043] Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Configuration of Image Forming Apparatus

[0044] A description is provided of an image forming apparatus 10 according to embodiments of the present disclosure with reference to the drawings.

[0045] FIG. 1 is an external views of the image forming apparatus 10. The image forming apparatus 10 forms an image on a sheet S (typically, a paper sheet).

[0046] As illustrated in FIG. 1, the image forming apparatus 10 includes a housing 11 and an image forming device 12.

[0047] The housing 11 has a box shape to form an internal space for accommodating components of the image forming apparatus 10. The housing 11 has an in-body space 13 that is accessible from the outside of the image forming apparatus 10. The in-body space 13 is located, for example, slightly above the center of the housing 11 in the vertical direction. The in-body space 13 is exposed to the outside by cutting out the outer wall of the housing 11. The in-body space 13 accommodates a sheet folding unit 20 as a sheet folder, a sheet binding unit 30 as a post-processing device and a sheet binder, and a punching unit 50 (see FIGS. 22A and 22B) that is described below.

[0048] The image forming device 12 forms an image on a sheet S contained in a tray and ejects the sheet S on which the image is formed, to the sheet folding unit 20, the sheet binding unit 30, or the punching unit 50. The image forming device 12 may include an inkjet image forming device that forms an image with ink or an electrophotographic image forming device that forms an image with toner. Since the image forming device 12 of FIG. 1 has a known configuration, a detailed description of the configuration and functions of the image forming device 12 is omitted.

[0049] The sheet folding unit 20 is in the in-body space 13 of the image forming apparatus 10 and is disposed downstream from the image forming device 12 and upstream from the sheet binding unit 30 in a conveyance direction of the sheet in a conveyance path of the sheet S from the image forming device 12 to the outside of the image forming apparatus 10. The conveyance path is indicated by a broken line and an arrow in FIG. 1. In other words, the sheet S on which the image is formed by the image forming device 12 is first conveyed to the sheet folding unit 20 to be subjected to a fold-line forming operation or a sheet folding operation described below, and subsequently conveyed to the sheet binding unit 30 to be subjected to a sheet binding operation process described below.

[0050] The sheet folding unit 20 is detachably attached to the image forming apparatus 10. After the sheet folding unit 20 is detached from the image forming apparatus 10, the sheet S on which the image is formed by the image forming device 12 is directly conveyed to the sheet binding unit 30 to be subjected to the sheet binding operation. Alternatively, the punching unit 50 may be detachably attached to the position of the in-body space 13 from which the sheet folding unit 20 is detached. After the punching unit 50 is attached, the sheet S on which the image is formed by the image forming device 12 is first conveyed to the punching unit 50 to be subjected to a punching operation described below, and then conveyed to the sheet binding unit 30 to be subjected to the sheet binding operation. Any unit to perform any operation on the sheet S including a punching unit is attachable at the position where the sheet folding unit 20 is detached from the in-body space 13.

Configuration of Sheet Folding Unit 20

[0051] FIG. 2 is a diagram illustrating an internal configuration of each of the sheet folding unit 20 and the sheet binding unit 30.

[0052] FIG. 3A is a diagram illustrating a configuration of the sheet folding unit 20 when the guide plate 26 is in a first posture.

[0053] FIG. 3B is a diagram illustrating a configuration of the sheet folding unit 20 when the guide plate 26 is in a second posture.

[0054] FIG. 4A is a perspective view of the guide plate 26.

[0055] FIG. 4B is a diagram illustrating the sheet folding unit 20 as viewed from a thickness direction of the sheet S on the main conveyance path Ph1.

[0056] Each of the sheet folding unit 20 and the sheet binding unit 30 is manufactured as a unit and has an input interface and an output interface that can be connected to each other to convey the sheet S. In other words, the input interface IN of the sheet folding unit 20 is connectable to an output interface of the image forming device 12. The input interface of the sheet binding unit 30 is connectable to the output interface of the image forming device 12 and the output interface OUT of the sheet folding unit 20.

[0057] The sheet folding unit 20 performs a sheet folding operation to form a given shape (e.g., Z-fold, letter fold-out, and half-fold) on a sheet S on which an image is formed by the image forming device 12, and a fold-line forming operation to form various fold lines on the sheet S. As illustrated in FIG. 2, the sheet folding unit 20 includes a housing 21, a conveyance roller pair 22, a first folding roller 23, a second folding roller 24, a third folding roller 25, a guide plate 26 as a guide, a first stopper 27a and a second stopper 27b, a first sensor 28a, a second sensor 28b and a third sensor 28c, and a driving force transmission mechanism 29. The first sensor 28a, the second sensor 28b and the third sensor 28c may be referred to collectively as sheet sensors 28a, 28b and 28c.

[0058] The housing 21 has a box shape to form an internal space for accommodating components of the sheet folding unit 20. In addition, a main conveyance path Ph1 and a return conveyance path Ph2, which are spaces through which the sheet S passes, are formed in the internal space of the housing 21. The main conveyance path Ph1 is a conveyance path from the input interface IN coupled to the image forming device 12 to the output interface OUT coupled to the sheet binding unit 30. In the following description, a direction from the input interface IN to the output interface OUT on the main conveyance path Ph1 is referred to as a conveyance direction. The return conveyance path Ph2 is an annular conveyance path that branches from the main conveyance path Ph1 at a branching portion A and joins the main conveyance path Ph1 at a joining portion B. The joining portion B is located upstream from the branching portion A in the conveyance direction.

[0059] The conveyance roller pair 22 conveys the sheet S along the main conveyance path Ph1 in the conveyance direction. The conveyance roller pair 22 includes a drive roller 22a and a driven roller 22b facing each other across the main conveyance path Ph1 and are arranged upstream from the branching portion A in the conveyance direction and downstream from the joining portion B in the conveyance direction. The conveyance roller pair 22 includes the drive roller 22a and the driven roller 22b between the branching portion A and the joining portion B. The drive roller 22a and the driven roller 22b are rotatably supported by the housing 21. In response to a transmission of the driving force of the conveyance motor 22c, the drive roller 22a is driven in a forward rotation, in other words, is rotated in a forward direction that is the conveyance direction of the sheet S (clockwise direction of FIG. 2). The driven roller 22b is disposed facing the drive roller 22a across the main conveyance path Ph1 and is driven by the rotation of the drive roller 22a. As the conveyance motor 22c is driven with the drive roller 22a and the driven roller 22b nipping the sheet S, the sheet S is conveyed in the conveyance direction along the main conveyance path Ph1.

[0060] The first folding roller 23 is disposed downstream from the conveyance roller pair 22 in the conveyance direction. The first folding roller 23 is rotatably supported by the housing 21 at a position facing both the main conveyance path Ph1 and the return conveyance path Ph2. The second folding roller 24 is rotatably supported by the housing 21 at a position facing the main conveyance path Ph1. The third folding roller 25 is rotatably supported by the housing 21 at a position facing the return conveyance path Ph2.

[0061] The first folding roller 23 and the second folding roller 24 are disposed to face each other across the main conveyance path Ph1 and are downstream from the branching portion A in the conveyance direction. Further, the first folding roller 23 and the third folding roller 25 are disposed between the branching portion A and the joining portion B to face each other across the return conveyance path Ph2.

[0062] As the driving force of a folder motor 23c is transmitted to the first folding roller 23, the first folding roller 23 rotates in forward and reverse directions. The rotation in the forward direction of the first folding roller 23 is a rotation in a direction to convey the sheet S on the main conveyance path Ph1 in the conveyance direction of the sheet S (counterclockwise direction in FIG. 2). The rotation in the reverse direction of the first folding roller 23 is a rotation in a direction opposite to the direction of the forward rotation. The folder motor 23c is rotatable in forward and reverse directions to rotate the first folding roller 23 in forward and reverse directions. The second folding roller 24 and the third folding roller 25 are rotated together with the rotation of the first folding roller 23.

[0063] The first folding roller 23 and the second folding roller 24 form a first nip region N1 in which the sheet S on the main conveyance path Ph1 is nipped. The first folding roller 23 and the third folding roller 25 form a second nip region N2 in which the sheet S on the return conveyance path Ph2 is nipped. The action nip indicates that a sheet S is sandwiched by the force that can convey the sheet S by a rotation of a pair of rollers.

[0064] The guide plate 26 is disposed between the conveyance roller pair 22 and the first folding roller 23 on the main conveyance path Ph1. In other words, the guide plate 26 is disposed downstream from the conveyance roller pair 22 in the conveyance direction and upstream from the first folding roller 23 in the conveyance direction. The guide plate 26 is rotatably supported by the housing 21 in the vicinity of the branching portion A. The guide plate 26 is rotatable (changeable) between the first posture illustrated in FIG. 3A and the second posture illustrated in FIG. 3B due to the transmission of the driving force of a guide motor 26c.

[0065] Further, as illustrated in FIG. 4A, the guide plate 26 has a slit 26a through which the sheet S passes. The guide plate 26 changes the destination of conveyance of the sheet S. The slit 26a is formed between a pair of guide faces including guide faces 26al and 26a2 as a first guide face and a second guide face. The guide faces 26al and 26a2 are disposed facing each other across the main conveyance path Ph1 at an interval having a distance through which the sheet S can pass. The guide faces 26a1 and 26a2 guide the sheet S that is conveyed by the conveyance roller pair 22 on the main conveyance path Ph1 in the conveyance direction. The interval of the guide faces 26a1 and 26a2 has an upstream side in the conveyance direction greater than a downstream side in the conveyance direction.

[0066] The first posture is a posture of the guide plate 26 in which the sheet S conveyed by the conveyance roller pair 22 to the first nip region N1 and the sheet S is allowed to be conveyed from second nip region N2 to the first nip region N1. The second posture is a posture of the guide plate 26 in which the sheet S conveyed by the conveyance roller pair 22 to the second nip region N2 and the sheet S is allowed to be conveyed from the first nip region N1 to the second nip region N2.

[0067] For example, as the conveyance roller pair 22 and the first folding roller 23 are rotated in the forward direction in the first posture of the guide plate 26 before the leading end of the sheet S (the downstream end in the conveyance direction) reaches the guide plate 26, the sheet S conveyed by the conveyance roller pair 22 passes the first nip region N1 through the slit 26a of the guide plate 26 in the first posture, in other words, the sheet S is conveyed in the conveyance direction on the main conveyance path Ph1.

[0068] As another example, as the conveyance roller pair 22 is rotated in the forward direction and the first folding roller 23 is rotated in the reverse direction with the guide plate 26 in the second posture before the leading end of the sheet S reaches the guide plate 26, the sheet S by the conveyance roller pair 22 passes the second nip region N2 through the slit 26a of the guide plate 26 in the second posture, in other words, the sheet S is conveyed to the return conveyance path Ph2 through the branching portion A.

[0069] As yet another example, as illustrated in FIG. 8A, as the first folding roller 23 is driven in the reverse rotation while changing the guide plate 26 from the first posture to second posture with the sheet S nipped by the conveyance roller pair 22 and the first nip region N1, the sheet S passes the second nip region N2 with a folding position C1 (see FIG. 5A) of the sheet S as the leading end of the sheet S. In other words, when the guide plate 26 is changed from the first posture to the second posture and then the first folding roller 23 is rotated in the reverse direction, with the sheet S nipped by the first nip region N1, the sheet S is folded in the second nip region N2. Due to this operation, as illustrated in FIG. 8B, the sheet S is folded in at the folding position C1.

[0070] As yet another example, as illustrated in FIG. 13A, as the first folding roller 23 is rotated in the forward direction while changing the guide plate 26 from the second posture to the first posture with the sheet S nipped by the conveyance roller pair 22 and the second nip region N2, the sheet S passes through the first nip region N1 with a folding position C2 (see FIG. 5A) of the sheet S as the leading end of the sheet S. In other words, when the guide plate 26 is changed from the second posture to the first posture and then the first folding roller 23 is rotated in the forward direction, with the sheet S nipped by the second nip region N2, the sheet S is folded in the first nip region N1. Due to this operation, as illustrated in FIG. 13B, the sheet S is folded outward at the folding position C2.

[0071] FIG. 5A is a diagram illustrating a variation of folding positions of a sheet.

[0072] FIG. 5B is a diagram illustrating another variation of folding positions of a sheet.

[0073] The folding position is any position between the leading end and the trailing end of a sheet S in the conveyance direction. The trailing end of a sheet S indicates an end on the upstream side of the sheet S in the conveyance direction). The sheet folding unit 20 forms fold lines, each of which passes the folding position and is unfolded in the width direction of the sheet S. The width direction of the sheet S is a direction orthogonal to the conveyance direction of the sheet S. The fold-in is a folding type that a valley fold is performed on the surface of the sheet S on which an image is formed by the image forming device 12 (the top face of the sheet S facing the drive roller 22a in FIG. 2). The fold-out is a folding type that a mountain fold is performed on the surface of the sheet S.

[0074] For example, as illustrated in FIG. 5A, as the sheet S is folded inward at the folding position C1 at the center of the sheet S in the conveyance direction, a fold line for half-fold can be applied to the sheet S. Further, as the sheet S is folded inward at the folding position C2 that is located one third from the leading end of the sheet S in the conveyance direction and further folded inward at a folding position C3 that is located one third from the trailing end of the sheet S in the conveyance direction, the fold lines for letter fold-in can be applied to the sheet S. Further, as the sheet S is folded outward at the folding position C2 and further folded inward at the folding position C3, the fold lines for letter fold-out can be applied to the sheet S. Further, as the sheet S is folded outward at the folding position C1 and further folded inward at a folding position C4 that is located one fourth from the trailing end of the sheet S, the fold lines for Z-fold can be applied to the sheet S.

[0075] Further, as illustrated in FIG. 5B, the folding positions of multiple sheets S sequentially supplied to the sheet folding unit 20 may be shifted in the conveyance direction. More specifically, when the multiple sheets S are bundled to perform the letter fold-in operation, the interval (first interval) may be narrower toward the sheet S placed inside in the folded bundle of all the intervals between the folding position C2 and the folding position C3 of the multiple sheets S of the sheet bundle, so that the interval (third interval) may be wider toward the sheet S placed outside in the folded bundle of all the intervals between the folding position C2 and the folding position C3 of the multiple sheets S of the sheet bundle. The relation between the folding type of the sheet S and the folding position of the sheet S is stored in advance in a hard disk drive (HDD) 104 (see FIG. 6). Further, the variation of fold lines applicable by the sheet folding unit 20 is not limited to the examples of FIGS. 5A and 5B.

[0076] As illustrated in FIG. 3A, the first stopper 27a contacts the guide plate 26 in the first posture to prevent the guide plate 26 from rotating in a direction away from the second posture (clockwise direction in FIG. 3A). As illustrated in FIG. 3B, the second stopper 27b contacts the guide plate 26 in the second posture to prevent the guide plate 26 from rotating in a direction away from the first posture (counterclockwise direction in FIG. 3B). Due to such configurations as described above, the guide plate 26 rotates between the first posture and the second posture only, in other words, between the first stopper 27a and the second stopper 27b only). In other words, the first stopper 27a and the second stopper 27b restrict the rotation range of the guide plate 26.

[0077] The sheet sensors 28a, 28b and 28c are disposed facing the main conveyance path Ph1 or the return conveyance path Ph2. The sheet sensors 28a, 28b and 28c detect the sheet S to face installation positions where the sheet sensors 28a, 28b and 28c are disposed, and output respective detection signals to a controller 100 that is described below. More specifically, each of the sheet sensors 28a, 28b and 28c outputs a detection signal when the sheet S is brought to the position to face the installation position of each of the sheet sensors 28a, 28b and 28c (ON), and stops the output of the detection signal when the sheet S is not at the position (OFF). Any detailed example of the sheet sensors 28a, 28b and 28c is not limited to any sensor but a sensor may be, for example, a reflection-type optical sensor.

[0078] The first sensor 28a is disposed facing the main conveyance path Ph1 and upstream from the conveyance roller pair 22 in the conveyance direction. The first sensor 28a detects the sheet S that is conveyed from the image forming device 12 toward the conveyance roller pair 22. The second sensor 28b is disposed facing the main conveyance path Ph1 and downstream from the first nip region N1 in the conveyance direction.

[0079] The second sensor 28b detects the sheet S that passes the first nip region N1 to be ejected to the sheet binding unit 30. The third sensor 28c is disposed facing the return conveyance path Ph2 and closer to the joining portion B from the second nip region N2. The third sensor 28c detects the sheet S that passes the second nip region N2 toward the joining portion B on the return conveyance path Ph2.

[0080] As illustrated in FIG. 4B, a rotation shaft 22ax of the drive roller 22a, a rotation shaft 23x of the first folding roller 23, a rotation shaft 24x of the second folding roller 24, and a rotation shaft 26x of the guide plate 26 extend in the width direction of the sheet S. The rotation shafts 22ax, 23x, 24x and 26x penetrate a partition 21a disposed inside the housing 21. Although a rotation shaft 22bx of the driven roller 22b and a rotation shaft 25x of the third folding roller 25 are not depicted in FIG. 4B, the rotation shafts 22bx and 25x have the same structure as the rotation shafts 22ax, 23x, 24x and 26x. The driving force transmission mechanism 29 is disposed opposite to the conveyance roller pair 22, the first folding roller 23, the second folding roller 24, the third folding roller 25 and the guide plate 26 across the partition 21a.

[0081] The driving force transmission mechanism 29 transmits the driving force of the conveyance motor 22c to the drive roller 22a via a drive gear 29a and a driven gear 29b, the driving force of the folder motor 23c to the first folding roller 23 via a drive gear 29c and a driven gear 29d, and the driving force of the guide motor 26c to the guide plate 26 via a drive gear 29e and a driven gear 29f. Further, the drive gear 29e includes a torque limiter 29g.

[0082] The conveyance motor 22c can perform a forward rotation to rotate the drive roller 22a in the forward direction. The driven roller 22b is rotated together with rotation of the drive roller 22a. The folder motor 23c can perform the forward rotation to rotate the first folding roller 23 in the forward direction and perform a reverse rotation to rotate the first folding roller 23 in the reverse direction. The second folding roller 24 and the third folding roller 25 are rotated together with the rotation of the first folding roller 23. The guide motor 26c can perform the forward rotation to change the guide plate 26 from the second posture to the first posture and perform the reverse rotation to change the guide plate 26 from the first posture to the second posture.

[0083] The torque limiter 29g transmits the driving force of the guide motor 26c to the driven gear 29f (in other words, the guide plate 26) while the rotational torque is less than a threshold value, in other words, the guide plate 26 is separated from the first stopper 27a and the second stopper 27b. In contrast, the torque limiter 29g releases (i.e., idles) the transmission of the driving force from the guide motor 26c to the driven gear 29f (in other words, the guide plate 26) while the rotational torque is equal to or greater than the threshold value, in other words, while the guide plate 26 is in contact with the first stopper 27a and the second stopper 27b).

[0084] The sheet folding unit 20 includes a rotary encoder 22z (see FIG. 6) that detects the number of rotations of the drive roller 22a, and a rotary encoder 23z (see FIG. 6) that detects the number of rotations of the first folding roller 23. The rotary encoders 22z and 23z output respective pulse signals according to the number of rotations of the drive roller 22a and the first folding roller 23, to the controller 100. In other words, the controller 100 can grasp the position of the sheet S on the main conveyance path Ph1 or the return conveyance path Ph2, based on the detection signals output from the sheet sensors 28a, 28b and 28c and the pulse signals output from the rotary encoders 22z and 23z. More specifically, the controller 100 grasps the position of the sheet S by counting the number of pulse signals output from the rotary encoders 22z and 23z from the start that the sheet sensors 28a, 28b and 28c start outputting the detection signals.

Configuration of Sheet Binding Unit 30

[0085] The sheet binding unit 30 performs the sheet binding operation as post-processing that binds a bundle of multiple sheets S on which images are formed by the image forming device 12. In the following description, the bundle of multiple sheets S is referred to as a sheet bundle Sb. In the present embodiment, the sheet binding unit 30 is described as an example of the post-processing device, but the post-processing device is not limited to this configuration of a post-processing device. As illustrated in FIG. 2, the sheet binding unit 30 includes a housing 31, an ejection tray 32, multiple conveyance roller pairs 33, 34, 35 and 36, an internal tray 37, a tapping roller 38, a return roller 39, end fences 40L and 40R, side fences 41L and 41R (see FIG. 19), and a sheet binding portion 42.

[0086] The housing 31 has a box shape to form an internal space for accommodating components of the sheet binding unit 30. In addition, the conveyance path Ph3 as a space through which the sheet S passes is formed in the internal space of the housing 31. The ejection tray 32 is supported on an outer side face of the housing 31. The ejection tray 32 supports the sheet S or the sheet bundle Sb conveyed by the conveyance roller pairs 33 to 36.

[0087] The conveyance roller pairs 33 to 36 are arranged on the conveying path Ph3 at given intervals. The conveyance roller pairs 33 to 36 convey the sheet S along the conveyance path Ph3. The basic configuration of the conveyance roller pairs 33 to 36 is common to the configuration of the conveyance roller pair 22 of the sheet folding unit 20. The conveyance roller pair 36 includes a drive roller 36a and a driven roller 36b that can be brought into contact with and separated from the drive roller 36a. The conveyance roller pair 35 may be slidable in the width direction in order to implement a sorting operation in which the sheets S are shifted in the width direction and ejected to the ejection tray 32.

[0088] The internal tray 37 temporarily supports and stacks multiple sheets S that are sequentially conveyed on the conveyance path Ph3. The tapping roller 38 is supported at the leading end of a rotation arm above the internal tray 37. As the rotation arm is rotated, the tapping roller 38 supplies the sheet S nipped by the conveyance roller pair 36 to the internal tray 37. The return roller 39 contacts the upper face of the sheet S supported by the internal tray 37 and rotates to guide the sheet S toward the end fences 40L and 40R.

[0089] The end fences 40L and 40R contact the downstream end of the sheets S supported by the internal tray 37 in the conveyance direction and align the positions of the sheets S in the conveyance direction. The side fences 41L and 41R contact both ends in the width direction of the sheets S supported by the internal tray 37, and align the positions of the sheets S in the width direction. The sheet binding portion 42 performs the sheet binding operation in which the sheet bundle Sb supported by the internal tray 37 is bound. The sheet binding operation performed by the sheet binding portion 42 may be a stapling operation in which a binding staple is inserted into the sheet bundle Sb to bind the sheet bundle Sb or a crimp binding operation in which the sheet bundle Sb is crimped and bound by pressing the sheet bundle Sb. The sheet binding unit 30 may include a staple binder that performs the stapling operation and a crimp binder that performs the crimp binding operation, which are operable separately from each other at positions spaced apart from each other in the width direction.

[0090] In addition, the housing 31 may have a manual staple slit disposed at a position facing the sheet binding portion 42. A user may insert the sheet bundle into the sheet binding portion 42 through the manual staple slit and press a manual staple button of a control panel 110 described below, and the sheet binding portion 42 performs the sheet binding operation.

Configuration of Controller 100

[0091] FIG. 6 is a block diagram illustrating a hardware configuration of the sheet folding unit 20.

[0092] As illustrated in FIG. 6, the sheet folding unit 20 includes a central processing unit (CPU) 101, a random-access memory (RAM) 102, a read-only memory (ROM) 103, a hard disk drive (HDD) 104, and an interface (I/F) 105. The CPU 101, the RAM 102, the ROM 103, the HDD 104, and the I/F 105 are connected to each other via a common bus 109.

[0093] The CPU 101 is an arithmetic unit and controls the general operations of the sheet folding unit 20.

[0094] The RAM 102 is a volatile storage medium that allows data to be read and written at high speed. The CPU 101 uses the RAM 102 as a working area for data processing.

[0095] The ROM 103 is a read-only non-volatile storage medium that stores programs such as firmware.

[0096] The HDD 104 is a non-volatile storage medium that allows data to be read and written and has a relatively large storage capacity. The HDD 104 stores, e.g., an operating system (OS), various control programs, and application programs.

[0097] In the sheet folding unit 20, the CPU 101 executes a control program stored in the ROM 103 and a data-processing program (application program) loaded into the RAM 102 from a recording medium such as the HDD 104 using an arithmetic function. Such processing configures a software controller including various functional modules of the sheet folding unit 20. The software controller thus configured cooperates with hardware resources of the sheet folding unit 20 to construct functional blocks that implement functions of the sheet folding unit 20. In other words, the CPU 101, the RAM 102, the ROM 103, and the HDD 104 construct the controller 100 as the circuitry that controls the operation of the sheet folding unit 20.

[0098] The I/F 105 is an interface that connects the conveyance motor 22c, the folder motor 23c, the guide motor 26c, the sheet sensors 28a, 28b and 28c, the rotary encoders 22z and 23z, and the control panel 110, to the common bus 109. The controller 100 acquires information from the sheet sensors 28a, 28b and 28c, the rotary encoders 22z and 23z, and the control panel 110 through the I/F 105, and operates the conveyance motor 22c, the folder motor 23c, and the guide motor 26c.

[0099] Although FIG. 6 illustrates only the components of the sheet folding unit 20, the controller 100 may also control the operations of the image forming device 12 and the sheet binding unit 30. Alternatively, the controller 100 as circuitry may operate the sheet folding unit 20 in conjunction with the image forming device 12 and the sheet binding unit 30 by mutually communicating with a controller that controls the operations of the image forming device 12 and a controller that controls the operations of the sheet binding unit 30.

[0100] The control panel 110 includes an operation device that receives instructions from the user and a display as a notification device that notifies the user of information. The operation device includes, for example, physical input buttons and a touch panel overlaid on a display. The control panel 110 acquires information from the operator through the operation device and provides the operator with information through the display. A specific example of the notification device is not limited to the display and may be a light-emitting diode (LED) lamp or a speaker.

Half-Fold Operation

[0101] FIG. 7 is a flowchart of a process of a half-fold operation.

[0102] FIGS. 8A, 8B and 8C are diagrams illustrating the sheet folding unit 20 in the half-fold operation.

[0103] FIGS. 9A, 9B, 9C and 9D are diagrams illustrating movement of the sheet S in the sheet folding unit 20 when changing a posture of the guide plate 26.

[0104] The half-fold operation is an operation or process that applies a fold line to be folded inward at the folding position C1 illustrated in FIG. 5A. The method of folding the sheet S may be instructed by the user through the control panel 110 or may be instructed by an external device via the communication network.

[0105] The controller 100 starts the half-fold operation illustrated in FIG. 7 in response to supplying the sheet S from the image forming device 12 via the input interface IN, in other words, turning the first sensor 28a ON. The controller 100 causes the guide motor 26c to drive in the forward direction to change the guide plate 26 from the second posture to the first posture. However, when the guide plate 26 is already in the first posture, this process is omitted. In step S701, the controller 100 causes the conveyance motor 22c and the folder motor 23c to drive in the forward direction to rotate the conveyance roller pair 22, the first folding roller 23, the second folding roller 24, and the third folding roller 25.

[0106] Further, in step S701, the conveyance speed of the conveyance roller pair 22, the conveyance speed of the first folding roller 23 and the second folding roller 24 are set to be equal to each other (speed V1). The conveyance speed indicates a distance by which the sheet S is conveyed per unit time by the rotation of a pair of rollers nipping the sheet S. In other words, the conveyance speed of the conveyance roller pair 22 corresponds to the circumferential speed of the drive roller 22a. On the other hand, the conveyance speed of the first folding roller 23 and the second folding roller 24 corresponds to the circumferential speed of the first folding roller 23. In a case where the gear ratio between the drive gear 29a and the driven gear 29b is equal to the gear ratio between the drive gear 29c and the driven gear 29d, and the diameter of the drive roller 22a is equal to the diameter of the first folding roller 23, the controller 100 may rotate the conveyance motor 22c and the folder motor 23c at the same number of rotations.

[0107] As a result, as illustrated in FIG. 8A, the sheet S nipped by the conveyance roller pair 22 is conveyed in the conveyance direction, passes through the slit 26a of the guide plate 26 in the first posture, and is nipped by the first nip region N1. Then, in step S702, the controller 100 determines whether the leading end of the sheet S passes through the first nip region N1 and the folding position C1 of the sheet S reaches the given position. When the leading end of the sheet S does not pass through the first nip region N1 or the folding position C1 of the sheet S does not reach the given position (NO in step S702), the controller 100 continues the process of step S701 until the leading end of the sheet S passes through the first nip region N1 and the folding position C1 of the sheet S reaches the given position. The controller 100 determines that the folding position C1 reaches the given position according to, for example, that the accumulated value of the pulse signal of the rotary encoder 22z after the first sensor 28a is turned ON or that the accumulated value of the pulse signal of the rotary encoder 23z after the second sensor 28b is turned ON.

[0108] The given position is a position where the sheet S can pass through the second nip region N2 with the folding position C1 as the leading end of the sheet S in step S703 described below. The given position is downstream from the slit 26a of the guide plate 26 in the conveyance direction (position close to the first nip region N1). Further, when the folding position C1 of the sheet S reaches the given position, the leading end of the sheet S from the folding position C1 is nipped by the first nip region N1 and the trailing end of the sheet S from the folding position C1 is nipped by the conveyance roller pair 22.

[0109] Subsequently, in response to arrival of the folding position C1 of the sheet S to the given position (YES in step S702), in step S703, the controller 100 causes the folder motor 23c and the guide motor 26c to rotate in the reverse direction to change the guide plate 26 from the first posture to the second posture, and the first folding roller 23 to rotate in the reverse direction, until the folding position C1 of the sheet S passes through the second nip region N2. As a result, as illustrated in FIGS. 8B and 9A, the sheet S enters the second nip region N2 with the folding position C1 as the leading end of the sheet S, so as to be folded inward at the folding position C1.

[0110] Then, in step S704, the controller 100 determines whether the sheet S reaches the position facing the third sensor 28c, in other words, the third sensor 28c is turned ON. When the sheet S has not reached the position facing the third sensor 28c, in other words, the third sensor 28c is not turned ON (NO in step S704), the controller 100 continues the process of step S703 until the sheet S reaches the position. As illustrated in FIG. 9A, when the folding position C1 of the sheet S passes through the second nip region N2 and reaches the position facing the third sensor 28c, the leading end of the sheet S from the folding position C1 is nipped by the first nip region N1, and the trailing end of the sheet S from the folding position C1 is nipped by the conveyance roller pair 22.

[0111] Subsequently, in response to passing of the folding position C1 of the sheet S through the second nip region N2 and turning of the third sensor 28c to ON (YES in step S704), in step S705, the controller 100 causes the guide motor 26c to rotate in the forward direction, rotate the conveyance motor 22c in the forward direction, and rotate the folder motor 23c in the forward direction. As a result, the controller 100 causes the guide plate 26 to change from the second posture to the first posture, the conveyance roller pair 22 to convey the trailing end of the sheet S from the folding position C1 in the conveyance direction, the first folding roller 23 and the second folding roller 24 to convey the leading end of the sheet S from the folding position C1 in the conveyance direction, and the first folding roller 23 and the third folding roller 25 to convey the part including the folding position C1 of the sheet S to the main conveyance path Ph1.

[0112] In step S705, the controller 100 causes the conveyance speed of the first folding roller 23 (speed V3) to be faster than the conveyance speed of the conveyance roller pair 22 (speed V2). As a result, as illustrated in FIGS. 9B, 9C and 9D, since the leading end of the sheet S from the folding position C1 is conveyed faster than the trailing end of the sheet S from the folding position C1, the sheet S is conveyed in the conveyance direction as the fold lines of the folding position C1 are unfolded. Further, the controller 100 gradually changes the posture of the guide plate 26 in conjunction with the rotation of each of the conveyance roller pair 22, the first folding roller 23, and the second folding roller 24 so that the guide plate 26 to be changed from the second posture to the first posture does not pull the sheet S nipped by the second nip region N2. In other words, as the guide plate 26 is changed from the second posture to the first posture, the controller 100 causes the conveyance roller pair 22 to rotate in the forward direction and the first folding roller 23 to rotate in the forward direction at a conveyance speed faster than the conveyance speed of the conveyance roller pair 22.

[0113] At this point, if the relation of V3>V2 is satisfied, V2=0 or V2<0 may be satisfied. In other words, the controller 100 may cause the conveyance roller pair 22 to stop or rotate in an opposite direction to the forward direction, in step S705. This action is also taken in step S1205 in the flowchart of FIG. 12. The magnitude relation between the conveyance speeds V1, V2, V3 and V4 described below is not particularly limited.

[0114] Then, in step S706, the controller 100 determines whether the predetermined time has elapsed. When the predetermined time has not passed (NO in step S706), the controller 100 continues the process of step S705 until the predetermined time elapses. The predetermined time is a time required for moving the folding position C1 of the sheet S from the second nip region N2 to the main conveyance path Ph1. In other words, the predetermined time is a time during which the sheet S can pass through the first nip region N1 with the fold line at the folding position C1 of the sheet S unfolded. The controller 100 may determine that the folding position C1 of the sheet S from the second nip region N2 to the main conveyance path Ph1, based on accumulated value of a pulse signal of the rotary encoder 23z instead of the predetermined time.

[0115] Subsequently, in response to passing of the predetermined time since the start of step S705 (YES in step S706), the controller 100 causes the conveyance motor 22c and the folder motor 23c to rotate in the forward direction (step S707). In step S707, the controller 100 causes the conveyance speed of the first folding roller 23 (speed V4) and the conveyance speed of the conveyance roller pair 22 (speed V4) to be equal.

[0116] Accordingly, the sheet S with the fold line of the folding position C1 unfolded passes through the first nip region N1 in the conveyance direction to be ejected to the sheet binding unit 30. Then, the controller 100 determines whether the second sensor 28b is turned OFF (step S708). When the second sensor 28b is turned OFF, in other words, the trailing end of the sheet S passes the position facing the second sensor 28b (YES in step S708), the controller 100 causes the conveyance motor 22c and the folder motor 23c are stopped to end the half-fold operation.

[0117] The controller 100 can achieve the half-fold operation in which the sheet S is folded in two by changing the process from and after step S703 of the half-fold operation illustrated in FIG. 7. First, in step S703, the controller 100 causes the conveyance motor 22c to rotate in the forward direction, the folder motor 23c to rotate in the reverse direction, and the guide motor 26c to rotate in the reverse direction. According to such a configuration, the sheet S conveyed by the conveyance roller pair 22, the first folding roller 23 and second folding roller 24 is guided to the second nip region N2 by the guide plate 26 in the second posture. Subsequently, when the controller 100 determines that the trailing end of the sheet S passes the position of the third sensor 28c, in other words, the third sensor 28c is turned OFF, the controller 100 causes the conveyance motor 22c, the folder motor 23c and the guide motor 26c to rotate in the forward direction. As a result, the sheet S folded in half is returned from the return conveyance path Ph2 to the main conveyance path Ph1 via the joining portion B, with the folding position C1 as the leading end of the sheet S folded in half, and is ejected to the sheet binding unit 30 through the conveyance roller pair 22, the guide plate 26 in the first posture and the first nip region N1.

Letter Fold-In Operation

[0118] FIG. 10 is a flowchart of a process of a letter fold-in operation.

[0119] FIGS. 11A and 11B are diagrams illustrating the sheet folding unit 20 in the letter fold-in operation.

[0120] The letter fold-in operation is an operation or process that applies a fold line to be folded inward at the folding position C2 and the folding position C3 illustrated in FIG. 5A. In other words, the letter fold-in operation is an operation or process that performs the half-fold operation at the folding position C2 and the folding position C3 in addition to the folding position C1. In addition, the detailed description is given below of the features of the letter fold-in operation common to the half-fold operation is omitted, and a description is given of the features of the letter fold-in operation different from the features of the half-fold operation.

[0121] The controller 100 continues the process of step S701 until the folding position C2 of the sheet S reaches the given position (NO in step S702). Subsequently, in step S1001, the controller 100 performs the process of steps S703 to S707 on the folding position C2 of the sheet S. Due to this operation, the sheet S is folded inward at the folding position C2 and the fold line of the folding position C2 of the sheet S is unfolded.

[0122] Subsequently, in step S1002, the controller 100 determines whether the process of step S1001 is performed on the sheet S at the folding position C2 and the folding position C3, in other words, the sheet folding operation is performed for two times. Then, when the controller 100 determines that the process of step S1001 is not performed on the sheet S at the folding position C3 (NO in step S1002), the controller 100 continues the process of step S707 until the folding position C3 of the sheet S reaches the given position (NO in step S702). Subsequently, in step S1001, when the folding position C3 of the sheet S reaches the given position (YES in step S702), the controller 100 performs the processes of steps S703 to S707 on the sheet S at the folding position C3. Due to this operation, the sheet S is folded inward at the folding position C2 and the folding position C3, as illustrated in FIG. 11A, and the fold lines of the folding position C2 and the folding position C3 are unfolded, as illustrated in FIG. 11B.

[0123] Subsequently, when the controller 100 determines that the sheet folding operation is performed for two times (YES in step S1002), in step S708, the controller 100 determines whether the second sensor 28b is turned OFF. The controller 100 continues the process of step S707 until the second sensor 28b is turned OFF (NO in step S708). Then, when the second sensor 28b is turned OFF (YES in step S708), the controller 100 causes the conveyance motor 22c and the folder motor 23c to stop so as to end the letter fold-in operation. In other words, in the letter fold-in operation, the controller 100 causes the sheet S to be folded inward at multiple folding positions, which are the folding position C2 and the folding position C3, of the sheet S shifted in the conveyance direction, and unfolds the fold lines of the multiple folding positions (i.e., the folding position C2 and the folding position C3), so as to eject the sheet S.

[0124] Further, as illustrated in FIG. 5B, the controller 100 may shift the folding positions of the multiple sheets sequentially supplied to the sheet folding unit 20 in the width direction. More specifically, the controller 100 provides a first interval that is an interval between the folding position C2 and the folding position C3 of the first sheet S, a second interval that is an interval between the folding position C2 and the folding position C3 of the second sheet S, and a third interval that is an interval between the folding position C2 and the folding position C3 of the third sheet S. The relation of the intervals is represented as the first interval <the second interval <the third interval. Accordingly, this configuration makes it easy to bundle the multiple sheets S to be folded inward in the letter fold-in operation.

[0125] The controller 100 can achieve the letter fold-in operation in which the sheet S is folded in three by changing the process of step S1001 of the letter fold-in operation in the flowchart of FIG. 10, similarly to the half-fold operation described above.

Letter Fold-Out Operation/Z-Fold Operation

[0126] FIG. 12 is a flowchart of an example letter fold-out operation.

[0127] FIGS. 13A, 13B and 13C are diagrams illustrating the sheet folding unit 20 in the letter fold-out operation to fold out the binding position C2 of the sheet S.

[0128] FIGS. 14A, 14B and 14C are diagrams illustrating the sheet folding unit 20 in the letter fold-in operation at the binding position C3.

[0129] FIGS. 15A, 15B, 15C and 15D are diagrams illustrating movement of the sheet S in the sheet folding unit 20 when changing the posture of the guide plate 26 from the first posture to the second posture.

[0130] The letter fold-out operation is an operation to apply the fold line of the sheet S to be folded outward at the folding position C2 of FIG. 5A, and the fold line of the sheet S to be folded inward at the folding position C3. In the process in the flowchart of FIG. 12, when a fold line of the sheet S is folded outward at the folding position C1 and another fold line of the sheet S is folded inward at the folding position C4, the fold lines of so-called Z-fold are applied to the sheet S. The detailed description is given below of the features of the letter fold-in operation common to the half-fold operation is omitted, and a description is given of the features of the letter fold-in operation different from the features of the half-fold operation.

[0131] When the sheet S is fed from the image forming device 12 via the input interface IN, in other words, the first sensor 28a is turned ON, the controller 100 starts the letter fold-out operation illustrated in FIG. 12. The controller 100 causes the guide motor 26c to rotate in the reverse direction to change the guide plate 26 from the first posture to the second posture. However, when the guide plate 26 is already in the second posture, this process is omitted. Further, the controller 100 causes the conveyance motor 22c to rotate in the forward direction and the conveyance roller pair 22 in the forward direction. In step S1201, the controller 100 causes the folder motor 23c to rotate in the reverse direction and, by so doing, causes the first folding roller 23, the second folding roller 24 and the third folding roller 25 to rotate in the reverse direction.

[0132] Further, in step S1201, the controller 100 sets the conveyance speed of the conveyance roller pair 22 and the conveyance speed of the first folding roller 23 and the third folding roller 25 to be equal to each other (speed V1). As a result, as illustrated in FIG. 13A, the sheet S nipped by the conveyance roller pair 22 is conveyed in the conveyance direction, passes through the slit 26a of the guide plate 26 in the second posture, and is nipped by the second nip region N2. Then, in step S1202, the controller 100 determines whether the leading end of the sheet S passes through the second nip region N2 and the folding position C2 of the sheet S reaches the given position. When the leading end of the sheet S does not pass through the second nip region N2 or the folding position C2 of the sheet S does not reach the given position (NO in step S1202), the controller 100 continues the process of step S1201. The controller 100 determines that the folding position C2 of the sheet S reaches the given position according to, for example, that the accumulated value of the pulse signal of the rotary encoder 22z after the first sensor 28a is turned ON or that the accumulated value of the pulse signal of the rotary encoder 23z after the third sensor 28c is turned ON.

[0133] The given position is a position where the sheet S can pass through the first nip region N1 with the folding position C2 of the sheet S as the leading end in step S1203 described below. The given position is downstream from the slit 26a of the guide plate 26 in the conveyance direction (position close to the second nip region N2). Further, when the folding position C2 of the sheet S reaches the given position, the leading end of the sheet S from the folding position C2 is nipped by the second nip region N2 and the trailing end of the sheet S from the folding position C2 is nipped by the conveyance roller pair 22.

[0134] Subsequently, in response to arrival of the folding position C2 of the sheet S to the given position (YES in step S1202), in step S1203, the controller 100 causes the folder motor 23c and the guide motor 26c to rotate in the forward direction to change the guide plate 26 from the second posture to the first posture, and the first folding roller 23 to rotate in the forward direction, until the folding position C2 of the sheet S passes through the first nip region N1. As a result, as illustrated in FIGS. 13B and 15A, the sheet S enters the first nip region N1 with the folding position C2 as the leading end of the sheet S, so as to be folded outward at the folding position C2.

[0135] Then, in step S1204, the controller 100 determines whether the sheet S reaches the position facing the second sensor 28b, in other words, the second sensor 28b is turned ON. When the sheet S has not reached the position facing the second sensor 28b, in other words, the second sensor 28b is not turned ON (NO in step S1204), the controller 100 continues the process of step S1203 until the sheet S reaches the position. As illustrated in FIG. 15A, when the folding position C2 of the sheet S passes through the first nip region N1 and reaches the position facing the second sensor 28b, the leading end of the sheet S from the folding position C2 is nipped by the second nip region N2, and the trailing end of the sheet S from the folding position C2 is nipped by the conveyance roller pair 22.

[0136] Subsequently, in response to passing of the folding position C2 of the sheet S through the first nip region N1 and turning of the second sensor 28b to ON (YES in step S1204), in step S1205, the controller 100 causes the guide motor 26c to rotate in the reverse direction, rotate the conveyance motor 22c in the forward direction, and rotate the folder motor 23c in the reverse direction. As a result, the controller 100 causes the guide plate 26 to change from the first posture to the second posture, the conveyance roller pair 22 to convey the trailing end of the sheet S from the folding position C2 in the conveyance direction, the first folding roller 23 and the third folding roller 25 to convey the leading end of the sheet S from the folding position C2 in the conveyance direction, and the first folding roller 23 and the second folding roller 24 to convey the part including the folding position C2 of the sheet S to the second nip region N2.

[0137] Further, in step S1205, the controller 100 causes the conveyance speed of the first folding roller 23 (speed V3) is faster than the conveyance speed of the conveyance roller pair 22 (speed V2). As a result, as illustrated in FIGS. 15B, 15C and 15D, since the leading end of the sheet S from the folding position C2 is conveyed faster than the trailing end of the sheet S from the folding position C2, the sheet S is conveyed in the return conveyance path Ph2 as the fold lines of the folding position C2 are unfolded. Further, the controller 100 gradually changes the posture of the guide plate 26 in conjunction with the rotation of each of the conveyance roller pair 22, the first folding roller 23, and the second folding roller 24 so that the guide plate 26 to be changed from the first posture to the second posture does not pull the sheet S nipped by the first nip region N1. In other words, as the guide plate 26 is changed from the first posture to the second posture, the controller 100 causes the conveyance roller pair 22 to rotate in the forward direction and the first folding roller 23 to rotate in the reverse direction at a conveyance speed faster than the conveyance speed of the conveyance roller pair 22.

[0138] Then, in step S1206, the controller 100 determines whether the predetermined time has elapsed. When the predetermined time has not passed (NO in step S1206), the controller 100 continues the process of step S1205 until the predetermined time elapses. The predetermined time is a time required for moving the folding position C2 of the sheet S from the first nip region N1 to the second nip region N2. In other words, the predetermined time is a time during which the sheet S can pass through the second nip region N2 with the fold line at the folding position C2 of the sheet S unfolded. The controller 100 may determine that the folding position C2 of the sheet S from the first nip region N1 to the second nip region N2, based on accumulated value of a pulse signal of the rotary encoder 23z instead of the predetermined time.

[0139] Subsequently, in response to passing of the predetermined time since the start of step S1205 (YES in step S1206), the controller 100 causes the conveyance motor 22c to rotate in the forward direction and the folder motor 23c to rotate in the reverse direction (step S1207). In step S1207, the controller 100 causes the conveyance speed of the first folding roller 23 (speed V4) and the conveyance speed of the conveyance roller pair 22 (speed V4) to be equal. As a result, as illustrated in FIG. 13C, the sheet S with the fold line at the folding position C2 unfolded passes through the second nip region N2, and returns from the return conveyance path Ph2 to the main conveyance path Ph1 via the joining portion B.

[0140] Then, in step S1208, the controller 100 determines whether the trailing end of the sheet S passes the position facing the third sensor 28c, in other words, the third sensor 28c is turned OFF. When the sheet S has not reached the position facing the third sensor 28c, in other words, the third sensor 28c is not turned ON (NO in step S1208), the controller 100 continues the process of step S1207 until the sheet S reaches the position. When the controller 100 causes the guide motor 26c to rotate in the forward direction in advance at the timing when the first sensor 28a is turned ON, the guide plate 26 is changed from the second posture to the first posture. Subsequently, in step S1209, when the third sensor 28c is turned ON (YES in step S1208), the controller 100 performs the half-fold operation on the sheet S at the folding position C3. As a result, as illustrated in FIGS. 14A, 14B and 14C, the sheet S is folded inward at the folding position C3, the fold line of the sheet S at the folding position C3 is unfolded, and the sheet S is ejected from the sheet binding unit 30.

[0141] The controller 100 can achieve the letter fold-out in which the sheet S is folded in three by changing the process from and after step S1204 of the letter fold-out operation illustrated in FIG. 12. The controller 100 continues the process of step S1203 until the folding position C3 of the sheet S reaches the given position. Instead of the processes of steps S1205 to S1209, the controller 100 performs the above-described half-fold operation on the sheet S at the folding position C3. By so doing, the sheet S subjected to the letter fold-out operation is ejected to the sheet binding unit 30. Further, instead of the folding position C2 and the folding position C3, the above-described operation is performed on the sheet S at the folding position C1 and a folding position C4. By so doing, the sheet S subjected to the Z-fold operation is ejected to the sheet binding unit 30.

Operations of Sheet Binding Unit 30

[0142] With reference to FIGS. 16A to 20B, a description is given of the operations of the sheet binding unit 30.

[0143] FIG. 16A is a diagram illustrating the sheet binding unit 30 that receives the sheet S.

[0144] FIG. 16B is a diagram illustrating the sheet binding unit 30 in which the sheet S reaches the conveyance roller pair 36.

[0145] FIGS. 17A and 17B are diagrams illustrating the sheet binding unit 30 when ejecting the sheet S to the ejection tray 32 without performing the sheet binding operation on the sheet S.

[0146] FIGS. 18A and 18B are diagrams illustrating the sheet binding unit 30 that performs the sheet binding operation.

[0147] FIG. 19 is a diagram illustrating the sheet binding unit 30 of FIG. 18B as viewed from a thickness direction of the sheet S.

[0148] FIGS. 20A and 20B are diagrams illustrating the sheet binding unit 30 when a sheet bundle Sb subjected to a sheet binding operation is ejected to an ejection tray 32.

[0149] As illustrated in FIGS. 16A and 16B, as the conveyance roller pairs 33 to 35 are rotated in the forward direction, the sheet binding unit 30 conveyed the sheet supplied from the sheet folding unit 20 along the conveyance path Ph3 in the conveyance direction. At this time, in the conveyance roller pair 36, the drive roller 36a and the driven roller 36b are separated from each other.

[0150] When the sheet binding unit 30 does not perform the sheet binding operation on the sheet S, the drive roller 36a and the driven roller 36b nip the sheet S as illustrated in FIG. 17A. Subsequently, as the conveyance roller pair 36 is rotated in the forward direction, the sheet binding unit 30 ejects the sheet S to the ejection tray 32 as illustrated in FIG. 17B.

[0151] On the other hand, when the sheet binding unit 30 performs the sheet binding operation on the sheet S, the tapping roller 38 and the return roller 39 contact on the sheet S after passing through the conveyance roller pair 35 and rotate to accommodate the sheet S in the internal tray 37 as illustrated in FIGS. 18A and 18B. Further, as illustrated in FIG. 19, the sheet binding unit 30 moves the side fences 41L and 41R in the width direction as illustrated in FIG. 19 to align the positions in the width direction of the sheets S accommodated in the internal tray 37.

[0152] Repeating the processes illustrated in FIGS. 16A, 16B, 18A, 18B and 19 in the sheet binding unit 30 forms the sheet bundle Sb on the internal tray 37.

[0153] Subsequently, as the sheet binding portion 42 is driven, the sheet binding unit 30 binds the sheet bundle Sb supported by the internal tray 37. Subsequently, as illustrated in FIG. 20A, the sheet binding unit 30 causes the drive roller 36a and the driven roller 36b to nip the sheet bundle Sb. As the conveyance roller pair 36 and the return roller 39 are rotated in the forward direction, the sheet binding unit 30 ejects the sheet bundle Sb to the ejection tray 32 as illustrated in FIG. 17B.

Operation and Effect of Embodiment

[0154] According to the above-described embodiments, fold lines of various folding method (for example, half-fold, letter fold-in, letter fold-out, and Z-fold) can be applied to the sheet S. The sheet folding unit 20 according to the above-described embodiment can eject the sheet S folded only by finely adjusting the processes of the flowcharts illustrated in FIGS. 7, 10 and 12. Due to such configurations as described above, a process to apply the fold lines on the sheet S and a process to fold the sheet S can be achieved by a single sheet folding unit 20. As a result, the above-described configuration enables manufacturing the sheet folding unit 20 that can be flexible to various kinds of user's needs.

[0155] Further, according to the above-described embodiments, the second folding roller 24 and the third folding roller 25 are brought into contact with the first folding roller 23 so as to be driven to rotate, and the guide plate 26 is changed from the first posture to the second posture. Accordingly, the sheet folding unit 20 can reduce in size.

[0156] Further, according to the above-described embodiments, as illustrated in FIG. 5B, the fold lines of the multiple sheets S are shifted in the conveyance direction, and thus the sheets S are less likely to be wrinkled when the user folds the multiple sheets S into a sheet bundle.

[0157] Further, according to the above-described embodiments, the first stopper 27a and the second stopper 27b limit the movable range of the guide plate 26 and the driving force transmission mechanism 29 includes the torque limiter 29g. Due to such a configuration, the movable range of the guide plate 26 can be limited with a simple configuration. The above-described configuration can further reduce the size of the sheet folding unit 20.

[0158] However, a specific method of limiting the movable range area of the guide plate 26 is not limited to the first stopper 27a and the second stopper 27b.

[0159] FIGS. 21A and 21B are diagrams illustrating another example in which a movable range of a guide plate is restricted.

[0160] The sheet folding unit 20 illustrated in FIGS. 21A and 21B may include posture sensors 27c and 27d instead of the first stopper 27a and the second stopper 27b. The posture sensor 27c outputs a detection signal when the guide plate 26 is in the first posture, and stops outputting the detection signal when the guide plate 26 is in a posture different from the first posture. The posture sensor 27d outputs a detection signal when the guide plate 26 is in the second posture, and stops outputting the detection signal when the guide plate 26 is in a posture different from the second posture. The controller 100 may stop the driving of the guide motor 26c when a detection signal is output from one of the posture sensors 27c and 27d. In this case, the torque limiter 29g is omitted.

[0161] According to the above-described embodiments, the first folding roller 23, the second folding roller 24, the third folding roller 25 and the guide plate 26 are disposed opposite to the driving force transmission mechanism 29 across the partition 21a. By so doing, the above-described configuration can prevent the sheet S from being contaminated by dust from the driving force transmission mechanism 29. In addition, the above-described configuration can prevent the dust coming out of the sheet S from clogging the driving force transmission mechanism 29 and can achieve the smooth transmission of the driving force.

[0162] The sheet folding unit 20 according to the above-described embodiments is particularly advantageous when the sheet folding unit 20 is mounted in the in-body space 13 of the image forming apparatus 10 having a limited space. However, a unit attached to the in-body space 13 is not limited to the sheet folding unit 20. The position of the sheet folding unit 20 is not limited to the in-body space 13.

Modification 1

[0163] FIGS. 22A and 22B are diagrams illustrating an internal structure of a punching unit 50 (puncher).

[0164] The punching unit 50 illustrated in FIGS. 22A and 22B is detachably attached to the in-body space 13 at the position from which the sheet folding unit 20 is detached. In other words, the image forming apparatus 10 is configured such that the sheet folding unit 20 and the punching unit 50 can be replaced according to the use. The punching unit 50 is configured, for example, as follows.

[0165] As illustrated in FIGS. 22A and 22B, the punching unit 50 includes a housing 51, a sheet sensor 52, punching pins 53a and 53b, and a punch chad container 54. The housing 51 has an internal space for accommodating components of the punching unit 50. In the internal space of the housing 51, a conveyance path is formed. The sheet on which the image is formed by the image forming device 12 passes through the conveyance path.

[0166] The sheet sensor 52 detects that the sheet S supplied from the image forming device 12 has reached a given position. The punching pins 53a and 53b punch holes in the sheet S detected by the sheet sensor 52. The punch chads that have fallen off from the sheet S fall into the punch chad container 54. The above-described punching unit 50 performs the punching operation for punching the sheet S.

Modification 2

[0167] FIG. 23 is a block diagram illustrating a hardware configuration of an image forming apparatus 10.

[0168] For example, as illustrated in FIG. 23, the image forming apparatus 10 may include a controller 200 to control the image forming device 12 and the control panel 110 in addition to the controller 100 illustrated in FIG. 6.

[0169] The controller 200 may include, for example, a CPU, a RAM, a ROM and an HDD, similarly to the controller 100. Alternatively, the controller 200 may control the image forming device 12 and the control panel 110 via an interface (I/F) 205. Further, the controllers 100 and 200 may communicate with each other. The operation of the image forming apparatus 10 may be controlled with cooperation of the controllers 100 and 200.

Modification 3

[0170] FIG. 24 is an external view of an image forming system 1.

[0171] As illustrated in FIG. 24, the image forming system 1 includes the image forming apparatus 10, a sheet folding unit 20, and a sheet binding unit 30. The image forming apparatus 10, the sheet folding unit 20 and the sheet binding unit 30 are apparatuses that can operate separately from each other and are connectable to each other. The sheet folding unit 20 has the same configuration as the sheet folding unit 20 described above, and the sheet binding unit 30 has the same configuration as the sheet binding unit 30 described above.

[0172] FIG. 25 is a block diagram illustrating a hardware configuration of the image forming system 1.

[0173] As illustrated in FIG. 25, the image forming system 1 does not include the controller 100 and the controller 200 centrally controls the components of the image forming apparatus 10 and the sheet binding unit 30. The configuration of the controller 200 of FIG. 25 is the same as the configuration of the controller 200 of in FIG. 23. The controller 200 may operate the image forming system 1 by controlling the operations of the components of the image forming apparatus 10 via the I/F 205 and controlling the operations of the components of the sheet binding unit 30 via the I/F 105.

[0174] The present disclosure is not limited to specific embodiments described above, and numerous additional modifications and variations are possible in light of the teachings within the technical scope of the appended claims. It is therefore to be understood that the disclosure of this patent specification may be practiced otherwise by those skilled in the art than as specifically described herein, and such, modifications, alternatives are within the technical scope of the appended claims. Such modifications are also included in the technical scope of the present disclosure.

[0175] In the above-described embodiment, the guide plate 26 is in the first posture in FIG. 3A and in the second posture in FIG. 3B. FIG. 3A may be the guide plate 26 in the second posture, and FIG. 3B may be the guide plate 26 in the first posture.

[0176] A description is given below of some aspects of the present disclosure.

Aspect 1

[0177] In Aspect 1, a sheet folder includes a conveyance roller pair, a first folding roller, a second folding roller, a third folding roller, a guide, and a controller. The conveyance roller pair conveys a sheet in a conveyance direction. The first folding roller is disposed downstream from the conveyance roller pair in the conveyance direction. The second folding roller forms a first nip with the first folding roller and is rotated along with rotation of the first folding roller. The third folding roller forms a second nip with the first folding roller and is rotated along with rotation of the first folding roller. The guide is disposed between the conveyance roller pair and the first nip in the conveyance direction and is switchable between a first posture that guides the sheet to the first nip and a second posture that guides the sheet to the second nip. The controller is to control the conveyance roller pair. The controller is to switch the guide from the first posture to the second posture and fold the sheet by the second nip, with the sheet nipped by the first nip, or switch the guide from the second posture to the first posture and fold the sheet by the first nip, with the sheet nipped by the second nip; and increase a conveyance speed of the first folding roller to be faster than a conveyance speed of the conveyance roller pair, with the sheet folded by the first nip or the second nip.

Aspect 2

[0178] In Aspect 2, in the sheet folder according to Aspect 1, the controller is to rotate the conveyance roller pair and the first folding roller in a reverse direction, with the sheet folded by the first nip or the second nip.

Aspect 3

[0179] In Aspect 3, in the sheet folder according to Aspect 1 or 2, the conveyance roller pair can perform a forward rotation in which the sheet is conveyed in the conveyance direction. The second folding roller is disposed opposite to the first folding roller across a main conveyance path. The third folding roller is disposed opposite to the first folding roller across a return conveyance path branched from the main conveyance path at a branching portion upstream from the first folding roller in the conveyance direction to join the main conveyance path at a joining portion upstream from the branching portion in the conveyance direction. The first folding roller can perform the forward rotation in which the sheet nipped by the first nip is conveyed in the conveyance direction and the sheet nipped by the second nip is conveyed from the return conveyance path to the main conveyance path; and a reverse rotation in which the sheet nipped by the first nip is conveyed in a direction opposite to the conveyance direction and the sheet nipped by the second nip is conveyed to the return conveyance path.

Aspect 4

[0180] In Aspect 4, in the sheet folder according to Aspect 3, the controller is further to change the guide to the first posture to perform the forward rotation of the conveyance roller pair and the first folding roller at conveyance speeds equal to each other, before a leading end of the sheet passes through the first nip and a folding position of the sheet reaches a given position; change the guide from the first posture to the second posture in response to arrival of the folding position of the sheet to the given position to rotate the first folding roller in the reverse direction until the folding position of the sheet passes through the second nip, and fold the sheet at the folding position; and perform the forward rotation of the conveyance roller pair and perform the forward rotation of the first folding roller at a conveyance speed faster than a conveyance speed of the conveyance roller pair while changing the guide from the second posture to the first posture, in response to passage of the folding position of the sheet through the second nip, to unfold a fold line of the sheet at the folding position and eject the sheet.

Aspect 5

[0181] In Aspect 5, in the sheet folder according to Aspect 4, the controller is further to fold the sheet at multiple folding positions including the folding position shifted in the conveyance direction, and unfold a fold line at each of the multiple folding positions, to eject the sheet.

Aspect 6

[0182] In Aspect 6, in the sheet folder according to Aspect 3, the controller is further to change the guide to the second posture to perform the forward rotation of the conveyance roller pair and the reverse rotation of the first folding roller, until a leading end of the sheet passes through the second nip and a folding position of the sheet reaches a given position; change the guide from the second posture to the first posture in response to arrival of the folding position of the sheet to the given position to perform the forward rotation of the first folding roller until the folding position of the sheet passes through the first nip, and fold the sheet at the folding position; perform the forward rotation of the conveyance roller pair and perform the reverse rotation of the first folding roller at a conveyance speed faster than a conveyance speed of the conveyance roller pair until the given time elapses while changing the guide from the second posture to the first posture, in response to passage of the folding position of the sheet through the first nip, to unfold a fold line of the sheet at the folding position and convey the sheet to the return conveyance path; and change the guide from the second posture to the first posture in response to elapse of the given time to perform the forward rotation of the conveyance roller pair and the first folding roller at conveyance speeds equal to each other, to eject the sheet.

Aspect 7

[0183] In Aspect 7, in the sheet folder according to any one of Aspects 1 to 6, the controller is further to shift respective folding positions of multiple sheets including the sheet to be sequentially supplied to the sheet folder, in the conveyance direction.

Aspect 8

[0184] In Aspect 8, a post-processing apparatus includes the sheet folder according to any one of Aspects 1 to 7, and a sheet binder to bundle multiple sheets provided with a fold line folded by the sheet folder.

Aspect 9

[0185] In Aspect 9, an image forming apparatus includes an image forming device to form an image on a sheet, and the sheet folder according to any one of Aspects 1 to 8 to provide a fold line on the sheet on which the image is formed by the image forming device.

Aspect 10

[0186] In Aspect 10, an image forming system includes an image forming apparatus, a conveyance roller pair, a first folding roller, a second folding roller, a third folding roller, a guide, and a controller. The image forming apparatus forms an image on a sheet. The conveyance roller pair conveys the sheet that has passed the image forming apparatus in a conveyance direction. The first folding roller is disposed downstream from the conveyance roller pair in the conveyance direction. The second folding roller forms a first nip with the first folding roller and is rotated along with rotation of the first folding roller. The third folding roller forms a second nip with the first folding roller and is rotated along with rotation of the first folding roller. The guide is disposed between the conveyance roller pair and the first nip in the conveyance direction and is switchable between a first posture that guides the sheet to the first nip and a second posture that guides the sheet to the second nip. The controller is to control the conveyance roller pair. The controller is to switch the guide from the first posture to the second posture and fold the sheet by the second nip, with the sheet nipped by the first nip, or switch the guide from the second posture to the first posture and fold the sheet by the first nip, with the sheet nipped by the second nip; and increase a conveyance speed of the first folding roller to be faster than a conveyance speed of the conveyance roller pair, with the sheet folded by the first nip or the second nip.

Aspect 11

[0187] In Aspect 11, a sheet folder includes a conveyance roller pair, a first folding roller, a second folding roller, a third folding roller, a guide, and circuitry. The conveyance roller pair conveys a sheet in a conveyance direction at a first speed. The first folding roller is downstream from the conveyance roller pair in the conveyance direction. The second folding roller is in contact with the first folding roller to form a first nip with the first folding roller. The second folding roller rotates along with the first folding roller. The third folding roller is in contact with the first folding roller to form a second nip with the first folding roller. The third folding roller rotates along with the first folding roller. The guide is disposed between the conveyance roller pair and the first nip in the conveyance direction. The guide is changeable between a first posture to guide the sheet from the conveyance roller pair to the first nip and a second posture to guide the sheet from the conveyance roller pair to the second nip. The circuitry is to control the guide at the first posture to guide the sheet from the conveyance roller pair to the first nip, control the guide to change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet, and control the first folding roller to rotate at a second speed faster than the first speed of the conveyance roller pair while the second nip nips and folds the sheet.

Aspect 12

[0188] In Aspect 12, in the sheet folder according to Aspect 11, the circuitry is further to control the guide at the second posture to guide the sheet from the conveyance roller pair to the second nip, and control the guide to change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.

Aspect 13

[0189] In Aspect 13, in the sheet folder according to Aspect 11 or Aspect 12, the circuitry is further to rotate the conveyance roller pair and the first folding roller in a forward direction while the first nip or the second nip nips and folds the sheet to convey the sheet in the conveyance direction, and rotate the conveyance roller pair and the first folding roller in a reverse direction opposite to the forward direction while the first nip or the second nip nips and folds the sheet.

Aspect 14

[0190] In Aspect 14, the sheet folder according to Aspect 11 further includes a return conveyance path to convey the sheet, nipped between the first folding roller and the third folding roller, from the second nip to an upstream of the conveyance roller pair in the conveyance direction.

Aspect 15

[0191] In Aspect 15, in the sheet folder according to any one of Aspect 11 to 14, the second folding roller faces the first folding roller across a main conveyance path in the conveyance direction. The third folding roller faces the first folding roller across the return conveyance path branched from the main conveyance path at a branching portion upstream from the first nip in the conveyance direction. The return conveyance path joins the main conveyance path at a joining portion upstream from the conveyance roller pair in the conveyance direction. The circuitry is further to control the conveyance roller pair to rotate in a forward direction to convey the sheet in the conveyance direction; control the first folding roller to rotate in a forward direction to convey the sheet nipped by the first nip in the conveyance direction, and convey the sheet nipped by the second nip from the return conveyance path to the main conveyance path; and control the first folding roller to rotate in a reverse direction opposite to the forward direction to convey the sheet nipped by the first nip in a direction opposite to the conveyance direction, and convey the sheet nipped by the second nip to the return conveyance path.

Aspect 16

[0192] In Aspect 16, in the sheet folder according to Aspect 15, the circuitry is further to change the guide to the first posture to rotate the conveyance roller pair and the first folding roller at conveyance speeds equal to each other in the forward direction, before a leading end of the sheet passes through the first nip and a folding position of the sheet reaches a given position, change the guide from the first posture to the second posture in response to arrival of the folding position of the sheet to the given position to rotate the first folding roller in the reverse direction until the folding position of the sheet passes through the second nip, to fold the sheet at the folding position, and rotate the conveyance roller pair in the forward direction while changing the guide from the second posture to the first posture and rotate the first folding roller in the forward direction at a conveyance speed faster than a conveyance speed of the conveyance roller pair, in response to passage of the folding position of the sheet through the second nip, to unfold a fold line of the sheet at the folding position and eject the sheet.

Aspect 17

[0193] In Aspect 17, in the sheet folder according to Aspect 16, the circuitry is further to fold the sheet at multiple folding positions including the folding position shifted in the conveyance direction, and unfold a fold line at each of the multiple folding positions and eject the sheet.

Aspect 18

[0194] In Aspect 18, in the sheet folder according to Aspect 15, the circuitry is further to change the guide to the second posture to rotate the conveyance roller pair in the forward direction and the first folding roller in the reverse direction, before a leading end of the sheet passes through the second nip and a folding position of the sheet reaches a given position, change the guide from the first posture to the second posture in response to arrival of the folding position of the sheet to the given position to rotate the first folding roller in the forward direction until the folding position of the sheet passes through the first nip, to fold the sheet at the folding position, rotate the conveyance roller pair in the forward direction while changing the guide from the first posture to the second posture until a given time elapses and rotate the first folding roller in the reverse direction at a conveyance speed faster than a conveyance speed of the conveyance roller pair, in response to passage of the folding position of the sheet through the first nip, to unfold a fold line of the sheet at the folding position and convey the sheet to the return conveyance path, and change the guide from the second posture to the first posture in response to elapse of the given time to rotate the conveyance roller pair and the first folding roller in the forward direction at conveyance speeds equal to each other, to eject the sheet.

Aspect 19

[0195] In Aspect 19, in the sheet folder according to any one of Aspects 11 to 18, multiple sheets including the sheet is sequentially conveyed from an image forming device. The circuitry is further to cause multiple sheets including the sheet to be sequentially conveyed, and shift respective folding positions of the multiple sheets in the conveyance direction of the sheet.

Aspect 20

[0196] In Aspect 20, a post-processing apparatus includes the sheet folder according to any one of Aspects 11 to 19, and a sheet binder to bundle multiple sheets including the sheet provided with a fold line folded by the sheet folder.

Aspect 21

[0197] In Aspect 21, an image forming apparatus includes an image forming device to form an image on a sheet, and the sheet folder according to any one of Aspects 11 to 20 to provide a fold line on the sheet on which the image is formed by the image forming device.

Aspect 22

[0198] In Aspect 22, an image forming system includes an image forming apparatus, a conveyance roller pair, a first folding roller, a second folding roller, a third folding roller, a guide, and circuitry. The image forming apparatus forms an image on a sheet. The conveyance roller pair conveys a sheet in a conveyance direction of the sheet that has passed the image forming apparatus at a first speed. The first folding roller is disposed downstream from the conveyance roller pair in the conveyance direction. The second folding roller is in contact with the first folding roller to form a first nip with the first folding roller. The second folding roller rotates along with the first folding roller. The third folding roller is in contact with the first folding roller to form a second nip with the first folding roller. The third folding roller rotates along with the first folding roller. The guide is between the conveyance roller pair and the first nip in the conveyance direction to change a posture between a first posture that guides the sheet to the first nip and a second posture that guides the sheet to the second nip. The circuitry is to control the guide at the first posture to guide the sheet from the conveyance roller pair to the first nip, control the guide to change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet, and control the first folding roller to rotate at a second speed faster than the first speed of the conveyance roller pair while the second nip nips and folds the sheet.

Aspect 23

[0199] In Aspect 23, in the image forming system according to Aspect 22, the circuitry is further to control the guide at the second posture to guide the sheet from the conveyance roller pair to the second nip, and control the guide to change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.

Aspect 24

[0200] In Aspect 24, a sheet folder includes a conveyance roller pair, a first folding roller, a second folding roller, a third folding roller, and a guide. The conveyance roller pair conveys a sheet in a conveyance direction at a first speed. The first folding roller is disposed downstream from the conveyance roller pair in the conveyance direction. The second folding roller is in contact with the first folding roller to form a first nip with the first folding roller. The second folding roller rotates along with the first folding roller. The third folding roller is in contact with the first folding roller to form a second nip with the first folding roller. The third folding roller rotates along with the first folding roller. The guide is downstream from the conveyance roller pair in the conveyance direction and has a first guide face facing a first face of the sheet and a second guide face facing a second face of the sheet, the guide being changeable between a first posture to guide the sheet from the conveyance roller pair to the first nip and a second posture that guides the sheet from the conveyance roller pair to the second nip. The guide is to guide the sheet at the first posture from the conveyance roller pair to the first nip, and change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet; or guide the sheet at the first posture from the conveyance roller pair to the second nip, and change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.

Aspect 25

[0201] In Aspect 25, in the sheet folder according to Aspect 24, the first guide face and the second guide face have an interval having an upstream side greater than a downstream side in the conveyance direction.

Aspect 26

[0202] In Aspect 26, an image forming apparatus includes an image forming device to form an image on a sheet, and the sheet folder according to Aspect 24 to provide a fold line on the sheet on which the image is formed by the image forming device.

[0203] The present disclosure is not limited to specific embodiments described above, and numerous additional modifications and variations are possible in light of the teachings within the technical scope of the appended claims. It is therefore to be understood that, the disclosure of this patent specification may be practiced otherwise by those skilled in the art than as specifically described herein, and such, modifications, alternatives are within the technical scope of the appended claims. Such embodiments and variations thereof are included in the scope and gist of the embodiments of the present disclosure and are included in the embodiments described in claims and the equivalent scope thereof.

[0204] The effects described in the embodiments of this disclosure are listed as the examples of preferable effects derived from this disclosure, and therefore are not intended to limit to the embodiments of this disclosure.

[0205] The embodiments described above are presented as an example to implement this disclosure. The embodiments described above are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, or changes can be made without departing from the gist of the invention. These embodiments and their variations are included in the scope and gist of this disclosure and are included in the scope of the invention recited in the claims and its equivalent.

[0206] Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above.

[0207] Each of the functions of the described embodiments may be implemented by one or more processing circuits or circuitry. Processing circuitry includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC), digital signal processor (DSP), field programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions.