JP6640296B2 - Post-processing apparatus and image forming system having the same - Google Patents

Description

  The present invention relates to a post-processing apparatus that stacks sheets sent from an image forming apparatus and performs post-processing, and relates to an improvement in a transport system that does not stop an upstream image forming process during a post-processing operation.

  Generally, this type of post-processing system is widely known as a system in which an image is formed on a sheet by an image forming apparatus on the upstream side, and the sheets are stacked for each copy by a post-processing apparatus on the downstream side to perform bookbinding and other post-processing. Have been. In such a system, it is required from the operating efficiency of the system that an image is continuously formed by the image forming apparatus on the upstream side and post-processing is performed on the downstream side in accordance with the processing speed.

  Therefore, during the execution of post-processing such as bookbinding, the sheets (bundles) that have been aligned and stacked in the post-processing device are temporarily suspended in the course of the subsequent sheet sent from the upstream side. A transport system for feeding the staying sheet to a post-processing unit is employed.

  For example, Patent Document 1 discloses a post-processing including a straight path that guides a sheet sent from an image forming apparatus to a first processing unit, and a switchback path that branches from this path and guides the sheet to a second processing unit. An apparatus is disclosed.

  According to the document, a succeeding sheet sent from the upstream side during the processing operation of the first processing unit is retained in a switchback path for guiding to the second processing unit, and during the processing operation of the second processing unit. A route configuration has been proposed in which a subsequent sheet sent from the upstream side stays in a straight path.

  In the image forming apparatus on the upstream side, an image is formed on a sheet at a predetermined timing regardless of the post-processing operation on the downstream side, and the sheet is carried out from the sheet discharge port. When the post-processing device receives the sheet and the post-processing mode is the first processing unit, the sheet stays on the switchback path for guiding the sheet to the second processing unit, and the post-processing mode is set to the second processing unit. At times, the sheet is retained on a straight path for guiding the sheet to the first processing unit. Then, after the job in each processing unit is completed, the staying sheet is sent to the processing unit, and the subsequent processing is performed.

Japanese Patent No. 5248785

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a post-processing apparatus that can transfer a stagnated sheet to a stacking unit in a short time when transferring a sheet to a first stacking position or a second different stacking position. I have.

  In order to solve the above-described problems, the present invention arranges a buffer section for temporarily retaining a sheet on a path for conveying a sheet to a first accumulation section or a second accumulation section, and accumulates a sheet on this path section. When the sheet is sent to one stacking section, the sheets are superimposed and transferred simultaneously, and when the sheet is sent to the second stacking section, the sheets are transferred one by one.

  The configuration is further described in detail. A transport path for transferring the sheet from the carry-in port (31) to the first stacking section (35) or the second stacking section (49) and a part of the transport path are provided. A buffer unit (Pb) for temporarily storing the fed sheets and a control unit (76) for controlling the conveyance of the sheets sent from the carry-in port to each stacking unit are provided.

  The control unit temporarily stores the sheets sequentially sent to the carry-in port 31 in the buffer unit Pb, and when the sheets are carried into the first stacking unit 35 from the buffer unit Pb, a plurality of sheets are stored in the buffer unit Pb. After the sheets are stacked, they are carried in the stacked state, and when the sheets are carried in from the buffer section Pb to the second accumulation section 49, at least one sheet retained in the buffer section Pb is carried in one by one. The first paper discharge roller and the second paper discharge roller pair are controlled.

In the post-processing apparatus according to the present invention, the staying sheets are accumulated in the first accumulating section in a short time, and the accumulated sheets are accumulated in the second accumulating section in a short time. There was no transfer.

FIG. 1 is an explanatory diagram of an overall configuration of an image forming system according to the present invention. FIG. 2 is an explanatory diagram of a configuration of a post-processing device in the system of FIG. 1. FIG. 3 is an explanatory diagram of a configuration of a first post-processing unit in the post-processing device of FIG. 2. FIG. 3 is an explanatory diagram of a configuration of a second post-processing unit in the post-processing device of FIG. 2. FIG. 3 is an explanatory diagram illustrating a sheet conveyance state in the post-processing apparatus in FIG. 2. (A) is an explanatory view of a state in which a sheet retained in a path buffer unit is transported to a post-processing unit, and (b) is an explanatory diagram of a mechanism for transferring a buffer sheet to a second post-processing unit. FIGS. 7A and 7B are explanatory diagrams of an operation state of transferring a buffer sheet to a first post-processing unit, in which FIG. 7A illustrates a state in which sheets are retained in a buffer unit, and FIG. 1 shows a state of being conveyed toward. FIGS. 7A and 7B are explanatory diagrams of an operation state of transferring a buffer sheet to a first post-processing unit, in which FIG. 7A illustrates a state in which the buffer sheet is positioned at a processing position on a processing tray, and FIG. Indicates the status. FIGS. 9A and 9B are explanatory diagrams of an operation state of transferring a buffer sheet to a second post-processing unit, wherein FIG. 10A shows a state in which sheets are retained in a buffer unit, and FIG. Shows the initial state of the transfer. FIG. 9 is an explanatory diagram of an operation state of transferring a buffer sheet to a second post-processing unit, and is an explanatory diagram illustrating a state where a first sheet is carried into the second post-processing unit from the buffer unit. FIG. 9 is an explanatory diagram of an operation state of transferring a buffer sheet to a second post-processing unit, and is an explanatory diagram showing a state of transporting the last sheet from the buffer unit to the second post-processing unit. FIG. 2 is an explanatory diagram of a control configuration in the image forming system of FIG. 1. 3 is a flowchart illustrating a procedure of a post-processing operation (first post-processing mode) in the image forming system of FIG. 1. 9 is a flowchart illustrating a procedure of a post-processing operation (second post-processing mode) in the image forming system of FIG. 1.

  Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. The image forming system illustrated in FIG. 1 includes an image forming apparatus A that forms an image on a sheet, and a post-processing apparatus B that performs post-processing (finishing processing) on the sheet on which the image is formed. In this image forming system, a host device (such as a computer) that is networked and creates image data is arranged upstream of the image forming apparatus A. Hereinafter, the image forming apparatus A and the post-processing apparatus B will be described in this order.

[Image forming apparatus]
The image forming apparatus A is arranged on the upstream side of the post-processing apparatus B, forms an image on a sheet, and sends the image from the sheet discharge port 21 to the downstream post-processing apparatus B. The illustrated image forming apparatus A includes a sheet feeding unit 11, an image forming unit 13, a sheet discharging unit 19, and a data processing unit 18 in an apparatus housing 10.

  The paper supply unit 11 includes paper supply stackers 12a, 12b, and 12c (paper supply cassettes) for feeding sheets for image formation, and feeds out sheets of a size selected by the operator one by one to the image forming unit 13 on the downstream side.

  The image forming unit 13 forms an image with the designated image data on the sheet of the size selected and fed from the sheet feeding unit 11. As the image forming mechanism, various image forming mechanisms such as an electrostatic printing mechanism, an inkjet printing mechanism, a transfer ribbon printing mechanism, a thermal printing mechanism, and an offset printing mechanism can be adopted.

  Describing the illustrated electrostatic printing mechanism, a latent image is formed on the photosensitive drum 14 by an optical beam (light emitting device) 15 and toner ink is adhered by a developing device 16 to form an image on the drum surface. Then, the image is transferred to the sheet sent from the sheet feeding unit 11 by the charger 17. The paper discharge unit 19 heats the sheet sent from the charger 17 to fix the image, and transfers the image from the paper discharge path 20 to the paper discharge port 21. A duplex path 22 is connected to the paper discharge port 21, the conveyance direction of the sheet conveyed from the paper discharge port 21 is reversed (switchback conveyance), the sheet is reversed, and the sheet is again fed to the image forming unit 13. Then, after an image is formed on the back side of the sheet, the sheet is carried out from the sheet discharge port 21.

  FIG. 23 shows a scanner unit, which is a platen 24 on which a document is set, a reading carriage 25 which scans the document on the platen and reads an image, and an image which transfers the read image data to the data processing unit 18 of the image forming apparatus A. A processing unit 26 is provided.

  In the drawing, a feeder unit 27 separates the original sheets set on the paper feed stacker 28 one by one and feeds them to the platen 24, and stores the read original sheets in the paper discharge stacker 29.

[Configuration of post-processing device]
The post-processing apparatus B connected to the above-described image forming apparatus A accumulates the sheets on which the images are formed in a bundle (for each group) in a bundle and performs the binding process, or the bundle is formed in a bundle. Or the second post-processing mode, in which the sheet is folded, and any post-processing is performed and stored in the downstream storage unit. The illustrated system further includes a “third post-processing mode (printout mode)” for storing the sheet on which the image is formed in the storage unit on the downstream side.

  For this reason, as shown in FIG. 2, the post-processing device B sets a first post-processing unit (first stacking unit; hereinafter the same) 35 for executing the first post-processing mode on the casing 30 and a second post-processing mode. A second post-processing unit (second stacking unit; hereinafter the same) 49 for execution is provided. The sheet is distributed to a first post-processing section 35 and a second post-processing section 49 from a conveyance path 32 having a carry-in port 31 connected to the main body discharge port 21 and conveyed.

[Configuration of transport route]
The transport path 32 includes a straight path 33 and a branch path 34. The branch path 34 is branched from the straight path 33 at a path branching section 32a (hereinafter, referred to as a “branch section”), and is configured to sort sheets carried in from the carry-in port 31 in the straight path direction and the branch path direction. For this reason, the path switching means 44 is disposed in the branching section 32a, and guides the sheet to each path discharge port by a signal from the control means 76 described later.

  The illustrated straight path 33 is a substantially straight path in which the carry-in port 31 is located on one side surface (right side wall) of the casing 30 and the path discharge port 33a is located on the opposite side surface (left side wall). That is, as shown in FIG. 2, a straight path 33 is formed by a substantially linear (may be curved) path that traverses the housing 30 in the horizontal direction, and a path discharge port 33a (hereinafter referred to as a “first discharge port”). ) Is disposed downstream of the first post-processing unit 35.

  The branch path 34 is disposed in a direction intersecting the straight path 33, and the branch path 34 is disposed substantially vertically in the housing 30 in a substantially horizontal direction. As shown in FIG. 2, the branch path 34 branches from the horizontal straight path 33, guides the sheet in the vertical direction, and passes through the path discharge port 34a (hereinafter, referred to as "second discharge port") to the second rear path. The sheet is guided to the processing unit 49.

  A path switching means 44 is disposed in the branching section 32a to guide the sheet sent from the carry-in port 31 to the discharge port (first discharge port) 33a of the straight path 33 or to discharge the sheet of the branch path 34. It is guided to the mouth (second paper ejection port) 34a. For this reason, the path switching means 44 is constituted by a movable guide member (flapper member) and a shift means (operating solenoid, motor, etc .; not shown) for deflecting the angular posture of this member.

In the straight path 33 and the branch path 34, conveying means for conveying a sheet is arranged. In the embodiment shown in FIG. 3, a carry-in roller 45 and a paper discharge roller 46 (first paper discharge roller pair ) are arranged in the straight path 33 in the paper discharge direction, and the roller 45 is in the carry-in port 31 and the roller 46 is paper discharge. The transport roller (intermediate roller) 43 is disposed between the two rollers. The branch path 34 includes a discharge roller 47 (second discharge roller pair ) disposed at a branch path opening (branch portion) 32a, and a third discharge roller (third discharge roller pair ) downstream of the discharge roller 47 . ) Is arranged.

  Each of the rollers 45, 46, 47, and 48 (the carry-in roller and the first, second, and third paper-discharge rollers) is configured such that a conveyance force for conveying the sheet in the conveyance direction is transmitted from a drive motor (not shown). I have. A conveying force for transferring the sheet in the sheet discharging direction is transmitted from the drive motor to the carry-in roller 45 and the intermediate roller 43, and a conveying force (for conveying the sheet in the first sheet discharging direction) to the first sheet discharging roller 46. A forward rotation) and a conveying force (reverse rotation) for conveying the sheet in the branch path direction are transmitted from the drive motor.

  A conveying force for conveying the sheet is transmitted to the second sheet discharging roller 47 from the drive motor in both forward and reverse directions. Further, a conveying force for carrying out the sheet from the second discharge port 34a is transmitted to the third discharge roller 48. The illustrated apparatus is connected so that a conveying force is transmitted from a single drive motor to a carry-in roller 45 and first, second, and second discharge rollers 46, 47, 48 via a clutch mechanism.

  A switchback is provided between the first discharge port 33a and the first post-processing section 35 to reverse the transport direction of the sheet conveyed by the first discharge roller 46 and to retreat the sheet to a predetermined post-processing position. A path 60 (hereinafter, referred to as “first switchback path”) is formed. Similarly, a switchback path 61 (hereinafter referred to as a “second switchback path”) that reverses the conveyance direction when the rear end of the sheet passes through the branch portion 32a and guides the sheet to the second discharge port 34a is provided in the branch path 34. ) Is formed. These switchback paths 60 and 61 are configured by forward / reverse control of a path for guiding a sheet (the straight path 33 and the branch path 34) and a transport roller (the first and second discharge rollers 46 and 47 described above).

  Therefore, the sheet carried in from the carry-in entrance 31 enters the first post-processing section 35 (a processing tray 36 described later) from the straight path 33 from the sheet rear end opposite to the carrying direction, and from the branch path 34 to the second rear section. The sheet enters the processing section (accumulation guide 49a described later) from the rear end of the sheet opposite to the carrying direction. The first switchback path 60 is located downstream and the second switchback path 61 is located upstream in the sheet discharging direction of the straight path 33 (see FIG. 2).

  In the straight path 33, sheet sensors Se1 and Se2 for detecting a sheet passing through the carry-in port 31 and the first sheet discharge port 33a are arranged. The detection signals of these sensors Se1 and Se2 are used as reference signals for sheet conveyance control, for example, control of the guide direction of the path switching means 44, control of starting and stopping of the conveyance rollers, and control of discrimination of sheet jam.

  In the illustrated apparatus, the first discharge roller 46 and the second discharge roller 47 opposed to each other with the branch portion 32a interposed therebetween are in a pressurized state in which the sheet is pressed at a predetermined pressure and in a depressurized state in which the sheet is separated or reduced in pressure. And a pair of rollers separated from each other. Although the configuration is not shown, a pair of rollers that press against each other supports one of the shafts movably in the pressing direction. Then, pressure is applied in a direction in which they are pressed against each other by an urging spring, and the pressing force is released or reduced by a release lever connected to an actuator such as an operating solenoid. By shifting the pressure of the roller pair between the pressurized state and the pressure-reduced state in this way, the pressure is applied when the sheet is moved by the roller pair, and the pressure is reduced when the sheet is transferred by the adjacent roller pair. Do not hinder the transport.

  Then, the roller is shifted between the pressurized state and the pressurized release state by the release lever 67 and an actuator such as the electromagnetic solenoid 48. This configuration is such that when a plurality of sheets are transported in a predetermined direction in an overlapping state, the roller pair is rotated in a pressed state, and when the sheets are transported by an adjacent roller, they are separated from the sheet (or the pressing force is reduced). This is because the transport is not disturbed.

[First post-processing unit]
The first post-processing unit 35 disposed downstream of the first paper outlet 33a will be described with reference to FIG. A processing tray 36 having a paper mounting surface 36a on which a sheet is mounted by forming a step is disposed downstream of the first paper discharge port 33a. A transport rotator 62 (paddle rotator, belt rotator, etc.) that transports the sheet toward a predetermined post-processing position is disposed above the processing tray 36.

  A sheet end regulating means 38 for locking the sheet at a predetermined position (post-processing position) on the paper mounting surface 36a, and an aligning means 39 for positioning the widthwise orientation of the sheet stacked on the paper mounting surface at the reference position. A post-processing means (staple unit) 37 for binding the sheets is provided.

  As shown in FIG. 3, in the processing tray 36, a sheet carry-in unit 42 for guiding a sheet from the first discharge port 33a to the paper stacking surface 36a, and a post-processed sheet (bundle) on the downstream side from the paper stacking surface. A sheet discharging means 40 for discharging to one storage stacker 41 is arranged.

  The sheet carrying means 42 is disposed between the first paper outlet 33a and the processing tray 36, and reverses the transport direction (switchback path) of the sheet carried out from the paper outlet to the sheet loading surface 36a. Send to The sheet carrying means 42 is composed of a lifting roller, a paddle rotating body, a belt rotating body, and the like. The one shown in the figure is constituted by an elevating roller which can move up and down between an operating position for engaging with a sheet conveyed from the first discharge port 33a and a standby position retracted from the first discharge port 33a. The motor is rotated in the forward direction until it is carried out of the motor 33a, and then connected to a not-shown elevating motor and a forward / reverse rotation motor so as to rotate in the opposite direction.

  The sheet unloading means 40 is configured by a conveyor mechanism that reciprocates between the processing position and the storage stacker 41 on the downstream side along the paper loading surface 36a. The conveyor mechanism includes an engaging member 40a that engages with the edge of the sheet bundle on the paper carrying surface, and a belt (not shown) that reciprocates the engaging member along the paper carrying surface. Further, a roller (fixed roller) 63 facing the above-described sheet carrying-in means 42 (elevating roller; the same applies hereinafter) is disposed on the paper loading surface 36a. Transfer to

[Second post-processing unit]
The second post-processing unit 49 disposed downstream of the second paper discharge port 34a will be described with reference to FIG. The second post-processing unit 49 includes a stacking guide 49a for stacking and aligning and stacking the sheets sent from the branch path 34, a binding processing unit 52 for binding and processing the stacked sheet bundle, and a sheet bundle from the center. Folding processing means 53 and 54 for folding are arranged.

  The stacking guide 49a is formed of a guide member having a stacking surface 49b for supporting and stacking the sheet sent from the second sheet discharge port 34a in a vertically upright state (standing posture). In this stacking guide 49a, a leading end regulating means 50 for locking the end portion (leading end portion) of the sheet to regulate the position is movably arranged along the stacking surface. An alignment means 51 for positioning the stacked sheets in the width direction at a reference position is arranged in the stacking guide 49a.

  The binding processing means 52 is constituted by a saddle stapling unit that binds the central portion of the sheet bundle accumulated on the stacking surface 49b. Since the configuration of the staple unit is widely known, description thereof will be omitted. The folding processing means includes a folding roll 53 and a folding blade 54. The folding roll 53 is a pair of pressed rolls, and is connected to a driving motor (not shown) that rotates clockwise in FIG. 4 (direction for discharging the folded sheet).

  The folding blade 54 is formed of a plate-like member that inserts the folding position of the sheet bundle between the rolls, and a shift motor (not shown) reciprocates between a standby position separated from the roll pair and an operating position between the rolls. (Shown). The alignment means 51 is composed of a pair of left and right alignment plates capable of moving the sheet supported on the stacking surface in the width direction, and includes an alignment motor (not shown).

  A discharge path 65 and a discharge roller 66 (fourth discharge roller) for discharging the folded sheet bundle are disposed downstream of the folding roller 53, and a second storage stacker 55 is disposed downstream thereof. I have. The paper discharge path 65 is arranged in a direction substantially perpendicular to the stacking surface 49b of the second post-processing section 49, and carries out the sheet in the same direction as the straight path 33. The second storage stacker 55 is disposed below the first storage stacker 41.

"Buffer part"
In the above-described configuration, the sheet sent to the carry-in entrance 31 is guided from the first discharge port 33a to the first post-processing section 35 via the straight path 33, or is guided to the second post-processing section 49 from the branch path 34. Is done. Then, the sheet bundle accumulated for each copy (each print group) in the first post-processing unit 35 is stored in the first storage stacker 41 after the binding process (first post-processing mode). Further, the sheet bundle accumulated for each copy in the second post-processing unit 49 is stored in the second storage stacker 55 after performing the binding process and the folding process (second post-processing mode).

Therefore, during the post-processing operation in the first post-processing section 35 or the second post-processing section 49, the sheet sent to the carry-in port 31 is retained in the middle of the path until the post-processing operation in the downstream post-processing section is completed. It is necessary to control the conveyance of the sheets to be put on standby. This is because the printing process for forming an image on a sheet by the image forming apparatus A on the upstream side proceeds without interruption (during the post-processing operation).

  For this reason, a path buffer section Pb (hereinafter referred to as a buffer section) is provided in the transport path (the straight path 33 and the branch path 34) to temporarily store sheets sent from upstream during the post-processing operation. Depending on the length of the post-processing time, the number of sheets retained in this path may be one or plural. When the process speed in the upstream image forming apparatus A increases, the number of sheets retained in the buffer unit Pb of the post-processing apparatus B increases.

  In the illustrated device, as shown in FIG. 3, a buffer section Pb is disposed on a straight path 33 and a branch path 34 located downstream of the branch section 32a. In the figure, a buffer unit Pb is provided between a first paper discharge roller 46 (first transport roller; the same applies hereinafter) on the straight path 33 and a second paper discharge roller 47 (second transport roller; the same applies hereinafter) on the branch path 34. And supports the sheet in a state of straddling both rollers (bridge support structure). In other words, the distance between the first discharge roller 46 and the second discharge roller 47 is shorter than the length of the minimum size sheet to be post-processed in the transport direction.

  The first and second paper discharge rollers 46 and 47 are connected to a drive motor (not shown) so as to be able to rotate forward and backward. Then, the control means 76 described later inverts the first discharge roller 46 from the forward rotation to the reverse rotation, guides the sheet sent to the straight path 33 to the branch path 47, and sends the sheet to the buffer unit Pb. The sheet retained in the buffer unit Pb by rotating the first and second discharge rollers 46 and 47 clockwise (forward rotation) at the subsequent sheet supply timing is guided to the first post-processing unit 35, and Then, the sheet is transferred to the second post-processing section 49 by rotating the second paper discharge rollers 46 and 47 counterclockwise (reverse rotation).

  Note that, in the present invention, the first and second transport rollers for temporarily retaining the sheet include a “roller pair 46 disposed at a discharge port (first discharge port) of the straight path 33” and a “branch”. In this case, a roller pair 47 disposed at the entrance of the path 34 is shown. If the pair of rollers is a pair of front and rear rollers that engage with the sheet at a span (interval) shorter than the length of the sheet in the conveying direction, the position is not limited to the sheet discharge port and the path entrance, but may be any location along the path. . Further, the first and second transport rollers are preferably a pair of rollers capable of normal and reverse rotation, but may be constituted by a plurality of pairs of rollers capable of transporting a sheet in a sheet discharging direction and in a direction opposite to the sheet discharging.

  Control of each of the transport rollers (paper discharge rollers) when a sheet stays in the buffer section Pb will be described. The sheet sent to the carry-in port 31 rotates the carry-in roller 45 and the first paper discharge roller 46 (first carry roller) in the paper discharge direction (forward rotation direction; clockwise direction in FIG. 3; the same applies hereinafter), and the rear end of the sheet is rotated. At the stage after passing through the branch portion 32a, the first paper discharge roller 46 is rotated in a direction opposite to the paper discharge (reverse rotation direction; counterclockwise in FIG. 3; the same applies hereinafter). At the same time, the path switching means 44 is deflected to the position for guiding the sheet to the second paper discharge port side (the state shown by the broken line in FIG. 3), and the second paper discharge roller 47 (second transport roller) is rotated counterclockwise in FIG. Then, the sheet is guided to the branch path 34 from the rear end side.

  The control of the path switching means 44 and the conveyance rollers (discharge rollers) 46 and 47 controls the drive mechanism based on the detection signals from the sheet sensors Se1 and Se2. The control means 75, which will be described later, rotates the first paper discharge roller 46 and the second paper discharge roller 47 by a predetermined rotation amount according to the sheet size, and stops both rollers. Then, the sheet sent from the carry-in port 31 is sent to the buffer section Pd of the branch path 34, and temporarily stops at this position.

[Control configuration]
A control configuration in the image forming system of FIG. 1 will be described. FIG. 12 is a block diagram of the control configuration, which includes an image forming control unit 70 and a post-processing control unit 75. The image forming control unit 70 includes a paper feed control unit 72 and a mode setting unit 71. The mode setting means 71 includes an input unit 73 such as a control panel. The image forming control section 70 forms an image on a sheet under the image forming conditions set by the mode setting means 71. The paper feed control unit 72 controls a paper feed operation for feeding a sheet of the size set by the mode setting unit 71 from the paper feed unit 11 to the image forming unit 13. The mode setting means 71 sets image forming conditions such as color / monochrome setting, reduction ratio setting, and cover printing setting. At the same time, the mode setting means 71 sets a post-processing mode for post-processing the sheet on which the image is formed.

  The illustrated post-processing apparatus B is configured to be capable of setting a first post-processing mode (edge binding processing mode), a second post-processing mode (bookbinding binding mode), and a third post-processing mode (printout mode). ing. In the first post-processing mode, the sheets on which images have been formed are aligned and stacked on the processing tray 36 (first stacking unit), bound, and stored in the first storage stacker 41. In the second post-processing mode, the sheets on which images have been formed are aligned and stacked in the stacking guide 49a (second stacking unit), subjected to saddle stitching, folded, and stored in the second storage stacker 55. In the third post-processing mode, the sheet sent to the carry-in entrance 31 is stored in the first storage stacker 41 without post-processing. Here, the “edge binding process” is a finishing process of binding at one or a plurality of locations along the end face of the collated sheet bundle, and the “saddle binding process” is a finishing process of the collated sheet bundle. This means finishing processing in which a plurality of locations in the central portion (sheet center) are bound.

  The post-processing control unit 75 includes a control CPU 76 for operating the post-processing device B in accordance with a specified post-processing mode (finishing process), a ROM 77 storing an operation program, and a RAM 78 storing control data. The control CPU 76 includes a conveyance control unit 76a that controls the conveyance of the sheet sent to the carry-in entrance 31, a stacking operation control unit 76b that controls the sheet stacking operation, and a binding operation control that controls the sheet bundle binding process. And a folding operation control unit 76d for controlling a bundle folding operation of sheets.

Each of the control units 76a to 76d includes an operation mode in which the first post-processing unit 35 performs post-processing on the sheet (first post-processing mode) and an operation mode in which the second post-processing unit 49 performs post-processing on the sheet (second post-processing). Mode) to operate one of the modes.

  The transport control section 76a is connected to the control circuit (driver) of the carry-in roller 45 (the intermediate roller 43) and the drive motor (not shown) of the first paper discharge roller 46 in the transport path 32, and the transport path 32a. , A detection signal is received from the sheet sensors Se1 and Se2 disposed in the first position. The transport controller 76a is connected to a control circuit (driver) of a drive motor (not shown) for the second and third discharge rollers 47 and 48, and receives a detection signal from the sheet sensor Se3 in the branch path 34. .

  The transport control unit 76a causes the sheet sent to the carry-in port 31 to stay in the buffer unit Pb during the processing operation (for example, the post-processing operation, the folding processing operation, etc.) in the first and second post-processing units 35 and 49. Execute control. Therefore, the transport control unit 76a includes a buffer sheet number calculating unit 79 for calculating the number of sheets to be retained during the post-processing operation, and a buffer sheet transport amount setting unit 80 for transporting the buffer sheet at the carry-in port 31 to the buffer unit Pb. Are inherent. The details of the buffer sheet number calculation means 79 and the buffer sheet conveyance amount setting means 80 will be described later.

  The drive motor for the straight path 33 and the drive motor for the branch path 34 may be configured as a single motor or may be configured as individual motors. In the case of a single motor, the drive is transmitted to each transport roller via the clutch means. The stacking operation control unit 76b sends a control signal to the drive circuit of the forward / reverse rotation motor of the above-described sheet carry-in unit 42 (elevation roller) and the discharge motor of the sheet carry-out unit 40 in order to stack the sheets on the first stacking unit 35. Send. Further, the binding operation control unit 76c transmits a control signal to a drive circuit of a drive motor (not shown) incorporated in the end binding stapling device 37 of the first stacking unit 35 and the saddle stapling device 52 of the second stacking unit 49. I do.

  The folding operation control unit 76d is connected to a drive circuit of a roll drive motor that drives and rotates the folding roll pair 53, and the control unit includes the second and third discharge rollers 47 and 48 of the branch path 34 and the stacking guide. A control signal is transmitted to a control circuit of a shift means for controlling the movement of the tip regulating means 50 of 49a to a predetermined position, and a detection signal is received from a sheet sensor (not shown) arranged on these paths.

[Buffer sheet number calculation means]
Next, the buffer sheet number calculating means 79 will be described. The calculating means 79 is included in the transport control section 76a. The calculating means 79 determines the length (size information) of the sheet sent from the image forming apparatus A in the conveying direction and the post-processing time (for example, the sheet alignment time + the binding processing time + the folding processing time) stored in the RAM 78 in advance. The number of sheets to be retained in the path is calculated from (+ processing sheet unloading time). This is calculated by [Bs = Td / Tp] (Equation 1), where Td is the post-processing time, Tp is the process time of image formation, and Bs is the number of buffer sheets. In this way, the number of sheets in which the sheets sent from the image forming apparatus A stay in the buffer unit Pb during the post-processing operation in the first and second post-processing units 35 and 49 is set.

[Buffer sheet conveyance amount setting means]
When the buffer sheet calculated by the buffer sheet number calculating means 79 is transferred to the buffer unit Pb and temporarily stopped (resides), the transport control unit 76a offsets the buffer sheet back and forth in the path direction and superimposes it. Stop. This is to transfer the buffer sheet to the first and second post-processing units 35 and 49 quickly (speedily) and surely (without jam) after the post-processing operation is completed.

  The illustrated apparatus conveys the first buffer sheet n to the buffer unit Pb, offsets the second buffer sheet by a preset offset amount δ upstream in the conveying direction (shifts the position), and stops. . For this reason, the transport control unit 76a sets the transport amounts of the first and second discharge rollers 46 and 47 according to the number of buffer sheets (to different transport amounts) based on, for example, a signal at which the leading edge of the sheet is detected by the sheet discharge sensor Se2. Set.

  For example, when the transport amount of the first buffer sheet is set to (Ln), the transport amount of the second buffer sheet is (Ln−δ), and the transport amount of the third buffer sheet is (Ln−2). × δ), and thereafter, similarly, gradually reduce the transport amount. The reason why the plurality of sheets are retained by being displaced (offset) in the transport direction will be described later.

[Description of post-processing operation]
The post-processing control unit 75 configured as described above causes the post-processing device B to execute the next processing operation. As described above, the post-processing control unit 75 includes the first post-processing mode (edge binding processing in the first post-processing unit 35), the second post-processing mode (bookbinding processing in the second post-processing unit 49), and the third post-processing mode. (Print sheet storage processing in the first post-processing unit 35). Then, the sheets sent from the image forming apparatus A according to the mode set by the mode setting means 71 are collected in the first post-processing section 35 or the second post-processing section 49 and post-processed. In the stackers 41 and 55. Hereinafter, the description will be made in the order of [explanation of sheet conveyance order to post-processing unit], [explanation of buffer sheet transfer operation], [first post-processing mode operation], and [second post-processing mode operation].

[Explanation of sheet conveyance order to post-processing unit]
As shown in FIG. 5, the sheet at the carry-in entrance 31 is transferred to the first post-processing section 35 via the first switchback path 60 and to the second post-processing section 49 via the second switchback path 61. The sheets are sent to the carry-in entrance 31 in the order of image formation (n) (n + 1) (n + 2). The control means (control CPU) 76 transfers the sheet from the straight path 33 to the first post-processing section 35 and from the branch path 34 to the second post-processing section 49. The first and second post-processing units 35 and 49 temporarily store the sheet in the buffer unit Pb during the post-processing operation time.

  In the first post-processing unit 35, the sheets sent to the carry-in entrance 31 are stacked and stacked in the order (n, n + 1, n + 2) above the paper loading surface 36a of the processing tray 36. Also in the buffer section Pb, they are accumulated in the path in the same order (n, n + 1, n + 2) and stay there. Further, the second post-processing unit 49 also stacks and accumulates in the same order (n, n + 1, n + 2). At this time, the first post-processing unit 35 and the buffer unit Pb have the same vertical position of the sheet, but the second post-processing unit 49 integrates them so that the vertical position of the sheet is different.

[Explanation of transfer of buffer sheet to post-processing unit]
The plurality of sheets retained in the buffer unit Pb are simultaneously transferred in a state of being stacked in a bundle when being transferred to the first post-processing unit 35, and are transferred to the second post-processing unit 49 when the sheets are transferred. The sheets are transported one by one in the order in which they were sent to 31. The state will be described with reference to FIG. The sheet is sent to the carry-in entrance 31 in the order of image formation (n) (n + 1) (n + 2). The sheets are stacked on the buffer unit Pb in the same order, that is, (n), (n + 1), and (n + 2).

  When the post-processing operation of the post-processing unit 35 (49) is completed, the control unit 76 rotates the first and second discharge (conveyance) rollers 46 and 47 located in the buffer unit Pb in the sheet conveying direction. Control. At this time, the control means 76 simultaneously transfers the buffer sheets stacked in a bundle to the first processing unit 35 in a bundle state, and sends the buffer sheets stacked in a bundle to the second post-processing unit 49. Transfer one by one.

[First post-processing mode]
The operation procedure in the first post-processing mode (edge binding processing mode) will be described with reference to FIG. When the apparatus power is turned on, the control means 76 executes an initialization operation (St01). Although the description of the initialization operation is omitted, the path switching unit 44 guides the sheet along the straight path 33 in the sheet discharging direction. The front and rear ends of the sheet are detected by the sensors Se1 and Se2, and a timer is started based on the detection signal (St02). Which of the detection signals of the two sensors Se1 and Se2 is used as a reference to determine (monitor) the sheet conveyance state is appropriately set.

  At the timing when the leading edge of the sheet is carried out of the first paper outlet 33a, the elevating roller 42 (sheet carrying means) is lowered from the standby position to the operating position where the sheet engages with the sheet. At the same time, the lifting roller 42 is rotated in the sheet discharging direction to transfer the sheet in the sheet discharging direction (St03). At the timing when the rear end of the sheet is carried out from the first paper discharge port 33a, the elevating roller 42 is reversed in the direction opposite to the paper discharge (St04). Then, the sheet is conveyed from the rear end side into the processing tray 36 disposed downstream of the first sheet discharge port 33a with the transport direction reversed (switched back), and is brought into contact with the sheet end regulating means 38 on the tray. It is stopped (St05). Then, the control means 76 positions the sheet carried into the first post-processing section 35 at the reference position in the width direction.

  The control unit 76 repeats the above-described operations from Step St02 to Step St05 until a job end signal is received from the image forming apparatus A. As a result, the sheets on which images are formed by the image forming apparatus A are collated and accumulated in the first post-processing unit 35. Upon receiving the job end signal from the image forming apparatus A, the control unit 76 causes the post-processing unit 37 (stapler unit) of the first post-processing unit 35 to execute a post-processing operation (St06). Next, when receiving the operation end signal from the post-processing means 37, the control means 76 carries out the processed sheet bundle to the first storage stacker 41 on the downstream side (St07).

  At the same time as the execution of the above-mentioned post-processing operation, the control unit 76 sets the post-processing mode from the image forming apparatus A (in this case, the first post-processing mode), the image forming processing speed (process speed), and the sheet size information. And retrieves post-processing operation time data in the first post-processing unit 35 stored in the RAM 78 of the post-processing device B. The number of sheets to be retained in the path is calculated by the number-of-buffers calculating means 79 based on the information, and the transport amount of the buffer sheets is calculated by the transport amount setting means 80 (St08).

  When the succeeding sheet arrives at the carry-in entrance 31, the control means 76 detects this by the carry-in sensor Se1, and obtains the estimated time for the trailing end of the sheet to reach the branch portion 32a from the timer time of the RAM 78. Then, the timer is started by the detection signal of the carry-in sensor Se1.

  Next, when the estimated time that the rear end of the sheet has passed the branch portion 32a has elapsed (timer up), the control means 76 changes the path switching means 44 in the direction of the broken line in FIG. The paper discharge roller 47 is rotated in the direction opposite to the paper discharge (St09). Then, the sheet enters the branch path 34 from the rear end side, and the control means 76 rotates the first and second discharge rollers 46 and 47 by the amount set by the conveyance amount setting means 80 and stops (St10).

  Next, when the succeeding next sheet (n + 1) reaches the carry-in entrance 31, the control unit 76 similarly carries this sheet into the buffer unit Pb. The transport amount of this sheet is set to be smaller by the offset amount δ than the transport amount of the previous sheet (n). Similarly, the next sheet (n + 2) is also conveyed to the buffer section Pb and conveyed by a smaller amount by the offset amount δ than the previous sheet (n + 1) (St11).

  As described above, the sheet sent from the image forming apparatus A during the execution of the post-processing operation in the first post-processing unit 35 is in a state of bridging between the straight path 33 and the branch path 34 with the branch part 32a interposed therebetween (the bridge state). ) Is temporarily held (execution of St11). Then, the control means 76 receives a sheet carry-in permission signal from the first post-processing section 35 (St12). Based on this signal, the first and second paper discharge rollers 46 and 47 rotate in the paper discharge direction (clockwise in FIG. 3). Then, the buffer sheets are transported from the buffer section Pb to the first paper discharge port 33a in a state where a plurality of the buffer sheets are overlapped (St13). The control means 76 rotates the elevating roller 42 and the transport rotating body 62 to abut the sheet bundle against the sheet end regulating means 38 of the first post-processing section 35 of the post-processing apparatus B and stops the sheet bundle.

[Second post-processing mode]
Next, a second post-processing mode (bookbinding processing mode) will be described with reference to FIG. When the apparatus power is turned on, an initialization operation of the apparatus is executed (St01). When a sheet is sent to the carry-in entrance 31, the leading end is detected and a timer is started (St02). At an estimated time (timer up) at which the rear end of the sheet has passed the branch portion 32a, the path switching means 44 is deflected, and the first and second sheet discharge rollers 46 and 47 are rotated in the opposite direction to the sheet discharge to move the sheet straight. From 33, it is guided to a branch route 34. This sheet is sent from the second discharge port 34a to the second post-processing section 49 and is stacked on the stacking guide 49a (St20). When the control means 76 receives the job end signal from the image forming apparatus A, it moves the sheets stacked on the stacking guide 49a to the binding processing position and performs the binding processing by the binding means (St21).

  Next, the control means 76 moves the sheet bundle to the folding position, rotates the folding roll pair 53 in the folding direction, and simultaneously moves the folding blade 54 from the standby position to the operating position. Then, the sheet bundle is folded from the center, and a folding operation is performed (St22). After the execution of the folding process, the sheet bundle is sent to the second storage stacker 55 and stored (St23).

  Simultaneously with the execution of the post-processing operation, the control means 76 calculates the number of sheets to be retained by the buffer sheet number calculating means 79 and the transport amount of each buffer sheet by the transport amount setting means 80 as in the first post-processing mode ( St24).

  Then, when the succeeding sheet arrives at the carry-in port 31, the controller 76 conveys the succeeding sheet to the buffer unit Pb and makes it stay there, as in the first post-processing mode (St25). Similarly to the first post-processing mode, the buffer sheet stays in a state in which a plurality of sheets are overlapped (in a superimposed manner) with the transport amount reduced by the offset amount δ.

  As described above, the sheet sent from the image forming apparatus A during the execution of the post-processing operation (the binding processing operation and the folding processing operation) in the second post-processing unit 49 is interposed between the straight path 33 and the branch path 34 with the branch part 32a interposed therebetween. Temporarily (bridge state). Then, the control means 76 receives a sheet carry-in permission signal from the second post-processing section 49 (St26). Based on this signal, the third paper discharge roller 48 is rotated in the paper discharge direction (counterclockwise direction in FIG. 3). Then, the buffer sheet n that has been retained first is carried into the stacking guide 49a from the second paper discharge port 34a.

  At this time, the stopper 56 is locked at that position so that the overlapping subsequent buffer sheets (n + 1, n + 2) are not drawn. Then, the control means 76 transfers the plurality of sheets retained in the buffer section Pb to the accumulation guide 49a in the order in which the sheets are retained sequentially. At this time, the conveying speed of the sheet (the peripheral speed of the third discharge roller 48) is set higher than the process speed of the image forming apparatus A. The operation of transferring the buffer sheet to the second post-processing section 49 will be described later.

As described above, the sheet sent from the image forming apparatus A during the execution of the post-processing operation in the second post-processing unit 49 is transferred to the buffer unit disposed between the straight path 33 and the branch path 34 with the branch unit 32a interposed therebetween. Pb, and is temporarily held in a state of being bridged by the first discharge roller 46 and the second discharge roller 47 at a predetermined interval. (Execution of St25). Then, when the second post-processing section 49 becomes capable of carrying in the sheets, the control means 76 sends the buffer sheets (n to n + 2) one by one from the second paper output port 34a in the order of sending (the order of being sent to the carry-in port 31). It is transferred to the accumulation guide 49a. After all the buffer sheets have been conveyed onto the stacking guide, subsequent sheets are stacked thereon.

  The sheet sent from the image forming apparatus A to the carry-in port 31 during the operation of transferring the buffer sheet to the accumulation guide 49a is retained in the buffer unit Pb. Then, the conveyance is repeated until all the sheets are transferred from the buffer unit Pb to the second post-processing unit 49. For this purpose, the speed Vb at which the buffer sheet is transported to the second post-processing unit 49 (the peripheral speed of the third discharge roller 48 in the illustrated embodiment) is changed to the speed Va (process speed) at which the image forming apparatus A forms an image. ) It is necessary to set a higher speed (Vb> Va). When the speed difference reaches the transport amount of the staying sheets, all the staying sheets are transferred to the stacking section 49 on the downstream side.

[Explanation of buffer sheet transport operation status]
"First post-processing mode"
The transport state of the buffer sheet in the first post-processing mode will be described with reference to FIG. FIG. 7A shows a state in which a plurality of sheets are conveyed to the buffer unit Pb and temporarily stay there. The sheet sent from the carry-in entrance 31 to the buffer unit Pb is stacked on the first sheet (n), the second sheet (n + 1), and the third sheet (n + 3) in that order. The sheet is held by a second sheet discharging roller 47. The plurality of sheets are stacked in a scale in the feeding order (the order in which they are sent to the carry-in entrance 31) with the offset amount δ.

  When loading the buffer sheet into the first post-processing unit 35, the control unit 76 controls the stopped first and second discharge rollers 46 and 47 to discharge the sheet as shown in FIG. It rotates in the direction (clockwise in the figure) to guide through the mouth 33a. Then, the plurality of superimposed sheets are sent from the first discharge port 33a to the first stacking unit (processing tray) 35, and the sheet is regulated to the sheet end regulating unit 38 in the state of FIG. Hit.

  At this time, a conveying force is applied to the plurality of sheets from the conveying rotating body 62. As shown in FIG. 8B, the conveying force (f1, f2, f3) is the largest in the conveying force f3 acting on the uppermost superimposed sheet (n + 2) engaged with the conveying rotating body 62. The conveying force f2 of the lower sheet (n + 1) decreases in the order of f1. At this time, each sheet is displaced so as to approach the sheet end regulating means 38 by the offset amount δ.

  Therefore, in the sheets that are shifted by a predetermined amount in the order of feeding and stacked, the sheet located in the lowermost layer of the overlap is closest to the stopper (sheet end regulating means 38), and the sheet located in the uppermost layer of the overlap is farthest from the stopper. It is misaligned to be. Contrary to this, the maximum conveying force is applied to the sheet located on the uppermost layer with respect to the conveying force f applied to each sheet.

"Second post-processing mode"
The transport state of the buffer sheet in the second post-processing mode will be described with reference to FIGS. FIG. 7A shows a state in which a plurality of sheets are conveyed to the buffer unit Pb and temporarily stay there. The sheet sent from the carry-in entrance 31 to the buffer unit Pb is stacked on the first sheet (n), the second sheet (n + 1), and the third sheet (n + 3) in that order. The sheet is held by a second sheet discharging roller 47. The plurality of sheets are stacked in a feeding order (order sent to the carry-in entrance) in a scale-like manner with an offset amount δ. The offset amount δ is set to the same or a different interval from the offset amount in the first post-processing mode.

  When the sheet can be carried into the second post-processing unit 49 (when the post-processing operation in the second post-processing unit is completed), the control unit 76 outputs the sheets retained in the buffer unit Pb one by one in the order of their feeding. The sheet is carried into the stacking guide 49a from the second sheet discharge port 33a. Therefore, the control means 76 rotates the second discharge roller 47 and the third discharge roller 48 in the sheet conveying direction. At this time, the first paper discharge roller 46 rotates in the same direction or is separated from the sheet.

  Next, the control means 76 shifts the first paper discharge roller 46 and the second paper discharge roller 47 to a state where they are separated from the sheet (standby posture). Then, as shown in FIG. 10, the sheet is nipped by the third discharge roller 48, and is fed to the accumulation guide 49a by the rotation. At this time, the locking stopper 56 is operated so that the overlapping upper sheets (n + 1, n + 2) are not fed along.

  The plurality of sheets retained in the buffer section Pb in this manner are sent to the accumulation guide 49a in order from the lowermost sheet (n; the sheet retained first) to the upper sheet (n + 1, n + 2).

  The transport mechanism of the branch path 34 shown in FIG. 6B will be described. As described above, the second paper discharge roller 47 and the third paper discharge roller 48 are arranged at an interval in the branch path 34, and the sheet is transferred from the second paper discharge port 34a to the second post-processing unit (stacking guide 49a). It is configured to send. Between the third discharge roller 48 and the second discharge roller 47, a separating means for preventing double feeding of the sheets is arranged, and the sheet when one of the overlapped sheets (the lowermost sheet) is carried out is discharged. Prevent them from being dragged.

  FIG. 11 shows a state in which the succeeding sheet has been sent from the image forming apparatus A to the carry-in entrance 31 during the operation of transporting the sheets (n, n + 1, n + 2...) Retained in the buffer section Pb to the second post-processing section 49. Is shown. In this state, at the first paper discharge roller 46, the rear end of the buffer sheet is sent in the direction of arrow A in the figure, the succeeding sheet sent from the carry-in port 31 is sent in the direction of arrow B, and both sheets overlap in the opposite direction. Move in passing directions.

  Then, the control means 76 rotates the third discharge roller 48 in the direction of the arrow in FIG. (Either the second paper discharge roller 47 rotates in the same direction, or stops and separates.) The sheet retained in the buffer unit Pb is transferred from the second paper discharge port 34a to the second post-processing unit 49. Sent to At this time, the control means 76 separates the first paper discharge roller 46 (the roller pair). As a result, the progress of the succeeding sheet sent to the first sheet discharging roller 46 in the opposite direction is not hindered.

  Although not shown, one of the pair of rollers is axially supported so as to be movable in a pressing direction and a separating direction, and is biased by a biasing spring in the pressing direction. A release lever is provided for moving (shifting) the movable roller in a direction of separating the movable roller against the spring, and the release lever is moved by driving means such as an operating solenoid or an operating cam.

  The separating means shown in FIG. 6B includes a braking lever 56 having a locking portion, and an operating solenoid 57 that swings the braking lever between a standby position and an operating position. When the lower sheet (for example, the first buffer sheet) is transferred from the second discharge port 34a to the stacking guide 49a, the upper sheet (the second buffer sheet) is prevented from being locked and fed together. I have.

Reference Signs List A Image forming apparatus B Post-processing apparatus 31 Carry-in entrance 32 Transport path 32a Branch 33 Straight path 33a First discharge port 34 Branch path 34a Second discharge port 35 First post-processing section (first stacking section)
36 processing tray 37 post-processing means (stapler unit)
41 First storage stacker 42 Elevating roller (sheet carrying means)
43 Transport roller (intermediate roller)
44 Route switching means 45 Conveying roller (loading roller pair)
46 First paper discharge roller (first paper discharge roller pair)
47 Second paper ejection roller (second paper ejection roller pair)
48 Third discharge roller (third discharge roller pair)
49 Second Post-Processing Unit (Second Stacking Unit)
49a Stacking guide 52 Saddle stitching means 56 Brake lever 66 Discharge roller (fourth discharge roller)
70 image forming control unit 75 post-processing control unit 76 control unit 79 buffer sheet number calculation unit 80 transport amount setting unit Pb buffer unit

Claims (7)

A loading port for receiving sheets,
A path for guiding the sheet received from the carry-in port toward the first discharge port; and a second discharge port that branches off from the path via a branch portion and is different from the first discharge port. A conveyance path including a branch path that guides the sheet received from the carry-in port toward the conveyance path;
A first pair of discharge rollers provided on the path between the branching section and the first discharge port and conveying a sheet toward the first discharge port;
A second discharge roller pair provided on the branch path and configured to convey a sheet toward the second discharge port;
A first stacking unit that stacks the sheets conveyed by the first discharge roller pair;
A second stacking unit for stacking the sheets conveyed by the second sheet discharging roller pair;
At least one of the first paper discharge roller pair and the second paper discharge roller pair presses and holds the sheet received from the carry-in port and stays using a part of the transport path, and the first paper discharge roller pair. And a buffer unit capable of superimposing a stagnant sheet stagnated by using the second pair of paper discharge rollers and a subsequent sheet received from the carry-in port in a bundle.
When transporting the staying sheet to the first stacking unit, a plurality of sheets including the staying sheet are bundled and transported from the first discharge roller pair to the first stacking unit;
When transporting the staying sheet to the second stacking unit, the first sheet discharging roller pair and the second sheet discharging roller are transported one by one from the second sheet discharging roller pair to the second stacking unit. And a control means for controlling the second paper discharge roller pair.   The buffer unit includes a first buffer area in the transport path for retaining sheets transported to the first stacking unit, and a second buffer area for retaining sheets transported to the second stacking unit. 2. The post-processing device according to claim 1, wherein the first buffer area and the second buffer area partially overlap. A third sheet transporting unit that is located between the second sheet discharging roller pair and the second stacking unit and that conveys the sheet conveyed by the second sheet discharging roller pair from the second sheet discharging port to the second stacking unit; A discharge roller pair,
The controller presses and holds the sheet with at least the second discharge roller pair of the first discharge roller pair and the second discharge roller pair when conveying the staying sheet to the first stacking unit. And the plurality of sheets including the stagnated sheets are conveyed in a bundle by the first paper discharge roller pair and the second paper discharge roller pair, and the stagnated sheets are conveyed to the second stacking unit. When the first discharge roller pair and the second discharge roller pair are used, at least the first discharge roller pair presses and holds a sheet with the first discharge roller pair, and then holds the sheet. in order to convey the residence sheet in the second sheet discharge roller pair and the third pair of sheet discharge rollers, wherein for controlling said first sheet discharge roller pair, the second pair of sheet discharge rollers and the third discharge roller pair Item 3. The post-processing device according to item 1 or 2. When the control unit conveys the staying sheet to the first stacking unit, at least the second paper discharge roller pair and the second paper discharge roller pair excluding the third paper discharge roller pair When the sheet is pressed and held by the discharge roller pair , and when the staying sheet is transported to the second stacking unit, the first discharge roller pair and the second discharge roller pair excluding the third discharge roller pair 4. The control unit according to claim 3, wherein the first discharge roller pair , the second discharge roller pair, and the third discharge roller pair are controlled so that at least the first discharge roller pair presses and holds the sheet. Post-processing equipment. The buffer unit, when conveying the staying sheet to the first stacking unit,
The post-processing apparatus according to claim 1, wherein the plurality of sheets including the staying sheets are stacked on top of each other in the order in which the sheets are received from the carry-in port. The first paper discharge roller pair is configured to be able to press and separate freely,
The control means presses the first discharge roller pair when conveying the staying sheet to the first stacking unit, and presses the first discharge roller when conveying the staying sheet to the second stacking unit. The post-processing apparatus according to claim 1, wherein the first discharge roller pair is controlled to separate the pair. An image forming apparatus for forming an image on a sheet,
A post-processing device for post-processing the sheet sent from the image forming apparatus,
Composed of
The image forming system according to claim 1, wherein the post-processing device is the post-processing device according to claim 1.

Images