JP2018131281A - Sheet discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet discharge device capable of conveying accurately a sheet to a predetermined position on a mounting surface of the sheet.SOLUTION: Braking of a sheet (S) by nipping the sheet with a pair of sheet holding members (91, 93) is variably controlled according to at least any one of basis weight information of the sheet, size information, paper quality information and sheet discharge number information to thereby reduce dispersion in a loading position of the sheet in a sheet loading part. Braking of the sheet is variably controlled by variation of a nipping force applied by nipping the sheet with the sheet holding members, variation of an acting direction of a nipping force applied by nipping the sheet with the sheet holding members, or variation of timing of nipping the sheet with the sheet holding members.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a paper discharge device.

In general, in an image forming apparatus configured with a post-processing device such as a printer or a copying machine, a plurality of sheets on which an image has been formed is temporarily stored inside the apparatus or discharged outside the apparatus. A paper mounting table such as a paper discharge tray is provided for loading stacked paper.
Conventionally, when the paper is discharged to these paper placement tables, the placement position is shifted between the paper transporting roller immediately before the paper placement table and dropping and placing on the paper placement table by its own weight, There was a problem that the paper was not placed on the paper placement table with the edges of the paper aligned.
This problem is likely to occur regardless of whether the loading surface of the paper mounting table is horizontal or inclined, especially when the paper transport speed is high or when the environmental conditions are severe, such as high temperature and high humidity or low temperature and low humidity. Easy to get up in case.
In order to improve the alignment of the paper placed on the paper placement table, it is necessary to stabilize the behavior of the ejected paper, and a grip conveyance system is known as a means for holding and transporting the paper. (Patent Documents 1 and 2).

In the conventional grip transport system, as shown in FIGS. 13A and 13B, the paper S transported in the discharge direction E by the paper discharge roller 80a at a predetermined speed is the final paper discharge roller 80a before the paper placement surface SS. Then, the rear end of the sheet S is clamped by a pair of sheet clamping members 91 and 93.
Thereafter, as shown in FIG. 13C, the sheet holding members 91 and 93 move to a predetermined position while holding the sheet S so that the sheet S follows the movement of the sheet holding members 91 and 93.

JP 2011-201668 A JP2013-151345A

However, according to the research of the present inventors, it has been found that there are the following problems.
FIG. 14 shows a movement trajectory in the discharge direction E of the rear end position of the sheet S until it reaches a predetermined position on the sheet placement surface SS with the horizontal axis as time.
In the graph of FIG. 14, a region g1 indicates a region where the paper S is moved by the paper discharge roller 80a before the paper clamping members 91 and 93 touch the paper S. A region g1 corresponds to the scene of FIG.
Subsequently, a region g2 indicates a region where the sheet S is braked (decelerated) by the sheet clamping members 91 and 93 being pressed, and the region g2 corresponds to the scene of FIG.
Subsequently, a region g3 shows a region where the paper S is being carried to a predetermined position by the movement of the grip portion of the paper clamping members 91 and 93 holding the paper S. The region g3 is shown in the scene of FIG. Correspond. The last region g4 is a region that has reached a predetermined position.
In order to sandwich the paper S conveyed at a predetermined speed by the paper discharge roller 80a by the paper clamping members 91 and 93 at an appropriate position, the paper S conveyed by the paper discharge roller 80a is braked and decelerated, and then the paper is The sheet holding members 91 and 93 holding the predetermined position of S need to move to the predetermined position, and it is desirable that the movement path of the rear end of the sheet as shown in FIG.

FIG. 15 shows the movement trajectory of the trailing edge of the paper, similar to FIG. 14, but shows various paper weight, size, and paper quality conditions.
As shown in FIG. 15, it can be seen that, although the region g1 has the same moving speed, the degree of braking in the region g2 is different, which affects the stop position in the final region g4.
According to the research of the present inventor, it has been found that the cause of the difference in braking condition in the region g2 is the difference in basis weight, size, and paper quality of the paper. It was also found that in the case of a paper having a small basis weight, braking is too strong in the region g2 and the paper may be wrinkled.

  The present invention has been made in view of the above-described problems in the prior art. A sheet that moves to a sheet placement surface at a predetermined speed is sandwiched by a sheet sandwiching member, and the sheet sandwiching member is moved to move the sheet to the sheet. It is an object of the present invention to provide a paper discharge device that transports paper onto a placement surface, and accurately transports the paper to a predetermined position on the paper placement surface without damaging the paper.

The invention according to claim 1 for solving the above-described problems is a paper stacking unit for stacking sheets discharged one by one or a plurality of sheets stacked by the discharge unit;
A paper position detection sensor for detecting the position of the paper being moved by the discharging means;
A pair of sheet nipping members for nipping the sheet in a state where each sheet or a plurality of sheets are stacked and moving the sheet to the sheet stacking unit;
A drive mechanism for the sheet clamping member;
A control unit that controls the operation of the pair of sheet clamping members via the drive mechanism based on a detection signal from the sheet position detection sensor;
The control unit uses at least one piece of information on basis weight information, size information, paper quality information, and same number of pieces of paper as information on the number of sheets to be discharged in a single sheet or in a stacked state. Accordingly, the paper discharge device reduces the variation in the paper placement position on the paper stacking unit by variably controlling the braking of the paper by the narrow pressure of the pair of paper clamping members.

  According to a second aspect of the present invention, the control section variably controls the braking of the paper by variably controlling a narrow pressure for narrowing the paper by the pair of paper clamping members. It is.

  According to a third aspect of the present invention, the control unit variably controls the braking of the paper by variably controlling an action direction of a narrow pressure for constricting the paper by the pair of paper clamping members. This is a paper discharge device.

  According to a fourth aspect of the present invention, in the paper discharge device according to the first aspect, the control unit variably controls the braking of the paper by variably controlling the timing at which the paper is narrowed by the pair of paper clamping members. is there.

In the invention according to claim 5, a plurality of the paper position detection sensors are arranged along a paper transport path by the discharge means,
The control unit triggers the control to start the operation of the pair of sheet clamping members triggered by the detection by the upstream sheet position detection sensor on the sheet conveyance path, and the detection by the downstream sheet position detection sensor. The sheet discharge device according to claim 4, wherein the timing for narrowing the sheet by the pair of sheet nipping members is variably controlled by selecting the control to start the operation of the pair of sheet nipping members.

  According to the present invention, the braking of the sheet due to the narrow pressure of the pair of sheet clamping members is variably controlled according to at least one of the basis weight information, the size information, the paper quality information, and the number-of-sheets information. Therefore, control according to the quantity and quality of the paper to be discharged becomes possible, and the paper can be accurately conveyed to a predetermined position on the paper placement surface without damaging the paper.

1 is an overall configuration diagram of an image forming system in the present embodiment. FIG. 6 is a perspective view illustrating a paper discharge mechanism and a paper nipping and conveying unit. It is a block diagram which shows the control structure of an image forming system. It is sectional drawing in the AA of FIG. 2, Comprising: It is a figure for demonstrating operation | movement of a pressing member and a supporting member. It is sectional drawing in the AA of FIG. 2, Comprising: It is a figure for demonstrating operation | movement of a pressing member and a supporting member. It is sectional drawing in the AA of FIG. 2, Comprising: It is a figure for demonstrating operation | movement of a pressing member and a supporting member. It is a flowchart of selection of braking nature in this embodiment. FIG. 3 is a schematic cross-sectional view taken along the line AA in FIG. FIG. 3 is a schematic cross-sectional view taken along line AA in FIG. 2 and relates to a variable braking example 1; FIG. 3 is a schematic cross-sectional view taken along line AA in FIG. 2 and relates to a variable braking example 2; It is a schematic diagram showing a moving mechanism of a pressing member that is one of the sheet clamping members. FIG. 3 is a schematic cross-sectional view taken along line AA in FIG. 2 and relates to a variable braking example 3; It is a figure which shows the paper discharge operation | movement in the conventional grip conveyance system. It is a graph which shows the movement locus | trajectory of the discharge direction of the rear-end position of the paper S until it arrives at the predetermined position on a paper mounting surface by making a horizontal axis into time, and a desirable example is shown. It is a graph showing the movement trajectory in the discharge direction of the trailing edge position of the paper until it reaches a predetermined position on the paper placement surface with the horizontal axis as time, and various conditions such as paper basis weight, size, and paper quality are varied. Several examples are shown.

  An embodiment of the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention.

[System configuration example]
First, a configuration example of an image forming system in which the paper discharge device is mounted will be described.
As shown in FIGS. 1 to 3, the image forming system 1000 according to the present embodiment is a control that performs overall control of the large-capacity paper feeding device A, the image forming device B, the post-processing device C, and the entire image forming system 1000. Unit 100.

(Large capacity feeder A)
The large-capacity paper feeding device A includes a paper storage unit 7A, a first paper feeding unit 7B, and the like.
The sheet storage unit 7A stores a large amount of sheets S such as A4 size and A3 size, for example. The paper S stored in the paper storage unit 7A is continuously sent to the image forming apparatus B by the first paper supply unit 7B.

(Image forming apparatus B)
The image forming apparatus B includes an image reading unit 1, an image writing unit 3, an image forming unit 4, a paper feeding / conveying unit 5, a fixing unit 6, an automatic document conveying unit B1, an operation display unit B2, and the like.

  The image reading unit 1 includes a scanner below a contact glass on which an original is placed, and reads an image on a sheet to acquire image data. The scanner is composed of a light source, a CCD (Charge Coupled Device) image sensor, an A / D converter, and the like. The reflected light of the light scanned from the light source to the original is imaged and photoelectrically converted to convert the original image into RGB. The signal read and photoelectrically converted as a signal is sent to the image writing unit 3 after undergoing processing such as A / D conversion, shading correction, and image compression processing.

  In the image writing unit 3, the output light from the semiconductor laser is applied to the photosensitive drum 4A of the image forming unit 4, and an electrostatic latent image is formed on the photosensitive drum 4A.

The image forming unit 4 includes a photosensitive drum 4A, a charging unit 4B, a developing unit 4C, a transfer unit 4D, a separation unit 4E, a cleaning unit 4F, and the like.
In the image forming unit 4, processes such as charging, exposure, development, transfer, separation, and cleaning are performed on the electrostatic latent image formed on the photosensitive drum 4A.

The sheet feeding / conveying unit 5 includes a plurality of sheet feeding cassettes 5A, a first sheet feeding unit 5B, a second sheet feeding unit 5C, a conveying unit 5D, a sheet discharging unit 5E, an automatic duplex copying sheet feeding device (ADU) 5F, and the like. Has been.
In the paper feed cassette 5A, paper S identified in advance for each paper type (paper quality, basis weight, size) is stored, and the paper S is fed one by one from the top by the first paper feed unit 5B. The sheet is conveyed toward the second sheet feeding unit 5C.
The second paper feeding unit 5C conveys the paper S conveyed from the paper supply tray to the transfer unit 4D of the image forming unit 4. The sheet S on which the image is transferred by the transfer unit 4D is transported to the fixing unit 6 by the transport unit 5D.

The fixing unit 6 includes a heating roller having a heat source and a pressure roller that presses against the heating roller to form a nip portion, and heat-fixes the toner image transferred to the paper S. The sheet S on which the toner image is fixed by the fixing unit 6 is sent to the post-processing device C from the paper discharge unit 5E.
When images are formed on both sides of the paper S, the front and back sides are reversed by the automatic double-sided copy paper feeder 5F after the paper S is fixed, and sent again to the image forming unit 4 to form an image. It is sent to the processing device C.

  The automatic document feeder B1 feeds the documents placed on the document table one by one and supplies them to the image reading unit 1. A document supplied from the document table of the automatic document feeder B1 to the image reading unit 1 is scanned on one or both sides of the document by the optical system of the image reading unit 1, and the photoelectrically converted signal is A / D converted. After being subjected to processing such as shading correction and image compression processing, it is sent to the image writing unit 3.

The operation display unit B2 includes a touch panel display having an LCD (Liquid Crystal Display), and various setting screens, device status displays, operation states of functions, and the like on the display screen according to instructions of display signals input from the control unit 100. Is displayed.
The touch panel display is configured by covering the LCD display screen with a pressure-sensitive (resistive film pressure) touch panel configured by arranging transparent electrodes in a grid pattern, and is pressed with a finger or a touch pen. The position coordinate is detected by the voltage value.
The operation display unit B2 outputs the detected position signal to the control unit 100 as an operation signal.

  Note that the image forming apparatus B in FIG. 1 forms a monochrome image on the paper S, but may form a color image on the paper S.

(Post-processing device C)
The post-processing device C is a device that performs post-processing such as binding processing, and includes an entrance transport unit 20, a paper discharge transport unit 30, a connection transport unit 40, an insertion paper feed unit 50, a binding processing unit 60, and a stack unit 65. A folding unit 70, a paper discharge mechanism unit 80, a paper nipping and conveying unit 90, and the like are arranged.

In the entrance conveyance unit 20, the sheets S discharged from the post-processing apparatus C are sequentially received and conveyed.
The paper discharge conveyance unit 30 conveys the paper S that does not require post-processing such as binding processing. The paper S conveyed via the paper discharge conveyance unit 30 is discharged to the liftable paper discharge tray 80b via the paper discharge roller 80a.

  The connected transport unit 40 transports the paper S from the entrance transport unit 20 to the stack unit 65. The sheets S transported by the connection transport unit 40 are stacked in the stack unit 65 and the binding processing unit 60 performs the binding process. As a result, a partial booklet composed of a plurality of sheets S is produced.

  The insertion sheet feeding unit 50 feeds a sheet to be inserted into a predetermined position in the binding process. The sheets fed from the insertion sheet feeding unit 50 are stacked in the stack unit 65 via the connection conveyance unit 40.

The binding processing unit 60 executes a binding process using a plurality of sheets S stacked in the stack unit 65 as a part of a booklet.
In the case of one-sided binding in which the staple in the binding process is performed on one side of the sheet bundle, the booklet is discharged to the elevating sheet discharge tray 80b. The sheet is folded halfway at the section 70 and discharged to the sheet discharge tray 82.
The folding unit 70 folds the booklet when performing saddle stitching in the binding process.

  The paper discharge mechanism unit 80 includes a paper discharge roller 80a as a discharge unit that discharges the paper S to the paper stacking unit. The paper discharge mechanism 80 includes a liftable paper discharge tray 80b on which the discharged paper S is stacked, an abutting portion 80c that abuts the rear end of the paper S, and the like.

The paper discharge roller 80a is connected to a variable speed paper discharge drive motor M1 and discharges the paper S.
A paper position detection sensor PS is disposed upstream of the paper discharge roller 80a in the discharge direction. Then, after the arrival of the paper S is detected by the paper position detection sensor PS, the rotational speed of the paper discharge roller 80a is decelerated in time.
By reducing the rotational speed of the paper discharge roller 80a, the paper discharge operation of the paper nipping and conveying unit 90 can be made more reliable.

  A paper stacking surface SS as a paper stacking section on which the paper S is stacked is formed on the liftable paper discharge tray 80b, and the paper S discharged by the paper discharge roller 80a is stacked thereon.

The abutting portion 80c is two plate-like members arranged with a predetermined gap on the upstream side with respect to the discharge direction of the paper S discharged by the paper discharge roller 80a.
The abutting portion 80c serves as a reference for aligning the rear ends of the sheets S when the sheets S are stacked on the elevating type discharge tray 80b.

  The paper nipping / conveying unit 90 is a mechanism that is disposed near the paper discharge mechanism unit 80 and that stacks the paper S discharged by the paper discharge roller 80a on the liftable paper discharge tray 80b. .

  The sheet nipping / conveying unit 90 serves as a pair of sheet nipping members that nipping the sheets S one by one or a plurality of sheets at the sheet nipping position and moving them to the sheet loading position at the sheet stacking unit. A pressing member 91 and a supporting member 93 are provided.

  In the present embodiment, as shown in FIG. 2, two pairs of paper nipping members (pressing member 91 and supporting member 93) are provided in the gap between the two abutting portions 80c. .

As shown in FIG. 4A and the like, the pressing member 91 is swingably held around a rotation shaft 91a parallel to the width direction of the paper S on the upper side of the paper S discharged by the paper discharge roller 80a. Yes.
Specifically, the pressing member 91 is formed in an arm shape, and a rotating shaft 91a that holds the pressing member 91 in a swingable manner is fixed to one end thereof, and the supporting member 93 is pressed to the other end via a sheet. It has a pressing portion 91b.
Further, the pressing member 91 is engaged with a spring member SP that applies a pressing force for pressing the supporting member 93 to the pressing portion 91b, and the spring member SP is rotated in a direction in which the pressing member 91 is rotated counterclockwise. Energized.
The pressing member 91 is separated from the support member 93 and waits at the upper retracted position until the sheet S approaches the sheet nipping position.

In addition, a pressure regulating member 92 that regulates the position of the pressing member 91 is provided at a position adjacent to the pressing member 91, and the pressure regulating member 92 has a forward / reverse rotatable press that drives the pressing regulating member 92. A regulating member drive motor M2 is connected.
The pressing restricting member 92 includes a shaft portion 92a that is connected to the pressing restricting member driving motor M2 and holds the pressing restricting member 92 so as to be rotatable in both forward and reverse directions, and an engaging portion 92b that engages with the pressing member 91. The pressing member 91 swings while being engaged with the engaging portion 92b of the pressing restricting member 92 that rotates in both forward and reverse directions.
Specifically, the pressing member 91 is restricted from rotating counterclockwise by the engagement of an engaging portion 92b attached to one end of a rotating pressing restricting member 92.
Then, when the pressing restricting member drive motor M2 rotates the pressing restricting member 92 counterclockwise according to the control of the control unit 100, the restriction of the counterclockwise rotation of the pressing member 91 is released.
Further, when the pressing restriction member driving motor M2 rotates the pressing restriction member 92 clockwise according to the control of the control unit 100, the counterclockwise rotation of the pressing member 91 is restricted.
Note that the control unit 100 operates the pressing restricting member driving motor M2 in accordance with the conveyance timing of the paper S detected by the paper position detection sensor PS.
Specifically, when the paper S is conveyed by the paper discharge roller 80a and reaches the paper nipping position, the pressure regulating member 92 rotates counterclockwise in response to detection by the paper position detection sensor PS, and Regulations are lifted.

  In the present embodiment, the pressing member 91 is configured to swing while being engaged with the engaging portion 92b of the pressing regulating member 92 that rotates in both forward and reverse directions. However, the pressing member 91 is moved in both forward and reverse directions at a predetermined timing. Any configuration other than the pressure regulating member 92 may be used as long as it can rotate to the right.

  On the other hand, the support member 93 is held on the lower side of the paper S discharged by the paper discharge roller 80a so as to be rotatable around a rotation shaft 94a parallel to the width direction of the paper S.

Specifically, the support member 93 is fixed to one end of a pair of rotating plates 94 having the same size and shape through a pair of shafts 94b.
A pair of rotating shafts 94 a are fixed to the other end of the pair of rotating plates 94, and the pair of rotating shafts 94 a are rotatably held by a holding plate 95.
The pair of rotating shafts 94a is connected to a supporting member driving motor M3 as a supporting member driving means for rotating each of the rotating shafts 94a in the counterclockwise direction. The supporting member driving motor M3 is controlled by the control unit 100. The rotating operation is performed at the same speed and in the same direction at the same time.
The pair of rotating plates 94 are out of phase in the direction of the rotation axis and are arranged so as not to interfere with each other during rotation.

The support member 93 is rotatable by such a pair of rotating plates 94, a pair of rotating shafts 94a, a holding plate 95, a supporting member drive motor M3, and the like. That is, the pair of rotating plates 94 rotate simultaneously in the same direction at the same speed to rotate the support member 93.
Under the control of the control unit 100, the support member drive motor M3 causes the pair of rotating plates 94 to rotate once for the single holding operation of the pressing member 91 and the support member 93 on the paper S.

In addition, the support member 93 is formed with a paper nipping surface 93a with which the pressing portion 91b of the pressing member 91 contacts via the paper S. It is preferable that the sheet holding surface 93a is configured to be always horizontal regardless of the rotation angle of the pair of rotating plates 94, or to be a surface that maintains a constant angle with respect to the horizontal.
As described above, the sheet nipping surface 93a is always a horizontal surface or a surface that maintains a certain angle with respect to the horizontal, so that the nipping operation of the sheet S by the pressing member 91 and the support member 93 is stable and smooth. Done.

The paper nipping surface 93a is roughened so as to increase the friction coefficient. The friction coefficient of the surface of the sheet holding surface 93 a is set to be larger than the friction coefficient of the pressing portion 91 b of the pressing member 91 and larger than the friction coefficient between the sheets S.
In this way, by setting the friction coefficient of the sheet holding surface 93a of the support member 93 to be larger than the friction coefficient of the pressing portion 91b of the pressing member 91 and larger than the friction coefficient between the sheets S, the ascending and descending Even if the paper S stacked on the uppermost surface of the paper discharge tray 80b is shifted downstream in the discharge direction, the position can be easily corrected.
The configuration for increasing the coefficient of friction is not limited to the roughing process, and the support member 93 may be formed of a resin molded part, and a large number of minute protrusions may be formed on the paper holding surface 93a. Another member made of rubber, foamed soft resin, or the like may be attached.

Further, a friction member 96 is provided on the lower surface of the support member 93 (the surface opposite to the sheet nipping surface 93a) via a spring member 96a.
The friction member 96 is a friction plate formed of a material made of rubber or foamed resin. The friction coefficient at the sheet contact surface (lower surface) of the friction member 96 is set to a value larger than the friction coefficient between the sheets of the plurality of sheets S stacked on the elevating sheet discharge tray 80b.
The paper contact surface of the friction member 96 can be displaced by a spring member 96a. Since the contact surface of the friction member 96 with the sheet S is displaceable, the frictional resistance to the sheet S can be kept substantially constant even when the thickness of the sheet bundle loaded on the elevating type discharge tray 80b changes. it can.

Further, as shown in FIG. 2, the sheet nipping and conveying unit 90 is a sheet for aligning the end position of the sheet S in a direction perpendicular to the discharge direction of the sheet S discharged to the elevating sheet discharge tray 80b. A pair of alignment members 97 and 98 are provided as alignment means. The pair of alignment members 97 and 98 are disposed on the downstream side in the discharge direction and above the elevating type discharge tray 80b.
The pair of alignment members 97 and 98 are installed so as to face each other with a predetermined gap in the sheet width direction, and can be rotated in a direction in which they are in contact with and away from the elevating type discharge tray 80b.

(Control unit 100)
As shown in FIG. 3, the control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like.
The ROM 102 of the control unit 100 stores a control program and various processing programs for controlling the above-described units, and the RAM 103 includes a work area for the CPU 101.
The CPU 101 comprehensively controls the operation of each part of the image forming system 1000 in cooperation with this control program and various processing programs.

The control unit 100 is electrically connected to an operation display unit B2 to which various operation instructions and various information are input, and the control unit 100 corresponds to the operation instruction and various information input to the operation display unit B2. Execute the process.
Here, information input to the operation display unit B2 includes paper quality information indicating paper quality (mechanical properties of paper) such as coated paper (paper coated on the surface) and plain paper, and paper quality (paper mechanical properties). There are basis weight information indicating the basis weight of the paper, and size information indicating the size of the paper. Based on information input to the operation display unit B2 and the like, the control unit 100 calculates and holds the same-sheet number information, which is the number of sheets ejected by the sheet ejection roller 80a or one by one, in consideration of productivity.

The control unit 100 selects a braking property to be described later according to at least one of the basis weight information, the size information, the paper quality information, and the number-of-outs information of the paper, so that the pair of paper clamping members 91 and 93 The braking of the sheet S by the narrow pressure is variably controlled.
In the present embodiment, the paper discharge mechanism 80, the paper nipping and conveying unit 90, and the control unit 100 described above constitute a paper discharge device according to the present invention.

  Next, the operation of the paper nipping and conveying unit 90 in the present embodiment will be described with reference to FIGS.

Before the discharged paper S reaches the paper nipping position, when the leading edge of the paper S is sandwiched between the paper discharge rollers 80 a, the pressing member 91 stands by at a retracted position separated from the support member 93. Further, the support member 93 stands by at a sheet nipping position where the sheet S is nipped (see FIG. 4A).
During this standby, the control unit 100 selects the braking performance of the paper S by the narrow pressure of the pair of paper clamping members 91 and 93.

  Next, when the paper S is conveyed by the paper discharge roller 80a and reaches the paper nipping position, the pressure regulating member 92 rotates counterclockwise in response to the detection by the paper position detection sensor PS, and accordingly, the pressure member 91 is rotated. The pressing member 91 abuts against and presses the support member 93 so as to rotate counterclockwise by the urging force of the spring member SP and pinch the rear end portion of the sheet S (FIG. 4 ( b)).

The control unit 100 controls the support member drive motor M3 so that a predetermined speed is reached after a predetermined time has elapsed since the detection of the paper S by the paper position detection sensor PS. When the support member drive motor M3 rotates, the support member 93 starts to move due to the rotation of the pair of rotation plates 94 associated therewith. The support member 93 is rotated counterclockwise at a predetermined operating speed by rotating the pair of rotation plates 94.
When the support member 93 rotates, the pressing member 91 moves following the support member 93 that moves at the predetermined operation speed while pressing the support member 93 while holding the sheet S therebetween (see FIG. 5 (a)).

When the paper S is sandwiched between the pressing member 91 and the support member 93 before the paper S passes through the nip portion of the paper discharge roller 80a, the paper S is held between the pressing member 91 and the support member 93 at the paper clamping position. Until the trailing edge of the paper S is discharged from the paper discharge roller 80a (until the rear edge of the paper S comes out of the nip portion of the paper discharging roller 80a). Is conveyed by the conveying force of the paper discharge roller 80a.
When the trailing edge of the paper S comes out of the nip portion of the paper discharge roller 80a, the conveying force by the paper discharge roller 80a disappears, and the paper S is held between the pressing member 91 and the support member 93. It moves according to the movement of the support member 93. That is, the moving speed of the sheet S is the same as the operation speed of the pair of sheet holding members.

When the paper S reaches the paper placement position, the paper holding surface 93a of the support member 93 is separated from the paper S, and the support member 93 is separated from the pressing member 91 and moves upstream in the direction opposite to the discharge direction. (See FIG. 5B).
Then, the pressing member 91 is urged by the spring member SP, and presses the sheet S against the liftable sheet discharge tray 80b (see FIG. 6A). In this state, the stacking of the sheets S on the liftable sheet discharge tray 80b is completed.
Thereafter, the pressing member 91 rotates clockwise in accordance with the clockwise rotation of the pressing restricting member 92, returns to the original retracted position locked to the pressing restricting member 92, and the support member 93 rotates counterclockwise. It rotates and returns to the paper nipping position (see FIG. 6B).

  At this time, since the friction coefficient of the paper nipping surface 93a of the support member 93 is larger than the friction coefficient between the pressing portion 91b of the pressing member 91 and the paper, the rear end of the paper S may abut against the abutting portion 80c. it can.

In addition, when the rear end of the uppermost sheet S stacked on the elevating sheet discharge tray 80b is shifted to the downstream side in the discharge direction from the rear end of the sheet S, the friction member 96 contacts the uppermost sheet S. The shift can be corrected by the action when contacting.
That is, as shown in FIG. 5B, the friction member 96 provided on the support member 93 comes into contact with the upper surface of the uppermost sheet S, and the sheet S is urged toward the upstream side in the discharge direction. The rear end of S is abutted against the abutting portion 80c.

At this time, since the spring member 96a expands and contracts in accordance with the thickness of the bundle of sheets stacked on the elevating type discharge tray 80b, the friction member 96 always has a suitable height of the elevating type discharge tray 80b. It comes into contact with the uppermost sheet.
Thereafter, similarly, the paper S is discharged from the paper discharge roller 80a, and the paper bundle is stacked on the liftable paper discharge tray 80b.

[Variable braking control]
In the paper discharge device (80, 90, 100) described above, if any one of the basis weight, size, paper quality, and number of papers of the paper S is different, the braking performance by the paper clamping members 91, 93 is constant. As shown in FIG. 15, the rear end position of the sheet S varies as shown in FIG.
In order to prevent this and to accurately convey the paper S to the paper placement position without damaging the paper, the control unit 100 is combined with the control described with reference to FIGS. The following variable braking control is executed.

(Selection of braking performance)
First, the control unit 100 executes the above-described braking performance selection as shown in FIG.
That is, when the control unit 100 starts image formation in response to an instruction from the operation display unit B2 (S1), the basis weight information, the size information, the paper quality information, and the number-of-issues information of the paper S are acquired (S2-S5). The braking performance is selected (S6).
An example of a braking performance selection table is shown in Table I.

The “paper basis weight” in Table I is (same number of sheets) × (basis weight per sheet). This corresponds to a change in the number of sheets held simultaneously by the paper discharge roller 80a and the basis weight of the paper.
As shown in Table I, the correspondence between each piece of information and braking performance is as follows.
The greater the slipperiness, such as coated paper, the greater the braking performance.
The greater the paper basis weight, the greater the braking performance. This is because the larger the basis weight, the more difficult it is to decelerate due to inertia. The smaller the paper basis weight, the more susceptible to damage, so the braking performance is set to be small.
The larger the paper size, the smaller the braking performance. This is because when the paper size is large as shown in FIG. 8, the leading edge of the paper S hits the paper stacking surface SS and braking is applied.

Next, one of the variable brakings according to Examples 1 to 3 below is executed according to the selected braking performance.
(Variable braking example 1)
As an example 1, the control unit 100 variably controls the braking of the paper S by variably controlling the narrow pressure that narrows the paper S by the pair of paper clamping members 91 and 93. For example, as shown in FIG. 9, the braking force of the paper S is variably controlled by variably controlling the pressing force F by the pressing member 91 which is one of the paper clamping members.
When the braking performance “low” shown in Table I is selected, the control unit 100 sets the narrow pressure for narrowing the paper S by the paper clamping members 91 and 93 to a relatively small value set in advance, and selects the braking performance “high”. In this case, the narrow pressure for narrowing the paper S by the paper sandwiching members 91 and 93 is set to a relatively large value set in advance, and when the braking property “medium” is selected, the paper S is narrowed by the paper sandwiching members 91 and 93. The narrow pressure is set to a preset value in between. Note that the three stages are only examples.
This example is implemented by changing the configuration in which the pressing member 91 is rotated by a mechanism capable of variable torque driving to the configuration example described above.

(Variable braking example 2)
As an example 2, the control unit 100 variably controls the braking of the sheet S by variably controlling the action direction of the narrow pressure that narrows the sheet S by the pair of sheet clamping members 91 and 93. For example, as shown in FIG. 10, by moving the position of the pressing member 91, which is one of the paper clamping members, to the downstream side in the discharge direction E, the direction of action of the narrow pressures P1 and P1 is variably controlled. The braking force is variably controlled. The braking force is minimum when the direction of action of the narrow pressures P1 and P1 is perpendicular to the discharge direction E by the paper discharge roller 80a, as shown in FIG. As shown in FIG. 4, the width of the paper S discharged by the paper discharge roller 80 a increases as it tilts about the axis. For example, as shown in FIG. 11, this example is implemented by adopting a configuration in which a rotating shaft 91 a that holds the pressing member 91 in a swingable manner is supported by a moving mechanism 99 that moves in the paper discharge direction.
When the braking performance “low” shown in Table I is selected, the control unit 100 sets a relatively small value (in FIG. 10 (b), which is the minimum 0) for the inclination of the acting direction of the narrow pressure P1, P1. ), When the braking performance “high” is selected, the inclination of the direction of action of the narrow pressure P1, P1 is set to a relatively large value, and when the braking performance “medium” is selected, the operation of the narrow pressure P1, P1. The inclination of the direction is set to a preset value between them.

(Variable braking example 3)
As an example 3, the control unit 100 variably controls the braking of the paper S by variably controlling the timing at which the paper S is narrowed by the pair of paper clamping members 91 and 93. That is, the control is performed to increase or decrease the braking distance from the sheet holding members 91 and 93 to the target stop position of the sheet S by increasing or decreasing the timing of starting the braking. . For example, as shown in FIG. 12, a plurality (PS1, PS2) of paper position detection sensors PS are arranged along the paper transport path by the paper discharge roller 80a. The control unit 100 controls the start of the operation of the pair of paper clamping members 91 and 93 triggered by the detection by the upstream paper position detection sensor PS1 in the paper conveyance path, and the detection by the downstream paper position detection sensor PS2. As a trigger, the control to start the operation of the pair of sheet clamping members 91 and 93 is selected, so that the timing for narrowing the sheet S by the pair of sheet clamping members 91 and 93 is variably controlled.
In the case of a paper condition with a large paper basis weight and a large inertia, the trailing edge of the paper causes the paper discharge roller 80a to be triggered by the detection by the paper position detection sensor PS1 as shown in FIG. Before slipping out, braking is started by the sheet clamping members 91 and 93. If the paper basis weight is large, the stiffness of the paper is strong. Therefore, even if conveyance by the paper discharge roller 80a and braking by the paper clamping members 91 and 93 are performed simultaneously, the influence on the paper S is small.
On the other hand, when the paper basis weight is small and the paper can be controlled stably even with a short braking distance, the trailing edge of the paper from the paper discharge roller 80a is triggered by detection by the paper position detection sensor PS2, as shown in FIG. Immediately after being discharged, control is performed so as to apply braking by the sheet clamping members 91 and 93, and a load is not applied to the sheet as much as possible.
However, the control unit 100 selects the braking start timing at a relatively downstream position set in advance when the braking performance “small” shown in Table I is selected, and sets the braking performance “high” in advance when the braking performance “high” is selected. When the braking start timing at the relatively upstream position is selected and the braking performance “medium” is selected, the braking start timing at a preset position between them is selected.
The number of paper position detection sensors may be set as appropriate. In addition, it is possible to replace the single sheet position detection sensor with the braking start timing variably controlled by the time based on the detection time. By providing a plurality of paper position detection sensors along the paper conveyance path and using them, the paper position detection accuracy is improved, and finally the paper placement position accuracy is improved.

As described above, the paper discharge device according to the present embodiment allows the pair of paper holding members 91, 91 to correspond to at least one of the basis weight information, the size information, the paper quality information, and the same number information of the paper S. By variably controlling the braking of the sheet S due to the narrow pressure of 93, the variation in the sheet placement position in the sheet stacking unit is reduced.
As described above, the paper S can be accurately conveyed to a predetermined position on the paper placement surface.

  In the above embodiment, as shown in Table I, control is performed in accordance with all combination conditions of the basis weight information, size information, paper quality information, and number-of-payout information of the paper S. Control according to two, or control according to two or three combination conditions may be performed. Variations in the paper placement position due to changes in the conditions indicated by the respective information can be reduced, and the paper can be accurately conveyed to a predetermined position on the paper placement surface.

80 Paper discharge mechanism 80a Paper discharge roller (discharge means)
80b Elevating type discharge tray 80c Abutting section 90 Paper nipping and conveying section 91 Pressing member (paper clamping member)
91a Rotating shaft 91b Pressing portion 93 Support member (paper clamping member)
93a Paper holding surface 94 Rotating plate 94a Rotating shaft 100 Control unit 1000 Image forming system A Large-capacity sheet feeding device B Image forming device B1 Automatic document feeder B2 Operation display unit C Post-processing device g1 region g2 region g3 region g4 region P1, P1 Narrow pressure PS Paper position detection sensor PS1 Paper position detection sensor PS2 Paper position detection sensor S Paper SS Paper placement surface

Claims (5)

A paper stacking unit for stacking sheets discharged one by one or in a stacked state by a discharge means;
A paper position detection sensor for detecting the position of the paper being moved by the discharging means;
A pair of sheet nipping members for nipping the sheet in a state where each sheet or a plurality of sheets are stacked and moving the sheet to the sheet stacking unit;
A drive mechanism for the sheet clamping member;
A control unit that controls the operation of the pair of sheet clamping members via the drive mechanism based on a detection signal from the sheet position detection sensor;
The control unit uses at least one piece of information on basis weight information, size information, paper quality information, and same number of pieces of paper as information on the number of sheets to be discharged in a single sheet or in a stacked state. Accordingly, the paper discharge device reduces the variation in the paper placement position on the paper stacking unit by variably controlling the braking of the paper by the narrow pressure of the pair of paper clamping members. The paper discharge device according to claim 1, wherein the control unit variably controls the braking of the paper by variably controlling a narrow pressure that narrows the paper by the pair of paper clamping members. 2. The sheet discharge device according to claim 1, wherein the control unit variably controls braking of the sheet by variably controlling a direction in which a narrow pressure is applied to the sheet by the pair of sheet clamping members. 2. The sheet discharge device according to claim 1, wherein the control unit variably controls braking of the sheet by variably controlling a timing at which the sheet is narrowed by the pair of sheet clamping members. A plurality of the paper position detection sensors are disposed along a paper conveyance path by the discharge means,
The control unit triggers the control to start the operation of the pair of sheet clamping members triggered by the detection by the upstream sheet position detection sensor on the sheet conveyance path, and the detection by the downstream sheet position detection sensor. The sheet discharge device according to claim 4, wherein the timing for narrowing the sheet by the pair of sheet nipping members is variably controlled by selecting the control to start the operation of the pair of sheet nipping members.