JP4827646B2 - Sheet stacking apparatus, sheet processing apparatus, and image forming apparatus including the same - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a multifunction machine, and also relates to a stacking device for sheets (recording media) on which images are formed and a sheet processing apparatus for performing post-processing on the sheets.

  As a sheet processing apparatus to which a sheet on which an image has been formed by an image forming apparatus is fed, one having the following configuration is well known. When an image-formed sheet discharged from the image forming apparatus main body is received, a buffer roller is provided to wrap the received sheet several times and temporarily wait before sending the received sheet to a post-processing mechanism such as a stapler or saddle stitch. That is, while the processing is being performed on the preceding sheet bundle in the processing tray, the first several sheets of the succeeding sheet bundle are temporarily held by the buffer roller. When the processed preceding sheet bundle is discharged from the processing tray, several subsequent sheets sent out from the buffer roller are sent to the processing tray. An example of the sheet post-processing apparatus configured as described above is a sheet processing apparatus described in Patent Document 1. The sheet processing apparatus will be schematically described with reference to FIGS.

  A winding path 32 is formed by the buffer roller 5 that overlaps and winds a plurality of sheets P1, P2,. For example, three sheets P1, P2, and P3 are overlapped and temporarily waited, then sent out from there, conveyed, and sent to the processing tray 101 by the discharge roller 7 and the bundle discharge rollers 180a and 180b. When the rear end of the sheet passes through the discharge roller 7, the bundle discharge rollers 180a and 180b rotate in the reverse direction so that the sheet bundle formed of the three sheets P1, P2, and P3 comes into contact with the rear end stopper 3 of the processing tray 101. return. Just before the rear end of the sheet bundle comes into contact with the rear end stopper 3, the bundle discharge roller 180b is moved away from the bundle discharge roller 180a, so that the sheet bundle is brought into contact with the rear end stopper 3 by a moving repulsive force. . At that time, alignment in the direction orthogonal to the transport direction is performed by the alignment plate.

  When all the sheets of the first sheet bundle are aligned on the processing tray 101 in such a manner, the swing guide 150 descends and the bundle discharge roller 180b gets on the sheet bundle, as shown in FIG. The sheet bundle is bound by a processing machine such as a stapler indicated by reference numeral 4.

  By processing according to such a procedure, the time until the first plurality of sheets of the second sheet bundle is wound around the temporary storage unit called the buffer roller 5 and waits until the processing of the first sheet bundle is completed. Earn. This corresponds to a high-speed high-processing image forming apparatus in which the interval between sheets discharged from the image forming apparatus main body is small.

Japanese Patent Laid-Open No. 10-181988

  Incidentally, in recent years, the quality and size of sheets have been further diversified, and in the sheet processing apparatus illustrated in FIGS. 9A to 9C, for example, the sheet is a special paper having a surface processed such as coated paper. However, it is difficult to deal with cardboard and large-sized paper.

  Even though these sheets can be reliably aligned one by one, it is difficult to align them in a stacked state. That is, the rear ends of a plurality of sheets having special sheet quality and sheet size are brought into contact with the rear end stopper 3 on the processing tray 101 and aligned. At this time, a situation occurs in which all of the three sheets P1, P2, and P3 having a large coefficient of friction cannot be reliably returned to the trailing edge stopper 3, such as coated paper. In particular, the return failure in which the overlapped intermediate second sheet P2 and the like cannot be fully returned is serious, which lowers the quality of post-processing and consequently reduces productivity. In addition, when a plurality of thick paper sheets or large sized sheets are transported in a stacked manner, they have a larger inertial force than when transported one by one, and bounce when they strike the rear end stopper 3 while maintaining momentum. May cause misalignment. Moreover, there is a possibility that the end portion of the seat is buckled or broken.

  Accordingly, the object of the present invention is to be able to accurately align several sheets for post-processing corresponding to sheets of special quality and size, and to be applied to an image forming apparatus of a high-speed processing machine to improve productivity. It is an object of the present invention to provide a sheet stacking apparatus and a sheet processing apparatus that can be improved.

  In order to achieve the above object, a typical sheet stacking apparatus according to the present invention includes a stacking unit that stacks sheets, a sheet end regulating member that regulates one end of a sheet stacked on the stacking unit, and a sheet stacking unit. A conveying unit capable of conveying a plurality of sheets in a stack, a conveying unit configured to convey a plurality of sheets conveyed to the stacking unit toward the sheet end regulating member, and a controller for controlling the conveying unit. The controller determines, based on the sheet information, the speed at which the plurality of stacked sheets are brought into contact with the sheet end regulating member, and the plurality of stacked sheets conveyed to the sheet end regulating member. The inertial force at the time of contact is changed so as to be constant.

  In order to achieve the above object, a typical image forming apparatus of the present invention includes an image forming unit that forms an image on a sheet, and the sheet stacking apparatus according to claim 1. Features.

  According to the sheet stacking apparatus of the present invention, even in the case of special sheets such as coated paper, thick paper, and large-sized sheets, the return is poor by changing the speed of returning to the processing tray at the time of alignment corresponding to the attributes of those sheets. Thus, it is possible to reliably align a plurality of stacked sheets without generating any.

  Further, according to the image forming apparatus of the present invention, the sheet discharged from the image forming unit and sent to the sheet stacking apparatus is processed without causing a defect in sheet alignment before the post-processing in the sheet processing apparatus. As a result, productivity can be maintained or increased.

  Hereinafter, preferred embodiments of a sheet stacking apparatus, a sheet processing apparatus, and an image forming apparatus according to the present invention will be described in detail with reference to the drawings.

<Image forming apparatus>
As shown in FIG. 1, the image forming apparatus main body 300 includes a platen glass 906 as a document placement table, a light source 907, and a lens system 908, and an automatic document feeder 500 that feeds a document to the platen glass 906. Further, the image forming apparatus main body 300 includes a feeding unit 909 that supplies a sheet P (recording medium) to the image forming unit 902. The sheet post-processing apparatus 100 is connected to the image forming apparatus main body 300 and the required post-processing is performed on the image-formed sheet P discharged from the image forming unit 902. .

  The feeding unit 909 stacks and stores sheets P in, for example, upper and lower two-stage sheet cassettes 910 and 911 and is detachably attached to the image forming apparatus main body 300. In addition, a deck 913 disposed on the pedestal 912 is included. The sheet P fed from the sheet cassettes 910 and 911 is fed into the image forming unit 902. The image forming unit 902 includes a photosensitive drum 914 that is a cylindrical image carrier, and a developing unit 915, a transfer charger 916, a separation charger 917, a cleaner 918, a primary charger 919, and the like are provided around the drum. I have. Further, a conveying device 920, a fixing device 904, a discharge roller pair 905, and the like are disposed on the downstream side of the image forming unit 902.

  In addition, the image forming apparatus main body 300 is equipped with a control device 930 that supervises overall control of the entire apparatus, and operates each unit according to a control signal and an operation instruction signal output from the control device 930.

  Thus, when a signal instructing sheet feeding is output from the control device 930, feeding of the sheet P is started from the sheet cassette 910, 911 or the deck 913. Light irradiated from the light source 907 is applied to the document D on the document table 906, and the reflected light is irradiated to the photosensitive drum 914 through the lens system 908. The photosensitive drum 914 is charged in advance by a primary charger 919, and an electrostatic latent image is formed by irradiation with light. Then, the electrostatic latent image is developed by a developing device 915 to form a toner image. .

  The sheet P fed from the feeding unit 909 is corrected in skew by the registration roller 901, and further fed to the image forming unit 902 at the same timing. In the image forming unit 902, the toner image on the photosensitive drum 914 is transferred to the sheet P by the transfer charger 916, and the sheet P on which the toner image is transferred is reversed by the separation charger 917 to have a polarity opposite to that of the transfer charger 916. It is charged and separated from the photosensitive drum 914. The separated sheet P is conveyed to the fixing device 904 by the conveying device 920, and the transfer image is permanently fixed on the sheet P by the fixing device 904. The sheet P on which the image is fixed is in a straight paper discharge mode in which the image surface is on the upper side, or in a reverse paper discharge mode in which the image surface is on the lower side after being transferred to the sheet reverse path after image fixing. The paper is discharged from the apparatus main body 300 by the discharge roller pair. In this way, an image is formed on the sheet P fed from the feeding unit 909, and then discharged toward the sheet post-processing apparatus 100. Hereinafter, the configuration of the sheet post-processing apparatus 100 will be described.

<Sheet stacking device>
2 to 4 show the sheet post-processing apparatus 100 that receives the image-formed sheet P discharged from the image forming apparatus main body 300 and performs post-processing as appropriate. In contrast to FIGS. 9A to 9C shown as conventional examples, the same or similar members are denoted by the same reference numerals, and description of overlapping portions is omitted.

  As shown in FIG. 2, the delivery timing of the sheet P is simultaneously detected by an entrance sensor 109 that has an entrance-side roller pair 102 that receives the image-formed sheet P and is disposed facing the conveyance path 103 in the vicinity thereof. . The sheet P is conveyed on the conveyance path 103 by the inlet side roller pair 102. When the sheet P is discharged to the upper tray (stacking tray) 136, the upper path switching flapper 118 is operated by driving means such as a solenoid (not shown). The sheet P is guided to the upper path conveyance path 117 and is discharged to the upper tray 136 by the upper discharge roller 120.

  When the sheet P is not discharged to the upper tray 136 and a plurality of sheets are bundled and appropriately subjected to post-processing, the sheet P is guided to the bundle conveyance path 122 by switching by the upper path switching flapper 118. For example, when the sheet P is subjected to saddle stitching processing, the saddle stitching path switching flapper 125 is operated to convey the sheet P to the saddle stitching path 133 and guided to the saddle stitching unit 135 by the saddle stitching entrance roller pair 134. Therefore, saddle stitching processing is performed.

  On the other hand, when the sheet P is discharged to the lower tray 201, the sheet P is conveyed to the lower path 126 by the saddle stitching switching flapper 125. Thereafter, the sheet P discharged to the processing tray 101 as the stacking means by the lower discharge roller pair 7 is aligned by a returning means including a paddle 131 and a knurled belt 129. At the same time, the sheet P is aligned in the conveying direction by a trailing end stopper (sheet end regulating member) 3 that is an alignment means in the conveying direction. Alignment in the direction orthogonal to the conveyance direction is performed by alignment plates 1 and 2 that are movable in a direction orthogonal to the conveyance direction and that are moved by a driving source (not shown) to align the sheet P in the width direction. Thereby, a predetermined number of sheets P are aligned on the processing tray 101. Thereafter, after a binding process is performed by a stapler as a sheet processing unit as necessary, the sheet is discharged to the lower tray 201 by a bundle discharge roller pair (transfer unit) 180a and 180b.

  The pair of bundle discharge rollers 180a and 180b is the rotation direction at the time of discharge only when a plurality of sheets (sheet bundle) stacked by buffer processing described later are sandwiched and conveyed toward the rear end stopper 3. Rotate in the opposite direction. On the other hand, the returning means including the paddle 131 and the knurled belt 129 is for returning one sheet (aligned by the rear end stopper 3), and retracts upward when returning a plurality of sheets (sheet bundle). To do.

  Here, as shown in FIGS. 6A and 6B to be described later, the processing tray 101 is directed downward from the upstream bundle discharge roller pair 180a, 180b toward the processing mechanism such as the stapler. It is inclined with an appropriate inclination angle. The bundle discharge roller pair 180a and 180b can be rotated in the forward and reverse directions by switching control. During the forward rotation, the sheet bundle after the stapling process is discharged to the lower tray 201. On the other hand, the bundle discharge roller pair 180a, 180b is reversely rotated in the direction of arrow A in FIGS. 6A and 6B, and the upper bundle discharge roller pair 180b is moved from the lower bundle discharge roller pair 180a. Separation operation is possible. Therefore, the sheet bundle sandwiched between the bundle discharge roller pair 180a and 180b is released by such an operation. Then, the sheet bundle released from the nipping slides back on the inclined processing tray 101 by its own weight. Then, the rear end of the sheet bundle can come into contact with the rear end stopper 3 waiting on the lower side.

  If the speed of the sheet bundle sliding down on the processing tray 101 is the return speed Vb, the return speed Vb is controlled on the sheet post-processing apparatus 100 side as a controller shown in FIG. 5 according to conditions such as sheet quality and size. Variable control is performed by the device 151. In this embodiment, the sheet bundle speed at the time of abutting against the trailing edge stopper 3 is controlled by changing at least one of the return speed Vb of the bundle discharge roller pair 180a and 180b serving as the transfer means and the separation timing described later. It is a summary.

  FIG. 5 is a functional block diagram showing a configuration of the sheet post-processing apparatus 100 of the present embodiment, centering on the control device 930 on the image forming apparatus main body 300 side. However, only the configuration of the portion related to the control device 151 on the sheet post-processing apparatus 100 side is shown, and control signals and operation signals are transmitted to and received from the control device 930 on the image forming apparatus main body 300 side.

  The control device 151 as a controller is configured by a microcomputer system and includes a CPU 50, a ROM 51, a RAM 52, and the like. The ROM 51 stores a puncher processing program, a stapling processing program, and the like in advance. The CPU 50 executes each program and creates a predetermined control signal by performing input data processing while appropriately exchanging data with the RAM 52.

  A sheet detection sensor 54, an alignment position detection sensor 56, and a sheet condition detection unit 55 are provided, and detection signals from these detection units are input as input data to the CPU 50 via the input interface circuit 53. Various control signals are output from the CPU 50 via the output interface circuit 57. The output signal is transmitted to a control device such as a motor driver, and the control device is controlled to control the swing guide motor 20, the drive motor 21 for the sheet conveying rollers 180a and 180b, and the drive motor 22 for the alignment members 1 and 2. And so on.

  In addition, data communication is transmitted and received between the main body side CPU provided on the image forming apparatus main body 300 side and the CPU 50. The CPU 50 obtains various types of information such as the document size and the number of document copies by ADF from the main body side CPU. Further, sheet information and conditions relating to the sheet type (plain paper, coated paper, special paper) and sheet size are input from the operation panel of the image forming apparatus main body by a user operation, and the CPU 50 can acquire and recognize these sheet conditions. In addition to the above sheet size, the sheet conditions include physical properties such as stiffness, thickness, basis weight, surface resistance, and smoothness (surface properties), sheet types such as punched paper, tab paper, and the like. In particular, the surface resistance is affected by the printed image and humidity. Therefore, it is also useful to detect the image density (toner applied amount) printed on the paper or to detect the humidity and add the value to the sheet condition. In general, as the amount of applied toner increases, the surface resistance decreases relatively. In addition, the surface resistance increases as the humidity increases. The CPU 50 may be provided in the sheet post-processing apparatus 100. In this way, when the optional sheet post-processing apparatus 100 is not installed, it is only necessary to provide the main body side CPU, so the cost can be reduced. It can be said that the sheet post-processing apparatus 100 can be equally controlled as a controller either directly from the control apparatus 930 on the image forming apparatus main body 300 side or via the control apparatus 151 on the sheet post-processing apparatus 100 side. Not too long.

  Usually, when post-processing such as stapling processing or saddle stitching processing is executed by the sheet post-processing apparatus 100, time and distance are required between the preceding sheet bundle and the succeeding sheet bundle. Although there are aspects depending on the image forming speed in the image forming apparatus main body 300, the interval is generally longer than the normal sheet interval. A buffer (temporary accumulation standby) process is executed to perform post-sheet processing without interrupting image formation in the image forming apparatus main body 300.

The apparatus of the present invention will be described for sheet buffer processing.

With respect to the sheet winding operation, for example, in the sheet processing apparatus shown in FIG. 9, for example, in the sheet processing apparatus shown in FIG. Thus, winding is performed around the buffer roller 5 under the condition that the processing tray 101 is processing the previous bundle.

Specifically, when all sheets of the first copy are discharged onto the processing tray 101 and aligned, the swing guide 150 descends as shown in FIGS. 4 and 11, and the roller 180b rides on the sheet bundle. The stapler 132 staples the sheet bundle.

On the other hand, the sheet P1 discharged from the image forming apparatus main body 300 in the meantime is wound around the buffer roller 5 by the rotation of the flapper as shown in FIG. When the next sheet P2 advances a predetermined distance from the paper detection sensor 109, as shown in FIG. 9B, the buffer roller 5 rotates to superimpose the first sheet P1 and the second sheet P2, and the buffalo Wrap around the roller 5 and stop at a predetermined distance. On the other hand, the sheet bundle on the processing tray 101 is discharged to the stack tray 201 by the rollers 180a and 180b.

As shown in FIG. 9B, when the third sheet P3 reaches a predetermined position, the buffer roller 5 rotates, the sheets P3 are overlapped, the flapper is switched, and the three sheets P are transferred to the conveying roller 122. Transport.

As shown in FIG. 10A, three sheets P are received by the rollers 180a and 180b while the swing guide 150 is lowered. Then, as shown in FIG. 10B, when the trailing edge of the sheet P passes through the roller 7, the rollers 180a and 180b are reversed. Then, as shown in FIG. 11A, the swing guide 150 is raised before the rear end comes into contact with the stopper 3. Accordingly, as shown in FIG. 11B, the roller 180b is separated from the sheet surface. Then, alignment with the trailing edge regulating member 3 of the sheet bundle is performed. Thereafter, alignment in the direction orthogonal to the conveying direction is performed by the alignment plate. The fourth and subsequent sheets P are discharged onto the processing tray through the same path as the operation of the first copy. Then, a predetermined process is performed. For the third and subsequent copies, the same operation as the second copy is performed, and the set number of copies are stacked on the stack tray 201 and the process is terminated.

Next, characteristics when the plurality of sheets P1, P2, and P3 are overlaid will be described.

  As can be seen from FIG. 11, the sheets P1, P2, and P3 to be overlapped are overlapped with each other by a predetermined amount b with respect to the transport direction.

  This is to prevent the lower sheet from being overtaken by the upper sheet, and the uppermost sheet (P3 in the figure) can be returned by another return means (for example, the knurled belt 129 in FIG. 2). The sheet cannot be returned. Therefore, they are offset as in this example.

  However, this is not the case when the overlay accuracy can be sufficiently secured, and the offset amount between the sheets does not necessarily have to be the same.

  FIG. 6A schematically shows the alignment operation of the sheet P in the processing tray 101 in association with the buffer processing. A bundle of a plurality of offset sheets P is returned to the processing tray 101 by reverse rotation and separation operation of the bundle discharge roller pair 180a and 180b, and aligned by being abutted against the rear end stopper 3. That is, several sheets P that are accumulated with an offset are sandwiched between the bundle discharge roller pair 180a and 180b. In this sandwiched state, the bundle discharge roller pair 180a, 180b is rotated in the reverse direction in the direction of arrow A, and the upper bundle discharge roller pair 180b is separated from the lower bundle discharge roller pair 180a before the rear end stopper 3. With this operation, the bundle of sheets P is released from the nipping, and the inclined processing tray 101 is moved downward in the right direction in the drawing and slid at the returning speed Vb, and is eventually abutted against the rear end stopper 3 that waits downward to be aligned. It is.

  As information about the sheet P, a typical sheet (paper) size and coated paper are taken as an example, and the return speed Vb to the rear end stopper 3 by the bundle discharge rollers 180a and 180b for each sheet type is collectively shown in the table of FIG. . As will be understood from this, the inertia force is large when a large sheet having a large size is piled up and slid, so the return speed Vb is set to a low speed, and in the case of coated paper having a large friction coefficient, the return speed Vb is set. Speed up. Also in the case of thick paper, if the number of sheets to be stacked increases, the weight increases, so the return speed Vb may be set to a low speed. Further, even when a small size and thin paper are transferred, if the number of sheets to be stacked is changeable, the return speed Vb needs to be set to a low speed for a predetermined number or more.

  Therefore, when the sheet P is abutted against the trailing edge stopper 3, there is a state where the distance between the trailing edge of the sheet P and the trailing edge stopper 3 is a distance indicated by a symbol L in FIG. In this state, the upper bundle discharge roller 180b is moved upward together with the swing guide 150 (see FIGS. 4 and 9A to 9C) to be separated. This separation operation is controlled by a control signal from the control device 930. That is, the sheet P is released by separating the upper bundle discharge roller 180b from the lower bundle discharge roller 180a. The sheet P slides down on the inclined surface of the processing tray 101 by its own weight, that is, is returned to the rear end stopper 3 by the inertial movement energy (inertial force) of the sheet P. The inertial force (W) when hitting the rear end stopper 3 can be calculated by the following equation.

W = 1 / 2MVb2- [mu] xK-T (1)
In the equation, M represents the mass of the sheet P (paper or the like), μx represents the friction coefficient of the sheet, K represents a coefficient, and T represents a correction coefficient.

  From the above equation (1), the inertial force W is affected by the mass M of the sheet, the return speed Vb, and the friction coefficient μx. Further, when the inertial force W when hitting the rear end stopper 3 is out of a predetermined range, a return failure occurs and alignment shift occurs. That is, if the inertial force W is larger than a predetermined value, a misalignment occurs due to rebound (bound) after hitting the rear end regulating member. Further, when the inertial force W is small, a misalignment occurs due to a return failure.

  Therefore, even if the sheet types are different, it is important that the inertial force W does not change and becomes a predetermined constant value, and the following equation must be satisfied.

WNL ≒ WNS ≒ WCS (2)
In the formula, WNL represents the large-size kinetic energy of plain paper, WNS represents the small-size kinetic energy of plain paper, and WCS represents the small-size kinetic energy of coated paper.

  Since the mass M and the friction coefficient μx are values determined mainly by the sheet type from the above equation (1), the inertial force W can be made constant by changing the return speed Vb. The table in FIG. 7 is an example in which the return speed Vb is set based on such a basis.

  As described above, in the sheet post-processing apparatus 100 according to the present embodiment, the sheet P is detected from the processing tray 101 based on the information on the sheet condition detected from the image forming apparatus main body 300 or the condition of the sheet P. The return speed Vb at the time of matching is changed. That is, the reverse rotation speeds of the pair of bundle discharge rollers 180a and 180b are controlled, and the return speed Vb when returning in the direction of abutting against the rear end stopper 3 is changed to align the sheets P. Steps S1 to S6 in the operation flowchart of FIG. 8 show control examples of the return speed Vb based on such sheet conditions.

  As described above, in the present embodiment, the number of sheets P to be transported in an overlapped manner is exemplified in the case of three sheets. However, of course, the number is only an example, and the number of sheets P is also effective for two sheets or four or more sheets. Although the number of sheets to be stacked is described as being unchanged, the transfer speed may be controlled not by the size but by the number of sheets, as long as the apparatus can change the setting of the number of sheets to be stacked. The offset amount of the sheet P is determined by the processing capability of the image forming apparatus main body 300 and the size of the apparatus, and is set to an offset amount (L = 2 to 10 mm) in the present embodiment, but is not limited thereto. .

  Next, the case where the return speed Vb is controlled by the separation timing of the bundle discharge roller pair 180a and 180b as the transfer means will be described with reference to FIG. The rising timing of the swing guide 150 is determined by the processing capabilities of the image forming apparatus main body 300 and the sheet post-processing apparatus 100. In this embodiment, in the case of plain paper, the return speed due to the reverse rotation speed of the bundle discharge roller pair 180a, 180b is set to 500 mm / s, for example. In addition, the timing at which the upper bundle discharge roller 180b is separated from the lower bundle discharge roller pair 180a is set to the time when the sheet P1 reaches about 40 mm before the rear end stopper 3 comes into contact (the value of L). Yes. Further, while the sheet P is returned by the bundle discharge roller pair 180a and 180b and until the end of the sheet reaches the rear end stopper 3 and abuts against it, the inertial force W is not affected by an external force that exerts another load. . In other words, the inertial force W is not excessively helped until several stacked sheets P sufficiently slide down the inclined surface of the processing tray 101 with the inertial force W and are aligned by the rear end stopper 3. Like that. For this reason, it is desirable that the returning means (paddle 131 or knurled belt 129) be separated from the position where it does not contact the sheet P, but this is not restrictive.

  On the other hand, FIG. 6B schematically shows an alignment mode in the case of a sheet whose sheet length Lp is shorter than the distance L1 between the bundle discharge roller pair 180a, 180b and the rear end stopper 3.

  At the moment when the sheet end Pb is separated from the bundle discharge roller pair 180a and 180b, the distance Lp1 between the opposite end Pa of the sheet and the trailing end regulating member 3 varies depending on the sheet size. The inertial force W in the case of FIG. 6A varies depending on the inclination angle of the processing tray 101 and the surface material, but also varies depending on the length of the distance Lp1.

  That is, in the case of FIG. 6B, the speed at which the stacked sheets P are discharged varies depending on the distance Lp1 between the sheet end and the trailing end stopper 3, or the sheet size (sheet length in the transport direction). This is an advantage. Further, when a short sheet as described above is discharged to the stack tray, the sheet pusher 6 as shown in FIG. 3 at least reaches the position where the sheet P reaches the bundle discharge roller pair 180a, 180b. Transport.

As is apparent from the two forms showing the sheet alignment state in FIGS. 6A and 6B, the controller 151 as a controller corresponds to the sheet condition of the quality and size of the sheet P. The reverse rotation speed of 180a, 180b is controlled to change the return speed Vb. At the same time, it controls the timing of free up the bundle of sheets P by separating the upper bundle discharge roller pair 180b. Here those of on a sheet conditions the quality and size of the sheet P to the upper side of the bundle discharge roller pair 180b by separating the by sheet P similarly trailing end stopper 3 be changed only when to free up bundles of Since the contact energy can be changed, the same effect can be obtained. Further, it is only necessary to control the reverse rotation speed of the bundle discharge roller pair 180a and 180b. However, in order to obtain a reliable alignment state, it is more desirable to perform the two controls together. As a result, there are no sheets or sheets of any quality or size that cannot be returned in a state in which a plurality of sheets P are overlapped, and all the sheets P of the sheet bundle are accurately abutted against the trailing edge stopper 3 and aligned. The As a result, accurate and quick sheet alignment in the sheet post-processing apparatus 100 is possible, which contributes to maintaining or improving total productivity in the high-speed processing image forming apparatus main body 100. In the above embodiment, the control for changing at least one of the return speed Vb of the bundle discharge roller pair 180a, 180b and the separation timing via the control device 151 on the sheet post-processing device 100 side has been described. You may control directly from the control apparatus 930 of 300 side.

  The present invention is not limited to the above-described embodiment, and other embodiments, application examples, modifications, and combinations thereof are possible as long as they do not depart from the spirit of the present invention.

1 is an overall view showing a sheet post-processing apparatus of the present embodiment and an image forming apparatus equipped with the apparatus. It is a figure which shows the sheet | seat post-processing apparatus by this embodiment. It is a perspective view which shows a sheet | seat post-processing apparatus. It is a perspective view which shows a sheet | seat post-processing apparatus. It is a functional block diagram showing a configuration of a sheet post-processing apparatus. It is a figure which shows typically two forms of the return speed at the time of the alignment by this embodiment. It is a table | surface which lists and shows return speed Vb according to sheet | seat kind and sheet size. It is a flowchart which shows the operation example of this embodiment. It is a figure which shows the conventional sheet | seat alignment form in order. It is a figure which shows a buffer sheet discharge operation in order. It is a figure which shows a buffer sheet discharge operation in order.

Explanation of symbols

3. Rear end stopper (sheet end regulating member)
4 ... Stapler (post-processing mechanism)
DESCRIPTION OF SYMBOLS 100 ... Sheet post-processing apparatus 101 ... Processing tray 180a, 180b ... Bundle discharge roller (transfer means)
136 ... Upper tray (stacking tray)
151... Control device (controller)
201 ... Lower tray 300 ... Image forming apparatus main body 930 ... Control device

Claims (10)

A stacking means for stacking sheets;
A sheet end regulating member for regulating one end of the sheets stacked on the stacking means;
Transfer means for transferring a plurality of stacked sheets toward the sheet end regulating member, and releasing the sheet before the sheet contacts the sheet end regulating member;
A controller for controlling the transfer means,
The controller controls the transfer means so that a speed of the sheet when the plurality of stacked sheets are released from the transfer means and abuts against the sheet end regulating member is changed according to sheet information; Characteristic sheet stacking device. The transfer means has a pair of separable rollers for nipping and transferring the plurality of stacked sheets,
The controller changes a speed at which the sheet contacts the sheet end regulating member by changing at least one of a rotation speed of the roller pair and a timing at which the roller pair is separated to release the sheet. The sheet stacking apparatus according to claim 1, wherein: 3. The sheet information is a surface property of the sheet, and the controller increases the sheet transfer speed by the transfer unit as the friction coefficient of the sheet transferred by the surface property increases. The sheet stacking apparatus described in 1. 3. The sheet stacking according to claim 2, wherein the sheet information is a sheet weight, and the controller reduces the sheet transfer speed by the transfer unit as the weight of the sheet to be transferred increases. apparatus. 3. The sheet stacking according to claim 2, wherein the sheet information is a sheet size, and the controller reduces the sheet transfer speed by the transfer unit as the size of the sheet to be transferred increases. apparatus. 3. The sheet stacking according to claim 2, wherein the sheet information is a sheet rigidity, and the controller reduces the sheet transfer speed by the transfer unit as the rigidity of the sheet to be transferred increases. apparatus. 3. The sheet according to claim 2, wherein the sheet information is a thickness of the sheet, and the controller reduces the sheet transfer speed of the transfer unit as the sheet of the sheet to be transferred is thicker. Loading device. A sheet stacking apparatus according to any one of claims 1 to 7,
And a sheet processing unit for processing the sheets stacked on the sheet stacking apparatus. An image forming unit for forming an image on a sheet;
An image forming apparatus comprising: the sheet stacking apparatus according to claim 1. An image forming unit for forming an image on a sheet;
An image forming apparatus comprising: the sheet processing apparatus according to claim 8.

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