Patent Publication Number: US-6666445-B2

Title: Sheet discharge apparatus and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a sheet discharge control method, a sheet discharge apparatus and an image forming apparatus for stacking sheets with images formed thereon discharged from an image forming apparatus such as a copier or a printer. 
     Conventionally, a sheet discharge apparatus that stacks sheets with images formed thereon by an image forming apparatus such as a copier or a printer onto a stacking tray has been well known. 
     In the sheet discharge apparatus, if a sheet is removed from the stacking tray while the apparatus is operating and continuously discharging sheets, the sheets will not be stacked on the stacking tray at a specific position in an aligned state. 
     For this reason, in Japanese Patent Publication (Tokkai) No. 63-247267, a sheet finishing apparatus includes a sheet stacking device moving relative to a sheet discharging unit for stacking the sheets, a detection device for detecting whether a sheet is removed from the sheet stacking device, and a control device for temporarily stopping the sheet discharge unit from discharging the sheets according to an output of the detection device. 
     In this sheet finishing apparatus, if the sheets are already fed to a recording unit or a transport unit in the image forming apparatus when the sheet is removed from the stacking tray, the sheets will jam in the image forming apparatus such as a copier or a printer by temporarily stopping the discharge operation of the sheet finishing apparatus. 
     In the type of technology described above, problems regarding the poor sheet alignment and the discharging performance exist. According to this technology, when the sheet is removed and the discharging operation of the sheet finishing apparatus is temporarily stopped, the image forming apparatus such as a copier or a printer may have a sheet jam or a folded sheet, and thus have a poor discharge performance. 
     An objective of the present invention is to solve the problems associated with the conventional technology and to provide a sheet discharge control method, a sheet discharge apparatus, an image forming apparatus and a program that eliminate the sheet jam or the folded sheet in the image forming apparatus or the sheet discharge apparatus (including a sheet finishing apparatuses) and improve the alignment of the sheets and the discharging performance. 
     SUMMARY OF THE INVENTION 
     In order to attain the aforementioned objective, according to the present invention, a sheet discharge apparatus is equipped with discharge means for discharging sheets from an image forming apparatus, storage means for storing the sheets discharged from the aforementioned discharge means; elevator means for raising and lowering the aforementioned storage means relative to the aforementioned discharge means; position detection means for detecting a surface of the upper most sheet stored in the aforementioned storage means or a surface of the aforementioned storage means on which the sheet is to be stacked; reception means for receiving a signal from the aforementioned image forming apparatus indicating a sheet transport status in the aforementioned image forming apparatus; and control means for temporarily stopping the aforementioned discharge means when the aforementioned position detection means detects the upper most surface of the sheets stored on the aforementioned storage means or the surface of the aforementioned storage means for stacking the sheets to be away from a predetermined position and the aforementioned reception means detects the sheet is being transported in the aforementioned image forming apparatus, after the sheet being transported is discharged to the aforementioned storage means by the aforementioned discharge means. 
     In the sheet discharge apparatus according to the present invention, the control means controls the aforementioned elevator means to move the aforementioned storage means back to the aforementioned predetermined position while the aforementioned discharge means is temporarily stopped discharging the sheets. 
     Also, according to the sheet discharge apparatus of the present invention, the aforementioned control means starts a drive of the aforementioned elevator means during a period of time between when the aforementioned reception means detects the sheet being transported exists in the aforementioned image forming apparatus and when the aforementioned discharge means discharges the sheet to the aforementioned storage means, and controls the aforementioned elevator means to move the aforementioned storage means to a predetermined position. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet size reception means for receiving a signal from the aforementioned image forming apparatus indicating a size of the sheet being transported in the aforementioned image forming apparatus, and the aforementioned control means controls a timing to start the aforementioned elevator means according to the size of the sheet received by the aforementioned sheet size reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned elevator means to start the drive earlier as the size of the sheets received by the aforementioned sheet size reception means becomes smaller. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet length reception means for receiving a signal from the aforementioned image forming apparatus indicating the length of the sheets being transported in a transport direction in the aforementioned image forming apparatus, and the aforementioned control means controls a timing to start the aforementioned elevator means according to the length of the sheet in the transport direction received by the aforementioned sheet length reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned elevator means to start a drive thereof earlier as the length of the sheets in the transport direction received by the aforementioned sheet length reception means becomes shorter. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet size reception means for receiving a signal from the aforementioned image forming apparatus indicating the size of the sheet being transported in the aforementioned image forming apparatus, and the aforementioned control means controls the aforementioned elevator means to change an elevating speed of the aforementioned storage means according to the size of the sheet received by the aforementioned sheet size reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned storage means to increase a rising and lowering speed of the aforementioned elevator means as the size of the sheets received by the aforementioned sheet size reception means becomes smaller. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet length reception means for receiving a signal from the aforementioned image forming apparatus indicating the length of the sheet being transported in the transport direction in the aforementioned image forming apparatus, and the aforementioned control means controls the aforementioned elevator means to change a rising and lowering speed of the aforementioned storage means according to the length of the sheet in the transport direction received by the aforementioned sheet length reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned elevator means to increase the elevating speed of the aforementioned storage means earlier as the length of the sheets in the transport direction received by the aforementioned sheet length reception means becomes shorter. 
     The sheet discharge apparatus according to the present invention may be further equipped with support means for supporting the sheets discharged by the aforementioned discharge means, and further equipped with finishing means for finishing the sheets while straddling between the aforementioned support means and the aforementioned storage means. 
     The sheet discharge apparatus according to the present invention performs alignment, binding or opening hole on the sheets as the aforementioned finishing means. 
     An image forming apparatus according to the present invention comprises stacking means for stacking the sheets; sheet supply means for supply the sheets from the aforementioned stacking means one sheet at a time; image forming means for forming an image onto the sheet supplied from the aforementioned sheet supply means; storage means for storing the sheets with the image formed thereon by the aforementioned image forming means; a transport path for guiding the sheet from the aforementioned image forming means to the aforementioned storage means; transport means for transporting the sheet along the aforementioned transport path and storing the sheet in the aforementioned storage means; sheet presence detecting means for detecting a presence of the sheet in the aforementioned transport path; elevator means for raising and lowering the aforementioned storage means relative to a downstream end of the aforementioned transport means in the sheet transport direction, position detection means for detecting the uppermost surface of the sheets stored in the aforementioned storage means or a surface of the aforementioned storage means for stacking the sheets; and control means for temporarily stopping the aforementioned sheet supply means when the aforementioned position detection means detects that the uppermost surface of the sheets stored in the aforementioned storage means or the surface of the aforementioned storage means for stacking the sheets are away from a predetermined position and the aforementioned sheet presence detection means detects the sheet in the aforementioned transport path, after the aforementioned sheet being transported is stored in the aforementioned storage means. 
     According to the present invention, a sheet discharge apparatus is equipped with discharge means for discharging sheets from an image forming apparatus; storage means for storing the sheets discharged from the aforementioned discharge means; elevator means for raising and lowering the aforementioned storage means relative to the aforementioned discharge means; position detection means for detecting a surface of the upper most sheet stored in the aforementioned storage means or a surface of the aforementioned storage means on which the sheet is to be stacked; and control means for temporarily stopping the aforementioned discharge means when the aforementioned position detection means detects the upper most surface of the sheets stored on the aforementioned storage means or the surface of the aforementioned storage means for stacking the sheets to be away from a predetermined position and the aforementioned reception means detects the sheet is being transported in the aforementioned image forming apparatus, after the sheet being transported is discharged to the aforementioned storage means by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet size reception means for receiving a signal from the aforementioned image forming apparatus indicating a size of the sheet, and the aforementioned control means controls a timing to start the aforementioned elevator means according to the size of the sheet received by the aforementioned sheet size reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned elevator means to start the drive earlier as the size of the sheets received by the aforementioned sheet size reception means becomes smaller. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet length reception means for receiving a signal from the aforementioned image forming apparatus indicating the length of the sheets in a transport direction, and the aforementioned control means controls a timing to start the aforementioned elevator means according to the length of the sheet in the transport direction received by the aforementioned sheet length reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned elevator means to start a drive thereof earlier as the length of the sheets in the transport direction received by the aforementioned sheet length reception means becomes shorter. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet size reception means for receiving a signal from the aforementioned image forming apparatus indicating the size of the sheet, and the aforementioned control means controls the aforementioned elevator means to change an elevating speed of the aforementioned storage means according to the size of the sheet received by the aforementioned sheet size reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned storage means to increase a rising and lowering speed of the aforementioned elevator means as the size of the sheets received by the aforementioned sheet size reception means becomes smaller. 
     The sheet discharge apparatus according to the present invention may be further equipped with sheet length reception means for receiving a signal from the aforementioned image forming apparatus indicating the length of the sheet in the transport direction, and the aforementioned control means controls the aforementioned elevator means to change a rising and lowering speed of the aforementioned storage means according to the length of the sheet in the transport direction received by the aforementioned sheet length reception means. 
     The control means in the sheet discharge apparatus according to the present invention controls the aforementioned elevator means to increase the elevating speed of the aforementioned storage means earlier as the length of the sheets in the transport direction received by the aforementioned sheet length reception means becomes shorter. 
     The structures of the present invention described above effectively eliminate a sheet jam and a folded sheet in the image forming apparatus or the sheet discharge apparatus (the sheet finishing apparatus) to improve the alignment of the discharged sheets and the discharging performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing an entire configuration of an embodiment of the present invention; 
     FIG. 2 is a perspective view showing an essential external configuration of a finisher apparatus shown in FIG. 1; 
     FIG. 3 is a side view showing the essential external configuration of the finisher apparatus shown in FIG. 1; 
     FIG. 4 is a side view showing a configuration of a stacking tray in FIG. 1; 
     FIG. 5 is a flowchart representing a processing procedure in the first embodiment; 
     FIG. 6 is a view showing a state that a sheet is removed from a stacking tray according to the first embodiment of the present invention; 
     FIG. 7 is a view explaining a control of raising the stacking tray according to the first embodiment of the present invention; 
     FIG. 8 is a flowchart representing a processing procedure in the second embodiment; 
     FIG. 9 is a flowchart representing a processing procedure in the third embodiment; 
     FIG. 10 is a flowchart representing a processing procedures in the fourth embodiment; and 
     FIG. 11 is a view showing a mechanism for detecting a position of the stacking tray  15 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereunder, embodiments of a program together with a sheet discharge control method, a sheet discharge apparatus and an image forming apparatus according to the present invention in reference to the accompanied drawings. 
     FIG. 1 is a view showing an entire configuration of the embodiment of the present invention. 
     In FIG. 1, the general configuration of the example of the sheet discharge apparatus includes an image forming apparatus G, such as a copier or a printer, and a finisher apparatus  11 . The finisher apparatus  11  is detachably mounted to the image forming apparatus G (a combination of the image forming apparatus G and the finisher apparatus  11  corresponds to the image forming apparatus). 
     The image forming apparatus G shown in FIG. 1 shows an essential structure of a conventional copier or printer and is equipped with a scanner  2  below an automatic document feeder (or ADF)  1 . An image generation portion (printer engine)  3  is arranged below the scanner  2 . 
     In the image generation portion  3 , an electrostatic body  3   b , a developer  3   c , a cleaner  3   d  and a transfer device  3   e  are arranged on a circumference of a photoconductor body  3   a . Also, a plurality of rollers (from a pick-up roller  3   h  to a discharge roller  3   i ) is established along a transport path P to accommodate a sheet S (paper) according to a size thereof and a control of a series of printing processes from charging at the photoconductor  3   a  to removal of toner. A paper cassette ( 3   g ) for stacking and storing the sheets with various sizes is arranged below them. 
     The following describes a configuration of the finisher apparatus  11  in detail according to FIG.  2  and FIG.  3 . 
     In the image forming apparatus G and finisher apparatus  11  of the embodiment, a microprocessor unit (MPU) GA in the image forming apparatus G performs control of a series of the known various printing processes from charging to removal of toner and drive of motors, and executes a variety of display and input processes on the touch panel  3   j  relating to printing. 
     Also, in the finisher  11 , a microprocessor unit (MPU)  11 A controls a variety of processes according to ‘a straight operation mode’ and ‘a shift operation mode’, described in detail below, and motor drive to process the sheets discharged from the image forming apparatus G. 
     Also, the microprocessors GA and  11 A are working together to execute control according to the present invention described in detail below. In this process, a status signal is sent from the image forming apparatus G to the finisher apparatus  11 , and a control command is sent from the finisher apparatus  11  to the image forming apparatus G. 
     Note that in the example in FIG. 1, the two separate microprocessors GA and  11 A are arranged. However, the microprocessor GA in the image forming apparatus G may execute the control of the finisher apparatus  11  (for example, time division multiplex control). 
     The following will describe the finisher apparatus  11  in detail. 
     FIG. 2 is a perspective view showing an external configuration of the essential portions of the finisher apparatus  11 , and FIG. 3 is a side view showing the internal configuration of the essential portions of the finisher apparatus  11 . 
     According to FIG. 1 to FIG. 3, the finisher apparatus  11  is provided with a main apparatus  12 , a staple unit  13  mounted to one side frame of the main apparatus  12 , and a drive transmission mechanism, not shown in the drawings, arranged on the other side frame of the main apparatus  12 . Furthermore, the finisher apparatus  11  is provided with an inlet  18 , to which the sheets with the images formed thereon discharged from the image forming apparatus G are supplied, a discharge outlet  20  formed on a side opposite to the inlet  18  and a stacking tray  15  for stacking the sheet S discharged from the discharge outlet  20 . 
     Note that the staple unit  13  may be a device for binding a bundle of the sheets S with staples, or may be provided with a punching unit for punching holes. 
     The main apparatus  12  comprises the first transport path for guiding the sheet S from the inlet  18  into the main apparatus  12 , the second transport path for discharging the sheet S to the stacking tray  15  through the discharge outlet  20 , and the third transport path having a step relative to the second transport path for guiding the sheet S in the processing tray  39  for temporary storage after switching back a transport direction of the sheet. At the processing tray  39 , an adjacent edge of each of the sheet S is aligned by, for example, a pressing drive member (not shown in the drawings) having an alignment plate, then the aforementioned staple unit  13  stables the sheet bundle or the punching unit, not shown in the drawings, punches the holes. 
     The following will describe only the case of binding the sheet bundles. 
     Note that the finisher apparatus  11  has the following operation modes to transport the sheet S using the first to third transport paths. 
     (1) Straight operation mode 
     The sheet S is discharged directly to the stacking tray  15  through the first transport path and the second transport path. 
     (2) Shift Operation Mode (the stapling operation) 
     The sheet S transported from the first transport path to the second transport path is switch-backed along the second transport path and the third transport path, and while a plurality of the sheet S is stacked and placed on the processing tray  39 , the edges thereof are aligned. Then, the staple unit  13  binds the aligned sheet S bundle at a predetermined position, and the sheet S bundle is discharged to the stacking tray  15 . 
     The first transport path comprises an inlet sensor  21  and an endless transport belt  28  that transports the sheet S to the second transport path. Below the endless transport belt  28  is disposed a processing tray unit  30 . The processing tray unit  30  temporarily stacks and places the sheet S so that the endless transport belt  28  rotates to sequentially take up the sheet S to be bound in a predetermined number of the sheets by the staple unit  3 . 
     Above the second transport path is disposed a rotating unit  24  that rotates upward and downward around a paddle drive roller shaft  24   a  as a pivot. 
     In the rotating unit  24 , a follower discharge roller (a bundle discharge roller)  25  is disposed. When the sheet S is discharged directly to the stacking tray  15  from the first transport path through the second transport path in the straight operation mode, or the sheet S bundle is discharged to the stacking tray  15  in the processing tray unit  30  in the shift operation mode, the rotating unit  24  moves downward to a position where the rotating unit can grip the sheet S or the sheet S bundle between the follower discharge roller  25  and the discharge roller  36  to discharge the sheet S or the sheet S bundle to the stacking tray  15  from the discharge outlet  20 . When the sheet S is guided to the third transport path leading to the processing tray unit  30 , the rotating unit  24  moves upward, as shown in FIG. 3, so that the rotating unit does not interfere with the sheet S being transported and switched back. 
     A sheet abutting member  12   a  is integrated with a front surface frame of the main apparatus  12  under the discharge roller  36  for regulating the edges of the sheet S stacked in the stacking tray  15 . A sheet holder lever  78  is established on the sheet abutting member  12   a  near the discharge roller  36 , and is able to protrude toward the second transport path through a disposed opening from an upper portion of the sheet abutting member  12   a.    
     A holding lever solenoid  83  disposed on a backside of the sheet abutting member  12   a  drives the sheet holder lever  78  to protrude toward the stacking tray  15  from the sheet abutting member  12   a  every time when the discharge roller  36  and the follower discharge roller  25  discharge the sheet S or the sheet S bundle. 
     As shown in FIG. 11, the sheet holder lever  78  rotates around the rotating shaft  82  as a pivot. While the sheet holder lever  78  is pressing the sheet S, sheet stacking amount detection sensors  85   a  and  85   b  detect the first flag  79   a  and the second flag  79   b  of a detection flag  79  disposed on an edge of the sheet holder lever to determine a position of the uppermost surface of the sheets stacked on the stacking tray  15 . Based on the signal, an elevator drive motor M (not shown in the drawings) for the stacking tray  15  is controlled to rotate in forward or reverse, thereby accurately maintaining a level of the uppermost surface of the sheets stacked on the stacking tray  15 . 
     Note that a notch portion  79   c  is provided between the first flag  79   a  and the second flag  79   b  of the detection flag  79 , and does not react to the sheet stacking amount detection sensors  85   a  and  85   b.    
     A sensor  40  is established under the processing tray  39 . The sensor  40  is composed of a sensor lever  40   c  extending into the second transport path at a side of the discharge outlet  20 , a sensor flag  40   b  rotatably supported by the sensor rotation shaft under the processing tray  39 , and a sheet presence sensor  40   a  for detecting the sensor flag  40   b.    
     The sensor lever  40   c  extends into the second transport path when no sheet S is present therein. 
     This sensor  40  is able to detect the presence of the sheet S in the second transport path and the presence of the sheet S on a sheet stacking portion of the processing tray  39 . 
     That is, the sensor  40  functions as a transport pass-through sensor for detecting the sheet S whose a trailing edge is discharged, when there is no sheet stacked in the stacking portion and the sheets are stacked on the stacking tray  15  one by one after passing through the first transport path and the second transport path. Also, the sensor  40  is able to detect the sheets as a discharged sheet S bundle passing sensor when a bundle of the sheets is discharged from the processing tray  39 . 
     Also, a passing detection signal from the sensor  40  is used as a signal for activating the holding lever solenoid  83  to move the sheet holder lever  78 . 
     Next, the stacking tray  15  will be explained. 
     FIG. 4 is a side view showing a configuration of the stacking tray  15 . 
     In the stacking tray  15  shown in FIG. 4, a base  69  having a mounting portion detachable to the main apparatus  12  shown in FIG.  1  and in FIG. 2, a sheet storage portion  71  held to the base  69  via the elevator control portion  70  and being able to move up and down, and a support bracket  72  fixed to a bottom of the sheet storage portion  71  are mounted on an upper surface of the movable gear  74 . 
     The elevator control portion  70  is equipped with an arc-shaped fixed gear  73  fixed to the base  69 ; an arc-shaped movable gear  74  fixed to the support bracket  72 ; a planetary gear  75  moving through an engagement with the gears  73  and  74 ; a shift arm  76  connecting the gears  73  and  74  and the planetary gear  75  for maintaining their relative distances; a coil spring  77  disposed between an upper surface of the base  69  and a bottom of the support shaft  72  for constantly urging the sheet storage portion  71  upward. 
     The coil spring  77  has an elasticity constant being set to change a position of the sheet storage portion  71  downward according to the weight of the sheet S stacked sequentially on the upper surface of the sheet storage portion  71 , so that the top surface of the stacked sheets S remains substantially a constant height as the next sheet is sequentially stacked on the previous sheet. Also, when the sheet storage portion  71  as a surface for supporting the sheets S moves downward against the elasticity of the coil spring, an upper surface of the sheet storage portion  71 , which is mounted on an upper surface of the movable gear  74  via the support bracket  72 , moves in substantially parallel from an upper position in the figure to a lower limit position of an arrow according to a displacement of the meshing positions of the planetary gear  75  and the gears  73 ,  74  as an amount of the stacked sheets S is increased. 
     A motor M, not shown in the drawings, is established to the planetary gear  75 , and the microprocessor  11 A in FIG. 1 controls to adjust a height of the stacking tray  15  when the sheet S is removed, explained below. 
     The following will describe the embodiment according to the present invention. 
     Here, there are four embodiments (1), (2), (3), (4) for adjusting the height of the stacking tray  15  when removing the sheet S. 
     (1) First embodiment 
     When the sheet S is removed from the stacking tray  15 , the stacking tray  15  is raised to a home position (HP) more quickly than normal, thereby shortening a recovery time to the home position. 
     (2) Second embodiment 
     When the sheet S is removed from the stacking tray  15 , after the sheet S is discharged from the image forming apparatus G, the height of the stacking tray  15  is raised to the home position, thereby improving the alignment and the discharging performance of the sheet S, and also eliminating a sheet jam and a folded sheet in the sheet finishing apparatus. 
     (3) Third embodiment 
     When the sheet S is removed from the stacking tray  15 , the height of the stacking tray  15  is raised according to the size of the sheet S, thereby improving the alignment and the discharging performance of the sheet S. This prevents the sheet S with a smaller size from curling and being inverted front to back when the sheet drops into the stacking tray  15  from the discharge outlet  20 . 
     (4) Fourth embodiment 
     When the sheet S is removed from the stacking tray  15 , the speed to raise the stacking tray  15  is changed according to the size of the sheet S, thereby improving the alignment and the discharging performance of the sheet S. Similarly in this case, this prevents the sheet S with a smaller size from curling and being inverted front to back when the sheet drops into the stacking tray  15  from the discharge outlet  20 . 
     FIG. 5 is a flowchart representing a processing procedure of the second embodiment. FIG. 6 is a view showing a state that the sheet S is removed from the stacking tray  15 , and FIG. 7 a view explaining a rising control of the stacking tray  15 . 
     From FIG. 1 to FIG. 5, it is determined whether the sheet S has been removed from the stacking tray  15  as shown in FIG.  6 . If it is the case, the microprocessor  11 A on the finisher apparatus  11 , as shown in FIG. 1, is interrupted according to the detection signal from the sheet stacking amount detection sensors  85 . The microprocessor  11 A receives in the detection signal from the sheet stacking amount detection sensors  85 , thereby recognizing that the height of the sheet S is lowered (step S 51 ). Next, a chattering absorption processing is performed. This is a process for obtaining a stable converged detection signal for the rising control of the stacking tray  15 , since the detection signal from the sheet stacking amount detection sensors  85  is varied (chattering) by the removal of the sheet S. 
     In the chattering absorption processing, the microprocessor  11 A determines whether a built-in counter is counting (step S 52 ) after step S 51 . If it is not the case (No), the timer is set (step S 53 ) and it returns to step S 51 . If it is the case (Yes) at step S 52 , a counting (timer) value is subtracted (step S 54 ) Then, it is determined that the time is up (step S 55 ) in which a predetermined counting value (a chattering convergence time) has been reached. 
     If it is not the case at step S 55 , it returns to step S 51  and repeats the subsequent routine. At step S 55 , if it is the case (Yes), it is determined whether the image forming apparatus G is executing a job, in other words, the sheet S is being discharged (being transported using the rollers  3   h  to  3   i  in the image forming apparatus), by a sensor not shown in the drawings. Here, when it is discharging the sheet (Yes), the microprocessor  11 A sends a signal to the microprocessor GA in the image forming apparatus G, so that a sheet in a unfed state in the paper cassette  3   g  will not be fed by the pick-up roller  3   h  in the image forming apparatus G, while setting a rising speed of the stacking tray  15  high (step S 57 ). 
     A reason why the stacking tray  15  is raised at such a high speed is because different from a normal state, in which it is possible to take a long time to recover the stacking tray  15  to the home position as the next sheet S will not be discharged, the stacking tray  15  needs to move to the home position in time before the next sheet is discharged. 
     Note that at step S 56 , if it is not discharging the sheets (No), it is possible to raise the stacking tray  15  with a plenty of time because the next sheets will not be discharged. Therefore, step S 57  is not executed (the raising speed of the stacking tray  15  is not set high). Then, the microprocessor  11 A in the finisher apparatus  11  drives the motor M, not shown in the drawings, to rotate the planetary gear  75  shown in FIG. 4, to raise the stacking tray  15  to the predetermined position, namely the home position, illustrated in FIG. 7 (step S 58 ). Next, it is determined if the stacking tray  15  has risen to the home position (step S 59 ). The microprocessor  11 A determines this by determining whether a value of the detection signal from the sheet stacking amount detection sensors  85  reaches a predetermined value of the home position. Then, the rising of the stacking tray  15  is stopped (step S 60 ). 
     At step S 60 , after the stacking tray  15  stops at the home position, only the sheets S being discharged (being transferred by each of the rollers  3   h  to  3   i  in the image forming apparatus) are completely discharged from the rollers  3   h  to  3   i  to the stacking tray  15  through nipping of the follower discharge roller  25  and the discharge roller  36 . The follower discharge roller  25  and the discharge roller  36  temporarily stop after all the sheets S being discharged is completely discharged to the stacking tray  15 . 
     Each of the rollers including the discharge roller  3   i  as the transport means in the image forming apparatus temporarily stops after all the sheets S being discharged (being transferred by each of the rollers  3   h  to  3   i  in the image forming apparatus) is completely discharged to the finisher apparatus  11 , and the pickup roller  3   h  as the sheet supply means temporarily stops at step S 56 , after the sheets being fed are supplied and it is determined that the discharging of the sheets S is being processed (transferred by each of the rollers  3   h  to  3   i  in the image forming apparatus). 
     FIG. 8 is a flowchart representing a processing procedure in the second embodiment. 
     From FIG. 1 to FIG.  4  and FIG. 8, in the same manner as described in the first embodiment, the microprocessor  11 A recognizes that the sheets S is removed from the stacking tray  15 , as shown in FIG. 6, by receiving a detection signal, thereby recognizing that the height of the sheets S is lowered (step S 81 ). Next, the chattering absorption processing is performed until the variances (chattering) in the sheet holder lever  78  caused by the removal of the sheets S is converged (steps S 82  to S 85 , see the explanation of steps S 52  to S 55  in the first embodiment). 
     Next, at step S 85 , if the time is up (Yes), it is determined whether the image forming apparatus G is executing the job, in other words the sheet S is being discharged (transported using the rollers  3   h  to  3   i  in the image forming apparatus) by a sensor, not shown in the drawings (step S 86 ). Here, when it is discharging the sheet (Yes), the microprocessor  11 A sends a signal to the microprocessor GA in the image forming apparatus G so that an unfed sheet in the paper cassette  3   g  is not fed by the pick up roller  3   h  in the image forming apparatus G, and controls to stop the stacking tray  15  (step S 87 ). Next, it is determined if the job is completed, in other words the discharge of the sheets S is completed (the sheets S being transported in the image forming apparatus are discharged to the stacking tray  15 ) (step S 88 ). If the discharging is completed at this point (Yes), and there is no execution of the job at step S 86  (No), it proceeds to the next processing of step S 89 . 
     Then, the microprocessor  11 A in the finisher apparatus  11  drives the motor M, not shown in the drawings, to rotate the planetary gear  75  shown in FIG. 4, thereby raising the stacking tray  15  to the predetermined home position, as shown in FIG. 7 (step S 89 ). 
     There, it is determined that the job is completed at step S 88 . Therefore, there is a plenty of time to raise the stacking tray  15  because a subsequent sheet will not be discharged, and there is no need to set the rising speed of the stacking tray  15  high, as in step S 57  of FIG.  5 . Next, it is determined if the stacking tray  15  is risen to the home position (step S 90 ). The microprocessor  11 A determines this by determining whether a value of the detection signal from the sheet stacking amount detection sensors  85  reaches the predetermined value of the home position. Then, the rising of the stacking tray  15  is stopped (step S 91 ). 
     Thus the sheets being discharged (being transported in the image forming apparatus) are discharged to the stacking tray  15 . 
     FIG. 9 is a flowchart representing a processing procedure in the third embodiment. 
     From FIG. 1 to FIG.  4  and FIG. 9, in the same manner as described in the first embodiment, the microprocessor  11 A recognizes that the sheets S is removed from the stacking tray  15 , as shown in FIG. 6, by receiving the detection signal from the sheet stacking amount detection sensors  85 , thereby recognizing that the height of the sheets S is lowered (step S 101 ). Next, the chattering absorption processing is performed until the variance in the sheet holder lever  78  caused by the removal of the sheets S is converged (steps S 102  to S 105 , see the explanation for steps S 52  to S 55  in the first embodiment). 
     Next, at step S 105 , if the time is up (Yes), the image forming apparatus G determines whether the job is being executed, in other words, that the sheet S is being discharged (transported using the rollers  3   h  to  3   i  in the image forming apparatus) by a sensor not shown in the drawings (step S 106 ). 
     Note that at step S 106 , if no sheet is being discharged (No), it is possible to raise the stacking tray  15  with a plenty of time because the next sheet will not be discharged. Therefore, step S 111  is not executed (the raising speed of the stacking tray  15  is not set high). 
     Here, when the sheet is being discharged (Yes), the microprocessor  11 A sends a signal to the microprocessor GA in the image forming apparatus G not to feed the unfed sheet in the paper cassette  3   g  using the pick-up roller  3   h  in the image forming apparatus G and verifies the size of the sheet being discharged. To perform the verification, the microprocessor  11 A in the finisher apparatus  11  verifies through a status signal from the microprocessor GA in the image forming apparatus G, or the finisher apparatus  11  verifies through a period of time for the sheet to pass from the inlet sensor  21  (step S 107 ) when the finisher apparatus  11  receives the transport of the sheet S from the image forming apparatus G from the inlet  18  shown in FIG.  3 . 
     A counting value (timer) corresponding to the size of the sheet S is set according to the verification, and subsequently the subtraction is performed (steps S 108  and S 109 ). The timer is set to be shorter as the sheet S has a shorter length in the transport direction. In other words, the startup timing of the sheet storage portion  71  on the stacking tray  15  is made earlier to move more quickly to the appropriate position. Through this, when the sheet S with a smaller size or a shorter length in the transport direction is discharged from the processing tray  39  to the sheet storage portion  71  of the stacking tray  15 , the sheet storage portion  71  of the stacking tray  15  rises to the appropriate position, for example the home position, at an earlier timing, thereby preventing the sheet S with a smaller size or a shorter length in the transport direction from being stored with upside down. Then, it is determined if the time is up (step S 110 ), namely if the count reaches the predetermined counting (timer) value. If the time is not up at step S 104 , it returns to step S 103  and repeats the subsequent routine. If the time is up (Yes) at step S 104 , the raising speed of the stacking tray  15  is set high (step S 111 ), as shown in the aforementioned step S 57 . Then, the microprocessor  11 A in the finisher apparatus  11  drives the motor M, not shown in the drawings, to rotate the planetary gear  75  shown in FIG. 4 to raise the stacking tray  15  to the determined home position, illustrated in FIG. 7 (step S 112 ). Next, it is determined if the stacking tray  15  is risen to the home position (step S 113 ). The microprocessor  11 A determines this by determining whether a value of the detection signal from the sheet stacking amount detection sensors  85  reaches the predetermined value of the home position. Then, the rising of the stacking tray  15  is stopped (step S 114 ). 
     Thus, the sheet being discharged (being transported in the image forming apparatus) is discharged to the stacking tray  15 . 
     FIG. 10 is a flowchart representing a processing procedure in the fourth embodiment. 
     From FIG. 1 to FIG.  4  and FIG. 10, in the same manner as described in the first embodiment, the microprocessor  11 A recognizes that the sheets S is removed from the stacking tray  15 , as shown in FIG. 6, by receiving the detection signal from the sheet stacking amount detection sensors  85 , thereby recognizing that the height of the sheets S is lowered (step S 201 ). Next, the chattering absorption processing is performed until the variance in the sheet holder lever  78  caused by the removal of the sheets S is converged (steps S 202  to S 205 , see the explanation in steps S 52  to S 55  in the first embodiment). 
     Next, at step S 205 , if the time is up (Yes), the image forming apparatus G determines whether the job is being executed, in other words, that the sheet S is being discharged (transported using the rollers  3   h  to  3   i  in the image forming apparatus) by a sensor not shown in the drawings (step S 206 ). 
     Note that at step S 206 , if no sheet is being discharged (No), it is possible to raise the stacking tray  15  with a plenty of time because the next sheet will not be discharged. Therefore, step S 208  is not executed (the raising speed of the stacking tray  15  is not set high). 
     Here, when the sheet is being discharged (Yes), the microprocessor  11 A sends a signal to the microprocessor GA in the image forming apparatus G not to feed the unfed sheet in the paper cassette  3   g  using the pick-up roller  3   h  in the image forming apparatus G and verifies the size of the sheet being discharged (step S 207 ). To perform the verification, the microprocessor  11 A in the finisher apparatus  11  verifies through a status signal from the microprocessor GA in the image forming apparatus G, or the finisher apparatus  11  verifies through a period of time for the sheet to pass from the inlet sensor  21  when the finisher apparatus  11  receives the transport of the sheet S from the image forming apparatus G from the inlet  18  shown in FIG.  3 . 
     As the next sheet will not be discharged, the raising speed of the stacking tray  15  is set higher than that in the normal state in which there is a plenty of time to raise to the home position (step S 208 ). The speed is set to be higher as the sheet S has a shorter length in the transport direction as verified in step S 207 . 
     Through this, when the sheet S with a smaller size or a shorter length in the transport direction is discharged from the processing tray  39  to the sheet storage portion  71  of the stacking tray  15 , the sheet storage portion  71  of the stacking tray  15  rises to the appropriate position, for example the home position, at an earlier timing, thereby preventing the sheet S with a smaller size or a shorter length in the transport direction from being stored with upside down due to a difference in levels between the processing tray  39  and the sheet storage portion  71  of the stacking tray  15 . 
     After setting the raising speed, if there is no discharging being conducted at step S 206 , the tray is raised (step S 209 ). The microprocessor  11 A in the finisher apparatus  11  drives the motor M, not shown in the drawings, to rotate the planetary gear  75  shown in FIG. 4, to raise the stacking tray  15  to the home position as shown in FIG.  7 . 
     Next, it is determined if the stacking tray  15  is raised to the home position (step S 210 ). The microprocessor  11 A determines this by determining whether a value of the detection signal from the sheet stacking amount detection sensors  85  reaches the predetermined value of the home position. Then, the raising of the stacking tray  15  is stopped (step S 211 ). Thus, the sheet being discharged (transported in the image forming apparatus) is discharged to the stacking tray  15 . 
     According to the descriptions of the first, third and fourth embodiments of the present invention, by controlling the startup timing and the raising speed of the stacking tray  15 , all the sheets S being discharged (transported using the rollers  3   h  to  3   i  in the image forming apparatus) are discharged and are stored with good alignment while the stacking tray  15  is recovered to the home position. However, it is not necessarily to discharge all the sheets S while the stacking tray is recovered to the home position, and it is possible to control the startup timing and the raising speed of the stacking tray  15  so that some or all of the sheets S being discharged (transported using the rollers  3   h  to  3   i  in the image forming apparatus) are stored in the stacking tray  15  as the stacking tray  15  is recovering to the home position. 
     According to the explanation for the first to the fourth embodiments of the present invention, the stacking tray  15  is configured to raise and lower with regard to the follower discharge roller  25  and the discharge roller  36  as the sheet discharge means. However, it is also perfectly acceptable to raise and lower the sheet discharge means and transport means such as the follower discharge roller  25  and the discharge roller  36  with regard to the stacking tray  15 . 
     In the explanations for the first to the fourth embodiment of the present invention, when the sheet S is removed from the stacking tray  15 , only the sheet S being transported in the image forming apparatus G is discharged to the stacking tray. Controlling the rising and lowering of the stacking tray  15  is performed based on a premise that the subsequent sheet feeding and transporting operations performed by the image forming apparatus G and the sheet discharging operation by the finisher apparatus  11  as the sheet discharge apparatus are temporarily stopped. However, it is also perfectly acceptable to control the rising and lowering of the stacking tray  15  with a premise that the sheet feeding and transporting operations in the image forming apparatus G and the sheet discharging operation using the finisher apparatus  11  until the last sheet are continued, even after the sheets S is removed from the stacking tray  15 . 
     According to the sheet discharge control method, the sheet discharge apparatus, the image forming apparatus and program according to this invention, it is possible to effectively eliminate the sheet jam and the folded sheet in the image forming apparatus or the sheet discharge apparatus, and to greatly improve the alignment of the discharged sheets and the discharging performance.