Patent Publication Number: US-6663102-B2

Title: Sheet discharge control method and sheet discharge apparatus

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     This invention relates to a sheet discharge control method and a sheet discharge apparatus for stacking sheets formed thereupon with images discharged from an image forming apparatus such as a copier or printer. 
     Conventionally, a sheet discharge apparatus (or a so-called finisher) is used for stacking sheets formed thereupon with images by an image forming apparatus such as a copier or printer on a stacking tray. These types of sheet discharge apparatuses have a straight operating mode and a shift operating mode that performs later processes such as stapling the sheets or punching holes therein, according to the operating instructions on the image forming apparatus. 
     In the straight operating mode, sheets are discharged directly to the stacking tray passing through the transport path while in the shift operating mode, a plurality of sheets sequentially switched back to a processing tray along a transport path undergo subsequent processing such as stapling or hole punching after having been aligned by an aligning means, then are discharged to a stacking tray as a sheet bundle. 
     FIG. 22 illustrates the state of discharge of sheets formed with images in the conventional sheet discharge apparatus, FIG. 23 is a flowchart showing the processing procedures relating to the positioning control of a stacking tray on a conventional sheet discharge apparatus. 
     In FIG.  22  and FIG. 23, the sheet S is sent to the sheet discharge apparatus  11  from the image forming apparatus G such as a copier or printer. At the same time, a command specifying the binding mode is received from the image forming apparatus to the sheet discharge apparatus  11  thereby setting this mode. A paper surface detection lever, not shown in the drawings, protrudes to hold the sheet S with this operation setting. The position of the stacking tray  15  is determined after a set time has passed and is positioned (step S 1 ). Also, if not already positioned at the predetermined home position, the stacking tray  15  is controlled to be elevated to the home position. 
     Firstly, if the stacking tray  15  is at its lowest position, a control is executed to raise it. When it is recognized at its home position, the raising of the stacking tray  15  is stopped (steps S 2 , S 3  and S 4 .) If the stacking tray  15  is at its home position at step S 1 , the stacking tray  15  is not moved (step S 5 ). Then, if the stacking tray  15  is at its highest position, a control is executed to lower it (step S 6 ). When it is recognized to be at its home position, the lowering of the stacking tray  15  is stopped (steps S 7  and S 8 .) 
     Thus sheets are discharged to the stacking tray  15  at the home position. In other words, sheets are discharged to their normal position in the stacking tray  15  at the home position. In such cases, if the stacking tray  15  is positioned lower than the home position, sheets will fall into the stacking tray  15 , as shown in FIG.  22 . 
     With this shift mode, a sheet is transported while a processing weight, not shown in the drawings, rotatably supported above the endless transport belt  28  presses against to touch the endless transport belt  28  to the sheet S, but the sheet S experiences curls (the edges of the sheet curl upward) caused by the image forming process in the image forming portion of the image forming apparatus G. Because the upstream edge of the sheet S curls upward, after the upstream edge of the sheet in the direction of transport passes the nipping region pressed to the endless transport belt by the aforementioned processing weight, there is less contact surfaces therebetween the sheet and caterpillar roller thus making it difficult to transmit the endless transport belt  28 &#39;s transport force to the sheet S, thus causing the problem of not fully switching back the sheet S in the processing tray  39 . 
     Furthermore, as shown in FIG. 22, if the gap between the stacking tray  15  and processing tray  39  is large in the vertical direction, the sheet S will slip down into the stacking tray  15 , the upstream edge of the sheet S in the transport direction being urged in a direction away from the endless transport belt  28 . This makes it even more difficult to transmit the transport force from the endless transport belt  28  to the sheet S. Even if the sheet S were to be in contact with the sheet S, a bending would develop in the sheet S between the stacking tray  15  and the caterpillar roller thereby increasing the transport load and making it difficult for the sheet to be completely switch-back transported by the endless transport belt  28 . 
     Note that when the second or subsequent sheet is transported, it passes over the first sheet and the transport is executed without error and such bending stops occurring. 
     To resolve the issues of the prior art, an object of the present invention is to provide a program for a sheet discharge control method and a sheet discharge control apparatus that can control the relative heights and angles of a stacking tray and to process according to the number of sheets discharged and to control the height and angle of the stacking tray when discharging sheets and when discharging sheet bundles to improve the alignment of discharged sheets and the characteristics of transport thereof. 
     SUMMARY OF THE INVENTION 
     To attain the aforementioned objectives, the sheet discharge apparatus according to the present invention is equipped with a discharge means for discharging sheets received from an image forming apparatus, a support means established downstream of the aforementioned discharge means in the direction of sheet discharge, a storage means established downstream of the aforementioned support means in the direction of sheet discharge, a transport means for transporting to the aforementioned storage means a sheet discharged by the aforementioned discharge means straddling the aforementioned support means and the aforementioned storage means, an elevator means for relatively raising or lowering the aforementioned support means and the aforementioned storage means and a control mean to control the aforementioned elevator means to vary the position of the aforementioned storage means to the aforementioned support means according to the number of sheets discharged by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned elevator means so that the relative position of the aforementioned storage means is lower with regard to the aforementioned support means after a determined number of sheets are discharged by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned elevator means so that the downstream edge in the direction of transport of a sheet discharged by the aforementioned discharge means is higher than the highest level of the aforementioned support means until a determined number of sheets are discharged by the aforementioned discharge means. 
     To attain the aforementioned objectives, the sheet discharge apparatus according to the present invention is equipped with a discharge means for discharging sheets received from an image forming apparatus, a support means established downstream of the aforementioned discharge means in the direction of sheet discharge, a storage means established downstream of the aforementioned support means in the, direction of sheet discharge, a transport means for transporting to the aforementioned storage means a sheet discharged by the aforementioned discharge means straddling the aforementioned support means and the aforementioned storage means, an inclining means for varying the relative angle of incline of the aforementioned support means and the aforementioned storage means and a control means to control the aforementioned inclining means so that the angle of incline of the aforementioned storage means to the aforementioned support means is different. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned inclining means so that the angle of incline of the aforementioned storage means is smaller with regard to the aforementioned support means after a determined number of sheets are discharged by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned inclining means so that the downstream edge in the direction of transport of a sheet discharged by the aforementioned discharge means is higher than the highest level of the aforementioned support means until a determined number of sheets are discharged by the aforementioned discharge means. 
     To attain the aforementioned objectives, the sheet discharge apparatus according to the present invention is equipped with a discharge means for discharging sheets received from an image forming apparatus, a support means established downstream of the aforementioned discharge means in the direction of sheet discharge, a storage means established downstream of the aforementioned support means in the direction of sheet discharge, a transport means for transporting to the aforementioned storage means a discharged sheet by the aforementioned discharge means straddling the aforementioned support means and the aforementioned storage means, an elevator means for relatively raising or lowering the aforementioned support means and the aforementioned storage means, an inclining means for varying the relative angle of incline of the aforementioned support means and the aforementioned storage means and a control means for controlling the aforementioned elevator means so that the position of the aforementioned storage means to the aforementioned support means varies when discharging the sheet with the aforementioned discharge means and when transporting the sheet with the aforementioned transport means. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned elevator means so that the relative position of the aforementioned storage means is lower with regard to the aforementioned support means after a determined number of sheets are discharged by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned elevator means so that the downstream edge in the direction of transport of a sheet discharged by the aforementioned discharge means is higher than the highest portion of the aforementioned support means when sheets are discharged by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention is equipped with a discharge means for discharging sheets received from an image forming apparatus, a support means established downstream of the aforementioned discharge means in the direction of sheet discharge, a storage means established downstream of the aforementioned support means in the direction of sheet discharge, a transport means for transporting to the aforementioned storage means a discharged sheet by the aforementioned discharge means straddling the aforementioned support means and the aforementioned storage means, an elevator means for relatively raising or lowering the aforementioned support means and the aforementioned storage means, and a control means for controlling the aforementioned inclining means so that the angle of incline of the aforementioned storage means to the aforementioned support means is different when discharging the sheet with the aforementioned discharge means and when transporting the sheet with the aforementioned transport means. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned inclining means so that the angle of incline of the aforementioned storage means is smaller with regard to the aforementioned support means for the sheet transfer by the aforementioned transfer means that the discharge of sheets by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention has a control means for controlling the aforementioned inclining means so that the downstream edge in the direction of transport of a sheet discharged by the aforementioned discharge means is higher than the highest portion of the aforementioned support means when sheets are discharged by the aforementioned discharge means. 
     The sheet discharge apparatus according to the present invention is further equipped with a finishing means that finishes sheets discharged by the aforementioned discharge means, while straddling the aforementioned support means and the aforementioned storage means 
     This structure controls the height and the incline of the stacking tray according to the number of sheets discharged and controls the height and the inclining of the stacking tray according to sheet discharge and to sheet bundle discharge. Therefore, it improves the alignment of discharged sheets and transporting characteristics. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a model drawing indicating the entire configuration of the embodiment of the present invention; 
     FIG. 2 is a perspective view of the essential external configuration of the finisher apparatus shown in FIG. 1; 
     FIG. 3 is a side view of the essential external configuration of the finisher apparatus shown in FIG. 1; 
     FIG. 4 illustrates the mechanism for detecting the stacking tray position; 
     FIG. 5 is a side view of the configuration of the stacking tray of FIG. 1; 
     FIG. 6 illustrates the sheet holder lever position of an embodiment of the invention; 
     FIG. 7 illustrates the detection signals for the sheet holder lever position of an embodiment of the invention; 
     FIG. 8 is a flowchart representing the general procedures for processing of the first embodiment; 
     FIG. 9 is a flowchart representing the detailed processing procedures for the second embodiment; 
     FIG. 10 is a flowchart representing the processing procedures for the sub-routine of FIG. 8; 
     FIG. 11 is a flowchart representing other sub-routine processing procedures of FIG. 8; 
     FIG. 12 is a side view to illustrate the first upward curl countering position of an embodiment of the present invention; 
     FIG. 13 is a side view to illustrate a further example of the first upward curl countering position of an embodiment of the present invention; 
     FIG. 14 is a side view to illustrate the second upward curl countering position of an embodiment of the present invention; 
     FIG. 15 is a side view to illustrate the third upward curl countering position of an embodiment of the present invention; 
     FIG. 16 is a side view to illustrate a further example of the third upward curl countering position of an embodiment of the present invention; 
     FIG. 17 is a side view to illustrate the stacking tray position when discharging sheet bundles from the stacking tray in an embodiment of the invention; 
     FIG. 18 is a flowchart representing the general procedures for processing of the second embodiment of the present invention; 
     FIG. 19 is a flowchart representing the detailed processing procedures for the second embodiment of the present invention; 
     FIG. 20 is a flowchart representing the processing procedures for the sub-routine of FIG. 19; 
     FIG. 21 is a flowchart representing other sub-routine processing procedures of FIG. 19; 
     FIG. 22 illustrates the discharge of sheets formed with images in sheet discharge apparatus according to the prior art; and 
     FIG. 23 is a flowchart representing the procedures for processing of the stacking tray position control according to the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following shall describe in detail the embodiment of a program together with the sheet discharge control method and sheet discharge apparatus according to the present invention in reference to the drawings provided. The same numbers are used for the same structural elements as were used in the prior art shown in FIG.  22 . 
     FIG. 1 is a model drawing indicating the entire configuration of the embodiment of the present invention. In FIG. 1, G is the image forming apparatus such as a copier or a printer.  11  is a finisher apparatus as an example of the sheet discharge apparatus detachably configured to the image forming apparatus G. 
     The image forming apparatus G shown in FIG. 1 indicates the essential structures of well known copiers or printers and is equipped with a scanner  2  below an automatic document feeder (or ADF)  1 . The image generation portion (printer engine)  3  is arranged below the scanner  2 . 
     The electrostatic body  3   b , the developer  3 C, the cleaner  3   d  and the transfer device  3   e  are arranged on the circumference of the photoconductor body  3   a  in the image generation portion  3 . Also, a plurality of rollers (from the pick-up roller  3   h  to the discharge roller  3   i ) are established along the transport path P to correspond to the control for a series of printing processes from discharging at the photoconductor  3   a  to removal of toner, for the size of the sheet S (paper). A paper cassette ( 3   g ) that stores sheets of the same size is arranged therebelow. 
     The following describes the configuration of the finisher apparatus  11  in detail according to FIG.  2  and FIG.  3 . 
     In image forming apparatus such as the type illustrated with the image forming apparatus G and finisher apparatuses  11 , a microprocessor (MPU) GA controls well known and various printing processes in the series thereof from discharging to removal of toner and the control of the motor&#39;s drive, and executes a variety of display and input processes on the touch panel  3   j  relating to printing. 
     Also, the finisher  11  controls a variety of processes according to each of the straight operation and the shift operation modes, described in detail below, on sheets discharged from the image forming apparatus G and motor drive control according to the microprocessor (MPU)  11 . 
     Also, the microprocessor GA and  11 A are interlocked to execute according to the present invention described in detail below. This interlock outputs the status signal from the image forming apparatus G to the finisher apparatus  11  and controls by control command outputs from the finisher apparatus  11  to the image forming apparatus G. 
     The following shall describe the finisher apparatus  11  in detail. FIG. 2 is a side view of the external configuration of the essential portions of the finisher apparatus  11  and FIG. 3 is a side elevation view of the internal configuration of the essential portions of the finisher apparatus  11 . 
     As clearly illustrated in FIG. 1 to FIG. 3, the finisher apparatus  11  is disposed with a main apparatus  12 , a staple unit  13  mounted to one side frame of this main apparatus  12  and a drive transmission mechanism, not shown in the drawings, arranged on the other side of the main apparatus  12 . Furthermore, it is equipped with an inlet  18  to which sheets formed thereupon with images discharged from the image forming apparatus G are supplied, the discharge outlet  20  formed on a side opposite to the inlet  18  and the storage means or stacking tray  15  for stacking the sheet S discharged from the discharge outlet  20 . 
     Note that the staple unit  13  can be a stapler for binding a bundle of the sheets S using staples, or it can be arranged with a punching unit for punching holes thereto. 
     The main apparatus  12  comprises the first transport path that guides the sheet S from the inlet  18  into the main apparatus  12  and the second transport path for the discharge of the sheet S to the stacking tray  15  through the discharge outlet  20  and the third transport path having a difference in level with the second transport path and guides the sheet S to inside of the processing tray  39  for temporary storage after switching back the direction of transport thereof. At the processing tray  39 , a pressing drive member (not shown in the drawings) presses the adjacent edges of each of the sheet S so that they are aligned, then the aforementioned staple unit  13  stables the sheet bundle or punches holes therein with a punching unit, which is not shown in the drawings. 
     The following shall describe only stapling of the sheet bundles. Note that the finisher apparatus  11  comprises the following operation mode to transport the sheet S, that is distinguished from the first to the third transport paths. 
     (1) Straight Operation Mode: 
     The sheet S is discharged directly to the stacking tray  15  from the first transport path through the second transport path. 
     (2) Shift Operation Mode (Performing the Stapling Operation): 
     The sheet S transported from the first transport path to the second transport path is transported for switch-back from the second transport path along 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 sheet S bundle having been aligned, at a determined position after aligning, the sheet S bundle is discharged to the stacking tray  15 . 
     The first transport path comprises the inlet sensor  21  and the endless transport belt  28  that transports the sheet S to the second transport path. Below the endless transport belt  28  is disposed support means or processing tray unit  30 . The processing tray unit  30  temporarily stacks and places the sheet S so that the sheet S bundle of a predetermined number of sheets sequentially drawn in by the rotation of the endless transport belt  28  can be bound by staples by the staple unit  13 . 
     Above the second transport path is disposed the pivoting unit  24  that pivots upward and downward on the shaft pivot of the paddle drive roller shaft  24   a.    
     In the pivoting unit  24  the follower discharge roller (bundle discharge roller)  25  is disposed. The pivoting unit  24  pivots downward to a position where it 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 discharging the sheet S directly to the stacking tray  15  from the first transport path through the second transport path in the straight operation mode and when discharging the sheet S bundle to the stacking tray  15  in the processing tray unit  30  when in the shift operation mode. Conversely, when leading the sheet S to the third transport path to the processing tray unit  30 , the pivoting unit  24  pivots upward, as shown in FIG. 3, so that it does not interfere with the sheet S being switch-back transported. 
     Below the discharge roller  36  the sheet abutting member  12   a  that regulates the edges of the sheet S stacked in the stacking tray  15  is configured to be unitized with the front surface frame of the main apparatus  12 . To a position near the discharge roller  36  on the sheet abutting member  12   a  is established the sheet holder lever  78  that appears and disappears toward the second transport path from the upper position on the sheet abutting member  12   a , passing through the aperture established. 
     The sheet holder lever  78  is driven to appear and disappear from within the sheet abutting member  12   a  toward the stacking tray  15  by the holding lever solenoid  83  positioned on the back side of the sheet abutting member  12   a  each time the sheet S or the sheet S bundle is discharged by the discharge roller  36  and the follower discharge roller  25 . 
     As shown in FIG. 4, the sheet holder lever  78  rotates with the rotating shaft  82  as the shaft pivot, but when the sheet holder lever  78  is pressing the sheet S, the first flag  79   a  on the detection flag  79  and the second flag  79   b  established on the edge of this lever are detected by the sheet stacking amount detection sensors  85   a  and  85   b  to detect the uppermost sheet surface position stacked on the stacking tray  15 . Based on this signal, the elevator drive motor M (not shown in the drawings) for the stacking tray  15  is accurately controlled to rotate in forward or reverse, thereby maintaining a constant level for the uppermost sheet surface stacked on the stacking tray  15 . 
     Note that the between the first flag  79   a  and the second flag  79   b  on the detection flag  79  is established the notch portion  79   c  which does not act upon the sheet stacking amount detection sensors  85   a  and  85   b.    
     A sensor  40  is established below the processing tray  39 . This sensor  40  is composed of the sensor lever  40   c  extending into the second transport path on the discharge outlet  20  side, the sensor flag  40   b  rotatingly supported by the sensor rotation shaft below the processing tray  39  and the sheet presence sensor  40   a  that detects the sensor flag  40   b.    
     This sensor lever  40   c  extends into the second transport path when no sheet S is present therein. This sensor  40  detects the presence of the sheet S in the second transport path and the presence of the sheet S at the sheet stacking portion on the processing tray  39 . 
     In other words, the sensor  40  functions as a transport pass-through sensor for the trailing edge of the sheet discharged, when stacking a sheet on the stacking tray  15  when passing from the first transport path to the second transport path without being stacked in the sheet stacking portion. Also, the sensor  40  detects the passing through for discharge of the sheet S bundle when discharging them as a bundle from the processing tray  39 . 
     Also, the passing detection signal produced by the sensor  40  is used as the activating signal for the holding lever solenoid  83  to actuate the sheet holder lever  78 . 
     Next, we shall describe the stacking tray  15 . FIG. 5 is a side view of the configuration of the stacking tray  15 . 
     The stacking tray  15  in FIG. 5 is mounted to the base  69  comprising a detachable mounting portion on the main apparatus  12  shown in FIG.  1  and in FIG. 2, and the sheet storage portion  71  elevatingly held to the base  69  via the elevator control portion  70 . The support bracket  72  fastened to the undersurface of the sheet storage portion  71  is mounted to the upper surface of the movable gear  74 . 
     The elevator control portion  70  is equipped with the arc-shaped fixed gear  73  mounted to the base  69 , the arc-shaped movable gear  74  mounted to the support bracket  72 , the planetary gear  75  that meshes and displaces the gears  73  and  74 , the shift arm  76  mounted at a relative distance and interlocked with the planetary gear  75  and the coil spring  77  that constantly urges the sheet storage portion  71  upward, established between the upper surface of the base  69  and the support shaft  72 . 
     This coil spring  77  displaces the sheet storage portion  71  downward in correspondence to the weight of the sheet S stacked sequentially on the upper surface of the sheet storage portion  71 , the elasticity constant being set so that the top surface of the sheet S sequentially stacked remains substantially a constant height as the previous sheet that was stacked thereupon. Also, as the sheet storage portion  71 , which is the support surface for the sheet S, displaces downward in resistance to the elasticity of the coil spring, lowers as the volume of the sheet S stacked upon the upper surface thereof from the upward direction in the figure, mounted via the support bracket  72  on the uppers surface of the movable gear  74  in accordance to the displacement of the meshing positions of the gears  73  and  74  and the planetary gear  75  to move substantially parallel to the lower limit position on the arrow. 
     To the planetary gear  75 , the motor M (not shown in the drawings) is established to execute the height adjustment control for the stacking tray  15  when the sheet S is removed, explained below, by the microprocessor  11 A. Furthermore, the sheet storage portion  71  and the support bracket  72  are configured as separate bodies. For example, while the sheet storage portion  71  is rotatingly supported with the support bracket  72  as the pivot point, a drive mechanism for rotating the sheet storage portion  71  is disposed between the sheet storage portion  71  and the support bracket  72 . Control of this drive mechanism by the microprocessor  11 A changes the angle of inclination of the sheet storage portion  71  (stacking tray  15 ) to enable attaining the same effect. 
     The following shall describe the embodiment according to the present invention. First, we shall explain the relationship of the position of the sheet holder lever  78  and the detection signals. 
     FIG. 6 illustrates the position of the sheet holder lever  78 , FIG. 7 illustrates the detection signal in the sheet holder lever  78  position, FIG. 4 illustrates the peripheral mechanisms of the sheet holder lever  78 . 
     In FIG.  6  and FIG. 7, the sheet holder lever  78  positions ( 1 ), ( 2 ), ( 3 ) and ( 4 ) are detected by the sheet stacking amount detection sensors  85   a  and  85   b  (sheet holding lever sensors) in FIG.  4 . In other words, the first sheet stacking amount detection sensors  85   a  and the second sheet stacking amount detection sensors  85   b  detect the height of the sheets stacked on the stacking tray  15  at a plurality of levels. 
     The sheet holder lever  78  position (1) is where it is stored inside of the sheet abutting member  12   a  and the first sheet stacking amount detection sensors  85   a  is OFF, the second sheet stacking amount detection sensors  85   b  sheet surface detection sensor is ON. 
     The sheet holder lever  78  position (2) is where the sheet S is detected to be stacked on the stacking tray  15 , and the first sheet stacking amount detection sensors  85   a  is ON, the second sheet stacking amount detection sensors  85   b  sheet surface detection sensor is ON. 
     The sheet holder lever  78  position (3) is the home position, and the first sheet stacking amount detection sensors  85   a  is ON, the second sheet stacking amount detection sensors  85   b  sheet surface detection sensor is OFF. 
     The sheet holder lever  78  position (4) is where the sheet S is detected to be removed, and the first sheet stacking amount detection sensors  85   a  is OFF, the second sheet stacking amount detection sensors  85   b  sheet surface detection sensor is OFF. 
     FIG. 4 shows the appropriate position for the sheet holder lever  78  to hold the sheet S, or in other words, positioned at the home position of (3). 
     From this state, each time the sheet S is sequentially discharged to the stacking tray  15 , the sheet holder lever  78  reciprocally moves between the stored position of (1) to the home position of (3), or the positions of dotted lines shown in FIG.  4 . 
     Furthermore, as the sheet S is stacked on the stacking tray  15 , the detection flag  79  moves in the clockwise direction, the first flag  79   a  on the detection flag  79  is detected by the first sheet stacking amount detection sensors  85   a  and turns ON, the second flag  79   b  on the detection flag  79  is detected by the sheet stacking amount detection sensors  85   b  and turns ON. At this point, the signal to lower the stacking tray  15  is output from the microprocessor  11 A on the finisher apparatus  11  and based on this signal, the motor M (not shown in the drawings) lowers the stacking tray  15  for a predetermined amount. 
     The combination of these signals (2 bits) of the sheet holder lever sensor and sheet surface detection sensor being ON and OFF are taken in by the microprocessor (MPU)  11  on the finisher apparatus  11  to recognize the status of the sheets stacked on the stacking tray  15  (including the absence of sheets) to execute the following controls. 
     In the following ordinary operations, at the (1) position, it executes to lower the stacking tray  15 , at (2), it controls to lower the stacking tray  15 . Furthermore, at position (3), because it is at the home position, it controls the stacking tray  15  to stop. At position (4), it controls to raise the stacking tray  15 . 
     In this operation, while transporting the sheet S from the microprocessor GA on the image forming apparatus G, the shift operation request signal (which here is stabling in the aforementioned shift operation) is sent to the microprocessor  1 A on the finisher apparatus  11 . The shift operation mode and the straight operation mode switch according to this signal. The holding lever solenoid  83  operates with the drive signal from the microprocessor  11 A. 
     In this operation, the sheet holder lever  78  protrudes and if it is not positioned at the home position after a prescribed amount of time, it moves to the home position. At this time, in the shift request, if the sheet S is a comparatively large size (for example, the length of 300 mm in the transport direction), the stacking tray  15  is raised from the home position. Then, after the shift operation is completed, the stacking tray  15  is controlled to lower to the home position. 
     The control to raise the stacking tray  15  from the home position is performed from the first sheet to a plurality of the sheet S, then the sheet S is received from the stacking tray  15  at the home position to execute the shift operation. In other words, after discharging the first sheet or a plurality of the sheet S, by receiving more discharged sheet S from the stacking tray  15  at the home position, the sheet S will drop into the stacking tray  15 , causing the problem of an improper shift operation. 
     Note that the height of the stacking tray  15  is variably controlled and the angle of inclination of the stacking tray  15  is also controlled. 
     The following will describe the variable control of the height of the stacking tray  15  and control of the angle of inclination of the stacking tray  15  with a fist and second embodiment. 
     In the first embodiment, the height of the stacking tray  15  is controlled according to the number of the sheet S. 
     In the second embodiment, the angle of the inclination of the stacking tray  15  is variably controlled when discharging the sheet S and the sheet S bundle. 
     (1) First Embodiment 
     FIG. 8 is a flowchart representing the general procedures for processing of the first embodiment. 
     In FIG. 8, the stacking tray  15  position is controlled to a high position as described below for the upward curl of the sheet S. First, the microprocessor  11 A on the finisher apparatus  11  determines whether or not the sheet S is discharged (step S 11 ), if no sheet S is discharged (No), it determines that it is a sheet S bundle (shift mode) (step S 12 ). If no sheet S bundle is discharged (No), it returns to step S 11  and idles. At step S 12 , if a sheet S bundle has been discharged (No), the stacking tray  15  is lowered (step S 13 ). Then, when it reaches the home position (step S 14 ), it stops the stacking tray  15  (step S 15 ). 
     At step S 11 , if a sheet S is discharged (Yes), it is determined whether it is the first sheet in a sheet S bundle to be discharged (step S 16 ). If it is not the first sheet (No), it proceeds to step S 15  to stop the stacking tray  15 . If at step S 16 , it is the first sheet (Yes), a predetermined timer (pulse count values) is set (step S 17 ) from the rise to the stop of the stacking tray  15 . Also, the stacking tray  15  is raised (step S 18 ) and by a time-up at the set value (step S 19 ), it proceeds to step S 14  with the stacking tray  15  stopped. 
     Note that in this example only the first sheet is determined at step S 16 , it is also perfectly acceptable to determine the fifth sheet, for example for a preset number of a plurality of sheets. This can also be set according to the characteristics of the sheet S and to the status of the curls therein. 
     By controlling the raising of the stacking tray  15 , the downstream edge of the sheet S is lifted, as shown in the FIG. 12 described below, the upward curl of the sheet S at this opposite end touching the endless transport belt  28 . The rotation of the endless transport belt  28 , pulls in the direction indicated by the arrow, and as shown in FIG. 13, described below, stacks on a predetermined position on the processing tray  39 . 
     FIG. 9 is a flowchart representing the detailed processing procedures for the first embodiment. FIG. 10 is a flowchart representing the sub-routine processing procedures of those in FIG. 9, FIG. 11 is a flowchart representing the other sub-routine processing procedures of those in FIG.  9 . 
     In FIG. 9, the microprocessor  11 A on the finisher apparatus  11  recognizes the position of the stacking tray  15  with the signals (ON or OFF) output from the sheet stacking amount detection sensors  85  (the sheet holder lever sensor) and the sheet presence sensor  40  (sheet surface detection sensor) indicated in FIG.  6  and FIG.  7 . 
     The position (1) for the stacking tray  15  is when the sheet S is in the stacking tray  15  (no sheets). Also, the position (2) is where the sheet S is detected to be stacked in the stacking tray  15  and the position (3) is the home position. The position (4) is where the sheet S is detected to have been removed. 
     At step S 21 , the position (4) and the position (3) (step S 50 ) and the position (1) and (2) (step S 70 ) are identified and the appropriate steps are taken. 
     When the position (4) at step S 21  is recognized, the microprocessor  11 A executes a control to raise the stacking tray  15  (step S 22 ) With the stacking tray  15  raised, it determines that the stacking tray  15  has reached the home position (3) and determines if the next sheet S is the first sheet of the bundle (step S 23  and S 24 ). If it is the first sheet of the sheet S bundle (Yes), it is determined whether the shift operation request is taken in from the image forming apparatus G. If the shift operation request has been taken in (Yes), next the size of the sheet S is determined by sheet size determination means (for example 300 mm in length in the direction of transport) (step S 25  and step S 26 ). If the sheet S size is small, it is unnecessary to control to change the stacking tray  15  position for the upward curl thereof. 
     Note that in this example only the first sheet is determined at step S 16 , but that it is also perfectly acceptable to determine the fifth sheet, for example for a preset number of a plurality of sheets. This is also set according to the characteristics of the sheet S and to the status of the curls therein. 
     In this case, the process is completed when there is a No at steps S 24  to S 26 . For a large size (Yes) at step S 26 , a control is executed to raise the stacking tray  15  position (step S 27 ). The following describes in detail the raised position (the position for upward curls) according to FIG. 12 to FIG.  16 . 
     After starting to raise the stacking tray  15  position, a timer is set up to the position of the upward curl (step S 28 ). Next, when the time is up, the stacking tray  15  position is stopped (steps S 29  and S 30 ). Next, it is determined to align the sheet S (the stack on the processing tray unit  30 ) (step S 31 ), the stacking tray  15  position is lowered (step S 32 ) and when it reaches the home position (3), the stacking tray  15  is stopped (steps S 33  and S 34 ). 
     In FIG. 10, at the position (3) (step S 50 ), it is determined whether the sheet S is the first sheet of the sheet S bundle (step S 51 ) with the same routine as shown in FIG. 9 (steps  24  to S 34 ). Next, it is determined whether the shift operation mode request has been taken in from the image forming apparatus and determines that the sheet S is a large size sheet. A control is executed to raise the stacking tray  15  position (steps S 52 , S 53  and S 54 ). 
     Next, the timer is set up to the position for the upward curl, the stacking tray  15  position is stopped, and it is determined to align the sheet S (the stack on the processing tray unit  30 ) (steps S 55 , S 56 , S 57  and S 58 ). Next, the stacking tray  15  position is lowered and when it reaches the home position (3), the stacking tray  15  is stopped (steps S 59 , S 50  and S 61 ). 
     In FIG. 11, at the positions (1) and (2) (step S 70 ), first the microprocessor  11 A executes (step S 71 ) a control to lower the stacking tray  15 . With the stacking tray  15  raised, it is determined that the stacking tray  15  has reached the home position (3) and the stacking tray  15  is stopped (step S 72  and S 73 ). After this, it is determined whether it is the first sheet of the sheet S (step S 74 ) in the same routine as in FIG. 9 (steps S 24  to S 34 ). Next, it is determined whether the shift operation mode request has been taken in from the image forming apparatus and determines that the sheet is a large size sheet. A control is executed to raise the stacking tray  15  position (steps S 75 , S 76  and S 77 ). 
     Next, the timer is set up to the position for the upward curl, the stacking tray  15  position is stopped, and it is determined to align the sheet S (the stack on the processing tray unit  30 ) (steps S 78 , S 79 , S 80  and S 81 ). Next, the stacking tray  15  position is lowered and when it reaches the home position (3), the stacking tray  15  is stopped (steps S 82 , S 83  and S 84 ). 
     The following shall describe the position for upward curls on the stacking tray  15 . FIG. 12 is a side view to illustrate the first position for upward curls, FIG. 13 is a side view to illustrate the first position for upward curls in continuation to FIG.  12 . 
     In FIG.  12  and FIG. 13, by controlling the raising of the stacking tray  15 , the downstream edge of the sheet S is lifted, so the upward curl of the sheet S at the upstream edge touches the endless transport belt  28 . The rotation of the endless transport belt  28 , pulls in the direction indicated by the arrow and stacks on a predetermined position on the processing tray  39 , as shown in FIG.  13 . 
     FIG. 14 is a side view to illustrate the second position of the stacking tray  15  for upward curl. In FIG. 14, the position of the stacking tray  15  in this example is arranged in a position lower than the discharge roller  36 . At this position of the stacking tray  15 , the downstream edge of the sheet S is stacked on the stacking tray  15  and the central region of the sheet S is laid on the discharge roller  36 , the upstream edge of the sheet S being stacked at a determined position on the processing tray  39 . Next, when the second sheet S is arranged on top of the first sheet S, it is easily arranged at a determined position on the processing tray  39  without any sagging occurring therein. 
     FIG. 15 is a side view to illustrate the third position for upward curls, FIG. 16 is a side view to illustrate the third position for upward curls in continuation to FIG.  15 . 
     In FIG. 15, the stacking tray  15  position is set so that the upstream side from the downstream side of the sheet S on the discharge roller  36  is arranged in a direct line with the stacking tray  15  and the processing tray  39 . In this case, the sheet S is arranged so that the endless transport belt  28  can easily pull the sheet S into the processing tray  39 . As shown in FIG. 16, the sheet S to a determined number of sheets after the second sheet are arranged to be pulled into the processing tray  39  by the endless transport belt  28  in the same way. 
     FIG. 17 is a side view to illustrate the stacking tray  15  position when discharging a sheet S bundle. In FIG. 17, the position of the stacking tray  15  is arranged in a position lower than the discharge roller  36  when discharging the sheet S bundle. In this state, the sheet S bundle is discharged into the stacking tray  15  by the follower discharge roller  25  (the bundle discharge roller). In this case, the sheet S is discharged to hang into the stacking tray  15  with the weight of the leading edge of the sheet S bundle. 
     Second Embodiment 
     FIG. 18 is a flowchart representing the general procedures for processing of the second embodiment. 
     In FIG. 18, the stacking tray  15  position is set to a high position to counter upward curls of the sheet S in the same way as the first embodiment in FIG. 8, but the angle of incline of the stacking tray  15  is controlled. This inclination is set to face the discharge roller  36  side toward the lower side or conversely setting to face the discharge roller  36  side toward the upper side or to set the stacking tray  15  sheet S stacking surface to be horizontal. This makes it easier for the endless transport belt  28  to pull the sheet S into the processing tray  39  in correspondence to the weight of the paper or the status of the upward curl of the paper. 
     In FIG. 18, it is determined whether or not the sheet S is discharged or not, in the same manner as in FIG. 8, and whether a sheet S bundle is discharged. The stacking tray  15  is lowered or the angle of incline is set as described above (step S 93 ). Then, the stacking tray  15  is stopped at the home position (steps S 94  and S 95 ). 
     If at step S 91 , the sheet S is to be discharged (Yes), it is determined whether it is the first sheet in a sheet S bundle to be discharged and a predetermined timer (pulse count values) (steps S 96  and S 97 ) is set from the rise to the stop of the stacking tray  15 . Next, the stacking tray  15  is raised and the aforementioned angle of incline is set. Furthermore, after the time is up at the set value (steps S 98  and S 99 ), it proceeds to step S 14  to stop the stacking tray  15 . 
     FIG. 19 is a flowchart representing the detailed processing procedures for the second embodiment. FIG. 20 is a flowchart representing the sub-routine processing procedures of those in FIG. 19, FIG. 21 is a flowchart representing the other sub-routine processing procedures of those in FIG.  19 . 
     In FIG. 19, in the same manner as the first embodiment in FIG. 9, the stacking tray  15  positions (1), (2), (3) and (4) are recognized (step S 101 ). 
     If the position (1) is recognized at step S 21 , the stacking tray  15  is raised. It is determined while raising whether the stacking tray  15  has reached the home position of (3). Next, it is determined whether or not it is the first sheet of the sheet S bundle (steps S 102 , S 103  and S 104 ). Next, it is determined if the shift operation mode request has been taken in from the image forming apparatus and it is determined that the sheet S is a large size sheet (steps S 105  and S 106 ). Further, the stacking tray  15  position is raised and a control is stated to set the aforementioned angle of incline and a timer is set for a position to counter for the upward curl of the paper. When the time is up, the stacking tray  15  position is stopped (steps S 107 , S 108 , S 109  and S 110 ). Later, it is determined whether or not to align the sheet S (the stack on the processing tray unit  30 ) (step S 111 ). Next, the stacking tray  15  position is lowered and the angle of incline is set (step S 112 ). When the time is up, the stacking tray  15  is stopped (steps S 113  and S 114 ). 
     In FIG. 20, at the position (3) in step S 120  in FIG. 19, it is determined whether it is the first sheet of a sheet S bundle in the same manner as was used in the routine of FIG. 19 (steps S 104  to S 1114 ), it is determined whether the shift operation request was taken in from the image forming apparatus G and it is determined that the sheet S is a large size. A control is executed to raise the stacking tray  15  position and to set the angle of incline (steps S 121 , S 122 , S 123  and S 124 ). 
     Next, the timer is set to the position to counter for the upward curl, the stacking tray  15  position is stopped, and it is determined to align the sheet S (steps S 125 , S 126 , S 127  and S 128 ). Next, the stacking tray  15  position is lowered and the angle of incline is set. When the determined time is up, the stacking tray  15  is stopped (steps S 129 , S 130  and S 131 ). 
     In FIG. 21, at the positions (1) and (2) of step S 140  in FIG. 19, first the microprocessor  11 A executes (step S 141 ) a control to lower of the stacking tray  15 . It is determined whether the stacking tray  15  has reached the home position (3) while raising and the stacking tray  15  is stopped (step S 142  and S 143 ). 
     After this, it is determined whether it is the first sheet of the sheet S (step S 144 ) in the same routine as in FIG. 19 (steps S 104  to S 114 ). Next, it is determined whether the shift operation mode request has been taken in from the image forming apparatus and it is determined that the sheet S is a large size. A control is executed to raise and to incline the stacking tray  15  position (steps S 145 , S 146  and S 147 ). 
     Next, the timer is set to the position to counter for the upward curl, the stacking tray  15  position is stopped, and it is determined to align the sheet S (steps S 148 , S 149 , S 150  and S 151 ). Next, the stacking tray  15  position is lowered and the angle of incline is set. When the time is up, the stacking tray  15  is stopped (steps S 152 , S 153 , and S 154 ). 
     Note that in the second embodiment, only the first sheet of the sheet S is determined but it is also perfectly acceptable to determine the fifth sheet, for example for a preset number of a plurality of sheets. This is also set according to the characteristics of the sheet S and to the status of the curls therein. 
     As described in detail above, the sheet discharge control method and the sheet discharge apparatus according to the present invention controls the height and the inclination of the stacking tray according to the number of sheets discharged thereto and it controls the height and the inclination of the stacking tray when discharging sheets and sheet bundles. The result is vastly improved alignment of discharged sheets and transporting characteristics.