Patent Publication Number: US-10773918-B2

Title: Sheet discharging apparatus and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet discharging apparatus for discharging sheets and an image forming apparatus including the sheet discharging apparatus. 
     Description of the Related Art 
     Japanese Patent Application Publication No. 2013-82556 proposes a sheet processing apparatus including an intermediate stacking portion on which a sheet is temporarily stacked, a pair of aligning portions which can move relative to each other in a width direction, and a sheet discharging tray disposed below the pair of aligning portions. Each of the aligning portions has a supporting portion to support the lower surface of the sheet, and a vertical portion extending upward from the supporting portion. The vertical portion is provided with a projection portion. Thus, two projection portions contact side edges of the sheet, and the sheet supported by the intermediate stacking portion is aligned in the width direction. When an aligning process and a stapling process for a sheet bundle is completed, the pair of aligning portions retracts outward in the sheet width direction, and the sheet bundle is stacked on the sheet discharging tray. 
     However, the intermediate stacking portion and the pair of aligning portions described in Japanese Patent Application Publication No. 2013-82556 are used only in post-processes such as the aligning process and the stapling process, and thus are not used when the post-processes are not performed. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a sheet discharging apparatus includes a discharging portion configured to discharge a sheet in a sheet discharging direction, a first supporting portion configured to support the sheet in a state where at least a part of the sheet is exposed to an outside, a second supporting portion disposed downstream of the first supporting portion in the sheet discharging direction and configured to support the sheet discharged by the discharging portion, and a control portion configured to execute a first mode and a second mode, the first mode being a mode where the first supporting portion is selected as a destination of the discharged sheet and where the first supporting portion supports the sheet, the second mode being a mode where the second supporting portion is selected as the destination of the discharged sheet and where the second supporting portion supports the sheet by discharging the sheet supported on the first supporting portion to the second supporting portion by the discharging portion in a state where the sheet is not supported on the first supporting portion. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall schematic diagram of a printer of a first embodiment. 
         FIG. 2  is a perspective view illustrating a sheet aligning apparatus. 
         FIG. 3  is a plan view illustrating a second aligning member. 
         FIG. 4  is a plan view illustrating a first aligning member. 
         FIG. 5  is a control block diagram of the first embodiment. 
         FIG. 6A  is a plan view for illustrating a sheet aligning operation performed on A4-size sheets. 
         FIG. 6B  is a side view for illustrating the sheet aligning operation performed on A4-size sheets. 
         FIG. 7  is a plan view illustrating a state where the sheet aligning operation has been completed. 
         FIG. 8A  is a plan view for illustrating a sheet aligning operation performed on A3-size sheets. 
         FIG. 8B  is a perspective view for illustrating the sheet aligning operation performed on A3-size sheets. 
         FIG. 8C  illustrates the sheet aligning apparatus as viewed from an A-direction of  FIG. 8B . 
         FIG. 8D  is a plan view illustrating the aligning members positioned at a retracting position. 
         FIG. 9A  is a plan view illustrating a modification of the second aligning member. 
         FIG. 9B  is a plan view illustrating another modification of the second aligning member. 
         FIG. 10A  is a side view for illustrating a holding mode. 
         FIG. 10B  is a side view for illustrating a stacking mode. 
         FIG. 10C  is a side view illustrating a state where a sheet is supported on a discharging tray in the stacking mode. 
         FIG. 10D  is a side view illustrating a state where sheets are supported on the discharging tray, an intermediate tray, and the aligning members. 
         FIG. 10E  is a side view illustrating a state where the holding mode is being released. 
         FIG. 11  is a flowchart illustrating processes related to the holding mode and the stacking mode. 
         FIG. 12  is a flowchart illustrating processes related to the holding mode and the stacking mode. 
         FIG. 13A  is a side view for illustrating a holding mode of a second embodiment. 
         FIG. 13B  is a side view for illustrating a stacking mode of the second embodiment. 
         FIG. 14A  is a side view for illustrating a holding mode of a third embodiment. 
         FIG. 14B  is a side view for illustrating a stacking mode of the third embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an image forming apparatus of the present disclosure will be described with reference to the accompanying drawings. Examples of the image forming apparatus include printers, copying machines, facsimiles, and multifunction printers having functions of these products. 
     First Embodiment 
     Overall Configuration 
     As illustrated in  FIG. 1 , a printer  10  of the present embodiment, which serves as an image forming apparatus, is a multifunction printer including an image forming apparatus body  100  and a sheet processing apparatus  200 . The image forming apparatus body  100  includes an electrophotographic image forming portion  102 , and the sheet processing apparatus  200  performs processes, such as stapling, on sheets S on which images are formed. 
     The sheet processing apparatus  200  is detachably attached to an upper portion of the image forming apparatus body  100 , and an image reading apparatus  300  to read image data from a document is disposed above the sheet processing apparatus  200 . In the following description, a “front side” and a “back side” are intended to mean the front side and the back side with respect to  FIG. 1 . 
     The image forming apparatus body  100  includes the direct-transfer image forming portion  102  which directly transfers a toner image formed on a photosensitive drum  111  to a sheet S. The photosensitive drum  111  is a photosensitive member. Examples of the sheet S include a piece of plain paper; a piece of specialized paper such as coated paper; an envelope; a piece of recording material, such as index paper, which has a specialized shape; and a recording medium which may be a cloth or a plastic film used for overhead projectors. 
     When the image forming portion  102  is required to start an image forming operation, the photosensitive drum  111  of the image forming portion  102  is rotated. The surface of the photosensitive drum  111  is uniformly charged by a charging apparatus  112 , and exposed by an exposure apparatus  113 . The exposure apparatus  113  modulates and outputs a laser beam in accordance with image data which is read by the image reading apparatus  300  or sent from a host computer connected with the printer  10  via a network; and forms an electrostatic latent image on the surface of the photosensitive drum  111 . The electrostatic latent image is then visualized (developed) by the toner supplied from a developing apparatus  114 . 
     In synchronization with such an image forming operation, a sheet feeding portion  101  performs a feeding operation which feeds the sheet S toward the image forming portion  102 . The sheet feeding portion  101  includes sheet supporting apparatuses  105  and  106 , and feed rollers  107  and  108 . The sheet supporting apparatuses  105  and  106  support sheets S, and may be cassettes. The feed rollers  107  and  108  feed the sheets S supported by the sheet supporting apparatuses  105  and  106 . The sheet S sent by the feed roller  107  or  108  is separated, one by one, by a separation mechanism; and conveyed to a registration portion  110 . The separation mechanism may be a retard separation system or a separation pad system. 
     The registration portion  110  corrects skew of the sheet S, and conveys the sheet S toward a transfer roller  115  in synchronization with image forming operation of the image forming portion  102 . The transfer roller  115  transfers a toner image carried on the photosensitive drum  111  onto the sheet S by using electrostatic bias, at a transfer nip portion formed between the transfer roller  115  and the photosensitive drum  111 . The sheet S on which the unfixed-toner image has been transferred is delivered to a fixing apparatus  103 , and heated and pressurized while being held between a fixing roller  116  and a pressure roller  117 . With this operation, the toner is melted and fixed to the sheet S. The sheet S on which the fixed image is formed is delivered to a discharging unit  104 . 
     The discharging unit  104  includes a reversing roller pair  121  and a flap-like switching member  120 . The reversing roller pair  121  can rotate in a forward or a reverse direction, and the switching member  120  can switch the conveyance direction of the sheet S between a path toward a discharging tray  124  disposed in the body and a path toward the sheet processing apparatus  200 . When the sheet S is not processed by the sheet processing apparatus  200 , the sheet S is guided toward a discharging roller pair  123  by the switching member  120  and a discharging guide pair  122 . The discharging roller pair  123  discharges the sheet S to the discharging tray  124 , disposed in an upper portion of the image forming apparatus body  100 , in a face down state. Here, the face down state is a state in which a surface of the sheet S on which the toner image is formed faces downward. Above the discharging tray  124  disposed in the body, a full load detecting sensor  125  is disposed to detect a state in which sheets S are fully stacked on the discharging tray  124  disposed in the body. When the image forming apparatus body  100  determines depending on a detection signal from the full load detecting sensor  125  that the amount of stacked sheets exceeds a predetermined value, the image forming apparatus body  100  stops the image forming operation. 
     On the other hand, when the printer  10  is set so that processes including stapling are performed on the sheet S on which an images is formed, the sheet S is guided toward the later-described sheet processing apparatus  200  by the switching member  120 . In addition, also when the printer  10  is set so that any process is not performed on the sheet S, and that the sheet S is discharged to the intermediate tray  203  or the discharging tray  210  of the sheet processing apparatus  200 , the switching member  120  guides the sheet S toward the sheet processing apparatus  200 . 
     When duplex printing is performed to form images on both sides of the sheet S, the reversing roller pair  121  rotates in the reverse direction to convey the sheet S in the opposite direction, and the sheet S is guided to a duplex conveyance path  126  by a switching member  127 . The sheet S guided to the duplex conveyance path  126  is conveyed to the registration portion  110  again. Then an image is formed on the back side of the sheet S by the image forming portion  102 , and the sheet S is conveyed to the discharging tray  124  disposed in the body or the sheet processing apparatus  200  through a path which is selected as appropriate by the switching member  120 . 
     Here, the above-described image forming portion  102  is one example of image forming means to form an image on the sheet S, and may be a tandem-type intermediate-transfer color-image forming portion or an image forming engine (such as an ink-jet image forming system) other than the electrophotographic image forming system. 
     Sheet Processing Apparatus 
     Next, the sheet processing apparatus  200  which serves as a sheet discharging apparatus will be described. In the present disclosure, the processing of sheets includes binding process such as stapling, aligning process performed for each sheet or for a predetermined number of sheets, punching, and folding process. 
     As illustrated in  FIGS. 1 and 2 , the sheet processing apparatus  200  includes conveyance roller pairs  201   a  to  201   c , the intermediate tray  203 , a discharging-direction aligning portion  205 , a pair of aligning members  206  and  207 , a discharging roller pair  204 , and the discharging tray  210 . In addition, the sheet processing apparatus  200  includes a stapler  209 , which can perform stapling. The stapler  209  is one example of a processing mechanism to process a sheet supported on the intermediate tray  203 . The intermediate tray  203  which is a first supporting portion, the discharging-direction aligning portion  205 , and the aligning members  206  and  207  constitute a sheet aligning apparatus  202  which aligns the sheet S. 
     The conveyance roller pairs  201   a  and  201   b  receive the sheet S, discharged upward from the image forming apparatus body  100 , and deliver the sheet S to the conveyance roller pair  201   c . The conveyance roller pair  201   c  which is a first discharging portion further delivers the sheet S to the sheet aligning apparatus  202 . The sheet aligning apparatus  202  causes the intermediate tray  203  and the aligning members  206  and  207  to support the sheet S, and causes the discharging-direction aligning portion  205  and the aligning members  206  and  207  to align the sheet S so that the sheet S is positioned at a target aligning position. Here, the target aligning position is a sheet position which is set in accordance with a corresponding process. For example, when the stapling is performed, the target aligning position is set in accordance with a binding position of the stapler  209 . 
     As illustrated in  FIG. 2 , the discharging-direction aligning portion  205  is disposed above the intermediate tray  203 , and includes friction rollers  205   a  and  205   a . The friction rollers  205   a  and  205   a  can rotate around an axis extending in a direction orthogonal to a sheet discharging direction (arrow D), that is, in a width direction of the sheet S. The discharging-direction aligning portion  205  can move between an abutment position at which the friction rollers  205   a  and  205   a  abut against the upper surface of the sheet S supported on the intermediate tray  203  and a separation position at which the friction rollers  205   a  and  205   a  are separated upward from the sheet S. The discharging-direction aligning portion  205  is moved up and down between the abutment position and the separation position by the driving force of a first motor M 1  (see  FIG. 5 ). 
     The intermediate tray  203  which supports the sheet S to be processed by the sheet processing apparatus  200  has a supporting surface  203   a  and a first reference wall  203   b . The supporting surface  203   a  supports an upstream portion of the sheet S in the conveyance direction, and the first reference wall  203   b  extends upward from an upstream edge of the supporting surface  203   a . Both sides of the intermediate tray  203  in the width direction are provided with a second reference wall  208  and a third reference wall  215 . The second reference wall  208  is linked with the aligning member  206  via a link mechanism (not illustrated) so that the second reference wall  208  moves with the aligning member  206 . 
     The aligning members  206  and  207  constitute a pair of aligning members. The aligning member  206  which is a first aligning member  206  is disposed on the back side with respect to the sheet processing apparatus  200 , that is, on one side in the width direction. The aligning member  207  which is a second aligning member  207  is disposed on the front side with respect to the sheet processing apparatus  200 , that is, on the other side in the width direction. Each of the aligning members  206  and  207  has a cross section which is C-shaped and opened toward a center position between the aligning members  206  and  207  in the width direction, when viewed from the sheet discharging direction. In other words, the aligning member  206  has a side wall  206   c  which faces one side edge of the sheet S, that is, one edge portion of the sheet S in the width direction; and the aligning member  207  has a side wall  207   c  which faces the other side edge of the sheet S, that is, the other edge portion of the sheet S in the width direction. A supporting lower surface  206   a  extends from the lower edge of the side wall  206   c  toward the center position in the width direction, and a supporting upper surface  206   b  extends from the upper edge of the side wall  206   c  toward the center position in the width direction. A supporting lower surface  207   a  extends from the lower edge of the side wall  207   c  toward the center position in the width direction, and a supporting upper surface  207   b  extends from the upper edge of the side wall  207   c  toward the center position in the width direction. 
     As illustrated in  FIGS. 3 and 4 , the side wall  207   c  of the second aligning member  207  is provided with a fourth reference wall  207   d  which protrudes toward the center position in the width direction, and the first aligning member  206  is provided with two pressing members  211  and  212  which protrude from the side wall  206   c  toward the center position in the width direction. The pressing member  211  is supported so that the pressing member  211  can move along a guide portion  211   a  in the width direction, and is urged by an elastic member  213  toward the center position in the width direction. The pressing member  212  is supported so that the pressing member  212  can move along a guide portion  212   a  in the width direction, and is urged by an elastic member  214  toward the center position in the width direction. In a natural state of the pressing members  211  and  212  where the sheet S is not pressed by the pressing members  211  and  212 , the pressing member  212  protrudes slightly closer to the center position in the width direction, than the pressing member  211 . 
     As illustrated in  FIGS. 2 to 4 , the fourth reference wall  207   d  of the second aligning member  207  contacts one side edge of the sheet S, and the pressing members  211  and  212  of the first aligning member  206  contact the other side edge of the sheet S. That is, the fourth reference wall  207   d  and the side wall  207   c  are an abutment surface against which the sheet S can abut, and the pressing members  211  and  212  and the side wall  206   c  are also an abutment surface against which the sheet S can abut. Here, only the side wall  206   c  of the first aligning member  206  and the side wall  207   c  of the second aligning member  207  may contact the side edges of the sheet S. The supporting lower surfaces  206   a  and  207   a  are lower-surface supporting portions which face the lower surface of the sheet S which is in contact with the abutment surfaces. 
     The aligning members  206  and  207  can be moved relative to each other in the width direction by the driving force of a second motor M 2  (see  FIG. 5 ). Each of the aligning members  206  and  207  can move between a retracting position (for example, a position illustrated in  FIG. 8D ) and an aligning position (for example, a position illustrated in  FIG. 7 ). The retracting position is a position to which each of the aligning members  206  and  207  retracts in the width-direction, outside the sheet S discharged by the discharging roller pair  204 . The aligning position corresponds to the target aligning position of the sheet S. In addition, each of the aligning members  206  and  207  can also move to a sheet receiving position (see  FIG. 6A ) which is a holding position between the retracting position and the aligning position. Here, the aligning position is a position which is set in accordance with a sheet width of the sheet S, so that the abutment surfaces of the aligning members  206  and  207  contact the side edges of the sheet S when the sheet S is positioned at the target aligning position. 
     As illustrated in  FIG. 2 , the discharging roller pair  204  is one example of a second discharging portion which discharges the sheet aligned by the sheet aligning apparatus  202 , and is disposed between the intermediate tray  203  and the aligning members  206  and  207  in the sheet discharging direction. The discharging tray  210  is one example of a second supporting portion which supports the sheet discharged by the discharging roller pair  204 , and is disposed below the aligning members  206  and  207 . The discharging roller pair  204  is a so-called comb-teeth roller pair in which a plurality of upper rollers  204   a  and a plurality of lower rollers  204   b  are alternately disposed in the width direction, and in which outer circumferential portions of the plurality of upper rollers  204   a  partly overlap with outer circumferential portions of the plurality of lower rollers  204   b  when viewed from the width direction. The upper rollers  204   a  and the lower rollers  204   b  can move relative to each other in the vertical direction. Thus, the discharging roller pair  204  can be switched between a close state and an open state. The close state is a first state in which the discharging roller pair  204  can hold and convey the sheet S. The open state is a second state in which the upper rollers  204   a  and the lower rollers  204   b  are separated from each other in the vertical direction. In the open state, the discharging roller pair  204  cannot hold the sheet S. In the present embodiment, the upper rollers  204   a  which serve as a second rotary member can be contacted to or separated from the lower rollers  204   b  which serve as a first rotary member, by the driving force of a third motor M 3  (see  FIG. 5 ). However, the discharging roller pair  204  may not be a comb-teeth roller pair, and the upper rollers  204   a  and the lower rollers  204   b  may form a nip. 
     Control Block 
       FIG. 5  is a control block diagram of the present embodiment. The control block of  FIG. 5  may be partly or wholly disposed in the sheet processing apparatus  200 , or disposed in the image forming apparatus body  100 . A control portion  20  controls the system of the printer  10 , and includes a CPU  21 , a ROM  22 , and a RAM  23 . The CPU  21  is connected, via an address bus and a data bus, with the ROM  22  in which a control program is written, and with the RAM  23  in which data used for the control is written. 
     Input terminals of the control portion  20  are connected with a sheet sensor SE 1  which detects whether the discharging tray  210  supports sheets, and with a full load detecting sensor SE 2  which determines whether sheets are fully stacked on the discharging tray  210 . Output terminals of the control portion  20  are connected with the first motor M 1 , the second motor M 2 , and the third motor M 3 . 
     Sheet Aligning Operation 
     With reference to  FIGS. 6A to 8D , a sheet aligning operation of the sheet aligning apparatus  202  having the above-described configuration will be described.  FIGS. 6A, 7, 8A , and  8 D are plan views in which main parts of the sheet processing apparatus  200  are viewed from above. For convenience of description, the supporting upper surfaces  206   b  and  207   b  of the aligning members  206  and  207  are omitted in the figures. In addition,  FIGS. 6A to 7  illustrate states where an A4-size sheet S 1  is conveyed into the sheet aligning apparatus  202 , and  FIGS. 8A to 8D  illustrate states where an A3-size sheet S 2  is conveyed into the sheet aligning apparatus  202 . 
     First, with reference with  FIGS. 6A to 7 , a sheet aligning operation performed when the A4-size sheet S 1  is conveyed into the sheet aligning apparatus  202  will be described. When the sheet aligning operation of the sheet aligning apparatus  202  is requested, the aligning members  206  and  207  are moved in advance toward the center position in the width direction, and positioned at a sheet receiving position, as illustrated in  FIG. 6A , at which the supporting lower surfaces  206   a  and  207   a  can support the lower surface of the sheet S. At this time, the fourth reference wall  207   d  of the second aligning member  207  is substantially flush with the third reference wall  215 . In addition, the first aligning member  206  is positioned at a position at which the pressing members  211  and  212  do not prevent the conveyance of the sheet S 1 . 
     The pressing member  212  is not used when the A4-size sheet S 1  is aligned, but used when the A3-size sheet S 2  is aligned, as described later. In addition, as illustrated in  FIG. 6B , a downstream edge of the sheet S 1  in the sheet discharging direction is supported by the aligning members  206  and  207 , and thus the sheet S 1  is placed on the aligning members  206  and  207  in a state where a center portion of the sheet S 1  does not bend and protrude downward, and where the sheet S 1  is substantially flat. 
     Then the sheet aligning apparatus  202  waits until the sheet S 1  is conveyed into the sheet aligning apparatus  202 , in a state where the friction rollers  205   a  and  205   a  of the discharging-direction aligning portion  205  are positioned at the separation position, and where the discharging roller pair  204  is kept in the open state. When the sheet S 1  is conveyed into the sheet aligning apparatus  202  by the conveyance roller pair  201   c , the sheet S 1  is supported on the intermediate tray  203  and the aligning members  206  and  207 . That is, an upstream portion of the sheet S 1  in the conveyance direction is supported by the supporting surface  203   a  of the intermediate tray  203 , and side portions (in the width direction) of a downstream portion (in the conveyance direction) of the sheet S 1  are supported on the supporting lower surfaces  206   a  and  207   a  of the aligning members  206  and  207 . In this state, the sheet aligning operation of the sheet aligning apparatus  202  is started. 
     First, the first aligning member  206  is moved toward the second aligning member  207  by the driving force of the second motor M 2 . Then, as illustrated in  FIG. 7 , the pressing member  211  pushes one edge of the sheet S 1  in the width direction, moves the sheet S 1  toward the third reference wall  215  and the fourth reference wall  207   d , and thereby aligns the sheet S 1 . Since the second reference wall  208  moves in synchronization with the first aligning member  206 , the sheet S 1  is aligned in the width direction by the second reference wall  208 , the third reference wall  215 , the fourth reference wall  207   d , and the pressing member  211 . Like the pressing member  211 , the second reference wall  208  is supported so that the second reference wall  208  can move in the width direction, and is urged by an elastic member toward a center position in the width direction. 
     The fourth reference wall  207   d  of the second aligning member  207  and the pressing member  211  align a downstream edge portion of the sheet S 1 , which is in the sheet discharging direction; and the second reference wall  208  and the third reference wall  215  align an upstream edge portion of the sheet S 1 , which is in the sheet discharging direction. Thus, when aligned, the sheet S 1  can be moved in the width direction, without being rotated. 
     In addition, the first aligning member  206  moves to a position at which a gap between the supporting lower surfaces  206   a  and  207   a  in the width direction becomes smaller than a length of the sheet S 1  in the width direction. With this operation, even when an apparent length of the sheet S 1  is shortened due to tolerance of components and sheet width, or curl, the edge portion of the sheet S 1  in the width direction can reliably reach the third reference wall  215  and the fourth reference wall  207   d , keeping high aligning accuracy for the sheet S 1 . Here, the elastic force of the elastic members  213  and  214  is set so that the elastic force does not damage the sheet S 1  after the edge portion of the sheet S 1  in the width direction reaches the third reference wall  215  and the fourth reference wall  207   d . Thus, when the sheet S 1  pushes back the pressing member  211 , the pressing member  211  moves outward in the width direction, and contracts from its natural state. As a result, a positional difference between the pressing members  211  and  212  in the width direction becomes larger. 
     When the aligning operation in the width direction for the sheet S 1  is completed, the aligning operation in the sheet discharging direction is started. The friction rollers  205   a  and  205   a  of the discharging-direction aligning portion  205  move to the abutment position, rotates in a direction opposite to the sheet discharging direction, and thereby causes the trailing edge of the sheet S 1  to abut against the first reference wall  203   b  of the intermediate tray  203 . Then the friction rollers  205   a  and  205   a  move to the separation position, and the aligning members  206  and  207  move to the sheet receiving position and wait until a following sheet is conveyed into the sheet aligning apparatus  202 . Here, in the vicinity of the intermediate tray  203 , a holding member (not illustrated) is disposed to hold the sheet S 1  between the holding member and the supporting surface  203   a  of the intermediate tray  203 . Thus, once aligned, the sheet S 1  is kept in an aligned state. 
     The above-described aligning operation for the single sheet S 1  is repeated until a series of jobs to discharge sheets is completed. Then, the stapler  209  performs a binding process on a sheet bundle supported on the intermediate tray  203  and the aligning members  206  and  207 . After that, the discharging roller pair  204  enters the close state; the aligning members  206  and  207  move to the retracting position, which is the separation position; and the discharging roller pair  204  rotates to stack the processed sheet bundle on the discharging tray  210 . 
     Here, the order of operations of the discharging-direction aligning portion  205  and the aligning members  206  and  207  may be reversed. That is, the discharging-direction aligning portion  205  may align the sheet S 1 , earlier in the sheet discharging direction, and then the aligning members  206  and  207  may align the sheet S 1  in the width direction. In addition, when the sheet S 1  is moved upstream in the sheet discharging direction and aligned as in the present embodiment, it is desirable that the sheet S 1  is supported in a state where a downstream portion of the sheet S 1  in the sheet discharging direction is raised with respect to an upstream portion of the sheet S 1 . With this configuration, the sheet S 1  can slide upstream in the sheet discharging direction, due to the weight of the sheet S 1  itself. 
     Next, a supported state of the A3-size sheet S 2  conveyed into the sheet aligning apparatus  202  will be described with reference to  FIGS. 8A to 8D . Here, the aligning operation for the A3-size sheet is the same as that for the A4-size sheet. As illustrated in  FIGS. 8A and 8B , when the A3-size sheet S 2  is conveyed into the sheet aligning apparatus  202 , a downstream edge portion of the sheet S 2  in the sheet discharging direction is not supported by the aligning members  206  and  207 . In addition, as illustrated in  FIG. 8C , when the aligning members  206  and  207  are positioned at a sheet receiving position or an aligning position, a center portion of the sheet S 2  in the width direction bends and protrudes downward. That is, the sheet S 2  is U-shaped. Since the sheet S 2  is supported so as to be U-shaped, a downstream portion of the sheet S 2  in the sheet discharging direction does not hang because of to the stiffness of the sheet S 2 , even though the downstream portion is not supported by the aligning members  206  and  207 . Thus, even when a long sheet is used, the sheet can be supported on the intermediate tray  203  and the aligning members  206  and  207 . 
     When the downstream portion of the sheet S 2  is supported so as to be U-shaped in this manner, an apparent width of the downstream portion of the sheet S 2  becomes shorter than the nominal value. In addition, as described for the aligning operation performed on the A4-size sheet S 1  in the width direction, when the aligning operation is performed, it is desirable for preventing rotation of the sheet that an upstream portion and a downstream portion of the sheet in the sheet discharging direction are pushed at their side edges. Here, the upstream portion and the downstream portion are disposed, with a center of gravity of the sheet being interposed between the upstream portion and the downstream portion in the sheet discharging direction. 
     Based on the above-described two points, it is preferable that the pressing member  212  protrudes closer to a center point in the width direction, than the pressing member  211 . The amount of protrusion of the pressing member  212  with respect to the pressing member  211  is required to be larger than the amount by which an apparent width of the sheet becomes shorter by supporting the sheet so as to be U-shaped. This is because, for preventing rotation of the A3-size sheet S 2  in the alignment, the pressing member  212  is required to contact the side edge of the sheet S 2  in the width direction, earlier than the pressing member  211 . If the sheet S 2  was rotated by the pressing member  212 , the rotation would hardly produce negative effect on the alignment of the sheet S 2 , because the sheet S 2  would be rotated in a direction (clockwise in  FIG. 8A ) in which an upstream edge portion of the sheet S 2  moves closer to the first reference wall  203   b.    
     However, if the pressing member  212  is disposed downstream in the sheet discharging direction and excessively separated from the pressing member  211 , the U-shape of the sheet S 2  may cause the side edges of the sheet S 2  to move upward when the first aligning member  206  moves toward the second aligning member  207  in the aligning operation for the sheet S 2 . Thus, it is preferable that the U-shape is formed in the sheet S 2  from a position slightly downstream of the pressing member  211  in the sheet discharging direction. 
     In addition, in the present embodiment, a cutout  207   e  is formed in the supporting lower surface  207   a , as illustrated in  FIG. 3 . Specifically, the cutout  207   e  is formed in a portion of the supporting lower surface  207   a  on the downstream edge side in the sheet discharging direction, and on the center side in the width direction. The cutout  207   e  has an edge line which connects a point  207   f  and a point  207   g , and along which the cutout  207   e  is cut out. Similarly, a cutout  206   e  is formed in the supporting lower surface  206   a , as illustrated in  FIG. 4 . Specifically, the cutout  206   e  is formed in a portion of the supporting lower surface  206   a  on the downstream edge side in the sheet discharging direction, and on the center side in the width direction. The cutout  206   e  has an edge line which connects a point  206   f  and a point  206   g , and along which the cutout  206   e  is cut out. With the cutouts  206   e  and  207   e  formed in this manner in the supporting lower surfaces  206   a  and  207   a , a center portion of the sheet in the width direction can easily bend and protrude downward. 
     Preferably, an upstream portion of the sheet S 2  in the sheet discharging direction is flat so as to allow the stapler  209  to highly precisely perform the binding process, and only a downstream portion of the sheet S 2  is U-shaped. Thus, the cutouts  206   e  and  207   e  are widened in the width direction as the cutouts  206   e  and  207   e  extend downward in the sheet discharging direction. The sheet S 2  is supported in a state where the sheet S 2  is in contact with the edge line connecting the points  206   f  and  206   g , and with the edge line connecting the points  207   f  and  207   g ; and thus is U-shaped. Preferably, the points  206   g  and  207   g  are positioned closer to the center position in the width direction, than the side edges of the sheet in the width direction, which is conveyed into the sheet aligning apparatus  202 . 
     Here, the shape of the cutouts  206   e  and  207   e  of the aligning members  206  and  207  is not limited to the shape formed by connecting the points  206   f  and  206   g  by using a straight line, and the shape formed by connecting the points  207   f  and  207   g  by using a straight line. For example, as illustrated in  FIGS. 9A and 9B , the shape of the cutout  207   e  may be formed by connecting the points  207   f  and  207   g  by using a curved line. However, when the second aligning member  207  is formed as illustrated in  FIG. 9B , it is difficult to stably support the sheet because only a contact point  207   h  contacts the sheet. For this reason, the second aligning member  207  is preferably formed as illustrated in  FIG. 9A . 
     The above-described sheet aligning operation has been described for the A4-size and A3-size sheets for example, but is not limited to the operation for these two size sheets. For example, the present invention is also applicable for a sheet processing apparatus which can align sheets having, for example, the LTR size, the LDR size, and other sheet sizes. 
     Holding Mode and Stacking Mode 
     Next, a holding mode and a stacking mode which are main features of the present invention will be described. In the above-described sheet aligning operation, the aligning process and the binding process are performed on sheets discharged to the intermediate tray  203  and the aligning members  206  and  207 . In the present embodiment, however, even when these processes are not performed, sheets can be discharged to and supported on the intermediate tray  203  and the aligning members  206  and  207 . 
     As illustrated in  FIG. 10A , in the holding mode, when a sheet discharging job (for example, an image forming job which forms an image on a sheet and discharges the sheet to the sheet processing apparatus  200 ) is inputted, the intermediate tray  203  is selected as a destination of the discharged sheet. In the holding mode, when the job is completed, the sheet is supported on the intermediate tray  203  and the aligning members  206  and  207 . More specifically, when the control portion  20  (see  FIG. 5 ) executes the holding mode serving as a first mode, the discharging roller pair  204  enters the open state, and the aligning members  206  and  207  are positioned at the sheet receiving position. In this state, a sheet S 3  is discharged by the conveyance roller pair  201   c  to the intermediate tray  203  and the aligning members  206  and  207 . Here, the discharging roller pair  204  may be in the close state, provided that the discharging roller pair  204  is in the open state while the sheet S 3  conveyed by the conveyance roller pair  201   c  is passing through between the upper rollers  204   a  and the lower rollers  204   b  of the discharging roller pair  204 . The length of the supporting surface  203   a  of the intermediate tray  203  in the sheet discharging direction is shorter than the length of a minimum-size sheet which is applicable for the sheet processing apparatus  200 . Consequently, at least a part of the sheet S 3  supported on the intermediate tray  203  and the aligning members  206  and  207  is exposed to the outside. Thus, the sheet S 3  supported on the intermediate tray  203  and the aligning members  206  and  207  can be taken out by a user. 
     As illustrated in  FIGS. 10B and 10C , in the stacking mode, when a sheet discharging job is inputted, the discharging tray  210  is selected as a destination of the discharged sheet. In the stacking mode, the sheet S 3  supported on the intermediate tray  203  is discharged to the discharging tray  210  by the discharging roller pair  204 . When the job is completed, the sheet S 3  is supported on the discharging tray  210  in a state where the sheet S 3  is not supported on the intermediate tray  203 . More specifically, when the control portion  20  executes the stacking mode serving as a second mode, the discharging roller pair  204  enters the close state, and the aligning members  206  and  207  are positioned at the retracting position. In this state, the sheet S 3  supported on the intermediate tray  203  is discharged to the discharging tray  210  by the discharging roller pair  204 . Here, the aligning members  206  and  207  may be positioned not at the retracting position but at the sheet receiving position until the trailing edge of the sheet S 3  under the discharge passes through the discharging roller pair  204 . In addition, the discharging roller pair  204  may be in the open state, provided that the discharging roller pair  204  is in the close state while the discharging roller pair  204  is discharging the sheet S 3 . 
     Next, with reference to the flowchart illustrated in  FIGS. 11 and 12 , processes related to the holding mode and the stacking mode will be described. As illustrated in  FIG. 11 , the control portion  20  (see  FIG. 5 ) determines whether a predetermined time has elapsed from the last job which discharged a sheet to the sheet processing apparatus  200  (Step S 1 ). If the control portion  20  determines that the predetermined time has elapsed, that is, a job to discharge a sheet is not inputted during the predetermined time (Step S 1 : YES), then the control portion  20  releases the holding mode (Step S 2 ). As illustrated in  FIGS. 10E and 10C , when the holding mode is released, the aligning members  206  and  207  are positioned at the retracting position, and a sheet supported on the intermediate tray  203  is discharged to the discharging tray  210  by the discharging roller pair  204 . Thus, in a case where the holding mode was executed in the above-described last job, the sheet supported on the intermediate tray  203  and the aligning members  206  and  207  is conveyed to the discharging tray  210  in Step S 2 . 
     If the predetermined time has not elapsed from the last job which discharged a sheet to the sheet processing apparatus  200  (Step S 1 : NO), or if the holding mode is released (Step S 2 ), then the control portion  20  proceeds to Step S 3 . Then the control portion  20  determines whether a new (succeeding) job to discharge a sheet is inputted (Step S 3 ). If the succeeding job is not inputted (Step S 3 : NO), then the control portion  20  returns to Step S 1 . If the succeeding job is inputted (Step S 3 : YES), then the control portion  20  determines whether the holding mode was executed in the preceding job (Step S 4 ). The preceding job, which is a first job, is a job performed immediately before the succeeding job, which is a second job. If the holding mode was executed in the preceding job (Step S 4 : YES), then the control portion  20  determines whether user information associated with the preceding job is equal to user information associated with the succeeding job (Step S 5 ). 
     If the user information associated with the preceding job is not equal to the user information associated with the succeeding job (Step S 5 : NO), the control portion  20  releases the holding mode (Step S 6 ). The operation performed when the holding mode is released is the same as that in Step S 2 . If the preceding job was executed in the stacking mode (Step S 4 : NO), if the user information associated with the preceding job is equal to the user information associated with the succeeding job (Step S 5 : YES), or if the holding mode is released in Step S 6 , the control portion  20  determines whether the sheet sensor SE 1  is ON or OFF (Step S 7 ). 
     As illustrated in  FIG. 12 , if the sheet sensor SE 1  is ON, that is, if a sheet is supported on the discharging tray  210  (Step S 7 : YES), then the control portion  20  executes the holding mode. With this operation, as illustrated in  FIG. 10D , while a sheet S 4  discharged in the preceding job is supported on the discharging tray  210 , a sheet S 3  can be discharged to and supported on the intermediate tray  203  and the aligning members  206  and  207 . 
     If the sheet sensor SE 1  is OFF, that is, if any sheet is not supported on the discharging tray  210  (Step S 7 : NO), then the control portion  20  executes the stacking mode (Step S 9 ). Then, if the full load detecting sensor SE 2  becomes ON while sheets are being discharged in the stacking mode, that is, if sheets are fully stacked on the discharging tray  210  (Step S 10 : YES), then the control portion  20  switches the mode from the stacking mode to the holding mode (Step S 11 ). With this operation, even when sheets are fully stacked on the discharging tray  210 , the control portion  20  allows another sheet to be discharged to the intermediate tray  203  and the aligning members  206  and  207  instead of the discharging tray  210 , without stopping the sheet discharging operation. 
     If the full load detecting sensor SE 2  is OFF, that is, if sheets are not fully stacked on the discharging tray  210  (Step S 10 : NO), then the control portion  20  determines whether the sheet discharging operation is completed in the job (Step S 12 ). If the sheet discharging operation is not completed (Step S 12 : NO), then the control portion  20  returns to Step S 9 . If the sheet discharging operation is completed (Step S 12 : YES), then the control portion  20  completes the process. 
     As described above, in the present embodiment, while a sheet discharged in the preceding job is supported on the discharging tray  210 , another sheet can be discharged, in the next job, to the intermediate tray  203  and the aligning members  206  and  207 . In addition, when sheets are fully stacked on the discharging tray  210 , the control portion  20  allows another sheet to be discharged to the intermediate tray  203  and the aligning members  206  and  207 , without stopping the job. Thus, even when the aligning process and the binding process are not performed on sheets, the present embodiment allows the intermediate tray  203  and the aligning members  206  and  207  to support sheets, and thus can effectively use the intermediate tray  203  and the aligning members  206  and  207 . For example, sheets more than a stacking capacity of the discharging tray  210  can be supported on using the intermediate tray  203  and the aligning members  206  and  207 . 
     In addition, when user information associated with the preceding job is not equal to the user information associated with the succeeding job, the control portion  20  releases the holding mode, and then allows a sheet of the succeeding job to be discharged to the intermediate tray  203  and the aligning members  206  and  207 . Thus, as illustrated in  FIG. 10D , the sheet S 4  of a user on which printing is performed in the preceding job is not mixed with the sheet S 3  of another user on which printing is performed in the succeeding job. This improves usability. Here, in the present embodiment, the holding mode is released only when user information associated with the preceding job is not equal to user information associated with the succeeding job. However, the holding mode may be released, regardless of the agreement of user information. In addition, in the present embodiment, the holding mode is executed when the sheet sensor SE 1  is ON. However, the sheet sensor SE 1  may not be provided. Moreover, when a plurality of jobs to discharge sheets are inputted, the control portion  20  may execute jobs other than the last job (of the plurality of jobs) in the stacking mode, and execute only the last job in the holding mode. Also in this case, since a sheet of a user who inputted the last job is not mixed with sheets of other users who inputted the other jobs, usability can be improved. 
     In addition, in the present embodiment, the holding mode is released, for example, when a predetermined time has elapsed from the last job. However, the holding mode may not be released when the full load detecting sensor SE 2  is ON, even though the predetermined time has elapsed. Furthermore, in the present embodiment, the above-described processes are performed, as illustrated in the flowchart of  FIGS. 11 and 12 . However, other processes may be performed using the holding mode and the stacking mode. Thus, the use of the holding mode and the stacking mode can effectively use the intermediate tray  203  and the aligning members  206  and  207 . 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. The second embodiment has a configuration in which the aligning members  206  and  207  of the first embodiment are not provided. Thus, the same components as those of the first embodiment are omitted in the drawings, or described with the same symbols given to the drawings. 
     In the second embodiment, a discharging tray  410  is provided so that the discharging tray  410  can move between a first position illustrated in  FIG. 13A  and a second position illustrated in  FIG. 13B . In the holding mode, when a sheet discharging job (for example, an image forming job which discharges a sheet to a sheet processing apparatus  400 ) is inputted, the sheet is supported on an intermediate tray  303  and the discharging tray  410 . More specifically, when the holding mode which is a first mode is executed, the discharging roller pair  204  enters the open state, and the discharging tray  410  is positioned at the first position. In this state, a sheet S is discharged by the conveyance roller pair  201   c  to the intermediate tray  303  and the discharging tray  410 . In this time, at least a part of the sheet S, supported on the intermediate tray  303  and the discharging tray  410 , is exposed to the outside. Thus, the sheet S can be taken out by a user. 
     In the stacking mode, when a sheet discharging job is inputted, the sheet S supported on the intermediate tray  303  is discharged to the discharging tray  410  by the discharging roller pair  204 , and the sheet S is supported on the discharging tray  410  in a state where the sheet S is not supported on the intermediate tray  303 . More specifically, when the stacking mode which is a second mode is executed, the discharging roller pair  204  enters the close state, and the discharging tray  410  is positioned at the second position. In this state, the sheet S supported on the intermediate tray  303  is discharged to the discharging tray  410  by the discharging roller pair  204 . 
     The processes related to the holding mode and the stacking mode are the same as those in the flowchart of  FIGS. 11 and 12  of the first embodiment, and thus the description thereof will be omitted. In the second embodiment, when the holding mode is released, the discharging tray  410  moves down from the first position to the second position, and the sheet S on the intermediate tray  303  is discharged to the discharging tray  410  by the discharging roller pair  204 . As described above, the second embodiment can produce the same effects as those of the first embodiment by providing the discharging tray  410  so as to move up and down, instead of the aligning members  206  and  207 . 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described. The third embodiment has a configuration in which the holding mode and the stacking mode are achieved not by the sheet processing apparatus but by an image forming apparatus body  500 . Thus, the same components as those of the first embodiment are omitted in the drawings, or described with the same symbols given to the drawings 
     As illustrated in  FIG. 14A , the image forming apparatus body  500  includes an upper guide  222   a , a lower guide  222   b , and a trailing-edge supporting portion  401 . The upper guide  222   a  and the lower guide  222   b  guide the sheet S to the discharging roller pair  123 , and the trailing-edge supporting portion  401  supports the trailing edge of the sheet S which is in contact with the lower guide  222   b . The lower guide  222   b , which is a guide member, and the trailing-edge supporting portion  401  constitute a supporting unit  222  which is a first supporting portion. The trailing-edge supporting portion  401  can move between a non-interference position at which the trailing-edge supporting portion  401  does not interfere with the sheet which is being conveyed, and a supporting position at which the trailing-edge supporting portion  401  supports the trailing edge of the sheet. In the third embodiment, the discharging tray  124  disposed in the body is a second supporting portion. 
     In the holding mode, when a sheet discharging job (for example, an image forming job which discharges a sheet to the discharging tray  124  disposed in the body) is inputted, the sheet S is supported on the supporting unit  222 . More specifically, when the holding mode which is a first mode is executed, the discharging roller pair  123  which is a discharging portion enters the open state, and the sheet S is conveyed to the supporting unit  222  by the reversing roller pair  121 . After the trailing edge of the sheet S, conveyed by the reversing roller pair  121 , passes the trailing-edge supporting portion  401 , the trailing-edge supporting portion  401  moves to the supporting position to support the trailing edge of the sheet S. The length of the lower guide  222   b  in the sheet discharging direction is shorter than the length of a minimum-size sheet which is applicable for the image forming apparatus body  500 . Consequently, at least a part of the sheet S supported on the supporting unit  222  is exposed to the outside. Thus, the sheet S supported on the supporting unit  222  can be taken out by a user. 
     As illustrated in  FIG. 14B , in the stacking mode, when a sheet discharging job is inputted, the sheet S supported on the supporting unit  222  is discharged to the discharging tray  124  disposed in the body, by the discharging roller pair  123 . Furthermore, the sheet S is supported on the discharging tray  124  disposed in the body, in a state where the sheet S is not supported on the supporting unit  222 . More specifically, when the stacking mode which is a second mode is executed, the discharging roller pair  123  enters the close state, and the trailing-edge supporting portion  401  is positioned at the non-interference position. In this state, the sheet S supported on the lower guide  222   b  is discharged to the discharging tray  124  disposed in the body, by the discharging roller pair  123 . 
     The processes related to the holding mode and the stacking mode are the same as those in the flowchart of  FIGS. 11 and 12  of the first embodiment, and thus the description thereof will be omitted. In the third embodiment, when the holding mode is released, the discharging roller pair  123  enters the close state, the sheet S supported on the lower guide  222   b  is discharged to the discharging tray  124  disposed in the body, by the discharging roller pair  123 . As can be seen from the above, the image forming apparatus body  500  can also produce the same effects as those of the first embodiment. 
     Other Embodiments 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2017-250192, filed Dec. 26, 2017, which is hereby incorporated by reference herein in its entirety.