Patent Publication Number: US-2023148210-A1

Title: Sheet feeder apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet feeder apparatus for feeding originals. 
     Description of the Related Art 
     Ordinarily, an image reader device is known that is arranged in an upper portion of an image forming apparatus and reads images in originals. The image reader device has an ADF (Auto Document Feeder) for feeding originals placed on an original tray while separating the originals one by one. The ADF cannot separate and feed so-called bound originals, such as stapled originals and glued originals, and if originals to be conveyed are bound originals, the originals may be wrinkled or torn in a mechanism in the ADF for separating originals. Also, if bound originals are fed as-is without being separated in the ADF, there is concern that jamming will occur on a conveyance path. 
     When bound originals are fed by the ADF, only the uppermost sheet of the bound originals is picked up and fed to the conveyance path by a pick-up roller provided in the ADF. However, the uppermost sheet is bound by a staple or the like, and thus rotates and skews around the position of stapling or the like. A technology for stopping feeding originals upon skewing of an original being detected is known (Japanese Patent Laid-Open No. 2012-101900). Also, an image reader device is proposed in which a plurality of original detection sensors are arranged in the width direction of an original conveyance path, skewing of a conveyed sheet is detected by these original detection sensors, and jamming caused by bound originals is determined (Japanese Patent Laid-Open No. 2012-101900, Japanese Patent Laid-Open No. 2006-193287). 
     With the technology in Japanese Patent Laid-Open No. 2012-101900, skewing of originals with different sizes in the width direction cannot be detected accurately. That is to say, to increase the detection accuracy, it is effective to increase the distance in the width direction between two sensors for detecting skewing. However, if the distance between the sensors is increased, then small-size originals cannot be detected. 
     In Japanese Patent Laid-Open No. 2006-193287, a plurality of, namely three or more paper detection sensors are arranged in a line. A plurality of skew angles are obtained with respect to a plurality of detection sections based on differences in time when a sheet leading end passes two of the paper detection sensors, in each detection section, and the distance between the two paper detection sensors arranged. Japanese Patent Laid-Open No. 2006-193287 also gives no consideration to handling originals with different width sizes. 
     SUMMARY OF THE INVENTION 
     The present invention provides a sheet feeder apparatus capable of accurately detecting a plurality of bound originals with different sizes. 
     The present invention has the following configuration. That is to say, according to a first aspect of the present invention, there is provided a sheet feeder apparatus comprising: a width detection unit configured to detect a width of a sheet placed on a sheet placement portion; a conveyance unit configured to convey sheets placed on the sheet placement portion while separating the sheets one by one; a first sheet detection unit configured to detect a sheet having a first width conveyed by the conveyance unit, at a plurality of first positions that differ from each other in a width direction perpendicular to a conveyance direction; a second sheet detection unit configured to detect a sheet having a second width that is conveyed by the conveyance unit and is not detected by the first sheet detection unit, at a plurality of second positions that differ from each other in the width direction; and a control unit configured to determine skewing of a sheet based on a result of the detection performed by the first sheet detection unit if the width of the sheet detected by the width detection unit is the first width, and determine skewing of a sheet based on a result of the detection performed by the second sheet detection unit if the width of the sheet detected by the width detection unit is the second width. 
     According to a second aspect of the present invention, there is provided a sheet feeder apparatus comprising: a width detection unit configured to detect a width of a sheet placed in a sheet placement portion; a conveyance unit configured to convey sheets placed on the sheet placement portion while separating the sheets one by one; a first sheet detection unit configured to detect a sheet having a first width conveyed by the conveyance unit, at a plurality of first positions that differ from each other in a width direction perpendicular to a conveyance direction; a second sheet detection unit configured to detect a sheet having a second width that is conveyed by the conveyance unit and is not detected by the first sheet detection unit, at a plurality of second positions that differ from each other in the width direction; and a control unit configured to cause the conveyance unit to stop conveying a sheet based on a result of the detection performed by the first sheet detection unit if the width of the sheet detected by the width detection unit is the first width, and cause the conveyance unit to stop conveying a sheet based on a result of the detection performed by the second sheet detection unit if the width of the sheet detected by the width detection unit is the second width. 
     According to the present invention, feeding of a plurality of bound originals with different sizes can be detected accurately. 
     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 A  is an overall schematic diagram showing an image forming apparatus. 
         FIG.  1 B  is a schematic diagram of an image forming engine. 
         FIG.  2    is an illustrative diagram of a skew detection portion according to a first embodiment. 
         FIG.  3    is a control block diagram according to the first embodiment. 
         FIG.  4    is a flowchart showing operations according to the first embodiment. 
         FIG.  5    is a flowchart of an S 11 -S 12  skew detection process according to the first embodiment. 
         FIG.  6 A  shows the state before bound originals are fed. 
         FIG.  6 B  shows the state after the bound originals have entered a separation drive roller. 
         FIG.  7 A  shows ideal skewing. 
         FIG.  7 B  shows actual skewing. 
         FIG.  7 C  shows actual skewing after a lapse of time. 
         FIG.  8    is a flowchart showing operations according to a second embodiment. 
         FIG.  9    is a flowchart showing operations according to a third embodiment. 
         FIG.  10    illustrates an operation of an automatic original feeding portion of an image forming apparatus according to a fourth embodiment. 
         FIG.  11    is a flowchart showing processing performed by the image forming apparatus according to the fourth embodiment. 
         FIG.  12    shows an external appearance of an operation portion of an image forming apparatus according to a fifth embodiment. 
         FIG.  13    is a flowchart showing processing performed by the image forming apparatus according to the fifth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made an invention that requires all such features, and multiple such features may be combined as appropriate. 
     Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted. 
     First Embodiment 
     First, the first embodiment of the present invention will be described. An image forming apparatus  100  according to the first embodiment is, for example, a multifunction machine or a multifunctional copier that has an image scanner and a printer, and has an electrophotographic laser beam printer as a printer.  FIG.  1 A  is an overall schematic diagram of the image forming apparatus  100 , and  FIG.  1 B  is a schematic diagram of an image forming engine. As shown in  FIG.  1 A , the image forming apparatus  100  includes an image forming apparatus body  70 , and an image reader device  10  that is attached to an upper portion of the image forming apparatus body  70 . Note that, in the following description, a “sheet” may include not only plain paper but also special paper such as coated paper, a recording material with a special shape, such as an envelope or an index paper, a plastic film for an overhead projector, cloth, and so on, and an original is also an example of a sheet. In addition, a paper feeder device for receiving print sheets placed thereon and a postprocessing device for performing postprocessing such as stapling may also be provided, but are omitted here. An original may be referred to as an original copy. 
     The image forming apparatus body  70  contains an image forming engine  60 . As shown in  FIG.  1 B , the image forming engine  60  includes an electrophotographic image forming unit PU and a fixing device  7 . If an instruction to start an image forming operation is given, a photosensitive drum  1 , which is a photoreceptor, rotates, and the drum surface is uniformly charged by a charging device  2 . Then, an exposure device  3  modulates a laser beam based on image data transmitted from the image reader device  10  or an external computer and outputs the modulated laser beam, and scans the surface of the photosensitive drum  1  to form an electrostatic latent image thereon. This electrostatic latent image is visualized (developed) by toner supplied from a developing device  4  and is rendered into a toner image. 
     In parallel with this image forming operation, a feeding operation to feed a sheet placed in a paper feed cassette or a manual feed tray provided in a paper feeder device (not shown) toward the image forming engine  60  is performed. The fed sheet is conveyed through a conveyance path  8  or the like in accordance with the progress of the image forming operation performed by the image forming unit PU. The toner image carried by the photosensitive drum  1  is transferred onto the sheet by a transfer roller  5 . Toner that remains on the photosensitive drum  1  after the toner image has been transferred is collected by a cleaning device  6 . The sheet to which an unfixed toner image has been transferred is delivered to the fixing device  7 , and is sandwiched by a roller pair to be heated and pressed. The sheet to which the toner has been melted and fixed and an image has been fixed is discharged by a discharging means, such as a discharge roller pair. 
     The image forming apparatus  100  also includes a control portion  81  for controlling the entire apparatus and an operation portion  506  with which an operator performs operations. The control portion  81  includes a CPU for executing programs, a memory for storing the programs and data, and 
     Image Reader Device 
     Configuration of Image Reader Device  10   
     Next, the image reader device  10  will be described in detail. As shown in  FIG.  1 A , the image reader device  10  includes a sheet feed unit (Auto Document Feeder: also called “ADF”)  20  for feeding placed originals one by one, and a reader unit (also called “original reader unit)  40  for reading originals conveyed by the ADF  20 . The ADF  20 , which serves as a sheet feeder device, is rotatably supported with respect to the reader unit  40  by a hinge such that an original glass  41  of the reader unit is exposed. Note that originals D, each of which is an example of a sheet, may be white paper, or may be paper on which an image is formed on one of or both faces thereof. 
     The ADF  20  has an original tray  21 , which is a sheet placement portion on which a bundle of originals is placed, regulating plates  21   a  and  21   b , which are arranged at two original-end portions (in the distal direction of the diagram) on the original tray  21  and can be moved so as to come into contact with the two original-end portions, and a discharge tray  32 , on which originals are placed that have been fed from the original tray  21 , subjected to image-reading, and then discharged. The ADF  20  also has, as feed rollers, a pick-up roller  22  for sending out the uppermost one of the placed sheets, a separation drive roller  23  and a separation follower roller  24  for separating one sheet from the other sheets. One separated sheet is guided to a reading portion by a conveyance roller pair  25  and a leading roller pair  26 , and is discharged to the discharge tray by a leading roller pair  30  and a discharge roller pair  31 . The ADF  20  also has an original detection sensor S 31  for detecting an original D on the original tray  21 , a post-separation sensor S 32  that is arranged downstream of the separation drive roller  23  in a sheet feeding direction and detects an original D, and skew detection sensors S 11 , S 12 , S 21 , and S 22  that are arranged downstream of the separation drive roller  23  and detects skewing of an original D in an original width direction. The post-separation sensor S 32  is located at the center of conveyed sheets in the direction (width direction) perpendicular to a sheet conveyance direction. The skew detection sensors S 11 , S 12 , S 21 , and S 22  are arranged symmetrically in the width direction with respect to the post-separation sensor S 32 . In the conveyance direction, the skew detection sensor S 11  and S 12  are provided at the same position, and the skew detection sensors S 21  and S 22  are also provided at the same position. In this example, the pair of skew detection sensors S 11  and S 12  are located upstream of the pair of skew detection sensors S 21  and S 22 , and are located downstream of the post-separation sensor S 32 . Note that the skew detection sensors may be sensors for detecting sheets that pass through the conveyance path. Each of the skew detection sensors S 11 , S 12 , S 21 , and S 22  turns on when detecting a sheet passing through the conveyance path. Each pair of skew detection sensors are located at the same position in the conveyance direction, and are located at different positions in the width direction. In the width direction, each pair of skew detection sensors are arranged symmetrically with respect to the center of conveyed originals in the width direction. 
     The reader unit  40  has a platen glass  28 , which is located at the position at which an original conveyed by the AFD  20  is to be read, and a jump base  29  for guiding an original that has pass through the platen glass  28  toward the conveyance path. The reader unit  40  also has a reference white plate  42  for shading correction, and an original glass  41  on which originals are placed when in a fixed-original reading mode. A first mirror base  43 , a second mirror base  44 , a lens  45 , and a CCD line sensor  46  are provided. A lamp  47  and a mirror  48  are arranged within the first mirror base  43 , and mirrors  49  and  50  are arranged within the second mirror base  44 . The first mirror base  43  and the second mirror base  44  can be moved in a sub-scanning direction, which is the left-right direction in the diagram, by a wire and a drive motor (not shown). 
     The image reader device  10  reads image information from an original D using a flowing-original reading mode, in which images in originals are scanned while originals D placed in on the original tray  21  are fed by the ADF  20 , and a fixed-original reading mode, in which an original placed on the original glass  41  is scanned. The flowing-original reading mode is selected if an original D placed on the original tray  21  is detected by the original detection sensor S 31 , or if a user explicitly gives an instruction to select the flowing-original reading mode through the operation portion  506  or the like of the image forming apparatus body  70 . 
     Reading of Original in Respective Reading Modes 
     Upon the flowing-original reading mode being executed, the pick-up roller  22 , which is supported by an arm (not shown), is lowered and comes into contact with the uppermost original D on the original tray  21 . The originals D are then fed by the pick-up roller  22  and are separated one by one by a separation nip N, which is formed by the separation drive roller  23  and the separation follower roller  24  and serves as a separation means. The separation drive roller  23  is made of a rubber material or the like that has friction that is slightly less than that of the separation follower roller  24 . A torque limiter is disposed on a drive transmission path to the separation follower roller  24 , and the separation follower roller  24  rotates in conjunction with the separation drive roller  23  when one original is fed, and does not rotate when two or more originals are fed. With this configuration, originals can be separated one by one. Note that the separation follower roller  24  may be driven in a direction opposite to the sheet feeding direction. 
     A leading end and a trailing end of the original that has passed through the separation nip N are detected by the post-separation sensor S 32 , and serve as references for the timing of lifting and lowering the pick-up roller  22 , the timing of starting and stopping driving the pick-up roller  22 , and the timing of starting and stopping driving the conveyance roller pair  25 . 
     The original D to be conveyed is conveyed by the conveyance roller pair  25 , and is conveyed toward the platen glass  28  by the leading roller pair  26 . A platen guide roller  27  is disposed opposing the platen glass  28 , and the platen guide roller  27  guides the original D that passes through the platen glass  28  such that this original D is not detached upward from the platen glass  28 . 
     Then, an image on the surface of the original D is read via the platen glass  28  by the reader unit  40 . Specifically, the conveyed original D is irradiated with light from the lamp  47 , and the reflected light from the original D is guided to the lens  45  via the mirrors  48 ,  49 , and  50 . The light that has passed through the lens  45  forms an image on a light receiving portion of the CCD line sensor  46 , is then subjected to photoelectric conversion as well as AD conversion, and is transmitted, as image data, to the control unit  80 , specifically the CPU  81 . Note that the reference white plate  42  serves as a reference for the brightness when the original D is read. The original D that has passed through the platen glass  28  is guided to the leading roller pair  30  by the jump base  29 , and is discharged to the discharge tray  32  by the discharge roller pair  31 . 
     On the other hand, the fixed-original reading mode is selected if an original D placed on the original glass  41  is detected by the device, or if the user explicitly gives an instruction through the operation portion  506  or the like of the image forming apparatus body  100 . In this case, the original D on the original glass  41  does not move, but the first mirror base  43  and the second mirror base  44  move along the original glass  41 . The original D is scanned with light emitted by the lamp  47 . Image information that has been subjected to photoelectric conversion by light-receiving elements of the CCD line sensor  46  is transferred to the CPU  81 . 
     The two modes differ from each other regarding whether an original or the light source moves, but in the both modes, raster image data, for example, is generated by scanning an original image. 
     Skew Detection Mechanism 
       FIG.  2    shows a skew detection mechanism according to the first embodiment. Note that, although the skew detection mechanism according to the first embodiment is constituted by two sensor pairs, this needs not be the case. The skew detection mechanism is constituted by the skew detection sensor pair S 11 -S 12  and the skew detection sensor pair S 21 -S 22 . The skew detection sensor pair S 11 -S 12  is arranged downstream, in the paper feeding direction, of the separation drive roller  23  and the post-separation sensor S 32 , and the skew detection sensor pair S 21 -S 22  is arranged downstream, in the paper feeding direction, of the skew detection sensor pair S 11 -S 12 . The skew detection sensor pair S 11 -S 12  is arranged such that the width (210 mm) of the A4R size&gt;the length [S 11 -S 12 ] between the skew detection sensors S 11  and S 12 , and the skew detection sensor pair S 21 -S 22  is arranged such that the width (297 mm) of the A3 size&gt;the length [S 21 -S 22 ] between the skew detection sensors S 21  and S 22 &gt;the width (210 mm) of the A4R size. Originals D are placed on an original placement portion  21 , and two sides of the originals are aligned by the regulating plates  21   a  and  21   b  on the original tray. The regulating plates  21   a  and  21   b  are interlocked by a link mechanism, for example, such that they are at an equal distance from the center of the sheet conveyance path in the width direction (the position of the post-separation sensor S 32  in the width direction). Thus, the sheets placed on the original tray  21  aligned with the regulating plates  21   a  and  21   b  are located at the center of the conveyance path in the width direction. The uppermost paper of the originals D is sent to the position of the separation drive roller  23  by the pick-up roller  22 , and is fed thereby. That is to say, if the conveyed sheet is not skewing, an A4R sheet can be detected by the skew detection sensor pair S 11 -S 12  but cannot be detected by the skew detection sensor pair S 21 -S 22 . On the other hand, A4 and A3 sheets can be detected by both the skew detection sensor pair S 11 -S 12  and the skew detection sensor pair S 21 -S 22 . 
     Control Block 
       FIG.  3    is a block diagram of the control portion  80 . The skew detection sensors S 11 , S 12 , S 21 , and S 22 , the original detection sensor S 31 , the post-separation sensor S 32 , and an original width determination portion (which is also simply called a width determination portion or a width detection portion)  508 , each of which serves as an input signal source, are connected to the CPU  81 . A value corresponding to the width between the regulating plates  21   a  and  21   b  is input from the original width determination portion  508  to the CPU  81 , and thus the width of originals is understood. A pick-up motor  84  and a separation drive motor  85  are connected, via a motor control portion  83 , to the output side of the CPU  81 . The pick-up motor  84  drives the pick-up roller  22 , and the separation drive motor  85  drives the separation drive roller  23 . The operation portion  506  and a storage portion  507  are also connected to the CPU  81 . The operation portion  506  has an operation panel that is constituted by a touch panel and keys, for example, and makes it possible to start a copy job and configure various settings. A threshold Tth [ms] for detecting skewing of an original using the skew detection sensors S 11 , S 12 , S 21 , and S 22  is stored in the storage portion  507 . In addition, programs with which the CPU  81  performs processing according to later-described flowcharts are also stored in the storage portion  507 . The CPU  81  may also be connected to other sensors and control circuits, but a description thereof is omitted here. Note that the storage portion  507  may include a RAM, a ROM, a hard disk, and the like, and these specific media are properly used in accordance with information to be stored. 
     Bound Originals Detection Flow 
     Next, a copying operation performed when bound originals are fed will be described in accordance with a flowchart.  FIG.  4    is a flowchart showing the copying operation according to the first embodiment that is performed when originals are fed. 
     First, the CPU  81  determines whether or not an original is placed on the original tray  21 , based on a signal from the original detection sensor S 31  (step S 101 ). If it is determined that no original is placed on the original tray  21  (step S 101 : No), the CPU  81  does not proceed to the next process but waits until an original is placed on the original tray  21 . 
     If it is determined that an original is placed on the original tray  21  (step S 101 : Yes), the CPU  81  determines whether or not an instruction to start a job that accompanies feeding of an original using the ADF  20 , such as a copy job, has been input (step S 102 ). The following description takes a copy job as an example, but jobs that accompany reading of an original, such as scan transmission and facsimile transmission, fall under the job that accompanies feeding of an original. If no instruction to start a copy job has been input from the operation portion  506  (step S 102 : No), the CPU  81  does not proceed to the next process but waits until an instruction to start a copy job is input. If it is determined that an instruction to start a copy job has been input (step S 102 : Yes), in step S 103 , a sheet placed on the original tray  21  starts being fed. Upon paper feeding being started, it is determined whether or not the original size is smaller than the A4R size (step S 104 ). This determination may be made based on the input from the original width determination portion  508 . 
     If the original size is smaller than A4R (step S 104 : Yes), a skew detection process is carried out by the skew detection sensor pair S 11 -S 12  (step S 105 ). Step S 105  will be described later with reference to  FIG.  5   . If the original size is larger than or equal to A4R (step S 104 : No), a skew detection process is carried out by the skew detection sensor pair S 21 -S 22  (step S 106 ). Step S 106  will be described later. After processing in step S 105  or step S 106  has been finished, it is determined whether or not skewing has been detected in step S 105  or step S 106  (step S 107 ). If skewing has been detected in step S 105  or step S 106  (step S 107 : Yes), the pick-up motor  84  and the separation drive motor  85  are stopped to stop feeding paper (step S 108 ). If skewing is not detected in step S 105  or step S 106  (step S 107 : No), it is determined whether or not the original being conveyed is the last original (step S 109 ). If the original being conveyed is the last original (step S 109 : Yes), the pick-up motor  84  and the separation drive motor  85  are stopped to stop feeding paper (step S 108 ). If the original being conveyed is not the last original (step S 109 : No), the processing returns to step S 103  to resume feeding the next original. 
     Thus, skewing is determined based on the result of a skew detection sensor pair corresponding to the original size detecting an original. 
     Step S 105 : S 11 -S 12  Skew Detection Process 
     The aforementioned step S 105 : S 11 -S 12  skew detection process will be described in accordance with a flowchart.  FIG.  5    is a flowchart showing the S 11 -S 12  skew detection process according to the first embodiment.  FIGS.  6 A and  6 B  will be referenced to give a detailed description.  FIGS.  6 A and  6 B  show skewing viewed from above that occurs when bound originals are fed.  FIG.  6 A  shows a state where bound originals are placed, and  FIG.  6 B  shows a state where bound originals are fed and skewing occurs. Note that, in this example, the skew detection sensors S 21  and S 22  are omitted. 
     A first original D 1  and a second original D 2 , which are bound with a staple ST, are placed as shown in  FIG.  6 A . Upon paper feeding being started and the bound originals D 1  and D 2  being advanced to the position of the separation drive roller  23  by the pick-up roller  22 , the bound originals D 1  and D 2  are fed such that the first original D 1  and the second original D 2  are separated into individual sheets by the separation drive roller  23 . However, the first original D 1  is advanced by the pick-up roller  22  and the separation drive roller  23 , whereas the second original D 2  is not conveyed by the separation drive roller  23 , and thus, the first original D 1  begins to rotate around the staple ST ( FIG.  6 B ). At this time, the side of the first original D 1  where it is bound with the staple ST is not conveyed, and therefore the skew detection sensor S 11  is in an OFF state. On the other hand, an end portion of the first original D 1  on the side where it is not bound with the staple ST is conveyed, and thus the skew detection sensor S 12  turns ON. Such a state is entered if stapled originals are conveyed and skewing occurs. For this reason, in step S 105 , such a situation is determined using the skew detection sensors S 11  and S 12 . Since there may also be the case where originals are stapled on the sensor S 12  side, the occurrence of the aforementioned situation is determined line-symmetrically with respect to an axis extending in the conveyance direction. 
     In  FIG.  5   , first, it is determined whether or not the skew detection sensor S 11  is ON (step S 201 ). If it is determined that the skew detection sensor S 11  is not ON, then it is determined whether or not the skew detection sensor S 12  has turned ON (step S 202 : Yes). If, in step S 202 , the skew detection sensor S 12  is ON, the processing proceeds to step S 203 . In step S 203 , it is determined whether or not the skew detection sensor S 11  turns ON after the skew detection sensor S 12  has turned ON in step S 202 . If it is determined that the skew detection sensor S 11  is OFF (step S 203 : No), there is possibility that a sheet being conveyed is skewing. In this case, it is determined that skewing has occurred if the difference in time when the sheet was detected between the two sensor S 11  and S 12  exceeds the threshold Tth [ms]. This difference in time indicates a degree of skewing of the sheet. It is then determined whether or not the threshold (predetermined time) Tth [ms], which is stored in the storage portion  507 , has elapsed before the sheet is detected by the sensor S 11  after the sheet has been detected by the sensor S 12  (step S 204 ). Here, the threshold Tth is a value that is determined in accordance with the conveyance speed, and is 30 mS, for example. But this need not be the case. The degree of skewing can be determined based on the tilt of a sheet front edge. The threshold Th is time corresponding to this tilt. The higher the conveyance speed, the shorter the threshold Tth, and the lower the conveyance speed, the longer the threshold Tth. It is determined that skewing has occurred if the difference in the detection timing between the skew detection sensors corresponds to 1 cm in terms of the difference in distance, for example. In this case, the time required to convey the sheet by 1 cm may be used as the threshold Tth. That is to say, Tth may be a value obtained by dividing the difference in distance by the conveyance speed. 
     If, in step S 204 , the threshold Tth [ms] has not elapsed (step S 204 : No), the processing returns to step S 203  to determine whether or not the skew detection sensor S 11  turns ON. That is to say, the processing loops between steps S 203  to S 204  until the skew detection sensor S 11  turns ON or the time Tth has elapsed. If steps S 203  and S 204  are repeated and the threshold Tth [ms] elapses (step S 204 : Yes), it is determined that the original being fed has entered the state shown in  FIG.  6 B . Then, the determination result indicating that skewing has occurred is stored in a predetermined storage area or the like (step S 205 ), and the S 11 -S 12  skew detection process ends. 
     If fed originals are not bound originals but normal originals, usually, the skew detection sensor S 11  turns ON before the threshold Tth [ms] elapses in step S 204  (step S 203 : Yes), and therefore it is determined that the fed original passes through the post-separation sensor S 32  (step S 208 ). Upon the fed original passing through the post-separation sensor S 32  (step S 208 : Yes), the determination result indicating that the original being conveyed is not skewing is stored in a predetermined storage area or the like (step S 209 ), and the S 11 -S 12  skew detection process ends. 
     On the other hand, if it is determined in step S 201  that the skew detection sensor S 11  has turned ON, the processing branches to step S 206  to determine whether or not the skew detection sensor S 12  has turned ON. If it is determined in step S 206  that the skew detection sensor S 12  is OFF, there is possibility that the sheet being conveyed is skewing. Then it is determined whether or not the threshold Tth [ms] has elapsed before the sheet is detected by the sensor S 12  after the sheet has been detected by the sensor S 11  (step S 207 ). 
     If, in step S 207 , the threshold Tth [ms] has not elapsed (step S 207 : No), the processing returns to step S 206  to determine whether or not the skew detection sensor S 12  turns ON. That is to say, the processing loops between steps S 206  and S 207  until the skew detection sensor S 12  turns ON or the time Tth elapses. If steps S 206  and S 207  are repeated and the threshold Tth [ms] elapses (step S 207  Yes), it is determined that the original being fed has entered a state that is an inversion of the state shown in  FIG.  6 B . Then, the determination result indicating that skewing has occurred is stored in a predetermined storage area or the like (step S 205 ), and the S 11 -S 12  skew detection process ends. 
     If the fed originals are not bound originals but normal originals, the processing branches to step S 208 . Processing to be performed thereafter is as described above. 
     Step S 106 : S 21 -S 22  Skew Detection Process 
     This processing is processing in  FIG.  5    in which the skew detection sensors S 11  and S 12  are replaced with S 21  and S 22 . In this example, the threshold Tth may take the same value as that used in the procedure in  FIG.  5   . The other parts are also the same as those in  FIG.  5   , and a description thereof is omitted accordingly. 
     Configuration of Skew Detection Sensor Pair S 11 -S 12  and Skew Detection Sensor Pair S 21 -S 22   
     The detection method performed using the skew detection sensor pairs S 11 -S 12  and S 21 -S 22  has been described so far, and now, a description will be given below of the reason why two or more skew detection sensor pairs S 11 -S 12  and S 21 -S 22  are needed.  FIGS.  7 A to  7 C  show examples of skewing states when bound originals of the A3 size are fed.  FIG.  7 A  shows skewing that does not cause the sheet front edge to distort and is ideal for detection,  FIG.  7 B  shows a state in which skewing has begun to occur and the sheet front edge has bent and that often occurs in reality, and  FIG.  7 C  shows a state in the case where conveyance is continued from the state in  FIG.  7 B . The skew detection sensor pair S 11 -S 12 , the skew detection sensor pair S 21 -S 22 , the separation drive roller  23 , the post-separation sensor S 32 , the original placement portion  21 , and the regulating plates  21   a  and  21   b  on the original tray have respective configurations and functions that have been described with reference to  FIG.  2   . Skewing that is ideal for detection when bound originals are fed is shown in  FIG.  7 A , where the first original D 1  rotates around the staple ST, and the original leading end is linear with respect to the staple ST. However, in reality, the portion of the first original D 1  where the staple ST is present remains at the position of the separation drive roller  23 , whereas the side of the first original D 1  where the staple ST is not present is often conveyed along the regulating plates while remaining parallel to the conveyance path to some extent, as shown in  FIG.  7 B . Thus, skewing does not significantly occur on the inner side of the original where the skew detection sensor pairs S 11 -S 12  is present. Accordingly, to detect skewing of a larger-size original, not only the skew detection sensor pair S 11 -S 12  but also the skew detection sensor pair S 21 -S 22  are needed. If time passes from the state in  FIG.  7 B , the side of the first original D 1  where the staple ST is not present proceeds and enters the state shown in  FIG.  7 C , turning ON the skew detection sensor S 22  on the outer side, and thus, skewing of a larger-size original can be detected. 
     Second Embodiment 
     Next, the second embodiment of the present invention will be described. In the second embodiment, the image forming apparatus basically has the same configuration as that of the first embodiment, but the operation flowchart thereof differs. In this embodiment, diagrams and descriptions are given of differences from the first embodiment.  FIG.  8    is a flowchart of processing relating to detection of bound originals according to this embodiment that is performed by the CPU  81 . In this embodiment, a value Tth 2  corresponding to the distance between the skew detection sensors S 21  and S 22  is used as the threshold Tth. 
     Step S 301  to step S 304  of determining the original size in the flowchart according to the second embodiment in  FIG.  8    are the same as step S 101  to step S 104  in the first embodiment, and a description thereof is omitted accordingly. If it is determined in step S 304  that the original size is smaller than A4R (step S 304 : Yes), in step S 306 , the detection threshold Tth is set to Tth 1 , which is stored in the storage portion  507 . On the other hand, if it is determined in step S 304  that the original size is greater than or equal to A4R (step S 304 : No), in step S 307 , the detection threshold Tth is set to Tth 2 , which is stored in the storage portion  507 . Here, the threshold Tth 1  and the threshold Tth 2  are values that are determined in accordance with the original conveyance speed. For example, values such as Tth 1 =30 [mS] and Tth 2 =45 [mS] may be employed. However, the values and the relationship regarding which of the thresholds is larger or smaller are not limited to those described here. 
     Nevertheless, since the distance between the skew detection sensors S 21  and S 22  is greater than the distance between the skew detection sensors S 11  and S 12 , it is desirable to accordingly make the threshold Tth 2  greater than the threshold Tth 1 . The threshold Tth 2  is defined as being Tth 1  (distance between S 21  and S 22 /distance between S 11  and S 12 ), and the threshold Tth in the first embodiment may be replaced with this value. This is to match the tilt of the front edge according to which the occurrence of skewing is determined, with that in the case of processing in  FIG.  5   . Needless to say, since a sheet being conveyed often distorts as described with reference to  FIGS.  7 B and  7 C , the threshold Tth 2  may also be set accordingly. 
     After the threshold Tth 1  has been set in step S 305 , the processing proceeds to step S 306  to perform the S 11 -S 12  skew detection process. The S 11 -S 12  skew detection process here is the same as the S 11 -S 12  skew detection process in step S 105  in the first embodiment except that the detection threshold Tth is changed to Tth 1 , and a description thereof is omitted accordingly. After the detection threshold Tth is set to Tth 2  stored in the storage portion  507  in step S 307 , the processing proceeds to step S 308  to perform the S 21 -S 22  skew detection process. The S 21 -S 22  skew detection process here is the same as the S 21 -S 22  skew detection process in step S 106  in the first embodiment except that the detection threshold Tth is changed to Tth 2 , and a description thereof is omitted accordingly. 
     After the processing in step S 307  or step S 308  has been finished, it is determined whether or not skewing has been detected in step S 307  or step S 308  (step S 309 ). The subsequent processing is the same as processing in steps S 108  and S 109  in the first embodiment, and a description thereof is omitted accordingly. 
     With the above-described procedure, the threshold for determining skewing is changed in accordance with the distance between sensors that constitute each skew detection sensor pair (sensor pair), and thus, skewing can be detected more accurately. 
     Third Embodiment 
     Next, the third embodiment of the present invention will be described. The basic configuration of the third embodiment is the same as that of the second embodiment, but the operation flowchart thereof differs. In this embodiment, diagrams and descriptions are given of differences from the second embodiment.  FIG.  9    is a flowchart relating to detection of bound originals according to this embodiment. The difference between  FIG.  9    and  FIG.  8   , which is the flowchart of the second embodiment, lies in that, in  FIG.  9   , steps S 408   a  and S 408   b  are performed in place of step S 308  in  FIG.  8   . The other steps are the same as those in the second embodiment, and a description thereof is omitted accordingly. 
     After the detection threshold Tth has been set to Tth 2  stored in the storage portion  507  in step S 407 , steps S 408   a  and S 408   b  are performed in parallel. Step S 408   a  is the same as the S 11 -S 12  skew detection process in step S 306  in the second embodiment, and step S 408   b  is the same as the S 21 -S 22  skew detection process in step S 308  in the second embodiment. The reason why steps S 408   a  and S 408   b  are performed in parallel is because, although stapled large-size originals often skew as shown in  FIG.  7 B , skewing that is close to the ideal skewing shown in  FIG.  7 A  can also be detected by the skew detection sensor pair S 21 -S 22 . 
     For this reason, if skewing is detected in either step S 408   a  or step S 408   b , the other step may be stopped, and the processing may proceed to step S 409 . Note that, for example, a real-time operating system that controls the image forming apparatus  100  would usually have the ability to perform tasks in parallel, and therefore the tasks can be carried out under the control thereof. 
     The above-described configurations and processing make it possible to detect skewing of an original more quickly. This embodiment is particularly effective in the case of larger-size originals. 
     Fourth Embodiment 
     The following issue is raised if mixed originals with different widths is attempted to be handled in the above embodiments that use two pairs of sensors. “Mixed originals with different widths” refers to a state where originals with different sizes in the width direction are stacked on the original tray  21 . In the case of increasing the number of sensor pairs for detecting originals to deal with respective original sizes as in the above embodiments, sensors are installed on two ends, in the width direction, of the originals to be detected, as much as possible, to increase the accuracy in detecting the skew tilt. Here, when mixed originals with different widths are to be read, these originals are usually placed on the original tray while aligning one side of the bundled originals with one of the regulating plates. To read the thus-aligned originals with different widths, a sensor for detecting larger-size originals that is located on the side opposite to the side where the originals are aligned is distant, to some extent, from a sensor for detecting smaller-size originals. For this reason, when mixed originals with different widths are to be read, if a small-size original is read, the sensor for detecting larger-size originals that is located on the side opposite to the side where the originals are aligned cannot detect the small-size original. Accordingly, even if the small-size original has been correctly conveyed in reality, it is determined that a large-size original is skewing, and conveyance of the original is stopped. For this reason, when mixed originals with different widths are to be read, the skew detection setting needs to be disabled, making the operation very bothersome for the user. 
     This embodiment employs a configuration described below. Note that the image forming apparatus  100  according to this embodiment may be the same as that of the first embodiment. 
     Skew Detection and Mixed Originals with Different Widths 
       FIG.  10    schematically illustrates an operation of the ADF  20  according to this embodiment. A skew detection operation performed by the ADF  20  will be described below with reference to  FIG.  10   .  FIG.  10    is a plan view of the original tray  21  of the ADF  20  and therearound viewed from above. 
       FIG.  10    shows mixed originals with different width sizes that are placed on and conveyed by the ADF  20 . An operation performed for mixed originals with different widths will be described based on  FIG.  10   . Here, an original D 1 , which is a horizontally-placed A4 original, and an A3 original D 2  are placed on the original tray  21 . Thus, “placement of mixed originals with different widths” refers to a function of placing originals with lengths different in a direction (i.e. width direction) perpendicular to the conveyance direction to cause these originals to be read, and performing image formation processing corresponding to the respective sizes, using the ADF  20 . To use the function of the placement of mixed originals with different widths, a set value for the placement of mixed originals with different widths needs to be set to ON. This setting of the placement of mixed originals with different widths is configured by the user making input to the operation portion  506 . The setting of the placement of mixed originals with different widths may also be used as a default setting when the ADF  20  is used. This is a setting to automatically make the set value for the placement of mixed originals with different widths ON while assuming that the user is to use the ADF  20 , if originals are placed on the original tray  21  of the ADF  20 . As for the default setting of the placement of mixed originals with different widths, a default value can be set independently for each user if users are managed on the image forming apparatus. 
     In  FIG.  10   , the regulating plates  21   a  and  21   b  are arranged so as to be aligned with the larger-size original D 2 , and thus, the current size detected by the ADF  20  is the width size of the original D 2 . Thus, two pairs of skew detection sensors, namely the sensors S 12  and S 11  and the sensors S 22  and S 21  are used. In the case of the placement of mixed originals with different widths, skewing of the smaller-size original D 1  cannot be prevented by holding the original D 1  from two sides using the regulating plates  21   a  and  21   b . For this reason, skewing is prevented by aligning a longitudinal side with either one of the regulating plates. Usually, a longitudinal side of the smaller-size original D 1  is aligned with the regulating plate  21   a  located on the distal side of the original tray  21 , i.e. the upper side of the diagram. 
     In  FIG.  10   , the small-size original D 1  is conveyed in the mode of reading mixed originals with different widths. At this time, only the original D 1  is conveyed leftward of the diagram by the pick-up roller  22  and the separation drive roller  23 . Here, the sensor pair S 12 -S 11  for smaller sizes in skew detection detect the original substantially simultaneously. However, of the sensor pair S 22 -S 21  for large sizes, S 22  is a sensor on the distal side and thus can detect the original, but S 21  cannot detect the original because the smaller-size original does not have a sufficient length in the width direction. Accordingly, after the skew detection sensor S 22  has detected the original, the skew detection sensor S 21  cannot detect the original even after a given time based on which it is determined that skewing has been detected, and, as a result, it is determined that the original is skewing. This incorrect determination occurs when mixed originals with different widths are read. To avoid such an incorrect determination, for example, an operation to turn off the skew detection needs to be necessarily performed when mixed originals with different widths are to be read. This operation is very difficult for the user to understand, and is also bothersome, causing a problem in that the operability is degraded when mixed originals with different widths are to be read. 
     Operation Portion 
     First, the operation portion  506  will be described. Note that, although the operation portion  506  have not been specifically described in the first to fourth embodiments, the same operation portion  506  as that of this embodiment may be used.  FIG.  12    shows an external appearance of the operation portion  506  of the image forming apparatus according to this embodiment. A display portion  401  displays various indications and settings of the apparatus on its screen, which is an LCD or the like. A touch panel is installed on the surface of the display portion  401 , and accepts an input operation performed by the user. As a result of the user operating a software touch button or the like displayed on the display portion  401  via the touch panel, the CPU  81  determines the content of the user operation based on the coordinates of the pressed position on the touch panel and the displayed content, and performs processing according to the operation input. A ten key  403  is a physical key for inputting numerical values, such as a PIN number. An ID key  404  is a key for displaying an authentication screen to which a user ID and a password are to be input when users are managed on the image forming apparatus. A start key  405  is a key for giving an instruction to start a job, such as a copy job or a scan job. Note that the displayed screen is a user login screen, which will be described later. 
     Skew Detection Procedure 
       FIG.  11    is a flowchart showing processing performed by the control portion  80  of the image forming apparatus  100  according to this embodiment when reading originals. Steps in the flowchart in  FIG.  11    are processed by the CPU  81  executing a program stored in the storage portion  507 . 
     First, the control portion  80 , specifically the CPU  81  determines whether or not an instruction to start a job that accompanies reading of originals, such as a copy job or a scan job, has been given by the user (S 601 ). Specifically, it is determined whether or not an instruction has been given by pressing the start button  405  while a screen for configuring settings for copying or scanning is displayed on the operation portion  506 . If it is determined that no instruction to execute a job has been given, step S 601  is repeated to wait for a user instruction. 
     If it is determined in step S 601  that an instruction to start executing a job such as a copy job or a scan job has been given, it is then determined whether or not originals are placed on the original tray  21  of the ADF  20  (S 602 ). This determination is made by acquiring, from the ADF  20 , information indicating whether or not the original detection sensor S 31  has detected originals. 
     If it is determined that originals are set in the original tray  21 , it is then determined whether or not a set value for the placement of mixed originals with different widths is currently ON (S 603 ). The set value for the placement of mixed originals with different widths is set via the operation portion  506  by the user before job execution is started, and is temporarily stored in the storage portion  507 . 
     If it is determined in step S 603  that the set value for the placement of mixed originals with different widths is ON, a set value for original skew detection is set to OFF (S 604 ). This setting may be made using any manner, e.g. a method in which the ADF  20  ignores original detection information from the skew detection sensors S 12  to S 21  to not perform skew detection processing itself, or a method in which the control portion  80  ignores a skew detection notification acquired from the reader unit  40 . If it is determined in step S 603  that the set value for the placement of mixed originals with different widths is not ON, the set value for the original skew detection is set to ON (S 606 ). Thus, original skew detection of the ADF  20  is enabled. 
     After step S 604  or S 606 , the ADF  20  performs original reading processing in the flowing-original reading mode (S 605 ). 
     On the other hand, if it is determined in step S 602  that no original is set in the original tray  21 , the reader unit  40  reads originals in the fixed-original reading mode (S 607 ). In reality, processing to be performed is determined based on whether or not an original is present on the original glass  41 , set value conditions of the user, of the like, but a description thereof is omitted. 
     Thus, if the setting of the placement of mixed originals with different widths is ON, i.e. when a plurality of originals with different width sizes are read, and these originals are to be read by the ADF  20 , skew detection itself can be automatically disabled to prevent the aforementioned incorrect detection of skewing. Also, if the setting of the placement of mixed originals with different widths is OFF, and originals are to be read by the ADF  20 , skew detection is automatically enabled. Thus, the user does not need to enable or disable the skew detection function depending on the setting for the placement of mixed originals, and can always use skew detection if it can be used without giving consideration to use conditions or the like. Accordingly, operability for the user is improved when originals are read. 
     Fifth Embodiment 
     The hardware configuration and the control block configuration according to the fifth embodiment are the same as those described in the first embodiment, and a description thereof is omitted accordingly. The fifth embodiment will describe a method for controlling a set value employed when a default set value for the placement of mixed originals with different widths is set in the image forming apparatus  100  on which users are managed. Note that the fifth embodiment will only describes differences from the fourth embodiment. 
     In the fifth embodiment, users are managed on the image forming apparatus  100 . User names for identifying users and passwords associated therewith are stored in the storage portion  507  of the control portion  80 . Each user is authenticated by inputting a user name and a password before using the apparatus, and if the user is successfully authenticated, the user can also use the apparatus with set values for each user stored in the storage portion  507  reflected. The aforementioned default value for the placement of mixed originals with different widths is one of the set values for each user. 
       FIG.  12    shows an example of a user authentication screen displayed on the display portion  401  of the operation portion  506  in the fifth embodiment. This user authentication screen is displayed as the result of a user pressing the ID key  404  in the operation portion  506  before using the apparatus. A user name input portion  702 , a password input portion  703 , and a login button  704  are displayed in an authentication dialog  701 . Upon the user name input portion  702  being pressed, a software keyboard dialog is displayed on the display portion  401 , making it possible to input a user name. The input user name is displayed in the user name input portion  702  after the software keyboard dialog is closed. 
     Upon the password input portion  703  being pressed, a software keyboard dialog is displayed similarly, making it possible to input a password similarly. If a set password only includes numerals, the software keyboard dialog is not displayed, and the password can also be directly input using the ten key  403 . After the password has been input, symbols such as “*****” is displayed in place of characters in the password input portion  703 , and thus it can be understood that the password has been input. 
     The login button  704  is a button for authenticating the user after the user name and the password have been input. After the login button  704  has been pressed, it is checked whether or not the input user name and password match a pair of user name and password stored in the storage portion  507 . If the input user name and password agree with the stored pair, this authentication dialog  701  is closed and a setting screen is displayed. At this time, if set values for each user are stored in the storage portion  507 , the setting screen is displayed while reflecting these set values. If authentication fails, a massage indicating that authentication has failed is displayed on the authentication dialog  701 , and the user is prompted to input a user name and a password again. 
     Skew Detection Procedure 
       FIG.  13    is a flowchart showing processing performed by the control portion  80  when reading originals in the fifth embodiment. Steps in the flowchart in  FIG.  13    are processed by the CPU  81  executing a program stored in the storage portion  507 . 
     First, the control portion  80 , specifically the CPU  81  determines whether or not the user has logged in by being authenticated (S 801 ). Specifically, it is determined whether or not the login button  704  in the authentication dialog  701  has been pressed, and whether or not the user name and the password match in the user authentication performed after it has been determined that the login button  704  was pressed. If it is determined that the user has not logged in, step S 801  is repeated to wait for a user instruction. Note that, if authentication is performed by another device, the names of logged-in users or the like stored in a predetermined storage location are referenced, and it may be determined that the user has logged in if the user name is stored. 
     If it is determined in step S 801  that the user has logged in, the set values for the logged-in user is read out from the storage portion  507 , and the setting screen is displayed after reflecting the read set values (S 802 ). 
     Next, it is determined whether or not originals are placed on the original tray  21  of the ADF  20  (S 803 ). This is the same processing as that in step S 602  in  FIG.  11    in the fourth embodiment. Here, if it is determined that originals are placed, a default mixture setting for the user who is currently logged in is reflected in the set values stored for the user (S 804 ). 
     Furthermore, it is determined whether or not the set value for the placement of mixed originals with different widths in the configured default setting of the placement of mixed originals is ON (S 805 ). This is the same processing as that in step S 603  in  FIG.  11    in the fourth embodiment. 
     If it is determined in step S 805  that the set value for the placement of mixed originals with different widths is ON, the skew detection setting is turned OFF (S 806 ). On the other hand, if the set value for the placement of mixed originals with different widths is OFF, the skew detection setting is turned ON (S 809 ). Processing in these steps is the same as processing in steps S 604  and S 606 , respectively, in  FIG.  11    in the fourth embodiment. 
     After the processing in step S 806  or step S 809 , it is determined whether or not an instruction to start executing a job such as a copy job or a scan job has been given by the user (S 807 ). This is the same processing as that in step S 601  in  FIG.  11    in the fourth embodiment. If it is determined in step S 807  that no user instruction has been given, the processing returns to step S 803  to wait for a user instruction. If it is determined in step S 807  that a user instruction has been given, processing to read the originals in the flowing-original reading mode is performed (S 808 ). This is the same processing as that in step S 605  in  FIG.  11    in the fourth embodiment. 
     If it is determined in step S 803  that no original is placed, the default setting of the placement of mixed originals of the user who is currently logged in is cleared in the set values stored for the user (S 810 ). Thus, if no original is set, regarding the setting of the placement of mixed originals, the setting of the placement of mixed originals is configured such that the set values including that for the placement of mixed originals with different widths are set to OFF. Next, it is determined whether or not an instruction to start executing a job such as a copy job or a scan job has been given by the user (S 811 ). This step is the same as the aforementioned step S 808  and step S 601  in  FIG.  11    in the fourth embodiment. If it is determined in step S 811  that no user instruction has been given, the processing returns to step S 803  to wait for a user instruction. If it is determined in step S 811  that a user instruction has been given, processing to read the originals in the fixed-original reading mode is performed (S 812 ). This is the same processing as that in step S 607  in  FIG.  11    in the fourth embodiment. 
     As described above, even if users are managed and set values for a user is automatically reflected upon the user logging in, it is possible to change, without inconsistency, two set values that may cause a malfunction if both values are set at the same time, such as the placement of mixed originals with different widths and the skew detection setting. Thus, the user can use the two functions after logging in without being particularly conscious of these two set values, and convenience and operability are improved. 
     OTHER EMBODIMENTS 
     In the above embodiments, the skew detection sensor pair S 21 -S 22  are provided downstream of the skew detection sensor pair S 11 -S 12 , but the skew detection sensor pair S 11 -S 12  may alternatively be provided on the downstream side, or both sensor pairs may be provided at the same position in the conveyance direction. 
     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. 2019-046383, filed Mar. 13, 2019 which is hereby incorporated by reference herein in its entirety.