Patent Publication Number: US-2015062604-A1

Title: Transport apparatus and scanner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2013-181108 filed on Sep. 2, 2013. The entire disclosure of Japanese Patent Application No. 2013-181108 is hereby incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a technique where a transport medium is transported by feedback control being performed. 
     2. Related Art 
     A multifunctional device is known which reads a document in a state where the documents is being pressed using a pressing plate (refer to Japanese Unexamined Patent Application Publication No. 2011-43732). It is possible to read the document in Japanese Unexamined Patent Application Publication No. 2011-43732 in a state where the document is stabilized due to being pressed using the pressing plate. 
     There is variation in load on the document due to the pressing plate in a case where the document is read while being transported and the effect of the variation in load appears in the transport speed of the document. In a case where transporting of the document is performed using feedback control, the transport speed lapses into an oscillating state due to the feedback control responding to the variation in the transport speed which accompanies the variation in load. In particular, it is not possible to accurately read the document in a case where reading of the document is performed in a state where the transport speed has lapsed into an oscillating state. 
     SUMMARY 
     The present invention is carried out in consideration of these problems and has the object of providing a technique where a document is more favorably read. 
     A transport apparatus which is for achieving the object comprises a transport section configured to transport a transport medium and a control section configured to carry out feedback control on the transport section according to a transport state of the transport medium. The control section is further configured to reduce the gain in the feedback control in a case where the transport medium is transported in a first region where a load on the transport medium varies compared to a case where the transport medium is transported in a second region which is on an upstream side of the first region or in a third region which is on a downstream side of the first region. Since the gain in feedback control is reduced in a case where the transport medium is transported in the first region where the load on the transport medium varies, it is possible to prevent the transport speed from lapsing into an oscillating state in a case where the transport medium is transported in the first region. On the other hand, since the gain in feedback control is not reduced in a case where the transport medium is transported in the second region or the third region, it is possible for the transport speed of the transport medium to quickly converge to the target transport speed. 
     In addition, the transport apparatus of the invention may be further provided with a reading section configured to acquire image data by reading the transport medium and a pressing section configured to press the transport medium with regard to the reading section. Then, the first region may include a region where the pressing section starts to come into contact with the transport medium or a region where the pressing section finishes coming into contact with the transport medium. Due to this, it is possible to prevent the transport speed from lapsing into an oscillating state due to variation in load on the transport medium which is from when the pressing section starts to come into contact with the transport medium or when the pressing section finishes coming into contact with the transport medium. Since it is possible to prevent the transport speed of the transport medium from lapsing into an oscillating state, it is possible for the reading section to acquire image data which is accurately read from the transport medium. 
     Furthermore, the control section may be further configured to continuously decelerate the transport medium during a period of time in which the transport medium is transported in the second region and during a period of time in which the transport medium is transported in the first region. Then, the control section may be further configured to reduce the gain in the feedback control in a case where the transport medium is transported in the first region compared to a case where the transport medium is transported in the second region. Since the gain in feedback control is not reduced in a case where the transport medium is transported in the second region, it is possible for the transport medium to quickly be transferred to a decelerating state. Since the gain in feedback control is reduced in the first region in a state where a decelerating force is already acting in the transport section, it is possible for the decelerating state to continue even when the gain in feedback control is reduced. 
     Furthermore, the control section may be further configured to set the gain in the feedback control to zero during a period of time when the transport medium is transported in the first region. Due to the gain in feedback control being set to zero, it is possible to reliably prevent the transport speed of the transport medium from lapsing into an oscillating state. 
     In addition, the technical concept of the invention may be realized as a scanner. The scanner may comprise a transport section configured to transport a transport medium, a control section configured to carry out feedback control on the transport section according to a transport state of the transport medium, and a reading section configured to acquire image data by reading the transport medium. Then, the control section may be further configured to reduce a gain in the feedback control in a case where a travelling distance from the transport medium to the reading section is between a first distance which is designated and a second distance which is shorter than the first distance compared to a case where the travelling distance is equal to or less than the second distance. Due to this, it is possible to suppress the transport speed from oscillating in a case where the travelling distance until the reading section is between the first distance and the second distance which is shorter than the first distance. After this, since the gain in feedback control is increased in a case where the travelling distance until the reading section is equal to or less than the second distance, it is possible to accurately control the transport speed at the reading section. Accordingly, it is possible for the reading section to acquire image data which is accurately read from the transport medium. 
     Furthermore, a method for specifying the size of the document as above is established as an invention of a transport method, a reading method, a transport control program, or a reading control program. In addition, there are cases where an apparatus with multiple functions is realized by using shared parts in cases where the apparatuses as above (the transport apparatus or scanner), a program, or a method are realized as a single apparatus and various formats are included. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG. 1A  is a block diagram of a transport apparatus and a scanner; 
         FIG. 1B  is a block diagram of a scanning section; 
         FIG. 2A  is a block diagram of a drive circuit; 
         FIG. 2B  is a cross sectional schematic diagram of the scanning section; and 
         FIG. 3  is a timing chart of a scanning section. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Embodiments of the present invention will be described below in the following order while referencing the attached drawings. 
     First Embodiment 
     Other Embodiments 
     First Embodiment 
       FIG. 1A  is a block diagram illustrating the configuration of a transport apparatus and a scanner according to an embodiment of the present invention. The transport apparatus and the scanner configure a portion of a multi-function printer (MFP)  10 . The MFP  10  is provided with functions such as a printing function, a scanning function, and a facsimile (FAX) function. Then, the MFP  10  is connected with a host computer such as a PC  6  via a network such as a LAN  5 . 
     The MFP  10  is provided with a controller  11 , a user I/F section  12 , a communication section  13 , a printing section  14 , a scanning section  15 , and a FAX section  16 . The controller  11  is formed from a CPU, a nonvolatile memory, a RAM, an ASIC, and the like and controls the entirety of the MFP  10  by the CPU executing various programs which are recorded in the nonvolatile memory. In detail, the controller  11  performs communication procedures using various methods by controlling the communication section  13 . The communication section  13  is provided with an interface circuit or the like for realizing wired LAN communication or wireless LAN communication. 
     In addition, when a printing job is acquired through the communication section  13 , the controller  11  executes printing by controlling the printing section  14  based on the printing job which is acquired. The printing section  14  is provided with an actuator, a sensor, a drive circuit, and a mechanical section for executing printing on a printing medium such as photo paper, normal paper, and OHP sheets using a known printing method such as an ink jet method or a digital photo method. The user I/F section  12  is provided with a touch panel display, various operation keys, and the like. 
     In addition, the FAX section  16  is provided with a modem which performs sending and receiving of FAX data through telephone lines, a circuit for detecting and generating control signals for sending and receiving FAX data, a circuit for decoding FAX data which is received and encoding FAX data which is sent, and the like. The FAX section  16  saves the FAX data which is received through the telephone lines in a nonvolatile memory and the like. In addition, when an execution command for sending FAX data or FAX data to be sent is acquired through the communication section  13 , the controller  11  sends out FAX data to be sent to the telephone lines by controlling the FAX section  16 . 
       FIG. 1B  is a block diagram of the scanning section  15 . The scanning section  15  includes a drive circuit  15   a,  a paper supplying motor  15   b,  a reading motor  15   c,  rotary encoders  15   d  and  15   e,  a resist sensor  15   f,  a PF sensor  15   g,  a front surface reading unit  15   i,  and a rear surface reading unit  15   j.  The drive circuit  15   a  is a circuit for feedback control of the paper supplying motor  15   b  and the reading motor  15   c  which are the transport section. 
       FIG. 2A  is a block diagram of the drive circuit  15   a.  The drive circuit  15   a  is provided with a first circuit  15   a   1  for feedback control of the paper supplying motor  15   b  and a second circuit  15   a   2  for feedback control of the reading motor  15   c.  The first circuit  15   a   1  and the second circuit  15   a   2  will be described and shown in the diagram as the first circuit  15   a   1  since the circuits are the same as each other. The first circuit  15   a   1  acquires target rotation speed data VD which regulates the target rotation speed at each transport position of the document and gain data GD which regulates gain in feedback control at each transport position of the document from the controller  11  and records the data in a memory which is not shown in the diagram. The target rotation speed data is the rotation speed which is ideal for the paper supplying motor  15   b  and is derived based on the ideal transport speed of the document. The transport position is the position of the leading end or the trailing end of the document on the transport path and is a position with the position where the resist sensor  15   f  or the PF sensor  15   g  is provided as a reference. It is possible for the transport position to be specified based on the position of the resist sensor  15   f  or the PF sensor  15   g,  the detection timing when the resist sensor  15   f  or the PF sensor  15   g  detects (the leading end or the trailing end of) the document, and the rotation angle by which the paper supplying motor  15   b  is rotated since the detection timing. 
     A position calculating section  101  derives the current transport position of the document based on the output of the rotary encoders  15   d  and  15   e.  A speed calculating section  102  derives the current rotation speed of the paper supplying motor  15   b  based on the output of the rotary encoder  15   d.  A target rotation speed setting section  103  references the target rotation speed data VD which regulates the target rotation speed at each transport position and sets the target rotation speed which corresponds to the current transport position of the document. A gain setting section  104  references the gain data GD which regulates proportional gain, integral gain, and derivative gain at each transport position and sets the proportional gain, the integral gain, and the derivative gain according to the current transport position of the document based on the current transport position of the document. A proportional multiplying section  105  derives the product of the proportional gain and difference in the current transport speed with regard to the target rotation speed. An integral multiplying section  106  derives the product of the integral gain and an integral value, for a designated period of time, of difference in the current transport speed with regard to the target rotation speed. A derivative multiplying section  107  derives the product of the derivative gain and a derivative value, for a designated period of time, of difference in the current transport speed with regard to the target rotation speed. 
     A PWM circuit  108  corrects the duty ratio (−100% to +100%) of a drive pulse by a correction amount which corresponds to the sum of the outputs of the proportional multiplying section  105 , the integral multiplying section  106 , and the derivative multiplying section  107 . The duty ratio is a ratio of a period of time in which the drive pulse which is a rectangular pulse is ON. The period of time in which the drive pulse is ON is a period of time when the current value of the drive pulse is a constant value which is not zero (a constant positive value or a constant negative value). In a case where the current value of the drive pulse is a constant positive value, the duty ratio is positive. In a case where the current value of the drive pulse is a constant negative value, the duty ratio is negative. An output circuit  109  generates a drive pulse based on the duty ratio and the drive pulse which is generated is supplied to the paper supplying motor  15   b.    
     Due to feedback control being executed as described above, it is possible to control the transport position of the document as per the target. Here, the second circuit  15   a   2  is a circuit, which acquires the rotation angle of the reading motor  15   c  from the rotary encoder  15   e  and carries out feedback control on the reading motor  15   c  based on the rotation angle, and has a configuration which is the same as the first circuit  15   a   1 . 
       FIG. 2B  is a cross sectional schematic diagram of the scanning section  15 . A transport path R (solid line) is formed in the scanning section  15 . The transport path R is a path for the document with a paper supplying tray  200  as a start point and a paper discharging tray  201  as an end point. Below, the paper supplying tray  200  side on the transport path R is expressed as the upstream side and the paper discharging tray  201  side on the transport path R is expressed as the downstream side. The documents are placed so as to overlap on the paper supplying tray  200  with the front surface facing upward. Here, the document is a transport medium which is a target for reading. A pickup roller  202  is a roller for introducing the document which is placed on the paper supplying tray  200  onto the transport path R and is rotated due to driving of the paper supplying motor  15   b.  In addition, the pickup roller  202  is lowered until the pickup roller  202  comes into contact with the document which is placed on the paper supplying tray  200  in a case of introducing the document onto the transport path R. A separating roller  203  is provided on the downstream side of the pickup roller  202  and is rotated due to driving of the paper supplying motor  15   b.  The separating roller  203  is a roller for transporting only the uppermost document to the downstream side in a case where two or more sheets of the documents overlap and are introducing onto the transport path R. For example, the separating roller  203  may be a roller which generates a frictional force with the uppermost document which is larger than a frictional force which is generated between overlapping documents. In addition, an opposing plate  203   a  which pinches the documents may be provided between the documents and the separating roller  203 , and the opposing plate  203   a  may generated a frictional force with the lowermost document which is larger than a frictional force which is generates between overlapping documents 
     The resist sensor  15   f  is provided on the downstream side of the separating roller  203 . A resist roller  204  is provided on the downstream side of the resist sensor  15   f  and is rotated due to driving of the paper supplying roller  15   b.  A driven roller is provided on the opposite side to the resist roller  204  so as to interpose the document and it is possible to transport the document by rotating of the resist roller  204  in a state where the document is interposed between the resist roller  204  and the driven roller. The PF sensor  15   g  is provided on the downstream side of the resist roller  204 . The resist sensor  15   f  and the PF sensor  15   g  are photo sensors and detect whether or not the documents is present based on a state where detection light is blocked by the document. A PF1 roller  205  is provided on the downstream side of the PF sensor  15   g  and is rotated due to driving of the reading motor  15   c.  A driven roller is provided on the opposite side to the PF1 roller  205  so as to interpose the document and it is possible to transport the document by rotating of the PF1 roller  205  in a state where the document is interposed between the PF1 roller  205  and the driven roller. The front surface reading unit  15   i  is provided on the downstream side of the PF1 roller  205  and a pressing plate  206  is provided at a position which corresponds with the front surface reading unit  15   i  so as to interpose the document with a transparent support plate  15   i   1 . 
     The pressing plate  206  is an elastic member with a plate shape which is substantially parallel with the transport path R, and an end section of the pressing plate  206  on the downstream side in the transport path R is rigidly bonded in practice with regard to a casing of the MFP  10 . On the other hand, an end section of the pressing plate  206  on the upstream side in the transport path R is a free end. The gap between the transparent support plate  15   i   1  and the lowermost section on the free end side of the pressing plate  20  is zero in practice and is smaller than the thickness of the document. Accordingly, when the document is transported between the pressing plate  206  and the front surface reading unit  15   i  (the transparent support plate  15   i   1 ), the free end side of the pressing plate  206  is pressed upward to the opposite side of the front surface reading unit  15   i  and the elastic force acts on the document according to the displacement of the free end side of the pressing plate  206 . Accordingly, the load on the document varies (increases) in a case where the document starts to come into contact with the free end of the pressing plate  206 . The front surface reading unit  15   i  is provided with a line sensor  15   i   2  as the reading section, and the free end of the pressing plate  206  is provided on the upstream side of the line sensor  15   i   2 . The rear surface reading unit  15   j  is provided on the downstream side of the front surface reading unit  15   i  and is provided with a transparent support plate  15   j   1  and a line sensor  15   j   2 . 
     A PF2 roller  207  is provided on the downstream side of the rear surface reading unit  15   j  and is rotated by driving of the reading motor  15   c.  A driven roller is provided on the opposite side to the PF2 roller  207  so as to interpose the document and it is possible to transport the document by rotating of the PF2 roller  207  in a state where the document is interposed between the PF2 roller  207  and the driven roller. A discharge roller  208  is provided on the downstream side of the PF2 roller  207  and is rotated by driving of the reading motor  15   c.  A driven roller is provided on the opposite side to the discharge roller  208  so as to interpose the document and it is possible to transport the document by rotating of the discharge roller  208  in a state where the document is interposed between the discharge roller  208  and the driven roller. The paper discharging tray  201  is provided on the downstream side of the discharge roller  208 . Next, the operational timing of the scanning section  15  will be described. 
       FIG. 3  is a timing chart which describes the operational timing of the scanning section  15 . Each stage of C1 to C6 is provided in  FIG. 3  and the horizontal axis of C1 to C6 has the meaning of a timing schedule. C1 indicates the timing where the resist sensor  15   f  detects the document and C2 indicates the timing where the PF sensor  15   g  detects the document. 
     C3 indicates the rotation speed of the paper supplying motor  15   b  and C4 indicates the rotation speed of the reading motor  15   c.  The rotation speed of C3 is positive in a case where the paper supplying motor  15   b  is rotated in a designated reference direction and the rotation speed of C3 is negative in a case where the paper supplying motor  15   b  is rotated in the opposite direction to the reference direction. A power transmission mechanism (gears, belts, or the like) is configured so that the pickup roller  202  and the separating roller  203  are forward rotated and the resist roller  204  does not rotate in a case where the paper supplying motor  15   b  is rotated in the reference direction. In addition, the power transmission mechanism is configured so that the resist roller  204  is forward rotated and the pickup roller  202  and the separating roller  203  do not rotate in a case where the paper supplying motor  15   b  is rotated in the opposite direction to the reference direction. Forward rotating has the meaning of each of the rollers rotating in a direction in which the document is transported to the downstream side of the transport path R. The rotation speed of C4 is positive in a case where the reading motor  15   c  is rotated in a designated reference direction. The PF1 roller  205 , the PF2 roller  207 , and the discharge roller  208  are forward rotated in a case where the reading motor  15   c  is rotated in the reference direction. C5 indicates the proportional gain in feedback control of the drive circuit  15   a  (the first circuit  15   a   1  and the second circuit  15   a   2 ). C6 indicates the timing of reading of the document using the front surface reading unit  15   i.    
     Firstly, the controller  11  lowers the pickup roller  202  so as to come into contact with the document which is placed on the paper supplying tray  200  and the drive circuit  15   a  forward rotates the pickup roller  202  due to driving of the paper supplying motor  15   b.  At this time, the separating roller  203  is forward rotated and the resist roller  204  is not rotated. Next, the drive circuit  15   a  temporarily stops the pickup roller  202  and the separating roller  203  and forward rotates the pickup roller  202  and the separating roller  203  again. Due to this, the document which is introduced into the transport path R using the pickup roller  202  is transported to the downstream side of the transport path R. Then, when the leading end of the document is detected by the resist sensor  15   f  which is provided on the upstream side of the resist roller  204 , the drive circuit  15   a  forward rotates the pickup roller  202  and the separating roller  203  until the leading end of the document reaches the resist roller  204 . 
     When the leading end of the document reaches the resist roller  204 , the drive circuit  15   a  stops the paper supplying motor  15   b,  and the paper supplying motor  15   b  rotates in the opposite direction to the reference direction. Due to this, the resist roller  204  is forward rotated and the pickup roller  202  and the separating roller  203  are stopped. Due to forward rotating of the resist roller  204 , the document is transported further to the downstream side and the trailing end of the document is detected by the resist sensor  15   f  which is provided on the upstream side of the resist roller  204 . When the trailing end of the document is detected by the resist sensor  15   f,  the drive circuit  15   a  forward rotates the resist roller  204  until the trailing end of the document is out of the resist roller  204 , and after this, the resist roller  204  is stopped. 
     During a period of time when the resist roller  204  is forward rotated, the drive circuit  15   a  is already rotating the reading motor  15   c  in the reference direction and forward rotating the PF1 roller  205 . In addition, during a period of time when the resist roller  204  is forward rotated, the document reaches the PF1 roller  205  and the document is transported using the PF1 roller  205  after the resist roller  204  is stopped. When the trailing end of the document is out from the resist roller  204 , the drive circuit  15   a  drives the paper supplying motor  15   b  in order to transport the next (second) document which is placed on the paper supplying tray  200 . In parallel with transporting of the next document, the drive circuit  15   a  continues to transport the initial (first) document due to driving of the reading motor  15   c.  In this manner, it is possible to efficiently read a plurality of the documents since it is possible for two of the documents to be transported in parallel by providing the paper supplying motor  15   b  and the reading motor  15   c.    
     The drive circuit  15   a  acquires the transport position of the leading end of the document based on the rotation angle of the reading motor  15   c  at the timing from when the leading end of the document, which is being transported by using the PF1 roller  205 , passes by the PF sensor  15   g.  The drive circuit  15   a  accelerates the rotation speed of the reading motor  15   c  in a case where the transport position of the leading end of the document reaches an acceleration starting position P1 which is designated. Next, the drive circuit  15   a  maintains the rotation speed of the reading motor  15   c  at a high-speed transport speed VH which is constant in a case where the transport position of the leading end of the document reaches a constant speed starting position P2 which is designated. Furthermore, the drive circuit  15   a  decelerates the rotation speed of the reading motor  15   c  at a rate of deceleration which is constant in a case where the transport position of the leading end of the document reaches a deceleration starting position P3 which is designated. Next, the drive circuit  15   a  maintains the rotation speed of the reading motor  15   c  at a reading speed VL which is constant in a case where the transport position of the leading end of the document reaches a deceleration ending position P4 which is designated. A position, where the interval between the deceleration starting position P3 and the deceleration ending position P4 is divided in half is a contact position PC where the leading end of the document comes into contact with the lowermost section on the free end side of the pressing plate  206 . 
     When the transport position of the leading end of the document reaches a front surface reading position PF where the line sensor  15   i   2  (the reading section) of the front surface reading unit  15   i  is provided, the controller  11  starts reading of the document using the line sensor  15   i   2 . Furthermore, when the transport position of the leading end of the document reaches a rear surface reading position PB where the line sensor  15   j   2  of the rear surface reading unit  15   j  is provided, the controller  11  starts reading of the document using the line sensor  15   j   2 . When the transport position of the trailing end of the document reaches the front surface reading position PF where the line sensor  15   i   2  of the front surface reading unit  15   i  is provided, the controller  11  ends reading of the document using the line sensor  15   i   2 . Furthermore, when the transport position of the trailing end of the document reaches the rear surface reading position PB where the line sensor  15   j   2  of the rear surface reading unit  15   j  is provided, the controller  11  ends reading of the document using the line sensor  15   j   2 . During a period of time when the front surface reading unit  15   i  and the rear surface reading unit  15   j  are performing reading of the document, the drive circuit  15   a  maintains the rotation speed of the reading motor  15   c  at the reading speed VL which is constant. In addition, the drive circuit  15   a  transports the document which reaches the downstream side of the rear surface reading unit  15   j  and discharges the document to the paper discharging tray  201  due to forward rotating of the PF2 roller  207  and the discharge roller  208 . 
     The drive circuit  15   a  normally performs feedback control during operation of the scanning section  15  as described above. The gain setting section  104  sets the proportional gain in feedback control based on the transport position of the leading end of the document. The drive circuit  15   a  acquires the gain data GD, which regulates the proportional gain which is set for each transport position of the leading end of the document, from the controller  11  and records the gain data GD in the memory. The gain setting section  104  sets the gain which corresponds to the transport position of the leading end of the document by referencing the gain data GD which is recorded in the memory. As shown by C5, the gain setting section  104  basically sets the gain to a standard value which is constant. However, the gain setting section  104  sets the proportional gain where the standard value is multiplied by a transition ratio (a ratio of zero or more and less than one, for example, 0.1) in a case where the leading end of the document is transported in a first region A1 which is a region from the contact position PC, where the leading end of the document comes into contact with the free end side of the pressing plate  206 , to the deceleration ending position P4. 
     In the present embodiment, the gain setting section  104  sets the gain where the standard value is multiplied by the transition ratio also for the integral gain and the derivative gain in a case where the leading end of the document is transported in the first region A1. The first region A1 is a region where the document starts to receive load due to the pressing plate  206  and is a region where the load on the document varies. Accordingly, the gain setting section  104  which is the control section reduces the gain in feedback control in a case where the document is transport in the first region A1 where the load on the document varies compared to a case where the document is transported in a second region which is on the upstream side of the first region A1 and a third region which is on the downstream side of the first region A1. Here, a region which is on the upstream side of the first region A1 and a region which is from the deceleration starting position P3 to the contact position PC is defined as a second region A2. 
     As described above, since the gain in feedback control is reduced in a case where the document is transported in the first region A1 where the load on the document varies, it is possible to prevent the transport speed (rotation speed) from lapsing into an oscillating state in a case where the document is transported in the first region A1. On the other hand, since the gain in feedback control is not reduced in a case where the document is transported in the second region A2 or the third region, it is possible for the transport speed of the document to quickly converge to the target transport speed (rotation speed). 
     In addition, the first region A1 includes a region where the lowermost section on the free end side of the pressing plate  206  which is the pressing section starts to come into contact with the document. Due to this, it is possible to prevent the transport speed of the document from lapsing into an oscillating state due to variation in the load on the document due to the lowermost section on the free end side of the pressing plate  206  starting to come into contact with the document. Since it is possible to prevent the transport speed of the document from lapsing into an oscillating state, it is possible for the reading section to acquire image data which is accurately read from the transport medium. 
     Furthermore, the drive circuit  15   a  continuously decelerates the document during a period of time in which the leading end of the document is transported in the second region A2 and during a period of time in which the leading end of the document is transported in the first region A1. Since the gain in feedback control is not reduced in a case where the document is transported in the second region A2, it is possible for the document to quickly be transferred to a decelerating state. Since the gain in feedback control is reduced in the first region A1 in a state where a decelerating force is already acting in the reading motor  15   c,  it is possible for the decelerating state to continue even when the gain in feedback control is reduced. 
     In addition, a distance until the leading end of the document reaches the front surface reading position PF on the transport path R is defined as a travelling distance, the travelling distance when the leading end of the document passes by the contact position PC is defined as a first distance, and the travelling distance when the leading end of the document passes by the deceleration ending position P4 is defined as a second distance (which is less than the first distance). In this case, the gain setting section  104  reduces the gain in feedback control in a case where the travelling distance until the leading end of the document reaches the front surface reading position PF is between the first distance which is designated and the second distance which is shorter than the first distance compared to a case where the travelling distance is equal to or less than the second distance. Due to this, it is possible to suppress the transport speed of the document from oscillating in a case where the travelling distance to the line sensor  15   i   2  which is the reading section is between the first distance and the second distance which is shorter than the first distance. After this, since the gain in feedback control is increased in a case where the travelling distance to the line sensor  15   i   2  is equal to or less than the second distance, it is possible to accurately control the transport speed at the line sensor  15   i   2 . Accordingly, it is possible for the line sensor  15   i   2  to acquire image data which is accurately read from the transport medium. 
     Other Embodiments 
     Here, the technical scope of the present invention is not limited to the embodiment described above and it is obvious that it is possible to add various modifications within the scope which does not depart from the gist of the present invention. 
     For example, the gain setting section  104  need not carry out setting basically using the standard value as shown by C5 in  FIG. 3 , and the gain may be set to a size which is different for each region on the transport path R to which the transport positions of the document belong, for each transport state of the document (constant speed, accelerating, or decelerating), and for each transport speed of the document. Even in this case, it is possible to suppress the transport speed of the document from oscillating due to the gain setting section  104  setting the gain to be reduced in a region where the load on the document varies compared to a region which is adjacent on the upstream side or the downstream side. The gain setting section  104  may set the gain in feedback control to be zero in a case where the document is transported in the first region A1. Due to this, it is possible to reliably prevent the transport speed of the transport medium from lapsing into an oscillating state. Furthermore, it is sufficient if the gain setting section  104  sets at least one of the derivative gain, the proportional gain, and the integral gain to be reduced in a case where the document is transported in the first region A1, and the gain setting section  104  may set only the derivative gain, which has the largest contribution to the responsiveness of feedback, to be reduced. 
     In addition, the first region A1 is on the upstream side of the line sensor  15   i   2  which is the reading section in the embodiment described above, but the first region A1 need not be on the upstream side of the reading section. This is because suppressing of oscillating of the transport speed is effective even in a case where the document is transported anywhere on the transport path R. Furthermore, oscillating of the transport speed on the transport path R may be suppressed even in a case where a transport medium, which is the target for scanning, other than the document is transported. For example, oscillating of the transport speed on the transport path R may be suppressed in the printing section  14  where a printing medium which is a target for printing is transported. In particular, in a case of providing a pressing plate which starts pressing on the printing medium at the upstream side of a region where printing is performed on the printing medium, a region where the pressing plate starts to press on the printing medium may be the first region A1. Here, it is possible for the present invention to be applied to an apparatus where a transport medium is transported and it is possible for the present invention to be applied to various types of processing apparatuses where processing is performed with regard to a transport medium. 
     It is sufficient if the first region A1 is a region where the load on the transport medium varies and the first region A1 need not be a region where the pressing plate  206  starts to come into contact with the document. For example, the first region A1 may be a region where the pressing plate  206  finishes coming into contact with the document. This is because there is variation in load, in that the load on the document is reduced, due to finishing of the trailing end of the document coming into contact with the pressing plate  206 . Furthermore, it is sufficient if the first region A1 is a region where the load on the transport medium varies due to the pressing pate  206 , and the first region A1 may be a region where the friction coefficient at the sliding surface of the transport medium changes. Furthermore, the first region A1 may be a region where the weight of the transport medium changes in various types of processing apparatuses. 
     GENERAL INTERPRETATION OF TERMS 
     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least±5% of the modified term if this deviation would not negate the meaning of the word it modifies. 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.