Patent Publication Number: US-11639278-B2

Title: Media feeding apparatus and image reading apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-231087, filed Dec. 23, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a media feeding apparatus for feeding media sheets and an image reading apparatus having the media feeding apparatus. 
     2. Related Art 
     Image reading apparatuses such as scanners and recording apparatuses such as printers are, for example, provided with a separation roller for separating media sheets and a feed roller that rotates in a media feeding direction, and the separation roller and the feed roller nip and separate the media sheets. For example, JP-A-2018-016484 discusses a structure that includes a pick roller disposed on an upstream of a feed roller and a separation roller, and a pressing section for pressing media sheets against the pick roller, and the pick roller feeds the media sheets toward the feed roller and the separation roller. In JP-A-2018-016484, the separation roller is referred to as a retard roller. 
     In the document feeding apparatus in JP-A-2018-016484, when a first detection section disposed on the upstream of the feed roller detects media sheets, the document feeding apparatus reduces the pressing force applied by the pressing section and reduces the rotation speed of the pick roller. After a predetermined period of time has passed, when no media sheet is detected by a second detection section disposed on the downstream of the feed roller, the document feeding apparatus determines that a jam has occurred. As described above, upon detecting the media sheets with the first detection section disposed on the upstream of the feed roller, the document transport apparatus reduces the pressing force applied by the pressing section and reduces the rotation speed of the pick roller, and thus the feeding force of the pick roller is reduced at the time. Accordingly, in particular, when a number of media sheets are mounted, large back tension exerted on the media sheets to be fed may cause the media sheets to stop when the feeding force of the pick roller is reduced and the media sheets cannot reach the feed roller. In such a case, the document feeding apparatus may determine that a jam has occurred. 
     SUMMARY 
     A media feeding apparatus according to an aspect of the present disclosure for solving the above-described problem includes a media mounting section on which a plurality of media sheets to be fed are to be mounted, a first feed roller disposed at a position where the first feed roller faces a lowermost media sheet of the media sheets mounted on the media mounting section, the first feed roller being configured to apply feeding force to the media sheets, a media pressing section configured to press the media sheets against the first feed roller, a pressing force adjuster configured to adjust the pressing force of the media pressing section for pressing the media sheets against the first feed roller, a second feed roller disposed on a downstream of the first feed roller in a media feeding direction, the second feed roller being configured to feed the media sheets fed by the first feed roller in the media feeding direction, a separation roller configured to nip and separate the media sheets with the second feed roller between the separation roller and the second feed roller, a first detector disposed on an upstream of the second feed roller in the media feeding direction, the first detector being configured to detect a passage of the media sheet, a second detector disposed on the downstream of the second feed roller in the media feeding direction, the second detector being configured to detect a passage of the media sheet, and a controller configured to control the pressing force adjuster and the feeding of the media sheets based on the results of the detection by the first detector and the second detector. The controller sets the pressing force of the media pressing section to first pressing force and drives the first feed roller and the second feed roller in a forward rotation direction, and in a first case in which the first detector detects a passage of a leading edge of the media sheet and the second detector detects no passage of the leading edge of the media sheet after predetermined first set time has passed, the controller continues the rotation of the first feed roller and the second feed roller with second pressing force of the media pressing section greater than or equal to the first pressing force. 
     A media feeding apparatus according to another aspect of the present disclosure for solving the above-described problem includes a media mounting section on which a plurality of media sheets to be fed are to be mounted, a tilt angle adjuster configured to adjust a tilt angle of the media mounting section, a first feed roller disposed at a position where the first feed roller faces a lowermost media sheet of the media sheets mounted on the media mounting section, the first feed roller being configured to apply feeding force to the media sheets, a media pressing section configured to press the media sheets against the first feed roller, a second feed roller disposed on a downstream of the first feed roller in a media feeding direction, the second feed roller being configured to feed the media sheets fed by the first feed roller in the media feeding direction, a separation roller configured to nip and separate the media sheets with the second feed roller between the separation roller and the second feed roller, a first detector disposed on an upstream of the second feed roller in the media feeding direction, the first detector being configured to detect a passage of the media sheet, a second detector disposed on the downstream of the second feed roller in the media feeding direction, the second detector being configured to detect a passage of the media sheet, and a controller configured to control the tilt angle adjuster and the feeding of the media sheets based on the results of the detection by the first detector and the second detector. The controller sets the tilt angle of the media mounting section to a first tilt angle and drives the first feed roller and the second feed roller in the forward rotation direction, and in a first case in which the first detector detects a passage of a leading edge of the media sheet and the second detector detects no passage of the leading edge of the media sheet after predetermined first set time has passed, the controller sets the tilt angle of the media mounting section from the first tilt angle to a second tilt angle that is greater than the first tilt angle and continues the rotation of the first feed roller and the second feed roller. In still another aspect of the present disclosure, an image reading apparatus includes a reader configured to read a surface of a media sheet, and the media feeding apparatus according to the first aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of a document feeding path in a scanner according to an embodiment of the present disclosure. 
         FIG.  2    is a side view of a document feeding path in a scanner according to an embodiment of the present disclosure. 
         FIG.  3    is a block diagram of a control system in a scanner according to an embodiment of the present disclosure. 
         FIG.  4    is a flowchart illustrating a flow of document feeding control processing performed by a controller. 
         FIG.  5    is a flowchart illustrating a flow of document feeding control processing performed by a controller. 
         FIG.  6    is a flowchart illustrating a flow of document feeding control processing performed by a controller. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, an overview of the present disclosure will be described. A media feeding apparatus according to an aspect of the present disclosure includes a media mounting section on which a plurality of media sheets to be fed are to be mounted, a first feed roller disposed at a position where the first feed roller faces a lowermost media sheet of the media sheets mounted on the media mounting section, the first feed roller being configured to apply feeding force to the media sheets, a media pressing section configured to press the media sheets against the first feed roller, a pressing force adjuster configured to adjust the pressing force of the media pressing section for pressing the media sheets against the first feed roller, a second feed roller disposed on a downstream of the first feed roller in a media feeding direction, the second feed roller being configured to feed downstream the media sheets fed by the first feed roller in the media feeding direction, a separation roller configured to nip and separate the media sheets with the second feed roller between the separation roller and the second feed roller, a first detector disposed on an upstream of the second feed roller in a media feeding direction, the first detector being configured to detect a passage of the media sheet, a second detector disposed on the downstream of the second feed roller in a media feeding direction, the second detector being configured to detect a passage of the media sheet, and a controller configured to control the pressing force adjuster and the feeding of the media sheets based on the results of the detection by the first detector and the second detector. The controller sets the pressing force of the media pressing section to first pressing force and drives the first feed roller and the second feed roller in a forward rotation direction, and in a first case in which the first detector detects a passage of a leading edge of the media sheet and the second detector detects no passage of the leading edge of the media sheet after predetermined first set time has passed, the controller continues the rotation of the first feed roller and the second feed roller with second pressing force of the media pressing section greater than or equal to the first pressing force. 
     According to the aspect, in the first case in which the first detector detects a passage of a leading edge of the media sheet and the second detector detects no passage of the leading edge of the media sheet after predetermined first set time has passed, the controller continues the rotation of the first feed roller and the second feed roller with the second pressing force of the media pressing section greater than or equal to the first pressing force. Accordingly, a decrease in the media feeding force of the first feed roller can be prevented or reduced, and it can be expected that the leading edge of the media sheet reaches the media detection position of the second detector. 
     According to a second aspect, in the first aspect, after the controller sets the pressing force of the media pressing section to the first pressing force and drives the first feed roller in the forward rotation direction, when the first detector detects no passage of the leading edge of the media sheet after predetermined second set time has passed, the controller may set the pressing force of the media pressing section to third pressing force greater than the first pressing force, and continue the rotation of the first feed roller. 
     According to the aspect, after the controller sets the pressing force of the media pressing section to the first pressing force and drives the first feed roller in the forward rotation direction, when the first detector detects no passage of the leading edge of the media sheet after predetermined second set time has passed, the controller sets the pressing force of the media pressing section to third pressing force greater than the first pressing force, and continues the rotation of the first feed roller. By increasing the media feeding force of the first feed roller, it can be expected that the leading edge of the media sheet reaches the media detection position of the first detector. 
     According to a third aspect, in the second aspect, after the controller sets the pressing force of the media pressing section to the third pressing force, when the first detector detects a passage of the leading edge of the media sheet within a predetermined third set time, the controller may change the pressing force from the third pressing force to the first pressing force, and when the first detector detects no passage of the leading edge of the media sheet after the predetermined third set time has passed, the controller may stop the first feed roller and the second feed roller and issue an alert. 
     According to the aspect, after the controller sets the pressing force of the media pressing section to the third pressing force, when the first detector detects a passage of the leading edge of the media sheet within a predetermined third set time, the controller changes the pressing force from the third pressing force to the first pressing force. Consequently, multi-sheet feeding of the media sheets due to an excessive pressing force can be prevented or reduced. 
     According to a fourth aspect, in any one of the first to third aspects, the media feeding apparatus may include a nipping force adjuster configured to adjust nipping force for nipping the media sheets between the separation roller and the second feed roller. In the first case in which the first detector detects a passage of a leading edge of the media sheet and the second detector detects no passage of the leading edge of the media sheet after predetermined first set time has passed, the controller may set the nipping force to second nipping force greater than the first nipping force applied when the feeding of the media sheet is started, and continue the rotation of the first feed roller and the second feed roller. The media feeding apparatus may include a tilt angle adjuster configured to adjust a tilt angle of the media mounting section, and the controller may control the tilt angle adjuster. The controller may set the tilt angle of the media mounting section to a first tilt angle and drive the first feed roller and the second feed roller in the forward rotation direction, and the controller, in the first case, may set the tilt angle of the media mounting section to a second tilt angle greater than the first tilt angle, and continue the rotation of the first feed roller and the second feed roller. The controller, in the first case, may increase the rotation speed of the second feed roller. The media feeding apparatus may include a regulator that is disposed on the downstream of the media pressing section in the media feeding direction and is configured to regulate the number of media sheets to be fed into the nip portion between the second feed roller and the separation roller, and a multi-sheet feed detector configured to detect multi-sheet feeding of the media sheets fed by the second feed roller. The controller may control the regulator, and the controller, when the multi-sheet feed detector detects multi-sheet feeding, may change the position of the regulator to the upstream. 
     According to the aspect, in the first case in which that the first detector detects a passage of a leading edge of the media sheet and the second detector detects no passage of the leading edge of the media sheet after a predetermined first set time has passed, the controller sets the nipping force to the second nipping force greater than the first nipping force applied when the feeding of the media sheet is started, and continues the rotation of the first feed roller and the second feed roller. By increasing the media feeding force of separation roller and the second feed roller, it can be expected that the leading edge of the media sheet reaches the media detection position of the second detector. 
     According to a fifth aspect, a media feeding apparatus includes a media mounting section on which a plurality of media sheets to be fed are to be mounted, a tilt angle adjuster configured to adjust a tilt angle of the media mounting section, a first feed roller disposed at a position where the first feed roller faces a lowermost media sheet of the media sheets mounted on the media mounting section, the first feed roller being configured to apply feeding force to the media sheets, a media pressing section configured to press the media sheets against the first feed roller, a second feed roller disposed on a downstream of the first feed roller in a media feeding direction, the second feed roller being configured to feed the media sheets fed by the first feed roller in the media feeding direction, a separation roller configured to nip and separate the media sheets with the second feed roller between the separation roller and the second feed roller, a first detector disposed on an upstream of the second feed roller in the media feeding direction, the first detector being configured to detect a passage of the media sheet, a second detector disposed on the downstream of the second feed roller in the media feeding direction, the second detector being configured to detect a passage of the media sheet, and a controller configured to control the tilt angle adjuster and the feeding of the media sheets based on the results of the detection by the first detector and the second detector. The controller sets the tilt angle of the media mounting section to a first tilt angle and drives the first feed roller and the second feed roller in the forward rotation direction, and in a first case in which the first detector detects a passage of a leading edge of the media sheet and the second detector detects no passage of the leading edge of the media sheet after predetermined first set time has passed, the controller sets the tilt angle of the media mounting section from the first tilt angle to a second tilt angle that is greater than the first tilt angle and continues the rotation of the first feed roller and the second feed roller. 
     According to the aspect, when the second detector detects no passage of the leading edge of the media sheet after a predetermined first set time has passed, the controller sets the tilt angle of the media mounting section from the first tilt angle to a second tilt angle greater than the first tilt angle and continues the rotation of the first feed roller and the second feed roller. By setting the tilt angle to the second tilt angle, a transport load that acts on the media sheets can be reduced, and it can be expected that the leading edge of the media sheet reaches the media detection position of the second detector. 
     An image reading apparatus according to a sixth aspect includes a reader configured to read a surface of a media sheet, and the media feeding apparatus according to any one of the first to fifth aspects. According to the aspect, in an image reading apparatus, any one of the effects in the above-described first to fifth aspects can be achieved. 
     Hereinafter, an embodiment of the present disclosure will be described. In the description below, as an example image reading apparatus, a scanner  1  that can read at least one side of a front side and a back side of a document, which is an example of media, will be described. The scanner  1  is a document scanner that reads a document while transporting the document with respect to a reader. 
     In an X-Y-Z coordinate system in the drawings, an X-axis direction denotes an apparatus width direction and also denotes a document width direction. A Y-axis direction denotes an apparatus depth direction and also denotes a direction along a horizontal direction. A Z-axis denotes a direction along a vertical direction. 
     In the following description, a direction (+Y direction) in which a document is transported may be referred to as “downstream” and an opposite direction (−Y direction) may be referred to as “upstream”. The +Y direction denotes a document feeding direction. In  FIG.  1   , the scanner  1  includes a substantially linear document feeding path, and on a most upstream of the path, includes a document mounting section  5  on which a plurality of document sheets are mounted. In a document mounting area defined by the document mounting section  5 , a feed roller  13  that is driven by a feed motor  52  (see  FIG.  3   ) is disposed. The feed roller  13  is disposed at a position where the feed roller  13  faces a lowermost document of document sheets mounted on the document mounting section  5 . In  FIG.  1   , a document P 1  is a lowermost document of the document sheets mounted on the document mounting section  5 , and a document P 2  is a document on the document P 1 . 
     Above the feed roller  13 , a document pressing section  6  that presses documents against the feed roller  13  is disposed. The document pressing section  6  is switched by a switching mechanism (not illustrated) between a state in  FIG.  1    in which the document pressing section  6  is in contact with an uppermost document of the documents mounted on the document mounting section  5  and a state (not illustrated) in which the document pressing section  6  is separated from the uppermost document. The switching mechanism can be implemented with a solenoid (not illustrated) for switching a state between an energized state and a de-energized state under the control of a controller  50  (see  FIG.  3   ). 
     While the document pressing section  6  presses the documents against the feed roller  13 , the feed roller  13  that rotates in a forward direction, that is, in a counterclockwise direction in  FIG.  1   , applies a feeding force to the lowermost document P 1  of the documents mounted on the document mounting section  5 , and thereby the document P 1  is fed downstream. 
     The document pressing section  6  is pressed against the feed roller  13  by a compression spring  8 , which is an example pressing section. A rotatable eccentric cam  9  is disposed on the compression spring  8 . As a phase of the eccentric cam  9  changes, the spring length of the compression spring  8  changes to adjust the pressing force of the document pressing section  6  for pressing the documents. The eccentric cam  9  receives the power of a motor (not illustrated) that is controlled by the controller  50  (see  FIG.  3   ) and rotates. The motor, the eccentric cam  9 , and the compression spring  8  function as a pressing force adjuster  7  for adjusting the pressing force of the document pressing section  6  for pressing documents against the feed roller  13 . 
     On a downstream of the document pressing section  6 , a space regulating section  10  is disposed. The space regulating section  10  regulates the number of document sheets to be fed to a document nip position, which will be described below, between a feed roller  14  and a separation roller  15 . The document mounting section  5  includes a pivot shaft (not illustrated) near its end portion on the downstream, and the document mounting section  5  swings about the pivot shaft to change its position. The position of the document mounting section  5  is changed by a motor (not illustrated) under the control of the controller  50  (see  FIG.  3   ). The document mounting section  5  is normally positioned at a horizontal position illustrated in  FIG.  1   , and documents that are mounted thereon are also in the horizontal position. The document mounting section  5  is tilted to a tilt position illustrated in  FIG.  2    as necessary. In  FIG.  2   , an angle θa indicates a tilt angle of the mounted documents. The motor for changing the position of the document mounting section  5  functions as a tilt angle adjuster  40  (see  FIG.  3   ). 
     On the downstream of the feed roller  13 , the feed roller  14  that feeds documents downstream and the separation roller  15  that nips and separates documents with the feed roller  14  between the separation roller  15  and the feed roller  14  are disposed. To the feed roller  14 , torque in a counterclockwise direction in  FIG.  1   , that is, torque in a direction in which documents are fed downstream is transmitted from the feed motor  52  (see  FIG.  3   ) through an one way clutch  23 . Since the torque is transmitted through the one way clutch  23 , when the feed motor  52  (see  FIG.  3   ) rotates in the reverse direction, the feed roller  14  does not rotate in the reverse direction. When the feed motor  52  is stopped, the feed roller  14  can come into contact with a document being transported and rotate in the forward rotation direction. 
     To the separation roller  15 , rotation torque is transmitted from a separation motor  54  (see  FIG.  3   ) through a torque limiter  24 . From the separation motor  54 , torque in a forward rotation direction (clockwise direction in  FIG.  3   ) for feeding a document downstream with respect to the separation roller  15  or torque in a reverse direction (counterclockwise direction in  FIG.  3   ) for returning a document upstream is transmitted. 
     When no document is provided or only one document sheet is provided between the feed roller  14  and the separation roller  15 , rotation torque from the feed roller  14  that causes the separation roller  15  to rotate in the forward rotation direction exceeds limit torque of the torque limiter  24 , resulting in the slippage in the torque limiter  24 . As a result, regardless of the rotation torque from the separation motor  54 , the separation roller  15  is driven to rotate in the forward rotation direction, that is, it idles. During a document feeding operation, basically, the separation motor  54  rotates in the reverse direction, that is, generates drive torque for rotating the separation roller  15  in the reverse direction. 
     In addition to a document to be fed, when a second document and subsequent documents are fed between the feed roller  14  and the separation roller  15 , a slippage will occur between the documents, and then the separation roller  15  rotates in the reverse direction with the drive torque from the separation motor  54 . This reverse rotation feeds back the second document and subsequent documents that are likely to be multi-fed to the upstream, that is, the multi-sheet feeding of the documents can be prevented. Accordingly, to increase the separating force produced by the separation roller  15  at the occurrence of multi-sheet feeding, the reverse rotation speed of the separation motor  54  may be increased. 
     The separation roller  15  is pressed against the feed roller  14  by a compression spring  36 , which is an example pressing section. A rotatable eccentric cam  37  is disposed on the compression spring  36 . As a phase of the eccentric cam  37  changes, the spring length of the compression spring  36  changes to adjust a nipping force for nipping documents between the separation roller  15  and the feed roller  14 . The eccentric cam  37  receives the power of a motor (not illustrated) that is controlled by the controller  50  (see  FIG.  3   ) and rotates. The motor, the eccentric cam  37 , and the compression spring  36  function as a nipping force adjuster  35  for adjusting the nipping force for nipping documents between the separation roller  15  and the feed roller  14 . 
     The above-described document mounting section  5 , the feed roller  13 , the document pressing section  6 , the pressing force adjuster  7 , the feed roller  14 , the separation roller  15 , and the nipping force adjuster  35  are a part of a document feeder  2  for feeding documents. Furthermore, the controller  50 , the feed motor  52 , and the separation motor  54 , which will be described below, are also a part of the document feeder  2 . From another point of view, the document feeder  2  can be regarded as an apparatus that has the functions of the scanner  1  other than a document reading function, that is, a reader  20 , which will be described below. Consequently, although the scanner  1  has the document reading function, the scanner  1  can be regarded as a document feeder from the viewpoint of document feeding. 
     On the downstream of the feed roller  14  and the separation roller  15 , a transport roller pair  16  is disposed, and on the downstream of the rollers, the reader  20  that functions as a reading device for reading images. On the downstream of the reader  20 , a discharge roller pair  17  is disposed. The transport roller pair  16  includes a transport driving roller  16   a  that is driven by a transport motor  53  (see  FIG.  3   ) and a transport driven roller  16   b  that is driven to rotate. A document that is nipped by the feed roller  14  and the separation roller  15  is fed downstream, is nipped by the transport roller pair  16 , and is transported to a position at which the document faces an upper sensor unit  20 A and a lower sensor unit  20 B, which are disposed on the downstream of the transport roller pair  16 . 
     The reader  20  includes the upper sensor unit  20 A and the lower sensor unit  20 B. The upper sensor unit  20 A is disposed above a document feeding path, and the lower sensor unit  20 B is disposed below the document feeding path. Each of the upper sensor unit  20 A and the lower sensor unit  20 B comprises a contact image sensor (CIS) module (CISM). The upper sensor unit  20 A, which is disposed above the document feeding path, reads an upper surface of a document, and the lower sensor unit  20 B, which is disposed below the document feeding path, reads a lower surface of the document. 
     After an image on at least one of the upper surface and the lower surface of a document has been scanned in the reader  20 , the document is nipped by the discharge roller pair  17  that is disposed on the downstream of the reader  20  and is discharged from a discharge slot  18 . The discharge roller pair  17  includes a discharge driving roller  17   a  that is driven to rotate by the transport motor  53  (see  FIG.  3   ) and a discharge driven roller  17   b  that is driven to rotate. 
     Hereinafter, a control system in the scanner  1  will be described with reference to  FIG.  3    and as needed,  FIG.  1   . The controller  50  controls feeding, transporting, discharging, and reading of a document, and performs various kinds of control of the scanner  1 . To the controller  50 , signals are input through an operation panel  51 , and from the controller  50 , signals for display on the operation panel  51 , more specifically, signals for implementing a user interface (UI) are sent to the operation panel  51 . 
     The operation panel  51  according to the embodiment is a touch panel through which both of a displaying operation and an inputting operation can be performed. The operation panel  51  functions as an operation section for performing various operations and as a display section for displaying various kinds of information. The controller  50  controls the feed motor  52 , the transport motor  53 , and the separation motor  54 . Each of the motors according to the embodiment is a direct current (DC) motor. To the controller  50 , read data is input from the reader  20 , and from the controller  50 , signals for controlling the reader  20  are sent to the reader  20 . To the controller  50 , signals from a first detector  26 , a second detector  27 , a third detector  28 , and a multi-sheet feed detector  29  are also input. In addition, to the controller  50 , detection values from rotary encoders (not illustrated) that are disposed to the feed motor  52 , the transport motor  53 , and the separation motor  54  respectively are input, and based on the detection values, the controller  50  can grasp amounts of rotation of the respective motors. 
     The controller  50  includes a central processing unit (CPU)  55 , a flash read-only memory (ROM)  56 , and a random access memory (RAM)  57 . The CPU  55  performs various arithmetic processing in accordance with a program stored in the flash ROM  56  and performs overall operational control of the scanner  1 . The flash ROM  56 , which is an example storage device, is a readable and writable nonvolatile memory, and stores various control programs, parameters, and the like necessary for document feeding control and document reading. Various kinds of setting information input by a user via the operation panel  51  is also stored in the flash ROM  56 . In the RAM  57 , which is an example storage device, various kinds of information is temporarily stored. The controller  50  includes an interface  58 , and through the interface  58 , communicates with an external computer  90 . 
     Now, detectors that are disposed in the document transport path will be described mainly with reference to  FIG.  1   . The first detector  26  is disposed on the upstream of the feed roller  14 , and more specifically, in the document feeding direction, disposed at a position between the feed roller  13  and the feed roller  14  and close to the feed roller  14 . The controller  50  receives a signal from the first detector  26  and using the signal, detects passage of a leading edge and a trailing edge of a document at the position where the first detector  26  is disposed. The second detector  27  is disposed on the downstream of the feed roller  14  in the document feeding direction, and more specifically, disposed at a position between the feed roller  14  and the transport roller pair  16  and close to the feed roller  14 . The controller  50  receives a signal from the second detector  27  and using the signal, detects passage of a leading edge and a trailing edge of a document at the position where the second detector  27  is disposed. 
     The third detector  28  is disposed at a position between the transport roller pair  16  and the reader  20  in the document feeding direction. The controller  50  receives a signal from the third detector  28  and using the signal, detects passage of a leading edge and a trailing edge of a document at the position where the third detector  28  is disposed. It should be noted that each of the first detector  26 , the second detector  27 , and the third detector  28  may be a non-contact sensor or a contact sensor. 
     The multi-sheet feed detector  29  is disposed between the feed roller  14  and the transport roller pair  16 , and includes an ultrasonic transmitter and an ultrasonic receiver that face each other across the document feeding path. The controller  50  detects multi-sheet feeding of documents using a signal transmitted from the multi-sheet feed detector  29 . 
     Hereinafter, control processing to be performed by the controller  50  in document feeding will be described mainly with reference to  FIG.  4    and subsequent drawings. In  FIG.  4   , in response to receiving a feeding start instruction, the controller  50  sets a pressing force to be produced by the document pressing section  6  to a first pressing force (step S 101 ). Then, the controller  50  sets a nipping force for nipping a document with the separation roller  15  and the feed roller  14  to a first nipping force (step S 102 ). In the following description, the nipping force is referred to as “separation nipping force”. The controller  50  sets a tilt angle of the document mounting section  5  to a first tilt angle (step S 103 ). The first tilt angle according to the embodiment is zero degrees, and at the angle, the document mounting section  5  is set to a horizontal position. 
     Then, the controller  50  starts driving of the feed roller  13  and the feed roller  14  in the forward rotation direction (step S 104 ), and at the same time, starts time counting of time count Tb (step S 105 ). The controller  50  monitors a change in a detection signal from the first detector  26  from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (step S 106 ). As a result of the monitoring, when the time count Tb exceeds a predetermined second set time before the detection signal from the first detector  26  changes from OFF to ON (Yes in step S 110 ), the process proceeds to B 1  in the flowchart illustrated in  FIG.  5   . The second set time can be obtained by experiment in advance, and may be set to a time with a certain margin added to an estimated time when a document is properly fed. 
     In  FIG.  5   , first, the controller  50  sets the pressing force of the document pressing section  6  to a third pressing force that is larger than the first pressing force (step S 201 ). Then, the controller  50  sets the tilt angle of the document mounting section  5  to a second tilt angle that is larger than the first tilt angle (step S 202 ). Then, the controller  50  starts time counting of a time count Tc (step S 203 ). The controller  50  continues the forward rotation of the feed roller  13 . It should be noted that in the processing in step S 201  and S 202 , the forward rotation of the feed roller  13  may be performed without interruption, or may be temporarily stopped. By setting the pressing force of the document pressing section  6  to the third pressing force that is larger than the first pressing force, the document feeding force of the feed roller  13  can be increased. In addition, by setting the tilt angle of the document mounting section  5  to the second tilt angle that is larger than the first tilt angle, a transport load that acts on the documents mounted on the document mounting section  5  can be reduced. With this control, it can be expected that the leading edge of the document reaches the document detection position of the first detector  26 . 
     The controller  50  monitors a change in the detection signal from the first detector  26  from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (step S 204 ). As a result of the monitoring, when the time count Tc exceeds a predetermined third set time before the detection signal from the first detector  26  changes from OFF to ON (Yes in step S 207 ), the controller  50  stops driving of the feed roller  13  and the feed roller  14  (step S 208 ), and causes the operation panel  51  to issue an alert that indicates that the document is jammed. 
     Before the time count Tc exceeds the predetermined third set time (No in step S 207 ), when the detection signal from the first detector  26  is changed from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (Yes in step S 204 ), the controller  50  sets the pressing force of the document pressing section  6  to the first pressing force (step S 205 ). At the same time, the controller  50  sets the tilt angle of the document mounting section  5  from the second tilt angle to the first tilt angle (step S 206 ). Then, the process proceeds to B 2  in the flowchart illustrated in  FIG.  4   , and the controller  50  performs the processing from step S 107 . As described above, after the controller  50  sets the pressing force of the document pressing section  6  to the third pressing force, when the first detector  26  detects a passage of a leading edge of a document within the predetermined third set time, the controller  50  changes the pressing force from the third pressing force to the first pressing force, and thus multi-sheet feeding of the documents due to an excessive pressing force can be prevented or reduced. In addition, after the controller  50  sets the tilt angle of the document mounting section  5  to the second tilt angle, when the first detector  26  detects a passage of a leading edge of a document within the predetermined third set time, the controller  50  changes the tilt angle from the second tilt angle to the first tilt angle, and thus multi-sheet feeding of the documents can be prevented or reduced. 
     Returning to  FIG.  4   , before the time count Tb exceeds the predetermined second set time (No in step S 110 ), when the detection signal from the first detector  26  is changed from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (Yes in step S 106 ), or when the process proceeds from step S 206  in  FIG.  5   , the controller  50  starts time counting of the time count Ta (step S 107 ). 
     Then, the controller  50  monitors a change in a detection signal from the second detector  27  from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (step S 108 ). As a result of the monitoring, when the time count Ta exceeds a predetermined first set time before the detection signal from the second detector  27  changes from OFF to ON (Yes in step S 111 ), the process proceeds to A 1  in the flowchart illustrated in  FIG.  6   . The first set time can be obtained by experiment in advance, and may be set to a time with a certain margin added to an estimated time when a document is properly fed. 
     In  FIG.  6   , first, the controller  50  sets the pressing force of the document pressing section  6  to a second pressing force that is larger than the first pressing force (step S 301 ). Then the controller  50  sets a separation nipping force to a second nipping force that is greater than or equal to first nipping force (step S 302 ). Then, the controller  50  sets the tilt angle of the document mounting section  5  to the second tilt angle that is larger than the first tilt angle (step S 303 ). At the same time, the controller  50  starts time counting of a time count Td (step S 304 ). The controller  50  continues the forward rotation of the feed roller  13 . It should be noted that in the processing in step S 301 , S 302 , and S 303 , the forward rotation of the feed roller  13  may be performed without interruption, or may be temporarily stopped. 
     By setting the pressing force of the document pressing section  6  to the second pressing force that is larger than the first pressing force, a decrease in the document feeding force with the feed roller  13  can be prevented or reduced. In addition, the controller  50  sets the separation nipping force to the second nipping force that is greater than or equal to first nipping force, the document feeding force with the separation roller  15  and the feed roller  14  can be increased. In addition, by setting the tilt angle of the document mounting section  5  to the second tilt angle that is larger than the first tilt angle, a transport load that acts on the documents mounted on the document mounting section  5  can be reduced. With this control, it can be expected that the leading edge of the document reaches the document detection position of the second detector  27 . It should be noted that the second pressing force may be greater than or equal to the first pressing force. Accordingly, the second pressing force may be equal to the first pressing force. The second pressing force may be equal to the third pressing force (step S 201  in  FIG.  5   ), or may be smaller than the third pressing force, or may be larger than the third pressing force. 
     Them, the controller  50  monitors a change in the detection signal from the second detector  27  from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (step S 305 ). As a result of the monitoring, when the time count Td exceeds a predetermined fourth set time before the detection signal from the second detector  27  changes from OFF to ON (Yes in step S 309 ), the controller  50  stops driving of the feed roller  13  and the feed roller  14  (step S 310 ), and causes the operation panel  51  to display an alert that indicates that the document is jammed. 
     Before the time count Td exceeds the predetermined fourth set time (No in step S 309 ), when the detection signal from the second detector  27  is changed from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (Yes in step S 305 ), the controller  50  releases the pressing force of the document pressing section  6  (step S 306 ). Then, the controller  50  resets the separation nipping force to the first nipping force (step S 307 ). Then, the controller  50  resets the tilt angle of the document mounting section  5  to the first tilt angle (step S 308 ). As described above, after the controller  50  sets the pressing force of the document pressing section  6  to the second pressing force, when the second detector  27  detects a passage of a leading edge of a document within the predetermined fourth set time, the controller  50  releases the pressing of the document by the document pressing section  6 , and thus multi-sheet feeding of the documents can be prevented or reduced. In addition, after the controller  50  sets the tilt angle of the document mounting section  5  to the second tilt angle, when the second detector  27  detects a passage of a leading edge of a document within the predetermined fourth set time, the controller  50  changes the tilt angle from the second tilt angle to the first tilt angle, and thus multi-sheet feeding of the documents can be prevented or reduced. Then, the process proceeds to A 2  in the flowchart illustrated in  FIG.  4   , and the controller  50  performs the processing from step S 109 . 
     Returning to  FIG.  4   , before the time count Ta exceeds the predetermined first set time (No in step S 111 ), when the detection signal from the second detector  27  is changed from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists (Yes in step S 108 ), or when the process proceeds from step S 308  in  FIG.  6   , the controller  50  continues the subsequent feeding operation (step S 109 ). 
     Before the detection signal from the third detector  28  is changed from OFF, that is, a state in which no document exists, to ON, that is, a state in which a document exists, when the multi-sheet feed detector  29  detects multi-sheet feeding of documents, the controller  50  may drive the feed roller  14 , the separation roller  15 , and the feed roller  13  in the reverse direction by a predetermined amount to move upstream the multi-fed documents. The operation of moving the multi-fed documents to the upstream may be performed, for example, by providing the space regulating section  10  in advance such that the space regulating section  10  can change its position along the feeding direction, and then changing the position of the space regulating section  10  to the upstream. With this structure, the multi-fed documents can be effectively moved to the upstream. A mechanism for operating the space regulating section  10  may include a motor and a rack-and-pinion mechanism that is driven by the motor. 
     It is to be understood that the present disclosure is not limited to the above-described embodiment, various modifications can be made within the scope of the following claims, and these modifications are included within the scope of the present disclosure. For example, as illustrated in  FIG.  3   , this embodiment includes three adjusters, that is, the pressing force adjuster  7 , the nipping force adjuster  35 , and the tilt angle adjuster  40 ; however, at least one of the pressing force adjuster  7  and the tilt angle adjuster  40  may be provided. In addition, only one of the processes in step S 201  and step S 202  illustrated in  FIG.  5    may be performed. In such a case, the processes in step S 205  or step S 206  may be omitted as appropriate. Furthermore, in the processes in steps S 301 , S 302 , and S 303  in  FIG.  6   , only one of the processes in step S 301  and step S 303  may be performed, or the process in step S 302  may be omitted. In such a case, the processes in step S 306 , step S 307 , or step S 308  may be omitted as appropriate. 
     For example, when Yes in step S 106  in  FIG.  4   , that is, after the first detector  26  detects a leading edge of a document, the pressing force of the document pressing section  6  may be changed to a pressing force that is smaller than the first pressing force, and monitoring of the detection signal from the second detector  27  (step S 108 ) may be performed. In the above-described embodiment, the nipping force for nipping a document with the separation roller  15  and the feed roller  14  is increased to increase the document feeding force with the separation roller  15  and the feed roller  14 . Alternatively, or in addition to this, the rotation speed of the feed roller  14  may be increased to increase the document feeding force. In the above-described embodiment, the tilt angle of the document mounting section  5  is increased to solve the problem that no document is fed. Alternatively, or in addition to this, the feed roller  13  may be provided such that an amount of protrusion of the feed roller  13  from the document mounting section  5  can be adjusted, and then, the amount of protrusion may be increased.