Patent Publication Number: US-9884737-B2

Title: Sheet separating apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent Application No. 2014-031688 filed on Feb. 21, 2014, the entire subject-matter of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a sheet separating apparatus. 
     BACKGROUND 
     There has been disclosed an example of a sheet separating apparatus. This sheet separating apparatus has a stacking unit, a separation roller, and a separation piece. The stacking unit has a sheet supporting surface capable of supporting a plurality of sheets stacked. The separation roller rotates around a first shaft center parallel to the width direction of the sheet supporting surface, thereby coming into contact with a sheet fed from the stacking unit and conveying the sheet to the downstream side in a conveyance direction perpendicular to the width direction. The separation piece faces the separation roller, and separates sheets one at a time in cooperation with the separation roller. 
     However, in the above-described related-art sheet separating apparatus, according to whether the number of sheet stacked on the sheet supporting surface is large or small, a trajectory of the leading end of the sheet fed from the stacking unit to the separation roller may be likely to significantly vary. For example, in the related-art sheet separating apparatus, as will be described below, according to whether the number of sheet stacked on the sheet supporting surface is large or small, the sheet separating apparatus may not reliably separate the sheets one at a time. 
     For example, it is assumed that the separation roller is provided to be able to contact each sheet which is fed from the stacking unit, from a side that is opposite to a side facing the sheet supporting surface, such that the uppermost sheet of the sheets supported on the sheet supporting surface is fed to the separation roller. A nip position is defined as a position where a sheet is nipped by the separation roller and the separation piece when the sheet is fed. 
     In this case, if the number of sheets stacked on the sheet supporting surface is large, the trajectory of the leading end of the uppermost sheet passes a position close to the separation roller and proceeds toward the nip position. Therefore, the leading end of the corresponding sheet easily reaches the nip position. However, in this case, simultaneous conveyance of sheets may occur. Meanwhile, if the number of sheets stacked on the sheet supporting surface is small, the trajectory of the leading end of the uppermost sheet passes a position separated from the separation roller and close to the separation piece, and proceeds toward the nip position. Therefore, the leading end of the corresponding sheet may be unlikely to reach the nip position. In this case, failure of sheet conveyance may occur. 
     Also, the sheet separating apparatus is required to be reduced in size. 
     SUMMARY 
     Therefore, it is preferably to provide a sheet separating apparatus capable of implementing a decrease in size and capable of reliably separating sheets, one at a time, regardless of the number of sheets stacked on a sheet supporting surface. 
     According to one aspect of the disclosure, a sheet separating apparatus comprises: a stacker including a sheet supporting surface for supporting a sheet; a separation roller configured to rotate around a first shaft center that is parallel to a width direction of the sheet supporting surface, wherein the separation roller is configured to contact the sheet fed from the stacker and to convey the sheet to a downstream side in a conveyance direction that is perpendicular to the width direction; a separation piece, which faces the separation roller, and which is configured to separate the sheet one at a time in cooperation with the separation roller, the separation roller and the separation piece being configured to nip the sheet being fed at a first nip position; and a pinch roller, which is provided on an upstream side with respect to the first nip position in the conveyance direction, and which is configured to abut on the separation roller so as to be rotatable around a second shaft center, which is parallel to the width direction, by a rotation of the separation roller, wherein the pinch roller has a portion overlapping the separation piece as seen from the width direction. 
     In another aspect of the disclosure, a sheet separating apparatus comprises: a stacker that has a sheet supporting surface for supporting a plurality of sheets stacked; a separation roller configured to rotate around a first shaft center that is parallel to a width direction of the sheet supporting surface, wherein the separation roller is configured to contact a sheet fed from the stacker and to convey the sheet to a downstream side in a conveyance direction that is perpendicular to the width direction; a separation piece, which face the separation roller, and which is configured to separate the sheet one at a time in cooperation with the separation roller, the separation roller and the separation piece being configured to nip the sheet being fed at a first nip position; and a pinch roller, which is provided on the upstream side from the first nip position in the conveyance direction, and which is configured to abut on the separation roller so as to be rotatable around a second shaft center, which is parallel to the width direction, by a rotation of the separation roller, the separation roller and the pinch roller are configured to nip the sheet being fed at a second nip position, wherein as seen from the width direction, an extension plane extending from the sheet supporting surface toward the downstream side in the conveyance direction, with a gap from an outer circumferential surface of the separation roller, and wherein the outer circumferential surface of the pinch roller includes an arc that extends from a position adjacent to an end portion of the sheet supporting surface at the downstream side in the conveyance direction to the second nip position while swelling toward the separation roller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated, and not limited, by way of example by the accompanying figures in which like reference numerals indicate similar elements. 
         FIG. 1  is a perspective view illustrating an image reading apparatus of a first illustrative embodiment; 
         FIG. 2  is a side view schematically illustrating the image reading apparatus of the first illustrative embodiment; 
         FIG. 3  is a cross-sectional view schematically illustrating a portion of the image reading apparatus of the first illustrative embodiment; 
         FIG. 4  is a perspective view illustrating a portion of the image reading apparatus of the first illustrative embodiment which includes a separation roller, a sheet supporting surface, a separation piece, a separation piece holder, pinch rollers, a holding unit, and so on; 
         FIG. 5  is an exploded perspective view illustrating the sheet supporting surface, the separation piece, the separation piece holder, the pinch rollers, the holding unit, and the like of the image reading apparatus of the first illustrative embodiment; 
         FIG. 6  is a top view illustrating a portion of the image reading apparatus of the first illustrative embodiment which includes the sheet supporting surface, the separation piece, the separation piece holder, the pinch rollers, the holding unit, and the like; 
         FIG. 7  is a schematic view for explaining the operations of a feeding roller, the separation roller, the separation piece, the pinch rollers, and the like in the image reading apparatus of the first illustrative embodiment; 
         FIG. 8  is a schematic view for explaining the operations of the feeding roller, the separation roller, the separation piece, the pinch rollers, and the like in the image reading apparatus of the first illustrative embodiment; 
         FIG. 9  is a perspective view illustrating pinch rollers and a holding unit of an image reading apparatus of a second illustrative embodiment; 
         FIG. 10  is a top view illustrating a portion of the image reading apparatus of the second illustrative embodiment which includes a sheet supporting surface, a separation piece, a separation piece holder, the pinch rollers, the holding unit, and the like; and 
         FIG. 11  is a perspective view illustrating pinch rollers and a linear motion type holding unit of an image reading apparatus of a third illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, first to third illustrative embodiments will be described with reference to the accompanying drawings. 
     (First Illustrative Embodiment) 
     As shown in  FIG. 1 , an image reading apparatus  1  of a first illustrative embodiment is a specific example of a sheet separating apparatus. In  FIG. 1 , on the assumption that the operation panel ( 8 P) side is referred to as the front side of the apparatus, and the left hand side of a user facing the operation panel  8 P is referred to as the left side of the apparatus, the front side, rear side, left side, right side, upper side, and lower side of the apparatus are indicated. Further, directions shown in  FIGS. 2 to 11  are indicated so as to correspond to the directions shown in  FIG. 1 . Hereinafter, individual components of the image reading apparatus  1  will be described with reference to some drawings such as  FIG. 1 . 
     &lt;Configuration&gt; 
     As shown in  FIGS. 1 to 3 , the image reading apparatus  1  includes a main body unit  8 , an opening/closing unit  9 , an image forming unit  5 , a reading unit  3 , a feeding tray  91 , a discharge tray  92 , and a conveyor  4 . The main body unit  8  is a flat body having substantially a box shape. As shown in  FIG. 1 , on the front surface of the main body unit  8 , the operation panel  8 P which is a touch panel or the like is provided. 
     As shown in  FIGS. 1 and 2 , the image forming unit  5  is accommodated in a lower portion of the inside of the main body unit  8 . The image forming unit  5  forms images on sheets by an inkjet scheme or a laser scheme. 
     As shown in  FIG. 3 , on the top surface of the main body unit  8 , first platen glass  81  and second platen glass  82  are disposed. A document supporting surface  81 A is formed by the top surface of the first platen glass  81 . When the reading unit  3  reads the image of a document which is a read target while being in a stop state, the document supporting surface  81 A supports the document from the below. Examples of the document which is a read target include sheets such as paper sheets and OHP sheets, books, etc. The second platen glass  82  is positioned on the left side of the first platen glass  81  and extends in an elongated shape in a front-rear direction. A read surface  82 A is formed by the top surface of the second platen glass  82 . When the reading unit  3  reads the images of sheets SH which are conveyed one at a time by the conveyor  4 , the read surface  82 A guides each conveyed sheet SH from the blow. 
     As shown in  FIG. 1 , the opening/closing unit  9  is supported by a hinge (not shown) disposed at the upper end edge of the rear surface side of the main body unit  8  such that it can swing around an opening/closing shaft center X 9  extending in a left-right direction. In a state where the opening/closing unit  9  is closed as shown in  FIGS. 1 to 3 , the opening/closing unit covers the document supporting surface  81 A from the above. Although not shown in the drawings, the opening/closing unit  9  swings around the opening/closing shaft center X 9  such that its front end portion side is displaced to the upper rear side, whereby the opening/closing unit is displaced to an open position for exposing the document supporting surface  81 A. Therefore, a user can make the document supporting surface  81 A support a document which is a read target. 
     As shown in  FIG. 3 , the reading unit  3  includes a read sensor  3 S which is accommodated in an upper portion of the inside of the main body unit  8 , and a scanning mechanism (not shown). The read sensor  3 S is positioned below the document supporting surface  81 A and the read surface  82 A. The scanning mechanism reciprocates the read sensor  3 S in the left-right direction below the document supporting surface  81 A and the read surface  82 A inside the main body unit  8 . As the read sensor  3 S, a known image reading sensor such as a contact image sensor (CIS) or a charge coupled device (CCD) may be used. 
     As shown in  FIGS. 2 and 3 , the conveyor  4  is provided at the opening/closing unit  9 . The conveyor  4  includes the feeding tray  91  and the discharge tray  92 . The feeding tray  91  is formed in a right portion of the opening/closing unit  9  by spreading a closed cover  9 C shown by a solid line in  FIG. 1  as shown by an alternate long and two short dashes line in  FIG. 2 . 
     As shown in  FIG. 3 , the feeding tray  91  has a sheet supporting surface  91 A. The sheet supporting surface  91 A is formed by a first sheet supporting surface  9 A which is a surface of the spread cover  9 C directed to the upper side, and a second sheet supporting surface  93 A which is a right area of the top surface of a chute member  93 . The sheet supporting surface  91 A is a flat surface inclined toward the lower left side. If a plurality of stacked sheets SH needs to be conveyed as s a read target by the conveyor  4 , the sheet supporting surface  91 A supports the sheets SH from the below. The width direction of the sheet supporting surface  91 A is the front-rear direction in the present illustrative embodiment. A height direction perpendicular to the sheet supporting surface  91 A is a direction Dh shown in  FIGS. 3, 7, and 8 . The height direction Dh is inclined with respect to a vertical direction. 
     The discharge tray  92  is positioned on the lower side from the feeding tray  91 . After the image of a sheet SH is read by the read sensor  3 S, the sheet SH is conveyed by the conveyor  4 , thereby being discharged onto the discharge tray  92 . 
     The conveyor  4  defines a conveyance path P 1  as a space surrounded by guide surfaces, a conveying roller (to be described below), and the like. The guide surfaces extend inside the opening/closing unit  9  so as to be capable of abutting on both sides of each sheet SH. The conveyance path P 1  first includes a portion extending almost horizontally from an end portion of the sheet supporting surface  91 A of the feeding tray  91  positioned on the downstream side in the conveyance direction, toward the left side. Next, the conveyance path P 1  includes a portion curved downward and making a U-turn. Next, the conveyance path P 1  includes a short portion extending toward the right side along the read surface  82 A. Finally, the conveyance path P 1  includes a portion inclined from the downstream side of the read surface  82 A in the conveyance direction toward the upper right side and leading to the discharge tray  92 . 
     The conveyance direction of a sheet SH which is conveyed by the conveyor  4  may be a leftward direction in the substantially horizontal portion of the upper path of the conveyance path P 1 , and varies to be a rightward direction in the portion of the conveyance path P 1  curved downward and making the U-turn, and may be a rightward direction in the portion of the lower path of the conveyance path P 1  passing the read surface  82 A and leading to the discharge tray  92 . The conveyance direction is perpendicular to the front-rear direction which is the width direction of the sheet supporting surface  91 A. 
     As shown in  FIGS. 3 to 8 , the conveyor  4  has the chute member  93 , a feeding roller  41 , a separation roller  42 , a separation piece  43 , a pair of front and rear pinch rollers  100 , a holding unit  120 , and an inclined surface  130 . 
     As shown in  FIG. 3 , the chute member  93  is a resin molding whose top surface has substantially a flat plate shape. An area of the top surface of the chute member  93  positioned on the left side from second sheet supporting surface  93 A forms a guide surface  93 B. More specifically, as shown in  FIGS. 4 to 6 , the right end portion of the guide surface  93 B is connected to an end portion  91 E of the sheet supporting surface  91 A positioned on the downstream side in the conveyance direction, that is, the left end portion of the second sheet supporting surface  93 A. The guide surface  93 B is inclined from its right end portion toward the upper left side, and then extends almost horizontally. As shown in  FIG. 3 , the guide surface  93 B forms a flat surface capable of abutting on each sheet SH from the below if the corresponding sheet SH is fed from the feeding tray  91 . The guide surface  93 B defines the substantially horizontal portion of the upper path of the conveyance path P 1  from the below. 
     The separation roller  42  is provided at a position which faces the guide surface  93 B of the chute member  93  from the above and is close to the second sheet supporting surface  93 A of the chute member  93 . The separation roller  42  is fit on a drive shaft  42 S, which has a first shaft center X 1  extending in the front-rear direction, as a central axis. The separation roller  42  is a roller which rotates around the first shaft center X 1  integrally with the drive shaft  42 S. That is, the separation roller  42  is provided so as to be able to contact each sheet SH from a side that is opposite to a side facing the sheet supporting surface  91 A if the corresponding sheet SH is fed from the feeding tray  91 . 
     On the drive shaft  42 S, a holder  42 F is supported so as to be able to swing around the first shaft center X 1 . The holder  42 F protrudes from the drive shaft  42 S toward the right side. 
     The feeding roller  41  is provided on the right side with respect to the separation roller  42 , that is, on the upstream side with respect to the separation roller  42  in the conveyance direction such the feeding roller  41  faces the second sheet supporting surface  93 A of the chute member  93  from the above. The feeding roller  41  is supported on the right portion of the holder  42 F so as to be rotatable around a third shaft center X 3  extending in the front-rear direction. That is, the feeding roller  41  is provided so as to be able to contact the sheet SH from the side that is opposite to the side facing the sheet supporting surface  91 A if the sheet SH are supported on the sheet supporting surface  91 A of the feeding tray  91 . Although not shown in the drawings, on the holder  42 F, a transmission gear group (not shown) is provided so as to transmit a rotation drive force from the drive shaft  42 S to the feeding roller  41 . 
     As shown in  FIGS. 3, 7, and 8 , on the holder  42 F, a pressing lever  42 L is provided. Between the pressing lever  42 L and the holder  42 F, a pressing spring (not shown) is provided. The upper end portion of the pressing lever  42 L is pressed by the pressing spring, thereby being pressed against the upper wall  9 D of the opening/closing unit  9 . As a result, the holder  42 F swings around the first shaft center X 1  such that the feeding roller  41  approaches the sheet supporting surface  91 A. 
     The position of the feeding roller  41  shown in  FIG. 3  is a contact position where the feeding roller  41  is in direct contact with the sheet supporting surface  91 A. As shown in  FIGS. 7 and 8 , according to whether the number of sheets SH which are supported on the sheet supporting surface  91 A is large or small, the feeding roller  41  moves closer to or farther from the sheet supporting surface  91 A, thereby coming into contact with the uppermost sheet SH. The position of the feeding roller  41  shown in  FIG. 7  is a maximum separation position where the feeding roller  41  is farthest away from the sheet supporting surface  91 A. 
     If a plurality of sheets SH is supported on the sheet supporting surface  91 A of the feeding tray  91 , the feeding roller  41  rotates around the third shaft center X 3 , thereby applying a conveyance force to the uppermost sheet SH, thereby sending the corresponding sheet SH toward the separation roller  42 . If the sheet SH is fed from the feeding tray  91 , that is, from the upstream side in the conveyance direction, the separation roller  42  rotates while being in contact with the sheet SH, thereby conveying the sheet SH toward the left side, that is, toward the downstream side in the conveyance direction, along the substantially horizontal portion of the upper path of the conveyance path P 1 . 
     As shown in  FIGS. 3 to 6 , a portion of the chute member  93  positioned on the lower side from the separation roller  42  is cut out, whereby an opening  93 H is formed. As shown in  FIGS. 5 and 6 , in the inner walls of the front side and rear side of the opening  93 H, a pair of front and rear shaft receiving portions  93 S is formed in a recess shape. Each shaft receiving portion  93 S is positioned on the right side with respect to the first shaft center X 1 , that is, on the upstream side with respect to the first shaft center X 1  in the conveyance direction. 
     The sheet supporting surface  91 A includes a protruding portion  93 D which protrudes toward the left side so as to penetrate into the left portion of the opening  93 H. The left end edge of the protruding portion  93 D configures an end portion  91 EE which is a portion of the end portion  91 E of the sheet supporting surface  91 A positioned on the downstream side in the conveyance direction. That is, the end portion  91 EE which is included in the end portion  91 E of the sheet supporting surface  91 A positioned on the downstream side in the conveyance direction and faces the opening  93 H is positioned on the right side from the other portion of the end portion  91 E, that is, on the upstream side from the other portion of the end portion  91 E in the conveyance direction. In wall surfaces extending downward from the front end edge and rear end edge of the protruding portion  93 D, a pair of front and rear shaft receiving portions  93 T is formed in a recess shape. The shaft receiving portions  93 T are positioned on the right side with respect to the shaft receiving portions  93 S. 
     As shown in  FIGS. 3 to 8 , the separation piece  43  is provided on the chute member ( 93 ) so as to face the separation roller  42  from the below. The separation piece  43  is a plate-shaped member which is formed of a soft material such as rubber or elastomer. The separation piece  43  is held by a separation piece holder  150 . 
     As shown in  FIGS. 5 and 6 , the separation piece holder  150  is a resin molding which has a base portion  151  and a pair of front and rear protruding portions  152 . 
     The base portion  151  is formed in a substantially rectangular plate shape. At the right portion of the top surface of the base portion  151 , the inclined surface  130  is formed. The inclined surface  130  is inclined toward the upper left side. On the left portion of the top surface of the base portion  151 , the separation piece  43  is attached. 
     The front protruding portion  152  protrudes from the front left corner of the base portion  151  toward the front side, and then is curved so as to protrude toward the right side. The rear protruding portion  152  protrudes from the rear left corner of the base portion  151  toward the rear side, and then is curved so as to protrude toward the right side. At the right end portions of the protruding portions  152 , shaft parts  152 S are formed, respectively. The front shaft part  152 S and the rear shaft part  152 S are cylindrical shafts, which have a pivot shaft center X 150  extending in the front-rear direction, as a central axis. The pivot shaft center X 150  is positioned on the right side with respect to the first shaft center X 1 , that is, on the upstream side with respect to the separation roller  42  in the conveyance direction. The front shaft part  152 S and the rear shaft part  152 S protrude in opposite directions. 
     As shown in  FIG. 6 , the shaft parts  152 S of the separation piece holder  150  are fit into the shaft receiving portions  93 S of the chute member  93 , whereby the separation piece holder  150  is supported on the chute member  93  so as to be able to swing around the pivot shaft center X 150 . 
     As shown in  FIG. 3 , between the base portion  151  of the separation piece holder  150  and the bottom of the opening  93 H of the chute member  93 , a compression spring  43 S is disposed. The compression spring  43 S presses the base portion  151  upward, whereby the separation piece  43  is pressed against the separation roller  42 . In a case where a plurality of stacked sheets SH is conveyed from the feeding roller  41  to the separation roller  42 , the separation piece  43  separates the sheets SH one at a time, in cooperation with the separation roller  42 . 
     A first nip position N 1  is defined as a position where a sheet SH is nipped by the separation roller  42  and the separation piece  43  as shown in  FIGS. 7 and 8  when the sheet SH is fed. 
     As shown in  FIG. 4 , the inclined surface  130  is positioned on the end portion ( 91 E) (end portion ( 91 EE)) of the sheet supporting surface  91 A positioned on the downstream side in the conveyance direction. Further, as shown in  FIGS. 3, 4, 7, and 8 , the inclined surface  130  extends toward the left side, that is, toward the downstream side in the conveyance direction, and is inclined with respect to the sheet supporting surface  91 A so as to approach the separation roller  42 . 
     As shown in  FIGS. 4 to 6 , inside the opening  93 H, the pinch rollers  100  are supported by the holding unit  120 . That is, the pinch rollers  100  are provided to be able to contact the sheet SH from the same side as the sheet supporting surface  91 A if the sheets SH are fed from the feeding tray  91 . As shown in  FIGS. 7 and 8 , the pinch rollers  100  are positioned on the right side with respect to the first nip position N 1 , that is, on the upstream side with respect to the first nip position N 1  in the conveyance direction. 
     More specifically, as shown in  FIGS. 4 and 6 , the pinch rollers  100  are disposed in the vicinity of the inner wall of the front side of the opening  93 H and in the vicinity of the inner wall of the front side of the opening  93 H, respectively. The pinch roller  100  positioned on the front side and the other pinch roller  100  positioned on the rear side are identical components, and are different from each other only in their directions. 
     As shown in  FIG. 6 , each pinch roller  100  is formed by integrally forming a main pinch roller body  101 , a shaft part  102 , and a locking part  103 . The main pinch roller body  101  has a disc shape having a second shaft center X 2  as a central axis. The shaft part  102  is columnar shaft, which has the second shaft center X 2  as a central axis and protrudes from the main pinch roller body  101 . The locking part  103  protrudes outward in a radial direction from an end portion of the shaft part  102  positioned on the opposite side to the main pinch roller body  101 , so as to have a flange shape. In each pinch roller  100 , the outer circumferential surface ( 100 A) of the main pinch roller body  101  is formed of rubber, and the other part is formed of a resin. That is, the outer layer  100 S of each pinch roller  100  is formed of rubber. 
     As shown in  FIGS. 5 and 6 , the holding unit  120  is formed by integrally forming a bottom wall portion  121  and a pair of front and rear side wall portions  122 . The bottom wall portion  121  extends in the front-rear direction and has a rectangular plate shape, and the side wall portions  122  protrude upward from the front end portion and rear end portion of the bottom wall portion  121 , respectively. 
     As shown in  FIG. 6 , each side wall portion  122  is cut out downward from its upper end edge, whereby a shaft receiving groove  122 C is formed. The shaft parts  102  of the pinch rollers  100  are fit into the shaft receiving grooves  122 C, respectively, whereby the pinch rollers  100  are supported by the holding unit  120  so as to be rotatable around the second shaft center X 2  extending in the front-rear direction. The second shaft center X 2  is positioned on the right side with respect to the first shaft center X 1 , that is, on the upstream side with respect to the first shaft center X 1  in the conveyance direction. 
     As shown in  FIGS. 5 and 6 , each side wall portion  122  protrudes toward the right side, and has a shaft part  122 S formed at its right end portion. The shaft part  122 S of the front side and the shaft part  122 S of the rear side are columnar shafts, which have a fourth shaft center X 4  extending in the front-rear direction, as a central axis. The shaft part  122 S of the front side and the shaft part  122 S of the rear side protrude so as to approach each other. 
     As shown in  FIG. 6 , the shaft parts  122 S of the holding unit  120  are fit into the shaft receiving portions  93 T of the chute member ( 93 ), whereby the holding unit  120  is supported by the chute member  93  so as to be able to swing around the fourth shaft center X 4 . The fourth shaft center X 4  is positioned on the right side with respect to the first shaft center X 1  and the second shaft center X 2 . That is, the fourth shaft center X 4  is positioned on the upstream side with respect to the separation roller  42  and the pinch rollers  100  in the conveyance direction. 
     The bottom wall portion  121  of the holding unit  120  is positioned on the lower side with respect to the base portion  151  of the separation piece holder  150 . The side wall portion  122  of the front side of the holding unit  120  and the front pinch roller  100  are positioned between the base portion  151  and front protruding portion  152  of the separation piece holder  150 . The side wall portion  122  of the rear side of the holding unit  120  and the rear pinch roller  100  are positioned between the base portion  151  and rear protruding portion  152  of the separation piece holder  150 . 
     As shown in  FIG. 3 , on the lower side from the opening  93 H of the chute member  93 , a guide member  94  is disposed. The guide member  94  defines the portion of the conveyance path P 1  passing the read surface  82 A and leading to the discharge tray  92 , from the above. 
     Between the bottom wall portion  121  of the holding unit  120  and the guide member  94 , a compression spring  100 T is disposed. The holding unit  120  swings around the fourth shaft center X 4 , whereby the pinch rollers  100  advance or retreat with respect to the separation roller  42 . The compression spring  100 T presses the bottom wall portion  121  upward, whereby the pinch rollers  100  are pressed against the separation roller  42 . As a result, each pinch roller  100  may be driven to rotate around the second shaft center X 2  by the separation roller  42  while abutting on the separation roller  42 . 
     A second nip position N 2  is defined as a position where a sheet SH is nipped by the separation roller  42  and the pinch rollers  100  as shown in  FIGS. 7 and 8  when the sheet SH is fed. An extension plane which extends from the sheet supporting surface  91 A toward the left side, that is, toward the downstream side in the conveyance direction is denoted by a reference symbol E 1 . 
     As shown in  FIG. 7 , a distance L 1  between the sheet supporting surface  91 A and the feeding roller  41  being at the maximum separation position is equal to a distance L 2  between the second nip position N 2  and the extension plane E 1  extending from the sheet supporting surface  91 A toward the downstream side in the conveyance direction. Here, the expression “the distance L 1  is equal to the distance L 2 ” includes not only a case where the distance L 1  and the distance L 2  are completely equal to each other, but also a case where the distance L 1  and the distance L 2  are slightly different from each other. As seen from the front-rear direction, the second shaft center X 2  is on the extension plane E 1  extending from the sheet supporting surface  91 A toward the downstream side in the conveyance direction. 
     As shown in  FIGS. 7 and 8 , as seen from the front-rear direction, each pinch roller  100  includes a portion  100 D which overlaps the separation piece  43 . As seen from the front-rear direction, the inclined surface  130  includes portions  130 D which overlap the pinch rollers  100 , respectively. 
     As seen from the front-rear direction, the extension plane E 1  extending from the sheet supporting surface  91 A toward the downstream side in the conveyance direction extends below the outer circumferential surface  42 A of the separation roller  42  with a gap. As seen from the front-rear direction, the outer circumferential surface  100 A of each pinch roller  100  (main pinch roller body  101 ) includes an arc  100 C. The arc  100 C extends from a position adjacent to the end portion  91 EE which is included in the end portion  91 E of the sheet supporting surface  91 A positioned on the downstream side in the conveyance direction, to the second nip position N 2 , while swelling upward toward the separation roller  42 . 
     As shown in  FIG. 3 , the conveyor  4  includes a conveying roller  44  and pinch rollers  44 P, which are provided in the substantially horizontal portion of the upper path of the conveyance path P 1  so as to be positioned on the left side with respect to the separation roller  42  and the separation piece  43 , that is, on the downstream side with respect to them in the conveyance direction. The conveyor  44  and the pinch rollers  44 P nip each sheet SH separated by the separation roller  42  and the separation piece  43 , and conveys the corresponding sheet SH to the downstream side in the conveyance direction. 
     The conveyor  4  includes a conveying roller  45  having a large diameter, a curved guide surface  45 G, and pinch rollers  45 P and  45 Q, which are provided in the portion of the conveyance path P 1  curved downward and making the U-turn. The outer circumferential surface of the conveying roller  45  forms an inner guide surface of the portion of the conveyance path P 1  curved downward and making the U-turn. The curved guide surface  45 G is disposed with a predetermined gap from the outer circumferential surface of the conveying roller  45 . The curved guide surface  45 G forms an outer guide surface of the portion of the conveyance path P 1  curved downward and making the U-turn. The conveying roller  45  conveys each sheet SH to the read surface  82 A, in cooperation with the pinch rollers  45 P and  45 Q abutting on the outer circumferential surface of the conveying roller  45 . 
     The conveyor  4  includes a pressing member  49  which is disposed at a position facing the read surface  82 A from the above. If a sheet SH is conveyed from the conveying roller ( 45 ), the pressing member  49  presses the sheet SH from the above, thereby coming the sheet SH into contact with the read surface  82 A. 
     The conveyor  4  includes a discharging roller  48  and pinch rollers  48 P which are disposed in a portion of the conveyance path P 1  positioned on the right side with respect to the pressing member  49  and inclined upward. The discharging roller  48  and the pinch rollers  48 P are adjacent to the discharge tray  92 . If a sheet SH passes the read surface  82 A, the discharging roller  48  and the pinch rollers  48 P discharge the sheet SH onto the discharge tray  92 . 
     &lt;Image Reading Operation&gt; 
     In the image reading apparatus  1 , in a case of reading the image of a document supported on the document supporting surface  81 A, the scanning mechanism (not shown) of the reading unit  3  operates such that the read sensor  3 S moves in the left-right direction between the lower side of the left end edge of the document supporting surface  81 A and the lower side of the right end edge of the document supporting surface  81 A, whereby the read sensor  3 S reads the image of the document supported on the document supporting surface  81 A. Thereafter, the scanning mechanism (not shown) operates such that the read sensor  3 S moves from the right end side to the left end side in the reading unit  3 , thereby returning to the original position. 
     Also, in the image reading apparatus  1 , in a case of reading the images of sheets SH put on the feeding tray  91 , the scanning mechanism (not shown) of the reading unit  3  operates such that the read sensor  3 S stops at a predetermined read position below the read surface  82 A. The read sensor  3 S which is at the predetermined read position is located on the downstream side with respect to the separation roller  42  in the conveyance direction. If the sheets SH on the feeding tray  91  are sequentially conveyed along the conveyance path P 1  by the conveyor  4 , since each sheet SH passes the upper side of the read sensor  3 S being at the predetermined read position while being in contact with the read surface  82 A, the read sensor  3 S reads the image of the corresponding sheet SH. After the image of the sheet SH is read, the sheet SH is discharged onto the discharge tray  92  by the discharging roller  48  and the pinch rollers  48 P. 
     &lt;Advantages&gt; 
     In the image reading apparatus  1  of the first illustrative embodiment, as shown in  FIG. 7 , if the number of sheets SH stacked on the sheet supporting surface  91 A is large, the leading end of the uppermost sheet SH is likely to first come into contact with the separation roller  42 . Then, the leading end of the corresponding sheet SH is guided to the separation roller  42  rotating, thereby being nipped at the second nip position N 2  by the separation roller  42  and the pinch rollers  100 , and then reaches the first nip position N 1 . 
     Meanwhile, in the image reading apparatus  1 , as shown in  FIG. 8 , if the number of sheets SH stacked on the sheet supporting surface  91 A is small, the leading end of the uppermost sheet SH is likely to first come into contact with the outer layers  100 S of the pinch rollers  100 . Then, the leading end of the corresponding sheet SH is guided by the pinch rollers  100  driven to rotate by the separation roller  42 , thereby being nipped at the second nip position N 2  by the separation roller  42  and the pinch rollers  100 , and then reaches the first nip position N 1 . 
     That is, in the image reading apparatus  1 , the leading end of each sheet SH is nipped at the second nip position N 2  by the separation roller  42  and the pinch rollers  100 , and then reaches the first nip position N 1 . Therefore, regardless of the number of sheets SH stacked on the sheet supporting surface  91 A, the trajectory of the leading end of each sheet SH which is fed from the feeding tray  91  to the separation roller  42  is stable. Since the leading end of each sheet SH which is conveyed along the stable trajectory reaches the first nip position N 1  positioned on the downstream side with respect to the second nip position in the conveyance direction, it is possible to stabilize the accuracy of separation of each sheet SH at the first nip position N 1 . 
     Also, in the image reading apparatus  1 , if the separation piece  43  is simply arranged in series with the pinch rollers  100  in the conveyance direction, that is, in the left-right direction, in the substantially horizontal portion of the upper path of the conveyance path P 1 , a space (the length in the conveyance direction) for disposing the separation piece  43  and the pinch rollers  100  needs at least a length which is the sum of the length of the separation piece  43  in the conveyance direction and the length of one pinch roller  100  in the conveyance direction, that is, the outside diameter of one pinch roller body  101 . Therefore, it becomes difficult to reduce the size of the apparatus in the left-right direction which is the conveyance direction. In contrast to this, in the image reading apparatus  1 , as shown in  FIGS. 7 and 8 , as seen from the front-rear direction, the pinch rollers  100  include the portions  100 D which overlap the separation piece  43 . Therefore, a space (the length in the conveyance direction) for disposing the separation piece  43  and the pinch rollers  100  may be reduced in the left-right direction. 
     Therefore, in the image reading apparatus  1  of the first illustrative embodiment, regardless of the number of sheets SH stacked on the sheet supporting surface  91 A, it is possible to reliably separate the sheets SH one at a time. Further, it is possible to reduce the size of the apparatus. 
     Also, in the image reading apparatus  1 , as shown in  FIG. 7 , the distance L 1  between the sheet supporting surface  91 A and the feeding roller  41  being at the maximum separation position is equal to the distance L 2  between the second nip position N 2  and the extension plane E 1  extending from the sheet supporting surface  91 A toward the downstream side in the conveyance direction. Therefore, in the image reading apparatus  1 , it is possible to reduce the size of the apparatus in the height direction Dh while increasing the maximum number of sheets SH which can be stacked on the sheet supporting surface  91 A. 
     Further, in the image reading apparatus  1 , as shown in  FIGS. 7 and 8 , as seen from the front-rear direction, the second shaft center X 2  is on the extension plane E 1  extending from the sheet supporting surface  91 A toward the downstream side in the conveyance direction. Therefore, in the image reading apparatus  1 , it is possible to reliably guide the leading end of each sheet SH toward the first nip position N 1  by the pinch rollers  100  while increasing the maximum number of sheets SH which can be stacked on the sheet supporting surface  91 A. 
     Also, in the image reading apparatus  1 , as seen from the front-rear direction, the inclined surface  130  includes the portions  130 D which overlap the pinch rollers  100 , respectively. Therefore, in the image reading apparatus  1 , even in a section between the sheet supporting surface  91 A and the pinch rollers  100 , it is possible to reliably guide the leading end of each sheet SH by the inclined surface  130 . 
     Further, in the image reading apparatus  1 , as shown in  FIGS. 4 to 6 , the pinch rollers  100  are supported by the holding unit  120  so as to be able to advance or retreat with respect to the separation roller  42 . Therefore, in the image reading apparatus  1 , when the user sets a sheet SH on the sheet supporting surface  91 A, even if the sheet SH is strongly inserted between the separation roller  42  and the pinch rollers  100 , since the pinch rollers  100  retreat with respect to the separation roller  42 , it is possible to suppress problems such as a problem in which the leading end of the sheet SH is folded. 
     Also, in the image reading apparatus  1 , the pinch rollers  100  are held by the holding unit  120  swinging around the fourth shaft center X 4  positioned on the right side with respect to the separation roller  42 , that is, on the upstream side with respect to the separation roller  42  in the conveyance direction. Therefore, for example, as compared to a case of using a configuration in which the holding unit moves linearly, it is possible to reduce the size of the apparatus in the height direction Dh. 
     Further, in the image reading apparatus  1 , the outer circumferential surface side of each main pinch roller body  101  is formed of rubber as the outer layer  100 S of a corresponding pinch roller  100 . Therefore, in the image reading apparatus  1 , it becomes difficult for the leading end of a sheet SH being in contact with the outer layers  100 S of the pinch rollers  100  to slip from the pinch rollers  100 , and thus it is possible to more reliably guide the leading end of each sheet SH by the pinch rollers  100 . 
     Also, in the image reading apparatus  1 , since the separating performance of the separation roller  42  and the separation piece  43  is stable due to the pinch rollers  100 , it is possible to stabilize the image reading quality of the read sensor  3 S positioned on the downstream side with respect to the separation roller  42  in the conveyance direction. 
     (Second Illustrative Embodiment) 
     As shown in  FIGS. 9 and 10 , an image reading apparatus of a second illustrative embodiment uses a holding unit  220  instead of the holding unit  120  of the image reading apparatus  1  of the first illustrative embodiment. The other configuration of the second illustrative embodiment is the same as that of the first illustrative embodiment. Therefore, components identical to those of the first illustrative embodiment are denoted by the same reference symbols, and will be described in brief or will not be described. 
     In the image reading apparatus of the second illustrative embodiment, as shown in  FIG. 10 , the size of an opening  293 H in the left-right direction is smaller than that of the opening  93 H of the first illustrative embodiment. 
     As shown in  FIG. 10 , on the left side of the opening  293 H, a pair of front and rear protrusions  293 T are formed. The protrusions  293 T protrudes upward from the bottom of the opening  293 H. The front protrusion  293 T is positioned between the base portion  151  and front protruding portion  152  of the separation piece holder  150 . The rear protrusion  293 T is positioned between the base portion  151  and rear protruding portion  152  of the separation piece holder  150 . In each protrusion  293 T, a shaft hole  293 U is formed. 
     As shown in  FIGS. 9 and 10 , the holding unit  220  is formed by integrally forming a bottom wall portion  221  and a pair of front and rear side wall portions  222 . The bottom wall portion  221  extends in the front-rear direction and has a rectangular plate shape, and the side wall portions  222  protrude upward from the front end portion and rear end portion of the bottom wall portion  221 , respectively. The bottom wall portion  221  has the same configuration as that of the bottom wall portion  121  of the first illustrative embodiment. 
     As shown in  FIG. 10 , each side wall portion  222  is cut out downward from its upper end edge, whereby a shaft receiving groove  222 C is formed. The shaft parts  102  of the pinch rollers  100  are fit into the shaft receiving grooves  222 C, respectively, whereby the pinch rollers  100  are being supported by the holding unit  120  so as to be rotatable around the second shaft center X 2 . 
     As shown in  FIGS. 9 and 10 , each side wall portion  222  protrudes toward the left side, and has a shaft part  222 S formed at its left end portion. The shaft part  222 S of the front side and the shaft part  222 S of the rear side are columnar shafts, which have a fourth shaft center X 24  extending in the front-rear direction, as a central axis. The shaft part  222 S of the front side and the shaft part  222 S of the rear side protrude so as to approach each other. 
     As shown in  FIG. 10 , the shaft parts  222 S of the holding unit  220  are fit into the shaft holes  293 U formed in the protrusions  293 T, whereby the holding unit  220  is supported by the chute member  93  so as to be able to swing around the fourth shaft center X 24 . The fourth shaft center X 24  is positioned on the left side with respect to the first shaft center X 1 , that is, on the downstream side with respect to the separation roller  42  in the conveyance direction. 
     The side wall portion  222  of the front side of the holding unit  220  and the front pinch roller  100  are positioned between the base portion  151  and front protruding portion  152  of the separation piece holder  150 . The side wall portion  222  of the rear side of the holding unit  220  and the rear pinch roller  100  are positioned between the base portion  151  and rear protruding portion  152  of the separation piece holder  150 . The holding unit  220  swings around the fourth shaft center X 24 , whereby the pinch rollers  100  advance or retreat with respect to the separation roller  42 . 
     In the image reading apparatus of the second illustrative embodiment configured as described above, similarly to the image reading apparatus  1  of the first illustrative embodiment, regardless of the number of sheets SH stacked on the sheet supporting surface  91 A, it is possible to reliably separate the sheets SH one at a time. Further, it is possible to reduce the size of the apparatus. 
     Also, in this image reading apparatus, the pinch rollers  100  are held by the holding unit  220  swinging around the fourth shaft center X 24  positioned on the downstream side with respect to the separation roller  42  in the conveyance direction. Therefore, for example, as compared to a case of using a configuration in which the holding unit moves linearly, it is possible to reduce the size of the apparatus in the height direction Dh shown in some drawings such as  FIG. 3 . 
     (Third Illustrative Embodiment) 
     As shown in  FIG. 11 , an image reading apparatus of a third illustrative embodiment uses a linear motion type holding unit  320  instead of the holding unit  120  of the image reading apparatus  1  of the first illustrative embodiment. The other configuration of the third illustrative embodiment is the same as that of the first illustrative embodiment. Therefore, components identical to those of the first illustrative embodiment are denoted by the same reference symbols, and will be described in brief or will not be described. 
     In the image reading apparatus of the third illustrative embodiment, in the opening  93 H (not shown), a pair of front and rear protrusions  393 T are formed. The protrusions  393 T protrude upward from the bottom of the opening  93 H (not shown). Although not shown in  FIG. 11 , the front protrusion  393 T is positioned between the base portion  151  and front protruding portion  152  of the separation piece holder  150 . The rear protrusion  393 T is positioned between the base portion  151  and rear protruding portion  152  of the separation piece holder  150 . On the front surface of the front protrusion  393 T and the rear surface of the rear protrusion  393 T, guide rails  393 U are formed in a rib shape so as to extend downward from their upper end portions. 
     The linear motion type holding unit  320  is formed by integrally forming a bottom wall portion  321  and a pair of front and rear side wall portions  322 . The bottom wall portion  221  extends in the front-rear direction and has a rectangular plate shape, and the side wall portions  322  protrude upward and downward from the front end portion and rear end portion of the bottom wall portion  221 , respectively. The bottom wall portion  321  has the same configuration as that of the bottom wall portion  121  of the first illustrative embodiment. 
     Although not shown in  FIG. 11 , in each side wall portion  322 , a shaft receiving groove identical to the shaft receiving grooves  122 C formed in the side wall portions  122  of the first illustrative embodiment is formed. The shaft parts  102  of the pinch rollers  100  are fit into the shaft receiving grooves, respectively, whereby the pinch rollers  100  are supported by the linear motion type holding unit  120  so as to be rotatable around the second shaft center X 2 . 
     The portions of the side wall portions  322  protruding downward from the bottom wall portion  321  are cut out upward from their lower end portions, whereby guide grooves  322 S are formed. 
     The guide rails  393 U formed on the protrusions  393 T are inserted into the guide grooves  322 S of the linear motion type holding unit  320 , respectively. As a result, the linear motion type holding unit  320  is supported by the chute member  93  so as to be linearly movable in a vertical direction, and operates such that the pinch rollers  100  linearly advance or retreat with respect to the first shaft center X 1 . 
     In the image reading apparatus of the third illustrative embodiment configured as described above, similarly to the image reading apparatuses  1  of the first and second illustrative embodiments, regardless of the number of sheets SH stacked on the sheet supporting surface  91 A, it is possible to reliably separate the sheets SH one at a time. Further, it is possible to reduce the size of the apparatus. 
     Also, in this image reading apparatus, the linear motion type holding unit  320  is not bulky in the left-right direction. Therefore, it is easy to reduce the size of the apparatus in the left-right direction. 
     Although the present invention has been described above on the basis of the first to third illustrative embodiments, the present invention is not limited to the above-described first to third illustrative embodiment, and can be appropriately modified and applied without departing from the scope of the present invention. 
     In the first illustrative embodiment, the separation roller  42  is provided so as to be able to contact the sheet SH fed from the feeding tray  91 , from the side that is opposite to the side facing the sheet supporting surface  91 A, such that the uppermost sheet SH is first fed to the separation roller  42 . However, the present invention is not limited thereto. For example, the separation roller may be provided so as to be able to contact the sheet fed from the feeding tray, from the same side as the sheet supporting surface, such that the lowermost sheet is first fed to the separation roller. 
     In the illustrative embodiments, as seen from the width direction, the second shaft center X 2  is on the extension plane E 1  extending from the sheet supporting surface  91 A toward the downstream side in the conveyance direction. However, the present invention is not limited thereto. As seen from the width direction, the second shaft center may be located across the extension plane, which extends from the sheet supporting surface toward the downstream side in the conveyance direction, from the separation roller. 
     In the illustrative embodiments, the outer layers  100 S of the pinch rollers  100  are formed of rubber. However, the present invention is not limited thereto. At least the outer layers of the pinch rollers may be friction members such as elastomer or sponge. Alternatively, the whole of each pinch roller may be formed of a resin. 
     The present invention can be applied to apparatuses such as an image reading apparatus, an image forming apparatus, and a multi-function apparatus.