Patent Publication Number: US-2023137449-A1

Title: Paper feeding device and image processing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation of application Ser. No. 17/013,888 filed on Sep. 8, 2020, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a paper feeding device and an image processing apparatus. 
     BACKGROUND 
     In the related art, there is known a paper feeding device including a paper feeding roller that conveys a sheet and a separation roller that applies a load to the conveyed sheet. The separation roller separates overlapped sheets. 
     The separation roller is slidably supported in a state of being pressed against the paper feeding roller. If the sliding resistance is large in a sliding portion, the pressing of the separation roller against the paper feeding roller becomes incomplete. The paper feeding device is required to reduce the sliding resistance of the sliding portion that supports the separation roller. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating an image processing apparatus of an embodiment; 
         FIG.  2    is a perspective view of a paper feeding device of the embodiment; 
         FIG.  3    is a sectional view of the paper feeding device; 
         FIG.  4    is a schematic diagram of a supporting portion and a rotation stopping portion; and 
         FIG.  5    is a partially enlarged view of an area V of  FIG.  2   . 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a paper feeding device includes a paper feeding roller and a separation roller. The paper feeding roller and the separation roller are arranged in a parallel direction. The paper feeding roller and the separation roller interpose a sheet. The paper feeding device includes a paper feeding roller, a separation roller, a shaft, a holder, and a rotation stopping portion. The paper feeding roller is configured to convey the sheet in a conveyance direction orthogonal to the parallel direction. The separation roller is configured to be pressed against the paper feeding roller. The shaft is configured to rotatably support the separation roller via a torque limiter. The holder is configured to include a supporting portion. The supporting portion is provided with a first guide surface and a second guide surface facing each other and extending in the parallel direction. The rotation stopping portion is configured to be attached to the shaft. The rotation stopping portion is configured to be inserted between the first guide surface and the second guide surface. The rotation stopping portion is configured to include a first sliding surface and a second sliding surface. The first sliding surface faces the first guide surface on the paper feeding roller side of the parallel direction and a downstream side of the conveyance direction with respect to a rotation axis of the separation roller. The second sliding surface faces the second guide surface on an opposite side of the paper feeding roller of the parallel direction and an upstream side of the conveyance direction with respect to the rotation axis of the separation roller. 
     Hereinafter, embodiments for carrying out the invention are described below with reference to the drawings. In each figure, the same parts are denoted by the same reference numerals. 
       FIG.  1    is a perspective view illustrating an image processing apparatus  90  including a paper feeding device  1  of the embodiment.  FIG.  2    is a perspective view of the paper feeding device  1  of the embodiment.  FIG.  3    is a sectional view of the paper feeding device  1  of the embodiment. 
     In the following, the description is made by using an orthogonal coordinate system of X, Y, and Z, if necessary. A predetermined direction in a horizontal plane is set as an X direction, a direction orthogonal to the X direction in the horizontal plane is set as a Y direction, a direction orthogonal to each of the X direction and the Y direction (that is, a vertical direction) is set as a Z direction. Among the X, Y, and Z directions, an arrow direction in the figure is set as a plus (+) direction, and a direction opposite to the arrow is set as a minus (−) direction. The +X direction is set as the front direction, the −X direction is set as the rear direction, the +Y direction is set as the right direction, the −Y direction is set as the left direction, the +Z direction is set as the upward direction, and the −Z direction is set as the downward direction. 
     The image processing apparatus  90  is described. 
     The image processing apparatus  90  of the present embodiment is a multifunction printer (MFP). For example, the image processing apparatus  90  forms an image on paper with a developer such as a toner. For example, the paper is paper or label paper. The paper may be any paper as long as an image can be formed on the surface thereof. In the example of  FIG.  1   , the image processing apparatus  90  includes a display  91 , a printer unit  92 , a control panel unit  93 , a paper containing unit  94 , and an image reading unit  95 . The paper containing unit  94  includes a plurality of stages of paper feed cassettes arranged in the vertical direction (Z direction). The paper feeding device  1  of the embodiment is disposed inside the image processing apparatus  90  and on the upper side of at least one paper feed cassette. The paper feeding device  1  of the embodiment may be disposed in a sheet feeding port of a paper feeding tray for manual feeding. 
     According to the present embodiment, as an image processing apparatus on which the paper feeding device  1  is mounted, a multifunction printer is exemplified. However, the paper feeding device  1  may be mounted on other image processing apparatuses. As the image processing apparatus on which the paper feeding device  1  is mounted, an automatic document feeder, a scanner, and a decoloring device are exemplified. 
     The paper feeding device  1  is described. 
     As illustrated in  FIGS.  2  and  3   , the paper feeding device  1  includes a paper feeding roller  10 , a separation roller  20 , a torque limiter  39 , a shaft  30 , two rotation stopping portions  40 , a holder  60 , a sheet guide member  70  (see  FIG.  3   ), and a pressure unit  80  (see  FIG.  2   ). The paper feeding device  1  may further include a pickup roller (not illustrated). Here, the pickup roller supplies the uppermost sheet of the stacked paper bundle to the paper feeding roller  10 . 
     As illustrated in  FIG.  2   , the paper feeding roller  10  has a cylindrical shape with a first rotation axis J 1  as the center. The first rotation axis J 1  of the present embodiment is parallel to the horizontal direction (X axis). The paper feeding roller  10  is connected to a drive unit (not illustrated). The paper feeding roller  10  is driven and rotated with the first rotation axis J 1  as the center. 
     The separation roller  20  is a cylindrical shape with a second rotation axis J 2  as the center. The second rotation axis J 2  of the present embodiment is parallel to the horizontal direction (X axis). The first rotation axis J 1  and the second rotation axis J 2  are parallel to each other. 
     As illustrated in  FIG.  3   , the separation roller  20  is arranged with the paper feeding roller  10  in a parallel direction PD. Here, the parallel direction PD is a direction in which the paper feeding roller  10  and the separation roller  20  are arranged. More specifically, the parallel direction PD is a direction in which a line segment that connects the first rotation axis J 1  and the second rotation axis J 2  extends when being viewed from the axial direction of the first rotation axis J 1  and the second rotation axis J 2 . The parallel direction PD is orthogonal to the first rotation axis J 1  and the second rotation axis J 2 . 
     As illustrated in  FIG.  2   , the separation roller  20  is supported by the shaft  30  via the torque limiter  39 . The separation roller  20  is pressed against the paper feeding roller  10  by the pressure unit  80 . The separation roller  20  is rotatable about the second rotation axis J 2  as the center. The separation roller  20  rotates together with the paper feeding roller  10  by the frictional force acting on the outer peripheral surface. 
     A sheet S is interposed between the paper feeding roller  10  and the separation roller  20 . The sheet S comes into contact with the paper feeding roller  10  on the upper surface. The sheet S comes into contact with the separation roller  20  on the lower surface. The paper feeding roller  10  is driven and rotated to convey the sheet S. If two or more of the sheets S are overlapped and fed, the separation roller  20  applies a load to the sheet S on the lower side due to the action of the torque limiter  39  and separates the upper sheet S. 
     As illustrated in  FIG.  3   , the sheet S interposed between the paper feeding roller  10  and the separation roller  20  is conveyed in a conveyance direction TD. Here, the conveyance direction TD is a direction orthogonal to the parallel direction PD when being viewed from the axial direction of the first rotation axis J 1  and the second rotation axis J 2 . The conveyance direction TD is orthogonal to the first rotation axis J 1  and the second rotation axis J 2 . In the present specification, a side to which the sheet S is discharged is referred to as “a downstream side of the conveyance direction TD”. A side from which the sheet S is drawn is referred to as “an upstream side of the conveyance direction TD”. In the present embodiment, the downstream side of the conveyance direction TD is a +Y side. In the present embodiment, the upstream side of the conveyance direction TD is a −Y side. 
     As illustrated in  FIG.  2   , the torque limiter  39  is disposed inside the separation roller  20 . The torque limiter  39  includes an outer cylinder portion  38  fixed to the separation roller  20  and an inner cylinder portion  37  fixed to the shaft  30 . Frictional force occurs between the outer cylinder portion  38  and the inner cylinder portion  37 . The outer cylinder portion  38  and the inner cylinder portion  37  relatively rotate if a torque of a predetermined value or more is applied. 
     The shaft  30  extends in the horizontal direction with the second rotation axis J 2  as the center. The shaft  30  has a cylindrical shape. The torque limiter  39  is fixed to the outer peripheral surface of the shaft  30 . The shaft  30  rotatably supports the separation roller  20  via the torque limiter  39 . 
     An upward force is applied from the pressure unit  80  to the end portions  32  on both sides of the shaft  30 . As illustrated in  FIG.  2   , the pressure unit  80  includes two pressure levers  81  and a pressure spring  89 . The pressure levers  81  includes cylinder portions  84 , arm portions  82 , and hook portions  83 . The cylinder portion  84  has a tubular shape with a third rotation axis J 3  as the center. The third rotation axis J 3  extends along the Y axis. A support shaft (not illustrated) is inserted into the cylinder portion  84 . The shaft  30  is rotatable about the third rotation axis J 3 . The arm portion  82  and the hook portion  83  are connected to the outer peripheral surface of the cylinder portion  84 . The arm portions  82  are disposed on the lower sides of the end portions  32  of the shaft  30 . The pressure spring  89  is hooked on the hook portions  83 . The pressure spring  89  causes the pressure levers  81  to rotate about the third rotation axis J 3 . The pressure spring  89  presses the arm portions  82  against the end portions  32  of the shaft  30 . The shaft  30  is pressed against the paper feeding roller  10  side by the pressure unit  80 . 
     End portions  32  are provided with D-cut surfaces  31  on the both sides of the shaft  30 . A cross section of the end portion  32  of the shaft  30  has a D shape. The rotation stopping portions  40  are attached to the end portions  32  on the both sides of the shaft  30 . The torque limiter  39  and the separation roller  20  are disposed between the two rotation stopping portions  40  in the axial direction of the shaft  30 . 
     The rotation stopping portion  40  has a flat plate shape along a plane (Y-Z plane) orthogonal to the second rotation axis J 2 . The rotation stopping portions  40  are provided with outer ribs  49  extending along the outer shape. The outer ribs  49  project on both sides of the rotation stopping portions  40  in the plate thickness direction. The outer ribs  49  reinforce the rotation stopping portions  40 . 
     As illustrated in  FIG.  3   , the rotation stopping portion  40  includes a substantially rectangular main body portion  45  and a leg portion  46  extending downward from the main body portion  45 . The leg portion  46  extends from the main body portion  45  in the parallel direction PD. The leg portion  46  extends in a direction of separating from the paper feeding roller  10 . 
     Support holes  47  penetrate the main body portion  45  in the plate thickness direction. The support hole  47  has a D shape. The end portions  32  of the shaft  30  are inserted into the support holes  47 . The relative rotation of the shaft  30  and the rotation stopping portions  40  is limited. Inner ribs  48  are provided on the inner edge of the support holes  47 . The inner ribs  48  protrude in the plate thickness direction of the rotation stopping portions  40 . The inner rib  48  enhances the rigidity of the rotation stopping portion  40  near the support hole  47 . The inner rib  48  stabilizes the support of the shaft  30  by the rotation stopping portion  40 . 
     A first end edge  55  and a second end edge  56  are provided on the outer peripheral edge of the rotation stopping portion  40 . The first end edge  55  and the second end edge  56  each extend in substantially straight-line shapes in the parallel direction PD. 
     The first end edge  55  is positioned on the downstream side of the conveyance direction TD with respect to the second rotation axis J 2 . The first end edge  55  is an end edge of the main body portion  45 . The second end edge  56  is positioned on the upstream side of the conveyance direction TD with respect to the second rotation axis J 2 . Meanwhile, the second end edge  56  is an end edge mounted over the main body portion  45  and the leg portion  46 . 
     The first end edge  55  includes a first sliding surface  51  and a third sliding surface  53 . Meanwhile, the second end edge  56  includes a second sliding surface  52  and a fourth sliding surface  54 . That is, the rotation stopping portion  40  includes the first sliding surface  51 , the second sliding surface  52 , the third sliding surface  53 , and the fourth sliding surface  54 . 
     The first sliding surface  51  and the third sliding surface  53  face the downstream side of the conveyance direction TD. The first sliding surface  51  and the third sliding surface  53  are planes orthogonal to the conveyance direction TD. The first sliding surface  51  is disposed on the upper end side of the first end edge  55 . Meanwhile, the third sliding surface  53  is disposed on the lower end side of the first end edge  55 . The third sliding surface  53  is positioned on the opposite side of the paper feeding roller  10  in the parallel direction PD with respect to the first sliding surface  51 . The third sliding surface  53  is disposed in the same planar shape as the first sliding surface  51 . The first sliding surface  51  and the third sliding surface  53  are provided with recesses  59  containing grease. 
     A first cutout portion  57  is provided between the first sliding surface  51  and the third sliding surface  53 . The first cutout portion  57  opens on the downstream side of the conveyance direction TD. The first cutout portion  57  depresses on the upstream side of the conveyance direction TD with respect to the first sliding surface  51  and the third sliding surface  53 . 
     The second sliding surface  52  and the fourth sliding surface  54  face the downstream side of the conveyance direction TD. The second sliding surface  52  and the fourth sliding surface  54  are planes orthogonal to the conveyance direction TD. The second sliding surface  52  is disposed on the lower end side at the second end edge  56 . The second sliding surface  52  is provided in the distal end portion of the leg portion  46 . Meanwhile, the fourth sliding surface  54  is disposed on the upper end side at the second end edge  56 . The main body portion  45  is provided with the fourth sliding surface  54 . The fourth sliding surface  54  is positioned on the paper feeding roller  10  side of the parallel direction PD with respect to the second sliding surface  52 . The fourth sliding surface  54  is disposed in the same planar shape as the second sliding surface  52 . The second sliding surface  52  is provided with the recess  59  containing grease. 
     A second cutout portion  58  is provided between the second sliding surface  52  and the fourth sliding surface  54 . The second cutout portion  58  opens on the upstream side of the conveyance direction TD. The second cutout portion  58  depresses on the downstream side of the conveyance direction TD with respect to the second sliding surface  52  and the fourth sliding surface  54 . 
     The holder  60  supports the end portions  32  of the shaft  30  via the rotation stopping portions  40 . The holder  60  is configured with a resin material. The holder  60  is disposed on the lower side of the separation roller  20 . 
     The holder  60  includes two supporting portions  69  that each support the rotation stopping portions  40 . As illustrated in  FIG.  3   , the supporting portion  69  of the present embodiment has a notch shape that opens upward. The supporting portion  69  includes a first facing wall  61 , a second facing wall  62 , and a bottom wall portion  63 . 
     The first facing wall  61  and the second facing wall  62  face each other in the conveyance direction TD. The first facing wall  61  and the second facing wall  62  each extend in the parallel direction PD. The bottom wall portion connects the lower end portion of the first facing wall  61  and the lower end portion of the second facing wall  62 . 
     The first facing wall  61  includes a first guide surface  66  that faces the upstream side of the conveyance direction TD. The second facing wall  62  includes a second guide surface  67  that faces the downstream side of the conveyance direction. The supporting portion  69  is provided with the first guide surface  66  and the second guide surface  67 . The first guide surface  66  and the second guide surface  67  each include a flat surface extending in the parallel direction PD. The first guide surface  66  and the second guide surface  67  face each other in the conveyance direction TD. 
       FIG.  4    is a diagram schematically illustrating a relationship between the supporting portion  69  and the rotation stopping portion  40 . 
     The rotation stopping portion  40  is inserted between the first guide surface  66  and the second guide surface  67 . 
     The first guide surface  66  faces the first sliding surface  51  and the third sliding surface  53  of the rotation stopping portion  40 . The first sliding surface  51  and the third sliding surface  53  face the first guide surface  66  on the downstream side of the conveyance direction TD with respect to the second rotation axis J 2 . The first sliding surface  51  faces the first guide surface  66  on the paper feeding roller  10  side of the parallel direction PD with respect to the second rotation axis J 2 . The third sliding surface  53  faces the first guide surface  66  on the opposite side of the paper feeding roller  10  in the parallel direction PD with respect to the second rotation axis J 2 . 
     The second guide surface  67  faces the second sliding surface  52  and the fourth sliding surface  54  of the rotation stopping portion  40 . The second sliding surface  52  and the fourth sliding surface  54  face the second guide surface  67  on the upstream side of the conveyance direction TD with respect to the second rotation axis J 2 . The second sliding surface  52  and the fourth sliding surface  54  face the second guide surface  67  on the opposite side of the paper feeding roller  10  in the parallel direction PD with respect to the second rotation axis J 2 . 
     The shaft  30  is pressed against the paper feeding roller  10  side by the pressure unit  80 . If the sheet S is interposed between the paper feeding roller  10  and the separation roller  20 , the interaxial distance between the first rotation axis J 1  and the second rotation axis J 2  changes. Here, the first sliding surface  51  and the third sliding surface  53  slide in the parallel direction PD with respect to the first guide surface  66 . The second sliding surface  52  and the fourth sliding surface  54  slide in the parallel direction PD with respect to the second guide surface  67 . 
     The width dimension of the rotation stopping portion  40  in the conveyance direction TD is slightly smaller than the distance between the first guide surface  66  and the second guide surface  67 . The rotation stopping portion  40  can smoothly slide between the first guide surface  66  and the second guide surface  67 . 
     The rotation stopping portion  40  faces the first guide surface  66  on the two sliding surfaces (the first sliding surface  51  and the third sliding surface  53 ) on the downstream side of the conveyance direction TD with respect to the second rotation axis J 2 . The rotation stopping portion  40  faces the second guide surface  67  on the two sliding surfaces (the second sliding surface  52  and the fourth sliding surface  54 ) on the upstream side of the conveyance direction TD with respect to the second rotation axis J 2 . According to the present embodiment, a large sliding area of the rotation stopping portion  40  in the parallel direction PD can be secured, and sliding efficiency can be improved. A plurality of sliding surfaces realize the rotation stop regardless of the direction of the rotation stopping portion  40  to which the moment is applied. 
     In the first end edge  55  of the rotation stopping portion  40 , the first cutout portion  57  is provided between the first sliding surface  51  and the third sliding surface  53 . The first sliding surface  51  and the third sliding surface  53  are partitioned by the first cutout portion  57 . In the second end edge  56 , the second cutout portion  58  is provided between the second sliding surface  52  and the fourth sliding surface  54 . The second sliding surface  52  and the fourth sliding surface  54  are partitioned by the second cutout portion  58 . The rotation stopping portion  40  comes into contact with the first guide surface  66  and the second guide surface  67  in a limited area. The dimension of the rotation stopping portion  40  is easily managed. 
     In the present embodiment, a portion between the first sliding surface  51  and the third sliding surface  53 , and the first guide surface  66  is filled with grease that reduces the sliding resistance. A portion between the second sliding surface  52  and the fourth sliding surface  54 , and the second guide surface  67  is filled with grease that reduces the sliding resistance. 
     The first sliding surface  51 , the second sliding surface  52 , and the third sliding surface  53  are provided with the recesses  59  containing grease. The recess  59  has a groove shape extending in the axial direction of the second rotation axis J 2 . The grease in the recess  59  is supplied to the first sliding surface  51 , the second sliding surface  52 , and the third sliding surface  53  and constantly reduces the sliding resistance. 
     According to the present embodiment, the fourth sliding surface  54  is not provided with the recess  59 . However, all of the sliding surfaces (the first sliding surface  51 , the second sliding surface  52 , the third sliding surface  53 , and the fourth sliding surface  54 ) may be provided with the recesses  59 . If at least one sliding surface of all of the sliding surfaces is provided with the recess  59 , a consistent effect can be obtained in view of the smoothness of sliding. 
     If the sheet S is conveyed to the downstream side of the conveyance direction TD, the moment is applied to the rotation stopping portion  40  as the reaction force of the torque limiter  39 . The direction of the moment applied to the rotation stopping portion  40  is clockwise in  FIG.  4   . If the sheet S is conveyed to the downstream side, the first sliding surface  51  is pressed against the first guide surface  66 . If the sheet S is conveyed to the downstream side, the second sliding surface  52  and the fourth sliding surface  54  are pressed against the second guide surface  67 . The first guide surface  66  and the second guide surface  67  restrict the clockwise rotation of the rotation stopping portion  40 . In contrast, if the sheet S moves backward to the upstream side, the third sliding surface  53  is pressed against the first guide surface  66 . The first guide surface  66  restricts counterclockwise rotation of the rotation stopping portion  40 . The first guide surface  66  and the second guide surface  67  restrict the rotation in any direction of the rotation stopping portion  40 . 
     According to the present embodiment, the rotation stopping portion  40  includes the first sliding surface  51  and the second sliding surface  52 . The first sliding surface  51  comes into contact with the first guide surface  66  on the downstream side of the conveyance direction TD and the separation roller  20  side of the parallel direction PD with respect to the second rotation axis J 2 . Meanwhile, the second sliding surface  52  comes into contact with the second guide surface  67  on the upstream side of the conveyance direction TD and the opposite side of the separation roller  20  in the parallel direction PD with respect to the second rotation axis J 2 . The moment applied to the separation roller  20  during the conveyance of the sheet S is effectively received on the first guide surface  66  and the second guide surface  67 . The first sliding surface  51  and the second sliding surface  52  each are separated from the second rotation axis J 2  in the parallel direction PD. The reaction force of the first guide surface  66  and the second guide surface  67  decreases. As a result, the sliding resistance applied between the first sliding surface  51  and the first guide surface  66  and between the second sliding surface  52  and the second guide surface  67  is reduced. 
     As illustrated in  FIG.  4   , the distance between the second rotation axis J 2  and the first sliding surface  51  in the parallel direction PD is set as a first distance L 1 . The distance between the second rotation axis J 2  and the second sliding surface  52  in the parallel direction PD is set as a second distance L 2 . 
     Slight gaps are provided between the first sliding surface  51  and the first guide surface  66  and between the second sliding surface  52  and the second guide surface  67 . If the clockwise moment ( FIG.  4   ) is applied to the rotation stopping portion  40 , the first sliding surface  51  comes into contact with the first guide surface  66  at a point farthest from the second rotation axis J 2  in the plane. A slight gap is provided between the first sliding surface  51  and the first guide surface  66 . If the clockwise moment ( FIG.  4   ) is applied to the rotation stopping portion  40 , the second sliding surface  52  comes into contact with the second guide surface  67  at the farthest point from the second rotation axis J 2  in the plane. Therefore, the first distance L 1  is a distance between the farthest point from the second rotation axis J 2  and the second rotation axis J 2  in the first sliding surface  51 . In the same manner, the second distance L 2  is a distance between the farthest point from the second rotation axis J 2  and the second rotation axis J 2  in the second sliding surface  52 . 
     Based on  FIG.  4   , the balance of the moment of the rotation stopping portion  40  during the conveyance of the sheet S is considered. 
     The force that the separation roller  20  applies to the sheet S during the conveyance of the sheet S is set as separating force T. The separation roller  20  receives the force of the separating force T from the sheet S as the reaction force. A moment of a product of the separating force T and a radius Lt of the separation roller  20  (T×Lt) is applied to the rotation stopping portion  40 . 
     Meanwhile, the rotation stopping portion  40  comes into contact with the first guide surface  66  in the first sliding surface  51  and receives first reaction force N 1 . The rotation stopping portion  40  comes into contact with the second guide surface  67  in the second sliding surface  52  and receives second reaction force N 2 . A moment of a sum of a product of the first reaction force N 1  and the first distance L 1  (N 1 ×L 1 ) and a product of the second reaction force N 2  and the second distance L 2  (N 2 ×L 2 ) is applied to the rotation stopping portion  40 . 
     In view of the balance of the moment of the rotation stopping portion  40 , Equation (1) is established. 
         T×Lt =( N 1× L 1)+( N 2× L 2)  (1)
 
     The balance of the force of the rotation stopping portion  40  during the conveyance of the sheet S is considered. 
     The separating force T and the second reaction force N 2  as the reaction force toward the downstream side of the conveyance direction TD and the first reaction force N 1  as the reaction force toward the upstream side of the conveyance direction TD are applied to the rotation stopping portion  40 . 
     In view of the balance of the force of the rotation stopping portion  40 , Equation (2) is established. 
         T+N 2= N 1  (2)
 
     From Equation (2), the first reaction force N 1  is always larger than the second reaction force N 2 . In order to smooth the sliding of the rotation stopping portion  40  in the supporting portion  69 , it is important to reduce the first reaction force N 1 . 
     From Equations (1) and (2), Equations (3) and (4) are derived. 
         N 1= T ×( Lt+L 2)/( L 1+ L 2)  (3)
 
         N 2= T ×( Lt−L 1)/( L 1+ L 2)  (4)
 
     From Equations (3) and (4), the first reaction force N 1  and the second reaction force N 2  are reduced by causing the first distance L 1  to be a value of larger than 0. According to the present embodiment, since the first distance L 1  is a value of larger than 0, the first reaction force N 1  is reduced, and the sliding of the rotation stopping portion  40  in the supporting portion  69  is smoothed. 
     The first distance L 1  of the present embodiment is larger than a half of the radius Lt of the separation roller  20 . The first reaction force N 1  is effectively reduced by causing the first distance L 1  to be larger than a half of the radius Lt of the separation roller  20 . 
     The first distance L 1  is preferably smaller than the radius Lt of the separation roller  20 . If the first distance L 1  is larger than the radius Lt of the separation roller  20 , the first sliding surface  51  is disposed on the paper feeding roller  10  side with respect to the sheet S. Here, in order not to allow the rotation stopping portion  40  to prevent the conveyance of the sheet S, the first sliding surface  51  is disposed on the outside of the passage area of the sheet S. Here, there is a concern that the size of the paper feeding device  1  increases. According to the present embodiment, by causing the first distance L 1  to be smaller than the radius Lt of the separation roller  20 , the size of the paper feeding device  1  can be reduced. 
     From Equation (4), it is understood that the second reaction force N 2  can be reduced by increasing the second distance L 2 . According to the present embodiment, since the second distance L 2  is a sufficiently large value, the second reaction force N 2  can be reduced, and the sliding of the rotation stopping portion  40  in the supporting portions  69  can be smoothed. 
     The second distance L 2  of the present embodiment is larger than the radius Lt of the separation roller  20 . The second reaction force N 2  is effectively reduced by causing the second distance L 2  to be larger than the radius Lt of the separation roller  20 . 
     According to the present embodiment, the rotation stopping portions  40  are attached to the shaft  30  in the end portions  32  that interpose the separation roller  20 . The holder  60  includes the two supporting portions  69  that each support the rotation stopping portions  40 . The first reaction force N 1  and the second reaction force N 2  are received by the two rotation stopping portions  40  in a dispersed manner. The first reaction force N 1  and the second reaction force N 2  applied to each of the rotation stopping portions  40  can be reduced, and the sliding of the rotation stopping portions  40  can be smoothed. The rotation of the shaft  30  is restricted by the end portions  32  on both sides, and the skew of the shaft  30  is reduced. 
       FIG.  5    is a partially enlarged view of an area V of  FIG.  2   . As illustrated in  FIG.  5   , the first facing wall  61  of the supporting portion  69  includes a first rib (rib)  65 . 
     As illustrated in  FIG.  3   , the first rib  65  extends in the parallel direction PD. The first rib  65  protrudes to the upstream side of the conveyance direction TD. The first rib  65  is provided with the first guide surface  66 . The contact area between the supporting portion  69  and the first sliding surface  51  can be limited by providing the first guide surface  66  at the distal end of the first rib  65 . Accordingly, the dimension of the first guide surface  66  is easily managed. 
     The second facing wall  62  of the supporting portion  69  includes a second rib (rib)  68 . The second rib  68  extends in the parallel direction PD. The second rib  68  protrudes to the downstream side of the conveyance direction TD. The second rib  68  is provided with the second guide surface  67 . The contact area between the supporting portion  69  and the second sliding surface  52  can be limited by providing the second guide surface  67  at the distal end of the second rib  68 . Accordingly, the dimension of the second guide surface  67  is easily managed. 
     As illustrated in  FIG.  3   , a through hole  64  penetrates the bottom wall portion  63  of the supporting portion  69  in the thickness direction. The leg portion  46  of the rotation stopping portion  40  is inserted into the through hole  64 . 
     According to the present embodiment, the leg portion  46  having the second sliding surface  52  is inserted into the through hole  64  of the holder  60 . The second distance L 2  can be secured to be large by providing the second sliding surface  52  in the leg portion  46 . The dimension of the holder  60  in the parallel direction PD is reduced by inserting the leg portion  46  to the through hole  64 . The size of the paper feeding device  1  can be reduced. 
     As illustrated in  FIG.  3   , the sheet guide member  70  includes a plate-shaped guide plate  71 . The guide plate  71  covers the holder  60  from the upper side. An opening (not illustrated) that exposes the separation roller  20  is provided on the guide plate  71 . The guide plate  71  includes a sheet guide surface  72  that faces the upper side. That is, the sheet guide member  70  is provided with the sheet guide surface  72 . The sheet guide surface  72  guides the conveyed sheet S. 
     According to the present embodiment, the sheet guide surface  72  is inclined to the conveyance direction TD. More specifically, the sheet guide surface  72  is inclined to the paper feeding roller  10  side toward downstream side of the conveyance direction TD when being viewed in the axial direction of the separation roller  20 . 
     The sheet S is conveyed between the paper feeding roller  10  and the separation roller  20  in the conveyance direction TD. The sheet S is conveyed in a manner of being bent in contact with the sheet guide surface  72  on the downstream side of the paper feeding roller  10  and the separation roller  20 . 
     The space of the separation roller  20  on the downstream side of the conveyance direction TD is secured to be large by causing the sheet guide surface  72  to be inclined to the paper feeding roller  10  side on the downstream side of the conveyance direction TD. The position of the first sliding surface  51  in the parallel direction PD can come closer to the paper feeding roller  10  side. The first distance L 1  becomes large, and the sliding between the rotation stopping portion  40  and the supporting portion  69  becomes smooth. 
     As illustrated in  FIG.  4   , the distance between the second rotation axis J 2  and the first sliding surface  51  in the conveyance direction TD is set as a third distance L 3 . According to the present embodiment, the third distance L 3  is larger than the radius Lt of the separation roller  20 . As described above, the sheet guide surface  72  comes closer to the paper feeding roller  10  side on the downstream side of the conveyance direction TD. The first sliding surface  51  can become closer to the paper feeding roller  10  side in the parallel direction PD by causing the third distance L 3  to be large and disposing the first sliding surface  51  on the downstream side of the conveyance direction TD. The first distance L 1  becomes large, and the sliding between the rotation stopping portion  40  and the supporting portion  69  becomes smooth. 
     While certain embodiments have been described these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms: furthermore various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and there equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.