Patent Publication Number: US-11643289-B2

Title: Sheet feeding apparatus and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet feeding apparatus to feed a sheet and an image forming apparatus. 
     Description of the Related Art 
     Generally, an image forming apparatus such as a copy machine, a printer, a facsimile, and a composite machine having a plurality of these functions includes a sheet feeding unit to feed a sheet stored in a feed cassette to an image forming unit. Also, the sheet feeding unit described above includes a separation conveyance unit to convey the sheet with separating the sheet from another sheet so as not to feed 2 or more overlapping sheets. 
     The separation conveyance unit which includes a feed roller synchronously rotating in the same direction with a pickup roller and includes a retard roller being in a pressure contact with the feed roller with a predetermined force of the pressure contact (hereinafter referred to as “retard pressure”) is hitherto known. For example, Japanese Patent Laid-Open No. 2014-185000 discloses the separation conveyance unit in which the retard roller is supported in a manner of being capable of swinging freely by an arm member and the retard roller is in the pressure contact with the feed roller with a predetermined retard pressure provided by an urging member. 
     Incidentally, the retard pressure described above is one of parameters which affect a sheet separation performance at the separation conveyance unit, and control of these parameters are important to obtain a stable separation performance at the separation conveyance unit. In this regard, as the feed roller is driven via a torque limiter in a configuration disclosed in Japanese Patent Laid-Open No. 2014-185000 described above, the arm member is pressed in a pivoting direction of the arm member by a torque given by the torque limiter, and moves the retard pressure upwards and downwards. An amount of an increase and decrease in the retard pressure changes with relative positional relations among the feed roller, the retard roller and a swing shaft. Therefore, when these positions changes, the retard pressure changes, and it becomes difficult to obtain the stable separation performance. 
     Accordingly, variance in the retard pressure has been conventionally inhibited by reducing the variance in the positions as much as possible by means of improving accuracy of a component and assembly. Also, for a case where feeding of a plurality of sheets in overlapping occurs, an adjustment of an urging force of a spring used as the urging member of the retard roller is suggested (refer to Japanese Patent Laid-Open No. 2006-315827). 
     However, even if the accuracy of the component and the assembly is improved, the variance of the relative positional relations among the feed roller, the retard roller, and the swing shaft of the retard roller may affect the retard pressure due to dimensional tolerance of the component and the variance in the assembly. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a sheet feeding apparatus includes a sheet supporting portion configured to support a sheet, a rotary feeding member configured to feed the sheet supported on the sheet supporting portion, a rotary separation member configured to abut on the rotary feeding member and form a separation nip in which the sheet is conveyed with separation from another sheet, a support member configured to support a rotation shaft of the rotary separation member, a swing shaft configured to support the support member with the support member being swingable, an urging member configured to urge the rotary separation member toward the rotary feeding member, a frame member including a first support portion configured to fix a first end portion of the swing shaft and a second support portion configured to movably support a second end portion of the swing shaft, and an adjustment mechanism including a long hole formed in the second support portion and a fixing member configured to fix the second end portion of the swing shaft to the frame member. The second end portion of the swing shaft can be fixed at a plurality of positions to the second support portion with the fixing member. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a drawing showing an image forming apparatus according to a first embodiment. 
         FIG.  2    is a partial perspective view of a sheet feeding unit. 
         FIG.  3    is a schematic diagram of the sheet feeding unit. 
         FIG.  4    is a schematic diagram showing positional relations among a feed roller, a retard roller, and a swing shaft. 
         FIG.  5    is a diagram showing an adjustment mechanism. 
         FIG.  6 A  is a diagram showing the sheet feeding unit in a state of Θ&gt;Θ 0 . 
         FIG.  6 B  is a diagram showing the sheet feeding unit in the state of Θ=Θ 0 . 
         FIG.  7 A  is a diagram showing the sheet feeding unit in the state of Θ&lt;Θ 0 . 
         FIG.  7 B  is a diagram showing the sheet feeding unit in the state of Θ=Θ 0 . 
         FIG.  8    is a diagram showing another example of the sheet feeding unit. 
         FIG.  9    is a diagram showing a sheet feeding unit according to a second embodiment. 
         FIG.  10 A  is a diagram showing the sheet feeding unit in the state of Θ&gt;Θ 0 . 
         FIG.  10 B  is a diagram showing the sheet feeding unit in the state of Θ=Θ 0 . 
         FIG.  11 A  is a diagram showing the sheet feeding unit in the state of Θ&lt;Θ 0 . 
         FIG.  11 B  is a diagram showing the sheet feeding unit in the state of Θ=Θ 0 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An image forming apparatus according to embodiments of the present invention will be described below. However, it should be noted that sizes, materials, shapes, relative arrangements, and the like of components set forth in these embodiments are to be appropriately changed depending on configurations and various conditions of an apparatus to which the present invention is applied, and do not limit the scope of the present invention unless it is specifically stated otherwise. 
     First Embodiment 
     A printer  1  according to a first embodiment of the present invention is, as illustrated in  FIG.  1   , an image forming apparatus including a so-called intermediate transfer tandem type image forming unit  10  including 4 process cartridges  10 Y,  10 M,  10 C, and  10 K inside an apparatus body  2 . The printer  1  forms and outputs an image on a sheet S based on an image information read from a document and input from an external apparatus. To be noted, the sheet S is a recording medium which includes, other than a standard paper, a special paper such as a coated paper, a recording material of a special shape such as an envelope and an index sheet, a plastic film used for an overhead projector, a cloth, and the like. Also, the document is an example of the sheet S, and may be a blank sheet of paper, or with single-sided or double-sided image formation thereon. 
     The process cartridges  10 Y,  10 M,  10 C, and  10 K are the image forming units to form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. As structures of the process cartridges are basically same except for colors of stored toners, the structure of the process cartridge  10 Y of yellow is described below as a representative. 
     The process cartridge  10 Y includes a photosensitive drum  11 , a charge unit  12 , a developing unit  14 , and a cleaning unit. Also, an exposing unit  13  capable of scanning the photosensitive drum  11  based on the image information is arranged inside the apparatus body  2 . When an image forming process starts, the photosensitive drum  11  is drivingly rotated, and a surface of the photosensitive drum  11  is uniformly charged by the charge unit  12 . Thereafter, an electrostatic latent image is formed on the photosensitive drum  11  by the exposing unit  13 . The electrostatic latent image formed on the photosensitive drum  11  is visualized (developed) to a toner image by a toner supplied from the developing unit  14 . 
     In the image forming unit  10 , an intermediate transfer belt  21 , which is an intermediate transfer member, is arranged, and is wound around a driving roller  22 , a tension roller  23 , and a secondary transfer inner roller  24 . The intermediate transfer belt  21  is, with being moderately stretched by the tension roller  23 , drivingly rotated by the driving roller  22  in a direction which follows rotation of the photosensitive drum  11 . 
     On an inner circumference of the intermediate transfer belt  21 , a primary transfer roller  15  is arranged facing each of the photosensitive drum  11  of the process cartridges  10 Y,  10 M,  10 C, and  10 K. The toner image formed on each of the photosensitive drums  11  is primarily transferred to the intermediate transfer belt  21  at a primary transfer portion T 1  formed between the primary transfer roller  15  and the photosensitive drum  11  in a manner of superimposing each other. To be noted, extraneous matter, such as a transfer residual toner, remaining on the photosensitive drum  11  after passing the primary transfer portion T 1  is removed by a belt cleaning unit. 
     On a circumference of the intermediate transfer belt  21 , a secondary transfer roller  25  is arranged facing the secondary transfer inner roller  24  across the intermediate transfer belt  21 . The toner image born and carried on the intermediate transfer belt  21  is collectively transferred to the sheet S at a secondary transfer portion T 2  formed between the secondary transfer roller  25  and the secondary transfer inner roller  24 , and the toner image is formed on the sheet S. To be noted, the extraneous matter, such as the transfer residual toner, remaining on the intermediate transfer belt  21  after passing the secondary transfer portion T 2  is removed by the belt cleaning unit. 
     In parallel with the image forming process as described above, a sheet feeding unit  30  provided in the apparatus body  2  performs a feeding process to feed the sheet S to the image forming unit  10 . The sheet feeding unit  30  as a sheet feeding unit includes at least one feed cassette  31 , and a feeding unit  32  provided for each feed cassette  31 . The feed cassette  31  serving as a sheet supporting portion includes a sheet supporting portion  31   a  (refer to  FIG.  3   ) which is capable of ascending and descending, and maintains an uppermost sheet at an appropriate height by ascending and descending the sheet supporting portion  31   a.    
     The feeding unit  32  includes a pickup roller  33  abutting on the uppermost sheet of the sheet S stored on the feed cassette  31  and sending out the sheet S, and includes a pair of separation rollers  34  arranged on a downstream side of the pickup roller  33  in a sheet conveyance direction. The pair of the separation rollers  34  include a feed roller  35 , which rotates in the same direction as the pickup roller  33 , and a retard roller  36 , which is drivingly rotated in a reverse direction to the sheet conveyance direction in a case of the sheet being fed in overlapping. Also, the pair of the separation rollers  34  convey the sheets along the sheet conveyance direction with separating the sheet delivered by the pickup roller  33  into one by one at a separation nip  34 N formed between the feed roller  35  and the retard roller  36  (refer to  FIG.  3   ). 
     The sheet S fed by the sheet feeding unit  30  is delivered to a pair of registration rollers  39  arranged immediately in front of the secondary transfer portion T 2 . The pair of the registration rollers  39  correct sheet skew, and also convey the sheet S to the secondary transfer portion T 2  in synchronizing with a progress of the image forming process at the image forming unit  10 . 
     The sheet S with an unfixed toner image transferred at the secondary transfer portion T 2  is delivered to a fixing unit  40 . The fixing unit  40  includes a heating roller  41 , which is heated by a heat source such as a halogen heater, and a counter roller  42 , which is in a pressure contact with the heating roller  41 . By conveying the sheet S in a sandwiched manner between the heating roller  41  and the counter roller  42  and by providing heat and pressure, the toner is fusion-bonded, and the image is fixed on the sheet S. 
     When the sheet S with the toner image fixed at the fixing unit  40  is delivered to a pair of sheet discharge rollers  46 , the sheet S is discharged to a discharge tray  50 . Also, in a case of a double-sided printing, at a branch conveyance portion  47  disposed between the fixing unit  40  and the pair of the sheet discharge rollers  46 , the sheet S is guided toward a reverse conveyance unit  48 , and is delivered to a duplex conveyance unit  49  with reversing a first surface (front surface) and a second surface (back surface) at the reverse conveyance unit  48 . Then, the sheets S is conveyed to the pair of the registration rollers  39  by the duplex conveyance unit  49 , and the toner image is transferred to the sheet S again at the secondary transfer portion T 2 . Thereafter, the toner image is fixed by the fixing unit  40 , and the sheet S is discharged to the discharge tray  50 . 
     Feeding Unit 
     Next, a configuration of the feeding unit  32  described above will be described in detail with reference to  FIGS.  2  and  3   . As described above, the feeding unit  32  includes the pickup roller  33 , the feed roller  35 , and the retard roller  36 . These rollers, i.e. the pickup roller  33 , the feed roller  35 , and the retard roller  36 , are driven by a feeding motor M 1  which serves as a common driving motor to these rollers. 
     The feed roller  35  is a rotary feeding member to feed the sheet supported in the feed cassette  31 , and includes a feed roller shaft  35   s  supported by a support frame  70  of the apparatus body  2  and a roller member  35   a  held by the feed roller shaft  35   s . The roller member  35   a  is configured to integrally rotate with the feed roller shaft  35   s , and the feed roller  35  is rotated by rotation of the feed roller shaft  35   s.    
     The pickup roller  33  is supported by a pickup arm  33   b  which is rotatable around the feed roller shaft  35   s  above as a rotation center, and a pickup roller shaft  33   s  is supported at a tip portion of the pickup arm  33   b . A roller member  33   a  of the pickup roller  33  is held by the pickup roller shaft  33   s.    
     Furthermore, the retard roller  36  is arranged to face the feed roller  35 , and, by abutting on the feed roller  35 , becomes a rotary separation member which forms a separation nip  34 N for conveying the sheet with separating the sheet into one by one. The retard roller  36  includes a retard roller shaft  36   s , and a roller member  36   a , which is held by the retard roller shaft  36   s  via a torque limiter  62 . 
     At the time of feeding the sheet S, the feeding motor M 1  drivingly rotates in a first direction in a state where the pickup roller  33  is abutting on the uppermost sheet of the sheet S supported on the sheet supporting portion  31   a  of the feed cassette  31  with the predetermined urging force. Hereupon, the pickup roller  33  is drivingly rotated in the sheet conveyance direction, and the sheet on the sheet supporting portion  31   a  is sent out to the separation nip  34 N. When the feed motor M 1  rotates in the first direction, the feed roller  35  is drivingly rotated in the sheet conveyance direction, same as the pickup roller  33 . On the other hand, a driving force to drivingly rotate the retard roller  36  in a reverse direction to the sheet conveyance direction is input to the retard roller  36  via the torque limiter  62  as described above. 
     Therefore, in a state where the sheet S is not at the separation nip  34 N or one sheet of the sheet S is being conveyed by the separation nip  34 N, the torque limiter  62  slides and the retard roller  36  is rotated in the sheet conveyance direction which is the reverse direction to a rotational direction of the retard roller shaft  36   s . On the other hand, when a plurality of the sheet S enter the separation nip  34 N in overlapping, the retard roller  36  is rotated in a driven direction of the retard roller shaft  36   s , and by a slide between overlapping sheets, the sheet S abutting on the feed roller  35  is conveyed in the sheet conveyance direction. Also, the sheet S abutting on the retard roller  36  is conveyed in a direction of returning to the feed cassette  31 . In this manner, the sheet sent out to the separation nip  34 N is conveyed with being separated into one by one, and is delivered to a pair of drawing rollers  37  for further transportation. The pair of drawing rollers  37  are drivingly rotated by a drawing motor M 2 , which is a different driving motor from the feeding motor M 1 . 
     As regard to the retard roller  36 , which is the rotary separation member described above, the retard roller shaft  36   s , which is the rotational shaft of the rotary separation member, is supported by an arm member  61 , which is a support member, and is capable of swinging around a swing shaft  60 , which is a center of a swing. In addition, the retard roller  36  is urged toward the feed roller  35  by an urging force of a compression spring  80  which is an urging member, and is in the pressure contact with the feed roller  35  by the urging force of the compression spring  80 . To be noted, a pressure provided by the retard roller  36  toward the feed roller  35  for the pressure contact is hereinafter referred to as a “retard pressure”, and the retard pressure is a parameter which affects a separation performance at the separation nip  34 N. Although the compression spring  80  is applied to the urging member in this embodiment, any elastic body, for example, such as a rubber may be applied to configure the urging member. 
     Adjustment Mechanism 
       FIG.  4    is a cross-sectional diagram of the feeding unit  32  cut in a plane perpendicular to the swing shaft  60  at the separation nip  34 N. When the retard pressure described above is referred to as F, the retard pressure F is a resultant force of a force from the compression spring  80  and a moment of the arm member  61  generated at a time of a feeding drive. Incidentally, size of the moment of the arm member  61  at the time of the feeding drive changes with an angle Θ formed by a first imaginary line L 1  and a second imaginary line L 2  in  FIG.  4   . To be noted, the first imaginary line L 1  is an imaginary line connecting a rotation center  35   c  of the feed roller  35  and a rotation center  36   c  of the retard roller  36 , and the second imaginary line L 2  is the imaginary line connecting the rotation center  36   c  of the retard roller  36  and an axial center  60   c  of the swing shaft  60 . 
     Therefore, although each of the feed roller shaft  35   s , the retard roller shaft  36   s , and the swing shaft  60  is supported by the support frame  70  in a manner where the angle Θ described above is equal to a design angle Θ 0 , there are cases where the angle Θ is not equal to Θ 0  due to the tolerance of the component and inaccuracy of the assembly. Then, in a case where Θ is larger than Θ 0 , the retard pressure becomes larger than a design retard pressure (F&gt;F 0 ). Also, in a case where Θ is smaller than Θ 0 , the retard pressure becomes smaller than the design retard pressure (F&lt;F 0 ). 
     Therefore, the feeding unit  32  according to this embodiment includes an adjustment mechanism  90  which enables to adjust relative positional relations among the rotation center  35   c  of the feed roller  35 , the rotation center  36   c  of the retard roller  36 , and the axial center  60   c  of the swing shaft  60 . The adjustment mechanism  90  will be described in detail below. To be noted, by variances of shaft positions described above, the urging force also alters due to a change in length of the compression spring  80 . However, since an impact of the change in the spring length on the retard pressure is adequately small as compared with the impact of the variance in the angle Θ, the impact of the change in the spring length is considered negligible herein. 
     A first end portion of the swing shaft  60  is, as illustrated in  FIG.  2   , fixed to a first support portion  71  of the support frame  70 , and also a second end portion of the swing shaft  60  at an opposite side of the first end portion in an axial direction is movably supported by a second support portion  72  of the support frame  70 . Specifically, as illustrated in  FIG.  5   , the support frame  70  is a frame member to fix the swing shaft  60  which supports the arm member  61  in a manner of being capable of swinging, and supports from below the second end portion of the swing shaft  60  by the second support portion  72  formed in U-shape. Therefore, the second end portion of the swing shaft  60  is movable within the second support portion  72  in a vertical direction in  FIG.  2   . 
     Also, a wall member  91  is placed upright facing the swing shaft  60  described above in a direction orthogonal to the axial direction of the swing shaft  60 , and a long hole  91   h  which is long in the vertical direction is formed in the wall member  91 . Furthermore, a screw hole  60   h  is provided in the swing shaft  60  at a position facing the long hole  91   h  described above, and the wall member  91  fixes the swing shaft  60  with a captive screw  92 , which is a fixing member, so that a height position of the swing shaft  60  is changeable within a limit of the long hole  91   h.    
     That is, the adjustment mechanism  90  includes the wall member  91  having the long hole  91   h  described above and the screw hole  60   h , and enables to fix the swing shaft  60  at a plurality of positions to the supporting frame  70 . Specifically, the captive screw  92  described above and the long hole  91   h  are positioning members which determine the position of the second end portion of the swing shaft  60  at the second support portion  72 , these positioning members enable to change the position of the swing shaft  60 . When the angle Θ deviates from the design angle Θ due to the variances of the component and the assembly, it is possible to bring the retard pressure F near to the design retard pressure F 0  by changing a fixing position of the swing shaft  60  to the supporting frame  70  by use of the adjustment mechanism  90 . 
     For example, in a case, as shown in  FIG.  6 A , where Θ is larger than Θ 0  and the retard pressure F is larger than the design value F 0 , as illustrated in  FIG.  6 B , the swing shaft  60  is moved in a direction of +Z and fixed at a position of Θ being equal to Θ 0 . It is possible to correct positional relations among the feed roller  35 , the retard roller  36 , and the swing shaft  60  by this adjustment, and adjust the retard pressure F equal to F 0 . On the other hand, in a case, as shown in  FIG.  7 A , where Θ is smaller than Θ and the retard pressure F is smaller than the design value F 0 , as illustrated in  FIG.  7 B , the swing shaft  60  is moved in a direction of −Z and fixed at a position of Θ being equal to Θ 0 . It is possible to correct the positional relations among the feed roller  35 , the retard roller  36 , and the swing shaft  60  by this adjustment, and adjust the retard pressure F equal to F 0 . 
     To be noted, although the swing shaft  60  is fixable at the plurality of positions which are different in the vertical direction in the embodiment describe above, the swing shaft  60  may be configured to be fixable at the plurality of positions in a crosswise direction of  FIG.  6   . For example, as shown in  FIG.  8   , the position of the swing shaft  60  may be configured to be changeable by making the relative position of the swing shaft  60  screwed with the captive screw  92   a  changeable in an axial direction of the captive screw  92   a  in a configuration where the second support portion  72   a  supports the swing shaft  60  movable in the crosswise direction. Furthermore, it is acceptable to configure the adjustment mechanism being capable to move the swing shaft  60  in both vertical and crosswise directions. 
     That is, it is acceptable to move the swing shaft  60  in any direction, not limited to the direction of Z, to adjust the angle Θ described above. Also, although, in this embodiment, the angle Θ described above is changed by changing a phase between the first end portion and the second end portion, it is not limited to this, and acceptable to configure the adjustment mechanism to move the swing shaft  60  in a parallel direction. In addition, the swing shaft  60  is fixed with the captive screw  92  ( 92   a ) in the embodiment described above, it is not limited to this. For example, the adjustment mechanism may be configured to change and fix the fixing position of the swing shaft  60  with various methods such as a pin, a slide mechanism, and a rack mechanism. 
     As described above, since the swing shaft  60  is fixable at the plurality of positions to the supporting frame  70  in this embodiment, it is possible to adjust the angle Θ formed between the first imaginary line L 1  and the second imaginary line L 2 . In particular, by changing the fixing position of the swing shaft  60  in the vertical direction (direction of Z), the angle of inclination of the second imaginary line L 2  against the first imaginary line L 1  is changed, and an adjustment of the angle Θ described above is enabled. That is, in this embodiment, the adjustment mechanism is configured to enable to fix the swing shaft  60  at the plurality of the positions in the vertical direction to the frame member  70 . In addition, it is possible to adjust the angle Θ described above by changing the fixing position of the swing shaft  60  in the crosswise direction (direction of X) and changing the angle of the inclination of the first imaginary line L 1  against the second imaginary line L 2 . That is, in a case where the crosswise direction (direction of X) is the direction orthogonal to the vertical direction and the axial direction of the swing shaft  60 , it is acceptable to configure the adjustment mechanism to be capable of fixing the swing shaft  60  in the plurality of the positions to the frame member  70  in the crosswise direction. As described above, by fixing the swing shaft  60  at the plurality of positions in the directions of Z and/or the direction of X in  FIGS.  3 ,  6  and  7    to the frame member  70 , it is possible to fix the swing shaft  60  at the plurality of the positions with the different angle Θ described above. 
     Therefore, it is possible to adjust the relative positional relations among the rotary feed member (the feed roller), the rotary separation member (the retard roller), and the swing shaft, and possible to adjust the pressure of the pressure contact (the retard pressure) of the rotary separation member to the rotary feed member. Also, for example, in a case where the angle Θ described above deviates from the design angle Θ 0  at a time of a product shipment due to the tolerance of the component and inaccuracy in the assembly, it is possible to adjust the angle Θ so as to bring the retard pressure F to the design value F 0 , and suppress the variance of the retard pressure. Also, in a case where the retard pressure has changed by wear of rollers during use, a service person and the like can adjust the retard pressure by adjusting the angle Θ described above. Specifically, since in this embodiment it is possible to adjust the position of the second end portion of the swing shaft  60  continuously (lineally) within the limit of the length of the long hole  91   h  and is possible to adjust the retard pressure F lineally, it is attainable to accurately bring the retard pressure F near to the design target value F 0 . To be noted, in this case, the angle Θ described above is adjusted to deviate from the design angle Θ 0 . Furthermore, for example, if the adjustment mechanism is configured to automatically change the position of the swing shaft  60  by use of a driving power source such as a motor and a solenoid, it is possible to change the retard pressure in accordance with a type of the sheet and a feeding environment. 
     In addition, although an impact of the angle Θ described above on the retard pressure F becomes the greater the smaller a diameter of the retard roller  36  is, it is possible to decrease the design diameter of the retard roller  36  since the angle Θ is adjustable in a case of this embodiment. Accordingly, it is possible to improve a degree of freedom at the design, and is also possible to pursue a reduction of apparatus size and costs. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. To be noted, the second embodiment is different from the first embodiment only in a supporting method of the swing shaft  60 . Therefore, description will be given only to different aspects from the first embodiment, and the description of other aspects will be omitted herein by putting a same mark as in the first embodiment. 
     As illustrated in  FIG.  9   , an adjustment mechanism  901  includes a holder  100  which is a holding member to hold the second end portion of the swing shaft  60 , and the holder  100  movably holds the second support portion  72   b  of the support frame  70  in the plurality of positions. The holder  100  is provided with a control lever  110  for a worker to manipulate the holder  100 , and the worker is able to move the holder  100  in the vertical direction to the second support portion  72   b  by shifting the control lever  110  by gripping with hands. Specifically, it is possible to move the holder  100  described above continuously in the vertical direction via a rail mechanism provided between the holder  100  and the support frame  70 , and is possible to fix the holder  100  at a desired position by use of a lock mechanism which is manipulated with the control lever  110 . When the position of the second support portion  72   b  to the holder  100  is determined, the holder  100  is fixed to the support frame  70  with the fixing member (for example, the captive screw) similar to the first embodiment. 
     In particular, for example, in a case where Θ is larger than Θ 0  as shown in  FIG.  10 A  and the retard pressure F is larger than the design value F 0 , the holder  100  is moved in the direction of +Z as shown in  FIG.  10 B  and fixed at the position of Θ being equal to Θ 0 . By this adjustment, it is possible to correct the positional relations among the feed roller  35 , the retard roller  36 , and the swing shaft  60 , and is possible to adjust the retard pressure F equal to F 0 . On the other hand, in a case where Θ is smaller than Θ 0  as shown in  FIG.  11 A  and the retard pressure F is smaller than the design value F 0 , the holder  100  is moved in the direction of −Z as shown in  FIG.  11 B  and fixed at the position of Θ being equal to Θ 0 . By this adjustment, it is possible to correct the positional relations among the feed roller  35 , the retard roller  36 , and the swing shaft  60 , and possible to adjust the retard pressure F equal to F 0 . 
     As described above, by configuring the holder  100  to support the second end portion of the swing shaft  60  and providing the holder  100  with the control lever  110 , the worker is able to easily adjust the position of the swing shaft  60 . To be noted, similar to the first embodiment, any fixing methods or any moving directions are acceptable for fixing or moving of the holder  100  to the support frame  70 . 
     Furthermore, although an example of adjusting the position of the swing shaft  60  to the support frame  70  is described in the embodiment described above, it is, for example, acceptable to adjust the angle Θ by changing the position of the support frame  70  to the apparatus body  2 . In this case, the adjustment mechanism moves the position of the swing shaft  60  by collectively moving a retard roller unit, and the apparatus body  2  becomes the frame member to which the swing shaft  60  is fixed via the support frame  70 . 
     Also, although the retard roller which is input to be drivingly rotated in the reverse direction to the feed roller is described as an example of the rotary separation member in the embodiment described above, the present invention is not limited to this. For example, the retard roller configured to stop rotation with a one-way clutch which engages in a case of the plurality of the sheets entering into the separation nip  34 N is also acceptable as the rotary separation member. Furthermore, in the embodiment as described above, the sheet feeding unit which feeds the sheet from the feed cassette  31  to the image forming unit  10  is described as an example of the application, the present invention is not limited to this. For example, the present invention is applicable to the sheet feeding unit feeding the sheet to an image reading unit which reads an image in an image reading apparatus such as a scanner. In addition, the present invention is also applicable to the sheet feeding unit which feeds the sheet from a manual feed tray to the image forming unit. Furthermore, the present invention is applicable to the sheet feeding unit of a various image forming apparatus such as a facsimile and an ink jet printer. In addition, the inventions in the embodiments described above may be combined in any forms. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-089433, filed May 10, 2019, which is hereby incorporated by reference herein in its entirety.