Patent Publication Number: US-10308453-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 for feeding sheets and an image forming apparatus including the sheet feeding apparatus. 
     Description of the Related Art 
     In general, image forming apparatuses, such as copying machines and printers, include a feed cassette which stores sheets to be fed to an image forming portion, and which is inserted to and drawn from an image forming apparatus body (hereinafter referred to as an apparatus body). In these image forming apparatuses, when the feed cassette is attached, a feed roller moves down to a feed position to feed the sheets, and abuts against a sheet in the feed cassette. The feed roller then rotates in a sheet feed direction in accordance with a feed signal, and thereby sends the sheets of the feed cassette downstream, sequentially from an uppermost one of the sheets. 
     Conventionally, Japanese Patent Laid-Open No. 2015-086071 proposes an image forming apparatus in which a feed roller is supported by a supporting member. The supporting member is urged downward by a feed pressure spring. Thereby the feed roller abuts against a sheet in the feed cassette at a predetermined nip pressure. The supporting member moves up when the feed cassette is drawn, and is held by a holding member in a state where the feed roller is positioned at a standby position. The standby position of the feed roller is set so that the feed roller does not interfere with the feed cassette and the sheets stacked in the feed cassette while the feed cassette is drawn. The holding member is disposed out of a conveyance area, whereas the feed roller and the feed pressure spring are disposed at a substantially center portion of the conveyance area in a sheet width direction. 
     However, the supporting member described in Japanese Patent Laid-Open No. 2015-086071 receives forces from directions opposite to each other by the holding member and the feed pressure spring, when the supporting member is held in a state where the holding member resists the urging force of the feed pressure spring and holds the feed roller at the standby position. That is, in the supporting member, torsional stress occurs in a portion between the holding member and the feed pressure spring. In a case where the supporting member is formed of, for example, a resin member having a relatively low stiffness, the above-described torsional stress promotes creep deformation of the supporting member, and thus causes the feed roller to be positioned lower than the predetermined standby position. 
     In this case, to prevent the interference between the feed roller and the sheets of the feed cassette caused when the feed cassette is inserted and drawn, a space needs to be secured in consideration of the deformation of the supporting member. This leads to upsizing of the apparatus. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a sheet feeding apparatus includes a sheet supporting portion configured to support a sheet, a feeding portion configured to feed the sheet supported by the sheet supporting portion, a swing unit configured to swingably support the feeding portion between a feed position and a separation position, the feed position being a position at which the feeding portion abuts against the sheet supported by the sheet supporting portion and feed the sheet, the separation position being a position at which the feeding portion is separated from the sheet supported by the sheet supporting portion, a swing shaft configured to swingably support the swing unit, an urging portion configured to contact with the swing unit at a first position so as to urge the swing unit toward the feed position, and a holding portion configured to contact with the swing unit at a second position so as to hold the swing unit at the separation position against an urging force of the urging portion, the second position being different from the first position in an axial direction of the swing shaft. The swing unit includes a first bearing portion configured to slidingly support the swing shaft, a second bearing portion disposed offset to the first bearing portion and configured to slidingly support the swing shaft, a metal member configured to hold the first bearing portion and the second bearing portion, and a resin member having a guide surface configured to guide the sheet fed by the feeding portion. 
     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 an overall schematic diagram of a printer of a first embodiment. 
         FIG. 2  is a plan view illustrating a feed cassette and a drawing unit. 
         FIG. 3A  is a perspective view illustrating a roller support mechanism and each roller. 
         FIG. 3B  is a cross-sectional view illustrating a state where a pickup roller abuts against a top face of a sheet. 
         FIG. 4A  is a perspective view illustrating the roller support mechanism and a holding mechanism. 
         FIG. 4B  is a perspective view illustrating a first holding member and a second holding member. 
         FIG. 5A  is a perspective view illustrating the holding mechanism in a state where the pickup roller is positioned at a standby position. 
         FIG. 5B  is a perspective view illustrating a configuration of a vicinity of a guided portion of the feed cassette. 
         FIG. 6A  is a side view illustrating the second holding member. 
         FIG. 6B  is a perspective view illustrating the first holding member and the second holding member. 
         FIG. 7A  is a perspective view illustrating the first holding member in a state where the pickup roller is positioned at a feed position. 
         FIG. 7B  is a side view illustrating the second holding member. 
         FIG. 8A  is a perspective view illustrating the roller support mechanism. 
         FIG. 8B  is a perspective view illustrating a roller support frame. 
         FIG. 8C  is a perspective view illustrating a roller support guide. 
         FIG. 9  is a cross-sectional view taken along a line  8 A- 8 A of  FIG. 8A . 
         FIG. 10A  is a perspective view illustrating the roller support mechanism. 
         FIG. 10B  is a partially enlarged view illustrating a contact portion between the first holding member and the roller support mechanism. 
         FIG. 10C  is a partially enlarged view illustrating an abutment portion between the feed pressure spring and the roller support frame. 
         FIG. 11A  is a perspective view illustrating a roller support mechanism of a second embodiment. 
         FIG. 11B  is a perspective view illustrating the roller support frame. 
         FIG. 11C  is a perspective view illustrating a guide portion and bearings. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     Overall Configuration 
     First, a first embodiment of the present invention will be described. A printer  100  of the first embodiment, which serves as an image forming apparatus, is an electrophotographic laser-beam printer. As illustrated in  FIG. 1 , the printer  100  includes an apparatus body  100   a , which includes a sheet feeding apparatus  6  and an image forming portion  20 . The image forming portion  20  includes an intermediate transfer belt unit  10 , an exposure apparatus  7 , and process cartridges  17   a  to  17   d.    
     The sheet feeding apparatus  6  is provided with a feed cassette  54 , which stores sheet S and serves as a drawer portion. The feed cassette  54  holds a sheet-stacking plate  54   a , on which the sheet S is stacked and which can raise and lower the sheet S. The sheet-stacking plate  54   a  serves as a sheet supporting portion. The process cartridges  17   a  to  17   d  are disposed along an intermediate transfer belt  11  of the intermediate transfer belt unit  10 , and include photosensitive drums  8   a ,  8   b ,  8   c , and  8   d , respectively. 
     The process cartridges  17   a  to  17   d  are configured to form toner images of yellow, magenta, cyan, and black, respectively in this order. Each of the photosensitive drums  8   a ,  8   b ,  8   c , and  8   d  is driven to rotate in a clockwise direction in  FIG. 1 . The exposure apparatus  7  irradiates the photosensitive drums  8   a ,  8   b ,  8   c , and  8   d  with laser beams in accordance with image information sent from a read portion (not illustrated) or an external computer (not illustrated). 
     The photosensitive drums  8   a ,  8   b ,  8   c , and  8   d  are electrically charged in advance by chargers (not illustrated), and thus the laser beams from the exposure apparatus  7  form electrostatic latent images on the surfaces of the photosensitive drums  8   a ,  8   b ,  8   c , and  8   d . The electrostatic latent images on the photosensitive drums  8   a ,  8   b ,  8   c , and  8   d  are developed into toner images by development portions of the process cartridges, and then the toner images are sequentially transferred onto the intermediate transfer belt such that one toner image is superposed on another. With this operation, four colors of toner image are formed on the intermediate transfer belt  11 . 
     The intermediate transfer belt unit  10  includes the intermediate transfer belt  11 , which is wound and stretched around a driving roller  12 , a driven roller  14 , and a tension roller  16 , which are disposed so as to have a predetermined positional relationship. A secondary transfer roller  13  is disposed at a position which faces the driving roller  12 . The secondary transfer roller  13  holds the intermediate transfer belt  11  between the secondary transfer roller  13  and the driving roller  12 . The secondary transfer roller  13  and the intermediate transfer belt  11  form a transfer nip N, which transfers the toner images onto the sheet. 
     The sheet feeding apparatus  6  includes a pickup roller  51  which serves as a feeding portion, a feed roller  52 , and a retard roller  53  which is in pressure contact with the feed roller  52 . The sheet S fed by the pickup roller  51  is sent, one by one, by the feed roller  52  and the retard roller  53 , and conveyed to a registration roller pair  22  constituted by conveyance rollers  55   a  and  55   b . The retard roller  53  is driven by the feed roller  52 , when a limit value of a torque limiter is exceeded. The retard roller  53  is applied with a driving force toward a direction opposite to a sheet conveyance direction, but the driving force may not be applied. The sheet S is once stopped at the registration roller pair  22  in a state where the sheet S abuts against a nip of the registration roller pair  22 . After that, the sheet S is sent into the transfer nip N at a predetermined timing by the registration roller pair  22 . 
     The transfer nip N is applied with transfer bias via the secondary transfer roller  13 , and thereby secondary transfer of the four colors of toner image formed on the intermediate transfer belt is performed on the sheet S, which is sent from the sheet feeding apparatus  6  and conveyed by the registration roller pair  22 . In addition, a belt cleaning apparatus  33  is disposed at a position which faces the tension roller  16 , so as to abut against the surface of the intermediate transfer belt  11 . 
     Above the transfer nip N, a fixing apparatus  15  is disposed. The fixing apparatus  15  includes a fixing roller  15   a  and a pressure roller  15   b . The sheet S, onto which the toner images have been transferred, is conveyed to a fixing nip portion between the fixing roller  15   a  and the pressure roller  15   b , and is heated and pressurized by the fixing roller  15   a  and the pressure roller  15   b . Thus, the transferred toner images are fixed on the surface of the sheet S. After the toner images are fixed on the sheet S by the fixing apparatus  15 , the sheet S is discharged onto a discharge tray  19  via a discharge roller pair  18 . 
     Feed Cassette 
     Next, the feed cassette  54  will be described. As illustrated in  FIG. 2 , the feed cassette  54  is configured to be attached to and drawn from the apparatus body  100   a . The feed cassette  54  includes the sheet-stacking plate  54   a  on which the sheet S is stacked, side regulation members  54   b  which regulate side edges of the sheet S stacked on the sheet-stacking plate  54   a , and a trailing edge regulation member  54   c  which regulates a trailing edge of the sheet S. The feed cassette  54  is supported by guide rails  21  (see  FIG. 6B ) so that the feed cassette  54  can move between an attachment position and a drawn position. The attachment position is a position for feeding the sheet, and the drawn position is a position to which the feed cassette  54  is drawn out from the attachment position. 
     The feed cassette  54  is drawn from the apparatus body  100   a  to refill the feed cassette  54  with the sheet. Thus, the feed cassette  54  may be restricted from drawing by a regulation portion (not illustrated), during the drawing, at a position at which the feed cassette  54  can be refilled with the sheet; or may be drawn out of the apparatus body  100   a . In addition, the feed cassette  54  is configured to be drawn toward a direction perpendicular to the feed direction in which the pickup roller  51  feeds the sheet, that is, toward a frontward direction on the sheet of  FIG. 1 . 
     Drawing Unit 
     As illustrated in  FIG. 2 , the sheet feeding apparatus  6  is provided with a drawing unit  66 , which is configured to draw the feed cassette  54  into the apparatus body  100   a . On a back-side side wall  54   d  of the feed cassette  54 , a swing arm  64  is supported so that the swing arm  64  can swing on a shaft  64   a  which serves as a supporting point. The swing arm  64  has a swing pin  65  at a leading end portion of the swing arm  64 . The drawing unit  66  is formed on a back-side inner wall surface  100   b  of the apparatus body  100   a . The drawing unit  66  includes a drawing unit base  69  and a drawing arm  68 . The drawing arm  68  has a drawing hook  67  at a leading end of the drawing arm  68 , and is supported so that the drawing arm  68  can pivot on a fulcrum  70  disposed on the drawing unit base  69 . 
     The drawing hook  67  of the drawing arm  68  is provided with a concave portion  91 , which locks the swing pin  65  of the swing arm  64 . In addition, an arm pin  81  is provided between the drawing hook  67  of the drawing arm  68  and the fulcrum  70 ; a base pin  82  is provided on the drawing unit base  69 ; and an extension spring  83  is provided such that one end of the extension spring  83  is locked by the arm pin  81  and the other end is locked by the base pin  82 . The extension spring  83  urges the drawing arm  68  so that the drawing arm  68  pivots around the fulcrum  70 . The extension spring  83  and the drawing arm  68  form a toggle mechanism, and the urging direction of the drawing arm  68  by the extension spring  83  is changed when the drawing arm  68  is positioned at a predetermined pivot position. 
     Specifically, in a case where the feed cassette  54  is to be drawn out, while the concave portion  91  locks the swing pin  65 , the drawing arm  68  pivots counterclockwise, i.e., drawing direction, around the fulcrum  70  against an urging force of extension spring  83  from a position illustrated in  FIG. 2 . After that, when the feed cassette  54  is further drawn, the drawing arm  68  pivots until the lock of the swing pin  65  and the concave portion  91  is released. Then, the drawing arm  68  is urged counterclockwise by the extension spring  83 , and is positioned at a position at which the swing pin  65  is to be received by a stopper (not illustrated). 
     When the feed cassette  54  is to be attached to the apparatus body  100   a , the drawing arm  68  is positioned at a position at which the swing pin  65  of the swing arm  64  is capable of entering the concave portion  91  of the drawing hook  67 . Thus, when the feed cassette  54  is inserted into the apparatus body  100   a , the swing pin  65  enters the concave portion  91  of the drawing hook  67 . After this, when the feed cassette  54  is further pushed, the drawing arm  68  is pushed backward against the urging force of the extension spring  83 , via the swing pin  65  and the drawing hook  67 . 
     With this operation, the drawing arm  68  pivots clockwise around the fulcrum  70  against the extension spring  83 . After pivoting to a predetermined position, an urging force by the extension spring  83  is additionally applied to the drawing arm  68 , and thereby the drawing arm  68  pivots clockwise. As a result, the feed cassette  54  is attached to the apparatus body  100   a  by the extension spring  83 , via the drawing arm  68 . 
     The feed cassette  54  is provided with a stopper  90 . Thus, when the feed cassette  54  is attached to the apparatus body  100   a , the feed cassette  54  abuts against a body frame  79  of the apparatus body  100   a , and thereby the feed cassette  54  is positioned with respect to the apparatus body  100   a . That is, when the feed cassette  54  is drawn into the apparatus body  100   a  by the drawing unit  66 , the stopper  90  of the feed cassette  54  abuts against the body frame  79 , so that the feed cassette  54  is stopped at the attachment position. With the feed cassette  54  positioned at the attachment position, the sheet can be fed from the feed cassette  54  by the pickup roller  51 . 
     Detailed Configuration of Sheet Feeding Apparatus 
     Next, a detailed configuration of the sheet feeding apparatus  6  will be described. As illustrated in  FIG. 3A , the sheet feeding apparatus  6  includes a feed frame  57 , which is fixed on the apparatus body  100   a  (see  FIG. 1 ) and by which the feed roller  52 , the retard roller  53 , and the conveyance roller  55   a  are supported. Specifically, as illustrated in  FIG. 4A , the feed roller  52  is fixed to an end portion of a feed driving shaft  59 , which is made of metal and connected to a motor M. The pickup roller  51  is attached to a shaft  51   a  which is rotatably disposed in a roller support mechanism  200 . The roller support mechanism  200  is swingably supported by the feed driving shaft  59 . The shaft  51   a  is disposed parallel to the feed driving shaft  59 . The feed driving shaft  59  and the shaft  51   a  are coupled with each other via a gear train G. 
     With this configuration, the driving force from the motor M is transmitted to the feed driving shaft  59 , and to the shaft  51   a  via the gear train G, so that the pickup roller  51  rotates. The pickup roller  51  abuts against the top face of the sheet S stacked on the sheet-stacking plate  54   a , and rotates with the rotation of the shaft  51   a , so that the sheet is sent. With this operation, the pickup roller  51  sends an uppermost sheet downstream in the sheet feed direction (direction indicated by an arrow A in  FIG. 3A ). 
     The pickup roller  51  is configured so that it can move between a feed position and a standby position, depending on the attachment or drawing operation of the feed cassette  54 . The feed position is a position at which the pickup roller  51  abuts against the sheet S of the feed cassette  54  and feeds the sheet S (see  FIG. 3B ). The standby position is a position at which the pickup roller  51  is separated from the sheet S and waits (see  FIG. 5A ). The pickup roller  51  moves from the feed position to the standby position, with the roller support mechanism  200  being raised. That is, the roller support mechanism  200 , which serves as a swing unit, swingably supports the pickup roller  51  between a feed position, at which the pickup roller  51  can feed the sheet, and a separation position at which the pickup roller  51  is separated from the sheet. 
     As illustrated in  FIG. 4A , the sheet feeding apparatus  6  includes a feed pressure spring  60 , which serves as an urging portion and a first urging portion. The feed pressure spring  60  urges the roller support mechanism  200  toward the feed position so that the pickup roller  51  is in pressure contact with the top face of the sheet S stacked on the sheet-stacking plate  54   a . The feed pressure spring  60  is constituted by a torsion coil spring, which loosely fits the feed driving shaft  59 . One end of the torsion coil spring is connected to the roller support mechanism  200 , and the other end is connected to a frame of the apparatus body  100   a . The roller support mechanism  200  is swingably supported by the feed driving shaft  59  which serves as a swing shaft, and rotatably supports the shaft  51   a  of the pickup roller  51 . 
     Holding Mechanism 
     As illustrated in  FIGS. 4A and 5A , the sheet feeding apparatus  6  is provided with a holding mechanism  30 , which holds the roller support mechanism  200  at the separation position so that the pickup roller  51  is positioned at the standby position. The holding mechanism  30  releases the holding of the roller support mechanism  200  when the feed cassette  54  is attached to the apparatus body. As illustrated in  FIG. 4B , the holding mechanism  30  includes a first holding member  71  and a second holding member  1 , which can hold the roller support mechanism  200  at the separation position in a state where the feed cassette  54  is positioned at the drawn position. The second holding member  1  is disposed on the back side with respect to the first holding member  71  in an attachment direction of the feed cassette  54 . In addition, the first holding member  71  is disposed at a position different from a position of the feed pressure spring  60  in an axial direction AD of the feed driving shaft  59 . More specifically, the feed pressure spring  60  contacts with the roller support mechanism  200  at a first position, and the first holding member  71  contacts with the roller support mechanism  200  at a second position different from the first position in the axial direction AD. 
     The first holding member  71  loosely fits the feed driving shaft  59 , and can pivot between a holding position and a non-holding position. The holding position is a position at which the first holding member  71  holds the roller support mechanism  200  at the separation position. The non-holding position is a position at which the first holding member  71  is separated from the roller support mechanism  200  and thus does not hold the roller support mechanism  200 . When the first holding member  71  is positioned at the holding position, the pickup roller  51  is held at the standby position. When the first holding member  71  releases the holding of the roller support mechanism  200 , the pickup roller  51  can be moved to the feed position by the feed pressure spring  60 . Similarly, when the second holding member  1  holds the roller support mechanism  200  at the separation position, the pickup roller is held at the standby position. When the second holding member  1  releases the holding of the roller support mechanism  200 , the pickup roller  51  can be moved to the feed position by the feed pressure spring  60 . 
     As illustrated in  FIGS. 4A, 4B, and 5A , the first holding member  71 , which serves as a holding portion, is formed like a plate, and can pivot between the holding position and the non-holding position, in a direction perpendicular to the attachment direction in which the feed cassette  54  is attached to the apparatus body. In addition, the first holding member  71  is urged toward a direction indicated by an arrow Y in  FIG. 5A , by a tension coil spring  73  which is disposed between the first holding member  71  and the feed frame  57  and which serves as a second urging portion. The first holding member  71  has an upper edge portion  71   b  which serves as a pressing portion. In a state where the feed cassette  54  is positioned at the drawn position, the upper edge portion  71   b  abuts against an abutment portion  202   d  of the roller support mechanism  200  from a downward direction, and holds the roller support mechanism  200  at the separation position. 
     The first holding member  71  also has a pressed portion  71   a  formed in a lower portion of the first holding member  71 . When the pressed portion  71   a  is pushed by the feed cassette  54  which is being attached to the apparatus body  100   a , the first holding member  71  rotates toward a direction opposite to the direction indicated by the arrow Y in  FIG. 5A , against the urging force of the tension coil spring  73 . With this operation, the upper edge portion  71   b  of the first holding member  71  is separated from the roller support mechanism  200  and releases the holding of the roller support mechanism  200 , and thus the pickup roller  51  abuts against the top face of the sheet of the feed cassette  54  at a predetermined feed pressure, due to the urging force of the feed pressure spring  60 . 
     The second holding member  1 , which serves as a second holding portion, is configured to pivot with the attachment of the feed cassette  54 . Next, a configuration of the second holding member  1  will be described. As illustrated in  FIGS. 4B and 5A , the second holding member  1  is constituted by a resin spring which is made from synthetic resin, and is attached to the feed frame  57  so that the second holding member  1  can pivot around a pivot supporting shaft  4 . The pivot supporting shaft  4  extends in a direction perpendicular to the insertion-and-removal direction of the feed cassette  54 . The second holding member  1  includes a body portion  1   a , which is disposed so as to extend in a vertical direction, and an arm portion  1   b , which is formed like an arm and elongated upstream in the sheet feed direction and which engages with a side wall  57   a  of the feed frame  57 . 
     The body portion  1   a  has a hook-like holding hook portion  1   c  formed on the upper end of the body portion  1   a . As illustrated in  FIGS. 5A and 6A , the holding hook portion  1   c  protrudes from the side wall  57   a  of the feed frame  57  due to a resin spring property by the arm portion  1   b . In addition, the second holding member  1  is positioned at a position illustrated in  FIG. 6A , by a rotation stopper (not illustrated). Thus, when the body portion  1   a  is pushed downstream (direction indicated by an arrow E in  FIG. 6A ) in the attachment direction of the feed cassette  54 , the second holding member  1  is retracted into the interior of the side wall  57   a . In a state where the holding hook portion  1   c  protrudes from the side wall  57   a , the holding hook portion  1   c  abuts from below against the abutment portion  202   d , which is formed on the roller support mechanism  200  and protrudes from the same, and thus holds the roller support mechanism  200  at the separation position. 
     Next, a configuration on the feed cassette  54  side of the holding mechanism  30  will be described.  FIG. 5B  illustrates a portion of the feed cassette  54 , located downstream in the attachment direction of the feed cassette and on one side (that is, the back side of a right portion of  FIG. 1 ). The feed cassette  54  is configured to be attached to and drawn from the apparatus body  100   a  in the insertion-and-drawing direction, which is a front-back direction of  FIG. 1 . The feed cassette  54  is provided so as to be inserted into and drawn from the apparatus body  100   a , and includes guided portions  2  on both right and left sides of the feed cassette  54 . The guided portions  2  are guided by the guide rails  21  (see  FIG. 6B ). The guided portions  2  have guide rollers  5  disposed on top portions of the leading ends of the guided portions  2 . The guide rollers  5  roll in the guide rails  21 , and smooth the attachment/removal of the feed cassette  54  to/from the apparatus body  100   a.    
     The feed cassette  54  is provided with a second release portion  3 , which has a flat surface perpendicular to the attachment direction of the feed cassette  54 . The second release portion  3  is used to push the second holding member  1  disposed on the apparatus body  100   a , against the urging force of the second holding member  1 . The second release portion  3  is formed to pivot the second holding member  1  toward a release direction and release the holding of the roller support mechanism  200  when the attachment of the feed cassette  54  to the apparatus body  100   a  is completed. 
     Furthermore, the feed cassette  54  is provided with a first release portion  74  which has a sloping surface  74   a . The sloping surface  74   a  slidingly contacts the pressed portion  71   a  of the first holding member  71 , and pivots the first holding member  71  toward the counterclockwise direction of  FIG. 5A , against the elastic urging force of the tension coil spring  73  which is an elastic member. Since the insertion-and-removal direction of the feed cassette  54  and the pivot direction of the first holding member  71  are perpendicular to each other, the sloping surface  74   a  is sloping such that the sloping surface  74   a  is further upstream in the attachment direction as the sloping surface  74   a  extends downstream in the sheet feed direction. The sloping surface  74   a  of the first release portion  74 , which serves as a pressing surface, pivots the first holding member  71  from the holding position toward the non-holding position, with the attachment operation of the feed cassette  54 . The position of the first release portion  74  and the position the second release portion  3  of the feed cassette  54  are shifted from each other in the attachment direction of the feed cassette  54 . 
     Operations of Feed Cassette and Holding Mechanism 
     Next, an operation of the holding mechanism  30  performed with the attachment and drawing operation of the feed cassette  54  will be described in detail. First, in a state where the feed cassette  54  is drawn from the apparatus body  100   a , the first holding member  71  does not touch the first release portion  74  of the feed cassette  54 . In this time, the first holding member  71  is positioned at the holding position by the tension coil spring  73  urging the first holding member  71 , as illustrated in  FIG. 5A . In addition, the upper edge portion  71   b  of the first holding member  71  is pushing up the abutment portion  202   d  of the roller support mechanism  200  against the urging force of the feed pressure spring  60 , and thus the first holding member  71  holds the roller support mechanism  200  at the separation position. In this time, the pickup roller  51  is positioned at the standby position at which the pickup roller  51  does not touch the feed cassette  54  and the sheet stored in the feed cassette  54 . 
     Also, the second holding member  1  does not touch the second release portion  3  of the feed cassette  54 , and the holding hook portion  1   c  protrudes downstream in the drawing direction, from the side wall  57   a  of the feed frame  57 , due to the resin spring property by the arm portion  1   b , as illustrated in  FIGS. 5A and 6A . When a user tries to attach the feed cassette  54  to the apparatus body  100   a , the sloping surface  74   a  of the first release portion  74  first abuts against the pressed portion  71   a  of the first holding member  71 . Then, the sloping surface  74   a  pivots the first holding member  71  from the holding position toward the non-holding position against the urging force of the tension coil spring  73 , with the attachment operation of the feed cassette  54 . 
     With this operation, the first holding member  71  is positioned at the non-holding position as illustrated in  FIG. 6B , but the second release portion  3  of the feed cassette  54  still does not touch the second holding member  1  in this time. Thus, although the holding of the roller support mechanism  200  by the first holding member  71  is released, the roller support mechanism  200  remains held at the separation position by the second holding member  1 . In this time, the upper edge portion  71   b  of the first holding member  71  is separated from the abutment portion  202   d  of the roller support mechanism  200 . 
     When the user further pushes the feed cassette  54  toward the apparatus body  100   a , the second release portion  3  abuts against the body portion  1   a  of the second holding member  1 , and pushes the body portion  1   a  toward the direction indicated by the arrow E in  FIG. 6A . Then, when the feed cassette  54  abuts against the stopper  90  (see  FIG. 2 ) and is positioned at the attachment position, the second holding member  1  is retracted into the interior of the side wall  57   a  as illustrated in  FIG. 7B , and the holding of the roller support mechanism  200  by the holding hook portion  1   c  is released. With this operation, the holding of the roller support mechanism  200  by the first holding member  71  and the second holding member  1  is released as illustrated in  FIG. 7A , and the roller support mechanism  200  is swung to the feed position by the urging force of the feed pressure spring  60 . 
     Next, an operation of the holding mechanism  30  performed when the feed cassette  54  is drawn from the apparatus body  100   a  will be described. In a state where the feed cassette  54  is attached to the apparatus body  100   a , the holding hook portion  1   c  of the second holding member  1  is in contact with a side surface of the abutment portion  202   d  of the roller support mechanism  200 , and the second holding member  1  is stored in the side wall  57   a . When the feed cassette  54  is drawn from the apparatus body  100   a  by a user, the first holding member  71  is pivoted along the sloping surface  74   a  of the first release portion  74  toward the direction indicated by the arrow Y in  FIG. 5A , by the urging force of the tension coil spring  73 . With this operation, the upper edge portion  71   b  of the first holding member  71  pushes up the abutment portion  202   d  of the roller support mechanism  200  from below. Here, the urging force of the tension coil spring  73  is larger than that of the feed pressure spring  60 . 
     When the upper edge portion  71   b  of the first holding member  71  pushes up the abutment portion  202   d  of the roller support mechanism  200  to the holding position, the holding hook portion  1   c  of the second holding member  1  moves to a space located below the abutment portion  202   d  of the roller support mechanism  200 . With this operation, the roller support mechanism  200  is held at the separation position by the first holding member  71  and the second holding member  1 , and the pickup roller  51  can be held at the standby position. Thus, the first holding member  71  has a function that pushes up the roller support mechanism  200  to move the roller support mechanism  200  to the separation position, and to move the pickup roller  51  to the standby position. The second holding member  1  has a function that releases the holding of the roller support mechanism  200  when the feed cassette  54  is positioned at the attachment position as illustrated in  FIG. 7B , and thereby causes the pickup roller  51  to move down to the feed position. 
     Roller Support Mechanism 
       FIG. 8A  is a perspective view illustrating a state where a roller support frame  201  and a roller support guide  202 , which constitute the roller support mechanism  200 , are combined with each other.  FIG. 8B  is a perspective view illustrating the roller support frame  201 .  FIG. 8C  is a perspective view illustrating the roller support guide  202 .  FIG. 10A  is a perspective view illustrating the roller support mechanism  200  positioned at the separation position.  FIG. 10B  is a partially enlarged view illustrating a contact portion between the first holding member  71  and the roller support mechanism  200 .  FIG. 10C  is a partially enlarged view illustrating an abutment portion between the feed pressure spring  60  and the roller support frame  201 . 
     As illustrated in  FIG. 8A , the roller support mechanism  200  includes the roller support frame  201  constituted by a metal plate made of a metal material, and the roller support guide  202  made of a resin material having a high sliding property. The roller support guide  202  serving as a resin member has a first stiffness, and the roller support frame  201  serving as a metal member has a second stiffness higher than the first stiffness. The roller support frame  201  and the roller support guide  202  are fastened to each other with a plurality of screws  203  to  205 . 
     As illustrated in  FIG. 8B , the roller support frame  201  includes a screw fastened surface  201   a , to which the screws  203  to  205  are fastened and which serves as a body portion, and pivot supporting surfaces  201   b  and  201   c  which are formed on both ends of the screw fastened surface  201   a  and which extend perpendicular to the screw fastened surface  201   a . That is, the screw fastened surface  201   a  extends in an axial direction AD of the feed driving shaft  59 . The pivot supporting surface  201   b , which serves as a first bearing holding portion, extends from a first end portion  201   e , in the axial direction AD, of the screw fastened surface  201   a  towards a cross direction CD which crosses the axial direction AD. The pivot supporting surface  201   c , which serves as a second bearing holding portion, extends from a second end portion  201   f  of the screw fastened surface  201   a  toward the cross direction CD. The pivot supporting surfaces  201   b  and  201   c  respectively have through-holes  201   b   1  and  201   c   1 , through which the feed driving shaft  59  passes. 
     As illustrated in  FIG. 8C , the roller support guide  202  includes a guide surface  202   a , which extends in the axial direction AD of the feed driving shaft  59  and guides the sheet S fed by the pickup roller  51 . The roller support guide  202  also includes bearing portions  202   b  and  202   c  formed at both ends of the guide surface  202   a . The bearing portion  202   b  is interposed between the through-hole  201   b   1  of the roller support frame  201  and the feed driving shaft  59  and slidingly supports the feed driving shaft  59 , the bearing portion  202   c  is interposed between the through-hole  201   c   1  of the roller support frame  201  and the feed driving shaft  59  and slidingly supports on the feed driving shaft  59 . The bearing portions  202   b  and  202   c , which serves as a first bearing portion and a second bearing portion, are disposed at different positions in the axial direction AD, and supported by the pivot supporting surfaces  201   b  and  201   c , respectively. The guide surface  202   a  and the bearing portions  202   b  and  202   c  are formed of a resin material as a one piece. The guide surface  202   a  has screw fastened portions  202   a   1  to  202   a   3 , to which the screws  203  to  205  are fastened. The screw fastened portions  202   a   1  to  202   a   3  are concaved with respect to the guide surface  202   a  so that the sheet S is not caught. 
       FIG. 9  is a cross-sectional view illustrating an  8 A- 8 A cross section which is perpendicular to the axial direction AD of  FIG. 8A . As illustrated in  FIG. 9 , the guide surface  202   a  of the roller support guide  202  is disposed below the feed driving shaft  59 , and partly overlapped with the feed driving shaft  59  in the sheet feed direction. In addition, if an imaginary line VL is drawn so as to extend from a downstream edge portion  202   e , in the sheet feed direction, of the guide surface  202   a , the imaginary line VL lies below the feed driving shaft  59 . With the guide surface  202   a  formed in this manner, even when a curled sheet by the pickup roller  51  is fed, the sheet can be prevented from touching the feed driving shaft  59 . With this configuration, the sheet can be prevented from entering a space between the guide surface  202   a  and the feed driving shaft  59 , and thus from being jammed. 
     If such guide surface  202   a  is made of a metal material, the cost will increase, partly because the guide surface  202   a  has a complex shape. In contrast, a resin material can achieve a desired shape, with less cost than the metal material. Thus, in the present embodiment, a problem in which the roller support mechanism  200  is deformed is resolved by the roller support frame  201  made of a metal material, and a problem in which the sheet is not properly guided is resolved by the roller support guide  202  made of a resin material. 
     As illustrated in  FIG. 8C , one end portion of the guide surface  202   a  is provided with the abutment portion  202   d , which is disposed out of a sheet conveyance area and can abut against the upper edge portion  71   b  of the first holding member  71 . The sheet conveyance area is a space through which the sheet fed by the pickup roller  51  passes. As illustrated in  FIG. 4A , the first holding member  71 , which abuts against the abutment portion  202   d , is also disposed out of the sheet conveyance area in the axial direction AD of the feed driving shaft  59 . On the other hand, the pickup roller  51  is disposed at a substantially center portion of the sheet conveyance area in the axial direction AD of the feed driving shaft  59 . The feed pressure spring  60  is disposed in the vicinity of the pickup roller  51 . 
     The bearing portions  202   b  and  202   c , respectively, have collar portions  207   b  and  207   c  which are inserted into the through-holes  201   b   1  and  201   c   1 , and flange portions  208   b  and  208   c  which extend radially along the pivot supporting surfaces  201   b  and  201   c . With the collar portions  207   b  and  207   c  and the flange portions  208   b  and  208   c , the roller support guide  202  can be easily positioned with respect to the roller support frame  201 . 
     As illustrated in  FIGS. 10A and 10B , in a state where the roller support mechanism  200  is positioned at the separation position, the upper edge portion  71   b  of the first holding member  71  abuts against the abutment portion  202   d  of the roller support guide  202 , from the downward direction, and is in contact with the abutment portion  202   d . In addition, the abutment portion  202   d  is in contact with an end portion  201   d  of the pivot supporting surface  201   c  of the roller support frame  201 , on a side of the abutment portion  202   d  opposite to the upper edge portion  71   b . With this configuration, a force from the first holding member  71  which is urged upward by the tension coil spring  73  can be received by the end portion  201   d  of the roller support frame  201 , which serves as a contact portion, via the abutment portion  202   d . That is, the end portion  201   d  is in contact with a first surface, of the abutment portion  202   d , opposite to a second surface on which the upper edge portion  71   b  presses the abutment portion  202   d  in the swing direction of the roller support mechanism  200 . 
     In addition, as illustrated in  FIG. 10C , one end portion  60   a  of the feed pressure spring  60  is supported on the first end portion  201   e  of the screw fastened surface  201   a  of the roller support frame  201 . With this configuration, the urging force of the feed pressure spring  60  can be received by the roller support frame  201 . The end portion  201   d  of the pivot supporting surface  201   c  and the first end portion  201   e  of the screw fastened surface  201   a  constitute a receiving portion  400 , and are disposed separately at one end side and the other end side of the roller support frame  201  in the axial direction of the feed driving shaft  59 . Since a direction in which the end portion  201   d  receives one force and a direction in which the first end portion  201   e  receives another force are substantially opposite to each other, torsional stress occurs in the roller support frame  201 . 
     As described above, in the present embodiment, the roller support mechanism  200  is constituted by the roller support frame  201  formed of a metal material having a high stiffness, and the roller support guide  202  formed of a resin material having a high sliding property. Since the roller support frame  201  receives the urging force of the feed pressure spring  60  and the urging force of the tension coil spring  73 , and the roller support guide  202  slidingly contacts with the sheet S and the feed driving shaft  59 , torsional stress occurs in the roller support frame  201 . However, the deformation of the roller support mechanism  200  can be reduced because the roller support frame  201  is made of a metal material having a high stiffness. Furthermore, the sheet feeding apparatus  6  needs not to be designed larger in consideration of the deformation of the roller support mechanism  200 , and thus the sheet feeding apparatus  6  can be prevented from being designed larger. In addition, the roller support guide  202  having a high sliding property enables better sliding properties for the sheet S and the feed driving shaft  59 . 
     The roller support frame  201  and the roller support guide  202  are fixed to each other via the screws in the present embodiment, but the present disclosure is not limited to this. In addition, the holes  201   b   1  and  201   c   1  on which the roller support mechanism  200  pivots are formed in a circular shape in the figures, but the present disclosure is not limited to the circular shape as long as the holes are formed so that the bearing portions  202   b  and  202   c  of the roller support guide  202  fit the holes. For example, the holes may be formed so as to have two parallel planes. 
     In addition, although the upper edge portion  71   b  of the first holding member  71  abuts against the abutment portion  202   d  of the roller support guide  202 , the upper edge portion  71   b  may directly contact the end portion  201   d  of the pivot supporting surface  201   c  of the roller support frame  201 . Similarly, the holding hook portion  1   c  of the second holding member  1  may directly contact the end portion  201   d  of the pivot supporting surface  201   c  of the roller support frame  201 . Regarding the feed pressure spring  60 , although the one end portion  60   a  contacts the roller support frame  201  for urging, the one end portion  60   a  may not necessarily contact the roller support frame  201  as long as the roller support frame  201  receives the urging force. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. The second embodiment is configured such that the roller support mechanism  200  of the first embodiment is achieved by another configuration. Thus, the same components as those of the first embodiment are omitted in the drawings, or described with the same symbols given to the drawings. 
       FIG. 11B  is a perspective view illustrating the roller support frame  201 .  FIG. 11C  is a perspective view illustrating bearings  300  and  301 , and a guide portion  302 .  FIG. 11A  is a perspective view illustrating a roller support mechanism  200 A in which the roller support frame  201 , the bearings  300  and  301 , and the guide portion  302  are combined with each other. As illustrated in  FIG. 11A , the roller support mechanism  200 A, which serves as a swing unit, includes the roller support frame  201 , the guide portion  302  which is a resin member, and the bearings  300  and  301  which serve as the first bearing portion and the second shaft bearing portion. The roller support frame  201  is the same as that of the first embodiment, and thus the description thereof is omitted. The guide portion  302  and the bearings  300  and  301  are made of a resin material having a high sliding property and have a first stiffness, and the roller support frame  201  has a second stiffness higher than the first stiffness. The guide portion  302  is fixed to the roller support frame  201  with the plurality of screws  203 ,  204 , and  205 , and has a guide surface  302   a  which guides the sheet S fed by the pickup roller  51 . 
     The bearings  300  and  301  are formed separately from the guide portion  302 . The bearing  300  is interposed between the pivot supporting surface  201   b  of the roller support frame  201  and the feed driving shaft  59 ; the bearing  301  is interposed between the pivot supporting surface  201   c  of the roller support frame  201  and the feed driving shaft  59 . The bearings  300  and  301  are formed, for example, so as to have one plane or two parallel planes, and formed integrally with the pivot supporting surfaces  201   b  and  201   c  of the roller support frame  201 . Also in the second embodiment, the same effects as those of the first embodiment can be obtained. 
     The bearings  300  and  301  may have any material other than the resin material and may be other bearings such as sintered bearings or ball rolling bearings, as long as the other bearings function as the bearings. 
     Also, although the description is made using the electrophotographic printer  100  in any of the embodiments describe above, the present invention is not limited to this. For example, the present invention may also be applied to an ink-jet image forming apparatus that forms images on sheets by injecting ink from its nozzle. 
     OTHER EMBODIMENTS 
     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. 2016-250093, filed Dec. 22, 2016, and Japanese Patent Application No. 2017-208373, filed Oct. 27, 2017, which are hereby incorporated by reference wherein in their entirety.