Patent Publication Number: US-11655113-B2

Title: Sheet conveyance apparatus, image reading apparatus and image forming apparatus

Description:
This application is a continuation of application Ser. No. 16/442,945, filed Jun. 17, 2019. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet conveyance apparatus for conveying sheets, and an image reading apparatus and an image forming apparatus equipped with the same. 
     Description of the Related Art 
     Generally, an image forming apparatus such as a printer is known, which is connected to an upper portion of the image forming apparatus body and capable of reading images on documents. The image reading apparatus is capable of reading the image on a document conveyed by an auto document feeder (hereinafter referred to as ADF). 
     Hitherto, a printer capable of having a sheet feed cover of ADF opened to replace a conveyance roller unit provided on the sheet feed cover is proposed (refer to Japanese Patent Application Laid-Open Publication No. 2015-229538). A pickup roller and a sheet feed roller are rotatably supported on the conveyance roller unit, and in a state where a holding portion provided on the conveyance roller unit is held, engagement between the sheet feed cover and the conveyance roller unit is released. By drawing out the conveyance roller unit in a state where the engagement between the sheet feed cover and the conveyance roller unit is released, the conveyance roller unit can be removed from the sheet feed cover. 
     The conveyance roller unit disclosed in Japanese Patent Application Laid-Open Publication No. 2015-229538 is arranged in an exposed manner to the conveyance path, but if there is an area on the conveyance roller unit where the document may be caught, the area may be covered by a cover. However, if such cover is attached to the sheet feed cover, such cover must first be removed if there is a need to replace the conveyance roller unit, and the replacement workability is deteriorated thereby. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a sheet conveyance apparatus includes a cover unit including a first guide, a base unit configured to support the cover unit in an openable and closable manner, and including a second guide, the first guide and the second guide forming a conveyance path in a state where the cover unit is closed with respect to the base unit, a roller unit configured to be detachable from the cover unit, and comprising a roller configured to convey the sheet along the conveyance path and a holder configured to rotatably support the roller, the holder comprising an arm portion configured to extend in a width direction orthogonal to a sheet conveyance direction, a cam arranged on an outside of the conveyance path in the width direction and configured to abut against the arm portion, the cam being configured to swing the holder by rotating, and a cover member configured to be openable and closable with respect to the cover unit and configured to cover at least a portion of the arm portion against the conveyance path in a closed state, the cover member being opened by being pressed by the arm portion in a case where the roller unit is detached from the cover unit. 
     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 entire schematic diagram illustrating a printer according to a present embodiment. 
         FIG.  2    is a cross-sectional view illustrating an image reading apparatus. 
         FIG.  3    is a side view illustrating the image reading apparatus in a state where a cover unit is opened. 
         FIG.  4    is a perspective view illustrating the cover unit. 
         FIG.  5    is a perspective view illustrating a sheet feed unit. 
         FIG.  6    is a front view illustrating the sheet feed unit. 
         FIG.  7    is a perspective view illustrating the sheet feed unit and a lifting unit. 
         FIG.  8    is a control block diagram according to the present embodiment. 
         FIG.  9    is a cross-sectional view taken in arrow P-P direction of  FIG.  7    illustrating a cover member in a state where a cam surface and a cam follower are abutted. 
         FIG.  10    is a cross-sectional view taken in arrow P-P direction of  FIG.  7    illustrating a cover member in a state where a smooth surface and the cam follower are abutted. 
         FIG.  11    is a perspective view illustrating a coupling and a retaining lever. 
         FIG.  12    is a cross-sectional view taken in arrow K-K direction of  FIG.  11    illustrating a peripheral configuration of the coupling. 
         FIG.  13    is a perspective view illustrating a bearing portion and a shaft clamping portion of an upper guide member. 
         FIG.  14    is a perspective view illustrating the bearing portion, the shaft clamping portion and a separation arm retaining portion. 
         FIG.  15    is an enlarged perspective view illustrating the bearing portion, the shaft clamping portion and the separation arm retaining portion. 
         FIG.  16    is a cross-sectional view taken in arrow W-W direction of  FIG.  15    illustrating the bearing portion and the shaft clamping portion. 
         FIG.  17    is a perspective view illustrating a state in which the sheet feed unit is attached to the cover unit. 
         FIG.  18    is a perspective view illustrating a position in which the sheet feed unit is in midway of being detached from the cover unit. 
         FIG.  19    is a perspective view illustrating an opening angle of the cover unit and the cover member. 
         FIG.  20    is a side view illustrating a projection provided on the cover member. 
         FIG.  21    is a side view illustrating a state in which the projection and a lower guide member are abutted. 
         FIG.  22    is a side view illustrating a closed state of the cover member and the cover unit. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     General Configuration 
     A printer  100  serving as an image forming apparatus is a laser beam printer adopting an electrophotographic system for forming a monochrome toner image. The printer  100  includes, as illustrated in  FIG.  1   , a printer main body  100 A and an image reading apparatus  101  mounted on an upper portion of the printer main body  100 A. The printer main body  100 A includes a sheet feeding apparatus  120  for feeding stacked sheets, an image forming unit  114  for forming an image on the sheet fed by the sheet feeding apparatus  120 , a fixing unit  106 , and a sheet discharge roller pair  109 . 
     If a command to form an image is output to the printer  100 , an image forming process by the image forming unit  114  is started based on image information entered from an external computer connected to the printer  100 , the image reading apparatus  101  and so on. The image forming unit  114  includes a photosensitive drum  110 , a charge roller  115 , a developing apparatus not shown, a laser scanner  104 , and a transfer roller  111 . 
     The laser scanner  104  irradiates laser beams toward the photosensitive drum  110  based on the image information being entered. In this state, the photosensitive drum  110  is charged in advance by the charge roller  115 , and an electrostatic latent image is formed on the photosensitive drum  110  by having laser beams irradiated thereto. Thereafter, the electrostatic latent image is developed by a developing apparatus not shown, and a monochrome toner image is formed on the photosensitive drum  110 . 
     Simultaneously as the image forming process described above, a sheet P is fed from the sheet feeding apparatus  120 . The sheet feeding apparatus  120  includes a cassette  113  for storing sheets P, a pickup roller  105 , and a separation roller pair  116 . The sheet P stored in the cassette  113  is fed by the pickup roller  105  and separated one by one by the separation roller pair  116 . The cassette  113  is capable of supporting the sheet in a liftable manner by a sheet supporting portion not shown, and the separation roller pair  116  may have one of the two rollers constituting the roller pair composed of a separation pad. 
     The sheet P separated one by one by the separation roller pair  116  is abutted against a registration roller pair  117  in a stopped state, by which skewing of the sheet P is corrected, and the registration roller pair  117  conveys the sheet P by rotating at a matched timing with the transfer of toner image. The toner image on the photosensitive drum  110  is transferred to the sheet P conveyed by the registration roller pair  117  through electrostatic load bias applied to the transfer roller  111 . 
     Predetermined heat and pressure is applied by the fixing unit  106  to the sheet P to which the toner image has been transferred, by which toner is melted and fixed. The sheet P having passed through the fixing unit  106  is discharged by the sheet discharge roller pair  109  onto a sheet discharge tray  112 . The sheet can be fed not only from the cassette  113  but also from a multi-tray  108 . The multi-tray  108  is supported in an openable and closable manner with respect to the printer main body  100 A, and it is designed to support the sheet in an opened state. 
     If images are to be formed on both sides of the sheet P, the sheet P on which an image has been formed on a first side, i.e., front side, is subjected to switch-back by the sheet discharge roller pair  109  and sent into the duplex conveyance path  107 . The sheet P sent into the duplex conveyance path  107  is conveyed again to the registration roller pair  117 , and an image is formed on a second side, i.e., rear side, by the photosensitive drum  110  and the transfer roller  111 . The sheet P passes through the fixing unit  106  and is discharged by the sheet discharge roller pair  109  onto the sheet discharge tray  112 . 
     Image Reading Apparatus 
     Next, the image reading apparatus  101  will be described in detail. The image reading apparatus  101  includes, as illustrated in  FIG.  2   , an auto document feeder, hereinafter referred to as ADF,  103  that conveys a document D supported on a document tray  15  and discharges the document onto a document discharge tray  16 . Further, the image reading apparatus  101  includes a reading unit  102  that reads the document D conveyed by the ADF  103 . The ADF  103  serving as a sheet conveyance apparatus is supported pivotably by a hinge not shown to a front side and a depth side of  FIG.  2    with respect to the reading unit  102  such that a platen document glass  4  can be exposed. In the present embodiment, a sheet includes both a recording material on which an image is formed by the image forming unit  114  and a document having an image thereon read by the image reading apparatus  101 . The document can be blank paper or can have an image formed on one side or both sides thereof. 
     The ADF  103  includes a shutter member  17 , a pickup roller  43  serving as a roller, a feed roller  44 , a separation roller  20 , and a plurality of conveyance roller pairs  251 ,  252  and  123 . The ADF  103  includes a platen roller  121  arranged opposed to a platen glass  2 , and a second reading portion  7 . 
     The reading unit  102  includes the platen glass  2 , the platen document glass  4  capable of supporting the document D and a first reading portion  3 , and the first reading portion  3  is configured movable in a sub-scanning direction, that is, in the direction of arrow A. The first reading portion  3  and the second reading portion  7  include a light source not shown, a photoelectric conversion element and the like, wherein a CCD sensor, a CMOS sensor and the like can be adopted as the photoelectric conversion element. The light emitted from the light source is reflected by the document D and reflected light from the document D will be incident on the photoelectric conversion element. The photoelectric conversion element performs photoelectric conversion of reflected light from the document D, by which image on the document D can be obtained as image information. 
     The platen glass  2  is formed of a transparent member such as glass that transmits light. A configuration of reading the document conveyed by the ADF  103  is called document feeding-reading, and a configuration of reading the document positioned on the platen document glass  4  by the first reading portion  3  while moving the first reading portion  3  in the sub-scanning direction is called document fixed reading. 
     In the case of document fixed reading, the user opens the ADF  103  and places the document on the platen document glass  4 . Then, the user operates an operation panel not shown to start document fixed reading by the image reading apparatus  101 . When document fixed reading is started, the first reading portion  3  moves in the sub-scanning direction while reading the image on the document placed on the platen document glass  4 . 
     In the case of document feeding-reading, the user places the document D on the document tray  15  while abutting a leading edge of the document D against the shutter member  17 , and the user operates the operation panel to start document feeding-reading by the image reading apparatus  101 . In this state, the first reading portion  3  reads the image while stopping at a position below the platen glass  2 . In a state where the document feeding-reading is started, the shutter member  17  retreats upward, and the document D placed on the document tray  15  is conveyed by the pickup roller  43  and separated one by one by the feed roller  44  and the separation roller  20 . The document D is conveyed along a document conveyance path  25  serving as the conveyance path by the conveyance roller pairs  251 ,  252  and  123 , and is pressed against the platen glass  2  by the platen roller  121 . 
     The image on a first side, i.e., front side, of the document D is read by the first reading portion  3  through the platen glass  2  while the document D is being guided by the platen roller  121 . If images on both sides of the document D are to be read, after the image on the document D has been read by the first reading portion  3 , the image on the second side, i.e., rear side, of the document D is read by the second reading portion  7 . A platen glass and the like are provided to face the second reading portion  7 , but the description thereof is omitted. Then, the document D is discharged to the exterior of the apparatus by a sheet discharge roller pair  131  and supported on the document discharge tray  16 . 
     The ADF  103  includes, as illustrated in  FIG.  3   , an ADF main body  103 A serving as a base unit, and a cover unit  60  serving as an apparatus body that is supported to open and close about a fulcrum  59  with respect to the ADF main body  103 A. The cover unit  60  includes an upper guide member  61  including a first guide  25   a , and a sheet feed unit  40  serving as a roller unit supported detachably on the upper guide member  61 . The ADF main body  103 A includes a lower guide member  90  including a second guide  25   b  forming a portion of the document conveyance path  25  together with the first guide  25   a . The cover unit  60  is opened for treating jammed sheets caught in the document conveyance path  25  or for replacing the sheet feed unit  40 . 
     As illustrated in  FIG.  4   , the sheet feed unit  40  is, as described later, positioned by bearing portions  65  and  77  formed on the upper guide member  61 , and retained by a coupling  66 , a shaft clamping portion  64  and a separation arm retaining portion  76 . A cover member  62  is supported on the upper guide member  61  to open and close around opening and closing shafts  62   a  and  62   b , and the cover member  62  covers the coupling  66  and the like that transmits drive to the sheet feed unit  40 . In other words, the cover member  62  is supported pivotably with respect to the upper guide member  61  around an axis extending in a width direction. Further, the cover member  62  includes a guide surface  62   e  that guides sheets, and the guide surface  62   e  forms the document conveyance path  25  that guides the document D together with the first guide  25   a  and the second guide  25   b  (refer to  FIG.  3   ). 
     Sheet Feed Unit 
     The sheet feed unit  40  includes, as illustrated in  FIGS.  5  and  6   , a feed roller shaft  46  serving as a rotation shaft, a feed roller  44  supported rotatably on the feed roller shaft  46 , a holder member  45 , and a swing arm  41 . The feed roller  44  is attached to the feed roller shaft  46  via a one-way clutch  48 , and by driving the feed roller shaft  46 , the one-way clutch  48  can rotate in a sheet conveyance direction, that is, in a direction of arrow E of  FIG.  6   . Meanwhile, in a state where the feed roller shaft  46  is stopped, the feed roller  44  can rotate in the direction of arrow E of  FIG.  6    by co-rotating with the document D conveyed by the conveyance roller pair  251  (refer to  FIG.  2   ), but is prevented from rotating in the direction of arrow F. 
     The holder member  45  covers a first end of the feed roller shaft  46  by a cover portion  45   a  and is supported swingably on the feed roller shaft  46 . A swing arm  41  is swingably supported on the feed roller shaft  46  and fixed to the holder member  45 . A separation arm  55  described later is attached to the holder member  45 , and the holder member  45 , the swing arm  41  and the separation arm  55  constitute a holder unit  91  serving as a holder. 
     The swing arm  41  rotatably supports a pickup shaft  52  that extends in parallel with the feed roller shaft  46 , and [on] the pickup shaft  52  is rotatably supported the pickup roller  43 . The pickup roller  43  is composed of two rollers  43   a  and  43   b , and on an end portion of the pickup shaft  52  on a roller  43   b  side is provided a driven pulley  50  via a one-way clutch. A transmission belt  51  is wound around the driven pulley  50  and a drive pulley  49  provided on the feed roller shaft  46 , and the transmission belt  51  rotates by the rotation of the feed roller shaft  46 . 
     The pickup roller  43  conveys the sheet by the transmission belt  51  rotating while being in contact with the sheet. Meanwhile, in a state where the feed roller shaft  46  and the transmission belt  51  are stopped, the pickup roller  43  is capable of rotating in the direction of arrow E of  FIG.  6    by being co-rotated with the document D conveyed by the conveyance roller pair  251  (refer to  FIG.  2   ). 
     Further, the swing arm  41  is connected to a coil spring not shown that is loosely fit to the feed roller shaft  46 , and the coil spring functions as a spring clutch. That is, in a state where the feed roller shaft  46  is rotating in a direction of normal rotation, that is, sheet conveyance direction, the coil spring tightens, by which the feed roller shaft  46  together with the swing arm  41  rotates downward. In a state where a reading job is completed and drive supplied to the feed roller shaft  46  is stopped, the force to rotate the swing arm  41  downward is lost, and the swing arm  41  is lifted to a standby position by a return spring not shown. 
     The swing arm  41  includes an arm portion  41   a  that extends in a width direction orthogonal to the sheet conveyance direction of the pickup roller  43  and that has a cam follower  41   b  formed on a leading end thereof, and a flag portion  41   c  for detecting the standby position of the swing arm  41 . The cam follower  41   b  abuts against a lifting cam  85  described later, and the holder unit  91  is lifted along the cam surface of the lifting cam  85 . Further, the swing arm  41  includes a tongue rib  41   d  that the user holds together with a pressing portion  55   b  of the separation arm  55 . The separation arm  55  serving as the holding portion also includes a projection  55   a  in addition to the pressing portion  55   b.    
     Lifting Unit 
     Next, we will describe a lifting unit  95  for lifting, or swinging, the swing arm  41 . The lifting unit  95  is provided on the ADF main body  103 A (refer to  FIG.  3   ), and in a state where the cover unit  60  is closed, the lifting unit  95  is arranged adjacent to a driven gear  69  (refer to  FIG.  4   ) that enters drive to the coupling  66 . 
     The lifting unit  95  includes, as illustrated in  FIGS.  7  and  8   , a lifting motor  80 , a motor pulley  81 , a driven pulley  82 , a transmission belt  83 , a cam shaft  84 , the lifting cam  85 , a cam position detecting flag  86 , and a cam position detecting sensor  87 . The cam position detecting sensor  87  and the lifting motor  80  are connected to a control unit  96 , and the control unit  96  controls the lifting motor  80  based on a detection result of the cam position detecting sensor  87 . The control unit  96  may be provided on either the printer main body  100 A or the image reading apparatus  101 . The motor pulley  81  is attached to a motor shaft of the lifting motor  80 , and the transmission belt  83  is wound around the motor pulley  81  and the driven pulley  82 . 
     The driven pulley  82  is fixed to the cam shaft  84 , wherein on the first end of the cam shaft  84  is attached the cam position detecting flag  86  serving as a flag portion that rotates integrally with the cam shaft  84 , and on a second end of the cam shaft  84  is fixed the lifting cam  85 . The lifting cam  85  rotates in a direction of arrow M along with the rotation of the cam shaft  84 . The cam position detecting flag  86  is formed in a disk shape with a portion cut out, and it is capable of blocking or opening an optical path between a light emitting component and a photosensing portion of the cam position detecting sensor  87 . The cam position detecting sensor  87  serving as a sensor outputs detection signals according to the position of the cam position detecting flag  86 . The phase of the lifting cam  85  can be detected by the cam position detecting sensor  87  and the cam position detecting flag  86  configured in this manner. 
     The lifting cam  85  serving as a cam is formed in an approximately crescentic shape and includes a cam surface  85   a  formed of an arc-shaped surface and a smooth surface  85   b . The lifting cam  85  is constantly abutted against the cam follower  41   b  of the swing arm  41 , and the swing arm  41  swings according to the rotational phase of the lifting cam  85 . That is, if a reading job to read the document D placed on the document tray  15  is entered, the feed roller shaft  46  rotates, the swing arm  41  swings, and the pickup roller  43  abuts against an upper surface of the document D. The document D is fed by having the pickup roller  43  rotate in this state. 
     In this state, the lifting motor  80  controls the phase of the lifting cam  85  based on the detection result of the cam position detecting sensor  87 , and while the document D is fed by the pickup roller  43 , the smooth surface  85   b  of the lifting cam  85  is abutted against the cam follower  41   b . Meanwhile, while the document D is not fed by the pickup roller  43 , the cam surface  85   a  of the lifting cam  85  abuts against the cam follower  41   b . Thereby, the swing arm  41  is lifted slightly, and the pickup roller  43  is separated from the document D. 
     Recently, it is attempted to improve productivity by increasing the sheet conveyance speed or narrowing interval between sheets, or distance between a preceding sheet and a subsequent sheet. Further, there are demands for the printer to convey various types of sheets including thin paper and thick paper. In a printer having improved productivity and capable of conveying various types of sheets, the pickup roller  43  and the document D must be abutted against and separated from each other highly accurately so as not to cause conveyance failure of document. According to the configuration of the present embodiment, the swing arm  41  is lifted by the lifting cam  85 , according to which the pickup roller  43  is abutted against or separated from the document D with high accuracy. 
       FIG.  9    is a cross-sectional view taken in direction of arrow P-P of  FIG.  7    illustrating the cover member  62  in a state where the cam surface  85   a  is abutted against the cam follower  41   b , that is, in a state where the document D and the pickup roller  43  are separated. In this state, the cover member  62  and the arm portion  41   a  are separated by gap Q.  FIG.  10    is a cross-sectional view taken in direction of arrow P-P of  FIG.  7    illustrating the cover member  62  in a state where the smooth surface  85   b  is abutted against the cam follower  41   b , that is, in a state where the document D is abutted against the pickup roller  43 . In this state, the cover member  62  and the arm portion  41   a  are separated by gap Q′ (0&lt;Q′&lt;Q). As described, regardless of the phase of the lifting cam  85 , the arm portion  41   a  of the swing arm  41  and the cover member  62  are in a non-contact positional relationship. 
     Support Configuration of Sheet Feed Unit 
     Next, a support configuration of the sheet feed unit  40  will be described. As illustrated in  FIG.  11   , the feed roller shaft  46  of the sheet feed unit  40  has its first end side positioned by a bearing portion  77  of the upper guide member  61  and connected to the coupling  66 . The coupling  66  is capable of being connected to and separated from the feed roller shaft  46 . As illustrated in  FIG.  5   , a spring pin  47  is provided on a first end of the feed roller shaft  46 , and in a state where the spring pin  47  and the coupling  66  are engaged, the rotation of the coupling  66  is transmitted to the feed roller shaft  46 . 
     In this configuration, a retaining lever  67  is arranged upstream in the sheet conveyance direction of the coupling  66 , and the retaining lever  67  is supported pivotably on the upper guide member  61 . Lever claws  67   a  and  67   b  are provided on the retaining lever  67 , and in a state where the lever claws  67   a  and  67   b  are engaged with engagement hole portions  62   c  and  62   d  formed on the cover member  62  (refer to  FIG.  4   ), the cover member  62  is maintained in a closed state. The retaining lever  67  is urged by a spring not shown so that the lever claws  67   a  and  67   b  are engaged with the engagement hole portions  62   c  and  62   d . A recess portion  67   c  is formed in the vicinity of the retaining lever  67  on the upper guide member  61 , and the user can open the cover member  62  in a closed state by inserting a finger to the recess portion  67   c.    
     The coupling  66  is provided on a drive shaft  68 , as illustrated in  FIG.  11   , and on an end portion of the drive shaft  68  opposite to the coupling  66  is fixed the driven gear  69  to which rotation from a drive gear not shown is transmitted.  FIG.  12    is a cross-sectional view taken from arrow K-K direction of  FIG.  11   . The drive shaft  68  is supported rotatably on the upper guide member  61  by bearings  70  and  71 , as illustrated in  FIG.  12   , and regulated from moving in the axial direction by E rings  72  and  73 . 
     The coupling  66  includes a first cylindrical portion  66   a  storing a parallel pin  74  provided at an end portion of the drive shaft  68 , and a second cylindrical portion  66   b  having a smaller radius than the first cylindrical portion  66   a  and capable of sliding on the drive shaft  68 . A compression spring  75  is arranged between the second cylindrical portion  66   b  and the E ring  72 , and the parallel pin  74  is pressed against a stepped portion between the first cylindrical portion  66   a  and the second cylindrical portion  66   b  in a natural state by urging force of the compression spring  75 . The coupling  66  is capable of sliding toward the driven gear  69  along the axial direction against urging force of the compression spring  75 , and when the sheet feed unit  40  is being attached or detached, the coupling  66  is moved in sliding motion by the user. 
     As illustrated in  FIGS.  13  and  14   , a second end side of the feed roller shaft  46  of the sheet feed unit  40  is positioned by an arc-shaped bearing portion  65  provided on the upper guide member  61 . Further, the shaft clamping portion  64  is arranged adjacent to the bearing portion  65  on the upper guide member  61 , and a pair of shaft nipping pieces  64   a  and  64   b  are provided on the shaft clamping portion  64 . A nipping surface  64   c  capable of nipping the cover portion  45   a  of the holder member  45  that covers the first end of the feed roller shaft  46  is formed on the respective shaft nipping pieces  64   a  and  64   b . The nipping surface  64   c  and the bearing portion  65  are formed in an arc shape along the outer circumference of the cover portion  45   a , as illustrated in  FIG.  16   . As described, a downstream side in the detaching direction in which the sheet feed unit  40  is detached from the cover unit  60  of the shaft clamping portion  64  serving as the retaining portion is formed to be opened. That is, the shaft clamping portion  64  has an opening portion  64   d  whose downstream side in the detaching direction is opened. 
     The shaft nipping pieces  64   a  and  64   b  are capable of elastically deforming in directions moving away from each other by the cover portion  45   a  being pushed in, and the cover portion  45   a  is nipped by the nipping surface  64   c  of the respective shaft nipping pieces  64   a  and  64   b . That is, the sheet feed unit  40  is positioned by the bearing portion  65  through the cover portion  45   a  of the feed roller shaft  46  and the holder member  45 , and capable of being retained by the shaft clamping portion  64 . 
     As illustrated in  FIGS.  14  and  15   , the separation arm retaining portion  76  serving as an engaged portion is formed in the vicinity of the shaft clamping portion  64  on the upper guide member  61 . The separation arm retaining portion  76  is capable of being engaged with the projection  55   a  serving as the engagement portion of the separation arm  55  provided on the sheet feed unit  40 . In further detail, as illustrated in  FIG.  14   , the separation arm retaining portion  76  includes an inclined surface  76   a  and an engagement surface  76   b . Further, the projection  55   a  includes, as illustrated in  FIG.  5   , an inclined surface  55   c  and an engagement surface  55   d.    
     In a state where the sheet feed unit  40  is mounted on the cover unit  60 , the separation arm retaining portion  76  is elastically deformed while the inclined surface  76   a  of the separation arm retaining portion  76  slides against the inclined surface  55   c  of the projection  55   a . Then, if the inclined surface  55   c  of the projection  55   a  exceeds the inclined surface  76   a of the separation arm retaining portion  76 , deformation of the separation arm retaining portion  76  is returned, and the engagement surface  55   d  of the projection  55   a  engages with the engagement surface  76   b  of the separation arm retaining portion  76 . The projection  55   a  of the separation arm  55  is configured movable between a first position where the projection  55   a  is engageable with the separation arm retaining portion  76  and a second position where engagement with the separation arm retaining portion  76  is released. As illustrated in  FIG.  15   , in a state where the user holds the tongue rib  41   d  and the pressing portion  55   b , the projection  55   a  is deformed elastically in the direction of arrow L from the first position to the second position, and engagement with the separation arm retaining portion  76  can be released. It is also possible to hold the tongue rib  41   d  and the pressing portion  55   b  while mounting the sheet feed unit  40  to elastically deform the projection  55   a.    
     Attaching and Detaching Operation of Sheet Feed Unit 
     Next, attaching and detaching operation of the sheet feed unit  40  will be described. First, a detaching operation of the sheet feed unit  40  will be described. In removing the sheet feed unit  40 , the user opens the cover unit  60  from the ADF main body  103 A, as illustrated in  FIG.  3   . At this time, as illustrated in  FIG.  17   , in a state where the sheet feed unit  40  is mounted to the cover unit  60 , the separation arm  55  is engaged to the separation arm retaining portion  76 . Further, the cover member  62  is in a closed state with respect to the upper guide member  61 . 
     The user, including a service technician, holds the tongue rib  41   d  and the pressing portion  55   b  to deform the separation arm  55  in the direction of arrow L. Thereby, as illustrated in  FIG.  18   , the engagement of the projection  55   a  of the separation arm  55  and the separation arm retaining portion  76  (refer to  FIG.  14   ) is released, and the sheet feed unit  40  can be detached. Further, the user can easily hold the sheet feed unit  40 , for example, by holding the tongue rib  41   d  with the right index finger and holding the pressing portion  55   b  with the right thumb. 
     The user can detach the cover portion  45   a  from the shaft clamping portion  64  (refer to  FIG.  14   ) by pulling the sheet feed unit  40  in the arrow R direction in a state where the engagement between the projection  55   a  and the separation arm retaining portion  76  is released. In this state, the pair of shaft nipping pieces  64   a  and  64   b  of the shaft clamping portion  64  is pressed by the cover portion  45   a  and deformed in a mutually separating direction, and it is restored after the cover portion  45   a  is detached from the shaft nipping pieces  64   a  and  64   b.    
     If the user pulls up the separation arm  55  side of the sheet feed unit  40  in this state, the arm portion  41   a  of the swing arm  41  contacts the cover member  62  in the closed state at a contact portion S. In this state, the coupling  66  maintains contact with the feed roller shaft  46 , and the sheet feed unit  40  can be inclined in the arrow R direction corresponding to a looseness between a groove portion of the coupling  66  and the spring pin  47  provided on the first end of the feed roller shaft  46 . That is, in a process in which the sheet feed unit  40  is detached from the cover unit  60  in a state where the coupling  66  is connected to the feed roller shaft  46 , the arm portion  41   a  abuts against the cover member  62 . Further, in a state where the sheet feed unit  40  is moved from the state being mounted to the cover unit  60  to the detaching direction, the arm portion  41   a  abuts against the cover member  62  before the feed roller shaft  46  and the cover portion  45   a  are separated from the shaft clamping portion  64 . The shaft clamping portion  64  can be configured to retain not only the feed roller shaft  46  and the cover portion  45   a  but also other portions of the sheet feed unit  40 . 
     The cover member  62  is arranged to contact the arm portion  41   a  of the sheet feed unit  40  in the detaching direction of the sheet feed unit  40 . The detaching direction of the sheet feed unit  40  is determined, for example, by the shapes of the bearing portions  65  and  77  and the shaft clamping portion  64 , and in the configuration of the present embodiment, the bearing portions  65  and  77  and the shaft clamping portion  64  have arc-shaped, i.e., U-shaped, grooves, so that the direction in which the grooves are opened is the detaching direction. 
     The lifting cam  85  is provided on an outside of the document conveyance path  25  (refer to  FIG.  3   ) in the width direction so as not to interfere with the document conveyance path  25 . Therefore, the cam follower  41   b  capable of being abutted against the lifting cam  85  must also be provided on the outside of the document conveyance path  25  in the width direction, but the pickup roller  43  swingably supported by the swing arm  41  must be provided on an inner side of the document conveyance path  25  in the width direction. Therefore, the arm portion  41   a  of the swing arm  41  extends in the width direction so as to arrange the cam follower  41   b  on the outside of the document conveyance path  25 . 
     In the configuration of the present embodiment, the cover member  62  covers at least a portion of the coupling  66  and the arm portion  41   a  with respect to the document conveyance path  25 , and a guide surface  62   e  capable of guiding the document D is formed on a lower side of the cover member  62 . Therefore, it becomes possible to reduce jamming caused by the document D being caught in the arm portion  41   a  or the coupling  66  that swing by the rotation of the lifting cam  85 . 
     The cover member  62  is pressed in a direction of arrow V by the arm portion  41   a  of the swing arm  41  by the sheet feed unit  40  being detached from the cover unit  60 . Thereby, engagement between the cover member  62  and the retaining lever  67  (refer to  FIG.  11   ) is released, and as illustrated in  FIG.  19   , the cover member  62  opens in the direction of arrow G. The connection between the coupling  66  and the feed roller shaft  46  is released by pulling the sheet feed unit  40  in the axial direction of the feed roller shaft  46  after tilting the sheet feed unit  40  in the direction of arrow R and opening the cover member  62 . The releasing of connection between the feed roller shaft  46  of the sheet feed unit  40  and the coupling  66  can be performed either before or after opening the cover member  62 . As described, in a state where the sheet feed unit  40  is removed, the cover member  62  is pushed by the arm portion  41   a  and the cover member  62  is opened, so that the sheet feed unit  40  can be removed easily. 
     In a state where the cover unit  60  is opened, an opening angle T of the cover unit  60  with respect to the ADF main body  103 A (refer to  FIG.  3   ) is set to approximately 80 degrees. Further, in a state where the cover member  62  is opened, an opening angle U of the cover member  62  to the cover unit  60  is set to approximately 60 degrees. 
     Next, a mounting operation of the sheet feed unit  40  will be described. In a state where the cover member  62  is opened, the user holds the tongue rib  41   d  and the pressing portion  55   b  of the sheet feed unit  40  and attaches the sheet feed unit  40  to the cover unit  60 . In this state, the coupling  66  is slid in the axial direction against the urging force of the compression spring  75  (refer to  FIG.  12   ), by which the feed roller shaft  46  of the sheet feed unit  40  is connected to the coupling  66 . 
     Then, the user presses the cover portion  45   a  of the sheet feed unit  40  into the shaft clamping portion  64  and engages the separation arm  55  with the separation arm retaining portion  76 . Thereby, the sheet feed unit  40  is retained in the cover unit  60 . Lastly, the user pushes the cover member  62  in the closing direction, i.e., direction of arrow H of  FIG.  19   , and closes the cover member  62  with respect to the upper guide member  61 . 
     If the user is required to press the cover member  62  manually to close the cover member  62 , the user might forget to close the cover member  62 . Further, the operation of closing the cover member  62  should be omitted for simplification. Therefore, according to the configuration of the present embodiment, as illustrated in  FIG.  20   , a projected portion  62   f  that is projected toward the ADF main body  103 A is formed on the cover member  62 . The projected portion  62   f  is arranged on the outside of the document conveyance path  25  (refer to  FIG.  3   ) in the width direction, and it will not hinder conveyance of the document D. 
     As illustrated in  FIG.  21   , if the cover unit  60  is closed in the arrow C direction in a state where the cover member  62  is opened, the projected portion  62   f  of the cover member  62  abuts against the lower guide member  90 . If the cover unit  60  is further closed in the arrow C direction in this state, only the cover unit  60  will move closer to the lower guide member  90  while the cover member  62  abuts against the lower guide member  90 . Then, as illustrated in  FIG.  22   , in a state where the cover unit  60  is closed, the cover member  62  will be retained by the retaining lever  67  (refer to  FIG.  11   ) of the cover unit  60  and closing operation of the cover member  62  will be completed. As described, the cover member  62  will be in a closed state in linkage with the closing operation of the cover unit  60  even if the user does not close the cover member  62  manually, so that it becomes possible to omit the closing operation of the cover member  62  and prevent the cover member  62  from being left unclosed. 
     As described, according the configuration of the present embodiment, during detaching operation of the sheet feed unit  40 , the cover member  62  is pressed by the arm portion  41   a  of the swing arm  41  and the cover member  62  is configured to open automatically. Thereby, in detaching the sheet feed unit  40 , there is no need to open the cover member  62  manually, and the sheet feed unit  40  can be removed easily. 
     Furthermore, since the projected portion  62   f  is provided on the cover member  62 , even if the cover unit  60  is closed without closing the cover member  62  after mounting the sheet feed unit  40  to the cover unit  60 , the cover member  62  will close automatically. As described, attaching and detaching operation of the sheet feed unit  40  can be performed with ease, and the replacement workability of the sheet feed unit  40  can be improved. 
     Moreover, the cover member  62  covers a portion of the coupling  66  and the arm portion  41   a , and the guide surface  62   e  for guiding the document D is formed on a lower side of the cover member  62 . Thus, it becomes possible to reduce the probability of the document D being caught by the arm portion  41   a  or the coupling  66  that swing by the lifting cam  85  being rotated and causing jamming. 
     According to the configuration of the present embodiment, the sheet feed unit  40  included the feed roller  44 , but it is also possible to omit the feed roller  44 . Further, the sheet feed unit  40  can adopt a configuration where the pickup roller  43  is not supported liftably, but instead, one of the two rollers of the conveyance roller pair can simply be configured to move toward or away from the other roller. 
     According further to the configuration of the present embodiment, the cover member  62  is supported pivotably with respect to the upper guide member  61  around the axis extending in the width direction, but the present invention is not limited thereto. For example, the cover member  62  can be pivotably supported with respect to the upper guide member  61  around the axis extending in the direction orthogonal to the width direction, or it can be supported detachably with respect to the upper guide member  61 . Any configuration can be adopted as long as the cover member  62  is opened with respect to the cover unit  60  when the sheet feed unit  40  is detached from the cover unit  60 . The detachment of the cover member  62  includes opening of the cover member  62  with respect to the cover unit  60 . 
     All the above-described configurations were illustrated based on the printer  100  adopting the electrophotographic system, but the present invention is not restricted thereto. For example, the present invention is applicable to an ink-jet image forming apparatus in which ink is discharged through nozzles to form an image on a sheet. 
     Other Embodiments 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     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. 2018-129519, filed Jul. 6, 2018, which is hereby incorporated by reference herein in its entirety.