Patent Publication Number: US-2023150783-A9

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

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet feeding apparatus suitable for an image forming apparatus such as an electrophotographic copying machine that forms an image on a sheet using an electrophotographic process or a laser beam printer, or an image reading apparatus such as a scanner. 
     Description of the Related Art 
     Conventionally, the image reading apparatus that reads an image on a sheet while conveying the sheet has a sheet feeding apparatus that feeds the sheet toward an image reading portion. The configuration of the sheet feeding apparatus is known that includes a feeding roller that feeds sheets, a conveying roller that conveys the sheets fed by the feeding roller, a separation roller that forms a separation nip portion by pressing the conveying roller, and that separates one by one at the separation nip portion the sheets conveyed by the conveying roller. 
     Further, Japanese Patent Application Laid-Open No. 2017-052573 discloses the configuration in which a sheet-like guide is provided upstream of the separation nip portion in the sheet feeding direction to guide the sheets. 
     However, although the separation roller and the sheet-like guide are attached to a common part, when the separation roller should be replaced, it is necessary to remove a sheet holder attached by snap-fit from the common part due to the positional relationship between the separation roller and the sheet-like guide. 
     When such a snap-fit mechanism is adopted, there is difficulty in terms of positional accuracy between the separation roller and the sheet-like guide because there exists a certain amount of play between the sheet holder and the common part. This problem cannot be ignored when the diameter of the separation roller is reduced. 
     SUMMARY OF THE INVENTION 
     A representative configuration of a sheet feeding apparatus according to the present invention, comprises: 
     a feeding roller configured to feed sheets; 
     a conveying roller configured to convey the sheets fed by the feeding roller; 
     a separation roller configured to form a nip portion by being pressed on the conveying roller, and to separate one by one the sheets at the nip portion, the sheets being conveyed by the conveying roller; 
     a guide configured to guide the sheets fed by the feeding roller to the nip portion; and 
     a holder configured to hold the separation roller and the guide, and to be detachably attachable to the sheet feeding apparatus, 
     wherein the guide adheres to the holder and the separation roller is replaceable on the holder that has been removed from the sheet feeding apparatus. 
     This configuration improves the positional precision of the separation roller and the guide, improves sheet feeding performance, and facilitates the replaceability of the separation roller. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic cross-sectional view of an image forming apparatus. 
         FIGS.  2 A and  2 B  are a perspective view of a separation roller unit. 
         FIG.  3    is a cross-sectional view of the separation roller unit. 
         FIG.  4    is a schematic cross-sectional view of the image reading unit. 
         FIG.  5    is a perspective view showing the case where the separation roller unit is mounted on a sheet feeding apparatus. 
         FIG.  6    is a perspective view showing the case where the separation roller unit is removed from the sheet feeding apparatus. 
         FIG.  7    is a view showing another configuration of the sheet-like guide. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     &lt;Image Forming Apparatus&gt; 
     Hereinafter, the overall configuration of the image forming apparatus A including the sheet feeding apparatus according to the present invention will be described together with the image forming operation with reference to the drawings. The dimensions, materials, shapes, and relative arrangements of the components described below are not intended to limit the scope of the present invention only to them unless otherwise specified. 
       FIG.  1    is a schematic cross-sectional view of the image forming apparatus A. As shown in  FIG.  1   , the image forming apparatus A is provided with the image forming portion  211  that forms an image on the sheet S. The image forming portion  211  includes the process cartridges  7  ( 7 Y,  7 M,  7 C, and  7 K), the laser scanner unit  3 , the primary transfer rollers  5  ( 5 Y,  5 M,  5 C, and  5 K), the intermediate transfer belt  216 , the secondary transfer roller  217 , the secondary transfer counter roller  214 , the drive roller  215  and so on. 
     The process cartridges  7  are configured to be detachably attachable to the image forming apparatus A. The process cartridges  7  for respective colors include the photosensitive drums  1  ( 1 Y,  1 M,  1 C, and  1 K), the charging rollers  2  ( 2 Y,  2 M,  2 C, and  2 K), and the developing rollers  4  ( 4 Y,  4 M,  4 C, and  4 K), respectively. 
     The image reading apparatus  100  that reads an image of a document is provided at the upper portion of the image forming apparatus A. The image reading apparatus  100  includes the reader  80  and the ADF  90  (Automatic Document Feeder). The reader  80  reads the image of a document placed on the document table glass  82 . The ADF  90  automatically conveys a document placed on the document tray  91  to read the image. The detailed configuration of the image reading apparatus  100  will be described later. 
     Next, the image forming operation of the image forming apparatus A will be described. When forming an image, an image forming job signal is first input to the control portion (not shown). As a result, the sheet S stored in the sheet cassette  20  is conveyed to the registration roller  240  by the pickup roller  21 , the feeding roller  22 , and the conveying roller  105 . Thereafter, the sheet S is sent at a predetermined timing by the registration roller  240  to the secondary transfer portion formed by the secondary transfer roller  217  and the secondary transfer counter roller  214 . 
     On the other hand, in the image forming portion  211 , the surface of the photosensitive drum  1 Y is first charged by the charging roller  2 Y. Thereafter, the laser scanner unit  3  irradiates the surface of the photosensitive drum  1 Y with laser light according to the image data of the document read by the image reading apparatus  100 , and forms an electrostatic latent image on the surface of the photosensitive drum  1 Y. Then, yellow toner is attached to the electrostatic latent image formed on the surface of the photosensitive drum  1 Y by the developing roller  4 Y, and a yellow toner image is formed on the surface of the photosensitive drum  1 Y. The toner image formed on the surface of the photosensitive drum  1 Y is primarily transferred to the intermediate transfer belt  216  by applying a bias to the primary transfer roller  5 Y. 
     By the same process, magenta, cyan, and black toner images are also formed on the photosensitive drums  1 M,  1 C, and  1 K, respectively. Then, by applying a bias to the primary transfer rollers  5 M,  5 C, and  5 K, these toner images are transferred superposedly on the yellow toner image on the intermediate transfer belt  216 . As a result, a full-color image is formed on the surface of the intermediate transfer belt  216 . 
     Thereafter, the full-color toner image is sent to the secondary transfer portion by the intermediate transfer belt  216  that is rotated by the driving force transmitted from the driving roller  215 . Then, a bias is applied to the secondary transfer roller  217  at the secondary transfer portion, so that the full-color toner image on the intermediate transfer belt  216  is transferred to the sheet S. 
     Next, the sheet S to which the toner image has been transferred is conveyed to the fixing device  220  where the sheet S is subjected to a fixing process of heating and pressing. As a result, the toner image on the sheet S is fixed on the sheet S. Thereafter, the sheet S to which the image is fixed is discharged to the discharge tray  250  by the discharge roller  225 . 
     &lt;Image Reading Apparatus&gt; 
     Next, the configuration of the image reading apparatus  100  will be described. 
     As shown in  FIG.  1   , the reader  80  includes the image reading unit  81  (image reading portion) that optically reads the image data of the sheet S that is a document and converts the image data into an electric signal, the document table glass  82 , and the platen glass  83 . The image reading unit  81  is moved by a driving unit (not shown) in the direction of the arrow T in the space below the document table glass  82  and the platen glass  83 . 
     When the image data of the sheet S should be read with the reader  80 , a user first places the sheet S on the document table glass  82 . Thereafter, the image reading unit  81  reads the image data of the sheet S by irradiating the sheet S with light while moving in the direction of the arrow T, receiving the reflected light, and converting it to an electric signal. The ADF  90  is rotatably supported on the reader  80 . After rotating the ADF  90  upward to open it, a user can get access to the document table glass  82 . 
     The ADF  90  includes the document tray  91  on which the sheets S, which are documents, are stacked, the feeding roller  92  for feeding sheets S stacked on the document tray  91  (stacking portion), and the conveying roller  93  for conveying the sheets S fed by the feeding roller  92 . The ADF  90  also includes the sheet conveying rollers  95  ( 95   a  to  95   f ) that convey the sheets S conveyed by the conveying roller  93 . The feeding roller  92  is configured to be able to be lifted and lowered by a moving mechanism (not shown). When the feeding roller  92  should feed the sheets S, the pickup roller  92  is lowered and comes into contact with one of the sheets S stacked on the document tray  91 . 
     Further, the ADF  90  includes the separation roller  94   a  that presses the conveying roller  93  to form the separation nip portion N where the separation roller  94   a  separates one by one the sheets S conveyed to the conveying roller  93 . The torque limiter  61  is attached to the separation shaft  94   b  that rotatably supports the separation roller  94   a  (refer to  FIG.  2   ). The document tray  91 , the conveying roller  93 , and the separation roller  94   a  constitute the sheet feeding apparatus  300  that feeds the sheet S toward the image reading unit  81 , together with the holder  62 , the sheet-like guide  63 , the supporting member  67 , and so on, which will be described later. 
     When one sheet S enters the separation nip portion N, the torque input to the conveying roller  93  is transmitted to the separation roller  94   a  with the frictional force of the sheet S, so that a torque above a predetermined value is applied to the separation roller  94   a . As a result, the transmission of torque between the separation roller  94   a  and the torque limiter  61  is cut off, and the separation roller  94   a  is driven to rotate in the feeding direction of the sheet S by the rotation of the conveying roller  93 . 
     In contrast, when two sheets S enter the separation nip portion N, slippage occurs between the two sheets S and the torque of the conveying roller  93  escapes, so that a torque above a predetermined value is not applied to the separation roller  94   a . As a result, the rotation of the separation roller  94   a  is restricted by the load of the torque limiter  61 . The sheet S that is in contact with the separation roller  94   a  is then separated from the sheet S that is in contact with the conveying roller  93 , and the sheets S are separated one by one. 
     The ADF  90  further includes the image reading unit  96  (image reading portion) that optically reads the image of the sheet S that is a document and converts the image data into an electric signal. The platen glass  97  is provided at a position facing the image reading unit  96 . Further, in the ADF  90 , the platen rollers  98  and  99  are provided at positions facing the platen glasses  83  and  97 , respectively. 
     The ADF  90  further includes the opening/closing cover  71  that supports the feeding roller  92  and the conveying roller  93 . The opening/closing cover  71  is rotatably supported on a support shaft (not shown) of the apparatus main body of the ADF  90 . The opening/closing cover  71  can be rotated between an open position at which the opening/closing cover  71  is open from the apparatus main body of the ADF  90  and a closed position at which the opening/closing cover  71  is closed to the apparatus main body of the ADF  90 . The opening/closing cover  71  forms a conveying path for the sheet S when the opening/closing cover  71  is located at the closed position, and the conveying path is opened and the separation roller  94   a  is exposed when the opening/closing cover  71  is located at the open position. The closed position of the opening/closing cover  71  is a pressing position where the separation nip N is formed by the conveying roller  93  and the separation roller  94   a . The open position of the opening/closing cover  71  is a separating position where the pressing of the separation nip N formed by the conveying roller  93  and the separation roller  94   a  is released. 
     When the image of the sheet S is read by the ADF  90 , the sheets S stacked on the document tray  91  are first conveyed to the first reading position by the feeding roller  92 , the conveying roller  93 , and the sheet conveying rollers  95   a  to  95   d  while being separated one by one by the separation roller  94   a . The first reading position is located between the platen glass  83  and the platen roller  98 . Next, the image of the first surface of the sheet S is read by the image reading unit  81  at the first reading position. 
     Next, the sheet S is conveyed by the sheet conveying rollers  95   e  to a second reading position located between the platen glass  97  and the platen roller  99 . When an instruction is provided from a user that the image on the second surface of the sheet S should be read, the image reading unit  96  reads the image on the second surface of the sheet S at the second reading position. Thereafter, the sheet S is conveyed by the sheet conveying rollers  95   f  and discharged onto the discharge tray  73  by the discharge rollers  72 . 
     &lt;Separation Roller Unit&gt; 
     Next, the detailed configuration of the separation roller unit will be described. 
       FIGS.  2 A and  2 B  are a perspective view of the separation roller unit viewed at different angles.  FIG.  3    is a cross-sectional view of the separation roller unit cut by the K-K cross-section shown in  FIG.  2 B . The separation roller unit includes the separation roller  94   a , the separation shaft  94   b , the torque limiter  61 , the holder  62 , and the sheet-like guide  63 . As shown in  FIGS.  2 A,  2 B and  3   , the separation roller  94   a  is pressed against the conveying roller  93  to form the separation nip portion N, and is in contact with the sheet S to separate the sheet S. The separation roller  94   a  and the torque limiter  61  are rotatably supported by the separation shaft  94   b.    
     The torque limiter  61  is arranged at a position adjacent to the separation roller  94   a  in the direction of the rotation axis of the separation roller  94   a . The outer diameter of the torque limiter  61  is smaller than that of the separation roller  94   a , so that the torque limiter  61  does not interfere with the sheet S passing by the separation roller  94   a.    
     Further, the holder  62  for holding the separation shaft  94   b  is provided, and the holder  62  has the grip portion  62   c  for an operator who replaces the separation roller unit to grip. The holder  62  holds the separation roller  94   a  via the separation shaft  94   b . An uneven portion is formed on the grip portion  62   c  for an operator to easily grip the grip portion  62   c  with fingers. 
     The separation shaft  94   b  is attached to the holder  62  by press fitting when both ends of the separation shaft  94   b  are inserted into the holder  62 . That is, the holder  62  holds both ends of the separation roller  94   a  on the separation shaft  94   b  in the direction of the rotation axis of the separation roller  94   a . One end of the separation shaft  94   b  has a D-shaped cut portion (not shown) and fits with one end of the holder  62 . The portion of the holder  62  on the other end of the separation shaft  94   b  is formed in a C-shape and the other end of the separation shaft  94   b  is attached to the holder  62  by press fitting. By releasing the press fitting of the separation shaft  94   b  by pulling out from the holder  62 , the holder  62  and the separation shaft  94   b  can be separated. By doing so, the separation roller  94   a  can be replaced. The method of attaching the separation shaft  94   b  to the holder  62  is not limited to press fitting, and the separation shaft  94   b  may be fixed to the holder  62  using screws, for example. 
     The one end of the holder  62  has the D-shaped cut rotation restricting portion  62   a  that restricts rotation of the separation shaft  94   b  following the rotation of the separation roller  94   a . The other end of the holder  62  is provided with the grip portion  62   c . Further, the holder  62  has the guiding surface  62   d  for guiding the movement of the sheet S by being in contact with the lower surface of the sheet S, and the positioning boss  62   b  (the positioning portion) to be positioned with respect to the support member  67  (described later) to which the separation roller  94   a  is attached. 
     The sheet-like guide  63 , which is a polyester sheet (PET sheet) with a thickness of 100 μm, is attached to the holder  62 . The sheet-like guide  63  is applied to the holder  62  with double-sided adhesive tape. The function of the sheet-like guide  63  will be described later. 
     &lt;Attachment/Detachment of Separation Roller Unit&gt; 
     A force in the feeding direction of the sheet S by the conveying roller  93  and a force in the direction opposite to the feeding direction of the sheet S by the torque limiter  61  act on the separation roller  94   a . Therefore, the separation roller  94   a  is more easily worn than the conveying roller  93  or the like on which only the force in the feeding direction of the sheet S acts. Therefore, it is often necessary to replace the separation roller  94   a  with a new one within a period shorter than the product life of the ADF  90 . Next, the configuration for replacing the separation roller unit will be described. 
       FIG.  4    is a schematic cross-sectional view of the sheet feeding apparatus having the separation roller unit.  FIG.  5    is a perspective view showing a state in which the separation roller unit is mounted on the support member  67 .  FIG.  6    is a perspective view of a state in which the separation roller unit is being removed from the support member  67 . In addition, since the opening/closing cover  71  is located at the open position in  FIGS.  5  and  6   , the feeding roller  92  and the conveying roller  93  are not shown in these figures. 
     As shown in  FIGS.  4  to  6   , the separation roller unit is mounted on the support member  67 . The mounting recess  67   f  is formed on the support member  67 . The separation roller  94   a  is mounted on the support member  67  by fitting the separation shaft  94   b  of the separation roller unit into the mounting recess  67   f . Further, the rotation restricting hole  67   d  is formed on the support member  67 . The rotation restricting portion  62   a  of the holder  62  of the separation roller unit is fitted into the rotation restricting hole  67 . The separation roller  94   a  is mounted on the support member  67  with the separation roller  94   a  being held by the holder  62  via the separation shaft  94   b.    
     Further, a recess (not shown) is formed on the lower surface of the separation shaft  94   b . The separation roller  94   a  is positioned with respect to the support member  67  by fitting the protruding portion  67   c  formed on the support member  67  into the recess (not shown). Further, the support member  67  is rotatably supported by the rotating portion  67   a  with respect to the frame body  90   a  of the ADF  90 . Further, the support member  67  is urged by the spring  68  (an urging member). The separation roller  94   a  mounted on the support member  67  is pressed against the conveying roller  93  by the urging force of the spring  68 . 
     Further, the positioning hole  67   e  is formed on the support member  67 . When the separation roller unit is mounted on the support member  67 , the positioning boss  62   b  of the holder  62  is fitted with the positioning hole  67   e  of the support member  67 . 
     Further, the support member  67  has the guide portion  67   b  that comes into contact with the lower surface of the sheet S fed by the feeding roller  92  and guides the sheet S to the separation nip portion N. Namely, the support member  67  works as a mounting portion which the separation roller unit is attached to and detached from, and a guide member for guiding the sheet S to the separation nip portion N. The guide portion  67   b  of the support member  67  is exposed on the side of the conveying path of the sheet S and comes into contact with the sheet S. That is, the guide portion  67   b  includes a portion arranged on the upstream side of the separation roller  94   a  and the holder  62  in the feeding direction of the sheet S. The inclined surface  67   b   1  is formed on the guide portion  67   b  of the support member  67 . This inclined surface  67   b   1  is inclined such that the more a position on the inclined surface  67   b   1  becomes downstream in the feeding direction of the sheet S, the larger the height of the inclined surface  67   b   1  at the position is. The sheets S that are double-fed by the feeding roller  92  are separated by the resistance of the inclined surface  67   b   1 . 
     When the separation roller unit is mounted on the support member  67 , the sheet-like guide  63  applied to the holder  62  is located at a position where the sheet-like guide  63  covers a portion of the gap G between the holder  62  and the separation nip portion N in the feeding direction of the sheet S. The sheet-like guide  63  is in contact with the lower surface of the sheet S to be conveyed to the separation nip portion N at the position between the holder  62  and the separation nip portion N, and guides the sheet S to the separation nip portion N. 
     With the provision of the sheet-like guide  63 , the accuracy of guiding the sheet S to the separation nip portion N is improved since the sheet S can be guided close to the separation nip portion N. As a result, it is suppressed that the leading end of the thin sheet S with a small amount of basis weight abuts against a portion of the separation roller  94   a  or the conveying roller  93  other than the separation nip portion N and the sheet S is folded. Further, it is suppressed that the leading end of the thick sheet S with a large amount of basis weight abuts against one of the rollers to leave a scratch on it. Furthermore, it is suppressed that the sheet S enters the gap G between the separation holder  67  and the separation nip portion N, and the sheet S is folded. 
     Further, as described above, the holder  62  has a configuration in which the separation shaft  94   b  is held by both sides. As a result, the separation shaft  94   b  can be stably held as compared with the configuration in which the separation shaft  94   b  is held by a single side. Therefore, the position accuracy between the holder  62  and the separation roller  94   a  as well as the position accuracy between the sheet-like guide  63  and the separation nip portion N can be improved. 
     As in the present embodiment, it is preferable that the sheet-like guide  63  is disposed such that the sheet-like guide  63  is not in contact with the outer surface of the separation roller  94   a . When the sheet-like guide  63  is disposed such that the sheet-like guide  63  is in contact with the separation roller  94   a , the precision of guiding the sheet S to the separation nip portion N might be improved. However, in this case, there are concerns that the sheet-like guide  63  might work as resistance for the rotation of the separation roller  94   a  and that scratches are made due to the contact of the sheet-like guide  63  with the separation roller  94   a . Taking these concerns into consideration, the above described configuration is adopted in this embodiment. 
     When replacing the separation roller  94   a , an operator performing the replacement grips the grip portion  62   c  of the holder  62  holding the separation roller  94   a  with fingers and lifts it upward. The separation roller  94   a  is removed from the mounting recess  67   f  of the support member  67  with the separation roller  94   a  held by the holder  62 . At this time, the sheet-like guide  63  is removed from the support member  67  together with the separation roller  94   a  since the sheet-like guide  63  is fixed to the holder  62 . As a result, it is suppressed that the sheet-like guide  63  is folded due to the interference between the separation roller  94   a  and the sheet-like guide  63  when the separation roller  94   a  is removed. 
     In the present embodiment, the guide surface  62   d  of the holder  62  extends in the feeding direction of the sheet S toward the torque limiter  61  to narrow the gap between the torque limiter  61  and the support member  67  in the feeding direction of the sheet S. This configuration suppresses that the sheet S is folded by entering the gap. However, the present invention is not limited to this configuration and may adopt the configuration in which the guide surface  62   d  of the holder  62  is further extended such that the guide surface  62   d  covers the entire area of the torque limiter  61 . 
     Further, as shown in  FIG.  7   , the configuration may be adopted in which the sheet-like guide  63  is further widened such that the width of the sheet-like guide  63  in the direction of the rotation axis of the separation roller  94   a  corresponds to the width of the combination of the separation roller  94   a  and torque limiter  61 . Even with the configuration in which the sheet-like guide  63  covers at least a portion of the gap between the holder  62  and the torque limiter  61  in the feeding direction of the sheet S, the same effect as described above may be obtained. 
     The present embodiment exemplifies the sheet feeding apparatus  300  that feeds the sheet S toward the image reading units  81  and  96  provided in the ADF  90 . However, the present invention is not limited to this configuration. Namely, the configuration of the present embodiment may be applied to a sheet feeding apparatus that feeds a sheet toward the image forming portion  211  provided in the image forming apparatus A. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-211144, filed Nov. 22, 2019, which is hereby incorporated by reference herein in its entirety.