JP2005194023A - Automatic document feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the manufacturing cost and to reduce the weight of an automatic document feeder by simplifying the structure of a paper feeding unit and reducing the number of components. <P>SOLUTION: The automatic document feeder 1 comprises a pick up roller 13 for taking out a document P mounted on a paper feeding tray 5, a separate roller 12 for separating the uppermost paper Pt and delivering it to a feed passage 6, a pick up arm 34 of which base end is rockably mounted to a roller shaft 33 of the separate roller 12 and tip supports a roller shaft 35 of the pick up roller 13 rotatably, a belt transmitting mechanism 39 having a first pulley 36 fixed to the roller shaft 33, a second pulley 37 fixed to the roller shaft 35, and a transmission belt 38 stretched between the pulleys, and a coil spring 44 for pressure-contacting friction plates 42 and 43 with a side part of the second pulley 37 and a side part of the pick up arm 34, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic document conveying apparatus that separates a document placed on a sheet feeding tray one by one from the uppermost sheet and feeds it to a conveying path, and in particular, a rotationally driven separation roller and a roller of the separation roller The present invention relates to an automatic document feeder that includes an arm that is swingably supported by a shaft, and a pickup roller that is rotatably supported at the tip of the arm.

  Copiers, fax machines, scanners, and the like are equipped with an image reading device that reads an original image. FIG. 6 is a schematic longitudinal sectional view showing an example of a conventional image reading apparatus (see Patent Document 1). As shown in the figure, the image reading apparatus 80 includes an automatic document feeder (auto document feeder: ADF) 83 that conveys a document P from a paper feed tray 81 to a paper discharge tray 82, and a document P that is transported by the ADF 83. And a reading unit 84 for reading the image.

  As shown in FIG. 6, the ADF 83 is configured so that the original P set on the paper feed tray 81 is sequentially fed into the transport path 86 by the paper feed unit 85 and is appropriately disposed along the transport path 86. The sheet is conveyed downstream by 87 and discharged to the sheet discharge tray 82 by a discharge roller 88 disposed at the most downstream end of the transfer path 86. Here, the paper feed unit 85 includes a separate roller 89 that is driven to rotate, and a pickup roller 90 that is swingable with respect to the separate roller 89. The retard roller 91 is in pressure contact.

  FIG. 7 is a schematic plan view showing the configuration of the paper feed unit 85. The paper feed unit 85 is provided on a separate roller 89 that is rotatably supported by a drive shaft 92 that is driven to rotate by a motor (not shown), and the driving force of the drive shaft 92 is not shown. The first gear 93 transmitted via the one-way clutch, the pair of pickup arms 94 swingably attached to the drive shaft 92 via bearings (not shown), and supported at the tip of each pickup arm 94 A pickup roller 90 rotatably supported by a rotation shaft 95 and a third gear 97 provided on one end side of the pickup roller 90 and transmitting the rotational driving force of the first gear 93 via a second gear 96. And one end thereof is attached to the pickup arm 94 and the other end is shown in FIG. Those formed by and a torsion spring 99 which is attached to the cover portion 98 of the F83.

  In the paper feeding unit 85, when the paper feeding unit 85 is in a stopped state, that is, when a rotational driving force is not applied to the drive shaft 92, the pickup arm 94 receives the urging force of the torsion spring 99 and rotates upward. The pickup roller 90 stands by in a state of being separated from the original P. Here, when the drive shaft 92 is rotationally driven, the rotation of the drive shaft 92 is transmitted to the separate roller 89 and the first gear 93 via a one-way clutch (not shown), and the separate roller 89 and the first gear 93 are rotated. Start. At this time, the third gear 97 meshed with the first gear 93 via the second gear 96 does not rotate because its rotation is limited by a torque limiter (not shown), and the pickup arm 94 is centered on the drive shaft. As below. The pickup arm 94 stops rotating downward when the pickup roller 90 supported at the tip of the pickup arm 94 comes into contact with the uppermost paper Pt of the document P. By stopping the rotation, the rotational driving force transmitted from the first gear 93 to the third gear 97 becomes larger than the force received from the torque limiter, and the third gear 97 starts to rotate. As a result, the rotational driving force of the rotary shaft 95 that rotates integrally with the third gear 97 is transmitted to the pickup roller 90 via a spring clutch (not shown), and the pickup roller 90 starts to rotate. By the rotation of the pickup roller 90, the uppermost sheet Pt of the document P is fed out between the separation roller 89 and the retard roller 91 pressed against the separation roller 89.

  The fed document P is nipped by the separation roller 89 and the retard roller 91 and conveyed downstream, and its leading end is nipped by the conveyance roller 87 and further conveyed downstream. The transport roller 87 is driven to rotate at a higher speed than the separate roller 89. Accordingly, when the document P is transported at high speed by the transport roller 87, the separation roller 89 is pulled by the document P in the direction of increasing the number of rotations. At this time, the transmission of the driving force to the separation roller 89 and the first gear 93 is interrupted by the one-way clutch. As a result, the pickup arm 94 is turned off by the downward rotation and is rotated upward by the urging force of the torsion spring 99.

  After that, when the trailing edge of the document P is conveyed downstream of the separation roller 89 and the retard roller 91, the separation roller 89 returns to the speed driven by the drive shaft 92, and the rotational driving force of the drive shaft 92 is changed to the one-way. By being transmitted to the first gear 93 through the clutch, the pickup arm 94 is rotated downward again, and the pickup roller 90 contacts the uppermost paper Pt of the document P. By repeating the above operation, the originals P placed on the paper feed tray 81 are sequentially fed out to the conveyance path 86.

JP 2001-233471 A

  However, the conventional automatic document feeder 80 has a problem that the number of parts constituting the paper feed unit 85 is large, the assembly thereof is complicated, and the production cost is high.

  Since the pickup arm 94 is swingably attached to the drive shaft 92, a bearing is attached to the base end side thereof. Accordingly, since the weight of the pickup arm 94 is increased by the weight of the bearing, it is necessary to use a larger torsion spring 99 having a stronger urging force, which increases the production cost and the weight of the entire image reading device 80. There was also a problem of increasing.

  The present invention has been made in view of such problems, and by simplifying the structure of the paper feed unit and reducing the number of parts, the production cost can be reduced and the image reading apparatus can be reduced in weight. Provide a means.

  In order to achieve the above object, a first aspect of the present invention is directed to a conveyance path that communicates a paper feed tray and a paper discharge tray, a pickup roller that picks up the uppermost document from a bundle of documents placed on the paper feed tray, and An automatic document feeder comprising: a separation roller that separates the uppermost paper from the document supplied from the pickup roller and feeds the uppermost paper to a conveyance path; and a conveyance roller that conveys the document downstream. A pickup arm that is swingably attached to the roller shaft of the separate roller and rotatably supports the roller shaft of the pickup roller at a tip portion, and a first that rotates integrally with the roller shaft of the separate roller. A pulley, a second pulley that is pivotally supported by a roller shaft of the pickup roller, and a transmission belt stretched between the pulleys. A belt transmission mechanism, in which anda coil spring that presses the friction plates, respectively to said second pulley side and side of the pickup arm.

  According to a second aspect of the present invention, the roller shaft of the separate roller is attached to an upper cover provided so as to be openable and closable in the vertical direction with respect to the main body frame. And a locking piece that is engaged with the upper cover opened upward.

  According to a third aspect of the present invention, the pickup arm is attached by fitting a concave notch formed at a base end portion thereof to the roller shaft of the separate roller, and the pickup arm moves in the axial direction of the roller shaft. A ring member for restricting the movement is attached to the roller shaft.

  According to the image reading apparatus of the present invention, the pickup roller for taking out the uppermost document from the bundle of documents placed on the paper feed tray, and the conveyance path by separating the uppermost paper from the document supplied from the pickup roller. An automatic document feeder comprising a separation roller that feeds out and a conveyance roller that conveys a document downstream, wherein a proximal end portion is swingably attached to a roller shaft of the separation roller, and a pickup roller is provided at a distal end portion A pickup arm on which the roller shaft of the roller is rotatably supported, a first pulley that is pivotally supported by the roller shaft of the separate roller, a second pulley that is pivotally supported by the roller shaft of the pickup roller, and each pulley A belt transmission mechanism including a transmission belt stretched between pulleys, and a side of the second pulley and a side of the pickup arm. Compared with the case where the pick-up arm is urged by the torsion spring, the number of parts constituting the paper feeding unit is reduced to facilitate assembly and reduce the production cost. Reduction and weight reduction of the entire image reading apparatus can be achieved.

  Further, according to the present invention, the roller shaft of the separate roller is attached to the upper cover provided to be openable and closable in the vertical direction with respect to the main body frame. Since the locking piece that engages with the cover opened upward is provided, when the upper frame is opened upward to remove documents jammed in the transport path or to perform maintenance of the image reader, When the paper unit is rotated downward beyond the operating range during image reading, the pick-up roller is obstructed by work such as maintenance, or when it collides with the upper surface of the intermediate second frame when closing the upper frame. It can be prevented from being damaged.

  Further, according to the present invention, the pickup arm is attached by fitting the recessed portion formed in the base end portion thereof to the roller shaft of the separate roller, and the pickup arm moves in the axial direction of the roller shaft. Since the ring member that restricts the movement is attached to the roller shaft, the weight of the pickup arm can be reduced by the amount that the bearing is not attached, and the pickup arm can be swung with a smaller coil spring. As a result, the production cost can be reduced and the overall weight of the image reading apparatus can be reduced.

  A structure of a paper feeding unit that includes a separation roller that is driven to rotate and a pickup roller that is swingable with respect to the separation roller, and that feeds a document placed on a paper feeding tray to a conveyance path The purpose of facilitating assembly, facilitating assembly, reducing the production cost, and reducing the weight of the image reading apparatus is realized with the minimum number of parts and at a low cost.

  Hereinafter, an automatic document feeder (ADF) 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing a configuration of an image reading apparatus 2 having the ADF 1. As shown in the figure, the ADF 1 is provided inside the document pressing plate 4 in the image reading apparatus 2 including the reading table 3 and the document pressing plate 4. The ADF 1 is used when reading a sheet-like document P. The document P set on the paper feed tray 5 is separated from the top sheet Pt one by one and sent to the conveyance path 6. The image on the front surface is read by the reading means 7, the image on the back surface is read by the contact image sensor (CIS) 8, and is discharged to the paper discharge tray 9. On the other hand, the reading table 3 is provided with a flat bed scanner (hereinafter referred to as “FBS”) 10. Although not shown in detail in the figure, the FBS 10 is used when reading a thick original P or the like, and an image on the surface of the original P placed on the platen glass 11 of the reading table 3 is read. It is to be read by means 7.

  As shown in FIG. 1, the ADF 1 includes a paper feed tray 5 on which a bundle of documents P to be read is placed, a horizontal U-shaped conveyance path 6 that connects the paper feed tray 5 and the paper discharge tray 9, A separation roller 12 and a pickup roller 13 are provided, and a sheet feeding unit 14 that separates the uppermost sheet Pt from the bundle of documents P and feeds it to the conveyance path 6, a separation pad 15 that is pressed against the separation roller 12, and the separation roller 12. A shutter 16 that regulates the leading end position of the document P, a feed roller 17 and a press roller 18, and a transport roller 19 that is appropriately disposed in the transport path 6 and transports the document P downstream, and a press. A pressing spring 20 that presses the roller 18 against the feed roller 17, a pressing spring mounting member 21 that is fitted with the pressing spring 20, and a reading unit 7 that is disposed at the lowest position of the conveyance path 6. The platen roller 23 that is rotatably contacted with the CIS 8 disposed on the downstream side of the reading unit 7, the reading glass 22 disposed immediately below the CIS 8, and that closely contacts the original P with the reading glass 22, and the uppermost of the conveyance path 6. A discharge roller 24 disposed at the downstream end, a pressure roller 25 pressed against the discharge roller 24, a discharge tray 9 for receiving the document P discharged from the discharge port, and a rear end portion of the discharged document P , A drop assisting rib 26 that guides from the peripheral surface of the discharge roller 24 to the discharge tray 9, a read start timing by the CIS 8, and a lead sensor 27 that detects completion of discharge of the document P. is there.

  In this embodiment, as shown in FIG. 1, the apparatus body of the ADF 1 is composed of an upper frame (upper cover) 28, an intermediate first frame 29, an intermediate second frame 30, and a lower frame (main body frame) 31, Each member is attached to each frame. Here, the upper frame 28 is attached to the lower frame 31 via a hinge 32 so as to be opened and closed in the vertical direction. When the maintenance of the image reading apparatus 2 is performed or the document P jammed in the conveyance path 6 is loaded. In the case of removal, as shown in FIG. 2, it is possible to perform the work by exposing the transport path 6 by rotating the upper frame 28 upward.

  3 is a schematic perspective view showing the configuration of the paper feed unit 14, FIG. 4 is a schematic plan view, and FIG. 5 is a schematic cross-sectional view showing the internal structure. The sheet feeding unit 14 is provided on a drive shaft (roller shaft) 33 that is rotationally driven by a motor (not shown), a separate roller 12 that is rotatably supported on the drive shaft 33, and left and right sides of the separate roller 12. , A pair of pickup arms 34 whose base end portions 34a are swingably attached to the drive shafts 33, rotation shafts (roller shafts) 35 rotatably supported at the distal end portions of the respective pickup arms 34, and the rotations The pickup roller 13 rotatably supported by the shaft 35, the first pulley 36 that is supported by the drive shaft 33 and rotates integrally, the second pulley 37 that is supported by the rotation shaft 35 and rotates integrally, A belt transmission mechanism 39 including a transmission belt 38 stretched between pulleys 36 and 37, and a first clutch that transmits only the forward rotation of the drive shaft 33 to the separation roller 12. 0, a second clutch 41 that transmits only the forward rotation of the drive shaft 33 to the pickup roller 13, and coils that press the friction plates 42, 43 against the side of the second pulley 37 and the side of the pickup roller 13, respectively. A spring 44 and an e-ring (ring member) 45 that restricts the movement of the pickup arm 34 in the thrust direction are provided.

  The separation roller 12 works integrally with the separation pad 15 and separates the uppermost paper Pt from a plurality of documents P supplied from the pickup roller 13 and feeds it to the transport path 6. As shown in FIG. 5, the separate roller 12 includes a separate core 46 that is rotatably provided around the drive shaft 33, and a separate roller main body 47 that is press-fitted around the separate core 46. Thus, it is rotatable with respect to the drive shaft 33. Further, as shown in the figure, the separate roller 12 has a shape in which one end side of the separate core 46 is depressed, and the one end portion of the first pulley 36 can be fitted to the portion. Further, the separation pad 15 has a friction coefficient with respect to the original that is lower than the friction coefficient with respect to the original P of the separation roller main body 47 and higher than the friction coefficient between the originals P, and can be formed of, for example, urethane resin. . Such a separation pad 15 is stuck on the upper surface of the separation pad holder 48 as shown in FIG. The separation pad holder 48 is fitted to the intermediate second frame 30 so as to be swingable and is urged upward by a coil spring 49, whereby the separation pad 15 is pressed against the separating roller 12, It can be rotated downward in accordance with the thickness of the original P passing therethrough. Here, the intermediate second frame 30 to which the separation pad holder 48 is fitted is not shown in detail in the drawing, but the upper guide member 50 formed with the locking claw is provided with a locking groove thicker than the locking claw. Is attached to the lower guide member 51 so as to be movable up and down by fitting a locking claw into the locking groove, and the separation pad holder 48 is fitted to the upper guide member 50. . Accordingly, vibration generated when the document P passes between the separation roller 12 and the separation pad 15 is not easily transmitted to the lower guide member 51, and the reading accuracy of the CIS 8 attached to the lower guide member 51 is the vibration. To prevent deterioration.

  The pickup roller 13 takes out several originals P positioned on the uppermost layer from a bundle of originals P placed on the paper feed tray 5 and supplies them between the separation roller 12 and the separation pad 15. As shown in FIG. 5, the pickup roller 13 includes a pickup core 52 that is rotatably provided around the rotation shaft 35, and a pickup roller body 53 that is press-fitted around the pickup core 52. Thus, the rotary shaft 35 is rotatable. Further, as shown in the drawing, the pickup roller 13 has a shape in which one end side of the pickup core 52 is depressed, and the one end portion of the second pulley 37 can be fitted into the portion.

  The pickup arm 34 is made of resin or the like, and supports the pickup roller 13 at the tip thereof. As shown in FIG. 5, the pickup arm 34 is formed by integrally forming a pair of left and right support pieces 54 that respectively support both ends of the rotating shaft 35 and a connecting piece 55 that connects the support pieces 54 to each other. It is. As shown in FIG. 3, the support piece 54 is formed with a recessed portion 56 shaped to fit the drive shaft 33 at the base end portion, and a recessed shape shaped to fit the rotating shaft 35 at the distal end portion. A notch 57 is formed. By fitting the recessed portion 56 of the base end portion to the drive shaft 33, it is swingably attached to the drive shaft 33, and both end portions of the rotating shaft 35 are fitted to the recessed portion 57 of the distal end portion. Thus, the rotary shaft 35 is supported rotatably. Further, the drive shaft 33 and the rotary shaft 35 are wound around the outside of the pickup arm 34 in order to restrict the proximal end portion and the distal end portion of the pickup arm 34 from moving in the thrust direction of the drive shaft 33 and the rotary shaft 35. In this manner, the e-rings 45 are provided. As described above, the pickup arm 34 can be reduced in weight by attaching the base end portion of the pickup arm 34 to the drive shaft 33 so as to be swingable without using a bearing. Since a smaller one can be used as the coil spring 44 for applying the rotational force, there is an advantage that the automatic document feeder 1 itself can be reduced in weight. In addition, a convex portion 58 is formed at the tip of the support piece 54 so as to protrude from the side surface.

  Further, as shown in FIG. 3, a locking piece 59 is projected from each support piece 54. The top of the sag prevention piece 59 is bent approximately 90 degrees outward to form a locking surface 60, and the locking surface 60 is formed on a locking rib 61 provided on the inner surface of the upper frame 28. It is to be locked. When the upper frame 28 is opened upward in order to remove the document jammed in the conveyance path 6 or perform maintenance of the ADF 1, the locking piece 59 rotates the sheet feeding unit 14 downward beyond a predetermined range. This is to prevent this. In more detail, in this embodiment, the sheet feeding unit 14 is rotated upward at times other than the time of image reading, and the pickup arm 34 is rotated upward to be substantially horizontal. It is to wait. Here, in the present embodiment, although not shown in detail in the figure, the drive shaft 33 transmits the rotational driving force of the motor to the gear attached to one end thereof via a plurality of gear groups. A gear of a predetermined size is applied to the gear attached to the drive shaft 33 by meshing with an adjacent gear. Therefore, even when the pickup arm 34 is substantially horizontal, the drive shaft 33 does not rotate due to the weight of the paper feed unit 14. However, when the upper frame 28 is opened upward, the gear attached to the drive shaft 33 is disengaged from the adjacent gear so that no load is applied to the drive shaft 33, and the drive shaft 33 is not fed to the paper feed unit 14. The paper feeding unit 14 is rotated downward by being rotated by the weight of. Here, if the rotation of the sheet feeding unit 14 is allowed without limitation, the sheet feeding unit 14 rotates until the pickup arm 34 becomes substantially vertical. When the frame 28 is closed, the pickup roller 13 may strike the upper surface of the intermediate second frame violently, and the pickup roller 13 may be damaged by the impact. Therefore, it is preferable to restrict the sheet feeding unit 14 from rotating downward beyond a predetermined range. On the other hand, the sheet feeding unit 14 moves from the operating range at the time of image reading, that is, from the state where the pickup arm 34 is substantially horizontal, so that the pickup arm 34 rotates downward and the pickup roller 13 is placed on the upper surface of the intermediate second frame 30. The range until contact is required to be rotatable. Therefore, in the present embodiment, when the upper frame 28 is opened, the locking piece 59 of the pickup arm 34 is placed on the upper frame 28 at a position where the paper feeding unit 14 is rotated slightly below the operation range during image reading. By locking with the locking rib 61, the downward rotation of the paper feeding unit 14 is restricted.

  The locking rib 61 is provided on the inner surface of the upper frame 28. When the upper frame 28 is opened upward, the pickup roller 13 hangs down by locking the locking piece 59 with respect to the upper frame 28. This is to prevent this. As shown in FIG. 3, a receiving surface 62 that receives the locking surface 60 of the locking piece 59 from below is formed at the lower end of the locking rib 61. The receiving surface 62 is located slightly below the position of the locking surface 60 when the pickup arm 34 swings downward and the pickup roller 13 contacts the upper surface of the intermediate second frame 30. As a result, the locking surface 60 does not come into contact with the receiving surface 62 during normal image reading, and the locking rib 61 does not interfere with the operation of the paper feeding unit 14 during image reading.

  The belt transmission mechanism 39 transmits the rotational driving force of the drive shaft 33 to the pickup roller 13 and the pickup arm 34. The first pulley 36 is non-rotatably attached to the drive shaft 33 and rotates integrally with the drive shaft 33. As shown in FIG. 5, convex portions 63 are formed on both side portions of the first pulley 36 in order to fit one end portion of the first pulley 36 to one end portion of the separation roller 12. Similarly, convex portions 64 for fitting to one end portion of the pickup roller 13 are also formed on both side portions of the second pulley 37. As a means for transmitting the rotational driving force of the drive shaft 33 to the pickup roller 13 and the pickup arm 34, gears (not shown) are attached to the drive shaft 33 and the rotation shaft 35 in addition to the belt transmission mechanism 39 of the present embodiment. Thus, the rotation of the gear of the drive shaft 33 can be transmitted to the gear of the rotation shaft 35 via a predetermined number of gears.

  The first clutch 40 transmits only the forward rotation of the drive shaft 33 to the separation roller 12, and the second clutch 41 transmits only the forward rotation of the drive shaft 33 to the pickup roller 13. In the present invention, the forward rotation of the drive shaft 33 means that the drive shaft 33 rotates so as to feed the document P placed on the paper feed tray 5 into the conveyance path 6, and rotates in the opposite direction. This is called reverse rotation. The first clutch 40 is a so-called one-way clutch. As shown in FIG. 5, a one-way spring 64 is wound around the separation core 46 of the separation roller 12 and the convex portion 62 of the first pulley 36. One end is attached to the separate core 46 and the other end is attached to the convex portion 63. The one-way spring 65 is slightly larger in diameter than the separate core 46 and the convex portion 63, and is wound in such a direction that the diameter is reduced by the forward rotation of the drive shaft 33. In the first clutch 40 configured as described above, when the drive shaft 33 rotates in the forward direction, the diameter of the one-way spring 65 is reduced, and the separate core 46 and the convex portion 63 are tightened so that both can be integrally rotated. It is supposed to be. Thereby, the forward rotation of the first pulley 36, that is, the forward rotation of the drive shaft 33 is transmitted to the separate roller 12. On the other hand, when the drive shaft 33 rotates in the reverse direction, the diameter of the one-way spring 65 increases, and the tightening of the separate core 46 and the convex portion 63 is released. Therefore, the reverse rotation of the drive shaft 33 is not transmitted to the separate roller 12. Similarly, the second clutch 41 is configured by winding a one-way spring 66 around the pickup core 52 of the pickup roller 13 and the convex portion 64 of the second pulley 37, and the operation thereof is the same as that of the first clutch 40. Therefore, detailed description is omitted here.

  The coil spring 44 is disposed in a compressed state between the pickup arm 34 and the second pulley 37, and controls the transmission of the rotational driving force from the second pulley 37 to the pickup arm 34. As shown in FIG. 5, the coil spring 44 is slightly larger in diameter than the convex portion 58 of the pickup arm 34 and the convex portion 64 of the second pulley 37, and is provided by winding around both convex portions 58 and 64. One end thereof is fixed to the friction plate 42 provided in close contact with the side portion of the pickup arm 34, and the other end is fixed to the friction plate 43 provided in close contact with the side portion of the second pulley 37. . As a result, the coil spring 44 presses the friction plates 42 and 43 against the pickup arm 34 and the second pulley 37 by the urging force, and rotates integrally with the friction plates 42 and 43, so that the second pulley 37. The rotational driving force of the friction plate 43 on the side is transmitted to the friction plate 42 on the pickup arm 34 side. The friction plates 42 and 43 are formed in a donut shape with members having a high friction coefficient with respect to the resin or the like constituting the pickup arm 34 and the second pulley 37. As shown in FIG. Of the second pulley 37 and the convex portion 64 of the second pulley 37. The friction plates 42 and 43 generate a static friction force of a predetermined magnitude between the pickup arm 34 and the second pulley 37, and while a force having a magnitude not exceeding the static friction force is acting, It operates integrally with the pickup arm 34 and the second pulley 37. In addition, when a force exceeding the static friction force is applied, slip occurs between the pickup arm 34 and the second pulley 37. As a result, the friction plate 43 rotates integrally with the second pulley 37 as the second pulley 37 rotates, and the rotational driving force is transmitted to the friction plate 42 via the coil spring 44. The rotational driving force transmitted to the friction plate 42 is transmitted to the pickup arm 34, and the pickup arm 34 swings downward about the drive shaft 33.

  Hereinafter, the operation of the paper feeding unit 14 at the time of image reading will be described. Although not shown in detail in the figure, when the document set sensor detects that the document P is placed on the paper feed tray 5, the motor starts rotating under the control of the control unit, and a plurality of gear groups are selected. Thus, the driving force of the motor is transmitted to the drive shaft 33, and the drive shaft 33 starts to rotate forward. Accordingly, the first pulley 36 that rotates integrally with the drive shaft 33 also starts to rotate forward, and the driving force of the first pulley 36 is transmitted to the separate roller 12 via the first clutch 40, and the separate roller 12 is also Start forward rotation. On the other hand, the driving force of the first pulley 36 is also transmitted to the second pulley 37 via the belt transmission mechanism 39, and the second pulley 37 starts to rotate forward. The driving force of the second pulley 37 is transmitted to the pickup roller 13 via the second clutch 41, and the pickup roller 13 starts to rotate. The rotation of the second pulley 37 is transmitted to the pickup arm 34 through the friction plates 42 and 43 and the coil spring 44, and the pickup arm 34 starts swinging downward about the drive shaft 33.

  When the pickup arm 34 swings downward and the pickup roller 13 comes into contact with the uppermost paper Pt of the original P, the uppermost paper Pt or several sheets on the uppermost layer are picked up by the pickup roller 13 which has started rotating as described above. It is taken out by the roller 13 and supplied between the separation roller 12 and the separation pad 15. The separation roller 12 and the separation pad 15 separate the uppermost paper Pt from the supplied document P and feed it to the conveyance path 6. Further, when the pickup roller 13 comes into contact with the uppermost paper Pt, the swing of the pickup arm 34 is restricted, so that a force exceeding the static friction force acts between the friction plate 42 and the pickup arm 34. However, slippage occurs between the two. As a result, the driving force of the second pulley 37 is not transmitted to the pickup arm 34, and the pickup arm 34 stops swinging downward.

  The original P fed into the transport path 6 is transported further downstream by the separation roller 12, and its leading end is transported by the transport roller 19 disposed downstream of the separate roller 12. Here, since the transport roller 19 is rotated at a higher speed than the separation roller 12, when the leading end of the document P is transported by the transport roller 19, the separation roller 12 is rotated by the transported document P. It is pulled in the direction that increases. At this time, in the first clutch 40, since the rotation of the separate core 46 is faster than the rotation of the first pulley 36, the one-way spring 64 is loosened, and the separate core 46 and the convex portion 63 of the first pulley 36 are integrated. The rotation is stopped and the driving force transmission from the first pulley 36 to the separate core 46 is interrupted. Accordingly, the pickup roller 13 is in a freely rotatable state, and is rotated at a speed equal to the rotation speed of the conveying roller 19 following the original P. As described above, when the leading end portion of the document P is transported by the transport roller 19 that rotates at a high speed, the separate roller 12 and the separation pad 15 act as a brake, and the document P chatters at the reading position, and the reading accuracy deteriorates. It is possible to prevent this.

  Thereafter, when the rear end portion of the document P conveyed at a high speed is conveyed downstream from the separation roller 12 and the separation pad 15, the driving force of the first pulley 36 is again applied to the first clutch 40 by the separation core 46. Then, the separation roller 12 returns to the speed driven by the drive shaft 33 and starts conveying the next original P. Thereafter, the above operation is repeated.

  When it is detected by the document set sensor that the document P is no longer in the sheet feed tray 5, the motor starts reverse rotation under the control of the control unit, and the driving force of the motor is driven through the plurality of gear groups. 33, the drive shaft 33 starts reverse rotation. Along with this, the first pulley 36 that rotates integrally with the drive shaft 33 also starts reverse rotation. However, as described above, the first clutch 40 does not transmit the reverse rotation of the first pulley 36 to the separate roller 12. The separation roller 12 is stopped. On the other hand, the reverse rotation of the first pulley 36 is transmitted to the second pulley 37 via the belt transmission mechanism 39, and the second pulley 37 starts the reverse rotation. Here, since the second clutch 41 does not transmit the reverse rotation of the second pulley 37 to the pickup roller 13, the pickup roller 13 is also stopped. The reverse rotation of the second pulley 37 is transmitted to the pickup arm 34 via the friction plates 42 and 43 and the coil spring 44, and the pickup arm 34 starts swinging upward and becomes substantially horizontal. It stops in the state and waits for the next image reading operation.

  In this standby state, when the upper frame 28 is opened upward in order to remove the document P jammed in the conveyance path 6 or perform maintenance, as described above, the gear attached to the drive shaft 33 and the gear are adjacent to the gear. Since the engagement with the gear to be released is disengaged and no load is applied to the drive shaft 33, the drive shaft 33 rotates forward by the weight of the paper feed unit 14. Along with this, the pickup arm 34 also rotates downward, and the rotation of the pickup arm 34 stops when the locking surface 60 of the locking piece 59 comes into contact with the receiving surface 62 of the locking rib 61. . Accordingly, it is possible to prevent the paper feeding unit 14 from hanging down and obstructing work such as maintenance, and when the upper frame 28 that is opened is closed, the pickup roller 13 is moved to the upper surface of the intermediate second frame 30. It is possible to reduce the impact of the collision and prevent the pickup roller 13 from being damaged.

  When the work such as maintenance is completed and the upper frame 28 is closed, the pickup roller 13 is in contact with the upper surface of the intermediate second frame 30. At this time, the motor starts reverse rotation under the control of the control unit, and the drive shaft 33 starts reverse rotation. As a result, the reverse rotation of the first pulley 36 is transmitted to the second pulley 37 via the belt drive mechanism 39 and is transmitted to the pickup arm 34 via the friction plates 42 and 43 and the coil spring 44. Start swinging upward. The pickup arm 34 stops in a substantially horizontal state and waits for the next image reading operation.

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic document conveying apparatus that separates a document placed on a sheet feeding tray one by one from the uppermost sheet and feeds it to a conveying path, and in particular, a rotationally driven separation roller and a roller of the separation roller The present invention can be applied to an automatic document feeder including an arm that is swingably supported by a shaft and a pickup roller that is rotatably supported at the tip of the arm.

1 is a schematic longitudinal sectional view showing an automatic document feeder 1 according to an embodiment of the present invention. FIG. 3 is a schematic longitudinal sectional view showing the automatic document feeder 1 in a state where an upper frame is opened. FIG. 3 is a schematic perspective view illustrating a configuration of a paper feeding unit 14. FIG. 3 is a schematic plan view showing a configuration of a paper feeding unit 14. FIG. 3 is a schematic cross-sectional view showing the internal structure of the paper feeding unit 14. FIG. 10 is a schematic longitudinal sectional view showing an automatic document feeder 83 according to a conventional example. FIG. 10 is a schematic plan view showing a configuration of a paper feeding unit 85 according to a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Automatic document feeder 5 Paper feed tray 6 Carriage path 9 Paper discharge tray 12 Separating roller 13 Pickup roller 19 Transport roller 28 Upper frame (upper cover)
31 Lower frame (main frame)
33 Drive shaft (roller shaft)
34 Pickup arm 35 Rotating shaft (roller shaft)
36 First pulley 37 Second pulley 38 Transmission belt 39 Belt transmission mechanism 42, 43 Friction plate 44 Coil spring 45 e-ring (ring member)
56 Recessed part 59 Locking piece 61 Locking rib P Original Pt Top paper

Claims (3)

A conveyance path that connects the paper feed tray and the paper discharge tray, a pickup roller that picks up the uppermost document from a bundle of documents placed on the paper feed tray, and the uppermost paper separated from the document supplied from the pickup roller An automatic document feeder comprising a separation roller that feeds out to a conveyance path and a conveyance roller that conveys the document downstream,
A pickup arm whose base end portion is swingably attached to the roller shaft of the separate roller and the roller shaft of the pickup roller is rotatably supported at the distal end portion, and is pivotally supported by the roller shaft of the separate roller. A belt transmission mechanism comprising: a first pulley that rotates; a second pulley that is pivotally supported by a roller shaft of the pickup roller; and a transmission belt that is stretched between the pulleys; and the second pulley. And a coil spring that presses the friction plate against the side of the pickup arm and the side of the pickup arm, respectively. The roller shaft of the separate roller is attached to an upper cover that can be opened and closed vertically with respect to the main body frame,
The automatic document according to claim 1, wherein a locking piece that engages with a locking rib provided on the upper frame and an upper cover being opened upward is provided on the pickup arm. Conveying device.   The pick-up arm is attached by fitting a recessed portion formed at the base end thereof to the roller shaft of the separate roller, and restricts the pick-up arm from moving in the axial direction of the roller shaft. The automatic document feeder according to claim 1, wherein the automatic document feeder is attached to the roller shaft.

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