JP2016000630A - Sheet feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeder for not generating a squeak caused between a sheet such as a document and a separation member, while having a durability-excellent and inexpensive constitution.SOLUTION: In a document feeding part, separation carrier roller pairs 44 comprise a separation roller 5 for rotating in the direction for carrying a document D and a driven roller 6 energized so as to be capable of pressure contact with the separation roller 5 and forming a separation nip part 33. The driven roller 6 comprises a small diameter part 6b having a first frictional coefficient and capable of pressure contact with the separation roller 5 and a large diameter part 6a having a second frictional coefficient smaller than the first frictional coefficient and positioned on the side of the small diameter part 6b. The separation carrier roller pairs 44 contact with the document D between the separation roller 5 and the large diameter part 6a by separating the separation roller 5 and the small diameter part 6b by the carried document D when the document D carried by the separation roller 5 and the small diameter part 6b is started to be carried by register roller pairs 7.

Description

  The present invention relates to a sheet feeding apparatus such as a document feeding apparatus used in an image reading apparatus such as a copying machine or a facsimile, or a feeding apparatus that feeds a sheet to an image forming unit of the image forming apparatus.

  Generally, a sheet feeding device such as a document feeding device in a copying machine, a facsimile, or a printer is configured to feed a sheet such as a document from a stacking tray to a separation unit by a pickup roller, and to feed the sheets one by one by separating the sheets at the separation unit. It has. Therefore, the separation unit of the sheet feeding apparatus is provided with a multifeed prevention mechanism so that the sheets can be separated and sent out one by one.

  As a retard roller used in such a double feed prevention mechanism, the roller surface has a textured surface composed of a mountain-shaped portion and a sea-shaped portion recessed from the mountain-shaped portion, and a textured surface composed of the mountain-shaped portion and the sea-shaped portion. A surface whose surface is constituted by finer uneven portions has been proposed (see Patent Document 1).

  In addition, as a separating member used in the above-described multifeed preventing mechanism, a member provided with a multifeed preventing member configured as follows has been proposed (see Patent Document 2). In this configuration, a polyurethane rubber material obtained by reaction-curing a polycaprolactone ester containing 30% by weight or more of a caprolactone component and having an average molecular weight of 1000 to 4000 and polyisocyanate is used as a multifeed preventing member.

Japanese Patent Laid-Open No. 2002-120952 Japanese Patent Laid-Open No. 11-334915

  However, in the case of the configuration described in Patent Document 1, the durability of the retard roller is low, and after the repetition (endurance) of the feeding operation, the manuscript and the retard roller rub against each other to generate abnormal noise (especially at low speed). There was a problem that "screaming") occurred. Further, in the case of the configuration described in Patent Document 2, there is a problem in that the production of the multifeed prevention member is costly and causes a significant cost increase.

  Accordingly, an object of the present invention is to provide a sheet feeding device that does not generate a so-called squeak that occurs between a sheet such as a manuscript and a separation member, while having an excellent and inexpensive configuration. And

  According to the present invention, in a sheet feeding apparatus, a feeding member that feeds stacked sheets, and a sheet that is disposed downstream of the feeding member in a sheet feeding direction and that is fed by the feeding member is 1 Separation and conveyance means for separating and conveying the sheets one by one, and a conveyance speed from the separation and conveyance means that is arranged downstream of the separation and conveyance means in the sheet conveyance direction and conveys the sheet conveyed from the separation and conveyance means further downstream And a separating member that forms a separation nip part by being urged by a predetermined urging force to the conveying rotating body. And the separation member has a first friction coefficient and a small-diameter portion that can be pressed against the transport rotating body, and a second friction coefficient smaller than the first friction coefficient. The small diameter portion located on the side of the small diameter portion The separating and conveying means is conveyed when a sheet conveyed by the conveying rotating body and the small diameter portion is started to be conveyed by the conveying means. Thus, the conveying rotating body and the small diameter portion are separated from each other, and the conveying rotating body and the large diameter portion are in contact with the sheet.

  According to the present invention, in a sheet feeding apparatus, a feeding member that feeds stacked sheets, and a sheet that is disposed downstream of the feeding member in a sheet feeding direction and that is fed by the feeding member is 1 Separation and conveyance means for separating and conveying the sheets one by one, and a conveyance speed from the separation and conveyance means that is arranged downstream of the separation and conveyance means in the sheet conveyance direction and conveys the sheet conveyed from the separation and conveyance means further downstream And a separating member that forms a separation nip part by being urged by a predetermined urging force to the conveying rotating body. And the separation member has a first friction coefficient and can be pressed against the conveying rotator, and the second friction coefficient smaller than the first friction coefficient and the depression. A convex portion located on the side of the When the sheet conveyed by the conveyance rotating body and the concave portion is started to be conveyed by the conveying means, the separation conveying means separates the conveyance rotary body from the concave portion by the conveyed sheet, The conveyance rotating body and the convex portion are in contact with the sheet.

  According to the present invention, the sheet separation function can be satisfied by starting the conveyance of the sheet by the portion having the large friction coefficient and the conveyance rotating body. When the leading edge of the sheet reaches the conveying means and is pulled, the sheet is conveyed by actively using a portion having a small friction coefficient and a conveying rotating body, which is particularly likely to occur when feeding a color document or the like. It is possible to prevent “squeal”. Accordingly, it is possible to prevent the so-called squeak that occurs between the sheet and the separation member, while having an excellent durability and an inexpensive configuration.

1 is a schematic cross-sectional view illustrating an image forming apparatus including a sheet feeding device (original feeding unit) according to an embodiment of the present invention. (A), (b) is a figure explaining the isolation | separation part with which the original feeding part in this embodiment was equipped. (A)-(c) is a figure explaining the separation conveyance roller pair with which the original feeding part in this embodiment was equipped, (d) is a figure explaining the separation conveyance roller pair in a modification. FIG. 3 is a schematic cross-sectional view along the document transport direction of the document feeding unit according to the present embodiment. (A)-(c) is operation | movement explanatory drawing in the case of reading the single side | surface of a document in the document feeding part in this embodiment. (A)-(c) is operation | movement explanatory drawing of the original feeding part in this embodiment. (A)-(d) is operation | movement explanatory drawing in the case of reading both surfaces of a document in the document feeding part in this embodiment.

[Image forming apparatus]
Hereinafter, an image reading apparatus and an image forming apparatus including the image reading apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a copying machine, which is an example of an image forming apparatus according to the present embodiment, taken along a sheet conveying direction.

  The image forming apparatus 40 such as a copying machine includes an apparatus main body 40a and an image reading device 43 provided on the upper part of the apparatus main body 40a. The image reading device 43 includes an image reading unit 102 and a document feeding unit (ADF) 1 as a sheet feeding device provided on the image reading unit 102. The image reading device 43 reads an image of the sheet-like document D, converts the image into an electric signal, and forms image data based on the electric signal. In the apparatus main body 40a, an image is formed on the sheet Sh based on an electrical signal or image data of the image.

  The document feeding unit 1 is configured to automatically convey a document (sheet) D before image reading placed on the document feeding tray 2 by a user or the like to the image reading unit 102. The image reading unit 102 receives reflected light of the light irradiated on the conveyed document D at the image reading position R (see FIG. 4), optically reads the document D and converts it into an electrical signal, and the electrical signal The image data (image reading information) is created based on the above.

  The apparatus main body 40a of the image forming apparatus 40 forms a copy image on the sheet Sh based on the image data. The apparatus main body 40 a operates the exposure unit 123 based on the electrical signal and image data of the image of the document D, and forms an electrostatic latent image on the surface of the rotating photosensitive drum 121. The electrostatic latent image is developed (supplied with toner) by the developing device 124 and becomes a toner image.

  On the other hand, sheet placement units 137a, 137b, 137c, and 137d loaded with sheets Sh of various sizes are disposed below the apparatus main body 40a. The sheets Sh of the sheet placement units 137a to 137d are sent out one by one by the feeding rollers 138a, 138b, 138c, and 138d, and are delivered to the conveying roller 131. The sheet Sh is transferred from the manual feed tray 137e to the feeding roller 138e.

  Thereafter, the sheet Sh is straightly corrected by the registration roller pair 136 and aligned with the toner image on the photosensitive drum 121, and is supplied between the photosensitive drum 121 and the transfer charger 125. The sheet Sh is transferred with the toner image on the photosensitive drum by the transfer charger 125 and separated from the photosensitive drum 121 by the separation charger 126. The cleaner 127 cleans the surface of the photosensitive drum 121 to which the toner image is transferred. The charger 122 charges the surface of the photosensitive drum 121 in preparation for the next exposure.

  On the other hand, the sheet Sh to which the toner image is transferred is conveyed to the fixing device 129 by the belt conveying unit 128, and is heated and pressurized by the fixing device 129 to fix the toner image on the surface. Then, the sheet Sh on which the toner image is fixed is discharged to the discharge tray 130.

  The image forming apparatus 40 described above is controlled by the control unit 132 having a CPU provided in the apparatus main body 40a. The photosensitive drum 121, the charger 122, the developing device 124, and the like constitute an image forming unit 133.

[Original Feeder]
Next, the document feeder 1 according to the present embodiment will be described with reference to FIGS. 4 to 7 are schematic cross-sectional views of the document feeding unit 1 according to the present embodiment taken along the document transport direction.

  As shown in FIG. 4, the document feeding unit 1 has a separation unit 31 and is configured to automatically feed a document (sheet) D placed on the document feeding tray 2 to the image reading position R. ing. The document feeding unit 1 extends in an elongated shape along a width direction (front-back direction in FIG. 4) orthogonal to the document feeding direction (sheet feeding direction: the direction of arrow A) of the document D on which an image is formed. An automatic document feeder 21 is provided.

  In the document feeding section 1, a registration roller pair (hereinafter referred to as a registration roller pair) 7, a registration roller pair 7, and a drive motor M1 (see FIG. 4) that rotationally drives the second conveyance roller pair 9 are disposed. . 4, M2 is a drive motor that rotationally drives the first holding roller pair 14, M3 is a drive motor that rotationally drives the reverse roller pair 15, and M4 is a drive motor that rotationally drives the second holding roller pair 16. , M5 is a drive motor that rotationally drives the discharge roller pair 11. Further, M6 is a drive motor that rotationally drives the separation roller 5. These drive motors M1 to M6 are driven and controlled by the control unit 132 (FIG. 1).

  4 is a switching solenoid that switches the feeding roller 4 between a position indicated by a solid line (hereinafter referred to as a solid line position) and a position indicated by a broken line (hereinafter referred to as a broken line position). Further, SL2 is a switching solenoid that moves the nip portion of the discharge roller pair 11 in and out of contact, and SL3 is a switching solenoid that moves the nip portion of the reverse roller pair 15 in and out of contact. SL4 is a switching solenoid that switches the first conveyance switching member 10 between a solid line position and a broken line position. These switching solenoids SL1 to SL4 are driven and controlled by the control unit 132 (FIG. 1).

  At the upper position on one end surface side (the right end surface side in the figure) of the automatic document feeder 21, the document feed tray 2 on which the documents D for reading images are placed in a stacked manner protrudes substantially horizontally in a cantilever state. It is attached as follows. The document feed tray 2 constitutes a sheet stacking unit on which sheets are stacked.

  A document discharge tray 3 is disposed below the document feed tray 2 to receive the document D that is read from the image reading position R and sent from the automatic document feeder 21. The document discharge tray 3 is attached so as to protrude substantially horizontally from a lower position on one end surface side in the automatic document transport unit 21. The document discharge tray 3 is configured such that the documents D discharged on the upper surface side are placed in a stacked manner. The document feed tray 2 and the document discharge tray 3 are arranged so as to face each other vertically with a predetermined interval in the vertical direction, and are in a superposed arrangement relationship in a plan view.

  Next, the single-sided reading operation in which the original feeding unit 1 conveys the original D to the image reading unit 102 and causes the image reading unit 102 to read only the front surface of the original D is shown in FIG. ) To (c) and FIGS. 6 (a) to (c). 6A to 6C, the driven roller 6 in the separation conveyance roller pair 44 is not shown.

  In FIG. 5A, a plurality of documents D are stacked on the document feed tray 2, and after the user selects a reading mode, the document is positioned on the upstream side of the feed roller 4. Presence or absence of the document D is determined by the document detection sensor S10.

  When the document D is detected, the feeding roller 4 is lowered from the broken line position to the solid line position by the switching operation of the switching solenoid SL1 under the control of the control unit 132, and the document D is transported on the entrance side in the automatic document transport unit 21. Send it to the path space AR. The document D conveyed by the rotational driving force of the feeding roller 4 to the separation roller 5 provided in the entrance-side conveyance path space AR is between the driven roller 6 spring-biased below the separation roller 5. Are separated one by one by the frictional force.

  The separation roller 5 and the driven roller 6 constitute a separation conveyance roller pair 44. The separation conveyance roller pair 44 is disposed downstream of the feeding roller 4 in the document conveyance direction (sheet feeding direction), and separates the document D fed by the feeding roller 4 one by one at the separation nip portion 33. A separating and conveying means for conveying is configured. The separation conveyance roller pair (separation conveyance means) 44 includes a separation roller 5 as a conveyance rotation body that rotates in a direction in which the document (sheet) D is conveyed, and a separation nip portion that is urged by the separation roller 5 with a predetermined urging force. And a driven roller 6 as a separating member for forming 33. The feeding roller 4 constitutes a feeding member that feeds the stacked originals D.

  The driven roller 6 that is in pressure contact with the separation roller 5 in the pair of separation and conveyance rollers 44 enters the second and subsequent originals D when two or more originals D are fed out by the feeding roller 4 and sandwiched between the separation nips 33. Is blocked by the gripping force of the driven roller 6. Then, only the first uppermost document D is sent out by the separation roller 5 and conveyed to the registration roller pair 7. That is, the driven roller 6 is driven to rotate by the frictional force of the separation roller 5 when only one document D is introduced into the separation nip portion 33, but two or more documents D are introduced into the separation nip portion 33. In this case, the gripping force is generated by stopping without being driven to rotate.

  As shown in FIG. 5B, the leading edge of the document D is abutted against the conveyance nip portion 32 of the resist roller pair 7 that is stopped. The leading edge of the document D conveyed to the registration roller pair 7 is detected by a flag (not shown) of the first document detection sensor S1 installed on the upstream side of the registration roller pair 7 in the document conveyance direction. The flag of the first document detection sensor S1 is arranged so as to cross both the transport paths P1 and P5 so that the document D passing through the transport paths P1 and P5 can be detected.

  The registration roller pair 7 is configured to stop rotation for a certain period of time by interrupting drive transmission by an electromagnetic clutch (not shown) provided in the drive motor M1. Since the document D is continuously conveyed by the separation roller 5 while the registration roller pair 7 stops rotating, the registration roller is in a state where a loop is formed at the leading end portion of the document D as shown in FIG. By contacting the nip portion of the pair 7, the skew of the document D is removed.

  Here, the control unit 132 (FIG. 1) sets the pair of registration rollers that are rotationally driven by the drive motor M1 rather than the conveyance speed of the separation conveyance roller pair (separation conveyance means) 44 having the separation roller 5 that is rotationally driven by the drive motor M6. Control is performed so that the conveyance speed of 7 is faster. The registration roller pair 7 is arranged downstream of the separation conveyance roller pair 44 in the document conveyance direction, and conveys the document D conveyed from the separation conveyance roller pair 44 further downstream, and has a higher conveyance speed than the separation conveyance roller pair 44. Conveying means is configured.

  A second document detection sensor S2 is disposed in the conveyance path P2 between the registration roller pair 7 and the first conveyance roller pair 8. An image reading position R is located in the conveyance path P3 between the first conveyance roller pair 8 and the second conveyance roller pair 9. The image reading position R is provided in the image reading unit 102 (see FIG. 1), and is disposed below the original platen glass (not shown) that is transparent and guides the original D. Since the image reading position R and the platen glass are known, detailed description thereof is omitted.

  In FIG. 5B, the document D on which the skew feeding (skew correction) has been performed is transported to the first transport roller pair 8 by the registration roller pair 7 as shown in FIG. The document D is read by the second document detection sensor S2 between the leading edge and the image reading position R, and sent to the image reading position R by the first conveying roller pair 8.

  The document D is read by the image reading position R while being conveyed by the first conveyance roller pair 8 and the second conveyance roller pair 9. The length of the document D in the transport direction is specified at the timing when the trailing edge passes through the second document detection sensor S2.

  As shown in FIG. 6A, on the downstream side of the second conveyance roller pair 9 in the document conveyance direction, a first conveyance switching member 10 is rotatably provided between a solid line position and a broken line position. Yes. The first conveyance switching member 10 includes a conveyance path P4 between the second conveyance roller pair 9 and the discharge roller pair 11, and a conveyance path P6 between the second conveyance roller pair 9 and the reverse roller pair 15. It is comprised so that rotation is possible.

  The first conveyance switching member 10 is configured to be switched by a switching solenoid SL4. The first transfer switching member 10 is normally configured to select the transfer path P4 at the solid line position, and to switch to the broken line position and select the transfer path P6 when the switching solenoid SL4 is turned on.

  As shown in FIG. 6A, the document D is guided to the transport path P4 by the first transport switching member 10 rotated to the solid line position, and is ejected by pushing away the second transport switching member 12 described later. Guided to the roller pair 11. Then, the document D is discharged onto the placement surface of the document discharge tray 3 by the discharge roller pair 11 as shown in FIGS. 6 (b) and 6 (c). When there are a plurality of documents D, this operation is repeated and sequentially discharged onto the placement surface of the document discharge tray 3 and stacked.

  The document feeder 1 sequentially transports the document D placed on the document feed tray 2 with the image forming surface facing upward from the uppermost document D to the image reading position R, and the document surface ( The front side is read and sequentially discharged and stacked on the document discharge tray 3 with the image forming surface facing downward. This operation can be performed if the document D has a size that can be placed on the document feed tray 2.

  Next, the document feeding unit 1 transports the front (front) surface of the document D to the image reading position R, and then reverses the document D so that the document D is reversed and transported to the image reading position R again. A double-sided reading operation in which the back side of the document D is read at the position R will be described. The front (front) surface of the document D is a surface on the upper side when the document D is placed on the document feed tray 2, and the back surface is a surface on the lower side. Note that the operation of the document feeding unit 1 to transport the front surface of the document D to the image reading position R is the same as the operation shown in FIGS. 5A to 6B.

  First, as shown in FIG. 6B, the downstream end of the transport path P4 and the upstream end of the transport path P5 between the discharge roller pair 11 and the registration roller pair 7 are a common part. . A discharge roller pair 11 is disposed in the common part. Inside the conveyance path P4 and the conveyance path P5, the second conveyance switching member 12 is rotatably arranged with the left side in FIG. 6B as the rotation center. The tip of the second transfer switching member 12 (the right side in FIG. 6B) reaches a common site between the downstream end of the transfer path P4 and the upstream end of the transfer path P5. The tip of the second transfer switching member 12 is inclined downward by its own weight so as to select the transfer path P5.

  Accordingly, the document D shown in FIG. 6A is transported by pushing away the second transport switching member 12. When the trailing edge of the document D reaches the discharge roller pair 11, the discharge roller pair 11 temporarily stops and then reverses from the state shown in FIG. As for the length of the document D, the leading edge and the trailing edge of the document D have already been detected by the detection operation of the second document detection sensor S2. Therefore, the stop and reverse rotation of the discharge roller pair 11 can be timed according to the length of the document D by the control unit 132 (see FIG. 1). The forward rotation of the discharge roller pair 11 is the rotation in the arrow direction indicated by the solid line in FIG. 4, and the reverse rotation is the rotation in the arrow direction indicated by the broken line.

  The document D is transported along the transport path P5 by the reverse rotation of the discharge roller pair 11 and the guidance of the second transport switching member 12. When the document D is guided from the transport path P4 to the transport path P5, the document D is switched back and turned upside down. For this reason, as shown in FIG. 7A, the document D becomes the leading edge when it is transported along the transport path P5, as it is the rear end when transported along the transport path P4. 7A to 7D, the driven roller 6 in the separation conveyance roller pair 44 is not shown.

  The third document detection sensor S3 disposed between the discharge roller pair 11 and the registration roller pair 7 detects the leading edge of the document D (the portion that was the trailing edge in the transport path P4). Then, the document D is continuously conveyed by the first holding roller pair 14 disposed on the downstream side of the third document detection sensor S3, and is conveyed again to the registration roller pair 7.

  Then, as shown in FIG. 7A, the document D is subjected to skew feeding (skew correction) by the stopped registration roller pair 7. When skew feeding is performed by the registration roller pair 7, the document D is again imaged by the registration roller pair 7 and the first conveyance roller pair 8 that have started to rotate, as shown in FIG. It is conveyed to the reading position R. At this time, since the document D has already been turned upside down, the back side is read by the image reading position R and is continuously conveyed by the second conveyance roller pair 9.

  In the conveyance path P4, the conveyance path P6 is branched at a portion slightly downstream of the second conveyance roller pair 9. Between the reverse roller pair 15 and the second transport roller pair 9 in the transport path P6, a transport path P8 leading from the reverse roller pair 15 to the discharge roller pair 11 is branched. A third transfer switching member 13 is provided at the branch point. The third conveyance switching member 13 has its tip (the right end in FIG. 7B) always facing downward due to its own weight, and guides the document D from the conveyance path P7 to the conveyance path P8.

  When the document D passes the image reading position R, the first transport switching member 10 has already been switched by the switching solenoid SL4 after the second document detection sensor S2 detects the leading edge of the document D as shown in FIG. The conveyance path P6 is selected by rotating to the position of the broken line to block the conveyance path P4. Accordingly, as shown in FIG. 7C, the document D is guided by the first transport switching member 10 and guided to the transport path P <b> 7 on the downstream side of the reverse roller pair 15.

  At this time, the document D is transported by pushing away the third transport switching member 13. Since the length of the document D is detected in advance, when the trailing end of the document D passes through the third conveyance switching member 13, the reverse roller pair 15 is temporarily stopped and the rotation direction is reversed. Then, the document D is reversed in the conveyance direction and is guided to the conveyance path P8 by the third conveyance switching member 13. At this time, the document D is switched back and is turned upside down. The forward rotation of the reverse roller pair 15 is the rotation in the arrow direction indicated by the solid line in FIG. 4, and the reverse rotation is the rotation in the arrow direction indicated by the broken line.

  Then, the document D is conveyed to the discharge roller pair 11 by the second holding roller pair 16 provided between the reverse roller pair 15 and the discharge roller pair 11 on the conveyance path P8. Finally, the document D is discharged to the document discharge tray 3 by the discharge roller pair 11 (FIG. 7D). Since the document D discharged to the document discharge tray 3 is turned upside down by the switchback conveyance while passing through the conveyance paths P6, P7, and P8, it is stacked with the front (front) side down.

  Hereinafter, a configuration provided with a separation conveyance unit (separation conveyance roller pair 44) and the like will be described with reference to FIGS. 2A and 2B are diagrams illustrating the separation unit 31 in the present embodiment. FIGS. 3A to 3C are diagrams for explaining in detail the separation conveyance roller pair 44 in the separation unit 31. FIG. 3D is a diagram for explaining a modification of the separation conveyance roller pair 44.

  That is, as shown in FIGS. 3A to 3C, the separation unit 31 includes a separation roller (conveyance rotating body) 5 for separating the fed originals D one by one, and an outer periphery of the separation roller 5. And a driven roller (separating member) 6 that is rotated while being in contact with the surface.

  The driven roller 6 has a large diameter portion 6a and a small diameter portion 6b formed continuously in the axial direction. That is, the driven roller 6 as the separation member has a small diameter portion 6b having a first friction coefficient and capable of being pressed against the separation roller 5, and a small diameter portion having a second friction coefficient smaller than the first friction coefficient. And a large-diameter portion 6a having a larger diameter than the small-diameter portion 6b located on the side of the 6b (both sides in the present embodiment). The driven roller 6 has a small diameter portion 6b and large diameter portions 6a located at both ends of the small diameter portion 6b in the axial direction. The small diameter portion 6b is brought into contact with the driven roller 6 and is rotated with the separation roller 5.

The roller μ (friction coefficient μ) and the radius size of the large-diameter portion 6a and the small-diameter portion 6b in the separating and conveying roller pair 44 are expressed by the following equations (1) and (2).
(1) Roller μ of large diameter portion 6a <roller μ of small diameter portion 6b
(2) Radius of large-diameter portion 6a−radius of small-diameter portion 6b ≧ 0.5 mm

  With this configuration, when separating the fed documents D one by one, separation is performed by the separation roller 5 and the small-diameter portion 6 b of the driven roller 6. By increasing the roller μ of the small diameter portion 6b, it is possible to satisfy the function of good separability. In addition, said Formula (1), (2) is applied similarly to the convex part 60a and the recessed part 60b of the sheet | seat member 60 in the modification mentioned later.

  When the separated document D is conveyed by the registration roller pair 7, the document D is positively brought into contact with the separation roller 5 and the large-diameter portion 6 a due to the rigidity (roughness) of the document D, and the separation roller 5 and the small-diameter portion 6 a. The portion 6b is separated (FIG. 3B), and the contact between the document D and the small diameter portion 6b is reduced. By making the roller μ of the large-diameter portion 6a of the driven roller 6 as small as possible, an abnormal noise (squeaking) due to rubbing between the driven roller 6 and the document D that occurs when the document D is conveyed by the registration roller pair 7 is generated. Can be reduced.

  As described above, in the present embodiment, the separation conveyance roller pair (separation conveyance means) 44 is conveyed when the document D conveyed by the separation roller 5 and the small diameter portion 6 b is started to be conveyed by the registration roller pair 7. The document D separates the separation roller 5 from the small diameter portion 6b. Then, the separation roller 5 and the large diameter portion 6a are in contact with the document D. That is, the document D is started to be conveyed by the separation roller 5 and the small diameter portion 6b, and when the leading end of the document D reaches the registration roller pair 7 and is pulled, the document D is conveyed by the separation roller 5 and the large diameter portion 6a.

  Accordingly, the original separation function can be satisfied by starting the conveyance of the original D with the small diameter portion 6b having a large friction coefficient and the separation roller 5. When the leading edge of the document D reaches the registration roller pair 7 and is pulled by the registration roller pair 7 whose conveyance speed is faster than the separation conveyance roller pair 44, the large-diameter portion 6a having a small friction coefficient and the separation roller 5 are positively moved. The original document D is conveyed by using it. Thus, it is possible to effectively prevent “squeal” that is likely to occur particularly when a color original is fed. Thereby, it is possible to prevent the squeal generated between the document D and the driven roller 6 from occurring while having an excellent durability and an inexpensive configuration.

  As shown in FIG. 2, the registration roller pair 7 has a conveyance nip portion 32 for nipping and conveying the conveyed document D, and the height direction position of the conveyance nip portion 32 is the separation conveyance roller pair. 44 is located below the position in the height direction of the separation nip 33. That is, since the conveyance nip portion 32 is located below the separation nip portion 33, a conveyance force F1 is generated in the conveyance direction of the document D. Then, a force F1 × cos θ in the direction opposite to the compression force Po of the spring 35 pressing the driven roller 6 via the roller holder 34 is generated.

  As a result, the driven roller 6 can be lowered downward, and the contact between the document D and the small diameter portion 6b of the driven roller 6 is further reduced. The relationship between the positions in the height direction of the transport nip portion 32 and the separation nip portion 33 is similarly applied to modified examples described later.

  Next, the numerical value of the step (radius difference) between the large diameter portion 6a and the small diameter portion 6b necessary for further improving the above effect will be described.

  That is, as described above, the separation roller 5 and the small-diameter portion 6b are separated from each other to reduce contact between the original D and the small-diameter portion 6b. However, various types of original D are conveyed and squeal is generated. The easy-to-work document D is a color document, and this color document is often printed on thick paper.

The posture of the document D during separation may be bent downward to the small diameter portion 6b by the thickness of one document as in the document D1 indicated by a broken line in FIG. For this reason, in consideration of the thickness of the document D1 and the deflection amount of the document D1, it is preferable to have a step based on the following equation.
0.25 mm: Thick paper color original thickness × 2: Deflection amount of one original document = 0.5 mm

  Considering that the user passes various documents, it can be seen that a step of 0.5 mm (radius difference) is necessary. Further, even when a sheet member (separation sheet) 60 described later contacts the outer peripheral surface of the separation roller 5, the present invention can be similarly applied only by changing the roller to a sheet member.

  That is, as shown in the modification of FIG. 3D, the surface (convex portion 60a) protruding from the other surface (concave portion 60b) of the sheet member 60 protrudes 0.5 mm from the other surface (concave portion 60b). Can be configured. The sheet member 60 in the present modified example constitutes a separating member that integrally has a concave portion 60b and a convex portion 60a on the side of the concave portion 60b (both sides in the present modified example), and that makes the concave portion 60b slidably contact the separation roller 5. To do.

  That is, in this modification, the sheet member (separation member) 60 has a first friction coefficient and a concave portion 60b that can be pressed against the separation roller 5, and a second friction coefficient smaller than the first friction coefficient. And a convex portion 60a located on the side of the concave portion 60b. Then, when the document D transported by the separation roller 5 and the recess 60b is started to be transported by the registration roller pair 7, the separation transport roller pair 44 causes the separation roller 5 and the recess 60b to be moved by the transported document D. The separation roller 5 and the convex portion 60a are in contact with the original D.

  That is, the conveyance of the document D is started by the separation roller 5 and the concave portion 60b, and when the leading end of the document D reaches the registration roller pair 7 and is pulled, the separation roller 5 and the convex portion 60a convey the document D. Even with such a configuration, the same effects as those of the above-described embodiment can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Sheet feeding apparatus (original feeding part) / 2 ... Sheet stacking part (original feeding tray) / 4 ... Feeding member (feeding roller) / 5 ... Conveyance rotating body (separating roller) / 6 ... Separating member ( Driven roller) / 6a ... large diameter part / 6b ... small diameter part / 7 ... conveying means (registration roller pair) / 32 ... conveying nip part / 33 ... separation nip part / 44 ... separation conveying means (separation conveying roller pair) / 60 ... Separation member (sheet member) / 60a ... Convex part / 60b ... Concave part / D ... Sheet (original)

Claims (6)

A feeding member for feeding the stacked sheets;
Separating and conveying means that is disposed downstream of the feeding member in the sheet feeding direction and separates and conveys the sheets fed by the feeding member one by one;
A transport unit that is disposed downstream of the separation transport unit in the sheet transport direction and transports the sheet transported from the separation transport unit further downstream; a transport unit having a transport speed faster than the separation transport unit;
The separation conveyance unit includes a conveyance rotation body that rotates in a direction in which a sheet is conveyed, and a separation member that is urged by the conveyance rotation body with a predetermined urging force to form a separation nip portion.
The separation member has a small diameter portion that has a first friction coefficient and can be press-contacted with the conveying rotating body, and has a second friction coefficient that is smaller than the first friction coefficient and is located on a side of the small diameter portion. A large-diameter portion having a larger diameter than the small-diameter portion located,
When the sheet conveyed by the conveying rotating body and the small diameter portion is started to be conveyed by the conveying means, the separating conveying means separates the conveying rotating body from the small diameter portion by the conveyed sheet. The conveyance rotating body and the large diameter portion are in contact with the sheet.
A sheet feeding apparatus characterized by that. The separation member is a driven roller that has the large-diameter portion at both axial ends of the small-diameter portion and rotates the conveyance rotating body by bringing the small-diameter portion into contact with each other.
The sheet feeding apparatus according to claim 1. A feeding member for feeding the stacked sheets;
Separating and conveying means that is disposed downstream of the feeding member in the sheet feeding direction and separates and conveys the sheets fed by the feeding member one by one;
A transport unit that is disposed downstream of the separation transport unit in the sheet transport direction and transports the sheet transported from the separation transport unit further downstream; a transport unit having a transport speed faster than the separation transport unit;
The separation conveyance unit includes a conveyance rotation body that rotates in a direction in which a sheet is conveyed, and a separation member that is urged by the conveyance rotation body with a predetermined urging force to form a separation nip portion.
The separation member is located on a side of the recess having a first friction coefficient and having a recess that can be press-contacted to the conveying rotating body, and a second friction coefficient that is smaller than the first friction coefficient. A convex portion, and
When the sheet conveyed by the conveyance rotating body and the concave portion is started to be conveyed by the conveying means, the separation conveying means separates the conveyance rotary body from the concave portion by the conveyed sheet, The conveyance rotating body and the convex portion are in contact with the sheet.
A sheet feeding apparatus characterized by that. The separation member is a sheet member that integrally includes the concave portion and the convex portions on both sides of the concave portion, and makes the concave portion slide in contact with the transport rotating body.
The sheet feeding apparatus according to claim 3. The transport means includes a transport nip portion that sandwiches and transports the transported sheet,
The height direction position of the conveyance nip portion is below the height direction position of the separation nip portion of the separation conveyance means,
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. A sheet stacking unit on which sheets are stacked;
In the sheet stacking unit, documents on which images are formed are stacked as sheets.
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus.

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