JP2007031122A - Sheet feeding device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeding device capable of feeding various sorts of sheets at stable timings irrespective of the device environment, and an image forming device equipped with it. <P>SOLUTION: Arrangement according to the invention includes a feed roller 18 capable of being driven into rotation, a separation roller 101 able to rotate with a rotational torque at or over the prescribed level, and a middle plate 16 to abut the sheets placed in a stack to the feed roller, wherein the the feed roller 18 has a rubber part 18A to feed the sheet when it abuts to the sheet and rotates and a front rotary part 18B1 which slips when abutting to the sheet and rotating and rotates the separation roller 101 when abutting to the separation roller 101 and rotating, and the front rotary part 18B1 is positioned ahead of the rubber part 18A about the rotating direction while the front rotary part 18B1 and the rubber part 18A are positioned in region overlapping in the sheet width direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet feeding apparatus that separates and feeds sheets stacked and placed on a sheet placing section one by one using a feeding member and a separating member, and an image forming apparatus such as a printer, a copy, and a facsimile using the sheet feeding apparatus.

  In recent years, there has been an increasing demand for image formation not only on plain paper but also on various sheets other than paper, such as cardboard, OHP sheets, envelopes, cards, films, postcards, and stickers, with a printer or the like. Therefore, there is a demand for a sheet feeding apparatus that can reliably separate and feed one sheet at a time even if the types of sheets are varied.

  As the sheet separation method, there is a retard separation method comprising a feeding roller and a separation roller. This separates and feeds only the sheet abutting on the feeding roller by nipping the sheet between a feeding roller that rotates in the sheet feeding direction and a separation roller that rotates in the sheet returning direction. . This retard separation system has an advantage of high separation performance for various sheets.

  However, when the sheet enters the nip portion between the feeding roller and the separation roller, there is a possibility that the leading end of the sheet hits and the leading end is bent or creased. Therefore, a paper feeding device has been proposed in which ribs that rotate integrally with the feeding roller on both sides in the sheet width direction of the feeding roller and have a slightly larger diameter than the feeding roller are disclosed (for example, Patent Document 1). .

  In the sheet feeding device, when the feeding roller rotates, the rib portion contacts the sheet before the rubber portion contacts the sheet, and further contacts the separation roller. And even if it rotates in the state which the rib contact | abutted to the sheet | seat, it slips, and in the state contact | abutted with the separation roller, a separation roller is rotated in a sheet feeding direction. Accordingly, before the rubber portion of the feeding roller contacts the sheet and feeds the sheet, the rib contacts the separation roller and rotates the separation roller. Therefore, the sheet enters the nip portion between the feeding roller and the separation roller in a state where the separation roller is rotated in the sheet feeding direction. Therefore, it is possible to effectively prevent the leading edge from being bent when the leading edge of the sheet enters the nip portion.

JP-A-10-226428

  However, in the configuration shown in Patent Document 1 described above, when feeding a sheet having deteriorated flatness or a curled sheet that is left in an environment such as low temperature and low humidity or high temperature and high humidity, the following There was such a problem.

  That is, since the ribs provided on the feeding roller are on both sides of the rubber part, the sheet may come into contact with the rubber part between the left and right ribs when the ribs are in contact with the sheet and rotating. There is. There is no problem when the flatness of the sheet is good, but in the case of a sheet with poor flatness or a curled sheet, the rubber part between the left and right ribs tends to come into contact. For this reason, the timing of contacting the rubber portion when the feeding roller rotates may not be constant between a sheet having good flatness and a sheet having poor flatness.

  In that case, a deviation occurs in the sheet feeding timing. For this reason, in order to solve this, it is necessary to increase the sheet feeding interval to some extent.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet feeding apparatus capable of feeding various sheets at a stable timing regardless of the apparatus environment, and an image forming apparatus using the sheet feeding apparatus. To do.

  In order to solve the above-described problems, the present invention provides a sheet feeding apparatus that separates and feeds sheets stacked and placed one by one by nipping sheets between a feeding rotating body and a separating rotating body. A feeding rotator, a separating rotator that is rotatable with a rotational torque equal to or greater than a predetermined value, and sheet placing means for bringing the stacked and placed sheets into contact with the feeding rotator, wherein the feeding rotator is A feeding region that feeds the sheet when rotating in contact with the sheet; the slipping area when rotating in contact with the sheet; and A non-feeding area for rotating the separation rotating body, and the non-feeding area is disposed in front of the feeding area in the rotation direction, and the non-feeding area and the feeding area are in a sheet feeding direction. Placed in a region that overlaps in a direction perpendicular to The features.

  In the present invention, since the non-feeding area of the feeding rotator and the feeding area are arranged in an overlapping area in a direction orthogonal to the sheet feeding direction, the non-feeding area of the feeding rotator is arranged on the sheet. It is possible to eliminate the state in which the feeding area is in contact with the sheet when the sheet is in contact. Therefore, the sheet can be fed at a stable timing regardless of the type, flatness, and apparatus environment of the sheet. For this reason, the sheet feeding timing can be shortened, and the image can be formed at high speed.

  Next, a sheet feeding apparatus according to an embodiment of the present invention will be described together with an image forming apparatus using the sheet feeding apparatus.

[First Embodiment]
{Image forming device}
FIG. 1 is a schematic sectional view of a color laser printer that is an image forming apparatus according to the first embodiment.

  The image forming apparatus 100 includes four image forming stations that form yellow, magenta, cyan, and black color images from the bottom in the vertical direction in the apparatus body. In the image forming station, a photosensitive drum 1 (1a, 1b, 1c, 1d) as an image carrier is individually rotated counterclockwise in the drawing by a driving unit (not shown). Around each photosensitive drum 1, there are a charging device 2 (2a, 2b, 2c, 2d), a developing device 4 (4a, 4b, 4c, 4d), and a cleaning device 6 (6a, 6b, 6c, 6d). Etc. are arranged.

  The photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 are detachably attached to the apparatus main body as process cartridges 7 (7a, 7b, 7c, and 7d) that are integrally formed as cartridges, thereby forming an image. Means.

  When forming an image, the surface of the rotating photosensitive drum 1 is uniformly charged by the charging device 2, and laser light corresponding to the image signal is emitted from the scanner unit 3 (3a, 3b, 3c, 3d) to the surface. Thus, an electrostatic latent image is formed. The latent image is developed with toner by the developing device 4 to be visualized. Then, in synchronization with the image formation, a sheet fed from a sheet feeding device 200 described later via a pair of conveying rollers 19 is electrostatically attracted and conveyed by the transfer conveying belt 5.

  The transfer / conveying belt 5 is stretched around four rollers including a driving roller 13, driven rollers 14a and 14b, and a tension roller 15, and the sheets adsorbed thereto are all photosensitive drums 1a, 1b, 1c and 1d. It is conveyed in contact with. At this time, by applying a transfer bias to the transfer roller 12 (12a, 12b, 12c, 12d), the toner image on each photosensitive drum 1 is transferred to a sheet to form a color image. On the other hand, the toner remaining on the photosensitive drum 1 without being transferred to the sheet is collected by the cleaning device 6.

  The sheet onto which the toner image has been transferred is conveyed to the fixing unit 20 where the toner image is heated and fixed, and then discharged and stacked on the discharge unit 24 at the top of the apparatus by the discharge roller pair 23.

{Sheet feeding device}
Next, a sheet feeding apparatus 200 that feeds sheets to the image forming unit will be described with reference to FIGS. 2 is an explanatory perspective view of the sheet feeding device, FIG. 3 is an explanatory perspective view when the feeding roller is viewed from below, and FIG. 4 is an explanatory side sectional view of the sheet feeding device.

  As shown in FIG. 2, a feeding roller 18 as a feeding rotating body that can be driven and rotated, a separation roller 101 as a separating rotating body that can be rotated by a rotational torque that is greater than or equal to a predetermined value, and a stacked sheet are fed. An intermediate plate 16 is provided as a sheet placing unit that is brought into contact with the roller 18.

  The feeding roller 18 is fixed to the feeding shaft 102. The feed shaft 102 is controlled to rotate once by a drive unit (not shown), and the feed roller 18 is driven to rotate once in accordance with the feed timing.

  The intermediate plate 16 is swingably supported with respect to the cassette tray 103 and, as shown in FIG. 4, is urged by a coil spring 104 from below to feed the sheets S stacked on the upper surface of the intermediate plate 16. The roller 18 is urged with a predetermined contact pressure.

  The separation roller 101 according to the present embodiment is configured integrally with the torque limiter 101A and rotates when a predetermined rotational torque or more is applied, but the separation roller 101 itself is not rotationally driven. However, the separation roller 101 may be a so-called retard roller that drives in a direction to return the sheet.

  As shown in FIG. 3, the separation roller 101 includes a torque limiter 101A and a rubber portion 101B fixed to the outer periphery of the torque limiter 101A. A shaft 101A1 of the torque limiter 101A is formed by a holder member 105 (see FIG. 4). Is retained. Thereby, it rotates when a predetermined or higher rotational torque is applied.

  As shown in FIG. 4, the holder member 105 is biased substantially upward in the vertical direction with respect to the sheet guide member 107 by a coil spring 106. The holder member 105 is held by the rail portion so as to be movable in a substantially vertical direction with respect to the sheet guide member 107. As shown in FIG. 2, the sheet guide member 107 is fixed to the cassette tray 103 by two right and left screws 108A and 108B.

(Conveying area and non-conveying area of feeding roller)
The feeding roller 18 feeds a sheet when rotating in contact with the sheet, and non-feeding that does not feed the sheet by slipping against the sheet when rotating in contact with the sheet And have a region.

  Specifically, as shown in FIGS. 3 and 4, the feeding roller 18 has a rubber part 18A and a holder part 18B, and the rubber part 18A is fixed to the holder part 18B. The rubber portion 18A serves as a feeding area for feeding the sheet when rotating in contact with the sheet. Further, the holder portion 18B is provided with a front rotating portion 18B1, which is a non-feeding region in which the sheet slips even if it rotates in contact with the sheet and does not feed the sheet.

  The front rotating portion 18B1 is disposed in front of the rubber portion 18A and adjacent to the rubber portion 18A in the rotation direction of the feeding roller 18. The front rotating portion 18B1 is disposed so as to contact the separation roller 101 when the feeding roller 18 rotates and the rubber portion 18A contacts the sheet on the intermediate plate 16. As described above, the front rotating portion 18B1 slips even if it rotates while in contact with the sheet. However, when it rotates in contact with the separation roller 101, it rotates the separation roller 101.

  As shown in FIG. 3, the front rotating portion 18B1 is disposed in a region overlapping the rubber portion 18A in the sheet width direction, which is a direction orthogonal to the sheet feeding direction. In the present embodiment, a plurality of rib portions are formed in the sheet width direction, and the rib portions constitute a front rotating portion.

  Here, the sheet feeding operation by the feeding roller 18 configured as described above will be described with reference to FIGS.

  The state of FIG. 4 is an initial state before sheet feeding. At this time, the front rotating portion 18B1 faces the sheet on the intermediate plate 16. When a sheet feeding signal is input from this state, the feeding roller 18 is rotationally driven from a driving unit (not shown) via a driving shaft. With this rotation, the height position restricting means (not shown) of the sheets S stacked on the upper surface of the intermediate plate 16 is released, and the sheets S stacked on the front rotating portion 18B1 of the feeding roller 18 and the upper surface of the intermediate plate 16 are released. Abut.

  The holder portion 18B is made of a thermoplastic plus tip such as polyacetal. The friction coefficient between the front rotation portion 18B1 which is a part of the holder portion 18B and the sheet S is lower than the friction coefficient between the sheets S. For this reason, even if the front rotating portion 18B1 comes into contact with the sheet S, the sheet S is not fed by slipping along with the rotation of the feeding roller 18.

  When the feeding roller 18 rotates, the front rotating portion 18B1 comes into contact with the separation roller 101, and at the same time, the rubber portion 18A comes into contact with the sheet S as shown in FIG. When the feeding roller 18 rotates in this state, the friction coefficient between the front rotating portion 18B1 and the separating roller 101 is sufficiently high against the torque limiter 101A1 as the feeding roller 18 rotates because the friction coefficient of the rubber portion 101B is sufficiently high. Thus, the separation roller 101 is driven to rotate.

  At this time, the rubber portion 18A feeds the sheet S. For this reason, as shown in FIG. 6, when the leading edge of the sheet enters the nip portion between the feeding roller 18 and the separation roller 101 (hereinafter referred to as “separation nip portion”), the separation roller 101 is in a rotating state. It has become. Therefore, the sheet S entering the separation nip portion does not have a feeding failure such as a bent end or a mesh.

  The rubber portion 18A and the front rotation portion 18B1 are disposed in an overlapping region in the sheet width direction, and are disposed at different positions in the rotation direction of the feeding roller. For this reason, even if the sheet is left in an environment such as low temperature and low humidity or high temperature and high humidity and the flatness is deteriorated or the sheet has a curled tip, the front rotating portion 18B1 is in contact with the sheet. The sheet does not contact the rubber part 18A.

  Therefore, the sheet is not inadvertently fed, the double feeding is prevented, and the timing at which the rubber portion 18A comes into contact with the sheet due to the rotation of the feeding roller 18 is stabilized. For this reason, the sheet feeding interval can be shortened, and high-speed continuous image formation becomes possible.

  In the present embodiment, the shape of the feeding roller 18 is a so-called half-moon shape. As described above, in the case of the half-moon shape, it can be easily configured that the feeding roller 18 and the separation roller 101 do not contact at the initial position shown in FIG. Therefore, in this case, there is an advantage that there is no resistance to the downstream conveying means and it does not cause image defects such as shock and blurring.

  However, the front rotating portion 18B1 of the feeding roller 18 needs to have a shape that does not cause damage such as scratches when contacting the sheet S and the separation roller 101. If the cross-sectional shape of the front rotating part 18B1 is substantially the same diameter as the rubber part 18A, there is no position fluctuation of the separation roller 101 when the sheet leading edge reaches the separation nip part, and more stable feeding performance is realized. it can. Accordingly, the feeding roller 18 is not necessarily a half-moon shaped roller, and may be circular.

[Second Embodiment]
Next, a sheet feeding apparatus according to the second embodiment will be described with reference to FIG. Note that the basic configuration of the apparatus of this embodiment is the same as that of the above-described embodiment, and thus a duplicate description is omitted. Here, a configuration that is a feature of this embodiment will be described. Moreover, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above.

  The difference between the sheet feeding apparatus of the present embodiment and the first embodiment is that roller members 109A and 109B are arranged on both sides of the feeding roller 18 in the sheet width direction. The roller members 109A and 109B are rotatably held on the rotation shaft of the feeding roller 18, and come into contact with the separation roller 101 when the feeding roller 18 is not driven to rotate.

  The diameters of the roller members 109A and 109B are smaller than the diameters of the rubber part 18A and the front rotating part 18B1 of the feeding roller 18. For this reason, the front rotating portion 18B1 does not interfere with the separation roller 101 and the rubber portion 18A does not interfere with the sheet S.

  In this embodiment, when the feeding roller 18 is not rotationally driven, even if the sheet stacked on the intermediate plate 16 may be conveyed with the preceding sheet, the roller member The sheet is stopped by the nip between 109A and 109B and the separation roller 101. Therefore, the sheet can be prevented from being further fed. In this way, the sheet double feed prevention performance is further enhanced than in the first embodiment.

  Since the roller members 109A and 109B are rotatably held by the feeding roller 18, the resistance force to the conveying means downstream of the roller members 109A and 109B is sufficiently small, and may cause image defects such as shock and blurring. Absent.

[Third Embodiment]
Next, a sheet feeding apparatus according to a third embodiment will be described with reference to FIGS. The basic configuration of the apparatus according to the present embodiment is also the same as that of the first embodiment described above, and a duplicate description is omitted. Here, the configuration that is a feature of the present embodiment will be described. Moreover, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above.

  The difference between the sheet feeding apparatus of this embodiment and the first embodiment is that a roller member 110 is provided instead of the roller members 109A and 109B. The roller member 110 is disposed in front of the front rotating portion 18B1 and adjacent to the front rotating portion 18B1 in the rotation direction of the feeding roller 18. The roller member 110 is rotatably provided in a region overlapping the rubber portion 18A and the front rotation portion 18B1 in the sheet width direction.

  The roller member 110 is in contact with the separation roller 101 when the feeding roller 18 is not driven to rotate.

  Even in this embodiment, as in the second embodiment, when the feeding roller 18 is not driven to rotate, a sheet stacked on the intermediate plate 16 is conveyed along with the preceding sheet. Even if there is, the sheet is stopped by the nip between the roller member 110 and the separation roller 101. For this reason, further double feeding is prevented, and the sheet double feeding prevention performance is improved as compared with the first embodiment.

  Since the roller member 110 is rotatably held by the feeding roller 18, the resistance force to the conveying means downstream thereof is sufficiently small and does not cause image defects such as shock and blurring.

1 is a side sectional view showing a schematic configuration of an image forming apparatus. FIG. 3 is an upper perspective view illustrating the sheet feeding apparatus according to the first embodiment. FIG. 3 is a lower perspective view illustrating the sheet feeding apparatus according to the first embodiment. FIG. 3 is a side cross-sectional view illustrating the sheet feeding apparatus according to the first embodiment. FIG. 5 is a side cross-sectional view illustrating a feeding operation of the sheet feeding apparatus according to the first embodiment. FIG. 5 is a side cross-sectional view illustrating a feeding operation of the sheet feeding apparatus according to the first embodiment. FIG. 6 is an upper perspective view illustrating a sheet feeding device according to a second embodiment. FIG. 10 is a lower perspective view illustrating a sheet feeding apparatus according to a third embodiment. FIG. 10 is a side sectional view illustrating a sheet feeding apparatus according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS S ... Sheet 1 ... Photoconductor drum 2 ... Charging apparatus 4 ... Developing apparatus 5 ... Transfer conveyance belt 6 ... Cleaning apparatus
12… Transfer roller
13… Drive roller
14a, 14b ... driven roller
15… Tension roller
16… Middle plate
18… Feeding roller
18A ... Rubber part
18B ... Holder part
18B1 ... Front rotating part
20… Fixing part
23… discharge roller pair
24… discharge section
100 ... Image forming apparatus
101… Separation roller
101A ... Torque limiter
101A1 axis
101B ... Rubber part
102 ... Feed axis
103… cassette tray
104… Coil spring
105… Holder member
106… coil spring
107… Sheet guide member
108A, 108B ... screw
109A, 109B ... Roller member
110… Roller member
200 ... Sheet feeding device

Claims (6)

In a sheet feeding apparatus that separates and feeds sheets stacked and stacked by nipping sheets by a feeding rotating body and a separating rotating body,
A feeding rotating body capable of driving rotation;
A separation rotating body that can be rotated by a rotational torque of a predetermined value or more;
Sheet placing means for bringing the stacked sheets into contact with the feeding rotating body;
Have
The feeding rotating body feeds a sheet when rotating in contact with the sheet, slips against the sheet when rotating in contact with the sheet, and contacts the separation rotating body. A non-feeding region for rotating the separation rotating body when rotating,
The non-feeding area is arranged in front of the feeding area in the rotation direction, and the non-feeding area and the feeding area are arranged in an area overlapping in a direction perpendicular to the sheet feeding direction. Sheet feeding device. The sheet feeding apparatus according to claim 1, wherein the feeding rotating body has a half-moon shape. The sheet feeding apparatus according to claim 1, wherein the feeding area and the non-feeding area of the feeding rotating body have substantially the same diameter. The feeding rotating body is a roller member that is rotatable on a rotation axis of the feeding area on both sides in a direction orthogonal to the sheet feeding direction and has a smaller diameter than the feeding area and the non-feeding area. Have
The sheet feeding device according to claim 1, wherein the roller member is in contact with the separation rotating body when the feeding rotating body is stopped. The feeding rotating body has a roller member provided rotatably,
The sheet feeding device according to claim 1, wherein the roller member is in contact with the separation rotating body when the feeding rotating body is stopped. In an image forming apparatus that forms an image by feeding a sheet,
A sheet feeding device according to any one of claims 1 to 5,
Image forming means for forming an image on a fed sheet;
An image forming apparatus comprising:

Images