JP2004083270A - Sheet feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a smooth feeding operation of a feeding device using separation claws, without having a sheet of paper getting caught on other members by forcibly reducing problematic bending of the sheet. <P>SOLUTION: The sheet feeder is provided with a flapper 32 inside a feeding cassette 5 and feeding claws 38 on both ends of the front end part of the flapper 32. Above the flapper 32, two pickup rollers 40 are provided with predetermined intervals therebetween and mounted on a shaft 42. A pressing roller 41 is provided on the shaft 42 between the separating claws 38 and the pickup rollers 40 which forcibly presses the bending of the sheet occurring between the separating claws 38 and the pickup rollers 40 upon a feeding operation, thereby preventing the sheet from bending unnecessarily and getting caught on other members. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sheet feeding device used for an image forming apparatus such as a copying machine and a facsimile machine.
[0002]
[Prior art]
In the above-described paper feeder, a plurality of sheets of paper are stacked in advance in a paper feed cassette, and are fed one by one as needed. As such a paper feeding method, separation pawls are set at both ends of the leading edge of the paper, and a pickup roller is rotated on the upper surface of the paper to feed the paper in the paper feeding direction. There is a way to do that.
[0003]
In a paper feeding method using such a separation claw, various measures are taken to cope with a paper feeding trouble. For example, in Japanese Patent Application Laid-Open No. 7-101572, in a feeding apparatus provided with a feeding auxiliary roller used for feeding a large-sized sheet in addition to a plurality of feeding rollers, a plurality of feeding rollers are provided. There is described a feeding device in which a pressing plate for pressing a sheet against a feeding roller and a feeding auxiliary roller do not come into contact with each other so that a pressing force does not differ between the feeding rollers. It is described that since the feeding auxiliary roller does not abut on the pressure plate, the pressing force on the feeding roller is not biased by the contact of the feeding auxiliary roller with the pressing plate.
[0004]
Japanese Patent Application Laid-Open No. H11-139587 discloses an example using such an auxiliary paper feed roller. In this publication, an auxiliary paper feed roller having the same shape as the drive shaft of the paper feed roller is separated from the uppermost paper by a small distance in a state where the paper feed roller is in contact with the uppermost paper. Is fixed. It is described that by providing such a small interval, the large-sized paper can be normally fed by being slightly brought into contact with the auxiliary paper feed roller due to the bending generated when the large-sized paper is fed.
[0005]
[Problems to be solved by the invention]
In the prior art described above, studies have been made on how to apply the pressing force to the paper feed roller in a well-balanced manner to normally operate the paper feed. However, the separation sheet feeding method using the separation claw has a problem peculiar to this method in that the sheet is caught on the separation claw and greatly bent at the start of the sheet feeding operation. That is, when the paper feed roller feeds the paper in a state where the paper comes in contact with the separation claw, both ends of the leading end of the paper are largely bent upward while being caught by the separation claw. Then, when the sheet is further fed and the amount of deflection increases to a certain extent, both ends of the leading end of the sheet are separated from the separation claws and fed as it is.
[0006]
When the paper is greatly bent, there is a possibility that the paper may be caught by a member disposed above the paper. Therefore, in the related art, the paper is prevented from being caught by disposing no member or the like in the bending region of the paper. . However, in the case of large-sized paper, the distance between the both ends of the leading end of the paper and the paper feed roller increases, and the amount of bending of the paper increases accordingly. Is a problem in designing the sheet feeding device.
[0007]
In view of the above, the present invention provides a paper feeding apparatus using a separation claw, which can forcibly reduce the deflection of a paper sheet, which is a problem, so that the paper sheet can be smoothly fed without being caught by other members. Is to do so.
[0008]
[Means for Solving the Problems]
A paper feeder according to the present invention includes a flapper on which a plurality of papers are stacked, a separation claw that presses both ends of the paper from above at a leading end side of the paper on the flapper, and an abutting surface of the paper on the flapper. A pick-up roller that feeds the paper sheet, and a paper pressing member that is provided between the separation claw and the pickup roller and that presses the bending of the paper from above. Further, the paper pressing member is a pressing roller attached to a rotation shaft of the pickup roller. Further, the pressing roller has a smaller diameter than the pickup roller. The press roller has a fan-shaped cross section in a direction perpendicular to the rotation axis.
[0009]
With the above configuration, at the start of the sheet feeding operation, both ends of the sheet are caught by the separation claw at the leading end of the sheet, and when the sheet is bent upward, the sheet is pressed from above by the sheet pressing member. Therefore, the amount of bending of the sheet can be reduced. That is, since the sheet pressing member is provided between the separation claw, which is an area where the sheet is bent, and the pickup roller, it is possible to surely reduce the deflection of the sheet. Further, by forcibly reducing the deflection of the sheet, the timing at which both ends of the sheet are detached from the separation claw is advanced, and the risk of the occurrence of a sheet jam during the sheet feeding operation can be reduced. In particular, in recent years, various papers having different sizes and materials have been used, and the amount of flexure and the shape of flexure are various. However, according to the present invention, the same amount of flexure is forced with the same amount of flexure. Such a bent shape can be obtained, and the timing of detachment from the separation claw is also substantially the same, so that the paper feeding mechanism may be designed in accordance with the timing, and the paper feeding operation may be simplified.
[0010]
Further, by using the paper pressing member as a pressing roller attached to the rotating shaft of the pickup roller, it is possible to suppress the bending of the paper while following the paper feeding operation, and to reduce the amount of bending of the paper more smoothly. be able to. Further, by making the diameter of the pressing roller smaller than that of the pickup roller, the bending of the sheet can be suppressed so as not to hinder the feeding operation of the pickup roller. In addition, as for the shape of the pressing roller, by making the cross-sectional shape in the direction perpendicular to the rotation axis into a sector shape, it can be brought into contact with the paper only when performing the paper feeding operation.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments according to the present invention will be described in detail. FIG. 1 schematically shows an entire image forming apparatus provided with a sheet feeding device according to the present invention. A document reading section 1 for transporting a document and reading both sides of the document is disposed above the image forming apparatus, and a recording section 2 for recording an image, a sheet transport section 3 for transporting a sheet for recording an image, and a paper feed section below the document reading section 1. A paper device 4 is provided. A plurality of sheets are stacked and set on a sheet feeding cassette 5 in the sheet feeding device 4, and are fed one by one to the sheet conveying unit 3 by a pickup roller described later. The fed sheet is conveyed to the recording unit 2 by the conveying rollers 6 and the like of the sheet conveying unit 3 to record an image, and is discharged to the sheet discharge tray 16 by the discharge rollers 15. In FIG. 1, the paper transport path is indicated by a dotted line. The recording unit 2 includes a developing unit 7, a charging drum 10, a transfer roller 11, an exposure head 12, a removing brush 13, and a fixing roller 14 for recording an image on a sheet conveyed by the sheet conveying unit 3. The charging drum 10 is charged by exposing it in accordance with an image recording signal by the exposure head 12, and the toner in the developing device 7 is attached to the charging drum 10 by the supply roller 8 and the developing roller 9, and is transferred by the transfer roller 11. The toner adhered to the surface of the charging drum 10 is transferred to a sheet, and the toner transferred by the fixing roller 14 is fixed to the sheet. The toner remaining on the charging drum 10 after the transfer is removed by the removing brush 13.
[0012]
The document reading unit 1 includes a cover unit 17 having a document conveying device therein and a reading main unit 18 having a scanner 19. The document transport device includes a transport roller that transports the document placed on the document tray 22, and the transported document is discharged to a document discharge tray 23. On the upper surface of the reading main body 18, a platen glass 20 is disposed at a portion for reading a conveyed document, and a placing bed 21 made of a transparent glass material is disposed at a portion for placing and reading a document or a book. I have. When reading a conveyed document, the scanner 19 is stopped at a position facing the platen glass 20 to perform a reading operation. When reading a document or the like placed on the placing bed 21, the scanner 19 is scanned and read. To do. A document holder 24 is attached to a surface of the cover 17 facing the mounting bed 21.
[0013]
FIG. 2 and FIG. 3 are schematic views of a plan view and a side view of the sheet feeding device 4. The paper feed cassette 5 is provided with a grip 31 for attaching and detaching the paper feed cassette 5 to the side of a housing 30 that accommodates sheets. Inside the housing 30, a flapper 32 for placing a sheet, side guides 33 provided on both sides of the flapper 32 for positioning a side edge of the sheet, and a rear portion of the flapper 32 for positioning a rear end of the sheet. The end guide 34 provided is provided, and the sheet is placed at a predetermined position by these members. The flapper 32 is rotatably supported up and down by hinges 35 provided at both ends of a rear portion. Reinforcement grooves 36 for enhancing strength are formed on the surface in front, rear, left and right. A spring 37 is provided between the front end of the flapper 32 and the bottom of the housing 30, and the flapper 32 is constantly urged upward by the spring 37.
[0014]
Above the front end of the flapper 32, two pickup rollers 40 are disposed at a predetermined interval on the shaft 42. In the flapper 32, a cork pad 39 is fixed to a portion that comes into contact with the pickup roller 40. I have. The separation claw 38 is provided along the front end of the flapper 32, and is attached so as to be positioned in conjunction with the side guide 33. The pressing roller 41 is disposed on the shaft 42 between the separation claw 38 and the pickup roller 40. The cross section of the pickup roller 40 and the pressing roller 41 is formed in a circular shape, and the diameter of the pressing roller 41 is slightly smaller than the diameter of the pickup roller 40.
[0015]
When storing paper in the paper cassette 5, the flapper 32 is rotated toward the bottom of the housing 30, and the end guide 34 is set in the guide mounting hole 43 in accordance with the size of the paper. Is loaded. When the side guide 33 is moved until it comes into contact with the side of the sheet, the separation claw 38 moves in conjunction therewith and comes into contact with both ends on the leading end side of the sheet. In this state, when the sheet cassette 5 is mounted in the image forming apparatus in the direction of arrow A, the flapper 32 rotates upward around the hinge 35 by the urging force of the spring 37, and the uppermost surface of the sheet presses the pickup roller 40. Is done. By rotating the shaft 42 in this state, the pickup roller 40 feeds the topmost sheet in the direction of arrow B.
[0016]
FIG. 4 is a diagram illustrating a state in which the sheet is being fed as viewed from the leading end of the sheet. When the uppermost sheet is fed by the pickup roller 40, the sheet between the separation claw 38 and the pickup roller 40 bends, but the bending 44 is forcibly pressed at a constant height by the pressing roller 41. . Since the pressing roller 41 has a smaller diameter than the pickup roller 40, the pressing roller 41 comes into contact with the sheet only when the sheet is bent, and thus does not participate in the sheet feeding operation.
[0017]
In the above-described embodiment, the pickup roller 40 and the pressing roller 41 are formed in a circular cross section. However, as shown in FIG. 5, the pickup roller 40 and the pressing roller 41 may be formed in a fan shape and used. Only when the paper is being fed, the fan-shaped arc is pressed against the paper. Otherwise, the arc is positioned above and is in non-contact with the paper. In addition, the paper is not carelessly pressed, and the pressure is not always applied to the pickup roller 40. In FIG. 5, the pickup roller 40 and the pressing roller 41 have the same shape, and a belt-shaped elastic member is mounted on the surface thereof so that the pickup roller 40 and the pressing roller 41 are detachably fitted to the shaft 42. With this configuration, it is possible to change the arrangement of the rollers and to use the pressing roller 41 in the transport operation when using various sizes of paper or various types of paper.
[0018]
【The invention's effect】
As described above, according to the present invention, at the start of the sheet feeding operation, when both ends of the sheet are caught by the separation claw at the leading end side of the sheet and the sheet is bent upward, the sheet is pressed from above by the sheet pressing member. Therefore, the amount of bending of the sheet can be reduced. That is, since the sheet pressing member is provided between the separation claw, which is an area where the sheet is bent, and the pickup roller, it is possible to surely reduce the deflection of the sheet. Further, by forcibly reducing the deflection of the sheet, the timing at which both ends of the sheet are detached from the separation claw is advanced, and the risk of the occurrence of a sheet jam during the sheet feeding operation can be reduced. In particular, in recent years, various papers having different sizes and materials have been used, and the amount of flexure and the shape of flexure are various. However, according to the present invention, the same amount of flexure is forced with the same amount of flexure. Such a bent shape can be obtained, and the timing of detachment from the separation claw is also substantially the same, so that the paper feeding mechanism may be designed in accordance with the timing, and the paper feeding operation may be simplified.
[0019]
Further, by using the paper pressing member as a pressing roller attached to the rotating shaft of the pickup roller, it is possible to suppress the bending of the paper while following the paper feeding operation, and to reduce the amount of bending of the paper more smoothly. be able to. Further, by making the diameter of the pressing roller smaller than that of the pickup roller, the bending of the sheet can be suppressed so as not to hinder the feeding operation of the pickup roller. In addition, as for the shape of the pressing roller, by making the cross-sectional shape in the direction perpendicular to the rotation axis into a sector shape, it can be brought into contact with the paper only when performing the paper feeding operation.
[Brief description of the drawings]
FIG. 1 is a schematic side view of an entire image forming apparatus having an embodiment according to the present invention.
FIG. 2 is a schematic plan view of an embodiment according to the present invention.
FIG. 3 is a schematic side view of an embodiment according to the present invention.
FIG. 4 is a diagram illustrating a state during paper feeding according to the embodiment of the present invention.
FIG. 5 is a schematic side view of another embodiment according to the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 document reading unit 2 recording unit 3 paper transport unit 4 paper feeder 5 paper feed cassette 30 housing 31 gripper 32 flapper 33 side guide 34 end guide 35 hinge 36 reinforcing groove 37 spring 38 separation claw 39 cork pad 40 pickup roller 41 Pressing roller 42 Shaft shaft 43 Guide mounting hole 44 Deflection of paper

Claims (4)

A flapper on which a plurality of papers are stacked; a separation claw that presses both ends of the paper from above at the leading end side of the paper on the flapper; a pickup roller that feeds the paper by contacting the upper surface of the paper on the flapper; A sheet feeder, comprising: a sheet pressing member provided between a separation claw and the pickup roller, and pressing a sheet from above. The paper feeding device according to claim 1, wherein the paper pressing member is a pressing roller attached to a rotation shaft of the pickup roller. The paper feeder according to claim 2, wherein the pressing roller has a smaller diameter than the pickup roller. 4. The sheet feeder according to claim 2, wherein the pressing roller has a fan-shaped cross section in a direction perpendicular to a rotation axis thereof. 5.

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