JP2005067806A - Sheet feeder and image forming device equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeder to feed sheets of paper using a feed roller couple capable of feeding the sheets without generating wrinkles and exerting the intended effect irrespective of the sheet width at low cost. <P>SOLUTION: An image forming device 1 is structured so that a sheet fed from a sheet feeding part 11 rises in a vertical feed path 13 to undergo image formation by an image formation part 20, with the image fixed by a fixation part 30, and the sheet is ejected to a sheet ejection part 12. The arrangement includes a feed roller couple 17a just in front of a resist roller couple 16, wherein each of drive rollers constituting one of the roller couples is divided in a plurality of drive roller segments. Among them the drive roller segments 41b and 41c in pair located symmetrically to the left and right about the sheet feeding center line L are formed in a taper symmetrical to the left and right in which the side with the sheet feeding center line L is thicker and its opposite side is thinner. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to a sheet conveying device used in an image forming apparatus such as a printer or a copying machine. The present invention also relates to an image forming apparatus equipped with the sheet conveying device.

Inside an image forming apparatus such as a printer or a copying machine, a pair of conveying rollers are arranged at various points along the sheet conveying path. One of the pair of conveying rollers is a driving roller that is rotated by power, and the other is a driven roller that is pressed against the driving roller. An example of the sheet conveying apparatus configured as described above can be seen in Japanese Patent Application Laid-Open No. 2004-133830.
JP-A-5-92837 (page 3-4, FIG. 1)

    It is desirable that the paper on which the image is formed has no wrinkles. However, in reality, a situation in which the pair of conveyance rollers themselves wrinkles the paper often occurs. In order to cope with this problem, in the paper conveying device described in Patent Document 1, the nip roller member pressed against the long drive roller is divided into a main nip roller at the center and auxiliary nip rollers on both sides thereof. The main nip roller is hardened, and the auxiliary nip roller is formed by providing a plastic color member around the sponge roller so as not to cause a difference in nip pressure in the width direction of the paper, thereby preventing wrinkles. It is out.

    In the configuration described in Patent Document 1, an auxiliary nip roller having a special structure must be prepared, which increases costs. Also, it is effective for wide paper that covers the auxiliary roller completely, but the left and right edges of the paper do not reach the auxiliary roller, or even if it reaches, only a part of the auxiliary roller is covered. The effect cannot be expected when the paper is narrow.

    SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and in a paper transport device that feeds paper by a pair of transport rollers, the paper can be transported without generating wrinkles, is inexpensive, and is effective regardless of the width of the paper. It is an object of the present invention to provide a paper transport device that can be used. It is another object of the present invention to provide a high-function image forming apparatus equipped with this sheet conveying apparatus.

    (1) In the present invention, in a sheet conveying apparatus that feeds a sheet by a pair of conveying rollers, at least one of which is a driving roller, a pair of driving roller segments arranged at left and right symmetrical positions of a sheet feeding center line are provided. The pair of drive roller segments are formed in a symmetrical taper shape in which the paper feed center line side is thick and the opposite side is thin.

    (2) In the present invention, in the paper conveying apparatus configured as described above, an actuator for a paper passing detection switch is disposed on the paper feed center line.

    (3) Further, in the present invention, the above-described sheet conveying device is mounted on the image forming apparatus.

    (1) According to the configuration of the present invention, the drive roller segment has a tapered shape in which the paper feed center line side is thick and the opposite side is thin, so the drive roller segment on the left side of the paper feed center line The drive roller segment on the right side tries to turn the paper to the right, and as a result, the paper is fed forward in a form in which the wrinkles are stretched, so that the paper does not wrinkle. Since this configuration can realize the shape of the drive roller segment, it is not costly. Also, if the distance between the left and right drive roller segments is not increased, even a narrow sheet can be fed while preventing wrinkles.

    (2) Further, in the present invention, since the actuator for the sheet passing detection switch is arranged on the sheet feeding center line in the sheet conveying apparatus configured as described above, the sheet passing detection is reliably performed using an inexpensive switch. However, it is possible to prevent the sheet from being deflected by the contact of the actuator.

    (3) Further, the present invention provides a high-function image forming apparatus that does not output paper in a wrinkled state because the sheet conveying apparatus configured as described above is mounted on the image forming apparatus. be able to.

    Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic vertical sectional view of the image forming apparatus, FIG. 2 is a front view of a pair of conveying rollers, and FIG. 3 is an explanatory view of the structure and operation of a driving roller.

    The image forming apparatus 1 is a printer and includes a housing 10. The housing 10 includes a paper feeding unit 11 at the bottom and a paper discharge unit 12 at the top. A vertical conveyance path 13 for conveying the paper in the vertical direction is formed inside the housing 11.

    The lower end of the vertical conveyance path 13 is connected to the paper feeding unit 11 and receives paper fed from the paper feeding unit 11. At the upper end of the other vertical conveyance path 13, a paper discharge path 14 for discharging the fixed sheet to the paper discharge unit 12 is provided in a continuous manner. The paper discharge path 14 is substantially horizontal, and a pair of paper discharge rollers 15 is disposed at the end thereof. A registration roller pair 16 and a conveyance roller pair 17 are arranged in the vertical conveyance path 13. The conveyance roller pairs 17 are provided at several locations on the vertical conveyance path 13.

    An image forming unit 20 and a fixing unit 30 are arranged in the vertical conveyance path 13. In FIG. 1, only the photosensitive drum 21 and the transfer roller 22 that presses the paper against the photosensitive drum 21 are illustrated in the image forming unit 20. A fixing unit 30 is disposed above the image forming unit 20, that is, on the downstream side in the vertical conveyance path 13. The fixing unit 30 includes a fixing roller 31 incorporating a heat source such as a halogen lamp, and a pressure roller 32 that presses against the fixing roller 31 to form a nip.

    During printing, the paper that has exited the paper supply unit 11 rises vertically toward the image forming unit 20. The registration roller pair 16 captures the sheet, and sends it to the image forming unit 20 at an appropriate timing. After the toner is transferred by the image forming unit 20, the sheet enters the fixing unit 30, and the toner is fixed by heat and pressure. The sheet after toner fixing further rises in the vertical conveyance path 13 and enters the paper discharge path 14, and is discharged to the paper discharge unit 12 by the paper discharge roller 15 and stacked.

    Among the plurality of transport roller pairs 17, the transport roller pair 17a located immediately before the registration roller pair 16 is configured as follows. That is, one of the conveying roller pair 17a is a driving roller that is rotated by power, and the other is a driven roller that is pressed against the driving roller. The driving roller is made of rubber, and the driven roller is made of synthetic resin.

    As shown in FIG. 2, the driving roller has a configuration in which a plurality of driving roller segments 41 are fixed to a horizontal shaft 40. The driven roller is also divided into the same number of driven roller segments 42 as drive roller segments 41. The driven roller segment 42 is not attached to a common shaft like the drive roller segment 41, but is supported by a separate short shaft (not shown), and is individually attached to the drive roller segment 41 by a spring (not shown). It is pressed.

    The number of drive roller segments 41 depicted in FIG. 2 is a total of four, but it is also possible to have an even number having a larger value than this, that is, six or eight. Conversely, it may be an even number with a small value, that is, two. For convenience of explanation, the four drive roller segments 41 are given identification codes “a”, “b”, “c”, and “d” in order from the left. The drive roller segments 41a, 41b, 41c and 41d have the same length and are arranged at equal intervals.

    As shown in FIG. 3, the drive roller segments 41 b and 41 c closer to the center are arranged at symmetrical positions on the left and right of the paper feed center line L. The drive roller segments 41a and 41d have a simple cylindrical shape, whereas the drive roller segments 41b and 41c are thicker on the paper feed center line L side (maximum diameter Dmax) and thinner on the opposite side. (It has a minimum diameter Dmin) and is formed into a symmetrical taper shape.

    When the shaft 40 rotates, the drive roller segment 41b attempts to feed the paper larger toward the portion closer to the paper feed center line L (the arrow in FIG. 3 is a symbol of the paper feed amount). For this reason, the portion of the paper that contacts the drive roller segment 41b tends to turn to the left. The drive roller segment 41c also tries to feed the paper larger as it is closer to the paper feed center line L. However, since the shape is reversed left and right with respect to the drive roller segment 41b, the portion of the paper that contacts the drive roller segment 41c should face to the left. And Since these movements occur at the same time, the paper is fed forward in a form that is crumpled.

    Between the conveyance roller pair 17a and the registration roller pair 16, a sheet passing detection switch 50 (see FIG. 3) for detecting whether or not a sheet exists at that position is disposed. The actuator 51 of the notification detection switch 50 is placed on the paper feed center line L. At this position, the actuator 51 does not apply a biasing force to the paper, and the paper does not deflect to the left or right.

    The distance G between the drive roller segments 41b and 41c can be further reduced than the state depicted in FIG. However, only the sheet width C passing through the actuator 51 of the sheet passing detection switch 50 is left.

    The taper shape that “the paper feed center line L side is thick and the opposite side is thin” can be applied not only to the drive roller segments 41b and 41c but also to the drive roller segments 41a and 41d. Further, one of the conveying roller pair 17a is not a driving roller and the other is a driven roller, and both can be driving rollers. Furthermore, the structure described so far can be applied not only to the conveying roller pair 17a immediately before the registration roller 16 but also to the conveying roller pair 17 at other locations.

    Although the embodiments of the present invention have been described above, various modifications can be made without departing from the spirit of the invention.

    The present invention can be used for an apparatus that conveys paper or a web with a roller, such as a printing machine or a bookbinding machine, in addition to an image forming apparatus.

Model vertical sectional view of image forming apparatus Front view of transport roller pair Explanatory drawing of structure and action of drive roller

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Housing 11 Paper feed part 12 Paper discharge part 13 Vertical conveyance path 14 Paper discharge path 15 Paper discharge roller pair 16 Registration roller pair 17, 17a Carrying roller pair 20 Image forming part 30 Fixing part 40 Shaft 41a, 41b, 41c, 41d Drive roller segment 42 Driven roller segment 50 Paper passing detection switch 51 Actuator L Paper feed center line

Claims (3)

In a paper transport device that feeds paper by a pair of transport rollers, at least one of which is a drive roller,
A pair of drive roller segments disposed at symmetrical positions on the left and right sides of the paper feed center line, and the pair of drive roller segments are thicker on the paper feed center line side and thinner on the opposite side. A paper transporting device having a shape.   2. The paper conveying apparatus according to claim 1, wherein an actuator of a paper passing detection switch is disposed on the paper feeding center line.   An image forming apparatus comprising the sheet conveying device according to claim 1.

Images