JP2010169877A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, improving carrying stability of paper at an image transfer part in a belt-less direct transfer system. <P>SOLUTION: In the image forming apparatus, paper is carried without supporting, by a belt, a plurality of image transfer parts including a photoreceptor drum and a transfer roller 13, and an image is transferred on the paper. The apparatus includes a side regulating member for regulating one side part of the paper carried along the image transfer parts. A plurality of elastic projections 53 are disposed spirally on the surface of the transfer roller 13. The elastic projections 53 are tilted to the side-regulating member side when it comes into pressure contact with the photoreceptor drum, thereby biasing the paper to abut against the side-regulating member. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that transfers an image onto a sheet while transporting the sheet without carrying a plurality of image transfer units composed of a photoreceptor and a transfer member with a belt.

  Generally, an intermediate transfer system and a direct transfer system are known for electrophotographic tandem color image forming apparatuses such as copying machines and printers. In the intermediate transfer method, images of four colors (Y: yellow, M: magenta, C: cyan, Bk: black) are overlaid on a transfer belt that rotates endlessly, and then primary transfer is performed, followed by secondary transfer onto paper. To do. In the direct transfer method, a sheet is carried on a belt that rotates in an endless manner, and images of four colors are superimposed and transferred on the sheet. Since these endless belts are used in these image forming apparatuses, the conveyance state of the paper is stable, and adjustment of the image to be superimposed is performed by optically reading a test pattern formed on the belt and feeding it back to the image forming operation. It is dealt with in.

  On the other hand, a beltless transfer system has been developed for the purpose of reducing the cost and reducing the size of the conventional transfer system. In the beltless transfer system, an image is transferred onto a sheet while the sheet is conveyed without being carried by a belt. However, this beltless transfer system has a problem that the conveyance state of the paper is unstable and color misregistration occurs due to the skew or meandering of the paper.

  Therefore, in Patent Document 1, an elastic protrusion is provided on the surface of the transfer roller for the purpose of keeping the transfer material conveyance speed at the transfer nip portion substantially constant even when the thickness, type, and durability of the transfer material change. It is described that a formed elastic layer is provided. Japanese Patent Application Laid-Open No. 2004-228561 describes that there is little decrease in the conveyance force due to the deterioration of the elastic protrusion, but does not mention prevention of skewing and meandering of the paper.

  Japanese Patent Application Laid-Open No. H10-228667 describes that a skew feeding roller that is inclined and rotated with respect to the conveyance direction is provided, and the transfer material is conveyed against the end positioning member. In this improvement measure, since a plurality of skew feeding rollers are provided, the number of parts increases.

JP 2003-302845 A JP 2006-65111 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that improves the sheet conveyance stability in an image transfer unit in a beltless direct transfer system.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention includes:
A plurality of image transfer units each including a toner image carrier and a transfer member disposed to face the toner image carrier are juxtaposed, and the plurality of image transfer units are transported without carrying the plurality of image transfer units by a belt. In an image forming apparatus for transferring an image on paper,
A side regulating member that regulates one side of the sheet conveyed through the plurality of image transfer units;
A plurality of elastic protrusions are spirally arranged on the surface of the transfer member, and when the elastic protrusions are pressed against the toner image carrier, the elastic member protrudes toward the side regulating member.
It is characterized by.

  In the image forming apparatus, the sheet conveyed through the image transfer portion (between the toner image carrier and the transfer member) is urged toward the side regulating member by elastic protrusions arranged spirally on the surface of the transfer member. . As a result, the sheet is conveyed while its one side is reliably regulated by the side regulating member, so that skew and meandering are prevented, and as a result, an image free from color misregistration can be obtained.

  According to the present invention, paper transportability is stabilized and image quality is improved. Further, the number of parts does not increase.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment. It is a top view which shows schematic structure of an image transfer part. It is sectional drawing which shows a transfer roller. It is explanatory drawing which shows the state of the elastic protrusion formed in the surface of a transfer roller. It is a perspective view which expands and shows the edge part of the transfer roller which has arrange | positioned the elastic protrusion of another shape.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings. The letters Y, M, C, and Bk attached to the reference numerals indicate that the members are for forming yellow, magenta, cyan, and black images.

(Schematic configuration of image forming apparatus, see FIG. 1)
As shown in FIG. 1, an image forming apparatus to which the present invention is applied includes an image forming unit 10 (10Y) for forming images of Y (yellow), M (magenta), C (cyan), and Bk (black). , 10M, 10C, 10Bk) are sequentially arranged from the lower stage to the upper stage. Each image forming unit 10 includes a photosensitive drum 11 (11Y, 11M, 11C, 11Bk), a developing device 12 (12Y, 12M, 12C, 12Bk), a charging charger (not shown), and the like. A transfer roller 13 (13Y, 13M, 13C, 13Bk) that is paired with each of the photosensitive drums 11 is disposed.

  In each image forming unit 10, the sheet is conveyed upward through a nip portion (image transfer portion) formed by the photosensitive drum 11 and the transfer roller 13. Note that the sheet conveyance path here is slightly curved as shown by a dotted line in FIG.

  Further, the laser scanning optical unit 15 emits a modulated laser beam based on the image data from the gaps between the image forming units 10 toward the photosensitive drums 11 and electrostatically strikes the surface of the photosensitive drums 11. A latent image is formed. The image data is transmitted to the control unit 5 of the image forming apparatus directly from a computer (not shown) or via a network. The control unit 5 performs control for printing operation such as paper conveyance and control associated therewith, including processing of image data.

  A plurality of sheets are stored in a stacked state in the automatic sheet feeding tray 20, and are fed one sheet at a time by a sheet feeding roller 21, with a predetermined timing by a timing roller pair 22, and the sheet Is fed into the conveyance path, and during the color image formation, yellow, magenta, cyan, and black images are transferred from the photosensitive drums 11Y, 11M, 11C, and 11Bk to form a monochrome image. Sometimes a black image is transferred from the photosensitive drum 11Bk. After the image is transferred, the paper is fixed with toner by the fixing unit 30 and is discharged from the pair of discharge rollers 31 onto the tray 32. Note that this type of image forming process is well known, and a detailed description thereof will be omitted.

  At the time of image formation, each transfer roller 13 comes into contact with each photoconductor drum 11 with a predetermined pressure, and a sheet is a nip formed by each photoconductor drum 11 and each transfer roller 13 that are rotationally driven at a predetermined speed. It is conveyed by the part. The transfer roller 13 is driven to rotate in contact with the photosensitive drum 11 or is transmitted with a rotational driving force having the same peripheral speed as that of the photosensitive drum 11.

  By the way, in this type of beltless transfer system, since the paper is not carried by the belt, the conveyance of the paper is unstable, and there is a possibility that the image transfer unit may be skewed or meandered. Therefore, in this embodiment, as shown in FIG. 2, the side regulating member 40 that regulates one side portion of the sheet conveyed through the plurality of image transfer units is provided as one end of each of the photosensitive drum 11 and the transfer roller 13. Placed adjacent to. The side regulating member 40 may be an integrated member over the entire length of the image transfer portion or may be divided into a plurality of members.

  Further, in order to ensure the sheet conveyance stability, a plurality of elastic protrusions 53 are spirally arranged on the surface of the transfer roller 13 as shown in FIGS. The elastic protrusion 53 is a thin and short bar-shaped protrusion, and is disposed over the entire surface of the transfer roller 13. The transfer roller 13 includes a shaft member 51 and an elastic material 52 having a circular cross section. The elastic material 52 is formed of, for example, a foamed urethane material. A recess for forming the elastic protrusion 53 is formed in a mold for foaming the urethane material, and the elastic protrusion 53 is formed simultaneously with foaming. In addition, the formation method of the elastic protrusion 53 is not limited to this, It may be by flocking.

  The transfer roller 13 is pressed against the photosensitive drum 11 with a certain elastic force as indicated by an arrow X in FIG. The elastic protrusion 53 stands up when not in contact with the photosensitive drum 11. When the elastic protrusion 53 is pressed against the photosensitive drum 11, the elastic protrusion 53 falls to the side regulating member 40 side by the pressing force, and urges the one side portion of the conveyed paper S to be pressed against the side regulating member 40. Thus, the sheet S is regulated at one side by the side regulating member 40 and is stably conveyed without causing skew or meandering. Therefore, an image without color misregistration can be obtained.

  When the elastic protrusion 53 is pressed against the photosensitive drum 11 via the paper S, the elastic protrusion 53 falls on the surface of the transfer roller 13 and is embedded in the surface of the elastic material 52. In this state, a transfer voltage is applied from the shaft member 51. The elastic protrusions 53 may be arranged in a state where the elastic protrusions 53 are tilted in advance on the side regulating member 40 side so as to easily fall on the side regulating member 40 side.

  Further, the elastic protrusions 53 may be disposed only at both end portions of the transfer roller 13. That is, in the image transfer portion, the transfer characteristics of the both end portions are unstable, so that the central portion is set as the image forming range A. Therefore, the elastic protrusion 53 may be provided outside the image forming range A (non-image forming range B). Although the force for urging the conveyed paper toward the side regulating member 40 is inferior to the elastic protrusion 53 provided on the entire surface of the transfer roller 13, adverse effects on the transfer characteristics are eliminated.

  The elastic protrusions 53 may have various shapes other than the thin and short bar-shaped protrusions as shown in FIG. For example, it may be a tapered needle-like protrusion. Alternatively, as shown in FIG. 5, it may be a triangular plate-like protrusion.

(Other examples)
Note that the image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  In particular, the basic configuration of the image forming apparatus is arbitrary, and may be a copying machine or a facsimile multifunction peripheral in addition to a single printer.

  As described above, the present invention is useful for an image forming apparatus of a beltless direct transfer system, and is particularly excellent in that the sheet conveyance stability is improved.

DESCRIPTION OF SYMBOLS 10 ... Image forming unit 11 ... Photosensitive drum 13 ... Transfer roller 40 ... Side regulating member 52 ... Elastic material 53 ... Elastic protrusion

Claims (5)

A plurality of image transfer units each including a toner image carrier and a transfer member disposed to face the toner image carrier are juxtaposed, and the plurality of image transfer units are transported without carrying the plurality of image transfer units by a belt. In an image forming apparatus for transferring an image on paper,
A side regulating member that regulates one side of the sheet conveyed through the plurality of image transfer units;
A plurality of elastic protrusions are spirally arranged on the surface of the transfer member, and the elastic protrusions fall to the side regulating member side when pressed against the toner image carrier.
An image forming apparatus.   The image forming apparatus according to claim 1, wherein the elastic protrusion is disposed outside an image forming range in the image transfer unit.   The image forming apparatus according to claim 1, wherein the transfer member is made of an elastic material having a circular cross section.   The image forming apparatus according to claim 3, wherein the transfer member is made of a foam material.   The image forming apparatus according to claim 4, wherein the elastic protrusion is formed when the foaming material is foamed.

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