JP2010107869A - Transfer roller and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer roller and an image forming apparatus for preventing skew of paper by reducing a difference in speed between the paper and the surface of the roller in simple constitution, and achieving favorable transfer performance. <P>SOLUTION: The transfer roller 13 is driven to rotate in contact with a photoreceptor drum with predetermined pressure, and adapted to apply transfer voltage while carrying the paper between the transfer roller and the photoreceptor drum. The transfer roller 13 includes: a core bar 61 and a plurality of axially split elastic body rollers 13a-13f rotatably mounted on the core bar 61. The elastic body rollers 13a, 13f disposed at both ends are tapered so that the outside diameter of an outside part is larger than the outside diameter of an inside part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer roller and an image forming apparatus, and more particularly to a transfer roller that applies a transfer voltage to a sheet while conveying the sheet in contact with a toner image carrier such as a photosensitive drum, and an image forming apparatus including the transfer roller Relates to the device.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, it is necessary to prevent skew (lateral shift) of a conveyed sheet. In particular, for paper conveyed between a toner image carrier such as a photoconductor and a transfer roller, it is highly necessary to prevent paper skew in order to suppress deterioration in toner image transfer performance. Usually, by managing the parallelism between the photosensitive drum and the transfer roller and the accuracy of the outer diameter of the transfer roller, the straightness of conveyance of the sheet is ensured. However, this is complicated and expensive.

  Patent Document 1 describes a configuration in which a side regulation plate is provided in a paper conveyance path, and a paper is conveyed while being regulated by a side regulation plate by a short roller inclined with respect to the conveyance direction, as a skew prevention measure. Yes. In this paper transport device, the inclined roller holds the pressing force that advances the paper along the side regulating plate, but does not securely grip the paper. That is, since there is a deviation between the rotation direction of the tilt roller and the paper transport direction, microscopically, slip occurs between the tilt roller and the paper.

  Incidentally, it is difficult to apply the configuration described in Patent Document 1 to a transfer roller. That is, since the transfer roller is in contact with the photosensitive drum over the entire width of the sheet, it is extremely difficult to microscopically slip the sheet while maintaining the sheet conveying force.

  In addition, since the core roller and the elastic body are integrally formed in the transfer roller, the rotation speed is uniform in the axial direction. In addition, even if the outer diameter accuracy of the transfer roller is accurately controlled, manufacturing errors in the outer diameter cannot be avoided. Therefore, a speed difference between the sheet and the surface of the transfer roller occurs in the width direction of the sheet (axial direction of the roller), and the occurrence of skew is inevitable.

Patent Document 2 describes a transfer roller that is formed by forming a plurality of radial grooves in an elastic body to make an apparently short roller. However, the purpose of this transfer roller is to average the resistance value in the axial direction by forming a plurality of grooves, and it is not considered to prevent paper skew. Further, the transferability of the groove portion is deteriorated.
JP 2002-370850 A JP 11-52765 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a transfer roller and an image forming apparatus that can reduce the speed difference between the sheet and the roller surface with a simple configuration, prevent sheet skew, and achieve good transferability. It is to provide.

In order to achieve the above object, a transfer roller according to an aspect of the present invention is
Transfer that applies a transfer voltage to the toner image carrier that is driven to rotate in one direction, contacts the toner image carrier, rotates in accordance with the toner image carrier, and conveys the paper to and from the toner image carrier. Laura,
A cored bar and a plurality of axially divided elastic rollers mounted on the cored bar so as to be rotatable and movable in the axial direction;
The pair of elastic rollers disposed at both ends of the elastic roller has a tapered shape in which the outer diameter of the outer portion is larger than the outer diameter of the inner portion,
It is characterized by.

  An image forming apparatus according to another aspect of the invention includes the transfer roller.

  In the transfer roller, each of the elastic rollers divided in the axial direction is rotatable with respect to the cored bar, and thus can be driven to rotate with respect to the paper at a rotation speed independent of each other. Therefore, even if there is a slight difference in the outer diameter of each elastic roller, a speed difference does not occur between the paper and each elastic roller, and paper skew is suppressed. Moreover, it consists of a simple configuration in which a plurality of elastic rollers are rotatably mounted on the core metal, and it is not necessary to manage the outer diameter of each elastic roller so strictly as compared to an integrated roller, which is cost effective. It is advantageous. In addition, the pair of elastic rollers disposed at both ends have a tapered shape in which the outer diameter of the outer portion is larger than the outer diameter of the inner portion, so that the elastic rollers at both ends are rotated during the driven rotation with the photosensitive drum. It is urged inward in the axial direction to prevent a gap from being generated between the elastic rollers. If a gap is generated between the elastic rollers, the transferability of the toner image may be deteriorated. However, since the gap is filled in the transfer roller, the transfer property is good.

  Hereinafter, embodiments of a transfer roller and an image forming apparatus according to the present invention will be described with reference to the accompanying drawings. Note that, in each embodiment, the same members and parts are denoted by the same reference numerals, and redundant descriptions are omitted.

(Schematic configuration of image forming apparatus, see FIG. 1)
FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. In this image forming apparatus, image forming units 10Y, 10M, 10C, and 10Bk for forming images of Y (yellow), M (magenta), C (cyan), and Bk (black) are sequentially arranged from the lower stage to the upper stage. It is a thing. Each of the image forming units 10Y, 10M, 10C, and 10Bk includes photosensitive drums 11Y, 11M, 11C, and 11Bk, developing units 12Y, 12M, 12C, and 12Bk, a charging charger (not shown), and the like. Transfer rollers 13Y, 13M, 13C, and 13Bk that are paired with the photosensitive drums 11Y, 11M, 11C, and 11Bk are disposed so as to face each other.

  In the image forming units 10Y, 10M, 10C, and 10Bk, the sheet is conveyed upward through a nip portion formed by the photosensitive drums 11Y, 11M, 11C, and 11Bk and the transfer rollers 13Y, 13M, 13C, and 13Bk. Note that the sheet conveyance path here is slightly curved as shown by a dotted line in FIG.

  The laser scanning optical unit 15 emits a laser beam based on the image data from the gaps between the image forming units 10Y, 10M, 10C, and 10Bk toward the photosensitive drums 11Y, 11M, 11C, and 11Bk. Electrostatic latent images are formed on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11Bk. Note that this type of image forming process is well known, and a detailed description thereof will be omitted.

  A plurality of sheets are housed in a stacked state in the automatic sheet feeding tray 20 and are fed one by one upward. When the color image is formed while being conveyed through the conveyance path, the photosensitive drums 11Y, 11M, 11C, A yellow, magenta, cyan, and black image is transferred from 11Bk, and a black image is transferred from the photosensitive drum 11Bk when a monochrome image is formed. 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.

  At the time of image formation, the transfer rollers 13Y, 13M, 13C, and 13Bk come into contact with the photosensitive drums 11Y, 11M, 11C, and 11Bk with a predetermined pressure, and the respective image forming units 10Y, 10M, 10C, and 10Bk are driven. The sheet is conveyed at a nip portion formed by the photosensitive drums 11Y, 11M, 11C, and 11Bk that are driven to rotate and the transfer rollers 13Y, 13M, 13C, and 13Bk that are driven to rotate.

(See Example of transfer roller, FIG. 2 and FIG. 3)
Next, the configuration and operation of an embodiment of the transfer rollers 13Y, 13M, 13C, and 13Bk will be described. In the following description, the symbols Y, M, C, and Bk are omitted for each member.

  The photosensitive drum 11 includes a cored bar 51, flanges (not shown) provided at both ends of the cored bar 51, and a drum 53 having a photosensitive layer formed on the surface thereof, and is driven to rotate at a predetermined speed in the direction of arrow a. The The transfer roller 13 includes a cored bar 61 and a plurality of axially divided elastic rollers 13 a to 13 f mounted on the cored bar 61 via bearing members 62. The elastic rollers 13a to 13f are made of an elastic material such as foam rubber, EPDM, or silicon rubber, and have conductivity.

  Of the elastic rollers 13a to 13f, the pair of elastic rollers 13a and 13f arranged at both ends have a tapered shape in which the outer diameter of the outer portion is larger than the outer diameter of the inner portion. Incidentally, the total length of the transfer roller 13 corresponds to the lateral width of the maximum size sheet to be transported (length in the direction orthogonal to the transport direction). For example, when the entire length of the transfer roller 13 corresponds to A3 size lateral feed, the length of the elastic rollers 13a and 13f at both ends is about 30 mm, and the length of the inner elastic rollers 13b to 13e is axial. The length is about 70 mm. The outer diameter difference between the outer and inner portions of the elastic rollers 13a and 13f at both ends is 0.1 to 0.2 mm.

  The cored bar 61 is fixed to a frame (not shown). The elastic rollers 13 a to 13 f are fixed to the bearing member 62. The bearing member 62 is attached to the core bar 61 so as to be rotatable and movable in the axial direction. Further, the bearing member 62 is restricted from moving outward in the axial direction by a stopper member 63 such as an E-ring at the end of the cored bar 61. The elastic rollers 13 a to 13 f are movable in the axial direction within a range regulated by the stop member 63.

  That is, each of the elastic rollers 13a to 13f is driven by the photosensitive drum 11 and rotates in the arrow b direction. The sheet is conveyed in the direction of arrow c through the nip portion between the photosensitive drum 11 and the transfer roller 13. In addition, a transfer voltage having a predetermined value is applied to each of the elastic rollers 13a to 13f via the cored bar 61 and the bearing member 62 during the conveyance.

  In the above configuration, when the paper is conveyed in the direction of the arrow c, each of the elastic rollers 13 a to 13 f is driven to rotate at an independent rotation speed according to the rotation speed of the photosensitive drum 11. Each of the elastic rollers 13a to 13f divided in the axial direction is driven to rotate at a rotation speed independent of each other with respect to the paper. Therefore, even if there is a slight difference between the outer diameters of the elastic rollers 13a to 13f, a speed difference does not occur between the paper and the elastic rollers 13a to 13f, and the skew of the paper is suppressed. The Moreover, it has a simple configuration in which a plurality of elastic rollers 13a to 13f are rotatably mounted on the cored bar 61, and the outer diameters of the elastic rollers 13a to 13f are managed so strictly as compared with the integrated roller. It is not necessary and can be manufactured inexpensively.

  Further, the pair of elastic rollers 13 a and 13 f disposed at both ends have a tapered shape in which the outer diameter of the outer portion is larger than the outer diameter of the inner portion. The rollers 13a and 13f are urged inward in the axial direction as indicated by an arrow G in FIG. 2 to prevent a gap from being generated between the elastic rollers 13a to 13f. If a gap is generated between the elastic rollers 13a to 13f, the transferability of the toner image may be deteriorated. However, the transfer roller 13 fills the gap, so that the transferability is good.

  Each of the elastic rollers 13 a to 13 f acts so that the gap is filled by elastic deformation caused by pressure contact with the photosensitive drum 11.

(See another embodiment of transfer roller, see FIG. 4)
FIG. 4 shows a main part of a transfer roller 13 which is another embodiment. The elastic rollers 13a to 13f have a large coefficient of friction, and if the adjacent end surfaces come into contact with each other, the rotational speed is affected. Therefore, as shown in FIG. 4, a donut-shaped sliding member 64 is rotatably arranged with respect to the core bar 61 between the adjacent elastic rollers 13 d, 13 e, 13 f (the same applies to the other rollers). The sliding member 64 is preferably formed of a material having a small friction coefficient such as a polyester film.

(Other examples)
The transfer roller and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

  In particular, the basic configuration of the image forming apparatus is arbitrary, and may be a printer, a copier, or a function such as a facsimile. Further, the number of divisions in the axial direction of the elastic roller is arbitrary.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. It is a longitudinal cross-sectional view which shows one Example of a transfer roller. It is a cross-sectional view showing an embodiment of a transfer roller. It is a longitudinal cross-sectional view which shows the principal part of the other Example of a transfer roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Photosensitive drum 13 ... Transfer roller 13a-13f ... Elastic body roller 61 ... Core metal 62 ... Bearing member 64 ... Sliding member

Claims (4)

Transfer that applies a transfer voltage to the toner image carrier that is driven to rotate in one direction, contacts the toner image carrier, rotates in accordance with the toner image carrier, and conveys the paper to and from the toner image carrier. Laura,
A cored bar and a plurality of axially divided elastic rollers mounted on the cored bar so as to be rotatable and movable in the axial direction;
The pair of elastic rollers disposed at both ends of the elastic roller has a tapered shape in which the outer diameter of the outer portion is larger than the outer diameter of the inner portion,
A transfer roller characterized by   The transfer roller according to claim 1, wherein a sliding member is rotatably disposed between the plurality of elastic rollers with respect to the core metal.   An image forming apparatus comprising the transfer roller according to claim 1.   A plurality of toner image carriers are arranged in parallel to each other, and the transfer roller is arranged corresponding to each toner image carrier, and a sheet is continuous between each toner image carrier and each transfer roller. The image forming apparatus according to claim 3, wherein the image forming apparatus is conveyed.

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