JP2002311726A - Transfer means and image forming device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent inconveniences such as the defective rotation of a transfer roller, the defective carrying of a recording material, the short lives of the transfer roller and a photoreceptor drum due to such a trouble that toner enters the bearing of a transfer means. SOLUTION: By storing the bearing 22 in a cylindrical covering member 21 with a cap, one axial end part is closed, while being different from a conventional manner where both axial end part are open. Besides, a flange part 20a is arranged on the cap 20 near an opening part 21c of the covering member 21 so as to cover the opening part 21c from the inside. Besides, the inside diameter of the cylindrical part 21b at the opening part 21c is set smaller than the outside diameter of the flange part 20a. Besides, a part of the cylindrical part 21b and a part of the cap 20 overlap each other in the axial direction. Thus, the scattered toner at the transfer is effectively prevented from entering the bearing 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer means used for a printer, a copying machine, a facsimile, and the like, and an image forming apparatus provided with the transfer means.

[0002]

2. Description of the Related Art In an image forming apparatus such as a printer, a copying machine, a facsimile, etc., a toner image composed of a powder is formed on an image carrier (for example, a photosensitive drum), and the toner image is formed on the surface of a recording material such as paper. After the image is transferred onto the sheet, fixing is performed by applying heat and pressure.

FIG. 4 shows a schematic configuration of a laser printer as an example of such an image forming apparatus. When the recording material fed by the registration roller pair 6 and the pre-transfer roller pair 7 turns on the top sensor 8, an image signal is input, and a laser beam is applied to the charged surface of the photosensitive drum 1 from a laser scanner (not shown). Irradiation forms an electrostatic latent image. Toner is attached to the electrostatic latent image by the developing device 3 and is developed as a toner image. The toner image thus developed is
By applying a transfer bias to the transfer roller 11 of the transfer means 4, the image is transferred from the surface of the photosensitive drum 1 to the surface of the recording material. The recording material onto which the toner image has been transferred is transported by the transport guide 14.
The toner image is fixed to the surface by being heated and pressed here. The recording material after the fixing of the toner image is discharged to the outside of the image forming apparatus main body, thereby completing the image formation. Note that, among the reference numerals in the drawing, those which have not been described yet will be described in the embodiments described later.

FIGS. 5 and 6 show an enlarged front view and an enlarged top view of the transfer means 4, respectively. The transfer roller 11 is rotatably supported on the distal end side of a transfer arm 12 that is swingable about a shaft 12a on the base end side. A support hole 12 b is formed at the tip of the transfer arm 12.
Is provided with a bearing 22 to reduce the load during rotation. In the transfer roller 11 described above, insulating caps 25 are fitted at both ends in the longitudinal direction of the shaft 23, and the cap 25 allows the transfer roller 1 to be used during transfer.
When a charging bias is applied to the transfer roller 1
1 to the photosensitive drum 1 is prevented.
The above-described bearing 22 is fitted to a portion of the shaft 23 of the transfer roller 11 that extends further outward than the cap 25. The distal end of the transfer arm 12 is urged upward by a compression spring 13, whereby the transfer roller 11 comes into contact with the surface of the photosensitive drum 1 to form a transfer nip N (see FIG. 4). .

[0005]

However, according to the above configuration, both ends of the support hole 12b of the transfer arm 12 are open, and a gap g (see FIG. 6) is formed between the cap 25 and the transfer arm 12. Therefore, when a part of the toner floats during the transfer of the toner image in the nip portion N during the transfer, the floating toner is transferred to the support hole 7 of the transfer arm 12.
It is easy to enter the bearing 22 through b. And
When the toner enters the bearing 22, the bearing 22
Is prevented, the sliding friction between the transfer roller 11 and the transfer arm 12 increases, and rotation failure of the transfer roller 11 occurs. In addition, poor rotation causes poor conveyance of the recording material, causing jams (paper jam) and image defects. In addition, the surface layer of the transfer roller 11 is shaved due to poor rotation of the transfer roller 11, resulting in a short life,
If the surface layer of the transfer roller 11 is shaved and roughened, the photosensitive drum 1 may be damaged and the life of the drum may be shortened. In addition, such a defect,
Not only when the bearing 22 is used as the bearing, but also when a cylindrical bush is used.

Accordingly, the present invention prevents toner from entering the bearing of the transfer roller, thereby preventing problems such as poor rotation of the transfer roller, poor conveyance of the recording material, and shortened life of the transfer roller and the image carrier. It is an object of the present invention to provide a transfer unit which prevents the transfer and an image forming apparatus provided with the transfer unit.

[0007]

According to a first aspect of the present invention, there is provided a transfer means for transferring a toner image on the image carrier to a recording material, the transfer means having a transfer roller abutting on the surface of the image carrier. A cylindrical leak prevention member attached to both ends in the longitudinal direction of a shaft of the transfer roller; a bearing rotatably supporting a portion of the shaft outside the leak prevention member; and a lid portion. A cylindrical cover member having a cylindrical portion and covering the bearing from the outside in the axial direction; and urging the cover member toward the image carrier to bring the transfer roller into contact with the image carrier. And a biasing member.

According to a second aspect of the present invention, in the transfer means according to the first aspect, a part of the cylindrical portion of the cover member overlaps a part of the leak prevention member in the axial direction. It is characterized by.

[0009] The present invention according to claim 3 is the invention according to claim 1 or 2.
Wherein the leak preventing member has a flange portion opposed to the opening of the cylindrical portion of the cover member and arranged close to the opening.

According to a fourth aspect of the present invention, in the transfer means according to any one of the first to third aspects, the bearing is a bearing.

According to a fifth aspect of the present invention, in the transfer means according to any one of the first to third aspects, the bearing is a bush.

According to a sixth aspect of the present invention, in the transfer means according to the fifth aspect, the bearing is formed integrally with the cover member.

According to a seventh aspect of the present invention, there is provided an image carrier on which a toner image is formed on a toner made of powder on the surface, and a transfer means for transferring the toner image formed on the image carrier to a recording material. Wherein the transfer means is the transfer means according to any one of claims 1 to 6.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. It is to be noted that components denoted by the same reference numerals in the drawings have the same configuration or operation, and redundant description thereof will be omitted as appropriate.

First Embodiment FIG. 1 shows an example of an image forming apparatus according to the present invention. FIG. 1 is a longitudinal sectional view of a schematic configuration of an electrophotographic laser printer viewed from the front.
2 and 3 are an enlarged front view and an enlarged top view of the transfer unit in FIG. 1 of the present invention, respectively. The dimensions, materials, shapes, relative positions, and the like of the configurations described in the following description are examples unless otherwise specified.
It is not intended to limit the scope of the present invention thereto.

A laser printer (hereinafter, referred to as "image forming apparatus") shown in FIG. 1 includes a drum-type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as an image carrier. The photosensitive drum 1 has a photosensitive layer of, for example, OPC (organic optical semiconductor) on its surface, and is driven to rotate in a direction indicated by an arrow by driving means (not shown). The surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the charging roller 2. In the charged photosensitive drum 1, the top end of the recording material turns on the top sensor 8 on the downstream side of the pre-transfer roller pair 7.
Thereby, a laser beam is emitted from a laser scanner (not shown) based on image information obtained from an external device such as a personal computer, thereby forming an electrostatic latent image. The electrostatic latent image is developed as a toner image by attaching powder toner to the toner by the developing device 3.

On the other hand, the recording material stored in a paper feed cassette (not shown) is separated and fed one by one from here, and is conveyed by a pair of registration rollers 6 and a pair of pre-transfer rollers 7. After being detected, the sheet is guided to the pre-transfer upper guide 9 and the pre-transfer lower guide 10, and is conveyed to the transfer nip portion (transfer portion) N. The toner image on the photosensitive drum 1 is transferred by the transfer unit 4 to the recording material conveyed to the transfer nip N. The transfer unit 4 includes a transfer roller 11 that forms a transfer nip N with the photosensitive drum 1. The transfer roller 11 is supported by a transfer arm 12 and is urged by a compression spring 13 against the photosensitive drum 1 at a predetermined pressure. In this manner, the transfer nip N
The toner image formed on the photosensitive drum 1 is transferred to the recording material at the transfer nip N. A cleaner 5 is disposed downstream of the transfer nip N along the rotation direction of the photosensitive drum 1 to remove toner (residual toner) remaining on the surface of the photosensitive drum 1 after transfer. The photosensitive drum 1 from which the residual toner has been removed is used for the next image formation.

A transport guide 1 is located downstream of the transfer nip N.
And a fixing device (fixing means) 15 for fixing the recording material.
Transported to The recording material is heated and pressed in the fixing device 15 to fix a toner image on the surface. The recording material after the toner image is fixed is discharged to the outside of the image forming apparatus main body by a discharge roller pair (not shown), thereby completing the image formation.

The above-described transfer roller 6 and the like are connected to a shaft 16 on the right end side.
It is arranged on a support 16 that can swing up and down about a. The support 16 has a lower roller, a top sensor 8, and a lower pre-transfer guide 10 in order from the upstream side along the recording material conveyance direction (the direction of arrow K in the figure). , A transfer arm 12, a transfer roller 11, a compression spring 13, a transport guide 14, and the like. The support member 16 is formed by rotating a cam 18 integral with a rotation base 17 disposed below the fixing device 15 around a shaft 17a to drive a spring member 19 swingable about a shaft 19a. Ascend and descend. As a result, the transfer roller 11 comes into contact with the photosensitive drum 1 and separates from the photosensitive drum 1.

Next, the transfer means 4 will be described in detail with reference to FIGS. FIG. 2 is an enlarged surface view of the transfer unit 4, and FIG. 3 is an enlarged top view of the transfer unit 4.

The transfer means 4 in the present embodiment includes a transfer roller 11, a cap (leak prevention member) 20, a transfer arm 12, a cover member 21, a bearing (bearing) 22, and a spring member (biasing member). 13). In the following description, the lower part in FIG. 3 is described as “left” and the upper part is described as “right”.

The transfer roller 11 has a shaft 23 which is long in the width direction of the recording material (the left-right direction in the direction in which the recording material is conveyed), and a roller member provided so as to surround the outer peripheral surface of the shaft 23 at the center side. 24. The shaft 23 penetrates the center of the roller member 24 in the left-right direction, and the left and right ends (only the left end is shown in FIG.
Protruding portions 23a are formed to protrude from both left and right end surfaces 24a. The cap 20 is fitted to the protrusion 23a.

The cap 20 is formed in a substantially cylindrical shape, and is fitted to the center of the projection 23a of the shaft 23. At an axial center of the cap 20, a flange portion 20a is annularly protruded. The entire cap 20 is formed of, for example, an insulating synthetic resin, and prevents current from leaking from the transfer roller 11 to the photosensitive drum 1 when a transfer bias is applied to the transfer roller 11 during transfer of a toner image. Things.

The transfer arm 12 is supported by the above-described support 16 so as to be able to swing substantially vertically about a shaft 12a on the base end side. A compression spring 13 is interposed between the transfer arm 12 and the support 16 below the distal end of the transfer arm 12, whereby the distal end of the transfer arm 12 is urged toward the photosensitive drum 1. A cover member 21 is fixed to the distal end side of the transfer arm 12.

The cover member 21 is a covered cylindrical member. The cover member 21 has a lid 21a and a cylindrical portion 21b formed integrally with each other.
In addition to being arranged coaxially with the first shaft 23, the opening 21 c faces the inside, that is, toward the end surface 24 a of the roller member 24. The opening 21c of the cover member 21 is disposed so as to be located immediately near the flange 20a of the cap 20, so that the gap g between the opening 21c and the flange 20a is reduced. The inner diameter of the cylindrical portion 21b in the opening 21c is set smaller than the outer shape of the flange portion 20a. Further, a part of the cylindrical portion 21b,
A part of the cap 20 overlaps in the axial direction.

The bearing 22 is formed of the cover member 21 described above.
Is fitted to the inner surface of the cylindrical portion 21b, and rotatably supports the protruding portion 23a of the shaft 23 of the transfer roller 11 described above. That is, the bearing 22 is housed in the covered cylindrical cover member 21.

As described above, the spring member 13 supports the support 1.
6 and the transfer arm 12, the transfer arm 1
2 is urged upward, whereby the transfer roller 11 is brought into contact with the surface of the photosensitive drum 1 via a cover member 21 and a bearing 22 which are integral with the transfer arm 12, so that the transfer roller 11 is in contact with the photosensitive drum 1. The transfer nip N described above is formed at the same time.

As described above, since the bearing 22 is housed in the covered cylindrical cover member 21, one end is closed unlike the conventional case where both ends in the axial direction are open. In addition, a flange portion 20a is provided near the opening 21c of the cover member 21 so as to cover the opening 21c from the inside, and the inner diameter of the cylindrical portion 21b in the opening 21c is larger than the outer diameter of the flange 20a. Since it was set to be small and a part of the cylindrical portion 21b was overlapped with a part of the cap 20 in the axial direction,
It is possible to effectively prevent the toner scattered during the transfer from entering the bearing 22. Therefore, it is possible to prevent problems such as poor rotation of the transfer roller, poor conveyance of the recording material, and shortened life of the transfer roller and the image carrier, which are caused by the toner entering the bearing 22.

The configuration of the shaft 23 of the transfer roller 11 in the vicinity of the other end (not shown) is the same, and redundant description thereof will be omitted.

In the above, the case where the bearing for rotatably supporting the shaft 23 of the transfer roller 11 is the bearing 22 has been described. Is also effective.
In this case, a bush may be fitted on the inner surface of the cover member 21 and the projecting portion 23a of the shaft 23 may be rotatably supported by the bush. Alternatively, the bush may be omitted and the cover member 21 directly The protrusion 23a of the shaft 23 may be rotatably supported.

Further, the cover member 21 is connected to the transfer arm 1.
2 instead of, for example, a cover member 2
1 may be directly supported by a guide member so as to be able to move up and down, and the cover member 21 may be urged toward the photosensitive drum 1 by a spring member 13.

[0032]

As described above, according to the present invention,
It is possible to prevent toner from entering the bearing of the transfer roller, thereby preventing problems such as poor rotation of the transfer roller, poor conveyance of the recording material, and shortened life of the transfer roller and the image carrier.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is an enlarged front view of a transfer unit.

FIG. 3 is an enlarged top view of a transfer unit.

FIG. 4 is a longitudinal sectional view illustrating a schematic configuration of a conventional image forming apparatus.

FIG. 5 is an enlarged front view of a conventional transfer unit.

FIG. 6 is an enlarged top view of a conventional transfer unit.

[Explanation of symbols]

 Reference Signs List 1 image carrier (photosensitive drum) 4 transfer means 11 transfer roller 12 arm member 13 urging member (spring member) 20 leak prevention member (cap) 20a flange portion 21 cover member 21a cover portion 21b cylindrical portion 21c opening 22 bearing ( Bearing) 23 Transfer roller shaft

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H200 FA02 FA08 FA17 GA16 GA23 GA34 GA44 HA02 HB12 HB22 JA02 JB10 LA06 LA17 LA29 3J016 AA02 BA02 BB16 3J103 AA02 CA66 DA01 FA26 GA02 GA57 GA58 GA60

Claims (7)

[Claims] 1. A transfer means for transferring a toner image on an image carrier onto a recording material, the transfer means having a transfer roller abutting on the surface of the image carrier, wherein both ends in the longitudinal direction of the axis of the transfer roller are provided. A cylindrical leak preventing member attached to the shaft; a bearing rotatably supporting a portion of the shaft outside the leak preventing member; a lid and a cylindrical portion; A cover member having a closed cylindrical shape that covers from the outside, and an urging member that urges the cover member toward the image carrier and abuts the transfer roller against the image carrier. Transfer means. 2. The transfer unit according to claim 1, wherein a part of the cylindrical portion of the cover member overlaps a part of the leak prevention member in an axial direction. 3. The device according to claim 1, wherein the leak prevention member has a flange portion facing the opening portion of the cylindrical portion of the cover member and being arranged close to the opening portion. The transfer means described in the above. 4. The transfer means according to claim 1, wherein said bearing is a bearing. 5. The transfer means according to claim 1, wherein said bearing is a bush. 6. The transfer unit according to claim 5, wherein the bearing is formed integrally with the cover member. 7. An image forming apparatus comprising: an image carrier on which a toner image is formed on a toner made of powder on the surface; and a transfer unit for transferring the toner image formed on the image carrier to a recording material. The image forming apparatus according to claim 1, wherein the transfer unit is the transfer unit according to any one of claims 1 to 6.