JPH04335685A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an excellent image without having winkles and irregularities in a toner image by improving the coefficient of the friction of the surface of a transfer roller elastic part. CONSTITUTION:In this image forming device having a photosensitive drum 1 and a transfer roller 8 press-contacting thereto, and performing a transfer in such a manner that a recording form passes between these both rollers, one end of, at least, the paper nonpassing part of the surface of the elastic body 10 of the transfer roller 8 is roughened. The surface of the transfer roller 8 is formed by roughning, at least, the paper nonpassing part, so that even of a thick envelope, etc., pass, and the contact pressure of the paper nonpassing part is reduced, the friction can be sufficiently secured by the roughness of the surface. Thus, both rollers can be rotated at the same speed, so that the winkles and the irregularities in the toner image can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic process in a copying machine, a printer, etc., and more particularly to a transfer apparatus using an electrostatic transfer process.

0002

2. Description of the Related Art A printing device using a transfer roller for an electrophotographic process uses a transfer roller having a conductive member arranged around its shaft and a bias in order to transfer a toner image formed on an image carrier to a recording medium. The transfer device includes a bias control device for applying bias.

The transfer roller of such a transfer device is made of an elastic material such as rubber, and is connected to a drive source.

According to such a device, when transferring the toner image formed on the image carrier, the transfer roller is elastically deformed due to its elasticity to ensure a contact area with the recording carrier and transfer the toner image. Transfer can be performed by supplying the necessary electric field between the toner image surface and the recording carrier.

[0005]

However, the external shape of the transfer roller of a transfer device having a drive source is difficult to stabilize due to variations in external precision, wear, and environmental changes. Therefore, there is a problem that the paper passing speed changes and the toner image becomes misaligned.

As a means to solve this problem, there is a method in which the transfer roller is configured to rotate following the image carrier. In such a transfer roller, when paper such as an envelope that is thicker than plain paper is passed through, the contact area between the image carrier and the transfer roller non-passing area becomes smaller, and the frictional force between the image carrier and the transfer roller is reduced. There is a problem in that the speed decreases, slippage is more likely to occur, and a speed difference occurs between one side and the other side of the envelope, resulting in wrinkles and misalignment of the toner image.

The present invention has been developed in view of the above circumstances, and can be applied to thick paper, especially double-layered recording carriers such as envelopes, without causing wrinkles or misalignment of toner images. An object of the present invention is to provide a new image forming apparatus that can transfer good images. Yet another object is to provide a transfer roller that is easy to manufacture and low cost.

[0008]

[Means for Solving the Problems] In order to solve these problems, the present invention includes an image carrier and an elastic transfer roller that comes into pressure contact with the image carrier, and provides a recording medium between the image carrier and the transfer roller. In an image forming apparatus that transfers images by passing the image through a carrier, at least one end of the non-sheet passing portion of the surface of the elastic portion of the transfer roller is roughened.

Further, the image forming apparatus of the present invention includes an image carrier and an elastic transfer roller that is in pressure contact with the image carrier, and forms an image by passing a recording carrier between the image carrier and the transfer roller to transfer the image. In the apparatus, the elastic portion of the transfer roller is electrically conductive.

Furthermore, the image forming apparatus of the present invention includes an image carrier and an elastic transfer roller that is in pressure contact with the image carrier, and the image is transferred by passing a recording carrier between the image carrier and the transfer roller. In the forming apparatus, the transfer roller is configured to rotate following the image carrier.

[0011]

[Operation] Even when a thick recording medium such as an envelope is inserted between the image bearing member and the transfer roller, the contact pressure of the parts of the image bearing body and the transfer roller that do not contact the recording medium decreases. Since sufficient friction is ensured by the rough surface, the image carrier and the transfer roller rotate at the same speed without slipping.

0012

【Example】

(Embodiment 1) The details of the present invention will be explained below based on the illustrated embodiment. FIG. 1 is a schematic sectional view showing the main parts of an electrophotographic printing apparatus using a transfer roller of the present invention, and reference numeral 6 in the figure represents a recording carrier such as paper. or,
Reference numeral 1 denotes a photoreceptor drum which is an image carrier, and is rotated by a drive gear (not shown) in the direction of arrow D in the figure, that is, in the direction of moving the record carrier 6 to the left, and a light beam is generated at the upper part. An optical signal generator 2 is provided.

A charging unit 3, a developing device 4, and an erase unit 5 are arranged around the photosensitive drum 1. A transfer device 7, which is a feature of the present invention, is arranged below the photosensitive drum 1 to transfer a toner image onto a recording medium 6.

FIG. 2 shows an embodiment of the transfer device of the present invention, in which reference numeral 8 is a transfer roller, 14 is a bias control device for applying a bias to the transfer roller,
It is connected to the transfer roller shaft 9. Further, the transfer roller 8 is held by a bearing 15, and a pressure spring 16 is disposed so as to press the transfer roller against the photosensitive drum 1 via the bearing 15.

Next, the transfer roller 8 will be explained. As shown in FIG. 3, an elastic body 10 such as silicone rubber is placed around the transfer roller shaft 9, and at least one end of the surface of the elastic body 10 where the recording carrier 6 does not pass is sandblasted to a surface roughness Rz of 5 μm or more. The surface is roughened. As a result, the surface of the portion where the record carrier 6 does not pass becomes roughened.

The material of the elastic body 10 is preferably a soft rubber material, such as urethane rubber, fluororubber, ethylene propylene rubber, chloroprene rubber, silicone rubber, etc., or rubber foam having a solid layer on the surface. It can be used for. Further, as a manufacturing method for roughening the surface of the elastic body 10, in addition to polishing such as sandblasting, there are also methods such as roughening the mold surface of a rubber mold. In any case, since it can be manufactured through a simple process, a low-cost transfer roller can be manufactured.

[0017] The elastic body can also be made from 1011 to 10 by dispersing conductive fine powder such as carbon black or metal.
The conductivity is 12 Ωcm or less, preferably 103
A resistance of about 1010 Ωcm is preferable in terms of transfer function.

In this embodiment, when a print command is input, the record carrier 6 is sent to the photosensitive drum 1 from a stacker (not shown). A toner image is formed on the photosensitive drum 1 in the following order: charging by the charging unit 3, formation of an electrostatic latent image by the optical signal generating device 2, and toner adhesion to the electrostatic latent image by the developing device 4. The toner image on the photosensitive drum 1 and the recording medium 6 fed from the stacker move to a nip formed by the transfer roller 8 and the photosensitive drum 1.

Next, the bias control device 14 applies an electric field necessary for transfer to the transfer roller shaft 9 between the toner image and the recording medium 6.
A bias is applied to form a gap between the two. The applied bias is applied from the transfer roller shaft 9 to the elastic body 10 made of a conductive member. Next, by the applied bias and the pressure of the transfer roller 8, the toner carried on the photosensitive drum 1 is transferred onto the recording medium 6, and then sent out.

On the other hand, when a thick recording medium such as an envelope is fed into the contact area between the photosensitive drum 1 and the transfer roller 8, the transfer roller 8 is prevented from coming into contact with the recording medium 6 due to its elasticity. While elastically deforming the area to allow the passage of the record carrier 6, both ends that do not contact the record carrier 6 are kept in elastic contact with the photoconductor drum 1, and the roughened surface allows the photoconductor to pass through. A large friction coefficient is ensured between the drum 1 and the drum 1. As a result, the transfer roller 8 receives the driving force from the photoreceptor drum 1 through both ends and rotates while maintaining the same circumferential speed as the photoreceptor drum 1. The paper and the paper on the other side will be fed out at the same speed. Furthermore, since the transfer roller 8 of this embodiment has a roughened surface on the non-sheet passing portion, generally speaking, even if toner tries to adhere to the non-sheet passing portion of the photosensitive drum 1 due to toner scattering, the surface Because the surface is rough, toner is difficult to adhere to. Therefore, fluctuations in frictional force can be reduced.

[0021] Therefore, since the recording carrier is stably conveyed, a good image can be obtained without wrinkles or deviations of the toner image due to wrinkles.

[0022]

[Effects of the Invention] As explained above, in the present invention,
In an image forming apparatus that includes an image carrier and an elastic transfer roller that is in pressure contact with the image carrier, and transfers a recording carrier by passing the recording carrier between the image carrier and the transfer roller, at least one end of the non-sheet passing portion of the surface of the elastic portion of the transfer roller Because the surface is roughened, even when a thick record carrier such as an envelope is inserted between the image carrier and the transfer roller, there is no contact between the image carrier and the transfer roller at the parts that do not contact the record carrier. Even if the pressure decreases, sufficient friction is ensured by the rough surface, so the image bearing member and the transfer roller can rotate at the same speed, and wrinkles and misalignment of the toner image can be reliably prevented. In addition, even if the surface of only one end of the non-paper passing area is roughened, the frictional force necessary for paper passing can be secured.
It is possible to manufacture a low-cost transfer roller with fewer processing steps.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus of the present invention.

FIG. 2 is a front view and a sectional view of a transfer device in Example 1 of the present invention.

FIG. 3 is a front view and a side view of a transfer roller in Example 1 of the present invention.

[Explanation of symbols]

7 Transfer device 8 Transfer roller 9 Transfer roller shaft 10 Elastic body 14 Bias control device 15 Bearing 16 Pressure spring

Claims (3)

[Claims] 1. An image forming apparatus comprising an image carrier and an elastic transfer roller in pressure contact with the image carrier, and in which a recording carrier is passed between the image carrier and the transfer roller to transfer the image.
An image forming apparatus characterized in that at least one end of the non-sheet passing portion of the surface of the elastic portion of the transfer roller is roughened. 2. An image forming apparatus comprising an image carrier and an elastic transfer roller that is in pressure contact with the image carrier, and in which a recording carrier is passed between the image carrier and the transfer roller to transfer the image.
The image forming apparatus according to claim 1, wherein the elastic portion of the transfer roller is electrically conductive. 3. An image forming apparatus comprising an image carrier and an elastic transfer roller in pressure contact with the image carrier, and in which a recording carrier is passed between the image carrier and the transfer roller to transfer the image.
3. The image forming apparatus according to claim 1, wherein the transfer roller is configured to rotate in a driven manner with respect to the image carrier.