JPH06149096A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which prevents deterioration in image quality by stabilizing the application of a transfer bias to a transfer roller. CONSTITUTION:A cleaning member 16 which cleans a transfer roller shaft 3 by the rotation of the transfer roller 2 is attached to the connecting member 5 of a transfer bias application power source 6, and is provided in contact with a transfer roller shaft 3. Therefore, toner 11 sticking to the transfer roller shaft 3 is removed by the rotation of a transfer roller 2, accumulating and firm sticking of toner to the transfer roller shaft 3 is prevented, and the electrical contact of the connecting member 5 with the transfer roller shaft 3 is made stable, so that deterioration of image quality is 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 for forming an electrophotographic image by using an insulating toner.

[0002]

2. Description of the Related Art In recent years, image forming apparatuses using electrophotography have been widely used in copying machines, printers, facsimiles and the like.

Conventionally, in this type of image forming apparatus, when the toner image formed on the surface of the photoconductor is transferred to the paper, the paper is passed between the photoconductor and the transfer roller, and
A well-known electrophotographic technique is used in which a voltage having a polarity opposite to that of the toner is applied to the transfer roller to form an electric field for transfer.

A conventional image forming apparatus will be described below with reference to FIG. In the figure, 1 is a photosensitive drum, and a photoconductive layer is applied on an aluminum tube. A transfer roller 2 made of conductive rubber or sponge is pivotally supported by a metal transfer roller shaft 3 and is pressed against the photosensitive drum 1. Reference numeral 4 is a chassis of the apparatus body. 5 is a metal leaf spring connecting member, which is attached to the apparatus main body chassis 4,
The transfer roller 2 and the transfer bias applying power source 6 are electrically connected in close contact with the transfer roller shaft 3. 7 is a photoconductor 1
This is the paper onto which the toner image above is transferred.

In the above structure, first, a toner image is formed on the photosensitive drum 1 by a well-known electrophotographic technique. In synchronization with the formation of the toner image, the sheet 7 is conveyed between the photosensitive drum 1 and the transfer roller 2 by a sheet feeding section (not shown) of the apparatus main body. When the paper 7 arrives between the photosensitive drum 1 and the transfer roller 2, the transfer bias applying power source 6 connects the transfer toner to the transfer roller shaft 3 through the connecting member 5 (hereinafter referred to as insulating toner).
A transfer bias having a polarity opposite to that of toner) is applied, and an electric field is formed between the transfer roller 2 and the photosensitive drum 1.
As a result, the toner image on the photosensitive drum 1 is transferred onto the sheet 7 by the electrostatic force and pressure. The sheet 7 on which the toner image has been transferred is conveyed to a fixing unit (not shown) by the rotation of the photosensitive member 1 and the transfer roller 2, and after fixing, the sheet is discharged outside the apparatus main body and the image formation is completed.

In such an image forming apparatus, Japanese Patent Laid-Open No. 62-47671 discloses that a large amount of toner adheres to the surface of the roller when a jam occurs, and the toner is adhered to the paper at the time of transfer after the jam is resolved. Means for solving the problem of adhesion and deterioration of image quality are shown.

[0007]

In such a conventional image forming apparatus, when a toner image is formed on the photosensitive drum 1, a part of the toner may scatter and float in the apparatus body. At the time of transfer, the floating toner is attracted to the transfer roller shaft 3 though a slight amount due to an electrostatic force because a transfer bias having a polarity opposite to the charging polarity of the toner 8 is applied to the transfer roller shaft 3. The toner attached to the transfer roller shaft 3 due to such an action increases in amount as the image formation is repeated, and is rubbed by the rotation of the connection member 5 and the transfer roller 2 which are in contact with the transfer roller shaft 3. It adheres to the surface of the transfer roller shaft 3. As a result, the transfer roller shaft 3 and the connecting member 5
There is a problem in that the electrical connection with is unstable and the transfer electric field is not stable, so that a transfer failure occurs and the image quality is significantly deteriorated.

The present invention solves the above problems, and an object of the present invention is to provide an image forming apparatus which stabilizes application of a transfer bias to a transfer roller and does not deteriorate image quality.

[0009]

In order to achieve the above-mentioned object, the present invention is directed to a transfer roller having a photoconductor for forming a toner image with an insulating toner and a conductive roller shaft pressed against the photoconductor. A power supply unit for applying a transfer bias voltage to the transfer roller shaft, a connecting member for contacting the transfer roller shaft to electrically connect the power supply unit and the transfer roller shaft, and the connecting member for contacting each other. A cleaning member for cleaning the transfer roller shaft is provided.

[0010]

In the above structure, since the insulating toner attached to the transfer roller shaft is cleaned by the cleaning member by the rotation of the transfer roller shaft, the electric contact between the transfer roller shaft and the connecting member becomes stable.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

The same parts as those shown in the conventional example are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 1A, 8 is a charging unit, which uniformly charges the photosensitive drum 1 by corona discharge. 9 is an LED unit, which is the photosensitive drum 1
To form an electrostatic latent image on the photosensitive drum 1. 10
In the developing section, a developing roller 12 that visualizes the toner 11 on the photosensitive drum 1 and a blade 13 that frictionally charges the toner on the developing roller 12 are provided. Reference numeral 14 denotes a paper feeding unit, which feeds the paper 7 between the photosensitive drum 1 and the transfer roller 2,
Transport. A fixing unit 15 fixes the toner image on the sheet 7. A paper discharge unit 16 discharges the paper 7 after fixing from the apparatus main body.

In FIG. 1B, reference numeral 16 is a cleaning member for cleaning the transfer roller shaft 3, which is made of felt,
It is formed of an appropriate material suitable for cleaning, such as sponge or non-woven fabric, and is attached to the arm 17 extending to the connection member 5 by an appropriate means such as a double-sided tape 18. The arm 17 is in contact with the transfer roller shaft 3 due to its elasticity.

In the above structure, first, the surface of the photosensitive drum 1 is uniformly charged to -650 V by the corona discharge of the charging section 18. Next, the uniformly charged surface of the photosensitive drum 1 is exposed according to the image data by the LED unit 9, and an electrostatic latent image is formed. Then, the toner 11 on the developing roller 12 is negatively charged by the rotation of the developing roller 12 of the developing unit 10 and the friction of the blade 13. The electrostatic latent image on the photoconductor 1 is developed by the toner 11 on the developing roller 12 to which a transfer bias of −300V is applied, and becomes a toner image. Then, the paper 7 prepared in the paper feed unit 14 is fed and conveyed between the photosensitive drum 1 and the transfer roller 2. When the paper 7 reaches between the photosensitive drum 1 and the transfer roller 2, a transfer bias of about 700 V is applied to the transfer roller shaft 3 from the transfer bias applying power source 6 via the connecting member 5. As a result, an electric field is formed between the photosensitive drum 1 and the transfer roller 2, and the toner image on the photosensitive drum 1 is transferred onto the paper 7 by electrostatic force and mechanical pressure.

In this series of operations, the developing section 10 is sealed to prevent the toner 11 from scattering during development, but a part of the toner 11 leaks out from both ends of the developing roller 2. May float inside the device body. A small amount of the floating toner 11 is attracted and adhered to the developing roller shaft 3 which is electrostatically charged by applying a transfer bias. However, the toner 11 adhering to the transfer roller shaft 3 is cleaned by the cleaning member 16 that is in contact with the transfer roller shaft 3 when the transfer roller 2 rotates, so that the toner 11 is prevented from being deposited and fixed on the transfer roller shaft 3.

As described above, according to the image forming apparatus of the embodiment of the present invention, the transfer roller shaft 3 is rotated by the rotation of the transfer roller 2.
By providing the cleaning member 16 for cleaning the transfer roller shaft 3 in contact with the transfer roller shaft 3, the toner 11 attached to the transfer roller shaft 3 is removed by the rotation of the transfer roller 2 and is deposited and fixed on the transfer roller shaft 3. Without this, there is an effect that electrical contact between the transfer roller shaft 3 and the connection member 5 can be stabilized.

[0017]

As is apparent from the above description of the embodiments, according to the present invention, the cleaning member for cleaning the transfer roller shaft by the rotation of the transfer roller is attached to the connecting member, and the cleaning member is used as the transfer roller. By providing in contact with each other, the toner adhering to the transfer roller shaft can be removed by the rotation of the transfer roller, and the accumulation and fixing of the toner on the transfer roller shaft can be eliminated. This stabilizes the electrical contact between the connecting member and the transfer roller,
It is possible to prevent deterioration of image quality.

As described above, according to the present invention, it is possible to provide the image forming apparatus which stabilizes the application of the transfer bias to the transfer roller and does not deteriorate the image quality.

[Brief description of drawings]

FIG. 1A is a side view of an image forming apparatus according to an embodiment of the present invention, and FIG. 1B is a side view of the main part.

FIG. 2 is a side view of a main part of a conventional image forming apparatus.

[Explanation of symbols]

 1 Photosensitive Drum 2 Transfer Roller 3 Transfer Roller Shaft 5 Connection Member 6 Transfer Bias Applying Power Supply 11 Insulating Toner 16 Cleaning Member

Claims (2)

[Claims] 1. A photosensitive drum that forms a toner image with insulating toner, a transfer roller that is pressed against the photosensitive drum and has a conductive transfer roller shaft, and a transfer bias voltage is applied to the transfer roller shaft. Power supply means, a connection member for contacting the transfer roller shaft to electrically connect the power supply means and the transfer roller shaft, and a cleaning member for cleaning the transfer roller shaft with which the connection member contacts An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein the cleaning member is attached to the connecting member.