JP2697711B2 - Brush charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brush charging device used in an image forming apparatus such as a printer, a facsimile, a copying machine or the like using an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, as a method of charging the surface of an image carrier such as a photoreceptor in a brush charging apparatus of this type, there are a method of rotating a brush roller and a method of fixing a flat brush. . Among them, the brush roller has a configuration in which a band-shaped brush having a density of 50,000 F (filament) / inch ² to 100,000 F / inch ² is wound around a shaft, and has a seam of the brush.

[0003]

When the above-described brush charging device is used, friction between the charged object and the toner carrier generates shaving powder or the like having a polarity opposite to the charging characteristic of the charged object. I do. Fine particles of the opposite polarity, such as shavings, which have adhered to the member to be charged cannot be sufficiently removed by the cleaning device, and thus adhere to the brush charging device. As a result, poor charging occurs and image defects occur. In particular, in the brush roller, the fine powder easily accumulates at the joint of the brush, so that poor charging occurs at the joint, and a problem such as fogging occurs in the joint pattern.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brush charging apparatus which can solve the disadvantages of the prior art and can maintain a constant charging ability for a long period of time.

[0005]

According to the present invention, there is provided a belt-shaped conductive brush constituting a brush roller, wherein a brush density at a joint side of a charging brush is made higher than other portions. did.

By increasing the brush density at the seams of the brushes of the brush roller, the difference between the number of brushes in contact with the object to be charged in a portion other than the seam and the number of brushes in contact with the object to be charged near the seam is reduced. Is made uniform. In addition, it is possible to prevent toner and dirt from entering the joint, and to perform uniform charging over a long period of time.

[0007]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view of an image forming apparatus (electrophotographic cartridge) using a brush charging device as one embodiment of the present invention. The device includes a charging brush roller 1, a photosensitive member 3, and a toner carrier. 4, supply roller 5, regulating blade 6, toner 7, stirring member 8
, A transfer roller 9 and a charge removing brush 10. A voltage is applied to the charging brush roller 1 to
(Organic Photoconductor), a photoconductor 3 of Se type or the like is uniformly charged, and an initial potential is applied to the outer peripheral surface thereof. Then, a laser, LED, not shown,
Exposure 2 of image data is performed from a light source such as a liquid crystal to form an electrostatic latent image.

The toner 7 as a developer is guided to a supply roller 5 by a stirring member 8, and further guided to a toner carrier 4. The supply roller 5 is made of a conductive or insulating urethane or silicon foam, a material such as aluminum, and the toner carrier 4 is made of silicon rubber, urethane rubber, nitrile butylene rubber, natural rubber, or urethane or silicon foam. It is made of a flexible material such as a body or a member having a surface treatment applied thereto.

The toner 7 guided to the toner carrier 4 is regulated by a regulating blade 6 (made of a metal spring member such as stainless steel, phosphor bronze, nickel silver, etc.) and is formed into a more uniform thin layer. At this time, the toner 7 is charged by friction. A voltage having the same polarity as that of the toner 7 is applied to the toner carrier 4. When the charged thin layer toner 7 on the toner carrier 4 faces the photoconductor 3, the electric field is applied to the photoconductor 3 by the electric field. Attached to the upper electrostatic latent image and developed,
A toner image is formed.

The toner image on the photoconductor 3 is transferred to a transfer roller 9.
The toner image is transferred onto a recording medium such as paper, an OHP sheet, a postcard, or the like, and the toner image is fixed on the recording medium by a fixing unit (not shown) to obtain an image.

The charging brush roller 1 has the structure shown in FIG. 2, in which a belt-like brush 1A is spirally affixed to a conductive shaft 1B to form a seam 1C.

The details of the charging brush roller 1 are shown in FIG. 3 (a sectional view taken along line AA in FIG. 2). The brush 1A and the base cloth 1D are woven from a conductive rayon fiber having an electric resistance of about 1 × 10 ⁴ Ω · cm and a thickness of 6 denier, and the base cloth 1D is fixed to the conductive shaft 1B by a conductive double-sided tape 1E. doing. The brush width of the brush 1A to be wound is 5 cm, and the diameter as a brush roller is 13 mm in this embodiment.

The circumference of the brush 1A is set at 0.
The position of the charging brush roller 1 is set so as to bite about 5 to 1 mm, and the charging brush roller 1 is rotated in the reverse direction with respect to the photosensitive member 1 at a peripheral speed ratio of 1.5.

(Embodiment 1) Embodiment 1 will be described with reference to FIG. The brush 1A of FIG. 4 is woven so that the width d1 (about 1 mm) on one side of the brush width is 200,000 F / inch ² and the other portion D is 100,000 F / inch ² . When the brush 1A is spirally attached to the conductive shaft 1B, the brush density is increased at the joint.

When a constant voltage of -1300 V was applied to the charging brush roller 1 at a process speed of 33 mm / sec with respect to the photosensitive member 3 having an A4 size width, a charging potential of -700 V was obtained stably.

(Embodiment 2) Embodiment 2 will be described with reference to FIG. The brush 1A shown in FIG. 5 has two sides d ₁ ,
d ₂ consists ones (each approximately 1mm) 200,000 F / inch ^2, a woven the other portions D to a density to be 100,000 F / inch ^2, spiral brush 1A to the conductive shaft 1B When attached in a shape, the brush density was increased at the joint.

When a constant voltage of -1300 V was applied to the charging brush roller 1 at a process speed of 33 mm / sec with respect to the photosensitive member 3 having an A4 size width, the charging potential of -700 V was stabilized as in the first embodiment. I was able to get.

Next, a comparative test of density unevenness was performed on the charging brush rollers of Examples 1 and 2 and a conventional charging brush roller (normal) having a uniform brush density. That is, running evaluation was performed on the three brush rollers, and the number of pages at which density unevenness due to charging unevenness began to occur in halftone patterns such as halftone dots was confirmed. The results shown in Table 1 were obtained.

[0019]

[Table 1]

As shown in Table 1 above, the charging brush rollers of Embodiments 1 and 2 in which the brush density of the brush seam is high can provide an image without charge unevenness on 5000 pages or more. Also, it can be seen that the case where the portion having a high brush density is provided on both sides of the belt-shaped brush (Example 2) is more effective than the case where it is provided on one side (Example 1). In the above embodiment, a mechanism for cleaning the photoreceptor is not provided.
An image without charge unevenness of 000 pages or more could be obtained.

In the above description, an example in which the belt-shaped brush is spirally wound has been described. However, the present invention is not limited to this, and the belt-shaped brush may be wound concentrically. A brush roller is applicable.

[0022]

According to the brush charging device of the present invention, the brush density at the seam of the brush of the brush roller is increased, so that the number of brushes in contact with the object to be charged in a portion other than the seam and the object to be charged at the seam are reduced. The difference in the number of brushes in contact with each other is reduced, and charging is made uniform. Further, since the fine powder adheres to the portion where the brush density is high, it is possible to prevent toner and dirt from entering the joint, and to perform uniform charging over a long period of time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electrophotographic cartridge using a brush charging device according to one embodiment of the present invention.

FIG. 2 is an external view of a charging brush roller.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a detailed view of a charging brush according to the first embodiment.

FIG. 5 is a detailed view of a charging brush according to a second embodiment.

[Explanation of symbols]

1 charging brush roller 1A brush 1B conductive shaft 1C seam 1D backing 1E conductive double-sided tape 2 exposure 3 photoconductor 4 toner carrying member 5 supply roller 6 regulating blade 7 toner 8 agitating member 9 transfer roller 10 discharging brush d _1, d ₂ Width of high brush density part D Width of low brush density part

Claims (3)

(57) [Claims] 1. A brush charging device comprising: a brush roller arranged to contact a surface of a member to be charged in order to charge the member to be charged, wherein the brush roller connects a belt-shaped conductive brush to a conductive shaft. A brush charging device, which is provided on the outer periphery, wherein the brush density on the seam side of the belt-shaped conductive brush is higher than other portions. 2. The brush charging device according to claim 1, wherein the brush density on both sides of the belt-shaped conductive brush is higher than other portions. 3. The conductive belt according to claim 1, wherein the conductive belt is spirally attached to an outer periphery of the conductive shaft.
4. The brush charging device according to 1.