JPH11327257A - Contact type electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact type electrifying device having a long service life and capable of obtaining a stable image under environment where temperature and humidity change to a large extent. SOLUTION: In this contact type electrifying device using a roll type electrifying brush 1 formed of a pile; the rotating brush 1 on which voltage is previously applied comes in contact with a photoreceptor 2. In such a contact state, the brush 1 whose length is <=1.5 mm and whose thickness is <=3 deniers is rotated in the same direction as the photoreceptor 2 so that the ratio of circumferential speed may be >=2. While the brush 1 is rotated, it is brought into contact with the photoreceptor 2 with a biting <=0.5 mm, whereby service life is prolonged and a stable image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device provided with a brush-like charging member in an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, a charging device in an electrophotographic apparatus charges a photosensitive member by a charger called a scorotron charger. However, the charging by this charging device has a problem that ozone is generated. Since ozone has an adverse effect on the human body, there is a demand for an electrophotographic apparatus to be ozone-free. As one of the methods for achieving the ozone-free operation, a brush charging device has been attracting attention in recent years. Among the brush charging devices, there are a fixed brush charging device and a rotating brush charging device. However, the fixed brush charging device has a problem that it is not possible to improve the quality of the image because vertical stripes called "strokes" occur in the image. On the other hand, the rotating brush charging device has an advantage that high image quality can be achieved without generating vertical stripes called "stroke" on an image.

[0003]

However, since the rotating brush charging device is in contact with the photoreceptor and rotates, the pile of the brush falls off during use, and image defects such as the appearance of the removed pile appearing in an image occur. There is a problem to do. In order to solve this problem, it is necessary to reduce the load on the rotating brush due to contact with the photoconductor. Therefore, the biting of the rotating brush into the photoreceptor is reduced, and the load is reduced. However, if the bite is reduced, the charging ability of the brush is reduced, and there is a problem that a stable image cannot be obtained, for example, the charging ability changes due to the influence of the environment such as a temperature change and a humidity change.

Accordingly, an object of the present invention is to provide a contact charging device capable of achieving a long life and obtaining a stable image.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a contact-type charging device using a roll-shaped charging brush formed of a pile, wherein a charging brush to which a voltage is applied in advance contacts a photosensitive member while rotating. In this contact state, the bite between the photosensitive member and the charging brush is set to 0.5 mm or less.

According to this configuration, a contact charging device that can achieve a long life and obtain a stable image can be obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is a contact-type charging device using a roll-shaped charging brush formed of a pile, wherein the charging brush, to which a voltage is applied in advance, rotates while rotating the photosensitive member. And in this contact state, the bite between the photosensitive member and the charging brush is set to 0.5 mm or less.

According to a second aspect of the present invention, the length of the pile of the charging brush is 1.5 mm or less.

According to a third aspect of the present invention, the thickness of the pile of the charging brush is 3 denier or less.

According to a fourth aspect of the present invention, the rotating direction of the charging brush is the same as that of the photosensitive member.

According to a fifth aspect of the present invention, the peripheral speed of the charging brush is twice to three times the peripheral speed of the photosensitive member.

According to the inventions having the above-described configurations, the life can be extended and a stable image can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus using a roll-shaped charging brush according to an embodiment of the present invention, and FIG. 2 is a roll when the biting of the charging brush / photoreceptor is set to 0.5 mm. FIG. 3 is a diagram showing the change in resistance between the charging brush and the ground, and FIG. 3 is a diagram showing the change in resistance between the charging brush and the ground when the bite of the charging brush / photoreceptor is set to 1.0 mm. It is a schematic structure figure of the same resistance measuring device.

In FIG. 1, 1 is a roll-shaped charging brush, 2 is a photosensitive member, 3 is a power supply, 4 is a developing device, 5 is a transfer device, and 6 is an exposure device. ,
Reference numeral 7 denotes a recording medium.

When the peripheral speed of the photosensitive member 2 is set to 200 mm / sec and a constant voltage of -1.25 kv is applied to the charging brush 1 in the form of a roll, the charging brush in the form of a roll / biting of the photosensitive member, the charging brush in the form of a roll Peripheral speed, pile thickness,
The image was evaluated when the length was changed.

The results are shown in Table 1 when the bite of the roll-shaped charging brush / photoreceptor was set to 0.5 mm.
1.0mm roll-in charging brush / photoreceptor bite
(Table 2).

[0017]

[Table 1]

[0018]

[Table 2]

As apparent from Tables 1 and 2, the peripheral speed of the roll-shaped charging brush is from -1000 mm / sec to -400 mm / sec, and the pile thickness is 3D or 6
Good images were obtained from 00 mm / sec to 1000 mm / sec and the pile thickness 3D.

Next, under conditions of good image quality, high temperature and high humidity (32.5 ° C., 80% RH), normal temperature and normal humidity (25 ° C.,
60% RH, low temperature and low humidity (10 ° C., 20% RH), roll-shaped charging brush / bite of photoconductor, roll-shaped charging brush when changing pile length /
The resistance change between the grounds is shown. Here, the reason for the resistance change between the roll-shaped charging brush and the ground is that the surface potential on the photosensitive member needs to be constant in order to obtain a stable image under any conditions. In order to achieve this, it is desired that the resistance change between the roll-shaped charging brush and the ground is small. Then, the resistance change between the roll-shaped charging brush and the ground was shown.

FIG. 3 shows a high-temperature, high-humidity (32.
5 ° C, 80% RH, normal temperature and normal humidity (25 ° C, 60% RH)
H) under low temperature and low humidity (10 ° C., 20% RH)
The change in resistance between the roll-shaped charging brush and the ground when the length and thickness of the pile were changed was shown. Also in FIG.
The outline of the roll-shaped charging brush / ground resistance measuring device is shown. In FIG. 4, reference numeral 8 denotes an Al tube.
9 is a constant current power supply. In the resistance measurement method, the voltage was measured when a low current of 1 mA was passed from the constant current power supply 9 to the roll-shaped brush 1, and the resistance value was determined from these values. In practice, the resistance change between the roll-shaped charging brush and the ground needs to be 10 times or less in a low-temperature and low-humidity environment compared to a high-temperature and high-humidity environment.

As is clear from FIGS. 2 and 3, the condition in which the resistance between the roll-shaped charging brush and the ground is stable in each environment is when the biting of the roll-shaped charging brush / photoreceptor is 0.5 mm. When the pile length is 1.5 mm or less and the bite of the roll-shaped charging brush / photoreceptor is 1.0 mm, the resistance is stable under all conditions.

Next, the life of the contact charging device of the present invention was measured under conditions of good image quality and under conditions where the resistance was stable in each environment. The method of measuring the life is to measure the change over time of the surface potential on the photoreceptor,
The time until the% decreased was measured. In practical use, if the surface potential of the photoreceptor drops by 10% or more, an image defect occurs, and further, a life of 15 hours or more is required.

The results are shown in (Table 3) when the bite of the roll-shaped charging brush / photoreceptor was set to 0.5 mm.
1.0mm roll-in charging brush / photoreceptor bite
(Table 4).

[0025]

[Table 3]

[0026]

[Table 4]

As is clear from Tables 3 and 4, the penetration of the charging brush / photoreceptor in the form of a roll was reduced by 0.5.
mm, and the peripheral speed of the roll-shaped charging brush is -800 mm
From / sec to -600 mm / sec, a practically sufficient life can be obtained.

As described above, the pile length is set to 1.5
mm and a denier of 3 denier or less, a roll-shaped charging brush is rotated in the same direction as the photoreceptor at a peripheral speed ratio of 2 or more, and makes contact with the photoreceptor at a depth of 0.5 mm or less to provide a long life. And a stable image can be obtained.

[0029]

As described above, according to the present invention, it is possible to realize a contact charging device capable of prolonging the service life and obtaining a stable image under an environment where temperature and humidity change are large.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus using a roll-shaped charging brush according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a change in resistance between a roll-shaped charging brush and a ground when the biting of the roll-shaped charging brush / photoconductor is set to 0.5 mm according to an embodiment of the present invention;

FIG. 3 is a diagram showing a change in resistance between the roll-shaped charging brush and the ground when the bite of the roll-shaped charging brush / photoconductor is set to 1.0 mm according to the embodiment of the present invention;

FIG. 4 is a schematic configuration diagram of a resistance measuring device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Roll-shaped charging brush 2 Photoconductor 3 Power supply 4 Developing device 5 Transfer device 6 Exposure device 7 Recording medium

Claims (5)

[Claims] 1. A contact-type charging device using a roll-shaped charging brush formed of a pile, wherein a charging brush to which a voltage is applied in advance contacts a photoreceptor while rotating. A contact charging device, wherein the bite between the body and the charging brush is 0.5 mm or less. 2. The length of a pile of the charging brush is 1.5 m.
2. The contact charging device according to claim 1, wherein the value is not more than m. 3. The contact charging device according to claim 1, wherein the thickness of the pile of the charging brush is 3 deniers or less. 4. The contact charging device according to claim 1, wherein the rotating direction of the charging brush is the same as that of the photosensitive member. 5. The contact charging device according to claim 1, wherein the peripheral speed of the charging brush is not less than twice and not more than three times the peripheral speed of the photosensitive member.