JPH1063069A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which surely removes particles, for example toner, from an electrifying roller without damaging the electrifying roller and maintains satisfactory image quality. SOLUTION: In the image forming device having a photoreceptor 1 and the electrifying roller 2 for electrifying the photoreceptor 1 by rotating in contact with the surface of the photoreceptor 1, a cleaning roller 3 which rotates in contact with the electrifying roller 2 while following it is provided, and the roller hardness (by JIS - A type hardness meter) of the cleaning roller 3 is made smaller than the roller hardness (by JIS - A type hardness meter) of the electrifying roller 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to an image forming apparatus such as a facsimile, and more particularly, to an image forming apparatus provided with a charging roller that rotates in contact with a photosensitive member and charges the photosensitive member.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, a corona discharge device utilizing corona discharge has been generally used as a means for charging a photosensitive member. However, in the case of a corona charger, ozone and nitrogen oxides are generated due to corona discharge, and these have a bad influence on the human body and the environment. Also, these adhere to the photoreceptor charger, optical system, etc.,
This may cause image deterioration.

In order to avoid such inconvenience due to corona discharge, a contact charging system in which the photosensitive member is charged by directly contacting the photosensitive member is proposed in, for example, Japanese Patent Application Laid-Open No. 63-149668.

[0004] By adopting such a contact charging system, improvement in charging efficiency can be expected. However, in this method, since the charging member comes into contact with the photoreceptor, fine powder toner (3 μm or less) on the photoreceptor that passes through the photoreceptor without being caught by the cleaning device (for example, a cleaning blade) flows downstream of the cleaning device. A new problem arises in that the toner adheres to the charging roller located at the position (1) and the surface of the charging roller becomes dirty, thereby causing poor charging.

[0005] In particular, since the charging roller is charged by contact with the photoreceptor, toner powder, paper powder and the like tend to adhere to the charging roller due to adhesion such as electrostatic force and van der Waals force.

For example, Japanese Patent Application Laid-Open No. Hei 2-301777 proposes that a cleaning member made of a felt material or the like is brought into contact with a contact charging member such as a charging roller to remove toner powder and the like adhering to the charging roller. doing.

[0007]

However, in the conventional apparatus, streak unevenness is apt to occur when removing toner powder or the like adhering to the charging roller, and the quality cannot be maintained for a long period of time. In addition, the charging member is damaged by the cleaning member made of a felt material or the like, and the charging performance is deteriorated.

The toner powder adhering to the charging roller passes through the cleaning blade of the photoreceptor. Therefore, the particle diameter of the toner powder is often very small (3 μm or less). It is extremely difficult to remove the powder by rubbing the surface of the charging roller.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of reliably removing particles such as toner from the charging roller without damaging the charging roller and maintaining good image quality. Aim.

[0010]

In order to achieve the above object, the present invention has an image carrier and a charging roller which rotates in contact with the surface of the image carrier to charge the image carrier. In the image forming apparatus, a cleaning roller that rotates in contact with the charging roller is provided, and the roller hardness of the cleaning roller (according to a JIS-A hardness meter) is determined by the roller hardness of the charging roller (according to a JIS-A hardness meter). The present invention provides an image forming apparatus characterized in that the image forming apparatus is smaller than the image forming apparatus.

Further, the present invention provides an image forming apparatus, wherein the surface of the cleaning roller is made of rubber.

Further, the present invention provides an image forming apparatus, wherein the surface roughness of the cleaning roller is smaller than the surface roughness of the charging roller.

[0013]

According to the present invention, when the cleaning roller is pressed against the charging roller, the surface of the cleaning roller is more deformed than the surface of the charging roller with respect to the toner on the charging roller. Accordingly, the surface of the cleaning roller has a larger contact area with the toner than the surface of the charging roller, and the surface of the cleaning roller has a larger adhesive force to the toner than the surface of the charging roller. Therefore, when the cleaning roller is driven to rotate in accordance with the rotation of the charging roller, the toner on the charging roller is reliably transferred and adhered to the cleaning roller.

Further, according to the present invention, the surface of the cleaning roller becomes more flexible.

Further, according to the present invention, the contact probability of the cleaning roller with the toner is larger than the contact probability of the charging roller with the toner, and the adhesion to the toner is further increased.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a structure around a photoreceptor 1 of an image forming apparatus embodying the present invention, and FIG. First, referring to FIG.
Is a charging roller, 3 is a cleaning roller for the charging roller, 4 is exposure light, 5 is a developing unit, 6 is a transfer roller, 7 is a cleaning unit, 8 is quenching light,
9 is a transfer paper.

The charging roller 2 is rotatably supported, and is in constant contact with the surface of the photoconductor 1. When the photoconductor 1 rotates, the charging roller 2 also rotates. When a predetermined voltage is applied to the charging roller 2, a discharge is generated in a minute gap between the charging roller 2 and the photoconductor 1, whereby the photoconductor 1 is charged.

As shown in FIG. 2, the charging roller 2 has an elastic layer 12 having a volume resistivity of 10 ⁶ to 10 ¹² Ω · cm on a cored bar 11, so that a pinhole or the like on a photosensitive member is formed. The current is prevented from being concentrated on a portion having a small resistance. The elastic layer 12 is made of rubber (elastic body), and absorbs the occurrence of uneven pressure contact between the charging roller 2 and the photoconductor 1 by its elasticity. In this embodiment, the elastic layer 12 of the charging roller 2 has a volume resistivity of 10 ⁸ Ω.
Cm epichlorohydrin rubber was used, and the thickness of the rubber layer was 3 mm. The pressing force against the photoconductor 1 was 300 mN / cm (length direction). The elastic layer 1
2 can be about 1 to 5 mm if necessary, and the pressing force against the photoreceptor 1 is 50 to 500 mN / cm.
(Length direction).

A surface layer 13 having high releasability is formed on the surface of the elastic layer 12 of the charging roller 2. The surface layer 13 has a function of preventing adhesion between the photoconductor 1 and the particles of toner or paper powder remaining on the photoconductor after cleaning upstream. The surface layer 13 of this example is formed by applying a fluororesin in which epichlorohydrin rubber is dispersed to a thickness of 10 μm and imparting conductivity.
High surface release properties. In addition, the thickness of this surface layer can be set to 2 to 50 μm as needed.

In the vicinity of the charging roller 2, there is provided a cleaning roller 3 which is rotatably supported by being pressed against the charging roller 2. Therefore, when the charging roller 2 rotates, the cleaning roller 3 rotates accordingly. The cleaning roller 3 is configured such that a surface layer 15 is provided on a cored bar 14. In this embodiment, the surface layer 15 is made of epichlorohydrin rubber of the same material as the elastic layer 12 of the charging roller 2, has a thickness of 3 mm, and is 300 mN / cm (length direction) with respect to the charging roller 2. ). The thickness of the surface layer 15 may be 1 to 5 m if necessary.
m, and the pressing force against the charging roller 2 can be about 50 to 500 mN / cm (length direction).

In this embodiment, the charging roller 2 has a roller hardness of 50 degrees (according to a JIS-A type hardness meter), and the cleaning roller 3 has a roller hardness of 35 degrees (according to a JIS-A type hardness meter).

Here, the roller hardness will be described. Roller hardness means hardness measured by a JIS-A type hardness meter in a state where a roller material is formed in a roller shape,
It differs from the rubber hardness (JIS-A) of the roller material measured in a state where the roller material is not formed. Since the roller hardness is a hardness in a state where the roller material is formed in a roller shape, it accurately represents the hardness of the roller surface in a state where the roller is actually used. Then, the roller hardness can be obtained by setting the roller in a measuring instrument, bringing the pressure surface into contact with the roller perpendicularly, and immediately reading the memory.

As described above, in this embodiment, the roller hardness of the cleaning roller 3 is smaller than the roller hardness of the charging roller 2. Therefore, when the cleaning roller 3 is pressed against the charging roller 2, the surface of the cleaning roller 3 is more in contact with the toner on the charging roller 2.
Deforms more than the surface. As a result, the surface of the cleaning roller 3 has a larger contact area with the toner than the surface of the charging roller 2, and the surface of the cleaning roller 3 has a larger adhesive force to the toner than the surface of the charging roller 2. Become. Therefore, when the cleaning roller 3 is driven to rotate by the rotation of the charging roller 2, the toner on the charging roller 2 is reliably transferred and adhered to the cleaning roller 3. As described above, in this embodiment, since the fine powder adhering to the charging roller 2 is transferred to the cleaning roller 3, it is possible to prevent the charging roller 2 from being excessively adhered.

Further, in this embodiment, in order to prevent the toner particles from the charging roller 2 from being laminated in multiple layers on the cleaning roller 3, a cleaning member 16 arranged to be in pressure contact with the surface of the cleaning roller 3 is provided. Further provided. The cleaning member 16 is a flexible member, and can be made of, for example, a material such as foamed polyurethane or felt, or a flocked brush made of a material such as nylon, Teflon, acrylic, or polyester. Instead of the cleaning member 16, a scraper member made of, for example, a polyurethane rubber blade, a thin steel plate or the like may be arranged.

The surface roughness of the charging roller 2 is set to 5 to 10
μmRz, and the surface roughness of the cleaning roller 3 is 1 to
By setting it to 5 μmRz, the contact probability of the cleaning roller 3 with the toner can be made larger than the contact probability of the charging roller 2 with the toner, and the adhesion to the toner can be further increased to improve the cleaning property.

In the above embodiment, the charging roller 2 having a roller hardness of 50 degrees and the cleaning roller 3 having a roller hardness of 35 degrees have been described. A roller having a roller hardness of 25 to 40 degrees is preferably used.

In the above embodiment, the case where the charging roller 2 has the elastic layer 12 and the surface layer 13 has been described.
Even when the charging roller 2 is composed of only the elastic layer 12, the same effect as in the above embodiment can be obtained by making the roller hardness of the cleaning roller 3 smaller than the roller hardness of the charging roller 2. .

In the above embodiment, the surface layer 13 of the charging roller 2 is made of a fluororesin in which epichlorohydrin rubber is dispersed. However, a fluororesin, a nylon resin, or a Teflon resin may be used as it is. Good and
Rubber may be dispersed and used. Further, in this embodiment, epichlorohydrin rubber is used as the material of the surface layer 15 of the cleaning roller 3, but other various materials such as silicon rubber, polyurethane rubber, and chloroprene rubber can be used.

[0029]

As described above, according to the present invention, the roller hardness (according to the JIS-A type hardness meter) of the cleaning roller which rotates following the charging roller is determined by the roller hardness (JIS-A type) of the charging roller. (According to a mold hardness meter), it is possible to reliably remove particles such as toner from the charging roller without damaging the charging roller. Therefore, it is possible to provide an image forming apparatus capable of maintaining good image quality.

Further, according to the present invention, since the material of the surface of the cleaning roller is made of rubber, it is possible to easily obtain the surface of the cleaning roller having a hardness smaller than the hardness of the material of the surface of the charging roller.

Further, according to the present invention, since the surface roughness of the cleaning roller is made smaller than the surface roughness of the charging roller, particles such as toner can be more reliably removed.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a main part of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged front view showing a part of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Cleaning roller

Claims (3)

[Claims] 1. An image forming apparatus comprising: an image carrier; and a charging roller which rotates in contact with a surface of the image carrier and charges the image carrier. An image forming apparatus comprising: a cleaning roller; and a roller hardness (based on a JIS-A type hardness meter) of the cleaning roller is smaller than a roller hardness (based on a JIS-A type hardness meter) of the charging roller. 2. The image forming apparatus according to claim 1, wherein:
An image forming apparatus, wherein a material of a surface of the cleaning roller is rubber. 3. The image forming apparatus according to claim 1, wherein:
An image forming apparatus, wherein the surface roughness of the cleaning roller is smaller than the surface roughness of the charging roller.