JP2006133373A - Manufacturing method of electrifying roller and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the fouling of roller surface by suppressing fluctuations of an electrifying potential in the axial direction with respect to an electrifying roller having a thermoplastic resin layer. <P>SOLUTION: The manufacturing method of electrifying roller is characterized in that it has a process of machining thermoplastic resin after molding. When elastic material is used for the electrifying roller, because an elastic layer is not hard, the manufacturing method of electrifying roller gets along only with a subsequent grinding process and does not require a machining process. On the contrary, when thermoplastic resin is used as electrifying roller material, the machining process is disposed because of the hard thermoplastic resin layer, thereby, the roundness is secured and the fluctuations of an electrifying potential in the axial direction are reduced. Further, because the flatness of the surface is secured by the grinding process, attachment of the fouling to the roller surface is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus used for a copying machine, a facsimile machine, a printer, and the like, and more particularly to a method of manufacturing a charging roller in a charging device that performs a charging process on an image carrier.

As a general charging method in an image forming apparatus, there is a contact charging method in which a charging roller is brought into contact with a photosensitive drum. However, this contact charging method has the following problems.

The constituent material of the charging roller oozes out from the charging roller and adheres to the surface of the photosensitive drum. When this adhesion progresses, a trace of the charging roller remains on the surface of the photosensitive drum.
When an AC voltage is applied to the charging roller, the charging roller in contact with the photosensitive drum vibrates and a charging sound is generated.
The toner on the surface of the photosensitive drum adheres to the charging roller and the charging performance is deteriorated. In particular, when the above-described seepage of the charging roller occurs, the toner becomes more easily attached.
If the photosensitive drum is not driven for a long time, permanent deformation occurs in the charging roller.

In order to deal with such a problem, a proximity charging method has been devised in which the charging roller is brought close to the photosensitive drum instead of contacting (Patent Document 1 or the like). In this proximity charging method, the charging roller and the photosensitive drum are opposed to each other so that the closest distance is 0.005 to 0.3 mm, and a voltage is applied to the charging roller to charge the photosensitive drum. It is. In the proximity charging method, the charging roller and the photosensitive drum are not in contact with each other. Therefore, the problem that occurs in the contact charging method is “adhesion of the constituent material of the charging roller to the photosensitive drum” and “charging roller caused by long-term non-use. "Permanent deformation" is not a problem. In addition, regarding the “decrease in charging performance of the charging roller due to toner adhesion”, the proximity charging method is superior because less toner adheres to the charging roller.

The required characteristics of the charging roller used in the proximity charging method are different from those of the charging roller used in the contact charging method. This is because, in the contact charging method, the charging roller needs to be in uniform contact with the photosensitive drum in order to uniformly charge the photosensitive drum. For this reason, the charging roller has an elastic body such as vulcanized rubber around the core metal. This is because such a charging roller has the following problems when used in the proximity charging system.

In order to ensure a certain gap with the photosensitive drum, it is necessary to provide spacers or the like in the non-image areas (areas not involved in image formation) at both ends in the axial direction of the charging roller. If the spacer is made of an elastic material like this, the charging roller will be deformed when the spacer receives external force (from the photosensitive drum). Cause image unevenness.

If the charging roller is made of vulcanized rubber, the charging roller may be deformed by its own weight and the gap may change, and the vulcanized rubber is liable to sag or deform over time. There is also concern about changes over time.
Therefore, in order to deal with such a problem, a charging roller is known in which a resistance adjustment layer is formed using a thermoplastic resin that is an inelastic material instead of vulcanized rubber or the like (Patent Document 2).
Since this thermoplastic resin is hard, it has been difficult to obtain sufficient roundness by polishing after being formed into a cylindrical shape.

Further, a charging roller having a conductive elastic layer and a surface layer based on a fluorine-based resin is known (Patent Document 3).
Furthermore, a charging roller manufactured by polishing and grinding an elastic body is known (Patent Document 4).

Japanese Patent Laid-Open No. 3-240076 JP 2002-244402 A JP 2002-251053 A JP 2002-364633 A

  An object of the present invention is to suppress variation in the charging potential in the axial direction in a charging roller having a thermoplastic resin layer and to reduce contamination on the roller surface.

As means for solving the above problems, the present invention has the following features.
The method for manufacturing a charging roller according to claim 1, wherein a molding step for molding a cylindrical thermoplastic resin layer, a cutting step for cutting the surface of the molded thermoplastic resin layer, and the thermoplastic resin that has been cut. And a polishing step for polishing the surface of the resin layer.
According to a second aspect of the present invention, the thermoplastic resin layer further includes an ABS resin.
According to a third aspect of the present invention, there is provided a method for producing a charging roller, wherein the thermoplastic resin layer in the molding step is molded around a core shaft.
6. The charging roller manufacturing method according to claim 4, further comprising the step of forming a release layer on the surface of the polished thermoplastic resin layer. The method for manufacturing a charging roller according to claim 4, wherein the release layer includes a fluororesin.
The image forming apparatus according to claim 6, further comprising: a photosensitive member; and a charging roller disposed in proximity to and non-contact with the photosensitive member. One of the charging rollers is provided.

As described above, in the charging device of the present invention, roundness is easily ensured even in the case of a hard thermoplastic resin layer by the cutting step, so that variation in charging potential in the axial direction is reduced. .
In addition, since the smoothness of the surface is ensured by the polishing step, adhesion of dirt to the surface of the charging roller is reduced.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present invention, and shows the configuration of main members such as a photoreceptor 2 and a charging roller 3.
FIG. 2 shows a schematic view of a charging roller according to the present invention. The charging roller 3 is disposed close to the photoreceptor 2 by the GAP holding member 20. The charging roller 3 is close to and non-contact with the photoreceptor 2, and the end of the charging roller 3 is in contact with the photoreceptor 2.
FIG. 3 is a schematic explanatory diagram of a charging roller molding process according to the present invention. A thermoplastic resin, which is a material, is injection-molded with respect to the core bar installed in the mold.
FIG. 4 is a schematic view from the charging roller molding to polishing according to the present invention.

The method for manufacturing the charging roller 3 of the present invention is characterized by having a step of cutting the molded thermoplastic resin. In the case of the charging roller 3 using an elastic material, since the elastic layer is not hard, only a subsequent polishing step is required, and a cutting step is not necessary. On the other hand, when a thermoplastic resin is used as the material of the charging roller 3, the thermoplastic resin layer is hard and sufficient roundness cannot be ensured only by the polishing step. In contrast, in the present invention, by providing a cutting step, roundness is ensured, and variation in charging potential in the axial direction is reduced.
Moreover, since the smoothness of the surface is ensured by the polishing step, the adhesion of dirt to the surface of the charging roller 3 is reduced. The effect of reducing the adhesion of dirt to the surface of the charging roller 3 by this polishing step is also effective for the adhesion of spherical toner by a polymerization method or the like.
Polishing is performed by tape polishing, for example. This is a processing method in which a lapping tape for polishing is pressed against the charging roller 3 at a constant pressure, and the lapping tape is polished while being fed. The lapping tape is coated with abrasive grains having a particle size of 0.1 to 60 μm. A polyester film having a thickness of 30 to 100 μm is used.

The thermoplastic resin layer of the charging roller 3 of the present invention includes polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene (PS), and copolymers thereof (AS, ABS, etc.). It is most preferable that an ABS resin is included.
As another embodiment of the present invention, the thermoplastic resin layer may be one in which a conductive material is dispersed as in Patent Document 1.

  The thermoplastic resin layer of the charging roller 3 of the present invention is characterized in that it is molded around the shaft core in the molding step (see FIG. 3). Further, as another embodiment, it may be formed around the axis via an intermediate layer.

The thermoplastic resin layer of the charging roller of the present invention is characterized in that a release layer is formed on the surface after the polishing step.
A release layer is formed on the surface layer through a coating process (not shown) on the charging roller. For example, the release layer may be formed by spray coating. Spray coating is a method of spraying fine paint in the form of a fine mist onto an object to be coated by applying compressed air to the paint.
Thereby, the adhesion of dirt on the surface of the charging roller 3 is further reduced. The effect of reducing the adhesion of dirt to the surface of the charging roller 3 by the release layer is also effective for the adhesion of spherical toner by a polymerization method or the like.

  The release layer of the present invention includes a fluororesin. By containing a fluororesin, it is excellent in non-adhesiveness, hardly gets dirty, and has excellent corrosion resistance and wear resistance, and can be used stably for a long time. As another embodiment, the fluororesin may contain a conductivity imparting agent as in Patent Document 2.

Here, general properties of the fluororesin will be described.
Since the fluororesin is non-adhesive and has a low surface energy, it does not attract any adhesive substance, and therefore has a property that the adhesive substance is difficult to stick and easily removed.
Moreover, the fluororesin has excellent corrosion resistance and is not affected by corrosive substances. For this reason, no harmful substances are generated during use and it does not contaminate, so it exhibits excellent power against acids, alkalis, solvents and the like.

In addition, the fluororesin is excellent in abrasion resistance, and the fluorine-modified paint system is advantageous for high-load friction because it combines the slipperiness of the fluororesin and the improved coating film by the organic binder resin.
The electrical properties of fluoropolymers include non-adhesiveness and corrosion resistance in terms of surface resistance, no moisture absorption or contamination, and high insulation resistance, and low insulation damage due to low degree of damage caused by arc discharge. Can keep you.

An image forming apparatus according to the present invention includes the photosensitive member and the charging roller according to the present invention, which is disposed in proximity to and in non-contact with the photosensitive member.
The configuration and operation of the image forming apparatus will be described below with reference to FIG.
This image forming apparatus includes a photosensitive drum 2, a charging roller 3, a developing roller 72, a transfer roller 62, and a cleaning device 63.

The charging roller 3 is supplied with power from a power pack (not shown) and charges the photosensitive drum 2. The photosensitive drum 2 is rotated in the direction of the arrow by a driving mechanism (not shown). The surface potential meter is provided immediately after the charging roller 2 along the rotation direction, and measures the surface potential of the photosensitive drum 2.

The developing roller 72 attaches toner to the charged photosensitive drum 2, and the transfer roller 62 transfers the toner attached to the photosensitive drum 2 to the recording paper 10. The cleaning device 63 removes the toner remaining on the photosensitive drum 2 and cleans the photosensitive drum 4.

In the image forming process by the image forming apparatus, first, the surface of the photosensitive drum 2 is charged to a negative high potential by the charging roller 3. Subsequently, the charged photosensitive member surface is irradiated with an exposure L made of reflected light or laser light from the document. This exposure L has a light amount distribution corresponding to the black / white of the image to be formed, and the potential of each part (negative potential) on the surface of the photoconductor is decreased in accordance with the amount of received light. A potential distribution corresponding to the light amount distribution, that is, an electrostatic latent image is formed.

When the photosensitive drum 2 rotates and a portion of the surface where the electrostatic latent image is formed passes through the developing roller 72, toner corresponding to the potential distribution adheres to the surface of the photosensitive member, and the electrostatic latent image becomes a toner image. Is visualized as The toner image is transferred to the recording paper 10 fed at a predetermined timing by the transfer roller 62, and the recording paper 10 is conveyed toward a fixing unit (not shown).

On the other hand, after the transfer, the photosensitive drum 2 is cleaned by removing the toner remaining on the surface of the photosensitive member by the cleaning device 63, and the residual charge is removed by the quenching lamp 64, and the process proceeds to the next image forming process. To do.

1 is an overall configuration diagram of an image forming apparatus showing an embodiment of the present invention. It is an enlarged view of a charging roller showing an embodiment of the present invention. It is explanatory drawing of the formation step of a charging roller. It is explanatory drawing from the shaping | molding of a charging roller to a grinding | polishing process.

Explanation of symbols

2 Photosensitive drum 3 Charging roller 10 Recording paper 16 Spring 18 Image forming means 20 GAP holding member 62 Transfer roller 63 Cleaning device 64 Quenching lamp 72 Developing roller

Claims (6)

A molding step of molding a cylindrical thermoplastic resin layer;
A cutting step of cutting the surface of the molded thermoplastic resin layer;
A charging roller manufacturing method, comprising: a polishing step of polishing the surface of the cut thermoplastic resin layer. The manufacturing method according to claim 1,
The method for manufacturing a charging roller, wherein the thermoplastic resin layer contains an ABS resin. In the manufacturing method of Claim 1 or 2,
The method of manufacturing a charging roller, wherein the thermoplastic resin layer in the molding step is molded around a core axis. In the manufacturing method in any one of Claim 1 thru | or 3,
The manufacturing method includes a step of forming a release layer on the surface of the polished thermoplastic resin layer. In the manufacturing method of Claim 4,
The method for manufacturing a charging roller, wherein the release layer contains a fluororesin. In an image forming apparatus comprising a photoconductor and a charging roller disposed in proximity and non-contact with the photoconductor,
An image forming apparatus comprising the charging roller according to claim 1.

Images