JPH06167868A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device using an elastic roller formed to obtain optimum hardness and surface roughness by using the elastic roller capable of obtaining moderate outer diameter displacement and an outer periphery not having ruggedness as a developing roller. CONSTITUTION:In molding for forming a foamed material layer of a prescribed diameter on the circumference of an axial center, the temperature for molding and foaming, and a time are set for a prescribed value, so that a skin layer generated on the outer periphery of the foamed material layer coming into contact with a molding die is formed in hardness suitable for being used as the developing roller 6. After the molding is completed, the skin layer is ground to turn surface roughness in the circumferential direction of the skin layer into the surface roughness suitable for being used as the developing roller 6 and finishing with the outer diameter dimensional precision and deflection accuracy of the prescribed value is attained to manufacture the elastic roller. By the adoption of the elastic roller, the carrying properties of toner to a photosensitive body 5 are stabilized and image formation excellent in resolution is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an image forming apparatus such as a copying machine. More specifically, a skin layer formed on the surface of a foaming layer constituting a developing roller is suitable for the developing roller. The present invention relates to a developing device using an elastic roller formed to have hardness and roughness.

[0002]

2. Description of the Related Art As one method of a developing device using non-magnetic one-component toner, a developing roller is pressed against a photoconductor and the toner is supplied from the developing roller to an electrostatic latent image formed on the photoconductor. A contact type that visualizes is known.
The developing roller in this type of developing device is formed of a material having appropriate elasticity, and is configured by an elastic roller so that uniform contact property in the axial direction of the roller and a predetermined nip amount (contact width) can be stably obtained. To be done. Rubber rollers and sponge rollers are known as elastic rollers that can be used as the developing roller. However, it is difficult for the rubber roller to obtain a sufficient elastic displacement due to the limit of rubber hardness, while the sponge roller can obtain a sufficient elastic displacement, but the surface of the sponge roller has unevenness so that the adhesion with the contact object is low. There are drawbacks such as lack of. In addition, in order to secure the outer diameter dimensional accuracy and runout accuracy, there is a problem in that the workability in polishing the outer diameter is poor, and it is difficult to ensure sufficient accuracy. As an elastic roller for solving the above-mentioned problems of a rubber roller and a sponge roller, there is disclosed in Japanese Patent Laid-Open No. 4-1.
It can show what is indicated by 43769 gazette. As shown in FIG. 3, the elastic roller 20 shown in the publication integrally includes a shaft 21, a foam member 22 formed around the shaft 21, and a cylindrical member 23 formed around the foam member 22. It is formed by molding. In this elastic roller 20, a shaft 21 is fixed at a central position in a mold for molding a foamed member 22, and a cylindrical member 23 is fixed concentrically with the shaft 21, and then the shaft 21 is fixed.
It is manufactured by injecting a foam material between the cylindrical member 23 and the cylindrical member 23 and performing foam molding. According to this structure, since the cylindrical member 23 is formed to be thin, sufficient elastic displacement of the foam member 22 formed between the cylindrical member 23 and the shaft 21 causes sufficient displacement of the outer diameter when pressed against a contact object. In addition to being obtained, a cylindrical surface having no irregularities on the outer peripheral surface is obtained.

[0003]

However, when integrally molding an elastic roller having a multi-layer structure, the molding process is complicated and the production cost is inevitably high. The present invention was devised in view of the above-mentioned problems, and it is possible to easily mold an elastic roller that has an outer peripheral surface without unevenness and unevenness equivalent to that of the elastic roller having the above-mentioned conventional structure, and to use it as a developing roller. An object of the present invention is to provide a developing device using an elastic roller formed to have optimum hardness and surface roughness.

[0004]

In order to achieve the above-mentioned object, the means adopted by the present invention is to develop a visible image by pressing toner against a photoconductor and supplying toner to the electrostatic latent image formed on the photoconductor. In a developing device using an elastic roller in which a foam material layer is provided around a shaft center made of a rigid material and an elastic material layer is provided around the foam material layer, the elastic material layer is It is constituted by a skin layer of a foam material layer, and the hardness of the skin layer is set to 40 to 60 degrees as measured by an Asuka C hardness tester, and the circumferential surface roughness of the skin layer is set to Ra3 to 6 And a developing device using an elastic roller.

[0005]

According to the present invention, at the time of molding for forming a foam material layer with a predetermined diameter around the shaft core, by setting the temperature and time of molding and foaming to predetermined values, the foam material contacting the molding die. The skin layer formed on the outer circumference of the layer can be formed to have a hardness of 40 to 60 degrees as measured by an Asuka C hardness meter, which is a hardness suitable for use as a developing roller, and a skin layer corresponding to an elastic material layer on the outer circumference of the foam material layer. Is molded. Further, after the molding is completed, the surface roughness in the circumferential direction of the skin layer is Ra3 to 6
By polishing the outer diameter and the runout accuracy to the specified values, the outer peripheral surface has no uneven surface and the elastic material layer has good adhesion to the contact object, and this outer material layer has sufficient outer diameter displacement. An elastic roller having a foam material layer capable of giving a pressure is easily formed. When the elastic roller formed in this manner is used as a developing roller, the toner can be conveyed to the photosensitive member in a stable manner, so that an image can be formed with good resolution without uneven development.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention. FIG. 1 is a schematic view showing the structure of a developing device using an elastic roller according to the embodiment of the present invention, and FIG. 2 is a sectional view of the elastic roller according to the embodiment. First, a method of manufacturing an elastic roller used as the developing roller 6 of the developing device 10 shown in FIG. 1 will be described. The elastic roller 1 shown in a sectional view in FIG. 2 is formed by integrally molding a foam 3 around a shaft core 2 made of a metal material. That is, the shaft core 2 is fixed at the central axis position in the mold formed to have a mold size suitable for forming the outer diameter of the elastic roller 1, and the foam material is injected into the mold to set the mold. The foam material is heated to a predetermined temperature to foam, and the skin layer 4 is formed on the inner surface of the mold with which the foam material is in contact so as to have a predetermined thickness and hardness. Since the thickness and hardness of the skin layer 4 depend on the heating temperature of the mold, the heating time, the composition of the foam material, etc., these elements are selected so as to obtain a predetermined skin layer 4, and the outer peripheral portion is selected. A foam body 3 having a skin layer 4 having a predetermined thickness and hardness is formed around the shaft core 2. The formation of the skin layer 4 is realized by the following molding method when a thermosetting resin is used as the foam material. (1) A foaming material which starts a foaming action at a temperature lower than the curing temperature of the thermosetting resin is mixed with the thermosetting resin in an amount such that a desired foaming rate is obtained to obtain a foaming material. (2) The foamed material is injected into the mold so that the heating temperature of the mold becomes the curing temperature of the thermosetting resin. At this time, the foamed material in contact with the inner surface of the mold and the foamed material located at the closest position to the inner surface of the mold are rapidly heated, so that they pass the foaming temperature all at once and reach the curing temperature to be cured. Therefore, the rate at which the thermosetting resin cures exceeds the pressure of foaming, and the foaming material at the contact position with and close to the inner surface of the mold becomes the skin layer 4 without forming bubbles. (3) The foam material located away from the inner surface of the mold stays in the foaming temperature for a long time because the heat conduction from the mold is delayed, and after sufficient foaming is achieved, the foaming material is heated to the curing temperature. A foam is formed. (4) After a predetermined time from the completion of foaming and curing, the heating of the mold is stopped, and then the mold is cooled, and then the foamed product that has been molded is taken out. After the molding is completed as described above, the elastic roller 1 is completed by polishing the skin layer 4 for the outer diameter dimension and runout accuracy of the elastic roller 1 and the finishing of the outer peripheral surface. The skin layer 4 is a thin elastic material layer having no unevenness and serves as an outer peripheral surface having excellent adhesion to a contact object, and the foam 3 is a foam material made of a sponge-like material having a predetermined layer thickness and excellent in elastic deformation. As a layer, it becomes an elastic roller having sufficient adhesion and elastic deformation. Elastic roller 1 formed as described above
1 is adopted as the developing roller 6 of the developing device 10 shown in FIG. 1, the foaming material is selected, and the heating temperature and the heating time of the mold are set so that the hardness of the skin layer 4 is 40 as measured by an Asuka C hardness tester. Molding is performed by setting the angle to be ~ 60 degrees. Further, in the surface polishing after molding, the surface roughness is polished to Ra3 to 6 so that the runout accuracy and the outer diameter dimension are finished to predetermined values. Since the developing roller 6 flexibly contacts the photosensitive drum 5, the rubbing development can be stably performed without changing the nip amount. Therefore, the toner is formed in a thin layer on the surface and is conveyed, and the action of supplying the toner to the electrostatic latent image formed on the photosensitive drum 5 is constantly performed. As a result, development with high resolution is realized. In the case of the developing device 10 having the above structure, the nip amount between the developing roller 6 and the photosensitive drum 5 is 0.1 to 0.35 mm, and the peripheral speed ratio between the developing roller 6 and the photosensitive drum 5 is 1.5 to 2 0.0, the volume resistance value of the developing roller 6 is set to 10 ⁵ to 10 ⁸ Ωcm, and a bias voltage of +100 to 500 V is applied to the axis of the developing roller 6 so that a predetermined developing performance is exhibited. It

[0007]

As described above, according to the present invention, the skin layer generated when the foam is molded into the shaft core is formed to have a hardness corresponding to the purpose of use as a developing roller, and the surface of the skin layer is formed. By polishing to a surface roughness corresponding to the purpose of use, an elastic roller having appropriate adhesion to the photoconductor and appropriate elastic deformation and good runout accuracy and outer diameter dimension accuracy can be easily formed. When this elastic roller is used as the developing roller, it is possible to provide a developing device that has good toner transportability to the photosensitive drum and excellent resolution.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a developing device according to an embodiment of the present invention.

FIG. 2 is a sectional view of an elastic roller according to an embodiment.

FIG. 3 is a cross-sectional view of an elastic roller according to a conventional example.

[Explanation of symbols]

 1--Elastic Roller 2 --Shaft Core 3 --- Foam Body (Foam Material Layer) 4 --Skin Layer 5 --Photosensitive Drum (Photoconductor) 6 --Developing Roller 10 --Developing Device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Umeno 1-22 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka Mita Industry Co., Ltd. (72) Inventor Masao Uyama 1-2-chome, Chuo-ku, Osaka-shi, Osaka No. 28 Mita Industry Co., Ltd.

Claims (1)

[Claims] 1. A developing material roller which is brought into pressure contact with a photosensitive member and supplies toner to an electrostatic latent image formed on the photosensitive member to visualize the electrostatic latent image. In a developing device using an elastic roller provided with an elastic material layer around the foam material layer, the elastic material layer is constituted by a skin layer of the foam material layer, and the hardness of the skin layer is Aska C.
A developing device using an elastic roller, characterized in that the skin layer has a circumferential surface roughness Ra of 3 to 6 and a hardness measured by a hardness meter of 40 to 60 degrees.