JPS6295563A - Developing roller of electrostatic recording device - Google Patents

Abstract

PURPOSE:To prevent a load placed on a driving motor from increasing and the temperature of a conductive sleeve which constitutes a developing roller from rising by providing a conductive layer which has 10<5>-10<-3>OMEGA-m resistivity on at least the surface of the conductive sleeve. CONSTITUTION:The conductive sleeve 1 formed of a conductive layer wholly is provided with a magnet roll 2 and the conductive layer is formed of a conductive material with 10<5>-10<-3>OMEGA-m resistivity. This conductive material has the resistivity much larger than any other normal metallic material and materials formed by mixing conductive powder of carbon, metal, etc., with synthetic resin, mixing conductive fiber such as metallic fiber and carbon fiber with synthetic resin, and mixing conductive powder of conductive ceramic, metal, etc., with nonconductive ceramic; and the mixing ratio of mixed metal, carbon, etc., is adjusted to obtain desired resistivity. Consequently, an eddy current generated in the conductive sleeve is suppressed and the load on the driving motor is reduced to prevent the conductive sleeve from generating heat.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a development roller for developing an electrostatic latent image with a powder developer.

2. Description of the Related Art As shown in FIG. 3, this type of apparatus has a developing roller consisting of a rotatable conductive sleeve 103 and a stationary magnet roll 102 inside the developing roller. The developer 103 is rotated, the developer 106 is attached to its surface, and the developer 106 is conveyed in the direction of the arrow 107, brought into contact with the latent image on the photoreceptor 101 moving in the direction of the arrow 106, and at the same time, the developer 106 is deposited on the conductive sleeve 103). A pressure is applied, and at the development point, an electrostatic force generated by the potential difference between the surface potential of the latent image formed on the photoreceptor 101 and the bias potential is used to perform the phenomenon.Here, 104
is a doctor blade that regulates the amount of developer coming out, 108
is a bias voltage applying means for preventing image fogging and for performing reversal development.

Recently, image quality has been improved by stirring the developer 105 on the surface of the conductive sleeve 103, and rotating the magnet roll 102 inside the conductive sleeve at high speed is effective for stirring the developer. As a result, a device in which the magnet roll 103 is rotated at high speed separately from the conductive sleeve has been developed and put into practical use.

Problems to be Solved by the Invention However, when the magnet roll is rotated at high speed as described above, a problem arises in that a large load is placed on the motor for driving the magnet roll and the conductive sleeve. It has also been found that the temperature of the conductive roller increases, which heats the photoreceptor disposed close to it, thereby affecting its characteristics and lifespan.

The present invention has been made in view of such conventional problems, and it is an object of the present invention to provide a developing roller that can reduce the load on the drive motor and prevent the temperature rise of the conductive sleeve.

The present invention has made the following findings as a result of intensive investigation into the causes and solutions to the above-mentioned problems.

(1) When the magnet roll rotates inside the conductive sleeve, the magnetic field around it changes, and this change generates eddy currents within the conductive sleeve, causing eddy current loss. As a result, the load on the motor for driving the magnet roll and the conductive sleeve increases, and Joule heat is generated within the conductive sleeve, causing a rise in temperature.

(2) Regarding the eddy current loss caused by changes in magnetic flux passing through the conductive material, the following formula holds true when viewed for each unit volume of the conductive material.

・2 Peoc 1 / η=ηBrn2f2 where Pe:
Eddy current loss i: Eddy current resistance η: Electrical conductivity of the conductive material Bm: Maximum magnetic flux density when the magnetic flux changes f: Frequency at which the magnetic flux changes (→ Applying this to the developing roller, η The electrical conductivity of the sleeve Bm: Surface magnetic flux density f of the magnet roll This is the relative rotational speed of the magnet roll to the sleeve.By the way, since conventional conductive sleeves are made of metal materials such as aluminum, the electrical resistance ( Since the specific resistance) is small and the conductivity η is large, a large eddy current loss occurs, which is the cause of the above problems.

(4) As can be seen from the above equation regarding eddy current loss Pa,
The generation of eddy currents can be suppressed by reducing the amount of magnetization of the magnet roll or by lowering the rotation speed of the magnet roll. However, they cause drastic changes in image quality and are ultimately not a solution to the problem.

(5) It is possible to reduce eddy current to some extent by using a material that has relatively high electrical resistance among metal materials, such as stainless steel, as the material for the conductive sleeve, but it is not possible to reduce the eddy current to a satisfactory degree. does not decrease.

(6) The conductive sleeve is designed to apply a developing bias, to release charges in the carrier generated by frictional charging with the toner, and to prevent charges generated by frictional charging with the toner from accumulating. conductivity is required;
Conventionally, it was thought that conductivity comparable to that of metal materials was required, but as a result of research conducted by the present inventors, even if the conductivity is much smaller than that of metals, it has almost no effect on image quality. It turned out to be usable.

Means for Solving the Problems The present invention has been made based on this knowledge, and is based on the above findings.
The structure includes a conductive layer having a specific resistance of 05 to 10<-6 >[Omega]-m.

Function As described above, in the present invention, the conductive layer of the conductive sleeve is made of a material having a specific resistance greater than 10-5 Ω-m. , 5,9 of corrosion-resistant aluminum (A 5083-H32)
X10 Ω-m1 austenitic stainless steel 'A (S
It is much larger than the 7,2X10-7 Ω-m of US304), and can suppress the generation of eddy current to a practically negligible level. Also, the specific resistance is smaller than 1Q Ω-m, so it can be used within this range. If the conductive layer has a specific resistance of , it is possible to apply a developing force to the conductive sleeve, prevent accumulation of charge on the sleeve, and obtain good image quality.

Embodiment FIG. 1 is a cross-sectional view showing a schematic structure of a developing roller of a developing device according to an embodiment of the present invention, in which numeral 1 denotes a conductive sleeve formed entirely of a conductive layer, and 2 denotes a magnet roll.

FIG. 2 shows another embodiment of the present invention. In this embodiment, a conductive sleeve 11 is used which is composed of a conductive layer 11a on the surface and a support layer 11b inside the conductive layer 11a. In any of the examples, the conductive layer has a specific resistance of 105 to 10-3.
It is made of a conductive material with a resistance of Ω-m.

The conductive materials used in the present invention have a much higher specific resistance than ordinary metal materials, such as synthetic resin mixed with conductive powder such as carbon or metal powder, and synthetic resin mixed with metal. A mixture of fibers or conductive fibers such as carbon fibers, a mixture of non-conductive ceramics and conductive powder such as conductive ceramic or metal powder, etc. can be used. The specific resistance of these materials can be set to a desired value by adjusting the mixing ratio of a conductive material such as a metal or carbon. Among these materials, carbon fiber reinforced synthetic resin composite material (hereinafter abbreviated as CFRP), which is made by mixing carbon fiber with synthetic resin, is suitable in terms of strength, dimensional stability, weight, etc. required for sleeves. be.

Examples of resins used as the base material of this CFRP include synthetic resins such as epoxy, phenol, Teflon, and nylon. CFRPO resistivity varies depending on the amount of carbon fiber mixed, and is usually 102-109Ω.
-m, it can be used as a material for conductive sleeves.

As the support layer 11b in the embodiment shown in FIG. 2, for example, a glass fiber reinforced synthetic resin composite material (hereinafter abbreviated as GFRP) is used. This support layer 11b needs to have a resistivity at least equal to or higher than that of the conductive layer 11a, and to have a strong resistance in order to suppress the generation of eddy currents. GFRP is suitable in this respect. In this way, when the conductive sleeve 11 has a two-layer structure consisting of a conductive layer and a support layer, the support layer has the strength necessary for the conductive sleeve, so there is greater freedom in selecting the conductive material used for the conductive layer. It is possible to reduce costs by reducing the amount of expensive conductive material used.

When the conductive sleeve 1 or 11 having the above structure is used, even if the magnetic roll 2 is rotated inside and the toner on the conductive sleeve is stirred, almost no eddy current is generated in the conductive sleeve. Since the surface has the conductivity necessary to apply a developing bias and to release charges, there is no problem with development and good image quality can be obtained.

Example A recording experiment was conducted using the developing roller shown in FIG. The specifications of the conductive sleeve 1 used are as follows ○ Material: CFRP (base material: epoxy resin) Outer diameter: 31
,4+m++inner diameter: 30. Own length = 256 Specific resistance: Longitudinal direction (carbon fiber arrangement direction) 6 Xl 0
"Ω-m Circumferential direction (orthogonal direction to carbon fiber) 6.7XIQ2Ω-m Also, related development conditions are: Surface magnetic flux density: 8Q□ Gauss (on sleeve) Magnet rotation speed: 1600 rpm Sleeve rotation speed: 160 rpm (in the opposite direction to the magnet). As a result of the above experiments, the image quality was comparable to that obtained when using a metal sleeve, and there was no particular inferiority. It was confirmed that even if the resistance was much larger than that of metal, it would not affect the same image quality and the generation of eddy current could be suppressed.

In addition to the eddy current suppressing effect, the CFRP conductive sleeve described above also has the effect of reducing weight. The following table shows a comparison of the densities of CF RP and conventionally used metal materials.

In this way, CFRP has a density of about 3/6 of aluminum, and stainless steel has a density of 115, so for example, when comparing the sleeves used in the above experimental example, CF RP sleeve...31g, stainless steel sleeve ...
...There is a large weight difference of 160g, and this weight difference directly appears as a difference in the load on the drive motor.Effects of the InventionAs is clear from the above explanation, the present invention can be used as a conductive sleeve for a developing cola. , at least on its surface, 10~
Since it is equipped with a conductive layer with a specific resistance of 10-5 Ω-m, it is possible to suppress the eddy current generated in the conductive sleeve due to the rotation of the magnet roll inside the layer without deteriorating the image quality. This has the effect of reducing the load on the motor and preventing the conductive sleeve from generating heat.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing roller showing an embodiment of the present invention;
FIG. 2 is a sectional view of a developing roller showing another embodiment, and FIG. 3 is a schematic diagram of a conventional developing device and its surroundings. 1.11... Conductive sleeve, 11a...
...Conductive layer, 11b...Support layer, 2...
・Magnetic roll. Name of agent: Patent attorney Toshio Nakao and one other person
2--77' Buttotle Figure 3

Claims (4)

[Claims] (1) At least on the surface, 10^5 to 10^-^3Ω-
A developer roller of an electrostatic recording device having a sleeve with a conductive layer having a specific resistance of m. (2) A developing roller for an electrostatic recording device according to claim 1, wherein the sleeve is composed of the conductive layer and an insulating support layer provided inside the conductive layer. (3) A developing roller for an electrostatic recording device according to claim 1 or 2, wherein the conductive layer is made of a synthetic resin containing carbon fibers. (4) A developing roller for an electrostatic recording device according to claim 1 or 2, wherein the conductive layer is made of ceramic.