JPH02155183A - Manufacture of electric brush - Google Patents

Abstract

PURPOSE:To improve durability and reduce noise by adding raw rubber to graphite powder covered with a binder or a mixture of graphite powder and metal powder so as to be contained by 0.5-3wt.%, then carrying out mixing, molding, and thereafter heat treatment at a temperature whereat the raw rubber is not decomposed. CONSTITUTION:Raw rubber is added to graphite powder covered with a binder or a mixture of graphite powder and metal powder so as to be contained by 0.5-3wt.%, then mixing, molding, and thereafter heat treatment at a temperature whereat the raw rubber is not decomposed, are carried out. After the graphite powder is kneaded with a binding material such as phenol resin, it is dried and ground to produce binder covered graphite powder to be used. In case where copper powder is added, preferably electrolytic copper powder is used. Namely, powder raw rubber is added and heat treated under the condition that it is not decomposed to be scattered over the boundary of the copper powder or the graphite powder to decrease the elastic modulus so that bouncing of the electric brush can be absorbed. By decreasing elastic modulus in this way, sliding noise and abrasion loss can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a low-noise electric brush used in a DC motor.

(Prior art) Conventionally, electric motors have been manufactured using conductive metal powder such as copper in order to reduce the contact resistance between electric brushes and commutators to improve output, or to use them under high current density conditions. Metal-graphite electric brushes made from graphite powder and graphite powder are used.

(Problem to be solved by the invention) The electric brush is an elastic body, but the vibration of the motor.

Vibrations caused by minute irregularities on the commutator surface and various other phenomena combine to make the commutator more susceptible to vibrations, resulting in higher sliding noise. Also, 1! As the electric brush dances, the rectifying spark becomes larger and the wear of the electric brush increases.

There was a problem that the motor output decreased.

The present invention provides a method for manufacturing an electric brush that eliminates the above-mentioned drawbacks.9 It is an object of the present invention to reduce the sliding noise and the amount of wear by reducing the elastic modulus.

(Means for Solving the Problem) Powdered raw rubber is added to graphite powder coated with a binder or a mixture of the graphite powder and metal powder so that it contains 0.5 to 3% by weight. This invention relates to a method for producing an electric brush, which is mixed, molded, and then heat-treated at a temperature that does not decompose raw rubber.

In the present invention, the graphite powder used is a binder-coated graphite powder that is mixed with a binder such as a phenol resin, dried, and crushed. When adding copper powder, it is preferable to use electrolytic copper powder.

Raw rubber powder is added to improve the grip of electric brushes, and its types are NBR, SBR, and CR.

Powder of artificial rubber such as fluororubber is preferred. The particle size of the raw rubber powder is preferably 150 mesh or less because it can be uniformly dispersed within the electric brush. If it is exceeded during blending, the amount of graphite will be relatively reduced, resulting in insufficient a-lubricity and increased electrical loss in single-rotation electric machines.

The material for the electric brush is obtained by mixing and molding graphite powder and raw rubber powder, or a mixture thereof with copper powder, by a known method, and heat-treating the mixture at a temperature that does not decompose the raw rubber. The heat treatment temperature varies depending on the type of raw rubber powder, but is preferably 200°C.
is considered to be less than

(By adding powdered raw rubber and heat-treating it under conditions that do not cause it to decompose, it is dotted at the boundaries of copper powder or graphite powder, lowering the elastic modulus and absorbing the movement of the electric brush.

(Example) Next, the present invention will be explained in detail.

80% by weight of scaly graphite (manufactured by Nipponjima Lead Co., Ltd., CB100) and phenolic resin face (manufactured by Hitachi Chemical Group).

VP-11N) 20i quantity was put into the kneading machine and after kneading, 90
It was dried at ℃ and then ground to 150 meshes or less to obtain resin-coated graphite powder. This graphite powder.

Mix electrolytic copper powder (manufactured by Fukuda Metal Foil and Powder Industry Co., Ltd., CE-25) and raw rubber powder (Japanese Synthetic Rubber Powder Nitrile PN30A) in the proportions shown in Table 1 (no raw rubber powder was added in the comparative example), using a ■-type mixer. Mixed. 3.0 of mixed powder with powder molding press
After molding at a pressure of '$-/c-.

A material for an electric brush was obtained by heat treatment in a reducing atmosphere furnace at the temperatures shown in Table 1.

Next, this material was processed into an electric brush for testing, and the voltage was 12V.
It was installed in a 170W class automobile blower motor, and the initial output characteristics and sliding noise were measured. Furthermore, continuous durability tests were conducted using a sirocco fan as a load, and the amount of wear on the electric brush was measured. The test results are shown in Table 1. The rotational speed in the table is 1 to 9 torque, and the sliding noise is 140 without load.
Orpm and wear amount are based on the fan load (13.5V)
This is the value when .

Table 1 (Effects of the Invention) According to the present invention, an electric brush with excellent durability and low noise can be obtained.

From Table 1, the elastic modulus decreases by adding powdered raw rubber. In addition, the amount of raw rubber added should be 0.5% by weight or more.
Regarding K containing 3% by weight, the rotational speed is increased compared to the comparative example, and both the sliding noise and the amount of drag are decreased. However, it is thought that the addition of 0.3% by weight of raw rubber had no effect, and the addition of 4% by weight caused the sliding properties to deteriorate due to a decrease in lubricity.

Claims (1)

[Claims] 1. Add raw rubber powder to graphite powder coated with a binder or a mixture of the graphite powder and metal powder so that it contains 0.5 to 3% by weight, mix and shape, and then heat at a temperature that does not decompose the raw rubber. A method for manufacturing an electric brush characterized by heat treatment.