JPH03245752A - Manufacture of carbon brush - Google Patents

Abstract

PURPOSE:To prevent generation of a film onto the surface of a commutator of a rotary electric machine from being excessive by mixing a specific aluminum powder an a thermosetting resin for a graphite powder, by performing heat treatment at a specified temperature after formation, and then performing exposure into steam or dipping into water or dilute acid. CONSTITUTION:A main raw material graphite powder is a powder of a refined natural graphite with less ash content, an artificial graphite obtained by graphitization of an oil coke, a pyrolitic graphite etc. An aluminum powder and a thermosetting resin with 0.1-3wt.% and 200 mesh or less are mixed with this graphite powder, they are subjected to heat treatment at 750-1000 deg.C after formation, and then they are exposed within steam or dipped into water or dilute acid. Also, a thermosetting resin used as a binding agent is not limited specially but phenol resin or epoxy resin is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a carbon brush for rotating electric machines, particularly for small-sized rotating electric machines.

(Prior art) In order to maintain the sliding contact of carbon brushes (hereinafter referred to as brushes), a method of removing an excessive film formed on the commutator surface is disclosed in Japanese Patent Publication No. 16363/1983. In the brush, amorphous silica and alkali metals and alkaline earth metals are present.

Contains metals that promote silica crystallization, such as manganese, aluminum, bismuth, nickel, etc., and
There is a method of manufacturing brushes by heat treatment at about 0°C to 1000°C.

As shown in Japanese Publication No. 58-58787, a film made of a small amount of aluminum powder contained! ! l1
The 1i action prevents the formation of harmful commutator skin layers and improves the sitting comfort of the brush.

A brush that maintains stable performance even at high speed rotation has been proposed.

For the same purpose, aluminum powder, aluminum powder and a phosphorus-containing compound, or aluminum powder and boric acid ester metal salts are mixed and heated at a temperature in the range of 500 to 650°C. Treated brushes have been proposed.

(Problems to be Solved by the Invention) Although the brush shown in Japanese Patent Publication No. 39-16363 has the effect of removing the film on the commutator surface, it does not strengthen the abrasive effect, and it does not increase the coefficient of friction and its fluctuation. There was a problem in that the efficiency of the rotating electric machine was lowered because of the increase in the size of the rotary electric machine.

Also, Japanese Patent Publication No. 58-58787 and Japanese Unexamined Patent Publication No. 58-58-
Although the brush disclosed in Japanese Patent Publication No. 148642 is effective in reducing the coefficient of friction, it cannot be said to be sufficient in terms of brush life and degree of reduction in the coefficient of friction based on today's required brush performance.

That is, for today's high-speed rotating electric machines with rotational speeds of 30,000 r/m or higher, there are problems in that the amount of brush wear is large and the brush life is short.

The present invention has a small coefficient of friction, small fluctuations, and a small contact voltage drop.In other words, it prevents excessive formation of a skin film on the commutator surface, and has stable siding characteristics even at high speed rotation. In addition, the present invention provides a brush for a rotating electrical machine that has a long brush life.

(l!Means for solving the problem) The present invention provides graphite powder, 0.1 to 3 weight -
The present invention relates to a method for producing a carbon brush, in which aluminum powder of 200 mesh or less and a thermosetting resin are mixed, molded, heat treated at a temperature of 750 to 1000°C, and then exposed to steam or immersed in water or dilute acid.

The main raw material graphite powder used in the present invention is refined natural graphite with a low ash content.9 Artificial graphite obtained by graphitizing petroleum coke, coal coke, etc., pyrolytic graphite, and Kish graphite powder. There are no particular restrictions on the particle size. If the ash content is too large, the sleeving properties may become unstable when a brush is used, or streaks may appear on the commutator, so the ash content is preferably less than 1 weight.

The thermosetting resin used as the binder is not limited to 1%, but phenol resin or epoxy resin is preferable.

The aluminum powder may be in the form of granules or flakes, but any of these may be used in the present invention.

The particle size Fi is 200 mesh or less. If the particle size is large, it tends to be unevenly distributed in the brush material. The amount of aluminum powder is 0.1 to 3% by weight based on graphite powder.

If it is less than 0.1% by weight, there is no effect of reducing the coefficient of friction or extending the lifespan, and if it exceeds 0.0% by weight, the friction properties will become unstable, and the heat treatment in the ridge process will cause it to turn into aluminum carbide. Methane gas is generated by the moisture absorption treatment in the ninth step, resulting in too many pores, resulting in a decrease in mechanical strength.

Graphite powder, aluminum powder in the above amount, and thermosetting resin are mixed to form a molded powder. If the resin is solid, crush it appropriately and mix it with a regular powder mixer.

If the resin is liquid, add an appropriate amount of solvent and use a known kneader.
After kneading the mixture under high pressure, the bath agent is removed and the mixture is crushed to form a molded powder.

The molded powder was molded by a known method and heated under a non-oxidizing atmosphere for 7
It is heat treated at 50 to 1000°C and further subjected to moisture absorption treatment to form a brush material. The moisture absorption treatment is performed to convert a portion of the aluminum carbide generated during the heat treatment into aluminum hydroxide. Aluminum hydroxide becomes γ-alumina due to frictional heat during use of the brush or the rise in brush temperature when energized.

It has the effect of preventing the formation of an excessive skin film on the commutator surface.

If the heat treatment temperature is less than 750°C, less aluminum carbide will be produced, and therefore the amount of aluminum hydroxide produced in the next step will be less. Moreover, if the temperature exceeds 1000°C, not only will the effect of extending the life of the brush be small, but also energy will be wasted in the heat treatment.

The moisture absorption treatment is performed by exposing the heat-treated brush material to a steam atmosphere or immersing it in water or dilute acid.

The water may be hot or cold water, and the dilute acid used is hydrochloric acid, nitric acid, etc. with a weight of 5 or less. There is no particular limit to the processing time, but
The amount of micropores in the brush material generated by methane gas generated by hygroscopic decomposition of aluminum carbide can be determined appropriately by visually checking.

The brush is made by removing moisture from the moisture-absorbing brush material.
Obtained by machining.

(Example) Comparative Example Main raw material consisting of 80 parts by weight of pitch coke-based artificial graphite powder with an ash content α2% by weight crushed to 200 mesh or less and 20 parts by weight of powder of novolak type phenol resin (manufactured by Hitachi Chemical Co., Ltd., HP-208NK) To the graphite powder, 1%, 0.5%, 1%, 2%, 3%, 4%, and 5% of granular aluminum powder with an average particle size of 350 mesh was added to the graphite powder, respectively. Mix with a mold mixer, 1 t
/an'' pressure and then molded at 80℃ under nitrogen gas atmosphere.
A type 811 brush material was obtained by heat treatment at a temperature of 0° C. 1. This material was then machined to obtain a brush.

Example 1 A brush material obtained in the same manner as the comparative example was placed in a steam atmosphere for 30 minutes.
The brush was exposed for 1 day, dried at 110° C. for 1 hour, and then machined to obtain a brush.

The contact voltage drop and friction coefficient were measured for each brush obtained in Comparative Example and Example 1, and the relationship between the aluminum powder content and the contact voltage drop and friction coefficient is shown in Figures 1 and 2. . The dotted line in the figure is a comparative example, and the actual 1#A is Example 1 which was subjected to moisture absorption treatment.

From Figures 1 and 2, the aluminum powder content is 0.1 to 3.
Although the comparative example of weight - shows low values for both the contact voltage drop and the coefficient of friction, it is shown that the values of Example 1, which was subjected to moisture absorption treatment, are even lower.

In particular, the one containing 1% by weight is the smallest.

Example 2 A brush material obtained in the same manner as in Comparative Example was immersed in IIk degree 3 weight % hydrochloric acid for 2 days, dried at 110° C. for 1 hour, and then machined to obtain a brush.

Brushes with aluminum powder content of 0.1% by weight in Comparative Example and Example 1, α5 inch, 1 inch, and 3 inch brushes, and brushes with aluminum powder blended amount of 0.5 inch and 2 inch by weight in Example 2 AClooV, 650W, rotation speed 3
A brush abrasion test was conducted by attaching the brush to an AC luxury electric motor running 4,000 times/min.

Conditions of rectifying sparks and amount of wear converted to 100 hours (
m) are shown in Table 1.

As is clear from Table 1,! # Both the amount of wear and the number of rectified sparks in the examples of samples Nal~6 are smaller than those in the comparative examples of samples Nal~10.

(Effects of the Invention) The carbon brush obtained by the present invention has a
The film adjustment effect of alumina prevents excessive film formation on the commutator surface of single-rotation cage machines, reduces contact voltage drop and friction coefficient, and maintains stable force characteristics. . Therefore, there is less brush loss even at high speed rotation.
It also has a long lifespan.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing the relationship between the amount of aluminum powder mixed, the contact voltage drop, and the coefficient of friction.

Claims (1)

[Claims] 1. Graphite powder, 0.1 to 3% by weight of 20 to the graphite powder
A method for producing a carbon brush, which comprises mixing aluminum powder of 0 mesh or less and a thermosetting resin, heat-treating at a temperature of 750 to 1000°C after molding, and then exposing to steam or immersing in water or dilute acid. .