JPH0398439A - Carbon brush and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the excessive production of a skin film on the surface of a commutator, provide a carbon brush with stabilized rubbing characteristics even in a high-speed rotation and obtain a brush for a rotary electric machine having a long life by a method wherein graphite powder is added with tin powder, silicon carbide powder and thermosetting resin to mix them. CONSTITUTION:A brush is obtained by a method wherein a main material is added with a granular tin powder to mix them in a V-shape mixer and former under the pressure of 1.2t/cm<2> and, thereafter, heat treatment is effected in a non-oxidizing atmosphere at the temperature of 700 deg.C, and then, machining is applied to the compact. The values of the friction coefficient and the contact voltage drop of the brush show relatively low value when the adding amount of the tin powder 0.1-3weight%. When the amount of added silicon carbide is 0.1weight%, the friction coefficient, the contact voltage drop and the wearing amount of the brush are very small and the riding property of the brush is good. According to this method, electric loss and mechanical loss is reduced even in a high-speed rotation.

Description

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

(Prior art) In order to maintain the sliding contact of carbon brushes (hereinafter referred to as brushes).As shown in Japanese Patent Publication No. 39-16363, a method for removing an excessive film formed on the commutator surface. , Amorphous silica and alkali metals, alkaline earth metals, manganese, aluminum, bismuth,
There is a method in which a brush is manufactured by containing a metal such as nickel that promotes silica crystallization and heat-treating the brush at a temperature of about 700°C to 1000°C.

1, as shown in Publication No. 58-58787. A brush that prevents the formation of a harmful commutator skin layer through the coating adjustment effect of a small amount of aluminum powder contained in it, improves the seating properties of the brush, and maintains stable sliding characteristics even at high speed rotation. is proposed.

For the same purpose, as shown in JP-A-58-148642, 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 5oO to 650℃. Treated brushes have been proposed.

(Problem to be solved by the invention) The brush shown in Japanese Patent Publication No. 39-16363 is. Although it has the effect of removing the film on the commutator surface. This increases the polishing effect and increases the coefficient of friction and its fluctuations, resulting in a problem of lowering the efficiency of the rotating electrical machine.

Kakitata, Japanese Patent Publication No. 58787-1987 and Japanese Patent Application Publication No. 58-58-
Although the brush shown in Publication No. 148642 is effective in reducing the coefficient of friction. Considering the brush performance required today, it is difficult to say that the brush life and the degree of reduction in the coefficient of friction are sufficient.

In other words. Today's rotation number 3 0. 0 0 0 r /
For use in high-speed rotating electric machines with speeds exceeding 100 m, there are problems in that the amount of brush wear is large and the brush life is short.

The present invention is. The coefficient of friction is extremely small and fluctuations are small, resulting in a small contact voltage drop, which prevents excessive formation of a skin film on the commutator surface. It has stable sushi characteristics even at high speed rotation, and has a long brush life.
We provide brushes for rotating electric machines that meet the demands of the times.

(Means for Solving the Problems) The present invention provides a graphite powder mainly composed of graphite powder and a thermosetting resin.
0 for skeleton graphite powder. 1-3% by weight tin powder and 0.1-1
The present invention relates to a carbon brush containing silicon carbide powder with a weight percent of 150 mesh or less, and a method for producing the same.

The main raw material graphite powder used in the present invention is. Refined natural graphite with low ash content. There are no particular restrictions on the particle size of powders such as artificial graphite, pyrolytic graphite, kitsch graphite, etc. obtained by graphitizing petroleum coke, coal coke, etc. If the amount of ash is too large, the properties will become unstable when a brush is used, and streaks will appear on the commutator, so it is preferable that the amount of ash be less than 1 weight.

The thermosetting resin used as the binding material is not particularly limited, but phenol resin or epoxy resin is preferable.

In the present invention, tin powder and silicon carbide powder are used together with the above-mentioned raw materials. Tin powder is added to reduce the friction coefficient of the brush. There is no limit to its provenance. The particle size is preferably 200 mesh or less. If the particles are large, they will be unevenly distributed and the product will be less effective in reducing the coefficient of friction. The amount added is 0 for graphite powder.
．． It is said to be 1 to 3 weights. Outside this range, there is no effect of reducing the friction coefficient and the contact voltage drop increases. I like it〈is 0
, 3~zO weight da. However, tin powder has no film-adjusting effect. As the operating time passes, tin adheres to the commutator surface, causing unstable sliding and increasing brush wear.

In addition to improving this. Silicon carbide powder is added to prevent excessive film formation on the commutator surface, and there are no restrictions on its origin. The particle size is 150 mesh or less. 15
If the mesh size is as large as 0 mesh, streaks will occur on the commutator surface. 1
The amount added is 0.1 to 1.0% by weight based on the graphite powder. If the weight is less than 0.1, there is no effect (but if it exceeds 1.0, the coefficient of friction increases due to the abrasive action of silicon carbide, resulting in unstable sliding.

The brush of the present invention is prepared by adding the above amounts of tin powder and silicon carbide powder to graphite powder, and then adding and mixing a thermosetting resin. If the resin is solid, it is crushed to an appropriate level and mixed in an ordinary powder mixer to form a molded powder. When the resin is in liquid form, it is placed in a known seconder or the like along with graphite powder, tin powder, and silicon carbide powder, and a solvent for the resin is added thereto to mix the mixture, and the solvent is removed and the mixture is crushed to form a molded powder.

Hereinafter, the shaped powder is molded by a known method, then heat-treated at 500 to 750 DEG C. in a non-oxidizing atmosphere to form a brush material, and further machined to form a brush.

(Function) Tin powder melts when energized and lowers the coefficient of friction. It is thought that the film adjustment effect of the silicon carbide powder reduces the contact voltage drop and maintains stable brush sliding.

(Example) Next, embodiments of the present invention will be described.

Experimental Example A main raw material consisting of 80 parts by weight of pitch coke-based artificial graphite powder pulverized to 200 mesh or less and 20 parts by weight of powder of noporac type phenolic resin (manufactured by Hitachi Chemical Co., Ltd., HP-208NK) was added to the graphite powder. On the other hand, granular tin powder having the particle size distribution shown in Table 1 was used as 0%, 0.1%, 0.5%, 1%, and 2nd powder by weight. Add 3 liters and 5 liters and mix in a mixer, 1.2t/aI
l! After molding at a pressure of 100.degree. C., the material was heat treated at a temperature of 700.degree. C. in a non-oxidizing atmosphere, and then machined to obtain a brush.

The friction coefficient and contact voltage drop values of each brush are shown in FIG. It can be seen from FIG. 1 that both the friction coefficient and the contact voltage drop exhibit relatively low values when the amount of pan flour added is 0.1 to 3%.

Example The composition of the graphite powder and phenol resin in the experimental example was the same, and the tin powder of the experimental example was added by 1 weight more to the graphite powder, and the silicon carbide powder having the particle size distribution shown in Table 1 was added by weight to 0. %. 0.1%. 0.3%, 0.5%. 1%. 2% and 3% were added and mixed in a V-type mixer, and a brush was manufactured under the same conditions as in the experimental example below.

The friction coefficient and contact voltage drop values of each brush obtained in the Examples were measured and the results are shown in FIG. ! For each brush obtained in the example, AC 100
V. A brush wear test was conducted using a single-phase 650W vacuum cleaner motor.

The results are shown in FIG. As is clear from FIGS. 2 and 3, when the amount of silicon carbide added is 0.1 to 1%, the coefficient of friction increases. The contact voltage drop and amount of brush wear were extremely small, indicating that the brush seating was good.

(Effects of the Invention) The brush of the present invention maintains the good rubbing properties of graphite powder, and has a coating effect on the commutator surface of rotating electric machines due to the friction coefficient lowering effect of a small amount of pan powder and the film adjustment effect of silicon carbide powder. This prevents excessive film formation and improves the sitting comfort of the brush.

Therefore, there is no electrical loss even under high speed rotation. Mechanical loss is reduced and a brush with a long life is obtained.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the amount of tin powder added, friction coefficient, and contact voltage drop, and Figure 2 is a graph showing the relationship between the amount of silicon carbide powder added, friction coefficient, and contact voltage drop. FIG. 3 is a graph showing the relationship between the amount of silicon carbide powder added and the wear amount of the brush 7.

Claims (1)

[Claims] 1. Mainly composed of graphite powder and thermosetting resin, 0.1 to 3% by weight of tin powder and 0.1 to 1% by weight of the graphite powder.
A carbon brush containing silicon carbide powder of 150 mts or less. 2. Graphite powder, 0.1 to 3% by weight of tin powder based on the graphite powder, 0.1 to 1% by weight of silicon carbide powder of 150 mesh or less, and a thermosetting resin are mixed, pressure molded, and then heated. The method for manufacturing a carbon brush according to claim 1, wherein the carbon brush is treated.