JPH077892A - Metal graphite brush - Google Patents

Abstract

PURPOSE:To provide a metal graphite brush that is excellent in lubricity in high current, temperature conditions, and in conditioning characteristics in film formation on commutator surfaces for the improvement of durability in high speed rotation, and that maintains the output characteristics of a rotating electric machine and prolongs their lives. CONSTITUTION:The metal graphite brush is obtained by forming and firing a powder mix for metal graphite brushes containing 0.02-0.5wt.% of boron carbide of an average grain size of 2-60mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal graphite electrobrush,
More specifically, the present invention relates to a metal graphite electric brush for a rotating electric machine, particularly for a small rotating electric machine.

[0002]

2. Description of the Related Art A metal-graphite electrobrush obtained by molding and firing a mixed powder of graphite, lead, a lubricant and the like is used in rotary electric machines such as electric motors that require low voltage and large current. . Conventionally, rotating electrical machines have been made smaller and lighter,
In recent years, high-speed rotation and large current have progressed, and vibration sparks often occur due to sliding of the electric brush, resulting in blackening and unevenness on the commutator surface, increasing electrical loss and increasing wear of the electric brush. There is a problem. As a method for reducing the wear of the electric brush, a method of adding MoS ₂ or WS ₂ (JP-A-58)
-121582 discloses), a method of adding a CuS (JP 58-18978 JP), phosphorus compounds, MoS _2, W
A method of adding S _{2 and the} like (Japanese Patent Publication No. 58-18978) has been proposed.

However, the above-mentioned method is effective as a lubricating aid for abrasion of the metal graphite electrobrush, but it is difficult to maintain the output directed to the recent rotary electric machines and improve the service life. That is, an electric brush added with MoS ₂ or WS ₂ or an electric brush added with a phosphorus compound, MoS ₂ , WS ₂ or the like has excellent wear resistance, but when used at high temperature, the electric brush and the commutator are There is a drawback that an excessive film is formed in the meantime and the output is reduced. Further, the CuS-added electrobrush has excellent abrasiveness under high-speed rotation and under low-temperature conditions, but has a drawback of damaging the commutator surface which is a mating member of the electrobrush.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, has excellent lubricity under high current and high temperature, and improves durability under high speed rotation. (EN) Provided is a metal-graphite electrobrush which has an excellent effect of adjusting the film formation in the above, and can maintain the output characteristics of a rotary electric machine and can prolong the life thereof.

[0005]

The present invention has an average particle size of 2 to
The present invention relates to a metal graphite electrobrush formed by molding and firing a mixed powder for a metal graphite electrobrush containing 0.02 to 0.5% by weight of boron carbide of 60 μm. In the present invention, by specifying the content of boron carbide contained in the mixed powder and its average particle size, the formation of an excessive film formed between the electric brush and the commutator and the commutator surface due to the commutation spark It is possible to appropriately correct the blackening, stabilize the contact voltage that affects the output, and improve the sliding contact.

The boron carbide used in the present invention has an average particle size in the range of 2 to 60 μm, preferably 2 to 40 μm, and the content of boron carbide contained in the mixed powder is 0.02 to 0 μm. 0.5% by weight, preferably 0.02-0.4
It is in the range of% by weight. When the content of boron carbide is less than 0.02% by weight and the average particle size is less than 2 μm, the film adjusting effect is small and the contact voltage drop increases. If the content exceeds 0.5% by weight and the average particle size exceeds 60 μm, the abrasiveness becomes excessive and the commutator is damaged.

The mixed powder for metallic graphite electrobrush used in the present invention generally contains copper powder, graphite powder, lead powder and the like in addition to the above-mentioned boron carbide, but the composition and content thereof are not particularly limited. . It is preferable to use electrolytic copper powder having a particle size of 75 μm or less from the viewpoint of reducing mechanical wear and improving output and mechanical strength as the copper powder that is the main raw material of the metal graphite electrobrush. As the graphite, it is preferable to use naturally occurring flake graphite with well-developed crystals and good lubricity. The flake graphite may be particles of about 30 to 150 μm, but for machines requiring high output such as an electric rotating machine, from the viewpoint of output characteristics and wear resistance, the particles are granulated with a binder such as resin.
It is preferable to use particles of about 0 to 300 μm.

Normal conditions are applied to the molding and firing of the mixed powder, and there is no particular limitation. For example, the mixed powder is mixed for about 1 hour with a mixer, and after confirming that the mixture is sufficiently mixed, it is pressed with a molding press at 3 ton / cm ² to be molded, and then heat-treated in an inert atmosphere. It can be done by The material of the electro-graphite metal graphite thus obtained is machined into the final shape to obtain the electro-graphite metal brush.

[0009]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 0.4% by weight of boron carbide having an average particle size of 40 μm and 40 copper powders
% By weight, natural graphite and resol type phenolic resin were blended in a ratio of graphite 90: resin 10 (% by weight) and mixed by heating at 60 ° C. to form granules.
The raw material component was 9.6% by weight. These components were mixed for 1 hour, then molded with a copper stranded wire pigtailing molding press at a pressure of 3.0 ton / cm ² , and heat-treated in a nitrogen gas atmosphere at a temperature of 750 ° C. for 6 hours. . The obtained electric brush material was machined to obtain a metal graphite electric brush for a small electric motor.

Examples 2 to 5 and Comparative Examples 1 to 4 In the same manner as in Example 1 except that the average particle diameter and content of boron carbide are as shown in Table 1, metal graphite for small electric motors is used. I got a brush.

[Test Example] Examples 1 to 5 and Comparative Examples 1 to 1
A test was conducted by passing a current through the metallic graphite electrobrush obtained in 4. The test conditions are a 30 mm diameter Cu slip ring,
Energizing current 15A / cm ² , rotation speed 10,000min ^-1 (rp
m), the amount of abrasion of the electric brush, the contact voltage drop and the ring roughness when sliding for 200 hours at a spring pressure of 1 kg / cm ² were determined.
The results are shown in Table 1.

[0012]

[Table 1]

From Table 1, as compared with Comparative Example 4 using a conventional electric brush material to which boron carbide is not added, in Examples 1 to 5, the electric brush wear amount, contact voltage drop and ring roughness are significantly improved. It is shown that On the other hand, in Comparative Examples 1 and 3 to which boron carbide was added, the electric brush wear amount was significantly improved and the contact voltage drop was also improved, but in Comparative Example 1, the boron carbide content was 0.6% by weight. In Comparative Example 3, the average grain size of boron carbide is 70 μm, so that the roughness of the ring surface increases. In Comparative Example 2, the average particle size of boron carbide is 1 μm.
Therefore, the effect of improving the abrasion amount of the electric brush cannot be seen.

[0014]

EFFECT OF THE INVENTION The metallic graphite electrobrush of the present invention is excellent in lubricity under high current and high temperature, and is excellent in adjusting the film formation on the commutator surface for improving durability under high speed rotation. It is possible to maintain the output characteristics of the rotating electric machine and prolong the service life thereof.

Claims (1)

[Claims] 1. Boron carbide having an average particle size of 2 to 60 μm 0.0
A metal graphite electrobrush formed by molding and firing a mixed powder for a metal graphite electrobrush containing 2 to 0.5% by weight.