JPS6156186B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal graphite brush used in electric motors and the like.

Conventional metal-graphite brushes are made by dry mixing graphite granulated powder, etc., which is made by adding binders such as synthetic resin, coal tar, and pitch to metal powders such as copper and silver, and graphite powder, and then kneading and granulating the mixture, then molding and firing. It was manufactured using However, it is difficult to mix such dry mixed powder uniformly due to the large difference in specific gravity between metal and graphite, and the mixed powder is likely to separate due to slight vibrations during the molding process. As a result, local deviations occur between the metal powder and the graphite powder, which significantly deteriorates the brush's sliding properties, wear resistance, and other properties.

On the other hand, a method of manufacturing homogeneous composite particles by wet-mixing metal powder, graphite powder, lubricating oil, binder, etc. simultaneously and granulating them is considered, but in this method, the metal powder is coated around the metal powder with binder. Therefore, a problem arises in that the specific resistance does not become as low as expected.

The object of the present invention is to provide a method for manufacturing metal-graphite brushes that does not have the above-mentioned drawbacks.

The present invention produces a metal-graphite brush by dry heating mixing metal powder, graphite powder, and a powdered binder at a temperature below the softening point of the binder to produce composite particles with good fluidity, which are then pressure-molded and fired. Regarding the method.

In the present invention, metal powders such as copper, silver, lead, and silver are used, and these metal powders may be used alone or in a mixture of two or more types. There are no particular restrictions. Further, it is necessary to use a binder that is in powder form at room temperature and becomes liquid when heated to a certain temperature, and it is desirable to use a thermosetting resin such as a phenolic resin or an epoxy resin.

In the present invention, in addition to the above-mentioned components, lubricants such as molybdenum disulfide, tungsten disulfide, and lead oxide are added as necessary. The blending ratio of these components is determined depending on the specific resistance of the brush and is not particularly limited.

Further, in the present invention, in order to produce composite particles with good fluidity, it is necessary to dry heat mix the above composition at a temperature below the softening point of the binder. If the binder is heated and mixed at a temperature above the softening point of the binder, the binder will begin to harden before the mixing is completed, causing deviation of the binder and making the mixture structurally non-uniform, even if the mixture is sufficiently mixed. The disadvantage is that the strength after firing decreases and wear increases.

Pressure molding and firing are not particularly limited and may be carried out by generally known methods, for example, preferably at a molding pressure of 2 to 4 tons/cm ² and a firing temperature of 600 to 800°C.

The present invention will be explained below with reference to Examples.

Example 1 20 parts by weight of copper powder of 50 μm or less (electrolytic copper powder manufactured by Fukuda Metals, trade name CE-25), 77 parts by weight of graphite powder of 70 μm or less (manufactured by Nippon Graphite, trade name CB-150), 5 μm
3 parts by weight of molybdenum disulfide (manufactured by Hitachi Powder Metallurgical Co., Ltd., trade name MD-108) and novolak-type phenolic resin (manufactured by Hitachi Chemical Co., Ltd., trade name HP-).
After adding 12 parts by weight of 208NK) and stirring thoroughly while gradually heating with an agitation mixer, the temperature of the mixture was 85℃.
Since the resin started to soften near there, mixing was stopped and the mixture was taken out. As a result, composite particles with a uniform structure of 200 μm or less were obtained. Next, the composite particles were placed in a mold and pressed at a pressure of 3 tons/cm ² , and fired at 700°C, resulting in specific gravity of 2.08 g/cm ³ , specific resistance of 3400 μΩ・cm, bending strength of 210 Kg/cm ² , and friction. coefficient
0.19, and a wear amount of 0.4 mm/100 hours was obtained.

Example 2 65 parts of the same copper powder used in Example 1,
When 6 parts by weight of novolak type phenolic resin was added to 35 parts by weight of graphite powder and stirred in the same manner as in Example 1, composite particles with a uniform structure of 150 μm or less were obtained. Next, these composite particles were placed in a mold and press-molded at a pressure of 3 tons/cm ² , and fired at 700°C, resulting in specific gravity of 3.65 g/cm ³ , specific resistance of 90 μΩ・cm, bending strength of 350 Kg/cm ² , and friction. A metal graphite brush with a coefficient of 0.20 and a wear rate of 1.4 mm/10,000 cycles was obtained.

Comparative Example 1 A conventional metal graphite brush obtained by mixing the same components as in Example 1 with 10 parts by weight of methanol in a wet process, molding and firing in the same manner as in Example 1 had a specific gravity of 2.24. g/cm ³ , specific resistance 6400μΩ・cm,
Bending strength 190Kg/cm ² , friction coefficient 0.24, wear amount 1.3
mm/100 hours.

Comparative Example 2 A conventional metal graphite brush obtained by mixing the same components as in Example 2 with 20 parts by weight of methanol in a wet process, molding and firing in the same manner as in Example 1 had a specific gravity of 3.60. g/cm ³ , specific resistance 120μΩ・cm, bending strength 360Kg/cm ² , friction coefficient 0.23, wear amount 2.9mm/
It was a million times.

The wear amount test was conducted under the following test conditions.

In Example 1 and Comparative Example 1, a 24V, 40W DC motor was continuously operated and the wear amount of the brushes was measured. In Example 2 and Comparative Example 2, the wear amount of the brushes was measured when a 12V, 1.4KW DC motor was repeatedly operated for 2 seconds and stopped for 28 seconds.

According to the present invention, metal powder, graphite powder, and binder can be mixed uniformly, so physical properties related to resistivity and sliding properties related to wear coefficient are better than metal-graphite brushes manufactured by conventional methods. Furthermore, the wear resistance properties related to the amount of wear can be significantly improved.

Claims (1)

[Claims] 1. A metal graphite material characterized in that composite particles with good fluidity are produced by dry heating mixing metal powder, graphite powder, and a powdered binder at a temperature below the softening point of the binder, followed by pressure molding and firing. How to make brushes.