JPH0651894B2 - Manufacturing method of metallic graphite brush - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a metal-graphite brush having low electric resistance, high current collecting ability, and excellent wear resistance.

(Prior Art) Conventionally, a metal graphite brush is obtained by mixing and mixing metal powder such as lead and tin mainly with copper powder and natural graphite coated with a binder such as resin, molding, and then firing. It was being done. Also,
In order to improve the wear resistance, there are those in which a small amount of metal sulfide powder such as molybdenum disulfide or tungsten disulfide is added.

(Problems to be solved by the invention) However, when a large amount of copper powder and other metal powders are used to collect a large amount of current and the amount of graphite is reduced, the electric resistance decreases but the friction coefficient increases, and There is a drawback that the wear resistance is poor and the mating material (current collecting ring or commutator) is worn quickly. Moreover, a large amount of metal sulfide powder cannot be added, which is not suitable for collecting a large current.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks and provide a method for producing a metal graphite brush having excellent wear resistance.

(Means for Solving the Problems) In the present invention, a short fiber of a carbon fiber having a length of 0.2 to 10 mm, which is copper-plated on a mixture of a highly conductive metal powder and a graphite powder, is added to the mixture in an amount of 5 to 5 The present invention relates to a method for producing a metal graphite brush in which 15% by weight is added, mixed, molded and fired.

In the present invention, copper powder or silver powder having excellent oxidation resistance is used as the highly conductive metal powder, and usually copper powder is used from the viewpoint of cost. Tin powder may be added to increase the strength of copper powder, and a small amount of other metal powder such as lead powder may be added to impart lubricity. The graphite powder may be natural graphite or artificial graphite, but it is preferable to use one having a particle surface coated with a phenol resin or the like because it helps increase the strength of the brush. The mixture mainly comprises the metal powder and the graphite powder, but in addition to this, a small amount of a solid lubricant other than graphite such as molybdenum disulfide may be contained to improve the wear resistance. The particle size of the metal powder, graphite powder, and solid lubricant may be appropriately selected according to the purpose of use and is not particularly limited. When copper powder is used, its content in the mixture is selected according to the purpose of use, but is preferably 50 to 70% by weight in consideration of conductivity, abrasion resistance and the like.

Copper-plated carbon fiber is a short fiber with a length of 0.2 to 10 mm. If the length is less than 0.2 mm, the abrasion resistance of the brush is slightly improved, while if it exceeds 10 mm, it is even in the mixture. Dispersion becomes difficult and abrasion resistance is not improved. The plating thickness is appropriately selected according to the diameter of the fiber, but is 1 to 10
μm is preferred. Plating may be performed by any method such as electroplating and chemical plating. The copper-plated carbon fiber is added in an amount of 5 to 15% by weight based on the mixture of the metal powder and the graphite powder. If it is less than 5% by weight, there is no effect of improving the wear resistance, and if it exceeds 15% by weight, the lubricity is lowered and the wear resistance is not improved.

A known mixing method using a mixer may be used to add the copper-plated carbon fiber to the mixture, the molding may be performed by a known powder molding method, and the firing may be performed using a known reducing atmosphere furnace. The firing temperature is preferably 700 to 900 ° C. The fired product obtained by firing after uniaxial molding is preferably processed so that the surface perpendicular to the molding pressure surface becomes the sliding surface of the brush.

(Function) In the metal-graphite brush obtained by the present invention, the copper of the copper-plated fiber and the copper of the metal powder are firmly bonded by sintering, and the electrical resistance is low, the mechanical strength is high, and the wear resistance is high. . This tendency is remarkable in the uniaxially molded product in which the surface perpendicular to the molding pressure surface is the sliding surface.

(Example) Next, the Example of this invention is described.

A pitch-based carbon fiber having a diameter of 14.5 μm and a length of 3 mm (Kureka Chemical Co., Ltd., Creca Chop C-103S) was copper-plated with a thickness of 5 μm by an electroplating method. On the other hand, electrolytic copper powder with an average particle size of 20 μm (CE, manufactured by Fukuda Metal Foil & Powder Industry, CE
-25) 60 parts by weight, crushed lead powder (Toyo Metal Co., Pb-2
50) 2 parts by weight, scaly graphite (manufactured by Nippon Graphite Industry Co., Ltd., CB-1
50) is a phenol resin varnish (Hitachi Chemical Co., Ltd., V
36 parts by weight of graphite powder having an average particle diameter of 30 μm obtained by kneading, drying, pulverizing and classifying with P-11N) and 2 parts by weight of molybdenum disulfide powder (MD-108 manufactured by Hitachi Powder Metallurgy Co., Ltd.) are V-type mixers. Mixed in. For 100 parts by weight of this mixture,
The amount of the copper-plated carbon fiber shown in Table 1 was added and mixed in a V-shaped mixer, and molded by a uniaxial powder molding machine at a pressure of 4 $ / cm ² , and then an atmosphere of NH ₃ decomposition gas. 85 in the furnace
Baked at 0 ° C. A test piece of 10 × 10 × 50 mm was taken from the fired product, and the bending strength and the specific resistance of the pressing surface for molding were measured. The results are shown in FIG. On the other hand, 32 x 20 x so that the surface perpendicular to the molding pressure surface from the fired product becomes the sliding surface.
Take a 32 mm sliding test piece and press it against a 300 mmφ silver-containing copper current collector ring with a surface pressure of 1.5 kg / cm ² , and the current collector ring 1500
While rotating at D.P. C. The wear amount was measured through 600A for 5 hours, and the percentage of the wear amount of the A material, B material, C material, and D material in Table 1 with respect to the wear amount of the E material was obtained and defined as the wear rate. The results are shown in FIG.

As is clear from FIGS. 1 and 2, the one to which the copper-plated carbon fiber is added has a lower electric resistivity and wear rate than the one without the addition, and the addition amount of the present invention is 5 to 15% by weight. In the part, the mechanical strength (bending strength) was remarkably improved.

(Effects of the Invention) According to the present invention, it is possible to obtain a metal-graphite brush having a small electric resistance, capable of collecting a large current, and having improved abrasion resistance.

[Brief description of drawings]

FIG. 1 and FIG. 2 are graphs showing the relationship between the specific resistance, bending strength and wear rate with respect to the amount of copper-plated carbon fiber added.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-53-104508 (JP, A) JP-A-61-250127 (JP, A) JP-A-60-12269 (JP, A)

Claims (1)

[Claims] 1. A mixture of highly conductive metal powder and graphite powder, copper-plated with short fibers of carbon fibers having a length of 0.2 to 10 mm being added in an amount of 5 to 15% by weight, and mixed. A method for producing a metal graphite brush, which comprises molding and firing.