JP3045268B2 - Method for producing metallic graphite unfired brush - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallic graphite brush most suitable for a micromotor.

[0002]

2. Description of the Related Art Conventionally, a binder is added to graphite, kneaded and dried, and then the dried product is pulverized, and a metal powder and a solid lubricant are added to the resulting pulverized product to form a mixture. Then, the mixture was compression-molded to form a brush molded body, and the brush molded body was fired at 400 to 900 ° C. to produce a brush.

In general, copper powder has been used as metal powder.

In the invention of Japanese Patent Publication No. 1-2690, an epoxy resin is mixed at a predetermined ratio with graphite,
After drying at 0 ° C., the mixture is pulverized, mixed with a phenol resin varnish, dried at 80 ° C., and then pulverized. This is mixed with copper powder and molybdenum disulfide, molded at 3 t / cm ² , and calcined at 750 ° C. for 4 hours in a reducing atmosphere to produce a metal graphite brush having a porosity of 18 to 34%.

[0005]

According to the conventional method,
Since the brush molded body is fired, the brush is hardened by shrinkage during firing, and the elastic modulus of the brush is increased, thereby causing a problem that sliding property is reduced and sliding noise is increased.

In general, in order to improve the slidability, the porosity of the brush is increased or the content of metal powder (copper powder) is reduced. However, there is a disadvantage that the specific resistance and contact resistance of the brush are increased.

An object of the present invention is to provide a method of manufacturing a metallic graphite brush capable of improving the sliding noise and slidability by lowering the elastic modulus of the brush.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is to form a granulated powder by adding a binder to graphite to form granulated powder, and to subject the granulated powder to a reduction heat treatment at a carbonization temperature of the binder. A step of forming a mixture by mixing the metal powder and the solid lubricating oil with the granulated powder subjected to the reduction heat treatment in such a manner, and a step of compressing and forming the mixture to form a molded body. This is a method for producing a graphite-based unfired brush.

[0009]

According to the present invention, since the brush molded body is not fired, there is no increase in density due to shrinkage during firing, and a low elastic modulus is easily obtained.

Since the granulated powder is compression-molded after the reduction heat treatment, the brush has a brush structure in which the fine powder is less likely to fall off when the brush is used and has many fine pores. In the conventional method in which graphite is not granulated, fine graphite powder is dispersed at the time of brush molding, so that the number of fine pores is relatively small, the specific resistance increases, and the graphite powder easily falls off when the brush is used, so that the wear is accelerated. Would.

When a metal powder (for example, copper powder) is subjected to a reduction heat treatment before use, the surface is activated and then molded, whereby the strength of the brush can be improved.

Further, since both graphite and metal powder are subjected to reduction heat treatment and then compression-molded, it is possible to suppress an increase in specific resistance and contact resistance.

[0013] Generally speaking, according to the method of the present invention,
The specific resistance, the contact resistance, the amount of wear, and the like are equal to or more than those of the conventional brush, and the sliding noise can be significantly reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a method for manufacturing a brush used for a micromotor will be described.

A binder is mixed with graphite at a predetermined mixing weight ratio (for example, 5 to 30%) and kneaded, and the mixture is granulated to form granulated powder. The granulated powder has a diameter of 50 to 800 μm 50
% Is preferable. As the binder, phenol resin, pitch, tar, coumarone-indene resin, or the like is used. If necessary, not only a binder but also a metal powder (for example, copper powder) may be mixed and kneaded with graphite, and the resulting mixture may be granulated to form granulated powder.

The above-mentioned granulated powder is mixed with the binder at the carbonization temperature (30
(At 0 ° C. or higher). For example, the reduction heat treatment is performed at about 450 ° C. under hydrogen reduction, and thereafter, pulverization and classification.

On the other hand, a metal powder such as a copper powder is heated at 200.degree.
A reduction heat treatment is performed at a temperature of 00 ° C. Preferred copper powder is 250
C. to 450.degree. C., then pulverized and classified to break up the lumps.

The metal powder previously subjected to the reduction heat treatment is mixed with the above-mentioned granulated powder together with the solid lubricant to form a mixture. The solid lubricant used here is preferably molybdenum dioxide, WS ₂ , BN, fluorinated graphite, Pb or the like.
In some cases, a solid lubricant can be mixed into the granulated powder.

The above mixture is compression-molded with a mold to obtain a brush molded body. The molding pressure is preferably 3 t / cm ²
Ｔ4 t / cm ² .

Although such a brush molded body can be used as it is, it may be finished if necessary. In any case, the brush molding is not fired.

Next, an example in which a brush for a wiper micromotor is actually manufactured will be described.

50 parts by weight of natural graphite having an average particle size of about 30 μm and 15 parts by weight of a phenol resin (binder) were kneaded.
Thereafter, the kneaded material was subjected to a reduction heat treatment at 450 ° C. in a hydrogen reducing atmosphere, and crushed to an average particle size of about 150 μm. On the other hand, electrolytic copper powder having an average particle size of 20 μm was subjected to a reduction heat treatment at 250 ° C. in a hydrogen reducing atmosphere, and passed through a sieve of about 80 mesh to loosen the lump. The granulated powder and the copper powder each subjected to the reduction heat treatment were mixed to form a mixture. This mixture was mixed with molybdenum disulfide as a solid lubricant. The mixing ratio of the granulated powder, the copper powder, and the solid lubricant was 50: 50: 3 by weight. Further, the above mixture was molded by a mold at a pressure of 3 t / cm ² .

When the brush thus obtained was used for a 12V wiper motor, the favorable effects shown in Table 1 were obtained.

[0024]

[Table 1]In Table 1, the conventional product is the raw material mixture used in the examples,
After kneading the lead, dry and crush it to the same particle size as in the examples.
After that, the same copper powder and lubricant were blended and 3 t / cm ^TwoMolding
Then, it was calcined at 450 ° C. under hydrogen reduction. Also,
B. D is the bulk density, Sp. r is the specific resistance; st is a song
Strength, S.I. H. Is Shore hardness; M. Is the Young's modulus,
C. D. Means the contact voltage drop, and the sliding noise is
The wear was measured by the brush length before and after the test.
It was measured by

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Sugu 378, Ogunimachi, Ogunimachi, Ogunimachi, Nishiokitama-gun, Yamagata Prefecture Toshiba Ceramics Co., Ltd. Oguni Works (56) References JP-A-1-103140 (JP, A) JP-A-2-197238 (JP, A) JP-B Hei 1-21690 (JP, B2) JP-B 48-25847 (JP, B1) (58) Field (Int.Cl. ⁷ , DB name) H01R 39/20 H01R 39/26 H01R 43/12 H02K 13/00

Claims (1)

(57) [Claims] 1. A step of forming a granulated powder by adding a binder to graphite to form a granulated powder, a step of subjecting the granulated powder to a reduction heat treatment at a carbonization temperature of the binder, and a step of performing the reduction heat treatment as described above. A process of forming a mixture by mixing a metal powder and a solid lubricant into a mixture, and a step of forming a molded body by compression-forming the mixture.