JPH06349559A - Brush material for electric machine - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an electrographitic brush material for electrical use that exhibits excellent wear resistance. [Constitution] An electric brush material having a porosity of 20% or less as determined by mercury porosimetry and having an average pore diameter of 1.2 to 1.9 μm and having a graphitic texture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric graphite brush material for electric machinery, which is used for rectifying electric vehicles and the like and has excellent wear resistance.

[0002]

2. Description of the Related Art Electric graphite brush materials for electric machines are made by kneading soot-based, coke-based, and graphite-based main raw materials together with a binder such as tar and pitch, and crushing them into a predetermined shape. It is manufactured by a process of firing, carbonizing and graphitizing after molding, and is widely used as an electric brush product for various DC machines. This kind of brush material for electric machines is required to have excellent performances such as sliding, rectifying, and friction, and at the same time, wearability which governs brush life is also an important evaluation characteristic.

Generally, wear of brushes for electric machines is caused by the materials of the brush and the commutator, the pressure of the brush during use, the cycle,
Since it is delicately affected by various material, mechanical, and electrical factors such as electric density, polarity, temperature, humidity, and atmosphere, the cause of wear has not been clarified yet. For this reason, a study to improve the wear resistance, especially from the viewpoint of the material of the brush, has been a major issue.

[0004]

DISCLOSURE OF THE INVENTION In order to solve such a problem, the present inventor has conducted multifaceted research on the correlation between the electrical and mechanical characteristics of the brush material and the wear resistance, and as a result, For example, characteristics such as specific gravity, hardness, elastic modulus, and electrical resistivity of the graphite material that constitutes the brush material have no causal relationship with wear, but the porosity and pore diameter of the tissue have a great influence on wear resistance. It was confirmed that the wear amount was significantly reduced when these measured values were less than a certain value.

The present invention was developed on the basis of the above findings, and an object thereof is to provide an electrographitic brush material for an electric machine, which exhibits excellent wear resistance.

[0006]

The brush material for electric machines according to the present invention for achieving the above object has a porosity of 20% or less and an average pore diameter of 1.
The structural feature is that it has a graphite texture of 2 to 1.9 μm.

In the graphite structure constituting the brush material for electric machines, the porosity measured by the mercury penetration method is 20% or less, and the average pore diameter is 1.2 to 1.9 μm. This is a requirement, and unless both of these properties are satisfied, it becomes impossible to impart the desired high degree of wear resistance. If the porosity exceeds 20%, mechanical wear increases, and even if the porosity is 20% or less, the average pore diameter is 1.2 to 1.9μ.
If it is out of the range of m, mechanical and electrical wear increase and excellent wear resistance cannot be obtained. In particular, the suppression of electrical wear becomes remarkable when the average pore diameter is in the range of 1.3 to 1.8 μm.

The graphite brush material having the above-mentioned texture can be basically obtained by the conventional method for producing an electrographite brush material. That is, suit type,
One or more main raw materials of coke type and graphite type are mixed with a binder such as coal tar and pitch and kneaded, and the kneaded product is crushed and molded into a primary firing, followed by graphitization treatment. It is manufactured using the basic process of controlling the volatile content of the kneaded material, pulverized particle size, molding pressure, graphitization temperature, etc., and impregnating the material after graphitization with a thermosetting resin liquid to cure it. By providing the conditions such as the above, the porous graphite material structure specified in the present invention can be formed.

[0009]

The electric brush according to the present invention is characterized in that the constituent material has a graphite composition property having a specific porosity and an average pore diameter measured by the mercury intrusion method. Together they work effectively to control mechanical and electrical wear. That is, the characteristic of the porosity of 20% or less enhances the denseness of the material, and exhibits effective resistance to mechanical wear due to friction or scratching during sliding contact.

However, it has been clarified that the wear of the brush material is controlled more largely by the electric wear during energization than by the mechanical wear. The mechanism of this electrical wear is that the apparent contact area in the process of current contact between the brush material and the commutator decreases during power transmission, leading to an increase in current density, and sparks are generated at the contact interface to cause a sudden increase. It is brought about by causing wear. The graphite structure having a porosity of 20% or less maintains a sufficient apparent contact area that does not cause the abnormal wear during the power transmission process, but is intercalated in the structure even if the porosity is 20% or less. Average pore diameter of open pores is 1.9μ
If it exceeds m, the periphery of the pores on the contact surface becomes a part that cannot conduct electricity, and instead of being subject to electrical wear, it projects as a convex part. If the protrusions become large to some extent, mechanical abrasion due to a scratching action occurs during sliding contact with the commutator, and the abrasion is greatly scraped off to accelerate the progress of abrasion.

On the other hand, in the case of fine pores having an average pore diameter of less than 1.2 μm, a current also flows through this portion, causing particles to collapse from the pore portion of comparatively weak strength, resulting in electrical wear. When this particle disintegration occurs, the particles in other contact parts are also scraped off at the same time, and abnormal wear progresses.

Therefore, the constitutional graphite structure has a porosity of 20% or less and an average pore diameter of 1.2 to 1.9.
The brush material for electric machines of the present invention satisfying the range of μm, preferably 1.3 to 1.8 μm functions to skillfully suppress mechanical wear and electrical wear, and through its action, excellent brush resistance is always maintained. Abrasion performance is demonstrated.

[0013]

EXAMPLES Examples of the present invention will be described in detail below in comparison with comparative examples. The porosity and average pore diameter of the brush materials used in each example were measured by mercury porosimetry with a mercury porosimeter [Micromeritex Co., Ltd., 9230], and the abrasion resistance was evaluated by a brush current of 50 A / c.
m ² , brush pressure 1.2 kg / cm ² , rotation speed 1200 rpm,
The wear amount was measured under the condition of a peripheral speed of 252 m / sec.

Examples 1 to 3 and Comparative Examples 1 to 3 Soot raw material having an average particle size of 5 to 30 μm was blended with a coal tar binder in the range of 55 to 75% by weight and charged into a kneading machine to 200 to 280 ° C. It was kneaded at the temperature of. The kneaded product that has been left to cool after the treatment is crushed to an average particle size of 20 to 50 μm to obtain a molding powder, which is then filled in a mold and then 1300 to 2500 kg / cm ²
220mm long, 110mm wide, 5 thick
It was molded into a 0 mm brick shape. Then, the molded body is primarily fired at a temperature of 1000 to 1200 ° C. in a firing furnace in a non-oxidizing atmosphere, and then transferred to a graphitization furnace to be 2500 to 3000 ° C.
Graphitization was performed in the temperature range of.

In the above manufacturing process, the particle size of the molding powder,
The molding pressure and the graphitization temperature were appropriately controlled, and the conditions were changed in the graphite block to impregnate the resin with a phenolic resin to prepare six kinds of graphite materials having different porosities and average pore diameters. This graphite material was processed to produce a soot-based electrographitic brush for electrical machinery, and its abrasion resistance was evaluated. The obtained measurement results of the amount of wear are shown in Table 1 in comparison with the porosity and the average pore diameter of the brush material.

[0016]

[Table 1]

From the results shown in Table 1, it was confirmed that all of the Examples satisfying the requirements of the present invention had a low wear amount and exhibited excellent wear resistance especially when the average pore diameter was around 1.55 μm. Moreover, no sparks were generated at the contact interface, and there was no danger of fire. On the other hand, the brush material of Comparative Example 1 having a porosity of more than 20% and the porosity of 2 were used.
Comparative Examples 2 and 3 in which the average pore diameter was out of the specific range of the present invention even though it was 0% or less showed significantly higher wear amount results than the Examples. The sliding characteristics, the rectifying characteristics, and the frictional characteristics were good in each example, and the performance was equivalent.

Examples 4 to 8 and Comparative Example 4 The same soot as in Example 1 was added in an amount of 60 to 90% by weight and a particle size of 5 μm.
As a raw material, 40 to 10% by weight of petroleum coke powder of m 3 was blended, and the following process was performed under the same conditions as in Example 1 except that the porosity and the average pore diameter were different from each other. Was manufactured. The abrasion resistance of these brush materials was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

[0019]

[Table 2]

The results shown in Table 2 also show that the examples of the present invention have superior wear resistance as compared with the comparative examples. However, Examples 7 and 1.8852 with an average pore diameter of 1.2223 μm
In Example 8 having a thickness of μm, there was a tendency that the amount of wear was slightly increased as compared with the brush material having an average pore diameter range of 1.3 to 1.8 μm.

[0021]

As described above, according to the present invention, by selecting a graphite structure having a specific range of porosity and average pore diameter, an electrographitic electric machine brush exhibiting excellent wear resistance. Material can be provided. Therefore, it becomes possible to greatly improve the durable life of the brush material while always maintaining a stable use state, which is a great contribution to the industry.

Claims (1)

[Claims] 1. The porosity measured by mercury porosimetry is 2
A brush material for an electric machine, which is characterized by having a graphite structure texture of 0% or less and an average pore diameter of 1.2 to 1.9 μm.