JPH0456787B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a carbon material for sliding and current collection using metal fibers with improved performance. [Conventional technology] Sliding current collecting materials for electric vehicles, etc. have been developed in order to cope with the increasing speed of vehicles and the increase in power consumption due to air conditioning equipment, etc.
Carbon-metal composite materials are being developed that take advantage of the excellent sliding properties of carbon and the electrical conductivity of metals. For example, (1) Japanese Patent Publication No. 56-14732 proposes a method in which the pores of a carbon material are impregnated with a specific metal under pressure. Furthermore, (2) Japanese Patent Publication No. 58-39216 proposes a current collecting material made of a specific metal with 10 to 70% by volume of carbon fiber interposed therein. [Problems to be solved by the invention] However, although methods (1) and (2) described above are devised to composite carbon and metal, for example, method (1) Since there is not enough metal in the pores, the electrical resistance is not reduced efficiently.
In addition, in order to impregnate metal, special equipment that can reduce and pressurize at the high temperature where the metal melts is required. In addition, in method (2), the blending ratio of carbon fibers is less than 70% by volume, so the excellent sliding properties of carbon are not fully exhibited. Therefore, the purpose of the present invention is to lower electrical resistance to the same level as metal in order to increase current collection efficiency, maintain carbon impregnation rate at 70 volume (vol)% or more so as not to impair sliding properties, and provide impact resistance. The objective is to provide a carbon material with excellent wear resistance. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention uses a raw material for carbon materials obtained by kneading or mixing carbon aggregates and a binder and then crushing them, or an oil component generated by heat treating coal tar. This method involves actively removing carbon fibers by vacuum distillation and then pulverizing the raw material for carbon materials, adding metal fibers of 2 vol% or more and less than 30 vol%, followed by molding and firing. [Function] In the present invention, the metal fibers were studied to efficiently reduce the electrical resistance of the carbon material and to function effectively as a reinforcing material, and it was discovered that metal fibers are effective in this respect. . In other words, by dispersing metal fibers in the carbon material, when compared with the conventional method at the same amount of metal content, the continuity of the metal fibers in the carbon material significantly lowers the electrical resistance, which is a disadvantage of carbon. It was found that the "brittleness" and "easiness to chip" were improved by using metal fibers, the impact resistance was significantly improved, and a bending strength test gave the material the ability to bend without breaking even after passing the yield point. . In this way, the mixture of metal fibers lowers the electrical resistance of the carbon material to that of metal, improves the impact resistance, and makes it possible to produce a carbon material that is difficult to chip. Furthermore, we use raw materials for carbon materials that have been crushed after kneading or mixing carbon aggregates and binders, or raw materials for carbon materials that have been crushed after heat-treating coal tar and actively removing the oil produced by vacuum distillation. By filling molding and firing, conventional methods leave fine bubbles in the carbon material due to the generation of gas during firing, making it difficult to obtain a dense carbon material and making it easy to chip. By reducing the amount of material used or actively removing oil through vacuum distillation, reducing the amount of gas generated during the firing process, and combining this with molding, it is possible to obtain a dense carbon material. It is possible to obtain a carbon material that has excellent conductivity and durability and is suitable for sliding and current collection purposes even without metal impregnation. [Specific Examples of the Invention] The present invention will be explained in further detail below. The raw material for carbon materials used in the present invention is obtained by kneading aggregates such as crushed coke and binder components such as coal tar, then heat-treating the crushed powder or coal tar, and actively removing the generated oil by vacuum distillation. It refers to raw material powder that can be used to produce carbon materials by press-molding and sintering the raw materials that have been removed and then crushed. The composition of the metal fiber is copper, iron, etc. or a mixture thereof, but is not particularly limited,
A metal with low electrical resistance, high strength, and high melting point is desirable. Copper or copper alloys are optimal in this respect. If the melting point of the metal is low, the metal will melt out during firing of the carbon material, making it impossible to raise the firing temperature, which is not preferable. Although the shape of the metal fiber is not particularly limited, it is preferable that the fiber diameter be 1 mm or less and the fiber length be 10 mm or less. In addition, the blending ratio of metal fibers is 2 to 30 vol%.
Preferably 6 to 20 vol% (excluding 30 vol%) is suitable. When the blending ratio of metal fibers is 2 vol % or less, the effect of the metal fibers, such as reduction in electrical resistance, does not appear. Furthermore, if the blending ratio of metal fibers exceeds 30 vol%, the carbon material cannot sufficiently bond the metal fibers, resulting in a decrease in strength, which is not preferable. Next, the carbon material and metal fiber may be mixed by a general method such as a shaking method or a V-blender.
Although not particularly limited, it is not preferable if the metal fibers are bent into a spherical shape due to forced mixing using a kneader. After the mixed raw material obtained as described above is molded by a method such as uniaxial pressure molding or isotropic pressure molding, it is fired for carbonization and graphitization in a non-oxidizing atmosphere. The firing temperature is around the melting point of the metal fiber. After the firing process is completed, it can be processed into a predetermined shape to obtain a carbon material for sliding and current collection. At this time, metal impregnation is not performed. [Examples and Comparative Examples] Petroleum coke was finely pulverized to an average particle size of 30 μm, and 30% by weight of medium pitch with a softening point of 80° C. was blended, and the mixture was kneaded for 5 hours while heating to about 120° C. in a kneader. After this mixture was allowed to cool, it was crushed to obtain raw material powder for carbon material. Next, as an example, the thread diameter is 50 μm and the thread length is about 3
Mix a specified amount of mm copper fiber or steel fiber, shake thoroughly, and put this mixed powder into a mold.
After molding into a plate shape of 50 x 90 mm and 15 mm thickness at a molding pressure of 2t/ ^cm2 , the molded body was buried in an iron box filled with coke powder and heated to 1050°C at a rate of 10°C/hr in a nitrogen atmosphere. The temperature was raised and maintained for 5 hours. The results are shown in Table 1. Examples 1 to 3 are those in which the blending ratio of copper fiber is within the range of the present invention, Examples 4 to 6 are in the case of steel fiber, and cases where no metal fiber is blended.
Comparative Examples 1 and 2 contained 50 vol% of copper fiber, and Comparative Example 3 contained 20 vol% of copper powder with a particle size of 20 μm. In addition, the amount of wear was determined by rotating a copper disk whose surface roughness was evened out with 120 # side paper at 1200 rpm, pressing a test piece of size 8φ x 40 mm against it with a pressure of 6 kg, and rotating the copper disk 5 x 10 ⁵ times. Shown in capacity.

【table】

〔Effect of the invention〕

As described above, according to the present invention, by pre-treating the carbon material raw material, selecting the molding method, and blending the metal fiber, the electrical resistance is significantly lower than when blending metal powder, and the extra step of metal impregnation is eliminated. Carbon materials with excellent wear resistance and impact resistance can be produced without the need for carbon materials.

Claims (1)

[Claims] 1 Metal fibers are added to raw materials for carbon materials that are obtained by kneading or mixing carbon aggregates and binders and then crushed, or raw materials for carbon materials that are obtained by heat-treating coal tar and actively removing the oil generated by vacuum distillation and then crushing the materials.
After mixing 2vol% or more and less than 30vol%, molding,
A method for manufacturing a carbon material for sliding and current collection, characterized by firing.