JPS5935155B2 - Manufacturing method of electrographite brush - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brush manufacturing method that provides a new electrographitic brush material that can withstand use in high-temperature atmospheres.

Conventionally, a method for manufacturing an electrographite brush takes steps as shown in FIG. 1, for example.

Depending on the purpose, oil smoke, coke, graphite, etc. are used as the main raw materials, and these are mixed with tar, pitch as a binder, and in some cases, silicon, microwave, etc. are added as additives. Pour it in, bake it, and then crush it to reduce the particle size. This process is repeated several times as necessary, followed by compression molding, firing, and graphitization treatment in which the material is heated to a temperature of about 2,700 degrees Celsius to complete the brush raw material. This graphitization treatment is the most important step, and because it allows the optimum characteristics of the brush material to be obtained, this step is considered essential to the brush manufacturing method.
The graphitized brush raw material is subjected to microwave treatment, etc., if necessary, and then subjected to the required processing steps to be completed as a brush material. The electrographite brush manufactured by the process described above and generally available has satisfactory characteristics under normal usage conditions, but according to experiments conducted by the inventors, the slip ring during use There is a large difference in wear resistance depending on the temperature, and the properties are not necessarily satisfactory.

Figure 2 shows the results of an abrasion test using a slip ring tester containing a heating element in a ring temperature range of 40 to 150 [°C]. It is in the shaded range, and it can be seen that the temperature dependence of brush wear is extremely large. Abnormal wear phenomena in such a temperature range are observed when the ring temperature is 120 [℃] or higher.
Possible causes include a lack of an adsorbed water molecule layer on the sliding surface, a lack of copper oxide, cuprous oxide, and graphite films, but the inventors focused on the fact that graphite's lubrication was not working effectively. An attempt was made to add a solid lubricant during brush molding. However, according to the above-mentioned conventional manufacturing method shown in Figure 1, since it includes a graphitization process that reaches temperatures as high as 2,700 degrees Celsius, the added lubricant (e.g. BN, MoS2, etc.) decomposes and loses most of its lubricating effect. I can't demonstrate it. For this reason, we conducted research to find a method for manufacturing electrical brushes without graphitizing the raw material powder and added solid lubricant after mixing and compression molding, and as a result, we came up with a manufacturing method that has the steps shown in Figure 3. Accordingly, it was found that it is possible to manufacture brush materials with the desired characteristics. That is, the gist of the present invention is to obtain a brush material by using electrographite powder as the main raw material, adding a solid lubricant thereto, further adding a binder, mixing them, compressing them, and firing them. This method is characterized by omitting the graphitization treatment after molding, which was conventionally considered indispensable for brush manufacturing.
The outline of the manufacturing process of the brush material by this manufacturing method is shown in FIG.

In the same figure, the raw material powder is oil smoke or coatus, which is mixed with a binder such as tar or pitch, then fired,
After graphitization, it is pulverized and the particle size is adjusted to obtain electrolytic graphite powder, which is the main raw material. Next, the solid lubricant is added to the already graphitized main material, and a binder is added and mixed. After compression molding, the brush material is fired under conditions that do not oxidize and decompose the added solid lubricant. Manufacture. In the brush material manufactured by this method, the added solid lubricant is present on the brush sliding surface, so effects such as an adsorbed water molecular layer and cuprous oxide cannot be expected, and the ring vorticity is 1.
It maintains good sliding characteristics even under conditions of 20 [° C.] or higher and exhibits satisfactory wear resistance.

As an example of this method, the wear characteristics of the prototype brush made are within the range shown by the dotted line in Figure 2, which is clearly compared to commercially available brush materials for electrical machinery produced using the conventional method. It can be seen that the wear characteristics in the high temperature range are improved.

In this example, a prototype was made using a weight ratio of BN2O, which is commercially available as a solid lubricant, and Pitch 30 as a binder to 100 of the main raw material of 200 mesh or less. Since the presence of hard residual coke contained in the binder is considered, it is desirable that the amount of binder added is as small as possible within a moldable range. Since the electrographite brush material made by this manufacturing method has a solid lubricant on its sliding surface, it effectively reduces the abrasiveness caused by the residual coke mentioned above and provides good sliding retention. However, the added solid lubricant has poor bonding properties with the electrographite powder, so it reduces the mechanical strength of the brush material.

Therefore, in order to obtain a mechanical strength of the brush material that can withstand practical use, it is necessary to limit the amount of solid lubricant added or to make the binder work effectively. In the manufacturing method described in claim 2, in order to increase the mechanical strength of the brush material without impairing the advantages of adding the solid lubricant, the surface of the lubricant is coated with a binder such as pitch or tar in advance. This treatment is intended to make the binder more effective during molding.

[Brief explanation of the drawing]

Figure 1 is a diagram of the manufacturing process of a conventional electrographite brush, and Figure 2 is a diagram of the temperature/wear test results using a slip ring tester.
shows the wear characteristics of the prototype brush manufactured by the manufacturing method of the present invention, and the third
The figure is a manufacturing process diagram of an electrographite brush according to the present invention.

Claims (1)

[Claims] 1. A solid lubricant is added to electrographite powder, a binder is further added, and after these are mixed and molded, the process is performed only through a firing process without graphitization treatment. A method of manufacturing an electrographite brush. 2. A method for producing an electric black viscous brush according to claim 1, characterized in that a solid lubricant whose surface is treated with a binder such as pitch or tar is used.