JPH069435B2 - Manufacturing method of carbon brush for rotating electric machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a carbon brush for a rotating electric machine, particularly for a small rotating electric machine.

(Prior Art) In order to maintain good sliding contact of the carbon brush, the surface film that is excessively generated on the commutator surface is removed.
As disclosed in Japanese Patent Publication No. 39-16363, the brush contains amorphous silica and a metal having an action of promoting crystallization of silica such as alkali metal, alkaline earth metal, manganese, aluminum, bismuth and nickel. Then, there is a method of manufacturing a brush by heat treatment at a temperature of 700 to 1000 ° C. Further, as described in Japanese Patent Publication No. 58-58787, it is possible to prevent the formation of a harmful commutator surface film and to obtain stable abrasion characteristics even at high speed rotation. % Aluminum powder is added and heat treated at a temperature of 350 ° C. or lower. This suppresses the excessive formation of the surface film on the commutator surface due to the film adjusting action of a small amount of aluminum powder.
This is to improve the sitting comfort of the brush. For the same purpose, aluminum powder and silicon carbide powder were added to graphite powder as shown in Japanese Patent Publication No. 60-13382, and
Brushes heat-treated at a temperature of 50 ° C to 350 ° C,
Further, as disclosed in JP-A-58-148642, aluminum powder or aluminum powder and a phosphorus-containing compound, aluminum powder and a metal salt of borate ester are added to graphite powder, and heat-treated at a temperature in the range of 500 to 650 ° C. Brushes have been proposed.

(Problems to be Solved by the Invention) Although the brush disclosed in Japanese Patent Publication No. 39-16363 has an effect of removing the surface film on the commutator surface, it enhances the polishing effect and the friction coefficient and its variation There is a problem in that the efficiency of the rotating electric machine is lowered because of the increase in size. Also, Japanese Patent Publication No. 58-58787 and Japanese Patent Publication No. 60-133.
Although the brushes disclosed in Japanese Patent Publication No. 82 and Japanese Patent Laid-Open No. 58-148642 are effective in reducing the friction coefficient, they are not effective for rotating a rotating electric machine of a small electric motor such as an electric vacuum cleaner or an electric tool. Due to the increased capacity, the surface film generated on the commutator surface becomes excessive, and the fluctuations in the friction coefficient and contact voltage drop are large, which tends to lead to shortened brush life and increased commutator wear. However, it is hard to say that it is sufficient in terms of brush life and commutator wear.

INDUSTRIAL APPLICABILITY The present invention has a friction coefficient lower than that of a conventional brush and its fluctuation is small, and further, a contact voltage drop is small, that is, it is possible to prevent excessive formation of a surface film on the commutator surface.
The present invention provides a method of manufacturing a carbon brush for a rotating electric machine, which has stable sliding characteristics even at high-speed rotation, has a long life, and has a small amount of commutator wear.

(Means for Solving Problems) The present invention relates to a method for producing a carbon brush containing graphite powder as a main component and a thermosetting resin as a binder. A carbon brush for a rotating electric machine, which comprises press-molding a raw material prepared by mixing 3.0 wt% aluminum powder and 2-10 wt% copper powder with a thermosetting resin, and then heating and firing the mixture at a temperature of 500-750 ° C. Regarding manufacturing method.

The graphite powder which is the main raw material used in the present invention is a powder of artificial graphite, pyrolytic graphite, Kushiyu graphite or the like obtained by purifying natural graphite, petroleum-based coke, coal-based coke, etc., which has a low ash content, and has a particle size. Is not particularly limited, but is preferably 150 mesh or less. The thermosetting resin used as the binder is preferably a novolak type phenol resin, a resole type phenol resin, a bisphenol A type epoxy resin or the like.

In the present invention, aluminum powder and copper powder are used together with the above-mentioned raw materials. The aluminum powder may be granular or scaly. The type of copper powder is not limited, but dendritic electrolytic copper powder is preferable in order to prevent the excessive film from being formed on the commutator surface and to strengthen the proper film adjusting action.

The amount of aluminum powder added is 0.2 to 3.0% by weight, and preferably 0.5 to 2.
It is 0% by weight. Similarly, the amount of copper powder added is 2 to 10% by weight, preferably 4 to 8% by weight, based on the graphite powder.
Is. When the aluminum powder deviates from the range of 0.2 to 3.0% by weight and the copper powder deviates from the range of 2 to 10% by weight, the friction coefficient and the contact voltage drop increase. The coefficient of friction is 0.14 ~
When 0.17 and the contact voltage drop are in the range of 0.75 to 1 V, it is possible to prevent the surface film from being excessively formed on the commutator surface,
Thereby, the sliding of the brush is improved, the electric loss and the mechanical loss are low, the mechanical wear is reduced, the life is long, and the wear of the commutator is reduced. The particle size of the aluminum powder and the copper powder is preferably 200 mesh or less, because if the particle size is large, they are likely to be unevenly distributed in the carbon brush. The molding pressure is preferably 600 to 2000 kg / cm ² . If the pressure is low, the mechanical strength tends to be low, and if it is high, the sliding performance tends to deteriorate.

Firing is performed in an oxygen-blocking atmosphere, for example, in an atmosphere of nitrogen or hydrogen. The firing temperature is 500 to 750 ° C. If the firing temperature is less than 500 ° C, the carbonization of the resin will be insufficient and the electric resistance will not be sufficiently stable, and if it exceeds 750 ° C, the energy loss will increase.

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

Example 1 80 parts by weight of Pitch coke-based artificial graphite powder crushed to 250 mesh or less was used as a main raw material, and 20 wt. Parts and 1% by weight of granular aluminum powder of 200 mesh or less to the graphite powder, and further to 20% of the graphite powder.
0%, 1%, 2% by weight of electrolytic copper powder of 0 mesh or less,
3%, 5%, 7%, 10%, 12% or 15% was added and mixed, that is, the granular aluminum powder was kept constant at 1% by weight, and the amount of electrolytic copper powder was changed and mixed at 1400 kg / cm ² . After pressure molding, it was fired at a temperature of 650 ° C. to obtain a carbon brush. The friction coefficient value and contact voltage drop value of each brush are shown in FIG.

Table 1 shows the particle size distribution of the granular aluminum powder and electrolytic copper powder used in the present invention.

Example 2 Using the same main raw material and binder as in Example 1, 5% by weight of electrolytic copper powder of 200 mesh or less was added to graphite powder, and further, granular aluminum powder of 200 mesh or less was added to graphite powder. 0%, 0.2%, 0.5%, 1%, 2
%, 3%, 4% or 6% are added and mixed, that is, electrolytic copper powder is added to 5%.
The amount of the granular aluminum powder was changed to be constant with the weight percentage being constant, and the mixture was mixed and molded and fired in the same manner as in Example 1 to obtain a carbon brush. The values of the friction coefficient and the contact voltage drop of each brush are shown in FIG.

The carbon brushes obtained in Example 1 with different amounts of added copper powder were subjected to actual machine tests of brush life and commutator wear using a 100V, 1kW cleaner motor. The results are shown in Table 2. The commutator wear amount in the table shows the change in commutator diameter per 100 hours.

As is clear from FIG. 1, the carbon brush with 5% by weight of copper powder has the lowest friction coefficient of 0.14 and the contact voltage drop of 0.75V. The coefficient is 0.14 to 0.16, and the contact voltage drop is 0.
While it shows a low value of 75 to 1 V, when it is less than 2% by weight or more than 10% by weight, the friction coefficient and the contact voltage drop are higher than the above values, and stable sliding characteristics cannot be obtained at high speed rotation. Brush life will be reduced.

As is clear from FIG. 2, the friction coefficient is 0.14 to 0.1 when the amount of aluminum added is 0.2 to 3% by weight.
7. While the contact voltage drop is as low as 0.75 to 1V, when it is less than 0.2% by weight or more than 3% by weight, the friction coefficient and the contact voltage drop are higher than the above values, and at high speed rotation. Stable sliding characteristics cannot be obtained, and the brush life is reduced.

Furthermore, as is clear from Table 2, No. 3 in which 1% by weight of aluminum and 5% by weight of copper powder are added to graphite powder has the longest brush life and less commutator wear.

That is, when only aluminum powder or only copper powder is added, the friction coefficient and contact voltage drop do not decrease, but aluminum powder is added in an amount of 0.2 to 3% by weight and copper powder is added in an amount of 2 to 10% by weight. This prevents excessive formation of surface film on the commutator surface, reduces both the friction coefficient value and the contact voltage drop value, and provides an extremely excellent carbon brush with long life and less commutator wear.

In Example 1 of the present invention, 1% by weight of aluminum powder was added (constant amount) and copper powder was added in different amounts. In Example 2, 5% by weight of copper powder was added (constant amount). , The aluminum powders were added in different amounts, respectively. However, even when the addition amounts of the aluminum powder and the copper powder are not fixed and the respective addition amounts are changed, it is almost the same as those in the first and second embodiments. The same effect can be obtained.

(Effects of the Invention) According to the present invention, it is possible to prevent the excessive formation of the surface film on the commutator surface of the rotating electric machine due to the film adjusting action of a small amount of aluminum powder and copper powder. And the contact voltage drop can be reduced.

Therefore, even under high-speed rotation, the rotating electric machine has low electrical loss and mechanical loss, long brush life, and little commutator wear, maintaining extremely good operation.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the added amount of copper powder and the friction coefficient and the contact voltage drop, and FIG. 2 is a graph showing the relationship between the added amount of aluminum and the friction coefficient and the contact voltage drop.

Claims (1)

[Claims] 1. A method for producing a carbon brush comprising graphite powder as a main component and a thermosetting resin as a binder, wherein graphite powder and 0.2 to 3.0% by weight of aluminum powder relative to the graphite powder and A method for producing a carbon brush for a rotating electric machine, comprising: forming a raw material, which is a mixture of 2 to 10% by weight of copper powder and a thermosetting resin, under pressure, followed by heating and firing at a temperature of 500 to 750 ° C.