JPH01295642A - Electric brush - Google Patents

Abstract

PURPOSE:To lengthen service life by mixing organic fibers or particles coated with metal into powder material for the brush in an electric rotary machine then molding the mixture and sintering thereby remaining many bubbles in a brush and absorbing vibration. CONSTITUTION:Phenol varnish of flaky graphite powder having average grain size of 40mum is added end mixed then it is granulated through a spray drier thus producing graphite powder containing binder having average grain size of 150mum. Chemical galvanization is applied onto the surface of polyester fibers having diameter of 20mum and length of 0.3mm to form a copper galvanization layer 4 having average thickness of 4mum so as to produce copper galvanized polyester fibers containing 50wt.% copper. Then 10wt.% of the fibers, 33wt.% of electrical copper powder having average grain size of 30mum and 57wt.% of the graphite powder are mixed, thereafter the mixture is molded through a compression press and sintered. Consequently, the polyester fibers in the mixture material decompose to form many bubbles 3. As a result, elastic modulus of brush is reduced to absorb vibration while spark is suppressed to lengthen service life.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electric brush used in a rotating electric machine.

(Prior Art) Conventional 9 For example, when reducing the contact resistance between an electric brush and a commutator in an electric motor to improve output, or when using an electric brush under conditions requiring high current density, A so-called metal graphite electric brush containing a large amount of highly conductive metal powder such as copper powder was used.

(Problem to be Solved by the Invention) In the case of a metal-graphite electric brush, if the content of metal powder is increased, the resistance of the electric brush body and the contact resistance between the electric brush and the commutator will decrease, which will increase the output. Although it can be made larger, on the other hand, the elastic modulus of the electric brush increases and the amount of lubricating graphite decreases, making it difficult for the electric brush to sit on the commutator when a motor or the like is operated. In other words, the electric brush becomes less likely to dance and sparks are more likely to be generated, resulting in greater wear and tear, and the sliding noise between the electric brush and commutator becomes louder.

On the other hand, if the content of metal powder is reduced and the content of graphite powder is increased, the above problems will be solved, but the resistance of the electric brush itself and the contact resistance between the electric brush and commutator will increase, resulting in a decrease in motor output. There are problems such as a decrease in current density and an inability to obtain a large current density.

An object of the present invention is to provide an electronic brush that solves the above-mentioned problems.

The present invention relates to an electric brush made by adding and mixing metal-coated fibers or granular organic matter to electric brush raw material powder, molding the mixture, and then firing the mixture.

In the present invention, the metal to be coated on the surface of the organic material is not particularly limited, but metals with good conductivity such as copper and silver are preferred. Steel is usually used due to cost considerations. There are no restrictions on the organic material, but materials such as polyethylene resin, polystyrene resin, nylon, etc. that can be easily coated with metal on the surface and that are easily thermally decomposed during firing of the electric brush are preferred. The reason for this is that by sintering, only the metal coating layer around the organic substance is left behind, and by increasing the porosity and increasing the porosity of the surrounding metal in the structure of the electric brush, the 2 elastic modulus is lowered. Along with improving rideability.

This is because the coated metal remains in a mesh shape and reduces the electrical resistivity. If a fibrous organic substance is used, the metal remaining after firing will be continuous and form a grain, resulting in an electric brush with low electrical resistivity. In this case, it is natural to select an organic substance that is easily attached to the fibers, but the length of the fibers is preferably α4tm or less. If it is too long, it will be difficult to uniformly disperse it into the electric brush raw material powder.

When using a granular organic substance, the particle size is preferably 200 μm or less. If it is too large, the mechanical strength of the electric brush will decrease. The metal coating on the fibrous or granular organic substance may be applied by known chemical plating or the like, and the thickness of the coating is not particularly limited, but is preferably 1 to 10 μm.

In the present invention, electric brush raw material powder is mainly explained as a mixture of metal powder such as copper powder and graphite powder, that is, raw material powder for Kaniso graphite electric brushes, but is not limited thereto. It also includes binder-containing graphite powder obtained by mixing natural graphite and/or artificial graphite powder with, for example, a thermosetting resin solution and then drying the mixture. If the content of graphite powder in the electric brush raw material powder consisting of metal powder and graphite powder is large and it is difficult to maintain the strength by sintering the metal powder, use graphite powder containing a binder as described above. Further, it is preferable to use a metal powder of the same element as the metal coating the organic substance, since this facilitates sintering, lowers the electrical resistivity, and increases the mechanical strength. Although there is no particular restriction on the amount of the organic substance added to the electric brush raw material powder, it is preferably contained in an amount of 5 to 20% by weight in the molded powder after mixing. Mixing, shaping and baking are carried out by known methods.

When the metal powder content is large, the metal powder is fired at a temperature at which the metal powder is sintered, and when a binder is used separately, the binder is fired at a temperature at which the binder is sufficiently carbonized.

(Example) Next, the present invention will be explained in detail.

Example 1 A phenolic resin face (manufactured by Hitachi Chemical Co., Ltd., VPIIN) was added to scaly graphite powder with an average particle size of 40 μm and kneaded to form a slurry, and the slurry was granulated using a spray dryer to obtain a phenol resin with a solid content of 9% by weight. A binder-containing graphite powder having an average particle diameter of 150 μm was obtained.

Steel-plated polyester fiber with a copper content of 50% by weight, electrolytic copper with an average particle size of 30μm and a copper content of 50% by weight, which is made by chemically plating the surface of a polyester fiber with a diameter of 20μm and a length of 0.3m with an average thickness of 4μm. 33% by weight of the powder and 57% by weight of the binder-containing graphite powder were mixed in a V-shaped mixer, and the mixed powder was molded with a compression press at a pressure of 3t/am'', and then heated in a firing furnace at 600°C under a nitrogen gas atmosphere. Baked 7t x 8
An electric brush of X12 (■) was obtained. Figure 1 is an enlarged cross-sectional view of the electric brush obtained as described above, showing steel powder 1 and graphite powder 2.
It can be seen that a copper plating layer 4 having pores 3 is present in contact with the .

Example 2 The surface of polystyrene beads with an average diameter of 30 μm was plated with steel to an average thickness of 4 μm by chemical plating, and the copper content was 50% by weight - 10% by weight of copper-plated polystyrene beads.
, 33% by weight of electrolytic copper powder with an average particle size of 30 μm and Example 1
57% by weight of the binder-containing graphite powder obtained in Example 1 was mixed in a V-type mixer, and an electric brush was obtained in the same manner as in Example 1.

40 of electrolytic copper powder and binder-containing graphite powder in Comparative Example Example 1
% by weight and 60% by weight were mixed in a V-type mixer, and an electric brush was obtained in the same manner as in Example 1.

(Physical properties and sliding test of electric brush) Table 1 shows the physical properties of the electric brushes obtained in the examples and comparative examples. Further, this electric brush was installed in a 12V, 170W automobile blower motor, and the initial output (rotation speed) and sliding noise were measured. Furthermore, a continuous durability test was conducted using Shirotsukotsutan as a load, and the amount of wear of the electric brush was measured. The results are shown in Table 2.

Table 2 The electric brush in the example shown in Table 1 has a lower resistivity and a lower modulus of elasticity than the electric brush in the comparative example with the same steel content.

As a result, as shown in Table 2, the electric brush of the example has superior rotating performance than the electric brush of the comparative example, and has features such as low sliding noise and low electric brush wear.

(Effects of the invention) According to the present invention, the surface is coated with metal, fibrous or granular organic matter is added to the electric brush raw material powder, molded, and then fired to decompose the organic matter, thereby forming pores in the electric brush. Since many remain, the elastic modulus becomes small.

As a result, the vibrations generated when the electric brush slides are easily absorbed, the electric brush is more comfortable to sit on, and the sliding noise is reduced. In addition, since the conductive metal layer remains in the electric brush structure, the resistivity is low and the output of the motor is improved. Furthermore, as the sitting comfort of the electric brush is improved, rectifying sparks are reduced, so that wear of the electric brush is reduced and an electric brush with a long life can be obtained.

The electric brush of the present invention can be effectively used in rotating electric machines that require high output, low sliding noise, and long life of the electric brush.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view showing the structure of an electric brush according to a second embodiment of the present invention. Explanation of symbols 1... Steel powder 2... Graphite powder 3... Pores 4... Copper plating layer piece 1 Figure

Claims (1)

[Scope of Claims] 1. An electric brush made by adding and mixing a metal-coated fibrous or granular organic substance to electric brush raw material powder, molding the mixture, and then firing the mixture. 2. The electric brush according to claim 1, wherein the electric brush raw material powder contains metal powder of the same element as the metal coating the organic substance.