JPH0374159A - Metal graphite brush for small-sized motor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an abrasion resistant metal graphite brush having stable commutation characteristic by purifying graphite material, mixing graphite containing extremely small quantity of impurities with metal powder, pressure molding and then baking it. CONSTITUTION:Graphite material 20 is charged in a furnace 30 to be heated in a purifying step, CCl4 is saturated in inert gas at the time of about 1800 deg.C, and supplied through a halogen gas tube 32. It is switched with CCl2F2 at the time of 1900 deg.C or higher, and it is refined continuously for 4 hours or more at 2500 deg.C or higher. It is flushed with inert gas even in a cooling step to remove halogen while preventing impurities from reversely diffusing. The graphite contains 0.05wt.% or less of ash content by this process. Then, the graphite is mixed with metal powder, the mixture is pressure molded, and baked to form a metal graphite brush. Thus, the abrasion resistant brush having stable commutation characteristic can be obtained.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a carbon brush used in a small motor having a permanent magnet field.

The objective is to provide a carbon brush that has excellent rectifying properties and improved environmental resistance.

The graphite raw material used for metal graphite brushes is processed to high purity.
After adjusting the particle size using graphite powder whose ash content is refined to 0.05 wt% or less, it is mixed with metal powder, pressure molded, and fired.

[Industrial application field]

The present invention relates to a carbon brush used in a small motor, particularly a metal graphite brush used in a small motor having a permanent magnet field, and a method for manufacturing the same.

[Conventional technology]

Conventionally, carbon brushes in small motors are
A binder is added to the graphite raw material refined to about 98% to 99.5%, and the solidified material with the binder added is crushed and sieved to give the desired conductivity as necessary. After that, a metal powder addition and mixing process is performed, followed by a pressure molding process and a firing process.

Manufactured products are used.

That is, FIG. 4 shows a conventional manufacturing method for manufacturing carbon brushes for small motors using graphite raw material with a purity of about 98% to 99.5%.

As shown in the figure, a binder is added to graphite that has been refined to a purity of about 98% to 99.5%, and the solidified material is crushed and sieved.

Next, metal powder is added and mixed to give the desired conductivity, followed by pressure molding and firing to complete the product.

Furthermore, the so-called! J! Copper graphite brushes are known.

This tssim graphite brush is made by copper plating on powder particles of graphite raw material that has been refined to about 99%, and then pressurizing the copper-plated graphite powder as it is without adding a binder. , manufactured by performing a firing process.

[Problem to be solved by the invention]

In conventional metal graphite brushes, natural graphite is physically refined with a binder, then crushed and sieved.
In the above-mentioned physical refining alone, S i O2, A as impurities
J2z Os+Fez○1 silicate, MnO, MgO
The content of oxides such as 0.5 wt% to 1. About Owt% remains in the graphite in the form of ash.

FIG. 5 shows an enlarged electron micrograph of such ash (impurities) contained in graphite.

However, if a metal graphite brush is made by adding a binder to the graphite raw material of the above purity, there is little binder left during the firing process, and the surface area of the metal particles is small, so they are easily attacked by corrosive gases and oxidized. It has good environmental resistance.

However, a carbon brush plated with metal such as steel has a porosity of 10% to 30%. For this reason, the surface area of the thin film metal becomes large and it becomes easily oxidized, resulting in the disadvantage that it becomes more easily attacked by corrosive gases.

In this way, the relatively large amount of impurities that remain can damage or destroy the lubricating film on the commutator, accelerating wear and disrupting the commutator waveform.

FIG. 6 shows a photograph of an oscilloscope waveform of a metal graphite brush according to the prior art. As shown in the figure, it can be seen that the waveform of the motor current is disturbed. As the wear progresses further, the insulator contained in the carbon brush appears on the sliding surface of the carbon brush with the commutator, impairing commutation, and in the worst case, the motor will stop.

[Means to solve the problem]

Therefore, an object of the present invention is to solve the above-mentioned problems and provide a metal graphite brush that has stable rectifying characteristics and is less abraded.

For this reason, in the present invention, the graphite raw material is purified to a high degree, so that the graphite containing extremely few impurities is mixed with metal powder, pressure molded, and then fired to complete the product.

FIG. 1 shows a principle diagram of the present invention, FIG. 1(A) shows a principle configuration diagram, and FIG. 1(B) shows a manufacturing process explanatory diagram.

In the figure, 1 is a commutator, 2 is a commutator/piece, 3 is a rotating shaft,
4 represents a carbon brush, and 5 represents a brush elastic body.

The carbon brush 4 is held between conductive brush elastic bodies 5 and supported so as to slide on the commutator pieces 2, 2.2. The carbon brush 4 is fired into a convex shape, for example, as shown in Figure A-1, which is a perspective view.
The convex-shaped head is held between the brush elastic bodies 5. A somewhat curved surface is formed on the surface corresponding to the base of the convex shape, and the curved surface slides on the commutator piece 2.

Further, in FIG. 1(B), 20 is a graphite raw material that has been refined to, for example, a purity of about 98% to 99.5%, 21 is a high purity treatment process according to the present invention, 22 is a binder treatment process, and 23 2 is a crushing and sieving process; 24 is a mixing process of mixing high-purity graphite powder and metal powder;
5 represents a pressure molding process, and 26 represents a firing process.

The carbon brush 4 shown in FIG. 1(A) is shown in FIG. 1(B).
In other words, the graphite raw material 20 undergoes a high purity treatment step 21. Binder treatment step 22. Grinding/sieving process 23. Mixing treatment process 24° Pressure molding process 25. The carbon brush 4 is processed through a firing process 26 and manufactured as a carbon brush 4.

[For production]

A feature of the present invention is that a high purity treatment step 21 is performed.

In the state before the binder treatment step 22 is executed,
The graphite powder is made to have an impurity (ash content) of 0.05 wt% or less, and therefore, in all the metal-plated, pressure-formed and fired particles in the manufactured carbon brush 4, no impurities are present. Particles corresponding to 0.0 of graphite particles
5 wt% or less.

Therefore, since the metal graphite brush is formed, it has extremely less impurities than the carbon brush that uses graphite produced by conventional physical smelting or chemical processing, so it has excellent rectification characteristics and is less likely to wear out. few.

〔Example〕

Fig. 2 shows a conceptual diagram of an embodiment of a refining furnace used in the high purity treatment process according to the present invention.
0 represents a furnace body, 31 represents a transformer, and 32 represents a halogen gas pipe.

The high-purity treatment process uses substances such as CC that easily release halogens at high temperatures in an inert gas such as nitrogen or argon.
Impurities in the graphite raw material are removed using L or CCl1tFz (corresponding to the process).

That is, the graphite raw material 20 is put into the furnace body 30, and the graphite raw material 2
A halogen gas pipe 32 is placed under 0. When the furnace temperature reaches approximately 1800°C.

CCZ, is saturated with inert gas and halogen gas pipe 3
Feed from 2. In this case, it may be considered that a first-order reaction takes place. That is.

CCI! , 4→C+ 2 Cf z 3 C+ F ez03 + 3 Cj2z →2 F
e Cl x + 3 G O and 1900
CCZ when the temperature exceeds °C.

was switched to CCL F, and the scouring treatment was continued at a temperature of 2500° C. or higher for 4 hours or more. During the cooling process, flushing with an inert gas such as nitrogen or argon is continued to prevent back diffusion of impurities and remove halogen.

The purity of graphite obtained in this high purity treatment process is 99
．． It becomes 95 wt% or more. In other words, impurities are 0°05w
It becomes t% or less.

1. In order to improve the purity of graphite used in metal graphite brushes, the inventors refined the graphite using a zero-order method in addition to the above-mentioned high-precision treatment process, manufactured copper-coated graphite brushes, and applied them to motors. I applied it and tested it.

(i) Physical scouring flotation is used to separate impurities and graphite by utilizing physicochemical differences on the surface of solid particles.

Target particles are approximately 300μ or less. Since graphite can be sorted using air bubbles, graphite powder was placed in oil and air bubbles, and was collected by floating on the air bubbles. In this case, a purity of 98% or more and less than 99.5% can be obtained.

Therefore, about 0.5% or more and about 2.0% of impurities are contained.

(ii) Chemically treated impurities contained in graphite are dissolved with a highly concentrated acid or alkaline solution, and at the same time heated (160 @ ~ 170 ° C) and pressurized (5 ~
6 atmospheres) is applied. This treatment method is called an autoclave method, and the reaction of the main components can be considered as follows. That is.

Fetus +6HCIl→ 2FeCL +3Ht O 2S i Ox + 4 N a OH → 2 NazS
i Os + 2 Ht O 99 in this case
% or more and less than 99.95% purity is obtained. Therefore, it contains impurities in an amount of about 0.05% to 1.0%.

By subjecting the graphite raw material to high-purity treatment in a high-temperature inert atmosphere in this way, a carbon brush with extremely low impurities can be obtained.

FIG. 3 shows an oscilloscope photograph of a rectified waveform when a carbon brush manufactured by the method according to the present invention is used. In the case of the brush of the present invention, unlike the rectified waveform according to the prior art shown in FIG. 6, as can be seen from the oscilloscope photograph of FIG. 3, the rectified waveform during commutation appears regularly. Therefore, it can be seen that the rectification characteristics are excellent.

[Effects of the Invention] As explained above, according to the second invention, graphite raw material is processed to a high purity to have very few impurities, and then mixed with metal powder, pressure molded, and fired to produce graphite. Therefore, a metal graphite brush with stable and excellent rectifying properties can be obtained.

In addition, the metal graphite brush according to the present invention has a small surface area of the residual carbon of the binder and the metal powder particles, so it is difficult to oxidize.
It also has excellent environmental resistance.

[Brief explanation of drawings]

Figure 1 (A) is a diagram of the principle configuration of the present invention, Figure 1 (B) is an example of the manufacturing method according to the present invention, and Figure 2 is a conceptual diagram of an example of a refining furnace used in the high purity treatment process of the present invention. 3 is an oscilloscope photograph of the rectified waveform of the metal graphite brush according to the present invention, FIG. 4 is a manufacturing process diagram of the metal graphite brush according to the prior art, and FIG. Figure 6 is an oscilloscope photograph of the rectified waveform of a metal graphite brush according to the prior art. are shown respectively. In the figure, 1 is a commutator, 2 is a commutator piece, and 3 is a rotating shaft. 4 is a carbon brush, 5 is a brush elastic body, 20 is a graphite raw material, 21 is a high purity treatment process, 22 is a binder treatment process, and 23 is a crushing/sieving process. 24 represents a mixing process, 25 represents a pressure molding process, and 26 represents a firing process. (A) (B) Figure 1 $ 2 Figure 〃 Official〃Jz Procedural amendment (method) % formula % ) ) ) Title of invention Metal graphite brush for small motors and its relationship to the case of a person amending its manufacturing method Patent Applicant Address: 430 Matsuhidai, Matsudo City, Chiba Prefecture Name: Mapuchi Motor Co., Ltd. Representative: Takashi Umabuchi −

Claims (2)

[Claims] (1) Used in a small motor that is equipped with a permanent magnet as a field and rotated by commutation through a commutator, and is formed by bonding graphite powder and slides on the commutator. A carbon brush is a metal graphite brush that is formed by processing a graphite raw material to high purity, mixing it with metal powder, press-forming it, and firing it.The graphite powder used in the metal graphite brush is A metal graphite brush for a small motor, characterized in that the graphite powder has an ash content as an impurity refined to 0.05 wt% or less. (2) Used in a small motor that is equipped with a permanent magnet as a field and rotated by commutation through a commutator, and is formed by bonding graphite powder and slides on the commutator. A method for manufacturing a metal graphite brush includes a high-purity treatment step in which a graphite raw material is purified using a substance that liberates halogen in a high-temperature inert gas atmosphere, and a binder treatment in which a binder is added to the purified graphite raw material. , a crushing and sieving process for crushing and sieving; a mixing process for mixing metal powder with high-purity graphite powder whose sieving particle size has been adjusted; a pressure forming process for press-molding the mixed powder; A method for manufacturing a metal graphite brush for a small motor, characterized in that the metal graphite brush is manufactured by performing the following steps: a firing step of firing the pressure molded product.