JP2768504B2 - Metal graphite brush for small motor and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Carbon used for a small motor having a permanent magnet field
Regarding brushes, in particular, to provide a carbon brush with improved rectifying characteristics and abrasion properties, a graphite powder used for a metal-plated graphite brush, which has been refined to an ash content of less than 0.05 wt%, An oxide powder having a particle size of 50 microns or less as an abrasion-resistant substance is added to the graphite powder by 0.1 to 10 wt% forcibly during the binder treatment or during the mixing treatment for mixing the metal additive.

[Industrial applications]

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

[Conventional technology]

Conventionally, as a carbon brush for a small motor, a binder was added to a graphite raw material refined to about 98% to 99.5%, and the material solidified by adding the binder was ground and sieved. In this method, a metal powder is added and mixed to give a desired electrical conductivity according to the above-mentioned conditions, and then subjected to a pressure molding process and a firing process.

Further, a so-called plated graphite brush is known as one which eliminates the use of the binder. The copper-graphite brush is subjected to copper plating on powder particles of a graphite raw material refined to about 99%, and the copper-plated graphite powder is subjected to pressure molding, that is, pressure molding without adding a binder. It is manufactured by performing a baking process.

[Problems to be solved by the invention]

In the former case described in the above-mentioned prior art, graphite powder (including ash) is to be press-formed and fired together with a binder. A conventional graphite graphite brush manufactured by crushing and sieving a graphite raw material that has been hardened by adding a binder to a metal powder, mixing the resulting powder with a metal powder, and pressing and molding the resulting mixture is fired. Usually, impurities having a particle size of about 1 to 500 microns are contained therein.

FIG. 6 shows an electron micrograph of impurities contained in the graphite raw material, and it can be seen that impurities having a considerably large particle size are contained.

The main components of such impurities are SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MnO, M
It is an oxide such as gO, TiO ₂ or silicate. If these oxides as impurities have a particle size of 50 microns or more, they must be pressed and fired and used as carbon brushes, unless otherwise treated before mixing the metal powder. Particles enter between the brushes, deteriorating the rectifying characteristics. In some cases, the motor is stopped by insulating the commutator and the brush.

Fig. 7 shows the rectification waveform of a conventional metal graphite brush manufactured by mixing, pressing, and firing metal powder without any pretreatment before the mixing process of mixing metal powder with graphite raw material. A photograph is shown. As shown in the figure, it can be seen that the rectification waveform is disturbed because the ash particles as impurities are large, and the rectification characteristics are not preferable.

[Means for solving the problem]

Therefore, according to the present invention, a graphite material is first subjected to a high-purity treatment, and then an oxide as an anti-wear substance is forcibly added during a binder treatment of a specific weight% or a mixing treatment for mixing a metal additive. Crushing and particle size adjustment,
It is an object of the present invention to provide a metal graphite brush for a small motor having excellent rectifying characteristics and low abrasion, which is manufactured by mixing metal powder, pressing and firing.

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, reference numeral 1 denotes a commutator, 2 denotes a commutator piece, 3 denotes a rotating shaft, 4 denotes a carbon brush, and 5 denotes a brush elastic body.

The carbon brush 4 is sandwiched between conductive brush elastic members 5 and is supported so as to slide on the commutator pieces 2,2,2. The carbon brush 4 is fired in, for example, a convex shape as shown in A-1 shown in the perspective view.
A convex-shaped head is held by the brush elastic body 5. A slightly curved surface is formed on the surface corresponding to the bottom of the convex shape, and the curved surface slides on the commutator piece 2.

In FIG. 1 (B), reference numeral 20 denotes a graphite raw material which is the basis of the carbon brush of the present invention, for example, having a purity of 98%.
To 99.5%, 21 is a high-purity treatment step according to the present invention, and 22 is an oxide (SiO ₂ ,
Al ₂ O ₃ , Fe ₂ O ₃ , MnO, TiO, silicate, etc.) with a particle size of 50 μm or less is added to the binder in an amount of 0.1 to 10 wt%. A sieving process, 24 is a mixing process for adding and mixing the treated graphite powder and metal powder, 25 is a pressure forming process, and 26 is a firing process.

The carbon brush 4 shown in FIG. 1 (A) is manufactured by the manufacturing method shown in FIG. 1 (B), that is, the graphite raw material 20 is subjected to a high-purity treatment step 21, and a binder treatment step 22 ′ containing 0.1 to 10% by weight of the oxide. , Crushing and sieving processing step 23, mixing processing step 2
4, It is manufactured through a pressure forming step 25 and a firing step 26.

Needless to say, the above values of each wt% are values with respect to the total weight.

(Operation)

One feature of the present invention is that the high-purity processing step 21 is performed,
In a state before the binder processing step 22 'is executed,
The graphite powder has an impurity (ash content) of less than 0.05% by weight, so that the particles corresponding to the impurities in the manufactured carbon brush 4 are less than 0.05% by weight of the graphite particles. is there. Therefore, the rectification characteristics are excellent because the impurities are extremely small.

Further, the graphite raw material thus treated with a high purity is forcibly added to the binder in an amount of 0.1 to 10% by weight of the oxide having a particle size of 50 μm or less in the binder treatment, thereby making the carbon brush resistant. The experimental results also revealed that the abrasion can be enhanced.

The time for adding the oxide may be the time for mixing the metal additive.

〔Example〕

FIG. 2 is a conceptual diagram of a refining furnace used in the high-purity treatment step according to the present invention. Reference numeral 20 in the figure is a graphite raw material, 30 is a furnace body, 31
Represents a transformer, and 32 represents a halogen gas tube.

The high-purity treatment process is a substance that easily releases halogen at high temperature in an inert gas such as nitrogen or argon.
l ₄ and Cl ₂ F _2, etc. using corresponds to the step of removing the impurities in the graphite material. That is, the graphite raw material 20 is put into the furnace body 30, and the halogen gas pipe 32 is placed under the graphite raw material 20. When the temperature of the furnace is increased to about 1800 ° C., CCl ₄ is saturated with an inert gas and is fed from a halogen gas pipe 32.
In this case, the following reaction may be considered. That is, CCl ₄ → C + 2Cl ₂ 3C + Fe ₂ O ₃ + 3Cl ₂ → 2FeCl ₃ + 3CO When the temperature becomes 1900 ° C or more, CCl ₄ is switched to CCl ₂ F ₂ and the refining treatment is performed at a temperature of 2500 ° C. or more for 4 hours or more. Continue. Also in the cooling process, flushing is continued with an inert gas such as nitrogen or argon to prevent back diffusion of impurities and remove halogen.

The purity of the graphite obtained in the high-purity treatment step is 9
It becomes 9.95wt% or more. That is, the impurities are less than 0.05 wt%.

In addition, in order to increase the purity of the graphite used for the metal-plated graphite brush, the present inventors, in addition to the high-precision processing step,
After refining using the following method, a copper-plated graphite brush was manufactured and tested by applying it to a motor.

(I) Physical refining Flotation is used to separate impurities and graphite using the physicochemical difference on the surface of solid particles, and particles of approximately 300μ or less are targeted. Since graphite can be separated by air bubbles, graphite powder was put into oil and air bubbles, and the powder was collected by floating on the air bubbles. In this case, a purity of 98% or more and less than 99.5% is obtained. Therefore, about 0.5% or more and about 2.0% are contained as impurities.

(Ii) Chemical treatment The impurities contained in graphite are dissolved in a high concentration acid or alkali solution, and simultaneously heated (160 ° -170 ° C.) and pressurized (5-6 atm) are applied. This processing method is called an autoclave method, and the reaction of the main component may be considered as follows. That is, Fe ₂ O ₃ + 6HCl → 2FeCl ₃ + 3H ₂ O 2SiO ₂ + 4NaOH → 2Na ₂ SiO ₃ + 2H ₂ O In this treatment, a purity of 99% or more and less than 99.5% is obtained. Therefore, the impurities contain about 0.05% or more and about 1.0% as impurities.

The graphite raw material thus refined through the high-purity processing is subjected to the conventional subsequent manufacturing steps, namely, normal binder processing, grinding and sieving, metal powder mixing, pressure molding,
It has been found that the commutation characteristics of a small motor can be significantly improved by using a metal graphite brush manufactured by firing, as shown in the oscilloscope photograph of FIG.

However, it has been found that there is an unavoidable tendency that the brush wear is accelerated and the life of the motor is shortened.

Therefore, in the present invention, as described above, in the binder treatment step 22 'of the manufacturing method shown in FIG. 1B, oxides such as SiO ₂ , Al ₂ O ₃ , Fe ₂ O
₃ , for example, MnO, MgO, TiO, silicate, etc., having a particle size of 50 μm or less, about 0.1 to 10% by weight, forcibly added to the binder and subjecting it to binder treatment. Using metal graphite brushes manufactured through Nos. 26 to 26 made it possible to produce a small motor with excellent commutation characteristics and wear resistance.

FIG. 4 shows a binder processing step 2 in FIG. 1 (B).
2 'shows experimental data showing the relationship between the range of powder particle size of the oxide added to the binder and the degree of wear, and FIG. 5 shows that the powder particle size of the oxide was reduced to 50 microns or less. The data of the result of experimenting the degree of wear while changing the content of the oxide while maintaining is shown.

The data of the experimental results shown in FIGS.
Each brush was manufactured and tested for up to 80 hours of operation. The mark x in the figure indicates the timing at which operation was disabled.

As is clear from FIG. 4, in order to suppress the degree of wear, the particle size of the oxide powder should be 50 microns or less (Test No. 2). In other cases, for example, when no oxide is added (test No. 1), the degree of wear increases, and when the particle size is 50-60 microns (test
No.3), four of them could not be operated in a short time (average 24 hours), and in other cases (Test No.5 to Test No.5)
7) is unsuitable because all the units become inoperable in a short time (3.2 to 4.3 hours on average).

As is clear from FIG. 5, when the content of the oxide powder is in the range of 0.1 to 10.0 wt% (test No. 1 to test No. 6), the degree of wear is 41 to 67%, so that it is practically used. There is no problem. However, when the content is 12.0 wt% (Test No. 7), it is not suitable because all the units cannot be operated in a short time (49 hours on average).

Based on the experimental results described above, the carbon brush of the present invention contains 0.1 to 10.0 wt% of an oxide powder having a particle size of 50 μm or less in a binder to improve abrasion as well as the rectifying characteristics. In the processing step 22 ', it is formed by adding to the binder. The time for adding the oxide may be the time for mixing the metal additives.

〔The invention's effect〕

As described above, in the present invention, the first
In the high-purity treatment step 21 shown in FIG.
After increasing the concentration to 99.95% or more (therefore, impurities are less than 0.05 wt%), a rectification characteristic is improved by performing a pretreatment so that the next treatment is not performed. In addition to hardening the graphite powder with such a binder, by adding 0.1 to 10 wt% of the oxide having a particle size of 50 microns or less, a metal graphite brush having improved wear resistance can be realized.

[Brief description of the drawings]

FIG. 1 (A) is a diagram showing the principle configuration of a metal graphite brush according to the present invention, FIG. 1 (B) is an embodiment of a manufacturing process according to the present invention, and FIG. 2 is a purification furnace used in a high-purity processing step according to the present invention. Fig. 3 is an oscilloscope photograph of the commutation waveform of a small motor using the metal graphite brush according to the present invention, and Fig. 4 is an experiment showing the relationship between the particle size of the oxide added to the binder and the degree of wear. Result data, FIG. 5 is experimental result data showing the relationship between the content of oxide added to the binder and the degree of wear, FIG. 6 is a photograph of a metal structure showing the state of impurities contained in the graphite raw material, FIG. 7 and FIG. 7 are oscilloscope photographs of rectified waveforms of a conventional metal graphite brush. In the figure, 1 is a commutator, 2 is a commutator piece, 3 is a rotating shaft, and 4 is a carbon
Brush, 5 is a brush elastic body, 20 is a graphite raw material, 21 is a high-purity processing step, 22 'is a binder processing step, 23 is a pulverizing / sieving processing step, 24 is a metal powder mixing processing step, 25 is a pressure forming step, Two
6 represents a firing step.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02K 13/00 H01R 39/26 H01R 43/12

Claims (3)

(57) [Claims] 1. A small-sized motor which has a permanent magnet as a field, and is used for a small motor which is rotated by commutation through a commutator, and which is formed by combining graphite powder and slides on the commutator. In a carbon brush in a motor, a graphite raw material is subjected to a high-purity treatment by purifying a graphite raw material using a substance that releases halogen in a high-temperature atmosphere of an inert gas, and ash contained as an impurity in the graphite powder. Is refined to less than 0.05 wt%, and during the binder treatment or the mixing process of mixing metal additives, an oxide with a particle size of 50 microns or less is added in the range of 0.1 to 10.0 wt%, and then pressurized. A metal graphite brush for a small motor, which is formed by molding and firing. 2. The brush according to claim 1, wherein said oxide is an impurity mainly composed of SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MnO, MgO, TiO, silicate or the like. A metal graphite brush for small motors, characterized in that: 3. A small-sized motor which has a permanent magnet as a field, and is used for a small motor which is rotated by commutation through a commutator, and which is formed by combining graphite powder and slides on the commutator. In the method of manufacturing a carbon brush for a motor, a high-purity processing step of purifying graphite raw material using a substance that releases halogen in a high-temperature atmosphere of an inert gas, and an impurity contained in graphite powder through the high-purity processing step A binder treatment step of solidifying the graphite powder purified to a ash content of less than 0.05 wt% with a binder, and crushing and sieving the binder-treated and solidified graphite substance, and then adding a metal powder. A mixing step of mixing, a pressing step of pressing the mixed powder, and a firing step of firing the pressed article. And producing a metal graphite brush by adding an oxide powder having a particle size of 50 μm or less in a range of about 0.1 to 10 wt% in the binder treatment step or the mixing treatment step. A method for producing a metal graphite brush for a small motor, characterized by the following.