JPH0614770B2 - Metallic graphite brush for small motor and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] A carbon brush for use in a small motor having a permanent magnet field, particularly a graphite brush with improved commutation characteristics and wear resistance. The graphite powder used for the ash is refined to have an ash content of 0.05 wt% or less, and the graphite powder contains wear resistant and electrically conductive substance powder having a particle size of 50 microns or less in an amount of 0.1 to 15.0 wt%.
The composition of the brush is added to the total weight of the brush.

[Industrial application field]

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

[Conventional technology]

Conventionally, as a carbon brush for small motors,
A binder was added to the graphite raw material refined to about 98% to 99.5%, and the solidified material added with the binder was crushed and sieved to give the desired conductivity as necessary. A product manufactured by performing a metal powder addition and mixing treatment, then a pressure molding treatment, and a firing treatment is used.

Further, a so-called glazed copper graphite brush is known as one that eliminates the use of the binder. The copper-plated graphite brush is obtained by performing copper plating on powder particles of a graphite raw material that has been refined to about 99%, and press-molding the copper-plated graphite powder as it is, that is, without adding a binder. ， Manufactured by firing.

[Problems to be Solved by the Invention]

In the former case described in the above-mentioned conventional technique, graphite powder (including ash) is pressure-molded and fired together with a binder. In a conventional metal graphite brush manufactured by crushing and sieving a graphite raw material that has been hardened by adding a binder in this way, mixing the metal powder, and then firing it, the graphite raw material Impurities with a particle size of about 1 to 500 microns are usually contained in it.

FIG. 6 shows an electron micrograph of impurities contained in the graphite raw material. 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
It is an oxide such as O ₃ , Fe ₂ O ₃ , MnO, MgO, TiO ₂ , and silicate. The particle size of these oxides as impurities is 50
If it is more than micron, if it is not subjected to any treatment before adding and mixing the metal powder, it will be pressure-molded and fired, and during use as a carbon brush, particles will enter between the commutator and the brush to improve the rectification characteristics. make worse. In some cases, the motor is stopped by insulating the commutator from the brush.

Therefore, in one of the special applications already filed by the same applicant, the graphite raw material is first subjected to high-purity treatment to reduce the proportion of impurities contained in the graphite to 0.05 wt% or less, and In the binder treatment step or the mixing step of the above, oxides (SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MnO, MgO, T
We have proposed a metal graphite brush, in which iO, silicate) is added in the range of 0.1 to 10.0 wt% and treated with a binder, and then crushed and sieved, metal powder is mixed, pressure-molded and fired, and a manufacturing method thereof.

When the metal graphite brush manufactured by the manufacturing method proposed in the above application was used for a small motor, both its commutation characteristics and wear resistance were improved. However, oxides are generally insulative substances and therefore have no conductivity, and graphite containing the oxides has a problem in that it is difficult for current to flow.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems existing in the prior art, and to provide a metal graphite brush for a small motor, which has excellent rectifying characteristics, and has great wear resistance and conductivity, and a manufacturing method thereof. .

[Means for Solving the Problems]

In order to achieve the above-mentioned object, firstly, in the first invention, a permanent magnet is provided as a magnetic field, and it is used in a small motor that is commutated via a commutator to rotate.
In a metal graphite brush for small motors, which was formed by combining graphite powders and slid the commutator, the graphite raw material was subjected to high-purity treatment, and the ash contained as impurities in the graphite powders was 0.0. To the refined material of 5 wt% or less, add 0.1 wt% to 15.0 wt% of wear-resistant and conductive material with particle size of 50 μm or less during binder treatment or mixing treatment with metal additives. We adopted the technical means of press forming after doing so.

In the present invention, as the wear-resistant and conductive material, Ti is used.
C, ZrC, HfC, VC, NbC, TaC, Cr
₃ C _2, MoC, carbides mainly one or two or more of WC such as, TiN, ZrN, NbN, TaN , C
A nitride containing one or more of r ₂ N and VN as a main component, TiB ₂ , ZrB ₂ , NbB ₂ , TaB ₂ , CrB,
A boride containing at least one of MoB, WB, LaB, VB _{2 and the} like as a main component, or TiSi ₂ , ZrSi ₂ , N
_{bSi 2, TaSi 2, CrSi 2} , MoSi 2, a silicide as a main component one or two or more of WSi _2, etc. can be used.

Next, in the second invention, the permanent magnet is used as a magnetic field, and it is used for a small motor that is commutated through a commutator to rotate.
A high-purity treatment process for purifying a graphite raw material by using a substance that releases halogen in a high-temperature inert gas atmosphere in a metal graphite brush for a small motor that is formed by combining graphite powder and is configured to slide on the commutator. And a binder treatment step of solidifying the graphite powder that has undergone the high-purity treatment step with a binder, and a mixing treatment of adding and mixing metal powder after crushing and sieving the graphite material solidified with the binder. Performing a step, a processing step of pressing the mixed powder, and a firing step of firing the pressure-pressed molded article, and the binder treatment step or the mixing step. In order to manufacture a metal graphite brush, the wear resistance and conductive substance powder having a particle size of 50 microns or less are added in the range of 0.1 wt% to 15.0 wt%. Cormorants adopted the technical means.

FIG. 1 shows the principle of the metal graphite brush of the present invention.
FIG. 1A is a principle configuration diagram, and FIG. 1B is a manufacturing process explanatory diagram.

In FIG. 1A, reference numeral 1 is a commutator, 2 is a commutator piece, 3 is a rotating shaft, 4 is a carbon brush, and 5 is a brush elastic body.

The carbon brush 4 is sandwiched by conductive brush elastic bodies 5 and supported so as to slide on the commutator pieces 2, 2, 2. The carbon brush 4 is fired, for example, in a convex shape as shown in A-1 shown in the perspective view, and the convex head is sandwiched between the brush elastic bodies 5. A curved surface is formed on a surface corresponding to the bottom 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 which is a source of the carbon brush 4 according to the present invention, which is purified to, for example, about 99%, 21 is a high purity treatment step according to the present invention, 22 ′ Is a binder treatment process, that is, a wear-resistant material, and a conductive material such as carbide, nitride, boride, or silicide having a particle size of 50 microns or less is 0.1 wt% to 15.0 wt%, A process for adding and solidifying the graphite powder, a process 23 for crushing and sieving, a process 24 for mixing the processed graphite powder and a metal powder, a process 25 for pressure molding, and a process 26 for firing. .

As shown in FIG. 1 (B), the carbon brush 4 shown in FIG. 1 (A) has a high-purity processing step 21, a binder processing step 22 ', and a crushing / sieving processing step for a graphite raw material 20. 23, metal powder mixing process 24, pressure molding process
It is manufactured by performing 25 and the firing process 26.

[Work]

In the above manufacturing process, the graphite powder has 0.05 wt% or less of impurities (ash content) before the high-purity processing process 21 and the binder processing process 22 'are executed. The amount of particles corresponding to the impurities in the carbon brush 4 is less than 0.05 wt% of the graphite particles.

Therefore, since the impurities are extremely small, the rectifying characteristics of the carbon brush manufactured through the subsequent processing steps are excellent.

Furthermore, in the binder treatment step 22 'or the mixing step for the graphite raw material thus treated with high purity, the wear-resistant and conductive material having a particle size of 50 μm or less is forcibly applied in an amount of 0.1 to 15 wt% with respect to the total weight of the brush. It was also clarified from the experimental results that the wear resistance of the carbon brush of the present invention can be increased by adding it in a specific amount.

〔Example〕

FIG. 2 shows 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
Is a transformer and 32 is a halogen gas tube.

The high-purity treatment process is performed using a substance such as CC which easily releases halogen at high temperature in an inert gas such as nitrogen or argon.
l ₄ and by using a _CCl 2 _{F 2} corresponds to the step of removing the impurities in the graphite material. That is, the graphite raw material 20 is placed in the furnace body 30.
And a halogen gas pipe 32 is placed below the raw material 20. When the temperature of the furnace is raised to about 1800 ° C, CCl ₄
Is saturated with an inert gas and fed from the halogen gas pipe 32. In this case, it can be considered that the following reactions take place. That is, CCl ₄ → C + 2Cl ₂ 3C + Fe ₂ O ₃ + 3Cl ₂ → 2FeCl ₃ + 3CO, and when it becomes 1900 ° C. or higher, CCl _{4 is changed} to CCl ₂
Switch to F ₂ and continue refining treatment at a temperature of 2500 ° C or higher for 4 hours or longer. 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 graphite obtained in the high-purity treatment step is 99.9.
It will be 5 wt% or more. That is, the impurities are 0.05 wt% or less.

In addition, in order to increase the purity of graphite used for the graphite brush, the present inventor refined it by the following method in addition to the high precision treatment step, manufactured the graphite brush, and applied it to the motor. I did a test.

(I) Physical refining Flotation is used to separate impurities and graphite by utilizing the physicochemical differences on the surface of solid particles, and particles of approximately 300 μ or less are targeted. Since graphite can be sorted by bubbles,
Graphite powder was placed in oil and air bubbles, attached to air bubbles and collected. In this case, a purity of 98% or more and less than 99.5% can be obtained. Therefore, 0.5% to 2.0% is included as impurities.

(Ii) Chemical treatment Impurities contained in graphite are dissolved in a high-concentration acid or alkali solution, and at the same time, heating (160 ° to 170 ° C) and pressurization (5 to 6 atm) are applied. This treatment method is called the autoclave method, and the reaction of the main components can 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 99.95% is obtained. Therefore, the impurity content is 0.05% to 1.0%.

In this manner, the carbon brush according to the present invention is applied to the graphite raw material refined through the high-purity treatment step 21 and further in the binder treatment step 22 'shown in FIG. 1 (B) as described at the beginning. For example, conductive hard carbides with a particle size of 50 microns or less are 0.1 wt% to 15.0 wt
%, Forcibly added in the process of treating the graphite raw material or the mixing process. The metal graphite brush according to the present invention added as described above and manufactured through the subsequent steps can be excellent not only in rectifying characteristics and wear resistance but also in conductivity.

Fig. 3 shows that, in the manufacturing process shown in Fig. 1 (B), the graphite raw material refined to a purity of 99.95% through the high-purity treatment step 21 is added with the binder treatment step 22 'or the mixing step. When it is not mixed, that is, when it is not added, an oxide (for example, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , MnO, Mg
(O, TiO, silicate, etc.) is added, and experimental result data of a small motor using each carbon brush when conductive carbide is added is shown.

In this experiment, each brush was tested for up to 80 hours. In this case, if oxides or carbides are added, the particle size is 50 microns or less,
The amount added was 3 wt%.

As shown in Fig. 3, in the 80-hour test,
Abrasion rate of 100% without additive, 33 with oxide added
%, And those with carbonization additives were 19%. Therefore, when carbide is added, the wear resistance can be increased.

Fig. 4 shows the results of the addition of carbide (particle size,
(50 microns or less), the test results to see the change of the wear degree when the addition amount is changed are shown. In this case, 10 brushes with carbide added were manufactured and tested for a maximum of 80 hours. The crosses in the figure indicate the time when operation is impossible.

As shown in the figure, when the amount of carbide added is 0.5 wt%, the wear degree is 32% after 80 hours, but at 1.0 to 15.0 wt% it is 2%.
The degree of wear is relatively low, 0 wt% to 26 wt%. Then, the wear of the commutator at 20 wt% became extremely high, so the small motor was stopped.

From this, it is understood that the addition amount of carbide is preferably up to about 1.0 to 15.0 wt%.

FIG. 5 shows the results of an abrasion test when the amount of carbide added was kept constant (3 wt%) and the grain size was changed.

As shown in the figure, the wear rate is 22% after 80 hours when the particle size is 50 microns or less, 20% when the particle size is 50 to 74 microns, and 105 to 149
In the micron range, it is 30%, the average motor stop time is shortened to 53 hours, and in the range of 149 to 174 microns, the wear rate is suddenly increased and almost all of the motors become inoperable (average 38 hours). ), Is not suitable.

Based on the experimental results described above, the particle size and amount of carbide to be added are determined, and it is optimal to add those with a particle size of 50 microns or less in the range of 0.1 wt% to 15.0 wt%. .

In this embodiment, an example in which a carbide is used as the wear-resistant and conductive substance is described, but the wear-resistant and conductive substance is not limited to carbide, and nitride, boride, or silicide may be used. It is possible to exhibit the same action and effect as in the case of the above-mentioned carbide. Further, even if two or more kinds of the above-mentioned carbides, nitrides, borides or silicides are mixed, the action and effect are the same.

〔The invention's effect〕

As described above, according to the present invention, the purity of the graphite raw material is 99.95% in the high purity treatment step 21 of FIG. 1 (B).
Since the pretreatment is carried out so that the next treatment is started after raising the above (therefore, the impurities are 0.05 wt% or less), the rectification characteristics are improved, while the graininess in the binder treatment process or the mixing process is improved. Wear-resistant and conductive material with a diameter of 50 microns or less 0.1 wt% to 1 of the total brush weight
The addition of 5.0 wt% makes it possible to realize a metal graphite brush having improved wear resistance and conductivity.

[Brief description of drawings]

FIG. 1 (A) is a principle block diagram of the metal graphite brush of the present invention,
FIG. 1 (B) is an explanatory view of the production process of the metal graphite brush of the present invention, FIG. 2 is a conceptual diagram of a refining furnace used in the high purity treatment step of the present invention, and FIG. Results data of brush wear test with addition of carbide and addition of carbide, Fig. 4 is an experiment of wear test with variation of addition amount of carbide with constant grain size. Result data, Fig. 5 is the experimental result data when the wear degree was tested when the grain size was changed while the addition amount of carbide was kept constant, and Fig. 6 is the metallographic structure of the impurities contained in the graphite raw material. , Respectively, are shown. In the figure, 1 is a commutator, 2 is a commutator piece, 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 processing step, 22 'is a binder processing step, 23 is a crushing / sieving processing step, 24 is a metal powder mixing processing step, 25
Is a pressure forming step, and 26 is a firing step.

Claims (6)

[Claims] 1. Used in a small motor that has a permanent magnet as a field and is commutated through a commutator to rotate, and is formed by combining graphite powder to slide the commutator. In the metal graphite brush for small motors configured as above, the graphite raw material was subjected to high-purity treatment, and the ash contained as impurities in the graphite powder was refined to less than 0.0.5 wt%. Small size characterized by adding wear resistant and electrically conductive material with particle size of 50 microns or less in the range of 0.1 wt% to 15.0 wt% during the mixing process of mixing metal additives, followed by pressure molding and firing. Metal graphite brush for motor. 2. A wear-resistant and conductive material is TiC, ZrC,
HfC, VC, NbC, TaC, Cr ₃ C ₂ , MoC,
The metal graphite brush for a small motor according to claim 1, which is a carbide containing one or more of WC as a main component. 3. The wear-resistant and conductive material is TiN, ZrN, N.
The metal graphite brush for a small motor according to claim 1, which is a nitride containing one or more kinds of bN, TaN, Cr ₂ N, VN and the like as a main component. 4. The wear-resistant and conductive material is TiB ₂ , Zr.
B ₂ , NbB ₂ , TaB ₂ , CrB, MoB, WB, L
The metal graphite brush for a small motor according to claim 1, which is a boride containing one or more of aB, VB _{2 and the} like as a main component. 5. The wear-resistant and conductive material is TiSi ₂ , ZrSi.
₂ , NbSi ₂ , TaSi ₂ , CrSi ₂ , MoS
The metal graphite brush for a small motor according to claim 1, which is a silicide containing one or more of i ₂ , WSi ₂ or the like as a main component. 6. A small motor which has a permanent magnet as a magnetic field and is commutated through a commutator to rotate, and is formed by combining graphite powder to slide the commutator. In the method of manufacturing a metal graphite brush for a small motor configured as described above, a high-purity treatment step of purifying a graphite raw material using a substance that releases halogen in an inert gas high temperature atmosphere, and a graphite powder that has undergone the high-purity treatment step are A binder treatment step of hardening with a binder, a mixing treatment step of adding and mixing metal powder after crushing and sieving treatment of the graphite substance hardened with the binder, and pressure molding of the mixed powder. The pressure molding step and the firing step of firing the pressure-molded pressure-molded article are performed, and the binder treatment step or the mixing treatment step is performed. A metal graphite brush for a small motor characterized in that a powder of wear-resistant and electrically conductive material having a particle size of 50 microns or less is added in the range of 0.1 wt% to 15.0 wt% to produce a metal graphite brush. Manufacturing method.