JP4476458B2 - Carbon brush for electric machine - Google Patents

Description

【００３４】
表１より、基材表面に形成された銅メッキ膜の表面にＢＴＡによるキレート錯体からなる耐酸化性被覆層を形成した実施例１のブラシは、推定寿命が従来の銅メッキのみをしたブラシに比較して、その推定寿命が約２５％上昇した。また、酒石酸によって耐酸化性被膜を形成した比較例２のブラシに比べて約１０％上昇した。
【００３５】
【発明の効果】
本発明は以上のように構成されており、基材表面に形成された銅メッキ膜の表面にトリアゾール誘導体、特にＢＴＡによるキレート錯体の耐酸化性被覆層を形成することにより、銅自身の酸化を抑制することができる。これによって、製品の変色防止、酸化による抵抗の上昇を抑制することができ、高出力、高速回転でも長時間に亘って、安定した整流特性を示す長寿命のブラシとできる。
【図面の簡単な説明】
【図１】本発明に係るブラシの概略斜視図である。
【図２】飽和水蒸気圧中における基材表面に形成した銅メッキ膜の抵抗の変化を示す図である。
【符号の説明】
１ ブラシ
２ 整流子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carbon brush for an electric machine, and more particularly, to a carbon brush for an electric machine that is used for a commutator electric motor such as a vacuum cleaner or an electric tool and requires high output and high speed rotation.
[0002]
[Prior art]
In recent years, carbon brushes for electric machines (hereinafter referred to as “brushes”) used in commutator motors have been particularly reduced in size, increased in output, and increased in speed. For this reason, a brush that is small in size, low in wear, and low in temperature rise under high current density conditions has been demanded.
[0003]
However, the conventional brush has a tendency that the rectification characteristics deteriorate, brush wear increases, and the brush temperature also increases under the conditions of high current density and high speed rotation. For this reason, the miniaturization of the brush has not progressed much compared to the miniaturization of the commutator.
[0004]
As is generally known, when a brush made of a substrate having a high resistivity is used for the commutator motor, rectification is stabilized. This is because when a brush made of a base material having a high resistance is used, a short-circuit current flowing between adjacent commutator pieces via the brush is suppressed. However, when a material having high resistance is used, the brush itself generates heat due to resistance heat generation, and the temperature rises. Furthermore, when the electric motor has a high output, a small size, and a high speed rotation, the current flowing through the commutator increases and the temperature of the commutator also increases. For this reason, stick-slip occurs due to excessive coating. As a result, commutation sparks increased, leading to further temperature rise and increased brush wear.
[0005]
In addition, in motors with high rotation speeds such as vacuum cleaners, it is desirable to extend the service life so that rectification is good even at high speed rotation and brush replacement is not required during use of the vacuum cleaner body. For this reason, resin-bonded materials in which graphite powder is bonded with a resin binder may be used. However, when used for a long time, due to the temperature rise, the lubricity of the brush itself is lowered, and further a vicious cycle of temperature rise occurs.
[0006]
Therefore, the present inventors applied a good electrical conductivity metal, such as nickel, copper, gold, silver, etc., on the outer surface around the base material of the brush, in particular, a cheap and excellent electrical conductivity copper film. Japanese Laid-Open Patent Publication No. 5-182733 discloses a technique for reducing the apparent resistance and suppressing the temperature rise by forming by plating. The technique of Japanese Patent Laid-Open No. 5-182733 has made it possible to suppress temperature rise to some extent.
[0007]
[Problems to be solved by the invention]
However, the copper film formed by plating on the surface is easily oxidized in the air, and the surface has been oxidized when used for a long time. For this reason, there is a problem that the electric resistance is increased by the formed oxide film, the effect of suppressing the temperature rise of the brush is reduced, and the purpose of extending the life of the brush cannot be achieved.
[0008]
Therefore, the present invention provides a carbon brush for an electric machine that requires a high output and a high speed rotation that enables a stable rectification characteristic over a long period of time even if the temperature rises is small. Objective.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors used a surface of a copper plating film formed on the surface of a brush substrate by an electroless plating method as a triazole dielectric such as triazole, alkyltriazole, and benzotriazole, particularly benzotriazole. (hereinafter, referred to. BTA) is contacted with a solution comprising, by forming the chelate complex by BTA on the surface of the copper plating film to prevent oxidation of the copper plating film, high output, prolonged use and in high-speed rotation However , the present inventors have found that a brush with stable rectification characteristics can be obtained , and completed the present invention.
[0010]
That is, the brush of the present invention, in the electric machinery carbon brush ing with copper plating film is formed on the surface of the carbon substrate, the copper plating film, nuclei grown while being formed by electroless plating overlap And an oxidation-resistant coating layer that is a chelate complex of a triazole derivative is formed on each surface of the nucleus . In addition, it is preferable that the substrate has a specific resistance of 100 μΩ · m or more. The copper plating film preferably has a thickness of 0.1 to 100 μm and is formed by electroless plating. The carbon base material is preferably made of graphite powder kneaded with a binder and cured. As a result, an oxidation-resistant coating layer can be formed by forming a chelate complex with a triazole derivative, particularly BTA, on the surface of the copper plating film , and formed on the surface of the base material of the brush by an electroless plating method. The effect of the copper plating film can be maintained for a long time.
[0011]
The base material of the brush in the present invention is (1) a so-called resin bond (resin bond type), which is obtained by kneading graphite powder with a binder such as a thermosetting resin and curing it. Examples thereof include carbon graphite (CG-based), which is obtained by kneading graphite powder with a binder such as a thermosetting resin or pitch, firing it at a low temperature, and carbonizing the binder component.
[0012]
Among them, it is preferable to use artificial graphite powder that is not so high in crystallinity, add thermosetting resin as a binder, knead, and mold to a predetermined size. As the thermosetting resin used as the binder, phenol resin, epoxy resin, maran resin, or the like can be used. And in this production | generation stage, it becomes possible by adjusting mixing conditions, baking conditions, etc. to make a base material into the specific resistance of 100 microhm * m or more of a desired range.
[0013]
In order to stably maintain the lubricity at high temperature, molybdenum disulfide, tungsten disulfide, or the like can be added as a solid lubricant to the brush base material. Since these solid lubricants such as molybdenum disulfide and tungsten disulfide that are added and mixed are insulative, when mixed alone with a resin or the like, they are likely to aggregate due to the influence of static electricity or the like, and difficult to disperse evenly in the resin. However, since it is first mixed with the graphite material having electrical conductivity, aggregation due to static electricity is extremely reduced. Furthermore, after adding a binder and kneading, it grind | pulverizes. For this reason, these solid lubricants are completely dispersed by the mechanochemical effect, and are firmly bonded and bonded to the binder and the graphite powder. The mixed powder mainly composed of the graphite powder thus obtained is molded and cured or fired to obtain a base material.
[0014]
However, brushes containing these solid lubricants such as molybdenum disulfide and tungsten disulfide tend to form a film on the surface of the commutator during use. When this film becomes too thick, it becomes easy to peel off, and when peeling occurs partially, the current concentrates on that part and the rectification characteristics deteriorate. In some cases, the commutator itself may be damaged and replaced. Therefore, the solid lubricant to be added is desirably 0.5 to 10 parts by mass of the entire brush base material. When the amount is less than 0.5 parts by mass, the lubricity is not exhibited, and when the amount is more than 10 parts by mass, the film formed on the surface of the commutator becomes excessive and the rectification characteristics deteriorate.
[0015]
In order to adjust the film formed on the surface of the commutator by the solid lubricant, it is preferable to add an abrasive to the brush base material. As the abrasive, alumina, silica, silicon carbide, or the like is used. If the amount of this abrasive is too large, or if the particle size is too large or the particles are not uniformly dispersed but agglomerated, it may cause damage to the commutator surface. Therefore, the added abrasive is desirably 0.1 to 1.5 parts by weight of the entire brush base material. If the amount is less than 0.1 parts by weight, the film adjusting function is not exhibited, and if the amount is more than 1.5 parts by weight, the surface of the commutator may be damaged. In addition, if the particle size of the abrasive is too coarse than 100 μm, the grinding action is strong, the commutator surface is roughened, and the commutator wear increases, and if it is finer than 5 μm, the action of removing the film on the commutator surface is low. Become. Accordingly, the particle size is preferably in the range of 5 to 100 μm. In addition, since these abrasives have high affinity and dispersibility with resins, etc., these additives can be added after mixing and grinding with graphite powder, binder and lubricant even if they are added and mixed together with the lubricant first. You may mix.
[0016]
Next, copper is formed and coated as a metallic film on the side surfaces 1a to 1d extending in the direction in which the brush surface shown in FIG. 1 is pressed against the commutator by an electroless plating method. As the electroless plating method, known methods are widely used from literatures and the like. For example, it is described in detail in “electroless plating” (Tsubaki Shoten, written by Tokuzo Kobe (1986)), and a strong film can be formed on the surface of the brush substrate according to the present invention.
[0017]
When the thickness of the copper plating film coated in this way is too thick, the mating sliding surface is roughened during sliding, and wear of the brush and mating material (commutator) tends to increase. On the other hand, if it is extremely thin, the effect of covering the base material of the brush is small, the resistance of the brush does not decrease much, and it becomes difficult to suppress the increase in the temperature of the brush. Accordingly, the thickness of the copper plating film is preferably about 0.1 to 100 μm.
[0018]
Moreover, the copper plating film formed by electroless plating is formed by growing the generated nuclei substantially uniformly and laminating the grown nuclei. Therefore, unlike copper produced by a general manufacturing method, the nuclei overlap each other, and electricity is a good conductor by propagating through the nuclei. Therefore, if the surface of the nucleus is oxidized, the propagation of electricity is not performed well, and the rate of increase in resistance tends to be larger than that of general copper.
[0019]
After copper plating, the plating film on the contact surface with the commutator 2 is removed by machining. Moreover, it is preferable to remove the plating film by machining the front surface 1a or the rear surface 1c or both surfaces 1a and 1c of the side surfaces 1a and 1c orthogonal to the rotation direction of the commutator 2 with respect to the rotation direction of the commutator. By removing the plating film formed on the side surface 1a, it is possible to prevent the plating film formed on the surface 1a from entering between the brush and the commutator 2 and damaging the commutator 2 when the brush is worn. it can. Further, by removing the plating film formed on the side surface 1c, it is possible to prevent a short circuit between the commutator pieces that may be generated by the plating film formed on the surface when the brush is worn. In addition, both of these can be prevented by removing the plating films on both side surfaces 1a and 1c.
[0020]
Next, the copper-plated brush is immersed in a triazole derivative such as triazole, alkyltriazole, or BTA, preferably BTA dissolved in water or alcohol, or the solution is applied to the surface by any method. Thus, the surface of the copper plating film is brought into contact with a solution containing BTA, chelated complexes according BTA on the copper plating film surface formed, oxidation resistant coating layer is formed on the surface of the copper. The generation of the chelate complex by the BTA is the removal of the copper plating film of the contact surface and the side surface of the aforementioned brush and the commutator may be after the formation of the chelate complex by BTA.
[0021]
The chelate complex by BTA is formed on the surface of each copper nucleus of the copper plating film formed by electroless plating. For this reason, since the oxidation of the surface of the nucleus can be prevented, the resistance of the copper plating film formed by the electroless plating method in which the nucleus overlaps and propagates electricity can be prevented, and the temperature rise of the brush can be prevented. .
[0022]
Thus, by forming an oxidation-resistant coating layer containing BTA on the surface of a brush made of a relatively high resistance base material having a specific resistance of 100 μΩ · m or more, the characteristics of the copper plating film formed on the surface Can be maintained over a long period of time, and temperature rise during use of the brush can be suppressed, and stable rectification characteristics are exhibited even when used for a long time at high output and high speed. You can do it with a brush.
[0023]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. In addition, this invention is not limited to a following example.
Example 1
25 parts by mass of a bisphenol-based epoxy resin and acetone were added to 75 parts by mass of artificial graphite powder having an average particle size of 50 μm and an ash content of 0.5% or less, and the mixture was kneaded at room temperature for 2 hours. Acetone is then evaporated to dryness, pulverized to a particle size of 40 mesh or less, embossed to a size of 7 × 11 × 31.5 mm at a pressure of 100 MPa, cured at 180 ° C., and a resistivity of 500 μΩ · m brush substrates were obtained. This brush base material was immersed in a copper sulfate solution complexed by adding sodium hydroxide and potassium tartrate, and formalin was added as a reducing agent to form a 10 μm copper film on the surface of the base material. Next, the brush base material with the copper plating film formed on the surface was immersed in a mixed solution of BTA and water for 1 minute to form a chelate complex with BTA on the surface to obtain a brush.
[0024]
(Comparative Example 1)
A brush was produced in the same manner as in Example 1 except that a chelate complex of BTA was not formed on the surface of the copper plating film.
[0025]
(Comparative Example 2)
A brush was produced in the same manner as in Example 1 except that the surface of the copper plating film was brought into contact with tartaric acid for 1 minute to form an oxidation resistant film on the surface.
[0026]
About each brush of Example 1 and Comparative Examples 1 and 2, the estimated life was measured by a change in resistance of the copper plating film formed on the surface of the base material and an actual machine test.
[0027]
(Change in resistance)
The brushes according to Example 1 and Comparative Examples 1 and 2 were installed in an atmosphere maintained at a saturated water vapor pressure of 40 ° C., and the change in resistance due to oxidation of the copper plating film formed on the base material surface of each brush was measured. .
[0028]
FIG. 2 summarizes the results.
[0029]
As shown in FIG. 2, the brush of Example 1 having a BTA chelate complex formed on the surface showed a constant resistance without changing the initial resistance even after 6 weeks. On the other hand, the brush of Comparative Example 1 started to turn red after about 3 weeks, and an increase in resistance was observed. Further, the resistance of the brush of Comparative Example 2 was increased after 4 weeks.
[0030]
Further, as a result of quantitative analysis of surface elements by XMA for each brush installed in an atmosphere of saturated water vapor pressure of 40 ° C. for 6 weeks, the oxygen concentration on each surface was 5.75% for the brush of Example 1. The brush of Comparative Example 1 was 17.05%, and the brush of Comparative Example 2 was 12.55%. Further, as a result of qualitative analysis of the surface by XRD, the brush of Example 1 was not detected except for copper, but the brushes of Comparative Examples 1 and 2 had copper oxide (Cu ₂ O And CuO) were detected.
[0031]
(Measurement of estimated life)
The estimated life was calculated from the test time, the wear length of the brush, and the effective wear length of the brush.
[0032]
Table 1 summarizes the results.
[0033]
[Table 1]

[0034]
From Table 1, the brush of Example 1 in which an oxidation-resistant coating layer made of a chelate complex of BTA is formed on the surface of the copper plating film formed on the surface of the substrate is a brush with an estimated life of only the conventional copper plating. In comparison, the estimated life increased by about 25%. Moreover, it rose about 10% compared with the brush of the comparative example 2 which formed the oxidation resistant film with tartaric acid.
[0035]
【The invention's effect】
The present invention is configured as described above. By forming an oxidation-resistant coating layer of a chelate complex with a triazole derivative, particularly BTA, on the surface of the copper plating film formed on the substrate surface, the oxidation of copper itself is performed. Can be suppressed. As a result, it is possible to prevent discoloration of the product and suppress an increase in resistance due to oxidation, and a long-life brush that exhibits stable rectification characteristics for a long time even at high output and high speed rotation.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a brush according to the present invention.
FIG. 2 is a diagram showing a change in resistance of a copper plating film formed on the surface of a substrate under saturated water vapor pressure.
[Explanation of symbols]
1 Brush 2 Commutator

Claims (4)

In the carbon brush for electric machines in which a copper plating film is formed on the surface of the carbon substrate,
The copper plating film is formed by electroless plating and grown nuclei are overlapped,
A carbon brush for an electric machine , wherein an oxidation-resistant coating layer that is a chelate complex of a triazole derivative is formed on each surface of the nucleus .   The carbon brush for an electric machine according to claim 1, wherein the specific resistance of the base material is 100 μΩ · m or more. The carbon brush for an electric machine according to claim 1 or 2 , wherein the copper plating film has a thickness of 0.1 to 100 µm. The carbon brush for an electric machine according to any one of claims 1 to 3, wherein the carbon base material is made of graphite powder kneaded with a binder and cured.

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