JP2002084715A - Carbon brush for electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon brush for an electric machine, for which high output and high-speed rotations are required, the temperature rise of which is minimal even when used for many hours, and that can maintain stable commutation characteristics over the long period of time. SOLUTION: In a carbon brush provided with copper plating on the surface of a carbon base material for the electric machine, a chelating complex by a triazole derivative is formed on the surface of the copper plating. To provide a carbon brush for an electric machine, high output and high-speed rotations are required, the temperature rise thereof is minimal even when used for many hours, and that stable commutation characteristics can be maintained over the long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 for a commutator motor such as a vacuum cleaner or a power tool, which requires high output and high speed rotation.

[0002]

2. Description of the Related 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 rotation speed. Therefore, there has been a demand for a brush that is small in size, has low wear, and has a small temperature rise even under high current density conditions.

[0003] However, in the conventional brush, the rectifying characteristics are deteriorated under the condition of high current density and high speed rotation, the brush wear tends to increase, and the brush temperature tends to increase. Therefore, at present, brush miniaturization has not progressed much in comparison with miniaturization of commutators.

As is generally known, when a brush made of a substrate having a high resistivity is used for a commutator motor, commutation is stabilized. This is because when a brush made of a substrate having a large resistance is used, short-circuit current flowing between adjacent commutator pieces via the brush is suppressed. However,
When a material having a large resistance is used, the brush itself generates heat due to resistance heat, and the temperature rises. Furthermore, when the 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 (stick-sl
ip). As a result, the commutation spark increased, resulting in a further increase in temperature and an increase in brush wear.

[0005] In addition, a motor having a high rotation speed such as a vacuum cleaner has good commutation even during high-speed rotation, and has a long service life so that the brush need not be replaced during use of the vacuum cleaner body. Resin-bonded materials obtained by binding graphite powder with a resin binder have been used in some cases in order to increase the length of the resin. However, if the brush is used for a long time, the lubricating property of the brush itself is reduced due to the temperature rise, and a vicious cycle is created in which the temperature further rises.

Therefore, the inventors of the present invention have proposed a method of forming a conductive metal such as nickel, copper,
Japanese Patent Application Laid-Open No. 5-182733 discloses a technique in which an apparent resistance is reduced and a temperature rise is suppressed by forming a coating of gold, silver or the like, in particular, copper, which is inexpensive and excellent in electrical conductivity, by plating. The technology disclosed in Japanese Patent Application Laid-Open No. 5-182733 has made it possible to suppress the temperature rise to some extent.

[0007]

However, since the copper film formed on the surface by plating is easily oxidized in the air, the surface has been oxidized when used for a long time.
For this reason, there is a problem in that the electrical resistance is increased by the formed oxide film, the effect of suppressing the temperature rise of the brush is reduced, and the object of extending the life of the brush cannot be achieved.

Accordingly, the present invention provides a carbon brush for an electric machine, which requires a high output and a high speed rotation, with a small rise in temperature and a stable commutation characteristic over a long period of time even when used for a long time. The purpose is to do.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have proposed a method of coating a copper plating surface formed on a base material of a brush by electroless plating with a triazole dielectric material such as triazole or alkyltriazole. , Benzotriazole, etc., especially a solution containing benzotriazole (hereinafter referred to as BTA), and B
By forming a chelate complex by TA, oxidation of copper plating is prevented, and it has been found that a brush having stable rectification characteristics can be obtained even when used for a long time at high output and high speed rotation, and completed the present invention.

That is, the brush of the present invention is characterized in that a surface of a carbon substrate is plated with copper, and a chelate complex of a triazole derivative is formed on the surface of the copper plating. Further, the specific resistance of the base material,
Those having a resistance of 100 μΩ · m or more are preferable. Preferably, the copper plating has a thickness of 0.1 to 100 μm and is formed by electroless plating. by this,
By forming a chelate complex with a triazole derivative, particularly BTA, on the surface of copper plating, an oxidation-resistant coating layer can be formed, and the effect of copper plating formed by electroless plating on the base material surface of the brush Can be maintained for a long time.

In the present invention, the base material of the brush is (1)
A so-called resin binder (resin bond type) obtained by kneading graphite powder with a binder such as a thermosetting resin and hardening it, (2) so-called carbon graphite (CG)
Examples thereof include those obtained by kneading graphite powder with a binder such as thermosetting resin or pitch, firing at a low temperature, and carbonizing the binder component.

Above all, it is preferable to use artificial graphite powder which has not too high crystallinity, add a thermosetting resin as a binder, knead the mixture, and mold it to a predetermined size. As the thermosetting resin used as the binder, a phenol resin, an epoxy resin, a maran resin, or the like can be used. And in this generation stage, mixing conditions,
By adjusting the firing conditions and the like, the substrate can have a specific range of a specific resistance of 100 μΩ · m or more.

In order to stably maintain the lubricity at a high temperature, molybdenum disulfide, tungsten disulfide or the like may be added to the brush substrate as a solid lubricant. Since molybdenum disulfide, tungsten disulfide, and the like, which are added and mixed, are insulative, if they are mixed alone with a resin or the like, they are easily aggregated by the influence of static electricity or the like, and are difficult to be uniformly dispersed in the resin. However, since it is first mixed with a graphite material having electrical conductivity, aggregation due to static electricity is extremely reduced. Further, the mixture is kneaded with a binder, and then pulverized. For this reason, these solid lubricants are completely dispersed by the mechanochemical effect, and are firmly bonded to the binder and the graphite powder. The mixed powder mainly composed of the graphite powder thus obtained is molded, cured or fired to obtain a base material.

However, brushes containing these solid lubricants such as molybdenum disulfide and tungsten disulfide tend to form a film on the commutator surface during use. If this film is too thick, it will be easy to peel off, and if partial peeling or the like occurs, the current will concentrate on that part and the rectification characteristics will deteriorate. In some cases, the commutator itself may be damaged and must be replaced. for that reason,
The solid lubricant to be added is desirably 0.5 to 10 parts by mass of the entire brush substrate. If the amount is less than 0.5 part by mass, the lubricating property is not exhibited. If the amount is more than 10 parts by mass, the film formed on the commutator surface becomes excessive, and the rectifying characteristics deteriorate.

Further, in order to adjust the film formed on the commutator surface 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. When the amount of the abrasive is too large, when the particle size is too large, or when the particles are aggregated without being uniformly dispersed, they 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. When the amount is less than 0.1 part by weight, the film adjusting function is not exhibited, and when the amount is more than 1.5 parts by weight, the surface of the commutator may be damaged. If the particle size of this abrasive is too coarse than 100 μm, the grinding action is strong, and the commutator surface is roughened, and commutator wear is increased. If it is smaller than 5 μm, the action of removing the film on the commutator surface is low. Become. Therefore, the particle size is preferably in the range of 5 to 100 μm. In addition, since these abrasives have a high affinity and dispersibility with resins and the like, even if these additives are added and mixed together with a lubricant at first, they are added after kneading and grinding of graphite powder, a binder and a lubricant. You may mix.

Next, copper is formed as a metal film on the side surfaces 1a to 1d extending in the pressing direction of the brush against the commutator shown in FIG. As the electroless plating method, a method known from literatures and the like is widely used. For example, it is described in "Electroless Plating" (Maki Shoten, Tokuzo Kobe (1986)), and a robust film can be formed on the surface of the base material of the brush according to the present invention.

If the thickness of the copper plating film coated in this manner is too large, the sliding surface of the mating member tends to be roughened during sliding, and the abrasion of the brush and the mating material (commutator) tends to increase.
On the other hand, if the thickness is extremely thin, the effect of covering the base material of the brush is small, and the resistance of the brush does not decrease so much that it is difficult to suppress an increase in the temperature of the brush. Therefore, the thickness of the copper plating film is preferably about 0.1 to 100 μm.

The copper plating film formed by the 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, each nucleus is in an overlapping state, and electricity is a good conductor by propagating through each nucleus. Therefore, when the surface of the nucleus is oxidized, electricity does not propagate well, and the rate of increase in resistance tends to increase as compared with general copper.

After the copper plating, the plating on the contact surface with the commutator 2 is removed by machining. Further, of the side surfaces 1a and 1c orthogonal to the rotation direction of the commutator 2, it is preferable to remove the plating by machining the front surface 1a or the rear surface 1c or both surfaces 1a and 1c in the rotation direction of the commutator. By removing the plating formed on the side surface 1a, it is possible to prevent the plating formed on the surface 1a from entering between the brush and the commutator 2 when the brush is worn and damaging the commutator 2. In addition, by removing the plating formed on the side surface 1c, it is possible to prevent a short circuit between commutator pieces that may be caused by plating formed on the surface when the brush is worn. In addition, both sides 1
By removing the platings a and 1c, both of these can be prevented.

Next, this copper-plated brush is immersed in a triazole derivative such as triazole, alkyltriazole or BTA, preferably a solution in which BTA is dissolved in water or alcohol, or the solution is applied to the surface by any method. I do. Thus, the surface of the copper plating is brought into contact with the solution containing BTA, a chelate complex of BTA is formed on the surface of the copper plating, and an oxidation-resistant coating layer is formed on the surface of the copper. The formation of the chelate complex by BTA may be performed after the above-described removal of the copper plating on the contact surface and the side surface between the brush and the commutator after the formation of the chelate complex by BTA.

The chelate complex by BTA is formed on the surface of each nucleus of copper in copper plating formed by electroless plating. For this reason, since oxidation of the surface of the nucleus can be prevented, the resistance of the copper plating formed by the electroless plating method in which the nuclei overlap and propagate electricity is prevented,
The temperature rise of the brush can be prevented.

As described above, the surface of the brush made of a relatively high-resistance base material having a specific resistance of 100 μΩ · m or more,
By forming the oxidation-resistant coating layer containing BTA, the characteristics of the copper plating film formed on the surface can be maintained for a long time, and it is possible to suppress a temperature rise due to the use of the brush. Even if the brush is used for a long time at a high output and a high rotation speed, the brush can exhibit stable rectification characteristics.

[0023]

The present invention will be described below in detail with reference to examples. Note that the present invention is not limited to the following embodiments. Example 1 Bisphenol-based epoxy resin 2 was 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.
5 parts by mass and acetone were added and kneaded at room temperature for 2 hours.
Thereafter, the acetone was dried and evaporated, and pulverized so that the particle size became 40 mesh or less, and 7 × 11 at a pressure of 100 MPa.
It was embossed to a size of 31.5 mm, cured at 180 ° C., and a brush substrate having a resistivity of 500 μΩ · m was obtained. This brush substrate 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 substrate. Next, a brush substrate having a copper plating film formed on
It was immersed in a mixed solution of TA and water for 1 minute to form a chelate complex of BTA on the surface to form a brush.

(Comparative Example 1) A brush was manufactured 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.

Comparative Example 2 The surface of a copper plating film was contacted with tartaric acid for 1 minute to form an oxidation-resistant film on the surface.
A brush was produced in the same manner as in Example 1.

For each of the brushes of Example 1 and Comparative Examples 1 and 2, the change in resistance of the copper plating film formed on the surface of the base material and the estimated life thereof were measured by an actual machine test.

(Change in Resistance) The brushes according to Example 1 and Comparative Examples 1 and 2 were installed in an atmosphere maintained at a saturated steam pressure of 40 ° C., and oxidation of copper plating formed on the base material surface of each brush was performed. And the change in resistance due to the pressure was measured.

FIG. 2 summarizes the results.

As shown in FIG. 2, the brush of Example 1 in which the chelate complex of BTA was formed on the surface showed a constant resistance without change in the initial resistance even after 6 weeks. On the other hand, the brush of Comparative Example 1 began to turn red after three weeks, and the resistance was increased. Further, the resistance of the brush of Comparative Example 2 was increased after 4 weeks.

Further, each of the brushes installed in an atmosphere of a saturated steam pressure of 40 ° C. for 6 weeks was subjected to a quantitative analysis of surface elements by XMA. As a result, the oxygen concentration on each surface was 5% for the brush of Example 1. 0.75%, the brush of Comparative Example 1 was 17.
05%, and the brush of Comparative Example 2 was 12.55%. In addition, as a result of qualitative analysis of the surface by XRD, the brush of Example 1 did not detect anything other than copper, but the brushes of Comparative Examples 1 and 2 contained copper oxide (Cu
₂ O and CuO) were detected.

(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.

Table 1 summarizes the results.

[0033]

[Table 1]

From Table 1, it can be seen that the brush of Example 1 in which the oxidation-resistant coating layer composed of the chelate complex of BTA was formed on the surface of the copper plating formed on the substrate surface had an estimated life of only the conventional copper plating. Its life expectancy was increased by about 25% compared to the brush. In addition, the value was increased by about 10% as compared with the brush of Comparative Example 2 in which an oxidation-resistant film was formed with tartaric acid.

[0035]

The present invention is configured as described above.
Oxidation of copper itself can be suppressed by forming an oxidation-resistant coating layer of a triazole derivative, particularly a chelate complex with BTA, on the surface of copper plating formed on the substrate surface. As a result, it is possible to prevent discoloration of the product and suppress an increase in resistance due to oxidation, and it is possible to obtain a long-life brush that exhibits stable rectifying 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 copper plating formed on a substrate surface during a saturated steam pressure.

[Explanation of symbols]

 1 brush 2 commutator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3B006 FA01 4K026 AA06 AA21 BA01 BB08 CA16 CA37 4K044 AA13 AB05 BA06 BA21 BB03 BC02 BC14 CA15 CA16 CA53 5H613 AA01 AA03 BB04 BB15 GA09 GB01 GB05 GB06 GB08 GB09 SS04

Claims (3)

[Claims] An electromechanical carbon brush comprising a carbon substrate and a copper plating applied to a surface of the carbon substrate, wherein a chelate complex of a triazole derivative is formed on the surface of the copper plating. brush. 2. The method according to claim 1, wherein the specific resistance of the substrate is 100 μΩ · m.
The carbon brush for an electric machine according to claim 1, which is the above. 3. The method according to claim 1, wherein the copper plating has a thickness of 0.1 to 100 μm.
The carbon brush for an electric machine according to claim 1, wherein the carbon brush is formed by electroless plating.