JP2007129897A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor having a metallic coating carbon brush with uniform film thickness of metal coated on a surface, and reduced a color unevenness on the surface. <P>SOLUTION: The metallic coating carbon brush is used which is obtained by coating the metal on the surface of a base material composed of a carbonaceous material, in which an average pore radius is 0.1 to 2.0 μm and accumulated pore volume is 50 to 600 mm<SP>3</SP>/g. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a metal-coated carbon brush used in an electric machine.

  In recent years, electric motors using carbon brushes for electric machines (hereinafter referred to as “brushes”) have been particularly reduced in size and increased in capacity, and the brushes used therefor are electrically conductive resistance loss (hereinafter referred to as resistance loss). There is a demand for brushes that are small and wear less.

  For brushes used in slip rings and low-voltage motors, metallic materials that have been obtained by mixing and sintering graphite powder and metal powder have been used so far, but in order to reduce the resistance loss of the brush When the metal content is increased, there is a problem that the lubricity and arc resistance are deteriorated and the wear amount is increased.

  Further, in the case of an AC commutator motor, there is a problem that if a material having a low resistance is used in order to reduce the resistance loss, the rectification becomes worse and the wear increases.

  Conversely, when a material with high resistance is used, the brush temperature rises due to resistance heat generation when a large current is passed. The brush usually embeds the lead wire with copper powder and compresses it, joins it, and supplies the current.However, if the brush temperature is high, the copper powder and lead wire in the caulked part will be oxidized and the current will go bad. There was a possibility that the problem that the motor stopped would occur.

  Also, among AC commutator motors, motors with high rotation speeds, such as those for electric vacuum cleaners, have good rectification even at high rotations and do not require brush replacement during the use of the vacuum cleaner body. As described above, resin bond-type materials in which graphite powder is bonded with a resin binder and hardened are sometimes used because of the required characteristic that it is desired to have a very long life. However, in the case of resin-bonded materials, when used under conditions where the current density is large, the resistance of the brush body is large, so that the temperature rises and the resin used for the binder is thermally deteriorated.

  In order to solve these problems, carbon brushes are known that contain carbon as at least one component and have an electrically conductive metal layer coated on the surface of the brush base so that the electrical resistance of the entire carbon brush is reduced. (For example, refer to Patent Document 1).

JP-A-5-182733

  However, since it was difficult to coat metal with a uniform thickness on the surface of carbonaceous material, color unevenness may occur on the surface of the coated metal due to variations in the coating thickness. There was a risk of discomfort for the user. Moreover, it causes oxidation and cannot maintain good electrical resistance.

  An object of the present invention is to provide a metal-coated carbon brush in which the film thickness of the metal coated on the surface is made uniform and color unevenness on the surface is suppressed.

The metal-coated carbon brush according to the present invention for solving the above-described problems is obtained by applying a metal to the substrate surface made of a carbonaceous material having an average pore radius of 0.1 to 2.0 μm and a cumulative pore volume of 50 to 600 mm ³ / g. Is coated. Moreover, the said metal is chosen from the silver formed in the surface of copper, silver, or copper. Moreover, the film thickness of the said metal is 1-10 micrometers. The metal is formed by an electroless plating method.

As described above, a carbonaceous material having an average pore radius of 0.1 to 2.0 μm and a cumulative pore volume of 50 to 600 mm ³ / g is used as a sensitizer in advance for electroless plating. By immersing in a pretreatment solution to which SnCl ₂ and PdCl ₂ are added as an activator, it becomes possible to coat the metal firmly with no color unevenness, satisfying the aesthetic sense of the user and preventing oxidation. It becomes possible.

  As a brush base material made of a carbonaceous material used in the present invention, (1) graphite powder kneaded with a binder such as a thermosetting resin and cured (resin bond type), (2) graphite Powder is kneaded with a binder such as thermosetting resin or pitch, fired at low temperature, carbonized binder component (CG), (3) fired at higher temperature, and at least part of the carbon component There is a graphitized product (EG type). In the present invention, in particular, the resin bond base material (1) is the main target. In a resin-bonded base material, the resin used as a binder is used in a cured state and is not carbonized or graphitized, so that the electrical insulation is relatively high. Therefore, there is an advantage that resistance is large and rectification is good. On the other hand, the resistance loss due to the large resistance is large, resulting in the disadvantage that the heat generation is large, and the disadvantage that the resin deteriorates and the characteristics change due to long-time use under high temperature conditions.

  The requirement of such conflicting characteristics is that the resistance of the internal substrate is reduced by coating the outer surface around the brush substrate with a metal selected from copper, silver, or silver formed on the copper surface. Even if it is high, it can compensate for all the disadvantages of resin-bonded base materials, such as lowering the apparent resistance due to the action of the metal coated on the outer surface, suppressing temperature rise, and preventing performance changes due to the use of brushes. Combined with this, you can make a very high performance brush.

And as a brush base material which coat | covers a metal, an average pore radius is 0.1-2.0 micrometers, Preferably it is 0.5-1.5 micrometers, A cumulative pore volume is 50-600 mm < ³ > / g, Preferably it is 100-500 mm. Adjust to ² / g. Then, by coating the metal so that the film thickness of the metal on the surface is 1 to 10 μm, preferably 2 to 5 μm, it is possible to suppress color unevenness on the metal surface when the metal is coated on the surface. it can.

  As a method of coating the surface of the brush substrate with metal, an electroless plating method is preferable. As the electroless plating method, known methods are widely adopted from literatures and the like. For example, it is described in detail in “electroless plating” [Tsubaki Shoten, written by Tokuzo Kobe (1986)], and a robust coating can be formed on the surface of the brush substrate according to the present invention. As described in this document, the principle of electroless plating is, for example, copper. For example, an alkaline salt of tartaric acid or EDTA is added as a complexing agent to an aqueous copper salt solution, and the complexed state is weakly alkaline. The copper film is folded and formed on the substrate using formaldehyde, hydrazine salt or the like as the reducing agent.

In the electroless plating method, stannous chloride (SnCl ₂ ) as a sensitizer and palladium chloride (PdCl ₂ ) as an activator are added to the pretreatment liquid. Then, by treating the electrolytic temperature at room temperature within 30 minutes, preferably within 15 minutes, the substrate surface can be coated with a metal having a uniform film thickness of 1 to 10 μm. Here, some commercially available electroless plating solutions have an optimum electrolysis temperature of 80 ° C. ± 5 ° C. However, with carbonaceous materials such as brush base materials, the reaction rate is slowed down and the metal crystal structure is dense. Therefore, the electrolysis temperature is set to room temperature.

  Hereinafter, the metal-coated carbon brush according to the present invention will be described specifically by way of examples.

ここで、ｒは気孔半径、δは水銀の表面張力（通常、４．８×１０^−３Ｎを採用）、Ｐは加えられて圧力、θは接触角（１４１．３°を採用）を示す。また、計測範囲は、気孔半径が７５μｍ〜０．００６８μｍ（９．８×１０^３Ｐａ〜１０．８×１０^７Ｐａ）とし、平均気孔半径は、半径０．０１μｍの累積気孔容積の１／２値に対応する半径を示している。なお、これらブラシ基材の平均気孔半径及び累積気孔容積は、メッキの前後によって、変化することはなかった。 Example 1
75% by mass of graphite particles having an average particle diameter of 50 μm and 25% by mass of an epoxy resin as a binder were mixed and kneaded. The kneaded product was pulverized to a predetermined size, then formed into a predetermined shape at 15 MPa, heat-treated at 180 ° C., the binder was cured, the average pore radius was 1.1 μm, and the cumulative pore volume was 339 mm ² / g brush substrate was prepared. Next, this base material was washed with water and then immersed in a pretreatment liquid formed of water / alcohol to which 1.0 mass% of SnCl _{2 serving as} a sensitizer was added. After washing with water again, immersed in the pretreatment solution formed by water PdCl ₂ as the activator is added 1.0% by weight. In the pretreatment liquid, each was immersed for 3 minutes, allowed to react chemically, washed with water, immersed in an aqueous solution of copper sulfate adjusted to 20 to 25 ° C., and then sodium hydroxide was added to this solution for 10 minutes. Then, the surface of the substrate was coated with copper having a substantially uniform film thickness of 2 μm. In addition, the average pore radius and cumulative pore volume of the substrate were measured by a mercury intrusion method (manufactured by FISONS: Porosimeter 2000 type) and calculated by the following formula.
[Formula 1]

Here, r is the pore radius, δ is the surface tension of mercury (usually 4.8 × 10 ⁻³ N is adopted), P is applied pressure, and θ is the contact angle (141.3 ° is adopted). . The measurement range is a pore radius of 75 μm to 0.0068 μm (9.8 × 10 ³ Pa to 10.8 × 10 ⁷ Pa), and the average pore radius is ½ of the cumulative pore volume with a radius of 0.01 μm. The radius corresponding to the value is shown. The average pore radius and cumulative pore volume of these brush base materials did not change before and after plating.

(Example 2)
75% by mass of graphite particles having an average particle diameter of 50 μm and 25% by mass of an epoxy resin as a binder were mixed and kneaded. This kneaded product was pulverized to a predetermined size, then formed into a predetermined shape at 20 MPa, heat-treated at 180 ° C., the binder was cured, the average pore radius was 0.12 μm, and the cumulative pore volume was 56 mm ² / g brush substrate was prepared. Thereafter, copper was coated on the surface in the same manner as in Example 1.

(Example 3)
75% by mass of graphite particles having an average particle diameter of 50 μm and 25% by mass of an epoxy resin as a binder were mixed and kneaded. The kneaded product is pulverized to a predetermined size, molded into a predetermined shape at 10 MPa, heat-treated at 180 ° C., the binder is cured, the average pore radius is 1.9 μm, and the cumulative pore volume is 571 mm ² / g brush substrate was prepared. Thereafter, copper was coated on the surface in the same manner as in Example 1.

(Comparative Example 1)
In the same manner as in Example 1 except that SnCl _{2 serving as} a sensitizer and PdCl _{2 serving} as an activator were not added to the pretreatment liquid, a metal-coated carbon brush having a brush base coated with copper was formed.

(Comparative Example 2)
75% by mass of graphite particles having an average particle diameter of 50 μm and 25% by mass of an epoxy resin as a binder were mixed and kneaded. The kneaded product was pulverized to a predetermined size, then formed into a predetermined shape at 23 MPa, heat-treated at 180 ° C., the binder was cured, the average pore radius was 0.08 μm, and the cumulative pore volume was 44 mm ² / g brush substrate was prepared. Thereafter, copper was coated on the surface in the same manner as in Example 1.

(Comparative Example 3)
75% by mass of graphite particles having an average particle diameter of 50 μm and 25% by mass of an epoxy resin as a binder were mixed and kneaded. The kneaded product was pulverized to a predetermined size, then formed into a predetermined shape at 9 MPa, heat-treated at 180 ° C., the binder was cured, the average pore radius was 2.2 μm, and the cumulative pore volume was 658 mm ² / g brush substrate was prepared. Thereafter, copper was coated on the surface in the same manner as in Example 1.

  In FIG. 1, the photograph of the surface of the metal-coated carbon brush of Example 1 and Comparative Example 1 is shown. In Comparative Example 1, color unevenness can be observed on the surface metal.

  In Comparative Examples 2 and 3, peeling of the plating film occurred, and color unevenness was observed on the plating surface.

2 is a photograph comparing the appearance of carbon brushes according to Example 1 and Comparative Example 1. FIG.

Claims (4)

It has a metal-coated carbon brush in which a metal is coated on a substrate surface made of a carbonaceous material having an average pore radius of 0.1 to 2.0 μm and a cumulative pore volume of 50 to 600 mm ³ / g. Electric motor.   2. The electric motor according to claim 1, wherein the metal is selected from copper, silver, or silver formed on a copper surface.   The electric motor according to claim 1, wherein the metal film has a thickness of 1 to 10 μm.   The electric motor according to any one of claims 1 to 3, wherein the metal is formed by an electroless plating method.

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