JPH11103562A - Electric brush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric brush with an improved wear resistance whose sliding characteristic can be kept smooth, even in the environment of either high or low humidity. SOLUTION: Added to metallic powder and graphite powder with a total 100 pts.wt. or to a metallic powder, graphite powder, and solid lubricant of total 100 pts.wt. a liquid absorptive water-retaining agent of 0.01-5 wt.%, a binder is added to the resultant raw material to apply a heat treatment to the intermediate after its pressing and molding. For the electric brush obtained this way in a condition of a low humidity, the water held in the liquidity absorptive water holding agent is discharged gradually, the lubricative quality of graphite is improved to make the wear of the electric brush reduced. Also, in the high humidity condition, the liquid absorptive water-holding agent is made to absorb an excess water, the state of the film formed between the electric brush and the commutator of a motor is stabilized to satisfactorily make maintainable the sliding characteristic of the electric brush as a result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric brush used for an electric motor or the like, and more particularly to an electric brush which is excellent in lubricity and can achieve a long life with improved wear resistance.

[0002]

2. Description of the Related Art For example, low-voltage
In general, an electric brush used in a high current density environment is obtained by subjecting a material mainly composed of a metal powder and a graphite powder to pressure molding and firing. That is, in this type of metal-graphitic brush, a metal powder such as copper is used as the metal, and for example, a thermosetting synthetic resin powder is added as a binder to the copper metal powder and the graphite powder. ing. Further, in order to improve the wear resistance of the electric brush, any one of solid lubricants such as molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), and boron nitride (BN), or a mixture thereof is used. Are further added, pressurized to form them into a predetermined shape, and then heated to cure the binder, or by utilizing the binding force generated when the binder is carbonized, to produce a solid electric brush product. I'm trying to get.

[0003]

By the way, the aforementioned M
Solid lubricants such as oS ₂ , WS ₂ , and BN have excellent properties as a measure against wear at high temperatures and low humidity, but graphite, which is the main component of electric brushes, has a higher moisture content in air than specified. It has the characteristic that the friction coefficient increases sharply as it decreases. Therefore, despite the addition of MoS ₂ , WS ₂ , BN, and the like, there is a technical problem that the lubricating performance is extremely reduced under the above-mentioned environment. For this reason, in an environment where the humidity is lower than a predetermined value, there is a technical problem that the wear resistance of the electric brush is deteriorated and the life is shortened. In addition, there is a technical problem in that sliding in a high-humidity atmosphere results in an excessive film, and the temperature of the electric brush increases, the contact voltage decreases, and the wear of the electric brush increases.

The present invention has been made to solve the above-mentioned technical problems, and exhibits excellent lubrication performance under high temperature and low humidity environments. It is an object of the present invention to provide an electric brush capable of suppressing a contact voltage drop between a commutator and a commutator due to excessive film formation.

[0005]

An electric brush according to the present invention, which has been made to solve the above-mentioned problems, comprises adding an absorbent water-retaining agent to an electric brush material comprising a metal powder and a graphite powder, and applying a pressure to the material. An electric brush formed by molding, wherein the liquid-absorbent water-retaining agent is contained in an amount of 0.01 to 5% by weight based on a total amount of 100% by weight of the metal powder and the graphite powder. I do. Here, it is preferable that the liquid-absorbing water retention agent is contained in an amount of 0.01 to 5% by weight based on 100% by weight of the total amount of the metal powder graphite powder and the solid lubricant. Molybdenum (MoS
₂ ), tungsten disulfide (WS ₂ ), boron nitride (B
Those composed of one or more of N) are preferred. It is preferable to use N-vinylacetamide (NVA) or polyacrylic acid (PAS) -based water absorbing agent as the liquid absorbing water retaining agent.

As the metal powder used here, for example, copper, silver, aluminum, tin, lead, manganese, iron, nickel and the like can be used, and copper and silver are particularly preferable. When copper or silver is used, it is possible to take advantage of its excellent conductivity. Examples of the graphite powder include natural graphite powder such as flaky graphite and earthy graphite, and artificial graphite such as carbon black and coke powder. In particular, it is preferable to use natural graphite powder. When natural graphite powder is used, the lubricating property is superior to that of artificial graphite, so that the sliding characteristics can be improved and the life as an electric brush can be extended.

The graphite powder is granulated by adding a binder. As the binder to be added to the graphite powder, it is preferable to use a thermosetting resin such as a phenol resin or an epoxy resin which is in a powder form at normal temperature and becomes liquid by heating. Further, the amount of the binder to be added is set so that a necessary and sufficient bonding strength can be obtained by heat treatment after molding, and the addition of an amount larger than that is not preferable because motor noise increases. Preferably,
The amount of the binder added is 1 to 30% by weight.

The particle size distribution of the granulated graphite powder is from 20 μm to 1 μm.
000 μm (or 15 mesh pass) is used, and more preferably 50 μm to 300 μm. When the particle size distribution of the graphite granulated powder exceeds 1000 μm, a problem that the mechanical strength is reduced occurs. On the other hand, when the particle size distribution is less than 20 μm,
The disadvantage that the specific resistance is significantly increased occurs.

Further, as the solid lubricant, any one or more of molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), and boron nitride (BN) are used. Further, it is preferable to use electrolytic copper powder as the metal powder and to use MoS ₂ , WS ₂ , BN as the solid lubricant because of its excellent lubricity at high temperatures.

The mixing ratio of the metal powder and the granulated graphite powder is not particularly limited, but when the metal content is increased, the conductivity of the brush body can be increased, but the wear resistance of the brush is reduced. This will adversely affect the performance and the noise reduction characteristics of the motor. Preferably, the metal powder and the graphite granulated powder are blended in a ratio of 40:60 to 60:40. Furthermore, used as a liquid-absorbing water retention agent,
N-vinylacetamide (NVA) and polyacrylic acid (PAS) -based water-absorbing agents are used with respect to 100% by weight of the total amount of the metal powder and the graphite granulated powder, or the total amount of the metal powder, the graphite granulated powder and the solid lubricant. For 100% by weight, 0.0
It is preferable to contain 1 to 5% by weight. When the content of the water-absorbing water retention agent is less than 0.01% by weight,
As will be described later, no improvement in the sliding characteristics can be expected, and as a result, the life of the electric brush cannot be extended.
When the content of the water-absorbing water retention agent exceeds 5% by weight, there arises a technical problem that the strength of the shaped body after compression molding is reduced and molding is impossible. From the practical point of view, the content of the liquid absorbing water retaining agent is more preferably in the range of 0.01 to 1% by weight.

Further, the pressure molding is not particularly limited, and it is carried out by an ordinary known method. For example, it is preferable to carry out molding at a molding pressure of 2 to 4 ton / cm ² . It is necessary to perform the heat treatment at a temperature of 300 ° C. or less, at which the liquid absorbent does not decompose.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a preferred embodiment of an electric brush according to the present invention will be described. First, for the material constituting the electric brush, the electrolytic copper powder was 50% by weight as metal powder, the molybdenum disulfide was 4% by weight, the graphite granulated powder using natural graphite powder was 46% by weight, and the total amount was 10%.
0% by weight. Then, 0.01% by weight of N-vinylacetamide (NVA) was added as a liquid-absorbing water retention agent.
The electrolytic copper powder has an average particle size of 40 to 50 μm.
m (or 300 mesh pass), and the graphite granulated powder has a particle size of 50 to 300 μm (or 5
0 mesh pass).

A phenol resin powder as a binder was further added by 15% by weight, molded into a prism at a molding pressure of 3 ton / cm ² , and heat-treated at 200 ° C. for 2 hours. By this heat treatment, a 4 × 5 × 7 mm solid-state electric brush was obtained. Incorporate this brush into a DC motor, 5A
The DC motor was driven at -12 V and 15000 rpm. As a result, it was confirmed that the sliding characteristics of the electric brush could be kept good and the life thereof could be extended under any of the conditions of high temperature and high humidity and low temperature and low humidity as described later.

[0014]

EXAMPLE Here, a metallic graphite electric brush (Example 1) obtained by the above-described specific materials, molding conditions and heat treatment conditions, and Examples and Comparative Examples in which a part of the composition was further changed were described. The effect of the present invention will be described more specifically with reference to FIG.
In Example 2, 50 electrolytic copper powder was used as the metal powder.
% By weight, and 50% by weight of graphite granulated powder using natural graphite powder, and the total amount was 100% by weight. Then, N-vinylacetamide (NVA) is used as a water-absorbing water retention agent in an amount of 0.01.
% By weight and kneaded. Using this kneaded material, 4 × 5 × 7 under the same molding conditions and heat treatment conditions as in Example 1.
mm was obtained.

In Example 3, 50% by weight of electrolytic copper powder was used as the metal powder and 50% by weight of graphite granulated powder using natural graphite powder, and the total amount was 100% by weight. And
N-vinylacetamide (NVA) as a water-absorbing water retention agent
Was added and kneaded. Using this kneaded material, the same molding conditions and heat treatment conditions as in Example 1 were used for 4 hours.
A 5 x 7 mm metallic graphite brush was obtained. Further, as Example 4, 60% by weight of electrolytic copper powder as a metal powder,
Molybdenum disulfide was 4% by weight, and graphite granulated powder using natural graphite powder was 36% by weight, and the total amount was 100% by weight. Then, 1.0% by weight of N-vinylacetamide (NVA) was added and kneaded as a liquid-absorbing water retention agent. Using this kneaded material, a 4 × 5 × 7 mm metallic graphite brush was obtained under the same molding conditions and heat treatment conditions as in Example 1.

In Example 5, as the metal powder, 70% by weight of electrolytic copper powder and 4% by weight of molybdenum disulfide were used.
And 26% by weight of graphite granulated powder using natural graphite powder, and the total amount was 100% by weight. And 5.0% by weight of N-vinylacetamide (NVA) was used as a water-absorbing water retention agent.
It was added and kneaded. Using this kneaded material, a 4 × 5 × 7 mm metallic graphite brush was obtained under the same molding conditions and heat treatment conditions as in Example 1.

The compounding ratio (% by weight) of each material in Examples 2 to 5 is described in Table 1 described later together with Example 1. The particle diameter of the electrolytic copper powder used in Examples 2 to 5 and the particle diameter of the graphite granulated powder using natural graphite powder were the same as those of Example 1. Further, in Examples 2 to 5, 15% by weight of phenol resin was used as a binder.

As Comparative Example 1, 50% by weight of electrolytic copper powder and 4% by weight of molybdenum disulfide were used as metal powders.
And 46% by weight of graphite granulated powder using natural graphite powder, and the total amount was 100% by weight. Then, the mixture was kneaded without adding N-vinylacetamide (NVA) as a liquid-absorbing water retention agent. Using this kneaded material, 4 × 5 × 7 mm under the same molding conditions and heat treatment conditions as in Example 1.
Was obtained. As Comparative Example 2, 50% by weight of electrolytic copper powder and 50% by weight of graphite granulated powder using natural graphite powder as the metal powder, and the total amount was 100% by weight.
And Then, the mixture was kneaded without adding N-vinylacetamide (NVA) as a liquid-absorbing water retention agent. Using this kneaded material, a 4 × 5 × 7 mm metallic graphite brush was obtained under the same molding conditions and heat treatment conditions as in Example 1.

As Comparative Example 3, 50% by weight of electrolytic copper powder and 4% by weight of molybdenum disulfide were used as metal powders.
And 46% by weight of graphite granulated powder using natural graphite powder, and the total amount was 100% by weight. Then, N-vinylacetamide (NVA) was adjusted to 8% by weight as a water-absorbing water retention agent, and kneaded. Using this kneaded material, a 4 × 5 × 7 mm metallic graphite brush was obtained under the same molding conditions and heat treatment conditions as in Example 1.

The mixing ratio (% by weight) of each material in Comparative Examples 1 to 3 is described in Table 1 below. The particle diameter of the electrolytic copper powder used in Comparative Examples 1 to 3 and the particle diameter of the graphite granulated powder using natural graphite powder were the same as those in Example 1. Further, in Comparative Examples 1 to 3, 15% by weight of a phenol resin was used as a binder.

The electric brushes according to Examples 1 to 5 and the electric brushes according to Comparative Examples 1 to 3 were assembled into a DC motor, and 5000R at 5A to 12V.
The DC motor was driven under the condition of pm, and the service life of each brush was measured. The results are shown in Tables 1 and 2. First, Table 1 shows the service life of the electric brush under the operating conditions of a humidity of 20% and a temperature of 100 ° C.

[0022]

[Table 1]

As shown in Table 1, under low humidity conditions, N-vinylacetamide was used as a water-absorbing water-retaining agent in an amount of 0.1 to 1%.
It was found that the electric brushes of Examples 1 to 5 in which 01 to 5% by weight were added had a much longer service life (use time) than Comparative Examples 1 and 2 in which N-vinylacetamide was not added. . Examples 1 and 3 to
As shown in FIG. 5, it was also found that when molybdenum disulfide (MoS ₂ ) was further added, the practical life was further extended as compared with the other examples in which molybdenum disulfide was not added. When N-vinylacetamide is added as a water-absorbing water retention agent, the moisture retained in N-vinylacetamide is gradually released under low-humidity conditions, thereby improving the lubricity of graphite. However, it is considered that the brush wear is reduced.

Next, the electric brushes of Examples 6 to 10 using a polyacrylic acid-based water-absorbing agent (PAS) as a water-absorbing water-retaining agent were prepared and subjected to the same practical life test. In addition,
The blending ratio (% by weight) of each material in Examples 6 to 10 is as shown in Table 2, and the same blending ratio as in Examples 1 to 5 shown in Table 1 above. The particle diameters of the electrolytic copper powder used in Examples 6 to 10 and the particle diameter of the graphite granulated powder using natural graphite powder were the same as those in Example 1 described above. In Examples 6 to 10, a 4 × 5 × 7 mm metallic graphite brush was obtained under the same molding conditions and heat treatment conditions as in Example 1 described above. The thus-obtained electric brush was incorporated in a DC motor in the same manner as described above, and the DC motor was driven at 5A-12V under the condition of 5000 rpm to measure the service life of each electric brush.
Table 2 shows the results.

Table 2 compares the practical life of the brushes in Examples 6 to 10 under the conditions of 70% humidity and 160 ° C.

[0026]

[Table 2]

As shown in Table 2, even under high humidity conditions, a polyacrylic acid-based water-absorbing agent was used as a water-absorbing water-retaining agent.
The electric brushes of Examples 6 to 10 in which the addition of the polyacrylic acid-based water-absorbing agent was not added in any of Examples 6 to 10 in which the addition of the polyacrylic acid-based water-absorbing agent was added had a practical life (use time) far greater. It was found to grow. In the case of an embodiment in which a polyacrylic acid-based water-absorbing agent is added as a liquid-absorbing water retention agent, under conditions of high humidity, the polyacrylic acid-based water-absorbing agent does not act to absorb excess moisture,
It is considered that the state of the film formed between the electric brush and the commutator of the motor is stabilized, and as a result, good sliding characteristics are maintained.

[0028]

As is apparent from the above description, the electric brush according to the present invention comprises the metal powder, the graphite powder and the water-absorbing water-retaining agent in a total amount of 100% by weight. 0
By containing 1 to 5% by weight, the sliding characteristics of the electric brush can be kept smooth under both high and low humidity environments due to the liquid absorbing and water retaining functions of the liquid absorbent water retaining agent. Therefore, the wear resistance of the electric brush can be significantly improved, and a motor or the like having excellent durability can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Watanabe 378 Oguni-machi, Oguni-machi, Nishiokitama-gun, Yamagata Pref.

Claims (4)

[Claims] 1. An electric brush formed by adding a water-absorbing water retention agent to an electric brush material comprising a metal powder and a graphite powder and press-molding the same, wherein the total amount of the metal powder and the graphite powder An electric brush comprising the liquid-absorbing water retention agent in an amount of 0.01 to 5% by weight based on 100% by weight. 2. An electric brush formed by adding a water-absorbing water retention agent to an electric brush material composed of a metal powder and a graphite powder, followed by press molding, wherein the metal powder, the graphite powder, and the solid The liquid-absorbing water retention agent is 0.01 to 5% by weight based on 100% by weight of the total amount of the lubricant.
The electric brush according to claim 1, which is contained. 3. The solid lubricant according to claim 1, wherein the solid lubricant comprises one or more of molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), and boron nitride (BN). An electric brush according to claim 1 or 2. 4. The electric brush according to claim 1, wherein N-vinylacetamide or a polyacrylic acid-based water absorbing agent is used as the liquid absorbing water retaining agent.