JPH08283885A - Sliding contact material and clad material and direct current compact motor using the same - Google Patents

Abstract

PURPOSE: To provide a high-quality sliding contact material used for an electrical and mechanical sliding part, free from toxicity and particularly having low and stable contact resistance and excellent electric properties, and also to provide a clad material. CONSTITUTION: This sliding contact material is an AgAl alloy or AgAlNi alloy, constituting a sliding contact material for an electrical and mechanical sliding part. In each alloy composition, Al is contained by 0.01-<1wt.% and the additive quantity of Ni is regulated to 0.01-0.5wt.%. Further, in the alloy composition, Al is allowed to enter into solid solution in an Ag α-phase and Ni is uniformly dispersed in the form of grains in an Ag α-phase. This sliding contact material composed of AgAl alloy or AgAlNi alloy is used for a D.C. compact motor for household electrical appliances, as a commutator composed of a two-layer- lined clad material where the surface layer is formed of the sliding contact material and the base layer is formed of Cu or Cu alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding contact material used for an electrical or mechanical sliding part, and more specifically, a small DC power source used for household electric appliances driven by a rechargeable battery. The present invention relates to a sliding contact material having low contact resistance used for a commutator for motors (others such as an earth ring and a rotary switch).

[0002]

2. Description of the Related Art In the technical field, research and development on new sliding contact materials and wear have been actively conducted at present, and this wear and contact resistance are important for sliding contact materials and clad composite materials. Where the problem is
This wear phenomenon is a difficult problem because it is complicated and there are many points that have not been scientifically elucidated.

Usually, even if the metal surface of the sliding contact material is intended to be finished to be fairly smooth, microscopic observation shows that it is not a perfect flat surface but has fine irregularities. Looking at the contact state of the two metals, it seems that they are in contact with each other over a wide area, but in reality, there are some irregularities and they are in contact only with isolated protrusions.

The wear due to friction is basically proportional to the magnitude of the contacting force and inversely proportional to the hardness. In addition, temperature, humidity, corrosive components, organic vapor, dust, etc. cause wear and change in electrical characteristics (contact resistance).

The manner of wear of the sliding contact material is roughly classified into adhesive wear and scratch wear. Adhesive wear is wear that occurs when metals are welded to each other at a true contact portion, that is, a protruding portion, and a softer metal is torn and converted to a harder metal.

[0006] Scratch wear is wear caused when materials having greatly different hardness are rubbed against each other, or when soft metals or hard metals are contained in one of them.

For example, due to the high speed rotation between the commutator and the brush in a small DC motor, the clad composite material composing the commutator is subjected to long-term contact friction and heat is also applied, so that the micron-order precious metal alloy surface layer of the composite material is generated. It is ground and wear powder is generated, filling the gap of the commutator, and conducting and short-circuiting to cause an electrical trouble or noise.

Moreover, various electrical troubles are caused by the oxide of the base layer, which is easily worn and oxidized even in the intermediate layer of the clad composite material.
Therefore, research into improving alloy materials and alloy compositions forming two or three layers constituting the composite material becomes a very important problem.

Recently, as a commutator material for a small DC motor used in household appliances driven by a rechargeable battery, the surface layer is 1 to 2% by weight of Cd, and the balance Ag is Ag.
Cd alloy, a clad composite material in which the base layer is Cu or a Cu alloy double-layered (for example, AgCd1 / Cu), or Cd whose surface layer is 1 to 2% by weight, 0.01 to 0.7% by weight
Ni, an AgCdNi alloy with the balance Ag, and a clad composite material (for example, AgCd2Ni0.3 / Cu) in which the base layer is a double layer of Cu or a Cu alloy are usually used.

These AgCd alloys and AgCdNi alloys are materials excellent in electrical function, hardness and contact resistance. For example, in Japanese Patent Publication No. 2-60745, at least one of Sn and Cd is 1 in total. ~ 5 wt% balance A of A
There is a disclosure of a sliding contact material for a DC small-sized motor commutator made of g-alloy.

[0011] As an important point, at present, the problem of living environment pollution is being screamed, and in order to avoid pollution of the human body by Cd, large-scale environmental measures are required and implemented at the manufacturing plant, but general consumers From, the electrical components containing Cd of the damaged equipment are discarded as they are,
It is a big social problem.

In addition, AgCu alloys and AgCuCd alloys are also used, but the problem is that the product value of a shaver using a rechargeable battery is poor because the contact resistance changes with time even if the initial contact resistance is low. This is because when the contact resistance becomes high, the starting voltage of the motor increases and the time that can be used in one charge becomes short, and further, the starting cannot be started by the electromotive force of the battery. Therefore, the emergence of a commutator material that has a low contact resistance and does not change with time has been required at an early stage.

Further, in JP-A-58-84949,
Ca, Mn, Zr, Bi, Be, Al, Mg in Ag,
At least one of Sb, Sn, In, and Cd is 1 to in total.
Although sliding contact materials containing 10% by weight are disclosed, the object of these inventions is to prevent the adhesion phenomenon during the rotary sliding of the commutator, and to make the contact resistance low and stable. .

However, since the material disclosed in the above-mentioned publication, for example, the AgAl0.5Cd0.5 alloy of Example 1 has a contact resistance of 10 mΩ, AgCu alloy or AgC is used.
In contrast to the uCd alloy, the point intended by the present invention is that "a low starting voltage that causes the motor to start even when the electromotive force of the battery decreases, and thus, after charging once, Regarding the solution to the problem of "extending the continuous use time that the time until charging becomes long", the conventional one is not satisfactory, and further improvement is required.

With the trend toward miniaturization of household electric appliances driven by rechargeable batteries, particularly in headphone stereos, cameras, and shavers, motors with low starting voltage are used to reduce the size and weight of rechargeable batteries. There is an urgent need to develop a commutator for micromotors that enables

However, the micromotors for these applications do not require an extremely long life which is in competition with brushless motors. For example, even if the user shaves for 10 minutes every day, it only takes about 609 hours in 10 years.

[0017]

Therefore, the present invention has a contact resistance that is low and stable, an electric function is good, does not change with time, and is practically comparable to those manufactured by the prior art. As a technical subject of the present invention, the development of a sliding contact material that maintains sufficient wear resistance and can sufficiently replace Cd has been studied for a long period of time, and as a result, the metal composition and composition ratio of the alloy, the metal structure The technique of reducing the contact resistance can be achieved by the following constitution by the improvement.

[0018]

The constitution of the present invention is as follows. 1 Ag used as a sliding contact material for electrical and mechanical sliding parts
A sliding contact material comprising an Al alloy with 0.01 to less than 1.0% by weight of Al and the balance Ag. 2. The sliding contact material as described in 1 above, wherein Al is a solid solution in the Agα phase of the AgAl alloy. 3 Ag used for sliding contact materials of electrical and mechanical sliding parts
AlNi alloy, 0.01 to less than 1.0 wt% Al,
A sliding contact material comprising 0.01 to 0.5% by weight of Ni and the balance Ag. 4 Al solid-dissolved in the Agα phase of AgAlNi alloy,
The above-mentioned 3 characterized in that Ni is dispersed as particles.
The sliding contact material described. 5. A clad composite material, wherein the surface layer is made up of Al of 0.01 to less than 1.0% by weight, the rest is AgAl alloy with Ag, and the base layer is made of Cu or Cu alloy. 6 surface layer of 0.01-1.0 wt% Al, 0.
Ag of 0.1 to 0.5% by weight or less of Ni and the balance Ag
1. A clad composite material, wherein the base layer is a double layer of Cu or Cu alloy. 7. A small direct current motor characterized in that the clad composite material according to the above 5 or 6 in which the surface layer is a double layer of AgAl alloy or AgAlNi alloy and the base layer is Cu or Cu alloy is used as a commutator.

In the present invention, various experiments were carried out on sliding contact materials, and Ag was contained in an amount of 0.01 to less than 1.0% by weight, and the Al was uniformly dissolved in the Agα phase. In the case of the structure of No. 1, it has a very low contact resistance that contributes to lubricity, maintains wear resistance comparable to that produced by the conventional technique, and has sufficient Cd.
It was found that a clad composite material that can replace the above can be obtained.

Similarly, Al is contained in Ag in an amount of 0.01 to less than 1.0% by weight, and Ni is added in an amount of 0.01 to 0.
Dispersion as 5 wt% particles prevents aging softening, and since the matrix is an Agα phase with a very small amount of solid solution element Al, it can be oxidized even when left in the air (against aging). Since no band is formed, the contact resistance will not increase.

[0021]

As described above, Al is contained in the Agα phase in an amount of 0.01 to
A solid solution of less than 1.0% by weight does not form an oxide film (oxidation band) on the surface of the alloy unnecessarily, and a slight amount of Al ₂ O ₃ is generated during sliding of the commutator and the brush. The film has the effect of reducing frictional resistance while maintaining good lubricity.

What is important in the present invention is that the oxide film formed on the metal surface during sliding, that is, a slight oxide band, catches smooth sliding and improves wear resistance, but it is a sliding contact material. Since it can be an element that hinders the contact function as
Minimizing the adverse effect of the oxidation band on the sliding characteristics is the deciding factor of quality.

In conventional AgCu and AgCuCd, even if a small amount of solid solution element (Cu) is added, an oxide of the solid solution element is generated as an oxidation band on the contact surface when left in the air (eg CuO), The contact resistance is high.

The above-mentioned prior art (Japanese Patent Laid-Open No. 58-84949).
It has been found that the AgAl alloy containing no elements other than Al at all is better than the AgAl alloy and the AgAlNi alloy according to No.), in order to achieve the object of the present invention. However, if it is added in an amount of less than 0.01% by weight, it has no effect, and if it is added in an amount of 1% by weight or more, Al will oxidize to form a band when left in the air, resulting in a high contact resistance. The most effective amount of Al added is 0.2 to 0.5% by weight.

However, Ag containing a small amount of Al added to Ag
An Al alloy, for example, Ag99.6Al0.4 alloy, has a Vickers hardness of 125 Hv after processing, but may be left to stand for several days at room temperature to cause aging softening and decrease the Vickers hardness to 110 Hv. This phenomenon itself is
It does not deteriorate the sliding characteristics so that it becomes a problem in practical use. However, a dimensional error when punching the clad composite material with a press may cause a problem in assembling the motor. Therefore, in order to prevent such age softening of the material, A
It is advisable to add a small amount of Ni to the gAl alloy.

If the amount of addition of Ni is less than 0.01% by weight, there is no noticeable effect, and if it exceeds 0.5% by weight, Ni is added.
Is non-uniformly segregated, and Ni particles dispersed on the contact surface generate oxides during sliding of the commutator, which locally increases the contact resistance. The most effective amount of Ni added to prevent this softening is 0.2 to 0.4% by weight.

The micromotor incorporating the sliding contact material of the present invention has a low contact resistance between the commutator and the brush, is stable, does not change with time, and always rotates the micromotor at a lower starting voltage without any trouble. You can
The same effect can be obtained in a clad composite material in which Au or Au alloy is further laminated on the surface of the two-layered structure to form a three-layered structure. Next, the present invention will be described in detail based on examples.

[0028]

Examples 1 to 6, Conventional Examples 1 to 2 and Comparative Examples 1 to 4 The materials having the component compositions shown in Table 1 below are sequentially melt-cast-
Face milling-groove roll processing to 5.5 mm square, then heat treatment (conveyor furnace, 650 ° C, 250 mm / min)
Then, wire drawing was further performed to obtain materials of Examples, Conventional Example and Comparative Example having a diameter of 2 mm. (See Table 1)

[0029]

[Table 1]

However, the test materials of Examples 1 to 6, Conventional Examples 1 and 2 and Comparative Examples 1 to 4 having the above-mentioned composition were used in the form of a round bar having a diameter of 2 mm and crossed with a round bar having the same diameter of 50% by weight of AgPd. Then, a sliding test was performed under the following test conditions, and the wear amount (wear volume) and other characteristics were determined, and the results shown in Table 2 were obtained. (Note) The conventional example and the comparative example refer to the prior art of the commutator of the present applicant.

[0031]

[Test conditions] Current DC 170 mA Load 25 g Rotation speed 300 rpm Amplitude 0.5 mm Temperature, humidity 25 ° C., 50% RH Cycle number 100,000 cycles Moving contact material Test material Fixed contact material AgPd 50 wt% Test number n = 10

[0032]

[Abrasion Volume] In the test material after the sliding test, the material was transferred from the movable contact material (test material) to the fixed contact material (50% by weight of AgPd).
This wear part was approximated to an ellipsoid and the wear volume was calculated (V
= 4πabc / 3). The results of the wear volume of each material obtained from the SEM (electron microscope) photograph are shown in Table 2. Since a 10-point sliding test was performed for each material, the average value of the wear volume was calculated.

During the sliding test, the test material and A
The coefficient of friction of gPd50 usually changes as follows. At the initial stage of the sliding test, the coefficient of friction is low (about 0.3) and the state of so-called mild wear is present. At this time, the adhesive transfer of the material is considered to have hardly occurred. In the middle period of the sliding test, the friction coefficient gradually increases, and in the latter period of the sliding test, the friction coefficient remains high and remains constant (1,
2).

This is the so-called severe wear state. By this time, it is considered that the adhesive transfer of the material has occurred and the wear has advanced. Therefore, the number of times of severe wear-mild wear transition sliding, which evaluates the likelihood of adhesion transfer of the material, was used as one parameter for evaluating the life of the sliding material. Then, the number of times of transitional sliding of severe wear-mild wear (n = 10) was plotted on a Weibull probability paper to statistically predict the life of the sliding material.

The shape parameter m value can classify the phenomenon of occurrence of a failure according to the value of m. When the m value exceeds 1, it means a wear-type failure in which the instantaneous failure rate monotonically increases with the passage of time, and when the m value is 1, the instantaneous failure rate increases even if time elapses. It always means a constant random failure. Further, when the m value is less than 1, it means an initial failure type failure in which the instantaneous failure rate monotonously decreases with the passage of time.

Generally, if the m value is larger than 1, it takes a long time until the first one in the population fails, which is good for guaranteeing quality or life. The average lifetime is not a simple weighted average of n = 10, but represents the average lifetime assuming that the population has a Weibull distribution. Table 2 on the next page summarizes the m value and average life from the above Weibull probability paper.

[0037]

[Table 2]

Table 3 below shows the results of evaluation of changes in contact resistance over time. In addition, as an accelerated evaluation, 20 in the atmosphere
It heat-processed at 0 degreeC for 6 hours, and performed the aging process which produces an oxide film. The contact resistance of each sample was measured and averaged at 50 points by an AC probe and a contact load of 10 g using a milliohm meter 4328A manufactured by Yokogawa Hewlett Packard before and after the aging treatment.

[0039]

[Table 3]

As can be seen from Tables 2 and 3, the conventional example 1 has a short average life of 341 times,
Further, in Conventional Example 2, the change with time of the contact resistance changes from 1.5 mΩ before the aging treatment to 3.7 mΩ after the aging treatment.
In Comparative Examples 1 to 4, the wear volume and the average life are good, but the contact resistance changes with time are extremely poor at 20, 190, 12, and 15 mΩ, respectively.

On the other hand, in Examples 1 to 6,
In particular, the present invention has been solved by developing a sliding contact material that has low contact resistance and is stable, has an excellent electrical function, does not change with time, is practically comparable in wear resistance, and can sufficiently replace Cd. It turns out to be worth the challenge.

[0042]

The sliding contact material and the clad composite material made of the alloy composition according to the present invention have a noble metal surface layer A.
Since a specific amount of Al is solid-dissolved in the gα phase or Ni is further dispersed uniformly as particles, the surface layer shows excellent electrical characteristics without adverse effects of oxidation bands and has a contact resistance. In addition, it has a high commercial value, with low deterioration, no change over time, and wear resistance far beyond the expected range.

Moreover, even if the Al dissolved in the Agα phase matrix and the dispersed Ni particles are selectively oxidized during sliding, the total oxidation that increases the contact resistance is avoided. It has the unexpected effect that it can be done. Therefore, the sliding contact material of the present invention effectively maintains a low contact resistance and has a particularly remarkable function and effect that enables long-term use, especially in household appliances including a DC small-sized motor using a rechargeable battery, It is a sliding contact material and clad composite material with excellent functions.

Claims (7)

[Claims] 1. A sliding contact material comprising an AgAl alloy used as a sliding contact material for electrical and mechanical sliding parts, wherein Al is 0.01 to less than 1.0% by weight and the balance is Ag. . 2. The sliding contact material according to claim 1, wherein Al is a solid solution in the Agα phase of the AgAl alloy. 3. An AgAlNi alloy used as a sliding contact material for electrical and mechanical sliding parts, wherein Al is 0.01 to less than 1.0% by weight, 0.01 to 0.5% by weight Ni, and the balance. A sliding contact material characterized by being made of Ag. 4. Al in the Agα phase of the AgAlNi alloy
4. The sliding contact material according to claim 3, wherein is a solid solution and Ni is dispersed as particles. 5. A clad composite material, wherein the surface layer is made up of Al of 0.01 to less than 1.0% by weight, the balance is made of an AgAl alloy and the base layer is made of Cu or a Cu alloy. 6. A two-layer structure comprising a surface layer of 0.01 to less than 1.0% by weight of Al, 0.01 to 0.5% by weight of Ni, an AgAlNi alloy with the balance being Ag, and a base layer of Cu or a Cu alloy. Clad composite material characterized by being upholstered. 7. The surface layer is AgAl alloy or AgAlNi
A small direct current motor using the clad composite material according to claim 5 or 6 as a commutator, wherein the alloy and the base layer are made of Cu or a Cu alloy.