JPH0114982B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a sliding contact material for a commutator of a small DC motor (hereinafter referred to as sliding contact material) for making a contact piece on the outer periphery of a commutator of a small motor. Conventionally, Ag has been mainly used as a sliding contact material to make the contact pieces around the commutator of small motors, but since Ag has a low softening temperature, the contact pieces do not stick together while the commutator rotates and slides. The disadvantages are that the commutator is easily activated, consumes a lot of water, has high contact resistance, becomes unstable, and causes large variations in the commutator rotational speed. For this reason, Cd, In, Cu, Sn, etc. are added to Ag.
Efforts have been made to increase the softening temperature of Ag to improve wear resistance and contact resistance. However, when the amount of the above-mentioned elements added increases, wear resistance improves to some extent, but The contact resistance has not yet been sufficiently improved by oxidation. The present invention was made in view of such circumstances,
The purpose of this invention is to provide a sliding contact material in which oxides are uniformly and finely dispersed in Ag to strengthen the dispersion of Ag, reduce wear, and have a low and stable contact resistance. The sliding contact material of the present invention contains Ta and Ta in Ag.
At least one type of Nb is added in a total amount of 0.5 to 3% by weight, and the mixture is internally oxidized at high temperature. In the sliding contact material of the present invention, a total of 0.5 to 3 of at least one of Ta and Nb is added to Ag.
The reason for adding weight% is to disperse and strengthen Ag.
If it is less than 0.5% by weight, there is no effect, and if it exceeds 5% by weight, processing becomes difficult. Furthermore, the reason why the material in which the above-mentioned elements are added to Ag is internally oxidized at high temperature is that the oxide of the added element is uniformly and finely dispersed to disperse and strengthen Ag, reduce wear, and reduce Ag-oxidation. This is to lower and stabilize the contact resistance of objects. Next, a contact piece for the outer periphery of a commutator of a small motor made of a sliding contact material according to the present invention and a conventional sliding contact material will be explained. A contact piece with a thickness of 0.2 mm was made using the sliding contact material according to the embodiment of the present invention and the conventional sliding contact material having the composition shown in the left column of the table below, and this contact piece is shown in the drawing. 6 mm in diameter and 9 in length with 3 pieces on the outer periphery
Au-Ag-Cu-
A commutator rotation test was conducted under the test conditions described below by sliding brush contacts 3 having three brush wires 2 made of Pt with a diameter of 0.25 mm and a length of 10 mm so as to face each other. When we measured the amount of wear and variation in commutator rotation speed, we obtained the results shown in the right column of the table below. Test conditions Voltage: 12V Current: DC 60mA Commutator rotation speed: 2800 rotations/min Commutator rotation time: 500 hours Brush contact force: 5g/3 pieces

[Table] As is clear from the above table, the amount of wear of the contact piece of the conventional example was 20 μm, whereas the amount of wear of the contact piece of the example was significantly reduced to 4 to 5 μm, indicating that it has excellent wear resistance. It turns out that it is excellent. In addition, the variation in rotation speed of the commutator with conventional contact pieces is 10 to 15%.
On the other hand, it can be seen that the variation in the rotational speed of the commutator having the contact piece of the example is significantly reduced to 3 to 4%. This is simply because in the contact piece of the example, the oxide of the additive element is uniformly and finely dispersed through high-temperature internal oxidation, the Ag is dispersed and strengthened, and the contact resistance is low and stable. As detailed above, the sliding contact material of the present invention is
Since the oxide is uniformly and finely dispersed in the Ag and the Ag is dispersed and strengthened, the wear resistance of the commutator contact pieces of small motors made using this method is significantly improved. In addition, since oxide particles are not generated on the sliding surface of the contact piece during sliding, the contact resistance is low and stable, and the variation in the rotation speed of the commutator of small motors is greatly reduced. effective.

[Brief explanation of drawings]

The figure is a perspective view showing the state of contact between the commutator and brush contacts of a small motor. 1...Commutator, 1a...Contact piece, 2...Brush wire, 3...Brush contact.

Claims (1)

[Claims] 1 A material made of silver-tantalum oxide or niobium oxide that has been internally oxidized at high temperature, and the weight percent of the alloy before internal oxidation is a total of 0.5 to 3 weight percent of at least one of Ta and Nb, and the balance A sliding contact material for a commutator of a small DC motor, characterized by being made of Ag.