JPH0260745B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in rectifying sliding contact materials for small DC motors. Conventionally, Ag has been mainly used as a sliding contact material to make contact pieces around the commutator of small DC motors, but because Ag has a low softening temperature, it is difficult to condense during rotation and sliding of the commutator of small DC motors. It is easy for the wear phenomenon to occur, and as a result, there is a large amount of contact wear on the outer circumference of the commutator, which has the disadvantage of high contact resistance and instability.Practically speaking, the amount of contact wear on the outer circumference of the commutator is 15 μm.
Hereinafter, there has been a demand for a sliding contact material for a commutator of a small DC motor that has a contact resistance of about 10 to 50 mΩ. The present invention has been made to eliminate these drawbacks, and is a compact DC-powered device that increases the softening temperature of Ag to prevent adhesion, thereby reducing contact wear around the commutator's outer periphery and keeping contact resistance low and stable. The present invention aims to provide a sliding contact material for a motor commutator. The sliding contact material for a commutator of a small DC motor of the present invention is made of a silver alloy containing at least one of Sn and Cd in a total of 1 to 5% by weight and the balance being Ag. In the sliding contact material for a commutator of a small DC motor of the present invention, adding at least one of Sn and Cd in a total of 1 to 5% by weight to Ag is as follows:
The softening temperature of Ag is raised to prevent the contact pieces on the outer periphery from sticking during the rotation of the commutator of a small DC motor.
This is to keep the contact resistance low and stable with little variation. If it is less than 1% by weight, the effect of increasing the softening temperature of Ag will be small and it will not be possible to prevent the adhesion of the contact piece, and if it exceeds 5% by weight, it will be oxidized. As the amount of material produced increases, the contact resistance of the contact pieces becomes high and the variation becomes large, resulting in instability. Next, contact pieces on the outer periphery of a commutator of a small DC motor made of the sliding contact material for a commutator of a small DC motor according to the present invention and the sliding contact material for a commutator of a conventional small DC motor will be described. A sliding contact material for a commutator of a small DC motor according to an embodiment of the present invention and a conventional sliding contact material for a commutator of a small DC motor having the compositions shown in the left column of the table below, as shown in the drawings. DC small motor diameter 10
A contact piece 1a with a thickness of 0.1 mm is formed on the outer periphery of a commutator 1 with a length of 10 mm and a diameter of 0.3 mm made of an Au-Ag-Cu-Pt alloy.
Three brush wires 2 with a length of 10 mm were brought into sliding contact with the brush contacts 3 facing each other, and a commutator rotation test was performed under the test conditions described below, and the amount of contact wear and contact resistance was measured. The results shown in the right column of the table below were obtained. Test conditions Voltage: 12 volts Current: DC 250 mA Commutator rotation speed: 2000 revolutions/min Commutator rotation time: 300 hours Contact force of sliding contacts: 5 g/3 pieces

【table】

[Table] As is clear from the above table, the amount of contact wear of the contact pieces on the outer periphery of the commutator in the conventional example is 20 to 30 μm, while the amount of contact wear of the contact pieces of the example is 8 to 14 μm.
It can be seen that the wear resistance is extremely low. In addition, the contact resistance of the conventional contact piece is 20 to 30 mΩ.
On the other hand, the contact resistance of the contact piece of the example is 10
It can be seen that the value is ~14 mΩ, which is extremely low and stable with little variation. As detailed above, since the sliding contact material for the commutator of the small DC motor of the present invention has a high softening temperature, the contact pieces on the outer periphery of the commutator of the small DC motor made using this material may stick together during sliding. This has the excellent effect of providing a small DC motor with a stable rotational speed with little variation, low contact wear, low contact resistance, and little variation in rotational speed.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1 At least one of Sn and Cd in total of 1
A sliding contact material for a commutator of a small DC motor, characterized by comprising a silver alloy of ~5% by weight and the balance being Ag.