JPH0156131B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in a sliding contact material (hereinafter referred to as "sliding contact material") for a commutator of a small DC motor. Traditionally, Cu has been mainly used as a sliding contact material to make the contact pieces around the commutator of small DC motors, but Cu has a low softening temperature and does not condense during rotating sliding contact of the commutator used to rectify DC current. Adhesion phenomenon easily occurs, contact resistance is high and unstable,
It also had the disadvantage of poor wear resistance and variations in the rotational speed of the small DC motor. The present invention has been made in order to eliminate such drawbacks, and aims to provide a sliding contact material that has a high softening temperature, low and stable contact resistance, and has excellent wear resistance. The sliding contact material of the present invention contains a total of 0.5 to 2% by weight of at least one of Nb and In, and Mg.
It consists of a Cu alloy of 0.5 to 5% by weight and the balance Cu. In the sliding contact material of the present invention, Mg0.5
The reason for setting the content to ~5% by weight is to increase the softening temperature of Cu to prevent the contact pieces on the outer periphery from adhering during the rotation of the commutator of a small DC motor, resulting in a stable contact resistance with low and small variations. If it is less than 0.5% by weight, the effect of increasing the softening temperature of Cu is small;
The adhesion phenomenon of the contact pieces cannot be prevented, and if the amount exceeds 5% by weight, the amount of oxide produced increases, resulting in high contact resistance and wide variation in the contact pieces, resulting in instability. In addition, the reason why the total amount of at least one of Nb and In is 0.5 to 2% by weight is to increase lubricity and improve wear resistance. If the amount of oxide is too small to act as a lubricant and the wear resistance is not improved, and if it exceeds 2% by weight, the amount of oxide generated will be large, resulting in high contact resistance and instability. Next, a contact piece for the outer periphery of a commutator of a small DC 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 was molded around the outer periphery as shown in the drawing. 3 pieces, diameter 10mm, length 6mm
A brush plate material 2 made of Ag-Cu alloy with a width of 1 mm, a thickness of 0.2 mm, and a length of 10 mm is placed above and below the outer peripheral surface of the commutator 1.
A rotation test was carried out on the commutator 1 under the test conditions described below by bringing brush contacts 3 having one brush contact piece 3 facing each other into sliding contact, and the wear amount and contact resistance of the contact piece 1a were measured. The results shown in the right column were obtained. Test conditions Voltage: 12V Current: DC 250mA Commutator rotation speed: 2000 rotations/min Commutator rotation time: 500 hours Contact force of brush contact: 10g

[Table] As is clear from the table above, the wear amount of the contact pieces on the outer circumference of the commutator in the conventional example is 30 to 40 μm, whereas
The amount of wear of the contact piece on the outer periphery of the commutator in the example is 8 to 16μ
It can be seen that the wear resistance is extremely low at m, indicating that the wear resistance is excellent. In addition, the contact resistance of the conventional contact piece is 1 to 2Ω, whereas the contact resistance of the contact piece of the example is 1 to 2Ω.
It can be seen that it is extremely low at 0.3 to 0.5Ω and stable with little variation. As detailed above, the sliding contact material of the present invention has a high softening temperature, so the contact pieces on the outer circumference of the commutator of a small DC motor made using this material do not stick together during sliding contact, and the contact resistance is low and uneven. Since the oxide of the added element acts as a lubricant, wear resistance is significantly improved, and a small DC motor with stable rotation can be obtained.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1 At least one type of Nb and In in total
0.5-2% by weight, 0.5-5% by weight of Mg and balance Cu
A sliding contact material for a commutator of a small DC motor, characterized by being made of a Cu alloy.