PURPOSE: To improve the wear resistance and contact resistance characteristics of the brush of a sliding contact device and to also improve the wear resistance of a commutator by adding Si and Zr to the conventional material to the brush, and using an Ag-Cu alloy as the material of the commutator.

CONSTITUTION: To an alloy consisting of 8W12% Au, 8W12% Pt, 33W37% Pd, 2 28W32% Ag, 12W16% Cu and 0.1W2% Zn as the conventional material of the brush of a sliding contact device is added 0.5W10% in total of Si and Zr without changing the ratio in the composition. An Fe group metal such as Fe, Ni or Co may be substituted for part of the Si and Zr to be added within the range of 0.01W0.5%. An Ag alloy contg. 3W12% Cu or further contg. <5% Cd is used as the material of a commutator or a slip ring is place of an Ag alloy contg. 0.5W 15% Cd as the conventional material.