PURPOSE: To prevent the abrasion of brushes and prolong their lives by performing control so as to heat spring bodies made of shape memory raw material through the medium of heating means to a specified temperature or higher and separate the brushes from a commutator, at the time of specified mode operation.

CONSTITUTION: Brushes 29 of four corresponding to the number of poles are provided, and springs 30a are formed into a spiral shape and arranged so that each one-side end part may press the base end of each brush 29. Besides, heaters 31 are arranged in the spiral parts. And the springs 30a are formed beforehand so as to increase the numbers of turns and separate the end parts from the brushes 29 at a specified temperature or higher. And at the time of heating operation, the springs 30a press the base ends of the brushes 29 and bring their tip ends into contact with a commutator 27, and the DC motor is driven. At the time of cooling operation, the shape of the springs 30a changes by causing currents to flow in the heaters 31 and raising the temperature of the springs 30a to a specified temperature or higher, and the brushes 29 are separated and become in a noncontact state with the commutator 27.