Stillstandsdetektor und Bremsgerät für einen Gleichstrommotor.

摘要

A DC motor (12) is supplied, from a motor driver (13), with a brake voltage constituted by a forward drive voltage, a reverse drive voltage, and a stop voltage of a zero potential level. An operational current of the motor driver (13) is supplied to a low-pass filter (14) whose output is supplied to first and second sample and hold (S/H) circuits (15, 16). The first S/H circuit (15) performs its sampling operation after a minute period of time in which the brake voltage goes through a polarity inversion from the reverse drive voltage to the forward drive voltage. The second S/H circuit (16) performs its sampling operation after a minute period of time in which the voltage applied is changed from the forward drive voltage to the reverse drive voltage. The outputs or sampled values of both S/H circuits (15, 16) are compared with each other by a comparator (17). When the sampled values equal each other, i.e., when the number of rotations of the motor (12) becomes zero, the comparator (17) outputs a coincidence pulse. This pulse is supplied to a stop detector (18). When detecting this coincidence pulse a predetermined number of times in a row, the stop detector (18) discriminates that the number of rotations of the motor (12) has become zero.