Patent ID: 6873124
Filing Date: 2005-03-29
Classification: B25D,H02P

Abstract:
1. A rotational speed controller for controlling a rotational speed of a motor, comprising: a semiconductor device that controls a voltage applied to the motor; a rotational speed detector that detects an actual rotational speed of the motor and outputs a rotational speed detection signal indicative of the actual rotational speed; a rotational speed setter that sets a target rotational speed of the motor and outputs a rotational speed setting signal indicative of the target rotational speed; a comparator that compares the rotational speed detection signal with the rotational speed setting signal and outputs a signal indicative of a comparison result; a phase controller that controls the semiconductor device based on the signal output from the comparator; and a current detector that detects a current flowing in the motor and outputs a current detection signal indicative of the current flowing in the motor, wherein the rotational speed setter outputs selective one of a first rotational speed setting signal indicative of a first rotational speed when the current detection signal output from the current detector is equal to or less than a first predetermined value, a second rotational speed setting signal indicative of a second rotational speed higher than the first rotational speed when the current detection signal output from the current detector is equal to or higher than a second predetermined value, and a third rotational speed setting signal indicative of a speed in a range between the first rotational speed and the second rotational speed when the current detection signal output from the current detector is between the first predetermined value and the second predetermined value, the speed indicated by the third rotational speed setting signal changing corresponding to a change in the current detection signal.