| 摘要 |
PROBLEM TO BE SOLVED: To prevent the heat generation or the stress fatigue of a tool or the like by increasing a vibrational amplitude up to a rated value when the rate of change of a load applied on an ultrasonic vibrator transducer driven by a small vibrational amplitude during a non-load time exceeds a fixed value. SOLUTION: In a non-load state at the tip of a drill 4, the change of a current for a vibrator transducer does not occur, the output of a DC amplifier 25 is not changed as well and all of the output of a window comparator 27, a timer 30 and the like are in an L level state. Therefore, a vibrational amplitude control circuit 34 and a frequency control circuit 35 recognize a non-load mode to rotate a motor 13 at a slow speed. When a load is applied on the drill 4, the signal of the DC amplifier 25 is largely changed and the output of a differential circuit 26 is produced. When the output exceeds the setted standard level of the window comparator 27, the output of the window comparator 27 is changed to an H level and the vibrational amplitude control circuit 34 and the frequency control circuit 35 are changed to a load applied mode. As the result, the vibrational amplitude becomes a rated value, a motor 13 is rotated in a rated state to enable a usual working. |
