SPEED CONTROLLABLE ROTARY TOOL

摘要

PROBLEM TO BE SOLVED: To control the rotating speed of a rotary tool in the condition that the rotary tool is securely held without providing a trigger nor switch for operating stroke by controlling the rotating speed of a bit in response to the pressure for pushing the bit. SOLUTION: A circular piezoelectric element 19 is arranged in depth of a bit fitting hole 9 provided in an output shaft 5. When a rear end 8a of a bit 8 is pushed to a front surface of the piezoelectric element 19, resistance value of the piezoelectric element 19 is changed. This resistance value is detected by a pushing force detecting unit, and a signal is sent to a PWM control unit so as to control the number of revolution of a motor 7 with the PWM control. With this structure, since rotating speed of the bit 8 can be controlled by adjusting the pressure for pushing the bit 8, rotating speed of a rotary tool can be controlled in the condition that the rotary tool is securely held.