| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an impact rotary tool capable of preventing a structure of an impact rotary tool itself from being complicated, preventing an excessive temperature rise under severe service conditions, and preventing any trouble of a motor. Ž<P>SOLUTION: A shape memory spring 50 made of an shape memory alloy is arranged coaxially with a spring 32 on the retracting direction side in a hammer 30. When an impact rotary tool 1 is brought closer to a severe service condition, the temperature of the shape memory spring 50 rises, and when the temperature exceeds the transformation point in the shape memory spring 50, the modulus of transverse elasticity is abruptly increased to function as a coil spring for impeding the retraction of the hammer 30. The load of a motor 17 is increased with the hammer 30 impeded in its retraction, an overcurrent flows in the motor 17, and a control circuit 41 stops the motor 17, on the condition that the overcurrent reaches the overcurrent protective threshold. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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