Reading method of screw rotation angle of hand-held impact wrench, hand-vibration detection method, tightening evaluation method and control method of hand-held power screw loosening tool

Abstract

A hand-held powered screw tightening tool has a detecting device to detect a rotation angle of a rotary member in a clockwise direction and a counterclockwise direction. In screw tightening, an angle obtained by subtracting a cumulative total of the rotation angle of the rotary member with rebound, if any, in a counterclockwise direction from a cumulative total of the rotation angle of the rotary member in the clockwise direction is detected and accumulated as a total rotation angle (P) and a rotation angle formed during the deceleration at the hammering is detected as &Dgr;H and accumulated, and a preset design angle Pd for hammering is accumulated. A wobbling angle is calculated from Equation: A wobbling angle=P−a cumulative total of Pd−a cumulative total of &Dgr;H (where Pd is a design value of the impact wrench, indicating an angle corresponding to 360°/m for the case of the m number of hammerings per rotation of the rotary member). When the cumulative total of the rotation angle &Dgr;H reaches the predetermined design angle for screw tightening, the rotation of the rotary member is stopped. In screw loosening, the rotary member is rotated in the opposite direction, so that when the rotation angle of the rotary member reaches a predetermined number of rotations in the loosening direction similarly, the rotation of the rotary member is stopped.