| 摘要 |
PROBLEM TO BE SOLVED: To execute the fastening of high quality by calculating an angle of rotation to a yield point stop point by a present position at the time point of passing a yield point of an elastic limit point and an angle of rotation from the present position to the yield point, and terminating the fastening when a bolt reaches the angle of rotation. SOLUTION: An angle of rotation or the elongation amount from a yield point is determined by executing the pre-experiment, and these numerical values are stored in a memory in a control circuit 9 as the parameter. In the fastening of a bolt, the output signals from a torque sensor 1, an angle of rotation sensor 2, a rotating speed sensor 3 and a current detector 4 embedded in a nut runner are input to the control circuit 9, and a linear part of a reference torque rate which is an elastic range of a bolt in the start of the fastening of the bolt is calculated. Then an angle of rotation to a stop point is calculated by a present position at a time when passing through the yield point is judged, and an angle of rotation from the present position and the fastening is terminated when a bolt reaches the angle of rotation.
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