Wrenching method and apparatus, wrenching attachment, and medium storing wrenching torque control program

摘要

An elevator carrying a motor for rotating a socket wrench is lowered by a hydraulic cylinder while being guided by a linear guide, such that the socket wrench is rotated by the motor while the socket wrench is in engagement with the head of a bolt, with a compressive force being applied to the bolt based on a hydraulic pressure of the cylinder, and such that a wrenching torque and the compressive force acting on the bolt is detected by a detector. A coefficient of friction between thread surfaces of the bolt and an internal thread is evaluated based on the wrenching torque in an initial stage of wrenching operation in which the bolt head is spaced apart from a workpiece, while a coefficient of friction between the bolt head and the workpiece is evaluated based on the wrenching torque in an intermediate stage in which the thread surfaces of the bolt and the internal thread are spaced apart from each other immediately after contacting of the bolt head and the workpiece. The wrenching operation is terminated when actual wrenching torque reaches a target wrenching torque determined from the friction coefficients.