| 摘要 |
PURPOSE:To perform accurate screw tightening, by comparing no-load torque before a start of screw tightening with a value, in which preset torque is subtracted from detected torque after the start of screw tightening, and stopping the screw tightening when the latter value is larger than the former torque. CONSTITUTION:If a rotary shaft 13 is tilted, the gravity of a screw tightening device 1 itself causes distortion in a shaft 16, and fixed torque relating to an attitude of the device 1 is detected by a distortion element 20 even at no-load, then correction is applied by the amount of this offset torque to calibrate the zero point of a measuring system. In consequence, a distortion amount detected by the element 20 is fed to an input/output interface 53 via a converter 52 and processed in accordance with a processing instruction of a CPU50. Then preset torque is corrected by no-load torque to obtain a new target of tightening torque, drive a motor 14 and perform screw tightening, and the load torque is compared with the new target value, if the load torque becomes larger than the target value, driving of the motor 14 is stopped. |
