| 摘要 |
A method and apparatus for correcting torque overshoot in power tools wherein torque per angle rate is sensed on each rundown and the speed of the tool is automatically adjusted to maintain torque accuracy on higher torque rate joints while maintaining speed on lower torque rate joints, automatically minimizing tool heating and maximizing job rate. In the setting of threaded fasteners, joint rates are defined as high (hard), medium or low (soft). Two torque points are defined, a first torque point and a second torque point, which are percentages of the target torque, for example 25% and 50% respectively. Two angle values are defined corresponding to the number of degrees of tool spindle rotation measured along the portion of the torque/angle curve between the first torque point and the second torque point on typical linear hard and medium joints. Two final tightening speeds are defined as percentages of full speed corresponding to the tool system requirements for accurate shutoff on the two types of joints, hard and medium. A controller counts the number of angle degrees between the first torque point and the second torque point. The angle counted is compared with the values of hard and medium angles to determine the joint rate. If the angle is less than or equal to the hard angle, the joint is considered hard and the controller immediately downshifts the tool to the hard speed. If the angle is greater than the hard angle but less than or equal to the medium angle, the joint is considered medium and the controller immediately downshifts the tool to the medium speed. If the angle is greater than the medium angle, the joint is considered soft and the speed is not changed. |
