A POWER TOOL FOR TIGHTENING A FASTENER AND A METHOD

摘要

The invention relates to a power tool and a method for tightening a fastener comprising an angle measurement means (101) for measuring a rotational angle (α) of the fastener and a torque measurement means (102) for measuring the torque (T) delivered to the fastener during tightening. A processor (103) is arranged for calculating a tightening energy (Et) needed to complete tightening of the fastener from the measured rotational angle to a predetermined target angle, wherein the tightening energy is calculated based on the measured rotational angle (α), target angle (αt) and the stiffness (k) of the joint. The tool comprises a motor (104) connected to rotatable parts of the power tool for driving the tightening of the fastener. A regulator (105) is connected to the motor to regulate the rotational speed (ω) of the motor to provide rotational energy (Er) in the form of rotational inertia in the rotatable parts of the power tool to meet the needed tightening energy (Et).