abstract |
The invention relates to a power screwdriver ( 10 ) comprising a motor ( 12 ) as the drive, a desired torque default element ( 52 ) and an actual torque determination element ( 46 ), a torque gradient determination element ( 48 ) and a motor control ( 40 ) which controls the motor ( 12 ) depending on the torque gradient (dmd_lst/dt). The invention is characterized by a torque threshold determination element ( 50 ) which provides a torque threshold value (Md_Lim, Md_Lim1, Md_Lim2) that depends on the torque gradient (dmd_lst/dt) and lies below the desired torque value (Md_Soll). If the actual torque value (md_Ist) exceeds the torque threshold value (Md_Lim, Md_Lim1, Md_Lim2), a motor control ( 40 ) presets a speed reduction for the motor ( 12 ) or already completely switches off the motor ( 12 ). The power screwdriver ( 10 ) according to the invention avoids torque overshoots and yet allows the desired torque value (Md_Soll) to be exactly reached in the shortest time possible. |