| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately detect an over-discharge state of a battery without being affected by use environment. Ž<P>SOLUTION: In an electrical screwdriver, a strain gage installed either on a shaft that screws a screw or on a motor portion connected to the shaft detects the over-discharge state when torsion of the shaft is reduced, assuming that a residual capacity of the battery has been decreased. The detection of the over-discharge state is judged by comparing detected values such as a voltage value based on resistance detected according to the torsional amount with a prescribed threshold. When the battery has a large residual capacity, generated torque is large so that the torsion is generated to the shaft by a drive power for rotating the shaft generated at a part of the shaft connecting the motor portion and repulsion force created at a part of the shaft contacting the screw. Therefore, the state of the battery can be accurately grasped by judging the residual capacity of the battery based on such torsion actually generated. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
|
