Patent ID: 9604284
Date: 2017-03-28
CPC Classifications: B23B

Claim:
1. A portable drilling machine comprising: a drive motor for rotationally driving a cutting tool; a motor control unit for controlling actions of the drive motor; a portable main body mounted with the drive motor and the motor control unit; and a fixing unit for fixing the main body to a workpiece; the motor control unit comprising: a switching element and a relay that are connected in series with the drive motor to power-supply terminals; a first resistor connected in parallel with the relay, connected in series with the drive motor, and connected in series with the switching element to the power supply terminals; a first determining unit connected in parallel with the switching element, for determining whether the switching element has a short-circuit failure; a switching control unit that provides switching control for the switching element to control a motor current flowing through the drive motor; and an on-off control unit for controlling the relay, wherein the relay is kept off during the determining by the first determining unit, and the relay is kept on in making the drive motor take rotational actions.