发明授权
US5563482A Power tools 失效
电动工具

Power tools
摘要:
A drill/driver (eg. an electric drill) with a screwdriver attachment, and a method of controlling the drill/driver, are described. A control circuit (30) controls the speed of rotation of the motor (38, 39) through a time delay circuit (42) and a triac (41). The control circuit (30) uses the time delay information and information inputted from a rotational speed sensor (43) to monitor the current in the motor or a parameter related at least in part to current in the motor. When a change corresponding to an increase in the rate of change of current in the motor is detected, the control circuit (30) stops the motor to provide an automatic torque control feature for a screwdriving operation.
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