Patent ID: 9114519
Filing Date: 2015-08-25
Classification: B25B,B25F,H02H,H02P

Abstract:
1. An electric rotating tool comprising: an operating part; a power source part; a motor having a rotor and a stator coil; an inverter circuit part which has a semiconductor switching element inserted between the power source part and the stator coil; a rotation number detection part configured to detect the rotational rate of the rotor relative to the stator coil and outputs a signal corresponding to a result of the detection; and a control part which generates and outputs a pulse-width modulation (PWM) signal for driving the semiconductor switching element of the inverter circuit part, wherein the control part includes a computer and the computer generates a first rotational speed threshold value that changes in accordance with a PWM duty of the PWM signal, the duty being varied in accordance with an operated degree of the operating part, the control part being used to control the operation of the electric rotating tool in response to the rotational rate of the rotor detected by the rotation number detection part dropping below the first rotational speed threshold.