Electric rotating tool

摘要

A current detection circuit (18) detects that a drive current of the stator coil (2d) is exceeding a threshold value Ir. A rotation number detection circuit (17) detects that the number of rotations of a rotor (2a) is lower than a threshold value Nr. A computing part (20) outputs a PWM signal which switches a semiconductor switching element (3a) of the inverter circuit part (3). The computing part (20) changes the threshold values Ir and Nr in accordance with the PWM duty of the PWM signal determined in accordance with a pressed distance of a switch trigger (7) and detects a locked state of the motor (2) on the conditions that the motor current I is exceeding the set threshold value Ir and that the number of rotations N thereof is lower than the threshold value Nr.

主权项

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.