Electric power tool
AssigneeKoki Holdings Co., Ltd.
InventorsKazutaka Iwata, Toshiaki Koizumi
Life of this patent
Estimating the term…
Abstract
An electric power tool includes: a brushless motor having a plurality of stator windings and configured to rotate in accordance with voltages applied to the plurality of stator windings, an induced voltage being generated in accordance with a rotation of the brushless motor; a rectifier circuit configured to rectify an AC voltage; a smoothing capacitor configured to smooth the AC voltage rectified by the rectifier circuit to a pulsation voltage having a maximum value larger than the induced voltage and a minimum value smaller than the induced voltage; and an inverter circuit configured to perform switching operations to output the pulsation voltage to the plurality of stator windings by rotation.
Claims8
An electric power tool comprising:
- a brushless motor having a plurality of stator windings;
- a rectifier circuit configured to rectify an AC voltage;
- a smoothing capacitor connected to the rectifier circuit and configured to smooth the AC voltage rectified by the rectifier circuit to a pulsation voltage and to output the pulsation voltage and a motor-current;
- an inverter circuit connected to the smoothing capacitor and the brushless motor, the inverter circuit being configured to perform switching operations to output the pulsation voltage and the motor-current to the plurality of stator windings by rotation;
- an end tool configured to be driven in accordance with the rotation of the brushless motor;
- a motor-current detecting circuit configured to detect the motor-current flowing through the brushless motor;
- and
- an arithmetic section connected to the inverter circuit and the motor-current detecting circuit, the arithmetic section being configured to control the inverter circuit;
- wherein, when the motor-current exceeds a target current, the arithmetic section is configured to restrain the motor-current, and thereafter stop restraining the motor-current flowing through the brushless motor when the detected motor-current is restrained to a value less than or equal to the target current, and
- wherein the arithmetic section is configured:
- to set the target current to a first current value while the rotational speed of the brushless motor is a first speed value, and
- to set the target current to a second current value smaller than the first current value while the rotational speed of the brushless motor is a second speed value lower than the first speed value.
Dependencies are inferred from the claim text.