US 10,256,701 B2 · Electric power tool and method for driving brushless motor thereof

Abstract

An electric power tool and a method for driving a brushless motor in the electric power tool. The electric power tool includes a driving circuit for driving the brushless motor and position sensors (D1, D2, D3) for detecting positions of the rotor. The rotor of the brushless motor, when rotating in a normal direction, sequentially passes by a commutation position, where a signal of at least one of the position sensors (D1, D2, D3) in the brushless motor changes, and a reference position, where a back electromotive force of the stator winding of at least one phase in the brushless motor is at a midpoint position of the waveform of the back electromotive force. An electrical angle between the commutation position and the reference position ranges from 20° to 40°. The position sensors (D1, D2, D3) are configured such that performance of the brushless motor is improved.

Claims17

Dependent claims

An electric power tool comprising:

a housing;
a brushless motor supported by the housing, the motor comprising a rotor and a stator winding including at least two phases;
and
a driving system, comprising:
a driving circuit for driving the brushless motor;
position sensors for detecting positions of the rotor;
and
a controller configured for controlling the driving circuit according to signals corresponding to the positions of the position sensors such that the rotor of the brushless motor, when rotating in a normal direction, sequentially passes by commutation positions, where the signal of at least one of the position sensors in the brushless motor changes, and a reference position, where a back electromotive force of at least one of the at least two phases of the stator winding in the brushless motor is at a midpoint position of a waveform of the back electromotive force;
wherein a difference between an electrical angle of one of the commutation positions and an electrical angle of the reference position ranges from 20° to 40°.

6 more elements

A method for driving a brushless motor in an electric power tool, the electric power tool comprising position sensors and a driving circuit, the method comprising:

detecting, by the position sensors, positions of a rotor of the brushless motor;
and
changing, by the driving circuit, a state of a voltage applied to a stator winding according to signals corresponding to the positions of the position sensors;
wherein the state of the voltage applied to the stator winding by the driving circuit is defined as a driving state of the driving circuit, when the rotor of the brushless motor rotates in a normal direction, the driving circuit is sequentially in a first forward driving state, in a second forward driving state and in a third forward driving state according to changes in the signals of the position sensors, when the rotor of the brushless motor rotates in a reverse direction, the driving circuit is sequentially in a first backward driving state, in a second backward driving state and in a third backward driving state according to the changes in the signals of the position sensors, a voltage applied to the rotor by the driving circuit in the first backward driving state is opposite to a voltage applied to the rotor by the driving circuit in the second forward driving state, a voltage applied to the rotor by the driving circuit in the second backward driving state is opposite to a voltage applied to the rotor by the driving circuit in the first forward driving state, and a voltage applied to the rotor by the driving circuit in the third backward driving state is opposite to a voltage applied to the rotor by the driving circuit in the third forward driving state.

1 more element

Dependencies are inferred from the claim text.

Electric power tool and method for driving brushless motor thereof

Life of this patent

Electric power tool and method for driving brushless motor thereof

Life of this patent

Abstract

Claims17