Brushless motor and electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-2016111985-A1
Application number	US-201514882677-A
Country	US
Kind code	A1
Filing date	Oct 14, 2015
Priority date	Oct 15, 2014
Publication date	Apr 21, 2016
Grant date	—

Abstract

On the basis of an energization phase signal being output from a rotational phase sensor and changing its output at every predetermined rotational phase corresponding to a stepwise change (increase or decrease) in rotational phase, a motor controller switches a phase current passing through the corresponding phase coil, and changes the magnitude of the phase current passing through the corresponding phase coil such that an actual motor torque detected by a torque sensor coincides with a target motor torque.

First claim

What is claimed is:

1 . A brushless motor comprising:
a rotor rotating integrally with a rotating shaft and having a plurality of permanent magnets circumferentially arranged to serve as magnetic poles; a stator having a plurality of phase coils arranged to face the rotor with a gap therebetween; a rotational phase sensor configured to detect, as a rotational phase, a rotational position of a magnetic pole of one of the permanent magnets in accordance with the rotation of the rotor, and to generate an energization phase signal that changes an output thereof at every predetermined rotational phase, the predetermined rotational phase corresponding to a stepwise change in the rotational phase; a torque sensor attached to the rotating shaft and configured to detect an actual motor torque; and a motor controller configured to pass a phase current to the respective phase coils, wherein, on the basis of the energization phase signal that changes the output thereof at the every predetermined rotational phase, the motor controller switches the phase current passing through the respective phase coils, and changes the magnitude of the phase current passing through the respective phase coils such that the actual motor torque detected by the torque sensor coincides with a target motor torque.

2 . The brushless motor according to claim 1 , wherein when the phase coils are three phase coils of a U-phase coil, a V-phase coil, and a W-phase coil, the rotational phase sensor is configured to generate the energization phase signal that changes the output thereof at every 60 degrees in electrical angle, which is the predetermined rotational phase; and
the motor controller passes the phase current sequentially through pairs of phase coils, the U- and V-phase coils, the U- and W-phase coils, the V- and W-phase coils, the V- and U-phase coils, the W- and U-phase coils, and the W- and V-phase coils while changing a phase of the phase current by a 120-degree energization range on the basis of the energization phase signal.

3 . The brushless motor according to claim 2 , wherein a waveform showing changes in magnetic flux density of the permanent magnets during half a period of phase, including the 120-degree energization range of each phase current, has a substantially trapezoidal waveform with rounded corners, not a rectangular waveform or a sinusoidal waveform.

4 . The brushless motor according to claim 1 , wherein the torque sensor is a magnetostrictive torque sensor.

5 . The brushless motor according to claim 1 , wherein the rotational phase sensor includes
a rotating member configured to rotate integrally with the rotating shaft, the rotating member including a plurality of sensor permanent magnets circumferentially arranged to correspond to respective positions of the magnetic poles; and a magnetic detector fixed in place to face the rotating member, the magnetic detector being configured to detect changes in rotation of the sensor permanent magnets of the rotating member.

6 . The brushless motor according to claim 1 , wherein the rotational phase sensor includes a Hall element sensor or a magnetoresistive element sensor.

7 . An electric power steering apparatus comprising the brushless motor according to claim 1 .

8 . The brushless motor according to claim 1 , wherein the rotational phase sensor detects the rotational phase stepwise with a predetermined resolution in electrical angle.

9 . The brushless motor according to claim 8 , wherein the rotational phase sensor detects the rotational phase stepwise at the every predetermined rotational phase.

10 . The brushless motor according to claim 3 , wherein the actual motor torque is a function of the magnetic flux density of the permanent magnets and the phase current, and the motor controller compensates variation in the magnetic flux density by changing the magnitude of the phase current.

11 . The brushless motor according to claim 1 , wherein the motor controller changes timing of the phase current passing through the respective phase on the basis of the energization phase signal.

Assignees

• Honda Motor Co Ltd

Inventors

• Yoneda Atsuhiko

Classifications

• H02K11/0021

  Electricity · mapped topic

• H02P6/16

  Circuit arrangements for detecting position · CPC title

• H02P6/08 Primary

  Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) · CPC title

• B62D5/0463

  calculating assisting torque from the motor based on driver input · CPC title

• H02K11/0042

  Electricity · mapped topic