Sensorless driving apparatus and sensorless driving method for brushless motor

Patent metadata

Field	Value
Publication number	US-9729091-B2
Application number	US-201314025358-A
Country	US
Kind code	B2
Filing date	Sep 12, 2013
Priority date	Sep 21, 2012
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

The present relates to a sensorless driving apparatus and a sensorless driving method for a brushless motor. In a state that the brushless motor is driven by rectangular waves, when the driving apparatus detects that a rotation speed of the brushless motor becomes higher than a predetermined speed and thereafter it detects that an angle of a rotor of the brushless motor becomes a predetermined angle, the driving apparatus switches the drive from rectangular wave drive to sign wave drive. The driving apparatus sets as the predetermined angle an angle at which energizing mode is switched in the rectangular wave drive or an angle at which a motor torque is at a peak value in the rectangular wave drive.

First claim

What is claimed is:

1. A sensorless driving apparatus for a brushless motor, comprising:
a driving circuit; and
a controller programmed to output drive control signals to the driving circuit to drive the brushless motor in a first drive mode by rectangular waves and drive the brushless motor in a second drive mode by sign waves, detect a motor rotation speed that exceeds a predetermined value, detect a rotor reaching a predetermined angle at a time after the predetermined value has been exceeded, and perform switching from the first drive mode to the second drive mode after reaching the predetermined angle of the rotor of the brushless motor;
wherein the predetermined angle is an angle of the rotor at which a torque, which varies in accordance with the angle of the rotor, is at a peak value.

2. The sensorless driving apparatus for a brushless motor according to claim 1 ,
wherein the predetermined angle is an angle of the rotor at which a current of the brushless motor is at a peak value.

3. The sensorless driving apparatus for a brushless motor according to claim 1 ,
wherein the controller detects the predetermined angle based on a voltage of a non-energized phase in a state that the brushless motor is driven by the first drive mode.

4. The sensorless driving apparatus for a brushless motor according to claim 1 ,
wherein the predetermined angle is an angle of the rotor at which an energizing pattern is switched by the first drive mode.

5. The sensorless driving apparatus for a brushless motor according to claim 1 ,
wherein the predetermined angle is an angle of the rotor at which the torque of the brushless motor is greater than the torque of the brushless motor at an angle of the rotor at which an energizing pattern is switched by the first drive mode.

6. The sensorless driving apparatus for a brushless motor according to claim 1 ,
wherein the predetermined angle is between an angle at which an energizing pattern is switched by the first drive mode last time and an angle at which the energizing pattern is switched by the first drive mode next time.

7. The sensorless driving apparatus for a brushless motor according to claim 1 ,
wherein the controller performs the switching from the first drive mode to the second drive mode when a rotation speed of the brushless motor is higher than a predetermined speed.

8. The sensorless driving apparatus for a brushless motor according to claim 7 ,
wherein the controller changes the predetermined speed to a higher speed when the rotation speed of the brushless motor does not rise in a state that the brushless motor is driven by the second drive mode.

9. The sensorless driving apparatus for a brushless motor according to claim 1 ,
wherein the brushless motor is a three-phase brushless motor and the first drive mode switches an energizing pattern among six energizing patterns at every 60 degrees.

10. A sensorless driving apparatus for a brushless motor, comprising:
a drive means for driving the brushless motor in a first mode by rectangular waves and
driving the brushless motor in a second mode by sign waves; and
switching means for detecting a motor rotation speed that exceeds a predetermined value, detecting a rotor reaching a predetermined angle at a time after the predetermined value has been exceeded, and performing switching from the first mode to the second mode after reaching the predetermined angle of the rotor of the brushless motor;
wherein the predetermined angle is an angle of the rotor at which a torque, which varies in accordance with the angle of the rotor, is at a peak value.

11. A sensorless driving method for a brushless motor, comprising the following steps of:
detecting a motor rotation speed that exceeds a predetermined value;
detecting whether or not an angle of a rotor of the brushless motor is a predetermined angle at a time after the predetermined value has been exceeded; and
switching drive of the brushless motor from rectangular wave drive mode to sign wave drive mode after the angle of the rotor of the brushless motor has reached the predetermined angle;
wherein the step of detecting whether or not the angle of the rotor of the brushless motor is the predetermined angle includes the step of detecting whether or not the angle of the rotor is an angle at which the torque, which varies in accordance with the angle of the rotor, is at a peak value.

12. The sensorless driving method for a brushless motor according to claim 11 ,
wherein the step of detecting whether or not the angle of the rotor of the brushless motor is the predetermined angle includes the step of detecting whether or not the angle of the rotor is an angle at which the current of the brushless motor is at a peak value.

13. The sensorless driving method for a brushless motor according to claim 11 ,
wherein the step of detecting whether or not the angle of the rotor of the brushless motor is the predetermined angle includes the step of detecting a voltage of a non-energized phase in a state that the brushless motor is driven by the rectangular wave drive mode, and the step of comparing the voltage of the non-energized phase with a threshold value.

14. The sensorless driving method for a brushless motor according to claim 11 ,
wherein the step of detecting whether or not the angle of the rotor of the brushless motor is the predetermined angle includes the step of detecting an angle of the rotor at which an energizing pattern is switched in the rectangular wave drive mode.

15. The sensorless driving method for a brushless motor according to claim 11 ,
wherein the step of detecting whether or not the angle of the rotor of the brushless motor is the predetermined angle includes the step of detecting an angle of the rotor at which a first torque of the brushless motor is greater than a second torque of the brushless motor at an angle of the rotor at which an energizing pattern in the rectangular wave drive mode is switched.

16. The sensorless driving method for a brushless motor according to claim 11 ,
wherein the step of detecting whether or not the angle of the rotor of the brushless motor is the predetermined angle includes the step of detecting an angle of the rotor between an angle at which an energizing pattern is switched last time and an angle at which an energizing pattern is switched next time in the rectangular wave drive mode.

17. The sensorless driving method for a brushless motor according to claim 11 ,
wherein the step of switching from the rectangular wave drive mode to the sign wave drive mode includes the step of detecting whether or not a rotation speed of the brushless motor is higher than a predetermined speed, and the step of switching drive of the brushless motor from the rectangular wave drive mode to the sign wave drive mode when the rotation speed of the brushless motor is higher than the predetermined speed and the angle of the rotor of the brushless motor is the predetermined angle.

18. The sensorless driving method for a brushless motor according to claim 17 , further comprising the step of changing the predetermined speed to a higher speed when the rotation speed of the brushless motor does not rise in the sign wave drive mode.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Hano Masaki
• Iwaji Yoshitaka

Classifications

• H02P6/14 Primary

  Electronic commutators · CPC title

• H02P6/181 Primary

  using different methods depending on the speed · CPC title

• H02P6/18 Primary

  without separate position detecting elements · CPC title