Device for driving three-phase brushless motor

Patent metadata

Field	Value
Publication number	US-9543865-B2
Application number	US-201415023189-A
Country	US
Kind code	B2
Filing date	Sep 19, 2014
Priority date	Sep 20, 2013
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

The present invention allows a driving device, which drives a three-phase brushless motor in a sensorless manner, to detect an initial position of the brushless motor and start drive of the motor without performing positioning processing. In a device for driving a brushless motor by sequentially switching six energizing modes, in which two phases to be energized are selected out of three phases, energization is performed sequentially in six energizing modes before start of drive so that the motor does not rotate, and each induced voltage of an opened phase is acquired, induced voltage difference is obtained in each predetermined combination of energizing modes, and it is estimated to which one of six divided regions an initial position of the brushless motor corresponds based on a maximum value of induced voltage differences obtained.

First claim

The invention claimed is:

1. A device for driving a three-phase brushless motor, wherein the device performs energization between one phase, and the rest of two phases out of three phases of a brushless motor so that current in the one phase become positive and negative, and detects an initial position of the brushless motor based on a difference between induced voltage in an opened phase when current of the one phase becomes positive, and induced voltage of an opened phase when current of the one phase becomes negative.

2. The device for driving a three-phase brushless motor according to claim 1 , wherein the device detects an initial position of the brushless motor based on a deviation between the induced voltage differences among a plurality of combinations in which the induced voltage differences are obtained.

3. A device for driving a three-phase brushless motor according to claim 2 , wherein the device configured to drive the brushless motor by sequentially switching six energizing modes in which two phases to be energized are selected out of the three phases,
wherein the device performs sequentially energization in the six energizing modes to detect each induced voltage of an opened phase, obtains the induced voltage difference in each of six combinations of the energizing modes, and detects to which one of six divided regions an initial position of the brushless motor corresponds based on the six induced voltage differences.

4. The device for driving a three-phase brushless motor according to claim 3 , wherein the device obtains twelve mutual differences of induced voltage differences in respective twelve types of combinations of the six induced voltage differences, and compares the twelve differences to one another to detect to which one of twelve divided regions an initial position of the brushless motor corresponds.

5. The device for driving a three-phase brushless motor according to claim 3 , wherein the device acquires induced voltage of the opened phase within a time in which rotational torque of the brushless motor is not generated.

6. The device for driving a three-phase brushless motor according to claim 3 , having a structure that drives the brushless motor by sequentially switching six energizing modes in which two phases to be energized are selected out of the three phases,
wherein the device selects an energizing mode at the time of start of drive of the brushless motor in accordance with an initial position of the brushless motor, and, after energization is performed for a predetermined time in the energizing mode, the device switches to a next energizing mode to start up the brushless motor.

7. The device for driving a three-phase brushless motor according to claim 3 , wherein the device detects an initial position of the brushless motor based on a maximum value of induced voltage differences obtained in the respective six combinations.

8. The device for driving a three-phase brushless motor according to claim 3 , wherein the device detects an initial position of the brushless motor based on a minimum value of induced voltage differences obtained in the respective six combinations.

9. The device for driving a three-phase brushless motor according to claim 3 , wherein the device sets a duty ratio in energization for detection of the initial position so that a deviation of induced voltage differences among a plurality of combinations, in which the induced voltage differences are obtained, exceeds a predetermined value.

10. The device for driving a three-phase brushless motor according to claim 3 , wherein, after the motor is started up in an energizing mode in accordance with an initial position of the brushless motor, the device executes the first switching of the energizing mode when it is determined that a level of induced voltage of the opened phase is a level that corresponds to energizing mode after the switching, and the device executes the second switching of the energizing mode and after when it is determined that a level of induced voltage of the opened phase is changed from a level corresponding to energizing mode before switching to a level corresponding to energizing mode after switching.

11. The device for driving a three-phase brushless motor according to claim 3 , wherein, before starting drive of the three-phase brushless motor, the device applies voltage for a predetermined time in each energizing mode without rotating the three-phase brushless motor to acquire induced voltage of a non-energized phase, and detects an initial position of the three-phase brushless motor based on the acquired induced voltage.

12. The device for driving a three-phase brushless motor according to claim 1 , wherein the device performs detection of an initial position based on the induced voltage differences under a condition that rotation speed of the brushless motor is within a predetermined low rotation speed area including a stopped state.

13. The device for driving a three-phase brushless motor according to claim 1 , wherein the device detects an initial position of the brushless motor based on the induced voltage difference within a predetermined range.

14. The device for driving a three-phase brushless motor according to claim 13 , wherein the device changes the predetermined range in accordance with temperature of the brushless motor.

15. A method for detecting an initial position of a three-phase brushless motor, wherein energization is performed between one phase, and the rest of two phases out of three phases of a brushless motor so that current in the one phase becomes positive and negative, and an initial position of the brushless motor is detected based on a difference between induced voltage of an opened phase when current of the one phase becomes positive, and induced voltage of an opened phase when current of the one phase becomes negative.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Hano Masaki

Classifications

• H02P6/18 Primary

  without separate position detecting elements · CPC title

• H02P27/08

  with pulse width modulation · CPC title

• H02P6/182

  using back-emf in windings · CPC title

• H02P21/32

  Determining the initial rotor position (H02P21/34 takes precedence) · CPC title

• H02P6/20

  Arrangements for starting (H02P6/08 takes precedence) · CPC title