Phase-shift detection device, motor drive device, brushless motor, and phase-shift detection method

1. A phase-shift detection device for detecting a phase shift caused by misalignment in rotational position detection of a motor that comprises:

a rotor and multi-phase drive coils; and

magnetic pole position sensors, corresponding in number to the multi-phase drive coils, configured to detect positions of rotating magnetic poles of the rotor,

the phase-shift detection device comprising:

a measurement signal generator configured to output a sinusoidal measurement signal induced in one of the multi-phase drive coils during rotation of the rotor in a non-driving state;

a level difference calculator configured to receive a pulse-shaped position detection signal formed based on a sensor signal from one of the magnetic pole position sensors and calculate a level difference between a level of the sinusoidal measurement signal measured at a rising timing of the pulse-shaped position detection signal and a level of the sinusoidal measurement signal measured at a falling timing thereof; and

a phase-shift calculator configured to calculate a degree of the phase shift, based on the level difference from the level difference calculator.

2. The phase-shift detection device of claim 1 , wherein

the level difference calculator is configured to calculate a series of level differences (L(h(i))−L(t(i))), where

(a) i is an integer from 1 through n,

(b) h( 1 ) . . . h(i) . . . h(n) represent a series of equally intervalled timings, and timing h(i) has a relative time interval from the rising timing of the pulse-shaped position detection signal,

(c) t( 1 ) . . . t(i) . . . t(n) represent a series of similarly intervalled timings, and timing t(i) has the same relative time interval from the falling timing of the pulse-shaped position detection signal,

(d) L(h(i)) represents a level of the sinusoidal measurement signal measured at timing h(i), and

(e) L(t(i)) represents a level of the sinusoidal measurement signal measured at timing t(i), and

the phase-shift calculator is configured to determine a timing at which the level difference is zero, using the series of level differences, and calculate the degree of the phase shift based on the timing at which the level difference is zero.

3. The phase-shift detection device of claim 1 , further comprising:

an acquisition timing generator configured to generate the rising timing and the falling timing of the pulse-shaped position detection signal; and

a timing controller configured to control the timings generated by the acquisition timing generator,

wherein the level difference calculator calculates the level difference in the sinusoidal measurement signal acquired at the timings generated by the acquisition timing generator,

the timing controller controls such that an advance or a delay of the phase is detected using a sign of the level difference, and the timings generated by the acquisition timing generator are adjusted in a direction causing the level difference to be zero, and

the phase-shift calculator calculates the degree of the phase shift, based on the adjusted timing.

4. The phase-shift detection device of claim 3 , wherein the acquisition timing generator, the level difference calculator and the timing controller perform a feedback loop for adjusting the timing generated by the acquisition timing generator so that the level difference becomes zero.

5. The phase-shift detection device of claim 1 , wherein the multi-phase drive coils are three-phase drive coils, and

the measurement signal generator includes a bias circuit for applying a bias voltage to one of the three-phase drive coils and outputs an induced voltage produced from another of the three-phase drive coils as the sinusoidal measurement signal.

6. The phase-shift detection device of claim 1 , wherein the multi-phase drive coils are three-phase drive coils, and

the measurement signal generator includes a bias circuit for applying bias voltages, respectively, to the three-phase coils, and outputs induced voltages produced from the three-phase drive coils as the sinusoidal measurement signals.

7. The phase-shift detection device of claim 1 , further comprising:

an interphase-shift detector configured to detect degrees of interphase shifts between every combination of two of the sensor signals, and calculate an average of the detected degrees of the interphase shifts; and

a phase-shift corrector configured to correct the degree of phase shift calculated by the phase-shift calculator, using the average degree of the interphase shifts, and outputting the corrected results.

8. The phase-shift detection device of claim 1 , wherein measurement periods each having a predetermined period width are set from time points before the rising timing and the falling timing of the pulse-shaped position detection signal to time points after the rising timing and the falling timing thereof, and driving of the motor is stopped to be set in the non-driving state in the measurement periods.

9. The phase-shift detection device of claim 8 , wherein a drive phase in which the motor is driven is corrected, using the detected degrees of phase shifts, and an operation of detecting a phase shift is repeated.

10. A motor drive device for driving a motor having a rotor and multi-phase drive coils, comprising:

the phase-shift detection device of claim 1 ;

an inverter configured to energize and drive the multi-phase drive coils; and

a drive phase corrector configured to correct the phase shift caused by misalignment in rotational position detection in motor driving based on the degree of phase shift calculated in the respective phases.

11. The motor drive device of claim 10 , wherein

the multi-phase drive coils are three-phase drive coils,

the phase-shift calculator calculates the degree of the phase shift in the respective phases, and

the drive phase corrector corrects the phase shift in the respective phases, based on the degree of phase shift in the respective phases.

12. The motor drive device of claim 10 , wherein the drive phase corrector corrects timings of the sensor signals produced by the magnetic pole position sensors.

13. The motor drive device of claim 12 , further comprising:

a driving waveform generator configured to generate a waveform signal, the waveform signal driving each of the multi-phase drive coils;

a PWM circuit configured to generate a drive pulse signal obtained by pulse width modulation using the waveform signal; and

an inverter configured to energize the multi-phase drive coils, based on the drive pulse signals,

wherein the waveform signal generated by the driving waveform generator is output to the PWM circuit at a timing of a correction position signal corrected in the drive phase corrector.

14. A brushless motor comprising:

a rotor holding a permanent magnet and disposed for rotation with a rotating shaft in a center;

a stator including a stator iron core that has a plurality of salient poles and multi-phase drive coils being wound one the salient poles; and

the motor drive device of claim 10 .

15. A phase-shift detection method for detecting a phase shift caused by misalignment in rotational position detection in motor driving of a motor that comprises:

a rotor and multi-phase drive coils; and

magnetic pole position sensors, corresponding in number to the multi-phase drive coils, configured to detect positions of rotating magnetic poles of the rotor, the method comprising:

measuring a sinusoidal measurement signal induced in one of the multi-phase coils in a non-driving state;

calculating a level difference between a level of the sinusoidal measurement signal measured at a rising timing of a pulse-shaped position detection signal formed based on a sensor signal from one of the magnetic pole position sensors and a level of the measurement signal measured at a falling timing thereof; and

calculating a degree of phase shift based on the level difference from the level difference calculator.

16. The phase-shift detection method of claim 15 , wherein

calculating a level difference comprises calculating a series of level differences (L(h(i))−L(t(i))), where

(a) i is an integer from 1 through n,

(b) h( 1 ) . . . h(i) . . . h(n) represent a series of equally intervalled timings, and timing h(i) has a relative time interval from the rising timing of the pulse-shaped position detection signal,

(c) t( 1 ) . . . t(i) . . . t(n) represent a series of similarly intervalled timings, and timing t(i) has the same relative time interval from the falling timing of the pulse-shaped position detection signal,

(d) L(h(i)) represents a level of the sinusoidal measurement signal measured at timing h(i), and

(e) L(t(i)) represents a level of the sinusoidal measurement signal measured at timing t(i), and

determining a timing at which the level difference is zero, using the series of level differences, and calculating the degree of the phase shift based on the timing at which the level difference is zero.

17. The phase-shift detection method of claim 15 , further comprising:

a timing at which the level difference is zero is determined by detecting an advance or a delay of the phase using a sign of the level difference, and adjusting the timings of level difference detection in a direction causing the level difference to be zero, and

the degree of phase shift from the timing is calculated.

18. The phase-shift detection method of claim 17 , wherein the timing at which the level difference is zero is determined by forming a feedback loop for adjusting the timings of level difference detection in a direction causing the level difference to be zero.

19. The phase-shift detection method of claim 15 , wherein the multi-phase coils are three-phase coils,

a bias voltage is applied to one of the three-phase drive coils, and

an induced voltage produced from another of the three-phase drive coils is measured as the measurement signal.

20. The phase-shift detection method of claim 15 , wherein the multi-phase coils are three-phase coils,

bias voltages are applied, respectively, to the three-phase drive coils, and

induced voltages produced from the three-phase drive coils are measured as the measurement signals.

21. The phase-shift detection method of claim 15 , wherein degrees of interphase shifts between every combination of two of the sensor signals are detected, the degree of phase shift in motor driving is corrected using an average of the detected degrees of the interphase shifts, and the corrected results are output.

22. The phase-shift detection method of claim 15 , wherein measurement periods each having a predetermined period width are set from time points before the rising timing and the falling timing of the pulse-shaped position detection signal to time points after the rising timing and the falling timing thereof, and driving of the motor is stopped to be set in the non-driving state in the measurement periods.

23. The phase-shift detection method of claim 22 , wherein a drive phase in which the motor is driven is corrected, using the detected degrees of phase shifts, and an operation of detecting a phase shift is repeated.