Brushless motor driving apparatus and brushless motor driving method

1. A brushless motor driving apparatus that rotates and drives a brushless motor, which has a plurality of coils,

wherein the brushless motor driving apparatus rotates and drives the brushless motor by switching energization modes corresponding to phases of the brushless motor, and comprises a computer configured to:

sequentially switch the energization modes based on a non-energized phase voltage and a voltage threshold,

regulate an upper limit for an energization amount causing an induced voltage greater than the voltage threshold, based on the voltage threshold and a change in the non-energized phase voltage at a time of switching the energization mode, and

prohibit setting the voltage threshold when a non-energized phase voltage obtained immediately after switching the energization mode falls outside of a predetermined range.

2. The brushless motor driving apparatus according to claim 1 , wherein the computer is configured to set the voltage threshold based on the non-energization voltage at the time of switching from a state in which the brushless motor is kept stopped while one energization mode is continued, to a subsequent energization mode.

3. The brushless motor driving apparatus according to claim 2 , wherein a design value has been set in advance as an initial value for the voltage threshold.

4. The brushless motor driving apparatus according to claim 1 , wherein the computer is configured to correct the upper limit of the energization amount based on at least one of a power source voltage and a temperature of the brushless motor.

5. The brushless motor driving apparatus according to claim 1 , wherein, when the brushless motor is driven under low-speed sensorless control, the computer is configured to regulate a voltage applied to the brushless motor so as to prevent a power source electric current from increasing to or exceeding an electric current corresponding to the upper limit of the energization amount.

6. The brushless motor driving apparatus according to claim 5 , wherein the computer is configured to correct the voltage applied to the brushless motor based on at least one of a power source voltage and a temperature of the brushless motor.

7. The brushless motor driving apparatus according to claim 1 , wherein, when the energization amount of the brushless motor exceeds a predetermined value, the computer is configured to gradually decrease the voltage threshold.

8. The brushless motor driving apparatus according to claim 1 , wherein, when the brushless motor stops, the computer is configured to decrease the voltage threshold by a predetermined proportion thereof when the brushless motor is actuated again.

9. The brushless motor driving apparatus according to claim 1 , wherein the computer is configured to regulate the upper limit of the energization amount only when the brushless motor rotates at a predetermined rotational speed or lower.

10. A brushless motor driving apparatus that rotates and drives a brushless motor, which has a plurality of coils,

wherein the brushless motor driving apparatus rotates and drives the brushless motor by switching energization modes corresponding to phases of the brushless motor, and comprises a computer configured to:

sequentially switch the energization modes based on a non-energized phase voltage and a voltage threshold,

regulate an upper limit for an energization amount causing an induced voltage greater than the voltage threshold, based on the voltage threshold and a change in the non-energized phase voltage at a time of switching the energization mode, and

adjust the upper limit of the energization amount based at least on a temperature of the brushless motor.

11. The brushless motor driving apparatus according to claim 10 , wherein the computer is configured to set the voltage threshold based on the non-energization voltage at the time of switching from a state in which the brushless motor is kept stopped while one energization mode is continued, to a subsequent energization mode.

12. The brushless motor driving apparatus according to claim 11 , wherein, when the non-energized phase voltage obtained right after the energization mode is switched falls outside a predetermined range, the computer is configured to prohibit the setting of the voltage threshold.

13. The brushless motor driving apparatus according to claim 11 , wherein a design value has been set in advance as an initial value for the voltage threshold.

14. The brushless motor driving apparatus according to claim 10 , wherein the computer is configured to correct the upper limit of the energization amount based on a power source voltage and the temperature of the brushless motor.

15. The brushless motor driving apparatus according to claim 10 , wherein, when the brushless motor is driven under low-speed sensorless control, the computer is configured to regulate a voltage applied to the brushless motor so as to prevent a power source electric current from increasing to or exceeding an electric current corresponding to the upper limit of the energization amount.

16. The brushless motor driving apparatus according to claim 15 , wherein the computer is configured to correct the voltage applied to the brushless motor based on at least one of a power source voltage and a temperature of the brushless motor.

17. The brushless motor driving apparatus according to claim 10 , wherein, when the energization amount of the brushless motor exceeds a predetermined value, the computer is configured to gradually decrease the voltage threshold.

18. The brushless motor driving apparatus according to claim 10 , wherein, when the brushless motor stops, the computer is configured to decrease the voltage threshold by a predetermined proportion thereof when the brushless motor is actuated again.

19. The brushless motor driving apparatus according to claim 10 , wherein the computer is configured to regulate the upper limit of the energization amount only when the brushless motor rotates at a predetermined rotational speed or lower.