Vehicle drive control system, motor control device and a method for drive control of a vehicle

Abstract

A vehicle drive control system including a motor brake control device. The motor brake control device causes an AC motor to generate a braking force, and selectively executes a first three-phase (3-phase) short-circuiting mode for simultaneously turning on switching elements of an upper arm of an inverter and a second 3-phase short-circuiting mode for simultaneously turning on switching elements of a lower arm of the inverter. The first 3-phase short-circuiting mode and the second 3-phase short-circuiting mode are selectively executed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing an embodiment of the present invention;

FIG. 2 is a block diagram showing the details of a motor control in accordance with an embodiment of the invention;

FIG. 3 is a circuit diagram showing an inverter and its peripheral circuit in accordance with an embodiment of the invention;

FIG. 4 is a circuit diagram showing a field reduction circuit in accordance with an embodiment of the invention;

FIG. 5 is a circuit diagram showing another field reduction circuit in accordance with an embodiment of the invention;

FIG. 6 is a flow chart showing a processing flow of a motor brake control process in a first embodiment of the present invention;

FIG. 7 is a timing chart showing operations of the first embodiment;

FIG. 8 is a flow chart showing a processing flow of a motor brake control process in a second embodiment of the present invention;

FIG. 9 is a timing chart showing operations of the second embodiment;

FIG. 10 is a flow chart showing a processing flow of a motor brake control process in a third embodiment of the present invention;

FIG. 11 is a flow chart showing a processing flow of a motor brake control process in a fourth embodiment of the present invention; and

FIG. 12 is a flow chart showing a calculating flow of a process for calculating the lifetime consumption rates of arms of an inverter.

Claims

1. A vehicle drive control system for a vehicle having a multi-phase AC motor for selectively driving auxiliary driven wheels; the vehicle drive control system comprising: an inverter configured to supply electric power to the AC motor from the generator, the inverter having an upper arm comprising a first plurality of switching elements and a lower arm comprising a second plurality of switching elements; anda motor brake control device configured to control the inverter to generate a braking force to decrease the rotation speed of the AC motor to a target rotation speed when a predetermined condition is met;wherein the motor brake control device selectively executes a first short-circuiting mode in which the first plurality of switching elements are simultaneously turned on and a second short-circuiting mode in which the second plurality of switching elements are simultaneously turned on.

2. The vehicle drive control system according to claim 1, wherein the motor brake control device switches the first short-circuiting mode and the second short-circuiting mode until the rotation speed of the AC motor reaches the target rotation speed.

3. The vehicle drive control system according to claim 1, wherein the motor brake control device includes a motor rotation speed detector that detects the rotation speed of the AC motor, and the motor brake control device switches between the first short-circuiting mode and the second short-circuiting mode when an amount of decrease in rotation speed of the AC motor reaches a predetermined amount of decrease.

4. The vehicle drive control system according to claim 3, wherein the motor brake control device sets the predetermined amount of decrease on the basis of equal distribution of a difference between the current rotation speed and the target rotation speed.

5. The vehicle drive control system according to claim 1, wherein the motor brake control device comprises a temperature detector that detects or estimates temperatures of the switching elements of the inverter, and wherein the motor brake control device switches between the first short-circuiting mode and the second short-circuiting mode when the temperatures of the selected switching elements of the inverter reach a predetermined temperature.

6. The vehicle drive control system according to claim 1, wherein the motor brake control device selects the first short-circuiting mode or the second short-circuiting mode when the predetermined condition is satisfied, and the motor brake control device executes the selected short-circuiting mode until the rotation speed of the AC motor reaches the target rotation speed.

7. The vehicle drive control system according to claim 6, wherein the motor brake control device selects a short-circuiting mode different from the short-circuiting mode executed in the previous motor brake control.

8. The vehicle drive control system according to claim 6, wherein the motor brake control device further comprises: a temperature detector which detects or estimates temperatures of the switching elements of the inverter; anda lifetime estimating unit which estimates lifetime consumption rates of the upper and lower arms of the inverter on the basis of the temperatures detected by the temperature detector,wherein the motor brake control device selects a short-circuiting mode in which the one of the first plurality of switching elements and the second plurality of switching elements having the smaller lifetime consumption rate as estimated by the lifetime estimating unit are simultaneously turned on.

9. The vehicle drive control system according to claim 6, wherein the motor brake control device further comprises: a motor rotation speed detector that detects the rotation speed of the AC motor; anda lifetime estimating unit that estimates the lifetime consumption rates of the upper and lower arms of the inverter on the basis of the rotation speed of the motor detected by the motor rotation speed detector,wherein the motor brake control device selects a short-circuiting mode in which the one of the first plurality of switching elements and the second plurality of switching elements having the smaller lifetime consumption rate as estimated by the lifetime estimating unit are simultaneously turned on.

10. The vehicle drive control system according to claim 5, wherein the temperature detector comprises a temperature sensor provided on at least one of the upper and lower arms of the inverter.

11. The vehicle drive control system according to claim 8, wherein the temperature detector comprises a temperature sensor provided on at least one of the upper and lower arms of the inverter.

12. The vehicle drive control system according to claim 5, wherein the temperature detector comprises one temperature sensor provided at a mid point between the upper and lower arms of the inverter.

13. The vehicle drive control system according to claim 8, wherein the temperature detector comprises one temperature sensor provided at a mid point between the upper and lower arms of the inverter.

14. The vehicle drive control system according to claim 5, wherein the temperature detector comprises a current sensor which detects current of at least one of the upper and lower arms of the inverter.

15. The vehicle drive control system according to claim 8, wherein the temperature detector comprises a current sensor which detects current of at least one of the upper and lower arms of the inverter.

16. The vehicle drive control system according to claim 1, wherein the motor brake control device controls current in a field coil of the AC motor during motor brake control.

17. A motor control device for controlling a multi-phase AC motor by controlling an inverter connected to the AC motor, comprising; a motor brake control device which selectively executes a first short-circuiting mode in which switching elements of an upper arm of the inverter are simultaneously turned on and a second short-circuiting mode in which switching elements of a lower arm of the inverter are simultaneously turned on during motor brake control.

18. A vehicle comprising: an engine for driving main driving wheels;a generator driven by the engine;a multi-phase AC motor for selectively driving auxiliary driven wheels;an inverter configured to supply electric power to the AC motor from the generator, the inverter having an upper arm comprising a first plurality of switching elements and a lower arm comprising a second plurality of switching elements; anda motor brake control means for controlling the inverter to generate a braking force to decrease the rotation speed of the AC motor to a target rotation speed when a predetermined condition is met, the motor brake control means selectively executes a first short-circuiting mode in which the first plurality of switching elements are simultaneously turned on and a second short-circuiting mode in which the second plurality of switching elements are simultaneously turned on.

19. A method for drive control of a vehicle having: an engine for driving main driving wheels;a generator driven by the engine;a multi-phase AC motor for selectively driving auxiliary driven wheels;an inverter configured to supply electric power to the AC motor from the generator, the inverter having an upper arm comprising a first plurality of switching elements and a lower arm comprising a second plurality of switching elements; andthe method comprising:detecting when a predetermined condition is met;upon detection of the predetermined condition, selectively executing a first short-circuiting mode in which the first plurality of switching elements are simultaneously turned on and a second short-circuiting mode in which the second plurality of switching elements are simultaneously turned on; andcontinuing the selective execution until the rotation speed of the AC motor decreases to a target rotation speed.