Device/method for controlling turning behavior of vehicle

1. A vehicle turning behavior control apparatus comprising:

a controlling section to limit a vehicle turning behavior of a vehicle accompanying a steering operation, to a limit turning behavior corresponding to an actual steering speed of the steering operation, by a vehicle speed decrease, the controlling section being configured to calculate a modified steering speed from the actual steering speed, and to calculate the limit turning behavior in accordance with the modified steering speed;

wherein the vehicle turning behavior control apparatus comprises an apparatus configured to limit the turning behavior due to the steering operation to the limit turning behavior corresponding to the steering speed, by the vehicle speed decrease,

wherein the controlling section is configured to use

the actual steering speed as the modified steering speed, when the actual steering speed is increasing during a turning steering for increasing a turning amount, or

a highest value of the actual steering speed before a decrease of the actual steering speed, as the modified steering speed, when the actual steering speed is decreasing during the turning steering, so that the modified steering speed is higher than the actual steering speed,

wherein the controlling section is configured to continue a selective use of the modified steering speed at least until a start of a returning steering for decreasing the steering amount, and

wherein the controlling section is further configured to determine, from the actual steering speed, a turning steering speed which is equal to the actual steering speed during the turning steering for increasing the turning amount and which is held equal to zero during the returning steering,

to calculate the modified steering speed in accordance with the turning steering speed so that the modified steering speed is higher than the turning steering speed when the turning steering speed decreases during the turning steering for increasing the turning amount, and

to determine the limit turning behavior in accordance with the modified steering speed.

2. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to continue to use, as the modified steering speed for determining the limit turning behavior, the highest value of the actual steering speed for a predetermined time period after the start of the returning steering.

3. The vehicle turning behavior control apparatus as recited in claim 2 , wherein the controlling section is configured to make the predetermined time period longer as a state variable representing the vehicle turning behavior increases.

4. The vehicle turning behavior control apparatus as recited in claim 3 , wherein the state variable representing the vehicle turning behavior is a lateral acceleration.

5. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to decrease the limit turning behavior as the modified steering speed becomes higher.

6. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to decrease the modified steering speed used for determining the limit turning behavior, at a predetermined time rate of change at the start of and after an end of the vehicle speed decrease for limiting the vehicle turning behavior to the limit turning behavior.

7. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to terminate the vehicle speed decrease for limiting the vehicle turning behavior to the limit turning behavior when a target vehicle speed to be used as a target in the vehicle speed decrease for limiting the vehicle turning behavior to the limit turning behavior becomes higher than a vehicle speed of the vehicle.

8. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to terminate the vehicle speed decrease for limiting the vehicle turning behavior to the limit turning behavior when a target deceleration to be used as a target in the vehicle speed decrease for limiting the vehicle turning behavior to the limit turning behavior becomes smaller than or equal to zero.

9. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to decrease the limit turning behavior corresponding to the modified steering speed as the vehicle speed of the vehicle becomes higher.

10. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to decrease the limit turning behavior corresponding to the modified steering speed as a steering angle becomes smaller.

11. A vehicle turning behavior control apparatus comprising:

a controlling section which is configured to determine an actual steering speed, to determine a limit turning behavior dependent on the actual steering speed, to produce a control signal in accordance with the limit turning behavior, to decrease a vehicle speed by controlling the vehicle speed in accordance with the control signal, and thereby to limit a vehicle turning behavior to the limit turning behavior, the controlling section being further configured to produce a signal representing a modified steering speed in accordance with the actual steering speed, and to modify the control signal in accordance with the modified steering speed, the controlling section being further configured to make the modified steering speed higher than the actual steering speed when the actual steering speed decreases during a turning steering in a steering amount increasing direction;

wherein the controlling section is configured to calculate, as the modified steering speed, a peak-hold turning steering speed which is increased with the actual steering speed so that the peak-hold turning steering speed remains equal to the actual steering speed while the actual steering speed is increasing during the turning steering, and which is held equal to a peak value which is the highest value of the actual steering speed before a decrease of the actual steering speed while the actual steering speed during the turning steering is decreasing,

wherein the controlling section is configured to hold the peak-hold turning steering speed equal to the peak value until a start of the returning steering, and

wherein the controlling section is further configured to determine, from the actual steering speed, a turning steering speed which is equal to the actual steering speed during the turning steering in the steering amount increasing direction and which is held equal to zero during the returning steering,

to calculate the modified steering speed in accordance with the turning steering speed so that the modified steering speed is higher than the turning steering speed when the turning steering speed decreases during the turning steering, and

to determine the limit turning behavior in accordance with the modified steering speed.

12. The vehicle turning behavior control apparatus as recited in claim 11 , wherein the controlling section is configured to determine a target deceleration in accordance with the limit turning behavior, to control the vehicle speed by producing the control signal in accordance with the target deceleration, and thereby to limit the vehicle turning behavior to the limit turning behavior, the controlling section being configured to modify the target deceleration in accordance with the modified steering speed, and to control a vehicle driving/braking force by producing the control signal in accordance with the target deceleration.

13. A vehicle turning behavior control process comprising:

a first operation of determining an actual steering speed, determining a limit turning behavior dependent on the actual steering speed, producing a control signal in accordance with the limit turning behavior, decreasing a vehicle speed by controlling the vehicle speed in response to the control signal and limiting a vehicle turning behavior to the limit turning behavior,

the vehicle turning behavior control process further comprising a second operation of producing a signal representing a modified steering speed in accordance with the actual steering speed, and modifying the control signal in accordance with the modified steering speed, in the second operation, the modified steering speed being made higher than the actual steering speed when the actual steering speed decreases during a turning steering in a steering amount increasing direction;

wherein the modified steering speed is increased with the actual steering speed so that the modified steering speed remains equal to the actual steering speed while the actual steering speed is increasing during the turning steering, and the modified steering speed is held equal to a peak value which is the highest value of the actual steering speed before a decrease of the actual steering speed while the actual steering speed during the turning steering is decreasing, and the modified steering speed is held equal to the peak value until a start of the returning steering, and

wherein a turning steering speed is determined from the actual steering speed, the turning steering speed being equal to the actual steering speed during the turning steering in the steering amount increasing direction and being held equal to zero during the returning steering,

the modified steering speed is calculated in accordance with the turning steering speed so that the modified steering speed is higher than the turning steering speed when the turning steering speed decreases during the turning steering in the steering amount increasing direction, and

the limit turning behavior is determined in accordance with the modified steering speed.

14. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to calculate, as the modified steering speed, a peak-hold turning steering speed which is increased with the actual steering speed so that the peak-hold turning steering speed is equal to the actual steering speed while the actual steering speed is increasing during the turning steering, and which is held equal to a peak value which is the highest value of the actual steering speed before the decrease of the actual steering speed while the actual steering speed during the turning steering is decreasing, and the controlling section is configured to hold the peak-hold turning steering speed equal to the peak value until the start of the returning steering.

15. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to start a vehicle speed decrease control to decrease a vehicle speed when the vehicle turning behavior exceeds the limit turning behavior.

16. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to start a vehicle speed decrease control to decrease a vehicle speed when a lateral acceleration of the vehicle representing the vehicle turning behavior exceeds a limit lateral acceleration representing the limit turning behavior.

17. The vehicle turning behavior control apparatus as recited in claim 16 , wherein the limit lateral acceleration is increased with increase in the steering speed.

18. The vehicle turning behavior control apparatus as recited in claim 1 , wherein the controlling section is configured to discriminate a turning steering operation of turning a steering wheel of the vehicle away from a neutral position from a returning steering operation of turning the steering wheel toward the neutral position, to detect an instant of the start of the returning steering operation, and to hold the modified steering speed constantly equal to the highest value of the actual steering speed before the decrease of the actual steering speed while the actual steering speed during the turning steering is decreasing.

19. A vehicle turning behavior control apparatus comprising:

a controlling section to limit a vehicle turning behavior of a vehicle accompanying a steering operation, to a limit turning behavior corresponding to an actual steering speed of the steering operation, by a vehicle speed decrease, the controlling section being configured

to determine, from the actual steering speed, a turning steering speed which is equal to the actual steering speed during a turning steering operation of turning a steering wheel of the vehicle away from a neutral position and which is held equal to zero during a returning steering operation of turning the steering wheel toward the neutral position,

to determine a modified steering speed in accordance with the turning steering speed, and

to determine the limit turning behavior in accordance with the modified steering speed,

the controlling section being further configured to make the modified steering speed higher than the turning steering speed when the turning steering speed decreases during the turning steering operation.

20. The vehicle turning behavior control apparatus as recited in claim 19 , wherein the controlling section is configured to calculate a product quantity of a steering angle and the actual steering speed which is a derivative of the steering angle, to set the turning steering speed equal to the actual steering speed when the product quantity is positive, and to set the turning steering speed equal to zero when the product quantity is negative.