Differential limiting force control system responsive to vehicle speed and steering angle

• US 5,075,854 A
• Filed: 08/09/1990
• Issued: 12/24/1991
• Est. Priority Date: 10/09/1987
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Imaseki, Takashi, Kobari, Yuji
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): TRANS, VINCENT N
• Application Number:
  US07/565,207
• Time in Patent Office: 502 Days
• Field of Search: 364/424.05, 364/426.01, 364/426.03, 364/424.1, 74/710, 74/710.5, 74/711, 74/713, 180/248, 180/79.1, 180/197
• US Class Current: 701/36
• CPC Class Codes: B60K 23/04 for differential gearing
• CPC Class Codes: Y10T 74/19172 Reversal of direction of power flow changes power transmission to alternate path
• CPC Class Codes: Y10T 74/19177 Input and output exchange functions

Abstract

A differential limiting force control system for controlling a slip limiting force by controlling an engagement force of a clutch assembly of a limited slip differential provided between left and right drive wheels of a vehicle includes a control unit having a basic control section for increasing the differential limiting force with increase of a vehicle speed, and an adjusting section for decreasing the differential limiting force when a steering angle is equal to or lower than a predetermined angle, or when a steering angular speed is equal to or higher than a predetermined angle.

Claims

1. A differential limiting force control system for a vehicle, comprising:

a differential driving mechanism provided between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a vehicle speed of the vehicle and producing a first signal representing said vehicle speed;

means for sensing a steering condition of the vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of the vehicle, the steering speed being an angular speed of a steering wheel of the vehicle;

determining means for determining a command value in accordance with said first signal;

controlling means for producing said control signal in accordance with said first signal; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value;

wherein said determining means increases said command value when said vehicle speed increases, and said controlling means increases a differential limiting force for limiting the differential action of said differential mechanism by varying said control signal when said vehicle speed increases.

2. A control system according claim 1 wherein said differential limiting means comprises a clutch assembly provided between the left and right drive wheels, and operated by a fluid pressure which is controlled by said control signal.

3. A control system according to claim 1 wherein said steering condition sensing means comprises means for sensing movement of a predetermined movable member of a steering system of the vehicle to determine said steering speed.

4. A control system according to claim 1 wherein said determining means comprises means for producing a first command signal in accordance with said vehicle speed, said decreasing means comprises means for producing a second command signal which is set equal to zero when said steering speed is smaller than said predetermined steering speed value, and which is set equal to a predetermined command value when said steering speed is equal to or greater than said steering speed value, and subtracting means for producing a final command signal by subtracting said second command signal from said first command signal.

5. A control system according to claim 4 wherein said first command signal producing means produces said first command signal so that a magnitude of said first command signal is zero when said vehicle speed is lower than a predetermined first vehicle speed value, increases from zero to a first high value as said vehicle speed increases from said first vehicle speed value to a predetermined second vehicle speed value, and is equal to said first high value when said vehicle speed is higher than said second vehicle speed value.

6. A control system according to claim 5 wherein said steering condition sensing means comprises a steering angle sensor for sensing a steering wheel angle of the steering wheel of the vehicle, and differentiating means for determining said steering speed which is a time derivative of said steering wheel angle.

7. A control system according to claim 1 wherein said decreasing means comprises means for comparing said steering speed with said predetermined steering speed value.

8. A differential limiting force control system for a vehicle, comprising:

a differential driving mechanism provided between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a vehicle speed of the vehicle and producing a first signal representing said vehicle speed;

means for sensing a steering condition of the vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of the vehicle, said steering speed being an angular speed of a steering wheel of the vehicle;

determining means for determining a command value in accordance with said first signal;

controlling means for producing said control signal in accordance with said command value; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value;

wherein said decreasing means decreases a differential limiting force for limiting the differential action of said differential mechanism by decreasing said command value both when said steering wheel of the vehicle is turned away from a straight ahead position of said steering wheel, and when said steering wheel is returned toward the straight ahead position, as long as said angular speed of said steering wheel is equal to or greater than said predetermined steering speed value.

9. A control system according to claim 8 wherein said steering condition sensing means comprises a steering angle sensor for sensing a steering angle of the vehicle, and differentiating means for determining said steering speed which is a time rate of change of said steering angle, and said decreasing means decreases said differential limiting force when an absolute value of said steering speed is equal to or higher than said predetermined steering speed value.

10. A differential limiting force control system for a vehicle, comprising:

a differential driving mechanism provided between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a vehicle speed of the vehicle and producing a first signal representing said vehicle speed;

means for sensing a steering condition of the vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of the vehicle, the steering speed being an angular speed of a steering wheel of the vehicle;

determining means for determining a command value in accordance with said first signal;

controlling means for producing said control signal in accordance with said command value; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value;

wherein said decreasing means decreases a differential limiting force for limiting the differential action of said differential mechanism by decreasing said command value only when said steering wheel is turned away from a straight ahead position of said steering wheel, and simultaneously said angular speed of said steering wheel is equal to or greater than said predetermined steering speed value.

11. A control system according to claim 10 wherein said steering condition sensing means comprises a steering angle sensor for sensing a steering wheel angle of said steering wheel, and differentiating means for determining a time rate of change of said steering wheel angle, and said decreasing means comprises discriminating means for determining whether said steering wheel is turned away from said straight ahead position or not, by determining whether said steering wheel angle is increasing or not.

12. A differential limiting force control system for a vehicle, comprising:

a differential driving mechanism provided between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a vehicle speed of the vehicle and producing a first signal representing said vehicle speed;

means for sensing a steering condition of the vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of the vehicle, said steering speed being an angular speed of a steering wheel of the vehicle;

determining means for determining a command value in accordance with said first signal;

controlling means for producing said control signal in accordance with said command value; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value;

wherein said decreasing means decreases a differential limiting force for limiting the differential action of said differential mechanism by decreasing said command value only when a steering wheel angle of said steering wheel is equal to or smaller than a predetermined steering angle value.

13. A differential limiting force control system for a vehicle, comprising:

a differential driving mechanism provided between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a vehicle speed of the vehicle and producing a first signal representing said vehicle speed;

means for sensing a steering condition of the vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of the vehicle;

determining means for determining a command value in accordance with said first signal;

controlling means for producing said control signal in accordance with said command value; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value;

wherein said determining means includes means for decreasing said command value with a decrease in said vehicle speed even when the steering angle of said vehicle is held equal to zero, to drive the vehicle straight, said controlling means includes means for decreasing a differential limiting force for limiting the differential action of said differential mechanism with a decrease in said vehicle speed by varying said control signal even when the steering angle of said vehicle is held equal to zero, to drive said vehicle straight.

14. A differential limiting force control system for a vehicle, comprising:

a differential mechanism provided between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a speed of the vehicle and producing a first signal representing said vehicle speed;

means for sensing a steering condition of the vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of the vehicle, the steering condition sensing means comprising a steering angle sensor for sensing a steering wheel angle of the vehicle;

determining means for determining a command value in accordance with said first signal, the determining means comprising a first function generating means for producing a first command signal whose magnitude is zero when said vehicle speed is lower than a predetermined first vehicle speed value, and which increases from zero to a first high value as said vehicle speed increases from said first vehicle speed value to a second vehicle speed value, and is equal to said first high value when said vehicle speed is higher than said second vehicle speed value, said determining means further comprising means for producing a final command signal whose magnitude is equal to a difference obtained by subtracting the magnitude of said second command signal from the magnitude of said first command signal;

controlling means for producing said control signal in accordance with said command value; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value, the decreasing means comprising differentiating means for determining a time derivative of said steering wheel angle, means for determining an absolute value of said time derivative and second function generating means for producing a second command signal whose magnitude is zero when said absolute value of said time derivative is smaller than a predetermined angular speed value, and is equal to a second high value when said absolute value of said time derivative is higher than said predetermined angular speed value.

15. A differential limiting force control system for a vehicle, comprising:

a differential mechanism provided between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a speed of the vehicle and producing a first signal representing the speed of said vehicle;

means for sensing a steering condition of said vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of the vehicle;

said steering condition sensing means comprising a steering angle sensor for sensing a steering wheel angle of the vehicle;

determining means for determining a command value in accordance with said first signal, said determining means comprising first function generating means for producing a first command signal whose magnitude is zero when said vehicle speed is lower than a predetermined first vehicle speed value and increase from zero to a first high value as said vehicle speed increases from said first vehicle speed value to a second vehicle speed value and is equal to said higher value when said vehicle speed is higher than said second vehicle speed value, said determining means further including means for producing a final command signal whose magnitude is equal to a difference obtained by subtracting the magnitude of the second command signal from the magnitude of the first command signal;

controlling means for producing said control signal in accordance with said command value; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value, said decreasing means comprising comparing means for comparing said steering wheel angle with a predetermined angle value and means for producing a second command signal whose magnitude is zero when said steering wheel angle is equal to or lower than said predetermined angle value, and equal to a second high value when said steering wheel angle is higher than said predetermined angle value.

16. A differential limiting force control system for a vehicle, comprising;

a differential mechanism between the left and right drive wheels of the vehicle, said differential mechanism comprising means for limiting a differential action in accordance with a control signal;

means for sensing a speed of the vehicle and producing a first signal representing said vehicle speed;

means for sensing a steering condition of the vehicle and producing a second signal representing said steering condition, said steering condition being a steering speed of said vehicle, said steering condition sensing means further including a steering angle sensor for sensing a steering wheel angle of the vehicle;

determining means for determining a command value in accordance with the first signal, said determining means including a first function generating means for producing a first command signal whose magnitude is zero when said vehicle speed is lower than a predetermined first vehicle speed value, increases from zero to a first high value as said vehicle speed increases from said first vehicle speed value to a second vehicle speed value, and is held equal to said first high value when said vehicle speed is higher than said second vehicle speed value;

controlling means for producing said control signal in accordance with said command value; and

decreasing means for decreasing said command value when said steering speed is equal to or greater than a predetermined steering speed value, said decreasing means further including differentiating means for determining a time derivative of said steering wheel angle, discriminating means for determining if said steering wheel angle is increasing, and second function generating means for producing a second command signal whose magnitude is normally equal to a second high value only when said steering angle is increasing and at the same time said time derivative of said steering wheel angle is higher than a predetermined value.