Control system for distributing braking forces applied to left and right wheels in automotive vehicles

• US 5,224,765 A
• Filed: 12/04/1991
• Issued: 07/06/1993
• Est. Priority Date: 12/21/1990
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Matsuda, Toshiro
• Primary Examiner(s): Graham, Matthew C.
• Assistant Examiner(s): SCHWARTZ, CHRISTOPHER P
• Application Number:
  US07/802,297
• Time in Patent Office: 580 Days
• Field of Search: 303/9.62, 303/9.67, 303/9.71, 303/9.73, 303/100, 303/111, 303/113 AP, 180/197
• US Class Current: 303/9.62
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B60T 8/1766 Proportioning of brake forces according to vehicle axle loads, e.g. front to rear of vehicle
• CPC Class Codes: B60T 8/246 Change of direction
• CPC Class Codes: B60T 8/266 using valves or actuators with external control means B60T8/261 takes precedence

Abstract

A control system for distributing braking forces applied to left and right wheels in an automotive vehicle, comprises two fluid pressure control valves, normally controlling a left-wheel brake fluid pressure distribution between front and rear-left wheels and a right-wheel brake fluid pressure distribution between front and rear-right wheels such that a rear-wheel brake fluid pressure is less than a front-wheel brake fluid pressure in a range above a respective critical fluid pressure at which the brake fluid pressure distribution between front and rear wheels is essentially varied, a lateral acceleration sensor for monitoring a degree of turn of the vehicle, and a set of reversible motors and return springs employed in each fluid pressure control valve for varying the respective critical fluid pressures independently of each other depending on the degree of turning such that the critical fluid pressure of the outer-wheel side is set at a higher level than the critical fluid pressure of the inner-wheel side.

Claims

1. A control system for distributing braking forces applied to left and right wheels in an automotive vehicle, comprising:

a first fluid pressure control valve for controlling left-wheel brake fluid pressure distribution between front-left and rear-left wheels such that rear-left wheel brake fluid pressure is reduced by a designated ratio when compared with front-left wheel brake fluid pressure in a range above a first critical fluid pressure at which said brake fluid pressure distribution between said front-left and rear-left wheels is essentially varied, while said rear-left wheel brake fluid pressure is equivalent to said front-left wheel brake fluid pressure in a range below said first critical fluid pressure;

a second fluid pressure control valve for controlling right-wheel brake fluid pressure distribution for front-right and rear-right wheels such that rear-right wheel brake fluid pressure is reduced by a designated ratio when compared with front-right wheel brake fluid pressure in a range above a second critical fluid pressure at which said brake fluid pressure distribution between said front-right and rear-right wheels is essentially varied, while said rear-right wheel brake fluid pressure is equivalent to said front-right wheel brake fluid pressure in a range below said second critical fluid pressure;

means for monitoring whether said vehicle turns to generate a signal representative of a turning state of said vehicle; and

means for compensating steering characteristics of said vehicle toward neutral steering during braking on turns by varying said first and second critical fluid pressures independently of each other in response to said signal representative of a turning sate of said vehicle such that a critical fluid pressure of an outer-wheel side is set at a higher level than a critical fluid pressure of an inner-wheel side.

2. The control system as set forth in claim 1, wherein:

said monitoring means includes means for detecting a degree of turn of the vehicle, and

said means for compensating varying said first and second critical fluid pressures independently of each other in dependence on said degree of turn detected by said detecting means.

3. The control system as set forth in claim 2, wherein said means for detecting said degree of turn includes a lateral acceleration sensor for monitoring lateral acceleration of said vehicle to generate a signal representative of said lateral acceleration, said detecting means determining said degree of turn on the basis of said signal from said lateral acceleration sensor.

4. The control system as set forth in claim 3, wherein a pressure difference between said first and second critical fluid pressures is varied in dependence on said degree of turn.

5. The control system as set forth in claim 4, wherein said pressure difference is increased in proportion to said degree of turn.

6. A control system for distributing braking forces applied to left and right wheels in an automotive vehicle, comprising:

a first fluid pressure control valve for controlling left-wheel brake fluid pressure distribution between front-left and rear-left wheels, such that rear-left wheel brake fluid pressure is reduced by a designated ratio when compared with front-left wheel brake fluid pressure in a range above a first critical fluid pressure at which said brake fluid pressure distribution between said front-left and rear-left wheels is essentially varied, while said rear-left wheel brake fluid pressure is equivalent to said front-left wheel brake fluid pressure in a range below said first critical fluid pressure;

a second fluid pressure control valve for controlling right-wheel brake fluid pressure distribution between front-right and rear-right wheels, such that rear-right wheel brake fluid pressure is reduced by a designated ratio when compared with front-right wheel brake fluid pressure in a range above a second critical fluid pressure at which said brake fluid pressure distribution between said front-right and rear-right wheels is essentially varied, while said rear-right wheel brake fluid pressure equivalent to said front-right wheel brake fluid pressure in a range below said second critical fluid pressure;

means for monitoring whether said vehicle turns to generate a signal representative of a turning state of said vehicle;

means for deriving a magnitude of braking force of said vehicle to generate a signal representative of said magnitude of braking force; and

means for compensating steering characteristics of said vehicle toward a neutral steering during braking on turns, by varying said first and second critical fluid pressures independently of each other in response to said signal representative of said turning sate of said vehicle, such that critical fluid pressure of an outer-wheel side is set at a higher level than critical fluid pressure of an inner-wheel side, said means for compensating being responsive to said braking force for additionally increasing both said first and second critical fluid pressures in accordance with an increase in said braking force.

7. The control system as set forth in claim 6, wherein said means for compensating varies said first and second critical fluid pressures independently of each other in linear proportion to said magnitude of braking force.

8. The control system as set forth in claim 6, wherein said means for deriving said magnitude of braking force includes a longitudinal acceleration sensor for monitoring longitudinal acceleration of said vehicle to generate a signal representative of said longitudinal acceleration, said deriving means determining said magnitude of braking force on the basis of said signal from said longitudinal acceleration sensor.

9. A control system for distributing braking forces applied to left and right wheels in an automotive vehicle, comprising:

a first fluid pressure control valve for controlling left-wheel brake fluid pressure distribution between front-left and rear-left wheels, such that rear-left wheel brake fluid pressure is reduced by a designated ratio when compared with front-left wheel brake fluid pressure in a range above a first critical fluid pressure at which said brake fluid pressure distribution between said front-left and rear-left wheels is essentially varied, while said rear-left wheel brake fluid pressure is equivalent to said front-left wheel brake fluid pressure in a range below said first critical fluid pressure;

a second fluid pressure control valve for controlling right-wheel brake fluid pressure distribution between front-right and rear-right wheels, such that rear-right wheel brake fluid pressure is reduced by a designated ratio when compared with front-right wheel brake fluid pressure in a range above a second critical fluid pressure at which said brake fluid pressure distribution between said front-right and rear-right wheels is essentially varied, while said rear-right wheel brake fluid pressure is equivalent to said front-right wheel brake fluid pressure in a range below said second critical fluid pressure;

means for detecting a degree of turn of said vehicle;

means for deriving a magnitude of braking force of said vehicle to generate a signal representative of said magnitude of braking force; and

means for compensating steering characteristics of said vehicle towards neutral steering during braking on turns, by varying said first and second critical fluid pressures independently of each other in accordance with said degree of turn, such that a critical fluid pressure of an outer-wheel side is set at a higher level than a critical fluid pressure of an inner-wheel side with a given ratio proportional to said degree of turn so as to eliminate oversteering tendencies occurring due to light braking on turns, and both of said first and second critical fluid pressures are additionally increased in accordance with an increase in said magnitude of braking force with a given increasing ratio so as to eliminate understeering tendencies occurring due to hard braking on turns.