Brake control system for preventing rear wheel lock in automotive vehicles

• US 5,217,287 A
• Filed: 12/04/1991
• Issued: 06/08/1993
• 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): Oberleitner, Robert J.
• Assistant Examiner(s): Muratori, Alfred
• Application Number:
  US07/802,296
• Time in Patent Office: 552 Days
• Field of Search: 303/9.62, 303/9.67, 303/9.73, 303/24.1, 303/97, 303/104, 303/105, 303/107, 303/113 AP
• US Class Current: 303/113.5
• CPC Class Codes: B60T 8/1764 Regulation during travel on surface with different coefficients of friction, e.g. between left and right sides, mu-split or between front and rear
• 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 8/266 using valves or actuators with external control means B60T8/261 takes precedence

Abstract

A brake control system for preventing a rear-wheel lock in an automotive vehicle comprises a fluid pressure control valve controlling a brake fluid pressure distribution between front and rear wheels such that a rear wheel-cylinder brake fluid pressure is kept substantially constant in a range above a critical fluid pressure at which the brake fluid pressure distribution is essentially varied, a longitudinal acceleration sensor for monitoring a deceleration of the vehicle body, and a set of reversible motor and return spring for increasing the critical fluid pressure in accordance with an increase in the deceleration of the vehicle body only when the deceleration is increased.

Claims

1. A brake control system for preventing a rear-wheel lock in an automotive vehicle, comprising:

a fluid pressure control valve for controlling brake fluid pressure distribution between front and rear wheels such that a rear wheel-cylinder brake fluid pressure is kept substantially constant after said rear wheel-cylinder brake fluid pressure reaches a critical fluid pressure;

means for monitoring a deceleration exerted on said vehicle; and

means for varying said critical fluid pressure in accordance with said deceleration such that critical fluid pressure varies in a non-linear fashion asymptotically to a given ideal brake fluid pressure distribution characteristic curve wherein said front and rear wheels are simultaneously locked, while keeping said critical fluid pressure at a level lower than said ideal brake fluid pressure distribution characteristic curve.

2. A brake control system as recited in claim 1, wherein said means for varying said critical fluid pressure sets said critical fluid pressure in said fluid pressure control valve at a fluid pressure which is downwardly offset from a rear wheel-cylinder brake fluid pressure indicated by said ideal brake fluid pressure distribution characteristic curve by an offset value which is based upon pressure fluctuations in said fluid pressure control valve.

3. A brake control system for preventing a rear-wheel lock in an automotive vehicle, comprising:

a cut-off type fluid pressure control valve for controlling brake fluid pressure distribution between front and rear wheels, such that a rear wheel-cylinder brake fluid pressure is kept substantially constant after said rear wheel-cylinder brake fluid pressure reaches a critical fluid pressure so that front-wheel lock gets priority over rear-wheel lock;

means for cyclically monitoring a deceleration exerted on said vehicle at a controlled cycle to generate a deceleration indicative signal; and

means for varying said critical fluid pressure in accordance with said deceleration such that said critical fluid pressure varies in a non-linear fashion asymptotically to a given ideal brake fluid pressure distribution characteristic curve wherein said front and rear wheels are simultaneously locked, while keeping said critical fluid pressure at a level lower than said ideal brake fluid distribution characteristic curve by designating a ratio based on fluctuations in said rear wheel-cylinder brake fluid pressure generated by said fluid pressure control valve.

4. A brake control system as recited in claim 3, wherein said means for varying said critical fluid pressure sets said critical fluid pressure in said fluid pressure control valve at a fluid pressure which is downwardly offset from a rear wheel-cylinder brake fluid pressure indicated by said ideal brake fluid pressure distribution characteristic curve by an offset value which is based upon pressure fluctuations in said fluid pressure control valve.

5. A brake control system as recited in claim 4, wherein said deceleration monitoring means includes a longitudinal acceleration sensor for monitoring a longitudinal acceleration exerted on said vehicle to generate a signal representative of the longitudinal acceleration, said deceleration monitoring means determining said deceleration on the basis of said signal from said longitudinal acceleration sensor and wherein said means for varying said critical fluid pressure varies said critical fluid pressure in proportion to a square root of said deceleration.