Method and circuit configuration for controlling an anti-lock brake system for automotive vehicles with all-wheel drive

A method for controlling an anti-lock brake system for automotive vehicles with all-wheel drive, wherein electric signals representative of the rotational behavior of the vehicle wheels are generated, wherein after the electronic processing and logic combining of said signals braking pressure control signals are derived which, upon the occurrence of a tendency to lock, serve to reduce the braking pressure or to keep it constant and to re-increase it at a later time, and wherein wheel slip and wheel acceleration as well as deceleration are evaluated as control criteria, the individual wheel speeds being compared with a vehicle reference speed with is defined in consideration of the rotational behavior of all wheels and which serves as a reference value for the control of the braking pressure of the single wheels, said method comprising the steps of:

• modifying the control concept until a specific point of time in the event of a wheel rotational behavior typical of spinning or a spinning tendency;
• and deleting the instantaneous wheel slip as a control criterion for this time span and wherein the wheel acceleration or the wheel deceleration solely becomes decisive for the braking pressure control;
• wherein after at least one vehicle wheel has re-adopted a stable rotational behavior, this wheel takes charge of leading the vehicle reference speed (V.sub.REF);
• and,
• wherein the braking pressure reduction is delayed 5 msecs to 70 msecs depending on the wheel rotational behavior, a shorter delay time being selected in the event of little wheel deceleration, in the event of a deceleration below 1 g to 2 g approximately, while a longer delay time is selected in the event of great wheel deceleration.

A circuit configuration for implementing a method for controlling an anti-lock brake system for automotive vehicles with all-wheel drive, comprising sensor means operatively coupled to a motor vehicle for the generation of electric signals representative of the rotational behavior of the vehicle wheels, and comprising circuit means for the conditioning, processing and logic combining of the sensor signals and for the generation of braking pressure control signals as a function of slip and deceleration or acceleration of the individual wheels, wherein a vehicle reference speed is derived from the information about the rotational behavior of the wheels and which is compared with the instantaneous speed of the individual vehicle wheels, and comprising switching means for influencing the control upon the occurrence of spinning tendencies, wherein upon detection of a wheel rotational behavior typical of spinning or a spinning tendency and upon attainment of predetermined start conditions and attainment or exceeding of predetermined limit values,

• said switching means are operable to effect a change-over of a control cycle to a second control concept in which the instantaneous wheel slip is deleted as a control signal whereby the braking pressure is controllable as a function of the wheel acceleration and wheel deceleration;
• wherein the switching means are operable to cause a switching back of the control cycle to a normal control, in which the braking pressure is controllable in dependence on wheel slip and wheel deceleration or wheel acceleration, as soon as at least one vehicle wheel shows a stable rotational behavior;
• and,
• wherein a digital counter is included as a feedback integrator means (8) which, as soon as the start conditions are fulfilled, is put into operation and which integrates the rise, i.e., the differential quotient (b.sub.REF), of the vehicle reference speed (V.sub.REF) with a predetermined time constant.