Anti-skid brake control system for automotive vehicle with feature of variable timing of derivation of wheel acceleration data

An anti-skid brake control system for an automotive vehicle, comprising:

• a braking circuit including first and second wheel cylinders for generating a braking force for decelerating first and second vehicular wheels in response to a manual braking operation;
• first and second pressure control valves respectively disposed within said braking circuit for controlling said braking force to be generated in said wheel cylinder depending upon the vehicular braking condition, each of said first and second pressure control valves increasing said braking force in said wheel cylinder in a first mode and decreasing said braking force in said wheel cylinder in a second mode;
• a first wheel speed sensor means for monitoring rotation speed of said first vehicular wheel to produce a first wheel speed indicative signal;
• a second wheel speed sensor means for monitoring rotation speed of said second vehicular wheel to produce a second wheel speed indicative signal;
• first means for deriving first and second wheel speed data respectively on the basis of said first and second wheel speed indicative signals;
• second means for periodically deriving a first wheel acceleration data based on said first wheel speed data having a first precision level and a first lag time with respect to each of said first and second wheels;
• third means for periodically deriving a second wheel acceleration data based on said second wheel speed data having a second precision level and a second lag time, said second precision level is lower than said first precision level and second lag time is shorter than said first lag time with respect to each of said first and second wheels;
• and
• fourth means responsive to said first wheel acceleration data indicative of wheel deceleration greater than a predetermined wheel deceleration threshold, for initiating skid control cycles for said respective first and second pressure control valves, in which the operation mode of each of said pressure control valves is selectively controlled between said first mode and second mode so as to maintain wheel slippage at a predetermined optimum value according to a predetermined schedule, said fourth means further detecting a peak value of said second wheel acceleration data and causing braking pressure to increase in said first mode in each of said pressure control valves.

An anti-skid brake control system for an automotive vehicle, comprising:

• a braking circuit including a wheel cylinder for generating a braking force for decelerating a vehicular wheel in response to a manual braking operation;
• a pressure control valve disposed within said braking circuit for controlling said braking force to be generated in said wheel cylinder depending upon the vehicular braking condition, said pressure control valve increasing said braking force in said wheel cylinder in a first mode and decreasing said braking force in said wheel cylinder in a second mode;
• a sensor means for monitoring rotation speed of said vehicular wheel to produce a wheel speed indicative signal;
• first means for deriving a wheel speed data on the basis of said wheel indicative signal;
• second means for periodically deriving a wheel acceleration data on the basis of said wheel speed data;
• third means for deriving a vehicle speed representative data on the basis of said wheel speed data;
• fourth means for receiving said vehicle speed representative data and modifying the received data for producing a modified vehicle speed representative data;
• fifth means for receiving said vehicle speed representative data from said third means and said modified vehicle speed representative value for selecting a greater one of the received data to output as said vehicle speed representative data;
• and
• sixth means responsive to said wheel acceleration data indicative of wheel deceleration greater than a predetermined wheel deceleration threshold, for initiating skid control cycle in which operation mode of said pressure control valve is selectively controlled between said first mode and second mode so as to maintain wheel slippage at a predetermined optimum value according to a predetermined schedule on the basis of said wheel speed data and said selected vehicle speed representative data.