Synchronizing circuit for four-wheel antilock brake control system

Abstract

Abstract A FOUR-WHEEL ANTILOCK BRAKE CONTROL SYSTEM HAS AT LEAST THREE WHEEL SPEED SENSORS, EACH HAVING ONE SIDE GROUNDED. ONE SENSOR FOR A NON-DRIVEN WHEEL IS MONITORED TO ASSURE CIRCUIT CONTINUITY BETWEEN THE SENSOR AND THE CONTROL CIRCUIT. ALL THE SENSOR OUTPUTS ARE MONITORED BY A SELF-CHECK CIRCUIT TO DETECT ANY SENSOR MALFUNCTION AND TO DISABLE THE CONTROL IN THE EVENT OF A MALFUNCTION. THE SELF-CHECK CIRCUIT FURTHER DISABLES THE CONTROL IF A SUBSTANTIALLY ZERO REAR WHEEL SPEED IS INDICATED DURING PERIODS OF SUBSTANTIAL FRONT WHEEL SPEED, THUS PREVENTING THE OCCURENCE OF ANTILOCK BRAKE CYCLING IN THE FRONT WHEELS WHEN THE REAR WHEELS APPROACH A LOCK-UP CONDITION. THE SELF CHECK CIRCUIT FURTHER DISABLES THE CONTROL WHEN ANY BRAKE MODULATOR IS NOT IN ITS NORMAL POSITION PRIOR TO A REQUEST BY THE CONTROL FOR ANTILOCK OPERATION. IN EACH CASE, THE SELF-CHECK CIRCUIT WILL DISABLE THE CONTROL ONLY AFTER SOME PREDETERMINED TIME DELAY. TWO DIFFERENT TIME DELAYS ARE ACCOMPLISHED USING A SINGLE TIMING CAPACITOR. A CIRCUIT IS PROVIDED TO RELEASE THE REAR BRAKES BRIEFLY WHEN AND IF THE FRONT BRAKES ARE RELEASED FIRST BY THE ANTILOCK CONTROL.

Inventors

• 👤 Douglas W Sweet

Bibliographic Details