Four wheel skid control system

Abstract

Abstract A FOUR WHEEL HYDRAULIC SKID CONTROL VALVING SYSTEM INCLUDING A PUMP FOR DEVELOPING A FLUID PRESSURE WHICH IS PROPORTIONAL TO THE SPEED OF AT LEAST ONE OF THE VEHICLE WHEELS AND MEANS FOR COUPLING THE FLUID PRESSURE FROM THE PUMP DIRECTLY TO BOTH THE REAR WHEEL CYLINDERS AND THE FRONT WHEEL CYLINDERS OF A FOUR WHEEL BRAKING SYSTEM. FLUID PRESSURE FROM THE PUMP IS NORMALLY BYPASSED THROUGH A PUMP RETURN AND ACCORDINGLY DOES NOT BUILD UP SUFFICIENT PRESSURE TO ACTUATE THE WHEEL BRAKE CYLINDERS. HOWEVER, WHEN BRAKING IS DESIRED, THE OPERATOR DEPRESSES THE BRAKING PEDAL AND FLUID PRESSURE FROM THE REAR MASTER CYLINDER IS APPLIED TO A SPOOL VALVE WHICH IN TURN MOVES IN SUCH A WAY AS TO THROTTLE THE FLOW OF FLUID TO THE PUMP RETURN THEREBY INCREASING THE FLUID PRESSURE IN THE SYSTEM TO A POINT SUFFICIENT TO ACTUATE THE RESPECTIVE WHEEL CYLINDERS. A CROSSOVER VALVE IS PROVIDED IN BOTH THE REAR BRAKING AND THE FRONT BRAKING PORTIONS OF THE SYSTEM. THE CROSSOVER VALVES ARE NORMALLY BIASED BY FLUID PRESSURE FROM THE RESPECTIVE SECTIONS OF THE MASTER CYLINDER TO CLOSE OFF THE FLOW OF FLUID FROM THE PUMP TO THE WHEEL BRAKES. HOWEVER, WHEN THE PUMP PRESSURE IS SUFFICIENTLY HIGH AS IS THE CASE WHEN THE VEHICLE IS IN MOTION, THE PUMP PRESSURE OVERCOMES THE PRESSURE OF THE RESPECTIVE SECTIONS OF THE MASTER CYLINDER TO MAINTAIN THE CROSSOVER VALVES IN AN OPEN CONDITION. THIS IS NOT BECAUSE THE PUMP PRESSURE EXCEEDS THE MASTER CYLINDER PRESSURE BUT RATHER BEACUSE THE EFFECTIVE AREAS FACING THE PUMP PRESSURE AND THE MASTER CYLINDER PRESSURE ARE APPROXIMATELY SEVEN TO ONE WITH THE LARGER AREA FACING THE PUMP FLUID PRESSURE. SUCH A SYSTEM IS FAIL-SAFE SINCE THE CROSSOVER VALVES WILL MOVE INTO POSITION FOR CLOSING OFF THE FLOW OF PUMP FLUID WHEN THE PUMP PRESSURE IS TOO LOW AND AT THE SAME TIME WILL COUPLE THE MASTER CYLINDER FLUID DIRECTLY TO THE REAR AND FRONT BRAKE LINES SO THAT NORMAL MANUAL BRAKING CAN BE ACHIEVED.

Inventors

• 👤 Rupert L Atkin
• 👤 Gilbert H Drutchas

Bibliographic Details