Skid control valve assembly

Abstract

Abstract A skid control valve assembly including a force motor assembly for controlling the skidding of a vehicle under braked conditions, the force motor assembly being provided with variable duty cycle pulses from a control system which provides a signal wave form to control the position of the fluid pressure controlling device in one of three conditions; the first being ''''dump'''' mode of operation wherein the force motor is controlled to preclude braking pressure from being supplied to the wheels of the vehicle, the ''''hold'''' mode of operation wherein the braking force present at the time the system goes into the hold mode of operation is maintained, and the ''''return'''' mode of operation wherein braking pressure is returned to the vehicle wheels. The control system is effectively responsive, during the deceleration portion of the wheel cycle, to a critical slip signal, the signal being generated in response to a sensed difference between a hypothetical vehicle deceleration, as approximated by a decreasing ramp signal, and the vehicle wheel speed. The system is also responsive during the acceleration portion of the wheel cycle, to the sensing of certain conditions of a wheel acceleration signal and a change in sign of the rate of change of wheel acceleration. The signal from the circuit described above is fed to a logic circuit which controls the operation of a variable duty cycle pulse generator, the duty cycle of the pulse generator being modulated in accordance with the sensed condition at the wheel, the initial, increasing portion of the duty cycle range creating the dump mode of operation, the intermediate, constant range duty cycle creating the hold mode of operation and the final, decreasing duty cycle range providing the return mode of operation. The force motor includes a movable element in the form of a nonferrous cup and coil which may be operated in two fixed positions and a third variable position, the coil being energized with the variable duty cycle pulses to cause the pressure controlling plunger to be either in the return or deactuated position where no signal is provided from the control circuit or a decreasing-to-a-minimum duty cycle signal, a skid signal or dump mode of operation which disconnects the manually actuated brake cylinder hydraulically to the wheel cylinders to provide substantially zero braking pressure, and the hold position which maintains the pressure being fed to the wheels at the time the hold position is achieved. This latter position is actually a range of positions for the armature, the position being selected as a function of the position of the armature when the hold mode is entered.

Inventors

• 👤 F Hill
• 👤 H Riordan
• 👤 P Every

Bibliographic Details