Fail-safe system in anti-skid brake control system for automotive vehicles

A fail-safe system for an anti-skid brake control system comprising:

• a hydraulic brake circuit including a wheel cylinder for applying hydraulic braking pressure for decelerating rotation of a vehicular wheel;
• a pressure control valve disposed in said brake circuit for increasing hydraulic brake pressure in said wheel cylinder in a first position, and decreasing hydraulic brake pressure in said wheel cylinder in a second position;
• an actuator associated with said pressure control valve for operating said pressure control valve between said first and second positions according to a control signal, said actuator being connected to an electric power source to receive power therefrom, said actuator operating said pressure control valve in said first position while in a nonactive state thereof and in said second position in an active state thereof;
• a sensor for detecting wheel speed and producing a sensor signal indicative of wheel speed;
• a detector for monitoring operations of components of said anti-skid brake control system and producing a fault indicative signal whenever fault in at least one of said components is detected;
• a controller receiving said sensor signal and processing the sensor signal for deriving brake-controlling parameters on the basis of said sensor signal and deriving said control signal based on said sensor signal and said brake controlling parameters, and said controller performing a first fail-safe operation for disconnecting said actuator from said power source for forcing said actuator to assume said non-active state, and a second fail-safe operation for fixedly holding said control signal at a value affecting said first position of said pressure control valve, such that, if said first fail-safe operation fails to occur, said second fail-safe operation will occur.

A fail-safe system for an anti-skid brake control system comprising:

• a hydraulic brake circuit including a wheel cylinder for applying hydraulic brake pressure to a vehicular wheel for deceleration of the latter;
• a pressure control valve disposed in said brake circuit for increasing hydraulic brake pressure in said wheel cylinder in a first position and decreasing hydraulic brake pressure in said wheel cylinder in a second position;
• an actuator cooperatively associated with said pressure control valve and variable in positions between a first inoperative position for positioning said pressure control valve in said first position and a second operative position for positioning said pressure control valve in said second position and connected to an electric power source, said actuator being responsive to a control signal to vary positions between said first inoperative position and said second operative position;
• a sensor for detecting wheel speed and producing a sensor signal indicative of wheel speed;
• a detector for monitoring operations components of said anti-skid brake control system for producing a fault indicative signal whenever fault in at least one of said components is detected;
• and
• a controller receiving said sensor signal and processing the sensor signal for deriving brake controlling parameters on the basis of said sensor signal and deriving said control signal based on said sensor signal and said brake controlling parameters, said controller being responsive to perform a first fail-safe operation for disconnecting said actuator from said electric power source, for holding said actuator in said first inoperative position, for holding said pressure control valve in said first position, and a second fail-safe operation for fixing said control signal value at a value ordering said first position of said pressure control valve, such that, if said first fail-safe operation fails to occur, said second fail-safe operation will occur.