Anti-skid brake system

An anti-skid brake system for a vehicle, comprising:

• a master cylinder generating a hydraulic braking pressure in response to operation of a brake operating member of the vehicle;
• at least one brake cylinder for applying a brake to a wheel of the vehicle;
• a primary fluid passage for connecting said at least one brake cylinder and said master cylinder;
• a reservoir for storing a brake fluid;
• a solenoid-operated directional control valve disposed in said primary fluid passage for providing communication of said at least one brake cylinder selectively with either said master cylinder or said reservoir;
• a control device sensing a skidding condition of said wheel and controlling said directional control valve according to the sensed skidding condition of the wheel;
• a restrictor disposed in said primary fluid passage in series connection with said directional control valve;
• a shut-off valve disposed in said primary fluid passage in parallel connection with said restrictor and controlled by said control device, said shut-off valve being normally in an open position thereof, and brought into a closed position thereof at the time when said control device has started to activate said directional control valve for preventing said wheel from skidding;
• and
• a single solenoid connected to said control device, said directional control valve and said shut-off valve both being operated when said solenoid is energized;
• and wherein said directional control valve comprises:
• a housing having a valve chamber, and a first passage, a second passage and a third passage communicating with said master cylinder, said reservoir and said at least one brake cylinder, respectively, said third passage being kept in communication with said valve chamber, said primary fluid passage comprising said valve chamber, and said first and third passages;
• a cylindrical member axially movably received in said valve chamber;
• first and second valving members disposed in said cylindrical member movably in an axial direction of the cylindrical member, said first and second valving members being movable away from each other within a predetermined range of distance therebetween;
• a first spring biasing said first and second valving members in opposite directions away from each other in said axial direction;
• a first valve seat formed in a portion of said housing opposite to said first valving member, said first passage being open in said first valve seat;
• a second valve seat formed in another portion of said housing opposite to said second valving member, said second passage being open in said second valve seat;
• and
• a second spring biasing said cylindrical member toward said second valve seat with a biasing force greater than a biasing force of said first spring, to normally hold said second valving member seated on said second valve seat, and said first valving member away from said first valve seat;
• said solenoid being supported by said housing and connected to said control device, said solenoid cooperating with said housing to generate a first magnetic force which is greater than a difference between the biasing forces of said first and second springs but smaller than a sum of said biasing forces, and a second magnetic force which is greater than said sum, said first magnetic force causing said first valving member to be seated on said first valve seat while holding said second valving member seated on said second valve seat, and said second magnetic force causing said second valving member to be separated from said second valve seat while holding said first valving member seated on said first valve seat.

A fluid control device including a solenoid-operated directional control valve;

• a solenoid-operated shut-off valve;
• and a restrictor disposed in parallel connection with said shut-off valve;
• and wherein said directional control valve comprises:
• a housing having a valve chamber, and a first passage, a second passage and a third passage communicating with respective elements in a pressure-operated system;
• a cylindrical member axially movably received in said valve chamber;
• first and second valving members disposed in said cylindrical member movably in an axial direction of the cylindrical member, said first and second valving members being movable away from each other within a predetermined range of distance therebetween;
• a first spring biasing said first and second valving members in opposite directions away from each other in said axial direction;
• a first valve seat formed in a portion of said housing opposite to said first valving member, said first passage being open in said first valve seat;
• a second valve seat formed in another portion of said housing opposite to said second valving member, said second passage being open in said second valve seat;
• a second spring biasing said cylindrical member toward said second valve seat with a biasing force greater than a biasing force of said first spring, to normally hold said second valving member seated on said second valve seat, and said first valving member away from said first valve seat;
• a solenoid supported by said housing and connected to said control device, said solenoid cooperating with said housing to generate a first magnetic force which is greater than a difference between the biasing forces of said first and second springs but smaller than a sum of said biasing forces, and a second magnetic force which is greater than said sum, said first magnetic force causing said first valving member to be seated on said first valve seat while holding said second valving member seated on said second valve seat, and said second magnetic force causing said second valving member to be separated from said second valve seat while holding said first valving member seated on said first valve seat;
• and
• said shut-off valve being connected with said directional control valve through one of said first and second passages, and comprising a valve seat formed in a portion of said housing which defines a part of said one of the first and second passages, said portion of the housing being magnetized by said solenoid upon energization thereof, said shut-off valve further comprising a ball made of a magnetic material which is disposed opposite to and normally spaced from said valve seat, said ball being seated on said valve seat with a magnetic force upon energization of said solenoid.

An anti-skid brake system for a vehicle, comprising:

• a master cylinder generating a hydraulic braking pressure in response to operation of a brake operating member of the vehicle;
• at least one brake cylinder for applying a brake to a wheel of the vehicle;
• a primary fluid passage for connecting said at least one brake cylinder and said master cylinder;
• a reservoir for storing a brake fluid;
• a solenoid-operated directional control valve disposed in said primary fluid passage for providing communication of said at least one brake cylinder selectively with either said master cylinder or said reservoir;
• a control device sensing a skidding condition of said wheel and controlling said directional control valve according to the sensed skidding condition of the wheel;
• a restrictor disposed in said primary fluid passage between and in series connection with said master cylinder and said directional control valve;
• a shut-off valve disposed in said primary fluid passage in parallel connection with said directional control valve and said restrictor and controlled by said control device, said shut-off valve being normally in an open position thereof, and brought into a closed position thereof at the time when said control device has started to activate said directional control valve for preventing said wheel from skidding;
• and
• a single solenoid connected to said control device, said directional control valve and said shut-off valve both being operated when said solenoid is energized.