Brake fluid pressure control apparatus

A brake fluid pressure control apparatus to be provided on a brake fluid pressure control circuit for antiskid control of wheeled vehicles, the brake fluid pressure control circuit including a brake pedal for initiating braking of the wheels, a master cylinder for providing brake fluid pressure to the circuit, and wheel cylinders for providing brake fluid pressure to brakes of the wheels, the brake fluid pressure control apparatus comprising:

• a first valve which opens when brake fluid pressure decreases, and closes when brake fluid pressure increases;
• a reservoir for receiving brake fluid;
• a pump having an intake side for taking in brake fluid from said reservoir, and an outlet side for discharging brake fluid;
• a flow control means communicating with the master cylinder, the wheel cylinders, the reservoir, and the pump, said flow control means controlling the fluid flow so that the fluid pressure of said wheel cylinders undergo pressure decrease and pressure increase;
• said flow control means comprising:
• a casing comprising:
• a master cylinder communication port communicating to said master cylinder;
• a wheel cylinder communication port communicating to said wheel cylinders;
• a reservoir communication port communicating with the intake side of said pump and said reservoir via said first valve;
• and
• a pump communication port which connects to the discharge side of said pump;
• a spool, providing as a movable element inside of said casing;
• said spool having an interior orifice on an interior portion thereof,
• a spring which provides force to said spool in one direction,
• wherein said spool is in a motionless state in which force is provided in one direction by said spring, connects said master cylinder communication port and said wheel cylinder communication port;
• and during brake fluid pressure decrease, moves by means of a difference in pressure generated on body sides by means of the opening of said first valve restricts the communication between said master cylinder communication port and said wheel cylinder communication port, connects said wheel cylinder communication port and said reservoir communication port, and restricts the communication between said pump communication port and said master cylinder communication port;
• said spool which, during brake fluid pressure decrease, when said first valve is in the open state, supplies brake fluid discharged from said pump from said pump communication port to said reservoir communication port via said interior orifice at roughly a fixed flow amount;
• and said spool during brake fluid pressure increase, when said first valve returns to a closed condition, supplies brake fluid discharged from said pump from said communication port to said wheel cylinder communication port a roughly a fixed flow amount via said interior orifice;
• a first bypass channel which joins the intake side and discharge side of said pump in a bypass manner;
• and
• a relief valve provided in said first bypass channel, which, in the case when brake fluid pressure between the discharge side of said pump and said flow control means exceeds a predetermined pressure, controls the flow amount of brake fluid to said flow control means by means of allowing surplus brake fluid pressure to escape to the intake side of said pump.