Hydraulic pressure control valve and vehicle brake device using the same

A vehicle brake device comprising:

• a hydraulic pressure control device, including a housing formed with an input port connected to a hydraulic pressure source, an output port connected to wheel brakes, and a discharge port, a spool valve mounted in said housing so as to be acted by a brake operating force, a first valve portion formed between said spool valve and said discharge port so as to close to disconnect said output port from said discharge port when said spool valve advances, and when the spool valve further makes advancing displacement, a second valve portion formed between said spool valve and said input port so as to open when said spool valve advances further, whereby bringing said input port into communication with said output port, the degrees of opening of said respective valve portions being adjusted according to the amount of displacement of said spool valve, whereby outputting a hydraulic pressure balancing with the brake operating force acted on said spool valve, an offset spring for biasing said spool valve in a backward direction to impart an offset force corresponding to the amount of pressure reduction required for pressure-reducing control, and a pressure chamber for applying hydraulic pressure introduced from outside to said spool valve in an advancing direction;
• a hydraulic pressure source connected to said input port of said hydraulic pressure control device,
• a reservoir,
• a pressure-adjusting valve for receiving a substantially constant pressure P1, from said hydraulic pressure source and supplying it to said pressure chamber,
• a first valve for pressure increase control for opening and closing a fluid passage connecting between said pressure-adjusting valve and said pressure chamber, and
• a valve for pressure reduction control for opening and closing a fluid passage connecting between said pressure chamber and said reservoir,
• wherein the area a of a pressure-receiving portion of said spool valve which faces said pressure chamber, the force F of said offset spring, and the pressure P1 adjusted by said pressure-adjusting valve are set so as to satisfy the formula a·P1<F.