Hydraulic brake apparatus for vehicle

A hydraulic brake apparatus for a vehicle comprising:

• a brake assist mechanism which includes a power piston and a driving hydraulic pressure chamber, and which is driven by a hydraulic pressure introduced into the driving hydraulic pressure chamber;
• a master cylinder which includes a master hydraulic pressure chamber and a master piston, wherein the mater piston is actuated by a force assisted by the brake assist mechanism to generate a hydraulic pressure in the master hydraulic pressure chamber;
• an electronic control device which is configured to determine whether a braking force control is necessary and output a control command when necessary;
• a hydraulic control device which includes a power driven pump, and which is configured to apply braking force to a wheel of the vehicle based on the hydraulic pressure of the master cylinder under a control of the electronic control device;
• a high hydraulic pressure source which is configured to supply a hydraulic pressure to the driving hydraulic pressure chamber;
• a liquid reservoir which has an inner pressure lower than the hydraulic pressure of the high hydraulic pressure source;
• a driving pressure regulating valve mechanism which is configured to respectively switch a communication/interrupting state between the high hydraulic pressure source and the driving hydraulic pressure chamber and a communication/interrupting state between the driving hydraulic pressure chamber and the liquid reservoir according to an operation amount of a brake operating member so as to regulate the hydraulic pressure in the driving hydraulic pressure chamber to a value corresponding to the operation amount of the brake operating member;
• and
• a driving pressure reducing valve which includes:
• a valve body;
• a master pressure input port which is formed in the valve body and is connected with the master hydraulic pressure chamber;
• a driving pressure input port which is formed in the valve body and is connected with the driving hydraulic pressure chamber;
• and
• a valve main body which receives a hydraulic pressure in the master pressure input port and a hydraulic pressure in the driving pressure input port in opposite directions,
• wherein when the hydraulic pressure in the master pressure input port is higher than the hydraulic pressure in the driving pressure input port by a predetermined value, the valve main body opens a hydraulic pressure discharge path extending from the driving hydraulic pressure chamber to the liquid reservoir such that the pressure in the driving hydraulic pressure chamber is reduced.