Hydraulic brake apparatus for a vehicle

A hydraulic brake apparatus for a vehicle, comprising:

• a brake operating member;
• a hydraulic pressure generating source for generating and outputting a predetermined hydraulic pressure regardless of a brake operation applied to the brake operating member;
• a regulating valve regulating the hydraulic pressure outputted from the hydraulic pressure generating source in response to a brake operating force applied to the brake operating member and for outputting a regulated hydraulic pressure;
• a first master cylinder including:
• a first master piston operated in response to the hydraulic pressure outputted from the regulating valve;
• and
• a first pressure chamber outputting a first brake hydraulic pressure;
• a second master cylinder including:
• a second master piston operated in response to the brake hydraulic pressure outputted from the first master cylinder;
• and
• a second pressure chamber outputting a second brake hydraulic pressure;
• a first hydraulic system for supplying the first brake hydraulic pressure outputted from the first pressure chamber to a first wheel brake cylinder;
• a second hydraulic system for supplying the second brake hydraulic pressure outputted from the second pressure chamber to a second wheel brake cylinder, wherein an output diameter of the first master piston differs from an output diameter of the second master piston;
• a pressure detecting means connected to the second pressure chamber for detecting the second brake hydraulic pressure outputted from the second pressure chamber;
• a brake operating amount detecting means for detecting a brake operating amount of the brake operating member;
• and
• a judging means for judging a hydraulic pressure condition of the first and second hydraulic systems based upon the brake hydraulic pressure detected by the pressure detecting means relative to the brake operating amount detected by the brake operating amount detecting means.