Vehicle brake apparatus

A vehicle brake apparatus comprising:

• a boosted hydraulic pressure chamber;
• a master cylinder comprising:
• a master piston of which back side faces the boosted hydraulic pressure chamber;
• and
• a casing accommodating the master piston in a slidable manner;
• a hydraulic pressure generating source;
• a reservoir;
• and
• a pressure regulating valve unit which regulates output hydraulic pressure of the hydraulic pressure generating source in response to an input of brake application effort from a brake operation member for application to the boosted hydraulic pressure chamber;
• and
• a detection unit which detects an amount of the brake application effort of the brake operation member,
• wherein the master cylinder is connected to wheel brakes,
• in accordance with a detection value of the detection unit the pressure regulating valve unit is electrically driven to switch over following states of the vehicle brake apparatus:
• a state where the boosted hydraulic pressure chamber communicates with the hydraulic pressure generating source and the boosted hydraulic pressure chamber is separated from the reservoir;
• a state where the boosted hydraulic pressure chamber is separated from the hydraulic pressure generating source and the boosted pressure chamber communicates with the reservoir;
• and
• a state where the boosted hydraulic pressure chamber is separated from both the hydraulic pressure generating source and the reservoir;
• and
• wherein the master piston is formed into a stepped configuration, comprising:
• a larger diameter portion at front end;
• and
• a smaller diameter portion at a rear end corresponding to a side of the boosted hydraulic pressure chamber, the smaller diameter portion being slidable on a secondary bore cylinder.