Vehicle brake device

A vehicle brake device for supplying brake fluid to a wheel cylinder of a friction brake provided for a wheel to generate a friction brake force by the friction brake, the vehicle brake device comprising:

• a master cylinder;
• a master piston arranged in the master cylinder slidably in an axial direction and composed of a pressurizing piston portion defining together with an internal surface of the master cylinder a master chamber for pressurizing the brake fluid supplied to the wheel cylinder, a servo pressure receiving portion defining together with the internal surface of the master cylinder a servo chamber filled with the brake fluid, and a protruding portion protruding rearward from a rear end of the pressurizing piston portion;
• an input piston arranged at a rear part in the master cylinder slidably in the axial direction, being behind the protruding portion to be separated from the protruding portion, and defining together with the internal surface of the master cylinder and the protruding portion a separation chamber filled with the brake fluid;
• an input piston moving amount detecting section that detects the moving amount of the input piston;
• a reaction force generating unit that communicates with the separation chamber and that generates a reaction force pressure depending on the moving amount of the input piston;
• a servo pressure generating section that generates a servo pressure acting in the servo chamber, in dependence on the moving amount of the input piston detected by the input piston moving amount detecting section;
• a reaction force pressure detecting section that detects the reaction force;
• a servo pressure detecting section that detects the servo pressure;
• and
• a contact inferring section that infers the contact of the input piston with the protruding portion based on the reaction force pressure detected by the reaction force pressure detecting section and the servo pressure detected by the servo pressure detecting section.