Patent ID: 6705682
Filing Date: 2004-03-16
Classification: B60T

Abstract:
A hydraulic brake apparatus for a vehicle comprising:a hydraulic pressure generator which generates a power pressure irrespective of operation of a brake pedal and outputs the power pressure; a regulation valve which regulates the power pressure outputted from the hydraulic pressure generator to a predetermined pressure corresponding to an operation force of the brake pedal and outputs the predetermined pressure to an output chamber; a master cylinder including a master cylinder piston and a master cylinder pressure chamber which is located forward the master cylinder piston to generate a master cylinder pressure by forward movement of the master cylinder piston; a wheel brake cylinder connected to the master cylinder chamber and operated by the master cylinder pressure to apply braking force to a wheel of the vehicle; an auxiliary piston located backward the master cylinder piston to define an auxiliary pressure chamber between the master cylinder piston and the auxiliary piston and to move the master cylinder piston forward by an auxiliary pressure in the auxiliary pressure chamber; a pressure modulating device which modulates the auxiliary pressure in the auxiliary pressure chamber to a pressure less than the predetermined pressure in the output chamber of the regulation valve; and a pressure chamber which communicates with the output chamber of the regulation valve to bias the auxiliary piston backward by a pressure in the pressure chamber; wherein the auxiliary piston is biased backward by both the auxiliary pressure in the auxiliary pressure chamber and the pressure in the pressure chamber when both of the hydraulic pressure generator and the regulation valve are a normal condition in which the predetermined pressure can be outputted to the output chamber of the regulation valve, and the auxiliary piston is moved forward by the operation force of the brake pedal to move the master cylinder piston forward when at least one of the hydraulic pressure generator and the regulation valve is an abnormal condition in which the predetermined pressure cannot be outputted to the output chamber of the regulation valve.