Hydraulic brake apparatus for a vehicle

Abstract

The invention is directed to a hydraulic brake apparatus which includes a master cylinder having a cylinder body and a master piston slidably disposed therein for defining a pressure chamber ahead of the master piston and a power chamber behind the master piston. A control piston is slidably disposed in the cylinder body ahead of the master piston for defining the pressure chamber behind the control piston. The control piston is moved in response to movement of the master piston. An auxiliary pressure source is provided for pressurizing brake fluid to generate a power pressure. A valve assembly is communicated with the auxiliary pressure source to regulate the power pressure into a regulated pressure in response to movement of the control piston, and adapted to supply the regulated pressure into the power chamber to assist the operation of a brake pedal. And, a pressure decreasing device which is activated in response to operation of the brake pedal is provided for decreasing the pressure in the power chamber irrespective of the pressure in the pressure chamber when the brake pedal is released. For example, the pressure decreasing device is disposed in the master piston for communicating the power chamber with the reservoir or blocking the communication between the power chamber and the reservoir in accordance with a position of the master piston in the cylinder body.