Servo-assisted hydraulic master cylinder

摘要

A servo-assisted hydraulic master cylinder has a variable ratio effect so that brake fluid is initially displaced to the brakes at a high rate with respect to driver pedal movement and then at a low rate when an appropriate pressure has developed. A stepped piston assembly comprising a first piston slidable in a second piston defines a first chamber which is directly connected to the brakes and a second chamber in which a variable pressure is developed. The first piston is operated directly by the pedal through the servo valve and is subject only to brake pressure in the first chamber so that brake pressure is proportional to driver effort during normal operation. The second piston is operated by the servo diaphragm through the servo valve housing.