Hydraulic servo for motor vehicle braking - has pressure relief valve located between external pressure source and brake valve

摘要

The pump (26) and reservoir (35) provide an external pressure source. A servo piston (8) forms the limit of a surge chamber (12). A pedal-operated brake valve with a servo valve spool (14) which moves relative to the piston regulates the external pressure and feeds it to the surge chamber which connects with a pressureless reservoir (22) when the brake is released. A pressure relief valve (37) is located between the external pressure source (26,35) and the brake valve connects directly with a pressure limiter (56). The valve shuts when a plunger (57) inside the pressure limiter is acted on by the pressure in the surge chamber or the pressure of a brake circuit (4,5) attached to a tandem main cylinder (1). ADVANTAGE - Improved operational safety.