Pressure relief valve for compression engine braking system

Abstract

A compression braking system for an internal combustion engine having at least one working piston including a master piston operated by an engine component such as a fuel injector actuating mechanism and a slave piston fluidically connected with the master piston to open an engine exhaust valve wherein a pressure relief valve is provided to prevent excessively high pressure supply fluid from a low pressure supply circuit from reaching the high pressure circuit connecting the master and slave pistons thereby preventing inadvertent and excessive movement of the slave piston and possible damage to the engine. The pressure relief valve is fluidically connected to the low pressure supply circuit upstream of a control valve which separates the low and high fluid circuits and opens to vent fluid from the low pressure circuit while allowing continuous, uninterrupted operation of the engine in the braking mode. The pressure relief valve may include a spring biased check valve normally biased in a closed position and movable into the open position whenever the pressure in the low pressure circuit reaches a predetermined level to maintain the fluid in the low pressure circuit below a predetermined pressure level equivalent to a maximum high pressure level in the high pressure circuit capable of moving the slave piston.