Hydraulic valve gear for IC engine - has oil relief port operated by auxiliary piston controlled by engine load to vary valve opening

摘要

A cam (2) moves a pushrod (3) through a hydraulic follower (1). The follower has an upper piston (7) which moves the pushrod and slides within the lower piston (6) which is moved by the cam. Ports (22,21) in the pistons admit oil under pressure to the space (8) between the pistons at the appropriate point in the stroke. A port (18) releases oil to the sump (R). The opening of the release port is governed by an auxiliary piston (12) which is moved according to engine load. The opening of the valve depends on the relative movement of the two pistons which is controlled by the cam and the auxiliary piston.