Variable lift valve drive - has secondary piston and pressure chamber

摘要

A lift valve (2) and the cam (5) which operates it are connected by a hydraulic power transmission system comprising a cup tappet (9) and an operating piston (14) which between them bound a pressure chamber (16). The tappet (9) contains an auxiliary annular piston (12) acted on by a compression spring (19). The auxiliary piston (12) encloses the pressure chamber (16) and forms a secondary chamber (17) linked to the pressure chamber (16) between itself and the base (7) of the tappet (9). The auxiliary chamber (17) is connected to an external supply of medium (24) at a controlled pressure via a non-return valve (22). USE/ADVANTAGE - A space-saving method of altering the length of the pressure chamber.