Variable valve drive with cams driving inner and outer valve stems - has stems coupled by radially sliding pistons in outer stem, engaging inner stem stops during the cam base circle phase

摘要

A variable valve drive, esp. for an I.C. engine cylinder head valve, has the valve (1) selectively driven either via a first cam (4) and inner valve stem (8) or at least one further cam (5, 6) and a concentric outer stem (10). The cams are actuated synchronously and have identical base circle zones. The outer stem (10) has radially sliding hydraulic pistons (12), which, when pressurised, slide inwards to engage axial stops (18) on the inner stem (8) during the cam`s base circle phase. ADVANTAGE - Compact construction, esp. in axial direction.