IC engine inlet valve with back-up valve for charge variation - has hydraulic advance and spring retraction by operating units in port wall

摘要

The IC engine inlet valve with backup valve for charge variation is basically a conventional poppet valve (2). However there is an additional sleeve valve (4), shaped to seal against and free to move axially with the main valve. This backup valve is fixed to two hollow pistons (8, 9) free to move axially in diametrically opposed cylinders (6, 7) set into the port wall. Springs (11, 12) inside the pistons, bearing against the valve seat insert (14), hold the sleeve retracted. Timed by a speed-and/or load-responsive unit, fluid under pressure is admitted to the cylinders through ports (10) in the top, causing the sleeve first to seal against and then to move with the opening valve, until piston travel (a) is taken up. When fluid pressure is released the sleeve retracts again, leaving the full area for inflow.