Patent ID: 7588005

Claim:
An intake valve assembly of an internal combustion engine including a combustion chamber and an intake passage fluidly communicating with said combustion chamber through an intake port, said intake valve assembly comprising: a primary valve provided to seal against a primary valve seat formed in said intake port; said primary valve being movable into and out of engagement with said primary valve seat between respective closed and open positions so that in said closed position of said primary poppet valve said combustion chamber being sealed from said intake passage; a hollow secondary valve mounted about said primary valve substantially coaxially therewith and provided to seal against a secondary valve seat formed in said intake port; said secondary valve being movable into and out of engagement with said secondary valve seat between respective closed and open positions so that in said closed position of said secondary valve said combustion chamber being sealed from said intake passage; a secondary valve lifter fixed to said primary valve so as to be axially spaced from said secondary valve when both said primary valve and said secondary valve are in said closed position; a primary valve spring for normally biasing said primary valve toward said closed position thereof; and a secondary valve spring for normally biasing said secondary valve toward said closed position thereof; said secondary valve being operated both mechanically by said secondary valve lifter and fluidly in response to pressure differential between said intake passage and said combustion chamber; said secondary valve being engageable with said primary valve through said secondary valve lifter after opening of said primary valve so that further movement of said primary valve away from said primary valve seat moving said secondary valve away from said secondary valve seat; said primary valve spring being normally contracted for continuously biasing said primary valve toward said closed position thereof; and said secondary valve spring being normally contracted for continuously biasing said secondary valve toward said closed position thereof.