Intake device for internal combustion engine

Claim 1

An air inlet for a valve controlled internal combustion engine having a cylinder head within which an inlet valve is reciprocable relative to a valve seat and which air inlet includes an air inlet passage means for partial closure of said passage, the improvement comprising: said cylinder head being formed with an intake port extending from one side of said cylinder head toward substanially the center of said valve seat, said intake port comprising a straight section and a spiral section arranged along the direction of intake air flow and defining an upper half and a lower half respectively in a vertical section of said cylinder head, said spiral section including a portion of said straight section and further including a swirl producing chamber, said swirl producing chamber extending laterally outwardly beyond the outer periphery of said straight section at a position adjacent to and preceeding said valve seat, said straight section communicating with a combustion chamber through said valve seat; whereby operation of said closure means results in flow being directed to the lower portion of said straight section and being diverted to said swirl producing chamber of said spiral section; said straight section, when unobstructed, providing for flow directly into said valve seat in the substantial absence of swirl.