Valve mechanism having variable valve timing

Claim 1

A valve mechanism for an internal combustion engine comprising: a camshaft rotatable about a longitudinal axis and having a cam formed thereon, a swingable member mounted for swinging movement about the longitudinal axis of the camshaft and formed with a tappet receiving hole, a valve tappet received in said tappet receiving hole for a slidable movement along the tappet receiving hole, said tappet having a cam engaging surface at one end and a stem engaging surface at the other end, a valve stem mounted for axial movement and engaged at one end with said stem engaging surface of the tappet to be actuated thereby, valve timing control means for swingably moving said swingable member and said tappet about the camshaft axis in accordance with predetermined engine operating conditions to thereby change valve opening and valve closing timing, said control means including means for holding said swingable member at a first position wherein the tappet and valve stem are in contact at a first position on the stem engaging surface of said tappet and the direction of the slidable movement of the tappet is aligned with the direction of the axial movement of the valve stem at least under heavy load, high speed engine operation, and for moving said swingable member from said first position to a second position wherein the tappet and valve stem are in contact at a second position on the stem engaging surface of said tappet at low speed engine operation to effect a change in valve opening and valve closing timing.