Variable lift valve train

Abstract

A variable lift valve train mechanism for an internal combustion engine. The valve train varies valve lift depending on engine RPM, providing a relatively lower valve lift at lower engine RPMs for increased bottom-end torque and a relatively higher valve lift at higher engine RPMs for increased overall top-end performance. The valve train includes a rocker arm at one end engaging a valve and at its other end engaging a cam such that upward movement of the cam causes downward opening movement of the valve. The rocker arm has a convex fulcrum-engaging upper surface extending between the rocker arm ends. A variable-position fulcrum assembly includes a pivot arm, the lower end of which is pivotally mounted to a pivot point, and the upper end of which carries a fulcrum roller element engaging the fulcrum-engaging upper surface of the rocker arm to define a variable fulcrum point. A control element in the form of a control piston driven by engine oil pressure positions the pivot arm and thus the fulcrum point to vary valve lift. To selectively restrict engine performance, a pressure relief valve may be provided for limiting the oil pressure to the control piston.

Dependencies are inferred from the claim text.