Valvetrain for overhead valve engine

摘要

An engine assembly may include an engine structure, a camshaft rotationally supported within the engine structure and including a lobe, a first rocker arm, a valve lift mechanism, a valve, and a second rocker arm. The first rocker arm may include a first end rotationally coupled relative to the engine structure and a second end defining a cam engagement surface engaged with the lobe and a convex lift surface opposite the cam engagement surface. The valve lift mechanism may have a first end engaged with the lift surface of the first rocker arm. The second rocker arm may be supported relative to the engine structure and engaged with a second end of the valve lift mechanism and the valve to selectively open the valve based on displacement of the lift mechanism by the first rocker arm.

主权项

1. A valve actuation assembly comprising:
a first rocker arm including a first end defining a pivot axis to rotationally couple the first rocker arm to an engine structure and a second end defining a cam engagement surface adapted to engage a camshaft lobe and a convex lift surface opposite the cam engagement surface, an entirety of the convex lift surface being spaced for the pivot axis by a first distance greater than a second distance the cam engagement surface is spaced from the pivot axis; a valve lift mechanism having a first end engaged with the lift surface of the first rocker arm; and a second rocker arm engaged with a second end of the valve lift mechanism to selectively open a valve based on displacement of the lift mechanism by the first rocker arm, wherein the first rocker arm is adapted to be displaceable from a first position where a base circle of the camshaft lobe is engaged with the cam engagement surface to a second position where a peak of the camshaft lobe is engaged with the cam lift surface, the first rocker arm adapted to axially displace the valve lift mechanism a first distance at least ten percent greater than a second distance defined radially between the base circle and the peak of the camshaft lobe, wherein the valve lift mechanism is adapted to slide along the lift surface from a first point on the lift surface to a second point on the lift surface as the first rocker arm is displaced from the first position to the second position, wherein the second point is located radially outward from the first point relative to the pivot axis of the first rocker arm by a distance of at least ten percent.