US 11,352,918 B1Granted

Variable valve timing method and mechanism

OwnerAnthony John Peilainventor

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Abstract

This invention describes a variable valve timing mechanism which may be fitted to an internal combustion engine to provide precise control over timing of the valve opening and closing events of the camshaft relative to the crankshaft. Various methods for its application are described to provide settable valve timing at either predetermined angle selected by the operator, or automatic variable valve timing as governed by parameters of the operating engine. Said mechanism comprised of oppositely located idler rollers, whereas not bound to a single yoke or carrier, are driven by a cam to achieve independent movement of the rollers, which bear against both tension and slack sides of the belt between the crankshaft and camshaft pulleys causing predictable and repeatable variation in valve timing. Thus, this invention, whereby coordinated but non-uniform movements of the idler rollers is achieved by the mechanical appurtenances described herein, including a specially developed cardioid cam to actuate said idler rollers, produces precise changes in camshaft phase angle.

A variable valve timing (VVT) mechanism for an internal combustion engine including a camshaft and a crankshaft disposed in an engine block, whereby a driven pulley of the camshaft is driven by a drive pulley of the crankshaft via a flexible band, the VVT mechanism comprising:

a backing plate mounted to the engine block, the backing plate including through-openings configured to receive the camshaft and the crankshaft such that the backing plate is interposed between the engine block and the driven and drive pulleys;
a cardioid cam rotatably coupled to the backing plate, the cardioid cam configured to be selectively rotated via an actuator assembly;
a guide track integrally formed on the backing plate, the guide track defining a linear translation path extending horizontally between the driven pulley and the drive pulley;
a first linkage disposed in the guide track, the first linkage including:
a first end defining a first follower configured to engage a first lateral side of the cardioid cam, and
a second end defining a first idler roller configured to engage an outer surface of the flexible band on an advance side of the driven pulley;
and
a second linkage disposed in the guide track, the second linkage including:
a first end defining a second follower configured to engage an opposing second lateral side of the cardioid cam, and
a second end defining a second idler roller configured to engage the outer surface of the flexible band on a retard side of the driven pulley,
wherein the first and second linkages translate along the translation path asymmetrically with respect to each other based on a contour of the cardioid cam as the cardioid cam rotates,
wherein the first and second idler rollers act on the flexible band in accordance with a respective position of the first and second followers so as to adjust a phase angle of the camshaft with respect to the crankshaft, and
wherein the flexible band is one of a belt or a chain.

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Abstract

Claims12