Multi input CAM actuated mechanisms and their application to internal combustion engine variable valve timing

Variable valve timing (VVT) relates both to the ability to vary the opening/closing timing of an IC engine's valves relative to the piston's position, and also to the abiliry to vary the duration of the valve open intervals. It has long been known that varying valve timing as a function of engine operating parameters can produce significant gains in engine efficiency and power, as well as other benefits. Over 750 VVT mechanism patents have been issued in the USA since 1880. Over 110 of these patents were issued in the last three years alone.; We study some broader aspects of VVT: its potential benefits, its ideal timing laws, mechanisms to produce it, and the difficulties that can result from its use. We conclude that VVT has much potential, but that very little of this potential has yet been realized.; We propose a two-degree-of-freedom mechanism, actuated by two cams acting in series, that is well-suited for VVT applications. This mechanism avoids the serious limitations, particularly that of high impact velocities, that characterize virtually all other VVT mechanisms. We examine this mechanism in depth, including both its kinematic and dynamic properties. Tests on a prototype verified the mechanism's properties.; We propose a single-degree-of-freedom method for the dynamic analysis of flexible cam-follower systems. This method isour best combination of the most effective and the simplest of the features used by previous researchers. Also, we extend the use of such single-degree-of-freedom methods to multi-input systems for the first time.; We redefine the concept of cam-follower system pressure angle to assure meaningful results for all such systems, including, for the first time, multi-input systems.; We recommend further work to gain experience with our proposed mechanism and to prove it practical for VVT use, as well as for other applications.