1997-02-24

A Low-Friction Variable-Valve Actuation Device Part II: Analysis and Simulation 970339

A relatively simple, low-friction Variable-Valve-Actuation (VVA) device is presented. The device can be characterized as a four-bar mechanism consisting of a crank, a rocker and a coupler, all supported on a carrier body. Description of the prototype hardware, and the results of the friction measurements are presented in an accompanying paper [1].In the present paper, a kinematic analysis/synthesis and a rigid-body dynamic analysis are outlined. Also included is a flexible-body model where the coupler link, which was suspected to be the most severely stressed member, is modeled as a flexible component. A sensitivity-uncertainty analysis employing the Fourier-Amplitude-Sensitivity-Test (FAST) method is conducted to identify the dominant design parameters, and to predict the variations in mechanism's performance due to the uncertainties in the design parameters.Dynamometer tests reported in [1] confirmed the predictions that, due primarily to the rocking motion at the lifter interface, the mechanism consumes much less frictional-energy than a direct-acting non-roller type valvetrain. It is demonstrated that the mechanism can provide late valve opening, early valve closing, and lower lift.

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