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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.

Variable valve actuation (VVA) has been recognized as a potential method to improve engine efficiency, low-end torque, high-end power, idle stability, and emissions. This paper presents a low-friction VVA device that can modulate the valve lift and timing, and potentially provide many of the benefits listed. In order for the VVA-related additional losses not to out-weigh the benefits, energy consumed in friction and activating the VVA mechanism must be comparable to the total energy consumed by friction in a conventional valvetrain. To confirm this point, hardware was built and installed on a General Motors L-4 cylinder head employing 4 valves per cylinder. The frictional-energy loss and the actuation torque for the mechanism were measured at different speeds and oil temperatures. The dynamometer tests confirmed the simulation results that the mechanism consumes less frictional energy than a direct acting, non-roller type valvetrain.