This content is not included in your SAE MOBILUS subscription, or you are not logged in.
A Camshaft With Variable Lift-Rotation Characteristics; Theoretical Properties and Application to the Valve Gear of a Multicylinder Piston Engine
Published January 01, 1974 by Societe des Ingenieurs de l'Automobile in France
A camshaft is described in which the effective cam shape is determined by the transmission properties of a mechanism interposed between the driving shaft and each driven cam. This mechanism includes an intermediate member whose axis of rotation is displaced from the axis of the shaft. The camshaft properties are varied by rotating this axis of the intermediate member around that of the shaft by means of a geared control shaft.
A kinematic analysis confirmed by valve lift measurements shows that the effective width of a typical cam can be varied over a range of 60 degrees and the point of maximum lift over a range of 34 degrees, both angles measured at the crankshaft.
Variable camshafts of this design have been fitted into the standard camshaft spaces of a Fiat 1438 cm3 OHC engine and have run for an extended period with little deterioration. Optimisation of the camshaft settings at each speed is realisable by an automatic control system and has led to substantial improvements in torque and fuel consumption. The settings corresponding to the greatest increases in torque also provided significant reductions in hydrocarbon and carbon monoxide emissions by promoting more complete combustion.