Abstract
The 3Cam is a compact and highly integrated solution for a fully mechanical valve actuation system. Especially, the option given in this system to design the coupling of the valve lift height and valve lift phasing to the needs of the powertrain leads to a compact cylinder head and relatively simple control and therefore to an attractive cost to benefit ratio supporting engine trends like downsizing and hybridization.
The concept and special features of the contiuously variable shifting valve train (3Cam) are presented in this paper. Additionally, a view on the 3D-cam manufacturing method enabling the production of different sets of valve lift families is given. The adaption of the system to a conventional series production type cylinder head was accomplished virtually with minimum modifications to the base cylinder head. The first evaluation measurements exhibited a highly dynamic open-loop and a precise closed-loop control behavior.
To investigate the benefit in fuel consumption, pumping loss reductions were calculated using the simulation tool GT-Power and data of manufactured 3Cam profiles by applying a calibrated engine model. Predictions of fuel economy benefits over different driving cycles were derived from these calculations.
Further, a drive cycle simulation of a downscaled low resistance vehicle with a highly downsized engine from 1,5l to 660ccm demonstrates base challenges to be overcome and key parameters in realizing very low fuel consumption values.
Keywords: variable valve train, lift, phasing, engine