The VVH System - Variabler (variable) Ventil (valve) Hub (lift) - is a variable valve timing system suitable for an unthrottled load control of spark ignition engines. This mechanical valve train system allows a continuously variable intake valve lift from zero to maximum with a corresponding variable intake closing. Based on a first introduction of the VVH system during the SAE '98 Annual Congress this paper gives a more detailed description of this technology and reports about the progress of development.
In a first part of this paper a systematic design study showing application variants of the principle design proves that the VVH technology can be designed for all kinds of combustion engines with poppet valves including two and multi-valve cylinder heads, engines with over-head cam drive or pushrod valve train, inline or V-engines.
The second part describes the mechanical valve train function including the layout of the cam lobes, the kinematic functional parameters, the valve lift characteristics and the dynamical behaviour.
The description of the combustion system in the third part concentrates on specific parameters to optimize the thermodynamic performance of a VVH controlled engine such as combustion chamber, inlet port, injection and valve lift characteristics. Based upon these development strategies the current results will be presented demonstrating the potentials of the VVH system.