A Fully Variable Hydraulic Valve Train Concept with Continuous Measuring of the Valve Lift Movement 2015-01-0323
The global development of oil prices and ongoing discussions with regard to meet future CO2-emission commitments necessitate new technologies and concepts in individual motor car traffic. While hybridization and electrification become more and more important on a small scale, the improvement in efficiency of conventional drive, especially in respect of SI engines, currently offers the highest potential in reducing fuel consumption and exhaust emissions.
Thereby valve trains play a key role in the optimization of SI engines e. g. in connection with technologies and processes such as in-cylinder air-fuel mixing, combustion, HCCI, gas exchange, lean operation etc. Modern valve train systems entering mass production are despite of the fact of being called fully variable, yet cam-actuated systems. Thus variability and application are limited compared to direct (non-cam-actuated) engine control systems.
OptiVent is a patented new way controlling the mass air flow in the cylinder of a combustion engine using opening valves during the compression phase of a four stroke engine especially for opening the valves more than one time during a cycle. The engine control and combustion system uses a real fully variable electro-hydraulic valve train on the inlet and exhaust valves providing the opportunity to control valve timing independently from crankshaft drive in both - phase and speed. Therefore preconditions for the following engine control strategies are given: Controlling engine load via exhaust valves, reduction of gas exchange loses, setting up a cylinder-selective decompression during engine starting process lowering the corresponding mechanical losses and the realization of hydraulic recuperation respectively.
West Saxon University of Applied Sciences in cooperation with industrial partners created a cylinder head concept using mass production parts for realizing a very high level of freedom in controlling the gas exchange of a combustion engine. The paper presents the development of the system with focus on mechanical design as well as technical features. Besides sophisticated cooling of the solenoids and the implementation of the hydraulic system, the installation of a continuous/undelayed valve measurement required for prohibiting collision between valves and piston, as it may occur in direct valve trains, has been conducted. Towards this end an engine test stand using a current VW EA211 SI engine as the basis for the superimposed system was established. The research is funded by government and industrial partners.