ELECTROHYDRAULIC SYSTEM FOR HIGH SPEED GAS EXCHANGE VALVE ACTUATION

抄録

Diesel engine performance can be improved and emissions reduced by improving the power density and combustion cycle efficiency. It can be done by increasing combustion pressure and engine speed which also necessitates improving the controllability of the engine. One of the key elements in improving overall controllability of the engine is the valvetrain. During recent years various camless valvetrain designs for automotive size engines have been introduced, but in bigger engines camless valve actuation is only applied to low speed two stroke marine diesels. Feasible way to realize camless valve actuation in modern and future medium speed diesels is electrohydraulic valvetrain. It, how ever, has numerous shortcomings and difficulties to overcome.
An electrohydraulic valvetrain for experimental engine, having performance characteristics twice the level of current medium speed engines, has been developed. Valvetrain offers significant benefits in comparison to traditional cam actuated valvetrain. Valvetrain is able to operate up to engine speed of 1600 rpm and combustion pressure of 400 bar at speed level twice the tradional cam actuation. Hydraulic peak power of the valvetrain is approx 100 kW and shortest controlled actuation time is approx 6 ms for 18 mm stroke. Main challenges in valvetrain design are are keeping the continuous power consumption at reasonable level, controlling the valve speed, precission of valve timing and dynamics of the system in whole as well as individual components.
The paper will introduce the system and component design of the prototype system. System and component performance is discussed on basis of Amesim simulation models. Control system design, realization and valvetrain prototype testing are also discussed.