Electrohydraulic Fully Flexible Valve Actuation System With Internal Feedback

Fully flexible valve actuation (FFVA) system, often referred to as camless valvetrain, employs electronically controlled actuators in place of the camshaft to drive the intake or exhaust valves for internal combustion engines (ICEs). This system offers significant fuel economy benefits, emissions reduction, and better torque output performance for the ICE. It could also enable a number of advanced combustion concepts, such as homogeneous charge compression ignition. It further provides a common platform that incorporates the functions of cam phasing, two/three step cam or continuously variable lift, cylinder deactivation, port deactivation, etc. Therefore it is desirable to develop FFVA systems for future engines. In this paper, we first outline the technical barriers for developing production-viable FFVA systems. To address those challenges, a new electrohydraulic valve actuation concept with the “internal feedback” mechanism is presented. Key technical issues, such as dynamic range capability, valve motion performance, and energy consumption, are analyzed. Experimental results based on a prototype system are shown to demonstrate the capabilities and performance of the proposed system.