2019 Volume 64 Issue 2 Pages 81-90
Variable Valve Actuation System (VVA) enables to change valve lift characteristics, such as lift amount, duration, opening timing, and closing timing. VVA was adapted to automotive engines in 1980’s, for improvement of driving performance and thermal efficiency. With environment issue, VVA was applied to reduce exhaust emission and CO2, and VVA has been widely installed. VVA has been developed in not only actuation mechanism, but also tribotechnology. This paper summarizes VVA, such as oscillating cam type, hydraulic lost-motion type, cam switching type, and cam phaser type, and explains tribological characteristics which support them.
