Abstract
Keywords :
HLA(Hydraulic Lash Adjuster)
Abstract
A valve impact between cam and follower is one of the serious problems for mechanical valve lash adjusters because of the valve lash, which maintains valves tightly to the cam despite of thermal expansion. Therefore, valve designers started putting some short and constant ramps to control valve opening and closing velocities. In addition, many current valve trains take some form of Hydraulic Lash Adjuster, which holds no lash between cam and follower, to avoid the valve impact. This is one of the solutions to avoid it. But there are still problems remaining. Two of them are aeration of oil and valve sponge phenomenon, which occurs during cold start since oil supply to engine heads takes some seconds. It causes noise, deformation and damage of valve train. In this experiment, the characteristics of valve dynamics will be studied through comparison of valve movements in normal, sponge phenomenon and aeration of oil condition, by using non-contact laser vibrometer. Especially, valve lifts and velocities will be measured and analyzed to give some information to improve valve design.