Improvements of Valve Stem Seals to Meet Future Emission Requirements

Due to the current and future emission regulations, nearly every new internal combustion engine has to be equipped with valve stem seals. The optimal seal is designed to meet the increasingly severe emission regulations by constantly metering the oil flow to allow adequate lubrication of the valve stem/guide while at the same time minimizing oil flow to the combustion chamber and hence minimizing emissions. The seal has to compensate for manufacturing tolerances of the cylinder head and to provide stability of the oil metering rate for all different running conditions over the life of the engine. To increase the constancy of the oil flow metered by the seals, a new stepped lip design was developed using finite element analysis.