Transient elastohydrodynamic analysis of an overhead cam/tappet contact

The friction in automotive engines is mainly caused by three components: the engine bearings, the piston-ring assembly and the valve train. In order to improve reliability and performance and to reduce fuel consumption, manufacturers have to reduce engine friction. To do this a better understanding of these components is necessary. In this paper, the valve train is studied for a direct-acting system. A transient elastohydrodynamic lubrication analysis is developed. The model includes the variation in the radius of curvature of the cam, the variation in the hydrodynamic velocity and the variation in the load. The film thickness is calculated as a function of time and space. In order to reduce the computing time, multi-grid and multi-level multi-integration techniques are used. Results show squeeze-film effects and ejection of lubricant on hydrodynamic speed reversion.