Multi-body engine simulation including elastohydrodynamic lubrication for non-conformal conjunctions

Abstract

The evaluation of lubricated contacts is an essential step in modern internal combustion engine simulation to estimate run-time behaviour. A thorough investigation of the occurring thin oil films is critical to estimate friction, wear, noise, vibration and harshness and the overall dynamic behaviour. The prediction of contact pressure and oil film height poses a complex task, especially in non-conformal conjunctions, such as between a cam and a follower. This paper introduces a generic algorithm to solve the elastohydrodynamic lubrication problem and integrates it into a multi-body simulation environment. A focus is put on the versatile integration of the elastohydrodynamic lubrication model into the multi-body framework to create a basis for a full engine simulation. The Reynolds equation and the film thickness equation are treated as modular decoupled systems and, therefore, allow a modular structure of the elastohydrodynamic lubrication algorithm. The method introduced here incorporates existing relaxation techniques and uses them in a decoupled elastohydrodynamic lubrication solver for flexible multi-body dynamics simulation. The contact between a cam and a follower of an internal combustion engine is used as an exemplary contact to test the derived elastohydrodynamic lubrication model. A four-cylinder full engine model with 16 valves and two flexible camshafts is investigated as an example to outline effects of an oil film lubricated cam follower conjunctions in valve train simulation.