Analysis of the most important design parameters of the crank drive due to the NVH behaviour - Analysis of the crank shaft and the main bearings

The acoustic emissions of the combustion engine are one of the main contributors to the pass by noise of a passenger car, which is a main focus of current NVH activities.
In this context the crank drive has a dominant influence and has to be analyzed in detail to identify the most important design parameters concerning vibrations of the main bearings, which defines one excitation source of the engine's acoustic emission. Thereby, the main focus will be on design parameters, which can easily be changed in an already existing production line for mass production of passenger cars. For this purpose a multi-body-simulation model of the crank drive is build.
Beside the crankshaft, which will be modeled as an elastic body (using the floating frame of reference approach - elastic deformations are superimposed to the rigid body motion via a reduced FE-model), the remaining bodies are assumed as rigid. The bearings on the crank shaft are modeled by a transient solution of Reynolds PDE, which allows a detailed analysis of the bearing forces and the influence of bearing parameters. The exciting forces are determined by the transient combustion forces acting on the pistons. As it is assumed that a lower magnitude of excitation forces leads to lower acoustic emissions, the numerical results of interest are the forces in the main bearings, which can excite the crankcase and lead to a noticeable acoustic behaviour.