Prediction of Hydrodynamic Bearing Behaviour for Pre-layout of Cranktrain Dimensions

Calculating the bearing reliability and behavior is one of the primary tasks which have to be performed to define the main dimensions of the cranktrain of an internal combustion engine. Since the bearing results are essential for the pre-layout of the cranktrain, the conclusion on the bearing safety should be met as early as possible. Therefore detailed simulations like T-EHD or EHD analysis may not be applied to define the dimensions in such an early development phase. In the frame of this study a prediction methodology, based on a HD bearing approach, for bearing reliability of inline-4 crankshafts of passenger cars is proposed. In this way not only the design phase is shortened but also achieving the optimal solution is simplified. Moreover the requirement of a CAD model is eliminated for the preliminary design phase.

The influencing parameters on the bearing behavior are first selected and divided into two groups: geometry and loading. The effect of geometry and loading parameters on the output values are investigated separately within a DoE variation of beam crankshaft models. After defining the interactions between input and output values, empirical equations for predicting the minimum oil film thickness, specific bearing load and main bearing forces in vertical and horizontal directions are generated. The bearing behavior is predicted with the designated tool for the selected benchmark crankshafts and the results are compared with the calculation results. For the investigated parameter range ±10% deviation is observed for the stated output values. Hence the proposed approach showed potential for the pre-layout of the cranktrain dimensions concerning the bearing safety.