Lubrication Analysis of Crankshaft Bearing Considering Crankshaft Deformation

There is the direct interaction between the crankshaft and the crankshaft bearing in an internal combustion engine. Current lubrication analysis of the crankshaft bearing was generally limited in the tribology discipline, only the factors relating to the bearing were considered, and the journal axis was generally supposed to be parallel to the centerline of bearing. In reality, the crankshaft deformation under load will result in the journal misalignment in the bearing. Although the journal misalignment was considered in a few of the lubrication analyses of crankshaft bearings, the causes of journal misalignment were usually thought to be caused by the manufacture, the assembly errors and the deformation of cylinder block. In order to simplify the problem, the journal misalignment was generally assumed to have constant magnitude and direction in an operating cycle of engine. In this paper, a crankshaft-bearing system was taken as the research object and the lubrication performance of crankshaft bearing considering the crankshaft deformation under load were analyzed. The crankshaft deformation and the bearing load were calculated by the whole crankshaft beam-element method. The deformation of bearing under oil film pressure was calculated by the deformation matrix method. The axis orbit of the crankshaft bearing was calculated by the dynamic method. The results show that the local axis orbits on the front-end and the rear-end plane of crankshaft bearing are changed remarkably when the effect of crankshaft deformation is considered. The journal misalignment results in the maximum oil film pressure of bearing be increased obviously, the minimum oil film thickness of bearing be reduced in the most of time of an engine cycle and the oil film pressure distribution of bearing be changed, but has only a little effect on the end leakage flow-rate and the frictional coefficient of bearing.