Study on the hydrodynamic lubrication of engine main bearing coupled with the crankshaft axial movement

Abstract

When the engine is operated, the crankshaft rotates and moves along the axial direction meanwhile. In this paper, the crankshaft-bearing system of a four-cylinder four-stroke engine is taken as the object, and based on the established hydrodynamic lubrication model, the lubrication performance of the engine main bearing is studied considering the axial movement of crankshaft and the journal misalignment caused by the crankshaft deformation under load. In the analysis, the axial movement of crankshaft is measured by the engine bench test, the load of main bearing and the crankshaft deformation are calculated by the integral crankshaft finite element method, and the lubrication analysis of main bearing is carried out by the dynamic method. The results show that compared with excluding the axial movement of crankshaft, the journal center trajectory of main bearing is an unclosed three-dimensional curve when the axial movement of crankshaft is taken into account. The minimum oil film thickness, maximum oil film pressure, frictional power loss and end flow-rate of main bearing change significantly at some time of an engine working cycle. The influence of the axial movement of crankshaft on the lubrication characteristics of engine main bearings is not always negative. Therefore, in order to be more reasonable and close to the reality, it is necessary to consider the influence of the axial movement of crankshaft in the lubrication performance analysis of engine main bearing.