Abstract: The bearings in a crankshaft-bearing system of an internal combustion engine, which are typical ones applied by varying load, are studied in the idea that crankshaft and bearings are in one inseparable system and various mechanical behaviors happen simultaneously and influence each other when the machine is working. Based on this idea, a method to obtain the trajectory of the crankshaft journal center is put forward. First the dynamic control equations of crankshaft and the Reynolds’ equation of bearings are solved simultaneously to obtain the dynamic response of the crankshaft and the applying force on the bearings. And then, the tribological properties of the bearings are obtained through lubrication analysis. The trajectories of crankshaft journal center are three-dimensional and the axial trajectories can be obtained by the dynamic method while the two-dimensional trajectories can be only calculated by the static method. The obvious changes happen in the maximum pressure and minimum thickness of oil film in the bearings for the two different methods because the dynamic effect of the crankshaft-bearing system is considered in the dynamic method presented.

Key words: Crankshaft-bearing system, Dynamics, Internal combustion engine, Trajectory of journal center, Tribology