Analysis of journal bearings in a scroll compressor considering deflections and dynamics of the crankshaft

Engineers are trying to design a scroll compressor which covers wide range of speed to realize an efficient and compact air-conditioning system. Recently, a motor with inverter technology has been driven from 15 to 150 Hz in an advanced scroll compressor. The importance of design for a crankshaft and journal bearings has been emphasized in this trend because the lubrication characteristics are greatly affected by the operating speed. In this study, the lubrication characteristics of journal bearings in a scroll compressor are analyzed considering deflections and dynamics of a crankshaft. The Reynolds equation is solved using the finite difference method to determine the pressure distribution of journal bearings, and then deflections of the crankshaft and its four-degrees-of-freedom motions are calculated by the finite element method and the fourth-order Runge-Kutta method, respectively. It is confirmed from the results that the crankshaft deflections significantly affect the minimum clearance of journal bearings.