The Internal Combustion Engine Main Bearing Elastohydrodynamic Lubrication Study

The modern internal combustion engine needs more advanced design for the main bearing. The main bearing is the key friction part of engine, and it bears high temperature, high pressure and high rotating speed in the operating process. If the bad lubrication turns up, the bearing wear will increase, and it will affect the whole performance of the engine. Doing research on the bearing lubrication can predict the bearing performance accurately, calculate the minimum film thickness and analyze its duration. Also it provides help for reasonable oil hole layout and oil groove location, finally providing references for the best bearing lubrication design.This paper took the high-pressure common-rail four-cylinder diesel engine as research subject, doing elastohydrodynamic lubrication analysis for the main bearing. On the basis of analyzing elastohydrodynamic lubrication (EHD) theory of the main bearing systematically for the internal combustion engine, finite element simulation model of the internal combustion engine main bearing lubrication was established based on the software AVL EXCITE, taking into account the elastic deformation of the bearing seat, bearing tile and bearing neck surface shape synthetically, as well as oil fueling characteristics and boundary conditions' effects on the main bearing lubrication performance. Research has been done on relative clearance, bearing width, the location and dimension of oil groove, oil bore's effects on the main bearing lubrication, as well as the lubrication condition of the main bearing when being short of oil. The researching results show that the lubrication condition of the main bearing for four-cylinder diesel engine is basically good, and the design is reasonable. Minimum oil film thickness of the main bearing 1,2,3,4,5 are 1.54, 1.91,1.60,1.56,1.01μm respectively, the specifie film thickness is more than 1. Although the average oil film pressure of main bearing 5 is not the biggest, its peak oil film pressure is larger than the other four main bearings, turning up partial friction. So its lubrication is relatively poor and this main bearing need to optimize.Taking all the research above into consideration, the reasonable optimization program was brought forward for the main bearing 5 of the four-cylinder diesel engine. Increasing wide-diameter ratio of the main bearing and modifying oil bore location of the bearing tile were adopted. The results show that the peak oil film pressure of this bearing decreases to 151.8 MPa, and oil film thickness increases to 1.27μm. Also the consumption of friction power is greatly reduced.