Analysis And Improvement On Lubrication Performance Of Crankshaft Bearing Of A High Speed Gasoline Engine

Driven by the energy conservation and emission reduction situation,the demand for reducing engine fuel consumption is more and more urgent,and with the continuous improvement of engine’s lightening and strengthening,higher requirements for engine’s reliability is put forward.Crankshaft bearing,as the main friction pairs of the engine,its lubrication performance directly determines the reliability,durability and fuel economy of engine.Therefore,analyzing the lubrication performance of engine crankshaft bearing in detail are of great help for understanding the lubrication condition of the bearing,and revised design the bearing which do not meet the lubrication performance is important to ensure that the engine is operating efficiently for long periods time.This paper takes the crankshaft bearing of a high-speed gasoline engine as the study object.A flexible multi-body dynamics model of crankshaft bearing is established in AVL-EXCITE software in which the elastic fluid dynamics method is adopted,which is based on finite element and multi-body dynamics theory.The lubrication performance parameters of bearing load,peak oil film pressure,minimum oil film thickness,peak asperity contact pressure and friction power loss of main bearing and connecting-rod big-end bearing are calculated by multi-body dynamics model.The results show that the lubrication performance of the connecting-rod big-end bearings can meet the operating requirements,when the crankshaft speed at 2000 rpm,rough contact at both edges of the bearing shell.For the main bearing,main bearing 2,main bearing 3,main bearing 4 can meet the operating requirements,but the main bearing 1 and main bearing 5 exist serious rough contact in low-speed operation conditions.Especially the crankshaft speed at 3000 rpm,the main bearing 5 has the worst lubrication condition,which will cause serious wear and tear.so can not meet the operation requirement,and needs to improve the design.To the connecting-rod big-end bearing,a new bearing shell profile is used to improve the design and calculating,the results show that the wear condition of both edge of the bearing shell are ameliorated obviously.As for the poor lubrication condition of main bearing 5,the orthogonal experiment method is adopted,in order to meet the lubrication requirement and the bearing width-diameter ratio,radial clearance and oil supply pressure are optimized matching.The results show that the width-diameter ration has the greatest impact on the lubrication performance,scheme of4,5,6 can meet the operation requirement.In scheme 4,the radius clearance doesn’t change,and merely the width-diameter ratio and oil supply pressure are changed compared with the original scheme.Therefore,scheme 4 is used as the improving scheme,by calculating other operation condition,the main bearing 5 can also meet the requirement of lubrication performance.