The Research On Lubricating Property Of Engine Connecting Rod Bushing

Under the working state of reciprocating piston internal combustion engine, hightemperature and pressure make its working condition even worse. Together with its kineticcharacteristic of reciprocating movement, lubrication condition of each inner friction pair inthe engine is to be more complicated. Connecting rod bushing which is also called piston pinbearing is one of the major friction pairs. Its lubrication property affects the engine’sperformance directly.This paper starts with the analysis of piston pin bearing dynamics of a type of dieselengine, in combination with the extrusion effect and bearing surface roughness affectcharacteristics, come out to be the lubrication mathematics model of piston pin bearing. Thatmeans bringing in average flow factor to establish an average Reynolds Equation. Finitedifference method is used in solving the average Reynolds equation by which come out theapproximate solution and through MATLAB computer language program to calculate.In order to be more practical, effect on dynamic pressure lubrication by surfaceroughness is considered. Based on the convex body contact theory, this paper firstly analyzesthe characteristic of loading on both oil film and the convex body contact and the changetrend of lubrication fiction. The key point is to analyzing lubrication property at different time,different pressures and different crank position. During the process of analysis, MATLAB isused in order to obtain thickness of oil film, distribution of oil film pressure and axistrajectory of piston pins bearing. The micro-convex body contact model is adopted instudying the impact of bearing surface roughness during lubrication. Based on this model, itcorrespondingly gets the lubricated friction characteristics and the load bearing ofmicro-convex body and oil film. Through the analysis and calculation, it is proved that the thicker the oil film is, the stronger the load bearing is and smaller the film thickness ratio is. Aproper bearing clearance is good for forming the oil film. The optimal bearing clearance isobtained after comparing different bearing clearances by lubrication calculation.