| The connecting rod small end bearing is also known as connecting rod bushing, which isone of the friction pair of three main diesel engine, working in harsh environment of highdynamic load, the poor lubrication, high speed and high temperature. And the lubrication wayof connecting rod bushing is splash lubrication, which belongs to incomplete lubrication,prone to friction and wear phenomenon, so research on the lubrication characteristics ofconnecting rod bushing has important theoretical significance and practical value.A pair of friction is composed of connecting rod bushing and piston pin, and cooperationbetween them is a full-floating and they are separated with a layer of oil film, then thelubricant film flow is laminar flow, so the hydrodynamic lubrication is the rod bushinglubrication theory foundation.This article first carried out on the connecting rod bushing dynamics analysis, obtaininggas force and inertial force and carrying on the vector synthesis, in order to get the connectingrod bushing load and load angle. Then the Holland method is adopted to solve the threedimensional Reynolds partial differential equation. Reynolds equation is divided into two,rotating items and extruded items with different boundary conditions for solving. Accordingto the equilibrium condition namely dynamic equilibrium between external load and bearingcapacity of the rotating film and the squeeze film, the formula of axis orbit is deduced tocalculate axis orbit in a working cycle of the diesel engine. The maximum film pressure andthe minimum film thickness can be solved when axis orbit has been obtained within a workcycle. MATLAB program was compiled according to the calculation process, to further drawthe axis orbit, the maximum film pressure and minimum film thickness in Fig. Finally theconnecting rod bushing lubrication characteristics is analyzed under the different crankshaft rotation speed. The conclusions are that lubrication characteristic curve is consistent underdifferent rotational speed, and connecting rod bushings are prone to friction and wear in thearea near after the upper dead point of the power stroke. In addition the best relative gap is0.2in per thousand to0.5in per thousand between connecting rod bushing and piston pin. |
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