Study On The Lubrication Performance Of Crankshaft Bearing For Internal Combustion Engine In Different Operating Conditions

The current lubrication analyses of crankshaft bearings for internal combustion engine were generally carried out under the same operating condition (rated operating condition). However, all sorts of power machines as vehicles rarely work at rated operating condition, and it commonly works at different operating conditions of load and speed which are less than those of rated operating condition. Therefore, it is necessary to study the lubrication performance of crankshaft bearings of internal combustion engine at different operating conditions.In this paper, SD4105 diesel engine was taken as the studying object. The loads of crankshaft bearings and the lubrication performance of crankshaft bearing considering and not considering thermal effect were calculated at different operating conditions. The performance of crankshaft bearings considering thermal effect were compared with those not considering thermal effect at different operating conditions. In addition, the systematic experimental researches on temperature of main bearings for SD4105 diesel engine at different operating conditions were carried out. The results show that:Under the same load of internal combustion engine, the maximum load of connecting rod bearing reduces and the maximum loads of all main bearings change erratically when the rotational speed increases. The maximum loads of connecting rod bearing and all main bearing increase when the load of internal combustion engine increases under the same rotational speed.At different operating conditions, there are obvious difference of changes of lubrication performance of connecting rod bearing and main bearing. The changes of relations and values of axis trajectory, the maximum oil film pressure, minimum film thickness and friction coefficient of bearings are significantly different in an internal combustion engine working cycle. It indicates that only the lubrication of crankshaft bearings at rated operating condition was analyzed in the past design of crankshaft bearing for internal combustion engine is not reasonable enough, and the lubrication performance of crankshaft bearings under different working conditions should be studied meanwhile.When considering thermal effect, the maximum oil film pressures of connecting rod bearing and main bearing of SD4105 diesel engine is greater than those not considering thermal effect, the minimum oil film thickness and average frictional power consumption of bearings are less than those not considering thermal effect, but the change of value is little. The axis trajectories of connecting rod bearing and main bearings of SD4105 diesel engine change little when considering and not considering the thermal effect.The temperature measurement test of main bearings of SD4105 diesel engine at different operating conditions shows that, each main bearing has different temperature, and the temperature of No. 5 main bearing at rated operating condition is the highest. At the same rotational speed, the temperatures of all the main bearings increase with the load increase of internal combustion engine, the temperature of No. 3 main bearing is close to the temperature of No. 5 main bearing at low load. At full load, the temperatures of all the main bearings increase with the speed increase, the temperature of No. 3 main bearing is close to the temperature of No. 5 main bearing at low speed, the temperature of No.4 main bearing is close to the temperature of No.5 main bearing at high speed.