计及曲轴轴向运动的内燃机主轴承润滑分析

Lubrication Analysis of Main Bearing for Internal Combustion Engine Considering Axial Movement of Crankshaft

内燃机工作中,曲轴进行旋转运动的同时,还存在沿轴线方向的运动.以某四缸四行程内燃机曲轴—轴承系统为对象,基于建立的三维流体动力润滑模型,进行了计及曲轴轴向运动和曲轴受载变形导致轴颈倾斜的主轴承润滑性能研究.分析中,曲轴轴向运动规律通过内燃机台架试验实测,采用整体曲轴体单元有限元法计算主轴承负荷和曲轴变形,应用动力学法进行曲轴主轴承的润滑分析.结果 表明:与不计曲轴轴向运动的影响相比,计及曲轴轴向运动时,主轴承的轴心轨迹为一条不封闭的三维空间曲线,内燃机一个工作循环中的部分时刻主轴承的最小油膜厚度、最大油膜压力、摩擦功耗和端泄流量变化显著;曲轴轴向运动对内燃机各主轴承润滑特性的影响不一定都是不利的.因此,为了更加合理、接近实际,内燃机曲轴主轴承润滑性能分析中有必要计及曲轴轴向运动的影响.

The crankshaft rotates and moves along the axis in internal combustion engine. A crankshaft-bearing system of a four-stroke four-cylinder internal combustion engine is taken as the object, lubrication analysis of main bearing considering axial movement of crankshaft and deformation of crankshaft under load are based on the three-dimensional hydrodynamic lubrication model. In the analysis, the axial movement of the crankshaft is measured by internal combustion engine test bench. Crankshaft main bearing load and crankshaft deformation of internal combustion engine is calculated by the whole crankshaft solid-element FE method. Lubrication of crankshaft main bearing is analyzed by dynamic method. The result show that the journal center trajectory of crankshaft main bearing is an unclosed and three-dimensional spatial curve when the axial movement of crankshaft is considered, and the minimum oil film thickness, maximum oil film pressure, frictional power loss and end leakage flow-rate of main bearing is changed obviously at some times of an internal combustion engine working cycle comparing with not considering the axial movement. The influence of crankshaft axial movement on the lubrication performance of main bearings of internal combustion engine is not always adverse. Therefore, in order to be more reasonable and closer to reality, it is necessary to take into account the influence of axial movement of crankshaft in the analysis of lubrication performance of crankshaft main bearing.