内燃机曲轴——轴承系统曲轴变形引起的轴承润滑状态变化对曲轴强度的影响

EFFECT OF LUBRICATION STATUS OF BEARING CAUSED BY CRANKSHAFT DEFORMATION ON CRANKSHAFT STRENGTH FOR CRANKSHAFT-BEARING SYSTEM OF INTERNAL COMBUSTION ENGINE

在计及曲轴变形的轴承润滑分析的基础上,应用得到的轴承油膜压力分布作为载荷边界条件计算曲轴应力和强度,以分析目前曲轴强度计算中作用在轴颈上的载荷普遍采用假设的轴承油膜压力分布形式对结果精度的影响。计算中采用整体曲轴梁单元法计算曲轴变形和轴承负荷,采用动力学法进行曲轴轴承的润滑分析,应用有限元法计算曲轴应力。结果表明,计及曲轴受载变形的影响时,轴承油膜压力产生偏布且最大油膜压力明显增加,导致曲轴轴颈过渡圆角表面局部区域的应力数值明显增大,曲轴安全系数减小。因此为使曲轴设计更加合理、更接近实际,曲轴强度计算时应取曲轴-轴承系统为研究对象,根据轴承润滑分析实际计算结果,确定作用在曲轴轴颈上的载荷分布。

In order to analyze the influence of given film pressure distribution of bearing used generally as load acted on journal in present calculation of crankshaft strength on the calculating precision, on the basis of lubrication analysis of bearing considering crankshaft deformation, the stress and strength of crankshaft are calculated when gained film pressure distribution status of bearing is used as boundary condition of load. The crankshaft deformation and bearing load are calculated by whole crankshaft beam-element method. The lubrication of crankshaft bearing is analyzed by kinetics method. The crankshaft stress is calculated by finite element method. The results show that when the effect of crankshaft deformation under load is considered, the offset distribution of film pressure of bearing appears and the maximum film pressure increases remarkably, which result in the stresses of local area on surface of journal circular bead of crankshaft increase obviously and the safety factor of crankshaft decreases. Therefore, in order to make crankshaft design more reasonable and close to the factual condition, the crankshaft-bearing system should be taken as the study object when calculating crankshaft strength, and the loads on crankshaft journal should be calculated by factual lubrication analysis of bearing.