Elastohydrodynamic Lubrication Analysis Of Crankshaft Bearing Considering Crankshaft Deformation Under Load And Roughness Surface

Journal misalignment exists generally in journal bearing when working. When serious journal misalignment takes place, the least film thickness of bearing reduces greatly and the highest film pressure of bearing increases remarkably. So, it is necessary to consider surface roughness, oil pressure-viscosity relationship and surface deformation of bearing when analyzing hydrodynamic lubrication characteristics of misaligned bearing.The elastohydrodynamic lubrication considering roughness surface of shaft-bearing system which is one of the most general and essential parts of support-transmission system in various mechanical devices is studied theoretically. The results show that the oil pressure-viscosity relationship has large effect on the lubrication characteristics of misaligned bearing, especially under condition of great misalignment angle. The surface roughness affects lubrication characteristics of misaligned bearing when eccentricity ratio and angle of journal misalignment are all large and not considering surface deformation of bearing. The directional parameter of surface has obvious effect on lubrication of misaligned bearing when ratio of least film thickness to surface roughness is small. The surface roughness and directional parameter of surface have little effect on lubrication of misaligned bearing when considering deformation of bearing surface. Although having little effect on lubrication of aligned bearing, the deformation of bearing surface has remarkable affects on lubrication of misaligned bearing. The larger the eccentricity ratio, the greater the effect of the deformation of bearing surface on lubrication of misaligned bearing.The difference of bearing's deformation under three kinds of load is analyzed when using ANSYS software. The method of defining load on four elements sharing one node is applied. An exact deformation-matrix is founded.The elastrohydrodymic lubrication properties of crankshaft-bearing system considering crankshaft deformation under load and roughness for IC engine are studied based on the anlysis of the elastrohydrodymic of msligment journal bearing considering roughness surface. The results show that roughness surfaces have great effect on the bearings orbit, but the bearing's deformation affect the connecting rod bearings orbit slightly. When the bearings' roughness is considered, the highest film pressure increased obviously, and the journal friction coefficient and the minimum film thickness have a slightly decreased, the effect on lubricant flow-rate can be neglected; when the bearing's deformation is considered, the highest film pressure decreased; the effect on lubricant flow-rate, journal friction coefficient and the minimum film thickness can be neglected.