精密多油楔动压轴系的楔形间隙参数与油膜运动稳定特性

摘要

针对精密仪器轴系的研制和精度分析,研究了立式三油楔动压轴系的结构、轴承轮廓结构,建立数学模型、分析模型,对轴系动压油膜的动力特性做了分析.对于主轴在动压油膜反力与外载荷作用下处于某一平衡位置(e,θb)运转时,能否经得起任意微扰动的干扰而失稳,建立了油膜运动稳定性的判据.应用数值模拟和计算机编程,深入研究了关键设计参数楔形间隙bm、cm相应的油膜运动稳定特性,揭示了楔形间隙值与轴系失稳的对应关系,给出了油膜稳定性因数Log(Sp)与偏心率ε(ε=e/c)之间的变化曲线图,并指出了楔形间隙参数最佳的取值范围.研究结果指出:楔形间隙是轴系设计和制造的重要敏感参数;最大楔形间隙bm和最小间隙cm值之间应保持一定的比例,否则油膜运动发散,轴系平衡失稳,导致主轴转动中产生较大的晃动.对于低速立式三油楔动压轴系,则bm-cm≥0.8 μm.比较研究结果与成功轴系实例,表明实例中bm、cm取得符合轴系的油膜稳定条件.证明研究结果对该类轴系的设计具有实用性.%The structure of vertical three-wedge hydrodynamic bearings and the profile structure of bearing bores are studied by study and performance analysis of precision bearings, and the dynamic characteristics of hydrodynamic oil film of the bearings are analyzed by building mathematics model and analytic models. A criterion has been set up for judging the stability of oil film motion so that it is possible to tell if the main shaft may fail to tolerate any microdisturbance, while it is rotating in an equilibrium position(e,θb)where the reverse force of hydrodynamic oil film counteracts the external load on the shaft. Furthermore,the stability of the oil film with respect to wedge gap parameters bm and cm of the bearings is investigated by numerical simulation and programming,and the interrelation between the failure of bearings and the value of wedge gap is revealed,the variation of oil film stability factor Log(Sp) with eccentricity ε(ε=e/c) is established, and the optimum range of wedge gap parameters bm and cm is given. The investigation indicates that wedge gap parameters bm and cm are important sensitive parameters for design and fabrication of bearings; a certain ratio must be maintained between maximum wedge gap bm and minimum wedge gap cm. Otherwise oil film whip may occur and bearing stability may be lost and the main shaft has considerable sway in rotation. For a low speed vertical three-wedge bearing system,bm-cm≥0.8 μm. The results of comparative research successful examples of bearing design and fabrication indicates that selected values of bm and cm meet the stability criteria,which proves that the results of research are very useful for the design of bearings.