机床主轴轴承热诱导预紧力及刚度计算与实验研究

Thermally Induced Preload and Stiffness Calculation for Machine Tool Spindle Bearing

为了研究机床主轴系统非均匀温升带来的热位移对轴承预紧力和动刚度的影响,建立了一种机床主轴系统热机耦合模型。在分析轴承摩擦损耗影响因素的基础上,确定了系统热载荷和边界条件,采用有限元方法求解了机床主轴瞬时温升和热变形,根据轴承载荷-位移关系式求解轴承的热诱导预紧力,基于改进的Jones模型计算了轴承径向刚度。最后,实验测定轴承预紧力,分析预紧力影响因素。理论计算与实验结果表明:在定位预紧下,主轴、隔圈、轴承座和轴承热位移会导致轴承预紧力和径向刚度的增加,且随着初始预紧力、转速和环境温度增加,预紧力变化幅值也增加。此外,局部冷却引起热位移的变化,从而改变轴承预紧力和径向刚度的变化规律。

To investigate the influence of thermal displacement due to non-uniform temperature rising in machine tool spindle system under bearing preload and dynamic stiffness, a thermo- mechanical coupling model is established. The factors to influence bearing friction loss are analyzed and thermal load and boundary conditions of machine tool spindle system are calculated. And the instantaneous temperature distribution and thermal deformation of machine tool spindle are solved by FEM. According to the bearing load-displacement equation, thermal induced preload is acquired, and the radial stiffness of bearing is evaluated by improved Jones＇ quasi- statics model. The laws and main influence factors of thermally induced preload are tested and analyzed. The theoretical and experimental results indicate that thermal displacements of spindle, baffle, bearing housing and bearing strengthen preload and bearing stiffness of the rigidly preloaded bearing; the increasing initial preload, rotating speed and environmental temperature extend the changing preload amplitude; bearing preload and stiffness are highly sensitive to local cooling which changes thermal displacement.