机床主轴-轴承系统热-力耦合模型及其动态性能研究

为了研究机床主轴系统在高速运转情况下的动态性能变化,建立了一种主轴-轴承系统的热-力耦合模型,该模型包括了主轴转子和轴承模型.采用有限元法得到主轴转子模型,该模型考虑了主轴的离心效应、陀螺力矩和轴承刚度软化效应.通过对Jones非线性轴承模型进行改进获得了轴承模型,它考虑了主轴与轴承的初始装配过盈量、离心力、温升等因素导致的轴承内圈径向变形及预紧力的变化.理论仿真结果表明:轴承内圈离心膨胀以及内外圈热膨胀会导致轴承刚度增大,而对于背靠背的轴承配置形式,热诱导预紧力会导致轴承刚度减小.此外,主轴离心效应比轴承的刚度软化对主轴-轴承系统动态特性的影响更明显.

Thermo-Mechanical Coupling Model and Dynamical Characteristics of Machining Spindle-Bearing System

To investigate the varying dynamical characteristics of CNC machine tool’s spindle system at high rotating speed,a thermo-mechanical coupling model of spindle-bearing system is established,which consists of a spindle shaft model and a bearing model.The spindle shaft model is generated by the finite element method considering the effects of centrifugal forces,gyroscopic moments and softening of bearing stiffness.Taking the effects of the radial deformation of bearing inner and outer rings and the change of bearing preload caused by the initial assembly interference between the spindle and bearings,the centrifugal forces and rising temperature into account,the bearing model is improved based on the nonlinear Jones’ bearing model.The simulations show that the induced centrifugal expansion of inner ring and thermal expansion of inner and outer rings will strengthen the bearing stiffness while the thermally induced preload lowers the bearing stiffness for the ’back to back’ bearing arrangement.In addition,the centrifugal effect of the spindle impacts the dynamical characteristics more obviously than the softening of bearing stiffness.