Research On Thermally Induced Preload Of Rotor System Of Cageless Ball Bearing With Local Variable Speed Surface

Bearing preloading is the main means to improve the accuracy of the spindle rotor system.At present,the key supporting component of the motorized spindle is the angular contact ball bearing with cage.Due to the friction between the rolling element and the cage during operation,a large amount of heat is generated,resulting in a large heat induced preload,which leads to the decline of the accuracy and stiffness of the spindle,while the number of rolling elements without cage increases due to the absence of cage,The stiffness of the bearing is improved and the friction heat generation is reduced.Some scholars have carried out the research on the discretization of the rolling element of cage free bearing with variable diameter raceway.Therefore,this paper applies the local variable diameter raceway cage free angular contact ball bearing to the motorized spindle rotor system to analyze the heat generation of cage free bearing with variable diameter raceway and its heating in the motorized spindle rotor system,the thermally induced preload produced during its operation was studied.Firstly,the self-heating of non-cage bearing with variable diameter raceway is analyzed.According to the different stress states of rolling element in conventional raceway and local variable diameter raceway,the force equation of rolling element is established;The contact stress is analyzed according to the discrete state of the rolling element,and the contact mechanical models of the rolling element and the rolling element,the rolling element and the inner and outer rings are established;According to the contact mechanics model,the friction torque equation of non-cage bearing with variable diameter raceway is established;Considering bearing lubrication and friction torque equation,a non-uniform self-heating model of angular contact ball bearing without cage with local variable diameter raceway is established.Secondly,the temperature rise of variable diameter raceway non-cage bearing in motorized spindle rotor system is analyzed.The loss of each heat generating part in the motorized spindle is analyzed,and the heat generating equation of the built-in motor is established;The boundary heat transfer between the components of the motorized spindle rotor system is analyzed,and the boundary heat transfer coefficient is calculated;Combined with the self-heating equation of non-cage bearing in variable diameter raceway,the heating equation and heat transfer coefficient of built-in motor,the digital model of motorized spindle temperature field is established;According to the boundary conditions obtained from the digital model,the temperature field simulation model of motorized spindle based on variable diameter raceway non-cage bearing is established by finite element method.Based on the above research,the thermally induced preload of variable diameter raceway angular contact ball bearing without cage is analyzed.According to the temperature field model of variable diameter raceway non-cage bearing motorized spindle,the temperature rise data of the bearing under different working conditions are calculated;The thermal displacement of variable diameter raceway non-cage bearing under different temperature rise parameters is analyzed,and the geometric deformation compatibility equation of non-cage angular contact ball bearing under preload considering thermal displacement is established;The geometric deformation compatibility equation is solved by numerical analysis method,and the thermally induced preload of variable diameter raceway non-cage bearing of rotor system under different working conditions is analyzed.Finally,in order to verify the heat generation theoretical model of local variable diameter raceway non-cage angular contact ball bearing and compare the temperature rise between the bearing and conventional bearing,the temperature of variable diameter raceway non-cage bearing is measured on t10-60 bearing testing machine;In order to compare the temperature rise of the bearing under different test environments,a physical prototype of the temperature measurement of the front bearing of the motorized spindle is built at the same time;Based on the experimental data,the temperature rise fitting prediction function is designed to determine the temperature rise of angular contact ball bearing without cage in motorized spindle.In this paper,the research on the thermally induced preload of cage free angular contact ball bearing with local variable diameter raceway provides a theoretical basis for the application of this kind of bearing in motorized spindle,which is of certain significance to improve the operation accuracy of motorized spindle and reduce the system temperature rise.