Analysis And Optimization Of Preload Characteristics Of Motorized Spindle Bearings

As one of the most important component of high-speed machine tools,the motorized spindle plays a key role in the stable operation of the machine.In order to ensure the adaptability of the dynamic performance of the bearing under multiple working conditions,a certain initial preload force is usually applied to the bearing during assembly of the motorized spindle to achieve the purpose of enhancing the rigidity of the motorized spindle,improving the precision and prolonging the bearing fatigue life.In this paper,the grinding motorized spindle is taken as the object,the dynamic analysis of the internal ball bearing is carried out,the influence of the preload force on the internal dynamic parameters of the bearing is analyzed,and then the dynamic stiffness characteristics of the motorized spindle bearing preloading are studied;the increase of the stiffness will result in the fatigue life of the bearing changes,so the fatigue life characteristics of the bearing under preloading are studied and the fatigue life under the preloading of the bearing is optimized;the temperature rise characteristic of motorized spindle under bearing preloading is also analyzed,to study the changes in perforrmance of various aspects under preloading,the main research contents are as follows:Firstly,based on hertz point contact theory and kinetic analysis method,considering the factors affecting the centrifugal force and gyro moment when the bearing rotates at high speed,under different preload forces,the variation of contact angle,contact area,centrifugal force anddynamic stiffness between rolling body and inner and outer ring of the angular contact ball bearing is analyzed.Secondly,using the L-P life theory,the fatigue life of the inner and outer rings of the angular contact ball bearing and the fatigue life of the bearing as a whole are calculated,and the effects of different preload and different speed on the fatigue life of the bearing are analyzed,and the variation between the fatigue life and the preload force of bearing and the relationship between fatigue life and rotating speed are obtained.Thirdly,according to the above contents,it is known that increasing the rated dynamic load of bearings can prolong the fatigue life of bearings.Therefore,taking the rated dynamic load of the bearing as the objective function,the diameter of rolling element,the pitch diameter of the bearing,the number of rolling elements and the curvature radius coefficient of inner and outer raceways as design variables,and the genetic algorithm is used to optimize the dynamic load ratings of the front and rear bearings,the result of the optimization of bearing fatigue life is finally obtained.Finally,taking the whole motorized spindle as the analysis object,the finite element modeling is carried out,and the main heat generation of the motorized spindle and the heat transfer coefficient and thermal convection coefficient between the components of the motorized spindle are calculated,the thermal steady state analysis of the motorized spindle with and without water cooling is carried out by using the finite element software,and the change of bearing temperature of the motorized spindle under different preload forces is analyzed and compared with the experimental data.