Analysis Of Preload Of High Speed Angular Contact Ball Bearing And Research On Controllable Preload Method

Angular contact ball bearing is the main support method for high-speed electric spindles,and bearing preloading is one of the critical technologies of high-speed electric spindles.studying the preload of high-speed angular contact ball bearings,determining the best preload of the bearing and adjust the preload according to the working conditions through dynamic adjustment method automatically are of great significance to improve the performance of the electric spindle and bearing.This thesis takes high-speed angular contact ball bearings as the research object.Based on the theoretical analysis of the thermal dynamic characteristics of the bearing,a mathematical model for calculating the bearing preload force is established.The calculation method is proposed and the corresponding program is written to analyze the dynamic characteristics of the bearing preload force.On this basis,a controllable pretensioning mechanism based on piezoelectric ceramics is proposed,and its feasibility is analyzed numerically and verification.The main research contents and conclusions of this article are as follows:(1)Based on Hertz contact theory,rolling bearing dynamics and raceway control theory,with 7012/CD type angular contact ball bearings as the research object,a quasi-dynamic model of high-speed angular contact ball bearings considering thermal displacement is established,combined with specific examples analysis.The calculation results show that the radial thermal displacement of the bearing inner ring is the largest,followed by the outer ring,and the rolling body is the smallest.When considering the influence of thermal displacement,the angular contact ball bearing increases with the rotation speed,the contact angle between the rolling body and the inner and outer ring decreases significantly,and the contact load between the rolling body and the inner and outer ring increases dramatically.(2)Based on the analysis of bearing pre-tightening force characteristic,the influences laws of rotation speed,thermal displacement,centrifugal displacement and preloaded on the pre-tightening force are analyzed,and to determine the required minimum pre-tightening force calculation method of bearing.The research results show that the bearing preload force increases with the grow up of the speed,and theinitial preload is increased,the amplitude of the change of preload is also increased.The effect of bearing thermal displacement on the preload force is greater than that of centrifugal displacement.When considering the thermal displacement of the bearing,the effect on the preload force is greater than that of the centrifugal force.The amplitude of the bearing preload force changes significantly under the positioning preload method,and the bearing preload force remains unchanged under the constant pressure preload method.(3)In order to realize that the spindle bearing can be dynamically adjusted under actual working conditions,a controllable method based on the speed and temperature feedback is designed by using the basic characteristics of piezoelectric ceramics,such as the inverse piezoelectric effect and fast response.The deformation of the steel and lead double sleeve is analyzed to verify the feasibility of the method.The results show that the influence of the thermodynamic characteristics of high-speed angular contact ball bearings on the preload force cannot be ignored.Considering its effect,the optimal preload force of the bearing can be determined more accurately;the controllable preload method can improve the stability of the system.