Research On Influence Of Tightening Technology Of Bearing Cap’s Bolts On Bearing Preload

With the continuous development of high-end equipment in the direction of high precision and heavy load,high requirements are also placed on the performance of key basic parts.Rolling bearing is an important supporting part of shafts,and the performance and reliability of the whole machine depends on its preload quality.The bearing cap plays an important role in controlling the pre-deformation of bearings and fixing the position of shafts in the pre-tightening structure,and is widely used in the shaft of high-end precision equipment.After bearing cap is fastened by bolts on it,under the action of the mechanical joints and elastic interaction between the bolts,the actual preload force of the bolts changes to different degrees.The bearing preload is changed by force of the bearing cap.The bearing cap fastening process now relies on experience and trial-and-error adjustment,and it is difficult to ensure the fastening quality which leads to the efficiency of machines lower.This paper takes angular contact ball bearing positioning pre-tightening as an example to study the improvement method of bearing cap’s bolts fastening technology On this basis,study the preload of rolling bearing under the action of bearing cap fastening.The main research contents are as follows:First,based on the basic theory of elastic interaction,with the goal of solving the actual preload and joints’ deformation of bolt group,an analytical model of the bolt group considering the mechanical joint surface is presented,and the analytical method of each equivalent spring stiffness in the model is studied;The influence of main structural parameters on the actual preload distribution is discussed,and a structural design method to reduce the dispersion of bolts’ preload is proposed.The influence of the tightening process parameters on the actual preload distribution of bolts is studied A reverse order compensation method for the preload of the bolt group assembly is proposed,which can eliminate the influence of elastic interaction and effectively reduce the dispersion of the bolt’s preload.The finite element model of the connecting structure of the bearing cap and the bearing housing is established,and results of the finite element numerical model and the analytical model are compared to verify the accuracy of model and the reverse order compensation method.Considering the bearing interference assembly friction and the change of the working contact angle,the relationship between the preload of bolts on bearing cap and the preload of the bearing is established.The influence of the contact surface roughness and bolt tightening torque on the preload of rolling bearing is studied,and the positioning pre-tightening design measures considering the tightening effect of the bearing cap are proposed.Finally.the research aims to present the design method of preload in bolts on bearing cap and improve the pre-tightening quality of rolling bearings.The friction torque of the bearing is taken as the optimization objective,and the rigidity of the bearing,the working reliability and the strength of the connected parts are the constraint conditions to establish the preload design model.Combined with the reverse order compensation method,a design method for the tightening process of bolts on bearing cap is proposed.Based on the above research content,a complete bearing cap process design method is formed to ensure the predictive quality of important significance for the tight cap process.