Research On The Design Of Adaptive Pretensioning Mechanism Based On Hydraulically Driven Elastomer

In order to adapt to the processing of high speed,high precision and high efficiency of modern processing sought,the speed range of the high speed spindle is not only expanded,but also requires the spindle with low speed,high torque and high speed and high power.And thus,this requires the spindle at high speed should have high rigidity,high speed and good stability.The preload of the bearing in the spindle unit is the main means to improve the rigidity and stability of the spindle.Therefore,its necessary for the bearings in the high speed spindle to adjust the preload dynamically at different speeds.Because of its high speed performance and supporting performance,high speed angular contact ball bearing has become the most widely used bearing type in high-speed spindle.And the analysis of its mechanical properties is the basis for the study of the best preload of bearing.In this paper,the mechanical characteristics of high-speed angular contact ball bearings and the establishment of controllable preload model are analyzed and studied.The main contents include:(1)Based on the Hertz contact theory,we analysised the regularaction of the commonly used high speed angular contact spindle stiffness,contact load,contact angle,ratio,friction torque,temperature parameters.Relying on the regularaction,It lays a theoretical foundation for the modeling of controllable preload.(2)On account of the preload analysis of bearing load distribution,the calculation method of minimum pvetightening force required for bearing is determined.Considering the problems existed in the prctightening mode of the spindle and the fixed pressure prctightening mcthod,a controllable pretension model with the reasonable temperature rise of the bearing as the control target is proposed.(3)In view of the limitations of pre tightening and constant pressure pre tightening methods in the spindle position,this paper presents a method of applying adjustable preload force to the outer ring of the bearing unit in the spindle unit,taking the hydraulic system as the driving unit and the deformation preload structure as an acluator.In order to study the deformation of pre tight structure,the mechanical model of hollow rod with irregular thickness is simplified,and its deformation is analyzed theoretically.By establishing the finite element model of the preload structure,the deformation analysis is carried out,and the simulation data are compared with the theoretical data.Finally,the feasibility and theoretical model of the adjustable preload structural model are verified.In view of the a?b wall thickness and internal cavity radius delta oil pre tightening structure is the main factor to determine the deformation,and by using the multi-objective fuzzy optimization design method to optimize the structure size of the adjustable preload model,through fuzzy optimization design,the line displacement along the X axis of increased by 54.36%.Along Y,Z axis line displacement decreased by 61.41%,61.41%.