Research On Mechanical Properties Of Angular Contact Ball Bearings In High-Speed Moterized Spindle

As one of the key structures of high-speed CNC machine tools, the performance of the motorized spindle will directly affect the overall machine efficiency and precision and it has put forward higher requirements for the stiffness of the spindle, the control system, lubrication system and so on. Angular contact ball bearings, due to its low friction, ability to withstand external loads in both axial and radial directions, low energy consumption and other characteristics, is the key supporting part of motorized spindle. The mechanical properties of angular contact ball bearings will affect the performance of the entire spindle. When the motorized spindle runs at high speeds, the change of internal parameters will affect the bearing stiffness, bearing rollers running status. Finally, it will result in failure of the ball bearings, descent of the critical speed of the motorized spindle. The bearing dynamics properties will seriously affect the dynamic characteristics of the bearing-rotor model. Therefore, the study of the mechanical properties of high speed angular contact ball bearing is very necessary, and it is also a key factor to improve the performance of motorized spindle.Through the establishment of the quasi-static bearing model of the angular contact ball bearings, this thesis studies the impact of the bearing force, the speed of motorized spindle on angular contact ball bearing internal parameters, as well as bearing stiffness. Then, the angular contact ball bearing dynamic model is established to study the impact of the bearings force, the speed of motorized spindle, bearing roller clearance on dynamics characteristics of the bearings. The work of this paper is organized as follows:In Chapter 1, the background and significance of this study are elaborated, an overview on researches and progress about the quasi-static, dynamic features of the angular contact ball bearings and the whirl frequency of the rotor at home and abroad, and then the research content and framework of this thesis is proposed.Based on the Hertz contact theory, Chapter 2 discusses the impact of the ball force, outer bearing ring curvature on the contact deformation and contact stress between the ball and the outer ring, where the finite element analysis software is employed to analyze the contact stress and deformation.By establishing the quasi-static model of the angular contact ball bearings and the deMul’s ball bearing stiffness calculation formulation, Chapter 3 investigates the impact of the bearing force, bearing speed on the contact force, the contact angle, the contact statues between the ball and the rings as well as the bearing stiffness.In Chapter 4, the bearing-rotor finite element model is established according to the Timoshenko beam theory to analyze the impact of the bearing stiffness softening phenomenon bearing preload, gyroscopic moment of the rotor torque and the bearing group spacing on the whirl frequency of the rotor.In Chapter 5, an angular contact ball-bearings model with five DOFs is established to analyze the impact of the bearing force, bearing roller clearance and the speed of the motorized spindle on the angular contact ball bearing dynamic characteristics, where the effect of the inner ring high-speed expansion is taken into account.In Chapter 6, the main work of the thesis is summarized, and the further research work is also proposed.