Friction Characteristics Of High Speed Motorized Spindle Angular Contact Ball Bearing

The high-speed motorized spindle is a combination of the machine tool spindle and the motor.At the same time,the spindle motor is equipped with components that realize the integrated function of the motor and the machine tool spindle.The angular contact ball bearing has the advantages of high joint load bearing capacity,high speed and high precision,so it is used for the main support of high-speed motorized spindle.When the high-speed motorized spindle runs under different working conditions,the friction performance inside the bearing will change,which will affect the stability of the bearing's running process,and it will also affect the dynamic characteristics of the motorized spindle's running process.Therefore,research and analysis on the friction characteristics of high-speed motorized spindle bearings can help provide guidance for friction reduction design and work efficiency of high-speed motorized spindle bearings.The main research contents include the following aspects:(1)The mechanical characteristics and motion law of angular contact ball bearing for high-speed motorized spindle are studied.Taking the motorized spindle angular contact ball bearing as the research object,the quasi-static model of the high-speed angular contact ball bearing and the equation of motion of the bearing were used to analyze the dynamic parameters such as the contact load between the rolling elements and the raceway inside the bearing,the dimensions of the contact ellipse,and the bearing.The kinematic parameters such as the spin angular velocity,revolution angular velocity,and rotational angular velocity provide a certain theoretical basis for the subsequent research on the internal friction torque and friction heat generation of the bearing.(2)The friction mechanism of motorized spindle bearing is discussed and the mathematical model of friction moment is established.The main shaft bearing of machine tool will be affected by overturning moment.This thesis considers this condition and calculates the sliding friction coefficient of the bearing according to the lubrication state between the rolling body and the raceway when the bearing is running at high speed.According to the model of sliding friction coefficient of bearing and the interaction between the components of bearing,three models of friction moment caused by differential sliding between bearing roller and raceway,friction moment caused by elastic lag of bearing raceway material and friction moment caused by spin sliding are established,which are respectively obtained by palmgren's empirical friction moment formula and SKF Bearing Manufacturer's experiment The correctness of the model is verified by the comparison of moment formulas.(3)Explore the influence law of different parameters of motorized spindle angular contact ball bearings on bearing friction torque.According to the established frictional torque mathematical model of angular contact ball bearings,the influence of bearing structural parameters,working condition parameters and thermal displacement on the frictional torque of bearings was studied.The analysis results show that the increase of the initial contact angle of the bearing,the curvature coefficient of the inner and outer grooves,and the axial force will cause the increase of the bearing friction torque.The differential sliding friction torque is the most obvious,and the elastic hysteresis friction torque is the weakest.The bearing friction torque increases with the increase of the radial thermal displacement;it almost changes with the increase of the axial thermal displacement;and the bearing thermal displacement has a more obvious effect on the friction torque when the bearing rotation speed is lower.The bearing thermal displacement has the largest impact on the bearing's differential sliding friction torque,the spin friction torque has the second largest impact,and the elastic hysteresis friction torque has the weakest impact.(4)Analysis of the thermal influence factors of bearing.Considering the size of the contact area between the rolling elements and the raceway in the bearing,the normal contact load between the rolling element and the raceway,the oil film thickness of the contact area,and the viscosity of the lubricant,a differential sliding friction shear stress calculation model is established.The calculation model of differential sliding friction shear stress bearing and sliding bearing spin caused by friction heat generating bearing local friction heating model is established.Then,based on the established frictional heat generation model,the thermal influence of the bearing is analyzed.The results show that when the bearing speed is below 10000 r/min,the frictional heat generated between the rolling elements and the raceway is mainly caused by the frictional friction caused by the spin sliding friction,and the heat generated by the differential sliding friction is very small,but with the increase of the speed,the frictional heat generation of the bearing is the main component in the frictional heat generation of the bearing under the condition of the high speed.At the same time,the inner groove curvature radius and axial load of the bearing have a great effect on the frictional heat generation of the bearing,and the outer groove curvature has a very small effect on the bearing.