Abstract
Working conditions such as lubrication, preload, and rotational speed have important influence on vibration and temperature rise of the spindle motor. In this study, controlled variable experiments are carried out on the silicon nitride (Si3N4) full-ceramic ball bearing and steel bearing of the same type, and the vibration signal characteristics and temperature rise of the spindle motor are tested and analysed, by changing the lubrication conditions, preloads, and rotational speeds of the spindle motor. Through the research, it is found that as the rotational speed increases, the vibration velocity of the Si3N4 full-ceramic bearing spindle motor under different preloads and lubrication conditions shows an overall increasing trend; kurtosis generally presents a downward trend and gradually flattens, indicating that although the vibration velocity increases at high speeds, the vibration signal shows a relatively stable state. As the rotational speed increases, the difference of vibration velocity under the condition of applying preload and no preload decreases, indicating that the influence of preload on the vibration of full-ceramic bearing spindle motor decreases with the increase in rotational speeds. At the same time, it is found that fr and 5fr have greater impact on the vibration of full-ceramic bearing spindle motor, where fr is the frequency of the bearing in normal operation, and 5fr is 5 times of the normal operating frequency. Lubrication conditions have little effect on the temperature rise of full-ceramic bearing spindle motor, and the temperature rise under nonlubricated conditions is even slightly lower than that under grease lubrication conditions. The research results show that the vibration velocity and temperature rise of Si3N4 full-ceramic bearing spindle motor are less than those of steel bearing with the same type, indicating that full-ceramic bearing has better performance than steel bearing under the same working conditions.
Highlights
As the main source of power, spindle motors are widely used in CNC machine tools, wind turbines, high-speed railway, and new energy automobiles and other fields [1,2,3], the performance and service life of spindle motors directly determine the service performance and life of mechanical equipment. e common sources of faults in spindle motors can broadly be classified as the followings [4, 5]: bearing faults, stator or armature faults, broken rotor bar and endring faults, and eccentricity-related faults
A large number of researches [31,32,33,34,35,36] have shown that, as a numerical statistic reflecting the distribution characteristics of random variables, kurtosis is sensitive to shock signals, and it can well reflect the large pulse signal generated by bearing vibration, especially suitable for early fault diagnosis of bearings. e vibration velocity and kurtosis of Si3N4 full-ceramic bearings and steel bearings spindle motors under different working conditions are shown in Figures 6–8, respectively
With the increase in rotational speed, the change of kurtosis tends to be gentle after 6000 r/min, indicating that the vibration signal is relatively stable. e kurtosis of the spindle motor with preload applied at lower rotational speed is obviously greater than that with no preload, but as the rotational speed increases, the gap decreases
Summary
As the main source of power, spindle motors are widely used in CNC machine tools, wind turbines, high-speed railway, and new energy automobiles and other fields [1,2,3], the performance and service life of spindle motors directly determine the service performance and life of mechanical equipment. e common sources of faults in spindle motors can broadly be classified as the followings [4, 5]: bearing faults, stator or armature faults, broken rotor bar and endring faults, and eccentricity-related faults. Excessive vibration and high temperature rise of the spindle motor will produce loud noises and aggravate bearing wear and may cause damage to the insulation layer or even burn the motor, which will affect the performance and reduce the service life of the spindle motor. E main factors affecting the service performance of rolling bearings include the following: bearing materials, structure, manufacturing accuracy, preload, working temperature, and lubrication conditions. Ere are many reasons for vibration and temperature rise in ceramic bearings during operation, such as frequent changes of rotational speeds, loads, external environment and other factors, friction and wear between the internal components of ceramic bearings, fatigue spalling and crack propagation of ceramic rings and rolling elements, cage fracture [11], existence of bearing clearance, viscosity and friction resistance of lubricating oil [12], and so on. Suitable lubrication [14, 15] can ensure effective lubrication of spindle motor bearings and reduce bearing wear and the generation of heat by friction, improving the performance and life of bearings. erefore, it is of great significance to carry out researches on spindle motor vibration and temperature rise, starting from the bearing material, preload, and lubrication conditions
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