Research On The Temperature Characteristics Of Bearings Of High-Speed Mechanical Spindle Using Oil/Air Lubrication

With the development of machine tools towards high speed, high precision and automation, people put forward higher and higher demands for the reliability of machine tools and machining accuracy. Among all kinds of error that affect the machining accuracy of machine tools, the thermal error accounts for about 40% to 70%. Especially, the spindle bearing occupies the largest part. Therefore, it's very important for improving the machining accuracy of machine tool system to control the temperature of bearings. As a kind of efficient and environmental protection way of lubrication, oil/air lubrication can effectively control the bearing's temperature rise. But it's found that oil/air lubrication is very sensitive to its parameters. Besides, the influence law of the parameters may vary largely for different objects under different conditions. With high-speed mechanical spindle using oil/air lubrication as the research object, the research contents mainly consist of thermal analysis of spindle's rolling bearing, the finite element simulation analysis of the bearings' temperature rise, experiment system design of oil/air lubricated mechanical spindle and experiment on the bearing's temperature rise.Thermal analysis model of the spindle's rolling bearing is established. Based on the theory of thermodynamics and heat transfer, the spindle's heat generation and heat transfer mechanism are analyzed. Considering the mechanical spindle's operating condition, the bearing's force condition is analyzed. Then the bearing's friction heating is calculated based on Palmgren's empirical formula. The spindle unit's heat transfer equation is established using thermal resistance network, and then the temperature formula of bearing outer ring's center node is derived.The spindle's temperature field is analyzed with the help of ANSYS software. The heat generation rate and convective heat transfer coefficient are calculated. The influence of speed, load, oil viscosity and compressed air flow on the bearing temperature rise is studied. Taking the front bearing's temperature rise for example, the rationality of ANSYS software's results is proved.Test platform for bearing's temperature characteristics of high-speed mechanical spindle using oil/air lubrication is constructed. The platform adopts horizontal layout of open power flow transmission scheme. It consists of mechanical and drive system, oil/air lubrication system, temperature measurement system and loading system.Research on temperature rise of the spindle's bearing is carried out. Experiment of the influence of oil quantity, speed, compressed air flow on bearing temperature rise is carried out. The results show that there exists a best oil quantity for the bearing to achieve the lowest temperature rise. Take the condition of testing speed 6000r/min for example, the best oil quantity is 0.45ml/h; the temperature rise increases with the increase of rotational speed; with the increase of the compressed air flow, temperature rise is reduced, and the greater the compressed air flow, the better the cooling effect. Through a comparative analysis of the experimental and simulational results, it is proved that the influence rules are well consistent.