Study On Heat Characteristics Of Spindle Bearings And Influences On Speed And Dynamics

The friction Heat in spindle bearings has obvious influences on the speed and dynamics, and is an important reason to limit machining tools for higher speed and precision. In theory and practice, it is important to build up the heat transfer equations, compute the friction heat and temperature and determine the influences on the speed and dynamics.On the basic theory of transfer heat, tribology of rolling bearings and rotor dynamics, Taking GDZ48A electrospindle as an example, the paper puts forward the spindle bearing's quasi-dynamics analysis model with the influences of the friction heat and preloadings analyzes the friction moment, velocities, contact loads, friction heat and stiffness and studies the influences of the friction heat, structure and application parameters on the speed and dynamics. Details of studies are as follows.1) Quasi-dynamics analysis of spindle bearings: The paper improves the quasi-dynamics analysis model including the influences of the friction heat and preloadings and establishes a series of equations on the velocities, contact loads, deformation, deflection and friction moment.2) Temperature analysis of spindle bearings: Using the basic theory of heat transfer, the paper founds the heat transfer model and derives the heat transfer resistance and heat transfer equations in spindle units.3) Running performance analysis of spindle bearings: The paper analyses the running performances with the influences of the friction heat, structure and application parameters through an example.4) Stiffness analysis and testing of spindle bearings: Using Hertz contact theory, the paper derives the stiffness formula, computes, analyzes and tests the stiffness through an example.5) Dynamics analysis of spindle units: Applying difference method, finite element method and vibration theory, the paper analyses and computes the deformation and resonant frequencies of the spindles through an example.6) Minimum preload analyses of spindle bearings: The paper puts forward the principles and computations of the minimum preload through an example.7) Speed experiment of spindle bearings: The paper testy studies the influences of (lie structure and lubrication parameters on the speed.From the results of analysis, computation and testing, the results show:1) The friction heat and preloadings of spindle bearings obvious influences the speed and dynamics. The friction heat and inertia effects in high speed deteriorate the speed and dynamics. The influences in pressure preloading are less than in position preloading and high-speed applications should use pressure preloading.2) The temperature rise with one land's outer rings is lower than with two land's outer rings. Ball number has a little influences on the temperature. The larger the balls and free contact angles, the higher the temperature and the influences are more obvious in pressure preloading than in position preloading. The larger and more the balls, the higher the stiffness, ball number has more obvious influences than ball diameter. The larger the free contactangles, the less the radial stiffness and the higher the axial and angular stiffness. But the large balls make the axial and angular stiffness degrease and large free contact angle makes axial and angular rigidities vary little in pressure preloading.3) As preloads increase, the temperature and stiffness increase a little. The preload should be increased as speed and loads increase in pressure preloading. The higher the environment temperature, the higher the temperature rise in position preloading, on the contrary in pressure preloading. In oil-mist lubrication, the quantity and viscosity of oils as well as air pressure influence the speed, synthetic oils are better for lubrication than mineral oils and mineral oils mixed with a little synthetic oils is the best. It can improve the speed to correctly select application parameters.4) Hybrid spindle bearing's running performances are obviously better than spindle bearings, especially in positio...