Development of High Speed Machine Tool Main Spindle Using Liquid-Gas Two Layer Film Hydrostatic Bearing

第一会计年度：(1)在设计前，分别通过真空泵和气孔出口形状的设计，解决了轴承表面供油的密封和排油和防止供油孔的油侵入两个问题。(2)在静态轴承性能数值计算的基础上，考虑上述方法，设计了一种新的液气两层膜流体润滑磨床主轴承模型，并进行了制造。上一会计年度：(3)通过试验估计了该轴承模型的静态性能。试验结果与设计计算结果吻合较好。(4)评价了油膜的存在对过载的抗癫痫性能。结果表明：(a)当轴在大偏心距下接触油膜时，轴承刚度急剧增大，因此，薄油膜可以有效地防止轴承过载损坏。(b)过载时油膜厚度几乎不受供油流量的影响，因此在油膜层存在的极限下，少量的油流量就足以防止轴承损坏。(5)尽管结构复杂，但这种新型轴承既能避免气体轴承的弱点——过载卡住，又能减小气体轴承的摩擦，证明了在机床上应用的可行性。

In the first fiscal year:(1) Before designing, the two problems of sealing and exhausting the oil supplied into the bearing surface and preventing oil intrusion into the air supply holes were solved by means of vacuum pump and design of the exit shape of air holes, respectively.(2) The new model of main bearing of grinder hydrostatically lubricated by liquid-gas two layer film was designed being based on the numerical calculation of the static bearing performance and considering the above mentioned method, and was manufactured.In the last fiscal year:(3) The static performance of this bearing model was estimated by the experiments. The experimental results were in good agreement with the results of the calculation for the design.(4) The anti-seizure performance against over load due to the existence of the oil film was evaluated. The results are shown as follows:(a) The bearing stiffness increases abruptly when the shaft contacts on the oil film at large eccentricity, and thus the thin oil film is effective to prevent bearing damages against over load.(b) The oil film thickness under over load is scarcely affected by the flow rate of supplied oil, and consequently a little oil flow rate is sufficient to prevent bearing damages with in the limit of the existence of the oil film layer.(5) It is concluded that the application feasibility of this new type of bearing for machine tools is demonstrated in spite of the structure complexity because it takes advantages of avoiding seizure at over loading which is a weak point of gas bearing as well as of low friction in gas bearing.