DEVELOPMENT OF ULTRA HIGH SPEED SPINDLE USING A POROUS FLOATING BUSH FOR DRILLING MACHINES

最近，与信息相关的设备的尺寸迅速缩小。因此，安装在这些设备上的印刷电路板上的孔直径越来越小，并且为了制造小孔，钻孔主轴对20000rpm以上的更高转速的要求也越来越高。考虑到这些设备的未来小型化趋势，必须开发转速超过300,000 rpm的高速主轴。在这项研究中，我们提出了带有多孔浮套的空气静压滑动轴承，以提高由空气静压轴承支撑的转子在高速下的稳定性。在所提出的轴承中，加压空气仅被馈送到两个浮动衬套端，但由于多孔材料的影响，浮动衬套的内外壁都可以作为气动静力轴承。此外，浮动轴瓦两端非常小的间隙可以避免加压供气的压力降低，这使得这种多孔轴承保持与普通多孔轴承相当的刚度和承载能力。我们从理论上研究了所提出的轴承的各种性能，如承载能力、刚度和高速不稳定性。然后在理论计算的基础上制造了所提出的浮动轴瓦滑动轴承，并将实验结果与理论计算结果进行了比较。结果得出以下结论：(1)。实验结果表明，多孔浮套气动滑动轴承具有良好的高速稳定性。通过与实验结果的比较，验证了理论计算的有效性。研究发现，使用所提出的轴承制造的高速主轴作为非常小的孔的钻床具有优异的性能。

Recently, the size of devices associated with information has been rapidly reduced.Accordingly the diameter of holes in printed circuit boards installed in these devices is getting smaller and the demand of higher rotational speed of more than 200,000 rpm is also increasing for drilling spindles to manufacture small holes.Considering the future trend for miniaturization in these devices, high speed spindles with rotational speed of more than 300,000 rpm has to be developed.In this research, we proposed aerostatic journal bearings with a porous floating bush to improve the stability of a rotor supported by aerostatic bearings at high speeds.In the proposed bearing, pressurized air is fed only to both floating bush ends, but both the outer and the inner walls of a floating bush can function as an aero static bearing due to the effect of porous material.In addition, a very small gap at both ends of a floating bush can avoid the pressure reduction of pressurized supply air, which makes this porous bearing maintain stiffness and load capacity comparable to an ordinary porous bearing. We theoretically investigated various performances of the proposed bearing such as load capacity, stiffness and instability at high speeds.Then we manufactured the proposed floating bush journal bearings based on, the theoretical calculations and compared experimental results with theoretical calculations.As a result, the following conclusions were obtained.(1).It was experimentally confirmed that the proposed aerostatic journal bearing with a porous floating bush has an excellent stability at high speeds.(2).The validity of theoretical calculations was confirmed by comparing them with experimental results.(3).It was found that the manufactured high speed spindle using the proposed bearings has excellent performances as a drilling machine for very small holes.