Development of spindle with motor function for ultra-precision machine tool

本研究的目的是开发一种用于超精密机床的新型主轴。超精密机床主轴与传统主轴的区别在于，该主轴利用水流产生动力供主轴运行。相比之下，超精密机床的传统主轴采用电力驱动。在主轴中，水流被用来实现主轴的三大重要功能。这三个功能是：(1)支撑功能：水静压轴承支撑主轴体；(2)电机功能：主轴体内部设计几何形状简单的流道，使水流通过流道产生扭矩，使主轴体转动；(3)冷却功能：温控水使主轴变形最小化。本文提出了主轴的工作原理和结构。然后介绍了主轴的设计过程。在此基础上，开发了确定最佳参数组合的软件，以获得最高的主轴效率。本文通过开发的软件，计算出以下规格主轴的最佳设计参数。(1)额定转速：10000rpm(2)额定功率：50W(3)水静压轴承额定刚度：50n /μm。对所研制的主轴进行了性能试验研究。实验结果表明，主轴运行平稳，说明主轴静压轴承和电机操作正确。此外，实验验证了电机性能和冷却功能满足设计要求。相比之下，水静压轴承的刚度没有达到规范的水平，主要是由于轴承中的限流器的特性。在今后的工作中，将通过改变节流器的直径来提高轴承的刚度。

A purpose of this study is to develop a new spindle for ultra-precision machine. A distinction between the spindle and conventional spindle for ultra-precision machine tools is that proposed spindle uses water flow to generate power for spindle operation. In contrast, conventional spindle for the ultra-precision machine tools uses electric power. In the spindle, the water flow is utilized for important three functions of the spindle. The three functions are the follows;(1) Support function: water hydrostatic bearings support the spindle body,(2) Motor function: flow channels with simple geometries are designed inside the spindle body so that the water flow through the channels generates torque to rotate spindle body, and(3) Cooling function: temperature controlled water minimizes the spindle deformation.This study proposes the principle and structure of the spindle. A design procedure for the spindle is then introduced. Based on the procedure, software to determine a combination of optimum parameters was developed so that highest efficiency of the spindle can be obtained. In this study, optimum parameters to design the spindle with the following specifications were calculated by developed software.(1) Rated rotational speed: 10,000 rpm(2) Rated power: 50W(3) Rated stiffness of the water hydrostatic bearings: 50 N/μm.Experiments were carried out to investigate performances of the developed spindle. The experiments show smooth operations of the spindle, which indicates correct operations of the hydrostatic bearings and motor of the spindle. In addition, the experiments verify that performances of the motor and cooling function satisfy the design requirements. In contrast, stiffness of the water hydrostatic bearings does not reach the level of the specification, due to mainly the characteristic of the restrictors in the bearings. In future work, improvements of the bearing stiffness will be attained by altering diameter of the restrictors.