超高速主轴液体静压轴承设计与特性研究

难加工材料具有强度高、硬度高和耐腐蚀等特点，在航空航天和医疗等领域应用广泛，其加工问题一直是学术界的研究热点。在已有研究中，超高速加工技术展现出对这类材料的加工优势，但其深入研究和应用受限于机床主轴的性能。超高速主轴中的支撑方式主要有气体静压轴承和液体静压轴承两种。气体静压轴承极限转速高，但刚度低、动态特性差，应用场合有限。液体静压轴承承载特性好，更适合用于难加工材料的超高速加工，但存在发热量大、动压效应明显等问题。本文研究内容将从轴承设计的角度出发，围绕如何削弱温升和动压效应对主轴的影响展开。

确定主轴支承方案和轴承结构。对比分析不同液体静压支承方式的优缺点，采用径向止推联合轴承-轴向预载轴承的形式作为主轴的支承方案，该方案具有更好的热稳定性。在充分研究轴承性能与结构参数的相关性后，以最大轴承刚度和最小润滑油温升为目标，运用NSGA-II算法对支承方案中的轴承进行了多目标优化设计，得到了一个综合性能最优的轴承设计方案。

研究轴承与主轴转子系统的承载特性、温度特性以及动态特性。在上述轴承设计方案的基础上，利用Fluent软件建立液体静压轴承的仿真模型，研究了芯轴偏心对轴承承载特性的影响，并分析了不同转速下油膜温度场的变化以及动压效应对轴承承载特性的影响，获得了不同工况下的轴承刚度参数。此外，基于ANSYS Workbench平台，构建了超高速主轴转子系统的仿真模型，探究了轴端受载位置对主轴轴端径向刚度的影响，并分析了转速和砂轮对芯轴模态频率及振型的影响，研究了芯轴在外部载荷作用下的稳态响应特性。

最后，对超高速主轴的部分性能进行了测试。测试结果显示，在润滑油供给压力为60 bar的条件下，主轴轴向刚度为99.58 N/μm，轴端径向刚度为83.38 N/μm。主轴径向固定敏感方向回转误差为0.16 μm，轴向跳动误差为0.08 μm；润滑油最大温升为20℃；主轴最高转速为45000 rpm。

Difficult-to-machine materials, characterized by high strength, hardness, and corrosion resistance, are widely used in aerospace and medical fields. The machining of these materials has always been a hot topic in academia. In existing research, ultra-high-speed machining technology has shown its advantages in processing these materials, but its in-depth research and application are limited by the performance of the machine tool spindle. The support methods in the ultra-high-speed spindle mainly include aerostatic bearing and hydrostatic bearing. Aerostatic bearing have a high limit speed, but low stiffness and poor dynamic characteristics, limiting their applications. Hydrostatic bearing have good load-bearing characteristics and are more suitable for ultra-high-speed machining of difficult-to-machine materials, but they have problems such as large heat generation and significant dynamic pressure effects. This article will start from the perspective of bearing design and focus on how to weaken the impact of temperature rise and dynamic pressure effect on the spindle.

The spindle support scheme and bearing structure are determined. By comparing the advantages and disadvantages of different hydrostatic bearing support methods, the form of radial thrust combined bearing - axial preload bearing is used as the spindle support scheme, which has better thermal stability. After fully studying the correlation between bearing performance and structural parameters, with the maximum bearing stiffness and minimum lubricating oil temperature rise as the goal, the NSGA-II algorithm is used to perform multi-objective optimization design on the bearings in the support scheme, and a comprehensive performance optimal bearing design scheme is obtained.

The load-bearing characteristics and temperature characteristics of the bearing and spindle rotor system are studied. Based on the above bearing design scheme, a simulation model of hydrostatic bearing is established using Fluent software, the influence of eccentricity on the bearing load-bearing characteristics is studied, and the changes in the oil film temperature field under different speeds and the impact of dynamic pressure effect on the bearing load-bearing characteristics are analyzed, and the bearing stiffness parameters under different working conditions are obtained. In addition, based on the ANSYS Workbench platform, a simulation model of the ultra-high-speed spindle rotor system is constructed to explore the influence of the load-bearing position at the spindle end on the radial stiffness of the spindle end, and the influence of speed and grinding wheel on the modal frequency and mode shape of the eccentric shaft is analyzed, and the steady-state response characteristics of the eccentric shaft under external load are studied.

Finally, some performances of the ultra-high-speed spindle are tested. The test results show that under the condition of lubricating oil supply pressure of 60 bar, the axial stiffness of the spindle is 99.58 N/μm, and the radial stiffness of the spindle end is 83.38 N/μm. The rotation error of the spindle radially fixed sensitive direction is 0.16 μm, and the axial runout error is 0.08 μm; the maximum temperature rise of the lubricating oil is 20℃; the highest speed of the spindle is 45000 rpm.

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