超高速磨削电机内置式液体悬浮电主轴结构及性能优化研究

发布时间：2019-07-01 08:50

【摘要】：超高速磨削是先进制造领域极具挑战性的一项高效精密加工技术。超高速磨削数控磨床是实现超高速磨削加工的装备基础。液体悬浮电主轴是超高速数控磨床的核心功能部件。采用电机内置式液体悬浮电主轴结构可克服电机后置式液体悬浮电主轴结构不紧凑，转子惯量大，动态响应慢，难以适应超高速磨削需要的弱点，但会带来密封难度大，温升高等问题；同时，高速化和结构集成化带来的油膜温升高、粘度下降问题，易导致“抱轴”或刮瓦事故。因此，迫切需要研究超高速磨削电机内置式液体悬浮电主轴结构及性能优化。参与开发了超高速磨削电机内置式液体悬浮电主轴，并实现了工程应用，克服了电机后置式液体悬浮电主轴结构不紧凑、转子惯量大、动态响应慢且难以满足超高速磨削需要的弱点；采用多级间隙密封的方式，解决了液体悬浮电主轴易漏油的问题，实现了电机的循环冷却方案；并从转子动力学和动平衡方面对主轴系统进行了分析计算，确保设计的主轴系统能达到预期的工作要求。建立了基于CFD的小孔节流径向轴承和止推轴承油膜流场数值计算模型；探讨了符合径向轴承和止推轴承油膜几何尺度特征的离散网格划分与边界条件及计算参数选择的方法，油膜三维离散网格模型划分拟采用结构网格，并利用强制网格尺寸函数来保证网格的协调性，以实现计算效率和计算精度的综合最优。利用所建立的模型和CFD计算方法分别研究了径向轴承和止推轴承流场特性，，分析了工作参数和结构参数对有周向回油槽径向轴承和四独立深浅腔止推轴承承载能力、刚度、流量和温升的影响规律。利用所开发的电主轴样机进行了实验研究，对电主轴油膜刚度、温升、振动和噪声等物理参量进行了检测。实验表明，该电主轴运行平稳，综合性能良好，在温升允许条件下油膜刚性高，油膜刚度理论计算值与实测值两者吻合较好。从而证实了所开发的电主轴整体结构设计、冷却密封设计和转子系统一阶临界转速设计以及转子动平衡是成功的；基于CFD的小孔节流径向轴承和止推轴承油膜流场数值计算方法是有效可行的。本文的研究工作对液体悬浮电主轴设计以及动静压轴承工作参数与结构参数优化具有工程参考价值。
[Abstract]:Ultra-high speed grinding is a challenging high efficiency precision machining technology in advanced manufacturing field. Ultra-high speed grinding CNC grinder is the equipment foundation to realize ultra-high speed grinding. Liquid suspension motorized spindle is the core functional component of ultra-high speed CNC grinder. The use of motor built-in liquid suspension motorized spindle structure can overcome the shortcomings of motor rear liquid suspension motorized spindle structure, such as non-compact structure, large rotor inertia, slow dynamic response, difficult to meet the needs of ultra-high speed grinding, but it will lead to the difficulty of sealing, temperature rise and other problems; at the same time, the oil film temperature caused by high speed and structural integration increases and the viscosity decreases, which is easy to lead to "holding shaft" or scraping accident. Therefore, it is urgent to study the structure and performance optimization of ultra-high speed grinding motor built-in liquid suspension motorized spindle. Participated in the development of ultra-high speed grinding motor built-in liquid suspension motorized spindle, and realized the engineering application, overcome the weakness of motor rear liquid suspension motorized spindle structure is not compact, rotor inertia is large, dynamic response is slow and difficult to meet the needs of ultra-high speed grinding, the multi-stage gap sealing method is adopted to solve the problem of easy oil leakage of liquid suspension motorized spindle, and the cycle cooling scheme of the motor is realized. The spindle system is analyzed and calculated from the aspects of rotor dynamics and dynamic balance to ensure that the designed spindle system can meet the expected working requirements. The numerical calculation models of oil film flow field of small orifice throttle radial bearing and thrust bearing based on CFD are established. The method of discrete grid division, boundary condition and calculation parameter selection in accordance with the geometric scale characteristics of oil film in radial bearing and thrust bearing is discussed. The three-dimensional discrete grid model of oil film is divided by structural grid, and the forced grid size function is used to ensure the coordination of grid, so as to realize the comprehensive optimization of calculation efficiency and calculation accuracy. The flow field characteristics of radial bearings and thrust bearings are studied by using the established model and CFD calculation method, and the effects of working parameters and structural parameters on the bearing capacity, stiffness, flow rate and temperature rise of radial bearings with circumferential return grooves and four independent deep and shallow cavities are analyzed. The experimental study is carried out by using the developed motorized spindle prototype, and the physical parameters such as oil film stiffness, temperature rise, vibration and noise of the motorized spindle are measured. The experimental results show that the motorized spindle runs smoothly and has good comprehensive performance. Under the allowable condition of temperature rise, the oil film rigidity is high, and the theoretical calculation value of oil film stiffness is in good agreement with the measured value. It is proved that the developed design of the whole structure of motorized spindle, the design of cooling seal, the design of first-order critical speed of rotor system and the dynamic balance of rotor are successful, and the numerical calculation method of oil film flow field of small orifice throttle radial bearing and thrust bearing based on CFD is effective and feasible. The research work in this paper has engineering reference value for the design of liquid suspension spindle and the optimization of working parameters and structural parameters of hydrostatic bearings.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH133.3

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