超精密机床自补偿液体静压轴承设计与特性研究
发布时间：2018-08-28 11:38
【摘要】：超精密加工技术与超精密机床的发展对机床轴系的静、动态特性提出了更高的要求,液体静压轴承是唯一可以综合实现高精度、高刚度和大阻尼的支承方式,因而在高性能精密机床中具有不可替代的优势。液态静压转台与主轴是超精密机床的关键功能部件,其研制具有非常重要的意义。本文着眼于液体静压转台与主轴的应用,设计了自补偿形式的液体静压轴承,并采用有限元方法对其静、动态特性进行了理论研究,最终将其应用于静压转台制造并测试了其刚度和运动精度。论文主要目的是系统研究自补偿圆锥液体静压轴承的设计方法、计算理论和特性参数,对高精度、高刚度和大阻尼的静压转台与主轴系统研制提供理论指导。论文的研究工作和主要结论包括以下几个部分:1.从自补偿节流原理出发,设计了节流单元进油的角面节流自补偿液体静压轴承,将传统的对置自补偿液体静压轴承中常用的节流单元结构引入角面节流自补偿轴承中,从而避免了节流表面上润滑剂扩散,且未引入对置油垫自补偿结构增加轴向长度的缺点。该类型轴承结构紧凑,零件简单,易于模块化设计与生产,而且轴承性能只需靠间隙来保证,因而有可能实现很高的刚度和精度,适用于精密机床轴系应用。2.建立了自补偿圆锥液体静压轴承理论模型,并基于小扰动理论研究了轴承静、动态特性参数的计算方法,以此为基础研究了节流方式对液体静压轴承承载力、流量、刚度和阻尼系数的影响。结果表明:自补偿液体静压轴承的承载能力高于固定节流轴承;在小偏心条件下其刚度系数大于固定节流轴承,但偏心对刚度的影响明显大于固定节流轴承;径向自补偿静压轴承阻尼系数大于固定节流轴承,轴向自补偿静压轴承阻尼系数介于毛细管/狭缝节流和小孔节流轴承之间。3.采用流量平衡理论研究了自补偿液体静压轴承刚度最大化的基本条件,即选择合适的节流比。对于本文设计的转台轴承,轴向最佳节流比为2,径向最佳节流比是内流系数的函数,其数值略小于2。根据功率方程讨论了尽可能减小轴承功耗的条件,结果表明轴承间隙和润滑油粘度的选用都不能太小。4.研究了初始节流系数、圆锥角度和油腔尺寸对于自补偿液体静压转台轴承的静、动态特性参数的影响,结果表明:随着节流系数的增大阻尼系数减小,但节流系数大于某一数值后对承载力和刚度的影响不显著,因而节流系数的选择范围可以适当放宽;圆锥角越大轴承的轴向承载能力、刚度和阻尼系数越大,圆锥角越小轴承的径向承载能力、阻尼和小偏心下径向刚度系数越大;油腔尺寸越大,轴承的承载力和刚度也越大,但是轴承消耗的润滑油流量随之增加,且轴承的阻尼系数有所降低。5.研究了自补偿液体静压轴承在高速运动下的速度特性,结果表明:高速运动下流体的惯性会降低油膜力,但是动压效应会增大油膜力,因而随着转速的提高轴承承载力增加,转子的偏位角增大,流量有所减少;轴承的交叉刚度和正交阻尼均随着转速升高而增大,转速较高偏心较大时轴承在受载方向可能出现负的正交刚度;节流系数选择最好在最佳节流系数附近取值,过大或过小的节流系数均可能对轴承的承载力、刚度和阻尼不利,但对稳定阈值的影响不显著;在小偏心下自补偿液体静压轴承的稳定质量阈值远大于毛细管或者小孔节流轴承,但是在大偏心下其稳定性不如传统的固定节流方式。6.研究了制造误差对自补偿液体静压轴承性能的影响,结果表明尺寸误差、轴承圆锥不同轴和节流环装配偏斜均会降低轴承的承载能力。制造了一台自补偿液体静压转台样机,并对其静刚度和运动精度进行了测试,供油压力1MPa条件下其初始状态的轴向刚度约为220N/μm,径向刚度约为120N/μm,运动精度优于0.4μm,要想充分发挥自补偿液体静压轴承的刚度和精度优势,必须提高轴承的制造精度。
[Abstract]:The development of ultra-precision machining technology and ultra-precision machine tools has put forward higher requirements for static and dynamic characteristics of machine tool shafting. Hydrostatic bearing is the only support mode which can realize high precision, high stiffness and large damping, so it has irreplaceable advantages in high-performance precision machine tools. This paper focuses on the application of hydrostatic turntable and spindle, designs a self-compensating hydrostatic bearing, and studies its static and dynamic characteristics by finite element method. Finally, it is applied to the hydrostatic turntable and its stiffness and operation are tested. The main purpose of this paper is to systematically study the design method, calculation theory and characteristic parameters of self-compensating conical hydrostatic bearing, and to provide theoretical guidance for the development of high precision, high stiffness and large damping hydrostatic turntable and spindle system. A self-compensating hydrostatic bearing with angular throttle is designed. The traditional structure of self-compensating hydrostatic bearing is introduced into the self-compensating bearing with angular throttle, thus avoiding the diffusion of lubricant on the throttle surface and increasing the axial length without introducing the self-compensating structure of opposing oil pad. This type of bearing has the advantages of compact structure, simple parts, easy modular design and production, and the bearing performance only needs clearance to ensure, so it is possible to achieve high stiffness and precision, which is suitable for precision machine tool shafting applications. 2. The theoretical model of self-compensating conical hydrostatic bearing is established, and the static and dynamic characteristics of the bearing are studied based on the theory of small disturbance. The results show that the bearing capacity of the self-compensating hydrostatic bearing is higher than that of the fixed throttle bearing, and the stiffness coefficient of the self-compensating hydrostatic bearing is greater than that of the fixed throttle bearing under the condition of small eccentricity. The damping coefficient of radial self-compensating hydrostatic bearing is larger than that of fixed throttle bearing, and the damping coefficient of axial self-compensating hydrostatic bearing is between capillary/slit throttle and orifice throttle bearing. The optimum throttle ratio in axial direction is 2, and the optimum throttle ratio in radial direction is a function of the internal flow coefficient, which is less than 2. The conditions of reducing the power consumption of the bearing as far as possible are discussed according to the power equation. The results show that the selection of bearing clearance and lubricating oil viscosity can not be too small. 4. The initial throttle ratio is studied. The results show that the damping coefficient decreases with the increase of throttling coefficient, but the influence of throttling coefficient on bearing capacity and stiffness is not significant when the throttling coefficient is greater than a certain value, so the choosing range of throttling coefficient can be widened appropriately. The larger the taper angle, the greater the axial bearing capacity, the greater the stiffness and damping coefficient, the smaller the taper angle, the greater the radial bearing capacity and the radial stiffness coefficient under damping and small eccentricity; the bigger the oil chamber size, the greater the bearing bearing capacity and stiffness, but the flow of lubricant consumed by the bearing increases, and the damping coefficient of the bearing decreases. 5. The velocity characteristics of the self-compensating hydrostatic bearing under high speed motion are studied. The results show that the inertia of the fluid will reduce the oil film force, but the dynamic pressure effect will increase the oil film force. Therefore, with the increase of the rotational speed, the bearing bearing capacity will increase, the rotor offset angle will increase, and the flow rate will decrease. When the rotational speed is higher and the eccentricity is bigger, the bearing may have negative orthogonal stiffness in the direction of loading; the throttling coefficient should be selected near the optimum throttling coefficient, too large or too small throttling coefficient may be unfavorable to bearing capacity, stiffness and damping, but the influence on stability threshold is not significant in small. The stability quality threshold of self-compensating hydrostatic bearing under eccentricity is much larger than that of capillary or orifice throttle bearing, but its stability is not as good as that of traditional fixed throttle bearing under large eccentricity. A prototype of self-compensating hydrostatic turntable was manufactured and its static stiffness and motion accuracy were tested. The axial stiffness and radial stiffness in the initial state were about 220N/micron, 120N/micron and the motion accuracy was better than 0.4 micron under the condition of 1 MPa oil supply pressure. The accuracy and accuracy of bearing bearing must be improved.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TH133.36;TG502.3
本文编号：2209286
[Abstract]:The development of ultra-precision machining technology and ultra-precision machine tools has put forward higher requirements for static and dynamic characteristics of machine tool shafting. Hydrostatic bearing is the only support mode which can realize high precision, high stiffness and large damping, so it has irreplaceable advantages in high-performance precision machine tools. This paper focuses on the application of hydrostatic turntable and spindle, designs a self-compensating hydrostatic bearing, and studies its static and dynamic characteristics by finite element method. Finally, it is applied to the hydrostatic turntable and its stiffness and operation are tested. The main purpose of this paper is to systematically study the design method, calculation theory and characteristic parameters of self-compensating conical hydrostatic bearing, and to provide theoretical guidance for the development of high precision, high stiffness and large damping hydrostatic turntable and spindle system. A self-compensating hydrostatic bearing with angular throttle is designed. The traditional structure of self-compensating hydrostatic bearing is introduced into the self-compensating bearing with angular throttle, thus avoiding the diffusion of lubricant on the throttle surface and increasing the axial length without introducing the self-compensating structure of opposing oil pad. This type of bearing has the advantages of compact structure, simple parts, easy modular design and production, and the bearing performance only needs clearance to ensure, so it is possible to achieve high stiffness and precision, which is suitable for precision machine tool shafting applications. 2. The theoretical model of self-compensating conical hydrostatic bearing is established, and the static and dynamic characteristics of the bearing are studied based on the theory of small disturbance. The results show that the bearing capacity of the self-compensating hydrostatic bearing is higher than that of the fixed throttle bearing, and the stiffness coefficient of the self-compensating hydrostatic bearing is greater than that of the fixed throttle bearing under the condition of small eccentricity. The damping coefficient of radial self-compensating hydrostatic bearing is larger than that of fixed throttle bearing, and the damping coefficient of axial self-compensating hydrostatic bearing is between capillary/slit throttle and orifice throttle bearing. The optimum throttle ratio in axial direction is 2, and the optimum throttle ratio in radial direction is a function of the internal flow coefficient, which is less than 2. The conditions of reducing the power consumption of the bearing as far as possible are discussed according to the power equation. The results show that the selection of bearing clearance and lubricating oil viscosity can not be too small. 4. The initial throttle ratio is studied. The results show that the damping coefficient decreases with the increase of throttling coefficient, but the influence of throttling coefficient on bearing capacity and stiffness is not significant when the throttling coefficient is greater than a certain value, so the choosing range of throttling coefficient can be widened appropriately. The larger the taper angle, the greater the axial bearing capacity, the greater the stiffness and damping coefficient, the smaller the taper angle, the greater the radial bearing capacity and the radial stiffness coefficient under damping and small eccentricity; the bigger the oil chamber size, the greater the bearing bearing capacity and stiffness, but the flow of lubricant consumed by the bearing increases, and the damping coefficient of the bearing decreases. 5. The velocity characteristics of the self-compensating hydrostatic bearing under high speed motion are studied. The results show that the inertia of the fluid will reduce the oil film force, but the dynamic pressure effect will increase the oil film force. Therefore, with the increase of the rotational speed, the bearing bearing capacity will increase, the rotor offset angle will increase, and the flow rate will decrease. When the rotational speed is higher and the eccentricity is bigger, the bearing may have negative orthogonal stiffness in the direction of loading; the throttling coefficient should be selected near the optimum throttling coefficient, too large or too small throttling coefficient may be unfavorable to bearing capacity, stiffness and damping, but the influence on stability threshold is not significant in small. The stability quality threshold of self-compensating hydrostatic bearing under eccentricity is much larger than that of capillary or orifice throttle bearing, but its stability is not as good as that of traditional fixed throttle bearing under large eccentricity. A prototype of self-compensating hydrostatic turntable was manufactured and its static stiffness and motion accuracy were tested. The axial stiffness and radial stiffness in the initial state were about 220N/micron, 120N/micron and the motion accuracy was better than 0.4 micron under the condition of 1 MPa oil supply pressure. The accuracy and accuracy of bearing bearing must be improved.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TH133.36;TG502.3
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