超精密機床自補償液體靜壓軸承設計與特性研究
發(fā)布時間：2018-08-28 11:38
【摘要】：超精密加工技術與超精密機床的發(fā)展對機床軸系的靜、動態(tài)特性提出了更高的要求,液體靜壓軸承是唯一可以綜合實現高精度、高剛度和大阻尼的支承方式,因而在高性能精密機床中具有不可替代的優(yōu)勢。液態(tài)靜壓轉臺與主軸是超精密機床的關鍵功能部件,其研制具有非常重要的意義。本文著眼于液體靜壓轉臺與主軸的應用,設計了自補償形式的液體靜壓軸承,并采用有限元方法對其靜、動態(tài)特性進行了理論研究,最終將其應用于靜壓轉臺制造并測試了其剛度和運動精度。論文主要目的是系統(tǒng)研究自補償圓錐液體靜壓軸承的設計方法、計算理論和特性參數,對高精度、高剛度和大阻尼的靜壓轉臺與主軸系統(tǒng)研制提供理論指導。論文的研究工作和主要結論包括以下幾個部分:1.從自補償節(jié)流原理出發(fā),設計了節(jié)流單元進油的角面節(jié)流自補償液體靜壓軸承,將傳統(tǒng)的對置自補償液體靜壓軸承中常用的節(jié)流單元結構引入角面節(jié)流自補償軸承中,從而避免了節(jié)流表面上潤滑劑擴散,且未引入對置油墊自補償結構增加軸向長度的缺點。該類型軸承結構緊湊,零件簡單,易于模塊化設計與生產,而且軸承性能只需靠間隙來保證,因而有可能實現很高的剛度和精度,適用于精密機床軸系應用。2.建立了自補償圓錐液體靜壓軸承理論模型,并基于小擾動理論研究了軸承靜、動態(tài)特性參數的計算方法,以此為基礎研究了節(jié)流方式對液體靜壓軸承承載力、流量、剛度和阻尼系數的影響。結果表明:自補償液體靜壓軸承的承載能力高于固定節(jié)流軸承;在小偏心條件下其剛度系數大于固定節(jié)流軸承,但偏心對剛度的影響明顯大于固定節(jié)流軸承;徑向自補償靜壓軸承阻尼系數大于固定節(jié)流軸承,軸向自補償靜壓軸承阻尼系數介于毛細管/狹縫節(jié)流和小孔節(jié)流軸承之間。3.采用流量平衡理論研究了自補償液體靜壓軸承剛度最大化的基本條件,即選擇合適的節(jié)流比。對于本文設計的轉臺軸承,軸向最佳節(jié)流比為2,徑向最佳節(jié)流比是內流系數的函數,其數值略小于2。根據功率方程討論了盡可能減小軸承功耗的條件,結果表明軸承間隙和潤滑油粘度的選用都不能太小。4.研究了初始節(jié)流系數、圓錐角度和油腔尺寸對于自補償液體靜壓轉臺軸承的靜、動態(tài)特性參數的影響,結果表明:隨著節(jié)流系數的增大阻尼系數減小,但節(jié)流系數大于某一數值后對承載力和剛度的影響不顯著,因而節(jié)流系數的選擇范圍可以適當放寬;圓錐角越大軸承的軸向承載能力、剛度和阻尼系數越大,圓錐角越小軸承的徑向承載能力、阻尼和小偏心下徑向剛度系數越大;油腔尺寸越大,軸承的承載力和剛度也越大,但是軸承消耗的潤滑油流量隨之增加,且軸承的阻尼系數有所降低。5.研究了自補償液體靜壓軸承在高速運動下的速度特性,結果表明:高速運動下流體的慣性會降低油膜力,但是動壓效應會增大油膜力,因而隨著轉速的提高軸承承載力增加,轉子的偏位角增大,流量有所減少;軸承的交叉剛度和正交阻尼均隨著轉速升高而增大,轉速較高偏心較大時軸承在受載方向可能出現負的正交剛度;節(jié)流系數選擇最好在最佳節(jié)流系數附近取值,過大或過小的節(jié)流系數均可能對軸承的承載力、剛度和阻尼不利,但對穩(wěn)定閾值的影響不顯著;在小偏心下自補償液體靜壓軸承的穩(wěn)定質量閾值遠大于毛細管或者小孔節(jié)流軸承,但是在大偏心下其穩(wěn)定性不如傳統(tǒng)的固定節(jié)流方式。6.研究了制造誤差對自補償液體靜壓軸承性能的影響,結果表明尺寸誤差、軸承圓錐不同軸和節(jié)流環(huán)裝配偏斜均會降低軸承的承載能力。制造了一臺自補償液體靜壓轉臺樣機,并對其靜剛度和運動精度進行了測試,供油壓力1MPa條件下其初始狀態(tài)的軸向剛度約為220N/μm,徑向剛度約為120N/μm,運動精度優(yōu)于0.4μm,要想充分發(fā)揮自補償液體靜壓軸承的剛度和精度優(yōu)勢,必須提高軸承的制造精度。
[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.
【學位授予單位】：國防科學技術大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TH133.36;TG502.3
本文編號：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.
【學位授予單位】：國防科學技術大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TH133.36;TG502.3
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，本文編號：2209286
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