無限幅の無次元特性パラメータをくふうすることにより部分放物面, 部分傾斜面および階段平行面の特性を定量的に比較した. 同じ無次元表示を円筒面にも適用し, 円筒面チルティングパッド軸受および円筒面の油の供給不足時の特性を統一的に解析した. 結果は軸受の最小油膜厚さを直接読みとれるような無次元パラメータの組合せのグラフで示した.

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This paper describes the step response characteristics of a hydrostatic thrust bearing with an actively-controlled restrictor using a voice coil motor (VCM). This new type of restrictor can control the mass flow rate through the restrictor by using both the balance of the fluid forces exerted on the disk and the electromagnetic force of VCM. The floating disk is controlled by VCM through PI controller according to the shaft displacement. The effects of various design parameters on the step response characteristics are investigated theoretically and experimentally. It was shown that the proposed bearing could remarkably reduce the settling time of the shaft after the step load was imposed.

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Recently, lithographic technologies using electron-beam (EB) or extreme ultra violet (EUV) illumination source have been developed as a next generation advanced lithography. Generally, aerostatic bearings have been used in the lithography machine because they have a very higher accuracy of motion. However, lithography technologies using EB or EUV illumination source have to operate in a high vacuum and require higher precision accuracy than current lithography technology. Therefore, in this paper, an aerostatic porous bearing with deep feed groove is proposed to achieve required accuracy in the next generation lithography technology. Aerostatic porous bearing have relatively high stiffness and higher damping coefficient than another types of aerostatic bearings. In addition, the proposed bearings can supply pressurized air from a stationary guide-way to a moving table through a deep feed groove without any disturbances of air supply tubes. The static and dynamic characteristics of aerostatic porous bearings with a deep feed groove are investigated theoretically and experimentally.

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The lubricant temperature rise in hydrostatic bearings becomes large under the condition of high load and high speed operation. Therefore the effects of lubricant viscosity change on bearing performance are not negligible. In this study, the performance characteristics of capillary compensated multi recess hydrostatic thrust bearings are analysed theoretically and experimentally considering the lubricant viscosity change. The relations between the lubricant viscosity change and the load carrying capacity or the bearing clearance variation are shown quantitatively. The close agreement was obtained between theoretical results and experimental ones. Consequently, it was pointed out that the hydrostatic bearings should be analysed considering the lubricant viscosity change.

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Bubbles will be produced in the lubricant film of hydrostatic bearings caused by the hydrodynamically generated negative pressure. The production of bubbles should be avoided because bubbles in lubricant films give the undesirable effects on bearing performances. In this study, the limit of bubbles production in the sector-shaped recesses of hydrostatic thrust bearings is experimentally and theoretically investigated. Effects of the spindle tilt on bubbles production in recesses are also analysed. The analysis lead to the results as follows. (1) Bubbles production in recesses are caused by the air drawing through the bearing clearance or the so-called aeration. (2) The limit of bubbles production is given in terms of the speed parameter and the tilting ratio. (3) The bubbles production in recesses can be supposed theoretically by calculating the region of the negative pressure in the lubricant film by means of the finite element method.

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This paper proposes a method of improving the dynamic characteristics of infinitely stiff hydrostatic thrust bearing using a miniaturized self-controlled restrictor. This bearing has a very small self-controlled restrictor of 3.0 mm diameter and can obtain a very high static bearing stiffiness(nearly infinite stiffness). Influences of various design parameters on the dynamic characteristics of the proposed bearing are investigated, theoretically and experimentally. As a result, it was found that the miniaturization of a self-controlled restrictor can greatly improve the step response and the frequency response characteristics of this kind of hydrostatic thrust bearing.

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In this paper, the theoretical studies on the optimization of the operating condition of the hydrostatic thrust bearings are presented. Total amount of power consumption is treated as an objective function, while the bearing clearance, static stiffness, damping ratio of the bearing, lubricant viscosity and the initial lift up pressure are considered as constraints throughout the optimization procedure. Through the study, it is pointed out that the constraints of the minimum permissible value of the bearing clearance, static stiffness and lubricant viscosity are especially in higher degree responsible to the total amount of power consumption. Simplified design procedure which offers designers the optimum values is drawn from these results.

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It is well known that aerostatic bearings with compound restrictors tend to cause pneumatic hammer instability at the optimum bearing clearance for the maximum stiffness. In this paper, the improvement of such an instability in the aerostatic thrust bearings are discussed. An orifice restrictor put in series into an air supply line is used as a stabilizer. The static and dynamic characteristics of aerostatic thrust bearings with this stabilizer are investigated experimentally and theoretically, and the usefulness of this method for improving the stability of this kind of bearings is confirmed. It is consequently found that the proposed method is very efficient in avoiding the pneumatic hammer instability.

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The purpose of this paper is to analyse the basic characteristics, which include the hydrodynamic effect caused by the high rotating speed of the spindle, and to propose the optimal design principle which attains the maximum stiffness of the bearing. The finite element method with the Galerkin criterion is applied to solve the nonlinear Reynolds equation, and the pressure distribution of the lubrication film is numerically caculated.

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