設計開發適用氣靜壓軸承之放電加工製成平面節流孔與特性探討

Abstract

氣靜壓軸承被廣泛應用於高速與高精度系統中，但是高精度加工之需求及低承載能力也阻礙了它的發展。本論文設計開發新型式節流孔，探討平面節流孔幾何形狀和尺寸對氣靜壓軸承特性之影響，以放電加工製成之平面節流孔解決了微小節流孔切削加工之困難問題，並且大幅提昇節流孔之造型和尺寸變異性，有助於達成各種氣靜壓軸承性能需求。平面節流孔和另一對應平面組合即可建構出徑向或軸向軸承，放電線加工方式可以大幅改善徑向節流孔對位問題以及節流孔深寬比之限制。首先以流體分析軟體FLUENT進行氣靜壓軸承設計參數對壓力分佈之探討分析，並透過數值分析運算，求得軸承承載力和剛性之變化。除了理論和有限元素分析之外，還藉由實驗測試對開發之氣靜壓軸承進行性能驗證分析，釐清設計參數與軸承性能之關連性，檢驗實驗和分析數據之差異和成因。

Aerostatic bearings have been widely applied in high-speed and high-precision systems, but the need of high precision machining and low loading capacity retard their development. This thesis is to design and develop a novel type of restrictor, and to study the influences of the geometric shape and size of the surface orifice on the aerostatic bearing characteristics. The electro discharge machined surface orifice can avoid machining difficulties in drilling the tiny orifice and can also afford diverse variation possibilities in shape and size which are very useful to fulfill different requirements on the aerostatic bearings. Through uniting the surface orifice and the corresponding surface, the radial or the axial aerostatic bearing can be realized. The electro discharge machining process can substantially solve the misalignment problem of the radial orifices and get rid of the restriction of the aspect-ratio. By using the fluid analysis software FLUENT, the influences of design parameters on the pressure distribution over the bearing gap are studied. Furthermore, the loading capacity and the stiffness are derived by the numerical analytical calculation. Besides the theoretical and the finite element analyses, the performances of the developed aerostatic bearing are verified by the experimental testing. It comprehends the relationship between the design parameters and the bearing performance and examines the deviations between the experimental and the analytical data and their occasions.