臺灣博碩士論文加值系統

本文為針對垂直立式的渦輪分子真空幫浦，分析其內部被動式磁浮軸承的動態剛性。真空幫浦為精密機械，體積小，且運轉轉速高（多為3,000~60,000 rpm），使得非接觸式軸承系統成為開發的必然趨勢。為了在狹小空間進行無接觸運轉，被動式磁浮軸承的設計必須達到微米級的精準度，如何設計被動式磁浮軸承以提供合適剛性，是本文探討的重點。
本文分為兩大部分，第一部份：以磁迴路觀點分析被動磁浮軸承的磁場，架設磁場量測機台，分析多層磁鐵的磁場分佈；第二部份：以有限元素法為理論基礎的工程分析軟體Ansoft來作為分析磁場與磁力的工具，進而分析位移對被動磁浮軸承剛性的影響，隨著被動磁浮軸承的參數變化下，以3D模擬何種設計最佳。最後，分析結果將與實驗測試結果進行比較。

Turbo molecular pump, an accurate mechanism, is characterized by the small volume and high rotary speed (3,000~60,000rpm). To achieve contact-free rotor spinning in the confined space, passive magnetic bearing system inside the pump must be designed accurately to avoid the unstableness of the rotor, which requires the design of the bearing to attain the preciseness in the micrometer’s level. Thus, the study aims to analyze the dynamic stiffness of passive magnetic bearing and to design the stiffness of the bearing for the system.
Two parts are covered in this paper. In the first part, we measured the magnetic flux of passive magnetic bearing and analyzed the magnetic field by the standpoint of magnetic circuits. Besides, we compared the results of multiplayer magnets with different materials. In the second part, I used computer program Ansoft, which is based on finite element method, to analyze magnetic field and force. Furthermore, we analyzed the effect of displacement to magnetic bearing stiffness. Implementing 3D simulation with different parameters, we then discussed what the best design is. Finally, the result of simulation and the experimental data were compared and suggestions were further provided.

Abstract I
Contents II
List of Figures IV
List of Tables VIII
Nomenclature X
Chapter 1 Introduction 1
1.1 Introduction to the passive magnetic bearing in the turbo molecular pump 2
1.2 Overview of the passive magnetic bearing system 4
1.3 The motivation of the research 8
1.4 The introduction of the contents 10
Chapter 2 Analytic theory of the passive magnetic bearing system 12
2.1 The structure of the passive magnetic bearing 12
2.2 The fundamental theory 15
2.2.1 Earnshaw’s Theorem 15
2.2.2 J. P. Yonnet theory 17
2.3 The magnetic circuit derivative 23
2.4 The dynamic analysis 31
Chapter 3 The experiment of the magnetic field 33
3.1 The measurements and apparatus 34
3.2 The radial magnetic field 36
3.2.1 Single-layer ring magnet 36
3.2.2 Multi-layer ring magnet 42
3.3 The axial magnetic field 48
3.3.1 Single-layer ring magnet 48
Chapter 4 Numerical simulation 52
4.1 Finite element method 52
4.2 The flow chart 53
4.3 The solver 54
4.4 Single-ring magnetic force and stiffness 55
4.5 Multiple-ring magnetic force and stiffness 69
Chapter 5 Result and discussion 73
5.1 Comparison between the experimental data and the numerical simulation 73
Chapter 6 Conclusion 77
6.1 Significance of results 77
6.2 Suggestions for future studies 78
Bibliography 79

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