魯氏泵葉輪線形特性分析

Abstract

摘 要 魯氏泵在工業上的應用有越來越廣的趨勢，如半導體製程中的薄膜沈積或是乾蝕刻等，均需要在低壓真空的環境下操作，由於半導體製程技術不斷往更小線寬與更高密度的方向改善，因此半導體製程環境對真空度與潔淨度的要求也越來越高。由於魯氏真空泵屬於乾式真空泵，在操作時不會產生油氣的污染，同時因其具有廣泛的工作區域及容易維修等優點，所以乾式真空泵在半導體工業以及其他薄膜相關產業之應用也越來越廣泛。而魯氏泵因有加工容易與技術成熟等優點，在乾式真空泵中應用最廣。 本論文是以解析法求解魯氏泵葉輪的共軛曲線，由於魯氏泵在沿著旋轉軸方向每一截面均相同，故在設計與分析時可將其簡化成二維問題處理。依據主動轉子外形設計與參數，以齒輪原理與微分幾何的觀念，找出被動轉子的葉輪齒形，探討其外形之連續性與過切情形並計算其面積效率。轉子的效能除了面積效率之外，本論文亦以解析法模擬出具間隙的葉輪外形方程式，並以日本Sawada教授的洩漏分析模式來探討魯氏葉輪間之間隙洩漏狀況。此外，為了討論葉輪工作時因升溫導致熱膨脹的問題，吾人亦使用有限元素法分析軟體的電腦模擬，探討魯氏葉輪因升溫膨脹後的外徑變化及內部應力、應變的分佈情形，並反推間隙預留值的增加量。

Abstract Dry pumping based on non-contacting and non-lubricated pump impellers, is nowadays the best available solution for pumping vapors in general and organic solvents in particular. Compared with a traditional pump that uses oil or water as the lubricants, a dry-pump is an economical and energy efficient alternative when environmental considerations are paramount. The Root's pump is one of the dry-type pumps that will not generate oil-vapor pollution, therefore, the applications of the Root's pump to air dischargers for vacuum equipments are more and more extensive. In some new advanced technology fields, such as semiconductor process equipment, the Root's pump plays a very important role. This paper designs the lobe profile of Root's pumps, and investigates it's characteristics. The profile, continuity and undercutting of the lobes as well as the area efficiency of the Root's pump are also investigated based on the theory of gearing and the concept of differential geometry. This paper also determines the profile equations with clearance considerations by employing the analysis method, and estimates the divulgence of Root's pumps according to Dr. Sawada's divulgence model. In order to verify the thermal expansion situation, the finite element method is also applied to investigate the profile changes of Root's lobes accounting for the raised working temperature.