Abstract
飛輪齒形之設計對變速性能有決定性的影響，一般可區分為上鏈齒形和下鏈齒形二種。結合上、下鏈功能於同一飛輪組時，在鏈輪相角、齒尖導角以及路徑規劃等諸多方面是彼此互相衝突矛盾的，故整合上、下鏈之齒形設計相當具有挑戰性。本文建立一套完整的齒形設計方法，以提高換鏈之平順性及穩定性為目標，設計出兼具上鏈及下鏈功能之飛輪齒形。設計的方法，首先分析各組件對換鏈性能的影響，並定義各組件相關之參數，接著探討非換鏈點的問題，分析影響齒尖導角的參數，以解決非換鏈點齒尖導角相違背的現象。在齒形設計方面，採用非直線形換鏈路徑為基礎，設計兼具上、下鏈之飛輪齒形，並且提出一種較為穩定的換鏈模式，解決非直線形路徑在支承上的困難，用以提高換鏈的穩定性。根據以上的設計準則，以CAD/CAM進行原型品的設計與製造，經測試之結果，該齒形在功能上具有良好的效果，驗證了本文設計理念的正確性與可行性。The sprocket design of the freewheel of the rear derailleursystem possessing a specified tooth profile for the up- anddown-shifting motions is determinate to the shiftingperformance of a bicycle. The design variables, such assprocket phase angle, chamfers on the sprocket teeth, andshifting path, etc., conflict with each other when designing afreewheel providing both up- and down-shifting performance. Inthis study, a comprehensive design method for trimming thesprocket teeth was established to improve the smoothness aswell as the stability in both the up-shifting and down-shifting. First, the parameters of the relevant componentswere defined and their effects on the shifting performance wereanalyzed. To solve the problem in the violation of chamfertrimming, the parameters that affect the trimming values on thetips of the " nonshifting " teeth were analyzed, too. Thesprocket design that integrated both the up-shifting and down-shifting perform- ance was based on the nonlinear shiftingpath. A mathematical model for stable shifting was alsoproposed to overcome the difficulty in supporting such adesign. The prototype designed and manufactured by CAD/CAMaccording to the proposed design methodology was tested andverified to have excellent performance. Thus, it proved thefeasibility and accuracy of the design methodology developed inthis thesis.