自行車內變速系統之可靠度研究

闕延洲(Yen-Chou Chueh)

指導教授 ： 吳文方

國立臺灣大學/工學院/機械工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01373

摘要

自行車內變速系統具有體積小、換檔動作穩定、外殼保護等優點，以往國內少數學者對其研究大多著重於機構方面的創新設計及機械性能的改善，少有力學與可靠度方面的探討，所以本論文即著眼於此，首先針對自行車內變速系統進行失效模式與影響性分析(Failure Mode Effect Analysis, FMEA)，並繪製出風險矩陣(risk matrix)，以了解系統內各元件可能之失效模式，並找出旋轉變速握把之彈片為一關鍵性失效元件，針對此元件我們再深入進行有限元素與可靠度之分析與計算，藉以評估此彈片之應力、應變場分佈及其可靠度。有限元素分析結果顯示，彈片之安全係數為1.08；而在可靠度計算上，我們發現彈片磨耗壽命經機率圖紙與卡方測試檢定後可以對數常態分佈表示，其平均壽命為17,520 cycle。本論文最後並針對自行車內變速系統各元件進行可靠度分配，其結果可提供我們在最小成本的考量下，達到我們所設定之系統可靠度目標。

關鍵字

內變速器 ； 有限元素法 ； 可靠度 ； 失效模式與影響性分析 ； 旋轉變速握把 ； 自行車

並列摘要

Mechanics and reliability related issues of the multi-speed hub system of a bicycle are studied in the present thesis. First, failure mode and effect analysis (FMEA) is carried out to find possible failure modes of each component of the system, and identify the key component that is vulnerable to failure. Finite element analysis is then performed to find the maximum stress of the key component. The expected life and reliability of the component are evaluated based on a wear model. Finally, reliability allocation is performed to find an optimal selection of each component of the system in view of its individual cost and reliability. The result shows that an elastic shifter is the key component of the multi-speed hub system. Its maximum stress is 1.08 times of the material’s yield strength. If wear is considered, the reliability degradation of the shifter with respect to its usage cycle is found, and it has a mean life of 17,520 cycles. Finally, it is demonstrated that appropriate reliability can be allocated to each component of the hub system to obtain a minimum cost design while maintaining the required system reliability.

並列關鍵字

multi-speed hub ； failure mode effect analysis (FMEA) ； elastic shifter ； finite element method ； bicycle ； reliability

參考文獻

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