本研究的目的在於利用一套系統化的方法設計出一種沙發床之機構。首先定義沙發床，介紹沙發床的起源，蒐集沙發床機構的相關資料，分析相關專利，將沙發床機構依其開闔方式分為延展式沙發床、拉出式沙發床、及靠背向下壓式沙發床等三類，分別整理出此三類沙發床機構的演進史，比較此三類沙發床的優缺點後，並選出拉出式沙發床機構進行設計。其後，本研究應用品質機能展開法(QFD)，將定性的顧客需求轉換為可以量化的工程需求與限制，並決定出設計沙發床機構的工程目標。然後，利用一套系統化的方法進行概念設計，計合成出十五種新型機構，並利用決定矩陣法評估出一種最可行的新型機構。接著，利用向量迴路法進行位置分析，建立各運動接頭位移的數學模式，再利用最佳化方法針對此新型機構進行尺寸合成，得到可達到指定開闔位置的機構尺寸。再來，加入彈簧和鎖死裝置於所合成的沙發床機構中，並針對兩種不同彈簧配置進行力量分析及計算其機械利益。最後，進行電腦模擬及模型實作，驗證出本設計是可行的。

The purpose of this work is to design a sofa bed mechanism by a systematic approach. Firstly, the definitions of sofa beds are studied, and the origination of sofa beds are introduced. Based on the way that they are converted between sofas and beds, sofa bed mechanisms are classified into three types. Then, the development of each type of sofa bed mechanisms is addressed. By comparing the advantages of the three types sofa bed mechanisms, pull-out sofa bed mechanism is chosen for further design. The QFD method is applied to define design specifications of pull-out sofa bed mechanisms. Based on Yan’s creative mechanism design methodology, 15 feasible mechanisms are synthesized. One of the feasible mechanisms is further selected by using decision-matrix method. After that, vector loop approach is used to obtain the positions of the links. In addition, an optimization method is performed to obtain the dimensions of the links. Furthermore, springs and locking means are added, and force analysis and mechanical advantage analysis are performed. Finally, based on the developed computer animation and the built prototype, the proposed design of this work is proven to be practical and feasible.

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