四行程引擎的引擎正時系統用以控制汽門開關時序，使閥桿能夠配合活塞的位置
順利完成進氣、壓縮、爆炸與排氣四個動作。當引擎運轉時，動力由汽缸內油氣爆炸
帶動主動輪旋轉，經鏈條傳遞至從動輪，使凸輪旋轉並驅動閥桿移動，控制汽門開關。
其中由於閥彈簧與機構慣性的影響，施加於從動輪的輸入扭矩將隨凸輪軸角位置的改
變呈上下波動，此一扭矩波動將造成從動輪的轉速震盪、機構的振動、噪音與耗能等
問題。
有鑒於此，本文針對機車汽門機構建立其數學模型，以得到機構各接頭在不同轉
速下的受力情形及從動輪扭矩，並探討不同彈簧預壓與勁度的影響。同時在忽略扭矩
平衡機構慣性的影響下，利用能量守恆的概念設計平衡凸輪輪廓，使總扭矩可在目標
轉速下達到完全平衡。
接著則在考慮平衡機構慣性及接頭間受力的情況下，利用最佳化方法設計一扭矩
平衡機構，使其能於機車常用轉速區間有較好的扭矩平衡效果且同時兼顧其耐用程度。
最後藉由商用軟體以及製作機構原型分別進行模擬與實驗，可將其結果與理論作比較，
並探討三者間的差異。

This thesis presents the design and experiment of a balancing cam mechanism to minimize
the torque fluctuation of engine camshafts. Torque fluctuation of rotary machines causes
unwanted vibration that would impair their performance and reliability. The combination of
inertia, driving, and resistive torque fluctuations on engine crankshafts and camshafts is the
major source of vehicle vibration. While previous methods focused on suppressing or
isolating vibration motion from engine to chassis, the proposed method seeks to directly
reduce the torque fluctuation on engine shafts. The balancing mechanism consists of a cam,
rocker, and spring. Given torque curves of a camshaft at different rotational speeds, the cam
profile can be synthesized such that the output balancing torque cancels with most of
original camshaft torque at the speed interval which user specified. Based on a derived
camshaft torque model, a optimization process of the cam profile is presented. Finally, a
prototype and its associated experiments are presented to demonstrate the torque balancing
performance.

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