可變汽門正時機構之類型合成與運動分析

Type Synthesis and Motion Analysis of Variable Valve Timing Mechanisms

范姜韶華(Shao-Hua Fan Chiang)

指導教授 ： 吳隆庸

國立清華大學/工學院/動力機械工程學系/碩士(2012年)

https://doi.org/10.6843/NTHU.2012.00146

摘要

可變汽門正時與升程之機構，可依據引擎在不同轉速下之需求條件，適時控制引擎汽門開啟與關閉時間以及改變汽門升程，進而有效提升引擎的容積效率，達到提高引擎輸出動力、降低油耗量與廢氣量之目的。
本文嘗試以創意性設計法將引擎汽門機構進行創新設計，期望使用較少桿件數之機構即可達到可變汽門正時及升程之目的並同時保持汽門原有的運動效果。首先將現有之頂置單凸輪軸汽門機構，透過創造設計系統化的方法步驟， 找出其他與原始機構具有相同構造功能的新的可變汽門正時機構。接著設定限制條件來篩選出可用之五桿凸輪連桿組合式可變汽門正時機構。再從中選出一適當之新型機構，給定適當之單暫停凸輪運動曲線與桿件尺寸，利用瞬心向量法即可推導出完整的凸輪輪廓向量參數方程式。接著，計算其從動件位移、速度、加速度與輸入桿件旋轉角之關係。最後，在不同的調整相位角條件下，分析比較汽門的位移、速度、加速度所受到的影響，並計算出開、關汽門作動時產生重疊區之大小。
本文所建議的可變汽門正時與升程機構可提供二種不同的調整相位角條件，而且此機構可達成預期的調整汽門開啟與關閉時間以及改變汽門升程的功能。

關鍵字

可變汽門正時 ； 創造設計 ； 凸輪機構 ； 汽門機構 ； 數目合成

並列摘要

Depending on the engine speed, the variable valve timing system can correspondingly change the valve open and close timing as well as the valve lifting position. As a result, not only the volumetric efficiency and the output torque can be effectively enhanced, but also the fuel consumption and emissions can be reduced.
The purpose of this work is to develop a new variable valve timing mechanism using the creative design method. This new mechanism is expected to improve the valve open and close timing as well as the valve lifting position, using more efficient mechanism with a less number of the mechanism links. As a first step, the creative design method is used to find all the new and feasible variable valve timing mechanisms, which are capable of achieving the same function as the existing single over-head cam-shaft mechanism. Then, based on imposed constraints, we can select acceptable variable valve timing mechanisms with five-bar cam-link features. Furthermore, an appropriate new mechanism can be chosen to potentially offer superior performance. After the link lengths and the follower motion program are specified, the cam profile parametric equations are derived by applying the concept of velocity instant center. Consequently, the follower displacement, velocity, and acceleration with respect the input link rotation angle of the chosen new mechanism are calculated. Finally, under different adjusted phase angle conditions, the proposed variable valve timing mechanism can be used to study the effects on the existing mechanism. These effects include the variable valve timing and lift, the resulting valve displacement, velocity, and acceleration. Additionally the overlapping area of the valve opening and closing are calculated and compared.
This proposed variable valve timing mechanism can provide two available phase angle adjusting conditions, and this new mechanism can achieve the expected variable timing and lift effect improvement.

並列關鍵字

variable valve timing ； creative mechanism design ； cam mechanism ； valve mechanisms ； number synthesis

參考文獻

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