Abstract
皮帶式無段變速器(CVT)具有換檔平順,構造簡單,操作容易,重量輕,少維修等優點,這些正是促成速克達機車在台灣及東南亞地區普及的主因.但長期以來,CVT的效率不佳似乎是無法克服的難題,也是安裝於電動機車的最大障礙.本研究即是企圖在不犧牲CVT特點的情況下,有效提升其效率.為了釐清CVT效率低落的原因,本研究將功率損失分為速度損失與扭力損,並借用V型皮帶驅動器的運動特性,以解釋各項損失的成因.由這些運動特性知,皮帶沿切線方向之滑移是影響速度損失的主要原因,皮帶之彎曲遲滯損失則是造成扭力損失的最大因子.在進行實驗之前,為了使數據合理可信,設備的不準度、實驗的重複性等都列入考慮;而為了確保實驗狀態能配合實際的騎乘條件,文中預先計算各行車型態下的車輛負載.田口試驗及靜態實驗都是用來分析各參數對效率的影響;至於動態實驗不僅可提供換檔期間及實際行車時的效率狀況,更能再次驗證靜態實驗中所得到的結果.基於理論及實驗可知,CVT的高效率是發生於高扭力而低轉速,且減速比接近1時.欲使CVT始終工作在這種效率較高的操作區,就必須調整其減速比範圍,並配合調整傳動系統,才能大幅提升效率,同時又維持傳動系統所需的總減速比.文中提出的前級減速齒輪及兩段式變速器都能提供這類功能.而兩個測試實驗更明顯展示了這種改善設計對提升CVT效率的效益.此外,若考慮匹配問題,必須使用設計軟體,修正CVT的部參數,才能使改善設計更為完整.The advantage of smoother speed change,simpler mechanisms,easier operation,lighter weight,lower cost and less maintenance,etc., may be the main reasons for the rubber V-beltcontinuously variable transmission (CVT) being popular in mostAsia countries. However,the low efficiency of the CVT has beena serious problem and is actually the major barrier for theinstallation of the CVT on the electrical motorcycle.The objectof this research is to improve the efficiency of CVT withoutdeteriorate any advantages. To understand the reasons for lowefficiency,the power loss was divided into speed loss andtorque loss,and the motion characteristics of the V-belt drivewere introduced to explain the loss mechanisms.The uncertaintyof each instrument and the repeatability of the experimentalsetup were investigated to ensure the reliability ofexperimental data.The external loading was also calculatedaccording to the driving pattern to simulate the actual roadconditions.The effects of the parameters on the efficiency ofthe CVT were analyzed by both Taguchi method and steady-stateexperiments.This test not only revealed the trend of theefficiency during the interval of speed-ratio change but alsoverified the results from prior experiments. Based on thetheoretical and experimental analysis,the key method for theimprovement may be the adjustment of speed ratio. To fulfillthis idea,the parameters of the CVT must be modified tomaintain the speed ratio of the entire power train.