This creation system is related to the speed changer of various power devices,It includes a shell,One variable transmission mechanism and a volume change part； By volume change part is arranged in shell,And its volume in response to the inner space of shell pressure change and passively change,Therefore when the intracorporal hydraulic oil of shell expands with heat and contract with cold,Volume change part is adjusted the intracorporal spatial volume of shell and remains unchanged pressure； The venthole of shell is sealed by what volume change part,Therefore the air in the external world,Aqueous vapor and rainwater cannot be introduced into shell,To safeguard the quality of hydraulic oil,And lubricating oil can not also leak outside from venthole,And then it is convenient to use； The intracorporal a part of space of shell is occupied by what volume change part,Therefore the lubricating oil using relatively small amount is only needed,It can make the mechanism engagement place of lubricating oil covering variable transmission mechanism.本創作係涉及各種動力裝置的變速器，其包含一殼體、一變速傳動機構及一體積變換件；藉由在殼體內設置體積變換件，並且其體積因應殼體的內部空間的壓力變化而被動地改變，因此當殼體內的液壓油熱脹冷縮時，體積變換件可調節殼體內的空間體積而使壓力保持不變；由於體積變換件封住殼體的通氣孔，因此外界的空氣、水氣及雨水無法進入殼體內，以維護液壓油的品質，而潤滑油亦無法從通氣孔外漏，進而方便使用；由於體積變換件佔據了殼體內的一部分空間，因此僅需使用相對少量的潤滑油，便可使潤滑油覆蓋變速傳動機構的機構嚙合處。
