齒輪軸指支承轉(zhuǎn)動(dòng)零件并與之一起回轉(zhuǎn)以傳遞運(yùn)動(dòng)、扭矩或彎矩的機(jī)械零件。一般為金屬圓桿狀，各段可以有不同的直徑。機(jī)器中作回轉(zhuǎn)運(yùn)動(dòng)的零件就裝在軸上。

　　根據(jù)軸線形狀的不同，軸可以分為曲軸和直軸兩類。根據(jù)軸的承載情況，又可分為：①轉(zhuǎn)軸，工作時(shí)既承受彎矩又承受扭矩，是機(jī)械中最常見的軸，如各種減速器中的軸等。②心軸，用來支承轉(zhuǎn)動(dòng)零件只承受彎矩而不傳遞扭矩，有些心軸轉(zhuǎn)動(dòng)，如鐵路車輛的軸等，有些心軸則不轉(zhuǎn)動(dòng)，如支承滑輪的軸等。③傳動(dòng)軸，主要用來傳遞扭矩而不承受彎矩，如起重機(jī)移動(dòng)機(jī)構(gòu)中的長光軸、汽車的驅(qū)動(dòng)軸等。

　　Gear shaft refers to mechanical parts that support rotating parts and rotate with them to transmit motion,torque or bending moment.Generally,it is in the shape of metal round rod,and each section can have different diameters.The rotating parts of the machine are installed on the shaft.

　　According to the shape of the axis,the shaft can be divided into two types:crankshaft and straight shaft.According to the bearing condition of the shaft,it can be divided into:①rotating shaft,which bears both bending moment and torque when working,is the most common shaft in machinery,such as the shaft in various reducers.②Mandrels are used to support rotating parts that only bear bending moment without transmitting torque.Some mandrels rotate,such as the axle of railway vehicles,and some mandrels do not rotate,such as the axle of supporting pulley.③The transmission shaft is mainly used to transmit torque without bearing bending moment,such as the long optical shaft in the crane moving mechanism and the drive shaft of the car.