An arrangement of gears in an epicyclic train permitting the rotation of two shafts at different speeds, used on the rear axle of automotive vehicles to allow different rates of wheel rotation on curves.差动齿轮：在周围轮系中的齿轮排列方式，可使两旋转轴在不同的速度下旋转，可装在汽车后车轴上，拐弯时可改变车轮的旋转速度