When the car is turning, the left and right wheels have different trajectory radii, so they have different distances when turning. The outer wheels have to pass a longer distance. If the power is transmitted to the same size wheel through a complete shaft, the two wheels The rotation speed is the same, the diameter is the same, and the distance traveled by the two wheels is different when turning. Then the wheels on the inner side of the curve need to be slipped and idling (not walking), making it difficult to turn; in order to overcome and improve this problem, the vehicle drive shaft Divided into two halves, left and right, connected by a "differential" in the middle, when the vehicle is driving straight, the two wheels can get the same driving force, and when turning, due to the action of the differential, the rotation speed of the inner wheel is lower than that of the outer wheel In this way, the goal of driving the vehicle forward by two wheels at the same time is achieved, but the movement distance of the outer wheels is larger than that of the inner side.

The use of two half shafts for the drive shaft is designed to improve the turning performance of the vehicle.