Steering and driving functions of the front axle of cars

With the development of automotive technology and the demand for automotive performance, four-wheel drive systems and front-wheel drive systems have gradually been developed. This requires the front axle of the car to have both steering and driving functions.

At present, most of the cars, SUVs, MPVs, etc. are all front-engine transversely mounted and front steering wheel knuckle independent suspension systems. The driving and steering modes of this structure are different from the above-mentioned integral bridge steering drive axle. It does not have an axle in the strict sense. The gearbox is combined with the main reducer and differential and is called a “transaxle”. The half shaft is exposed to the outside and directly drives the front wheels; the connection between the wheels and the body is independent Suspension, the steering gear directly push the wheel to deflect, so the wheel not only swings from side to side, but also jumps up and down, which requires the half shaft to adapt to this position change at any time.

In order to be able to transmit power between parts whose angles often change at any time, the half shaft is generally divided into three sections and connected by two ball cages. The inner half shaft is connected with the differential of the transaxle to receive the power output by the gearbox; then the power is transmitted to the inner ball cage, which is a telescopic ball cage universal joint (VL joint), which is characterized by transmitting and turning In the process of moment, the main and slave shafts can not only rotate relative to each other, but also produce axial displacement to adapt to the change in the length of the half shaft when the wheel jumps up and down; then the power is transmitted to the middle half shaft and then to the outer cage , It is a fixed ball cage universal joint (RF joint), which is characterized in that in the process of transmitting torque, the driving and driven shafts can only rotate relative to each other without axial displacement, and can adapt to the wheel’s Large-angle deflection; finally the power is transmitted to the outer half shaft, which is connected with the hub through the spline on the outer half shaft to drive the wheel to rotate. In this way, the car can transmit power to the wheels while turning, which is what we call both steering and driving.

There are still many rear-wheel independent suspension and rear-wheel drive models. How is their power transmitted? It also has no axle in the strict sense, only a drive axle consisting of a main reducer and a differential. Since the rear wheel can jump up and down, the half shaft cannot be integral, and it needs to be disconnected from the middle to meet the need to transmit power between the two parts that are constantly changing. This is the split half shaft. It is equipped with two universal transmission devices on the half shaft to realize the change of power transmission angle. After the power is output from the drive axle, it is first transmitted to a ball cage, then to the half shaft, and then to the driving wheel through a ball cage at a position close to the driving wheel. When the car is driving, the wheels will jump up and down, but the ball cage allows the half shaft to bend at a certain angle, so the power transmission will not be interrupted. However, due to the limited range of the driving wheels to jump up and down, the angle at which this half-shaft can be bent is small, and can only be used to transmit force but not to turn.

The reason why the front wheels of front-wheel drive vehicles and four-wheel drive vehicles can both steer and drive is because of the steering drive axle. The key technologies are two: one is the split-center steering king pin, which allows the half shaft to pass through and connects with the front wheels to transmit power to the front wheels; the second is the split half shaft, which allows the half shaft to pass through. The axle can automatically bend with the deflection of the front wheels, which will not interfere with the steering of the front wheels, and can ensure uninterrupted power transmission.