According to different classification methods, automobile axles can be divided into many types, such as integral axle and disconnected axle according to structure, and steering axle, drive axle, steering drive axle and support axle according to function. The drive axle can be subdivided into single-stage reduction axle (half axle axle) and two-stage reduction axle (wheel side axle and wheel reducer axle). The portal axle we are going to talk about today is strictly a variety of wheel side axle.

As we all know, the diameter of the main reducer teeth of the wheel side axle is small, the volume of the axle package is smaller, the ground clearance of the vehicle is large, and the trafficability is good, which is suitable for use on complex road conditions. However, in some extreme road conditions, ordinary wheel side bridges may not meet the requirements. At this time, portal axles are needed.

The design principle of the portal axle is simply to say that the axle originally installed at the center of the wheel moves up to the top of the wheel center, and transmits the rotary movement to the wheel through the gear transmission. As a result, the size of the wheels and the stroke of the shock absorbers have not changed, but the ground clearance of the chassis, half shaft, transmission shaft and differential has been improved.

Because the axle installed in this way looks like a doorframe on the whole, it is named "portal axle".

As for the characteristics of the portal axle, we will simply analyze the advantages and disadvantages:

Advantages:

1. The ground clearance of the vehicle chassis is higher, and the vehicle trafficability is greatly improved, which is suitable for climbing mountains and jungles.

2. The components of the transmission system, such as the gearbox and transmission shaft, are more lightweight to reduce the vehicle's center of gravity.

inferiority:

1. Production costs, purchase costs and post maintenance costs are on the high side.

2. The design of the hub assembly is more complex, which is easy to increase the unsprung weight and affect the handling stability. It is not suitable for ordinary vehicles that often run on urban roads.

3. More solid shaft control elements are required. The more parts, the higher the failure rate.

The portal axle is specially designed for extreme environments. It was first used in combat vehicles, and later gradually applied to some off-road vehicles. However, as mentioned above, to some extent, the portal axle achieves higher trafficability at the expense of vehicle handling stability. It is suitable for extreme road conditions in the wild, but not suitable for ordinary road conditions in the wild or on urban roads. This is also the reason why many off-road vehicles are not equipped with door type axles.

In addition, I don't know if you have noticed that in the early years, the city buses that you usually take had two or three steps, but now some models have become the type of cars that can be entered in one step. Some of the buses with particularly low chassis and one-step carriages also use portal bridges, which are used in reverse. They have changed from high chassis to low chassis, making it easier for passengers to get on and off. For example, it is easier to get on and off wheelchairs and baby carriages. With air springs, driving comfort has also been greatly improved.