The axle is an important part of the transmission system. The power from the engine is transmitted to the main reducer in the axle through the gearbox, and the main reducer further reduces the speed and increases the torque, which drives the differential and the half shafts connected on both sides to transmit the power to the wheels and drive the vehicle to run. Because trucks are basically non-independent suspension of integral bridge, the axle has become an indispensable part of every truck. The characteristics of axle directly affect the driving performance and fuel consumption performance of vehicles. Axles are divided into four categories: steering axle, driving axle, steering driving axle and trailer axle.

The structure of steering bridge and trailer bridge is very simple, because there is no need for power input, so its structure is basically the bridge body plus two wheels. Steering drive axle exists on all-wheel drive special trucks, which is hard to see at ordinary times. Therefore, this paper mainly introduces the types and characteristics of drive axle. There are two types of drive axles, single-stage deceleration bridge and wheel deceleration bridge (wheel deceleration bridge is divided into ordinary wheel deceleration bridge and portal bridge).

Single-stage reduction bridge As the name implies, the power transmitted from the transmission shaft to the axle only passes through the primary speed reduction and torque increase of the main reducer, so it is called a single-stage speed reduction bridge. The advantages are simple structure, the main reducer is composed of a driving bevel gear (commonly known as corner gear) and a driven bevel gear (commonly known as basin gear), which has no complicated structure, is easy to maintain, and has low failure rate in normal maintenance. At the same time, because of its simple structure and light weight, it is very suitable for standard load transportation on paved roads. However, there are advantages and disadvantages. When faced with severe working conditions such as off-road or low-speed and heavy-load, the single-stage deceleration bridge is a little overwhelmed. First, the torque amplification is not enough. Second, the large size of the bridge package affects the clearance from the ground and reduces the truck's passability. Therefore, in order to meet the use requirements of heavy-load or off-road bad roads, the wheel-side deceleration bridge came into being.

2.1 wheel deceleration bridge The difference between wheel-side reduction bridge and single-stage reduction bridge lies in that a set of planetary gear reduction mechanism is added at the wheel end, which continues to slow down and increase torque on the basis of the main reducer's speed reduction and increase torque. It is terrible that the torque amplified by two stages is transmitted to the wheels. Therefore, it is a practical and cost-effective scheme to use wheel-side reduction bridge when extra-large torque output is needed. After all, compared with adding hydraulic torque converter or replacing high-horsepower engine, the increased cost of wheel-side reduction bridge is much smaller. For off-road conditions, wheel reduction bridge also has the advantage of high ground clearance, because its reduction mechanism is divided into two parts, so the volume of bridge package is greatly reduced and the passability is better. Of course, the wheel deceleration bridge is not without its shortcomings. Firstly, the complex structure reduces its transmission efficiency. Secondly, it is easy to overheat when driving at high speed, because its wheel deceleration is easy to undertake most of the tasks of speed change and torque increase. Meanwhile, the heat generated by the friction between tires and the ground when driving at high speed is also concentrated at the wheel end, resulting in poor heat dissipation conditions and easy overheating.

2.2 portal bridge The portal bridge moves the axle head from the center line of the hub to the upper part of the hub, which improves the ground clearance of the axle body and makes the vehicle pass through better when driving off-road. In order to achieve the effect of shaft head moving up, the wheel reduction mechanism of portal bridge is changed from the planetary gear set with ordinary wheel reducing bridge to the ordinary gear set.

Conclusion Axle is an important part of truck. Suitable and durable axle can greatly improve efficiency. Domestic axle enterprises have made progress in recent years, and developed many good axle products. In order to make good products become more productive, users should also have a general understanding of the advantages and disadvantages of various axles and know what products are suitable for their actual situation. Hope that through this article, friends who have no concept of axle structure can know more about axle. After all, good products and reasonable collocation, coupled with the correct choice of users, can maximize the benefits of technology.