What is the specific composition of the drive axle?

The drive axle is mainly composed of the main reducer, differential, half shaft and drive axle housing.

Main Decelerator
The main reducer is generally used to change the transmission direction, reduce the speed, increase the torque, and ensure that the car has enough driving force and appropriate speed. There are many types of main reducers, such as single-stage, double-stage, two-speed, and wheel-side reducers.

1) Single-stage main reducer
A device that realizes deceleration by a pair of reduction gears is called a single-stage reducer. It is simple in structure and light in weight, and is widely used in light and medium-duty trucks such as Dongfeng BQl090.

2) Two-stage main reducer
For some heavy-duty trucks, a large reduction ratio is required, and the single-stage main reducer is used for transmission, and the diameter of the driven gear must be increased, which will affect the ground clearance of the drive axle, so two reductions are used. Usually called a two-stage reducer. The two-stage reducer has two sets of reduction gears, which realizes two reductions and torque increases.
In order to improve the meshing stability and strength of the bevel gear pair, the first-stage reduction gear pair is a spiral bevel gear. The secondary gear pair is a helical cylindrical gear.
The driving bevel gear rotates, which drives the driven bevel gear to rotate, thereby completing the first stage of deceleration. The driving cylindrical gear of the second-stage deceleration rotates coaxially with the driven bevel gear, and drives the driven cylindrical gear to rotate to carry out the second-stage deceleration. Because the driven spur gear is mounted on the differential housing, when the driven spur gear rotates, the wheels are driven to rotate through the differential and the half shaft.

The differential is used to connect the left and right half shafts, which can make the wheels on both sides rotate at different angular speeds and transmit torque at the same time. Ensure the normal rolling of the wheels. Some multi-axle-driven vehicles are also equipped with differentials in the transfer case or between the shafts of the through drive, which are called inter-axle differentials. Its function is to generate a differential effect between the front and rear drive wheels when the car is turning or driving on uneven roads.
Domestic sedans and other types of cars basically use symmetrical bevel gear ordinary differentials. The symmetrical bevel gear differential consists of planetary gears, side gears, planetary gear shafts (cross shafts or a straight pin shaft) and differential housings.
Most cars use planetary gear differentials, and ordinary bevel gear differentials consist of two or four conical planetary gears, planetary gear shafts, two conical side gears, and left and right differential housings.

Half Shaft
The half shaft is a solid shaft that transmits the torque from the differential to the wheels, driving the wheels to rotate and propelling the car. Due to the different installation structure of the hub, the force of the half shaft is also different. Therefore, the half shaft is divided into three types: full floating, semi floating and 3/4 floating.

1) Full floating half shaft
Generally, large and medium-sized vehicles adopt full floating structure. The inner end of the half shaft is connected with the half shaft gear of the differential with splines, and the outer end of the half shaft is forged with a flange and connected with the wheel hub by bolts. The hub is supported on the half shaft sleeve by two tapered roller bearings which are far apart. The axle bushing and the rear axle housing are press-fitted into one body to form the drive axle housing. With this type of support, the half shaft is not directly connected with the axle housing, so that the half shaft only bears the driving torque without any bending moment. This kind of half shaft is called “full floating” half shaft. By “floating” it is meant that the half shafts are not subject to bending loads.
Full-floating half shaft, the outer end is a flange plate and the shaft is integrated. But there are also some trucks that make the flange into a separate part and fit it on the outer end of the half shaft by means of splines. Therefore, both ends of the half shaft are splined, which can be used with interchangeable heads.

2) Semi-floating half shaft
The inner end of the semi-floating half-shaft is the same as the full-floating one, and does not bear bending and torsion. Its outer end is directly supported on the inner side of the axle housing through a bearing. This type of support will allow the outer end of the axle shaft to bear the bending moment. Therefore, this semi-sleeve not only transmits torque, but also partially bears bending moment, so it is called semi-floating semi-shaft. This type of structure is mainly used for small passenger cars.
The picture shows the drive axle of the Hongqi CA7560 luxury car. The inner end of the half shaft is not subject to the bending moment, while the outer end has to bear all the bending moment, so it is called a semi-floating bearing.

3) 3/4 floating half shaft
The 3/4 floating half shaft is between the semi-floating and full floating. This type of semi-axle is not widely used, and is only used in individual sleeper cars, such as Warsaw M20 cars.
axle housing
1. Integral axle housing
The integral axle housing is widely used because of its good strength and rigidity, which is convenient for the installation, adjustment and maintenance of the main reducer. Due to different manufacturing methods, the integral axle housing can be divided into integral casting type, mid-section casting press-in steel tube type, and steel plate stamping and welding type.
2. Segmented drive axle housing
The segmented axle housing is generally divided into two sections, and the two sections are connected by bolts. Segmented axle housings are easier to cast and machine.

Post time: Nov-01-2022