Based on structural form, drive axle can generally be divided into two types: non-disengageable type and detachable type. The non-detachable type is also called integral type and is mainly used in rear wheel drive trucks. ;
Disconnected drive axles are mainly used on vehicles with independent suspension
Its main function is to change speed, increase torque, change direction of rotation by 90°, and act as a differential speed. Engine power is transmitted to drive axle through clutch, transmission and universal transmission. The main gearbox in drive axle can reduce speed, increase torque and change direction of rotation. After speed is distributed by differential, it is transmitted to wheels through axle shaft and hub. When vehicle turns or travels on a rough road, final drive differential may cause left and right drive wheels to rotate at different speeds, resulting in a differential effect.
Which way of driving is better
Ordinary cars usually only have two rear wheels as a drive and two front wheels as a drive, or two front wheels as a drive and two rear wheels as a drive, while SUVs and full-time four-wheel drive vehicles All wheels are leading. In order to distinguish ordinary cars from SUVs, it is often expressed by multiplying total number of wheels by number of driving ones, for example: 4x2 (two-wheel drive), 4x4 (four-wheel drive). four-wheel drive), 6x6 (six-wheel drive), etc.
According to relative position of engine and drive axle, running forms of car can also be divided into following types:
(1) Front engine, rear wheel drive:
This type of drive is mainly used in large and medium trucks, but is also used in some high-end vehicles, as well as miniature and light trucks. It connects engine, clutch and transmission as a whole and installs them at front of car, while main gear, differential and axle shafts are installed in rear axle housing at rear of car. universal joint shaft. The advantage is that weight distribution of front and rear wheels is more reasonable, which can increase driving force; disadvantage is that a longer transmission shaft is required, which not only increases weight, but also affects transmission efficiency, and driving stability on slippery road is poor.
(2) Front engine, front wheel drive:
This type of driving is mainly used in cars. It assembles engine, clutch, transmission, gearbox and differential into a very compact unit and mounts it at front of car. The engine can be installed longitudinally or transversely, and front wheels have both steering and driving functions. The advantage is that transmission system layout is most compact, making operation relatively easy; saves a long transmission shaft, reduces power transmission losses, and also lowers center of gravity of car body to improve stability; back seat is stable and comfortable, and noise is low. The downside is that maximum tractive power is not as good as rear wheel drive. When driving uphill, shifting weight back reduces attached mass of front drive wheel, and when driving downhill, weight moves forward, overloading front wheel. Since front wheel has two steering and driving functions, structure becomes more complicated and cost is higher.
3) Rear engine, rear wheel drive:
This type of driving is mainly used in large and medium-sized passenger cars, as well as some miniature cars and cars. The engine, clutch and transmission are located transversely behind drive axle, and drive axle has an independent suspension. The advantage is that this shape of large and medium-sized passenger cars allows a more reasonable distribution of total weight of car on front and rear axles, and front axle is not easy to overload; this allows you to reduce height of body. body floor by 2, which is convenient for boarding and disembarking passengers, reduces noise in cabin and increases area of \u200b\u200buse of car. The disadvantage is that heat dissipation is somewhat affected by fact that engine is at rear of car; since driver is far from engine, it is difficult to judge operating condition by sound of engine; remote control complicates joystick and conveyor.
(4) Four wheel drive:
This type of driving is mainly used on off-road vehicles, special vehicles and military vehicles. Some high-end and sports cars use permanent four-wheel drive to improve traction and stability. For SUVs that need to drive on bad roads or off-road, in order to take full advantage of traction between all wheels and ground for maximum grip, all wheels are usually driven, and front axle is both steering wheel and steering wheel. Axle is again a drive axle. To distribute power transmitted from engine to transmission to front and rear drive axles, a transfer case is added at rear end of transmission, and a driveshaft is added from transfer case to front and rear drive. axes are added accordingly. The front drive axle of some models can be turned on and off by manipulating transfer case lever depending on road conditions. The advantage is that driving force is large, flotation is good, and stability is improved. The disadvantage is complexity of design of transmission system and high cost of manufacturing.