1. Introduction
is the main component from the main reducer to reduce speed in the drive train, acting to increase the torque, when the engine torque to change the vertical position with the rotational direction Shihai role . It is to rely on a small number of teeth with the gear teeth of the gear reduction is achieved using a conical gear torque rotational direction may be changed. The final drive is disposed before the power split position to the drive wheels, it is advantageous to reduce the foregoing transmission member (such as clutch, transmission, drive shaft, etc.) the transmitted torque, thereby reducing the size and quality of these components. 
2, the origin
When the cars normal driving, the engine speed is usually about 2000 to 3000r / min, if such a high transmission speed is reduced down alone, then the sub-transmission gear is required within the transmission is large, and the secondary transmission gear ratio is larger, the greater the radius of the gear ratio of two, in other words, will be larger than the size of the transmission. Further, the rotational speed decreases and the torque will increase, will increase the load transmission gearbox and a transmission mechanism after the gearbox. So, before setting a final drive power split to the left and right wheel differential.
3, action
in the presence of the main gear unit has two functions, the first is to change the direction of power transmission, and the second is to provide a common transmission for each transmission gear position as an extension ratio. The output of the transmission is a moment about the longitudinal axis, the wheel must be rotated about the transverse axis of the vehicle, which requires a means to change the power transmission direction. The reason is called final drive, a factor that is because no matter what gear transmission on the transmission of this device is more than the total gear ratio. With this ratio, can effectively reduce the requirement for deceleration of the transmission capacity, benefits of this design is effective to reduce the size of the transmission, so that the overall arrangement of the vehicle morePlus reasonable.
final drive car the most important role is to slow down by twisting. We know the output power of the engine is constant, according to the power calculation formula W = M * v (power = torque * speed) When the gear speed reducer through the main down, to obtain a relatively high output torque, to thereby obtain greater driving force. Moreover, the final drive automotive power output also changes direction, the left and right wheels to achieve the speed differential or rear axle differential function.
4, Category
divided by number
by the number of the sub-gear downshifts participate can be divided into single-stage and two-stage final drive main reducer . In addition to requiring a large number of gear ratios, a heavy vehicles two-stage final drive, in general, micro-light, the car substantially single-stage final drive.
1. The two-stage reduction gear
When the main drive gear unit is relatively large, having automobile in order to ensure a sufficient ground clearance is required at this time the two-stage final drive. A plurality of two-stage reducer intermediate transmission gear, the active portion of the vertebral engagement left bevel gear and the intermediate gear, meshing with a bevel gear coaxial with a small diameter spur gear, spur gear and the driven gear. Such intermediate gear to turn back, forward rotation driven gear. There are two intermediate deceleration. Double reduction volume increases since the axle, past mainly used in the low vehicle match engine power is now mainly used in low speed high torque mechanical engineering.
In the dual-stage final drive, when a second reduction stage carried out in the vicinity of the wheel, in fact constitute a separate member at the two wheels, the wheel speed reducer referred to. Such advantage is made possible to reduce the torque transmitted by axle, it is advantageous in reducing the size and quality of the axle. Wheel reduction gear may be a planetary gear type, may be constituted by a pair of cylindrical sub gears. When using the sub-wheel reduction gear may be cylindrical by adjusting the mutual position of the two gears, the positional relationship between the change the vertical axis of the wheel axle. This is called portal axle axle, commonly used in the special requirements of the low position of the vehicle axle
2. The single-stage reduction gear
Single stage gear reducer is an active vertebrae (commonly known as the angle of the teeth), and a driven bevel gear (commonly known as Crown gear), the active vertebral geared shaft, rotating clockwise, driven bevel gear attached to the right side thereof, the engagement point rotated downward, it is consistent with the forward direction of the wheel. Since the diameter of the driving bevel pinion gear, driven bevel gear having a larger diameter, reaches the deceleration function. Gear ratio by the number of bins
by the number of gear ratios of the main gear can be divided into single-speed and two-speed type two. At present, domestic car basically using a single fixed speed type main gear ratios. In the two-speed type main speed reducer, provided with two alternative gear ratios, final drive actually has such functions as the auxiliary transmission. By structure type
divided by the sub-structure type reduction gear can be classified into a cylindrical gear, bevel gears and hypoid gears and other types.
In the engine transversely disposed axle drive motor vehicle, often using simple main reducer helical cylindrical gear; longitudinally arranged in the engine vehicle drive axle, often using a final drive bevel gear and hypoid gear and other types . Compared with the bevel gear, hypoid gear work better stability, higher flexural strength and contact strength, but also with respect to the axis of the main driving gear driven gear axis offset. When the drive gear axis shifted downwards, the position of the drive shaft can be reduced, thereby facilitating a reduction of the vehicle body and the vehicle center of gravity height and improve vehicle driving stability. A final drive
modern automobiles, widely used spiral bevel gear and the hypoid gear. When hypoid work, the pressure between the sliding surface and the larger tooth, the tooth surface film susceptible to damage, must be lubricated hypoid gear oil, gear oil must not be allowed ordinary place, otherwise the tooth surface would quickly wear and abrasion and greatly reduce service life.