LSD System
Speaking of the AWD car drive system, people can't help but think of Audi Quattro. It is Audi's bold innovation and no turning back that makes more and more people enjoy the driving pleasure brought by AWD, and the core of Audi Quattro AWD is Torsen LSD differential The device system, who would have thought that it still maintains the mechanical purity today when electronic components are rampant.
Every car must be equipped with a differential, we know the function of the ordinary differential: first, it is a set of reduction gears, which converts the high speed output from the gearbox into normal vehicle speed; second, it can make the left and right drive The wheel speed is different, that is, the inner and outer wheels output different rotational speeds to maintain balance when cornering. Its disadvantage is that it loses traction due to slippage when passing over wet roads. And if the limited slip function is added to the differential, it can meet the needs of the car to have good handling on bad roads. This is the Limited Slip Differential (LSD for short). The basic composition of the all-wheel drive car AWD system is to have three differentials, which respectively control the torque distribution of the front wheels, the rear wheels, and the front and rear drive shafts. These 3 differentials are not just the common simple differentials, they are LSD differentials with self-locking function to ensure that the driving wheels always have sufficient torque output when the tires slip on wet roads. Good handling in road conditions. There are several forms of LSD differentials in the world, today we will take a look at the Torsen self-locking differential system.
The origin of the name Torsen comes from Torque-sensing Traction - feeling torque traction, even the brand name is derived from traction control, professional enough!
Torsen core system
Haldex multi-plate clutch center differential
When there is no wheel slippage when driving on a curve, the front and rear differentials function as traditional differentials, and the worm gear does not affect the difference in the output speed of the axle shaft. For example, when the car turns left, the right wheel is faster than the differential, while the left speed is lower, and the worm gears with different left and right speeds can closely match the synchromesh gears. At this time, the worm gear and worm are not locked, because the torque is from the worm gear to the worm gear, and the power transmission in this direction is unobstructed.
When the left wheel slips, the traditional differential will transmit power to the left wheel, so that the engine power can only be consumed in vain. The Torsen differential is different, in which the rapidly spinning left half shaft drives the left worm and, via a synchromesh gear, drives the right worm.
Torsen differentials are used on the full-time four-wheel drive system, and traction is distributed to each wheel, resulting in good cornering, dry/wet drivability. The Torsen center differential ensures an even distribution of power to the front and rear wheels. For example, when the tire encounters a road with a lack of friction, such as ice, the system will respond quickly, and most of the torque will be transferred to the wheel with a slower speed, that is, the wheel with grip.
The locking intervention of the Torsen differential has no time delay and does not consume the size of the total torque value. It does not have the multi-plate clutch equipped with the traditional locking differential, and the wear is very small, which can be maintenance-free.
In addition to its own performance advantages, the Torsen differential also has other advantages. For example, it can be matched with many common transmissions and transfer cases, and is compatible with ABS, TCS, ESP and other electronic equipment on the vehicle. Vehicle safety and handling services.
However, there are still two difficult problems with the Torsen differential. One is the high cost, so the Torsen differential is generally used in high-end cars; the second is that the weight is too large, and the acceleration of the vehicle after it is installed is A drag.
It has also been used in cars as a mainstream differential for more than 20 years. However, due to its outstanding mechanical stability, the development has not been fast for many years. In 2011, only the third generation "Torsen C" was developed. The new C-generation Tosen differential is commonly used in the Audi B7-generation RS4, S8 and Q7's "Quattro" full-time four-wheel drive system. The biggest change in the new Torsen center differential is that the front and rear torque distribution ratio is generally controlled at 40:60, the proportion of torque on the front axle can vary between 15% and 65%, and the proportion of torque on the rear axle can be between 35% and 85%. change between.
As the main four-wheel-drive sedan manufacturer, Audi has always insisted on using the Torsen differential. Except for the A3 and TT, all other Audi "quattros" use the Torsen center differential. But Torsen differentials are not only used in Audi cars. There are more and more companies using Torsen differentials, including Ford, GM, Toyota, Mazda, Land Rover, Volkswagen and Lexus. It's just that the front, rear and center use positions are different, and they are not of the same generation.
In short, the Torsen differential is a very precise and creative invention, and it has always maintained its purely mechanical characteristics. Today, when major car manufacturers are rapidly and continuously introducing various electronic devices, it has been able to maintain a leading position in many aspects, which has to make us full of admiration for the "Torson Differential" and its designers.
TORSEN LSD is based on the principle of worm gear and worm to achieve limited sliding, and its degree of limitation increases with the increase of relative rotation, so it is called TORQUE SENSING (torque sensing). Torsen differentials are mainly composed of worm planetary gears, differential case Body, front output shaft and rear output shaft are composed of four sets of large parts. The power output by the engine is directly used to drive the casing of the Torsen differential (the power input gear in the figure is connected to the casing), and the rotation of the casing will drive the three sets of worm planetary gears to rotate. It is connected by straight teeth, and is connected with the front and rear output shafts by a worm. In this way, the power can be smoothly distributed to the front and rear output shafts through the planetary gears so that the front and rear axles can be driven. It is precisely because of the worm design of the planetary gear that it has a self-locking function. Once a wheel encounters greater resistance, the Torsen differential transmits more power to that wheel.
TORSEN LSD is based on the principle of worm gear and worm to achieve limited sliding, and its degree of limitation increases with the increase of relative rotation, so it is called TORQUE SENSING (torque sensing).
-The core of Torsen
From the structural view of the Torsen differential, we can see the double worm gear and worm gear structure. It is their intermeshing and interlocking and the unidirectional transmission of torque from the worm gear to the worm gear to achieve the differential locking function. Positive It is this feature that limits sliding.
Torsen differential
When the right wheel slips, the worm gear assembly works, and a conventional differential will not transmit power to the left wheel. For the Torsen LSD differential, the fast-spinning right half shaft will drive the right worm and the left worm through the synchromesh gear, where the worm gear characteristics come into play. When the worm drives the worm gear, they lock, and the left and right worms interlock, ensuring sufficient traction for the non-slip wheels.
