XDrive ['eks'draiv]
The XDrive intelligent all-wheel drive system is a BMW patent. XDrive sets new standards in all-wheel drive agility. Its job is to quickly change the torque distribution of the front and rear axles to provide real driving stability, driving pleasure and safety performance. The BMW X1, X3, and X5 currently on sale all have basically the same xDrive system.
How XDrive works:
The core technology of the XDrive all-wheel drive system is a transfer case developed by Magna Steyr of Austria to distribute torque differently. Adjust intermittently. The XDrive system continuously changes the torque distribution according to road conditions, transmitting the required torque to the front and rear wheels. The default front-to-rear torque distribution is 40:60, and the maximum front-to-rear torque distribution ratio is between 0:100 and 100:0. Torque distribution can be completed in 0.1 seconds.
During driving, if the system detects that the vehicle may understeer, that is, the front wheels begin to be dragged toward the outside of the bend, it will reduce the torque allocated to the front axle and transfer almost all power to the rear axle. . The system also constantly exchanges information with the dynamic stability system DSC, making it possible to detect wheel slip from the outset. Once wheel slip occurs, the electric motor will lock the XDrive's diaphragm clutch and use additional driving torque to give the wheel better adhesion. At the same time, the idling wheel will also be effectively controlled by the braking device. This means that no matter how sudden the road surface changes, the right amount of torque will be sent to the wheel with the best grip, even on partially icy roads.
XDrive's multi-disc clutch is located between the gearbox and the cardan shaft, which can freely distribute drive power between the front and rear axles. Like all BMW cars, one driveshaft leads to the rear axle, while the other leads to the front axle next to the engine. An electronically controlled motor presses the clutch discs together in an instant. The greater the pressure, the greater the power transmitted to the front axle through the chain cardan shaft. When the pressure is lost, the clutch discs disengage and all power is sent to the rear axle.
Under normal driving conditions, the XDrive system distributes engine power in a 40:60 ratio. When the road conditions are complex, XDrive predicts changes in body posture, controls the hydraulic pressure and presses the multi-disc clutch via computer, thereby allocating the front and rear axles. Reacts to changes in road and driving conditions, changing the distribution of longitudinal drive force.