 |
This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2007) |
BMW xDrive is BMW's four-wheel drive system that powers the X1, X3, X5, X6 and 2006 and later xd and xi 3 Series, 5 Series and 7 Series models. BMW confirmed it has plans for an xDrive M5.
Before xDrive, BMW offered 4WD as an option in the 1980s for the 3 series and the 5 series. The system had a planetary center differential with a permanent 38-62 (front-back) torque split. Both the center and rear differential had a viscous lock which would engage automatically if slippage occurred (one shaft rotated at a significantly different speed compared to the other). The front differential had no lock of any kind.
4WD was again offered for the X5 and the 2001 3 series. The system was similar to the earlier system except without any of the locks. Instead, slipping wheels would be braked with the DSC system, helping transfer power to the wheels with traction.
xDrive was introduced in 2003 with the new X3. Instead of a permanent torque split (which the earlier systems exhibit), xDrive provides torque split between the front and rear axles through the use of a multi-plate wet clutch located in the gearbox on the output to the front drive shaft. This setup allows xDrive to modulate the torque split between the front and the rear. If wheel slip was detected by the ABS/DSC system, xDrive will react quickly to adjust torque bias. The wet clutch is applied through a high speed electric servo motor turning a cam shaped actuator disc.
xDrive is connected to the ABS and DSC systems. In the case that wheelspin or directional instability still occurs while xDrive is or has been modulating the torque split, DSC will brake independent wheels to regain traction and improve directional stability without driver intervention.
The front and rear differentials in xDrive vehicles are an open differential design, thus relying on brake application by the DSC system to transfer power from the slipping wheel to the wheel with traction.
External links
|
|||||||||||||||||||||||||||||||||||||||||||||||
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article BMW xDrive.
