BMW xDrive is the marketing name for all-wheel drive systems found on BMW X1, X2, X3, X4, X5, X6, and X7 crossover activity vehicles. It is also optional on Series 1 (2012-present), Series 2 (2015-Present), Series 3 (2000-Present), 4 Series (2014-Present), 5 Series (2005-Present), Series 6 (2012-present ) -present), and Series 7 (2010-present).
Video BMW xDrive
Description
Instead of a permanent torque split (shown in the previous system), xDrive provides a variable torque split between the front and rear axle through the use of a multi-plate wet clutch located in the gearbox at the output to the front drive shaft. This setting allows xDrive to modulate the torque separator between the front and rear axles, which are usually divided at a ratio of 40:60, respectively. If the wheel slip is detected by the ABS/DSC system, xDrive can react within a tenth of a second to redistribute up to 100% of the engine power to the front or rear axle. The wet clutch is applied through a high-speed electric servo motor that rotates the cam-actuator dish. Because the rear drive shaft is difficult to combine with the transmission output, full torque transfer to the front axle can only be achieved if the rear wheels have no traction and both slip.
xDrive is connected to ABS and DSC systems. In the case of directional wheels or instability still occurring when xDrive is or has modulated a torque split, the DSC will brake the wheels independently to regain traction and improve direction stability without driver intervention.
The front and rear differences in the xDrive vehicle are usually an open differential design, thus relying on the brake application by the DSC system to transfer power from the wheels that slip into the wheels with traction.
Variations on the xDrive system are present in the BMW X1 2015 (F48), which is based on the design of the front-wheel drive with a transverse mounted engine. In the FWD xDrive variant, the front wheel receives 100% of the torque when the xDrive clutch opens, giving it a forward bias instead of the usual xDrive back bias.
Apps
xDrive is available on X1, X3 and is standard on X4, X5, and X6 and BMW X6 M sport crossover activities. It is also optional on Series 1 (2012-present) Series 3 (2002-present for sedan, 2007-2013 for coupe), Series 4 (2014-present), 5 Series (2005-present), Series 6 (2012- present) present for coupe and Gran Coupe), and 7 Series (2010-present).
BMW is gradually expanding the availability of xDrive throughout its ranks to better compete with quattro Audi and Mercedes-Benz 4Matic, the latter two being widely available throughout each offer. In 2010-12 models, BMW Canada has even stopped offering RWD trims if xDrive partners are available for Series 5, Series 6, and 7 Series cars, a major reversal of the 2009 model and earlier where only BMW 528i and 535i are available with xDrive. The BMW Canada switch has surprised some observers, because AWD is "once the only scope of Audi with some weird Mercedes-ducks mixed, the switch to the AWD is so strong that many luxury models are now dominated AWD, though the 650 is the first high-end defect sport coupe among BMWs.. Even more surprising is that the Coupe will only be available in the AWD guise; if you want a 650 that only drives the rear wheels, you should choose the ragtop version. "
xDrive was introduced in 2003 with the new X3 and the updated BMW 3 Series (E46).
The first xDrive app on BMW-powered V8 cars (compared to crossover sport activity vehicles) is at the 2010 BMW 750i xDrive (F01), 2010 550i Gran Turismo xDrive (F07), and 2011 BMW 550i xDrive (F10).
xDrive was first used on BMW M vehicles starting with BMW X5 M 2010 and X6 M. The sixth generation BMW M5 comes with xDrive.
Maps BMW xDrive
Dynamic Performance Control
The torque-vectoring control system The BMW Dynamic Performance works in conjunction with the all-wheel drive xDrive and Dynamic Stability Control. DPC is a drivetrain and chassis control system that serves to regulate traction and is especially over-and understeer by actively propagating the driving force across the rear axle. The torque is divided not only between the front axle and the rear axle (xDrive), but also between the rear wheels to improve agility and add stability (via the rear axle DPC). DPC works at all normal speeds and rides, not just when cornering hard, to direct the car. The DPC also interfaces with the DSC to initially try to repair the vehicle path using torque vectoring which results in a smooth spin, whereas DSC by itself will only reduce engine power and apply the brakes to drive the vehicle.
Differences DPC features coupling packets on both sides of the output driven by an electric motor. The coupling package activates the planetary gear causing one wheel to overdrive. Conventional control systems, such as the typical BMW xDrive system without Dynamic Performance Control, rely on the brakes to reduce the speed of the moving wheels faster (which is one with less grip) and reduce engine power to limit the slip on the wheel. This causes increased brake wear, and slows the vehicle's optimal progress. Conversely, xDrive when integrated with DPC will accelerate the slower moving wheel, not slip (which has the most traction) to maintain stability when needed. For example, during vehicle spins, exterior wheel excess to provide greater acceleration, using traction advantage through dynamic loading of outboard wheels in cornering. Meanwhile, in an oversteer situation, the inner wheels overdrive to regain the balance of traction. This provides additional traction along the vehicle's axle, while at the same time maintaining more optimum vehicle progress through turns.
The first application of DPC was introduced on the BMW X6, which started production in 2008 as a 2009 model, where it is standard equipment. A test found that "X6 feels lighter hundreds of pounds on its legs than the X5 [without DPC]" because of the DPC benefits even though both vehicles have the same chassis dimensions. The BMW X5 M high performance variant also has DPC standards.
the predecessor AWD system
Prior to xDrive, BMW offered AWD as an option in 1980 for the 3rd and 5th series. The system has a thick coupling in the center and rear differential. Until the wheel slip occurs, the transfer case has a 37:63 torque split (front-back) due to planetary equipment. When one shaft rotates faster than the other, the shear strength of the silicone fluid increases as the VC slip (because of the perforated plate in the unit). It will instantly transfer up to 80% of the available torque to the gripping shaft. This same function works in the rear differential of the car. The front differences do not have any keys.
AWD is once again offered for X5 and series 3 2001. The system is similar to the previous system except without keys. Instead, the slipped wheels will be braked with the DSC system, helping to transfer power to the wheels with traction.
References
External links
- The winter driving test: BMW xDrive
- BMW website
- BMW xDrive
- The BMW xDrive UnixNerd page with photos, history, and BMW winter driving tips.
- BMW xDrive - From First Analog System to All-Wheel-Drive Hybrid
Source of the article : Wikipedia
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