quattro® Highlights

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2005: The self-locking center differential in the RS 4

In 2005, Audi ignited the next stage in the evolution of its classic quattro drive system in the second-generation RS 4. The new self-locking center differential, which is used in most models today, remained true to the principle of mechanical function, yet represented significant progress versus the Torsen differential.

Under normal driving conditions, power is distributed 40:60 between the front and rear axles. This asymmetric and dynamic distribution of torque results in sporty handling with a rear end bias. The center differential can divert up to 60 percent of the a rotating housing. They distribute the torque asymmetrically – power to the front and up to 80 percent to the rear, if necessary. the somewhat large fraction flows to the rear via the internal gear If one wheel on an axle begins to spin, this is eliminated by the and the output shaft connected to it. The smaller fraction is trans- electronic differential lock EDL without any brake application ferred to the sun gear, from where it is sent to the front axle. If being needed – not that such a situation arises very often. traction at one of the axles declines, the helical form of the gears and their oblique splines produce axial forces in the differential. The self-locking center differential is configured as a planetary These forces act on friction disks to provide the desired locking gear. An internal gear encloses a sun gear; rotating between torque and to divert the power to the wheels with the better these two elements are roller-shaped planet gears connected to friction values.

Source: DVD quattro® Highlights 2010 | Status: 03/2010