Torsen

Torsen differentials are differential with self-locking effect, which belong to the group of limited-slip differentials. Today they are used primarily as a center differential in four-wheel vehicles, especially in the Audi quattro models.

The name " Torsen " comes from the English words for " torque " (torque ) and " sensitive " ( sensitive). This word describes the art torque-sensing feature of these limited-slip differentials.

The basic invention already goes back to the year 1918. Developers of type A was Vern Gleasman in 1958 registered the differential for a patent. In Germany Torsen is a registered trademark of JTEKT Corporation, headquartered in Osaka ( Japan) since 1983. The Torsen system was first used in 1983 in the HMMWV to the market. From 1986 it was used by Audi.

Technology

Like all limited-slip differentials, the Torsen differential in principle an open differential, its ability to torque balance between the output shafts is worsened by low efficiency.

In the market, especially the first two Torsen types are represented today:

• In type A, the differential gears ( planet gears ) and the side wheels (output ) is designed as helical gears, ie the Verrzahnung is at a 45 ° angle to the axis, and the axes are perpendicular to each other. The sliding movement in the toothing and the easy storage, thereby causing high friction losses, which produce the desired blocking effect, if a rotational speed difference occurs on the output side.
• In type B, the axes of all the wheels are parallel, so it is sometimes called "parallel axis differential ". The toothing is embodied as helical gearing ( helical gear ) with extremely large skew angles, again caused in the meshing forces urging the end faces of the gear wheels relative to the housing. There is produced a great deal of friction.
• The type C is constructed as a planetary gear. By large helix angle of the gears and splines inclined arise in large differential axial forces which produce the desired locking torque on friction. The type C can be combined with an open differential to a compact unit. In type C, the torque split is not 50:50, as usual in other axle differentials usual; Therefore, the Type C is used exclusively as a center differential between the axles (especially Audi).

The Type A reached much higher values ​​than the barrier type B. As with all torque-sensitive differentials, if not ESP exists, hardly produces thrust with a raised wheel. For vehicles without ESP may have an impact when starting. A remedy for such situations, a light application of the brake, whereby the force is distributed to all four wheels. Another advantage is the ESP compatibility and the influence on driving dynamics in sport.

Construction type A

In place of the four bevel gears in a conventional differential gear the Torsen more screws act toothed roller pairs 45 ± n degrees pitch, by means of spur gears on the two ends of the screw rollers coupled to each other in the pair of worm gear drive shaft engage. This speed difference can be compensated; by the worm gears own, high friction loss and by additional friction arises the blocking effect.

Influence on the dynamics

Torsen differentials lock depends on the transmitted torque. One can distinguish several modes of operation with Torsen differentials (as with all torque -sensing limited-slip differential ):

• In traction mode, the vehicle is driven by the motor. Transmits an axis less driving forces, so is loss of traction before, more driving force is automatically ( usually those with more traction ) transferred to the slower rotating axis through the Torsen differential. If an axis or a wheel is lifted (or standing on mirror smooth ice ), the blocking effect of the Torsendifferentials has no effect - the wheel or the axle with the least traction spins by. One remedy differential lock or traction control here.
• In thrust operation of the engine is towed, that is driven by the vehicle. Judging from the gas, the power flows in the reverse Torsen differential. If the driver has disengaged, it acts like an open ( unblocked ) differential, and the axes are largely decoupled. Thus, the engagement of the ABS and ESP is undisturbed possible.
• When cornering, the Torsen differential distributes drive forces more and more to the slower rotating axis, which is usually the rear axle. If the rear axle lose traction, the Torsen automatically provides more power to the front axle.

Application

In the first Audi Quattro all-wheel vehicles from the introduction in 1980 manually lockable differentials of the conventional type of construction were initially built, which were then replaced in the course of the facelift in 1986 by Torsen differentials of type A. For Audi and VW wheel drive vehicles, which were based on transverse-mounted engines to the direction of the front, Visco and Haldex couplings were installed.

From 1990, 2.0 Turbo a Torsen gear was installed in the Rover 220 Coupe.

In the third - generation RX -7 ( FD) Mazda ( 1992-2002), a Torsen rear differential is integrated, as in the 1.9 -liter models of the Mazda MX -5 ( NB) as well as in the Honda S2000. Also developed by Subaru and Toyota in cooperation and in 2012 presented the Toyota GT86 and Subaru BRZ equipped with a Torsen rear differential -.

The front-wheel drive vehicles, the standard a Torsen differential was installed, including the Ford Focus RS and the special series " Championship White Edition " of the Honda Civic Type R.

To date, Torsen differentials are installed as a center differential especially in the Audi cars with longitudinally installed engines as an important feature and image carrier.