Torsen Limited Slip Differential

Torsen Limited Slip Differential houses a set of complicated gear system, but is the most effective of all the LSDs. This product is the trademark of the JTEKT corporation. Torsen was first patented by Gleasman in 1958.

Construction:


The components used inside torsen are unique and they provide the most brilliant way of providing differential action and also overcoming the traction difference problem.

It has a pair of specially designed gear assembly. These are designed on the basis of spur gear (Worm wheel) and worm gear assembly. This is the basic principle behind the working of a torsen. The unique feature of worm gear and worm wheel assembly is that the spinning worm gear can rotate the worm wheel, whereas the vice-versa is not possible. It means that the rotating worm wheel cannot spin the worm gear (the assembly is locked in this case).

A pair of this worm wheel and worm gear assembly is attached to the differential case. The half output shafts are connected on either side of the worm gears that drive the wheels.

The power from the transmission is transferred to the pinion and ring gear assembly which is standard in any differential. The worm wheels rotate along with the ring gear. Each end of the worm wheels is fitted with a spur gear. The spur gears are meshed so that both the worm gears rotate at the same speed and in opposite directions.

Case 1 (Vehicle moving straight):

In this case, the power from the ring gear is directly transferred to the output shafts via the differential casing. The worm wheels and worm gears are locked and rotate as a single solid unit. The worm wheels do not spin on its own axis and the worm gears do not rotate about its own axis. Equal amount of power is distributed to the wheels.

Case 2 (Vehicle taking a right turn):

In this case, the left wheel has to rotate at a higher speed compared to right wheel. The worm gear of the faster moving left axle will rotate the corresponding worm wheel about its own axis at a higher speed. Whereas, the right axle rotates in opposite direction when considering its relative motion with the left axle. Thus the right worm wheel will rotate in the opposite direction.

The spur gears which are meshed at the end of worm wheels will make sure that the worm gears rotate at the same speeds but in opposite direction. This ensures a perfect differential action.

Case 3 ( One wheel on a slippery surface and the other on a non slippery surface ):

In this case, a vehicle equipped with a conventional differential will allow majority of the power to be transferred to the slippery wheel. Therefore the vehicle will get stuck.

In a torsen LSD, the excessive speed of the slipping wheel can be used to its advantage. As the slipping wheel ( say the right wheel) starts spinning at a higher speed, this speed increase will be transferred to the right worm wheel via the right worm gear. The right worm wheel starts rotating in its own axis, therefore transferring the power to the left worm wheel as they both are connected with the help of spur gears.

We know that the unique feature of worm wheel and worm gear arrangement is that the worm wheel cannot spin the worm gear. This principle is applied in the torsen as the left worm wheel cannot spin the left worm gear and the entire mechanism gets locked. As a result, both the left and right wheels start rotating at the same speed.

To withstand the heavy vehicle load, two more pairs of worm gear and worm wheel assembly is added to the differential case.