Japan-based supplier NSK took the opportunity of last month’s CTI transmissions symposium in Berlin to display a rig demonstrating the operating principle of a novel front axle system combining several familiar functions into a single unit.
What the as-yet unnamed system does is use a pair of half-toroidal variators to achieve both overall transmission ratio change and left-right differential action, promising a dramatic simplification of vehicle front-end packaging.

The toroidal variators are mounted at the inboard ends of the driveshafts to the front wheels: drive from the engine is introduced between the two variators, thus turning both driveshafts at the same time. Applying the same ratio change to the two variators (by altering the angle of incidence of the rotors on their toroidal shells) allows a stepless raising or lowering of the vehicle’s overall gearing.

During cornering, where the vehicle’s outside wheel tracks a bigger circle than the inside one and thus needs to rotate faster, outboard and inboard toroidal IVT unit adjust their ratios in opposite directions in order to cater for the required rotational speed differential.
In this way, the NSK unit eliminates the need for the differential as well as for the conventional stepped gearbox.

What was not shown on the NSK display was any form of launch device and there was no statement of how reverse could be achieved.
NSK Deutschland manager of advanced technology Dr-Ing Naser Emamdjomeh says a torque coverter launch is most likely. The sytem, he says, can handle torques of up to 350 Nm, making it suitable for the Golf class of lower-medium cars.

“There has been strong interest from one automaker,” he told DCTfacts.com.

In addition to its use as a differential substitute, the device could have other important applications – not least on the real axle, where its ability to actively manage the relative speeds of the wheels could give it the potential to provide torque vectoring (the overspeeding of the outside rear wheel) as well as differential action.

Story Filed: 1/16/2009
By Tony Lewin, managing editor DCTfacts.com