HYUNDAI

South Korean giant presents transmission for electric cars that does not require axles

The Universal Wheel Drive System, or Uni Wheel to friends, is a Hyundai invention that makes the sets made up of electric motors and their transmissions even smaller and less bulky. It is already known that substantially smaller electric motors allow vehicles to be designed with shorter fronts, maximizing cabin and boot space. This Uni Wheel takes these advantages even further for battery-powered cars.

It has been reported countless times that vehicles powered by electric motors do not need gearboxes, but rather reducers, so that the approximately 20,000 rotations of the electrical unit are converted into the rotation of the wheel that is equivalent to the desired maximum speed. But, until now, electric cars continue to use the same solutions to transmit power to the wheels, with axle shafts equipped with constant velocity joints, the latter being a weakness of the system since, to allow vertical movement of the wheel, in addition to of its ability to turn, as with the front wheels in a conventional car, they require constant velocity joints, and these tend to degrade over time and kilometers travelled. Hyundai says that its Uni Wheel system moves the reducer to the inside of the wheel and joints are no longer necessary, due to the curious system invented by the South Koreans.

It is easier to understand how everything works through the video prepared by Hyundai, although we have some difficulty understanding how the wheels can turn at the direction of the steering to, for example, describe a curve, without the previously mentioned articulated joints. But while the builder does not clarify this point, there is no doubt that the advantages are evident. To the point of making it easier to move the electric motor (now less bulky) closer to each of the wheels, since the transmission is now inside the wheel hub. The potential is great, as it allows sports vehicles to mount a motor per wheel and benefit from torque vectoring in each wheel, with less cost and complexity, but then, if applied to electric chairs, it allows descending and climbing stairs, such as seen in the video. Remember below how a traditional drive shaft works, with a constant velocity joint:

The system appears more fragile than the conventional solution, but Hyundai guarantees that it has fewer power losses and handles different levels of power and torque. At the same time, if the current prototype has a suspension travel of 150 mm, solutions between 75 and 200 mm have already been tested, which allows the Uni Wheel to surpass current systems with CV joints and the transmission close to the engine and not inside the wheel.

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