Hyundai Motor Company and the Kia Corporation have unveiled what they have dubbed the Universal Wheel Drive System, aka ‘Uni Wheel’, which they describe as a “paradigm-shifting vehicle drive system”.
Uni Wheel is a functionally integrated wheel drive system stated to dramatically improve available space inside an electric vehicle (EV) by moving the main drive system components to the vacant space within the wheel hub. By moving the reduction drive inside the wheel, packaging space within the vehicle is freed up.
The Uni Wheel uses a planetary gear configuration consisting of a sun gear in the center, four pinion gears on each side and a ring gear surrounding this arrangement. Power generated by the motor is transmitted to the sun gear, which in turn engages the pinion gears to rotate the ring gear. This is connected to the wheel to drive the vehicle. The pinion gears are connected to each other to form two linkages, and this multi-link mechanism enables multi-axis movement to allow a wide range of suspension articulation.
The companies note that a conventional drive system using a regular CV joint suffers from a decrease in efficiency and durability as the angle of drive shaft deflection increases when travelling over bumpy, undulating surfaces. The Uni Wheel can transmit power with “almost no change to efficiency regardless of wheel movement”, ensuring high durability and ride comfort.
Furthermore, by moving the reduction gear to the wheel hub, the Uni Wheel’s high reduction ratio delivers a significant torque output and allows for a more compact electric motor. With independent control of up to four efficient electric drive units, the Uni Wheel also allows for unprecedented levels of torque vectoring to boost dynamic ability and deliver high levels of steering and driving stability.