Kia Corporation and Hyundai Motor Company have unveiled the Uni Wheel, a Universal Wheel Drive System that they hope will revolutionise the design of future mobility devices. Uni Wheel is a functionally integrated wheel drive system that dramatically improves available space inside an electric vehicle (EV) by moving the main drive system components to the vacant space within the wheel hub. In doing so, Kia and Hyundai Motor have designed a completely new structure for the drive system.
In internal combustion engine (ICE) vehicles power is transmitted from the engine through the transmission and to the wheels via drive shafts and constant velocity (CV) joints. In EVs, the engine and transmission are replaced by a motor and reduction gear, but the final method of transmission to the wheels is the same. Uni Wheel opens new possibilities and enables a flat-floor configuration by moving an EV’s reduction gear inside the wheel hub, locating a compact individual motor close to each wheel, reducing the length of the drive shafts. The system frees up significantly more interior space compared with conventional drive systems, enabling future mobility products optimised for various applications, such as Purpose-Built Vehicles (PBVs).
“We are pleased to showcase innovative ideas that could become game changers in the future mobility market,” said Jongsool Park, Senior Fellow at the Institute of Advanced Technology Development of Hyundai Motor Group. “We will perfect the technology so that customers can experience mobility in a completely different and new way.”
Recent advances in electrification, autonomous driving and connectivity technologies are transforming mobility products into living spaces. Kia and Hyundai Motor’s focus on space utilisation in future vehicle architectures will further boost customer value and provide owners with richer user experiences as a result.
Uni Wheel uses a special planetary gear configuration consisting of a sun gear in the centre, 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 Uni Wheel’s pinion gears are connected to each other to form two linkages, and this multi-link mechanism enables Uni Wheel’s multi-axis movement to allow a wide range of suspension articulation.
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. Uni Wheel can transmit power with almost no change to efficiency regardless of wheel movement, ensuring high durability and ride comfort.