SEOUL—Engineers at Hyundai Motor Co. and Kia Corp. have developed a paradigm-shifting drive system called the Uni Wheel. The Universal Wheel Drive System dramatically improves available space inside an electric vehicle. It 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.
Uni Wheel uses a special 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.
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. However, the Uni Wheel can transmit power with almost no change to efficiency regardless of wheel movement, ensuring high durability and ride comfort.
When combined with electronic air suspension that can adjust ride height according to the driving situation, this can be increased to stabilize the vehicle on rough roads, or decreased for high-speed driving to improve power and stability.
By moving the reduction gear to the wheel hub, 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, Uni Wheel also allows for unprecedented levels of torque vectoring to boost dynamic ability and deliver high levels of steering and driving stability.
“We are pleased to showcase innovative ideas that could become game changers in the future mobility market,” says 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.”
