Hyundai Motor, Kia unveil innovative drive system Uni Wheel

[Courtesy of Hyundai Motor Group]

Hyundai Motor Co. and Kia Corp., two subsidiaries under South Korean auto giant Hyundai Motor Group, have developed a new drive system that integrates the drive components with the wheels. The space created by merging multiple components with the wheels can be filled with batteries, enabling electric vehicles (EVs) to travel longer distances, an accomplishment that is sure to boost Hyundai Motor and Kia’s EV competitiveness.

Hyundai Motor and Kia held the “Uniwheel Tech Day” at the Community House Masil in Jung District, Seoul on Tuesday, where they unveiled the Universal Wheel Drive System, also known as “Uni Wheel.”

The Uni Wheel system has moved the main driving parts, including the reducer and the drive shaft that used to occupy a large space in the center between the two wheels, to the inside of the wheels. The motor has also shrunk in size and split in two to be placed right next to each wheel.

The relocation of these components creates an empty center between the wheels, allowing the space to be used for installing batteries to increase driving range or as an additional loading space. It also allows for a new design for the era of autonomous driving, moving away from the current seating arrangements designed around the driver.

Uni Wheel is made of a planetary gear structure with a sun gear at the center, four pinion gears on the left and right, and a ring gear on the outside. A planetary gear has a sun gear rotating in the center, pinion gears located around it, and a ring gear on the outermost part. When the motor-generated power is transmitted to the sun gear, the pinion gears mesh to rotate the ring gear, which, when connected to the wheel, transmits power to the wheel.

With such an organic structure, Uni Wheel can stably deliver power from the motor to the wheels and freely respond to the movement of the wheels along the road surface. It can also replace the role of an EV reducer, slowing the rotation of the motor to create strong rotational force for the wheels.

This development is noteworthy as it innovates a driving system that has long remained the norm. In a conventional internal combustion engine vehicle, power is transmitted through the engine and transmission to the wheels via a drive shaft and constant velocity joints. EVs have the same drive transmission system, except that the engine and transmission are replaced by a motor and reducer. With this structure, the only way to increase the interior space was to make the car body larger.

The wheels and the essential power-related components located between them were also considered sacred, a space no company dared to change. But Hyundai Motor and Kia were not bound by conventional thinking and made these innovative changes. “It is significant that we have devised a completely new drive system with an unprecedented structure,” an official from Hyundai Motor Group said.

Once the Uni Wheel system is commercialized, it is expected to create a new interior space for vehicles and future mobility optimized for various uses such as purpose-built vehicles (PBVs). The timeline for commercialization is yet to be decided given there are still many issues to resolve, such as increased weight of the wheels and ride comfort. The companies plan to continue the development process with a focus on lubrication and cooling systems and interior finishing to achieve commercialization.