Uniwheel replaces differential and axles
Allows for smaller electric motors, more cabin space
Hyundai has just shown off a truly unique drive system. It’s called the Universal Wheel Drive System and it puts, well, basically everything into a “functionally integrated wheel.”
Current cars, gas or electric, have a differential, drive shaft, and (for most) CV joints to send power from motor to wheel. As Hyundai points out, these parts take up space. They also contribute to ride and handling limitations.
Hyundai’s Uniwheel puts everything into the wheel. Reduction gearing and everything else needed are combined into one single unit. But unlike other wheel-mounted motors, this one doesn’t make the motor move with the wheels, saving on unsprung weight. Hyundai then uses two smaller motors instead of one big one, freeing up even more space.
If you want the nitty-gritty details, Hyundai’s video goes into the sun and pinion gears and their arrangement. The short version is that the gearing can move inside the unit, allowing the wheel to move up and down (and fore and aft) with the suspension while the motor stays fixed in place.
Because the gearing (6.24:1) is built into the wheel, there’s no need for a differential. Removing the large central motor, differential, and axles, means there’s much more space in the center of the vehicle. Space for passengers and cargo. Or more battery capacity.
It’s not yet ready for production, but Hyundai said that the Uniwheel is well into development. It’s also scalable, so it can be small enough for a delivery robot and big enough for an SUV.