Such an interesting idea as motor-wheels designed for electric vehicles is not so widespread. The reason is already known to everyone – high price and large under-resource masses. However, the idea of downsizing electric motors to free up useful space inside the chassis is a major concern for automotive engineers. Hyundai and Kia offers a new solution in this area. Koreans have developed a system called Uni Wheel with a separated engine and reduction gear.
The idea is very simple: the heavy electric motor remains in the body or frame, the relatively light reduction gear is mounted in the space inside the wheel. The Uni Wheel system does not have an articulated joint, instead it has a four-pass system with a multi-stage planetary transmission. The mobility of such a structure allows it to transmit the torque to the wheel, compensating for the work of the suspension.
Using a “reducer-wheel” promises a number of advantages. Traction electric motors without large reducers should be more compact. Due to the use of individual motors in each wheel, useful space should be freed up inside the body. Hyundai engineers suggest filling this space with additional cells of the traction battery. By the way, individual engines with properly configured control electronics can work as a full-scale traction vector control system.
As mentioned, the rejection of joint connections will reduce losses when transmitting the torque to the wheels, and should increase efficiency and mileage reserve. In addition, it opens the way to a wider range of adjustment of the air suspension in the vertical direction. The Uni Wheel system can be used with wheels ranging from 4 to 25 inches in diameter – covering the widest range of vehicles, from small personal mobility vehicles to off-roaders and trucks.
Hyundai has already completed a full cycle of robustness and durability tests of the Uni Wheel system. The system passed these tests successfully. It is not yet known when the innovative device will go into series production. Koreans have already patented this technology in South Korea, Europe and the United States, that is, in the main markets.
Source: Hyundai Motor and Kia Unveil Paradigm-Shifting ‘Uni Wheel’ Drive System to Transform Mobility Design