New motor designs in next-generation electric cars
In-wheel motor technology has been around for a century, but interest has been revived in these motors now that electric vehicles have grown in popularity. However, the technology has long remained in a prototype stage of development. Researchers within the EUNICE (Eco-design and validation of in-wheel concept for electric vehicles) project successfully developed and tested an in-wheel motor system for B electric-drive vehicles, helping these motors gain traction once again. Integrating motors into the wheels brings a host of advantages for A and B electric-drive vehicles, allowing further modularisation, providing more passenger space and improving driving behaviour. In addition, such motors eliminate the need for mechanical transmission — gearboxes, differentials, drive shafts and drive axles — leading to significant weight and manufacturing cost savings while also decreasing environmental impact. Except for the wheel and the electric motor, EUNICE’s prototype includes power electronics, structural parts, brakes and a reduction gear. A widely used front suspension system — the MacPherson strut — provides a mounting for the wheel. Considerable efforts were devoted to keeping the unsprung mass light, as it can adversely affect handling and ride. Air cooling of the in-wheel motor minimises the danger of overheating. The design features an air inlet zone in the corner of the front bumper, a spoiler in front of the tyre that redirects air flow and deflectors aligning the air flow towards the in-wheel system. With the proposed cooling concept, enough air flow is provided to the in-wheel system to evacuate the heat in urban and motorway driving cycles. Forced air cooling is also employed when the vehicle stops after fast travel, ensuring quick heat removal. Researchers also conducted a life-cycle assessment analysis of motor components to see how all phases, from production to use to dismantling, affect the environment. With its activities, EUNICE has established the basis for a world-level European industry manufacturing electric motors and components with the required performances at competitive costs. The in-wheel electric motor concept has the potential to become one of the motors of the future, improving vehicle driving behaviour in terms of comfort and safety.
Electric vehicles, in-wheel motor, EUNICE, unsprung mass, air cooling