A research group comprised of NSK, Fujimoto Laboratory of the Graduate School of Frontier Sciences at the University of Tokyo, Bridgestone Corporation, ROHM and Tokyo Electric Manufacturing have succeeded in developing and testing a third-generation wireless in-wheel motor (W-IWM) capable of charging from coils embedded in the road while in motion.

Automakers across the world are promoting the development and spread of automobile electrification. Not having an internal combustion engine, nor emitting CO2, electric vehicles (EV) are seen as a particularly effective means to solve the emissions issue. Nevertheless, there have been concerns raised regarding the convenience of charging EV and the amount of resources required to produce large amounts of battery cells. EV capable of running efficiently with a minimal amount of battery cells is required for the sustainable spread of EV. To that effect, wireless charging while the EV is on the road (in motion) has been drawing attention to realise EV with small batteries. A significant amount of research is being conducted around the world to make in-motion charging a reality.

This project is being carried out through industrial-academic collaboration with many companies, led primarily by the University of Tokyo. In order to take advantage of open innovation to accelerate the practical implementation of the in-motion wireless charging system proposed by the joint research group, the group has agreed to make the basic patents associated with this project open.

The Upgrade
NSK and the University of Tokyo unveiled the second-generation W-IWM in 2017. This project was recently selected for support under the Japan Science and Technology Agency's Mirai Program and additional companies have joined the industrial-academic project team. In terms of motor performance, compared to the second generation W-IWM for light vehicles announced in 2017 (12kW per wheel), this third-generation W-IWM was created for use in larger passenger cars (25kW per wheel). Compared to the second generation W-IWM which had a 10kW per wheel charging capacity with in-motion charging, in the third-generation unit, the joint research team was able to achieve an increase in in-motion charging performance to 20kW per wheel. 

The research group claims that the third-generation W-IWM has vastly improved in-motion charging capability, motor performance, and ease of mounting, bringing together features required for practical application. If smart cities become a reality in which in-motion wireless charging systems are installed in the road even only at traffic signals, EV drivers will be able to travel without having to worry about charging, dramatically increasing convenience. NSK is looking into installing in-motion charging infrastructure by analyzing public road traffic data and conducting simulations.