NSK Develops Third-Generation In-Wheel Motor with Wireless Charging In Motion

A research group comprised of NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President & CEO: Toshihiro Uchiyama), the Fujimoto Laboratory of the Graduate School of Frontier Sciences at the University of Tokyo, Bridgestone Corporation, ROHM Co., Ltd., and Toyo Electric Mfg. Co., Ltd. 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.

Development Background

Reducing CO2 emissions in order to realize a low-carbon society is a challenge we face on a global scale, which also strongly calls for emissions reductions in automobiles. In light of this, 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 realize EV with small batteries. A significant amount of research is being conducted around the world to make in-motion charging a reality.

NSK has been carrying out research and development with the University of Tokyo group for a number of years, and announced the successful demonstration of second-generation W-IWM in 20171 with the capability of charging in motion. Recently, the project was selected for support under the Japan Science and Technology Agency's Mirai Program2, and additional companies have joined the industrial-academic project team.

The third-generation W-IWM developed by the joint group has vastly improved in-motion charging capability, motor performance, and ease of mounting, bringing together features required for practical application.

Features

• 1. Comprehensive in-wheel design

• The joint research group developed the W-IWM unit so that the in-motion wireless power receiver circuit, as well as the EV's driving mechanism, comprised of a motor and inverter, fit entirely inside the wheel. 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).

  NSK is leveraging the knowledge gained from developing IWM up until now to design and manufacture the mechanical elements of the unit.

• 2. Freedom from stationary charging systems

• 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. 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.

• 3. Industrial-academic open innovation

• 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.

Future Development

While the joint research group is in the process of testing and evaluating third-generation W-IWM, it will eagerly push forward to prototype the next-generation unit incorporating new ideas. The group will integrate not only the expertise of current project members, but also a wide range of knowledge from various fields held by other organizations and companies as it aims to move into the verification phase in 2025 for the real-world testing of an in-motion wireless charging system.

Through the joint research in this project, NSK hopes to contribute to the realization of a sustainable society, and make advancements in development focused on creating new motion in the automotive industry.