NSK successfully developed the world's first new way of driving power supply

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Japan Seiko Co., Ltd. (Headquarters: Shinagawa-ku, Tokyo, representative: Executive Director of the Board of Directors, Nakayama Junhiro, hereinafter referred to as NSK) and Associate Professor of the New Field Innovation and Research Division of the University of Tokyo, Professor Fujimoto Boshi, and Toyo Electric Manufacturing Co., Ltd. (hereinafter referred to as the research group), we have cooperated to successfully develop the power supply mode from the road to the wheel-side motor in the world's first real-time driving (Figures 1, 2).

Development background

Under the environmental problems such as global warming, the development of automotive technology is changing with each passing day, such as energy-saving technologies such as electrification, and safety technologies targeting zero traffic accidents in automatic driving. Under this trend, NSK began to pay attention to the new generation of driving forms of wheel motors (hereinafter referred to as IWM) and related technology development. IWM is characterized by reducing the weight of the engine, reducing the weight of the car body, controlling the driving force of the single wheel, and expanding the space inside the car, thereby improving the environmental performance, safety performance and comfort performance of the car (Fig. 3).

However, compared with fuel vehicles, etc., the distance that an electric vehicle is charged for one trip is too short, which is an urgent problem to be solved. In order to solve this problem, NSK has developed a wireless power supply method for electric vehicles from the road to the road, that is, the "running power supply" technology that is of concern to the world, without increasing the number of batteries installed in electric vehicles. In the past, it was the case that a coil was placed in the lower part of the vehicle body to wirelessly supply power to the running vehicle, but this method does not apply to IWM.

Development features

Based on the above background, the research team proposed a new driving mode of driving, that is, directly supplying power from the road to the IWM during driving, and the world's first real vehicle driving success (Figures 1, 2). This is based on the development of wireless technology between IWM and bodywork published in May 2015.

IWM needs to be laid out in a limited space near the wheel, so it is necessary to balance sufficient drive performance and miniaturization. So NSK developed the "off-axis reducer built-in hub bearing unit" (Figure 4). The speed reduction mechanism of the developed product shifts the motor shaft and the wheel shaft to ensure the reduction ratio of the drive performance and at the same time achieves miniaturization.

Future prospects

Through joint research, NSK plans to commercialize the built-in wheel hub bearing units, small cages & needle bearings, and electric corrosion resistant bearings for off-axis reducers, and continue research and development based on the future development of the car.

Figure 1 Power supply "2nd generation wireless wheel-side motor" during driving

(Photo courtesy of the University of Tokyo Graduate School of Science, Graduate School of Science and Technology, Fujimoto Research Laboratory)

Figure 2 Conceptual diagram of power supply from road to IWM while driving

Figure 3 Wheel Motor Features

Figure 4 Off-axis reducer built-in hub bearing unit