Honda Motor Company and Daido Steel have demonstrated the practical application of a hot deformed neodymium magnet containing no heavy rare earth that has the heat resistance properties and magnetic performance required for use in the driving motor of a hybrid vehicle.

The magnet will be introduced in the Honda FREED, scheduled to go on sale this fall.

A heavy rare earth-free magnet (left) and a rotor for the i-DCD drive motor. Image credit: Honda Motor Company.A heavy rare earth-free magnet (left) and a rotor for the i-DCD drive motor. Image credit: Honda Motor Company.To achieve the high heat resistance properties required for use in the drive motors of electric vehicles, heavy rare earth (dysprosium and/or terbium) is typically added to neodymium magnets. However, major deposits of heavy rare earth elements are spread unevenly around the world and are categorized as rare metals. A reduction in the use of heavy rare earth elements has been one of the major challenges needing to be addressed to use neodymium magnets in the drive motors of hybrid vehicles.

For some time, Daido Electronics, a wholly owned subsidiary of Daido Steel, has been mass producing neodymium magnets using the hot deformation method, which the company says enables alignment of nanometer-scale crystals to achieve a grain structure approximately ten times smaller than that of a sintered magnet, giving it greater heat resistance properties.

Daido Steel and Honda have now worked jointly to develop a new neodymium magnet with altered shape, while the latter designed a new motor to accommodate it. Honda says the motor's new rotor optimizes the flow of the magnetic flux to achieve torque, output and heat resistance performance equivalent to that of a motor that uses the conventional type of magnet.

Starting in August 2016, Daido Electronics will begin mass production and shipment of the new magnet using a new production line that the company has built in its Nakatsugawa factory. Honda will incorporate the new magnet in its Sport Hybrid i-DCD*2—a hybrid system the company is adopting for its all-new FREED—and plans to introduce the technology to other new models in the future.

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