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NHK Spring and Daido Steel: Pushing the Boundaries of EV Motor Performance with Two New Types of Rotors
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Exclusive Interview
NHK Spring Co., Ltd. Daido Steel Co., Ltd.
Mr. Koji Ishikawa (NHK Spring), Mr. Hiroshi Miyawaki (Daido Steel) and Mr. Jumpei Hinata (Daido Steel)
About This Interview
NHK Spring Co., Ltd. (NHK Spring) and Daido Steel Co., Ltd. (Daido Steel) have jointly developed a "high-speed, high-output SPM rotor" and a "spring-fixed IPM rotor" for electric vehicle drive motors. Both products utilize Daido Steel’s heavy rare-earth-free hot-formed magnets, combined with NHK Spring’s CFRP (carbon fiber-reinforced plastic) assembly technology and spring design technology. The SPM rotor, designed for 30,000 rpm, achieves more than 1.5 times higher rotational speed and approximately 50% higher output compared to conventional products. The spring-fixed IPM rotor uses leaf springs instead of resin to secure the magnets, making disassembly and recycling easier. Both companies exhibited both products at the JSAE Automotive Engineering Exposition in May and June 2026 and have begun presenting them to customers. We spoke with Koji Ishikawa, Executive Director of the Electrification Business Promotion Dept. at NHK Spring (pictured left); Hiroshi Miyawaki, Manager, Customer Creation Sect. No. 3, Material Solution Dept. at Daido Steel (pictured center); and Jumpei Hinata, Senior Research Engineer, Hard Magnet Products Development Section, Nakatsugawa Advanced Magnetic Materials Development Center, Corporate Research & Development Center, Daido Steel (pictured right), about the background to the joint development, the technical challenges involved, and future efforts toward mass production.
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Question List
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About This Interview
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Q1Please tell us how the two companies came to collaborate on this joint development project.
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Q2How are roles divided in the development process?
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Q3What were the biggest challenges you faced in developing the SPM rotor?
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Q4The CFRP sleeve is said to be 2 mm thick, but is the thickness the key point?
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Q5What development challenges did Daido Steel face regarding its magnets?
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Q6Did you set the following goals from the outset: a speed increase of at least 1.5 times that of conventional models, a power increase of approximately 50%, and a reduction in size of approximately 50% for the same power output?
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Q7I heard that development was carried out in a short period of time. Please tell us about the development timeline and the measures you took to speed up the process.
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Q8What problems does the spring-fixed IPM rotor solve?
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Q9How do you determine which to use: the SPM rotor or the spring-fixed IPM rotor?
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Q10What was the reaction at the exhibition?
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Q11Please tell us about the challenges that lie ahead in terms of practical application and mass production.
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Q12What insights did both companies gain from this joint development project?
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Q13Will the two companies continue their joint development efforts in the future?
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Editor's note
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