Toyota’s New Patent for In-Wheel Electric Motors: A Step Toward Lightweight and Efficient EVs

Toyota’s New Patent for In-Wheel Electric Motors: A Step Toward Lightweight and Efficient EVs
Image credit: The Boston Globe

Toyota has recently filed a new patent application, signaling its ongoing interest in developing in-wheel electric motor technology. The patent, published by the United States Patent and Trademark Office (USPTO) on July 18, 2024, was initially filed by Toyota on October 30, 2023. This application focuses on a gear-case design that employs two helical gears and thrust bearings. According to Toyota, this design enables the gear case to handle thrust loads on the gears with minimal weight increase.

The Challenge of Reducing Unsprung Mass

Minimizing weight is a critical objective in automotive engineering, especially when it comes to reducing unsprung mass—a significant challenge in the development of in-wheel motors. Unsprung mass refers to the mass not supported by the vehicle's suspension, such as motors attached to wheel hubs. Excessive unsprung mass can complicate tuning for ride comfort and handling, making it a crucial factor in the design of in-wheel motor systems. Toyota's patent aims to address this issue by keeping the weight of the gear case to a minimum.

Toyota in-wheel patent design 
Image credit: Green Car Report 

Toyota's History with In-Wheel Motors

While patent applications do not always translate into immediate product plans, Toyota’s consistent filings in this area suggest a continued focus on in-wheel motors. In the past, Toyota, along with General Motors, had an in-house in-wheel motor program, which indicates that the company’s interest in this technology may either persist or has been revived. Toyota had previously considered in-wheel motors for efficiency and packaging in its vehicles, such as the iQ EV over 15 years ago. Although the iQ EV eventually launched with a standard inboard motor, the idea of in-wheel motors has remained a topic of interest, as seen in Toyota’s Lunar Cruiser concept.

The Future of In-Wheel Motors in Passenger Vehicles

In-wheel motors are slowly making their way into passenger vehicles, but there are still many questions regarding their durability and safety. For instance, the electric vehicle startup Aptera has integrated in-wheel motors into its design, claiming it will result in a super-efficient electric 3-wheeler. Meanwhile, Hyundai has explored an alternative approach by positioning in-wheel motors close to the wheels, though not directly within them. However, Hyundai has yet to announce any concrete production plans for this technology.

Conclusion: Toyota’s Innovation in Electric Motor Technology

Toyota’s latest patent application for in-wheel electric motors underscores the automaker’s commitment to advancing this technology. By focusing on reducing unsprung mass and improving the efficiency of gear cases, Toyota is working to overcome some of the significant challenges associated with in-wheel motors. As the technology continues to evolve, it may play a crucial role in the future of electric vehicles, potentially offering enhanced efficiency and innovative design possibilities.