The EV sector continues to evolve in different directions technologically speaking. Astemothe brand founded in 2021 by Hitachi Automotive Systems, Keihin, Showa and Nisshin Kogyo, has recently unveiled its own vision of the matter with what the company calls “electric motor integrated into the direct drive wheel.”
The Japanese company explains that “Thanks to its patented natural air cooling technology with rotating fins and advanced power density technologies, the engine offers powerful performance in a compact format”. Its design integrated into the wheel helps this, providing greater flexibility.
Likewise, the direct drive configuration offers a more comfortable driving experience. “dynamic and agile, expanding the possibilities of next-generation electric motorcycles”they conclude. Now they show us a preview of its possible applications by installing the system in a prototype based on the Ninja Kawasaki e-1. The idea is to be able to extrapolate it to other types of motorcycles and segments.
Integrated electric motor in different formats
Since its founding, Astemo has been working hand in hand with Hitachi in the development of this technology. Already in 2021, it was the parent company itself that offered its first conclusions regarding this innovation in a report titled “Compact and lightweight direct transmission system to bring electric vehicles integrated into the wheels closer to the reality of production.”
Although in these early stages of development the automobile industry was used as a platform for the project, the idea is to have a technology that is scalable in both size and power, as we can prove in the information table published by Astemo last year. Already then the company stated that the “12-inch air-cooled model achieves a continuous power of 5.5 kW.”
| wheel size | 12 inches | 16 inches | 19 inches |
|---|---|---|---|
| maximum output | 13 kW | 70 kW | 100 kW |
| maximum torque | 370Nm | 900Nm | 1700Nm |
| Supply voltage | 400 Vdc | 400/800 Vdc | 400/800 Vdc |
| Cooling type | Air | Oil | Oil |
The 16- and 19-inch oil-cooled versions enable a wide range of in-wheel electric vehicle applications, from small cars to SUVs. Starting from this premise, it is clear that Astemo seeks to initially focus on motorcycle models equivalent to other low and medium displacement internal combustion models.
Up to 100 KW of power and 1,700 Nm of torque
From Astemo they say they aspire to implement direct transmission systems in electric vehicles of various sizes by 2030. Along the way there are a series of technical challenges that must be solved to bring the project to a successful conclusion. In this context, oil cooling systems require piping and auxiliary components, which is a problem for small cars and motorcycles with significant space and cost limitations.
Regarding the electric motor integrated into the air-cooled direct drive wheel, the brand admits that another challenge is presented to them, “since the small size of the wheels limits the heat dissipation surface necessary for cooling”they comment. Returning to the access version, already tested by the brand, it has overcome these problems by adopting a new air-cooling structure that uses the rotation of the motor in the wheel to increase heat dissipation.
Specifically, the rotating fin structure, in which the heat dissipating fins are arranged on the entire outer surface of the rotating parts of the motor, has greatly improved the heat dissipation performance. As a result, it achieves a continuous rated power of 5.5 kW per wheel and a maximum power of 13 kW.. In addition, this system uses concentrated coils that are easy to disassemble, thus offering greater engine efficiency.
Finally, Astemo points out that these coils are designed “to be recyclable and offer a high space factor while being easy to dismantle”. They conclude: “In addition, they will be applied to 16- and 19-inch systems as common technology. With all three model applications, the direct drive system can be used in electric vehicles of various sizes.”offering powers between 13 KW and 100 KW and a maximum torque that can reach 1,700 Nm.
