Hitachi combines motor, inverter, and brake unit in EV wheel
At the Aachen Colloquium Sustainable Mobility, Japanese giant Hitachi is showing these days its new lightweight direct–drive system for EVs that incorporates electromotor, inverter, and brake unit into a 19-inch wheel. It can be installed without significant changes to the existing suspension and other components, Hitachi says in a press release.
By eliminating drive shafts and ‘other indirect mechanisms’ and with a power density of 2,5 kW/kg, the in-wheel motor reduces energy loss by 30% compared to existing electric vehicles. The maximum output is 60 kW and 960 Nm.
Joint venture with Honda
The direct-drive system was developed with Hitachi Astemo, a joint venture between Hitachi and Honda Motor Co., Ltd. That technology company develops, manufactures, sells, and services automotive and transportation components and industrial machinery and systems.
According to the partners, fitting an electromotor into the wheel generally increases its weight, requiring ‘sweeping changes’ to the existing brake and suspension components. However, that’s not the case with this one.
“Hitachi and Hitachi Astemo have succeeded in improving drive force by increasing the effective magnetic flux of each magnetic pole. Using beam welding to create a high–density array of flat coils, they made the motor lighter. This way, they achieved world–class 2,5 kW/kg power density. This configuration limits the in–wheel weight increase of the EV,” the press release states.
“The newly developed system uses direct–cooling technology, in which high–insulating cooling oil directly cools the power semiconductors and is cycled to the motor to cool the coils directly. This combined with the single-unit drive system, which integrates a motor, brake, and inverter significantly reduces the space taken up by cooling pipes and enables in-wheel installation.”
Hitachi says it will now, with Hitachi Astemo, further look into possibilities for optimizing interior and battery space in EVs by integrating the new direct-drive system. The latter will be applied as a start to Hitachi Astemo’s global EV product line-up.