Development of Resin Water Jacket Case for Traction Inverter Aiming to Downsizing and Light-Weighting 2022-01-0719

The size and weight of the traction inverter needs to be reduced to ensure a sufficient cruising range of an electric vehicle. To this end, one approach involves changing materials of the inverter case from aluminum to resin. However, the resin in use of inverter case causes technical issues in terms of collision performance, electromagnetic compatibility (EMC), and cooling performance because of the difference in the material properties between the resin and the conventionally used aluminum.

By solving the abovementioned issues, a resin water jacket case (hereinafter, resin water jacket) was successfully adopted with inverters designed for next-generation electric powertrain in mass production models for the first time. The resin-based structure had advantages to reduce the weight of the inverter case by ~35% and decrease the number of parts to ~3/5, compared to that for the conventional cases.

The inverter case was reviewed and consisted of a flat resin water jacket and a box-shaped aluminum case to ensure collision safety assurance. This structure enabled the aluminum case to protect the resin water jacket and the components inside the inverter case. Further, a shield plate was installed on the bottom side of the resin water jacket to ensure electromagnetic wave shielding performance. It is not easy to connect the resin to the ground, and hence, there is a need for a component that can connect the noise filter to the ground. Therefore, nuts for earthing were incorporated into the resin water jacket and grounded to the metal shield plate. Furthermore, special nuts were installed to cool the busbar of the DC capacitor for guaranteeing the cooling performance.

In this paper, we report the technical features of the resin water jacket and solve its major technical challenges such as EMC and cooling performance.