Lightweight Bubble Sheet Panel To Reduce Inverter Noise and Vibration for Electric Vehicles

Inverters are typically integrated into electric drive units for electric vehicles (EVs) to reduce packaging size and cost. However, coupled vibrations from the electric motor and gears are transmitted to the inverter, which, due to its large radiative panel, becomes a dominant noise source. Metal panels are required for electromagnetic interference (EMI) compliance, yet these covers usually lack sufficient stiffness or damping for noise control. Adding ribs and applying damping treatments results in excessive mass, cost, and packaging challenges. A new, patented bubble sheet panel design has been developed to enhance the structural strength and damping of the inverter while significantly reducing its mass. A thin sheet of aluminum or magnesium is welded onto the cover in an optimized pattern that enhances stiffness and damping performance while accommodating packaging requirements. The welding pattern can include logos or artistic designs to improve the panel’s appearance. The metal sheets are blown apart between the welds to form a 3D structure that is up to three times stiffer and twice as strong as a flat monolithic sheet of the same thickness. The composite dual bubble sheets with an air pocket structure achieve impedance mismatch and effectively reduce structural vibration. Damping materials, such as liquid-applied sound deadener (LASD), can be injected into the bubble sheet cavities to significantly improve its damping performance. Prototype bubble sheets have been designed, analyzed, and tested for an integrated inverter used in front-wheel-drive (FWD) electric drive unit for EV applications. Analysis and modal tests show a reduction of up to 15 dB at panel resonances with a 30% reduction in mass. The bubble sheet panel was installed on the integrated inverter and tested in the electric drive unit. Measured sound power data confirms a reduction of up to 10 dB in inverter panel vibration.