The automotive industry continues to develop new powertrain and vehicle technologies aimed at reducing overall vehicle-level fuel consumption. While the use of electrified propulsion systems is expected to play an increasingly important role in helping OEMs meet fleet CO2 reduction targets, hybridized propulsion solutions will continue to play a vital role in the electrification strategy of vehicle manufacturers.
Plug-in hybrid electric vehicles (PHEV) and range extender vehicles (REx) come with unique NVH challenges due to their different possible operation modes. First, the paper outlines different driveline and vehicle architectures for PHEV and REx. Given the multiple general architectures, as well as operation modes which typically accompany these vehicles, NVH characterizations and noise source-path analysis can be more complicated than conventional vehicles.
In the following steps, typical NVH related challenges are highlighted and potential solutions for NVH optimization are discussed. While the overall noise levels are low in electric mode, the NVH behavior of electrified vehicles can be objectionable due to the presence of tonal noise coming from electric machines and geartrain components. Additionally, road and wind noise shares can be relatively high during mid/high vehicle speed operation.
The switch-over from pure electric drive to operation with the combustion engine introduces transient NVH challenges, such as engine start and hybrid architecture dependent drivetrain torque disturbances. Downsizing and boosting of modern combustion engines can increase the combustion related excitation and hence requires detailed attention during vehicle NVH integration. Further, operation strategy of the combustion engine during operation must be refined for pleasant NVH while not compromising fuel economy of the vehicle. The NVH assessment of PHEV drivetrains require evaluations under multiple operating conditions for identification and characterization of the various issues which may be experienced by the driver. Examples from case studies are provided to illustrate the NVH challenges and solutions.