Geely Hybrid System’s Noise, Vibration, and Harshness Development 2020-01-5063
During the development of the Geely Hybrid System (GHS), which combines a 15T Miller engine with an Electric Motor (EM) integrated into a 7-speed Dual-Clutch Transmission (P2.5), several hybrid-specific Noise, Vibration, and Harshness (NVH) issues have been encountered.
The technology used, the system features, and the hybrid operating modes are analyzed. Changes within driving modes and their transitions are among the new challenges faced by NVH and system engineers [1, 2, 3]. The lack of engine combustion noise masking during electric drive and hybrid mode brings new requirements for gear design and structural integrity. These requirements ensure the system is robust and insensitive to the excitation. Attachment points and its dynamic stiffness are important to prevent structure-borne frequency content of gear whine and EM magnetic noise being transmitted to the vehicle cabin via powertrain mounts. Idle speed selection has also become an important requirement to keep a suitable NVH comfort.
This paper exposes the main challenges, root causes, and countermeasures applied during pure electric mode and combustion engine idle speed selection in order to create a competitive and refined hybrid propulsion system.