Moan Noise Diagnosis and Research of Certain E-axle BUS

Abstract As the mainstream power system of new energy commercial vehicles, the E-axle system directly drives the wheels. Since there is no suspension, the drive motor and reducer are directly assembled on the axle, connected to the body or frame through leaf springs and shock absorbers. Without the traditional engine noise masking, the NVH problem of E-axle poses a great challenge to NVH engineers. This article is aimed at the obvious Moan problem in a commercial passenger vehicle with E-axle under medium and high speed conditions, with the “source-path-response” theory used in analysis. Based on the investigation and analysis of test results and CAE methods, the main reason is that the imbalance excitation of the first axis of the E-axle is too large. By changing the speed ratio of the reducer, the first axis rotating speed of the E-axle corresponding to the same vehicle speed is reduced, then the high-speed Moan noise of this vehicle can get reduced.