Hybrid transmission, as the power core of hybrid vehicles, has a whining problem which affects the driving experience seriously. It is of great engineering value to carry out Noise, Vibration, and Harshness (NVH) research. In this paper, a combined methodology of finite element simulation, multi-body dynamics analysis, and real-vehicle experiment is adopted to improve the whine of the hybrid transmission. Firstly, a finite element model of the DHT assembly is established, with the frequency deviation between modal simulation and test being less than 5%, meeting the accuracy requirements. Through real-vehicle tests in electric vehicle (EV) mode, the 8th and 24th orders are identified as the key whine orders, and the deviation between simulation and test for the noise of these relevant orders is ≤5 dB(A). The research clarifies that the coupling resonance between the local modes of the upper and lower cover plates of the DHT and the excitations of the P3 motor is the core mechanism leading to the whine, and the motor control unit (MCU) is confirmed as the main noise emission source. Notably, the weak structural stiffness of the MCU lower cover plate is the critical inducing factor. To address this, three support blocks are added at the center of the MCU lower cover plate for structural reinforcement. After optimization, the 8th-order vibration is reduced by an average of approximately 35 dB in the speed range above 3500 rpm, and the 24th-order vibration is decreased by an average of about 20 dB within the range of 1000–1500 rpm. Specifically, the 24th-order noise near 1300 rpm is reduced by around 13 dB, and the 8th-order noise above 3500 rpm is fully suppressed. The increasing trend of noise with rising speed is significantly curbed, and the overall NVH performance of the vehicle is greatly improved.
Wang et al. (Fri,) studied this question.