Control Of Vehicle Interior Structural-borne Noise Excited By Engine Excitation

The vehicle NVH performance has become an important design specification, and also is one of the specifications for consumer interests to the vehicle performances. It is one of the hot points in the vehicle design study to reduce vehicle interior noise and improve vehicle NVH performance. The powertrain system is a major component of a vehicle. It is not only the source of the power for the vehicle movement but also the source of many noise and vibration. The inertia excitation and the unbalanced force generated by the engine excite the vehicle panel, and then radiate a low-frequency noise to the car cavity. The traditional acoustic package target at reducing the high-frequency air noise, which have little effect to reduce the low-frequency structure-borne noise. It is an important research domain in vehicle NVH performance to reduce the vehicle interior noise excited by the engine inertia excitation.Aimed at reducing the vehicle interior structure-borne noise excited by the engine inertia excitation, the transfer path analysis (TPA) based on frequency response function (FRF) is applied to analyze the interior structure-borne noise. Taking a microcar as an example, the technology of controlling the vehicle interior structure-borne noise excited by the engine inertia excitation is studied in-depth. Main research contents are as follows:1. Powertrain - Body Structure Vibration and Noise Modeling and SimulationAimed at reducing the vehicle interior structure-borne noise excited by the engine inertia excitation, a vibration and noise transfer system model is established by using of finite element method,which is composed of power-train rigid body model and finite element model of body in white. According to the theoretical formula of the engine inertia excitation, a force is calculated. Based on that, the vehicle interior structure-borne noise excited by the engine inertia excitation is predicted.2. Analyze interior structure-borne noise based on transmission path analysisIn order to investigate the problem of controlling the interior structure-borne noise excited by the engine excitation,the TPA is applied to analyze the interior structure-borne noise . The vibration and noise transfer system model is established. The powertrain is connected to the vehicle body by engine mounts. The vibration energy is transferred from the engine mounts to the interior passenger compartment. Based on the structure- acoustic transfer function, transmission forces, and transfer path noise contribution, the most significant transfer path of the vehicle interior noise are identified by using the TPA technology. The result provides guidance for noise control.3. Panels acoustic contribution analysis for the vehicle interior structure–borne noiseThe dissertation applies the PCA (Panels acoustic contribution analysis) technology to analyze the special structural acoustic transfer function which made the greatest contribution to the vehicle interior structure-borne noise. According to the result of the analysis of panel contribution ,the panel of outstanding contribution to the body structure-acoustic transfer function is evaluated and ensured. The result can provide guidance to improve NVH performance.4. Control technology of the vehicle interior structure–borne noiseAccording to the mechanism of vibration and noise, and based on the result of the PCA, two measures are taken to control the vehicle interior structure-borne noise excited by the engine inertia excitation. The first, optimizing the panel which made the outstanding contribution to the body structure-acoustic transfer function is taken to reduce the vehicle interior structure-borne noise, such as applying topography technology to optimize the firewall panel, improving the stiffness of the roof, and so on. The result shows that the sound pressure level is decreased 2dB (A). The second, many damping patches are added to the special panels, such as the front, rear floor and roof. The optimized result also shows that the damping treatments in the microcar improve NVH performance and the sound pressure level is decreased 2dB (A).For the purpose of reducing the vehicle interior structure-borne noise excited by the engine inertia excitation, taking a microcar as an example, on the basis of powertrain - body structure vibration and noise modeling, predicting the vehicle interior structure-borne noise excited by the engine inertia excitation, analyzing the main transfer path analysis noise of the vehicle interior noise, taking the measures of reducing the vehicle interior noise, the control technology of reducing the vehicle interior structure-borne noise is studied. The studying results provide guidance for identifying the transfer path of the vehicle interior structure-borne noise and controlling the interior noise in the design process of automotive.