摘要
随着生活水平的提高,汽车的乘坐舒适性变得日益重要。车内噪声是其中极为重要的一个方面。本文课题来源为某汽车制造厂的减振降噪项目,探索了车内噪声分析与控制的可行办法,为以后的研究工作做了一些铺垫。
本文首先对车内噪声进行了评价,与同档次对标车车内振动和噪声级对比,确定了降噪目标。通过频谱和阶次分析,获得了车内噪声特性。然后分析了车身的声振特性,包括白车身实验模态分析,发动机振动噪声传递和车身各部件隔声量分析。分析提出了相应的改进方案,包括车身声学处理和发动机悬置系统优化两方面。
然后应用驻波管方法,对不同的隔声和吸声材料性能进行实验对比,选择最优的材料对车身进行了处理。并以声响感度实验评价了车身阻尼处理的效果。
最后对动力总成悬置系统进行了优化设计。首先对悬置系统进行建模,并获取动力总成几何和动力学参数,之后分析计算激励力。优化的设计变量为各个悬置的刚度,目标为传递到车身的动反力最小。同时设定约束,使在不同工况下各个悬置的静变形和振动幅值都在允许的范围内。优化算法为序列二次规划方法(SQP)。通过与原设计的对比,分析了优化后系统的隔振机理。
With the fast developing of the automotive industry, the customers are becoming less tolerant of unwanted noise and vibrations. Vehicle interior noise is one of the key factors. Combined with project of local car manufacturer, the vehicle interior noise reduction and control are discussed.
Firstly, conducted the evaluation of the car's noise performance and benchmarking, defined the object. According to spectrum analysis and order analysis, the property of the interior noise is obtained. Then the vibro-acoustic analysis of total car is analyzed via experimental modal analysis of the car body in white and experiment of the transfer loss performance of different component of the car. The improvement methods include adding sealing, damping and sound-absorbing materials and optimization of the engine mount system.
Secondly, in the experiment method for transfer loss, TMP method was used to get the transfer loss according to present standing wave tube method. Measurement of acoustic sensitivity is used to evaluate the damping effects on the car body.
Finally, Design optimization of a 4-cylinder 4-stroke engine-mount system for vibration control is presented in this paper. The total force transmitted from the engine to the floor is minimized by choosing the stiffness of each mount. The SQP (Sequential Quadratic Programming) method is used as the optimization algorithm. The static and dynamic deflections are also kept within the desired limits. Compared with the original system, the force transmission is only half. The mechanism of vibration isolation is investigated with the frequency response of the system.
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