基于传递函数的发动机附件振动预测

阐述整车异常振动噪声的排查过程,确定问题为发电机和空调压缩机组件1阶共振。通过模态试验和有限元分析结果对比,保证仿真模型准确性,为下一步传递函数分析提供输入。通过测试第三主轴承盖到空压机远端处传递函数,得到结构阻尼信息。采用相同阻尼值,对空调压缩机支架更改前后传递函数进行对比,改进后第1阶模态共振频率提高,同时幅值也有降低。对改进后样件进行整车试验,结果表明,在默认激励保持不变基础上,可通过传递函数来间接反应最终响应结果,从而验证可以利用传递函数对发动机外附件振动进行预测。

Engine Accessory Vibration Forecast Based on Transfer Function

The abnormal vibration and noise is caused by the first resonance of the alternator and air compressor by checking the reason for the vehicle vibration unusually. Accuracy of the finite element model is guaranteed by comparing results of modal testing with those of simulation, providing input for the transfer function analysis . The modal damping can be got by testing the transfer function from the third main bearing cap to the air compressor far-end. With the same damping value, the transfer function was compared between before and after the air compressor bracket modified. The results show that the first modal frequency increases as well as the amplitude decreases. The vehicle trial was done with the modified bracket .The results demonstrate that the response can be represented through transfer function with engine excitation invariable. Thus transfer function can be used to forecast the engine accessory vibration.