动力总成异常振动的固有特性识别研究

Identification research of abnormal vibration for powertrain on natural characteristics

针对某SUV车柴油机动力总成在常用工作转速条件下产生异常振动的实际问题,给出改进脉冲激振法与有限元计算模态分析法相结合的方法进行不同条件下柴油机动力总成的固有特性识别研究。通过整车道路试验,发现柴油机工作转速的二阶激励激起动力总成系统共振,采用基于变时基技术的改进脉冲激振法进行整车和台架条件下动力总成的振动模态试验,结合有限元模型仿真计算,识别动力总成的固有频率和振型参数,发现飞轮壳结构是导致动力总成弯曲固有频率偏低引起系统共振的薄弱环节。根据识别结果,进行改进设计飞轮壳薄弱结构,提高动力总成系统的固有频率,消除异振。

With regard to the abnormal vibration in the diesel powertrain of a SUV in normal working speed conditions, an improved pulse excitation method combined with finite element modal analysis was proposed to identify the intrinsic property of the diesel powertrain under different conditions. It is found in vehicle road test that powertrain system resonance was caused under the excitation of the second-order excitation frequency of the diesel working speed. The improved pulse excitation method based on the technique of variable time base was applied to carry out the vibration mode test for powertrain in both test beds and real vehicles. According to the simulation calculations of the finite element model,the natural frequency and vibration mode parameters of the powertrain were identified and the cause of abnormal vibration was discovered accordingly： the structure of the flywheel shell was the vulnerable spot of the powertrain that resulted in low natural bending frequency. According to the identification results,the structure of the flywheel shell was improved,whereby the natural frequency of the powertrain was increased and the abnormal vibration eliminated.