汽油发动机配气机构异响分析及优化

Analysis and Optimization of Abnormal Noise in Valve Train of Gasoline Engine

为改善某三缸汽油发动机怠速声品质,通过对异响噪声进行短时傅里叶变换(STFT),提取信号的半阶次特性,推测出异响来源于配气机构;又通过小波变换对异响信号能量进行精确的定位,并结合相位匹配,发现进排气凸轮轴相位与之匹配良好;通过对异响的振动特性进行分析,发现第一凸轮轴盖轴向振动与异响噪声特征一致,最终确定异响为第一凸轮轴轴承与进排气凸轮轴敲击所致。通过仿真建模对凸轮轴盖进行动刚度优化,经验证发现优化后半阶次噪声的响度、粗糙度和音调度分别降低3.3%,8.3%和13.7%,车内主观舒适感评价提升显著。

In order to improve the idling sound quality of a three-cylinder gasoline engine,STFT was used to extract the half-order characteristics of the abnormal noise,and the source of the abnormal noise was presumed to be the valve train,by analyzing the vibration characteristics of the first camshaft cover. It is found that the axial vibration characteristics of the first camshaft cover are consistent with the abnormal noise characteristics. Finally,it is determined that the abnormal sound is caused by the striking of the first camshaft bearing and the intake and exhaust camshaft. The dynamic stiffness of the camshaft cover is optimized by simulation modeling,and the results show that the loudness,roughness and pitch of the second-order noise are reduced by 3. 3%,8. 3% and 13. 7% respectively.