关键词: 发动机；敲击异响；时域分析；小波分析

Abstract: Engine is one of the important parts in a vehicle, when knock noise inside the cylinder occurs, people will perceive "rattling" or "dangdang" noise, which is often leading to customer complaints and negatively impacts the brand image. In this paper, by investigating the abnormal vibration and noises of a V6 engine after cold start via testing and analysis, the location of knock is identified, and the main frequency range of the knock noises is determined. By analyzing the angle domain of timing signal, the positions of each cylinder valve, piston and other moving pairs at the time of knock are deduced. The components and parts which are most likely to generate knocking noises are analyzed and verified. Finally, the issue of the abnormal knocking noises is resolved through structural optimization.

Key words: Engine; Knocking noise; Time domain analysis; Wavelet analysis