Abstract
KEY WORDS -NVH, ticking noise, wavelet analysis, multi body dynamics , EHD Analysis
ABSTRACT - This study aims at the mechanism of piston pin noise of full floating system and resolving the piston pin noise problem at hot idle condition. The piston pin noise sounds like ticking noise, and generates by the collision between the piston pin and connecting rod when working at big clearance. The noise is annoyed and unacceptable. The NVH measurement results show the range of piston pin noise frequency is range from 1500Hz to 4000Hz. When crank run two circles, there is one time ticking noise, it means one time ticking noise per 4 strokes of engine. The ticking noise occurs at around 30 deg. after TDC of exhaust stroke. Then, multi body dynamics analysis and center orbit of piston pin simulation are used to reveal the mechanism of piston pin noise of full floating system. By dominating the NVH testing and CAE methods, the relationship between the ticking noise and the clearance of piston pin and connecting rod is obtained, and the heat distortion of connecting rod can be simulation when hot. The ticking noise is more clearly with more clearance between piston pin and connecting rod. The ticking noise shows strong dependence on the distortion of connection rod. But there are some limitations of this study, for example, the vibration sensors cannot be installed on the surface of piston pin or the connecting rod because of the high temperature and high rotating speed, therefore, we cannot get the vibration that cause by the pin collide with connecting rod directly. So, in this paper we will test the acceleration on the engine block for analyzing the collision. And we can estimate the piston pin movement behave by CAE analysis. In this study, two main proposals are researched to decrease piston pin noise at hot idle condition, one is reduce the clearance of piston pin and connecting rod, another one is increase the stiffness of connecting rod. The piston pin noise have been decreased effectively by the two proposals in the NVH testing results, and cannot be identify any more in the subjective rate