Research And Application Of Engine Crankshaft Vibration Noise Control

With the improvement of people's quality of life,the NVH(noise,vibration and sound roughness)performance of vehicle is getting more and more attention.Vehicle quality laws and regulations are increasingly stringent.Chinese car policy on warranty services of repair,replacement and refund begun to implement in 2013.Recently,In the domestic market some kind of car was reported engine abnormal sound complain.In order to adapt to the competitive market,the automobile manufacturers should take the improvement measures quickly.Through the automobile noise test,the frequency and time domain characteristics of noise vibration are tested.Engine abnormal sound sources are crankshaft vibration noise and the crankshaft vibration damper knocking the oil pump rotor caused by crankshaft vibration.Using FFT,wavelet analysis method we find the noise is 300~800Hz broadband noise in the engine compartment and 370~420Hz narrowband noise in the cab.Using Butterworth band pass filter analysis method we find the engine compartment noise and the vibrations of engine timing system side mount?oil pump casing and NO.1 main bearing seat both have peak value at the same time,and occur once per Engine two revolutions in the 51°CA after NO.1 cylinder TDC and 22.7°CA after NO.1 cylinder peak pressure.Crankshaft vibration noise is affected by many factors.Based on Solving the engineering problems of automobile enterprises,we take some countermeasures:(1)Modify the fitting table of NO.1 crankshaft bearing hole by using thicker bearing to reduce oil clearance.(2)Improve the axial force of the mounting bolt of the main bearing seat to reduce oil clearances of all crankshaft bearing holes.(3)Implement T5 treatments for engine blocks to reduce the thermal deformation of crankshaft bearing holes.(4)Reduce the width of crankshaft vibration damper end face.(5)Adjust position tolerance of installation location hole of engine oil pump.The vibration of engine timing system side mount is used to evaluate the nose.After implementing the crankshaft bearing hole oil clearance countermeasures,the vibration is reduced from 14.3m/s2 to 4.6m/s2.with the clearance between crankshaft vibration damper and oil pump rotor countermeasures implementation,the vibration is reduced to 3.5 m/s2 at last.so that the engine abnormal sound has been significantly improved.