The Analysis Of Shaft Torsional Vibration And Gear Noise Fault Diagnosis Of 5L21/31 Genset

This thesis aims to eliminate the noise from timing gear and analyze its origin.Something work done in this thesis:Firstly, some test was done to analyze the characteristic of noise and vibration from timing gear. The result shown that sound pressure level was time-varying and changed sharply.Several repair measures, including checking gear tooth, adjusting tooth space, were done to eliminate this noise. However, this noise still existed. According correlation and coherence analysis, the source of noise and vibration was confirmed. And the model of fault analysis was established. It indicated that impeded running of gear system which lead to this noise,was caused by abnormal condition of oil supply system. However, this guess can't be proved on the basis of current theory.Gear is always regarded as rigid body in tradition way. However, it can't be used to explain origin of noise. Thus, a new viewpoint was presented that gear is flexible. And torsional stiffness of gear was calculated. A torsional vibration model was established,including crankshaft, camshaft and timing gear. The torsional vibration test was done to prove the validity of new model.This thesis also analyzed strained condition of camshaft and timing gears. Torsional excitation moment of camshaft and timing gears was calculated, however, moment of crank shaft was the main excitation of model in tradition way. The torsional excitation of camshaft was resisting torque, which was used to drive valve mechanism and oil supply system. The exciting force of timing gear caused by time-variable stiffness, gear error and meshing shock.A coupling model was established in this thesis, including explosion pressure, crank shaft,timing gear, camshaft. The relation between oil supply system and timing gear was explained. Torsional response of new model was calculated in misfire condition. The result show that fluctuation of torsional angle happen when cylinder acted inconsistently. And the guess of fault source was proved. Finally, noise from timing gear disappeared through exchanging oil injectors.