The Study Of Noise Mechanism In Valve Train Of Internal Combustion Engine

While modern engine is being developed toward high speed and high strength constantly, engine designer gradually place great emphasis on vibration and noise in valve train which not only influences engine performance but also have great influence on engine dependability and life-span. The design of valve train with high performance which can decreases impulse, vibration and noise between the parts while keeping the engine power performance has always been the subject engine designers concern. The mechanism of valve system's mechanical noise is thoroughly analyzed and studied by means of test analysis and dynamic simulation based on the study of a single cylinder four stroke air-cooled engine.Main noise sources in valve train are recognized through test method at first in this paper. A geometric model and a multi-body dynamics model of valve train are established based on the mechanism of noise production. The influencing factors of noise are obtained by the virtual test simulation analysis. Some correlative improve measurements are given according to the sequent analysis at the end.Test result indicates that the main noise source is the valve clearance impact under the condition of low speed, while the main source is valve-seating impact under the condition of high speed. Through frequency analysis, it has been found that the noise was generated by the continual impact between components. Though the virtual experimental simulation, it has been found that the rotational speed of the engine is one of the factors influencing the valve impact. This model has been proved correct by the analysis of valve impact law of each rotational speed. The reasons for excessive impact that valves produce which has been found through analyzing the vibration characteristic of valve train is that both the cam contour and their parameter are chosen unreasonably. By the means of Matlab's optimization toolbox, the cam contour has been optimized after analyzing the influencing law that cam parameter impact on the valve. A optimum cam design scheme is obtained by adopting the orthogonal experimental design method. Finally, the optimum cam is evaluated by virtual experimental method. It has been proved that the valve impact can be decreased obviously.In a word, the influencing factors of valve train's impact and improvement plan are discussed and dynamic simulation of valve train is accurately conducted in this paper. It...