engleski

The influence of active coils on the natural frequency of valve spring

The paper considers the problems of the surge of a helical valve spring. Using the method of harmonic analysis, the periodic valve lift function can be replaced by a series of sinus harmonics. At resonance, the frequency of excitation harmonic corresponds to the revolution frequency of the cam. However, during the steady rotation of the camshaft, the valve spring compresses and expands. Consequently, due to the influence of end coils, the number of active coils changes and the natural frequency of the spring turns from one single point into a wider band. As the result of that, there is also more than only one resonant harmonic. The paper briefly presents the fundamental theory of resonant frequencies of the spring. The main topic, i.e. the discussion of problems related to the calculation of resonant frequencies, is illustrated on the selected example. The analytical results are compared to the numerical ones which were obtained through the analysis of the FEM-model of the spring, using I-DEAS.

helical spring; resonant frequency; resonant harmonics

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