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International Journal of Automotive Technology > Volume 10(4); 2009 > Article
International Journal of Automotive Technology 2009;10(4): 413-420.
EFFECTS OF END COILS ON THE NATURAL FREQUENCY OF AUTOMOTIVE ENGINE VALVE SPRINGS
H. LIU, D. KIM
University of Ulsan
ABSTRACT
In this paper, we present a method for estimating the natural frequencies of various engine valve springs such as constant pitch, two-step variable pitch, three-step variable pitch, and progressive springs. Since a valve spring’s surging amplitude is magnified when the spring’s natural frequency coincides with the frequency of the cam profile harmonic components, estimating the natural frequency of the spring is the first step in predicting valve spring surging phenomena. A new method for calculating the valve spring’s natural frequency is proposed in this paper that considers the end coil effect. This method predicts not only the natural frequency of a helical spring at a fixed number of active turns, but also the change in the natural frequency as the spring is compressed. The experimental results demonstrate that nonlinear characteristics of engine valve springs can be predicted from the given initial pitch curves.
Key Words: Valve spring, Variable pitch spring, Natural frequency, Spring surging, End coil effect
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