The valve spring is located between the cylinder head and the spring seat at the end of the valve stem. The function of the valve spring is to ensure that the valve can be closely attached to the valve seat or valve seat ring when the valve is closed, and to overcome the inertial force generated by the valve mechanism when the valve is opened, so that the transmission parts are always controlled by the cam without separating from each other.
The valve springs are mostly made of high-quality alloy steel wires and are heat treated to improve their fatigue strength. In order to avoid corrosion of the spring, the surface of the spring should be galvanized and phosphated. The two ends of the spring must be ground flat and perpendicular to the spring axis to prevent the spring from skewing during operation.
Valve springs are mostly cylindrical coil springs. When the working frequency of the valve spring is equal to or an integral multiple of its natural frequency, the valve spring will resonate and increase the probability of breaking. In order to prevent the occurrence of resonance, variable pitch springs can be used. At present, most engines use double springs that are installed concentrically. The rotation directions of the inner and outer springs are opposite, and the stiffness of the outer spring is greater than that of the inner spring. The double spring can not only prevent resonance, but also shorten the length of the spring. And when one of the springs is broken, the other spring can continue to work, so that the valve does not fall into the cylinder.
