Inspection steps and emergency treatment of valve springs

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 fit tightly with the valve seat or valve seat ring when it is closed, and to overcome the inertia force generated by the valve mechanism when the valve is open, so that the transmission parts are always controlled by the cam and do not separate from each other.
Valve springs are mostly made of high-quality alloy steel wire and heat-treated to improve their fatigue strength. In order to avoid spring corrosion, the spring surface should be galvanized and phosphated. The two end surfaces of the spring must be ground and perpendicular to the spring axis to prevent the spring from being skewed during operation.
Valve springs are mostly cylindrical helical springs, as shown in Figure 1. When the operating frequency of the valve spring is equal to or an integer multiple of its natural frequency, the valve spring will resonate and increase the probability of breaking. In order to prevent the occurrence of resonance, a variable pitch spring can be used. At present, most engines use concentrically installed double springs. The inner and outer springs have opposite rotation directions, and the outer spring has a greater stiffness than the inner spring. Double springs can not only prevent resonance, but also shorten the length of the spring. And when one of the springs breaks, the other spring can continue to work and prevent the valve from falling into the cylinder.
Valve spring inspection steps
(1) Check the free length of the valve spring. Use a caliper to measure the free length of the valve spring. The value should meet the standard value. If not, it should be replaced.
(2) Check the verticality of the valve spring. Use a square and a flat plate to check the verticality of the valve spring. The value should meet the standard value, otherwise it must be replaced.
(3) Check the preload of the valve spring. Use a dynamometer to detect the preload of the valve spring. The value should meet the standard. If the preload is lower than the standard value, the valve spring should be replaced.
(4) To prevent damage, compress the spring frequently.
Emergency treatment of valve springs
If the diesel engine valve spring is found to be broken while the car is driving, the broken spring can be removed first, and then the working surfaces at both ends of the spring can be aligned and reinstalled for temporary use. If the spring breaks into several pieces, you can remove the adjusting bolts of the intake and exhaust valves of the cylinder to keep the valves closed, and then remove the high-pressure oil pipe of the injection pump leading to the cylinder to prevent it from spraying oil into the cylinder, allowing the car to continue driving to its destination.