The calculation of valve springs is a complex system design issue. A good spring design minimizes friction and wear in the valve train. Now, an analytical method for valve spring design based on the construction of the parameter sensitivity design diagram is summarized as follows:
(1) In the first step, by analyzing the downhill driving performance and engine braking of the vehicle, determine the design target of the fly-off speed of the valve train, so as to determine the required valve spring preload and spring stiffness;
(2) The second step is to establish a dynamic model of the valve train in order to accurately predict the flyout and evaluate the influence of the recompression pressure in the cylinder on the flyout;
(3) In the third step, the parameter map of the valve train dynamics is constructed by performing parameter sweep calculation for different values of the spring preload and spring stiffness to check their influence on the valve train vibration. The pushrod force, valve train acceleration, and spring deceleration need to be plotted against crankshaft angle in the figure to show the design margin for flyout, so that spring preload and spring preload can be chosen conveniently and wisely in step 4. The target value that the spring stiffness needs to have;
(4) The fourth step calculates the required spring preload to prevent the exhaust valve from jumping based on the static force balance of the exhaust valve head. Select the exhaust valve spring preload for engines with and without exhaust brakes, and use the design parameter map in Step 3 to select a matching spring rate;
(5) The fifth step is to perform parameter sweep value calculation on the design parameters, and use the graphical design method to construct a parameter sensitivity design diagram for the spring design. The average diameter of the spring, the diameter of the coil wire and the number of coils are selected, while satisfying design constraints such as spring torsional stress, natural frequency, and coil gap. Alternatively, an analytical optimization method can be used to directly solve the equation.
