Research On Design Method Of Variable Stiffness Valve Spring

The valve spring is an important part of the valve train.The performance of the spring determines the economy and power of the engine.The advantage of the variable stiffness spring is that its characteristic curve is gradually increasing when the loading reaches a certain level.It also can achieve the effect of eliminating or alleviating the resonance as well as meeting the requirements of the working load and at the same time it doesn’t making the pre-tightening force of the valve spring too large.To some extent,it reduces mechanical losses and improves the efficiency of the internal combustion engine.The current experimental method for engine-matched valve springs is selected the one which comes from one of several alternative springs to ensure that the normal mechanism operates while performing best.But this method is not the optimal choice,and takes time and energy.According to this phenomenon,this paper studies the design method of variable stiffness valve spring.Studying this research,it can reduce the design cost of valve spring and improve the efficiency,also it has certain economical efficiency and practicability.Taking the gas distribution mechanism of a four-cylinder gasoline engine as the research object experiments with the dynamics and kinematics tests of the gas distribution mechanism.In the course of the experiment,through comparative analysis between the results of kinematics and dynamics of multiple valve springs at different rotational speeds,the reason for the failure of the drive train of the valve actuation mechanism was learned.We obtain an optimized stiffness curve by analyzing the kinematics curve and the data of organization and calculation.This paper is based on the design of the cylindrical coil spring and study the design method of the truncated cone spiral spring,so as to achieve the purpose of describing the characteristic curve of the truncated cone spiral spring in the mathematical language.According to the characteristics of the spring to find out the factors that affect the line type,and summarize the design method.This paper also optimize the design of the valve spring according to the stiffness curve,the condition of design valve spring constraints and the boundary conditions.According to the dimensions of the designed spring,a three-dimensional solid model of the valve spring is established in Pro-E and static analysis and modal analysis are performed.The finite element analysis of the spring is performed from the aspects of stress,deformation and resonance to verify the rationality of the design.This thesis will use The AVL-EXCITE Time Drive to establish a single-valve dynamic simulation system for the valve train,have a simulated analysis about the dynamics and kinematics of the designed spring,anticipate the design flaws and optimize adjustment of the deficiencies in real time.The main difficulty is that the stiffness of the variable stiffness spring changes with the change of the compression state and the nonlinear is difficult to operation mapping in a specific design analysis.The paper has studied and sorted out a set of design methods for variable-throttle valve springs,intending to provide a new reference for future spring designs.