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For the development of engine valve springs it is highly required to establish valve train dynamic analysis method in order to predict durability and dynamic performance of springs in the design stage. On the other hand, in order to meet the demand for the reduction in time of prototyping, production technology that materializes spring design fulfilling requirements in short period is essential. To overcome these problems, we have developed and integrated valve spring design system, valve train dynamic analysis system and a digital data based production support system. With the help of those one can evaluate performance and durability of valve springs at working state in the design stage and realize specifications accurately in the production.

This subject focuses on the simulated shot peening analysis of the collision energy and simulated collision energy distribution on coil spring. The authors studied hit condition by changing peening angle, and checked relationship between collision energy and residual stress. There have been no report that describe an analysis on the simulated shot peening effect on helical-shaped whereas reports on flat material exist1)2). In this paper, shot size, peening angle, spring wire overlapping are considered. The effectiveness of this analysis is verified in comparison with the previous test result where light was used to check the shadow of shot shower.

Many advances have been made in engine development applications of Computer Aided Engineering in recent years. In valve spring development, simulations predicting durability and dynamic capability are so critical that the establishment of valve train dynamic analysis technology is of the utmost urgency. Nor can we ignore the importance of a technology that can manufacture product in a short time while still maintaining the required precision. There have been reports on valve train dynamic analysis conducted in the past. Although they are adequate to approximate their dynamic behavior, it is difficult to interpret details of the stress state or the shape effect in each part of a valve spring. It is also not suitable to predict durability or optimize shape. Therefore, a valve train dynamic analysis technology whose main purpose is the parametric design of a valve spring was developed.

Hot-formed coil spring material (SUP 190) has been developed in order to achieve weight reduction and corrosion fatigue strength and is currently used from the viewpoint of environmental protections(1). In the meanwhile, we have further developed a means of applying a high frequency induction heat treatment to the hot-formed coil spring material to create cold-formed coil spring material with features such as excellent formability and high shape freedom, as well as corrosion fatigue strength. Consequently, a weight reduction of approximately 20% can be achieved in comparison with cold-formed coil springs using SAE 9254, which has been used up to this point.

For the weight reduction of suspension coil springs for automobiles, high-strength steel has been developed. But, in general, strength and corrosion fatigue are contradictory. Then the technological basis is to raise durability and sag resistance, and further improvement of the corrosion fatigue strength is important. As a solution for the problem, element design which improved the performance against corrosion and optimum condition of shot peening process were studied. Thus high-strength suspension coil springs have superior corrosion fatigue strength, compared with the spring made of SAE9260 were developed. Moreover, as a new basic evaluation, corrosion fatigue test of springs with an artificial pit was worked out.