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This paper describes the results of the study and research on ovate wire helical springs which have been jointly conducted by the members of the Japan Society for Spring Research consisting of the engineers from material suppliers, wire and spring producers and automotive manufacturers as well as researchers at Japanese universities. Attention is focused particularly on two types of wire cross sections, typical elliptical shape and Fuchs' egg-shape. Stresses on these two cross sections were analyzed by numerical calculations within the range of practical specification, and then the results have been compared with those of round wire spring. As a result, it has been found that the elliptical wire spring is superior to Fuchs- egg-shaped one for general application. Simple designing methods for the both types of wire helical springs have been developed based on the findings from the stress analysis.

A new heat resistant steel wire was developed for automotive valve springs. The purpose of the development is to apply a high temperature carbo-nitriding process to the springs to have a longer fatigue life. The valve spring processed at an optimal temperature was found to have a fatigue life about five times as long as the conventional Si-Cr oil-tempered wire springs processed at a conventional low temperature.