2006 年 2006 巻 51 号 p. 27-34
Coil springs with rectangular wire cross section, named ‘rectangular wire coil springs’, can store more strain energy than circular wire coil springs in limited space. Therefore, they have been used mainly in press dies and other special machine tools. Recently, rectangular wire coil springs come to have different uses like suspension springs in which light weight design are demanded. On the other hand, it is necessary to reduce the number of coils by adopting the large pitch angle with improved strength of wires. However, in the stress and the spring constant formulae for rectangular wire coil springs derived by Liesecke in 1930's, the effects of the pitch angle are not considered. Therefore, as pitch angle becomes larger, the difference between the calculated results and experiment becomes outstanding. Though we have design formulae for rectangular wire coil springs of large pitch angle proposed by Watanabe et al., they are the formulation of the results by FEM analysis. In other words, theoretical derivation of the design formulae for the rectangular wire coil spring has not been performed yet. In this research, new design formulae are derived theoretically. Furthermore, the validity of the new design formulae is presented in this research by comparing the results with experiment and improved FEM analysis.