抄録
There are many kinds of irregular shaped coil spring like an elliptically coiled, a rectangularly coiled and a squarely coiled spring. Especially an elliptically coiled spring is used in limited space like a gun magazine or precision instruments. Recently, elliptic coil springs are used in the coin shooter of vending machines thanks to their flexibility. Though the irregular shaped coil spring has numerous uses, its design formulae on the spring constant and the maximum stress of the wire have not been derived yet. In this study, general formulae for the spring constant and the principal stress for the springs with relatively small pitch angle are derived theoretically. Moreover, experimental study and FEA (Finite Element Analysis) are conducted. The theoretical results are compared with experiment and FEA. Then the stress correction factor for an elliptically coiled spring is derived by comparing theoretical value with FEA. The theoretical results multiplied by the correction factor are compared with FEA.
