Shape Optimization of the Cross Section for a Non-circular Spring Wire of Valve Springs for an Automotive Engine

Abstract : Valve springs with non-circular cross-section are widely used in automotive engines. Because of the reduced height, the oval cross-section provides some merits in its install height and stress distribution. This paper introduces a new method to generate optimal shape of the non-circular cross-section. For given width and height, arbitrary shape of the cross-section are described using the Hermite spline curves. Cross-section area and maximum stress level are chosen as performance indices, and nonlinear optimization problems are formulated with inequality constraints. Compared to a production spring wire, cross-section area can be reduced about 2.4 [%] without increasing maximum stress level. In addition, the other approach gives an optimum cross-section which reduces maximum stress level of 2.0 [%] without increasing cross-section area. Key words : Valve spring(밸브 스프링), Wire cross-section(선 단면), Non-circular cross-section(비원형 단면), Automotive engine(자동차 엔진), Shape optimization(형상 최적화)