Spring Force Line Based Damper Friction Control for Coil-Over-Shock Applications

Coil spring force line control is an important aspect of spring design for coil-over-shock suspension type applications, such as MacPherson strut and coil-over-shock trailing arm applications, from the standpoint of riding comfort, steering stability and damper durability. A method based on simple statics to determine a unique spring force line for damper friction minimization has previously been investigated. Typically that method led to a unique specification of the spring force line, and a tolerance was arbitrarily determined. However, there are actually an infinite number of force line positions that obtain the same damper friction. Therefore, the spring force line determined by the conventional method is only a sufficient condition, but not a necessary condition to minimize the damper friction. Targeting a different spring force line position may contribute to reducing a cost of spring. In this paper, a wide range of allowable spring force line positions is theoretically calculated by scanning the spring force line positions in a static model of the suspension system. Also one of the reasonable methods to determine the spring force line and specification tolerance to control or minimize damper friction is discussed.