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Traditionally coil springs were used for applications to exert one-dimensional force along a given spring coil axis. However, in recent years, there has been an increasing trend in using coil springs to provide forces in a multi-dimensional space. In this paper, an approach to construct a model of a coil spring for suspension systems using a spatial six degree-of-freedom parallel mechanism is presented. In kinematics and dynamics simulation, the use of a parallel mechanism to model a coil spring allows a designer to simulate six degrees of freedom spring characteristics with vehicle kinematics without using FEA feature embedded in the simulation software. This requires a significant amount of computational load and maybe a file format converter.

As for the McPherson strut, a force from the tire acts on the shock absorber producing a bending moment, which causes an increase in the friction acting on the shock absorber. Reducing the friction is one of the most important issues to improve the riding comfort of an automobile. The bending moment can be reduced by controlling the load axis of the coil spring assembled with the shock absorber. In order to control the load axis, several types of coil springs have been recently reported. This paper proposes another shape-controlled coil spring, called L-shape. The L-shape spring has the following advantages: (1) The load axis can be precisely controlled with ease; (2) Additional space is unnecessary; (3) Manufacturing tractability is increased. The proposed L-shape spring is validated analytically and experimentally in this paper. The effect of the L-shape spring for reducing the friction on a shock absorber is also experimentally confirmed.

Friction caused by side force on a damper axis results in riding discomfort. In order to cancel the side force, accurate shape control for coil springs have been recently become crucial. After designing a target coil shape using a finite element analysis (FEA), actual coiling processes can be done by a NC coiling machine(C/M). The problem with this method is that the NC coiling machine has its own characteristics which coiling experts have to consider when adjustments are made to the control points of the NC machine. This adjustment process usually takes significant amounts of time in order to meet the target coil shape, because the coiling experts do their adjustments by a conventional method based on their experience. This paper describes how to automate the control point design process to reduce the coiling effort and to save time. An ARMA model is used for the coiling machine modeling and its dimensions are determined by the physical dimension of the actual coiling machine.

Today's suspension coil spring design requires not only accounting for one-dimensional force along the coil spring axis, but also exerting a complex multi-dimensional force and torque field between the spring seats [1,2,3,4,5]. This paper describes the design of a 6-DOF parallel mechanism to mimic the force and torque characteristics of a coil spring. This mechanism can physically generate the 6-DOF force and torque field of a coil spring, allowing designers to experimentally evaluate the quasi-static force effects of a coil spring while still at the design stage. Examples are presented for a physically generated force and torque field of a coil spring used in a McPherson Strut suspension, and its effect is correlated to the side force acting upon the suspension strut. As an extension, this mechanism can be widely used to investigate the relationship between spring characteristics and damper friction.

Finite element analysis of suspension coil springs is standard practice for investigating spring behavior during compression. One increasingly important aspect of spring behavior under recent demand is precise control of the spring's force line. Proper control reduces side loading on the damper assembly, which increases ride comfort. The force line is the reaction force axis produced by a coil spring and its interaction with the spring seats during compression. Not only does the geometric configuration of the spring and seats affect the force line, but it has also been seen experimentally that the spring seat material has an effect. Elastomeric materials such as rubber are used in spring assemblies to reduce noise, vibration, and harshness (NVH), but their influence to spring force line axis has yet to be investigated. The construction and results of several finite element simulations will be presented, correlating various configurations and experimental data.

The automotive industry has recently increased emphasis on the control of a coil spring's load axis to reduce sideforce in a suspension system. Reduced sideforce improves ride comfort. A coil spring's shape, or profile, is the main contributing factor in sideforce control. After a spring's final profile is designed, a coiling profile must be determined which accounts for the setting process of the spring. Setting of helical coil springs is a common practice for inducing beneficial residual stresses in a spring cross section. This reduces later sag and settling of the spring. Finite element methods for the prediction of coil profiles are not suitable because of manufacturing process complexity and difficulty in practice. A new approach utilizing system engineering is proposed. The development of the approach and its application to stress and profile prediction are presented. An example demonstrates the attractiveness and accuracy of coil profile prediction with this new approach.

The purpose of this study is to validate a reverse engineering based design method for automotive trunk lid torsion bars (TLTB) in order to determine a free, or unloaded, shape that meets a target closed shape as well as a specified torque. A TLTB is a trunk lid component that uses torsional restoring force to facilitate the lifting open of a trunk lid, as well as to maintain the open position. Bend points and torque of a TLTB at a closed trunk position are specified by a car maker. Conventionally, a TLTB supplier determines bend points of the free shape by rotating the given bend points from a closed position around a certain axis to satisfy the specified torque at the closed position. Bend points of a deformed TLTB shape in the closed position often do not match the target bend points given by a car maker when designed by the conventional method, which can potentially cause interference issues with surrounding components.

The MacPherson strut is widely used in the automotive industry. Many investigations regarding the minimization of damper friction force have been published; however, this is not the case with vehicle self steer. There are several methods to reduce the amount of vehicle self steer. The objective of this paper is to minimize vehicle self steer with respect to spring force line position. To investigate the relationship between vehicle self steer and spring force line, a mathematical model of suspension system was developed and then solved to obtain the optimum force line position that minimizes vehicle self steer. The solution to the mathematical model found was that the force line must pass through the upper mount center in order to minimize vehicle self steer, or the force line must be on the same plane as the kingpin axis. Sensitivity analysis was performed to investigate the variability of the force line position on vehicle self steer.

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.