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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.

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.

In McPherson strut applications for automotive suspension systems, the desired coil spring reaction force vector (FLP: force line position) that minimizes damper friction and king pin moment is typically determined by Statics/Kinematics calculations. There is not a device available on the open market today which can mimic the coil spring reaction force vector within the suspension system. Such a programmable coil spring reaction force vector generator, named “Universal Spring”, was developed in 2003 (USPG2003), and was then improved in 2013 (USPG2013) from the standpoint of accuracy, durability and reliability. The device is actuated by six hydraulic cylinders constructing a Stewart platform type parallel mechanism. Accuracy of FLP generated by USPG2013 is 1.1mm at maximum in ϕ80mm area around strut axis.

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.

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.

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.