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Recently, the following two new items are strongly required for coil springs used in automotive suspensions. One of them is the control of the force action line of the spring. The second item is to design the geometry of the spring so that the spring can be installed within the space allowed. In order to meet these demands, precise design and production technology is required. However, it has been difficult to produce the springs exactly as they are designed. The developed CAD-CAM system is capable of materializing the designed geometry of the spring without the help of workers' skills and experiences. This system allows us to automatically generate NC data for coiling from the geometry of the spring obtained by the finite element analysis.

Macpherson struts popularly used in vehicle front suspension has a subject for minimizing frictional forces of each portion of suspension, especially in a shock absorber, so as to improve its performance. To overcome the subject and obtain better riding comfort, we have developed a new spring design that gives us an optimum force action line to minimize frictional absorber forces. For the design of the spring, we also developed a calculation system which consists of the finite element analysis and the mechanical system analysis. By means of this system, we can provide springs suited for each strut immediately.

As the design stress of the helical coil spring is increased to reduce the mass, the problem of riding comfort has come to the fore. To find out the solutions which compatibly satisfy the riding comfort and the mass reduction, we made the study of the side force of helical coil springs by using the finite element code ABAQUS. In the present analysis, the specifications of the spring which minimize the side force are discussed. Moreover, the effect of the tilting angle of a spring seat and of the kinematic condition of the spring on the side force is investigated.

This paper presents the discussion of the optimal shape for the wire cross section of helical springs. Since the stress at the inner side of a coil is higher than that at the outer side in a helical spring with a round cross section, the mass may be saved through stress equalization by the improvement of the cross sectional shape. Shape optimization is performed by the modification of the cross sectional shape so as to minimize the mass of the helical spring under constraints such as spring rate, coil diameter, applied load and maximum design stress. In the present analysis, stress distributions are calculated by the finite element analysis based on a stress function. In consequence, the optimized shapes are found to be almost oval and the mass is reduced by about 10% for the springs of small spring index.