Takahiko Kunoh

Development of a new-type suspension spring for rally cars

Abstract The functions of the suspension springs for an automobile are to keep the control stability good and to improve riding comfort. Keeping control stability is important, especially for motor sports such as rallying. A new type rectangular wire helical spring is contrived by the authors, which joins the first coil part and the second coil part with a twisting part. If this spring is used as suspension springs for rally cars, the control stability can be kept good while absorbing impact from the road. It was clarified in this study that the spring characteristic is non-linear. Although the stress was checked by FEM analysis and theory on the twisting part, stress concentration was not detected. Furthermore manufacturing equipment for this spring was proposed by the authors.

Effect of Vertical Displacement of Coiling Pin on Dimension of Helical Compression Springs Formed by Two Coiling Pin System.

In this paper, it is the purpose to clarify the effect of a vertical displacement of the coiling pin as the influencing factors on the dimension of helical compression springs, and moreover to obtain the instruction to set up a vertical displacement of the coiling pin for forming them with highly dimensional accuracy. First, the effects of a vertical displacement of the coiling pin on the dimension of helical compression springs and on the initial tension of solid coil springs are analyzed by the differential geometry. Next, the experiments of forming springs are carried out in order to confirm the analyzed results. As the results, it is confirmed that the experimental results qualitatively agree with the analytical ones. Moreover, it is obtained the instruction to set up a vertical displacement of the coiling pin for forming helical compression springs with highly dimensional accuracy. Namely, helical compression springs can be formed with highly dimensional accuracy by setting up a vertical displacement of the coiling pin in the constant range of the initial tension of solid coil springs.

Effect of Torsion of Wire generated by Feed Rollers on Free Height of Helical Compression Springs.

The purpose of this paper is to improve the accuracy of free height of helical compression springs. A pair of feed rollers generate torsion of wire at feeding of wire. Torsion of wire makes the accuracy of free height of helical compression springs lower at the continuous production. And then, the mechanism that a pair of feed rollers getaerate torsion of wire is analyzed with a geometric approach in order to estimate torsional angle of wire. Moreover, the relationship between torsional angle of wire generated by a pair of feed rollers and free height of helical compression springs is analyzed with a geometric approach. And it is shown experimentally that these analyses are available. As the results of the analysis and the experiments, it is important that the upper roller and the lower one should be set on the position not to generate torsion of wire. Namely, the effect of torsion of wire generated by a pair of feed rollers can be removed on the accuracy of free height of helical compression springs.

Coiling Loads in Two-Finger Systems

The loads on tools for coiling close coils are analyzed in a two-finger coiling system. The experimental results are compared with the theoretical results. The main results are as follows: (1) The loads on working tools are inversely proportional to the spring indices of coils. (2) The mean diameters of coils are related to the load on the 2nd finger. The load is in proportion to the square of the wire diameter and to the yield stress of wires. (3) Within the range of this experimental condition, the dynamical friction coefficient seems to be a value between 0.3 and 0.6.