The goal of the authors’ development of a seat suspension with a 60mm stroke and Duffing-type spring characteristics was to meet the requirements of EM7 specified in ISO7096:2020 (resonance magnification shall be less than 2 in a damping test; the SEAT value shall be less than 0.6 at 3.3Hz on an excitation waveform). This suspension is a vertically moving friction-type damper and spring suspension with a single-degree-of-freedom vibration system. The three spring types are torsion bars, coil springs (whose spring forces acting on the housing relative to displacement in a vertical plane are described by a quadratic function), and a magnet-spring with both positive and negative springing forces. In the friction-type damper, sliding resistance is produced by a slider made of three-dimensional knitted fabric and a stopper positioned close to the top and bottom dead centers of the stroke and sandwiched by V-shaped metallic spring components. As a result, the damping brought on by the sliding resistance force predominates at the area where the slider stroke speed is reduced near both dead centers, where motion ceases. On the other hand, the non-linearity of the static load-displacement characteristics, which is described as a quintic function, has a significant impact on the displacement response when an impact force operates. The reaction gain dropped below 1.0 at this point without bottoming out or rebounding. Additionally, the created seat suspension's resonant response magnification decreased to less than 1.4 (at a resonance frequency of 1.5Hz), and the response gain decreased to less than 0.5 at 3.3Hz, which raised the chance that it would meet the requirements of ISO7096:2020.

Delta Tooling Co Ltd: Masahiro Mashino, Shigeyuki Kojima, Souich Makita, Jun Fukuda, Yumi Ogura, Etsunori fujita; Chubu University: Hajime Takada; Waseda University: Shigehiko Kaneko