Abstract: The pneumatic hydromechanics model of air spring is constructed and the relation functions of air spring’s vertical characteristics and its hysteresis curves are derived. Based on the pneumatic model, the relations of the air spring structural parameters, which include the bellow volume, the auxiliary tank volume and the orifice diameter, and the static and dynamic stiffness and the damping characteristics are revealed by the static and dynamic simulation tests. On this basis, the air spring model is implemented in the high-speed electric multiple units(EMU) dynamics model and a parametric study on the vertical comfort is conducted. The study results show that, the increment of the bellow volume can improve the vertical comfort; when the auxiliary tank volume is large enough, its influence on the vertical comfort becomes little, so the volume of the auxiliary tank should be at least 35 L; with the increase of the orifice diameter, the vehicle vertical comfort index first rapidly decreases and then increases slowly, which means that there exists a preferable range, about 15-25 m, for the value of orifice diameter, which makes the vertical comfort become best.

Key words: air spring, high-speed electric multiple units(EMU), structural parameters, vertical comfort