Research On Some Issues Of Air Spring With Serials Double Attaching Gas Chambers

In this dissertation, according to the vibration isolation need of airborne calculating unit in large airplane, a new type of restriction diaphragm air spring with series double attaching gas chambers is brought forward and then designed. On basis of the hydromechanics theory and the thermodynamics theory, the differential equation of air spring's vibration is deduced. And then the air spring is analyzed by the numerical simulation method and the attained result is satisfactory. The structure of air spring is first designed in the dissertation and then the establishment process of air spring's kinetic model is gradually deduced in detail. Moreover, the relative factors which affect the air spring's performance is analyzed in depth and the relative conclusions is attained. The design and research on air spring in the dissertation can offer the aid of theory.Integrating the characteristic of diaphragm air spring, the air spring with double attaching gas chamber is designed and the main structure dimensions are ascertained. On basis of the supposed conditions which are the no stretched-out generatrix of air spring's diaphragm and the circular arc shape of unconstrained diaphragm part, the vertical static stiffness formula of air spring with the series double attaching gas chambers is deduced in detail. Moreover, on basis of the static stiffness model, the free vibration differential equation of air spring's main gas chamber is established, which is in favor for the design of air spring. The static stiffness and the free vibration differential equation are programmed and calculated. The results show that the vertical static stiffness of main gas chamber in the vibration is a periodic non-linear variance, the static stiffness increases with the compression of air spring and the stiffness increases with the increase of air spring's initial pressure. Moreover, the natural vibration frequency of main gas chamber unobviously decreases with the increase of initial velocity and the vibration non-linear of air spring is more and more obvious with the increase of initial velocity.In order to verify the rightness of the deduced vertical stiffness of air spring's main gas chamber, the material non-linear of air spring, the non-linear of curtain line in the rubber diaphragm, the geometric non-linear in the process of diaphragm's deformation and the contact non-linear between the upper sheet and the rubber capsule or between the lower seat and the rubber capsule are discussed. Afterwards, the implement methods of air spring's different non-linear in the finite element software Msc.Marc are analyzed. The effect of different initial pressure on the vertical stiffness in the air spring's loading process and the stretched length of diaphragm generatrix under the different initial pressure of different position are researched. The results show that the vertical force and vertical stiffness increase with the increase of air spring's initial pressure. Moreover, the change percent is less than 1.0% under the different initial pressure and the error can be accepted. The contrast between the results of air spring's vertical stiffness attained by simulation method and the results attained by theoretical deduction explains the rightness of vertical stiffness formula of air spring's main gas chamber in the dissertation.The kinetic model of air spring's main gas chamber is established, on basis of supposing adiabatic change, using the hydromechanics theory and the thermodynamics theory, integrating the energy equation and the continuity equation of gas in air spring and consulting the moving characteristic of air spring. Moreover, in the process of modeling, the discrete states are related together by the use of state controlled functions, so the deduction procedure of equation is simplified and the programming difficulty of numerical solver decreases. And then the free vibration, the throttle orifice diameter and the volume ratio between the two attaching gas chambers of air spring with series double attaching gas chambers are researched in detail by the numerical simulation method. The results show that the vertical kinetics performance is better than that of other analogous air springs. Moreover, the damping ratio's maximum value of air spring is first relative to the throttle orifice I and then is only relative to the orifice II when the diameter of throttle orifice I is enough big. The damping ratio increases with the decrease of the first attaching gas chamber's volume, when the diameter of orifice I is big enough, the diameters of two throttle orifices are invariable and the volume sum of the two attaching gas chambers is invariable.On basis of establishing the free vibration differential equation of air spring, the kinetics model of air spring system under the condition of displacement excitation is deduced. The control mode of air spring is researched, the pressure of main gas chamber is ascertained as the controlled member and then the system kinetics equation adding the controlled actuating mechanism is set up. The air spring's model under the displacement excitation and the air spring's model adding control are analyzed by the numerical simulation method. The results show that the displacement excitation's response of air spring with series double attaching gas chambers under the low frequency and high frequency is smaller than that of air spring with one attaching gas chamber. Moreover, the system vibration response adding the controlled variable is obviously decreased, which verifies that the air spring designed in the dissertation owns the better effect of vibration isolation under the effect of control system.