| Hydraulic poppet valve have been widely used in various hydraulic systems because of the advantages of simple structure, good sealing performance, strong flow capacity and so on. However, the low damping characteristic of the "spool-spring" makes the dynamic characteristics of the poppet valve system poor, and it is easy for vibration. During normal operation of the poppet valve, the poppet spool in the liquid flow in the suspended state, when the hydraulic system disturbance, the poppet spool deviating from the stable state into the unstable state, resulting in the poppet valve vibration. poppet valve vibration affects the hydraulic system control accuracy and stability, which can cause serious damage to the hydraulic control system or component failure. In recent years with the development of hydraulic technology towards high pressure, high speed and high power, the performance of poppet valve has been proposed more rigorous requirements, so for the engineering application of poppet valve vibration characteristics of has important reality value.By common poppet valve and five kinds of poppet valve with damping structure as the object to thesis, in depth studied the influence of poppet valve vibration theory and hydraulic system parameters from the damping aspect, and studied five kinds of poppet valve with damping structure. Considering this nonlinear factors of the volume cavity effect, flow power and pipeline characteristics, the mathematical model of the poppet valve system is established by state space method and power bond graph method, The system dynamics simulation model is established by using MATLAB/Simulink platform, which improved the precision of calculation and comprehensiveness of analysis.The thesis mainly includes four parts:(1) based on the force balance equation, valve port flow equation, the flow continuity equation, the mathematical model of common poppet valve and five kinds of poppet valve with damping structure is established and converted the differential equation to state equation. Lumped parameter model and state equation are established for straight pipe by using the power bond graph method, and poppet valve simulation calculation model including pipeline is established by using MATLAB/Simulink platform. (2) The vibration mechanism of ordinary poppet valve and the influence of system parameters are studied. Respectively considering viscous damping force, the steady state solution, the transient flow dynamics, pipe characteristics and so on, which studied the factors effects of vibration characteristics of the poppet valve. The results show that the hydrostatic pressure, the spring force and steady flow force is not the reason of the poppet valve vibration, which only have certain effect on poppet valve vibration amplitude; the main reasons of poppet valve vibration may include viscous damping of the system, transient flow force and pipeline characteristics; conditions and structure parameters have certain influence on the vibration characteristics of the common poppet valve. (3) Respectively studied the key parameters effects on five kinds of poppet valve with damping structure. The results show that all of the flow, the damping diameter, poppet angle and aperture parameters and so on have certain effects on the vibration characteristics of the five kinds of poppet valve with damping structure, and some parameters will cause high frequency vibration of the five kinds of poppet valve with damping structure if too large or small. (4) Respectively studied the parameters adaptability of the common type and the five kinds of poppet valve with damping structure. The results show that, compared to the common type, the system parameters adaptability of the five kinds of poppet valve with damping structure also have certain degree enhancement. Among them, the system parameters adaptability of the front ring gap damping type and the spool orifice damping type are optimal, the side of damping type is the second, the orifice damping type and the independent damping type are slightly worse. |
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