Research Of Double Tube Valve Plate Type Shock Absorber Characteristics And Its Effects On Vehicle Dynamics

The vibration of off-road vehicle,such as agricultural vehicles,forestry vehicles,tractors and some engineering vehicles,is more poignant than cars,buses and trucks.With the increasing of running speed,the problem is increasingly outstanding.More attention will be paid to the comfort.The influence of the internal components of the shock absorber is deeply studied.Based on the requirements of the vehicle to the damping characteristics of the shock absorber,combined with the current research situation of shock absorber,taken the S30 type valve type shock absorber as prototype.Based on the parameter of it,the removable damping adjustable shock absorber and test rig is design and manufactured.The structure of the shock absorber is deeply analyzed.Based on the theory of fluid mechanics,a theoretical mathematical model of the shock absorber is put forward in the paper.The deformation of the throttle slice of the piston valve is analyzed,and the deformation of throttle slice is studied by using the finite element method and fluid structure coupling method.CAISIM software is chosen to analyze the influence of the damping of shock absorber,the asymmetry characteristic of the shock absorber,and the different mathematical models of shock absorber on the vehicle dynamics.The finished work and achieved results are generalized as following:1.On the basis of analyzing the structure of the shock absorber,the mathematical model of the shock absorber is established.The detachable adjustable shock absorber is designed and developed.It is detailed experimental studied that the damping variation law which is influenced of the diameter of the piston orifice,,the diameter of the piston,the number of the throttle valve,the diameter of the limiting valve and the diameter of the bypass valve.The results show that the diameter of the piston orifice,the diameter of the limiting valve and the diameter of the bypass have large influence on the damping characteristics of the shock absorber.The number of the orifice plate is out of a certain range,with the increase of the number of the throttle orifice plate,the influence of the damping is small.The adjustment of the outer diameter of the limiting valve is the greatest influence on the damping of the shock absorber.Bypass throttle hole diameter in the?0??3 mm range and recovery damping force decreases greatly.In diameter?3 mm??4mm,the damping force change is smaller.When the bypass hole diameter with a diameter larger than?4 mm,the damping force change is no longer obvious.2.Using the finite element method,the deformation of throttle slice of the shock absorber.According to the working process of the shock absorber,the deformation calculation of the throttle slice of the shock absorber is analyzed with the results of the experiments.The finite element model of the single chip valve and the valve plate is built according to the vibration absorber.The STRUCTURE module is used to study the deformation of the valve plate.The results show that the deformation of the valve plate is limited by the small deflection theory and the large deflection theory.Define the new coefficient of deformation:"C_n",the deformation of the valve plate in the deformation calculation formula of the valve plate deformation coefficient.3.Use of fluid solid coupling method,the throttle valve of the shock absorber is developed.Based on the theory of fluid mechanics and solid mechanics,fluid solid coupling model is established to calculate the deformation of throttle slice of shock absorber.Using the STRUCTURE module,FLUENT module and COUPLING SYSTEM module,the deformation of throttle slice of shock absorber is simulated,and the deformation law of valve plate is further analyzed.The comparison analysis of three kinds of different methods for calculating the deformation of the valve plate is made.Calculation results of valve plate that use of the finite element method is largest.4.The influence of the damping characteristics of the shock absorber on the vehicle dynamic characteristics is studied.Based on CARSIM software,the simulation test program is developed for the influence of damping characteristics of shock absorber on the vehicle dynamics,and the influence of four different kinds of typical operating conditions,respectively,are carried out.The results show that the damping force of the shock absorber has a greater effect on the vibration of vehicle.By step input of the road conditions(small obstacle and large slope),as the recovery of the damping force increases,the vibration energy of the vehicle decreases.The comfort of the vehicle increases with the increase of the damping force.At the situation of vehicle(washboard road)movement on the rough road,with the shock absorber damping recovery increased,the vibration of the vehicle decreases first and then increases.It indicate that on the rough road sports car,damping greater or smaller cause the aggravation of the vibration.In the condition of double lane change movement of vehicles,with the increase of the shock absorber damping values,vehicle vertical vibration and pitch vibration energy reduction,vehicle roll angle,roll angle,yaw angular velocity,dynamic load were less affected.The vehicle with asymmetric damping is obviously enhanced than the vehicle has a symmetrical damping.Three kinds of mathematical models of shock absorber are established:linear model,the two section of asymmetric model and polynomial model.With the increase of the complexity of the mathematical model of the shock absorber,the vibration response of the vehicle is close to the actual damping characteristic of the shock absorber.Among them,the response value of the two segment asymmetric model and the polynomial model is close.This work can provide the theoretical basis and technical support for the structure design of the shock absorber,the matching of the suspension,the setting and controlling strategy of the controllable suspension,and the development of the theory of vehicle.