Research On Oil Charging And Discharging Electro Hydraulic Control System Of Continuously Variable Transmission

Metal belt continuously variable transmission(CVT)is a kind of vehicle power transmission device which can realize the continuous change of transmission ratio.It has the advantages of high comprehensive efficiency,good ride comfort and strong energy saving.It is one of the most widely used automatic transmissions.The electro-hydraulic control system is the core part of CVT to realize CVT,and its overflow loss and throttling loss are the key reasons for the CVT efficiency can not be further improved.Therefore,how to improve the transmission efficiency by reducing the power loss of the electrohydraulic control system is the current research hotspot.At present,compared with the traditional vehicle,the new energy vehicle has the special feature of adding large capacity battery and DC motor,so the electro-hydraulic control system can control the DC motor to start and stop quickly to supply oil to the variable speed hydraulic cylinder.In view of the above problems,this paper proposes an energy-saving CVT oil charging and discharging electro-hydraulic control system.The specific work contents are as follows:(1)The design of CVT oil charging and discharging electro-hydraulic control system.According to the requirement that the CVT electro-hydraulic control system should be able to track the target clamping force and target speed ratio in time and accurately,the CVT oil charging and discharging electro-hydraulic control system is designed,and its basic structure and working principle are described in detail.The CVT oil charging and discharging electro-hydraulic control system drives the hydraulic pump to fill oil rapidly by controlling the speed of DC motor,and controls the valve core of high-speed on-off valve to quickly discharge oil.The two control systems can realize the precise tracking of target clamping force and target speed ratio.When the CVT speed ratio and clamping force change,it is necessary to accurately control the flow rate of hydraulic cylinder charging and discharging to further reduce the energy consumption of CVT.(2)Modeling and Simulation of CVT oil charging and discharging electro-hydraulic control system.The structure and working principle of the control valve are analyzed,and the mathematical model of the control valve is established.The dynamic response model of control valve spool displacement is established by AMESim software,and its working characteristics are analyzed.The model of oil charging and discharging electro-hydraulic control system for CVT is constructed.(3)The control algorithm of CVT oil charging and discharging electro-hydraulic control system is established.The advantages and disadvantages of traditional PID controller are analyzed,and the speed ratio control algorithm is formulated.Based on the model of CVT oil charging and discharging electro-hydraulic control system,PID controller and parameter adaptive fuzzy PID controller are designed by using Simulink,and their respective control models are established.The model and controller of CVT oil charging and discharging electro-hydraulic control system are simulated by AMESim Simulink.The simulation results show that the system can achieve the effect of energy saving.(4)Experimental study on the electro-hydraulic control system of CVT.The test device of CVT oil charging and discharging electro-hydraulic control system is built and debugged.The experimental results show that the CVT oil charging and discharging electro-hydraulic control system can accurately track the target speed ratio.