| The metal pushing V-Belt continuously variable transmission (CVT), which can improve the fuel and dynamic performance by changing the gear ratio continuously and automatically according to the driving environment, is a perfect transmission mechanism. Hydraulic control system is the actuating mechanism of CVT, which carries out the functions of transmitting engine's torque and changing the gear radio. The design method of CVT's hydraulic system was studied in the dissertation, which got sustentation from national natural science fund, whose sequence number is 50122101. The following contents were involved: 1. In order to prevent the metal pushing V-Belt skidding and guarantee the engine torque is transmitted efficiently and reliably, by analyzing the forces acting on the metal ring and the metal block, the torque transmitting mode was worked out, and the axial forces acting on driven wheel needed for transmitting torque was calculated, and the formula, which was used to calculate axial force from ratio to torque, for ensuring the equilibrium of axial forces was deduced. The dynamic model of hydraulic system was established. 2. In order to realize the ratio being fast response to satisfy the requirements from driving environment, the dynamic simulation model, which was based on CVT's work characteristic, was established. A design flow and method for calculating the rate of ratio for avoiding energy loss caused by flux overrunning in the hydraulic pump was educed by analyzing the distributing law of the rate of the ratio. The rate of the ratio was the integrated result of the simulation by the car SC7130 in the cases of ECE city cycle driving, EUDC suburb cycle driving, American FTP city and highway cycle driving. The design flow and method established the base for flux model, which is a must for designing hydraulic systems. 3. By discussing characteristics and working conditions of some kinds of electro-hydraulic control system, designing CVT hydraulic control system scheme building hydraulic system flux model, and establishing mathematical model of control valve clamping force, the control process characteristics of hydraulic control system due to system main pressure and speed ratio were analyzed. So an improved hydraulic system dynamical mathematic model was built, based on this, the effect that the hydraulic control system contributes to speed ratio was analyzed clearly, and completing CVT hydraulic system control scheme and construction parameters design based on SC7130 car. 4. In order to realize designing control algorithm effectively, the working characteristic of control valves which can adjust CVT clamping force and speed ratio was analyzed, and a conclusion of hydraulic valve control method was drawn, then based on dynamical characteristic of control valve with SC7130, a PWM signal control algorithm was designed, and simulation model of hydraulic system was built, then a simulation is made which a vehicle startups to 100km/h during emergency acceleration and emergency brake.
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