Study On Power Simulation, Matching And Control Of The Hydraulic System Of Metal V-Belt Type Continuously Variable Transmission

Efficiency of a transmission can effect the economy and performance characteristics of a vehicle. Although Metal v-belt type continuously variable transmission(CVT) has the optimum transmission characteristics, its transmission efficiency still can not achieve the level of mechanical transmission, which makes the fuel economy and performance of a vehicle with CVT not so good as multi-gear mechanical transmission. Therefore, how to improve the efficiency of CVT is one of recently research items with CVT recently. In order to solve the problem that the hydraulic system of CVT has a large power loss, study on power matching-control and simulation with the hydraulic system of CVT has been made. This research has important value in theoretical area and engineering application for realizing CVT hydraulic system power-matched control and improving the efficiency of CVT. The paper includes follow content:1. The pressure, flux and power characteristics of CVT hydraulic system is analyzed and its mathematic models is also built. Based on the power loss analysis of hydraulic system, power-matched-principle of hydraulic system is brought forward to realize the optimum control of the oil pressure and flux and improve the efficiency of hydraulic system.2. The dynamic simulation model of the power characteristics of CVT hydraulic system is built. Based on the model, the pressure, flux and power of CVT hydraulic system is simulated under the vehicle typical driving conditions such as start up, instant acceleration and instant braking and vehicle run cycle of ECE and EUDC, which obtains the change rule and characteristics of hydraulic system. This establishes the foundation of the matching and control of CVT hydraulic system.3. The double-pump control system and the electronic-pump control system are designed. To the double-pump control system, the principle of control system and the static characteristics and on-off mechanism of the PWM fast electromagnetic valve are analyzed. Analysis indicate that PWM fast electromagnetic valve satisfies the demand of double-pump control system. To the electronic-pump control system, the DC motor double-closed-loop digital PWM speed-adjusting system is designed and its controller is also designed. Simulation results indicate that the control precision and the dynamic response characteristics of DC motor have good performance.4. The dynamic simulation model of the double-pump control system and the electronic-pump control system are respectively built. Based on each model, the power characteristics of CVT hydraulic system is simulated under vehicle run cycle of ECE and EUDC. Simulation results indicate that the double-pump control system can improve the efficiency of hydraulic system to a large extent, whereas the electronic-pump can improve the efficiency to a large extent.5. The and analysis of power matching characteristic between the double-pump control system and the electronic-pump system are made. Results indicate that in virtue of the double-pump system having simple structure and control, it is a very applied system, whereas the electronic-pump is a very ideal and good foreground one owing to its realizing power matching of hydraulic system preferably.