| The car as an important means of transportation has been closely linked with people’sdaily life. About the automobile power device selection, traditional high-speed internalcombustion engine,because of its mature technology, high power, reliable operation, smallsize and low cost advantages, are still the main market.However, high-speed internalcombustion engine with high speed, small torque, torque and narrow scope, cann’t matchcomplex vehicle driving conditions. So we must set the transmission device in between theengine and driving wheels, in order to slowing and increasing torque to match vehicle drivingcondition.Continuously variable transmission (CVT) is the ideal transmission device of the vehicle.It can realize the best matching with the engine power, and significantly improve vehicledynamic performance and fuel economy, and lower emissions, therefore CVT has a very hugemarket space. The metal belt CVT has the advantages of compact structure, long using life,easy automatic control, so it is very important to research it.Control device of metal V-belt type CVT by liquid initial control to electro-hydrauliccontrol now, electro-hydraulic control system has become the core component of CVT, itscontrol performance determines vehicle performance. So the study of electro-hydraulicsystem is very necessary.The electro-hydraulic digital control technology with hydraulic can transfer large powercontrol superiority and flexibility of the computer, has the advantages of high control accuracy,low cost. Hydraulic components and the control unit is the basic composition unit of theelectro-hydraulic system. in recent years, with the development of digital electro-hydrauliccontrol technology gradually mature, the development of hydraulic components and itscontrol unit will also move toward to digital direction.This paper mainly introduces two numerical control valves for CVT (for NCproportional relief valve clamping force control and for the control of proportional pressurereducing valve speed ratio control) of the structure and working principle. The structure issimplified based on the mathematical model of two control valve is established. Two kinds ofnumerical control valve for CVT electro-hydraulic control system, the electro-hydrauliccontrol system improvement are analyzed. Computer simulation software based on theAMESim,set up the simulation model of two kinds of numerical control valve andelectro-hydraulic control system. Based on the analysis of the static and dynamiccharacteristics of two kinds of control valve, and its characteristics and effects of parameters of the output characteristics are simulated and analyzed. The electro-hydraulic control systemimproved the bench test of speed ratio following experimental. The results show that theperformance of electro-hydraulic control system of numerical control valve based on areimproved. |
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