| Supplying convenient transportation for people and materials, the vehicle has been closely related with people's works and life. In recent years, the rapid development of the automotive industry has become an important global economic power. The development of automotive technology, not only reflects the quality of people's lives, but also demonstrates the strength of the development of the country's economic strength and the level of comprehensive technical strength, so the countries competing for the development of the country's automotive technology. Increasing the relative energy shortages and environmental problems become more serious in reality, a huge vehicle energy consumption and emission of pollution to the environment has also become a vehicle of development in today's most important issues that must be addressed. It's inevitable to apply automatic transmission with people's requirement improving in mobility, economy, security and comfort of vehicles.There are several methods to realize automotive transmission shifting. For the moment, Automatic Trasmission(AT), Electronically Controlled Automatic Mechanical Transmission(AMT)and Continuously Variable Transmission(CVT) are widely used all round the world. CVT is an ideal transmission device for it can realize the continuous change of transmission ratio, get the optimum matching between the transmission and the engine and improve the whole vehichle's fuel economy, mobility, the handing facility and comfort. Compared with AT and AMT, the efficiency of CVT is higher than that of AT, and the handing facility and comfort of CVT better than that of AMT. Therefore, automobiles equipped with CVT can meet the requirement of saving energy and protecting environment. Metal transmission efficiency and longer life, so it has been the most widely used.The electro-hydraulic control system is the core of CVT, Continuously Variable Transmission for the realization and enhancement of vehicle performance play a key role. The initial stage of development in the CVT used in mechanical - hydraulic servo control system, because of structural complexity and a wide range of transmission performance to match the requirements of the lack of flexibility of new products now in general use of electro-hydraulic control, known as ECVT. After the hydraulic system integration between the various components all rely on the same original into a pipeline by block, connecting plate, to simplify design, reduce the size of pipes to improve efficiency and overcome the disturbance, noise, oil spills and other defects, so the research and development of precision high, high reliability and high efficiency, small size, low-cost integrated electro-hydraulic control module is the direction of future efforts. To further improve and optimize the electro-hydraulic control system for the performance of the various components, can improve the overall performance of CVT and the CVT is more widely applied.The clutch control of the CVT to the transmission efficiency as well as driving security comfortableness play the decision role. If slow-off control, which not only reduces the transmission efficiency, it also reduces security; If the clutch to control the speed too fast, the friction will increase unnecessary losses would also reduce the driving comfort. Under the operating conditions of motor vehicles, only to start-off control in a small range of the target in order to effectively improve the efficiency of transmission system to improve driving safety and comfort. Digital electro-hydraulic control technology to fill the traditional switch-type hydraulic control and servo control the gap between, has become a fluid transmission and control technology in most of a branch of vitality. Therefore, the number of the ratio of the flow valve in the automatic transmission and its application is even more valuable.The hydraulic pressure part and the system modeling and the optimized design, the hydraulic pressure part dynamic model including many elements of certainty, unifies through the theoretical analysis and the experiment, enhances to the hydraulic pressure part modelling precision, thus guarantee optimization design result accuracy.At present the tiny hydraulic actuating mechanism in our country is long-term dependent on overseas importing, the dyadic electro-hydraulic control valve already to become restricted our country high technology and new technology industry development the bottleneck technology. This research direction namely based on the high-speed solenoid valve, the flow control valve development which the electrical machinery realizes is precisely for our country automobile industry, the hydraulic pressure industry provides the reliability high, the structure compact, the price low, the performance fine hydraulic pressure part. It has important practical and immediate significance to attacks and captures this difficulty, which can improve the domestic saloon development of technology through our own efforts and short the gap between the developed country and our country.This article is from the above-mentioned needs for CVT of the electro-hydraulic control system of the CVT ratio control theory and digital control applications in the CVT, the main figures of the automatic transmission valve flow (based on high-speed switch valve the realization of the pilot-type flow control valve) design and simulation studies, papers were divided into six chapters, the main contents are:1, On the basis of referring to massive literature foundation of the domestic and foreign, on the basis of the CVT, introduced the history, current situation and development trends, and MT, AT, AMT, such as transmission compared commonly used to analyze the advantages and disadvantages of CVT on the significance of the study subjects.2, introduced the CVT of the typical structure and working principle with the clamping force control, ratio control, start-off control is closely related to the mechanism of metal belt drive.3, on the electro-hydraulic proportional control system, classification and basic characteristics. Introduced the electro-hydraulic proportional control system, the proportion of solenoid, stepper motor, high-speed switch valve commonly used in mechanical and electrical conversion components and the optional throttle test structure and the basic principles. 4, electro-hydraulic proportional control technology is an important area of vehicle control control technology, its control and high precision, easy, reliability and control are to meet increasingly stringent control requirements. In the original electro-hydraulic control system based on digital proportional control technology into the CVT, self-designed high-speed on-off valve to achieve the ratio of NC flow valve.5, the mathematical model through simulation analysis and comparison of NC test valve, from which design parameters have been better. Test results show that the NC flow valve to adjust flow to achieve a smaller and higher system stability, simple control, high precision and reliability are the advantages of open-loop control can achieve higher accuracy, to meet the actual application requirements.The main innovation of this paper is to test the simulation analysis and optimization, design and development applicable to electro-hydraulic control system of CVT digital flow valve, and select high-speed switch valve as a flow valve of the pilot valve, and thus digital proportional control technology to CVT electro-hydraulic control system. Tests showed that the number of flow control valve with high accuracy and reliability of digital control technology to reduce the proportion of CVT electro-hydraulic control system costs and improve the overall performance of the CVT, CVT increased stability and reliability, thereby enhancing the competitiveness of CVT force, so that the CVT is more widely applied. Thus applies to the number of CVT ratio control technology has very broad prospects for development.
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