| With the help of continuously variable transmission, the engine could be made to work in ideal condition according to the actual travel situation and the intention of the driver. The dynamic property would be improved and the specific fuel consumption rate could be decreased at certain level. For these reasons, it has already taken a considerable market share in our country by far. Electronically controlled continuously variable transmission (ECVT) is relatively newly-developed transmission, compared with traditional CVT, it is combined with electronic control technology that could control the ratio, clamping force and clutch pressure more precisely. With the application of torque converter, the starting performance is improved further more. The elctro-hydraulic system of electronically controlled continuously variable transmission is assembled into a valve body which consists of two parts:the upper body and the lower body, which makes the gear-box with compact construction and higher efficiency of control system. This paper proposed to conduct intensive research on elctro-hydraulic system in connection with the CVT electro-hydraulic valve body. The main contents of this article were as followed:1. The developing situation of CVT and its electo-hydraulic system were summarized separately, and the construction and working principle of ECVT was analyzed.2. The key technologies involved in ECVT were presented specifically, and the working process of hydraulic circuit of ECVT electro-hydraulic system according to actual vehicle driving cycle was analyzed in detail.3. Based on the analysis of structure and characteristics of on-off solenoid valve and proportional pressure valve, the mathematic models of duty solenoid valve (high speed on-off valve), ratio control valve (proportional pressure-reducing valve), and clamping force control valve (proportional overflow valve) had been established, and the established models were simulated by MATLAB/Simulink. On this basis, the simplified model of ECVT electro-hydraulic system was then established.4. The static characteristic and dynamic characteristic experiment of high speed on-off valve, proportional pressure-reducing valve, and proportional overflow valve were carried out separately through bench tests, and the experiment curves were acquired. The working region and top response frequency of high speed on-off valve was obtained to be less than 25Hz. The maximum control pressure of proportional pressure-reducing valve was less than 2.15MPa, and the maximum output pressure of proportional overflow valve was less than 4.4MPa. The models of three solenoid valves were verified by comparing the experiment results with the simulation results.5. The static characteristic and dynamic characteristic experiment of clutch pressure control circuit and clamping force and ratio control circuit were executed through certain conditional real car tests, and the corresponding experiment curves were obtained. In associate with solenoid valve tests and control circuit tests of electro-hydraulic system, the characteristics of ECVT electro-hydraulic system was further analyzed. Lastly, the relevant experiment characteristic curves were compared with the simulation result simulated in the same condition, and the relevant experiment characteristic curves matched the simulation results of the system well. In a word, the conclusion that the electro-hydraulic system model was created correctly could be obtained.The contents of this paper have referential value and practical significance on further study and development of CVT.
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