Overall hydraulic continuously variable transmission device (Hydrostatic Transmission, referred to as HST) is a kind of hydraulic technology and machinery to achieve the perfect combination of the new transmission gear. The work of the hydraulic mechanical continuously variable transmission is essentially the use of mechanical transmission in the transmission system to ensure that the advantages of high transmission efficiency, the use of controlled hydraulic drive and mechanical transmission speed of the combination of characteristics to achieve continuously variable transmission. HST device used to achieve the overall type continuously variable transmission, power transmission structure can be simplified, without stopping the state, can be achieved by simple manipulation of the handle full range of variable speed, forward, backward, etc., simplifying the driving member of operation and less mechanical power split hydraulic control system of its low cost. Integral HST device is widely used in small and medium sized agricultural machinery, engineering machinery. Of HST hydraulic variable speed applications the device features to enhance its level of utilization of agricultural machinery, agricultural machinery to further optimize the design of continuously variable transmission. This mainly includes the following: (1) Based on research situation, systematically expounded the theory of hydraulic mechanical continuously variable transmission, hydraulic system summed up the importance of relationship characteristics, and analyzes the key parameters on the characteristics of the hydraulic system. (2) the efficiency of hydraulic components for the current formula does not accurately refer to the problem, the use of hydraulic components calculation of test data derived HST device efficiency formula, reflecting the intuitive system pressure, the input speed, displacement adjustment parameters on the efficiency than the characteristics of the three influence, and use the request system efficiency formula of the HST device features a detailed analysis. (3) combined with knowledge of hydraulic theory, characteristics of the hydraulic stepless transmission system, torque characteristics and efficiency characteristics, traction characteristics of static characteristics are analyzed, focusing on analysis of the variable speed feature. (4) based on HST devices and established the mathematical model of the engine, the application MATLAB / SIMULINK simulation software, on the HST transmission and engine modeling and simulation analysis carried out to study the HST hydraulic mechanical continuously variable transmission system dynamics. (5) of the engine and CVT matching HST proposed drive system for agricultural tractors matching index, on the basis of selecting the match HST device, the reference index on the continuously variable transmission using HSTtractor and tractor for traditional comparative analysis of performance.
Key words: hydraulic mechanical continuously variable transmission, static and dynamic characteristics, matching, simulation
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