| Our country is an agricultural country, and the goal of agricultural modernization and mechanization is need urgently to realize in the agricultural development. Tractor is a major agricultural machinery, the automation degree of tractor is an important norm for a country’s agricultural mechanization level. At present, most of the domestic tractors use traditional manual mechanical transmission which has some disadvantages, such as shifting operation too frequently, shifting power interruption and so on. When tractor with DCT is shifting, DCT could continue to output power and don’t interrupt, improving the power, economy and automatic operation level of the tractor.Based on comparison of various transmission scheme of DCT, a set of DCT transmission scheme which was suitable for tractor was designed. Based on the simplified model of tractor’s DCT, Shifting process of DCT was analyzed by dynamics. The shifting process was divided into five stages. System dynamics equation and torque transmission lines of every stage were given. Aimed at the working condition of heavy load, in which tractor with DCT shifts in the field, original shifting quality evaluation indexes could not fully investigate their impact on performance, and two new evaluation indexes, which were transmission coefficient of transmission output torque and the transmission output torque, were proposed. And on this basis, shifting process and shifting quality simulation model of DCT was established. Factors that could influence shifting quality, the relationship of shifting quality and shifting law, the effect of clutch engagement and separation sequence on the shifting quality are analyzed. At the same time, the view of research of shifting quality based on shifting was put forward. YTO-1804 tractor with DCT was selected as the reference object. The three gears to four gears as example, method which was used to calculate the three parameters of the tractor optimal power shift schedule point, by which three gears to four gear optimum shift point was obtained in the plough condition. In this shifting point, the shifting process of different clutch engagement and separation sequence condition was simulation analysis. The simulation results show that: within a certain range, as the lag time of oil pressure in closing clutch rise increases, the shifting time becomes long, jerk and slipping work become small, transmission torque transfer coefficient and transmission output torque becomes small, transmission output torque becomes small. Two new shifting quality evaluation indexes could fully evaluate tractor dynamic and dynamic load which is generated in the process of shifting; they are good compliments to original shift quality evaluation and improve shifting quality evaluation system of tractor DCT. Above all research results of this paper provide some theoretical basis for the further research on tractor DCT shifting performance. |
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