This paper introduces a fuzzy-based evaluation method of a specific portion of the power train. In this case study was evaluated a specific combination of a commercial high-performance tractor engine and power split hydrostatic infinitely variable transmission (IVT). The first part of the study describes the field test of the power train, then the mathematical model of this power train is introduced. The objective of this study was the evaluation of the power train in some specific phases. The tractor is one of the most important machines in the agricultural mechanization and the mostly used tractor speed ranges were generated by different engine speed and transmission ratio combinations. In each case the engine consumption and the transmission efficiency were calculated based on this mathematical model. These results were evaluated with the method of corrected fuzzy mean (CFM). All of these calculations were performed in MATLAB. This study gives a design guide for the future processes of the engine-transmission matching as a result.

Since late 1995, when the high-powered (194 kW) Fendt Favorit 926 equipped with a "Vario" transmission was launched, power machines with CVT (Continuously Variable Transmission) have appeared on the palette of all major tractor manufacturing companies as well. The CVT unit in the transmission of these power machines is not included directly in the power flow, but in one of the power branches after a split. By modifying the gear ratio of a properly selected CVT unit, the transmission can be geared neutral and the direction of progress of the vehicle can be changed. The transmission structure produced so is called power split IVT (Infinitely Variable Transmission).The paper presents the ways of producing an IVT drive and analyzes the Fendt "Vario" driving mechanism with OC-RSC structure and the same elements but with IC-RSC structure. There is detailed analysis on both structures on power flows (power split, positive/negative power circulating), the Geared Neutral and the backward operational stages, taking into account the significant states from efficiency calculation point of view, together with changes thereof in function of output revolution. Based on these investigations it is highlighted that the entire range of the course of the vehicle can be covered by an output coupled system adjusting the gear of the CVT unit within the high-efficiency range. The task is the same for input coupled systems, to be realized by planetary gears installed after the IVT unit and by the proper control of their engagement. gyetem rkp.3, HungaryPower flows and efficiency analysis of out-and input coupled IVT Per. Pol. Mech. Eng.

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