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 ratio gear 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, analyzing power flows within the drive. Taking into consideration power flows and the efficiency of basic components, a method to calculate the efficiency of an IVT drive is presented, together with changes thereof in function of time. 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. The year 2009 brought about countless novelties [2], including New Holland's low power tractor series (30 kW - 74 kW) 'Boomer' with EasyDrive transmission, using a chain vanator (PIV) as a series component in tractors for the first time. Depending on the structure and current operational state of the system, total transmission efficiency is affected most by the efficiency of the component of variable gear and by the changes thereof. The second is loss by tooth friction, and the third is loss by bearing friction, the values of which increase as the speed increases.
Analysis of power flows and efficiency in infinitely variable transmissions of agricultural power machines
2010
10 Seiten, 11 Bilder, 1 Tabelle, 14 Quellen
Aufsatz (Konferenz)
Englisch
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