US Patent 7200980 Drive system of a self-propelled working machine

A self-propelled forage harvester includes front and rear sets of driven ground wheels. The front set of wheels is driven through a transmission including an input shaft driven by a variable displacement motor and coupled to the front set of wheels by a gear train including one planetary gear set, (in one embodiment), and two planetary gear sets, (in a second embodiment). In both cases, the transmission is shiftable so as to establish at least first and second gear ratios. The shifting of the transmission is accomplished automatically by a control arrangement which takes into account the operating mode of the harvester so that a ratio for producing the correct velocity range for harvesting is established when the harvester is in a working operating mode, and a higher velocity range is established when the harvester is in a transport operating mode. Other operating parameters are sensed and used to automatically control hydraulic pump and/or motor displacement, and for controlling engine speed.