PROBLEM TO BE SOLVED: To improve a travel safety in case of requiring a low-speed travel in a combine harvester in which a travel HST having a variable displacement hydraulic pump and a variable displacement hydraulic motor and a mechanical multistage transmission are inserted into a travel system transmission path in series and the travel hydraulic motor is selectively turned into a small-displacement state or a large-displacement on the basis of a manual operation to a travel mode change operation member.SOLUTION: When a controller judges that the multistage transmission is connected to a minimum speed stage on the basis of a signal from an auxiliary speed change detection sensor, a travel mode change operation mechanism is forcedly operated and controlled so that the travel hydraulic motor may turn into a large displacement state regardless of a manual operation signal from the travel mode change operation member.COPYRIGHT: (C)2010,JPO&INPIT【課題】可変容積型油圧ポンプ及び可変容積型油圧モータを有する走行用HSTと機械式の多段変速装置とが走行系伝動経路に直列的に介挿され、前記走行用油圧モータが走行モード切替操作部材への人為操作に基づき選択的に小容積状態又は大容積状態とされるコンバインにおいて、低速走行させる必要がある場合における走行安全性を向上させる。【解決手段】制御装置は、副変速検出センサからの信号に基づき前記多段変速装置が最低速段に係合していると判断する場合には、前記走行モード切替操作部材からの人為操作信号に拘わらず前記走行用油圧モータが大容積状態となるように走行モード切替作動機構を強制的に作動制御する。【選択図】図9
