PROBLEM TO BE SOLVED: To stably perform turning traveling with a turning radius optionally changed and adjusted to be larger than that in clutch releasing turning maintaining a steering clutch in a released state, in addition to the clutch releasing turning.SOLUTION: This travel transmission device includes a shift transmission portion 50 interlocking with a travel device 1L on a left side and an electric motor 70 transmitting to the shift transmission portion 50. The shift transmission portion 50 is freely switched into a shift transmission state in which engine driving force from an output shaft 36 of a transmission portion 30 for left and electric driving force from the electric motor 70 are synthesized, the synthesized driving force having lower speed than the output shaft 36 of the transmission part 30 is generated by being continuously shifted and the travel device 1L on the left side is shifted and driven by the synthesized driving force in thrown-in states of the steering clutch 33 for left and the steering clutch 43 for right, and a non-transmission state in which the travel device 1L is made into a free rotation state in the released state of the steering clutch 33 and the thrown-in state of the steering clutch 43.COPYRIGHT: (C)2012,JPO&INPIT【課題】操向クラッチを切り状態に維持したクラッチ切り旋回の他に、クラッチ切り旋回よりも旋回半径を大きく任意に変更調節した旋回走行を安定的に行なえるようにする。【解決手段】左側の走行装置1Lに連動する変速伝動部50と、変速伝動部50に伝動する電動モータ70を設けてある。左用の操向クラッチ33及び右用の操向クラッチ43が入り状態において、左用の伝動部30の出力軸36からのエンジン駆動力と電動モータ70からの電動駆動力を合成して、左用の伝動部30の出力軸36よりも低速の合成駆動力を無段階に変速して発生させ、合成駆動力で左側の走行装置1Lを変速駆動する変速伝動状態と、左用の操向クラッチ33が切り状態で、右用の操向クラッチ43が入り状態において、左側の走行装置1Lを自由回転状態にする非伝動状態とに変速伝動部50を切換え自在である。【選択図】図2
