PROBLEM TO BE SOLVED: To avoid sudden change of tilling depth and to facilitate the return to the tilling depth control by quickening the recovery of loading factor in correcting a target tilling depth according to the loading factor.SOLUTION: A control part 20 of a tractor includes a target tilling depth correcting means for preventing engine stall by correcting the target tilling depth when the loading factor L of an engine ENG exceeds a prescribed value I during the automatic tilling depth control. When the loading factor L of the engine ENG exceeds the prescribed value I, a proportional control amount T in proportion to the deviation of the current loading factor L from the target loading factor H is computed. In determining a correction value E of the target tilling depth by integrating a deviation D between the proportional control amount T and the last correction value E, the correction value E is determined by adding the deviation D to the previously integrated value K if reduction of the loading factor L is not found, and the correction value E is determined by subtracting the deviation D from the previously integrated value K if reduction of the loading factor L is found.COPYRIGHT: (C)2012,JPO&INPIT【課題】負荷率に応じて目標耕深を補正するにあたり、耕耘深さの急激な変化を回避すると共に、負荷率の回復を早めて耕深制御への復帰を促す。【解決手段】耕深自動制御中に、エンジンENGの負荷率Lが所定値Iを超えたとき、目標耕深を補正してエンジンストールを防止する目標耕深補正手段を備えるトラクタの制御部20において、エンジンENGの負荷率Lが所定値Iを超えたとき、目標とする負荷率Hと現在の負荷率Lとの偏差に比例する比例制御量Tを算出すると共に、該比例制御量Tと前回の補正値Eとの差分Dを積分して目標耕深の補正値Eを決定するにあたり、負荷率Lの減少が見られないときは、それまでの積分値Kに差分Dを加算して補正値Eを決定し、負荷率Lの減少が見られるときは、それまでの積分値Kから差分Dを減算して補正値Eを決定する。【選択図】図4
