PROBLEM TO BE SOLVED: To provide an automatic tilling-depth control device which is prevented from a phenomenon that undulations or continuous irregularities occur in tillage traces in a farm field, thereby to make the evenness of the farm field satisfactory.SOLUTION: A control unit 19 controls the rise and fall of a tiller 3 connected to a running machine body 1, to a set tilling depth on the basis of the detection result of a depth sensor 8. A first insensitive band on the rising side and the falling side is set by adding and subtracting a first predetermined value to and from a target value or the reference of the rising or falling value. When the detected value of the depth sensor 8 deviates from the upper limit or the lower limit of the first insensitive band, the rising output or the falling output of the tiller 3 is performed. Moreover, a second predetermined value smaller than the first predetermined value is added to or subtracted from the target value or the reference of the rising output is set. When the detected value of the depth sensor 8 enters the upper limit or the lower limit of the second insensitive zone, moreover, the rising output or the falling output of the tiller 3 is stopped, and the insensitive band width on the rising side of the first insensitive band is made larger than the insensitive band width of the falling side.COPYRIGHT: (C)2014,JPO&INPIT【課題】耕深自動制御において、圃場によっては耕耘跡にうねりや、連続した凹凸が発生するという現象を防止し、圃場の均平性を良好とする。【解決手段】走行機体1に連結した耕耘装置3を設定された耕深となるように深さセンサ8の検出結果に基づいて昇降制御するトラクタの制御部19であって、昇降出力の基準となる目標値に第lの所定の値を加減して上昇側及び下降側の第1の不感帯を設定し、深さセンサ8の検出値が第1の不感帯の上限又は下限から外れると、耕耘装置3の上昇出力又は下降出力を行い、また、昇降出力の基準となる目標値に第1の所定の値より小さい第2の所定値を加減して上昇側及び下降側の第2の不感帯を設定し、深さセンサ8の検出値が第2の不感帯の上限又は下限に入ると、耕耘装置3の上昇出力又は下降出力を停止させ、さらに、第1の不感帯の上昇側の不感帯幅を下降側の不感帯幅より大きくする。【選択図】図7
