Problem to be solved: to provide a control technology capable of appropriately determining an initial abnormality of a fan belt while employing a rational configuration in a working machine for transmitting the power of the engine to an operating portion by hydraulic pressure or the like to operate the operating portion.Solution: the speed control of the rotation speed of the engine 10 to perform the control of the engine to maintain the rotation speed of the engine 10 at a predetermined low rotational speed during the non operation of the operation part a, and to return the rotation speed of the engine 10 to a predetermined rated rotational speed lower than the low rotational speed during operation of the operation part a An automatic cell control means 31 is provided which detects the occurrence of slip of the fan belt 15 during the period of the rotation speed rising while the rotational speed return control is performed by the auto cell control meansThe slip detecting means 32 is provided with a belt condition determination means 35 for judging the state of the fan belt based on the detection result of the slip detecting means 32.Diagram【課題】エンジンの動力を操作部の操作に伴って油圧等で作動部に伝達させて当該作動部を作動させる作業機械において、合理的な構成を採用しながらファンベルトの初期異常を適切に判定することができる制御技術を提供する。【解決手段】操作部Aの非操作時にエンジン10の回転速度を所定の低回転速度に維持するデセル制御を実行すると共に、操作部Aの操作時にエンジン10の回転速度を低回転速度からそれよりも大きい所定の定格回転速度に復帰させる回転速度復帰制御を実行するオートデセル制御手段31を備え、オートデセル制御手段31による回転速度復帰制御の実行中の回転速度上昇期間内において、ファンベルト15のスリップの発生を検出する第1スリップ検出手段32と、スリップ検出手段32の検出結果に基づいてファンベルトの状態を判定するベルト状態判定手段35とを備える。【選択図】図2
