| 摘要 |
PROBLEM TO BE SOLVED: To prevent a control device from recognizing by mistake hydraulic control operation in a hydraulic circuit on the non-supply side to be abnormal when selectively supplying pressure oil to an existing hydraulic circuit or an added hydraulic circuit with the change-over operation of an external hydraulic pressure takeout valve. SOLUTION: A crawler tractor 1 with the hydraulic circuit comprises a second external hydraulic pressure takeout valve 19 provided in a supply oil path which supplies pressure oil to the existing hydraulic circuit (a rear working machine inclination control circuit) for taking the pressure oil out of the supply oil path when adding a hydraulic circuit thereto. With the change-over operation of the second external hydraulic pressure takeout valve 19, the pressure oil is selectively supplied to the existing hydraulic circuit or the added hydraulic circuit (a douser attitude control circuit). The change-over operation of the second external hydraulic pressure takeout valve 19 is detected, and hydraulic control operation in the hydraulic circuit on the non-supply side is checked. COPYRIGHT: (C)2008,JPO&INPIT
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