| 摘要 |
PROBLEM TO BE SOLVED: To maintain constant in an actuating quantity of a steering wheel by control means correcting an opening of a control valve for compensating a reduction of a flow amount of a pressure oil accompanied with a deceleration of an engine speed. SOLUTION: In a tractor provided with both steering control device and a engine speed control device, a selector control valve 4 capable of changing a flow amount of oil is provided in an oil passage between a power steering device 30 and a hydraulic cylinder 3 for steering. When the engine speed control device is operated, the control valve 4 is shifted to an oil chamber 34 in which a great flow amount can flow, and when the engine speed control device is not operated, the control valve 4 is shifted to an oil chamber 33 in which a little flow amount flows, thereby pressure oil to the hydraulic cylinder 3 for steering is maintained constant in amount. |
