| 摘要 |
<p>PURPOSE:To save space by simplifying the whole circuit structure through a process of decreasing the number of switching valves, and by compactly forming the whole circuit. CONSTITUTION:An opening and closing control valve 64 for opening and closing a center bypass line 20 is provided between a switching valve 26 for an arm and a contact 42A of a control line, and the opening and closing control valve 64 is closed when a switching valve 35 for a bucket is switched from the neutral position. Moreover, one end side of a pressure oil supplying line 65 is connected to the center bypass pipeline 20 between the opening and closing control valve 64 and the switching valve 26 for the arm, and the other end side is connected to a pressure oil supplying port 35C side of the switching valve 35 for the bucket, and pilot pressure to be output to a switching valve 34 for the boom and the switching valve 26 for the arm is controlled by pilot pressure from an operation detecting line 74 through pressure decreasing valves 73A, 73B, 78A, 78B, so as to be decreased.</p> |
