| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a hydraulic control device for a construction machine capable of surely operating a meter-out control means in the work needing the positive driving of a specific actuator. <P>SOLUTION: This hydraulic control device is composed of a valve device 5 having a flow rate control valve 31 for controlling the flow of the pressure oil supplied to an arm cylinder 4 as the specific actuator, and an arm operation lever device 6. The valve device 5 comprises a meter-out control valve 42 mounted on a meter-out branch line 41 branched to a tank 33 from an actuator line 35 at a meter-out side when the arm cloud command is issued, and a switch valve 43 for switching and controlling the meter-out control valve 42, and a bottom pressure of a bucket cylinder 7 is led to a pressure receiving part 43b of the switching valve 43. When the bottom pressure of the bucket cylinder 7 is over a specific value, the switch valve 43 and the meter-out control valve 42 are switched to the open direction, and a meter-out opening area of the flow rate control valve 31 is equal to a sum of an opening area of meter-out restrictions 23a, 23b and an opening area of the meter-out control valve 42. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
