| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a hydraulic control device for a hydraulic shovel capable of controlling boom pressure to an appropriate value with simple control. <P>SOLUTION: In the hydraulic shovel 1, the set values of relief pressure in main relief valves 21f, 22f are set larger than the high pressure side set value of relief pressure in a boom driving valve (Lo) 22c equivalent to a port relief valve. A controller 30 controls to switch relief pressure of the boom driving valve (Lo) 22c from 150 kg/cm<SP>2</SP>on the low pressure side to 300 kg/cm<SP>2</SP>on the high pressure side when pump pressure in hydraulic pumps 23a, 23b received from hydraulic sensors 24a, 24b is 120 kg/cm<SP>2</SP>or more and an intention display (selection of switches 8aa-8ac in a touch panel switch 8a) of boom lowering operation by an operator is received. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
