| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a hydraulic driving device capable of utilizing pressure oil on a holding side of a first hydraulic cylinder to increase speed of a second hydraulic cylinder when performing composite operation of the first and second hydraulic cylinders. <P>SOLUTION: This hydraulic driving device is provided with a main hydraulic pump 21, a boom cylinder 6 and an arm cylinder 7, a direction control valve 23 for boom and a direction control valve 24 for arm, an operation device 25 for boom and an operation device 26 for arm, and a pressure oil supply means for supplying pressure oil in a rod side chamber 6b of the boom cylinder 6 to the upstream side of the direction control valve 24 for arm when bottom pressure of the arm cylinder 7 becomes high pressure exceeding a predetermined pressure. The pressure oil supply means includes a confluence change-over valve 44 which is provided in a tank passage 42 capable of communicating with the rod side chamber 6b of the boom cylinder 6 and holds a communicating passage 40 connecting the tank passage 42 with the upstream side of the direction control valve 24 for arm in a condition in which pressure oil can be supplied to the upstream side of the direction control valve 24 for arm when bottom pressure of the arm cylinder 7 exceeds a predetermined pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
