| 摘要 |
<p>PROBLEM TO BE SOLVED: To control the changeover of a joining/branching changeover valve surely, in a hydraulic drive device which can join the discharge flow rates of two oil hydraulic pumps and supply them to plural hydraulic actuators. SOLUTION: A joining circuit 100 consisting of a joining/branching changeover valve 14 which can change over to a branching position and a joining position for communicating through a throttle 50 is installed between the discharge circuits 11, 12 of oil hydraulic pumps 1, 6. By a joining/branching changeover control circuit 200 including a circuit pressure comparison detection valve 60, a maximum slanting detection valves 61, 62 and a shuttle valve 63, the branching position is changed over to the joining position when one oil hydraulic pump reaches a maximum slanting position and the discharge pressure of the other oil hydraulic pump is higher than that of one oil pump.</p> |
