| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve properties of combined operation by appropriately controlling quantity of flow to attachment actuator of a hydraulic drive device for construction equipment. SOLUTION: A junction selector valve 20 having three selector positions I, II, III is provided and a hydraulic circuit including a specific permanent actuator that is often operated in combination with an attachment actuator 21 is not connected to a fourth hydraulic circuit 104 and other circuit than at least the circuit described above is connected to the fourth hydraulic circuit 104. Since hydraulic circuit not connected to the fourth hydraulic circuit 104 in each selector position I, II, III is different each other, the attachment actuator 21 can be insulated from influence of hydraulic fluid flow fluctuation caused by a permanent actuator operated in combination by switching the selector positions I, II, III of the junction selector valve 20 to the position where the hydraulic circuit connecting the specific permanent actuator is not connected to the fourth hydraulic circuit.</p> |
