| 摘要 |
<p>PURPOSE:To ensure optimum efficient operation of hydraulic circuit by a method wherein the discharge oil of hydraulic pump S are supplied to a given main actuator for turning for example in accordance with the mode of combining actuators for turning, arm operction and boom operction. CONSTITUTION:The discharge oil of a hydraulic pump P1 is returned to a tank 10 after passing flow control valves 21-24 in the order of mention. In the meanwhile, the discharge oil of a hydraulic pump P2 is fed to the first flow course 61 through the upper position 41a of a preferential valve 41 and returned to the tank 10 after passing flow control valves 43-46 in the order of mention. When wall excavation is made after turning and arm contraction, the flow control valve 43 for turning is transferred to the upper position 43a for example, and the ones 24 and 45 for arm to lower positions 26b and 45b. Consequently, the discharge oil of the pump P1 is fed to the push-side oil chamber of an arm cylinder C2 through circuits 11 and (c). Further, the discharge oil of the pump P2 is fed to a flow course 61 after passing the initial valve 41 and further to a turning motor M3. The discharge pressure gradually raised of the pump P2 is introduced into the lower pilot chamber of the valve 41 to transfer the valve 41 to lower position 41B.</p> |
