摘要 |
<p>PROBLEM TO BE SOLVED: To provide a shovel on which a hydraulic circuit is mounted for allowing efficient operation of two hydraulic pumps and one pump motor.SOLUTION: The shovel includes a first pump 14L for discharging first working oil, a second pump 14R for discharging second working oil, an arm cylinder 8, a boom cylinder 7, a pump motor 14A for receiving working oil flowing out of the boom cylinder 7 to produce a back pressure in the boom cylinder 7 and to discharge third working oil, and a confluence valve 55 for selecting the joint of the first working oil and the second working oil or the cut-off of the joint. When the operation of the arm cylinder 8 and the operation of the boom cylinder 7 with the deadweight of a boom are performed at the same time, the confluence valve 55 cuts off the joint of the first working oil and the second working oil, the arm cylinder 8 is driven by the first working oil and the third working oil, and the pump motor 14A produces the back pressure to control the operating speed of the boom cylinder 7.</p> |