| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic drive unit capable of reducing loads to drive body driven by hydraulic cylinders in compound operation capable of realizing increase of speed of either hydraulic cylinder. SOLUTION: This device, provided on a hydraulic shovel, is provided with a main hydraulic pump 21, a boom cylinder 6, an arm cylinder 7, and a communication control means including a selector valve 64, a check valve 41, and a communication passage 40 to communicate a rod side chamber 6b of the boom cylinder 6 with a bottom side chamber 7a of the arm cylinder 7 to supply hydraulic oil from the rod side chamber 6b to the bottom side chamber 7a when drive pressure of the arm cylinder 7 exceeds a prescribed pressure. It is also provided with a pressure setting means provided with a main relief valve 80 and an overload relief valve 84 related to the boom cylinder 6 for setting drive pressure of the arm cylinder 7 to be lower than relief pressure of the overload relief valve 84 when the boom cylinder 6 is communicated with the arm cylinder 7. COPYRIGHT: (C)2004,JPO |
