| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic drive system capable of guiding a required flow amount of pressure liquid to each actuator even when a boom, an arm or a bucket is operated concurrently with revolving operation.SOLUTION: A hydraulic drive system 1 includes first-third hydraulic pumps 11-13, and control valves 21, 32, 34, 41, 42. The first boom control valve 21 is connected to the first hydraulic pump 11, and a second arm control valve 34 and the first bucket control valve 32 are each connected to the second hydraulic pump 12. Besides, the revolving control valve 41 and the second bucket control valve 42 are each connected to the third hydraulic pump 13. A command changeover device 60 outputs a pilot pressure XAk1 to the first bucket control valve 32 when a pilot pressure XAk0 is output from a bucket operation device 54 during revolving operation, and outputs a pilot pressure XAk2 to the second bucket control valve 42 when the pilot pressure XAk0 is output from the bucket operation device 54 during no revolving operation. |
