CONSTRUCTION MACHINE HYDRAULIC DRIVE SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a construction machine hydraulic drive system for correcting a malfunction if a boom lifting operation and a revolving operation are performed simultaneously.SOLUTION: A construction machine hydraulic drive system 1A includes: a first hydraulic pump 11 and a second hydraulic pump 12 tilt angles of which can be independently regulated; a revolving control valve 51 for controlling supply of a working fluid to a revolving motor 19; and a boom main-control valve 41 and a boom sub-control valve 42 for controlling supply of the working fluid to a boom cylinder 13. The revolving control valve 51 and the boom sub-control valve 42 are arranged on a first bleed line 21 whereas the boom main-control valve 41 is arranged on a second bleed line 31. A revolving operation valve 50 outputs a pilot pressure to the revolving control valve 51, and a boom operation valve 40 outputs a pilot pressure to the boom main-control valve 41. If a revolving operation and a boom lifting operation are simultaneously performed, a boom restriction valve 7 restricts the pilot pressure from being output to the boom sub-control valve 42.