| 摘要 |
Provided is an apparatus for driving a boom of a construction machine, allowing required power to be reduced. The construction machine includes a boom cylinder 6, a variable-displacement hydraulic pump 10, a control valve 12 guiding hydraulic oil discharged by the variable-displacement hydraulic pump 10 to the boom cylinder 6, a boom-raising-operation detector 42 which detects a boom raising operation, boom-cylinder pressure detectors 46A and 46B, a supply selector valve 30 switchable between a permitting position for permitting the hydraulic oil to be supplied from the hydraulic pump 10 to a head-side chamber 6a of the boom cylinder 6 and a blocking position for blocking the supply, a supply oil passage 34 permitting hydraulic oil to be supplied to the head-side chamber 6a during the blocking, and a controller 50 which brings the supply selector valve 30 into the blocking position and reduces volume of the hydraulic pump 10 upon judging that excavation reaction force extends the boom cylinder 6 even with no supply of hydraulic oil from the hydraulic pump 10 to the head-side chamber 6a. |
