HYDRAULIC CONTROL DEVICE AND CONSTRUCTION MACHINE WITH SAME

摘要

A boom cylinder circuit (16) is provided with a boom control valve (24) for controlling supply and discharge of hydraulic oil to and from a boom cylinder (9), and a merge switching valve (25) operable to be switched between a supply position (P4) at which hydraulic oil is suppliable from a first hydraulic pump (14) to the boom control valve (24), and a blocking position (P5) at which a flow of hydraulic oil is blocked. A controller (23) switches the merge switching valve (25) to the blocking position (P5) when a combined operation of a boom lowering operation and an arm pushing operation is detected by pilot pressure sensors (20, 22), and switches the merge switching valve (25) to the supply position (P4) when only one of the boom lowering operation and the arm pushing operation is detected.