HYDRAULIC CONTROL DEVICE AND CONSTRUCTION MACHINE WITH SAME

摘要

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