US Patent 7788915 Hydraulic circuit

A hydraulic circuit 100 having a simple structure can recover energy of fluid. Hydraulic circuit 100 comprises a boom cylinder 22, a hydraulic pump 31, a motion switchover valve 32, a hydraulic pressure regulation system 37 and a recovery pipe 36. Hydraulic pump 31 is driven by a drive source 15 so as to deliver fluid to boom cylinder 22. Motion switchover valve 32 is disposed between boom cylinder 22 and hydraulic pump 31 so as to switch a motion of boom cylinder 22. Hydraulic pressure regulation system 37 adjusts a differential pressure of motion switchover valve 32 between a delivery port 31a of hydraulic pump 31 and a suction port of boom cylinder 22 to a predetermined value. Recovery pipe 36 supplies hydraulic pump 31 with fluid from motion switchover valve 32 to which the fluid is drained from a drain port of boom cylinder 22.