FLUID PRESSURE CIRCUIT, ENERGY RECOVERY DEVICE, AND FLUID PRESSURE RECOVERY CIRCUIT FOR WORKING MACHINE

摘要

A hydraulic circuit that enables smooth absorption of the energy of a return fluid from a hydraulic actuator by means of an energy recovery motor, as well as stable functioning of the hydraulic actuator, is provided. A return fluid passage 55 to which the fluid discharged from a boom cylinder 8bmc is branched is provided at the tank passage side of a solenoid valve 49 of a boom control circuit 45. The return fluid passage 55 comprises two return passages 56,57, which are provided with a flow rate ratio control valve 58,59 for controlling a ratio of fluid that branches off into the return passages 56,57. The flow rate ratio control valve 58,59 is comprised of a solenoid valve 58 disposed in the return passage 56, which is provided with an energy recovery motor 26, and a solenoid valve 59 disposed in the return passage 57, which branches off the upstream side of the solenoid valve 58.