Hydraulic drive device

A hydraulic drive device that supplies a working fluid to a plurality of hydraulic cylinders including a first hydraulic cylinder, the hydraulic drive device comprising:

• a plurality of hydraulic drive systems that are respectively associated with the plurality of hydraulic cylinders and each of which supplies the working fluid to a corresponding one of the plurality of hydraulic cylinders;
• and
• one or more communication valves that place the plurality of hydraulic drive systems in communication with each other according to a communication command that is input to the one or more communication valves, wherein:
• each of the plurality of hydraulic drive systems includes:
• a hydraulic pump motor that discharges the working fluid and when supplied with the working fluid, rotates;
• an electric motor that rotatably drives the hydraulic pump motor to cause the working fluid to be discharged from the hydraulic pump motor, and generates power by being rotatably driven by the hydraulic pump motor;
• and a directional control valve that switches, according to an operation command, a flow direction of the working fluid flowing between the hydraulic pump motor and a corresponding one of the plurality of hydraulic cylinders;
• a first hydraulic drive system that is one of the plurality of hydraulic drive systems that is associated with the first hydraulic cylinder includes a first directional control valve that is the directional control valve;
• the first directional control valve causes the working fluid to flow from the first hydraulic cylinder to the hydraulic pump motor of a corresponding one of the plurality of hydraulic drive systems according to a first operation command that is input to the first directional control valve, to cause the electric motor to regenerate electrical energy;
• and
• one of the one or more communication valves distributes part of the working fluid flowing from the first hydraulic cylinder, to the hydraulic pump motor of a different one of the plurality of hydraulic drive systems that is in communication with the corresponding one of the plurality of hydraulic drive systems, to cause the electric motor that is rotatably driven by the hydraulic pump motor to regenerate electrical energy.