Hydraulic driving apparatus of work machine

A hydraulic driving apparatus for respectively driving a first driving subject and a second driving subject included in a work machine by way of hydraulic pressure, comprising:

• a first pump motor that can be switched between a first pump operation state of being driven by a prime mover, thereby sucking hydraulic oil for driving the first driving subject from a tank, and discharging the hydraulic oil and a first motor operation state of receiving a supply of the hydraulic oil, thereby generating power;
• a second pump motor that is coupled to the first driving subject, and can be switched between a second motor operation state of receiving a supply of the hydraulic oil discharged from the first pump motor in the first pump operation state, thereby moving the first driving subject and a second pump operation state of receiving a supply of energy held by the first driving subject, thereby operating so as to suck the hydraulic oil from the tank, and discharge the hydraulic oil;
• a first pump motor line that connects the first pump motor and the second pump motor with each oilier so that the hydraulic oil can be supplied from the first pump motor to the second pump motor;
• a first accumulator that is connected to the first pump motor line, and receives the hydraulic oil discharged from the second pump motor in the second pump operation state, thereby accumulating a pressure;
• a pressure holding valve that is interposed between the first accumulator and the first pump motor, and preventing a pressure release from the first accumulator to the first pump motor so as to hold the pressure in the first accumulator;
• a regeneration subject hydraulic actuator that is coupled to the second driving subject, and receives a supply of the hydraulic oil, thereby moving the second driving subject;
• a hydraulic pump that sucks the hydraulic oil to be supplied to the regeneration subject hydraulic actuator from the tank, and discharges the hydraulic oil;
• a second accumulator that receives the hydraulic oil pressurized by way of energy held by the second driving subject, and discharged from the regeneration subject hydraulic actuator, thereby accumulating a pressure;
• a second pump motor line that connects the second accumulator to the first pump motor so that the pressure of the hydraulic oil accumulated in the second accumulator is released to the first pump motor in the first motor operation state, thereby enabling the drive of the first pump motor;
• a pressure release changeover valve that can be switched between an open state of opening the second pump motor line, thereby enabling the pressure release from the second accumulator to the first pump motor and a closed state of blocking the second pump motor line, thereby blocking the pressure release;
• a circuit switching unit that has a plurality of modes, wherein the plurality of modes include:
• a drive mode of bringing the pressure release changeover valve into the closed state, bringing the first pump motor into the first pump operation state, and bringing the second pump motor into the second motor operation state, thereby enabling the second pump motor to be driven by the hydraulic oil discharged by the first pump motor,
• a first regeneration mode of bringing the pressure release changeover valve into the closed state, and bringing the second pump motor into the second pump operation state, thereby enabling the hydraulic oil discharged by the second pump motor to be introduced into the first accumulator, and
• a second regeneration mode of bringing the pressure release changeover valve into the open state, and bringing the first pump motor into the first motor operation state, thereby enabling the first pump motor to operate as a motor by way of the pressure release from the second accumulator to the first pump motor;
• and
• an operation apparatus that receives an operation for a command for the driving of the first driving subject;
• and
• a circuit switching control unit that switches the mode of the circuit switching unit based on the operation given to the operation apparatus,
• wherein the circuit switching control unit switches the circuit switching unit to the drive mode while such a condition that an operation of driving the first driving subject at a constant speed or an operation of accelerating the first driving subject is given to the operation apparatus is required as a necessary condition, switches the circuit switching unit to the first regeneration mode while such a condition that an operation of decelerating the first driving subject is given to the operation apparatus is required as a necessary condition, and switches the circuit switching unit to the second regeneration mode while such a condition that the operation relating to the driving of the first driving subject is not given to the operation apparatus is required as a necessary condition.