In some embodiments, the working machine may include a third operator input device 106 that receives a request from the operator to activate (turn on) or deactivate (turn off) an energy recovery function that recovers energy from fluid discharged from the boom actuator.

The flow of fluid from the boom actuator to the recovery path 501 can only occur when a boom down request, in which the boom is lowered, is input to the second operator input device 105. Additionally, the flow of fluid from the boom actuator to the recovery path 501 can only occur when a request to activate the energy recovery function is input to the third operator input device 106.

When a request to activate the energy recovery function is input to the third operator input device 106 and a request for boom down operation is input to the second operator input device 105, the directional control valve 409 can prevent pressurized fluid from being supplied from the pump 403 to the boom actuator.

On the other hand, when a request to activate the energy recovery function is not input to the third operator input device 106 and a request for boom down operation is input to the second operator input device 105, the directional control valve 409 can cause fluid to be discharged from the boom actuator to the tank 101 through the directional control valve 409.

Specifically, when a boom down request is input to the second operator input device 105 while a request to turn on the energy recovery function is input to the third operator input device 106, the control unit 107 controls the electronic proportional pressure reducing valve 117 to prevent pilot fluid from being supplied to the directional control valve 409, thereby switching the directional control valve 409 to a neutral position, thereby blocking the flow of fluid between the actuator and the energy consumption circuit 400. Accordingly, with the energy recovery function turned on, the boom down operation can be performed only by its own weight without supplying pressurized fluid from the pump, and the fluid discharged from the load chamber 313a can be supplied to the energy recovery circuit 500, i.e., the recovery path 501, instead of the energy consumption circuit 400. When a request to turn off the energy recovery function is input to the third operator input device 106, the control unit 107 can switch the return valve 513, the regeneration valve 509, and the charging valve 517 to block the flow of fluid between the actuator and the energy recovery circuit 500.

In some embodiments, during a boom down operation, the regeneration valve 509 may be operated to allow regeneration flow of fluid from the bottom chamber 313a to the load chamber 313b. During a boom down operation, the charging valve 517 can be operated to allow fluid flow from the bottom chamber 313a to the accumulator 508.

In some embodiments, the energy recovery circuit 500 may include a recovery path 501 and a regeneration path 503. As described above, the recovery path 501 can connect the bottom chamber 313a and the accumulator 508 to allow the flow of fluid from the bottom chamber 313a to the accumulator 508. The regeneration path 503 can be connected to the load chamber 313b.

In some embodiments, a return valve 513 may be provided between the recovery path 501 and the tank 101 to allow or block the flow of fluid from the bottom chamber 313a to the tank 101. In some embodiments, the regeneration valve 509 is connected to the recovery path 501 and the regeneration path 503 to allow or block the flow of fluid from the recovery path 501 to the regeneration path 503.

In some embodiments, the energy recovery circuit 500 may include an assist path 523 connecting the bottom chamber 313a and the assist motor 525. In some embodiments, the assist path 523 may connect the accumulator 508 and the assist motor 525 to allow fluid flow from the accumulator 508 to the assist motor 525. In some embodiments, a discharging valve 521 may be provided on the assist path 523. The discharging valve 521 can allow or block the flow of fluid from the accumulator 508 to the assist motor 525 through the assist path 523.

In some embodiments, the working machine may include a first sensor 507 for measuring a first pressure in the bottom chamber 313a and a second sensor 505 for measuring a second pressure in the load chamber 313b.

Unexplained drawing symbol 511 represents a valve, and 519 represents a pressure sensor.

In FIG. 2, an embodiment is shown in which the second operator input device 105 is an electric input device, but in some alternative embodiments, the second operator input device is a hydraulic input device incorporating a pressure reducing valve, and the working machine may include an auxiliary valve. In these embodiments, the pilot pump 115 is connected to a pressure reducing valve of the second operator input device, and the pressure reducing valve can send a hydraulic signal corresponding to an operator's request input through the second operator input device to the auxiliary valve. In some embodiments, the working machine includes a sensor capable of measuring the pressure of a hydraulic signal sent from the pressure reducing valve to the auxiliary valve, and the sensor can generate an electrical signal corresponding to the hydraulic signal and provide it to the control unit 107. Accordingly, even if the control unit 107 is not directly connected to the second operator input device, the control unit 107 can identify whether there is any request from the operator, i.e., whether there is a request for a boom down operation or a request for a boom up operation. When a request to turn off the energy recovery function is input through the third operator input device 106, the hydraulic signal generated by the second operator input device can be provided to the directional control valve 409 through the auxiliary valve. However, when a request to turn on the energy recovery function is input through the third operator input device 106, the control unit 107 controls the auxiliary valve to prevent the pilot fluid from being supplied to the directional control valve 409, thereby switching the directional control valve 409 to a neutral position, thereby blocking the flow of fluid between the actuator and the energy consumption circuit 400.

In some embodiments, the working machine may include a sensor 335 that detects the position of the bucket.

FIG. 3 is a drawing showing a preset correspondence between an input of a first operator input device of a working machine and an opening amount of a return valve according to some embodiments.

In some embodiments, the command generating device may be a first operator input device 104 that receives a request for an operating speed of the actuator from an operator. The control unit 107 can control the opening amount of the return valve 513 according to the above request. In some embodiments, the first operator input device