A hydraulic circuit of a construction machinery for supplying hydraulic oil to a first travel motor, a second travel motor and other hydraulic actuator, the hydraulic circuit comprising:
- a capacity-variable hydraulic pump,
- a capacity-variable hydraulic pump,
- a first pump line in which hydraulic oil discharged from the first hydraulic pump flows,
- a second pump line in which hydraulic oil discharged from the second hydraulic pump flows,
- a first travel switch valve connected to the first pump line and the second pump line and configured to switch a flow direction of hydraulic oil relative to the first travel motor,
- a second travel switch valve connected to the second pump line and configured to switch a flow direction of hydraulic oil relative to the second travel motor,
- an actuator switch valve connected to at least the first pump line and configured to switch a flow direction of hydraulic oil relative to the other hydraulic actuator;
- a first open-close valve provided between the first hydraulic pump and the first travel switch valve,
- a second open-close valve provided between the second hydraulic pump and the first travel switch valve,
- a communication line communicating the first pump line and the second pump line,
- a communication valve provided in the communication line,
- a first travel operator configured to output a signal for operating the first travel motor,
- a second travel operator configured to output a signal for operating the second travel motor,
- an actuator operator configured to output a signal for operating the other hydraulic actuator, and
- a controller that performs circuit control based on signals output from the first travel operator, the second travel operator, and the actuator operator,
- wherein the controller:
- opens the first open-close valve and closes the second open-close valve when a signal is output from the first travel operator and/or the second travel operator and no signal is output from the actuator operator, thereby causing the first hydraulic pump to supply hydraulic oil to the first travel switch valve and/or causing the second hydraulic pump to supply hydraulic oil to the second travel switch valve and closing the communication valve;
- and
- on the other hand, when signals are output from the first travel operator, the second travel operator, and the actuator operator, causes hydraulic oil to be supplied from the first hydraulic pump to the actuator switch valve, and by closing the first open-close valve and opening the second open-close valve, causes hydraulic oil to be supplied from the second hydraulic pump to the first travel switch valve and the second travel switch valve, and at the same time, adjusts an opening degree of the communication valve in response to the signal output from the actuator operator to control an amount of hydraulic oil supplied from the first pump line to the second pump line.