Hydraulic control device for work machine

A hydraulic control apparatus to be provided in a work machine that includes a first traveling body and a second traveling body, which are provided on the left and right and configured to perform respective traveling motions, and a work attachment configured to perform a work motion, the hydraulic control apparatus comprising:

• a first pump that discharges hydraulic fluid;
• a second pump that is separately provided from the first pump and discharges hydraulic fluid:
• a first traveling motor that is driven by supply of hydraulic fluid to make the first traveling body perform the traveling motion;
• a second traveling motor that is driven by supply of hydraulic fluid to make the second traveling body perform the traveling motion;
• a work actuator that is driven by supply of hydraulic fluid to make the work attachment perform a target work motion included in the work motion;
• a flow-path selector valve configured to make a flow-path switching motion for switching a flow path of hydraulic fluid discharged by the first pump and the second pump, the flow-path switching motion being a motion of being shifted between a first position for forming a flow path for allowing hydraulic fluid discharged from the first pump to be supplied to the first traveling motor and allowing hydraulic fluid discharged from the second pump to be supplied to the second traveling motor and the work actuator without being supplied to the first traveling motor and a second position for forming a first flow path for allowing hydraulic fluid discharged from the first pump to be supplied to the work actuator and a second flow path for allowing hydraulic fluid discharged from the second pump to be supplied to the first traveling motor and the second traveling motor and forming a communication flow path providing communication between the first flow path and the second flow path, the communication flow path having an opening area variable by the flow-path switching motion;
• a driving state detector that detects a physical quantity which is an index of a driving state of the work actuator and varied with a variation in the load of the work actuator;
• and
• a flow-path switching control unit that makes the flow-path selector valve perform the flow-path switching motion, the flow-path switching control unit configured to shift the flow-path selector valve to the first position in a single operation state where only one of a target work operation that is an operation for making the work attachment perform the target work motion and a traveling operation that is an operation for making the first traveling motor and the second traveling motor perform the respective traveling motions and configured to shift the flow-path selector valve to the second position in a combined operation state where the target work operation and the traveling operation are simultaneously performed, wherein
• the flow-path switching control unit stores an allowable range of the physical quantity, the allowable range being set in correspondence with a target work operation amount which is a magnitude of the target work operation, and operates the flow-path selector valve so as to make the opening area of the communication flow path smaller in a case where the physical quantity detected by the driving state detector in the combined operation state is deviated from the allowable range corresponding to the target work operation amount than the opening area in a case where the detected physical quantity is within the allowable range,
• the driving state detector is a speed detector that detects a target work motion speed which is a speed of the target work motion, as the physical quantity to be the index of the driving state, and
• the flow-path switching control unit stores a speed allowable value that is preset in correspondence with the target work operation amount, and makes the opening area of the communication flow path smaller, in a case where the target work motion speed detected by the speed detector is equal to or less than the speed allowable value corresponding to the target work operation amount, than that in a case where the target work motion speed is greater than the speed allowable value.

A hydraulic control apparatus to be provided in a work machine that includes a first traveling body and a second traveling body, which are provided on the left and right and configured to perform respective traveling motions, and a work attachment configured to perform a work motion, the hydraulic control apparatus comprising:

• a first pump that discharges hydraulic fluid;
• a second pump that is separately provided from the first pump and discharges hydraulic fluid:
• a first traveling motor that is driven by supply of hydraulic fluid to make the first traveling body perform the traveling motion;
• a second traveling motor that is driven by supply of hydraulic fluid to make the second traveling body perform the traveling motion;
• a work actuator that is driven by supply of hydraulic fluid to make the work attachment perform a target work motion included in the work motion;
• a flow-path selector valve configured to make a flow-path switching motion for switching a flow path of hydraulic fluid discharged by the first pump and the second pump, the flow-path switching motion being a motion of being shifted between a first position for forming a flow path for allowing hydraulic fluid discharged from the first pump to be supplied to the first traveling motor and allowing hydraulic fluid discharged from the second pump to be supplied to the second traveling motor and the work actuator without being supplied to the first traveling motor and a second position for forming a first flow path for allowing hydraulic fluid discharged from the first pump to be supplied to the work actuator and a second flow path for allowing hydraulic fluid discharged from the second pump to be supplied to the first traveling motor and the second traveling motor and forming a communication flow path providing communication between the first flow path and the second flow path, the communication flow path having an opening area variable by the flow-path switching motion;
• a driving state detector that detects a physical quantity which is an index of a driving state of the work actuator and varied with a variation in the load of the work actuator;
• and
• a flow-path switching control unit that makes the flow-path selector valve perform the flow-path switching motion, the flow-path switching control unit configured to shift the flow-path selector valve to the first position in a single operation state where only one of a target work operation that is an operation for making the work attachment perform the target work motion and a traveling operation that is an operation for making the first traveling motor and the second traveling motor perform the respective traveling motions and configured to shift the flow-path selector valve to the second position in a combined operation state where the target work operation and the traveling operation are simultaneously performed, wherein
• the flow-path switching control unit stores an allowable range of the physical quantity, the allowable range being set in correspondence with a target work operation amount which is a magnitude of the target work operation, and operates the flow-path selector valve so as to make the opening area of the communication flow path smaller in a case where the physical quantity detected by the driving state detector in the combined operation state is deviated from the allowable range corresponding to the target work operation amount than the opening area in a case where the detected physical quantity is within the allowable range,
• the driving state detector detects an actuator thrust that is a thrust of the work actuator, as the physical quantity to be the index of the driving state, and
• the flow-path switching control unit stores a thrust allowable value that is preset in correspondence with the target work operation amount, and makes the opening area of the communication flow path smaller, in a case where the actuator thrust detected by the driving state detector is equal to or greater than the thrust allowable value corresponding to the target work operation amount, than the opening area in a case where the actuator thrust is less than the thrust allowable value.