A hydraulic drive apparatus includes a flow-path selector valve and a flow-path switching control unit that operates the valve. The flow-path selector valve has a first position for a single operation state and a second position for a combined operation state, configured to, at the first position, form a first flow path connected to a first pump, a second flow path connected to a second pump, and a connecting flow path providing communication between the first flow path and the second flow path. When a driving state of a work actuator is deviated from an allowable range in the combined operation state, the flow-path switching control unit reduces an opening area of the connecting flow path as compared with that when the driving state is within the allowable range.

Disclosed is a hydraulic control apparatus including a flow-path selector valve that switches a supply flow path and a flow-path switching control unit that operates the same, a regeneration valve and a regeneration release valve capable of the regenerative operation, and a regeneration control unit that operates the same. The flow-path switching control unit makes the flow-path selector valve form a flow-path providing communication between first and second pumps in a combined operation state. The regeneration control unit judges the propriety of the regenerative operation on the basis of the second pump pressure which is the discharge pressure of the second pump in a single operation state and judges the propriety of the regenerative operation on the basis of whether or not the driving state of the work actuator is within an allowable range corresponding to the target work operation amount in the combined operation state.

Provided is a construction machine. The construction machine includes a boom cylinder driving a boom, a rotation motor rotating a rotary body, an arm cylinder driving an arm, a bucket cylinder driving a bucket, a first main pump supplying working fluid to the boom cylinder and discharging the working fluid in opposite directions, a second main pump supplying working fluid to the rotation motor and discharging the working fluid in opposite directions, and a third main pump supplying working fluid to the arm cylinder or the bucket cylinder.

A work vehicle includes computing system is configured to receive a first and seconds inputs associated with controlling an operation of first and second hydraulic loads. Furthermore, the computing system is configured to control the operation of the first or second flow control valve corresponding to the one of the first or second hydraulic loads associated with the greater hydraulic fluid pressure based on the corresponding received first or second input. Additionally, the computing system is configured to determine the first or second pressure of the hydraulic fluid being supplied to another of the first or second hydraulic loads. Moreover, the computing system is configured to control the first or second flow control valve corresponding to the other of the first or second hydraulic loads based on the corresponding received first or second input and the determined first or second pressure.

The object of the present invention resides in provision of a construction machine in which a hydraulic cylinder can be driven in a high efficiency by an accumulator. To this end, the construction machine including: a hydraulic cylinder; a first accumulator that accumulates return fluid from the hydraulic cylinder with a first set pressure; a tank that stores hydraulic fluid therein; a first hydraulic pump that delivers the hydraulic fluid sucked from the tank; a hydraulic actuator that is driven by the first hydraulic pump; and a second accumulator that accumulates return fluid from the hydraulic actuator with a second set pressure, includes a first control valve placed in a first hydraulic line that connects the first accumulator and the hydraulic cylinder to each other, and a second control valve placed in a second hydraulic line that connects the second accumulator and the hydraulic cylinder to each other. The second set pressure is set to a value higher than that of the first set pressure.

A work vehicle a computing system configured to receive first and second input associated with controlling the operation of the first and second hydraulic load, respectively. Furthermore, the computing system is configured to control the operation of a first or second flow control valve corresponding to the one of the first or second hydraulic loads associated with the greater hydraulic fluid pressure such that the corresponding adjustable orifice is at a maximum flow position. Additionally, the computing system is configured to determine the first and second pressures of the hydraulic fluid being supplied to the first or second hydraulic loads. Moreover, the computing system is configured to control the operation of the first or second flow control valve corresponding to another of the first or second hydraulic loads based on the corresponding received first or second input and the determined first and second pressures.

When a first control valve and a second control valve are in non-neutral positions, respectively, a fifth fluid passage and a second fluid passage are closed, thereby generating a first pressure within a fifth portion of the fifth fluid passage and a second pressure within a second portion of the second fluid passage, so that the first pressure is applied to a first valve through a fourth fluid passage to move the first valve to close the third fluid passage and a second pressure is applied to the confluence valve through a first fluid passage to move the confluence valve to a confluence position. When the confluence valve is in the confluence position, the confluence valve directs working fluid from a first working fluid supply to the second control valve.

To enable to arbitrarily change a hydraulic pump which supplies pressure oil to a hydraulic actuator at first in a hydraulic control system equipped with the hydraulic actuator using both first and second hydraulic pumps as a pressure oil source. An operation means is installed which can arbitrarily change working order of the first flow rate control valves for boom and stick for controlling the supply flow rate from first hydraulic pump to boom cylinder and stick cylinder and second flow rate control valves for boom and stick for controlling the supply flow rate from second hydraulic pump to boom cylinder and stick cylinder.

A working machine includes a machine body, a first hydraulic actuator mounted on the machine body, a first control valve that controls the first hydraulic actuator, a controller that controls the first control valve, and a second hydraulic actuator that is different from the first hydraulic actuator. When the second hydraulic actuator and the first hydraulic actuator are operated in combination, the controller reduces the amount of change in the flow rate of a hydraulic fluid supplied from the first control valve to the first hydraulic actuator with respect to changes in a manipulation amount to operate the first hydraulic actuator to a value smaller than that when the first hydraulic actuator is solely operated.

Provided is a work machine which can achieve both of excellent operability when an operator manually operates a machine body or a work device and an accuracy of control of the machine body or the work device when a controller performs automatic control. The controller is configured to, in a case where the automatic control function selector switch gives an instruction to disable the automatic control function, adjust an opening amount of a bleed-off valve to a maximum opening amount or an opening amount corresponding to input amounts of control levers, and in a case where the automatic control function selector switch gives the instruction to enable the automatic control function, adjust the opening amount of the bleed-off valve, in at least part of an operation region of the control levers, so as to be smaller than the opening amount with the instruction to disable the automatic control function being given.