A double-power-supply complex control device includes a main body. Four control sections and two load flow ways are disposed in the main body. A main flow way is disposed in control section. Four switch members of a switch assembly are assembled and disposed in the main flow ways. A circumference of each main flow way is in communication with multiple bypasses. The main flow ways of each two of the control sections are in communication with a fluid output passage and a fluid input passage of a power device. Some of the bypasses of control section are in communication with each other. A lower flow guide window is disposed on switch member in indirect communication with main flow way. When switch member is operated under external force, the lower flow guide window is switchable between the bypasses to selectively communicate with the bypasses to make different power devices drive.

A hydraulic system includes a first hydraulic actuator, a second hydraulic actuator, a first pump to supply operation fluid to the first hydraulic actuator, a second pump to supply operation fluid to the second hydraulic actuator, a second control valve to control operation fluid to be supplied from the second pump to the second hydraulic actuator, and a first control valve including a main control valve to control operation fluid to be supplied from the first pump to the first hydraulic actuator, and a subordinate control valve configured to control operation fluid to be supplied from the second pump to the second control valve and to the first hydraulic actuator. The operation fluid supplied from the second pump is confluent with operation fluid to be supplied from the first pump to the first pump, in a case of activating both of the first hydraulic actuator and the second hydraulic actuator.

A hydraulic control apparatus includes an output-side oil passage into which oil from a first oil passage and oil from a second oil passage flow, and a pressure regulating check valve regulating a hydraulic pressure in the second oil passage. The pressure regulating check valve includes first and second elastic portions housed in a spool hole between a valve body and a bottom of the spool hole. A natural length of the second elastic portion is shorter than a distance between the valve body and the bottom when the valve body closes an inflow hole. The second elastic portion applies an elastic force to the valve body in a state in which the valve body opens the inflow hole.

There is provided a work machine that is capable of realizing operability and energy saving ability that are equivalent to those of work machines that have a joint line to be used during swinging/boom raising operation, without incorporating a joint line for supplying a pressurized fluid from a second pump to a bottom-side chamber of a boom cylinder. The controller is configured to compute a hypothetical flow rate representing a flow rate in a hypothetical joint line, compute a first pump provisional target flow rate on the basis of an operation amount of a boom operation device, compute a second pump provisional target flow rate on the basis of an operation amount of a swing operation device, compute a first pump final target flow rate by adding the hypothetical flow rate to the first pump provisional target flow rate, and compute a second pump final target flow rate by subtracting the hypothetical flow rate from the second pump provisional target flow rate.

A digital pump axis control system having a circuit including an electric engine, powering first and second hydraulic machines connected in a rotationally locked manner to each other. At least one cylinder has a first chamber connected through a first pipeline to the first hydraulic machine and a second chamber of the cylinder is connected through a second pipeline to the second hydraulic machine. A first valve is arranged in the first pipeline; a second valve is arranged in the second pipeline; a third valve is arranged in a third pipeline, wherein the third pipeline connects a portion of the first pipeline between the first hydraulic machine and the first valve and a portion of the second pipeline between the second hydraulic machine and the second valve. An open tank provides hydraulic fluid to inlets of the first and second hydraulic machines. The first and second hydraulic machines are digital variable displacement pumps, each providing a positive and a negative displacement of hydraulic fluid.

A first required flow rate is calculated as a function of a first maximum allowable flow rate and a value of a first signal. A second required flow rate is calculated as a function of a value of the second signal. When the first maximum allowable flow rate is higher than a first capacity, the value of the first signal is a maximum level, and the value of the second signal is equal to or higher than a minimum level and equal to or lower than a maximum level, a first working fluid supply is controlled to discharge working fluid at a flow rate equal to the first capacity, and a second working fluid supply is controlled to discharge working fluid at a flow rate obtained by deducting the first capacity from the first maximum allowable flow rate, added to the second required flow rate.

An object of the present invention is to provide a construction machine that has a hydraulic closed-circuit system mounted therein and capable of selectively connecting some of a plurality of hydraulic pumps driven by two engines to any one of a plurality of hydraulic actuators and that can downsize the engines while maintaining high work efficiency. A controller 80 includes an actuator/engine allocation computing section F6 that, at the time of connecting closed-circuit pumps that are not connected to any of the hydraulic actuators 1, 3, 5, and 7 to any one of the hydraulic actuators, allocates closed-circuit pumps driven by a right engine 9b to the one hydraulic actuator in a case in which an estimated maximum load on a left engine 9a is heavier than an estimated maximum load on the right engine, and allocates closed-circuit pumps driven by the left engine to the one hydraulic actuator in a case in which the estimated maximum load on the right engine is heavier than the estimated maximum load on the left engine.

A hydraulic system includes a hydraulic pump to output an operation fluid, first and second hydraulic devices to be operated by the operation fluid, first and second control valves to control the first and second hydraulic device, respectively, first and second communication tubes connecting the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve, the supply fluid tube being configured to supply the return fluid to the second control valve, first and second connection fluid tubes disposed on the first control valve, a discharge fluid tube connected to the first control valve, first and second branching fluid tubes branched from the first and second connection fluid tubes, respectively, first and second throttles disposed on the first and second branching fluid tubes, respectively, the second throttle being smaller than the first throttle.

A first required flow rate is calculated as a function of a first maximum allowable flow rate and a value of a first signal. A second required flow rate is calculated as a function of a value of the second signal. When the first maximum allowable flow rate is higher than a first capacity, the value of the first signal is a maximum level, and the value of the second signal is equal to or higher than a minimum level and equal to or lower than a maximum level, a first working fluid supply is controlled to discharge working fluid at a flow rate equal to the first capacity, and a second working fluid supply is controlled to discharge working fluid at a flow rate obtained by deducting the first capacity from the first maximum allowable flow rate, added to the second required flow rate.

An object of the present invention is to provide a construction machine that has a hydraulic closed-circuit system mounted therein and capable of selectively connecting some of a plurality of hydraulic pumps driven by two engines to any one of a plurality of hydraulic actuators and that can downsize the engines while maintaining high work efficiency. A controller 80 includes an actuator/engine allocation computing section F6 that, at the time of connecting closed-circuit pumps that are not connected to any of the hydraulic actuators 1, 3, 5, and 7 to any one of the hydraulic actuators, allocates closed-circuit pumps driven by a right engine 9b to the one hydraulic actuator in a case in which an estimated maximum load on a left engine 9a is heavier than an estimated maximum load on the right engine, and allocates closed-circuit pumps driven by the left engine to the one hydraulic actuator in a case in which the estimated maximum load on the right engine is heavier than the estimated maximum load on the left engine.