A hydraulic excavator drive system includes: a first pump that supplies hydraulic oil to a boom cylinder via a boom control valve, and supplies the hydraulic oil to a bucket cylinder via a first bucket control valve; a second pump that supplies the hydraulic oil to an arm cylinder via an arm control valve; a third pump that supplies the hydraulic oil to a slewing motor via a slewing control valve, and supplies the hydraulic oil to the bucket cylinder via a second bucket control valve; and a controller that moves one of the first bucket control valve and the second bucket control valve when a bucket excavating operation or a bucket dumping operation is performed concurrently with another operation, and moves both the first bucket control valve and the second bucket control valve when a bucket excavating operation is performed alone.

A hydraulic excavator drive system includes: a first pump that supplies hydraulic oil to a boom cylinder via a boom control valve, and supplies the hydraulic oil to a bucket cylinder via a first bucket control valve; a second pump that supplies the hydraulic oil to an arm cylinder via an arm control valve; a third pump that supplies the hydraulic oil to a slewing motor via a slewing control valve, and supplies the hydraulic oil to the bucket cylinder via a second bucket control valve; and a controller that moves one of the first bucket control valve and the second bucket control valve when a bucket excavating operation or a bucket dumping operation is performed concurrently with another operation, and moves both the first bucket control valve and the second bucket control valve when a bucket excavating operation is performed alone.

Provided is a hydraulic circuit, for a construction machine, which drives an actuator by merging pressure oil from a fixed-volume pump into a center bypass oil path from a variable-volume pump to an oil tank, wherein the flow rate of flow from the fixed-volume pump to the center bypass oil path can be controlled in accordance with a requested flow rate of the actuator. A distribution direction-switching valve, which has a first oil path from a fixed-volume pump to an oil tank and a second oil path from the fixed-volume pump to a first center bypass oil path, has a first signal reception unit which causes a spool to slide in a direction in which the first oil path is formed, and a second signal reception unit which causes a spool to slide in a direction in which the second oil path is formed, and determines a distribution ratio of pressure oil flowing to the first oil path and the second oil path in accordance with the difference in size of the signals received by the first signal reception unit and the second signal reception unit, the first signal reception unit receiving a signal based on a negative control signal.

The hydraulic excavator 1 includes a work implement 7, a detection device that detects an obstacle around the hydraulic excavator 1, and a controller 27 that controls the operation of the work implement 7. The controller 27 has a driving assistance function and a work assistance function. The work assistance function is switchable between enabled and disabled. When the work assistance function is switched to enabled, the controller 27 suppresses, for an obstacle detected in a monitoring range but outside of a work range, the driving assistance function in comparison with when the work assistance function is switched to disabled.

A hydraulic system of a working machine includes a hydraulic pump to output a hydraulic fluid, at least one proportional valve to deliver the hydraulic fluid to a supply target, a valve body including the proportional valve, a heat-up fluid passage in the valve body and into which the hydraulic fluid flows, a switching valve switchable between an open position in which the hydraulic fluid passing through the heat-up fluid passage is supplied to a hydraulic device and a closed position in which the hydraulic fluid is not supplied thereto and the hydraulic fluid from the hydraulic device is to be returned, a controller to operate the switching and proportional valves, and a return circuit through which the hydraulic fluid flowing into the heat-up fluid passage is returned as a result of at least one of the switching and proportional valves being operated by the controller.

To make it possible to prevent a decrease in work speed due to a decrease in the speed of a given actuator when an operator unintentionally performs a fine operation of the control lever of the other actuator in a state in which the given actuator is driven by the hydraulic fluid delivered from a plurality of pumps, a controller (41) sets, as a composite dead zone line serving as a boundary of a composite dead zone, a composite dead zone line such that as an operation amount in one direction of a control lever (12L) or (13L) of a control lever device (12) or (13) is increased, the width of the composite dead zone corresponding to an operation amount in the other direction of the control lever is widened, and corrects the operation amount in the other direction such that the demanded flow rate of an actuator increases from zero, when the control lever is operated in the other direction in a state in which the operation amount in the one direction of the control lever remains within a range of the composite dead zone, and the operation amount in the other direction exceeds the composite dead zone line.

A vehicle includes: a prime mover; a hydraulic fluid manifold; a hydraulic machine; a hydraulic accumulator; one or more hydraulic actuators; a valve arrangement; and a controller. The controller is configured to receive an actuator demand signal indicative of a demand to move the one or more hydraulic actuators; and to control the hydraulic machine and the valve arrangement to cause movement of the one or more actuators in accordance with the actuator demand signal by bringing the hydraulic accumulator into fluid communication with a first actuator chamber of the one or more hydraulic actuators, and to synchronise therewith changing a pressure in a second actuator chamber of the one or more hydraulic actuators. The second actuator chamber is in fluid communication with the hydraulic machine.

Systems and apparatuses include a primary hydraulic pump including a primary displacement actuator and a primary pressure port, a primary load sense system fluidly coupled to the primary displacement actuator, a secondary hydraulic pump including a secondary displacement actuator and a secondary pressure port, a secondary load sense system fluidly coupled to the secondary displacement actuator, and a crossover pressure controller coupled between the primary pressure port and the secondary pressure port and including: a selectively energizable crossover pressure solenoid, and a crossover pressure spool movable by the crossover pressure solenoid between a combined pressure position providing fluid communication between the primary pressure port and the secondary pressure port, and a separate pressure position inhibiting fluid communication between the primary pressure port and the secondary pressure port.

The present invention relates to a hydraulic system comprising a first actuator, a first variable displacement pump fluidly connected to the first actuator via a first circuit and adapted to drive the first actuator. The system further comprises a second actuator and a second pump fluidly connectable to the second actuator via a second circuit and adapted to drive the second actuator, wherein the second pump is fluidly connectable to the first actuator via a first control valve, and wherein the second pump is fluidly connectable to the second actuator via a second control valve.

A working machine includes a prime mover, a hydraulic pump to be driven by power of the prime mover and to output operation fluid, a hydraulic actuator to be operated by the operation fluid, and a control device. The control device has a revolving-speed controller to increase and decrease a revolving speed of the prime mover, a first setting portion to set a limit value of the revolving speed of the prime mover, and a revolving-speed limiter to limit the revolving speed of the prime mover set by the revolving-speed controller to the limit value set by the first setting portion.