A construction machine that precisely enables derivation of the operation characteristics of hydraulic actuators in a high-velocity area with less calibration operation is provided. A controller (10) has a calibration mode in which the controller (10) derives operation characteristics (α(xs)) representing a relation among a spool position (xs) of a meter-in valve (8a1), an operation velocity (Va) of a hydraulic actuator (4a), and a differential pressure (ΔP) across the meter-in valve (8a1), and is configured to, in a case where the spool position (xs) of the meter-in valve (8a1) has changed in a direction to increase the opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to increase the opening area of a bleed-off valve (8b1) to a bleed-off solenoid proportional pressure-reducing valve (8b2) as a command signal to reduce the differential pressure (ΔP).

Provided is a hydraulic drive apparatus including a specific working actuator making a working arm perform a traveling assist motion upon the slip, first and second traveling motors, first and second hydraulic pumps, a traveling selector valve switchable to a neutral position and a straight traveling position, a communication throttle portion between a working fluid passage and a traveling fluid passage in the straight traveling position, and a switching control part switching the traveling selector valve to the neutral position when a single operation action is performed and to the straight traveling position when a specific combined operation action including a forward traveling operation and the specific working operation is performed. The switching control section adjusts the opening of the communication throttle section to decrease the flow rate therethrough with an increase in the difference between the first and second pump pressures.

There is provided a work machine which can improve accuracy of control of an actuator when a pressure difference between a hydraulic pump and the actuator is large and the demanded flow rate of the actuator is small. An auxiliary flow rate controller is configured such that an opening area of a main valve changes between a maximum opening area and zero according to the opening area of a pilot variable restrictor when the opening area of the pilot variable restrictor is equal to or more than a predetermined opening area and that the opening area of the main valve is zero irrespective of the opening area of the pilot variable restrictor when the opening area of the pilot variable restrictor is less than the predetermined opening area.

A hydraulic system is provided. The hydraulic system may include a fluid pressure source in fluid communication with a supply line, a return line in fluid communication with a tank, a hydraulic function having a workport, a first control valve having a first proportional solenoid, a second control valve having a second proportional solenoid, and a controller. The controller being configured to selectively energize the first proportional solenoid, the second proportional solenoid, or the first proportional solenoid and the second proportional solenoid to control a system pressure differential, defined between the return line and the workport, within a range that is defined by a sum of a first predefined range defined by the first control valve and a second predefined range defined by the second control valve.

A balancing valve includes four ports. While the pressures at a pair of balancing ports of a hydraulic balancing valve are equal, the valve maintains two other ports in a closed position. Upon a pressure differential between the balancing ports, fluid communication can occur between one of the balancing ports and either of the other ports based upon the direction of the pressure differential. A hydraulic ride control system utilizes the balancing valve together with other control valves to provide ride control functionality.

A valve, in particular for use as a pressure compensator or maintenance-type component (38) in hydraulically actuated hoisting devices (2), has a valve housing (54) with a control port (40), a fluid inlet (64) and a fluid outlet (66). A regulating piston (68) is longitudinally displaceably in the valve housing (54) and acts against an energy storage device (70) in the form of a compression spring, bringing the regulating piston (68) into positions forming a fluid-conveying connection between the fluid inlet (40) and the fluid outlet (66) or blocking this connection by a control pressure existing at the control port (40). A first orifice (88) in the regulating piston (68) connects the control port (40) to a receiving space (62) for the energy storage device (70) in a fluid-conveying manner. A second orifice (90) is in an intermediate part (72) in the valve housing (54). The receiving space (62) can be connected to a compensating chamber (92), which connected to the fluid outlet (66) in a fluid-conveying manner (98).

A construction machine that precisely enables derivation of the operation characteristics of hydraulic actuators in a high-velocity area with less calibration operation is provided. A controller (10) has a calibration mode in which the controller (10) derives operation characteristics (α(xs)) representing a relation among a spool position (xs) of a meter-in valve (8a1), an operation velocity (Va) of a hydraulic actuator (4a), and a differential pressure (ΔP) across the meter-in valve (8a1), and is configured to, in a case where the spool position (xs) of the meter-in valve (8a1) has changed in a direction to increase the opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to increase the opening area of a bleed-off valve (8b1) to a bleed-off solenoid proportional pressure-reducing valve (8b2) as a command signal to reduce the differential pressure (ΔP).

A system for controlling hydraulic fluid flow within a work vehicle includes a pilot conduit configured to receive a pilot flow of hydraulic fluid from a fluid supply conduit such that the operation of a compensator valve is controlled based on a pressure of the pilot flow within the pilot conduit. Furthermore, a pilot conduit valve is configured to adjust the pressure of the pilot flow within the pilot conduit. In addition, the system includes a load sense conduit configured to receive a bleed flow of the hydraulic from the fluid supply conduit such that the operation of the pump is controlled based on a pressure of the bleed flow within the load sense conduit. Moreover, a load sense valve is configured to adjust the pressure of the bleed flow within the load sense conduit.

A crane hydraulic system and a controlling method of the system is provided in order to fundamentally reduce impact in start and stop operations of a load sensing winch system. The load sensing subsystem is arranged, at the start and stop moments of a winch system, the pressure compensator can be opened, and the variable pump oil inlet line communicates with the oil return line to realize pressure relief, so as to reduce the pressure impact.

A passive fluidic valve for fixed flow rate distribution comprising: a hollow valve body; a valve member for blocking a passage to one of the two outlets; and communications to impose the pressure of the upstream and downstream cavities at the ends of the valve member. The valve body further comprises: an inlet; a first outlet comprising a first restriction delimiting an upstream cavity and a downstream cavity; a second outlet comprising a second restriction delimiting an upstream cavity and a downstream cavity; and a first and a second cavity. The valve member further comprises: a first end in the first cavity delimiting a first and a third chambers, and a second end in the second cavity delimiting a second and a fourth chambers.