A hydraulic system for a work vehicle includes a first pump providing a first flow to a first circuit. A first pressure sensor measures a first pressure in the first circuit. A first swashplate angle sensor measures a first angle of a first swashplate of the first pump. A supplemental pump provides a supplemental flow to a supplemental circuit. A supplemental pressure sensor measures a supplemental pressure in the supplemental circuit. A supplemental valve adjusts the load sense signal provided to a supplemental load sensing compensator of the supplemental pump. A first valve selectively enables flow from the supplemental circuit to the first circuit when the supplemental pressure is equal to or greater than the first pressure. A controller determines to operate the supplemental pump in one of a standby condition and a use condition based in part on the first angle of the first swashplate.

A hydraulic system for a work vehicle includes a first pump with a first swashplate providing a first flow in a first circuit and a second pump with a second swashplate providing a second flow in a second circuit. A supplemental pump with a supplemental swashplate provides a supplemental flow to a supplemental circuit. A first valve selectively enables flow from the supplemental circuit to the first circuit. A second valve selectively enables flow from the supplemental circuit to the second circuit. A controller determines to operate the supplemental pump in one of a standby condition and a use condition based in part on a first angle of the first swashplate and a second angle of the second swashplate.

A hydraulic system for a work vehicle includes a first pump providing a first flow in a first circuit having a first pressure. A first load sense circuit connected to a first load sensing compensator of the first pump. The first load sense circuit having a first load sense pressure. A supplemental pump provides a supplemental flow to a supplemental circuit having a supplemental pressure. A supplemental load sense circuit connected to a supplemental load sensing compensator of the supplemental pump. A first supplemental valve selectively enables flow from the first load sense circuit to the supplemental load circuit based in part on a first pressure differential between the first pressure and the first load sense pressure. A first valve selectively enables flow from the supplemental circuit to the first circuit when the supplemental pressure is equal to or greater than the first pressure.

The present invention provides an engineering machinery hydraulic system with compensation differential pressure controllable, uses an electronic pressure compensating valve to solve the problem of flow mismatch under conditions of pressure over-limit and flow saturation, and realizes proportional shunt control and high-precision flow distribution of the system. The engineering machinery hydraulic system disclosed in the present invention has the advantages of low energy consumption, fast response speed, and high flow control precision.

A hydraulic system includes first and second valve assemblies connected to a common pump. The first valve assembly includes a main valve housed inside a manifold. A pressure compensator valve maintains a constant pressure drop across a variable orifice of the main valve. A pressure limiter valve is in communication with the main valve and the pressure compensator valve, and allows an actuator connected to the first valve assembly to operate independently of the second valve assembly so that fluid flow to a work port of the first valve assembly is not interrupted by operation of the second valve assembly.

A hydraulic arrangement is disclosed for distributing a fluid in pressure coming from a source of fluid in pressure among hydraulic units of a work vehicle. The hydraulic arrangement includes a priority valve configured to divide the flow of the fluid source between a subset of the hydraulic units on the base of an equivalent load sensing signal derived from the hydraulic units. The hydraulic arrangement further includes by-pass means fluidly interposed between the source and the subset of the hydraulic units and configured to allow direct passage of fluid by-passing priority valve from the source to the subset of the hydraulic units according to a predefined condition.

A hydraulic control arrangement for simultaneously supplying at least two hydraulic consumers with predefinable individual pressure medium flow rates includes a hydraulic pump having an adjustable swept volume, and at least two valve arrangements each including a variable metering restrictor and a pressure balance arranged downstream of the variable metering restrictor. Each pressure balance is configured to be acted on in an opening direction by pressure downstream of the respective variable metering restrictor and to be acted on in a closing direction by a highest load pressure or by a pressure derived therefrom. Each valve arrangement is arranged between a pump line, which leads away from the hydraulic pump, and a consumer of the at least two hydraulic consumers. The arrangement further includes an electronic control device, by which the hydraulic pump is actuatable such that it conveys a sum of the predefinable individual pressure medium flow rates.

Even where the differential pressure across a directional control valve associated with each actuator is very small, flow dividing control of the plurality of directional control valves can be performed stable, and even where a demanded flow rate suddenly changes at the time of transition from composite action to single action or the like, a sudden change of the flow rate of hydraulic fluid to be supplied to each actuator is prevented to implement superior combined operability. Further, the meter-in loss of the directional control valves can be reduced to implement a high energy efficiency. To this end, a plurality of pressure compensating valves 7a, 7b and 7c for controlling such that the pressure in the downstream side of the meter-in opening of a plurality of directional control valves 6a, 6b and 6c becomes equal to the highest load pressure are individually arranged in the downstream side of meter-in openings of the plurality of directional control valves 6a, 6b and 6c, and demanded flow rates for the directional control valves 6a, 6b and 6c are calculated from input amounts of operation levers. Besides, the meter-in pressure loss of a predetermined directional control valve is calculated from the demanded flow rates for and meter-in opening areas of the directional control valves 6a, 6b and 6c, and the set pressure of the unloading valve 15 is controlled using the value of the meter-in pressure loss.

A control device for a hydraulic machine such as a revolving excavator work machine in which a load-sensing pump control system is adopted The control device prevents variation in pump control characteristics among a plurality of hydraulic machines and also prevents variation in the operating speed of individual drive units in the hydraulic machines The control device; and it is configured to perform, by using a storage unit and a calculation unit outside the hydraulic machine, a process of causing an engine rotation state and a hydraulic actuator operation state to be specific states and calculating a correction rate for a control output value of an electromagnetic proportional valve for generating a control pressure, based on detection of an error in the flow rate of a hydraulic pump or its substitute numerical value such as the rotational speed and the like of a traveling motor which is easily detectable from outside.

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.