The present disclosure relates to a load-sense system such as a load-sense steering system that operates in a static load-sense mode for low flows and operates in a dynamic load-sense mode for high flows.

Provided is a working vehicle capable of increasing lifting operation speed of a working device without increasing cost, even when provided with a circuit configuration that prioritizes a steering operation over a working device operation. A wheel loader 1 comprises a priority valve 451 configured to allow hydraulic oil discharged from a hydraulic pump 41 to flow into a steering drive circuit 43 preferentially over a working device drive circuit 44, and further comprises: an electric steering lever 30; a pair of solenoid control valves 34A, 34B configured to control a steering directional control valve 33; and a controller 5. The controller 5 is configured to control the pair of solenoid control valves 34A, 34B so as to limit operation speed of a steering 3 when determining that an engine 40 is in a low idle state and a lift arm 21 is performing a lifting operation.

A pressure supply device for prioritised volume flow splitting, in particular in mobile working machines, includes at least one adjusting pump (2) controllable by an LS signal as main pump, a constant-displacement pump (4) as an auxiliary pump, and two pressure balances. A system is supplied primarily, in particular in the form of steering hydraulics (PL), which outputs an LS signal. A system is supplied secondarily, which outputs a further LS signal, in particular in the form of working hydraulics (PA). A further system is supplied hydraulically, in particular in the form of brake hydraulics (PB). One pressure balance (DW1) is used to supply the system (PL) to be supplied primarily and/or the further hydraulic system (PB), the other pressure balance (DW2) is used to supply the system (PL) to be supplied primarily and/or the system (PA) to be supplied secondarily, The respective pressure balance (DW1, DW2) can be activated by an LS signal in such a way that the constant-displacement pump (4) is also used to supply the system (PA) to be supplied secondarily.

Disclosed embodiments include steering circuits utilizing a controllable cross-feed loop between left and right drive motor sides of an articulated power machine to reduce skidding caused by a turning operation in which an articulation actuator changes an articulation joint angle between a front frame member and a rear frame member of the power machine.

A hydraulic steering arrangement (1) including a supply port (2), a return port (4), a working port arrangement having two working ports (5, 6), a main flow path (7) between the supply port (2) and one of the working ports (5) and a return flow path (8) between the other working port (6) and the return port (4), wherein the main flow path (7) includes a main orifice (A1), a flow meter (9), a first flow meter orifice (A2) upstream the flow meter (9), a second flow meter orifice (A3) downstream the flow meter (9), and a first working port orifice (A4), the return flow path (8) includes a second working port orifice (A5), a load sensing point (17) is arranged between the main orifice (A1) and the first flow meter orifice (A2), a drain orifice (Ad) is arranged between the load sensing point (17) and the return port (4), and a priority valve arrangement (10) is arranged between the supply port (2) and the main orifice (A1). Such a steering arrangement should enable a high steering speed without loss of comfort. To this end a load sensing port (16) of the priority valve arrangement (10) is connected to the load sensing point (17), characterized in that a priority outlet (CF) of the priority valve arrangement (10) is directly connected to the main orifice (A1), the load sensing port (16) of the priority valve arrangement (10) is directly connected to the load sensing point (17) and the main flow path (7) includes a check valve (24) between the load sensing point (17) and the working port (5) of the main flow path (7), the check valve (24) opening in a direction towards the working port (5).

A hydraulic control device includes: a hydraulic pump connected in parallel to steering and boom cylinders; a steering control valve that controls the direction of operating oil flowing through the steering cylinders; a boom control valve that connects the hydraulic pump to a tank when the valve is at a neutral position and controls the direction of the oil flowing through the boom cylinders when the valve is at an offset position; a meter-in pressure compensator that increases flow rate of the oil flowing through a variable restrictor of the steering control valve in accordance with pressure in front of and behind the restrictor; and a bleed-off pressure compensator that decreases flow rate of the oil flowing through the boom control valve in accordance with the increase in pressure of the oil flowing through the steering cylinders to maintain the predetermined pressure of the oil in the steering control circuit.

A hydraulic system (40) for a work machine comprising a priority circuit (41) including at least a first priority actuator (47, 48) and a priority control valve (58) for controlling the supply of hydraulic fluid to the first priority actuator (47, 48) and for providing a load sense signal indicative of the load acting on the first priority actuator (47, 48); an auxiliary circuit (42) including at least a first auxiliary actuator (51) and at least a first auxiliary control valve (80) for controlling the supply of hydraulic fluid to the first auxiliary actuator (51); at least a first pump (46) for producing a flow of hydraulic fluid; and a priority valve (74) for distributing the flow from the pump (46) to the priority circuit (41) and auxiliary circuit (42) for operating the respective actuators thereof, with priority being given to the priority circuit (41) as a function of the load sense signal.

A hydraulic steering system 1 is described comprising a steering unit and a priority valve, said steering unit comprising a working port arrangement having two working ports, a supply port arrangement having a high pressure port and a low pressure port, a load sensing port, a main flow path having a main bleed and a metering device and being arranged between said high pressure port and said working port arrangement, an amplification flow path having an amplification bleed and being arranged between said high pressure port and said working port arrangement, said main bleed and said amplification bleed being controlled together by means of a steering handle and being closed in neutral position of said steering handle, wherein said priority valve comprises a priority outlet connected to said high pressure port of said steering unit, a valve element moveable in a priority direction to connect an inlet of said priority valve to said priority outlet, and a load sensing connection connected to said load sensing port of said steering unit, said priority outlet being connected to said load sensing connection via a priority valve bleed, a pressure at a point downstream said priority bleed acting on said valve element in said priority direction, wherein said load sensing port is connected to said low pressure port via a drain bleed being open in neutral position of said steering handle and closing upon actuation of said steering handle out of said neutral position.

A dual pressure margin priority circuit and method for controlling flow from a pump to steering valve and low priority inlets. A steering pressure valve controls flow from pump to steering valve inlets, and provides a steering valve load sense pressure. A priority valve controls flow from pump to low priority inlets. A load sense cutoff valve has a first inlet receiving the steering valve load sense pressure. The load sense cutoff valve controls flow through the priority valve based on steering valve load sense pressure at the first cutoff valve inlet. The cutoff valve can include a second inlet coupled to tank, and a load sense input coupled to the steering valve load sense pressure. The cutoff valve can be a pressure limiter valve. The priority and steering pressure valves can be 2-way proportional flow spool valves with bias springs, and contributing and opposing load sense inputs.

A throttle check valve includes: a poppet valve body that has an orifice formed at one end and has a hole portion formed at a side portion; a plug that has a tubular shape to surround the poppet valve body, and functions as a valve seat to come into contact with the poppet valve body; and a spring that biases the poppet valve body and the plug functioning as the valve seat in directions to come into contact with each other. When the spool is at the second position, the plug forming the distal end portion of the spool and the plug arranged in the housing come into contact with each other. The plug is provided with a protruding portion that comes into contact with the poppet valve body.