Load-sensing system

A load-sense priority valve unit comprising:

• a priority valve housing defining a pump port, an auxiliary port, a control flow port;
• a valve member for modulating flow from the pump port between the control flow port and the auxiliary port, the valve member being movable to open and close fluid communication between the pump port and the auxiliary and control flow ports, and the valve member being movable to vary an orifice area of a control flow orifice corresponding to the control flow port;
• a control spring that biases the valve member toward a position where the control flow orifice is open;
• a pilot line for applying a pilot pressure to the valve member in a direction that opposes the control spring;
• a load sense line for applying a load-sense pressure to the valve member in a direction that assists the control spring;
• and
• a dynamic load-sense line for boosting the load-sense pressure applied to the valve member, the dynamic load-sense line including a dynamic load-sense orifice having a variable orifice area.

A load-sense steering system for controlling a steering actuator, the load-sense steering system comprising:

• a manually actuated steering component;
• a hydraulic pump;
• a steering control unit including a directional valve operatively coupled to the manually actuated component, the directional valve including first and second actuator ports adapted to be coupled in fluid communication with the steering actuator, the directional valve also including a tank port adapted to be coupled to tank, a pressure port, and a load-sense port, the directional valve being operable in a first active state, a second active state and a neutral state, the directional valve being biased toward the neutral state and being moveable from the neutral state to the first active state or the second active state in response to input from the manually actuated steering component, wherein when the directional valve is in the neutral state the first and second actuator ports are not in fluid communication with the pressure port or the tank port, wherein when the directional valve is in the first active state:
• a) the pressure port is in fluid communication with the first actuator port via a first flow path;
• b) the tank port is in fluid communication with the second actuator port via a second flow path;
• c) a first variable orifice controls flow between the pressure port and the first actuator port;
• and d) the load-sense port is in fluid communication with the first flow path at a location downstream from the first orifice so as to sense a load pressure, and wherein when the directional valve is in the second active state:
• a) the pressure port is in fluid communication with the second actuator port via a third flow path;
• b) the tank port is in fluid communication with the first actuator port via a fourth flow path;
• c) a second variable orifice controls flow between the pressure port and the second actuator port;
• and d) the load-sense port is in fluid communication with the third flow path at a location downstream from the first orifice so as to sense the load pressure;
• a load-sense priority valve unit including a control flow port, a pump port, and an auxiliary port, the control flow port being fluidly coupled to the pressure port of the directional valve by a control flow line, the pump port being fluidly coupled to an outlet of the hydraulic pump by a pump line, the load-sense priority valve unit including a control flow orifice for controlling flow outputted though the control flow port, the load-sense priority valve unit including a spool valve member that is moveable along a valve axis to vary a size of the control flow orifice, the load-sense priority valve unit including a spring that that applies a control pressure to the spool valve member that biases the spool valve member in a first direction along the valve axis toward a valve position in which the control flow orifice is fully open;
• a load-sense line that applies a load-sense pressure to the spool valve member in direction that assist the spring, the load sense being in fluid communication with the load-sense port of the steering control unit;
• a pilot line that applies a pilot pressure to the spool valve member in a direction that opposes the spring, the pilot line being in fluid communication with the control-flow port;
• and
• a dynamic load-sense line for boosting the load-sense pressure applied to the spool valve member, the dynamic load sense line including a variable dynamic load-sense orifice for controlling flow through the dynamic load-sense line, the variable dynamic load-sense orifice being integrated at least partially with the spool valve member, the variable dynamic load-sense orifice varying in size based on a position of the spool valve member, the dynamic load-sense line directing hydraulic fluid flow from the control flow line to the load-sense line when the dynamic load-sense orifice is open.

A load-sense system for controlling operation of an actuator, the load-sense system comprising:

• an actuator control valve arrangement defining an actuator control orifice having an orifice area that is variable;
• a compensator valve arrangement for controlling hydraulic fluid flow to the actuator control orifice to maintain a substantially constant pressure drop across the actuator control orifice, the compensator valve arrangement defining a compensator valve orifice for controlling the hydraulic fluid flow provided to the actuator control orifice, the compensator valve arrangement including a compensator valve member that is movable to vary an orifice area of the compensator valve orifice, the compensator valve arrangement also including a control spring that biases the compensator valve member toward a position where the compensator valve orifice is open;
• a pilot pressure line for providing pilot pressure that acts on the compensator valve member in a direction that opposes the control spring, the pilot pressure line being in fluid communication with a control flow line that extends between the compensator valve orifice and the actuator control orifice;
• and
• a load-sense arrangement for applying a load-sense pressure that acts in the compensator valve member in a direction that assists the control spring, the load-sense arrangement including a dynamic load-sense line including a dynamic load-sense orifice that varies in orifice size based on a position of the compensator valve member.