Pressure regulating valve for aircraft engine
The fluid pressure regulating valve is for use in an aircraft engine. The valve has at least a first fluid inlet, a first fluid outlet and a second fluid outlet. The valve comprises: a valve housing having a first valve spool interior cavity; a first fluid path within the valve housing from the fluid inlet to the first fluid outlet; a second fluid path within the valve housing from the fluid inlet to the second fluid outlet; a first valve spool mounted for reciprocal motion within the first valve spool cavity between a first position and a second position, the first valve spool having a second valve spool interior cavity and being spring-biased to its first position; and a second valve spool mounted for reciprocal motion within the second valve spool cavity between a first position and a second position, the second valve spool being spring-biased to its first position, the second valve spool closing the first fluid path at its second position when the first valve spool is substantially at its first position.
1. A fluid pressure regulating valve for a pressurized fluid system of an aircraft engine, the pressurized fluid system including at least a main supply circuit, a supply pump and a fluid tank, the valve comprising:
a valve housing, the valve housing comprising a hollow valve housing body and an elongated sleeve having at least a portion inserted in the valve housing body, the sleeve having a plurality of axially spaced-apart ports, a first one of the ports receiving a first reference pressure, a second one of the ports in fluid communication with the main supply circuit, a third one of the ports in fluid communication with a location upstream the supply pump, a fourth one of the ports in fluid communication with the fluid tank, a fifth one of the ports receiving a second reference pressure, and a sixth one of the ports receiving a third reference pressure;
a first valve spool in sliding engagement with an interior of the sleeve, the first valve spool being movable along a longitudinal axis of the sleeve between a first position and a second position in response to a first pressure differential between the first port and the fifth port; and
a second valve spool in sliding engagement with an interior of the first valve spool, the second valve spool being movable along the longitudinal axis between a first position and a second position, the second valve spool preventing fluid from passing between the second port and the third port when a second pressure differential between the fifth port and the sixth port exceeds a minimum threshold and the first valve spool is substantially at its first position.
2. The valve as defined in claim 1 , wherein the valve comprises a first spool actuator mounted to the first valve spool and a second spool actuator mounted to the second valve spool, the first spool actuator generating a first actuating force in response to the first pressure differential and the second spool actuator generating a second actuating force in response to the second pressure differential.
3. The valve as defined in claim 2 , wherein the valve comprises a first spring generating a first preload force acting on the first valve spool, the preload force being opposite the first actuating force and biasing the first valve spool toward its first position, the valve further comprising a second spring generating a second preload force on the second valve spool, the second preload force being opposite the second actuating force and biasing the second valve spool towards its first position.
4. The valve as defined in claim 3 , wherein the first spool actuator and the second spool actuator each include a piston, at least a portion of one side of the first spool actuator piston being in fluid communication with one side of the second spool actuator piston through an internal channel longitudinally extending inside a portion of the second valve spool.
5. The valve as defined in claim 1 , wherein the valve comprises a fluid path including a first portion passing through a first annular chamber provided between the interior of the sleeve and a recessed segment on the first valve spool, and a second portion passing through a second annular chamber provided between the interior of the first valve spool and a recessed segment of the second valve spool.
6. The valve as defined in claim 5 , wherein the first valve spool includes a port for providing a fluid communication between the first and the second annular chamber when the first valve spool port is in registry with the second annular chamber, the first valve spool port and the second annular chamber being out of registry when the first valve spool is substantially at its first position and the second valve spool is substantially at its second position.