Claims
- 1. A differential pressure signaling device comprising a casing divided by a movable wall to provide respective chamber spaces on opposite sides of the wall, a first sensing port for communicating a first pressure to a first of the chamber spaces and a second sensing port for communicating a second pressure to a second of the chamber spaces, and a signaling mechanism for signaling change in differential pressure between the two chamber spaces comprising a first magnet, a second magnet, and a magnetoresistive sensor arranged such that movement of the wall that occurs in consequence of change in pressure differential between the chamber spaces changes the magnetic flux acting on the magnetoresistive sensor.
- 2. A differential pressure signaling device as set forth in claim 1 wherein the magnets are arranged to magnetically oppose each other.
- 3. A differential pressure signaling device as set forth in claim 2 wherein the first magnet is disposed on the movable wall for movement therewith and the second magnet is fixedly disposed within one of the chamber spaces.
- 4. A differential pressure signaling device as set forth in claim 3 wherein the casing comprises opposite axial end walls, each bounding an end of a respective chamber space, the magnetoresistive sensor is disposed on the end wall that bounds the end of the one chamber space, and the second magnet is disposed on the magnetoresistive sensor.
- 5. A differential pressure signaling device as set forth in claim 4 including a third magnet fixedly disposed on the casing end wall that bounds the end of the other chamber space.
- 6. A differential pressure signaling device as set forth in claim 5 wherein the movable wall comprises a piston that can be displaced sufficiently under certain conditions to allow communication between the ports.
- 7. A differential pressure signaling device as set forth in claim 1 wherein the magnetoresistive sensor is disposed on the casing.
- 8. A differential pressure signaling device as set forth in claim 7 wherein the casing comprises an end wall bounding an end of one of the chamber spaces and the magnetoresistive sensor is disposed on the end wall.
- 9. A differential pressure signaling device as set forth in claim 1 wherein the first magnet is disposed to move with the movable wall and the second magnet disposed in a fixed location within one of the chamber spaces in magnetic opposition to the first magnet, and further including a source of bias force for biasing the magnets toward each other.
- 10. A differential pressure signaling device as set forth in claim 9 wherein the source of bias force for biasing the magnets toward each other comprises a third magnet that magnetically opposes the first magnet.
- 11. A differential pressure signaling device comprising a casing divided by a movable wall to provide respective chamber spaces on opposite sides of the wall, a first sensing port for communicating a first pressure to a first of the chamber spaces and a second sensing port for communicating a second pressure to a second of the chamber spaces, a magnetic circuit that exhibits change in a characteristic of magnetic flux in the circuit as differential pressure between the two chamber spaces changes, and a magnetoresistive sensor arranged to respond to change in the characteristic of magnetic flux in the circuit as differential pressure between the two chamber spaces.
- 12. A method for signaling change in differential pressure between first and second chamber spaces of a casing that are divided by a movable wall within the casing and to which respective pressures are communicated, the method comprising:
providing a magnetic circuit that exhibits change in a characteristic of magnetic flux in the circuit as differential pressure between the two chamber spaces changes; and magnetoresistively sensing change in the characteristic of magnetic flux in the circuit.
- 13. A leak test device for vapor containment space of a motor vehicle fuel system that holds volatile liquid fuel for operating the vehicle, the leak test device comprising:
a casing divided by a movable wall to provide respective chamber spaces on opposite sides of the wall; a first sensing port for communicating a reference pressure to a first of the chamber spaces; a second sensing port for communicating pressure representative of pressure in vapor containment space of the fuel system to a second of the chamber spaces; and a signaling mechanism for signaling change in differential pressure between the two chamber spaces comprising a magnetic circuit that exhibits change in a characteristic of magnetic flux in the circuit as differential pressure between the two chamber spaces changes, and a magnetoresistive sensor arranged to respond to change in the characteristic of magnetic flux in the circuit as differential pressure between the two chamber spaces changes.
- 14. A leak test device as set forth in claim 13 wherein the magnetic circuit comprises a first magnet, a second magnet, and the magnets are arranged to magnetically oppose each other.
- 15. A leak test device as set forth in claim 14 wherein the first magnet is disposed on the movable wall for movement therewith and the second magnet is fixedly disposed within one of the chamber spaces.
- 16. A leak test device as set forth in claim 15 wherein the casing comprises opposite axial end walls, each bounding an end of a respective chamber space, the magnetoresistive sensor is disposed on the end wall that bounds the end of the one chamber space, and the second magnet is disposed on the magnetoresistive sensor.
- 17. A leak test device as set forth in claim 16 including a third magnet fixedly disposed on the casing end wall that bounds the end of the other chamber space.
- 18. A leak test device as set forth in claim 13 wherein the magnetoresistive sensor is disposed on the casing.
- 19. A leak test device as set forth in claim 18 wherein the casing comprises an end wall bounding an end of one of the chamber spaces and the magnetoresistive sensor is disposed on the end wall.
- 20. A leak test device as set forth in claim 13 wherein the first magnet is disposed to move with the movable wall and the second magnet disposed in a fixed location within one of the chamber spaces in magnetic opposition to the first magnet, and further including a source of bias force for biasing the magnets toward each other.
- 21. A leak test device as set forth in claim 20 wherein the source of bias force for biasing the magnets toward each other comprises a third magnet that magnetically opposes the first magnet.
- 22. A leak test device as set forth in claim 13 wherein the reference pressure communicated via the first sensing port to the first of the chamber spaces comprises atmospheric pressure.
- 23. A method for signaling leakage in a motor vehicle fuel system that holds volatile liquid fuel for operating the vehicle, the method comprising:
providing a magnetic circuit that exhibits change in a characteristic of magnetic flux in the circuit as differential pressure between a reference pressure and pressure in vapor containment space of the fuel system changes; and magnetoresistively sensing change in the characteristic of magnetic flux in the circuit.
- 24. A method as set forth in claim 23 wherein the reference pressure is atmospheric pressure.
CROSS REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM
[0001] This application claims the benefit of U.S. Provisional Application No. 60/413,300 (Attorney Docket No. 2002 P 15778 US) filed on Sep. 25, 2002 in the name of Gary Everingham and entitled DIFFERENTIAL PRESSURE SIGNALING DEVICE AND METHOD EMPLOYING A MAGNETORESISTIVE SENSOR, which is incorporated by reference herein in its entirety.
Provisional Applications (1)
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Number |
Date |
Country |
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60413300 |
Sep 2002 |
US |