Microminiature gauging displacement sensor

• US 20040129095A1
• Filed: 10/02/2003
• Published: 07/08/2004
• Est. Priority Date: 10/02/2002
• Status: Active Grant

• Current Assignee: Hottinger Bruel & Kjaer Incorporated
• Original Assignee: David L. Churchill, Steven Ward Mundell
• Inventors: Churchill, David L., Mundell, Steven Ward
• Granted Patent: US 8,022,691 B2
• Time in Patent Office: Days
• US Class Current: 73/866.5
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence

Abstract

A device for providing displacement information includes a housing holding a displacement sensor. The displacement sensor includes a coil and a captive core. An electrical measurement of the coil provides information about displacement of the core. The coil has an axis extending in a first direction, wherein the housing has a minimum outside dimension that is less than 3.00 mm when measured perpendicular to that first direction. The housing has an inner surface having a housing inside dimension. The housing is for holding a displacement sensor and a guidance mechanism. The displacement sensor includes a coil and a captive core having a core outside dimension. The guidance mechanism includes a first part and a second part for guiding the core. The first part includes a bearing connected to the housing. The bearing has an axial hole having a hole dimension about equal to the core outside dimension. The core slidably extends through this axial hole. The second part has a second part outside dimension about equal to the housing inside dimension. The guidance mechanism is for resisting lateral movement and lateral rotation of the core while allowing axial movement of the core into and out of the coil.

Claims

1. A device for providing displacement or velocity information, said device comprising a housing holding a sensor, said sensor including a coil and a captive core, wherein an electrical measurement of said coil provides information about displacement or velocity of said captive core, further wherein said coil has an axis extending in a first direction, wherein said housing has a minimum outside dimension that is less than 3.00 mm when measured perpendicular to said first direction.

2. A device as recited in claim 1, wherein said housing has a minimum outside dimension that is less than 2.50 mm when measured perpendicular to said first direction.

3. A device as recited in claim 1, wherein said housing has a minimum outside dimension that is less than 2.00 mm when measured perpendicular to said first direction.

4. A device as recited in claim 1, wherein said housing has a minimum outside dimension that is less than 1.80 mm when measured perpendicular to said first direction.

5. A device as recited in claim 1, wherein said housing has a minimum outside dimension that is less than 1.60 mm when measured perpendicular to said first direction.

6. A device as recited in claim 1, wherein said housing has a minimum outside dimension that is less than 1.40 mm when measured perpendicular to said first direction.

7. A device as recited in claim 1, wherein said captive core extends into said coil.

8. A device as recited in claim 1, wherein said captive core has a first portion having a first diameter, wherein said captive core further includes a second portion having a diameter greater than said first diameter for retaining said core within said housing, and wherein said captured core is supported in said housing by a first bearing and by a second bearing.

9. A device as recited in claim 8, wherein said first bearing is connected to said housing, wherein said core slides within a hole in said first bearing.

10. A device as recited in claim 8, wherein said second bearing is mechanically mounted to said coil or to said housing, wherein said core slides within a first hole in said first bearing and within a second hole in said second bearing, wherein said core extends out from said housing from said first bearing, wherein said second bearing is spaced a distance from said first bearing to provide resistance to lateral forces on said core where it extends from said housing while allowing free axial movement of said core.

11. A device as recited in claim 8, wherein said second bearing is integral with said second portion and mechanically connected to said core, wherein said second bearing moves with said core.

12. A device as recited in claim 11, wherein said first bearing and said second bearing are jewel bearings.

13. A device as recited in claim 11, wherein said captive core comprises steel, stainless steel, titanium, aluminum, plastic, or a super-elastic material.

14. An sensor as recited in claim 13, wherein said superelastic material comprises nitinol.

15. A device as recited in claim 1, wherein said displacement or velocity sensor comprises an inductive sensor or an eddy current sensor.

16. A device as recited in claim 15, wherein said inductive sensor or said eddy current sensor is a one-coil device.

17. A device as recited in claim 15, wherein said inductive sensor or said eddy current sensor is a two-coil device.

18. A device as recited in claim 15, wherein said inductive sensor or said eddy current sensor is a three-coil device.

19. A device as recited in claim 1, wherein said sensor further comprises a spring to provide a return force to said core.

20. A device as recited in claim 19, wherein said core extends through said spring and into said coil.

21. A device as recited in claim 1, wherein said core includes a ferromagnetic material.

22. A device as recited in claim 21, wherein said ferromagnetic portion comprises iron, nickel, ferrite, or steel.

23. A device as recited in claim 1, wherein said core further comprises a contact point for making contact with an object to be measured, wherein said contact point is made of a hard material that resists wear.

24. A device as recited in claim 23, wherein said hard material comprises alumina, ruby, sapphire or hardened steel.

25. A device as recited in claim 1, wherein said core further comprises a core stop to capture said core within said housing, wherein said core stop further limits extension of said spring.

26. A device as recited in claim 1, wherein said housing has in inside diameter, and wherein said core stop is sized to have an outside diameter approximately equal to said inside diameter to provide a bearing function for guiding said core.

27. A device as recited in claim 1, further comprising lead wires electrically connected to said coil and extending to a circuit.

28. A device for providing displacement information, comprising a housing having an inner surface having a housing-inside dimension, said housing for holding a displacement sensor and a guidance mechanism, said displacement sensor including a coil and a captive core, said captive core having a core-outside dimension, wherein said guidance mechanism comprises a first bearing and a second bearing for guiding said core, wherein said first bearing is connected to said housing, wherein said first bearing has an axial hole having an axial-hole dimension about equal to said core-outside dimension, wherein said core slidably extends through said axial hole, wherein said second bearing has a second-bearing-outside dimension about equal to said housing-inside dimension, wherein said guidance mechanism is for resisting lateral movement and lateral rotation of said core while allowing axial movement of said core into and out of said coil.

29. A device as recited in claim 28, wherein said second bearing is connected to said captive core.

30. A device as recited in claim 28, wherein said second bearing is connected to said housing or connected to said coil.

31. A device as recited in claim 28, wherein said second bearing includes said coil.

32. A device as recited in claim 28, further comprising a sleeve within said coil.

33. A device as recited in claim 28, wherein said coil has an axis extending in a first direction, wherein said housing has a housing outside dimension, wherein said housing has a minimum outside dimension that is less than 3.00 mm when measured perpendicular to said first direction.

34. A device as recited in claim 28, further comprising a spring for spring loading said core.

35. A system for providing displacement or velocity information, comprising an array of displacement sensors capable of providing displacement or velocity measurements, wherein said displacement or velocity measurements are on center to center spacing of less than 3 mm.