Claims
- 1. An apparatus for measuring relative displacement between a first end and a second end of a shaft the first and second ends being centered on a shaft axis, comprising:
a first ferromagnetic plate having a first side and a second side and being connected to the first end, the first ferromagnetic plate being centered on the shaft axis and having a plurality of ferromagnetic teeth extending from the first side and in a first direction parallel to the shaft; a second ferromagnetic plate having a first side and a second side and being connected to the second end, the second ferromagnetic plate being centered on the shaft axis, the first and second ferromagnetic plates forming a gap; a plurality of magnets having a magnetic field and being coupled to the first side of the second ferromagnetic plate, the magnets extending in a second direction, the second direction being opposite the first direction; and, a first sensing device disposed within the gap for sensing a magnetic flux of the magnetic field.
- 2. An apparatus, as set forth in claim 1, further comprising a compliant member coupled between the first and second ends of the shafts for allowing relative movement therebetween.
- 3. An apparatus, as set forth in claim 2, the first end of the shaft having a first coaxial extension and the second end of the shaft having a second coaxial extension, each of the first and second coaxial extensions forming an interior bore and an open end, the open end of each of the first and second coaxial extensions facing one another, the compliant member being located within the interior bore.
- 4. An apparatus, as set forth in claim 1, the first ferromagnetic plate having a circular cross-section and a flange extending from an outer edge of the first ferromagnetic plate in the first direction.
- 5. An apparatus, as set forth in claim 3, the second ferromagnetic plate having a circular cross-section and a flange extending from an outer edge of the second ferromagnetic plate in the second direction.
- 6. An apparatus, as set forth in claim 1, wherein the first and second ferromagnetic plates are made using a stamping process or a metal injection molding process or a casting process.
- 7. An apparatus, as set forth in claim 1, wherein the first and second ferromagnetic plates are made from a powdered metal using a sintering or bonding process.
- 8. An apparatus, as set forth in claim 1, the first and second ferromagnetic plates being made from a ferromagnetic material.
- 9. An apparatus, as set forth in claim 1, the first and second ferromagnetic plates being made from a non-ferromagnetic material, further comprising a ferromagnetic layer disposed on the first side of each of the first and second ferromagnetic plates.
- 10. An apparatus, as set forth in claim 1, the magnets being magnetized with alternating polarity in a direction normal to the first side of the second ferromagnetic plate.
- 11. An apparatus, as set forth in claim 10, the shape and size of the teeth and magnets being identical.
- 12. An apparatus, as set forth in claim 10, the shape and size of the teeth and magnets not being identical.
- 13. An apparatus, as set forth in claim 10, the first ferromagnetic plate having K ferromagnetic teeth, the number of magnets being equal to 2×K.
- 14. An apparatus, as set forth in claim 1, the magnets being magnetized with the same polarity in a direction normal to the first side of the second ferromagnetic plate.
- 15. An apparatus, as set forth in claim 14, the shape and size of the teeth and magnets being identical.
- 16. An apparatus, as set forth in claim 14, the shape and size of the teeth and magnets not being identical.
- 17. An apparatus, as set forth in claim 14, the first ferromagnetic plate having K ferromagnetic teeth, the number of magnets being equal to K.
- 18. An apparatus, as set forth in claim 1, the first and second ferromagnetic plates being movable between a relative angular deflection of zero and an angular deflection of +/−αmax.
- 19. An apparatus, as set forth in claim 18, wherein the relative angular deflection, α, between the first and second ferromagnetic plates is proportional to a torque being applied to the shaft.
- 20. An apparatus, as set forth in claim 18, wherein the ferromagnetic teeth having a width, Wt, and the magnets having a width, WPM, and Wt+WPM=θPM Pitch, where θPM Pitch is the magnet pole pitch.
- 21. An apparatus, as set forth in claim 20, where Wt and WPM are expressed as angular arcs.
- 22. An apparatus, as set forth in claim 21, where Wt and WPM are averages between an inner radius and an outer radius of the teeth and the magnets, respectively.
- 23. An apparatus, as set forth in claim 18, wherein the ferromagnetic teeth having a width, Wt and the magnets having a width, WPM, where Wt=WPM.
- 24. An apparatus, as set forth in claim 18, wherein the ferromagnetic teeth having a width, Wt and the magnets having a width, WPM, where Wt+WPM<θPM Pitch, where θPM Pitch is the magnet pole pitch.
- 25. An apparatus, as set forth in claim 18, wherein the ferromagnetic teeth having a width, Wt and the magnets having a width, WPM, where Wt+WPM>θPM Pitch, where θPM Pitch is the magnet pole pitch.
- 26. An apparatus, as set forth in claim 18, each of the teeth being positioned between adjacent magnets when the first and second ferromagnetic plates have a relative angular deflection of zero.
- 27. An apparatus, as set forth in claim 18, each of the teeth being positioned midway between adjacent magnets when the first and second ferromagnetic plates have a relative angular deflection of zero.
- 28. An apparatus, as set forth in claim 27, wherein the ferromagnetic teeth have a width, Wt, and the magnets have a width, WPM, expressed as average angular arcs between an inner radius and an outer radius of the teeth and the magnets, respectively, the ferromagnetic teeth overlapping the magnets when the first and second ferromagnetic plates have an angular deflection of zero.
- 29. An apparatus, as set forth in claim 27, wherein the ferromagnetic teeth have a width, Wt, and the magnets have a width, WPM, expressed as average angular arcs between an inner radius and an outer radius of the teeth and the magnets, respectively, further comprising a gap between the ferromagnetic teeth and the magnets when the first and second ferromagnetic plates have an angular deflection of zero.
- 30. An apparatus, as set forth in claim 26, each of the teeth overlapping a magnet when the first and second ferromagnetic plates have an angular deflection of +/−αmax.
- 31. An apparatus, as set forth in claim 26, each of the teeth being aligned with a magnet when the first and second ferromagnetic plates have an angular deflection of +/−αmax.
- 32. An apparatus, as set forth in claim 1, the second ferromagnetic plate having a plurality of ferromagnetic poles, a magnet being set on each ferromagnetic pole.
- 33. An apparatus, as set forth in claim 1, further comprising a second sensing device disposed within the gap for sensing a magnetic flux of the magnetic field.
- 34. An apparatus, as set forth in claim 33, wherein first and second sensing devices are radially spaced N·θPM Pitch, where θPM Pitch is the magnet pole pitch and N is an odd number.
- 35. An apparatus, as set forth in claim 34, wherein N=1.
- 36. An apparatus, as set forth in claim 1, the first sensing device being disposed midway in the gap between the first and second ferromagnetic plates.
- 37. An apparatus, as set forth in claim 1, said gap between the first and second ferromagnetic plates including a first portion between said teeth and said magnets, the first sensing device being disposed in a second portion of the gap, said second portion of the gap being closer to one of the first and second ferromagnetic plates.
- 38. An apparatus, as set forth in claim 37, said second portion of the gap being closer to the first ferromagnetic plate.
- 39. An apparatus, as set forth in claim 1, the first ferromagnetic plates including an annular ring disposed between the first sensing device and the ferromagnetic teeth.
- 40. An apparatus, as set forth in claim 1, the second ferromagnetic plate including an area of reduced thickness adjacent one or more of the magnets.
- 41. An apparatus, as set forth in claim 1, the second ferromagnetic plate including an area of increased thickness between one or more pairs of adjacent magnets.
- 42. An apparatus for measuring relative displacement between a first end and a second end of a shaft, the first and second ends being centered on a shaft axis, comprising:
a first ferromagnetic plate having a first side and a second side and being connected to the first end, the first ferromagnetic plate being centered on the shaft axis and having a plurality of ferromagnetic teeth extending from the first side and in a first direction parallel to the shaft; a second ferromagnetic plate having a first side and a second side and being connected to the second end, the second ferromagnetic plate being centered on the shaft axis, the first and second ferromagnetic plates forming a gap; a plurality of magnets having a magnetic field and being coupled to the first side of the second ferromagnetic plate, the magnets extending in a second direction, the second direction being opposite the first direction, the magnets being magnetized with alternating polarity in a direction normal to the first side of the second ferromagnetic plate, the number of ferromagnetic teeth being K and the number of magnets being equal to 2×K; and, a sensing device disposed within the gap for sensing a magnetic flux of the magnetic field.
- 43. An apparatus for measuring relative displacement between a first end and a second end of a shaft, the first and second ends being centered on a shaft axis, comprising:
a first ferromagnetic plate having a first side and a second side and being connected to the first end, the first ferromagnetic plate being centered on the shaft axis and having a plurality of ferromagnetic teeth extending from the first side and in a first direction parallel to the shaft; a second ferromagnetic plate having a first side and a second side and being connected to the second end, the second ferromagnetic plate being centered on the shaft axis, the first and second ferromagnetic plates forming a gap; a plurality of magnets having a magnetic field and being coupled to the first side of the second ferromagnetic plate, the magnets extending in a second direction, the second direction being opposite the first direction, the magnets being magnetized with the same polarity in a direction normal to the first side of the second ferromagnetic plate, the number of ferromagnetic teeth and the number of magnets being equal; and, a sensing device disposed within the gap for sensing a magnetic flux of the magnetic field.
Parent Case Info
[0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 60/478,874 filed Jun. 16, 2003.
Provisional Applications (1)
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Number |
Date |
Country |
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60478874 |
Jun 2003 |
US |