Magnetic transducer with ferrofluid end bearings

• US 20040251750A1
• Filed: 05/13/2004
• Published: 12/16/2004
• Est. Priority Date: 02/19/2002
• Status: Active Grant

• Current Assignee: Teledyne Scientific & Imaging, LLC (Teledyne Technologies Incorporated)
• Original Assignee: Rockwell Scientific Licensing LLC
• Inventors: Xin, Hao, Cheung, Jeffrey T.
• Granted Patent: US 7,288,860 B2
• Time in Patent Office: Days
• US Class Current: 310/23
• CPC Class Codes: H02K 35/02 with moving magnets and stationary coil systems
• CPC Class Codes: H02K 7/088 radially supporting the rotor directly

Abstract

An electrical generator includes one or more magnets that move relative to one or more conductors to generate an electrical signal in each conductor. Each magnet has ferrofluid bearings in the vicinity of its opposite ends to provide a low friction interface between the magnet and a support structure. The ferrofluid bearings establish a field expansion medium that directs at least a portion of the magnetic field so that a greater portion of the field intersects the conductors than in the absence of the medium. The magnet aspect ratio is preferably on the order of unity.

Claims

1. An electrical generator, comprising:

a support structure,

a conductor supported relative to said support structure,

a magnet constrained by said support structure for movement relative to said conductor over a range, with at least a portion of the magnet'"'"'s magnetic field intersecting the conductor over at least a portion of said range, and

ferrofluid bearings in the vicinity of the opposite ends of said magnet to provide a low friction interface between said magnet and said support structure,

said conductor arranged with said magnet so that movement of said magnet over said range generates an electrical signal in said conductor.

2. The electrical generator of claim 1, said conductor comprising a coil on an opposite side of said support structure from said magnet.

3. The electrical generator of claim 1, said ferrofluid bearings causing the magnetic field from said magnet to extend on average further away from said magnet than if said magnet were immersed in a ferrofluid, so that a greater portion of said field intersects said conductor.

4. The electrical generator of claim 1, said magnet having an aspect ratio on the order of unity.

5. The electrical generator of claim 1, further comprising a pair of end magnets on opposite sides of, and opposing polarity to, said magnet to limit said magnet'"'"'s motion.

6. The electrical generator of claim 1, said support structure including a raceway for said magnet.

7. The electrical generator of claim 1, wherein said support structure is arranged for said magnet to move in response to a generally horizontal movement of the support structure.

8. The electrical generator of claim 1, wherein said support structure is arranged to be carried by a person and for said magnet to move in a reciprocating motion in response to motion of the person.

9. The electrical generator of claim 1, further comprising at least one additional magnet constrained by said support structure for movement over a respective range, and additional respective ferrofluid bearings in the vicinity of the opposite ends of each additional magnet to provide a low friction interface between each additional magnet and said support structure.

10. The electrical generator of claim 9, further comprising at least one additional conductor supported relative to said support structure.

11. The electrical generator of claim 9, wherein said magnets are aligned along a common axis in successive polar opposition to each other.

12. The electrical generator of claim 11, further comprising a pair of end magnets limiting the travel of said moving magnets, said end magnets oriented in polar opposition to the nearest respective moving magnet.

13. The electrical generator of claim 11, said magnets having multiple oscillation modes relative to said support structure.

14. The electrical generator of claim 9, said support structure orienting said magnets for movement in a primarily horizontal direction.

15. The electrical generator of claim 9, each of said magnets having an aspect ratio on the order of unity.

16. The electrical generator of claim 9, wherein at least some of said magnets have different properties.

17. The electrical generator of claim 16, said at least some magnets having different magnetic strengths.

18. The electrical generator of claim 16, said at least some magnets having different sizes.

19. The electrical generator of claim 9, comprising an even number of magnets.

20. The electrical generator of claim 1, further comprising output circuitry for coupling energy out from said conductor.

21. The electrical generator of claim 20, said output circuitry comprising a rectifier.

22. The electrical generator of claim 20, further comprising an operating system coupled to be powered by energy coupled out from said output circuitry.

23. The electrical generator of claim 22, said operating system comprising a battery charger having a battery contact, said output circuitry connected to supply a battery charging signal to said contact.

24. The electrical generator of claim 22, said operating system comprising an environmental sensor powered by said output circuitry and arranged to produce an output signal indicative of an environmental condition.

25. The electrical generator of claim 22, said operating system comprising a transmitter powered by said output circuitry and arranged to transmit a communication signal.

26. The electrical generator of claim 22, said operating system comprising a cellular telephone powered by said output circuitry.

27. The electrical generator of claim 22, said operating system comprising a flashlight powered by said output circuitry.

28. An electrical generator, comprising:

a support structure,

at least one magnet supported by and moveable with respect to said support structure,

at least one conductor disposed with respect to said support structure so that an electrical signal is induced in said at least one conductor in response to movement of said at least one magnet through a range of movement, and

a field expansion medium interfacing between said at least one magnet and said support structure, said medium directing at least a portion of the magnetic field from said at least one magnet so that a greater portion of said field intersects said at least one conductor, as said at least one magnet moves through said range of movement, than in the absence of said medium.

29. The electrical generator of claim 28, said medium comprising a ferrofluid.

30. The electrical generator of claim 29, said ferrofluid comprising respective bearings at opposite ends of each said magnet.

31. The electrical generator of claim 30, wherein said ferrofluid bearings direct at least a portion of the magnetic field from said at least one magnet so that a greater portion of said field intersects said at least one conductor, as said at least one magnet moves through said range of movement, than if said at least one magnet were immersed in said ferrofluid.

32. The electrical generator of claim 28, further comprising an operating system connected to be powered by said electrical signal.

33. The electrical generator of claim 28, wherein the aspect ratio of each said magnet is on the order of unity.