Wide-band vibration energy harvester with stop

• US 8,154,177 B1
• Filed: 09/01/2010
• Issued: 04/10/2012
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Hottinger Bruel & Kjaer Incorporated
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Churchill, David L., Arms, Steven W., Hamel, Michael J., Leas, James Marc
• Primary Examiner(s): Rosenau, Derek
• Application Number:
  US12/873,700
• Time in Patent Office: 587 Days
• Field of Search: 310329-332, 310/339, 310/348
• US Class Current: 310/339
• CPC Class Codes: H02N 2/181 Circuits; Control arrangements or methods
• CPC Class Codes: H02N 2/186 Vibration harvesters
• CPC Class Codes: H10N 30/304 Beam type
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

A device for harvesting an external source of energy includes an electricity generating device, a flexure, and a first stop. Displacement of the flexure is limited by the first stop. The flexure has a vibration amplitude, wherein the vibration amplitude is amplitude the flexure would have if unconstrained by the first stop. The first stop allows the flexure to oscillate with a vibration amplitude that is higher than displacement of the flexure as limited by the first stop. The electricity generating device generates electrical energy while the first stop allows the flexure to oscillate with the higher vibration amplitude.

Claims

1. A device for harvesting an external source of energy, comprising an electricity generating device, a flexure, and a first stop, wherein displacement of said flexure is limited by said first stop, wherein said flexure has a vibration amplitude, wherein said vibration amplitude is amplitude said flexure would have if unconstrained by said first stop, wherein said first stop allows said flexure to oscillate with a vibration amplitude that is higher than displacement of said flexure as limited by said first stop, wherein said electricity generating device generates electrical energy while said first stop allows said flexure to oscillate with said higher vibration amplitude.

2. A device as recited in claim 1, further comprising a housing, wherein said flexure is connected to said housing.

3. A device as recited in claim 1, further comprising a second stop, wherein displacement of said flexure is limited by said second stop.

4. A device as recited in claim 3, wherein said flexure is connected to said housing to vibrate across a center line, wherein said center line has a first side and a second side, wherein said first stop is on said first side and said second stop is on said second side.

5. A device as recited in claim 4, further comprising a third stop and a fourth stop wherein displacement of said flexure is limited by said third stop and by said fourth stop, wherein said third stop is on said first side and said fourth stop is on said second side.

6. A device as recited in claim 3, further comprising a pivot, wherein said pivot allows said flexure to move freely between said first stop and said second stop.

7. A device as recited in claim 1, wherein said electricity generating device provides a voltage, further comprising a circuit for reducing voltage provided by said electricity generating device.

8. A device as recited in claim 7, wherein said circuit includes a voltage dependent switch and an inductor, wherein said voltage dependent switch is electrically connected between said electricity generating device and said inductor, wherein said voltage dependent switch has a first threshold, wherein said voltage dependent switch remains open until voltage applied across said voltage dependent switch from said electricity generating device to said inductor reaches said first threshold.

9. A device as recited in claim 8, wherein said electricity generating device, said voltage dependent switch, and said inductor are all electrically connected in series.

10. A device as recited in claim 8, wherein said voltage dependent switch has said first threshold and a second threshold, wherein said second threshold is below said first threshold, wherein when said voltage applied across said voltage dependent switch reaches said first threshold said voltage dependent switch closes so charge from said electricity generating device flows through said voltage dependent switch and through said inductor, wherein when said voltage applied across said voltage dependent switch then falls below said second threshold said voltage dependent switch reopens.

11. A device as recited in claim 8, wherein said voltage dependent switch is a solid state voltage dependent switch.

12. A device as recited in claim 1, wherein said first stop has a shape matching shape of said flexure when said flexure is displaced to reach said first stop.

13. A device as recited in claim 1, wherein said first stop allows said flexure to oscillate over a wide range of vibration levels.

14. A device as recited in claim 1, wherein said first stop allows said flexure to freely oscillate and vibrate.

15. A device as recited in claim 1, wherein said first stop reduces effective length of said flexure when said flexure encounters said first stop, wherein said first stop provides said flexure with a higher frequency resonance point than said flexure would have without said first stop, wherein said first stop allows said energy generating device to convert higher frequency mechanical energy into electricity each time said flexure strikes said first stop.

16. A device as recited in claim 1, wherein said constraining element includes a first stop, wherein displacement of said flexure is limited by said first stop.

17. A device for harvesting an external source of energy, comprising an electricity generating device, a flexure, a constraining element, and a circuit, wherein said circuit includes a voltage dependent switch and an inductor, wherein said constraining element provides that movement of said flexure is constrained from free vibration, wherein said voltage dependent switch is electrically connected between said electricity generating device and said inductor, wherein said voltage dependent switch has a first threshold, wherein said voltage dependent switch remains open until voltage applied across said voltage dependent switch from said electricity generating device to said inductor reaches said first threshold.

18. A device as recited in claim 17, wherein said flexure includes a first stable position and a second stable position, wherein said flexure includes a piezoelectric patch mounted to receive a mechanical pulse and generate a pulse of electricity when said flexure moves from said first stable position toward said second stable position.

19. A device as recited in claim 18, wherein said mechanical pulse is a separate individual mechanical pulse.

20. A device as recited in claim 17, wherein motion of said flexure is limited by two stops.

21. A device as recited in claim 17, wherein said flexure has a bowed shape.

22. A device as recited in claim 17, wherein said flexure has a bowl shape.

23. A device as recited in claim 17, wherein said flexure includes a piezoelectric patch and a substrate, wherein said piezoelectric patch is mounted on said substrate.

24. A device as recited in claim 23, wherein said substrate includes a first side and a second side, wherein said flexure includes said piezoelectric patch mounted on said first side and a second piezoelectric patch mounted on said second side.

25. A device as recited in claim 23, wherein said substrate includes at least one from the group consisting of steel, titanium, and a nickel-titanium alloy.

26. A device as recited in claim 17, wherein said flexure includes a mass.

27. A device as recited in claim 26, wherein said flexure includes a first stable position and a second stable position, wherein if sufficient force is provided to said mass said flexure snaps from said first stable position toward said second stable position.

28. A device as recited in claim 27, wherein said force includes an inertial load.

29. A device as recited in claim 27, further comprising a restoring spring, wherein said restoring spring is positioned so when said flexure snaps toward said second stable position said restoring spring acts to restore said flexure toward said first stable position, wherein said flexure has said second stable bowl-shaped position when presence of said restoring spring is disregarded.

30. A device as recited in claim 29, wherein said restoring spring is positioned so said restoring spring does not apply a restoring force on said flexure until said flexure snaps toward said second stable bowl-shaped position.

31. A device as recited in claim 26, further comprising a support structure, wherein said flexure has a first flexure end and a second flexure end, wherein said first flexure end is mounted to said support structure, wherein said mass is located at said second flexure end.

32. A device as recited in claim 31, wherein said second flexure end is unconstrained.

33. A device as recited in claim 17, further comprising at least one from the group consisting of a storage device and an energy using element, wherein said storage device is connected for storing electricity generated by said electricity generating device, wherein said energy using element is connected for using electricity generated by said electricity generating device.

34. A device as recited in claim 33, wherein said energy using element includes at least one from the group consisting of a light, a sensing node, a wireless communications device and a processor.

35. A device as recited in claim 17, wherein said voltage dependent switch has said first threshold and a second threshold, wherein said second threshold is below said first threshold, wherein when said voltage applied across said voltage dependent switch reaches said first threshold said voltage dependent switch closes so charge from said electricity generating device flows through said voltage dependent switch and through said inductor, wherein when said voltage applied across said voltage dependent switch then falls below said second threshold said voltage dependent switch reopens.

36. A device as recited in claim 35, wherein said voltage dependent switch is a solid state voltage dependent switch.

37. A device as recited in claim 17, wherein said flexure includes a first stable position and a second stable position, wherein said flexure has a resonance frequency, wherein said electricity generating device provides about the same amount of electrical energy with each movement from said first stable position toward said second stable position at a range of frequencies substantially broader than said resonance frequency.

38. A device for harvesting an external source of energy, comprising an electricity generating device, a flexure, and a constraining element, wherein said flexure has an effective length wherein said constraining element allows said flexure to oscillate with a higher vibration amplitude than an amplitude said flexure would have if unconstrained by said constraining element, wherein said flexure has a first resonance frequency based on said effective length, wherein said constraining element reduces effective length of said flexure and allows said flexure to have a second resonance frequency that is higher than said first resonance frequency so said electricity generating device can provide electricity at substantially different frequencies.