Electromagnetic device for converting mechinal vibrational energy into electrical energy, and manufacture thereof

• US 20070007827A1
• Filed: 08/13/2004
• Published: 01/11/2007
• Est. Priority Date: 08/28/2003
• Status: Active Grant

• Current Assignee: University of Southampton
• Original Assignee: University of Southampton
• Inventors: White, Neil, Glynne-Jones, Peter, Harris, Nicholas, Beeby, Stephen, Tudor, Michael
• Granted Patent: US 7,535,148 B2
• Time in Patent Office: Days
• US Class Current: 310/15
• CPC Class Codes: H02K 35/04 with moving coil systems and stationary magnets

Abstract

An electromagnetic generator comprising a multilayer assembly of a first layer carrying at least one magnet, a second layer carrying at least one coil, and a third layer carrying at least one magnet, the at least one magnet of the first and third layers being configured to define therebetween a region of magnetic flux in which the at least one coil is disposed, at least one of the layers being shaped to define a respective displaceable portion thereof which is displaceable by vibration of the electromagnetic generator thereby to cause relative movement between the coil and the magnets and generate an electrical current in the coil.

Claims

1. An electromagnetic generator comprising a multilayer assembly of a first layer carrying at least one magnet, a second layer carrying at least one coil, and a third layer carrying at least one magnet, the at least one magnet of the first and third layers being configured to define therebetween a region of magnetic flux in which the at least one coil is disposed, at least one of the layers being shaped to define a respective displaceable portion thereof which is displaceable by vibration of the electromagnetic generator thereby to cause relative movement between the coil and the magnets and generate an electrical current in the coil.

2. An electromagnetic generator according to claim 1 wherein the displaceable portion comprises an integral central body of the respective layer which is connected to a peripheral frame of the respective layer by an integral cantilever beam element.

3. An electromagnetic generator according to claim 1 or claim 2 wherein each magnet comprises a layer applied on a surface of the first and third layers respectively.

4. An electromagnetic generator according to claim 1 or claim 2 wherein each magnet comprises a magnetic body attached to the respective layer.

5. An electromagnetic generator according to claim 4 wherein each magnet is located in a recess in the respective layer.

6. An electromagnetic generator according to any foregoing claim wherein each magnet is disposed on a surface of the first or third layer respectively which faces the second layer.

7. An electromagnetic generator according to any foregoing claim wherein two magnets are carried on each of the first and third layers, the two magnets of each layer presenting faces of opposite polarity towards the second layer.

8. An electromagnetic generator according to any foregoing claim wherein the at least one coil comprises a layer applied on a surface of the second layer

9. An electromagnetic generator according to claim 8 wherein the at least one coil is a printed layer.

10. An electromagnetic generator according to any one of claims 1 to 7 wherein the at least one coil is a wound coil attached to a surface of the second layer.

11. An electromagnetic generator according to claim 10 wherein the wound coil is disposed in a recess formed in the surface of the second layer.

12. An electromagnetic generator according to any foregoing claim wherein the at least one coil is disposed on a displaceable portion of the second layer.

13. An electromagnetic generator according to any foregoing claim further comprising at least one piezoelectric region which is disposed on at least one of the layers and is adapted to generate electrical current when the displaceable portion is displaced.

14. An electromagnetic generator according to claim 13 wherein the at least one piezoelectric region is disposed on a surface of the displaceable portion which is subjected to strain when the displaceable portion is displaced.

15. An electromagnetic generator according to claim 13 or claim 14 wherein the at least one piezoelectric region is disposed on a surface of at least one of the layers which is subjected to impact when the displaceable portion is displaced beyond a preset amplitude.

61. A health and usage monitoring system (HUMS) for an aircraft, the system incorporating at least one electromagnetic generator according to claim 1, claim 33 or claim 50.

62. A health and usage monitoring system (HUMS) for an aircraft according to claim 61, the system including a sensor and a local wire less transmission system, both the sensor and the wire less transmission system being powered by the electromagnetic generator.

63. A sensing system for railway lines and associated components, the system incorporating at least one electromagnetic generator according to claim 1, claim 33 or claim 50.

64. A sensing system for railway lines and associated components according to claim 63, wherein the electromagnetic generator is adapted to generate power from the vibration provided by the passage of a train, either directly from the rail line or via a cantilever attached to the rail line.

65. A sensing system for railway lines and associated components according to claim 64, wherein the sensing system includes a sensor and means to telemeter the output data to a remote location.

66. A vehicle battery charger system incorporating at least one electromagnetic generator according to claim 1, claim 33 or claim 50.

67. A vehicle battery charger system according to claim 66 incorporated into a battery recharging system for a tracking system for a lorry or truck trailer.

68. A mobile telecommunications equipment incorporating at least one electromagnetic generator according to claim 1, claim 33 or claim 50.

69. A conditioning monitoring system incorporating at least one electromagnetic generator according to claim 1, claim 33 or claim 50.

16. A method of manufacturing an electromagnetic generator, the method comprising the steps of:

(a) forming a first layer carrying at least one magnet, forming a second layer carrying at least one coil and forming a third layer carrying at least one magnet, at least one of the layers being shaped to define a respective displaceable portion thereof which is displaceable by vibration, the displaceable portion carrying either the at least one magnet of the first and third layers or the at least one coil of the second layer; and

(b) assembling together the first, second and third layers to form a multilayer structure in which the magnets of the first and third layers are configured to define therebetween a region of magnetic flux in which the at least one coil is disposed, the at least one displaceable portion being displaceable by vibration of the multilayer structure thereby to cause relative movement between the coil and the magnets and generate an electrical current in the coil.

17. A method according to claim 16 wherein in step (a) each of the first, second and third layers is formed as a part of a wafer, in which an array of a plurality of first, second and third layers, respectively, are formed.

18. A method according to claim 17 wherein in step (b) wafers each having formed thereon the array of the plurality of first, second and third layers, respectively, are assembled together to form a multilayer wafer assembly, and further comprising the step (c) of cutting the multilayer wafer assembly into a plurality of individual multilayer structures.

19. A method according to claim 17 or claim 18 wherein the displaceable portion comprises an integral central body of the respective layer which is connected to a peripheral frame of the respective layer by an integral cantilever beam element, and is formed by etching of the respective layer.

20. A method according to any one of claims 17 to 19 wherein each magnet comprises a layer applied on a surface of the first and third layers respectively.

21. A method according to any one of claims 17 to 19 wherein each magnet comprises a magnetic body attached to the respective layer.

22. A method according to claim 21 wherein each magnet is located in a recess in the respective layer.

23. A method according to any one of claims 17 to 22 wherein each magnet is disposed on a surface of the first or third layer respectively which faces the second layer.

24. A method according to any one of claims 17 to 23 wherein two magnets are carried on each of the first and third layers, the two magnets of each layer presenting faces of opposite polarity towards the second layer.

25. A method according to any one of claims 17 to 24 wherein the at least one coil comprises a layer applied on a surface of the second layer

26. A method according to claim 25 wherein the at least one coil is a printed layer.

27. A method according to any one of claims 17 to 24 wherein the at least one coil is a wound coil attached to a surface of the second layer.

28. A method according to claim 27 wherein the wound coil is disposed in a recess formed in the surface of the second layer.

29. A method according to any one of claims 17 to 28 wherein the at least one coil is disposed on a displaceable portion of the second layer.

30. A method according to any one of claims 17 to 29 further comprising the step of applying at least one piezoelectric region on at least one of the layers which is adapted to generate electrical current when the displaceable portion is displaced.

31. A method according to claim 30 wherein the at least one piezoelectric region is disposed on a surface of the displaceable portion which is subjected to strain when the displaceable portion is displaced.

32. A method according to claim 30 or claim 31 wherein the at least one piezoelectric region is disposed on a surface of at least one of the layers which is subjected to impact when the displaceable portion is displaced beyond a preset amplitude.

33. An electromagnetic generator comprising at least two magnets and at least one coil disposed therebetween, the at least two magnets being configured to define therebetween a region of magnetic flux in which the at least one coil is disposed whereby relative movement between the coil and the magnets generates an electrical current in the coil, and at least one piezoelectric region which is adapted to generate additional electrical current by relative movement between the coil and the magnets.

34. An electromagnetic generator according to claim 33 wherein at least one of the at least two magnets and at least one coil is carried on a displaceable portion which is displaced by vibration to cause the relative movement between the coil and the magnets, and the at least one piezoelectric region is disposed on a surface of the displaceable portion which is subjected to strain when the displaceable portion is displaced.

35. An electromagnetic generator according to claim 33 or claim 34 wherein at least one of the at least two magnets and at least one coil is carried on a displaceable portion which is displaced by vibration to cause the relative movement between the coil and the magnets, and the at least one piezoelectric region is disposed on a surface of the electromagnetic generator which is subjected to impact when the displaceable portion is displaced beyond a preset amplitude.

36. A magnetic core for an electromagnetic generator, the magnetic core comprising four magnets disposed in two magnet pairs, with each pair of magnets being assembled with a respective keeper, the two pairs of magnets being mounted in an opposing manner so that a front end of each magnet of one magnet pair is spaced, in a first direction, from and faces a front end of a corresponding magnet of the other magnet pair, the facing front ends being of opposite magnetic polarity, thereby to define in the magnetic core a pair of gaps between the front ends of the four magnets, and with rear ends of the magnets of each pair contacting a respective keeper, the magnets of each pair being mutually spaced in a second direction, and wherein the ratio between the width of each magnet in the second direction to the height of the magnetic core in the second direction is from 0.40 to 0.55.

37. A magnetic core according to claim 36 wherein the ratio between the width of each magnet in the second direction to the height of the magnetic core in the second direction is from 0.43 to 0.53.

38. A magnetic core according to claim 37 wherein the ratio between the width of each magnet in the second direction to the height of the magnetic core in the second direction is about 0.48.

39. A magnetic core according to any one of claims 36 to 38 wherein the ratio between the length of each magnet in the first direction to the height of the magnetic core in the second direction is from 0.1 to 0.24.

40. A magnetic core according to claim 39 wherein the ratio between the length of each magnet in the first direction to the height of the magnetic core in the second direction is about 0.17.

41. A magnetic core according to any one of claims 36 to 40 wherein the ratio between the length of each gap in the first direction to the height of the magnetic core in the second direction is from 0.14 to 0.26.

42. A magnetic core according to claim 41 wherein the ratio between the length of each gap in the first direction to the height of the magnetic core in the second direction is about 0.2.

43. A magnetic core according to any one of claims 36 to 42 wherein the ratio between the thickness of each keeper in the first direction to the height of the magnetic core in the second direction is from 0.06 to 0.12.

44. A magnetic core according to claim 43 wherein the ratio between the thickness of each keeper in the first direction to the height of the magnetic core in the second direction is about 0.09.

45. A magnetic core according to any one of claims 36 to 44 wherein the ratio between the length of the magnetic core in the first direction to the height of the magnetic core in the second direction is from 0.61 to 0.81.

46. A magnetic core according to claim 45 wherein the ratio between the length of the magnetic core in the first direction to the height of the magnetic core in the second direction is about 0.71.

47. A magnetic core according to any one of claims 36 to 46 wherein the parameter ψ

,

which is defined by the equation

$\mathrm{\psi <br><br>}=\frac{{\int <br><br>}^{\mathrm{airgap}}<br><br>B^2<br><br>d<br><br>A}{\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{area}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{core}},$

wherein B is the magnet flux density; and

A is the total face area of each magnet pair of the core, the faces defining the gaps; and

the total area of the core is the total face area of each magnet pair plus the face area of the gap therebetween, has a value of from 0.04 to 0.06 Tesla².

48. A magnetic core according to claim 47 wherein the parameter ψ

has a value of about 0.05 Tesla².

49. A magnetic core according to any one of claims 36 to 48 wherein the average magnetic field across the gaps is about 0.366 Tesla.

50. An electromagnetic generator, the electromagnetic generator comprising a magnetic core according to any one of claims 36 to 49, a coil disposed in the pair of gaps and a vibration sensitive mount for mounting one of the magnetic core and the coil whereby vibration of the electromagnetic generator causes relative movement of the magnetic core and the coil thereby to generate an electrical current in the coil.

51. A method of producing a magnetic core for an electromagnetic generator, the magnetic core comprising four magnets disposed in two magnet pairs, with each pair of magnets being assembled with a respective keeper, the two pairs of magnets being mounted in an opposing manner so that a front end of each magnet of one magnet pair is spaced, in a first direction, from and faces a front end of a corresponding magnet of the other magnet pair, the facing front ends being of opposite magnetic polarity, thereby to define in the magnetic core a pair of gaps between the front ends of the four magnets, and with rear ends of the magnets of each pair contacting a respective keeper, the magnets of each pair being mutually spaced in a second direction, the method comprising the steps of:

(a) establishing a model for the geometrical parameters of the magnetic core, the parameters including the width of each magnet in the second direction (t_m) the height of the magnetic core in the second direction (l_c), the length of each magnet in the first direction (l_m)and the length of the gap in the first direction (g);

(b) varying the parameters to provide an output value ψ

in units of Tesla² which is

defined by the equation

$\mathrm{\psi <br><br>}=\frac{{\int <br><br>}^{\mathrm{airgap}}<br><br>B^2<br><br>d<br><br>A}{\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{area}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{of}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{core}};<br><br>$

wherein B is the magnet flux density; and

A is the total face area of each magnet pair of the core, the faces defining the air gaps; and

the total area of the core is the total face area of each magnet pair plus the face area of the gap therebetween;

(c) determining a maximum for the parameter ψ

;

(d) determining values of at least the parameters (t_m), (l_c), (l_m) and (g) to provide a range for the parameter ψ

which encompasses the maximum for the parameter ψ

; and

(e) producing the magnetic core having the determined values of the parameters (t_m), (l_c), (l_m) and (g) within a particular tolerance.

52. A method according to claim 51 wherein the ratio between the width of each magnet in the second direction (t_m) to the height of the magnetic core in the second direction (l_c) is from 0.40 to 0.55.

53. A method according to claim 52 wherein the ratio between the width of each magnet in the second direction (t_m) to the height of the magnetic core in the second direction (l_c) is from 0.43 to 0.53.

54. A method according to claim 53 wherein the ratio between the width of each magnet in the second direction (t_m) to the height of the magnetic core in the second direction (l_c) is about 0.48.

55. A method according to any one of claims 51 to 54 wherein the ratio between the length of each magnet in the first direction (l_m) to the height of the magnetic core in the second direction (l_c) is from 0.1 to 0.24.

56. A method according to claim 55 wherein the ratio between the length of each magnet in the first direction (l_m) to the height of the magnetic core in the second direction (l_c) is about 0.17.

57. A method according to any one of claims 51 to 56 wherein the ratio between the length of each gap (g) in the first direction to the height of the magnetic core in the second direction (l_c) is from 0.14 to 0.26.

58. A method according to claim 57 wherein the ratio between the length of each gap (g) in the first direction to the height of the magnetic core in the second direction (l_c) is about 0.20.

59. A method according to any one of claims 51 to 58 wherein the ratio between the thickness of each keeper in the first direction (t_c) to the height of the magnetic core in the second direction (l_c) is from 0.06 to 0.12.

60. A method according to claim 59 wherein the ratio between the thickness of each keeper in the first direction (t_c) to the height of the magnetic core in the second direction (l_c) is about 0.09.

70. An electromagnetic generator substantially as hereinbefore described with reference to the accompanying drawings.

71. A method of manufacturing an electromagnetic generator substantially as hereinbefore described with reference to the accompanying drawings.

72. A magnetic core for an electromagnetic generator substantially as hereinbefore described with reference to the accompanying drawings.

73. A method of producing a magnetic core for an electromagnetic generator substantially as hereinbefore described with reference to the accompanying drawings.