Residual magnetic devices and methods

• US 7,969,705 B2
• Filed: 03/30/2005
• Issued: 06/28/2011
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Strattec Security Corporation
• Original Assignee: Strattec Security Corporation
• Inventors: Feucht, Michael G., Organek, Gregory J., Dimig, Steven J.
• Primary Examiner(s): Leja; Ronald W
• Application Number:
  US11/094,802
• Publication Number:
  US 20060227488A1
• Time in Patent Office: 2,281 Days
• Field of Search: 361/143
• US Class Current: 361/143
• CPC Class Codes: H01F 7/04 Means for releasing the attractive force

Abstract

Residual magnetic locks, brakes, rotation inhibitors, clutches, actuators, and latches. The residual magnetic devices can include a core housing and an armature. The residual magnetic devices can include a coil that receives a magnetization current to create an irreversible residual magnetic force between the core housing and the armature.

Claims

1. A controller for a brake or clutch having a core housing defining a first surface, a coil, and an armature defining a second surface, at least one of the core housing and armature rotatable with respect to the other of the core housing and armature about an axis to transfer torque therebetween in a braking or clutching action, the controller comprising:

a processor connected to the coil;

the processor causing a magnetization current to be provided to the coil to create a substantially closed magnetic path with flux lines extending between the second surface of the armature and the first surface of the core housing separated by an air gap of 0.005 inches or less in order to create an irreversible residual magnetic force with a residual magnetic air gap energy of at least 6700 (line-amp-turn)/cm³, the irreversible residual magnetic force sufficient to transfer the torque exerted between the core housing and armature in a plane parallel to the first surface when the magnetization current is no longer provided to the coil, wherein the axis extends through the plane.

2. The controller of claim 1 wherein the processor causes a demagnetization current to be provided to the coil to substantially null the irreversible residual magnetic force between the core housing and the armature.

3. The controller of claim 1 and further comprising a state determination port that determines whether the irreversible residual magnetic force is present between the core housing and the armature.

4. The controller of claim 3 wherein the state determination port determines an inductance of the core housing and the armature in order to determine whether the core housing and the armature are substantially in contact.

5. The controller of claim 4 wherein the inductance of the core housing and the armature is greater than approximately 100 milli-Henrys when the core housing and the armature are not in contact.

6. The controller of claim 4 wherein the inductance of the core housing and the armature is greater when the core housing and the armature are in contact than when the core housing and the armature are not in contact.

7. The controller of claim 4 wherein the processor causes a power supply to pulse a voltage to the coil, and the state determination port determines a current rise time in order to determine the inductance of the core housing and the armature.

8. The controller of claim 3 wherein the state determination port is connected to a Hall effect sensor to determine whether the irreversible residual magnetic force is present.

9. The controller of claim 3 wherein the state determination port stores a first state corresponding to the irreversible residual magnetic force being present and a second state corresponding to the irreversible residual magnetic force not being present.

10. The controller of claim 9 wherein the controller provides the magnetization current to create the irreversible residual magnetic force, the controller provides the magnetization current again to ensure the irreversible residual magnetic force has been created, and the controller provides a demagnetization current to null the irreversible residual magnetic force.

11. The controller of claim 3 and further comprising a strain gauge to determine whether the irreversible residual magnetic force is present between the core housing and the armature.

12. The controller of claim 3 and further comprising a switch to determine whether the irreversible residual magnetic force is present between the core housing and the armature, and wherein the armature moves in order to actuate the switch.

13. The controller of claim 12 wherein the switch includes at least one of a microswitch, a load pad, a membrane pad, a piezoelectric device, a force-sensing resistor, a proximity sensor, and a photointerrupter.

14. The controller of claim 1 and further comprising a power supply, wherein the processor causes the power supply to provide the magnetization current for approximately 100 milliseconds in order to saturate the core housing and the armature.

15. The controller of claim 14 wherein substantially all portions of the core housing and the armature saturate at approximately the same time.

16. The controller of claim 1 and further comprising a power supply, wherein the power supply provides a supply voltage of approximately 8 Volts to approximately 42 Volts.

17. The controller of claim 1 wherein the processor causes a power supply to provide a demagnetization current to substantially null the irreversible residual magnetic force and wherein the demagnetization current is a constant value due to the core housing and the armature being fully saturated when the irreversible residual magnetic force is created.

18. The controller of claim 17 wherein the processor causes the power supply to provide the demagnetization current having the constant value of approximately 700 milliamps to approximately 800 milliamps.

19. The controller of claim 1 wherein the processor causes a power supply to pulse a demagnetization current for approximately 60 milliseconds to approximately 120 milliseconds in order to null the irreversible residual magnetic force.

20. The controller of claim 1 wherein the processor causes a power supply to provide the magnetization current at a value of approximately five amps.

21. The controller of claim 1 wherein the processor causes a power supply to provide the magnetization current at a value of up to approximately ten amps.

22. The controller of claim 1 wherein the processor causes a power supply to provide a demagnetization current of up to approximately two amps.

23. The controller of claim 1 wherein the coil is a single coil, and further comprising a bipolar drive circuit including an H-bridge comprised of one of four transistors, four relays, and a combination of four total transistors and relays.

24. The controller of claim 1 wherein the coil is a double coil, and further comprising two unipolar drive circuits comprised of at least one of transistors and relays.

25. The controller of claim 1 wherein the magnetization current is semi-calibrated according to coil parameters and a demagnetization current is calibrated by current regulation.

26. The controller of claim 25 wherein the current regulation is one of linear regulation and pulse-width modulation.

27. The controller of claim 1 wherein the magnetization current is greater than approximately seven amps, and further comprising a discrete transistor drive circuit.

28. The controller of claim 1 wherein the processor causes a power supply to provide a demagnetization current including alternating polarity pulses that decrease in amplitude.

29. The controller of claim 1 wherein the processor causes a power supply to provide a demagnetization current by applying an increasing pulse-width modulated voltage.

30. The controller of claim 1 wherein the processor causes a power supply to provide a demagnetization current in order to approach a nominal release point, and wherein the demagnetization current is generated by a calibrated pulse-width modulated voltage whose duty cycle is based on a supply voltage level.

31. The controller of claim 1 and further comprising hardware interlock circuitry to substantially prevent a power supply from providing inadvertent magnetization or demagnetization currents.

32. The controller of claim 1 and further comprising a bus transceiver that communicates with a vehicle control system in one of a controller area network and a layered interconnection network.

33. The controller of claim 1 wherein a power supply is sourced by a vehicle ignition switch.

34. The controller of claim 1 wherein the processor includes a universal asynchronous receiver-transmitter, an analog-to-digital converter, and flash memory.

35. The controller of claim 1 and further comprising a power supply including at least one of a piezoelectric device powered by human movement, a solar power source, a generator powered by human movement, a static electricity power source, and a nuclear power source.

36. A method of controlling a brake or clutch having a core housing defining a first surface, a coil, and an armature defining a second surface, at least one of the core housing and armature rotatable with respect to the other of the core housing and armature about an axis to transfer torque therebetween in a braking or clutching action, the method comprising:

providing a magnetization current to the coil to create a substantially closed magnetic path with flux lines extending between the first surface of the core housing and the second surface of the armature separated by an air gap of 0.005 inches or less in order to create an irreversible residual magnetic force with a residual of at least 6700 (line-amp-turn)/cm³;

stopping supply of the magnetization current to the coil;

transferring the torque exerted between the core housing and armature in a plane parallel to the first surface due to the irreversible residual magnetic force when the magnetization current is no longer provided to the coil, wherein the axis extends through the plane; and

providing a demagnetization current to the coil to substantially null the irreversible residual magnetic force between the core housing and the armature.

37. The method of claim 36 and further comprising determining whether the irreversible residual magnetic force is present between the core housing and the armature.

38. The method of claim 37 and further comprising determining an inductance of the core housing and the armature in order to determine whether the core housing and the armature are substantially in contact.

39. The method of claim 38 and further comprising pulsing a voltage to the coil;

and

determining a current rise time in order to determine the inductance of the core housing and the armature.

40. The method of claim 37 and further comprising using a Hall effect sensor to the determine whether the irreversible residual magnetic force is present.

41. The method of claim 37 and further comprising storing a first state corresponding to the irreversible residual magnetic force being present and a second state corresponding to the irreversible residual magnetic force not being present.

42. The method of claim 37 and further comprising providing the magnetization current to create the irreversible residual magnetic force, providing the magnetization current again to ensure the irreversible residual magnetic force has been created, and providing the demagnetization current to substantially null the irreversible residual magnetic force.

43. The method of claim 37 and further comprising using a strain gauge to determine whether the irreversible residual magnetic force is present between the core housing and the armature.

44. The method of claim 37 and further comprising using a switch to determine whether the irreversible residual magnetic force is present between the core housing and the armature, and moving the armature to actuate the switch.

45. The method of claim 36 and further comprising providing the magnetization current for approximately 100 milliseconds in order to saturate the core housing and the armature.

46. The method of claim 45 and further comprising saturating substantially all portions of the core housing and the armature at approximately the same time.

47. The method of claim 36 and further comprising providing a supply voltage of approximately 8 Volts to approximately 42 Volts.

48. The method of claim 36 and further comprising providing the demagnetization current to substantially null the irreversible residual magnetic force and wherein the demagnetization current is a constant value due to the core housing and the armature being fully saturated when the irreversible residual magnetic force is created.

49. The method of claim 48 and further comprising providing the demagnetization current having the constant value of approximately 700 milliamps to approximately 800 milliamps.

50. The method of claim 36 and further comprising pulsing the demagnetization current for approximately 60 milliseconds to approximately 120 milliseconds in order to substantially null the irreversible residual magnetic force.

51. The method of claim 36 and further comprising providing the magnetization current at a value of up to approximately ten amps.

52. The method of claim 36 and further comprising providing the demagnetization current at a value of up to approximately two amps.

53. The method of claim 36 and further comprising semi-calibrating the magnetization current according to coil parameters and calibrating the demagnetization current by current regulation.

54. The method of claim 53 and further comprising calibrating the demagnetization current by one of linear regulation and pulse-width modulation.

55. The method of claim 36 and further comprising providing the magnetization current at a value greater than approximately seven amps with a discrete transistor drive circuit.

56. The method of claim 36 and further comprising providing the demagnetization current includes alternating polarity pulses that decrease in at least one of duration and amplitude.

57. The method of claim 36 and further comprising providing the demagnetization current includes an increasing pulse-width modulated current.

58. The method of claim 36 and further comprising providing the demagnetization current in order to approach a nominal release point;

and providing the demagnetization current including a calibrated pulse-width modulated voltage whose duty cycle is based on a supply voltage level.

59. The method of claim 36 and further comprising substantially preventing a power supply from providing inadvertent magnetization or demagnetization currents.

60. The method of claim 36 and further comprising communicating with a vehicle control system in one of a controller area network and a layered interconnection network.

61. The method of claim 36 and further comprising supplying power through a vehicle ignition switch.

62. The method of claim 36 and further comprising physically increasing an air gap between the armature and the core housing to cancel the irreversible residual magnetic force.

63. The method of claim 62 and further comprising increasing the air gap by rotating a screw between the armature and the core housing.

64. The method of claim 62 and further comprising increasing the air gap by moving at least one of a cam, a wedge, and a lever arm between the armature and the core housing.

65. A controller for an electromagnetic brake or clutch having a core housing defining a first surface, a coil, and an armature defining a second surface, at least one of the core housing and armature rotatable with respect to the other of the core housing and armature about an axis to transfer torque therebetween in a braking or clutching action, the controller comprising:

power supply means for providing a magnetization current; and

processor means for causing the power supply means to provide the magnetization current to the electromagnetic brake or clutch to create a substantially closed magnetic path with flux lines extending between the second surface of the armature and the first surface of the core housing separated by an air gap of 0.005 inches or less and to create an irreversible residual magnetic force with a residual magnetic air energy of at least 6700 ( line- amp- turn )cm³ and sufficient to transfer the torque exerted between the core housing and armature in a plane parallel to the first surface when the magnetization current is no longer srovided to the coil, wherein the axis extends through the plane.

66. A method of controlling a brake or clutch having a core housing defining a first surface, an armature defining a second surface, and a coil, at least one of the core housing and armature rotatable with respect to the other of the core housing and armature about an axis to transfer torque therebetween in a braking or clutching action, the method comprising:

measuring a supply voltage;

setting a demagnetization value based on the supply voltage;

measuring a sensor input from at least one of the core housing and the armature;

determining an irreversible residual magnetic force state in which flux lines extend between the second surface of the armature and the first surface of the core housing separated by an air gap of 0.005 inches or less based on the sensor input;

establishing a hardware interlock circuitry state; and

initiating one of a magnetization current and a demagnetization current based on the irreversible residual magnetic force state and the hardware interlock circuitry state, the magnetization current creating an irreversible residual magnetic force with a residual magnetic air gap energy of at least 6700 (line-amp-turn)/cm³, and sufficient to transfer the torque exerted between the core housing and armature in a plane parallel to the first surface when the magnetization current is no longer provided to the coil, wherein the axis extends through the plane, the demagnetization current nulling the irreversible residual magnetic force such that at least one of the core housing and armature moves independently of the other of the core housing and armature.

67. The method of claim 66 and further comprising setting the demagnetization value includes a pulse-width modulation value.

68. The method of claim 66 and further comprising setting a pulse-width modulation demagnetization value based on the supply voltage and at least one of a look-up table and a calculation.

69. The method of claim 66 wherein the sensor input is a Hall effect sensor input.

70. The method of claim 66 and further comprising initiating one of the magnetization current and the demagnetization current via a discrete input from a vehicle ignition switch.

71. The method of claim 66 and further comprising putting a controller connected to the coil to sleep when not in use and awakening the controller when in use.