Crash sensor for a passive motor vehicle occupant restraint system

• US 5,153,393 A
• Filed: 10/07/1991
• Issued: 10/06/1992
• Est. Priority Date: 03/22/1990
• Status: Expired due to Fees

• Current Assignee: American Vehicular Sciences LLC (Acacia Research Corporation)
• Original Assignee: David S. Breed
• Inventors: Sanders, William T., Pruzsenski, Anthony S. Jr., Castelli, Vittorio, Breed, David S.
• Primary Examiner(s): Scott, J. R.
• Application Number:
  US07/771,831
• Time in Patent Office: 365 Days
• Field of Search: 200/61.45 R, 200/61.53
• US Class Current: 200/61.45R
• CPC Class Codes: B24B 49/105 using eddy currents
• CPC Class Codes: H01H 2300/052 Controlling, signalling or testing correct functioning of a switch see also H01H2300/056 - H01H2300/066 and H01H11/0062
• CPC Class Codes: H01H 35/14 Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch wherein the liquid constitutes a contact of the switch H01H29/002
• CPC Class Codes: H01H 35/142 Damping means to avoid unwanted response

Abstract

A crash sensor for a passive motor vehicle occupant restraint system, such as an inflatable air bag or seat belt tensioner. The crash sensor comprises a tubular passageway having a central, longitudinal axis; a sensing mass arranged to move within the passageway in the direction of the longitudinal axis between a first location and a second location; a device for biasing the sensing mass toward the first location in the passageway; and a device for closing an electrical circuit when the sensing mass moves to the second location in the passageway.

The invention provides methods for reducing the motion of the sensing mass and the tubular passageway in a direction perpendicular to the longitude, and/or methods for reducing the angular momentum of the sensing mass, during motion of the sensing mass in the longitudinal direction.

Claims

1. A sensor for detecting a motor vehicle crash, comprising:

(a) a housing;

(b) means for mounting said housing on a motor vehicle, the center of mass of said vehicle defining an inertial frame of reference;

(c) a longitudinal tubular wall defining a passageway within said housing;

(d) a sensing mass arranged tomove within said passageway in the longitudinal direction between a first position and a second position;

(e) means for biasing said sensing mass toward said first position in said passageway;

(f) means responsive to the motion of said sensing mass to said second position in said passageway for detecting a motor vehicle crash; and

(g) means for substantially reducing the vibrations of said sensing mass with respect to said inertial frame of reference in directions perpendicular to the longitude during motion of said sensing mass.

2. The crash sensor defined in claim 1, wherein said resilient mounting means is designed such that the natural frequency of vibration, with respect to said inertial frame of reference, of said wall and said sensing mass does not exceed 200 Hertz.

3. The crash sensor defined in claim 1, wherein said biasing means includes a mechanical spring.

4. The crash sensor defined in claim 1, wherein the movement of said sensing mass with respect to said passageway is damped.

5. The crash sensor defined in claim 1, wherein said biasing means includes a mechanical spring, and wherein said spring forms one electrical contact.

6. The invention in accordance with claim 1, wherein the motion of said sensing mass is magnetically damped.

7. The crash sensor defined in claim 1, further comprising means for reducing the angular momentum imparted to said sensing mass during motion of said sensing mass within said passageway.

8. The crash sensor defined in claim 7, wherein said angular momentum reducing means includes a low friction coating on the inner surface of said passageway.

9. The crash sensor defined in claim 8, wherein said low friction coming is Teflon.

10. The crash sensor defined in claim 8, wherein said low friction coating is tungsten disulfide.

11. The crash sensor defined in claim 8, wherein said low friction coating is molybdenum disulfide.

12. The crash sensor defined in claim 7, wherein said angular momentum reducing means includes a low friction coating on the outer surface of said sensing mass.

13. The crash sensor defined in claim 12, wherein said low friction coating is Teflon.

14. The crash sensor defined in claim 12, wherein said low friction coating is tungsten disulfide.

15. The crash sensor defined in claim 1, wherein said vibration reducing means include resilient means disposed mechanically between said vehicle and said wall for resiliently mounting said wall with respect to said vehicle, thereby to isolate said wall and said sensing mass from vibrations perpendicular to the longitude.

16. The crash sensor defined in claim 15, wherein said resilient mounting means comprises resilient material disposed between said housing and said wall.

17. The crash sensor defined in claim 16, wherein said resilient material comprises silicone rubber.

18. The crash sensor defined in claim 16, wherein said resilient material comprises closed-cell foam rubber.

19. The crash sensor defined in claim 16, wherein said resilient material has an elastic modulus which varies less than 4 to 1 over a temperature range from -40 to 160 degrees F.

20. The crash sensor defined in claim 16, wherein said resilient material is Hytrel.

21. The crash sensor defined in claim 15, wherein said resilient mounting means comprises a a plurality of hollow tubes made of elastomeric material and disposed between said housing and said wall.

22. The crash sensor defined in claim 21, wherein said tubes are mounted with their respective axes substantially in parallel with the longitudinal axis of said passageway.

23. The crash sensor defined in claim 21, wherein said resilient mounting means comprises four hollow tubes disposed equilaterally around said passageway.

24. The crash sensor defined in claim 15, wherein said resilient mounting means permits motion of said passageway with respect to said vehicle, in a direction perpendicular to the longitude, of at least 0.020 inches.

25. The crash sensor defined in claim 24, wherein said resilient mounting means permits motion of said passageway with respect to said vehicle, in a direction perpendicular to the longitude, of at least 0.050 inches.

26. The crash sensor defined in claim 15, wherein said vibration reducing means includes means for pivotally mounting said member at one end, and means for resiliently mounting said member at the other end.

27. The crash sensor defined in claim 26, wherein said pivot mounting means includes a projection and a corresponding recess.

28. The crash sensor defined in claim 26, wherein said resilient mounting means imparts an axially directed force to said member in the direction of one end.

29. The crash sensor defined in claim 26, wherein said resilient mounting means include spring means disposed between said member and said housing.

30. The crash sensor defined in claim 29, wherein said spring means comprises at least one flat spring.

31. The crash sensor defined in claim 30, wherein said spring means includes two U-shaped flat springs.

32. A sensor for detecting a motor vehicle crash, comprising:

(a) a housing;

(b) means for mounting said housing on a motor vehicle;

(c) a longitudinal tubular wall defining a passageway within said housing;

(d) a spherical sensing mass arranged to move within said passageway in the longitudinal direction between a first position and a second position;

(e) means for biasing said sensing mass toward said first position in said passageway;

(f) means responsive to the motion of said sensing mass to said second position in said passageway for detecting a motor vehicle crash; and

(g) means for reducing the angular momentum imparted to said sensing mass during motion of said sensing mass within said passageway in the longitudinal direction.

33. The crash defined in claim 32, wherein said angular momentum reducing means includes a low friction coating on the inner surface of said passageway.

34. The crash sensor defined in claim 33, wherein said low friction coating is Teflon.

35. The crash sensor defined in claim 33, wherein said low friction coating is tungsten disulfide.

36. The crash sensor defined in claim 32, wherein said angular momentum reducing means includes a low friction coating on the outer surface of said sensing mass.

37. The crash sensor defined in claim 36, wherein said low friction coating is Teflon.

38. The crash sensor defined in claim 36, wherein said low friction coating is tungsten disulfide.

39. In a sensor for detecting a motor vehicle crash, comprising:

(a) a housing;

(b) means for mounting said housing on a motor vehicle;

(c) a longitudinal tubular wall defining a passageway within said housing;

(d) a sensing mass arranged to move within said passageway in the longitudinal direction between a first position and a second position;

(e) means for biasing said sensing mass toward said first position in said passageway; and

(f) means responsive to the motion of said sensing mass to said second position in said passageway for detecting a motor vehicle crash;

the improvement wherein said biasing means comprises a ribbon spring member having two ends rigidly mounted with respect to one of said vehicle and said wall.

40. The crash sensor defined in claim 39, wherein said two ends of said ribbon spring member are attached to said passageway.

41. The crash sensor defined in claim 39, wherein said two ends of said ribbon spring member are attached to said housing.

42. The crash sensor defined in claim 39, wherein the position of at least one end of said ribbon spring member is adjustable.

43. The crash sensor defined in claim 39, wherein the movement of said sensing mass with respect to said passageway is damped.

44. The crash sensor defined in claim 39, further comprising means for adjusting the location of said first position in said passageway relative to said second position.

45. The crash sensor defined in claim 39, wherein said ribbon spring member exerts a substantially constant nearly constant biasing force on said sensing mass.

46. The crash sensor defined in claim 39, wherein said response means comprises first and second electrical contacts and said ribbon spring member forms said first electrical contact.

47. The crash sensor defined in claim 46, wherein a rigid member forms said second electrical contact.

48. The crash sensor defined in claim 47, wherein the position of said second electrical contact is adjustable.

49. The crash sensor defined in claim 47, wherein a second spring member forms said second electrical contact.

50. The crash sensor defined in claim 49, wherein said second spring member is a second ribbon spring member.

51. The crash sensor defined in claim 50, wherein said first and second ribbon spring members each contain a section which is substantially transverse to the longitudinal direction.

52. The crash sensor defined in claim 51, wherein said transverse sections of said first and second ribbon spring members are substantially transverse to each other.

53. A sensor for detecting a motor vehicle crash, comprising:

(a) a housing;

(b) a longitudinal tubular passageway within said housing;

(c) a sensing mass arranged to move within said passageway in the longitudinal direction between a first position and a second position;

(d) means for biasing said sensing mass toward said first position in said passageway; and

(e) means responsive to the motion of said sensing mass to said second position in said passageway;

the improvement wherein said biasing means comprises means for exerting a biasing force on said sensing mass which is substantially constant as said sensing mass moves from said first position to said second position.

54. A sensor for detecting a motor vehicle crash, comprising:

(a) a housing;

(b) a tubular passageway within said housing;

(c) a spherical sensing mass arranged to move within said passageway between a first position and a second position;

(d) means for biasing said sensing mass toward said first positon in said passageway;

(e) means responsive to the motion of said sensing mass to said second position in said passageway;

(f) means for dampening the motion of said sensing mass, said means utilizing the flow of a gas through a tight clearance between said sensing mass and said tubular passageway; and

(g) means for testing that said sensor is operational after installation on the vehicle.

55. A sensor for detecting a motor vehicle crash, comprising:

(a) a housing;

(b) a tubular passageway within said housing;

(c) a sensing mass arranged to move within said passageway between a first position and a second position, said sensing mass being susceptible to cross axis vibrations during such motion;

(d) means for biasing said sensing mass toward said first position in said passageway;

(e) means responsive to the motion of said sensing mass to said second position in said passageway;

(f) means for dampening the motion of said sensing mass, said means utilizing the flow of a gas through a tight clearance between said sensing mass and said tubular passageway; and

(g) means for substantially reducing the effects of said cross axis vibrations on the operation of said sensor.

56. A sensor for detecting a motor vehicle crash, comprising:

(a) a housing;

(b) a longitudinal tubular passageway within said housing having an internal sliding surface;

(c) a sensing mass having an external sliding surface and arranged to move within said passageway in the longitudinal direction between a first position and a second position;

(d) means for biasing said sensing mass toward said first position in said passageway;

(e) means responsive to the motion of said sensing mass to said second position in said passageway; and

(f) a tungsten disulfide coating disposed on at least one of said internal and external sliding surfaces, thereby to reduce the angular momentum imparted to said sensing mass during motion of said sensing mass within said passageway in the longitudinal direction.