Seat belt tension sensor

• US 6,311,571 B1
• Filed: 07/26/2000
• Issued: 11/06/2001
• Est. Priority Date: 01/31/2000
• Status: Expired due to Fees

• Current Assignee: Peter Norton
• Original Assignee: Peter Norton
• Inventors: Norton, Peter
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US09/625,765
• Time in Patent Office: 468 Days
• Field of Search: 738/26, 738/28, 738/623.91, 738/624.2, 738/623.92, 738/626.37
• US Class Current: 73/862.637
• CPC Class Codes: G01L 5/10 using electrical means
• CPC Class Codes: G01L 5/103 using sensors fixed at one end of the flexible member
• CPC Class Codes: G01L 5/105 using electro-optical means

Abstract

A seat belt tension sensor has an anchor, a seat belt tension receiver, a moving arm force responder, and an arm sensor. The seat belt tension receiver applies force received from a seat belt to the moving arm force responder. The moving arm force responder is made of spring metal bent to have a base for receiving force and one or two arms that are urged to move by the received force. The arm sensor responds to the arm or arms by generating an electric signal. The anchor has an opening through which a seat belt, the seat belt tension receiver and the moving arm force responder pass. A cross member of the anchor spans the opening and withstands the large forces applied by the seat belt when the vehicle strikes an obstacle. An edge of the cross member is grooved to engage the base of the moving arm force responder in a way that provides low friction during flexing of the base. The base of the moving arm force responder operates as a low friction bearing for the movement of the seat belt tension receiver. A flexible suspension element made of spring metal operates as a second bearing and also operates as a preloading spring. In a preferred embodiment, the arm sensor comprises a semiconductor capacitance sensor responsive to the capacitance between two capacitor plates and two arms of a moving arm force responder.

Claims

1. In an occupant protection system of a vehicle of the type comprising processing means for deploying occupant protection means, a seat belt tension sensor comprising:

an anchor,

a force sensing means, and

a tension receiver, and wherein;

said anchor comprising a plate comprising an opening spanned by a cross member,

said tension receiver being adapted for receiving force from a seat belt, said tension receiver also being connected with said force sensing means for applying force thereto,

said force sensing means being connected with said cross member for applying force thereto,

said force sensing means being adapted for generating an electric signal responsive to said force received from said tension receiver when said force received from said tension receiver is in the range of zero to a predetermined force, said predetermined force being less than one thousand pounds, and including

means for protecting said force sensing means when said force received from said seat belt is greater than said predetermined force.

2. The invention as defined by claim 1 and wherein

said tension receiver being movable in the direction of an axis, and including:

means for selecting from said force received from a seat belt the component of said force received from a seat belt having the direction of said axis, and wherein;

said tension receiver being adapted to apply said selected component of said force through said connection to said force sensing means.

3. The invention as defined by claim 2 wherein:

said means for selecting said axial component comprising bearing means providing low friction movement of said tension receiver in the direction of said axis.

4. The invention as defined by claim 3 and wherein:

said bearing means comprising flexible suspension means engaging said anchor and said tension receiver.

5. The invention as defined by claim 4 wherein:

said flexible suspension means providing a preload force urging said tension receiver in the direction of said axis.

6. The invention as defined by claim 1 wherein:

said force sensing means comprising a flexible member,

said flexible member being connected with said tension receiver for receiving force therefrom, and

said flexible member being adapted to flex in response to said force received from said tension receiver.

7. The invention as defined by claim 6 wherein:

said electric signal being a measure of said flexing of said flexible member.

8. The invention as defined by claim 7 and including:

a capacitance sensing means, two capacitor elements, and means linking a said capacitor element with said flexible member for causing relative movement between said capacitor elements upon said flexing, and wherein;

said capacitance sensing means being responsive to capacitance between said capacitor elements by generating said electric signal.

9. The invention as defined by claim 6 and wherein:

said flexible member engaging said anchor for applying force thereto, and

said flexible member and said anchor being adapted for minimizing friction between said flexible member and said anchor during said flexing.

10. The invention as defined by claim 6, and wherein:

said cross member comprising a grooved edge,

said grooved edge comprising salient edges,

said flexible member engaging said salient edges,

at times when said force received by said flexible member from said tension receiver is small, there being a gap between said flexible member and said groove, said gap being delimited by said salient edges,

there being a predetermined level of said force received by said flexible member from said tension receiver above which seat belt tension measurement is not desired, and

said flexible member and said groove being adapted such that, at levels of said force received by said flexible member from said tension receiver greater than said predetermined level, said flexible member and said groove abut at points between said salient edges.

11. The invention as defined by claim 6 wherein:

said flexible member comprising a base adapted to flex in response to said force received from said tension receiver, and including;

two arms linked with said base for movement consequent to said flexing, and wherein;

said two arms having a distance therebetween,

said distance between said arms being responsive to said force received by said flexible member from said tension receiver, and

said force sensing means comprising means responsive to said distance between said arms.

12. The invention as defined by claim 11 and including:

a capacitance sensor and two capacitor elements, and wherein;

there being a first capacitance between one of said two capacitor elements and one of said two arms, said arms being electrically connected,

there being a second capacitance between the other of said two capacitor elements and the other of said two arms,

said capacitance sensor being connected to said capacitor elements for sensing the capacitance therebetween,

said capacitance sensor being adapted for generating a signal responsive to said capacitance between said capacitor elements, and

said signal being said electric signal.

13. The invention as defined by claim 11 wherein:

said base being a low friction bearing operating to bear said tension receiver in its said axial movement.

14. The invention as defined by claim 11 and including:

a permanent magnet for providing a magnetic field between said arms, and

a magnetic field sensor responsive to said magnetic field, and wherein;

said arms comprise ferromagnetic material,

said magnetic field sensor being adapted for generating a signal responsive to said magnetic field between said arms, and

said signal being said electric signal.

15. In an occupant protection system of a vehicle of the type comprising processing means for deploying occupant protection means, a seat belt tension sensor comprising:

an anchor, said anchor comprising a cross member,

a flexible member,

a tension receiver, and

sensing means for generating an electric signal for transmission to said processing means, and wherein;

said flexible member being connected with said cross member for applying force thereto,

said tension receiver being adapted for receiving seat belt tension,

said tension receiver being connected with said flexible member for applying thereto force derived from said seat belt tension,

said flexible member being responsive to said force received from said tension receiver by flexing, and

said electric signal being indicative of said flexing of said flexible member.

16. The invention as defined by claim 15 and including:

a capacitor element, and wherein;

said sensing means for generating an electric signal comprising a capacitance sensing means, and

said capacitance sensing means being responsive to the capacitance between said capacitor element and said flexible member by generating said electric signal.

17. The invention as defined by claim 15 wherein:

said tension receiver being adapted for receiving force from a seat belt, and

said tension receiver being movable with respect to said anchor in the direction of an axis, and including;

means for selecting the axial component of said force from a seat belt received by said tension receiver from other components of said force from a seat belt received by said tension receiver, and wherein;

said force applied to said flexible member by said tension receiver comprising said axial component.

18. The invention as defined by claim 17 and including:

low friction bearing means for bearing said movement of said tension receiver relative to said anchor in the direction of said axis, and wherein;

said means for selecting comprising said bearing means.

19. The invention as defined by claim 18 wherein:

said low friction bearing means comprising a first flexible suspension means engaging both said anchor and said tension receiver.

20. The invention as defined by claim 19 wherein:

said first flexible suspension means being adapted to apply a preload force urging said tension receiver in the direction of said axis.

21. The invention as defined by claim 19 wherein:

said flexible member being a second flexible suspension means engaging both said anchor and said tension receiver for providing a low friction bearing for said tension receiver in its said axial movement.

22. The invention as defined by claim 15 wherein:

said connection between said flexible member and said cross member being adapted for minimizing friction therebetween during said flexing.

23. The invention as defined by claim 15 and including:

an arm, and wherein;

said flexible member being linked with said arm for moving said arm consequent to said flexing.

24. The invention as defined by claim 23 and including:

a capacitor element, and wherein;

said sensing means for generating an electric signal comprising a capacitance sensing means, and

said capacitance sensing means being responsive to the capacitance between said capacitor element and said arm by generating said electric signal.

25. In an occupant protection system of a vehicle of the type comprising processing means for deploying occupant protection means, a seat belt tension sensor comprising:

a tension receiver, and

a moving arm force responder, and wherein;

said moving arm force responder comprising a base adapted to receive force from said tension receiver,

said moving arm force responder also comprising two arms having a distance therebetween, said distance being responsive to said force received from said tension receiver, and including;

means responsive to said distance by generating an electric signal for transmission to said processing means.

26. The invention as defined by claim 25 and including:

a capacitance sensor and two capacitor elements, and wherein;

there being a first capacitance between one of said two capacitor elements and one of said two arms, said arms being electrically connected,

there being a second capacitance between the other of said two capacitor elements and the other of said two arms,

said capacitance sensor being connected to said capacitor elements for sensing the capacitance therebetween,

said capacitance sensor being adapted for generating a signal responsive to said capacitance between said capacitor elements, and

said signal being said electric signal.

27. The invention as defined by claim 25 and including:

an anchor comprising a cross member, and wherein;

said cross member comprising a grooved edge,

said grooved edge comprising salient edges, and

said base engaging said salient edges.

28. The invention as defined by claim 27 wherein:

said base being adapted to flex in response to said force received from said tension receiver, and

said base and said groove being adapted for minimizing friction between said base and said salient edges during said flexing.

29. The invention as defined by claim 27 wherein;

at times when said force received from said tension receiver is small, a gap exists between said base and said groove,

said gap being delimited by said salient edges,

there being a predetermined level of said force received from said tension receiver above which seat belt tension measurement is not desired, and

said base and said groove being adapted such that, at levels of said force received from said tension receiver that are greater than said predetermined level of said force received from said tension receiver, said base and said groove abut at points between said salient edges.

30. The invention as defined by claim 25, and including:

an anchor, and

a first bearing means, and wherein;

said tension receiver being movable in the direction of an axis,

said first bearing means bearing said tension receiver in said movement, and

said first bearing means comprising first flexible suspension means engaging said anchor and said tension receiver.

31. The invention as defined by claim 30 wherein:

said first flexible suspension means being adapted to apply a preload force urging said tension receiver in the direction of said axis.

32. The invention as defined by claim 30, and including:

a second bearing means, and wherein;

said second bearing means bearing said tension receiver in said movement, and

said second bearing means comprising said base of said moving arm force responder engaging both said grooved edge of said anchor and said tension receiver.