Seat belt tension sensor

• US 6,776,056 B2
• Filed: 06/28/2002
• Issued: 08/17/2004
• Est. Priority Date: 08/06/2001
• Status: Expired due to Fees

• Current Assignee: CTS Corporation
• Original Assignee: CTS Corporation
• Inventors: Garver, Ryan, Teeters, Dale, Kaijala, Murray
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): DAVIS, OCTAVIA L
• Application Number:
  US10/185,242
• Publication Number:
  US 20030024327A1
• Time in Patent Office: 781 Days
• Field of Search: 731/60, 738/623.91, 738/62, 738/26, 280/804, 280/735, 280/801.1, 180/268, 701/45, 701/862.451, 701/862.453, 701/862.474, 701/862.391, 701/862.452
• US Class Current: 73/862
• CPC Class Codes: B60R 2021/01272 Belt tensioners
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/0155 sensing belt tension
• CPC Class Codes: B60R 21/01556 Child-seat detection systems
• CPC Class Codes: B60R 22/18 Anchoring devices
• CPC Class Codes: G01L 5/101 using sensors inserted into the flexible member
• CPC Class Codes: G01L 5/103 using sensors fixed at one end of the flexible member
• CPC Class Codes: G01L 5/108 for measuring a reaction force applied on a single support, e.g. a glider

Abstract

A seat belt tension sensor for measuring the magnitude of tension in a seat belt. The seat belt tension sensor has a housing with a cavity. An anchor plate has a portion located in the cavity. The housing moves relative to the anchor plate between a first position and a second position. A sensor is mounted to the housing. The housing presses on the sensor as the housing moves from the first to the second position. The sensor generates an electrical signal in response to the housing moving between the first and second positions. The electrical signal changes as a function of tension on the seat belt. The sensor is a strain gage. The housing engages the anchor plate in the second position to protect the sensor from damage in a vehicle crash situation.

Claims

1. A seat belt tension sensor for attachment between a seat belt and a vehicle structure comprising:

a housing having a cavity;

an anchor plate having a first portion located in the cavity, the housing movable relative to the anchor plate between a first position and a second position;

a strain gage sensor mounted to the housing, such that the housing presses on the sensor as the housing moves from the first to the second position, the sensor generating an electrical signal in response to the housing moving between the first and second positions, the electrical signal changing as a function of tension on the seat belt;

a spring located between the sensor and the anchor plate, the spring urging the housing toward the first position, wherein the housing has a flange with a hole extending through the flange adapted to receive a seat belt loop and the anchor plate has a corresponding aperture for receiving the flange.

2. The seat belt tension sensor according to claim 1 wherein the anchor plate has a second portion extending outside of the housing, the second portion defining a second aperture for receiving a fastener mountable to a vehicle structure.

3. The seat belt tension sensor according to claim 1 wherein the housing has a pair of posts extending therefrom, the sensor being retained in the posts.

4. The seat belt tension sensor according to claim 1 wherein the anchor plate has a cutout, the sensor and the spring extending into the cutout.

5. The seat belt tension sensor according to claim 1 wherein a wire harness is attached to the sensor.

6. The seat belt tension sensor according to claim 1 wherein the anchor plate has a projection that extends into the spring.

7. The seat belt tension sensor according to claim 1 wherein the housing has a narrow portion adjacent the hole that an end of the seat belt wraps around.

8. The seat belt tension sensor according to claim 1 wherein the strain gage sensor is a substrate having at least one resistor mounted thereon.

9. The seat belt tension sensor according to claim 8, wherein the substrate has a first surface and a second surfaces, the resistor mounted on the first surface and the spring in contact with the second surface.

10. The seat belt tension sensor according to claim 1 wherein the sensor includes four resistors.

11. The seat belt tension sensor according to claim 1 wherein the sensor includes resistors are connected to form a wheatstone bridge.

12. A seat belt tension sensor for measuring the amount of tension in a seat belt in a vehicle comprising:

a housing, the seat belt attached to the housing;

an anchor plate having a first end mounted to the housing and a second end adapted for mounting to a vehicle structure;

a strain gage sensor mounted to the housing, the sensor adapted to provide an electrical signal indicative of the tension in the seat belt; and

a spring mounted between the sensor and the anchor plate;

the housing movable relative to the anchor plate as tension is placed on the seat belt such that the tension of the seat belt is transferred to the sensor where it is detectable.

13. The seat belt tension sensor according to claim 12 wherein the housing has a flange, the flange contacting the anchor plate after a first magnitude of tension in the seat belt is exceeded.

14. The seat belt tension sensor according to claim 13 wherein the amount of strain transferred from the seat belt to the sensor is limited to the first magnitude of tension.

15. The seat belt tension sensor according to claim 13 wherein the flange contacting the anchor plate protects the sensor from damage.

16. The seat belt tension sensor according to claim 12 wherein the housing defines a flange and the anchor plate defines an aperture receiving the flange such that a gap is defined between the flange and the anchor plate within the aperture and wherein the anchor plate defines a cutout for receiving the sensor and the spring.

17. The seat belt tension sensor according to claim 12 wherein, the second end is adapted to receive a fastener.

18. The seat belt tension sensor according to claim 12 wherein the housing has a pair of posts extending therefrom, each post having a slot, the sensor retained in the slots.

19. The seat belt tension sensor according to claim 12 wherein the anchor plate defines a projection, the spring mounted over the projection.

20. The seat belt tension sensor according to claim 16, wherein the flange has a hole for receiving a seat belt webbing.

21. The seat belt tension sensor according to claim 12, wherein the housing has a narrow portion adjacent the flange that the seat belt wraps around.

22. The seat belt tension sensor according to claim 12 wherein the strain gage is a substrate having at least one resistor mounted thereon.

23. The seat belt tension sensor according to claim 22, wherein the substrate has a first surface and a second surface, the resistor mounted on the first surface and the spring in contact with the first surface.

24. The seat belt tension sensor according to claim 12, wherein a printed circuit board is mounted in the housing.

25. The seat belt tension sensor according to claim 24, wherein a terminal connects the strain member to the printed circuit board.

26. The seat belt tension sensor according to claim 24 wherein a wire harness is connected to the printed circuit board.

27. The seat belt tension sensor according to claim 24 wherein an electronic circuit is mounted to the printed circuit board, the electronic circuit adapted to amplify the electrical signal.

28. The seat belt tension sensor according to claim 23, wherein the anchor plate is contact with the second surface.

29. A seat belt tension sensor suitable for use with a vehicle connection bolt, the device comprising:

an apertured anchor plate having a first end defining a first opening for securing a seat belt webbing and having a second end defining a second opening for the bolt,

a housing slidably mounted around the first end, the housing defining a hole and a flange around the hole extending into the first opening, whereby the flange, the hole and the first opening are together adapted to receive a seat belt webbing;

a strain gage secured within the housing;

a spring set between the anchor plate and the strain gage such that the strain gage is responsive to a force applied by the seat belt webbing to the housing.

30. The seat belt tension sensor device according to claim 29 further comprising an actuator support set between the spring and the strain gage to actuate the strain gage.

31. The seat belt tension sensing device according to claim 29 wherein the housing includes a channel for receiving the spring.

32. The seat belt tension sensing device according to claim 29 wherein the first opening in the anchor plate is sized to provide limited sliding motion of the housing with respect to the anchor plate.

33. A seat belt tension sensor suitable for use with a vehicle connection bolt, the device comprising:

an apertured anchor plate having a first end portion defining a first opening and having a second end portion defining a second opening for the bolt, the anchor plate further defining a cutout having a pair of opposing portions;

a housing slidably mounted around the first end, the housing defining a hole and a flange around the hole, the flange extending into the first opening, whereby the flange, the hole and the first opening are together adapted to secure a seat belt webbing;

a spring set between the pair of opposing portions;

a strain gage secured to the housing and positioned between one of the opposing portions and the spring such that the strain gage is responsive to a force applied by the seat belt webbing to the housing,

whereby the flange extending into the first opening serves to limit the sliding motion of the housing such that the housing is movable from positions in which increasing force of seat belt tension is detectable by the strain gage and a limit position in which increasing force of seat belt tension is countered by the anchor plate.

34. The seat belt tension sensor according to claim 33 wherein the cutout is defined between the first and second openings.

35. The seat belt tension sensor according to claim 33 wherein the opposing portions are opposing sides of an opening defined by the anchor plate and wherein at least one of the opposing portions includes a projection into the opening in the plane of the anchor plate for connection to the spring.

36. The seat belt tension sensing according to claim 33 further comprising an actuator support set between the spring and the strain gage to actuate the strain gage.

37. The seat belt tension sensing according to claim 33 wherein the housing defines a guide channel for receiving the spring.