Apparatus for measuring tension in seat belt webbing

• US 20040232670A1
• Filed: 04/07/2004
• Published: 11/25/2004
• Est. Priority Date: 03/12/2002
• Status: Abandoned Application

• Current Assignee: TRW Vehicle Safety Systems Incorporated (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: TRW Vehicle Safety Systems Incorporated (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Malott, Brian P., Badyna, Michael, Cabrera, Jorge J., Delventhal, Neal H., Wolyniec, Randall J., Devereaux, Scott D., McFalls, Bob
• Application Number:
  US10/819,821
• Publication Number:
  US 20040232670A1
• Time in Patent Office: Days
• US Class Current: 280/735
• CPC Class Codes: B60R 21/0152 using strain gauges
• CPC Class Codes: B60R 21/01544 detecting seat belt parameters, e.g. length, tension or height-adjustment
• CPC Class Codes: B60R 21/0155 sensing belt tension
• CPC Class Codes: B60R 22/18 Anchoring devices
• CPC Class Codes: B60R 22/1952 Transmission of tensioning power by cable; Return motion locking means therefor

Abstract

An apparatus (510) includes seat belt webbing (24). An elongated member (520) is connected with the seat belt webbing (24). Tension in the seat belt webbing (24) is transmitted to the elongated member (520). A sensor of the apparatus 510 includes an arm (560) that is associated with the elongated member (520). The elongated member (520) moves at least a portion of the arm (560) in response to a change in tension in the seat belt webbing (24). The sensor also includes a device (558) that is responsive to movement of the arm (560) to provide an output signal indicative of the tension in the seat belt webbing (24). Structure (604) of the apparatus (510) reduces a variable moment acting on the arm as a result of off-axis loading of the seat belt webbing (24).

Claims

1. An apparatus comprising:

seat belt webbing;

an elongated member connected with the seat belt webbing, tension in the seat belt webbing being transmitted to the elongated member;

a sensor comprising;

an arm associated with the elongated member, the elongated member moving at least a portion of the arm in response to a change in tension in the seat belt webbing, and

a device responsive to movement of the at least a portion of the arm to provide an output signal indicative of the tension in the seat belt webbing; and

structure for reducing a variable moment acting on the arm as a result of off-axis loading of the seat belt webbing.

2. The apparatus as defined in claim 1 wherein the structure includes a bushing for maintaining a predetermined angle between the arm and the elongated member independent of a position of the seat belt webbing relative to the arm.

3. The apparatus as defined in claim 2 further including a guide wall, tension in the seat belt webbing moving the arm relative to the guide wall, the guide wall supporting the bushing, a biasing element interposed between the bushing and the arm for resisting movement of the arm relative to the guide wall.

4. The apparatus as defined in claim 3 wherein the bushing is movable relative to the guide wall for setting a force of the biasing element to a predetermined value.

5. The apparatus as defined in claim 2 wherein the structure includes an anchor arm that is pivotally connected to the arm and that connects the elongated member and the arm, the anchor arm pivoting during off-axis loading of the seat belt webbing.

6. The apparatus as defined in claim 1 further including an anchor plate, a fastener connecting the arm to the anchor plate and defining an axis of rotation of the arm, the arm rotating relative to the anchor plate in response to a change in tension in the seat belt webbing.

7. The apparatus as defined in claim 6 wherein the anchor plate supports the structure.

8. The apparatus as defined in claim 6 wherein at least a portion of the device is mounted on the anchor plate adjacent the arm, the device measuring movement of the arm relative to the anchor plate.

9. The apparatus as defined in claim 8 wherein the device is a magnetoresistive sensor and includes a magnet and a sensor for monitoring movement of the magnet, a first one of the magnet and the sensor moving during rotation of the arm and a second one of the magnet and the sensor being fixed to the anchor plate adjacent the arm.

10. The apparatus as defined in claim 6 further including a biasing element, the biasing element extending between the arm and the anchor plate for biasing the arm in a first direction relative to the anchor plate, the arm rotating in a second direction, opposite the first direction, when the tension in the seat belt webbing overcomes a biasing force of the biasing element.

11. The apparatus as defined in claim 6 wherein the fastener is a torsion bar having opposite first and second ends, the first end of the torsion bar being attached to the anchor plate and the second end of the torsion bar being attached to the arm, the change in tension in the seat belt webbing rotating the second end of the torsion bar relative to the first end so as to twist the torsion bar.

12. The apparatus as defined in claim 11 wherein the device is a torsion sensor for measuring torsion in the torsion bar.

13. The apparatus as defined in claim 11 wherein the device is a magnetoresistive sensor and includes a magnet and a sensor for monitoring movement of the magnet, a first one of the magnet and the sensor being fixed to the second of the torsion bar and a second one of the magnet and the sensor being fixed to the anchor plate.

14. The apparatus as defined in claim 1 wherein at least a portion of the device is mounted adjacent the arm and measures rotation of the arm.

15. The apparatus as defined in claim 14 wherein the device is a magnetoresistive sensor and includes a magnet and a sensor for monitoring movement of the magnet, a first one of the magnet and the sensor moving as the arm rotates and a second one of the magnet and the sensor being stationary during movement of the arm.

16. The apparatus as defined in claim 1 further including an overtravel stop, the overtravel stop extending through a portion of the arm and preventing further movement of the arm when tension in the seat belt webbing increases above a threshold value.

17. The apparatus as defined in claim 1 further including a buckle assembly and a tongue, the tongue being attached to the seat belt webbing and the buckle assembly being attached to the elongated member, the buckle assembly receiving the tongue to connect the elongated member with the seat belt webbing.

18. The apparatus as defined in claim 1 wherein the elongated member is one of an anchor cable, webbing, and a strap.