Load limiting seatbelt retractor

1. A seatbelt retractor comprising:

a housing having a first end and a second end;

a spool having a first end and a second end each rotatably supported by the housing, the spool being elongated on an axis from the first end to the second end; and

a torsion bar having a first end fixed to the first end of the spool and a second end operatively engageable with the housing;

the torsion bar having a rod elongated from the first end of the torsion bar to the second end of the torsion bar, the torsion bar being designed to rotationally yield so that the first end of the torsion bar rotates relative to the second end of the torsion bar when the second end of the torsion bar is engaged with housing and rotational force applied to the torsion bar through the spool exceeds a threshold force of the rod; and

the torsion bar including a wire elongated along the axis and connected to the first end of the torsion bar and the second end of the torsion bar, the wire being designed to deform about the axis and to release from the rod during the rotation of the first end of the rod relative to the second end of the rod.

2. The seatbelt retractor of claim 1 , wherein a connection of the wire to the second end is weaker than a connection of the wire to the first end.

3. The seatbelt retractor of claim 1 , wherein the torsion bar includes a first cap connected to the rod at the first end of the torsion bar and a second cap connected to the rod at the second end of the torsion bar, the wire being connected to the first cap and the second cap.

4. The seatbelt retractor of claim 3 , wherein a connection of the wire to the second cap is weaker than a connection of the wire to the first cap.

5. The seatbelt retractor of claim 3 , wherein the wire is bonded to the second cap with an adhesive, the failure strength of the adhesive being less than the failure strength of the wire.

6. The seatbelt retractor of claim 5 , wherein the wire and the adhesive are designed so that the adhesive fails when the first end of the torsion bar rotates 0.5 to 1.0 revolutions about the axis relative to the second end.

7. The seatbelt retractor of claim 3 , wherein the second cap includes a slot receiving the wire, the wire being bonded to the slot with an adhesive, the failure strength of the adhesive being less than the failure strength of the wire.

8. The seatbelt retractor of claim 1 , further comprising a plurality of wires including the wire, each of the wires being elongated along the axis and connected to the first end of the torsion bar and the second end of the torsion bar.

9. The seatbelt retractor of claim 8 , wherein the plurality of wires are spaced from each other circumferentially about the axis.

10. The seatbelt retractor of claim 8 , wherein the torsion bar includes a first cap connected to the rod at the first end of the torsion bar and a second cap connected to the rod at the second end of the torsion bar, the wires being connected to the first cap and the second cap.

11. The seatbelt retractor of claim 10 , wherein the plurality of wires are spaced from each other circumferentially about the axis.

12. The seatbelt retractor of claim 10 , wherein connections of the wires to the second cap are weaker than a connection of the wires to the first cap.

13. The seatbelt retractor of claim 10 , wherein the wires are bonded to the second cap with an adhesive, the failure strength of the adhesive being less than the failure strength of the wires.

14. The seatbelt retractor of claim 10 , wherein the wires and the adhesive are designed so that the adhesive fails when the first end of the torsion bar rotates 0.5 to 1.0 revolutions about the axis relative to the second end.

15. The seatbelt retractor of claim 10 , wherein the second cap includes slots receiving the wires, the wires being bonded to the slots with an adhesive, the failure strength of the adhesive being less than the failure strength of the wires.

16. The seatbelt retractor of claim 1 , further comprising a webbing supported by the spool.

17. The seatbelt retractor of claim 1 , further comprising a locking device supported on the second end of the housing and being operatively engageable with the second end of the torsion bar.

18. The seatbelt retractor of claim 1 , wherein the wire and the rod each have a diameter, the diameter of the wire being smaller than the diameter of the rod.

19. A seatbelt retractor comprising:

a housing having a first end and a second end;

a spool having a first end and a second end each rotatably supported by the housing, the spool being elongated on an axis from the first end to the second end;

a torsion bar having a first end fixed to the first end of the spool and a second end operatively engageable with the housing;

the torsion bar including a wire elongated along the axis and connected to the first end of the torsion bar and the second end of the torsion bar; and

a connection of the wire to the second end is weaker than a connection of the wire to the first end.

20. A seatbelt retractor comprising:

a housing having a first end and a second end;

a spool having a first end and a second end each rotatably supported by the housing, the spool being elongated on an axis from the first end to the second end; and

a torsion bar having a first end fixed to the first end of the spool and a second end operatively engageable with the housing;

the torsion bar including a wire elongated along the axis and connected to the first end of the torsion bar and the second end of the torsion bar; and

the torsion bar including a rod elongated from the first end of the torsion bar to the second end of torsion bar, a first cap connected to the rod at the first end of the torsion bar, and a second cap connected to the rod at the second end of the torsion bar, the wire being connected to the first cap and the second cap.