Seat airbag

1. An assembly comprising:

a seatback;

an airbag including an upper panel and a lower panel spaced from each other and an intermediate panel disposed therebetween, the upper panel and the lower panel each uninflatable and each supported by the seatback; and

the intermediate panel supported by the seatback and inflatable to an inflated position, the intermediate panel in the inflated position including a valley elongated in a direction from the lower panel towards the upper panel;

wherein the intermediate panel defines an inflation chamber,

the intermediate panel including a plurality of tethers disposed in the inflation chamber and extending from the valley across the inflation chamber, the plurality of tethers being spaced from each other along the valley.

2. The assembly of claim 1 , further comprising a retractor disposed on the seatback, the upper panel is retractably engaged with the retractor.

3. The assembly of claim 2 , further comprising a processor and a memory storing instructions to actuate the retractor in response to detecting the intermediate panel in the inflated position.

4. The assembly of claim 1 , wherein the intermediate panel includes a first portion and a second portion disposed on opposite sides of the valley, the first portion and the second portion in fluid communication with each other.

5. The assembly of claim 4 , wherein the first portion extends transverse to the second portion and the seatback.

6. The assembly of claim 1 , wherein the intermediate panel includes a distal end spaced from the seatback in the inflated position, the upper panel and the lower panel each extending across the valley towards the distal end.

7. The assembly of claim 6 , wherein the distal end is disposed outboard of the valley.

8. The assembly of claim 1 , wherein the upper panel and the lower panel each extend from the intermediate panel to the seatback.

9. The assembly of claim 8 , wherein the valley is spaced from at least one of the upper panel and the lower panel.

10. The assembly of claim 1 , wherein the upper panel and the lower panel are triangular, the upper panel and the lower panel each include a base extending along the intermediate panel and a vertex spaced from the intermediate panel and engaged with the seatback.

11. The assembly of claim 1 , wherein the seatback includes an upper end and an inboard side and an outboard side spaced from each other and each extending downwardly from the upper end, the intermediate panel is disposed on the inboard side of the seatback.

12. The assembly of claim 11 , further comprising a seatbelt assembly having a webbing extending from the outboard side of the seatback downwardly across the seatback in an extended position, the intermediate panel spaced from the webbing in the extended position.

13. The assembly of claim 11 , wherein the upper panel is engaged with the upper end and the lower panel is engaged with the inboard side.

14. The assembly of claim 11 , wherein the intermediate panel includes an inboard side facing the outboard side of the seatback in the inflated position, the valley is disposed on the inboard side of the intermediate panel.

15. The assembly of claim 1 , further comprising a processor and a memory storing instructions to inflate the intermediate panel in response to detecting one of a far side oblique impact and a frontal impact.

16. The assembly of claim 1 , wherein the valley is configured to be disposed adjacent to a shoulder of an occupant between 5th-percentile female and 95th-percentile male stature sitting against the seatback.

17. An assembly comprising:

a seatback;

an airbag including an upper panel and a lower panel spaced from each other and an intermediate panel disposed therebetween, the upper panel and the lower panel each uninflatable and each supported by the seatback;

the intermediate panel supported by the seatback and inflatable to an inflated position, the intermediate panel in the inflated position including a valley elongated in a direction from the lower panel towards the upper panel; and

a retractor disposed on the seatback, the upper panel is retractably engaged with the retractor.

18. An assembly comprising:

a seatback;

an airbag including an upper panel and a lower panel spaced from each other and an intermediate panel disposed therebetween, the upper panel and the lower panel each uninflatable and each supported by the seatback; and

the intermediate panel supported by the seatback and inflatable to an inflated position, the intermediate panel in the inflated position including a valley elongated in a direction from the lower panel towards the upper panel;

wherein the upper panel extends above an upper edge of the intermediate panel and the lower panel extends below the intermediate panel.