Side airbag system and method of manufacturing side airbag

1. A side airbag system comprising:

a side airbag that includes

an upper bag portion that is formed of a piece of upper base fabric and that is located on a vehicle upper side;

a lower bag portion that is formed of a piece of lower base fabric and that is located on a vehicle lower side of the upper bag portion;

a tether portion that is formed of upper regions of the lower base fabric and that serves as a partition between the upper bag portion and the lower bag portion; and

a tube that is formed of a piece of tube base fabric, that extends through the tether portion to the lower bag portion and to the upper bag portion, that has an opening at one end located adjacent to the lower bag portion and an opening at the other end located adjacent to the upper bag portion, and that distributes inflation gas between the upper bag portion and the lower bag portion, wherein

the side airbag is supplied with gas to inflate and deploy in the event of a side impact crash,

a lower end portion of the upper base fabric is sewed to a bag outer surface at lower ends of the upper regions, used as the tether portion, in the lower base fabric,

the tube is formed into a cylindrical shape in such a manner that the tube base fabric, sewed to the lower base fabric, is further sewed to the upper regions of the lower base fabric and folded toward a vehicle front side along a fold axis and then front ends of the folded tube base fabric are sewed together in a longitudinal direction of the tube,

the tether portion is formed in such a manner that the upper regions of the lower base fabric folded along the fold axis are sewed together, and

the upper bag portion is formed in such a manner that an outer periphery of the upper base fabric and another outer periphery of the upper base fabric are sewed together, and the lower bag portion is formed in such a manner that an outer periphery of the lower base fabric and another outer periphery of the lower base fabric are sewed together.

2. The side airbag system according to claim 1 , wherein

the tube base fabric is sewed to the upper region of the lower base fabric before a seam between the front ends of the folded tube base fabric so as to leave the seam to form a sewed portion, and

the upper regions of the lower base fabric are sewed together to the sewed portion, terminating before the seam, between the tube base fabric and the upper regions of the lower base fabric.

3. The side airbag system according to claim 1 , wherein the upper bag portion covers at least one of a chest and shoulder of an occupant seated on a vehicle seat, and the lower bag portion covers a hip of the occupant.

4. The side airbag system according to claim 3 , further comprising an inflator that is arranged inside the tube, wherein

the tube is supplied with inflation gas from the inflator to inflate and deploy prior to the upper bag portion and the lower bag portion in the event of a side impact crash.

5. The side airbag system according to claim 4 , wherein, when the side airbag inflates and deploys, the one end of the tube, located adjacent to the lower bag portion, opens at a location corresponding to the hip of the occupant, and the other end of the tube, located adjacent to the upper bag portion, opens at a location corresponding to the shoulder of the occupant.

6. The side airbag system according to claim 4 , wherein, when the side airbag inflates and deploys, the one end of the tube, located adjacent to the lower bag portion, opens at a location corresponding to the hip of the occupant, and the other end of the tube, located adjacent to the upper bag portion, extends toward a vehicle front side along the outer periphery of the upper bag portion and opens at a location corresponding to the chest of the occupant.

7. The side airbag system according to claim 6 , wherein an opening area of the other end of the tube, located adjacent to the upper bag portion, is smaller than an opening area of the one end of the tube, located adjacent to the lower bag portion.

8. The side airbag system according to claim 3 , wherein, when the side airbag inflates and deploys, an internal pressure in the lower bag portion is higher than an internal pressure in the upper bag portion.

9. The side airbag system according to claim 8 , wherein the lower base fabric is made of a material that is stronger than that of the upper base fabric.

10. The side airbag system according to claim 3 , further comprising an additional sewed portion provided for the upper bag portion, wherein the additional sewed portion extends from a vehicle front side end of the opening at the other end of the tube, located adjacent to the upper bag portion, toward a vehicle front side and terminates before a sewed portion at the outer periphery of the upper bag portion, wherein

the upper bag portion is partitioned by the additional sewed portion into an uppermost bag portion and an intermediate bag portion.

11. The side airbag system according to claim 10 , wherein the additional sewed portion is set at a portion corresponding to an upper arm of the occupant.

12. The side airbag system according to claim 10 , wherein, when the side airbag inflates and deploys, the lower bag portion covers the hip of the occupant, the intermediate bag portion covers the chest of the occupant, and the uppermost bag portion covers the shoulder of the occupant.

13. The side airbag system according to claim 10 , wherein the intermediate bag portion has a vent hole.

14. The side airbag system according to claim 10 , wherein, when the side airbag inflates and deploys, an internal pressure in the lower bag portion is the highest and an internal pressure in the intermediate bag portion is the lowest among the lower bag portion, the intermediate bag portion and the uppermost bag portion.

15. The side airbag system according to claim 1 , wherein an inner surface of the lower base fabric is treated with coating for improving airtightness, and an inner surface of the upper base fabric is not treated with such coating.

16. A method of manufacturing a side airbag, comprising:

a first step of sewing a piece of tube base fabric to a bag inner surface of a piece of lower base fabric;

a second step of sewing a lower end portion of a piece of upper base fabric to a bag outer surface at lower ends of upper regions, used as a tether portion, in the lower base fabric;

a third step of sewing the tube base fabric to bag inner sides of the upper regions in the lower base fabric;

a fourth step of folding the tube base fabric toward a vehicle front side along a fold axis and then sewing front ends of the folded tube base fabric together to form a cylindrical tube;

a fifth step of folding the lower base fabric along the fold axis and then sewing the upper regions of the lower base fabric together to form the tether portion; and

a sixth step of sewing an outer periphery of the lower base fabric and another outer periphery of the lower base fabric together to form a lower bag portion and sewing an outer periphery of the upper base fabric and another outer periphery of the upper base fabric together to form an upper bag portion, wherein

the tether portion serves as a partition between the upper bag portion and the lower bag portion, and the tube extends through the tether portion to the lower bag portion and to the upper bag portion.

17. The method of manufacturing a side airbag according to claim 16 , wherein

the tube base fabric is sewed to the upper regions of the lower base fabric in the third step before a seam between the front ends of the folded tube base fabric so as to leave the seam to form a sewed portion, and

the upper regions of the lower base fabric are sewed together to the sewed portion, terminating before the seam, between the tube base fabric and the upper regions of the lower base fabric.

18. The method of manufacturing a side airbag according to claim 16 , further comprising a seventh step of providing an additional sewed portion for the upper bag portion so as to extend from a vehicle front side end of an opening at an end of the tube, located adjacent to the upper bag portion, toward a vehicle front side and terminate before a sewed portion at the outer periphery of the upper bag portion, wherein

the additional sewed portion partitions the upper bag portion into an uppermost bag portion and an intermediate bag portion.

19. The method of manufacturing a side airbag according to claim 16 , wherein the first step to the third step are processed in selected order, and the fourth step to the sixth step are processed in order of step numbers.