Side airbag device

1. A side airbag device for restraining an occupant of a vehicle seat from side impacts,

comprising:

an inflator which generates gas; and

a cushion which receives the gas and inflates and deploys at a side of a seat back of the vehicle seat during a vehicle impact, wherein

the cushion includes:

a rear chamber having a middle restraining part, with at least a portion which protrudes from the seat back toward the front of the vehicle to restrain a part of a body of the occupant, and a main part positioned at a rear side of the vehicle with respect to the middle restraining part;

a sectioning wall which constitutes a front edge and an upper edge of the rear chamber and which has a prescribed width in a vehicle width direction;

a front chamber which inflates and deploys toward the front of the vehicle and the upper part of the vehicle from the sectioning wall;

an upper opening which is formed on the sectioning wall in a rear part of the upper edge of the rear chamber configured for supplying gas from the rear chamber to the front chamber; and

a lower opening which is formed on the sectioning wall in a lower part of the front edge of the rear chamber configured for supplying gas from the rear chamber to the front chamber.

2. The side airbag device according to claim 1 , further comprising wherein

the rear chamber further includes:

a partition which divides the main part and the middle restraining part from each other, which is provided so as to be positioned along a vehicle front edge of a side part of the seat back when the cushion inflates and deploys, and which has a prescribed width in the vehicle width direction; and

a vent hole on the partition.

3. The side airbag device according to claim 2 , further comprising wherein the gas is supplied to the main part of the rear chamber and flows through the vent hole to inflate the middle part of the rear chamber such that completion of inflation and deployment of the middle restraining part of the rear chamber occurs later than completion of inflation and deployment of the main part.

4. The side airbag device according to claim 1 , further comprising:

an inner bag which has a bag shape and which receives gas from the inflator prior to the rear chamber, wherein

the inner bag includes:

a main body part which inflates and deploys inside the rear chamber;

an upper protrusion which is continuous to the main body part which protrudes into the front chamber through the upper opening;

a lower protrusion which is continuous to the main body part which protrudes into the front chamber through the lower opening;

a central vent hole which is provided on the main body part and which supplies gas to the rear chamber;

an upper vent hole which is provided on the upper protrusion and which supplies gas to the front chamber; and

a lower vent hole which is provided on the lower protrusion and which supplies gas to the front chamber.

5. The side airbag device according to claim 4 , further comprising wherein

the upper protrusion is joined to the upper opening, and

the lower protrusion is joined to the lower opening.

6. The side airbag device according to claim 4 further comprising, wherein a plurality of the central vent hole is provided in a vicinity of the middle restraining part.

7. The side airbag device according to claim 4 further comprising wherein completion of inflation and deployment of the middle restraining part of the rear chamber occurs later than completion of inflation and deployment of the main body part of the inner bag.

8. The side airbag device according to claim 4 further comprising wherein the inflator is placed in an supplies the gas to the inner bag main body part.

9. The side airbag device according to claim 1 further comprising wherein the upper opening and the lower opening each include a slit formed on the sectioning wall.

10. The side airbag device according to claim 9 further comprising wherein the upper opening causes the gas to flow in a generally upward direction through the upper opening and the lower opening causes the gas to flow in a generally downward direction through the lower opening.

11. The side airbag device according to claim further comprising 1 wherein the middle restraining part protrudes toward the front of the vehicle from the seat back to at least a position where a shoulder of the occupant at a proper sitting position of the vehicle seat is restrained.

12. The side airbag device according to claim 1 further comprising wherein the inflator is placed in an supplies gas to the rear chamber main part.