Side airbag device

A side airbag device adapted to be mounted on a back portion of a seat of a vehicle, the airbag device comprising:

• an airbag that is housed in a housing in a folded-up configuration and is configured to be deployed forward when fed with an inflation gas by an inflator, the folded-up airbag having an elongated outer contour extending generally in an up and down direction as mounted on the seat;
• a limitation member that is arranged around the folded-up airbag for constraining the airbag from protruding forward at airbag deployment, the limitation member being formed of a flexible sheet member and having a band shape, the limitation member comprising:
• a pair of joint regions that are located at opposite ends of the limitation member and joined with the folded-up airbag;
• and
• a loose region that is disposed between the joint regions and arranged around the folded-up airbag in such a manner as to be remote from the folded-up airbag, the loose region being disposed on a side of the folded-up airbag towards which the airbag protrudes, wherein a length of the loose region between the joint regions is longer than a length of an outer circumference of the folded-up airbag and shorter than a film length of the airbag as deployed, and wherein the loose region includes, in a region thereof in a deployment direction of the airbag, a tearable region that is tearable in such a manner as to split up the loose region between the joint regions at the airbag deployment,
• wherein:
• the tearable region includes a starting point of tearing at one end thereof in the up and down direction;
• the inflator is generally cylindrical in outer contour and is housed in a rear end region of the folded-up airbag;
• the inflator is provided with gas discharge ports at a lower end thereof;
• a lower edge of the loose region is located in a vicinity of a front region of the gas discharge ports;
• the loose region includes a cut-out region that tapers towards the tearable region, the cut-out region constitutes the starting point of tearing of the tearable region;
• the airbag includes a pelvis protecting portion for protecting a pelvis of an occupant seated in the seat at a lower end region of the airbag at deployment;
• and
• the pelvis protecting portion protrudes out of the limitation member downwardly in the folded-up airbag.