Air bag device

An airbag device for restraining a forward movement of an occupant seated on a vehicle seat of a vehicle adapted for use with a collision sensor, comprising:

• an inflator which is operated by a signal from the sensor that detects a collision of the vehicle and which discharges an expansion gas;
• and
• a plurality of airbags which expand and deploy due to the expansion gas, wherein the plurality of airbags includes a first airbag which deploys to the front of the occupant;
• and a second airbag which is joined to a side part of the first airbag on a cabin center side with respect to the occupant and is adapted to restrain an obliquely forward movement of the occupant when deployed,
• the collision sensor of a type capable of discriminating between a first collision mode which is not accompanied by a significant rotation of the vehicle in a horizontal plane and a second collision mode which is accompanied by a significant rotation of the vehicle in the horizontal plane, and
• the first airbag is deployed in the first and the second collision modes and the second airbag is deployed only when the second collision mode occurs and the second airbag is not deployed when the first collision mode occurs, the inflator discharges the expansion gas into the first airbag in the first collision mode and in the second collision mode,
• a joint of the first airbag and the second airbag is provided with an openable and closable inflation vent opening which communicates with both the first and the second airbags, and
• the inflation vent opening is configured so that the gas flows into the second airbag from the first airbag during the second collision mode.