It has become common to mount an airbag device to absorb an impact occurring on a passenger in vehicles such as an automobile by inflating and deploying an airbag in a vehicle at a collision, rapid deceleration or the like. Various types of the airbag devices have been developed/employed, such as a driver airbag device built in a steering, a passenger airbag device built in an instrument panel, a side airbag device built in a side portion of a vehicle or in a seat, a curtain airbag device built in an upper part of a door and a knee airbag device corresponding to a knee portion of a passenger.
These airbag devices generally have an airbag which is folded normally and inflated and deployed in an emergency and an inflator that supplies gas to the airbag. Especially since the passenger compartment has a wide space for inflation and people with various body types such as children, adult women, adult men are seated on the passenger seat, a capacity of the airbag, a speed of the inflation and deployment, an internal pressure of the airbag, a balance of an impact absorbing force and the like need to be considered. In view of such demand, an airbag as described in Japanese Unexamined Patent Application Publication No. 2007-1471 has been already proposed.
Japanese Unexamined Patent Application Publication No. 2007-1471 discloses an airbag, known as a twin bag, having a left airbag section that is inflated and deployed on the left front side of a passenger and a right airbag section that is inflated and deployed on the right front side of the passenger. The end portions of the left airbag section and the right airbag section are not connected to each other so that a space portion opened toward the passenger is formed between the end portions of the left airbag section and the right airbag section in the inflated and deployed state. Intermediate portions in the inflating and deploying direction of the left airbag section and the right airbag section are connected to each other by a connection portion. The connection portion is disposed lower than the middle in the vertical direction of the left airbag section and the right airbag section. In the left airbag section and the right airbag section, a tether for regulating the width that regulates the width in the width direction of each section in the inflated and deployed state is disposed.
The above-described twin bag can restrain the shoulder portion of a passenger by the airbag and can also receive the head portion so as to sandwich from both right and left sides, thereby having excellent passenger retraining force and impact absorbing force. However, the demand for the airbag has been increased recently, and there are problems that the impact absorbing force is to be improved and the airbag is to be inflated and deployed more efficiently.