Airbag and airbag apparatus

1. An airbag including a front panel disposed on an occupant side, and a rear panel disposed on a side opposite to the occupant side, in which in the front panel and the rear panel, peripheral edge portions thereof are connected to each other, and

an opening for use in a gas-generator is provided at a center of the rear panel, and

a halfway portion disposed halfway between a respective center portion and a peripheral edge portion of the front and rear panels, said halfway portion being disconnectably connected by means of circular line-shaped connecting portions extending in a peripheral direction, and

the line-shaped connecting portions being provided in a plurality and arranged approximately concentrically, and

the line shaped connecting portions having a communicating portion allowing an inner periphery side and an outer periphery side of the line shaped connecting portions to communicate with each other, the communication portions partially interrupting a connection of the front panel and the rear panel, said communicating portions provided in an extending direction of each of the line-shaped connecting portions at the halfway portion,

wherein the individual communicating portions are positioned on sides opposite to each other while a center of the airbag is sandwiched between the individual line-shaped connecting portions, wherein the line-shaped connecting portions are provided next to each other in a radial direction.

2. The airbag according to claim 1 , wherein both end sides of the line-shaped connecting portions facing the communicating portion extend toward a center side of the airbag.

3. The airbag according to claim 1 , wherein a venthole is provided in an area that forms an outer periphery side relative to the line-shaped connecting portion of an outermost periphery side in the rear panel, and the communicating portion of the line-shaped connecting portion of the outermost periphery side and the venthole are positioned on sides opposite to each other while sandwiching the center of the airbag.

4. The airbag according to claim 1 , wherein the venthole is provided in the rear panel, and a lid member for covering the venthole is provided inside the airbag, and wherein one end side of the lid member is connected to the front panel and the rear panel by means of the line-shaped connecting portion on at least an outermost periphery side, and the other end side is connected to the rear panel by means of a connecting device that is different from the line-shaped connecting portion, and wherein the communicating portion of the line-shaped connecting portion on the outermost periphery side is positioned on a side opposite to the one end side of the lid member while sandwiching the center of the airbag.

5. The airbag according to claim 4 , wherein a connecting portion having a smaller width than that of the lid member extends from the one end portion of the lid member, and the connecting portion is connected to the front panel and the rear panel by means of the line-shaped connecting portion on at least the outermost periphery side.

6. An airbag apparatus including an airbag and a gas-generator for expanding the airbag, wherein the airbag is the airbag according to claim 1 .

7. The airbag according to claim 1 , wherein the line-shaped connecting portion on an innermost periphery side is disposed within an area from 400 to 600 mm in radius from the center of the airbag.

8. The airbag according to claim 1 , wherein a distance between the individual line-shaped connecting portions provided next to each other in the radial direction of the airbag is set to be from 10 to 50 mm.