Airbag device

1. An airbag device adapted to be mounted on a vehicle, comprising:

an airbag that is inflatable with an inflation gas, the airbag including a bag body that is formed of a base material having flexibility, an insert opening that is formed on the bag body, and a flap member that has a sheet-shape and is disposed inside the bag body for covering the insert opening:

an inflator that feeds the airbag with the inflation gas, the inflator including a leading end region provided with a gas release section and a root end region; and

a retainer that mounts the airbag and the inflator on a vehicle body member,

wherein the retainer comprises: a holding section that is tubular in outer contour and holds the inflator therein; and a mounting bolt that protrudes out of a bottom region of the holding section and is adapted to be secured to the vehicle body member in order to mount the airbag and the inflator on the vehicle body member; and

wherein the retainer is placed inside the airbag with the mounting bolt protruded out of the airbag, and holds the inflator with the holding section such that the leading end region of the inflator is disposed inside the airbag whereas the root end region of the inflator protrudes from the insert opening of the airbag,

wherein the flap member entirely covers the insert opening of the bag body as flatly unfolded, the flap member includes a leading edge which is disposed towards the leading end region of the inflator, and is joined to the bag body, with a continuous seam, by a circumferential edge of the flap member except the leading edge, the flap member covering the inflator as held by the holding section of the retainer;

wherein the holding section of the retainer comprises:

an opening-side tube section that is disposed in a vicinity of the insert opening of the airbag and that extends from the bottom region of the holding section and holds the inflator therein; and

an open region that is formed at an area of a periphery of the opening-side tube section distant from the bottom region of the holding section, and that exposes an outer periphery of the inflator as set in the opening-side tube section towards the flap member;

wherein the leading edge of the flap member is located at a position to be pressed against the outer periphery of the inflator via the open region of the retainer at airbag deployment;

wherein:

the insert opening of the airbag is composed of at least one slit and the retainer includes a retaining pawl that is formed at an end of the opening-side tube section disposed towards the insert opening of the airbag, and that protrudes from the slit and is disposed outside of the bag body in order to be engaged with a periphery of the insert opening; and

wherein:

the at least one slit comprises a plurality of slits; and

one or more regions among the slits are folded inward and brought into contact with the outer periphery of the inflator.

2. The airbag device of claim 1 , wherein the seam is formed in such a manner that an unsewn region is left between the leading edge of the flap member and a terminal of the seam disposed towards the leading edge, and in such a manner that a position of the terminal in an axial direction of the inflator falls within an area of the open region of the retainer.

3. The airbag device of claim 1 adapted to be used for knee protection, wherein:

the airbag and the inflator are adapted to be stored in a case that includes a bottom wall which is arranged vertically on the vehicle and a generally tubular circumferential wall which extends rearward from a circumferential edge of the bottom wall; and

the airbag and the inflator are adapted to be mounted on the bottom wall of the case.