Inflator securing structure and airbag system

1. An inflator securing structure for securing an inflator having substantially cylindrical shape to a retainer in an airbag system, comprising:

a fixed shaft having a substantially D-shaped cross section and formed at one end of the inflator along an axial direction of the inflator; and

a locking structure having a locking hole with a substantially D shape and formed in the retainer so that the locking hole is engaged with the fixed shaft,

wherein one of the fixed shaft and the locking hole has at least one groove, and other of the fixed shaft and the locking hole has at least one convex portion engaging the groove.

2. An inflator securing structure according to claim 1 , wherein the convex portion projects from an inner periphery of the locking hole toward a center thereof, and the groove is formed on a lateral surface of the fixed shaft and extends to a free end thereof along the axial direction of the inflator.

3. An inflator securing structure according to claim 2 , wherein the fixed shaft has two said grooves, and the locking hole has two said convex portions, each of the convex portions engaging each of the grooves corresponding thereto.

4. An inflator securing structure according to claim 3 , wherein the two grooves and the two convex portions are spaced apart from each other by approximately 90 degrees in phase angle, respectively.

5. An inflator securing structure according to claim 4 , wherein the grooves are located in a curved lateral surface of the fixed shaft, and the convex portions are located on the inner periphery of the locking hole corresponding to the grooves.

6. An airbag system comprising:

an airbag;

the inflator for inflating the airbag;

the retainer to which the airbag and the inflator are mounted; and

the inflator securing structure according to claim 1 .

7. An airbag system comprising:

a folded airbag;

a substantially cylindrical inflator for inflating the airbag, said inflator having a fixed shaft formed at one end thereof extending along an axial direction of the inflator, said fixed shaft having a substantially D-shaped cross section and at least one convex portion or groove at an outer portion thereof; and

a retainer for receiving the folded airbag and the inflator, said retainer having an inflator attaching portion having a substantially D-shape hole for receiving the fixed shaft, and at least one groove or convex portion formed around the hole and engaging the at least one convex portion or groove of the fixed shaft.

8. An airbag system according to claim 7 , wherein said fixed shaft has the groove extending axially from an end of the fixed shaft, and said hole has the convex portion extending inwardly from a periphery of the hole so that the shaft is inserted into the hole by engaging the groove with the convex portion.