Gas generator

A gas generator, comprising:

• a housing having therein an ignition device chamber, which is provided with a gas discharge port and accommodates an ignition device, and a pressurized gas chamber filled with a pressurized gas;
• a partition wall having a communication hole therein for separating the ignition device chamber and the pressurize gas chamber,
• the partition wall being in a cup-like shape which includes a bottom surface and a circumferential wall surface, and which projects from the pressurized gas chamber toward the ignition device chamber, the partition wall having a flange portion provided at a portion corresponding to an opening of the partition wall in the cup-like shape and being fixed to the housing,
• the communication hole being provided only in the circumferential wall surface,
• an annular closing member being disposed outside the partition wall to be movable in the axial direction of the housing with a distance from the flange portion,
• prior to activation, the communication hole being closed by an inner circumferential surface of the annular closing member abutting against an outer circumferential wall surface of the partition wall, and
• at the time of activation, the annular closing member being moved toward the flange portion by combustion products generated by activation of the ignition device, thereby opening the communication hole and making communication between the ignition device chamber and the pressurized gas chamber.