A gas generator comprising:
- a first ignition device;
- a first combustion chamber in which the first ignition device is disposed;
- a housing including a peripheral wall portion having a tubular shape, a top plate portion provided at one end of the peripheral wall portion, and a bottom plate portion provided at another end of the peripheral wall portion and facing the top plate portion, the bottom plate portion defining the first combustion chamber together with the peripheral wall portion and the top plate portion, the first ignition device being fixed to the bottom plate portion;
- a first inner tube member including a surrounding wall portion that has a tubular shape and surrounds the first ignition device, the first inner tube member forming an ignition unit chamber between the first inner tube member and the first ignition device, the first inner tube member including one or a plurality of communication holes formed in the surrounding wall portion, the one or plurality of communication holes allowing the ignition unit chamber and an outside of the first inner tube member to communicate with each other;
- a first gas generating agent disposed in the first combustion chamber and surrounding the surrounding wall portion, the first gas generating agent being configured to be burned by a combustion product discharged from the ignition unit chamber through the one or plurality of communication holes by activation of the first ignition device;
- and
- a plurality of gas discharge ports formed in the housing, the plurality of gas discharge ports allowing the first combustion chamber and an outside of the housing to communicate with each other by opening upon receiving a combustion pressure of the first gas generating agent, wherein
- the plurality of gas discharge ports include a first gas discharge port and a second gas discharge port, the second gas discharge port having an opening pressure higher than an opening pressure of the first gas discharge port,
- the surrounding wall portion is divided, in a circumferential direction of the surrounding wall portion, into a combustion product discharge region in which the one communication hole is disposed or the plurality of communication holes are collectively disposed and a combustion product non-discharge region being a region other than the combustion product discharge region,
- the peripheral wall portion is divided, in a circumferential direction of the peripheral wall portion, into a communication hole-associated region associated with the combustion product discharge region and a communication hole non-associated region associated with the combustion product non-discharge region, and
- of the communication hole-associated region and the communication hole non-associated region, the first gas discharge port is formed only in the communication hole-associated region, and the second gas discharge port is formed only in the communication hole non-associated region.