Patent ID: 8469398

Claim:
A gas generator comprising: a tubular housing having both ends closed and a gas discharge port on a circumferential surface, and forming an outer shell of the gas generator, a first closing member having an ignition device fixed thereto and closing one end of the tubular housing, a second closing member closing another end of the tubular housing, and a partition member dividing a space between the first closing member and the second closing member, among spaces divided by the partition member, a space that is closer to the first closing member and the ignition device, serving as a first combustion chamber charged with a first gas generating agent, a space that is closer to the second closing member, serving as a second combustion chamber charged with a second gas generating agent, the spaces satisfying a relationship where capacity of the first combustion chamber≧capacity of the second combustion chamber, the gas discharge port, that is formed in a side of the first combustion chamber, including at least two gas discharge port groups, the at least two gas discharge port groups including a first gas discharge port group formed in the circumferential direction of the tubular housing and closed, from the inside, by a seal member, and a second gas discharge port group separated axially from the first gas discharge port group, formed in the circumferential direction of the tubular housing and closed, from the inside, by a seal member, a transfer charge chamber housing being a cup-like shape and including a plurality of flame-transferring holes formed in a bottom surface thereof, the transfer charge chamber housing being provided so as to surround the ignition device, such that, upon activation of the gas generator, a pressure gradient is created in an axial direction of the housing within the first combustion chamber where a pressure at an area closer to the first closing member is higher than a pressure at an area closer to the partition member, pressure (opening pressure P 1 ), that is necessary for opening the first gas discharge port group, and pressure (opening pressure P 2 ), that is necessary for opening the second gas discharge port group, satisfying a relationship of P 1 <P 2 , the first gas discharge port group being positioned at a center portion in the axial direction between the first closing member and the partition member, or in the vicinity thereof, and the second gas discharge port group being positioned at a center portion in the axial direction between the first gas discharge port group and the partition member, or in the vicinity thereof.