Patent ID: 6945561

Claim:
A gas generator for an air bag, comprising: a cylindrical housing having a gas discharge port; an inner cylindrical member provided inside the cylindrical housing and defining therein an ignition means accommodating chamber, the inner cylindrical member having a flame-transferring hole and a through-hole; ignition means provided inside the ignition means accommodating chamber, the ignition means including an igniter activated by an activation signal and generating flame or heat due to an activation of the igniter; a first combustion chamber provided outside the inner cylindrical member in a radial direction of the cylindrical housing and storing a first gas generating agent adapted to be ignited and burned by the flame or heat generated by the ignition means and ejected from the flame-transferring hole and into the first combustion chamber to generate a combustion gas; a second combustion chamber provided inside the inner cylindrical member and adjacent to the ignition means accommodating chamber in an axial direction of the cylindrical housing, the second combustion chamber accommodating a second gas generating agent adapted to generate a combustion gas, the through-hole allowing a combustion gas generated due to combustion of the second gas generating agent to flow into the first combustion chamber; cylindrical coolant/filter means provided outside the first combustion chamber in the radial direction, the cylindrical coolant/filter means at least one of cooling and purifying the combustion gas; and a porous tube member provided between the inner cylindrical member and the coolant/filter means, the porous tube member having a porous annular portion provided with a plurality of openings and a flame-preventing annular portion provided with no opening, the flame-preventing annular portion being formed at a position where the flame-preventing annular portion opposes an ejecting direction of the flame or heat ejected from the flame-transferring hole, wherein the through-hole and the gas discharge port are provided at positions with respect to the axial direction of the cylindrical housing, such that the through-hole does not oppose the discharge port.