A trigger device which, when it is used in a seat belt tightening device or in an air bag device, prevents the malfunction to enhance reliability and also which is simple in structure, is easy to assemble and is inexpensive. The trigger device includes an ignition circuit which, when an opening/closing switch 24 is closed, allows the electricity of a power supply 23 to flow to ignite a gas generator 8, a movable magnet 22 which, when a car is suddenly decelerated, can be inertially moved to a first position to close the opening/closing switch 24 to electrically energize the ignition circuit, and a fixed magnet 21 fixed to a frame 20 of a non-magnetic member so as to be able to hold the movable magnet 22 at a second position, in which the opening/closing switch 24 is opened, by a repelling magnetic force acting between the movable and fixed magnets. And, when a predetermined or greater acceleration is applied to the movable magnet 22, then the movable magnet 22 is moved to the direction of the first position against the repelling magnetic force acting between the fixed and movable magnets so as to be able to electrically energize the ignition circuit.
展开▼
