1. Field of the Invention
The present invention relates to an igniter for an air bag system utilizing a bus system, and a method for controlling an operation of an air bag system using the same.
2. Description of Related Art
An air bag system for protecting a passenger from an impact at the time of a vehicle collision is indispensable, and the air bag system needs to be lighter because of a demand for lighter vehicles. Recently, types and the total number of air bags, such as an air bag for a driver side, a passenger side, rear seats, and a side impact mounted on a single vehicle are increasing. Therefore, there are increased demands for lighter air bag systems.
In a conventional air bag system, an electronic control unit (ECU), connected to a power source (a battery in a vehicle), and an impact detecting sensor are individually connected to each gas generator (a gas generator and an air bag are accommodated in a module case). An aspect of the connection between the ECU and the individual gas generators is shown in FIG. 13.
As shown in FIG. 13, the ECU and an igniter (shown in FIG. 14) provided in each gas generator are necessarily connected to each other through two conductors. Therefore, twice as many conductors than the number of igniters are required. Having many conductors contributes largely to a weight increase in the air bag system. In view of constraints at the time of assembling vehicle parts, the ECU and the individual gas generators are connected not only by the conductors but also via a plurality of connectors. Accordingly, a serious problem such as a weight increase due to the use of the connectors and a cost increase due to the increased number of the connectors occurs. Further, an increase in volume (weight) of the ECU due to an increase in volume of a capacitor incorporated in the ECU as a backup power source for activating all the igniters (serving at the time of a disconnection between the power source and the ECU) is another serious problem.
In view of the above, a trial for reducing the weight of the conductors by utilizing a bus system in the air bag system has been examined.
Incidentally, JP2000-241098A, JP2000-513799A, and Japanese Patent No. 2707250 disclose art that utilize the bus system.