Patent ID: 7155353
Filing Date: 2006-12-26
Classification: B60R,F42B,G01R

Abstract:
1. A method of determining a charging capacitance of a capacitor in an air bag system having an electronic control unit for controlling activation of a gas generator, a bus line having a loop wire extending from the electronic control unit, a plurality of gas generators connected to the loop wire, each gas generator having an igniter connected to the loop wire via a connector, one of the igniter and the connector being provided with an integrated circuit having, the capacitor for providing power to a heat generating portion for igniting a priming, a switching circuit for turning ON/OFF a supplying of current to the heat generating portion, and a microcomputer unit for controlling the switching circuit, the method comprising: determining a minimum charging capacitance of the capacitor necessary to operate the igniter by the following formula (I): where, C represents a capacitor charging capacitance, V represents a charging voltage, and E represents a minimum ignition energy required for making the heat generating portion of the igniter generate heat to ignite the priming, the minimum ignition energy being obtained by the following formula (II): where, Imin: a minimum ignition current value (A), Rmax: a maximum resistance value of the heat generating portion (W), r 1 : a maximum ON resistance value of the switching circuit at 150° C.(W), r 2 : a resistance value of elements other than the switching circuit (W), T: a time period in which a current flows in the heat generating portion (sec), and w: a power consumed by an entire integrated circuit when the switching circuit is OFF, and where 10 in w′10 is a maximum time period elapsed from a first collision to a second collision which may occur during a vehicle collision.