Ammunition and explosives – Igniting devices and systems – Ignition or detonation circuit
Reexamination Certificate
2003-01-24
2004-11-23
Jordan, Charles T. (Department: 3644)
Ammunition and explosives
Igniting devices and systems
Ignition or detonation circuit
C102S206000, C280S735000
Reexamination Certificate
active
06820557
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
The present invention relates to an igniter for an air bag system used in an air bag system using a bus system and a method for controlling operation of an air bag system using the same.
Prior Art
An air bag system for protecting a passenger from an impact at a time of collision of a vehicle is indispensable, and the air bag system needs to be reduced in weight from a demand for reducing weight of a whole vehicle. Recently, kinds and the total number of air bags such as an air bag for a driver side, an air bag for a passenger side next to the driver, an air bag for a rear seat side, and an air bag for an side impact are increasing, and therefore, a lighter air bag system is in greater demand.
In a current 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 individual gas generators (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 (
FIG. 14
) of each of the individual gas generators are necessarily connected to each other through two conductors, and thereby, conductors double the number of the total number of igniters are required. Having many conductors contributes largely to weight increase in an air bag system. In view of constraints at a time of assembling vehicle parts, the ECU and the individual gas generators are not connected by only the conductors but connected by connecting plural conductors via plural connectors, and thereby, there occurs a serious problem such as a weight increase due to use of the connectors and a cost increase due to increase of the number of the connectors. Further, increase in volume (weight) of the ECU due to increase in volume of a capacitor incorporated into the ECU as a backup power source for activating all the igniters (serving at a time of a disconnection between the power source and the ECU) is another serious problem.
In view of the above, a trial for reducing a conductor weight required for connection between the ECU and the individual gas generators by utilizing a bus system in the air bag system has been examined. An aspect of the air bag system utilizing this bus system is shown in FIG.
1
.
As shown in
FIG. 1
, an air bag system is constituted by providing bus lines comprising plural loop wires passing through the ECU and connecting each of the individual gas generators to the bus line through two conductors (three or more conductors when occasion demands). In a case of such an air bag system as shown in
FIG. 1
, since only gas generators required corresponding to a collision situation of a vehicle are activated, an integrated circuit receiving information transmission from the ECU and a capacitor supplying a current for activating an igniter are provided in each of the individual gas generators. In the case of utilizing a bus system, the total number of capacitors is increased, but since the capacitors are distributed and arranged in the ECU and the respective igniters, the capacitance and weight of the capacitor per igniter is reduced. As a result, since the weight of the capacitors in this case is remarkably reduced as compared with the weight of the capacitors for backup in the air bag system shown in
FIG. 13
, a large weight reduction is achieved as the whole system in addition to largely reducing the amount of use of conductor, which is expected to be put in a practical use in the air bag system. Incidentally, there have been known JP2000-241098A, JP2000-513799A and Japanese Patent No. 2707250 as the prior art utilizing the bus system.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an igniter for an air bag system which achieves a large weight reduction in an entire air bag system by introducing a bus system into the air bag system, and which can ensure reliability and rapidness of operation similar to those in a conventional art, and which can obtain a high reliability, and an operation control method of an air bag system utilizing the same.
(1) First Solving Means
An invention described in claim
1
provides, as one means for solving the above problem, an igniter, for an air bag system, which is one or at least two igniters incorporated in the plural of the gas generators and used in an air bag system comprising an electronic control unit connected to a power source and an impact detecting sensor, and plural module cases which are connected to the electronic control unit and accommodate plural gas generators and plural air bags, wherein,
in the air bag system, a bus line comprising plural loop wires which pass through the electronic control unit is provided to supply and transmit currents and required information, and individual gas generators accommodated in the plural module cases are connected operationally by plural conductors branched at predetermined portions from the bus line,
the one or at least two igniters incorporated in the gas generator is an electric igniter which is provided with a heat generating portion and a priming coming in contact with the heat generating portion, and the igniter and the bus line are connected to each other through plural conductors, and the capacitor and the integrated circuit recorded with information to exhibit required functions are provided in the igniter, and a current for igniting the priming is supplied to the one or at least two igniters through a capacitor inside the igniter.
The numbers of the loop wires forming the bus line and the conductors for connecting the bus line and the gas generators may be two, three, or four or more, respectively, but, in view of simplification of the entire system, two is preferable.
The priming is not limited to a specific one, but a combination of a metal or the like and an oxidizing agent such as perchlorate is preferable, a combination of a metal such as zirconium, titanium, and hafnium and perchlorate is more preferable, and a mixture (ZPP) of zirconium and potassium perchlorate is particularly preferable. Desirably, the ZPP is formed in particle shape and particle diameters of zirconium and potassium perchlorate are adjusted.
A capacitance of the capacitor is preferably not more than 24 &mgr;F, more preferably not more than 12 &mgr;F, further more preferably not more than 6 &mgr;F.
Preferably, the air bag system using an igniter for an air bag system of the present invention is activated such that a current for igniting the priming in one or at least two igniters is supplied via the capacitor inside the igniter, and that a time period for supplying a current from the capacitor to the heat generating portion is the period from the point where a current value reaches the current value corresponding to 5% of the maximum current value to the point where it is reduced down to the current value corresponding to 5% of the maximum current value, which is within 500 &mgr;sec. In this case, the maximum current value in the period for supplying a current is a current value sufficient to ignite the priming. The period for supplying a current is preferably within 200 &mgr;sec, and more preferably within 100 &mgr;sec. Incidentally, a current value at this time varies depending on a resistance value of the heat generating portion in the igniter, and it is determined on the basis of presence or absence of the waveform converting circuit, the constitution of the waveform converting circuit, a particle diameter of a priming, a shape of the heat generating portion and the like.
In the case of a conventional air bag system, since a current for activating an igniter flows from a power source (a battery) with a relatively large capacitance at 1.2 A for about 2 msec, that is, at a relatively low current for a relatively long time, a waveform of an ignition current (a vertical axis denotes a current value (A) and a horizontal axis denotes a time (&mgr; sec)) becomes rectangular.
In the present invention, however,
Oda Shingo
Okamoto Mitsuyasu
Daicel Chemical Industries Ltd.
Jordan Charles T.
Nguyen T.
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