JPH0742731U - Gas generator igniter for passenger protection device - Google Patents

Abstract

(57) [Abstract] [Purpose] An igniter for a gas generator for an occupant protection device that has a stable ignition performance without sacrificing safety and that can reduce the resistance value of the bridge wire of the squib. provide. An igniter comprising an igniting agent for igniting a gas generator for an occupant protection device such as an airbag, and electric bridge wires 31a, 31b for generating heat and igniting the igniting agent by energization. A plurality of 31a and 31b are arranged in parallel.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an igniter of a gas generator for an occupant protection device mounted on an automobile.

[0002]

[Prior art]

 A specific example of the ignition circuit of the gas generator for an occupant protection device of this type will be described with reference to FIG. In FIG. 4, 11 is an on-vehicle battery, 12 is a booster circuit that boosts the voltage from the on-vehicle battery, and 13 is a backup capacitor that stores the boosted voltage. Switch circuit 14 which conducts by input 19 of the squib, squib (firing device) 15 built in the gas generator 25, and safing sensor (collision sensor which conducts at a smaller acceleration than the above collision determination circuit) 16 for preventing accidental explosion or the like. Are connected in series. The gas generator 25 is connected to an occupant protection device 26 such as an airbag. The backup capacitor 13 described above is provided in order to cope with the detachment of the vehicle-mounted battery 11 in the event of a collision, and the booster circuit 12 is provided to reduce the capacity of the backup capacitor 13. The power supply to the collision determination circuit 17 is normally supplied (20) from the vehicle-mounted battery 11, but when the battery is removed, the power is supplied from the backup capacitor 13 via the switch 22.

The above-mentioned squib 15 will be described in detail with reference to FIG. 5 which is a sectional view and FIG. 6 which is a view taken in the direction of arrow A in FIG. In FIG. 5, the squib 15 has an insulating pipe member 5 fitted and inserted into the inner periphery of cylindrical pipe bodies 7a and 7b, and an ignition powder 6 is filled therein. A fragile portion 7c communicating with the transfer charge 28 of the gas generator is provided on the tip surface. At the base end, a disk-shaped insulating base material 4 for sealing the ignition powder is fitted and inserted into the inner circumference of the insulating pipe material 5, and a pair of positive and negative electrodes 2a and 2b are provided penetrating the insulating base material 4. The bridge wire 1 is laid between the upper ends of the electrodes 2a and 2b along the upper surface of the insulating base material 4 so as to be embedded in the ignition powder 6. The bridge line 1 is usually a single round wire made of nichrome wire or platinum. On the other hand, the lower ends of both electrodes 2a and 2b are connected to lead wires 9 and 9, and the lead wires 9 and 9 are connected to the ignition circuit of FIG. Then, the penetrating portions of the insulating base material 4 of both electrodes 2a, 2b are sealed with a sealing material 3 in order to prevent moisture absorption of the ignition powder 6, and the lower surface side of the insulating base material 4 is connected to the lower ends of the electrodes 2a, 2b. It is filled with potting material 8 for protection. Further, in FIG. 6, the above-mentioned electrodes 2a and 2b have a rectangular cross section, and the bridge wire 1 is installed between the electrodes 2a and 2b.

In FIG. 4, when a collision occurs, the switch circuit 14 and the safing sensor 16 are conducted and the squib 15 is energized, and in FIG. 5, the bridge wire 1 generates heat due to Joule heat and the ignition powder 6 is heated. To be done. When the ignition powder 6 reaches the ignition temperature, it is ignited and its flame is ejected from the fragile portion 7c to ignite the transfer charge 28, thereby operating the gas generator.

Changes in the backup capacitor voltage V (t) and the current I (t) flowing in the bridge line at the time of ignition are shown in FIGS. 7 (a) and 7 (b). That is, when the switch circuit 14 of FIG. 4 is provided with a current control function, the current I (t) is maintained at a constant value I ₁ , as indicated by the solid line 22, and therefore the voltage V (t) of the backup capacitor is It decreases linearly from V ₀ to V ₁ . On the other hand, when the switch circuit 14 does not have a current control function, the current I (t) decreases from I ₀ to I ₁ ′ in a discharge curve as shown by the chain double-dashed line 21, and the voltage V of the backup capacitor V Similarly, in (t), a discharge curve is drawn and the voltage drops from V ₀ to V ₁ . Hereinafter, the relationship between those characteristics will be described assuming that the switch circuit 14 has a current control function. For simplification, the resistance of the squib wiring system and the capacitor capacity for power backup of the collision determination circuit are described. Will be omitted.

The temperature T (t) of the ignition powder is represented by the following formula, and if T (τ) exceeds the ignition temperature T _i of the ignition powder at the energization time (t = τ), the ignition powder is ignited. It will be possible.

[0007]

[Equation 1]

Here, p (t) is the heat generation amount [W] of the bridge wire per hour [W] q (t) is the heat capacity of the ignition powder [J / ° C] η is the electrothermal efficiency of the ignition powder.

In the case of having a current control function, the current value is considered to be constant and set to I _1, and the change in the resistance value R (t) of the bridge wire and the heat capacity q (t) of the ignition charge with time, that is, Assuming that changes due to temperature are negligible, given constant values R ₁ and q ₁ ,

P (t) = R ₁ * I ₁ ² and q (t) = q ₁ .

Therefore, from the above equation, T (τ) at T = τ is T (τ) = η * R ₁ * I ₁ ² * τ / q ₁ ...

As described above, T (τ) must exceed the ignition temperature T _i of the ignition charge, so T (τ) ≧ T _i , and the minimum necessary condition is T (τ). = T _i .

In the equation, if τ cannot be changed by the ignition request and squib structure is not changed, η and q ₁ cannot be changed. Therefore, to set T (τ) = T _i , R _{1 ^{* I 1 2 (= p (}} t)) and must be kept constant, represents the p a (t) and P _1. Immediately, P ₁ = R ₁ * I ₁ ² ...

Further, the capacitor voltage V ₁ after the lapse of time τ needs to satisfy V ₁ ≧ R ₁ * I ₁ as a condition for securing the current I ₁ , and the minimum necessary condition is V ₁ = R ₁ * I ₁ ...

On the other hand, when the quantity of electricity discharged during the energization time (T = τ) is Q and the required minimum capacitance of the capacitor is C ₁ , the following relationship is established. Q = I ₁ * τ = C ₁ (V ₀ −V ₁ ) That is, C ₁ = I ₁ * τ / (V ₀ −V ₁ ).

Substituting the equation and the equation into the equation, the following equation is obtained. C ₁ = τ / [V ₀ * √ (R ₁ / P ₁ ) −R ₁ ] ...

In the equation, FIG. 8 shows the relationship between C ₁ and R ₁ with V ₀ as a parameter when τ and P ₁ are constant due to the ignition request and the squib structure constraint. . According to this, it can be seen that there is R ₁ that minimizes C ₁ with respect to V ₀ , as seen in the portions A, B, and C of FIG.

[0018]

[Problems to be solved by the device]

There is a strong demand for miniaturization of in-vehicle products, and in particular, the demand is increasing along with the recent trend toward higher functionality and lower fuel consumption of vehicles. The ignition device of an occupant protection device is no exception, and it is desired to minimize the shape of the ignition device by reducing the capacity of the capacitor, which is a relatively large component among the components. Therefore, generally, as can be understood from FIG. 8, a method of further boosting the voltage of the on-vehicle battery to thereby reduce the capacitor capacity has been adopted. However, there is a drawback that not only the space for the booster is required, but also the cost is increased. Further, conventionally, there is no idea of selecting a combination of V ₀ and R ₁ that can minimize C ₁ as shown in FIG. 8, and simply by using a booster device, for example, as shown in D of FIG. It was used in various areas and was not always the optimum combination of power supply voltage and squib resistance.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to combine a power supply voltage and a squib resistance in an ignition device of an occupant protection device. To optimize, it is to provide a method for varying the squib resistance while having a stable ignitability.

According to FIG. 8, it is ideal to increase the voltage V ₀ and increase the squib resistance R ₁ in order to reduce the capacitance of the capacitor, but to increase the squib resistance R _1. In order to determine the structure, it is necessary to lengthen or narrow the bridge wire, which may complicate the structure, which may lead to deterioration of electrothermal efficiency or decrease in reliability. Requires a great deal of development time.

[0021]

[Means for Solving the Problems]

 In order to solve the above problems, the igniter of the gas generator for an occupant protection device of the present invention is an igniting agent that ignites a gas generator for an occupant protection device such as an air bag, and heats the ignition agent by energizing it. An igniter having a bridge line for igniting, wherein a plurality of bridge lines are arranged in parallel.

[0022]

[Action]

 Since a plurality of bridge wires are arranged in parallel, the electric resistance of the igniter can be reduced by using the bridge wire having the same structure as the conventional one. Therefore, it is possible to reduce the electric resistance of the igniter while maintaining the same stable ignition performance and heat transfer efficiency to the ignition charge as in the conventional case.

[0023]

Embodiments Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a top view showing an essential part of an igniter of a gas generator for an occupant protection device of the present invention, FIG. 2 is a view showing an effect on electric heat efficiency of the igniter, and FIG. 3 is another embodiment of the igniter. It is a top view shown. It should be noted that in FIGS. 1 to 3, portions having the same functions as those in FIGS. 4 to 7 are denoted by the same reference numerals, and the description thereof will be omitted.

1 is different from FIG. 6 in that the single bridge line 1 is replaced with two bridge lines 31a and 31b having the same structure as the bridge line 1 in parallel between the electrodes 2a and 2b. It is the point where it is arranged. This reduces the resistance of the squib in half.

As a result, in FIG. 8, when V ₀ is lowered, that is, when the boosted voltage is not used, it is possible to obtain a particular effect, and by using squibs in series, the squib resistance becomes Even if it increases too much, the effect can be obtained by using this method.

Further, in order to reduce the resistance of the bridge wire, (1) a method of changing the material to a material having a small specific resistance, (2) a method of shortening the length of the bridge wire, and (3) an electric wire Although it is possible to make the bridge wire thicker, it is not easy to obtain a stable material in the method of (1), and in the methods of (2) and (3), the electrode of the bridge wire is used for the heating part of the bridge wire. Since the ratio of the joint portion with and increases, the heat radiation to the electrode portion increases. That is, the heat transfer efficiency η decreases. Therefore, the effect of reducing the resistance cannot be sufficiently obtained. In this respect, in the present invention, the length and thickness of the bridge wire are not significantly changed, and the number of bridge wires is increased, so that the heat transfer efficiency η is hardly changed (1/2) R, (1 / 3) The resistance of R can be obtained. Moreover, even if one bridge line is broken, the rest of the bridge lines will function, so reliability can be expected to improve.

As shown in FIG. 3, if the number of bridge wires 41a, 41b, 41c is three (or more), the time required for ignition when one bridge wire is broken. Does not grow too much.

Further, if a plurality of bridge wires are provided and the distances between them are arranged as close as possible, it becomes possible to concentrate the heat generation amount of the bridge wire in a narrow range. The electric heating efficiency of the F portion of FIG. 3 is improved, and as shown in FIGS. 2 (a) and 2 (b), the electric heat amount to the E portion or the B portion is increased, that is, with a smaller electric current, It is possible to raise the temperature of the explosive to the ignition temperature T _i during the required time τ. As a result, it can be expected that the capacitance of the capacitor will be reduced.

[0029]

[Effect of device]

 The igniter of the occupant protection device gas generator of the present invention is provided with a bridge wire as described above, which heats and ignites the ignition powder that ignites the occupant protection device gas generator such as an air bag. In the igniter, since a plurality of bridge wires are arranged in parallel, it is possible to maintain the same stable ignition performance and heat transfer efficiency to the ignition charge as before by using the same bridge wire as before. Alternatively, the electrical resistance of the igniter can be reduced while further improving the electrothermal efficiency. As a result, the capacity of the backup capacitor can be minimized or the booster circuit can be eliminated.

[Brief description of drawings]

FIG. 1 is a top view showing a main part of an igniter of a gas generator for an occupant protection device of the present invention.

FIG. 2 is a diagram showing an effect on electric heat efficiency of an igniter of a gas generator for an occupant protection device of the present invention.

FIG. 3 is a top view showing another embodiment of the igniter of the gas generator for an occupant protection device of the present invention.

FIG. 4 is a circuit diagram showing an ignition circuit of a gas generator for an occupant protection device.

FIG. 5 is a sectional view of an igniter of a conventional gas generator for an occupant protection device.

6 is a view on arrow A of FIG.

FIG. 7 is a voltage and current change diagram showing the operation of an igniter of a conventional gas generator for an occupant protection device.

FIG. 8 is a relationship diagram of a squib resistance value and a required capacitor capacity with a power source voltage of an igniter as a parameter.

[Explanation of symbols]

 6 Ignition agent 13 Squib (igniter) 31a Electric bridge line 31b Electric bridge line 25 Gas generator

Claims (1)

[Scope of utility model registration request] 1. An igniter equipped with an igniting agent for igniting a gas generator for an occupant protection device such as an airbag, and an electric bridge wire for generating heat and igniting the igniting agent by energizing the ignition wire. An igniter for a gas generator for an occupant protection device, which is arranged in parallel.