JPH05147491A - Air bag starting controller - Google Patents

Abstract

PURPOSE:To provide an air, bag starting controller at a low cost without increasing the contact point capacity of a safing sensor over necessity. CONSTITUTION:If a large negative accelerating speed is applied on a vehicle, a collision judging means 23 detects the negative accelerating speed and outputs a collision detecting signal. At this time, a safing sensor 1 detects the contact between the electrodes 13, 14 and a contact pole 12. Since, at this time point, the output of a delaying circuit 21 is at L level, the output of an AND gate 22 becomes 'L' level, and an FET 24 is in turned-OFF state. Accordingly, no electric current flows in the electrodes 13 and 14, and the contact point is photeted. Then, in a delaying circuit 21, the output signal is set to 'H' level after the predetermined delay. Accordingly, the output of the and gate 22 becomes 'H' level, and the FET 24 is tuned ON.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air bag activation control device for activating an air bag by detecting a large negative acceleration, and more particularly to an air bag activation control device capable of detecting acceleration satisfactorily. Is.

[0002]

2. Description of the Related Art In recent years, in order to protect an occupant from a shock generated during a collision of a vehicle, when a large negative acceleration is applied to the vehicle, the airbag is sensed and activated, and the airbag is instantly inflated. Occupant protection devices are widespread.

FIG. 8 is a schematic diagram showing an example of a conventional air bag activation control device. The safing sensor 1 includes a U-shaped magnet 11 having one open, a contact ball 12 complemented by the U-shaped magnet 11 in the normal state, first and second electrodes 13 arranged in a C-shape, It is composed of 14.

In the safing sensor 1 having such a structure, when a large negative acceleration (-G) is applied to the vehicle due to a collision, the contact ball 12 is separated from the magnet 11 and the electrode 13 is removed.
And 14 to bring the electrodes 13 and 14 into conduction. As a result, it is possible to detect a negative acceleration equal to or higher than a predetermined value.

A squib ignition capacitor 3 is connected to the first electrode 13, and the squib ignition capacitor 3 is charged by the battery 2 in normal times. By using the squib ignition capacitor 3, even if the battery is damaged or the terminal comes off due to a collision, the device can be reliably started.

One end of the squib 5 is connected to the second electrode 14, and the other end of the squib 5 is grounded via a cowl sensor 6 that detects a weak negative acceleration and closes the contact. The squib 5 is composed of a filament having an internal resistance of several ohms, and a gunpowder is provided around the filament.

In the air bag activation control device having such a structure, when a negative acceleration (-G) exceeding a predetermined value is applied to the vehicle, the cowl sensor 6 is first turned on, and the safing sensor 1 causes the contact ball 12 to come into contact. Pops out in the -G direction and contacts the first and second electrodes 13 and 14. As a result, the electrodes 13 and 14 are brought into conduction via the contact balls 12, so that the squib ignition capacitor 3 is rapidly discharged, and a large current I flows through the squib 5.

At this time, the squib 5 is heated to a high temperature,
Gunpowder placed around it ignites. Further, the heat and pressure generated by this ignition cause a chemical reaction of the solid fuel (eg, sodium nitride) to generate nitrogen gas. This nitrogen gas spreads inside the airbag (not shown) and inflates the airbag in an instant.

Regarding the airbag start-up control device having the above structure, for example, Nikkei Mechanical, 1991 Sep.
In the 2nd issue of the month, it is discussed under the heading "A new method appears mainly in diversifying airbag sensors."

[0010]

However, in the above-mentioned conventional structure, when a large negative acceleration (-G) is applied, the contact ball 12 of the safing sensor 1 causes the contact ball 12 to move to the electrode 1.
Since the cowl sensor 6 is turned on before the contact with the electrodes 3 and 14, the contact ball 12 causes the contact ball 12 to contact the electrodes 13 and 14 in this state.
When it contacts with, a large electric current will momentarily flow to the contact.

On the other hand, since the capacitor 3 is used as a current supply source for the squib 5, the current value I thereof depends on the discharge characteristic of the capacitor as shown in FIG. Therefore, although the energy required to ignite the squib is the amount defined by the hatched area in the figure, an unnecessarily large current flows at the initial stage of discharge.

Therefore, the conventional safing sensor 1
Then, in order to secure a predetermined safety factor against a large current as described above, a large capacitance is required for the contact of the safing sensor 1, that is, the contact of the first and second electrodes 13 and 14, and this is required. There was a problem that it caused an increase in cost.

An object of the present invention is to solve the above-mentioned problems of the prior art and to propose an inexpensive air bag activation control device which does not require a large contact capacity.

[0014]

In order to achieve the above-mentioned object, the present invention has a contact ball captured by the supplemental means in normal times, and is separated from the supplemental means upon receiving an acceleration of a predetermined value or more. Acceleration detection means for closing a set of contacts via a contact ball; collision determination means for determining a collision when acceleration exceeds a predetermined value; squib connected to one of the set of contacts; In an air bag starting control device comprising a squib ignition capacitor connected to the other of the contacts and a switch means connected in series with the set of contacts, the following means are further characterized. is there. (1) When the pair of contacts are closed and a collision is determined,
A switch control means for closing the contact of the switch means is provided after the voltage of the other contact is stabilized. (2) The switch means is composed of an FET (field effect transistor), and when the set of contacts is closed and collision is determined, a predetermined constant voltage is supplied to the gate electrode of the FET to conduct it. A switch control means for setting the state is provided.

[0015]

According to the above configuration (1), the squib ignition current flows after the set of contacts of the acceleration detecting means and the contact ball come into contact with each other and the contact state is stabilized, so that the capacity of each contact is required. There is no need to make it larger than that.

According to the above configuration (2), a constant current flows through the set of contacts regardless of the discharge characteristics of the squib ignition capacitor, so that it is not necessary to increase the capacity of each contact more than necessary. ..

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram of an airbag start control device according to a first embodiment of the present invention, and the same reference numerals as those used above represent the same or equivalent portions.

In FIG. 1, the squib 5 is grounded via the FET 24, and the connection point N1 between the electrode 14 and the squib 5 is
The input terminal of the delay circuit 21 is connected to the. The delay circuit 21 is a circuit that supplies an output signal with a predetermined delay, such as a buffer with hiss.

The output signal of the delay circuit 21 is the AND gate 2
The collision detection signal output from the collision determination means 23 is input to one of the two input terminals and the other input terminal. The output signal of the AND gate 22 is input to the gate terminal of the FET 24.

The collision determination means 23 is provided with an electronic acceleration sensor (not shown), and outputs a collision detection signal when the acceleration sensor detects -G above a predetermined value.

In such a structure, when a negative acceleration (-G) exceeding a predetermined value is applied to the vehicle, the collision determining means 23
Detects this and outputs a collision detection signal. At this time,
In the safing sensor 1, as described above, the first and second
The electrodes 13 and 14 and the contact ball 12 come into contact with each other. However, since the output of the delay circuit 21 is still at "L" level at this point, the output of the AND gate 22 is "L".
The FET 24 is turned off and the FET 24 is off. Therefore, the squib ignition current does not flow through the electrodes 13 and 14,
That contact will be protected.

After that, the delay circuit 21 sets the output signal to the "H" level with a predetermined delay. As a result,
The output of the AND gate 22 becomes "H" level and the FET
24 is turned on, a current for squib ignition flows through the electrodes 13 and 14, and the squib 5 is heated.

According to this embodiment, the safing sensor 1
Since the contact is closed and the squib ignition current flows after the contact state is stabilized, no load is applied to the electrodes 13 and 14, and it is not necessary to increase the contact capacity more than necessary.

FIG. 2 is a block diagram of an air bag activation control device according to a second embodiment of the present invention, in which the same symbols as those used above represent the same or equivalent parts.

In this embodiment, even if the collision determination means 25 detects a large -G, the collision detection signal is not immediately output, but the collision detection signal is confirmed after confirming that the voltage at the connection point N1 is stable. I am trying to output.

Since the voltage at the connection point N1 is about 0 to 14V because it depends on the battery voltage, and the collision determination means 25 is driven by a logic voltage (generally 5V), it collides with the connection point N1. It is desirable to provide a level conversion buffer between the determination unit 25 and the determination unit 25 as needed.

According to this embodiment, the safing sensor 1
FET24 is closed after the contact is closed and the contact is stable.
Is turned on and the current for squib ignition flows, so that no load is applied to the electrodes 13 and 14, and it is not necessary to increase the contact capacitance more than necessary.

FIG. 3, FIG. 4, FIG. 5, and FIG. 6 are configuration diagrams of the air bag activation control device according to the third, fourth, fifth, and sixth embodiments of the present invention, respectively. The reference numerals represent the same or equivalent parts. In each embodiment, the above-mentioned 2
Among the two problems, it is to prevent a large current from flowing immediately after the start of discharge.

Each of the embodiments is intended to limit the amount of current by utilizing the VDS (drain / source voltage) -ID (source current) characteristic of the FET.

As is well known, the source current ID of the FET depends on the drain-source voltage VDS and the gate-source voltage VGS, and both have the relationship shown in FIG.

Therefore, in each of the embodiments, paying attention to this point and limiting the gate-source voltage VGS, the source current ID (squib ignition current) is generated regardless of the discharge characteristic of the capacitor, that is, the drain-source voltage VDS. ) Is constant.

In the embodiment shown in FIG. 3, the pulse signal is smoothed by the integrating circuit of the resistor R1 and the capacitor C1 and converted into a DC voltage, and the DC voltage is applied to the gate electrode of the FET 24 to limit the source current ID. is doing. In this example,
The source current ID can be controlled by setting the pulse width of the pulse signal appropriately.

Therefore, according to this embodiment, a constant current can be supplied to the safing sensor 1 regardless of the discharge characteristics of the squib ignition capacitor.
It is not necessary to increase the contact capacitance of the electrodes 13 and 14 more than necessary.

In the embodiment shown in FIG. 4, the reference voltage Vf output from the CPU is divided by the resistor R2 and the variable resistor R3, and the control voltage Vc obtained by the division is applied to the gate electrode of the FET 24. The source current ID is limited.

Further, since the shunt resistor Rb is added in this embodiment, when the source current ID increases and the source potential increases, the gate-source voltage VGS decreases and the source current ID decreases, and vice versa. When ID decreases and the source potential drops, the gate-source voltage VGS rises and the source current ID current increases so that self-feedback works and more accurate control becomes possible.

According to this embodiment, by adjusting the variable resistor R3 to control the control voltage Vc, a constant current can be supplied to the safing sensor 1 regardless of the discharge characteristic of the squib ignition capacitor. Therefore, the same effect as described above can be achieved.

In the embodiment shown in FIG. 5, a plurality of resistors 52-1 to 52-n having different resistance values and an analog switch 51 are used to output an arbitrary voltage according to a selection signal from a channel selector (not shown). A voltage supply source and a negative feedback circuit composed of an operational amplifier OP1 and a feedback resistor Rc are provided, and the output voltage from the voltage supply source is applied to the gate electrode of the FET 24 through the negative feedback circuit to limit the source current ID. is doing.

In this embodiment, the source current ID can be controlled by appropriately turning on / off the contact of the analog switch 51 by the channel selector. The effect similar to the above is achieved also by this embodiment.

In the embodiment shown in FIG. 6, the source current ID
In response to, the voltage appearing across the terminals of the resistor Rd is amplified by the voltage amplifier circuit 61 and fed back to the differential amplifier 62,
The gate-source voltage VGS of the FET 24 can be controlled more accurately. The effect similar to the above is achieved also by this embodiment.

In each of the above-mentioned embodiments, the embodiment for dealing with the large current when the contacts are closed and the embodiment for dealing with the large current at the initial stage of discharge are described separately. The invention is not limited to this, and it is also possible to combine both to deal with both the large current at the time of closing the contact and the large current at the initial stage of discharge.

[0041]

As is apparent from the above description, according to the present invention, the following effects can be achieved. (1) Since the contact of the safing sensor is closed and the squib ignition current is made to flow after the contact state is stabilized, no load is applied to the contact of the safing sensor and the contact capacity is increased more than necessary. No need. (2) Control the gate-source voltage VGS of the FET to limit the source current (squib ignition current) so that a constant current is supplied to the safing sensor regardless of the discharge characteristics of the squib ignition capacitor. Therefore, the contact of the safing sensor is not loaded, and it is not necessary to increase the contact capacity more than necessary.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an airbag activation control device that is a first embodiment of the present invention.

FIG. 2 is a circuit diagram of an airbag activation control device that is a second embodiment of the present invention.

FIG. 3 is a circuit diagram of an airbag activation control device that is a third embodiment of the present invention.

FIG. 4 is a circuit diagram of an airbag activation control device that is a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram of an airbag activation control device that is a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram of an airbag activation control device that is a sixth embodiment of the present invention.

FIG. 7 is a diagram showing the characteristics of an FET.

FIG. 8 is a circuit diagram of a conventional airbag activation control device.

FIG. 9 is a diagram showing discharge characteristics of a squib ignition capacitor.

[Explanation of symbols]

1 ... Safing sensor, 2 ... Battery, 3 ... Squib ignition capacitor, 5 ... Squib, 6 ... Cowl sensor,
11 ... U-shaped magnet, 12 ... Contact ball, 13, 14 ...
Electrode, 21 ... Delay circuit, 22 ... AND gate, 23, 2
5 ... Collision determination means, 24 ... FET, 51 ... Analog switch, 61 ... Amplifier circuit, 62 ... Differential amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Suzuki 1-4-1 Chuo, Wako-shi, Saitama Stock Research Institute Honda Technical Research Institute

Claims (3)

[Claims] 1. An acceleration detecting means having a set of contacts and a contact ball captured by the supplementing means in normal times, and closing the contact via the contact ball separated from the supplementing means upon receiving an acceleration of a predetermined value or more. A collision detecting means for converting acceleration into an electric acceleration signal and detecting a collision when the acceleration signal exceeds a predetermined value; a squib connected to one of the pair of contacts; A squib ignition capacitor connected to the other one of the contacts, a switch means connected in series with the set of contacts, and the pair of contacts are closed and the collision detection is performed,
An air bag activation control device comprising: a switch control means for closing the contact of the switch means after the voltage of the other contact is stabilized. 2. An acceleration detecting means having a set of contacts and a contact ball captured by the supplementing means in normal times, and closing the contact via the contact ball separated from the supplementing means upon receiving an acceleration of a predetermined value or more. A collision detecting means for converting acceleration into an electric acceleration signal and detecting a collision when the acceleration signal exceeds a predetermined value; a squib connected to one of the pair of contacts; A squib ignition capacitor connected to the other of the contacts, a field effect transistor connected in series with the set of contacts, and the pair of contacts is closed and the collision detection is performed,
Switch control means for supplying a predetermined constant voltage to the gate electrode of the field-effect transistor to bring it into a conductive state, wherein the predetermined constant voltage is a discharge current of the squib ignition capacitor is the field-effect transistor. An airbag activation control device characterized by being set so as to be restricted by 3. The airbag activation control device according to claim 2, wherein the switch control means supplies the predetermined constant voltage after the voltage of the other contact is stabilized.