JPH01233136A - Ignition detecting device for air bag system - Google Patents

Abstract

PURPOSE:To surely improve the ignition detection precision in simple ways by connecting a resistance in parallel to an ignitor and comparing the voltage generated at the both edges of the ignitor with a standard voltage in a voltage comparator and detecting the flow of the ignition current. CONSTITUTION:When an automobile is collided, the switches S2-S4 of a number of G sensors 2-4 are closed, and an electric current flows in an ignitor 5, and an air bag is expanded. The voltage comparators 7 and 10 compare a plurality of different standard voltages generated in a standard voltage generator 8 and the voltage S at the both edges of the ignitor 5, and detects the ignition of the ignitor 5. A resistance 6 is connected in parallel to the ignitor 5, and when the ignitor 5 is cut off or the resistance value increases, the resistance value of the resistance 6 is set so that the synthesized resistance value of the ignitor 5 and the resistance 6 does not become larger than the resistance value of a number of wire breakage detecting resistances 21-41. Therefore, it is prevented that the outputs of the voltage comparators 7 and 8 erroneously becomes to be the logic '1'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition detection device for an air bag system for an automobile, which is capable of storing information about the deployment of an air bag in a memory element.

[Conventional technology]

For example, a failure detection device for an air bank device for protecting occupants in the event of a car collision is disclosed in Japanese Patent Publication No. 61-5721.
This is disclosed in Publication No. 9, and in the case of this publication, a voltage drop is caused in the starting means by a minute current flowing to the starting means through a resistor connected in parallel with the normally open collision detection switch, and a voltage drop is caused at both ends of the starting means. A differential amplifier circuit that inputs a voltage and a comparison circuit that compares its output with a reference value are provided to detect short circuits, open failures of the normally open type collision detection switch, and open failures of the starting means.

Further, Japanese Patent Publication No. 61-51176 discloses an accidental explosion recording device for an airbag device, which is constructed by connecting a resistor in series to a plurality of squibs and connecting a recording device in parallel with the resistive layer. There is.

FIG. 2 is a block diagram showing the configuration of a conventional airbag ignition detection device. In the figure, 1 is a battery, 2, 3 and 4 detect acceleration at the time of a car collision, and send it to an igniter (squib) 5. Acceleration sensor (hereinafter referred to as G
6 is a shunt resistor that causes a voltage drop when the ignition current flows.

21, 31, and 41 respectively at the G sensor 2.3°4 and the switch S2. S3. This is a disconnection detection resistor connected in parallel with S.

7 is a voltage comparator that compares the voltage generated across the shunt resistor 6 with the voltage generated by the reference voltage source 8 to detect that the airbag has been deployed; 9 receives the output signal of the voltage comparator 7; -1 is a storage device that records that the airbag has been deployed.

Next, the operation will be explained. When a car collides, acceleration occurs, and when the acceleration exceeds a certain value, switch S2 of G sensor 2 closes, and at least one of G sensors 3 or 4 closes switch S3 or S4.

As a result, the current necessary for ignition is supplied from the igniter 5 to the igniter 1, and the airbag is deployed.

Since the ignition current also flows through the shunt resistor 6, a voltage is generated across the shunt resistor 6.

The voltage comparator 7 detects the generation of this voltage and generates an ignition detection signal, but the voltage generated across the shunt resistor 6 is compared with a reference voltage generated by a reference voltage generator 8. ing.

This reference voltage is equal to the voltage across the shunt resistor 6 when the minimum current necessary for ignition flows through the shunt resistor 6.

[Problem to be solved by the invention]

The ignition detection device of the conventional airbag system is configured as described above, so if a failure such as a disconnection occurs in the shunt resistor 6, the switch S of the G sensor 2, 3 or 4 is activated.
Even if S2 and S3 or S4 were closed, there was a risk that current would no longer flow.

In addition, since the resistance value of the igniter 5 is small, the value of the shunt resistor 6 needs to be made even smaller than this value. Therefore, the voltage generated across the shunt resistor 6 becomes low, and the voltage comparator 7 There was a problem that not only was it susceptible to noise, but there was also a risk of the shunt resistor breaking.

This invention was made in order to solve the above-mentioned problems, and there is no need to insert a shunt resistor into the ignition current path, and detection using minute voltage is possible without reducing the reliability of the airbag system. The purpose of the present invention is to obtain an ignition detection device for an air puncture system that does not require any noise and is resistant to noise.

[Means to solve the problem]

The ignition detection device for an airbag system according to the present invention includes:
It is equipped with a voltage comparator that detects the potential difference that occurs across the igniter when ignition current flows through the igniter.

[For production]

In this invention, the igniter itself is used as a shunt resistor, and the potential difference across the igniter is applied to a voltage comparator and compared with a reference voltage to detect whether ignition current has flowed to the igniter.

〔Example〕

Embodiments of the present invention will be described below.

FIG. 1 is a block diagram showing the configuration of one embodiment.
In this FIG. 1, 1 is, for example, an automobile battery, 2 is
, 3 and 4 are G sensors for detecting the acceleration at the time of a collision of the automobile and passing a current to the igniter 5, and 21.31.41 are switches Sz, S in the G sensors 2, 3 and 4.
3, a disconnection detection resistor connected in parallel with Ss; 6, a resistor connected in parallel with the igniter 5; 7.8, the voltage across the igniter 5 as a reference generated by the reference voltage generator 9; A voltage comparator detects that the airbag has been deployed by comparing the voltage. 10 is a gate (logic calculator) that takes the AND of the outputs of the voltage comparators 7 and 8. This is a storage device that stores the information that the airbag was deployed in response to the airbag being deployed.

Next, the operation will be explained. When a car collides, acceleration occurs and G sensors 2, 3.4 Suinochi S2, S
3, S4 is closed, current flows through the igniter 5, and a potential difference is generated across it.

At this time, the voltage at the position A becomes approximately equal to the voltage of the battery 1, and the voltage at the position A becomes approximately equal to the ground potential (○■).

Therefore, the voltage comparator 7 detects that the voltage A has become lower than the constant voltage ■1 generated by the reference voltage generator 9, and the voltage comparator 8 detects that the voltage A has become lower than the constant voltage ■1 generated by the reference voltage generator 9. If it is detected that the voltage has become higher than the constant voltage (2) generated at , (V2 Vl) is the potential difference generated across the igniter 5.

Since the resistance value of the igniter 5 is known, the current flowing is i. If the resistance value of the igniter 5 is R8, then i
o −(V 2 V +)/Ro.

Minimum current value i required for airbag deployment.

(min) and a constant voltage v2 from the resistance value R8 of the igniter 5
The constant voltages V, , V2 are generated by the reference voltage generator 9 and input to the voltage comparators 7 and 8 manually.

The voltage comparator 7 generates a logic "1" signal when the voltage of A becomes lower than the constant voltage ■1, and the voltage comparator 8 generates a logic "1" signal when the voltage of A becomes higher than the constant voltage ■2. , it is indicated that current has flowed through the igniter 5 only when the outputs of the voltage comparators 7 and 8 are both logic "1". Gate 10 outputs a logic "1" when the outputs of voltage comparators 7 and 8 are both logic "1". That is, it is an AND gate.

By the way, as is well known, the G sensor used in the air pack system includes switches S2 and S3.
, S4, a disconnection detection resistor 21°31.41 is inserted. Therefore, although a small current always flows through the igniter 5, the values of the disconnection detection resistors 21 and 31.41 are as follows.
Since it is much larger than the resistance value of the igniter 5, the voltage A at this time is sufficiently lower than the constant voltage V2, and the voltage B is sufficiently higher than the constant voltage V, so that the outputs of the voltage comparators 7 and 8 are It will never be logical ``1''.

However, when the igniter 5 is disconnected or its resistance value becomes sufficiently larger than the disconnection detection resistor 21, 31, 41, the voltage A is higher than the constant voltage V2,
Voltage A becomes lower than constant voltage ■1, and the ignition detection signal is sent to gate 10 even though the airbag is not deployed.
will occur.

To prevent this, a resistor 6 is connected in parallel with the igniter 5. That is, even when the igniter 5 is disconnected or its resistance value increases, the combined resistance value of the igniter 5 and the resistor 6 will not become too large compared to the disconnection detection resistors 21, 31, 41. If the resistance value of resistor 6 is set as shown in FIG.
” will never occur.

〔Effect of the invention〕

As described in Part 2, according to the present invention, a resistor is connected in parallel to the igniter, and the voltage generated across the igniter is compared with a constant voltage using a voltage comparator to determine whether the ignition current has flowed. Since it is configured to detect this, there is no need to lower the reliability of the airbag system by inserting a shunt resistor into the ignition current path, and there is no need to detect using minute voltages, making it resistant to noise. It has the excellent effect of being able to

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ignition detection device for an air bag system according to an embodiment of the present invention, and FIG. 2 □ is a circuit diagram of a conventional ignition detection device for an air bag system. 1...Battery, 2,3.4...G sensor, 5 is igniter, 6...Resistor, 7.8...Voltage comparator, 9...
・Reference voltage generator, 10...gate, 11 is a memory device. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] A first acceleration sensor that detects acceleration by closing a switch when a car crashes, and second and third acceleration sensors connected in parallel.
of the first acceleration sensor and the second or third acceleration sensor inserted between the first acceleration sensor and the second and third acceleration sensors connected in parallel. When at least one of the above detects a collision of the automobile, a current flows through an igniter to deploy the airbag, and the voltage across the igniter is compared with a predetermined constant reference voltage that is different from each other, and the above-mentioned ignition is started. first and second voltage comparators for detecting that the device has ignited;
a logic circuit that performs logical calculations on the output of the second voltage comparator;
A storage device that stores the output of this logic circuit is connected in parallel with the igniter, and when the igniter is disconnected or exhibits an abnormal resistance value, the first and second voltage comparators erroneously detect a potential difference. An ignition detection device for an airbag system having a resistance for preventing detection.