JPH02158445A - Failure detection device for air bag apparatus - Google Patents

Abstract

PURPOSE:To prevent an air bag apparatus in which a monitoring current runs through a detonating resistance so as to detect a failure in the apparatus in accordance with a detected value, from being erroneously operated, by determining an upper limit of the monitoring current so that a warning signal is produced when the monitoring current exceeds the upper limit. CONSTITUTION:When an ignition switch 2 is turned on, a failure detection device composed of a differential amplifier circuit 11, a window comparator 17 and a voltage monitor circuit 25 is energized. The voltage monitor circuit 25 monitors a monitoring current which runs through a detonator 3, and which is determined by a voltage at a point (f) on the cathode side of a back-flow preventing diode 10, and it turns on an indication lamp 24 when the voltage at the point (f) exceeds a predetermined value, so as to warn the driver. Even when a power source voltage of a battery 1 is increased due to a cause, although no failure in short circuit and opening of collision detectors 4, 5 and the detonator 3 occurs, the output of the voltage monitor circuit 25 is lowered, and accordingly, the indication lamp 24 is turned on by means of an AND gate circuit 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a failure detection device for an airbag device that protects occupants of high-speed moving objects, particularly automobiles, in the event of a collision.

[Conventional technology]

For devices that electrically activate the airbag device,
Since the power supply that forms the main circuit, the activation means for deploying the airbag, and the normally open collision detection switch form a closed circuit, the activation means and the normally open collision detection switch may short-circuit or open, causing the device to malfunction. In order to avoid a loss of functionality, a failure detection circuit is attached to promptly detect any failure.

Conventionally, regarding failure detection devices for air hang devices, for example, Japanese Patent Application Laid-Open No. 52-33233 and Japanese Patent Application Laid-Open No. 54-47
This is disclosed in Publication No. 244 and the like.

FIG. 3 is a circuit diagram of a conventional failure detection device for an airbag device disclosed in the latter publication. 2a.

The negative electrode of this DC battery 1 is connected to a power supply line 1a.

Further, 3 is a detonator that ignites an explosive for detonating a gas generator and deploying an air bag when a current of a predetermined value or more is supplied. 3a and 3b are electrical wirings connected to both ends of the detonator 3.

Collision detection circuits 4 and 5 detect a collision and form an energizing circuit for the detonator 3, and have mechanical contact-type normally open collision detection switches 4a and 5a, respectively, and electrical wiring 4c and 4.
It is connected to d, 5c, and 5d.

Electrical wiring 4c is connected to power line 2a via backflow prevention diode 1o, electric wiring 5d is connected to power line 1a, and electric wiring 4d and 3a.

3b and 50 are connected.

Thus, the collision detector 4.5 and the detonator 3 are connected in series between the power lines 2a and 1a.

In addition, 4b and 5b are respectively normally open type collision detection switches 4.
It is a resistor connected in parallel with the normally open collision detection switches 4a and 5a, and even if the normally open collision detection switches 4a and 5a are open,
It supplies the detonator 3 with a minute current that is not enough to deploy the airbag.

Reference numeral 6 denotes a control unit integrated into one case.

In this control section 6, 7 is a hack-up capacitor made of a large-capacity aluminum electrolytic capacitor, and 8 is a discharge diode of this hack-up capacitor 7, which is connected to the power line 2a and the line la through the reverse current prevention diode 10. connected in series between.

9 is a charging resistor for the bank amplifier capacitor 7 connected in parallel to the discharging diode 8. The hack-up capacitor 7 is used as an auxiliary power source for the starting circuit, and when the ignition switch 2 is closed, it is charged from one point to almost the battery voltage of the DC battery 1 through the reverse current prevention diode 10 and the charging resistor 9, and the collision is prevented. When both normally open collision detection switches 4a and 5a of the detector 45 are closed, the accumulated charge is discharged through the discharge diode 8, and even if the power lines 1a and 2a are cut or short-circuited, the detonator Supply sufficient current to 3 to detonate it and deploy the airbag.

Reference numeral 11 denotes a differential amplifier circuit, which is composed of an operational amplifier 12 and gain adjustment resistors 13 to 16, and outputs an output voltage Vd corresponding to the voltage Vs across the detonator 3.

The resistance value R13 of the gain adjustment resistor 13 - the resistance value R14 of the gain adjustment resistor 14, the resistance value R15 of the gain adjustment resistor 15 = the resistance value R16 of the gain adjustment resistor 16 is set so that There is.

17 is a window comparator, operational amplifier 1B,
19, Reference voltage setting resistor 2'0, 21°22 and A
The output voltage vL of the differential amplifier circuit 11 is set by reference voltage setting resistors 20 and 2.
1.22, point a (reference voltage setting resistors 20 and 2
1) and point b (reference voltage setting resistors 21 and 22
The comparison is made with two reference voltages of different levels generated at the connection point).

As a result of this comparison, if the output voltage of the operational amplifier 11 is not within the range of the reference voltage, one of the operational amplifiers 18.1
9, the output C or d of either one becomes low level,
The output e of the AND gate circuit 23 is set to a low level.

Reference numeral 24 denotes an indicator lamp, which is configured to turn on when the output e of the AND gate circuit 23 becomes low level to indicate a failure and to warn the driver.

Next, the operation will be explained. Now, when the ignition switch 2 is closed, the energizing circuit for the detonator 3, which is directly related to the airbag deployment of the device, becomes in a standby state, and the normally open collision detection switch 4a of the collision detector 4.5 is activated. When 5a is closed, a current of a predetermined value or higher flows directly through the detonator 3, causing the airbag to deploy.

Further, when the ignition switch 2 is turned on, the hack-up capacitor 7 is quickly charged to approximately the battery voltage, and the energizing energy necessary for the detonator 3 is saved even if the power supply lines 2a, la are disconnected.

On the other hand, when the ignition switch 2 is turned on, the failure detection device consisting of the differential amplifier circuit 11 and the window comparator 17 is activated, and if a short-circuit or open failure occurs in either the detonator 3 or the collision detectors 4 and 5, the AND
The output of the gate circuit 23 is inverted to a low level and the warning indicator light 24 is turned on.

According to the experimental example, resistance value R4b of resistor 4b - resistance value R5 of resistor 5b, b = 500Ω, resistance value R3 of detonator 3 =
1Ω and the battery voltage is 12V, if there is no failure in the collision detectors 4, 5 and the detonator 3,
A voltage of Vs-12 mV is generated across the detonator 3.

This voltage Vs is input to the differential amplifier circuit 11, and assuming that its gain G is 100 (G=R15/R13=R16/R
14), the output voltage Vd of the differential amplifier circuit 11 is Vd=1
．． It becomes 2V.

In the window comparator 17, if the reference voltage at point a is set to 1.8V and the reference voltage at point b is set to 0.6V, the outputs C1d of operational amplifiers 18 and 19 are both at high level, and the AND gate The output e of the circuit 23 is also at a high level, and the indicator lamp 24 does not light up.

However, if one of the collision detectors 4 and 5 is short-circuited or has an open failure, or if the detonator 3 is short-circuited or has an open failure, the voltage and output level at each location will be as shown in Table 1 below. In either case, the output of the AND gate circuit 23 is at a low level, so the failure indicator lamp 24 lights up.

Note that rHJ, which indicates the output level in Table 1, is a high level.
"L" indicates a low level.

<Table 1> [Problems to be Solved by the Invention] Since the conventional failure detection device for the air hang device is configured as described above, the detonator 3 deploys the air hang when a current of more than a predetermined value is supplied. Although this predetermined value is a large current of several amperes for a short period of time, it is a very small current of about several tens of milliamperes in a continuous period.

In addition, a monitor current is passed through the detonator 3 through the resistors 4b and 5b connected in parallel with the normally open collision detection switches 4a and 5a, and a voltage V is generated by amplifying the voltage Vs generated across the detonator 3.
6 and reference voltages at points a and b to detect a failure.

Furthermore, since these resistors 4b, 5b, detonator 3, and reference voltage setting resistors 20, 21.22 constitute a bridge circuit, if the power supply voltage increases for some reason, the monitor current flowing through detonator 3 exceeds a predetermined value. When , the voltage Vd, which is the amplified voltage Vs generated across the detonator 3, rises, but the reference voltages at points a and b also rise in the same way.

In other words, the battery voltage constantly fluctuates, and the monitoring current also fluctuates accordingly, and even if this monitoring current fluctuates somewhat, it is not a particular problem when determining failures such as disconnections or short circuits, whether they are ``0'' or ``1''. ,Therefore, there were problems such as failure being not detected, which may cause malfunction of the airbag.

This invention was made to solve the above-mentioned problems, and when the monitor current exceeds a predetermined value, it is possible to promptly detect a failure and turn on an indicator light to warn the driver. It is an object of the present invention to provide a failure detection device for an airbag device that can prevent malfunction of an airbag and obtain high reliability.

[Means to solve the problem]

The failure detection device for an airbag device according to the present invention is provided with a warning means for determining an upper limit value of a monitoring current flowing through a detonation resistor and outputting a warning signal when the monitoring current exceeds this upper limit value.

[For production]

In this invention, for example, when the power supply voltage becomes abnormally high and a large current exceeding the upper limit of the monitoring current flows through the detonation resistor, the warning means detects this and outputs a warning signal.

〔Example〕

Embodiments of a failure detection device for an air hang device according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of one embodiment.

In this Figure 1, as is clear from comparison with Figure 3,
In addition to adding the voltage monitoring circuit 25 to the configuration shown in FIG.
This uses a human-powered AND gate circuit 23. The other configurations are the same as in FIG. 3.

The voltage monitoring circuit 25 is composed of a comparator 26 and one resistor 27.28, and the resistor 27.28 is connected in series between the point f and the ground.

The connection point between these resistors 27 and 28 is the comparator 26 (7
)(-) input terminal, and the (+) of the comparator 26.
A reference voltage E is applied to the input terminal.

The output of the comparator 26 is the third
It is designed to be added to the input end of .

The voltage monitoring circuit 25 detects that when the voltage at point f exceeds a predetermined value,
The output g is set to a low level, and the output e of the AND gate circuit 23 is
I am trying to keep it at a low level.

When the output e of the AND gate circuit 23 becomes low level, the indicator light 24 lights up to indicate a failure and to warn the driver.

Next, the operation will be explained. ignition switch 2
When the f When an abnormal voltage failure occurs at a point, the output e of the AND gate circuit 23 is inverted to a low level, and the indicator lamp 24 lights up to display a warning.

Here, the above operation will be briefly explained in detail.

As shown in FIG. 2, the monitor current flowing through the detonator 3 is smaller than the detonating current and has a magnitude within a predetermined range. Determined.

Therefore, by monitoring the voltage at point f, abnormalities in the monitor current can be detected, and the collision detector 4
.

In other words, when ignition switch 2 is closed, detonator 3
A monitor current flows through the control unit 6, and each part of the control unit 6 operates as explained in FIG. , the indicator light 24 is turned on.

On the other hand, a short circuit between these collision detectors 4, 5 and detonator 3,
If an open fault has not occurred and the power supply voltage of DC battery 1 rises for some reason and the voltage at point f, which is being monitored, exceeds a predetermined value (reference voltage E), voltage monitoring is performed. The output g of the comparator 26 of the circuit 25 becomes low level.

This low level signal is input to the AND gate circuit 23 as described above. As a result, the AND gate circuit 23
The output e becomes a low level, and the indicator light 24 is turned on.

Next, explanation will be given using specific numerical examples. However, since the case of a short-circuit or open failure in either the detonator 3 or the collision detectors 4, 5 is the same as the case in FIG. 3, the explanation thereof will be omitted here.

The current value that causes the detonator 3 to ignite the explosive is, for example, 2A/2mS in a short period of time, and the current value that does not cause accidental detonation is a maximum of 20mA/continuously, which is a very small current value.

R4b=R5b=500Ω, resistance value of detonator 3 R3-1Ω
Then, in order to suppress the monitoring current flowing through the detonator 3 to 20 mA or less, the voltage at point f must be 20 V or less.

Therefore, the voltage monitoring circuit 25 is set so that the output g is set to a low level when the point f becomes 20V or higher.

Now, if the power supply voltage rises for some reason and the voltage at point f becomes 20V, the voltage between both ends of detonator 3 is V.
s=2On+V occurs. This voltage Vs is input to the differential amplifier circuit 11, and assuming that its gain G is 100, the output voltage Vd of the differential amplifier circuit 11 is Vd=2V.

In the window comparator 17, when the power supply voltage is 12 V, if the reference voltage at point a is set to 1.8 V and the reference voltage at point b is set to 0.6 V, then the voltage at point f is 20 V.
When the reference voltage increases to V, point a is 3.
0■, point b is 1. OV, and the outputs c and d of the operational amplifiers 18 and 19 both remain at high level.

However, since the voltage monitoring circuit 25 is set so that the output g is set to a low level when the f point becomes 20 V or higher,
The output g becomes a low level, and the output e of the AND gate circuit 23 that receives it also becomes a low level, causing the indicator light 24 to light up.

Therefore, according to the embodiment shown in FIG. 1, not only short-circuit and open failures of the snow gap 3 and collision detectors 4 and 5, but also power supply voltage abnormalities that may cause the airbag device to malfunction (erroneous explosion) are detected. It has a very good effect.

In the above embodiment, by monitoring the voltage at point f, it is monitored whether the monitoring current flowing through the detonating resistor (detonator 3) exceeds a predetermined range. A similar effect can be obtained by monitoring the output voltage Vd of the circuit 11.

In addition, in the air hang device, in order to reduce the capacity of the bank-up capacitor 7, a voltage is created by further boosting the hunter voltage inside the control unit 6, and this voltage is used to ignite the airbag and charge the bank-up capacitor 7. It may be used.

In such an airbag device, it is also possible to detect an abnormality in the booster circuit by monitoring the voltage at point f at +[.

〔Effect of the invention〕

As described above, according to the present invention, a monitoring current is passed through the detonation resistor, and when this monitoring current exceeds an upper limit value, the warning means outputs a warning signal. This has the advantage that the current can be constantly monitored, malfunctions of the air hang device can be prevented, and high reliability can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a failure detection device for an airbag device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the monitoring current flowing through the detonation resistor of the same device, and Fig. 3 is a diagram of a conventional airbag device. FIG. 3 is a circuit diagram of a failure detection device. 1... DC battery, 3... Detonator (resistance for detonation)
, 6...control unit, 11...differential amplifier circuit, 17...
- Window comparator, 11 to 17... Failure detection circuit, 24... Indicator light, 25... Voltage monitoring circuit, 24
~25... Warning means. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A detonation resistor is energized by an automotive DC power supply, and when a predetermined detonation current is exceeded, the gas generator is detonated to deploy the airbag, and a monitoring current is passed through the detonation resistor from the DC power supply to monitor In a failure detection device for an airbag device that is equipped with a failure detection circuit that detects failure of the device according to the value of current, an upper limit value of the monitoring current is determined, and a warning is issued when the monitoring current exceeds the upper limit value. A failure detection device for an airbag device, characterized in that a warning means for outputting a signal is provided.