JP3316142B2 - Airbag device failure determination device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure determination device for an airbag device, and more particularly to an airbag for determining whether or not a switching element is turned on after supplying a signal for turning on the switching element. The present invention relates to a device failure determination device.

[0002]

2. Description of the Related Art Conventionally, an airbag system is designed such that when a vehicle suddenly decelerates, a safing sensor is turned on, an ignition transistor is turned on, and a voltage equal to or higher than a predetermined value is applied to a squib resistance. Has been expanded.

As described above, since the ignition transistor needs to be turned on to deploy the airbag, it is necessary to determine whether or not the ignition transistor is normally turned on.

Therefore, after a base current is supplied to the ignition transistor in a state where a voltage less than a predetermined value is applied to the squib resistance (in this case, a voltage less than the predetermined value is applied to the squib resistance). The failure of the ignition transistor is determined by comparing the potential on the high potential side of the squib resistance with the threshold value to determine whether or not the ignition transistor is turned on.

[0005]

However, if the failure of the ignition transistor is determined in a state where the squib resistor is disconnected, the potential on the high potential side of the squib resistor increases. Does not accurately determine the failure of the ignition transistor.

That is, when determining the failure of the ignition transistor,
If the squib resistance is broken, it is determined that the ignition transistor has failed even if the ignition transistor is normal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to provide a failure determination device for an airbag device capable of accurately determining a failure of a switching element.

[0008]

According to the first aspect of the present invention, there is provided an airbag having a series connection with a resistor for deploying an airbag when a voltage higher than a predetermined value is applied or a current higher than a predetermined value is supplied. A connected switching element, an auxiliary resistor connected in parallel to the switching element, and an application supply unit that applies a voltage less than the predetermined value to the resistor and the auxiliary resistance or supplies a current less than the predetermined value, Disconnection determining means for determining whether or not the resistor is disconnected based on one of a voltage of the resistor, a potential on a high potential side of the resistor, and a current flowing through the resistor; and disconnection by the disconnection determining means. If it is determined that the switching element is not turned on, a supply unit for supplying a signal for turning on the switching element, a voltage of the resistor after the signal is supplied by the supply unit, and the resistor. High potential side potential, and based on any of the current flowing through the resistor, and a, determining means for determining whether or not the switching element is turned on.

That is, the switching element according to the first aspect of the present invention is connected in series to the resistor. When a voltage equal to or higher than a predetermined value is applied to the resistor or a current equal to or higher than the predetermined value is supplied, the airbag is deployed.

An auxiliary resistor is connected in parallel to the switching element. Therefore, the auxiliary resistor is connected in series to the resistor.

The application supply means applies a voltage less than a predetermined value to the resistance and the auxiliary resistance or supplies a current less than the predetermined value. Note that the application and supply unit applies a voltage less than a predetermined value to the resistance and the auxiliary resistance or supplies a current less than the predetermined value, so that the airbag does not deploy.

Here, when the resistor is disconnected, the voltage of the resistor is higher than when the resistor is not disconnected, the potential on the high potential side of the resistor is larger, and the current flowing through the resistor is smaller. Note that the case where the resistor is disconnected includes, for example, a case where the resistor is completely disconnected and a case where a part is connected.

Therefore, after supplying a signal for turning on the switching element without determining whether or not the resistor is disconnected, the voltage of the resistor, the potential on the high potential side of the resistor, and the current flowing through the resistor are determined. Even if it is determined whether or not the switching element is turned on based on any of the above, it cannot be accurately determined.

Therefore, the disconnection determining means determines whether or not the resistor is disconnected based on one of the voltage of the resistor, the potential on the high potential side of the resistor, and the current flowing through the resistor.

When it is determined by the disconnection determining means that there is no disconnection, the supplying means supplies a signal for turning on the switching element, and the determining means supplies a signal after the supply means supplies the signal. It is determined whether or not the switching element is turned on based on any one of the voltage, the potential on the high potential side of the resistor, and the current flowing through the resistor.

If it is determined by the disconnection determining means that a disconnection has occurred, it is not determined whether or not the switching element has been turned on.

As described above, when it is determined that the resistor is not disconnected, after supplying a signal for turning on the switching element, it is determined whether or not the switching element is turned on. When it is determined, it is not determined whether or not the switching element is turned on, so that it is possible to prevent the determination that the switching element has failed even if the switching element has not failed because the resistor is disconnected. An element failure can be accurately determined.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the failure judging device for an airbag device according to the present embodiment has a squib resistance Rsq. When a voltage equal to or higher than a predetermined value is applied to the squib resistance Rsq or a current equal to or higher than the predetermined value is supplied, an airbag (not shown) is deployed.

One end of the squib resistor Rsq has a resistor R ₁
Are connected at one end. One end of the squib resistor Rsq is connected to one end of the safing sensor 14 and is connected to an input port P ₁ of a microcomputer 12.

As described above, since one end (high potential side) of the squib resistor Rsq is connected to the input port P ₁ of the microcomputer 12, the microcomputer 12 determines the potential on the high potential side of the squib resistor Rsq (hereinafter referred to as the monitor voltage). it is possible to incorporate a) V ₁ that.

[0022] One end of the resistor R1 is a voltage V _B is connected to a power supply circuit (not shown) is applied. As a result, a voltage is applied to the squib resistance Rsq, but the voltage applied to the squib resistance Rsq by the power supply circuit is less than the above-described predetermined value, and the current supplied to the squib resistance Rsq is also less than the predetermined value. Airbag does not deploy.

The other end of the safing sensor 14 is connected to the high potential side of the backup capacitor C. The low potential side of the backup capacitor C is grounded. The other end of the safing sensor is connected to the above-mentioned power supply circuit (not shown) via a resistor _RC .

The other end of the squib resistor Rsq has a resistor R2
Is connected, and the other end of the resistor R2 is grounded. Further, the other end of the squib resistor Rsq, collector side of the ignition transistor T _r is connected. The base side of the ignition transistor _Tr is connected to the microcomputer 12,
Emitter side of the ignition transistor T _r is grounded.

Further, one end of the squib resistor Rsq is connected to the input terminal 16i ₁ of the operational amplifier 16, and the other end of the squib resistor Rsq is connected to the input terminal 16i _{2 of the} operational amplifier 16.
It is connected to the. Output terminal 16o of operational amplifier 16
It is connected to the input port P ₂ of the microcomputer 12.
Therefore, the microcomputer 12 may capture the output voltage from the input port P ₂ op 16 (voltage by a predetermined amplification factor times the voltage of the squib resistance).

Next, a failure determination processing routine executed by the microcomputer 12 will be described with reference to FIG. In addition,
Here, the failure determination is to determine whether the ignition transistor has failed by determining whether or not the ignition transistor is turned on after supplying the base current to the ignition transistor.

In step 30 of FIG. 2, the output voltage V ₂ of the operational amplifier 16 is fetched.
_It is determined whether or not ₂ is larger than the threshold value Vth0.

Here, the threshold value Vth0 will be described. The resistance value of the squib resistance Rsq behaves as it increases as the squib resistance changes from a state in which the squib resistance is not disconnected to a state in which the squib resistance is disconnected. Further, as described above, the voltage V
_{When B} is applied to the resistor R ₁ squib resistor Rsq and the resistor R ₂ , as the squib resistor becomes disconnected, the voltage between the squib resistors increases, and the output voltage V ₂ of the operational amplifier 16 becomes, for example, as shown in FIG. As shown, it increases accordingly.

[0029] The resistance value can be determined that the squib resistor Rsq is disconnected Rsq0 (e.g., 10 [Omega]) When the output voltage V ₂ of the operational amplifier 16 at this time is a threshold Vth0. That is, if the output voltage V ₂ of the operational amplifier 16 is greater than the threshold Vth0, can determine the resistance value of the squib resistance greater than Rsq0, thereby it can be determined that the squib resistance is disconnected state.

The output voltage V _{2 of the} operational amplifier is equal to the threshold value Vt.
If it is greater than h0, the squib resistance is in a disconnected state, and this routine ends. That is, no failure determination is made. This is because the squib resistance Rsq is in disconnected state, when the failure determination of the ignition transistor in this state, is larger than the threshold value Vth to monitor voltage V ₁ is below the ignition transistor even normal squib This is because it is determined that a failure has occurred by disconnection of the resistor.

As described above, in the present embodiment, the squib resistance R
resistance of sq is greater than Rsq0, i.e., the output voltage V ₂ of the operational amplifier is greater than the threshold value Vth0 is not determined whether the ignition transistor T _r is faulty (see FIG. 3 reference numeral E1). Therefore, the squib resistance R
Even if the ignition transistor Tr has not failed because the sq is disconnected, it can be determined that the ignition transistor _Tr has failed.

On the other hand, when the resistance value of the squib resistance Rsq is Rs
q0 below, i.e., the output voltage V ₂ of the operational amplifier is the case of the threshold Vth0 below, determines whether the ignition transistor T _r is faulty (see FIG. 3 reference numeral E2). That is, when the output voltage V ₂ of the operational amplifier is the threshold Vth0 below, since the squib resistance Rsq is not disconnected state, at step 34, to turn on the ignition transistor T _r by supplying the base current, in step 36 , The monitor voltage V ₁ is taken in, and it is determined in a step 38 whether the monitor voltage V ₁ is larger than the threshold value Vth.

Here, the threshold value Vth will be described. Monitor voltages V ₁ when the ignition transistor T _r is not defective can be obtained from equation (1).

[0034]

(Equation 1)

Here, since R ₁ ≫Rsq, (1)
The equation can be further transformed into equation (2).

[0036]

(Equation 2)

[0037] (2) As understood from the formula, if the ignition transistor is normal, monitor voltages V ₁ becomes substantially zero.

On the other hand, when the ignition transistor T _r is faulty, the current in resistor R2 flows, monitoring the voltage V ₁₁ is obtained from equation (3).

[0039]

(Equation 3)

[0040] Therefore, a 0 <Vth ≦ V _11, the monitor voltage V ₁ is, by determining whether greater than the threshold value Vth, it is possible to ignite the transistor to determine whether a failure.

If the monitor voltage V ₁ is larger than the threshold value Vth, a flag F is set to 1 at step 40 to indicate that the ignition transistor has failed.
This routine ends. Note that the monitor voltage V ₁ is the case of less than the threshold value Vth, the routine ends.

Here, as shown in FIG. 2, the failure is determined by supplying a base current to the ignition transistor and then determining whether or not the ignition transistor is turned on, thereby determining whether the ignition transistor is defective. When the safing sensor 14 is turned on due to vehicle vibration or the like after supplying the base current to the ignition transistor, a voltage equal to or higher than the above-described predetermined value is applied to the squib resistance Rsq or a current equal to or higher than the predetermined value is supplied. Therefore, in order to prevent this, a switching element (for example, a transistor or an FET) is provided between the safing sensor 14 and the backup capacitor C, thereby disconnecting the safing sensor 14 and the backup capacitor C from each other. To In the case of a rapid deceleration state, the switching element is also turned on. Alternatively, the control routine of FIG.
After the IG switch is turned on, the operation is performed within a few seconds when the vehicle is not running (during the primary check).

[0043] In the embodiment described above, to determine the disconnection of the squib resistor, which compares the output voltage V ₂ and the threshold Vth0 is a constant value (see FIG. 2, step 32), The present invention is not limited to this,
The monitor voltage V ₁ may be taken in, and the output voltage V ₂ may be compared with a threshold th · V ₁ determined by the monitor voltage V ₁ .

That is, R ₂ ≫Rsq, and R ₂ + Rs ≒
R ₂ . Also, the current i flowing through the squib resistance Rsq
Is i = V ₁ / R _2, the voltage Vsq squib resistor Rsq is _{Vsq = (Rsq / R 2)} · V 1.

Therefore, the output voltage V ₂ is obtained from the equation (4), where G is the amplification degree of the operational amplifier.

[0046]

(Equation 4)

Rsq = Rsq0 and G · (Rsq0
/ R ₂ ) = th, the threshold value th · V ₁ is obtained.

As described above, the monitor voltage V ₁ is acquired,
The determination of the disconnection of the squib resistance by comparing the output voltage V ₂ with the threshold value th · V ₁ determined by the monitor voltage V ₁ is based on the variation in the resistance values of the resistors R ₁ and R ₂ and the voltage applied from the power supply circuit. This is because the variation in the applied voltage was considered. That is, since these variations the output voltage V ₂ varies, it may not be possible to determine the disconnection of accurately squib resistor Rsq be compared with a threshold value Vth0 constant value.

On the other hand, if the squib resistance Rsq is not disconnected, for example, even if the monitor voltage V ₁ rises due to the above-mentioned variation, the output voltage V ₂ will remain at the monitor voltage V
Because increases in proportion to ₁ increase, the output voltage V ₂ does not exceed the threshold th · V _1. However, when the squib resistor Rsq is broken, not proportional to the increase in the monitor voltage V _1, the output voltage V _2, in order to increase greater than increase of the monitor voltage V _1, the output voltage V ₂ is the threshold th・
More than V _1.

Therefore, if the monitor voltage V ₁ is taken in and the output voltage V ₂ is compared with the threshold value th · V ₁ to determine the disconnection of the squib resistance Rsq, the voltage applied from the power supply circuit, the resistance R ₁ , even if the resistance value, monitors the voltage V ₁ of the R ₂ are varied can be determined disconnection accurately squib resistor Rsq.

The disconnection of the squib resistance may be determined based on the current flowing through the squib resistance.

Further, in the above-described embodiment, it is determined whether or not the ignition transistor has failed based on the monitor voltage. However, the present invention is not limited to this, and the output voltage or the squib resistance of the operational amplifier is not limited to this. The determination may be based on the flowing current.

In the above-described embodiment, when the above-mentioned determination is made based on the current flowing through the squib resistor, a shunt resistor may be further provided, and the current flowing through the squib resistor may be taken in via the shunt resistor. Good.

In the above-described embodiment, the case where the collector side of the ignition transistor is connected to the squib resistor is described as an example. However, the present invention is not limited to this, and the emitter side of the ignition transistor is connected to the squib resistance. The present invention can be applied to a case where a resistor is connected.

Further, in the above-described embodiment, an ignition transistor has been described as an example of a switching element. However, the present invention is not limited to this, and a switching element that turns on when a signal for turning on is supplied is provided. Any element can be applied.

[0056]

As described above, according to the first aspect of the present invention, it is possible to prevent the switching element from being determined to have failed even if the switching element has not failed because the resistor is disconnected. Since the failure of the airbag device can be accurately determined, the reliability of the failure determination device for the airbag device can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present embodiment.

FIG. 2 is a flowchart illustrating a control routine according to the embodiment.

FIG. 3 is a graph showing an area for determining a failure of an ignition transistor.

[Explanation of symbols]

Rsq squib resistance _Tr ignition transistor R2 resistance 12 microcomputer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-72281 (JP, A) JP-A-7-257314 (JP, A) JP-A-8-113104 (JP, A) JP-A-7- 156743 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60R 21/32

Claims (1)

(57) [Claims] 1. A switching element connected in series to a resistor that deploys an airbag when a voltage equal to or higher than a predetermined value is applied or a current equal to or higher than a predetermined value is supplied, and an auxiliary resistor connected in parallel to the switching element. Applying means for applying a voltage less than the predetermined value to the resistor and the auxiliary resistance or supplying a current less than the predetermined value; a voltage of the resistor, a potential on a high potential side of the resistor, and the resistor Disconnection determining means for determining whether or not the resistor is disconnected, based on any of the currents flowing through the switching element, when the disconnection determining means determines that the disconnection has not occurred, the switching element is turned on. A supply unit that supplies the signal of any one of a voltage of the resistor, a potential on a high potential side of the resistor, and a current flowing through the resistor after the signal is supplied by the supply unit. Based on the failure determination device for an airbag device wherein the switching element is provided with a judging device for judging whether or not turned on, the.