JP3346709B2 - Control device for airbag 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 control device for an airbag device, and more particularly to a control device for an airbag device that determines whether a squib resistance for deploying an airbag is disconnected.

[0002]

2. Description of the Related Art Conventionally, an airbag system has been provided with a filament (hereinafter referred to as a squib resistance) for deploying an airbag in an ignition device (hereinafter referred to as a squib). When a predetermined current is supplied in a normal state, the airbag is deployed. However, if the connection line of the squib resistor is, for example, short-circuited or disconnected, a current having a value different from the normal state is supplied to the squib resistor. Therefore, as a self-diagnosis and failure detection function, a control device for an airbag device having a function of flowing a monitor current (a current at which the airbag does not deploy) to the squib resistance and detecting a disconnection and a short circuit of the squib resistance of the ignition device is provided. Proposed.

[0003] Such a control device for an airbag device detects a voltage applied to a squib resistance in a squib, amplifies the voltage to a preset amplification degree and outputs the amplified voltage, and an output voltage from the operational amplifier. CPU to which is input
And In the CPU, the output voltage of the operational amplifier according to the voltage applied to the squib resistor is not a threshold value and an output of the operational amplifier that are set in advance for disconnection determination,
The disconnection of the squib resistance is determined by comparing with a threshold value for the voltage of the squib upstream or downstream. That is, the control device for the airbag device determines that the squib resistance is normally connected if the output voltage is equal to or less than the threshold value for determining disconnection and equal to or greater than the threshold value for determining short circuit. are doing.

[0004]

However, since the connection line of the squib resistance is provided on the substrate together with the ground wire, dust may be interposed between the ground wire and the connection line of the squib resistance, or the ground wire and the squib resistance may be connected. When the contact state between the resistance connection line and the squib resistance connection line is continued due to vibration or the like, a short-circuit failure (hereinafter, referred to as ground (GND) short) with the ground line may occur in the squib resistance connection line. G
When an ND short-circuit occurs, the magnitude of the current flowing through the squib resistance changes, thereby changing the voltage of the squib resistance. When the voltage between both ends of the squib resistor changes in this way, the output voltage of the operational amplifier may change and exceed the threshold set for disconnection determination. In this case, there is a problem that a disconnection is determined due to a GND short even though both ends of the squib resistor are in a normal state.

On the other hand, if a voltage exceeding the common-mode input voltage range is input to the operational amplifier, the output may be difficult to predict. That is, unless the voltage is within the common-mode input voltage range that is a certain range with respect to the power supply voltage, normal operation of the operational amplifier may not be expected.

The present invention has been made in consideration of the above-described facts, and has as its object to provide a control device for an airbag device capable of accurately determining whether or not a disconnection of a squib resistance has occurred.

[0007]

The invention according to claim 1 is a control device for an airbag device for detecting a disconnection of a squib resistance for controlling the operation of an ignition device for an airbag, wherein the ignition device comprises: At least one auxiliary resistance connected in series to the squib resistance provided in the device; application means for applying a predetermined voltage to both ends of a combined resistance value of the squib resistance and the auxiliary resistance; an operational amplifier voltage across is input, a short-circuit determination means for connecting line between the auxiliary resistor and the squib resistor based on the voltage applied to the squib resistance to determine whether or not the ground short, the Short-circuit judgment means
If it is determined that there is no land short,
Based on the voltage applied to the quib resistor and the auxiliary resistor
First to set the threshold for non-ground shorts
The ground setting is performed by the threshold value setting means and the short-circuit determination means.
If it is determined that the
Select and set the ground short threshold
Second threshold setting means and the first threshold setting means
Or disconnection determining means for determining whether or not the squib resistor is disconnected from a threshold value set by a second threshold value setting means and an output voltage from the operational amplifier. And

According to the present invention, it is determined whether or not the connection line between the squib resistance for deploying the airbag and the auxiliary resistance is short-circuited to GND, and when it is determined that the short-circuit is not detected, both ends of the squib resistance are determined. The voltage between the amplifiers is amplified by an operational amplifier and compared with the output voltage and the threshold value set for disconnection determination, and when the amplified and output voltage exceeds the threshold value, the squib resistance is reduced. It is determined that a disconnection has occurred.

Here, at least one auxiliary resistance is connected to the squib resistance, and when a GND short occurs, the voltage of the connected auxiliary resistance decreases. As a result,
The voltage applied to the squib resistance has a value different from the voltage when the squib resistance is normally connected without a GND short. Therefore, the output voltage from the operational amplifier when the disconnection is determined is different between the case where the GND is short-circuited and the case where the GND is not short-circuited. Therefore, the disconnection determination means determines that the normal connection state where the GND is not short-circuited and the GND connection.
The case where the squib is short-circuited is clearly distinguished from the squib resistance, and the presence or absence of disconnection of the squib resistance is determined using a threshold value according to the result of the judgment. At this time, the case where the GND is short-circuited and the case where it is not short-circuited are clearly distinguished, and the threshold value corresponding to each case is set. The threshold value used for determining the disconnection for the output voltage of the squib resistor and the auxiliary resistor is not used for determining the presence or absence of the disconnection based on the output voltage from the operational amplifier when the connection line between the squib resistor and the auxiliary resistor is short-circuited to GND.

[0010]

[0011]

[0012]

According to the present invention, the threshold used when the GND is not short-circuited is set based on the voltage applied to the squib resistor and the auxiliary resistor, and the threshold used when the GND is short-circuited Is selected from preset threshold values. As described above, when a GND short occurs, the output voltage from the operational amplifier differs, so that an appropriate threshold can be set by changing the equation for setting the threshold.

If no GND short occurs, the threshold value for the non-GND short is set based on the voltages applied to the squib resistance and the auxiliary resistance.
The presence / absence of disconnection can be determined with higher accuracy based on the voltages actually applied to the squib resistance and the auxiliary resistance. Further, when a GND short-circuit occurs, a preset threshold value for the GND short-circuit is selected and set, so that the presence / absence of disconnection of the squib resistance can be reliably determined. Thus, even if the connection line between the squib resistance and the auxiliary resistance is short-circuited to GND and the output voltage from the operational amplifier changes, whether or not the squib resistance has been disconnected based on the threshold value when the short-circuit occurs. Can be determined. As a result, the disconnection of the squib resistance can be determined by an appropriate threshold value regardless of whether or not the GND is short-circuited.

As described above, the short-circuit judging means allows the
Presence / absence of a ground short in the connection line between the resistor and the auxiliary resistor
Judge. In other words, if there is a ground short,
The voltage of the operational amplifier to which the voltage between both ends of the squib resistor is input
If the output is ground shorted, the operational amplifier output
Is judged to be larger than the non-ground short
can do. On the other hand, it is determined to be a ground short
A phenomenon similar to that at the time is disconnection. That is,
If the squib resistance is broken, the
The pressure increases, and the output of the operational amplifier increases. others
In case of non-ground short, set the first threshold
Set the threshold value by means, and when there is a non-ground short
Sets the threshold value by the first threshold value setting means,
If it is determined that a short circuit has occurred, the second threshold value is set.
For the ground short preset by the
Set the threshold. This allows a ground short
And determination of disconnection can be distinguished.

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

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

As shown in FIG. 1, a control device 10 for an airbag device according to an embodiment of the present invention includes a squib resistance Rs. The control device 10 deploys the airbag when a current of a predetermined value or more is applied to the squib resistance Rs. One end of the squib resistor Rs is connected to one end of a resistor R1 via a diode 22, and the other end of the resistor R1 is connected to a power supply circuit 23 as application means .
Incidentally, at all times the voltage V _B is applied from the power supply circuit 23.

One end of the squib resistor Rs is connected to the CPU 1
2, and a high-potential-side voltage Vs of the squib resistor Rs is input to the CPU 12.

Further, a backup capacitor 1 is connected to one end of the squib resistance Rs via a safing sensor 18.
6 is connected to the high potential side, and the low potential side of the backup capacitor 16 is grounded. Squib resistance Rs
Is connected to one end of a dummy resistor Rd between itself and the resistor R1, and the other end of the dummy resistor Rd is grounded.

The other end of the squib resistor Rs is connected to one end of the resistor R2, and the other end of the resistor R2 is grounded.

The other end of the squib resistor Rs is connected to the collector side of the drive transistor 20, and the base side of the drive transistor 20 is connected to the CPU 12.
The emitter side is grounded.

Further, one end of the squib resistor Rs is connected to one input terminal 14b of the operational amplifier 14, and the other end of the squib resistor Rs is connected to the other input terminal 14c of the operational amplifier 14.
It is connected to the. The output terminal 14a of the operational amplifier 14 is connected to the CPU 12, to which the output voltage Ds applied between the squib resistors Rs and amplified by the operational amplifier 14 is input.

Next, a disconnection detection routine of the control device 10 for the airbag device will be described with reference to FIG.

[0029] At step 30, captured the voltage Vs of the high potential side of the squib resistor Rs, the voltage Vs is whether or voltage .beta.v _B is determined in step 32. As shown in FIG. 3A, a resistor R1 and a resistor R2 are connected to the squib resistor Rs. The squib resistance Rs and the resistance R2 and the dummy resistance Rd are connected in parallel. At this time, the voltage vs ₁ on the high potential side of the squib resistor Rs in a normal connection state is represented by the formula (1).

[0030]

(Equation 1)

On the other hand, for example, as shown in FIG.
As shown in the figure, the GND
When the short circuit occurs, the voltage applied to the squib resistance Rs
vs _TwoIs represented by equation (2).

[0032]

(Equation 2)

The combined resistance from the input terminal side of Vs to the downstream side is:
Since the time of GND short is smaller (β> γ), vs1
And the relationship between vs2 is as shown in equation (3). vs1> vs2 ··· (3) Therefore, by comparing the voltage Vs inputted to the voltage βVs applied to squib resistance Rs in the normal connection condition, whether the voltage Vs input voltage .beta.v _B above GND
It is possible to determine whether or not a short has occurred. Therefore, when the voltage Vs is equal to or higher than the voltage βV _B , it can be determined that the GND is not short-circuited, and the process proceeds to Step 34.

[0034] At step 34, the voltage Vs applied to the squib resistance Rs of the normal connection state, whether small or not than the maximum value V _MAX of common-mode input voltage range.

The operational amplifier 14 amplifies the input voltage with an amplification factor G and outputs the amplified voltage. However, if a voltage outside the common-mode input voltage range is input, the output voltage value becomes unstable and malfunctions easily occur. As a result, an erroneous determination may occur.

[0036] Thus, the disconnection voltage Vs applied to the squib resistance Rs when exceeds the maximum value V _MAX of the common mode input voltage range, because it is not output based on the operation of the output of the operational amplifier 14 is expected, to be described later It is determined that the determination process cannot be executed accurately, and this routine ends.

On the other hand, the voltage applied to the squib resistance Rs
Vs is the maximum value V of the common mode input voltage range. _MAXIf
, The determination is affirmative and the routine proceeds to step 36.

In step 36, the output voltage Ds amplified by the operational amplifier 14 connected to both ends of the squib resistor Rs is fetched.

Since the squib resistance Rs is sufficiently smaller than the resistance R2 (R2 >> Rs), the current I flowing through the squib resistance Rs is approximated by the value of the voltage Vs and the resistance R2 (Equation (4)). )reference). Therefore, the output voltage ds in the normal connection state is represented by Expression (5).

[0040]

(Equation 3)

When the disconnection of the squib resistance Rs occurs, the squib resistance Rs behaves as if the value of the squib resistance Rs has increased, and the potential difference between the squib resistances Rs increases.
4, the output voltage Ds increases. Therefore, the normal ds
Is set as the threshold value αVs, and by comparing the threshold value αVs with the output voltage Ds, it is possible to determine whether or not the squib resistance Rs is disconnected.

Therefore, at step 38, the threshold value αVs is compared with the taken-in output voltage Ds. If the output voltage Ds is equal to or higher than the threshold value αVs, the judgment is affirmative and the routine proceeds to step 40. The squib disconnection flag F is set (F = 1), and the process ends. When the flag F is set, a warning lamp (not shown) connected to the CPU 12 is turned on to warn that the squib resistance Rs is disconnected.

If the output voltage Ds is smaller than the threshold value αVs, it can be determined that no disconnection of the squib resistance Rs has occurred, and the routine ends.

On the other hand, in step 32, when a GND short occurs and the voltage Vs applied to the squib resistance Rs becomes smaller than the voltage βV _B and the judgment is denied, in step 42, the GND is shorted. The output voltage Ds amplified by the operational amplifier 14 connected to both ends of the squib resistor Rs in the case is taken in.

For example, as shown in FIG.
In the case of D short-circuit, the output voltage ds ₂ amplified by the operational amplifier 14 has a different value higher than the output voltage ds _{1 in the} case of no GND short (see FIG. 4A). For this reason, the threshold value αVs used when the GND short circuit is not performed in order to detect the disconnection of the squib resistance Rs is not applied.

Therefore, from the relational expression between the value of the squib resistance Rs when the GND is short-circuited at 0Ω (worst condition) and the corresponding output voltage ds ₂ , the squib resistance Rs
Voltage ds when the value of the squib resistor Rs is Rx when the connection line between the resistor and the resistor R2 is short-circuited to GND.
Calculate the value of ₂ and set this as the threshold value TH.
This makes it possible to determine whether or not the squib resistance Rs is disconnected even in the state where the GND is short-circuited.

Accordingly, in step 44, the output voltage Ds is compared with the threshold value TH. If it is determined that the output voltage Ds is equal to or higher than the threshold value TH, the result is affirmative and the routine proceeds to step 46. In step 46, the squib resistance R
It is determined that the s disconnection has occurred, the squib disconnection flag F is set (F = 1), and the routine ends. When the squib disconnection flag F is set, a warning lamp (not shown) connected to the CPU 12 is turned on to warn that the disconnection of the squib resistance Rs has occurred.

On the other hand, if the output voltage Ds is lower than the threshold value TH, the determination is denied, and it is determined that the squib resistance Rs is not disconnected but the squib resistance Rs is disconnected, and the process ends.

Therefore, the disconnection of the squib resistance Rs is
Since it is determined depending on whether or not and if the maximum value V _MAX less whether the common-mode input voltage range is D shorted, GND
Even if a short circuit occurs, there is no misjudgment,
The disconnection of the squib resistance Rs can be reliably determined.

In particular, it is determined whether or not the GND is short-circuited based on the voltage Vs on the high potential side of the squib resistance Rs, and the processing is changed in accordance with the determination result. Can be determined.

The voltage applied between the squib resistors Rs is the maximum value V _MAX of the common mode input voltage range of the operational amplifier 14.
Is exceeded, execution of the determination process of the disconnection of the squib resistor Rs is prohibited, so that an uncertain determination based on the output of the operational amplifier, which is difficult to predict, can be eliminated, and erroneous determination of the disconnection of the squib resistor can be prevented. it can.

In this embodiment, the dummy resistor Rd is connected in parallel with the squib resistor Rs. Thereby, when a complete disconnection of the squib resistance Rs occurs, the operational amplifier 1
4 can be protected, it can also be to avoid that the voltage Vs applied to the squib resistor Rs is equal to or greater than the maximum value V _MAX of the common mode input voltage for detecting the complete disconnection state. The dummy resistance Rd is effectively used when the squib resistance Rs is single as in the case where the airbag is provided only on the driver's seat side. However, the squib resistance is used when the airbag is provided in the driver's seat and the passenger's seat. In the case of a so-called multi-channel squib in which the resistors Rs are connected in parallel, the dummy resistor Rd need not be provided.

[0053] Further, when the stop determination process of the presence or absence of disconnection of the squib resistor Rs by the input voltage exceeds the maximum value V _MAX of common mode input range, it is notified that the process has been aborted Good. For example, by turning on a predetermined warning lamp when the stop of the process is repeated a plurality of times, it is possible to notify that the presence or absence of disconnection of the squib resistance Rs is not detected.

[0054]

As described above, according to the present invention, it is determined whether or not the connection line between the squib resistance and the auxiliary resistance is short-circuited to GND. Therefore, the squib resistance is determined by the threshold value according to the determination result. It is determined whether or not the wire is disconnected.
An erroneous determination due to an ND short circuit can be prevented. In particular, when the GND short-circuit occurs and when the GND short-circuit does not occur, the corresponding thresholds are set by different methods, so that the disconnection of the squib resistance is surely generated regardless of whether the GND short-circuit occurs. Can be determined. Therefore, it is possible to appropriately determine whether or not the disconnection has occurred irrespective of the connection state of the squib resistance, and it is possible to increase the reliability of the determination.

[0055]

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a control device for an airbag device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of a squib disconnection detection process according to the embodiment of the present invention.

FIG. 3A is a partial circuit diagram of a control device for an airbag device during a non-GND short, and FIG. 3B is a partial circuit diagram of a control device for the airbag device during a GND short.

FIG. 4A is a partial circuit diagram of a control device for an airbag device during a non-GND short circuit, and FIG. 4B is a partial circuit diagram of a control device for an airbag device during a GND short circuit.

[Explanation of symbols]

 Reference Signs List 10 control device for airbag device 12 CPU 14 operational amplifier R1 resistor R2 resistor Rs squib resistor Rd dummy resistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60R 21/32

Claims (1)

(57) [Claims] 1. A control device for an airbag device for detecting disconnection of a squib resistor for controlling the operation of an ignition device of an airbag, the control device being connected in series to a squib resistor provided in the ignition device. At least one auxiliary resistance, and a combined resistance value of the squib resistance and the auxiliary resistance
And applying means for applying a predetermined voltage across the op amp voltage across the squib resistor is input, connecting lines of the squib the squib resistor based on the voltage applied to the resistor and the auxiliary resistor Short-circuit determining means for determining whether or not ground short-circuiting has occurred; and
If determined, the squib resistance and the auxiliary resistance
Non-ground short based on the voltage applied to
The first threshold value setting means for setting a threshold value and the short-circuit determination means determine that a ground short-circuit has occurred.
If the power is turned off, a preset ground short
Threshold setting method for selecting and setting a threshold value for
A step and the first threshold setting means or the second threshold setting means;
Disconnection determination means for determining whether or not the squib resistance is disconnected, based on a threshold value set in a stage and an output voltage from the operational amplifier, and a control for the airbag device. apparatus.