JP3080494B2 - Airbag ignition device testing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test device for an ignition device for igniting explosive for inflating an airbag for protecting an occupant from the impact of a vehicle collision.

[0002]

2. Description of the Related Art In order to protect an occupant from an impact in the event of a collision, an airbag device comprises a flexible bag-like body folded and embedded in a handle or an instrument panel.
This is a device that expands with nitrogen gas or the like from a gas generation source. The nitrogen gas is generated by a chemical reaction, and the chemical reaction is initiated by a squib, which is a primer, igniting an explosive.

[0003] In such a test device for testing an ignition device of an airbag device, a test current is suppressed to a very small current that never ignites an explosive, for example, about 25 mA.

Further, the test current is supplied to the squib from a high side of a power supply via a supply means composed of a switching transistor and a current limiting resistor connected in series. The current is fed back to the low side of the power supply through a feedback unit configured by connecting the current limiting resistor and the switching transistor in series. In a typical conventional technique in such a test apparatus, for example, an abnormality is determined by detecting a potential at one end of a squib.

[0005]

Therefore, the squib and the wire harness to the squib are, for example, several hundred ohms.
In the following, when the power supply is short-circuited to the high side or the low side, the detection voltage fluctuates due to a large fluctuation in the test current, and the occurrence of the short-circuit can be detected.

On the other hand, in order to prevent the squib from explosion, the wire harness is, for example, twisted on the high side and the low side with the harness of the horn. Therefore, when a slight short-circuit, that is, a so-called rare short-circuit, occurs, an undetectable error occurs in the test current value. For example, when a test current of 25 mA is supplied and the rare short circuit occurs in the wire harness on the high side of the squib, a current flowing into the squib by the current flowing from the harness of the horn to the squib is about 50 mA. When the wire harness at the lower end is rarely short-circuited to the vehicle body or the harness of the horn, the current flowing through the squib is about 10 mA due to the current flowing from the squib.
Therefore, when such a rare short circuit occurs, an error occurs in the test current value, and the squib resistance value is erroneously detected.

An object of the present invention is to provide a test apparatus for an ignition device for an airbag which can perform a test with high accuracy.

[0008]

According to the present invention, a first switching means, a squib, and a second switching means are interposed in series in this order between both terminals of a power supply, and the first switching means is provided. An ignition current flows through the squib when the second switching means and the second switching means are conducted to ignite a gas generating source for inflating the airbag. Supply means for supplying a test current from one terminal of a power supply via a first resistor to a connection point A between the first resistor and the squib; and the second switching means Feedback means for returning the test current from a connection point B between a second resistor and the squib to the other terminal of the power supply via the second resistor; Connection point A in the supply means side of the
Measuring means for measuring a potential difference between a connection point A on the supply means side and a connection point B on the feedback means side, and a measuring means connected to a connection point B on the feedback means side of the squib; The potential of the connection point A on the side of the squib or the potential of the connection point B on the side of the feedback means of the squib is higher than the power supply voltage and the potential defined by the first and second resistors. A test current value is obtained from the potential of the connection point A on the side of the supply means and the power supply voltage or from the potential of the connection point B on the side of the feedback means of the squib, and the test current value and the voltage drop due to the test current are determined. And a determination means for determining an abnormality of the squib based on the squib.

[0009]

According to the present invention, the ignition device for an airbag generally includes a first switching means, a squib, and a second switching means, which are connected in series in this order. The first switching means is turned on by a predetermined first level of impact, and the second switching means is turned on by a second level of impact greater than the first level. Further, the first switching means includes:
The second switching means is connected to one terminal of the power supply, and the second switching means is connected to the other terminal of the power supply. Therefore, when the first and second switching means are turned on, an ignition current flows through the squib to ignite the gas generation source, and the gas generated from the gas generation source inflates the airbag to support the occupant. it can.

[0010] A test device for testing the ignition device of the airbag thus configured includes a supply unit, a return unit, and a determination unit. The supply means is interposed in parallel with the first switching means and supplies a small test current defined by a first resistor to the squib from one terminal of a power supply. The test current flows through the squib to the feedback means. The feedback means is interposed in parallel with the second switching means, and returns the test current to the other terminal of the power supply by defining the test current with a second resistor.

In the test current supplied in this manner, the test current value is determined by measuring the potential of the connection point A on the supply means side or the connection point B on the feedback means side of the squib measured by the measurement means by the power supply voltage and the power supply voltage. Depending on whether the potential is higher than the potential defined by the first and second resistors, the potential at the connection point A on the supply means side of the squib and the power supply voltage or the connection point on the feedback means side of the squib And B potential. That is, for example, when the potential of the connection point A on the squib supply means side is higher than the specified potential, it is determined that the power supply side of the squib is short-circuited, and the potential of the connection point B on the feedback means side of the squib is determined. The test current value is obtained from the following formula. If the potential is lower than the specified potential, it is determined that the ground side of the squib is short-circuited. Ask for.

Based on the test current value obtained in this way and the voltage drop due to this test current, the determination means
Since it is determined whether the squib is normal or not, when the high power supply side of the squib is short-circuited, it is possible to prevent the detection error due to the current flowing into the squib. Can be prevented. As a result, it is possible to more accurately test the ignition device of the airbag, which must operate reliably in the event of a collision and must reliably prevent malfunction.

[0013]

FIG. 1 is an electric circuit diagram of an airbag ignition device 1 having a test device 11 according to one embodiment of the present invention. The ignition device 1 generally includes a safing sensor switch S1, a squib 2, a plurality of front sensor switches S2 and S3 connected in parallel with each other,
It is comprised including. Between both terminals of the battery 4, a safing sensor switch S1 and a line L1
, The squib 2, the line L2, the line L3, and the front sensor switches S2 and S3 are connected in series in this order and interposed.

The front sensor switches S2 and S3
Is provided, for example, near the front grill in the engine room, and is, for example, -10G (G is gravitational acceleration).
Conducted by the impact of. Further, the safing sensor switch S1 is provided for fail-safe operation, and conducts at -2G, for example. When these switches S1, S2 or S3 are turned on by the impact at the time of the collision, an ignition current flows through the squib 2 and the gas generation source is ignited.

The test apparatus 11 includes a supply circuit 12 for supplying a test current from the battery 4 to the squib 2, a feedback circuit 13 for returning the test current from the squib 2 to the battery 4, and a test circuit for the squib 2 by the test current. An operational amplifier 14 for measuring a potential difference generated between terminals, an analog / digital converter 15 for converting an output of the operational amplifier 14 into a digital value, and a microcomputer are provided to control the supply of the test current, And a processing circuit 16 for determining whether or not the squib 2 is normal based on the potential difference. The operational amplifier 14
And the analog / digital converter 15 constitute a measuring means for measuring a potential difference between the connection points A and B.

The supply circuit 12 includes a transistor Q1 and a test current limiting resistor R1 connected in series with each other, and is provided between a high-side terminal, which is one terminal of the battery 4, and a line L1. It is connected in parallel with the safing sensor switch S1. The feedback circuit 13 includes a test current limiting resistor R2 and a transistor Q2 connected in series with each other, and is connected between the line L2 and a ground terminal, which is the other terminal of the battery 4, that is, a front sensor. The switches are connected in parallel with the switches S2 and S3.

The test current needs to be suppressed to a very small current that never ignites the explosive, for example, about 25 mA. Therefore, when the voltage of the battery 4 is set to 12 V, the resistances R1 and R2 are set to about 240Ω. To be elected. The front sensor switches S2 and S3 are provided in the engine room as described above, whereas the electronic control unit (abbreviated as "ECU") is configured by housing the test apparatus 11 in a housing. Reference numeral 20 is provided in the interior of the vehicle, for example, behind the instrument panel. Therefore, the wire harness of the line L3 becomes relatively long, and it is necessary to detect the disconnection of the line L3 as described later. Resistance R
3, R4 are interposed. When the test result of the squib 2 and the test result of the line L3 are abnormal, the processing circuit 16 turns on the warning lamp 17 to notify the driver.

In the test apparatus 11 configured as described above, the resistance value of the squib 2 is determined by the processing circuit 16 conducting the transistors Q1 and Q2 to supply the test current to the supply circuit 12-line L1-squib 2- The test current is supplied through the line L2-feedback circuit 13, and is measured based on the potential difference between the lines L1 and L2 caused by the test current. Also,
The disconnection of the line L3 is detected based on the voltage drop of the parallel resistors R3 and R4 due to the test current in a state where the transistor Q1 is turned on and the transistor Q2 is turned off.

In the present invention, the resistance value of the squib 2 measured in this manner is such that the wire harness portions of the lines L1 and L2 are short-circuited to the high-side power supply line or the ground-side line for horn in the steering wheel. Even so, it is required so as not to cause a detection error. That is, the line L
When the portion of the wire harness on the first side is short-circuited to the high side of the battery 4, both the potentials at the connection points A and B rise. At this time, the test current value IL is detected by detecting the potential of the connection point B, and a detection error due to the current flowing into the squib 2 due to the short circuit is prevented. Further, when the wire harness on the line L2 side is short-circuited to the ground side of the battery 4, both the potentials at the connection points A and B drop. At this time, the test current value IH is detected by detecting the potential of the connection point A, and a detection error due to the current flowing out of the squib 2 due to the short circuit is prevented.

FIG. 2 is a flowchart showing an operation for detecting the resistance value of the squib 2 described above. In step n1, the power supply voltage Vd is detected, and in step n2, the potential difference ΔV between the lines L1 and L2 caused by the test current is detected. In step n3, the potential VA of the connection point A is detected. In step n4, the potential VA of the connection point A detected in step n3 is determined by the power supply voltage Vd and the voltage defined by the resistors R1 and R2, that is, Vd × R2 / It is determined whether the voltage is higher than the voltage obtained by the equation (R1 + R2). If not, it is determined that there is a possibility that the wire harness on the line L2 may be short-circuited to the ground, and the process proceeds to step n5.

In step n5, the test current value IH at this time is obtained by the formula of (Vd-VA) / R1, and the process proceeds to step n6, where the threshold voltage V for squib abnormality determination is determined.
SH and VOH are determined. That is, when the current value is IH
, The threshold voltage V at which it is determined that the squib 2 is short-circuited
SH is obtained by IH × S where S is the resistance value due to the short circuit, and the threshold voltage VOH determined to be disconnected is obtained by IH × P where P is the resistance value by the disconnection.

In step n4, when the potential VA at the connection point A is higher than the power supply voltage Vd and the voltage defined by the resistors R1 and R2, the wire harness on the line L1 may be short-circuited to the high side of the power supply. It is determined that there is a possibility, and the process proceeds to step n7. In step n7, the potential VB of the connection point B is detected. In step n8, the test current value IL at this time is obtained by the equation of VB / R2, and the process proceeds to step n9, where the squib abnormality is determined in the same manner as in step n6. , The threshold voltages VSL and VOL are determined.

In step n6 and step n9, when the respective thresholds are determined, in step n10, the potential difference ΔV detected in step n2 is compared with the threshold voltage V
It is determined whether it is smaller than SH and VSL. If it is smaller, the process proceeds to step n11, where it is determined that the squib 2 is short-circuited. The process proceeds to step n15 to turn on the warning lamp 17, and the operation ends. If not in step n10, that is, if the potential difference ΔV is equal to the threshold voltages VSH and VSH
If not less than SL, the process proceeds to step n12, where it is determined whether or not the potential difference ΔV is greater than the threshold voltages VOH and VOL. If so, the process proceeds to step n13, where it is determined that the squib 2 is disconnected and the process proceeds to step n15. Then, the warning light 17 is turned on and the operation is completed. Step n1
2, the potential difference ΔV is equal to or higher than the threshold voltages VOH and VOL, and
If the difference is less than SH or VSL, the process proceeds to step n14, where the squib 2 is determined to be normal, and the operation ends.

As described above, when there is a possibility that the wire harness on the line L1 is short-circuited to the high side of the power supply and when the wire harness on the line L2 is short-circuited to the ground, it is determined. Of the test current values IH and IL of the squib 2, and the threshold voltage V at which the squib 2 is determined to be abnormal
SH and VSL and VOH and VOL are switched and set. Therefore, an error in the test current value can be prevented even for a change in the test current value due to a rare short circuit of the wire harness, and a short circuit and disconnection between the lines L1 and L2 of the squib 2 can be accurately determined.

[0025]

As described above, according to the present invention, the judging means compares the value of the test current flowing from the power supply through the supply means to the squib and the feedback means with the connection point A on the supply means side of the squib. Alternatively, depending on whether the potential of the connection point B on the feedback means side is higher than the power supply voltage and the potential defined by the first and second resistors, the potential on the supply side of the squib and the power supply voltage are Alternatively, it is determined from the potential on the feedback means side of the squib. Based on the test current value thus obtained and the voltage drop due to the test current, the determination means determines whether the squib is normal.

Therefore, when the high side of the power supply of the squib is rarely short-circuited, the detection error due to the current flowing into the squib can be prevented. When the ground side of the squib is rarely short-circuited, the detection error due to the current flowing out of the squib can be prevented. Can be prevented. This allows
It is possible to more precisely test the ignition device of the airbag, which must operate reliably in the event of a collision and must reliably prevent malfunction.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an airbag ignition device 1 including a test device 11 according to one embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation for detecting a resistance value of a squib 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air bag ignition device 2 Squib 4 Battery 11 Test device 14 Operational amplifier 16 Processing circuit A, B Connection point R1, R2 Resistance Q1, Q2 Transistor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-287749 (JP, A) JP-A-2-14946 (JP, A) JP-A-4-791142 (JP, A) JP-A-4- 100755 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60R 21/32 G01M 13/00 G01M 17/007

Claims (1)

(57) [Claims] A first switching means, a squib, and a second switching means are interposed in series in this order between both terminals of a power supply, and the first switching means, the second switching means, In the test apparatus for an airbag igniter for igniting a gas generation source for inflating the airbag by causing an ignition current to flow through the squib when the squib conducts, the squib is interposed in parallel with the first switching means, Supply means for supplying a test current from one terminal via a first resistance to a connection point A between the first resistance and the squib; and a test means interposed in parallel with the second switching means, Feedback means for returning a current from a connection point B between a second resistor and the squib to the other terminal of the power supply via the second resistor; and Connection point A and a connection point B on the return means side of the squib, and a connection point A on the supply means side and a connection point B on the return means side
Measuring means for measuring a potential difference between the squib and the potential at the connection point A on the supply means side or the potential at the connection point B on the feedback means side of the squib by a power supply voltage and first and second resistors. The test current is calculated from the potential of the connection point A on the supply means side of the squib and the power supply voltage, or from the potential of the connection point B on the feedback means side of the squib, depending on whether the potential is higher than a prescribed potential. A determination means for determining a value of the squib based on the test current value and a voltage drop caused by the test current.