JPH06171456A - Testing device of air bag igniter - Google Patents

Abstract

PURPOSE:To test an igniter for an air bag in a highly accurate manner. CONSTITUTION:At a time when there is such a possibility that wire harness at the side of a line L1 might be short-circuited to the high side of a battery 4 or a power source, electric potential in a connecting point B is detected, detecting a testing current value IL. Likewise when there is such a possibility that another wire harness at the side of a line L2 might be short-circuited to a grounding side of the battery 4, another electric potential in a connecting point A is detected, detecting a testing current value IH. Thus, this testing current value is sought, whereby a value of resistance in a squib 2 is detected from a voltage drop in this squib 2. With this constitution, even to a variation in this testing current value due to a rare short or the like in the wire harness, the resistance value of the squib 2 can highly accurately be detected, so that any abnormality can accurately be grasped in this way.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An air bag device has a flexible bag-like body which is folded and embedded in a steering wheel, an instrument panel or the like in order to protect an occupant from a shock at the time of a collision.
It 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 squib, which is a detonator, igniting explosive.

In the test device for testing the ignition device of such an air bag device, the test current is suppressed to a minute current which never ignites the explosive, for example, about 25 mA.

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

[0005]

Therefore, the squib and the wire harness to the squib are, for example, several hundreds Ω.
When a short circuit is made to the high side or the low side of the power source below, the detection voltage also changes due to a large change in the test current, and the occurrence of the short circuit can be detected.

On the other hand, in the wire harness, in order to prevent non-explosion of the squib, for example, a horn harness, a high side and a low side are twisted together. Therefore, when a slight short circuit, a so-called rare short circuit, occurs, an undetectable error occurs in the test current value. For example, when the test current of 25 mA is supplied and the rare short occurs in the wire harness on the high side of the squib, the current flowing from the horn harness into the squib causes the current flowing through the squib to be about 50 mA. When the wire harness on the lower end side is short-circuited to the vehicle body or the horn harness, the current flowing from the squib causes the current to flow to about 10 mA.
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 device for an airbag ignition device that can perform a test with high accuracy.

[0008]

According to the present invention, there is provided a first switching means which conducts by a predetermined first level impact, a squib, and a second switching which conducts by a second level impact larger than the first level. A gas generating source for inflating the air bag by injecting an ignition current into the squib by electrically connecting the first and second switching means by interposing two switching means in series in this order between both terminals of the power supply. In a test device for an airbag ignition device that ignites, a first switching means is interposed in parallel,
A supply means for supplying a minute test current to the squib from one terminal of a power supply to supply a minute test current and a second switching means are provided in parallel, and the test current is defined by the second resistance. Corresponding to the feedback means for feeding back to the other terminal of the power source and the potential on the supply means side or the feedback means side 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 on the supply means side of the squib and the power supply voltage, or from the potential on the feedback means side of the squib, and a squib abnormality determination is made based on the test current value and the voltage drop due to this test current. A testing device for an ignition device for an airbag, comprising: determining means for performing.

[0009]

According to the present invention, the airbag ignition device is generally constituted by the first switching means, the squib and the second switching means, which are connected in series in this order. The first switching means conducts by a first level shock that is predetermined, and the second switching means conducts by a second level shock that is greater than the first level. The first switching means is
The second switching means is connected to one terminal of the power source and the other terminal of the power source. 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 may inflate the airbag to support the occupant. it can.

The test apparatus for testing the airbag ignition device thus constructed includes a supply means, a return means, and a determination means. The supply means is interposed in parallel with the first switching means and supplies a minute test current defined by the first resistance from one terminal of the power supply to the squib. The test current flows through the squib to the feedback means. The feedback means is interposed in parallel with the second switching means and regulates the test current by the second resistance to feed back to the other terminal of the power supply.

In the test current thus supplied, the test current value is such that the potential of the squib on the supply means side or the feedback means side is higher than the power supply voltage and the potentials defined by the first and second resistors. Depending on whether or not
It is obtained from the potential of the squib on the supply means side and the power supply voltage, or from the potential of the squib on the feedback means side. That is, for example, when the potential of the supply means side of the squib is higher than the prescribed potential, it is determined that the power supply side of the squib is short-circuited, the test current value is obtained from the potential of the feedback means side of the squib, and When the potential is lower than the specified potential, it is determined that the ground side of the squib is short-circuited, and the test current value is obtained from the potential of the supply means side of the squib and the power supply voltage.

Based on the test current value thus obtained and the voltage drop due to this test current, the judging means
Since it determines whether the squib is normal, if the high power supply side of the squib is short-circuited, detection error due to the current flowing into the squib can be prevented, and if the ground side of the squib is short-circuited, the detection error due to the current flowing out from the squib Can be prevented. As a result, it is possible to perform a more precise test of the airbag ignition device, which must operate reliably in the event of a collision and must also prevent malfunctions.

[0013]

FIG. 1 is an electric circuit diagram of an airbag ignition device 1 including a test device 11 according to an 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 to each other, and a test device 11.
It is configured to include and. Between both terminals of the battery 4, a safing sensor switch S1 and a line L1
, Squib 2, line L2, line L3, and front sensor switches S2, S3 are connected in series in this order and interposed.

The front sensor switches S2 and S3
Is provided, for example, in the vicinity of the front grill in the engine room, and is, for example, −10 G (G is gravitational acceleration).
Conducted by the impact of. Further, the safing sensor switch S1 is provided for so-called fail safe, and conducts at -2G, for example. When these switches S1 and S2 or S3 are turned on by the impact at the time of 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. It is realized by 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, a microcomputer, etc., and controls the supply of the test current and And a processing circuit 16 which determines whether or not the squib 2 is normal based on the potential difference.

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

The test current must be suppressed to a minute 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 240 Ω. To be elected. Further, the front sensor switches S2 and S3 are provided in the engine room as described above, whereas the test apparatus 11 is housed in the housing to control the electronic control unit (abbreviated as "ECU"). 20 is provided in the vehicle interior, for example, on the back side of the instrument panel. Therefore, since 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, the safing sensor switches S2 and S3 are connected to each other in parallel for detection. 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 light 17 to notify the driver.

In the test apparatus 11 configured as described above, the resistance value of the squib 2 is such that the processing circuit 16 conducts the transistors Q1 and Q2 to supply the test current to the supply circuit 12-line L1-squib 2-. The voltage is supplied through the line L2-feedback circuit 13 and 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 across the parallel resistors R3 and R4 due to the test current with the transistor Q1 conducting and the transistor Q2 shut off.

In the present invention, the resistance value of the squib 2 measured in this way is such that the wire harness portions of the lines L1 and L2 are short-circuited to the high side line or the ground side line of the power source for the horn in the handle. However, it is required that no detection error occurs. That is, line L
When the part of the wire harness on the first side is short-circuited to the high side of the battery 4, both potentials at the connection points A and B rise. At this time, the potential of the connection point B is detected to detect the test current value IL, and the detection error due to the current flowing into the squib 2 due to the short circuit is prevented. When the wire harness on the line L2 side is short-circuited to the ground side of the battery 4, the potentials at the connection points A and B both drop. At this time, the potential of the connection point A is detected to detect the test current value IH, and the detection error due to the current flowing out of the squib 2 due to the short circuit is prevented.

FIG. 2 is a flow chart showing the 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, and in step n4, the potential VA of the connection point A detected in step n3 is a voltage defined by the power supply voltage Vd and the resistors R1 and R2, that is, Vd × R2 / It is determined whether or not the voltage is higher than the voltage calculated by the equation (R1 + R2). If not, it is determined that the wire harness on the line L2 side may be short-circuited to the ground side, and the process proceeds to step n5.

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

In step n4, if the potential VA of 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 side may be short-circuited to the high side of the power supply. It is judged that there is also a property, and the process moves to step n7. In step n7, the potential VB of the connection point B is detected, and in step n8, the test current value IL at this time is obtained by the formula of VB / R2, then the process proceeds to step n9, and the squib abnormality determination is performed as in step n6. Threshold voltages VSL and VOL are determined.

When the respective threshold values are determined in step n6 and step n9, the potential difference ΔV detected in step n2 is determined by the threshold voltage V in step n10.
It is determined whether or not it is smaller than SH and VSL. If it is smaller than SH and VSL, it is determined that the squib 2 is short-circuited in step n11, the process proceeds to step n15, the warning lamp 17 is turned on, and the operation ends. If not in step n10, that is, the potential difference ΔV is equal to the threshold voltages VSH and V
If it is not smaller than SL, the process proceeds to step n12, and it is determined whether or not the potential difference ΔV is larger than the threshold voltages VOH and VOL. If it is larger, the process proceeds to step n13, it is determined that the squib 2 is disconnected, and the process proceeds to step n15. Then, the warning lamp 17 is turned on and the operation is completed. Step n1
2, otherwise, that is, the potential difference ΔV is greater than or equal to the threshold voltages VOH and VOL, and the threshold voltage V
When it is below SH and VSL, the process proceeds to step n14, where it is determined that the squib 2 is normal, and the operation ends.

As described above, the wire harness on the line L1 side may be short-circuited to the high side of the power source and the wire harness on the line L2 side may be short-circuited to the ground side. Of the test current values IH and IL of the squib 2 are determined to be abnormal, and the threshold voltage V is determined to be abnormal.
SH, VSL and VOH, VOL are switched and set. Therefore, an error in the test current value can be prevented even when the test current value changes due to a rare short circuit of the wire harness, and a short circuit and a 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 current value of the test current flowing from the power supply to the squib and the feedback means via the supply means is determined by the potential of the squib's supply means side or feedback means side. The voltage is determined from the potential on the supply side of the squib and the power supply voltage, or from the potential on the feedback means side of the squib, depending on whether the voltage is higher than the potential defined by the first and second resistors. Based on the test current value thus obtained and the voltage drop due to the test current, the determination means determines whether or not the squib is normal.

Therefore, when the high side of the power source of the squib is rarely short-circuited, the detection error due to the current flowing into the squib can be prevented, and when the ground side of the squib is rarely short-circuited, the detection error due to the current flowing out from the squib is prevented. Can be prevented. By this,
It is possible to perform a more accurate test of the airbag ignition device, which must operate reliably in the event of a collision and must also prevent malfunctions.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 Airbag 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

Claims (1)

[Claims] 1. A first switching means for conducting a shock of a predetermined first level, a squib, and a second switching means for conducting a shock of a second level higher than the first level in this order. An air bag ignition device that is interposed in series between both terminals of a power supply, and an ignition current flows through the squib by conduction of the first and second switching means to ignite a gas generation source for inflating the air bag. In the test apparatus, the first switching means is provided in parallel, and the squib is provided with a small test current defined by a first resistance from one terminal of the power supply, and a parallel supply means with the second switching means. And a feedback means for defining the test current by the second resistor and feeding back to the other terminal of the power supply, and a squib supply means side or Depending on whether the potential on the feedback means side is higher than the power supply voltage and the potential defined by the first and second resistors, from the potential on the supply means side of the squib and the power supply voltage, or the feedback of the squib. A test device for an airbag ignition device, comprising: a test current value from a potential on the means side; and a determination means for determining a squib abnormality based on the test current value and a voltage drop due to the test current. .