JPH10147205A - Air bag controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such an air bag controller as facilitates the inspection work. SOLUTION: In an air bag controller, a diode 2 is connected between a squib 1 and a drive circuit 42 and in such a manner that the direction from a squib 1 toward a drive circuit 42 becomes the forward direction, while a first bias circuit 44, which impresses the bias voltage to the squib side of the diode 2, and a second bias circuit 45, which impresses the bias voltage to the drive circuit side of the diode 2, are provided. In addition, a microcomputer 12 diagnoses the short circuit as the one occurred either on the squib side or not on the squib side, based on voltage information consisting of the diode terminal voltage B on the first bias circuit side, the diode terminal voltage A on the second bias circuit side, and a drop in the diode voltage Vd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airbag control device, and more particularly to a failure diagnosis of the airbag control device.

[0002]

2. Description of the Related Art A prior art airbag control device is disclosed in Japanese Patent Application Laid-Open No. 52-33233. According to the disclosed technology, a bag body, an igniting agent for opening a bag, and an igniting agent are disclosed. An airbag device including a squib to be ignited is disposed on a handle, and a control circuit including a drive circuit for driving the squib is connected to the squib via a harness. This control circuit
The airbag device is installed at a vehicle body other than the handle where the airbag device is installed.

[0003]

However, the above prior art does not disclose whether a squib (also called an ignition device) is short-circuited to ground or a drive circuit is short-circuited to ground. It is unclear whether the short is inside the control circuit, the wiring arranged in the vehicle, or the squib circuit on the bag side, and there remains a problem that a long time is spent in inspection and determination of the airbag. For this reason, it is strongly desired to judge where the short-circuit is due to its serviceability.

Accordingly, it is an object of the present invention to provide an airbag control device which makes it possible to diagnose whether a short circuit is a squib or a drive circuit, and facilitates an inspection work.

[0005]

An object of the present invention is to provide an airbag control apparatus including a squib for deploying an airbag, a drive circuit for driving the squib, and a microcomputer for operating the drive circuit. A first bias circuit that connects a diode between the drive circuit and the squib so that the direction from the squib to the drive circuit is forward, and further applies a bias voltage to the squib side of the diode; And a second bias circuit for applying a bias voltage to
The microcomputer compares the diode terminal voltage on the first bias circuit side with the diode terminal voltage on the second bias circuit side and the diode drop voltage, and determines any one of the short circuit on the squib side and the short circuit on the other side than the squib circuit. Achieved by diagnosing.

According to the present invention, since the magnitude relationship between the diode terminal voltage and the diode drop voltage indicates a short-circuit point, diagnosis can be made.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an airbag control device according to one embodiment of the present invention. FIG.
In the configuration, the airbag control device includes a control circuit 40 disposed in a vehicle body (vehicle compartment), an airbag device 50 disposed in a steering wheel, a power supply circuit 60, and a harness 70 connected thereto. Is done. The power supply circuit 6
0 may be separate and independent from the airbag control device. The control circuit 40 includes the microcomputer 12 and
The drive circuit includes a drive circuit, a first bias circuit, a second bias circuit 45, and the diode 2.
The airbag device 50 includes a bag (not shown), an igniter (not shown) for opening the bag, and a squib 1 for igniting the igniter.

The principle of diagnosing whether the squib side short or the squib side short according to the present invention is as follows. A diode 2 connected in a forward direction from the squib to the drive circuit is inserted between the squib 1 and the drive circuit 42, and a first bias circuit 44 and a second bias circuit 45 are provided at both ends of the diode 2, respectively. Apply voltage.

The relationship between the voltage B as the diode terminal voltage on the first bias circuit side and the voltage A as the diode terminal voltage on the second bias circuit side (voltage state of each bias circuit block) is shown in Table 1 below. It becomes like the contents shown in.

[0010]

[Table 1]

Here, the voltage Vd represents a forward drop of a diode (a forward diode drop voltage). “Low” is when the voltage A or the voltage B as the diode terminal voltage is a value smaller than the voltage Vd, and “High” is when the voltage is equal to or more than the voltage Vd.
For example, it is a signal determined and set by the microcomputer 12.

In Table 1, when the state of the squib with respect to the ground is open and the state of the drive circuit with respect to the ground is also open, that is, when the state is normal, both the voltage A and the voltage B become High. When the state of the drive circuit with respect to one ground is short, the voltage A becomes low, the voltage B becomes equal to the voltage Vd, and it can be diagnosed that the drive circuit is ground short. When the state of the squib with respect to one of the grounds is short, the voltage A is high.
h, the voltage B becomes Low, and it can be diagnosed that the squib is ground short. When both the voltage A and the voltage B are low, it can be diagnosed that both are short-circuited.

That is, the feature of the airbag control device according to the present invention is that the airbag control device is provided between the squib 1 and the drive circuit 42.
The diode 2 is connected so that the direction from the squib 1 to the drive circuit 42 is the forward direction, and a first bias circuit 4 for applying a bias voltage to the squib side of the diode 2
A second bias circuit 45 for applying a bias voltage is provided on the drive circuit side of the diode 4 and the diode 2, and a bias voltage is applied to each of them. The microcomputer 12 determines that the diode terminal voltage (voltage B) on the first bias circuit side and the second Diode terminal voltage (voltage A) on the bias circuit side and diode drop voltage V
It is to diagnose whether a squib-side short or a short-circuit other than the squib-side is short based on the voltage information with d.

The short on the squib side in FIG. 1 refers to the short on the squib other than the squib side at the boundary between the anode side of the diode 2 and the microcomputer 12.
This indicates a short circuit occurring in a harness, an element, or the like on the drive circuit side between the cathode side of the diode 2 and the microcomputer 12.

FIG. 2 is a circuit diagram showing an airbag control device according to a first embodiment of the present invention. Block diagram of FIG.
(Principle diagram) is shown expanded to a specific circuit.
In FIG. 2, a voltage _VDC from a battery or a capacitor as a power supply circuit 60 (shown in FIG. 1) is applied to the squib 1. The squib 1 is connected to a driver 3 as a drive circuit 42 via a diode 2. Although not described, the state of _VDC is normally open and no voltage is applied. However, in the event of a collision, a voltage is applied.

The second bias circuit 45 on one drive circuit side is connected to a power supply V _CC (normally 5 V) via the resistor 4.
Is a circuit for applying the bias voltage from the drive circuit 2 to the drive circuit side of the diode 2. The other squib-side first bias circuit 44 includes a power supply V _CC , an operational amplifier 5, a resistor 6,
7, 8, 9, 10, and 11, a circuit for applying a bias voltage to the squib side of the diode 2. still,
The first bias circuit 44 of the present embodiment is what is generally referred to as a squib 1 resistance value detection circuit, and this resistance value detection circuit is also used as a circuit for applying a bias voltage. The effect is obtained.

That is, the operational amplifier 5 and the resistors 8 and 9 are circuits for amplifying the voltage at both ends of the squib 1. Although not described, the squib 1 is detected by detecting the voltage when a constant current flows through the squib 1. The resistance value (squib resistance) of No. 1 is measured. The output of the operational amplifier 5 with a single power supply is
The linearity deteriorates at low voltage. To detect the squib resistance, a bias circuit is required. This voltage is applied as a bias voltage to the squib side of the diode 2 via the squib 1 and the resistor 6. On the other hand, the diode terminal voltage (voltage A) on the first bias circuit side and the second
The diode terminal voltage (voltage B) on the bias circuit side is detected by being connected to the AD terminal of the microcomputer 12. Therefore, the microcomputer 12 also detects the diode drop voltage Vd.

With this configuration, the diode terminal voltage (voltage A) on the second bias circuit side and the diode terminal voltage (voltage B) on the first bias circuit side have voltages as shown in Table 1. Then, as described above, the microcomputer 1
2 can determine whether the squib is ground short or the drive circuit is ground short by executing a determination based on the voltage Vd. Further, for example, a diagnosis result may be output from the notification terminal 12a of the microcomputer 12, and the notification device 80 may notify the inspector of the short-circuited portion.

In the first embodiment shown in FIG. 2, a method using two AD terminals of a microcomputer has been described. Next, a method using two DI terminals (DI1, DI2) of a microcomputer will be described. . FIG. 3 is a circuit diagram showing an airbag control device according to a second embodiment of the present invention. In FIG. 3, the first configuration of the airbag control device of the second embodiment is shown.
The difference from the embodiment is that the first bias circuit 4 on the squib side
4a and input terminals of the microcomputer 12 (DI1 and DI2 terminals)
And there. Then, the first bias circuit 44 of the second embodiment
a is a power supply V _CC , a transistor 33, and resistors 31 and 3
2, 34. That is, the resistance to the DI1 terminal 31, connect the transistor 33, the resistor from V _CC 3
This circuit is connected to the squib 1 via the squib 2 and 34 and applies a bias voltage to the squib side of the diode 2. Then, a diode terminal voltage B is detected at the DI1 terminal. A second bias circuit 45 for applying a bias voltage to the drive circuit side of the diode 2 is the same as that of the first embodiment, except that the diode terminal voltage A is detected at the DI2 terminal.

With such a configuration, both diode terminal voltages A and B are as shown in Table 2 below.

[0021]

[Table 2]

In Table 2, when the state of the squib with respect to the ground is open and the state of the drive circuit with respect to the ground is also open, that is, in a normal state, the voltage A becomes High and the voltage B becomes Low. When the state of the drive circuit with respect to one of the grounds is short, both the voltage A and the voltage B are low, and it can be diagnosed that the drive circuit is ground short. When the state of the squib with respect to one of the grounds is short-circuited, both the voltage A and the voltage B are High.
It can be diagnosed that the squib is ground short. When both are short, the voltage A is Lo
Since the voltage B becomes high at w, diagnosis can be performed.

As described above, the microcomputer 12 using Table 2 diagnoses whether the squib 1 is short-circuited or the driver 3 is short-circuited based on the voltage A and the voltage B in the same manner as described above. Then, for example, the notification terminal 1 of the microcomputer 12
The diagnostic result is output from 2a, and the short-circuit point is notified by turning on the warning lamp 35.

By the way, in the second embodiment (FIG. 3), the first
The diode terminal voltage (voltage B) on the bias circuit side is the first
This is not a direct diode terminal voltage directly detected from the squib side terminal of the diode 2 as shown in the embodiment (FIG. 2), but an indirect diode terminal voltage detected inside the first bias circuit. In addition, these are defined as “the diode terminal voltage on the first bias circuit side”. Therefore, with the configuration of the first bias circuit 44a of this embodiment including the transistor 33, even if the DI terminal is used,
Can be avoided. As a result, a DI terminal having a relatively simple configuration can be used inside the microcomputer, and there is an effect that a low-cost microcomputer can be used.

Next, an embodiment relating to notification of a diagnosis result will be described. FIG. 4 is a diagram showing the notification means of one embodiment according to the present invention. In the embodiment shown in FIG. 4, the result diagnosed by the inspector is connected to a well-known tester and a notification terminal of a microcomputer built in the airbag control device, and the microcomputer is connected via the tester. It executes serial communication and notifies an abnormal part. Specifically, the configuration is as shown in FIGS.

That is, the microcomputer 12 reports the diagnosis result of the microcomputer to a notification device 80 (for example, a display device or an alarm device) provided as an external notification device. The tester according to the present embodiment is a display unit that appeals visually and informs, but may be an alarm unit that appeals and informs auditory. A digital tester is desirable because it is easy to see.

FIG. 5 is a diagram showing display means of one embodiment according to the present invention. Examples of other display means for notifying an inspector or a passenger visually of the diagnosis result include a lamp and a light emitting diode (hereinafter, LED). It is possible to indicate whether the squib is short or the drive circuit is short by using a color lamp or LED.
Warning light 35 (for example, lamp or LED) as notification means
Is located on the instrument panel of the vehicle. Of course, a warning light may be provided on the main body of the airbag control device. The configuration in which the warning light 35 is used is effective for convenience, and in particular, the light emitting diode is effective for miniaturization.

Although the present embodiment has been described with reference to an example in which the airbag device 50 is mounted on (the handle of) the driver's seat, the present invention is directed to an airbag device 50 mounted on the passenger's seat.
It goes without saying that the present invention is also applied to the airbag control device.

[0029]

According to the present invention, it is possible to diagnose whether the airbag module is in an abnormal state, that is, whether it is a squib short or a drive short. If the diagnosis result is provided to the driver using the communication means of the microcomputer, it is possible to determine whether the drive is short on the control side or the squib short on the bag side. The effect that becomes easy is obtained.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing an airbag control device according to a first embodiment of the present invention.

FIG. 3 is a circuit diagram showing an airbag control device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a notification means of one embodiment according to the present invention.

FIG. 5 is a diagram showing display means of one embodiment according to the present invention.

[Explanation of symbols]

1. Squib, 2. Diode, 3. Driver, 4,
6, 7, 8, 9, 10, 11, 31, 32, 34 ... resistor, 5 ... operational amplifier, 12 ... microcomputer, 12a ... notification terminal, 33 ... transistor, 35 ... warning light, 40 ... control circuit, 42 ... drive Circuit, 44, 44a: first bias circuit, 45: second bias circuit, 50: airbag device, 60: power supply circuit, 70: harness, 80: notification device

Continuing from the front page (72) Inventor Kenji Ota 2520 Oji Takaba, Hitachinaka City, Ibaraki Prefecture Inside the Automotive Equipment Division of Hitachi, Ltd. (72) Inventor Yoji Watanabe 2477 Takaba Hitachinaka City, Ibaraki Prefecture Inside

Claims (4)

[Claims] 1. An airbag control device including a squib for deploying an airbag, a drive circuit for driving the squib, and a microcomputer for operating the drive circuit, wherein a squib is provided between the squib and the drive circuit. A diode is connected so that the direction toward the drive circuit is forward, and a first bias circuit that applies a bias voltage to the squib side of the diode and a second bias circuit that applies a bias voltage to the drive circuit side of the diode A bias circuit, and the microcomputer compares the diode terminal voltage on the first bias circuit side with the diode terminal voltage on the second bias circuit side and the diode drop voltage. Airbag system characterized by diagnosing any short circuit other than Apparatus. 2. The airbag control device according to claim 1, wherein the first bias circuit also serves as a resistance value detection circuit for the squib. 3. The airbag control device according to claim 1, wherein the microcomputer notifies a diagnosis unit provided outside the microcomputer of a diagnosis result of the microcomputer. 4. The airbag control device according to claim 3, wherein said notification means is a warning light.