JPH07137599A - Occupant crash protection - Google Patents

Abstract

PURPOSE:To diagnose a diode to elucidate a trouble position in a simple structure, by providing squibs whose one ends are connected to a power source and the other ends are connected to the earth through a diode and an acceneration switch, and connecting a constant current circuit between the cathode of the diode and the earth. CONSTITUTION:When the short circuit between lines of sqibs 10 and 11 which develop an air bag, and a trouble of diodes 45 and 46 are diagnosed, in a CPU 14 to output the ignition signal of the air bag, when generation a collision is recognized by an acceleration signal from a G sensor, transistors Tr4 and 5, and the transistor Tr7 of a constant current circuit 16 connected between the cathodes of the diodes 45 and 46, and the earth, are made in the continuety condition, and a constant current is fed to the squibs 10 and 11. And when the trouble of an SS interface 15 is diagnosed, the Tr 4 and 5 are made in the uncontinued condition so as to operate the constant current circuit 16. Since the Tr7 is made in the continued condition, and the voltage at the upstream side of a mechanical accaleration switch 13 is varied, in this case, the trouble can be diagnosed by monitoring the input voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an occupant protection device for deploying an airbag to protect an occupant when a vehicle or the like collides.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing a conventional occupant protection device for a vehicle, for example, 10 and 11 are squibs, and these squibs 10 and 11 are airbags when a deployment current passes through them. Is to be developed. The squib 10 is for an airbag for a driver's seat, and the squib 11 is for a passenger seat.

Further, 12 is a G sensor for detecting a vehicle collision, and 13 is a mechanical acceleration switch (SS (Safing Sensor)) for preventing erroneous deployment of an airbag. The switch 13 is turned on when it receives an acceleration equal to or higher than a predetermined value obtained at the time of collision. In addition,
The switch 13 is installed in series with the squibs 10 and 11.

Numeral 15 is a mechanical acceleration switch 1
S installed to apply a predetermined voltage to the input side of S3
This is the S interface. This SS interface 15
Is to detect ON / OFF of the mechanical acceleration switch 13 by detecting a voltage change applied to the input side of the mechanical acceleration switch 13. Therefore, the SS interface 15 includes a pull-up resistor 68 connected to the power supply 70 and a diode that protects the input of the A / D converter 17. The output of this A / D converter 17 is the CPU
When the voltage value supplied to the mechanical acceleration switch 13 falls below a predetermined value, the CPU 140 determines that the mechanical acceleration switch 13 is in the ON state.

Further, when the 140 judges based on the detection signal from the G sensor 12 that a collision has occurred to deploy the airbag, it outputs an airbag ignition signal and deploys the squibs 10 and 11 with a deployment current. Is a CPU for supplying the. At the same time, the CPU 140 causes the transistor 4,
5, ON / OFF of the transistor 8 and the constant current circuit 16 is controlled to diagnose a failure of each part of the ignition system of the device.

Further, 1 and 2 are transistors 3 described below.
When it is turned on by the control of the squib 1 from the expansion current power source (capacitors 71 and 72 for backup power source).
A switching transistor (TR) 3 for transmitting and supplying a developing current to 0 and 11 is a drive transistor that drives the transistors 1 and 2 to be in an ON state when receiving an ignition signal from the CPU 140. Also, 4 and 5 are CP
When turned on by the control of U140, the squib 1 produces a diagnostic current that is sufficiently smaller than the deployment current when the airbag is deployed.
It is a switching transistor for supplying to 0 and 11. In addition, 73 and 74 are diagnostic power supplies.

Further, 71 and 72 are capacitors (C) for backup power supply, 50 to 68 are resistors (R), and 80 is a voltage detection circuit comprising a differential amplifier for inputting the voltage between the terminals of the squibs 10 and 11. 31 to 42 are diodes (D) for preventing reverse current flow, and in particular, a diode 40 is connected to the diode 39 and a diode 42 is connected to the diode 41 for redundancy.
That is, when each of the diodes 39 and 41 has an open failure, it cannot be detected by the diagnosis.

Reference numeral 16 is a constant current circuit. This constant current circuit 16 has diodes 37 and 38 when the transistor 6 is turned off and the transistor 7 is turned on for diagnosis by the CPU 140. It draws a constant current from. Reference numeral 75 is a power source for the constant current circuit 16.

Next, the operation will be described. First, the operation at the time of collision will be described. When the vehicle collides with an impact sufficient to deploy the airbag, the G sensor 12
Outputs a detection signal to that effect to CPU 140.
Also, the mechanical acceleration switch 13 is turned on by this collision.
It becomes a state.

Then, when a signal is received from the G sensor 12, it is judged as a collision, and when the mechanical acceleration switch 13 is turned on through the SS interface 15, C
The PU 140 outputs an ignition signal to the drive transistor 3 to turn on the transistors 1 and 2. As a result, the deployment current from the deployment current power supply is sent to the squibs 10 and 11, and the squibs 10 and 11 receiving the deployment current deploy the airbag.

Even if the battery is destroyed by a collision, the backup power supply capacitor 31,
The development current is sent to the squibs 10 and 11 by 32,
The same processing as described above is performed.

Next, the operation of the circuit diagnostic processing will be described. When diagnosing a short circuit between the squibs 10 and 11, C
The PU 140 first turns on one transistor 4 of the transistors 4 and 5 and the transistor 7 of the constant current circuit 16 so that a constant current of an insufficient level for ignition flows through the one squib 10.

Then, the voltage detection circuit 80 corresponding to the squib 10 measures the voltage generated between both ends of the squib 10, the voltage value is supplied to the CPU 140, and is compared with a reference value to make a diagnosis. , A short circuit between lines of the squib 10 is detected. The squib 11 is diagnosed by turning on the other transistor 5 and repeating the same procedure as above.

Further, when diagnosing the SS interface 15, the CPU 140 turns on / off the transistor 8.
Then, the input voltage from the SS interface 15 supplied at that time is monitored. As a result, the CPU 140 determines whether the SS interface 15 is normally turned on / off according to the input side voltage of the mechanical acceleration switch 13. I can diagnose.

[0015]

Since the conventional occupant protection device is constructed as described above, it is not possible to diagnose the open failure of the diode for isolating the faulty part, and the diode for isolating the faulty part becomes redundant. There was a problem such as being lost.

The invention of claim 1 has been made in order to solve the above problems, and provides an occupant protection device capable of diagnosing a diode for isolating a faulty part and simplifying the structure of the device. The purpose is to get.

[0017]

An occupant protection system according to the present invention comprises a squib having one end connected to a power source via a switch means and the other end connected to a ground via a diode and an acceleration switch. , Connect the constant current circuit between the cathode of the diode and the ground, and connect the constant current circuit to the CPU
Controlled by.

[0018]

In the occupant protection system according to the first aspect of the present invention, one end of the occupant protection device is connected to the power supply through the switch means, and the other end is connected to the ground through the diode and the acceleration switch. By passing a diagnostic current through the diode, a constant current circuit is connected between the cathode of the backflow prevention diode and ground by means of an interface circuit for measuring Further, if the interface circuit is normal, the detection signal can be obtained from the detection means according to the ON / OFF control of the acceleration switch.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an occupant protection device for a vehicle. In the drawing, 10 and 11 are squibs, and one end of each of these squibs 10 and 11 is a developing current through transistors (switch means) 1 and 2. Connected to power supply.
The other ends of the squibs 10 and 11 are connected to the ground via diodes (backflow prevention diodes) 45 and 46 and a mechanical acceleration switch (acceleration switch) 13.

16 is a constant current circuit, and this constant current circuit 16 is connected between the cathodes of the diodes 45 and 46 and the ground. Reference numeral 15 is an SS interface. The SS interface 15 has an input terminal connected to a connection point between the mechanical acceleration switch 13 and the diodes 45 and 46, and sends a detection signal from the A / D converter 17 to the CPU 14. Connected to output. Further, 12 is a G sensor (acceleration sensor), 3 is a transistor as a part of the switch means of the claims, 4 and 5 are transistors as diagnostic switch means of the claims, 71, 7
2 is a capacitor for backup power supply, 50 to 68 are resistors, 80 is a voltage detection circuit, 31 to 36 are diodes, 7
3, 74 and 75 are power supplies. The individual circuits described above are as described in the prior art example.

Reference numeral 14 denotes a CPU which outputs an ignition signal for the airbag when it recognizes that a collision has occurred to deploy the airbag based on a detection signal indicating the acceleration from the G sensor 12. Also, the CPU 14 uses the squib 1
The short circuit between 0 and 11 is diagnosed, and the failure of the diodes 45 and 46 is diagnosed.
5. The transistor 7 of the constant current circuit 16 is controlled to be conductive so that a constant current is supplied to the squipes 10 and 11. Further, when diagnosing the failure of the SS interface 15, the CPU 14 controls the transistors 4 and 5 to be in the OFF state and operates the constant current circuit 16 to supply no current, so that the transistor 7 is in the conductive state. The voltage at the upstream portion of the mechanical acceleration switch 13 fluctuates, and the failure is diagnosed by monitoring the input voltage from the SS interface 15. If there is no fluctuation, the mechanical acceleration switch 13 is in the conductive state and the failure is judged.

Next, the operation will be described. The airbag deployment operation is similar to that of the conventional example. The circuit diagnosis processing will be described below.

First, when diagnosing a short circuit between the lines of the squibs 10 and 11 and an open failure of the diodes 45 and 46, the CPU 14 first turns on one of the transistors 4 and 5, for example, the transistor 4. A voltage is applied to the upstream side of the squib 10. Along with this, the CPU
14 indicates that the transistor 6 of the constant current circuit 16 is turned off, the transistor 7 is turned on, and the transistor 7 is turned on.
Is operated at a constant current to draw a constant diagnostic current from the upstream side into the constant current circuit 16.

At this time, if the line between the squibs 10 is normal, the voltage between both terminals of the squib is the voltage V shown in the following equation (1).
Occurs, and the generated voltage corresponds to the voltage detection circuit 8
If the differential voltage is equal to or lower than a certain voltage based on the detection information, it is determined that the short circuit between the squib lines or the open failure of the fault portion isolation diode 46 is made. V = I · R _SQ : I = constant, V = voltage across squib (1) R _SQ = squib resistance By switching the other transistor 5 to ON, the other transistor 5 is turned on. Squib 1
1 and the diode 46 are diagnosed.

The CPU 14 uses the SS interface 1
By comparing the magnitude of the output voltage from 5 with the reference voltage, it is possible to determine whether the squib line is short-circuited or the faulty part isolation diode is open.

Further, if the mechanical acceleration switch 13 is normal, C
When the SS interface 15 is diagnosed after the PU 14 makes a determination, the CPU 14 first turns off both the transistors 4 and 5 and turns on the constant current circuit 16. As a result, the transistor 7 of the constant current circuit 16 having no power supply source is turned on, the upper end voltage of the mechanical acceleration switch 13 changes, and the output voltage of the SS interface 15 also changes. If the CPU 14 cannot detect this variation, S
The S interface 15 determines that it is abnormal.

As a result, if the SS interface 15 is normal and the connection between the SS interface 15 and the mechanical acceleration switch 13 is normal, the A / D converter 1
From 7, the signal corresponding to the ON / OFF is sent to the CPU.
It is output to 14.

At the time of the above diagnosis, if the signal according to the ON / OFF is not sent, the CPU 14 has an abnormality in the SS interface 15 or the connection between the SS interface 15 and the mechanical acceleration switch 13. Determine that there is.

In this example, the CPU 14 controls ON / OFF of the mechanical acceleration switch 13, but ON / OFF may be controlled by an external control other than the CPU 14. . In the above description, the failure diagnosis of the mechanical acceleration switch 13 is CP
U14 is the input side (upstream side) of the mechanical acceleration switch 13
If the voltage is 0 (V) at the time of diagnosing the squibs 10 and 11, it is determined that there is a failure in the conductive state.

[0030]

As described above, according to the first aspect of the invention, the passage of the diagnostic current to the backflow prevention means is tested, and the detection signal from the detection means for detecting ON / OFF of the acceleration switch is diagnosed. Since it is configured as described above, each part of the device can be widely diagnosed, the reliability of the device is improved, the device can be simplified, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an occupant protection device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an occupant protection device in a conventional example.

[Explanation of symbols]

 1, 2, 3 transistors (switch means) 4, 5 transistors (diagnostic switch means) 10, 11 squib 12 G sensor (acceleration sensor) 13 mechanical acceleration switch (acceleration switch) 14 CPU 15 SS interface (interface circuit) 16 Current circuit 45,46 Diode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Shibata, 1910 Nisshincho, Omiya City, Saitama Prefecture Kansei Co., Ltd.

Claims (1)

[Claims] 1. A squib, one end of which is connected to a power source through a switch means and the other end of which is connected to a ground through a diode and an acceleration switch, and which deploys an airbag when a current is received from the power source, and an acceleration sensor. A CPU for turning on the switch means based on the signal
Diagnostic switch means for receiving a diagnostic signal from the U to apply a diagnostic voltage to the squib, a constant current circuit for receiving a diagnostic signal from the CPU and conducting a constant current through the squib, and a power source side of the acceleration switch. An occupant protection device comprising an interface circuit for transmitting a terminal voltage to the CPU, wherein the constant current circuit is connected between the cathode of the diode and ground.