JPH0747914A - Fault detector of control circuit for vehicle safety device - Google Patents

Abstract

PURPOSE:To monitor circuit abnormality with a simple circuit composition in a fault detector for the control circuit of a vehicle safety device. CONSTITUTION:As to a control circuit equipped with a booster circuit 10 connected to a vehicle battery, capacitors C3-C4 connected to the booster circuit 10, and a No.1 resistor R5 connected in parallel to an abnormality detecting switch SW2, No.2 resistors R3, R4 mounted between the booster circuit 10 and capacitors C3, C4, and a voltage setting means 15 presetting the range of voltage between inflators IN1, IN2 under normal condition and the abnormality detecting switch SW2, are provided. This is a fault detector of a control circuit for a vehicle safety device which is further equipped with a comparison means 12 which detects the voltage between the inflators IN1, IN2 and the abnormality detecting switch SW2 and performs fault output when the detected voltage is not within voltage range Of the voltage setting means 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a booster circuit connected to a vehicle battery, a capacitor connected to the output of the booster circuit, an abnormal state of the vehicle, and an abnormality detection that closes when the vehicle is abnormal. The present invention can be applied to a control circuit of a vehicle safety device that includes a switch and a resistor connected in parallel to the abnormality detection switch, and in which the capacitor, the starting element of the vehicle safety device, and the abnormality detection switch are connected in series.

[0002]

2. Description of the Related Art Conventionally, vehicle safety devices such as airbags and seat belt restraint devices have been developed. The control circuit of such a vehicle safety device uses a DC-DC to provide high energy to a starting element of the vehicle safety device.
A booster circuit such as a converter and a capacitor for storing the output voltage of the booster circuit are provided, and the capacitor, the starting element, and the abnormality detection switch are connected in series. Since the voltage boosted by the booster circuit is stored in the capacitor, high energy is given to the starting element when the abnormality detection switch is closed.

As a control circuit of this type of vehicle safety device, there is a technique disclosed in Japanese Patent Laid-Open No. 3-16854. In this technology, a booster circuit, a capacitor connected to the output of the booster circuit, and an abnormal state of the vehicle are detected,
An abnormality detection switch that is closed when the vehicle is abnormal, and a resistor connected in parallel to the abnormality detection switch are provided. Further, the capacitor, the starting element of the vehicle safety device, and the abnormality detection switch are connected in series. In order to detect a failure of this circuit, a transistor provided between the capacitor and the starting element is provided, and a conduction control unit that opens and closes this transistor to periodically discharge the capacitor is provided. The current flowing from the booster circuit through the starting element and the resistor is measured.

In the above technique, the conduction control section
The capacitor is discharged periodically, and the failure is judged by the change in the output voltage of the booster circuit and the change in the current flowing from the booster circuit through the starting element and the resistor.

[0005]

However, in the above technique, it is necessary to provide a conduction control unit having a transistor that opens and closes at an arbitrary time for failure determination, and the circuit configuration is complicated.

Therefore, it is an object of the present invention to be able to monitor a circuit abnormality with a simple circuit configuration.

[0007]

In order to solve the above problems, the first means used in the invention of claim 1 is that a second resistor interposed between a booster circuit and a capacitor and the control circuit are provided. The voltage between the starting element and the abnormality detecting switch is set in advance, and the voltage between the starting element and the abnormality detecting switch is detected. And a comparison means for performing a failure output when the voltage is not within the voltage range of the setting means.

In order to solve the above-mentioned problems, the second means used in the invention of claim 2 is that the capacitor further has a function of absorbing a power supply fluctuation of the booster circuit.

[0009]

According to the first means, the capacitor stores the voltage boosted by the booster circuit through the second resistor. The abnormality detection switch closes when an abnormality such as a collision of a vehicle is detected, a current flows from the capacitor to the starting element, the electric energy stored in the capacitor is given to the starting element, and the safety device operates. When the safety device is not operating, if the control circuit is normal, a weak current flows through the starting element and the first resistor. This weak current causes a voltage drop in the first resistor. Since the second resistor and the capacitor form a smoothing circuit that absorbs the ripple of the booster circuit, the potential difference across the capacitor is almost stable. Therefore, the potential difference across the first resistor is stable. The voltage between the starting element and the abnormality detection switch is within the voltage range of the voltage setting means,
The comparison means does not output a failure. Here, when a failure of the booster circuit, a short circuit of the capacitor, a disconnection of the starting element, a disconnection of the first resistor, a disconnection of wiring connecting each element, or the like occurs, the voltage between the starting element and the abnormality detection switch becomes The voltage is out of the range of the voltage setting means, and the comparing means outputs a failure. Further, when the capacitor comes off or the open failure occurs, the ripple of the booster circuit appears in the voltage between the starting element and the abnormality detection switch as it is, and it goes out of the voltage range of the voltage setting means, and the comparing means outputs a failure. Therefore, it is possible to detect the failure including the open failure of the capacitor with a simple circuit.

According to the second means, the power supply fluctuation of the booster circuit is absorbed by the capacitor, so that the voltage applied to the comparing means becomes stable. This capacitor is also a capacitor for energy storage given to the starting element.

[0011]

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

FIG. 1 is a circuit diagram of a control circuit and a safety device therefor for energizing the inflators IN1 and IN2 of the airbag by using the energy of the battery BT of the vehicle to provide inflation air into the airbag. The control circuit includes a booster circuit 10 and a smoothing circuit 11.

The battery BT is connected to the converter IC1 via an ignition switch SW1, a diode D1 and a coil L1. Converter IC1 is DC
A DC converter. The converter IC1 includes a reference voltage source IC11, a comparator IC10, and a transistor TR1. The collector of the transistor TR1 is connected to the anode of the diode D2. Diode D2
The resistors R1 and R2 are arranged in series between the cathode side of the battery and the ground terminal of the battery BT. Coil L
1, the converter IC 1, the diode D2, and the resistors R1 and R2 form a booster circuit 10. Comparator I
C10 compares the voltage on the cathode side of the diode D2 divided by the resistors R1 and R2 with the output voltage of the reference voltage source IC11 to open / close the transistor TR1. The comparator IC10 turns off the transistor TR1 when the voltage on the cathode side of the diode D2 rises,
When the voltage on the cathode side of the diode D2 drops, the transistor TR1 is turned on to control the voltage on the cathode side of the diode D2 to a voltage value determined by the ratio of the resistors R1 and R2.

The cathode side of the diode D2 is connected to the capacitor C3 via the diode D3 and the resistor R3. The cathode side of the diode D2 is connected to the capacitor C4 via the diode D4 and the resistor R4. Zener diodes ZD1 and ZD2 are connected in parallel to the capacitors C3 and C4, respectively.
The resistor R3 and the capacitor C3 form a smoothing circuit 11, which smoothes the output voltage of the booster circuit 10, and the capacitor C3 stores electric charges. The resistor R4 and the capacitor C4 form a smoothing circuit 11, smooth the output voltage of the booster circuit 10, and the capacitor C4 stores electric charges. The electric energy stored in the capacitors C3 and C4 is the booster circuit 1
Higher energy becomes 0. Zener diode ZD
1 and ZD2 are very high voltage capacitors C3 and C
4 is prevented from being applied to both ends.

The capacitor C3 detects an abnormal state of the vehicle through an inflator IN1 which is an airbag starting element and a diode D5, and is connected to an abnormality detection switch SW2 which is closed when the vehicle is in an abnormal state. The capacitor C4 is connected to the abnormality detection switch SW2 inside the acceleration sensor 16 via the airbag inflator IN2 and the diode D6.
Connected to. The abnormality detection switch SW2 detects the acceleration acting on the vehicle and operates to close when the vehicle has a large acceleration that cannot occur during normal traveling.

For the acceleration detection, a commercially available acceleration sensor may be used, or the movement of the weight may be detected.
When the abnormality detection switch SW2 is closed, the charges stored in the capacitors C3 and C4 are stored in the inflator IN of the airbag.
1 and IN2, which causes inflation air to flow into the airbag (not shown) to inflate the airbag.

A resistor R is provided in parallel with the abnormality detection switch SW2.
5 are arranged. As a result, a minute current flows through the resistor R5, and a potential difference is generated across the resistor R5. Failure can be determined by measuring this potential difference.

The inflator IN1 and the diode D5 are connected to the non-inverting input terminal of the comparator IC2 and the inverting input terminal of the comparator IC3 via resistors R6 and R7. A capacitor C5 is arranged between the resistors R6 and R7 and the ground terminal of the battery BT, and constitutes a noise filter together with the resistor R6. Resistors R9 and R are provided between the inflator IN2 and the diode D6.
It is connected via 10 to the non-inverting input terminal of the comparator IC4 and the inverting input terminal of the comparator IC5. A capacitor C6 is arranged between the resistors R9 and R10 and the ground terminal of the battery BT, and constitutes a noise filter together with the resistor R9.

The constant voltage circuit IC9 generates a constant voltage (Vcc) from the battery voltage. The constant voltage Vcc serves as a power source for the integrated circuit used in this circuit.

Resistors R12, R13, R14 and R15
Is connected in series between the constant voltage Vcc and the ground terminal of the battery BT, and the voltage between the resistor R13 and the resistor R14 is the first reference voltage VH and the resistor R14 and the resistor R15. The voltage between them is set to the second reference voltage VL. When the booster circuit 10 and the smoothing circuit 11 are normal, the resistance values of the resistors R13, R14 and R15 are equal to the non-inverting input terminal of the comparator IC2 and the comparator IC2.
The voltage value appearing at the inverting input terminal of 3 is the reference voltages VL and VH.
It is set to be in between. The voltage range between the reference voltages VL and VH is set so as not to be erroneously determined due to an error in the value of each element or noise. Resistors R12, R1
3, R14 and R15 thus constitute the voltage setting means 15. The reference voltage VH is connected to the inverting input terminal of the comparator IC2 and the non-inverting input terminal of the comparator IC3. The reference voltage VL is connected to the inverting input terminal of the comparator IC4 and the non-inverting input terminal of the comparator IC5. Comparators IC2, IC3, IC4 and I
The output of C5 is input to the OR circuit IC6. Resistor R
6 to 11, capacitors C5 and C6, comparator IC2
5 to 5 and the OR circuit IC6 constitute the comparison means 12.

If the booster circuit 10 and the smoothing circuit 11 are normal, the voltage at the non-inverting input terminal of the comparator IC2 becomes lower than the voltage VH at the inverting input terminal, and the comparator I2
The voltage at the inverting input terminal of C3 is the voltage VL at the non-inverting input terminal.
The voltage at the non-inverting input terminal of the comparator IC4 becomes lower than the voltage VH at the inverting input terminal, and the voltage at the inverting input terminal of the comparator IC5 becomes higher than the voltage VL at the non-inverting input terminal.
3, the outputs of IC4 and IC5 are all at low level, and the output of the OR circuit IC6 is maintained at low level.

The output of the OR circuit IC6 is input to the inverting input clear terminal of the D-type flip-flop circuit IC7. The data terminal of the flip-flop circuit IC7 is connected to the ground. The inverting output terminal is connected to the input of the OR circuit IC8. The preset terminal and other inputs of the OR circuit IC8 are the start circuit 1 described later.
It is connected to the output of 3. The output of the OR circuit IC8 is connected to the base of the transistor TR5 via the resistor R21. The emitter of the transistor TR5 is connected to the ground. A lamp LU1 and a resistor R23 are connected between the battery BT and the collector of the transistor TR5.

When the output of the OR circuit IC6 is low level and the preset terminal of the flip-flop circuit IC7 is low level, the inverting output terminal of the flip-flop circuit IC7 is held at low level. At this time, the OR circuit I
The output of C8 becomes low level, the transistor TR5 is turned off, and the lamp LU1 is turned off. On the other hand, the OR circuit IC
6 is high level or flip-flop circuit I
When the preset terminal of C7 is at high level, the inverting output terminal of the flip-flop circuit IC7 is held at high level. At this time, the output of the OR circuit IC8 becomes high level, the transistor TR5 is turned on, and the lamp LU1 is turned on. Thus, the flip-flop circuit IC7, the OR circuit IC8, the resistors R21, R22, R23, and the transistor TR5 form the output circuit 14.

The start circuit 13 is a circuit for turning on the lamp LU1 for a predetermined time after the ignition switch SW1 is turned on. The transistor TR2 is a PNP type, the emitter is a constant voltage Vcc, and the base is a resistor R.
12 and the resistor R13. The collector is connected to the emitter of the transistor TR3 via the resistor R16. The transistor TR3 is a PNP type,
The collector is connected to ground. Transistor TR
A resistor R17 is connected between the base and the emitter of No. 3. A capacitor C7 is connected between the base of the transistor TR3 and the ground. Transistor TR3
The base of is connected to the base of an NPN transistor TR4 via a resistor R18. A resistor R19 is connected between the base and the emitter of the transistor TR4, and the emitter of the transistor TR4 is connected to the ground.
The collector of the transistor TR4 is connected to the constant voltage Vcc via the resistor R20, and is also connected to the preset terminal of the flip-flop circuit IC7 as the output of the start circuit 13.

The value of the resistor R12 is set to a value that can turn on the transistor TR2 while the constant voltage Vcc is stable. After the ignition switch SW1 is turned on, the constant voltage circuit IC9 operates to generate a constant voltage Vcc, but until the voltage rises sufficiently and stabilizes, the resistor R1
The potential difference between both ends of 2 is small, and the transistor TR2 is turned off. When the constant voltage Vcc stabilizes, the transistor TR
2 turns on, resistors R16 and R17 and transistor TR
Capacitor C7 is charged via 3. The transistor TR3 constitutes a current limiting circuit and adjusts the charging time of the capacitor C7. When the voltage across the capacitor C7 is low, the base voltage of the transistor TR9 determined by the voltage division ratio of the resistors R18 and R19 is low, the transistor TR9 is turned off, the preset terminal of the flip-flop circuit IC7 becomes high level, and the lamp LU1 lights up. To do. When the capacitor C7 is sufficiently charged, the voltage across the capacitor C7 increases, the base voltage of the transistor TR9 increases, the transistor TR9 turns on, the preset terminal of the flip-flop circuit IC7 becomes low level, and the lamp L
U1 goes out. With the start circuit 13, when the ignition switch SW1 is turned on, the lamp LU1 is always turned on for a predetermined period if the circuit is normal. Therefore, the output circuit 14
And the failure of the lamp LU1 can be seen.

The diode D7 of the start circuit 13 is a capacitor C7 when the ignition switch SW1 is off.
Capacitor C7 and constant voltage Vcc to discharge the electric charge of
Are placed between.

The comparing means 12 is connected to the inflator IN1 when the booster circuit 10 and the smoothing circuit 11, which are control circuits, the inflators IN1 and IN2, the diodes D6 and D6, and the acceleration sensor 16 are all normal except when starting. The voltage VA between the diode D5 or the inflator IN2 and the diode D6 is the reference voltage VL as shown in FIG.
And VH, and the comparison unit 12 and the output circuit 14 turn off the lamp LU1. As shown in FIG. 2, the reference voltages VL and VH are set so that the voltage VA may slightly vary depending on whether the transistor TR1 is on or off. Here, when the booster circuit 10 generates an unnecessarily high voltage, when the diodes D5 and D6 are disconnected, or when the acceleration sensor 16 is disconnected, the voltage VA constantly increases as shown in FIG. The lamp LU1 is turned on by the comparison means 12 and the output circuit 14. Further, when the booster circuit 10 does not generate a sufficient voltage and the smoothing circuit 11 does not generate a sufficient voltage, the diodes D3, D of the smoothing circuit
4 and resistors R3 and R4 are disengaged, the inflator I
In the event of a failure such as when N1 and IN2 are disconnected or when both ends of the acceleration sensor 16 are short-circuited, the inflator IN
The voltage VA between 1 and the diode D5 or between the inflator IN2 and the diode D6 constantly decreases as shown in FIG. 5, and the lamp LU1 is turned on by the comparison means 12 and the output circuit 14. Furthermore, when the capacitance of the capacitor C3 is abnormally low or the capacitor C3 is disconnected, the voltage VA fluctuates significantly as shown in FIG.
It goes up and down beyond the range between L and VH, and the comparison unit 12 and the output circuit 14 turn on the lamp LU1.

In the above embodiment, the booster circuit 10 and the judgment circuit 12
The above is only an example, and may be replaced with other circuit configurations as necessary.

Further, in the above embodiment, two inflators IN1 and IN2 are arranged, but this is for operating the airbag at two places, the driver's seat and the passenger's seat. When only the driver's seat is installed, only one system may be provided. In case of one system, diodes D3, D4,
D5 and D6 are no longer needed. Further, when the airbags are required at a plurality of places such as the rear seats and the lateral direction of the vehicle, the number of systems may be three or more.

In this embodiment, the activation element is the airbag inflator, but it may be replaced with another vehicle safety device such as a seat belt restraint device.

As described above, in this embodiment, the booster circuit 10 connected to the vehicle battery and the capacitors C3 and C4 connected to the output of the booster circuit 10 are used.
And an abnormality detection switch SW2 that detects an abnormal state of the vehicle and closes when the vehicle has an abnormality, and a first resistor R5 connected in parallel to the abnormality detection switch SW2. In the control circuit in which the inflators IN1 and IN2 which are the starting elements of the device and the abnormality detection switch SW2 are connected in series, the booster circuit 10
Resistor R interposed between the capacitor and capacitors C3 and C4
3, R4, voltage setting means 15 for presetting a range of voltage between the inflator IN1, IN2 which is a starting element when the control circuit is normal, and the abnormality detection switch SW2.
And a comparison means 12 for detecting a voltage between the inflators IN1 and IN2, which are start-up elements, and the abnormality detection switch SW2, and performing a failure output when the detected voltage is not within the voltage range of the voltage setting means 15. .

Therefore, the capacitors C3 and C can be formed by a simple circuit.
Failure detection including open failure of No. 4 can always be performed. Therefore, the cost is low.

The capacitors C3 and C4 are used in the booster circuit 1.
It also has the function of absorbing zero power fluctuations. In this embodiment, the capacitor C2 removes high frequency noise with a capacitance of several thousand pF, and the capacitors C3 and C4 remove low frequency noise. The capacitors C3 and C4 serve both as a smoothing capacitor for the booster circuit 10 and as a capacitor for accumulating the ignition energy of the airbag, so that the cost is low.

[0034]

As described above, according to the present invention, it is possible to always detect a failure including an open failure of a capacitor with a simple circuit. Therefore, the cost is low.

Further, since the capacitor also has the function of absorbing the fluctuation of the power source of the booster circuit, it becomes more inexpensive.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a time chart when no failure occurs in the embodiment of the present invention.

FIG. 3 is a time chart when a failure occurs in the embodiment of the present invention.

FIG. 4 is a time chart when a failure occurs in the embodiment of the present invention.

FIG. 5 is a time chart when a failure occurs in the embodiment of the present invention.

[Explanation of symbols]

10 Booster circuit 11 Smoothing circuit 12 Comparison means 13 Start circuit 14 Output circuit 15 Voltage setting means 16 Acceleration sensor BT Battery C1, C2, C3, C4, C5, C6, C7 Capacitors D1, D2, D3, D4, D5, D6 D7 diode IC1 converter IC2, IC3, IC4, IC5, IC10 comparator IC6, IC8 OR circuit IC7 flip-flop circuit IC9 constant voltage circuit IC11 reference voltage source IN1, IN2 inflator L1 coil LU1 lamp R1, R2, R3, R4, R5, R6 , R7, R8, R
9, R10, R11, R12, R13, R14, R1
5, R16, R17, R18, R19, R20, R2
1, R22, R23 Resistor SW1 Ignition switch SW2 Abnormality detection switch TR1, TR2, TR3, TR4, TR5 Transistor VH 1st reference voltage VL 2nd reference voltage ZD1, ZD2 Zener diode

Claims (2)

[Claims] 1. A booster circuit connected to a vehicle battery, a capacitor connected to the output of the booster circuit, an abnormality detection switch that detects an abnormal state of the vehicle and closes when the vehicle is abnormal, and the abnormality. A first resistor connected in parallel to the detection switch; and the capacitor, a starting element of a vehicle safety device,
And a control circuit of a vehicle safety device in which the abnormality detection switch is connected in series, a second resistor interposed between the booster circuit and a capacitor, and the starting element when the control circuit is normal. A voltage setting unit that presets a voltage range between the abnormality detection switch and a voltage between the starting element and the abnormality detection switch, and the detected voltage is not within the voltage range of the voltage setting unit. A failure detection device for a control circuit of a vehicle safety device, comprising: a comparison unit that outputs a failure time. 2. The capacitor also has a function of absorbing fluctuations in the power supply of the booster circuit.
The described failure detection device.