JPH0961479A - System failure detector - Google Patents

Abstract

The present invention relates to a system failure detection device that issues an alarm when a system failure is detected, and an object thereof is to enable detection and warning of a failure in a power supply system. A microcomputer 26 is provided which changes an output signal of an abnormality output port 26a from a high signal to a low signal when a system abnormality is detected. A latch circuit 30 is provided which changes an output signal from a high signal to a low signal when a malfunction of the microcomputer 26 is detected. The abnormal output port 26a and the output terminal 30a are connected to the abnormal output line 36 via the diodes 32 and 34. The drive circuit 24 lights the warning lamp 12 when the potential of the abnormal output line 36 is low level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system failure detection device, and more particularly to a system failure detection device that issues an alarm when a system failure is detected.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Laid-Open Patent Publication No. 1-27462.
As disclosed in No. 8, when a system failure is detected, a device for issuing an alarm regarding the failure is known. The above-mentioned conventional device is a device for detecting a failure of an airbag system mounted on a vehicle, and when a failure is detected in the airbag system, a warning lamp in an instrument panel is turned on. , Alert the driver of the occurrence of the failure.

The above-mentioned conventional device is a circuit for detecting a system abnormality inside an electronic control unit of an airbag system, and a microcomputer for outputting a high signal from an abnormality output port when a system abnormality is detected. And a lamp drive circuit for lighting the warnig lamp when a high signal is output from the abnormal output port of the microcomputer.

With the above arrangement, when the airbag system is functioning normally, a low signal is output from the abnormal output port of the microcomputer. Therefore, in such a case, the warning lamp is kept off. On the other hand, when an abnormality occurs in the airbag system, a high signal is output from the abnormality output port of the microcomputer and the warning lamp is turned on.

[0005]

In the above-mentioned conventional apparatus, in order for the microcomputer to output a high signal from its abnormal output port, it is necessary that the driving power is normally supplied to the microcomputer. is there. In other words, the microcomputer, when a failure related to the power supply system of the microcomputer occurs,
A high signal cannot be output from the abnormal output port.

Therefore, depending on the above-mentioned conventional device, a warning is issued when a power supply circuit for supplying power to the microcomputer fails, or when a power supply line connected to the airbag system fails. I cannot turn on the lamp. As described above, the conventional device has a problem that when a failure occurs in the power supply system, an alarm for the failure cannot be issued.

The present invention has been made in view of the above-mentioned points, and when a system failure occurs, an alarm is generated by a low signal to solve the above-mentioned problems. An object is to provide a detection device.

[0008]

The above object is to provide a high signal when a system failure is not detected in a system failure detection device that issues an alarm using a failure display means when a system failure is detected. And a failure detection means for outputting a low signal when a failure of the system is detected, and a failure detection means that does not drive the failure display means when a high signal is output from the failure detection means. And a drive means for driving the failure display means when a low signal is output.

In the present invention, the failure display means drives the failure display means to generate an alarm when a low signal is supplied from the failure detection means. A low signal is output from the failure detection unit when a failure in the system is detected by the failure detection unit, and when a failure occurs in the power supply system of the system and power supply to the failure detection unit is stopped. Output. Therefore, in addition to the case where the system failure is detected from the failure display means,
An alarm is also issued if the system's power system fails.

[0010]

FIG. 1 is a circuit diagram of a failure detecting device according to an embodiment of the present invention. In this embodiment, an example in which the failure detection device is incorporated into a vehicle airbag system will be described. The airbag system includes an in-vehicle battery (hereinafter, referred to as a battery) 10, a warning lamp 12, an airbag ignition device 14, an airbag sensor (hereinafter, referred to as a sensor) 16, and an electronic control unit for the airbag (hereinafter, referred to as a sensor). , Airbag 20).

The battery 10 produces a voltage of 12V. The negative electrode terminal of the battery 10 is grounded to the vehicle body. On the other hand, a warning lamp 12 and an airbag ECU 20 are connected to the positive terminal of the battery 10. The warning lamp 12 is a lamp that is turned on when an abnormality occurs in the airbag system, and is stored in an instrument panel of the vehicle.

The ignition circuit 14 is a circuit for detonating a squib incorporated in a steering wheel or the like when an ignition signal is supplied from the airbag ECU 20. When the squib is detonated, the airbag stored in the steering wheel or the like is expanded. The sensor 16 is composed of a deceleration sensor or the like that detects deceleration acting on the vehicle.
The sensor 16 is provided in the airbag ECU 20. When the sensor 16 detects deceleration exceeding a predetermined level, the airbag ECU 20 determines that the posture of the vehicle occupant should be restrained, and supplies an ignition signal to the ignition circuit 14.

The air bag ECU 20 controls the operation of the air bag system, and a control circuit 22 provided for detecting a failure of the air bag system, and a warning circuit when a failure of the air bag system is detected. And a drive circuit 24 for turning on the lamp 12.

The control circuit 22 is the microcomputer 2
6 is provided. The ignition circuit 14 and the sensor 16 described above are connected to the microcomputer 26.
The output signal of the sensor 16 is captured by the microcomputer 26. The microcomputer 26 processes the captured output signal according to a predetermined rule and outputs the ignition signal to the ignition circuit 14 under a predetermined condition.

Further, the microcomputer 26 has a function of determining whether or not the connection state of the ignition circuit 14 is proper by circulating a minute current through the ignition circuit 14. The microcomputer 26 outputs a high signal to the abnormality output port 26a when the disconnection or the like of the ignition circuit 14 (hereinafter referred to as system abnormality) is not detected. On the other hand, when the system abnormality is detected, the microcomputer 26 outputs a low signal to the abnormality output port 26a.

The microcomputer 26 has a 5V power source
Power is supplied from a 5V terminal 28a of a microcomputer monitoring circuit (hereinafter, simply referred to as 5V power source) 28. The 5V power supply 28 is supplied with a voltage of 12V from the battery 10. The 5V power supply 28 has a function of stepping down the voltage of 12V to 5V and outputting it, and also has a watch dog pulse (hereinafter,
It has a function of monitoring the operating state of the microcomputer 26 based on the W / D pulse).

That is, the microcomputer 26 is
When the device itself is operating normally, the W / D pulse signal is periodically output from the W / D terminal. 5V power supply 28
If the W / D pulse is output at an appropriate cycle, it is determined that the microcomputer 26 is functioning normally. From the W / D terminal of the microcomputer 26,
When the W / D pulse is not output in the proper cycle, the 5V power supply 28 determines that an abnormality has occurred in the microcomputer 26 and outputs the reset pulse from the reset terminals R ₁ and R ₂ .

The reset terminal R ₁ of the 5V power source 28 is connected to the reset terminal R of the microcomputer 26. The microcomputer 26 has its reset terminal R
When a reset pulse is supplied to, the process to be executed is restarted. By such processing, the microcomputer 26
If it returns to the normal state, the W / D pin will
The pulse starts to be output. In this case, the 5V power supply 28 is
Stops output of reset pulse. On the other hand, if the microcomputer 26 does not return to the normal state, W / D
Pulse output does not resume. In this case, 5V power supply 28
Outputs a reset pulse repeatedly at a predetermined cycle.

The reset terminal R ₂ of the 5V power supply 28 is connected to the latch circuit 30. Latch circuit 30 is 5V
It is a circuit driven by the 5V voltage output from the 5V terminal 28a of the power supply 28, and normally outputs a high signal to its output terminal 30a. Reset terminal R ₂ of 5V power supply 28
When the reset pulse is output from the latch circuit 30, the latch circuit 30 receives the output and outputs a low signal from the output terminal 30a for a predetermined period.

The abnormal output port 26a of the microcomputer 26 and the output terminal 30a of the latch circuit 30 are connected to the cathode terminal of the diode 32 and the cathode terminal of the diode 34, respectively. Diode 32
The anode terminals of both and 34 are connected to an abnormal output line 36 connecting the control circuit 22 and the drive circuit 24. The input impedance at the abnormal output port 26a of the microcomputer 26 and the input impedance at the output terminal 30a of the latch circuit 30 are both sufficiently small values.

The drive circuit 24 includes a resistor 38 connected to the 5V terminal 28a of the 5V power source 28, and two resistors 40 and 42 connected in series to the resistor 38. The above-mentioned abnormal output line 36 is connected between the resistors 38 and 40. The gate terminal of the first transistor 44 is connected between the resistors 40 and 42. Further, the resistor 42 is connected to the ground line.

According to the above configuration, the abnormal output line 36
Has a potential of 5V, the voltage obtained by dividing the voltage of 5V by the combined resistance composed of the resistors 38 and 40 and the resistor 42 is applied to the gate terminal of the first transistor 44. Supplied. The first transistor 44 is a switching element composed of an n-channel FET, and has a characteristic of being turned on when the above potential is supplied to the gate terminal. On the other hand, when the potential of the abnormal output line 36 is at the ground level, the ground level voltage is introduced to the gate terminal of the first transistor 44. First transistor 4
No. 4 has a characteristic that it is turned off when a ground level voltage is introduced to the gate terminal.

The drive circuit 24 includes two resistors 46 and 48 connected in series with the battery 10. The drain terminal of the first transistor and the gate terminal of the second transistor 50 described above are connected between the resistors 46 and 48. The source terminal of the first transistor 44,
The source terminals of the second transistor 50 and the second transistor 50 are both connected to the ground line.

According to the above configuration, the first transistor 4
4 is off, a voltage of 12 V is applied to the resistor 4
The voltage divided by 6 and 48 is supplied to the gate terminal of the second transistor 50. The second transistor 50 is a switching element composed of an n-channel FET similarly to the first transistor 44, and has a characteristic of being turned on when the above potential is supplied to the gate terminal.
On the other hand, if the first transistor is in the ON state, the second transistor
A ground level voltage is introduced to the gate terminal of the transistor 50. The second transistor 50 has a characteristic of being turned off when a voltage at the ground level is introduced to the gate terminal.

A resistor 52 is connected to the drain terminal of the second transistor 50. The warning lamp 12 receiving a voltage of 12 V is connected to the other end of the resistor 52. When the second transistor 50 is on, current flows through the warning lamp 12 and the resistor 52, and the warning lamp 12 is turned on. On the other hand, when the second transistor 50 is off,
No current flows through the warning lamp 12, and the warning lamp 12 is turned off.

FIG. 2 is a time chart for explaining the operation when the microcomputer 26 detects a system abnormality. FIG. 2A shows a change in the state of the system detected by the microcomputer 26. The change shown in the figure indicates that the system abnormality is detected at time t ₁ .

FIG. 2B shows a microcomputer 26.
The signal level output from the abnormal output port 26a is shown. The microcomputer 26, the system is time t ₁ before it is operating normally, and outputs a high signal to the abnormal output port 26a. On the other hand, when a system abnormality is detected at time t ₁ , thereafter, a low signal is output from the abnormality output port 26a.

FIG. 2C shows changes in the potential of the abnormal output line 36. In the abnormal output line 36, the diode 3
The abnormal output port 26a of the microcomputer 26 and the output terminal 30a of the latch circuit 30 are connected via 2, 34. When both the abnormal output port 26a and the output terminal 30a are maintained at the high level, no current flows through the diodes 32 and 34. In this case, as the potential of the abnormal output line 36, the voltage of 5V is applied to the resistor 3
8 and the combined resistance composed of the resistors 40 and 42, that is, the potential obtained by the voltage division, that is, the high level potential is maintained. On the other hand, the abnormal output port 26a and the output terminal 30a
When at least one of the two is set to the low level, a current flows through at least one of the diodes 32 and 34. In this case, the resistor 38 causes a voltage drop of approximately 5 V, and the potential of the abnormal output line 36 changes to approximately the ground level, that is, the low level. Therefore, when the system abnormality is detected at time t _{1 as} described above, the voltage of the abnormal output line changes from high level to low level around time t _{1 as} shown in FIG. 2 (C).

2D and _2E show changes in the gate voltage V _GS1 applied to the gate terminal of the first transistor 44 and changes in the on / off state of the first transistor 44, respectively. As described above, the first transistor 4
A high signal is output to the gate terminal of No. 4 when the abnormal output line 36 is at a high level, and the abnormal output line 36
Is low level, a low signal is supplied. Then, the first transistor 44 is turned on when a high signal is supplied to the gate terminal and is turned off when a low signal is supplied to the gate terminal. Therefore, when the potential of the abnormal output line 36 changes from the high level to the low level at time t ₁ as described above, the first transistor 44 changes from the on state to the off state at time t _{1 as} shown in FIG. Changes to.

2F and 2G show changes in the gate voltage V _GS1 applied to the gate terminal of the second transistor 50 and changes in the on / off state of the second transistor 50, respectively. As described above, the second transistor 5
A high signal is applied to the gate terminal of 0 when the first transistor 44 is off, and
When 4 is on, a low signal is provided. Then, the second transistor 44 is turned on when a high signal is supplied to the gate terminal and is turned off when a low signal is supplied to the gate terminal. Therefore, when the on / off state of the first transistor 44 changes as described above, the second transistor 50 changes from the off state to the on state at time t _{1 as} shown in FIG.

FIG. 2H shows the state change of the warning lamp 12. The warning lamp 12 is turned on when the second transistor 50 is on, and is turned off when the second transistor 50 is off. Therefore, when the second transistor 50 changes from the off state to the on state at time t _{1 as} described above, the warning lamp 12
Changes from the extinguished state to the lit state at time t _{1 as} shown in FIG. 2 (H).

As described above, the potential of the abnormal output line 36 becomes low level because at least one of the potential of the abnormal output terminal 26a of the microcomputer 26 and the potential of the output terminal 30a of the latch circuit 30 becomes low level. Become. Therefore, even when an abnormality occurs in the microcomputer 26 and the signal output from the output terminal 30a of the latch circuit 30 changes from the high signal to the low signal at the time t ₁ , the above-described FIG. 2C to FIG. The operation shown in FIG.

Therefore, according to the system of this embodiment,
As shown in Table 1, the warning lamp 12 is in the off state when both the abnormal output port 26a of the microcomputer 26 and the output terminal 30a of the latch circuit 30 output a high signal, and the microcomputer 2
When at least one of the abnormal output port 26a of No. 6 and the output terminal 30a of the latch circuit 30 outputs a low signal, the light is turned on.

[0034]

[Table 1]

By the way, in the airbag ECU 20, a path connecting the battery 10 and the 5V power supply 28, a path connecting the 5V terminal 28a of the 5V power supply 28 and the microcomputer 26, or a 5V terminal 28a of the 5V power supply 28.
If a disconnection occurs in the path connecting the latch circuit 30 and the latch circuit 30, or if an abnormality occurs in the 5V power supply 28 itself, the power cannot be supplied normally and the microcomputer 26 and the latch circuit 30 cannot operate normally. Become. When the microcomputer 26 and the latch circuit 30 do not operate normally, the airbag system cannot operate normally. Therefore, the above-mentioned abnormality of the power supply system should be detected as a system failure.

In the system of this embodiment, when the above-mentioned abnormality of the power supply system occurs in the airbag ECU 20, a low signal is output from at least one of the abnormality output port 26a of the microcomputer 26 and the output port 30a of the latch circuit 30. To be done. In this case, the warning lamp 12 is turned on as described above. in this way,
According to the system of the present embodiment, it is possible to detect a system abnormality that occurs in the ignition circuit 14 and the like, a malfunction of the microcomputer 26, and issue an alarm, and also to detect an abnormality in the power supply system that occurs in the airbag ECU 20. It can detect and issue an alarm. Therefore, according to the system of the present embodiment, the warning lamp drive circuit is more reliable than a system in which the lamp is turned on by receiving a high level signal (hereinafter referred to as a positive logic system). The failure of can be detected.

By the way, in the system of this embodiment, since the high-level signal is supplied to the gate terminal of the first transistor 44 during the normal operation of the system, the resistors 38, 40, 42 are supplied with the 5V power source. The bias current is supplied from 28. In order to suppress the power consumption of the 5V power supply 28, it is preferable that the power consumption by the bias current is small. In a positive logic system that supplies a high signal to the drive circuit of the warning lamp 12 when a system failure occurs, it is not necessary to constantly supply such bias current. In this respect, the system of the present embodiment is disadvantageous in comparison with the positive logic system from the viewpoint of suppressing the power consumption of the 5V power supply 28.

However, in this embodiment, the first
A FET is used for the transistor 44, and a resistor 38,
A sufficiently large resistance value is given to 40 and 42.
When the first transistor 44 is composed of a FET,
Since it is not necessary to secure a large bias current, the resistance 3
A large resistance value can be given to 8, 40 and 42. Further, when a large resistance value is given to the resistors 38, 40, 42, the power consumed by the resistors 38, 40, 42 when the system is normal can be suppressed. Therefore, according to the system of the present embodiment, it is possible to suppress the power consumption of the 5V power supply 28 in the same manner as the positive logic system.

In the above embodiment, the warning lamp 12 has the above-mentioned failure display means and the control circuit 22.
Corresponds to the failure detection means described above, and the drive circuit 24 corresponds to the drive means described above. By the way, in the above embodiment, the failure detection is limited to be executed in the airbag system, but the present invention is not limited to this, and it can be used for the failure detection of other systems. is there. Further, in the above embodiment, the failure display means is limited to the warning lamp, but the present invention is not limited to this, for example,
It is also possible to use an alarm buzzer or the like instead of the warning lamp.

[0040]

As described above, according to the present invention, an alarm can be issued when a low signal is issued from the failure detecting means. Therefore, in addition to the case where the failure detection unit detects a system failure and outputs a low signal, an alarm is generated even when a failure occurs in the system power system and the failure detection unit cannot output a high signal. Can be generated. As described above, according to the system failure detection device of the present invention, when a failure occurs in a power supply system that supplies power to the failure detection unit, an alarm can be reliably generated.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an airbag system that is an embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of the system that is an embodiment of the present invention.

[Explanation of symbols]

10 Car Battery (Battery) 12 Warning Lamp 14 Ignition Circuit 16 Sensor 20 Airbag Electronic Control Unit (Airbag EC
U) 22 control circuit 24 drive circuit 26 microcomputer 26a abnormal output port 28 5V power supply / microcomputer monitoring circuit 28 (5V power supply) 30 latch circuit 30a output terminal 36 abnormal output line 44 first transistor 50 second transistor

Claims (1)

[Claims] 1. A system failure detection device which issues an alarm using a failure display means when a system failure is detected, outputs a high signal when the system failure is not detected, and detects the system failure. Failure detection means that outputs a low signal when the failure detection means outputs the failure signal, and the failure display means is not driven when the failure detection means outputs a high signal, and the failure detection means outputs the low signal when the failure detection means outputs the low signal. A failure detection device for a system, comprising: a drive unit that drives a failure display unit.