JPH08188113A - Occupant crash protection for vehicle - Google Patents

Abstract

PURPOSE: To enable it to diagnose a backup condenser without using any discharge circuit subjected to hard composition. CONSTITUTION: When an ignition switch is turned off, a diagnostic function of a microcomputer is operated, having a power transistor 16 turned off, and a voltage variation between both input and output sides of this power transistor 16 feeding a circuit system power source 25 from a backup condenser 6 is diagnosed, thereby diagnosing the backup condenser 6 and the power transistor 16. Then, in the case where there is something wrong with them, it is stored in a memory, and the storage contents is informed with an alarm lamp or the like, for example, at the time when the ignition switch is turned to ON subsequently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle occupant protection device such as an airbag system for protecting a vehicle occupant from a collision accident.

[0002]

2. Description of the Related Art A conventional vehicle occupant protection system of this type will be described with reference to a vehicle occupant protection system shown in FIG. In FIG. 2, 1 is an in-vehicle battery, 2
Is an ignition switch, 4 is a DC / DC converter that boosts and outputs the output voltage of the battery 1, and its input terminal is connected to the battery 1 through a first backflow prevention diode 3 and an ignition switch 2 in series. There is. Reference numeral 5 denotes a second backflow prevention diode, the anode of which is connected to one end of the ignition switch 2 and the cathode of which is the connection point between the emitter terminal of the switching transistor that constitutes the switch circuit 9 described later and the cathode of the discharge diode 8. It is connected. Reference numeral 6 denotes a backup capacitor, which is connected to the output terminal of the DC / DC converter 4 via a resistor 7, and the anode of the discharging diode 8 is connected to the connection point with the resistor 7.

The cathode of the discharging diode 8 is connected to the emitter terminal of the switching transistor of the switch circuit 9 described later. The switch circuit 9 is composed of a switching transistor or the like, and the collector terminal of the switching transistor forming the output terminal thereof is the detonator 1
0 and the acceleration switch 11 are grounded via the series. A control signal from a third output port P3 of the microcomputer 26, which will be described later, is input to the base terminal of the switching transistor of the switch circuit 9 and is turned on / off by the control signal. Voltage dividing resistors 12 and 13 are connected in series and are connected to the output side of the DC / DC converter 4 to divide the output voltage of the DC / DC converter 4.

Reference numeral 15 is a switching transistor for discharging, the collector terminal of which is connected to the connection point of the back-up capacitor 6 and the resistor 7 via the resistor 14, the emitter terminal of which is grounded, and the base terminal of which is a microcomputer which will be described later. Immediately after being connected to the first output port P1 of 26 and turning on the ignition switch 2, an ON signal and an OFF signal are supplied in a predetermined mode,
The electric charge of the backup capacitor 6 is discharged or charged through the resistor 14.

Reference numeral 16 is a power switching transistor, the emitter terminal of which is the back-up capacitor 6
Is connected to the connection line between the resistor and the resistor 7, and the collector terminal is
Circuit system power supply 25 via third backflow prevention diode 28
Of the control transistor 20. The base terminal of the control transistor 20 is connected to the collector terminal of the control transistor 20 via the resistor 19.

Numerals 17 and 18 are resistors for voltage division, which are connected in series, and are interposed between the collector terminal of the power switching transistor 16 and the ground. The control transistor 20 has a collector terminal connected to the resistor 19 and an emitter terminal grounded. Further, its base terminal is connected to the second output port P2 of the microcomputer 26, and when the output voltage of the circuit system power supply 25 drops below a predetermined voltage for some reason, the microcomputer 26 supplies an ON signal. Reference numeral 21 is a bias resistor, 22 and 23 are serially connected resistors for voltage division, which are interposed between the emitter terminal of the power switching transistor 16 and the ground. 24 is the fourth
A backflow prevention diode is inserted between the ignition switch 2 and the input terminal of the circuit system power supply 25.

Reference numeral 25 denotes a circuit system power supply which constantly supplies a constant current output to a microcomputer 26 described later, and is supplied with power from the battery 1 through a fourth backflow prevention diode 24, while at the same time, a power switching transistor 16 and Three
Power is also supplied through the backflow prevention diode 28, and a predetermined voltage lower than the supplied voltage, for example, 5 V is supplied to the microcomputer 26.

Reference numeral 26 is a microcomputer having a collision judgment function and a diagnosis function, and having an A / D converter (not shown) built in on the input side.
Based on an analog acceleration signal (output from an acceleration sensor (not shown)) supplied to the input terminal A, the magnitude of the collision is determined, and when it is determined that the occupant will be seriously injured, the third output port P3 Supplies a pulsed control signal to the switch circuit 9 to turn on the switching transistor for a predetermined time.

The diagnostic function of the microcomputer 26 is for diagnosing the magnitude of the capacitance value of the backup capacitor 6, and when the turn-on of the ignition switch 2 is detected by the power supply voltage detection circuit 29, it is received. The microcomputer 26 has a first output port P
The discharge transistor 15 is alternately turned on and off several times in a predetermined mode from 1 to 1, and the waveforms of the discharge voltage and the charge voltage of the backup capacitor 6 at that time are changed. The connection points of the resistors 22 and 23 are connected in series. When the voltage of D is input and the capacity is calculated from the charge / discharge curve, and it is determined that the calculation result is an abnormal value, the nonvolatile memory 2
The content is stored in 9 and an alarm lamp (not shown) gives an alarm.

Further, the diagnostic function of the microcomputer 26 inputs the voltage at the connection point B of the series resistors 12 and 13, and diagnoses the function of the DC / DC converter 4 from the magnitude thereof. When the off signal of the ignition switch 2 is input from the power supply voltage detection circuit 27, the drive transistor 20 and the power switching transistor 16 are turned on, and the series resistor 1 at that time is turned on.
The function of the power switching transistor 16 is diagnosed by inputting the voltage at the connection point C between the nodes 7 and 18.

Next, the operation of the above configuration will be described. First,
When the ignition switch 2 is turned on, it is detected by the power supply voltage detection circuit 27, the diagnostic function of the microcomputer 26 starts to operate, and the discharge transistor 15 is turned on and off, and the voltage at the point D at that time. The value is read and the backup capacitor 6 is diagnosed.

Next, the voltage value at the point B is read by the microcomputer 26, and the function of the DC / DC converter 4 is diagnosed. On the other hand, when the ignition switch 2 is turned off and the power supply voltage detection circuit 27 detects it, the microcomputer 26 turns on the control transistor 20 and further turns on the power supply switching transistor 16.

As a result, the voltage value at the point C obtained by resistance division of the output voltage of the power switching transistor 16 is read by the microcomputer 26, the function of the power switching transistor 16 is diagnosed from the voltage value at that time, and When any one of the diagnostic functions is diagnosed to be abnormal, an alarm signal is generated and the nonvolatile memory 29
And is read by the microcomputer 26 the next time the ignition switch 2 is turned on, and an alarm lamp (not shown) gives an alarm.

Next, the operation of the system will be described. First, the microcomputer 26 is supplied with electric power at a constant voltage and a constant current from the circuit system power supply 25 which is normally fed through the ignition switch 2 and the backflow prevention diode 24 in series. When the acceleration signal is supplied to the input terminal A, the magnitude of the collision is determined based on the acceleration signal, and the switching transistor of the switch circuit 9 is turned on from the first output port P1 for a predetermined time if necessary. Is supplied to the detonator 10 from the bag-up capacitor 6 to operate the airbag or the like. At this time, it is assumed that the input and output of the acceleration switch 11 are closed.

Next, when the connection line between the anode side of the fourth backflow prevention diode 24 and the ignition switch 2 is broken due to the destruction of the battery 1 at the time of collision, the power supply voltage detection circuit is accordingly caused. 27
However, judging from the fact that the input voltage supplied to it becomes 0 (V), it supplies a signal indicating this to the microcomputer 26. After that, the microcomputer 26
The driving transistor 20 is turned on via the second output port P2. As a result, the power switching transistor 16 is turned on, and the charge of the backup capacitor 6 is supplied to the circuit system power supply 25 via the power switching transistor 16 and the third backflow prevention diode 28.

[0016]

However, in such a vehicle occupant protection device, a discharge circuit of a discharge transistor 15 and a resistor 14 is specially provided in order to diagnose the capacity of the backup capacitor 6. The cost was increased because of the necessity, and it was a place that had to be devised in an industry where cost competition was fierce.

The present invention has been made in view of such a problem, and an object thereof is to enable diagnosis of a backup capacitor without using a special discharge circuit.

[0018]

A vehicle occupant protection system according to the present invention is a DC / DC converter for boosting and outputting a voltage supplied from a battery via an ignition switch, and an output of the DC / DC converter. Backup capacitor connected to the side, detonator, the DC · D
A switch circuit inserted between the output terminal of the C converter and the detonator, and a control signal for controlling the switch circuit on / off by determining the size of the collision accident based on the acceleration signal. The capacity value of the collision judging means, the power supply from the battery for supplying at least the collision judging means to the collision judging means, and the capacity value of the backup capacitor are diagnosed, and the capacity value is judged to be different from the set value. In the case of doing so, a diagnostic means for storing it in the memory, a power supply switching circuit which is inserted between the backup capacitor and the input line of the circuit system power supply and is turned on when the ignition switch is off, and the ignition switch. Power source voltage detecting means for detecting off, and the diagnostic means receives a detection output from the power source voltage detecting means. Then, an ON signal is supplied to the power supply switching circuit, the output voltage of the DC / DC converter, the discharge voltage of the backup capacitor, and the output voltage of the power supply switching circuit are read, and their values deviate from a predetermined reference value. At this time, an alarm signal is created and stored in the memory.

[0019]

According to the vehicle occupant protection system of the present invention, when the ignition switch is turned off, the power transistor is turned on by the diagnostic means of the microcomputer 26, and the power transistor is supplied from the backup capacitor to the circuit system power source. The backup capacitor and the power transistor are diagnosed by diagnosing the voltage change between the input side and the output side, and if there is an abnormality, it is stored in the memory, and the stored contents are, for example, When the ignition switch is turned on, an alarm lamp or the like notifies.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIG.
Although the configuration will be described based on FIG. 1, the hardware configuration is the same in FIG. 1 except that the discharging transistor 15 and the resistor 14 in FIG. 2 are omitted. The diagnostic method is different.

The microcomputer 26 in FIG. 2 starts the diagnostic function when the ignition switch 2 is turned on, while the microcomputer 26 'starts the diagnostic function when the ignition switch 2 is turned off. That is, when the microcomputer 26 'diagnoses the backup capacitor 6 and the power transistor 16, the diagnosis is performed at the following timing.

The microcomputer 26 'starts the diagnostic function when a signal indicating that the ignition switch 2 is turned off is supplied from the power supply voltage detection circuit 27, and the emitter terminal and collector terminal of the power transistor 16 are started. When the voltages at points C and D indicating the side voltage are input and the voltages at points C and D linearly drop from a predetermined voltage to a predetermined voltage in a predetermined time, the backup capacitor 6 and When the voltage at the points C and D, which is judged to be normal with the power transistor 16, drops from a predetermined voltage to a predetermined voltage in a time shorter than a predetermined time, the capacity of the backup capacitor 6 decreases, and It is determined that the transistor 16 is normal. The voltage at the point D linearly drops from a predetermined voltage to a predetermined voltage in a predetermined time.
When the voltage at the point C does not reach the predetermined voltage, the power transistor 16 is determined to be abnormal.

[0023]

As described above, according to the present invention, the circuit configuration can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional circuit.

[Explanation of symbols]

 3, 5, 24, 28 Backflow prevention diode 4 DC / DC converter 6 Backup capacitor 8 Discharge diode 9 Switch circuit 10 Detonator 11 Acceleration switch 16 Power transistor 25 Circuit system power circuit 26 'Microcomputer 27 Power voltage detection circuit 29 memory

Claims (1)

[Claims] 1. A DC / DC converter (4) for boosting and outputting a voltage supplied from a battery (1) through an ignition switch (2), and a backup connected to an output side of the DC / DC converter. Capacitor (6)
And the detonator (10) and the DC / DC converter (4)
And a switch circuit (9) inserted between the output terminal of the switch and the detonator (10) and on / off control the switch circuit (9) by judging the size of a collision accident based on an acceleration signal. For determining the capacity value of the backup capacitor (6) and the circuit system power supply (25) that is supplied from the battery (1) to supply power to the collision determination means at least. Then, when it is judged that the magnitude of the capacitance value is different from the set value, the diagnostic means for storing it in the memory (29), the backup capacitor (6) and the input line of the circuit system power supply (25) And a power supply switching circuit (16, which is inserted between the ignition switch (2) and the ignition switch (2) is turned off).
20) and a power supply voltage detection means (27) for detecting the turning off of the ignition switch (2), and the diagnosis means receives the detection output from the power supply voltage detection means (27). Power supply switching circuit (16, 2
0) for supplying an ON signal to the output voltage of the DC / DC converter (4) and the backup capacitor (6)
Of the discharge voltage and the output voltage of the power supply switching circuit (16, 20), and when those values deviate from a predetermined reference value, an alarm signal is generated and stored in the memory (29). Vehicle occupant protection device.