JP3902328B2 - Vehicle occupant protection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an occupant protection device that protects an occupant by deploying an air bag or the like as needed in an accident.
[0002]
[Prior art]
A conventional vehicle occupant protection device of this type will be described below with reference to FIG.
That is, the output voltage of the on-vehicle battery 1 is supplied to the booster circuit 3 via the ignition switch 2 and boosted, and then the backup capacitor 4 is charged by the boosted voltage. If the microcomputer 6 determines that the microcomputer 6 is a serious accident based on the acceleration signal output from the acceleration sensor 5, the microcomputer 6 turns on the switch circuit 7 to charge the squib 8 and the backup capacitor 4. Discharge the power and deploy the airbag. At this time, the mechanical acceleration switch 9 is naturally turned on.
[0003]
Next, the power supply circuit system of the microcomputer 6 will be described.
When the ignition switch 2 is turned on, the power supply circuit 10 of the circuit system is supplied with power from the in-vehicle battery 1 via the backflow prevention diode 11, supplies a constant voltage V0 to the microcomputer 6, and the program operation of the microcomputer 6 is performed. Be started. Thereafter, the microcomputer 6 detects that the power supply circuit 10 is supplied with power from the in-vehicle battery 1 by reading the first A / D converter 6a incorporated in the microcomputer 6 through the first resistance dividing circuit 12. . On the other hand, when the ignition switch 2 is turned off (or a disconnection equivalent to the ignition switch 2), the second A / D converter 6b incorporated in the microcomputer 6 reads the battery voltage via the second resistance dividing circuit 13. , And the switching transistor 14 is turned on. As a result, the power supply circuit 10 switches to the power supply from the backup capacitor 4 instead of the power supply from the in-vehicle battery 1, and is maintained until the power supply voltage decreases from, for example, 29V to 6V. The computer 6 prohibits turning on the switch circuit 7 for any acceleration signal from the acceleration sensor 5.
[0004]
[Problems to be solved by the invention]
However, in the vehicle occupant protection device described above, when the ignition switch is turned off, if the microcomputer cannot detect the off, for example, an A / D that inputs the output voltage from the second resistance divider circuit. When the input stage of the converter has an open failure, there is a problem that it cannot be determined whether or not the ignition switch is turned off.
[0005]
Therefore, the present invention has been made paying attention to the above problems, and an object thereof is to make it possible to reliably detect the ignition switch being turned off.
[0006]
[Means for Solving the Problems]
According to a first aspect of the vehicle occupant protection device, a backup capacitor that is charged by an output of a booster circuit that inputs an output of a vehicle-mounted battery via an ignition switch, and a charge that is charged in the backup capacitor are converted into a trigger signal. A switch circuit that supplies power to the squib, a microcomputer that determines the scale of a collision based on an acceleration signal, and outputs the trigger signal as necessary, and power is supplied from the in-vehicle battery via the ignition switch And a vehicle occupant protection device including a power supply circuit that is supplied with power from the backup capacitor and supplies a constant voltage to the microcomputer, wherein the microcomputer includes a voltage on an output side of the ignition switch, the power supply The voltage on the input side of the circuit and said When the voltage on the output side of the backup capacitor is input, the voltage on the input side of the power supply circuit is equal to the output voltage of the backup capacitor, and when the voltage on the input side of the power supply circuit falls below a predetermined voltage, the trigger signal Is prohibited from being output.
[0007]
According to a second aspect of the present invention, the microcomputer according to the first aspect inputs the output side voltage of the ignition switch, the input side voltage of the power supply voltage, and the charging voltage of the backup capacitor, and the input side of the power supply circuit. When the voltage is equal to the output voltage of the backup capacitor and the voltage on the input side of the power supply circuit is lower than the predetermined voltage, and the voltage on the output side of the ignition switch is lower than the predetermined voltage, and the input of the power supply circuit When the side voltage falls below a predetermined voltage, the output of the trigger signal is prohibited, and when the voltage on the output side of the ignition switch exceeds a predetermined value, or when the output voltage of the backup capacitor exceeds a predetermined value The trigger signal can be created.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Embodiment 1 of the Invention Will be described with reference to FIG.
In FIG. 1, the same components as those shown in FIG. 2 or the equivalent components thereof are denoted by the same reference numerals, and detailed description thereof is omitted.
That is, in FIG. 1, 20 is a microcomputer, and a third A / D converter 20c is added to the microcomputer 6 of FIG. The first A / D converter 20a and the second A / D converter 20b are the same as the first A / D converter 6a and the second A / D converter 6b shown in FIG. Similarly to the conventional microcomputer 6, when the ignition switch 2 is turned on, the microcomputer 20 supplies a constant voltage V0 to the microcomputer 20 by the power supply circuit 10 of the circuit system, and starts the program operation. .
[0009]
Thereafter, the microcomputer 20 confirms that the power supply circuit 10 is supplied with power from the in-vehicle battery 1 through the first and third resistance dividing circuits 12 and 21, and the first and third A / When the D converters 20a and 20c read and detect, the collision determination is made based on the acceleration signal from the acceleration sensor 5, and the switch circuit 7 can be turned on as necessary.
[0010]
On the other hand, the second A / D converter 20b built in the microcomputer 20 reads through the second resistance dividing circuit 13 that the ignition switch 2 has been turned off (or it may be disconnected). The battery voltage is input and detected, and the voltage supplied from the second resistor divider circuit 13 to the second A / D converter 20b is also input to the comparison circuit 22, and the input voltage falls below the reference voltage 22a. In this case, the switching transistor 14 is turned on, assuming that the ignition switch 2 is turned off. The input terminal of the reference voltage 22 a of the comparison circuit 22 is connected to the microcomputer 20 via the diode 23.
Accordingly, the power supply circuit 10 switches to power supply from the backup capacitor 4 instead of power supply from the in-vehicle battery 1. Further, when the supply voltage to the second A / D converter 20b decreases and the voltages of the first and third A / D converters 20a and 20c become equal, the voltage supplied to the first A / D converter 20a is monitored, When the power supply voltage to the first A / D converter 20a decreases from, for example, 29V to 6V, the microcomputer 20 prohibits the switch circuit 7 from being turned on for any acceleration signal supplied from the acceleration sensor 5. .
[0011]
The third resistance dividing circuit 21 resistance-divides the charging voltage of the backup capacitor 4 and supplies it to the third A / D converter 20 c of the microcomputer 20. A comparison circuit 22 has a reference voltage 22a for determining whether the ignition switch 2 is turned on or off, for example, 6V. When the output voltage from the second resistance divider circuit 13 falls below the reference voltage 22a, the ignition switch 2 Is turned off and a signal for turning on the switching transistor 14 is output.
[0012]
Next, the operation of the above configuration will be described.
(When everything works normally)
When the ignition switch 2 is turned on, the microcomputer 20 is supplied with the constant voltage V0 from the power supply circuit 10, and when the first A / D converter 20a reads a voltage higher than a predetermined value, the microcomputer 20 performs a program operation. Is started, a collision is determined based on the acceleration signal supplied from the acceleration sensor 5, the switch circuit 7 is turned on as necessary, and an ignition current is supplied from the backup capacitor 4 to the squib 8.
[0013]
On the other hand, when the ignition switch 2 is turned off (or it may be an equivalent disconnection), the voltage supplied from the second resistance divider circuit 13 to the comparison circuit 22 falls below the reference voltage 22a. The circuit 22 switches the output to a low level, and the power supply circuit 10 switches to the power supply from the backup capacitor 4 instead of the power supply from the in-vehicle battery 1 so as to extend the operation of the diagnostic function of the microcomputer 20 for a long time. .
Further, the voltage from the second resistance dividing circuit 13 is supplied to the second A / D converter 20b of the microcomputer 20, and recognizes that the ignition switch 2 is turned off by the microcomputer 20 and outputs a high level signal via the diode 23. Then, the switching transistor 14 is turned on by switching to a voltage higher than the reference voltage 22a. Further, the voltage of the backup capacitor 4 is lowered, and the input voltage of 20a to the power supply circuit 10 is read, for example, 6V or less, and it is prohibited to turn on the switch circuit 7 for any acceleration signal supplied from the acceleration sensor 5. .
[0014]
(When the input terminal of the second A / D converter 20b fails and the microcomputer 20 reads the intermediate potential)
When the ignition switch 2 is turned off, the voltage supplied from the second resistance dividing circuit 13 to the microcomputer 20 should drop to a predetermined value or less, but the second A / D converter 20b is broken. The microcomputer 20 can read only the intermediate potential. On the other hand, since the output from the second resistance dividing circuit 13 is input to the comparison circuit 22, when the voltage falls below the reference voltage 22a, the switching transistor 14 is turned on and the power charged in the backup capacitor 4 is supplied to the vehicle. The power is supplied to the power supply circuit 10 instead of the power from the battery 1. As a result, the input voltages of the first and second A / D converters 20a and 20b become equal, so that the microcomputer 20 recognizes that the ignition switch has been turned off and the voltage of 20a becomes, for example, 6 V or less. It is prohibited to turn on the switch circuit 7 for any acceleration signal supply.
[0015]
On the other hand, when the ignition switch 2 is turned on, the comparison circuit 22 turns off the switching transistor 14 because the voltage from the second resistance dividing circuit 13 exceeds the reference voltage 22a. Thereafter, when the microcomputer 20 receives the supply of the constant voltage V0 from the power supply circuit 10 and further reads that the first A / D converter 20a and the third A / D converter 20c are not equal, the microcomputer 20 performs the program operation. Start.
[0016]
【The invention's effect】
As described above, according to the present invention, even if the function (open failure) of the A / D converter of the microcomputer is lost, it is possible to reliably turn on the changeover switch and further to inhibit the generation of the ignition signal. Demonstrated.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a circuit block according to a first embodiment of the present invention.
FIG. 2 is a circuit block diagram of a conventional device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vehicle-mounted battery 2 Ignition switch 4 Backup capacitor 5 Acceleration sensor 7 Switch circuit 10 Power supply circuit 20 Microcomputer

Claims (2)

A backup capacitor that is charged by the output of the booster circuit that inputs the output of the in-vehicle battery via the ignition switch, a switch circuit that supplies the charge charged to the backup capacitor to the squib upon receipt of a trigger signal, and acceleration The microcomputer determines the size of the collision based on the signal and outputs the trigger signal as necessary, and is supplied from the vehicle battery via the ignition switch and supplied from the backup capacitor, In the vehicle occupant protection device including a power supply circuit that supplies a constant voltage to the computer, the microcomputer includes: an output side voltage of the ignition switch; an input side voltage of the power supply circuit; and an output side of the backup capacitor. Input voltage The vehicle is characterized by prohibiting the output of the trigger signal when the voltage on the input side of the power supply circuit is equal to the output voltage of the backup capacitor and the voltage on the input side of the power supply circuit falls below a predetermined voltage. Occupant protection device. The microcomputer inputs the voltage on the output side of the ignition switch, the voltage on the input side of the power supply voltage, and the charging voltage of the backup capacitor, and the voltage on the input side of the power supply circuit and the output voltage of the backup capacitor are And when the voltage on the input side of the power circuit falls below a predetermined voltage, and the voltage on the output side of the ignition switch falls below a predetermined voltage, and the voltage on the input side of the power circuit falls below a predetermined voltage, The trigger signal is prohibited from being output, and the trigger signal can be created when the voltage on the output side of the ignition switch exceeds a predetermined value or when the output voltage of the backup capacitor exceeds a predetermined value. The vehicle occupant protection device according to claim 1.

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