JPH06171454A - Air bag unit - Google Patents

Abstract

PURPOSE:To provide an air bag unit equipped with a backup power source which is compact in size and excellent in reliability. CONSTITUTION:This air bag unit is provided with a booster circuit to be normally operated by a battery 4 and a backup power source 1 with a condenser being always made into a charged state at fairly higher voltage than that of the battery 4 owing to this circuit, through which two air bags 11 and 12 are unfolded and driven by electric power to be fed out of this backup power source 1 only in the case where a supply of power from the battery 4 is interrupted. With this constitution, the condenser of the backup power source 1 is in an unloaded state when power out of the battery 4 is feeding, and that since it is charged by a sufficiently higher voltage than that of the battery 4, the booster circuit and the condenser can be miniaturized, so that this compact and highly reliable air bag unit is readily provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air bag device for protecting an occupant when a vehicle is subjected to an extreme deceleration such as a collision, and more particularly to an air bag device suitable for an automobile.

[0002]

2. Description of the Related Art In recent years, the usefulness of an air bag device has come into widespread attention as a device for protecting an occupant from extreme deceleration such as when an automobile collides. It is customary that the control operation requires electric power, and therefore, in order to ensure its reliability, it is necessary to ensure the supply of electric power to the airbag device even in the event of a collision.

Therefore, various types of backup systems for power supplies for airbag devices have been proposed in the past. For example, in Japanese Patent Publication No. 58-23263, a main power source using a battery and a backup system charged by the main power source are proposed. A method in which an auxiliary power supply with a capacitor is provided, and this auxiliary power supply is connected in parallel to the main power supply via a diode so that when the power supply from the main power supply is cut off, the auxiliary power supply supplies power. Is proposed. In this conventional example, a mechanical acceleration sensor is used as the crash sensor.

In addition to the above-mentioned conventional technique, as a method of backing up the power source of the air bag device, the power source voltage is boosted, the backup capacitor is charged with this boosted voltage, and the air bag is always used from this capacitor. Methods of supplying power to the device are also known.

[0005]

The above-mentioned prior art does not take into consideration the case of applying it to an electronic air bag device using an electronic crash sensor and a micro computer, and it has a large size. Since a backup capacitor is required, there is a problem in terms of downsizing the device.

That is, as described above, the role of the auxiliary power source is to protect the airbag device by destroying the battery, which is the main power source, or disconnecting the power source wiring when the airbag needs to be operated due to a collision or the like. Even if the supply of power to the air bag is cut off, there is no problem in starting the airbag device.

However, in the air bag device having a mechanical type acceleration sensor as a main constituent element as in the above-mentioned prior art, the electronic circuit used for its operation is small in scale, and therefore the power consumption is also low. The backup capacitor was also small in size, because it works well with a small number of small auxiliary power supplies.

However, in recent years, an electronic air bag device using an electronic crash sensor, which is becoming mainstream in recent years, and using a micro computer, requires a large number of electronic circuits and consumes several times as much as the conventional technology. Requires electric current. Therefore, when the above-mentioned conventional technique is applied to an air bag system that uses a large number of electronic circuits like such an electronic device, an extremely large backup capacitor is required, which makes the air bag device compact. It becomes an obstacle to the conversion.

On the other hand, the same applies to the prior art in which the power source voltage is boosted and the boosted voltage is charged in the backup capacitor to always be used as the power source of the air bag device. In this case, it is applied to the electronic air bag device. If so, the output current of the backup power supply requires a current close to 100 milliamperes, and thus a large-scale power supply circuit is also required.

At this time, it is possible to reduce the capacitance value of the backup capacitor by further increasing the charging voltage of the backup capacitor. In this case, however, the output voltage is increased as the voltage of the booster circuit increases. Although the current decreases, the capacity of the backup capacitor can be reduced, but the scale of the booster circuit also increases, and there is a problem that the circuit scale must be increased.

An object of the present invention is to provide a power supply to an air bag device even after the power supply to the air bag device has been cut off.
It is an object of the present invention to provide an air bag device equipped with a compact and highly reliable backup power supply that can normally operate an air bag for several seconds.

[0012]

The above-described object is to provide a power supply using a boosting means that operates by being supplied with power from a power supply and a backup capacitor that is charged with a voltage boosted from the power supply voltage by this boosting means. This is achieved by operating the airbag device by the electric charge (electric power) charged in the backup capacitor only when the power supply from the power supply is cut off.

[0013]

The boosting means charges the backup capacitor with a voltage boosted from the power supply voltage when the power supply is normal. In this state, the backup capacitor is cut off from other circuit systems, so the load of the boosting means is only the charging power of the backup capacitor. Therefore, at this time, the power required to charge the backup capacitor is extremely high. Since it is a minute value, the boosting means need only have a small capacity.

Since the amount of electric power that can be charged in the backup capacitor is represented by the product of the capacitance value of the backup capacitor and the charged voltage value, the backup capacitor having the same capacitance value can be obtained by increasing the voltage by the boosting means. Since a large amount of electric power can be charged, the backup capacitor can be miniaturized, and the boosting means can be miniaturized, so that an airbag device having a compact backup power source can be obtained. Become.

[0015]

The air bag device according to the present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is an embodiment of the present invention, in which the present invention is applied to an air bag device for an automobile. In the figure, 1 is a backup power supply, 2 is a switching circuit, 3 is an ignition switch, 4 is a battery, 5 is a crash sensor, 6
Is a microcomputer 6, 7, 8, 13 is a drive circuit,
9, 10 are squibs, 11 and 12 are airbags, 14
Is a safing sensor, 15 is an alarm lamp, and 16
Is a crash recorder 16.

The operating power for the air bag device is
The power supply wiring a directly connected to the battery 4 and the battery 4
The power supply wiring b is connected via the ignition switch 3 from the two wirings. The backup power supply 1 serves as a standby power supply for normally operating the device for a certain period of time when the battery 4 is broken due to a collision or when the power supply to the airbag device is stopped due to the disconnection of the power supply wiring. It is a thing.

The switching circuit 2 supplies power to the device.
The power source wiring a is directly connected to the battery 4 and the power source wiring b is connected to the battery 4 via the ignition switch 3. The crash sensor 5 detects a large acceleration (deceleration) due to a collision of an automobile, and inputs this signal to the microcomputer 6.

The microcomputer 6 determines the presence / absence of a collision from the signal from the crash sensor 5, and when it determines that there is a collision, it drives the drive circuits 7, 8 and 13 to ignite the squibs 9 and 10. Squib 9 and 10,
It is a well-known thing that generates compressed gas by the explosion of explosive, and the compressed gas generated by ignition of these squibs 9 and 2
The individual airbags 11 and 12 are inflated to protect the occupants.

The safing sensor 14 includes a squib 9,
10 is a mechanical switch connected in series between the drive circuit 13 and the drive circuit 13 to close the contacts at low acceleration, and has a function of preventing the squibs 9 and 10 from being erroneously ignited by a malfunction of the microcomputer 6. To do. The alarm lamp 15 functions to inform the driver of a failure of the airbag device. The crash recorder 16 has a function of recording information when a failure occurs and information when a collision occurs.

2 and 3 show the details of the switching circuit 2. The switching circuit 2 in this embodiment is
It is composed of a transistor 201, resistors 204, 205 and 207, diodes 202 and 203, and a drive gate (inverter) 206.
Is connected to the backup power supply 1 via the transistor 201 which functions as a switch for turning it on and off, and the diode 203.
Power wiring b connected via the ignition switch 3
Are connected to the backup power supply 1 via the diode 202.

The transistor 201 is on / off controlled by the microcomputer 6 via the drive gate 206 and the resistor 204, so that the power supply line a directly connected to the battery 4 is connected or disconnected. It has become. Further, the power supply wiring b via the ignition switch 3 is connected to the microcomputer 6 via the resistors 205 and 207, and when the ignition switch 3 is closed, the voltage value of the power supply wiring b is changed to the microcomputer 6 In this way, the microcomputer 6 can detect the on / off state of the ignition switch 3.

Next, the control contents of the switching circuit 2 will be described with reference to the flowchart of FIG. When this process is started, first, the microcomputer 6 causes the transistor 20 to
1 is turned on (S1). Then, after this, the state of the ignition switch 3 is constantly monitored (S2), and when the ignition switch 3 is turned off, the transistor 201 is turned off after 10 seconds (S3, S).
4).

In this embodiment, by providing the switching circuit 2, the following advantages can be obtained. That is, first of all, two power supply lines can be secured. That is, even if one of the power supply lines is cut due to a collision of an automobile, power can be supplied from the other power supply line. Therefore, the reliability of the airbag device can be greatly improved. Secondly, when the ignition switch 3 is turned off, both power supplies are completely cut off after 10 seconds, so that the current consumption can be reduced to zero. Therefore, the load on the battery 4 when the ignition switch 3 is off can be reduced. Thirdly, since the power supply to the backup circuit 1 can be made completely zero, the backup power supply 1 can be self-diagnosed every time the ignition switch 3 is turned off. That is, since the backup power supply 1 can be frequently diagnosed, the failure of the backup power supply 1 can be detected early.

Next, FIG. 4 shows the details of the backup power supply 1 in this embodiment. The backup power supply 1 in this embodiment includes a coil 401 and a transistor.
(FET) 403, 411, resistor 407, diode 40
2, 404, 405, 406, backup capacitors 408, 409, 410, a comparator 412, and a reference voltage source 413.

The coil 401 and the transistor 403 form a booster circuit, and when electric power (voltage) is supplied to the microcomputer 6 from the power source battery 4 through the switching circuit 2, the microcomputer 6 causes the transistor 403 to operate. A pulse signal is supplied so that the transistor 403 is on / off controlled at a predetermined cycle.

As a result, the transistor 403 is connected to the coil 4
The current flowing through 01 is turned on and off, which causes the coil 40
A high voltage is generated at both ends of 1 to operate as a booster circuit. Therefore, the high voltage generated in the coil 401 is rectified by the diodes 404, 405, 406 to obtain a DC voltage higher than the voltage of the power supply, and the backup capacitors 408, 409, 410 are charged with this voltage.

On the other hand, the comparator 412 compares the voltage supplied from the battery switching circuit 2 with the voltage of the reference voltage source 413. Therefore, the microcomputer 6
Detects that the power supply from the battery switching circuit 2 is turned off by the output of the comparator 412,
1 is turned on, whereby the electric charge charged in the backup capacitor 410 is controlled so as to be supplied as the power source of the microcomputer 6. This allows the microcomputer 6 to operate normally for several seconds even after the power supply from the battery 4 is interrupted.

Also, backup capacitors 408, 4
The electric charges charged in 09 are supplied to the drive circuits 7 and 8, respectively. As a result, each squib 9, 10 can be guaranteed sufficient energy necessary for its operation even after the power supply is stopped, so that the squib 9, 10 can be reliably ignited.

It should be noted that this is the same as in this embodiment.
It is further clarified by comparing the case where the backup capacitors 408 and 409 are provided independently in the drive circuits 7 and 8 and the case where one backup capacitor is provided in common to these. That is, the squibs 9 and 10 are ignited with a time lag. Therefore, if the backup capacitor is common, the squib that is first ignited will discharge the charge stored in the backup capacitor, and when igniting the second squib, the charge in the backup capacitor will ignite the squib. This is because the amount of electric charge required for the operation is insufficient and the second squib cannot be ignited.

Therefore, according to the backup power source 1 according to the embodiment shown in FIG. 4, even when the battery 4 is destroyed and the power source of the air bag device is shut off at the time of collision of the automobile,
The plurality of airbags 11 and 12 can be surely inflated, and sufficient safety can be ensured.

Next, FIG. 5 shows the drive circuits 7, 8 and 1
3, the driving circuit 7 is a microcomputer.
It operates by the signal generated at the terminal P1 of the power supply 6 and functions to connect the squib 9 to the output of the backup power supply 1,
Further, the drive circuit 8 is connected to the terminal P2 of the microcomputer 6.
The squib 10 is connected to the output of the backup power supply 1 by the signal generated by the backup power supply 1. The drive circuit 13 is connected to the terminals P3 and P of the microcomputer 6.
It operates by the signal generated in 4 and the safing sensor 1
It functions to turn on the connection of the squibs 9 and 10 to the ground via the switch 4 and to turn on the alarm lamp 15. These drive circuits will be sequentially described in detail below.

First, the drive circuit 7 includes a transistor 70.
4 and 705 and resistors 701, 702 and 703. When the terminal P1 of the microcomputer 6 is low level, the transistor 704 and the transistor 70 are provided.
Both 5 are turned off so that the backup power supply 1 and the squib 9 are cut off so that the squib 9 does not ignite. When the terminal P1 of the microcomputer 6 becomes high level, the transistor 704
And the transistor 705 are both turned on, and serve to connect the backup power supply 1 and the squib 9.

Therefore, at this time, the safing sensor 1
4 and the drive circuit 13 are both on, the squib 9
A current flows through the squib 9 and the squib 9 can be ignited.

Next, the drive circuit 8 includes a transistor 80.
No. 4, 805 and resistors 801, 802, 803 have the same internal configuration as the drive circuit 7, and are controlled by the signal level of the terminal P2 of the microcomputer 6, and , When the safing sensor 14 and the drive circuit 13 are both in the ON state, they serve to control the ignition of the squib 10.

The drive circuit 13 includes a transistor 13
01, 1303, 1306 and resistors 1302, 130
4, 1305, and AC amplifiers 1307 and 1308. Then, the transistors 1303 and 1
Reference numeral 306 denotes an N-type junction field effect transistor, which functions as a switching element that is turned off when the voltage between the gate and the source is negative, and turned on when it is zero or positive.
The AC amplifiers 1307 and 1308 are circuits that output negative voltage when a specified number of pulse signals or more are input to the input and output zero when the input has a fixed value (high level or low level). is there. The internal configuration and operation of these AC amplifiers 1307 and 1308 will be described later.

First, the operation of connecting the squibs 9, 10 to the ground, which is the first purpose of the drive circuit 13, will be described. The squibs 9 and 10 are connected to the ground when the microcomputer 6 applies a pulse signal to both the signals P3 and P4.

That is, when a pulse signal is applied to the signals P3 and P4, the outputs of the AC amplifiers 1307 and 1308 become negative voltage. This negative voltage turns on transistor 1301 and connects squibs 9 and 10 to ground. Then, when the signal P4 is a fixed output (high level or low level), the output of the AC amplifier 1308 is zero, and therefore the transistor 1303 is turned on, so that even if one of the AC amplifiers is turned on. 130
Even if a pulse signal is given to 7, the AC amplifier 130
The output of 7 cannot go negative and is kept at zero,
Therefore, the transistor 1301 remains off and the squibs 9, 10 remain isolated from ground.

Here, the AC amplifier 1307 outputs the signal P3.
Is designed to generate a negative voltage at the output, while the AC amplifier 1308 generates a negative voltage at the output when a pulse signal of 10 or more pulses is applied to the signal P4. In addition, the output is designed to be zero when the input signal is interrupted for a time corresponding to one pulse or more.

Therefore, in order to ignite the squibs 9 and 10 to inflate the airbag, a pulse signal of 10 or more pulses is given as the signal P4 and one pulse is given as the signal P3. Due to
The signal P4 serves as a normal signal, and the signal P3 serves as a signal for igniting the squib.

As a result, after the microcomputer 6 is reset, the signal P4 is not generated during the unstable period until the microcomputer 6 operates normally and during the runaway. Therefore, according to this embodiment, the squibs 9 and 10 are generated. The risk of erroneous ignition can be eliminated, and the ignition responsiveness of the squibs 9 and 10 at the time of collision can be secured.

Next, the driving of the alarm lamp 15 will be described. The alarm lamp 15 is turned on when the transistor 1306 is turned on, and therefore the signal P
4 is turned on when the pulse signal is not given, and is turned off when the pulse signal is given to the signal P4.

Therefore, when the microcomputer 6 runs out of control and cannot output a pulse signal to the terminal P4, or when the switching circuit 2 or the backup power supply 1 fails, the microcomputer 6 is not supplied with power. Further, even when the power supply wiring is disconnected and the air bag device is not supplied with power, the alarm lamp 15 is turned on, and the occupant can be notified of the failure.

Next, FIG. 6 shows AC amplifiers 1307 and 13
08 shows the details of each of them, and they have the same circuit configuration, and capacitors 601 and 604, respectively.
And diodes 602 and 603, and a resistor 605.

Therefore, when a high level (5 volt) signal is applied to the input IN of these circuits, a current flows through the capacitor 601 through the diode 602, and the capacitor 601 is charged to the voltage of 5 volt. Next, immediately after this, when the input IN is set to low level (0 volt), the voltage at the other end of the capacitor 601 (right side in the drawing) becomes -5 volt,
Therefore, the capacitor 604 is charged with this -5 volt voltage through the diode 603. By repeating such an operation, by applying a pulse signal to the input IN, a negative voltage (-5 volts) can be generated at the output OUT.

Then, at this time, by appropriately selecting the capacitance values of the capacitors 601 and 604, the response characteristic of this circuit, that is, a negative voltage (-5 V) at the output is obtained.
It is possible to change the number of input pulses required to generate the pulse current.
As a signal 07, when one pulse is given to the signal P3, it is designed to generate a negative voltage at the output.
Is designed so that a negative voltage is generated in the output when a pulse signal of 10 pulses or more is given to the signal P4, and conversely, the output becomes zero when the input signal is interrupted for a time corresponding to one pulse or more. Of.

Therefore, according to the above embodiment, even when the power supply to the air bag device is cut off,
It is possible to easily obtain a small-sized and highly reliable backup power supply which can sufficiently operate the airbag normally for several seconds after the power supply is cut off.

Further, according to the above embodiment, since two power supply lines are secured, even if one power supply line is cut due to a collision of a car, the other power supply line can supply power. Therefore, the reliability of the airbag device can be greatly improved. Furthermore, in the above embodiment, the power is completely disconnected from the power source 10 seconds after the ignition switch is turned off, so that the current consumption can be reduced to zero, thus reducing the load on the battery when the ignition switch is off. can do. As a result, the power supply to the backup circuit can be made completely zero, so that the backup power supply can be self-diagnosed every time the ignition switch is turned off. That is, since the backup power supply can be frequently diagnosed, the failure of the backup power supply can be detected early.

Further, according to this embodiment, there is no risk that the squib will be erroneously ignited during an unstable period after the reset of the microcomputer until it normally operates, or during a microcomputer runaway. It is possible to secure ignition response of the squib at the time of collision.

In this embodiment, when power is not supplied to the microcomputer due to a runaway of the microcomputer or due to a failure of the switching circuit or the backup power supply, the power supply wiring is disconnected and the air is blown. When power is not supplied to the bag device, the alarm lamp is turned on, and the occupant can be notified of the failure.

[0050]

According to the present invention, when the power supply is normal, the voltage boosted from the power supply voltage is constantly charged in the backup capacitor, and in this state, the backup capacitor is cut off from other circuit systems. As a result, the load of the boosting means can be reduced, and therefore the boosting means need only have a small capacity.

Since the amount of electric power that can be charged in the backup capacitor is represented by the product of the capacitance value of the backup capacitor and the charged voltage value, the backup capacitor having the same capacitance value can be obtained by increasing the voltage by the boosting means. Since a large amount of electric power can be charged, the booster can be downsized and the backup capacitor can be downsized, the backup power supply can be sufficiently downsized, the reliability is high, and the overall size is sufficiently low. A simplified air bag device can be provided easily and surely.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an airbag device according to the present invention.

FIG. 2 is a configuration diagram of a switching circuit according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating a control process of a switching circuit according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a backup power supply according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a drive circuit according to an embodiment of the present invention.

FIG. 6 is a configuration diagram of an AC amplifier according to an embodiment of the present invention.

[Explanation of symbols]

 1 Backup Power Supply 2 Switching Circuit 3 Ignition Switch 4 Battery 5 Crash Sensor 6 Micro Computer 7 Drive Circuit 8 Drive Circuit 9, 10 Squibb 11, 12 Airbag 13 Drive Circuit 14 Safing Sensor 15 Alarm Lamp 16 Crash Recorder

Front page continuation (72) Inventor Satoshi Kuragaki No. 1-1 Omika-cho, Hitachi City, Hitachi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Masayoshi Suzuki, Katsuta City, Ibaraki 2520 Takaba, Hitachi Ltd. Factory Automotive Equipment Division

Claims (4)

[Claims] 1. A device for deploying and driving an airbag, which has a sensor for detecting a collision acceleration of a vehicle, and means for boosting the power supply voltage when the power supply voltage is normally maintained, and charging by the boosted voltage. And the capacitance that is
An air bag device characterized in that when the power supply voltage drops, the air bag is inflated and driven by using the electric charge charged in the capacitance as a power source. 2. The air bag device according to claim 1, wherein a plurality of the air bags are installed, and the capacitance is installed for each of the plurality of air bags. 3. The invention according to claim 1, wherein the wiring from the power source for the means for boosting the power source voltage is directly connected to the power source and the wiring connected to the power source through an ignition switch of an automobile engine. The air bag device is characterized by being provided with a means for cutting off the supply of electric power by the wiring directly connected to the power source and a means for detecting the state of the ignition switch. 4. The invention according to claim 1, wherein the driving of expanding the air bag is controlled by a microcomputer, and a signal generated when the microcomputer is operating normally and a signal detected by the sensor. An air bag device, characterized in that the deployment drive of the air bag is executed according to a logical product condition of both.