JP4248233B2 - Airbag starter - Google Patents

Description

  The present invention relates to an airbag device that is mounted on an automobile or the like and protects an occupant when a collision accident occurs, and more particularly to an airbag activation device that reliably inflates an airbag.

  FIG. 1 is a circuit diagram showing a conventional air bag starting device. In FIG. 1, 101 is a squib for inflating an air bag, 102 and 103 are semiconductor switches connected in series across the squib 101, 104 is a collision, etc. This mechanical sensor detects an impact, and is connected in series with the semiconductor switch 102 and is connected to the power source 120 via a backflow prevention diode 118 and an ignition switch 119.

A current control circuit 105 conducts a limited current that causes the semiconductor switch 102 to conduct and inflate the air bag to the squib 101, and 106 periodically sends a constant current that does not cause the air bag to expand to the squib 101, thereby causing a potential difference between both ends of the squib. The squib measurement circuit 107 detects a reference power supply, 107 is connected in series to the reference power supply 107 via a resistor 109, and is a resistor that determines the input of the current control circuit 105, that is, the potential at the connection point P, and 110 is current control A resistor 111 is connected between the circuit 105 and the reference power source 107. A microcomputer 111 drives the current control circuit 105 and calculates a squib resistance value based on the potential difference detected by the squib measurement circuit 106 (hereinafter referred to as a microcomputer). , 112 abbreviated as a microcomputer), 112 is an acceleration sensor for detecting an impact such as a collision, 13 is a backup capacitor connected between the power supply side and ground 114 of the mechanical sensor 104. Note that the current control circuit 105, the squib measurement circuit 106, and the peripheral circuits thereof are constituted by semiconductor integrated circuits.

FIG. 2 shows a specific configuration of the current control circuit 105. The comparator 115 compares the potential of the connection point P between the resistor 108 and the resistor 109 and the potential of the reference power source 107 via the resistor 110, and the resistor 110. And a squib 101 are connected in series, and a semiconductor switch 116 that conducts in response to the output from the comparator 115, and a semiconductor switch 117 that is conduction-controlled by the microcomputer 111 and connects the comparator 115 to the reference power source 107, Have Note that the comparator 115 changes the input voltage to be compared due to the voltage drop of the resistor 110 due to the current flowing through the semiconductor switch 116, and as a result, changes the output to keep the current flowing through the semiconductor switch 102 constant. Operates on.

  FIG. 3 shows a specific configuration of the squib measuring circuit 106. A first reference power source 121, a switching element 122, and a constant current circuit 123 are connected in series with the squib 101, and second and third reference power sources 124 are connected. , 125 and an amplifier 126 for detecting and amplifying a potential difference between both ends of the squib 101. The amplifier 126 includes resistors 127 and 128 connected to respective terminals of the squib 101, a comparator 129, a resistor 130 connected between the non-inverting terminal of the comparator 129 and the third reference power supply 125, The resistor 131 is connected between the inverting terminal of the comparator 129 and the output terminal. The first to third reference power supplies 121, 124, and 125 may be prepared as separate and independent power supplies, but may be created based on one reference power supply, for example.

Next, the operation will be described.
When the ignition switch 119 is closed, the backup capacitor 113 is charged via the backflow prevention diode 118. On the other hand, a reference current flows from the reference power source 107 to the series circuit of the resistor 109 and the external resistor 108 , and a constant potential is generated at the connection point P.

In this state, when the switching element 122 of the squib measurement circuit 106 is turned on in response to a conduction signal periodically supplied from the microcomputer 111, the first reference power supply 121 passes through the switching element 122, the squib 101, and the constant current circuit 123. Thus, a constant current without causing the air bag to expand in the squib 101 flows. At this time, the potential difference of the squib 101 is detected by the amplifier 126 and the detected value is supplied to the microcomputer 111. If this potential difference cannot be detected, it is possible to detect that the squib circuit is disconnected or the like. The microcomputer 111 calculates the resistance value of the squib 101 based on the supplied detection value and stores it in an internal memory (not shown).

  When a shock is applied to the vehicle and a detection signal required to deploy an air bag is supplied from the acceleration sensor 112 to the microcomputer 111, the semiconductor switch 117 is turned on in response to the conduction signal from the microcomputer 111, and the comparator 115 is turned off. The semiconductor switches 102 and 116 are turned on by an output based on the potential of the connection point P input to the inverting terminal and the potential of the reference power supply 107 input to the inverting terminal via the resistor 110.

  Due to the conduction of the semiconductor switch 116, a voltage drop occurs in the resistor 110 based on the flowing current, and an output determined by comparing the potential based on this voltage drop and the potential of the resistor 109 at the point P is output from the comparator 115 to the semiconductor switch. 102, the conduction amount of the semiconductor switch 102 is kept constant, and a prescribed air bag developed current flows from the backup capacitor 113 and the power source 120 to the squib 101.

Since the conventional air bag device is configured as described above, it is possible to measure whether or not the squib is normal, but the outputs of the resistors 109 and 110 and the comparator 115 that determine the input potential of the comparator are used. Due to variations in the characteristics of the semiconductor switches 102 and 116 that determine the amount of conduction, the amount of conduction of the semiconductor switch 102 cannot be maintained at a specified amount, and the amount of current flowing through the squib varies when the air bag is deployed. For this reason, if the squib allows the current close to the specified value necessary for the squib to inflate the air bag, the current flowing through the squib also changes due to the above variation, and the air bag cannot be inflated. Cases arise. For this reason, a large-capacity backup capacitor is required so that the air bag can be reliably inflated even if the above variations occur, and a large-capacity, large-scale backup capacitor must be used. There is a problem that the configuration becomes large and expensive.

  The present invention has been made to solve the above-described problems, and a backup capacitor having a small size and a small capacity capable of flowing a current close to a specified value necessary for the squib to inflate the air bag device. An object of the present invention is to obtain an air bag activation device that can be used to reliably activate an air bag.

An air bag starter according to the present invention includes a squib for inflating an air bag, a mechanical sensor for impact detection connected in series with the squib, and a semiconductor connected in series with the squib to change the energization amount based on the input amount. A switch, an acceleration sensor for detecting the magnitude of impact at the time of a collision, a squib measuring circuit for periodically detecting a potential difference between both ends of the squib by supplying a constant current that does not cause the air bag to expand on the squib, and a reference power source and the ground. It has at least two resistors connected in series and a comparator that inputs the potential of the connection point of the two resistors to one input terminal and inputs the potential of the reference power supply to the other input terminal via the resistor. A current control circuit that changes the output of the comparator in response to a change in the potential of the point, and one of two resistors connected in series selectively connected in parallel and connected in series A plurality of resistors that change the potential at the connection point of the two resistors and a constant current that does not cause the air bag to expand from the squib measurement circuit to the squib measurement circuit are periodically activated and detected via the squib measurement circuit. A resistance value of the squib is calculated based on the potential difference of the squib and stored in a built-in memory, and when it is determined that air bag expansion is necessary based on the detection signal from the acceleration sensor, a comparator in the current control circuit The resistance value stored in the memory by inputting the potential difference generated in the squib through the squib measurement circuit at that time, causing the semiconductor switch to conduct by the output of this comparator and causing the current in the air bag development to flow through the squib. To calculate the current value that flows through the squib, and connect and disconnect multiple resistors so that this current value exceeds the specified value. Selectively performed, by increasing the input amount to the semiconductor switch from the comparator of the current control circuit, in which an arithmetic circuit to flow a sufficient predetermined amount of current to deploy the airbag squib .

  As a result, when the airbag is inflated, the current flowing through the squib can be adjusted to a specified value at all times, and the current necessary for inflating the airbag can be reliably passed through the squib. As a result, since it is not necessary to use a backup capacitor having a larger capacity than necessary, it is possible to use a small-sized backup capacitor having a small capacity.

Arithmetic circuit airbag activation apparatus according to the present invention is a microcomputer, Ri by the switching of the port of the microcomputer, and performs connection and disconnection of the resistor.
Depending on this, there is the effect that the connection and disconnection of the resistor can be automatically performed by the microcomputer.

  According to the airbag starter according to the present invention, when the airbag is inflated, the current flowing through the squib can always be adjusted to a specified value, and a small-sized backup capacitor having a small capacity can be used. Further, the resistance can be automatically connected and disconnected by a microcomputer which is an arithmetic circuit.

Hereinafter, in order to describe the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
In FIG. 4, 1 is a squib for inflating an air bag, 2 is a semiconductor switch connected in series across the squib 1, and 4 is a mechanical sensor for detecting an impact such as a collision. In addition to being connected, it is connected to a power source 20 via a backflow preventing diode 18 and an ignition switch 19.

Reference numeral 5 denotes a current control circuit for causing the semiconductor switch 2 to conduct and supplying a specified amount of current to inflate the air bag to the squib 1. Reference numeral 6 denotes a constant current that does not cause the air bag to expand periodically. squib measurement circuit for detecting, 7 reference power supply, 8 connected in series through a resistor 9 to the reference power supply 7, resistance that determine the input of the current control circuit 5, 8a-8n by switch 9a~9n a resistor which is selectively connected in parallel with the resistor 8. Reference numeral 10 denotes a resistor connected between the reference power supply 7 and the current control circuit 5, and reference numeral 11 denotes a microcomputer as an arithmetic circuit that drives the current control circuit 5 and calculates the resistance value of the squib based on the potential difference detected by the squib measurement circuit 6. (Hereinafter abbreviated as a microcomputer), 12 is an acceleration sensor for detecting an impact such as a collision, and 13 is a backup capacitor connected between the power supply side of the mechanical sensor 4 and the ground 14. Note that the current control circuit 5, the squib measurement circuit 6, and its peripheral circuits are constituted by semiconductor integrated circuits.

Figure 5 shows a specific configuration of the current control circuit 5, a comparator 15 for comparing the potential of the reference power source 7 via the potential and resistance 10 of the connection point P between the resistor 8 and the resistor 9, A semiconductor switch 16 connected in series between the resistor 10 and the squib 1 and conducting by receiving an output from the comparator 15, and a semiconductor switch 17 connected by the microcomputer 11 and connected to the reference power supply 7 by the microcomputer 11. And have. The semiconductor switch 16 changes the difference in the input voltage of the comparator 15 due to the voltage drop of the resistor 10 due to the current flowing therethrough, and as a result, the output flows to change the current flowing through the semiconductor switch 2 to a specified amount. Operates to keep.

FIG. 6 shows a specific configuration of the squib measuring circuit 6, in which a first reference power source 21, a switching element 22, and a constant current circuit 23 are connected in series with the squib 1, and second, third reference power sources 24, 25, and has an amplifier 26 for detecting and amplifying a potential difference between both ends of the squib 1. The amplifier 26 includes resistors 27 and 28 connected to respective terminals of the squib 1, a resistor 29 connected between the non-inverting terminal of the comparator 15 and the third reference power supply 25, and an inverting terminal of the comparator 15. And a resistor 30 connected between the output terminals. The first to third reference power sources 21, 24, and 25 may be prepared as independent power sources, but may be created based on one reference power source, for example.

Next, the operation will be described.
When the ignition switch 19 is closed, the backup capacitor 13 is charged via the backflow prevention diode 18. On the other hand, a constant potential to a connection point P reference current flows through the series circuit of the resistors 9 and resistor 8 is generated from the reference power source 7.

  In this state, when the switching element 22 is turned on by receiving a conduction signal periodically supplied from the microcomputer 11, the squib 1 is fixed from the first reference power supply 21 through the switching element 22, the squib 1, and the constant current circuit 23. Current flows. At this time, the potential difference of the squib 1 is detected by the amplifier 26, and the detected value is amplified and supplied to the microcomputer 11. The microcomputer 11 calculates the resistance value of the squib 1 based on the supplied detection value and stores it in an internal memory (not shown).

  When an impact is applied to the vehicle and a detection signal from the acceleration sensor 12 is supplied to the microcomputer 11, the microcomputer 11 supplies a conduction signal to the semiconductor switches 3 and 17 when the microcomputer 11 determines that air bag expansion is necessary based on the detection signal. And make it conductive. For this reason, the comparator 15 outputs the semiconductor switches 2 and 16 with outputs based on the potential of the connection point P input to the non-inverting terminal and the potential of the reference power supply 7 input to the inverting terminal via the resistor 10. Is made conductive.

  Due to the conduction of the semiconductor switch 16, a voltage drop occurs in the resistor 10 according to the flowing current, and an output determined by comparing the potential due to this voltage drop and the potential of the resistor 9 at the point P is supplied to the semiconductor switch 2. At this time, an airbag expansion current corresponding to the conduction amount of the semiconductor switch 2 flows from the backup capacitor 13 and the power supply 20 to the squib 1.

  The squib measurement circuit 6 detects the potential difference generated in the squib 1 by the current at the initial stage of the air bag deployment, and the microcomputer 11 determines the current value flowing through the squib 1 based on the potential difference and the resistance value calculated and stored in the memory. Is calculated.

When the microcomputer 11 is the current value of the squib 1 calculated is determined to less than the specified value set inside the microcomputer, the resistance 8b~8n you are switch 9a or pre OFF the resistor 8a that have previously ON switch 9b selectively OFF the ～9N, and it turned oN, to connect the selected resistor 8a~8n in parallel with the resistor 8, increasing the potential of the node P. As a result, the output of the comparator 15 increases to increase the conduction amount of the semiconductor switch 2 so that a specified amount of current sufficient to deploy the air bag in the squib 1 flows. Incidentally, the illustrated example has been illustrated mechanical switch 9A～9n, the mechanical switch 9A～9n Instead connection resistance by utilizing the port of the microcomputer 11, and can be performed detach.

Thus, by setting the value of the current flowing through the squib to the specified value, the conduction amount of the semiconductor switch 2 can be sufficiently maintained by the output of the comparator 15 when an actual collision accident occurs. As a result, when the semiconductor switch 3 is turned on by the output of the microcomputer 11 that has received the output of the acceleration sensor 12 and the collision state has been determined, and when the mechanical sensor 4 is closed due to the impact of the collision, the ignition switch 19 and the backflow prevention diode 18. A large current flows from the power supply 20 and the backup capacitor 13 to the squib 1 through the mechanical switch 4, the semiconductor switch 2, the squib 1, and the semiconductor switch 3, so that the air bag can be reliably inflated.

As described above, according to the first embodiment, the potential difference between both ends of the squib when the constant current is supplied is detected, the resistance value of the squib is calculated based on the potential difference, and the squib resistance at the time of air bag deployment is calculated. calculating a current value flowing through the squib from the calculated potential difference resistance, by selectively connecting the plurality of resistors to the input side of the current control circuit so that the current value becomes the prescribed value, reliably A current necessary for inflating the air bag can be passed through the squib 1.

It is a circuit diagram which shows the conventional air bag starting device. It is a circuit diagram which shows the electric current control circuit of the air bag starting device in detail. It is a circuit diagram which shows the squib measurement circuit of the air bag starting device in detail. It is a circuit diagram which shows the air bag starting device by Embodiment 1 of this invention. It is a circuit diagram which shows the electric current control circuit of the air bag starting device in detail. It is a circuit diagram which shows the squib measurement circuit of the air bag starting device in detail.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Squib, 2, 3 Semiconductor switch, 4 Mechanical sensor, 5 Current control circuit, 6 Squib measurement circuit, 7 Reference power supply, 8, (8a-8n), 9 Resistance, 9a-9n, 10 Switch, 11 Microcomputer, 12 Acceleration sensor, 13 Backup capacitor .

Claims (2)

A squib that inflates the airbag,
A mechanical sensor for impact detection connected in series with the squib;
A semiconductor switch connected in series with the squib to change the energization amount based on the input amount;
An acceleration sensor that detects the magnitude of impact during a collision;
A squib measuring circuit for periodically detecting a potential difference between both ends of the squib by passing a constant current that does not cause the air bag to expand on the squib;
At least two resistors connected in series between a reference power source and ground;
A comparator that inputs the potential of the connection point of the two resistors to one input terminal and inputs the potential of the reference power supply via the resistor to the other input terminal, and according to a change in the potential of the connection point A current control circuit for changing the output of the comparator;
A plurality of resistors that are selectively connected in parallel to one of the two resistors connected in series to change the potential at the connection point of the two resistors connected in series;
A squib measurement circuit is periodically activated to pass a constant current from the squib measurement circuit so as not to deploy an air bag to the squib, and at this time, the squib potential is detected based on the squib potential difference detected through the squib measurement circuit. The resistance value is calculated and stored in a built-in memory. When it is determined that air bag expansion is necessary based on the detection signal from the acceleration sensor, the comparator in the current control circuit is activated, and the comparator The semiconductor switch is made conductive with an output, and an electric current at the initial stage of air bag development is caused to flow through the squib, and a potential difference generated in the squib at that time is input through the squib measurement circuit and stored in the memory according to the resistance value. Calculate the current value flowing through the squib, and connect and disconnect the resistors so that the current value exceeds the specified value. Selectively performed, by increasing the input amount for the semiconductor switch from the comparator of the current control circuit, an arithmetic circuit to flow a sufficient predetermined amount of current to deploy the airbag to the squib Airbag activation device. Connection of a plurality of resistors that are connected in parallel to one of two resistors connected in series by changing the port of the microcomputer constituting the arithmetic circuit and change the potential at the connection point of the two resistors connected in series The air bag starting device according to claim 1, wherein the air bag starting device selectively performs separation and separation .

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