JPH0624289A - Trouble decision device for occupant protecting system in vehicle - Google Patents

Abstract

PURPOSE:To provide a trouble decision device whereby whether a continuity trouble is provided or not in a squib is always accurately decided regardless of proper offset voltage to an operational amplifier applied as a circuit element in the case of deciding the continuity trouble of the squib in an air bag system for a vehicle. CONSTITUTION:In a microcomputer 80, the first monitor current from a battery B flows in a squib 10 through a resistor 60a by conducting a transistor 60, to generate terminal voltage, and further the second monitor current from the battery B flows in the squib 10 through both resistors 60a, 50a by conducting both transistors 40, 50 under conduction of the transistor 60, to generate the terminal voltage. A differential amplifier 71 generates each terminal voltage respectively as differentially amplified voltage. The microcomputer 80 calculates a difference between the differentially amplified voltages, to decide whether a short-circuit trouble of the squib 10 is provided or not. However, a resistance value of the resistor 60a is determined so as to maintain an output of an operational amplifier 71 positive.

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 system, and more particularly to a failure determination device suitable for determining whether or not there is a failure in the occupant protection system.

[0002]

2. Description of the Related Art Conventionally, a failure determination device for a vehicle occupant protection system of this type is disclosed in, for example, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent No. 55031, the terminal voltage generated between both terminals of the squib is detected, the terminal voltage is differentially amplified by an operational amplifier, and the presence or absence of a short circuit fault of the squib by the differential amplified voltage. There is one that is made to judge.

[0003]

However, in such a configuration, in the differential amplification of the operational amplifier as described above, the offset voltage peculiar to the differential amplifier is inevitably caused as an error in the differential amplification voltage. Therefore, there is a problem that an error occurs in the determination result of the presence or absence of the above-mentioned short-circuit failure.

Therefore, in order to cope with such a situation, the present invention is concerned with an offset voltage peculiar to the operational amplifier means adopted as a circuit element in the determination of the conduction failure of the starting element in the vehicle occupant protection system. Without
An object of the present invention is to provide a failure determination device that always accurately determines whether or not there is a conduction failure in a startup element.

[0005]

To solve the above-mentioned problems, the present invention has a starting element 2 which is started when a starting current is received from a power source 1, as shown in FIG. 1. The starting element 2 is started. In the vehicle occupant protection system that protects the occupant in accordance with the above, there is a feature in its configuration in that the following is done.

That is, the structural feature of the present invention is that the first operating means for causing the first monitor current to flow from the power supply 1 to the starting element 2 in the operating state so that the first terminal voltage is generated from the starting element 2. 3 and second operating means for causing a second monitor current to flow from the power source 1 to the starting element 2 in the operating state so that the second element voltage is generated from the starting element 2 in the operating state of the first operating means 3. 4, an operation state control means 5 for controlling the first operation means 3 to be in an operation state and controlling the second operation means 4 to be in an operation state in this operation state;
Differentially amplifying the first and second terminal voltages respectively to obtain the first and second
Differential amplification means 6 which is generated as a differential amplification voltage of
Holding means 7 for controlling the differential amplifying means 6 so as to hold each of the differential amplified voltages positive in the operating state of the operating means 3;
An arithmetic means 8 for arithmetically operating the difference between the first and second differential amplified voltages, and an adjunct means 9 for deciding the presence / absence of a conduction failure of the starting element 2 based on the arithmetical difference of the arithmetic means 8 are provided. There is something I did.

[0007]

With the above construction of the present invention, when the operating state control means 5 controls the first operating means 3 to the operating state, the first operating means 3 starts from the power source 1 to the starting element. A first monitor current is caused to flow into 2, and the starting element 2 generates a first terminal voltage. Then, the differential amplifier 6
, Differentially amplify the first terminal voltage to generate a first differential amplified voltage. After that, when the operating state control means 5 controls the second operating means 4 in the operating state of the first operating means 3, the second operating means 4 changes from the power source 1 to the starting element 2. The second monitor current is caused to flow into the starting element 2 to generate the second terminal voltage. Then, the differential amplifier 6
Generates a second differential amplified voltage by differentially amplifying the second terminal voltage. In such a case, the holding means 7 controls the differential amplifying means 6 so as to hold each of the differential amplified voltages positive while the first operating means 3 is in the operating state. Then, in such a state, the calculation means 8 calculates the difference between the first and second differential amplified voltages, and the determination means 9 calculates the difference of the starter element 2 based on the calculation difference of the calculation means 8. Determine if there is a continuity fault.

Therefore, even if the offset voltage peculiar to the differential amplifying means 6 is mixed into the first and second differential amplifying voltages respectively, the first voltage is calculated during the calculation by the calculating means 8.
Since the offset voltages in the second differential amplified voltage cancel each other out, the determination by the determination means 9 is made based on the arithmetic difference of the arithmetic means 8 that does not include the offset voltage of the operational amplification amplification means 6. It will be. As a result, an error due to the offset voltage peculiar to the operational amplifier 6 does not occur in the determination of the presence or absence of the conduction failure of the starting element 2. Further, as described above, the holding means 7 causes the differential amplification means 6 to
Since the output voltage is controlled to be maintained positive, the polarity of the output voltage of the operational amplification unit 6 can be prevented from changing regardless of the polarity of the offset voltage of the operational amplification unit 6. As a result, if the holding means 7 has a simple circuit configuration such as a resistor, a short circuit failure of the starting element 2 can be achieved by adding an inexpensive and simple circuit without adopting a special circuit necessary for securing a positive potential. It is possible to increase the determination accuracy of.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an example in which the present invention is applied to a vehicle airbag system. This airbag system is designed so that when the current flowing into the squib 10 increases to the starting current,
Gas is generated from a gas generation source equipped in the steering wheel of the vehicle according to the heat energy of the squib 10, and an airbag equipped in the steering wheel is inflated by the generated gas to protect an occupant. There is. The internal resistance value of the squib 10 is 2 (Ω)
It is ~ 3 (Ω).

Further, this airbag system, as shown in FIG. 2, is provided with a starting device S which constitutes an essential part of the present invention. The starting device S has a pair of normally-open acceleration detection switches 20 and 30.
0 is attached to the front bumper of the vehicle and has a predetermined high acceleration (for example, 100 to 200) of the acceleration of the vehicle.
It closes when it goes up to G). On the other hand, the acceleration detection switch 30 is attached to a proper place in the vehicle interior of the vehicle, and the acceleration detection switch 30 is closed when the acceleration of the vehicle rises to a predetermined low acceleration (for example, 2G) or more. It is like this. Further, the acceleration detecting switch 20 is grounded at its terminal, and the other terminal of the acceleration detecting switch 20 is connected to the battery via the ignition switch IG and the fuse f of the vehicle via the squib 10 and the acceleration detecting switch 30. It is connected to the positive terminal of B.

The acceleration detecting switch 20 includes a resistor 20a.
Are connected in parallel, while the acceleration detection switch 3
A resistor 30a is connected to 0 in parallel. However, both resistors 20a and 30a play a role of limiting the inflow current from the battery B to the squib 10 to a minute current. In such a case, the same minute current is much smaller than the starting current.
The resistance values of the resistors 20a and 30a are the same as those of the squib 10
It is considerably larger than the internal resistance value of.

The starting device S has a transistor 40, which is grounded at its emitter and whose resistor 40c and squib 1 are connected at its collector.
0, the parallel circuit of the acceleration detection switch 30 and the resistor 30a, the ignition switch IG, and the fuse f are connected to the positive terminal of the battery B. Then, the transistor 40 is controlled by the microcomputer 80, which will be described later, under the control of the resistor 40.
It receives the bias action of a and 40b and selectively conducts to serve as a switching element.

On the other hand, the transistor 50 has its emitter connected to the positive terminal of the battery B through the ignition switch IG and the fuse f, and the collector of the transistor 50 has the resistor 50a, the squib 10, and It is grounded through a parallel circuit of the acceleration detection switch 20 and the resistor 20a. Then, this transistor 50
Under the control of the microcomputer 80, is subjected to the bias action of the resistors 50b and 50c at its base and selectively conducts to serve as a switching element.

The emitter of the transistor 60 is connected to the positive terminal of the battery B via the ignition switch IG and the fuse f, and the collector of the transistor 60 has the resistor 60a, the squib 10, and It is grounded through a parallel circuit of the acceleration detection switch 20 and the resistor 20a. Then, this transistor 60
Under the control of the microcomputer 80, is subjected to the biasing action of the resistors 60b and 60c at its base and selectively conducts to serve as a switching element. However, the resistance value of the resistor 60a is the same as that of the transistor 6
When 0 is in the conductive state, the potential of the non-inverting input terminal of the operational amplifier 71 is controlled to be positive in order to maintain the output of the operational amplifier 71 described later at a positive value, regardless of the terminal voltage of the squib 10. , Is preset. This means that even if both transistors 50 and 60 are conducting, both resistors 50
This means that the non-inverting input terminal of the operational amplifier 71 is controlled to a positive potential because the parallel resistance value of a, 60a or each resistance 30a, 50a, 60a is smaller than the resistance value of only the resistance 60a.

The differential amplifier circuit 70 includes the operational amplifier 7 described above.
This operational amplifier 71 has its inverting input terminal connected to the common terminal between the squib 10 and both resistors 20a and 40c via the input resistor 72. On the other hand, the non-inverting input terminal of the operational amplifier 71 is connected to the squib 10 and the resistors 50a, 6 via the input resistors 73, 74.
0a is connected to a common terminal. In such cases,
The input resistor 74 is connected at its negative end to the non-inverting input terminal of the operational amplifier 71, while being grounded at its other end.

A feedback resistor 75 is connected between the inverting input terminal and the output terminal of the operational amplifier 71.
Therefore, the differential amplifier circuit 70 differentiates the terminal voltage generated between both terminals of the squib 10 according to the differential amplification action of the operational amplifier 71 by the cooperation of both the input resistors 72 and 73 and the feedback resistor 75. It is amplified, and the result of this differential amplification is the same operational amplifier 71.
It is generated as a differential amplified voltage from the output terminal of. The sum of the resistance values of the resistors 73 and 74 is considerably larger than the resistance value of the resistor 20a.

The microcomputer 80 executes a computer program in accordance with the flowcharts shown in FIGS. 2 and 3 in cooperation with the operational amplifier circuit 70. During this execution, conduction control of each of the transistors 40, 50, 60 and Arithmetic processing required to determine whether or not the squib 10 has a short circuit fault is performed. However, the computer program described above is stored in advance in the ROM of the microcomputer 80. The microcomputer 80 is connected to the battery B via the ignition switch IG and the fuse f.
It operates by receiving a DC voltage from the positive terminal of.

The backup power supply 90 has a backup capacitor 91, which is grounded at one end and is connected at the other end.
Resistor 92, ignition switch IG and fuse f
Is connected to the positive terminal of the battery B through. Therefore, the backup capacitor 91 includes the battery f, the fuse f, the ignition switch IG, and the resistor 9.
It is charged by receiving a DC voltage through 2 to generate a backup voltage. In FIG. 2, reference numeral 93 indicates a reverse current blocking diode.

In the present embodiment constructed as above,
When the ignition switch IG is closed, the microcomputer 80 receives a direct current voltage from the battery B to be in an operating state, and starts execution of the computer program in step 100 according to the flowcharts of FIGS. At, initialization processing is performed. In such a state, the squib 10 and the starter S
It is assumed that the electric circuit elements such as the acceleration detection switches 20 and 30 are in a normal state. Therefore, at this stage, when the vehicle is stopped, the two acceleration detection switches 2
It is assumed that both 0 and 30 are open and that each of the transistors 40, 50 and 60 is non-conductive. In such a state, the direct current from the battery B flows as a minute current through the resistor 30a, the squib 10 and the resistor 20a. Since this minute current is very small, the output of the differential amplifier 71 cannot be held positive, but it is useful for reducing current consumption. In the backup power supply device 90, the backup capacitor 91 receives a DC voltage from the battery B with the closing of the ignition switch IG to generate a backup voltage.

After the initialization at step 110, the microcomputer 80 generates at step 120 the first transistor output signal necessary for making the transistor 60 conductive, and at the next step 130, 30 (msec.).
Just wait for time. Then, the transistor 60
When biased by both resistors 60b and 60c in response to the first transistor output signal from the microcomputer 80 to conduct, the direct current from the battery B causes the parallel circuit of the resistors 30a and 60a, the squib 10 and the resistor 20a.
And flows as a first monitor current, and a terminal voltage proportional to the first monitor current is generated between both terminals of the squib 10.

In such a case, as the transistor 60 becomes conductive, both resistors 30a and 60a have the following parallel resistance values.
As described above, the non-inverting input terminal of the operational amplifier 71 is controlled to a positive potential in order to maintain the output voltage of the operational amplifier 71 at a positive value regardless of the terminal voltage of the squib 10.
Therefore, in the operational amplifier circuit 70, the operational amplifier 7
1 keeps its non-inverting input terminal at a positive potential,
The terminal voltage of the squib 10 is received through the resistors 72 to 74,
This terminal voltage is differentially amplified under the feedback action of the feedback resistor 74 and is generated as a differential amplified voltage (hereinafter referred to as a first differential amplified voltage). In such a case, regardless of whether the offset voltage of the operational amplifier 71 is positive or negative, the non-inverting input terminal of the operational amplifier 71 is maintained at the positive potential as described above. The differential amplified voltage is maintained positive without becoming negative. Further, since the transistor 60 waits for the time in step 130, the conduction of the transistor 60 is appropriately realized, and then the operational amplifier 7
1 produces a first differential amplified voltage.

When the time waiting in step 130 is finished as described above, the microcomputer 80 AD converts the first differential amplified voltage from the operational amplifier 71 and sets it as the monitor voltage Vx in step 140. Then, the microcomputer 80 generates the second and third transistor output signals necessary for making the respective transistors 40 and 50 conductive in step 150, and only 30 (msec.) In step 160. Wait for time.

In this way, the microcomputer 80
When the second and third transistor output signals are generated from the above, the transistor 40 responds to the second transistor output signal and is biased by the resistors 40a and 40b to be conductive to short-circuit the resistor 20a. On the other hand, the transistor 50
Responds to the third transistor output signal from the microcomputer 80 and is biased by the resistors 50b and 50c to be rendered conductive. In such a case, due to the waiting time in step 160, the conduction of the transistors 40 and 50 described above is properly realized.

Therefore, the direct current from the battery B flows as a second monitor current through the parallel circuit of the resistors 30a, 50a and 60a, the squib 10 and the parallel circuit of the resistors 20a and 40c. Therefore, a terminal voltage proportional to the second monitor current flowing into the squib 10 is generated between both terminals of the squib 10. In such a case, as the transistor 50 conducts while the transistor 60 conducts, each resistor 30
The parallel resistance values of a, 50a, and 60a make it possible to maintain the output voltage of the operational amplifier 71 at a positive value regardless of the terminal voltage of the squib 10, as described above. Is controlled to a positive potential. Therefore, in the operational amplifier circuit 70, the operational amplifier 71 is
Similarly to the above, the terminal voltage of the squib 10 is received via each of the resistors 72 to 74 while maintaining the non-inverting input terminal at a positive potential, and this terminal voltage is differentially generated under the feedback action of the feedback resistor 74. It is amplified and generated as a differential amplification voltage (hereinafter referred to as a second differential amplification voltage). At this time, regardless of whether the offset voltage of the operational amplifier 71 matches the polarity of the offset voltage when the first differential voltage is generated, as described above, the non-inverting input terminal of the operational amplifier 71 has a positive potential. The second differential amplification voltage is maintained positive as in the case of the first differential amplification voltage.

When the waiting time in step 160 is completed, the microcomputer 80 AD converts the second differential amplified voltage from the operational amplifier 71 and sets it as the monitor voltage Vy in step 170. Then, in the next step 180, the microcomputer 80 stops the generation of the above-mentioned first to third transistor output signals to stop the respective transistors 40, 50, 6 from being generated.
0 both non-conducting, and in step 190,
From the monitor voltage Vy in step 170 to step 1
40 is subtracted from the monitor voltage Vx to obtain a monitor voltage difference (V
y-Vx). In such a case, as described above, the first and second differential amplified voltages from the operational amplifier 71 are always maintained positive regardless of the polarity variation of the offset voltage of the operational amplifier 71. The set of each monitor voltage Vx, Vy at 140, 170 is always correct. Therefore, the calculation of the monitor voltage difference (Vy−Vx) in step 190 is always performed correctly without being affected by the positive / negative variation of the offset voltage of the operational amplifier 71.

After the calculation in step 190, the microcomputer 80 executes the computer program in step 2
00, the monitor voltage difference (Vy-Vx) is set to the reference voltage V.
Compare and distinguish with dif. However, the reference voltage Vdif is previously stored in the ROM of the microcomputer 80 as a value smaller than the internal resistance value of the squib 10 in order to determine the short-circuit failure of the squib 10. At this stage, since the squib 10 is normal as described above, (Vy-V
x)> Vdif holds. Therefore, the microcomputer 80 determines “NO” in step 200 and returns the computer program to step 120. On the other hand, when the squib 10 has a short circuit failure in the determination of step 200 as described above, (Vy−Vx) ≦
Since Vdif is established, the microcomputer 80
In step 200, it is determined to be "YES", and in step 210, it is determined that there is a short circuit failure of the squib 10, and execution of the computer program is stopped in step 220. In this case, since the arithmetic processing in step 190 is always performed correctly as described above, the determination in step 200 is performed accurately without being influenced by the variation in the polarity of the offset voltage of the operational amplifier 71, and the skipping is performed. It is possible to prevent the occurrence of erroneous determination of the short circuit failure of 10. Further, in the present embodiment, there is a peculiar effect when the above-described operational effects are realized by adding the simple circuit configuration of the transistor 60 and the resistor 60a as described above.

As described above, in determining whether or not there is a short circuit fault in the squib 10, each of the transistors 40 and 5 is determined.
When a small current flows through the squib 10 in the non-conducting state of 0 and 60, first, when the first monitor current is supplied to the squib 10 while the transistor 60 is conducting, when the first monitor current flows between both terminals of the squib 10. The generated terminal voltage is transferred to the differential amplifier circuit 7
By 0, differential amplification is performed as the first differential amplification voltage, and this first differential amplification voltage is set as the monitor voltage Vx. Then both transistors 4 with transistor 60 conducting
When a second monitor current is passed through the squib 10 under the conduction of 0 and 50, the terminal voltage generated between both terminals of the squib 10 is differentially converted into a second differential amplified voltage by the differential amplifier circuit 70. It is amplified and set to the monitor voltage Vy. After that, the difference between the monitor voltage Vy and the monitor voltage Vx is calculated as the monitor voltage difference (V
y-Vx) to compare with the reference voltage Vdif to determine whether there is a short circuit fault in the squib 10.

In such a case, the offset voltage peculiar to the operational amplifier 71 is equal to both the first and second differential amplified voltages, that is, the monitor voltages Vx and Vy, so that the offset voltage is the monitor voltage. The difference (Vy−Vx) is canceled during the calculation, and as a result, the monitor voltage difference (V
y-Vx) is formed as a value that does not include the offset voltage. Therefore, the above-mentioned monitor voltage difference (Vy-V
x) and the reference voltage Vdif are compared and determined by the operational amplifier 71.
Can always be done properly without being affected by the offset voltage inherent in the.

Further, under the above-described operation of the simple circuit configuration of the resistor 60a and the transistor 60 set to the resistance value as described above, the non-inverting input terminal of the operational amplifier 71 is maintained at a positive potential and the operational amplifier 71 is maintained. Since the output voltage of the operational amplifier 71 caused by the variation in the polarity of the offset voltage of 71 is maintained positive while preventing the variation of the polarity, the special circuit necessary for securing the positive potential is not adopted. By adding an inexpensive and simple circuit as described above, the accuracy of determining a short circuit failure of the squib 10 can be further improved. Further, as described above, since the time waiting is performed in each of the steps 130 and 160, after the change from the first monitor current to the second monitor current is surely made, the monitor voltage difference (V
y-Vx) will be calculated. Therefore, the determination of the short circuit failure of the squib 10 can be made more surely. Further, the above-described operational effects can be achieved similarly even if it depends on the backup voltage from the backup power supply 80. When the connecting lead of the battery B is broken, the starting device S
Protects the occupant in response to the start-up current flowing into the squib 10 based on the backup voltage from the backup capacitor 91.

In implementing the present invention, the present invention may be applied to an occupant protection system attached to a seat belt of a vehicle.

In the above embodiment, the example in which the transistors 60 and 50 are made conductive after the transistor 60 is made conductive has been described. However, instead of this, after both the transistors 40 and 50 are made conductive. The transistor 60 may be made conductive. In such a case, in step 190, the monitor voltage is set to (Vx-V
y), and at step 200, (Vx
-Vy) is compared with Vdif.

Further, in the above-described embodiment, the example in which the transistor 60 and the resistor 60a are adopted to maintain the non-inverting input terminal of the operational amplifier 71 at a positive potential has been described, but the invention is not limited to this, and for example, a constant current is used. A diode may be used instead of the resistor 60a for implementation.

In each of the above embodiments, the squib 1
Although an example of determining a short-circuit failure of 0 has been described, the present invention is not limited to this, and it may be performed by determining a conduction failure such as an insufficient conduction state of the squib 10.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the description of the claims.

FIG. 2 is a schematic electric circuit diagram showing an embodiment of the present invention.

FIG. 3 is a front part of a flowchart showing the operation of the microcomputer of FIG.

4 is a latter part of a flowchart showing the operation of the microcomputer of FIG.

[Explanation of symbols]

10 ... squib, 20a, 30a, 50a ... resistance, 40,
50, 60 ... Transistor, 70 ... Operational amplifier circuit, 71
... operational amplifier, 72 to 74 ... input resistance, 75 ... feedback resistance, 80 ... microcomputer, B ... battery.

Claims (1)

[Claims] 1. A vehicle occupant protection system, comprising: a starting element that is activated when a starting current is received from a power source, and protecting an occupant according to the activation of the starting element. A first actuating means for causing a first monitor current to flow from the power source to the actuating element in an actuated state so as to generate a voltage;
Second operating means for causing a second monitor current to flow from the power source to the starting element in an operating state so as to generate a terminal voltage, and the first operating means for operating the first operating means, and for operating the first operating means in the operating state. An operating state control means for controlling the two operating means to be in an operating state; and a first differential amplifier for amplifying the first and second terminal voltages respectively.
And differential amplifying means generated as a second differential amplifying voltage, and holding means for controlling the differential amplifying means so as to hold each of the differential amplified voltages positive in the operating state of the first operating means. And a calculating means for calculating the difference between the first and second differential amplified voltages, and a judging means for judging the presence or absence of the conduction failure of the starting element based on the difference between the calculating means. A failure determination device for a vehicle occupant protection system.