JP3270014B2 - Collision sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision sensor suitable for detecting a collision of a vehicle used in a starting system of an occupant protection device such as an airbag.

[0002]

2. Description of the Related Art Conventionally, collision sensors suitable for detecting a collision of a vehicle used in a starting system of an occupant protection device such as an airbag are classified into a sensor using a sensing mass and an electronic sensor using an accelerometer. You. As an electronic type, there is known an electronic type in which an acceleration waveform from an accelerometer is time-integrated, and when the time-integrated value exceeds a predetermined value, an occupant protection device such as the airbag is started. (See, for example, US Pat. No. 3,701,903). Further, as a modified example, by subtracting a constant acceleration from the acceleration waveform before performing the time integration, when an acceleration waveform that does not cause injury to the occupant such as when the vehicle is traveling on an uneven road is input. There is also a device designed so that the occupant protection device does not start (JP-A-49-55031).

[0003] However, the above-mentioned collision sensor cannot always start the occupant protection device within the start request time required for all types of collisions predicted for the actual vehicle. In particular, the acceleration waveforms of a low-speed head-on collision in which the occupant protection device does not need to be started and a high-speed diagonal collision or a pole collision (which collides with a pole) in which the occupant protection device needs to be started are shown in FIG. They are very similar at the start request time of the device, and are difficult to determine. That is, as shown in FIG. 8, an acceleration waveform (shown by a dotted line) of a low-speed head-on collision that does not require the start of the occupant protection device, and a high acceleration that requires the start of the occupant protection device. The acceleration waveform of the oblique velocity collision (shown by a solid line) is very similar to the start request timing (between) when it is necessary to determine whether to start the occupant protection device. Therefore, as shown in FIG. 9, even if a collision sensor subtracts a constant acceleration from the acceleration waveform and integrates the subtracted acceleration with time (V1 '), the collision sensor discriminates them and starts the airbag within the start request time. It is difficult to do that. As a result, when the starting condition is prioritized, an unnecessary start for a low-speed head-on collision is caused. Conversely, when the non-starting condition is prioritized, a start delay or a non-start due to a high-speed oblique collision or the like is caused. There was a problem.

Accordingly, the applicant has disclosed in Japanese Patent Application No. 2-74457 (Japanese Unexamined Patent Application Publication No. 3-253441) that a collision of a vehicle is detected from an acceleration waveform of an accelerometer, and an occupant protection device such as an airbag is started by a trigger circuit. A collision sensor, an integrating means for performing a peak cut equal to or less than a predetermined value on the acceleration waveform to perform time integration, a subtraction means for subtracting a time integrated value of a predetermined function from the integrated value; There has been proposed a collision sensor including first comparing means for comparing a predetermined time function value. The operation principle of this collision sensor is as follows. First, both acceleration waveforms of the low-speed frontal collision and the high-speed oblique collision are almost the same in the average acceleration in the initial part of the collision, which is the start request time, but FIG.
As shown in (1), the acceleration waveform of the high-speed oblique collision has a considerable vibration component due to buckling, vibration, etc. of the vehicle body. On the other hand, since most of the impact energy of the low-speed head-on collision is absorbed by an energy absorbing device such as a bumper, the vibration component is not so large. Paying attention to the difference between the characteristics of the two acceleration waveforms, the one obtained by removing the valley of the acceleration waveform is time-integrated to obtain a subtraction integral value. As shown in FIG. 3, the subtraction integral value of the acceleration of a high-speed oblique collision having a large vibration component is
It becomes a large value as compared with a value obtained by simply subtracting a constant acceleration and integrating over time, so that the first comparison means can reliably discriminate the two.

[0005]

However, in recent years,
The demand level for preventing the malfunction of the airbag when the vehicle is running on a rough road (hereinafter referred to as a rough road) has become strict, and it has become necessary to deal with this. Under such demands, in the case of particularly severe rough roads, vibration components may be generated due to the bottoming of the body and the like. As shown in FIG. 10A, the vibration component due to the bottoming of the body occurs at the same time as the airbag start request time. In this case, in the above-described collision sensor, the one obtained by removing the valley of the acceleration waveform is time-integrated to obtain a subtraction integral value. Therefore, the subtraction integral value V1 is, as shown in FIG. In some cases, the collision may exceed the case of the collision, and there is a problem that a judgment of the operation tends to be made.

[0006] Also, as shown in FIG. 11 (a), a collision wave of an automobile is generally a wave having a few undulations 80 and 81. Therefore, the subtraction integral value V1 is also calculated as shown in FIG.
As shown in (b), the waves have undulations 82 and 83,
In some cases, the subtraction integral value V1 reaches the predetermined time function 62 (reference numeral 82) earlier than the start request time 84, and the operation may be early. If the first undulation 84 is not so large as shown in FIG. 12A, the subtraction integral value V1 becomes the undulation 85 at the start request timing 84 as shown in FIG. There was a problem that it could not be caught and became inoperative.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art.
Not only normal high-speed diagonal collisions and pole collisions, but also an electronic system that can prevent malfunctions even on severe rough roads, and can control operation timing and prevent early operation and non-operation for a wider range of collision waves The object of the present invention is to provide a collision sensor.

[0008]

In order to solve the above-mentioned problems, a collision sensor according to the present invention detects a vehicle collision from an acceleration waveform of an accelerometer, and starts a passenger protection device such as an airbag by a trigger circuit. A sensor,
A peak cut means for performing a peak cut of a predetermined value or less on the acceleration waveform, a first integrating means for integrating the peak cut waveform obtained by the peak cut means with time, and a first integrating means obtained by the first integrating means. From the time integration value, the first of the predetermined function
First subtraction means for subtracting the subtraction value, and comparing the first subtraction integrated value obtained by the first subtraction means with a first reference value of a predetermined time function, and comparing the first subtraction integration value with the first reference value. A first comparison means for outputting a start signal when the value is equal to or more than a value, a second integration means for time-integrating the acceleration waveform before the peak cut,
A second comparing means for comparing the second time integrated value obtained by the integrating means with a predetermined second reference value and outputting a start signal when the second time integrated value is equal to or greater than the second reference value; Means for calculating the amount of change in the integral value per predetermined time of the first subtraction integrated value, and comparing the amount of change in the integral value obtained by the means for calculating the amount of change in the integrated value with a predetermined reference value for the amount of change. A third comparing means for outputting a start signal when the integrated value change amount is equal to or greater than the change amount reference value; a start signal from the third compare means and a start signal from the first compare means; ,and,
An OR circuit, an AND circuit, a switching circuit for switching connection to one of the first comparing means and the third comparing means, or a combination circuit in which these circuits change with time;
Connecting means for outputting the input start signal in accordance with these circuits; and starting the trigger circuit when both the start signal from the connection means and the start signal from the second comparing means are input. AND means for outputting a signal.

Further, as a modified example of the above method, the second
In the comparing means, instead of comparing the second time integrated value with the second reference value, a predetermined second time integrated value is calculated from the second time integrated value.
A second subtraction integrated value obtained by a second subtraction means for subtracting the subtraction value is compared with the second reference value, and when the second subtraction integral value is equal to or greater than the second reference value, the second comparison In some cases, a starting signal is output from the means. Further, a starting signal holding means for holding a starting signal output from the connection means is provided, and the holding signal from the starting signal holding means is transmitted to the AN.
If the start signal is input to the D means and the start signal from the second comparing means is input to the AND means in this state, the start signal can be output to the trigger circuit.

According to the present invention, by adopting the above configuration,
In the first comparing means, a normal high-speed diagonal collision or a pole collision as a starting condition is distinguished from a low-speed frontal collision as a non-starting condition to determine starting / non-starting, and in the second comparing means, The presence or absence of a speed change is determined by comparing the time integral value of the acceleration waveform without peak cut with a predetermined second reference value. As a result, a vibration component due to bottoming of the body or the like on a severe rough road hardly causes a speed change, so that it can be classified as a collision. Therefore, by performing an AND operation between the second comparing means and the first comparing means, it is possible to prevent a malfunction on a severe rough road.

Since the second comparing means can determine the change in speed and thus the magnitude of the collision energy, the second comparing means uses this as a means for setting the timing (timing) at which a start signal is issued. If the start signal holding means is provided between the first and second AND means, the start signal of the first comparing means can be output to the trigger circuit of the airbag at a predetermined time.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Here, the acceleration on the deceleration side will be described as a positive value, but making it negative will have the same effect if the positive and negative logics in each block are matched. FIG. 1 is a block diagram of a collision sensor of the present invention, and FIG.
FIG. 3 is an acceleration diagram showing calculation processing of the collision sensor of FIG. 1;
FIG. 4 is a graph showing a change in the first subtraction integral of the collision sensor of the present invention, FIG. 4 is a graph showing a change in the second subtraction integral of the collision sensor of the present invention, and FIG. 2
FIGS. 6 and 7 are block diagrams of the embodiment, and FIGS. 6 and 7 are graphs showing the change of the integral value showing the calculation processing of the collision sensor of FIG.

In FIG. 1, an accelerometer 1 includes an arithmetic circuit 3
, The reset circuit 4 and the trigger circuit 5 are connected, and the trigger circuit 5 starts the airbag 6 which is an occupant protection device. Next, the arithmetic circuit 3 will be described. First, in block 11, the accelerometer 1
T when the measured acceleration G exceeds the predetermined acceleration G1
0 is determined, and a predetermined calculation is started from this point. In block 12, an acceleration G3 that is equal to or greater than a predetermined acceleration G2 is calculated from the acceleration after the calculation start time t0 (the acceleration G2 or less is regarded as zero). Next, in block 13, which is the first integration means, time integration of the acceleration G3 is started, and a first time integration value V is calculated. In a block 14 which is a first subtraction means, a first subtraction value ΔV which is a time integral value of a predetermined function is subtracted from the first time integral value V. In the illustrated block 14, the first subtraction value ΔV is a constant value, and a first subtraction integral value V1 is calculated by subtracting a predetermined value ΔV per unit time. The first subtraction integral value V1 is calculated by using the block 15 and the third
It is output to a block 16 which is a comparison means. Then, the results of the blocks 15 and 16 are output to the AND circuit 36 via the block 17 as the connection means.

The block 15 which is a first comparing means will be described. In a block 21, a first reference value V2 (a reference value of a time function), which changes with time in a block 22, is compared with the first subtraction integral value V1 in a block 21. I do.
Here, when V1 becomes equal to or more than V2 (V1 ≧ V2), a start signal is output from the line 23 to the block 17 which is a connecting means. On the other hand, when V1 does not reach V2 (V1 <V
In 2), the signal is output from the line 24 to the block 18, and when the block 18 detects that V1 is close to zero (negative or slightly positive value), a signal is issued to the reset circuit 4 to perform time integration. Are stopped, and V, V1, V5, V6, t
Reset to zero. The first comparing means detects a normal high-speed oblique collision or a pole collision while classifying a low-speed head-on collision, and issues a start signal at a start request time.

To explain in block 16 which is a third comparison means, a change amount (ΔV1) of the first subtraction integral value per predetermined time is calculated in block 25, and then a predetermined change amount is calculated in block 27. Reference value ΔV4
And the change amount ΔV1 are compared in a block 26. Δ
When V1 becomes equal to or more than ΔV4 (ΔV1 ≧ ΔV4), line 2
8 outputs a start signal to a block 17 which is a connecting means. On the other hand, when ΔV1 does not reach ΔV4 (ΔV1 <Δ
V4) outputs the signal from line 29 to the block 18, and when the block 18 detects that V1 is near zero (negative or slightly positive value), it issues a signal to the reset circuit 4 to time The integration is stopped, and the above-described reset processing is performed. This third comparing means is used in place of the first comparing means when a sufficient acceleration is not transmitted to the room by the start request time due to the characteristics of the vehicle body, the type of collision, and the like. The start signal is issued by paying attention to the increase.

The block 17, which is a connecting means, comprises an OR circuit, an AND circuit, a switching circuit or a combination circuit for changing the combination of these circuits over time. In the case of the OR circuit, the first comparing means is used. As soon as a start signal is input to the connection means from any one of the third and third comparison means 16, the start signal is immediately output to the AND circuit 36. In the case of an AND circuit, a start signal is output from the connection unit 17 to the AND circuit 36 only when a start signal is input to the connection unit 17 from both the first comparison unit 15 and the third comparison unit 16. You. In the case of a switching circuit, when the switching reference is speed, the connecting means 17 is connected to a speedometer, and when the speed is equal to or higher than a predetermined speed, the first comparing means 15 and the AND circuit 36 are connected; If the speed is less than the predetermined speed, one of them is connected to the AND circuit 36 so that the third comparing means 16 and the AND circuit 36 are connected, and the starting is performed from either the connected first comparing means or the third comparing means. The signal is output to the AND circuit. or,
The connection to the first comparison means and the connection to the third comparison means are changed with the passage of time, or the OR circuit, A
It is also possible to change the combination form of the ND circuit and the switching circuit over time. For example, the first half of the start request time may be connected to the first comparing means 15, and the latter half of the start request time may be constituted by a combination circuit which is an OR circuit of the first comparing means 15 and the third comparing means 16. is there. Needless to say, these combinations are appropriately determined depending on the characteristics of the vehicle in which the collision sensor of the present invention is incorporated or the manner of setting the non-start condition.

On the other hand, in block 50, the noise G4 is removed from the acceleration G that has not been subjected to the peak cut processing from the above-mentioned calculation start time t0, and the obtained acceleration G
5, time integration is started in a block 31 serving as a second integration means, and a second time integration value V5 is calculated. Next, in a block 32 as a second subtraction means, a second subtraction value ΔV2 which is an integral value of a predetermined function is subtracted from the second time integral value V5. In the illustrated block 32, the second
This is a case where the subtraction value is a constant value ΔV2, and a second subtraction integration value V6 is calculated by subtracting a predetermined second subtraction value ΔV2 per unit time from the second time integration value V5 (however,
ΔV2 << ΔV). This second subtraction integral value V6 is output to the block 37 which is the second comparing means.

In a block 37 as a second comparing means, a second reference value V7 predetermined in the block 35 and the second subtracted integral value V6 are compared with a block 33 as a comparator.
To compare. Here, when V6 becomes equal to or higher than V7 (V6 ≧ V7), a start signal is output from the line 38 to the AND circuit 36. On the other hand, V6 does not reach V7 (V6 <V
7) In the case, from the line 39, the signal is
8, when it is detected that V1 is close to zero (negative or slightly positive value), a signal is issued to the reset circuit 4, the second time integration is stopped, and the above-described reset processing is performed. . The second comparing means focuses on the point that the vibration component due to the bottoming of the body hardly causes a speed change, and compares the second time integrated value based on the acceleration waveform without peak cut with a predetermined second reference value. By doing so, a start signal is issued in a normal high-speed oblique collision, a pole collision, and a collision of a vehicle with low body rigidity, but the start signal is not issued depending on the vibration component.

Then, as described above, the result of the first comparing means or the third comparing means 16 is ANDed via the connecting means 17.
The result of the second comparing means 37 is also inputted to the AND circuit 36 while being inputted to the circuit 36. The AND circuit 36 outputs a start signal to the trigger circuit 5 when both of the start signals from the connection means 17 and the second comparison means 37 are input. As a result, the first comparing means 15 and the third comparing means 16 distinguish a normal high-speed diagonal collision or a pole collision from a low-speed frontal collision, and determine a collision in the case of a vehicle with low body rigidity at an early stage. In addition, the second comparing means 37
This makes it possible to prevent malfunctions on severe rough roads. Here, the AND circuit 36 may be an AND means, and outputs a start signal to signals from both the connection means 17 and the second comparison means 37 by a determination using fuzzy inference or by weighting or the like. It is also possible to configure so that

Next, the arithmetic processing of the blocks 11 to 14 will be described with reference to the graph of FIG. In FIG. 2A, the calculation starts at time t0 when the acceleration G exceeds G1. Then, a value equal to or less than a predetermined value G2 is regarded as zero, and a value greater than G2 is time-integrated. Then, a predetermined first subtraction value ΔV per unit time of the hatched portion is subtracted. FIG.
In (b), the vertical line is time-integrated,
This is the first subtraction integral value V1. That is, the vertical line A is added as a negative value, but the portion B is cut. Also, by using the function of the reset circuit 4 described above, the start and reset of the integration can be performed without considering the start timing.

The first comparison circuit 15 and the third
The operation of the comparison circuit 16 and the connection means 17 (in the case of an OR circuit) will be described with reference to FIG. 3, which is a chart showing a change in the first subtraction integration value V1. As in the case of FIG. 8 described above, in the case where the constant acceleration is simply subtracted from the acceleration G and the time is integrated (V1 ′), the high-speed oblique collision and the low-speed frontal collision can hardly be distinguished. First subtraction integral value V in FIG.
In 1, the two are clearly separated. By setting a first reference value V2, which is a predetermined time function, in advance as shown by a line graph indicated by a dashed line, a start signal is sent from the first comparison circuit 15 to the connection means 17 of the OR circuit at point A. Is output. Therefore, it is possible to satisfy the inoperative condition of the low-speed frontal collision and the starting condition within the required start period of the high-speed oblique collision or the pole collision. In the case of a high-speed diagonal collision or a pole collision of a vehicle with low body rigidity, V
1 rapidly increases, the integrated value change amount ΔV1 per unit time Δt is equal to or larger than the change amount reference value ΔV4 (ΔV1
.Gtoreq..DELTA.V4) is detected at the point B, so that the third comparator 16 outputs the OR circuit within the start request time before the point V1 becomes equal to or more than the first reference value V2 (V1.gtoreq.V2) at the point C. A start signal is output to the connection means 17 of the above. As a result,
The airbag can be started within the required start period not only for a normal low-speed head-on collision or a pole collision, but also for a high-speed diagonal collision or a pole collision of a vehicle with low body rigidity.

In FIG. 1, the predetermined first subtraction value ΔV of the block 14 can be replaced with a function value, for example, a function value of the first time integration value V at that time. On the other hand, in the block 13, not only the simple time integration of the acceleration G3 but also the time integration of the acceleration G3 to the Kth power (K ≧ 1), the nth order integration of the acceleration G3, and a combination thereof, a low-speed head-on collision is performed. It is also possible to clarify the distinction between a high-speed oblique impact and a soft vehicle impact.
Further, the case where V1 of the block 18 becomes close to zero is defined as when V1 becomes equal to or less than a predetermined value V3, or when V1 becomes equal to or less than a predetermined value V4 which is a function of the acceleration G3 at that time. It can also be. Further, before the block 11, a value Gx obtained by subtracting a value Gf obtained by performing a filtering process on the acceleration G from the acceleration G with a time constant of 5 seconds or more from the acceleration G is used instead of the acceleration G to eliminate the effect of the zero drift of the accelerometer. Thereby, the calculation accuracy can be improved. Further, the mounting structure of the accelerometer 1 is vibrated at a frequency of 50 to 2000 Hz (in terms of vibration characteristics in the traveling direction of the vehicle), and the acceleration G
Or the electric circuit of the accelerometer 1 can have an amplification range of a specific frequency band.

Next, the arithmetic processing of the blocks 31 and 32 will be described with reference to the graphs of FIGS. FIG.
At 0 (a), 40 is a vibration component of acceleration due to rough road, 41 is an acceleration waveform of a high-speed oblique collision, and 42 is an acceleration waveform of a low-speed oblique collision. The acceleration vibration component 40 due to the rough road has a large amplitude on both the positive and negative sides of the acceleration. This is because waveform 4
Although the amplitude is basically one-sided in the positive direction like 1 and 42, the vibration component 40 due to the rough road is merely a simple vibration of the vehicle body caused by the bottoming of the body and the like, and hardly causes a deceleration. Therefore, in block 31, normal time integration is basically performed without applying a peak cut to the acceleration waveform, and in block 32, the integration is performed to the extent that minute zero drift of the accelerometer is removed. In FIG. 4, the change in the second subtraction integral value V6 is indicated by reference numeral 43 in the case of rough road.
As shown by, the value has been changing to a low value near zero.
It is clearly distinguished from the cases of the high-speed oblique collision and the low-speed frontal collision indicated by 4, 45. Therefore, as shown in the figure, by setting the predetermined second reference value V7 appropriately in advance, it is possible to prevent malfunction due to severe rough road.

In FIG. 1, when a high-pass filter is inserted between the block 11 and the block 31, the vibration component due to the rough road has a high frequency, so that the distinction between the rough road and the collision becomes clearer and the effect is improved. Can be. Also, in FIG.
If a low-pass filter is inserted between the high frequency component and the low frequency component, the acceleration waveform that affects the speed change at the time of the collision has a low frequency.

Next, a second embodiment of the collision sensor according to the present invention will be described with reference to FIGS. 5 is different from FIG. 1 in that the connecting means 1 of the first comparing means and the third comparing means is different.
7 is provided between the AND circuit 86 and the AND circuit 86. The block 51 is a means for holding a start signal from the connection means 17, and the block 51 is connected to the block 18. Then, upon receiving the start signal from the connection means 17, the start signal holding means 51 sets the register IF to 1. AND
The circuit 86 outputs a start signal to the trigger circuit 5 when a start signal is input from the second comparing means when the register IF is 1. When the block 18 detects that V1 is near zero, it issues a signal to the reset circuit 4,
The time integration in the blocks 13 and 31 is stopped, and the register IF of the starting signal holding means 51 is reset to 0. The second comparing means 37 is set so as to output a start signal at the start request time. Here, the second comparing means 37 is watching the speed, and the momentum, which is the product of the speed and the mass, and thus the magnitude of the collision energy, so that the starting timing is appropriately determined without being affected by the acceleration waveform. Can be set.

Next, the operation of the collision sensor of this embodiment will be described with reference to FIG.
And the graph of FIG. In FIG. 6, FIG.
When a collision wave having a swell as shown in FIG. 1A is input, the first subtracted integral value V1 also becomes a wave with a swell 82 as shown in FIG. Also earlier, the first subtraction integral value V1 reaches the first reference value 62 of the predetermined time function (reference numeral 65). Then, the first comparing means outputs a start signal, and when the connecting means 17 is an OR circuit, the register IF is set to 1 as shown in FIG. Then, as shown in FIG. 6C, when the second subtraction integral value V6 reaches a predetermined second reference value 69 (reference numeral 67) within the start request time 84, the second comparison means outputs a start signal. As a result, a start signal is output from the AND circuit, and the airbag is started. In a low-speed head-on collision (dotted line), which is a non-start condition, a start signal is output from the second comparing means at a point 68 in FIG. 6C, but as shown in FIG. 1. Since the start signal is not output from the comparing means, the start signal is not output from the AND circuit, and the airbag is not started. That is, since the start / non-start determination is made by the first comparing means, the second comparing means sets the second reference value 69 based on the first definition of the timing suitable for starting the airbag. It is possible to control the start timing of the airbag. The timing for starting the airbag is set by appropriately selecting the second reference value 69 and the degree of subtraction in the block 32 in FIG. As described above, since the start timing can be controlled, it is possible to prevent a start that is too early with respect to the start request timing and to reduce a variation in the start timing.

In FIG. 7, when a collision wave that is not so large as the first undulation 84 as shown in FIG. 12A is input, the first subtraction integral value V1 is shown in FIG. Thus, the waveform has a swell 85 before the start request time 84. Then, if a predetermined first reference value 70 is set as shown in the figure, the first comparing means outputs a start signal at the time of reference numeral 71, and the connection means 17 is an OR circuit as in the above case. , The register IF is set to 1, and FIG.
As shown in (c), when the second subtraction integral value V6 reaches the predetermined second reference value 74 within the start request time 84 (reference numeral 72), a start signal is output from the second comparing means 37 to the AND circuit. , A start signal is output from the AND circuit to the trigger circuit to start the airbag. As a result of such control of the starting timing, the airbag can be appropriately operated even for a collision wave in which the first undulation 84 is not so large. Since the first comparing means is not restricted by the start time, the judgment of the start / non-start can be considered firstly, and the degree of freedom of setting the first reference value 70 of the time function is increased, and the judgment accuracy is accordingly increased. It is possible to increase.

[0028]

According to the collision sensor of the present invention,
The first comparing means classifies the high-speed oblique collision or the pole collision from the low-speed frontal collision, and the third comparing means determines the first subtraction integral value V1.
The start signal is output by paying attention to the rapid increase of the vehicle speed. A sufficient acceleration is not transmitted to the company mainly due to the characteristics of the vehicle body and the type of collision, and the first comparison means cannot output the start signal within the start request period. In such a case, the first comparator is used in place of the first comparator, and the second comparator compares the time integral value of the acceleration waveform that does not peak-cut with a predetermined reference value to determine whether there is a speed change. Since the start signal from the second comparing means and the starting signal from the connecting means between the first comparing means and the third comparing means are connected by the AND means, the first and third comparing means are determined. Start by
The second comparing means can accurately classify the non-starting operation and classify the bottoming of the body, which is a vibration component that does not cause a speed change, from the collision by the second comparing means, thereby preventing a malfunction on a severe rough road.

Further, a starting signal holding means is provided between the output side of the connecting means of the first comparing means and the third comparing means and the AND means, and the second comparing means is used as means for setting a timing for issuing a starting signal. Then, the start-up signals of the first comparing means and the third comparing means can be output to the trigger circuit of the airbag at an appropriate timing to start the airbag, so that the starting timing can be controlled. Therefore, it is possible to control the operation timing of the airbag, to prevent early operation and non-operation for a wider range of collision waves, and to reduce variation in the start timing. Further, since the first comparing means and the third comparing means are not restricted by the starting time, the degree of freedom of the start / non-start judgment is increased, and the judgment accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a collision sensor according to the present invention.

FIG. 2 is an acceleration diagram showing calculation processing of the collision sensor of FIG. 1;

FIG. 3 is a graph showing a change over time of a first subtraction integral value of the collision sensor of the present invention.

FIG. 4 is a graph showing a change over time of a second subtraction integral value of the collision sensor of the present invention.

FIG. 5 is a block diagram of a second embodiment of the collision sensor according to the present invention.

FIG. 6 is a graph showing a change over time of an integral value indicating a calculation process of the collision sensor of FIG. 5;

FIG. 7 is a graph showing a change over time of an integral value indicating a calculation process of the collision sensor of FIG. 5;

FIG. 8 is a graph showing a change over time in acceleration.

FIG. 9 is a graph showing a change over time of a time integration value of a conventional collision sensor.

FIG. 10 is a graph showing a temporal change of an acceleration and a temporal change of a time integration value of a conventional collision sensor.

FIG. 11 is a graph showing a temporal change of acceleration and a temporal change of a time integrated value of a conventional collision sensor.

FIG. 12 is a graph showing a temporal change of an acceleration and a temporal change of a time integration value of a conventional collision sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Accelerometer 4 Reset circuit 5 Trigger circuit, 12 Peak cut means 13 1st integration means 14 1st subtraction means 15 1st comparison means 16 3rd comparison means 17 Connection means 31 2nd integration means 32 2nd subtraction means 36 AND circuit (AND means) 37 Second comparing means 51 Start signal holding means 86 AND circuit (AND means)

Continuation of front page (56) References JP-A-4-287748 (JP, A) JP-A-4-321455 (JP, A) JP-A-3-197256 (JP, A) JP-A-5-38997 (JP) , A) Hikaru 4-131566 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15/08 B60R 21/32 G01P 15/00

Claims (3)

(57) [Claims] 1. A collision sensor for detecting a vehicle collision from an acceleration waveform (G) of an accelerometer (1) and starting an occupant protection device such as an airbag (6) by a trigger circuit (5). A peak cut means (12) for performing a peak cut of a predetermined value (G2) or less on the waveform (G), and a first integrating means for time-integrating the peak cut waveform (G3) obtained by the peak cut means (12). (13) first subtraction means (14) for subtracting a first subtraction value (ΔV) of a predetermined function from the first time integration value (V) obtained by the first integration means (13); The first subtraction integral value (V) obtained by the first subtraction means (14)
1) is compared with a first reference value (V2) of a predetermined time function, and when the first subtraction integrated value is equal to or greater than the first reference value (V1 ≧ V2), a first comparing means ( 15), a second integration means (31) for time-integrating the acceleration waveform (G) before the peak cut, and a second time integration value (V) obtained by the second integration means (31).
5) is compared with a predetermined second reference value (V7), and a second comparison means (37) for outputting a start signal when the second time integration value is equal to or more than the second reference value (V5 ≧ V7). An integrated value change amount calculating means (2) for calculating an integrated value change amount (ΔV1) of the first subtracted integrated value (V1) per predetermined time;
5) and the integrated value change amount obtained by the integrated value change amount calculating means (25) is compared with a predetermined change amount reference value (ΔV4), and the integrated value change amount is equal to or greater than the change amount reference value (ΔV1). ≧ ΔV
Third comparing means (16) for outputting a start signal in the case of 4)
A starting signal from the third comparing means (16) and a starting signal from the first comparing means (15) are inputted, and an OR circuit, an AND circuit or the first comparing means and the third comparing means are inputted. A connection circuit (17) for switching the connection to any one of them or a combination circuit in which these circuits change over time, and a connection means (17) for outputting the input start signal in accordance with these circuits; AND means (36) for outputting a start signal to the trigger circuit (5) when both of the start signal from (17) and the start signal from the second comparing means (37) are input. A collision sensor comprising: 2. The method according to claim 1, wherein the second comparing means (37) replaces the second time integrated value (V5) with the second reference value (V7) and uses a predetermined second integrated value from the second time integrated value. The second subtracted integrated value (V6) obtained by the second subtracting means (32) for subtracting the 2 subtracted value (ΔV2) is compared with the second reference value (V7). 2 or more reference values (V6 ≧
The collision sensor according to claim 1, wherein in the case of V7), a start signal is output from the second comparison means (37). 3. A starting signal holding means (51) for holding a starting signal output from said connecting means (17), wherein a holding signal from said starting signal holding means (51) is transmitted to said AN.
When the start signal is input to the D means (86), and in this state, the start signal from the second comparing means (37) is input to the AND means (86), the start signal is output to the trigger circuit (5). Claim 1
Or the collision sensor according to 2.