JP3120290B2 - Collision detection method - 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 detection method for accurately starting a vehicle collision safety device such as an airbag device or a belt retraction device.

[0002]

2. Description of the Related Art In an airbag device for protecting an occupant from a secondary collision during a vehicle collision, if only an acceleration signal output from an acceleration sensor is used as a starting signal of the airbag device, the vehicle body is hardly damaged. There is a possibility that a start signal may be output only when a small object collides with the vicinity of the acceleration sensor, and a means for preventing the start signal is required. In addition, it is necessary to operate the airbag device not only for a collision having a large impact but also for a collision where the impact is small and lasts for a long time. Therefore, there is a need for a means to compensate for this.

In order to solve such a problem, a velocity obtained by integrating the acceleration output from the acceleration sensor, that is, a secondary collision velocity at which the occupant approaches a steering wheel, for example, is calculated by inertia due to the collision, and the secondary collision velocity is calculated. A device that outputs an activation signal of an airbag device when the next collision speed exceeds a predetermined reference value has been proposed (Japanese Patent Publication No. 59-85).
No. 74).

[0004]

However, in the above-mentioned conventional method, when a collision occurs in which the impact is small and lasts for a long time, a considerable amount of time is required from the moment of the collision until the activation signal of the airbag device is output. Time may elapse, which may cause a slight shift in the activation timing of the airbag device.

The present invention has been made in view of the above circumstances, and has as its object to provide a collision detection method capable of performing accurate collision detection within a very short time after a collision has occurred.

[0006]

In order to achieve the above object, the present invention provides a collision detection method for detecting a vehicle collision based on an acceleration signal output from an acceleration sensor. Detecting a vehicle collision when an integrated value integrated over a certain first period exceeds a predetermined value and a differential value of the acceleration signal exceeds a predetermined value ;
The acceleration signal over a second period longer than the first period
Is the magnitude of the differential value of the acceleration signal.
The <br/> Rukoto to detect a collision of the vehicle to feature when it exceeds a predetermined value regardless.

[0007]

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a battery 1 and a ground 2
A mechanical acceleration sensor 3, a squib 4, and a transistor 5 are arranged in series between the two. The mechanical acceleration sensor 3 detects an acceleration generated by a collision of the vehicle, and closes a contact to operate the airbag device when the detected acceleration exceeds a predetermined value. Squibb 4
The propellant for energizing the battery 1 to deploy the airbag when the contact of the mechanical acceleration sensor 3 is closed and the collision detection circuit 6 described below outputs a start signal to the base of the transistor 5 Ignite.

Reference numeral 7 denotes an electric acceleration sensor, which converts the acceleration generated by the collision of the vehicle into an electric signal, that is, a voltage signal by a strain gauge, and continuously outputs the electric signal. The output signal of the electric acceleration sensor 7 is amplified by the amplifier 8,
The acceleration signal G is input to the collision detection circuit 6.

As shown in FIG. 2, the collision detection circuit 6 to which the acceleration signal G is inputted includes a collision judgment logic 9 and a collision prediction logic 10, and the collision judgment logic 9 and the collision prediction logic 10 have an OR gate 11. And the transistor 5.

In the integrating means 12 of the collision determination logic 9,
The second period t ₂ where the acceleration signal G is relatively long (for example, 100
１５０150 ms), and an integrated value ΔVa is calculated. The integrated value ΔVa is determined by the collision during the second period t.
_{This corresponds} to the decrease in the vehicle body speed occurring in ₂ , that is, the increase in the speed at which the occupant who is not restrained by the seat approaches the steering wheel when considering the vehicle body as a reference.

The integral value .DELTA.Va is equal to a second
The calculation is performed over the period t ₂ , and the value is compared with a reference value ΔV ₀ set in advance by the comparing means 13. When the integrated value ΔVa exceeds the reference value ΔV ₀ , the OR gate 1
An activation signal is output via the switch 1.

According to the collision determination logic 9, even if a collision occurs in which the impact is small and lasts for a long time, the activation signal of the airbag device can be reliably output.

The waveform of the acceleration generated by the collision of the vehicle, that is, the waveform of the acceleration signal G detected by the electric acceleration sensor 7 is similar to a sine wave as shown in FIG. Period T
It is experimentally known that is a constant that depends on the individual vehicle body structure regardless of the magnitude of the acceleration. The area of the shaded area obtained by integrating the acceleration signal G over the half cycle T / 2 is the amount of deceleration of the vehicle body due to the collision, that is, the secondary collision velocity at which the occupant not restrained by the seat is thrown forward against the vehicle body by the collision. Almost corresponds to. The area of the hatched portion in the waveform of the acceleration signal G is the integrated value ΔVb (double hatched portion in FIG. 3) obtained by integrating the acceleration signal G over a relatively short first period t ₁ (for example, 15 to 20 ms). It increases when the area increases, and decreases when the integral value ΔVb decreases. The area of the hatched portion in the waveform of the acceleration signal G increases as the gradient of the tangent in the waveform, that is, the differential value dG / dt of the acceleration signal G increases, and decreases as the differential value dG / dt decreases. I do. In short, the final secondary collision speed can be predicted to some extent by the integral value ΔVb and the differential value dG / dt of the acceleration signal G,
In the collision prediction logic 10 described below, the integrated value ΔV
b and the differential value dG / dt are used as parameters for starting signal output.

Returning to FIG. 2, the integration means 14 of the collision prediction logic 10 integrates the acceleration signal G over a first period t ₁ shorter than the second period t ₂ , and calculates an integrated value ΔVb. This integral value ΔVb corresponds to the decrease in the vehicle body speed that occurs during the first period t ₁ due to the collision, and is used as a parameter for predicting the secondary collision speed of the occupant as described above. That is, the integrated value ΔVb is compared with a preset reference value ΔV ₁ by the comparing means 15, and the integrated value ΔVb is compared with the reference value ΔV _1.
Signal is output to the AND gate 16 exceeds V _1.

On the other hand, the acceleration signal G passes through a band-pass filter 17, where unnecessary components are filtered by a low-pass filter, and a G _BPF corresponding to a differential value of the acceleration signal G by a differential-type transfer function of a high-pass filter.
Is obtained. The average value calculating means 18 calculates G
_BPF is averaged over the first period t ₁ and the acceleration signal G
Is calculated as dG / dt. This differential value dG / d
t is also used as a parameter for predicting the secondary collision speed of the occupant, and is compared with a preset reference value ΔG by the comparing means 19, and the differential value dG / dt is compared with the reference value ΔG.
Is exceeded, a signal is output to the AND gate 16.

When signals are input to the AND gate 16 from both of the comparing means 15 and 19, the AND gate 16 outputs a start signal of the airbag device. As is clear from the graph of FIG. 4, the area where the AND gate 16 outputs the activation signal is the area A where the integrated value ΔVb exceeds the reference value ΔV ₁ and the differential value dG / dt exceeds the reference value ΔG. On the other hand, when only the conventional mechanical acceleration sensor is used, a start signal is output in the B region.

Integral value ΔVb in a general vehicle collision
And the change of the differential value dG / dt has a locus like a,
Than those of the present invention while activation signal A ₁ point is an intersection of the A region is output, than the conventional activation signal by B ₁ point is an intersection of the B region are output. In other words, the conventional collision detection method has a time delay corresponding to L compared to the collision detection method of the present invention.

In the case of a curb ride (see locus b)
In order to prevent the airbag device from acting in the event of a small impact at low speed or at a low speed (see trajectory c), the conventional collision detection method requires the B region to be largely separated to the upper right from the origin, and as a result The output of the start signal will be further delayed. However, according to the collision detection method of the present invention, even when the area A is set relatively wide, it is possible to avoid unnecessary operation of the airbag device in the event of a curb climb or a low-speed collision.

Incidentally, depending on the situation of the collision, the integral value ΔVb and the differential value dG / dt may draw a locus such as d.
In such a case, the output timing of the activation signal may be delayed. Further, the integral value ΔVb and the differential value dG /
When dt takes a locus like e, the activation signal may not be output. For this purpose, a region (A ′ region in FIG. 4) in which the integral value ΔVb and the differential value dG / dt are larger than the predetermined values ΔV ₁ ′ and ΔG ′, respectively, is added to the A region. A start signal may be output.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various small design changes can be made without departing from the present invention described in the appended claims. It is possible to do.

For example, instead of passing the acceleration signal G through the band-pass filter 17 to obtain a G _BPF corresponding to the differential value, a differential value may be obtained by directly differentiating the acceleration signal G. Further, the present invention is not limited to an airbag device, and can be applied to a seat belt retraction device.

[0024]

According to a first aspect of the above the present invention, obtains an integration value and the differential value of the acceleration signal within a very short first period of time after collision straight from the integrated value and the differential value Since the collision detection is performed by estimating the deceleration amount of the vehicle due to the collision, the collision safety device can be operated accurately without a time delay. Especially when a collision occurs
Within a very short period of time, the integrated value of the acceleration signal
Both when the fixed value is exceeded and when the derivative value exceeds the predetermined value
When both conditions are satisfied, it is judged as "collision"
Therefore, collision judgment is made based on both the integral value and the derivative value of the acceleration signal.
It can be performed accurately and with high accuracy.

According to a second feature of the present invention, when the integral value of the acceleration signal over a second period longer than the first period exceeds a predetermined value, regardless of the differential value of the acceleration signal. Since the collision detection is performed, it is possible to accurately detect a collision in which a small impact continues for a long time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

FIG. 2 is a block diagram of a collision detection circuit.

FIG. 3 is a diagram showing the principle of collision prediction logic.

FIG. 4 is a graph showing a start signal output area of the airbag device.

[Explanation of symbols]

7 ----- acceleration sensor G ----- acceleration signal t ₁ · · · · first period t ₂ · · · · second period

Claims (1)

(57) [Claims] 1. A collision detection method for detecting a collision of a vehicle based on an acceleration signal (G) output from an acceleration sensor (7), wherein the acceleration signal (G) is detected in a first period (t) immediately after the occurrence of the collision. ₁ ), the integrated value (ΔVb) exceeds a predetermined value (ΔV ₁ ) and the differential value (dG / dt) of the acceleration signal (G) exceeds a predetermined value (ΔG). A collision is detected, and the acceleration signal (G) is output from the first period (t ₁ ).
Is integrated over the long second period (t ₂ ) (ΔV
a) is different from the magnitude of the differential value of the acceleration signal (G).
A collision detection method characterized by detecting a collision of a vehicle even when a predetermined value (ΔV ₀ ) is exceeded .