JPH0560777A - Collision detecting method - Google Patents

Abstract

PURPOSE:To output the starting signal of a collision safety apparatus such as an air bag apparatus accurately without time delay from the occurrence of collision. CONSTITUTION:Acceleration signals G outputted from an acceleration sensor are integrated with an integrating means 14 of a collision estimating logic 10 for the first period t1 and differentiated with a band-pass filter 17. When the integrated value DELTAVb exceeds a reference value DELTAV1 and the average value dG/dt of the differentiated values during the first period t1 exceeds a reference value DELTAG, a starting signal S is outputted through an AND gate 16 because the large secondary collision speed is estimated. Meanwhile, the acceleration signals G are integrated for the second period t2, which is longer than the above described first period t1 in an integrating means 12 in a collision judging logic 9. When the integrated value DELTAVa exceeds a reference value DELTAV0, the starting signal is outputted regardless of the output of the collision estimating logic 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision detecting method for accurately activating a vehicle collision safety device such as an airbag device or a belt retracting 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 for the airbag apparatus, the vehicle body is hardly damaged. Since there is a possibility that the activation signal is output only when a small object collides with the vicinity of the acceleration sensor, means for preventing this may be required. Further, the airbag device needs to be activated not only when the impact is large, but also when the impact is small and lasts for a long time. In such a case, the start signal from the acceleration sensor is delayed. Since there is a possibility that there will be a problem, a means to compensate for it will be required.

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

[0004]

However, in the above-described conventional method, when a collision occurs in which the impact is small and continues 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. Since time may elapse, the activation timing of the airbag device may be slightly shifted.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a collision detection method capable of performing accurate collision detection within an extremely short time after a collision occurs.

[0006]

In order to achieve the above object, the present invention provides a collision detection method for detecting a collision of a vehicle based on an acceleration signal output from an acceleration sensor, wherein the acceleration signal is set to a certain first value. A first feature is to detect a collision of a vehicle when an integrated value integrated over a period exceeds a predetermined value and a differential value of the acceleration signal exceeds a predetermined value.

In addition to the first feature described above, the present invention also provides
When an integrated value obtained by integrating the acceleration signal over a second period longer than the first period exceeds a predetermined value, it is possible to detect a vehicle collision regardless of the magnitude of the differential value of the acceleration signal. There are two characteristics.

[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 portion 2
A mechanical acceleration sensor 3, a squib 4, and a transistor 5 are arranged in series between and. The mechanical acceleration sensor 3 detects the acceleration generated by the collision of the vehicle, and closes the contact so as to activate the airbag device when the detected acceleration exceeds a predetermined value. Squib 4
Is a propellant for expanding the air bag by being energized by the battery 1 when the contact point of the mechanical acceleration sensor 3 is closed and the collision detection circuit 6 described later outputs a start signal to the base of the transistor 5. Ignite

Reference numeral 7 is 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 input includes a collision judgment logic 9 and a collision prediction logic 10. The collision judgment logic 9 and the collision prediction logic 10 have an OR gate 11. It is connected to the transistor 5 via.

In the integrating means 12 of the collision judgment logic 9,
The second period t ₂ (for example, 100
(-150 ms), and the integrated value ΔVa is calculated. This integrated value ΔVa is the second period t due to collision.
_{It corresponds} to the decrease in the vehicle speed that occurs 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 as a reference.

The integrated value ΔVa is the second value for each sampling.
The value is calculated over the period t ₂ , and its value is compared with the preset reference value ΔV ₀ in the comparison means 13. When the integrated value ΔVa exceeds the reference value ΔV ₀ , the OR gate 1
An activation signal is output via 1.

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

By the way, 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 becomes a waveform similar to a sine wave as shown in FIG. Cycle T
It is experimentally known that is a constant that depends on the individual vehicle body structure, regardless of the magnitude of acceleration. The area of the hatched portion obtained by integrating the acceleration signal G over the half cycle T / 2 is the deceleration amount of the vehicle body due to the collision, that is, the secondary collision speed at which the occupant not restrained by the seat is thrown forward to the vehicle body due to the collision. Almost corresponds to. The area of the shaded portion in the waveform of the acceleration signal G is the integral value ΔVb (double shaded 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 as the area increases, and decreases as the integrated value ΔVb decreases. The area of the shaded portion in the waveform of the acceleration signal G increases when the slope of the tangent line in the waveform, that is, the differential value dG / dt of the acceleration signal G increases, and decreases when the differential value dG / dt decreases. To do. In short, the final secondary collision velocity 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 outputting the start signal.

Returning to FIG. 2, the integrator 14 of the collision prediction logic 10 integrates the acceleration signal G over the first period t ₁ which is shorter than the second period t ₂ , and calculates the integral value ΔVb. This integral value ΔVb corresponds to the amount of decrease in the vehicle body speed that occurs in 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 the preset reference value ΔV ₁ in the comparison unit 15, and the integrated value ΔVb is compared with the reference value ΔVb.
When V ₁ is exceeded, a signal is output to AND gate 16.

On the other hand, the acceleration signal G passes through the bandpass filter 17, where unnecessary components are filtered by the lowpass filter, and G _BPF corresponding to the differential value of the acceleration signal G is obtained by the differential transfer function of the highpass filter.
Is obtained. Then, the average value calculating means 18 causes the G
_{The BPF} is averaged over the first period t ₁ , and the acceleration signal G
The differential value dG / dt of is calculated. This differential value dG / d
t is also used as a parameter for predicting the secondary collision velocity of the occupant, and is compared with a preset reference value ΔG in the comparison means 19, and the differential value dG / dt is the reference value ΔG.
When it exceeds, a signal is output to the AND gate 16.

When signals are input to the AND gate 16 from both 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 in which the AND gate 16 outputs the activation signal is the area A in which 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, the activation signal is output in the B region.

Integral value ΔVb in a general vehicle collision
And the change of the differential value dG / dt becomes a locus like a,
In the present invention, the activation signal is output at the point A ₁ which is the intersection with the area A, whereas in the conventional one the activation signal is output at the point B ₁ which is the intersection with the area B. In other words, the conventional collision detection method has a time lag corresponding to L compared with the collision detection method of the present invention.

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

Depending on the situation of the collision, the integrated value ΔVb and the differential value dG / dt may draw a locus like d.
In such a case, the output timing of the activation signal may be delayed. Further, the integrated value ΔVb and the differential value dG /
When dt takes a locus like e, the start signal may not be output. For this purpose, areas (A 'area in FIG. 4) in which the integrated value ΔVb and the differential value dG / dt are larger than the predetermined values ΔV ₁ ′ and ΔG ′, respectively, are added to the A area, and in the A area and the A ′ area. You may make it output a starting signal.

Although the embodiments of the present invention have been described in detail above, 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 claims. It is possible to

For example, instead of passing the acceleration signal G through the bandpass filter 17 to obtain G _BPF corresponding to its differential value, the acceleration signal G may be directly differentiated to obtain the differential value. The present invention can be applied not only to the airbag device but also to a seat belt retracting device.

[0024]

As described above, according to the first feature of the present invention, the integrated value and the differential value of the acceleration signal in the extremely short first period after the occurrence of the collision are obtained, and the collision is calculated 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 safety device can be accurately operated without causing a time delay.

According to the second aspect of the present invention, when the integrated 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 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 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 a collision prediction logic.

FIG. 4 is a graph showing an activation signal output region of the airbag device.

[Explanation of Codes] 7 ... Acceleration sensor G ... Acceleration signal t ₁ ... First period t ₂ ... Second period

Claims (2)

[Claims] 1. A collision detection method for detecting a vehicle collision based on an acceleration signal (G) output from an acceleration sensor (7), wherein the acceleration signal (G) is applied for a certain first period (t ₁ ). A collision detection method, characterized in that a collision of the vehicle is detected when an integrated value obtained by integration as a result exceeds a predetermined value and a differential value of the acceleration signal (G) exceeds a predetermined value. 2. An integrated value obtained by integrating the acceleration signal (G) over a second period (t ₂ ) longer than the first period (t ₁ ) is larger or smaller than a differential value of the acceleration signal (G). The collision detection method according to claim 1, wherein a collision of the vehicle is detected when the predetermined value is exceeded regardless of the predetermined value.