JPH04292241A - Starting method of collisional safety device - Google Patents

Abstract

PURPOSE:To operate a collisional safety device, such as an air bag unit and a belt draw gear or the like, in a very short time after collision happening. CONSTITUTION:Supposing that a waveform of acceleration G being produced by a car crash is set down to a sinusoidal wave G=-Acosomegat+A (omega=2/T) of amplitude A and time T, a secondary collision velocity V, where an area V in a slanting line, namely, a rider unequipped with a seat belt is thrown forward due to collisional inertia, is operated by an equation of V=(T/2).{(dG/ dt)<2>/Gomega2+G} with the time T or a constant being determined by acceleration G at the initial stage of the crash, time differentiation dG/dt of acceleration G and a body structure. If this secondary collisional velocity goes beyond the reference value, a starting signal of a collisional safety device is outputted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for activating a collision safety device such as an air bag device or a belt retraction device in the event of a vehicle collision.

0002

[Prior Art] In an airbag system that protects occupants from secondary collision damage in the event of a vehicle collision, if only the acceleration signal output from an acceleration sensor is used as the activation signal, it is possible to avoid causing almost no damage to the vehicle body. There is a possibility that an activation signal will be output even if a small object collides near the acceleration sensor, so a means to prevent this is required. In addition, it is necessary to activate the airbag device not only in a collision with a large impact but also in a collision with a small impact that continues for a long time, but in such cases the acceleration sensor does not output an activation signal. Since this is a possibility, a means of compensating for this is required.

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

0004

[Problems to be Solved by the Invention] However, with the above conventional method, when a collision occurs where the impact is small and continues for a long time, it takes a considerable amount of time from the moment of the collision until the activation signal for the airbag device is output. Time may pass, 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-mentioned circumstances, and it is an object of the present invention to provide a method for activating a collision safety device that can accurately activate the collision safety device within a very short time after a collision occurs. .

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides activation of a collision safety device that activates the collision safety device based on an output signal of an acceleration sensor that detects acceleration caused by a vehicle collision. The method is characterized in that the amount of deceleration of the vehicle body due to a collision is estimated from the output signal of the acceleration sensor and the time rate of change of the output signal, and the collision safety device is activated when the amount of deceleration exceeds a predetermined value. do.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

As shown in FIG. 1, a battery 1 and a grounding section 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 acceleration caused by a vehicle collision, and closes a contact point to activate an airbag device when the detected acceleration exceeds a predetermined value. squib 4
is a propellant that is energized by the battery 1 to deploy the air bag when the contact of the mechanical acceleration sensor 3 is closed and the collision judgment circuit 6, which will be described later, outputs an activation signal to the base of the transistor 5. ignite.

Reference numeral 7 denotes an electrical acceleration sensor which converts the acceleration generated by a vehicle collision into an electrical signal, ie, a voltage signal, using a strain gauge and continuously outputs the signal. After the output signal of the electric acceleration sensor 7 is amplified by an amplifier 8, high frequency components are removed by a low-pass filter 9, and the signal is input to the collision determination circuit 6.

By the way, the waveform of acceleration generated by a vehicle collision, that is, the waveform of acceleration detected by the electric acceleration sensor 7, is a waveform similar to a sine wave that is synthesized with a high-frequency distortion component, as shown in FIG. It is experimentally known that this is the case. When the acceleration waveform is passed through the low-pass filter 9, a waveform similar to a sine wave as shown in FIG. 3 is obtained, and the period T in the waveform is
It is known that is a constant that depends on the individual vehicle body structure, regardless of the magnitude of acceleration. Therefore, assuming that the waveform of acceleration generated by a vehicle collision is a sine wave, from the constant T, the acceleration G at the initial stage of the collision, and its rate of change over time dG/dt, the area of the shaded part V, that is, the deceleration of the vehicle body due to the collision. Able to calculate quantities. Since the size of the area V corresponds to the speed at which an occupant who is not wearing a seatbelt is thrown forward against the vehicle body due to a collision, that is, the speed of a secondary collision, the value of V corresponds to Used as a parameter to start.

Next, constant T, acceleration G, and acceleration G
The process of calculating the secondary collision velocity V from the time rate of change dG/dt will be explained based on FIG. 4.

The waveform of acceleration G caused by a vehicle collision is a sine wave with amplitude A and period T. G=-A cosωt+
A (ω=2π/T)...■
Assuming that, by differentiating the formula ■ with respect to time t, we get
dG/dt=Aω sinωt
・・・
・■ is obtained, and by transforming this formula, sinωt=(dG/
dt)/Aω・
...■ is obtained.

On the other hand, by transforming the above equation (2),
cosωt=1-G/A
・・・
・■ is obtained.

[0014] The above equations ■ and ■ are expressed as the formula sin2 ωt
+ cos2 ωt = 1 to obtain {(dG/dt)/Aω}2 + (1
-G/A)2 = 1 is transformed into 2A=(dG/dt)2
/Gω2 +G...
■ is obtained.

Here, the area V of the shaded part in FIG.
V=AT

...Given by ■.

[0016] Therefore, by substituting the formula
)2 /Gω2 +G}...■ is obtained.

The above equation (2) shows that the secondary collision velocity V of the occupant can be estimated from the value of the acceleration G at a certain time and the value of its time differential dG/dt.

Next, the details of the collision determination performed in the collision determination circuit 6 will be explained based on the flowchart shown in FIG.

First, in step S1, G1 is set to 0, and in step S2, the value G2 of the output signal of the electrical acceleration sensor 7 that has passed through the amplifier 8 and the low-pass filter 9 is read. In the following step S3, the value of ΔG corresponding to the time rate of change dG/dt of the acceleration is determined as ΔG.
It is calculated by =(G2-G1)/ΔT. Here, ΔT is a predetermined sampling time.

Next, in step S4, the secondary collision velocity V is calculated based on the equation (2). At this time, dG/dt of the formula ■
The above ΔG is used instead of , and the above G
2 is used. When the secondary collision velocity V is calculated in this way, the value of the secondary collision velocity V is compared with a predetermined reference value V0 in step S5, and if V exceeds V0, the airbag device is activated. It is determined that it is necessary,
In step S6, an activation signal for the airbag device is output. Since the value of the secondary collision velocity V, that is, the area of the shaded part in FIG. 4 depends on the period T and amplitude A of the sine wave of the acceleration G, the activation signal of the airbag device is turned on as shown in FIG.
At the boundary between the region and the OFF region, the amplitude A is small when the period T is large, and conversely, the amplitude A is large when the period T is small. Further, if V is equal to or less than V0 in step S5, G1 is replaced with G2 in step S7, and the operations from step S2 onwards are repeated.

[0021] Since a collision can be determined based on the value of acceleration immediately after a collision and the value of its rate of change over time, the airbag device can be operated while ensuring sufficient operating time for the airbag to deploy. can output a start signal.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and various small design changes may be made without departing from the scope of the present invention as set forth in the claims. It can be carried out.

For example, the present invention is applicable not only to airbag devices but also to belt retraction devices for seat belts.

[0024]

As described above, according to the present invention, the amount of deceleration of the vehicle body due to the collision can be estimated by detecting the acceleration of the vehicle immediately after the collision, and the amount of deceleration is compared with a reference value to improve collision safety. A decision as to whether or not to activate the device can be made very early after a collision occurs. As a result, the activation signal can be outputted early, taking into full consideration the time required for the operation of the collision safety device, and it becomes possible to fully utilize the functions of the collision safety device.

[Brief explanation of drawings]

[Fig. 1] Block diagram showing the overall configuration of the present invention

[Figure 2] Graph showing the waveform of acceleration detected by the electrical acceleration sensor

[Figure 3] Graph showing the waveform of acceleration passed through a low-pass filter

[Figure 4] Explanatory diagram of how to calculate secondary collision velocity

[Fig. 5] Flowchart showing the content of collision determination performed in the collision determination circuit

[Figure 6] Graph showing criteria for collision judgment

[Explanation of symbols]

7... Electric acceleration sensor (acceleration sensor) G...
Acceleration (output signal of acceleration sensor) ΔG... Time rate of change of acceleration V... Secondary collision speed (deceleration amount)

Claims (1)

[Claims] 1. A method for activating a collision safety device in which the collision safety device is activated based on an output signal (G) of an acceleration sensor (7) that detects acceleration caused by a vehicle collision, comprising: The amount of deceleration (V) of the vehicle body due to a collision is estimated from the output signal (G) and the time rate of change (ΔG) of the output signal (G), and when the amount of deceleration (V) exceeds a predetermined value, the collision safety A method for activating a collision safety device, the method comprising activating the device.