JP2507796B2 - Airbag device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airbag device mounted on a vehicle as one of occupant protection devices.

2. Description of the Related Art An airbag device has a steering wheel 2 as shown in FIG. 8 (the airbag device is indicated by reference numeral 1 in the figure).
When the vehicle collides with the bag, the inflator (not shown) therein operates based on the detection of the deceleration sensor (not shown) so that the bag body 3 is rapidly deployed. There is. And this expanded bag body 3
The upper body of the occupant D who leans forward is restrained by this so that the occupant D does not hit the steering wheel 2 directly. In addition, in such an airbag device 1, an exhaust valve (not shown) is provided in addition to the inflator, and the occupant D collides with the bag body 3 and the internal pressure of the bag body 3 becomes equal to the set pressure. When the exhaust pressure is increased above, the exhaust valve is actuated so that the impact that the occupant D receives from the bag body 3 when restrained is reduced by the exhaust action as much as possible.

This similar technique is disclosed, for example, in Japanese Patent Laid-Open No. 47-72839, Japanese Utility Model Laid-Open No. 61-117051, and the like.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described conventional airbag device 1, the specifications of each part are set in advance based on the maximum physique of the occupant D, the vehicle speed at the time of a collision, and the like. For,
There is a problem that the device becomes large.

It is known that the kinetic energy possessed by an occupant at the time of a collision is different if the physique of the occupant is different even when the occupant collides at the same vehicle speed, and even if the occupants of the same physique are different at different vehicle speeds at the time of the collision. This means that even in the airbag device, more appropriate restraint of the occupant cannot be performed unless the restraint characteristic of the bag body is changed in accordance with the physique of the occupant and the vehicle speed at the time of collision. .

Therefore, the present invention provides an airbag device capable of automatically adjusting the restraint characteristics of the bag body one by one in response to the varying conditions such as the physique of the occupant and the vehicle speed at the time of a collision, and the device is downsized.

Means for Solving the Problems The present invention is, as means for solving the above-mentioned problems, in an airbag device in which a bag body is deployed to restrain the upper body of an occupant during a vehicle collision, the occupant collides with the bag body. Pressure adjusting means for adjusting the internal pressure of the bag main body and the internal pressure of the bag main body while the occupant is restrained in the bag main body, a weight detecting means for directly or indirectly detecting the weight of the upper body of the occupant, and the occupant. A collision speed detecting means for detecting the collision speed of the bag body against the bag body, and a calculating / controlling means for calculating / controlling the operating pressure of the pressure adjusting means based on the output values of the weight detecting means and the collision speed detecting means. It was done like this.

By taking such a measure, when the vehicle collides, the weight detection means and the collision speed detection means input the weight of the upper half of the occupant's upper body and the collision speed to the bag body to the calculation / control means. The control means converts the working pressure of the pressure adjusting means suitable for the occupant and the collision state at that time, and the working pressure of the pressure adjusting means is adjusted to an appropriate value based on this result. Here, the internal pressure of the bag body when the occupant collides with the occupant, which is adjusted by the pressure adjusting means, has a great influence on how the deceleration of the occupant increases after being restrained by the occupant bag body. By controlling the internal pressure of the bag body at the time of performing as described above, the impact of the occupant received from the bag body can be suppressed to a low value. Further, the internal pressure of the bag body adjusted by the pressure adjusting means while the occupant is restrained by the bag body affects the maximum deceleration of the occupant and the required back stroke of the bag body. By controlling the internal pressure of the bag body as described above while the vehicle is restrained by the bag body, the reaction force received by the occupant from the bag body can be suppressed to a low value within the range not exceeding the specifications of the bag body. Become.

Example Hereinafter, a specific example of the present invention will be described with reference to FIGS. 1 to 7. The same parts as those of the conventional technique shown in FIG. 8 are designated by the same reference numerals.

In FIGS. 1 and 2, the airbag device 1 is arranged in the center of the steering wheel 2 similarly to the one shown in FIG. 8, and the inflator 4 is activated based on the detection of a deceleration sensor (not shown) at the time of collision. The bag body 3 is rapidly expanded by this air pressure. The bag body 3 is fixed to the base plate 5 fixed to the steering wheel 2 at its outer peripheral end via a retainer 6, and is normally stored in the cover 7 in a folded state while the vehicle is traveling. . Further, the substrate 5 is provided with a first exhaust valve 8 and a second exhaust valve 9 which are pressure adjusting means, and the first exhaust valve 8 has a first internal pressure of the bag body 3 when the bag body 3 is deployed. When the occupant D collides with the occupant D, the second exhaust valve 9 keeps the internal pressure of the bag body 3 equal to Pa when the occupant D collides.
And the internal pressure of the bag body 3 reaches the second operation start pressure Pb, the internal pressure of the bag body 3 is maintained below Pb while opening and restraining the occupant D. The operation starting pressures Pa and Pb of the first exhaust valve 8 and the second exhaust valve 9 can be changed appropriately by an electric signal from the outside.

The first exhaust valve 8 and the second exhaust valve 9 are electrically connected to a central processing unit (hereinafter, referred to as CPU 10) as a calculation / control means, and the CPU 10 further directly measures the weight of the upper body of the occupant D. A load cell 12 installed on the seat back 11 for detection, and a vehicle speed sensor 1 installed on the transmission 13
4, electrically connected to a seat belt sensor 16 embedded in the base of the seat belt 15, a pressure gauge 18 installed in the intake hole 17 portion, a deceleration sensor (not shown) that detects a vehicle collision, and the like. The load cell 12 functions as a weight detecting means for detecting the weight of the upper half of the occupant D seated on the seat cushion 11, and the vehicle speed sensor 14 and the seatbelt sensor 16 serve as the occupant D.
It functions as a collision speed detecting means for detecting the collision speed of the bag body 3 against the bag body 3. The collision speed of the occupant D on the bag body 3 is almost the same as the vehicle speed on the verge of a collision unless the seat belt 15 is worn, but when the seat belt 15 is worn, the vehicle is restrained by the seat belt 15. Since it must be considered that the vehicle speed before the collision is reduced by the amount of the
The two output signals from the seat belt sensor 16 determine the speed at which the occupant D collides with the bag body 3.
Since the atmospheric pressure is one of the varying conditions that vary depending on the region, etc., the pressure gauge 18 is connected to the CPU 10 in this embodiment, but the difference in atmospheric pressure is not so large. The pressure gauge 18 does not have to be specially provided.

Here, how to obtain the value of the first operation starting pressure Pa will be described.

When the occupant D collides with the bag body 3 and compresses the bag body 3, the volume reduction amount ΔV of the bag body 3 in a minute time Δt is ΔV = −A · v · Δt ...... [A: occupant Contact area between D and the bag body 3, v: collision speed of the occupant D with the back body 3].

In addition, the force m applied to the bag body 3 by the occupant D during a collision
(D ² S / dt ² ) [m: weight of the upper half of the occupant D, S: displacement of the occupant D to the front], and the reaction force (P-Pc) · A [A] given to the occupant D by the bag body 3. P: Internal pressure of bag body 3, Pc: Atmospheric pressure, A:
The contact area between the occupant D and the bag body 3] is equal over the entire time that the bag body 3 restrains the occupant D. Therefore, m · (d ² S / dt ² ) = − (P−Pc) · The relational expression A ... is obtained.

From these equations, the following differential equation can be derived.

d ² V / dt ² = (P−Pc) · A ² / m ...... On the other hand, the decrease amount ΔPe of the internal pressure of the bag body 3 due to the exhaust of the gas at the minute time Δt is ΔPe = The internal pressure P of the bag body 3 when Δt time has elapsed from a certain time t is P = P ₀ , where P ₀ is the internal pressure at a certain time t when there is no exhaust gas. −ΔPe …….

Further, assuming that the bag body 3 is not exhausted from beginning to end, the internal pressure P ₀ and the volume V ₀ of the bag body 3 at a certain time t, and Δ
The relationship between the internal pressure P and the volume V of the bag body 3 when the time t has elapsed is represented by P · V = P ₀ · V ₀ ... From the equation of state of the ideal gas.

The following differential equation can be derived from these equations.

dP / dt =-(P / V) * (dV / dt) -c ... The deceleration of the occupant D can be calculated by performing a numerical analysis using the differential equation derived in this way.

By the way, FIG. 3 shows an example of the internal pressure waveform of the bag body 3 when the internal pressure of the bag body 3 when the occupant D contacts the bag body 6 is changed, and FIG. 4 shows the occupant D at this time.
An example of the deceleration waveform of is shown. M ₁ , M, M _{2 in} FIG. 3 indicate the contact start points between the occupant D and the bag body (a),
Contact pressure from 0.025kg / m ² to 0.2kg / m ^{2 in} order of (b) and (c)
It is gradually increasing until. The waveforms (a), (b) and (c) shown in FIG. 4 are the waveforms (a) and (b) shown in FIG.
It corresponds to (b) and (c). As is apparent from FIG. 4, when the internal pressure of the bag body 3 when the occupant D comes into contact is M (0.1 kg / m ² ), each peak of the internal pressure of the bag body 3 and the deceleration of the occupant D The value becomes the lowest, and each peak value rises at a slightly smaller value M ₁ (0.025 kg / m ² ) or a slightly larger value M ₂ (0.2 kg / m ² ). Further, FIG. 5 shows the relationship between the internal pressure of the bag body 3 and the peak deceleration of the occupant D (hereinafter referred to as the peak G) when the occupant D contacts, which is clear from this figure. As described above, the peak G of the occupant D when restrained by the bag body 3 depends on the magnitude of the internal pressure of the bag body 3 when the occupant D contacts the bag body 3, and the internal pressure is the value M (0.1 kg / 0.1 kg / The peak G is the lowest at m ² ). Here, when the internal pressure of the bag body 3 is smaller than the optimum value M, the peak G of the occupant D becomes large because the contact area between the occupant D and the bag body 3 suddenly increases because the bag body 3 is easily dented. In addition to the increase, the rate of change in pressure of the bag body 3 with respect to the same displacement amount of the occupant D becomes high, which causes a rapid increase in the reaction force of the occupant D obtained by multiplying the contact area and the internal pressure. There is. On the contrary, when the internal pressure of the bag body 3 is larger than the optimum value M, the peak G of the occupant D increases.
The cause is that the initial reaction force increases because the bag body 3 approaches the rigid body.

Therefore, if the first operation starting pressure Pa is set to the value M shown in FIGS. 3 and 5, the peak G becomes the lowest. The first operation start pressure Pa actually set is not strictly the lowest peak G, but the peak G should be within the range of the minimum peak G shown in the figure plus 0.5G. ing. The internal pressure region of the bag body 3 which meets this condition is indicated by the reference symbol E in FIG.

Next, how to obtain the value of the second operation starting pressure Pb will be described.

Occupant D kinetic energy just before hitting the bag body 3 is represented by m · v ^2/2. On the other hand, the energy absorbed by the bag body 3 is represented by F · l, where F is the reaction force applied to the occupant D by the bag body 3 and l is the stroke in the front-rear direction of the bag body 3. This reaction force F is F = P · A, where P is the internal pressure of the bag body 3 and A is the contact area, so the energy absorbed by the bag body 3 is further represented by P · A · l.

By the way, in order for the occupant D to be reliably restrained by the bag body 3 without bottoming on the steering wheel 2, the absorbed energy on the bag body 3 side must exceed the kinetic energy on the occupant D side. it ^{m · v 2/2 ≦ P} · a · l conditions, ^{i.e., P ≧ m · v 2/} 2 · a
-It means that the condition of l is satisfied. Further, in order to suppress the deceleration of the occupant D when restrained by the bag body 3, the internal pressure P of the bag body 3 must be set to a value as small as possible.

Accordingly, the second operation starting pressure Pb ^{of, P ≧ m · v 2/} 2 ·
While satisfying the conditions of A · l, set so that both satisfy value condition of small P become ^{P ≒ m · v 2/2} · A · l as possible.

The method for obtaining the first operation start pressure Pa and the second operation start pressure Pb is as described above, but in the CPU 10, the specific values of the first operation start pressure Pa and the second operation start pressure Pb. When calculating, the specific numerical values must be entered in the symbols that make up each conditional expression. Here, the values that are automatically determined when the specifications of the airbag device 1 are determined include the volume V of the bag body 3, the contact area A between the bag body 3 and the occupant D, and the exhaust hole. It is the pressure reduction rate c of the internal pressure of the bag main body due to gas exhaust. On the other hand, it is the weight m of the upper body of the occupant D, the collision speed v of the occupant D with respect to the bag body 3, and the atmospheric pressure Pc that change depending on the situation. Therefore, in the CPU 10, the airbag device 1
The optimum first operation pressure Pa from the values V, A, and c that are predetermined according to the specifications and the values m, v, and Pc that are input at the time of collision.
And the value of the second operation starting pressure Pb is calculated.

Next, the operation of the airbag device 1 in this embodiment will be described.

When a vehicle collision is detected by a deceleration sensor (not shown), the inflator 4 is actuated and the bag body 3 starts to be deployed. At that time, the load cell 14 provided in the seat back 11 causes the weight m of the upper body of the occupant D to rise. Is read, the vehicle speed is read by the vehicle speed sensor 14 in the transmission 13, and the atmospheric pressure Pc is detected by the pressure gauge 18, respectively.

As shown in the flowchart of FIG. 6, in the CPU 10, the signals of the weight m, the vehicle speed, and the atmospheric pressure Pc are read (step, step 2, step 3), and then the seat belt sensor 16 is ON or OFF. Is determined (step 4), and different calculation is performed depending on whether it is ON or OFF. That is, when the seat belt sensor 16 is ON, the collision speed v of the occupant D with respect to the bag body 3 when the seat belt 15 is worn is converted based on the vehicle speed at the time of the collision, and this speed v Optimal values of the first operation starting pressure Pa and the second operation starting pressure Pb are calculated based on the weight m (step 5). Further, when the seat belt sensor 16 is OFF, the vehicle speed at the time of the collision is regarded as it is as the collision speed v of the occupant D with respect to the bag body 3, and the first operation start pressure Pa based on this speed v and the weight m. And an optimum value of the second operation starting pressure Pb is calculated (step 6). Then, based on the calculation results of step 4 and step 5, the value of the first operation start pressure
The first exhaust valve 8 and the second exhaust valve 9 are controlled so that Pa and the value Pb of the second operation start pressure are optimal values (step 7). As a result, the first operation start pressure Pa and the second operation start pressure Pb are always set to the optimum values.

On the other hand, the internal pressure of the bag body 3 which has started to be expanded changes so as to draw the waveform shown in FIG. The internal pressure of the bag body 3 rapidly increases to break the module when the inflator 4 is actuated (D in the figure), but then becomes a negative pressure for a period of time because the bag body 3 rapidly expands due to inertia ( (E in the figure), and thereafter, when the bag body 3 is expanded to some extent, the number of the bags again increases rapidly (f in the figure).
When the internal pressure of the bag body 3 reaches the first operation start pressure Pa as it is, the first exhaust valve 8 opens and the subsequent internal pressure of the bag body 3 is maintained at the same pressure as the first operation start pressure Pa. (In the figure). Therefore, even if the occupant D collides with the bag body 3 at any time thereafter, the internal pressure of the bag body 3 at that time is always the same as Pa. In this state, when the occupant D collides with the deployed bag body 3, the internal pressure of the bag body 3 rapidly increases (C in the figure). Then, when the bag body 3 reaches the second operation start pressure Pb, the second exhaust valve 9 opens and the subsequent internal pressure of the bag body 3 is maintained at the same pressure as the second operation start pressure Pb (the same). Re in the figure).

The internal pressure of the bag body 3 when the occupant D collides is
Since the peak G is maintained at a value that is substantially the minimum, the impact that the occupant D receives from the bag body 3 when restrained is minimized. Further, after the second exhaust valve 9 is opened, the internal pressure of the bag body 3 is maintained at a pressure equal to or lower than the lowest pressure Pb at which the occupant D does not bottom on the steering wheel hull 2. The reaction force received from the bag body 3 before being restrained is also the minimum. As described above, in the present embodiment, the internal pressure of the bag body 3 is always optimally controlled, so that the size of the bag body 3 can be reduced to the required minimum and the apparatus can be downsized.

Although the first and second exhaust valves are used as the pressure adjusting means in the above-described embodiment, the present invention is not limited to this, and one pressure adjusting valve or another device may be used.
The weight of the upper body of the occupant D is not directly detected,
It is also possible to measure the total weight of the occupant D and convert the weight of the upper half of the body to detect it.

As described above, according to the present invention, the operating pressure of the pressure adjusting means suitable for the occupant and the collision state at that time is sequentially adjusted based on the weight of the upper body of the occupant and the collision speed to the bag body. The impact and reaction force that the occupant receives from the bag body can always be minimized in response to the varying conditions such as the physique of the occupant and the vehicle speed at the time of a collision. As a result, the restraint characteristic of the bag body is always optimized, and the device can be made compact.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an embodiment of the present invention, FIG. 2 is a sectional view of the same, and FIG. 3 is a graph showing the internal pressure waveform of the bag body when the internal pressure when an occupant collides is changed. FIG. 4 is a graph showing the deceleration waveform of the occupant D when the internal pressure when the occupant D collides is changed, and FIG. 5 is the internal pressure of the bag body and the deceleration of the occupant D when the occupant D collides. FIG. 6 is a flow chart showing the flow of processing in one embodiment of the present invention, and FIG. 7 is an internal pressure waveform of the bag body at the time of collision when the airbag device according to the present invention is adopted. The graph shown in FIG. 8 is a schematic side view showing a conventional technique. 1 ... Air bag device, 3 ... Bag body, 8 ... First exhaust valve (pressure adjusting means), 9 ... Second exhaust valve (pressure adjusting means), 10 ... CPU (calculation / control means), 12 …… load cell (weight detection means), 14 …… vehicle speed sensor (collision speed detection means), 16 …… seat belt sensor (collision speed detection means).

Claims (1)

(57) [Claims] 1. An airbag device for restraining an occupant's upper body by expanding a bag body at the time of collision of a vehicle, while the internal pressure of the bag body when the occupant collides with the bag body and the occupant being restrained by the bag body. A pressure adjusting means for adjusting the internal pressure of the bag body, a weight detecting means for directly or indirectly detecting the weight of the upper body of the occupant, a collision speed detecting means for detecting a collision speed of the occupant with the bag body, An airbag apparatus comprising: a weight detection means and a calculation / control means for calculating / controlling an operating pressure of the pressure adjusting means based on an output value of the collision speed detection means.