Passive restraint system for a vehicle occupant using an air bag

In a passive restraint system for a vehicle occupant using an inflatable air bag, an open base end of the air bag is clamped between an air bag housing for accommodating the air bag in its folded state and an inflator housing for receiving an inflator for producing the inflating gas therein. Thus, the base end of the air bag can be attached securely and tightly to the air bag system in a highly simple manner. The air bag housing diverges toward the opening for deploying the air bag, and the air bag can be therefore rapidly deployed without encountering any substantial resistance from the air bag housing. Also, the diverging shape of the air bag housing allows the air bag housing to be laterally deformed to absorb the energy of impact applied thereto.

TECHNICAL FIELD 
The present invention relates to a passive restraint system for protecting 
a vehicle occupant from the impact of a vehicle crash by using an 
inflatable air bag. 
BACKGROUND OF THE INVENTION 
An increasingly large number of automobiles are equipped with a passive 
restraint system which employs an inflatable air bag in case of a vehicle 
crash by detecting a large deceleration of the vehicle. Such an inflatable 
bag is normally installed inside a central part of a steering wheel for 
protecting the vehicle operator. To protect the vehicle occupant sitting 
next to the vehicle operator, an inflatable bag may be installed inside a 
part of the instrument panel opposing the vehicle occupant. To protect the 
vehicle occupants sitting in the rear seat, inflatable bags may be 
installed in the front seats or other suitable locations. 
When a vehicle runs into an oncoming vehicle or a stationary object, a 
large deceleration acts upon the vehicle, and the vehicle occupant 
experiences an apparent force or an inertia force which pushes the vehicle 
occupant forward. A passive restraint system restrains the vehicle 
occupant from such a forward movement upon detecting a strong 
deceleration, and thereby prevents the vehicle occupant from hitting the 
windshield or other parts of the vehicle, and being thereby injured. 
It is therefore essential for a passive restraint system using an 
inflatable air bag to be able to deploy the air bag in a short time period 
after detecting a large deceleration. For the air bag to be able to 
quickly deploy itself, the air bag must be free from leakage so that the 
gas for inflating the air bag may be fully utilized. Also, to fully 
utilize the energy of the gas for inflating the air bag, the air bag must 
inflate toward the vehicle occupant without excessively bulging in lateral 
directions. 
Normally, an air bag is made of nylon fabric coated with rubber, and its 
open base end is connected to a housing for an inflator or a gas producing 
unit. 
The air bag is normally folded, and received in an air bag housing. Upon 
detecting a strong deceleration, the inflator produces gas, and inflates 
the air bag. Because the production of the gas occurs in an almost 
explosive fashion so that the air bag may be deployed in a short time, gas 
pressure builds up extremely suddenly in the region near the open base end 
of the air bag, and an effective sealing arrangement is necessary in the 
open end of the air bag. Therefore, there has been a demand for a simple 
and economical structure which can firmly secure the open end of an air 
bag, and eliminate the possibility of gas leakage. 
Because of the need to be stowed in a relatively small compartment provided 
inside an instrument panel or the like, an air bag system is desired to be 
as compact as possible. On the other hand, the housing for the air bag 
should not hinder the deployment of the air bag. Furthermore, if the air 
bag housing has an insufficient rigidity, when the air bag is inflated, 
the housing may be deformed, and may allow the air bag to be inflated 
laterally. This reduces the impetus of the air bag to be properly 
deployed, and is therefore undesirable. Conversely, if the housing is too 
rigid, it will present a rigid surface in front of a vehicle, occupant, 
and the capability of the area accommodating the air bag to absorb impact 
is reduced. This is not desirable because additional padding may be 
necessary to achieve a desired impact absorbing capability in this area. 
The part of the instrument panel or the like in which an air bag system is 
installed is normally closed by a lid which can readily rupture when the 
air bag is deployed, and this lid may be mounted either on a housing 
accommodating the inflator for producing the gas and/or the air bag, or on 
the instrumental panel either directly or via a frame structure. 
In the former case, there is some difficulty in aligning the lid with the 
opening provided in the instrument panel. In the latter case, the 
instrument panel is significantly damaged whenever the air bag is 
activated, and the repair subsequent to the deployment of the air bag is 
unacceptably costly. 
BRIEF SUMMARY OF THE INVENTION 
In view of such problems of the prior art, a primary object of the present 
invention is to provide a passive restraint system for a vehicle occupant 
using an air bag which is compact in size, and can smoothly deploy the air 
bag. 
A second object of the present invention is to provide a passive restraint 
air bag system which is capable of absorbing impact. 
A third object of the present invention is to provide a passive restraint 
air bag system which is easy to install. 
A fourth object of the present invention is to provide a passive restraint 
air bag system which would not damage the instrument panel or other part 
of the vehicle body when it is deployed. 
A fifth object of the present invention is to provide a passive restraint 
air bag system which is free from leakage even when a pressure build up in 
the air bag is extremely rapid. 
According to the present invention, these and other objects can be 
accomplished by providing a passive restraint system for a vehicle 
occupant using an air bag that can be inflated upon detection of a 
deceleration exceeding a certain threshold level, comprising: an inflator 
housing containing an inflator for producing gas for inflating an air bag 
and having a first opening from which gas produced from the inflator may 
be expelled; an air bag housing attached to the inflator housing, and 
having a second opening disposed so as to be communicated with the first 
opening of the inflator housing when the air bag housing is attached to 
the inflator housing, and a third opening placed opposite to the second 
opening; and an air bag received in the air bag housing in a folded state, 
and adapted to be projected and deployed from the third opening of the air 
bag housing when the air bag is inflated by the gas, the air bag being 
provided with an open base end from which gas produced from the inflator 
may be introduced into the air bag to inflate the same, the base end being 
clamped between the inflator housing and the air bag housing when the air 
bag housing is attached to the inflator housing. 
Because the base end of the air bag can be clamped between the two housings 
over a relatively large area, it is possible to avoid any concentration of 
stress in the base end of the air bag, and a favorable sealing capability 
and a high mechanical strength can be accomplished at the same time. Thus, 
the reliability of the air bag system can be improved. Also, the air bag 
system can be built as a highly compact unit. 
The two housings can be arranged in a number of ways. For instance, a 
partition wall can be interposed between the inflator housing and the air 
bag housing, the partition wall being provided with at least one opening 
serving as a gas outlet for allowing gas produced from the inflator to be 
introduced into the air bag. Thus, the two housings can be assembled 
without being hampered by any poor accessibility. Alternatively, the 
partition wall may be integrally provided in the inflator housing, and the 
base end of the air bag may be interposed between sealing surfaces defined 
on the partition wall and an annular flange provided in the air bag 
housing. As yet another possibility, the inflator housing and the air bag 
housing may consist of an integrally formed common housing which is 
separated by the partition wall consisting of a separate member, the base 
end of the air bag being interposed between sealing surfaces defined on 
the partition wall and an inner surface of the common housing. 
Typically, the inflator housing is securely attached to a fixed part of a 
vehicle body, and the third opening is placed opposite to an opening of a 
part of a vehicle body such as an instrument panel. The vehicle body 
opening is closed by a lid member which can rupture when the air bag is 
deployed, the lid member being engaged by the instrument panel by first 
engagement means allowing a lateral movement of the lid member relative to 
the vehicle body opening. 
Thus, it is possible to properly position the lid member with respect to 
the vehicle body opening, and a favorable external appearance can be 
ensured. To accomplish this goal, the first engagement means may comprise 
a plurality of tongues depending from a reverse surface of the lid member, 
the tongues being each provided with a claw engaging an inner peripheral 
edge of the vehicle body opening. 
According to a preferred embodiment of the present invention, the lid 
member is provided with a peripheral part overlapping an inner peripheral 
edge of the vehicle body opening from exterior. Thus, even when the air 
bag is deployed, and the lid member is ruptured, the surrounding part of 
the vehicle body typically consisting of an instrument panel would not be 
damaged. Preferably, the lid member is engaged by the air bag housing by 
second engagement means which allows slight movement of the lid member 
away from the vehicle body part. Thus, when the lid member ruptures, 
because the lid member is initially pushed by the inflated air bag a short 
distance away from the surface of the vehicle body, the peripheral edge of 
the lid member would not hit the surface of the vehicle body, and the 
possibility of damaging the vehicle body upon deployment of the air bag 
can be reduced even further. 
The first engagement means may comprise a plurality of tongues depending 
from a reverse surface of the lid member, the tongues being each provided 
with a claw engaging an inner peripheral edge of the vehicle body opening. 
The second engagement means may comprise a hook member secured to the air 
bag housing, and a slot provided at least in one of the tongues or in a 
separately provided tongue depending from the lid member, and engaged by 
the hook member. Preferably, the hook member is provided with a stopper 
adapted to engage a free end of the tongue so as to limit an excessive 
inward displacement of the lid member into the vehicle body opening. 
Alternatively, it is also possible to join the lid member to the air bag 
housing with a belt passed around said inflator housing and said air bag 
housing and engaged to said lid member at two terminal ends thereof. 
To ensure the air bag to be properly projected upon its deployment, the air 
bag housing preferably diverges from the second opening toward the third 
opening, and is provided with at least one folding line about which the 
air bag housing can readily flex relative to the inflator housing. The 
divergent shape of the air bag housing contributes to a favorable and 
rapid deployment of the air bag. Also, the capability of the air bag 
housing to flex is desirable because it allows the air bag system to 
absorb impact energy when hit for instance by a vehicle occupant. 
Additionally, if there is an error in the positioning of the air bag 
housing relative to the vehicle body, such a flexibility of the air bag 
housing is helpful in adjusting the position of the air bag housing 
relative to the vehicle body opening. An excessive flexibility in the air 
bag system is not desirable because it will allow lateral expansion of the 
air bag housing upon deployment of the air bag, and dissipates some of the 
energy of the gas for inflating the air bag. A favorable impact absorbing 
capability and a resistance to lateral expansion can be readily 
accomplished if part of the air bag housing surrounding the third opening 
is relatively reinforced so as to have a relatively high rigidity against 
lateral deformation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 through 3 showing a first embodiment of the present 
invention, the air bag system 1 according to the present invention is 
provided with an inflator 2 for producing gas upon detecting a signal 
indicative of a large deceleration normally caused by a vehicle crash, a 
lower housing 3 for generally accommodating the inflator 2, an upper 
housing 4 connected to an upper end of the lower housing 3, an air bag 5 
made of rubber-coated nylon fabric and received inside the upper housing 4 
in a closely folded condition, and a lid 6 closing the open upper end of 
the upper housing 4. This air bag system 1 is adapted to be installed 
inside an opening 7a of an instrument panel 7 facing the vehicle occupant 
sitting next to the vehicle operator. 
The air bag 5 can be rapidly inflated by igniting a gas generating agent 
received in the inflator 2 such as sodium nitride, and the produced gas is 
introduced into the air bag 5. The inflated air bag 5 will restrain the 
forward movement of the vehicle occupant. The details of such an air bag 
system is well known in the art, and reference should be made to other 
documents for more details. 
The lower housing 3 has a cylindrical shape, and its two axial ends are 
closed. The lower housing 3 extends laterally, and receives the inflator 2 
therein. The upper surface of the lower housing 3 is provided with a 
plurality of gas outlets 8 arranged along a central axial line of the 
lower housing 3 for expelling the gas produced from the inflator 2, and 
these gas outlets 8 are flanked by a pair of sealing surfaces 9 on either 
side. Thus, the sealing surfaces 9 diverge downward as seen from an axial 
end. 
The upper housing 4 is rectangular in shape when viewed from above, and has 
an inverted trapezoidal shape when viewed from an axial end. The upper and 
lower ends of the upper housing 4 are both open. The lower end of the 
upper housing 4 is provided with flanges 10 which conform to the sealing 
surfaces 9 of the lower housing 3. The lower housing 3 and the upper 
housing 4 are integrally joined together by bolts and nuts, blind rivets 
or other suitable fastening means 11 with an open inlet end 5a of the air 
bag 5 closely interposed and clamped between the sealing surfaces 9 and 
the flanges 10. 
A plurality of hook members 12 are secured to the front and rear surfaces 
of an upper end of the upper housing 4. The lid 6 is integrally provided 
with a plurality of elastic tongues 13 depend from the reverse surface of 
the lid 6 and arranged laterally in two rows near the front and rear edges 
of the lid 6, respectively, and a vertical slot 14 is provided in each of 
the elastic tongues 13. The elastic tongues 13 are arranged so that the 
hook members 12 may be engaged with the slots 14 of these elastic tongues 
13. The lower end of each of the hook members 12 is bent laterally outward 
so as to define a stopper projection 12a for restricting the downward 
movement of the lid 6 beyond a certain limit by engaging the lower ends of 
the elastic tongues 13. 
A lateral groove 15 is formed centrally in the inner surface of the lid 6 
to provide a line of weakness, and a plurality of laterally projecting 
claws 16 are integrally provided along the front and rear edges of the lid 
6 for engaging the inner surface of the front and rear edges of the 
opening 7a of the instrument panel 7 which is covered and closed by the 
lid 6. In this embodiment, the claws 16 provided along the front edge of 
the lid 6 are provided in the elastic tongues 13 provided with the slots 
14, but the claws 16 provided along the rear edge of the lid 6 are 
provided in similar elastic tongues 13 which are however provided 
separately from the elastic tongues 13. 
When installing the lid 6 on the air bag system 1 described above, a 
stiffener member (not shown in the drawings) attached to the interior of 
the instrument panel 7 is secured to a part of the air bag system 1 such 
as the lower housing 3 in advance, and the lid 6 is pushed into the 
opening 7a of the instrument panel 7 so as to cover it. Then, the elastic 
tongues 13 are resiliently deformed outwardly, and ride over the hook 
members 12. Once the hook members 12 are lined up with the slots 14, the 
elastic tongues 13 are resiliently restored to their original shape, and 
the hook members 12 are fitted into the slots 14. At the same time, the 
claws 16 are engaged with the inner peripheral edge of the opening 7a, and 
the position of the lid 6 is determined relative to the instrument panel 
7. At this point, because the lid 6 can be moved within a range permitted 
by the play between the hook members 12 and the resilient tongues 13, and 
the size of the slots 14, the proper positioning of the lid 6 with respect 
to the opening 7a of the instrument panel 7 can be ensured. 
The air bag 5 which is normally folded and received in the interior of the 
upper housing 4 breaks through the lid 6 and is instantaneously deployed 
into the passenger compartment when the inflator gas produced upon 
detecting a large deceleration is rapidly introduced into the air bag 5. 
Therefore, the open inlet end 5a of the air bag 5 which is interposed 
between the sealing surfaces 9 and the associated sealing surface of the 
flanges 10 are subjected to a large tensile force due to the gas pressure. 
However, according to the present invention, because the area of contact 
between the open inlet end 5a of the air bag 5 and the interface between 
the two housings 3 and 5 can be made sufficiently large, it is possible to 
avoid concentration of stress and to increase the strength of the 
structure securing the open inlet end 5a of the air bag 5 without 
excessively increasing the contact pressure. Furthermore, the possibility 
of gas leakage from this part can be minimized. 
Because there is a gap A between the hook members 12 and the slots 14 of 
the elastic tongues 13, and the claws 16 can be easily disengaged from the 
edge of the opening 7a when lid 6 is pushed out, the lid 6 can be lifted 
from the upper surface of the instrument panel when the air bag 5 is 
inflated. It should be noted that the peripheral outer edge of the lid 6 
overlaps the peripheral inner edge of the opening 7a from exterior. As a 
result, a gap G is produced between the inner edge of the opening 7a of 
the instrument panel 7 and the outer edge of the lid 6. Therefore, it is 
possible to avoid interference between the front and rear edges of the 
opening 7a of the instrument panel 7 and the outer edge of the lid 6 when 
the lid 6 is ruptured at the groove 15, and the air bag 5 is deployed. 
Thus, the instrument panel 7 itself is not subjected to any excessive 
force, and can safely remain intact even after deployment of the air bag. 
In this embodiment, the upper housing 4 diverges upward as seen from an 
axial end thereof, and is provided with laterally extending fold lines 
17a, 17b and 17c which define readily flexible regions. 
Therefore, according to this embodiment, if an external force is applied to 
the lid 2 in the direction indicated by arrow B in FIG. 1, because the 
fold lines 17a through 17c allow the upper housing 4 to deform in its 
middle part or with respect to the lower housing 3, the upper housing 4 
can be relatively easily tilted or otherwise deformed, and absorb energy 
when impact is applied to the air bag system in the direction indicated by 
arrow B. Thus, the lid and the surrounding region of the instrument panel 
are provided with a capability to absorb impact energy, and no extra 
padding would be required. Also, the diverging shape of the middle portion 
of the upper housing 4 contributes to the rapid deployment of the air bag 
5. 
FIGS. 4 and 5 show a second embodiment of the present invention. In these 
drawings, the parts corresponding to those of the previous embodiments are 
denoted with like numerals. 
In the second embodiment, the inflator housing 21 accommodating the 
inflator 2 and the air bag housing 22 accommodating the air bag 5 are 
combined as a substantially integral and common main housing 23, and a 
separating wall 24 consisting of a separate member from that of the main 
housing 23 is secured inside the main housing 23 so as to separate the 
interior of the main housing 23 between the inflator housing 21 and the 
air bag housing 22. 
The separating wall 24 consists of a rectangular plate having its side 
edges bent downward along fold lines extending along the longitudinal 
direction, and is provided with a plurality, in this case five, of gas 
outlets 8 consisting of rectangular openings arranged centrally along its 
central longitudinal line. The separating wall 24 is provided with a pair 
of flat surfaces on its downwardly bent side edges which serve as sealing 
surfaces 9 each having an appropriate width similar to those provided on 
the upper surface of the lower housing 3 of the first embodiment. 
The inflator housing 21 is provided with a substantially U-shaped cross 
section while the air bag housing 22 is provided with an inverted, 
substantially trapezoidal cross section. The upper end of the air bag 
housing 22 is open. A vertically middle part of the main housing 23 is 
somewhat made narrower, and is provided with sealing surfaces 25 on its 
inner surface which cooperate with the sealing surfaces 9 of the 
separating wall 24. 
When assembling this air bag system 1, first of all, before installing an 
inflator 2 into the inflator housing 21, the separating wall 24 is 
introduced into the inflator housing 21 from the open upper end of the 
main housing 23. This can be accomplished by tilting the separating wall 
24 until it is received in the inflator housing 21. The base end 5a of an 
air bag 5 is likewise placed into the open upper end of the main housing 
24, and is placed between the sealing surfaces 9 and 25. Then, the 
separating wall 24 is secured to the main housing 23 with suitable 
fastening means 11 so as to securely clamp the base end 5a of an air bag 5 
between the sealing surfaces 9 and 25. This can be accomplished by putting 
a hand into the inflator housing 21 from an access opening 26 provided on 
an axial end of the inflator housing 21. 
The second embodiment may also be provided with hook members 12 and elastic 
tongues 13 similar to those of the previous embodiment, and the gap A 
which may be provided between the hook members 12 and the slots 14 of the 
elastic tongues 13 produces similar benefits. 
FIG. 6 shows a third embodiment of the present invention. According to this 
embodiment, the lid 6 is joined to the air bag system 1 by passing a pair 
of belts 28 around the upper housing 4 and the lower housing 3, and 
engaging the two ends 27 of each of the belts 28 with elastic tongues 13 
integrally depending from the lid 6. The belts 28 are given with some 
slack, and are secured to the bottom surface of the lower housing 3 with 
rivets 29. The lower housing 3 is secured to a fixed member of the vehicle 
body although it is not shown in the drawing. 
In this embodiment, the positioning of the lid 6 with respect to the 
opening 7a of the instrument panel 7 is accomplished by claws 16 
integrally formed in the lid 6 and engaging the inner edge of the opening 
7a of the instrument panel 7 in the same way as in the previous 
embodiments. Additionally, this embodiment allows the vertical positioning 
of the lid 6 with respect to the opening 7a of the instrument panel to be 
adjusted by changing the slack of the belts 28. 
The belts 28 may be secured to the housings in different ways. For 
instance, the fastening means 11 joining the two housings 3 and 4 may also 
be used for joining the belts 22 to the housings. The belts 28 may also be 
secured to a fixed member of the vehicle body. Also, at least one end of 
each belt 28 may be insert molded with the lid 6 or otherwise fixedly 
secured to the lid 6. 
According to these embodiments, the position of the lid can be easily 
adjusted along the surface of the instrument panel, and a favorable 
appearance can be ensured without any difficulty. Furthermore, the lid can 
be ruptured in a predictable way when the air bag is deployed, and a 
reliable operation of the air bag system is ensured. 
FIGS. 7 and 8 show a fourth embodiment of the present invention, which is 
similar to the first embodiment, in a simplified fashion to clarify the 
features of this embodiment. In these drawings, the parts corresponding to 
those of the first embodiment are denoted with like numerals. 
In this embodiment, the inflator 2 is received in an inflator housing 3, 
and an air bag housing 30 is attached to an upper end of the inflator 
housing 3, interposing the base end of the air bag 5 between the opposing 
surfaces of the two housings 3 and 30. The inflator housing 3 is 
substantially cylindrical in shape. The air bag housing 30 is rectangular 
in plan view, but generally diverges upward. It should be noted that the 
air bag housing 30 diverges upward as seen either from an axial end or 
from a lateral end (in other words, as seen either in FIG. 7 or FIG. 8). 
More specifically, the air bag housing 30 comprises a middle portion 30a, a 
frame portion 30b connected to the upper end of the middle portion 30a, 
and a flange portion 30c connected to the lower end of the middle portion 
30a and secured to the inflator housing 3. The base end of the air bag 5 
is interposed between the flange portion 30c and the inflator housing 3. 
As seen from an axial end, the middle portion 30a extends obliquely or 
diverges from the flange portion 30c, and the frame portion 30b extends in 
parallel from an upper end of the middle portion 30a. 
A plurality of hook members 12 are provided around the upper frame portion 
30b, and engage a plurality of elastic tongues depending from the reverse 
surface of the lid 6 by way of slots 14 provided in these elastic tongues 
13 to join the lid 6 to the upper frame portion 30b securely but so as to 
allow lateral adjustment of the lid 6 with respect to the instrument panel 
7. 
Thus, relatively flexible regions 31a and 31b are provided between the 
upper frame portion 30b and the middle portion 30a, and between the middle 
portion 30a and the lower flange portion 30c, respectively, while the 
upper frame portion 30b is reinforced by an annular reinforcement member 
32 having a relatively high rigidity and closely surrounding the upper 
frame portion 30b. 
According to this embodiment, if an external force is applied to the lid 2 
in the direction indicated by arrow A in FIG. 7, because the flexible 
regions 31a and 31b allow the upper frame portion 30b and the middle 
portion 30a, respectively, relative to the fixed lower flange portion 30c. 
This tendency is further enhanced by the reinforcement of the upper frame 
portion 30b with the annular reinforcement member 32. Thus, the lid and 
the surrounding region of the instrument panel are provided with a 
capability to absorb impact and energy. 
In spite of the capability to readily deform and absorb energy of impact, 
the upper frame portion 30b is provided with a sufficient rigidity to 
withstand pressure from the air bag as it is about to be deployed, and the 
gas produced from the inflator can be effectively used for rapidly 
forwarding the air bag in front of the vehicle occupant. The diverging 
shape of the middle portion 30a also contributes to the rapid deployment 
of the air bag. 
Although the present invention has been described in terms of specific 
embodiments, it is possible to modify and alter details thereof without 
departing from the spirit of the present invention.