Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
Air bag in an air bag unit
FI ELD OF THE INVENTI ON
The present invention relates to an air bag in an
air bag unit for protecting an occupant in a vehicle
by inflating with high pressure when the vehicle is
collided, and in particular to an air bag, which is
provided with exhaust holes to slowly discharge the gas
in order to alleviate the shock which occurs when the
occupant is collided against the air bag.
TECHNICAL BACKGROUND
The air bag unit installed on the fixed portion of
car body in front of seat in a vehicle plays an impor-
tant role in the protection of the occupant from injury
caused by the collision against car body as it is
instantaneously inflated by the pressure of combustion
gas released from an inflator, which is fixed on steer-
ing wheel or on dashboard.
As shown in Fig. 3, such air bag unit 1 comprises
an inflator, which is exploded by collision signal from
a collision detecting sensor and explodes gas generat-
ing agent when the deceleration of the vehicle exceeds
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a certain level, and an air bag 3 with its base fixed
on the inflator 2 and inflated by the gas coming out
of the inflator 2. This air bag unit l can be mounted,
for example, on the fixed portion of car body such as
central portion of the steering wheel 13 with the air
bag 3 folded up and placed in a pad.
When the vehicle is collided, gas generating agent
in the inflator 2 is exploded and the air bag 3 is
instantaneously inflated and expanded by the generated
gas as shown in Fig. 2.
As the result, the air bag 3 receives the occupant,
who is pushed forward by inertia and protects the
occupant from the injury caused by the collision against
car body.
A conventional type air bag 3 comprises an opening
9, through which the inflator penetrates, and exhaust
holes 8' (shown by two-dot chain lines Fig. l (A)) to
release the pressure in the air bag and to alleviate
the shock when the occupant is collided against the
inflated air bag. The dimension of these exhaust holes
8' is adequately determined in order to absorb the
shock most effectively, which occurs when the occupant
is collided against the air bag 3.
When the air bag 3 is inflated, high tensile force
A occurs on the base cloth of the air bag 3 in radial
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direction from the opening 9 of the air bag 3 by high
pressure gas blown out of the inflator 2. By this
tensile force A, stress is concentrated around said
exhaust holes 8', and there is the possibility that the
air bag 3 may be ruptured 12 from the exhaust holes 8'
as shown in Fig. 1 (C). The rupture 12 also occurs by
the shock when the occupant is collided against the
air bag. When such rupture 12 occurs, a large quantity
of gas is released through the ruptured hole 12, and
the function of the air bag to alleviate the shock is
not fulfilled.
To solve the above problem, study is now made on
the exhaust holes 8' of the air bag 3. As shown in
Figs. 1 (A) and (C),'the exhaust holes 8' are furnishe''
at the positions where warps 11 or wefts 10 of the air
bag 3 run in parallel to the straight line B which
connects the center of the opening 9 of the air bag
with the centers of the exhaust holes 8'. As the
result, the above tensile force A is intensively
applied either on warps 11 or on wefts 10 as shown by
the arrow A in Fig. 1 (A). Therefore, warps 11 or
wefts 10 are broken off as stress is intensively
applied as shown in Fig. 1 (C), and the rupture occurs
around the exhaust holes 8.
To solve the above problems, the object of the
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present inventlon is to offer an air bag, which can
prevent the rupture of the air bag from the portion of
exhaust holes when the air bag is inflated or the
occupant is collided against the air bag.
DISCLOSURB OF THE INVENTION
To solve the above problems, the air bag according
to the present invention is characterized in that the
exhaust holes are provided at the positions where warps
and wefts of the woven cloth of the air bag run diago-
nally to the straight line, which connects the centers
of said exhaust holes with the center of said opening.
In an air bag according to the present invention
with such arrangement, when the air bag is inflated by
the gas blown out from the inflator or when the occupar
is collided against the air bag b~ inertia, the stress
generated around the exhaust holes is supported by both
warps and wefts of the woven cloth of the air bag. As
the result, compared with the convention case where the
stress is supported only by either warps or wefts,
rupture occurs less frequently around the exhaust holes
of the air bag. Therefore, the rupture around the
exhaust holes of the air bag can be prevented, and this
extensively increases the reliability of the air bag.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 (A) is a cross-sectional view of an air bag
when it is inflated and expanded;
Fig. 1 (B) is an enlarged view of an exhaust hole
of the air bag according to the present invention;
Fig. 1 (C) is an enlarged view of an exhaust hole
of a conventional type air bag;
Fig. 2 is a cross-sectional view of an air bag of
an air bag unit commonly in use when it is inflated
and expanded; and
Fig. 3 is a schematical cross-sectional view show-
ing an example of an air bag unit when it is mounted on
steering wheel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in Fig. 2, air bag unit 1 normally com-
prises an inflator 2 and an air bag 3. The inflator 2
is formed in thin cylindrical shape where gas generat-
ing agent is sealed in. On its lateral side, a
plurality of gas blowing holes 4, 4, ...... are provided
in peripheral direction with adequate spacings.
On outer periphery of the inflator 2, a flange 5
is furnished outside the gas blowing holes 4, and this
flange 5 is mounted on an air bag holder 6. The base
of the air bag 3 is fixed on the holder 6 so that the
-- 5
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gas blowing holes 4, 4, ..... are enclosed by the air
bag 3,
As shown in Fig. 1 (A), the air bag 3 is made of
flexible and airtight material, which is a woven cloth
made up from warps 11 and wefts 10 and coated with
rubber or synthetic resin, and its center is provided
with an opening 9, through which the inflator 2 is
penetrating. Reinforcement cloths 7 are overlapped
around this opening 9 and are integrally bonded or sewn
together for reinforcement.
On the periphery of the mount of the air bag 3, a
pair of exhaust holes 8 and 8 are furnished at sym-
metrical points from the center of the opening 9. As
it is evident from Figs. 1 (A) and (B), the exhaust
holes 8 and 8 are located at the sites where the warps
11 and the wefts 10 of the woven cloth of the air bag 3
cross diagonally the straight line B, which connects
the center of the opening 9 with the centers of the
exhaust holes 8.
In an air bag 3 with the above arrangement, the
inflator 2 is penetrating through the opening as in
the conventional case as shown in Fig. 2 and Fig. 3,
and it is airtightly mounted on the inflator 2 by bolts
and nuts with the portion around the opening and the
reinforcement sloths 7 squeezed by ring-like hardware
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6' and the holder 6.
Next, description is given on the operation of
this embodiment.
When the vehicle is collided against an obstacle
and the decele ation exceeds a certain level, collision
signal is issued by a collision detecting sensor (not
shown), and the gas generating agent in the inflator 2
is exploded by this signal. As the result, gas is
generated, and the generated gas is blown out of the
blowing holes 4 as shown by the arrow "a" in Fig. 2.
The gas thus blown out inflates and expands
instantaneously the air bag 3, which safely receives
the occupant of the vehicle, who is pushed forward by
inertia. In this case, gas is released from the
exhaust holes 8 on the air bag 3 at adequate speed,
and this alleviates the shock, which occurs when the
occupant is collided against the air bag 3.
When the air bag 3 is rapidly inflated, or when
the occupant is collided against the air bag, stress
concentration occurs around the exhaust holes 8 by the
tensile force A, which is generated in radial direction
from the center of the opening 9 of the air bag 3.
However, on the woven cloth around the exhaust holes
8, both warps 11 and the wefts 10 are crossing diago-
nally relative to the direction, in which tensile
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force A works, and the tensile force A is perfectly
supported by both warps 11 and the wefts 10. Accord-
ingly, even when such tensile force A occurs, it is
possible to perfectly prevent the rupture 12, which is
very likely to occur around the exhaust holes 8.
Table 1 shows the results of the tensile test.
In Table 1, Type 1 sample has the exhaust holes 8' at
such points, where either warps or wefts of woven cloth
of the air bag are in parallel to the straight line,
which connects the center of the opening 9 of the air
bag with the centers of the exhaust holes 8' as shown
in Figs. 1 (A) and (C). Type 2 sample is an example
of the air bag according to the present invention, in
which exhaust holes are furnished at the points, where
both warps and wefts of woven cloth of the air bag
cross the straight line, which connects the center of
the opening 9 of the air bag with the centers of the
exhaust holes 8', at approximately 45 degrees. In this
case, the diameter is 32 mm in both of the exhaust
holes. The figures in Table 1 represent tensile load
at the moment when slit occurs on the exhaust holes.
As it is evident from Table 1, Type 2 has the
tensile strength by abot 1.4 times higher than that
of Type 1. In this way, the strength of the air bag
according to the present invention is extensively
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improved compared with the conventional type air bag.
In case the portion around the exhaust holes 8 of
the air bag 3 is reinforced by reinforcement cloths as
necessary, the exhaust holes 8 can be more effectively
reinforced if the exhaust holes 8 are provided on the
reinforcement cloths at the same points as in the
present invention.
Table 1 Results of tensile strength test for woven cloth
of air bag with exhaust hole
.
Sample No. Type 1 (N) Type 2 (N)
. 1 1,441 2,098
2 1,5882,196
3 1,5192,127
Average ~ 1,516 2,140
APPLICABILITY IN THE INDUSTRY
The air bag in the air bag unit of the present
invention can be used in a vehicle and applied for the
protection of the occupant by absorbing the shock,
which occurs when the vehicle is collided.
