Land vehicles – Wheeled – Attachment
Reexamination Certificate
1999-06-17
2001-08-14
Jordan, Charles T. (Department: 3641)
Land vehicles
Wheeled
Attachment
C280S740000, C280S742000, C280S743100, C280S736000, C280S737000, C102S530000, C102S531000
Reexamination Certificate
active
06273464
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an airbag gas generator for protecting an occupant from impacts and more specifically to a construction of an ignition unit of the gas generator.
RELATED ART
An example of a conventional airbag gas generator is illustrated in FIG.
3
. This gas generator includes: a housing
31
having gas discharge ports
30
; an ignition unit accommodating chamber
32
defined in a central part of the housing
31
; an ignition unit
33
installed in the ignition unit accommodating chamber
32
; a canister
34
containing a gas generating material, i.e. a gas generating agent that generates a gas when ignited by the ignition unit; and a cooling and cleaning unit, i.e., a coolant
35
and a filter
36
, for cooling and cleaning the generated gas.
The ignition unit
33
includes a transfer charge container
38
containing a transfer charge
37
and an igniter
39
that is activated by a signal to ignite the transfer charge
37
.
When a sensor (not shown) detects an impact, a sensor signal is sent to the igniter
39
, which is then activated to ignite the transfer charge
37
. The transfer charge, when ignited, generates high-temperature and high-pressure flames, which pass through openings
40
into a combustion chamber
41
, fracture the wall of the canister
34
and then ignite the gas generating agent. Then, the gas generating agent burns to generate a gas, which then enters a coolant filter chamber
43
from passing ports of a combustor cup
42
defining the combustion chamber. The gas is cooled and removed of combustion residues while it passes through the coolant
35
. And while the gas passes through the filter
36
, the remaining combustion residues are further removed, and the cooled and cleaned gas flows through the gas discharge ports
30
into an airbag (not shown). The inflow-gas inflates the airbag, forming a cushion between an occupant and a hard structure.
In the airbag gas generator used in an automobile, components are preassembled. For example, the transfer charge container and the igniter are installed in the ignition unit accommodating chamber so that they are in contact with each other.
A gap may occur between components due to tolerances of components and assembly errors. There is a possibility that the transfer charge container, for example, may move in this gap or strike against the igniter and destroyed.
To prevent the inner components from being dislocated or moving out of contact with associated components due to vibrations, the inner components need to be fixed. For this purpose, an resilient cushion is used.
In the above conventional gas generator, a cushion
45
is installed between the transfer charge container
38
and a hollow screw member
44
defining the ignition unit accommodating chamber
32
. This cushion
45
allows the transfer charge container
38
to be resiliently pressed against the igniter
39
, preventing the movement of the transfer charge container
38
and also preventing the transfer charge container
38
from hitting against the igniter
39
.
In the event a vehicle incorporating the airbag gas generator catches fire, the gas generator is heated causing its interior to reach several hundred degrees. When at this elevated temperature the gas generating agent and transfer charge in the gas generator spontaneously burn, the housing may be destroyed and the damaged components may scatter.
To prevent this, an automatic ignition material (AIM)
23
is installed in the transfer charge container. The AIM has a low ignition point and thus ignites before the gas generating agent and the transfer charge spontaneously burn. The ignition of this AIM ensures the combustion of the transfer charge and the gas generating agent, thus preventing their spontaneous combustion and destruction of the housing. This AIM is arranged close to the outer wall of the housing to ensure that the heat of the outer side of the gas generator is transferred well to the AIM.
The conventional gas generator, however, requires a cushion between the transfer charge container and the hollow screw member, which in turn increases the number of components and manhours for assembly.
Further, the presence of a cushion between the transfer charge container and the hollow screw member blocks heat conduction, preventing the heat of the outer side of the gas generator from being transferred to the AIM well, which in turn may delay the ignition timing of the AIM.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a novel airbag gas generator that solves the problems experienced with the above conventional airbag gas generator.
An airbag gas generator according to this invention comprises: a housing having gas discharge ports; an ignition unit accommodating chamber formed in a central part of the housing; an ignition unit installed in the ignition unit accommodating chamber; a gas generating unit to be ignited by the ignition unit and generate a gas; and a cooling and purifying unit for cooling and purifying the gas generated by the gas generating element; wherein the ignition unit includes a transfer charge container and an igniter, the transfer charge container having a cup for accommodating a transfer charge and a cover for hermetically closing the cup, the igniter to be activated by a signal and ignite the transfer charge; wherein the gas generated by the gas generating element in response to an impact is introduced into an airbag to protect an occupant against the impact; wherein the transfer charge container includes a cup part and a cover part, either of the bottoms of the cup part and the cover part being outwardly curved to form an outwardly convex surface, the container being resiliently held between a top wall portion of the ignition unit accommodating chamber and the igniter.
In the transfer charge container used in this gas generator, the bottom of the cover or cup has a convex surface. This convex bottom can resiliently deflect upon receiving a pressing force. The deflection of the convex bottom applies a resilient force to the top wall portion of the ignition unit accommodating chamber and to an igniter. In this way, the transfer charge container is resiliently held between the ceiling portion of the ignition unit accommodating chamber and the igniter.
Because of the above construction, this invention can eliminate the cushion installed between the transfer charge container and the top wall portion of the ignition unit accommodating chamber. This offers the advantages of reducing the number of components and manhours for assembly.
Further, because no cushion is provided between the transfer charge container and the top wall portion, the heat conduction is improved, allowing heat on the outer side of the gas generator to be transferred efficiently to the AIM, which can then be ignited at an appropriate timing. This in turn secures safety.
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patent: 5104466 (1992-04-01), Allard et al.
patent: 5221107 (1993-06-01), O'Loughlin
patent: 5372281 (1994-12-01), Herridge
patent: 5419578 (1995-05-01), Storey et al.
patent: 5431103 (1995-07-01), Hock et al.
patent: 5470406 (1995-11-01), Ochi et al.
patent: 5481978 (1996-01-01), Muller et al.
patent: 5556130 (1996-09-01), Fulmer
patent: 5738374 (1998-04-01), Marsaud et al.
patent: 5779267 (1998-07-01), Jordan et al.
patent: 4-78745 (1992-03-01), None
patent: 7112652 (1995-05-01), None
patent: WO 93/21037 (1993-10-01), None
patent: WO 93/21036 (1993-10-01), None
Ogawa Akihisa
Tokuda Masakazu
Daicel Chemical Industries Ltd.
Jordan Charles T.
Sanchez Glenda L.
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