Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2001-09-27
2004-04-06
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S323000, C428S324000, C428S325000, C428S328000, C428S500000, C280S728300
Reexamination Certificate
active
06716519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air bag cover comprising a TPE layer, or a surface sheet with a TPE layer provided.
Although an embodiment of an air bag cover for an air bag device to be assembled in an instrument panel is explained herein, the invention is not limited thereto, but it can be adopted in an air bag cover for an air bag device to be assembled in a side door, a pillar, a front or back sheet, or the like.
Hereafter, abbreviations for polymers mainly used in this specification are presented.
PE . . . polyethylene
PP . . . polypropylene
PS . . . polystyrene
PVC . . . polyvinyl chloride
BR . . . butadiene rubber
EPDM . . . ethylene propylene non-conjugated diene three element copolymer rubber
EPM . . . ethylene propylene copolymer rubber
IIR . . . butyl rubber
SBR . . . styrene butadiene rubber
TPE . . . thermoplastic elastomer
Moreover, the breaking elongation of the surface sheet (cutting elongation: E
B
) and the breaking strength (tensile strength: T
B
) in this specification are based on a specific tensile test in the test examples described later.
2. Description of the Related Art
As an air bag cover configuration in an air bag device assembly portion (the portion of the line II—II in
FIG. 1
) in an instrument panel
12
shown in
FIG. 1
, for example, those shown in
FIG. 2
have been provided. As a known published product with the similar configuration, Unexamined Japanese Patent Publication No. 11-222089, or the like can be presented.
That is, the configuration comprises a cover surface sheet part
14
a
and a cover base body
16
, with a base body door part
16
a
of the cover base body
16
provided with a hinge groove
18
and a tear line groove
20
on the back side. The cover base body
16
is produced as a first injection molding product, provided integrally with an instrument panel base body
22
as a second injection molding product, on the inner side thereof by two-part injection molding.
Here, the cover surface sheet part
14
a
is formed as a part of an instrument panel surface sheet
14
. The configuration of the surface sheet
14
can be, for example, a three layer configuration from the back side, of a barrier layer
24
made of a thermally resistant resin material, a foamed layer
26
made of a soft foamed resin material, and a decorative layer
28
made of a soft synthetic resin (in general, it is a thermoplastic elastomer “TPE”) as shown in the figure.
The air bag cover of the configuration is produced, in general, by shaping the three layer configuration sheet by vacuum molding, and two-part injection molding in the order of the cover base body
16
and the instrument panel base body
22
. At the time of the vacuum molding of the sheet, a relief line groove
30
is formed in the vicinity of the hinge groove
18
and the tear line groove
20
near the cover surface sheet part
14
a
by mold shaping. The relief line groove
30
is mainly for smoothly performing the hinge function and the tear line function. The tear line groove
20
is formed by, for example, providing a notch by an ultrasonic cutting, or the like.
At the time the air bag
34
is expanded, stress is concentrated on the tear line groove
20
formation portion (thick part) of the cover base body
16
so as to rupture the tear line groove
20
formation portion. In the foamed layer
26
, stress is concentrated on the portion of the cover base body
26
with the shortest distance with respect to the tear line groove
20
bottom part (minimum section portion) so as to form a crack toward the relief line groove
30
tip end portion. The relief line groove
30
is ruptured by stress concentration on the tip end portion of an embedded pleat part
28
a
of the surface sheet
14
.
An air bag cover
11
is jointed to the air bag device
10
via front and rear mounting walls
31
,
32
, projecting from the back surface of the cover base body
16
. The rear mounting wall
32
, which is formed straight at the time of molding, has a tip end mounting part
32
a
bendable like a hinge at the time of mounting (see FIG.
5
).
The air bag device
10
comprises basically an air bag
34
, an inflator
36
, a bag case
38
for storing and attaching the same with the air bag cover
11
, and a diffuser pipe
40
. In the example shown in the figure, the bag case
38
having a planar lateral rectangular box-like shape, comprises engaging claws
42
,
42
on both sides in the longitudinal direction each by a predetermined distance, and therebelow front and rear receiving bars
48
,
48
comprising front and rear receiving grooves
44
,
44
to be fitted with the lower ends of front and rear mounting walls
31
,
32
. Moreover, the diffuser pipe
40
having a configuration wherein upper and lower half-split member
40
a
,
40
b
are jointed on both sides by a flange, is integrated with a bottom part inside flange
38
a
of the bag case
38
by a bolt
52
, or the like by co-fastening. At the time, by co-fastening the opening part of the folded air bag
34
simultaneously via a retainer ring
35
, the air bag
34
is attached and stored in the bag case
38
. By pushing the front and rear mounting walls
31
,
32
into the receiving grooves
44
,
44
, the engaging claws
42
,
42
are fitted and engaged with engaging holes
50
,
50
formed in the front and rear mounting walls
31
,
32
so as to joint the air bag device
10
and the air bag cover
11
.
In the case of the air bag cover of the above-mentioned configuration, in order to support the rotation opening at the time of expanding the bag of the bag door part, existence of the relief line formed by embedding the surface sheet decorative layer, is essential. Due to the existence of the relief line, the air bag cover is limited in terms of design as well as a complicated vacuum molding mold of the surface sheet is needed as mentioned in the above-mentioned official gazette. Particularly in the case a sophisticated breaking rapidity is required in the tear line, the relief line is need to be formed relatively deeply so that a thin and high rib for a relief line needs to be formed in the vacuum molding mold. The rib formation further increases the difficulty in the mold production as well as deteriorates the mold durability.
SUMMARY OF THE INVENTION
In view of the circumstances, an object of the invention is to provide an air bag cover capable of relatively reducing the depth of or eliminating a relief line groove formed by the embedded pleat part of the surface sheet (decorative layer).
In order to solve the problems, the inventors have found out that the door opening performance can be ensured at the time of expanding the bag with a shallower depth of or without formation of the relief line groove by reducing the stretchability of the surface sheet in the effort in the elaborate development process so as to invent the air bag cover with the following configuration.
An air bag cover comprising a TPE layer, or a surface sheet with a TPE layer provided on the surface side, wherein the breaking elongation of the TPE material for the TPE layer is adjusted by containing a filler, is provided.
According to the configuration, stress is concentrated from the back side on the tear line groove formation portion, which is a notch portion, in the bag cover at the time of developing and inflating the air bag. At the time, since the breaking elongation is set at a lower level by containing an inorganic filler in the TPE material, it is broken rapidly at the tear line groove compared with the conventional examples. Therefore, the relief line groove can be provided shallower with respect to the tear line groove of the bag cover compared with the conventional examples, or can be eliminated.
As the embodiments of the air bag cover capable of adopting the invention, the following air bag covers can be presented.
An air bag cover having a surface sheet with a plural layer configuration comprising from the back side a barrier layer made of a thermally resistant resin material, and a decorative layer made of a TPE
Furuta Kenichi
Horiba Yukihiko
Nagano Akiyoshi
Nakano Akio
Shichida Yoshiaki
Kruer Kevin
Posz & Bethards, PLC
Thibodeau Paul
Toyoda Gosei Co,., Ltd.
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