Land vehicles: bodies and tops – Bodies – Body shell
Reexamination Certificate
2000-11-09
2002-05-21
Pape, Joseph D. (Department: 3612)
Land vehicles: bodies and tops
Bodies
Body shell
C296S039100, C280S751000
Reexamination Certificate
active
06390538
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle interior material, and more particularly to an impact absorbing member for vehicle interior suitably used for pillar garnish, roof side rail garnish, door waist garnish, etc., in an automobile.
2. Description of the Related Art
Polypropylene resins and rubber-enhanced styrene resins (ABS, AES, AAS) are widely used for the housings and components of home electric appliances, vehicle interiors and exteriors, etc., due to their superior impact-resistance, heat deform ability, and ease of molding.
On the other hand, vehicle interior materials include, as shown in
FIG. 15
, front pillar garnish
105
F, center pillar garnish
101
C and roof side rail garnish
101
S that are respectively mounted to the vehicle interior side of the front pillar
105
F, the center pillars
105
C and roof side rails
105
S. These vehicle interior materials are constructed not only in order to maintain the aesthetic appearance of the vehicle interior, but also to allow the impact received by a passenger from the vehicle body to be absorbed and reduced through plastic deformation at the area that comes into direct contact with a part of the passenger's body (i.e., the head) during a collision of the vehicle, for example.
A typical conventional front pillar garnish
105
F comprises, as described in Japanese Patent Application Laid-Open No. H9-175284, (i) a surface member
102
having an essentially C-shaped transverse cross-section, (ii) a panel-like vertical rib
103
L that extends along the length of and along the rear surface of the surface member
102
, and (iii) multiple panel-like horizontal ribs
103
W that are essentially perpendicular to the vertical rib
103
L and extend between the side walls of the surface member
102
, as shown in
FIG. 16
for example, and is fixed to the protrusion
107
of the inner panel comprising the front pillar
105
F such that the ribs are in contact with the protrusion
107
. In the event of a passenger collision, the impact is absorbed by the vertical rib
103
L and the horizontal ribs
103
W, which deform and become destroyed.
Incidentally, increased safety during vehicle collisions has been demanded in recent years in the United States. Impact absorption characteristics that meet a high safety standard in terms of HIC (head impact characteristic) provided by the FMVSS, a U.S. government agency, are demanded of molded products used in vehicle interiors or exteriors.
Various attempts have been made in order to meet this safety standard, as well as to maintain heat deformability and ease of molding, and the use of ABS resin using diene rubber and modified polypropylene as the molding materials has been proposed, but in any event, sufficient impact absorption characteristics have not yet been obtained.
In order to maintain a high level of impact absorption performance, the protrusion height of each rib must be large. Consequently, when the front pillar garnish
101
F is mounted to the front pillar
105
F, the front pillar garnish
101
F projects out into the vehicle interior gap to a significant extent, giving rise to such problems that the passenger feels closed in, the field of view is narrowed, and the garnish poses an obstacle when the passenger enters and exits the vehicle.
SUMMARY OF THE INVENTION
In view of the problems identified above, an object of the present invention is to provide an impact absorbing member for vehicle interior that, while maintaining superior heat deformability, offers improved impact resistance that satisfies the above safety standard, reduces the protrusion height of the ribs, and reduces the degree to which the material projects into the vehicle interior space.
In order to attain these objects, the vehicle interior material pertaining to the present invention may be obtained by molding synthetic resin that has a tan &dgr; (loss tangent) peak height of 0.04 or higher and a peak temperature between −40 and 50° C., as measured through viscoelasticity measurement. The impact absorbing member for vehicle interior of the present invention is suitable for use as a pillar garnish, roof side rail garnish or door waist garnish of an automobile.
The reason why the present invention has superior impact-resistance while maintaining heat deformability, and consequently can have a reduced rib protrusion height, will be explained below using pillar garnish as an example, based on the U.S. FMVSS201 standard.
First, the kinetic energy E
0
(J) of a dummy head (virtual passenger's head) is expressed by the following equation (1) based on the equation of motion.
E
0
=½mv
2
(1)
Here, m is the weight of the dummy head (4.6 kg), and v is the velocity (m/s) of the dummy head at the time of collision.
The dynamic energy W(J) absorbed by the deformation of the ribs is expressed by the following equation (2).
W=m·&agr;
CONST
·S (2)
Here, &agr;
CONST
is the average acceleration (m/s
2
) that is generated at the time of collision, and S is the amount of stroke (m).
Conventional vehicle interior materials are generally molded using a synthetic resin such as a polypropylene resin or a rubber-enhanced styrene resin (ABS, AES, AAS), and when the dummy head collides with the material, most of the kinetic energy E
0
is absorbed through the structural deformation of the ribs, as described above. As a result, the equation (1) and the equation (2) are deemed equal, and the following equation (3) is obtained.
m·&agr;
CONST
·S=E
0
(3)
As shown in FIG.
2
(
a
), the dummy head's kinetic energy E
0
is efficiently absorbed by the deformation of the ribs, the HIC(d) requirement is met, and the stroke becomes the smallest when there is no curve gradient caused by a rising or falling rate of acceleration, and the acceleration in between is constant.
On the other hand, the head injury characteristic HIC(d) provided by the U.S. FMVSS201 standard is calculated based on the following equation (4).
(
4
)
HIC
(
d
)
=
0.75446
×
(
1
t
2
-
t
1
∫
t1
t2
α
ⅆ
t
)
2.5
×
(
t
2
-
t
1
)
+
166.4
(
4
)
If the following equations are substituted in the equation (4) and calculated, the following equation (5) is obtained.
&agr;=&agr;
CONST
/g
g=9.8 (m/s
2
) [gravitational acceleration]
t
2
−t
1
=V
0
/&agr;
CONST
V
0
=6.67 (m/s) [15 mph (miles/h)]
&agr;
CONST
=(HIC(d)−166.4) /0.0167377)
0.667
(5)
Given that the HIC(d) level currently adopted as an internal standard by automobile manufacturers is 800 or less, and that the energy that can be absorbed by the distortion of the body panels (pillar outers, pillar inners, etc.) is approximately 100 in terms of HIC(d), the HIC(d) that should be substituted in the equation (5) when seeking the limit of the average acceleration is 900. If the average accelerate &agr;
CONST
is 1247.5 (ms
2
) or lower, the above standard is met.
If the equation (3) is calculated using this average acceleration &agr;
CONST
, the smallest value for the stroke amount S becomes 17.8 (mm), and therefore, it is seen that where a conventional vehicle interior material is concerned, the rib height must be 17.8 mm or more.
In addition, because the parts m and n that exist when the acceleration is rising and falling, respectively, are added, as shown in
FIG. 2
(
b
), to the acceleration actually measured for the dummy head, the stroke amount S, i.e., the required rib height, increases further, resulting in an actual rib height of 18 to 19 mm or higher.
Incidentally, at the time of the collision of the dummy head, only a small part of the kinetic energy E
0
is converted into loss energy such as heat energy. If the amount of this loss energy can be increased, the following equation (6) is obtained instead of the equation (3). It is therefore seen that by increasing the energy loss rate k, the average acceleration &agr;
CONST
to be absorbed via the deformation, d
Adachi Nagayoshi
Hashimoto Yoshihiko
Ishii Miwa
Mekata Tetsuo
Miyano Junji
Armstrong Westerman & Hattori, LLP
Kaneka Corporation
Pape Joseph D.
LandOfFree
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