U.S. patent application number 10/698537 was filed with the patent office on 2004-07-08 for impact absorbing member for vehicle.
Invention is credited to Inui, Hiroo, Ishii, Kenji, Tamada, Teruo, Tanji, Tadatoshi, Urakawa, Kiyotaka.
Application Number | 20040129518 10/698537 |
Document ID | / |
Family ID | 32234569 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040129518 |
Kind Code |
A1 |
Tamada, Teruo ; et
al. |
July 8, 2004 |
Impact absorbing member for vehicle
Abstract
A system is provided for absorbing energy from impacts to a
vehicle, the system comprising: a blow molded energy absorbing
member. The member including first and second opposing walls, at
least one rib or a pair of ribs disposed between said first and
second opposing walls, the rib(s) comprising the first and second
opposing walls dented toward other wall with top end part either
welded or separated with specified interval. In one embodiment, the
energy absorbing member is formed of thermoplastics composed of a
polyolefin based resin and 35 to 75 weight % of an amorphous
resin.
Inventors: |
Tamada, Teruo;
(Yokohama-shi, JP) ; Inui, Hiroo; (Nagoya-shi,
JP) ; Urakawa, Kiyotaka; (Katano-shi, JP) ;
Ishii, Kenji; (Nagoya-shi, JP) ; Tanji,
Tadatoshi; (Fujisawa-shi, JP) |
Correspondence
Address: |
MAINE & ASMUS
100 MAIN STREET
P O BOX 3445
NASHUA
NH
03061-3445
US
|
Family ID: |
32234569 |
Appl. No.: |
10/698537 |
Filed: |
October 31, 2003 |
Current U.S.
Class: |
188/377 |
Current CPC
Class: |
B29L 2031/3023 20130101;
B60R 21/0428 20130101; B29K 2055/02 20130101; B29K 2067/00
20130101; B29L 2031/3011 20130101; B29K 2069/00 20130101; B29C
2049/4812 20130101; F16F 9/0481 20130101; F16F 7/121 20130101; B60R
21/04 20130101; B29L 2031/3008 20130101; B29C 49/4802 20130101;
B29C 2049/4805 20130101; B29L 2031/30 20130101; B29L 2031/3026
20130101; B60R 2019/188 20130101; F16F 7/00 20130101; B29L 2031/302
20130101; B60R 19/18 20130101; B29K 2995/0089 20130101; B29L
2031/3005 20130101; B29L 2031/3044 20130101; B60R 2021/0435
20130101; F16F 2230/0047 20130101; B29K 2023/12 20130101; B29K
2025/00 20130101; B29L 2031/7138 20130101; B60R 2019/1866 20130101;
B29C 49/04 20130101; B29K 2023/06 20130101; B29L 2031/3014
20130101; B60R 2021/0414 20130101 |
Class at
Publication: |
188/377 |
International
Class: |
F16F 007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2002 |
JP |
2002-319160 |
Oct 31, 2002 |
JP |
2002-319161 |
Oct 31, 2002 |
JP |
2002-319162 |
Oct 31, 2002 |
JP |
2002-319163 |
Jan 31, 2003 |
JP |
2003-025254 |
Jan 31, 2003 |
JP |
2003-025255 |
Jan 31, 2003 |
JP |
2003-025256 |
Jan 31, 2003 |
JP |
2003-025257 |
Jan 31, 2003 |
JP |
2003-025258 |
Feb 28, 2003 |
JP |
2003-054856 |
Feb 28, 2003 |
JP |
2003-054857 |
Feb 28, 2003 |
JP |
2003-054858 |
Mar 31, 2003 |
JP |
2003-097349 |
May 14, 2003 |
JP |
2003-135249 |
Claims
We claim:
1. A system for absorbing energy from an impact, said system
comprising: an energy absorbing member comprising first and second
opposing walls; at least one rib disposed between said first and
second opposing walls; said energy absorbing member comprising a
thermoplastic, said thermoplastic comprising a polyolefin based
resin and 35-75% by weight of an amorphous resin.
2. The system according to claim 1, wherein said thermoplastic has
a flexural modulus of between about approximately 9,000 kg/cm.sup.2
and about approximately 22,000 kg/cm.sup.2.
3. The system according to claim 1, wherein said thermoplastic has
a 15 to 40 kg/cm.sup.2 Izod impact value at an ordinary
temperature.
4. The system according to claim 1, wherein said polyolefin based
resin is a polypropylene resin, and said amorphous resin is at
least one resin selected from the group of resins consisting of
polystyrene resin, impact resistant polystyrene resin,
acrylonitrile-butadiene-styrene resin, polyphenylene ether resin,
and mixtures thereof.
5. A system for absorbing energy from impacts, said system
comprising: a blow molded energy absorbing member comprising; first
and second opposing walls; at least one fused pair of first and
second recessed ribs disposed between said first and second
opposing walls; said first recessed rib being integrally molded
from said first wall and having a first recessed rib end; said
second recessed rib is integrally molded from said second wall and
having a second recessed rib end; said first and second recessed
ribs being integrally fused at a welded surface disposed between
said first and second recessed rib ends; said energy absorbing
member comprising a thermoplastic, said thermoplastic comprising a
polyolefin based resin and 35-75% by weight of an amorphous resin,
and having a 15 to 40 kg/cm.sup.2 Izod impact value at about
approximately normal temperature.
6. The system according to claim 5, wherein said polyolefin based
resin is a polypropylene resin, and said amorphous resin is at
least one resin selected from the group consisting of polystyrene
resin, impact resistant polystyrene resin,
acrylonitrile-butadiene-styrene resin, polyphenylene ether resin,
and mixtures thereof.
7. A system for absorbing energy from an impact, said system
comprising: an energy absorbing member comprising first and second
opposing walls; said energy absorbing member comprising blow molded
thermoplastic; at least one rib disposed between said first and
second opposing walls; and said thermoplastic comprising a first
resin, having a flexural modulus of not greater than about
approximately 2,000 kg/cm.sup.2, and a polyolefin based resin.
8. The system according to claim 7, wherein said first resin has a
flexural modulus not greater than 200 kg/cm.sup.2.
9. The system according to claim 7, wherein said first resin is at
least one resin selected from the group of resins consisting of
olefin based elastomers, styrene based elastomers, low density
polyethylene, straight chain-like low density polyethylene, low
density polyethylene, straight chain-like low density polyethylene
and mixtures thereof.
10. The system according to claim 7, wherein the polyolefin based
resin is at least one resin selected from the group consisting of a
polyethylene, a polypropylene and a mixture thereof.
11. The system according to claim 7, wherein said first resin
comprises an olefin based elastomer and said olefin based elastomer
is at least one elastomer selected from the group consisting of
ethylene-propylene copolymer rubber, ethylene-butene copolymer
rubber, propylene-butene copolymer rubber, hydrogenation product of
butadiene-styrene copolymer rubber, and mixtures thereof.
12. The system according to claim 7, wherein said first resin is
added to said polyolefin based resin in a proportion of about
approximately between 3 to 20 parts by weight.
13. The system according to claim 7, wherein said first resin to be
added to the polyolefin based resin is a thermoplastics resin
having a glass transition temperature not higher than about
approximately -30.degree. C.
14. A system for absorbing energy from an impact, said system
comprising: a blow molded hollow energy absorbing member
comprising; first and second opposing walls; at least one fused
pair of first and second recessed ribs disposed between said first
and second opposing walls; said first recessed rib is integrally
molded from said first wall and having a first recessed rib end;
said second recessed rib is integrally molded from said second wall
and having a second recessed rib end; said first and second
recessed ribs being integrally fused at a welded surface disposed
between said first and second recessed rib ends; said blow molded
hollow impact absorbing member comprising a polypropylene resin and
about approximately 3 to 20 parts by weight of an olefin based
elastomer, said olefin based elastomer having a flexural modulus of
not greater than 200 kg/cm.sup.2 and a glass transition temperature
not higher than -30.degree. C.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an impact energy absorbing
member, more particularly an energy absorbing member provided
inside a vehicle structural member such as a door, a door trim, a
body side panel, a roof panel, a pillar, and a bumper, for
absorbing the impact energy from the inside such as the collision
of a passenger against the inner wall of the vehicle structural
member or the impact energy from the outside such as the collision
with another vehicle.
BACKGROUND OF THE INVENTION
[0002] The official gazette of Japanese Patent Application Laid
Open (JP-A) No. 2002-187508 discloses a hollow double wall
structure for the absorption of impact energies to vehicles such as
automobiles. This structure is produced by blow molding of
thermoplastics, forming recessed ribs from the front surface wall
and the rear surface wall with the top end parts thereof bonded
with each other so as to be integrated for improving the energy
absorbing property. Moreover, the official gazette of Japanese
Patent No. 3,313,999 discloses an energy absorbing member made of a
polypropylene resin having a 5,000 kg/cm2 to 25,000 kg/cm2 flexural
modulus. Furthermore, the official gazette of Japanese Patent
Application Laid Open (JP-A) No. 2002-201322 discloses one made of
a polypropylene resin composition including a polypropylene
component and a copolymer component of a propylene and an ethylene.
According to the energy absorbing member disclosed in the
above-mentioned official gazette of Japanese Patent, a sufficient
shock absorbing property can be obtained by forming an interlocking
rib for integrally linking a plurality of recessed ribs, or the
like as shown in the official gazette of Japanese Patent
Application Laid Open (JP-A) No. 2002-187508. However, it has been
considered important that enhanced shock absorbing property
particularly at low temperature is obtained. Regarding the energy
absorbing member for a vehicle made of a polypropylene resin having
a 5,000 kg/cm2 to 25,000 kg/cm2 flexural modulus, disclosed in the
official gazette of Japanese Patent No. 3,313,999, it was
afterwards discovered that the stress change at the time of energy
absorption at 60.degree. C. to -15.degree. C. is large and the
energy absorbing performance is effected by the outside air
temperature. That is, with the load stress at a 50% compression
distortion of a polypropylene energy absorbing member provided as
the reference at an ordinary temperature, the stress change ratio
is 21% in the case the outside air temperature is -15.degree. C.,
and the stress change ratio is -34% in the case the outside air
temperature is 60.degree. C.
[0003] Since the stress change ratio of the energy absorbing member
for a vehicle is required to be kept within .+-.10% at the
temperature from -15 to 60, with respect to the compression
distortion at ordinary temperature, the impact absorbing member
formed of a polypropylene resin having a 5,000 kg/cm2 to 25,000
kg/cm2 flexural modulus disclosed in the official gazette of
Japanese Patent No. 3,313,999 can not provide the required level of
performance.
BRIEF SUMMARY OF THE INVENTION
[0004] One embodiment of the present invention provides a system
for absorbing energy from an impact, that system comprising: an
energy absorbing member comprising first and second opposing walls;
at least one rib disposed between the first and second opposing
walls energy absorbing member comprising a thermoplastic, the
thermoplastic comprising a polyolefin based resin and 35-75% by
weight of an amorphous resin.
[0005] Another embodiment of the present invention provides such a
system wherein the thermoplastic has a flexural modulus of between
about approximately 9,000 kg/cm.sup.2 and about approximately
22,000 kg/cm.sup.2
[0006] A further embodiment of the present invention provides such
a system wherein the thermoplastic has a 15 to 40 kg/cm.sup.2 Izod
impact value at an ordinary temperature.
[0007] Still another embodiment of the present invention provides
such a system wherein the polyolefin based resin is a polypropylene
resin, and the amorphous resin is at least one resin selected from
the group of resins consisting of polystyrene resin, impact
resistant polystyrene resin, acrylonitrile-butadiene-styrene resin,
polyphenylene ether resin, and mixtures thereof.
[0008] A still further embodiment of the present invention provides
a system for absorbing energy from impacts, that system comprising:
a blow molded energy absorbing member comprising; first and second
opposing walls; at least one fused pair of first and second ribs
disposed between the first and second opposing walls: the first
recessed rib being integrally molded from the first wall and having
a first recessed rib end; the second recessed rib is integrally
molded from the second wall and having a second recessed rib end;
the first and second recessed ribs being integrally fused at a
welded surface disposed between the first and second recessed rib
ends; the energy absorbing member comprising a thermoplastic, that
thermoplastic comprising a polyolefin based resin and 35-75% by
weight of an amorphous resin, and having a 15 to 40 kg/cm.sup.2
Izod impact value at about approximately normal temperature.
[0009] Even another embodiment of the present invention provides
such a system wherein the polyolefin based resin is a polypropylene
resin, and the amorphous resin is at least one resin selected from
the group consisting of polystyrene resin, impact resistant
polystyrene resin, acrylonitrile-butadiene-styrene resin,
polyphenylene ether resin, and mixtures thereof.
[0010] An even further embodiment of the present invention provides
a system for absorbing energy from an impact, that system
comprising: an energy absorbing member comprising first and second
opposing walls; the energy absorbing member comprising blow molded
thermoplastic; at least one rib disposed between the first and
second opposing walls; and the thermoplastic comprising a first
resin, having a flexural modulus of not greater than about
approximately 2,000 kg/cm.sup.2, and a polyolefin based resin.
[0011] Still another embodiment of the present invention provides
such a system wherein the first resin has a flexural modulus not
greater than 200 kg/cm.sup.2.
[0012] A still further embodiment of the present invention provides
such a system wherein the first resin is at least one resin
selected from the group of resins consisting of olefin based
elastomers, styrene based elastomers, super low density
polyethylene, straight chain-like low density polyethylene, low
density polyethylene, straight chain-like super low density
polyethylene and mixtures thereof.
[0013] Even still another embodiment of the present invention
provides such a system wherein the polyolefin based resin is at
least one resin selected from the group consisting of a
polyethylene, a polypropylene and a mixture thereof.
[0014] An even still further embodiment of the present invention
provides such a system wherein the first resin comprises an olefin
based elastomer and the olefin based elastomer is at least one
elastomer selected from the group consisting of ethylene-propylene
copolymer rubber, ethylene-butene copolymer rubber,
propylene-butene copolymer rubber, hydrogenation product of
butadiene-styrene copolymer rubber, and mixtures thereof.
[0015] Yet another embodiment of the present invention provides
such a system wherein the first resin is added to the polyolefin
based resin in a proportion of about approximately between 3 to 20
parts by weight.
[0016] A yet further embodiment of the present invention provides
such a system wherein the first resin to be added to the polyolefin
based resin is a thermoplastics resin having a glass transition
temperature not higher than about approximately -30.degree. C.
[0017] A yet even further embodiment of the present invention
provides a system for absorbing energy from an impact, that system
comprising: a blow molded hollow energy absorbing member
comprising; first and second opposing walls; at least one fused
pair of first and second ribs disposed between the first and second
opposing walls; the first recessed rib is integrally molded from
the first wall and having a first recessed rib end; the second
recessed rib is integrally molded from the second wall and having a
second recessed rib end; the first and second recessed ribs being
integrally fused at a welded surface disposed between the first and
second recessed rib ends; the blow molded hollow impact absorbing
member comprising a polypropylene resin and about approximately 3
to 20 parts by weight of an olefin based elastomer, the olefin
based elastomer having a flexural modulus of not greater than 200
kg/cm.sup.2 and a glass transition temperature not higher than
-30.degree. C.
[0018] The features and advantages described herein are not
all-inclusive and, in particular, many additional features and
advantages will be apparent to one of ordinary skill in the art in
view of the drawings, specification, and claims. Moreover, it
should be noted that the language used in the specification has
been principally selected for readability and instructional
purposes, and not to limit the scope of the inventive subject
matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a partially broken perspective view showing an
energy absorbing member for a vehicle according to an embodiment of
the present invention.
[0020] FIG. 2 is an enlarged cross-sectional view taken on the line
A-A of FIG. 1.
[0021] FIG. 3 is a view showing a first step for molding an energy
absorbing member for a vehicle according to one embodiment of the
invention by blow molding.
[0022] FIG. 4 is a view showing a second step for molding an energy
absorbing member for a vehicle according to one embodiment of the
invention by blow molding.
[0023] FIG. 5 is a cross-sectional view showing an embodiment with
an energy absorbing member for a vehicle according to one
embodiment of the invention provided inside a door trim of a
vehicle.
[0024] FIG. 6 is a cross-sectional view showing an embodiment with
an energy absorbing member for a vehicle according to one
embodiment of the invention provided inside a rear pillar of a
vehicle.
[0025] FIG. 7 is a rear view of a rear bumper with an energy
absorbing member for a vehicle according to one embodiment of the
invention provided therein.
[0026] FIG. 8 is a partially broken perspective view showing an
energy absorbing member for a vehicle according to another
embodiment of the present invention.
[0027] FIG. 9 is a graph showing the displacement with respect to
the compression load of an energy absorbing member for a vehicle
made of a resin with a modified PPE resin introduced to a PP
resin.
[0028] FIG. 10 is a graph showing the displacement with respect to
the compression load of an energy absorbing member for a vehicle
made of a resin with an olefin based elastomer introduced to a PP
resin.
[0029] FIG. 11 is a graph showing the displacement with respect to
the compression load of an energy absorbing member for a vehicle
made of a PP resin.
DETAILED DESCRIPTION OF THE INVENTION
[0030] In FIGS. 1 and 2, the reference numeral 1 denotes an energy
absorbing member. The energy absorbing member for a vehicle 1 made
of a thermoplastic resin, formed integrally by blow molding, has a
hollow part 2, and a plurality of recessed ribs 5, 6 formed, in one
embodiment by denting or impressing opposing first 3 and second 4
walls such that interior surfaces of ribs 5, 6 contact each other
and meet, forming a joint 7. This joint may be welded, fused or
otherwise configured so that the ribs are integrally joined.
[0031] The energy absorbing member is herein described, for the
purposes of clarity, in the context of a vehicle. The term vehicle
is intended in its broadest possible meaning, and includes but is
not limited to automobiles, trucks, aircraft, boats, ships,
tankers, carts, etc. One skilled in the art will readily appreciate
that other, non-vehicular applications such as helmets, riot gear,
and protective panels would also be within the scope of the present
invention.
[0032] According to one embodiment, the energy absorbing member for
a vehicle 1 may have a configuration with the ribs provided by
denting the first wall 3 toward the second wall 4 direction with
the top end part bonded with the second wall 4, or by denting the
second wall 4 toward the first wall 3 direction with the top end
part bonded with the first wall 3 as shown in FIG. 8.
[0033] According to an alternative embodiment, the rib may be
formed by impacting, impressing, or denting or otherwise molding
the rib 5 into only one of the two walls 3, 4. This would produce a
single rib rather than a pair of ribs.
[0034] An energy absorbing member for a vehicle 1 according to one
embodiment of the present invention is made of thermoplastics
produced by adding 35 to 75 wt % of an amorphous resin to a
polyolefin based resin, having a 9,000 kg/cm2 to 22,000 kg/cm2
flexural modulus. As the polyolefin based resin, a polypropylene
resin, a polyethylene resin, an ethylene-propylene copolymer resin,
or the like can be used. In one embodiment a polypropylene resin is
used. As the amorphous resin, at least one resin selected from the
group consisting of a polystyrene resin, an impact resistant
polystyrene resin, an acrylonitrile-butadiene-- styrene resin, a
polyphenylene ether resin, and a mixture thereof can be used. The
thermoplastics for providing the energy absorbing member 1 have a
15 to 40 kg/cm2 Izod impact value at an ordinary temperature.
[0035] FIGS. 9 to 11 show the result of compressing the energy
absorbing member for a vehicle 1 formed by blow molding and
measuring displacement (change of the compression distortion) with
respect to the compression loaded by a tensile tester. The curves
(a1), (b1), (c1) shown in the graph of FIG. 11 show the
displacement of the energy absorbing member for a vehicle 1 having
a recessed rib, made of only a polypropylene resin with respect to
the compression load in the environment of an ordinary or room
temperature (about approximately 20.degree. C.), -15.degree. C.,
and 60.degree. C., respectively. An ordinary temperature should be
understood to mean a temperature approximately equal to ambient
temperature.
[0036] In the graph of FIG. 11, the curves (b1), (c1) show the
dramatically different values of the compression load at each
displacement compared with the curve (a1) showing the displacement
with respect to the compression load at an ordinary temperature
(20.degree. C.). The curve (b1) shows a larger value of the
compression load thereof at 10 to 50 mm displacement than that of
the curve (a1), and the curve (c1) shows a smaller value of the
compression load thereof at 0 to 55 mm displacement than that of
the curve (a1). Accordingly, the energy absorbing member formed
only of a polypropylene resin has a large stress change with
respect to temperature and the energy absorbing performance thereof
is effected by the outside air temperature.
[0037] The curves (a2), (b2), (c2) in the graph of FIG. 9 show the
displacement of the energy absorbing member for a vehicle 1 having
a recessed rib, made of thermoplastics produced by adding 50 wt %
of a polyphenylene ether resin (modified PPE) to a polypropylene
(PP) resin with respect to the compression load in the environment
of an ordinary temperature (20.degree. C.), minus 15.degree. C.,
and 60.degree. C., respectively.
[0038] As shown in the graph of FIG. 9, according to the energy
absorbing member for a vehicle 1 according to one embodiment of the
invention, the curves (b2), (c2) illustrate compression load values
at each displacement which are approximately equal to those
illustrated in curve (a2) showing the displacement with respect to
the compression load at an ordinary temperature (20.degree. C.).
That is, the curve (b2) shows the substantially same value of the
compression load thereof at 0 to 50 mm displacement of the energy
absorbing member as that of the curve (a2), and the curve (c2) also
shows the substantially same value of the compression load thereof
at 0 to 50 mm displacement of the energy absorbing member as that
of the curve (a2). Accordingly, the energy absorbing member formed
from an amorphous resin such as a polyphenylene ether resin added
to a polypropylene resin has a smaller stress change with respect
to the temperature so that the energy absorbing performance thereof
is barely effected by the outside air temperature.
[0039] Although the case of using the polyphenylene ether resin as
the amorphous resin is explained in the embodiment, the same effect
can be obtained by using another amorphous resins such as a
polystyrene resin (PS), an impact resistant polystyrene resin
(HIPS), an acrylonitrile-butadiene-styrene resin (ABS), or the
like. However, in the case of an impact resistant polystyrene
resin, or the like is added, the Izod impact value tends to be
changed significantly according to the composition ratio.
Therefore, the Izod impact value should be specified in addition to
the resin mixing ratio. The Izod impact value for the energy
absorbing member for a vehicle should be 15 to 40 kg/cm2. As in the
case of adding the polyphenylene ether resin, the temperature
dependency of the energy absorbing member is improved by adding
another amorphous resin.
1 TABLE 1 Resin mixing ratio Izod impact PP/modified Stress change
value PPE -15.degree. C. 60.degree. C. (kg/cm.sup.2) Comparative
10/0 +21% -34% -- Example 1 Comparative 8/2 +18% -33% 18 Example 2
Example 1 65/35 +17% -19% 18 Example 2 5/5 0% -2% 22 Example 3 3/7
+2% -4% 20
[0040] Table 1 shows the stress change ratio (%) and the Izod
impact value (kg/cm2) in the case of adding a polyphenylene ether
resin (modified PPE) to a polypropylene resin (PP) with the mixing
ratio changed. The stress change ratio is calculated with the load
stress at an ordinary temperature with a 50% compression distortion
of the energy absorbing member provided as the reference. The 50%
compression distortion denotes the state within the energy
absorbing member is deformed to the half thickness from the initial
thickness by being crushed under the compression load. The results
of Comparative Examples 1, 2 and Examples 1 to 3 are as
follows.
COMPARATIVE EXAMPLE 1
[0041] An energy absorbing member was formed of only a
polypropylene resin without adding a polyphenylene ether resin. The
stress change ratio with the ordinary temperature, 50% displacement
provided as the reference was 21% at -15.degree. C., and it was
-34% at 60.degree. C. That is, the compression load is made higher
at a low temperature, and the compression load is made lower at a
high temperature.
COMPARATIVE EXAMPLE 2
[0042] An energy absorbing member was formed of a thermoplastic
resin produced by adding 20 wt % of a polyphenylene ether resin to
a polypropylene resin. In this case, the same result as in the
comparative example 1 was obtained.
EXAMPLE 1
[0043] An impact energy absorbing member was formed of a
thermoplastic resin produced by adding 35 wt % of a polyphenylene
ether resin to a polypropylene resin. In this case, the stress
change ratio was improved in particular at 60.degree. C. by the
addition of the polyphenylene ether so that the energy absorbing
property change with respect to the temperature change is
reduced.
EXAMPLE 2
An energy absorbing member was formed of a thermoplastic resin
produced by adding 50 wt % of a polyphenylene ether resin to a
polypropylene resin.
EXAMPLE 3
An energy absorbing member was formed of a thermoplastic resin
produced by adding 70 wt % of a polyphenylene ether resin to a
polypropylene resin.
[0044] According to the Examples 2, 3, the energy absorbing
property change was reduced to a considerable degree by the
addition of the polyphenylene ether resin so that an energy
absorbing member with a diminished temperature dependency was
obtained.
[0045] An energy absorbing member for a vehicle 1, according to one
embodiment of the present invention, is made of thermoplastics with
a soft resin having a 2,000 kg/cm2 or less, particularly preferably
200 kg/cm2 or less flexural modulus added to a polyolefin based
resin. Thereby, the energy absorbing property can be provided
having a diminished dependance on temperature fluctuations at low
temperatures, in particular at -30.degree. C. owing to the
multiplier effect of the ribs provided in the energy absorbing
member and the composition of a soft resin.
[0046] The energy absorbing member for a vehicle 1 formed by blow
molding was compressed by a tensile tester, and displacement
(change of the compression distortion) was measured with respect to
the compression load. The result is shown in FIG. 10. The curve (a)
in the graph of FIG. 10 shows the displacement of the energy
absorbing member for a vehicle 1 having a recessed rib without
addition of a soft resin, at an ordinary temperature. The impact
energy is sufficiently absorbed by supporting a high load without
lowering the compression load even in the case the displacement of
the energy absorbing member advances 15 mm. In contrast, the curve
(c) in the graph shows the displacement at -30.degree. C. with
respect to the compression load, of the energy absorbing member for
a vehicle 1 having a recessed rib without addition of a soft resin.
The compression load is lowered from the 10 mm displacement of the
energy absorbing member, so that a desirable energy absorbing
property was not obtained. That is, according to the energy
absorbing member for a vehicle 1 without addition of a soft resin,
the member 1 is vulnerable to destruction resulting from stress
cracks, and, as a result, at -30.degree. C., is unable to absorb
the energy from an impact, as required.
[0047] By adding a soft resin, a preferable energy absorbing
property can be provided even at low temperature as shown in the
curve (b) in the graph in FIG. 10. The curve (b) shown in the graph
shows the displacement at -30.degree. C. with respect to the
compression load in the case of adding a soft resin. Compared with
the graph (c), the compression load decline is restrained from the
10 mm displacement as a result of the addition composition of the
soft resin so that a desired energy absorbing property was
provided. That is, by providing the energy absorbing member for a
vehicle 1 having a recessed rib formed of thermoplastics including
a polyolefin based resin such as a polypropylene as the base
material resin and 3 to 20 parts by weight of a soft resin such as
a olefin based elastomer, the temperature dependency can be
restrained and damage from impact energy can be prevented or
minimized, without hardening of the energy absorbing member 1 even
at low temperature of -30.degree. C. and a desirable energy
absorbing property can be obtained. Moreover, since the energy
absorbing property at -30.degree. C. is required to the energy
absorbing member of a vehicle, the soft resin to be added should
have the glass transition temperature or the vulnerable temperature
at -30.degree. C. or lower.
[0048] As the resin having a 2,000 kg/cm2 or less flexural modulus
should be added to a polyolefin based resin, it needs to have an
excellent mixing property with respect to a polyolefin based resin
as the base material resin. An olefin based elastomer, a styrene
based elastomer, a low density polyethylene, a straight chain-like
low density polyethylene, a super low density polyethylene, and a
straight chain-like super low density polyethylene are preferable.
In particular, a desired energy absorbing property can be obtained
by adding 3 to 20 parts by weight of an olefin based elastomer to a
polyolefin based resin as the base material resin.
[0049] As an olefin based elastomer, an ethylene-propylene
copolymer rubber, an ethylene-butene copolymer rubber, a
propylene-butene copolymer rubber, a hydrogenation product of a
butadiene-styrene copolymer rubber, or the like can be used. As a
styrene based elastomer, a styrene-butadiene block copolymer, a
styrene-butadiene-styrene block copolymer, a styrene-isoprene-block
copolymer, a styrene-isoprene-styrene block copolymer, and a
hydrogenation product thereof can be used preferably. These
elastomers have a good mixing property with respect to a polyolefin
based resin.
[0050] The energy absorbing member 1 according to one embodiment of
the invention is blow molded as shown in FIGS. 3 and 4. The
reference numerals 12, 12 are a pair of split mold halves. The
split mold halves 12, 12 are provided with recessed rib forming
parts 13, 13 for forming the recessed ribs 5, 6. The reference
numeral 14 denotes a parison, and 15 an extrusion head.
[0051] The energy absorbing member 1 according to one embodiment of
the invention is provided inside a vehicle structural member such
as a door of, a door trim, a body side panel, a roof panel, a
pillar, a bumper, a seat, and an instrument panel, or the like.
FIG. 5 shows an embodiment of providing the energy absorbing member
1 according to one embodiment of the invention inside a door trim 8
of a door 9. FIG. 6 shows an embodiment of providing the same
inside a rear pillar 10 of an automobile, and FIG. 7 shows an
embodiment of providing the same inside a rear bumper 11. In FIG.
6, the mark A denotes a head of a passenger.
[0052] The foregoing description of the embodiments of the
invention has been presented for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Many modifications and
variations are possible in light of this disclosure. It is intended
that the scope of the invention be limited not by this detailed
description, but rather by the claims appended hereto.
* * * * *