U.S. patent application number 15/173967 was filed with the patent office on 2016-09-29 for thermoplastic jounce bumpers.
The applicant listed for this patent is E I DU PONT DE NEMOURS AND COMPANY. Invention is credited to PETER LASZLO SZEKELY, DAMIEN VAN DER ZYPPE.
Application Number | 20160280029 15/173967 |
Document ID | / |
Family ID | 44534669 |
Filed Date | 2016-09-29 |
United States Patent
Application |
20160280029 |
Kind Code |
A1 |
SZEKELY; PETER LASZLO ; et
al. |
September 29, 2016 |
THERMOPLASTIC JOUNCE BUMPERS
Abstract
The invention provides a vehicle suspension system, comprising a
jounce bumper made of elastomeric thermoplastic material, having
improved design to maximize energy absorption.
Inventors: |
SZEKELY; PETER LASZLO;
(PRINGY, FR) ; VAN DER ZYPPE; DAMIEN; (CHAMPIGNY
SUR MARNE, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E I DU PONT DE NEMOURS AND COMPANY |
Wilmington |
DE |
US |
|
|
Family ID: |
44534669 |
Appl. No.: |
15/173967 |
Filed: |
June 6, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14149927 |
Jan 8, 2014 |
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15173967 |
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13197991 |
Aug 4, 2011 |
8657271 |
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14149927 |
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61479458 |
Apr 27, 2011 |
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61372985 |
Aug 12, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 5/00 20130101; F16F
1/3605 20130101; F16F 9/58 20130101; B60G 11/24 20130101; F16F
1/3732 20130101; F16F 1/424 20130101; C08J 2367/00 20130101; B60G
11/22 20130101 |
International
Class: |
B60G 11/24 20060101
B60G011/24; F16F 1/42 20060101 F16F001/42; C08J 5/00 20060101
C08J005/00; F16F 1/36 20060101 F16F001/36 |
Claims
1. An automotive vehicle suspension system, comprising a jounce
bumper installed on a suspension rod of a vehicle, wherein the
jounce bumper is made of a copolyetherester, and wherein the jounce
bumper comprises: a hollow elongated tubular body having a wall,
the tubular body having at least two bellows, each bellow being
defined by a peak and a trough, the peak having a fillet radius of
rs, the trough having a fillet radius of rc and a maximum wall
thickness in the trough of Tmax; wherein rc is greater than rs, and
wherein the ratio of Tmax, the maximum thickness of the wall in a
trough to Tm, the thickness of the wall at intermediate points
between the peak and the trough, is greater than or equal to 1.5,
and wherein the trough is defined by a wall arc having end points
at said points where the wall thickness is Tm, wherein each of said
intermediate points is a point of tangency between a circle of
radius rc and a circle of radius rs, or if rs and rc are not
tangent, Tm is the wall thickness wherein each of said intermediate
points is a midpoint of a line drawn tangent to circles rs and
rc.
2. An automotive suspension system according to claim 1, wherein
(Tmax/Tm), the ratio of maximum wall thickness in the trough to the
thickness of the wall at an intermediate point, is greater than
(Tmax/Tm).sub.1, wherein (Tmax/Tm).sub.1=3.43-0.05 P-0.222 SQRT
(95-4.19 P+0.05 P.sup.2-0.23 Ri), where Tmax is the maximum wall
thickness at a trough; Tm is the wall thickness at the point of
tangency between a circle of radius rc and a circle of radius rs,
or if rs and rc are not tangent, Tm is the wall thickness at the
midpoint of a line drawn tangent to circles rs and rc; SQRT is
square root; P is the pitch; and Ri is the external radius at a
trough.
3. An automotive suspension system according to claim 1, wherein
the copolyetherester has a melt viscosity between 0.5 and 8 g/10
minutes, at 230.degree. C. under 5 kg load measured according to
ISO1133, and a hardness between at or about 45 and 60 D measured at
1 s according to IS0868.
4. An automotive suspension system according to claim 2, wherein
the copolyetherester has a melt viscosity between 0.5 and 8 g/10
minutes, at 230.degree. C. under 5 kg load measured according to
ISO1133, and a hardness between at or about 45 and 60 D measured at
1 s according to IS0868.
5. An automotive suspension system according to claim 1, wherein
the copolyetherester has a melt viscosity between 2 and 6 g/10
minutes, at 230.degree. C. under 5 kg load measured according to
ISO1133, and a hardness between at or about 45 and 60 D measured at
1 s according to IS0868.
6. An automotive suspension system according to claim 2, wherein
the copolyetherester has a melt viscosity between 2 and 6 g/10
minutes, at 230.degree. C. under 5kg load measured according to
ISO1133, and a hardness between at or about 45 and 60 D measured at
1 s according to IS0868.
7. An automotive suspension system according to claim 1, wherein
the copolyetherester has a melt viscosity between 3 and 5 g/10
minutes, at 230.degree. C. under 5kg load measured according to
ISO1133, and a hardness between at or about 45 and 60 D measured at
1 s according to IS0868.
8. An automotive suspension system according to claim 2, wherein
the copolyetherester has a melt viscosity between 3 and 5 g/10
minutes, at 230.degree. C. under 5kg load measured according to
IS01133, and a hardness between at or about 45 and 60 D measured at
1 s according to IS0868.
9. An automotive suspension system according to claim 1, wherein
the copolyetherester is a copolymer having a multiplicity of
recurring long-chain ester units and short-chain ester units joined
head-to-tail through ester linkages, said long-chain ester units
being represented by formula (A): ##STR00005## and said short-chain
ester units being represented by formula (B): ##STR00006## wherein
G is a divalent radical remaining after the removal of terminal
hydroxyl groups from poly(alkylene oxide)glycols having preferably
a number average molecular weight of between about 400 and about
6000; R is a divalent radical remaining after removal of carboxyl
groups from a dicarboxylic acid having a molecular weight of less
than about 300; and D is a divalent radical remaining after removal
of hydroxyl groups from a diol having a molecular weight preferably
less than about 250; and wherein said copolyetherester(s)
preferably contain from about 15 to about 99 wt-% short-chain ester
units and about 1 to about 85 wt-% long-chain ester units.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. National
application Ser. No. 13/197,991 filed Aug. 4, 2011, now pending,
which claims the benefit of U.S. Patent Application No. 61/372,985,
filed on Aug. 12, 2010, and U.S. Patent Application No. 61/479,458,
filed on Apr. 27, 2011, which are incorporated herein by reference
in their entirety.
FIELD OF INVENTION
[0002] The present invention relates to the field of vehicle
suspension systems, and more particularly to jounce bumpers.
BACKGROUND OF THE INVENTION
[0003] A jounce bumper (also called a bump stop, rebound bumper,
end-of-travel bumper, strike-out bumper, suspension bumper, or
compression bumper) is a shock-absorbing device ordinarily
positioned on the top of vehicle suspensions. Jounce bumpers for
use in motor vehicle suspension systems have long been used for
cushioning the impact between two suspension system components,
such as the axle and a portion of the frame, as well as for
attenuating noise and vibration to increase the ride comfort of the
passengers. Since displacement of the vehicle chassis causes
displacements of the strut, the strut undergoes cycles of
compression and extension in response to the displacement of the
vehicle chassis. Provision must be made for protecting the strut
assembly and the vehicle body from the jounce forces associated
with severe irregularities in the road surface leading to extreme
displacement of the suspension. For this reason, a jounce bumper is
attached to the suspension system at a point where impact is likely
to occur when the shock absorber fails to absorb the forces created
by extraordinary driving conditions. Particularly, during jounce
motions of the strut, the damper "bottoms out" and the jounce
bumper moves into contact with the jounce bumper plate and
compresses to dissipate energy resulting in cushioning the impact,
reducing noise, reducing the sensation of impact to the passengers
and reducing possible damage to the vehicle suspension system.
Jounce bumpers are elongated, generally cylindrical or conical,
members with or without convolutes, made of a compressible and
elastomeric material that extends around the piston rod. As taught
in U.S. Pat. No. 4,681,304, convoluted bumpers function by a
progressive stacking of the convolutions to provide resistance to
jounce forces.
[0004] Materials suitable for this application must be resilient,
i.e. capable of withstanding shock without undue permanent
deformation or rupture, and must have excellent flex life.
Conventional jounce bumpers are formed of foamed polyurethane and
vulcanized rubber. For example, jounce bumpers are often formed of
microcellular polyurethane (MCU). A microcellular polyurethane
jounce bumper is made by casting polyurethane precursors in a
jounce bumper mold. Microcellular foam is obtained from the
reaction of diisocyanate glycol with a blowing agent or with water
which produces carbon dioxide gas for foaming. This technology is
time-consuming since foaming requires prolonged times in the mold
due to the slow release of carbon dioxide. While jounce bumpers
made of foamed polyurethane have good ride characteristics, they
are expensive to produce since they require an energy- and
time-consuming technology due to the crosslinking.
[0005] With the aim of improving durability, inertness to
automotive fluids, and resistance to tear propagation of the
material used to form the jounce bumper, U.S. Pat. No. 5,192,057
discloses an elongated hollow body formed of an elastomer,
preferably from a copolyetherester polymer. As disclosed therein,
such pieces, including jounce bumpers having bellows shaped
sections with a constant thickness profile, are manufactured by
blow molding techniques. An alternative method for forming jounce
bumpers, i.e. corrugated extrusion, is described in U.S. Published
Patent Application No. 2008/0272529.
[0006] In a typical blow molding operation for manufacturing hollow
plastic articles a parison of plastic material that has been
produced by extrusion or injection molding and which is in a hot
moldable condition is positioned between two halves of an open blow
mold having a mold cavity of a shape appropriate to the required
external shape of the article to be manufactured. The parison
gradually moves and stretches under the influence of gravity. When
the parison reaches the proper length, the mold halves are closed
around it and pressurized air or other compressed gas is introduced
in the interior of the parison to inflate it to the shape of mold
or to expand it against the sides of the mold cavity. After a
cooling period, the mold is opened and the final article is
ejected.
[0007] In extrusion blow molding, the parison is produced by
extruders. Extrusion blow molding is less expensive than
foaming/casting but leads to less precise dimensions and leads also
to limitations in the wall thickness of the part. The stiffness of
a jounce bumper is directly related to its thickness. Thus, a small
variation of thickness (either variation from article to article,
along the longitudinal axis of a jounce bumper made from one shot,
or along the radius of the convolute of a jounce bumper made in a
single jounce bumper), for example 0.2 mm, will significantly
change the stiffness of the jounce bumper and its energy absorption
capacity and dampening performance.
[0008] Injection blow molding gives more precise dimensions than
extrusion blow molding. In this technique, the parison is formed by
injection molding, the inner core of the mold is removed and the
parison is quickly inflated while being enclosed in two mold halves
as in extrusion blow molding. The parison can be injection molded
to have a non-constant cross-section resulting in a better wall
thickness uniformity of the final part than from extrusion blow
molding. Injection blow molding allows more precise details in the
final blown structure but is more expensive than extrusion blow
molding.
[0009] In general, it is desired to maximize the absorption of
energy in a jounce bumper. The energy absorption behavior of a
jounce bumper can be measured, for example, by measuring
deformation versus applied force. Usually deformation is plotted on
the X-axis (in mm), and applied load (force) is plotted on the
Y-axis (in N). The area under the curve represents the energy
absorbed by the jounce bumper according to the formula
displacement.times.Force=energy.
[0010] Thermoplastic jounce bumpers made by any of the
above-mentioned techniques can exhibit different responses
depending on design, including specific configuration details, and
materials of manufacture. There remains a need to improve the
design of thermoplastic jounce bumpers so as to improve the
force-displacement behavior, thereby increasing the energy
absorbed.
SUMMARY OF THE INVENTION
[0011] In a first aspect, the invention provides a jounce bumper
made of elastomeric thermoplastic material, comprising: a hollow
elongated tubular body having a wall, the tubular body having at
least two bellows, each bellow being defined by a peak and a
trough, the peak having a fillet radius of rs, the trough having a
fillet radius of rc and a maximum wall thickness of the trough
being at a point within the trough and designated Tmax; wherein rc
is greater than rs, and wherein the ratio of Tmax, the maximum
thickness of the wall in a trough, to Tm, the thickness of the wall
at an intermediate point between peak and trough, is greater than
or equal to 1.2, and wherein the trough is defined by a wall arc
having end points Tm.
[0012] In a second aspect, the invention provides a jounce bumper
made of elastomeric thermoplastic material, comprising: [0013] a
hollow elongated tubular body having a wall, the tubular body
having at least two bellows, each bellow being defined by a peak
and a trough, the peak having a fillet radius of rs, the trough
having a fillet radius of rc and a wall thickness at the trough of
Tc (Tc being Tmax in the case when Tmax falls substantially in the
middle of the trough); wherein rc is greater than rs, and wherein
the ratio of Tc (Tmax), the thickness of the wall at a trough, to
Tm, the thickness of the wall at an intermediate point between peak
and trough, is greater than or equal to 1.2.
[0014] In a third aspect, the invention provides a method for the
manufacture of a jounce bumper, comprising the step of: [0015]
shaping elastomeric thermoplastic material into a hollow elongated
tubular body having a wall, the tubular body having at least two
bellows, each bellow being defined by a peak and a trough, the peak
having a fillet radius of rs, the trough having a fillet radius of
rc and a maximum wall thickness of the trough being at a point
within the trough and designated Tmax; wherein rc is greater than
rs, and wherein the ratio of Tmax, the maximum thickness of the
wall in a trough, to Tm, the thickness of the wall at an
intermediate point between peak and trough, is greater than or
equal to 1.2, and wherein the trough is defined by the wall arc
having end points Tm.
[0016] In a fourth aspect, the invention provides a method for the
manufacture of a jounce bumper, comprising the step of: [0017]
shaping elastomeric thermoplastic material into a hollow elongated
tubular body having a wall, the tubular body having at least two
bellows, each bellow being defined by a peak and a trough, the peak
having a fillet radius of rs, the trough having a fillet radius of
rc and a wall thickness at the trough of Tc (Tc being Tmax in the
case when Tmax falls substantially in the middle of the trough);
wherein rc is greater than rs, and wherein the ratio of Tc (Tmax),
the thickness of the wall at a trough, to Tm, the thickness of the
wall at an intermediate point between peak and trough, is greater
than or equal to 1.2.
[0018] In a fifth aspect, the invention provides a method for
absorbing shocks in an automobile suspension comprising using a
jounce bumper to absorb energy from displacement of the suspension,
wherein the jounce bumper is made of elastomeric thermoplastic
material and comprises a hollow elongated tubular body having a
wall, the tubular body having at least two bellows, each bellow
being defined by a peak and a trough, the peak having a fillet
radius of rs, the trough having a fillet radius of rc and a maximum
wall thickness of the trough being at a point within the trough and
designated Tmax; wherein rc is greater than rs, and wherein the
ratio of Tmax, the maximum thickness of the wall in a trough, to
Tm, the thickness of the wall at an intermediate point between peak
and trough, is greater than or equal to 1.2, and wherein the trough
is defined by the wall arc having end points Tm.
[0019] In a sixth aspect, the invention provides a method for
absorbing shocks in an automobile suspension comprising using a
jounce bumper to absorb energy from displacement of the suspension,
wherein the jounce bumper is made of elastomeric thermoplastic
material and comprises a hollow elongated tubular body having a
wall, the tubular body having at least two bellows, each bellow
being defined by a peak and a trough, the peak having a fillet
radius of rs, the trough having a fillet radius of rc and a wall
thickness at the trough of Tc (Tc being Tmax in the case when Tmax
falls substantially in the middle of the trough); wherein rc is
greater than rs, and wherein the ratio of Tc (Tmax), the thickness
of the wall at a trough, to Tm, the thickness of the wall at an
intermediate point between peak and trough, is greater than or
equal to 1.2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic broken view of an "inward" jounce
bumper, wherein Re designates the external radius at a peak, Ri
designates the external radius at a trough, and P represents the
distance from peak to peak (the pitch).
[0021] FIG. 2A is a schematic cross-section enlarged view of FIG.
1, wherein the dashed line represents the longitudinal axis of the
jounce bumper, rs designates the fillet radius of an outward
convolute, and rc designates the fillet radius on an inward
convolute, Ts designates the wall thickness at the peak of an
outward convolute, Tc (also Tmax) designates the wall thickness at
the trough (inward convolute) in the case where the maximum wall
thickness Tmax occurs at the middle of the trough, and Tm
designates the intermediate wall thickness at the point of tangency
between a circle having radius rc and a circle having radius rs.
The trough is defined by the wall arc having end points of Tm.
[0022] FIG. 2B is a schematic cross-section enlarged view of a
jounce bumper showing the case when circles of radius rs and rc are
not tangent. The dashed line represents the longitudinal axis of
the jounce bumper, rs designates the fillet radius of an outward
convolute, and rc designates the fillet radius on an inward
convolute, Ts designates the wall thickness at the peak of an
outward convolute, Tc (Tmax) designates the wall thickness at the
trough (inward convolute) in the case where the maximum wall
thickness Tmax occurs at the middle of the trough, and Tm
designates the intermediate wall thickness at the mid-point of a
line drawn tangent to both a circle having radius rc and a circle
having radius rs.
[0023] FIG. 3 illustrates percent deformation (deflection) (%) on
the X-axis vs. applied force (N) on the Y-axis for jounce bumpers
according to the invention, i.e. E1 and E2, and a comparative
jounce bumper, i.e. C1. The percent deformation is defined as the
ratio of actual deformation in mm to the initial height in mm of
the jounce bumper (after 2-4 preconditioning compressions). The
curve for E1 is designated with triangles, the curve for E2 is
designated with circles and the curve for C1 is designated with
diamonds.
[0024] FIG. 4 shows a partially cut-away view of one example of a
jounce bumper as installed in the suspension of an automobile.
DETAILED DESCRIPTION OF THE INVENTION
[0025] All documents referred to herein are incorporated by
reference. The inventors have found that in a jounce bumper made
from elastomeric thermoplastic material, when the ratio of
(Tmax/Tm) of the maximum wall thickness in a trough (Tmax) to the
thickness of the wall at an intermediate point between peak and
trough Tm is greater than or equal to 1.2, superior absorption of
energy is obtained, as measured, for example, by deformation versus
applied force. In a preferred embodiment, the maximum wall
thickness in the trough occurs substantially in the middle of the
trough, in which case Tmax is designated Tc.
[0026] The inventors have found that in a jounce bumper made from
elastomeric thermoplastic material, when the ratio (Tc/Tm) of
thickness of the wall at a trough (Tc) to the thickness of the wall
at an intermediate point between peak and trough (Tm) is greater
than or equal to 1.2, superior absorption of energy is obtained, as
measured, for example, by deformation versus applied force. As used
herein the term superior energy absorption means both a high force
along the displacement, i.e. at least 550N for 50% relative
deformation and at the same time a high level of deformation when
the force is very high, i.e. at least 65% relative deformation at
10 KN. The level of energy absorption can be estimated by the force
level at 50 and/or 60% relative deformation and the relative
deformation at 10 KN.
[0027] Tc (Tmax) and Tm are often measured for all convolutes in a
jounce bumper and the average values are taken as Tc (Tmax) and Tm,
due to small variations from convolute to convolute.
[0028] The invention relates to "inward" jounce bumpers, which are
those in which the peak fillet radius, rs, is smaller than the
trough fillet radius, rc (i.e. rc>rs), as exemplified in FIGS.
2A and 2B.
[0029] The principle of the invention can be better understood by
examining FIGS. 1, 2A and 2B. FIG. 1 shows a typical "inward"
jounce bumper. It is a hollow tube-shaped article, having outward
and inward convolutes. The geometry will be defined by a pitch (P)
which is the distance from one peak to the next, the external
radius at a peak (Re), and the external radius at a trough (Ri).
Both Re and Ri are measured from the longitudinal axis of the
jounce bumper (i.e. the imaginary line that passes longitudinally
through the centre of the jounce bumper). The outermost point on an
outward convolute is referred to as a peak, and the point of most
inward pinching (without taking into account the thickness of the
convolutes) is referred to as a trough.
[0030] FIG. 2A shows an enlargement of a bellows consisting of an
outward convolute and an inward convolute. The outward convolute
(top) is defined by a radius rs, and the inward convolute (bottom)
is defined by a radius rc. An "inward" jounce bumper is any jounce
bumper in which rc is greater than rs. If circles are drawn having
radii rs and rc, the point of tangency of these two circles is a
point on the wall of the jounce bumper intermediate between a peak
and a trough. The wall of the jounce bumper at this point has
thickness Tm. As shown in FIG. 2B, in cases in which there is no
point of tangency between circles rs and rc, Tm is defined as the
middle of the segment of the tangent to rs and rc circles. A trough
is defined by the wall arc having end points of Tm. The maximum
wall thickness in the trough is designated Tmax. In cases where
Tmax occurs substantially in the middle of the trough, Tmax is
designated Tc. The inventors have found that when the ratio
(Tmax/Tm) of maximum thickness of the wall in a trough (Tmax) to
the thickness of the wall at an intermediate point between peak and
trough (Tm) is greater than or equal to 1.2, a jounce bumper
showing superior absorption of energy is obtained.
[0031] In preferred embodiments, Tmax/Tm is greater than 1.3, more
preferably greater than 1.5, for example 1.62 or 2.03. The upper
value of Tmax/Tm is not particularly limited, although in practice
it is rare for Tmax/Tm to be greater than 10.
[0032] In all cases in which Tmax occurs substantially in the
middle of a trough, Tmax can be designated Tc.
[0033] Jounce bumpers according to the invention maximize the
energy absorbed, as measured by displacement (or deformation)
versus applied force. In a preferred embodiment, the jounce bumpers
also maximize the displacement achieved for a given applied force,
and maximize the displacement at maximum force (i.e. when the
jounce bumper is fully compressed). The displacement at maximum
force (full compression) is often measured at a force of ten
kiloNewtons (10 kN) and is referred to as X10 KN, for a relative
deformation X at an applied force of ten kiloNewtons. To maximize
energy absorption and maximize X10 KN, the inventors have found
that it is desirable not only that Tmax/Tm be greater than or equal
to 1.2, but also that the ratio of the maximum wall thickness in a
trough, Tmax, to the wall thickness at the intermediate point, Tm,
be greater than a certain value, which certain value is dependant
on the pitch, P, maximum wall thickness at a trough, Tmax, and the
external radius at a trough, Ri. This can be expressed by the
following combination of features:
Tmax/Tm.gtoreq.1.2; and
(Tmax/Tm)>(Tmax/Tm).sub.1 wherein (Tmax/Tm).sub.1=3.43-0.05
P-0.222 SQRT(95-4.19 P+0.05 P.sup.2-0.23 Ri).
Where:
[0034] Tmax is the maximum wall thickness at a trough; [0035] Tm is
the wall thickness at the point of tangency between a circle of
radius rc and a circle of radius rs, or in cases in which rs and rc
are not tangent, Tm is the wall thickness at the midpoint of a line
drawn tangent to circles rs and rc; [0036] SQRT is square root;
[0037] P is the pitch; and [0038] Ri is the external radius at a
trough.
[0039] Alternatively, in cases in which Tmax occurs substantially
in the middle of a trough, this can be expressed:
Tc/Tm.gtoreq.1.2; and
(Tc/Tm)>(Tc/Tm).sub.1 wherein (Tc/Tm).sub.1=3.43-0.05 P-0.222
SQRT (95-4.19 P+0.05 P.sup.2-0.23 Ri).
Where:
[0040] Tc is the maximum wall thickness at a trough; [0041] Tm is
the wall thickness at the point of tangency between a circle of
radius rc and a circle of radius rs, or in cases in which rs and rc
are not tangent, Tm is the wall thickness at the midpoint of a line
drawn tangent to circles rs and rc; [0042] SQRT is square root;
[0043] P is the pitch; and [0044] Ri is the external radius at a
trough. The pitch, P, may be constant, meaning that the distance
from peak to peak (or trough to trough) is always the same, or it
may be non-constant. Preferably it is constant.
[0045] For use with automobiles, a typical pitch, P, is between at
or about 10 and 30 mm, more preferably between at or about 13 and
23 mm, the thicknesses Tc and Tm are typically chosen between at or
about 2 and 5 mm, more preferably between at or about 2 and 4 mm,
and Ri is typically at or about 10 to 40 mm, more preferably at or
about 15 to 25 mm.
[0046] The number of convolutes and the overall height of the
jounce bumper can be chosen depending on the size and weight of the
vehicle.
[0047] The jounce bumper of the invention may be made from or
comprise any thermoplastic elastomer. Preferably, a thermoplastic
elastomer is used that has a relatively high melt viscosity (i.e. a
melt flow rate between 0.5 and 8 g/10 min, more preferably between
1 and 8 g/10 min, more preferably between 2 and 6 g/10 min, more
preferably between 3 and 5 g/10 min, particularly preferably 4 g/10
min at 230.degree. C. under 5kg load according to ISO1133).
Preferably the elastomer has a hardness between at or about 45 and
60 D, more preferably at or about 47 to 55 D (at 1 s according to
IS0868). Particularly preferably the elastomer is a segmented
copolyetherester having soft segments of polytetramethylene ether
glycol (PTMEG).
[0048] Examples of thermoplastic elastomers useful for the jounce
bumper of the present invention include those defined in ISO
18064:2003(E), such as thermoplastic polyolefinic elastomers (TPO),
styrenic thermoplastic elastomers (TPS), thermoplastic polyether or
polyester polyurethanes (TPU), thermoplastic vulcanizates (TPV),
thermoplastic polyamide block copolymers (TPA), copolyester
thermoplastic elastomers (TPC) such as copolyetheresters or
copolyesteresters, and mixtures thereof; also suitable materials
are thermoplastic polyesters and mixtures thereof.
[0049] Thermoplastic polyolefinic elastomers (TPO's) consist of
thermoplastic olefinic polymers, for example polypropylene or
polyethylene, blended with a thermoset elastomer. A typical TPO is
a melt blend or reactor blend of a polyolefin plastic, generally a
polypropylene polymer, with an olefin copolymer elastomer,
typically an ethylene-propylene rubber (EPR) or an
ethylene-propylene-diene rubber (EPDM). Common olefin copolymer
elastomers include EPR, EPDM, and ethylene copolymers such as
ethylene-butene, ethylene-hexene, and ethylene-octene copolymer
elastomers (for example Engage.RTM. polyolefin elastomer, which is
commercially available from The Dow Chemical Co.) and
ethylene-butadiene rubber.
[0050] Styrenic thermoplastic elastomers (TPS's) consist of block
copolymers of polystyrene and rubbery polymeric materials, for
example polybutadiene, a mixture of hydrogenated polybutadiene and
polybutadiene, poly(ethylene-propylene) and hydrogenated
polyisoprene. Specific block copolymers of the styrene/conjugated
diene/styrene type are SBS, SIS, SIBS, SEBS and SEPS block
copolymers. These block copolymers are known in the art and are
commercially available.
[0051] Thermoplastic polyurethanes (TPU's) consist of linear
segmented block copolymers composed of hard segments comprising a
diisocyanate, a short chain glycol and soft segments comprising
diisocyanate and a long chain polyol as represented by the general
formula
##STR00001##
wherein [0052] "X" represents a hard segment comprising a
diisocyanate and a short-chain glycol, "Z" represents a soft
segment comprising a diisocyanate and a long-chain polyol and "Y"
represents the residual group of the diisocyanate compound of the
urethane bond linking the X and Z segments. The long-chain polyol
includes those of a polyether type such as poly(alkylene
oxide)glycol or those of polyester type.
[0053] Thermoplastic vulcanizates (TPV's) consist of a continuous
thermoplastic phase with a phase of vulcanized elastomer dispersed
therein. Vulcanizate and the phrase "vulcanizate rubber" as used
herein are intended to be generic to the cured or partially cured,
crosslinked or crosslinkable rubber as well as curable precursors
of crosslinked rubber and as such include elastomers, gum rubbers
and so-called soft vulcanizates. TPV's combine many desirable
characteristics of crosslinked rubbers with some characteristics,
such as processability, of thermoplastic elastomers. There are
several commercially available TPVs, for example Santoprene.RTM.
and Sarlink.RTM. (TPV's based on ethylene-propylene-diene
copolymers and polypropylene) which are respectively commercially
available from Advanced Elastomer Systems and DSM; Nextrile.TM.
(TPV based on nitrile rubber and polypropylene) which is
commercially available from Thermoplastic Rubber Systems;
Zeotherm.RTM. (TPV based on acrylate elastomer and polyamide) which
is commercially available from Zeon Chemicals; and DuPont.TM. ETPV
from E. I. du Pont de Nemours and Company, which is described in
International Patent Application Publication WO 2004/029155
(thermoplastic blends comprising from 15 to 60 wt. % of
polyalkylene phthalate polyester polymer or copolymer and from 40
to 85 wt. % of a crosslinkable poly(meth)acrylate or
polyethylene/(meth)acrylate rubber dispersed phase, wherein the
rubber has been dynamically crosslinked with a peroxide free
radical initiator and an organic diene co-agent).
[0054] Thermoplastic polyamide block copolymers (TPA's) consist of
linear and regular chains of polyamide segments and flexible
polyether or polyester segments or soft segments with both ether
and ester linkages as represented by the general formula
##STR00002##
wherein [0055] "PA" represents a linear saturated aliphatic
polyamide sequence and "PE" represents for example a
polyoxyalkylene sequence formed from linear or branched aliphatic
polyoxyalkylene glycols or a long-chain polyol with either ether
linkages, ester linkages or linkages of both types and mixtures
thereof or copolyethers and copolyesters derived therefrom. The
softness of the copolyetheramide or the copolyesteramide block
copolymers generally decreases as the relative amount of polyamide
units is increased.
[0056] Suitable examples of thermoplastic polyamide block
copolymers for use in the present invention are commercially
available from Arkema or Elf Atochem under the trademark
Pebax.RTM..
[0057] For an excellent balance of grease resistance, high
temperature durability and low temperature flexibility, the jounce
bumper according to the present invention may be made from
thermoplastic polyester compositions. Preferred thermoplastic
polyesters are typically derived from one or more dicarboxylic
acids (where herein the term "dicarboxylic acid" also refers to
dicarboxylic acid derivatives such as esters) and one or more
diols. In preferred polyesters the dicarboxylic acids comprise one
or more of terephthalic acid, isophthalic acid, and 2,6-naphthalene
dicarboxylic acid, and the diol component comprises one or more of
HO(CH.sub.2).sub.nOH (I); 1,4-cyclohexanedimethanol;
HO(CH.sub.2CH.sub.2O).sub.mCH.sub.2CH.sub.2OH (II); and
HO(CH.sub.2CH.sub.2CH.sub.2CH.sub.2O).sub.zCH.sub.2CH.sub.2CH.sub.2CH.sub-
.2OH (III), wherein n is an integer of 2 to 10, m on average is 1
to 4, and z is on average about 7 to about 40. Note that (II) and
(III) may be a mixture of compounds in which m and z, respectively,
may vary and that since m and z are averages, they need not be
integers. Other dicarboxylic acids that may be used to form the
thermoplastic polyester include sebacic and adipic acids.
Hydroxycarboxylic acids such as hydroxybenzoic acid may be used as
comonomers. Specific preferred polyesters include poly(ethylene
terephthalate) (PET), poly(trimethylene terephthalate) (PTT),
poly(1,4-butylene terephthalate) (PBT), poly(ethylene
2,6-naphthoate), and poly(1,4-cyclohexyldimethylene terephthalate)
(PCT).
[0058] Copolyester thermoplastic elastomers (TPC) such as
copolyetheresters or copolyesteresters are copolymers that have a
multiplicity of recurring long-chain ester units and short-chain
ester units joined head-to-tail through ester linkages, said
long-chain ester units being represented by formula (A):
##STR00003##
and said short-chain ester units being represented by formula
(B):
##STR00004##
wherein [0059] G is a divalent radical remaining after the removal
of terminal hydroxyl groups from poly(alkylene oxide)glycols having
preferably a number average molecular weight of between about 400
and about 6000; R is a divalent radical remaining after removal of
carboxyl groups from a dicarboxylic acid having a molecular weight
of less than about 300; and D is a divalent radical remaining after
removal of hydroxyl groups from a diol having a molecular weight
preferably less than about 250; and wherein said
copolyetherester(s) preferably contain from about 15 to about 99
wt. % short-chain ester units and about 1 to about 85 wt. %
long-chain ester units.
[0060] As used herein, the term "long-chain ester units" as applied
to units in a polymer chain refers to the reaction product of a
long-chain glycol with a dicarboxylic acid. Suitable long-chain
glycols are poly(alkylene oxide) glycols having terminal (or as
nearly terminal as possible) hydroxy groups and having a number
average molecular weight of from about 400 to about 6000, and
preferably from about 600 to about 3000. Preferred poly(alkylene
oxide) glycols include poly(tetramethylene oxide) glycol,
poly(trimethylene oxide) glycol, poly(propylene oxide) glycol,
poly(ethylene oxide) glycol, copolymer glycols of these alkylene
oxides, and block copolymers such as ethylene oxide-capped
poly(propylene oxide) glycol. Mixtures of two or more of these
glycols can be used.
[0061] The term "short-chain ester units" as applied to units in a
polymer chain of the copolyetheresters refers to low molecular
weight compounds or polymer chain units. They are made by reacting
a low molecular weight diol or a mixture of diols with a
dicarboxylic acid to form ester units represented by Formula (B)
above. Included among the low molecular weight diols which react to
form short-chain ester units suitable for use for preparing
copolyetheresters are acyclic, alicyclic and aromatic dihydroxy
compounds. Preferred compounds are diols with about 2-15 carbon
atoms such as ethylene, propylene, isobutylene, tetramethylene,
1,4-pentamethylene, 2,2-dimethyltrimethylene, hexamethylene and
decamethylene glycols, dihydroxycyclohexane, cyclohexane
dimethanol, resorcinol, hydroquinone, 1,5-dihydroxynaphthalene, and
the like. Especially preferred diols are aliphatic diols containing
2-8 carbon atoms, and a more preferred diol is 1,4-butanediol.
[0062] Copolyetheresters that have been advantageously used for the
manufacture of the jounce bumper of the present invention are
commercially available from E. I. du Pont de Nemours and Company,
Wilmington, Del. under the trademark Hytrel.RTM. copolyetherester
elastomer.
[0063] According to a preferred embodiment, jounce bumpers
according to the present invention are made of copolyester
thermoplastic elastomers (TPC) such as copolyetheresters or
copolyesteresters, and mixtures thereof. More preferably a
copolyetherester is used that is made from an ester of terephthalic
acid, e.g. dimethylterephthalate, 1-4 butanediol and a
poly(tetramethylene ether) glycol. The weight percent of
short-chain ester units is about 50 where the remainder is
long-chain ester units. The copolyetherester elastomer has a high
melt viscosity with a melt flow rate of about 4 g/10 mn at
230.degree. C. under 5 kg load as measured according to ISO1133.
Its hardness is about 47 shore D at 1 s as measured according to
ISO868.
[0064] The material used to manufacture the jounce bumpers
according to the present invention may comprise additives including
plasticizers; stabilizers; antioxidants; ultraviolet absorbers;
hydrolytic stabilizers; anti-static agents; dyes or pigments;
fillers, fire retardants; lubricants; reinforcing agents such as
fibers, flakes or particles of glass; minerals, ceramics, carbon
among others, including nano-scale particles; processing aids, for
example release agents; and/or mixtures thereof. Suitable levels of
these additives and methods of incorporating these additives into
polymer compositions are known to those of skill in the art.
[0065] The jounce bumper of the invention may be made by any
shaping operation or method suitable for shaping thermoplastic
elastomer material. Examples of such shaping operations or methods
comprise operations that include: injection molding, extrusion
(e.g. corrugated extrusion), and blow molding (including extrusion
blow molding and injection blow molding). Blow molding is
particularly preferred as it allows good control over the final
geometry of the part and a good balance between the control of the
final geometry and the cost of the process.
[0066] Some dimensions of two examples of jounce bumpers according
to the invention are listed in Table 1 below. Table 1 concerns two
jounce bumpers in which Tmax occurs substantially at the middle of
the trough, and so Tmax is designated Tc:
TABLE-US-00001 TABLE 1 Dimensions of Two Examples of Jounce Bumpers
According to the Invention Unit Example A Example B Tc (=Tmax,
average for all mm 2.83 3.05 troughs) Tm (average for all mm 1.75
1.5 convolutes) Ratio Tc/Tm -- 1.62 2.03 Pitch (P) mm 15 15 Ri
(external radius at mm 21.6 21.6 trough)
[0067] In use, the jounce bumper is installed on a suspension rod
of a vehicle between the vehicle chassis and a shock absorber. An
example of an installation is shown schematically in FIG. 4.
Referring to FIG. 4, the jounce bumper (1) is installed over the
shock absorber rod (2), such that displacement of the shock
absorber (3) in the upward direction results in axial compression
of the jounce bumper between the shock absorber (3) and the chassis
(4). If desired, the jounce bumper (1) can be held in position by a
suspension support (5). The numeral (6) identifies the end of the
shock absorber connected to the wheel axle.
EXAMPLES
[0068] Jounce bumpers according to the invention, E1 and E2, were
prepared by blow molding copolyetherester elastomer made from an
ester of terephthalic acid, e.g. dimethylterephthalate, 1-4
butanediol and a poly(tetramethylene ether) glycol. Jounce bumpers
E1 and E2 both have Tmax substantially in the middle of the
troughs, as so Tmax is designated Tc). The weight percentage of
short-chain ester units was about 50 and the remainder of the ester
units were long-chain ester units. The copolyetherester elastomer
had a melt flow rate of about 4 g/10 minutes at 230.degree. C.
under 5 kg load according to ISO1133. Its hardness was about 47
shore D at 1 s according to IS0868. A comparative jounce bumper C1
was also prepared from this material.
[0069] The dimensions of the jounce bumpers are listed in Table 2.
The jounce bumpers according to the invention, E1 and E2, had
Tc/Tm>1.2 (alternatively expressed as Tmax/Tm>1.2), whereas
the jounce bumper of comparative example C1, had Tc/Tm=1.15 (i.e.
less than 1.2). Additionally, jounce bumpers E1 and E2 meet the
requirements:
Tc/Tm.gtoreq.1.2; and
(Tc/Tm)>(Tc/Tm).sub.1 wherein (Tc/Tm).sub.1=3.43-0.05 P-0.222
SQRT (95-4.19 P+0.05P.sup.2-0.23 Ri).
Where:
[0070] Tc is the maximum wall thickness at a trough (and is
alternatively designated Tmax); [0071] Tm is the wall thickness at
the point of tangency between a circle of radius rc and a circle of
radius rs, or in cases in which rs and rc are not tangent, Tm is
the wall thickness at the midpoint of a line drawn tangent to
circles rs and rc; [0072] SQRT is square root; [0073] P is the
pitch; and [0074] Ri is the external radius at a trough.
TABLE-US-00002 [0074] TABLE 2 Dimensions and Compression Behavior
of Jounce Bumpers Unit C1 E1 E2 Original height mm 29.1 29.4 29.8
Tc (average for all troughs) mm 2.42 2.83 3.05 Tm (average for all
convolutes) mm 2.1 1.75 1.5 Average thickness Ts mm 2.4 1.80 1.5
Ratio Tc/Tm -- 1.15 1.62 2.03 Pitch (P) mm 15 15 15 Ri (external
radius at trough) mm 21.6 21.6 21.6 Force at 50% rel. def. F50 N
529 603 775 Force at 60% rel. def. F60 N 793 1117 1362 Rel. Def. at
10 KN, .times.10 KN % 77.5 76.9 75.1
[0075] Results of calculations [i.e. calculated values of
(Tc/Tm).sub.1 as compared to Tc/Tm] are shown in Table 3.
[0076] For jounce bumpers E1 and E2, Tc/Tm>(Tc/Tm).sub.1,
whereas for comparative jounce bumper C1,
Tc/Tm<(Tc/Tm).sub.1.
TABLE-US-00003 TABLE 3 Tc/Tm of Jounce Bumpers Jounce bumper Tc/Tm
(Tc/Tm).sub.1 (calculated) C1 (comparative) 1.15 1.32 E1 1.62 1.32
E2 2.03 1.32
[0077] Compression response was measured using two isolated
bellows. The molded parts were cut in this fashion to avoid
artifacts from the ends of the jounce bumper. The zero mm reference
point was an external point located on the plate of the compression
machine.
[0078] The molded parts were conditioned by applying 3 compression
cycles from 0 to 10 KN at 50 mm/min at 23.degree. C. The parts were
then released and maintained for one hour at a temperature of
23.degree. C. without stress. The molded parts were then exposed to
a fourth compression cycle using the same conditions as the first
three cycles. This last cycle defined the static compression curve
of the jounce bumpers.
[0079] Table 2 lists force required to give 50% relative
deformation (F50), force required to give 60% relative deformation
(F60) and relative deformation at the application of 10 KN force
(X10 KN). It is clear that the force required to cause 50% relative
deformation of the jounce bumpers according to the invention, i.e.
E1 and E2, which have Tc/Tm of 1.62 and 2.03, respectively, is
substantially higher (603 N and 775 N, respectively) than the force
required to cause 50% relative deformation in the comparative
jounce bumper C1, which has Tc/Tm of 1.15 (529 N). This is also
true at 60% relative deformation. Jounce bumpers El and E2 require
forces of 1117 N and 1362 N to cause a deformation of 60%, whereas
comparative jounce bumper C1 requires only a force of 793 N to
cause the equivalent deformation. The relative deflection at 10 KN,
X10 KN, is still very high, in fact above 75%, and similar to that
exhibited by the comparative jounce bumper C1. This indicates that
jounce bumpers according to the invention, E1 and E2, are
significantly more effective with respect to absorbing energy than
the comparative jounce bumper C1.
[0080] Results for the comparative jounce bumper C1 and inventive
jounce bumpers E1 and E2 are shown graphically in FIG. 3, in which
percent deflection (%) is plotted on the X-axis and applied force
(N) is plotted on the Y-axis. The percent deformation is defined as
the ratio of actual deformation in mm to the initial height in mm
of the jounce bumper prior to its first compression. The results
for jounce bumper E1 are shown by the curve designated with
triangles. The results for jounce bumper E2 are shown by the curve
designated with circles. The results for comparative jounce bumper
C1 are shown by the curve designated by diamonds.
[0081] The area under the curve (Force X % Deflection) gives a
measure of the total energy absorbed. The compression curve for
comparative jounce bumper C1 (diamonds) is the lowest curve. Jounce
bumpers according to the invention E1 (triangles) and E2 (circles)
give higher curves, with greater area under the curve, showing
increased absorption of energy.
[0082] Additionally, it can be seen from FIG. 3 that jounce bumpers
according to the invention E1 and E2 do not significantly sacrifice
maximum displacement. X10 KN for E1 and E2 is not significantly
less than X10 KN for C1.
* * * * *