U.S. patent application number 12/093183 was filed with the patent office on 2009-02-26 for flexible polyurethane foam for tires, noise reducing device and tire.
Invention is credited to Atsushi Tanno, Hiroyuki Tsujimoto.
Application Number | 20090053492 12/093183 |
Document ID | / |
Family ID | 38048693 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090053492 |
Kind Code |
A1 |
Tanno; Atsushi ; et
al. |
February 26, 2009 |
FLEXIBLE POLYURETHANE FOAM FOR TIRES, NOISE REDUCING DEVICE AND
TIRE
Abstract
The present invention is to provide a flexible polyurethane foam
for tires that can effectively suppress damages, such as chips and
cracks, and deformation, such as compression (permanent set in
fatigue), even when attached to an inner face of a tire by using a
band member. A flexible polyurethane foam for tires 5 which is
attached to a gap between a tire and a wheel rim, wherein a density
is in the range from 7 to 40 kg/m.sup.3 and a tear strength (N/cm)
per unit density (kg/m.sup.3) is 0.30 or more, a noise reducing
device with the flexible polyurethane foam for tires 5 fixed to a
ring-shaped band member, and a tire 10 with the noise reducing
device attached thereto.
Inventors: |
Tanno; Atsushi; (Kanagawa,
JP) ; Tsujimoto; Hiroyuki; (Okayama, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
38048693 |
Appl. No.: |
12/093183 |
Filed: |
November 17, 2006 |
PCT Filed: |
November 17, 2006 |
PCT NO: |
PCT/JP2006/322992 |
371 Date: |
May 9, 2008 |
Current U.S.
Class: |
428/218 |
Current CPC
Class: |
B60C 19/002 20130101;
Y10T 428/24992 20150115 |
Class at
Publication: |
428/218 |
International
Class: |
E04B 1/74 20060101
E04B001/74 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 18, 2005 |
JP |
2005-333568 |
Claims
1. A flexible polyurethane foam for tires which is attached to a
gap between a tire and a wheel rim, wherein a density is in the
range from 7 to 40 kg/m.sup.3 and a tear strength (N/cm) per unit
density (kg/m.sup.3) is 0.30 or more.
2. The flexible polyurethane foam for tires of claim 1, wherein the
number of cells is 25 cells/25 mm or more.
3. The flexible polyurethane foam for tires of claim 1, which is
attached to an inner face of a tire by using a band member.
4. The flexible polyurethane foam for tires of claim 1, wherein the
tear strength (N/cm) per unit density (kg/m.sup.3) is 0.35 to
0.90.
5. A noise reducing device, comprising the flexible polyurethane
foam for tires of claim 1 which is fixed to a ring-shaped band
member.
6. A tire, comprising the noise reducing device of claim 5.
Description
TECHNICAL FIELD
[0001] The present invention relates to a flexible polyurethane
foam for tires which is attached between a tire and a wheel rim,
and in particular, relates to a flexible polyurethane foam for
tires which is attached to an inner face of a tire by using a band
member, a noise reducing device and a tire.
BACKGROUND ART
[0002] In a pneumatic tire, one of the causes of noise generation
is cavity resonance caused by vibrations of air filled in the
inside of the tire. This cavity resonance is generated when, upon
rolling a tire, a tread portion is vibrated by irregularities of a
road surface, and the vibration of the tread portion vibrates air
inside the tire.
[0003] With respect to a method for reducing noise due to such a
cavity resonance phenomenon, a method has been proposed in which a
sound absorbing material is placed in a cavity portion formed
between a tire and a wheel rim (Patent Documents 1 and 2). Specific
examples of sound absorbing materials include urethane foam, sound
absorbing felt, and foamed aluminum, and urethane foam is used in
most cases.
[0004] In particular, Patent Document 2 has disclosed urethane foam
with a thermal conductive material mixed therein, which has a
density adjusted in the range from 0.05 to 0.2 g/cm.sup.3 (50 to
200 kg/m.sup.3). In such urethane foam, the density is set to a
high level so as to prevent deformation, such as compression
(permanent set in fatigue), by improving the toughness thereof.
However, damages such as chips and cracks tend to occur in the
urethane foam. It is not desirable to attach a member having a high
density, that is, a heavy weight, to an inner face of a tire from
viewpoints of fuel costs and traveling stability.
[0005] In recent years, as shown in Patent Document 3, in order to
improve the attaching performance of a sound absorbing material to
an inner face of a tire, a method for attaching the sound absorbing
material to the inner face of a tire by using a band member has
been proposed. However, when the band member is used, a problem of
chips, cracks or the like tends to occur frequently in the sound
absorbing material.
Patent Document 1: JP-A No. 64-78902
Patent Document 2: JP-A No. 2005-104314
Patent Document 3: JP-A No. 2003-226104
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0006] An object of the present invention is to provide a flexible
polyurethane foam for tires that can effectively suppress damages,
such as chips and cracks, and deformation, such as compression
(permanent set in fatigue), even when attached to a gap between a
tire and a wheel rim, in particular, to an inner face of a tire by
using a band member.
[0007] Another object of the present invention is to provide a
noise reducing device and a tire, which can effectively suppress
damages, such as chips and cracks, and deformation, such as
compression (permanent set in fatigue), in flexible polyurethane
foam for tires.
Means to Solve the Problems
[0008] The present invention relates to flexible polyurethane foam
for tires which is attached to a gap between a tire and a wheel
rim, in particular, to an inner face of a tire, by using a band
member, and the flexible polyurethane foam is characterized by
having a density in the range from 7 to 40 kg/m.sup.3 and a tear
strength (N/cm) per unit density (kg/m.sup.3) of 0.30 or more, and
a noise reducing device in which the flexible polyurethane foam for
tires is fixed to a ring-shaped band member and a tire which has
such a noise reducing device.
Effects of the Invention
[0009] The flexible polyurethane foam for tires of the present
invention makes it possible to effectively suppress damages, such
as chips and cracks, and deformation, such as compression
(permanent set in fatigue), even when attached to a gap between a
tire and a wheel rim, in particular, to an inner face of a tire by
using a band member.
[0010] Since the flexible polyurethane foam for tires of the
present invention is light in weight, a tire to which the
polyurethane foam is attached does not impair a fuel cost
performance and a traveling stability of a car.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is an enlarged view showing an essential portion of
one example of a tire in which a flexible urethane foam for tires
of the present invention is attached to the inner face thereof.
[0012] FIGS. 2(A) to 2(D) are schematic sketch views each showing
one example of a noise reducing device having the flexible urethane
foam for tires of the present invention.
[0013] FIG. 3(A) is an enlarged view showing an essential portion
of a tire provided with the noise reducing device shown in FIG.
2(A), and FIG. 3(B) is an enlarged view showing an essential
portion of a tire provided with the noise reducing device shown in
FIG. 2(B).
EXPLANATION OF REFERENCE NUMERALS
[0014] 1: Tread portion, 2: Bead portion, 3: Side wall portion, 5:
Flexible polyurethane foam (PU Loam) for tires, 6: Ring-shaped
band, 7: Coupling portion, 10:10a:10b: Tire, 20a:20b:20c:20d: Noise
reducing device
BEST MODE FOR CARRYING OUT THE INVENTION
[0015] The tear strength (unit; N/cm) per unit density (kg/m.sup.3)
of flexible polyurethane foam for tires of the present invention is
0.30 or more, in particular, 0.33 or more, preferably in the range
from 0.35 to 0.90, more preferably from 0.39 to 0.70, most
preferably from 0.40 to 0.65. In the present invention, by setting
the tear strength per unit density to the above-mentioned range,
damages, such as chips and cracks, and deformation, such as
compression (permanent set in fatigue), can be effectively
suppressed even when the density is comparatively low. Hereinafter,
the flexible polyurethane foam for tires of the present invention
is referred to simply as "PU foam".
[0016] The tear strength per unit density is a value calculated
based on measured density and tear strength, and obtained by
dividing the tear strength by the density. In the case when this
value is too small, even if a comparatively high value is achieved
as the tear strength, damages, such as chips and cracks, tend to
occur, and the resulting foam fails to withstand the use as a tire.
A detailed mechanism has not been clarified, in which damages occur
in the case when the tear strength per unit density is smaller than
the above-mentioned range, even if the tear strength is
comparatively large. However, the following mechanism is presumed:
For example, when the tear strength per unit density is
comparatively low and the tear strength is comparatively high, the
density is comparatively high. In general, when the density is
high, damages hardly occur, and when the tear strength is also
high, it is considered that damages more hardly occur. However, in
a portion which rolls at a high speed, such as the inside of a
tire, even when the tear strength is comparatively high, the
increase in density serves as a factor that causes damages against
the general principle. Consequently, it is considered that when the
tear strength per unit density is smaller than the above-mentioned
range, damages tend to occur even if the tear strength is
comparatively high.
[0017] In the present specification, a value measured in accordance
with JIS K7222 is used as the density; however, not limited by the
measurements in accordance with this standard, any method may be
used for the measurements as long as it can measure in accordance
with the same principle and rule as the above-mentioned
standard.
[0018] The density of the PU foam of the present invention is 7 to
40 kg/m.sup.3, preferably 10 to 30 kg/m.sup.3. In general, in the
case when the density is made lower, it has been known that, since
the mechanical strength of the PU foam is lowered, damages tend to
occur; however, in the present invention, even if the density is
set to a comparatively small level, the damages to the PU foam can
be suppressed effectively.
[0019] With respect to the tear strength, the value, measured in
accordance with JIS K6400-5 by using a test piece with its shape
being formed into "an angle-shape without a notch", is used.
[0020] The tear strength of the PU foam of the present invention is
not particularly limited as long as the above-mentioned tear
strength per unit density is achieved, and is in the range from 3
to 28N/cm, in particular, preferably from 3 to 24N/cm. Only high
tear strength does not sufficiently complete the present invention.
In other words, even when a comparatively high value is achieved in
the tear strength, damages, such as chips and cracks, tend to occur
unless the tear strength per unit density is within the
above-mentioned range.
[0021] The number of cells of the PU foam of the present invention
is not particularly limited as long as the above-mentioned tear
strength per unit density has been achieved. From the viewpoint of
increasing the tear strength per unit density by reducing the
density, the number of cells is preferably 25 cells/25 mm or more.
The number of cells is defined by the number of cells per 25
mm.
[0022] The value, measured in accordance with attached document 1
of JIS K6400-1, is used as the number of cells.
[0023] The PU foam of the present invention is obtained, for
example, by the following method: That is, a urethane foam material
composition containing at least a polyol component, a
polyisocyanate component and a foaming agent as well as additives,
such as a foam-adjusting agent, a catalyst, a crosslinking agent,
an antioxidant, a UV-ray absorbing agent and a colorant, if
necessary, is allowed to react to foam by using a known
manufacturing method, such as a one shot method. For example, in
the one shot method, simultaneously as the respective components
are added to a mixing chamber at the same time, a strong stirring
process is carried out to mix the components to produce PU
foam.
[0024] The density, the tear strength and the number of cells of
the PU foam can be controlled by adjusting the kinds and added
amounts of the polyol component, polyisocyanate component, foaming
agent and foam-adjusting agent, the degree of stirring of the
material and the pressure and the like of the mixing chamber, the
material supply tank and the pipes.
[0025] The PU foam is mainly classified into polyester urethane
foam, polyether urethane foam and polyester ether urethane foam
depending on the kinds of polyol component, which is a main
material. In the present invention, any of these PU foam may be
used. From the viewpoint of controlling the tear strength per unit
density, polyester urethane foam and polyether urethane foam are
preferably used.
[0026] Since the polyester urethane foam can achieve the
above-mentioned tear strength per unit density even when it has
comparatively high tear strength and comparatively high density,
those having a density in the range from 18 to 40 kg/m.sup.3 are
preferably used. With respect to the polyester urethane foam, when
the density is less than 18 kg/m.sup.3, deformation, such as
compression (permanent set in fatigue), tends to occur. In
contrast, the density exceeding 40 kg/m.sup.3 is not desirable
because its own weight increases excessively. In particular, the
desirable density is from 18 to 30 kg/m.sup.3. The polyester
urethane foam is easily controlled in its number of cells, and from
the viewpoint of reducing the density properly by increasing the
number of cells to consequently increase the tear strength per unit
density, those having a large number of cells, that is, 25 cells/25
mm or more, are preferably used, and in particular, those having
cells in the range of 40 to 100 are more preferably used. With
respect to the polyester urethane foam, when the number of cells is
less than 25 cells/25 mm, there is a reduction in the tear
strength, with the result that the above-mentioned tear strength
per unit density is hardly achieved. In contrast, in the case when
the number of cells exceeds 100 cells/25 mm, the production
stability is lowered although no problems arise in the
performances.
[0027] Since the polyether urethane foam is superior in the
production stability and foams in a wide range can be stably
produced, those having a density in the range from 7 to 20
kg/m.sup.3 are preferably adopted. With respect to the polyether
urethane foam, when the density is less than 7 kg/m.sup.3, damages
tend to occur due to insufficient mechanical strength. In contrast,
the density exceeding 18 kg/m.sup.3 reduces the tear strength per
unit density, resulting in damages. In particular, the desirable
density is from 10 to 18 kg/m.sup.3. From the viewpoint of easiness
for control, the number of cells of the polyether urethane foam is
preferably 25 or more, in particular, in the range from 30 to
80.
[0028] With respect to the polyol component to be used for
producing the PU foam of the present invention, any of those
components may be used as long as they have two or more hydroxide
groups in one molecule, and are conventionally used for producing
polyurethane foam. Examples of the polyol component include
polyether polyol, polyester polyol and polyester ether polyol. One
kind or two or more kinds of the polyol components may be used in
combination.
[0029] Polyether polyol is a polyol component to be used for
producing polyether urethane foam, and such a material, prepared by
addition polymerizing an alkylene oxide using a compound having two
or more active hydrogen atoms in one molecule as an initiator, may
be used. Examples of the compound having two or more active
hydrogen atoms to be used in this case include ethylene glycol,
propylene glycol, glycerin, trimethylol propane, triethernol amine,
pentaerythritol, sorbitol, sucrose, and the like. Examples of the
alkylene oxide include ethylene oxide, propylene oxide, and the
like. With respect to the compound having two or more active
hydrogen atoms in one molecule and alkylene oxide, one kind or more
of those may be respectively used. Glycerin-based polyether polyol
is preferably used as the polyether polyol, and in particular, a
material, prepared by addition polymerizing propylene oxide using
glycerin as an initiator, may be preferably used.
[0030] Vinyl-based polymer fine particles may be evenly dispersed
in polyether polyol. Examples of a vinyl-based polymer include a
polymer obtained by polymerizing a vinyl-based monomer such as
acrylonitrile and styrene and a copolymer obtained by
copolymerizing a vinyl-based monomer with a monomer that is
copolymerizable with the vinyl-based monomer.
[0031] Polyester polyol is a polyol component to be used for
producing polyester urethane foam, and is obtained by
polycondensing a polycarboxylic acid with a compound having two or
more hydroxide groups in one molecule. A compound having two or
more carboxyl groups in one molecule is used as the polycarboxylic
acid, and specific examples thereof include adipic acid, maleic
acid, succinic acid, malonic acid, phthalic acid, and the like.
With respect to the compound having two or more hydroxyl groups in
one molecule, the same compounds as those compounds having two or
more active hydrogen atoms to be used as the initiator for the
polyether polyol may be used. With respect to the polycarboxylic
acid and the compound having two or more hydroxyl groups in one
molecule, one kind or more of those may be respectively used.
Polyester polyol can be produced by using a known method.
[0032] Polyester ether polyol is a polyol component to be used for
producing polyester ether urethane foam, and for example, it is
obtained by dehydration-condensing a semi-ester produced by
allowing dicarboxylic anhydride, such as phthalic anhydride, to
react with the above-mentioned polyether polyol, or is obtained by
adding epoxide to such a semi-ester in the presence of a basic
catalyst or the like.
[0033] The polyisocyanate component is not particularly limited as
long as it is a compound having two or more isocyanate groups in
one molecule, and is prepared by mixing, for example, one kind or
two or more kinds of aliphatic or aromatic polyisocyanates.
Examples of aliphatic polyisocyanates include hexamethylene
diisocyanate, isophorone diisocyanate, and the like. Specific
examples of aromatic polyisocyanates include: 2,4-tolylene
diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene
diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane
diisocyanate, polymethylene polyphenyl diisocyanate, and the like.
Here, the one normally used preferably is a mixture (TDI-80,
TDI-65) of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate,
or diphenylmethane diisocyanate.
[0034] With respect to the foaming agent, those agents,
conventionally used as a foaming agent in the field of polyurethane
foam, may be used, and only water is preferably used from the
viewpoint of environmental protection. Since water is allowed to
react with polyisocyanate to generate carbon dioxide gas, water is
used as a chemical foaming agent. Normally, the amount of the
foaming agent to be used is preferably in the range from 1 to 7
parts by mass with respect to 100 parts by mass of the polyol
component, and from the viewpoint of achieving the density of the
present invention, it is preferably in the range from 2 to 6 parts
by mass. A physical foaming agent may be used as the foaming agent
on demand. Examples of the physical foaming agent include:
methylene chloride, chlorofluorocarbons, hydroxychlorofluorocarbons
(HCFC-134a and the like), hydrocarbons (cyclopentene and the like),
carbon dioxide gas and liquefied carbon dioxide gas, and other
foaming agents may be used as foaming assistants in combination
with water. The amount of use of the physical foaming agent is
preferably 20 parts by mass or less with respect to 100 parts by
mass of a polyol component from the viewpoint of stabilizing
foaming, and in particular, is preferably 10 parts by mass or less
so as not to extremely reduce the tear strength.
[0035] With respect to the catalyst and the foam adjusting agent,
those generally used for producing flexible polyurethane foam may
be used, and the added amount is also an amount normally adopted
upon producing flexible polyurethane foam. In the present
invention, in addition to the above-mentioned additive components,
other additives, such as a flame retarder, an antioxidant, a
colorant and a ultraviolet-ray absorbing agent, may be added within
such a range as not to impair the performance of the flexible
polyurethane foam of the present invention.
[0036] Such PU foam is available, for example, as commercial
products, "Kuralafoam" series made by Kurabo Industries Ltd., or
the like.
[0037] The PU foam of the present invention is used as a so-called
noise reducing material that is attached to a gap between a tire
and a wheel rim, in particular, to the inner face of a tire, so as
to suppress cavity resonance generated at the time of rolling of
the tire.
[0038] FIG. 1 is an enlarged view of an essential portion showing
one example of a tire in which the PU foam of the present invention
is attached to the inner face thereof. In FIG. 1, a tire 10 is
provided with a tread portion 1, a pair of right and left bead
portions 2 and a side wall portion 3 that couples the tread portion
1 and each bead portion 2 with each other, and PU foam 5 of the
present invention is attached to the inner face of the tread
portion 1. Here, a band member, which will be described in detail
later, is not shown in FIG. 1.
[0039] Although not particularly limited, the shape of the PU foam
is preferably designed to have a thickness in the range from 3 to
30 mm, more preferably from 5 to 15 mm, by taking it into
consideration that upon attaching, the band member is used. When
the thickness is less than 3 mm, the attaching property to the band
member is lowered. The thickness exceeding 30 mm causes an increase
in the surface stress in response to a forceful dislocation due to
antiplane bending, and tends to cause chips or cracks. The width
ranges from 50 to 150% of the maximum width of an reinforcing layer
placed on the peripheral side of a carcass layer of a tire, that
is, a so-called belt layer, more preferably 80 to 130% thereof.
Here, the width of the PU foam member corresponds to the length of
the PU foam member attached to the tire in the tire rotary axis
direction.
[0040] With respect to the attaching method for the PU foam member,
not particularly limited as long as the PU foam member is attached
to the inner face of the tire, for example, (1) a method for
attaching the PU foam member directly to the tire inner face by
using a bonding agent or an adhesive tape, and (2) a method for
attaching the PU foam member to the tire inner face by using a band
member may be used. Preferably, the above-mentioned method (2) is
adopted. When generally-used urethane foam is attached by using a
band member, damages, such as chips and cracks, often occur in the
urethane foam; however, the present invention makes it possible to
effectively suppress such damages even in the case of using such a
band member, in particular, a ring-shaped band member. Here, by
taking it into consideration the attaching property to the band
member, the hardness of PU foam is preferably about 60 to 150N, in
particular, to 80 to 120N for better operability. Here, the
hardness is a value measured in accordance with JIS K 6400-2: D
method.
[0041] Upon adopting the above-mentioned method (2), the PU foam is
fixed to a band member to form a noise reducing device. More
specifically, the noise reducing device has a structure in which
the PU foam is fixed to the ring-shaped band member. Specific
examples of the noise reducing device are shown in FIGS. 2(A) to
2(D). In FIGS. 2(A) to 2(D), the same reference numerals and
symbols indicate the same members.
[0042] In FIG. 2(A), a noise reducing device 20a has PU foam 5 that
is continuously attached to the entire inner circumferential face
of a ring-shaped band member 6, and normally, the PU foam 5 is
provided with a coupling portion 7.
[0043] In FIG. 2(B), a noise reducing device 20b has the PU foam 5
that is continuously attached to the entire outer circumferential
face of a ring-shaped band member 6, and normally, the PU foam 5 is
provided with a coupling portion 7.
[0044] In FIG. 2(C), a noise reducing device 20c is constituted by
twelve divided pieces 5 of the PU foam, and these divided pieces
are placed side by side in the circumferential direction onto the
inner circumferential face of the ring-shaped band member 6. In
this case, a gap is preferably placed between the respective
divided pieces. Thus, no bonding portions between the mutual
urethane pieces are present, thereby eliminating the necessity of a
bonding agent. By placing the pieces of the PU foam with virtually
equal intervals, the weight balance in the circumferential
direction can be maintained evenly. In FIG. 2(C), the number of the
divided pieces of the PU foam is twelve; however, not particularly
limited by this, the number may be set, for example, from 3 to
20.
[0045] In FIG. 2(D), a noise reducing device 20d is constituted by
twelve divided pieces of the PU foam 5, and these divided pieces
are placed side by side in the circumferential direction onto the
outer circumferential face of the ring-shaped band member 6. In
this case, for the same reason as that of FIG. 2(C), a gap is
preferably placed between the respective divided pieces. By placing
the pieces of the PU foam with virtually equal intervals, the
weight balance in the circumferential direction can be maintained
evenly. In FIG. 2(D), the number of the divided pieces of the PU
foam is twelve; however, not particularly limited by this, the
number may be set, for example, from 3 to 20.
[0046] It is only necessary for the ring-shaped band member forming
the noise reducing device to be made from a material having an
elastic recovering force, and from the viewpoint of moldability
into the ring shape, it is preferably made from a thermoplastic
resin, in particular, polypropylene. When the band member is made
from a thermoplastic resin, by thermally fusing to adhere the two
ends of a string-shaped band member to each other, the ring-shaped
band member can be easily molded.
[0047] The securing of the PU foam to the band member may be
carried out by any means, and, for example, the securing may be
achieved by using a bonding agent or an adhesive tape, or a resin
layer, made from a thermoplastic resin such as polypropylene, is
preliminarily formed on the contact face of the PU foam to the hand
member so that the securing process may be achieved by using
thermal fusion of the resin layer. In the latter case, the thermal
fusion of the resin layer is preferably carried out by using an
ultrasonic wave welding machine.
[0048] Upon using any one of the securing means, the securing
process between the PU foam and the band member may be conducted
over the entire contact face between the PU foam and the band
member, or may be locally carried out on the contact face.
[0049] The dimensions of the noise reducing device, that is, the
dimensions of the ring-shaped band member and the PU foam, are not
particularly limited as long as the PU foam is attached to and held
on the inner face of a tire, in particular, on the tread portion
thereof, and is allowed to exert a noise reducing effect. In
particular, in the case when the ring-shaped band member is formed
into a true circle, the diameter is normally made virtually equal
to, or smaller than the inner diameter of a tire to which it is
attached.
[0050] Upon manufacturing the noise reducing device, after the PU
foam has been fixed onto a predetermined position of the
string-shaped band member, the two ends of the string-shaped band
member may be coupled to each other through thermal fusion or the
like, or after the two ends of the string-shaped band member have
been coupled to each other by using thermal fusion or the like, the
PU foam may be fixed to a predetermined position of the resulting
ring-shaped band member.
[0051] Even in the case when the noise reducing device is inserted
into a tire while being deformed by an external force, upon removal
of the external force, the ring-shaped band member is allowed to
restore its shape so as to continuously extend along the tire
circumferential direction because the ring-shaped band member has
an elastic restoring force. As a result, the noise reducing device
is held on the tire inner face so that the PU foam is attached and
held onto the tire inner face, in particular, onto the inner face
of the tread portion. The noise reducing device is freely
detachably attached to the tire, and its attaching and detaching
processes can be easily carried out.
[0052] FIG. 3(A) is an enlarged view showing an essential portion
of a tire 10a provided with a noise reducing device 20a shown in
FIG. 2(A). Since the noise reducing device 20a shown in FIG. 2(A)
has PU foam 5 on the inner circumferential face of a ring-shaped
band member 6, the ring-shaped band member 6 is placed between the
PU foam 5 and the tread portion 1, as shown in FIG. 3(A), when
attached to a tire. In a tire provided with the noise reducing
device 20c shown in FIG. 2(C), the enlarged view showing an
essential portion having the PU foam is virtually the same as that
of FIG. 3(A).
[0053] FIG. 3(B) is an enlarged view showing an essential portion
of a tire 10b provided with the noise reducing device 20b shown in
FIG. 2(B). Since the noise reducing device 20b shown in FIG. 2(B)
has the PU foam 5 on the outer circumferential face of a
ring-shaped band member 6, the ring-shaped band member 6 is placed
on the PU foam 5, as shown in FIG. 3(B), when attached to a tire.
In a tire provided with the noise reducing device 20d shown in FIG.
2(D), the enlarged view showing an essential portion having the PU
foam is virtually the same as that of FIG. 3(B).
EXAMPLES
Example 1
[0054] Commercially available polyurethane foam ("Kuralafoam 281",
made by Kurabo Industries Ltd.) was used. The flexible polyurethane
foam was cut into 12 pieces so that twelve board-shaped
polyurethane foams having a size of 150 mm in width.times.20 mm in
thickness.times.140 mm in length were prepared.
[0055] Next, a noise reducing device of a type shown in FIG. 2(C)
was manufactured. Specifically, twelve board-shaped polyurethane
foam members are placed at predetermined positions of a
string-shaped band member (20 mm in width.times.2 mm in
thickness.times.Tire inner circumferential length) made from
polypropylene, with equal intervals, and fixed thereto by using a
bonding agent (Super X: made by Cemedine Co., Ltd.), and the two
ends of the string-shaped band member were connected to each other
through fusion splicing.
Examples 2 to 3 and Comparative Examples 1 and 2
[0056] The same method as that of Example 1 was carried out except
that each of the following commercial products was used as the
polyurethane foam so that a noise reducing device was
manufactured.
[0057] Example 2 "Kuralafoam 241 (made by Kurabo Industries
Ltd.)";
[0058] Example 3 "Kuralafoam 38M8S (made by Kurabo Industries
Ltd.)";
[0059] Example 4 "Kuralafoam 38M4K (made by Kurabo Industries
Ltd.)";
[0060] Example 5 "Kuralafoam 311SS (made by Kurabo Industries
Ltd.)";
[0061] Comparative Example 1 "Kuralafoam 330NC (made by Kurabo
Industries Ltd.)";
[0062] Comparative Example 2 "Kuralafoam 38H2 (made by Kurabo
Industries Ltd.)"
[0063] (Evaluation)
[0064] Damage
[0065] Each of the noise reducing devices of Examples and
Comparative Examples was attached to a tire having a tire size of
215/55R16. More specifically, the noise reducing device was
inserted into the cavity portion inside a tire while being deformed
by an externally applied force, and by removing the external force,
the ring-shaped band member is restored so as to continuously
extend in the tire circumferential direction so that the
polyurethane foam was attached and held onto the inner face of the
tread portion. The tire with the noise reducing device attached
thereto was driven on a drum testing machine under a pneumatic
pressure of 120 kPa, a load of 8.1N, an ambient temperature of
38.+-.3.degree. C., a drum diameter .phi. of 1707 mm and a velocity
of 81 km/h for 80 hours. Thereafter, the noise reducing device was
taken out of the tire, and visually inspected for any chips or
cracks of all the board-shaped polyurethane foams, and evaluation
was made in accordance with the following criteria.
.circleincircle.: None of chips and cracks were observed;
.largecircle.: Chips and cracks were slightly observed; however,
the chipped pieces were less than 10 mm in the maximum length and
the cracked portions were less than 5 mm in depth, and there were
no practical problems. x: Chips and cracks were observed, and the
chipped pieces were in the range from 10 mm or more to less than 30
mm in the total length, and the cracked portions were in the range
from 5 mm or more to less than 10 mm, and there were practical
problems; and xx: Chips and cracks observed, and the chipped pieces
were 30 mm or more in the total length, and the cracked portions
were 10 mm or more in depth.
[0066] With respect to the damages, detailed portions of occurrence
are shown below.
[0067] In Example 1, chips and slight cracks were observed on the
corner portions and side end portions.
[0068] In Example 2, none of chips and cracks was observed on the
corner portions and side end portions.
[0069] In Example 3, none of chips and cracks was observed on the
corner portions and side end portions.
[0070] In Example 4, although slight chips were observed in only
one portion of the corner portion, none of chips and cracks was
observed in the other portions.
[0071] In Example 5, although a chip was observed in only one
portion of the corner portion, none of chips and cracks was
observed in the other portions.
[0072] In Comparative Example 1, a deep crack was observed in a
corner portion, and several large chipped portions were observed on
side end portions.
[0073] In Comparative Example 2, a large chipped portion was
observed in a corner portion.
TABLE-US-00001 TABLE 1 Example Example Example Comparative
Comparative Example Example Material 1 2 3 Example 1 Example 2 4 5
Form Type Ether Ether Ester Ether Ester Ester Ether Density
(Kg/m.sup.3) 18 14 28 23 28 28 20 Tear Strength (N/cm) 6 6 12 5 8
11 7 Tear Strength/Density 0.33 0.43 0.43 0.22 0.29 0.39 0.35 The
Number of Cell 50 43 50 40 28 40 41 (per 25 mm) Damage
.largecircle. .circleincircle. .circleincircle. XX X .largecircle.
.largecircle.
[0074] The density, the tear strength and the number of cells were
measured by using the aforementioned methods.
INDUSTRIAL APPLICABILITY
[0075] The flexible polyurethane foam of the present invention is
useful for a noise reducing material to be attached to a gap
between a tire and a wheel rim, in particular, to the inner face of
the tire.
* * * * *