U.S. patent application number 12/155623 was filed with the patent office on 2008-10-16 for assembly of pneumatic tire and rim, and a noise damper used therein.
Invention is credited to Atsuhiko Itakura, Yuji Sasaki, Naoki Yukawa.
Application Number | 20080251178 12/155623 |
Document ID | / |
Family ID | 35445822 |
Filed Date | 2008-10-16 |
United States Patent
Application |
20080251178 |
Kind Code |
A1 |
Yukawa; Naoki ; et
al. |
October 16, 2008 |
Assembly of pneumatic tire and rim, and a noise damper used
therein
Abstract
A pneumatic tire and a rim includes a noise damper, fixed to a
tire inner surface or a rim inner surface with the upper surface
facing a tire inner space, and extending in the tire
circumferential direction. The noise damper is made of a sponge
having a volume ranging from 0.4 to 20% of the volume of the tire
inner space. The noise damper is a laterally long and flat, with a
maximum thickness ranging from 5 to 45 mm and a width more than the
maximum thickness. The upper surface extends along a wavy curve
including a hilltop, valley bottoms on each side of the hilltop and
slopes extending down to the respective valley bottoms from the
hilltop. Each end of the upper surface is terminated at the valley
bottoms or the slopes. A thickness from the upper surface to the
bottom surface ranges from 1.0 to 15.0 mm.
Inventors: |
Yukawa; Naoki; (Kobe-shi,
JP) ; Sasaki; Yuji; (Anjo-shi, JP) ; Itakura;
Atsuhiko; (Anjo-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
35445822 |
Appl. No.: |
12/155623 |
Filed: |
June 6, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11269676 |
Nov 9, 2005 |
|
|
|
12155623 |
|
|
|
|
Current U.S.
Class: |
152/453 |
Current CPC
Class: |
B60B 3/04 20130101; Y10T
152/10036 20150115; B60C 19/002 20130101; Y10T 152/10495 20150115;
Y10T 152/10054 20150115 |
Class at
Publication: |
152/453 |
International
Class: |
B60C 3/02 20060101
B60C003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2004 |
JP |
2004-336574 |
Nov 19, 2004 |
JP |
2004-336575 |
Nov 19, 2004 |
JP |
2004-336576 |
Claims
1. A noise damper in the shape of a band, made of a sponge having a
volume in the range of 0.4 to 20% of the entire volume of a tire
inner space enclosed by a rim and a pneumatic tire, having a bottom
surface fixed on a tire inner surface or a rim inner surface
surrounding the tire inner space, an upper surface facing the tire
inner space, and extending in the tire circumferential direction in
the tire inner space, wherein the sponge is constituted of a water
repellent polyurethane sponge obtained by foam curing a mixed
composition including a polyisocyanate, polyol, a water repellent
and a foaming agent, wherein the polyol is a mixture of a polyester
polyol and a polyester polyether copolymer polyol, the polyol
includes: 3 to 60% by weight of polyester polyol; and 97 to 40% by
weight of polyester polyether copolymer polyol, and the water
repellent in quantity in the range of from 25 to 80 parts by weight
relative to 100 parts by weight of polyol is mixed into the mixed
composition.
2. The noise damper according to claim 1, wherein the foaming agent
is water and a mixing quantity thereof is in the range of from 2.5
to 6.0 parts by weight relative to 100 parts by weight of
polyol.
3. The noise damper of a tire according to claim 1, wherein the
water repellent is an ester, which is a coupled compound of a
monoalcohol having 14 to 36 carbon atoms and an aliphatic
dicarboxylic acid or an alicyclic dicarboxylic acid having 14 to 36
carbon atoms.
4. The noise damper of tire according to claim 1, wherein the
polyol is constituted of 15 to 35% by weight of polyester polyol,
85 to 65% by weight of polyester polyether copolymer polyol and the
water repellent is mixed into the mixed composition in the range of
from 30 to 50 parts by weight relative to 100 parts by weight of
the polyol.
Description
[0001] This application is a Divisional of co-pending application
Ser. No. 11/269,676 filed on Nov. 9, 2005, and for which priority
is claimed under 35 U.S.C. .sctn. 120, and this application claims
priority of Application Nos. 2004-336574, 2004-336575, and
2004-336576 filed in Japan on Nov. 19, 2004, under 35 U.S.C. .sctn.
119; the entire contents of all are hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to an assembly of a pneumatic tire and
a rim having a band-like noise damper made of a sponge in a tire
inner space, and to the noise damper used in the assembly.
[0004] 2. Description of the Background Art
[0005] It has been known that one of tire noises is a road noise
generated in the frequency region of from about 50 to about 400 Hz
and that a resonance vibration (cavity resonance) of air occurring
in the tire inner space is as a main cause. In order to reduce such
a road noise, the applicant has offered an assembly (c) of a tire
having a band-like noise damper (b) made of a sponge and extending
in the tire circumferential direction in a tire inner space (a),
which is shown in, for example, FIG. 22 and a rim (see, for
example, JP-A No. 2003-252003). The noise damper (b) converts
vibration energy of air in the tire inner space (a) to thermal
energy to thereby, enable cavity resonance in the tire inner space
(a) to effectively suppressed.
[0006] In a case where a pneumatic tire (d) is demounted from the
rim (e), air in the tire inner space (a) is at first exhausted and
then, a bead portion (d1), which is part of the tire (d), is
pressed down into a well portion (e2) of the rim. Thereafter, a
tire lever (f) is inserted into a clearance between the bead
portion (d1) and a flange (e1) of the rim (e), and the tire lever
(f) is inclined around the outer edge of the flange (e1) as a
fulcrum to thereby take out the bead portion (d1) outward from the
flange (e1).
[0007] A conventional noise damper (b), however, has a
comparatively large thickness and a sectional shape thereof is
rectangular or trapezoidal. That is, each side surface of the noise
damper (b) is of a steep slope that rises high upwardly. Therefore,
an inconvenience arises that the distal end of the tire lever (f)
is, as shown with an imaginary line in FIG. 22, brought into
contact with the noise damper (b) to thereby break the noise damper
(b) or separate the noise damper (b) from the tire (d).
[0008] On the other hand, since the noise damper (b) made of a
sponge is high in water absorptivity, there arises an unfavorable
possibility that the sponge is wetted by rain or the like while a
tire is stored or the tire and a rim are assembled. If a tire and a
rim are assembled in a water absorption state, problems occur that
the absorbed water adversely affects a weight balance to thereby
cause tire vibrations, or permeates into rubber of the tire to
thereby induce an internal damage. Therefore, in a case where a
tire and a rim are assembled, it is necessary to remove water
sufficiently, but a sponge having been once wetted is hard to be
dried instantly, which makes its handling cumbersome.
SUMMARY OF THE INVENTION
[0009] It is a first object of the invention to provide an assembly
of a pneumatic tire and a rim capable of diminishing a chance that
a tire lever is brought into contact with a noise damper when the
tire is demounted from the rim and preventing breakage of the noise
damper in tire exchange or the like.
[0010] It is a second object of the invention to provide a method
for forming a noise damper capable of efficiently forming the noise
damper used in the assembly of a pneumatic tire and a rim.
[0011] It is a third object of the invention to provide a noise
damper capable of exerting a excellent water repellent performance,
absorbing no water even in a case where the noise damper is exposed
to water for a long time, drying the noise damper quickly by wiping
off water or the like, improving handlability and preventing
various problems such as tire vibrations and internal damage of a
tire caused by water absorption.
[0012] The invention of an assembly of a pneumatic tire and a rim
includes:
[0013] a rim;
[0014] a pneumatic tire mounted to the rim; and
[0015] a band-like noise damper, made of a sponge having a volume
in the range of from 0.4 to 20% of the entire volume of a tire
inner space enclosed by the rim and the pneumatic tire, having a
bottom surface fixed on a tire inner surface or a rim inner surface
surrounding the tire inner space and an upper surface facing the
tire inner space, and a noise damper extending in the tire
circumferential direction in the tire inner space,
[0016] wherein in a tire meridian section including the tire
axis,
[0017] the noise damper is of a laterally long, flat sectional
shape having a maximum thickness value (tm) from the bottom surface
to the upper surface in the range of from 5 to 45 mm and having a
width (W1) of the bottom surf ace more than the maximum thickness
value (tm),
[0018] the upper surface extends along a wavy curve that is
repetition of a wavy element in the width direction including a
hilltop portion having the maximum thickness value (tm), valley
bottom portions on each side of the hill top portion having the
minimum thickness value (ti) and slope portions extending down to
the respective valley bottom portions from the hill top portion,
and
[0019] each end in the width direction of the upper surface is
terminated at the valley bottom portions or the slope portions, and
a thickness (te) from the upper surface to the bottom surface is in
the range of from 1.0 to 15.0 mm.
[0020] With such a construction adopted, when a tire is demounted
from a rim, a tire lever can have decrease in chance to be brought
into contact with a noise damper, thereby enabling breakage of the
noise damper in tire exchange or the like to be prevented.
[0021] The invention of a method for forming a noise damper, in a
case where the wavy curve is of a sine wave, includes:
[0022] a transport step of feeding a flat plate-like sponge having
first and second surfaces substantially parallel to each other in
the length direction perpendicular to the thickness direction;
[0023] a deformation step of deforming the fed sponge in the
profile of a sine wave in section perpendicular to the length
direction by pressing each of the first and second surfaces of the
sponge alternately toward the other surface;
[0024] a cutting step of obtaining two half sponges sections of
which each have the profile of a sine wave and are reversals of
each other in profile in a state where the pressing pressure is
removed, by slicing the sponge deformed in the profile of a sine
wave along a flat cutting plane continuously extending in the width
direction between the first and second surfaces; and
[0025] a division step of dividing the half sponges to said
plurality of noise dampers by cutting the half sponges at valley
portions thereof each having a smaller thickness along the length
direction.
[0026] The invention of a method for forming a noise damper, in a
case where the wavy curve is of a trapezoidal wave, includes:
[0027] a cutting step of obtaining two half sponges sections of
which each have the profile of a trapezoidal wave by slicing a flat
plate-like sponge having first and second surfaces substantially
parallel to each other between the first and second surfaces along
a combination of cutting planes continuously extending in the
profile of a trapezoidal wave in the width direction between the
first and second surfaces; and
[0028] a division step of dividing the half sponges to said
plurality of noise dampers by cutting the valley portions each with
a smaller thickness of a half sponge along the length
direction.
[0029] With such methods applied, a noise damper with the wavy
curve in the profile of a sine wave and a noise damper with the
wavy curve in the profile of a trapezoid can be efficiently
formed.
[0030] A noise damper of the invention made of a water repellent
polyurethane sponge obtained by foam curing a mixed composition
including a polyisocyanate, polyol, a water repellent and a foaming
agent, wherein
[0031] the polyol is a mixture of a polyester polyol and a
polyester polyether copolymer polyol,
[0032] the polyol includes: 3 to 60% by weight of polyester polyol;
and 97 to 40% by weight of polyester polyether copolymer polyol,
and
[0033] the water repellent in quantity in the range of from 25 to
80 parts by weight mixed into 100 parts by weight of polyol.
[0034] With such a composition adopted, a noise damper of the
invention can exert excellent water repellent performance and does
not absorb water even in a case where the noise damper is exposed
to water for a long time to thereby enable the noise damper to be
quickly dried by wiping off or the like.
[0035] Herein, a volume of the noise damper is an apparent volume
determined by an outer shape of the noise damper, including a
volume that bubbles inside the noise damper occupy. The term "the
entire volume of a tire inner space" is determined as a value V
approximately obtained by the following equation (1) in a no load
state where a normal inner pressure is provided into an
assembly.
V=A.times.{(Di-Dr)/2+Dr}.times..pi. (1)
[0036] In the equation (1), "A" indicates a tire inner space area
obtained by CT scanning of the tire inner space in the normal
state, "Di" the maximum outer diameter of a tire inner space in the
normal state shown in FIG. 1, "Dr" a rim diameter and ".pi." a
circular constant. The "normal inner pressure" indicates an air
pressure determined for each tire in the standard system including
standards on which a tire is based: in a case of JATMA, the maximum
air pressure; in a case of TRA, the maximum value shown in the
table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and
in a case of ETRTO, "INFLATION PRESSURE." In a case where a tire is
for an automobile, the normal inner pressure is 200 kPa
indiscriminately in consideration of an actual usage frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a sectional view showing an assembly of a
pneumatic tire and a rim of the invention;
[0038] FIG. 2 is a view taken on line I-I of FIG. 1;
[0039] FIG. 3 is an enlarged sectional view showing a composite of
a tire and a noise damper;
[0040] FIGS. 4(A) to 4(C) are perspective views showing other
examples of noise damper in a simple way;
[0041] FIG. 5 is a graph showing a relationship between a noise
damper volume and a reduction in road noise;
[0042] FIG. 6 is an enlarged view of a noise damper of a first
embodiment;
[0043] FIG. 7 is a partly sectional view describing a positional
relationship between the noise damper of the first embodiment and a
tire lever;
[0044] FIG. 8 is a sectional view showing another example of the
noise damper of the first embodiment;
[0045] FIGS. 9(A) to 9(D) are perspective views describing a method
for manufacturing a band-like member of the first embodiment;
[0046] FIG. 10(A) is a sectional view describing a deformation step
and a cutting step and FIG. 10(B) is a sectional view of a sponge
after the cutting step;
[0047] FIG. 11 is an enlarged view of a noise damper of a second
embodiment;
[0048] FIG. 12 is a partly sectional view describing a positional
relationship of the noise damper of the second embodiment and a
tire lever;
[0049] FIG. 13 is a sectional view showing another example of the
noise damper of the second embodiment;
[0050] FIG. 14 is a sectional view showing still another example of
the noise damper of the second embodiment;
[0051] FIG. 15 is a sectional view showing yet another example of
the noise damper of the second embodiment;
[0052] FIGS. 16(A) to 16(D) are perspective views describing a
method for manufacturing a band-like member of the second
embodiment;
[0053] FIGS. 17(A) to 17(D) are sectional views of noise dampers
used in a test of Example A;
[0054] FIGS. 18(A) to 18(D) are perspective views describing a
method for manufacturing band-like members of Comparative Examples
A2 and B2 used in tests of Examples A and B;
[0055] FIGS. 19(A) to 19(D) are perspective views describing a
method for manufacturing band-like members of Comparative Examples
A3 and B3 used in tests of Examples A and B;
[0056] FIGS. 20(A) to 20(F) are sectional views of noise dampers
used in a test of Example B;
[0057] FIG. 21 is a perspective view of an apparatus describing a
test on water repellency; and
[0058] FIG. 22 is a sectional view describing operations in
demounting a tire from a rim using a tire lever.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] Description will be given of an embodiment of the invention
based on the accompanying drawings as follows.
[0060] An assembly 1 of a pneumatic tire and a rim of the
embodiment, as shown in FIG. 1, includes: a rim 2; a tire 3 mounted
to the rim 2; and a noise damper 4 disposed in a tire inner space
(i) enclosed by the rim 2 and the tire 3.
[0061] The rim 2 has a well known structure that includes: an
annular rim main body 2a to which a bead portion 3b of the tire 3
is mounted; and a disc 2b fixing the rim main body 2a to an axle.
Illustrated in the example is a case where a normal rim defined in
the standards such as JATMA is adopted.
[0062] The tire 3 is a tubeless tire and, as shown in FIG. 3, has a
tread section 3t; a pair of side walls 3s extending inwardly in
radial directions of the tire 3 from each end thereof; bead
portions 3b located at inward ends of the respective side walls 3s,
wherein an inner surface 31 of the tire 3 is covered by an inner
liner made of rubber with a low air permeability. With such a
construction adopted, an airtight tire inner space (i) is formed
with the tire inner surface 31 and a rim inner surface 21. The tire
3 can be one of various tires without limitations on an internal
structure and a category. Preferably adopted, however, is a tire
for an automobile in which silence is strongly required in a
passenger compartment, especially an automobile radial tire with a
aspect ratio of 50% or less.
[0063] The tire 3 is reinforced by a cord layer including a carcass
6 extending between the bead portions 3b and 3b and a belt layer 7
provided outside the carcass in the radial direction thereof and in
the interior of the tread portion 3t.
[0064] The carcass 6 is formed with, for example, one or more
organic fiber cords arranged at an angle, for example, in the range
of from 70 to 90 degrees relative to the tire circumferential
direction: one carcass ply 6A in the example. Both ends of the
carcass ply 6A are folded back around bead cores 8. The belt layer
7 is constituted of a plurality of belt plies formed with, for
example, steel cords arranged at an angle, for example, in the
range of from 10 to 40 degrees relative to the tire circumferential
direction: two belt plies 7A and 7B in the example. The belt layer
7 can have higher belt stiffness by intersecting the steel cords
between the plies. Note that a known band layer or the like may be
provided outside the belt layer 7 when required.
[0065] The noise damper 4 has an almost the same sectional form and
is in the shape of a long band extending in the tire
circumferential direction. The reason for using the term "almost"
is that, as shown in FIG. 2, taper portions a height in section of
each of which is gradually reduced are formed at each end 4e of the
noise damper 4 in the circumferential direction for increasing
durability. The band-like noise damper 4 is adhered to the tire
inner surface 31 along the circumferential direction with a
pressure sensitive adhesive double coated tape or an adhesive. In
FIG. 2, there is shown a case where a clearance is formed between
ends 4e and 4e of the noise damper 4, while the ends 4e and 4e are
connected without leaving a clearance and thereby, the noise damper
4 may be formed as a ring. Besides, the noise damper 4 may also be
wound spirally in the tire circumferential direction as shown in
FIG. 4(A) and alternatively, as shown in FIG. 4(B), the noise
damper 4 is divided into two or more pieces and the pieces 4p are
arranged in the circumferential direction with a clearance between
adjacent pieces. As shown in FIG. 4(C), the noise damper 4 may also
be arranged in a plurality of rows (for example, two rows).
[0066] The noise damper 4 is made of a sponge. The sponge is of a
sponge-like porous structure and includes: a foam having, for
example, continuous bubbles and isolated bubbles obtained by
foaming rubber or synthetic resin and in addition thereto, a
web-like member obtained by entangling animal fibers, plant fibers,
synthetic fibers or the like to couple them into a single
piece.
[0067] Such noise dampers suppress cavity resonance in the tire
inner space (i) and decreases a road noises with the help of porous
portions on the surface and in the interior of a sponge. Since a
sponge is easy to be deformed, that is contracted or bent, no
substantial influence exerts on tire deformation during driving.
Hence, driving stability can be prevented from being degraded.
[0068] Examples of the sponge that can be preferably adopted
include: synthetic resin sponges such as ether-based polyurethane,
ester-based polyurethane sponge and polystyrene sponge; and rubber
sponges such as chloroprene rubber sponge (CR sponge), ethylene
propylene rubber sponge (EDPM sponge) and nitrile rubber sponge
(NBR sponge). Among them, preferable is a polyurethane sponge from
the viewpoints of silence, light weight, foaming adjustability,
durability and the like.
[0069] A sponge is easy to cause increase in tire weight if a
specific gravity is excessively large, while even if a specific
gravity is excessive small, an effect of suppressing cavity
resonance is lowered. From such viewpoints, the lower limit of a
specific gravity of a sponge is 0.005 or more and preferably 0.01
or more. The upper limit of a specific gravity thereof is 0.06 or
less, more preferably 0.04 or less and further more preferably 0.03
or less.
[0070] A volume (Vs) of the noise damper 4 is necessary to be in
the range of from 0.4 to 20% of the entire volume of a tire inner
space (V). In FIG. 5, there is shown empirical results when a load
noise is measured with a noise damper 4 arranged in a tire inner
space (i). The ordinate is used for plotting reduction in road
noise and the abscissa is assigned to a volume ratio (Vs/V).
Reduction in road noise is a reduction (dB) from that of an
assembly without a noise damper 4 in a tire inner space (i).
[0071] As is clear from FIG. 5, by securing a volume of a noise
damper 4 to a value of 0.4% or more relative to the entire volume
of a tire inner space (i), a road noise reduction effect of about 2
dB or more can be expected. This level of reduction in noise can be
said a value recognizable clearly in an automobile compartment.
From such a viewpoint, the lower limit of a volume (Vs) of a noise
damper 4 is preferably 1% or more, more preferably 2% or more and
further more preferably 4% or more of the entire volume (V) of a
tire inner space (i). On the other hand, if a volume (Vs) of a
noise damper 4 exceeds 20% of the entire volume (V) of a tire inner
space (i), not only is an effect of suppression of road noise
leveled off, but also a cost is increased or a weight balance of an
assembly 1 is degraded with ease. From such a viewpoint, the upper
limit of a volume (Vs) of a noise damper 4 is preferably 16% or
less and more preferably 10% or less of the entire volume (V) of a
tire inner space (V). Note that the results of experiments are
obtained in a case where one noise damper 4 is used, while in a
case where two rows of noise dampers 4 are used as well, it has
been confirmed that a similar effect is exerted as far as all the
volume (Vs) is in the numerical value range.
[0072] Herein, since a sponge is high in water absorptivity, the
sponge absorbs rain or the like during tire storage or assembly of
a tire and a rim, which brings a possibility of occurring a problem
that adversely affects a weight balance to thereby cause tire
vibrations, causes lower durability of the sponge, and induces
inner damage of a tire by absorbed water having permeated into
rubber of the tire.
[0073] Used as a sponge in the example is a water repellent
polyurethane obtained by foam curing a mixed composition containing
polyisocyanate, polyol, a water repellent and a foaming agent. On
this occasion, the polyol is a mixture of polyester polyol and
polyester polyether copolymer polyol. With such a construction
adopted, a noise damper 4 can exert excellent water repellent
performance while a necessary strength and an effect of reduction
in road noise are sufficiently secured, thereby enabling various
problems such as tire vibrations and tire inner damage caused by
the water absorption to be prevented.
[0074] A polyurethane sponge is, as is well known, formed by
foaming with a foaming agent during a reaction of polyisocyanate
and polyol with each other to form a urethane bond in a
cross-linked polyurethane.
[0075] In this process in the example, water is used as a foaming
agent. Water reacts with polyisocyanate in the mixed composition to
generate carbon dioxide to thereby enable the cross-linked
polyurethane to be foamed. Ordinarily used as a foaming agent is a
compound with a low boiling point vaporized by a reaction heat when
a urethane bond is formed such as a methylene chloride or pentane.
Such foaming agents cause rapid forming with difficulty of control
in foaming, leading to not only unevenness in water repellent
performance such as inhomogeneity in dispersion of a foaming agent,
but also difficulty obtaining a high quality foam uniform in bubble
diameter and bubble density. Hence, used in the example is only
water which is easy in control of foaming.
[0076] A mixing quantity of water is preferably in the range of
from 2.5 to 6.0 parts by weight relative to 100 parts by weight of
the polyol. If water is less than 2.5 parts by weight, insufficient
foaming is resulted, a specific gravity of a sponge is hard to be
set low in the range. On the contrary, if water exceeds 6.0 parts
by weight, a sponge is foamed excessively, tending to lose a
hardness or tearing strength of a sponge. Note that in order to
attain sufficient durability, a sponge preferably has a hardness of
30 N or more and a tearing strength of 10 N/cm or more. Even if the
hardness exceeds 150N, elasticity decreases to tend to lower
durability. If a tearing strength increases more than 10 N/cm, it
results in an excess in terms of quality, which leads to
disadvantages of increase in cost and decrease in productivity.
Note that a hardness of a sponge is a value measured according to
Method A (Section 6.3) of methods for a hardness of Section 6
stipulated in "Testing Method for Soft Urethane foam" of JIS K6400.
The tearing strength is a value on a test piece of Shape No. 1
measured according to the measuring method for a tearing strength
of Section 11.
[0077] Examples of the polycyanate that can be employed include:
polycyanates including aromatic polyisocyanates such as tolylene
diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric
MDI, naphthalene diisocyanate, paraphenylene diisocyanate, xylene
diisocyanate (XDI), tetramethylxylene diisocyanate and
dimethyldiphenyl diisocyanate; and aliphatic polyisocyanates such
as hexamethylene diisocyanate, hydrogenated MDI,
isophoronediisocyanate, lysinediisocyanate, hydrogenated XDI and
cyclohexyl diisocyanate, and modified compounds thereof. Among
them, especially preferable are TDI, MDI and modified compounds
thereof.
[0078] The polyol in the embodiment is a mixture of polyester
polyol and polyester polyether copolymer polyol. This is because a
noise damper, by including polyester polyether copolymer polyol,
not only can sufficiently secure a necessary strength as a noise
damper 4, but also can raise resistance to hydrolysis. Besides,
this is because a noise damper, by including polyester polyol, not
only can enhance dispersibility of a water repellent, but also
renders adjustment in viscosity of a mixed composition easy to
enable a foam low in viscosity (low specific gravity) to be
obtained.
[0079] If a proportion of a polyester polyol is excessive low,
compatibility between a water repellent and a polyester polyether
copolymer polyol is deteriorated to cause insufficient agitation,
which results in not obtaining a desired foam in which a water
repellent is uniformly dispersed. Contrary thereto, if a proportion
of polyester polyol is excessively large, no ether chain is
incorporated in a cross-linked polyurethane; therefore, a foam
tends to reduce a strength and lose resistance to hydrolysis.
Hence, it is preferable that a proportion of a polyester polyol is
in the range of from 3 to 60% by weight and a proportion of
polyester polyether copolymer polyol is in the range of from 97 to
40% by weight as a balance.
[0080] On this occasion, a mixing quantity of a water repellent is
preferably in the range of from 25 to 80 parts by weight relative
to 100 parts by weight of polyol. If a mixing quantity of a water
repellent is less than 25 parts by weight, water repellent
performance becomes insufficient, while on the contrary, if a
mixing quantity of a water repellent exceeds 80 parts by weight, it
becomes difficult to produce a foam since the water repellent acts
as a plasticizer as well.
[0081] Note that in order to enhance a strength, a resistance to
hydrolysis, water repellent performance, moldability in good
balance, it is preferable that in polyol, a proportion of polyester
polyol is in the range of from 15 to 35% by weight, polyester
polyether copolymer polyol is in the range of from 85 to 65% by
weight as a balance and a mixing quantity of a water repellent is
in the range of from 30 to 50 parts by weight relative to 100 parts
by weight of polyol.
[0082] Herein, examples of the polyester polyol that can be named
include: a compound obtained by condensing a low-molecular polyol
and a carboxylic acid and in addition thereto, lacton-based polyol
such as .epsilon.-caprolacton ring opening polymerization product
and .beta.-methyl-.delta.-valerolacton ring opening polymerization
product. Examples of the low-molecular polyol that can be named
include: ethylene glycol, diethylene glycol, propylene glycol,
1,4-butanediol, 1,6 hexanediol, 2,5-hexanediol,
3-methyl-1,5-pentanediol, neopentyl glycol, glycerin,
trimethylolpropane, trimethylolethane, pentaerythritol, diglycerin,
sorbitol, cane sugar and the like. Examples of the carboxylic acid
that can be named include: succinic acid, adipic acid, maleic acid,
fumaric acid, phtalic acid, isophthalic acid, succinic anhydride,
maleic anhydride, phthalic anhydride and the like.
[0083] The polyester polyether copolymer polyol can be a known
product. There can be exemplified a compound obtained by
esterification reaction (or ester exchange reaction) of an
aliphatic dicarboxylic acid (or an ester forming derivative
thereof) and a low-molecular diol to subject a product of the
reaction to a polycondensation. Or alternatively, there is
exemplified a compound obtained by ester exchange reaction of
polyester polyol and a polytetramethylene glycol. In the invention,
polyester polyether copolymer polyol is employed to thereby
increase a strength of a foam, improve resistance to hydrolysis and
exert good water repellency.
[0084] A water repellent described above that can be preferably
used is an ester, which is a coupled compound of a monoalcohol
having 14 to 36 carbon atoms and an aliphatic dicarboxylic acid (or
an alicyclic dicarboxylic acid) having 14 to 36 carbon atoms. If
the number of carbon atoms is 14 or more, hydrophobicity that a
long chain alkyl group has can effectively contribute to water
repellency of a foam. If the number of carbon atoms is excessively
large, a water repellent becomes easily a sold at room temperature
or a low temperature to make it to be hard to be handled.
Therefore, the upper limit of the number of carbon atoms is
preferably 36 or less.
[0085] Examples of such esters includes:
[0086] (a) isostearyl stearate,
[0087] (b) oleyl stearate,
[0088] (c) stearyl oleinate,
[0089] (d) dioleyl dimerate,
[0090] (e) distearyl dimerate and
[0091] (f) a diester of a mixture of a dimer acid and a
high-molecular alcohol having 32 to 36 carbons.
[0092] Note that a catalyst and a foam control agent ordinarily
used in formation of polyurethane sponge can be mixed into the
mixed composition in a similar way as conventional.
[0093] Not only does water repellent polyurethane sponge obtained
by foam curing such a mixed composition secure sufficiently a
mechanical strength necessary as a noise damper 4, but also
resistance to hydrolysis can be raised and water resistance can be
improved. Since a water repellent is incorporated and
dispersibility thereof is increased to achieve more of homogeneity,
an excellent water repellent performance is exerted, thereby
enabling various problems such as tire vibrations and tire inner
damage caused by absorption of water into a sponge to be prevented.
Besides, a sponge with a lower density (lower specific gravity) can
be achieved while such characteristics are sustained, thereby
enabling a high road noise reduction effect to be exerted.
[0094] Then, the noise damper 4, as shown in FIG. 3, has a bottom
surface 4A fixed to the tire inner surface 31 or the rim inner
surface 21; and an upper surface 4B facing the center of the tire
inner space (i) located on the other side of the noise damper 4
from the bottom surface 4A. The bottom surface 4A prevents the
noise damper 4 from freely moving in the tire inner space (i)
during driving to prevent the noise damper 4 from being damaged and
to be useful for exerting an effect of resonance suppression. Note
that the bottom surface 4A is a substantially smooth flat
surface.
[0095] Herein, the rim inner surface 21 has a chance that the bead
portion 3b is strongly pressed thereto when tires are exchanged.
Hence, the noise damper 4 is fixed preferably to the tire inner
surface 31, especially to a tread inner surface 3ti. Note that the
tread inner surface 3ti means a surface located in the tread
portion 3t brought into contact with a road surface. In the
specification, the tread inner surface includes the width region TW
disposed in the tire axial direction in which at least the belt
layer 7 is included. As a preferred embodiment, the noise damper 4
is fixed so that the width center of the bottom surface 4A is
located at a tire equator C. The noise damper 4 more preferably has
an arrangement and a sectional shape bilaterally in symmetry with
respect to the tire equator C as a center.
[0096] The noise damper 4, as shown in FIG. 6, preferably has the
maximum value (tm) of a thickness from the bottom surface 4A to the
upper surface 4B in the range of from 5 to 45 mm in the tire
meridian section including the tire axis and is formed in the shape
of a laterally long, flat section with a width W1 of the bottom
surface 4A more than the maximum value (tm) of a thickness. The
maximum value (tm) of a thickness and the width (W1) are measured
in a state where the noise damper 4 is mounted to the tire 3 and
the tire is not assembled with the rim (at an ordinary temperature
under an ordinary atmospheric pressure). The maximum value (tm) of
a thickness is measured in a direction perpendicular to the bottom
surface 4A and the width W1 is measured along the bottom surface
4A.
[0097] The inventors conducted a tire demounting test on an
assembly having a noise damper 4 in the sectional shape of a
rectangle placed on the tread inner surface 3ti. A breakage state
of the noise damper 4 was investigated. The tire demounting test
was performed, as shown in FIG. 22, by more than one workers using
a tire changer (not shown) and a tire lever (f). The workers have
no knowledge of the presence of the noise damper in advance.
Various noise dampers with different maximum thicknesses (tm) and
various kinds of tires with different aspect ratios are employed in
assemblies of samples.
[0098] When the tire 3 is demounted from the rim 2, the tire lever
(f) is inserted into the tire inner space (i) and a length of
insertion is different so as to be adaptable according to a kind of
a tire (a category, an aspect ratio or the like), or a technique
and a habitual practice of a worker. As a result of the test, it
was found, however, that assemblies each having a noise damper with
the maximum value of a thickness (tm) limited in the range of from
5 to 45 mm decrease the number of broken noise dampers. The reason
why is considered that a length of insertion of the tire lever (f)
is restricted by a general understanding of workers intending to
prevent contact of a tire lever (f) with the a inner surface 31;
therefore, a length of insertion of the tire lever (f) is
restricted and a chance of contact with noise dampers is less in a
case where a noise damper with a smaller thickness is used.
Especially flat tires each with an aspect ratio of 50% or less
showed a tendency of frequent contact with side surfaces of noise
dampers by a tire lever (f).
[0099] Therefore, further experiments were conducted with the
resulted findings as follows: Damage to be caused by a tire lever
(f) can be avoided with the following construction adopted: in the
tire meridian section, as shown in FIG. 6,
[0100] (1) the upper surface 4B extends along a wavy curve 14 that
is repetition of a wavy element 13 in the width direction which is
constituted of a hill top portion 10t having the maximum value (tm)
in thickness (t), valley bottom portions 11b having the minimum
value (ti) in thickness (t) on each side of the hill top portion
and slope portions 12 extending down to the respective valley
bottom portions lib from the hill top portion 10t,
[0101] (2) each end 4Be in the width direction of the upper surface
4B is terminated at the valley bottom portions 11b or the slope
portions 12, and
[0102] (3) a thickness (te) between the each end 4Be in the width
direction of the upper surface 4B and the bottom surface 4A is in
the range of from 1.0 to 15.0 mm.
[0103] In other words, the upper surface 4B extends along the wavy
curve 14 to thereby form a hill top portion 10 with a larger
thickness (t) and a valley portion 11 with a smaller thickness (t)
alternately. Not only is each end of the noise damper 4 terminated
at the valley portions 11, but a thickness (te) of each end from
the bottom surface 4A is restricted to a value in the range of from
1.0 to 15.0 mm. Note that not only is the hill top portion 10
defined as a portion with a larger thickness (t) above an amplitude
center line KL of the wavy curve 14 as a reference, but the valley
bottom portion 11 is also defined by a portion with a smaller
thickness (t) below the amplitude center line KL.
[0104] In FIGS. 1 to 10, there is shown a case where the wavy curve
14 is of a sine wave as the first embodiment of the noise damper
4.
[0105] Not only is each end of the noise damper 4, in this way,
terminated at the valley portions 11, but a thickness of each end
(te) is restricted to 15.0 mm or less. Therefore, contact of the
tire lever with the noise damper 4 is avoided at a more limited
chance. The noise damper 4 is profiled by the gradual slope
portions 12 from each end to the hill top lot. Adoption of such a
slope 12 eliminates, as shown in FIG. 7, a portion 15 easily
interfering with the lever (f). Therefore, contact of the tire
lever (f) with the noise damper 4 is avoided at a furthermore
limited chance. The slope portion 12 approximates an circular
arc-like locus (fL) depicted by the distal end of the tire lever
(f). Hence, even if the tire lever (f) was brought into contact
with the noise damper 4, a frictional force between the tire lever
(f) and the slope portion 12 would be small to thereby render a
thrust of the distal end of the tire lever (f) into the noise
damper 4 difficult. With the smaller frictional force and
difficulty in a thrust thereinto combined, extreme damage on the
noise damper 4 and separation thereof from the tire 3 can be
effectively prevented.
[0106] Note that if a thickness (te) of each end exceeds 15.0 mm,
each end of the noise damper 4 and the tire lever (f) interfere
easily with each other. Hence, the thickness (te) is preferably
15.0 mm or less, more preferably 10.0 mm or less and further more
preferably 7.0 mm or less from the viewpoint of prevention of
damage on the noise damper 4. If the thickness (te) is less than
1.0 mm, an effect of increase in productivity is harder to be
achieved, and accordingly, the thickness (te) is preferably 1.0 mm
or more, more preferably 3.0 mm or more, and further more
preferably 4.0 mm or more. Detailed description will be given in
this regard later.
[0107] The minimum thickness value (ti) is preferably 1.0 mm or
more, more preferably 3.0 mm or more and further more preferably
4.0 mm or more from the viewpoint of increase in productivity. It
is especially preferable that the thickness of the each end (te) is
equal to the minimum thickness value (ti), that is each end of the
noise damper 4 is terminated at the valley bottom portion 11b from
the viewpoints of prevention of damage of the noise damper 4 and
increase in productivity thereof. As far as the thickness range is
adopted, a thickness (te) may be more than the minimum value (ti),
that is the each end or one end of the noise damper 4 may be
terminated at a point on the slope portion 12, which is different
from the valley bottom portion 11b.
[0108] In connection with the wavy curve 14 determining a profile
of the upper surface 4B, if the amplitude H is excessively small,
the surface area of the upper surface 4B becomes small to thereby
lower a resonance suppression effect in the tire inner space (i)
with ease, while if the amplitude H is excessively large, the slope
portion becomes steep, which affects prevention of damage on the
noise damper 4 adversely. From such a viewpoint, the lower limit
value of the amplitude H is preferably 4 mm or more, more
preferably 8 mm or more, and further more preferably 10 mm or more,
while the upper limit value of the amplitude H is preferably 44 mm
or less, more preferably 40 mm or less, and furthermore preferably
35 mm or less. Note that in a case where the wavy curve 14 is of a
sine wave, a ratio of the amplitude H and a wave width Wp, which is
a width of the wavy element 13, H/Wp is preferably 0.3 or less and
more preferably 0.25 or less in order to approximate the slope
portion 12 to the locus (fL) of the tire lever (f).
[0109] In FIGS. 1, 3, 6 and 7, there is shown a case of a mode
having one hill top portion 10t on the upper surface 4B of the
noise damper 4, especially, with each end of the noise damper
terminates at the valley bottom portions 11b, that is a case where
the upper surface 4B is formed with one wavy element 13. Two or
more hill top portions 10t on the upper surface 4B may be adopted
and in FIG. 8, there is shown a mode having the upper surface 4B
including two wavy elements.
[0110] In a case where the number of the hill top portions 10t is 2
or more, a higher resonance suppression effect can be exerted
because of increase in surface area of the upper surface 4B. A
valley portion 11 is formed between hill top portions 10. The
valley portion 11 makes it easier to deform the hill portion 10 in
the width direction when the tire lever (f) is brought into contact
with the slope portion 12. Hence, the noise damper 4 can escape
from the tire lever (f) and a thrust of the tire lever (f) can be
suppressed to a smaller depth. The valley portion 1 is useful for
preventing thermal breakage of the noise damper 4 because of
exertion of a heat release effect.
[0111] Note that since the volume (Vs) of a noise damper 4 is
limited to the range relative to the entire volume (V) of the tire
inner space (i), a sectional area of the noise damper 4 is also
determined if a length of the noise damper 4 in the circumferential
direction is determined. The width W1 of the bottom surface 4A is
automatically determined in the presence of a limitation such as
the maximum thickness value (tm) and by determining a profile of
the wavy curve 14. If the width W1 of the bottom surface 4A is
excessively large, the working efficiency in attaching the noise
damper to the tire inner surface 31 tends to be decreased. From
such a viewpoint, in a case where the tire 3 is a radial tire for
an automobile, a width W1 of the bottom surface 4A is preferably in
the range of from 30 to 250 mm and more preferably in the range of
60 to 140 mm. A width W1 of the bottom surface 4A is also
preferably in the range of from 5 to 100% and more preferably in
the range of from 20 to 70%, of a tread width TW.
[0112] The noise damper 4 can be fixed to the tire inner surface 31
or the rim inner surface 21 in various kinds of ways. From the
viewpoints of cost and operability, preferable is adhesion with an
adhesive or a pressure sensitive adhesive double coated tape 23,
especially preferable is adhesion with the pressure sensitive
adhesive double coated tape 23. Various methods other than adhesion
can be adopted, for example a method using a screw or a mounting
metal tool, a method for integrating them into one piece in a
vulcanization process and the like. Then, the noise damper 4 is
fixed to the pneumatic tire 3, which can be sold as a composite of
the pneumatic tire 3 and the noise damper 4 in the form of a set
sale. It is desired to finish the tire inner surface 31 to be
smooth in order to improve of adhesion. While protrusion stripes
are usually formed on the tire inner surface 31 by transfer of
exhaust grooves formed on a bladder for vulcanization molding, it
is preferable to remove the protrusion stripes by smoothing in
polishing. Alternatively, a bladder without exhaust grooves on the
surface thereof can also be used to thereby finish the tire inner
surface as finished to be flat and smooth. It is preferably for the
tire to be vulcanization molded without coating a release agent on
the tire inner surface 31 in order to further better adhesion to
the tire inner surface 31.
[0113] Description will be given of a preferred method for forming
a noise damper 4 of the first embodiment having the wavy curve 14
in the profile of a sine wave.
[0114] The molding method includes a transport step of feeding a
sponge (S) (FIG. 9(A)); a deformation step of bend deforming the
transported sponge (S) in the profile of a sine wave (FIG. 10(A));
a cutting step of slicing the deformed sponge (S) into two half
sponges (Sa and Sb) along a horizontal cutting plane (FIGS. 10(A)
and 10(B)); and division step of dividing the half sponges (Sa and
Sb) along the length direction to thereby obtain a plurality of
noise dampers 4 (FIGS. 9(C) and 9(D)).
[0115] In the transport step, as shown in FIG. 9(A), a flat
plate-like sponge (S) having a first surface (P1) and a second
surface (P2) substantially parallel to each other is fed in the
length direction (A) perpendicular to the thickness direction (T).
The transport step can be implemented with ease using, for example,
a belt conveyor or the like. Note that the thickness (T) is equal
to the sum (tm+ti) of the maximum thickness value (tm) and the
minimum thickness value (ti).
[0116] In the deformation step, as shown in FIG. 10(A), the fed
sponge (S) is pressed alternatively from the first surface (P1) and
the second surface (P2) to each other in a section in the width
direction perpendicular to the length direction (A). Thereby, the
sponge (S) is deformed into the profile of a sine wave
corresponding to the wavy curve 14. In the deformation step,
employed are shafts 20 and 20 held at two levels, upper and lower,
and parallel to each other. Each roller 20 is constituted of a
shaft 20a freely rotatably supported and a plurality of rolling
body 20b mounted concentrically with the shaft 20a. The rolling
body 20b each are in the shape of a disc and the discs are all
equal in outer diameter and disposed with an equal pitch (L) in the
axial direction. Note that an outer surface of a rolling body 20b
is chamfered in the profile of a circular arc.
[0117] The rolling body 20b of the upper roller 20 and the rolling
body 20b of the lower roller 20 are shifted relative to each other
in the axial direction by a length of a half of the pitch (L). That
is, the rolling body 20b are arranged alternately above and below
the sponge (S) at a pitch of L/2 in the axial direction. Therefore,
when the sponge (S) passes through clearances between the rollers
20 and 20 at two levels, upper and lower, the sponge (S) is pressed
alternately by the rolling body 20b, upper and lower to deform the
sponge (S) into the profile of a sine curve.
[0118] In the cutting step, as shown in FIG. 10(A), the sponge (S)
deformed into the profile of a sine wave is sliced along a flat
cutting plane (CT) continuously extending in the width direction
between the first surface (P1) and the second surface (P2) into two
half sponges (Sa and Sb). The two half sponges (Sa and Sb) are, as
shown in FIG. 10(B), discharged from the rollers 20 and 20, and the
cutting plane (CT) assume the profile of a sine wave in a state
where the pressing pressure is removed, the cutting plane (CT) of
the upper half sponge (Sa) is a reversal of that of the lower half
sponge (Sb) and the first and second surfaces (P1 and P2) restore
to flat surfaces. Such a forming method is also called a profile
method.
[0119] In this way, in the deformation step and the cutting step
combined, two half sponges (Sa and Sb) in the same profile of a
sine wave can be efficiently formed in a single cutting from one
sponge (S). Note that the spacing AL between the rollers 20 and 20
is set so that the cutting plane is not brought into contact with
the upper or lower rolling body 20b. In the cutting step,
preferably used is a cutting blade capable of mechanically cutting
a sponge at an ordinary temperature, for example a split blade, but
a heat cutting using a high temperature wire is not preferable
since the surface of a sponge is melted to thereby tend to degrade
a noise absorption effect.
[0120] In the example, as shown in FIG. 9C, performed is a pressure
sensitive adhesive double coated tape adhering step of adhering one
surface of the pressure sensitive adhesive double coated tape 23
onto the first and second surfaces (P1) and (P2) of the half
sponges (Sa and Sb). In this step, one pressure sensitive adhesive
double coated tape with a large width is adhered to each of the
surfaces (P1 and P2) to cover almost all the surface thereof.
[0121] In the division step, as shown in FIGS. 9(C) and 9(D), the
half sponges (Sa and Sb) on each of which the pressure sensitive
adhesive double coated tape 23 is adhered is cut along the length
direction A together with the pressure sensitive adhesive double
coated tape 23 at positions each corresponding to the valley
portion 11 smaller in thickness (t) and preferably at a positions
each corresponding to the valley bottom portion 11b. Thereby, the
half sponges (Sa and Sb) are divided into the plurality of noise
dampers 4. Note that a length along the length direction A of the
noise damper 4 is preferably adjusted so as to be adapted for a
tire size in the state of a sponge (S) in advance, while a cutting
step or the like of adjusting a length thereof can also be applied
properly to each noise damper 4 after the division step. Each noise
damper 4 can also be formed properly so as to have a taper portion
at each end.
[0122] In the formation method, the plurality of noise dampers 4 in
substantially the same shape can be produced in this way with good
efficiency. Therefore, not only is a productivity improved, but
generation of waste material is also suppressed to thereby raise a
yield in terms of material. Besides, every second valley portion 11
is only required to be cut in order to obtain a noise damper 4
having, for example, two hill tops 10 (FIG. 8).
[0123] Herein, in a case where the minimum thickness (ti) is less
than 1.0 mm, a possibility is encountered that the valley portions
11 is broken at the stage of obtaining half sponges, which cause
reduced productivity due to degradation of work abilities in later
steps. Hence, the minimum thickness value (ti) is preferably 1.0 mm
or more, more preferably 3.0 mm or more and further more preferably
4.0 mm or more.
[0124] In the example, the sponge (S) is deformed into the profile
of a sine wave in the deformation step, followed by cutting, while,
for example, a blade is moved along the profile of a sine wave in a
state where the sponge (S) may be maintained in the initial shape
of a flat plate to thereby slice the sponge (S) adopting a
so-called contour forming. Half sponges obtained by slicing can be
formed into noise dampers 4 by way of operations similar to those
in the example.
[0125] Then, in FIGS. 11 to 15, there is shown a case where the
wavy curve 14 is in the profile of a trapezoid as a second
embodiment of the noise damper 4. In the second embodiment, as
shown in FIG. 11, the wavy curve 14 is a curve of the profile of a
trapezoidal wave which is repetition of a wave element 13 in the
width direction including the hill top portion lot constituted of a
linear upper side 30 parallel to the bottom surface 4A, the valley
bottom portion 11b constituted of a linear lower side 31 parallel
to the bottom surface 4A and the slope portion 12 constituted of a
linear oblique side 32.
[0126] Note that the oblique side 32 can be provided with an
circular arc portion having a sufficiently smaller curvature radius
as compared with all the length of the oblique side 32 at a
connection portion with the upper side 30 and/or the lower side 31.
Herein, a sufficiently smaller curvature radius as compared with
all the length of the oblique side 32 means 42% or less, preferably
35% or less and more preferably 20% or less of all the length of
the oblique side 32.
[0127] In a case of such a noise damper 4 of the second embodiment
as well, not only is each end of the noise damper 4 terminated in
the valley portion 11, but a thickness (te) of each end is also
restricted to 15.0 mm or less; therefore, contact of the tire lever
(f) with the noise damper 4 is avoided at amore limited chance. The
noise damper 4 is constructed including a gentle slope 12 from each
end to the hill top portion 10t. With the slope portion 12 adopted,
a portion 15 interfering easily with the tire lever (f) is, as
shown in FIG. 12, removed, which results in contact of the tire
lever with the noise damper 4 at a further more limited chance.
Since the oblique portion 12 approximates a locus in the shape of a
circular arc (fL) depicted by the distal end of the tire lever (f),
a frictional force between the tire lever (f) and the slope portion
12 would be small and a thrust of the distal end into the noise
damper 4 would become difficult even if the tire lever was brought
into contact with the noise damper 4. Hence, with both effects
combined, the noise damper 4 of the second embodiment can
effectively prevent extreme damage on the noise damper 4 and
separation of the noise damper 4 from the tire 3 from occurring in
a similar way to that in the noise damper 4 of the first
embodiment.
[0128] In the second embodiment, an angle .gamma. formed between
the slope portion and the bottom surface 4A is preferably 70
degrees or less, more preferably 60 degrees or less and further
more preferably 50 degrees or less in order to approximate the
oblique portion 12 to the locus (fL) of a tire lever to a profile
closer thereto.
[0129] In the second embodiment, in a similar way to that in a case
of the first embodiment, one or a plurality of hill tops 10t (the
upper side 30) in the upper surface 4B of the noise damper 4 may be
adopted. In FIGS. 11 and 13, there is illustrated a case where one
hill top portion 10t (the upper side 30) is included. Especially,
in FIG. 11, there is shown a mode that each end of the noise damper
4 is terminated at the valley bottom portions 11b (the lower side
31), that is a thin projection 35 along the lower side 31 is
provided at each end. Note that in the noise damper 4 of FIG. 11,
the upper surface 4B is formed with one wavy element 13. In FIG.
13, one end of the noise damper 4 is terminated at the slope
portion 12 (an oblique side 32), but each end thereof may be
terminated at the slope portions 12 (the oblique sides 32).
[0130] In FIGS. 14 and 15, there is illustrated a case where two
hill tops lot (two upper sides 30) are included. Especially, in
FIG. 14, there is shown a case where each end of a noise damper 4
are terminated at the valley bottom portions 11b (lower sides 31),
wherein the noise damper 4 has the upper surface 4B formed with two
wavy elements 13. In FIG. 15, each end of a noise damper 4 is
terminated at points on the respective slope portions 12 (the
oblique sides 32), but only one end thereof may also be terminated
at a point on the slop 12 (the oblique side 32).
[0131] Then, description will be given of a preferred method for
forming a noise damper 4 having the wavy curve 14 in the profile of
a trapezoid.
[0132] The formation method includes: a cutting step of slicing a
flat plate-like sponge (S) along a combination of cutting planes CT
extending in the width direction in the profile of trapezoidal wave
into two half sponges (Sa and Sb) (FIG. 16(B)); and a division step
of dividing the half sponges (Sa and Sb) into a plurality of noise
dampers 4 by cutting the half sponges (Sa and Sb) in the length
direction.
[0133] The flat plate sponge (S) is a sponge (S) having a first
surface (P1) and a second surface (P2) substantially parallel to
each other similar to that used in the formation method for the
noise damper 4 in the first embodiment. A thickness (T) of the
sponge (S) is equal to the sum (tm+ti) of the maximum thickness
(tm) and the minimum thickness (ti).
[0134] In the cutting step, as shown in FIG. 16(B), a cutter 18 is
moved along the profile of a trapezoidal wave in the width
direction between the first surface (P1) and the second surface
(P2). Thereby, the sponge (S) is sliced along the combination of
cutting planes (CT) extending along the profile of a trapezoidal
wave into two half sponges (Se and Sb). Such a forming is called a
contour forming. The cutter 18 has a length of a blade longer than
that of a length of the sponge (S). Preferable as a cutter 18 is of
a cutting blade capable of mechanically cutting the sponge at an
ordinary temperature, for example a split blade, but unpreferable
is a cutter using a high temperature wire or the like to thermally
cut the sponge since the cutter melts the surface of the sponge (S)
and have a tendency to degrade an noise absorption effect.
[0135] With such a contour forming adopted, two half sponges (Sa
and Sb) in the same combination of cutting planes (CT) of a
trapezoidal wave can be efficiently obtained in a single
process.
[0136] In the example, as shown in FIG. 16 (C), performed is a
pressure sensitive adhesive double coated tape adhering step of
adhering one surface of a pressure sensitive adhesive double coated
tape 23 on the first surface (P1) and the second surface (P2) of
the half sponges (Sa and Sb). In this step, one pressure sensitive
adhesive double coated tape 23 with a large width is adhered over
all the surface of each of the surfaces (P1 and P2).
[0137] In the division step, as shown in FIGS. 6(C) and 6(D), the
half sponges (Sa and Sb) on each of which the pressure sensitive
adhesive double coated tape 23 is adhered is cut together with the
pressure sensitive adhesive double coated tape 23 at positions
corresponding to the valleys 11 with a small thickness (t) and
preferably, at positions corresponding to the lower sides 31 (the
valley bottom portions 11b) along the length direction A. Thereby,
the half sponges (Sa and Sb) is divided into a plurality of noise
dampers 4.
[0138] Herein, in order to obtain two half sponges (Sa and Sb) in
the same profile by the contour forming, it is necessary that in
one wavy element 13 of the wavy curve 14 in the profile of a
trapezoidal wave, a width (Wy) of the upper side 30 is
substantially equal to the sum (Wt+Wt) of widths of the lower sides
31 located on each side of the upper side 30 in the width
direction.
[0139] In order to cut many of noise dampers 4 from one sponge (S)
with the most effectiveness, in a case where thin projections 35
are provided at each end of a noise damper 4, it is preferable that
the sum of the widths thereof (We) is larger than 0 mm and equal to
or less than the width (Wy) of the upper side 30 and more
preferable that the sum of the widths of the thin projections 35
(We) at each end is substantially equal to the width (Wy) of the
upper side 30. It is the most preferable that the widths of the
thin projections 35 (We) at both ends are equal to each other. Such
a noise damper 4 can be obtained by cutting the half sponges (Sa
and Sb) of FIG. 16(C) at middle points of the lower sides 31,
thereby enabling a yield in terms of material to be higher. A noise
damper 4 used in the invention is not limited to such a mode,
however.
[0140] While description was given of the embodiment of the
invention, the embodiment is only an example and needles to say
that the invention can be implemented as modifications or
alterations in various ways.
EXAMPLE A
[0141] With noise dampers of the first embodiment having
specifications shown in Table 1, not only were assemblies of
pneumatic tires (235/45ZR17) and rims (17.times.7.5 JJ) fabricated
as trials, but noise performance and damages when a tire was also
demounted were tested. Pneumatic tires were vulcanization molded
without coating a release agent coated on the inner surface of the
tire. A bladder molding the inner surface of a tire that was used
was without exhaust grooves on the surface. Hence, the inner
surface of a tire was finished as a smooth and flat surface and had
a good adherence to a noise damper.
[0142] Noise dampers were prepared using an ether-based
polyurethane sponge with a specific gravity of 0.016 (manufactured
by Marusuzu K.K. with a product number of E16), a length of which
were all 185 cm and each of which had, as shown in FIG. 2, a taper
cut at an angle of 45 degrees at each end in the tire
circumferential direction. In the examples, the entire volume (V)
of the tire inner space were all 26154 cm.sup.3. In Table 1, and
FIGS. 17(A) to 17(D), there were shown volumes (Vs) of the noise
dampers of the examples and the sectional profiles thereof (a unit
of numerical values used in the figures are a millimeter). A noise
damper and a tire inner surface (a tread inner surface) were
adhered to each other with a pressure sensitive adhesive double
coated tape (manufactured by Nitto Denko K.K. with a product number
5000NS).
[0143] A test method was as follows:
<Noise Performance>
[0144] A tire and a rim was assembled under an inner pressure of
200 kPa and all of the wheels of an automobile (a domestically
manufactured FR car with a piston displacement of 3000 cc) each
were mounted with the assembly. The noise in compartment when the
automobile drove at a speed of 60 km/H on a road noise measuring
road (a rough surface asphalt coated road) with one person on board
was measured at an ear of the person in a driver's seat on the
window side, and a sound pressure level of a peak value at a
frequency in the neighborhood of 230 Hz was shown with an increment
or a decrement above or below a noise in compartment of Comparative
Example 1 (an assembly without a noise damper) as a reference.
<Durability of Noise damper when Tire is Demounted>
[0145] A tire changer (manufactured by EIWA Co. with a model number
of WING320) and a tire lever were used to demount a tire of an
assembly from a rim. Twenty assemblies were prepared and twenty
workers demounted the tires. Evaluation was obtained by comparison
of the number (N1) of assemblies having suffered damage such as a
cut or a tear with the number (N2) of assemblies the noise damper
of each of which was separated from the tire inner surface.
<Cost of Noise Damper>
[0146] A manufacturing cost spent for manufacturing noise dampers
to be used in 100 assemblies was expressed with an index relative
to Comparative Example A2 as 100, wherein a smaller value is
better.
[0147] Note that noise dampers of the Comparative Example A2 were
formed in a way described below. As shown in FIGS. 18(A) and 18(B),
one pressure sensitive adhesive double coated tape 23 was adhered
all over one surface of a flat-plate sponge (S). The sponge was, as
shown in FIGS. 18(C) and 18(D), cut into a plurality of band-like
pieces and taper forming was applied to each end of each band-like
piece to thereby form a noise damper.
[0148] Noise dampers of Comparative Examples A3 were formed in a
way described below. As shown in FIGS. 19(A) and 19(B), a flat-like
sponge (S) is cut into a plurality of band-like pieces. Each
band-like piece is formed so as to have a section shape thereof and
each end thereof with a cutter and thereafter, a pressure sensitive
adhesive double coated tape 28 was adhered to obtain a noise
damper.
TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Example
Comparative Example Example Comparative Example Example Example A1
Example A2 Example A3 A1 Example A4 A2 A3 Example A5 A4 A5
Sectional shape -- FIG. FIG. FIG. 17(C) FIG. 17(A) 17(B) 17(D)
Formation -- FIG. 18 FIG. 19 Profile method (FIG. 9 and FIG. 10)
method Noise damper -- 2268 2344 2334 2020 2065 3322 3771 2334 4668
volume Vs (cm.sup.3) Maximum -- 20 22 22 22 22 22 22 22 22
thickness tm (mm) Minimum -- 20 0 4.0 0.5 1.0 15.0 20.0 4.0 5.0
thickness ti (mm) Width W1 (mm) -- 60 95 95 95 95 95 95 95 190
Ratio (Vs/V) (%) -- 8.7 9.0 8.9 7.7 7.9 12.7 14.4 8.9 17.8
Manufacturing -- 100 520 120 104 106 171 194 110 210 cost (index)
Noise (Reference) -7.8 -8.5 -8.2 -7.6 -7.5 -9.0 -10.7 -8.2 -11.2
performance (quantity of reduction) (dB) Number of -- 6 1 1 1 1 3 6
1 1 damaged noise dampers N1 Number of -- 2 0 0 0 0 1 2 0 0
separated noise dampers N2
EXAMPLE B
[0149] Noise dampers of the second embodiment with specifications
shown in Table 2 were employed and not only were assemblies of
pneumatic tires and rims are manufactured as trials, but a test
similar to that in the Examples A was conducted. Parameters such as
a sectional shape of noise dampers were as shown in Table and FIGS.
20(A) to 20(F) with a unit of millimeter.
[0150] A manufacturing cost spent for a noise damper was expressed
with an index relative to Comparative Example B2 as 100, wherein a
smaller value is better.
[0151] Note that a manufacturing method for noise dampers of
Comparative Examples B2 and B3 is a method in conformity with that
for noise dampers in Comparative Examples A2 and A3.
TABLE-US-00002 TABLE 2 Exam- Exam- Exam- Exam- Comparative
Comparative Comparative ple ple ple ple Example Example Example
Example Example B1 Example B2 Example B3 B1 B2 B3 B4 B5 B6 B7 B8
Sectional shape No data FIG. FIG. FIG. 20(C) FIG. FIG. FIG. 20(A)
20(B) 20(D) 20(E) 20(F) Formation method FIG. 18 FIG. 19 FIG. 16
(contour forming) Noise damper 3969 3969 3969 3374 3440 5292 5954
3969 4158 5292 volume Vs (cm.sup.3) Maximum thickness 30 30 25 25
25 25 25 25 30 25 tm (mm) Minimum thickness -- -- 5 0.5 1 15 20 5
-- 5 ti (mm) Width W1 (mm) 70 90 140 140 140 140 140 140 90 160
Width of hill top 70 50 40 40 40 40 40 40 50 40 portion Wy (mm)
Width of thin -- 0 20 20 20 20 20 20 5 0 projection Wt (mm) Ratio
(Vs/V) (%) 0 15.2 15.2 15.2 12.9 13.2 20.2 22.8 15.2 15.9 20.2
Manufacturing -- 100 500 120 117 118 125 127 120 130 230 cost
(index) Noise performance (Reference) -10.8 -10.7 -10.4 -9.0 -10.1
-11.1 -11.0 -10.3 -10.8 -11.1 (quantity of reduction) (dB) Number
of damaged -- 9 4 2 1 1 3 6 1 3 3 noise dampers N1 Number of -- 3 0
0 0 0 1 2 0 0 0 separated noise dampers N2
[0152] Brief description will be given of the test results.
COMPARATIVE EXAMPLES A2 AND B2
[0153] The noise dampers of Comparative Examples A2 and B2 were
suitable for mass production with a low manufacturing cost. The
noise dampers, however, interfere with a tire lever with ease and a
conventional fault that many of damages and separations occur was
not solved.
COMPARATIVE EXAMPLES A3 AND B3
[0154] The noise dampers of Comparative Examples A3 and B3 can
suppress damages thereon when tires were exchanged. However, since
a thickness (te) of each end of each noise damper was zero, forming
for sectional shape of each band-like piece and adhesion of a
pressure sensitive adhesive double coated tape 28 thereon was
necessary, as shown in FIGS. 19(B) and 19(C), after the sponge is
divided into a plurality of band-like pieces. Hence, a
manufacturing cost for a noise damper is high and the noise damper
is not suitable for mass production. As shown in FIG. 19(C), waste
sponge was large in quantity and a yield was low.
EAXAMPLES A1 TO A6 AND B1 TO B8
[0155] The noise dampers exert excellent noise performance and at
the same time, damages on the silences when tires were exchanged
were able to be suppressed. Besides, the noise dampers are suitable
for mass production and generation of waste material can be
suppressed to thereby enable a manufacturing cost to be suppressed
low.
EXAMPLE C
[0156] Noise dampers with water repellency were manufactured as
trials based on specifications of Table 3 and tests were conducted
on physical properties (a hardness, a tensile strength, an
elongation and water repellency) and productivity when sponges were
produced. The noise dampers were tested in terms of water
absorption using composites each obtained by adhering a noise
damper to a tread inner surface of a pneumatic tire (195/65R15).
Composites in a state of no absorption of water were mounted to
rims (in size of 15.times.6), which were subjected to a test for
noise performance.
[0157] The noise dampers were in the same shape and of the same
size except a material of a sponge and had a rectangular section
with a size of 3.0 cm high, 7.0 cm wide and 185 cm long. Both ends
of each noise damper were taper cut at an angle of 45 degrees.
[0158] In each example, the entire volume (V) of a tire inner space
was 30500 cm.sup.3, a volume (Vs) of a noise damper was 3822
cm.sup.3 and a ratio Vs/V was 12.5%. A noise damper and a tire
inner surface (a tread inner surface) were adhered to each other
with a pressure sensitive adhesive double coated tape (manufactured
by Nitto Denko K.K. with a product number of 5000NS)
[0159] Comparative Examples C1 and C2 used a conventional
ether-based polyurethane sponge without a water repellent
(manufactured by Maru Suzu K.K. with a product number E16) and in
Comparative Example 2, the surface of a noise damper is covered
with a water resistant sheet (a polyethylene film in the
example)
[0160] A test method is as follows:
<Hardness>
[0161] Hardness measured according to Method A (Section 6.3) of
methods for a hardness of Section 6 stipulated in "Testing Method
for Soft Urethane foam" of JIS K6400.
<Elongation>
[0162] Elongation was measured on a test piece in Shape No. 1
according to a measuring method of "Tensile Strength and an
Elongation" of Section 10 in said method.
<Tearing Strength>
[0163] Tearing strength measured according to a measuring method
for "A Tearing Strength" of Section 11 in said method.
<Water Repellency"
[0164] A test piece k of a sponge with a size of 300 mm long, 70 mm
wide and 30 mm high was, as shown in FIG. 21, immersed in a water
bath with a water depth of 150 mm and left at rest for 24 hr,
thereafter an increment in weight was measured and the weight was
compared with an initial weight (corresponding to a weight of a dry
test piece k).
[0165] A case where an increment in weight was less than 100% of
the initial weight was expressed with a symbol of .largecircle. and
a case of 100% or more was expressed with a symbol X.
[0166] A symbol n in the figure indicates a presser plate of a
punched metal with a hole diameter of 5 mm folded in U-shaped in
capital letter and a test piece k is immersed in the water by the
presser plate so that any load is imposed thereon. A symbol p is
weights (about 500 g/one weight) disposed at 4 corners of the
presser plate n to prevent the presser plate from floating on the
surface of water by buoyance.
<Productivity in Formation of Sponge>
[0167] The presence or absence of various problems arising in a
production process such as an agitation step for a mixed
composition and a foam molding step are shown (in a case of the
presence, the problem is described)
<Water Absorption Test>
[0168] Sets of 10 tires to which noise dampers were adhered were
erected and in this state, 3 l of water was poured into a vessel,
in which state the noise dampers are left at rest for 24 hr.
Thereafter, the water was discarded, the water on the tire inner
surface and the surface of a noise damper of each composite was
wiped off with a cloth, increases in weight were measured and the
averages are shown. Even in a case of no noise damper, a tire inner
surface is not perfectly dried; therefore, a weight was usually
increased by 10 g.
[0169] The tires after the water absorption test were mounted to
the right front wheel of an automobile (a domestically manufactured
FF car with a piston displacement of 2000 cc) to a rim (15.times.6
JJ) under an inner pressure of 200 kPa, and the automobile was
driven on a track at a speed of 100 km/h) and the presence or
absence of vibration in the driving was evaluated by sensation of a
driver. Of the ten test tires, there was shown the number of tires
causing vibrations.
<Noise Performance>
[0170] The tires to which dried noise dampers were adhered were
mounted to all the wheel of an automobile (a domestically
manufactured FF car with a piston displacement of 2000 cc) to rims
(15.times.6 JJ) under an inner pressure (2000 kPa) and the noise in
compartment when the automobile drove at a speed of 60 km/H on a
road noise measuring road (a rough surface asphalt coated road)
with a person on board was measured at an ear of the person in a
driver's seat on the window side, and was shown a sound pressure
level of a peak value at a frequency in the neighborhood of 230 Hz
with an increment or a decrement above or below a noise in
compartment of Comparative Example C1 (an assembly without a noise
damper) as a reference.
TABLE-US-00003 TABLE 3 Comparative Comparative Example Example
Example Example Example Example C1 Example C2 C1 C2 C3 C4 C5
Sectional shape rectangle rectangle rectangle rectangle rectangle
rectangle rectangle of noise damper polyisocyanate 57 57 57 57 57
57 57 <*1> Polyol 1 <*2> 100 100 3 58 25 25 25 Polyol 2
<*3> 0 0 97 42 75 75 75 Wafer 0 0 25 80 40 40 40 repellent
<*4> Foaming agent 6.0 6.0 4.5 3.5 4.5 2.8 6.0 (water) (parts
by weight) Others <*5> 1.6 1.6 1.6 1.6 1.6 1.6 1.6 (parts by
weight) Specific gravity 16 16 25 45 23 30 16 (density)
.times.10.sup.-3 Hardness <N> 90 90 100 100 100 100 100
Tensile strength 4 4 5 4 5 5 5 <kPa> Elongation <%> 180
180 180 180 180 180 180 Water repellency X X .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
Productivity good good good good good good good Water absorption
test Absorbed water 360 10-450 30 20 20 20 30 quantity <g>
Automobile 10/10 7/10 0/10 0/10 0/10 0/10 0/10 vibrations Road
noise -10.8 -10.2 -10.7 -11.1 -10.4 -11 -10.1 performance
<dB> Comparative Comparative Comparative Comparative
Comparative Example C3 Example C4 Example C5 Example C6 Example C7
Sectional shape rectangle rectangle rectangle rectangle rectangle
of noise damper polyisocyanate 57 57 57 57 57 <*1> Polyol 1
<*2> 2 65 25 25 25 Polyol 2 <*3> 98 35 75 75 75 Wafer
25 80 90 22 40 repellent <*4> Foaming agent 4.5 4.5 4.5 6.0
1.0 (water) (parts by weight) Others <*5> 1.6 1.6 1.6 1.6 1.6
(parts by weight) Specific gravity 30 35 -- 10 65 (density)
.times.10.sup.-3 Hardness <N> 100 100 -- 90 180 Tensile
strength 4 3 -- 4 5 <kPa> Elongation <%> 180 180 -- 180
180 Water repellency X X -- X .largecircle. Productivity
insufficient insufficient bad good good agitation agitation molding
Water absorption test Absorbed water 320 290 -- 340 20 quantity
<g> Automobile 10/10 10/10 -- 10/10 0/10 vibrations Road
noise -11.1 -11.2 -- -9.7 -5 performance <dB> The <*1>
to <*5> in the table are detailed as followed: <*1> is
polyisocyanate (manufactured by Nihon Urethane K.K. with a trade
name of T-80) <*2> is polyester polyol (manufactured by Sanyo
Kasei K.K. with a trade name of AH-405) <*3> is polyester
polyether copolymer polyol (manufactured by Mitsui Takeda Chemical
K.K. with a trade name of L-50) <*4> is distearyl dimerate
<*5> is a mixture of a catalyst (amine-based
N,N-dimethylaminoethanol (DMAE) 0.3 part by weight metal catalyst
(organic acid metal salt or stannous otoate) 0.3 part by weight a
foam control agent (manufactured by Toray Silicon K.K. with a trade
name of SH-193) 1.0 part by weight
[0171] Since comparative Example C1 is high in water absorption, a
noise damper acts as a large cause for automobile vibrations or the
like when exposed to wafer. Note that in the case of Comparative
example 2, no problem occurs by exposure in a short time of the
order of 1 hr since a silence is covered by a water resistant
sheet, whereas in a case where a noise damper is exposed to water
for a long time, automobile vibrations or the like tends to occur
by water intruded from a pin hole. Especially, in a case where
water intruded through a pin hole, there is available no drying
method for the sponge except for removal of a water resistant sheet
and Comparative Example C2 has, in a practical sense, more
problematical than Comparative Example C1 because of difficulty of
discovery of a pin hole.
[0172] Examples C1 to C5 not only can secure sufficiently physical
properties such as a hardness, a tensile strength and elongation,
but also can exert water repellent performance to reduce water
absorption and to thereby enable automobile vibrations or the like
to be prevented. The examples further can exert an excellent road
noise performance.
[0173] Since in Comparative Example C3, a mixing quantity of
polyester polyol is less than a value in the range of from 3 to 60%
by weight, compatibility between a water repellent and polyester
polyether copolymer polyol worsens, to generate insufficient
agitation, thereby disabling a water repellent to be uniformly
disposed. As a result, it was able to be confirmed that even in a
case where a water repellent is properly mixed, the water repellent
performance cannot be effectively exerted. As in Comparative
Example 4, however, even if a mixing quantity of polyester polyol
exceeds the range of from 3 to 60%, insufficient agitation is
caused to thereby disable water repellent performance to be
effectively exerted, which in turn decreases a tensile strength of
a foam and an elongation, thereby making it difficult to secure a
strength as a noise damper.
[0174] If a mixing quantity of a water repellent exceeds the range
of from 25 to 80 parts by weight as in Comparative Example 5, foam
cannot be produced since a water repellent acts as a plasticizer.
On the contrary, if a mixing quantity of a water repellent is
reduced to a value less than the range of from 25 to 80 parts by
weight, a water repellent performance cannot be effectively
exerted.
[0175] If water as a foaming agent is excessively smaller in
quantity, a specific gravity of a sponge is excessively larger
since no sufficient foaming is achieved, which in turn, not only
reduce road noise performance to a lower level, but also causes
increase in tire weight and deterioration in weight balance to
disadvantage of a tire.
* * * * *