U.S. patent application number 15/781968 was filed with the patent office on 2019-10-03 for pneumatic tire.
This patent application is currently assigned to Sumitomo Rubber Industries, Ltd.. The applicant listed for this patent is Sumitomo Rubber Industries, Ltd.. Invention is credited to Masataka HIRO, Takuya HORIGUCHI, Hiroshi ITO, Fumiya KATO, Takahiro KAWACHI, Takayuki NAGASE, Masako NAKATANI, Subaru TOYA, Ayuko YAMADA.
Application Number | 20190299722 15/781968 |
Document ID | / |
Family ID | 62491475 |
Filed Date | 2019-10-03 |
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United States Patent
Application |
20190299722 |
Kind Code |
A1 |
NAKATANI; Masako ; et
al. |
October 3, 2019 |
PNEUMATIC TIRE
Abstract
A pneumatic tire 1 comprises a carcass 6 extending between bead
cores of bead portions via a tread portion 2 and sidewall portions,
and a belt layer 7 arranged on an outer side in a tire radial
direction of the carcass 6 and inside of the tread portion 2. The
pneumatic tire 1 further comprises a damping rubber body 30
arranged between the carcass 6 and the belt layer 7, and a noise
damper 20 arranged on an inner cavity surface of the tread portion
2. A width W1 in a tire axial direction of the damping rubber body
30 is in a range of from 60% to 130% of a width W2 in the tire
axial direction of the belt layer 7, and a water absorption rate of
the noise damper 20 is in a range of from 10% to 25%.
Inventors: |
NAKATANI; Masako; (Kobe-shi,
JP) ; KAWACHI; Takahiro; (Kobe-shi, JP) ;
YAMADA; Ayuko; (Kobe-shi, JP) ; HORIGUCHI;
Takuya; (Kobe-shi, JP) ; HIRO; Masataka;
(Kobe-shi, JP) ; NAGASE; Takayuki; (Kobe-shi,
JP) ; ITO; Hiroshi; (Kobe-shi, JP) ; KATO;
Fumiya; (Kobe-shi, JP) ; TOYA; Subaru;
(Kobe-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sumitomo Rubber Industries, Ltd. |
Kobe-shi, Hyogo |
|
JP |
|
|
Assignee: |
Sumitomo Rubber Industries,
Ltd.
Kobe-shi, Hyogo
JP
|
Family ID: |
62491475 |
Appl. No.: |
15/781968 |
Filed: |
November 27, 2017 |
PCT Filed: |
November 27, 2017 |
PCT NO: |
PCT/JP2017/042349 |
371 Date: |
June 6, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60C 1/00 20130101; B60C
19/002 20130101; C08L 7/00 20130101; B60C 5/00 20130101; B60C 11/00
20130101; B60C 2009/1878 20130101; B60C 1/0016 20130101; C08L
2205/025 20130101; B60C 9/18 20130101; C08L 2205/035 20130101; B60C
2009/1828 20130101; C08L 9/06 20130101 |
International
Class: |
B60C 19/00 20060101
B60C019/00; B60C 9/18 20060101 B60C009/18; B60C 1/00 20060101
B60C001/00; C08L 9/06 20060101 C08L009/06; C08L 7/00 20060101
C08L007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2016 |
JP |
2016-237853 |
Claims
1. A pneumatic tire comprising a carcass extending between bead
cores of bead portions via a tread portion and sidewall portions, a
belt layer arranged on an outer side in a tire radial direction of
the carcass and inside of the tread portion, and a porous noise
damper arranged on an inner cavity surface of the tread portion,
wherein a water absorption rate of the noise damper is in a range
of from 10% to 25%, the water absorption rate being calculated by a
following formula (1): water absorption rate (%)=weight change
before and after immersion (g)/volume at 50% compression
(cm3).times.100 (1).
2. The pneumatic tire according to claim 1, wherein density of the
noise damper is in a range of from 10 to 40 kg/m3.
3. The pneumatic tire according to claim 1, wherein volume V1 of
the noise damper is in a range of from 0.4% to 30% of total volume
V2 of a tire inner cavity.
4. The pneumatic tire according to claim 1, wherein tensile
strength of the noise damper is in a range of from 70 to 115
kPa.
5. The pneumatic tire according to claim 1, wherein a loss tangent
tan .delta. at 0 degree Celsius of a tread rubber arranged on an
outer side in the tire radial direction of the belt layer is not
less than 0.4 and the loss tangent tan .delta. at 70 degrees
Celsius of the tread rubber is not more than 0.2.
6. The pneumatic tire according to claim 1, wherein a tread rubber
arranged on an outer side in the tire radial direction of the belt
layer is a rubber composition having a value not less than 20, the
value being calculated by a following formula: (1.4.times.carbon
black content (phr)+silica content (phr))/sulfur content (phr).
7. The pneumatic tire according to claim 1 further comprising a
damping rubber body arranged inside of the tread portion.
8. The pneumatic tire according to claim 7, wherein a width W1 in a
tire axial direction of the damping rubber body is in a range of
from 60% to 130% of a width W2 in the tire axial direction of the
belt layer.
9. The pneumatic tire according to claim 7, wherein the damping
rubber body is arranged between the carcass and the belt layer.
10. The pneumatic tire according to claim 7 further comprising a
band layer arranged on an outer side in the tire radial direction
of the belt layer and inside of the tread portion, wherein the
damping rubber body is arranged between the belt layer and the band
layer.
11. The pneumatic tire according to claim 7 further comprising a
band layer arranged on an outer side in the tire radial direction
of the belt layer and inside of the tread portion, wherein the
damping rubber body is arranged on an outer side in the tire radial
direction of the band layer.
12. The pneumatic tire according to claim 7, wherein thickness in
the tire radial direction of the damping rubber body is not less
than 0.3 mm.
13. The pneumatic tire according to claim 7, wherein relationship
between hardness H1 of the damping rubber body and hardness H2 of a
tread rubber arranged on an outer side in the tire radial direction
of the belt layer satisfies a following expression:
0.5.ltoreq.H1/H2.ltoreq.1.0.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pneumatic tire provided
with a noise damper on an inner cavity surface of a tread
portion.
BACKGROUND ART
[0002] Conventionally, as a technique for suppressing running noise
of a pneumatic tire, as disclosed in Patent Literature 1, a
pneumatic tire has been known in which a noise damper made of a
sponge material is arranged on the inner cavity surface of the
tread portion.
PRIOR ART DOCUMENT
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application Publication
No. 2009-292461
[0004] On the other hand, as a repair method when a pneumatic tire
is punctured, a method of sealing the punctured hole by spreading
puncture repair liquid including a puncture sealing agent on the
inner cavity surface is known.
[0005] In the puncture repair using the puncture repair liquid, it
is necessary to spread the puncture repair liquid on the inner
cavity surface of the repair spot where a through hole is formed,
therefore, firstly the pneumatic tire is rotated so that the repair
spot is positioned downward and then the puncture repair liquid is
injected into the pneumatic tire in that state.
[0006] However, when the puncture repair liquid is used for
repairing the puncture of the pneumatic tire provided with the
noise damper as disclosed in Patent Literature 1, the puncture
repair liquid is absorbed in pores of the noise damper. Thereby,
the puncture repair liquid is intensively absorbed by the noise
damper in the repair spot, thus, it is difficult for the puncture
repair liquid to be uniformly distributed in a tire circumferential
direction, therefore, it is possible that force variation, that is,
uniformity of the pneumatic tire after the puncture repair is
affected. The term "uniformity" as used herein refers to the
uniformity of the weight including the tire, the noise damper, and
the puncture repair liquid. If such uniformity is impaired, it is
possible that running noise tends to become large.
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0007] The present invention was made in view of the above, and a
primary object thereof is to provide a pneumatic tire capable of
suppressing influence on the uniformity after puncture repair while
suppressing the running noise.
Means for Solving the Problem
[0008] In one aspect of the present invention, a pneumatic tire
comprises a carcass extending between bead cores of bead portions
via a tread portion and sidewall portions, a belt layer arranged on
an outer side in a tire radial direction of the carcass and inside
of the tread portion, and a porous noise damper arranged on an
inner cavity surface of the tread portion, wherein a water
absorption rate of the noise damper is in a range of from 10% to
25%, the water absorption rate being calculated by a following
formula (1): water absorption rate (%)=weight change before and
after immersion (g)/volume at 50% compression (cm3).times.100
(1).
[0009] In another aspect of the invention, it is preferred that
density of the noise damper is in a range of from 10 to 40
kg/m3.
[0010] In another aspect of the invention, it is preferred that
volume V1 of the noise damper is in a range of from 0.4% to 30% of
total volume V2 of a tire inner cavity.
[0011] In another aspect of the invention, it is preferred that
tensile strength of the noise damper is in a range of from 70 to
115 kPa.
[0012] In another aspect of the invention, it is preferred that a
loss tangent tan .delta. at 0 degree Celsius of a tread rubber
arranged on an outer side in the tire radial direction of the belt
layer is not less than 0.4 and the loss tangent tan .delta. at 70
degrees Celsius of the tread rubber is not more than 0.2.
[0013] In another aspect of the invention, it is preferred that a
tread rubber arranged on an outer side in the tire radial direction
of the belt layer is a rubber composition having a value not less
than 20, the value being calculated by a following formula:
(1.4.times.carbon black content (phr)+silica content (phr))/sulfur
content (phr).
[0014] In another aspect of the invention, it is preferred that the
pneumatic tire according to the invention further comprises a
damping rubber body arranged inside of the tread portion.
[0015] In another aspect of the invention, it is preferred that a
width W1 in a tire axial direction of the damping rubber body is in
a range of from 60% to 130% of a width W2 in the tire axial
direction of the belt layer.
[0016] In another aspect of the invention, it is preferred that the
damping rubber body is arranged between the carcass and the belt
layer.
[0017] In another aspect of the invention, it is preferred that the
pneumatic tire according to the invention further comprises a band
layer arranged on an outer side in the tire radial direction of the
belt layer and inside of the tread portion, and the damping rubber
body is arranged between the belt layer and the band layer.
[0018] In another aspect of the invention, it is preferred that the
pneumatic tire according to the invention further comprises a band
layer arranged on an outer side in the tire radial direction of the
belt layer and inside of the tread portion, and the damping rubber
body is arranged on an outer side in the tire radial direction of
the band layer.
[0019] In another aspect of the invention, it is preferred that
thickness in the tire radial direction of the damping rubber body
is not less than 0.3 mm.
[0020] In another aspect of the invention, it is preferred that
relationship between hardness H1 of the damping rubber body and
hardness H2 of a tread rubber arranged on an outer side in the tire
radial direction of the belt layer satisfies a following
expression: 0.5.ltoreq.H1/H2.ltoreq.1.0.
Advantageous Effects of the Invention
[0021] According to the pneumatic tire of the present invention,
the noise damper is provided on the inner cavity surface of the
tread portion, therefore, cavity resonance in the tire inner cavity
is suppressed, thereby, the running noise of the pneumatic tire is
decreased. In the present invention, the water absorption rate of
the noise damper calculated by the above formula (1) is in a range
of from 10% to 25%, therefore, the absorption of the puncture
repair liquid by the noise damper is suppressed. Thereby, the
puncture repair liquid is likely to be uniformly distributed in the
tire circumferential direction without concentrating on a part of
the noise damper at the repair spot, therefore, it is possible that
the deterioration of the uniformity (that is the uniformity of the
weight including the pneumatic tire, the noise damper, and the
puncture repair liquid) is prevented, thereby, it is possible that
the running noise is effectively prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 a cross-sectional view of a pneumatic tire as an
embodiment of the present invention.
[0023] FIG. 2 a cross-sectional view of the pneumatic tire of FIG.
1 after puncture repair.
[0024] FIG. 3 a cross-sectional view of a pneumatic tire as another
embodiment of the present invention.
[0025] FIG. 4 a cross-sectional view of a pneumatic tire as another
embodiment of the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0026] An embodiment of the present invention will now be described
in detail.
[0027] FIG. 1 is a tire meridian section passing through a tire
rotational axis of a pneumatic tire 1 of the present embodiment in
a standard state. The standard state is a state in which the tire
is mounted on a standard rim, inflated to a standard inner
pressure, and loaded with no tire load. Hereinafter, dimensions and
the like of various parts of the tire are those measured under the
standard state, unless otherwise noted.
[0028] The "standard rim" is a wheel rim specified for the
concerned tire by a standard included in a standardization system
on which the tire is based, for example, the "normal wheel rim" in
JATMA, "Design Rim" in TRA, and "Measuring Rim" in ETRTO.
[0029] The "standard inner pressure" is air pressure specified for
the concerned tire by a standard included in a standardization
system on which the tire is based, for example, the "maximum air
pressure" in JATMA, maximum value listed in the "TIRE LOAD LIMITS
AT VARIOUS COLD INFLATION PRESSURES" table in TRA, and "INFLATION
PRESSURE" in ETRTO. When the tire is for a passenger car, it is set
to 200 kPa uniformly in consideration of the actual use frequency
and the like.
[0030] As shown in FIG. 1, the pneumatic tire (hereinafter may be
simply referred to as "tire") 1 in this embodiment is provided with
a carcass 6 extending between bead cores 5 of bead portions 4 via a
tread portion 2 and sidewall portions 3, and a belt layer 7
arranged on an outer side in a tire radial direction of the carcass
6 and inside the tread portion 2. In this embodiment, a tire for a
passenger car is shown as the tire 1.
[0031] The carcass 6 is formed by a single carcass ply 6A, for
example. The carcass ply 6A includes a main body portion 6a
extending between the bead cores 5 and turned up portions 6b each
being turned up around respective one of the bead cores 5 from
inside to outside in a tire axial direction so as to be engaged
with the respective one of the bead cores 5. In the carcass ply 6A,
organic fiber cords made of an organic material such as aromatic
polyamide and rayon are used as carcass cords, for example. The
carcass cords are arranged at an angle in a range of from 70 to 90
degrees with respect to a tire equator C, for example. The carcass
ply 6A is formed by a plurality of the carcass cords covered with
topping rubber. Between the main body portion 6a and each of the
turned up portions 6b, a bead apex rubber 8 extending radially
outwardly from respective one of the bead cores 5 in a tapered
manner is arranged.
[0032] On an outer side of the carcass 6, a tread rubber Tg for
forming a ground contacting surface, sidewall rubbers sg each for
forming an outer surface of respective one of the sidewall portions
3, bead rubbers Bg each for forming an outer surface of respective
one of the bead portions 4, and the like are arranged. On the other
hand, on an inner side of the carcass 6, an inner liner rubber Lg
for keeping tire inner pressure and the like are arranged.
[0033] The belt layer 7 in this embodiment is formed by two belt
plies 7A and 7B in which belt cords are arranged at an angle in a
range of from 15 to 45 degrees with respect to the tire equator C,
for example, and the belt plies 7A and 7B are overlapped in the
tire radial direction so that the belt cords of the belt ply 7A and
the belt cords of the belt ply 7B cross each other. For the belt
cords, steel, aramid, rayon or the like is suitably used, for
example. By covering a plurality of the belt cords with the topping
rubber, the belt plies 7A and 7B are formed.
[0034] The pneumatic tire 1 in this embodiment is provided with a
band layer 9 arranged on an outer side in the tire radial direction
of the belt layer 7. The band layer 9 includes a band ply 9A in
which band cords of an organic fiber, nylon cords in this
embodiment, are spirally wound at an angle not more than 10
degrees, preferably not more than 5 degrees with respect to the
tire circumferential direction.
[0035] The pneumatic tire 1 is provided with a noise damper 20
arranged on an inner cavity surface of the tread portion 2. The
noise damper 20 is made of a porous sponge material, for example.
The sponge material is a cavernous porous structure body including
not only a so-called sponge itself having interconnected cells
formed by foamed rubber or a synthetic resin but also a web body
formed of an animal fiber, a vegetable fiber, or a synthetic fiber
and the like integrally interwoven, for example. Further, the
"porous structure body" includes not only a body having the
interconnected cells but also a body having closed cells. For the
noise damper 20 in this embodiment, a sponge material made of
polyurethane having interconnected cells is used.
[0036] In the sponge material as described above, the pores on the
surface of or inside the sponge material convert vibration energy
of the vibrating air into thermal energy, therefore, the vibration
energy is consumed, thereby, sound (cavity resonance energy) is
decreased, therefore, the running noise of the pneumatic tire 1 is
decreased. Further, the sponge material is easy to deform such as
contraction, flexion, etc., therefore, deformation of the tire
during running is not substantially affected. Thereby, it is
possible that deterioration of steering stability is prevented.
Moreover, specific gravity of the sponge material is very small,
therefore, it is possible that deterioration of weight balance of
the tire is prevented.
[0037] As the sponge material, synthetic resin sponge such as ether
type polyurethane sponge, ester type polyurethane sponge,
polyethylene sponge, and rubber sponge such as chloroprene rubber
sponge (CR sponge), ethylene propylene rubber sponge (EDPM sponge),
nitrile rubber sponge (NBR sponge) can be preferably and suitably
used, and in particular, a polyurethane type or polyethylene type
sponge including an ether type polyurethane sponge is preferred
from the point of view of noise damping property, lightweight
property, controllability of foaming, durability, and the like.
[0038] The noise damper 20 has an elongated belt-like shape having
a bottom surface fixed to the inner cavity surface of the tread
portion 2 and extends in the tire circumferential direction. At
this time, outer end portions in the circumferential direction of
the noise damper may be in contact with each other to form a
substantially annular shape, or the outer end portions may be
spaced apart in the tire circumferential direction.
[0039] The noise damper 20 has substantially the same
cross-sectional shape at an arbitrary position in the tire
circumferential direction except for the outer end portions. In
order to prevent collapse and deformation during running, it is
preferred that the cross-sectional shape is a flat and horizontally
elongated shape in which a height is smaller than a width in the
tire axial direction. In particular, as in this embodiment, it is
preferred to have a concave groove 21 extending continuously in the
tire circumferential direction on a side of the radially inner
surface. The concave groove 21 increases a surface area of the
noise damper 20, therefore, it is possible that more resonance
energy is absorbed, and heat dissipation is increased, therefore,
it is possible that the temperature rise of the sponge material is
suppressed.
[0040] FIG. 2 is the pneumatic tire 1 after puncture repair by
using a puncture repair liquid. A through hole 40 formed in the
tread portion 2 by running over a nail and the like is filled with
puncture repair liquid 41, therefore, the through hole 40 is
sealed.
[0041] A water absorption rate of the noise damper 20 is in a range
of from 10% to 25%. Here, the water absorption rate of the noise
damper 20 is calculated by the following formula (1).
Water absorption rate (%)=Weight change before and after immersion
(g)/Volume at 50% compression (cm3).times.100 (1)
[0042] In this embodiment, for measuring the weight change before
and after immersion of the noise damper 20, a test piece having a
length of 50 mm, a width of 50 mm, and a thickness of 20 mm is
used. After measuring the weight before immersion, the test piece
was compressed by 50% in the thickness direction, then the weight
was measured after immersion in water at a temperature of 20
degrees Celsius and at water depth of 10 cm for 24 hours. Since the
volume at 50% compression can be calculated from the above
dimensions of the test piece, the water absorption rate (%) is
calculated from the measured weight by the above formula (1). Note
that the volume of the test piece described above is an apparent
volume similarly to a volume V1 described later.
[0043] In the calculation of the water absorption rate, the test
piece whose weight or the like is to be measured is not limited to
the test piece having the above dimensions. For example, the
dimensions of the test piece can be appropriately changed according
to the size, shape, etc. of the noise damper 20.
[0044] According to the pneumatic tire of the present invention,
the noise damper 20 is disposed on the inner cavity surface of the
tread portion 2, therefore, the cavity resonance in a tire inner
cavity is suppressed, thereby, the running noise of the pneumatic
tire 1 is reduced. In the present invention, the water absorption
rate of the noise damper 20 calculated by the above formula (1) is
not less than 10%. The noise damper 20 configured as such absorbs
more resonance energy by the cells connected with the surface of
the noise damper 20, therefore, large effect of suppressing the
cavity resonance is exerted.
[0045] Further, in the present invention, the water absorption rate
of the noise damper 20 calculated by the above formula (1) is not
more than 25%. By the noise damper 20 configured as such, local
absorption of the puncture repair liquid 41 is suppressed. Thereby,
by the rotation of the tire during running, the puncture repair
liquid 41 is likely to be uniformly distributed over the entire
circumference in the tire circumferential direction without
concentrating on a part of the noise damper 20 at the repair spot.
Thereby, the influence on the force variation after puncture repair
is suppressed, therefore, it is possible that deterioration of the
uniformity of the pneumatic tire 1 is suppressed. The term
"uniformity" as used herein refers to the uniformity of the weight
including the pneumatic tire 1, the noise damper 20, and the
puncture repair liquid 41. If such uniformity is impaired, it is
possible that the running noise tends to be large.
[0046] On the other hand, in the present invention, the upper limit
of the water absorption rate of the noise damper 20 is set as
described above, therefore, it is possible that the suppression
effect of the cavity resonance is small as compared with a
pneumatic tire in which a noise damper having a higher water
absorption rate is arranged.
[0047] Therefore, in this embodiment, it is preferred that a
damping rubber body 30 is disposed inside the tread portion 2. The
damping rubber body 30 is arranged between the carcass 6 and the
belt layer 7. A width W1 in the tire axial direction of the damping
rubber body 30 is in a range of from 60% to 130% of a width W2 in
the tire axial direction of the belt layer. The damping rubber body
30 configured as such suppresses the vibration of the tread portion
2 without contributing to the weight increase of the pneumatic tire
1, and in particular contributes to the reduction of the running
noise around 160 Hz. Thereby, it is possible that the deterioration
of the uniformity of the pneumatic tire 1 after puncture repair is
suppressed while effectively suppressing the running noise.
[0048] Further, the absorption of the puncture repair liquid 41 is
suppressed by the noise damper 20 having the water absorption rate
calculated by the above formula (1) is not more than 25%,
therefore, it is possible that a small amount of the puncture
repair liquid 41 is required for puncture repair of the pneumatic
tire 1.
[0049] The damping rubber body 30 is formed of a rubber different
from the topping rubber included in the carcass ply 6A and the belt
ply 7A. In a more preferred embodiment, the width W1 of the damping
rubber body 30 is in a range of from 70% to 120% of the width W2 of
the belt layer 7.
[0050] In this embodiment, the water absorption rate of the noise
damper 20 is limited as described above, therefore, it is possible
that the effect of suppressing the cavity resonance is small as
compared with a pneumatic tire provided with the noise damper
having a higher water absorption rate. However, in this embodiment,
the damping rubber body 30 described above is disposed between the
carcass 6 and the belt layer 7, therefore, the running noise is
effectively suppressed. Therefore, according to the pneumatic tire
1, it is possible that the deterioration of the uniformity of a
pneumatic tire after puncture repair is suppressed while
suppressing the running noise.
[0051] It is preferred that a thickness T1 in the tire radial
direction of the damping rubber body 30 is not less than 0.3 mm. By
setting the thickness T1 to not less than 0.3 mm, the vibration of
the tread portion 2 is more effectively suppressed. Further, by
setting a maximum thickness in the tire radial direction of the
damping rubber body 30 in a range of from 4% to 20% of a maximum
thickness of the tread portion 2, it is possible that the
suppression of the running noise of the pneumatic tire 1 and the
steering stability are obtained easily.
[0052] It is preferred that the relationship between hardness H1 of
the damping rubber body 30 and hardness H2 of the tread rubber Tg
disposed on an outer side in the tire radial direction of the belt
layer 7 is 0.5.ltoreq.H1/H2.ltoreq.1.0. Here, "rubber hardness" is
defined as rubber hardness measured in accordance with Japanese
Industrial Standard JIS-K 6253 by a type-A durometer under an
environment of 23 degrees Celsius. By the damping rubber body 30
having the hardness H1 described above, the vibration of the tread
portion 2 is more effectively suppressed while ensuring the
durability of the tread portion 2.
[0053] It is preferred that relationship between the hardness H1 of
the damping rubber body 30 and hardness H3 of the topping rubber
included in the carcass ply 6A and the belt ply 7A is
0.4.ltoreq.H1/H3.ltoreq.1.2. By the damping rubber body 30 of the
hardness H1, vibration of the tread portion 2 is more effectively
suppressed while securing the durability of the tread portion
2.
[0054] More specifically, it is preferred that the hardness H1 of
the damping rubber body 30 is in a range of from 30 to 73 degrees.
With the damping rubber body 30 of hardness H1 configured as such,
it is possible that the running noise is easily suppressed and the
steering stability is improved while suppressing manufacturing cost
of the pneumatic tire 1. Further, more specifically, it is
preferred that the hardness H2 of the tread rubber Tg is in a range
of from 55 to 75 degrees. By the tread rubber Tg of the hardness H2
configured as such, the rigidity of the tread portion 2 is
optimized, therefore, it is possible that the steering stability is
improved.
[0055] It is preferred that density of the noise damper 20 is in a
range of from 10 to 40 kg/m3. By the noise damper 20 having the
density not less than 10 kg/m3, it is possible that deterioration
of the uniformity of the pneumatic tire 1 after puncture repair is
suppressed. By the noise damper 20 having the density not more than
40 kg/m3, it is possible that the running noise in the vicinity of
250 Hz in particular is decreased without increasing the weight of
the pneumatic tire 1.
[0056] It is preferred that the volume V1 of the noise damper 20 is
in a range of from 0.4% to 30% of total volume V2 of the tire inner
cavity. The volume V1 of the noise damper 20 is apparent total
volume of the noise damper 20, which means the volume determined
from the outer shape including the inner cells. The total volume V2
of the tire inner cavity is to be approximately determined by the
following formula with respect to a pneumatic tire in the standard
state in which the pneumatic tire is mounted on a standard rim,
inflated to the standard inner pressure, and loaded with no tire
load.
V2=A.times.{(Di-Dr)/2+Dr}.times.n
In the above formula, "A" is a cross sectional area of the tire
inner cavity obtained by CT scanning a tire/rim assembly in the
standard state, "Di" is a maximum outer diameter of the inner
cavity surface of the tire in the standard state, "Dr" is a
diameter of the rim, and "n" is the circumference ratio.
[0057] If the volume V1 is less than 0.4% of the total volume V2,
it is possible that the vibration energy of the air is not
sufficiently converted. If the volume V1 is more than 30% of the
total volume v2, it is possible that the weight and manufacturing
cost of the pneumatic tire 1 increases, and that the uniformity of
the pneumatic tire 1 after the puncture repair deteriorates.
[0058] It is preferred that tensile strength of the noise damper 20
is in a range of from 70 to 115 kPa. If the tensile strength of the
noise damper 20 is less than 70 kPa, it is possible that the
durability of the noise damper 20 deteriorates. If the tensile
strength of the noise damper 20 is more than 115 kPa, when a
foreign object such as a nail sticks into the region including the
noise damper 20 of the tread portion 2, the noise damper 20 may be
pulled by the foreign object, therefore, it is possible that the
noise damper 20 comes off the inner cavity surface of the tread
portion 2.
[0059] It is preferred that a loss tangent tan .delta. at 0 degree
Celsius of the tread rubber Tg is not less than 0.4. Thereby, wet
grip performance of the pneumatic tire 1 is improved. Therefore, by
setting the volume of the grooves formed in the ground contacting
surface of the tread portion 2 to be small and the like, it is
possible to further reduce the running noise, for example. It is
preferred that the loss tangent tan .delta. at 70 degrees Celsius
of the tread rubber Tg is not more than 0.2. Thereby, rolling
resistance of the pneumatic tire 1 is suppressed and deterioration
of the fuel efficiency due to inclusion of the noise damper 20 and
the damping rubber body 30 is suppressed. Note that the loss
tangent tan .delta. at 0 degrees Celsius and the loss tangent tan
.delta. at 70 degrees Celsius were measured in accordance with
Japanese Industrial Standard JIS-K 6394 by using a viscoelasticity
spectrometer available from Iwamoto Quartz GlassLab Co., Ltd. under
a condition of respective temperature (0 degrees Celsius or 70
degrees Celsius), a frequency of 10 Hz, an initial tensile strain
of 10%, and an amplitude of dynamic strain of .+-.2%.
[0060] It is preferred that a value calculated by a following
formula: (1.4.times.carbon black content (phr)+silica content
(phr))/sulfur content (phr) of the tread rubber Tg, is not less
than 20. Thereby, anti-wear performance is improved. Therefore, by
setting depths of the grooves formed in the ground contacting
surface of the tread portion 2 to be small and the like, it is
possible that the running noise is further decreased, for example.
Further, even when distribution of the puncture repair liquid is
not uniform, occurrence of uneven wear is suppressed.
[0061] While detailed description has been made of the pneumatic
tire of the present invention, the present invention can be
embodied in various forms without being limited to the illustrated
embodiment.
[0062] FIG. 3 shows a pneumatic tire 1A as another embodiment of
the present invention, for example. The pneumatic tire 1A is
different from the pneumatic tire 1 in that the damping rubber body
30 is disposed between the belt layer 7 and the band layer 9. The
configuration of the pneumatic tire 1 can be applied to the
components of the pneumatic tire 1A that are not described below.
In the pneumatic tire 1A, the vibration of the belt layer 7 and the
band layer 9 is suppressed by the damping rubber body 30,
therefore, the vibration of the tread portion 2 is suppressed
eventually.
[0063] FIG. 4 shows a pneumatic tire 1B as yet another embodiment
of the present invention. The pneumatic tire 1B is different from
the pneumatic tire 1 in that the damping rubber body 30 is arranged
on an outer side in the tire radial direction of the band layer 9.
The configuration of the pneumatic tire 1 can be applied to the
components of the pneumatic tire 1B that are not described below.
In the pneumatic tire 1B, the vibration of the band layer 9 and the
tread rubber Tg is suppressed by the damping rubber body 30,
therefore, the vibration of the tread portion 2 is suppressed
eventually.
WORKING EXAMPLES (EXAMPLES)
[0064] Pneumatic tires of size 165/65R18 having the basic structure
shown in FIG. 1 were made by way of test according to the
specification listed in Table 1, then the test tires were tested
for uniformity performance and noise performance after puncture
repair. The specifications common to each of the Examples and the
References were as follows.
(1) Tread Rubber
[0065] The formulations were as follows.
[0066] Natural rubber (TSR20): 15 (phr)
[0067] SBR 1 (bound styrene content: 28%, vinyl group content: 60%,
glass transition point: -25 degrees Celsius, terminal modified): 45
(phr)
[0068] SBR 2 (bound styrene content: 35%, vinyl group content: 45%,
glass transition point: -25 degrees Celsius, terminal modified): 25
(phr)
[0069] BR (BR150B available from Ube Industries, Ltd.): 15
(phr)
[0070] Carbon black N220: 5 (phr)
[0071] Silica (VN3): 35 (phr)
[0072] Silica (1115MP): 20 (phr)
[0073] Silane coupling agent Si266: 4 (phr)
[0074] Resin (SYLVARES SA85 available from Arizona Chemical
Company): 8 (phr)
[0075] Oil: 4 (phr)
[0076] Wax: 1.5 (phr)
[0077] Age resistor (6C): 3 (phr)
[0078] Stearic acid: 3 (phr)
[0079] Zinc oxide: 2 (phr)
[0080] Sulfur: 2 (phr)
[0081] Vulcanization accelerator (NS): 2 (phr)
[0082] Vulcanization accelerator (DPG): 2 (phr)
[0083] The hardness of the tread rubber of the vulcanized tire was
64 degrees.
[0084] The maximum thickness of the tread rubber was 10 mm.
(2) Damping Rubber Body
[0085] The formulations were as follows.
[0086] Natural rubber (TSR20): 65 (phr)
[0087] SBR (Nipol 1502): 35 (phr)
[0088] Carbon black N220: 52 (phr)
[0089] Oil: 15 (phr)
[0090] Stearic acid: 1.5 (phr)
[0091] Zinc oxide: 2 (phr)
[0092] Sulfur: 3 (phr)
[0093] Vulcanization accelerator (CZ): 1 (phr)
[0094] The hardness of the damping rubber body of the vulcanized
tire was 58 degrees.
[0095] The maximum thickness of the damping rubber body was 1
mm.
(3) Noise Damper
[0096] The volume was 15% of the total volume of the tire inner
cavity.
[0097] The density was 27 kg/m3.
(4) Belt Cords
[0098] The angle of the belt cords with respect to the tire equator
was 41 degrees.
[0099] The test methods were as follows.
<Uniformity Performance>
[0100] Each of the test tires was mounted on a rim of 18.times.733
and injected with puncture repair material simulating puncture
repair, and then radial force variation (RFV) was measured under
the condition of the inner pressure of 320 kPa in accordance with
uniformity test condition of Japanese Automobile Standards
Organization JASO C607:2000. The evaluation speed was 10 km/h. The
results are indicated by an index based on Example 1 being 100,
wherein the larger the numerical value, the smaller the RFV is,
which is better.
<Noise Performance>
[0101] Each of the test tires was mounted on a rim of 18.times.733
and mounted on all wheels of a test car (domestically produced FR
car with displacement of 2500 cc) under the condition of the inner
pressure of 320 kPa. A total sound pressure (decibel) of
frequencies in a range of from 100 to 200 Hz and in a range of from
200 to 300 Hz was measured by using a sound concentrating
microphone attached to the center part of the backrest of the
driver's seat while the test car was driven on a road for measuring
road noise (rough asphalt surface road) at a speed of 60 km/h. The
results are indicated by an index based on Example 1 being 100,
wherein the larger the numerical value, the smaller the running
noise is, which is better.
TABLE-US-00001 TABLE 1 Ref. 1 Ref. 2 Ref. 3 Ex. 1 Ex. 2 Presence or
Absence of Noise damper absence presence presence presence presence
Water absorption rate of Noise damper [%] -- 5 40 10 25 Presence or
Absence of Damping rubber body absence absence absence absence
absence Uniformity performance [index] 100 100 80 100 95 Noise
performance [index] 80 85 105 100 105
[0102] As is clear from Table 1, it was confirmed that the
uniformity performance and the noise performance of the pneumatic
tires as Examples 1 and 2 were significantly improved in a good
balance as compared with References 1 to 3.
[0103] Further, as shown in Table 2, pneumatic tires as Examples 3
to 6 were made by way of test, and then the uniformity performance
and the noise performance were tested. The test methods were as
follows.
<Uniformity Performance>
[0104] The radial force variation (RFV) was measured by the same
method as described above. The results are indicated by an index
based on Example 3 being 100, wherein the larger the numerical
value, the smaller the RFV is, which is better.
<Noise Performance>
[0105] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 3 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
TABLE-US-00002 TABLE 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Presence or Absence
of Noise damper presence presence presence presence Water
absorption rate of Noise damper [%] 20 20 20 20 Presence or Absence
of Damping rubber body presence presence presence presence Width W1
of Damping rubber body/Width W2 of Belt layer [%] 100 60 70 130
Uniformity performance [index] 100 100 100 100 Noise performance
[index] 100 95 98 105
[0106] Further, as shown in Table 3, pneumatic tires as Examples 7
to 10 were made by way of test, and then the noise performance and
the steering stability were tested. The test methods were as
follows.
<Noise Performance>
[0107] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 9 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
<Steering Stability>
[0108] While the test car used in the test of the noise performance
was driven on a dry asphalt test course, characteristics related to
steering response, rigid impression, grip, and the like were
evaluated by the driver's feeling. The results are indicated by an
evaluation point based on Example 9 being 100, wherein a larger
numerical value is better.
TABLE-US-00003 TABLE 3 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Presence or Absence
of Noise damper presence presence presence presence Water
absorption rate of Noise damper [%] 20 20 20 20 Presence or Absence
of Damping rubber body presence presence presence presence Width W1
of Damping rubber body/Width W2 of Belt layer [%] 100 100 100 100
Thickness T1 of Damping rubber body [mm] 0.2 0.3 0.5 0.7 Noise
performance [index] 98 99 100 103 Steering stability [index] 100
100 100 98
[0109] Furthermore, as shown in Table 4, pneumatic tires as
Examples 11 to 15 having the damping rubber body of different
rigidity were made by way of test, and then the noise performance
was tested and manufacturing cost was calculated. The test method
and the calculation method were as follows.
<Noise Performance>
[0110] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 13 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
<Manufacturing Cost>
[0111] Manufacturing cost required to manufacture a single tire was
calculated. The results are indicated by an index based on Example
13 being 100, wherein the larger the numerical value, the smaller
the manufacturing cost is, which is better.
TABLE-US-00004 TABLE 4 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Presence
or Absence of Noise damper presence presence presence presence
presence Water absorption rate of Noise damper [%] 20 20 20 20 20
Presence or Absence of Damping rubber body presence presence
presence presence presence Width W1 of Damping rubber body/Width W2
of 100 100 100 100 100 Belt layer [%] Hardness H1 of Damping rubber
body/Hardness H2 of 0.4 0.5 0.7 1.0 1.2 Tread rubber Noise
performance [index] 96 98 100 102 102 Manufacturing cost [index]
102 102 100 98 96
[0112] Furthermore, as shown in Table 5, pneumatic tires as
Examples 16 to 20 were made by way of test, and then the uniformity
performance and the noise performance after puncture repair were
tested. The test methods were as follows.
<Uniformity Performance>
[0113] The RFV was measured by the same method as described above.
The results are indicated by an index based on Example 18 being
100, wherein the larger the numerical value, the smaller the RFV
is, which is better.
<Noise Performance>
[0114] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 18 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
TABLE-US-00005 TABLE 5 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Presence
or Absence of Noise damper presence presence presence presence
presence Water absorption rate of Noise damper [%] 20 20 20 20 20
Presence or Absence of Damping rubber body presence presence
presence presence presence Width W1 of Damping rubber body/Width W2
of 100 100 100 100 100 Belt layer [%] Density of Noise damper
[kg/m3] 5 10 27 40 50 Uniformity performance [index] 95 97 100 103
103 Noise performance [index] 103 103 100 97 95
[0115] Furthermore, as shown in Table 6, pneumatic tires as
Examples 21 to 25 were made by way of test, and then the uniformity
performance and the noise performance were tested. The test methods
were as follows.
<Uniformity Performance>
[0116] The RFV was measured by the same method as described above.
The results are indicated by an index based on Example 23 being
100, wherein the larger the numerical value, the smaller the RFV
is, which is better.
<Noise Performance>
[0117] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 23 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
TABLE-US-00006 TABLE 6 Ex. 21 Ex. 22 Ex. 23 Ex. 24 Ex. 25 Presence
or Absence of Noise damper presence presence presence presence
presence Water absorption rate of Noise damper [%] 20 20 20 20 20
Presence or Absence of Damping rubber body presence presence
presence presence presence Width W1 of Damping rubber body/Width W2
of 100 100 100 100 100 Belt layer [%] Volume V1 of Noise
damper/Total volume V2 0.3 0.4 15.0 30.0 35.0 of Tire inner cavity
[%] Uniformity performance [index] 103 103 100 97 95 Noise
performance [index] 95 97 100 103 103
[0118] Furthermore, as shown in Table 7, pneumatic tires as
Examples 26 to 31 were made by way of test, and then the durability
of the noise damper and separation resistance performance of the
noise damper when a nail sticks into the tire were tested. The test
methods were as follows.
<Durability of Noise Damper>
[0119] Each of the test tires was mounted on a rim of 18.times.7.17
and then, by using a drum testing machine, a distance until the
noise damper and its vicinity were damaged was measured under the
conditions of the inner pressure of 320 kPa, the tire load of 4.8
kN, and the speed of 80 km/h. The results are indicated by an index
based on Example 28 being 100, wherein the larger the numerical
value, the higher the durability is, which is better.
<Separation Resistance Performance of Noise Damper when Nail
Sticks>
[0120] Each of the test tires was mounted on a rim of 18.times.6.53
and punctured by rolling on a nail, then the damaged part was
disassembled to measure the area of separation of the noise damper
from the inner cavity surface of the tread portion due to the noise
damper being pulled by the nail. The results are indicated by an
index based on Example 28 being 100, wherein the larger the
numerical value, the higher the separation resistance performance
is, which is better.
TABLE-US-00007 TABLE 7 Ex. 26 Ex. 27 Ex. 28 Ex. 30 Ex. 31 Presence
or Absence of Noise damper presence presence presence presence
presence Water absorption rate of Noise damper [%] 20 20 20 20 20
Presence or Absence of Damping rubber body presence presence
presence presence presence Width W1 of Damping rubber body/Width W2
of 100 100 100 100 100 Belt layer [%] Tensile strength of Noise
damper [kPa] 60 70 90 115 125 Durability of Noise damper [index] 95
97 100 103 103 Separation resistance performance of Noise damper
103 103 100 97 95 when Nail sticks [index]
[0121] Furthermore, as shown in Table 8, pneumatic tires as
Examples 32 and 33 were made by way of test, and then the
uniformity performance and the noise performance after puncture
repair were tested. The test methods were as follows.
<Uniformity Performance>
[0122] The radial force variation (RFV) was measured by the same
method as described above. The results are indicated by an index
based on Example 1 being 100, wherein the larger the numerical
value, the smaller the RFV is, which is better.
<Noise Performance>
[0123] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 1 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
TABLE-US-00008 TABLE 8 Ex. 32 Ex. 33 Presence or Absence of Noise
damper presence presence Water absorption rate of Noise damper [%]
10 25 Presence or Absence of Damping presence presence rubber body
Width W1 of Damping rubber body/ [%] 100 100 Width W2 of Belt layer
Uniformity performance [index] 100 95 Noise performance [index] 106
111
[0124] Furthermore, as shown in Table 9, pneumatic tires as
Examples 34 to 38 were made by way of test, and then the uniformity
performance and the noise performance after puncture repair were
tested. The test methods were as follows.
<Uniformity Performance>
[0125] The radial force variation (RFV) was measured by the same
method as described above. The results are indicated by an index
based on Example 18 being 100, wherein the larger the numerical
value, the smaller the RFV is, which is better.
<Noise Performance>
[0126] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 18 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
TABLE-US-00009 TABLE 9 Ex. 34 Ex. 35 Ex. 36 Ex. 37 Ex. 38 Presence
or Absence of Noise damper presence presence presence presence
presence Water absorption rate of Noise damper [%] 20 20 20 20 20
Presence or Absence of Damping rubber body absence absence absence
absence absence Density of Noise damper [kg/m3] 5 10 27 40 50
Uniformity performance [index] 95 97 100 103 103 Noise performance
[index] 97 97 94 91 88
[0127] Furthermore, as shown in Table 10, pneumatic tires as
Examples 39 to 43 were made by way of test, and then the uniformity
performance and the noise performance after puncture repair were
tested. The test methods were as follows.
<Uniformity Performance>
[0128] The radial force variation (RFV) was measured by the same
method as described above. The results are indicated by an index
based on Example 23 being 100, wherein the larger the numerical
value, the smaller the RFV is, which is better.
<Noise Performance>
[0129] The in-car noise was measured by the same method as
described above. The results are indicated by an index based on
Example 23 being 100, wherein the larger the numerical value, the
smaller the running noise is, which is better.
TABLE-US-00010 TABLE 10 Ex. 39 Ex. 40 Ex. 41 Ex. 42 Ex. 43 Presence
or Absence of Noise damper presence presence presence presence
presence Water absorption rate of Noise damper [%] 20 20 20 20 20
Presence or Absence of Damping rubber body absence absence absence
absence absence Volume V1 of Noise damper/Total volume V2 0.3 0.4
15.0 30.0 35.0 of Tire inner cavity [%] Uniformity performance
[index] 103 103 100 97 95 Noise performance [index] 89 91 94 98
98
DESCRIPTION OF THE REFERENCE SIGNS
[0130] 1 pneumatic tire [0131] 2 tread portion [0132] 3 sidewall
portion [0133] 4 bead portion [0134] 5 bead core [0135] 6 carcass
[0136] 20 noise damper [0137] 30 damping rubber body
* * * * *