U.S. patent application number 11/655846 was filed with the patent office on 2007-05-24 for pneumatic tire.
Invention is credited to Minoru Nishi, Kazuki Numata, Kiyoshi Ueyoko.
Application Number | 20070113944 11/655846 |
Document ID | / |
Family ID | 27345691 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070113944 |
Kind Code |
A1 |
Ueyoko; Kiyoshi ; et
al. |
May 24, 2007 |
Pneumatic tire
Abstract
A pneumatic tire comprises a tread portion, a pair of sidewall
portions, a pair of bead portions, a bead core disposed in each
bead portion, a carcass comprising a ply of carcass cords extending
between the bead portions through the tread portion and sidewall
portions and turned up around the bead core in each bead portion,
and an inner liner made of air-impermeable rubber extending on the
tire cavity side of the carcass from one of the bead portions to
the other. The radially inner end of the inner liner is located
radially inside the radially innermost end of the carcass. In a
radial region between the radially innermost end of the carcass and
the radially outermost end of the bead core, the thickness of the
inner liner is not less than 0.15 time but not more than 4.0 times
the cross section diameter of the carcass cord.
Inventors: |
Ueyoko; Kiyoshi; (Kobe-shi,
JP) ; Nishi; Minoru; (Kobe-shi, JP) ; Numata;
Kazuki; (Kobe-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
27345691 |
Appl. No.: |
11/655846 |
Filed: |
January 22, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10250365 |
Dec 23, 2003 |
7172002 |
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PCT/JP02/00120 |
Jan 11, 2002 |
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11655846 |
Jan 22, 2007 |
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Current U.S.
Class: |
152/510 ;
152/543; 152/547 |
Current CPC
Class: |
B60C 2015/0614 20130101;
B60C 15/0027 20130101; B60C 5/142 20130101; B60C 2200/06 20130101;
B60C 15/06 20130101; Y10T 152/10846 20150115; B60C 5/14 20130101;
B60C 15/0607 20130101; Y10T 152/10828 20150115 |
Class at
Publication: |
152/510 ;
152/543; 152/547 |
International
Class: |
B60C 15/06 20060101
B60C015/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 2001 |
JP |
2001-3931 |
Feb 20, 2001 |
JP |
2001-43761 |
Mar 26, 2001 |
JP |
2001-88169 |
Claims
1. A pneumatic tire comprising: a tread portion, a pair of sidewall
portions, a pair of bead portions, a bead core disposed in each
said bead portion, a carcass comprising a ply of cords extending
between the bead portions through the tread portion and sidewall
portions and turned up around the bead core in each said bead
portion and an inner liner made of an air-impermeable rubber
extending on the tire cavity side of the carcass from one of the
bead portions to the other, wherein the radially inner end of the
inner liner is located radially inside the radially innermost end
of the carcass, and in a radial region defined between the radially
innermost end of the carcass and the radially outermost end of the
bead core, the thickness of the inner liner is not less than 0.15
time but not more than 4.0 times the cross section diameter of the
carcass cord.
2. The pneumatic tire according to claim 1, wherein the bead
portion is provided with a chafer made of a rubber having a 100%
modulus (M100) of from 440 to 830 N/sq.cm disposed along the bottom
surface and axially outer surface of the bead portion, and a
minimum rubber thickness of the chafer, which is defined as the
shortest distance from the bottom surface of the bead portion to
cords of an adjacent cord layer, is not less than 1.7 times but not
more than 6.0 times the cross section diameter of the carcass
cord.
3. The pneumatic tire according to claim 1 or 2, wherein in the
bead portion, an intersecting angle .alpha. between the bead bottom
surface and the tire inner surface at a bead toe (t) is set to be
not less than 38 degrees but not more than 90 degrees.
4. The pneumatic tire according to claim 1, wherein the radially
inner end of the inner liner is located in a region defined between
two radial lines, a radial line passing through the middle point in
the axial direction between the axially innermost point and axially
outermost point of the bead core, and a radial line passing through
the axially innermost point of the bead core, and a thickness of
the inner liner is in a range of from 0.5 to 2.0 mm when measured
along a straight line extending through the axially innermost point
and axially outermost point of the bead core.
5. The pneumatic tire according to claim 4, wherein the bead
portion is provided along the bottom surface, axially outer surface
and axially inner surface thereof with a chafer made of a rubber
having a 100% modulus (M100) of from 440 to 830 N/sq.cm, and the
radial distance between the radially outermost point of the bead
core and the radially outer end of a portion of the chafer which
portion extends upward along the axially inner surface of the bead
portion, is not more than 5 mm.
6. The pneumatic tire according to claim 1, wherein the bead
portion is provided at least on the axially inside of the bead core
with an insulation, and the insulation is disposed between the
inner liner and a rubber layer including a layer of topping rubber
for cords adjacent to the inner liner and made of a rubber having
an excellent adhesive property with the rubber layer and inner
liner.
7. The pneumatic tire according to claim 1, wherein in each said
bead portion, the carcass ply is turned up around the bead core
from the axially inside to the axially outside of the tire to form
a pair of turnup portions and a main portion therebetween, each
said turnup portion is wound substantially once around the bead
core to have a wound portion extending axially inwardly along the
radially outer surface of the bead core, a bead apex made of a hard
rubber is disposed on the radially outside of the wound portion so
as to secure the wound portion between the bead apex and bead core,
and the wound portion is bent before the carcass ply main portion
and then terminated after extending along the axially outside of
the carcass ply main portion for a small distance so that the bent
part is secured between the carcass ply main portion and the bead
apex.
8. The pneumatic tire according to claim 7, wherein the bent part
extends radially outwardly up to a point radially inwards of the
radially outer end of a flange of a wheel rim on which the tire is
mounted.
9. The pneumatic tire according to claim 1, wherein in each said
bead portion, a bead apex made of a hard rubber is disposed on the
radially outside of the bead core, and the carcass ply is turned up
around the bead core from the axially inside to the axially outside
of the tire to form a pair of turnup portions and a main portion
therebetween, each said turnup portion extends radially outwardly
along the axially outer surface of the bead apex, and each said
bead portion is provided along the carcass with a reinforcing layer
comprising a base portion beneath the bead core, an axially inner
portion extending radially outwardly from the base portion along
the carcass-ply main portion, and an axially outer portion
extending radially outwardly from the base portion along the
carcass-ply turnup portion.
10. The pneumatic tire according to claim 1, wherein in each said
bead portion, a bead apex made of a hard rubber is disposed on the
radially outside of the bead core, and the carcass ply is turned up
around the bead core from the axially inside to the axially outside
of the tire to form a pair of turnup portions and a main portion
therebetween, each said turnup portion extends radially outwardly
along the axially outer surface of the bead apex beyond the
radially outer end of the bead apex so that the turnup portion has
a part extending parallel with and closely to the main portion.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pneumatic tire, more
particularly to a structure of the bead portion being capable of
improving the durability performance.
BACKGROUND ART
[0002] In general, an annular bead core, which is disposed in each
bead portion of a pneumatic tire to provide a hoop effect, is made
of windings of a metal wire wound at a predetermined number of
time, and it has a function to secure the carcass ply by turning up
the carcass ply around the bead core from the axially inside to the
outside of the tire.
[0003] On the other hand, the inner surface of a tire is provided
with an inner liner of air-impermeable rubber extending over the
tread portion, sidewall portions and bead portions in order to
maintain an air pressure.
[0004] Conventionally, the radially inner end of the inner liner is
terminated near the bead cores, and usually, in a region axially
inside the bead core the axially inside of the bead portion is not
completely covered with the inner liner. This is because of the
idea that, as the bead portion is thick and its area is small for
the tire as a whole, the amount of leaked air is very small and
there is no substantial influence upon keeping of the air
pressure.
[0005] In a heavy duty pneumatic tire for trucks and buses which is
used under severe conditions at high tire pressure and heavy loads,
especially which has steel cords as the carcass cords and/or a bead
reinforcing layer,
even if there is no substantial problem of air leakage,
[0006] if small amount of air or moisture penetrates into the bead
portion and reaches to the surface of such a cord on which a small
separation or adhesion failure occurs, the cord will be eroded. If
the cords are steel cords, the rust may be caused. If the cord is
made of organic fibers, the strength may be decreased as they
absorb water, and as the result, there is occasionally seen a cord
damage and a separation of the cords from the topping rubber.
Usually, this does not expand into the deterioration of the bead
durability in the case of the light-load tires. However, in the
case of heavy-duty tires, as the deformation of the bead portions
and the shearing force between cords and rubber are large,
sometimes the durability of bead portions is impaired.
[0007] It is therefore, an object of the present invention to
provide a pneumatic tire in which the damages of the bead portions
caused by the cord damage and the separation between cords and
rubber is prevented, and the durability of the bead portions is
improved.
DISCLOSURE OF THE INVENTION
[0008] According to the present invention, a pneumatic tire
comprises: a tread portion; a pair of sidewall portions; a pair of
bead portions; a bead core disposed in each of the bead portions; a
carcass comprising a carcass ply made of carcass cords extending
between the bead portions through the tread portion and sidewall
portions and turned up around the bead core in each of the bead
portions; and an inner liner made of air impermeable rubber and
extending on the tire cavity side of the carcass from one bead
portion to the other, wherein
[0009] the above-mentioned inner liner has radially inner ends
located radially inside the radially innermost end of the carcass,
and in a radial region between the radially innermost end of the
carcass and the radially outermost ends of the bead core, the
thickness of the inner liner is not less than 0.15 times but not
more than 4.0 times the cross section diameter of the carcass
cord.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is a cross sectional view showing a bead portion of
a pneumatic tire, as a 1st embodiment of the present invention, in
a state that the tire is mounted on a regular rim and inflated to a
regular pressure.
[0011] FIG. 1B is a cross sectional view showing the same bead
portion in a free state not mounted on a rim.
[0012] FIGS. 2-9 are cross sectional views showing bead portions of
pneumatic tires as 2nd-9th embodiments of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0013] Taking a case, as an example, where the pneumatic tire of
the present invention is a heavy duty tubeless radial tire for
trucks, buses and heavy-duty vehicles of the similar type,
embodiments of the present invention will now be described in
detail in conjunction with the accompanying drawings.
[0014] The pneumatic tire has a tread portion, a pair of sidewall
portions and a pair of bead portions 1 which continue in a troidal
shape. The tire comprises a carcass 2 extending between the bead
portions through the tread portion the sidewall portions; an inner
liner 3 disposed inside the carcass 2; and a bead core C, bead apex
6 and chafer 4 which are disposed in each of the bead portions
1.
[0015] The tire is mounted on a standard rim J, that is, a
15-degree-taper drop center rim for heavy-duty tire.
[0016] Here, the standard rim is a rim specified in the standard
with which the tire is required to comply, such as JATMA (Japan and
Asia), T&RA (North America), ETRTO (Europe), STRO
(Scandinavia), etc. For example, the standard rim is the "standard
rim" in JATMA, "Design Rim" in TRA, "Measuring Rim" in ETRTO.
Similarly, the undermentioned standard pressure means the maximum
air pressure in JATMA, the maximum pressure given in the "TIRE LOAD
LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in TRA, the
"INFLATION PRESSURE" in ETRTO, etc.
[0017] In this specification, for the sake of simplification, the
"axial direction of the tire" and "radial direction of the tire"
may be referred to as the "axial direction" and "radial direction".
Further, the words "upper" and "lower" may be used to describe a
positional relationship "outside or inside" in the radial direction
of the tire. Furthermore, the words "inner" and "outer" may be used
to describe a positional relationship "inside or outside" in the
axial direction of the tire on each side of the tire equator.
[0018] The carcass 2 comprises at least one ply of carcass cords
which are arranged radially so that the cord angle becomes 70 to 90
degrees with respect to the tire equator.
[0019] The carcass ply extends between the bead portions through
the tread portion and sidewall portions and is turned up around the
bead core c in each bead portion 1 to be secured to the bead core
C, forming a pair of ply-turnup portion 2b and a ply-main portion
2a therebetween. In the carcass ply, metal cords such as steel
cords and organic cords such as polyester, aromatic polyamide,
nylon, rayon etc., may be used as the cords thereof. In each of the
following embodiments, the carcass 2 is composed of a single-ply of
steel cords whose cord angle is substantially 90 degrees with
respect to the tire equator.
[0020] The inner liner 3 is made of air-impermeable rubber disposed
along the inner surface of the tire so as to cover the entirety
thereof.
[0021] As to the air impermeable rubber, when all the rubber
content excluding additives and the like is regarded as 100 parts
by weights, one containing at least 60 parts by weights of butyl
rubber, for instance halogenated butyl rubber, brominated butyl
rubber, butyl rubber, is preferably used.
[0022] If butyl rubber is less than 60 parts by weights, the
air-impermeability falls, which is not desirable.
[0023] For example, in order to improve the cure rate, rubber
polymers made of the following brominated butyl rubber may be used:
TABLE-US-00001 (phr) Br-IIR 2255 100 N660 65 R500 65 Stearic acid
1.2 Zinc oxide 3 Sulfur 0.5 Accelerator 1.5
[0024] In the case where the inner liner 3 contains butyl rubber at
a relatively high rate, especially where the carcass cord is made
of steel, if the inner liner 3 directly contacts with the topping
rubber for the steel cords, a separation is liable to occur along
the boundary face. Therefore, it is preferable that an insulation 5
made of an adhesion-improving rubber compound containing natural
rubber or isoprene rubber as its main component is disposed between
the inner liner 3 and the carcass 2 so as to cover all over the
outer surface of the inner liner 3. An example of such
adhesion-improving rubber compound is shown below. TABLE-US-00002
(phr) Natural rubber 80 IR 20 N326 60 Antidegradant 2 Zinc oxide 3
Sulfur 1 Accelerator 1
[0025] The chafer 4 is made of a rubber whose 100% modulus (M100)
is 440 to 830 N/sq.cm, and is disposed along at least the bottom
and axially outer surface of the bead portion 1, forming a surface
contacting with the bead seat and flange of the wheel rim J. If the
100% modulus is less than 440 N/sq.cm, a rubber rupture tends to
occur.
[0026] If the 100% modulus exceeds 830 N/sq.cm, the rubber becomes
too hard and problems regarding processing tend to occur. Moreover,
the rubber becomes more rigid with the use of tire, leading to a
loss of elasticity, an increased fragility against deformation and
an increased heat generation, and a separation from other members
tends to occur.
[0027] The bead core c is formed by winding a single steel wire
spirally to have a specific cross-sectional shape.
[0028] In each of the following embodiments, the bead core c is a
layered structure made up of layers of the spirally wound steel
wire and having a hexagonal cross-sectional shape. The bead core
comprises lower layers of which numbers of windings increase one by
one from the radially inside to the radially outside up to the
maximum width layer, and upper layers of which numbers of windings
decrease one by one from the radially inside to the radially
outside. The spirally wound steel wire is wrapped in a wrapping
protection layer wound therearound and comprising organic fiber
cords so as to retain the above-mentioned cross-sectional shape and
to prevent the direct contact of the carcass cords with the steel
wire.
FIRST EMBODIMENT
[0029] FIGS. 1A and 1B show a first embodiment of the present
invention, wherein FIG. 1A shows a meridian section of the bead
portion 1 in a state of the pneumatic tire which is mounted on a
standard rim J and inflated to a standard inner pressure but loaded
with no tire load (hereinafter the "standard state"), and FIG. 1B
shows the meridian section of the bead portion 1 in a free state of
the tire which is not mounted on a rim.
[0030] The bead portions 1A are each provided between the ply-main
portion 2a and ply-turnup portion 2b of the carcass 2 with the bead
apex 6 extending radially outwards from the upper surface of the
bead core C.
[0031] The bead apex 6 in this example includes an inner apex 6a
disposed adjacent to the bead core and made of a hard rubber, and
an outer apex 6b disposed radially outside thereof and being softer
than the inner apex.
[0032] The above-mentioned ply-turnup portion 2b is extended
radially outwardly along the axially outer surface of the bead apex
6, and terminated in a position radially inside the upper end of
the bead apex 6.
[0033] The bead portions 1 are each provided along the carcass 2
with a reinforcing layer 7.
[0034] The reinforcing layer 7 in this example is made up of a base
portion 7b along the bottom surface of a part of the carcass 2
beneath the bead core,
an axially inner portion 7i extending radially outwardly from the
base portion 7b along the carcass-ply main portion 2a, and
an axially outer portion 7o extending radially outwardly from the
base portion 7b along the carcass-ply turnup portion 2b,
so the reinforcing layer has a U-shaped cross-sectional shape. Each
of the axially inner portion 7i and axially outer portion 7o
extends to a height of 0.8 to 2.5 times the height of a flange Jf
of the rim.
[0035] The reinforcing layer 7 in this example is made up of a
single rubberized ply of parallel steel cords. As to the cord angle
thereof, when the tire is viewed sideways facing the sidewall
portion normally thereto, the cords in the axially inner portion 7i
and axially outer portion 7o are inclined at an angle of 30 to 60
degrees with respect to a radially outward line.
[0036] Further, the above-mentioned carcass ply's turnup portion 2b
and reinforcing layer 7's ply are provided at their upper ends with
various kinds of buffer rubber layers for reducing stress between
each of the plies and the above-mentioned rubber layers.
[0037] The inner liner 3 continuously extends from one of the bead
portions 1 to the other through the tread portion and the sidewall
portions. In each of the bead portions, the radially inner end 3d
thereof is located at a position radially outside a bead toe (t)
but radially inside the radially innermost end 21e of the carcass
2.
[0038] Given that, under the above-mentioned standard state, a tire
radial region (A) is defined between the radially outermost end Coe
of the bead core C and the radially innermost end 21e of the
carcass 2, the inner liner 3 extends into this region (A) on the
axially inside of the bead core C. In the region (A), in view of
the prevention of adhesion failure, etc., the thickness Tb of the
inner liner 3 is preferably set to be 0.15 to 4.0 times the cross
section diameter D of the carcass cord.
[0039] If less than 0.15 times, the permeation of air and moisture
becomes increased or the impermeability deteriorates. If exceeds
4.0 times, no improvement is observed in the effect and such
increase simply leads to an increased tire cost.
[0040] In the region (A), in this example, the thickness Tb of the
inner liner 3 gradually decreases toward the radially inside.
[0041] A minimum value of the thickness Tb at the radially inner
end of the region (A) is not less than 0.15 times the cross section
diameter D of the carcass cord as described above, but more
preferably, not less than 0.3 times but not more than 1.8 times the
diameter.
[0042] Here, the cross section diameter D of the carcass cord means
the diameter of a circle circumscribing the elemental filaments
constituting a cord, except a wrapping wire, if any.
[0043] The chafer 4 in this example is made up of a base portion 4b
extending from the bead toe (t) to the bead heel (h) along the
bottom surface of the bead portion 1, an axially inner portion 4i
extending from the bead toe (t) toward the radially outside along
the inner surface of the tire, and an axially outer portion 40
extending from the bead heel (h) toward the radially outside along
the outer surface of the tire. The axially inner portion 4i in this
example is extended into the above-mentioned region (A) and
terminated at a point therein, covering the inner surface of the
radially inner end portion of the inner liner 3.
[0044] The insulation 5 in this example is disposed between the
inner liner 3 and carcass 2 and between the inner liner 3 and
reinforcing layer 7, and extends radially inwardly beyond the
radially inner end 3d of the inner liner 3 to the vicinity of the
bead toe (t), abutting on the chafer 4. Further, it extends axially
outwardly, abutting on the chafer 4, and terminates substantially
beneath the centroid of the cross-sectional shape of the bead
core.
[0045] As shown in FIG. 1B, on the bottom surface of the bead
portion 1 which is defined by the chafer 4, there is formed a
protrusion tp by making the inclination angle with respect to the
tire axial direction larger in a portion ranging from a position
substantially beneath the centroid G of the bead core to the bead
toe (t) than in the remaining portion.
[0046] In the meridian section of the tire under the
above-mentioned free state, an intersecting angle .alpha. between
the bottom surface of the bead portion and the tire inner surface
at the bead toe (t) is set to be not less than 38 degrees but not
more than 90 degrees. The reason for setting up like this is that,
due to the above-described properties of the chafer 4, if the angle
.alpha. is smaller than 38 degrees, then the strength around the
bead toe (t) will decrease, leading to a generation of rubber chip
and crack at the time of rim mounting. If the angle .alpha. is
larger than 90 degrees, the tire production will become
difficult.
[0047] Although the limitation of the intersecting angle .alpha. is
made in order to be applied suitably to this embodiment, it is
preferably applied as well to every embodiment explained
hereinafter.
[0048] The minimum rubber thickness Tc of the chafer 4 is set in
the range of not less than 1.7 times but not more than 6.0 times,
preferably 2.6 to 4.5 times the cross section diameter D of the
carcass cord, wherein the minimum rubber thickness is defined as
the minimum distance from the bottom surface of the bead portion to
the adjacent cords (the carcass cords if there is no reinforcing
cord layer between the bottom surface and the carcass such as the
above-mentioned reinforcing layer 7 OR the cords of such
reinforcing cord layer if there is).
[0049] By setting the minimum rubber thickness Tc within this
range, there may be prevented the adhesive failure between the
cords and rubber resulting from the large shearing stress and
compressive stress under the bead core repeatedly given during
running.
[0050] When the minimum rubber thickness Tc is less than 1.7 times
the cross section diameter D, the chafer 4 may be ruptured easily,
and when ruptured, the cord will contact with the rim, which is not
preferable. When the minimum rubber thickness Tc is more than 6.0
times the cross section diameter D, the hoopping force of the bead
core is decreased, and at the same time, the heat buildup from the
rubber increases, leading to a possibility of the adhesive failure
by heat.
[0051] Although the limitation of the minimum rubber thickness Tc
is made in order to be applied suitably to this embodiment, it may
be preferably applied as well to each embodiment explained
hereinafter.
[0052] It is desirable to avoid extending the above-mentioned
insulation 5 into a position at which the minimum rubber thickness
Tc occurs if it has a substantial thickness thereat. The bottom
surface of the insulation 5 is substantially parallel with the bead
bottom surface, and terminated near the radially innermost end 7bi
of the base portion 7b of the reinforcing layer 7 (which end 7bi is
in line with the innermost end 21e of the carcass 2), whereby the
insulation 5 covers an axially inner portion of the base portion 7b
and the inner portion 7i of the reinforcing layer.
SECOND EMBODIMENT
[0053] FIG. 2 shows a second embodiment of the present
invention.
[0054] The bead apex 6 is smaller in volume and size in comparison
with the above-mentioned first embodiment, and made up of an
equivalent to the above-mentioned inner apex 6a alone.
[0055] The turnup portion 2b of the carcass ply extends along the
axial outer surface of the bead apex 6, radially outwardly beyond
the upper end 6t of the bead apex 6.
[0056] Between the carcass cords in this portion beyond the upper
end 6t and the carcass cords in the carcass-ply main portion 2a, a
specific cord distance CS is provided.
[0057] The cord distance Cs in this example increases from the
upper end 6t of the bead apex toward the upper end 2t of the
turnup-portion 2b. As to the region from the upper end 6t to the
upper end 2t, in its 1/3 to 2/3 part from the upper end 6t, the
cord distance CS is substantially constant, but in the remainder or
radially outer part, the cord distance gradually increases.
However, it may be also possible that the cord distance CS is
substantially constant all over the region or that the cord
distance Cs is gradually increased across the entire region. When
increasing the cord distance Cs gradually, a relatively small
increasing rate such that the angle between the carcass-ply
main-portion 2a and the turned-up-portion 2b becomes about 1 to
about 5 degrees in the meridian section, is preferred. The minimum
cord distance CSmin is set in a range of from 0.15 to 7.0 times,
preferably about 1.2 to about 4.0 times the carcass cord diameter
D.
[0058] The inner liner 3 in this example is extended to the bead
toe (t) and terminated there. Accordingly, the tire inner surface
is completely covered with the inner liner 3.
[0059] As to the thickness Tb of the inner liner 3 in the
above-mentioned region (A), the numerical limitation explained
therefor in the first embodiment may be again applied to this
embodiment.
[0060] The insulation 5 extends to the bead toe (t), abutting on
the inner liner 3, to prevent the contact of the inner liner 3 with
the carcass and chafer 4. In this embodiment, the above-mentioned
reinforcing layer 7 is not disposed.
[0061] The chafer 4 extends from the bead toe (t) to a point in the
above-mentioned region (A), along the axially outside of the
insulation 5.
THIRD EMBODIMENT
[0062] FIG. 3 shows a third embodiment of the present
invention.
[0063] In the bead portion 1, the reinforcing layer 7 having a
u-shaped cross-sectional shape same as in the first embodiment is
disposed along the carcass 2. The axially inner portion 7i and
outer portion 70 of the reinforcing layer 7 are each extended
radially outwards of the radially outermost point Coe of the bead
core C up to, for example, a height corresponding to the point Coe
to which a height of about 0.5 to 2.0 times that of the region (A)
is added. Thus, while the carcass 2 is protected, the bending
rigidity of the whole bead portion increases, a deformation of the
bead portion when loaded is controlled, and strain of each part
decreases. As the result, the bead durability of the tire may be
improved.
[0064] The reinforcing layer 7 in this embodiment is made up of a
single rubberized ply of parallel steel cords. As to the cord angle
thereof, when the tire is viewed sideways facing the sidewall
portion normally thereto, the cords in the axially inner portion 7i
and axially outer portion 7o are inclined at an angle of from 15 to
45 degrees with respect to a radially outward line.
[0065] The inner liner 3 in this embodiment extends along the
carcass 2 and reinforcing layer 7, beyond the above-mentioned
region (A) radially inwardly to be wound upon the radially inside
of the bead core c. The axial position of the inner end 3d of the
inner liner 3 is set between
the axial position of the axially innermost point Caie of the bead
core C and
the axial position of the middle point Cc between the
above-mentioned axial innermost point Caie and axial outermost
point Caoe of the bead core C.
[0066] The thickness T of the inner liner 3 measured along a
straight line L passing through the innermost point Caie and
outermost point Caoe is set in a range of from 0.5 to 2.0 mm.
[0067] If the thickness is less than 0.5 mm, the permeating of air
and moisture may not be prevented enough, and a thickness over 2.0
mm is superfluous.
[0068] The insulation 5 in this embodiment is, similarly to the
inner liner 3, extended along the carcass 2 and wound toward the
radially inside of the bead core c so as to terminate at a position
slightly beyond the inner end 3d of the inner liner 3. At a
position radially inside the radially innermost point Cie of the
bead core C, the thickness (n) of the insulation 5 is set in a
range of from 1 to 1.5 mm. If less than 1 mm, cracks tend to occur
on the bead base.
[0069] As the inner liner 3 is wound upon the under side of the
bead core, while increasing its thickness from a position under the
bead core, the chafer 4 extends axially inwardly to the bead toe
(t) along the axially inner surface of the inner liner 3, and then
extends radially outwardly to a position whose radial height is in
a range between the radial height of the radially outermost point
Coe of the bead core c plus 5 mm and the same radial height minus 5
mm. If outside this plus/minus 5 mm range, the bead durability will
decrease.
FOURTH EMBODIMENT
[0070] FIG. 4 shows a fourth embodiment of the present invention
which is the same as the third embodiment except for the
reinforcing layer 7.
[0071] The reinforcing layer 7 comprises the base part 7b under the
bead core and the axially outer portion 7o in the same way as the
above-described embodiments, but the axially inner portion 7i is
eliminated for the purpose of weight reduction.
[0072] The axially inner end 7bie of the base part 7b is located
between a radial line passing through the axially innermost point
caie of the bead core c and a radial line passing through the
axially outermost point caoe of the bead core.
[0073] Further, the radially inner end of the insulation 5 and the
radially inner end 3d of the inner liner 3 are located axially
outwards of the inner end 7bie of the base portion 7b, but axially
inwards of a radial line passing through the above-mentioned middle
point cc of the bead core C.
FIFTH EMBODIMENT
[0074] FIG. 5 shows a fifth embodiment of the present invention,
wherein, for the purpose of weight reduction, the bead apex 6 is
made in a smaller volume and size like the above-explained second
embodiment, and the reinforcing layer 7 is eliminated.
[0075] As for the bead apex 6 and the carcass ply, in particular
the turnup portion 2b, the above descriptions of those in the
second embodiment can be applied here again. In this embodiment, a
part of the turnup portion 2b of the carcass ply which part extends
beyond the upper end 6t of the bead apex 6, is substantially
straight and substantially in parallel with the carcass-ply main
portion 2a.
[0076] The inner liner 3 and insulation 5 are extend along the
carcass 2 and wound toward the radially inside of the bead core c
in the same way as in the fourth embodiment, and the radially inner
ends thereof are located at positions radially inwardly beyond the
above-mentioned region (A).
[0077] With respect to the axial position, the inner end 3d of the
inner liner 3 is located between the axially innermost point Caie
and the middle point cc of the bead core c in the same way as in
the third embodiment.
[0078] Measured along a straight line L passing through the
innermost point Caie and outermost point caoe of the bead core C,
the thickness T of the inner liner 3 is set in a range of from 0.5
to 2.0 mm.
[0079] The radially inner end of the insulation 5 is located in a
position slightly axially outwardly beyond the inner end 3d of the
inner liner, in this example specifically, a position axially
outside the above-mentioned middle point Cc, at the radially
innermost end 21e of the carcass.
[0080] As for the chafer 4, the description of that in the third
embodiment can be applied.
[0081] When the reinforcing layer 7 which increases the rigidity of
the bead portion 1 is not provided, a separation between the chafer
4 and inner liner 3 tends to occur on the radially inside of the
bead core C. In order to prevent this, an insulation 8 is disposed
between the inner liner 3 and the chafer 4, too.
[0082] This second insulation 8 is made of a rubber compound
comprising polymers mainly of natural rubber and/or isoprene rubber
for improving the adhesive property, and a relatively high carbon
for providing strength. Further, it comprises organic-acid cobalt
since the second insulation contacts with the carcass ply
comprising steel cords. Examples of such rubber compound is shown
below. These rubber compounds correspond to compositions (a) and
(b) used in the undermentioned comparison test 2. TABLE-US-00003
Composition (a) (b) Natural rubber 80 80 IR 20 20 N219 65 60
Antidegradant 2 2 Zinc oxide 9.5 7.5 Stearic acid cobalt 1.5 0.7
Sulfur 4.5 4.5 Accelerator 1 1 (Unit: phr)
[0083] The second insulation 8 extends at least from a point
axially inside the bead core c to a point radially inside the bead
core C, in order to isolate the inner surface of the inner liner 3
from the chafer 4. The insulation 8 in this example extends beyond
the upper end 2t of the turnup portion 2b from in a region radially
inside the bead core C so as to cover the whole of the axially
outer surface of the carcass turnup portion 2b. Then it extends
along the axially inner surface of the inner liner 3, radially
outwardly beyond the region (A), and it is terminated near to and
slightly radially inside the radially outer end 41e of the axially
inner portion 4i of the chafer 4. The distance (m) of this
terminating point from the radially outer edge 41e is set to be not
more than 15 mm, preferably not more than about 8 mm.
[0084] Consequently, in the region (A), a four-layered structure of
the insulation 5, inner liner 3, second insulation 8 and chafer 4,
is formed on the axially inside of the carcass 2.
[0085] It is preferable for the second insulation 8 that its
thickness Ti at the inner end 3d of the inner liner is in a range
of from 1 to 1.5 mm. If less than 1 mm, the above-mentioned
separation between the inner liner 3 and chafer 4 may not be
prevented enough. If more than 1.5 mm, it becomes difficult to
ensure the necessary minimum thickness of the chafer 4.
SIXTH-NINTH EMBODIMENTS
[0086] FIG. 6-FIG. 9 show 6th-9th embodiments of the present
invention, wherein the carcass ply is secured by winding the turnup
portion 2b substantially once around the bead core c.
[0087] In order to make it easy to wind the carcass ply of
high-rigidity steel cords, the bead core c is formed by spirally
winding a single steel wire into a cross-sectional shape which is a
transformed hexagon approximate to an inverse triangle whose
maximum width position is radially outward of the center of the
height of bead core C.
[0088] In each of the following embodiments, the bead core is
provided with a five-layered structure made up of lower layers
which are the first, second and third layers whose numbers of
windings are 4, 5 and 6, respectively, a maximum-width layer whose
number of windings is 7, and an upper layer which is the fifth
layer whose number of windings is 6.
[0089] The carcass-ply turnup portion 2b is wound onto the upper
surface cu of the bead core c from the axially outside of the bead
core C to have a wound portion 2r which is defined as a portion
extending axially inwardly along the upper surface cu. It is
preferable that as shown in FIGS. 6-8 the wound portion 2r is
terminated before the main portion 2a, or as shown in FIG. 9 the
wound portion 2r is bent before the main portion 2a and then
terminated after extending parallel with the main portion 2a for a
small distance (g) in order to prevent a damage caused by the cut
ends of the carcass cords contacting with the cords of the
carcass-ply main portion 2a.
[0090] When terminated before the main portion 2a, it is preferable
that a small distance of about 0.3 to about 2.0 times the cross
section diameter of the carcass cord is provided between the end
2re of the winding portion 2r and the carcass cords of the
carcass-ply main portion 2a, and the winding end 2re is disposed
adjacently to the upper surface cu of the bead core C.
[0091] The bead apex 6 in this embodiment is made of a hard rubber
having a JIS-A hardness of from 70 to 100 degrees and disposed on
the radially outer surface of the wound portion 2r of the carcass
ply, so as to secure the wound portion 2r between the bead apex and
bead core C. Consequently, the wound portion end 2re is fixed in a
place where the strain is smallest, and therefor damages starting
from this end may be controlled.
[0092] In the above-mentioned region (A), the thickness Tb of the
inner liner 3 is set in a range of not less than 0.3 but not more
than 4.0 times the cross section diameter of the carcass cord. If
less than 0.3 time, the permeating of air and moisture may not be
prevented enough, and the effect to prevent the carcass cords from
rusting and decreasing in the strength may be decreased. On the
other hand, making the thickness more than 4.0 times the diameter
will not increase such effect, only to increase the tire cost.
[0093] Like the above embodiments, the chafer 4 comprises [0094]
the base portion 4b extending from the bead toe (t) to the bead
heel (h) along the bottom surface of the bead portion 1, and the
axially outer portion 40 extending radially outwardly from the bead
heel (h) along the outer surface of the tire. The outside portion
4o extends along the carcass 2 and bead apex 6 beyond the upper end
6t of the bead apex 6.
SIXTH EMBODIMENT
[0095] FIG. 6 shows a sixth embodiment of the present
invention.
[0096] The inner liner 3 is extended to the bead toe (t) along the
tire inner surface, and the insulation 5 is also extended to the
bead toe (t). The inner liner 3 and insulation 5 decrease their
thicknesses in the course from the region (A) towards the bead toe
(t), and the thicknesses become substantially zero at the position
of bead toe (t).
[0097] The chafer 4 in this embodiment has the axially inner
portion 4i which is extended radially outwardly from a position
near the bead toe (t) along the axially outer surface of the
insulation 5 while decreasing the thickness, and terminated within
the region (A).
SEVENTH EMBODIMENT
[0098] FIG. 7 shows a seventh embodiment of the present
invention.
[0099] The chafer 4 in this embodiment has the axially inner
portion 4i which is extended radially outwardly from a position
near the bead toe (t) along the tire inner surface while decreasing
the thickness, and terminated in the region (A).
[0100] The inner liner 3 and insulation 5 extend along the axially
outside of the axially inner portion 4i of the chafer 4, and their
radially inner end 3d is disposed at a position that is on the
radially inside of the above-mentioned region (A), at a distance of
more than the above-mentioned minimum rubber thickness Tc of the
chafer 4 from the bottom of the bead portion 1, and this position
is such that they have no substantial thickness at the position at
which the above-mentioned minimum rubber thickness TC occurs on the
chafer 4.
EIGHTH EMBODIMENT
[0101] Eighth embodiment of the present invention shown in FIG. 8
is a modification of the sixth embodiment, in which the bead apex 6
is formed with two hard and soft rubber layers, and the reinforcing
layer 7 is added.
[0102] This bead apex 6 consists of the inner apex 6a and the outer
apex 6b. The inner apex 6a is made of a hard rubber having a JIS A
hardness of from 80 to 100 degrees and extends radially outwardly
from the above-mentioned wound portion 2r of the carcass 2 while
gradually decreasing its thickness. The outer apex 6b is made of a
soft rubber having a JIS A hardness of from 40 to 60 degrees and
extends along the axially outer surface of the inner apex 6a from a
starting point on this axially outer surface positioned
substantially at the height of the upper surface cu of the bead
core to a position above the upper end of the axially outer surface
to terminate thereat.
[0103] The reinforcing layer 7 comprises the base portion 7b
radially inside the bead core C, and the axially outer portion 7o
which extends upward from the base portion 7b on the axially
outside of the bead core C. The radially outer portion 7o is
separated from the carcass 2 at or near the axially outermost end
of the carcass turnup portion 2b and then extends contacting with
the bead apex 6. The upper end 7oe thereof terminates at a position
on the radially outer surface of the outer bead apex 6b being lower
than the upper end of the inner apex 6a.
[0104] The base portion 7b is separated from the carcass 2 at or
near the radially innermost end 21e of the carcass 2, and extends
parallel with the bottom surface of the bead portion.
[0105] Between these two separating points, the reinforcing layer 7
abuts on the carcass (the lower part of the turnup portion 2b).
Between the carcass 2 and the separated part of the base portion
7b, there is disposed a pillow rubber 9 having a hardness of the
same level as or harder than the chafer 4.
[0106] The axially inner surface of the pillow rubber 9 contacts
with the inner portion 4i of the chafer 4.
[0107] The entire area of the outer surface of the reinforcing
layer 7 contacts with the chafer 4.
[0108] The reinforcing layer 7 in this embodiment is made up of a
single rubberized ply of parallel steel cords. As to the cord angle
thereof, when the tire is viewed sideways facing the sidewall
portion normally thereto, the cords in the axially inner portion 7i
and axially outer portion 7o are inclined at an angle of from 15 to
45 degrees with respect to a radially outward line.
[0109] With this construction as explained the above, the outer
apex 6b controls the concentration of strain at the upper end 7oe
of the reinforcing layer 7 made of metal cords, and prevents the
generation of a large searing force which may cause when the
reinforcing layer contacts with the hard bead apex, and thereby the
bead durability is improved.
NINTH EMBODIMENT
[0110] Ninth embodiment of the present invention shown in FIG. 9 is
a modification of the sixth embodiment, in which the wound portion
2r of the carcass is bent before the main portion 2a and extended
for a small distance in parallel with the main portion 2a and then
terminated.
[0111] In this embodiment, an axially inner end part of the wound
portion 2r is bent toward the radially outside, forming a bent part
2f extending along the axially outer surface of the main portion
2a. The bent part 2f is secured between the main portion 2a and the
above-mentioned bead apex 6, and as the result, the carcass 2 is
secured more surely. The radially outer end 2re of the bent part 2f
is preferably located radially inwards of the radially outer end Je
of the rim flange of the rim J in order to prevent a damage
starting from the outer end 2re.
Comparison Test 1
[0112] The test tires (tire size: 11R22.5, wheel-rim size:
8.25.times.22.5) having the bead structures shown in FIG. 1B and
FIG. 2 were prepared, and the following water-injection durability
test, durability test, and toe chip test were carried out. Test
results are shown in Tables 1A, 1B, 1C, and 1D. In the Tables, *1
represents that the radially inner end 3d of the inner liner is
located within the region (A) and inward of the radial center of
this region, *2 represents that the radially inner end 3d is
located within the region (A) and outward of the radial center of
this region, and *3 represents that the radially inner end 3d is
located radially outward of the radially outermost point of the
bead core.
[0113] The value of Tb/D shows the minimum value in the region
(A).
[0114] Water-Injection Durability Test:
[0115] using an indoor drum tester, the test tire was run under an
accelerated condition, a tire load of 9000 kg (88.26 KN), tire
pressure of 1000 kPa and travel-speed of 20 km/h, while injecting
200 cc water in the tire every 2000 km until the target complete
running distances of 10000 km, to obtain the travel distance until
damage in the appearance or until the tire became impossible to
run. In the tables, the travel distances are expressed by an index
based on the target complete running distance of 10000 km being
100.
[0116] Durability Test
[0117] Using the indoor drum tester, the test tire was run under an
accelerated condition, a tire load of 9000 kg (88.26 KN), tire
pressure of 1000 kPa and travel-speed of 20 km/h to obtain the
travel distance until damage in the appearance or until the tire
became impossible to run. In the tables, the travel distances are
expressed by an index based on the target complete running distance
of 10000 km being 100.
[0118] Toe Chip Test:
[0119] After repeating the tire mounting ten times without applying
lubricant to neither the tire bead portions nor the bead seats of
the rim, the chafer rubber was checked for chip. In the tables, the
degree of the chipping damage is indicated by an index which is 100
for no damage.
Comparison Test 2
[0120] The test tires (tire size: 11R22.5, wheel-rim size:
8.25.times.22.5) having the bead structures shown in FIGS. 3, 4 and
5 were prepared, and the following bead durability tests were
carried out.
[0121] Bead Durability Test:
[0122] using the indoor drum tester, the test tire was run under an
accelerated condition, a tire load of 58.52 KN, tire pressure of
800 kPa and travel-speed of 20 km/h to obtain the driving time
until damage in the appearance or until the tire became impossible
to run. The test results are shown in Table 2.
Comparison Test 3
[0123] The test tires (tire size: 11R22.5, wheel-rim size:
8.25.times.22.5) having the bead structures shown in FIGS. 6-9 were
prepared, and the above-mentioned water-injection durability test,
durability test, toe chip test were carried out. The test results
are shown in Tables 3A and 3B. TABLE-US-00004 TABLE 1A Tire E1a E2a
E3a E4a E5a E6a E7a E8a Bead Structure Carcass Steel Cord, 1 Ply,
(Cord Structure: 3 .times. 0.2 + 7 .times. 0.23, Cord Count: 38/5
cm) Carcass Cord Diameter(D) 0.89 mm Reinforcing Layer Steel Cord,
1 Ply Butyl Content in Inner Liner(%) 100 Tb/D 0.3 0.4 0.4 0.4 0.4
0.4 0.4 0.4 Tc/D 0.6 0.6 0.8 0.3 0.3 0.3 0.3 0.3 Toe Angle .alpha.
(degree) 63 63 63 63 38 50 50 35 100% Modulus (M100) of Chafer
Rubber 56 56 56 56 56 56 46 83 Toe Chip Test 100 100 100 100 95 100
100 70 Durability Test 100 100 100 125 125 125 100 110
Water-Injection Durability Test 100 115 100 125 125 125 100 120
[0124] TABLE-US-00005 TABLE 1B Tire R1a R2a R3a R4a R5a R6a R7a R8a
R9a R10a C1a Bead Structure Carcass Steel Cord, 1 Ply, (Cord
Structure: 3 .times. 0.2 + 7 .times. 0.23, Cord Count: 38/5 cm)
Carcass Cord Diameter(D) 0.89 mm Reinforcing Layer Steel Cord, 1
Ply Butyl Content in Inner Liner(%) 100 50 100 Tb/D 0(*1) 0(*1)
0(*1) 0(*1) 0(*2) 0(*3) 0(*1) 0(*1) 0(*1) 0(*1) 0(*2) Tc/D 0.6 0.6
0.6 0.1 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Toe Angle .alpha. (degrees) 63
63 63 63 63 63 37 63 63 63 35 100% Modulus (M100) 56 56 56 56 56 56
56 44 85 56 56 of Chafer Rubber Toe Chip Test 100 100 100 100 100
100 55 100 65 100 50 Durability Test 100 100 70 50 100 100 100 70
90 100 85 Water-Injection Durability Test 84 125 75 50 60 70 100 70
90 95 70
[0125] TABLE-US-00006 TABLE 1C Tire E9a E10a E11a E12a E13a E14a
E15a E16a Bead Structure Carcass Steel Cord, 1 Ply, (Cord
Structure: 3 .times. 0.2 + 7 .times. 0.23, Cord Count: 38/5 cm)
Carcass Cord Diameter(D) 0.89 mm Butyl Content in Inner Liner(%)
100 Tb/D 0.3 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Tc/D 0.6 0.6 0.8 0.3 0.3
0.3 0.3 0.3 Toe Angle .alpha. (degrees) 65 65 65 65 38 45 45 45
100% Modulus (M100) of Chafer Rubber 56 56 56 56 56 56 46 83 Toe
Chip Test 100 100 100 100 95 100 100 70 Durability Test 100 100 100
130 130 130 100 120 Water-Injection Durability Test 100 120 100 130
130 130 100 120
[0126] TABLE-US-00007 TABLE 1D Tire R11a R12a R13a R14a R15a R16a
R17a R18a R9a R10a C2a Tire Size 11R20.5 Bead Structure Carcass
Steel Cord, 1 Ply, (Cord Structure: 3 .times. 0.2 + 7 .times. 0.23,
Cord Count: 38.5 cm) Carcass Cord Diameter(D) 0.89 mm Butyl Content
in Inner Liner(%) 100 50 100 Tb/D 0(*1) 0(*1) 0(*1) 0(*1) 0(*2)
0(*3) 0(*1) 0(*1) 0(*1) 0(*1) 0(*2) Tc/D 0.6 0.6 0.6 0.1 0.3 0.3
0.3 0.3 0.3 0.3 0.6 Toe Angle .alpha. (degrees) 65 65 65 65 65 65
37 65 65 65 37 100% Modulus (M100) 56 56 56 56 56 56 56 44 85 56 56
of Chafer Rubber Toe Chip Test 100 100 100 100 100 100 60 100 65
100 50 Durability Test 100 100 70 50 100 80 80 70 90 100 83
Water-Injection Durability Test 85 120 60 50 60 80 100 70 90 95
60
[0127] TABLE-US-00008 TABLE 2 Tire E1b E2b E3b E4b E5b R1b R2b C1b
Bead Structure Carcass Steel Cord, 1 Ply, (Cord Structure: 3
.times. 1.2 + 7 .times. 1.25, Cord Count: 38/5 cm) T (mm) 1.0 1.0
1.0 1.0 1.0 1.3 1.5 0 m (mm) 3 3 3 3 3 3 3 3 2nd Inslation Not
Provided Not Provided Provided Provided Provided Provided Provided
Not Provided Composition(a) Composition(b) Composition(b)
Composition(a) Composition(a) Ti (mm) 1.5 1.5 1.5 1.5 1.5 Bead
Durability Test 450 Hr 400 Hr 600 Hr 600 Hr 100 Hr 150 HrCBU 600 Hr
350 Hr Results .asterisk-pseud. Base Crack
[0128] TABLE-US-00009 TABLE 3A Tire E1c E2c E3c E4c E5c E6c E7c E8c
Bead Structure Carcass Steel Cord, 1 Ply, (Cord Structure: 3
.times. 1.2 + 7 .times. 1.25, Cord Count: 38/5 cm) Carcass Cord
Diameter(D) 1.89 mm Butyl Content in Inner Liner(%) 100 Tb/D
1.3.about.1.4 1.4.about.1.8 1.4.about.1.8 1.4.about.1.8
1.4.about.1.8 1.4.about.1.8 1.4.about.1.8 1.4.about.1.8 Tc/D 1.6
1.6 1.8 1.3 1.3 1.3 1.3 1.3 Toe Angle .alpha. (degrees) 63 63 63 63
38 50 50 35 100% Modulus (M100) 540 540 540 540 540 540 46 83 of
Chafer Rubber Toe Chip Test 100 100 100 100 95 100 100 70
Durability Test 100 100 95 125 125 125 100 110 Water-Injection
Durability Test 100 115 100 125 125 125 100 100
[0129] TABLE-US-00010 TABLE 3B Tire E9c E10c E11c R1c R2c R3c R4c
R5c Bead Structure Carcass Steel Cord, 1 Ply, (Cord Structure: 3
.times. 1.2 + 7 .times. 1.25, Cord Count: 38/5 cm) Carcass Cord
Diameter(D) 1.89 mm Reinforcing Layer Not Provided Steel Cord Not
Provided Not Provided 1 Ply Butyl Content in Inner Liner(%) 100
Tb/D 1.3.about.1.4 1.3.about.1.4 1.3.about.1.4 0.about.0
0.about.1.3 1.1.about.1.5 1.4.about.1.8 1.4.about.1.8 Tc/D 1.6 1.6
1.6 1.6 1.6 1.3 1.3 1.3 Toe Angle .alpha. (degrees) 63 63 63 63 63
50 50 35 100% Modulus (M100) 540 540 540 540 540 540 46 83 of
Chafer Rubber Toe Chip Test 115 115 100 100 100 100 100 70
Durability Test 100 130 100 90 100 100 100 110 Water-Injection
Durability Test 100 115 100 50 70 85 100 120
[0130] In the pneumatic tires according to the present invention,
as apparent from the test results, an air leak into the bead
portion occurring in the axially inside area of the bead core is
effectively prevented to prevent the damage on the carcass cords
caused by moisture in the air, and thereby, the durability of the
bead portion may be improved.
INDUSTRIAL APPLICABILITY
[0131] The present invention can be suitably applied to heavy-duty
pneumatic tires in which steel cords are used for the carcass
and/or reinforcing layer, but it is also applicable to light truck
tires, passenger car radial-ply tires and the like.
* * * * *