U.S. patent application number 11/293222 was filed with the patent office on 2006-04-20 for safety tire with expansion-deforming toric air bag.
This patent application is currently assigned to BRIDGESTONE CORPORATION. Invention is credited to Osamu Saito, Tetsuhito Tsukagoshi, Yuji Yamaguchi, Masahiko Yamamoto, Yugo Zuigyo.
Application Number | 20060081318 11/293222 |
Document ID | / |
Family ID | 27345321 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060081318 |
Kind Code |
A1 |
Yamaguchi; Yuji ; et
al. |
April 20, 2006 |
Safety tire with expansion-deforming toric air bag
Abstract
A toric air bag for a safety tire capable of sufficiently and
equally contacting with a full inner face of a tire in the
expansion-deformation of the toric air bag by a drop of an internal
pressure in the tire, wherein at least an expansion-deforming
portion of the toric air bag having a hollow torus shape as a whole
is constructed with a tension support member, and to the
expansion-deforming portion is given a property indicating a
characteristic of extension ratio-tensile force that tensile force
per unit width is substantially and gradually increased with the
increase of elongation through the expansion-deformation.
Inventors: |
Yamaguchi; Yuji; (Kodaira
City, JP) ; Yamamoto; Masahiko; (Kodaira City,
JP) ; Zuigyo; Yugo; (Kodaira City, JP) ;
Saito; Osamu; (Kodaira City, JP) ; Tsukagoshi;
Tetsuhito; (Kodaira City, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
BRIDGESTONE CORPORATION
|
Family ID: |
27345321 |
Appl. No.: |
11/293222 |
Filed: |
December 5, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10182390 |
Jul 30, 2002 |
|
|
|
PCT/JP01/09831 |
Nov 9, 2001 |
|
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11293222 |
Dec 5, 2005 |
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Current U.S.
Class: |
152/340.1 ;
152/512; 152/519 |
Current CPC
Class: |
Y10T 152/10603 20150115;
Y10T 152/10513 20150115; B60C 17/02 20130101; Y10T 152/10594
20150115 |
Class at
Publication: |
152/340.1 ;
152/512; 152/519 |
International
Class: |
B60C 17/02 20060101
B60C017/02; B60C 5/22 20060101 B60C005/22; B60C 5/08 20060101
B60C005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2000 |
JP |
2000-365,025 |
Dec 27, 2000 |
JP |
2000-396,842 |
May 25, 2001 |
JP |
2001-156,368 |
Claims
1. A toric air bag adapted to be placed inside a safety tire and,
when inflated under a certain internal pressure and
expansion-deformed by a drop of an internal tire pressure,
subrogates a load support from the tire, wherein at least an
expansion-deforming portion of the toric air bag having a hollow
torus shape is made of a tension support member and the
expansion-deforming portion has a characteristic of extension
ratio-tensile force that, as an extension is increased by the
expansion-deformation, a tensile force per unit width is gradually
increased; wherein the tension support member is constructed with
one or more layers of a composite of fibrous member and rubber; and
wherein the fibrous member is constituted with plural fiber layers
in which the layers of fiber materials arranged side-by-side are
crossed with each other.
2. A toric air bag adapted to be placed inside a safety tire and,
when inflated under a certain internal pressure and
expansion-deformed by a drop of an internal tire pressure,
subrogates a load support from the tire, wherein at least an
expansion-deforming portion of the toric air bag having a hollow
torus shape is made of a tension support member and the
expansion-deforming portion has a characteristic of extension
ratio-tensile force that, as an extension is increased by the
expansion-deformation, a tensile force per unit width is gradually
increased; wherein the tension support member is constructed with
one or more layers of a composite of polymer sheet and rubber; and
wherein the polymer sheet in the composite has an initial modulus
of 0.1-1.3 GPa, a yield stress of 10-33 MPa and an elongation at
break of not less than 20%.
3. A toric air bag according to claim 2, wherein a property that
the contacting of the toric air bag with the inner face of the tire
is carried out in a plastic deformation zone of the composite is
given to the composite arranged in the toric air bag.
4. A toric air bag adapted to be placed inside a safety tire and,
when inflated under a certain internal pressure and
expansion-deformed by a drop of an internal tire pressure,
subrogates a load support from the tire, wherein at least an
expansion-deforming portion of the toric air bag having a hollow
torus shape is made of a tension support member and the
expansion-deforming portion has a characteristic of extension
ratio-tensile force that, as an extension is increased by the
expansion-deformation, a tensile force per unit width is gradually
increased; wherein the tension support member is constructed with
one or more layers of a composite of polymer sheet or fibrous
member and rubber; and wherein a low-rigidity part is annularly
arranged on at least one layer among the two or more composite
layers at least arranged over a full circumference of the portion
facing to the inner circumferential face of the tire tread portion
at one or more symmetrical positions with respect to the equatorial
plane of the tire.
5. A toric air bag according to claim 4, wherein the low-rigidity
part is arranged at plural places.
6. A toric air bag according to claim 4, wherein a rigidity is
gradually changed in the low-rigidity part.
7. A toric air bag according to claim 4, wherein the low-rigidity
part is arranged so as to separate away from a side edge of the
composite.
8. A toric air bag according to claim 4, wherein the low-rigidity
part is constructed with a thinned portion of the composite or with
a notched portion formed in the composite.
9. A toric air bag according to claim 4, wherein there are at least
two composite layers.
Description
RELATED APPLICATION
[0001] This is a divisional application based on Ser. No.
10/182,390 filed Jul. 30, 2002. The entire disclosure of prior
application Ser. No. 10/182,390 is considered part of the
disclosure of the accompanying divisional application and is hereby
incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to a toric air bag for a safety tire
which is used in a safety tire capable of continuing a safe running
over a given distance even if an internal tire pressure drops or
disappears due to puncture of the tire or the like and which is
expansion-deformed by the drop of the internal tire pressure or the
like to subrogate a load support from the tire.
BACKGROUND ART
[0003] Heretofore, there have been proposed various tires as a
safety tire capable of continuously and safely running to a place
provided with equipment for exchanging or repairing the tire even
if the internal tire pressure drops or disappears due to the
puncture of the tire, damage of an air valve or the like.
[0004] Among them, International Publication brochure WO98/23457
and International Publication brochure WO99/32308 disclose, for
example, safety tires each consisting of a combination of a tire
comprising a tread portion, a pair of sidewall portions and bead
portions with a toric air member placed in the tire and inflated
under an internal pressure and expansion-deformed by the drop of
the internal tire pressure to subrogate a load support from the
tire.
[0005] In the former safety tire, two cross cord layers similar to
a belt of the tire are arranged on an outer circumferential portion
of the toric air member as a reinforcing member for restraint, and
a pressure higher by 50-500 kPa than the internal pressure of the
tire is filled into the toric air member placed in the tire in use,
and if the puncture of the tire is caused, the cords of the
reinforcing member for restraint are broken by an expansion force
of the toric air member and hence the load support is subrogated by
the expanded toric air member from the tire. The latter is a safety
tire of a double tire system formed by assembling an outer tire and
a torus film (toric air member) placed therein and being similar to
a radial tire structure onto a rim, wherein the toric air member
provided with a turnup reinforcing ply is provided on its outer
circumferential portion with plural reinforcing annular elements
(cords) arranged at given intervals in a widthwise direction, and
if the tire is punctured, cords of the turnup reinforcing ply and
the reinforcing annular elements are broken by an expansion force
of the toric air member and hence the toric air member subrogates
the load support from the tire.
[0006] Among these safety tires, the type of breaking the cords in
the inside of the toric air member has a fear that the toric air
member itself is damaged and broken by the broken cord end to loss
a function as a safety tire, while the type of breaking the cords
at the outside of the toric air member becomes high in the fear
that the broken cords damage an outer face portion of the toric air
member and an inner face portion of the tire including a carcass.
In any types, therefore, it is difficult to sufficiently ensure a
safe runnable distance after the puncture of the tire required in
this type of the safety tire.
[0007] On the other hand, International Publication brochure
WO00/30877 discloses a safety tire wherein the turnup reinforcing
ply arranged in the toric air member is made of cords each
consisting of a core wire and winding wires helically wound around
the core wire, and the cord is durable to a pressure difference in
usual running and a centrifugal force and has a structure that the
core wire is broken but the winding wires are extended without
breaking in the occurrence of air loss due to the puncture and the
like, and a periphery sufficient to an expansion-deformation of the
toric air member is given to the winding wire, whereby the
occurrence of the aforementioned problem when the cords are broken
as a whole can be avoided.
[0008] In this safety tire, however, it is not guaranteed that the
core wire in the cord as a tension-resistant member is timely
broken over a full circumference and a full width of the toric air
member in the expansion-deformation of the toric air member. Up to
a time that the winding wires of the cord support the expansion
force of the toric air member after the breakage of the core wire
in the cord, the toric air member is violently expansion-deformed
under an action of a small tensile force or a small tensile stress,
so that there is a problem that the toric air member is equally
contacted with the full inner face of the tire.
[0009] The invention is to solve the above problems of the
conventional technique and to provide a toric air bag for a safety
tire capable of sufficiently and equally contacting with a full
inner face of a tire without causing problems in the durability and
the like resulted from the breakage of the cord itself when the
toric air bag is expansion-deformed accompanied with the drop of an
internal tire pressure or the like.
DISCLOSURE OF THE INVENTION
[0010] A toric air bag for a safety tire according to the invention
is placed inside a tire and inflated under a certain internal
pressure and expansion-deformed based on the drop of the internal
tire pressure to subrogate a load support from the tire, in which
at least an expansion-deforming portion of the toric air bag having
a hollow torus shape is made of a tension support member and
properties which indicate a characteristic of such extension
ratio-tensile force that as an extension is increased by the
expansion-deformation, a tensile force per unit width is gradually
increased, are given to the expansion-deforming portion.
[0011] The tension support member is preferable to be constructed
with one or more polymer sheets, or with one or more layers of a
composite of polymer sheet or fibrous member and rubber.
[0012] The safety tire comprised of such a toric air bag and a tire
accommodating the toric air bag is assembled onto a standard rim to
form a safety tire-rim assembly, which is put into use by filling a
given air pressure or gas pressure other than air into the inside
of the tire and filling an internal pressure higher than the
internal tire pressure into the inside of the toric air bag.
[0013] The term "standard rim" used herein means a rim defined in
JATMA YEAR BOOK (2000), ETRTO STANDARD MANUAL 2000, TRA (THE TIRE
and RIM ASSOCIATION INC.) 2000 YEAR BOOK and so on. In JATMA YEAR
BOOK, the standard rim means an approved rim described in general
information. A given air pressure means an air pressure specified
in accordance with a load capacity defined in the same JATMA YEAR
BOOK, ETRTO STANDARD MANUAL, TRA YEAR BOOK and so on.
[0014] In such a safety tire assembled onto the rim, when it is run
under loading in the presence of a given air pressure filled in the
tire, the rubbing of the expansion-deforming portion of the toric
air bag with an inner circumferential face of a tread portion or
the like by an action of centrifugal force or others can
effectively be prevented in a ground contact zone of the tread
portion by an action of the tension support member serving as a
size growth-restraining member in the toric air bag and hence the
polymer sheet or the composite.
[0015] On the other hand, when the pressure difference between the
inside and the outside of the toric air bag exceeds a given value
due to the drop or disappear of the internal tire pressure, the
expansion-deforming portion of the toric air bag is subjected to an
expansion-deformation under an extension-deformation of the polymer
sheet or the composite and approximately equally closed over a full
inner face of the tire, so that the toric air bag subrogates the
load support from the tire while holding the internal pressure and
suppressing the increase of bending deformation of the tire and
hence a continuous safe running can be attained even in the
puncture of the tire or the like.
[0016] In the expansion-deformation of the expansion-deforming
portion of the toric air bag made of the polymer sheet or the
composite as a tension support member due to the puncture of the
tire or the like, since the expansion-deforming portion has such an
extension ratio-tensile force characteristic that the tensile force
per unit width gradually increases as the extension increases, the
expansion-deforming portion and hence the toric air bag is
expansion-deformed in both directions of full circumference and
full width without concentration of local deformation, and as a
result the toric air bag is gradually and equally
expansion-deformed toward the inner face of the tire to surely
close to the full inner face of the tire.
[0017] Therefore, it can effectively prevent the degradation of the
durability in the tire and the toric air bag resulted from biased
contact or imbalanced contact of the toric air bag with the inner
face of the tire or the like.
[0018] Moreover, it is preferable that a region of the toric air
bag contacting with a wheel rim or facing thereto is substantially
a non-expansion deforming portion.
[0019] According to this construction, the property of the toric
air bag fitting to the rim is sufficiently ensured by the
non-expansion deforming portion, and the change in the contact
posture of the toric air bag to the inner face of the tire is
sufficiently prevented under the action of the toric air bag even
in the running of the safety tire under loading or a so-called
run-flat running, whereby the durability can be more improved.
[0020] Further, it is preferable that an initial rigidity in a
biaxial direction is given to the expansion-deforming portion of
the toric air bag. The term "initial rigidity" used herein means
that a tensile modulus determined from a gradient up to 5%
extension before the expansion-deforming portion or the tension
support member is directly subjected to the expansion deformation
is not less than 10 MPa, and the term "biaxial direction" means two
axial lines perpendicular to each other in an arbitrary
direction.
[0021] Such an initial rigidity in the biaxial direction enhances
the shape holding property of the toric air bag before the toric
air bag is expansion-deformed by the drop of the internal tire
pressure, and serves to sufficiently equalize the extensions in the
respective directions while effectively restraining the extension
in only one direction.
[0022] When the tensile modulus is less than 10 MPa, the shape
holding property of the toric air bag is lacking and an outer
diameter thereof or the like becomes large, and hence there is
caused a fear that the toric air bag is damaged by contacting with
the inner face of the tire.
[0023] Furthermore, it is preferable that a curve of tensile force
to extension ratio in the expansion-deforming portion of the toric
air bag is changed in substantially a hook form within an extension
range up to 100% extension ratio.
[0024] More concretely, an average gradient of tensile force to
extension ratio of 0-5% when the expansion-deforming portion of the
toric air bag expands based on the supply of an internal pressure
to the toric air bag is made larger than an average gradient of
tensile force to extension ratio of 5-100% when the
expansion-deforming portion is expansion-deformed accompanied with
the drop of the internal tire pressure.
[0025] According to this construction, an increasing ratio of
tensile force in the expansion-deforming portion of the toric air
bag to the extension ratio is large when the safety tire is
normally run under loading, so that a large force resisting to
centrifugal force or the like can be given to the
expansion-deforming portion, while when the expansion-deforming
portion extends over 5% and is expansion-deformed due to the
puncture of the tire or the like, the expansion-deforming portion
of the toric air bag is deformed smoothly and gently under a small
increasing ratio of tensile force to the extension ratio, whereby
the expansion-deforming portion and hence the toric air bag can be
sufficiently equally contacted with the full inner face of the
tire.
[0026] On the contrary, when the expansion-deforming portion of the
toric air bag is rapidly deformed, a region of the
expansion-deforming portion in the toric air bag prematurely
contacting with the inner face of the tire is locally produced, and
hence the biased contacting of the toric air bag with the inner
face of the tire, partial bending of the toric air bag and so on
are easily caused. Once they are caused, an appropriate contact
state can not be obtained by friction force between the toric air
bag and the tire, bending way of the toric air bag and the
like.
[0027] In order to realize the appropriate expansion-deformation of
the toric air bag as previously mentioned, a degree of lowering the
tensile force to the extension ratio of 5-100% from a maximum value
of the tensile force to the extension ratio of 0-5% in the
expansion-deforming portion of the toric air bag is rendered into
not more than 50% of the maximum value, preferably not more than
40%, more preferably not more than 30% at an atmospheric
temperature of 25.degree. C.
[0028] In other words, when the lowering degree of the tensile
force in the expansion-deforming portion of the toric air bag
exceeds over 50% of the maximum value in the expansion-deformation,
the violent deformation of the expansion-deforming portion of the
toric air bag is not deniable and a fear of locally and prematurely
contacting the toric air bag with the inner face of the tire
becomes higher.
[0029] Incidentally, when a nonwoven fabric is used as a fibrous
member, as an extension form of the nonwoven fabric, a portion
having a lowest tension resistance first starts the deformation,
and subsequently a portion having a lower tension resistance starts
the deformation before the first portion reaches a deformation
limit, and similar deformation is repeated until the extension over
a whole is completed, so that the tensile force may locally
somewhat lower on the way of the expansion-deformation of the toric
air bag, but viewing the nonwoven fabric as a whole, the tensile
force gradually increases with the increase of the
expansion-deformation, and hence the sufficiently equal contacting
of the toric air bag with the inner face of the tire can be
realized and the tension distribution of the toric air bag itself
can be made sufficiently uniform.
[0030] In the above composites, particularly the composite of
fibrous member and rubber, the unit thickness of the fibrous member
is preferable to be within a range of 0.05-2.0 mm because a
homogeneous penetration of rubber over a whole of the thickness of
the fibrous member or a uniform distribution of the fibrous member
to rubber is produced to properly develop a tension-resistance
function inherent to the composite, i.e., a shape holding function
for the toric air bag at a normal state of the tire and the
extension function at the puncture in the composite.
[0031] When the fibrous member is used in the composite, the
fibrous member is preferable to be constructed with a nonoriented
fiber material.
[0032] When the fibrous member is constructed with a fiber material
in which short fibers are randomly arranged, or with a nonoriented
material such as a nonwoven fabric or the like, the aforementioned
rigidity in the biaxial direction can be favorably developed. In
this case, when the tire is relatively largely broken, the
protrusion of the expansion-deformed toric air bag from the broken
portion toward the outside of the tire can be prevented to
effectively protect the toric air bag against an external
injury.
[0033] In other words, when the expansion-deforming portion of the
toric air bag is comprised of only rubber having no fibrous member,
or when the fibrous member in the composite has only a rigidity in
a uniaxial direction, the expansion-deforming portion of the
expansion-deformed toric air bag largely protrudes from the broken
portion of the tire toward outside and hence a fear of subjecting
the toric air bag to an external injury becomes higher.
[0034] Also, the fibrous member is preferable to have a structure
that ends of fibers are dispersed as in the nonwoven fabric.
Because, when the fiber ends are regularly aligned in the fibrous
member, a trouble resulted from stress concentration in locations
of the fiber ends is easily caused in the expansion-deformation of
the toric air bag.
[0035] As a fiber material used in the nonwoven fabric, mention may
be made of synthetic materials such as polyester, polyamide and
polyvinyl alcohol and natural fibers such as rayon, cellulose and
the like alone or in a combination of two or more thereof. Also,
fiber material other than the aforementioned ones may be used.
Furthermore, a fiber of two-layer structure in which an inner layer
and an outer layer of the fiber itself are made from different
materials may be used as a material for the nonwoven fabric.
[0036] Since rubber in the nonwoven fabric composite penetrates or
invades between the fibers through heat and pressure at a
vulcanization step, it is not generally necessary to take a
treatment such as an application of particular adhesive to the
nonwoven fabric or the like, but the application of the adhesive or
the like may be carried out if it is required to obtain a higher
adhesion force.
[0037] Also, it is preferable that the fiber quantity to rubber in
the nonwoven fabric is within a range of 4-50 mass % for
guaranteeing uniform dispersion of the fibers in rubber.
Furthermore, the weight of the nonwoven fabric is preferable to be
within a range of 100-3000 mN/m.sup.2 (10-300 g/m.sup.2).
[0038] When the weight is less than 100 mN/m.sup.2, the unevenness
of fiber distribution becomes large and it is difficult to ensure
the uniformity of the composite, and hence the scattering in the
strength, rigidity and elongation at break of the composite becomes
large, while when the weight exceeds 3000 mN/m.sup.2, the peeling
between fiber and rubber in the composite is apt to be easily
caused.
[0039] Also, it is preferable that the average diameter of the
fiber in the nonwoven fabric is within a range of 0.01-0.2 mm. When
the fiber diameter is less than 0.01 mm, the entanglement of the
fibers is sufficient but the penetrability of rubber is poor and a
fear of causing interlaminar peel or the like becomes high, while
when it exceeds 0.2 mm, the penetrability of rubber is high but the
entanglement of fibers is less and a fear of lacking the rigidity
of the composite or the like remains.
[0040] Moreover, the fibrous member may be constituted with plural
fiber layers, for example, plural fiber cord layers in which the
layers of fiber materials arranged side by side are crossed with
each other. In this case, the orientation of the fiber materials is
unavoidable, but it is possible to ensure the rigidities in biaxial
directions and also the protrusion of the expansion-deformed toric
air bag from the large broken portion of the tire or the like can
be effectively prevented.
[0041] In the aforementioned toric air bag, when two or more
composite layers are further arranged on a portion opposite to the
inner circumferential face of the tire tread portion, the
approaching deformation of the toric air bag to the inner
circumferential face of the tread portion resulted from the action
of centrifugal force or the like can be directly restrained. In
this case, the width of the composite is preferable to be 0.2 times
or more a maximum width of an inner face of a sidewall portion in
the safety tire assembled onto the rim as previously mentioned in
order to control creep of the composite resulted from the action of
centrifugal force. Moreover, the constructions of the composites
among two or more composite layers, for example, kinds of fibrous
members may be differed with each other.
[0042] Furthermore, two or more layers of the composite can be
arranged over mutual points corresponding to a position of a
maximum width of the toric air bag. In this case, the composite
directly serves as a member more countering to the centrifugal
force during the running of the safety tire under loading at normal
state of the tire.
[0043] Moreover, two or more layers of the composite may be
arranged on a portion corresponding to a bead base of the tire. In
this case, a force of restraining the toric air bag to a given
position is enhanced and particularly an accidental position
shifting of the toric air bag in the expansion-deformation and
after the expansion-deformation can be effectively prevented.
[0044] In case of arranging the composite on each portion of the
toric air bag as mentioned above, it is preferable that with
respect to the rigidities of constitutional portions, each of the
rigidity at a crown region and the rigidity at a region
corresponding to the bead base of the tire in the toric air bag at
a posture under an inflation of an internal pressure is made larger
than the rigidity at each side region adjacent to the crown region
in order to sufficiently prevent the position shifting of the toric
air bag as mentioned above and to sufficiently ensure a flat shape
of the toric air bag during the normal running at a high speed and
to ensure the maintenance of the flat shape of the toric air bag in
the application to a tire having a high flatness degree.
[0045] The polymer sheet in the composite is preferable to have an
initial modulus of 0.1-1.3 GPa, a yield stress of 10-33 MPa and an
elongation at break of not less than 20%, whereby the excellent
shape holding property of the toric air bag and the
expansion-deformation thereof can be attained. That is, when the
properties are less than the lower limits of the above numerical
values, it is difficult to ensure the sufficient shape holding
property, while when they exceeds the upper limits, it is difficult
to attain the sufficient expansion-deformation.
[0046] Also, when a property that the contacting of the toric air
bag with the inner face of the tire is carried out in a plastic
deformation zone of the composite is given to the polymer sheet
composite, it is possible to easily and surely identify the toric
air bag after the development of its function at once due to the
puncture of the tire or the like through visual observation, and
hence a mistaken reuse of the toric air bag can effectively be
prevented.
[0047] In such a toric air bag provided with the composite, it is
preferable that a ratio E.sub.P/E.sub.W of tensile stress E.sub.P
at 3% elongation in a circumferential direction to tensile stress
E.sub.W at 3% elongation in a widthwise direction at a portion
facing to the inner circumferential face of the tire tread portion
is not less than 1.
[0048] More preferably, a ratio E.sub.CP/E.sub.CW of tensile stress
E.sub.CP at 3% elongation in the circumferential direction to
tensile stress E.sub.CW at 3% elongation in the widthwise direction
at the portion of the toric air bag provided with the composite
facing to the inner circumferential face of the tread portion and a
ratio E.sub.SP/E.sub.SW of tensile stress E.sub.SP at 3% elongation
in the circumferential direction to tensile stress E.sub.SW at 3%
elongation in the widthwise direction at a side portion adjacent to
the portion facing to the inner circumferential face of the tread
portion satisfy a relation of
E.sub.CP/E.sub.CW.gtoreq.E.sub.SP/E.sub.SW.
[0049] In such a toric air bag provided with the composite, the
term "tensile stress at 3% elongation in the circumferential
direction" means a value obtained by dividing a force required for
providing 3% elongation by an initial sectional area when a test
piece of 200 mm in length and 25 mm in width is cut out from the
toric air bag in the circumferential direction and attached to a
tension testing machine and tensioned at a rate of 50 mm/min in a
longitudinal direction of the test piece, and the term "tensile
stress at 3% elongation in the widthwise direction" means a value
obtained by dividing a force required for providing 3% elongation
by an initial sectional area of the composite when a test piece of
200 mm in length and 25 mm in width is cut out from the toric air
bag in the widthwise direction and attached to a tension testing
machine and tensioned at a rate of 50 mm/min in a longitudinal
direction of the test piece. They are true in the tensile stress of
the other portions of the toric air bag.
[0050] When the expansion-deforming portion of the toric air bag is
expansion-deformed inside the tire, it is required that the
composite is extended by not less than 15% without rapture or
breakage, preferably along the circumferential direction of the
toric air bag, to accept the expansion of the expansion-deforming
portion. For this end, the ratio E.sub.P/E.sub.W of tensile stress
E.sub.P at 3% elongation in the circumferential direction to
tensile stress E.sub.W at 3% elongation in the widthwise direction
is preferable to be not less than 1.
[0051] When the ratio E.sub.P/E.sub.W is less than 1, the
reinforcing effect in the circumferential direction of the toric
air bag is not sufficient and it is difficult to sufficiently
control the extension of the toric air bag countering to a
centrifugal force produced by rotation during the normal running at
about 100 km/h and a tension produced by a difference of internal
pressure between the toric air bag and the tire. In other words,
even if the ratio E.sub.P/E.sub.W is less than 1, it is possible to
ensure the required strength in the circumferential direction by
increasing the number of the composite layers, but it is obliged to
increase the weight of the toric air bag and hence the weight of
the safety tire.
[0052] Furthermore, when the ratios of tensile stresses at 3%
elongation in the toric air bag itself satisfy
E.sub.CP/E.sub.CW.gtoreq.E.sub.SP/E.sub.SW, the ratio of rigidity
in the circumferential direction at the portion facing to the inner
circumferential face of the tread portion becomes higher and the
shape holding property corresponsive to a tire having a high
flatness degree can be provided.
[0053] Moreover, low-rigidity parts, e.g., low elastic members are
annularly arranged on at least one layer among the two or more
composite layers at least arranged over a full circumference of the
portion facing to the inner circumferential face of the tire tread
portion at one or more symmetrical positions with respect to the
equatorial plane of the tire.
[0054] According to this toric air bag, when the tire-rim assembly
is rotated under loading at a state of filling a given air
pressure, e.g., a maximum air pressure defined in a standard
according to JATMA YEAR BOOK, ETRTO STANDARD MANUAL, TRA YEAR BOOK
or the like into the tire and filling an air pressure higher than
the above air pressure into the toric air bag, the two or more
composite layers serve to more effectively control the size growth
of the toric air bag resulted from the centrifugal force or the
like and particularly it surely prevents the rubbing of the toric
air bag with the inner circumferential face of the tread at a
ground contact region of the tread.
[0055] As a gas filling into the tire and the toric air bag, a
nitrogen gas or other inert gas may be used instead of air.
[0056] On the other hand, when the difference in pressure between
the inside and the outside of the toric air bag exceeds a given
value due to the drop of the internal tire pressure or the like,
the composite is extension-deformed to not less than 15% in the
elastic region or from the elastic region toward the plastic region
and the expansion-deforming portion of the toric air bag is
expanded accompanied therewith.
[0057] In such an extension-deformation of the composite, since the
composite is provided with the low-rigidity part at a position
symmetrical with respect to the equatorial plane of the tire, for
example, at a widthwise central portion of the composite, the
extension-deformation starts from the central portion of the
composite being the low-rigidity part and hence the
expansion-deforming portion of the toric air bag is substantially
uniformly enlarged and deformed over a full circumference at the
portion corresponding to the central portion of the composite.
[0058] Such an enlargement-deformation of the toric air bag started
from a given position in the widthwise direction gradually
propagates to widthwise adjoining portions of the composite
symmetrically with respect to the equatorial plane and finally over
a full width of the composite, and hence the toric air bag is
approximately equally enlarged and deformed over the whole of the
composite in the widthwise direction.
[0059] Therefore, even if there is a scattering in the rigidity at
the side portions of the composite, the expansion-deformation of
the expansion-deforming portion in the toric air bag biasing toward
widthwise one side of the composite can sufficiently be prevented,
and as a result there are not caused problems such as local
thinning of the toric air bag, lowering of load supporting ability
and durability due to local contact with the inner face of the tire
and so on.
[0060] If the low-rigidity part is arranged in the composite at
plural places, the whole of the toric air bag can be more rapidly
expansion-deformed while maintaining the above function and
effects.
[0061] Also, when the rigidity is gradually changed in one
low-rigidity part, the start of the extension-deformation of the
composite and hence the start of the expansion-deformation of the
toric air bag can be conducted more prematurely and more smoothly,
and also the propagation of the expansion-deformation in the
widthwise direction can be conducted more smoothly.
[0062] Moreover, the low-rigidity part may be arranged on each
widthwise side portion of the composite, whereby the rigidities of
these side portions can be sufficiently decreased as compared with
those of the other portions to start the propagation of the
expansion-deformation of the toric air bag from these side
portions. However, considering that the propagation of the
expansion-deformation of the toric air bag is largely affected by
an influence of the scattering in the rigidity being apt to be
produced in the side portions of the reinforcing layer, it is
preferable to arrange the low-rigidity part at a position separated
from a side edge of the composite.
[0063] In this case, the low-rigidity part may be constructed with
a thinned portion of the composite, for example, a portion reducing
a gauge of the composite itself, or with an annular notched portion
formed in the composite.
[0064] In the other toric air bag, at least one protection layer
comprising a plurality of reinforcing elements extending in a
circumferential direction in substantially a wavy form, preferably
rubberized reinforcing elements is arranged on at least a portion
facing to the inner circumferential face of the tire tread portion
and frequently at an outer circumferential side of the composite
along a full circumference thereof, in which wavy pitch and
amplitude of the reinforcing element are selected so as to still
retain the wavy form in the reinforcing element at a posture of
closing the toric air bag to the inner face of the tire.
[0065] In this case, it is preferable that these reinforcing
elements are arranged side by side in the same phase of the wavy
form or in a regular phase shifting thereof.
[0066] According to this toric air bag, when the toric air bag is
closed to the inner face of the tire at an expansion posture for
supporting a load, if the tire tread portion is subjected to an
external injury through sharpened stone or other foreign matter to
arrive such a foreign matter at the toric air bag, since the
reinforcing elements of the protection layer, which are arranged in
the portion of the toric air bag facing to the inner
circumferential face of the tread portion or on an outer
circumferential face of the toric air bag or a vicinity thereof and
comprise cords or filaments extending in the wavy form, still
maintain the wavy form under the expansion-deformation of the toric
air bag to retain a sufficient extension margin and also a tensile
force is not substantially applied thereto, the protection layer
and hence the toric air bag can flexibly deform so as to envelop
the foreign matter therein and as a result the damages resulted
from the impaction of the toric air bag with the foreign matter can
be effectively prevented.
[0067] Moreover, the reinforcing element is preferable to be made
of a chemical fiber cord as compared with a steel cord in order to
attain the weight reduction of the toric air bag. Particularly,
when it is made of an aramid fiber cord, the strength of the cord
can be largely increased.
[0068] When a wavy belt comprised of steel cords extending in a
circumferential direction in substantially a wavy form is used as a
part of the tension support member, the strength of the toric air
bag can be more increased. Also, it can be used as an adjusting
means of the rigidity in the biaxial direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0069] FIG. 1 is a diagrammatically section view of an embodiment
of the toric air bag for a safety tire according to the invention
illustrating a state of assembling the safety tire onto a rim.
[0070] FIG. 2 is a graph showing a change of tensile force to
extension ratio in a composite constituting a tension support
member.
[0071] FIG. 3 is a graph showing a curve of a characteristic of
extension ratio-tensile force of the conventional technique.
[0072] FIG. 4 is a diagrammatically section view of another
embodiment of the toric air bag likewise FIG. 1.
[0073] FIG. 5 is a schematically section view illustrating the
other embodiment of the toric air bag.
[0074] FIG. 6 is a diagrammatically section view illustrating an
expansion-deformation embodiment of the toric air bag.
[0075] FIG. 7 is a diagrammatically section view illustrating an
unfavorable expansion-deformation embodiment of the toric air
bag.
[0076] FIG. 8 is a schematically section view illustrating an
embodiment of the low-rigidity part.
[0077] FIG. 9 is a schematically section view illustrating a
rigidity change in the low-rigidity part.
[0078] FIG. 10 is a schematically section view illustrating a
further embodiment of the toric air bag.
[0079] FIG. 11 is a plan view of a protection layer in the toric
air bag.
[0080] FIG. 12 is a schematically section view illustrating a state
of supporting a load by the toric air bag.
[0081] FIG. 13 is a view illustrating an initial existing state of
a reinforcing element.
[0082] FIG. 14 is a schematically section view of a toric air bag
in comparative tires.
[0083] FIG. 15 is a schematically section view of a toric air bag
in example tires.
[0084] FIG. 16 is a schematically section view of a toric air bag
in other example tires.
BEST MODE FOR CARRYING OUT THE INVENTION
[0085] In FIG. 1 is shown a section view of a toric air bag
according to the invention at an assembled state of a safety tire
and a rim, in which numeral 1 is a whole of a safety tire, and the
safety tire 1 is a combination of a tire 2 and a toric air bag 3
placed therein.
[0086] The tire 2 is the same as a general pneumatic tire and
comprises a tread portion 4, sidewall portions 5 connecting to both
sides thereof, and a bead portion arranged at an inner
circumferential side of the sidewall portion 5.
[0087] Also, the toric air bag 3 having a hollow torus as a whole
comprises on its periphery an expansion-deforming portion
contributing to support a load by expansion-deformation accompanied
with a drop or disappear of an internal pressure in the tire 2, and
a non-expansion deforming portion positioning opposite to or close
to a rim assembled onto the tire and not substantially conducting
expansion-deformation.
[0088] In such a toric air bag 3, at least an expansion-deforming
portion, which is extended outward from a position corresponding to
both bead bases 7 of the tire in a radial direction inclusive of a
portion adjacent thereto as a whole in the illustrated embodiment,
is constructed with a tension support member, and the tension
support member is formed by one or more polymer sheets, or by a
composite of a polymer sheet and rubber, or by at least one layer
of a composite of fiber member 8 and rubber 9 in the illustrated
embodiment.
[0089] In the toric air bag 3, therefore, it is possible to
construct the nonexpansion deforming portion with the tension
support member.
[0090] The safety tire 1 can be used as a rim assembly by
assembling the tire 2 onto an approved rim R previously mentioned,
and filling a given internal pressure P.sub.1, for example, a
maximum air pressure defined, for example, according to JATMA YEAR
BOOK or the like into the inside of the tire through a valve fixed
thereto, and also filling a given internal pressure P.sub.2 into
the inside of the toric air bag 3. Moreover, an objective for the
filling of the internal pressure may be an inert gas or other gas
in addition to air.
[0091] In this case, the outer diameter of the toric air bag 3 is
set to be smaller than the outer diameter of the inner
circumferential face of the tread portion. Also, the internal
pressure P.sub.2 of the toric air bag is usually a value higher
than the internal tire pressure P.sub.1.
[0092] A composite 10, particularly a polymer sheet or fibrous
member 8 as a tension support member is arranged at a distance
separated from the inner circumferential face of the tread portion
as a size growth controlling member countering to a force produced
by a centrifugal force and a difference of internal pressure in a
portion of the toric air bag 3 or a crown region thereof opposite
to the inner circumferential face of the tread portion 4 at a
ground contact region of the tread portion when the tire in such a
rim assembly is run under loading in the presence of the given
internal pressure P.sub.1.
[0093] On the other hand, when the pressure difference between the
inside and the outside in the toric air bag 3 exceeds a given value
due to the drop of the internal tire pressure to, for example, an
atmospheric pressure, the expansion-deforming portion of the toric
air bag 3 is expansion-deformed by the extension-deformation of the
composite 10, directly the polymer sheet or fibrous member 8 to
sufficiently and equally close to the inner face of the tire over a
whole thereof, and as a result the support of load is subrogated
from the tire 2 to the toric air bag 3.
[0094] Therefore, even if the tire is punctured or the like, the
sufficiently safe running can be continued under the action of the
toric air bag 3.
[0095] In the expansion-deformation of the toric air bag 3
accompanied with the drop of the internal tire pressure as
mentioned above, the expansion-deforming portion of the toric air
bag 3 has an extension ratio-tensile force characteristic that as
shown in FIG. 2 using two kind of the composites, tensile force per
unit width, for example, a width of 25 mm substantially gradually
increases as an elongation through the expansion-deformation, i.e.,
an elongation at an extension ratio exceeding 5% in the figure
increases.
[0096] Moreover, an extension up to 5% in the composite shown in
FIG. 2, i.e., the expansion-deforming portion thereof or a greater
part thereof is generated by filling the internal pressure P.sub.2
into the toric air bag 3 for rendering the safety tire 1 into the
rim assembly as previously mentioned.
[0097] The expansion-deforming portion of the toric air bag 3
indicating a characteristic of such an extension ratio-tensile
force is uniformly and gradually extended as a whole in both of
circumferential direction and widthwise direction of the
expansion-deforming portion based on the action of, for example,
the composite 10 arranged over a whole of the expansion-deforming
portion in the aforementioned expansion-deformation resulted from
the puncture of the tire or the like, and as a result the
expansion-deforming portion is equally and surely closed to the
full inner face of the tire.
[0098] In this case, it is preferable that a curve of tensile force
to extension ratio is changed in substantially a hook form within
an extension range of the expansion-deforming portion of the toric
air bag arriving to 100% extension ratio. For this purpose, it is
preferable that an average gradient of tensile force to extension
ratio of 0-5% in the expansion-deforming portion is made larger
than an average gradient of tensile force to extension ratio of
5-100%.
[0099] According to the above, the composite strongly withstands to
the expansion-deformation of the toric air bag 3 under a large
gradient of tensile force and can effectively control the size
growth thereof during the running of the safety tire under loading
before the tire 2 in the rim assembly causes troubles such as
puncture or the like, while in the expansion-deformation of the
toric air bag 3 by the puncture of the tire or the like, the toric
air bag 3 can be gradually expansion-deformed under a small
gradient of tensile force to more equally close the
expansion-deforming portion of the toric air bag 3 to the full
inner circumferential face of the tire.
[0100] This becomes particularly remarkable when the deformation
rate of the expansion-deforming portion of the toric air bag 3 is
more controlled when a degree of lowering tensile force to
extension ratio of 5-100% from a maximum value of tensile force to
extension ratio of 0-5% in the toric air bag is rendered into not
more than 50% of the maximum value, preferably not more than 30%
thereof.
[0101] On the contrary, when the tensile force of the
expansion-deforming portion of the toric air bag to the extension
ratio violently and largely lowers in the expansion-deformation of
the toric air bag and thereafter the tensile force hardly increases
with the increase of the elongation as shown in FIG. 3, the
expansion-deformation of the toric air bag by the drop of the
internal tire pressure violently proceeds, and hence a local
premature contact of the toric air bag with the inner face of the
tire is caused unless the proceeding rate of the
expansion-deformation in each portion of the toric air bag is
constantly regulated at a higher accuracy, which results in biased
contact of the toric air bag with the inner face of the tire,
partial bending of the toric air bag and the like. There is a
problem that the occurrence of such a phenomenon brings about the
degradation of a so-called run-flat durability of the toric air
bag.
[0102] Moreover, when initial rigidity in biaxial direction is
given to the aforementioned expansion-deforming portion of the
toric air bag, the shape holding property of the toric air bag 3 is
sufficiently enhanced in the safety tire 1 and rim assembly and
also the directionality in the expansion-deformation of the toric
air bag is controlled, whereby the equality of the
expansion-deformation can be further enhanced.
[0103] When the composite 10 is constructed with fibrous member 8
and rubber 9, it is preferable that a unit thickness of the fibrous
member 8 is within a range of 0.05-2.0 mm in order to ensure
relative uniform distribution of fibrous member 8 and rubber 9 to
sufficiently develop functions of the composite as being
expected.
[0104] In this case, it is preferable that the fibrous member 8 is
constructed with non-oriented materials, because the composite is
sufficiently equally extended in any directions with the removal of
the directionality in the extension though the extension ratio of
the expansion-deforming portion of the toric air bag is not less
than 5% or not more than 5%, and further if the tire is relatively
larger broken, the protrusion of the toric air bag 3 from the
broken portion toward the outside of the tire is more effectively
prevented under the restraint by the fibrous member 8 to improve
the resistance to external injury.
[0105] Furthermore, it is preferable to dispersedly arrange fiber
ends in the fibrous member 8 for preventing the concentration of
strain or stress in the fiber ends during the deformation of the
expansion-deforming portion of the toric air bag. For this purpose,
it is desirable to use a nonwoven fabric as the fibrous member
including a non-directionality.
[0106] Moreover, when the nonwoven fabric is used as the fibrous
member 8, it is preferable that a fiber quantity to rubber 9 in the
composite 10 is 4-50 mass % and a weight is within a range of
100-3000 mN/m.sup.2 for sufficiently uniformizing relative
distribution of rubber 9 and fibers to sufficiently develop the
required function of the composite 10.
[0107] That is, when the fiber quantity is less than 4% or the
weight is less than 100 mN/m.sup.2, the penetrability of rubber is
good, but the entanglement of fibers is lacking and it is difficult
to ensure the rigidity, tension resistance and the like required
for the composite 10, while when the fiber quantity exceeds 50% or
the weight exceeds 3000 mN/m.sup.2, the entanglement of fibers is
sufficient, but the penetrability of rubber is poor and the
interlaminar peeling in the nonwoven fabric or the like is easily
caused and also the scattering of fiber distribution to rubber 9
becomes large to make non-uniform the strength, rigidity and the
like in the one composite and hence it is difficult to stabilize
the performances.
[0108] More preferably, the fibers in the nonwoven fabric have an
average diameter of 0.01-0.2 mm and a length of not less than 8 mm.
That is, when the fiber diameter is less than 0.01 mm, the
entanglement of fibers is sufficient, but the penetrability of
rubber is poor and a fear of causing the interlaminar peeling in
the nonwoven fabric becomes high, while when it exceeds 0.2 mm, the
penetrability of rubber is high, but the entanglement of fibers
becomes less and a fear of making the rigidity or the like of the
composite 10 lacking remains. Also, when the fiber length is less
than 8 mm, the entanglement of fibers is less and the rigidity or
the like of the composite tends to be lacking.
[0109] To the composite 10 can be applied a fibrous member
comprised of plural fiber layers, fiber materials arranged side by
side of which layers being crossed with each other, instead of the
aforementioned fibrous member. Even in such a fibrous member, the
shape holding property, equality of expansion-deformation and the
like based on the rigidity in biaxial direction are sufficiently
ensured and also the protrusion of the toric air bag outward from
the broken portion of the tire can effectively be prevented.
[0110] In the invention, when the tension support member of the
toric air bag 3 is constructed with two or more composite layers,
the composites having the same kind of the fibrous members are
arranged in lamination, or it is possible to arrange the composites
having different kinds of the fibrous members in lamination.
[0111] Also, the tension support member constituting the
expansion-deforming portion of the toric air bag is not necessary
to be made uniform over the whole of the expansion-deforming
portion. For example, it is possible to partially change the
lamination number of the composites, if necessary.
[0112] FIG. 4 shows an example of the above, wherein two or more
composite layers including the tension support member as a
substrate are arranged in lamination on a crown region or a portion
11 corresponding to the inner circumferential face of the tire
tread portion 4, and also two or more composite layers are arranged
in lamination on a portion 12 corresponding to the bead base 7 of
the tire and adjacent thereto, and all of these layers are united
together.
[0113] In the illustrated embodiment, three layers of the composite
13 are added to the tension support member as a substrate in the
portion 11 corresponding to the tread portion, while two layers of
the composite 14 are added to the portion 12 corresponding to the
bead base, whereby the displacement of the expansion-deforming
portion of the toric air bag 3, particularly the portion 11
corresponding to the tread portion approaching to the tread portion
through centrifugal force or the like is effectively prevented and
the restraining force of the toric air bag 3 to a given position is
more enhanced.
[0114] In this figure, the composite arranged as an innermost layer
in the portion 11 is constructed by dividing the tension support
member as a substrate to form a part of the tension support member,
so that when the tension support member as a substrate is
integrally formed as shown in FIG. 1, the innermost layer of the
composite can be omitted from the structure shown in FIG. 4.
[0115] The composite 13 arranged in the portion 11 is preferable to
have a width w corresponding to not less than 0.2 times a maximum
width W between inner faces of the sidewall portions 5 in the
safety tire 1 and rim assembly. Therefore, the composite 13 may be
arranged over mutual positions of a maximum width of the toric air
bag itself. According to this arrangement, creep of the composite
13 resulted from the action of centrifugal force or the like can be
effectively prevented, and the function of the composite countering
to centrifugal force or the like can be further enhanced.
[0116] In the latter case, non-uniform deformation of the portion
11 corresponding to the tread in the widthwise direction can be
more effectively controlled in the expansion-deformation of the
toric air bag 3.
[0117] In case of the tension support member having such a
structure, it is preferable that each of the rigidity of the
portion 11 corresponding to the tread portion and the rigidity of
the portion 12 corresponding to the bead base is made larger than
the rigidity of a side region therebetween at a posture of filling
the internal pressure in the toric air bag 3 as shown in the
figure, whereby the toric air bag itself is rendered into a stable
flat form to prevent the undesirable contact of the portion 11
corresponding to the tread portion with the inner circumferential
face of the tread portion through centrifugal force or the like.
Also, this is preferable in the application of the toric air bag to
a tire having a high flatness ratio.
[0118] When the composite is formed by the polymer sheet and rubber
as mentioned above, it is preferable that the polymer sheet has an
initial modulus of 0.1-1.3 GPa, a yield stress of 10-33 MPa and an
elongation at break of not less than 20% for ensuring an excellent
shape holding property and a smooth expansion-deformability in the
toric air bag. Further, it is preferable that a property of
conducting the contact of the toric air bag with the inner face of
the tire in its plastic deformation region is given to the polymer
sheet composite, mainly the polymer sheet for simply and surely
conducting visual distinction between the toric air bag
expansion-deformed once to develop its function and another toric
air bag.
[0119] Also, the composites 13, 14 are integrally united with each
other as shown in the figure, or they may be arranged so as to
separate from each other.
[0120] In such a toric air bag 3 provided with the composites 10,
13, it is preferable that a ratio E.sub.P/E.sub.W of tensile stress
E.sub.P at 3% elongation in the circumferential direction of the
toric air bag 3 to tensile stress E.sub.W at 3% elongation in the
widthwise direction of the toric air bag in the portion 11
corresponding to the tread portion is not less than 1 for
controlling the size growth of the toric air bag 3 through
centrifugal force or the like and leading smooth propagation of the
expansion-deformation of the toric air bag 3 in the widthwise
direction.
[0121] Viewing the toric air bag provided with the composites as a
whole, it is preferable that a ratio E.sub.CP/E.sub.CW of tensile
stress E.sub.CP at 3% elongation in the circumferential direction
to tensile stress E.sub.CW at 3% elongation in the widthwise
direction at the portion 11 corresponding to the tread portion and
a ratio E.sub.SP/E.sub.SW of tensile stress E.sub.SP at 3%
elongation in the circumferential direction to tensile stress
E.sub.SW at 3% elongation in the widthwise direction at the side
portion adjacent to the portion 11 corresponding to the tread
portion satisfy the relation of
E.sub.CP/E.sub.CW.gtoreq.E.sub.SP/E.sub.SW. In this case, the
function of controlling the outer size can be more sufficiently
developed by enhancing the rigidity of the portion 11 corresponding
to the tread portion in the circumferential direction and hence the
weight reduction can be attained while ensuring the function of
controlling the outer size.
[0122] In FIG. 5 is schematically shown another embodiment of the
toric air bag, in which two or more composite layers including the
tension support member as a substrate, four composite layers in
total including three additional composite layers 13 in the
illustrated embodiment are arranged on at least a portion 11 of a
toric air bag 3 corresponding to the tread portion over a full
circumference thereof and at least one layer of these composites
10, 13, for example, an outermost layer is provided with a
low-rigidity part located at one or more positions in symmetry with
an equatorial plane C of the tire, one low-rigidity part 15 formed
by cutting out the outermost layer in an annular form across the
equatorial plane C of the tire. In the invention, the low-rigidity
part may be formed by decreasing the thickness of either the
composite 10 or 13.
[0123] When the tension support member of the toric air bag 3 has
such a structure, if the expansion-deforming portion of the toric
air bag 3 is expansion-deformed by the drop of the internal tire
pressure or the like, the low-rigidity part 13 of the composite 10,
13 having a smallest resistance to tensile force first starts
extension-deformation through the internal pressure P.sub.2 of the
toric air bag irrespectively of the integrally united body of the
composite 13 and the tension support member as the substrate or the
separate body thereof, and the expansion-deforming portion of the
toric air bag starts the expansion-deformation from the
low-rigidity part 15 accompanied therewith as shown in FIG. 6.
[0124] The thus generated expansion-deformation of the toric air
bag 3 gradually enlarges outward in the widthwise direction
substantially symmetrically with respect to the equatorial plane C
of the tire based on gradual propagation of the
extension-deformation of the composite 10, 13 from a portion
adjacent to the low-rigidity part 15 outward in the widthwise
direction of the composite and finally the toric air bag 3
substantially equally expansion-deforms over a whole of a
cross-sectional face shown in the figure.
[0125] On the contrary, when the above low-rigidity part is not
formed, the rigidities of left and right side portions of the
composite 10, 13 shown in the figure become non-uniform. As the
rigidity difference becomes large, the toric air bag starts the
biased expansion-deformation only at a side having a lower rigidity
as shown in FIG. 7 and then the deformation proceeds only at this
side, and in an extreme case, the composite 13 may be largely
push-displaced toward the other side as shown in the figure.
[0126] When such a biased expansion-deformation is generated in the
toric air bag, there is a fear of causing the thinning or the like
due to the local extension-deformation of a part of the toric air
bag in spite of the push-displacement of the composite 13, so that
an anxiety remains in the load supporting ability, durability and
the like of the toric air bag.
[0127] In the invention, therefore, even if there is a large
scattering in the rigidities of the side portions of the composite,
there can be sufficiently prevented the expansion-deformation of
the toric air bag biasing toward one side of the composite in the
widthwise direction, and hence there is not caused problems such as
lowering of the load supporting ability, lowering of the durability
and so on due to the local thinning of the toric air bag, local
contacting with the inner face of the tire and the like.
[0128] As shown in FIG. 8a, the low-rigidity part may be arranged
in each side portion of the composite 13 in the widthwise
direction. In this case, the rigidity of such side portions can be
sufficiently decreased as compared with the other portion to start
the propagation of the expansion-deformation of the toric air bag
from these side portions. However, considering that the propagation
of the expansion-deformation of the toric air bag is largely
affected by the scattering of the rigidity particularly apt to be
caused in the respective side portions of the composite, it is
preferable to arrange the low-rigidity part in a position separated
from the side edge of the composite as shown in FIG. 8b.
[0129] Even in these cases, the expansion-deformation of the toric
air bag starts from these low-rigidity parts at substantially the
same time, and the expansion-deformation region is enlarged
symmetrically with respect to the equatorial plane C of the tire
and then extends over a full width of the composite, and hence the
occurrence of the biased expansion-deformation of the toric air bag
can sufficiently be prevented and also a more rapid
expansion-deformation of the toric air bag as a whole can be
produced.
[0130] Also, the thus formed low-rigidity part can gradually change
the rigidity in its inside. In this case, the enlargement of the
expansion-deformation of the toric air bag 3, for example, from the
central portion of the low-rigidity part toward the side thereof
can be promoted smoothly and surely.
[0131] FIG. 9 is a view illustrating an example of gradually
changing the rigidity, in which the widths of cut-out portions of
the composites in the low-rigidity part 15 are changed stepwise to
gradually increase the rigidity from the center position of the
low-rigidity part 15 toward the side thereof.
[0132] FIG. 10 is a schematic view of a further embodiment of the
toric air bag, in which a protection layer for the toric air bag is
arranged on an outer circumferential side of the tension support
member in the portion 11 corresponding to the tread portion.
[0133] That is, one or more protection layers 17 comprised of
plural reinforcing elements such as cords or filaments, preferably
chemical fiber cords extending in the circumferential direction in
substantially wavy form, preferably rubberized reinforcing elements
16 are arranged on the outer circumferential side of the tension
support member.
[0134] FIG. 11 is a plan view exaggeratedly illustrating the
protection layer for the toric air bag shown in FIG. 10. The
reinforcing elements 16 in the protection layer 17 have a wavy form
shown in the figure even at a state of filling a given internal
pressure into the toric air bag 3. In this case, it is preferable
that the reinforcing elements 16 have a relative arranging relation
that the wavy form is aligned at the same phase or in a regular
phase shift in the plane.
[0135] Therefore, these reinforcing elements 16 have a wavy form
having a smaller wavy pitch and a larger amplitude before the
filling of the internal pressure into the toric air bag 3.
[0136] When the internal tire pressure is dropped, the above toric
air bag 3 is expansion-deformed from the state shown in FIGS. 10
and 11 to about 15-25% as a circumferential length under the action
of the internal pressure previously filled thereinto to subrogate
the support of load from the tire 2 at a posture of closing to the
inner face of the tire as shown by a cross section in FIG. 12. In
this case, the protection layer 8 has such a state that the
reinforcing elements 16 retain the wavy form even at the ground
contact region in accordance with the selection of initial wavy
pitch and amplitude in the reinforcing element 16 and hence the
reinforcing element 16 has yet a sufficient extension margin and
tension is not substantially applied thereto.
[0137] In order to leave the sufficient extension margin to the
reinforcing element 16 even at this state, if the increase of the
circumferential length of the toric air bag 3 from the state shown
in FIGS. 10 and 11 to the state shown in FIG. 12 is made 20%, it is
preferable that a ratio A/.lamda. of amplitude A to wavy pitch
.lamda. of the reinforcing element 16 as shown in FIG. 13 under the
state shown in FIGS. 10 and 11 is within a range of 0.35-0.50.
[0138] In a so-called run-flat state as shown in FIG. 12,
therefore, when foreign matter given external injury to the tread
portion 4 of the tire 2 arrives at the toric air bag 3, since the
toric air bag 3 has an excellent flexibility based on the extension
margin of the reinforcing element 16, it deforms so as to envelop
the foreign matter and hence the damage of the toric air bag 3 due
to the arrival of the foreign matter is sufficiently prevented.
EXAMPLES
Example 1
[0139] With respect to various safety tires wherein a structure of
a tension support member as an expansion-deforming portion of a
toric air bag placed in a tire having a size of 315/60R22.5 is
varied, the running durability, resistance to external injury and
resistance to piercing of foreign matter in the safety tire are
measured under a state that the toric air bag is completely
expansion-deformed by dropping an internal tire pressure to an
atmospheric pressure to obtain results as shown in Table 1. In this
table, the larger the index value, the better the result.
[0140] The running durability is determined by measuring a running
distance until the load can not be supported by the toric air bag
when a low internal pressure drum test is carried out at a state
(after the confirmation of run-flat state) that the internal tire
pressure is rapidly dropped from a state of normally running the
safety tire under loading (internal tire pressure: 900 kPa,
internal pressure of toric air bag: 950 kPa).
[0141] The resistance to external injury is determined by measuring
a running distance until the load can not be supported by the toric
air bag when a low internal pressure drum test is carried out at a
state that assuming a puncture due to side cut on markets, a cut
damage (cut of 60 mm in a radial direction) is previously formed in
a side portion of the tire and the internal tire pressure is at a
loss state and an internal pressure of 400 kPa is filled in the
toric air bag placed in the tire.
[0142] The resistance to piercing of foreign matter is determined
by measuring a running distance in the same manner as described
above when a low internal pressure drum test is carried out at a
state that assuming very severe running condition such as running
on bad road in markets or the like and such a state that foreign
matter scattered on a road is treaded by the tire and passes
through the tire to cause puncture of the tire and arrives at the
toric air bag to fear damage of the toric air bag by a sharp edge
of the foreign matter, a bolt of M10 is embedded to a depth of 40
mm in a center of a tire tread and an internal pressure of 400 kPa
is filled into the toric air bag.
[0143] In a conventional tire, the toric air bag is comprised of
only rubber as shown by a schematic section in FIG. 14a.
[0144] In a comparative tire 1, four layers of nonwoven fabric
composite are arranged on a crown region of the toric air bag as
shown in FIG. 14b.
[0145] In a comparative tire 2, as shown in FIG. 14c, a single cord
composite comprised of two cord layers containing cords arranged
side by side therein, cords of which layers being crossed with each
other, is arranged over a region ranging from a side portion of the
toric air bag to a portion corresponding to a bead base in addition
to the structure shown in FIG. 14b. In this case, the cord
composite has a characteristic of extension ratio-tensile force
shown in FIG. 3.
[0146] In a comparative tire 3, the cord composite in the toric air
bag of the comparative tire 2 is replaced with a cord composite
comprised of one cord layer containing cords extended in only one
direction and at a cord angle of 30.degree. with respect to a
meridianal line of the toric air bag.
[0147] In a toric air bag of an example tire 1, as shown in FIG.
15a, one layer of nonwoven fabric composite is arranged on a region
ranging from a side portion to a portion corresponding to a bead
base and four layers in total of nonwoven fabric composite are
arranged on a crown region.
[0148] In a toric air bag of an example tire 2, one layer of
nonwoven fabric composite is arranged over a whole of a region from
a portion corresponding to a bead base to a portion corresponding
to another bead base.
[0149] In a toric air bag of an example tire 3, as shown in FIG.
15b, two layers of nonwoven fabric composite are further arranged
on the portion corresponding to the bead base in addition to the
structure shown in FIG. 15a.
[0150] In a toric air bag of an example tire 4, the nonwoven fabric
composite of the example tire 3 is replaced with a polyethylene
sheet.
[0151] In a toric air bag of an example tire 5, as shown in FIG.
15c, a low-rigidity part located at a central portion in a
widthwise direction is formed in two outer layers of the composite
on a crown region in the same arrangement of the nonwoven fabric
composite as in the example tire 3.
[0152] In a toric air bag of an example tire 6, as shown in FIG.
16a, a protection layer comprised of aramid fiber cords extending
in a circumferential direction in substantially a wavy form is
arranged on an outer periphery of the crown region of the toric air
bag shown in FIG. 15b.
[0153] In a toric air bag of an example tire 7, as shown in FIG.
16b, one layer of the nonwoven fabric composite arranged over a
region from a side portion to a portion corresponding to a bead
base in the toric air bag shown in FIG. 15b is replaced with one
layer of cord composite comprised of two cord layers containing
cords arranged side by side therein, cords of which layers being
crossed with each other, and a cord angle with respect to a
meridianal line of the toric air bag is 45.degree.. TABLE-US-00001
TABLE 1 Conventional Comparative Comparative Comparative tire tire
1 tire 2 tire 3 Composite crown region None nonwoven nonwoven
nonwoven fabric: fabric: fabric: four layers four layers four
layers side region None none cross cord: unidirectional one layer
cord: one layer *1 portion None none cross cord: unidirectional
corresponding to one layer cord: one layer bead base low-rigidity
part None none none None Running durability (index) -- 50 80 100
Resistance to external injury no run-flat no run-flat 90 100
(index) running *3 running *3 Resistance to piercing of -- -- -- --
foreign matter (index) Figure Example tire 1 Example tire 2 Example
tire 3 Example tire 4 Composite crown region nonwoven nonwoven
nonwoven resin: four layers *2 fabric: fabric: fabric: four layers
one layer four layers side region nonwoven nonwoven nonwoven resin:
one layer fabric: fabric: fabric: one layer one layer one layer
portion nonwoven nonwoven nonwoven resin: corresponding to fabric:
fabric: fabric: three layers bead base one layer one layer three
layers low-rigidity part None none none None Running durability
(index) 140 130 180 180 Resistance to external injury not less than
not less not less not less than 200 (index) 200 than 200 than 200
Resistance to piercing of -- -- 100 -- foreign matter (index)
Figure -- Example tire 5 Example tire 6 Example tire 7 Composite
crown region nonwoven nonwoven nonwoven fabric: fabric: fabric:
four layers four layers four layers side region nonwoven nonwoven
cross cord: fabric: fabric: one layer one layer one layer portion
nonwoven nonwoven cross cord: corresponding to fabric: fabric: one
layer + nonwoven bead base three layers three layers fabric: two
layers low-rigidity part None presence none Running durability
(index) 200 180 170 Resistance to external injury not less than not
less not less (index) 200 than 200 than 200 Resistance to piercing
of -- not less foreign matter (index) than 200 Figure Specification
of nonwoven fabric Weight: 500 mN/m.sup.2 Thickness: 0.1 mm Fiber
diameter: 0.02 mm Fiber length: 44 mm Fiber quantity in composite:
28 mass % *1 Specification of cord Cord: 66Nr Cord diameter: 0.61
mm Treat gauge: 1.2 mm End count: 31 cords/5 cm *2 Specification of
resin Polyethylene sheet Initial modulus: 1.1 GPa Yield stress: 30
MPa Elongation at break: 650% Gauge: 0.8 mm *3 In case of a side
structure having no composite at a state of filling an internal
pressure, the toric air bag projects from a side cut damage of the
tire and hence the running at flat state is impossible.
[0154] As seen from this table, all example tires develop excellent
running durability and resistance to external injury, and the
example tire 6 provided with the protection layer can sufficiently
develop the resistance to piercing of foreign matter.
Example 2
[0155] In toric air bags of example tires having the same structure
as in the toric air bag of the example tire 1 shown in FIG. 15a,
when the construction of the composite itself in the nonwoven
fabric composite is varied, results measured on a run-flat running
durability are shown in Table 2.
[0156] The run-flat running durability is measured in the same
manner as in the running durability in Example 1. The larger the
index value, the better the result. TABLE-US-00002 TABLE 2 Example
tire 11 Ex- Ex- Ex- Ex- Com- Com- Com- Com- (Example Example
Example ample ample ample ample parative parative parative parative
tire 1) tire 12 tire 13 tire 14 tire 15 tire 16 tire 17 tire 11
tire 12 tire 13 tire 14 Weight of nonwoven 500 200 1000 2000 3000
500 4000 50 500 500 500 fabric mN/m.sup.2 Unit thickness of 0.1
0.05 0.2 0.4 0.7 0.15 2.1 0.02 0.2 0.06 0.1 nonwoven fabric mm
Fiber diameter 0.02 0.02 0.02 0.02 0.02 0.03 0.02 0.02 0.3 0.005
0.02 constituting nonwoven fabric mm Fiber length 44 44 44 44 44 51
44 44 44 44 6 constituting nonwoven fabric mm Fiber quantity in one
28 18 32 39 50 20 78 8 17 50 50 composite layer % Running
durability 140 125 140 135 120 120 110 90 no run-flat running
(index)
[0157] As seen from Table 2, since the weight of the nonwoven
fabric is too small and the entanglement of fibers is less in the
comparative tire 11, the gradual increase of tensile force per unit
width can not be produced with the increase of the elongation
through the expansion-deformation of the toric air bag, so that the
running durability is lower than that of the comparative tire 3 in
Example 1.
[0158] In the comparative tire 12, the fiber diameter in the
nonwoven fabric is too large and the entanglement of fibers is
less. In the comparative tire 13, the fiber diameter is too fine
and the rubber penetrability is poor. In the comparative tire 14,
the fiber length in the nonwoven fabric is too short and the
entanglement of fibers is less. In any case, the characteristic of
extension ratio-tensile force required in the expansion-deformation
of the toric air bag can not be realized and hence the running at
the flat state is substantially impossible.
[0159] On the contrary, all example tires 11-17 can develop an
excellent running durability.
Example 3
[0160] In toric air bags of example tires having the same structure
as in the toric air bag of the example tire 1 shown in FIG. 15a,
when a ratio E.sub.P/E.sub.W of tensile stress E.sub.P at 3%
elongation in a circumferential direction of the toric air bag to
tensile stress E.sub.W at 3% elongation in a widthwise direction of
the toric air bag in a portion corresponding to an inner face of
the tire is varied, and when a ratio E.sub.CP/E.sub.CW of tensile
stress E.sub.CP at 3% elongation in a circumferential direction to
tensile stress E.sub.CW at 3% elongation in a widthwise direction
at a portion corresponding to an inner face of the tire and a ratio
E.sub.SP/E.sub.SW of tensile stress E.sub.SP at 3% elongation in a
circumferential direction to tensile stress E.sub.SW at 3%
elongation in a widthwise direction at a side portion adjacent to
the portion corresponding to an inner face of the tire are varied,
results measured on a run-flat durability are shown in Table 3.
[0161] In this case, E.sub.P=E.sub.CP and E.sub.W=E.sub.CW, so that
they are shown in the same column of Table 3.
[0162] Also, the run-flat durability is measured in the same manner
as in the running durability of Example 1, wherein the larger the
index value, the better the result.
[0163] The number of the composite layers in the table is changed
for adjusting stress and stress ratio of the toric air bag itself,
in which the weight of the toric air bag increases as the layer
number increases. TABLE-US-00003 TABLE 3 Example tire 21 (Example
Example Example Example Comparative Comparative tire 1) tire 22
tire 23 tire 24 tire 21 tire 22 Number of composite 4 4 6 3 8 10
layers E.sub.CP/E.sub.CW (E.sub.P/E.sub.W) 2 2 1 3 0.75 0.5
E.sub.sp/E.sub.sw 2 1 1 0.75 0.75 0.75 Total weight of toric air
100 95 92 89 112 118 bag (index) Running durability 140 140 130 135
140 135 (index) Specification of nonwoven fabric Weight: 500
mN/m.sup.2 Thickness: 0.1 mm Fiber diameter: 0.02 mm Fiber length:
44 mm Fiber quantity in composite: 28 mass %
[0164] As seen from Table 3, the excellent run-flat durability can
be developed when satisfying stress conditions of
E.sub.P/E.sub.W.gtoreq.1 and
E.sub.CP/E.sub.CW.gtoreq.E.sub.SP/E.sub.SW. Also, it is understood
that it is obliged to highly increase the weight of the toric air
bag (increase of index value) in the comparative tires 21 and 22
increasing the number of composite layers for satisfying a given
stress condition.
INVENTION APPLICABILITY
[0165] As seen from the above, according to the invention, the
excellent run-flat durability can be developed by gradually
extension-deforming the toric air bag without breaking cords or the
like in the expansion-deformation of the toric air bag accompanied
with the internal tire pressure to equally contact the toric air
bag with the inner face of the tire.
* * * * *