JP2006327412A - Airbag for safety tire, and safety tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an airbag for a safety tire uniformly expanded and deformed without uneven swell when the internal pressure of the tire is dropped by adequately arranging a hoop reinforcing layer on a crown portion of the airbag, and capable of obtaining the consistent run-flat traveling performance, and the safety tire having the airbag. <P>SOLUTION: The airbag 1 is contained in a tire 2 to form a safety tire. When the safety tire is mounted on a rim 3 and air is filled in the airbag 1 and the tire 2, a space S1 and a space S2 are formed. The airbag 1 comprises an air impermeable tube 3 and a hoop reinforcing layer 4 to entirely surround an outer periphery of its crown portion. The hoop reinforcing layer 4 is constituted by spirally winding a ribbon-shaped material having the biaxial strength in an overlapping manner, and the tensile stress to the rate of elongation corresponding to the elongation reaching an inner surface of the tire is in a range of 70-90% of the internal pressure after the airbag is expanded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention is housed in a tire, filled with air at an internal pressure set in relation to a predetermined internal pressure of the tire, and when the internal pressure of the tire is normal, a space is formed between at least the tire inner surface, The present invention relates to a hollow-cylindrical safety tire air bag for supporting a load from the tire, which is expanded in diameter with a decrease in the internal pressure of the tire, and a safety tire having such an air bag. Durability is improved on the premise of weight reduction of tires.

  Reinforcing members such as a reinforcing tube, reinforcing rubber, and reinforcing belt, or a foam, elastic body, medium, and the like as a safety tire that can travel a certain distance even in a run-flat state in which the tire internal pressure has suddenly decreased due to puncture or the like There are known tires that support the load of the tire on the shoulder, tires that are coated or filled with a sealant agent, block damaged parts such as holes formed in the tire, and prevent a decrease in internal pressure, and the like. However, these conventional safety tires often have a high defect rate and a low manufacturing efficiency due to the complicated manufacturing method.

  In order to solve such a problem, for example, Patent Document 1 discloses that in a run-flat state in which the internal pressure of the tire is reduced and the internal pressure of the tire is reduced, the load is supported from the tire by expanding and deforming as the tire internal pressure is reduced. In a hollow tubular air bladder that replaces the shoulder, at least the crown portion of the air bladder is constituted by a tension support member to suppress the diameter growth during normal running, and as the tensile force gradually increases on the tension support member. In addition, it is described that the air bladder is uniformly brought into contact with the tire during the run-flat running by providing a physical property showing an elongation-tensile force characteristic in which the elongation due to the expansion deformation is substantially increased.

  However, when the air bladder described in Patent Document 1 is used for a long period of time, the air bladder is constituted by the action of the centrifugal force accompanying the rolling of the tire and the pressure of the air filled in the air bladder. In some cases, the rubber portion to be creep-deformed and grows in diameter and eventually reaches the inner surface of the tire, and the tension supporting member may be rubbed against the inner surface of the tire and damaged. In order to suppress such creep deformation, it is necessary to laminate a plurality of tension support members, which raises the problem of increasing the production cost of the air bladder, lowering the production efficiency, and increasing the mass. In view of this, the present applicant, in the specification of Japanese Patent Application No. 2004-142167, claims and drawings, comprises an air-impermeable tube and a hoop reinforcing layer surrounding the outer periphery of the crown portion of the tube over the entire circumference. In addition, we proposed an air bladder for safety tires in which this hoop reinforcement layer was formed by winding a spiral spiral while overlapping ribbon-like materials. Such air bladders can improve production efficiency remarkably, so that production costs can be kept low, and an increase in mass can be minimized. Moreover, creep deformation can also be suppressed by optimizing the material which comprises a hoop reinforcement layer.

International Publication No. 02/43975 Pamphlet

  However, it has been found that an air bag constructed by winding a ribbon-like material in a spiral manner may cause so-called one-sided bulging, in which either the left or right half expands during run-flat running. The air bladder that has undergone one-side swelling has a reduced thickness at the greatly expanded part, and the durability of this part is significantly reduced, which may cause a problem that the run-flat running durability is reduced.

  Therefore, the object of the present invention is to optimize the strength of the crown portion of the air bag, and on the premise of weight reduction, it suppresses creep deformation during normal travel and at the same time prevents flank during run flat travel Thus, an object of the present invention is to provide an air bladder for a safety tire having improved overall durability and a safety tire having such an air bladder.

  In order to achieve the above object, the air bladder for a safety tire of the first invention is housed in a tire and filled with air at an internal pressure set in relation to a predetermined internal pressure of the tire, so that the internal pressure of the tire is normal. In such a state, at least a space is formed between the inner surface of the tire, and the diameter of the tire is expanded with a decrease in the internal pressure of the tire. The air bladder includes an air-impermeable tube and at least one hoop reinforcing layer that surrounds the entire outer periphery of the crown portion of the tube, and the hoop reinforcing layer has biaxial strength. The ribbon-like material is overlapped and wound spirally, and the tensile stress corresponding to the elongation until reaching the tire inner surface is 70% of the internal pressure after expansion of the air bladder. Characterized in that in the range of 90%.

  Here, “predetermined internal pressure of the tire” refers to an industrial standard or standard that is effective in the area where the tire is manufactured, sold, or used, such as JATMA, TRA, ETRTO, etc. The internal pressure is specified according to the load capacity. The “internal pressure set in relation to the predetermined internal pressure” means that a space is formed between the outer surface of the air bladder and the inner surface of the tire in a gas-filled state in which the predetermined internal pressure is applied to the tire. On the other hand, in the run-flat state where the internal pressure of the tire is reduced, the air pressure is expanded and deformed as the tire internal pressure is reduced, and the internal pressure can be used to replace the load support from the tire. The internal pressure is in the range of +0 to 20%. Furthermore, “biaxial direction” refers to two directions orthogonal to each other in any direction, and “a material having biaxial strength” refers to an unstretched state in these biaxial directions. A material whose tensile stress required to reach a 5% stretched state is 0.1 MPa or more.

  In the first invention, it is preferable that a protective layer having strength in the width direction is further provided on the outer periphery of the hoop reinforcing layer.

  The air bladder for a safety tire according to the second invention is housed in a tire, filled with air at an internal pressure set in relation to the predetermined internal pressure of the tire, and at least the inner surface of the tire when the internal pressure of the tire is normal In a hollow tubular safety tire air bladder which forms a space between them and expands and deforms as the internal pressure of the tire decreases to support the load from the tire, the air bladder is airless. Comprising a permeable tube, at least one hoop reinforcing layer surrounding the entire outer periphery of the crown portion of the tube, and a protective layer having a widthwise strength disposed on the outer periphery of the hoop reinforcing layer, The hoop reinforcing layer is formed by helically winding a ribbon-like material having biaxial strength while being overlapped.

  In the second invention, it is preferable that the hoop reinforcing layer has a tensile stress with respect to an elongation rate corresponding to the elongation until reaching the tire inner surface is smaller than the internal pressure after expansion of the air bladder.

  Furthermore, in both the first invention and the second invention, the width of the hoop reinforcing layer is preferably in the range of 50 to 100% of the width of the tube to which an internal pressure of 5% of the predetermined internal pressure of the tire is applied, and 70 to 90 More preferably, it is in the range of%.

  Furthermore, in both the first invention and the second invention, the ribbon-like material constituting the hoop reinforcing layer has an average gradient of tensile stress with respect to an elongation rate of 0 to 5% and an elongation rate of 5 to 100%. It is preferably larger than the average gradient of tensile stress.

  In addition, in both the first invention and the second invention, it is preferable that the nonwoven fabric of at least one layer surrounds the entire tube over the entire circumference.

  And the safety tire of this invention has one of the above-mentioned air bladders.

  According to the present invention, by optimizing the strength of the crown portion of the air bladder, on the premise of weight reduction, creep deformation during normal traveling is suppressed and at the same time, flank during run flat traveling is prevented. Thus, it is possible to provide a safety tire air bladder having improved overall durability and a safety tire having such an air bladder.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view in the width direction showing a safety tire containing a typical safety tire pneumatic bladder (hereinafter referred to as “air bladder”) according to the first invention mounted on a rim and filled with a predetermined internal pressure. FIG. 2 is a perspective view of the hoop reinforcement layer, and FIG. 3 is a state in which a typical safety tire containing a pneumatic bladder according to the second invention is mounted on a rim and filled with a predetermined internal pressure. FIG.

The air bladder 1 shown in FIG. 1 has a hollow circular tube shape and is housed in a tire 2 to form a safety tire. The safety tire is mounted on the rim R to form a tire assembly. The tire 2 is filled with a predetermined internal pressure via an air filling valve (not shown), and the air bladder 1 is filled with a predetermined internal pressure of the tire 2 via another air filling valve (not shown). As a result, as shown in FIG. 1, a space S ₁ is formed in the tire 2 and a space S ₂ is formed in the air bladder 1. On the other hand, when the puncture or the like the internal pressure of the space S ₁ of the tire 2 decreases rapidly as a result of the internal pressure difference between the space S ₁ and the space S ₂ is increased, eventually the air bladder 1 is expanded in diameter deformed tire 2 reaches the inner surface of the tire 2 and shoulders the load from the tire 2.

  The main feature of the structure of the first invention is that the air bladder 1 is an air-impermeable tube 3 and at least one hoop reinforcing layer surrounding the outer periphery of the crown portion of the tube 3 over the entire circumference. In the illustrated example, a single hoop reinforcing layer 4 is provided. As shown in FIG. 2, the hoop reinforcing layer 4 is spirally wound while overlapping the ribbon-like material 5 having biaxial strength. The tensile stress corresponding to the elongation ratio corresponding to the elongation until reaching the tire inner surface is in the range of 70 to 90% of the internal pressure after expansion of the air bladder 1.

  The main feature of the structure of the second invention is that the air bladder 1 is an air-impermeable tube 3 and at least one hoop reinforcing layer surrounding the outer periphery of the crown portion of the tube 3 over the entire circumference. In the illustrated example, a single-layer hoop reinforcing layer 4 and a protective layer 7 having a widthwise strength disposed on the outer periphery of the hoop reinforcing layer 4 are provided, and the hoop reinforcing layer 4 is formed as shown in FIG. The ribbon-like material 5 having biaxial strength is formed by winding a spiral spiral while overlapping.

  In safety tires containing air bladders, it is common to increase the internal pressure of the air bladder higher than the internal pressure of the tire in order to rapidly expand and deform the air bladder when the internal pressure is reduced. In order to prevent the air bladder from expanding and deforming to reach the inner surface of the tire and rubbing against the inner surface of the tire even if such an internal pressure difference acts, It is necessary to arrange a hoop reinforcing layer having circumferential rigidity at the other crown portion to prevent expansion deformation at normal internal pressure. However, the inner diameter of the hoop reinforcement layer is substantially the same as the outer diameter of the tube, and the hoop reinforcement layer having circumferential rigidity hardly stretches, so it is very difficult to apply the hoop reinforcement layer on the tube, This has been a major factor in reducing manufacturing efficiency. On the other hand, if a hoop reinforcement layer is formed by spirally winding a ribbon-like material on the outer surface of a tube expanded by applying air pressure, a hoop reinforcement layer can be easily formed even from a material that does not stretch at all in the circumferential direction. Manufacturing efficiency is greatly improved.

  However, if the crown of the air bladder expands even in the direction perpendicular to the circumferential direction (hereinafter referred to as the “width direction”) even with a small tensile stress, the air bladder is exposed when the internal pressure of the tire decreases due to puncture or the like. The crown expands simultaneously in both radial and width directions. When the crown portion expands in the width direction as described above, as shown in FIG. 6, the hoop reinforcing layer 4 may be biased, and the air bladder 1 may swell. If the air bladder bulges, uneven contact of the tire and the thickness of the expanded air bladder may be caused, and the air bladder may be damaged early in the run-flat running. Therefore, by using a material having strength in the biaxial direction of the circumferential direction and the width direction as the ribbon-like material, the crown portion of the air bladder is mainly expanded in the circumferential direction, and the side portion of the air bladder is mainly expanded in the width direction. If the shoulder portion is expanded, it is possible to prevent a single bulge due to the bias of the hoop reinforcing layer and to improve the run-flat durability.

  From the standpoint of preventing half-blowing, the hoop reinforcing layer preferably exhibits a large elongation rate even with a small tensile stress, but such an air bladder tends to undergo creep deformation. On the other hand, from the viewpoint of preventing creep deformation, the hoop reinforcing layer preferably exhibits a small elongation rate even with a large tensile stress, but such air bladder tends to swell. Thus, the prevention of bulges and the suppression of creep deformation were in a trade-off relationship.

  FIG. 4 is a tensile stress-elongation rate curve (SS curve) in the circumferential direction of the hoop reinforcement layer. In the figure, point A on the horizontal axis represents the elongation corresponding to the elongation until the hoop reinforcement layer reaches the tire inner surface. Shows the rate. The inventor has conducted extensive research on the construction of an air bladder capable of achieving both of the above-described conflicting performances at a high level, and the tensile strength against the stretch ratio A corresponding to the stretch until the hoop reinforcement layer reaches the tire inner surface. It has been found that this can be realized by optimizing the stress a. That is, the inventors have conceived that the tensile stress a with respect to the elongation ratio A may be 70 to 90% of the internal pressure of the expanded air bag, and the first invention has been completed. The tensile stress a is limited to such a range. When this is less than 70%, if the air bladder is used for a long period of time, it is filled in the centrifugal force or the air bladder accompanying the rolling of the tire. Under the action of air pressure, the hoop reinforcement layer creeps and grows in diameter and may eventually reach the inner surface of the tire, and there is a concern that the air bladder may rub against the inner surface of the tire and be damaged. Because. Further, when the tensile stress a is more than 90% of the internal pressure of the air bag after the expansion deformation, the difference in expansion speed between the hoop reinforcing layer 4 and the shoulder portion 6 of the tube 3 when the internal pressure is reduced becomes too large. This is because the hoop reinforcing layer 4 may be biased as shown in FIG.

  In addition, the inventor does not provide the hoop reinforcement layer 4 with both a single swelling prevention function and a creep deformation suppression function, but provides a protective layer 8 on the outer periphery of the hoop reinforcement layer 4 to provide a single swelling prevention function and creep. It was also conceived to share the deformation suppression function. That is, if the protective layer 8 is strong in the width direction, the creep deformation suppressing function is mainly borne by the hoop reinforcing layer 4, and the one blistering preventing function is mainly borne by the protective layer 8, it is easy to prevent one blistering and creep deformation. The inventors found that the suppression can be achieved at a high level, and completed the second invention.

  From the viewpoint of more effectively preventing creep deformation, it is preferable to use, as the ribbon-like material, a low-tension resistant material such as a resin that has a low elongation even when a low tension is applied for a long time. In general, resin behaves as a high-rigidity material with a low elongation rate in a low tension region, but has a property that the elongation rate suddenly increases when a certain tension (yield strength) is exceeded, effectively preventing creep deformation. And can be expanded and deformed quickly.

  When the hoop reinforcement layer 4 is firmly joined to the tube 3 by vulcanization adhesion as in the case of conventional air, there is no displacement in the width direction of the hoop reinforcement layer 4 as shown in FIG. However, when the hoop reinforcing layer is made of a resin, vulcanization adhesion cannot be used, and the hoop reinforcing layer must be fixed with an adhesive or a double-sided tape. This fixing is weaker than the fixing by vulcanization adhesion, and as shown in FIG. 6, the hoop reinforcing layer may be biased in the width direction. However, if the protective layer 8 is provided on the outer periphery of the hoop reinforcing layer 4, the protective layer 8 restrains the movement of the hoop reinforcing layer 4, so that the bias of the hoop reinforcing layer does not occur. Further, the protective layer 8 also serves to protect the hoop reinforcing layer 4 from foreign matter that has entered the tire from the puncture hole. Therefore, also in the first invention, it is preferable to provide the protective layer 8 on the outer periphery of the hoop reinforcing layer 4. The protective layer 8 can be made of rubber or resin, and is preferably wider than the hoop reinforcing layer.

  In the second invention, the tensile stress a corresponding to the expansion ratio A in FIG. 4 is greater than the internal pressure of the air bladder after the expansion until the internal pressure of the tire decreases due to puncture or the like and the air bladder adheres to the tire inner surface. Small is preferable. If the tensile stress a with respect to the elongation ratio corresponding to the elongation until the hoop reinforcing layer reaches the tire inner surface is larger than the internal pressure after expansion of the air bladder, the tensile stress of the hoop reinforcing layer and the internal pressure of the air bladder are balanced. This is because the air bag expands only to the point, and thereafter, only the portion where the hoop reinforcing layer is not disposed is expanded and deformed, so that the air bladder swells.

The width W ₁ of the hoop reinforcement layer 4 is preferably in the 50-100% range of the width W ₂ of the tubes 3 to which the 5% of the internal pressure of a given internal pressure of the tire. When W ₁ / W ₂ is less than 50%, the shape retention of the air bladder in the normal internal pressure state is lowered, and both shoulder portions 6 and 6 where the hoop reinforcing layer 4 is not disposed when the internal pressure is reduced. The reason for this is that it may expand rapidly and induce a blister. Further, if the width of the shoulder portions 6 and 6 where the hoop reinforcing layer 4 is not disposed is large, the deformation of the shoulder portions 6 and 6 causes the hoop reinforcing layer 4 to face the tire equator as shown in FIG. There is a risk that it will also cause a blister. From the viewpoint of preventing such unevenness of the hoop reinforcing layer, it is more preferable that W ₁ / W ₂ is 60% or more.

The hoop reinforcement layer 4 may cover the entire width of the tube 3. However, since the shoulder portion 6 of the air bladder 1 has a diameter difference and is curved, the hoop reinforcing layer may not be brought into close contact with the tube and a gap may be generated. In particular, in the case of an air bladder with a large diameter difference of the shoulder portion 6, foreign matter that has entered the tire from the puncture hole may enter the gap between the hoop reinforcement layer and the tube, and may damage the tube. It is preferable to dispose the hoop reinforcing layer only in a small range, more specifically, W ₁ / W ₂ is 90% or less.

  In the SS curve shown in FIG. 4, it is preferable that the average gradient of the tensile stress with respect to the elongation rate between 0 to 5% of the hoop reinforcing layer is larger than the average gradient of the tensile stress with respect to the elongation rate between 5 to 100%. . As a result, under normal internal pressure conditions, under large tensile stress, it can resist the expansion deformation of the air bladder and effectively prevent its diameter growth, while the puncture etc. reduced the internal pressure of the tire In some cases, the air bladder is gradually expanded and deformed under a small tensile stress, so that the tire and the air bladder can be uniformly adhered.

  FIG. 5 is a cross-sectional view in the width direction showing a state in which another safety tire according to the present invention is mounted on the rim and filled with a predetermined internal pressure, and the entire tube 3 is surrounded by the nonwoven fabric 8 over the entire circumference. Such a non-woven fabric has an action of properly expanding the air bag without being biased and deformed in a specific direction at the time of vulcanization of the air bag or at the time of expansion deformation due to a decrease in internal pressure. As this non-woven fabric, aramid, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and the like can be used, but PET is particularly excellent from the viewpoint of cost reduction.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. .

  Next, a safety tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.

  The safety tires of Examples 1 to 3 are formed by storing air bladders in tires having a tire size of 495 / 45R22.5. This air bag has a width of 410 mm, the entire rubber tube is surrounded by a single layer of PET nonwoven fabric, and a single layer formed by spirally winding a PET ribbon-like material around the crown portion. With a hoop reinforcement layer. In this hoop reinforcing layer, the average gradient of the tensile stress with respect to the elongation ratio of 0 to 5% is larger than the average gradient of the tensile stress with respect to the elongation ratio of 5 to 100%, which corresponds to the elongation until reaching the tire inner surface. The tensile stress with respect to the stretching rate is 320 kPa. Further, the internal pressure of the air bladder during run-flat running of this safety tire is 400 kPa. Further, the air bladder of the safety tires of Examples 2 and 3 is provided with a protective layer made of soft polyolefin and having a width of 390 mm on the outer periphery of the hoop reinforcing layer. The safety tires of Examples 1 to 3 have the specifications shown in Table 1.

  For comparison, the conventional safety tire and the safety tires of Comparative Examples 1 to 3 in which the same tire size as in Examples 1 to 3 and the same air bladder as in Examples 1 to 3 are accommodated in the tire. And made a prototype. The air bag of the safety tire of the conventional example includes a five-layered aramid nonwoven fabric at the crown portion of the rubber tube. The pneumatic tires of the safety tires of Comparative Examples 1 to 3 were constructed by surrounding the entire rubber tube with a single layer of non-woven PET fabric and winding the PET ribbon-like material around the crown. Although it has one hoop reinforcing layer, it does not have a protective layer, and the tensile stress with respect to the elongation corresponding to the elongation until reaching the tire inner surface is outside the scope of the first invention. Further, the safety tire of the conventional example and the safety tires of Comparative Examples 1 to 3 have the specifications shown in Table 1.

  The air bladder mass of each of the test tires was measured. The results are shown in Table 1.

Further, each of the test tires is attached to a rim having a rim size of 17.00 × 22.5 to form a tire wheel, and the internal pressure of the tire (space S ₁ ) including the air bladder is set to 900 kPa (relative pressure), and the air The internal pressure of the sleeve (space S ₂ ) was 970 kPa (relative pressure), and the elongation rate from 10 hours to 100 hours was measured to evaluate the amount of creep deformation. The evaluation results are shown in Table 1.

Further, each tire wheel is mounted on a test vehicle, the internal pressure of the tire including the air bladder (space S ₁ ) is set to 900 kPa (relative pressure), and the internal pressure of the air bladder (space S ₂ ) is set to 970 kPa (relative pressure). ) And a tire load of 56.88 kN was applied. Next, after blasting the buttress part while running at a speed of 60 km / h to make it run-flat, the tire is disassembled and the shape of the air bladder taken out is visually confirmed, and the diameter of the air bladder is expanded and deformed. Was evaluated for uniformity. The evaluation results are shown in Table 1.

  From the results shown in Table 1, when comparing the safety tire of the conventional example and the safety tires of Examples 1 to 3, the safety tires of Examples 1 to 3 are light in weight while being uniform in diameter expansion deformation. And it is excellent in creep resistance, and it turns out that the durability at the time of normal driving improves. Further, when comparing the safety tires of Comparative Examples 1 to 3 with the safety tires of Examples 1 to 3, the safety tires of Examples 1 to 3 have the same mass and creep resistance, but the uniformity of the diameter expansion deformation. It can be seen that the durability during run-flat driving is improved.

  As is apparent from the above description, according to the present invention, by optimizing the strength of the crown portion of the air bag, it is lightweight and suppresses creep deformation during normal travel, and at the same time, a piece during run flat travel It has become possible to provide a safety tire that has improved overall durability by preventing swelling.

1 is a cross-sectional view in the width direction showing a state in which a typical safety tire containing a pneumatic bladder according to the present invention is mounted on a rim and filled with a predetermined internal pressure. It is a perspective view shown in the state which removed the hoop reinforcement layer of the air bag shown in FIG. FIG. 6 is a cross-sectional view in the width direction showing a state in which a safety tire containing another air bladder according to the present invention is mounted on a rim and filled with a predetermined internal pressure. It is a graph which shows the tensile stress-elongation rate curve of a hoop reinforcement layer. FIG. 6 is a cross-sectional view in the width direction showing a state in which a safety tire containing another air bladder according to the present invention is mounted on a rim and filled with a predetermined internal pressure. It is width direction sectional drawing of the air bladder which raise | generated the half-blowing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air bladder 2 Tire 3 Tube 4 Hoop reinforcement layer 5 Ribbon-shaped material 6 Tube shoulder part 7 Protective layer 8 Nonwoven fabric

Claims (9)

The tire is housed in a tire and filled with air at an internal pressure set in relation to a predetermined internal pressure of the tire. When the tire internal pressure is normal, a space is formed at least between the tire inner surface and the tire internal pressure. In the air bladder for a hollow circular safety tire that expands and deforms as it falls and replaces the load from the tire,
The air bladder comprises an air-impermeable tube and at least one hoop reinforcing layer that surrounds the entire outer periphery of the crown portion of the tube,
The hoop reinforcing layer is formed by spirally winding a ribbon-like material having biaxial strength, and has a tensile stress with respect to an elongation corresponding to the elongation until reaching the tire inner surface. An air bladder for a safety tire characterized by being in the range of 70 to 90% of the internal pressure after expansion of the air bladder.   The air bladder for a safety tire according to claim 1, further comprising a protective layer having strength in the width direction on an outer periphery of the hoop reinforcing layer. The tire is housed in a tire and filled with air at an internal pressure set in relation to a predetermined internal pressure of the tire. When the tire internal pressure is normal, a space is formed at least between the tire inner surface and the tire internal pressure. In the air bladder for a hollow circular safety tire that expands and deforms as it falls and replaces the load from the tire,
The air bladder includes an air-impermeable tube, at least one hoop reinforcing layer that surrounds the entire outer periphery of the crown portion of the tube, and a widthwise strength disposed on the outer periphery of the hoop reinforcing layer. Comprising a protective layer having
The hoop reinforcing layer is formed by winding a helical material while overlapping a ribbon-like material having biaxial strength, and is a pneumatic tire for a safety tire.   The air hoop for a safety tire according to claim 3, wherein the hoop reinforcing layer has a tensile stress with respect to an elongation rate corresponding to an elongation until reaching the inner surface of the tire is smaller than an internal pressure after expansion of the air bladder.   The width of the hoop reinforcement layer is in the range of 50 to 100% of the width of the tube to which an internal pressure of 5% of a predetermined internal pressure of the tire is applied. Air balloon.   The width of the hoop reinforcing layer is in the range of 70 to 90% of the width of a tube to which an internal pressure of 5% of a predetermined internal pressure of the tire is applied.   The ribbon-like material constituting the hoop reinforcing layer has an average tensile stress gradient with respect to an elongation between 0 and 5% greater than an average gradient of tensile stress with an elongation between 5 and 100%. The air bladder for safety tires as described in any one of -6.   The air bladder for a safety tire according to any one of claims 1 to 7, wherein at least one layer of nonwoven fabric surrounds the entire tube over the entire circumference.   The safety tire which has the air bladder for safety tires as described in any one of Claims 1-8.

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