JP4571394B2 - Run flat tire - Google Patents

Description

  The present invention relates to a ply body extending in a toroidal shape across a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions. A carcass composed of at least one ply that extends from the inner side and the outer side of the tire width direction around the bead core and the bead core, and is located on the outer peripheral side of the crown portion of the carcass. The belt includes at least one belt layer made of rubber-coated cord and at least one air-impermeable rubber inner liner disposed on the inner peripheral side of the carcass, and at least a crescent cross section in the side wall portion. Related to a run-flat tire having a rubber-like reinforcing rubber layer, Both durability Cal normal running time of the ride comfort of the tire and the run time of flat running is compatible at a high level.

  A run-flat tire that can run for a certain distance even when the tire internal pressure drops due to puncture, etc., is provided with a reinforcing rubber layer with a crescent-shaped cross section on the side wall, and the tire load is adjusted to the tire internal pressure during normal driving. On the other hand, a run-flat tire that supports a tire load with a reinforcing rubber layer as a shoulder during run-flat traveling, a so-called side-reinforced run-flat tire is known.

  In order to improve the durability of such side-reinforced run-flat tires during run-flat running, the deformation of the bead portion and the sidewall portion when a load is applied while the tire internal pressure is reduced due to puncture or the like is suppressed. However, if such deformation is suppressed by increasing the thickness of the bead filler or the reinforcing rubber layer, problems such as an increase in tire weight and deterioration in riding comfort during normal driving occur.

  Therefore, there is a demand for a side-reinforced run-flat tire that simultaneously achieves a high level of improvements in durability during run-flat driving, weight reduction, improved riding comfort during normal driving, and improved driving stability. Various studies have been made on these matters.

  For example, Patent Document 1 includes a reinforcing filler layer that includes at least one reinforcing ply that is arranged on the outer side in the tire width direction of the carcass from the sidewall portion to the bead portion and in which reinforcing cords are arranged and embedded in a topping rubber. Side-reinforced run-flat tires are described. In this tire, by providing a reinforcing filler layer in a portion where a tensile force acts when the tire internal pressure is reduced, the sidewall portion is prevented from bulging and deforming outward in the tire width direction, thereby improving run-flat durability. Is.

  Further, Patent Document 2 discloses a side-reinforced runflat in which a reinforcing cord layer is disposed inside a carcass tire and is disposed from the radially inner side of the reinforcing cord layer from the radially outer end of the bead filler to the radially inner side of the tire. Tires are described. Patent Document 3 describes a side-reinforced run-flat tire in which a cord reinforcing layer composed of a steel cord in which metal filaments having an elastic modulus of 16000 MPa or more are twisted is disposed outside the bead filler in the tire width direction. In Patent Document 4, at least one cord reinforcing layer made of a cord extending in a direction forming approximately 90 ° with respect to the radial line segment is disposed in the radially outer region from the vicinity of the bead core. A side-reinforced run-flat tire in which the width of the reinforcing layer in the tire radial direction is 10 to 50% of the tire cross-sectional height is described. These tires mainly improve the run-flat durability by suppressing the collapse of the sidewall portion toward the outside in the tire width direction.

  In these conventional tires, the main focus is only on the suppression of either the bulging deformation of the sidewall portion or the collapse deformation of the bead portion. It is necessary to effectively suppress both deformations.

Japanese Patent Laid-Open No. 7-315016 Japanese Patent Laid-Open No. 11-192822 JP 2001-180234 A JP 2001-239813 A

  Accordingly, an object of the present invention is to effectively suppress both the bulging deformation of the sidewall portion and the falling deformation of the bead portion by appropriately disposing the reinforcing cord layer, and to improve the riding comfort during normal traveling. An object of the present invention is to provide a side-reinforced run-flat tire in which both durability during run-flat running is compatible at a high level.

In order to achieve the above object, the present invention includes a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions. A carcass comprising at least one ply including a ply main body extending in a toroidal shape over each part, and a ply folding part extending from the ply main body to the outer side in the tire width direction around the bead core; In the run-flat tire, which is located on the outer peripheral side of the crown portion and includes at least one belt layer formed by rubber-covering the cord, and at least a crescent-shaped reinforcing rubber layer is disposed on the sidewall portion, The cord is covered with rubber on the outer side in the tire width direction of the carcass ply body. A reinforcing cord layer is disposed, and a second reinforcing cord layer formed by rubber covering the cord is disposed between the carcass ply main body portion and the reinforcing rubber layer, and the outer end in the tire radial direction of the first reinforcing cord layer The edge is positioned on the outer side in the tire radial direction of the tire radial direction outer edge and the tire maximum width position of the second reinforcing cord layer, and the tire radial direction outer end edge of the second reinforcing cord layer is attached to the standard rim. The inner end edge in the tire radial direction of the first reinforcing cord layer is located on the inner side in the tire radial direction from the tire maximum width position, and is located in the tire radial direction of the second reinforcing cord layer. The inner edge is attached to the standard rim and is located on the inner side in the tire radial direction from the rim flange, and the cord forming the first reinforcing cord layer has an angle between the tire circumferential direction of 20 to 40 °. Yes, the cord constituting the second reinforcing cord layer is a tie The run-flat tire is characterized in that an angle formed with the circumferential direction is in a range of 60 to 90 °.

  Here, the “maximum tire width position” refers to the position at which the cross-sectional width of the tire is measured. If there are patterns, characters, rim guards, etc. on the outer surface of the tire, the cross-section of the tire excluding these The position where the width is measured shall be said. “Standard rims” are standard rims (or “Approved Rim”, etc.) stipulated in industrial standards, standards, etc. that are effective in the areas where tires are manufactured, sold, or used, such as JATMA, TRA, ETRTO, etc. Recommended Rim ”). Furthermore, the “angle formed by the tire circumferential direction” of the cords constituting the reinforcing cord layer is, as shown in FIG. 2, cords 18 and 19 at the tire radial direction outer edges 15 and 16 of the reinforcing cord layers 13 and 14. The angles α1 and α2 formed by the extending direction of the tire and the tire circumferential direction C are angles measured from the acute angle side.

  The tire further includes a rim guard portion which is on the outer surface of the tire and protrudes outward in the tire width direction from the flange of the applied rim on which the tire is mounted, and the outer edge in the tire radial direction of the second reinforcing cord layer is the rim guard portion. It is preferable to be located on the outer side in the tire radial direction than the outermost end in the tire radial direction.

Furthermore, the first reinforcing cord layer and / or the second reinforcing cord layer has an elastic modulus of one cord as E, a cross-sectional area of one cord as A, N as the number of cords driven per mm, t = (A / When π) ^1/2 × 2, the elastic modulus Ef of the reinforcing cord layer represented by the following formula (2) is preferably in the range of 2 to 20 GPa.
Ef = (A × N × E) / t (2)

  Furthermore, it is preferable that the folded end of the carcass is located on the outer side in the tire radial direction than the outer end edge in the tire radial direction of the first reinforcing cord layer.

  In addition, it is preferable that the cords constituting the first reinforcing cord layer and / or the second reinforcing cord layer have initial elongation. Here, “initial elongation” means a load (vertical axis) -elongation (horizontal axis) characteristic curve obtained when a cord with rubber of a reinforcing cord layer is taken out from a product tire and a tensile test is performed using the cord as a test piece. Means the elongation value at the point where the straight line passing through the load points of 30% and 70% of the breaking load intersects the horizontal axis.

In this case, the initial elongation is more preferably 0.4 to 0.7%. Also, code that constitutes the first reinforcing cord layer and / or the second reinforcing cord layer, in the characteristic curve, from the origin, a straight line passing through the 30% and 70% of the load point of the breaking load intersects the horizontal axis It is preferable that the elastic modulus E ′ in the initial elongation region, which is the region up to the point, is 2 GPa or less.

  Moreover, it is preferable that the code | cord | chord which comprises a 1st reinforcement cord layer and / or a 2nd reinforcement cord layer is a steel cord.

  According to the present invention, the two reinforcing cord layers are disposed so that the extension angle of the cords constituting them and the position of the outer edge in the tire radial direction are appropriate, thereby expanding the side wall portion. As a result of effectively suppressing both the deformation and the falling-down deformation of the bead portion, a side-reinforced run-flat tire that achieves both a high level of ride comfort during normal driving and durability during run-flat driving is obtained. be able to.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a left half sectional view in the tire width direction showing a typical run-flat tire (hereinafter referred to as “tire”) according to the present invention assembled to a rim.

  A tire 1 shown in FIG. 1 includes a pair of bead portions 3 in which bead cores 2 are embedded, a pair of sidewall portions 4 that extend outward from the bead portion 3 in the tire radial direction, and a tread portion 5 that extends across both sidewall portions 4. At least one ply constituted by a ply body part 6 extending in a toroid shape over each part of the ply, and a ply folded part 7 extending from the ply body part 6 and folded around the bead core 2 from the inner side to the outer side in the tire width direction, In FIG. 1, a carcass 9 composed of a single ply 8 and at least one belt layer which is located on the outer peripheral side of the crown portion 10 of the carcass 9 and is made of rubber-coated cords, in FIG. 1, two belt layers 11a, 11b, and a reinforcing rubber layer 12 having a crescent-shaped cross section is disposed on at least the sidewall portion 4. In FIG. 1, a belt reinforcing layer 24 covering the entire width of the belt layers 11 a and 11 b is disposed on the outer periphery of the belt layer 11 a, and four circumferential grooves 25 are disposed in the tread portion 5. Yes.

The main structural feature of the present invention is that a first reinforcing cord layer 13 made of rubber covered with a cord is disposed on the outer side in the tire width direction than the ply main body portion 6 of the carcass 9, and the ply of the carcass 9 is arranged. Between the main body portion 6 and the reinforcing rubber layer 12 , a second reinforcing cord layer 14 formed by covering the cord with rubber is disposed, and a tire radial direction outer end edge 15 of the first reinforcing cord layer 13 is provided with a second reinforcing cord. The outer radial edge 16 of the cord layer 14 and the outermost tire width position 17 are positioned on the outer side in the radial direction of the tire, and the outer radial edge 16 of the second reinforcing cord layer 14 is attached to the standard rim. As shown in FIG. 2, the cord 18 constituting the first reinforcing cord layer 13 is positioned outside the rim flange 20 in the tire radial direction, and the angle α1 formed with the tire circumferential direction C is in the range of 20 to 40 °. Yes, the cord constituting the second reinforcing cord layer 14 No. 19 is that the angle α2 formed with the tire circumferential direction C is in the range of 60 to 90 °.

Hereinafter, how the present invention has adopted the above configuration will be described together with the operation.
To improve durability during run-flat running of side-reinforced run-flat tires, where a reinforcing rubber layer with a crescent-shaped cross section is provided on the sidewall, and the tire load is supported by the reinforcing rubber layer as a shoulder during run-flat running It is necessary to suppress deformation of the bead portion and the sidewall portion when a load is applied in a state where the tire internal pressure is reduced by puncture or the like. For example, by increasing the thickness of the bead filler or the reinforcing rubber layer, If such deformation is suppressed, problems such as an increase in tire weight and deterioration in riding comfort during normal driving occur. On the other hand, if the thickness of the reinforced rubber layer is reduced with emphasis on ride comfort, there is a problem that the tire will break down early as a result of increased longitudinal deflection of the tire during run-flat running.

  As a result of the inventor's extensive research on the cause of such failure, the failure of the side-reinforced run-flat tire is caused by the reinforcement rubber layer 103 (A portion in FIG. 6) and the rim corresponding to the vicinity of the maximum width position 102 of the tire 101. It has been found that the occurrence mainly occurs at two locations of the ply main body portion 105 (B portion in FIG. 6) corresponding to the vicinity of the position where the flange 104 abuts. When the inventor conducted further research on the cause of the failure at these two locations, the driving force transmitted to the bead portion via the rim and the friction between the tread portion and the road surface occurred on the tire wheels during running. However, as a result of the two forces, the resistance force acting in the opposite direction to the driving force of the tire wheel, the difference in angular velocity of rotation between the bead portion fixed to the rim and the tread portion contacting the road surface It was found that circumferential shear deformation occurred in the sidewall portion. Further, the shear deformation becomes larger as the bulging outward in the tire width direction becomes larger, and becomes maximum at the maximum width position 102 of the tire. Further, during the run-flat running, the bead portion 106 is strongly pressed against the rim flange 104 of the wheel, and the bead portion 106 largely falls outwardly in the tire width direction and deforms with the rim flange 104 as a fulcrum. It was found that deformation occurred and a failure occurred in part B. Therefore, the inventor arranges the first reinforcing cord layer so as to cover the portion A and the second reinforcing cord layer so as to cover the portion B, and the first reinforcing cord layer performs the bulging deformation described above. 2 If the above-described collapse deformation is suppressed by the reinforcing cord layers, the A portion and the B portion without significantly increasing the tire radial direction stiffness that affects the tire weight and the rigidity of the sidewall portion, particularly the riding comfort. I got the idea that it can prevent the failure that occurs.

  Furthermore, the inventor is known that the cord used for the reinforcing cord layer generally has a characteristic that it is strong against the tensile force but weak against the compressive force. If the first reinforcing cord layer and the second reinforcing cord layer are disposed on the portion where the tensile force acts, that is, the outer side in the tire width direction of the A portion and the inner side in the tire width direction of the B portion, respectively, the bulging deformation of the sidewall portion And it discovered that the fall-down deformation | transformation of a bead part can be suppressed efficiently.

  However, as disclosed in the prior art, a satisfactory ride comfort and run flat can be obtained simply by arranging a reinforcing cord layer that suppresses bulging deformation and a reinforcing cord layer that suppresses collapse deformation. It was not possible to achieve both durability. For the reason, the inventor conducted further research, and in order to cover part B and suppress the falling deformation, the outer end edge in the tire radial direction of the second reinforcing cord layer was attached to the standard rim, and the rim Although it is necessary to position the outer side in the tire radial direction from the flange, the outer end in the tire radial direction of the second reinforcing cord layer is greatly affected by the circumferential shear deformation as it goes outward in the tire radial direction. It turns out that the core of separation failure occurs. Therefore, the inventor arranges the outer edge in the tire radial direction of the first reinforcing cord layer on the outer side in the tire radial direction with respect to the outer end edge in the tire width direction of the second reinforcing cord layer. As a result of suppressing the direction shear deformation, it becomes possible to avoid the separation of the second reinforcing cord layer from the outer end edge in the tire radial direction and to achieve both riding comfort and run-flat durability. I found.

In addition, since the inventor generates bulging deformation in the tire width direction and shear deformation in the tire circumferential direction in the portion A, the first reinforcing cord layer has the tire circumferential tensile rigidity and the tire circumferential shear rigidity. It is required to be high, and since the collapse deformation occurs in the portion B, it has been found that the second reinforcing cord layer is required to have high tire radial bending rigidity to resist the collapse deformation of the bead portion. Therefore, the inventor has determined how the angle α formed by the cord constituting the reinforcing cord layer and the tire circumferential direction is related to the tire circumferential tensile stiffness, the tire circumferential shear stiffness, and the tire radial bending stiffness. Experiments were performed and results as shown in FIGS. 3 (a) and 3 (b) were obtained. From these results, the angle between the cord constituting the first reinforcing cord layer and the tire circumferential direction is in the range of 20 to 40 °, and the angle between the cord constituting the second reinforcing cord layer and the tire circumferential direction is made. If the angle is in the range of 60 to 90 °, bulge deformation in the tire width direction of the sidewall portion, shear deformation in the tire circumferential direction, and collapse deformation of the bead portion can be effectively suppressed, and riding comfort is impaired. The present inventors have found that run-flat durability can be improved without any problems, and have completed the present invention.

  As described above, since the circumferential shear deformation increases as the bulge outward in the tire width direction increases, the effect of suppressing the shear deformation as the first reinforcing cord layer 13 is disposed outward in the tire width direction is increased. At the same time, there is a possibility that separation of the first reinforcing cord layer 13 at the outer end edge 15 in the tire radial direction becomes large and separation may occur. In such a case, if the first reinforcing cord layer 13 is disposed between the carcass ply body portion 6 and the ply turn-up portion 7, it is possible to achieve both balanced suppression of shear deformation and prevention of separation. Therefore, it is preferable.

  Further, as shown in FIG. 4, the tire 1 may further include a rim guard portion 21 that protrudes outward in the tire width direction from the flange 20 of the applied rim on which the tire is mounted, on the outer surface of the tire. . In this case, since the portion where the rim guard portion 21 is disposed has high rigidity and is difficult to deform, the ply main body portion (B ′ in FIG. 4) corresponding to the outermost end 22 in the tire radial direction of the rim guard portion is substituted for the B portion. 2), the outermost edge 16 in the tire radial direction of the second reinforcing cord layer 14 is more in the tire radial direction than the outermost end 22 in the tire radial direction of the rim guard portion 21. It is preferable to arrange so as to be located outside. This is because by arranging the second reinforcing cord layer 14 in this manner, the bending rigidity of the B ′ portion is increased, and the occurrence of a failure in the B ′ portion can be suppressed.

  Further, the first reinforcing cord layer 13 and / or the second reinforcing cord layer 14 preferably has an elastic modulus Ef in the range of 2 to 20 GPa. When the elastic modulus Ef of the reinforcing cord layer is less than 2 GPa, the longitudinal spring index of the tire is small and the riding comfort is excellent, but the deformation suppressing effect is low and the run-flat durability cannot be sufficiently improved. If it exceeds 20 GPa, the run flat durability is excellent, but the longitudinal spring index of the tire becomes too large, and the riding comfort is remarkably reduced.

  Furthermore, the folded end 23 of the carcass 9 is preferably located on the outer side in the tire radial direction with respect to the outer end edge 15 in the tire radial direction of the first reinforcing cord layer 13. Since the angle α1 formed by the cord 18 constituting the first reinforcing cord layer 13 and the tire circumferential direction C is relatively small, separation from the outer edge 15 in the tire radial direction is likely to occur. By covering the tire radial direction outer edge 15 of the first reinforcing cord layer 13 with the portion 7, it is possible to suppress the occurrence of such separation and further improve the run-flat durability.

  In addition, the cords 18 and 19 constituting the first reinforcing cord layer 13 and / or the second reinforcing cord layer 14 preferably have an initial elongation as shown in FIG. This is because, when the cords 18 and 19 have initial elongation, the first reinforcing cord layer 13 and the second reinforcing cord layer 14 are deformed in the initial elongation region during normal running, so that the influence on riding comfort is reduced. . The means for imparting initial elongation to the cords 18 and 19 is not particularly limited, and examples thereof include a method of arranging the cords 18 and 19 while being bent in a wave shape or a zigzag shape, a method of changing the twisted structure of the cords, and the like. It is done.

In this case, the initial elongation of the cords 18 and 19 is further preferably 0.4 to 0.7%. This is because when the initial elongation is less than 0.4%, the longitudinal spring index of the tire becomes too large, and the riding comfort during normal driving is impaired, and when it exceeds 0.7%, deformation is suppressed. It is because the effect to do becomes inadequate. Also, the code 18 and 19 is preferably an elastic modulus in the initial elongation region E 'is not more than 2 GPa. This is because if the elastic modulus E ′ of the cord in the initial elongation region exceeds 2 GPa, the longitudinal spring index of the tire becomes too large and the riding comfort during normal running is impaired.

  Further, the cords 18 and 19 constituting the first reinforcing cord layer 13 and / or the second reinforcing cord layer 14 are preferably steel cords. During run-flat running, the vehicle runs while the side wall portion 4 is bent and deformed, so that the side wall portion 4 becomes high temperature due to self-heating. For this reason, as the cords 18 and 19 constituting the reinforcing cord layers 13 and 14, the run flat durability is further improved by using the cords 18 and 19 having excellent heat resistance and adhesiveness to rubber at high temperature. Because.

  The above description shows only a part of the embodiment of the present invention, and various modifications can be made in the claims.

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

  The tires of Examples 1 to 5 are tires for passenger cars having a tire size of 215 / 45R17, a radial carcass composed of one ply made of rubber coated 1650 D / 3 rayon fibers, A reinforcing rubber layer located on the circumferential side and a cord in which five 0.22 mm steel filaments are twisted in a layer are arranged in parallel, and the extension direction of the cord is 20 ° with respect to the tire circumferential direction. Reinforcement of belt made by spirally winding a belt made of aromatic polyamide fibers located on the outer circumference of the cross belt layer, and a belt layer made by laminating the belt layers so that the cords cross each other. And the first reinforcing cord layer is disposed between the ply body portion and the ply folded portion of the carcass and has the specifications shown in Table 1.

  For comparison, the tire size, carcass, belt layer, and belt reinforcing layer are the same as those in Examples 1 to 5, and have the specifications shown in Table 1, but have no first and second reinforcing cord layers ( Conventional examples 1 and 2), and tires (Comparative Examples 1 to 3) having first and second reinforcing cord layers but having an angle between the cords constituting them and the tire circumferential direction is outside the scope of the present invention. A prototype was also made.

  Each of the test tires was attached to a standard rim (7JJ) defined by JATMA to form a tire wheel, and the following tests were performed.

1. Run-flat durability The valve core of each tire wheel is removed, the tire internal pressure is 0 kPa (relative pressure), the tire load is 4165 N, and the running speed is 90 km / h. The mileage until failure occurred was measured, and the durability of the tire was evaluated based on the measured value. The evaluation results are shown in Table 1.

2. Riding comfort Each tire wheel was grounded on a flat plate at an air pressure of 230 kPa and a tire load load of 4165N, the maximum displacement in the tire radial direction (longitudinal spring index) was measured, and the riding comfort was evaluated based on the measured values. The evaluation results are shown in Table 1.

  Note that the “height” in Table 1 refers to the rim diameter line position (position at which the rim diameter is measured) or an extension line extending along the tire width direction from this point to the point to be measured in the tire radial direction. The distance measured along. The evaluation results in Table 1 are shown as index ratios when the run-flat durability of Conventional Example 1 is 100 and the riding comfort of Conventional Example 2 is 100. The smaller the numerical value, the better the riding comfort.

  From the results shown in Table 1, the tires of Examples 1 to 5 have riding comfort while maintaining runflat durability equal to or higher than that of Conventional Example 1 using a thick rubber rubber reinforcing rubber layer. It has improved. Moreover, the run-flat durability of the tires of Examples 1 to 5 is remarkably improved without significantly deteriorating riding comfort as compared with Conventional Example 2 using the same reinforcing rubber layer.

  According to this invention, the reinforcing cord layer is properly disposed to effectively suppress both the bulging deformation of the sidewall portion and the falling deformation of the bead portion, and both the riding comfort and the run flat durability are at a high level. It has become possible to provide a side-reinforced run-flat tire that is compatible.

1 is a left half sectional view in the tire width direction showing a typical run-flat tire according to the present invention assembled to a rim. (A) And (b) is a figure for demonstrating the angle | corner which the code | cord | chord which comprises a reinforcement cord layer and the tire circumferential direction make. (A) is a graph showing the relationship between the extension angle of the cord constituting the reinforcing cord layer, the tire circumferential direction tensile stiffness and the tire circumferential direction shear stiffness, and (b) is the extension of the cord constituting the reinforcing cord layer. It is a graph showing the relationship between a present angle and tire radial direction bending rigidity. It is a tire width direction left half sectional view shown in the state where other run flat tires according to this invention were attached to a rim. It is a graph showing the relationship between the elongation of the code | cord | chord which comprises a reinforcement cord layer, and a load. It is a tire width direction left half sectional view shown in the state where the conventional run flat tire was attached to the rim.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead core 3 Bead part 4 Side wall part 5 Tread part 6 Ply main-body part 7 Ply folding | turning part 8 Ply 9 Carcass 10 Crown part 11a, 11b Belt layer 12 Reinforcement rubber layer 13 1st reinforcement cord layer 14 2nd reinforcement cord layer 15 Tire radial direction outer edge of the first reinforcing cord layer 16 Tire radial direction outer end edge of the second reinforcing cord layer 17 Tire maximum width position 18, 19 Cord 20 Rim flange 21 Rim guard portion 22 Rim guard portion outermost in the tire radial direction End 23 Carcass folded end 24 Belt reinforcing layer 25 Circumferential groove

Claims (8)

A pair of bead portions in which bead cores are embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portions, and a ply main body portion extending in a toroid form across each portion of a tread portion extending between both sidewall portions, and the ply A carcass composed of at least one ply formed of a ply folded portion extending from the inner side to the outer side in the tire width direction and extending around the bead core around the bead core, and located on the outer peripheral side of the crown portion of the carcass, and the cord is made of rubber In a run-flat tire comprising at least one belt layer formed by covering, and a reinforcing rubber layer having a crescent-shaped cross section disposed on at least a sidewall portion,
A first reinforcing cord layer formed by rubber-covering the cord is disposed outside the carcass ply main body portion in the tire width direction, and the cord is rubber-coated between the carcass ply main body portion and the reinforcing rubber layer. A second reinforcing cord layer is provided,
The outer end edge in the tire radial direction of the first reinforcing cord layer is located on the outer side in the tire radial direction with respect to the outer end edge in the tire radial direction and the tire maximum width position of the second reinforcing cord layer,
The outer end edge in the tire radial direction of the second reinforcing cord layer is attached to the standard rim and is located on the outer side in the tire radial direction from the rim flange,
An inner edge in the tire radial direction of the first reinforcing cord layer is located on the inner side in the tire radial direction from the tire maximum width position,
The inner end edge in the tire radial direction of the second reinforcing cord layer is attached to the standard rim, and is located on the inner side in the tire radial direction than the rim flange,
The cord constituting the first reinforcing cord layer has an angle formed with the tire circumferential direction in the range of 20 to 40 °,
A run flat tire characterized in that the cord forming the second reinforcing cord layer has an angle formed by the tire circumferential direction in a range of 60 to 90 °.   The tire further includes a rim guard portion which is on the outer surface of the tire and protrudes outward in the tire width direction from the flange of the applied rim to which the tire is mounted, and the outer edge in the tire radial direction of the second reinforcing cord layer is the rim guard portion. The run-flat tire according to claim 1, wherein the run-flat tire is located on the outer side in the tire radial direction from the radially outermost end. In the first reinforcing cord layer and / or the second reinforcing cord layer, the elastic modulus of one cord is E, the cross-sectional area of one cord is A, the number of cords driven per mm is N, t = (A / π) when the ^1/2 × 2, run-flat tire according to claim 1 or 2 elastic modulus Ef of the reinforcing cord layer is in the range of each 2~20GPa represented by the following formula (1).
Ef = (A × N × E) / t (1)   The run-flat tire according to any one of claims 1 to 3, wherein the folded end of the carcass is located on the outer side in the tire radial direction with respect to the outer end edge in the tire radial direction of the first reinforcing cord layer. The cord constituting the first reinforcing cord layer and / or the second reinforcing cord layer is a load obtained when a cord with rubber of the reinforcing cord layer is taken out from the product tire and a tensile test is performed using the cord as a test piece ( The initial elongation, which is the elongation value at the point where the straight line passing through the load points of 30% and 70% of the rupture load intersects the horizontal axis in the elongation (horizontal axis) characteristic curve , is greater than 0%. The run flat tire as described in 1-4.   The run-flat tire according to claim 5, wherein the initial elongation is 0.4 to 0.7%. The cord constituting the first reinforcing cord layer and / or the second reinforcing cord layer is from the origin to a point where a straight line passing through the load points of 30% and 70% of the breaking load intersects the horizontal axis in the characteristic curve. The run flat tire according to claim 5 or 6, wherein an elastic modulus E 'in an initial elongation region which is a region of 2 GPa is 2 GPa or less.   The run flat tire according to any one of claims 1 to 7, wherein the cord constituting the first reinforcing cord layer and / or the second reinforcing cord layer is a steel cord.

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