JP4172995B2 - Run-flat radial tire - Google Patents

Description

【００４０】
表１によれば、周溝の形成によって、ランフラット時のトレッド部のバックリングが抑制されて、トラクション性能が大きく向上することが明らかであり、また、繊維補強層により、ランフラット耐久性能が大きく向上することが明らかである。そして、このランフラット耐久性能は、補強ゴム層の最大厚み部分の位置を選択することでより一層向上することになる。
この一方で、タイヤの正常時の振動乗り心地は、繊維補強層を配設してなお、周溝による、横断面内での曲げ剛性の低減によって有利に向上されることが解る。
【００４１】
【発明の効果】
かくしてこの発明によれば、通常はトレッド接地幅の外側に位置する少なくとも一対の周溝を設けることで、トレッドパターンの設計の自由度を挟めることなく、ランフラット時のトレッド部のバックリングを十分に防止することができ、同時に、周溝の形成に起因するランフラット耐久性の低下を、位置を選択して配設した繊維補強層によって十分に防止することができる。
【図面の簡単な説明】
【図１】 トレッド部へのバックリングの発生態様を例示する説明図である。
【図２】 バックリングの防止対策を例示する説明図である。
【図３】 この発明の実施の形態をタイヤの半部について示す横断面図である。
【図４】 他の実施形態を示す同様の横断面図である。
【図５】 他の実施形態を示す同様の横断面図である。
【図６】 他の実施形態を示す同様の横断面図である。
【図７】 他の実施形態を示す同様の横断面図である。
【図８】 さらに他の実施形態を示す同様の横断面図である。
【図９】 従来タイヤを示す同様の図である。
【図１０】 比較例タイヤ１を示す同様の図である。
【図１１】 比較例タイヤ２を示す同様の図である。
【符号の説明】
１ トレッド部
２ サイドウォール部
３ ビ−ド部
４ ショルダ部
５ ビ−ドコア
６ ラジアルカーカス
７ ベルト
８ ベルト補強層
９ インナライナ
１０ 補強ゴム層
１１，１３ 周溝
１２ 繊維補強層
Ｔ タイヤ総厚み
ｒ リム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a run-flat radial tire capable of ensuring safe driving even when the tire internal pressure leaks, and more particularly to a radial tire for a passenger car that is used at a relatively high speed and has an aspect ratio of 0.6 or less. In particular, it proposes a technology that effectively suppresses vibration under normal conditions of tire use, in addition to improving running durability under conditions of leakage of tire internal pressure, in other words, run-flat durability. It is.
[0002]
[Prior art]
For example, in a vehicle running at a high speed, in order to prevent the movement stability of the vehicle from being greatly impaired due to the tire internal pressure suddenly leaking or the like, resulting in the tire losing its load supporting ability, generally a high flexibility is required. The tire side wall is thickly reinforced with a rubber having a relatively large modulus, and even if the tire internal pressure drops to atmospheric pressure, the wheel load is not increased without significantly increasing the deformation of the side wall. Various types of run-flat tires have been proposed so far that can reduce the rolling radius of the tire and prevent the tire from being detached from the rim.
Such measures are particularly effective for tires having a low aspect ratio, especially 0.6 or less.
[0003]
However, in run-flat tires whose sidewalls have been reinforced with a reinforcing rubber layer in this way, it is inevitable that the vertical rigidity of the tire will increase under normal usage conditions before the tire has failed. Since the vibration of the tire is easily transmitted to the rim and thus to the upper side of the spring, for example, each component of the vibration transmission path is transmitted by transmitting the vibration of the tire caused by road surface unevenness from the suspension or the like to the body side. There was a problem that the durability of the steel was reduced.
[0004]
On the other hand, when the rigidity of the sidewall portion is significantly increased as compared with that of the tread portion, the central portion in the width direction of the tread surface is significantly raised from the road surface as the tire internal pressure leaks. The so-called buckling as shown in FIG. 2 occurs, and the tire is grounded only in its shoulder region, so that the ground contact area of the tire is reduced, and driving and braking performance, steering performance, etc. are greatly reduced. .
[0005]
That is, such a buckling in which the center part in the width direction of the tread surface is greatly lifted from the road surface has been examined for deformation in the contact area between the tire and the road surface and its vicinity during run flat. As shown in the half of the cross-section, before the failure of the tire, the cause is that the radially outward portion or the shoulder portion of the sidewall portion of the tire in contact with the ground as shown by the broken line in FIG. As described above, it has been clarified that this occurs based on the occurrence of a moment M in a direction to separate the central portion of the tread portion from the road surface.
This collapse deformation causes the point P existing outside the tread contact width before the failure of the tire to be drawn inside the tread contact width. This tendency is caused by the frictional force between the tire and the road surface. The smaller the size, the larger.
[0006]
By the way, when the moment M was analyzed, the moment M depends on the rigidity of each of the tread portion and the sidewall portion, the rigidity ratio thereof, the magnitude of the load, the above-described collapse deformation amount, It became clear that it depends directly on the bending stiffness in the cross section of the shoulder.
Therefore, one useful method for preventing buckling is to reduce the bending rigidity in the cross section of the shoulder portion and suppress the direct transmission of the moment M caused by the deformation of the sidewall portion to the tread portion. There is to do. In other words, the moment M usually increases according to the ratio of the sidewall rigidity to the tread rigidity, but a portion that functions as a hinge is provided in the shoulder portion that is grounded during run-flat. Thus, the occurrence of buckling can be effectively suppressed by eliminating the strong correlation between the deformation of the sidewall portion and the deformation of the tread portion.
[0007]
As a specific means for this, as shown in FIG. 2, it is conceivable to provide a circumferential groove G extending in the circumferential direction in the shoulder portion. Absorbing with deformation, the transmission of the deformation of the sidewall portion to the tread portion is suppressed. In other words, the moment M generated based on the deformation of the sidewall portion is relaxed by the circumferential groove G, and the tread portion The transmitted moment can be sufficiently reduced.
[0008]
In this regard, Japanese Patent Application Publication No. 2002-518231 discloses a tread having a tread rib disposed in a lateral direction, a contact surface with a drive surface during a run-flat operation, and a drive surface during a standard expansion pressure operation. Between the side wall ribs disposed in the vicinity of the outermost region in the radial direction of each side wall and the side wall ribs and the adjacent tread ribs in the circumferential direction. A pneumatic radial plastic comprising: a first separation groove disposed; and a second separation groove disposed in a circumferential direction between the tread rib and a tread central region adjacent thereto. An Iranian flat tire is disclosed.
[0009]
[Patent Document 1]
Japanese translation of PCT publication No. 2002-518231
[Problems to be solved by the invention]
However, the present invention requires the first and second separation grooves, and suppresses the transmission of bending force from the sidewall portion to the tread portion at the time of run flat under the cooperative action of both the grooves. In particular, the second separation groove present in the tread surface reduces the degree of freedom in designing the tread pattern, and because of the presence of the first separation groove, the run-flat durability of the tire is reduced. There was a problem that the decline could not be denied.
[0011]
The present invention has an object to solve such problems of the prior art, and the object of the present invention is to reduce the degree of freedom in designing the tread pattern without reducing the degree of freedom of the tread pattern. An object of the present invention is to provide a run-flat radial tire that can effectively prevent the occurrence of buckling and at the same time sufficiently prevent a decrease in run-flat durability caused by the formation of a circumferential groove.
[0012]
[Means for Solving the Invention]
A run-flat radial tire according to the present invention includes a tread portion, a pair of sidewall portions extending inward in the radial direction continuously to both side portions of the tread portion, and a bead portion continuing to the inner peripheral side of each sidewall portion. And a radial carcass composed of one or more carcass plies each having a side portion rolled back radially outwardly around a pair of bead cores disposed on each bead portion, and at least a sidewall portion In the corresponding part, it is provided with a reinforcing rubber layer arranged between the radial carcass and the inner liner on the inner periphery of the radial carcass. Under a posture with a load of 1x applied, it is located outside the tread contact width, while reducing the tire internal pressure to atmospheric pressure, corresponding to the maximum load capacity Under the mass-loaded posture, at least a pair of circumferential grooves that are located on the inner side of the tread ground contact width and are continuous in the circumferential direction are provided on the outer surface of the shoulder region, and the depth of each circumferential groove is set to The circumferential groove on the inner circumferential side of the circumferential groove is set to a quarter or more of the total tire thickness before the groove is formed, and the circumferential angle of the circumferential groove is in a range of 0 to 30 °. In addition to the carcass ply, an independent fiber reinforcing layer made of reinforcing members such as a belt layer and a circumferential reinforcing layer is disposed in a band shape in a region overlapping part or all of the belt. .
[0013]
Here, “rim” refers to the rim defined by the following standards, “maximum air pressure” refers to the air pressure corresponding to the maximum load capacity according to the following standards, and “maximum load capacity” The maximum mass allowed to be loaded on a tire according to the following standards.
Further, the “depth of the circumferential groove” here is ¼ of the total tire thickness measured from the smooth virtual extension line of the outer contour of the tire to the circumferential groove portion after the circumferential groove is formed. It can also be specified as above.
[0014]
The standard is an industrial standard effective in the region where tires are produced or used. For example, “Year Book of The Tire and Rim Association Inc.” in the United States, and The European Tire and Rim Technical Technical Organizaion in Europe. Standards Manral ”in Japan, and“ JATMA Year Book ”of the Japan Automobile Tire Association in Japan.
[0015]
In the tire configured as described above, when the tire is run flat, the circumferential groove formed in the shoulder region of the tire and having a specified position, extending direction, and depth is formed in the sidewall portion. In response to the falling on the road surface, the deformation of the tread due to the falling deformation is effectively suppressed based on its own groove width reduction deformation, and the transmission of the moment generated by the falling deformation to the tread is effectively reduced. Therefore, as shown by the solid line in FIG. 2, occurrence of buckling to the tread portion can be effectively prevented.
[0016]
Also, here, the fiber reinforced layer on the inner circumference side of the circumferential groove, and protecting the circumferential groove, especially the groove bottom, can sufficiently prevent the run-flat durability from being reduced due to the formation of the circumferential groove. can do. Here, this fiber reinforced layer is disposed in a belt shape in a required region, and in particular, it suppresses an excessive increase in vertical rigidity of the tire before the occurrence of the failure, and sufficiently reduces the riding comfort on the vehicle. In addition, an unnecessary increase in tire weight can be prevented.
[0017]
By the way, the pair of or more circumferential grooves here are positioned outside the tread contact width before the failure of the tire, so the presence of the circumferential grooves does not hinder the design of the tread pattern.
With respect to such circumferential grooves, the formation position thereof is set to be outside the tread contact width under the action of 1.1 times the maximum load capacity by filling the tire with the highest air pressure, so that run flat running In particular, an excellent hinge function can be exhibited at the location where the circumferential groove is formed.
[0018]
In addition, the depth of the circumferential groove is set to 1/4 or more of the total tire thickness, the bending rigidity of the shoulder portion including the circumferential groove in the cross section is lowered, and the width of the circumferential groove is reduced. By making the resistance to deformation sufficiently small, the falling deformation of the sidewall portion is more effectively absorbed by the peripheral groove, and the tread portion rising due to the falling deformation, and hence the occurrence of buckling, is effective. Can be prevented.
[0019]
In such a circumferential groove that functions effectively to prevent buckling, in order to prevent the occurrence of early failure around it, the angle of the circumferential groove with respect to the circumferential direction is preferably 0 to 30 °, preferably It is preferable that the shear strain in the circumferential direction generated at the groove bottom of the circumferential groove is somewhat dispersed in the tread width direction at an angle exceeding 0 °. In this case, if the extension angle exceeds 30 °, the amount of deviation from the optimum position of the so-called hinge is not negligible, and the buckling cannot be effectively suppressed, and the groove bottom portion of the circumferential groove Failure nuclei due to concentration of strain on the groove are likely to occur at the groove bottom.
[0020]
In such a tire, the fiber reinforcing layer is preferably disposed on at least the outer peripheral side of the radial carcass. According to this configuration, the protection function of the fiber reinforcement layer against failures such as groove bottom cracks in the circumferential groove can be more effectively exhibited as compared with the case where the reinforcement layer is disposed on the inner circumference side of the carcass. it can.
[0021]
Preferably, the radial position of the maximum thickness portion of the reinforcing rubber layer is positioned between the circumferential groove and the separation point between the rim and the tire in a posture in which the internal pressure of the rim-assembled tire is reduced to atmospheric pressure.
For example, when a circumferential groove as shown in FIG. 2 is provided in the shoulder portion, the modified form of the sidewall portion at the time of run flat is different from the case shown in FIG. 1 where no circumferential groove is provided. The portion of the sidewall portion of the deformed posture where the radius of curvature is the smallest is located in the former in the radial direction of the tire more closely to the circumferential groove than the latter, and the radius of curvature R is Since the latter is smaller than the radius of curvature R _{0, in} the former tire in which a circumferential groove is provided in the shoulder portion, the maximum thickness portion of the reinforcing layer rubber layer is positioned corresponding to the portion where the radius of curvature is the smallest, so that the radius of curvature is increased. By suppressing the excessive decrease of the reinforced rubber layer, it is possible to advantageously prevent the failure failure of the reinforced rubber layer itself.
Therefore, here, as described above, the maximum thickness portion is positioned between the circumferential groove and the separation point between the rim and the tire, more preferably, particularly in a portion close to the circumferential groove, and the reinforcing rubber layer More effectively prevent the destruction.
[0022]
Here, the fiber of the fiber reinforcing layer can be an untwisted or twisted organic or inorganic fiber, and the extending mode of the fiber can be a blind structure, a three-dimensional knitted structure, or the like. However, the fiber reinforcement layer is particularly effective as a unidirectional fiber reinforcement layer in which a cord formed by twisting rayon fibers is disposed so as to extend substantially in the radial direction, for example.
That is, the optimal cord extending direction of the fiber reinforcement layer is to separate both the deformation of the sidewall portion and the deformation of the tread portion and to avoid the concentration of strain on the cord end of the fiber reinforcement layer. For this purpose, it is preferable that the direction is a radial direction or a direction that forms a relatively small angle with respect to the radial direction, for example, an angle in the range of 0 to 30 °.
[0023]
Although the circumferential groove is effective for suppressing buckling, it is necessary to protect the circumferential groove against concentration of strain on the circumferential groove or the like in order to improve the run-flat durability. By the way, the durability involved in the circumferential groove, in particular, the strain related to the groove bottom crack of the circumferential groove is mainly the circumferential shear strain. In order to reduce this strain, the groove on the outer peripheral side of the radial carcass It is effective to dispose the fiber reinforcing layer in a band shape in a region corresponding to the bottom.
[0024]
In this case, the fibers of the fiber reinforcing layer may be formed of either an organic material or an inorganic material as long as an appropriate groove bottom protecting function can be exhibited, and may or may not be twisted. And the arrangement structure of the fibers can be a blind structure, a three-dimensional knitting structure, a woven structure, or the like. However, it is preferable to use rayon fibers in consideration of the thermal stability in a high temperature use environment at the time of run flat, and considering the destructibility of the fibrils inside the fibers, the fiber reinforcement layer is formed with the twist cord of the rayon fibers. In order to protect the groove portion more effectively from the circumferential shear strain of the circumferential groove, it is preferable that the extending direction of the cord is a substantially radial direction.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings.
FIG. 3 is a cross-sectional view showing an embodiment of the present invention with respect to a half portion of the tire.
In the figure, 1 is a tread portion, 2 is a sidewall portion extending radially inward continuously to the side portion of the tread portion 1, and 3 is a bead portion continuing to the inner peripheral side of the sidewall portion 2. 4 shows a shoulder which is also called a buttress at the boundary between the tread portion 1 and the sidewall portion 2 and protects the carcass with a thick rubber layer while promoting heat dissipation.
[0026]
Here, at least one carcass ply is extended toroidally between a pair of bead cores 5 arranged in the bead part 3, and the side part of the carcass ply is wound around the bead core 5 radially outward. A radial carcass 6 is formed, and on the outer peripheral side of the crown portion of the radial carcass 6, a belt 7 composed of two belt layers is disposed in such a manner that the belt layer cords cross between the layers, and Further, on the outer peripheral side of the belt 7, one or more belt reinforcing layers 8 substantially extending in the tread circumferential direction, for example, made of an organic fiber cord and somewhat wider than the belt width are disposed, At least a portion corresponding to the sidewall portion 2, in the figure, a region extending from the side region of the tread portion 1 to the bead portion 3, the radial carcass 6 and the inner peripheral side thereof Between Ina 9, disposed substantially crescent-shaped reinforcing rubber layer 10 made of relatively hard rubber.
[0027]
In addition, here, as shown in FIGS. 1 and 2, in a state where the tires assembled to the specified rim r are filled with the highest air pressure, a load of 1.1 times the maximum load capacity is applied and the tread ground contact width is maintained. While located outside, when the tire internal pressure is reduced to atmospheric pressure and a mass corresponding to the maximum load capacity is applied, at least a pair of left and right, in the figure, at least one circumference will be located inside the tread contact width. The groove 11 is provided on the outer peripheral surface of the shoulder region 4, and the circumferential groove 11 is formed continuously in a linear or zigzag manner at an angle in a range of 0 to 30 ° with respect to the circumferential direction. The circumferential groove 11 shown in this figure extends linearly.
Such a depth of the circumferential groove 11 is not less than ¼ of the total tire thickness T before the circumferential groove is formed, and the bending rigidity in the cross section of the shoulder region 4 is sufficiently reduced.
[0028]
Further, the radial carcass 6, the belt 7 and the belt are located in a region overlapping with a part or all of the circumferential groove 11 at a position on the inner circumferential side of the circumferential groove 11, preferably at least in an overlapping region with the groove bottom. The reinforcing layer 8 is provided with a fiber reinforcing layer 12 that is independent from other reinforcing members in a band shape. Preferably, the fiber reinforcing layer 12 is disposed by extending a cord in which rayon fibers are twisted so as to extend in a substantially radial direction. The unidirectional fiber reinforcement layer is provided and formed.
[0029]
The fiber reinforcing layer 12 can be disposed along the inner periphery of the radial carcass 6 as shown in FIG. 4 in addition to the outer periphery of the radial carcass 6 as shown.
Further, as shown in FIG. 5, the fiber reinforcing layer 12 can be disposed on the outer peripheral side of the radial carcass 6 and very close to the circumferential groove 11. Further, the fiber reinforcing layer 12 is sandwiched between the radial carcass 6. The circumferential groove reinforcing function can be further enhanced by disposing them on both the inner and outer sides.
[0030]
FIG. 6 is a diagram exemplifying this case. This is because each of the shoulder regions 4 and the peripheral grooves 11 are formed in order to further reduce the influence of the deformation of the sidewall portion 2 on the buckling of the tread portion 1. In addition, another circumferential groove 13 is provided. In this case, since the amount of distortion in the circumferential grooves 11 and 13 and the vicinity thereof increases, two-layer fiber reinforcement separated by the radial carcass 6 is provided. By providing the layer 12, the circumferential shear strain is sufficiently reduced.
[0031]
FIG. 7 shows another embodiment. In order to suppress the concentration of strain in the circumferential groove 11 and the vicinity thereof, the corner of the circumferential groove 11 in the cross section is curved, and at the time of run flat. In order to prevent breakage of the reinforcing rubber layer 10 and to provide excellent run-flat durability, the maximum thickness of the reinforcing rubber layer 10 is kept as it is, while maintaining the total volume of the reinforcing rubber layer 10, It is located between the rim and the separation point of the tire during run flat.
That is, the portion where the radius of curvature of the sidewall portion becomes the smallest at the time of run flat of the tire preventing buckling appears somewhat from the bead portion from the radially inner end of the fiber reinforcing layer 12. By matching the maximum thickness portion of the material to the portion, it is possible to prevent an extreme decrease in the radius of curvature and prevent a decrease in the durability of the reinforced rubber layer itself.
[0032]
FIG. 8 shows still another embodiment, and the cross-sectional shape of the circumferential groove 11 is curved like that shown in FIG. 7, and the circumferential groove 11 has an angle of 30 ° or less with respect to the circumferential direction. In this case, the groove bottom strain is distributed in a zigzag manner.
[0033]
【Example】
Below, the Example regarding the traction performance of the size 215 / 45R17 run flat tire used for a passenger car, the run flat durability performance, and the vibration riding comfort is described.
This run-flat tire is normally used under a load load of 4165 N at an air pressure of 230 kPa, but the inner circumference side of the radial carcass is also used to withstand use when the tire internal pressure is reduced to atmospheric pressure. In addition, a reinforcing rubber layer having a thick rubber thickness is provided, and as a reinforcing member, a radial carcass made of rayon fiber of 1650D / 3 and a cord twisted in five layers of 0.22 mm steel filaments are arranged in parallel, Two steel belt layers intersecting each other whose angle between the axis and the tire equator direction is 15 to 30 °, and the belt is arranged so as to cover the belt from the outside in the radial direction, and one or more layers are wound in the substantially circumferential direction. A belt reinforcing layer made of a ribbon-like aromatic polyamide fiber is provided.
[0034]
A shallow decorative groove is sculpted in the shoulder region of the conventional tire shown in FIG. The tire thickness before the groove formation at this decorative groove formation position is 13 mm, and the groove depth is 2.2 mm.
The comparative tire 1 shown in FIG. 10 is provided with a circumferential groove having a groove depth of 4.0 mm at a position closer to the tread 8 mm than the decorative groove position (tire thickness: 14 mm). This groove can exhibit a function of reducing buckling moment by separating sidewall rigidity and tread rigidity.
In the comparative example tire 2 shown in FIG. 11, the entire sidewall portion is covered with an interdigital reinforcing layer made of rayon fibers in the circumferential direction from the outside of the radial carcass in order to prevent early failure that occurs in the vicinity of the circumferential groove during the run-flat durability test. It is reinforced by turning.
[0035]
The example tire 1 shown in FIG. 3 is arranged so that the width of the fiber reinforcement layer used in the comparative example tire 2 is reduced and does not overlap with the folded portion of the carcass ply. The example tire 2 shown in FIG. Only the portion corresponding to the groove is reinforced from the inside of the radial carcass. And the Example tire 3 shown in FIG. 5 reinforces the vicinity of a circumferential groove on the outer side of a radial carcass.
[0036]
The tire 4 of the example shown in FIG. 6 has two circumferential grooves to further reduce the influence of the sidewall rigidity on the tread buckling phenomenon. In this case, since the strain in the vicinity of the circumferential groove increases, the fiber reinforced layer at the position is made into two layers.
The example tire 5 shown in FIG. 7 is based on the example tire 1, and optimizes the shape in the cross section of the circumferential groove to suppress the strain concentration in the vicinity thereof, and the maximum thickness position of the reinforcing rubber layer is This is between the radially inner end of the fiber reinforcement layer and the separation point between the rim and the tire.
[0037]
The example tire 6 shown in FIG. 8 is also based on the example tire 1, and the cross-sectional shape of the circumferential groove is optimized, and the circumferential groove is zigzag with a swing angle of 20 ° with respect to the circumferential direction. It has been extended to.
[0038]
For each of these tires, the tire internal pressure was reduced to atmospheric pressure, and the traction performance and drum durability performance when a load of 4165N was applied were measured. In addition, the tire internal pressure was 230 kPa and the load load was 4165N. When the vertical riding force was measured to determine the vibration ride comfort, the results shown in Table 1 with indices were obtained. It should be noted that the larger the index value, the better the result.
[0039]
[Table 1]

[0040]
According to Table 1, it is clear that the buckling of the tread portion at the time of run flat is suppressed by the formation of the peripheral groove, and the traction performance is greatly improved. It is clear that it is greatly improved. The run-flat durability performance is further improved by selecting the position of the maximum thickness portion of the reinforcing rubber layer.
On the other hand, it can be seen that the vibration ride comfort during normal operation of the tire can be advantageously improved by reducing the bending rigidity in the cross section due to the circumferential groove even when the fiber reinforcement layer is provided.
[0041]
【The invention's effect】
Thus, according to the present invention, by providing at least a pair of circumferential grooves that are usually positioned outside the tread ground contact width, the tread portion buckling at the time of run-flat can be sufficiently achieved without interposing a degree of freedom in designing the tread pattern. At the same time, a decrease in run-flat durability due to the formation of the circumferential groove can be sufficiently prevented by the fiber reinforcing layer arranged at a selected position.
[Brief description of the drawings]
FIG. 1 is an explanatory view exemplifying a mode of occurrence of buckling to a tread portion.
FIG. 2 is an explanatory diagram illustrating buckling prevention measures;
FIG. 3 is a transverse sectional view showing an embodiment of the present invention about a half portion of a tire.
FIG. 4 is a similar cross-sectional view showing another embodiment.
FIG. 5 is a similar cross-sectional view showing another embodiment.
FIG. 6 is a similar cross-sectional view showing another embodiment.
FIG. 7 is a similar cross-sectional view showing another embodiment.
FIG. 8 is a similar cross-sectional view showing still another embodiment.
FIG. 9 is a similar view showing a conventional tire.
10 is a similar view showing a comparative tire 1. FIG.
11 is a similar view showing a comparative tire 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Shoulder part 5 Bead core 6 Radial carcass 7 Belt 8 Belt reinforcement layer 9 Inner liner 10 Reinforcement rubber layer 11,13 Circumferential groove 12 Fiber reinforcement layer T Tire total thickness r Rim

Claims (5)

A tread portion, a pair of side wall portions extending radially inward from both side portions of the tread portion, and a pair of bead cores arranged on each bead portion, the bead portion being continuous on the inner peripheral side of each side wall portion. A radial carcass composed of one or more carcass plies each having a side portion rolled back radially outward, and at least a portion corresponding to the side wall portion of the radial carcass and an inner liner on the inner periphery thereof. A run-flat radial tire having a reinforcing rubber layer disposed between and
Under the posture in which the rim-assembled tire is filled with the maximum air pressure and the load of 1.1 times the maximum load capacity is applied, the tire is located outside the tread contact width, while the tire internal pressure is reduced to the atmospheric pressure to maximize the load capacity. Under the posture loaded with a mass equivalent to the above, at least a pair of circumferential grooves that are located on the inner side of the tread contact width and are continuous in the circumferential direction are provided on the outer surface of the shoulder region, and the depth of each circumferential groove is determined according to the formation location thereof. In addition, the circumferential thickness of the tire is not less than 1/4 of the total thickness of the tire before the circumferential groove is formed, and the extending angle of the circumferential groove with respect to the circumferential direction is in a range of 0 to 30 °. A run-flat radial tire in which a fiber reinforcing layer independent of other reinforcing members is disposed in a band shape in a region overlapping a part or all of a circumferential groove. The run-flat radial tire according to claim 1, wherein the fiber reinforcing layer is disposed on at least an outer peripheral side of the radial carcass. 2. The radial position of the maximum thickness portion of the reinforcing rubber layer is positioned between the circumferential groove and the separation point between the rim and the tire in a posture in which the internal pressure of the rim-assembled tire is reduced to atmospheric pressure. Or the run-flat radial tire of 2. The run-flat radial tire according to any one of claims 1 to 3, wherein the fibers of the fiber reinforcement layer are organic or inorganic fibers with or without twist. 5. The fiber reinforcing layer according to claim 1, wherein the fiber reinforcing layer is a fiber reinforcing layer in which a cord formed by twisting rayon fibers is disposed and the cord has an angle with respect to the radial direction of the tire in a range of 0 to 30 degrees. Run-flat radial tire described in 1.

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