WO2008001773A1

WO2008001773A1 - Run flat tire

Info

Publication number: WO2008001773A1
Application number: PCT/JP2007/062806
Authority: WO
Inventors: Masahiro Segawa; Kazutaka Hana; Koji Matsuyama
Original assignee: Toyo Tire & Rubber Co., Ltd.
Priority date: 2006-06-27
Filing date: 2007-06-26
Publication date: 2008-01-03

Abstract

A run flat tire having reinforced rubber layers (9a, 9b) disposed in the side wall parts has an annular swollen part (10) and an annular second bead (1b). The annular swollen part (10) is formed on the outer side, in the lateral direction of the tire, of a bead part (1) disposed on the outer side of a vehicle, and has an inner peripheral surface (11) facing the outer peripheral curved surface of a rim flange when a specified rim is installed on the tire. The annular second bead (1b) is disposed in the annular swelled part (10). Both the reinforced rubber layers (9a, 9b) disposed on both sides have a rubber hardness in the range from 65° to 82°. Belt layers (7) disposed on the lower side of the tread part (4) have longitudinal bending rigidity in the range from 0.9 to 2.1 × 106 N.m2.

Description

Run flat tire Technical field

[0001] The present invention is a so-called side reinforcing tape provided with a reinforcing rubber layer disposed in a sidewall portion.

Background art

Conventionally, a side reinforced type run flat tie in which a reinforcing rubber layer is disposed on a side wall portion

Is known. According to the strong run-flat tire, the inside of the

When the air pressure in the part decreases, the reinforced rubber layer supports the tire to suppress flattening, enabling run flat travel. However, when the air pressure inside the tire is reduced (runflat state), the pressure on the rim of the bead portion is weakened, so the fitting force with the rim is reduced, and the bead portion is easily detached from the rim. There was a problem.

[0003] On the other hand, in Patent Documents 1 and 2 below, the first bead disposed on the rim base outer peripheral side, and the second bead disposed on the annular bulging portion bulging outward in the tire width direction of the bead portion. A so-called double bead type run flat tire provided with a bead is disclosed. According to the run flat tire, since it is pressed against the outer peripheral side curved surface of the annular bulging portion cam flange reinforced by the second bead during run flat running, the fitting force with the rim is enhanced, and the tire is resistant to Bead detachment can be improved.

Further, in Patent Document 3 below, a run flat tire is adopted which adopts a double bead structure on the vehicle outer side and does not adopt the double bead structure on the vehicle inner side. It has been proposed that the hardness of the reinforcing rubber layer on the side to be balanced should be greater at the inside of the vehicle than at the outside. Further, Patent Document 3 discloses that the void ratio at the vehicle outer side than the equatorial line of the tread is smaller than the void ratio at the vehicle inner side, and the rubber hardness at the vehicle outer side of the tread is greater than the rubber hardness at the vehicle inner side. There is.

[0005] In the case of run-flat tires such as those described above, a thick steel or the like is used for the belt layer from the viewpoint of preventing tread buckling and improving bead resistance. The high rigidity of the layers sacrificed the ride comfort. [0006] Further, as another problem with bead dislodging, it is known that a noise called road noise is generated in a vehicle interior. The road noise is generated when the tire is vibrated by the unevenness of the road surface when traveling on a relatively rough road surface, and the vibration is transmitted along the route of the rim, axle, car body, and finally becomes noise in the vehicle interior. It is required to reduce this with the recent upgrading of automobiles.

[0007] Of the road noise, those in the frequency range of 200 to 400 Hz are called high frequency road noise. It is known that tire vibration that generates high frequency road noise forms a standing wave with a pair of bead portions at both ends to form a vibration mode in the radial direction. Generally, this vibration mode is considered to be related to a cross-sectional secondary mode in which the tire maximum width portion is a node and the buttress portion and the lower side are antinodes (see, for example, Patent Documents 4 and 5 below). It is also known that a center part (crown part) becomes an antinode of vibration with a part as a node.

As measures against this high frequency road noise, as described in Patent Documents 6 and 7 below, the rubber thickness of the portion that becomes the antinode of the tire vibration is increased, or a member with a large density is arranged in that portion. There are known methods for suppressing the amplitude. Regardless of which method is adopted, a significant increase in tire weight can not be avoided.

Patent Document 1: Japanese Patent Application Laid-Open No. 51 116507

Patent Document 2: Japanese Patent Application Laid-Open No. 53-138106

Patent Document 3: Japanese Patent Application Laid-Open No. 2006-218889

Patent Document 4: Japanese Patent Application Laid-Open No. 2001-130223

Patent Document 5: Japanese Patent Application Laid-Open No. 2002-205515

Patent Document 6: Japanese Patent Application Laid-Open No. 9 109621

Patent Document 7: Japanese Patent Application Laid-Open No. 91-118111

Disclosure of the invention

Problem that invention tries to solve

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a run-flat tire capable of improving the ride comfort while maintaining the bead removal performance. In addition, it is a further object of the present invention to prevent run-off during run-flat travel without deteriorating rim settability, and to obtain a sufficient run-noise reduction effect. To provide tires.

Means to solve the problem

The above object can be achieved by the present invention as described below. That is, the run flat tire according to the present invention comprises a pair of bead portions having an annular first bead, a sidewall portion extending outward from the bead portion in the tire radial direction, and a reinforcing rubber disposed on the sidewall portion. A run flat tire comprising: a layer; and a tread portion in which outer peripheral side ends of the side wall portions are connected via a shoulder portion, the run flat tire being provided on the outer side in the tire width direction of the bead portion disposed on the vehicle outer side; In addition to an annular bulging portion having an inner peripheral side surface facing the outer peripheral side curved surface of the rim flange when the rim is attached, and an annular second bead arranged on the annular bulging portion, the above-mentioned distributive members are disposed on both sides Each reinforcing rubber layer has a rubber hardness of 65 to 82 °, and the belt layer disposed below the tread portion has a bending rigidity with respect to the longitudinal direction of 200 mm in tire circumferential direction length X tire width direction As the flexural rigidity per length 100 mm, characterized in that from 0.9 to 2. A 1 X 10 ⁶ Nm ^2.

In the present invention, rubber hardness refers to the hardness according to JIS K6253 durometer hardness test (type A). Further, physical properties such as flexural rigidity are values measured by the method described in the examples.

According to the above configuration, the double bead structure adopted on the outside of the vehicle effectively removes the bead against the lateral force generated on the outside of the vehicle at the time of turning of the vehicle, which is the most likely cause of the bead coming off in the run flat traveling state. Can be prevented. For this reason, it is difficult to cause bead detachment due to buckling, and the rigidity of the belt layer can be lowered, so that the ride quality can be improved. In addition, since it is possible to effectively prevent bead detachment, it is possible to reduce the hardness of the reinforcing rubber layer which makes it unnecessary to make the hardness of the side reinforcing rubber layer greater than the outside on the vehicle inner side. It can improve.

In the above, in the tread pattern formed in the tread portion, it is preferable that the void ratio on the outer side of the vehicle is equal to or less than the void ratio on the inner side of the vehicle, with the tire equator line as a boundary. Here, the void ratio refers to a value as a percentage obtained by dividing the groove area of each region by the total area in the tread width. If the void ratio on the outer side of the vehicle is equal to or less than the void ratio on the inner side of the vehicle, the tread center buckles in a state where the internal pressure is lowered, and Even when the ground contact pressure at the dab portion increases, the pattern shear rigidity on the outer side of the vehicle with a small void ratio increases when turning the vehicle, and the cornering power increases, so the tire slip angle can be reduced. Since the moment in the bead removal direction which acts on the tire is smaller, the bead removal can be prevented more effectively.

In the above, in the tread portion, at least the cap rubber has a rubber boundary line of different hardness at a position of 40 to 60% of the tread width, and the rubber hardness of the boundary line on the vehicle outside of the vehicle inner side The hardness is preferably equal to or higher than the rubber hardness. Here, with the tread width, in the tire cross section, an imaginary line extended to the shoulder side with the curvature radius of the tread surface of the tread pattern and two imaginary lines extended to the shoulder side with the curvature radius of the buttress on both sides intersect Points to the width of the shoulder points on both sides. Even in this case, since the rubber hardness of the outer side of the vehicle is equal to or higher than the rubber hardness of the inner side of the vehicle, the tread center portion buckles in a state of reduced internal pressure and the contact pressure of the shoulder portion rises even when the vehicle turns. As the pattern shear rigidity on the outside of the vehicle with a low void ratio is higher, the cornering power is increased, so the tire slip angle can be reduced, and the moment in the bead removal direction acting on the tire is smaller. It is possible to prevent bead detachment more effectively.

In the present invention described above, the annular bulging portion is also provided on the outer side in the tire width direction of the bead portion disposed on the inner side of the vehicle, and the second bead is disposed in each of the pair of annular bulging portions. It is also possible. During run-flat travel, the pair of annular bulging portions reinforced by the second bead can abut on the rim flange, so the mounting stability with the rim is enhanced, and bead detachment can be effectively prevented. As a result, bead detachment due to buckling is less likely to occur, and the rigidity of the belt layer can be lowered, so that the riding comfort performance can be improved. Further, since the bead detachment can be effectively prevented, the hardness of the reinforced rubber layer disposed in the sidewall portion can be reduced, and even with this, the riding comfort performance can be improved.

In the above, the cross-sectional height Hi from the inner periphery of the first bead disposed on the vehicle inner side to the tire maximum diameter point, and the inner periphery of the second bead disposed on the vehicle outer side to the tire maximum diameter point The cross section height Ho and the one that satisfy the relationship of Hi_Ho> 15 mm are preferred. Here, the section height is the height in the tire radial direction in the tire meridional section, and the tire is defined as a rim. It shall be measured in the state of no load which was equipped and filled up with specified internal pressure. The specified rim refers to the standard rim determined by JATMA corresponding to the tire size. The prescribed internal pressure is the force S which is the air pressure determined by JATMA, and is 180 kPa when the tire is for a passenger car.

[0017] The inventors of the present invention conducted intensive studies to find that the amplitude can be suppressed by asymmetrizing vibration modes that are generally formed substantially symmetrically on both sides in the tire width direction. It was found to be effective for reduction. The above-described configuration of the present invention adopts the double bead structure only on the outside of the vehicle, and is most likely to be the cause of bead detachment during run flat traveling, and against lateral force generated on the vehicle outside during turning. It is possible to effectively prevent the bead from coming off. And, by adopting the double bead structure only on the outside of the vehicle, tire vibration occurs with both ends of the first bead disposed on the inside of the vehicle and the second bead disposed on the outside of the vehicle. By satisfying the above relationship (Hi−Ho> 15 mm), it is possible to achieve both of the assemblability of the rim and the anti-bead property, and the mouth noise can be reduced by the asymmetry of the structure.

In the above, on the outer circumferential side of the belt layer disposed in the tread portion near the tire equator, 5 to 15% of the maximum width of the belt, substantially at an angle of 0 ° with respect to the tire circumferential direction. It is preferable that the reinforcing material extending in the above is disposed. According to this configuration, it is possible to reduce the amplitude of the center portion from the shoulder portion that is the antinode of the tire vibration, and the above-described road noise reduction effect can be suitably enhanced.

Another run flat tire according to the present invention includes a pair of bead portions having an annular first bead, sidewall portions extending outward from the bead portions in the tire radial direction, and the sidewall portions. The run flat tire includes a reinforced rubber layer and a tread portion connecting the outer peripheral side ends of the side wall portions to each other via a shoulder portion, and from the bead portion disposed on the vehicle outer side. The tire has a ring-shaped bulging portion having a ring-shaped second bead while bulging outward in the tire width direction, and has a cross-sectional height Hi from the inner periphery of the first bead arranged on the vehicle inner side to the tire maximum diameter point The section height Ho from the inner periphery of the second bead disposed on the vehicle outer side to the maximum diameter point of the tire satisfies the relationship of the force Hi_Ho> 15 mm.

[0020] This tire adopts a double bead structure only on the outside of the vehicle, and has a run flat It is possible to effectively prevent bead detachment against lateral force generated on the outside of the vehicle during cornering, which is the most likely cause of bead detachment during traveling. And, by adopting the double bead structure only on the vehicle outer side, tire vibration occurs with the first bead arranged on the vehicle inner side and the second bead arranged on the vehicle outer side at both ends, and their sectional heights By satisfying the above relationship (Hi-Ho> 15 mm), it is possible to achieve both of the assemblability of the rim and the anti-bead property, and the road noise can be reduced by the asymmetry of the structure.

In the above, on the outer peripheral side near the tire equator of the belt layer disposed in the tread portion, an angle of substantially 0 ° with respect to the tire circumferential direction with a width of 5 to 15% of the maximum belt width. It is preferable that the reinforcing material extending in the above is disposed. According to this configuration, it is possible to reduce the amplitude of the center portion from the shoulder portion that is the antinode of the tire vibration, and the above-described road noise reduction effect can be suitably enhanced.

Brief description of the drawings

[FIG. 1] A tire meridional cross section showing a run flat tire according to a first embodiment of the present invention [FIG. 2] A developed view showing an example of a tread pattern of the run flat tire shown in FIG.

[FIG. 3] A tire meridian cross section showing a run flat tire according to a second embodiment of the present invention [FIG. 4] A tire meridian cross section showing a run flat tire according to a third embodiment of the present invention [FIG. ) Vibration mode diagram of a test tire according to Example 5-1 and (b) Comparative example 5-1 Description of symbols

1 bead part

la 1st bead

lb second bead

2 Side wall part

3 Shonoreda part

4 Tread fence B

7 Benolet layer

8 rims

8a rim flange

9a Reinforcement rubber layer (vehicle outside) 9b Reinforcement rubber layer (vehicle inside)

10 Annular bulge

11 Inner circumference side

P tire maximum diameter point

Boundary line of rubber with different TB hardness

W tread width

WB belt maximum width

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment

FIG. 1 is a tire meridional cross-sectional view showing a run flat tire according to a first embodiment of the present invention when the specified rim is attached. FIG. 2 is a development view showing an example of the tread pattern of the run flat tire shown in FIG.

The run flat tire of the present invention, as shown in FIG. 1, includes a pair of bead portions 1, sidewall portions 2 extending outward from the bead portions 1 in the tire radial direction, and sidewall portions 2. A tread portion 4 is provided, the outer peripheral side ends of which are connected via a shoulder portion 3.

[0027] In the bead portion 1, a bundle of bead wires made of, for example, steel wire is provided with an annular bead la (corresponding to the first bead) and a bead filler 15 arranged in an annular shape in the circumferential direction of the tire. There is. By winding back the end of the carcass layer 5 with the bead la and locking it, the bead portion 1 is firmly fitted on the tire casing 8 in a state of being reinforced by the carcass layer 5. At normal internal pressure, the bead portion 1 is disposed on the tire outer peripheral side of the rim base 8 b of the rim 8 and is pressed against the rim flange 8 a by the air pressure inside the tire.

On the inner peripheral side of the carcass layer 5, an inner liner layer 6 for air pressure retention is disposed. Further, on the outer peripheral side of the carcass layer 5, a belt layer 7 for reinforcing by squeezing effect is disposed, and on the outer peripheral surface of the belt layer 7, a tread pattern is formed by tread rubber.

As a constituent material of the carcass layer 5, organic fibers such as polyester, rayon, nylon, and aramid are used. All of these materials should improve adhesion to rubber. Usually, surface treatment, adhesion treatment and the like are performed. The belt layer 7 will be described later.

On the inner side of the carcass layer 5 of the sidewall portion 2, reinforcing rubber layers 9a and 9b having a tire meridional section having a substantially crescent shape are disposed. As a result, when the air pressure inside the tire decreases, flattening of the tire is suppressed and run flat travel becomes possible.

Examples of the raw material rubber for the above-mentioned rubber layer and the like include natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR) and the like, and these are used alone. Or used as a mixture of two or more. Further, these rubbers are reinforced with a filler such as carbon black and silica, and at the same time, a vulcanizing agent, a vulcanization accelerator, a plasticizer, an antiaging agent and the like are appropriately blended.

In the present embodiment, as shown in FIG. 1, a double bead structure is adopted only on the outer side of the vehicle when the tire is attached. That is, an annular bulging portion 10 having an inner circumferential side surface 11 provided on the outer side in the tire width direction of the bead portion 1 disposed on the vehicle outer side and facing the outer circumferential curved surface of the rim flange 8a when the specified rim is mounted And an annular bead lb (corresponding to the second bead) disposed in the bulging portion 10.

In the present embodiment, the inner peripheral side surface 11 of the annular bulging portion 10 is in contact with the outer peripheral curved surface of the rim flange 8a, and there is a reduced diameter portion that holds the tip of the rim flange 8a. A bead lb is provided on the outer periphery side of the diameter reducing portion. The annular bulging portion 10 is provided with a bead lb and is connected to the sidewall portion 2 gently with the portion at the top substantially. Further, the annular bulging portion 10 is not limited to the shape shown in the present embodiment, and may have, for example, a semicircular or trapezoidal cross section of the tire meridian line.

The hardness of the rubber mainly constituting the annular bulging portion 10 is determined by maintaining the bead release resistance and the rim shift performance while taking into consideration that the rubber hardness of the reinforcing rubber layer 9a on the vehicle outer side is reduced. 66 to 76 ° is preferable in improving the

[0035] The annular bulging portion 10 is provided with a bead lb in which a bead wire has an annular shape in the tire circumferential direction. The bead lb of the present embodiment is disposed so as to be positioned on the tire outer peripheral side and the tire width direction outer side from the outermost radius point of the center position force S rim flange 8a when the rim is attached. The bead wire constituting the bead lb is not limited to one composed of the same steel wire bundle as the bead la, for example, one composed of the organic fiber bundle or rubber made of fiber reinforced rubber. It may be a bead or the like.

On the other hand, in the present embodiment, the force rim protector 12 is provided with the rim protector 12 for protecting the rim flange 8a when the specified rim is mounted on the outer side in the tire width direction of the bead portion 1 disposed inside the vehicle. It is also possible to form a shape which is connected to the side wall portion 2 from the position separated from the rim flange 8a without providing it.

[0037] The reinforcing rubber layers 9a and 9b disposed on both sides each have a rubber hardness of 65 to 82 °, preferably a rubber hardness of 65 to 79 °. If the rubber hardness is less than 65 °, the run flat durability and the bead off performance become insufficient. If the rubber hardness exceeds 82 °, the ride comfort can not be improved.

Within the range of the above rubber hardness, the rubber hardness may be different between the reinforcing rubber layer 9 b disposed on the vehicle inner side and the reinforcing rubber layer 9 a disposed on the vehicle outer side. Also, in that case, it is preferable that the reinforcing rubber layer 9a be larger than the reinforcing rubber layer 9b as the rubber hardness that the lateral force generated on the outside during turning of the vehicle is likely to cause bead detachment during run flat traveling.

However, the reinforcing rubber layer 9a disposed on the vehicle outer side is preferably larger than the reinforcing rubber layer 9b disposed on the vehicle inner side, preferably having a maximum thickness of 0.5 mm or more, preferably 0.8 to 1: 1.5 mm. Only the maximum thickness is large. Specifically, for example, the maximum thickness of the reinforcing rubber layer 9a disposed on the vehicle outer side is 9. 8 to 13. 5 mm, and the maximum thickness of the reinforcing rubber layer 9b disposed on the vehicle inner side is 9 to 12 mm. Me. .

Further, the reinforcing rubber layers 9a and 9b are not limited to those formed of a single rubber layer, and may be formed of a plurality of rubber layers having different physical properties such as hardness. In that case, the average value of the rubber hardness of each layer may be within the above range.

In the illustrated example, the reinforcing rubber layer 9a disposed on the vehicle outer side is formed of a single rubber layer, and the reinforcing rubber layer 9b disposed on the vehicle inner side is formed of two rubber layers, A force layer 5 intervenes between the two layers. In this example, the carcass layer 5 is composed of two layers, and the reinforcing rubber layer 9 b is disposed on the inner side of each carcass layer 5 located in the side wall portion 2. At the outer side of the vehicle, a reinforcing rubber layer 9 a is disposed inside the two carcass layers 5 located in the sidewall portion 2.

In the present invention, the reinforcing layer 16 may be disposed substantially along the inner peripheral surface of the annular bulging portion 10. Thus, the inner peripheral surface of the annular bulging portion 10 can be reinforced to suppress abrasion. Examples of the reinforcing layer 16 include steel cords and chains made of organic fibers such as rayon, nylon, polyester, and aramid.

The belt layer 7 disposed below the tread portion 4 has a bending stiffness in the longitudinal direction of 200 mm in the circumferential direction of the tire and a length in the width direction of the tire of 0.9 to 2. 1 X as bending stiffness per 100 mm. It is 10 ⁶ N * m ² , preferably 1.2 to 2.0 × 10 ⁶ N.m ² . The bending stiffness is measured by sampling from a product tire. The belt layer is cut out to dimensions of 250 mm in the circumferential direction of the tire and 100 mm in the width direction of the tire, and this is used as a sample for the Shimadzu photograph tester Conduct a three-point bending test. At this time, by setting the distance between fulcrums to 200 mm and the test speed I mm Z sec, bending rigidity in the circumferential direction per 200 x 100 mm is obtained. The calculation method is according to Chapter 5 of Tire Engineering (Grand Prix publication).

[0044] If the bending rigidity of the belt layer 7 in the longitudinal direction is less than 0.9 X 10 ⁶ Nm ² , the buckling becomes extremely large during cornering, so that the bead is caused by the belt breakage or the belt breakage. There is a problem of detachment. In addition, if it exceeds 2. 1 × 10 ⁶ N * m ² , the ride quality can not be improved.

As a constituent material of such a belt layer 7, a material having a bending stiffness lower than that of a conventional run flat tire is used, and steel, aramid, PEN, polyester or the like is used. All of these materials are usually subjected to surface treatment, adhesion treatment and the like to improve adhesion to rubber. The bending stiffness can be adjusted by the thickness of the material, the number of threads, the inclination angle, etc. in addition to the type of cord.

The belt layer 7 has, for example, a two-layer structure, and cords are arranged symmetrically at an angle of preferably 19 to 27 ° with respect to the tire equator line. The outer layer of the belt layer 7 may be provided with a belt reinforcing layer, in which case the bending stiffness is measured without the belt reinforcing layer. The belt reinforcing layer is, for example, a cord arranged or spirally wound in the tire circumferential direction. As a constituent material of the belt reinforcing layer, organic fibers such as polyester, rayon, nylon, and aramid, metal fibers such as steel, and the like are used.

The tread portion 4 has, for example, a tread pattern as shown in FIG. The tread pattern formed in the tread portion 4 has a tire equatorial line CL as a boundary of the region A1 outside the vehicle. It is preferable that the void ratio be equal to or less than the void ratio of the area A2 inside the vehicle. More preferably, the void ratio of the region A1 outside the vehicle is 75 to 96% of the void ratio of the region A2 inside the vehicle. If this value is too small, uneven wear on the inside of the vehicle tends to increase.

[0048] Specifically, the void ratio of the region A1 outside the vehicle is 25 to 35. /. , The void ratio of area A2 inside the vehicle is 30 to 40. / o is preferable. In the illustrated example, four circumferential grooves and five types of oblique grooves are formed, but it is possible to adjust the void ratio S by the thickness and formation density of these.

In addition, the tread portion 4 has a boundary line TB of rubber different in hardness at least at a position A3 where the cap rubber is 40 to 60% of the tread width W, and the rubber hardness of the vehicle outside of the boundary line TB is the vehicle It is preferable that the hardness is equal to or higher than the inner rubber hardness. More preferably, the rubber hardness on the outside of the vehicle at the boundary line TB is 102 to 115% of the rubber hardness on the inside of the vehicle. If this value is too large, uneven wear on the inside of the vehicle tends to increase.

Specifically, the rubber hardness on the outer side of the boundary line TB of the vehicle is preferably 65 to 75 °, and the rubber hardness on the inner side of the vehicle is preferably 62 to 70 °. From the viewpoint of durability, the boundary line T of rubber with different hardness

B is preferably disposed at the bottom of the groove.

In the above embodiment, an example is shown in which the reinforcing rubber layer disposed on the inner side of the vehicle is formed of two rubber layers, but the reinforcing rubber layer disposed on the inner side of the vehicle includes one rubber layer. You may also form in. In that case, the reinforcing rubber layer is disposed on the inside of the two carcass layers located on the side wall also inside the vehicle.

In the above embodiment, an example in which the carcass layer is constituted by two layers is shown, but in the present invention, the force carcass layer may be constituted by one layer. In addition, the inner peripheral side surface of the annular bulging portion may be separated from the outer peripheral side curved surface of the rim flange at normal internal pressure.

In the above embodiment, as shown in FIG. 2, an example is shown in which the tread pattern has four circumferential grooves and five types of oblique grooves, and the tread pattern is particularly limited in the present invention. It is not decided.

Next, specific examples of the run flat tire according to the first embodiment of the present invention will be described. In addition, the evaluation item in an Example etc. measured as follows. (1) Flexural rigidity of the belt layer

A belt layer is cut out from the product tire to a dimension of 250 mm in the circumferential direction of the tire and 100 mm in the width direction of the tire, and this is used as a sample to carry out a 3-point bending test with an autograph tester manufactured by Shimadzu Corporation. At this time, by setting the distance between fulcrums to 200 mm and the test speed of 1 mm / sec, bending rigidity in the circumferential direction per 200 x 100 mm is obtained. The calculation method is based on Chapter 5 of Tire Engineering (Grand Prix Publishing).

(2) Anti-bead resistance

A test tire was mounted on the left front of a real car (domestic 3000cc class FR car), and the car went on a so-called J-turn traveling straight from a straight ahead to a 20 m radius circular course. Each test tire was run-flat at an internal pressure of OkPa, and the bead release resistance was evaluated by the running speed (proportional to the lateral G) when bead removal occurred. The driving speed started from 25 km / h, and the vehicle was driven in 5 km / h increments until bead detachment occurred. Comparative example 1 — 1 is evaluated as an index of 100, and the larger the value, the higher the running speed when bead detachment occurs, that is, the better the bead detachment resistance.

[0057] (3) Ride comfort

We compared by sensory evaluation with a real car (domestic 3000cc class FR car). The ride quality was rated as 10 points, with the ride quality in Comparative Example 1-1 as 5 points. The larger the index, the better the ride and the better.

Example 1 1 2

Flexural rigidity of the belt layer, rubber hardness (PAD hardness) of reinforcing rubber layers on both sides as shown in Table 1 having the structure shown in FIG. 1 (however, only one type of tread rubber) and the pattern shown in FIG. Furthermore, a test tire having a size of 245 / 40R18 was produced with a difference Omm in maximum thickness between the reinforcing rubber layers on both sides, a void ratio in the vehicle outer side Z ratio in the vehicle inner side = 1, and a tread rubber hardness of 68 °. The evaluation results are shown in Table 1 together.

Comparative Example 1 1:! To 1 1 5

The structure shown in Fig. 1 (but without the second bead, tread rubber is only one type) and the pattern shown in Fig. Rubber hardness (PAD hardness), and further, the maximum thickness difference between the reinforced rubber layers on both sides, Omm, A test tire with a size of 245/40 R18 was produced with an id ratio / void ratio inside the vehicle = 1, tread rubber hardness 68 °. The evaluation results are shown in Table 1 together.

Comparative Example 1 1 6-: 1 8

[0061] [Table 1]

As shown in the results of Table 1, the run-flat tire of each example can improve bead removal performance and ride comfort. On the other hand, in Comparative Example 1 1 to 5 where the double bead structure was not adopted, the bead declination was significantly deteriorated due to the decrease in the bending rigidity of the belt layer and the decrease in the PAD hardness. Further, even when only the vehicle outer side is made to have a double bead structure, the improvement effect of the riding comfort is reduced as in Comparative Example 1-16:! 18 unless the bending rigidity and PAD hardness of the belt layer are reduced.

Example 2 —:! — 2—5

Flexural rigidity of the belt layer, rubber hardness (PAD hardness) of the reinforcing rubber layers on both sides as shown in Table 2 having the structure shown in FIG. 1 (however, only one kind of tread rubber) and the pattern shown in FIG. Test tire with a size of 245 / 40R18 was produced with tread rubber hardness, void ratio on the outside of the vehicle and void ratio on the inside of the vehicle as well as the difference Omm in the maximum thickness of the reinforced rubber layer on both sides. The evaluation results are shown in Table 2 together.

Comparative Example 2—:! — 2 — 5

The structure shown in Figure 1 (but without the second bead, tread rubber is only one type) and the pattern shown in Figure 2, the bending stiffness of the belt layer as shown in Table 2, the reinforcement rubber layer on both sides Test tire with a size of 245 / 40R18, with rubber hardness (PAD hardness), tread rubber hardness, void ratio on the outside of the vehicle / void ratio on the inside of the vehicle, and the difference Omm in maximum thickness of the reinforced rubber layer on both sides. Made. The evaluation results are shown in Table 2 together.

[Table 2]

As shown in the results of Table 2, in the run flat tire of each example, it is possible to improve the bead removal performance and the ride comfort. In particular, in Examples 2-2 to 2-3 in which the void ratio on the outer side of the vehicle is sufficiently reduced, the bead detachment property is greatly improved. On the other hand, in the case of the double bead structure not adopted, in Comparative Example 2-:--2-5, the bead detachment property was significantly deteriorated due to the decrease in the bending rigidity of the belt layer and the decrease in the PAD hardness. .

[0067] Example 3-:!-3-4

With the structure shown in FIG. 1 and the pattern shown in FIG. 2, as shown in Table 3, bending stiffness of the belt layer, rubber hardness (PAD hardness) of reinforcing rubber layers on both sides, tread rubber hardness on both sides, vehicle outer side The void ratio of Z was made into the void ratio on the inside of the vehicle, and a test tire with a size of 245 / 40R18 was produced with the difference Omm between the maximum thicknesses of the reinforcing rubber layers on both sides. The evaluation results are shown in Table 3 together.

Comparative Example 3—:! — 3 — 4

Flexural rigidity of the belt layer, rubber hardness (PAD hardness) of the reinforcing rubber layers on both sides, as shown in Table 3, having the structure shown in FIG. 1 (but without the second bead) and the pattern shown in FIG. Test tires with a size of 245 / 40R18 were produced with tread rubber hardness on both sides, void ratio on the outside of the vehicle / void ratio on the inside of the vehicle, and a difference Omm between the maximum thickness of the reinforced rubber layers on both sides. The evaluation results are shown in Table 3 together.

[Table 3]

As the results in Table 3 show, the run-flat tire of each example can improve bead dislodging performance and ride comfort. In particular, the tread rubber hardness on the outside of the vehicle has been increased. In Example 3-:!-3-3, the bead detachment is greatly improved. On the other hand, in the case where the double bead structure was not adopted, in Comparative Example 3-:!-3-4, the bead detachment was significantly deteriorated due to the decrease in the bending rigidity of the belt layer and the decrease in the PAD hardness.

Second Embodiment

The second embodiment has the same configuration as the first embodiment except for the configuration described below, so the common points are omitted and the differences are mainly described. Note that the same reference numerals are given to the same members * portions as the members * portions described in the first embodiment, and the redundant description will be omitted.

FIG. 3 is a tire meridional cross-sectional view showing a run flat tire according to a second embodiment of the present invention when the specified rim is attached. In FIG. 3, the right side is the outside of the vehicle.

In the present embodiment, as shown in FIG. 3, double bead structures are adopted on both sides in the tire width direction. That is, a pair of annular bulging portions 10 having an inner peripheral side surface 11 provided on the outer side in the tire width direction of the bead portion 1 and facing the outer peripheral curved surface of the rim flange 8a when the specified rim is attached And an annular bead lb disposed on each of the

The reinforcing rubber layers 9a and 9b are not limited to those formed of a single rubber layer as in the present embodiment, but may be formed of plural rubber layers having different physical properties such as hardness. In that case, for example, when the reinforcing rubber layer 9a is composed of two rubber layers, according to the equation {(ha 'X ta') + (ha "X ta") / (ta, + ta ") The calculated value may be within the range of the rubber hardness of the above-mentioned reinforced rubber layer 9a, where ta ′, ha, is the maximum thickness of one of the rubber layers constituting the reinforced rubber layer 9a, and the rubber hardness And ta ", ha" are the other maximum thickness, rubber hardness.

In the present embodiment, the reinforcing rubber layers 9a and 9b on both sides are formed of a single rubber layer, and the force S disposed inside the two-layered carcass layer 5 located in the sidewall portion 2, The present invention is not limited to this. For example, at least one of the reinforcing rubber layers may be formed of two rubber layers, and the carcass layer 5 may be interposed between the two layers.

As in the first embodiment described above, the belt layer 7 disposed below the tread portion 4 has a bending stiffness in the longitudinal direction of 200 mm in the circumferential direction of the tire and 100 mm in the width direction of the tire. The flexural rigidity is 0.9 to 2. 1 x 10 ⁶ N 'm ² and preferably 1. 2 to 2. 0 Χ 10 ⁶ Ν m'. Next, specific examples of the run flat tire according to the second embodiment of the present invention will be described. In addition, the evaluation item in an Example etc. measured as follows.

(1) Flexural rigidity of the belt layer

The bending test was carried out in the same manner as in the first embodiment described above.

(2) Ride comfort

The sensory test was performed in the same manner as in the first embodiment described above. Comparative example 4 The riding comfort in 5 points is made into 5 points, and 10 points are evaluated as a full mark, and the bearing center is better, and the said index is large and preferable.

(3) Anti-bead resistance

The J-turn travel was performed in the same manner as in the first embodiment described above, and the bead resistance was evaluated.

Comparative Example 4 _ 1 is evaluated as an index of 100, and the larger the value, the higher the running speed when bead detachment occurs, that is, the bead is excellent in bead detachment resistance.

Comparative Example 4 1:! To 4 1 5

The flexural rigidity of the belt layer as shown in Table 4 and the rubber hardness (PAD hardness) of the reinforcing rubber layers on both sides as shown in Table 4 without the double bead structure in FIG. 3 and the difference in the maximum thickness of the reinforcing rubber layers on both sides Omm , Tread rubber hardness 68. Then, a test tire with a size of 245 / 40R18 was produced. The evaluation results are shown in Table 4 together.

Comparative Examples 4 6 to 4 8, Example 4 1:! To 4 2

The tire has the tire structure shown in FIG. 3, the bending rigidity of the belt layer as shown in Table 4, the rubber hardness (PAD hardness) of the reinforcing rubber layer on both sides, and the difference in the maximum thickness of the reinforcing rubber layer on both sides Omm A test tire having a tread rubber hardness of 68 ° and a size of 245Z40R18 was produced. The evaluation results are shown in Table 4 together.

[Table 4]

As shown in the results of Table 4, in the run flat tires of the respective examples, the riding comfort performance can be improved while maintaining the anti-bead performance. On the other hand, in Comparative Examples 4 to 45 in which the double bead structure is not employed, the anti-bead resistance performance is significantly deteriorated, and further, the flexural rigidity or PAD hardness of the belt layer is high, and Comparative Example 4 _ 1 At 4 to 3, the ride performance is degraded. Moreover, even when the double bead structure is adopted, the ride comfort performance is not improved as in Comparative Examples 4_ 6 to 4_8 unless the bending rigidity and the PAD hardness of the belt layer are reduced.

Third Embodiment

The third embodiment has the same configuration and effects as the first embodiment except for the configuration described below, so the common points are omitted and the differences are mainly described. Note that the same reference numerals are given to the same members * portions as the members * portions described in the first embodiment, and the redundant description will be omitted.

FIG. 4 is a tire meridional cross-sectional view showing a run flat tire according to a third embodiment of the present invention when the specified rim is attached.

On the outer periphery of the carcass layer 5, a belt layer 7 for reinforcement by hoop effect is disposed, and on the outer periphery thereof, a tread rubber 13 is disposed. The carcass layer 5 and the belt layer 7 are each made of a cord material arranged at a predetermined angle. As the cord material, organic fibers such as polyester, nylon, nylon, aramid, steel, etc. are preferably used.

FIG. 4 shows the outside of the vehicle on the right side and the inside of the vehicle on the left side, and in the present invention, the double bead structure is adopted only on the outside of the vehicle. That is, an annular bulging portion 10 having an annular bead lb is provided while bulging outward from the bead portion 1 disposed on the vehicle outer side in the tire width direction. The inner circumferential side surface 11 of the annular bulging portion 10 may be gradually separated from the outer peripheral curved surface of the rim flange 8a, but in the present embodiment, it is in contact with the outer peripheral curved surface.

[0089] Bending rigidity with respect to the longitudinal direction of belt layer 7 Tire circumferential direction length 200 mm X tire width Direction length 100 mm as bending stiffness, 0.9 to 2.1 X 10 ⁶ N'm ² As described in the first embodiment, the ride quality can be improved.

[0090] The hardness of the rubber mainly constituting the annular bulging portion 10 further maintains the bead detachment resistance and the rim deviation performance in consideration of reducing the rubber hardness of the reinforcing rubber layer 9a as described later. In order to improve the ride quality, 65 to 78 ° is preferable.

In the present embodiment, the cross-sectional height Hi from the inner periphery of the bead la disposed on the vehicle inner side to the tire maximum diameter point P and the tire from the inner periphery of the bead lb disposed on the vehicle outer side It is set to satisfy the relationship between the section height Ho and the force Hi_Ho> 15 mm, which makes it possible to achieve both reduction in road noise and improvement in anti-bead resistance performance.

That is, by adopting the double bead structure only on the outside of the vehicle, tire vibration occurs with both ends of the bead la disposed on the inside of the vehicle and the bead lb disposed on the outside of the vehicle. Since the section heights Hi and Ho satisfy Hi_Ho> 15 mm, the section heights at both ends of the tire vibration can be made to be appropriately different from each other. As a result, an asymmetric vibration mode can be formed with respect to the tire equator CL, and the amplitude can be suppressed to reduce road noise. Note that (Hi-Ho) is preferably 20 mm or less, in order to properly obtain the above-mentioned road noise reduction effect while maintaining anti-bead resistance.

As described above, since the present invention adopts the double bead structure only on the vehicle outer side, the difference in the amount of deflection of the side wall portions 2 on both sides in the run flat state tends to be large. Due to this, the asymmetry of the contact pressure distribution on the tread surface becomes large, which may cause problems such as occurrence of uneven wear and deterioration in steering stability. Therefore, in the present embodiment, the thickness of the reinforcing rubber layer 9a is reduced by increasing the rubber hardness of the reinforcing rubber layer 9b inside the vehicle with respect to the reinforcing rubber layer 9a outside the vehicle. It balances the amount of deflection.

[0094] Specifically, the rubber hardness of the reinforcing rubber layer 9a is 60 to 82 °, and the rubber hardness of the reinforcing rubber layer 9b is 65 to 90. The rubber hardness of the reinforcing rubber layer 9b is made equal to or higher than that of the reinforcing rubber layer 9a, and the maximum thickness is increased by 0.5 mm or more. By adjusting the relationship between the rubber hardness and the maximum thickness of the reinforcing rubber layers 9a and 9b in this way, it is possible to properly balance the amount of deflection on both sides. The vibration modes having the above-mentioned asymmetry can be formed without problems even if such balance adjustment is performed.

The rubber hardness of the reinforcing rubber layer 9a disposed on the vehicle outer side is 60 to 82 ° as described above, and preferably 65 to 78 °. If this is less than 60 °, the durability during runflat running becomes insufficient, and if it exceeds 82 °, balance with the deflection inside the vehicle should be taken. Tend to result in uneven wear on the tread surface and a deterioration in ride comfort.

On the other hand, the rubber hardness of the reinforcing rubber layer 9b disposed inside the vehicle is 65 to 90 ° as described above, and preferably the rubber hardness is 70 to 85 °. If this is less than 65 °, uneven wear tends to occur on the tread surface, which makes it difficult to balance the amount of sag on the outside of the vehicle, and if it exceeds 90 °, the ride comfort tends to deteriorate. The reinforcing rubber layer 9b preferably has a rubber hardness equal to or higher than that of the reinforcing rubber layer 9a within the range of 65 to 90 °, and preferably has a rubber hardness 5 ° or more higher than that of the reinforcing rubber layer 9a.

It is preferable that the reinforcing rubber layer 9b disposed inside the vehicle has a maximum thickness that is larger by 5% to 13% at which the maximum thickness is 4% or more larger than that of the reinforcing rubber layer 9a disposed outside the vehicle. That is, when the maximum thickness of the reinforcing rubber layer 9a is 100, it is more preferable that the maximum thickness of the reinforcing rubber layer 9b is 105 to 113, preferably 104 or more.

The reinforcing rubber layers 9a and 9b are not limited to those formed of a single rubber layer, and may be formed of a plurality of rubber layers having different physical properties such as rubber hardness. In that case, for example, in the case where the reinforcing rubber layer 9a is composed of two rubber layers, according to the equation {(ha 'X ta') + (ha "X ta") / (ta '+ ta ") Calculated value It should be within the range of rubber hardness of the above-mentioned reinforced rubber layer 9a, where ta,, ha, is the maximum thickness of one of the rubber layers constituting the reinforced rubber layer 9a, and the rubber hardness Yes, ta "and ha" are the other maximum thickness and rubber hardness. In the example shown in the figure, the reinforcing rubber layer 9a is formed of a single rubber layer, and the reinforcing rubber layer 9b intervenes one layer of the carcass layer 5 In the present embodiment, the carcass layer 5 is composed of two layers, and the reinforcing rubber layer 9 b is formed on the inner peripheral side of each carcass layer 5 located in the side wall portion 2. Are arranged.

In the present embodiment, on the outer peripheral side of the belt layer 7 near the tire equator CL, the width is substantially 5 to 15%, preferably 10 to 15% of the maximum belt width WB, substantially in the tire circumferential direction. It is preferable to provide a reinforcement (not shown) extending at an angle of 0 °. According to this configuration, it is possible to reduce the amplitude of the center portion that is the antinode of the tire vibration, and it is possible to preferably enhance the road noise reduction effect. As a constituent material of this reinforcing material, the constituent materials of the carcass layer 5 and the belt layer 7 described above can be preferably used. The road noise reduction effect according to the present invention is mainly due to the vibration mode having the asymmetry described above, and the arrangement of the reinforcing member does not excessively increase the weight of the tire. Next, specific examples of the run flat tire according to the third embodiment of the present invention will be described. In addition, the evaluation item in an Example etc. measured as follows.

(1) Anti-bead resistance

The J-turn travel was performed in the same manner as in the first embodiment described above, and the bead resistance was evaluated. Comparative Example 5-1 is evaluated on the basis of an index of 100, and the larger the value is, the larger the traveling speed when bead detachment occurs, that is, the better the bead detachment resistance.

(2) Road noise level

The test tire was mounted on a real car (domestic 3000cc class FR car) and air pressure was 200kPa for both front and rear, a microphone was attached to the driver's seat ear and road noise level of 200 ~ 400Hz was measured at constant speed of 60km Zh. . Comparative Example 5 _ 1 is taken as 100 to measure the measured value. The smaller the value is, the smaller the road noise level is.

(103) Rim setability

The hump pressure was evaluated as an index of rim setability. Comparative example 5-1 is evaluated as an index of 100, and the larger the value is, the worse the rim assembling property is, and it is shown.

Example 5-1 and 5-2

Tires having a tire structure shown in FIG. 4 and a tire size of 245/401 ^ 18 as shown in Table 5 are given as Examples 5-1 and 5-2. The rubber hardness of the reinforcing rubber layer on the outer side of the vehicle was 76 °, and the rubber hardness of the reinforcing rubber layer on the inner side of the vehicle was 78 °, in order to balance the deflection of the side wall portions on both sides. In addition, the maximum thickness of the reinforcing rubber layer disposed outside the vehicle was made smaller than that inside the vehicle, and the difference between them was 10% of the maximum thickness of the reinforcing rubber layer disposed outside the vehicle.

Comparative Example 5-1

A tire having a double bead structure in the tire structure shown in FIG. The reinforcing rubber layers on both sides were each composed of a single layer rubber layer having a rubber hardness of 77 °. Further, the reinforcing rubber layers on both sides were set to the same maximum thickness, and both of them were in the middle of the maximum thicknesses of the reinforcing rubber layers on both sides in the example.

Comparative Example 5—2, 5—3

The test tester is the same as Example 5-1 except that the value of Hi-Ho is as shown in Table 5. The samples were prepared and set as Comparative Examples 5-2 and 5-3, respectively. Table 5 shows the evaluation results of each example.

[0107] [Table 5]

As shown in Table 5, in Examples 5-1 and 5-2, the road noise can be reduced while exhibiting excellent bead detachment resistance, and the hump pressure is also equal to that of the conventional product and the rim I can prevent the deterioration of the teamability. On the other hand, in the case of the double bead structure, in Comparative Example 5-1, the road noise reduction effect with which the anti-bead resistance is low is also obtained. Also, in Comparative Examples 5-2 and 5-3 in which only the double bead structure is adopted only on the outer side of the vehicle, the hump pressure is significantly disadvantageous with respect to the force rim assembling property with which a sufficient road noise reduction effect is obtained.

FIG. 5 is a vibration mode diagram of a test tire according to (a) Example 5-1 and (b) comparative example 5-1, wherein the initial shape before the tire vibrates is indicated by a broken line BL, and the tire is shown in FIG. The vibration mode of is indicated by a solid line SL. Such a vibration mode diagram can be created from the experimentally obtained amplitude and phase of the transfer function. The transfer function is disclosed in detail in Japanese Patent Laid-Open No. 2004-82858. As shown in the figure, when vibration is input to the tread portion of the tire within a frequency range of 200 to 400 Hz, a plurality of measurement points (circles in FIG. It corresponds to the mark).

First, in (b) Comparative Example 5-1, vibration modes substantially symmetrical with respect to the tire equator are formed with the first beads arranged in the pair of bead portions at both ends, and it is possible to Part. This vibration mode is a cross-section secondary mode in which the tire maximum width portion is a node and the buttress portion and the lower side are antinodes. The vibration nodes and antinodes are substantially at the same position on the vehicle outer side and the vehicle inner side.

On the other hand, (a) In Example 5-1, the first bead disposed in the bead portion on the inner side of the vehicle and the second bead disposed in the annular bulging portion on the outer side of the vehicle are both ends, It can be seen that vibration modes asymmetric to the tire equator are formed. It has a double bead structure on the outside of the vehicle The vibration mode has an asymmetry to suppress the amplitude.

Claims

The scope of the claims

[1] A pair of bead portions having an annular first bead, a sidewall portion extending outward in the tire radial direction from the bead portion, a reinforcing rubber layer disposed on the sidewall portion, and the sidewall portion A run flat tire comprising: a tread portion in which respective outer peripheral side ends of each are connected via a shoulder portion;

An annular bulging portion provided on the outer side in the tire width direction of the bead portion disposed on the vehicle outer side and having an inner peripheral side surface facing the outer peripheral side curved surface of the rim flange when the specified rim is mounted, and the annular bulging portion And an annular second bead disposed on the

The reinforcing rubber layers disposed on both sides each have a rubber hardness of 65 to 82 °, and the belt layer disposed below the tread portion has a bending rigidity with respect to the longitudinal direction. Tire circumferential length 200 mm X tire width direction A run flat tire characterized by having a flexural rigidity of 0.9 to 2. 1 x 10 ⁶ N-m ² per 100 mm in length.

[2] The run flat tire according to claim 1, wherein in the tread pattern formed in the tread portion, the void ratio on the vehicle outer side is equal to or less than the void ratio on the vehicle inner side with the tire equatorial line as a boundary.

[3] In the tread portion, at least the cap rubber has a rubber boundary line of different hardness at a position of 40 to 60% of the tread width, and the rubber hardness of the vehicle outside of the boundary line is the rubber hardness of the vehicle inside The run flat tire according to claim 1, which is equal to or more than the same.

[4] The annular bulging portion is also provided on the outer side in the tire width direction of the bead portion disposed inside the vehicle, and the second bead is disposed in each of the pair of annular bulging portions. Run flat tire of description.

[5] The section height Hi from the inner periphery of the first bead disposed on the vehicle inner side to the tire maximum diameter point, and the section from the inner periphery of the second bead disposed on the vehicle outer side to the tire maximum diameter point The run flat tire according to claim 1, wherein the height Ho and the force Hi_Ho> 15 mm are satisfied.

[6] The belt layer disposed in the tread extends around the tire equator at an angle of substantially 0 ° with respect to the tire circumferential direction with a width of 5 to 15% of the maximum belt width. The run flat tire according to claim 5, wherein a reinforcing material is disposed.

[7] A pair of bead portions having an annular first bead, and the bead portions respectively from the bead radial direction A run flat tire comprising: a sidewall portion extending outward; a reinforcing rubber layer disposed on the sidewall portion; and a tread portion connecting outer peripheral side ends of the sidewall portions via a shoulder portion.

An annular bulging portion having an annular second bead while bulging outward from the bead portion disposed on the vehicle outer side in the tire width direction,

The section height Hi from the inner periphery of the first bead disposed on the vehicle inner side to the tire maximum diameter point, and the section height from the inner periphery of the second bead disposed on the vehicle outer side to the tire maximum diameter point Ho A run flat tire characterized by satisfying the relationship of “Hi−Ho> 15 mm”.

A reinforcing material extending at an angle of substantially 0 ° with respect to the tire circumferential direction with a width of 5 to 15% of the maximum belt width on the outer circumferential side of the belt layer disposed in the tread portion near the tire equator The run flat tire according to claim 7, which is arranged.