JP6953938B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire having an inner apex rubber and an outer apex rubber in a bead portion.

For example, Patent Document 1 below proposes a pneumatic tire that can enhance the durability of the bead portion. In this pneumatic tire, an inner apex rubber and an outer apex rubber are arranged on the bead portion. The inner apex rubber extends from the bead core outward in the radial direction of the tire in a triangular cross section. The outer apex rubber is located between the folded part of the carcass ply and the clinch rubber. In such a tire, the folded-back portion can be positioned more inward in the tire axial direction. Therefore, the strain acting on the folded-back portion when the tire is running is alleviated, and the breakage of the cord of the folded-back portion is suppressed.

However, in the above tire, the folded portion and the clinch rubber are arranged at relatively close positions. On the other hand, the topping rubber and the clinch rubber that cover the cord of the folded portion have a large difference in rubber hardness, and the amount of deformation when stress acts on them is greatly different. For this reason, the tires in which these tires are arranged close to each other tend to have separations in the vicinity of the folded portion.

Japanese Unexamined Patent Publication No. 2016-147567

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire having improved durability of a bead portion without impairing ride quality.

The present invention is a pneumatic tire having a carcass, wherein the carcass is connected to the main body portion from the tread portion to the bead core of the bead portion via the sidewall portion, and is connected to the main body portion and around the bead core in the tire axial direction. The bead portion includes a carcass ply having a folded portion that is folded from the inside to the outside and extends outward in the tire radial direction, and the bead portion is arranged between the main body portion and the folded portion and is arranged outside the bead core in the tire radial direction. An inner apex rubber extending in a triangular cross section, a clinch rubber forming at least a part of the outer surface of the bead portion in the tire axial direction, and a rubber arranged between the folded portion and the clinch rubber and lower than the clinch rubber. A tire shaft is provided with a hard outer apex rubber and is mounted on a regular rim and is filled with a regular internal pressure in a normal tire cross section under normal conditions, passing through the center position of the bead core in the tire radial direction. The distance between the first virtual line extending in the direction and the outer end of the flange of the regular rim in the tire radial direction from the first virtual line is 2.0 times the flange height hf in the tire radial direction. The ratio S2 / S1 of the cross-sectional area S2 of the outer apex rubber to the cross-sectional area S1 of the inner apex rubber is 1.5 to S1 in the region between the second virtual line extending in the tire axial direction at a position separated from the tire. It is 5.0.

In the pneumatic tire of the present invention, it is desirable that the outer end of the inner apex rubber in the tire radial direction is located inside the tire radial direction with respect to the outer end of the flange.

In the pneumatic tire of the present invention, the outer apex rubber crosses the second virtual line and the third virtual line extending in the tire axial direction through the outer end of the flange, and is on the third virtual line. The ratio t1 / t2 of the thickness t1 of the outer apex rubber to the thickness t2 of the outer apex rubber on the second virtual line is preferably 1.10 to 1.80.

In the pneumatic tire of the present invention, it is desirable that the outer end of the outer apex rubber in the tire radial direction is located outside the tire radial direction of the outer end of the clinch rubber in the tire radial direction.

In the pneumatic tire of the present invention, it is desirable that the outer apex rubber has a higher rubber hardness than the inner apex rubber.

In the pneumatic tire of the present invention, it is desirable that the bead portion is provided with a bead reinforcing rubber layer extending from the tip portion of the inner apex rubber on the outer side in the radial direction of the tire along the main body portion.

In the pneumatic tire of the present invention, it is desirable that the bead reinforcing rubber layer has a rubber hardness higher than that of the inner apex rubber.

The bead portion of the pneumatic tire of the present invention is arranged between the main body portion and the folded portion of the carcass ply, and has an inner apex rubber extending outward from the bead core in the radial direction of the tire in a triangular cross section, and at least the outer surface of the bead portion. A part of the clinch rubber and an outer apex rubber arranged between the folded portion and the clinch rubber and having a rubber hardness lower than that of the clinch rubber are provided. As a result, the folded portion of the carcass ply is located inside the tire axial direction with respect to the conventional tire, and the breakage of the cord of the folded portion is suppressed.

Generally, the bead portion includes a first virtual line extending in the tire axial direction through the center position of the bead core in the tire radial direction, and a flange in the tire radial direction from the first virtual line to the outer end of the rim flange in the tire radial direction. In the region between the second virtual line extending in the tire axial direction at a position separated from the first virtual line by 2.0 times the height hf, there is a tendency for the tire to be significantly deformed during running. In the above region, the inventors have improved the durability of the bead portion without impairing the riding comfort by specifying the ratio S2 / S1 of the cross-sectional area S2 of the outer apex rubber and the cross-sectional area S1 of the inner apex rubber. I found that I could let you.

In the pneumatic tire of the present invention, the ratio S2 / S1 is 1.5 or more in the region between the first virtual line and the second virtual line described above, so that the folded portion of the carcass ply is clinched rubber. Can be sufficiently far from. Therefore, the separation of the folded portion is suppressed.

Further, in the pneumatic tire of the present invention, since the ratio S2 / S1 is 5.0 or less, the rigidity of the bead portion is not excessively increased by the outer apex rubber, and the riding comfort performance is not impaired.

It is sectional drawing of the pneumatic tire of one Embodiment of this invention. It is an enlarged cross-sectional view of the bead part of FIG. It is an enlarged cross-sectional view of the inner apex rubber and the outer apex rubber of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of a tire meridian including a rotation axis in a normal state of a pneumatic tire (hereinafter, may be simply referred to as a “tire”) 1 of the present embodiment. The tire 1 of the present embodiment is suitably used, for example, for a light truck. However, the tire of the present invention is not limited to such an aspect, and may be used, for example, for a passenger car or as a heavy load.

The "normal state" is a state in which the tire is rim-assembled on the normal rim R and is filled with the normal internal pressure without load. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in this normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATTA and "Design Rim" for TRA. If it is ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

As shown in FIG. 1, the tire 1 of the present embodiment has, for example, a carcass 6 and a belt layer 7.

The carcass 6 is a toroid shape that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. The carcass 6 contains at least one carcass ply 6A. The carcass 6 of the present embodiment includes, for example, a first carcass ply 6A and a second carcass ply 6B.

The first carcass ply 6A includes a main body portion 6a and a folded-back portion 6b. The main body portion 6a reaches, for example, the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3. The folded-back portion 6b is connected to the main body portion 6a, is folded back from the inside in the tire axial direction to the outside around the bead core 5, and extends outward in the tire radial direction. The folded-back portion 6b of the present embodiment extends to a position exceeding the maximum tire width position 1w, for example, but is not limited to such an embodiment.

The second carcass ply 6B is composed of, for example, only a main body portion extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. The second carcass ply 6B of the present embodiment is arranged on the outer surface side of the tire with respect to, for example, the first carcass ply 6A. Further, the second carcass ply 6B is arranged on the outer surface side of the tire with respect to the folded-back portion 6b of the first carcass ply 6A. The inner end portion of the second carcass ply 6B in the tire radial direction is arranged, for example, on the outer side of the bead core 5 in the tire axial direction.

The carcass plies 6A and 6B have, for example, carcass cords arranged at an angle of 75 to 90 ° with respect to the tire circumferential direction. For the carcass cord, for example, an organic fiber cord such as nylon, polyester or rayon is preferably adopted.

The belt layer 7 includes, for example, three belt plies 7A to 7C. Each belt ply 7A to 7C is composed of a belt cord arranged so as to be inclined with respect to the tire circumferential direction. It is desirable that each belt cord is inclined at an angle of 10 to 45 ° with respect to the tire circumferential direction, for example.

FIG. 2 shows an enlarged view of the bead portion 4. As shown in FIG. 2, the bead portion 4 is provided with, for example, a bead core 5, a clinch rubber 10, an inner apex rubber 11, and an outer apex rubber 12.

The bead core 5 has a substantially rectangular cross section, for example, when the bead wire is wound a plurality of times in the tire circumferential direction.

The clinch rubber 10 constitutes at least a part of the outer surface of the bead portion 4. The clinch rubber 10 of the present embodiment covers, for example, the inner end portion of the second carcass ply 6B and constitutes at least the outer surface of the bead heel 4a.

It is desirable that the height h1 of the clinch rubber 10 from the bead baseline BL is, for example, 0.20 to 0.30 times the tire height SH (shown in FIG. 1 and the same applies hereinafter). The tire height SH is the distance in the tire radial direction from the bead baseline in the normal state to the outer end of the tread portion 2 in the tire radial direction (which is the tire equatorial line C in this embodiment). The bead baseline BL is a tire axial line that passes through a rim diameter position determined by a standard based on the tire.

The rubber hardness of the clinch rubber 10 is preferably 70 to 90 °, for example. In the present specification, the rubber hardness is the hardness according to the durometer type A measured in an environment of 23 ° C. based on JIS-K6253.

The inner apex rubber 11 is arranged between the main body portion 6a and the folded-back portion 6b of the carcass ply 6A. The inner apex rubber 11 extends from the bead core 5 outward in the radial direction of the tire in a triangular cross section. The cross-sectional triangular shape includes not only a perfect triangular shape but also a shape similar to a triangle including curved sides, for example.

The outer apex rubber 12 is arranged between the folded-back portion 6b and the clinch rubber 10. The outer apex rubber 12 has a rubber hardness smaller than that of the clinch rubber 10 and is distinguished from the clinch rubber 10.

In the tire 1 of the present invention, the outer apex rubber 12 prevents the folded-back portion 6b of the carcass ply 6A from being positioned inside the tire axial direction with respect to the conventional tire, and thus the breakage of the cord of the folded-back portion 6b is suppressed.

FIG. 3 shows an enlarged view of the inner apex rubber 11 and the outer apex rubber 12. As shown in FIG. 3, in general, the bead portion 4 tends to be significantly deformed when the tire is running in the region between the first virtual line 21 and the second virtual line 22. The first virtual line 21 extends in the tire axial direction through the center position of the bead core 5 in the tire radial direction. The second virtual line 22 extends in the tire axial direction at a position separated from the first virtual line 21 by a distance L1 that is 2.0 times the flange height hf. The flange height hf is the distance in the tire radial direction from the first virtual line 21 to the outer end of the flange of the rim R in the tire radial direction.

By specifying the ratio S2 / S1 of the cross-sectional area S2 of the outer apex rubber and the cross-sectional area S1 of the inner apex rubber in the above region, the inventors can improve the durability of the bead portion 4 without impairing the riding comfort. We found that it could be improved.

In the pneumatic tire 1 of the present invention, since the ratio S2 / S1 is 1.5 or more in the region between the first virtual line 21 and the second virtual line 22 described above, the carcass ply 6A The folded-back portion 6b can be sufficiently separated from the clinch rubber 10. Therefore, the separation of the folded-back portion 6b is suppressed.

Further, since the pneumatic tire 1 of the present invention has a ratio S2 / S1 of 5.0 or less, the rigidity of the bead portion 4 is not excessively increased by the outer apex rubber 12, and the riding comfort performance is impaired. There is no.

In order to improve the durability and riding comfort of the bead portion 4 in a well-balanced manner, the ratio S2 / S1 is preferably 2.0 or more, more preferably 2.5 or more, preferably 4.5 or less, more preferably. Is 4.0 or less.

In the present embodiment, it is desirable that the outer end 11o of the inner apex rubber 11 in the tire radial direction is located inside, for example, the outer end fo of the flange f in the tire radial direction. As a result, the folded-back portion 6b is further arranged inside in the tire axial direction, and the durability of the bead portion 4 is enhanced.

In order to obtain the above-mentioned effects while maintaining steering stability, the tire radial distance L2 from the first virtual line 21 to the outer end 11o of the inner apex rubber 11 in the tire radial direction is, for example, the tire height SH. It is desirable that the value is 0.05 to 0.20 times. In a preferred embodiment, the ratio L2 / W1 of the distance L2 to the maximum width W1 of the inner apex rubber 11 in the tire axial direction is, for example, 1.50 to 2.20.

The rubber hardness of the inner apex rubber 11 is, for example, 70 to 90 °. Such an inner apex rubber 11 can exhibit excellent durability and steering stability of the bead portion 4.

The outer apex rubber 12 crosses, for example, the third virtual line 23 extending in the tire axial direction through the outer end o of the flange f. The outer apex rubber 12 of the present embodiment also crosses the second virtual line 22. In a preferred embodiment, the outer end of the outer apex rubber 12 in the tire radial direction is located outside the tire radial direction of the outer end 10o of the clinch rubber 10 in the tire radial direction. In a more desirable embodiment, as shown in FIG. 1, the outer end 10o of the outer apex rubber 12 is located outside the tire maximum width position 1w in the tire radial direction.

The distance L3 in the tire radial direction from the first virtual line 21 to the outer end 12o of the outer apex rubber 12 is preferably, for example, 0.25 to 0.65 times the tire height SH. Such an outer apex rubber 12 can improve the durability, riding comfort and steering stability of the bead portion 4 in a well-balanced manner.

As shown in FIG. 3, the maximum width portion of the outer apex rubber 12 is arranged, for example, between the first virtual line 21 and the second virtual line 22. It is desirable that the width of the outer apex rubber 12 gradually decreases from its maximum width portion toward the outside in the radial direction of the tire, for example. In a more preferred embodiment, the outer apex rubber 12 gradually decreases in width from the maximum width portion toward the inside in the radial direction of the tire.

The width W2 of the maximum width portion of the outer apex rubber 12 is preferably 0.20 to 0.60 times the maximum rubber thickness from the carcass 6 to the outer surface of the tire in the bead portion 4, and more preferably 0.40 to 0.40. It is 0.55 times.

The ratio t1 / t2 of the thickness t1 of the outer apex rubber 12 on the third virtual line 23 and the thickness t2 of the outer apex rubber on the second virtual line 22 is preferably 1.10 or more, more preferably 1.10 or more. It is 1.25 or more, preferably 1.80 or less, and more preferably 1.65 or less. Such an outer apex rubber 12 can improve the durability and riding comfort of the bead portion 4 in a well-balanced manner.

As shown in FIG. 2, the outer apex rubber 12 is appropriately inclined with respect to the tire axial direction in the region of 0.25 to 0.35 times the tire height SH from the first virtual line 21. Is desirable. The fourth virtual line 24 connecting the first virtual point 16 on the outer surface of the outer apex rubber 12 and in the above region and the outer end 11o of the inner apex rubber 11 is, for example, 30 to 70 with respect to the tire axial direction. It is desirable to incline at an angle of ° θ1. The first virtual point 16 is a point on the outer surface of the outer apex rubber 12 that is 0.25 to 0.35 times the tire height SH on the outer side in the tire radial direction from the first virtual line 21 and is separated by L4. In the present embodiment, the distance L4 is 0.30 times the tire height SH.

It is desirable that the outer apex rubber 12 has a higher rubber hardness than, for example, the inner apex rubber 11. Specifically, the rubber hardness of the outer apex rubber 12 is preferably, for example, 75 to 90 °. Such an outer apex rubber 12 can further enhance the durability of the bead portion 4.

As a more desirable embodiment, the bead portion 4 of the present embodiment is provided with the bead reinforcing rubber layer 18.

The bead reinforcing rubber layer 18 is arranged between, for example, the main body portion 6a and the folded-back portion 6b, and extends along the main body portion 6a from the tip portion of the inner apex rubber 11 on the outer side in the radial direction of the tire. In a preferred embodiment, the bead reinforcing rubber layer 18 overlaps the tip of the inner apex rubber 11. Such a bead reinforcing rubber layer 18 can effectively enhance the durability and steering stability of the bead portion.

The bead reinforcing rubber layer 18 includes, for example, a first portion 18a and a second portion 18b. The first portion 18a extends, for example, to a certain thickness. The second portion 18b is connected to the outer side in the tire radial direction of the first portion 18a, and the width gradually decreases toward the outer side in the tire radial direction. Such a bead reinforcing rubber layer 18 suppresses the rigidity of the bead portion 4 from being excessively increased, and is useful for achieving both riding comfort and steering stability.

The outer end 18o of the bead reinforcing rubber layer 18 in the tire radial direction is located, for example, outside the tire radial direction with respect to the second virtual line 22 (shown in FIG. 3). In a preferred embodiment, the outer end 18o of the bead reinforcing rubber layer 18 is located outside the tire radial direction of the clinch rubber 10 with respect to the tire radial outer end 10o. Further, it is desirable that the outer end 18o of the bead reinforcing rubber layer 18 is located inside the outer end 12o of the outer apex rubber 12 in the radial direction of the tire. In a more desirable embodiment, it is desirable that the outer end 18o of the bead reinforcing rubber layer 18 is located inside the tire maximum width position 1w in the tire radial direction.

It is desirable that the height h2 of the bead reinforcing rubber layer 18 in the tire radial direction is, for example, 0.30 to 0.40 times the tire height SH. The height h2 is defined by the distance in the tire radial direction from the first virtual line 21 to the outer end 18o of the bead reinforcing rubber layer 18 on the outer side in the tire radial direction. Such a bead reinforcing rubber layer 18 can improve the durability, riding comfort, and steering stability of the bead portion 4 in a well-balanced manner.

It is desirable that the bead reinforcing rubber layer 18 has a rubber hardness higher than that of the inner apex rubber 11, for example. Specifically, it is desirable that the rubber hardness of the bead reinforcing rubber layer 18 is, for example, 75 to 90 °.

As shown in FIG. 3, it is desirable that the bead portion 4 of the present embodiment is provided with, for example, a rubber chafer 25. The rubber chafer 25 is configured to have a U-shaped cross section including, for example, an inner portion 26, a bottom portion 27, and an outer portion 28. The inner portion 26 forms a part of the outer surface of the bead portion 4 on the tire lumen surface side. The bottom portion 27 is connected to the inside of the inner portion 26 in the radial direction of the tire and extends outward in the tire axial direction, for example. The bottom portion 27 constitutes, for example, a part of the contact portion of the bead portion 4 with the rim R. The outer portion 28 is connected to, for example, the outer side of the bottom portion 27 in the tire axial direction, and extends the inside of the bead portion 4 to the outer side in the tire radial direction.

It is desirable that a part of the outer portion 28 is provided between, for example, the first carcass ply 6A and the second carcass ply 6B. In a more desirable embodiment, it is desirable that the outer portion 28 extends to the outside in the tire radial direction from, for example, the inner end in the tire radial direction of the outer apex rubber 12. Such an outer portion 28 can further reinforce the bead portion 4.

Although the pneumatic tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and may be modified to various embodiments.

A pneumatic tire for a light truck of size 205 / 85R16 having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1. Each test tire was tested for bead durability, ride comfort and steering stability. The common specifications and test methods for each test tire are as follows.
Mounting rim: 16 x 5.5J
Tire internal pressure: 600kPa

<Durability of bead part>
The test tire was run on the drum tester under the following conditions, and the mileage until the bead was damaged was measured. The result is an index with Comparative Example 1 as 100, and the larger the value, the better the durability of the bead portion.
Speed: 80km / h
Load: 16.79kN

<Riding comfort and steering stability>
Each test tire was installed on all wheels of a 3-ton 2-D vehicle with a displacement of 3000cc. Ride quality and steering stability when running on this test vehicle were tested. The result is a score with the ride quality or steering stability of Comparative Example 1 as 100, and the larger the value, the better the performance.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example had improved durability of the bead portion without impairing the riding comfort. It was also confirmed that the tires of the examples had improved steering stability.

2 Tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 6A carcass ply 6a body part 6b folded part 10 clinch rubber 11 inner apex rubber 12 outer apex rubber 21 first virtual line 22 second virtual line S1 inner apex rubber cross-sectional area S2 Outer apex rubber cross-sectional area

Claims (6)

Pneumatic tires with carcass
The carcass has a main body portion that reaches the bead core of the bead portion from the tread portion through the sidewall portion, and is folded back from the inside to the outside in the tire axial direction and extends outward in the tire radial direction so as to be connected to the main body portion and around the bead core. Including carcass ply with parts
The bead part
An inner apex rubber, which is arranged between the main body portion and the folded portion and extends outward in the radial direction of the tire from the bead core in a triangular cross section.
A clinch rubber constituting at least a part of the axially outer surface of the bead portion,
An outer apex rubber that is arranged between the folded portion and the clinch rubber and has a rubber hardness lower than that of the clinch rubber is provided.
A first virtual line extending in the tire axial direction through the center position of the bead core in the tire radial direction and the first virtual line in the normal state of the tire, which is mounted on the normal rim and is filled with the normal internal pressure and has no load. A distance of 2.0 times the tire radial flange height hf from the 1 virtual line to the outer end of the normal rim flange in the tire radial direction extends in the tire axial direction at a position separated from the 1st virtual line. In the area between the two virtual lines
The ratio S2 / S1 between the outer apex of the cross-sectional area S2 inside apex of the cross-sectional area S1 is Ri 1.5 to 5.0 der,
The outer end of the inner apex rubber in the tire radial direction is a pneumatic tire located inside the tire radial direction with respect to the outer end of the flange. Pneumatic tires with carcass
The carcass has a main body portion that reaches the bead core of the bead portion from the tread portion through the sidewall portion, and is folded back from the inside to the outside in the tire axial direction and extends outward in the tire radial direction so as to be connected to the main body portion and around the bead core. Including carcass ply with parts
The bead part
An inner apex rubber, which is arranged between the main body portion and the folded portion and extends outward in the radial direction of the tire from the bead core in a triangular cross section.
Clinch rubber forming at least a part of the outer surface of the bead portion in the tire axial direction,
An outer apex rubber that is arranged between the folded portion and the clinch rubber and has a rubber hardness lower than that of the clinch rubber is provided.
A first virtual line extending in the tire axial direction through the center position of the bead core in the tire radial direction and the first virtual line in the normal state of the tire, which is mounted on the normal rim and is filled with the normal internal pressure and has no load. A distance of 2.0 times the tire radial flange height hf from the 1 virtual line to the outer end of the normal rim flange in the tire radial direction extends in the tire axial direction at a position separated from the 1st virtual line. In the area between the two virtual lines
The ratio S2 / S1 of the cross-sectional area S2 of the outer apex rubber to the cross-sectional area S1 of the inner apex rubber is 1.5 to 5.0.
The outer apex rubber crosses the second virtual line and the third virtual line extending in the tire axial direction through the outer end of the flange.
A pneumatic tire in which the ratio t1 / t2 of the thickness t1 of the outer apex rubber on the third virtual line to the thickness t2 of the outer apex rubber on the second virtual line is 1.10 to 1.80. Pneumatic tires with carcass
The carcass has a main body portion that reaches the bead core of the bead portion from the tread portion through the sidewall portion, and is folded back from the inside to the outside in the tire axial direction and extends outward in the tire radial direction so as to be connected to the main body portion and around the bead core. Including carcass ply with parts
The bead part
An inner apex rubber, which is arranged between the main body portion and the folded portion and extends outward in the radial direction of the tire from the bead core in a triangular cross section.
Clinch rubber forming at least a part of the outer surface of the bead portion in the tire axial direction,
An outer apex rubber that is arranged between the folded portion and the clinch rubber and has a rubber hardness lower than that of the clinch rubber is provided.
A first virtual line extending in the tire axial direction through the center position of the bead core in the tire radial direction and the first virtual line in the normal state of the tire, which is mounted on the normal rim and is filled with the normal internal pressure and has no load. A distance of 2.0 times the tire radial flange height hf from the 1 virtual line to the outer end of the normal rim flange in the tire radial direction extends in the tire axial direction at a position separated from the 1st virtual line. In the area between the two virtual lines
The ratio S2 / S1 of the cross-sectional area S2 of the outer apex rubber to the cross-sectional area S1 of the inner apex rubber is 1.5 to 5.0.
The outer apex rubber is a pneumatic tire having a rubber hardness higher than that of the inner apex rubber. Pneumatic tires with carcass
The carcass has a main body portion that reaches the bead core of the bead portion from the tread portion through the sidewall portion, and is folded back from the inside to the outside in the tire axial direction and extends outward in the tire radial direction so as to be connected to the main body portion and around the bead core. Including carcass ply with parts
The bead part
An inner apex rubber, which is arranged between the main body portion and the folded portion and extends outward in the radial direction of the tire from the bead core in a triangular cross section.
Clinch rubber forming at least a part of the outer surface of the bead portion in the tire axial direction,
An outer apex rubber that is arranged between the folded portion and the clinch rubber and has a rubber hardness lower than that of the clinch rubber is provided.
A first virtual line extending in the tire axial direction through the center position of the bead core in the tire radial direction and the first virtual line in the normal state of the tire, which is mounted on the normal rim and is filled with the normal internal pressure and has no load. A distance of 2.0 times the tire radial flange height hf from the 1 virtual line to the outer end of the normal rim flange in the tire radial direction extends in the tire axial direction at a position separated from the 1st virtual line. In the area between the two virtual lines
The ratio S2 / S1 of the cross-sectional area S2 of the outer apex rubber to the cross-sectional area S1 of the inner apex rubber is 1.5 to 5.0.
A pneumatic tire provided with a bead reinforcing rubber layer extending from the tip portion of the inner apex rubber on the outer side in the radial direction of the tire along the main body portion. The pneumatic tire according to claim 4, wherein the bead reinforcing rubber layer has a rubber hardness higher than that of the inner apex rubber. The pneumatic tire according to any one of claims 1 to 5, wherein the outer end of the outer apex rubber in the tire radial direction is located outside the tire radial outer end of the clinch rubber in the tire radial direction.

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