pneumatic tires

Abstract

To improve bead durability performance further.SOLUTION: A pneumatic tire 1 includes a bead part 4. A reinforcement rubber part 10 which is located adjacent to the outer side of a carcass ply 6A in a tire axis direction is disposed at the bead part 4. The reinforcement rubber part 10 includes an inner rubber layer 11 and an outer rubber layer 12. An outer end e of the outer rubber layer 12 is located at the outer side in a tire radial direction relative to an outer end 11e of the inner rubber layer 11. An inner end 12i of the outer rubber layer 12 is located at the inner side in the tire radial direction relative to an inner end 11i of the inner rubber layer 11.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires.

Background Art

[0002] Patent Document 1 below describes a pneumatic tire in which bead apex rubber is disposed in the bead portion. The bead apex rubber includes a main apex extending from the outer surface in the tire radial direction of the bead core, and an outer patch apex disposed outside the main apex in the tire axial direction. This pneumatic tire is said to improve durability performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, there has been a demand to further improve the durability performance of the bead portion (hereinafter referred to as "bead durability performance"). In particular, there has been a high need for pneumatic tires for small trucks loaded with high loads.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object thereof is to provide a pneumatic tire capable of further improving bead durability performance.

Means for Solving the Problems

[0006] The present disclosure relates to a pneumatic tire comprising a pair of bead portions, each having a bead core embedded in it, and a carcass extending between the bead cores, wherein the carcass includes a carcass ply comprising a main body portion extending between the bead cores and a folded portion that is folded back from the inside in the tire axial direction to the outside in the tire radial direction around each bead core, and at least one of the pair of bead portions has a reinforcing rubber portion adjacent to the outside in the tire axial direction of the folded portion, wherein the reinforcing rubber portion comprises an inner rubber layer and an outer rubber layer adjacent to the outside in the tire axial direction of the inner rubber layer, the outer end of the outer rubber layer in the tire radial direction is located radially outward from the outer end of the inner rubber layer in the tire radial direction, and the inner end of the outer rubber layer in the tire radial direction is located radially inward from the inner end of the inner rubber layer in the tire radial direction. [Effects of the Invention]

[0007] The pneumatic tire of this disclosure can further improve bead durability by adopting the above configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is a meridian cross-sectional view of the tire of this embodiment. [Figure 2] This is a magnified view of the bead portion in Figure 1. [Figure 3] This is a perspective view of a sheet-shaped rubber component. [Modes for carrying out the invention]

[0009] One form of implementation of this disclosure will be described below with reference to the drawings. Figure 1 is a meridian cross-sectional view of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of this embodiment, including the tire rotation axis (not shown) in its normal state. This disclosure is used, for example, in a tire 1 of a light truck (including commercial vehicles). However, this disclosure may also be used in a tire 1 for a passenger car or heavy load.

[0010] Here, "normal state" refers to the unloaded state in which tire 1 is mounted on the normal rim R and adjusted to the normal internal pressure. Unless otherwise specified, the dimensions of each part of tire 1 are values ​​measured in this normal state.

[0011] "Regular Rim R" refers to the rim specified for each tire within the standard system that the tire is based on. For example, it is the "Standard Rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0012] The aforementioned "standard internal pressure" is the air pressure specified for each tire by each standard within the standards system that the tire is based on. For example, it is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO.

[0013] As shown in Figure 1, the tire 1 of this embodiment comprises a pair of bead portions 4, 4 in which bead cores 5 are embedded, and a carcass 6 extending between the bead cores 5, 5.

[0014] The carcass 6 includes a carcass ply 6A which comprises a main body portion 6a extending between the bead cores 5, 5 and a folded portion 6b which is folded back from the inside in the tire axial direction to the outside in the tire radial direction around each bead core 5 and extends outward. In this embodiment, the carcass 6 includes two carcass plies 6A, 6B which are arranged inside and outside in the tire radial direction. The carcass 6 may be formed of, for example, a single carcass ply 6A. The outer end 6e in the tire radial direction of the folded portion 6b of the inner carcass ply 6A is located inside the tire radial direction of the outer carcass ply 6B than the outer end 6i in the tire radial direction of the folded portion 6b of the outer carcass ply 6B.

[0015] A reinforcing rubber portion 10 is provided on at least one of the pair of bead portions 4, adjacent to the outer side in the tire axial direction of the folded portion 6b. The reinforcing rubber portion 10 increases the rigidity of the bead portion 4, suppressing deflection during driving and improving bead durability. In this embodiment, the reinforcing rubber portion 10 is provided on each bead portion 4. The reinforcing rubber portion 10 is, for example, adjacent to the outer side in the tire axial direction of the folded portion 6b of the inner carcass ply 6A.

[0016] The reinforcing rubber portion 10 includes an inner rubber layer 11 and an outer rubber layer 12 positioned outside the inner rubber layer 11 in the tire axial direction. The reinforcing rubber portion 10 may also include one or more intermediate rubber layers (not shown) positioned between the inner rubber layer 11 and the outer rubber layer 12.

[0017] The outermost edge 12e of the outer rubber layer 12 in the tire radial direction is located further outward in the tire radial direction than the outermost edge 11e of the inner rubber layer 11 in the tire radial direction. Furthermore, the innermost edge 12i of the outer rubber layer 12 in the tire radial direction is located further inward in the tire radial direction than the innermost edge 11i of the inner rubber layer 11 in the tire radial direction. Such an outer rubber layer 12 increases the rigidity of the bead portion 4, particularly its lateral rigidity, thereby improving bead durability. Additionally, the outer rubber layer 12 suppresses contact between the inner rubber layer 11 and the sidewall rubber 3G or clinch rubber 4G (described later), reducing the number of steps formed between the reinforcing rubber portion 10 and the sidewall rubber 3G or clinch rubber 4G, thereby suppressing the occurrence of bares. Therefore, the tire of this disclosure can further improve bead durability. Furthermore, on the outermost side of the reinforcing rubber portion 10 in the tire radial direction, the two outer edges 11e and 12e come into contact with the carcass ply 6A or 6B. Furthermore, on the radially inner side of the reinforcing rubber portion 10, the two inner ends 11i and 12i come into contact with the carcass ply 6A. This reduces the concentration of strain on the carcass ply 6A compared to the case where only the outer end 11e and the inner end 11i of the inner rubber layer 11 come into contact with the carcass ply 6A (for example, when the length of the inner rubber layer 11 is greater than the length of the outer rubber layer 12). As a result, looseness of the carcass ply 6A is suppressed. Therefore, the tire 1 of this disclosure can further improve bead durability.

[0018] In this embodiment, the bead portion 4 includes a bead apex rubber 8, a sidewall rubber 3G, and a clinch rubber 4G. The bead apex rubber 8 extends outward from the bead core 5 in the tire radial direction. The clinch rubber 4G is positioned on the outside of the reinforcing rubber portion 10 in the tire axial direction. The sidewall rubber 3G is adjacent to the outside of the clinch rubber 4G in the tire radial direction. The sidewall rubber 3G and the clinch rubber 4G form, for example, the outer surface of the tire 1.

[0019] The distance D1 in the tire radial direction between the outer end 11e of the inner rubber layer 11 and the outer end 12e of the outer rubber layer 12 is preferably 3 mm or more. Thereby, the distance between the outer ends 11e and 12e is ensured, and in the tire radial direction, the change in the rigidity of the bead portion 4 is reduced, so that the bead durability performance is further improved. Although not particularly limited, the distance D1 is more preferably 5 mm or more, preferably 15 mm or less, and more preferably 10 mm or less.

[0020] From the same viewpoint, the distance D2 (shown in FIG. 2) in the tire radial direction between the inner end 11i of the inner rubber layer 11 and the inner end 12i of the outer rubber layer 12 is preferably 3 mm or more, more preferably 5 mm or more, preferably 10 mm or less, and more preferably 7 mm or less.

[0021] The height H1 from the bead base line BL to the outer end 12e of the outer rubber layer 12 is preferably 20% or more of the tire section height H, more preferably 30% or more, preferably 50% or less, and 45% below is more preferably. Since the height H1 is 20% or more of the tire section height H, it can exhibit high lateral rigidity against the load during running. Since the height H1 is 50% or less of the tire section height H, damage in the buttress portion B where a relatively large load is applied is suppressed.

[0022] In this specification, the "tire section height H" is the distance in the tire radial direction from the bead base line BL to the outermost position in the tire radial direction. Also, the "bead base line BL" is a tire axial line passing through the rim diameter (refer to JATMA) position determined by the standard based on the tire.

[0023] In the present embodiment, the outer end 12e of the outer rubber layer 12 is located radially inside the outermost end 6t in the tire radial direction of the folded-back portion 6b. Thereby, unnecessary steps are eliminated, and the generation of bare due to air remaining between materials can be suppressed. Also, sufficient bead durability performance can be ensured.

[0024] Figure 2 is an enlarged view of the bead portion 4. As shown in Figure 2, in this embodiment, the inner end 12i of the outer rubber layer 12 is located inward in the tire radial direction from the outer end 5e of the bead core 5. This causes the outer rubber layer 12 and the bead core 5 to overlap in the tire radial direction, further suppressing deformation of the outer rubber layer 12 and improving bead durability. The inner end 12i of the outer rubber layer 12 is located inward in the tire radial direction from, for example, the center 5c of the bead core 5 in the tire radial direction. It is desirable that the inner end 12i of the outer rubber layer 12 is located outward in the tire radial direction from, for example, the inner end 5i of the bead core 5. This maintains bead durability while also maintaining high fitability to the rim.

[0025] The inner end 11i of the inner rubber layer 11 is located radially inward of, for example, the outer end 8e of the bead apex rubber 8 in the tire radial direction. This causes the bead apex rubber 8 and the inner rubber layer 11 to overlap in the tire radial direction, suppressing deformation of the inner rubber layer 11 and further improving bead durability. It is desirable that the inner end 11i of the inner rubber layer 11 is located radially outward of, for example, the outer end 5e of the bead core 5. This maintains bead durability while also maintaining a high degree of fit to the rim.

[0026] It is desirable that the loss tangent tanδ2 of the outer rubber layer 12 is greater than the loss tangent tanδ1 of the inner rubber layer 11. Such an outer rubber layer 12 has high rigidity and exhibits strain suppression and lateral rigidity improvement effects. In addition, since the inner rubber layer 11 has a smaller hysteresis loss than the outer rubber layer 12, its heat generation is suppressed. As a result, the inner rubber layer 11 suppresses the transfer of heat from the outer rubber layer 12 to the carcass ply 6A, and delamination between the inner rubber layer 11 and the carcass ply 6A is suppressed. Therefore, the bead durability performance is greatly improved.

[0027] To effectively exert the above-mentioned effects, the loss tangent tanδ2 of the outer rubber layer 12 is preferably 0.07 or higher, more preferably 0.12 or higher, preferably 0.20 or lower, and even more preferably 0.18 or lower. The loss tangent tanδ1 of the inner rubber layer 11 is preferably 50% or higher of the loss tangent tanδ2 of the outer rubber layer 12, more preferably 55% or higher, preferably 70% or lower, and even more preferably 65% ​​or lower.

[0028] In this specification, the loss tangent tanδ and the complex modulus E*, described later, are values ​​measured using a viscoelastic spectrometer under the conditions shown below, in accordance with the provisions of JIS K6394 "Vulcanized rubber and thermoplastic rubber - Determination of dynamic properties - General guidelines". Initial distortion: 10% Amplitude: ±2% Frequency: 10Hz Deformation mode: Tension Temperature: 70℃ Viscoelastic spectrometer: GABO Corporation's "Iplexer®" (registered trademark)

[0029] The complex modulus of elasticity E*2 of the outer rubber layer 12 is preferably 120% or more of the complex modulus of elasticity E*1 of the inner rubber layer 11. This maintains high lateral rigidity of the outer rubber layer 12, which is located on the outer side in the axial direction of the tire, and suppresses distortion under high load conditions, thereby improving bead durability. If the complex modulus of elasticity E*2 of the outer rubber layer 12 is excessively larger than the complex modulus of elasticity E*1 of the inner rubber layer 11, the rigidity step at the outer end 12e and inner end 12i of the outer rubber layer 12 will increase, which may actually decrease bead durability. For this reason, it is even more desirable for the complex modulus of elasticity E*2 of the outer rubber layer 12 to be larger than the complex modulus of elasticity E*1 of the inner rubber layer 11, preferably 200% or less of the complex modulus of elasticity E*1, and even more desirable 190% or less. While not particularly limited, the complex modulus of elasticity E*2 of the outer rubber layer 12 is preferably 40 MPa or higher, more preferably 50 MPa or higher, preferably 150 MPa or lower, and more preferably 120 MPa or lower.

[0030] The adhesive strength f2 of the outer rubber layer 12 is preferably 1.3 times or more the adhesive strength f1 of the inner rubber layer 11. Such an outer rubber layer 12 has high adhesion to the sidewall rubber 3G or clinch rubber 4G, which helps to improve bead durability. Although not particularly limited, the adhesive strength f2 of the outer rubber layer 12 is more preferably 1.4 times or more, preferably 2.0 times or less, and even more preferably 1.8 times or less, of the adhesive strength f1 of the inner rubber layer 11. Furthermore, the adhesive strength f2 of the outer rubber layer 12 is preferably 150N or more, and even more preferably 180N or more. Although not particularly limited, considering the application process of the outer rubber layer 12, the adhesive strength f2 is preferably 350N or less, and even more preferably 300N or less. The aforementioned "adhesion strength" is measured in the state of each rubber layer 11, 12 before vulcanization (sheet-like rubber member described later) using a PICMA tack tester manufactured by Toyo Seiki Co., Ltd. under the following conditions. Crimping load: 4.9N Peeling speed: 15mm / min Crimping time: 30 seconds Temperature: 20℃ Humidity: 55%

[0031] The inner rubber layer 11 and the outer rubber layer 12 are made of, for example, a sheet-like rubber member 13 (shown in Figure 3). The sheet-like rubber member 13 is obtained, for example, by cutting a sheet raw material (not shown) extruded from a well-known rubber extruder. Such a sheet-like rubber member 13 facilitates the manufacture of reinforcing rubber parts 10 for various tire sizes and increases their versatility. Figure 3 is a perspective view of each sheet-like rubber member 13. As shown in Figure 3, in this embodiment, the sheet-like rubber member 13 includes a first sheet-like rubber member 13a for forming the inner rubber layer 11 and a second sheet-like rubber member 13b for forming the outer rubber layer 12. In this embodiment, the reinforcing rubber part 10 is formed by laminating these sheet-like rubber members 13a and 13b in the direction of the tire axis. Each sheet-like rubber member 13 is vulcanized to form the inner rubber layer 11 and the outer rubber layer 12.

[0032] As shown in Figure 2, the inner rubber layer 11 and the outer rubber layer 12 have, for example, a uniform thickness section 14 and a reduced thickness section 15 toward the outer end 11e, 12e or inner end 11i, 12i of the inner rubber layer 11 or outer rubber layer 12. The reduced thickness section 15 helps to alleviate rigidity steps and improve bead durability. In this specification, the "uniform thickness" is the portion in the tire radial direction where the thickness changes by 0.2 mm / mm or less along the longitudinal direction (tire radial direction) of the inner rubber layer 11 and the outer rubber layer 12. The length Lc of the reduced thickness section 15 is preferably, for example, 3 to 5 mm or less.

[0033] The reinforcing rubber portion 10 includes a first portion 17 consisting of a portion on which sheet-like rubber members 13 (shown in Figure 3) are laminated, and a second portion 18 consisting of a portion on which sheet-like rubber members 13 are not laminated. In this embodiment, the first portion 17 is formed by a portion on which an inner rubber layer 11 and an outer rubber layer 12 are laminated. In this embodiment, the second portion 18 is formed by only the outer rubber layer 12. The second portion 18 includes, for example, an inner second portion 18a located inward in the tire radial direction from the inner end 11i of the inner rubber layer 11, and an outer second portion 18b located outward in the tire radial direction from the outer end 11e of the inner rubber layer 11. In this embodiment, the first portion 17 is located between the inner second portion 18a and the outer second portion 18b.

[0034] The first part 17 includes a maximum thickness portion 17a. The maximum thickness portion 17a is formed, for example, by overlapping an equal thickness portion 14 of the inner rubber layer 11 and an equal thickness portion 14 of the outer rubber layer 12. The portion 19a where a reduced thickness portion 15 including the outer end 11e of the inner rubber layer 11 overlaps with an equal thickness portion 14 of the outer rubber layer 12, and the portion 19b where a reduced thickness portion 15 including the inner end 11i of the inner rubber layer 11 overlaps with an equal thickness portion 14 of the outer rubber layer 12 are not included in the maximum thickness portion 17a.

[0035] In the normal state, it is desirable that the first portion 17 is located on the tire axial line K passing through the outer edge 21 in the radial direction of the tire at the contact point between the tire 1 and the normal rim R. The outer edge 21 is a point where a large bending load acts during vehicle operation. By positioning the first portion 17 at the same position in the tire radial direction as the outer edge 21, deformation at the outer edge 21 is suppressed, and the bead durability performance is further improved. To make this effect more effective, it is desirable that the thickest portion 17a of the first portion 17 is located on the tire axial line K.

[0036] The difference (Ta-Tb) between the thickness Ta of the first part 17 and the thickness Tb of the second part 18 is preferably 1 mm or more. Since the difference (Ta-Tb) is 1 mm or more, the rigidity of the first part 17 increases, improving durability. If the difference (Ta-Tb) is excessively large, the rigidity of the first part 17 becomes too high, which may, for example, worsen ride comfort. From this perspective, the difference (Ta-Tb) is preferably 3.5 mm or less, and even more preferably 3.0 mm or less. The thickness Ta of the first part 17 is the thickness of the maximum thickness portion 17a. The thickness Tb of the second part 18 is the thickness of the equal-thickness portion 14 of the outer rubber layer 12. T2 That is the case.

[0037] In order to effectively exert the above-mentioned effects, the thickness Ta of the first part 17 is preferably 1.5 times or more, more preferably 1.8 times or more, more preferably 2.5 times or less, and more preferably 2.3 times or less, of the thickness Tb of the second part 18.

[0038] The thickness T2 of the uniformly thick section 14 of the outer rubber layer 12 is preferably greater than the thickness T1 of the uniformly thick section 14 of the inner rubber layer 11. This allows the reinforcing rubber section 10 to suppress the occurrence of bare rubber while ensuring sufficient durability, thereby improving its appearance. Although not particularly limited, the thickness T2 of the outer rubber layer 12 is preferably 120% or more of the thickness T1 of the inner rubber layer 11, more preferably 150% or more, more preferably 350% or less, and more preferably 300% or less. The thickness T2 of the outer rubber layer 12 is preferably 0.5 mm or more, more preferably 0.8 mm or more, more preferably 2.0 mm or less, and more preferably 1.5 mm or less. If the thickness T2 of the uniformly thick section 14 of the outer rubber layer 12 is the same as the thickness T1 of the uniformly thick section 14 of the inner rubber layer 11, the inner rubber layer 11 and the outer rubber layer 12 can be manufactured by cutting a single sheet-like rubber member 13.

[0039] The bead apex rubber 8 is formed in a triangular shape, for example, in the tire meridian cross-section. Although not particularly limited, an inner rubber layer 11 and an outer rubber layer 12 are arranged at the height position in the tire radial direction of the outer end 8e of the bead apex rubber 8. In this embodiment, the maximum thickness portion 17a is arranged at the height position in the tire radial direction of the outer end 8e of the bead apex rubber 8.

[0040] The complex modulus E*3 of the bead apex rubber 8 is, for example, the complex modulus E*1 of the inner rubber layer 11. and It is desirable that they be equal. The complex modulus E*3 of the bead apex rubber 8 is preferably smaller than, for example, the complex modulus E*2 of the outer rubber layer 12.

[0041] As shown in Figure 1, the complex modulus E* of both the sidewall rubber 3G and the clinch rubber 4G is smaller than the complex modulus E*1 of the inner rubber layer 11. This ensures that the basic ride comfort performance is achieved.

[0042] Although one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the specific embodiment described above and can be implemented in various modified forms. [Examples]

[0043] A pneumatic tire with the basic structure shown in Figure 1 was prototyped based on the specifications in Table 1. The bead durability and appearance performance of each test tire were then tested. The common specifications and test methods for each test tire are as follows. The tanδ1:0.10 of the inner rubber layer in Comparative Example 1 E*1 of the inner rubber layer in Comparative Example 1: 20 MPa Adhesion strength of the inner rubber layer f1: 150N The tanδ1 and tanδ2 values ​​in the table are shown as exponents with tanδ1 of Comparative Example 1 set to 100. In the table, E*1 and E*2 are shown as indices with E*1 of Comparative Example 1 set to 100.

[0044] <Bead durability performance> Each test tire was run on a drum testing machine under the following conditions, and the distance traveled until the bead broke was measured. The results are shown as an index with the distance traveled in Comparative Example 1 set to 100. A higher number indicates better performance. Rim size: 6.0J Internal pressure: 220kPa Vertical load: 19.84kN Traveling speed: 20km / h

[0045] <Exterior Performance> The outer surface of the area where the sidewall rubber or clinch rubber was formed on each test tire was evaluated visually by the tester. The results are shown on a scale where Comparative Example 1 is rated at 100. A higher number indicates better performance, with less bearing due to the reinforcing rubber.

[0046] [Table 1]

[0047] The test results show that the tire in the example exhibits improved bead durability compared to the tire in the comparative example. Furthermore, the tire in the example maintains its appearance.

[0048] [Note] This disclosure includes the following aspects.

[0049] [Disclosure 1] It is a pneumatic tire, It comprises a pair of bead sections, each in which a bead core is embedded, and a carcass extending between the bead cores. The carcass includes a carcass ply comprising a main body portion extending between the bead cores and a folded portion that is folded back from the inside in the tire axial direction to the outside in the tire radial direction around each bead core. At least one of the pair of bead portions is provided with a reinforcing rubber portion adjacent to the outer side of the folded portion in the tire axial direction. The reinforcing rubber portion includes an inner rubber layer and an outer rubber layer adjacent to the outer side of the inner rubber layer in the tire axial direction. The outermost end of the outer rubber layer in the tire radial direction is located further outward in the tire radial direction than the outermost end of the inner rubber layer in the tire radial direction. The inner end of the outer rubber layer in the tire radial direction is located radially inward of the inner rubber layer in the tire radial direction. Pneumatic tires. [Disclosure 2] The pneumatic tire according to Disclosure 1, wherein the distance in the radial direction of the tire between the outer end of the inner rubber layer and the outer end of the outer rubber layer is 3 mm or more. [Disclosure 3] The pneumatic tire according to disclosure 1 or 2, wherein the distance in the tire radial direction between the inner end of the inner rubber layer and the inner end of the outer rubber layer is 3 mm or more. [Disclosure 4] The inner rubber layer and the outer rubber layer are made of a sheet-like rubber material. The reinforcing rubber portion includes a first portion consisting of a portion in which the sheet-like rubber member is laminated, A pneumatic tire according to any one of disclosures 1 to 3, wherein, in an unloaded state, when mounted on a regular rim and filled with regular internal pressure, the first portion is located on a tire axial line passing through the outer end in the radial direction of the tire at the contact point between the pneumatic tire and the regular rim. [Disclosure 5] The pneumatic tire according to disclosure 4, wherein the thickest portion of the first portion is located on the axial line of the tire. [Disclosure 6] The reinforcing rubber portion includes a second portion consisting of a part in which the sheet-like rubber member is not laminated, The pneumatic tire according to disclosure 4 or 5, wherein the difference (Ta-Tb) between the thickness Ta of the first portion and the thickness Tb of the second portion is 1 mm or more. [Disclosure 7] The pneumatic tire according to disclosure 6, wherein the thickness Ta of the first portion is 1.5 to 2.5 times the thickness Tb of the second portion. [Disclosure 8] The pneumatic tire according to any one of disclosures 1 to 7, wherein the loss tangent tanδ2 of the outer rubber layer is greater than the loss tangent tanδ1 of the inner rubber layer. [Disclosure 9] The pneumatic tire according to any one of disclosures 1 to 8, wherein the complex modulus E*2 of the outer rubber layer is 60% or more of the complex modulus E*1 of the inner rubber layer. [Disclosure 10] The pneumatic tire according to disclosure 9, wherein the complex modulus E*2 of the outer rubber layer is greater than the complex modulus E*1 of the inner rubber layer. [Disclosure 11] The pneumatic tire according to any one of disclosures 1 to 10, wherein the outer rubber layer and the inner rubber layer each include a portion of equal thickness which is of a constant thickness. [Disclosure 12] The pneumatic tire according to any one of disclosures 1 to 11, wherein the adhesive strength of the outer rubber layer is 1.3 times or more that of the inner rubber layer. [Explanation of Symbols]

[0050] 1. Pneumatic tire 4. Bead section 6A Carcass Ply 10 Reinforcement rubber section 11. Inner rubber layer 11e Outer edge of the inner rubber layer 11i Inner end of inner rubber layer 12. Outer rubber layer 12e Outer edge of the outer rubber layer 12i Inner end of outer rubber layer

Claims

1. It is a pneumatic tire, It comprises a pair of bead sections, each in which a bead core is embedded, and a carcass extending between the bead cores. The carcass includes a carcass ply comprising a main body portion extending between the bead cores and a folded portion that is folded back from the inside in the tire axial direction to the outside in the tire radial direction around each bead core. At least one of the pair of bead portions is provided with a reinforcing rubber portion adjacent to the outer side of the folded portion in the tire axial direction. The reinforcing rubber portion includes an inner rubber layer and an outer rubber layer adjacent to the outer side of the inner rubber layer in the tire axial direction. The outermost end of the outer rubber layer in the tire radial direction is located further outward in the tire radial direction than the outermost end of the inner rubber layer in the tire radial direction. The inner end of the outer rubber layer in the tire radial direction is located radially inward of the inner rubber layer in the tire radial direction. The loss tangent tanδ2 of the outer rubber layer is greater than the loss tangent tanδ1 of the inner rubber layer. Pneumatic tires.

2. A pneumatic tire, It comprises a pair of bead sections, each in which a bead core is embedded, and a carcass extending between the bead cores. The carcass includes a carcass ply comprising a main body portion extending between the bead cores and a folded portion that is folded back from the inside in the tire axial direction to the outside in the tire radial direction around each bead core. At least one of the pair of bead portions is provided with a reinforcing rubber portion adjacent to the outer side of the folded portion in the tire axial direction. The reinforcing rubber portion includes an inner rubber layer and an outer rubber layer adjacent to the outer side of the inner rubber layer in the tire axial direction. The outermost end of the outer rubber layer in the tire radial direction is located further outward in the tire radial direction than the outermost end of the inner rubber layer in the tire radial direction. The inner end of the outer rubber layer in the tire radial direction is located radially inward of the inner rubber layer in the tire radial direction. The complex modulus E*2 of the outer rubber layer is greater than the complex modulus E*1 of the inner rubber layer. Pneumatic tires.

3. A pneumatic tire, It comprises a pair of bead sections, each in which a bead core is embedded, and a carcass extending between the bead cores. The carcass includes a carcass ply comprising a main body portion extending between the bead cores and a folded portion that is folded back from the inside in the tire axial direction to the outside in the tire radial direction around each bead core. At least one of the pair of bead portions is provided with a reinforcing rubber portion adjacent to the outer side of the folded portion in the tire axial direction. The reinforcing rubber portion includes an inner rubber layer and an outer rubber layer adjacent to the outer side of the inner rubber layer in the tire axial direction. The outermost end of the outer rubber layer in the tire radial direction is located further outward in the tire radial direction than the outermost end of the inner rubber layer in the tire radial direction. The inner end of the outer rubber layer in the tire radial direction is located radially inward of the inner rubber layer in the tire radial direction. The adhesive strength of the outer rubber layer is 1.3 times or more that of the inner rubber layer. Pneumatic tires.

4. The tire radial distance between the outer end of the inner rubber layer and the outer end of the outer rubber layer is 3 mm or more, as described in any one of claims 1 to 3.

5. The tire radial distance between the inner end of the inner rubber layer and the inner end of the outer rubber layer is 3 mm or more, as described in any one of claims 1 to 4.

6. The inner rubber layer and the outer rubber layer are made of a sheet-like rubber member, The reinforcing rubber portion includes a first portion consisting of a portion in which the sheet-like rubber member is laminated, The pneumatic tire according to any one of claims 1 to 5, wherein, in an unloaded state, when mounted on a regular rim and filled with the regular internal pressure, the first portion is located on a tire axial line passing through the outer end in the radial direction of the tire at the contact point between the pneumatic tire and the regular rim.

7. The pneumatic tire according to claim 6, wherein the thickest portion of the first portion is located on the axial line of the tire.

8. The reinforcing rubber portion includes a second portion consisting of a portion in which the sheet-like rubber member is not laminated, The difference between the thickness Ta of the first portion and the thickness Tb of the second portion (Ta - Tb) is 1 mm or more, as described in claim 6 or 7.

9. The pneumatic tire according to claim 8, wherein the thickness Ta of the first portion is 1.5 to 2.5 times the thickness Tb of the second portion.

10. The pneumatic tire according to claim 2 or 3, wherein the loss tangent tanδ2 of the outer rubber layer is greater than the loss tangent tanδ1 of the inner rubber layer.

11. The pneumatic tire according to claim 1 or 3, wherein the complex modulus E*2 of the outer rubber layer is 60% or more of the complex modulus E*1 of the inner rubber layer.

12. The pneumatic tire according to claim 3, wherein the complex modulus E*2 of the outer rubber layer is greater than the complex modulus E*1 of the inner rubber layer.

13. The pneumatic tire according to any one of claims 1 to 12, wherein the outer rubber layer and the inner rubber layer each include a portion of equal thickness which is of a constant thickness.

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