Pneumatic tires

Abstract

A pneumatic tire with improved durability. A pneumatic tire (1) comprising a carcass (6). The carcass (6) is a carcass ply (8) comprising a main body (9) extending between respective bead cores (5) and a folded-back portion (10) folded back around the bead core (5). The bead portion (4) is provided with: a first apex rubber (11) disposed between the main body (9) and the folded-back portion (10); an insulating rubber (12) extending radially outwardly of the tire between the main body (9) and the folded-back portion (10); and a second apex rubber (13) disposed axially outwardly of the folded-back portion (10). The outer end (12e) of the insulating rubber (12) is closer to the outer side in the tire radial direction than the outer end (13e) of the second apex rubber (13). The complex elastic modulus (E*a) of the insulating rubber (12) is greater than the complex elastic modulus (E*b) of the topping rubber (8b) of the carcass ply (8).

Description

Technical Field

[0001] The present invention relates to a pneumatic tire. Background Art

[0002] Patent document 1 described below describes a pneumatic tire having a carcass, a belt, a cushion rubber, and an apex rubber. The carcass is composed of a cord layer, and the cord layer is formed with a main portion located axially inside the tire bead and a folded portion located axially outside the tire bead. The belt is composed of a high-hardness cross-linked rubber and extends radially outward from the apex rubber. The cushion rubber is composed of a high-hardness cross-linked rubber and is located axially outside the folded portion. Such a pneumatic tire has high rigidity and excellent durability.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-147567 Summary of the invention

[0004] However, the pneumatic tire of Patent Document 1 has a problem in that damage is easily generated near the outer end position in the tire radial direction of the cushion rubber.

[0005] The present invention has been made in view of the above actual situation, and a main object of the present invention is to provide a pneumatic tire capable of improving durability.

[0006] The present invention is an inflatable tire, which comprises: a pair of bead parts, each of which is embedded with a bead core; and a carcass, which spans between the pair of bead parts, the carcass comprises a carcass ply, the carcass ply comprises: a main body, which extends between the bead cores; and a folded portion, which is folded around each of the bead cores from the inner side to the outer side of the tire axial direction and extends radially outward of the tire, the carcass ply comprises a carcass cord and a topping covering the carcass cord, and in the bead part, a first apex is provided, which is located in the main body of the carcass ply The first apex rubber is disposed on the outer side of the tire axial direction of the folded portion of the carcass ply, the outer end of the isolation rubber in the radial direction of the tire is closer to the outer side of the tire radial direction than the outer end of the second apex rubber in the radial direction of the tire, and the complex elastic modulus E*a of the isolation rubber is greater than the complex elastic modulus E*b of the topping rubber.

[0007] In the pneumatic tire of the present invention, it is preferred that the complex elastic modulus E*a of the spacer rubber is smaller than the complex elastic modulus E*c of the second apex rubber.

[0008] In the pneumatic tire of the present invention, it is preferred that the outer end of the second apex in the tire radial direction is located within a range of 30% to 55% of the tire cross-sectional height from the bead base line toward the outer side in the tire radial direction.

[0009] In the pneumatic tire of the present invention, it is preferred that the inner end of the second apex in the tire radial direction is located within a range of 2% to 18% of the tire cross-sectional height from the bead base line toward the outer side in the tire radial direction.

[0010] In the pneumatic tire of the present invention, it is preferred that the second apex has a thickness of 1.0 mm to 2.0 mm.

[0011] In the pneumatic tire of the present invention, preferably, the insulation rubber has a thickness of 0.8 mm to 2.3 mm.

[0012] In the pneumatic tire of the present invention, it is preferable that the inner end of the spacer rubber is located radially inward of an outer end of the first apex rubber in the tire radial direction.

[0013] In the pneumatic tire of the present invention, it is preferred that the length of the first apex in the tire radial direction is 18 mm to 23 mm.

[0014] In the pneumatic tire of the present invention, it is preferred that the tread portion includes a belt layer disposed on the tire radially outer side of the carcass, and the outer end of the folded portion in the tire radial direction is sandwiched between the body portion and the belt layer.

[0015] In the pneumatic tire of the present invention, it is preferred that the carcass ply includes a first ply and a second ply adjacent to the first ply in the tire radial direction.

[0016] The present invention can improve durability by adopting the above-mentioned structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a tire meridian cross-sectional view of the right half of the pneumatic tire of the present invention.

[0018] Figure 2 yes Figure 1 An enlarged view of an inflated tire.

[0019] Figure 3 yes Figure 1 An enlarged view of an inflated tire.

[0020] Figure 4 This is a cross-sectional view for conceptually explaining a method for manufacturing a pneumatic tire.

[0021] Description of symbols

[0022] 1: pneumatic tire; 4: bead portion; 5: bead core; 6: carcass; 8: carcass cord layer; 8b: rubber patch; 9: main body; 10: folded portion; 11: first apex rubber; 12: isolation rubber; 12e: outer end of isolation rubber; 13: second apex rubber; 13e: outer end of second apex rubber. DETAILED DESCRIPTION

[0023] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0024] Figure 1 It is a tire meridian cross-sectional view of the right half including the tire rotation axis (not shown) in the standard state of a pneumatic tire (hereinafter, sometimes simply referred to as a “tire”) 1 according to the present embodiment. Figure 1 The tire 1 is shown as a tire for a light truck, for example. However, the present invention can also be applied to a tire 1 for a passenger car or a heavy-duty vehicle.

[0025] The "standard state" is an unloaded state in which the tire 1 is assembled on a standard rim (not shown) and filled with a standard internal pressure. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in the standard state.

[0026] "Standard rim" is a rim of the specification specified for the tire in the specification system including the specification on which the tire 1 is based, for example, "Standard rim" in JATMA, "Design rim" in TRA, and "Measuring rim" in ETRTO. "Standard internal pressure" is the air pressure determined for each specification in the standard system including the specification on which the tire 1 is based, for JATMA, "maximum air pressure", for TRA, the maximum value recorded in the table "TIRELOAD LIMITSATVARIOUSCOLD INFLATION PRESSURES", and for ETRTO, "INFLATIONPRESSURE".

[0027] The tire 1 of this embodiment includes a carcass 6 spanning between a pair of bead portions 4. In addition, the tire 1 includes, for example, bead cores 5 respectively embedded in the bead portions 4; a belt layer 7 arranged inside the tread portion 2 and arranged outside the carcass 6 in the tire radial direction; and a sidewall rubber 3G forming the outer surface of the sidewall portion 3. The outer end 3e of the sidewall rubber 3G in the tire radial direction is located, for example, between the belt layer 7 and the carcass 6. In addition, the tire 1 is not limited to such a form.

[0028] Figure 2 is an enlarged view of the tread portion 2. Figure 2As shown, the carcass 6 is formed of a carcass ply 8 including carcass cords 8a and a topping rubber 8b covering the carcass cords 8a. The carcass cords 8a are arranged at an angle of, for example, 70 to 90 degrees with respect to the tire circumferential direction.

[0029] like Figure 1 As shown, the carcass ply 8 of this embodiment includes a main body portion 9 extending between the bead cores 5 and a folded portion 10 folded from the inside to the outside in the tire axial direction around the bead core 5 and extending outward in the tire radial direction.

[0030] The first apex 11, the insulating rubber 12, and the second apex 13 are provided on at least one of the bead portions 4. In the present embodiment, the first apex 11, the insulating rubber 12, and the second apex 13 are provided on a pair of bead portions 4, respectively. The first apex 11 extends from the bead core 5 to the outside of the tire radial direction between the main body 9 and the folded portion 10. The insulating rubber 12 extends from the inner end 12i located between the first apex 11 and the main body 9 to the outside of the tire radial direction between the main body 9 and the folded portion 10. The second apex 13 is arranged on the outside of the folded portion 10 in the tire axial direction.

[0031] The outer end 12e of the spacer rubber 12 in the tire radial direction is located on the outer side in the tire radial direction than the outer end 13e of the second apex rubber 13. As a result, the change in rigidity between the inner and outer sides of the outer end 13e of the second apex rubber 13 in the tire radial direction is reduced, so that the deformation near the outer end 13e of the second apex rubber 13 during running of the tire is dispersed, and the damage such as loosening of the carcass ply 8 is suppressed, so that the durability is improved.

[0032] The complex elastic modulus E*a of the isolation rubber 12 is greater than the complex elastic modulus E*b of the top rubber 8b. As a result, the change in the rigidity can be suppressed to a smaller extent, so the durability is further improved. In addition, for example, during tire molding, the local deformation near the outer end 13e of the second apex rubber 13 can be suppressed, and the poor appearance caused by air residue can be suppressed. It is preferred that the complex elastic modulus E*a of the isolation rubber 12 is greater than the complex elastic modulus E*b of the topping rubber 8b.

[0033] The complex elastic modulus E* was measured according to the provisions of "JIS K6394" under the following measurement conditions using a viscoelasticity spectrometer (trade name "VESF-3" manufactured by Iwamoto Manufacturing Co., Ltd.).

[0034] Initial deformation: 10%

[0035] Amplitude: ±1.0%

[0036] Frequency: 10Hz

[0037] Deformation Mode: Stretch

[0038] Measurement temperature: 30℃

[0039] In the present embodiment, the belt layer 7 is composed of two belt plies 7A and 7B on the inner and outer sides of the tire radial direction. The inner belt ply 7A, for example, ends at the outer side of the tire axial direction than the outer belt ply 7B. In the present embodiment, each belt ply 7A, 7B has a highly elastic belt cord 7a such as a steel cord inclined at an angle of 15° to 40° relative to the tire equator C, and a rubber covering the belt cord 7b (such as Figure 2 shown).

[0040] In the present embodiment, the outer end 10e of the folded portion 10 in the tire radial direction is sandwiched by the main body 9 and the belt layer 7. Such a folded portion 10 improves the rigidity of the sidewall portion 3 of the tire 1 and helps to reduce the rigidity step difference caused by the outer end 10e. The outer end 10e of the folded portion 10 is, for example, sandwiched between the inner belt ply 7A and the main body 9. In addition, "sandwiched by the main body 9 and the belt layer 7" means that the outer end 10e is closer to the inner side of the tire axial direction than the outer end 7e of the belt layer 7 in the tire axial direction (for example, the outer end 7e1 of the inner belt ply 7A).

[0041] In the present embodiment, the carcass ply 8 is formed of two ply layers including a first ply layer 8A and a second ply layer 8B adjacent to the first ply layer 8A in the tire radial direction. For example, the second ply layer 8B is disposed on the outer side of the first ply layer 8A in the tire radial direction. The first ply layer 8A of the present embodiment has a main body portion 9a and a folded portion 10a. The second ply layer 8B has, for example, a main body portion 9b and a folded portion 10b. The folded portions 10a, 10b of each ply layer 8A, 8B terminate, for example, between the belt layer 7 and the main body portion 9. In addition, the carcass 6 is not limited to such a method, and can be formed, for example, by one carcass ply layer 8.

[0042] Figure 3 4 is an enlarged view of the tire bead portion 4. Figure 3 As shown, the bead core 5 is formed in a rectangular cross-section, for example. The bead core 5 includes: an outer surface 5a, which faces the outer side of the tire radial direction; an inner surface 5b, which faces the inner side of the tire radial direction; and a side surface 5c, which connects the outer surface 5a and the inner surface 5b. In addition, the bead core 5 is not limited to this mode.

[0043] The first apex rubber 11 is formed of, for example, a complex elastic modulus E*1 greater than the complex elastic modulus E*b of the topping rubber 8b. Such a first apex rubber 11 increases the rigidity of the bead portion 4 and exhibits excellent steering stability. The complex elastic modulus E*1 of the first apex rubber 11 is, for example, preferably 10 MPa or more, more preferably 15 MPa or more, and preferably 50 MPa or less, more preferably 45 MPa or less, but is not limited thereto.

[0044] In the present embodiment, the first apex 11 extends outward in the tire radial direction from the outer surface 5a of the bead core 5. The first apex 11 has a triangular cross section, for example.

[0045] The length L1 of the first apex rubber 11 in the tire radial direction is, for example, 18 mm to 23 mm. Since the length L1 of the first apex rubber 11 is 18 mm or more, the rigidity of the bead portion 4 is maintained high. Since the length L1 of the first apex rubber 11 is 23 mm or less, the folded portion 10 extending from the bead core 5 to the outside in the tire radial direction can be bent to the inside in the tire axial direction, and the compression deformation acting on the folded portion 10 can be reduced.

[0046] If the complex elastic modulus E*a of the isolation rubber 12 is too large compared to the complex elastic modulus E*b of the topping rubber 8b, the rigidity step difference near the outer end 12e of the isolation rubber 12 in the tire radial direction becomes large, which may deteriorate the durability performance. Therefore, the difference (E*aE*b) between the complex elastic modulus E*a of the isolation rubber 12 and the complex elastic modulus E*b of the topping rubber 8b is preferably 20 MPa or less, more preferably 10 MPa or less, and further preferably 5 MPa or less.

[0047] The complex elastic modulus E*a of the isolation rubber 12 is preferably, for example, 2 MPa or more, more preferably 4 MPa or more, and preferably 20 MPa or less, more preferably 10 MPa or less. The complex elastic modulus E*b of the topping rubber 8b is preferably, for example, 2 MPa or more, more preferably 4 MPa or more, and preferably 15 MPa or less, more preferably 8 MPa or less.

[0048] The complex elastic modulus E*a of the isolation rubber 12 is preferably smaller than the complex elastic modulus E*c of the second apex rubber 13. If the complex elastic modulus E*a of the isolation rubber 12 is larger than the complex elastic modulus E*c of the second apex rubber 13, the change in rigidity between the outer end 12e of the isolation rubber 12 in the tire radial direction and the inner and outer sides of the tire radial direction becomes larger, and the durability may be deteriorated. Therefore, the difference (E*cE*a) between the complex elastic modulus E*c of the second apex rubber 13 and the complex elastic modulus E*a of the isolation rubber 12 is preferably 4 MPa or more, and more preferably 8 MPa or more, for example.

[0049] like Figure 1 As shown, the outer end 12e of the spacer rubber 12 is preferably away from the outer end 13e of the second apex rubber 13 in the tire radial direction by a distance L2 of 30% or more of the tire cross-sectional height H. Thus, the effect of reducing the rigidity change at the outer end 13e of the second apex rubber 13 and the steering stability performance of the tire 1 can be effectively improved.

[0050] If the outer end 12e of the spacer rubber 12 is far away from the outer end 13e of the second apex rubber 13 in the tire radial direction, the mass of the tire 1 increases and the rolling resistance performance may deteriorate. Therefore, the distance L2 in the tire radial direction is preferably less than 55% of the tire cross-sectional height H, and more preferably less than 50%.

[0051] The distance L3 between the outer end 12e of the insulation rubber 12 and the base line BL in the tire radial direction is, for example, preferably 90% or less, more preferably 85% or less. The distance L3 is preferably 70% or more, more preferably 75% or more.

[0052] like Figure 3 As shown in the figure, in the present embodiment, the inner end 12i of the spacer rubber 12 in the tire radial direction is located inward in the tire radial direction than the outer end 11e of the first apex rubber 11 in the tire radial direction. In other words, the spacer rubber 12 overlaps the first apex rubber 11 in the tire radial direction. Thus, the rigidity near the inner end 12i of the spacer rubber 12 can be increased, so that better steering stability performance can be achieved.

[0053] The inner end 12i of the isolation rubber 12 is, for example, located outside the tire radial direction than the outer surface 5a of the bead core 5. The inner end 12i of the isolation rubber 12 is, for example, arranged outside the tire radial direction than the inner end 13i of the second apex rubber 13. In addition, the inner end 12i of the isolation rubber 12 may be, for example, located inside the tire radial direction than the inner surface 5b of the bead core 5.

[0054] The thickness t1 of the insulating rubber 12 is, for example, 0.8 mm to 2.3 mm. When the thickness t1 of the insulating rubber 12 is 0.8 mm or more, the change in rigidity generated at the outer end 13e of the second apex rubber 13 can be reduced. When the thickness t1 of the insulating rubber 12 is 2.3 mm or less, the increase in the mass of the tire 1 can be suppressed. In this specification, the thickness t1 of the insulating rubber 12 is the maximum thickness.

[0055] For example, the insulation rubber 12 may be formed of the same rubber material as the topping rubber 8b. Such insulation rubber 12 has a high bonding strength with the carcass 6, and can suppress loosening of the carcass ply 8.

[0056] The complex elastic modulus E*c of the second apex 13 is preferably 10 MPa or more, more preferably 15 MPa or more, and preferably 50 MPa or less, more preferably 45 MPa or less. Thus, the rigidity of the bead portion 4 is maintained at a high level. In the present embodiment, the complex elastic modulus E*c of the second apex 13 is the same as the complex elastic modulus E*1 of the first apex 11. The second apex 13 is preferably formed of the same rubber material as the first apex 11.

[0057] like Figure 1As shown, the outer end 13e of the second apex rubber 13 in the tire radial direction is preferably located within a range of 30% to 55% of the tire cross-sectional height H extending from the bead baseline BL to the outside in the tire radial direction. Since the outer end 13e is located at more than 30% of the tire cross-sectional height H extending outward from the bead baseline BL, the rigidity of the bead portion 4 can be improved, and the durability and handling stability can be maintained at a high level. Since the outer end 13e is located at less than 55% of the tire cross-sectional height H extending outward from the bead baseline BL, defects caused by bare shoulders during tire vulcanization molding, for example, can be suppressed, and high appearance performance can be maintained. From this point of view, it is more preferred that the tire radial distance L5 between the outer end 13e and the bead baseline BL is less than 50% of the tire cross-sectional height H, and more preferably less than 45%.

[0058] The above-mentioned “bead base line BL” is defined as a tire axial line passing through a rim diameter position determined by the specification on which the tire 1 is based.

[0059] From the viewpoint of improving appearance performance, the outer end 13e of the second apex 13 is preferably located radially inward of the tire maximum width position M. The tire maximum width position M in this specification is the position where the carcass ply 8 extends most outward in the tire axial direction.

[0060] like Figure 3 As shown, the inner end 13i of the second apex rubber 13 in the tire radial direction is preferably located within a range of 2% to 18% of the tire cross-sectional height H extending from the bead base line BL to the outer side in the tire radial direction. Since the distance L6 between the inner end 13i and the bead base line BL in the tire radial direction is located at more than 2% of the tire cross-sectional height H, it is possible to prevent the excessive increase in the mass of the tire 1 and suppress the deterioration of the rolling resistance performance. Since the distance L6 is located at less than 18% of the tire cross-sectional height H, the rigidity of the bead portion 4 is improved, and the durability and steering stability performance can be maintained at a high level. From this point of view, the distance L6 is more preferably more than 5% of the tire cross-sectional height H, and more preferably less than 15%.

[0061] In the present embodiment, the inner end 13i of the second apex rubber 13 is located inward in the tire radial direction relative to the outer surface 5a of the bead core 5, so the durability of the bead portion 4 is improved. In the present embodiment, the inner end 13i of the second apex rubber 13 is located inward in the tire radial direction relative to the middle position 5m in the tire radial direction of the bead core 5. In addition, when the inner end 13i of the second apex rubber 13 is located inward in the tire radial direction relative to the outer surface 5a, the mass increase of the tire 1 can be suppressed.

[0062] The thickness t2 of the second apex 13 is preferably 1.0 mm to 2.0 mm. This can improve rolling resistance performance, durability, and steering stability performance in a balanced manner. In this specification, the thickness t2 of the second apex 13 is the maximum thickness.

[0063] In the bead portion 4 of the present embodiment, a bead rubber 20, a chafer 21 and an inner liner 22 are also provided. The bead rubber 20 is, for example, arranged on the outer side of the second apex rubber 13 in the tire axial direction. The chafer 21 is, for example, arranged on the inner side of the return portion 10 in the tire radial direction in connection with the bead rubber 20. The bead rubber 20 and the chafer 21 are, for example, in contact with a standard rim (not shown). The inner liner 22 is, for example, arranged on the inner side of the main body 9. The bead rubber 20, the chafer 21 and the inner liner 22 are, for example, formed of a known rubber material.

[0064] Figure 4 1 is a cross-sectional view schematically showing a method for manufacturing a tire 1. Figure 4 As shown, the manufacturing method of the tire 1 of this embodiment includes: a step S1 of folding the folded portion 10 around the bead core 5 (as shown in FIG. Figure 4 and pasting the second apex adhesive 13 on the outer side of the folding portion 10 in step S2 (as shown in FIG. Figure 4 Since the other steps except the folding step S1 and the pasting step S2 adopt well-known steps, the description thereof will be omitted.

[0065] like Figure 4 As shown in (a), in the folding process S1, for example, the spacer rubber 12, the bead core 5 and the first apex rubber 11 are arranged outside the first carcass layer 8A and the second carcass layer 8B wound on the outer peripheral surface 25a of the cylindrical drum 25. And the folding portion 10 is folded around the bead core 5 by a known folding device (not shown). The spacer rubber 12 is formed into a sheet with a uniform thickness, for example.

[0066] Next, the pasting step S2 is performed. Figure 4 As shown in (b) of FIG. 1 , in the attaching step S2 of the present embodiment, the second apex rubber 13 formed in a sheet shape with a uniform thickness is wound around the outside of the folded portion 10. In this way, the tire 1 is manufactured.

[0067] As mentioned above, although the particularly preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, and can be implemented in various modified forms.

[0068] [Example]

[0069] Based on the specifications in Table 1 and Table 2, we have produced Figure 1 The pneumatic tires for light trucks with a basic structure of 205 / 85R16 were tested for durability, handling stability, rolling resistance, and appearance. The common specifications and test methods of the tires are shown below.

[0070] Rim: 18×5.0J

[0071] t2: 0.8mm

[0072] Complex elastic modulus E*c of the second apex: 30MPa

[0073] The inner end position of the spacer rubber "A" means the inner side in the tire radial direction than the outer end of the first apex rubber, and "B" means the outer side in the tire radial direction than the outer end of the first apex rubber.

[0074] <Durability>

[0075] The test tire was run on a drum under the following conditions, and the running distance until it broke was measured. The results were expressed as an index with Comparative Example 1 being 100. The larger the value, the better.

[0076] Internal pressure: 290kPa

[0077] Load: 8.94kN

[0078] Speed: 100km / h

[0079] <Handling stability performance>

[0080] Each test tire was mounted on all wheels of a passenger car with a displacement of 1800cc under the following conditions. In addition, the test driver drove the test vehicle on a test course that was a circle course on a dry asphalt road surface, and evaluated the handling stability performance related to responsiveness, rigidity, grip, stability, and transient characteristics at this time through the test driver's senses. The results were expressed as a score with Comparative Example 1 being 100. The larger the value, the better.

[0081] Internal pressure: 260KPa

[0082] Speed: 40Km / h~100Km / h

[0083] <Rolling resistance performance>

[0084] The rolling resistance of the test tire was measured under the following conditions using a rolling resistance tester. The results are expressed as an index with Comparative Example 1 being 100. The smaller the value, the better.

[0085] Internal pressure: 260kPa

[0086] Load: 5.26kN

[0087] Speed: 80km / h

[0088] <Appearance and performance>

[0089] The appearance of the sidewall of the test tire was evaluated by the visual inspection of the tester. The results were expressed as a score with Comparative Example 1 being 100. The larger the value, the fewer defects and the better the appearance performance.

[0090] The test results are shown in Table 1 and Table 2.

[0091]

Table 1

[0092]

[0093]

Table 2

[0094]

[0095] The test results show that the durability of the tires of the embodiment is improved compared with the tires of the comparative example. In addition, it is known that the appearance of the tires of the embodiment is improved compared with the tires of the comparative example.

Claims

1. A pneumatic tire, comprising: a pair of bead portions, each of which has a bead core embedded therein; and a carcass spanning between the pair of bead portions, The carcass includes a carcass ply, which includes: a main body portion extending between the bead cores; and a folded portion folded around each of the bead cores from the inner side to the outer side in the tire axial direction and extending to the outer side in the tire radial direction. The carcass ply layer comprises carcass cords and a topping covering the carcass cords. The bead portion is provided with: a first apex rubber extending radially outward from the bead core between the main body of the carcass ply and the folded portion; an insulating rubber extending radially outward from the main body and the folded portion between the inner end located between the first apex rubber and the main body; and a second apex rubber disposed axially outward of the folded portion of the carcass ply, The outer end of the spacer rubber in the tire radial direction is located closer to the outer side in the tire radial direction than the outer end of the second apex rubber in the tire radial direction. The complex elastic modulus E*a of the isolation rubber is greater than the complex elastic modulus E*b of the covering rubber, The carcass ply includes a first ply and a second ply adjacent to the first ply on the outer side in the tire radial direction. The tread portion includes a belt layer arranged on the outer side of the carcass in the tire radial direction. The outer ends of the folded portions of the first carcass layer and the second carcass layer in the tire radial direction are sandwiched between the main body portion and the belt layer. The second apex has an inner end in the tire radial direction and is configured to contact the folded portion of the first carcass layer from the outer end to the inner end of the second apex. The thickness of the second apex is a uniform thickness of 1.0 mm to 2.0 mm. The distance between the outer end of the isolation rubber and the tire bead base line in the tire radial direction is 75% to 90% of the tire cross-sectional height.

2. The pneumatic tire according to claim 1, wherein: The complex elastic modulus E*a of the isolation rubber is smaller than the complex elastic modulus E*c of the second apex rubber.

3. The pneumatic tire according to claim 1 or 2, wherein: The outer end of the second apex rubber in the tire radial direction is located in the range of 30% to 55% of the tire cross-sectional height from the bead base line toward the outer side in the tire radial direction.

4. The pneumatic tire according to claim 1 or 2, wherein: The inner end of the second apex rubber in the tire radial direction is located in the range of 2% to 18% of the tire cross-sectional height from the bead base line toward the outer side in the tire radial direction.

5. The pneumatic tire according to claim 1 or 2, wherein: The thickness of the isolation rubber is 0.8 mm to 2.3 mm.

6. The pneumatic tire according to claim 1 or 2, wherein: The inner end of the spacer rubber is located radially inward of the tire relative to the outer end of the first apex rubber in the tire radial direction.

7. The pneumatic tire according to claim 1 or 2, wherein: The length of the first apex rubber in the tire radial direction is 18 mm to 23 mm.

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