Pneumatic tire and method of manufacturing the same

Abstract

Provided is a pneumatic tire having the structure where a carcass ply is wound around bead cores from the outside in the tire width direction to the inside in the tire width direction, and both end portions of an inner liner extend between beads and the carcass ply. A lightweight and highly rigid tire can be acquired. The tire can also enhance steering stability performance thereof. The pneumatic tire includes: a pair of left and right beads including bead cores 3a; a carcass ply extending between the bead cores; and an inner liner 4 disposed on an inner peripheral side of the carcass ply 5, wherein the carcass ply 5 is wound around the bead cores 3a from the outside in the tire width direction to the inside in the tire width direction, and both end portions of the inner liner 4 extend between the beads and the carcass ply.

Claims

1. A pneumatic tire comprising: a pair of left and right beads including bead cores; a carcass ply extending between the bead cores; and an inner liner disposed on an inner peripheral side of the carcass ply, wherein the carcass ply is wound around the bead cores from the outside in the tire width direction to the inside in the tire width direction, and both end portions of the inner liner extend between the beads and the carcass ply respectively.

2. The pneumatic tire according to claim 1, wherein a winding height of the carcass ply is 55% or less of a tire cross-section height taken upwardly in the perpendicular direction from a nominal diameter.

3. The pneumatic tire according to claim 1, wherein the inner liner is wound around the bead cores from the inside in the tire width direction to the outside in the tire width direction.

4. The pneumatic tire according to claim 2, wherein a winding height of the inner liner is 5% or less of the tire cross-section height taken upwardly in the perpendicular direction from the nominal diameter.

5. The pneumatic tire according to claim 1, wherein a rubber chafer is disposed around the bead cores.

6. The pneumatic tire according to claim 5, wherein the rubber chafers are disposed so as to cover at least wound end portions of the carcass ply.

7. The pneumatic tire according to claim 5, wherein adhesion-reinforcing rubber layers for adhering the rubber chafers are provided to portions of the inner liner, and a 300% modulus value of the adhesion-reinforcing rubber layer is higher than a 300% modulus value of the inner liner and is lower than a 300% modulus value of the rubber chafer.

8. The pneumatic tire according to claim 7, wherein the 300% modulus value of the adhesion-reinforcing rubber layer falls within a range of from 4.1 MPa to 6.1 MPa, and the 300% modulus value of the inner liner falls within a range of from 3.0 MPa to 4.0 MPa.

9. The pneumatic tire according to claim 7, wherein the adhesion-reinforcing rubber layer is disposed within a range of 5% to 55% of a vertical height from a lower end of the bead to an upper end of the tire tread surface as counted from the lower end.

10. The pneumatic tire according to claim 7, wherein an upper end of the adhesion-reinforcing rubber layer is covered by the rubber chafer.

11. The pneumatic tire according to claim 5, wherein the rubber chafer has a low modulus layer and a high modulus layer which differ from each other in a 300% modulus value, and the low modulus layer is disposed at least at a position where the rubber chafer is brought into contact with the inner liner.

12. The pneumatic tire according to claim 11, wherein a 300% modulus value of the low modulus layer falls within a range of from 3.5 MPa to 8.0 MPa, and is more than or equal to the 300% modulus value of the inner liner.

13. The pneumatic tire according to claim 11, wherein the low modulus layer of the rubber chafer disposed on an outer surface side of the rubber chafer extends to a bead toe from an upper end portion of the rubber chafer on a tire inner surface side.

14. A method of manufacturing a pneumatic tire comprising the steps of: laminating an inner liner onto a building drum; placing a pair of beads including bead cores and bead fillers on the inner liner at equal distances with respect to the center of a tire width; winding both end portions of the inner liner around the beads to the outside in the tire width direction, and pressure-bonding the bead fillers to the inner liner; laminating a carcass ply to the bead fillers pressure-bonded to the inner liner; laminating side wall rubbers to the carcass ply; forming a green case by pressure-bonding the carcass ply and the side wall rubbers to wound portions of the inner liner, and by folding back both end portions of the carcass ply toward an inner peripheral side of the beads; and enlarging the green case, laminating a tread ring formed of a belt and a tread rubber to the green case and, thereafter, winding both end portions of the carcass ply around the beads to the inside in the tire width direction.

15. The method of manufacturing a pneumatic tire according to claim 14, further comprising the steps of: laminating the side wall rubbers to the carcass ply and laminating the rubber chafers to both end portions of the carcass ply; forming a green case by pressure-bonding the carcass ply and the side wall rubbers to the wound portions of the inner liner, and by folding back both end portions of the carcass ply toward an inner peripheral side of the beads together with the rubber chafers; enlarging the green case, laminating the tread ring formed of a belt and a tread rubber to the green case and, thereafter, winding both end portions of the carcass ply to the inside in the tire width direction of the beads together with the rubber chafers thus covering a winding portion of the carcass ply by the rubber chafers.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic partial cross-sectional view of a pneumatic tire according to an embodiment 1 of the present invention.

(2) FIG. 2 is a partially enlarged view of a bead shown in FIG. 1 and an area around the bead.

(3) FIG. 3 is a schematic view showing a step of a method of manufacturing the pneumatic tire of the present invention, and showing a state where an inner liner is laminated to a tire building drum.

(4) FIG. 4 is a schematic view showing a step of the method of manufacturing the pneumatic tire of the present invention, and showing a state where the bead is mounted on the inner liner.

(5) FIG. 5 is a schematic view showing a step of the method of manufacturing the pneumatic tire of the present invention, and showing a state where bead filler is pressure-bonded to the inner liner.

(6) FIG. 6 is a schematic view showing a step of the method of manufacturing the pneumatic tire of the present invention, and showing a state where a carcass ply is adhered to the inner liner.

(7) FIG. 7 is a schematic view showing a step of the method of manufacturing the pneumatic tire of the present invention, and showing a state where sidewall rubbers and rubber chafers are adhered to the carcass ply.

(8) FIG. 8 is a schematic view showing a step of the method of manufacturing the pneumatic tire of the present invention, and showing a state where both end portions of the carcass ply are folded to the inside of the beads.

(9) FIG. 9 is a schematic view showing a step of the method of manufacturing the pneumatic tire of the present invention, and showing a state where a tread ring is integrated on the carcass ply.

(10) FIG. 10 is a schematic view showing a step of the method of manufacturing the pneumatic tire of the present invention, and showing a state where both end portions of the carcass ply are wound to the inside of the bead.

(11) FIG. 11 is a schematic partial cross-sectional view of a pneumatic tire according to an embodiment 2 of the present invention.

(12) FIG. 12 is a partially enlarged view of the pneumatic tire shown in FIG. 11.

(13) FIG. 13 is a schematic partial cross-sectional view of a pneumatic tire according to an embodiment 5 of the present invention.

(14) FIG. 14 is a partially enlarged view of the pneumatic tire shown in FIG. 13.

(15) FIG. 15 is a partially enlarged view of a pneumatic tire according to an embodiment 6 of the present invention.

(16) FIG. 16 is a partially enlarged view of a pneumatic tire according to an embodiment 7 of the present invention.

(17) FIG. 17 is a partially enlarged view of a pneumatic tire according to a comparison example 3 of the present invention.

(18) FIG. 18 is a partially enlarged view of a pneumatic tire according to a comparison example 4 of the present invention.

(19) FIG. 19 is a partially enlarged view of a pneumatic tire according to a comparison example 5 of the present invention.

DESCRIPTION OF EMBODIMENTS

(20) A pneumatic tire according to the present invention has the structure where a carcass ply is wound around bead cores from the outside in the tire width direction to the inside in the tire width direction, and both end portions of the inner liner extend between the bead and the carcass ply.

(21) Hereinafter, preferred embodiments according to the present invention are explained in detail by reference to drawings.

Embodiment 1

(22) FIG. 1 and FIG. 2 show an embodiment 1. Symbol T in the drawings indicates a pneumatic tire. The pneumatic tire T includes a tire tread 1, sidewalls 2 and beads 3. The tire tread 1 includes a belt, a belt reinforcement 1a and a tread rubber 1b. The bead 3 includes: a bead core 3a; and a bead filler 3b made of hard rubber which extends outward in the tire radial direction from the bead core 3a.

(23) Symbol 4 indicates an inner liner disposed on a tire inner surface. Both end portions of the inner liner 4 extend between the bead and the carcass ply. Although the constitution of both end portions of the inner liner 4 is not particularly limited, it is preferable in view of durability that both end portions of the inner liner 4 be wound around the bead cores 3a from the inside to the outside in the tire width direction.

(24) Symbol 5 indicates a carcass ply. The carcass ply 5 is arranged so as to extend between the bead cores 3a in a straddling manner over the tire tread 1, the sidewalls 2 and the beads 3. The carcass ply 5 is wound around the bead cores 3a from the outside in the tire width direction to the inside in the tire width direction.

(25) The inner liner 4 and the carcass ply 5 are arranged such that the inner liner 4 is arranged inside the carcass ply 5 around the bead cores 3a.

(26) Symbol 6 indicates rubber chafers. The rubber chafers 6 are arranged so as to cover the inner liners 4 and the carcass ply 5 around the bead cores 3a. To be more specific, the rubber chafers 6 are arranged such that an end portion of each rubber chafer 6 is terminated on the inner liner 4 so as to cover a portion of the bead 3 which is brought into contact with a rim when the rim is assembled onto the tire and, at the same time, to cover at least a wound end portion 5a of the carcass ply 5. Due to such a constitution, none of the followings: the inner liner 4; the carcass ply 5; end portions 4a of the inner liner 4 and the end portions 5a of the carcass ply 5 are exposed on surfaces of the beads 3.

(27) A height Hi of the position of the wound end portion 4a of the inner liner 4 is designed to 5% of a tire cross-section height H in the perpendicular direction from a nominal diameter, that is, to 5% of a distance from a lower end 3a of the bead 3 to a top portion 1 of the tire tread 1 disposed above the lower end 3a in the perpendicular direction in a state where the tire of the present invention is assembled onto the rim. When the winding height Hi of the inner liner 4 exceeds 5% of the tire cross-section height H, an increase in an undesired mass is brought about thus giving rise to a possibility that performances of the tire such as rolling resistance are adversely affected.

(28) A height Hp of the position of the wound end portion 5a of the carcass ply 5 is designed to 55% of the tire cross-section height H in the perpendicular direction from the nominal diameter. When the winding height Hp of the carcass ply 5 exceeds 55% of the tire-cross section height H, an increase in strain in the tire is brought about due to the deflection of the tire generated during the rotation of the tire thus giving rise to a possibility that durability of the tire is adversely affected.

(29) As described above, the pneumatic tire T according to this embodiment has the structure where the carcass ply 5 is wound from the outside to the inside in the tire width direction. Accordingly, the distribution of tension applied to the carcass ply 5 changes, particularly, tension applied to the carcass ply 5 in an area ranging from a shoulder region 1c of the tire tread 1 to a maximum width position 2a of the tire is increased so that the tire exhibits high rigidity in such an area. In the pneumatic tire T according to this embodiment, the inner liner 4 is arranged between the bead 3 and the carcass ply 5 so that the bead core 3a and the carcass ply 5 are not brought into direct contact with each other. Due to such a constitution, it is unnecessary to additionally arrange a particular buffer member for preventing breaking of the bead core or the carcass ply due to the direct contact and rubbing between the bead core and the carcass ply which may occur when the pneumatic tire T is brought into a high tension state. Accordingly, it is possible to prevent the breaking of the bead core or the carcass ply without increasing a weight of the tire.

(30) Next, a method of manufacturing the pneumatic tire T shown in the above-mentioned embodiment 1 is explained.

(31) Firstly, as shown in FIG. 3, an inner liner 14 is laminated to a tire building drum 20 which includes bead sets 20a and cores 20b. Then, as shown in FIG. 4, a pair of beads 13 each of which includes a bead core 13a and a bead filler 13b is placed on the inner liner 14 at an equal distance with respect to the center of the tire width. Next, as shown in FIG. 5, the inner liner 14 is enlarged and, at the same time, both end portions 14a of the inner liner 14 are wound to the outside of the beads 13. Then, the bead fillers 13b are inclined toward the center side of the tire width, and are pressure-bonded to the inner liner 14.

(32) Then, as shown in FIG. 6, a carcass ply 15 is laminated to the bead fillers 13b which are pressure-bonded to the inner liner 14. Next, as shown in FIG. 7, sidewall rubbers 17 and rubber chafers 18 are laminated to the carcass ply 15. Then, as shown in FIG. 8, the rubber chafers 18 are folded back to areas below the bead cores 13a respectively together with both end portions 15a of the carcass ply 15 while covering both end portions 14a of the inner liner 14 which are wound to the outside of the bead 13 by the carcass ply 15 and the rubber chafers 18 thus forming a green case. Due to such a constitution, both end portions 14a of the inner liner 14 which are wound to the outside of the bead 13 are positioned inside the carcass ply 15. The term green case indicates an intermediate product of an unvulcanized tire formed by laminating the inner liner, the beads, the carcass ply, the sidewall rubbers, and the rubber chafers.

(33) Next, as shown in FIG. 9, the green case is expanded using a usual method, and a tread ring 11 formed of a belt and a tread rubber is laminated to the inner liner 14 in the green case. Thereafter, as shown in FIG. 10, the rubber chafers 18 are wound and pressure-bonded to the inside of the beads 13 together with both end portions 15a of the carcass ply 15 using stitcher rolls 20c. Accordingly, both wound end portions 15a of the carcass ply 15 are covered by the rubber chafers 18 respectively.

(34) By performing the above-mentioned steps, the pneumatic tire T shown in the embodiment 1 is manufactured.

(35) [Comparison Test]

(36) Next, a comparison test is carried out with respect to the pneumatic tire according to the present invention under the following conditions. The comparison test is carried out by comparing the above-mentioned embodiment 1 and the following comparison example 1 and conventional example 1.

(37) Size of test tire: 195/65R15 91H

(38) Vehicle used for test: sedan-type vehicle car made in Japan with displacement of 1.8 L

Constitution of Comparison Example 1

(39) In summary, the pneumatic tire of the comparison example 1 has the structure where a carcass ply is wound around bead cores from the outside to the inside in the tire width direction, and an inner liner is wound from the inside to the outside in the tire width direction in a state where the inner liner is disposed on an outer side of the carcass ply in an overlapping manner. That is, the difference between the pneumatic tire T of the embodiment 1 and the pneumatic tire of the comparison example 1 lies in that the inner liner is positioned inside the carcass ply in the pneumatic tire T of the embodiment 1, while the inner liner is positioned outside the carcass ply in the pneumatic tire of the comparison example 1.

Constitution of Conventional Example 1

(40) In summary, the pneumatic tire of a conventional example 1 has the structure where a carcass ply is wound around bead cores from the inside to the outside in the tire width direction, and an inner liner is wound from the inside to the outside in the tire width direction in a state where the inner liner is disposed on an outer side of the carcass ply in an overlapping manner. That is, the difference between the pneumatic tire T of the embodiment 1 and the pneumatic tire of the conventional example 1 lies in that the inner liner is positioned inside the carcass ply, the inner liner is wound from the inside to the outside in the tire width direction, and the carcass ply is wound from the outside to the inside in the tire width direction in the pneumatic tire T of the embodiment 1, while the inner liner is positioned outside the carcass ply, and both inner liner and carcass ply are wound from the inside to the outside in the tire width direction in the pneumatic tire of the conventional example 1.

(41) TABLE-US-00001 TABLE 1 conventional comparison example 1 example 1 embodiment 1 weight reduction effect 100 95 100 durability 100 90 100 lateral rigidity 100 110 110 steering stability 100 102 105

(42) In Table 1, weight reduction effect is provided for evaluating weight reduction effects of the embodiment 1 and the comparison example 1. The weight reduction effect is evaluated in such a manner that tire masses of the tire of the conventional example 1, the tire of the embodiment 1 and the tire of the comparison example 1 are measured respectively, and the weight reduction effects of the embodiment 1 and the conventional example 1 are evaluated respectively by indexes with the measurement result of the conventional example 1 taken as an index of 100. In weight reduction effect, the larger the index, the higher the weight reduction effect becomes.

(43) In Table 1, durability is provided for evaluating durability of the embodiment 1 and the durability of the comparison example 1. The durability is evaluated in such a manner that a traveling distance that a vehicle travels until a tire failure occurs is measured with respect to the tire of the embodiment 1, the tire of the comparison example 1 and the tire of the conventional example 1 using a test method in accordance with FMVSS139, and the durability of the embodiment 1 and the durability of the comparison example 1 are evaluated by indexes with the measurement result of the conventional example 1 taken as an index of 100. With durability, the larger the index, the higher the durability becomes.

(44) In Table 1, lateral rigidity is provided for evaluating lateral rigidity of the embodiment 1 and the comparison example 1. The lateral rigidity is evaluated as follows. In a state where a reference load value (4.2 kN) is applied to a tire using a compression testing machine, a force in the lateral direction which is 30% of the reference load is further applied to the tire. In such a state, an amount of lateral deflection is measured with respect to the tire of the embodiment 1, the tire of the comparison example 1 and the tire of the conventional example 1. Then, lateral rigidity is measured by dividing the force in the lateral direction by a measurement value of the amount of lateral deflection. The lateral rigidity of the embodiment 1 and the lateral rigidity of the comparison example 1 are evaluated by indexes with the measurement result of the conventional example 1 taken as an index of 100. With lateral rigidity, the larger the index, the higher the lateral rigidity becomes.

(45) In Table, steering stability is provided for evaluating steering stability of the embodiment 1 and the steering stability of the comparison example 1. The steering stability is evaluated in such a manner that a vehicle used for the test is subjected to actual vehicle traveling at a speed of 100 km/h on a dry road, and a driver performs a function evaluation with respect to the steering stability. The steering stability of the embodiment 1 and the steering stability of the comparison example 1 are evaluated by indexes with the function evaluation of the conventional example 1 taken as an index of 100. With steering stability, the larger the index, the higher the steering stability becomes.

(46) [Results of Comparison Tests]

(47) With respect to the weight reduction effect, the result is obtained that the pneumatic tire of the comparison example 1 is inferior to the pneumatic tire of the embodiment 1. From this result, it is found that the constitution where the inner liner is positioned inside the carcass ply enhances the weight reduction effect.

(48) With respect to durability, the result is obtained that the pneumatic tire of the comparison example 1 is inferior to the pneumatic tire of the embodiment 1. From this result, it is found that the constitution where the inner liner is positioned inside the carcass ply enhances durability.

(49) With respect to lateral rigidity, the result is obtained that the pneumatic tire of the embodiment 1 is substantially equal to the pneumatic tire of the comparison example 1, and is superior to the pneumatic tire of the conventional example 1. From this result, it is found that the constitution where the carcass ply is wound from the outside to the inside in the tire width direction enhances lateral rigidity.

(50) With respect to steering stability, the result is obtained that the pneumatic tire of the comparison example 1 is superior to the pneumatic tire of the conventional example 1, and the pneumatic tire of the embodiment 1 is superior to the pneumatic tire of the comparison example 1. From this result, it is found that the constitution where the carcass ply is wound from the outside to the inside in the tire width direction enhances the steering stability, and the constitution where the inner liner is positioned inside the carcass ply further enhances the steering stability.

(51) From the above-mentioned test results, it is found that the constitution where the carcass ply is wound from the outside to the inside in the tire width direction, and the inner liner is positioned inside the carcass ply enhances all of the weight reduction effect, the durability and the steering stability.

Embodiment 2

(52) FIG. 11 and FIG. 12 show an embodiment 2. Symbol T in the drawings indicates a pneumatic tire. The pneumatic tire T includes a tire tread 1, sidewalls 2 and beads 3. The tire tread 1 includes a belt, a belt reinforcement 1a and a tread rubber 1b. The bead 3 includes a bead core 3a and a bead filler 3b which is made of hard rubber and extends outward in the tire radial direction from the bead core 3a.

(53) Symbol 4 indicates an inner liner disposed on a tire inner surface. The inner liner 4 is wound around the bead cores 3a from the inside in the tire width direction to the outside in the tire width direction. Symbol 5 indicates a carcass ply. The carcass ply 5 is arranged so as to extend between the bead cores 3a in a straddling manner over the tire tread 1, the sidewalls 2 and the beads 3. The carcass ply 5 is wound around the bead cores 3a from the outside in the tire width direction to the inside in the tire width direction. The inner liner 4 and the carcass ply 5 are arranged such that the inner liner 4 is disposed inside the carcass ply 5 around the bead cores 3a.

(54) Symbol 6 indicates a rubber chafer. The rubber chafer 6 is arranged so as to cover the inner liner 4 and the carcass ply 5 around the bead cores 3a. Due to such a constitution, none of the followings: the inner liner 4; the carcass ply 5; end portions 4a of the inner liner 4 and end portions 5a of the carcass ply 5 are exposed on surfaces of the beads 3.

(55) In the inner liner 4, an adhesion-reinforcing rubber layer 7 is provided to a portion of an inner side in the tire width direction, and an upper end 7 of the adhesion-reinforcing rubber layer 7 is covered by the rubber chafer 6. That is, assuming a vertical height from a lower end 3a of the bead to an upper end 6 of the rubber chafer 6 as HRCH and a height from the lower end 3a of the bead to the upper end 7 of the adhesion-reinforcing rubber layer 7 as HA, a value of HRCH is set larger than a value of HA. On the other hand, when HA is set larger than HRCH, air permeability is deteriorated so that there exists a possibility that air will leak and, at the same time, the durability is lowered.

(56) Assuming that a vertical height from the lower end 3a of the bead to an upper end 1 of a tire tread surface as H, a height of the adhesion-reinforcing rubber layer 7 in the inner liner 4 occupies a value which falls within a range A of from 20% to 33% of the vertical height H. It is preferable that the adhesion-reinforcing rubber layer 7 occupy a value which falls within a range of from 5% to 55% of the vertical height H (5 to 25 mm in terms of a length) as measured from the lower end in the vertical height H. When the lower end of the adhesion-reinforcing rubber layer 7 is disposed at a position which is less than 5% of the vertical height H or when the upper end of the adhesion-reinforcing rubber layer 7 is disposed at a position which exceeds 55% of the vertical height H, the durability is lowered. When a length of the adhesion-reinforcing rubber layer 7 is less than 5 mm, sufficient adhesiveness cannot be acquired. On the other hand, when the length of the adhesion-reinforcing rubber layer 7 exceeds 25 mm, air permeability is deteriorated thus giving rise to a possibility that air will leak.

(57) In this embodiment, a 300% modulus value of the rubber chafer 6 is 10.0 MPa, a 300% modulus value of the inner liner 4 is 3.0 MPa, and a 300% modulus value of the adhesion-reinforcing rubber layer 7 is 4.2 MPa which is a value falling within a range between the 300% modulus value of the rubber chafer 6 and the 300% modulus value of the inner liner 4. By setting the 300% modulus values as described above, adhesiveness between the adhesion-reinforcing rubber layer 7 and the rubber chafer 6 is increased. It is preferable that a 300% modulus value of the adhesion-reinforcing rubber layer be set to a value which falls within a range of from 4.1 MPa to 6.1 MPa, a 300% modulus value of the inner liner be set to a value which falls within a range of from 3.0 MPa to 4.0 MPa, and a 300% modulus value of the rubber chafer be set to a value less than or equal to 14 MPa. With respect to hardness in accordance with JIS K 6253, it is preferable that hardness of the adhesion-reinforcing rubber layer be set to a value which falls within a range of from 56 to 65, hardness of the inner liner be set to a value which falls within a range of from 50 to 55, and hardness of the rubber chafer 6 be set to a value which falls within a range of from 66 to 70.

(58) Due to the above-mentioned constitution, this embodiment can increase adhesiveness and hence, durability is enhanced. Air permeability is also increased and hence, air does not leak.

(59) [Comparison Test]

(60) Next, a comparison test is carried out with respect to the pneumatic tire according to the present invention under the following conditions. The comparison test is carried out by comparing the following conventional example 2, the above-mentioned embodiment 2, the following embodiment 3, an embodiment 4 and a comparison example 2.

(61) Test tire: 195/65R15 91H

(62) Test Items

(63) To evaluate air permeability resistance, tires are assembled on rims of 156 J, the tires are filled with air until an inner pressure becomes 240 kPa, and the tires are left for 6 months in an environment where a temperature is 23 C. and a pressure is 1 atmospheric pressure. Thereafter, a lowering amount of the inner pressure is measured. The air permeability resistances of the embodiment 2, the embodiment 3, the embodiment 4 and the conventional example 2 are evaluated by indexes with an evaluation of the comparison example 2 taken as an index of 100. With air permeability resistance, the larger the index, the higher the air permeability resistance becomes.

(64) To evaluate the durability a traveling distance that a vehicle travels until a tire failure occurs is measured using a test method in accordance with FMVSS139. The durability of the tires are evaluated by indexes with the result of the conventional example 2 taken as an index of 100. With durability, the larger the index, the higher the durability becomes.

(65) In order to evaluate the lateral rigidity, in a state where a reference load value (4.2 kN) is applied to a tire using a compression testing machine, a force in the lateral direction which is 30% of the reference load is further applied to the tire, an amount of lateral deflection is measured, and the lateral rigidity is measured by dividing the force in the lateral direction by a measurement value of the amount of lateral deflection. The lateral rigidities are evaluated by indexes with the measurement result of the conventional example 2 taken as an index of 100. With lateral rigidity, the larger the index, the higher the lateral rigidity becomes.

Constitution of Conventional Example 2

(66) In summary, the structure of a pneumatic tire of the conventional example 2 is the general tire structure. That is, the pneumatic tire of the conventional example 2 has the structure where a carcass ply is wound around bead cores from the inside to the outside in the tire width direction, an inner liner is wound from the inside to the outside in the tire width direction in an overlapping manner on an outer side of the carcass ply, and the adhesion-reinforcing rubber layer is not provided.

Constitution of Comparison Example 2

(67) In summary, the pneumatic tire of the comparison example 2 has the structure where a carcass ply is wound around bead cores from the outside to the inside in the tire width direction, an inner liner is wound from the inside to the outside in the tire width direction in an overlapping manner on an outer side of the carcass ply. Further, in the structure of pneumatic tire of the comparison example 2, beads and the carcass ply are brought into direct contact with each other, rubber chafers and the inner liner are brought into direct contact with each other, and an adhesion-reinforcing rubber layer is not provided.

Constitution of Embodiment 2

(68) In summary, the pneumatic tire of the embodiment 2 has the structure where the carcass ply is wound from the outside to the inside in the tire width direction, and the adhesion-reinforcing rubber layers are covered by the rubber chafers.

Embodiment 3

Constitution of Embodiment 3

(69) A tire of the embodiment 3 has the substantially same structure as the tire of the embodiment 2, while a 300% modulus value of an adhesion-reinforcing rubber layer is set to 5.0 MPa.

Embodiment 4

Constitution of Embodiment 4

(70) A tire of the embodiment 4 has the substantially same structure as the tire of the embodiment 2, while a 300% modulus value of an adhesion-reinforcing rubber layer is set to 5.9 MPa.

(71) TABLE-US-00002 TABLE 2 conven- com- tional parison embodi- embodi- embodi- contents example 2 example 2 ment 2 ment 3 ment 4 covering ratio by 100% 100% 100% rubber chafer modulus value 3.0 3.0 3.5 3.5 3.5 of inner liner layer modulus value of 10.0 10.0 10.0 10.0 10.0 rubber chafer layer modulus value of 4.2 5.0 5.9 adhesion-reinforcing rubber layer air permeability 100 100 101 100 102 resistance durability 100 60 100 102 105 lateral rigidity 100 110 110 110 110 of tire
[Result of Comparison Test]

(72) The tire of the comparison example 2 has the structure where a carcass ply is wound around bead cores from the outside to the inside in the tire width direction, and the inner liner is wound from the inside to the outside in the tire width direction in an overlapping manner on an outer side of the carcass ply. Accordingly, the tire of the comparison example 2 exhibits excellent lateral rigidity. However, the tire of the comparison example 2 is not provided with the adhesion-reinforcing rubber layer and hence, the tire of the comparison example 2 exhibits low durability.

(73) The tire of the embodiment 2 has no problem with air permeability resistance. The embodiment 2 has the structure where the carcass ply is wound around bead cores from the outside to the inside in the tire width direction, and the inner liner is wound from the inside to the outside in the tire width direction and positioned inside of the carcass ply. Accordingly, the tire of the embodiment 2 exhibits excellent lateral rigidity. Further, the tire of the embodiment 2 is also provided with adhesion-reinforcing rubber layers and hence, durability of the tire of the embodiment 2 is enhanced compared with the durability of the tire of the comparison example 2. However, a 300% modulus value of the adhesion-reinforcing rubber layer is set to 4.2 MPa. Accordingly, the durability of the tire of the embodiment 2 is substantially equal to durability of the tire of the conventional example 2 having the general structure where the carcass ply is wound around bead cores from the inside to the outside in the tire width direction, and the inner liner is wound from the inside to the outside in the tire width direction in an overlapping manner on an outer side of the carcass ply.

(74) The tire of the embodiment 3 has no problem with air permeability resistance. In the same manner as the embodiment 2, the embodiment 3 has the structure where the carcass ply is wound around the bead cores from the outside to the inside in the tire width direction, and the inner liner is wound from the inside to the outside in the tire width direction and positioned inside of the carcass ply. Accordingly, the tire of the embodiment 3 exhibits excellent lateral rigidity. Further, a 300% modulus value of the adhesion-reinforcing rubber layer is set to 5.0 MPa and hence, the durability of the tire of the embodiment 3 is enhanced compared with the durability of the tire of the embodiment 2.

(75) The tire of the embodiment 4 has no problem with air permeability resistance. In the same manner as the embodiment 2, the embodiment 4 has the structure where the carcass ply is wound around the bead cores from the outside to the inside in the tire width direction, and the inner liner is wound from the inside to the outside in the tire width direction and positioned inside of the carcass ply. Accordingly, the tire of the embodiment 4 exhibits excellent lateral rigidity. Further, a 300% modulus value of the adhesion-reinforcing rubber layer is set to 5.9 MPa. and hence, the durability of the tire of the embodiment 4 is enhanced compared with the durability of the tire of the embodiment 3.

(76) From the above-mentioned test results, it is found that when the tire has the constitution where the carcass ply is wound from the outside to the inside in the tire width direction and the inner liner is positioned inside the carcass ply, and the adhesiveness between the inner liner and the rubber chafers is enhanced by providing the adhesion-reinforcing rubber layers having favorable adhesiveness to portions of the inner liner, the tire can enhance all of the air permeability resistance, the durability and the lateral rigidity.

Embodiment 5

(77) FIG. 13 and FIG. 14 show an embodiment 5. Symbol T in the drawings indicates a pneumatic tire. The pneumatic tire T includes a tire tread 1, sidewalls 2 and beads 3. The tire tread 1 includes a belt, a belt reinforcement 1a and a tread rubber 1b. The bead 3 includes a bead core 3a and a bead filler 3b made of hard rubber and extending outward in the tire radial direction from the bead core 3a.

(78) Symbol 4 indicates an inner liner disposed on a tire inner surface. The inner liner 4 is wound around the bead cores 3a from the inside in the tire width direction to the outside in the tire width direction. Symbol 5 indicates a carcass ply. The carcass ply 5 is arranged so as to extend between left and right bead cores 3a in a straddling manner over the tire tread 1, the sidewalls 2 and the beads 3. The carcass ply 5 is wound around the bead cores 3a from the outside in the tire width direction to the inside in the tire width direction. The inner liner 4 and the carcass ply 5 are arranged such that the inner liner 4 is disposed inside the carcass ply 5 around the bead cores 3a.

(79) Symbol 6 indicates a rubber chafer. The rubber chafers 6 are arranged so as to cover the inner liner 4 and the carcass ply 5 around the bead cores 3a. Due to such a constitution, none of the followings: the inner liner 4; the carcass ply 5; end portions 4a of the inner liner 4 and end portions 5a of the carcass ply 5 are exposed on surface of the beads 3.

(80) By setting a distance from an end portion of the carcass ply to an upper end of the rubber chafer such that at least the rubber chafer is arranged at a position where the rubber chafer is brought into contact with the inner liner, it is possible to acquire an adhesive effect between a low modulus layer of the rubber chafer and the inner liner.

(81) The position of the upper end of the rubber chafer is determined in accordance with a required performance and hence, the position is not particularly limited. However, in view of preventing the increase of a weight, it is preferable to set the position of the upper end of the rubber chafer at the position which is less than or equal to 55% of a length of a periphery from an end portion of a belt to an upper end portion of the carcass ply and/or at the position 10 mm away from the upper end portion of the carcass ply outwardly in the outer radial direction.

(82) The rubber chafer 6 includes the low modulus layer 6a and the high modulus layer 6b which differ from each other in a 300% modulus value. The low modulus layer 6a of the rubber chafer 6 covers the whole portion which is in contact with the inner liner 4 on the inside in the tire width direction from the outside in the tire radial direction to the end portion 5a of the carcass ply 5 which constitutes a terminal end. The high modulus layer 6b of the rubber chafer 6 covers all portions ranging from the end portion 5a of the carcass ply 5 which constitutes a start end to the outer portion of the bead 3 in the tire width direction by way of a bead toe 6c where the rubber chafer 6 is brought into contact with a rim.

(83) In this embodiment, a 300% modulus value of the low modulus layer 6a is set to 8 MPa, and a 300% modulus value of the high modulus layer 6b is set to 14 MPa. A 300% modulus value of the inner liner 4 is set to 3 MPa. The 300% modulus value of the low modulus layer 6a of the rubber chafer 6 is not limited to the above-mentioned modulus value. It is sufficient that the 300% modulus value of the low modulus layer 6a is higher than the 300% modulus value of the inner liner 4 and lower than the 300% modulus value of the high modulus layer 6b of the rubber chafer 6. The 300% modulus value of the low modulus layer 6a of the rubber chafer 6 is preferably set to a value which falls within a range of from 3.5 MPa to 8.0 Mpa (corresponding to hardness of 56 degrees to 65 degrees in accordance with JIS K 6253).

(84) The pneumatic tire T of this embodiment is configured as described above. Accordingly, the low modulus layer 6a of the rubber chafer 6 exhibits the higher adhesiveness to the inner liner 4 compared with the high modulus layer 6b of the rubber chafer 6. Accordingly, the adhesiveness between the rubber chafer 6 and the inner liner 4 which is brought into contact with the rubber chafer 6 is increased and hence, the durability is enhanced. Further, all portions ranging from the bead toe 6c where the rubber chafer 6 is brought into contact with the rim to the outer portion of the bead 3 in the tire width direction are covered with the high modulus layer 6b of the rubber chafer 6 and hence, a rim rubbing prevention function at the bead 3 is not lowered. From the above-mentioned results, the pneumatic tire of the embodiment 5 exhibits excellent steering stability.

Embodiment 6

(85) FIG. 15 shows the embodiment 6. In the same manner as the above-mentioned embodiment 5, a bead 23 of a pneumatic tire according to this embodiment includes a bead core 23a and a bead filler 23b made of hard rubber which extends outward in the tire radial direction from the bead core 23a. An inner liner 24 disposed on a tire inner surface is wound around the bead cores 23a from the inside in the tire width direction to the outside in the tire width direction. A carcass ply 25 is arranged so as to extend between the left and right bead cores 23a in a straddling manner over a tire tread, sidewalls 22 and beads 23. The carcass ply 25 is wound around the bead cores 23a from the outside in the tire width direction to the inside in the tire width direction. The inner liner 24 and the carcass ply 25 are arranged such that the inner liner 24 is disposed inside the carcass ply 25 around the bead cores 23a.

(86) Rubber chafers 26 are arranged so as to cover the inner liner 24 and the carcass ply 25 around the bead cores 23a. Due to such a constitution, none of the followings: the inner liner 24; the carcass ply 25; end portions 24a of the inner liner 24 and end portions 25a of the carcass ply 25 are exposed on surfaces of the beads 23.

(87) The rubber chafer 26 includes a low modulus layer 26a and a high modulus layer 26b which differ from each other in a 300% modulus value. The low modulus layer 26a of the rubber chafer 26 is disposed on a tire inner surface from the outside in the tire radial direction and at the inside of the tire width direction which terminates at a bead toe 26c, and covers the whole portion which is in contact with the inner liner 24. The high modulus layer 26b of the rubber chafer 26 covers all portions of the outer portion of the bead 23 in the tire width direction ranging from a bead toe 26c which constitutes a start end.

(88) In this embodiment, a 300% modulus value of the low modulus layer 26a is set to 5 MPa, and a 300% modulus value of the high modulus layer 26b is set to 14 MPa. A 300% modulus value of the inner liner 24 is set to 3 MPa. The 300% modulus value of the low modulus layer 26a of the rubber chafer 26 is not limited to the above-mentioned modulus value. It is sufficient that the 300% modulus value of the low modulus layer 26a be higher than the 300% modulus value of the inner liner 24 and lower than the 300% modulus value of the high modulus layer 26b of the rubber chafer 26. The 300% modulus value of the low modulus layer 26a of the rubber chafer 26 is preferably set to a value which falls within a range of from 3.5 MPa to 8.0 Mpa.

(89) The pneumatic tire of this embodiment is configured as described above. The low modulus layer 26a of the rubber chafer 26 exhibits higher adhesiveness to the inner liner 24 compared with the high modulus layer 26b of the rubber chafer 26. Accordingly, adhesiveness between the rubber chafer 26 and the inner liner 24 which is brought into contact with the rubber chafer 26 is increased and hence, the durability is enhanced. Further, all portions of the bead ranging from the bead toe 26c where the rubber chafer 26 is brought into contact with a rim to a portion of the bead outside in the tire width direction are covered with the high modulus layer 26b of the rubber chafer 26 and hence, a rim rubbing prevention function is not lowered. From the above-mentioned results, the pneumatic tire of the embodiment 6 exhibits excellent steering stability.

Embodiment 7

(90) FIG. 16 shows an embodiment 7. In the same manner as the above-mentioned embodiment 5, a bead 33 of a pneumatic tire according to this embodiment includes a bead core 33a and a bead filer 33b made of hard rubber which extends outward in the tire radial direction from the bead core 33a. An inner liner 34 disposed on a tire inner surface is wound around the bead cores 33a from the inside in the tire width direction to the outside in the tire width direction. A carcass ply 35 is arranged so as to extend between the left and right bead cores 33a in a straddling manner over a tire tread, sidewalls 32 and beads 33. The carcass ply 35 is wound around the bead cores 33a from the outside in the tire width direction to the inside in the tire width direction. The inner liner 34 and the carcass ply 35 are arranged such that the inner liner 34 is disposed inside the carcass ply 35 around the bead cores 33a.

(91) Rubber chafers 36 are arranged so as to cover the inner liner 34 and the carcass ply 35 around the bead cores 33a. Due to such a constitution, none of the followings: the inner liner 34, the carcass ply 35, end portions 34a of the inner liner 34 and end portions 35a of the carcass ply 35 are exposed on surfaces of the beads 33.

(92) The rubber chafer 36 includes a low modulus layer 36a and a high modulus layer 36b which differ from each other in a 300% modulus value. The low modulus layer 36a of the rubber chafer 36 is disposed only on an inner side of the rubber chafer 36 in the thickness direction of the rubber chafer 36. That is, in the rubber chafer 36 which extends from the inside in the tire width direction and covers the outside in the tire width direction by way of a bead toe 36c, the low modulus layer 36a is in contact with the inner liner 34 and the carcass ply 35, and the high modulus layer 36b of the rubber chafer 36 is exposed on an outer surface of the rubber chafer 36.

(93) In this embodiment, a 300% modulus value of the low modulus layer 36a is set to 3.5 MPa, and a 300% modulus value of the high modulus layer 36b is set to 14 MPa. A 300% modulus value of the inner liner 34 is set to 3 MPa. The 300% modulus value of the low modulus layer 36a of the rubber chafer 36 is not limited to the above-mentioned modulus value. It is sufficient that the 300% modulus value of the low modulus layer 36a be higher than the 300% modulus value of the inner liner 34 and lower than the 300% modulus value of the high modulus layer 36b of the rubber chafer 36. The 300% modulus value of the low modulus layer 36a of the rubber chafer 36 is preferably set to a value which falls within a range of from 3.5 MPa to 8.0 Mpa.

(94) The pneumatic tire of this embodiment is configured as described above. The low modulus layer 36a of the rubber chafer 36 exhibits higher adhesiveness to the inner liner 34 compared with the high modulus layer 36b of the rubber chafer 36. Accordingly, adhesiveness between the rubber chafer 36 and the inner liner 34 which is brought into contact with the rubber chafer 36 is increased so that the durability is enhanced. Further, all portions ranging from the bead toe 36c where the rubber chafer 36 is brought into contact with the rim to the portion of the bead 36 outside in the tire width direction are covered with the high modulus layer 36b of the rubber chafer 36 and hence, a rim rubbing prevention function is not lowered. From the above-mentioned results, the pneumatic tire of the embodiment 7 exhibits excellent steering stability.

(95) [Comparison Test]

(96) Next, a comparison test is carried out with respect to the pneumatic tire according to the present invention under the following conditions. The comparison test is carried out by comparing the following conventional example 3, the above-mentioned embodiments 5 to 7, and the following comparison examples 3 to 5.

(97) Test Item

(98) Test tire: 195/65R15 91H

(99) Vehicle used for test: sedan-type vehicle car made in Japan with displacement of 1.8 L

(100) To evaluate a rim rubbing prevention function, a time until the internal structure is exposed is measured using a drum durability testing machine under the conditions where an air pressure is 180 kPa, a load is 6 kN, and a speed is 80 km/h. The rim rubbing prevention functions are evaluated by indexes with the result of the conventional example 3 taken as an index of 100. The larger the index, the higher the rim rubbing prevention function becomes.

(101) To evaluate the durability, a traveling distance that a vehicle travels until a tire failure occurs is measured in accordance with FMVSS139. The durabilities are evaluated by indexes with the result of the conventional example 3 taken as an index of 100. The larger the index, the higher the durability becomes.

(102) To evaluate steering stability, a vehicle used for the test is subjected to actual vehicle traveling at a speed of 100 km/h on a dry road, and a driver performs a function evaluation with respect to the steering stability. The steering stabilities are evaluated by indexes with the evaluation of the conventional example 3 taken as an index of 100. The larger the index, the higher the steering stability becomes.

Constitution of Conventional Example 3

(103) Although not shown in the drawing, in summary, the structure of a pneumatic tire of the conventional example 3 is the general tire structure. That is, the pneumatic tire of a conventional example 3 has the structure where a carcass ply is wound around bead cores from the inside to the outside in the tire width direction, and an inner liner is wound from the inside to the outside in the tire width direction in an overlapping manner on an outer side of the carcass ply. A rubber chafer does not include a low modulus layer, and includes only a high modulus layer whose 300% modulus value is 14 MPa.

Constitution of Comparison Example 3

(104) As shown in FIG. 17, in summary, the structure of a pneumatic tire of the comparison example 3 is as follows. At beads 103, a carcass ply 105 is wound around bead cores 103a from the outside in the tire width direction to the inside in the tire width direction, an inner liner 104 is wound around the bead cores 103a from the inside in the tire width direction to the outside in the tire width direction such that both end port ions of the inner liner 104 extend between the beads 103 and the carcass ply 105, and rubber chafers 106 are disposed around the bead cores 103a. In such a pneumatic tire of the comparison example 3, the rubber chafer 106 does not include a low modulus layer, and includes only a high modulus layer 106b whose 300% modulus value is 14 MPa. That is, the high modulus layer 106b whose 300% modulus value is 14 MPa is in contact with the inner liner 104.

Constitution of Comparison Example 4

(105) As shown in FIG. 18, in summary, the structure of a pneumatic tire of a comparison example 4 is as follows. At beads 203, a carcass ply 205 is wound around bead cores 203a from the outside in the tire width direction to the inside in the tire width direction, an inner liner 204 is wound around the bead cores 203a from the inside in the tire width direction to the outside in the tire width direction such that both end portions of the inner liner 204 extend between the beads 203 and the carcass ply 205, and rubber chafers 206 are disposed around the bead cores 203a. In such a pneumatic tire of the comparison example 4, the rubber chafer 206 is formed as follows. A low modulus layer 206a whose 300% modulus value is 5 MPa is disposed only in an area in the vicinity of a lower center portion of the bead such that the low modulus layer 206a is in contact with a bottom surface of the carcass ply 205. A high modulus layer 206b whose 300% modulus value is 14 MPa is disposed at portions of the carcass ply 205 other than the area in the vicinity of a lower center portion of the bead including the whole surface of the bead. That is, the high modulus layer 206b whose 300% modulus value is 14 MPa is in contact with the inner liner 204.

Constitution of Comparison Example 5

(106) As shown in FIG. 19, in summary, the structure of a pneumatic tire of a comparison example 5 is as follows. At heads 303, a carcass ply 305 is wound around bead cores 303a from the outside in the tire width direction to the inside in the tire width direction, an inner liner 304 is wound around the bead cores 303a from the inside in the tire width direction to the outside in the tire width direction such that both end portions of the inner liner 304 extend between the beads 303 and the carcass ply 305, and rubber chafers 306 are disposed around the bead cores 303a. In such a pneumatic tire of the comparison example 5, the rubber chafer 306 is formed as follows. A low modulus layer 306a whose 300% modulus value is 5 MPa is disposed in a region ranging from an area in the vicinity of a lower center portion of the bead which is on a center portion of a bottom surface of the carcass ply 305a to the outside in the tire width direction, and a high modulus layer 306b whose 300% modulus value is 14 MPa is disposed in region ranging from the area in the vicinity of the lower center portion of the bead which is on the center portion of the bottom surface of the carcass ply 305 to the inside in the tire width direction. That is, the high modulus layer 306b whose 300% modulus value is 14 MPa is in contact with the inner liner 304.

(107) TABLE-US-00003 TABLE 3 conventional example 3 comparison comparison comparison Content general structure example 3 example 4 example 5 embodiment 5 embodiment 6 embodiment 7 arrangement of low only center only tire portion which from the inside only inside modulus layer (A outer side is in contact in tire width in thickness layer) of with inner direction to direction rubber chafer liner layer bead toe arrangement of high all all all (a portion only tire all other from the outside only outside modulus layer of of the center inner side than A in tire width in thickness rubber chafer being A layer) layer direction to direction bead toe modulus value of 3 3 3 3 3 3 3 inner liner modulus value of 5 5 8 5 3.5 low modulus layer modulus value of 14 14 14 14 14 14 14 high modulus layer rim rubbing 100 100 100 68 100 100 100 prevention function durability 100 75 75 75 105 103 100 steering stability 100 107 105 103 107 105 105
[Results of Comparison Test]

(108) In the pneumatic tires of the comparison examples 3 to 5, the high modulus layer whose 300% modulus value is 14 MPa is in contact with the inner liner and hence, compared with the pneumatic tires of the conventional examples having the general structure, the durability is lowered.

(109) In the pneumatic tire of the comparison example 5, the low modulus layer 306a whose 300% modulus value is 5 MPa is disposed in the region ranging from the area in the vicinity of the lower center portion of the bead on the center portion of the bottom surface of the carcass ply 305 which is in contact with the rim to the outside in the tire width direction and hence, a rim rubbing prevention function is largely lowered.

(110) With respect to the steering stability, in all of the embodiments 5 to 7 and the comparison examples 3 to 5, at beads, the carcass ply is wound around the bead cores from the outside in the tire width direction to the inside in the tire width direction, the inner liner is wound around the bead cores from the inside in the tire width direction to the outside in the tire width direction such that both end portions of the inner liner extend between the beads and the carcass ply, and the rubber chafers are disposed around the bead cores. Accordingly, all of the tires of the embodiments 5 to 7 and the comparison examples 3 to 5 exhibit favorable steering stability.

(111) From the above-mentioned test results, it is found that the pneumatic tire according to the present invention is configured such that the inner liner is in contact with the low modulus layers of the rubber chafers thus enhancing adhesiveness. Accordingly, the pneumatic tire according to the present invention exhibits excellent durability, a favorable rim rubbing prevention function and excellent steering stability.

(112) Although some embodiments of the present invention have been explained, these embodiments are provided as examples, and are not intended to limit the scope of the invention. These embodiments can be carried out in various modes, and various omissions, replacements or changes can be made thereto without departing from the gist of the invention. These embodiments and modifications of the embodiments are included in the scope and the gist of the invention and, in the same manner, are also included in the invention described in Claims and scopes equivalent thereto.

REFERENCE SIGNS LIST

(113) T: pneumatic tire 1: tire tread 1: top portion of tire tread 1a: belt and belt reinforcement 1b: tread rubber 1c: shoulder region 2: sidewall 2a: maximum width position of tire 3: bead 3a: bead core 3a: lower end of bead core 3b: bead filler 4: inner liner 4a: end portion of inner liner 5: carcass ply 5a: end portion of carcass ply 6: rubber chafer H: height in tire cross section (distance in tire radial direction from lower end of bead to top portion 1 of the tire tread 1 disposed above lower end of bead in perpendicular direction in a state where tire is assembled onto rim) Hi: height of wound inner liner (distance in tire radial direction from lower end of bead to wound upper end of inner liner in a state where tire is assembled onto rim) Hp: height of wound carcass ply (distance in tire radial direction from lower end of bead to wound upper end of carcass ply in a state where tire is assembled onto rim) 11: tread ring 13: bead 13a: bead core 13b: bead filler 14: inner liner 14a: both end portions of inner liner 15: carcass ply 15a: both end portions of carcass ply 17: sidewall rubber 18: rubber chafer 20: tire building drum 20a: bead set 20b: core 20c: stitcher roll 3a: lower end of bead 6: upper end of rubber chafer 7: adhesion-reinforcing rubber layer 7: upper end of adhesion-reinforcing rubber layer HRCH: vertical height from lower end of bead to upper end of rubber chafer HA: height from lower end of bead to upper end of adhesion-reinforcing rubber layer H: vertical height from lower end of bead to upper end of tire tread surface A: range of adhesion-reinforcing rubber layer in inner liner 6a: low modulus layer 6b: high modulus layer 6c: bead toe 22: sidewall 23: bead 23a: bead core 23b: bead filler 24: inner liner 24a: end portion of inner liner 25: carcass ply 25a: end portion of carcass ply 26: rubber chafer 26a: low modulus layer 26b: high modulus layer 26c: bead toe 32: sidewall 33: bead 33a: bead core 33b: bead filler 34: inner liner 34a: end portion of inner liner 35: carcass ply 35a: end portion of carcass ply 36: rubber chafer 36a: low modulus layer 36b: high modulus layer 36c: bead toe 103: bead 103a: bead core 104: inner liner 105: carcass ply 106: rubber chafer 106a: low modulus layer 106b: high modulus layer 203: bead 203a: bead core 204: inner liner 205: carcass ply 206: rubber chafer 206a: low modulus layer 206b: high modulus layer 303: bead 303a: bead core 304: inner liner 305: carcass ply 306: rubber chafer 306a: low modulus layer 306b: high modulus layer