Manufacturing method of pneumatic tire and pneumatic tire

Abstract

To provide a method for manufacturing a pneumatic tire capable of suppressing an occurrence of a recessed portion on a tire surface caused by a joint portion of a carcass ply, and the pneumatic tire.SOLUTION: A method for manufacturing a pneumatic tire includes a step for winding a carcass ply onto a molding drum to mold a carcass. The carcass has a joint portion at which ends of a carcass ply in a tire circumferential direction are overlapped to each other. The manufacturing method further includes a step for pasting a rubber tape that covers at least a part of the joint portion after winding the carcass ply. The rubber tape has a central portion pasted outside the joint portion and extending in the tire circumferential direction with a certain thickness, and tapered portions each extending in a tire circumferential direction as reducing thickness from both ends of the central portion in the tire circumferential direction and having a tip end with an angle of 45 degree or less.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a pneumatic tire and a pneumatic tire. [Background technology]

[0002] Conventionally, the carcass of a pneumatic tire is formed by overlapping and joining the circumferential ends of the carcass plies. The joints of such carcass plies have a higher tensile stiffness than the other parts, so that when the tire is deformed into a toroidal tire shape, the joints are less likely to stretch than the other parts, and a recess is likely to be formed on the tire surface corresponding to the joints. This recess remains in the pneumatic tire after vulcanization molding.

[0003] The following Patent Document 1 discloses a pneumatic tire in which the joints of the carcass plies are covered with a rubber tape in order to eliminate the unevenness of the sidewall caused by the joints. The rubber tape can eliminate the recesses that may occur on the tire surface, but since the cross-sectional shape is substantially rectangular, there is a risk that the ends of the rubber tape in the tire circumferential direction may instead generate protrusions on the tire surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-198314 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a manufacturing method for a pneumatic tire that can suppress the occurrence of recesses on the tire surface due to joints of carcass plies, and a pneumatic tire. [Means for solving the problem]

[0006] A method for manufacturing a pneumatic tire according to the present disclosure is a method for manufacturing a pneumatic tire, comprising a step of winding a carcass ply around a building drum to form a carcass, The carcass has a joint portion where end portions of the carcass plies in the tire circumferential direction are overlapped with each other, The manufacturing method further includes a step of attaching a rubber tape that covers at least a portion of the joint after winding the carcass ply, The rubber tape has a central portion that is attached to the outside of the joint and extends along the tire circumferential direction with a constant thickness, and a tapered portion that extends along the tire circumferential direction while reducing in thickness from both ends of the central portion in the tire circumferential direction and has a tip with an angle of 45 degrees or less.

[0007] The pneumatic tire of the present disclosure includes a carcass extending from a tread through a sidewall to a bead, The carcass has a joint portion where ends of the carcass plies in the tire circumferential direction are overlapped with each other, and a rubber tape that covers at least a part of the joint portion, The rubber tape has a central portion that is attached to the outside of the joint and extends along the tire circumferential direction with a constant thickness, and a tapered portion that extends along the tire circumferential direction while reducing in thickness from both ends of the central portion in the tire circumferential direction and has a tip with an angle of 45 degrees or less. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a main portion of a pneumatic tire according to an embodiment of the present invention taken along a tire meridian plane. [Diagram 2] FIG. 1 is a perspective view of a first carcass ply; [Diagram 3] FIG. 1 is a perspective view showing a state in which a first carcass ply is wound around a forming drum; [Figure 4] Enlarged cross-sectional view of the main part taken along line IV-IV in Figure 3. [Diagram 5] FIG. 1 is a cross-sectional view of a main portion of a pneumatic tire according to an embodiment of the present invention taken along a tire meridian plane. [Figure 6] FIG. 13 is an enlarged cross-sectional view of a main portion of a joint portion of a carcass ply according to another embodiment. [Figure 7] FIG. 13 is an enlarged cross-sectional view of a main portion of a joint portion of a carcass ply according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of a pneumatic tire and a manufacturing method thereof will be described with reference to Figures 1 to 5. Note that in each figure (as well as Figures 6 to 7), the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match either.

[0010] <Configuration of pneumatic tires> As shown in FIG. 1, the pneumatic tire 1 of this embodiment includes a pair of beads 11, 11 having a bead core 11a, a pair of sidewalls 12, 12 extending outward from each bead 11 in the tire radial direction D2, and a tread 13 connected to the outer ends of the pair of sidewalls 12, 12 in the tire radial direction D2.

[0011] In each drawing, the tire axial direction D1 is a direction parallel to the tire rotation axis which is the rotation center of the pneumatic tire 1, the tire radial direction D2 is a diameter direction of the pneumatic tire 1, and the tire circumferential direction D3 is a direction around the tire rotation axis. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and is located at the center of the tire axial direction D1 of the pneumatic tire 1, and the tire meridian plane is a plane including the tire rotation axis and perpendicular to the tire equatorial plane S1.

[0012] In the tire axial direction D1, the inner side means the side closer to the tire equatorial plane S1, and the outer side means the side farther from the tire equatorial plane S1. In the tire radial direction D2, the inner side means the side closer to the tire rotation axis, and the outer side means the side farther from the tire rotation axis.

[0013] The pneumatic tire 1 includes a carcass 14 that is bridged between a pair of bead cores 11a, 11a, and an inner liner 15 that is disposed inside the carcass 14 and has an excellent function of preventing gas permeation in order to maintain air pressure. The carcass 14 and the inner liner 15 are disposed along the inner circumference of the tire, spanning the beads 11, the sidewalls 12, and the tread 13.

[0014] The carcass 14 is composed of three carcass plies 21, 22, and 23. In the tread 13, the carcass plies 21, 22, and 23 are layered in this order from the inside to the outside in the tire radial direction D2. The first carcass ply 21 and the second carcass ply 22 are folded back around the bead core 11a so as to wrap around the bead core 11a. The third carcass ply 23 terminates on the outside of the bead core 11a in the tire axial direction D1. The carcass 14 is composed by joining the ends of the carcass plies 21, 22, and 23 in the tire circumferential direction D3 to each other.

[0015] 2 is a perspective view showing a part of the first carcass ply 21. The carcass 14 has a joint portion 14a where end portions in the tire circumferential direction D3 of the first carcass ply 21 are overlapped with each other. The carcass 14 also has a rubber tape 24 (details of which will be described later) that covers the joint portion 14a.

[0016] The first carcass ply 21 includes a plurality of carcass cords 211 (see FIG. 4) arranged in parallel in a direction substantially perpendicular to the tire circumferential direction D3, and a topping rubber 212 (see FIG. 4) covering the carcass cords 211.

[0017] The joint 14a where the first carcass ply 21 overlaps has a higher tensile stiffness than the other parts of the joint 14a. Therefore, as described below, when the cylindrical first carcass ply 21 is deformed into a toroidal shape, the joint 14a is less likely to stretch than the other parts of the joint 14a, and a recess is likely to occur on the tire surface corresponding to the joint 14a. The recess is particularly noticeable on the sidewall 12 where the rubber thickness is thin. By arranging the rubber tape 24 so as to cover the joint 14a, the amount of rubber at the joint 14a increases, and the occurrence of recesses on the tire surface can be suppressed.

[0018] <Manufacturing method of pneumatic tires> Next, a method for manufacturing the pneumatic tire 1 will be described with reference to Figs. 3 to 5. The following method is an example of a typical method for manufacturing a pneumatic tire. First, a cylindrical case is formed by disposing tire components including an inner liner, carcass ply, beads, etc. in predetermined positions on a cylindrical molding drum, and the case is deformed into a toroidal shape and a separately molded tread rubber is combined with the case to form an unvulcanized tire. The unvulcanized tire is then vulcanized to form a pneumatic tire.

[0019] Fig. 3 shows a state in which the first carcass ply 21 is wound around the forming drum 9. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. For ease of explanation, other members including the inner liner 15 and the like are not shown in Figs. 3 and 4.

[0020] The joint portion 14a is formed by overlapping the ends in the tire circumferential direction D3 of the first carcass ply 21 wound around the forming drum 9. As shown in Fig. 4, the first carcass ply 21 includes a plurality of carcass cords 211 arranged in parallel in a direction substantially perpendicular to the tire circumferential direction D3, and a topping rubber 212 covering the carcass cords 211. At the joint portion 14a, the carcass cords 211 are overlapped.

[0021] After the first carcass ply 21 is wound around the forming drum 9, a rubber tape 24 is applied so as to cover the joint 14a. The rubber tape 24 has a central portion 241 that is applied to the outside of the joint 14a and extends along the tire circumferential direction D3 with a constant thickness. The central portion 241 has a rectangular cross section. The central portion 241 completely covers the joint 14a. By applying the rubber tape 24 so as to cover the joint 14a, the recesses generated at the joint 14a can be filled with the rubber tape 24, so that the occurrence of recesses on the tire surface due to the joint 14a can be suppressed.

[0022] The rubber tape 24 has tapered portions 242 extending along the tire circumferential direction D3 while decreasing in thickness from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3. The tapered portions 242 extend along the tire circumferential direction D3 while decreasing in thickness at a constant rate from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3. An outer surface 242b of the tapered portion 242 in the tire radial direction D2 is a flat surface. An inner surface 242c of the tapered portion 242 in the tire radial direction D2 is a flat surface, and extends continuously to the inner surface of the central portion 241 in the tire radial direction D2. The tapered portion 242 has a triangular cross section. The tapered portion 242 of the rubber tape 24 has the tapered portion 242, which can suppress the occurrence of a convex portion on the tire surface at the end of the rubber tape 24 in the tire circumferential direction D3.

[0023] 4 shows the state immediately after the rubber tape 24 is applied, and the outer side surface 242b and the inner side surface 242c are flat, but the outer side surface 242b and the inner side surface 242c may be curved after the first carcass ply 21 is deformed into a toroidal shape and after vulcanization molding. However, in any of the above cases, the rubber tape 24 has a central portion 241 that is applied to the outside of the joint portion 14a and extends along the tire circumferential direction D3 with a constant thickness, and tapered portions 242 that extend along the tire circumferential direction D3 while reducing in thickness from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3 and have tip ends 242a with an angle θ of 45 degrees or less.

[0024] The angle θ of the tip 242a of the tapered portion 242 is 45 degrees or less. Preferably, the angle θ of the tip 242a is 30 degrees or less. If the angle θ exceeds 45 degrees, the tip 242a may cause a convex portion on the tire surface. The angle θ of the tip 242a is the angle between the outer side surface 242b and the inner side surface 242c. The angle θ of the tip 242a is the angle in a cross section perpendicular to the inner side surface 242c and along the tire circumferential direction D3.

[0025] The width w14 of the joint 14a in the tire circumferential direction D3 is 2.0 to 6.0 mm. If the width w14 of the joint 14a is 6.0 mm or more, recesses on the tire surface become more noticeable.

[0026] The width w24 of the rubber tape 24 in the tire circumferential direction D3 is 5 to 30 mm. The width w241 of the central portion 241 in the tire circumferential direction D3 is set to be equal to or larger than the width w14 of the joint portion 14a. However, taking into consideration variations when attaching the first carcass ply 21 and the rubber tape 24 to the forming drum 9, it is preferable that the width w241 of the central portion 241 is larger than the width w14 of the joint portion 14a by 2.0 mm or more.

[0027] The rubber tape 24 is made of the same rubber as the topping rubber 212. Specifically, the rubber tape 24 is made of a rubber composition whose rubber component is a blend of 5-20% trans-polyisoprene and 95-80% natural rubber and / or diene-based synthetic rubber, or a rubber composition whose rubber component is a blend of 5-35% trans-polyoctenemer and 95-65% natural rubber and / or diene-based synthetic rubber.

[0028] A thickness t241 of the center portion 241 of the rubber tape 24 is larger than a diameter d of the carcass cord 211. The thickness t241 of the center portion 241 is, for example, 1.0 to 1.5 mm. The diameter d of the carcass cord 211 is, for example, 0.6 to 1.0 mm. The thickness t21 of the first carcass ply 21 including the carcass cord 211 and the topping rubber 212 is, for example, 1.2 to 1.3 mm.

[0029] The rubber tape 24 may cover the entire joint 14a, but it is preferable to cover at least a portion of the joint 14a located on the sidewall 12. This makes it possible to suppress the occurrence of recesses in the sidewall 12, which are particularly noticeable. Specifically, as shown in Fig. 5, the rubber tape 24 is preferably disposed at least in a range from a point 24a that is 30 mm toward the tire equatorial plane S1 from a point where a perpendicular line is drawn from the ground contact edge 13a to the tire inner surface, to a point 24b that is 30 mm inward in the tire radial direction D2 from the tire maximum width position 1a.

[0030] Meanwhile, the second carcass ply 22 and the third carcass ply 23, like the first carcass ply 21, also include a plurality of carcass cords 211 arranged in parallel in a direction substantially perpendicular to the tire circumferential direction D3, and a topping rubber 212 covering the carcass cords 211. The carcass 14 also has a joint 14a where the ends of the second carcass ply 22 in the tire circumferential direction D3 are overlapped, and a joint 14a where the ends of the third carcass ply 23 in the tire circumferential direction D3 are overlapped. Therefore, although detailed description is omitted, the carcass 14 may have a rubber tape 24 that covers the joint 14a of the second carcass ply 22 and the joint 14a of the third carcass ply 23, respectively. Note that the positions of the joints 14a of the first carcass ply 21, the second carcass ply 22, and the third carcass ply 23 are preferably different in the tire circumferential direction D3.

[0031] As described above, the manufacturing method of the pneumatic tire 1 according to the present embodiment is a manufacturing method of the pneumatic tire 1 including a step of winding the carcass plies 21, 22, and 23 around the building drum 9 to build the carcass 14, The carcass 14 has a joint portion 14a where the ends of the carcass plies 21, 22, and 23 in the tire circumferential direction D3 are overlapped with each other, The manufacturing method further includes a step of attaching a rubber tape 24 that covers at least a part of the joint portion 14a after winding the carcass plies 21, 22, and 23, The rubber tape 24 has a central portion 241 that is attached to the outside of the joint portion 14a and extends along the tire circumferential direction D3 with a constant thickness, and a tapered portion 242 that extends along the tire circumferential direction D3 while reducing in thickness from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3, and has a tip 242a with an angle θ of 45 degrees or less.

[0032] According to this configuration, by attaching the rubber tape 24 so as to cover the joints 14a of the carcass plies 21, 22, 23, the recesses generated at the joints 14a can be filled with the rubber tape 24, thereby suppressing the generation of recesses on the tire surface due to the joints 14a. In addition, since the rubber tape 24 has the tapered portion 242, the generation of protrusions on the tire surface at the end (tip 242a) of the rubber tape 24 in the tire circumferential direction D3 can be suppressed.

[0033] In addition, in the manufacturing method of the pneumatic tire 1 according to this embodiment, the carcass plies 21, 22, 23 have a plurality of carcass cords 211 arranged in parallel and a topping rubber 212 covering the carcass cords 211, and the thickness t241 of the central portion 241 is greater than the diameter d of the carcass cords 211.

[0034] According to this configuration, the recesses occurring at the joints 14a can be appropriately filled with the rubber tape 24.

[0035] In the manufacturing method of the pneumatic tire 1 according to this embodiment, the tapered portion 242 extends along the tire circumferential direction D3 while reducing in thickness at a constant rate from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3.

[0036] This configuration makes it possible to appropriately prevent convex portions from being generated on the tire surface at the ends in the tire circumferential direction D3 of the rubber tape 24. Furthermore, by making the cross section of the tapered portion 242 triangular, the rubber tape 24 can be easily molded.

[0037] The pneumatic tire 1 according to the present embodiment includes a carcass 14 extending from the tread 13 through the sidewall 12 to the bead 11. The carcass 14 has a joint portion 14a where the ends of the carcass plies 21, 22, and 23 in the tire circumferential direction D3 are overlapped with each other, and a rubber tape 24 that covers at least a part of the joint portion 14a, The rubber tape 24 has a central portion 241 that is attached to the outside of the joint portion 14a and extends along the tire circumferential direction D3 with a constant thickness, and a tapered portion 242 that extends along the tire circumferential direction D3 while reducing in thickness from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3, and has a tip 242a with an angle θ of 45 degrees or less.

[0038] According to this configuration, by attaching the rubber tape 24 so as to cover the joints 14a of the carcass plies 21, 22, 23, the recesses generated at the joints 14a can be filled with the rubber tape 24, thereby suppressing the generation of recesses on the tire surface due to the joints 14a. In addition, since the rubber tape 24 has the tapered portion 242, the generation of protrusions on the tire surface at the end (tip 242a) of the rubber tape 24 in the tire circumferential direction D3 can be suppressed.

[0039] The above-mentioned dimensional values, positional relationships, and magnitude relationships are measured in a normal state in which the pneumatic tire 1 is mounted on a regular rim and inflated to a regular internal pressure under no load. For example, the tire maximum width position 1a is a position in the tire radial direction D2 of a position where the dimension in the tire axial direction D1 excluding structures such as patterns and letters protruding from the outer surface of the sidewall 12 is maximum when the pneumatic tire 1 is mounted on a regular rim, inflated to a regular internal pressure, and in an unloaded state. A regular rim is a rim that is determined for each pneumatic tire 1 by a standard system including the standard on which the pneumatic tire 1 is based, and is, for example, a standard rim for JATMA, and a "Measuring Rim" for TRA and ETRTO.

[0040] In addition, the normal internal pressure is the air pressure set for each pneumatic tire 1 by each standard in a system of standards including the standards on which the pneumatic tire 1 is based, and in the case of JATMA, it is the maximum air pressure, in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "INFLATION PRESSURE".

[0041] The pneumatic tire 1 is not limited to the configurations of the above-described embodiments, and is not limited to the above-described effects. Of course, the pneumatic tire 1 can be modified in various ways without departing from the spirit of the present invention. For example, the configurations and methods of the above-described embodiments may be arbitrarily adopted and combined, and one or more of the configurations and methods of the various modified examples described below may be arbitrarily selected and adopted in the configurations and methods of the above-described embodiments.

[0042] (1) In the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 according to the above embodiment, the carcass plies 21, 22, 23 have a plurality of carcass cords 211 arranged in parallel and a topping rubber 212 covering the carcass cords 211, and the thickness t241 of the central portion 241 is greater than the diameter d of the carcass cords 211. However, the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 are not limited to this configuration. For example, even if the thickness t241 of the central portion 241 is equal to or less than the diameter d of the carcass cords 211, it is possible to make recesses on the tire surface caused by the joints 14a less noticeable.

[0043] (2) In the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 according to the above embodiment, the tapered portion 242 extends along the tire circumferential direction D3 while decreasing in thickness at a constant rate from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3. However, the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 are not limited to such a configuration. The tapered portion 242 does not necessarily need to extend along the tire circumferential direction D3 while decreasing in thickness at a constant rate from both ends 241a, 241a of the central portion 241 in the tire circumferential direction D3. For example, as shown in FIG. 6, the outer side surface 242b may be a concave surface that is convex toward the inside, and the inner side surface 242c may be a flat surface. According to this configuration, the angle θ of the tip 242a of the tapered portion 242 can be made small, so that it is possible to effectively suppress the occurrence of a convex portion on the tire surface at the end (tip 242a) of the rubber tape 24 in the tire circumferential direction D3. An angle θ of a tip 242a of the tapered portion 242 shown in FIG. 6 is an angle between a tangent to an outer surface 242b at the tip 242a and an inner surface 242c.

[0044] (3) Furthermore, the tapered portion 242 may have an outer surface 242b that is convex outward and an inner surface 242c that is flat, as shown in Fig. 7. This configuration can prevent air from entering between the tapered portion 242 and the second carcass ply 22 disposed on the outer side of the tapered portion 242. The angle θ of the tip 242a of the tapered portion 242 shown in Fig. 7 is the angle between the tangent to the outer surface 242b at the tip 242a and the inner surface 242c.

[0045] (4) In the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 according to the above embodiment, the first carcass ply 21 has only one joint 14a in the tire circumferential direction D3. However, the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 are not limited to this configuration. For example, the ends of multiple first carcass plies 21 in the tire circumferential direction D3 may be overlapped with each other to provide the joints 14a at multiple locations in the tire circumferential direction D3. In this case, rubber tape 24 may be attached so as to cover each of the joints 14a.

[0046] (5) In the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 according to the above embodiment, the carcass 14 is composed of three carcass plies 21, 22, and 23. However, the manufacturing method of the pneumatic tire 1 and the pneumatic tire 1 are not limited to this configuration. For example, the carcass 14 may be composed of only the first carcass ply 21 and the third carcass ply 23 without providing the second carcass ply 22. [Explanation of symbols]

[0047] 1...pneumatic tire, 1a...maximum tire width position, 9...molding drum, 11...bead, 12...sidewall, 13...tread, 13a...ground contact edge, 14...carcass, 14a...joint, 15...inner liner, 21...first carcass ply, 22...second carcass ply, 23...third carcass ply, 24...rubber tape, 211...carcass cord, d...diameter of carcass cord, 212...topping rubber, 241...center portion, t241...thickness of center portion, 242...tapered portion, 242a...tip, D1...tire axial direction, D2...tire radial direction, D3...tire circumferential direction, θ...tip angle

Claims

1. A method for manufacturing a pneumatic tire, comprising a step of winding a carcass ply around a forming drum to form a carcass, The carcass has a joint portion where end portions of the carcass plies in the tire circumferential direction are overlapped with each other, The manufacturing method further includes a step of attaching a rubber tape that covers at least a portion of the joint after winding the carcass ply, the rubber tape has a central portion attached to an outer side of the joint portion, extending in the tire circumferential direction with a constant thickness, and completely covering the joint portion in the tire circumferential direction; and a tapered portion extending in the tire circumferential direction while reducing in thickness from both ends of the central portion in the tire circumferential direction, and having a tip with an angle of 45 degrees or less, A method for manufacturing a pneumatic tire, wherein the thickness of the tapered portion becomes thinner from the thickness of the central portion toward the tip.

2. The carcass ply has a plurality of carcass cords arranged in parallel and a topping rubber covering the carcass cords, The method for manufacturing a pneumatic tire according to claim 1 , wherein the thickness of the central portion is greater than a diameter of the carcass cord.

3. The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein the tapered portion extends in the tire circumferential direction while decreasing in thickness at a constant rate from both ends in the tire circumferential direction of the central portion.

4. The carcass is composed of a plurality of the carcass plies, The carcass has a plurality of the joint portions in which end portions of the plurality of carcass plies in the tire circumferential direction are overlapped with each other, The plurality of joints are each covered with the rubber tape, The method for manufacturing a pneumatic tire according to claim 1 , wherein positions of the plurality of joints vary in a circumferential direction of the tire.

5. It has a carcass that runs from the tread through the sidewall to the bead, The carcass has a joint portion where ends of the carcass plies in the tire circumferential direction are overlapped with each other, and a rubber tape that covers at least a part of the joint portion, the rubber tape has a central portion attached to an outer side of the joint portion, extending in the tire circumferential direction with a constant thickness, and completely covering the joint portion in the tire circumferential direction; and a tapered portion extending in the tire circumferential direction while reducing in thickness from both ends of the central portion in the tire circumferential direction, and having a tip with an angle of 45 degrees or less, The thickness of the tapered portion becomes thinner from the thickness of the central portion toward the tip.

Images