Green tire and tire

Abstract

In a green tire according to the present invention, the heating rate X1 of a high-heating-rate unvulcanized rubber layer is greater than the heating rate X2 of one or more unvulcanized main rubber layers. In this tire, the heating rate Y1 of a high-heating-rate rubber layer is greater than the heating rate Y2 of one or more main rubber layers.

Description

Raw tires and tires

[0001] The present invention relates to a green tire and a tire.

[0002] Conventionally, when vulcanizing and molding a tire using a rigid inner mold for tire vulcanization molding, a technology has been proposed that can shorten the vulcanization time by heating the rigid inner mold and the unvulcanized tire formed on the outer surface of the rigid inner mold to a predetermined temperature in advance using microwaves (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2007-022010

[0004] Even during vulcanization of retreading, by using microwaves and setting the irradiation position, it is possible to preheat only the unvulcanized tread rubber.

[0005] However, during vulcanization, vulcanization tends to be slower in the radially inner region of the tire that is far from the mold, and even when preheating is performed using microwaves, there is still room for improvement in shortening the vulcanization time.

[0006] Therefore, an object of the present invention is to provide a green tire that can shorten the vulcanization time during retreading, and a tire manufactured using the green tire.

[0007] The following is a summary of the present invention: (1) A raw tire for retreading, comprising unvulcanized tread rubber and a vulcanized case portion, wherein the unvulcanized tread rubber comprises one or more unvulcanized main rubber layers and a high-heating-rate unvulcanized rubber layer disposed radially inward of the one or more unvulcanized main rubber layers, the high-heating-rate unvulcanized rubber extending over at least a portion of a region in the tire width direction, and wherein, when a heating rate of the unvulcanized rubber due to microwaves is defined as the product of the dielectric constant and loss tangent of the unvulcanized rubber, the heating rate X1 of the high-heating-rate unvulcanized rubber layer is greater than the heating rate X2 of the one or more unvulcanized main rubber layers.

[0008] Here, the "dielectric constant" of unvulcanized rubber is measured by the coaxial cable method. The "loss tangent" of unvulcanized rubber refers to the ratio (E" / E') of the dynamic loss modulus E" to the dynamic storage modulus E', measured using a dynamic tensile viscoelasticity measuring instrument on a test piece of unvulcanized rubber 2 mm thick, 5 mm wide, and 20 mm long, under conditions of a temperature of 60°C, a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1%. In this specification, "microwaves" refers to electromagnetic waves with a frequency of 300 MHz to 300 GHz. The "thickness of the high-heating-rate unvulcanized rubber layer" refers to the maximum thickness measured in the tire radial direction.

[0009] (2) A retreaded tire comprising a tread rubber and a case portion, wherein the tread rubber comprises one or more main rubber layers and a high-heating-rate rubber layer disposed radially inward of the one or more main rubber layers, the high-heating-rate rubber extending in at least a portion of a tire width direction region, and wherein, when the heating rate of the vulcanized rubber due to microwaves is defined as the product of the dielectric constant and loss tangent of the vulcanized rubber, the heating rate Y1 of the high-heating-rate rubber layer is greater than the heating rate Y2 of the one or more main rubber layers, wherein the "dielectric constant" of the vulcanized rubber is measured by a coaxial cable method. The "loss tangent" of vulcanized rubber refers to the ratio (E" / E') of the dynamic loss modulus E" to the dynamic storage modulus E', obtained using a dynamic tensile viscoelasticity measuring machine on a test piece of vulcanized rubber 2 mm thick, 5 mm wide, and 20 mm long under conditions of a temperature of 60°C, a frequency of 52 Hz, an initial strain of 2%, and a dynamic strain of 1%. The "tread edge" of a tire refers to the outermost point in the width direction of the contact patch that comes into contact with the road surface when the tire is mounted on an applicable rim, inflated to the specified internal pressure, and subjected to a maximum load.

[0010] In this specification, the term "applicable rim" refers to the standard rim (referred to as "Measuring Rim" in the ETRTO STANDARDS MANUAL and "Design Rim" in the TRA YEAR BOOK) for the applicable size, which is an industrial standard valid in the region where the tire is produced and used, and which is described in the JATMA YEAR BOOK of the Japan Automobile Tire Manufacturers Association (JATMA) in Japan, the STANDARDS MANUAL of the European Tire and Rim Technical Organization (ETRTO) in Europe, and the YEAR BOOK of the Tire and Rim Association, Inc. (TRA) in the United States, or which will be described in the future. "rim" refers to the tire's width corresponding to the tire's bead width (i.e., the "rim" in the above "wheel" includes not only current sizes but also sizes that may be included in the above industry standards in the future. Examples of "sizes to be described in the future" include sizes listed under "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO). However, for sizes not listed in the above industry standards, it refers to a rim with a width corresponding to the tire's bead width. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size / ply rating listed in the above JATMA etc., and for sizes not listed in the above industry standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, "maximum applied load" refers to the load corresponding to the maximum load capacity. Here, the "1 / 4 point" refers to the midpoint when the tire is mounted on the applicable rim, inflated to the specified internal pressure, and no load is applied. Here, the "thickness of the high heating rate rubber layer" in a tire refers to the maximum thickness of the high heating rate rubber layer when the tire is mounted on an applicable rim, inflated to the specified internal pressure, and under no load, and measured in the radial direction of the tire.

[0011] According to the present invention, it is possible to provide a green tire that can shorten the vulcanization time during retreading, and a tire manufactured using the green tire.

[0012] Fig. 1 is a schematic partial cross-sectional view in the width direction of a raw tire according to one embodiment of the present invention; Fig. 2 is a schematic partial cross-sectional view in the width direction of a raw tire according to a first modified example; Fig. 3 is a schematic partial cross-sectional view in the width direction of a raw tire according to a second modified example; Fig. 4 is a schematic partial cross-sectional view in the width direction of a tire according to one embodiment of the present invention;

[0013]

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. <Green tire> Fig. 1 is a schematic partial cross-sectional view in the width direction of a green tire according to one embodiment of the present invention. This green tire 1 is a green tire for retreading, comprising unvulcanized tread rubber 2 and a vulcanized case portion 3.

[0014] The case portion 3 includes a pair of bead portions (not shown) and a sidewall portion (not shown) connected to the pair of bead portions. The carcass 7 extends toroidally between the pair of bead portions. A belt 6 consisting of one or more belt layers 6a, 6b (two layers in the illustrated example) is disposed on the radially outer side of the carcass 7. The configuration of the case portion 3 is not particularly limited. For example, a bead core may be embedded in the bead portion, or the tire may be coreless. The number of carcass plies is not particularly limited as long as it is one or more. The carcass structure may also have a carcass folded portion, or may be wrapped around a bead core. The belt structure is also not particularly limited. The number of belt layers, the width of the belt layer, the inclination angle with respect to the circumferential direction, and the like may vary. Various materials may also be used for the respective components.

[0015] The unvulcanized tread rubber 2 comprises one or more unvulcanized main rubber layers 4 and a high heating rate unvulcanized rubber layer 5 arranged radially inward of the one or more unvulcanized main rubber layers 4.

[0016] In the illustrated example, the one or more unvulcanized main body rubber layers 4 are made up of two unvulcanized main body rubber layers 4a, 4b. The two unvulcanized main body rubber layers 4a, 4b have a so-called cap and base structure, with the unvulcanized main body rubber layer 4a on the outer side in the tire radial direction being the cap rubber layer and the unvulcanized main body rubber layer 4b on the inner side in the tire radial direction being the base rubber layer. In the illustrated example, the unvulcanized main body rubber layer 4 has two layers, but it may also have one layer, or three or more layers.

[0017] The loss tangent tanδ1 of the unvulcanized main rubber layer 4a (cap rubber layer) is preferably larger than the loss tangent tanδ2 of the unvulcanized main rubber layer 4b (base rubber layer). This is because excessive heat generation in the base rubber layer can be suppressed while maintaining the grip performance of the cap rubber layer arranged on the radially outer side of the tire. The loss tangent tanδ1 of the unvulcanized main rubber layer 4a (cap rubber layer) is not particularly limited, but is preferably 0.01 or more and 0.08 or less. The loss tangent tanδ2 of the unvulcanized main rubber layer 4b (base rubber layer) is not particularly limited, but is preferably 0.13 or more and 0.6 or less. Furthermore, the dielectric constant of the unvulcanized main rubber layer 4a (cap rubber layer) is not particularly limited, but is preferably 2.0 (F / m) or more and 8.0 (F / m) or less. The dielectric constant of the unvulcanized main rubber layer 4b (base rubber layer) is not particularly limited, but is preferably 10 (F / m) or more and 60 (F / m) or less.

[0018] The high-heating-rate unvulcanized rubber layer 5 extends in at least a portion of the tire width direction region. In the illustrated example, the high-heating-rate unvulcanized rubber layer 5 extends in the tire width direction region including the region between the tread ends of the raw tire 1 (extending to the entire region between the tread ends and to regions on both outer sides in the tire width direction).

[0019] Here, the heating rate of unvulcanized rubber due to microwaves is defined as the product of the dielectric constant and loss tangent of the unvulcanized rubber. In this case, in the raw tire 1 of this embodiment, the heating rate X1 of the high-heating-rate unvulcanized rubber layer 5 is greater than the heating rate X2 of one or more unvulcanized main rubber layers 4. In particular, in this example, the loss tangent of the cap rubber layer is greater than the loss tangent of the base rubber layer, and the heating rate of the cap rubber layer is greater than that of the base rubber layer, but the heating rate X1 of the high-heating-rate unvulcanized rubber layer 5 is greater than that of the cap rubber layer. The effects of the raw tire 1 of this embodiment will be described below.

[0020] In the raw tire 1 of this embodiment, a high-heating-rate unvulcanized rubber layer 5 is disposed radially inward of one or more unvulcanized main rubber layers 4, and the heating rate X1 of the high-heating-rate unvulcanized rubber layer 5 is greater than the heating rate X2 of the one or more main rubber layers 4. The high-heating-rate unvulcanized rubber 5 extends over at least a portion of the tire width direction. The radially inner regions of the tread rubber 2 tend to be slower to vulcanize due to their greater distance from the mold. In contrast, in this embodiment, the high-heating-rate unvulcanized rubber layer 5 is disposed radially inward. Therefore, by preheating the tread rubber 2 with microwaves, the high-heating-rate unvulcanized rubber layer 5, which has a higher heating rate X1 (relative to the heating rate X2), is selectively heated in particular. This shortens the vulcanization time of the region that was previously the slowest to vulcanize, and also shortens the vulcanization time of the entire vulcanization process during retreading. As described above, according to the green tire 1 of this embodiment, the vulcanization time can be shortened during retreading.

[0021] The heating rate X1 is preferably at least twice the heating rate X2. This is because the vulcanization time can be further shortened during retreading. For the same reason, the heating rate X1 is more preferably at least five times the heating rate X2, even more preferably at least ten times, and particularly preferably at least twelve times. In the case of a cap-and-base structure, the heating rate X1 is preferably at least two times the heating rate of the cap rubber layer, more preferably at least five times, even more preferably at least ten times, and particularly preferably at least twelve times.

[0022] Although there are no particular limitations on how to adjust the heating rate X1 of the high heating rate unvulcanized rubber layer 5 to fall within the above ranges, the heating rate can be adjusted by appropriately adjusting the proportion of carbon black.

[0023] 1, it is preferable that the high-heating-rate unvulcanized rubber layer 5 extends in a region in the tire width direction including between the tread ends of the raw tire 1. This is because the above-mentioned effects can be obtained in a wide region in the tire width direction, and a further reduction in the vulcanization time can be expected.

[0024] 2 is a schematic widthwise partial cross-sectional view of a raw tire according to a first modified example. It is also preferable that the raw tire 1 includes a shoulder land portion defined between the tread edge of the raw tire 1 and a portion corresponding to the outermost circumferential main groove 8 (the raw tire 1 has no circumferential main grooves yet formed therein), and that the high-heating-rate unvulcanized rubber layer 5 is disposed in at least a portion of the tire widthwise region where the shoulder land portion is located. The shoulder land portion tends to have the thickest rubber gauge among land portions and may be the slowest location for vulcanization. Therefore, disposing the high-heating-rate unvulcanized rubber layer 5 having a high heating rate in such a location may be effective in further shortening the vulcanization time. More preferably, the high-heating-rate unvulcanized rubber layer 5 is disposed throughout the entire tire widthwise region where the shoulder land portion is located.

[0025] 3 is a schematic widthwise partial cross-sectional view of a raw tire according to a second modified example. When the midpoint in the tire width direction between the tire equatorial plane and the tread end of the raw tire 1 is defined as a quarter point (point P), it is also preferable that the high-heating-rate unvulcanized rubber layer 5 extends only in the tire widthwise region between the quarter points. Belts usually extend further outward in the tire width direction than the quarter point (i.e., the belt end is located further outward in the tire width direction than the quarter point). In such cases, by setting the extension range of the high-heating-rate unvulcanized rubber layer 5 as described above, a distance can be secured between the high-heating-rate unvulcanized rubber layer 5 (end) and the belt end, which can prevent peeling of the belt coating rubber at the belt end due to microwave heating.

[0026] The end of the high-heating-rate unvulcanized rubber layer 5 in the tire width direction is preferably located 5 mm or more inward from the belt end in the tire width direction. By setting the extension width of the high-heating-rate unvulcanized rubber layer 5 as described above, the distance between the (end of) the high-heating-rate unvulcanized rubber layer 5 and the belt end can be secured, and peeling of the belt coating rubber at the belt end due to heating by microwaves can be suppressed.

[0027] The thickness of the high-heat-rate unvulcanized rubber layer 5 is preferably 2 mm or less, because this allows the basic tire performance to be mainly borne by the (vulcanized) unvulcanized main rubber layer 4, and for example, even if the loss tangent of the high-heat-rate unvulcanized 5 rubber layer is large, low heat buildup and low rolling resistance can be achieved for the entire tire.

[0028] <Tire> Figure 4 is a schematic partial cross-sectional view in the width direction of a tire according to one embodiment of the present invention. This tire 10 is a retreaded tire including a tread rubber 20 and a case portion 30. The tire 10 of this embodiment can be obtained by vulcanizing the unvulcanized tread rubber 2 of the raw tire 1 of the above embodiment.

[0029] The case portion 30 includes a pair of bead portions (not shown) and a sidewall portion (not shown) connected to the pair of bead portions. The carcass 70 extends toroidally between the pair of bead portions. A belt 60 consisting of one or more belt layers 60a, 60b (two layers in the illustrated example) is disposed on the tire radially outer side of the carcass 70. The configuration of the case portion 30 is not particularly limited. For example, a bead core may be embedded in the bead portion, or the tire may be coreless. The number of carcass plies is not particularly limited as long as it is one or more. The carcass structure may also have a carcass folded portion, or may be wrapped around a bead core. The belt structure is also not particularly limited. The number of belt layers, the width of the belt layer, the inclination angle with respect to the circumferential direction, and the like may vary. Various materials may also be used for the respective components.

[0030] The tread rubber 20 includes one or more main rubber layers 40 and a high heating rate rubber layer 50 arranged radially inward of the one or more main rubber layers 40 .

[0031] In the illustrated example, the one or more main rubber layers 40 are made up of two main rubber layers 40a, 40b. The two main rubber layers 40a, 40b have a so-called cap and base structure, with the main rubber layer 40a on the outer side in the tire radial direction being the cap rubber layer and the main rubber layer 40b on the inner side in the tire radial direction being the base rubber layer. In the illustrated example, the main rubber layer 4 is made up of two layers, but it may also be made up of one layer, or three or more layers.

[0032] The loss tangent tanδ3 of the main rubber layer 40a (cap rubber layer) is preferably greater than the loss tangent tanδ4 of the main rubber layer 40b (base rubber layer). This is because excessive heat generation in the base rubber layer can be suppressed while maintaining the grip performance of the cap rubber layer disposed radially outward of the tire. The loss tangent tanδ3 of the main rubber layer 40a (cap rubber layer) is not particularly limited, but is preferably 0.01 or greater and 0.08 or less. The loss tangent tanδ4 of the main rubber layer 40b (base rubber layer) is not particularly limited, but is preferably 0.13 or greater and 0.6 or less. The dielectric constant of the main rubber layer 40a (cap rubber layer) is not particularly limited, but is preferably 2.0 (F / m) or greater and 8.0 (F / m) or less. The dielectric constant of the main rubber layer 40b (base rubber layer) is not particularly limited, but is preferably 10 (F / m) or greater and 60 (F / m) or less.

[0033] The high-heating-rate rubber 50 extends in at least a portion of the tire width direction region. In the illustrated example, the high-heating-rate rubber layer 50 extends in the tire width direction region including the region between the tread ends of the tire 10 (extending to the entire region between the tread ends and to regions on both outer sides thereof in the tire width direction).

[0034] Here, the heating rate of vulcanized rubber due to microwaves is defined as the product of the dielectric constant and loss tangent of the vulcanized rubber. In this case, in the tire 10 of this embodiment, the heating rate Y1 of the high heating rate rubber layer 50 is greater than the heating rate Y2 of the one or more main rubber layers 40. In particular, in this example, the loss tangent of the cap rubber layer is greater than the loss tangent of the base rubber layer, and the heating rate of the cap rubber layer is greater than the heating rate of the base rubber layer, but the heating rate Y1 of the high heating rate rubber layer 50 is greater than the heating rate of the cap rubber layer. The effects of the tire 10 of this embodiment will be described below.

[0035] As described above, the tire 10 of this embodiment is obtained by vulcanizing the unvulcanized tread rubber 2 of the raw tire 1 of the above embodiment. Furthermore, a high-heating-rate rubber layer 50 is disposed radially inward of one or more main rubber layers 40, and the heating rate Y1 of the high-heating-rate rubber layer 50 is greater than the heating rate Y2 of the one or more main rubber layers 40. The high-heating-rate rubber 50 extends over at least a portion of the tire width direction region. Therefore, when vulcanizing the raw tire 1 to obtain the tire 10 configured as described above, the vulcanization time during retreading can be shortened by preheating the tread rubber 2 with microwaves. As described above, the tire 10 of this embodiment allows the vulcanization time during retreading to be shortened when such a tire 10 is to be manufactured by retreading.

[0036] For the same reasons as those explained in the embodiment of the raw tire 1, the heating rate Y1 is preferably at least twice the heating rate Y2, more preferably at least five times, even more preferably at least 10 times, and particularly preferably at least 12 times. In the case of a cap-and-base structure, the heating rate Y1 is preferably at least twice the heating rate of the cap rubber layer, more preferably at least five times, even more preferably at least 10 times, and particularly preferably at least 12 times.

[0037] Although there are no particular limitations on how to adjust the heating rate Y1 of the high heating rate rubber layer 50 to fall within the above ranges, the heating rate can be adjusted by appropriately adjusting the ratio of carbon black.

[0038] 4, it is preferable that the high heating rate rubber layer 50 extends in a region in the tire width direction including between the tread ends of the tire 10. This is because the above-mentioned effects can be obtained in a wide region in the tire width direction, and a further reduction in vulcanization time can be expected.

[0039] It is also preferable that the tire 10 has a shoulder land portion defined between the tread edge and the outermost circumferential main groove of the tire 10, and that the high heating rate rubber layer 50 be disposed in at least a part of the tire width direction region where the shoulder land portion is located. The shoulder land portion tends to have the thickest rubber gauge among the land portions and may be the slowest part to vulcanize, so disposing the high heating rate rubber layer 50 with a high heating rate in such a part may be effective in further shortening the vulcanization time. More preferably, the high heating rate rubber layer 50 is disposed over the entire tire width direction region where the shoulder land portion is located.

[0040] When the midpoint in the tire width direction between the tire equatorial plane and the tread end of the tire 10 is defined as a quarter point (point P), it is also preferable that the high heating rate rubber layer 50 extends only in the region in the tire width direction between the quarter points. The belt usually extends further outward in the tire width direction than the quarter point (the belt end is located further outward in the tire width direction than the quarter point), and in this case, by setting the extension range of the high heating rate rubber layer 50 as described above, it is possible to ensure a distance between (the end of) the high heating rate rubber layer 50 and the belt end, and to prevent peeling of the belt coating rubber at the belt end due to heating by microwaves.

[0041] The end of the high-heating-rate rubber layer 50 in the tire width direction is preferably located 5 mm or more inward from the belt end in the tire width direction. By setting the extension width of the high-heating-rate rubber layer 50 as described above, the distance between the (end of) the high-heating-rate rubber layer 50 and the belt end can be secured, and peeling of the belt coating rubber at the belt end due to heating by microwaves can be suppressed.

[0042] The thickness of the high-heating-rate rubber layer 50 is preferably 2 mm or less. This allows the main rubber layer 40 to bear the basic tire performance, and for example, even if the loss tangent of the high-heating-rate rubber layer 50 is large, low heat generation and low rolling resistance can be achieved for the entire tire.

[0043] 1: Raw tire, 2: Tread rubber, 3: Case portion, 4: Unvulcanized main rubber layer, 5: High heating rate unvulcanized rubber layer, 6: Belt, 7: Carcass, 8: Portion corresponding to outermost circumferential main groove, 10: Tire, 20: Tread rubber, 30: Case portion, 40: Main rubber layer, 50: High heating rate rubber layer, 60: Belt, 70: Carcass

Claims

1. A raw tire for retreading, comprising unvulcanized tread rubber and a vulcanized case portion, wherein the unvulcanized tread rubber comprises one or more unvulcanized main rubber layers and a high-heating-rate unvulcanized rubber layer arranged radially inward of the one or more unvulcanized main rubber layers, the high-heating-rate unvulcanized rubber extending over at least a portion of the tire width direction, and wherein, when the heating rate of the unvulcanized rubber due to microwaves is defined as the product of the dielectric constant and loss tangent of the unvulcanized rubber, the heating rate X1 of the high-heating-rate unvulcanized rubber layer is greater than the heating rate X2 of the one or more unvulcanized main rubber layers.

2. The green tire according to claim 1, wherein the heating rate X1 is at least twice the heating rate X2.

3. The green tire according to claim 2, wherein the heating rate X1 is five times or more the heating rate X2.

4. A raw tire according to any one of claims 1 to 3, wherein the high-heating-rate unvulcanized rubber layer extends in a region in the tire width direction including between the tread ends of the raw tire.

5. A raw tire according to any one of claims 1 to 4, wherein the raw tire has a shoulder land portion defined between a tread edge of the raw tire and a portion corresponding to an outermost circumferential main groove, and the high-heating-rate unvulcanized rubber layer is disposed in at least a part of the tire width direction region in which the shoulder land portion is located.

6. The raw tire according to any one of claims 1 to 5, wherein, when a midpoint in the tire width direction between the tire equatorial plane and a tread end of the raw tire is defined as a quarter point, the high-heating-rate unvulcanized rubber layer extends only in a region in the tire width direction between the quarter points.

7. A raw tire according to any one of claims 1 to 6, wherein the end in the tire width direction of the high-heating-rate unvulcanized rubber layer is located 5 mm or more inward in the tire width direction from the belt end.

8. A raw tire according to any one of claims 1 to 7, wherein the high-heat-rate unvulcanized rubber layer has a thickness of 2 mm or less.

9. A retreaded tire comprising tread rubber and a case portion, wherein the tread rubber comprises one or more main rubber layers and a high heating rate rubber layer arranged radially inward of the one or more main rubber layers, the high heating rate rubber extending over at least a portion of the tire width direction region, and wherein when the heating rate of vulcanized rubber due to microwaves is defined as the product of the dielectric constant and loss tangent of the vulcanized rubber, the heating rate Y1 of the high heating rate rubber layer is greater than the heating rate Y2 of the one or more main rubber layers.

10. The tire according to claim 9, wherein the heating rate Y1 is at least twice the heating rate Y2.

11. The tire according to claim 10, wherein the heating rate Y1 is at least five times the heating rate Y2.

12. A tire according to any one of claims 9 to 11, wherein the high heating rate rubber layer extends in a region in the tire width direction including between the tread ends of the tire.

13. A tire according to any one of claims 9 to 12, wherein the tire comprises a shoulder land portion defined between a tread edge and an outermost circumferential main groove of the tire, and the high heating rate rubber layer is disposed in at least a part of the tire width direction region in which the shoulder land portion is located.

14. A tire as claimed in any one of claims 9 to 13, wherein, when a midpoint in the tire width direction between the tire equatorial plane and a tread end of the tire is defined as a quarter point, the high heating rate rubber layer extends only in a region in the tire width direction between the quarter points.

15. A tire according to any one of claims 9 to 14, wherein the end of the high heating rate rubber layer in the tire width direction is located 5 mm or more inward in the tire width direction from the belt end.

16. A tire according to any one of claims 9 to 15, wherein the high heating rate rubber layer has a thickness of 2 mm or less.

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