Pneumatic tire

Abstract

To provide a pneumatic tire than can make both rolling resistance performance and noise performance compatible at high level.SOLUTION: A pneumatic tire according to the present invention includes a tread part 2, a pair of side wall parts 3, a pair of bead parts 4, a carcass 6, a belt layer 7, a band layer 8 and an inner rubber 10. The inner rubber 10 includes a first portion 11 extending with a first thickness t1 and a second portion 12 extending with a second thickness t2. The first thickness t1 is larger than the second thickness t2. A band ply 8A includes a crown region 25, and a band cord 8c includes a first band cord 31 arranged in the crown region 25. The first band cord 31 is a nylon cord, whose fineness is 1150 dtex / 2 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 below proposes a pneumatic tire with a belt layer in the tread portion. This tire is expected to achieve both low rolling resistance and noise performance by specifying the reinforcing cords in the belt layer and the relationship between the tire weight and maximum load capacity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-106505 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the spread of hybrid and electric vehicles, which generate less noise while running, there has been a demand for further improvements in tire noise performance. One possible method for improving noise performance is to increase the volume of the tread to suppress vibrations in the tread, which are a source of noise.

[0005] However, the above method may increase the rolling resistance of the tire (hereinafter referred to as "deteriorating rolling resistance performance").

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that achieves both high levels of rolling resistance performance and noise performance. [Means for solving the problem]

[0007] The present invention is a pneumatic tire including a tread portion, a pair of sidewall portions, a pair of bead portions, a carcass extending between the pair of bead portions, a belt layer disposed inside the tread portion and on the outer side of the carcass in the tire radial direction, a band layer covering the entire width of the belt layer in the tire axial direction and consisting of one band ply equipped with a band cord extending at an angle of 5° or less with respect to the tire circumferential direction, and an inner rubber extending between the pair of bead portions inside the carcass, wherein the inner rubber a first portion extending through the tread portion at a first thickness and a second portion extending through the pair of sidewall portions at a second thickness, the first thickness being greater than the second thickness; the band ply including a crown region having a width that is 70% of the axial width of the band ply about the tire equator; and the band cord including a first band cord arranged in the crown region, the first band cord being a nylon cord and having a fineness of 1150 dtex / 2 or less. [Effects of the Invention]

[0008] By adopting the above-described configuration, the pneumatic tire of the present invention can achieve both high levels of rolling resistance performance and noise performance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the tread portion of FIG. 1. [Figure 3] FIG. 2 is a development view showing the cord arrangement of a belt layer and a band layer. [Figure 4] FIG. 3 is an enlarged cross-sectional view of a first belt ply. [Figure 5] 3 is an enlarged cross-sectional view of a first end of the first portion of FIG. 2. FIG. [Figure 6] FIG. 10 is an enlarged cross-sectional view of a first portion and a second portion of another embodiment of the present invention. [Figure 7] FIG. 10 is an enlarged cross-sectional view of a first portion and a second portion of yet another embodiment of the present invention. [Figure 8] FIG. 10 is an enlarged cross-sectional view of a sidewall portion according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a pneumatic tire 1 (hereinafter, sometimes simply referred to as "tire 1") illustrating one embodiment of the present invention. FIG. 1 is a cross-sectional view of tire 1 in a normal state, including the axis of rotation. As shown in FIG. 1, tire 1 of this embodiment is suitable for use as, for example, a pneumatic tire for passenger cars. However, the present invention is not limited to this embodiment and may be applied to, for example, a pneumatic tire for heavy loads.

[0011] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, a state in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal condition means a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition. Furthermore, for components that cannot be measured in the normal condition (for example, the internal materials of the tire 1), the values ​​are measured by placing the tire 1 in a state as close as possible to the normal condition.

[0012] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0013] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0014] The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portions 3 are connected to the axially outer side of the tread portion 2 and extend in the radial direction of the tire. The bead portions 4 are connected to the radially inner side of the sidewall portions 3. The tire 1 also includes a carcass 6 and an inner rubber 10. The carcass 6 extends between the pair of bead portions 4. In other words, the carcass 6 extends from one bead portion 4, through one sidewall portion 3, the tread portion 2, and the other sidewall portion 3, to the other bead portion 4. The inner rubber 10 is disposed inside the carcass 6 and extends between the pair of bead portions 4. As a result, the inner rubber 10 forms the tire cavity surface 1A. The inner rubber 10 is made of vulcanized rubber and is different from a sealant material used to prevent punctures.

[0015] The carcass 6 is composed of, for example, one carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a turned-up portion 6b. The main body portion 6a extends, for example, between the pair of bead portions 4. The turned-up portion 6b is, for example, continuous with the main body portion 6a and turned up around the bead core 5 from the inside to the outside in the tire axial direction.

[0016] The carcass ply 6A includes a plurality of carcass cords and a topping rubber covering the cords (not shown), and the carcass cords are made of organic fiber cords such as aramid, rayon, etc. The carcass cords are preferably arranged at an angle of 70 to 90 degrees with respect to the tire equator C, for example.

[0017] The inner rubber 10 includes a first portion 11 and a second portion 12. The first portion 11 extends through the tread portion 2 at a first thickness t1. The second portion 12 extends through the pair of sidewall portions 3 at a second thickness t2. The first thickness t1 and the second thickness t2 refer to the thickness from the inner surface 6i of the carcass 6 to the tire cavity surface 1A, and do not include the topping rubber of the carcass ply.

[0018] In the present invention, the first thickness t1 is greater than the second thickness t2. This configuration means that the average thickness of the first portion 11 is greater than the average thickness of the second portion 12. The average thickness of the first portion 11 corresponds to the value obtained by dividing the cross-sectional area of ​​the first portion 11 in the transverse cross section of the tread portion 2 by the length of the first portion 11 along the tire cavity surface. The same applies to the average thickness of the second portion 12. As a desirable aspect, in this embodiment, the above-mentioned thickness relationship is maintained over the entire circumference of the tire. However, the present invention is not limited to this aspect.

[0019] Fig. 2 shows an enlarged cross-sectional view of the tread portion 2 of Fig. 1. As shown in Fig. 2, the inside of the tread portion 2 of this embodiment includes, for example, a belt layer 7 and a band layer 8 arranged outside the carcass 6 in the tire radial direction.

[0020] FIG. 3 is a development view conceptually showing the cord arrangement of the belt layer 7 and the band layer 8. As shown in FIGS. 2 and 3, the belt layer 7 includes, for example, a first belt ply 7A adjacent to the carcass 6 and a second belt ply 7B disposed radially outward of the first belt ply 7A. As shown in FIG. 3, each of the first belt ply 7A and the second belt ply 7B includes a plurality of steel cords 7c arranged at an angle θ1 of 15 to 45° with respect to the tire circumferential direction, and a topping rubber 7g covering the steel cords 7c. The steel cords 7c of the first belt ply 7A and the steel cords 7c of the second belt ply 7B are inclined in opposite directions with respect to the tire circumferential direction. This effectively reinforces the tread portion 2.

[0021] 2, the axial length of the second belt ply 7B is preferably shorter than the axial length of the first belt ply 7A, so that a pair of axially outer ends 7b of the second belt ply 7B are positioned axially more inward than a pair of axially outer ends 7a of the first belt ply 7A.

[0022] 3, the band layer 8 is composed of one band ply 8A. The band ply 8A includes, for example, a band cord 8c extending at an angle of 5° or less with respect to the tire circumferential direction, and a topping rubber 8g covering the band cord 8c. The band layer 8 of this embodiment is arranged so as to cover the entire belt layer 7.

[0023] The band ply 8A includes a crown region 25 having a width W2 that is 70% of the width W1 of the band ply in the tire axial direction, centered on the tire equator C. The band cords 8c include first band cords 31 arranged in the crown region 25. As a preferred aspect, in this embodiment, all of the band cords 8c arranged in the crown region 25 are composed of the first band cords 31.

[0024] The first band cord 31 is a nylon cord and has a fineness of 1150 dtex / 2 or less. The tire 1 of the present invention has the above-mentioned characteristics, and thus can achieve both high rolling resistance performance and noise performance. The reason for this is as follows.

[0025] As shown in FIG. 1 , in the inner rubber 10 of the tire 1 of the present invention, the first thickness t1 of the first portion 11 is greater than the second thickness t2 of the second portion 12. Such a first portion 11 easily absorbs vibrations when the tread portion 2 comes into contact with the ground, improving noise performance. Also, as shown in FIG. 3 , in the present invention, the first band cord 31 arranged in the crown region 25 of the band ply 8A is a nylon cord and has a fineness of 1150 dtex / 2 or less. This makes it possible to reduce the weight of the band ply 8A, and therefore to prevent the weight of the tread portion 2 from being excessively increased by the first portion 11 of the inner rubber 10. Therefore, the tire 1 can maintain good rolling resistance performance.

[0026] The following describes the configuration of this embodiment in more detail. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even if it does not have the configuration described below. Furthermore, even if any one of the configurations described below is applied alone to a tire of the present invention having the above-described characteristics, performance improvements corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, combined performance improvements corresponding to those configurations can be expected.

[0027] As shown in Fig. 3, the fineness of the first band cord 31 is preferably 1100 dtex / 2 or less. This allows the rolling resistance performance to be reliably maintained. The fineness of the first band cord 31 is, for example, 800 dtex / 2 or more, preferably 900 dtex / 2 or more. This allows the band ply 8A to exert a sufficient tread reinforcing effect.

[0028] The band ply 8A includes shoulder regions 26 located on both axially outer sides of the crown region 25. The band cords 8c include second band cords 32 arranged in the shoulder regions 26. The second band cords 32 have a fineness of, for example, 1200 dtex / 2 or more, preferably 1400 dtex / 2 or more, and more preferably 1600 dtex / 2 or more. Such second band cords 32 have a high binding force and reliably suppress lifting of the ends of the belt layer 7. This improves the durability of the tread portion 2. As a more preferable aspect, in this embodiment, all of the band cords 8c arranged in the shoulder regions 26 are configured as second band cords 32.

[0029] On the other hand, the second band cord 32 has a fineness of, for example, 2800 dtex / 2 or less, preferably 2650 dtex / 2 or less, which prevents the weight of the band ply 8A from being excessively increased by the second band cord 32, and ensures that rolling resistance performance is maintained.

[0030] The second band cord 32 is preferably a composite cord containing nylon fiber and aramid fiber, which can suppress vibration of the tread portion 2, and is expected to improve noise performance and durability of the tread portion 2.

[0031] The end count of the band cords 8c per 5cm width of the band ply 8A (hereinafter referred to as "ends") is, for example, 20 to 50 / 5cm. The end count in the crown region 25 is preferably smaller than the end count in the shoulder region 26. This ensures that rolling resistance performance is maintained.

[0032] As shown in FIG. 2, the tread portion 2 includes a first tread edge T1, a second tread edge T2, and a plurality of circumferential grooves extending continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2.

[0033] The first tread edge T1 and the second tread edge T2 each correspond to the axially outermost contact points when the tire 1 in its normal state is loaded with 70% of the normal load and the tread portion 2 contacts the ground on a flat surface at a camber angle of 0°.

[0034] For pneumatic tires for which various standards are established, "normal load" refers to the load specified for each tire in the standard system including the standard on which the tire is based. For JATMA, this is "maximum load capacity," for TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, this is "LOAD CAPACITY." For tires for which various standards are not established, "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0035] The multiple circumferential grooves include a first shoulder circumferential groove 21, a second shoulder circumferential groove 22, a first crown circumferential groove 23, and a second crown circumferential groove 24. The first shoulder circumferential groove 21 is provided closest to the first tread edge T1. The second shoulder circumferential groove 22 is provided closest to the second tread edge T2. The first crown circumferential groove 23 is provided between the tire equator C and the first shoulder circumferential groove 21. The second crown circumferential groove 24 is provided between the tire equator C and the second shoulder circumferential groove 22.

[0036] The first shoulder circumferential groove 21 is preferably disposed closer to the tire equator C than the end 25a of the crown region 25 on the first tread edge T1 side. This causes the first shoulder circumferential groove 21, where a rigidity step in the tread portion 2 is likely to occur, and the end 25a of the crown region 25 to be misaligned in the tire axial direction, thereby improving the durability of the tread portion 2.

[0037] It is desirable that the second shoulder circumferential groove 22 is also disposed at the same position as the first shoulder circumferential groove 21. This ensures that the above-mentioned effects are obtained.

[0038] FIG. 4 is an enlarged cross-sectional view conceptually illustrating the steel cords 7c and the topping rubber 7g of the first belt ply 7A. As shown in FIG. 4, the thickness t5 of the topping rubber 7g on the radially outer side of the steel cords 7c in a region 36 20 mm from the axial end of the first belt ply 7A is preferably 0.1 to 1.0 mm larger than the thickness t3 of the topping rubber 7g on the radially outer side of the steel cords 7c in the axial center portion 35 of the first belt ply 7A. This reduces damage originating from the end of the first belt ply 7A without increasing the weight of the tread portion 2. Therefore, the tire 1 can maintain good rolling resistance performance while improving the durability of the tread portion 2. Note that in FIG. 4, the difference in the thickness of the topping rubber 7g is exaggerated to facilitate understanding of the above-described features. In other figures, the thickness of the topping rubber 7g is omitted.

[0039] It is also desirable that the thickness t6 of the topping rubber 7g on the radially inner side of the steel cord 7c in a region 36 20 mm from the axial end of the first belt ply 7A is 0.1 to 1.0 mm larger than the thickness t4 of the topping rubber 7g on the radially inner side of the steel cord 7c in the central portion 35.

[0040] Similarly, it is desirable that the above-described characteristics of the topping rubber 7g of the first belt ply 7A be applied to the thickness of the topping rubber 7g of the second belt ply 7B.

[0041] As shown in Fig. 2, the first portion 11 includes a first end portion 13 on the first tread edge T1 side and a second end portion 14 on the second tread edge T2 side. At the first end portion 13, the first thickness t1 continuously decreases toward the outer end 11a of the first portion 11 on the first tread edge T1 side. At the second end portion 14, the first thickness t1 continuously decreases toward the outer end 11b of the first portion 11 on the second tread edge T2 side. In this embodiment, the position where the reduction in the first thickness t1 ends corresponds to the axially outer ends 11a, 11b of the first portion 11.

[0042] From the viewpoint of reliably reducing interior noise, the outer end 11a of the first portion 11 of this embodiment on the first tread end T1 side is, for example, located closer to the first tread end T1 than the first crown circumferential groove 23, and more preferably, located closer to the first tread end T1 than the first shoulder circumferential groove 21.

[0043] FIG. 5 shows an enlarged cross-sectional view of the first end 13 of the first portion 11. As shown in FIG. 5, the outer end 11a of the first portion 11 on the first tread edge T1 side is preferably located axially at the same position as the axially outer end 7b of the second belt ply 7B, or is located axially more inward than the outer end 7b of the second belt ply 7B. In a more preferable embodiment, the axial distance L3 between the outer end 11a of the first portion 11 and the outer end 7b of the second belt ply 7B is set to 5 mm or less. This allows the belt layer 7 to suppress deformation around the outer end 11a of the first portion 11 during tire running while ensuring a sufficient axial length of the first portion 11, and ultimately suppresses separation of the inner rubber 10 around the outer end 11a.

[0044] Furthermore, the first end portion 13 is connected to a portion extending at a constant first thickness t1 on the tire equator C (shown in FIG. 1) side. The axial length L4 of the first end portion 13 is 2.0% to 4.0% of the tread width TW (shown in FIG. 1). This makes it possible to prevent a sudden change in the thickness of the inner rubber 10, and suppress damage such as peeling of the inner rubber 10. The tread width TW corresponds to the axial distance of the tire from the first tread edge T1 to the second tread edge T2 in the normal state.

[0045] As shown in FIG. 2 , the first portion 11 has the same configuration on the second tread edge T2 side as on the first tread edge T1 side. That is, the outer end 11b of the first portion 11 on the second tread edge T2 side is located, for example, closer to the second tread edge T2 than the second crown circumferential groove 24, and more preferably closer to the second tread edge T2 than the second shoulder circumferential groove 22. The outer end 11b of the first portion 11 on the second tread edge T2 side is preferably axially aligned with the axially outer end 7b of the second belt ply 7B, or is preferably axially inward of the outer end 7b of the second belt ply 7B. The axial distance between the outer end 11b of the first portion 11 and the outer end 7b of the second belt ply 7B is 5 mm or less. The second end 14 has the same configuration as the first end 13.

[0046] By arranging the outer ends 11a, 11b of the first portion 11 as described above, the axial length L5 of the first portion 11 of this embodiment is preferably set to 90% to 110% of the tread width TW, thereby making it possible to reliably reduce interior noise while suppressing an increase in tire weight.

[0047] In the first portion 11 of this embodiment, a first length L6 from the tire equator C to the outer end 11a on the first tread edge T1 side and a second length L7 from the tire equator C to the outer end 11b on the second tread edge T2 side are substantially the same. More specifically, the difference between the first length L6 and the second length L7 is set to 3% or less of the first length L6. This can improve tire uniformity.

[0048] The first portion 11 extends with a constant first thickness t1 between the first end 13 and the second end 14. As a result, the first thickness t1 is substantially constant at the tire equator C and at a position on the first tread edge T1 side of the first shoulder circumferential groove 21. In a desirable embodiment, the first thickness t1 is substantially constant from the tire equator C to a position beyond the first shoulder circumferential groove 21. Note that the term "substantially constant" means that unavoidable errors in rubber products such as tires can be tolerated, and includes an embodiment in which the difference between the maximum and minimum thickness values ​​is 5% or less of the maximum value.

[0049] The first portion 11 may have a region extending with a constant first thickness t1 that extends to the first tread edge T1 (not shown). In other words, the first thickness t1 may be substantially constant from the position of the tire equator C to the position of the first tread edge T1 (a virtual line that passes through the first tread edge T1 and extends parallel to the tire radial direction). In this case, the outer end 11a of the first portion 11 is located axially outward of the first tread edge T1. This embodiment can further reduce interior noise.

[0050] It is desirable that the first portion 11 has the same configuration as described above between the tire equator C and the second tread edge T2. That is, the first thickness t1 is substantially constant at the position of the tire equator C and at a position on the second tread edge T2 side of the second shoulder circumferential groove 22. In a desirable aspect, the first thickness t1 is substantially constant from the position of the tire equator C to a position beyond the second shoulder circumferential groove 22. In another embodiment, the first portion 11 may have a region extending with a constant first thickness t1 extending to the second tread edge T2.

[0051] The first thickness t1 is preferably 1.5 to 3.5 times, and more preferably 1.5 to 2.5 times, the second thickness t2 (shown in FIG. 1, and the same applies hereinafter). This makes it possible to maintain good noise performance while suppressing an increase in the weight of the tire 1.

[0052] From the same viewpoint, the maximum value of the first thickness t1 is preferably 2.0 mm or more, more preferably 2.5 mm or more, and preferably 4.5 mm or less, more preferably 4.0 mm or less, and even more preferably 3.5 mm or less. On the other hand, the second thickness t2 is, for example, greater than 0.5 mm and less than 2.0 mm. In a desirable embodiment, the second thickness t2 is 1.0 to 1.5 mm. Note that the second portion 12 of this embodiment is continuous with the first portion 11 and extends to the bead portion 4 (shown in FIG. 1), and the second thickness t2 is constant throughout the entire portion. However, the second portion 12 is not limited to this embodiment.

[0053] As shown in Figure 2, the first portion 11 and the second portion 12 of the inner rubber 10 are made of an air-impermeable rubber material. For example, a butyl-based or halogenated butyl-based rubber material can be used as the rubber material. In this embodiment, the first portion 11 and the second portion 12 are made of the same rubber material.

[0054] However, the present invention is not limited to this embodiment. Fig. 6 shows an enlarged cross-sectional view of the first portion 11 and the second portion 12 of another embodiment of the present invention. As shown in Fig. 6, the first portion 11 of the inner rubber 10 of this embodiment includes an inner liner layer 16 made of an air-impermeable rubber material (hereinafter referred to as the first rubber material), and an additional layer 17 disposed between the inner liner layer 16 and the carcass 6. This additional layer 17 is made of a second rubber material different from the first rubber material. As the second rubber material, for example, an air-permeable rubber material is adopted. That is, the first portion 11 of this embodiment is formed by combining an air-impermeable rubber material and an air-permeable rubber material.

[0055] In this embodiment, the first portion 11 includes the additional layer 17, thereby improving various performances. For example, a rubber material having a larger loss tangent tanδ than the first rubber material forming the inner liner layer 16 can be used as the second rubber material forming the additional layer 17. In this embodiment, the tread portion 2 can further absorb vibrations from the road surface, thereby further reducing interior noise. The loss tangent tanδ is measured under the following conditions using a viscoelasticity spectrometer in accordance with the provisions of JIS-K6394. Initial distortion: 5% Amplitude: ±1% Frequency: 10Hz Deformation mode: tension Measurement temperature: 70℃

[0056] The position of the additional layer 17 is not limited to the embodiment shown in Fig. 6. Fig. 7 shows an enlarged cross-sectional view of the first portion 11 and the second portion 12 of yet another embodiment of the present invention. As shown in Fig. 7, the additional layer 17 may be disposed radially inward of the inner liner layer 16 in the tire radial direction. The additional layer 17 may also constitute a part of the tire cavity surface 1A.

[0057] As shown in Figures 6 and 7, even in an embodiment in which the additional layer 17 is included in the first portion 11 of the inner rubber 10, the first thickness t1 corresponds to the thickness from the inner surface 6i of the carcass 6 in the tread portion 2 to the tire cavity surface 1A.

[0058] As shown in FIG. 2, the tread portion 2 includes a cap rubber layer 2C that forms the ground contact surface 2s, and a base rubber layer 2B disposed radially inward of the cap rubber layer 2C. The ratio Tc / Tb of the thickness Tc of the cap rubber layer to the thickness Tb of the base rubber layer is preferably 0.66 to 2.33. A ratio Tc / Tb of 0.66 or more can prevent the base rubber layer 2B from being exposed during wear for a long period of time, thereby improving the durability of the tread portion 2. From this perspective, the ratio Tc / Tb is more preferably 1.00 or more. Furthermore, a ratio Tc / Tb of 2.33 or less can maintain good rolling resistance performance.

[0059] The rubber hardness of the cap rubber layer 2C is preferably 45 to 75. When the rubber hardness of the cap rubber layer 2C is 45 or more, heat generation in the tread portion 2 can be suppressed and rolling resistance performance can be maintained. When the rubber hardness of the cap rubber layer 2C is 75 or less, good steering stability performance can be maintained. In this specification, rubber hardness means durometer A hardness measured in an environment of 23°C using durometer type A according to JIS-K6253.

[0060] The present invention is more likely to exhibit the above-described effects as the tire has a wider speed range. From this perspective, as shown in Fig. 1, the tire 1 of this embodiment has a speed symbol of preferably H or higher, and more preferably W or higher, in accordance with the JATMA standard.

[0061] FIG. 8 shows an enlarged cross-sectional view of the sidewall portion 3 of another embodiment of the present invention. As shown in FIG. 8, the second portion 12 of this embodiment includes an inner liner layer 16 made of a first rubber material having air impermeability and an intermediate layer 18 disposed between the inner liner layer 16 and the carcass 6. In FIG. 8, this intermediate layer 18 is dotted. The intermediate layer 18 is made of a rubber material different from the first rubber material. The intermediate layer 18 may be made of, for example, the same second rubber material as the additional layer 17 of the first portion 11 described in FIGS. 6 and 7. By including such an intermediate layer 18 in the second portion 12, transmission of vibrations generated in the tread portion 2 to the vehicle side can be further suppressed. Note that the intermediate layer 18 may be made of a rubber material different from the first rubber material and the second rubber material.

[0062] The intermediate layer 18 overlaps, for example, the band layer 8 in the tire axial direction. In a preferred embodiment, the intermediate layer 18 overlaps with the belt layer 7 in the tire axial direction. The intermediate layer 18 may be continuous with the first portion 11 of the inner rubber 10. Also, it is preferred that the intermediate layer 18 extends radially inward of the tire radially outer end of the turned-up portion 6b of the carcass 6. Such an intermediate layer 18 helps to further reduce interior noise.

[0063] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects. [Example]

[0064] Pneumatic tires of size 235 / 60R18 having the basic structure shown in Figure 1 were prototyped based on the specifications in Tables 1 and 2. As Comparative Examples 1 to 4, tires with band cord finenesses outside the range of the present invention were prototyped. The tires of Comparative Examples 1 to 4 are substantially the same as the tires of the Examples, except for the above-mentioned points. The rolling resistance performance and noise performance of each test tire were tested. The common specifications and test methods for each test tire are as follows: <Common specifications> Rim: 16x6.5 Tire pressure: 230kPa Test vehicle: 1800cc HV vehicle

[0065] <Rolling resistance performance> The rolling resistance of each test tire was measured using a rolling resistance tester. The results were expressed as an index by taking the reciprocal of the measured rolling resistance, with a larger index indicating a lower rolling resistance and a better result.

[0066] <Noise performance> A test vehicle fitted with test tires on all wheels was driven at a speed of 60 km / h on a road noise measurement road (rough asphalt road), and the interior noise (noise below 500 Hz) was measured. The results were expressed as an index, with the reciprocal of the interior noise being converted; the larger the index, the lower the interior noise and the better the noise performance.

[0067] The inventors have conducted a test on an embodiment in which nylon cords are used as band cords in the shoulder region, and the test results are shown in Table 1.

[0068] [Table 1]

[0069] As shown in Table 1, Comparative Example 1 does not have the first portion of the inner rubber, and therefore has a low noise performance of 90 points. In contrast, Comparative Example 2 and Examples 1 to 3 have the first portion of the inner rubber, and therefore have significantly improved noise performance of 95 to 120 points.

[0070] In addition, in Comparative Example 2, the fineness of the band cord in the crown region is outside the range of the present invention, and therefore the rolling resistance performance is 65 points, which is significantly lower than that of Comparative Example 1. In contrast, Examples 1 to 5 have rolling resistance performances of 70 to 95 points, and it can be seen that the rolling resistance performance is improved even compared to Comparative Example 2.

[0071] Furthermore, it was confirmed that the overall performance, which is evaluated by the sum of the rolling resistance performance and noise performance, was superior, with scores of 190 to 195 points for Examples 1 to 5, compared to 155 to 170 points for Comparative Examples 1 and 2. In other words, it can be confirmed from the results in Table 1 that the tire of the present invention achieves both rolling resistance performance and noise performance at a high level.

[0072] The inventors also conducted a study on an embodiment in which a composite cord containing nylon fiber and aramid fiber was used as the band cord in the shoulder region. The test results are shown in Table 2.

[0073] [Table 2]

[0074] As shown in Table 2, Comparative Example 3 does not have the first portion of the inner rubber, and therefore has a low noise performance of 135 points. In contrast, Comparative Example 4 and Examples 6 to 10 have the first portion of the inner rubber, and therefore have significantly improved noise performance of 140 to 165 points.

[0075] In addition, in Comparative Example 4, the fineness of the band cord in the crown region is outside the range of the present invention, so the rolling resistance performance is 20 points, which is low as in Comparative Example 3. In contrast, Examples 6 to 10 have rolling resistance performance of 50 to 55 points, and it can be seen that the rolling resistance performance is improved compared to Comparative Example 4.

[0076] Furthermore, it was confirmed that the overall performance, which is evaluated as the sum of the rolling resistance performance and noise performance, was superior, with 195 to 210 points for Examples 6 to 10, compared to 155 to 170 points for Comparative Examples 3 and 4. In other words, the results in Table 2 also confirm that the tire of the present invention achieves both rolling resistance performance and noise performance at a high level.

[0077] [Note] The present invention includes the following aspects.

[0078] [Invention 1] A pneumatic tire, A tread portion; A pair of sidewall portions; a pair of bead portions; a carcass extending between the pair of bead portions; a belt layer disposed inside the tread portion and on the outer side of the carcass in the tire radial direction; a band layer consisting of one band ply having a band cord covering the entire width of the belt layer in the tire axial direction and extending at an angle of 5° or less with respect to the tire circumferential direction; an inner rubber extending between the pair of bead portions on the inner side of the carcass, the inner rubber includes a first portion extending through the tread portion at a first thickness and a second portion extending through the pair of sidewall portions at a second thickness, the first thickness is greater than the second thickness; The band ply includes a crown region having a width that is 70% of the width of the band ply in the tire axial direction, the crown region being centered on the tire equator, the band cord includes a first band cord arranged in the crown region, The first band cord is a nylon cord and has a fineness of 1150 dtex / 2 or less. Pneumatic tires. [Invention 2] The pneumatic tire according to invention 1, wherein the first band cord has a fineness of 800 dtex / 2 or more. [Invention 3] The band ply includes shoulder regions located on both axially outer sides of the crown region, the band cord includes a second band cord arranged in the shoulder region, 3. The pneumatic tire according to claim 1 or 2, wherein the second band cord has a fineness of 1200 dtex / 2 or more. [Invention 4] A pneumatic tire according to invention 3, wherein the second band cord has a fineness of 2800 dtex / 2 or less. [Invention 5] The pneumatic tire according to invention 3 or 4, wherein the second band cord is a composite cord containing nylon fiber and aramid fiber. [Invention 6] the tread portion includes a first tread edge and a second tread edge, and a plurality of circumferential grooves extending continuously in the tire circumferential direction between the first tread edge and the second tread edge, the plurality of circumferential grooves include a first shoulder circumferential groove provided closest to the first tread end, The pneumatic tire according to any one of the first to fifth aspects of the present invention, wherein the first shoulder circumferential groove is arranged closer to the tire equator than the end of the crown region on the first tread edge side. [Invention 7] The belt layer includes a first belt ply including a plurality of steel cords arranged at an angle with respect to the tire equator and a topping rubber covering the steel cords, The pneumatic tire according to any one of claims 1 to 6, wherein the thickness of the topping rubber on the radially outer side of the steel cords in a region 20 mm from the end of the first belt ply in the tire axial direction is 0.1 to 1.0 mm larger than the thickness of the topping rubber on the radially outer side of the steel cords in a central portion of the first belt ply in the tire axial direction. [Invention 8] the belt layer includes a first belt ply on the carcass side and a second belt ply disposed on the outer side of the first belt ply in the tire radial direction, a pair of outer ends of the second belt ply in the tire axial direction are located axially more inward than a pair of outer ends of the first belt ply in the tire axial direction, The pneumatic tire according to any one of claims 1 to 7, wherein, on each side of the tire equator, an axially outer end of the first portion is located at the same position in the tire axial direction as the outer end of the second belt ply, or is located axially inward of the outer end of the second belt ply and within 5 mm in the tire axial direction. [Invention 9] the first portion includes a first end portion where the first thickness continuously decreases toward an outer end in the tire axial direction, 9. The pneumatic tire according to any one of Inventions 1 to 8, wherein the first thickness is 2.0 to 4.5 mm. [Explanation of symbols]

[0079] 2 Tread section 3 Sidewall 4 Bead section 6. Carcass 7 Belt Layer 8 Band Layer 8c band cord 8A Band Ply 10 Inner rubber 11 Part 1 12 Part 2 25 Crown area 31 1st Band Code t1 First thickness t2 Second thickness

Claims

1. A pneumatic tire, A tread portion; A pair of sidewall portions; a pair of bead portions; a carcass extending between the pair of bead portions; a belt layer disposed inside the tread portion and on the outer side of the carcass in the tire radial direction; a band layer consisting of one band ply including a band cord covering the entire width of the belt layer in the tire axial direction and extending at an angle of 5° or less with respect to the tire circumferential direction; an inner rubber extending between the pair of bead portions on the inner side of the carcass, the inner rubber includes a first portion extending through the tread portion at a first thickness and a second portion extending through the pair of sidewall portions at a second thickness, the first thickness is greater than the second thickness; The band ply includes a crown region having a width that is 70% of the width of the band ply in the tire axial direction, the crown region being centered on the tire equator, the band cord includes a first band cord arranged in the crown region, The first band cord is a nylon cord and has a fineness of 1150 dtex / 2 or less. Pneumatic tires.

2. The pneumatic tire according to claim 1 , wherein the first band cord has a fineness of 800 dtex / 2 or more.

3. The band ply includes shoulder regions located on both axially outer sides of the crown region, The band cord includes a second band cord arranged in the shoulder region, The pneumatic tire according to claim 1 or 2, wherein the second band cord has a fineness of 1200 dtex / 2 or more.

4. The pneumatic tire according to claim 3 , wherein the second band cord has a fineness of 2800 dtex / 2 or less.

5. The pneumatic tire according to claim 3 , wherein the second band cord is a composite cord containing nylon fibers and aramid fibers.

6. the tread portion includes a first tread edge and a second tread edge, and a plurality of circumferential grooves extending continuously in the tire circumferential direction between the first tread edge and the second tread edge, the plurality of circumferential grooves include a first shoulder circumferential groove provided closest to the first tread end, The pneumatic tire according to claim 1 or 2, wherein the first shoulder circumferential groove is disposed closer to the tire equator than an end of the crown region on the first tread edge side.

7. the belt layer includes a first belt ply including a plurality of steel cords arranged at an angle with respect to the tire equator and a topping rubber covering the steel cords, 3. The pneumatic tire according to claim 1, wherein a thickness of the topping rubber on the radially outer side of the steel cord in a region 20 mm from an end portion of the first belt ply in the tire axial direction is 0.1 to 1.0 mm larger than a thickness of the topping rubber on the radially outer side of the steel cord in a central portion of the first belt ply in the tire axial direction.

8. the belt layer includes a first belt ply on the carcass side and a second belt ply disposed on the outer side of the first belt ply in the tire radial direction, a pair of outer ends of the second belt ply in the tire axial direction are located axially more inward than a pair of outer ends of the first belt ply in the tire axial direction, 3. The pneumatic tire according to claim 1, wherein, on each side of the tire equator, an axially outer end of the first portion is located at the same position as the outer end of the second belt ply in the tire axial direction, or is located axially inward of the outer end of the second belt ply and within 5 mm in the tire axial direction.

9. the first portion includes a first end portion where the first thickness continuously decreases toward an outer end in the tire axial direction, The pneumatic tire according to claim 1 or 2, wherein the first thickness is 2.0 to 4.5 mm.

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