Pneumatic tire

Abstract

To provide a pneumatic tire than can improve noise performance, steering stability and rolling resistance performance.SOLUTION: A pneumatic tire 1 includes a tread part 2, a pair of side wall parts 3, a pair of bead parts 4, a carcass 6 extending between the pair of bead parts 4 and an inner rubber 10 extending between the pair of bead parts 4, inside the carcass 6. The inner rubber 10 includes a first portion 11 extending with a first thickness t1 on the tread part 2 and a second portion 12 extending with a second thickness t2 on the pair of side wall parts 3. The first thickness t1 is larger than the second thickness t2. The carcass 6 includes at least one carcass ply 6P in which a plurality of carcass cords are arranged in parallel, where angles of the carcass cords with respect to a tire equator are 66-86 degrees.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 below describes a pneumatic tire. The tire includes a pair of bead cores, a carcass layer having at least one carcass ply spanning the pair of bead cores via a tread portion and a pair of sidewall portions, a first bead apex rubber disposed radially outward of each bead core, and a belt layer disposed radially outward of the carcass layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-172159 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, efforts such as the SDGs have accelerated the development of environmentally friendly products and the shift to electric vehicles (EVs). This has led to demands for even greater improvements in tire fuel efficiency. One way to improve rolling resistance, which is directly linked to fuel efficiency, is by reducing tire weight. However, such weight reduction has led to problems such as reduced noise and poor handling stability.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that can improve noise performance, steering stability performance, and rolling resistance performance. [Means for solving the problem]

[0006] 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, and an inner rubber extending inside the carcass between the pair of bead portions, the inner rubber including 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 carcass including at least one carcass ply having a plurality of carcass cords arranged in parallel, the angle of the carcass cord relative to the tire equator being 66 to 86 degrees. [Effects of the Invention]

[0007] By adopting the above-described configuration, the pneumatic tire of the present invention can improve noise performance, steering stability performance, and rolling resistance performance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing an example of a pneumatic tire. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the tread portion of FIG. 1. [Figure 3] FIG. 2 is a planar development view of a carcass, a belt layer, and a band layer. [Figure 4] 3 is an enlarged cross-sectional view of the outer end of the first portion of FIG. 2. [Figure 5] FIG. 10 is an enlarged cross-sectional view of an inner rubber according to another embodiment of the present invention. [Figure 6] FIG. 10 is an enlarged cross-sectional view of an inner rubber according to another embodiment of the present invention. [Figure 7] FIG. 10 is an enlarged cross-sectional view of an inner rubber according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratios of actual structures in order to facilitate understanding of the contents of the invention. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0010] [Pneumatic tire (first embodiment)] FIG. 1 is a cross-sectional view showing an example of a pneumatic tire 1. FIG. 1 shows a cross-section including the rotation axis of a pneumatic tire (hereinafter sometimes referred to as "tire") 1 in a normal state. The tire 1 of this embodiment is suitable for use as a passenger vehicle tire, for example. However, the tire 1 is not limited to passenger vehicle tires, and can be applied to various types of tires, such as heavy-duty tires, motorcycle tires, and industrial vehicle tires.

[0011] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, that the tire is mounted on a normal rim, inflated to the normal internal pressure, and is in an unloaded state. In the case of a tire for which various standards are not established, the normal condition means that the tire is in a standard use state according to its intended use, that is, unmounted on a vehicle, and is in an unloaded state.

[0012] In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state. Furthermore, the dimensions of components that cannot be measured in the normal state (for example, internal materials of the tire 1) are values ​​measured by bringing the tire 1 into a state as close as possible to the normal state.

[0013] A "genuine rim" is a rim that is defined for each tire in a standard system that includes the standard to which tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO. If there is no standard system to which tire 1 is based, the rim with the smallest rim diameter and the smallest rim width among rims that can be mounted on tire 1 and do not cause air leakage can be identified as the "genuine rim."

[0014] If there is a standard system that includes the standard to which tire 1 is based, the "normal internal pressure" is the air pressure set for each tire by that standard, such as the "maximum air pressure" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO. Note that if tire 1 is not based on a standard system, the air pressure set for each tire by the manufacturer or other party is identified as the normal internal pressure.

[0015] The tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The bead portions 4 have, for example, an annularly extending bead core 5. The bead core 5 is formed of, for example, a steel wire.

[0016] Fig. 2 is an enlarged cross-sectional view of the tread portion 2 of Fig. 1. The tire 1 of this embodiment further includes a carcass 6 and an inner rubber 10. In the tread portion 2 of this embodiment, a belt layer 7 is arranged on the outer side of the carcass 6 in the tire radial direction. Furthermore, in the tread portion 2, a band layer 8 may be arranged on the outer side of the belt layer 7 in the tire radial direction.

[0017] [Carcass] As shown in FIG. 1, the carcass 6 extends between a pair of bead portions 4, 4. The carcass 6 includes at least one carcass ply 6P. In this embodiment, the carcass ply 6P is composed of two plies, an inner carcass ply 6A and an outer carcass ply 6B. The inner and outer plies are distinguished by the position of the tire equator C.

[0018] The carcass ply 6P (in this example, the inner carcass ply 6A and the outer carcass ply 6B) includes, for example, a main body portion 6a and a turned-up portion 6b. The main body portion 6a extends, for example, between the two 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 inner side in the tire axial direction to the outer side. A bead apex 9 extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the turned-up portion 6b.

[0019] 3 is a planar development view of the carcass 6, the belt layer 7, and the band layer 8. The carcass ply 6P (the inner carcass ply 6A and the outer carcass ply 6B) has a plurality of carcass cords 6c arranged in parallel. The carcass cords 6c may be made of organic fiber cords such as aramid or rayon.

[0020] When the carcass 6 is made up of a plurality of carcass plies 6P (in this example, an inner carcass ply 6A and an outer carcass ply 6B), as in this embodiment, it is preferable that the carcass cords 6c are overlapped in a direction crossing each other, thereby increasing the rigidity of the tread portion 2 and improving rolling resistance performance.

[0021] [Belt layer] 1 and 2, the belt layer 7 includes at least one belt ply 7P. The belt ply 7P in this embodiment includes a first belt ply 7A and a second belt ply 7B disposed radially outward of the first belt ply 7A.

[0022] 3, the belt ply 7P (first belt ply 7A and second belt ply 7B) has a plurality of belt cords 7c arranged in parallel. Steel cords are used as the belt cords 7c, but highly elastic organic fiber cords such as aramid and rayon may also be used as needed.

[0023] The belt cords 7c of the first belt ply 7A and the belt cords 7c of the second belt ply 7B are preferably inclined in opposite directions relative to the tire equator C (tire circumferential direction), thereby effectively reinforcing the tread portion 2 and improving rolling resistance performance.

[0024] As shown in Fig. 2, a pair of axially outer ends 7b of the second belt ply 7B are located axially more inward than a pair of axially outer ends 7a of the first belt ply 7A. This makes the axial length of the second belt ply 7B shorter than the axial length of the first belt ply 7A, preventing the second belt ply 7B from becoming larger than necessary. This maintains noise performance and ride comfort.

[0025] [Band Layer] The band layer 8 is composed of at least one band ply 8A, one band ply 8A in this embodiment. As shown in FIG. 3, the band ply 8A includes band cords 8c arranged at an angle of 5° or less with respect to the tire circumferential direction, for example. The band layer 8 in this embodiment is arranged so as to cover the entire belt layer 7. Such a band layer 8 effectively prevents the outer diameter of the tire 1 from increasing (i.e., outer diameter growth), thereby improving rolling resistance performance.

[0026] In recent years, efforts such as the SDGs have accelerated the development of environmentally friendly products and the shift to electric vehicles (EVs), which has led to demands for further improvements in fuel economy performance for tires 1. Although further improvements can be made to rolling resistance performance, which is directly linked to fuel economy performance, for example, by reducing the weight of tires, this tends to result in deterioration of noise performance and handling stability.

[0027] On the other hand, if the thickness of the tread rubber 2G (including the cap rubber 2A and the base rubber 2B in this example) shown in Figures 1 and 2 is increased in order to improve noise performance and handling stability, it is possible to achieve a vibration reduction effect, but this leads to an increase in the weight of the tire 1, which tends to deteriorate the rolling resistance performance. In this way, there is a trade-off between rolling resistance performance, noise performance, and handling stability.

[0028] In the tire 1 of this embodiment, the angle θ1 of the inner rubber 10 and the carcass cord 6c shown in Figure 3 relative to the tire equator C is configured as described below, thereby improving noise performance, handling stability performance, and rolling resistance performance.

[0029] [Inner rubber] As shown in Fig. 1, the inner rubber 10 extends between a pair of bead portions 4 inside the carcass 6. The inner rubber 10 of this embodiment forms the tire cavity surface 1i. For this reason, the inner rubber 10 is desirably formed from an air-impermeable rubber material. Examples of rubber materials include butyl-based or halogenated butyl-based rubber materials.

[0030] As shown in Figures 1 and 2, the inner rubber 10 of this embodiment is configured to include a first portion 11 and a second portion 12. The first portion 11 extends through the tread portion 2 at a first thickness t1. On the other hand, the second portion 12 extends through the pair of sidewall portions 3 at a second thickness t2. Here, 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 1i, and do not include the topping rubber of the carcass ply 6P (in this example, the inner carcass ply 6A and the outer carcass ply 6B).

[0031] In this embodiment, the first thickness t1 is greater than the second thickness t2. Here, the phrase "the first thickness t1 is greater than the second thickness t2" means that the average value of the first thickness t1 is greater than the average value of the second thickness t2. The average value of the first thickness t1 corresponds to the value obtained by dividing the cross-sectional area of ​​the first portion 11 in the tire meridian cross section by the length of the first portion 11 along the tire cavity surface 1i. The same applies to the average value of the second thickness t2. In this embodiment, as a preferred aspect, the first thickness t1 is set to be greater than the second thickness t2 over the entire circumference of the tire, but the present invention is not limited to this aspect.

[0032] In the tire 1 of this embodiment, the first portion 11 of the inner rubber 10 increases the rubber volume of the tread portion 2, and therefore, it is possible to obtain the same vibration-reducing effect as by increasing the thickness of the tread rubber 2G. Note that the inner rubber 10 increases the weight of the inner side of the carcass 6, which tends to deteriorate rolling resistance performance. Such an increase in the weight of the inner side of the carcass 6 has a smaller impact on deterioration of rolling resistance performance than, for example, increasing the weight of the outer side of the carcass 6 by increasing the thickness of the tread rubber 2G. Therefore, by providing the inner rubber 10 as described above, the tire 1 of this embodiment can improve noise performance while suppressing deterioration of rolling resistance performance.

[0033] The first thickness t1 is preferably 1.5 to 3.5 times the second thickness t2. By making the first thickness t1 1.5 times or more the second thickness t2, vibration of the tread portion 2 is effectively suppressed. This improves the noise performance of the tire 1. To further enhance this effect, the first thickness t1 is more preferably 1.7 times or more the second thickness t2, and even more preferably 1.9 times or more. On the other hand, by making the first thickness t1 3.5 times or less the second thickness t2, excessive weight increase is suppressed, and rolling resistance performance and ride comfort performance can be maintained. To further enhance this effect, the first thickness t1, in combination with any of the above lower limit values, is more preferably 2.7 times or less the second thickness t2, and even more preferably 2.2 times or less. As an example, the first thickness t1 is preferably 1.7 to 2.7 times, or even 1.9 to 2.2 times the second thickness t2.

[0034] The first thickness t1 is preferably set to 2.0 to 4.5 mm. By setting the first thickness t1 to 2.0 mm or more, vibration of the tread portion 2 is effectively suppressed, and the noise performance of the tire 1 is improved. To further enhance this effect, the first thickness t1 is more preferably set to 2.5 mm or more. On the other hand, by setting the first thickness t1 to 4.5 mm or less, excessive weight increase is suppressed, and rolling resistance performance and ride comfort performance can be maintained. To further enhance this effect, the first thickness t1, in combination with any of the above lower limit values, is more preferably set to 4.0 mm or less, and even more preferably set to 3.5 mm or less. As an example, the first thickness is preferably set to 2.5 to 4.0 mm.

[0035] The second thickness t2 is preferably set to 0.5 to 2.0 mm. When the second thickness t2 is set to 0.5 mm or more, the rigidity of the sidewall portion 3 is increased, and steering stability is improved. To further enhance this effect, the second thickness t2 is more preferably set to 1.0 mm or more. On the other hand, when the second thickness t2 is set to 2.0 mm or less, an excessive increase in weight and an excessive increase in rigidity of the sidewall portion 3 are suppressed, and the rolling resistance performance and ride comfort of the tire 1 are maintained. To further enhance this effect, the second thickness t2 is more preferably set to 1.5 mm or less in combination with any of the above lower limit values. As an example, the second thickness t2 is preferably set to 1.0 to 1.5 mm.

[0036] 2, the first portion 11 of this embodiment preferably includes a portion (end portion) 11A where the first thickness t1 continuously decreases toward the axially outer end 11a of the first portion 11. That is, the position where the decrease in the first thickness t1 ends corresponds to the outer end 11a of the first portion 11 of this embodiment. Such a first portion 11 (end portion 11A) suppresses stress concentration at the outer end 11a, improving the durability of the tire 1.

[0037] FIG. 4 is an enlarged cross-sectional view of the outer end 11a of the first portion 11 in FIG. 2. As shown enlarged in FIG. 4, on each side of the tire equator C shown in FIG. 2, the axially outer end 11a of the first portion 11 is preferably located at the same axial position as the 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 10 mm or less. This ensures a sufficient axial length of the first portion 11, improving noise performance. Furthermore, the belt layer 7 suppresses deformation around the outer end 11a of the first portion 11 during tire running. This can prevent peeling of the inner rubber 10 around the outer end 11a.

[0038] [Angle of carcass cord relative to tire equator] In the tire 1 of this embodiment, as shown in FIG. 3, the angle θ1 of the carcass cord 6c with respect to the tire equator C is limited to 66 to 86 degrees.

[0039] By limiting the angle θ1 of the carcass cords 6c to 86 degrees or less, the rigidity of the tread portion 2 shown in FIGS. 1 and 2 is increased. This not only offsets the deterioration in rolling resistance performance caused by the inner rubber 10, but also enables further improvement in rolling resistance performance. Furthermore, by limiting the angle θ1 of the carcass cords 6c shown in FIG. 3 to 86 degrees or less, axial shear deformation of the tire 1 shown in FIGS. 1 and 2 is suppressed, thereby improving steering stability. To further enhance this effect, the angle θ1 of the carcass cords 6c shown in FIG. 3 is preferably set to 84 degrees or less, more preferably 82 degrees or less, and even more preferably 80 degrees or less. Furthermore, by overlapping the carcass cords 6c of the inner carcass ply 6A and the carcass cords 6c of the outer carcass ply 6B in directions that intersect with each other, as in this embodiment, the rigidity of the tread portion 2 is effectively increased. Therefore, the above-mentioned effect can be effectively exerted.

[0040] On the other hand, by limiting the angle θ1 of the carcass cords 6c shown in Fig. 3 to 66 degrees or more, an increase in the vertical spring constant of the tire 1 shown in Fig. 1 is suppressed, and ride comfort and noise performance can be maintained. To further enhance this effect, the angle θ1 of the carcass cords 6c shown in Fig. 3 is preferably 68 degrees or more, more preferably 70 degrees or more, and even more preferably 72 degrees or more, in combination with any of the above upper limits. As an example, the angle θ1 of the carcass cords 6c is preferably 68 to 84 degrees, further preferably 70 to 82 degrees, and even more preferably 72 to 80 degrees.

[0041] As described above, the tire 1 of this embodiment is provided with the inner rubber 10 including the first portion 11 and the second portion 12 shown in Figures 1 and 2, thereby suppressing deterioration in rolling resistance performance and improving noise performance. Furthermore, by limiting the angle θ1 of the carcass cord 6c shown in Figure 3 to the above range, rolling resistance performance and handling stability performance are improved while ride comfort performance is maintained. Therefore, the tire 1 of this embodiment can achieve improved noise performance, handling stability performance, and rolling resistance performance.

[0042] [Belt cord angle] To more effectively exert the above-mentioned effects, the angle θ2 of the belt cord 7c with respect to the tire equator C shown in FIG. 3 is preferably set to 28 to 46 degrees. Setting the angle of the belt cord 7c to 28 degrees or greater suppresses angle change of the belt cord 7c during tire rotation, suppressing heat generation in the tread portion 2 shown in FIGS. 1 and 2, thereby improving rolling resistance. To further enhance these effects, the angle θ2 of the belt cord 7c shown in FIG. 3 is more preferably set to 32 degrees or greater, and even more preferably set to 36 degrees or greater. On the other hand, setting the angle θ2 of the belt cord 7c to 46 degrees or less suppresses a decrease in shear rigidity of the tread portion 2 shown in FIGS. 1 and 2, thereby improving steering stability. To further enhance these effects, the angle θ2 of the belt cord 7c, in combination with any of the above lower limit values, is more preferably set to 42 degrees or less, and even more preferably set to 40 degrees or less. As an example, the angle θ2 of the belt cord 7c is preferably set to 32 to 42 degrees, and even more preferably 36 to 40 degrees.

[0043] In this embodiment, the above-mentioned band layer 8 is arranged radially outside the belt layer 7, so the rolling resistance performance improved by limiting the angle θ1 of the carcass cord 6c and the angle θ2 of the belt cord 7c to the above-mentioned ranges can be further improved.

[0044] [Pneumatic tire (second embodiment)] As shown in Figures 1 and 2, the inner rubber 10 of the above-described embodiments has been shown as having the first portion 11 and the second portion 12 formed from a single rubber material, but is not limited to this. For example, the inner rubber 10 may be formed from a plurality of rubber materials. Figure 5 is an enlarged cross-sectional view of the inner rubber 10 of another embodiment of the present invention.

[0045] The first portion 11 of the inner rubber 10 in this embodiment includes an inner liner layer 16 made of an air-impermeable rubber material and an additional layer 17 arranged between the inner liner layer 16 and the carcass 6.

[0046] The additional layer 17 is made of a rubber material different from that of the inner liner layer 16. The additional layer 17 may be made of, for example, an air-permeable rubber material. In this case, the first portion 11 may be made of a composite of an air-impermeable rubber material and an air-permeable rubber material.

[0047] 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 rubber material of the inner liner layer 16 can be used as the rubber material of the additional layer 17. In this case, the tread portion 2 can better absorb vibrations from the road surface, further improving noise performance. 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℃

[0048] [Pneumatic tire (third embodiment)] The position of the additional layer 17 is not limited to the embodiment shown in Fig. 5. Fig. 6 is an enlarged cross-sectional view of the inner rubber 10 of another embodiment of the present invention. The additional layer 17 of this embodiment is disposed, for example, on the inner side of the inner liner layer 16 in the tire radial direction. In this case, the additional layer 17 forms part of the tire cavity surface 1i.

[0049] As with the inner rubber 10 shown in FIG. 5, the inner rubber 10 of this embodiment also has a wide variety of materials that can be selected for the additional layer 17, and various performances can be achieved at low cost.

[0050] [Pneumatic tire (third embodiment)] Figure 7 is an enlarged cross-sectional view of the inner rubber 10 of another embodiment of the present invention. The second portion 12 of this embodiment includes an inner liner layer 16 made of an air-impermeable rubber material, and an intermediate layer 18 disposed between the inner liner layer 16 and the carcass 6. In Figure 7, the intermediate layer 18 is shown in color.

[0051] The intermediate layer 18 in this embodiment is made of a different rubber material from that of the inner liner layer 16. The intermediate layer 18 may be made of the same rubber material as that of the additional layer 17 (shown in FIGS. 5 and 6), for example. Such an intermediate layer 18 further suppresses the transmission of vibrations generated in the tread portion 2 to the vehicle side, improving noise performance. Note that the intermediate layer 18 may be made of a different rubber material from that of the additional layer 17.

[0052] The intermediate layer 18 overlaps, for example, with the band layer 8 in the tire axial direction. The intermediate layer 18 in this embodiment 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, for example. It is also desirable that the intermediate layer 18 overlaps with the turned-up portion 6b of the carcass 6 in the tire radial direction. Such an intermediate layer 18 helps to suppress vibrations of the sidewall portion 3, improving noise performance.

[0053] Even when the second portion 12 of the inner rubber 10 includes an intermediate layer 18, the second thickness t2 is the thickness from the inner surface 6i of the carcass 6 in the sidewall portion 3 to the tire cavity surface 1i, and is the thickness excluding the topping rubber of the carcass ply 6P (in this example, the inner carcass ply 6A and the outer carcass ply 6B).

[0054] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways. [Example]

[0055] [Example A] Pneumatic tires having the basic structure of FIG. 1 were prototyped based on the specifications in Table 1 (Examples 1 to 6 and Comparative Examples 1 and 2). In Comparative Example 1, the first thickness of the first portion of the inner rubber was the same as the second thickness of the second portion. Furthermore, in Comparative Examples 1 and 2, the angle θ1 of the carcass cord with respect to the tire equator was set to 90 degrees. Then, using the prototype tires, the steering stability performance, rolling resistance performance, and noise performance were tested. The main common specifications and test methods are as follows:

[0056] <Common specifications> Tire size: 225 / 55R18 Rim size: 18 x 7J Air pressure: 230kPa Load: 5.15kN Test vehicle: Japanese-made FF passenger car (2000cc displacement) Tire mounting position: All wheels First part first thickness t1: 2.5 mm Second part second thickness t2: 1.2 mm Carcass layer: Carcass ply: Inner carcass ply Outer carcass ply Belt layer: Belt ply: First Belt Ply Second Belt Ply

[0057] <Handling stability> The prototype tires were mounted on a test vehicle, and the vehicle was driven on a test course with a dry asphalt surface, and the characteristics related to grip, steering response, and responsiveness were evaluated by the test driver's senses. The results are shown as a score based on Example 1 being 100. The higher the score, the better the handling stability.

[0058] <Rolling resistance performance> In accordance with ISO28580, the prototype tires were mounted on a rolling resistance tester and the rolling resistance was measured under the following conditions. The results are expressed as an index, with the reciprocal of the value in Example 1 being set to 100. A larger index indicates better rolling resistance performance. Load: 31.25kN Speed: 80km / h

[0059] <Noise performance> The prototype tire was mounted on a test vehicle, and microphones were placed on both the left and right sides of the driver's seat of the test vehicle. The test vehicle was then driven straight at 50 km / h on a test course with a dry asphalt road surface, and the average sound pressure measured by the microphones was calculated. The results are expressed as an index, with the reciprocal of the average sound pressure of Example 1 set to 100. The larger the index, the better the noise performance.

[0060] The test results are shown in Table 1. [Table 1]

[0061] As a result of the test, it was confirmed that the tires of the examples were able to improve noise performance, steering stability performance and rolling resistance performance compared to the tires of the comparative examples.

[0062] [Example B] Pneumatic tires having the basic structure shown in FIG. 1 were modeled as FEM models (Examples 7 to 12 and Comparative Example 3) based on the specifications in Table 1. Then, computer simulations were performed to calculate the vertical spring constant, lateral spring constant, and rolling resistance.

[0063] The reciprocal of the vertical spring constant was calculated to evaluate the ride comfort performance. This ride comfort performance was expressed as an index with Comparative Example 3 being 100. The larger the index, the better the ride comfort performance, and if it is 85 or higher, the ride comfort performance is maintained.

[0064] The lateral spring constant was calculated to evaluate the handling stability performance. The handling stability performance was expressed as an index, with Comparative Example 3 being 100. The larger the value, the better the handling stability performance.

[0065] The reciprocal of the rolling resistance was calculated to evaluate the rolling resistance performance. This rolling resistance performance was expressed as an index with Comparative Example 3 being 100. The larger the value, the better the rolling resistance performance. The common specifications are the same as those of Example A.

[0066] The test results are shown in Table 2. [Table 2]

[0067] As a result of the test, the tires of the examples had improved steering stability and rolling resistance compared to the tires of the comparative examples. On the other hand, although the tires of the examples had slightly lower ride comfort compared to the tires of the comparative examples, both scores were 85 or higher, and ride comfort was maintained.

[0068] [Note] The present invention includes the following aspects.

[0069] [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; 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 carcass includes at least one carcass ply in which a plurality of carcass cords are arranged in parallel, The angle of the carcass cord with respect to the tire equator is 66 to 86 degrees. Pneumatic tires. [Invention 2] A belt layer is disposed in the tread portion on the outer side of the carcass in the tire radial direction, The belt layer includes at least one belt ply in which a plurality of belt cords are arranged in parallel, The pneumatic tire according to invention 1, wherein the angle of the belt cord with respect to the tire equator is 28 to 46 degrees. [Invention 3] the belt plies include a first belt ply and a second belt ply disposed outward 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 Invention 2, 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 10 mm in the tire axial direction. [Invention 4] 4. The pneumatic tire according to any one of claims 1 to 3, wherein the first thickness is 1.5 to 3.5 times the second thickness. [Invention 5] 5. The pneumatic tire according to any one of claims 1 to 4, wherein the first thickness is 2.0 to 4.5 mm. [Invention 6] The pneumatic tire according to any one of claims 1 to 5, wherein the first portion includes a portion where the first thickness continuously decreases toward an outer end of the first portion in the tire axial direction. [Explanation of symbols]

[0070] 1 pneumatic tire 2 Tread section 3 Sidewall 4 Bead section 6. Carcass 6P carcass ply 10 Inner rubber 11 Part 1 12 Part 2

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; 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 carcass includes at least one carcass ply in which a plurality of carcass cords are arranged in parallel, The angle of the carcass cord with respect to the tire equator is 66 to 86 degrees. Pneumatic tires.

2. A belt layer is disposed in the tread portion on the outer side of the carcass in the tire radial direction, The belt layer includes at least one belt ply in which a plurality of belt cords are arranged in parallel, The pneumatic tire according to claim 1, wherein the angle of the belt cord with respect to the tire equator is 28 to 46 degrees.

3. the belt plies include a first belt ply and a second belt ply disposed outward 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 2, 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 10 mm in the tire axial direction.

4. The pneumatic tire according to claim 1, wherein the first thickness is 1.5 to 3.5 times the second thickness.

5. The pneumatic tire according to claim 1, wherein the first thickness is 2.0 to 4.5 mm.

6. The pneumatic tire according to claim 1 , wherein the first portion includes a portion in which the first thickness continuously decreases toward an axially outer end of the first portion.

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