Pneumatic tire

Abstract

To provide a pneumatic tire in which wear resistance and fuel consumption performance of a shoulder land part are improved in a specific tire size.SOLUTION: Provided is a pneumatic tire. A rim diameter RD of the tire is 10 to 18 inches. A ratio SH / SW of a cross section height SH to a cross section width SW is 0.30 to 0.45. A ratio RW / SW of a rim width RW to the cross section width SW is 0.78 to 0.99. A width W1 (mm) of a tread of a first shoulder land part 11 satisfies the following formula (1): W1>0.001×(SW×SH). The width W1 (mm), a thickness T1 (mm) of a first rubber layer 21, a thickness T2 (mm) of a second rubber layer 22, a loss tangent tanδ1 of the first rubber layer 21 at 30°C, and a loss tangent tanδ2 of the second rubber layer 22 at 70°C satisfy the following formula (2): W1×(T1×tanδ1+T2×tanδ2) / (T1+T2)≤4.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, small shuttle buses for transporting people and goods in urban areas have been proposed (see, for example, Patent Document 1 below). Such small shuttle buses are required to secure a large passenger compartment space. In addition, in-wheel motors may be employed in the small shuttle buses.

[0003] Patent Document 2 below proposes a pneumatic tire used for the small shuttle bus. In order to secure the passenger compartment space and a wide rim space capable of accommodating the in-wheel motor, the rim diameter, the ratio of the tire section height to the tire section width, and the ratio of the rim width of the rim to the tire section width are defined for this tire.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Due to its shape, the above-described tire has a problem that the shoulder land portion is easily worn. On the other hand, the above-described tire is often used in EV vehicles, and improvement in fuel efficiency performance is also required from the viewpoint of extending the driving range.

[0006] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a pneumatic tire that improves the wear resistance performance and fuel consumption performance of the shoulder land portion in a specific tire size.

Means for Solving the Problems

[0007] The present invention is a pneumatic tire to be mounted on a rim and used, wherein the rim diameter RD of the rim is 10 to 18 inches, the ratio SH / SW of the section height SH of the tire to the section width SW of the tire is 0.30 to 0.45, the ratio RW / SW of the rim width RW of the rim to the section width SW of the tire is 0.78 to 0.99, the pneumatic tire has a tread portion, the tread portion includes a first tread end, a second tread end, and a plurality of circumferential grooves continuously extending in the tire circumferential direction between the first tread end and the second tread end, and a plurality of land portions divided by the plurality of circumferential grooves, the plurality of circumferential grooves include a first shoulder circumferential groove arranged on the most first tread end side, the plurality of land portions include a first shoulder land portion divided on the tire axial direction outer side of the first shoulder circumferential groove, the first shoulder land portion includes a first rubber layer constituting a tread surface from the first tread end to the first shoulder circumferential groove, and a second rubber layer arranged on the tire radial direction inner side of the first rubber layer and made of a rubber material different from that of the first rubber layer, the width W1 (mm) of the tread surface of the first shoulder land portion in the tire axial direction satisfies the following formula (1), and the width W1 (mm), the thickness T1 (mm) of the first rubber layer, the thickness T2 (mm) of the second rubber layer, the loss tangent tanδ1 of the first rubber layer at 30°C, and the loss tangent tanδ2 of the second rubber layer at 70°C satisfy the following formula (2). It is a pneumatic tire. W1>0.001×(SW×SH)…(1) W1×(T1×tanδ1+T2×tanδ2) / (T1+T2)≦4…(2)

Effects of the Invention

[0008] By adopting the above configuration, the pneumatic tire of the present invention can improve the wear resistance performance and fuel consumption performance of the shoulder land portion.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Although the drawings include the features of the present invention, in order to assist in understanding the present invention, there may be included exaggerated expressions or expressions different from the dimensional ratios of actual structures. Also, throughout each embodiment, the same or common elements are denoted by the same reference numerals, and redundant descriptions are omitted. In addition, well-known configurations can be appropriately adopted for configurations not described in this specification.

[0011] FIG. 1 shows a cross-sectional view of a pneumatic tire 1 (hereinafter, may be simply referred to as "tire 1") according to an embodiment of the present invention. FIG. 2 is a perspective view conceptually showing a vehicle Ve on which the tire 1 of the present invention is mounted. As shown in FIGS. 1 and 2, the tire 1 of the present embodiment is mounted on a rim R and used, and is preferably used as a pneumatic tire for a vehicle Ve such as a minibus or a small shuttle bus.

[0012] As shown in FIG. 2, the above-described vehicle Ve is a four-wheeled vehicle. Note that the vehicle Ve is not limited to four wheels, and may have a six-wheel configuration or an eight-wheel configuration. Also, a predetermined number of tires 1 are mounted on the vehicle Ve according to the wheel configuration.

[0013] Vehicle Ve belongs to, for example, a small shuttle bus used for transporting people and goods within a city. The small shuttle bus is assumed to be a vehicle with a total length of 4m to 7m, a total width of about 2m, and a gross vehicle weight of around 3t. However, the tire 1 of the present invention is not only adopted for vehicles within the above range, but can be adopted for various vehicles.

[0014] In addition, vehicle Ve is not necessarily limited to transporting people, and may be used as a means for transporting goods, a mobile store, a mobile office, etc. Vehicle Ve is preferably, for example, an electric vehicle equipped with an automatic driving function. Also, since vehicle Ve is mainly focused on transporting people and goods within a city, a relatively low driving speed range (average speed of about 50 km / h) is assumed. However, vehicle Ve is not limited to such a mode.

[0015] When vehicle Ve is an electric vehicle, it is desirable that the motor be arranged within the rim. Also, in this case, vehicle Ve preferably has an independent steering function in which each wheel can be independently steered. This makes it easier to turn on the spot and can increase the passenger compartment space of vehicle Ve.

[0016] For the tire 1 of the present embodiment acting on such a vehicle Ve, high space efficiency is required. Therefore, the tire 1 is required to have a small rim diameter and a small cross-sectional height of the tire.

[0017] FIG. 1 is a cross-sectional view of the tire 1 in the normal state, including the rotation axis. The "normal state" means that in the case of a pneumatic tire with various specifications, the tire is rim-mounted on a standard rim and filled with the standard internal pressure, and moreover, it is in an unloaded state. In the case of a tire without various specifications, the "normal state" means a standard usage state according to the usage purpose of the tire, which means that the tire is not mounted on a vehicle and is in an unloaded state. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are the values measured in the normal state. Also, the dimensions of a structure that cannot be measured in the normal state (for example, an internal member of the tire) are the values measured in a state where the tire is approximated to the normal state as much as possible.

[0018] The "standard rim" is the rim defined for each tire in the standard system including the standards on which the tire is based. For example, in JATMA, it is the "Standard Rim", in TRA, it is the "Design Rim", and in ETRTO, it is the "Measuring Rim".

[0019] The "standard internal pressure" is the air pressure defined for each tire in the standard system including the standards on which the tire is based. In JATMA, it is the "Maximum Air Pressure", in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it is the "INFLATION PRESSURE".

[0020] The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portion 3 is continuous with the outer side of the tread portion 2 in the tire axial direction and extends in the tire radial direction. The bead portion 4 is continuous with the inner side of the sidewall portion 3 in the tire radial direction. Also, a bead core 5 for fixing the bead portion 4 to the rim R is embedded in the bead portion 4.

[0021] Further, the tire 1 includes a carcass 6. The carcass 6 extends between a 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.

[0022] The carcass 6 is composed of, for example, two carcass plies 6A and 6B. These carcass plies include, for example, a body portion 6a and a turned-back portion 6b. The body portion 6a extends between a pair of bead portions 4, for example. The turned-back portion 6b is connected to the body portion 6a and is turned back from the inner side in the tire axial direction to the outer side around the bead core 5.

[0023] The carcass plies 6A and 6B include a plurality of carcass cords and a topping rubber covering them (not shown). As the carcass cords, organic fiber cords such as aramid and rayon are adopted, for example. The carcass cords are preferably arranged at an angle of 70 to 90° with respect to the tire equator C, for example. However, the tire 1 of the present invention is not limited to such a mode.

[0024] In the tread portion 2 of the present embodiment, a belt layer 7 is provided. The belt layer 7 is composed of, for example, a first belt ply 7A and a second belt ply 7B. These belt plies include a plurality of belt cords arranged at an angle of 15 to 45° with respect to the tire circumferential direction, for example. Further, the belt cords included in the first belt ply 7A and the belt cords included in the second belt ply 7B are inclined in opposite directions with respect to the tire circumferential direction. Thereby, the tread portion 2 is effectively reinforced.

[0025] In the present invention, the rim diameter RD of the rim R is 10 to 18 inches. Further, the ratio SH / SW of the section height SH of the tire 1 to the section width SW of the tire is 0.30 to 0.45. The ratio RW / SW of the rim width RW of the rim R to the section width SW of the tire 1 is 0.78 to 0.99. The section width SW is, for example, 150 to 250 mm. As tire sizes, for example, 205 / 40R15, 205 / 30R15, etc. are assumed. However, the present invention is not limited to such tire sizes.

[0026] The rim diameter RD is the outer diameter of the rim body portion fitted by the bead core 5 of the bead portion 4. Further, the section width SW of the tire 1 corresponds to the width excluding convex portions (not shown) indicating patterns and characters on the sidewall of the tire 1. The section height SH of the tire 1 corresponds to 1 / 2 of the difference between the outer diameter of the tire and the rim diameter RD. In other words, the section height SH corresponds to the distance in the tire radial direction from the bead base line BL to the outer end in the tire radial direction of the tire 1. The bead base line BL means a tire axial line passing through the rim diameter position.

[0027] The rim width RW of the rim R corresponds to the distance in the tire axial direction from the inner surface of one rim flange Rf to the inner surface of the other rim flange Rf. When the inner surface is inclined, the distance is measured at the center position in the tire radial direction of the bead core 5 when the tire 1 is mounted on the rim R.

[0028] As described above, the tire 1 of the present invention has a relatively small rim diameter RD and section height SH, and a relatively large rim width RW with respect to the section width SW of the tire. Such a tire 1, for example, improves the space efficiency in the vehicle space when mounted on the vehicle Ve (shown in FIG. 2) described above, and can sufficiently secure the accommodation space in a vehicle in which a motor is arranged inside the rim. Further, such a tire 1 can hold a sufficient air volume to support the total vehicle weight.

[0029] Figure 3 shows an enlarged cross-sectional view of the tread portion 2. As shown in Figure 3, the tread portion 2 includes a first tread end Te1, a second tread end Te2, a plurality of circumferential grooves 8 that continuously extend in the tire circumferential direction between these, and a plurality of land portions 9 divided by the plurality of circumferential grooves 8.

[0030] The first tread end Te1 and the second tread end Te2 respectively correspond to the ends of the ground contact surface when 70% of the normal load is applied to the tire 1 in the normal state and the tread portion 2 is grounded on a plane at a camber angle of 0°.

[0031] For pneumatic tires with various standards defined, the "normal load" is the load defined for each tire in the standard system including the standards on which the tire is based. For JATMA, it is the "maximum load capacity"; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; for ETRTO, it is the "LOAD CAPACITY". Also, for tires without various standards defined, the "normal load" refers to the maximum load applicable in using the tire according to the above-mentioned standards.

[0032] The plurality of circumferential grooves 8 includes at least a first shoulder circumferential groove 16 provided on the side closest to the first tread end Te1. Further, the plurality of circumferential grooves 8 of the present embodiment includes a second shoulder circumferential groove 17, a first crown circumferential groove 18, and a second crown circumferential groove 19. The second shoulder circumferential groove 17 is provided on the side closest to the second tread end Te2. The first crown circumferential groove 18 is provided between the first shoulder circumferential groove 16 and the tire equator C. The second crown circumferential groove 19 is provided between the second shoulder circumferential groove 17 and the tire equator C.

[0033] From the viewpoint of ensuring the wet performance of the tire 1, the groove width Wa of each circumferential groove 8 is at least 3 mm or more, preferably 5 - 15 mm. From the same viewpoint, the depth of each circumferential groove 8 is at least 3 mm or more, preferably 5 - 10 mm.

[0034] The plurality of land portions 9 include at least a first shoulder land portion 11 that is demarcated on the tire axial direction outer side of the first shoulder circumferential groove 16. Further, the plurality of land portions 9 of the present embodiment include a second shoulder land portion 12, a first middle land portion 13, a second middle land portion 14, and a crown land portion 15. The second shoulder land portion 12 is demarcated on the tire axial direction outer side of the second shoulder circumferential groove 17. The first middle land portion 13 is demarcated between the first shoulder circumferential groove 16 and the first crown circumferential groove 18. The second middle land portion 14 is demarcated between the second shoulder circumferential groove 17 and the second crown circumferential groove 19. The crown land portion 15 is demarcated between the first crown circumferential groove 18 and the second crown circumferential groove 19.

[0035] Fig. 4 shows an enlarged cross-sectional view of the first shoulder land portion 11. As shown in Fig. 4, the first shoulder land portion 11 includes a first rubber layer 21 and a second rubber layer 22. The first rubber layer 21 constitutes the tread surface 11s of the first shoulder land portion 11. This tread surface 11s means a surface from the first tread end Te1 to the groove edge 16e of the first shoulder circumferential groove 16. The first rubber layer 21 of the present embodiment also constitutes a buttless surface outside the first tread end Te1. The second rubber layer 22 is disposed on the tire radial direction inner side of the first rubber layer 21, and in the present embodiment, the first rubber layer 21 and the second rubber layer 22 are continuous.

[0036] In the present invention, the tire axial direction width W1 (mm) of the tread surface 11s of the first shoulder land portion 11 satisfies the following formula (1). Further, in the present invention, the width W1 (mm), the thickness T1 (mm) of the first rubber layer 21, the thickness T2 (mm) of the second rubber layer 22, the loss tangent tanδ1 of the first rubber layer 21 at 30°C, and the loss tangent tanδ2 of the second rubber layer 22 at 70°C satisfy the following formula (2). W1 > 0.001×(SW×SH)…(1) W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≦ 4…(2)

[0037] The thickness T1 of the first rubber layer 21 and the thickness T2 of the second rubber layer 22 are the thicknesses measured at positions 5 mm away from the groove edge 16e of the first shoulder circumferential groove 16 toward the first tread end Te1 side, respectively.

[0038] In this specification, the loss tangent tanδ of rubber is a value measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the following conditions in accordance with the provisions of JIS-K6394. Initial strain: 10% Amplitude: ±1% Frequency: 10 Hz Deformation mode: Tension

[0039] In the present invention, from the viewpoint of allowing variations in each of the above parameters, it is desirable that the average values of the respective parameters be applied to the formulas (1) and (2). For this reason, for example, the average value of the widths W1 measured at a plurality of positions different in the tire circumferential direction is applied to the width W1 of the tread surface 11s of the first shoulder land portion 11. The same applies to other parameters (including those described below). The technical significance of the formulas (1) and (2) is as follows.

[0040] Tires of the size specified in the present invention have a problem that the shoulder land portion is likely to wear due to their shape and usage conditions (for example, usage conditions in a vehicle such as a minibus where there are many cases of controlled driving and right and left turns), causing a decrease in the tire usage period. Also, tires of this size are required to improve fuel consumption performance.

[0041] From the perspective of suppressing wear of the shoulder land portion, the inventors have obtained the knowledge that it is effective to set the lower limit by associating the size of the tread surface of the shoulder land portion with the size of the tire cross section (that is, the product of the cross-sectional height SH and the cross-sectional width SW of the tire). Also, from various experiments, the above-mentioned formula (1) was derived. That is, in the present invention, by satisfying the above-mentioned formula (1), the tread surface 11s of the first shoulder land portion 11 has a sufficient size with respect to the size of the tire cross section, and thus the wear resistance performance of the first shoulder land portion 11 can be improved. Further, due to the above-mentioned action, the progress of wear of the tread portion becomes uniform, and the service life of the tire can be extended.

[0042] Also, the inventors have found that in order to improve fuel consumption performance, it is effective to define the degree of energy loss of the first shoulder land portion 11 (in other words, the heat generation property of the land portion) in association with the size of the tread surface 11s of the first shoulder land portion 11. Also, the inventors have found that it is desirable to consider the thickness and loss tangent of each rubber layer with respect to the degree of energy loss of the first shoulder land portion 11. Also, the inventors have grasped the following tendency through various experiments.

[0043] Specifically, since the first rubber layer 21 constitutes the tread surface 11s, although the amount of deformation is large, the degree of cooling by air is also strong. Therefore, it is effective to define the energy loss in the first rubber layer 21 by the loss tangent tanδ1 at 30°C of this rubber layer. Also, since the second rubber layer 22 is difficult to cool compared to the first rubber layer 21, it is effective to define the energy loss in the second rubber layer 22 by the loss tangent tanδ2 at 70°C of this rubber layer. Furthermore, the inventors have found that the energy loss of the first shoulder land portion 11 can be more accurately defined by a parameter of "(T1×tanδ1 + T2×tanδ2) / (T1 + T2)" (hereinafter, may be referred to as "loss parameter").

[0044] In the present invention, the upper limit of the value obtained by multiplying the width W1 of the tread surface of the first shoulder land portion 11 by the above-described loss parameter is defined. That is, in the present invention, by satisfying the above-described formula (2), the energy loss of the first shoulder land portion 11 can be reduced, and excellent fuel consumption performance can be exhibited.

[0045] Hereinafter, a more detailed configuration of the present embodiment will be described. Each configuration described below shows a specific aspect of the present embodiment. Therefore, it goes without saying that the present invention can exhibit the above-described effects even if it does not have the configurations described below. Further, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-described features, an improvement in performance corresponding to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0046] As shown in FIG. 3, the tread portion 2 of the tire 1 of the present embodiment is substantially symmetric about the left-right direction. For this reason, the configuration of the first shoulder land portion 11 mainly described in this specification can also be applied to the second shoulder land portion 12.

[0047] As shown in FIG. 4, if the width W1 of the first shoulder land portion 11 is excessively large, the fuel consumption performance may be impaired, and the first shoulder circumferential groove 16 may not exhibit sufficient drainage performance. For this reason, it is desirable that the width W1 satisfies the following formula (3). W1 < 0.002×(SW×SH)…(3)

[0048] Further, if the left side of the above-described formula (2) is excessively small, it becomes difficult for the first shoulder land portion 11 to exhibit appropriate grip. For this reason, it is desirable that the width W1 of the tread surface 11s of the first shoulder land portion 11, the thickness T1 of the first rubber layer 21, the thickness T2 of the second rubber layer 22, the loss tangent tanδ1 of the first rubber layer 21 at 30°C, and the loss tangent tanδ2 of the second rubber layer 22 at 70°C satisfy the following formula (4). W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≧ 3…(4)

[0049] The loss tangent tanδ1 of the first rubber layer 21 at 30°C is, for example, 0.15 to 0.25, desirably 0.18 to 0.22. The loss tangent tanδ2 of the second rubber layer 22 at 70°C is, for example, 0.03 to 0.11, desirably 0.05 to 0.09. These rubber layers can be obtained by appropriately combining known rubber materials, and the description thereof is omitted here.

[0050] The thickness T1 of the first rubber layer 21 is, for example, 5.0 to 15.0 mm, desirably 8.0 to 12.0 mm. Also, the thickness T2 of the second rubber layer 22 is, for example, 1.0 to 5.0 mm, desirably 1.0 to 3.0 mm.

[0051] In this embodiment, the depth D1 of the first shoulder circumferential groove 16 is set to 5.0 to 10.0 mm. Also, the thickness T1 of the first rubber layer 21 is, for example, desirably 0.9 times or more, more desirably 1.0 times or more of the depth D1, and desirably 1.5 times or less, more desirably 1.3 times or less. Thereby, even when the tread portion 2 is worn to some extent, the wet performance can be maintained.

[0052] The profile of the first shoulder land portion 11 of this embodiment is not a square shape that locally bends at the first tread end Te1, but a so-called round shape. That is, the first shoulder land portion 11 has a curved profile 25 that extends from the first shoulder circumferential groove 16 to a position beyond the first tread end Te1. This curved profile 25 smoothly curves inward in the tire radial direction from the groove edge 16e of the first shoulder circumferential groove 16 toward the outside in the tire axial direction. Thereby, since the first shoulder land portion 11 has an appropriate round shape, an improvement in fuel consumption performance and wet performance can be expected.

[0053] From the viewpoint of enhancing the wear resistance performance and fuel efficiency performance of the first shoulder land portion 11 in a well-balanced manner, the radius of curvature Rt (mm) at the first tread edge Te1 of the curved profile 25 is desirably 0.3 times or more, more desirably 0.5 times or more of the width W1, and desirably 2.0 times or less, more desirably 1.8 times or less.

[0054] As described above in detail, the pneumatic tire according to one embodiment of the present invention has been described. However, the present invention is not limited to the above specific embodiments and can be implemented in various modes with modifications.

Example

[0055] A pneumatic tire having the basic structure shown in FIG. 1 and a rim diameter of 15 inches was prototyped based on the specifications in Table 1. Further, as Comparative Examples 1 to 6, tires not satisfying the above formula (1) or (2) were prototyped. The tires of the comparative examples are substantially the same as the tires of the example except for the above matters. The wear resistance performance and fuel efficiency performance of the shoulder land portion of each test tire were tested. The common specifications and test methods of each test tire are as follows. Mounting rim: 15×7.0J Tire internal pressure: 350 kPa Test vehicle: A small bus with a seating capacity of 8 passengers

[0056] <Wear resistance performance of the shoulder land portion> A test vehicle equipped with a test tire was run on a test course made of an asphalt road surface, and the wear energy of the first shoulder land portion during turning was measured. The result is the reciprocal of the wear energy indexed, and the larger the numerical value, the better the wear resistance performance of the shoulder land portion.

[0057] <Fuel efficiency performance> Using a rolling resistance tester, the rolling resistance of the test tire was measured according to ISO conditions. The result is the reciprocal of the rolling resistance indexed, and the larger the numerical value, the better the fuel efficiency performance.

[0058] The test results are shown in Table 1.

[0059]

Table 1

[0060]

Table 2

[0061]

Table 3

[0062] As shown in Tables 1 to 3, when tests were carried out by changing various parameters, it can be seen that Comparative Examples 1, 5, and 7 do not satisfy the formula (1) of the present invention, so the wear resistance of the shoulder land portion is low. Further, it can be seen that Comparative Examples 2 to 4, 6, and 8 do not satisfy the formula (2) of the present invention, so the fuel consumption performance is low. On the other hand, it can be understood that the tires of the examples significantly improve the wear resistance and fuel consumption performance of the shoulder land portion by satisfying the formulas (1) and (2).

[0063] [Appendix] The present invention includes the following aspects.

[0064] [Invention 1] A pneumatic tire mounted on a rim and used, wherein the rim diameter RD of the rim is 10 to 18 inches, the ratio SH / SW of the section height SH of the tire to the section width SW of the tire is 0.30 to 0.45, the ratio RW / SW of the rim width RW of the rim to the section width SW of the tire is 0.78 to 0.99, the pneumatic tire has a tread portion, the tread portion includes a first tread end, a second tread end, a plurality of circumferential grooves continuously extending in the tire circumferential direction between the first tread end and the second tread end, and a plurality of land portions divided by the plurality of circumferential grooves. The plurality of circumferential grooves include a first shoulder circumferential groove arranged closest to the first tread end side. The plurality of land portions include a first shoulder land portion divided on the outer side in the tire axial direction of the first shoulder circumferential groove. The first shoulder land portion includes a first rubber layer constituting a tread surface from the first tread end to the first shoulder circumferential groove, and a second rubber layer arranged on the inner side in the tire radial direction of the first rubber layer and made of a rubber material different from that of the first rubber layer. The width W1 (mm) in the tire axial direction of the tread surface of the first shoulder land portion satisfies the following formula (1). The width W1 (mm), the thickness T1 (mm) of the first rubber layer, the thickness T2 (mm) of the second rubber layer, the loss tangent tanδ1 of the first rubber layer at 30°C, and the loss tangent tanδ2 of the second rubber layer at 70°C satisfy the following formula (2). Pneumatic tire. W1 > 0.001×(SW×SH)…(1) W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≤ 4…(2) [Invention 2] The width W1 (mm) satisfies the following formula (3), the pneumatic tire according to Invention 1. W1 < 0.002×(SW×SH)…(3) [Invention 3] The width W1 (mm), the thickness T1 (mm) of the first rubber layer, the thickness T2 (mm) of the second rubber layer, the loss tangent tanδ1 of the first rubber layer at 30°C, and the loss tangent tanδ2 of the second rubber layer at 70°C satisfy the following formula (4), the pneumatic tire according to Invention 1 or 2. W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≥ 3…(4) [Invention 4] The thickness T1 (mm) is 0.9 times or more of the depth D1 (mm) of the first shoulder circumferential groove, the pneumatic tire according to any one of Inventions 1 to 3. [Invention 5] The pneumatic tire according to Invention 4, wherein the thickness T1 (mm) is 1.5 times or less the depth D1 (mm). [Invention 6] The pneumatic tire according to any one of Inventions 1 to 5, wherein the first shoulder land portion has a curved profile extending from the first shoulder circumferential groove to a position beyond the first tread end. [Invention 7] The pneumatic tire according to Invention 6, wherein the radius of curvature Rt (mm) at the first tread end of the curved profile is 0.3 times or more the width W1 (mm). [Invention 8] The pneumatic tire according to Invention 6 or 7, wherein the radius of curvature Rt (mm) is 2.0 times or less the width W1 (mm).

Explanation of Signs

[0065] 16 First shoulder circumferential groove 21 First rubber layer 22 Second rubber layer R Rim RD Rim diameter RW Rim width SW Section width of tire SH Section height of tire Te1 First tread end Te2 Second tread end W1 Axial width of the tread surface of the first shoulder land portion T1 Thickness of the first rubber layer T2 Thickness of the second rubber layer tanδ1 Loss tangent of the first rubber layer at 30°C tanδ2 Loss tangent of the second rubber layer at 70°C

Claims

1. A pneumatic tire to be mounted on and used with a rim, wherein the rim diameter RD of the rim is 10 to 18 inches, the ratio SH / SW of the section height SH of the tire to the section width SW of the tire is 0.30 to 0.45, the ratio RW / SW of the rim width RW of the rim to the section width SW of the tire is 0.78 to 0.99, the pneumatic tire has a tread portion, the tread portion includes a first tread end, a second tread end, a plurality of circumferential grooves continuously extending in the tire circumferential direction between the first tread end and the second tread end, and a plurality of land portions divided by the plurality of circumferential grooves, the plurality of circumferential grooves include a first shoulder circumferential groove arranged on the side closest to the first tread end, the plurality of land portions include a first shoulder land portion divided outside the first shoulder circumferential groove in the tire axial direction, the first shoulder land portion includes a first rubber layer constituting a tread surface from the first tread end to the first shoulder circumferential groove, and a second rubber layer arranged inside the first rubber layer in the tire radial direction and made of a rubber material different from that of the first rubber layer, the width W1 (mm) in the tire axial direction of the tread surface of the first shoulder land portion satisfies the following formula (1), the width W1 (mm), the thickness T1 (mm) of the first rubber layer, the thickness T2 (mm) of the second rubber layer, the loss tangent tanδ1 of the first rubber layer at 30°C, and the loss tangent tanδ2 of the second rubber layer at 70°C satisfy the following formula (2), a pneumatic tire. W1 > 0.001 × (SW × SH) … (1) W1 × (T1 × tanδ1 + T2 × tanδ2) / (T1 + T2) ≤ 4 … (2)

2. The pneumatic tire according to claim 1, wherein the width W1 (mm) satisfies the following formula (3). W1 < 0.002 × (SW × SH) … (3)

3. The pneumatic tire according to claim 2, wherein the width W1 (mm), the thickness T1 (mm) of the first rubber layer, the thickness T2 (mm) of the second rubber layer, the loss tangent tanδ1 of the first rubber layer at 30°C, and the loss tangent tanδ2 of the second rubber layer at 70°C satisfy the following formula (4). W1 × (T1 × tanδ1 + T2 × tanδ2) / (T1 + T2) ≥ 3 … (4)

4. The pneumatic tire according to any one of claims 1 to 3, wherein the thickness T1 (mm) is 0.9 times or more the depth D1 (mm) of the first shoulder circumferential groove.

5. The pneumatic tire according to claim 4, wherein the thickness T1 (mm) is 1.5 times or less of the depth D1 (mm).

6. The pneumatic tire according to any one of claims 1 to 3, wherein the first shoulder land portion has a curved profile extending from the first shoulder circumferential groove to a position beyond the first tread end.

7. The pneumatic tire according to claim 6, wherein the radius of curvature Rt (mm) at the first tread end of the curved profile is 0.3 times or more of the width W1 (mm).

8. The pneumatic tire according to claim 7, wherein the radius of curvature Rt (mm) is 2.0 times or less of the width W1 (mm).

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