Pneumatic tire

Abstract

The invention provides a pneumatic tire which improves wear resistance and fuel economy performance of a tire shoulder land portion under a specific tire size. The present invention relates to a pneumatic tire having a rim diameter (RD) of 10-18 inches. The ratio (SH / SW) of the cross-sectional height (SH) to the cross-sectional width (SW) is 0.30-0.45. The ratio (RW / SW) of the rim width (RW) to the cross-sectional width (SW) is 0.78 to 0.99. The width (W1) (mm) of the tread surface of the first shoulder land portion (11) satisfies the following formula (1). 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 (tan [delta] 1) of the first rubber layer (21) at 30 DEG C, and the loss tangent (tan [delta] 2) of the second rubber layer (22) at 70 DEG C satisfy the following formula (2): W1 > 0.001 * (SW * SH) (1) W1 * (T1 * tan [delta] 1 + T2 * tan [delta] 2) / (T1 + T2) < = 4 (2).

Description

Technical Field

[0001] The present invention relates to pneumatic tires. Background Art

[0002] In recent years, small shuttle buses for transporting people and goods in urban areas have been proposed (for example, refer to Patent Document 1 below). Such small shuttle buses are required to ensure a large cabin space. In addition, in-wheel motors are sometimes adopted for the above-mentioned small shuttle buses.

[0003] The pneumatic tire used for the above-mentioned small shuttle bus is proposed in Patent Document 2 below. In order to ensure the above-mentioned cabin space and a large rim space corresponding to the above-mentioned in-wheel motor, the rim diameter, the ratio of the tire cross-sectional height to the tire cross-sectional width, and the ratio of the rim width of the rim to the tire cross-sectional width are specified.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-075088

[0005] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2023-102627

[0006] The above-mentioned tire has a problem that the shoulder land portion is easily worn due to its shape. On the other hand, the above-mentioned tire is also often used for EV vehicles, and from the viewpoint of extending the driving distance, improvement in fuel economy performance is also required. Summary of the Invention

[0007] The present invention has been made in view of the above actual situation, and the main subject is to provide a pneumatic tire that improves the wear resistance of the shoulder land portion and the fuel economy performance under specific tire sizes.

[0008] The pneumatic tire of the present invention is mounted on a rim for use. Among them, 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, and 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 disposed 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 the tread surface from the first tread end to the first shoulder circumferential groove, and a second rubber layer disposed on the radially inner side of the tire of the first rubber layer and made of a rubber material different from that of the first rubber layer. The width W1 in the tire axial direction of the tread surface of the first shoulder land portion satisfies the following formula (1), and the width W1, the thickness T1 of the first rubber layer, the thickness T2 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). The units of the width W1, the thickness T1, and the thickness T2 are mm.

[0009] W1 > 0.001×(SW×SH)…(1)

[0010] W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≤ 4…(2).

[0011] By adopting the above structure, the pneumatic tire of the present invention can improve the wear resistance and fuel economy performance of the shoulder land portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a cross-sectional view of a pneumatic tire according to an embodiment of the present invention.

[0013] Figure 2 is a perspective view of a vehicle equipped with the tire of the present invention.

[0014] Figure 3 is Figure 1 an enlarged cross-sectional view of the tread portion.

[0015] Figure 4 is Figure 3 an enlarged cross-sectional view of the first shoulder land portion.

[0016] Explanation of the reference numerals: 16…first shoulder circumferential groove; 21…first rubber layer; 22…second rubber layer; R…rim; RD…rim diameter; RW…rim width; SW…cross-sectional width of the tire; SH…cross-sectional height of the tire; Te1…first tread end; Te2…second tread end; W1…axial width of the tread 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. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. The accompanying drawings include features of the present invention, but in order to help understand the present invention, sometimes include exaggerated representations and representations that are different from the actual structure in terms of dimensional ratio. In addition, in each embodiment, the same or common elements are marked with the same reference numerals and repeated descriptions are omitted. In addition, for structures not described in this specification, known structures can be appropriately adopted.

[0018] exist Figure 1 1 is a cross-sectional view of a pneumatic tire 1 (hereinafter, sometimes simply referred to as a “tire 1 ”) showing one embodiment of the present invention. Figure 2 1 is a perspective view schematically showing a vehicle Ve equipped with the tire 1 of the present invention. Figure 1 and Figure 2 As shown, the tire 1 of the present embodiment is mounted on a rim R for use, and is suitably used as a pneumatic tire for a vehicle Ve such as a minibus or a minibus.

[0019] like Figure 2 As shown, the vehicle Ve is a four-wheel vehicle. In addition, the vehicle Ve is not limited to four wheels, and may also be a six-wheel structure or an eight-wheel structure. In addition, a predetermined number of tires 1 are installed on the vehicle Ve according to the wheel structure.

[0020] The vehicle Ve is, for example, a small shuttle bus used to transport people and goods in a city. The small shuttle bus is assumed to have a total length of 4 to 7 meters, a total width of about 2 meters, and a total vehicle weight of about 3 tons. However, the tire 1 of the present invention is not limited to vehicles within the above range, but can be used for various vehicles.

[0021] In addition, the vehicle Ve is not limited to the transportation of people, but can also be used as the transportation of goods, mobile shops, mobile offices, etc. The vehicle Ve is preferably an electric car with an automatic driving function, for example. In addition, the vehicle Ve will focus on the transportation of people, goods, etc. in the city, so a relatively low driving speed range (average speed of about 50 km / h) is assumed. However, the vehicle Ve is not limited to such a mode.

[0022] In the case where the vehicle Ve is an electric vehicle, it is preferable that the motor be arranged inside the rim. Further, in this case, the vehicle Ve preferably has an independent steering function capable of independently steering each wheel. Thereby, rotation in place and the like become easy, and the cabin space of the vehicle Ve can be increased.

[0023] The tire 1 of the present embodiment applied to such a vehicle Ve is required to have high space efficiency. Therefore, the tire 1 is required to have a small rim diameter and a small cross-sectional height of the tire.

[0024] Figure 1 It is a cross-sectional view including the rotation axis of the tire 1 in the normal state. In the case of a pneumatic tire with various specified specifications, the "normal state" means a state in which the tire rim is assembled to a normal rim, filled with a normal internal pressure, and unloaded. In the case of a tire without various specified specifications, the above normal state means a standard use state corresponding to the use purpose of the tire, not installed on a vehicle and unloaded. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the above normal state. Further, the dimensions of a structure (for example, an internal part of the tire) that cannot be measured in the above normal state are values measured in a state in which the tire is made as close as possible to the above normal state.

[0025] The "normal rim" is a rim specified for each tire in a specification system including the specifications on which the tire is based. For example, in the case of JATMA, it is the "standard rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim".

[0026] The "normal internal pressure" is the air pressure specified for each tire in a specification system including the specifications on which the tire is based. In the case of JATMA, it is the "maximum air pressure", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "INFLATIONPRESSURE".

[0027] 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 connected to the outer side in the tire axial direction of the tread portion 2 and extends in the tire radial direction. The bead portion 4 is connected to the inner side in the tire radial direction of the sidewall portion 3. Further, a bead core 5 for fixing the bead portion 4 to the rim R is embedded in the bead portion 4.

[0028] In addition, 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.

[0029] The carcass 6 is composed of, for example, two carcass plies 6A and 6B. These carcass plies include, for example, a main body portion 6a and a turned-back portion 6b. The main body portion 6a extends between a pair of bead portions 4, for example. The turned-back portion 6b is connected to the main body portion 6a and turns back from the inner side to the outer side in the tire axial direction around the bead core 5.

[0030] The carcass plies 6A and 6B include a plurality of carcass cords and a skim coat (not shown) covering them. The carcass cords are, for example, organic fiber cords such as aramid and rayon. The carcass cords are preferably arranged at an angle of 70 to 90° with respect to the tire equator C. However, the tire 1 of the present invention is not limited to such a configuration.

[0031] 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, for example, a plurality of belt cords arranged at an angle of 15 to 45° with respect to the tire circumferential direction. In addition, 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 strengthened.

[0032] In the present invention, the rim diameter RD of the rim R is 10 to 18 inches. In addition, the ratio SH / SW of the section height SH of the tire to the section width SW of the tire 1 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 envisaged. However, the present invention is not limited to such tire sizes.

[0033] The rim diameter RD is the outer diameter of the rim main body portion engaged by the bead core 5 of the bead portion 4. In addition, when the sidewall of the tire 1 has convex portions (not shown) indicating patterns and letters, the section width SW of the tire 1 corresponds to the width after removing them. 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 above section height SH corresponds to the tire radial distance from the bead base line BL to the outer end in the tire radial direction of the tire 1. The bead base line BL is a tire axial line passing through the rim diameter position.

[0034] 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. In the case where the above inner surface is inclined, the above 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.

[0035] As described above, the tire 1 of the present invention has a smaller rim diameter RD and sectional height SH, and a larger rim width RW relative to the sectional width SW of the tire. Such a tire 1, for example, when mounted on the above vehicle Ve ( Figure 2 shown), can improve the space efficiency in the vehicle space, and in a vehicle where the motor is disposed within the rim, can sufficiently ensure its accommodation space. In addition, such a tire 1 can hold a sufficient amount of air for supporting the total vehicle weight.

[0036] In Figure 3 is shown an enlarged cross-sectional view of the tread surface 2. As Figure 3 shown, the tread surface 2 includes: a first tread end Te1, a second tread end Te2, a plurality of circumferential grooves 8 continuously extending in the tire circumferential direction therebetween, and a plurality of land portions 9 divided by the plurality of circumferential grooves 8.

[0037] The first tread end Te1 and the second tread end Te2 respectively correspond to the ends of the ground contact surface when the tire 1 in the above normal state is loaded with 70% of the normal load and the tread surface 2 is grounded on the plane with a camber angle of 0°.

[0038] The "normal load" is, in the case of a pneumatic tire for which various specifications are defined, in the specification system including the specifications on which the tire is based, a load defined for each tire according to the specifications. 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". In addition, in the case of a tire for which various specifications are not defined, the "normal load" means the maximum load that can be applied based on the above specifications when using the tire.

[0039] The plurality of circumferential grooves 8 at least include a first shoulder circumferential groove 16 provided on the side closest to the first tread end Te1. In addition, the plurality of circumferential grooves 8 of the present embodiment include: 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.

[0040] From the viewpoint of ensuring the wet road performance of the tire 1, the groove width Wa of each circumferential groove 8 is at least 3 mm or more, preferably 5 to 15 mm. From the same viewpoint, the depth of each circumferential groove 8 is at least 3 mm or more, preferably 5 to 10 mm.

[0041] The plurality of land portions 9 at least include a first shoulder land portion 11 that is divided on the axially outer side of the tire of the first shoulder circumferential groove 16. In addition, the plurality of land portions 9 of the present embodiment include: a second shoulder land portion 12, a first intermediate land portion 13, a second intermediate land portion 14, and a crown land portion 15. The second shoulder land portion 12 is divided on the axially outer side of the tire of the second shoulder circumferential groove 17. The first intermediate land portion 13 is divided between the first shoulder circumferential groove 16 and the first crown circumferential groove 18. The second intermediate land portion 14 is divided between the second shoulder circumferential groove 17 and the second crown circumferential groove 19. The crown land portion 15 is divided between the first crown circumferential groove 18 and the second crown circumferential groove 19.

[0042] In Figure 4 shows an enlarged cross-sectional view of the first shoulder land portion 11. As Figure 4 shown, 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. The tread surface 11s refers to the 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 tire side wall surface that is more outward than the first tread end Te1. The second rubber layer 22 is disposed on the radially inner side of the tire of the first rubber layer 21, and in the present embodiment, the first rubber layer 21 is connected to the second rubber layer 22.

[0043] In the present invention, the axial width W1 (mm) of the tread surface 11s of the first shoulder land portion 11 satisfies the following formula (1). In addition, in the present invention, the above 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),

[0044] W1>0.001×(SW×SH)…(1)

[0045] W1×(T1×tanδ1+T2×tanδ2) / (T1+T2)≤4…(2).

[0046] The thickness T1 of the first rubber layer 21 and the thickness T2 of the second rubber layer 22 are the thicknesses measured at a position 5 mm away from the groove edge 16e of the first shoulder circumferential groove 16 toward the first tread end Te1 side.

[0047] In this specification, the loss tangent tanδ of the rubber is a value measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions shown below in accordance with JIS-K6394.

[0048] Initial strain: 10%

[0049] Amplitude: ±1%

[0050] Frequency: 10 Hz

[0051] Deformation mode: Tension

[0052] In the present invention, from the viewpoint of allowing deviations of the above respective parameters, it is preferable to apply the average values of the respective parameters in the above formulas (1) and (2). Therefore, for example, the average value of the widths W1 measured at a plurality of different positions 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 the parameters described below). The technical meanings of the above formulas (1) and (2) are as described below.

[0053] In the present invention, for tires of a specific size, due to their shape and usage conditions (for example, usage conditions in a vehicle such as a minibus where the frequency of braking, driving, and turning left and right is high), the shoulder land portion is likely to wear, causing a problem of deterioration during tire use. In addition, for tires of this size, improvement in fuel economy performance is also required.

[0054] The inventors obtained the following insights: From the viewpoint of suppressing wear of the shoulder land portion, it is effective to establish a relationship between the size of the tread surface of the shoulder land portion and the size of the tire cross-section (that is, the value obtained by multiplying the cross-section height SH of the tire by the cross-section width SW) and set its lower limit. In addition, the above formula (1) was derived from various experiments. That is, in the present invention, by satisfying the above formula (1), the tread surface 11s of the first shoulder land portion 11 has a sufficient size relative to the size of the tire cross-section, and thus the wear resistance of the first shoulder land portion 11 can be improved. In addition, by the above action, the progress of wear of the tread portion becomes uniform, and the tire usage period can be extended.

[0055] In addition, the inventors found that: In order to improve fuel economy 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 relation to the size of the tread surface 11s of the first shoulder land portion 11. In addition, the inventors found that: Regarding the degree of energy loss of the first shoulder land portion 11, it is preferable to consider the thickness and loss tangent of each rubber layer. In addition, the inventors found the following trends through various experiments.

[0056] Specifically, since the first rubber layer 21 forms the tread surface 11s, although the amount of deformation is large, the degree of air cooling is also strong. Therefore, it is effective that the energy loss in the first rubber layer 21 is defined by the loss tangent tanδ1 at 30°C of this rubber layer. In addition, since the second rubber layer 22 is less likely to be cooled compared to the first rubber layer 21, it is effective that the energy loss in the second rubber layer 22 is defined by the loss tangent tanδ2 at 70°C of this rubber layer. Furthermore, the inventors found that the energy loss of the first shoulder land portion 11 can be more accurately defined by the parameter of "(T1×tanδ1 + T2×tanδ2) / (T1 + T2)" (hereinafter, sometimes referred to as the "loss parameter").

[0057] 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 loss parameter is defined. That is, in the present invention, by satisfying the above formula (2), the energy loss of the first shoulder land portion 11 can be reduced, and excellent fuel economy performance can be exhibited.

[0058] Hereinafter, a more detailed structure of the present embodiment will be described. In addition, each structure described below represents a specific manner of the present embodiment. Therefore, the present invention can of course exhibit the above effects even without the structures described below. In addition, even when the tire of the present invention having the above characteristics is applied alone to any one of the structures described below, an improvement in performance corresponding to each structure can be expected. In addition, when several of the structures described below are applied in combination, an improvement in composite performance corresponding to each structure can also be expected.

[0059] As Figure 3 shown, the tread surface portion 2 of the tire 1 of the present embodiment is substantially left - right symmetric. Therefore, the structure of the first shoulder land portion 11 mainly described in this specification can also be applied to the second shoulder land portion 12.

[0060] As Figure 4 shown, if the width W1 of the first shoulder land portion 11 is too large, the fuel economy performance may be impaired, and the first shoulder circumferential groove 16 may not exhibit sufficient drainage performance. Therefore, the above width W1 is preferably such that the following formula (3) is satisfied.

[0061] W1 < 0.002×(SW×SH)…(3)

[0062] In addition, if the left side of the above formula (2) is too small, the first shoulder land portion 11 is difficult to exert appropriate grip. Therefore, 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 are preferably such that the following formula (4) is satisfied.

[0063] W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≥ 3…(4)

[0064] The loss tangent tanδ1 of the first rubber layer 21 at 30°C is, for example, 0.15 to 0.25, preferably 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, preferably 0.05 to 0.09. These rubber layers can be obtained by appropriately combining known rubber materials, and the description thereof is omitted here.

[0065] The thickness T1 of the first rubber layer 21 is, for example, 5.0 to 15.0 mm, preferably 8.0 to 12.0 mm. In addition, the thickness T2 of the second rubber layer 22 is, for example, 1.0 to 5.0 mm, preferably 1.0 to 3.0 mm.

[0066] In the present embodiment, the depth D1 of the first shoulder circumferential groove 16 is 5.0 to 10.0 mm. In addition, the thickness T1 of the first rubber layer 21 is, for example, preferably 0.9 times or more, more preferably 1.0 times or more, and preferably 1.5 times or less, more preferably 1.3 times or less of the above depth D1. Thereby, even when the tread surface portion 2 is worn to a certain extent, wet road performance can be maintained.

[0067] The contour of the first shoulder land portion 11 of the present embodiment is not a square shape that is locally bent at the first tread end Te1, but a so-called circular shape. That is, the first shoulder land portion 11 has a curved contour 25 that extends from the first shoulder circumferential groove 16 to a position beyond the first tread end Te1. The curved contour 25 smoothly curves from the groove edge 16e of the first shoulder circumferential groove 16 toward the outer side in the tire axial direction and toward the inner side in the tire radial direction. Thereby, since the first shoulder land portion 11 becomes an appropriate circular shape, improvement in fuel economy performance and wet road performance can be expected.

[0068] From the viewpoint of evenly improving the wear resistance performance and fuel economy performance of the first shoulder land portion 11, the radius of curvature Rt (mm) at the first tread end Te1 of the curved contour 25 is preferably 0.3 times or more, more preferably 0.5 times or more, and preferably 2.0 times or less, more preferably 1.8 times or less of the width W1.

[0069] The pneumatic tire of one embodiment of the present invention has been described in detail above. However, the present invention is not limited to the above specific embodiments and can be implemented in various modified forms.

[0070]

Example

[0071] Based on the specifications in Table 1, a pneumatic tire with the Figure 1 shown basic structure and a rim diameter of 15 inches was trial-produced. In addition, as Comparative Examples 1 to 6, tires that did not satisfy the above formula (1) or (2) were trial-produced. The tires of the comparative examples were substantially the same as those of the example except for the above matters. The abrasion resistance performance and fuel economy performance of the shoulder land portions of the respective test tires were tested. The common specifications and test methods of the respective test tires are as follows.

[0072] Mounting rim: 15×7.0J

[0073] Tire internal pressure: 350 kPa

[0074] Test vehicle: A minibus with a seating capacity of 8 passengers

[0075] <Abrasion resistance performance of shoulder land portion>

[0076] The test vehicle equipped with the test tire was driven on a test route composed of an asphalt road surface, and the wear energy of the first shoulder land portion during turning was measured. As a result, the reciprocal of the above wear energy was exponentiated, and the larger the value, the more excellent the abrasion resistance performance of the shoulder land portion.

[0077] <Fuel economy performance>

[0078] Using a rolling resistance testing machine, the rolling resistance of the test tire was measured according to ISO conditions. As a result, the reciprocal of the above rolling resistance was exponentiated, and the larger the value, the more excellent the fuel economy performance.

[0079] The test results are shown in Table 1.

[0080]

Table 1

[0081]

[0082]

Table 2

[0083]

[0084]

Table 3

[0085]

[0086] As shown in Tables 1 to 3, tests were conducted by varying various parameters. Since Comparative Examples 1, 5, and 7 do not satisfy Formula (1) of the present invention, it can be seen that the wear resistance of the shoulder land portion is low. In addition, since Comparative Examples 2 to 4, 6, and 8 do not satisfy Formula (2) of the present invention, it can be seen that the fuel economy is low. On the contrary, the tires of the Examples satisfy Formulas (1) and (2), and thus it can be understood that the wear resistance of the shoulder land portion and the fuel economy are significantly improved.

[0087] [Supplementary Note]

[0088] The present invention includes the following aspects.

[0089] [Invention 1]

[0090] An inflated tire is mounted on a rim for use, wherein,

[0091] the rim diameter RD of the rim is 10 to 18 inches,

[0092] the ratio SH / SW of the sectional height SH of the tire to the sectional width SW of the tire is 0.30 to 0.45,

[0093] the ratio RW / SW of the rim width RW of the rim to the sectional width SW of the tire is 0.78 to 0.99,

[0094] the inflated tire has a tread portion,

[0095] 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,

[0096] the plurality of circumferential grooves include a first shoulder circumferential groove disposed closest to the first tread end side,

[0097] the plurality of land portions include a first shoulder land portion divided on the tire axial outer side of the first shoulder circumferential groove,

[0098] the first shoulder land portion includes: a first rubber layer constituting the tread surface from the first tread end to the first shoulder circumferential groove, and a second rubber layer disposed on the tire radial inner side of the first rubber layer and made of a rubber material different from that of the first rubber layer,

[0099] the width W1 in the tire axial direction of the tread surface of the first shoulder land portion satisfies the following Formula (1),

[0100] The width W1, the thickness T1 of the first rubber layer, the thickness T2 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).

[0101] The units of the width W1, the thickness T1, and the thickness T2 are mm.

[0102] W1>0.001×(SW×SH)…(1)

[0103] W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≤ 4…(2).

[0104] [Inventive Concept 2]

[0105] For the pneumatic tire according to Inventive Concept 1,

[0106] The width W1 satisfies the following formula (3).

[0107] W1<0.002×(SW×SH)…(3).

[0108] [Inventive Concept 3]

[0109] For the pneumatic tire according to Inventive Concept 1 or 2,

[0110] The width W1, the thickness T1 of the first rubber layer, the thickness T2 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).

[0111] W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≥ 3…(4).

[0112] [Inventive Concept 4]

[0113] For the pneumatic tire according to any one of Inventive Concepts 1 to 3,

[0114] The thickness T1 is 0.9 times or more of the depth D1 of the first shoulder circumferential groove.

[0115] The unit of the depth D1 is mm.

[0116] [Inventive Concept 5]

[0117] For the pneumatic tire according to Inventive Concept 4,

[0118] The thickness T1 is 1.5 times or less of the depth D1.

[0119] [Inventive Concept 6]

[0120] The pneumatic tire according to any one of 1 to 5 of the present invention

[0121] The first shoulder land portion has a curved profile extending from the first shoulder circumferential groove to a position beyond the first tread end.

[0122] [Invention 7]

[0123] The pneumatic tire according to 6 of the present invention

[0124] The radius of curvature Rt at the first tread end of the curved profile is 0.3 times or more of the width W1, and the unit of the radius of curvature Rt is mm.

[0125] [Invention 8]

[0126] For the pneumatic tire according to 6 or 7 of the present invention, the radius of curvature Rt is 2.0 times or less of the width W1.

Claims

1. A pneumatic tire, which is mounted on a rim for use, and is characterized in that 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 surface, the tread surface 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 disposed 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 disposed on the radially inner side of the first rubber layer and made of a rubber material different from the first rubber layer, the width W1 in the tire axial direction of the tread surface of the first shoulder land portion satisfies the following formula (1), the width W1, the thickness T1 of the first rubber layer, the thickness T2 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), the units of the width W1, the thickness T1, and the thickness T2 are mm, W1 > 0.001×(SW×SH)…(1) W1×(T1×tanδ1 + T2×tanδ2) / (T1 + T2) ≤ 4…(2).

2. The pneumatic tire according to claim 1, and is characterized in that the width W1 satisfies the following formula (3), W1 < 0.002×(SW×SH)…(3).

3. The pneumatic tire according to claim 2, and is characterized in that the width W1, the thickness T1 of the first rubber layer, the thickness T2 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, and is characterized in that the thickness T1 is 0.9 times or more of the depth D1 of the first shoulder circumferential groove, the unit of the depth D1 is mm.

5. The pneumatic tire according to claim 4, and is characterized in that the thickness T1 is 1.5 times or less of the depth D1.

6. The pneumatic tire according to any one of claims 1 to 3, and is characterized in that the first shoulder land portion has a curved profile extending from the first shoulder circumferential groove to a position exceeding the first tread end.

7. The pneumatic tire according to claim 6, and is characterized in that The radius of curvature Rt at the first tread end of the curved profile is more than 0.3 times the width W1, The unit of the radius of curvature Rt is mm.

8. The pneumatic tire according to claim 7, wherein the radius of curvature Rt is not more than 2.0 times the width W1.

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