tire

Abstract

This tire provides a higher level of off-road capability while suppressing external noise generation. [Solution] The shoulder lug groove 36 has a first end 36P, a second end 36T opposite the first end 36P, a narrowing section 40, a gradually decreasing section 42, and a gradually increasing section 44 located between the first end 36P and the second end 36T. The first end 36P is connected to the outermost main groove 20. The second end 36T is connected to the contact end E. The narrowing section 40 is located inward in the tire width direction from the contact end E and has a smaller groove cross-sectional area than the groove cross-sectional areas of the first end 36P and the second end 36T. The gradually decreasing section 42 is located between the first end 36P and the narrowing section 40, and the groove cross-sectional area gradually decreases from the first end 36P toward the narrowing section 40. The gradually increasing section 44 is located between the narrowing section 40 and the second end 36T, and the groove cross-sectional area gradually increases from the narrowing section 40 toward the second end 36T.

Description

【Technical Field】 【0001】 The present invention relates to a tire. 【Background Art】 【0002】 In recent years, automobile tires have been required to have excellent characteristics that can meet strict regulations on external noise. In addition, tires for sports utility vehicles (SUVs), which are currently gaining popularity, are required to have off-road durability, for example, earth removal performance. However, the low external noise performance for suppressing the above external noise and the off-road durability are contradictory. 【0003】 On the other hand, tires aiming to achieve both low external noise performance and off-road durability have been disclosed (for example, Patent Document 1). 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2021-178545 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 An object of the tire according to the present invention is to provide a tire that can obtain a higher level of off-road durability while suppressing the generation of external noise. 【Means for Solving the Problems】 【0006】 A tire according to one aspect of the present invention includes a tread portion having a tread surface. On the tread surface, a plurality of circumferential main grooves and a plurality of shoulder lug grooves arranged outside the tire width direction of the outermost main groove arranged on the outermost side in the tire width direction among the plurality of circumferential main grooves partition and form a plurality of land portions. The plurality of shoulder lug grooves have a first end, a second end opposite to the first end, a narrowing portion, a tapering portion, and a tapering portion located between the first end and the second end. The first end is connected to the outermost main groove, The second end is connected to the ground end, The aforementioned narrowed portion is located inward in the tire width direction from the contact end and has a smaller groove cross-sectional area than the groove cross-sectional area of ​​the first and second ends. The tapering portion is positioned between the first end and the narrowed portion, and the groove cross-sectional area gradually decreases from the first end toward the narrowed portion. The gradual increasing portion is positioned between the narrowed portion and the second end, and the groove cross-sectional area gradually increases from the narrowed portion toward the second end. [Effects of the Invention] 【0007】 According to the tire of the present invention, it is possible to achieve a higher level of off-road capability while suppressing the generation of external noise. [Brief explanation of the drawing] 【0008】 [Figure 1] This is a partial plan view showing the tread portion of a tire according to this embodiment. [Figure 2] This is a partial end view along line II-II in Figure 1. [Figure 3] This is a partially enlarged plan view showing the lug groove according to this embodiment. [Figure 4] This is a partial end view along the line IV-IV in Figure 3. [Figure 5] This is a partial end view along the VV line in Figure 3. [Figure 6] This is a partial end view along the line VI-VI in Figure 3. [Figure 7] This is a partial end view along the line II-II in Figure 1, relating to a modified example. [Modes for carrying out the invention] 【0009】 Embodiments of the present invention relate to the following aspects. 【0010】 [Aspect 1] It has a tread section with a tread surface, Multiple land areas are formed on the tread surface by a plurality of circumferential main grooves and a plurality of shoulder lug grooves located further out in the tire width direction than the outermost main groove located at the outermost edge in the tire width direction among the plurality of circumferential main grooves. The plurality of shoulder lug grooves have a first end, a second end opposite to the first end, a narrowing portion, a tapering portion, and a tapering portion located between the first end and the second end. The first end is connected to the outermost main groove, The second end is connected to the ground end, The aforementioned narrowed portion is located inward in the tire width direction from the contact end and has a smaller groove cross-sectional area than the groove cross-sectional area of ​​the first and second ends. The tapering portion is positioned between the first end and the narrowed portion, and the groove cross-sectional area gradually decreases from the first end toward the narrowed portion. The aforementioned gradually increasing portion is positioned between the narrowed portion and the second end, and the groove cross-sectional area gradually increases from the narrowed portion toward the second end, in a tire. [Aspect 2] The tire according to Embodiment 1, wherein, when the groove depth at the first end is D1 and the groove width is W1, and the groove depth at the constricted portion is DS and the groove width is WS, the rate of change of groove depth X (D1 / DS × 100 (%)) is 150% or more and 200% or less, and the rate of change of groove width Y (W1 / WS × 100 (%)) is 150% or more and 200% or less. [Aspect 3] The inner tip of the tapered portion in the tire width direction is positioned in a range of 20% or less of the length of the shoulder lug groove from the first end to the outer side in the tire width direction, from the first end to the contact end. The tire according to embodiment 1 or 2, wherein the constricted portion is located in a range of 50% to 100% of the length of the shoulder lug groove, extending outward from the first end in the tire width direction. [Aspect 4] The tire according to aspect 2, wherein a change rate X of the groove depth and a change rate Y of the groove width satisfy 1.0 ≤ X / Y ≤ 1.2. [Aspect 5] The tire according to any one of aspects 1 to 4, wherein an angle of a groove wall surface of the shoulder lug groove with respect to the tire radial direction gradually increases from the first end toward the constriction. [Aspect 6] The tread surface has a circumferential auxiliary groove intersecting the shoulder lug groove, The tire according to any one of aspects 1 to 5, wherein the circumferential auxiliary groove is disposed between the constriction and the second end. [Aspect 7] The tire according to aspect 6, wherein a groove width of the circumferential auxiliary groove is 30% or more and 60% or less of a groove width at the first end of the shoulder lug groove. 【0011】 (Definition) The tire radial direction means a direction orthogonal to the tire rotation axis. The tire radial direction inner side means the side facing the tire rotation axis in the tire radial direction, and the tire radial direction outer side means the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction means a circumferential direction centered on the tire rotation axis. The tire width direction means a direction parallel to the tire rotation axis. The tire width direction inner side means the side facing the tire equatorial plane (tire equator line) in the tire width direction, and the tire width direction outer side means the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane means a plane orthogonal to the tire rotation axis and passing through the center of the tire width of the tire. "Center" and "middle" mean a midpoint where the distances from two certain points are equal, and include a range of ±10% of the distance between the midpoint and the two points. The circumferential main groove is a circumferential groove having a wear indicator indicating the end stage of wear, and generally has a groove width of 5.0 [mm] or more and a groove depth of 7.5 [mm] or more. Note that the groove width and groove depth of the circumferential main groove are not limited to the above ranges. A sipe is a cut formed in the land portion and generally has a groove width of less than 1.5 [mm]. The groove width is measured as the maximum distance between opposing groove walls at the groove opening on the tread surface when the tire is mounted on a specified rim and filled to the specified internal pressure in an unloaded state. In the case of a configuration with a notch or chamfer at the groove opening, the groove width is the value measured with the endpoint being the intersection of the extension line of the tread surface and the extension line of the groove wall in a cross-sectional view parallel to the groove width direction and groove depth direction. Groove depth is measured as the maximum distance from the tread surface to the bottom of the groove when the tire is mounted on a specified rim, filled to the specified internal pressure, and under no load. If the groove in question has partial irregularities or sipes at the bottom of the groove, the groove depth shall be the value measured excluding these irregularities or sipes. The contact end is the maximum position in the tire width direction at the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, subjected to specified internal pressure, placed perpendicular to the flat plate in a stationary state, and subjected to a load corresponding to a specified load (80% of the maximum load capacity). Similarly, in the following explanation, "regular rim" refers to the "applicable rim" as defined by JATMA, the "Design Rim" as defined by TRA, or the "Measuring Rim" as defined by ETRTO. Similarly, in the following explanation, "normal internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. Furthermore, "normal load" refers to the "maximum load capacity" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "LOAD CAPACITY" specified by ETRTO. 【0012】 (Embodiment) One embodiment of the present invention will be described below with reference to the drawings. The tire 10 shown in Figure 1 has a tread portion 12 on the radially outer side of the tire. The tread portion 12 is made of rubber material (tread rubber). The tread portion 12 has a tread surface 14 that comes into contact with the road surface when the vehicle is running. 【0013】 The tread rubber is formed from a rubber material with excellent contact characteristics and weather resistance, and is exposed on the tread surface 14. Preferably, the tread rubber contains silica, wax, and an anti-aging agent. 【0014】 The wax can be selected from plant-derived waxes, paraffin wax, microcrystalline wax, polyethylene wax, or a mixture thereof. The tread rubber preferably contains 1.0 part by mass or more of wax when the rubber component is 100 parts by mass. 【0015】 The anti-aging agent is preferably an amine-based anti-aging agent. Examples of amine-based anti-aging agents include "N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine" and "2,2,4-trimethyl-1,2-dihydroquinoline polymer". 【0016】 The tread surface 14 is annular in shape with respect to the tire's axis of rotation and is continuous in the circumferential direction of the tire. The tread surface 14 has multiple circumferential main grooves 16, in the case of Figure 1, four of which are provided. The circumferential main grooves 16 are annular in shape and continuous in the circumferential direction of the tire. The circumferential main grooves 16 include a pair of center main grooves 18 located on both sides of the tire's equatorial plane CP, and a pair of shoulder main grooves (outermost main grooves) 20 located outward in the tire width direction from each of the center main grooves 18. 【0017】 The tread surface 14 is divided into five land sections 22 by four circumferential main grooves 16. The land sections 22 include a center land section 24, a pair of middle land sections 26 located outside the center land section 24 in the tire width direction, and a pair of shoulder land sections 28 located outside the middle land section 26 in the tire width direction. The center land section 24 is divided by a pair of center main grooves 18 and includes the tire equatorial plane CP. The inner side of the middle land section 26 in the tire width direction is divided by the center main grooves 18, and the outer side of the middle land section 26 in the tire width direction is divided by the shoulder main grooves 20. The inner side of the shoulder land section 28 in the tire width direction is divided by the shoulder main grooves 20. The outer side of the shoulder land section 28 in the tire width direction extends beyond the contact edge E. 【0018】 Each middle section 26 has a plurality of middle lug grooves 30. The plurality of middle lug grooves 30 extend in a direction intersecting the circumferential main groove 16 and are arranged at predetermined intervals in the tire circumferential direction. The middle lug groove 30 has an inner tip 30P in the tire width direction connected to the center main groove 18 via a sipe 32, and an outer tip 30T in the tire width direction connected to the shoulder main groove 20. The middle lug groove 30 shown in Figure 1 is inclined from one side in the tire width direction to the other side, towards one side in the tire circumferential direction. Each middle section 26 may have sipes 34 between the plurality of middle lug grooves 30 in the tire circumferential direction. 【0019】 Each shoulder section 28 has a plurality of shoulder lug grooves 36. The plurality of shoulder lug grooves 36 extend in a direction intersecting the circumferential main groove 16 and are arranged at predetermined intervals in the tire circumferential direction. Each shoulder lug groove 36 has a first end 36P on the inner side in the tire width direction connected to the shoulder main groove 20, and a second end 36T on the outer side in the tire width direction connected to the contact end E. Each shoulder section 28 may have sipes 38 between the plurality of shoulder lug grooves 36 in the tire circumferential direction. 【0020】 As shown in Figure 2, the shoulder lug groove 36 has a narrowed section 40, a gradually decreasing section 42, and a gradually increasing section 44 located between the first end 36P and the second end 36T. The narrowed section 40 is located inward in the tire width direction from the contact end E. The groove cross-sectional area of ​​the narrowed section 40 is smaller than that of the first end 36P and the second end 36T. The groove cross-sectional area is the area of ​​the space defined by the groove width and groove depth. The narrowed section 40 has a groove width and groove depth smaller than that of the first end 36P and the second end 36T. That is, the narrowed section 40 has a narrow groove wall 46 having a groove width smaller than that of the first end 36P and the second end 36T, and a narrow groove bottom 48 having a groove depth smaller than that of the first end 36P and the second end 36T. 【0021】 When the groove depth of the first end 36P is D1 and the groove width is W1, and the groove depth of the constricted portion 40 is DS and the groove width is WS, it is preferable that the rate of change of groove depth X (D1 / DS × 100 (%)) is 150% or more and 200% or less, and the rate of change of groove width Y (W1 / WS × 100 (%)) is 150% or more and 200% or less. The groove depth D1 may be, for example, 3 mm to 10 mm. 【0022】 The tire 10 has pitch variations in which the pitch arrangement is changed in the circumferential direction of the tire. The pitch arrangement consists of lug grooves, sipes, notches, etc., arranged at a predetermined pitch in the circumferential direction of the tire. Examples of pitch arrangements include single-pitch arrangements, periodic pitch arrangements, and random pitch arrangements. Pitch refers to the smallest unit of pattern elements when the same pattern is repeated along the circumferential direction of the tire. In the tire 10 according to this embodiment, it is preferable that the above-mentioned rate of change X and rate of change Y of the shoulder lug groove 36 within at least one pitch are within the above range. 【0023】 The narrowed portion 40 is preferably located in a range of 50% to 100% of the length of the shoulder lug groove 36 from the first end 36P. The length of the shoulder lug groove 36 is the length from the first end 36P to the contact end E. In this specification, the length of the shoulder lug groove 36 from the first end 36P to the contact end E is the length measured along the tread surface 14. In a plurality of adjacent shoulder lug grooves 36 in the circumferential direction of the tire, it is preferable that the positions of each narrowed portion 40 in the tire width direction are aligned in the circumferential direction of the tire. In this case, "aligned in the circumferential direction of the tire" means including a range of ±10% or less of the length of the shoulder lug groove 36 in the tire width direction centered on a certain narrowed portion 40. 【0024】 The tapering section 42 is positioned between the first end 36P and the narrowed section 40. The groove cross-sectional area of ​​the tapering section 42 gradually decreases from the groove cross-sectional area at the first end 36P toward the narrowed section 40. In this embodiment, the groove width and groove depth of the tapering section 42 gradually decrease from the groove width and groove depth at the first end 36P toward the narrowed section 40. That is, the tapering section 42 has a first groove wall 50 in which the groove width gradually decreases from the groove width at the first end 36P toward the narrowed section 40, and a first groove bottom 52 in which the groove depth gradually decreases from the groove depth at the first end 36P toward the narrowed section 40. 【0025】 As shown in Figure 2, the inner tip 42P of the tapered section 42 in the tire width direction is located in the starting region R. The starting region R has its inner outer edge in the tire width direction as the first end 36P, and its outer edge in the tire width direction is located at a position 20% of the length of the shoulder lug groove 36 from the first end 36P. The outer edge of the starting region R in the tire width direction may also be located at a position 10% of the length of the shoulder lug groove 36 from the first end 36P. The outer tip 42T of the tapered section 42 in the tire width direction is connected to the narrowed section 40. 【0026】 The gradually increasing section 44 is positioned between the narrowing section 40 and the second end 36T. The groove cross-sectional area of ​​the gradually increasing section 44 gradually increases from the groove cross-sectional area in the narrowing section 40 toward the second end 36. In this embodiment, the groove width and groove depth of the gradually increasing section 44 gradually increase from the groove width and groove depth in the narrowing section 40 toward the second end 36T. That is, the gradually increasing section 44 has a second groove wall 54 in which the groove width gradually increases from the groove width in the narrowing section 40 toward the second end 36T, and a second groove bottom 56 in which the groove depth gradually increases from the groove depth in the narrowing section 40 toward the second end 36T. The inner tip 44P of the gradually increasing section 44 in the tire width direction is connected to the narrowing section 40. The outer tip 44T of the gradually increasing section 44 in the tire width direction is connected to the second end 36T. 【0027】 In the tapered section 42, it is preferable that the rate of change X of the groove depth is greater than the rate of change Y of the groove width. That is, it is preferable that the rate of change X of the groove depth in the tapered section 42 and the rate of change Y of the groove width in the tapered section 42 satisfy the relationship 1.0 ≤ X / Y ≤ 1.2. 【0028】 Similarly, in the gradually increasing section 44, it is preferable that the rate of change of groove depth is greater than the rate of change of groove width. For example, if the groove depth in the gradually increasing section 44 is D2 and the maximum groove width is W2, it is preferable that the rate of change of groove depth X2 (D2 / DS × 100 (%)) and the rate of change of groove width Y2 (W2 / DS × 100 (%)) in the gradually increasing section 44 satisfy the relationship 1.0 ≤ X2 / Y2 ≤ 1.2. 【0029】 As shown in Figure 3, the shoulder lug groove 36 has a gradually decreasing groove width from the first groove wall 50 to the narrow groove wall 46, and a gradually increasing groove width from the narrow groove wall 46 to the second groove wall 54. Similarly, the groove depth gradually decreases from the first groove bottom 52 to the narrow groove bottom 48, and a gradually increasing groove depth from the narrow groove bottom 48 to the second groove bottom 56. 【0030】 Preferably, the angle of the groove wall surface of the shoulder lug groove 36 with respect to the tire diameter gradually increases from the first end 36P toward the narrowed portion 40. As shown in Figure 4, the angle α of the surface of the first groove wall 50 with respect to the tire diameter is smaller than the angle β of the surface of the narrow groove wall 46 with respect to the tire diameter, as shown in Figure 5. That is, the angle of the groove wall surface of the shoulder lug groove 36 with respect to the tire diameter gradually increases from the angle α of the surface of the first groove wall 50 toward the angle β of the surface of the narrow groove wall 46. Furthermore, as shown in Figure 6, the angle γ of the surface of the second groove wall 54 with respect to the tire diameter is smaller than the angle β shown in Figure 5. That is, the angle of the groove wall surface of the shoulder lug groove 36 with respect to the tire diameter gradually decreases from the angle β of the surface of the narrow groove wall 46 toward the angle γ of the surface of the second groove wall 54. The angles α, β, and γ can each be appropriately set within the range of 0° to 10°. For example, angles α and γ may be between 0° and less than 5°, and angle β may be between 5° and 10°. 【0031】 The tire 10 of this embodiment, although not shown in its entirety, has a meridional cross-sectional shape similar to that of a conventional pneumatic tire. That is, in a meridional cross-sectional view of the tire 10, the tire 10 of this embodiment has a bead portion, a sidewall portion, a shoulder portion, and a tread portion 12 extending from the inside to the outside in the radial direction of the tire. Furthermore, the tire 10 has, for example, a carcass layer extending from the tread portion 12 to the bead portions on both sides in a meridional cross-sectional view of the tire, wound around a pair of bead cores, and a belt layer and, optionally, a belt cover layer are provided on the radially outer side of the carcass layer. 【0032】 The tire 10 of this embodiment, as described above, is obtained through the usual manufacturing processes, namely the mixing process of the tire material, the processing process of the tire material, the molding process of the green tire, the vulcanization process, and the inspection process after vulcanization. When manufacturing the tire of this embodiment, protrusions and recesses corresponding to a predetermined tread pattern are formed on the inner wall of the vulcanization mold, and vulcanization is performed using this mold. 【0033】 The tire 10 configured as described above is mounted on a vehicle that may be used for off-road driving, for example. The tire 10 is mounted on a rim and inflated with air before being mounted on the vehicle. The tire 10 has circumferential main grooves 16 and lug grooves 30, 36 formed on the tread surface 14, and the shoulder lug grooves 36 are connected to the shoulder main grooves 20 and extend outward in the tire width direction from the contact edge E. This allows sand and soil that has entered the circumferential main grooves 16 and shoulder lug grooves 36 to be discharged to the outside of the tire from the contact edge E when driving on a road surface containing highly wet soil, such as sand or muddy roads. 【0034】 In this embodiment, the narrowed portion 40 of the shoulder lug groove 36, due to its small groove depth and width, suppresses the transmission of air column resonant sound generated in the shoulder main groove 20 to the outside of the tire 10 through the shoulder lug groove 36. Therefore, the tire 10 can suppress the generation of external noise during driving. 【0035】 In this embodiment, the shoulder lug groove 36 has a narrowed section 40 whose groove cross-sectional area is smaller than that of the first end 36P. As a result, the pressure within the shoulder lug groove 36 between the first end 36P and the narrowed section 40 increases on the tread surface 14 that is in contact with the road surface. The outer side of the narrowed section 40 in the tire width direction is open to the outside of the tire 10 through the contact end E. As a result, sand and soil that enter the shoulder lug groove 36 are compressed from the first end 36P toward the narrowed section 40. The shoulder lug groove 36 outside the narrowed section 40 in the tire width direction is open in the tire width direction through the contact end E. Therefore, the compressed sand and soil are depressurized in the narrowed section 40 and pushed out from the narrowed section 40 toward the outside in the tire width direction at a high flow velocity. 【0036】 Furthermore, because a tapering section 42 is provided between the first end 36P and the narrowed section 40, sand and soil that enter the shoulder lug groove 36 can move smoothly within the shoulder lug groove 36 along the first groove wall 50 and the first groove bottom 52. In addition, because a tapering section 44 is provided between the narrowed section 40 and the second end 36T, sand and soil pushed outward from the narrowed section 40 in the tire width direction moves smoothly from the narrowed section 40 along the second groove wall 54 and the second groove bottom 56, and is discharged to the outside of the tire 10 through the contact end E. In this way, the tire 10 has excellent sand and soil discharge capabilities. 【0037】 As a result, the tire 10 according to this embodiment can achieve a higher level of both low external noise and off-road capability. 【0038】 The shoulder lug groove 36 has a groove depth change rate X (D1 / DS × 100 (%)) of 150% to 200% and a groove width change rate Y (W1 / WS × 100 (%)) of 150% to 200%, which allows for more reliable reduction of external noise in the narrowed section 40. Furthermore, by more reliably increasing the pressure within the shoulder lug groove 36 on the inner side of the narrowed section 40 in the tire width direction and more reliably reducing the pressure within the shoulder lug groove 36 on the outer side of the narrowed section 40 in the tire width direction, excellent off-road performance can be achieved. 【0039】 In the shoulder lug groove 36, the groove width has a greater impact on external noise than the groove depth. In this embodiment, in both the gradually decreasing section 42 and the gradually increasing section 44, the rate of change X of the groove depth is greater than the rate of change Y of the groove width, thereby enabling the production of external noise while obtaining a tire 10 with excellent sand and soil removal capabilities. 【0040】 The tire 10 can be more reliably obtained with excellent sand and soil discharge capabilities while suppressing the generation of external noise, by ensuring that the rate of change X of the groove depth in the tapered section 42 and the rate of change Y of the groove width in the tapered section 42 satisfy the relationship 1.0 ≤ X / Y ≤ 1.2. 【0041】 The angle of the groove wall surface of the shoulder lug groove 36 with respect to the tire radial direction gradually increases from the first end 36P toward the constricted section 40. This allows for a reduction in the groove cross-sectional area of ​​the constricted section 40 by suppressing the rate of decrease in the groove width of the shoulder lug groove 36 while increasing the rate of decrease in the groove depth. Therefore, the tire 10 can achieve excellent sand and soil discharge capabilities by suppressing the rate of decrease in the groove width of the shoulder lug groove 36 while reducing the groove cross-sectional area of ​​the constricted section 40. 【0042】 (modified version) The present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the spirit of the invention. Each of the modified configurations shown below can be used individually or in combination of two or more with the embodiments described above as appropriate. 【0043】 The tread pattern provided on the tread surface is not limited to that shown in Figure 1. In other words, as long as the shoulder lug grooves are provided, the position and number of other circumferential main grooves and sipes can be selected as appropriate. 【0044】 The tread surface may also be provided with circumferential auxiliary grooves. A modified tire will be described using Figure 7, which uses the same reference numerals as the above embodiment for the same configuration. The modified tire 10A shown in Figure 7 has circumferential auxiliary grooves 58 on the shoulder land portion 28. The circumferential auxiliary grooves 58 are annular and continuous in the circumferential direction of the tire. The circumferential auxiliary grooves 58 communicate with the shoulder lug grooves 36. The circumferential auxiliary grooves 58 are located between the constricted portion 40 and the contact end E. It is preferable that the circumferential auxiliary grooves 58 are located closer to the contact end E than the midpoint between the constricted portion 40 and the contact end E. It is preferable that the groove width of the circumferential auxiliary grooves 58 is 30% to 60% of the groove width at the first end 36P of the shoulder lug grooves 36. 【0045】 The circumferential auxiliary groove 58 discharges sand and soil in the circumferential direction of the tire. By ensuring that the groove width of the circumferential auxiliary groove 58 is greater than or equal to the lower limit of the above range, sand and soil that have entered from the shoulder lug groove 36 can be discharged in the circumferential direction of the tire. By ensuring that the groove width of the circumferential auxiliary groove 58 is less than or equal to the upper limit of the above range, it is possible to suppress the outflow of air column resonant sound transmitted from the shoulder lug groove 36 to the outside of the tire. The tire 10, by providing a circumferential auxiliary groove 58 that communicates with the shoulder lug groove 36 on the outside in the tire width direction from the constricted portion 40, can obtain the same effects as in the above embodiment, and by receiving the sand and soil discharged from the constricted portion 40 to the outside in the tire width direction into the circumferential auxiliary groove 58, even better sand and soil discharge performance can be obtained. 【0046】 By having the groove width of the circumferential auxiliary groove 58 be between 30% and 60% of the groove width at the first end 36P of the shoulder lug groove 36, it is possible to achieve both low external noise and off-road capability. 【0047】 Furthermore, the shoulder lug groove 36 may have a raised base portion 60 in the starting region R. The groove bottom 62 of the raised base portion 60 is positioned higher than the groove depth at the inner tip in the tire width direction of the first groove bottom 52. That is, the groove depth of the raised base portion 60 is shallower than the groove depth at the inner tip in the tire width direction of the tapering portion 42. By having the raised base portion 60, the tire 10A can suppress a decrease in block rigidity at the connection portion between the shoulder lug groove 36 and the shoulder main groove 20. 【0048】 In the above embodiment, the case where the rate of change of groove depth X (D1 / DS × 100 (%)) is 150% or more and 200% or less, and the rate of change of groove width Y (W1 / WS × 100 (%)) is 150% or more and 200% or less has been described, but the present invention is not limited to this. That is, the rate of change of groove depth X and the rate of change of groove width Y may each be less than 150% or more than 200%. 【0049】 In the above embodiment, the case described was that the inner tip of the tapered portion in the tire width direction is separated from the first end in the tire width direction. However, the present invention is not limited to this, and the inner tip of the tapered portion in the tire width direction may be integral with the first end. 【0050】 In the above embodiment, the case where the rate of change X of groove depth and the rate of change Y of groove width satisfy 1.0 ≤ X / Y ≤ 1.2 was described, but the present invention is not limited to this, and may be less than 1.0 or greater than 1.2. 【0051】 In the above embodiment, the case described was that the angle of the groove wall surface of the shoulder lug groove with respect to the tire radial direction gradually increases from the first end toward the constricted portion. However, the present invention is not limited to this, and the angle may be constant between the first end and the constricted portion. In this case, "constant" includes cases where there is a difference of ±5° or less (the same applies hereinafter). 【0052】 In the above embodiment, the case described above was one in which the angle of the groove wall surface of the shoulder lug groove with respect to the tire radial direction gradually decreases from the constricted portion toward the second end. However, the present invention is not limited to this, and the angle may be constant between the constricted portion and the second end. 【0053】 In the above embodiment, the case described was one in which the constricted portion has a groove depth and groove width smaller than the groove width and groove depth of the first and second ends, but the present invention is not limited to this. That is, it is sufficient for the constricted portion to have a groove cross-sectional area smaller than the groove cross-sectional area of ​​the first and second ends, and this includes, for example, the case in which at least one of the groove depth and groove width of the constricted portion is smaller than at least one of the groove depth and groove width of the first and second ends. 【0054】 Furthermore, the decreasing section may have a portion where only the groove depth decreases and a portion where only the groove width decreases. In addition, the increasing section may have a portion where only the groove depth increases and a portion where only the groove width increases. [Examples] 【0055】 This document describes the results of manufacturing a tire corresponding to the invention defined in the claims of this application and evaluating its noise performance and off-road performance. 【0056】 (sample) Examples 1 to 14 were manufactured with a tire size of 265 / 65R17 112H (as defined by JATMA), and the rim-mounted state had the shape shown in Figure 1. The detailed specifications of these tires are shown in Table 1 below. 【0057】 In Tables 1 and 2, the "Connected to Shoulder Main Groove" column indicates whether the first end of the shoulder lug groove is connected to the shoulder main groove, with "Yes" indicating connected and "No" indicating not connected. The "Gradual Decrease, Narrowing, and Increasing Sections" column indicates whether the shoulder lug groove has a gradual decline, narrowing, or increasing section, respectively, with "Yes" indicating provided and "No" indicating not provided. The "X and Y (%)" column shows the rate of change of groove depth X and the rate of change of groove width Y. The "Tip Position of Gradual Decrease Section" column shows the ratio of the distance from the tip of the gradual decline section on the inside in the tire width direction to the first end to the length of the shoulder lug groove from the first end to the contact end. The "X / Y" column shows the ratio of the rate of change of groove depth X to the rate of change of groove width Y. The column for "Angle of groove wall surface with respect to tire radial direction (°)" shows the relationship between the angle of the groove wall surface of the shoulder lug groove with respect to the tire radial direction at the first end and the constricted section. If there is no change, it is written as "Constant," and if it is gradually increasing, it is written as the actual value, "0° to 5°." The column for "Circumferential auxiliary groove" is written as "Present" if a circumferential main groove is provided, and as "Absent" if it is not provided. The column for "Circumferential auxiliary groove width (%)" shows the ratio of the groove width of the circumferential auxiliary groove to the groove width at the first end of the shoulder lug groove. In each embodiment, the position of the constricted section in the tire width direction was assumed to be the same for all of them. 【0058】 The tires manufactured in this manner according to Examples 1 to 12 were mounted on rims with a rim size of 17 x 8J at an air pressure (F / R) of 230 kPa / 230 kPa. Each test tire was then mounted on a four-wheel drive test vehicle (engine displacement 2700cc), and its performance was evaluated according to the following procedure. 【0059】 (Noise performance) The noise levels at 60 km / h and 100 km / h on flat roads were evaluated by test drivers' subjective assessments and expressed as an index with Conventional Example 1 (described later) set to 100. A higher index indicates lower noise levels and superior noise performance when driving on flat roads. 【0060】 (Off-road performance) The driving performance on each evaluation surface—rocky terrain, muddy roads, and sandy areas—was evaluated by test drivers' subjective assessments. The overall score of the subjective assessments for each evaluation surface was expressed as an index, with Conventional Example 1 (described later) set to 100. A higher index indicates better off-road performance; a higher overall score on each evaluation surface indicates superior off-road capability. 【0061】 [Table 1] 【0062】 [Table 2] 【0063】 As shown in Tables 1 and 2, Examples 1 to 12 were found to have a first end of the shoulder lug groove connected to the main shoulder groove, and the shoulder lug groove provided with a gradually decreasing section, a narrowing section, and a gradually increasing section, thereby suppressing the generation of external noise while achieving a higher level of off-road performance. Examples 3 and 4 were found to have excellent off-road performance and noise performance because the rate of change of groove depth X and the rate of change of groove width Y were between 150% and 200%. Examples 5 and 6 were found to have excellent off-road performance and noise performance because the ratio of the distance from the tip of the inner side in the tire width direction of the gradually decreasing section to the first end to the length of the shoulder lug groove from the first end to the contact end was 20% and 10%, respectively. Examples 7 and 8 were found to have excellent off-road performance and noise performance because the ratio of the rate of change of groove depth X to the rate of change of groove width Y was 1.0 and 1.2, respectively. Example 9 showed that the angle of the groove wall surface of the shoulder lug groove with respect to the tire radial direction was 0° to 5° at the first end and the narrowed section, resulting in excellent off-road performance and noise performance. Example 10 showed that the presence of a circumferential auxiliary groove further improved off-road performance. From the results of Examples 11 and 12, it was found that the ratio of the groove width of the circumferential auxiliary groove to the groove width at the first end of the shoulder lug groove was 60% or less, which improved off-road performance while suppressing a decrease in noise performance. [Explanation of symbols] 【0064】 10 tires 10A Tire 12 Tread section 14 Tread surface 16 Circumferential main groove 18 Center main groove 20 Shoulder main groove (outermost main groove) 22 Land 24 Center Track and Field Club 26 Middle Track and Field Club 28 Shoulder Track and Field Club 30 Middle lug groove 30P Inner tip in the tire width direction 30T Outer tip in the tire width direction 32 sipes 34 sipes 36 Shoulder lug grooves 36P 1st end 36T 2nd end 38 sipes 40 Stenosis 42. Gradual decrease section 42P Inner tip in the tire width direction 42T Outer tip in the tire width direction 44. Gradual increase section 44P Inner tip in the tire width direction 44T Outer tip in the tire width direction 46 Narrow groove wall 48 Narrow groove bottom 50. First trench wall 52 1st groove bottom 54 Second trench wall 56 Second groove bottom 58 Circumferential auxiliary groove 60 Raised base 62 Groove bottom E Ground end R start area

Claims

[Claim 1] It has a tread section with a tread surface, Multiple land areas are formed on the tread surface by a plurality of circumferential main grooves and a plurality of shoulder lug grooves located further out in the tire width direction than the outermost main groove located at the outermost edge in the tire width direction among the plurality of circumferential main grooves. The plurality of shoulder lug grooves have a first end, a second end opposite to the first end, a narrowing portion, a tapering portion, and a tapering portion located between the first end and the second end. The first end is connected to the outermost main groove, The aforementioned second end is connected to the ground end, The aforementioned narrowed portion is located inward in the tire width direction from the contact end and has a smaller groove cross-sectional area than the groove cross-sectional areas of the first and second ends. The tapering portion is positioned between the first end and the narrowed portion, and the groove cross-sectional area gradually decreases from the first end toward the narrowed portion. The aforementioned gradually increasing portion is positioned between the narrowed portion and the second end, and the groove cross-sectional area gradually increases from the narrowed portion toward the second end, in a tire. [Claim 2] The tire according to claim 1, wherein, when the groove depth at the first end is D1 and the groove width is W1, and the groove depth at the constricted portion is DS and the groove width is WS, the rate of change of groove depth X (D1 / DS × 100 (%)) is 150% or more and 200% or less, and the rate of change of groove width Y (W1 / WS × 100 (%)) is 150% or more and 200% or less. [Claim 3] The inner tip of the tapered portion in the tire width direction is positioned in a range of 20% or less of the length of the shoulder lug groove from the first end to the outer side in the tire width direction, from the first end to the contact end. The tire according to claim 1, wherein the constricted portion is arranged in a range of 50% to 100% of the length of the shoulder lug groove outward from the first end in the tire width direction. [Claim 4] The tire according to claim 2, wherein the rate of change X of the groove depth and the rate of change Y of the groove width satisfy 1.0 ≤ X / Y ≤ 1.

2. [Claim 5] The tire according to claim 1, wherein the angle of the groove wall surface of the shoulder lug groove with respect to the tire radial direction gradually increases from the first end toward the constricted portion. [Claim 6] The tread surface has circumferential auxiliary grooves that intersect with the shoulder lug grooves, The tire according to claim 1, wherein the circumferential auxiliary groove is arranged between the constricted portion and the second end. [Claim 7] The tire according to claim 6, wherein the groove width of the circumferential auxiliary groove is 30% or more and 60% or less of the groove width at the first end of the shoulder lug groove.

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