tire

Abstract

Provided is a tire with which noise-reduction performance can be improved while ensuring excellent off-road performance and maintaining good pattern visibility. The tire has a shoulder lug groove 22 in the shoulder region of a tread portion 1, wherein: a bottom raised portion 40 comprising a plurality of upper surfaces 41, inclined surfaces 42 and chamfered portions 43 is provided on the groove bottom of the shoulder lug groove 22; a bottom raised depth DN from the tread footprint to an N-th upper surface 41 from a main groove 10 side satisfies the relationship DN<DN+1; a wall surface angle θ0 of the bottom raised portion 40 on the main groove 10 side and an inclination angle θN of an N-th inclined surface 41 from the main groove 10 side satisfy the relationships θ0<θN and θN<θN+1; and a radius of curvature R0 of a connecting portion 44 between the first upper surface 41 from the main groove 10 side and the wall surface of the bottom raised portion 40 on the main groove 10 side and a radius of curvature RN of the chamfered portion 43 on the upper end side of an N-th inclined surface 42 from the main groove 10 side satisfy the relationship R0<RN.

Description

tire 【0001】 The present invention relates to a tire intended for driving on unpaved roads and the like, and more specifically, to a tire that enables improved noise reduction while ensuring excellent off-road performance. 【0002】 Tires designed for driving on unpaved roads (rough terrain, muddy areas, sandy areas, rocky areas, etc.) in addition to paved roads (e.g., all-terrain tires, all-terrain tires, etc.) are required to have excellent driving performance on various road surfaces, and in particular, to have excellent snow performance (driving performance on snow-covered roads). Such tires tend to employ tread patterns that mainly consist of lug grooves and blocks with many edge components and have a large groove area (see, for example, Patent Document 1). On the other hand, tread patterns with many groove components tend to radiate noise (pattern noise) generated by the tread pattern to the outside of the vehicle through the grooves, and there is a need to reduce passing noise outside the vehicle. For example, it is possible to suppress the emission of noise through the grooves by creating a raised section in the groove that extends in the tire width direction, but there are concerns that the visibility of the tread pattern will decrease or that the off-road performance will be affected by the formation of the raised section. Therefore, it is required to maintain good pattern visibility and off-road performance even when a raised section is provided to reduce noise, and to achieve a high level of balance between these performances. 【0003】 Japanese Patent Application Publication No. 2018-034698 【0004】 The objective of the present invention is to provide a tire that ensures excellent off-road performance, maintains good pattern visibility, and enables improved low-noise performance. 【0005】In order to achieve the above object, a tire of the present invention includes a tread portion that extends in the tire circumferential direction and forms an annular shape. The surface of the tread portion has a plurality of main grooves that extend along the tire circumferential direction. In a shoulder region located outside the tire width direction of a pair of shoulder main grooves located on the outermost side in the tire width direction among the plurality of main grooves, a plurality of shoulder lug grooves that extend outward in the tire width direction from the main groove and are arranged at intervals in the tire circumferential direction, and a plurality of shoulder blocks that are partitioned by the main groove and the shoulder lug groove and are arranged in the tire circumferential direction are provided. A bottom raising portion is provided at the bottom of the shoulder lug groove. The bottom raising portion has a stepped shape including a plurality of upper surfaces with different raising heights from the groove bottom, and inclined surfaces arranged between adjacent upper surfaces in the tire width direction or between the upper surface and the groove bottom of the shoulder lug groove. The upper surface and the inclined surface are smoothly connected by a chamfer portion having a cross-sectional arc shape. When the bottom raising depth from the tread surface of the Nth upper surface from the main groove side is D N when, the bottom raising depths of the plurality of upper surfaces are D N <D N+1 satisfy the relationship of, and when the wall surface angle on the main groove side of the bottom raising portion is θ0 and the inclination angle of the Nth inclined surface from the main groove side is θ N when, the wall surface angle θ0 and the inclination angles of the plurality of inclined surfaces satisfy θ0 < θ N and θ N <θ N+1 satisfy the relationship of. The first upper surface from the main groove side and the wall surface on the main groove side of the bottom raising portion are connected by a connecting portion having a curvature radius R0 of 0 mm or more. When the curvature radius at the chamfer portion on the upper end side of the Nth inclined surface from the main groove side is R N when, the curvature radii of these chamfer portions satisfy R0 < R N satisfy the relationship of. It is characterized by this. 【0006】In the tire of the present invention, a shoulder lug groove that significantly contributes to the emission of noise to the outside of the vehicle is provided with a raised bottom portion, so the emission of noise through the shoulder lug groove is suppressed, and the passing noise outside the vehicle can be effectively reduced. On the other hand, since the raised bottom portion has the above-described stepped shape, the groove volume can be secured, and the off-road performance can be maintained well. In particular, due to the relationship of the above-described raised bottom depth, the raised bottom portion gradually expands toward the outer side in the tire width direction, so the soil discharge performance and snow discharge performance can be secured, and the off-road performance can be exhibited well. Also, due to the relationship between the above-described wall surface angle θ0 and the inclination angle θ N and the relationship between the curvature radii R0, R N , gentle ridge lines are formed at each step of the stepped raised bottom portion, so even if the raised bottom portion is formed, the impression of the pattern design inherent in the tread pattern is not impaired, and good pattern visibility can be ensured. By these collaborations, the off-road performance, pattern visibility, and low-noise performance can be highly compatible with each other. 【0007】 In the present invention, it is preferable that the curvature radius in the chamfered portion satisfies the relationship of R N < R N+1 . By increasing the curvature radius of the chamfered portion toward the outer side in the tire width direction in this way, a gentler ridge line is formed toward the outer side in the tire width direction, which is advantageous for improving the pattern visibility. 【0008】 In the present invention, it is preferable that the raised bottom depth D N is 10% to 90% of the depth of the main groove. Thereby, since all upper surfaces of the raised bottom portion have an appropriate raised bottom depth, it is advantageous for improving the off-road performance and low-noise performance. 【0009】 In the present invention, it is preferable that the curvature radius R0 is 0 mm to 1 mm and the curvature radius R N is 0.6 mm to 5 mm. Thereby, since the shapes of the connecting portion and the chamfered portion become good, it is advantageous for improving the pattern visibility by making the ridge line caused by the raised bottom portion gentle. 【0010】 In the present invention, the wall surface angle θ0 is 0° to 10°, and the inclination angle θ NIt is preferably 5° to 80°. Thereby, the shape in which the bottom raising portion gradually expands toward the outer side in the tire width direction becomes good, which is advantageous for improving off-road performance and pattern visibility. 【0011】 In the present invention, it is preferable that the ratio of the area of the bottom raising portion to the area of each shoulder lug groove provided with the bottom raising portion is 20% to 60%. By having the bottom raising portion occupy an appropriate ratio in each shoulder lug groove in this way, it is advantageous for improving off-road performance and low-noise performance. 【0012】 In the present invention, in the center region excluding the shoulder region, a plurality of center lug grooves that connect adjacent main grooves extending in the tire width direction and a plurality of center blocks partitioned by the main grooves and the center lug grooves are provided, and a center bottom raising portion can be provided at the groove bottom of the center lug groove. In this specification, the groove bottom of the main groove, the groove bottom of the center lug groove, and the upper surface of the center bottom raising portion form a stepped cross-sectional shape in which the depth becomes smaller toward the center in the extending direction of the center lug groove. The inclination angle of the side surface of the center bottom raising portion is larger than the groove wall angle of the main groove at the position where it connects to the center lug groove, and the radius of curvature at the chamfer portion between the upper surface and the side surface of the center bottom raising portion is preferably larger than the radius of curvature at the connecting portion between the groove bottom of the center lug groove and the groove wall of the main groove. By providing a center bottom raising portion also in the center lug groove in this way, the propagation of noise through the center lug groove can be suppressed, which is advantageous for improving low-noise performance. On the other hand, the stepped cross-sectional shape described above is formed by the center bottom raising portion, and the groove depth gradually expands from the center of the bottom raising portion toward the outer side in the tire width direction, so that earth removal performance and snow removal performance can be ensured, and off-road performance can be exhibited well. Also, by satisfying the above-mentioned relationship between the inclination angle and the radius of curvature, a gentle ridge line is formed in the bottom raising portion, so that pattern visibility can be maintained well. 【0013】In this invention, "contact end" refers to both ends in the axial direction of the tire in the contact area formed when a tire is mounted on a standard rim, filled with standard internal pressure, placed vertically on a plane, and a standard load is applied. "Standard rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, it may be a standard rim for JATMA, a "Design Rim" for TRA, or a "Measuring Rim" for ETRTO. "Regular internal pressure" refers to the air pressure specified for each tire in the tire standard system, including the standard on which the tire is based. For JATMA, it is the maximum air pressure; for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is "INFLATION PRESSURE," but for passenger car tires, it is set to 180 kPa. "Regular load" refers to the load specified for each tire by each standard within the standards system that the tire is based on. For JATMA, it is the maximum load capacity; for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is "LOAD CAPACATY". 【0014】 The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, it can be filled with air, an inert gas such as nitrogen, or other gases. 【0015】 Figure 1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. Figure 2 is a front view showing the tread surface of a tire according to an embodiment of the present invention. Figure 3 is a cross-sectional view taken along the line X-X in Figure 2. Figure 4 is a cross-sectional view taken along the line Y-Y in Figure 2. 【0016】 The configuration of the present invention will be described in detail below with reference to the attached drawings. 【0017】The tire of the present invention, when it is a pneumatic tire as shown in Figure 1, comprises a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. In Figure 1, the symbol CL indicates the tire equator, and the symbol E indicates the contact end. Although not depicted in Figure 1 because it is a meridian cross-sectional view, the tread portion 1, sidewall portions 2, and bead portions 3 each extend in the circumferential direction of the tire and form an annular shape, thereby forming the basic toroidal structure of the pneumatic tire. The following explanation using Figure 1 is basically based on the illustrated meridian cross-sectional shape, but each tire component extends in the circumferential direction of the tire and forms an annular shape. 【0018】 A carcass layer 4 is mounted between a pair of left and right bead sections 3. The carcass layer 4 includes multiple reinforcing cords extending in the tire radial direction and is folded back from the inside to the outside in the tire width direction around the bead core 5 located in each bead section 3. A bead filler 6 is also placed on the outer circumference of the bead core 5, and this bead filler 6 is enclosed by the main body and folded portion of the carcass layer 4. On the other hand, multiple belt layers 7 (two layers in Figure 1) are embedded on the outer circumference side of the carcass layer 4 in the tread section 1. Each belt layer 7 includes multiple reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of, for example, 10° to 40°. Furthermore, at least one belt reinforcement layer 8 (two layers in Figure 1) is provided on the outer circumference side of the belt layer 7. The belt reinforcement layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcement layer 8, the organic fiber cords are set to an angle of, for example, 0° to 5° with respect to the circumferential direction of the tire. 【0019】 As this invention relates to a tread pattern formed on the surface of the tread portion 1 of a tire, as described below, the internal structure (cross-sectional structure) of the tire is not limited to the general structure described above. Furthermore, it can be applied to various types of tires, including non-pneumatic tires, as long as they have a surface that contacts the road surface (a portion corresponding to the surface of the tread portion 1 in a pneumatic tire). 【0020】 The tread pattern in the tire of the present invention is preferably based on blocks. For example, in the example shown in Figure 2, a plurality of main grooves 10 (four in the figure) are provided on the surface of the tread portion 1, extending in a zigzag pattern along the circumferential direction of the tire. The main grooves 10 are grooves that carry the main drainage function, and the groove width is preferably 3 mm to 30 mm, more preferably 5 mm to 11 mm, and the groove depth is preferably 8 mm to 16 mm, more preferably 10 mm to 15 mm. A zigzag shape is a shape in which a straight portion inclined in one direction with respect to the circumferential direction of the tire and a straight portion inclined in the other direction are alternately connected in the circumferential direction of the tire. In the illustrated example, the main grooves 10 include a pair of inner main grooves 11 arranged on both sides of the tire equator CL, and a pair of shoulder main grooves 12 arranged on the outside in the tire width direction. Among these four main grooves 10, the pair of shoulder main grooves 12 are arranged on the outermost side in the tire width direction. In the following explanation, the area of ​​the shoulder main groove 12 on the inner side in the tire width direction (towards the tire equator CL) may be referred to as the center region, and the area of ​​the shoulder main groove 12 on the outer side in the tire width direction may be referred to as the shoulder region. 【0021】 Multiple rows (five rows in the figure) of land areas partitioned by the main groove 10 are provided with multiple lug grooves 20 extending in the tire width direction and spaced apart in the tire circumferential direction. These lug grooves 20 and the main groove 10 partition the multiple rows of land areas into multiple blocks 30. 【0022】 More specifically, in the example shown in Figure 2, the center area is divided into three rows of center land sections, each of which is provided with multiple center lug grooves 21 extending along the tire width direction. The center lug grooves 21 extend to connect adjacent center main grooves 11 in the tire width direction. The center lug grooves 21 may be curved as shown in the example. The center lug grooves 21 are spaced apart in the tire circumferential direction, and the center land section is divided into multiple center blocks 31 by the center main grooves 11 and the center lug grooves 21. 【0023】Multiple shoulder lug grooves 22 extending in the tire width direction are provided in the shoulder land area, which is partitioned within the shoulder region. The shoulder lug grooves 22 extend from the shoulder main groove 12 outward in the tire width direction, beyond the contact edge E. The shoulder lug grooves 22 are spaced apart in the tire circumferential direction, and the shoulder land area is partitioned into multiple shoulder blocks 32 by the shoulder main groove 12 and the shoulder lug grooves 22 (and the contact edge E). 【0024】 Since the present invention relates to a raised section (described later) provided at the bottom of the lug groove 20 (particularly the shoulder lug groove 22), the tread pattern is not limited to the illustrated example, as long as it is a block-based pattern with lug grooves 20. For example, in the illustrated example, in addition to the various grooves described above, there are notched grooves that open at one end into the main groove 10 and terminate at the other end within the block 30, auxiliary grooves that extend along the tire width direction other than the lug groove 20, and sipes, but these elements can be arbitrarily provided according to the desired tire performance. 【0025】As described above, in the present invention, a raised portion 40 is provided at the bottom of the shoulder lug groove 22. The raised portion 40 in the present invention has a stepped shape, as illustrated in Figure 3, consisting of a plurality of upper surfaces 41 with different elevation heights from the bottom of the shoulder lug groove 22, and inclined surfaces 42 arranged between adjacent upper surfaces 41 in the tire width direction or between the upper surfaces 41 and the bottom of the shoulder lug groove 22. At this time, the upper surfaces 41 and the inclined surfaces 42 are smoothly connected by a chamfered portion 43 with a circular arc cross-section. By providing such a raised portion 40, the radiation of noise through the shoulder lug groove 22 is suppressed, and the noise of vehicles passing outside the vehicle can be reduced. In particular, the shoulder lug groove 22 is located on the outermost side in the tire width direction and extends beyond the contact end E, so it contributes greatly to the radiation of noise to the outside of the vehicle, and by providing the raised portion 40 in this shoulder lug groove 22, the noise of vehicles passing outside the vehicle can be effectively reduced. Furthermore, because the raised section 40 has the aforementioned stepped shape, the groove volume can be secured even with the raised section 40 in place, and good off-road performance can be maintained. Figure 3 is a cross-sectional view taken along the line X-X in Figure 2, and is a cross-section taken by a line (dashed line in the figure) that passes through the center of the groove width of the shoulder lug groove 22 and is aligned with the extension direction of the shoulder lug groove 22. 【0026】 In the stepped raised section 40 described above, the raised depth from the tread surface of the Nth upper surface 41 from the main groove 10 (shoulder main groove 12) side is D N In this case, the depth of the raised top surface 41 is D N <D N+1 The following relationship must be satisfied. Also, the groove depth of the shoulder lug groove 22 is D SH Therefore, these depths are D N <D N+1 <D SH The relationship is satisfied. For example, in the illustrated example, the raised portion 40 has two upper surfaces 41, and the raised depth D1 of the first upper surface 41 from the main groove 10 (shoulder main groove 12) side is smaller than the raised depth D2 of the second upper surface 41 from the main groove 10 (shoulder main groove 12) side. Also, the relationship between the raised depths D1, D2 and the groove depth D SH Comparing this, groove depth D SH The bottom depth is greater than the bottom depths D1 and D2 (D1 < D2 < DSH ). Due to this relationship of varying depths of the raised base, the raised section 40 gradually widens outward in the tire width direction, ensuring soil and snow removal capabilities, and enabling the vehicle to exhibit good off-road performance. 【0027】 Raised depth D N and groove depth D SH The bottom depth D is preferably 10% to 90%, more preferably 20% to 85%, of the groove depth of the main groove 10 (shoulder main groove 12). N and groove depth D SH By setting this, all upper surfaces 41 of the raised section 40 have an appropriate raised depth, which is advantageous for improving off-road performance and low noise performance. Raised depth D N and groove depth D SH If the depth is less than 10% of the groove depth of the main groove 10 (shoulder main groove 12), sufficient groove volume cannot be secured, and the effect of improving off-road performance will be limited. N and groove depth D SH If the depth exceeds 90% of the main groove, the raised height of the bottom section 40 cannot be sufficiently secured, and the effect of reducing noise becomes limited. 【0028】 As shown in the illustrated example, when the raised portion 40 has two upper surfaces 41, the raised depth D1 of the first upper surface 41 from the main groove 10 (shoulder main groove 12) side is preferably 20% to 40% of the groove depth of the main groove 10 (shoulder main groove 12), the raised depth D2 of the second upper surface 41 from the main groove 10 (shoulder main groove 12) side is preferably 41% to 70% of the groove depth of the main groove 10 (shoulder main groove 12), and the groove depth D of the shoulder lug groove 22 SH The depth of the main groove 10 (shoulder main groove 12) is preferably 71% to 85% of the groove depth. Also, the difference in the raised depth between adjacent upper surfaces 41 in the tire width direction (for example, D2-D1), or the difference between the raised depth of the upper surface 41 and the groove depth (for example, D SH -D2) is preferably 20% to 60%, more preferably 30% to 50%, of the groove depth of the main groove 10 (shoulder main groove 12). 【0029】In the stepped raised section 40 described above, the angle of the wall surface on the main groove 10 (shoulder main groove 12) side of the raised section 40 (angle with respect to the normal of the tread surface) is θ0, and the angle of inclination of the Nth inclined surface 42 from the main groove 10 (shoulder main groove 12) side (angle with respect to the normal of the tread surface) is θ N In this case, the wall angle θ0 and the inclination angles of the multiple inclined surfaces 42 are θ0 < θ N and θ N <θ N+1 The following relationship must be satisfied. For example, in the illustrated example, there are two inclined surfaces 42, and the inclination angle θ1 of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side and the inclination angle θ2 of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side are greater than the wall angle θ0 of the raised section 40 on the main groove 10 (shoulder main groove 12) side. Also, comparing the inclination angles θ1 and θ2, the inclination angle θ2 of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side is greater than the inclination angle θ1 of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side. Due to this relationship between the wall angle and the inclination angle, the raised section 40 gradually widens outward in the tire width direction, ensuring soil and snow removal capabilities, and enabling good off-road performance. Furthermore, since gentle ridges are formed at each step of the stepped raised section 40, the impression of the tread pattern design is not impaired even when the raised section 40 is formed, and good pattern visibility can be ensured. 【0030】 The wall angle θ0 is preferably 0° to 10°, more preferably 1° to 5°. Also, the inclination angle θ N Preferably, the angle is 5° to 80°, more preferably 10° to 80°, and even more preferably 15° to 75°. Thus, the wall angle θ0 and the inclination angle θ N By setting the angle θ, the raised section 40 becomes a shape that gradually widens outward in the tire width direction, which is advantageous for improving off-road performance and pattern visibility. N If the angle is less than 5°, the upper surface 41 and the inclined surface 42 of the raised base 40 cannot form a gentle unevenness, making the ridges more prominent, thus limiting the effect of improving pattern visibility.N If the angle exceeds 80°, it becomes difficult to create a sufficient step between adjacent upper surfaces 41, making it difficult to form a stepped bottom section 40. 【0031】 As shown in the illustrated example, when the raised section 40 has two inclined surfaces 42, the wall angle θ0 is preferably 1° to 5°, the inclination angle θ1 of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side is preferably 5° to 55°, and the inclination angle θ2 of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side is preferably 56° to 75°. Furthermore, the difference in inclination angles between adjacent inclined surfaces 42 in the tire width direction (for example, θ2 - θ1), or the difference between the wall angle θ0 and the inclination angle θ1 of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side (θ1 - θ0), is preferably 5° to 60°, more preferably 10° to 50°. 【0032】 In the stepped raised section 40 described above, as previously stated, the upper surface 41 and the inclined surface 42 are smoothly connected by a chamfered section 43 with a circular arc cross-section. On the other hand, the wall surface of the raised section 40 on the main groove 10 (shoulder main groove 12) side and the first upper surface 41 from the main groove 10 (shoulder main groove 12) side are connected by a connecting section 44 with a radius of curvature R0 of 0 mm or more. In other words, the wall surface of the raised section 40 on the main groove 10 (shoulder main groove 12) side and the first upper surface 41 from the main groove 10 (shoulder main groove 12) side are connected in such a way that they form a corner (radius of curvature R0 = 0 mm), or they are connected by a connecting section 44 with a circular arc cross-section and a radius of curvature R0 greater than 0 mm. At this time, the radius of curvature of the chamfered section 43 on the upper end side of the Nth inclined surface 42 from the main groove 10 (shoulder main groove 12) side is R N Therefore, these radii of curvature are R0 < R N The following relationship must be satisfied. For example, in the illustrated example, there are two upper surfaces 41 and two inclined surfaces 42, and the radius of curvature R1 at the chamfered portion 43 on the upper end side of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side and the radius of curvature R2 at the chamfered portion 43 on the upper end side of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side are both larger than the radius of curvature R0 of the connecting portion 44. NBy setting the relative sizes of the elements, gentle ridges are formed at each step of the stepped raised section 40. As a result, even when the raised section 40 is formed, the impression of the tread pattern's original design is not impaired, and good pattern visibility can be ensured. 【0033】 Focusing on the relationship between the chamfered portions 43 at the upper end of the Nth inclined surface 42 from the main groove 10 (shoulder main groove 12) side, the radius of curvature is R N <R N+1 It is preferable that the following relationship is satisfied. For example, in the illustrated example, it is preferable that the radius of curvature R1 of the chamfered portion 43 at the upper end of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side and the radius of curvature R2 of the chamfered portion 43 at the upper end of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side satisfy the relationship R1 < R2. In this way, as the radius of curvature of the chamfered portion 43 increases toward the outside in the tire width direction, a gentler ridge is formed toward the outside in the tire width direction, which is advantageous for improving pattern visibility. 【0034】 The radius of curvature R0 is preferably 0 mm to 1.0 mm, more preferably 0 mm to 0.5 mm. N The radius of curvature R0 is preferably 0.6 mm to 5.0 mm, more preferably 0.6 mm to 3.0 mm. This improves the shape of the connecting portion 44 and the chamfered portion 43, which is advantageous for improving pattern visibility by making the ridge line caused by the raised portion 40 gentler. If the radius of curvature R0 exceeds 1.0 mm, the ridge line of the lug groove opening becomes unclear, and the visibility of the main groove decreases. Furthermore, from the viewpoint of improving the visibility of the main groove, it is preferable that the radius of curvature R0 is close to 0 mm (no chamfer). Radius of curvature R N If the radius of curvature R is less than 0.6 mm, the chamfered portion 43 is small, and the effect of smoothing the edge is limited. N If the diameter exceeds 5.0 mm, the chamfered portion becomes too large, making it difficult to form a stepped, raised base. 【0035】As shown in the illustrated example, when the raised portion 40 has two upper surfaces 41, the radius of curvature R0 is preferably 0 mm or more and 0.5 mm or less, the radius of curvature R1 is preferably 0.6 mm or more and 1.5 mm or less, and the radius of curvature R2 is preferably 1.6 mm or more and 3.0 mm or less. In addition, the difference in the radii of curvature between adjacent chamfered portions 43 in the tire width direction (for example, R2 - R1), or the difference between the radius of curvature R0 of the connecting portion 44 and the radius of curvature R1 of the chamfered portion 43 on the upper end side of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side (R1 - R0), is preferably 0.5 mm to 5 mm, more preferably 1 mm to 2 mm. 【0036】 Alternatively, if the raised base portion 40 has two upper surfaces 41, the radius of curvature R0 is preferably 0 mm or more and 0.5 mm or less, the radius of curvature R1 is 1.6 mm or more and 3.0 mm or less, and the radius of curvature R2 is 0.6 mm or more and 1.5 mm or less. In this case, the radii of curvature have the relationship R0 < R2 < R1, but even in this case, R1 and R2 have appropriate radii of curvature, so the edges can be made sufficiently smooth and good pattern visibility can be obtained. 【0037】 In the raised section 40 shown in the illustration, the wall surface of the raised section 40 on the main groove 10 (shoulder main groove 12) side and the groove bottom of the main groove 10 (shoulder main groove 12) are smoothly connected by a chamfered section with a radius of curvature of r0. At this time, the radius of curvature of the chamfered section (an arc-shaped chamfer that is convex inward in the tire radial direction) on the lower end side of the Nth inclined surface 42 from the main groove 10 (shoulder main groove 12) side is r N Therefore, the radius of curvature of these chamfered parts is r N <r N+1 It is desirable that the following relationship be satisfied. For example, in the illustrated example, there are two upper surfaces 41 and two inclined surfaces 42, and the radius of curvature r1 at the chamfered portion at the lower end of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side and the radius of curvature r2 at the chamfered portion at the lower end of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side satisfy the relationship r1 < r2. In this way the radius of curvature r of the chamfered portion NBy setting the relative sizes of the elements, gentle ridges are formed on each step (the lower end side of the inclined surface 42) of the stepped raised section 40. Therefore, even when the raised section 40 is formed, the impression of the tread pattern design is not impaired, and good pattern visibility can be ensured. The radius of curvature r0 is essentially the bottom of the main groove 10 (shoulder main groove 12) and is not directly related to the stepped portion (and its ridges) of the raised section 40, so the radius of curvature r N The relationship between the radius of curvature r0 and r is not particularly limited. In the illustrated example, these radii of curvature r0 and r N For example, r N <r0 ≤ r N+1 The relationship is (r1 < r0 ≤ r2). 【0038】 The raised portion 40 is preferably provided at the end of the shoulder lug groove 22 on the shoulder main groove 12 side. In particular, it is preferable that the wall surface of the raised portion 40 on the main groove 10 (shoulder main groove 12) side and the groove wall of the shoulder main groove 12 are flush. In this case, the wall surface of the raised portion 40 on the main groove 10 (shoulder main groove 12) side and the groove wall of the shoulder main groove 12 will have a common wall surface angle θ0. By positioning the raised portion 40 unevenly on the main groove 10 (shoulder main groove 12) side in this way, the propagation of noise through the shoulder lug groove 22 can be effectively suppressed. 【0039】 The ratio of the area of ​​the raised portion 40 (the projected area of ​​the upper surface 41, the inclined surface 42, and the chamfered portion 43 as viewed from the tread surface side) to the opening area within the contact area (inside the contact edge E) of each shoulder lug groove 22 provided with the raised portion 40 is preferably 20% to 60%, more preferably 30% to 50%. This ensures that the raised portion 40 occupies an appropriate proportion in each shoulder lug groove 22, which is advantageous for achieving both off-road performance and low noise performance. If the ratio of the area of ​​the raised portion 40 to the opening area of ​​the shoulder lug groove 22 is less than 20%, the raised portion 40 becomes small, making it difficult to form a stepped raised portion 40 including multiple upper surfaces 41. If the ratio of the area of ​​the raised portion 40 to the opening area of ​​the shoulder lug groove 22 exceeds 60%, it becomes difficult to secure sufficient groove volume, limiting the effect of improving off-road performance. 【0040】 In the present invention, a raised section can be provided in addition to the shoulder region (shoulder lug groove 22) described above. That is, in the center region excluding the shoulder region, if there are multiple center lug grooves 21 that extend in the tire width direction and connect adjacent main grooves 10 (center main grooves 11 to each other, or the center main groove 11 and the shoulder main groove 12), a specification can be made in which a center raised section 50 is provided at the bottom of the center lug groove 21. In this specification, as illustrated in Figure 4, it is preferable that the depth d1 at the upper surface 51 of the center raised section 50 is smaller than the depth d2 in the center lug groove 21, and the depth d2 in the center lug groove 21 is smaller than the groove depth of the main groove 10. In other words, it is preferable that the bottom of the main groove 10, the bottom of the center lug groove 21, and the upper surface 51 of the center raised section 50 form a stepped cross-sectional shape in which the depth decreases toward the center in the extension direction of the center lug groove 21. By providing the center base-raising section 50 in the center lug groove 21 in this way, the propagation of noise through the center lug groove 21 can be suppressed, which is advantageous for improving low-noise performance. On the other hand, the center base-raising section 50 creates the aforementioned stepped cross-sectional shape, and the groove depth gradually increases from the center of the center base-raising section 50 outward in the tire width direction, so soil and snow removal capabilities can be ensured, and off-road performance can be demonstrated well. 【0041】 The side surface 52 of the center base riser 50, which connects the upper surface 51 of the center base riser 50 to the groove bottom of the center lug groove 21, is preferably inclined with respect to the normal of the tread surface as shown in the figure, and its inclination angle α is preferably greater than the groove wall angle β of the main groove 10 at the position where it connects to the center lug groove 21. Furthermore, the upper surface 51 and the side surface 52 of the center base riser 50 are preferably connected by a chamfered portion 53 with a circular arc cross-section, and the radius of curvature R of this chamfered portion 53 is A However, the radius of curvature R at the connection portion 54 between the groove bottom of the center lug groove 21 and the groove wall of the main groove 10 BIt is preferable that it be larger than this. Furthermore, it is preferable that the side surface 52 of the center base rise portion 50 and the groove bottom of the center lug groove 21 are connected by a chamfered portion with a circular arc cross-section (a circular arc chamfer that is convex inward in the tire radial direction), and the radius of curvature r of this chamfered portion A This is the radius of curvature r between the groove wall and the groove bottom of the main groove 10 at the opening position of the center lug groove 21. B More than (r A ≥r B It is preferable that the above relationship is satisfied by the inclination angle of the side surface 52 of the center raised portion 50 and the radius of curvature of the chamfered portion 53, so that a gentle ridge line is formed in the center raised portion 50, and good pattern visibility can be maintained. Figure 4 is a cross-sectional view taken along the Y-Y arrow in Figure 2, and is a cross-section cut by a line (dashed line in the figure) that passes through the center of the groove width of the center lug groove 21 and is along the extension direction of the center lug groove 21. 【0042】 The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. 【0043】 The tire size is LT265 / 70R17 115T, and it has the internal structure (cross-sectional structure) illustrated in Figure 1, and the tread pattern illustrated in Figure 2, and the raised portion formed in the shoulder lug groove is as follows: presence or absence of the raised portion, the raised depth D1 of the first upper surface from the shoulder main groove side, the raised depth D2 of the second upper surface from the shoulder main groove side, and the groove depth D of the shoulder lug groove. SH、 の 【0044】 Regarding the shape of the center base, the number of which of shapes A to C shown in Table 3 was used is indicated in the respective columns of Tables 1 and 2. In Table 3, the shape of the center base is described as follows: d1 [%], which is the ratio of the base depth at the top surface of the center base to the groove depth of the center main groove; d2 [%], which is the ratio of the groove depth of the center lug groove to the groove depth of the center main groove; α, which is the inclination angle of the side surface of the center base connecting the top surface of the center base and the groove bottom of the center lug groove; β, which is the groove wall angle of the main groove at the position where it connects to the center lug groove; and R, which is the radius of curvature of the chamfered portion between the top surface and the side surface of the center base. A , the radius of curvature R at the connection between the groove bottom of the center lug groove and the groove wall of the main groove B This is shown. 【0045】 In all examples, the groove depth of the shoulder main groove and the center main groove was set to 10 mm. The groove depth of the raised bottom depth D1, D2, and the groove depth of the shoulder lug groove D SH All values ​​represent the percentage [%] of the shoulder main groove relative to the groove depth. The wall angle θ0, inclination angles θ1 to θ2, inclination angle α, and groove wall angle β all represent angles relative to the normal of the tread surface. In Tables 1 to 3, the radius of curvature of the chamfered portion (R1, R2, R) AAn example where ) is "0" means that no chamfered portion is provided. 【0046】 These pneumatic tires were evaluated for external passing noise, pattern visibility, and off-road performance using the evaluation method described below, and the results are shown in Tables 1 and 2. 【0047】 The test tire for external passing noise was mounted on a wheel with a rim size of 17 x 8J, inflated to an air pressure of 340 kPa, and mounted on a test vehicle (a four-wheel drive SUV). External passing noise was measured according to the tire noise test method specified in ECE R117-02. Specifically, the test vehicle was driven for 10 minutes before passing through the noise measurement section, the engine was stopped before reaching the section, and the vehicle was coasted. The maximum noise level (dB) in the noise measurement section (noise level in the frequency range of 800 Hz to 1200 Hz) was measured at multiple speeds, divided into eight or more equal intervals within a speed range of ±10 km / h from the reference speed (50 km / h), and the average value was taken as the external passing noise. The maximum noise level was the sound pressure measured using a stationary microphone placed 7.5 m laterally from the centerline of the vehicle and 1.2 m above the road surface at the midpoint of the noise measurement section, through an A-weighted frequency correction circuit. The evaluation results are shown in measured values ​​[unit: dB]. 【0048】 Pattern Visibility: Twenty testers visually inspected the tread pattern of each test tire and evaluated, on a scale of 1 to 5 points, whether the impression of the pattern design was maintained in comparison to Reference Example 1 (a tire with a tread pattern molded according to the original design without any raised sections). The evaluation results were expressed as an index, with Reference Example 1 set to 100, calculated by summing the scores of all testers. A higher index value indicates better pattern visibility. 【0049】For the off-road performance test, each test tire was mounted on a 17x8J rim wheel, inflated to 340 kPa, and mounted on a test vehicle (a four-wheel drive SUV). A test driver then performed a subjective evaluation of traction (starting performance) on a test track consisting of snow, representing an example of off-road conditions. The evaluation results are shown as an index, with the value of Reference Example 1 set to 100. A higher index value indicates superior off-road performance (especially snow traction performance). 【0050】 【0051】 【0052】 【0053】 As is clear from Tables 1-2, the tires of Examples 1-15 maintained good pattern visibility and off-road performance while reducing external passing noise compared to Reference Example 1. On the other hand, Comparative Example 1 had reduced pattern visibility and off-road performance because the raised portion did not have multiple upper surfaces (the raised height was constant and not stepped). Comparative Example 2 had reduced pattern visibility and off-road performance because the raised portion did not have a chamfered portion and the inclination angles θ1 and θ2 were equal to the wall angle θ0. Comparative Example 3 had a raised portion that did not have a chamfered portion and the inclination angle was θ N <θ N+1 Because the relationship (θ1 < θ2) is not satisfied, pattern visibility and off-road performance are reduced. 【0054】 1 Tread section 2 Sidewall section 3 Bead section 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 10 Main groove 11 Center main groove 12 Shoulder main groove 20 Lug groove 21 Center lug groove 22 Shoulder lug groove 30 Block 31 Center block 32 Shoulder block 40 Raised bottom section 41 Top surface 42 Inclined surface 43 Chamfered section 44 Connection section 50 Center raised bottom section CL Tire equator E Contact edge

Claims

1. In a tire having a tread portion that extends in the circumferential direction of the tire and forms an annular shape, the surface of the tread portion has a plurality of main grooves that extend along the circumferential direction of the tire. A pair of shoulder main grooves located on the outermost side in the tire width direction among the plurality of main grooves have a plurality of shoulder lug grooves that extend outward in the tire width direction from the main grooves and are arranged at intervals in the circumferential direction of the tire in the shoulder region located outside the tire width direction of the shoulder main grooves. The shoulder main grooves and the shoulder lug grooves define a plurality of shoulder blocks arranged in the circumferential direction of the tire. A raised portion is provided at the bottom of the shoulder lug grooves. The raised portion has a stepped shape composed of a plurality of upper surfaces with different raised heights from the groove bottom and inclined surfaces arranged between adjacent upper surfaces in the tire width direction or between the upper surface and the groove bottom of the shoulder lug groove. The upper surface and the inclined surface are smoothly connected by a chamfer portion having a circular arc-shaped cross section. When the raised depth from the tread surface of the Nth upper surface from the main groove side is D N , the raised depths of the plurality of upper surfaces are D N < D N+1 and satisfy the relationship. Let the wall surface angle of the raised portion on the main groove side be θ0, and the inclination angle of the Nth inclined surface from the main groove side be θ N . When, the wall surface angle θ0 and the inclination angles of the plurality of inclined surfaces satisfy θ0 < θ N and θ N < θ N+1 . The first upper surface from the main groove side and the wall surface of the raised portion on the main groove side are connected by a connecting portion having a curvature radius R0 of 0 mm or more. When the curvature radius of the chamfer portion on the upper end side of the Nth inclined surface from the main groove side is R N , the curvature radii of these chamfer portions satisfy R0 < R N . A tire characterized by satisfying the relationship.

2. The radius of curvature at the chamfered portion is R N <R N+1 The tire according to claim 1, characterized in that it satisfies the relationship.

3. The aforementioned base elevation depth D N The tire according to claim 1 or 2, characterized in that the depth of the main groove is 10% to 90%.

4. The radius of curvature R0 is 0 mm to 1.0 mm, and the radius of curvature R N A tire according to any one of claims 1 to 3, characterized in that the diameter is 0.6 mm to 5 mm.

5. The wall angle θ0 is 0° to 10°, and the inclination angle θ N A tire according to any one of claims 1 to 4, characterized in that the angle is between 5° and 80°.

6. The tire according to any one of claims 1 to 5, characterized in that the ratio of the area of ​​the raised portion to the area of ​​each shoulder lug groove provided with the raised portion is 20% to 60%.

7. The tire according to any one of claims 1 to 6, wherein the center region excluding the shoulder region is provided with a plurality of center lug grooves extending in the tire width direction and connecting adjacent main grooves, and a plurality of center blocks partitioned by the main grooves and the center lug grooves, a center raised portion is provided at the bottom of the center lug grooves, the bottom of the main grooves, the bottom of the center lug grooves, and the upper surface of the center raised portion form a stepped cross-sectional shape in which the depth decreases toward the center in the extension direction of the center lug grooves, the inclination angle of the side surface of the center raised portion is greater than the groove wall angle of the main groove at the position where it connects to the center lug groove, and the radius of curvature of the chamfered portion between the upper surface and the side surface of the center raised portion is greater than the radius of curvature of the connection portion between the bottom of the center lug groove and the groove wall of the main groove.

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