tire

Abstract

To provide a tire that ensures excellent off-road performance, maintains good pattern visibility, and enables improvement in low-noise performance. 【Solution means】 In a tire having a shoulder lug groove 22 in the shoulder region of the tread portion 1, a bottom raising portion 40 composed of a plurality of upper surfaces 41, inclined surfaces 42, and chamfered portions 43 is provided at the groove bottom of the shoulder lug groove 22, and the bottom raising depth D from the tread surface of the Nth upper surface 41 from the main groove 10 side N is D N < D N+1 satisfies the relationship, and the wall surface angle θ0 of the bottom raising portion 40 on the main groove 10 side and the inclination angle θ of the Nth inclined surface 41 from the main groove 10 side N are such that θ0 < θ N and θ N < θ N+1 satisfies the relationship, and the radius of curvature R0 of the connection portion 44 between the first upper surface 41 from the main groove 10 side and the wall surface of the bottom raising portion 40 on the main groove 10 side and the radius of curvature R of the chamfered portion 43 at the upper end side of the Nth inclined surface 42 from the main groove 10 side N are such that R0 < R N satisfies the relationship.

Description

Technical Field

[0001] The present invention relates to a tire intended to run on an unpaved road or the like, and more particularly to a tire that enables improvement of low-noise performance while ensuring excellent off-road performance.

Background Art

[0002] In addition to paved roads, tires (for example, all-terrain tires, all-terrain type tires, etc.) assumed to run on unpaved roads (rough roads, muddy areas, sandy areas, rocky fields, etc.) are required to have excellent running performance on various road surfaces, and in particular, to have excellent snow performance (running performance on snow-covered roads). Such tires mainly have lug grooves and blocks with many edge components, and tend to adopt a tread pattern with a large groove area (see, for example, Patent Document 1). On the other hand, a tread pattern with many groove components tends to easily radiate noise (pattern noise) caused by the tread pattern outside the vehicle through the grooves, and it is required to reduce the passing noise outside the vehicle. For example, by providing a raised bottom portion in the groove extending in the tire width direction, the divergence of noise through the groove can be suppressed, but there is a concern that the visibility of the tread pattern may be reduced or the off-road performance may be affected due to the formation of the raised bottom portion. Therefore, even if a raised bottom portion is provided for noise reduction, it is required to maintain good pattern visibility and off-road performance and to highly achieve both of these performances.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

Means for Solving the Problems

[0005] The tire of the present invention for achieving the above object is a tire provided with 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 pair of shoulder main grooves positioned on the outermost side in the tire width direction among the plurality of main grooves, there are provided 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 tire circumferential direction, and a plurality of shoulder blocks that are partitioned by the main grooves and the shoulder lug grooves and are arranged in the tire circumferential direction. A bottom raising portion is provided at the groove bottom of the shoulder lug groove. The bottom raising portion has a stepped shape composed of 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 the bottom raising depths of the plurality of upper surfaces satisfy D N <D N+1 When the wall surface angle of the bottom raising portion on the main groove side is θ0 and the inclination angle of the Nth inclined surface from the main groove side is θ N 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 bottom raising portion on the main groove side are connected by a connecting portion with 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 This is characterized by satisfying the relationship.

Advantages of the Invention

[0006] In the tire of the present invention, a raised section is provided in the shoulder lug groove, which contributes significantly to the emission of noise to the outside of the vehicle. Therefore, the emission of noise through the shoulder lug groove is suppressed, and the noise of vehicles passing outside the vehicle can be effectively reduced. On the other hand, because the raised section has the aforementioned stepped shape, the groove volume can be secured, and good off-road performance can be maintained. In particular, due to the relationship of the raised depth described above, the raised section widens in stages toward the outside in the tire width direction, so that soil and snow removal capabilities can be secured, and good off-road performance can be demonstrated. Furthermore, the aforementioned wall angle θ0 and inclination angle θ N The relationship between R0 and R0, and the radii of curvature. N Due to this relationship, gentle ridges are formed at each step of the stepped raised section, so even when the raised section is formed, the impression of the tread pattern's original pattern design is not impaired, and good pattern visibility can be ensured. Through the collaboration of these factors, a high level of balance between off-road performance, pattern visibility, and low noise performance can be achieved.

[0007] In this invention, the radius of curvature at the chamfered portion is R N <R N+1 It is preferable to satisfy this relationship. In this way, as the radius of curvature of the chamfered portion 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.

[0008] In this invention, the bottom height D N Preferably, the depth of the raised section is 10% to 90% of the depth of the main groove. This ensures that all upper surfaces of the raised section have an appropriate raised depth, which is advantageous for improving off-road performance and noise reduction.

[0009] In this invention, the radius of curvature R0 is 0 mm to 1 mm, and the radius of curvature R N It is preferable that the thickness is between 0.6 mm and 5 mm. This results in a good shape for the connection and chamfered parts, which is advantageous for smoothing out the ridges caused by the raised base and improving pattern visibility.

[0010] In this invention, the wall angle θ0 is 0° to 10°, and the inclination angle θ N It is preferable that the angle is between 5° and 80°. This results in a shape where the raised section gradually widens outward in the tire width direction, which is advantageous for improving off-road performance and pattern visibility.

[0011] In this invention, it is preferable that the ratio of the area of ​​the raised portion to the area of ​​each shoulder lug groove is 20% to 60%. Having the raised portion occupy an appropriate proportion in each shoulder lug groove is advantageous for improving off-road performance and noise reduction performance.

[0012] In this invention, the center region excluding the shoulder region is provided with a plurality of center lug grooves that extend in the tire width direction and connect adjacent main grooves, and a plurality of center blocks partitioned by the main grooves and center lug grooves. The specification allows for a center raised section to be provided at the bottom of the center lug grooves. In this specification, the bottom of the main grooves, the bottom of the center lug grooves, and the upper surface of the center raised section form a stepped cross-sectional shape in which the depth decreases toward the center in the extension direction of the center lug grooves. Preferably, the inclination angle of the side surface of the center raised section 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 side surface of the center raised section is greater than the radius of curvature at the connection portion between the groove bottom of the center lug groove and the groove wall of the main groove. By providing a center raised section in the center lug grooves in this way, the propagation of noise through the center lug grooves can be suppressed, which is advantageous for improving low-noise performance. On the other hand, the raised center section creates the aforementioned stepped cross-sectional shape, and the groove depth gradually increases from the center of the raised section outward in the tire width direction, ensuring soil and snow removal capabilities and enabling good off-road performance. Furthermore, because the inclination angle and radius of curvature satisfy the above-mentioned relationship, a gentle ridge is formed in the raised section, thus maintaining good pattern visibility.

[0013] In this invention, "contact edge" refers to both ends in the axial direction of the tire 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, including the standard on which the tire is based. For example, it is the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. "Standard internal pressure" refers to the air pressure specified for each tire in the 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". For ETRTO, it is the "INFLATION PRESSURE". However, if the tire is for a passenger car, 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 example, it is the maximum load capacity for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[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. [Brief explanation of the drawing]

[0015] [Figure 1] This is a meridian cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] This is a front view showing the tread surface of a tire according to an embodiment of the present invention. [Figure 3] This is a cross-sectional view taken along the arrow XX in Figure 2. [Figure 4] This is a cross-sectional view taken along the YY arrow in Figure 2. [Modes for carrying out the invention]

[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 toroidal basic 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 (2 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 (2 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] Since the present 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 diagram) 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 positioned 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 XX arrow 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 bottom of the multiple upper surfaces 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 When compared to this, groove depth D SHThe bottom depth is greater than D1 and D2 (D1 <D2<D SH Due to this relationship between the magnitudes of the raised base depths, the raised base section 40 gradually widens outward in the tire width direction, ensuring soil and snow removal capabilities, and enabling excellent off-road performance.

[0027] Raised depth D N and groove depth D SH The bottom height 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. Bottom height D 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 noise reduction effect 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 (e.g., D2-D1), or the difference between the raised depth of the upper surface 41 and the groove depth (e.g., 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. NIf 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 challenging to form a stepped base 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 (e.g., 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 NThe relationship must always be satisfied. For example, in the illustrated example, it has two upper surfaces 41 and two inclined surfaces 42. Let the radius of curvature at the chamfer portion 43 on the upper end side of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side be R1, and the radius of curvature at the chamfer portion 43 on the upper end side of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side be R2. Both are larger than the radius of curvature R0 of the connecting portion 44. By setting the size relationship of the radii of curvature R0 and R N In this way, by setting the size relationship, a gentle ridge line is formed at each step of the stepped bottom raising portion 40. Therefore, even when the bottom raising portion 40 is formed, the impression of the pattern design originally possessed by the tread pattern is not impaired, and good pattern visibility can be ensured.

[0033] Focusing on the relationship between the chamfer portions 43 on the upper end sides 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 to satisfy the relationship. For example, in the illustrated example, the radius of curvature R1 at the chamfer 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 chamfer portion 43 on the upper end side of the second inclined surface 42 from the main groove 10 (shoulder main groove 12) side preferably satisfy the relationship of R1 < R2. In this way, as the radius of curvature of the chamfer portion 43 increases toward the outer side in the tire width direction, a gentler ridge line is formed toward the outer side 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. Also, the radius of curvature R N is preferably 0.6 mm to 5 mm, more preferably 0.6 mm to 3.0 mm. Thereby, since the shapes of the connecting portion 44 and the chamfer portion 43 are improved, it is advantageous for softening the ridge line caused by the bottom raising portion 40 and improving pattern visibility. When 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. Incidentally, 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). The radius of curvature R NIf it is less than 0.6 mm, since the chamfer part 43 is small, the effect of smoothing the ridge line is limited. The radius of curvature R N If it exceeds 5 mm, the chamfer part becomes too large and it becomes difficult to form the stepped bottom raising part.

[0035] As in the illustrated example, when the bottom raising part 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 0.6 mm or more and 1.5 mm or less, and the radius of curvature R2 is 1.6 mm or more and 3.0 mm or less. Also, the difference in the radius of curvature between adjacent chamfer parts 43 in the tire width direction (for example, R2 - R1), or the difference (R1 - R0) between the radius of curvature R0 of the connecting part 44 and the radius of curvature R1 of the chamfer part at the upper end side of the first inclined surface 42 from the main groove 10 (shoulder main groove 12) side, is preferably 0.5 mm to 5 mm, more preferably 1 mm to 2 mm.

[0036] Alternatively, when the bottom raising part 40 has two upper surfaces 41, the radius of curvature R0 may be preferably 0 mm or more and 0.5 mm or less, the radius of curvature R1 may be 1.6 mm or more and 3.0 mm or less, and the radius of curvature R2 may be 0.6 mm or more and 1.5 mm or less. In this case, the radius of curvature has the magnitude relationship of R0 < R2 < R1, but in this case as well, since R1 and R2 have appropriate radii of curvature, the ridge line can be sufficiently smoothed and good pattern visibility can be obtained.

[0037] In the bottom raising part 40 of the illustrated example, the wall surface on the main groove 10 (shoulder main groove 12) side of the bottom raising part 40 and the groove bottom of the main groove 10 (shoulder main groove 12) are also smoothly connected by a chamfer part having a radius of curvature of r0. At this time, the radius of curvature at the chamfer part (arc-shaped chamfer convex toward the inner side in the tire diameter direction) at the lower end side of the Nth inclined surface 42 from the main groove 10 (shoulder main groove 12) side is r N If we set it as such, the radius of curvature of these chamfer parts is r N < r N+1It is preferable to satisfy the relationship. For example, in the illustrated example, it includes two upper surfaces 41 and two inclined surfaces 42, and the radius of curvature at the chamfer portion on the lower end side of the first inclined surface 42 from the side of the main groove 10 (shoulder main groove 12) is r1, and the radius of curvature at the chamfer portion on the lower end side of the second inclined surface 42 from the side of the main groove 10 (shoulder main groove 12) is r2, and they satisfy the relationship of r1 < r2. By setting the magnitude relationship of the radius of curvature r N of the chamfer portion in this way, a gentle ridge line is formed at each step of the stepped bottom raising portion 40 (the lower end side of the inclined surface 42). Therefore, even when the bottom raising portion 40 is formed, the impression of the pattern design originally possessed by the tread pattern is not impaired, and good pattern visibility can be ensured. The radius of curvature r0 is substantially the groove bottom of the main groove 10 (shoulder main groove 12) and is not directly involved with the stepped portion (and its ridge line) of the bottom raising portion 40. Therefore, the magnitude relationship between the radius of curvature r0 and the radius of curvature r N is not particularly limited. In the illustrated example, these radius of curvature r0 and radius of curvature r N are, for example, r N < r0 ≤ r N+1 (r1 < r0 ≤ r2).

[0038] The bottom raising portion 40 is preferably provided at the end on the shoulder main groove 12 side of the shoulder lug groove 22. In particular, it is preferable that the wall surface on the main groove 10 (shoulder main groove 12) side of the bottom raising portion 40 and the groove wall of the shoulder main groove 12 are flush. In this case, the wall surface on the main groove 10 (shoulder main groove 12) side of the bottom raising portion 40 and the groove wall of the shoulder main groove 12 will have a common wall surface angle θ0. By thus making the bottom raising portion 40 unevenly distributed on the main groove 10 (shoulder main groove 12) side, 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 of the center lug groove 21, and the depth d2 of 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 noise reduction 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 that 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 B It 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 YY 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. [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, raised depth D1 of the first upper surface from the shoulder main groove side, raised depth D2 of the second upper surface from the shoulder main groove side, and groove depth D of the shoulder lug groove. SH 、 の

[0044] Regarding the shape of the center base, the number of each shape (A to C) shown in Table 3 is indicated in each column. In Table 3, the following values ​​are provided for the shape of the center base: d1 [%], the ratio of the base depth at the top surface of the center base to the groove depth of the center main groove; d2 [%], the ratio of the groove depth of the center lug groove to the groove depth of the center main groove; α, 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, the groove wall angle of the main groove at the position where it connects to the center lug groove; and R, the radius of curvature of the chamfered portion between the top surface and the side surface of the center base. A , 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 bottom height D1, D2 and the groove depth D of the shoulder lug groove. SH All values ​​represent the percentage [%] of the shoulder main groove relative to the groove depth. The wall angle θ0, inclination angles θ1~θ2, inclination angle α, and groove wall angle β all represent angles relative to the normal of the tread surface. In Tables 1-3, the radius of curvature of the chamfered portion (R1, R2, R A An 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] Passing sound outside the vehicle The test tire was mounted on a 17x8J rim wheel, inflated to 340kPa, and mounted on a test vehicle (four-wheel drive SUV). The 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 prior to passing through the noise measurement section, the engine was stopped before reaching the section, and the vehicle was coasted. The maximum noise level (dB) (noise level in the frequency range of 800Hz to 1200Hz) in the noise measurement section was measured at multiple speeds, divided into eight or more equally spaced intervals within a speed range of ±10km / h from the reference speed (50km / 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 7.5m laterally from the centerline of the vehicle and 1.2m 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] Off-road performance Each test tire was mounted on a 17x8J rim wheel, inflated to 340kPa, and fitted to a test vehicle (a four-wheel drive SUV). A test driver then performed a subjective evaluation of traction (starting performance) on a snow-covered test track, representing an off-road scenario. 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).

[0050] [Table 1]

[0051] [Table 2]

[0052] [Table 3]

[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 section 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 section did not have a chamfered section and the inclination angles θ1 and θ2 were equal to the wall angle θ0. Comparative Example 3 had a raised section that did not have a chamfered section 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] This disclosure encompasses the following inventions: Invention [1] 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 extending along the circumferential direction of the tire, The shoulder region located on the outer side in the tire width direction of a pair of shoulder main grooves, which are the outermost of the plurality of main grooves in the tire width direction, has a plurality of shoulder lug grooves that extend outward from the main grooves in the tire width direction and are spaced apart in the tire circumferential direction, and a plurality of shoulder blocks that are partitioned by the main grooves and the shoulder lug grooves and arranged in the tire circumferential direction, and a raised portion is provided at the bottom of the shoulder lug grooves. The raised portion has a stepped shape consisting of multiple upper surfaces with different elevations from the groove bottom, and inclined surfaces positioned between adjacent upper surfaces in the tire width direction or between the upper surfaces and the groove bottom of the shoulder lug groove, and the upper surfaces and the inclined surfaces are smoothly connected by a chamfered portion with a circular arc cross-section. The depth of the rise from the tread surface of the upper surface of the Nth groove from the main groove side is D. N In that case, the depth of the raised bottom of the multiple upper surfaces is D N <D N+1 Satisfying the relationship, Let θ0 be the angle of the wall surface on the main groove side of the raised section, and let θ be the angle of inclination of the Nth inclined surface from the main groove side. NIn this case, the angle of the wall surface θ0 and the angle of inclination of the plurality of inclined surfaces are θ0 < θ N and θ N <θ N+1 Satisfying the relationship, The first upper surface from the main groove side and the wall surface of the raised section on the main groove side are connected by a connecting section with a radius of curvature R0 of 0 mm or more, and the radius of curvature of the chamfered section at the upper end of the Nth inclined surface from the main groove side is R N In this case, the radius of curvature of these chamfered parts is R0 <R N A tire characterized by satisfying the following relationship. Invention [2] The radius of curvature of the chamfered portion is R N <R N+1 The tire according to the invention [1], characterized in that it satisfies the following relationship. Invention [3] The raised depth D N The tire according to the invention [1] or [2], characterized in that the depth of the main groove is 10% to 90%. Invention [4] The radius of curvature R0 is 0 mm to 1.0 mm, the radius of curvature R N A tire according to any one of the inventions [1] to [3], characterized in that the diameter is 0.6 mm to 5 mm. Invention [5] The wall angle θ0 is 0° to 10°, and the inclination angle θ N A tire according to any one of the inventions [1] to [4], characterized in that the angle is between 5° and 80°. Invention [6] A tire according to any one of Inventions [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%. Invention [7] 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, and a center bottom raised portion is provided at the groove bottom of the center lug groove, The groove bottom of the main groove, the groove bottom of the center lug groove, 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 groove. The inclination angle of the side surface of the raised center section is greater than the groove wall angle of the main groove at the position where it connects to the center lug groove. A tire according to any one of the inventions [1] to [6], characterized in that the radius of curvature at the chamfered portion between the upper surface and the side surface of the raised center portion is greater than the radius of curvature at the connection portion between the groove bottom of the center lug groove and the groove wall of the main groove. [Explanation of Symbols]

[0055] 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 grooves 21 Center lug groove 22 Shoulder lug grooves 30 blocks 31 Center Block 32 Shoulder Blocks 40 Raised bottom section 41 Top surface 42 Slope 43 Chamfered section 44 Connection part 50 Center bottom raised section CL Tire Equator E Ground end

Claims

1. In a tire having a tread portion that extends in the circumferential direction and forms an annular shape, The surface of the tread portion has a plurality of main grooves extending along the circumferential direction of the tire, The shoulder region located on the outer side in the tire width direction of a pair of shoulder main grooves, which are the outermost of the plurality of main grooves in the tire width direction, has a plurality of shoulder lug grooves that extend outward from the main grooves in the tire width direction and are spaced apart in the tire circumferential direction, and a plurality of shoulder blocks that are partitioned by the main grooves and the shoulder lug grooves and arranged in the tire circumferential direction, and a raised portion is provided at the bottom of the shoulder lug grooves. The raised portion has a stepped shape consisting of multiple upper surfaces with different elevations from the groove bottom, and inclined surfaces positioned between adjacent upper surfaces in the tire width direction or between the upper surfaces and the groove bottom of the shoulder lug groove, and the upper surfaces and the inclined surfaces are smoothly connected by a chamfered portion with a circular arc cross-section. The depth of the rise from the Nth upper surface tread surface from the main groove side is D. N In that case, the depth of the raised bottom of the multiple upper surfaces is D N <D N+1 Satisfying the relationship, Let the wall surface angle on the main groove side of the bottom raising portion be θ 0 and when the inclination angle of the Nth inclined surface from the main groove side is θ N the wall surface angle θ 0 and the inclination angles of the plurality of inclined surfaces are such that θ 0 < θ N and θ N < θ N+1 satisfy the relationship The radius of curvature R is between the first upper surface from the main groove side and the wall surface on the main groove side of the raised section. 0 The connection is made by a connecting portion whose radius is 0 mm or more, and the radius of curvature at the chamfered portion on the upper end side of the Nth inclined surface from the main groove side is R N In this case, the radius of curvature of these chamfered parts is R 0 <R N A tire characterized by satisfying the following 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 R 0 The radius of curvature R is 0 mm to 1.0 mm. N The tire according to claim 1 or 2, characterized in that the diameter is 0.6 mm to 5 mm.

5. The aforementioned wall angle θ 0 The inclination angle is 0° to 10°, and the inclination angle θ N The tire according to claim 1 or 2, characterized in that the angle is between 5° and 80°.

6. The tire according to claim 1 or 2, 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. In the center region excluding the shoulder region, there are provided a plurality of center lug grooves that extend in the tire width direction and connect adjacent main grooves, and a plurality of center blocks partitioned by the main grooves and the center lug grooves, and a center bottom raised portion is provided at the groove bottom of the center lug groove. The groove bottom of the main groove, the groove bottom of the center lug groove, 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 groove. The inclination angle of the side surface of the raised center section is greater than the groove wall angle of the main groove at the position where it connects to the center lug groove. The tire according to claim 1 or 2, characterized in that the radius of curvature at the chamfered portion between the upper surface and the side surface of the raised center portion is greater than the radius of curvature at the connection portion between the groove bottom of the center lug groove and the groove wall of the main groove.

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