tire

Abstract

To provide a tire which can improve bad road running-through performance while securing excellent block durability.SOLUTION: There is provided a tire, wherein a plurality of shoulder blocks 12 are provided in a shoulder region of a tread part 1, a plurality of side blocks 13 are provided in a side region adjacent to outside in a tire width direction of the shoulder region, and the one side block 13 is arranged at a position outside in the tire width direction of a block group composed of two or more shoulder blocks 12 adjacent to each other in a tire circumferential direction, when a surface composed of a side face of the shoulder block 12 included in the block group and a top surface of the side block 13 is regarded as an upper layer surface, a first recess 15 including a middle layer surface recessed from the upper layer surface by 0.2 mm or more is provided on the center side of the upper layer surface, and a second recess 16 including a lower layer surface recessed from the middle layer surface by 0.2 mm or more is provided on the center side of the middle layer surface.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire intended for running on unpaved roads and the like, and more particularly to a tire which enables improved rough road running performance while ensuring excellent block durability. [Background technology]

[0002] Tires (e.g., all-terrain tires, all-terrain type tires, etc.) that are intended to run on unpaved roads (uneven ground, muddy ground, sandy ground, rocky ground, etc.) in addition to paved road surfaces are required to have excellent running performance on various road surfaces, and in particular, are required to have excellent off-road performance (bad road running performance). In such tires, not only the tread portion that contacts the road surface on paved roads, but also the side area (area located between the tread portion and the sidewall portion) that may contact mud, snow, sand, stones, rocks, etc. on the road surface on unpaved roads (hereinafter, these are collectively referred to as "mud, etc.") is provided with unevenness (side blocks, etc.), thereby biting into the mud, etc., and obtaining traction performance (see, for example, Patent Documents 1 and 2). In recent years, the performance required for tires has become more sophisticated, and further improvement in bad road running performance is required. In addition, since the side blocks tend to be easily damaged by stones, rocks, foreign objects, etc. on the road surface on unpaved roads (bad roads), it is also required to ensure durability. For this reason, there is a demand to improve off-road performance while ensuring durability (particularly block durability) and achieving a high level of both performance characteristics. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-124733 A [Patent Document 2] JP 2020-044882 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire which makes it possible to improve rough road running performance while ensuring excellent block durability. [Means for solving the problem]

[0005] In order to achieve the above object, a tire of the present invention includes a tread portion extending in a circumferential direction of the tire and forming an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, the tire having a surface of the tread portion, a pair of main grooves extending in the circumferential direction of the tire on both sides of the tire equator, a shoulder region located on the outer side in the tire width direction of the main grooves, a plurality of shoulder lug grooves extending from the main grooves toward the outer side in the tire width direction and spaced apart in the tire circumferential direction, and a plurality of shoulder blocks partitioned by the main grooves and the shoulder lug grooves and arranged in the circumferential direction of the tire, A plurality of side blocks are provided in a side region adjacent to the outer side of the shoulder region in the tire width direction, the side block being arranged at a position in the tire width direction outer side of a block group consisting of two or more shoulder blocks adjacent in the tire circumferential direction, and when a surface consisting of a side surface of the shoulder block included in the block group and a top surface of the side block is defined as an upper layer surface, a first recess is provided on the center side of the upper layer surface, the first recess is provided including a middle layer surface recessed by 0.2 mm or more from the upper layer surface, and a second recess is provided on the center side of the middle layer surface, the second recess is provided including a lower layer surface recessed by 0.2 mm or more from the middle layer surface. The first recess and the second recess are provided so as to straddle the side surface of the shoulder block and the top surface of the side block included in the block group. It is characterized by the fact that Effect of the Invention

[0006] In the tire of the present invention, when a plurality of side blocks are provided in the side region, one side block is disposed at the outer position in the tire width direction of a block group consisting of two or more shoulder blocks adjacent in the tire circumferential direction, so that the whole consisting of the block group and the side blocks functions as a substantially large block, thereby improving the block durability. Meanwhile, the first recess and the second recess are provided on the upper layer surface consisting of the side surface of the shoulder block included in the block group and the top surface of the side block, and the substantial block consisting of the block group and the side block is recessed stepwise toward the center toward the middle layer surface and the lower layer surface. This complex uneven shape allows mud, etc. to be efficiently bitten on unpaved roads, improving traction performance, and exhibiting excellent rough road running performance. At this time, the first recess and the second recess have a structure that is recessed stepwise toward the center of the substantial block consisting of the block group and the side block, and the upper layer surface is secured around the first recess and the second recess, so that the provision of the first recess and the second recess can suppress the decrease in block rigidity, and can improve the block durability. These cooperations can achieve a high degree of both block durability and rough road running performance.

[0007] In the present invention, the first recess and the second recess are provided so as to straddle the side surface of the shoulder block and the top surface of the side block included in the block group. However, In this case, the top surface of the side block constituting the upper layer surface is preferably composed of a pair of radial portions extending from the side surface of the shoulder block toward the inside in the tire radial direction on both sides of the first recess in the tire circumferential direction, and a circumferential portion connecting the pair of radial portions in the tire circumferential direction. This improves the uneven shape formed by the substantial block consisting of the block group and the side block, the first recess, and the second recess, which is advantageous for achieving both block durability and rough road driving performance.

[0008] In the present invention, a narrow groove is provided extending from the tread surface of the shoulder block to the outer side surface in the tire width direction, and the bottom of the narrow groove at the outer end in the tire width direction is preferably connected to the intermediate layer surface. This makes it possible to suppress a decrease in block rigidity caused by the narrow groove while ensuring the edge effect of the narrow groove, which is advantageous for achieving both block durability and rough road running performance.

[0009] In the present invention, it is preferable that the bottom of the shoulder lug grooves arranged between the shoulder blocks included in the block group be connected to the lower layer surface at the outer end in the tire width direction, which ensures the edge effect of the narrow grooves while suppressing the decrease in block rigidity caused by the narrow grooves, and is advantageous in achieving both block durability and rough road driving performance.

[0010] In the present invention, the first recessed portion preferably has a polygonal shape when viewed from the side surface of the tire, which allows the edge effect of the first recessed portion to be satisfactorily exhibited, and is advantageous in improving the rough road running performance.

[0011] In the present invention, it is preferable that the radially innermost end of the side block is located within a range of 20% to 50% of the tire cross-sectional height from the tire equator position toward the tire radially inward. By arranging the side blocks in an appropriate range in the tire radial direction in this way, when the tire is buried in mud while traveling on an unpaved road, the side blocks come into good contact with the mud on the road surface, making it possible to effectively improve the rough road running performance. In addition, since the size of the side blocks can be appropriately secured, it is advantageous for securing block rigidity and improving block durability.

[0012] In the present invention, a protrusion protruding from the groove bottom of the shoulder lug groove arranged between the shoulder blocks included in the block group is provided, and the protrusion is formed on the upper layer surface and the middle layer surface. ofBy providing a convex portion at the groove bottom of the shoulder lug groove in this manner, an edge effect due to the convex portion can be added, which is advantageous in improving running performance on rough roads.

[0013] 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, the inside of the tire can be filled with air, an inert gas such as nitrogen, or other gases. [Brief description of the drawings]

[0014] [Figure 1] 1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing a shoulder region and a side region of a tire according to an embodiment of the present invention. [Diagram 3] FIG. 1 is an explanatory diagram showing a schematic diagram of the shoulder block (side surface) and side block (top surface) of the present invention, where (a) shows the overall structure, (b) shows the upper surface, (c) shows the middle surface, and (d) shows the lower surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0016] When the tire of the present invention is a pneumatic tire as shown in Fig. 1, it includes 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 on the tire radial inner side of the sidewall portions 2. In Fig. 1, the symbol CL indicates the tire equator. Although not depicted in Fig. 1 because it is a meridian cross section, the tread portion 1, the sidewall portions 2, and the bead portions 3 each extend in the tire circumferential direction to form an annular shape, thereby forming a basic toroidal structure of a pneumatic tire. The following explanation using Fig. 1 is basically based on the meridian cross section shown in the figure, but each tire component extends in the tire circumferential direction to form an annular shape.

[0017] A carcass layer 4 is installed between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is arranged around a bead core 5 disposed in each bead portion 3. Tire width direction The bead core 5 is folded from the inside to the outside. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body and the folded-back part of the carcass layer 4. On the other hand, a plurality of belt layers 7 (two layers in FIG. 1) are embedded on the outer periphery side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are disposed so as to cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to, for example, 10° to 40°. Furthermore, at least one belt reinforcing layer 8 (two layers in FIG. 1) is provided on the outer periphery side of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the angle of the organic fiber cords with respect to the tire circumferential direction is set to, for example, 0° to 5°.

[0018] Since the present invention relates to the shoulder and side regions of a tire as described below, the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. In addition, the detailed shapes (tread pattern) of the grooves and blocks formed on the surface of the tread portion 1 are not particularly limited except for the shoulder region described below. The tread pattern of the portion excluding the shoulder region described below is preferably a pattern mainly composed of blocks suitable for unpaved roads. The present invention can be applied to various tires, including non-pneumatic tires, as long as they have an area (parts corresponding to the shoulder and side regions) that may come into contact with mud on the road surface when traveling on an unpaved road.

[0019] As shown in Figs. 1 and 2, a pair of main grooves 10 are formed on the surface of the tread portion 1, extending along the tire circumferential direction on both sides of the tire equator CL. The main grooves 10 may have a zigzag shape in which linear portions inclined in one direction with respect to the tire circumferential direction and linear portions inclined in the other direction are alternately connected in the tire circumferential direction. The region between the pair of main grooves 10 is a center region (a region in which the structure is not particularly limited in the present invention and any tread pattern can be adopted), and the regions on the outer sides of each main groove 10 in the tire width direction are shoulder regions. The main grooves 10 preferably have a groove width of 3 mm to 13 mm, more preferably 5 mm to 11 mm, and a groove depth of 8 mm to 16 mm, more preferably 10 mm to 15 mm.

[0020] A land portion (shoulder land portion) defined on the outer side of the main groove 10 in the tire width direction is provided with a shoulder lug groove 11 extending from the main groove 10 toward the outer side in the tire width direction. A plurality of shoulder lug grooves 11 may be provided at intervals in the tire circumferential direction. The shoulder lug grooves 11 define the shoulder land portion into a plurality of blocks (shoulder blocks 12). When the main groove 10 has a zigzag shape, the shoulder lug groove 11 may be connected to a bending point on the outer side of each main groove 10 in the tire width direction. The groove width of the shoulder lug groove 11 is not particularly limited, but is preferably 70% to 98%, more preferably 80% to 95% of the groove width of the main groove 10. The groove depth of the shoulder lug groove 11 is not particularly limited, but is preferably 75% to 100%, more preferably 80% to 98% of the groove depth of the main groove 10.

[0021] When the region adjacent to the shoulder region on the outer side in the tire width direction is defined as the side region, a plurality of side blocks 13 protruding from the outer surface of the sidewall portion 2 are provided in this side region. The protruding height of each side block 13 from the sidewall surface is not particularly limited, but can be set to, for example, 1 mm to 10 mm. As shown in FIG. 2 and FIG. 3(a), each side block 13 is disposed at a position on the outer side in the tire width direction of a block group consisting of two or more shoulder blocks 12 adjacent in the tire circumferential direction. For example, in the illustrated example, one side block 13 is disposed at a position on the outer side in the tire width direction of a block group consisting of two shoulder blocks 12. In other words, a side groove 14 extending along the tire width direction (tire radial direction) is formed between the side blocks 13 adjacent in the tire circumferential direction, and this side groove 14 is connected to at least every other one of the plurality of shoulder lug grooves 11 arranged at intervals in the tire circumferential direction. Between the shoulder lug grooves 11 and side grooves 14 connected in this manner, one side block 13 and two or more shoulder blocks 12 (and one or more shoulder lug grooves 11 that are not connected to the side groove 14) are arranged.

[0022] In the above arrangement, since the side block 13 is provided so as to straddle two or more shoulder blocks 12, the side block 13 and the shoulder block 12 can be regarded as a pseudo-large block. In particular, the surface consisting of the side surface of the shoulder block 12 included in the block group and the top surface of the side block 13 can be regarded as a surface of one large block, and this is defined as the upper surface P1 in the present invention. Furthermore, in the present invention, a first recess 15 including a middle surface P2 recessed by 0.2 mm or more from the upper surface P1 is provided on the center side of the upper surface P1, and a second recess 16 including a lower surface P3 recessed by 0.2 mm or more from the middle surface P2 is provided on the center side of the middle surface P2. That is, the pseudo-large block consisting of the block group and the side block 13 forms a stepped mortar-shaped uneven structure that is gradually recessed toward the center side of the upper surface P1, via the middle surface P2, to the lower surface P3.

[0023] In the tire of the present invention, the whole consisting of the shoulder block 12 (block group) and the side block 13 (a set of blocks shown in FIG. 3(a)) functions substantially as a large block, and the rigidity of the large block can be secured, thereby improving the block durability. On the other hand, the complex uneven shape formed by the first recess 15 and the second recess 16, which is recessed stepwise from the upper layer surface P1 through the middle layer surface P2 to the lower layer surface P3, can efficiently bite into mud on unpaved roads, improve traction performance, and exhibit excellent rough road running performance. At this time, the first recess 15 and the second recess 16 have a structure recessed stepwise toward the center side of the substantial block consisting of the shoulder block 12 and the side block 13, and the upper layer surface P1 is secured around the first recess 15 and the second recess 16, so that the provision of the first recess 15 and the second recess 16 can suppress the decrease in block rigidity and improve the block durability. These cooperations can achieve a high degree of both block durability and rough road running performance.

[0024] In the illustrated example, a protrusion 17 is present at the boundary (the boundary between the shoulder region and the side region) between the side of the shoulder block 12 on the outer side in the tire width direction and the top surface of the side block 13, protruding from the sidewall surface and extending over the entire circumference of the tire. This protrusion 17 is an element formed due to the die split position, etc., and does not necessarily need to be provided. This protrusion 17 can be ignored in the present invention (for example, even if the protrusion 17 exists, the upper layer surface P1, the middle layer surface P2, and the lower layer surface 3 can each be regarded as one surface). This protrusion 17 is an element that does not need to be considered in the present invention, but since it is an element formed during manufacturing, the shoulder region and the side region may be divided based on the protrusion 17. That is, the shoulder region can be regarded as the region adjacent to the protrusion 17 on the inner side in the tire width direction, and the side region can be regarded as the region adjacent to the protrusion 17 on the inner side in the tire radial direction.

[0025] The number of side blocks 13 and shoulder blocks 12 constituting the upper layer surface is preferably two shoulder blocks 12 for one side block 13. This provides a good balance between the numbers of side blocks 13 and shoulder blocks 12 included in the upper layer surface P1, which is advantageous for achieving both block durability and rough road performance.

[0026] The recess amount of the middle layer surface P2 relative to the upper layer surface P1 is 0.2 mm or more as described above, but is preferably 0.5 mm or more, more preferably 0.5 mm or more and 1.5 mm or less. Similarly, the recess amount of the lower layer surface P3 relative to the middle layer surface P2 is 0.2 mm or more as described above, but is preferably 0.5 mm or more, more preferably 0.5 mm or more and 1.5 mm or less. In this way, by sufficiently recessing the middle layer surface P2 and the lower layer surface P3, the uneven shape formed by the first recess 15 and the second recess 16 becomes good, and the edge effect by these recesses can be efficiently exhibited. If the recess amount of each is less than 0.2 mm, sufficient unevenness can be secured, and the edge effect cannot be improved.

[0027] When providing the first recess 15 and the second recess 16, it is not desirable to provide them only in either the side block 13 or the shoulder block 12 that constitutes the upper layer surface P1, and it is preferable that the first recess 15 and the second recess 16 are provided so as to straddle the side surface of the shoulder block 12 and the top surface of the side block 13, respectively. For example, in the illustrated example, at least a part of the first recess 15 (middle layer surface P2) and the second recess 16 (lower layer surface P3) is present in each of the two shoulder blocks 12 and one side block 13. In other words, each of the shoulder blocks 12 and the side blocks 13 included in the block group has three layers, namely, the upper layer surface P1, the middle layer surface P2, and the lower layer surface P3. By distributing the first recess 15 (middle layer surface P2) and the second recess 16 (lower layer surface P3) in this way, the rigidity of each of the shoulder blocks 12 and the side blocks 13 included in the block group can be secured, which is advantageous for improving the durability of the blocks.

[0028] Furthermore, the top surface of the side block 13 constituting the upper layer surface P1 is preferably composed of a pair of radial portions 13a extending from the side surface of the shoulder block toward the inside in the tire radial direction on both sides of the first recess 15 in the tire circumferential direction, and a circumferential portion 13b connecting the pair of radial portions in the tire circumferential direction. While the multiple shoulder blocks 12 included in the block group are partitioned by the shoulder lug grooves 11, by connecting the top surface of the side block 13 in the circumferential direction as described above (a substantially U-shaped configuration consisting of a pair of radial portions 13a and a circumferential portion 13b), it becomes easier to make the multiple shoulder blocks 12 and the side block 13 function as one large block, which is advantageous for improving block durability.

[0029] In the present invention, a narrow groove 18 extending from the tread surface of the shoulder block 12 to the side surface on the outer side in the tire width direction may be provided. When such a narrow groove 18 is provided, it is preferable that the narrow groove 18 is connected to the first recessed portion 15 from the viewpoint of ensuring block rigidity. In particular, it is preferable that the groove bottom at the end of the narrow groove 18 on the outer side in the tire width direction is connected to the middle layer surface P2. This makes the depth (depth relative to the upper layer surface P1) of the narrow groove 18 and the middle layer surface P2 the same, so that the narrow groove 18 and the first recessed portion 15 (middle layer surface) as a whole can exhibit a more excellent edge effect and ensure block rigidity. The number of narrow grooves 18 provided in each shoulder block 12 is not particularly limited, but for example, one to three (two in the illustrated example) can be provided. When a plurality of narrow grooves 18 are provided, it is preferable that at least one of them is connected to the first recessed portion 15 as described above. For example, in the illustrated example, one of the two narrow grooves 18 provided in one shoulder block 12 is connected to the first recess 15, and the other extends from the tread surface of the shoulder block 12 to the outer side surface in the tire width direction and terminates at the side surface.

[0030] As described above, the shoulder lug grooves 11 are disposed between the shoulder blocks 12 included in the block group, and it is preferable that these shoulder lug grooves 11 connect to the second recessed portion 16. In particular, it is preferable that the groove bottom at the end of the shoulder lug groove 11 on the outer side in the tire width direction connects to the underlying surface P3. This makes it possible for the shoulder lug groove 11 and the second recessed portion 16 (underlying surface P3) as a whole to exhibit a superior edge effect.

[0031] The first recess 15 (middle layer surface P2) preferably has a polygonal shape when viewed from the tire side surface. In particular, it is preferable that opposing sides of the polygon extend in the same direction. For example, in the illustrated example, the side extending at an angle in the tire circumferential direction on the side surface of the shoulder block 12 adjacent in the tire circumferential direction and the side extending in the tire circumferential direction on the top surface of the side block 13 extend in the same direction, and a pair of sides extending in the tire radial direction from the side surface of the shoulder block 12 to the top surface of the side block 13 extend in the same direction, so that the first recess 15 (middle layer surface P2) has an approximately parallelogram shape as a whole. By making it into such a shape, the edge effect by the edge of the first recess 15 can be well exhibited, which is advantageous for improving the rough road running performance.

[0032] The second recess 16 (lower surface P3) also preferably has a polygonal shape when viewed from the tire side surface. In particular, it is preferable that the second recess 16 (lower surface P3) has a shape similar to that of the first recess 15 (middle surface P2). For example, in the illustrated example, the second recess 16 (lower surface P3) has a substantially parallelogram shape similar to that of the first recess 15 (middle surface P2). In the illustrated example, the second recess 16 (middle surface P3) is composed of a main body portion 16a having a substantially parallelogram shape similar to that of the first recess 15, and groove portions 16a extending in the tire circumferential direction from two vertices on the diagonal of the main body portion 16a having a parallelogram shape.

[0033] Regardless of the shapes of the middle layer surface P2 and the lower layer surface P3, when the area of ​​the upper layer surface P1 (shaded area in FIG. 3(b)) is area A, the area of ​​the middle layer surface P2 (shaded area in FIG. 3(c)) is area B, and the area of ​​the lower layer surface P3 (shaded area in FIG. 3(d)) is area C, it is preferable that the ratio of the area B of the middle layer surface P2 to the total (A+B+C) of these areas A to C is 20% to 50%, and the ratio of the area C of the lower layer surface P3 is 5% to 30%. By setting the area of ​​each layer in this way, the uneven shape that recesses in a step-like manner from the upper layer surface P1 through the middle layer surface P2 to the lower layer surface P3 is well balanced, which is advantageous for achieving both block durability and rough road running performance.

[0034] The side blocks 13 are preferably arranged in an appropriate range in the tire radial direction so that they can appropriately contact the road surface when the tire is buried in mud or the like while traveling on an unpaved road. Specifically, the innermost end of the side block 13 in the tire radial direction is preferably present in a range of 20% to 50% of the tire cross-sectional height SH from the tire equator CL position toward the tire radially inward. In other words, the distance D from the tire equator CL position to the innermost end of the side block 13 in the tire radial direction is preferably 20% to 50% of the tire cross-sectional height SH. By arranging the side blocks 13 in an appropriate range in the tire radial direction of the sidewall portion 2 in this way, it is possible to effectively improve the running performance on unpaved roads. In addition, since the size of the side blocks 13 can be appropriately secured, it is advantageous to secure block rigidity and improve durability. If the distance D is less than 20% of the tire cross-sectional height SH, the side blocks 13 become small, making it difficult to maintain good block durability. If the distance D exceeds 50% of the tire cross-sectional height SH, the side blocks 13 become too large, which may affect normal running performance. In relation to the arrangement of the side blocks 13, the boundary between the shoulder region and the side region should be located within a range of 20% to 25% of the tire cross-sectional height SH from the tire equator CL toward the tire radially inward, regardless of the presence or absence of the protrusions 17.

[0035] In the present invention, a protrusion 19 protruding from the groove bottom of the shoulder lug groove 11 arranged between the shoulder blocks 12 included in the block group can also be provided. The protrusion 19 is preferably not a protrusion over the entire width of the groove bottom of the shoulder lug groove 11, but a part of the groove bottom. By providing the protrusion 19 at the groove bottom of the shoulder lug groove 11 in this way, the edge effect of the protrusion 19 can be added, which is advantageous for improving the rough road running performance. The protrusion height from the groove bottom of the protrusion 19 is preferably 2% to 20%, more preferably 5% to 15% of the groove depth of the shoulder lug groove 11. In particular, when the shoulder lug groove 11 is connected to the second recess 16 (lower layer surface P3), it is preferable that the protrusion 19 protrudes to a height not exceeding the middle layer surface P2 of the first recess 15. In addition, when the protrusion 19 is provided, it is preferable that the protrusion 19 is arranged so as to extend across the upper layer surface P1 and the middle layer surface P2 when viewed from the side of the tire.

[0036] 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

[0037] Seventeen types of pneumatic tires, namely Conventional Example 1, Comparative Examples 1-2, and Examples 1-14, were produced, with a tire size of LT265 / 70R17 121 / 118S, a basic structure (cross-sectional structure) as illustrated in FIG. 1, and structures of the shoulder region and side region based on FIG. 2. The number of shoulder blocks adjacent to one side block on the radially outer side of the tire, the shape of the upper layer surface, the presence or absence of a first recess (middle layer surface), the presence or absence of a second recess (lower layer surface), the presence or absence of a shoulder narrow groove, the connecting positions of the narrow grooves, the connecting positions of the shoulder lug grooves between the block groups, the shape of the first recess as viewed from the tire side direction, the ratio of the distance D to the tire cross-sectional height SH, and the presence or absence and arrangement of a convex portion at the groove bottom of the shoulder lug groove were set as shown in Tables 1-2, respectively.

[0038] The tread pattern in the center region is common to all examples, and has a structure in which a row of blocks is arranged between a pair of main grooves and on both sides of the tire equator. In addition, in the column "shape of upper surface" in Tables 1-2, as in the illustrated example, a case in which a pair of radial portions extending from the side of the shoulder block toward the tire radially inward on both sides of the first recess in the tire circumferential direction and a circumferential portion connecting the pair of radial portions in the tire circumferential direction are included is indicated as "continuous", and a case in which the above-mentioned "circumferential portion" is divided by the first recess is indicated as "discontinuous". In the column "connection position of fine groove" in Tables 1-2, it is indicated whether the fine groove is connected to the first recess (middle layer surface) or the second recess (lower layer surface) (if the fine groove is not connected to either the first recess (middle layer surface) or the second recess (lower layer surface), it is indicated as "unconnected"). In the column of "Connection position of shoulder lug groove" in Tables 1-2, it is indicated whether the shoulder lug groove is connected to the first recess (middle surface) or the second recess (lower surface) (if the shoulder lug groove is not connected to either the first recess (middle surface) or the second recess (lower surface), it is indicated as "not connected"). In the column of "Shape of first recess" in Tables 1-2, the basic structure in each example has a rectangular shape as shown in the figure, but if the opposite sides of the rectangle extend in the same direction, it is indicated as "approximately parallelogram", and if one pair of the opposite sides of the aforementioned rectangle extend in a different direction, it is indicated as "approximately trapezoid". In the column of "Arrangement of convex portion" in Tables 1-2, it is indicated whether the convex portion is arranged at a position overlapping with the upper surface / middle surface / lower surface (for example, if it is arranged to extend across the upper surface and the middle surface, it is indicated as "upper layer + middle layer").

[0039] The pneumatic tires were evaluated for rough road performance and block durability by the following evaluation methods, and the results are shown in Tables 1 and 2.

[0040] Rough road performance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire was set at an air pressure of 450kPa and the rear tire at an air pressure of 550kPa. The test vehicle (traction test vehicle) was then fitted with the tire and subjected to a sensory evaluation of traction (starting performance) on a test road consisting of an unpaved road (gravel surface) by a test driver. The evaluation results were expressed as an index, with the value of Conventional Example 1 being set at 100. The higher the index value, the better the snow performance. An index value exceeding "105" means that particularly excellent rough road performance was obtained.

[0041] Block durability (cut resistance) Each test tire was mounted on a wheel with a rim size of 17×8J, and the air pressure was set to 350 kPa and mounted on a test vehicle (four-wheel drive SUV). After driving 1000 km on an off-road durability road, the total length of the cuts on the side was measured. The evaluation results were expressed as an index with the reciprocal of the measurement value of Comparative Example 1 set to 100. The larger the index value, the smaller the total length of the cuts and the more excellent the block durability (cut resistance). An index value of "105" or more means that sufficient block durability (cut resistance) was obtained.

[0042] [Table 1]

[0043] [Table 2]

[0044] As is clear from Tables 1 and 2, the pneumatic tires of Examples 1 to 14 have improved snow performance and wear resistance compared to Conventional Example 1, and these performances are well balanced. On the other hand, Comparative Example 1 has a structure in which two shoulder blocks are adjacent to one side block, and therefore the rough road running performance is improved compared to Conventional Example 1, but is insufficient because the first recessed portion (middle layer surface) and the second recessed portion (lower layer surface) are not provided. Comparative Example 2 has a structure in which two shoulder blocks are adjacent to one side block, and although the first recessed portion (middle layer surface) is provided, the second recessed portion (lower layer surface) is not provided, and therefore the rough road running performance cannot be sufficiently improved as in Comparative Example 1.

[0045] The present disclosure includes the following inventions. Invention [1] A tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, A pair of main grooves extending along a tire circumferential direction on both sides of a tire equator are provided on a surface of the tread portion, A shoulder region located on the outer side of the main groove in the tire width direction is provided with a plurality of shoulder lug grooves extending from the main groove toward the outer side in the tire width direction and spaced apart in the tire circumferential direction, and a plurality of shoulder blocks partitioned by the main groove and the shoulder lug groove and arranged along the tire circumferential direction, A plurality of side blocks protruding from an outer surface of the sidewall portion are provided in a side region adjacent to an outer side of the shoulder region in the tire width direction, One side block is disposed at an outer position in the tire width direction of a block group consisting of two or more shoulder blocks adjacent in the tire circumferential direction, When a surface consisting of the side surface of the shoulder block and the top surface of the side block included in the block group is defined as an upper layer surface, a first recess is provided on the center side of the upper layer surface, the first recess includes a middle layer surface recessed by 0.2 mm or more from the upper layer surface, and a second recess is provided on the center side of the middle layer surface, the second recess includes a lower layer surface recessed by 0.2 mm or more from the middle layer surface. The first recess and the second recess are provided so as to straddle the side surface of the shoulder block and the top surface of the side block included in the block group, respectively. A tire characterized by the above. 。 Departure Light [ 2 The top surface of the side block constituting the upper layer surface is composed of a pair of radial portions extending from the side surface of the shoulder block toward the inside in the tire radial direction on both sides of the first recess in the tire circumferential direction, and a circumferential portion connecting the pair of radial portions in the tire circumferential direction. 1 ] A tire as described in the above. invention[ 3 The invention is characterized in that a narrow groove is provided extending from the tread surface of the shoulder block to the side surface on the outer side in the tire width direction, and the narrow groove has a groove bottom at an end portion on the outer side in the tire width direction connected to the intermediate layer surface. or [2] A tire as described in. invention[ 4 The shoulder lug grooves arranged between the shoulder blocks included in the block group have groove bottoms at their outer ends in the tire width direction connected to the lower layer surface. 3 ] A tire described in any one of the above. invention[ 5 The first recess has a polygonal shape when viewed from a side surface of the tire. 4 ] A tire described in any one of the above. invention[ 6 The invention [1] to [2] is characterized in that the radially innermost end of the side block is located within a range of 20% to 50% of the tire cross-sectional height from the tire equator position toward the tire radially inward. 5 ] A tire described in any one of the above. invention[ 7 A groove bottom of the shoulder lug groove disposed between the shoulder blocks included in the block group is provided with a protruding portion protruding from the groove bottom, and the protruding portion is disposed between the upper layer surface and the middle layer surface. of The invention [1] to [ 6 ] A tire described in any one of the above. [Explanation of symbols]

[0046] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt reinforcement layer 10 Main groove 11 Shoulder lug groove 12 Shoulder Block 13 Side Block 14 Side groove 15 First recess 16 Second recess 17 protrusion 18 Narrow groove 19 Convex P1 Upper surface P2 Middle surface P3 lower surface CL Tire Equator

Claims

1. A tire having a tread portion extending in a circumferential direction of the tire to form an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, A pair of main grooves extending along a tire circumferential direction on both sides of a tire equator are provided on a surface of the tread portion, A shoulder region located on the outer side of the main groove in the tire width direction is provided with a plurality of shoulder lug grooves extending from the main groove toward the outer side in the tire width direction and spaced apart in the tire circumferential direction, and a plurality of shoulder blocks partitioned by the main groove and the shoulder lug groove and arranged along the tire circumferential direction, A plurality of side blocks protruding from an outer surface of the sidewall portion are provided in a side region adjacent to an outer side of the shoulder region in the tire width direction, One side block is disposed at an outer side in the tire width direction of a block group consisting of two or more shoulder blocks adjacent in the tire circumferential direction, a first recess including a middle layer surface recessed by 0.2 mm or more from the upper layer surface on the center side of the upper layer surface, and a second recess including a lower layer surface recessed by 0.2 mm or more from the middle layer surface on the center side of the middle layer surface, the first recess and the second recess being provided so as to straddle the side surface of the shoulder block and the top surface of the side block, respectively, which are included in the block group.

2. 2. The tire according to claim 1, wherein the top surface of the side block constituting the upper layer surface is composed of a pair of radial portions extending from the side surfaces of the shoulder block toward the inside in the tire radial direction on both sides of the first recess in the tire circumferential direction, and a circumferential portion connecting the pair of radial portions in the tire circumferential direction.

3. 3. The tire according to claim 1, wherein a narrow groove is provided extending from the tread surface of the shoulder block to a side surface on an outer side in the tire width direction, and a groove bottom of the narrow groove at an outer end portion in the tire width direction is connected to the intermediate layer surface.

4. 3. The tire according to claim 1, wherein the shoulder lug grooves arranged between the shoulder blocks included in the block group have groove bottoms at their outer ends in the tire width direction connected to the underlying surface.

5. The tire according to claim 1 or 2, wherein the first recess has a polygonal shape when viewed from a side surface of the tire.

6. 3. The tire according to claim 1, wherein the radially innermost end of the side block is located within a range of 20% to 50% of the tire cross-sectional height from the tire equator position toward the radially inner side of the tire.

7. 3. The tire according to claim 1, wherein a protrusion protruding from a groove bottom of the shoulder lug groove arranged between the shoulder blocks included in the block group is provided, and the protrusion is arranged so as to extend across the upper layer surface and the intermediate layer surface.

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