Tire

Abstract

To provide a tire that can further improve performance in running on a bad road while securing excellent durability of blocks.SOLUTION: A plurality of shoulder blocks 12 are provided on a shoulder region of a tread part 1; a plurality of side blocks 13 are provided on a side region adjacent to outside in a tire width direction of the shoulder region; two or more shoulder blocks 12 arranged adjacently in a tire circumferential direction and one side block 13 arranged outsides in the tire width direction of the shoulder blocks are grouped into a block group B; and first thin grooves 21, second thin grooves 22 and third thin grooves 23 are each formed on the blocks included in the block group B, where the thin grooves constitute a series thin groove group 20 extending continuously from the one shoulder block 12 included in the block group B through the side block 13 to the other shoulder block 12.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 further improvement in 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 enables further improvement in rough road running performance while ensuring excellent block durability. [Means for solving the problem]

[0005] In order to achieve the above object, the tire of the present invention has a tread portion extending in a circumferential direction of the tire and forming an annular shape, and a pair of sidewall portions arranged on both sides of the tread portion, the tire having a surface of the tread portion having a pair of main grooves extending along the tire circumferential direction on both sides of the tire equator, and a shoulder region located on the outer side of the main grooves in the tire width direction is provided with 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 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 the outer side in the tire width direction of the shoulder region, and one of the side blocks is arranged at a position in the tire width direction outer side of two or more of the shoulder blocks adjacent in the tire circumferential direction. When a combination of two or more of the shoulder blocks and one of the side blocks is defined as a block group, a first narrow groove having one end opening into one of the shoulder lug grooves and the other end extending toward the side block is provided on a side surface of one of the shoulder blocks included in the block group, a second narrow groove having one end opening into the other of the shoulder lug grooves and the other end extending toward the side block is provided on a side surface of another of the shoulder blocks included in the block group, and a third narrow groove is provided on a top surface of one of the side blocks included in the block group, extending to connect the other end of the first narrow groove and the other end of the second narrow groove, so that the first narrow groove, the second narrow groove, and the third narrow groove form a series of narrow groove groups extending continuously from one of the shoulder blocks included in the block group through the side block to the other of the shoulder blocks. 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 block essentially functions as a large block, and thus the block durability can be improved. In addition, since only the first to third fine grooves are provided in each block, the rigidity of each block is maintained, and from this point of view, the block durability can also be improved. On the other hand, since the first to third fine grooves constitute a series of fine groove groups that continuously extend from one shoulder block included in the block group through the side block to another shoulder block, this series of fine groove groups (first to third fine grooves) functions as one long groove, and an excellent edge effect is exhibited in the whole block group, and the traction performance can be improved. These cooperations can achieve a high degree of both block durability and rough road running performance.

[0007] In the present invention, it is preferable that each of the first and second narrow grooves has at least one bending point, and the third narrow groove has at least two bending points, which allows each groove to include portions extending in various directions, improving the edge effect and being advantageous in enhancing traction performance.

[0008] In the present invention, the groove width of the first narrow groove, the second narrow groove, and the third narrow groove is preferably 0.5 mm to 3 mm. Also, the groove depth of the first narrow groove, the second narrow groove, and the third narrow groove is preferably 0.5 mm to 2 mm. By having the groove width and groove depth of each groove in such a moderate range, it is advantageous to achieve both block durability and rough road running performance.

[0009] In the present invention, the shoulder block may be provided with an auxiliary groove that branches off from the first or second fine groove and extends toward the tread side of the shoulder block. In this case, the auxiliary groove provides an edge effect, which is advantageous in improving traction performance.

[0010] In the present invention, it is preferable that the open ends of the first narrow groove and the second narrow groove are located on the same circumferential side of each shoulder block, so that the first narrow groove and the second narrow groove extend in the same direction, which is advantageous for improving the edge effect and enhancing traction performance.

[0011] In the present invention, the shoulder block may be provided with a parallel auxiliary groove extending parallel to the first narrow groove or the second narrow groove, which is advantageous in improving traction performance since the parallel auxiliary groove provides an edge effect.

[0012] In the present invention, it is preferable that the third fine groove includes a straight portion extending parallel to the contour line of the side block, which provides a good balance between the shape of the side block and the curved shape of the third fine groove, and is advantageous in achieving both block durability and rough road performance.

[0013] In the present invention, it is preferable that the positions of the opening ends of the first narrow groove and the second narrow groove are different in the tire radial direction. By making the end positions of each groove different in this way, these grooves can exert an edge effect at various positions in the tire radial direction, which is advantageous for improving traction performance.

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

[0015] [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. 2 is an explanatory diagram showing a schematic view of a shoulder block (side surface) and a side block (front surface) of the present invention. [Figure 4] 6 is an explanatory diagram showing a schematic view of a shoulder block (side surface) and a side block (front surface) in another embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] 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.

[0018] 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 folded back from the vehicle inner side to the vehicle outer side around the bead cores 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead cores 5, and the bead filler 6 is wrapped by the main body and the folded back portion of the carcass layer 4. Meanwhile, 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 arranged 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, a range of 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 organic fiber cords are set at an angle of, for example, 0° to 5° with respect to the tire circumferential direction.

[0019] 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.

[0020] As shown in Figs. 1 and 2, a pair of main grooves 10 are formed on the surface of the tread portion 1, extending all around the tire in 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.

[0021] 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.

[0022] 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 outer surface of the sidewall 2 is not particularly limited, but can be set to, for example, 1 mm to 10 mm. As shown in Figs. 2 and 3, each side block 13 is disposed on the outer side in the tire width direction at a position corresponding to 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 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. One side block 13 and two or more shoulder blocks 12 (and one or more shoulder lug grooves 11 not connected to the side groove 14) are disposed between the shoulder lug grooves 11 and side grooves 14 connected in this way.

[0023] 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.

[0024] In the illustrated example, a protrusion 15 is present at the boundary between the outer side surface of the shoulder block 12 in the tire width direction and the surface of the side block 13 (the boundary between the shoulder region and the side region), protruding from the sidewall surface and extending around the entire circumference of the tire. This protrusion 15 is an element formed due to the split position of the mold, and is not necessarily provided. This protrusion 15 is an element that does not need to be taken into consideration in the present invention, but since it is an element formed during manufacturing, the shoulder region and side region may be divided based on the protrusion 15. In other words, the shoulder region can be regarded as the region adjacent to the protrusion 15 on the inner side in the tire width direction, and the side region can be regarded as the region adjacent to the protrusion 15 on the inner side in the tire radial direction.

[0025] When the combination of two or more shoulder blocks 12 and one side block 13 is defined as a block group B, a first narrow groove 21 is provided on a side surface of one shoulder block 12 included in the block group B, the first narrow groove 21 having one end opening into one of the shoulder lug grooves 11 and the other end extending toward the side block 13. Similarly, a second narrow groove 22 is provided on a side surface of another shoulder block 12 included in the block group B, the second narrow groove 22 having one end opening into the other of the shoulder lug grooves 11 and the other end extending toward the side block 13. A third narrow groove 23 is provided on a top surface of a side block 13 included in the block group B, the third narrow groove 23 extending to connect the other end of the first narrow groove 21 and the other end of the second narrow groove 22. The first narrow groove 21, the second narrow groove 22, and the third narrow groove 23 constitute a series of narrow groove groups 20 that extend continuously along the blocks from one shoulder block 12 included in the block group B through the side block 13 to the other shoulder block 12.

[0026] In the tire of the present invention, the shoulder block 12 and the side block 13 function as a large block (block group B) and the rigidity of the large block can be secured, so that the block durability can be improved. In addition, since each block is provided mainly with the first fine groove 21, the second fine groove 22, and the third fine groove 23, the rigidity of each block is maintained, and the block durability can be improved from this point of view as well. On the other hand, the first fine groove 21, the second fine groove 22, and the third fine groove 23 constitute a series of fine groove groups 20 that extend continuously along the blocks from one shoulder block 12 included in the block group B through the side block 13 to another shoulder block 12, so that it is equivalent to a substantially large block (block group B) provided with a substantially long fine groove (fine groove group 20), and this series of fine groove groups 20 exerts an excellent edge effect in the entire block group B, and the traction performance can be effectively improved. These cooperations can achieve a high degree of both block durability and rough road running performance.

[0027] In the narrow groove group 20, the first narrow groove 21, the second narrow groove 22, and the third narrow groove 23 do not need to be completely continuous, and even if they are intermittently connected, they can be considered to constitute a continuous narrow groove group 20. For example, in the illustrated example, a protrusion 15 exists between the first narrow groove 21 and the third narrow groove 23 and between the second narrow groove 22 and the third narrow groove 23, and these grooves are interrupted, but since the end of the third narrow groove 23 exists at the extension position of the first narrow groove 21 and the second narrow groove 22, they can be considered to be substantially continuous. In addition, a notch is provided in the side block 13, which divides the third narrow groove 23, but since the third narrow groove 23 on both sides of the division exists on the extension line of each other, they can be considered to be substantially continuous. Specifically, if the sum of the lengths of the first thin groove 21, the second thin groove 22, and the third thin groove 23 is 80% or more of the total length of an imaginary line (dashed line in the figure) drawn along the thin groove group 20 from one end of the first thin groove 21 (the opening end relative to the shoulder lug groove 11) to one end of the second thin groove 22 (the opening end relative to the shoulder lug groove 11), then the thin groove group 20 can be regarded as a substantially continuous series.

[0028] If any one of the first fine groove 21, the second fine groove 22, and the third fine groove 23 is not formed and a series of fine groove groups 20 extending continuously along each block included in block group B is not formed, a sufficient edge effect cannot be ensured and rough road running performance cannot be improved. Even if the first fine groove 21, the second fine groove 22, and the third fine groove 23 are all formed, if these grooves are not positioned so as to be continuous with each other and the fine groove group 20 is not formed, the edge effect of each fine groove can be ensured but the synergistic effect of the fine groove group 20 cannot be ensured, and the effect of improving rough road running performance will be limited.

[0029] The number of shoulder blocks 12 and side blocks 13 included in block group B is preferably 2 to 3, and more preferably 2, for one side block 13. This provides a good balance between the number of blocks in the combination of side blocks 13 and shoulder blocks 12, which is advantageous for achieving both block durability and rough road performance. In a structure in which three shoulder blocks 12 are arranged for one side block 13, as shown in FIG. 4, a first narrow groove 21 and a second narrow groove 22 are provided in at least two of the three shoulder blocks 12 on the outer side in the tire circumferential direction, and a third narrow groove 23 is provided in the side block 13 to connect them. In this structure, no fine grooves are formed in one of the three shoulder blocks 12 that is located at the circumferential center, but a series of fine groove groups 20 are formed that extend continuously across multiple blocks included in block group B, so that it is possible to achieve a high level of both block durability and rough road performance, as in the above-mentioned embodiment (where two shoulder blocks 12 are arranged for one side block 13).

[0030] The groove widths of the first narrow groove 21, the second narrow groove 22, and the third narrow groove 23 are preferably 0.5 mm to 3 mm, and more preferably 1.0 mm to 2.5 mm. Setting the groove widths in an appropriate range in this way is advantageous for achieving both block durability and rough road running performance. If the groove width of each groove is less than 0.5 mm, the groove width is too small, making it difficult to ensure a sufficient edge effect. If the groove width of each groove exceeds 3 mm, it becomes difficult to ensure sufficient block rigidity. In order to form a series of narrow groove groups 20, it is preferable that the groove widths of the first narrow groove 21, the second narrow groove 22, and the third narrow groove 23 are the same.

[0031] The groove depth of the first narrow groove 21, the second narrow groove 22, and the third narrow groove 23 is preferably 0.5 mm to 2 mm, and more preferably 0.7 mm to 1.5 mm. Setting the groove depth within an appropriate range in this way is advantageous for achieving both block durability and rough road running performance. If the groove depth of each groove is less than 0.5 mm, the groove depth is too small, making it difficult to ensure a sufficient edge effect. If the groove depth of each groove exceeds 2 mm, it becomes difficult to ensure sufficient block rigidity. In order to form a series of narrow groove groups 20, it is preferable that the groove depth of the first narrow groove 21, the second narrow groove 22, and the third narrow groove 23 is the same.

[0032] Each of the first narrow groove 21 and the second narrow groove 22 may have at least one bending point as shown in the figure. By having such a bending point, each groove includes a component extending along the tire circumferential direction and a component extending along the tire radial direction, making it possible to exert an edge effect in each direction, which is advantageous for improving traction performance. The number of bending points is preferably 1 to 2.

[0033] On the other hand, the third narrow groove 23 preferably has at least two bending points. In detail, since the third narrow groove 23 connects the other end of the first narrow groove 21 and the other end of the second narrow groove 22 as described above, it is preferable that the third narrow groove 23 is composed of a portion extending along the tire radial direction from a position corresponding to the other end of the first narrow groove 21, a portion extending along the tire radial direction from a position corresponding to the other end of the second narrow groove 22, and a portion extending along the tire circumferential direction, and therefore it is preferable that the number of bending points is at least two. By having such bending points, the third narrow groove 23 includes components extending in various directions, making it possible to exert an edge effect in each direction, which is advantageous for improving traction performance. The number of bending points in the third narrow groove 23 is preferably two to three.

[0034] As described above, the third narrow groove 23 may be composed of a portion extending along the tire radial direction from a position corresponding to the other end of the first narrow groove 21, a portion extending along the tire radial direction from a position corresponding to the other end of the second narrow groove 22, and a portion extending along the tire circumferential direction. In this case, at least the portion extending along the tire circumferential direction may extend parallel to the contour line of the side block 13 (the edge portion on the inner side in the tire radial direction). In addition, it is preferable that the third narrow groove 13 includes a straight portion extending parallel to the contour line of the side block, not limited to this portion. This provides a good balance between the shape of the side block and the curved shape of the third narrow groove, which is advantageous for achieving both block durability and rough road running performance. It is assumed that the contour line of the side block and the straight portion of the corresponding third narrow groove 23 extend substantially parallel if the angle difference between the contour line of the side block and the straight portion of the corresponding third narrow groove 23 is 0° to 30°.

[0035] Both the first thin groove 21 and the second thin groove 22 have ends (opening ends) that open to the shoulder lug groove 11, but it is preferable that the opening ends of the first thin groove 21 and the second thin groove 22 are present on the same side in the tire circumferential direction with respect to the shoulder block 12 in which each groove is provided. For example, in the illustrated example, the first thin groove 21 opens to the shoulder lug groove 11 adjacent to one side in the tire circumferential direction (the right side in the figure) of the shoulder block 12 in which the first thin groove 21 is provided, and the second thin groove 22 opens to the shoulder lug groove 11 adjacent to one side in the tire circumferential direction (the right side in the figure) of the shoulder block 12 in which the second thin groove 22 is provided. With such an arrangement of the opening ends, the parts that are continuous with the opening ends of the first thin groove 11 and the second thin groove 12 extend in the same direction. As a result, it is advantageous for improving the edge effect and enhancing traction performance.

[0036] On the other hand, it is preferable that the positions of the opening ends of the first narrow groove 11 and the second narrow groove 12 in the tire radial direction are different from each other. For example, in the illustrated example, the opening end of the first narrow groove 21 is provided on the outer side in the tire radial direction (the side closer to the tread surface of the shoulder block 12) than the opening end of the second narrow groove 22. By having the end positions of each groove differ in this way, these grooves can exert an edge effect at various positions in the tire radial direction, which is advantageous for improving traction performance.

[0037] In the present invention, the rigidity of each block included in the block group B is maintained by mainly providing the first thin groove 21, the second thin groove 22, and the third thin groove 23 in the block group B, but auxiliary grooves can be added within a range that does not significantly reduce the block rigidity. For example, as shown in the example, an auxiliary groove 24 branching from the first thin groove 21 or the second thin groove 22 and extending toward the tread side of the shoulder block 12 can be provided on the side of the shoulder block 12. Also, a parallel auxiliary groove 25 extending parallel to the first thin groove 21 or the second thin groove 22 can be provided on the side of the shoulder block 12. By adding such auxiliary grooves, an edge effect is added by each groove, which is advantageous for improving traction performance. When providing these auxiliary grooves 24 and parallel auxiliary grooves 25, the groove width and groove depth of these grooves are preferably set to be equal to the groove width and groove depth of the first thin groove 21, the second thin groove 22, and the third thin groove 23 described above.

[0038] The side block 13 may also be provided with a recess 30 at a position surrounded by the third narrow groove 23 and on an extension of the shoulder lug groove 11 located between the shoulder blocks 12 included in block group B. Providing such a recess 30 complicates the unevenness formed by block group B, which is advantageous for improving traction performance. The recess 30 is disposed on an extension of the shoulder lug groove 11 like the side groove 14, but unlike the side groove 14, it terminates inside the side block 13, so that the rigidity of the side block 13 can be sufficiently maintained even if the recess 30 is provided.

[0039] 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

[0040] Thirteen types of pneumatic tires were produced: Conventional Example 1, Comparative Examples 1-4, and Examples 1-8. The tire size was LT265 / 70R17 121 / 118S, and the basic structure (cross-sectional structure) was as shown in FIG. 1. The structures of the shoulder and side regions were based on FIG. 2. The number of shoulder blocks adjacent to one side block on the radially outer side of the tire, the presence or absence of a first fine groove, the presence or absence of a second fine groove, the presence or absence of a third fine groove, the presence or absence of a fine groove group, the groove width of the fine groove, the groove depth of the fine groove, the presence or absence of an auxiliary groove, and the presence or absence of parallel auxiliary grooves were set as shown in Tables 1 and 2.

[0041] The tread pattern in the center region was common to all examples, with a structure in which a row of blocks was arranged between a pair of main grooves and on each side of the tire equator.

[0042] The "presence or absence of fine groove group" column in Tables 1-2 indicates whether or not a series of fine groove groups extending substantially continuously is formed by the first fine groove, the second fine groove, and the third fine groove. For example, Comparative Example 2 does not have the third fine groove, so a series of fine groove groups is not formed, and the presence or absence of a series of fine groove groups is "absent." Similarly, Comparative Example 3 does not have the first fine groove and the second fine groove, so a series of fine groove groups is not formed, and the presence or absence of a fine groove group is "absent." Comparative Example 4 is an example in which the first to third fine grooves are present, but the end positions of these grooves are shifted and do not extend substantially continuously, and the presence or absence of a fine groove group is "absent."

[0043] The groove width and groove depth of the first to third narrow grooves are common to the tires of each example. That is, the columns "narrow groove width" and "narrow groove depth" in Tables 1 and 2 indicate the common groove width and groove depth of all the first to third narrow grooves.

[0044] The auxiliary grooves in the "Auxiliary Groove Presence" columns of Tables 1 and 2 are auxiliary grooves that branch off from the first fine groove or the second fine groove and extend toward the tread side of the shoulder block, and the presence or absence of these auxiliary grooves is indicated in the columns. Also, the parallel auxiliary grooves in the "Parallel Auxiliary Groove Presence" columns of Table 1 are parallel auxiliary grooves that extend parallel to the first fine groove or the second fine groove, and the presence or absence of these auxiliary grooves is indicated in the columns. "No" in these columns means that the structure is based on FIG. 2, but the auxiliary groove and / or the parallel auxiliary groove has been removed.

[0045] 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.

[0046] 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 tire was then mounted on a test vehicle (traction test vehicle), and a sensory evaluation of traction performance (starting performance) was carried out by a test driver on a test road consisting of an unpaved road (gravel surface). The evaluation results were expressed as an index with the value of Conventional Example 1 being 100. The higher the index value, the better the rough road driving performance.

[0047] 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 endurance 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 better the block durability (cut resistance).

[0048] [Table 1]

[0049] [Table 2]

[0050] As is clear from Tables 1 and 2, the pneumatic tires of Examples 1 to 8 have improved rough road running performance and block durability 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, so that the block durability is improved compared to Conventional Example 1, but the first to third fine grooves are not provided and a series of fine groove groups are not formed, so the effect of improving the rough road running performance was not obtained. Comparative Example 2 does not have the third fine groove and a series of fine groove groups are not formed, so the rough road running performance could not be sufficiently improved. Comparative Example 3 does not have the first fine groove and the second fine groove and a series of fine groove groups are not formed, so the rough road running performance could not be sufficiently improved. Comparative Example 4 has the first to third fine grooves, but the arrangement of these grooves is inappropriate and a series of fine groove groups are not formed, so the rough road running performance could not be sufficiently improved.

[0051] 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, When one side block is disposed at a position on the outer side in the tire width direction of two or more shoulder blocks adjacent to each other in the tire circumferential direction, and a combination of the two or more shoulder blocks and one side block is defined as a block group, A first narrow groove is provided on a side surface of one of the shoulder blocks included in the block group, the first narrow groove having one end opening into one of the shoulder lug grooves and the other end extending toward the side block, A second narrow groove is provided on a side surface of another shoulder block included in the block group, the second narrow groove having one end opening into another of the shoulder lug grooves and the other end extending toward the side block, a third narrow groove extending to connect the other end of the first narrow groove and the other end of the second narrow groove is provided on a top surface of the side block included in the block group, a tire characterized in that the first narrow groove, the second narrow groove, and the third narrow groove form a series of narrow groove groups extending continuously from one of the shoulder blocks included in the block group through the side block to another of the shoulder blocks. Invention [2] The tire according to invention [1], wherein the first narrow groove and the second narrow groove each have at least one bending point, and the third narrow groove has at least two bending points. Invention [3] The tire according to invention [1] or [2], wherein the first narrow groove, the second narrow groove, and the third narrow groove each have a groove width of 0.5 mm to 3 mm. Invention [4] The tire according to any one of inventions [1] to [3], wherein the first narrow groove, the second narrow groove, and the third narrow groove each have a groove depth of 0.5 mm to 2 mm. Invention [5] A tire according to any one of inventions [1] to [4], characterized in that the shoulder block is provided with an auxiliary groove branching from the first narrow groove or the second narrow groove and extending toward the tread side of the shoulder block. Invention [6] The tire according to any one of inventions [1] to [5], characterized in that the opening ends of the first narrow groove and the second narrow groove are present on the same side in the tire circumferential direction of each shoulder block. Invention [7] The tire according to any one of inventions [1] to [6], characterized in that the shoulder block is provided with a parallel auxiliary groove extending parallel to the first narrow groove or the second narrow groove. Invention [8] The tire according to any one of inventions [1] to [7], wherein the third narrow groove includes a straight portion extending parallel to the contour line of the side block. Invention [9] The tire according to any one of inventions [1] to [8], characterized in that the positions of the opening ends of the first narrow groove and the second narrow groove in the tire radial direction are different. [Explanation of symbols]

[0052] 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 protrusion 20 Narrow groove group 21 First narrow groove 22 Second narrow groove 23 Third narrow groove 24 Auxiliary groove 25 Parallel auxiliary groove 30 Recess CL Tire Equator B Block Group

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, When one side block is disposed at a position on the outer side in the tire width direction of two or more shoulder blocks adjacent to each other in the tire circumferential direction, and a combination of the two or more shoulder blocks and one side block is defined as a block group, A first narrow groove is provided on a side surface of one of the shoulder blocks included in the block group, the first narrow groove having one end opening into one of the shoulder lug grooves and the other end extending toward the side block, A second narrow groove is provided on a side surface of another of the shoulder blocks included in the block group, the second narrow groove having one end opening into another of the shoulder lug grooves and the other end extending toward the side block, a third narrow groove extending to connect the other end of the first narrow groove and the other end of the second narrow groove is provided on a top surface of the side block included in the block group, a tire characterized in that the first narrow groove, the second narrow groove, and the third narrow groove form a series of narrow groove groups extending continuously from one of the shoulder blocks included in the block group through the side block to another of the shoulder blocks.

2. 2. The tire according to claim 1, wherein the first narrow groove and the second narrow groove each have at least one bending point, and the third narrow groove has at least two bending points.

3. 3. The tire according to claim 1, wherein the first narrow groove, the second narrow groove, and the third narrow groove each have a groove width of 0.5 mm to 3 mm.

4. 3. The tire according to claim 1, wherein the first narrow groove, the second narrow groove, and the third narrow groove each have a groove depth of 0.5 mm to 2 mm.

5. 3. The tire according to claim 1, wherein the shoulder block is provided with an auxiliary groove branching from the first narrow groove or the second narrow groove and extending toward the tread side of the shoulder block.

6. 3. The tire according to claim 1, wherein an open end of the first narrow groove and an open end of the second narrow groove are located on the same side of each shoulder block in the tire circumferential direction.

7. 3. The tire according to claim 1, wherein the shoulder block is provided with a parallel auxiliary groove extending parallel to the first narrow groove or the second narrow groove.

8. 3. The tire according to claim 1, wherein the third narrow groove includes a straight portion extending parallel to a contour line of the side block.

9. The tire according to claim 1 or 2, characterized in that the positions of the opening ends of the first narrow groove and the second narrow groove in the tire radial direction are different.

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