Tire

Abstract

Provided is a tire with which snow performance is further improved. This tire includes a plurality of lug grooves 10 extending in the tire radial direction from a tread part 1 toward a side wall part 2, a plurality of shoulder blocks 21 divided into shoulder regions by the lug grooves 10, and a plurality of side blocks 22 divided into side regions by the lug grooves 10, wherein: the plurality of lug grooves 10 include first lug grooves 11 and second lug grooves 12 alternately arranged along the tire circumferential direction; the first lug grooves 11 each have a first widened part 11A in which the groove width is locally enlarged, and the second lug grooves 12 each have a second widened part 12A in which the groove width is locally enlarged; and the first widened parts 11A and the second widened parts 12A are located in mutually different positions in the tire radial direction.

Description

tire

[0001] The present invention relates to a tire intended for running on unpaved roads and the like, and more particularly to a tire that enables further improvement in snow performance.

[0002] Tires (e.g., all-terrain tires, all-terrain tires, etc.) designed for running on unpaved roads (uneven terrain, muddy terrain, sandy terrain, rocky areas, snow-covered roads, etc.) in addition to paved roads are required to have excellent off-road performance. On the other hand, tires (e.g., highway terrain tires, etc.) that are not specialized for off-road performance but have sufficient off-road performance and also exhibit excellent running performance on paved roads are also known. The latter tires tend to emphasize running performance on snowy roads among the unpaved roads mentioned above. In other words, excellent snow performance is required to enable stable running even during snowfall. In such tires, unevenness (e.g., side blocks) is provided not only in the tread portion that comes into contact with the road surface on paved roads but also in the side region (region between the tread portion and the sidewall portion) that may come into contact with mud, sand, stones, rocks, snow, etc. on unpaved or snowy roads, thereby achieving traction performance (see, for example, Patent Document 1). However, as mentioned above, when considering driving performance on paved roads, it tends to be difficult to add large irregularities to the side areas, and measures to further improve snow performance are required.

[0003] Japanese Patent Application Publication No. 2020-044882

[0004] An object of the present invention is to provide a tire that enables further improvement in snow performance.

[0005] In order to achieve the above object, the tire of the present invention has a tread portion extending circumferentially to form an annular shape, and a pair of sidewall portions arranged on either side of the tread portion. The tread portion has a surface with a pair of main grooves extending circumferentially along the tire equator on both sides, and the tire has shoulder regions located on the tire widthwise outer side of the main grooves and side regions adjacent to the tire widthwise outer side of the shoulder regions. The tire has a plurality of lug grooves extending radially from the tread portion toward the sidewall portions, a plurality of shoulder blocks defined in the shoulder regions by the lug grooves, and a plurality of side blocks defined in the side regions by the lug grooves, the plurality of lug grooves including first lug grooves and second lug grooves arranged alternately along the tire circumferential direction, the first lug grooves having a first widened portion where the groove width is locally expanded, and the second lug grooves having a second widened portion where the groove width is locally expanded, and the first widened portion and the second widened portion are positioned differently in the tire radial direction.

[0006] As described above, the tire of the present invention has a plurality of lug grooves extending radially from the tread portion toward the sidewall portion, a plurality of shoulder blocks, and a plurality of side blocks. Furthermore, the plurality of lug grooves include two types (first lug grooves and second lug grooves) with different radial positions of the widened portions (first widened portions and second widened portions), which are alternately arranged along the tire circumferential direction, resulting in a complex uneven shape extending from the shoulder region to the side region, effectively improving snow performance. In particular, because the effect is obtained by the radial positional relationship of the widened portions (first widened portions and second widened portions) formed in the lug grooves (first lug grooves and second lug grooves), excellent snow performance can be obtained even in an embodiment with small side blocks.

[0007] In the present invention, it is preferable that the first lug groove has a first widened portion adjacent to the shoulder block, and the second lug groove has a second widened portion adjacent to the side block, which improves the radial positional relationship of the widened portions (first and second widened portions) in a pair of circumferentially adjacent lug grooves (first and second lug grooves), which is advantageous for improving snow performance.

[0008] In the present invention, it is preferable that the maximum groove width of the first widened portion and the maximum groove width of the second widened portion are 1.2 to 7.0 times the groove width of the lug groove at the ground contact edge of the tread portion. By providing sufficient groove width in the widened portions (first widened portion and second widened portion), the widened portions (first widened portion and second widened portion) can easily grip snow on the road surface, and the difference in groove width between the widened portion and other portions makes the edge shape complex, which is advantageous for improving snow performance.

[0009] In the present invention, the shoulder blocks or side blocks preferably have recesses adjacent to the lug grooves that are recessed below the side surfaces of the shoulder blocks and the top surfaces of the side blocks, and the depth of these recesses is preferably smaller than the depth of the lug grooves adjacent to the recesses. This creates a surface (bottom of the recess) at a height intermediate between the side surfaces of the shoulder blocks and the top surfaces of the side blocks (the uppermost surfaces in the shoulder and side regions) and the bottoms of the lug grooves (the lowermost surfaces in the shoulder and side regions), creating an uneven shape with gradually varying heights (depths), which is advantageous for improving snow performance.

[0010] In this case, it is preferable to form a fine groove on the bottom surface of the recessed portion, which can add an edge effect due to the fine groove, which is advantageous for improving snow performance.

[0011] In the present invention, the radial distance Hs from the ground contact edge to the radially innermost side block is preferably 15% to 40% of the tire cross-sectional height SH. This arrangement allows the side blocks to be positioned appropriately in the radial direction of the tire, which is advantageous for improving snow performance. Furthermore, the radial size of the side blocks can be ensured to be appropriate, which is also advantageous for improving snow performance.

[0012] In the present invention, the term "ground contact edge" refers to both ends in the axial direction of the tire of the ground contact area formed when the tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load. The term "standard rim" refers to the rim determined for each tire by the standard system that includes the standard on which the tire is based, and is, for example, the standard rim in the case of JATMA, the "Design Rim" in the case of TRA, or the "Measuring Rim" in the case of ETRTO. "Normal internal pressure" refers to the air pressure determined for each tire by the respective standards, including the standards on which the tire is based, and is the maximum air pressure in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO, but is set to 180 kPa when the tire is for a passenger car. The "normal load" is the load determined for each tire by each standard in the standard system including the standard on which the tire is based, and is the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO.

[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 interior thereof can be filled with air, an inert gas such as nitrogen, or other gases.

[0014] Fig. 1 is a meridian half cross-sectional view of a tire according to an embodiment of the present invention. Fig. 2 is a front view showing a shoulder region and a side region of a tire according to an embodiment of the present invention. Fig. 3 is an explanatory diagram schematically showing the cross-sectional shapes of the shoulder region and the side region of a tire according to an embodiment of the present invention.

[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 Figure 1, it comprises a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. In Figure 1, the symbol CL indicates the tire equator, and the symbol E indicates the contact edge. Although not depicted in Figure 1 because it is a meridian half cross section, the tread portion 1, sidewall portions 2, and bead portions 3 each extend in the tire circumferential direction and form an annular shape, thereby constituting the basic toroidal structure of a pneumatic tire. The following explanation using Figure 1 will be basically based on the meridian cross section shown, but each tire constituent member also extends in the tire circumferential direction and forms 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 multiple reinforcing cords extending in the tire radial direction and folded back from the inner side to the outer side in the tire width direction around bead cores 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of each bead core 5, and this bead filler 6 is wrapped by the main portion and folded back portion of the carcass layer 4. Meanwhile, multiple belt layers 7 (two layers in FIG. 1 ) are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes multiple reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to 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, for example, in the range of 10° to 40°. Furthermore, at least one belt reinforcing layer 8 (two layers in FIG. 1 ) is provided on the outer periphery 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.

[0018] Because 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. Furthermore, the detailed shape (tread pattern) of the grooves and blocks formed on the surface of the tread portion 1 is not particularly limited, except for the shoulder regions described below. The tread pattern in the portions excluding the shoulder regions described below is preferably a block-based pattern suitable for unpaved roads. The present invention can be applied to various tires, including non-pneumatic tires, as long as they have regions (regions corresponding to the shoulder and side regions) that may come into contact with snow or the like on the road surface when traveling on unpaved roads (snowy road surfaces).

[0019] As shown in FIG. 1 , a pair of main grooves 9 are formed on the surface of the tread portion 1, extending circumferentially around the entire tire on both sides of the tire equator CL. The main grooves 9 preferably have a zigzag shape in which linear portions inclined in one direction relative 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 9 is the center region (a region in which any tread pattern can be adopted without particular structural limitations in the present invention), and the regions on the outer side of each main groove 9 in the tire width direction are shoulder regions. When three or more main grooves 9 are provided, the regions on the outer side of the pair of outermost main grooves 9 in the tire width direction are shoulder regions. The main grooves 9 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 9 mm to 15 mm.

[0020] In the present invention, the region adjacent to the aforementioned shoulder region on the outer side in the tire width direction is referred to as the side region. In the illustrated example, a protrusion P protruding from the surface of the sidewall portion 2 and extending around the entire tire circumference is present at the boundary between the shoulder region and the side region. This protrusion P is an element formed due to the split position of the tire mold, and is therefore not necessarily provided and is not an element that does not need to be considered in the present invention (for example, even if the protrusion P crosses a groove, the groove is considered to be a single continuous groove). However, because it is an element that may be formed inevitably during manufacturing, the shoulder region and side region may be distinguished based on the protrusion P. In other words, the shoulder region can be considered to be the region adjacent to the protrusion P on the outer side in the tire width direction, and the side region can be considered to be the region adjacent to the protrusion P on the inner side in the tire width direction. Regardless of the presence or absence of the protrusion P, the boundary between the shoulder region and the side region should be located within a range of 15% to 40%, more preferably 20% to 25%, of the tire cross-sectional height SH from the tire equator CL position toward the tire radially inward.

[0021] When the tire is viewed from the sidewall portion 2 side as shown in Figure 2, a plurality of lug grooves 10 extending in the tire radial direction from the tread portion 1 toward the sidewall portion 2 are formed in the shoulder region and side region. The plurality of lug grooves 10 are arranged at intervals in the tire circumferential direction to define a plurality of blocks (shoulder blocks 21 and side blocks 22 described below). The ends of the plurality of lug grooves 10 on the outer side in the tire radial direction (inner side in the tire width direction) are connected to the main grooves 9. When the main grooves 9 have a zigzag shape, it is preferable that the lug grooves 10 are connected to the bending points of each main groove 9 on the outer side in the tire width direction.

[0022] The lug grooves 10 define a plurality of shoulder blocks 21 in the shoulder region and a plurality of side blocks 22 in the side region. Since the present invention is directed to the structure of the tire as viewed from the sidewall portion 2 side as shown in Figure 2, the shoulder blocks 21 are basically described with respect to their side surfaces (surfaces radially inward of the contact edge E), and the side blocks 22 are described with respect to their top surfaces (surfaces that protrude most from the surface of the sidewall portion 2).

[0023] The multiple lug grooves 10 include first lug grooves 11 and second lug grooves 12 arranged alternately along the tire circumferential direction. In other words, in the tire of the present invention, pairs of grooves each consisting of a first lug groove 11 and a second lug groove 12 are repeatedly arranged in the tire circumferential direction. The first lug groove 11 has a first widened portion 11A in which the groove width is locally expanded, and the second lug groove 12 has a second widened portion 12A in which the groove width is locally expanded. The first widened portion 11A and the second widened portion 12A are located at different positions in the tire radial direction.

[0024] Because the lug grooves 10 (first lug grooves 11 and second lug grooves 12) and their widened portions (first widened portion 11A and second widened portion 12A) are configured in this manner, the uneven shape from the shoulder region to the side region becomes complex, effectively improving snow performance. In particular, because the effect is achieved by the radial positional relationship of the widened portions (first widened portion 11A and second widened portion 12A) formed in the lug grooves 10 (first lug grooves 11 and second lug grooves 12), excellent snow performance can be obtained without significantly increasing the size of the side blocks 22.

[0025] If the multiple lug grooves 10 do not have widened portions (first widened portions 11A and second widened portions 12A), the effect of the widened portions biting into snow and the edge effect caused by the bending of the edge shape of the lug grooves 10 due to the difference in groove width between the widened portions and other portions cannot be expected, and the effect of improving snow performance is limited. If the first widened portions 11A and the second widened portions 12A are located at the same position in the tire radial direction (i.e., if all the lug grooves 10 have the same shape and there is no distinction between the first lug grooves 11 and the second lug grooves 12), the uneven shape from the shoulder region to the side region is not sufficiently complex, and the effect of improving snow performance is limited.

[0026] The first widened portion 11A and the second widened portion 12A may be located at different positions in the tire radial direction, but preferably, as shown in the figure, the first lug groove 11 has the first widened portion 11A at a position adjacent to the shoulder block 21, and the second lug groove 12 has the second widened portion 12A at a position adjacent to the side block 22. This positional relationship improves the positional relationship in the tire radial direction between the widened portions (first widened portion 11A and second widened portion 12A) in a pair of circumferentially adjacent lug grooves 10 (first lug groove 11 and second lug groove 12), which is advantageous for improving snow performance.

[0027] As described above, the widened portion is a portion where the groove width of each lug groove 10 is locally expanded, but the groove width may be expanded stepwise as in the illustrated first widened portion 11A, or may be expanded gradually as in the illustrated second widened portion 12A. In either case, the maximum groove width of the widened portion (first widened portion 11A and second widened portion 12A) is preferably 1.2 to 7.0 times the groove width of the lug groove 10 at the ground contact edge E of the tread portion 1. More specifically, when the first widened portion 11A is located adjacent to the shoulder block 21 in the first lug groove 11 as in the illustrated example, the maximum groove width W1 of the first widened portion 11A is preferably 1.2 to 7.0 times, more preferably 1.2 to 3.0 times, and even more preferably 1.5 to 2.5 times the groove width We of the first lug groove 11 at the ground contact edge E of the tread portion 1. Furthermore, when the second lug groove 12 has a second widened portion 12A adjacent to the side block 22 as in the illustrated example, the maximum groove width W2 of the second widened portion 12A is preferably 1.2 to 7.0 times, more preferably 3.0 to 7.0 times, and even more preferably 4.0 to 6.0 times the groove width We of the second lug groove 12 at the ground contact edge E of the tread portion 1. Having sufficient groove width in the widened portions (first widened portion 11A and second widened portion 12A) makes it easier for these widened portions to grip snow on the road surface, and the difference in groove width between the widened portion and other portions complicates the edge shape, which is advantageous for improving snow performance. If the maximum groove width of the widened portions (first widened portion 11A and second widened portion 12A) is less than 1.2 times the groove width of the lug groove 10 at the ground contact edge E of the tread portion 1, the groove width is barely increased, and the effect of providing the widened portions is limited. If the maximum groove width of the widened portion (first widened portion 11A and second widened portion 12A) exceeds 7.0 times the groove width of the lug groove 10 at the ground contact edge E of the tread portion 1, it becomes difficult to maintain the block rigidity of the portion adjacent to the widened portion, which may affect durability.

[0028] The groove width of the lug grooves 10 is not particularly limited, but is preferably 30% to 98%, more preferably 50% to 80%, of the groove width of the main groove 10. The groove depth of the lug grooves 10 is not particularly limited, but the groove depth of the lug grooves 10 on the tread surface of the tread portion 1 (inside the ground contact edge E in the tire width direction) is preferably 75% to 100%, more preferably 80% to 98% of the groove depth of the main groove 10. The groove depth of the lug grooves 10 in the side regions is preferably 0.2 mm to 5.0 mm, more preferably 0.3 mm to 3.0 mm.

[0029] In the present invention, the shoulder block 21 or the side block 22 preferably has a recess 31 adjacent to the lug groove 10. As shown in FIG. 3 , the recess 31 is a portion recessed from the side surface of the shoulder block 21 and the top surface of the side block 22, and the depth of the recess 31 is smaller than the depth of the lug groove 10 at a position adjacent to the recess 31. In other words, the recess 31 is a portion that is raised above the groove bottom of the lug groove 10 and has a surface recessed from the side surface of the shoulder block 21 and the top surface of the side block 22. Furthermore, it is preferable that the recess 31 does not connect to any groove other than the adjacent lug groove 10, and that its periphery is surrounded by the side surface of the shoulder block 21 or the top surface of the side block 22. By providing the recess 31 in this manner, a surface (bottom surface of the recess 31) is formed at an intermediate height between the side surface of the shoulder block 21 and the top surface of the side block 22 (the uppermost surface in the shoulder region and side region) and the groove bottom of the lug groove 10 (the lowermost surface in the shoulder region and side region), creating an uneven shape with a gradually changing height (depth), which is advantageous for improving snow performance.

[0030] The recesses 31 may be provided in either the shoulder blocks 21 or the side blocks 22, but are preferably provided on the side surfaces of the shoulder blocks 21, as shown in the example of Figure 2. In particular, it is preferable to provide the recesses 31 adjacent to the widened portions of the lug grooves 10 (first widened portions 11A of the first lug grooves 11) on the side surfaces of the shoulder blocks 21. This provides a good balance between the increase or decrease in groove width due to the widened portions and the height difference of the uneven shape due to the recesses 31, which is advantageous for improving snow performance.

[0031] When providing the recess 31, the recess amount d1 from the side surface of the shoulder block 21 or the top surface of the side block 22 to the bottom surface of the recess 31 is preferably 0.2 mm or more, more preferably 0.3 mm to 1.5 mm. Furthermore, the difference d2 between the recess amount d1 and the groove depth of the lug groove 10 is preferably 0.2 mm or more, more preferably 0.3 mm to 1.5 mm. Note that in Figure 3, the height differences of each part are exaggerated to clearly show the recess amount d1 and the difference d2.

[0032] As shown in the figure, narrow grooves 32 can also be formed on the bottom surfaces of the recesses 31 provided as described above. Providing narrow grooves 32 in this manner adds an edge effect to the narrow grooves 32, which is advantageous for improving snow performance. While the depth of the narrow grooves 32 is not particularly limited, it is preferable that the deepest portions of the narrow grooves 32 be flush with the groove bottoms of the lug grooves 10 or higher than the groove bottoms of the lug grooves 10. In other words, the groove depth d3 of the narrow grooves is preferably 50% to 100%, more preferably 70% to 100%, of the aforementioned d2 (the difference between the recess amount d1 and the groove depth of the lug grooves 10). Furthermore, the groove width of the narrow grooves 32 is not particularly limited, but is preferably 0.2 mm to 4.0 mm, more preferably 0.5 mm to 2.0 mm. The extension direction of the narrow grooves is not particularly limited and can be set to any inclined direction. In other words, while the narrow grooves 32 extend along the tire circumferential direction in the illustrated example, they may extend at an angle relative to the tire circumferential direction or along the tire radial direction. Regardless of the direction in which the narrow grooves 32 extend, an edge effect according to the extension direction can be added, thereby improving snow performance.

[0033] The side blocks 13 are preferably positioned within an appropriate radial range of the tire so that they can adequately contact the road surface when the tire is buried in mud or other debris while traveling on unpaved roads. Specifically, the radial distance Hs from the ground contact edge E to the radially innermost end of each side block 13 is preferably 15% to 40%, more preferably 20% to 35%, of the tire cross-sectional height SH. Positioning the side blocks 13 within an appropriate radial range of the sidewall portion 2 in this manner effectively improves driving performance on unpaved roads. Furthermore, since the size of the side blocks 13 can be appropriately ensured, this is advantageous for ensuring block rigidity and improving cut resistance. If the distance Hs is less than 15% of the tire cross-sectional height SH, the side blocks 13 become small, making it difficult to maintain good block rigidity. If the distance Hs exceeds 40% of the tire cross-sectional height SH, the side blocks 13 may be too large, potentially affecting normal driving performance.

[0034] The present invention will be further explained below with reference to examples, but the scope of the present invention is not limited to these examples.

[0035] Table 1 shows the tire size LT265 / 70R17 115H, the basic structure (cross-sectional structure) shown in Figure 1, and the presence or absence of a first widened portion in the first lug groove, the presence or absence of a second widened portion in the second lug groove, the difference in the positions of the first and second widened portions, the ratio W1 / We of the maximum groove width W1 of the first widened portion to the groove width We of the lug groove at the ground contact edge of the tread portion, the ratio W2 / We of the maximum groove width W1 of the second widened portion to the groove width We of the lug groove at the ground contact edge of the tread portion, the presence or absence of recesses formed in positions adjacent to the lug grooves, the presence or absence of narrow grooves in the recesses, and the ratio Hs / SH x 100 [%] of the tire radial distance Hs from the ground contact edge to the tire radially innermost side block to the tire cross-sectional height SH. Pneumatic tires of Conventional Example 1, Comparative Examples 1 to 4, and Examples 1 to 5 were produced.

[0036] The column "Presence or Absence of First Widened Portion in First Lug Groove" in Table 1 indicates whether one (first lug groove) of a pair of circumferentially adjacent lug grooves (first lug groove and second lug groove) has a widened portion (first widened portion). Similarly, the column "Presence or Absence of Second Widened Portion in Second Lug Groove" indicates whether the other (second lug groove) of a pair of circumferentially adjacent lug grooves (first lug groove and second lug groove) has a widened portion (second widened portion). In these columns, when a widened portion (first widened portion, second widened portion) is present, its position is also noted. That is, when a widened portion is provided in a shoulder region (a position adjacent to a shoulder block), it is noted as "present (shoulder)," and when a widened portion is provided in a side region (a position adjacent to a side block), it is noted as "present (side)." The column "Difference in Position of First / Second Widened Portion" indicates whether there is a difference in the radial position of the first widened portion and the second widened portion.

[0037] Regarding the "presence or absence of recesses" column in Table 1, in the example having recesses, the recesses are provided in the shoulder blocks (on both sides of the position adjacent to the first widened portion of the first lug groove) as shown in the example, and the recesses are recessed deeper than the side surfaces of the shoulder blocks and shallower than the first widened portion of the shoulder lug groove. Similarly, regarding the "presence or absence of narrow grooves" column, in the example having narrow grooves, two narrow grooves extending along the tire circumferential direction are provided in the groove bottom of each recess on both sides of the first lug groove as shown in the example. The deepest portions of the narrow grooves are flush with the groove bottom of the first lug groove.

[0038] The snow performance of these pneumatic tires was evaluated by the following evaluation method, and the results are shown in Table 1.

[0039] Snow Performance Each test tire was mounted on a wheel with a rim size of 17x8J, inflated to an air pressure of 230 kPa, and mounted on a test vehicle (four-wheel drive SUV). A test driver performed a sensory evaluation of the handling stability on a test course consisting of a snowy road 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 snow performance.

[0040]

[0041] As is clear from Table 1, the pneumatic tires of Examples 1 to 5 had sufficiently improved snow performance compared to Conventional Example 1. On the other hand, Comparative Examples 1 to 4 showed a slight improvement in the snow performance index value when compared to Conventional Example 1, which was provided with lug grooves without widened portions, but did not achieve a sufficient improvement effect. In more detail, Comparative Examples 1 and 2 had widened portions provided in only one of a pair of circumferentially adjacent lug grooves (first lug groove and second lug groove), and widened portions were provided in every other lug groove, so the effect of improving snow performance was limited. Comparative Examples 3 and 4 did not have sufficient improvement in snow performance because there was no difference in the radial positions of the first widened portion and the second widened portion.

[0042] REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer 9 main groove 10 lug groove 11 first lug groove 11A first widened portion 12 second lug groove 12A second widened portion 21 shoulder block 22 side block 31 recess 32 narrow groove P protrusion CL tire equator E ground contact edge

Claims

1. A tire having a tread portion extending circumferentially and forming an annular shape, and a pair of sidewall portions disposed on either side of the tread portion, and a pair of main grooves extending circumferentially on either side of the tire equator on the surface of the tread portion, and having shoulder regions located on the outer side of the main grooves in the tire width direction, and side regions adjacent to the outer side of the shoulder regions in the tire width direction, the tire having a plurality of lug grooves extending radially from the tread portion toward the sidewall portions, a plurality of shoulder blocks defined in the shoulder regions by the lug grooves, and a plurality of side blocks defined in the side regions by the lug grooves, the plurality of lug grooves including first lug grooves and second lug grooves arranged alternately along the tire circumferential direction, the first lug grooves having a first widened portion where the groove width is locally expanded, and the second lug grooves having a second widened portion where the groove width is locally expanded, the first widened portion and the second widened portion being positioned differently in the tire radial direction.

2. The tire according to claim 1, wherein the first lug groove has the first widened portion at a position adjacent to the shoulder block, and the second lug groove has the second widened portion at a position adjacent to the side block.

3. A tire as described in claim 1 or 2, characterized in that the maximum groove width of the first widened portion and the maximum groove width of the second widened portion are 1.2 to 7.0 times the groove width of the lug groove at the ground contact edge of the tread portion.

4. A tire as described in any one of claims 1 to 3, characterized in that the shoulder block or the side block has a recessed portion at a position adjacent to the lug groove that is recessed deeper than the side surface of the shoulder block and the top surface of the side block, and the depth of the recessed portion is smaller than the groove depth of the lug groove at a position adjacent to the recessed portion.

5. A tire according to claim 4, characterized in that a narrow groove is formed on the bottom surface of the recessed portion.

6. A tire according to any one of claims 1 to 5, characterized in that the distance Hs in the tire radial direction from the ground contact edge to the innermost side of the side block in the tire radial direction is 15% to 40% of the tire cross-sectional height SH.

Images