Tire

Abstract

To provide a tire capable of further improving snow performance.SOLUTION: In a tire including a plurality of lug grooves 10 extending in a tire radial direction from a tread portion 1 toward a sidewall portion 2, a plurality of shoulder blocks 21 defined in a shoulder region by the lug grooves 10, and a plurality of side blocks 22 defined in a side region by the lug grooves 10, the plurality of lug grooves 10 include a first lug groove 11 and a second lug groove 12 alternately arranged along a tire circumferential direction, and the first lug groove 11 includes a first widened portion side 11A having a locally widened groove. The second lug grooves 12 each have a second widened portion side 12A where the groove is locally widened, and the positions of the first widened portion side 11A and the second widened portion side 12A in the tire radial direction are different from each other.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 that enables further improvement in snow performance. [Background technology]

[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 aforementioned unpaved roads. In other words, excellent snow performance is required to enable stable running even during snowfall. In such tires, not only the tread portion that comes into contact with the road surface on paved roads, but also 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 is provided with unevenness (e.g., side blocks) to obtain 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2020-044882 Summary of the Invention [Problem to be solved by the invention]

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

[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, and has a pair of main grooves on the surface of the tread portion extending along the tire circumferential direction on both sides of the tire equator, and is equipped with 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, and is characterized in that the tire has a plurality of lug grooves extending in the tire radial direction 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 being positioned differently in the tire radial direction. [Effects of the Invention]

[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) of widened portions (first widened portions and second widened portions) with different radial positions, 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 achieved 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 achieved even in an embodiment in which the side blocks are small.

[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 midway 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 this invention, the term "tread edge" refers to both axial ends of the tire's contact area formed when a 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 specified for each tire by the standard system, including the standard on which the tire is based. For example, the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. The term "standard internal pressure" refers to the air pressure specified for each tire by the standard system, including the standard on which the tire is based. For JATMA, the maximum air pressure is specified, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" table for TRA, and the "INFLATION PRESSURE" for ETRTO. However, when the tire is for a passenger car, the standard pressure is 180 kPa. "Normal load" is the load specified for each tire by each standard in the standard system, including the standard on which the tire is based. In the case of JATMA, it is the maximum load capacity, in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "LOAD CAPACITY".

[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. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] 1 is a front view showing a shoulder region and a side region of a tire according to an embodiment of the present invention. [Figure 3] 1 is an explanatory diagram schematically showing the cross-sectional shapes of a shoulder region and a side region of a tire according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE 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 FIG. 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 FIG. 1 , the symbol CL indicates the tire equator, and the symbol E indicates the contact edge. Although not depicted in FIG. 1 because it is a meridian 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 FIG. 1 is basically based on the meridian cross section shown, but each tire component 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 a plurality of 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 a bead core 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead core 5, and this bead filler 6 is wrapped by the main portion and 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 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, 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 for 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 types of 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 sides 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 sides 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 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, since it is an element that may be inevitably formed 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 toward the inner side in the tire width direction.

[0021] When the tire is viewed from the sidewall portion 2 side as shown in FIG. 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] These 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 in terms of their side surfaces (surfaces radially inward of the contact edge E), and the side blocks 22 are described in terms of their top surfaces (surfaces that protrude most from the surface of the sidewall portion 2).

[0023] The plurality of 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 positioned differently 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 positional relationship in the tire radial direction 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 to hold in snow and the edge effect due to the bending of the edge shape of the lug grooves 10 caused by 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 lug grooves 10 have the same shape and do not include the first lug groove 11 and the second lug groove 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 lug grooves 10 (first lug groove 11 and second lug groove 12) adjacent in the tire circumferential direction, which is advantageous for improving snow performance.

[0027] As described above, the widened portion is a portion in each lug groove 10 where the groove width 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 provided in a position 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 shown in the 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. Furthermore, the difference in groove width between the widened portion and other portions creates a complex 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%, and 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 (on the inner side in the tire width direction from the ground contact edge E) is preferably 75% to 100%, and 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 mm, and 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 at a position 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 grooves 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 on the side surfaces of the shoulder blocks 21 adjacent to the widened portions of the lug grooves 10 (first widened portions 11A of the first lug grooves 11). 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, and 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, and 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 be formed on the bottom surfaces of the recesses 31 provided as described above. Providing the narrow grooves 32 in this manner adds an edge effect to the narrow grooves 32, which is advantageous for improving snow performance. The depth of the narrow grooves 32 is not particularly limited, but it is preferable that the deepest portions of the narrow grooves 32 are flush with the groove bottoms of the lug grooves 10 or are 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). 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 arranged within an appropriate range in the tire radial direction 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 distance Hs in the tire radial direction 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. Arranging the side blocks 13 within an appropriate range in the tire radial direction 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 ensured appropriately, this is advantageous for ensuring block rigidity and improving cut resistance. If the distance A 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. [Example]

[0035] Table 1 shows the tire size LT265 / 70R17 115H, the basic structure (cross-sectional structure) shown in Figure 1, and the following pneumatic tires were produced: Conventional Example 1, Comparative Examples 1 to 4, and Examples 1 to 5. The tire size was LT265 / 70R17 115H. The basic structure (cross-sectional structure) shown in Figure 1 had the following characteristics: presence or absence of first widened portions in the first lug grooves; presence or absence of second widened portions in the second lug grooves; 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; 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; the presence or absence of recesses formed 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.

[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 indicated. That is, if the widened portion is provided in the shoulder region (position adjacent to the shoulder block), it is indicated as "Present (Shoulder)," and if the widened portion is provided in the side region (position adjacent to the side block), it is indicated 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 with 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 with narrow grooves, two narrow grooves extending along the tire circumferential direction are provided at 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 using the following evaluation method, and the results are shown in Table 1.

[0039] Snow performance Each test tire was mounted on a 17x8J rim wheel, inflated to 230kPa, and mounted on a test vehicle (four-wheel drive SUV). A test driver then conducted 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 Conventional Example 1's value being 100. The higher the index value, the better the snow performance.

[0040] [Table 1]

[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. More specifically, in Comparative Examples 1 and 2, a widened portion was provided in only one of a pair of circumferentially adjacent lug grooves (first lug groove and second lug groove), and a widened portion was provided in every other lug groove, so the effect of improving snow performance was limited. In Comparative Examples 3 and 4, there was no difference in the radial positions of the first widened portion and the second widened portion, so snow performance could not be sufficiently improved.

[0042] The present disclosure encompasses the following inventions. Invention [1] A tire having a tread portion extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, and a pair of main grooves extending along the tire circumferential direction on both sides of the tire equator on the surface of the tread portion, and having shoulder regions located on the tire widthwise outer sides of the main grooves and side regions adjacent to the tire widthwise outer sides of the shoulder regions, a plurality of lug grooves extending radially from the tread portion toward the sidewall portion, a plurality of shoulder blocks defined in the shoulder region by the lug grooves, and a plurality of side blocks defined in the side region by the lug grooves, wherein the plurality of lug grooves include 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 widened, and the second lug grooves having a second widened portion where the groove width is locally widened, and the first widened portion and the second widened portion are positioned differently in the tire radial direction. Invention [2] The tire according to invention [1], characterized in that 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. Invention [3] A tire according to invention [1] or [2], characterized in that the maximum groove width of the first widening portion and the maximum groove width of the second widening portion are 1.2 to 7.0 times the groove width of the lug groove at the ground contact edge of the tread portion. Invention [4] A tire according to any one of inventions [1] to [3], characterized in that the shoulder block or the side block has a recessed portion 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. Invention [5] The tire according to invention [4], characterized in that a narrow groove is formed on the bottom surface of the recess. Invention [6] A tire according to any one of inventions [1] to [5], characterized in that the tire radial distance Hs from the ground contact edge to the tire radially innermost side of the side block is 15% to 40% of the tire cross-sectional height SH. [Explanation of symbols]

[0043] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt reinforcement layer 9 Main groove 10 Lug groove 11 First lug groove 11A First widening section 12 Second lug groove 12A Second widening section 21 Shoulder Block 22 Side Block 31 Recess 32 Narrow groove P protrusion CL Tire Equator E Ground end

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 in the tire circumferential direction on both sides of the tire equator on the surface of the tread portion, and a shoulder region located on the outer side of the main groove in the tire width direction, and a side region adjacent to the outer side of the shoulder region in the tire width direction, a plurality of lug grooves extending radially from the tread portion toward the sidewall portion, a plurality of shoulder blocks defined in the shoulder region by the lug grooves, and a plurality of side blocks defined in the side region by the lug grooves, wherein the plurality of lug grooves include 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 widened, and the second lug grooves having a second widened portion where the groove width is locally widened, and the first widened portion and the second widened portion are positioned differently in the tire radial direction.

2. 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. The tire according to claim 1 or 2, characterized in that the maximum groove width of the first widening portion and the maximum groove width of the second widening 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. 3. The tire according to claim 1, wherein the shoulder block or the side block has a recess 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 recess is smaller than the groove depth of the lug groove at a position adjacent to the recess.

5. The tire according to claim 4, wherein a narrow groove is formed on the bottom surface of the recess.

6. 3. The tire according to claim 1, wherein a distance Hs in the tire radial direction from a ground contact edge to the innermost side of the side block in the tire radial direction is 15% to 40% of a tire cross-sectional height SH.

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