Tire

Abstract

Provided is a tire with which snow performance can be improved without impairing cut resistance. The tire according to the present invention includes: a plurality of shoulder blocks 12 in a shoulder area of a tread part 1; and a plurality of side blocks 13 in a side area adjacent to the outside of the shoulder area in the tire width direction so that one of the side blocks 13 is disposed at a position on the outside in the tire width direction of a block group consisting of corresponding two or more shoulder blocks that are of the plurality of shoulder blocks 12 and are adjacent to each other in the tire circumferential direction. The tire includes: a shoulder lug groove 11 that is bent to one side in the tire circumferential direction and is on a side surface of a corresponding one of the shoulder blocks 12; a first side groove 14a connected to a corresponding one of the shoulder lug grooves 11 and extending linearly to partition corresponding side blocks 13; a second side groove 14b connected to a corresponding one of the shoulder lug grooves 11 and bent and terminated in a corresponding one of the side blocks 13; and a linear projection 20 at least partially extending in parallel with the contour line of a corresponding one of the side blocks 13 and a corresponding one of the shoulder blocks 11.

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 improved snow performance without impairing cut resistance.

[0002] Tires (e.g., all-terrain tires, highway terrain tires, all-terrain tires, etc.) designed for running on unpaved roads (uneven terrain, muddy terrain, sandy terrain, rocky areas, etc.) in addition to paved roads are required to have excellent off-road performance. They are also required to have excellent snow performance to enable stable running even during snowfall. In particular, in recent years, snow performance has become increasingly important, and tires are required to perform sufficiently even on snowy roads in extremely cold climates. 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 (the 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). Increasing the groove component of such side blocks to enhance the edge effect increases the groove area, making it difficult to ensure block rigidity, which raises concerns about the impact on cut resistance. Therefore, there is a demand for improved snow performance without compromising cut resistance, achieving a high level of compatibility between these two performance characteristics.

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

[0004] An object of the present invention is to provide a tire that enables improved snow performance without impairing cut resistance.

[0005] The tire of the present invention for achieving the above object includes a tread portion extending in a circumferential direction of the tire and forming an annular ring, and a pair of sidewall portions disposed on both sides of the tread portion, the tire having a surface of the tread portion having a pair of main grooves extending in 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, the shoulder region being 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 in the tire circumferential direction, and a side region adjacent to the shoulder region on the outer side in the tire width direction is provided with a plurality of side blocks protruding from an outer surface of the sidewall portion, and two or more of the shoulder blocks adjacent in the tire circumferential direction are provided with a plurality of side blocks protruding from an outer surface of the sidewall portion, a first side groove that is provided between adjacent side blocks in the tire circumferential direction and connects to the shoulder lug groove, extending linearly along the tire radial direction, and a second side groove that is connected to the shoulder lug groove, extending along the tire radial direction, and bending and terminating within the side block; linear protrusions that extend across the side blocks and shoulder blocks are formed on the side surfaces of the side blocks and shoulder blocks, and at least a portion of the linear protrusions extend parallel to the contour lines of the side blocks and shoulder blocks.

[0006] The tire of the present invention provides multiple side blocks in the side region to improve snow performance. Each side block is positioned on the tire widthwise outer side of a block group consisting of two or more circumferentially adjacent shoulder blocks. Therefore, the block group and the side blocks function as a single large block, thereby enhancing block rigidity and improving cut resistance. Furthermore, the block rigidity is also ensured at the point where the second side grooves provided within the side blocks terminate within the blocks, thereby improving cut resistance. Meanwhile, the shoulder lug grooves and second side grooves have bent portions, enhancing the edge effect and thereby improving snow performance. Furthermore, the linear protrusions, as described above, extend parallel to the contours of the side blocks and shoulder blocks (i.e., parallel to the edges of the shoulder lug grooves and first and second side grooves), thereby efficiently enhancing the edge effect of the linear protrusions and effectively improving snow performance. These combined effects enable a high level of both cut resistance and snow performance.

[0007] In the present invention, the linear protrusion preferably includes a portion connecting the terminal end of the second side groove with the first side groove and extending parallel to the radially inner contour line of the side block. By connecting the first side groove with the second side groove in this manner, the rigidity of the side block can be improved while ensuring snow column shearing, which is advantageous for achieving both snow performance and cut resistance.

[0008] In the present invention, the tip of the second side groove preferably has a tapered shape toward its terminal end, which is advantageous for preventing a decrease in block rigidity near the terminal end of the second side groove and improving cut resistance.

[0009] In the present invention, it is preferable that the bending angle θi of the shoulder lug grooves is 60° to 160°, and that the second side grooves are bent in the same direction as the shoulder lug grooves and that the bending angle θii of the second side grooves is 60° to 160°. This improves the bending shapes of the shoulder lug grooves and the second side grooves, which is advantageous for achieving both snow performance and cut resistance.

[0010] In the present invention, the radial distance A from the ground contact edge to the radially innermost side of the side block is preferably 15% to 40% of the tire cross-sectional height SH. This allows the side block to be positioned appropriately in the radial direction of the tire, which is advantageous for improving snow performance. Furthermore, this allows the radial size of the side block to be appropriately secured, which is advantageous for ensuring block rigidity and improving cut resistance.

[0011] 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.

[0012] 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.

[0013] 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 the tire according to an embodiment of the present invention. Fig. 3 is an explanatory diagram showing a simplified portion of Fig. 2.

[0014] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0015] 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.

[0016] 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.

[0017] 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).

[0018] As shown in Figures 1 and 2, a pair of main grooves 10 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 10 preferably have a zigzag shape in which linear sections inclined in one direction relative to the tire circumferential direction and linear sections inclined in the other direction are alternately connected in the tire circumferential direction. The region between the pair of main grooves 10 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 10 in the tire width direction are the 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 9 mm to 15 mm.

[0019] A land portion (shoulder land portion) defined on the outer side of the main groove 10 in the tire width direction is provided with shoulder lug grooves 11 extending outward in the tire width direction from the main groove 10. A plurality of shoulder lug grooves 11 are provided at intervals in the tire circumferential direction. These shoulder lug grooves 11 define the shoulder land portion into a plurality of blocks (shoulder blocks 12). When the main grooves 10 have a zigzag shape, the shoulder lug grooves 11 are preferably connected to the bending points of each main groove 10 on the outer side in the tire width direction. The groove width of the shoulder lug grooves 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 grooves 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.

[0020] When the region adjacent to the shoulder region on the outer side in the tire width direction is defined as a 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 protrusion 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, 0.5 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 circumferentially adjacent shoulder blocks 12. For example, in the illustrated example, one side block 13 is disposed on the outer side in the tire width direction of two shoulder blocks 12. In other words, a groove (first side groove 14a described below) extending along the tire width direction (tire radial direction) is formed between circumferentially adjacent side blocks 13, and this first side groove 14a is connected to at least every other shoulder lug groove 11 disposed at intervals in the tire circumferential direction. Between the shoulder lug grooves 11 and first side grooves 14a connected in this manner, one side block 13 and two or more shoulder blocks 12 (and one or more shoulder lug grooves 11 that are not connected to the side groove 14) are arranged.

[0021] 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 A from the ground contact edge E to the radially innermost end of each side block 13 is preferably 15% to 40%, more preferably 25% 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 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 A exceeds 40% of the tire cross-sectional height SH, the side blocks 13 may be too large, potentially affecting normal driving performance.

[0022] In the illustrated example, a protrusion 15 protruding from the sidewall surface and extending around the entire tire circumference is present at the boundary between the outer side 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). This protrusion 15 is an element formed due to the split position of the tire mold, and is therefore not necessarily required. Although this protrusion 15 is not a necessary element for the present invention, it is an element that may be formed during manufacturing, so the shoulder region and side region may be distinguished based on the protrusion 15. In other words, the shoulder region can be considered to be the region adjacent to the tire widthwise inward of the protrusion 15, and the side region can be considered to be the region adjacent to the tire radially inward of the protrusion 15. Regardless of the presence or absence of the protrusion 15, the boundary between the shoulder region and the side region should preferably 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.

[0023] The present invention relates to the shapes of grooves and protrusions when the combination of two or more shoulder blocks 12 (side surfaces) and one side block 13 is viewed as a substantially large block. First, in the present invention, the shoulder lug groove 11 is bent toward one side in the tire circumferential direction when viewed from the side of the shoulder block 12, as shown in FIG. 2 . In other words, the shoulder lug groove 11 has a bent shape consisting of a main body portion 11a extending linearly from the tread portion 1 side along the tire radial direction (tire width direction) and a bent portion 11b extending at an angle toward one side in the tire circumferential direction with respect to the extension direction of the main body portion 11a. The point where the main body portion 11a and the bent portion 11b of the shoulder lug groove 11 connect (the bent point) is preferably located near the center of the side surface of the shoulder block 12 in the tire radial direction.

[0024] As described above, the side region includes a first side groove 14a formed between circumferentially adjacent side blocks 13, connecting to the shoulder lug groove 11 and extending linearly in the tire radial direction. Specifically, the first side groove 14a connects to the bent portion 11b of the shoulder lug groove 11 and extends along the extension direction of the bent portion 11b. Furthermore, a second side groove 14b is formed in each shoulder lug groove 11 that is not connected to the first side groove 14a, extending along the tire radial direction and terminating within the side block 13. The second side groove 14b connects to the bent portion 11b of the shoulder lug groove 11 and has a bent shape consisting of a main portion extending along the extension direction of the bent portion 11b and a bent portion extending in a different direction from the main portion. The groove widths and depths of the first side groove 14a and the second side groove 14b are not particularly limited. However, since the first side groove 14a is a groove that defines the side block 13 as described above, its groove depth is equivalent to the protruding height of the side block 13. That is, the groove depth of the first side groove 14a is preferably 0.5 mm to 10 mm, more preferably 0.5 mm to 3 mm. The groove width of the first side groove 14a is preferably 1 mm to 12 mm, more preferably 2 mm to 8 mm. Furthermore, the groove width of the second side groove 14b is preferably 1 mm to 12 mm, more preferably 2 mm to 8 mm, and the groove depth is preferably 0.5 mm to 10 mm, more preferably 0.5 mm to 3 mm.

[0025] Furthermore, linear protrusions 20 are formed on the top surfaces of the side blocks 13 and the side surfaces of the shoulder blocks 12, extending across the side blocks 13 and shoulder blocks 12. The linear protrusions 20 are fine protrusions that extend linearly and have a width of preferably 0.2 mm to 5 mm, more preferably 0.3 mm to 3 mm, and a protruding height of preferably 0.2 mm to 5 mm, more preferably 0.3 mm to 3 mm. At least a portion of the linear protrusions 20 extends parallel to the contour lines of the top surfaces of the side blocks 13 and the side surfaces of the shoulder blocks 12. For example, as shown in Figure 3, if the linear protrusion 20 is shown in a simplified form and the symbol ">" is added to the parallel points on the line and the outline of the top surface of the side block 13 and the side surface of the shoulder block 12, the embodiment in Figure 3 includes a linear protrusion 20 that is parallel to the bent portion 11b of the shoulder lug groove 11 and the first side groove 14a, a linear protrusion 20 that is parallel to the bent portion 11b of the shoulder lug groove 11 and the main body portion of the second side groove, and a linear protrusion 20 that is parallel to the bent portion of the second side groove.

[0026] By configuring the shoulder blocks 12 and side blocks 13 in this manner, cut resistance and snow performance can be improved. Specifically, when providing multiple side blocks 13 in the side region to improve snow performance, one side block 13 is positioned on the tire widthwise outer side of a block group consisting of two or more circumferentially adjacent shoulder blocks 12. Therefore, the entire block group and side blocks 13 essentially function as a large block, thereby increasing block rigidity and improving cut resistance. Furthermore, the block rigidity is also ensured at the point where the second side grooves 14b provided within the side blocks 13 terminate within the blocks, thereby improving cut resistance. Meanwhile, the curved shape of the shoulder lug grooves 11 and the second side grooves 14b enhances the edge effect, thereby improving snow performance. Furthermore, by providing the linear protrusions 20 as described above, and in particular by making the linear protrusions 20 extend parallel to the contours of the top surfaces of the side blocks 13 and the side surfaces of the shoulder blocks 12 (i.e., parallel to the edges of the shoulder lug grooves 11, first side grooves 14a, and second side grooves 14b), the edge effect of the linear protrusions 20 can be efficiently added, effectively improving snow performance. This cooperation makes it possible to achieve both high levels of cut resistance and snow performance.

[0027] In the illustrated example, protrusions 15 are present between the shoulder lug groove 11 and the first side groove 14a and between the shoulder lug groove 11 and the second side groove 14b, and although these grooves are technically disconnected, these grooves can be considered to be substantially continuous because the ends of the first side groove 14a and the second side groove 14b are located at the extension of the shoulder lug groove 11. Similarly, although some of the linear protrusions 20 are also divided by protrusions 15, these can also be considered to be a series of linear protrusions 20 extending across the side blocks 13 and shoulder blocks 12 (see FIG. 3 , in which the protrusions 15 are omitted).

[0028] If the linear protrusions 20 do not include portions parallel to the top surfaces of the side blocks 13 and the contour lines of the side surfaces of the shoulder blocks 12, the edge effect of the linear protrusions 20 cannot be sufficiently ensured, and the effect of improving snow performance will be limited. The linear protrusions 20 and the contour lines of the blocks described above do not need to be completely parallel (at the same angle relative to the tire width direction); they can be considered parallel if the difference in angle between them is 15° or less. In other words, the linear protrusions 20 of the present invention include portions that are inclined in the same direction as the contour lines of the top surfaces of the side blocks 13 and the side surfaces of the shoulder blocks 12, with an angle difference of preferably 15° or less, more preferably 10° or less, and even more preferably 7° or less.

[0029] If the shoulder lug grooves 11 and the second side grooves 14b do not have a curved shape, the edge effect will not be sufficient and the effect of improving snow performance will be limited. Regarding the curved shapes of the shoulder lug grooves 11 and the second side grooves 14b, it is preferable that the curved direction of the bent portion 11b relative to the main body 11a of the shoulder lug groove 11 is the same as the curved direction of the bent portion relative to the main body of the second side groove 14b, as shown in the example. This improves the curved shapes of the shoulder lug grooves 11 and the second side grooves 14b, allowing these grooves to effectively exert their edge effect.

[0030] As shown in FIG. 3 , the shoulder lug groove bend angle (the angle formed by the bent portion 11b relative to the main body portion 11a of the shoulder lug groove 11) is θi, and the second side groove bend angle (the angle formed by the bent portion relative to the main body portion of the second side groove 14b) is θii. These bend angles θi and θii are preferably 60° to 160°, more preferably 100° to 150°. This improves the bend shape of the shoulder lug groove 11 and the second side groove 14b, which is advantageous for achieving both snow performance and cut resistance. If the bend angles θi and θii are less than 60°, the portion between the main body portion and the bent portion will form an acute angle, making it difficult to maintain the durability of that portion. If the bend angles θi and θii exceed 160°, the grooves will not bend substantially, limiting the effect of enhancing the edge effect. Note that the bend angles θi and θii are measured based on the widthwise centerline of each groove, as shown in FIG. 3 .

[0031] In the present invention, as described above, the entire combination of two or more shoulder blocks 12 (side surfaces) and one side block 13 is regarded as a substantially large block. In this case, the total length of the linear protrusions 20 included in this group of blocks is preferably 50% to 400%, more preferably 100% to 300%, of the length of the outer contour of this group of blocks. Note that the outer contour of the group of blocks at the ground contact edge E is defined ignoring the shoulder lug grooves 11 connected to the second side grooves 14b (see the dashed lines in Figure 3). Having the linear protrusions 20 of sufficient length in this way is advantageous for improving the edge effect.

[0032] Furthermore, the linear protrusions 20 do not need to be parallel to the contour lines of the top surfaces of the side blocks 13 and the side surfaces of the shoulder blocks 12 over their entire length, but as described above, at least a portion of them extends parallel to the contour lines of the top surfaces of the side blocks 13 and the side surfaces of the shoulder blocks 12. In this case, the total length of the linear protrusions 20 parallel to the contour lines is preferably 50% or more, and more preferably 70% or more, of the total length of the linear protrusions 20. Including a sufficient number of parallel portions in this way is advantageous for improving the edge effect.

[0033] The linear protrusions 20 preferably include a portion parallel to the bent portion 11b of the shoulder lug groove 11 and the first side groove 14a, a portion parallel to the bent portion 11b of the shoulder lug groove 11 and the main body of the second side groove, and a portion parallel to the bent portion of the second side groove 14b. Furthermore, the linear protrusions 20 preferably include a portion connecting the terminal end of the second side groove 14b to the first side groove 14a and extending parallel to the radially inner contour of the side block 13. By connecting the first side groove 14a and the second side groove 14b in this manner, the rigidity of the side block can be improved while ensuring snow column shearing, which is advantageous for achieving both snow performance and cut resistance. In the illustrated example, the bent portion of the second side groove 14b also extends parallel to the radially inner contour of the side block 13, and the linear protrusions 20 and the edge of the bent portion of the second side groove 14b extend in a substantially straight line, thereby more effectively improving snow performance.

[0034] The first side groove 14a also serves to separate the circumferentially adjacent side blocks 13, and its radially inner end is open toward the sidewall portion 2. On the other hand, the second side groove 14b terminates within the side block 13, and its tip preferably has a tapered shape toward the terminal end. This prevents a decrease in block rigidity near the terminal end of the second side groove 14b and is advantageous for improving cut resistance.

[0035] 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.

[0036] Pneumatic tires were produced for Conventional Example 1, Comparative Examples 1 and 2, and Examples 1 to 4, having a tire size of LT265 / 70R17 115H and the basic structure (cross-sectional structure) illustrated in FIG. 1 , with the presence or absence of side blocks, the number of shoulder lug blocks adjacent to the side blocks, the presence or absence of bending of the shoulder lug grooves, the presence or absence of first side grooves, the presence or absence of second side grooves, the presence or absence of linear protrusions, the presence or absence of parallel portions of the linear protrusions (portions parallel to the block contour lines), the presence or absence of connection between the first side grooves and the second side grooves by linear protrusions, the shape of the end of the second side grooves, the bending direction of the shoulder lug grooves and the second side grooves, the bending angles θi and θii, and the ratio A / SH of the tire radial distance A from the ground contact edge to the innermost side block in the tire radial direction to the tire cross-sectional height SH, all set as shown in Table 1.

[0037] In Table 1, the bending shape of the second side grooves (bent / non-bent) is also shown in the column "Presence or absence of second side grooves." In Comparative Example 2, the shoulder lug grooves are bent while the second side grooves are not bent, and therefore the bending direction is different, and therefore the column "Bending direction of shoulder lug grooves and second side grooves" is shown as "Different directions."

[0038] The snow performance and cut resistance of these pneumatic tires were evaluated by the following evaluation methods, 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] Cut Resistance 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). After driving 1000 km on an off-road endurance road, the total length of cuts that occurred 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, which means better block durability (cut resistance).

[0041]

[0042] As is clear from Table 1, the pneumatic tires of Examples 1 to 4 had improved snow performance and cut resistance compared to Conventional Example 1, achieving a good balance between these performances. On the other hand, Comparative Examples 1 and 2 showed slight improvements in the index values ​​of snow performance and cut resistance compared to Conventional Example 1, which did not have side blocks, but were unable to sufficiently improve these performances. Specifically, Comparative Example 1 had only one shoulder block adjacent to the side block and did not have linear protrusions, so snow performance and cut resistance could not be sufficiently improved. Comparative Example 2 had a non-bent second side groove and did not have linear protrusions, so snow performance and cut resistance could not be sufficiently improved.

[0043] 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 10 main groove 11 shoulder lug groove 12 shoulder block 13 side block 14a first side groove 14b second side groove 15 protrusion 20 linear projection CL tire equator E ground contact edge

Claims

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 either side of the tread portion, wherein the surface of the tread portion has a pair of main grooves extending circumferentially on both sides of the tire equator, and a shoulder region located on the tire widthwise outer side of the main grooves is provided with a plurality of shoulder lug grooves extending from the main grooves toward the tire widthwise outer side and spaced apart in the tire circumferential direction, and a plurality of shoulder blocks partitioned by the main grooves and the shoulder lug grooves and arranged in the tire circumferential direction, a plurality of side blocks protruding from the outer surface of the sidewall portion are provided in a side region adjacent to the shoulder region on the tire widthwise outer side, and one side block is disposed at the tire widthwise outer side of a block group consisting of two or more shoulder blocks adjacent in the tire circumferential direction, and the shoulder lug grooves are bent to one side in the tire circumferential direction when viewed from the side of the shoulder block, a first side groove that is provided between the side blocks adjacent in the tire circumferential direction and connects to the shoulder lug groove, extending linearly along the tire radial direction; and a second side groove that is connected to the shoulder lug groove, extends along the tire radial direction, and bends and terminates within the side block; and a linear protrusion that extends across the side block and the shoulder block is formed on the side surface of the side block and the shoulder block, and at least a portion of the linear protrusion extends parallel to the contour line of the side block and the shoulder block.

2. The tire according to claim 1, characterized in that the linear protrusion includes a portion that connects the terminal end of the second side groove with the first side groove and extends parallel to the radially inner contour line of the side block.

3. A tire according to claim 1 or 2, characterized in that the leading end of the second side groove is tapered toward the terminal end.

4. A tire according to any one of claims 1 to 3, characterized in that the shoulder lug grooves have a bending angle θi of 60° to 160°, the second side grooves are bent in the same direction as the shoulder lug grooves, and the second side grooves have a bending angle θii of 60° to 160°.

5. A tire according to any one of claims 1 to 4, characterized in that the distance A in the tire radial direction from the ground contact edge to the innermost radial side of the side block is 15% to 40% of the tire cross-sectional height SH.

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