Tire

Abstract

Provided is a tire with which a further improvement in rough road running performance can be achieved while ensuring excellent block durability. A plurality of shoulder blocks 12 are provided in a shoulder region of a tread portion 1, a plurality of side blocks 13 are provided in a side region that is adjacent to the shoulder region on the outer side thereof in the width direction of the tire, one side block 13 is disposed in a position on the outer side, in the width direction of the tire, of a block group comprising two or more shoulder blocks 12 adjacent to one other in the circumferential direction of the tire, a bent recessed portion 20 comprising a first recessed portion 21 and a second recessed portion 22 that extend in the circumferential direction of the tire and a third recessed portion 23 that connects the first recessed portion 21 and the second recessed portion 22 and that extends obliquely with respect to the circumferential direction of the tire is provided on a side surface of each shoulder block 12, and a bent projecting portion comprising a first projecting portion 31 and a second projecting portion 32 that extend in the circumferential direction of the tire and a third projecting portion 33 that connects the first projecting portion 31 and the second projecting portion 32 and that extends obliquely with respect to the circumferential direction of the tire is provided on the surface of each side block 13.

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 off-road performance while ensuring excellent block durability.

[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, etc.) in addition to paved roads are required to have excellent running performance on various road surfaces, and in particular, excellent off-road performance (rough road performance). Such tires have unevenness (e.g., side blocks) not only in the tread portion that contacts 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, snow, sand, stones, rocks, etc. (hereinafter, collectively referred to as "mud, etc.") on unpaved roads, thereby obtaining traction performance by gripping the mud, etc. (see, for example, Patent Documents 1 and 2). In recent years, tire performance requirements have become more stringent, and further improvements in rough road performance are required. Furthermore, since the side blocks tend to be easily damaged by stones, rocks, foreign objects, etc. on unpaved roads (rough roads), they are also required to have sufficient durability. Therefore, there is a demand for improving rough road performance while ensuring durability (particularly block durability), and achieving a high level of both performances.

[0003] Japanese Patent Publication No. 2017-124733 Japanese Patent Publication No. 2020-044882

[0004] An object of the present invention is to provide a tire that allows further improvement in off-road performance while ensuring excellent block durability.

[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 circumferential direction of the tire 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 outer side of the shoulder region in the tire width direction is provided with a plurality of side blocks protruding from the outer surface of the sidewall portion, and the shoulder lug grooves are disposed between the side blocks adjacent to each other in the tire width direction. The tire has a circumferentially adjacent shoulder block, and each shoulder block has a side groove extending radially from the side groove, and one side block is positioned on the tire widthwise outer side of a block group consisting of two or more shoulder blocks adjacent in the tire circumferential direction. Each shoulder block has a side surface provided with a bent recess that is recessed further than other parts of the side surface, and each bent recess consists of a first recess and a second recess that extend circumferentially of the tire, and a third recess that connects the first recess and the second recess and extends at an angle relative to the tire circumferential direction. The tire has a circumferentially adjacent shoulder block and a side groove that is connected radially from the side groove, and each side block has a bent protruding portion that is raised further than other parts of the surface, and each bent protruding portion consists of a first protruding portion and a second protruding portion that extend radially from the side groove, and a third protruding portion that connects the first protruding portion and the second protruding portion and extends at an angle relative to the tire circumferential direction.

[0006] The tire of the present invention provides multiple side blocks in a side region, with one side block positioned on the tire widthwise outer side of a block group consisting of two or more circumferentially adjacent shoulder blocks. This allows the block group and side blocks to function as a substantially large block, thereby improving block durability. Furthermore, each shoulder block is provided with a bent recess consisting of first to third recesses, and each side block is provided with a bent convex portion consisting of first to third convex portions. This creates a complex uneven shape from the side surface of the shoulder block to the surface of the side block, allowing the tire to efficiently grip mud and other debris on unpaved roads, improving traction performance and providing excellent off-road performance. In particular, the bent recess and bent convex portion each include portions extending circumferentially (first recess and second recess, first convex portion and second convex portion) and portions extending at an angle relative to the circumferential direction (third recess, third convex portion), providing an edge effect in various directions and efficiently enhancing traction performance. These combinations enable a high degree of both block durability and off-road performance.

[0007] In the present invention, it is preferable that the first recessed portion opens into the shoulder lug groove adjacent to one side of the shoulder block in the circumferential direction of the tire, and the second recessed portion opens into the shoulder lug groove adjacent to the other side of the shoulder block in the circumferential direction of the tire. This allows both ends of the flexed recessed portion to communicate with the shoulder lug grooves, making it easier for mud and the like to be discharged from the flexed recessed portion, which is expected to improve traction performance.

[0008] In the present invention, it is preferable that the first convex portion connects to the adjacent side groove on one circumferential side of the side block, and the second convex portion connects to the adjacent side groove on the other circumferential side of the side block, so that the bent convex portion extends across the entire width of the side block (the entire area from one circumferential end to the other), thereby increasing the rigidity of the side block and being advantageous for improving traction performance.

[0009] In the present invention, the circumferential length of one of the first convex portion and the second convex portion may be greater than the circumferential length of the other. By making the lengths of the first convex portion and the second convex portion different in this way, the unevenness of the curved convex portion becomes complex, which is advantageous for improving traction performance.

[0010] In the present invention, the depth of the bent recess with respect to the side surface of the shoulder block is preferably 0.5 mm to 2.0 mm, which is advantageous for achieving both block durability and rough road performance.

[0011] In the present invention, the height of the bent convex portion relative to the surface of the side block is preferably 0.5 mm to 15 mm, which is advantageous for achieving both block durability and rough road performance.

[0012] In the present invention, the angle formed by the third recess with respect to the tire circumferential direction is preferably 20° to 50°. Furthermore, the angle formed by the third protrusion with respect to the tire circumferential direction is preferably 30° to 60°. Setting the angles of each portion in this manner improves the shape of the bent recess and bent protrusion, which is advantageous for improving traction performance and rough road performance. Note that the "angle formed by the third recess with respect to the tire circumferential direction" is measured based on an imaginary line passing through the center of the third recess in the width direction. Similarly, the "angle formed by the third protrusion with respect to the tire circumferential direction" is measured based on an imaginary line passing through the center of the third protrusion in the width direction.

[0013] In the present invention, it is preferable that the third recessed portion and the third protruding portion are inclined in the same direction with respect to the tire circumferential direction, and the difference in the inclination angle with respect to the tire circumferential direction is 15° or less. When the third recessed portion and the third protruding portion are inclined in the same direction in this way, the bent recessed portion and the bent protruding portion have similar shapes, and the combination of these recessed and protruding portions improves the uneven shape of the region from the side surface of the shoulder block to the surface of the side block, which is advantageous for improving traction performance and off-road performance.

[0014] In the present invention, it is preferable that the second convex portion is located at the innermost side in the tire radial direction of the side block, the first convex portion is located at the outer side in the tire radial direction of the second convex portion, and the surface of the side block is recessed more than the bent convex portion at a position surrounded by the first convex portion and the third convex portion. This makes the unevenness of the side block complex, which is advantageous for improving traction performance and off-road performance.

[0015] 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.

[0016] Fig. 1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. Fig. 2 is a perspective view showing the shoulder and side regions of a tire according to an embodiment of the present invention. Fig. 3 is an explanatory diagram schematically showing the shoulder blocks (side surfaces) and side blocks (surface surfaces) of the present invention.

[0017] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] 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. Although not depicted in Figure 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 Figure 1 will be basically based on the meridian cross-section shape shown, but each tire constituent member also extends in the tire circumferential direction and forms an annular shape.

[0019] 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.

[0020] 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 of the grooves and blocks formed on the surface of the tread portion 1 (tread pattern) 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 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 mud or the like on the road surface when traveling on unpaved roads.

[0021] As shown in Figures 1 and 2, a pair of main grooves 10 are formed on the surface of the tread portion 1, extending along the tire circumferential direction on both sides of the tire equator CL. The main grooves 10 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 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 shoulder regions. The main grooves 10 preferably have a groove width of 3 mm to 13 mm, more preferably 5 mm to 11 mm, and a groove depth of 8 mm to 16 mm, more preferably 10 mm to 15 mm.

[0022] 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 may be 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 may be 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.

[0023] 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 sidewall surface is not particularly limited, but can be set to, for example, 1 mm to 10 mm. As shown in Figures 2 and 3 , each side block 13 is positioned on the outer side in the tire width direction of a block group consisting of two or more shoulder blocks 12 adjacent in the tire circumferential direction. For example, in the illustrated example, one side block 13 is positioned on the outer side in the tire width direction of a block group consisting of two shoulder blocks 12. In other words, side grooves 14 extending along the tire width direction (tire radial direction) are formed between adjacent side blocks 13 in the tire circumferential direction, and these side grooves 14 are connected to at least every other shoulder lug groove 11 spaced apart in the tire circumferential direction. Between the shoulder lug grooves 11 and side grooves 14 connected in this manner, one side block 13 and two or more shoulder blocks 12 (and one or more shoulder lug grooves 11 that are not connected to the side grooves 14) are arranged.

[0024] 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 becomes buried in mud or other debris while traveling on unpaved roads. Specifically, the radially innermost ends of the side blocks 13 are preferably located within a range of 20% to 50% of the tire cross-sectional height SH from the tire equator CL toward the tire's radially inward direction. In other words, the distance D from the tire equator CL to the radially innermost ends of the side blocks 13 is preferably 20% to 50% 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, the side blocks 13 can be appropriately sized, which is advantageous for ensuring block rigidity and improving durability. If the distance D is less than 20% of the tire cross-sectional height SH, the side blocks 13 become too small, making it difficult to maintain good block durability. If the distance D exceeds 50% of the tire cross-sectional height SH, the side blocks 13 become too large, which may affect normal running performance. With regard to the arrangement of the side blocks 13, it is preferable that the boundary between the shoulder region and the side region is located within a range of 20% to 25% of the tire cross-sectional height SH from the tire equator CL toward the tire radially inward, regardless of the presence or absence of the protrusions 17.

[0025] In the combination of two or more shoulder blocks 12 and one side block 13 described above, each side surface of the shoulder block 12 (the surface of the shoulder block 12 when viewed from the side of the tire) has a bent recess 20 that is recessed relative to the rest of the side surface of the shoulder block 12. Each bent recess 20 is composed of a first recess 21 and a second recess 22 that extend along the tire circumferential direction, and a third recess 23 that connects the first recess 21 and the second recess 22 and extends at an angle relative to the tire circumferential direction. Similarly, each surface of the side block 13 (the surface of the side block 13 when viewed from the side of the tire) has a bent protruding portion 30 that is raised relative to the rest of the surface of the side block 13. Each bent protruding portion 30 is composed of a first protruding portion 31 and a second protruding portion 32 that extend along the tire circumferential direction, and a third protruding portion 33 that connects the first protruding portion 31 and the second protruding portion 32 and extends at an angle relative to the tire circumferential direction.

[0026] In the tire of the present invention, the shoulder blocks 12 (block group) and side blocks 13 function as a single large block, ensuring the rigidity of the large block, thereby improving block durability. Each shoulder block 12 is provided with a flexed recess 20 consisting of a first recess 21, a second recess 22, and a third recess 23, and each side block 13 is provided with a flexed convex portion 30 consisting of a first convex portion 31, a second convex portion 32, and a third convex portion 33. This creates a complex uneven shape in the region extending from the side surface of the shoulder block 12 to the surface of the side block 13, allowing it to efficiently grip mud and other debris on unpaved roads, improving traction performance and providing excellent rough-road performance. In particular, each of the flexed recess 20 and flexed convex portion 30 includes a portion extending circumferentially along the tire (the first recess 21 and the second recess 22, the first convex portion 31 and the second convex portion 32) and a portion extending at an angle relative to the tire circumferential direction (the third recess 23, the third convex portion 33), providing an edge effect in various directions and efficiently improving traction performance. This collaboration makes it possible to achieve a high level of both block durability and off-road performance.

[0027] 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 mold split position, etc., and is therefore not necessarily required. While this protrusion 15 is not an element that needs to be considered in the present invention, because it is an element formed during manufacturing, 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 protrusion 15 on the inner side in the tire width direction, and the side region can be considered to be the region adjacent to the protrusion 15 on the inner side in the tire radial direction.

[0028] As described above, the bent recesses 20 are recessed portions from the side surfaces of the shoulder blocks 12, and the bent protrusions 30 are raised portions from the surfaces of the side blocks 13. Therefore, the bent protrusions 30 do not need to protrude from the side surfaces of the shoulder blocks 12. For example, in the illustrated example, the height relationship is such that the side surfaces of the shoulder blocks 12 and the upper surfaces of the bent protrusions 30 are connected across the protrusions 15. However, even with this shape, the bent recesses 20 are recessed from the side surfaces of the shoulder blocks 12, and the bent protrusions 30 are raised from the surfaces of the side blocks 13, so the concave and convex shapes intended by the present invention are satisfied.

[0029] In a combination of two or more shoulder blocks 12 adjacent in the tire width direction and one side block 13, the number of side blocks 13 and shoulder blocks 12 is preferably two for each side block 13. This provides a good balance between the number of blocks in the combination of side blocks 13 and shoulder blocks 12, which is advantageous for achieving both block durability and rough-road performance.

[0030] The depth of the flex recess 20 relative to the side surface of the shoulder block 12 is preferably 0.5 mm to 2.0 mm, more preferably 0.5 mm to 1.5 mm. This is advantageous for achieving both block durability and rough-road performance. If the depth of the flex recess 20 relative to the side surface of the shoulder block 12 is less than 0.5 mm, the flex recess 20 is not recessed sufficiently, and the flex recess 20 does not form sufficient unevenness, resulting in a failure to fully improve traction performance. If the depth of the flex recess 20 relative to the side surface of the shoulder block 12 exceeds 2.0 mm, the flex recess 20 is too deep, reducing the rigidity of the shoulder block 12 and making it difficult to maintain sufficient block durability.

[0031] The height of the bent convex portion 30 relative to the surface of the side block is preferably 0.5 mm to 15 mm, more preferably 1 mm to 3 mm. This is advantageous for achieving both block durability and rough-road performance. If the height of the bent convex portion 30 relative to the surface of the side block 13 is less than 0.5 mm, the bent convex portion 30 does not protrude sufficiently, and the bent convex portion 30 does not form sufficient unevenness, making it difficult to expect a sufficient effect of improving traction performance. If the height of the bent convex portion 30 relative to the surface of the side block 13 exceeds 15 mm, the bent convex portion 30 protrudes too much from the surrounding area, making the bent convex portion 30 itself more susceptible to damage, and thus making it more difficult to maintain block durability.

[0032] The specific shape of the bent recess 20 is not particularly limited as long as it has a bent shape consisting of the three portions (first recess 21, second recess 22, and third recess 23) described above. However, as in the illustrated example, the first recess 21 may be located radially outward of the second recess 22. In particular, in the illustrated example, the first recess 21 located on one circumferential side of the tire (the right side in the figure) is located radially outward of the second recess 22 located on the other circumferential side of the tire (the left side in the figure). Furthermore, in the illustrated example, the second recess 22 is located radially inward on the side of the shoulder block 12 and extends to contact the protrusion 17 described above. In the present invention, it is preferable that the bent recess 20 having the above-described shape be provided in each of two or more circumferentially adjacent shoulder blocks 12, and that the bent recess 20 of each shoulder block 12 have a similar shape. By providing the bent recess 20 in this manner, directional concaves and convexes based on the bent recess 20 are repeatedly arranged in the circumferential direction of the tire, which is advantageous for effectively trapping mud and improving rough-road performance.

[0033] The specific shape of the bent convex portion 30 is also not particularly limited as long as it has a bent shape made up of the above-mentioned three portions (first convex portion 31, second convex portion 32, and third convex portion 33), but as in the illustrated example, it is preferable that the first convex portion 31 is located further outward in the tire radial direction than the second convex portion 32. In particular, as in the illustrated example, it is preferable that the first convex portion 31 located on one side in the tire circumferential direction (the right side in the figure) is located further outward in the tire radial direction than the second convex portion 32 located on the other side in the tire circumferential direction (the left side in the figure). In other words, it is preferable that the bent convex portion 30 has a bent shape similar to that of the bent recessed portion 20, except that the convex and concave portions are reversed and the length in the tire circumferential direction is changed.

[0034] By satisfying the above-described arrangements of the first recessed portions 21 and the second recessed portions 22 and the arrangements of the first protruding portions 31 and the second protruding portions 32, the third recessed portions 23 and the third protruding portions 33 are inclined in the same direction relative to the tire circumferential direction while satisfying the above-described condition, but the difference in the inclination angle relative to the tire circumferential direction (the difference between the angles α and β described below) is preferably 15° or less, more preferably 10° or less. This makes the bent protruding portions 30 and the bent recessed portions 20 more similar in bend shape, so that the bent recessed portions 20 and the bent protruding portions 30 formed in the shoulder blocks 12 and the side blocks 13 become uneven with directionality overall, which is advantageous for effectively trapping mud and improving rough road performance.

[0035] When the third recessed portion 23 and the third protruding portion 33 are inclined in the same direction relative to the tire circumferential direction as described above, the angle α formed by the third recessed portion 23 with respect to the tire circumferential direction is preferably 20° to 50°, more preferably 30° to 40°. Furthermore, the angle β formed by the third protruding portion 33 with respect to the tire circumferential direction is preferably 30° to 60°, more preferably 40° to 50°. Setting the angles of each portion in this manner improves the shape of the flexed recessed portion 20 and the flexed protruding portion 30, which is advantageous for improving traction performance and rough road performance. If the angle α is less than 20°, the flexed recessed portion 20 will not flex sufficiently, limiting its effectiveness in improving traction performance. If the angle α exceeds 50°, cut resistance may be reduced. If the angle β is less than 30°, the flexed protruding portion 30 will not flex sufficiently, limiting its effectiveness in improving traction performance. If the angle β exceeds 60°, cut resistance may be reduced.

[0036] It is preferable that the first recess 21 opens into the shoulder lug groove 11 adjacent to one side of the shoulder block 12 in the tire circumferential direction, and the second recess 22 opens into the shoulder lug groove 11 adjacent to the other side of the shoulder block 12 in the tire circumferential direction. This allows both ends of the flex recess 20 to communicate with the shoulder lug groove 11, making it easier to discharge mud and the like from within the flex recess 20, which is expected to improve traction performance.

[0037] It is preferable that the first convex portion 31 connects to the adjacent side groove 14 on one circumferential side of the side block 13, and the second convex portion 32 connects to the adjacent side groove 14 on the other circumferential side of the side block 13. This allows the bent convex portion 30 to extend across the entire width of the side block 13 (the entire area from one circumferential end to the other end), thereby increasing the rigidity of the side block 13 and being advantageous for improving traction performance.

[0038] The first convex portion 31 and the second convex portion 32 may have the same circumferential length, or the circumferential length of one of these may be greater than the other. In the illustrated example, the second convex portion 32 located on the radially outer side of the tire has a greater circumferential length than the first convex portion 31 located on the radially inner side of the tire. More specifically, in the illustrated example, the first convex portion 31 and the third convex portion 33 are provided in an area corresponding to one shoulder block 12, and the second convex portion 32 is provided in an area corresponding to one shoulder block 12 and shoulder lug groove 11. This results in a relationship in the circumferential lengths of the first convex portion 31 and the second convex portion 32 (first convex portion < second convex portion). Forming the bent convex portion 30 in this manner creates a complex unevenness in the bent convex portion 30, which is advantageous for improving traction performance.

[0039] In the illustrated example, the second convex portion 32 is disposed radially inward of the first convex portion 31, and is disposed at the radially innermost position of the side block 13. Meanwhile, a surface of the side block 13 (reference numeral 13a in the drawing) that is recessed relative to the bent convex portion 30 is present in the position surrounded by the first convex portion 31 and the third convex portion 33. In other words, it is preferable that a surface of the side block 13 (a surface recessed relative to the bent convex portion 30) is present on both the inner and outer sides of the bent convex portion 30 in the radial direction of the tire. This results in a complex unevenness of the side block 13, which is advantageous for improving traction performance and rough road performance.

[0040] Because the present invention is primarily concerned with the flexion recess 20 and the flexion protrusion 30, other structures are not particularly limited, but as shown in the example, a side recess 34 recessed into the surface of the side block 13 may be provided on an extension of the shoulder lug groove 11 located between a block group consisting of two shoulder blocks 12. This side recess 34 terminates within the side block 13 so as to be interrupted by the flexion protrusion 30. Providing such a side recess 34 further complicates the unevenness of the side block 13, which is advantageous for improving traction performance and driving performance on rough roads.

[0041] 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.

[0042] Eighteen types of pneumatic tires (Conventional Example 1, Comparative Examples 1 to 3, and Examples 1 to 14) were produced, each with a tire size of LT265 / 70R17 121 / 118S and a basic structure (cross-sectional structure) as illustrated in FIG. 1 , with the shoulder region and side region structures based on FIG. 2 . The number of shoulder blocks adjacent to one side block radially outward from the tire, the presence or absence of a bent recessed portion, the angle α of the third recessed portion relative to the tire circumferential direction, the end shape of the first recessed portion, the end shape of the second recessed portion, the presence or absence of a bent convex portion, the angle β of the third convex portion relative to the tire circumferential direction, the end shape of the first convex portion, the end shape of the second convex portion, the angle difference |β|-|α| between the angle α of the third recessed portion relative to the tire circumferential direction and the angle β of the third convex portion relative to the tire circumferential direction, the depth of the bent recessed portion, the depth of the bent convex portion, and the presence or absence of a side block surface on the tire radially inner side of the bent convex portion were set as shown in Tables 1 and 2, respectively.

[0043] The tread pattern in the center region was common to all examples, with one row of blocks arranged between a pair of main grooves on each side of the tire equator.

[0044] In the column "angle α of third recess with respect to the tire circumferential direction" in Tables 1 and 2, when the number of shoulder blocks adjacent to one side block on the tire radial outside is "2" and a bent recess is provided in each shoulder block, each bent recess includes a third recess, and therefore the value of each angle α is presented. Note that in Example 13, one angle α is a negative value, which means that the inclination direction is opposite to that of the other angle α. Similarly, in the example (Example 14) where the angle β of the third protrusion with respect to the tire circumferential direction is a negative value, this means that the inclination direction of the third recess and the inclination direction of the third protrusion are opposite to each other.

[0045] The columns "End Shape of First Recess" and "End Shape of Second Recess" in Tables 1 and 2 indicate whether one end of the first recess or the second recess communicates with the shoulder lug groove, with "opening" indicating that it opens into the shoulder lug groove and "terminating" indicating that it terminates within the shoulder block. The columns "End Shape of First Convex Portion" and "End Shape of Second Convex Portion" in Tables 1 and 2 indicate whether one end of the first convex portion or the second convex portion connects to the side groove, with "connection" indicating that it connects to the side groove and "terminating" indicating that it terminates within the side block.

[0046] These pneumatic tires were evaluated for rough road running performance and block durability by the following evaluation methods, and the results are shown in Tables 1 and 2.

[0047] Rough Road Performance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire was air-pressurized to 450 kPa and the rear tire was air-pressurized to 550 kPa. The test vehicle (traction test vehicle) was then fitted with the tire, and a test driver performed a sensory evaluation of the traction (starting performance) on a test road consisting of an unpaved road (gravel surface). The evaluation results were expressed as an index, with the value of Conventional Example 1 being 100. The higher the index value, the better the snow performance.

[0048] Block durability (cut resistance) Each test tire was mounted on a wheel with a rim size of 17x8J, and the air pressure was set to 350 kPa. The test vehicle (four-wheel drive SUV) was fitted with the tire, and the total length of cuts on the side was measured after driving 1000 km on an off-road endurance road. The evaluation results were expressed as an index, with the reciprocal of the measurement value for Conventional Example 1 being set to 100. The larger the index value, the smaller the total length of the cuts, which means better block durability (cut resistance).

[0049]

[0050]

[0051] As is clear from Tables 1 and 2, the pneumatic tires of Examples 1 to 14 improved rough-road performance and block durability compared to Conventional Example 1, achieving a good balance between these performance characteristics. On the other hand, Comparative Example 1 had a structure in which two shoulder blocks were adjacent to one side block, and thus improved block durability compared to Conventional Example 1. However, since Comparative Example 1 did not have a flexed recess or flexed protrusion, it did not achieve the effect of improving rough-road performance. Comparative Example 2 had a flexed recess but no flexed protrusion, so it did not achieve the effect of sufficiently improving rough-road performance. Comparative Example 3 had a flexed protrusion but no flexed recess, so it did not achieve the effect of sufficiently improving rough-road performance.

[0052] 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 14 side groove 15 protrusion 20 bending recess 21 first recess 22 second recess 23 third recess 30 bending convex portion 31 first convex portion 32 second convex portion 33 third convex portion 34 side recess CL tire equator

Claims

1. A tire having a tread portion extending in a circumferential direction and forming an annular shape, and a pair of sidewall portions arranged on both sides of the tread portion, the surface of the tread portion having a pair of main grooves extending circumferentially on both sides of the tire equator, a shoulder region located on the outer side of the main groove in the tire width direction is provided with a plurality of shoulder lug grooves extending from the main groove toward the outer side in the tire width direction and spaced apart in the tire width direction, and a plurality of shoulder blocks partitioned by the main groove and the shoulder lug groove and arranged in the tire circumferential direction, a plurality of side blocks protruding from an outer surface of the sidewall portion are provided in a side region adjacent to the outer side in the tire width direction of the shoulder region, and a side groove connected to the shoulder lug groove and extending in the tire radial direction is provided between the side blocks adjacent in the tire circumferential direction, and one of the side blocks is arranged at a position in the tire width direction outer side of a block group consisting of two or more of the shoulder blocks adjacent in the tire circumferential direction, a bent recess formed on each side surface of the shoulder block that is recessed relative to other portions of the side surface, each of the bent recesses consisting of a first recess and a second recess extending along the tire circumferential direction, and a third recess connecting the first recess and the second recess and extending at an angle relative to the tire circumferential direction; and a bent convex portion formed on each surface of the side block that is raised relative to other portions of the surface, each of the bent convex portions consisting of a first convex portion and a second convex portion extending along the tire circumferential direction, and a third convex portion connecting the first convex portion and the second convex portion and extending at an angle relative to the tire circumferential direction.

2. A tire as described in claim 1, characterized in that the first recess opens into a shoulder lug groove adjacent to one side of the shoulder block in the tire circumferential direction, and the second recess opens into a shoulder lug groove adjacent to the other side of the shoulder block in the tire circumferential direction.

3. A tire as described in claim 1 or 2, characterized in that the first convex portion is connected to a side groove adjacent to one side of the side block in the tire circumferential direction, and the second convex portion is connected to a side groove adjacent to the other side of the side block in the tire circumferential direction.

4. A tire as described in any one of claims 1 to 3, characterized in that the circumferential length of one of the first convex portion and the second convex portion is greater than the circumferential length of the other one.

5. A tire as described in any one of claims 1 to 4, characterized in that the depth of the bending recess with respect to the side surface of the shoulder block is 0.5 mm to 2.0 mm.

6. A tire as described in any one of claims 1 to 5, characterized in that the height of the bent convex portion with respect to the surface of the side block is 0.5 mm to 15 mm.

7. A tire according to any one of claims 1 to 6, characterized in that the angle formed by the third recess with respect to the tire circumferential direction is 20° to 50°.

8. A tire according to any one of claims 1 to 7, characterized in that the angle formed by the third convex portion with respect to the tire circumferential direction is 30° to 60°.

9. A tire according to any one of claims 1 to 8, characterized in that the third recess and the third protrusion are inclined in the same direction with respect to the tire circumferential direction, and the difference in the angle of inclination with respect to the tire circumferential direction is 15° or less.

10. A tire as described in any one of claims 1 to 9, characterized in that the second convex portion is located at the innermost position in the tire radial direction of the side block and the first convex portion is located at the outer side in the tire radial direction of the second convex portion, while there is a surface of the side block that is recessed more than the bent convex portion at a position surrounded by the first convex portion and the third convex portion.

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