Tire

Abstract

Provided is a tire capable of improving poor road trafficability 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 sidewall blocks (13) are provided in a sidewall region adjacent to the outer side of the shoulder region in the tire width direction, and one sidewall block (13) is disposed at a position on the outer side in the tire width direction of a block group comprising two or more shoulder blocks (12) adjacent in the tire circumferential direction. When a surface composed of a side surface of a shoulder block (12) and a top surface of a sidewall block (13) included in a block group is defined as an upper layer surface, a first recess (15) including a middle layer surface depressed by 0.2 mm or more than the upper layer surface is provided on the center side of the upper layer surface, and a second recess (16) including a lower layer surface depressed by 0.2 mm or more than the middle layer surface is provided on the center side of the middle layer surface.

Description

Technical Field

[0001] This invention relates to tires intended for use on unpaved roads, and more specifically, to tires capable of improving performance on poor roads while ensuring excellent block durability. Background Technology

[0002] For tires designed to travel on unpaved roads (uneven surfaces, mud, sand, rocky terrain, etc.) in addition to paved roads (e.g., all-terrain tires, high-pass-rate tires), excellent performance on a wide variety of road surfaces is required, especially excellent off-road performance (poor road clearance). In such tires, not only are the tread portion, which contacts the road surface on paved roads, provided with grooves and protrusions, but also the sidewall portion (the area between the tread and sidewall) which may come into contact with mud, snow, sand, stones, rocks, etc. (hereinafter collectively referred to as "mud, etc.") on unpaved roads, are provided with grooves and protrusions (side blocks, etc.), thereby gripping the mud and providing traction (see, for example, Patent Documents 1 and 2). In recent years, the performance requirements for tires have become increasingly stringent, demanding further improvements in poor road clearance. Furthermore, the sidewalls are prone to damage on unpaved roads (poor roads) due to stones, rocks, and other debris, therefore, ensuring durability is also required. Therefore, it is required to improve the performance of vehicles navigating poor roads while ensuring durability (especially block durability), and to give high priority to these performance aspects.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-124733

[0006] Patent Document 2: Japanese Patent Application Publication No. 2020-044882 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The purpose of this invention is to provide a tire that can improve performance on poor roads while ensuring excellent block durability.

[0009] Methods for solving problems

[0010] The tire of the present invention, for achieving the above-mentioned objectives, comprises an annular tread portion extending circumferentially along the tire and a pair of sidewall portions disposed on both sides of the tread portion. The tread portion is characterized by having a pair of main grooves extending circumferentially along both sides of the tire equator on the surface of the tread portion. In a shoulder region located outside the main grooves in the tire width direction, a plurality of shoulder transverse grooves and a plurality of shoulder blocks are provided. The plurality of shoulder transverse grooves extend from the main grooves outward in the tire width direction and are spaced apart in the tire circumferential direction. The plurality of shoulder blocks are divided by the main grooves and the shoulder transverse grooves and arranged circumferentially along the tire. The tire is positioned relative to the tire shoulder region. The tire sidewall region adjacent to the outer sidewall in the tire width direction is provided with a plurality of sidewall blocks raised from the outer surface of the tire sidewall portion. One sidewall block is arranged at a position on the outer side of the tire width direction of a block group consisting of two or more adjacent shoulder blocks in the tire circumferential direction. When the surface formed by the side surface of the shoulder block included in the block group and the top surface of the sidewall block is defined as the upper surface, a first recess containing a middle surface that is recessed by more than 0.2 mm is provided on the center side of the upper surface, and a second recess containing a lower surface that is recessed by more than 0.2 mm is provided on the center side of the middle surface.

[0011] Effects of the Invention

[0012] In the tire of the present invention, when multiple sidewall blocks are provided in the sidewall region, one sidewall block is positioned outside the tire width direction of a block group consisting of two or more adjacent shoulder blocks in the tire circumferential direction. Therefore, the entire block group and the sidewall block function as a large block, thereby improving block durability. On the other hand, a first recess and a second recess are provided on the upper surface formed by the side surface of the shoulder block included in the block group and the top surface of the sidewall block. The actual block consisting of the block group and the sidewall block is recessed in stages towards the middle and lower surfaces toward its center. This complex concave-convex shape enables efficient gripping of mud and the like on unpaved roads, improving traction performance and providing excellent performance on rough roads. At this time, the first recess and the second recess have a structure that is recessed in stages toward the center of the actual block consisting of the block group and the sidewall block. The upper surface is secured around the first recess and the second recess. Therefore, by providing the first recess and the second recess, the reduction of block rigidity can be suppressed, and block durability can be improved. Through their collaboration, a high degree of balance can be achieved between block durability and performance on poor roads.

[0013] In this invention, it is preferable that the first and second recesses are respectively arranged across the side surface of the shoulder block and the top surface of the sidewall block included in the block group. In this case, it is preferable that the top surface of the sidewall block constituting the upper layer is formed by a pair of radial portions extending radially inward from the side surface of the shoulder block toward the radially inner side of the tire on both sides of the first recess in the tire circumferential direction, and a circumferential portion connecting the pair of radial portions in the tire circumferential direction. Thus, the concave-convex shape formed by the substantial block structure composed of the block group and the sidewall block, and the first and second recesses, becomes favorable, which is beneficial for balancing block durability and performance on poor road conditions.

[0014] In this invention, it is preferable to provide a groove extending from the tread surface of the shoulder block to the outer side of the tire in the width direction, with the bottom of the groove at its outer end in the tire width direction connected to the center layer. This allows for the suppression of block stiffness reduction caused by the groove while ensuring the edge effect generated by the groove, thus balancing block durability and performance on rough roads.

[0015] In this invention, it is preferable that the bottom of the shoulder transverse groove located at the outer end in the tire width direction of the shoulder lateral groove between the shoulder blocks included in the block group is connected to the lower surface layer. This allows for the suppression of the reduction in block rigidity caused by the grooves while ensuring the edge effect generated by the grooves, thus balancing block durability and performance on poor roads.

[0016] In this invention, it is preferable that the first recess has a polygonal shape when viewed from the side of the tire. This allows the edge effect generated by the first recess to be effectively utilized, thus improving performance on rough roads.

[0017] In this invention, it is preferable that the innermost radial end of the sidewall block is located within a range of 20% to 50% of the tire cross-sectional height from the tire equator towards the radially inner side of the tire. By configuring the sidewall block within such a suitable range in the tire's radial direction, the sidewall block will make good contact with mud or other debris on the road surface when the tire is buried in mud or the like while driving on unpaved roads, effectively improving performance on rough roads. Furthermore, since the size of the sidewall block can be appropriately ensured, it is beneficial to ensure block rigidity and improve block durability.

[0018] In this invention, it is preferable that a raised portion is provided at the bottom of the shoulder transverse grooves disposed between the shoulder blocks included in the block group, the raised portion being arranged in such a way that it extends across the upper and middle layers. By providing a raised portion at the bottom of the shoulder transverse groove in this way, an edge effect generated by the raised portion can be added, which is beneficial to improving the performance on rough roads.

[0019] The tire of the present invention is preferably a pneumatic tire, but it can also be a non-pneumatic tire. In the case of a pneumatic tire, it can be filled with an inert gas such as air or nitrogen, or other gases. Attached Figure Description

[0020] Figure 1 This is a radial cross-sectional view of a tire constructed according to an embodiment of the present invention.

[0021] Figure 2 This is a perspective view showing the shoulder region and sidewall region of a tire constructed according to an embodiment of the present invention.

[0022] Figure 3 This is an explanatory diagram schematically showing the tire shoulder block (side) and tire sidewall block (top) of the present invention. Figure 3 (a) indicates the overall structure. Figure 3 (b) indicates the upper level. Figure 3 (c) indicates the middle level. Figure 3 (d) indicates the lower level. Detailed Implementation

[0023] The structure of the present invention will now be described in detail with reference to the accompanying drawings.

[0024] The tire of the present invention is Figure 1 In the case of a pneumatic tire as shown, it includes a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed radially inside the sidewall portions 2. Figure 1 In the attached diagram, the symbol CL indicates the tire equator. Furthermore, Figure 1 Since this is a radial sectional view, it is not depicted, but the tread portion 1, sidewall portion 2, and bead portion 3 extend circumferentially along the tire and form a ring shape, thus constituting the basic ring-shaped structure of a pneumatic tire. The following uses... Figure 1 The description is basically based on the meridian cross-sectional shape shown in the figure, but each tire component extends in a ring shape along the tire circumference.

[0025] A carcass layer 4 is provided between a pair of left and right bead portions 3. The carcass layer 4 includes multiple reinforcing cords extending radially along the tire, folded back from the inside to the outside in the tire width direction around the bead core 5 disposed in each bead portion 3. Additionally, a bead filler 6 is disposed on the outer periphery of the bead core 5, and this bead filler 6 is enclosed by the main body and folded-back portion of the carcass layer 4. On the other hand, multiple layers (in...) are embedded on the outer periphery of the carcass layer 4 at the tread portion 1. Figure 1 The belt layer 7 consists of two layers. Each belt layer 7 contains multiple reinforcing cords inclined relative to the tire circumference, and the reinforcing cords are arranged in a manner that the reinforcing cords intersect each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords relative to the tire circumference is set, for example, in the range of 10° to 40°. Moreover, at least one layer (in the outer periphery of the belt layer 7) is provided. Figure 1The belt reinforcement layer 8 consists of two layers. The belt reinforcement layer 8 contains organic fiber cords oriented along the tire circumferential direction. In the belt reinforcement layer 8, the angle of the organic fiber cords relative to the tire circumferential direction is set, for example, 0° to 5°.

[0026] As described later, this invention relates to the shoulder and sidewall regions of a tire; therefore, the basic tire structure (cross-sectional structure) 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 region described later. The tread pattern in the portion other than the shoulder region described later preferably uses a pattern primarily suited for unpaved roads. This invention is applicable to various tires, including non-pneumatic tires, as long as it has an area that may come into contact with mud or other substances on the road surface when driving on unpaved roads (the portion corresponding to the shoulder and sidewall regions).

[0027] like Figure 1 , Figure 2 As shown, a pair of main grooves 10 extending circumferentially along both sides of the tire equator CL are formed on the surface of the tread portion 1. The main grooves 10 preferably have a serrated shape formed by alternating straight sections inclined in one direction and straight sections inclined in the other direction relative to the tire circumferential direction. The area between the pair of main grooves 10 is the central area (in this invention, the area with no particular structural limitation and which can adopt any tread pattern), and the area outside the tire width direction of each main groove 10 is the shoulder area. Regarding the main grooves 10, the groove width is preferably 3mm to 13mm, more preferably 5mm to 11mm, and the groove depth is preferably 8mm to 16mm, more preferably 10mm to 15mm.

[0028] Shoulder transverse grooves 11 extending outward from the main groove 10 in the tire width direction are provided on the land portion (shoulder land portion) located on the outer side of the main groove 10 in the tire width direction. It is preferable that multiple shoulder transverse grooves 11 are provided at intervals in the tire circumferential direction. These shoulder transverse grooves 11 divide the shoulder land portion into multiple blocks (shoulder blocks 12). When the main groove 10 has a serrated shape, it is preferable that the shoulder transverse grooves 11 connect to the bending points on the outer side of each main groove 10 in the tire width direction. The width of the shoulder transverse grooves 11 is not particularly limited, but is preferably 70% to 98% of the width of the main groove 10, more preferably 80% to 95%. The depth of the shoulder transverse grooves 11 is not particularly limited, but is preferably 75% to 100% of the depth of the main groove 10, more preferably 80% to 98%.

[0029] When the area adjacent to the outer side of the tire shoulder area in the tire width direction is defined as the sidewall area, a plurality of sidewall blocks 13 are provided in this sidewall area, protruding from the outer surface of the sidewall portion 2. The height of each sidewall block 13 protruding from the sidewall surface is not particularly limited, and can be set to, for example, 1mm to 10mm. Figure 2 and Figure 3 As shown in (a), each sidewall block 13 is positioned outside the tire width direction of a group of blocks consisting of two or more adjacent shoulder blocks 12 in the tire circumferential direction. For example, in the illustrated example, a sidewall block 13 is positioned outside the tire width direction of the group of blocks consisting of two shoulder blocks 12. In other words, a sidewall groove 14 extending along the tire width direction (tire radial direction) is formed between adjacent sidewall blocks 13 in the tire circumferential direction, and this sidewall groove 14 is connected to at least every other shoulder transverse groove 11 that is spaced apart in the tire circumferential direction. Between the shoulder transverse grooves 11 and the sidewall grooves 14 connected in this way, a sidewall block 13 and two or more shoulder blocks 12 (and one or more shoulder transverse grooves 11 not connected to the sidewall groove 14) are arranged.

[0030] In the above configuration, the sidewall blocks 13 are arranged across two or more shoulder blocks 12, thus these sidewall blocks 13 and shoulder blocks 12 can be approximated as large blocks. In particular, the surface formed by the side surface of the shoulder block 12 and the top surface of the sidewall block 13 included in the aforementioned block group can be considered as the surface of a substantially large block, which is defined as the upper layer P1 in this invention. Moreover, in this invention, a first recess 15 including a middle layer P2 that is recessed by more than 0.2 mm from the upper layer P1 is provided on the center side of the upper layer P1, and a second recess 16 including a lower layer P3 that is recessed by more than 0.2 mm from the middle layer P2 is provided on the center side of the middle layer P2. That is, the approximated large block formed by the block group and the sidewall blocks 13 has a staged mortar-shaped uneven structure that is progressively recessed towards the center side of the upper layer P1, through the middle layer P2, and down to the lower layer P3.

[0031] In the tire of the present invention, the entire assembly consisting of the aforementioned shoulder block 12 (block group) and sidewall block 13 ( Figure 3(a) The set of blocks shown essentially functions as a large block, ensuring its rigidity and thus improving block durability. On the other hand, the complex concave-convex shape formed by the first recess 15 and the second recess 16, which recesses in stages from the upper layer P1 through the middle layer P2 down to the lower layer P3, allows for efficient gripping of mud and other contaminants on unpaved roads, improving traction and providing excellent performance on rough roads. The first recess 15 and the second recess 16 have a structure that recesses in stages towards the center of the essentially block formed by the shoulder block 12 and the sidewall block 13. The upper layer P1 is secured around the first recess 15 and the second recess 16. Therefore, by providing the first recess 15 and the second recess 16, the reduction in block rigidity can be suppressed, improving block durability. Through their cooperation, both block durability and performance on rough roads can be highly balanced.

[0032] Furthermore, in the illustrated example, at the boundary between the outer side of the shoulder block 12 in the tire width direction and the top surface of the sidewall block 13 (the boundary between the shoulder region and the sidewall region), there is a protrusion 17 that rises from the sidewall surface and extends throughout the entire circumference of the tire. This protrusion 17 is an element formed due to the mold's cutting position, etc., and therefore does not necessarily need to be provided. In addition, this protrusion 17 can be ignored in this invention (for example, even if the protrusion 17 exists, the upper surface P1, the middle surface P2, and the lower surface 3 can each be considered as a surface). This protrusion 17 is an element that does not need to be considered in this invention, but since it is an element formed in manufacturing, the protrusion 17 can also be used as a reference to distinguish the shoulder region and the sidewall region. That is, it can be considered that the shoulder region is the region adjacent to the inner side of the protrusion 17 in the tire width direction, and the sidewall region is the region adjacent to the inner side of the protrusion 17 in the tire radial direction.

[0033] Regarding the relationship between the number of sidewall blocks 13 and shoulder blocks 12 constituting the upper layer, it is preferable to have two shoulder blocks 12 compared to one sidewall block 13. This achieves a good balance between the number of sidewall blocks 13 and shoulder blocks 12 included in the upper layer P1, which is beneficial for both block durability and performance on rough roads.

[0034] The recess amount of the middle layer P2 relative to the upper layer P1 is 0.2 mm or more, as described above, but preferably 0.5 mm or more, and more preferably 0.5 mm or more and 1.5 mm or less. Similarly, the recess amount of the lower layer P3 relative to the middle layer P2 is 0.2 mm or more, as described above, but preferably 0.5 mm or more, and more preferably 0.5 mm or more and 1.5 mm or less. In this way, by making the middle layer P2 and the lower layer P3 sufficiently recessed, the uneven shape formed by the first recess 15 and the second recess 16 becomes good, and the edge effect generated by these recesses can be effectively utilized. If the recess amount of each is less than 0.2 mm, sufficient unevenness cannot be ensured, and the edge effect cannot be improved.

[0035] When providing the first recess 15 and the second recess 16, it is not desirable to limit their placement to either the sidewall block 13 or the shoulder block 12 constituting the upper layer P1. Preferably, the first recess 15 and the second recess 16 are provided across the side surface of the shoulder block 12 and the top surface of the sidewall block 13, respectively. For example, in the illustrated example, each of the two shoulder blocks 12 and one sidewall block 13 contains at least a portion of the first recess 15 (middle layer P2) and the second recess 16 (lower layer P3). That is, the shoulder blocks 12 and sidewall blocks 13 included in the block group each have three layers: the upper layer P1, the middle layer P2, and the lower layer P3. By dispersing the first recess 15 (middle layer P2) and the second recess 16 (lower layer P3) in this way, the rigidity of each of the shoulder blocks 12 and sidewall blocks 13 included in the block group can be ensured, which is beneficial to improving block durability.

[0036] Furthermore, the top surface of the sidewall block 13 constituting the upper layer P1 is preferably composed of a pair of radial portions 13a extending from the side of the shoulder block toward the radially inner side of the tire on both sides of the first recess 15 in the tire circumferential direction, and a circumferential portion 13b connecting the pair of radial portions in the tire circumferential direction. The multiple shoulder blocks 12 included in the block group are divided by the shoulder transverse groove 11. In contrast, the top surface of the sidewall block 13 is connected in the circumferential direction with the above-described structure (a generally U-shaped structure composed of a pair of radial portions 13a and circumferential portions 13b). This makes it easy for the multiple shoulder blocks 12 and sidewall blocks 13 to function as a large block, which is beneficial to improving block durability.

[0037] In this invention, grooves 18 extending from the tread surface of the shoulder block 12 to the outer side of the tire in the width direction can also be provided. When such grooves 18 are provided, from the viewpoint of ensuring block rigidity, the grooves 18 are preferably connected to the first recess 15. It is particularly preferable that the bottom of the groove at the outer end of the groove 18 in the tire width direction is connected to the middle layer P2. Thus, the grooves 18 and the middle layer P2 have the same depth (relative to the depth of the upper layer P1), therefore, excellent edge effect can be achieved through the grooves 18 and the first recess 15 (middle layer) as a whole, and block rigidity can be ensured. The number of grooves 18 provided on each shoulder block 12 is not particularly limited; for example, one to three grooves can be provided (two in the illustrated example). When multiple grooves 18 are provided, it is preferable that at least one of them is connected to the first recess 15 as described above. For example, in the illustrated example, one of the two grooves 18 provided in a shoulder block 12 is connected to the first recess 15, and the other extends from the tread surface of the shoulder block 12 to the side of the tire width direction and forms an end on the side.

[0038] As described above, shoulder lateral grooves 11 are arranged between each other in the shoulder blocks 12 included in the block group, and these shoulder lateral grooves 11 are preferably connected to the second recess 16. It is particularly preferred that the bottom of the groove at the outer end of the shoulder lateral groove 11 in the tire width direction is connected to the lower layer P3. Thus, an excellent edge effect can be achieved by the entirety of the shoulder lateral groove 11 and the second recess 16 (lower layer P3).

[0039] Preferably, when viewed from the tire sidewall direction, the first recess 15 (middle layer P2) has a polygonal shape. In particular, it is preferable that the opposite sides of the polygon extend in the same direction. For example, in the illustrated example, the side extending obliquely in the tire circumferential direction on the sidewall of the adjacent shoulder block 12 and the side extending in the tire circumferential direction on the top surface of the sidewall block 13 extend in the same direction, and a pair of sides extending radially from the sidewall of the shoulder block 12 to the top surface of the sidewall block 13 extend in the same direction, giving the first recess 15 (middle layer P2) an overall approximately parallelogram shape. By adopting such a shape, the edge effect generated by the edge portion of the first recess 15 can be well utilized, which is beneficial for improving performance on rough roads.

[0040] Preferably, when viewed from the side of the tire, the second recess 16 (lower layer P3) also has a polygonal shape. In particular, it is preferable to have the same shape as the first recess 15 (middle layer P2). For example, in the illustrated example, the second recess 16 (lower layer P3) has the same generally parallelogram shape as the first recess 15 (middle layer P2). Furthermore, in the illustrated example, the second recess 16 (middle layer P3) is composed of a main body portion 16a with the same generally parallelogram shape as the first recess 15 and groove portions 16a extending circumferentially from the two vertices of the diagonal of the parallelogram-shaped main body portion 16a.

[0041] Regardless of the shapes of the middle layer P2 and the lower layer P3, it is preferable to have an area of ​​the upper layer P1 ( Figure 3 (b) The diagonal part is set as area A, and the area of ​​the middle layer P2 is ( Figure 3 (c) The diagonal part) is set as area B, and the area of ​​the lower layer P3 is ( Figure 3 When the area of ​​the sloping portion (d) is set to C, the area B of the middle layer P2 is 20% to 50% of the total area (A+B+C) of these areas A to C, and the area C of the lower layer P3 is 5% to 30%. By setting the area of ​​each layer in this way, the balance of the stepped concave-convex shape from the upper layer P1 through the middle layer P2 to the lower layer P3 is improved, which is beneficial to both block durability and poor road passability.

[0042] Preferably, the sidewall block 13 is positioned within a suitable range in the tire radial direction so that it makes proper contact with the road surface when the tire is buried in mud or the like while driving on unpaved roads. Specifically, it is preferable that the innermost radial end of the sidewall block 13 is within a range of 20% to 50% of the tire section height SH from the tire equator CL towards the innermost radial direction. In other words, the distance D from the tire equator CL to the innermost radial end of the sidewall block 13 is preferably 20% to 50% of the tire section height SH. By positioning the sidewall block 13 within such a suitable radial direction of the tire sidewall portion 2, driving performance on unpaved roads can be effectively improved. Furthermore, since the size of the sidewall block 13 can be appropriately ensured, it is beneficial to ensure block rigidity and improve durability. If the distance D is less than 20% of the tire section height SH, the sidewall block 13 becomes too small, making it difficult to maintain good block durability. If the distance D exceeds 50% of the tire section height SH, the sidewall block 13 becomes too large, which may affect normal driving performance. Furthermore, in relation to the configuration of the sidewall block 13, the boundary between the shoulder area and the sidewall area, whether or not there is a protrusion 17, is preferably located within a range of 20% to 25% of the tire section height SH from the tire equator CL towards the radial inward side of the tire.

[0043] In this invention, a protrusion 19 can be provided at the bottom of the shoulder transverse groove 11 between the shoulder blocks 12 included in the block group. It is preferable that the protrusion 19 is not a portion of the entire width of the bottom of the shoulder transverse groove 11, but rather a partial protrusion. By providing the protrusion 19 at the bottom of the shoulder transverse groove 11 in this way, an edge effect generated by the protrusion 19 can be added, which is beneficial to improving the performance on rough roads. The height of the protrusion 19 rising from the bottom of the groove is preferably 2% to 20% of the groove depth of the shoulder transverse groove 11, more preferably 5% to 15%. In particular, when the shoulder transverse groove 11 is connected to the second recess 16 (lower layer P3), the protrusion 19 preferably rises to a height not exceeding the middle layer P2 of the first recess 15. Furthermore, when the protrusion 19 is provided, it is preferably arranged in a manner that extends across the upper layer P1 and the middle layer P2 when viewed from the tire sidewall.

[0044] The present invention will be further illustrated below by way of examples, but the scope of the present invention is not limited to these examples.

[0045] Example

[0046] Tires with dimensions LT265 / 70R17 121 / 118S were manufactured. Figure 1 The illustrated basic structure (cross-sectional structure) and the structure of the shoulder and sidewall regions are based on Figure 2 Based on the above, the following 17 types of pneumatic tires were designed, including: the number of shoulder blocks adjacent to the radial outer side of a sidewall block; the shape of the upper layer; the presence or absence of the first recess (middle layer); the presence or absence of the second recess (lower layer); the presence or absence of shoulder grooves; the connection position of the grooves; the connection position of the shoulder transverse grooves between the block groups; the shape of the first recess as viewed from the tire sidewall direction; the ratio of distance D to tire section height SH; and the presence and configuration of the protrusions at the bottom of the shoulder transverse grooves, as shown in Tables 1-2.

[0047] Furthermore, the tread pattern in the central area is common in all examples, consisting of blocks arranged in rows between a pair of main grooves on both sides of the tire equator. Regarding the "Shape of Upper Layer" column in Tables 1-2, as illustrated in the examples, the case where a pair of radial portions extending from the side of the shoulder block toward the radially inward side of the tire on both sides of the first recess and the circumferential portion connecting the pair of radial portions in the tire circumferential direction are indicated as "continuous," while the case where the aforementioned "circumferential portion" is cut off by the first recess is indicated as "discontinuous." Regarding the "Connection Position of Grooves" column in Tables 1-2, it indicates which of the grooves is connected to either the first recess (middle layer) or the second recess (lower layer) (the case where the groove is not connected to either the first recess (middle layer) or the second recess (lower layer) is indicated as "non-connected"). Regarding the "Connection Position of Shoulder Transverse Groove" column in Tables 1-2, it indicates which of the first recess (middle layer) and the second recess (lower layer) the shoulder transverse groove connects to (a case where the shoulder transverse groove is not connected to either the first recess (middle layer) or the second recess (lower layer) is indicated as "non-connected"). Regarding the "Shape of First Recess" column in Tables 1-2, a case where the basic structure in any example has the illustrated quadrilateral shape but the opposite sides of the quadrilateral extend in the same direction is indicated as "approximately parallelogram," and a case where a pair of opposite sides of the aforementioned quadrilateral extend in different directions is indicated as "approximately trapezoidal." Regarding the "Arrangement of Protrusions" column in Tables 1-2, it indicates the position where the protrusion overlaps with which of the upper layer / middle layer / lower layer (for example, a case where it is arranged to extend across the upper layer and the middle layer is indicated as "upper layer + middle layer").

[0048] For these pneumatic tires, the performance on poor roads and block durability were evaluated using the following evaluation methods, and the results are shown in Tables 1-2.

[0049] Poor road handling performance

[0050] Each test tire was assembled onto a 17×8J rim size wheel. The front tire pressure was set to 450 kPa, and the rear tire pressure was set to 550 kPa. These tires were then mounted on a test vehicle (traction test vehicle). Traction (starting performance) was evaluated based on the test driver's sensory feedback on a test road consisting of an unpaved road (gravel surface). The evaluation results were expressed as an index with the value of Example 1 set to 100. A higher index value indicates better snow performance. Furthermore, an index value exceeding "105" indicates exceptionally good performance on rough roads.

[0051] Block durability (cut resistance)

[0052] Each test tire was assembled onto a 17×8J rim, with the tire pressure set to 350 kPa, and mounted on a test vehicle (a four-wheel drive SUV). After driving 1000 km on an off-road endurance road, the total length of cuts incurred on the tire sidewall was measured. The evaluation results were expressed as an index with the reciprocal of the measured value of Comparative Example 1 set to 100. The larger the index value, the smaller the total cut length and the better the block durability (cut resistance). Furthermore, an index value of "105" or higher indicates sufficient block durability (cut resistance).

[0053] [Table 1]

[0054]

[0055] [Table 2]

[0056]

[0057] As can be seen from Tables 1 and 2, compared with the conventional Example 1, the pneumatic tires of Examples 1 to 14 improved snow performance and wear resistance, achieving a good balance between these properties. On the other hand, Comparative Example 1 has a structure in which two shoulder blocks are adjacent to one sidewall block. Therefore, although it improved the performance on rough roads compared to the conventional Example 1, it was insufficient because it did not have a first recess (middle layer) and a second recess (lower layer). Comparative Example 2 has a structure in which two shoulder blocks are adjacent to one sidewall block and has a first recess (middle layer), but does not have a second recess (lower layer). Therefore, like Comparative Example 1, it cannot sufficiently improve the performance on rough roads.

[0058] Explanation of reference numerals in the attached figures

[0059] 1. Fetal face

[0060] 2. Side of the tire

[0061] 3. Bead area

[0062] 4. Fetal body layers

[0063] 5. Bead core

[0064] 6. Bead filling

[0065] 7. Belt layer

[0066] 8. Belt reinforcement layer

[0067] 10 main slots

[0068] 11. Tire shoulder transverse groove

[0069] 12 shoulder blocks

[0070] 13 Sidewall blocks

[0071] 14 Sidewall groove

[0072] 15 first recess

[0073] 16 Second recess

[0074] 17. Protruding bar

[0075] 18 fine grooves

[0076] 19 convex part

[0077] P1 Upper Level

[0078] P2 Middle Level

[0079] P3 Lower Level

[0080] CL Tire Equator

Claims

1. A tire, the tire having an annular tread portion extending circumferentially and a pair of sidewall portions disposed on both sides of the tread portion, characterized in that, The surface of the tread has a pair of main grooves extending circumferentially along both sides of the tire equator. Multiple shoulder transverse grooves and multiple shoulder blocks are provided in the shoulder region located outside the main groove in the tire width direction. The multiple shoulder transverse grooves extend from the main groove toward the outside in the tire width direction and are arranged at intervals in the tire circumferential direction. The multiple shoulder blocks are divided by the main groove and the shoulder transverse grooves and are arranged along the tire circumferential direction. A plurality of sidewall blocks protruding from the outer surface of the sidewall portion are provided in the sidewall region adjacent to the outer sidewall region in the tire width direction. A sidewall block is positioned on the outer side of the tire width direction of a group of blocks consisting of two or more adjacent shoulder blocks in the tire circumferential direction. When the surface formed by the side surface of the shoulder block and the top surface of the sidewall block included in the block group is designated as the upper surface, a first recess containing a middle surface that is recessed by more than 0.2 mm is provided on the center side of the upper surface, and a second recess containing a lower surface that is recessed by more than 0.2 mm is provided on the center side of the middle surface.

2. The tire according to claim 1, characterized in that, The first recess and the second recess are respectively arranged across the side surface of the shoulder block and the top surface of the sidewall block included in the group of blocks.

3. The tire according to claim 2, characterized in that, The top surface of the sidewall block constituting the upper layer is composed of a pair of radial portions extending from the side of the shoulder block toward the radially inner side of the tire on both sides of the first recess in the tire circumferential direction, and a circumferential portion connecting the pair of radial portions in the tire circumferential direction.

4. The tire according to any one of claims 1 to 3, characterized in that, The tire shoulder block has a groove extending from the tread surface to the outer side of the tire width direction, and the bottom of the groove at the outer end of the groove in the tire width direction is connected to the middle layer.

5. The tire according to any one of claims 1 to 4, characterized in that, The bottom of the shoulder lateral groove located at the outer end of the shoulder lateral groove in the tire width direction, which is disposed between the shoulder blocks contained in the block group, is connected to the lower layer.

6. The tire according to any one of claims 1 to 5, characterized in that, When viewed from the side of the tire, the first recess has a polygonal shape.

7. The tire according to any one of claims 1 to 6, characterized in that, The innermost radial end of the sidewall block exists in the range of 20% to 50% of the tire section height from the tire equator towards the inner radial side of the tire.

8. The tire according to any one of claims 1 to 7, characterized in that, A raised portion is provided at the bottom of the shoulder transverse groove between the shoulder blocks contained in the block group, the raised portion being arranged to extend across the upper layer and the middle layer.

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