Tire

Abstract

Provided is a tire which enables improvement of snow performance without impairing wear resistance. In the tire, a tread part is provided with a center land part, intermediate land parts, and shoulder land parts which are demarcated by four main grooves extending linearly along the tire circumferential direction. The center land part is divided into a plurality of center blocks by center inclined grooves. Each of the intermediate land parts is divided into a plurality of intermediate blocks by intermediate inclined grooves. Each of the shoulder land parts is divided into a plurality of shoulder blocks by shoulder lateral grooves. The center inclined grooves and the intermediate inclined grooves are inclined in opposite directions with respect to the tire width direction. Shallow grooves are provided at the positions extending from the intermediate inclined grooves in the center blocks in a manner as to extend in the same direction as the intermediate inclined grooves and to terminate within the center blocks without passing through the tire center line. Two or more sipes extending along the tire width direction are provided on each of the center blocks, the intermediate blocks, and the shoulder blocks.

Description

tire

[0001] The present invention relates to a tire having a block-based tread pattern, and more particularly to a tire that enables improved snow performance without sacrificing wear resistance.

[0002] Among tires for vehicles such as SUVs, "highway terrain tires" are known as a category of tires designed specifically for high-speed driving. Tires in this category have a block-based pattern and are required to be able to handle a variety of road conditions (dry, wet, and snowy roads) (see, for example, Patent Document 1). In recent years, emphasis has been placed on snow performance (driving stability on snow-covered roads). For example, increasing the groove area can improve snow performance by making it easier for the tires to grip snow. However, as mentioned above, because tires in this category have a block-based pattern, increasing the groove area can easily reduce the rigidity of the land portion, making it difficult to ensure sufficient wear resistance. Therefore, measures are needed to improve snow performance without compromising wear resistance.

[0003] Japanese Patent Application Publication No. 2019-137218

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

[0005] In order to achieve the above object, the tire of the present invention has a tread portion extending in a circumferential direction of the tire and forming an annular shape, the tread portion having four main grooves extending linearly along the tire circumferential direction and five rows of land portions partitioned by these four main grooves, the five rows of land portions including a center land portion located on the tire equator, intermediate land portions located on both sides of the center land portion in the tire width direction, and shoulder land portions located on the outermost sides in the tire width direction, the center land portion being partitioned into a plurality of center blocks by center oblique grooves formed at intervals in the tire circumferential direction, and the intermediate land portions being partitioned into intermediate blocks formed at intervals in the tire circumferential direction. The shoulder land portion is divided into a plurality of intermediate blocks by inclined grooves, the shoulder land portion is divided into a plurality of shoulder blocks by shoulder lateral grooves formed at intervals in the circumferential direction of the tire, the center inclined groove and the intermediate inclined groove are inclined in opposite directions with respect to the width direction of the tire, and at the extension position of the intermediate inclined groove in the center block, there is a shallow groove extending in the same direction as the intermediate inclined groove and terminating within the center block without crossing the tire equator, and the center block, the intermediate block, and the shoulder block each have two or more sipes extending along the width direction of the tire formed at intervals in the circumferential direction of the tire.

[0006] The tire of the present invention has a tread pattern configured as described above, thereby improving snow performance without sacrificing wear resistance. Specifically, the four main grooves extend linearly, ensuring rigidity at the widthwise ends of each block and ensuring wear resistance and uneven wear resistance. The grooves (center oblique groove, intermediate oblique groove) that define the center land portion and intermediate land portion are inclined with respect to the tire width direction, and the center oblique groove and the intermediate oblique groove are inclined in opposite directions, thereby effectively improving snow performance. A shallow groove extending in the same direction as the intermediate oblique groove is provided at the extension position of the intermediate oblique groove, allowing the intermediate oblique groove and shallow groove to function as a continuous groove, effectively improving snow performance. Meanwhile, the shallow groove has a groove depth smaller than the main groove and terminates within the center block without crossing the tire equator, thereby suppressing a decrease in block rigidity due to the provision of the shallow groove and ensuring wear resistance. Each block has two or more sipes extending along the tire width direction, thereby improving snow performance. These cooperations enable a high level of both wear resistance and snow performance to be achieved.

[0007] In the present invention, it is preferable that the intermediate sipes formed in the intermediate blocks open at both ends into the main grooves, and that the central sipes formed in the center blocks terminate at both ends within the center blocks. That is, for center blocks where shallow grooves are formed, the sipes (center sipes) terminate within the blocks to ensure block rigidity, and for intermediate blocks where shallow grooves are not formed, the sipes (intermediate sipes) open into the main grooves to ensure sufficient snow performance, which is advantageous for achieving both snow performance and wear resistance. In addition, the combination of the aforementioned sipes (central sipes terminating within the blocks and intermediate sipes opening into the main grooves) reduces the difference in rigidity between the center blocks and intermediate blocks, effectively ensuring wear resistance.

[0008] In the present invention, it is preferable that at least a portion of the shallow groove has a tapered shape in which the groove width narrows toward the end portion. By having the shallow groove have such a tapered shape, it is possible to suppress a decrease in the rigidity of the center block due to the formation of the shallow groove, which is advantageous for ensuring wear resistance.

[0009] In the present invention, it is preferable to provide a raised portion at the bottom of each of the center oblique groove and the intermediate oblique groove, which can maintain block rigidity without reducing the groove area, and is advantageous for achieving both snow performance and wear resistance.

[0010] In the present invention, it is preferable that the center oblique groove or the intermediate oblique groove has a narrow portion at at least one end. By narrowing the groove width of each oblique groove at the portion where it connects to the main groove, block rigidity can be ensured. Since the groove width is ensured in the center portion of each groove (other than the narrow portion), snow performance can also be ensured, which is advantageous for achieving both snow performance and wear resistance.

[0011] In the present invention, it is preferable that the intermediate sipes formed in the intermediate blocks extend in the same direction as the intermediate inclined grooves, the center sipes formed in the center blocks extend in the same direction as the center inclined grooves, and the shoulder sipes formed in the shoulder blocks extend in the same direction as the shoulder lateral grooves. By inclining the inclined grooves and sipes in each block in the same manner, block rigidity can be ensured, which is advantageous for maintaining wear resistance.

[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 cross-sectional view of a tire according to an embodiment of the present invention, Fig. 2 is a front view showing a tread surface of a tire according to an embodiment of the present invention, and Fig. 3 is an explanatory view showing a part 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 denotes the tire equator, and the symbol E denotes the ground contact edge. 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 circumferentially in the tire 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 component also extends circumferentially in the tire 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] As described below, the present invention relates to a tread pattern formed on the surface of the tire tread portion 1, and therefore the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. Furthermore, the following description will be based on the pneumatic tire shown in Fig. 1 etc., but the present invention can be applied to various tires, including non-pneumatic tires, as long as they have a surface that comes into contact with the road surface (a region corresponding to the surface of the tread portion 1 in a pneumatic tire).

[0018] As shown in FIG. 2 , the surface of the tread portion 1 of the tire of the present invention is provided with four main grooves 11 extending linearly along the tire circumferential direction. In the following description, pairs of the four main grooves 11, one on each side of the tire equator CL, may be referred to as inner main grooves 11i, and pairs of the four main grooves 11 arranged on the outer side of each inner main groove 11i in the tire width direction, may be referred to as outer main grooves 11o. The depth of each main groove 11 is not particularly limited, but may be set to, for example, 7.0 mm to 16.0 mm. Because the four main grooves 11 extend linearly in this manner, rigidity can be ensured at the widthwise ends of the land portions 12 (blocks) described below, and wear resistance and uneven wear resistance can be ensured.

[0019] These four main grooves 11 define five rows of land portions 12 extending along the tire circumferential direction. Specifically, the rows define a center land portion 12c defined between a pair of inner main grooves 11i, an intermediate land portion 12m defined between the inner main groove 11i and the outer main groove 11o, and shoulder land portions 12s defined on the outer side of the outer main groove 11o in the tire width direction. In other words, the center land portion 12c is a land portion located on the tire equator CL, the intermediate land portions 12m are land portions located adjacent to the center land portion 12c on both sides of the tire width direction with the inner main groove 11i in between, and the shoulder land portions 12s are land portions located on the outermost sides in the tire width direction, including the ground contact edge E.

[0020] The center land portion 12c is divided into multiple center blocks 14c by center oblique grooves 13c formed at intervals in the tire circumferential direction. The intermediate land portion 12m is divided into multiple intermediate blocks 14m by intermediate oblique grooves 13m formed at intervals in the tire circumferential direction. The shoulder land portion 12s is divided into multiple shoulder blocks 14s by shoulder lateral grooves 13s formed at intervals in the tire circumferential direction. The center oblique groove 13c extends at an angle with respect to the tire width direction, and both ends thereof open into a pair of inner main grooves 11i located on both sides of the center land portion 12c. The intermediate oblique groove 13m extends at an angle with respect to the tire width direction, and both ends thereof open into the inner main groove 11i and the outer main groove 11o located on both sides of the intermediate land portion 12m. The shoulder lateral grooves 13s extend along the tire width direction, and one end opens into the outer main groove 11o and the other end opens outward in the tire width direction beyond the ground contact edge E. The center oblique groove 13c and the intermediate oblique groove 13m are inclined in opposite directions relative to the tire width direction. In the following description, the center oblique groove 13c and the intermediate oblique groove 13m may be collectively referred to as the "inclined grooves." Since the center oblique groove 13c and the intermediate oblique groove 13m are inclined relative to the tire width direction and further inclined in opposite directions relative to the tire width direction, snow performance can be effectively improved.

[0021] The inclination angle of each inclined groove can be set to, for example, 10° to 50° with respect to the tire width direction. Specifically, the inclination angle θc of the center inclined groove 13c with respect to the tire width direction can be set to preferably 10° to 50°, more preferably 10° to 30°. The inclination angle θm of the intermediate inclined groove 13m with respect to the tire width direction can be set to preferably -10° to -50°, more preferably -10° to -30°, where the inclination direction of the center inclined groove 13c is expressed as a positive (+) value. Unlike these inclined grooves, the shoulder lateral grooves 13s preferably extend along the tire width direction, and their angle with respect to the tire width direction can be set to 0°±15°. The inclination angles θc and θm may be the same angle with the inclination direction (positive and negative) reversed; however, it is preferable that the absolute value of the inclination angle θm be greater than the absolute value of the inclination angle θc. By making the intermediate inclined groove 13m more inclined with respect to the tire width direction than the center inclined groove 13c, snow performance can be effectively improved.

[0022] The inclination angles θc and θm are the angles formed by a line connecting the groove width centers at the opening ends of the inclined grooves with respect to the tire width direction, as shown in Fig. 3. The angle of the shoulder lateral groove 13s is measured as the angle formed by a line connecting the groove width center at the opening end of the main groove 11 with the groove width center at the ground contact edge E with respect to the tire width direction, similar to the inclination angles θc and θm.

[0023] The groove depth of each oblique groove is preferably set to 20% to 100%, more preferably 50% to 100%, of the groove depth of the main groove 11. The groove depth of the shoulder lateral groove 13s is preferably set to 50% to 100%, more preferably 70% to 100%, of the groove depth of the main groove 11.

[0024] At the extension position of the intermediate oblique groove 13m in the center block 14c, a shallow groove 15 is formed, extending in the same direction as the intermediate oblique groove 13m and terminating within the center block 14c without passing beyond the tire equator CL. The shallow groove 15 has a groove depth smaller than that of the main groove 11 and the oblique grooves (particularly the intermediate oblique groove 13m), and its groove depth is preferably set to 10% to 80%, more preferably 30% to 60%, of the groove depth of the main groove 11. The extension position of the intermediate oblique groove 13m is a position where at least a portion of the opening end of the intermediate oblique groove 13m overlaps with the region (hatched area in FIG. 3 ) between the extension lines of the groove walls (dashed lines in FIG. 3 ). By providing the shallow groove 15 in this manner, the intermediate oblique groove 13m and the shallow groove 15 function as a continuous groove, effectively improving snow performance. On the other hand, since the shallow groove 15 has a smaller groove depth than the main groove 11 and terminates within the center block 14c without exceeding the tire equator CL, the provision of the shallow groove 15 suppresses a decrease in block rigidity and ensures wear resistance.

[0025] Each of the center blocks 14c, intermediate blocks 14m, and shoulder blocks 14s has two or more, preferably two to four, sipes 16 extending in the tire width direction and spaced apart in the tire circumferential direction. The shape of the sipes 16 is not particularly limited, but it is preferable that each block has a zigzag shape on the tread surface, as shown in the figure. The groove width of these sipes 16 can be set to, for example, 1.5 mm or less, and the groove depth of these sipes 16 can be set to, for example, 50% to 100% of the groove depth of the main groove 11. Having an appropriate number of sipes 16 in each block effectively improves snow performance.

[0026] Since the tire of the present invention has a tread pattern configured as described above, the above-mentioned effects of each element (ensuring wear resistance with the four straight main grooves 11, improving snow performance with the center inclined groove 13c and intermediate inclined grooves 13m, maintaining wear resistance and improving snow performance with the shallow grooves 15, and improving snow performance with the sipes 16) work together to achieve a high level of both wear resistance and snow performance.

[0027] Of the sipes 16 formed in each block, the intermediate sipes 16m formed in the intermediate blocks 14m preferably have both ends open into the main grooves. On the other hand, the center sipes 16c formed in the center blocks 14c preferably have both ends terminate within the center blocks 14c. In other words, for the center blocks 14c in which shallow grooves 15 are formed, the sipes 16 (center sipes 16c) should terminate within the blocks to ensure block rigidity. For the intermediate blocks 14m in which shallow grooves 15 are not formed, the sipes 16 (intermediate sipes 16m) should open into the main grooves 11 to ensure sufficient snow performance. This is advantageous for achieving both snow performance and wear resistance. In addition, the combination of the sipes 16 described above (the center sipes 16c terminating within the blocks and the intermediate sipes 16m opening into the main grooves 11) reduces the difference in rigidity between the center blocks 14c and the intermediate blocks 14m, effectively ensuring wear resistance. If the relationship between the opening and the end of the sipe 16 deviates from the above combination, it becomes difficult to achieve a good balance between improving snow performance and ensuring block rigidity, and it becomes difficult to fully achieve both of these performances.

[0028] The sipes 16 formed in each block preferably extend in the same direction as the grooves (center inclined groove 13c, intermediate inclined groove 13m, and shoulder lateral groove 13s) that define each block. Specifically, the intermediate sipes 16m formed in the intermediate block 14m preferably extend in the same direction as the intermediate inclined groove 13m, the center sipes 16c formed in the center block 14c preferably extend in the same direction as the center inclined groove 13c, and the shoulder sipes 16s formed in the shoulder block 14s preferably extend in the same direction as the shoulder lateral groove 13s. Having the grooves extending in the width direction of each block and the sipes 16 extend approximately parallel to each other ensures block rigidity, which is advantageous for maintaining wear resistance. If the inclination directions of these grooves and sipes 16 are opposite, it becomes difficult to maintain good block rigidity. In addition, the angle difference between the grooves (center inclined groove 13c, intermediate inclined groove 13m, shoulder lateral groove 13s) extending in the width direction in each block and the sipes (center sipe 16c, intermediate sipe 16m, shoulder sipe 16s) is preferably 0° to 10°, more preferably 0° to 5°.

[0029] The shape of the shallow grooves 15 is not particularly limited, but it is preferable that at least some of the multiple shallow grooves 15 have a tapered shape in which the groove width narrows toward the terminal end. The tapered shape may be a structure in which the groove width converges toward the groove tip (a V-shaped end), or, as in the illustrated example, a shape that includes a narrow portion at the terminal end where the groove width is narrow and a connecting portion where the groove width gradually decreases from the main portion of the shallow groove toward the narrow portion. In the illustrated example, among the multiple shallow grooves 15 that open to one side of the main groove 11 adjacent to the center land portion and are arranged at intervals in the tire circumferential direction, every other shallow groove 15 has a tapered shape. In other words, tapered shallow grooves 15 and shallow grooves 15 with a constant groove width are arranged alternately in the tire circumferential direction. In the illustrated example, in one center block 14c, when the shallow groove 15 opening into the main groove 11 on one side of the tire equator CL is tapered, the shallow groove 15 opening into the main groove 11 on the other side has a constant groove width. By providing the shallow groove 15 with a tapered shape in this manner, it is possible to suppress a decrease in the rigidity of the center block due to the formation of the shallow groove 15, which is advantageous for ensuring wear resistance.

[0030] In the present invention, it is preferable to provide a raised portion A at the bottom of each of the center oblique groove 13c and the intermediate oblique groove 13m. The raised portion A is a portion of each groove where the groove bottom is raised higher than other portions. The raised portion A is preferably provided at a position where each oblique groove communicates with the main groove 11. The raised portion A's raised amount is preferably 20% to 80%, more preferably 40% to 60%, of the depth of the main groove 11. The raised portion A's raised amount refers to the height of the groove from the bottom of the groove in which the raised portion A is formed to the top surface of the raised portion A. By providing the raised portion A in this manner, block rigidity can be maintained without reducing the groove area, which is advantageous for achieving both snow performance and wear resistance. If the raised portion A's raised amount is less than 20% of the depth of the main groove 11, there is no substantial difference from when the raised portion A is not present, and the effect of the raised portion A cannot be fully expected. If the amount of bottom raising exceeds 80% of the depth of the main groove 11, the groove depth cannot be ensured sufficiently in the region where the bottom raising portion A is provided, making it difficult to ensure sufficient snow performance.

[0031] The groove widths of the center oblique groove 13c and the intermediate oblique grooves 13m do not need to be constant, and each groove may have a narrow portion B with a small groove width at one end. In particular, at least some of the center oblique grooves 13c and at least some of the intermediate oblique grooves 13m may have a narrow portion B at one end. In the illustrated example, all of the intermediate oblique grooves 13m have a narrow portion B at one end. In the illustrated example, intermediate oblique grooves 13m having a narrow portion B at the end opening to the inner main groove 11i and intermediate oblique grooves 13m having a narrow portion B at the end opening to the outer main groove 11o are alternately arranged in the tire circumferential direction. In the illustrated example, the center oblique groove 13c does not have a narrow portion B, but some or all of the center oblique grooves 13c may have a narrow portion B. By narrowing the groove width of each oblique groove at the portion connecting to the main groove 11 in this manner, block rigidity can be ensured. In this case, the groove width is ensured in the central portion (other than the narrow portion B) of each main groove 11, ensuring sufficient snow performance, which is advantageous for achieving both snow performance and wear resistance. The groove width in the narrow portion B is preferably 20% to 80%, more preferably 40% to 60%, of the groove width in the main portion (other portions) of the same groove. When providing the narrow portion, one groove wall of the groove in which the narrow portion is provided should be common to both the narrow portion and the main portion (extending linearly). In other words, the other groove wall of the groove in which the narrow portion is provided should have a bent portion between the narrow portion and the main portion such that the groove width gradually decreases from the main portion toward the narrow portion. Furthermore, since the narrow portion B and the aforementioned raised bottom portion A are both preferably provided at the end opening into the main groove 11, they can also be provided in the same position.

[0032] 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.

[0033] Eight types of pneumatic tires, Conventional Example 1, Comparative Example 1, and Examples 1 to 6, were manufactured, each having a tire size of 265 / 70R17 115H and the basic structure (cross-sectional structure) illustrated in FIG. 1 , with the number of main grooves, the shape of the main groove, the inclination angle θc of the center oblique groove, the inclination angle θm of the intermediate oblique groove, the number of sipes in each block (center block, intermediate block, shoulder block), the shape of the center sipe, the shape of the intermediate sipe, the shape of the shallow groove, the presence or absence of a bottom-up portion in each oblique groove (center oblique groove, intermediate oblique groove), the presence or absence of a narrow portion in each oblique groove (center oblique groove, intermediate oblique groove), and the angle difference between the groove in each block (center oblique groove, intermediate oblique groove, shoulder lateral groove) and the sipes set as shown in Table 1.

[0034] In Table 1, in the column for "Main Groove Shape," a case in which the main groove extends linearly along the main direction is indicated as "Straight." In the columns for "Center Oblique Groove Angle θc" and "Intermediate Oblique Groove Angle θm," the angle θc of the center oblique groove is indicated as a positive (+) value (a negative (-) value means that it is inclined in the opposite direction to the center oblique groove). In the columns for "Center Sipe Shape" and "Intermediate Sipe Shape," a case in which both ends open to the main groove is indicated as "Opening," and a case in which both ends terminate within the block is indicated as "Terminating." In the column for "Shallow Groove Shape," a case in which the shallow groove has a constant groove width is indicated as "Constant Width," and a case in which the shallow groove has a tapered shape is indicated as "Tapered." In the columns for "Presence or Absence of Raised Bottom Portion" and "Presence or Absence of Narrow Width Portion," examples indicated as "Present" mean that each groove has a raised bottom portion or a narrow width portion, as shown in Figure 2.

[0035] The snow performance and wear resistance of these pneumatic tires were evaluated by the following evaluation methods, and the results are shown in Table 1.

[0036] Snow Performance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire and rear tire were inflated to an air pressure of 230 kPa and mounted on a test vehicle (four-wheel drive SUV). A test driver then conducted a sensory evaluation of the handling stability on a test course consisting of a snowy road surface. The evaluation results were expressed as an index, with Conventional Example 1 being given a value of 100. A higher index value indicates better snow performance.

[0037] Wear Resistance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire and rear tire were air-pressurized to 230 kPa and 230 kPa, respectively, and mounted on a test vehicle (four-wheel drive SUV). A test driver drove the tire on a test course, measuring the distance traveled (unit: km) until complete wear. The evaluation results were expressed as an index, with the value of Conventional Example 1 being 100. The larger the index value, the longer the distance traveled until complete wear, indicating superior wear resistance.

[0038]

[0039] As is clear from Table 1, the pneumatic tires of Examples 1 to 6 had improved snow performance and wear resistance, achieving a good balance between these performances, compared to Conventional Example 1. On the other hand, Comparative Example 1 had poor snow performance because shallow grooves were not provided at the extension positions of the intermediate inclined grooves in the center blocks and sipes were not formed in each block.

[0040] 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 11 main groove 11i inner main groove 11o outer main groove 12 land portion 12c center land portion 12m intermediate land portion 12s shoulder land portion 13c center inclined groove 13m intermediate inclined groove 13s shoulder lateral groove 14c center block 14m intermediate block 14s shoulder block 15 shallow groove 16 sipe 16c center sipe 16m intermediate sipe 16s shoulder sipe A bottom raised portion B narrow width portion CL tire equator E ground contact edge

Claims

1. A tire having a tread portion extending in a circumferential direction of the tire to form an annular shape, the tread portion having four main grooves extending linearly along the tire circumferential direction and five rows of land portions defined by these four main grooves, the five rows of land portions including a center land portion located on the tire equator, intermediate land portions located on both sides of the center land portion in the tire width direction, and shoulder land portions located on the outermost sides in the tire width direction, the center land portion being defined into a plurality of center blocks by center inclined grooves formed at intervals in the tire circumferential direction, the intermediate land portion being defined into a plurality of intermediate blocks by intermediate inclined grooves formed at intervals in the tire circumferential direction, the shoulder land portion being defined into a plurality of shoulder blocks by shoulder lateral grooves formed at intervals in the tire circumferential direction, the center inclined groove and the intermediate inclined groove being inclined in opposite directions with respect to the tire width direction, and a shallow groove extending in the same direction as the intermediate inclined groove and terminating within the center block without crossing the tire equator, at an extension position of the intermediate inclined groove in the center block, the shallow groove extending in the same direction as the intermediate inclined groove and terminating within the center block without crossing the tire equator, The tire is characterized in that the center block, the intermediate block, and the shoulder block each have two or more sipes extending in the tire width direction formed at intervals in the tire circumferential direction.

2. The tire according to claim 1, wherein among said sipes, the intermediate sipes formed in said intermediate block have both ends opening into said main grooves, and the center sipes formed in said center block have both ends terminating within said center block.

3. The tire according to claim 1 or 2, characterized in that at least a portion of the shallow groove has a tapered shape in which the groove width narrows toward the terminal end.

4. A tire as described in any one of claims 1 to 3, characterized in that a bottom raised portion is provided at the bottom of each of the center oblique groove and the intermediate oblique groove.

5. A tire according to any one of claims 1 to 4, characterized in that at least one end of the center oblique groove or the intermediate oblique groove has a narrow portion where the groove width is small.

6. A tire as described in any one of claims 1 to 5, characterized in that, of the sipes, intermediate sipes formed in the intermediate block extend in the same direction as the intermediate inclined groove, center sipes formed in the center block extend in the same direction as the center inclined groove, and shoulder sipes formed in the shoulder block extend in the same direction as the shoulder lateral groove.

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