JP7644386B2 - tire - Google Patents

Description

The present invention relates to a tire with a block-based tread pattern, and more specifically, to a tire that enables improved snow performance without compromising wear resistance.

Among tires for vehicles such as SUVs, "highway terrain tires" are known as a category of tires designed for high-speed driving. Tires in this category have a block-based pattern and are required to be able to handle various road conditions (dry roads, wet roads, snowy roads) (see, for example, Patent Document 1). In recent years, there has been a trend toward emphasis on snow performance (driving stability on snowy roads). For example, increasing the groove area makes it easier for snow to be trapped, improving snow performance, but as mentioned above, because tires in this category are block-based, increasing the groove area tends to reduce the rigidity of the land portion, making it difficult to ensure sufficient wear resistance. Therefore, measures are required to improve snow performance without compromising wear resistance.

JP 2019-137218 A

The objective of the present invention is to provide a tire that improves snow performance without compromising wear resistance.

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 to form an annular shape, the tread portion has 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 disposed on the tire equator, intermediate land portions disposed 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, and the shoulder land portions being defined into a plurality of intermediate blocks by shoulder lateral grooves formed at intervals in the tire circumferential direction. the center block has a shallow groove at an extension position of the intermediate diagonal groove, the shallow groove extends in the same direction as the intermediate diagonal groove and terminates within the center block without passing the tire equator; the center block, the intermediate block, and the shoulder block each have two or more sipes extending along the tire width direction and spaced apart in the tire circumferential direction ; the center diagonal groove and the intermediate diagonal groove each have a raised bottom portion at their groove bottoms; at least one end of the center diagonal groove and/or the intermediate diagonal groove has a narrow portion with a small groove width, and the narrow portion and the raised bottom portion are both disposed at ends opening into the main groove .

The tire of the present invention has a tread pattern configured as described above, so that it is possible to improve snow performance without impairing wear resistance. Specifically, since the four main grooves extend linearly, the rigidity of the widthwise end of each block can be ensured, and wear resistance and uneven wear resistance can be ensured. The grooves (center inclined groove, middle inclined groove) that divide the center land portion and the middle land portion are inclined with respect to the tire width direction, and further, the center inclined groove and the middle inclined groove are inclined in the opposite direction, so that it is possible to effectively improve snow performance. Since a shallow groove extending in the same direction as the middle inclined groove is provided at the extension position of the middle inclined groove, the middle inclined groove and the shallow groove function as a series of grooves, and it is possible to effectively improve snow performance. On the other hand, since the shallow groove has a groove depth smaller than the main groove and terminates within the center block without crossing the tire equator, it is possible to suppress the decrease in block rigidity due to the provision of the shallow groove and ensure wear resistance. Since two or more sipes extending along the tire width direction are provided in each block, it is possible to improve snow performance. Through these cooperation, it is possible to achieve a high degree of both wear resistance and snow performance.

In the present invention, it is preferable that the intermediate sipes formed in the intermediate block have both ends open into the main groove, and that the center sipes formed in the center block have both ends terminated within the center block. That is, for the center block in which the shallow groove is formed, the sipes (center sipes) terminate within the block to ensure block rigidity, and for the intermediate block in which the shallow groove is not formed, the sipes (intermediate sipes) open into the main groove to obtain sufficient snow performance, which is advantageous in achieving both snow performance and wear resistance. In addition, the combination of the sipes mentioned above (center sipes that terminate within the block and intermediate sipes that open into the main groove) suppresses the rigidity difference between the center block and the intermediate block, and wear resistance can be effectively ensured.

In the present invention, as described above, 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 rigidity of the center block due to the formation of the shallow groove, which is advantageous in ensuring wear resistance.

In the present invention, as described above, the center inclined groove and the intermediate inclined groove are provided at their bottoms with raised portions, which makes it possible to maintain block rigidity without reducing the groove area, and is advantageous in achieving both snow performance and wear resistance.

In the present invention, it is preferable that the center inclined groove or the intermediate inclined groove has a narrow portion with a small groove width at at least one end. In this way, the groove width of each inclined groove is narrowed at the portion that communicates with the main groove, thereby ensuring block rigidity. In this case, the groove width is ensured at the center portion of each groove (other than the narrow portion), so snow performance can be sufficiently ensured, which is advantageous for achieving both snow performance and wear resistance.

In the present invention, it is preferable that the intermediate sipes formed in the intermediate block extend in the same direction as the intermediate inclined grooves, the center sipes formed in the center block 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. In this way, by inclining the inclined grooves and sipes in the same way in each block, block rigidity can be ensured, which is advantageous for maintaining wear resistance.

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 inside of the tire can be filled with air, an inert gas such as nitrogen, or other gases.

1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. 1 is a front view showing a tread surface of a tire according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing a part of FIG. 2 .

The configuration of the present invention will be described in detail below with reference to the attached drawings.

When the tire of the present invention is a pneumatic tire as shown in FIG. 1, it has 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 on the tire radial inside of the sidewall portions 2. In FIG. 1, the symbol CL indicates the tire equator, and the symbol E indicates the ground contact edge. Although not depicted because FIG. 1 is a meridian cross section, the tread portion 1, the sidewall portions 2, and the bead portions 3 each extend in the tire circumferential direction to form an annular shape, which constitutes the basic toroidal structure of a pneumatic tire. The following explanation using FIG. 1 is basically based on the meridian cross section shown in the figure, but each tire component extends in the tire circumferential direction to form an annular shape.

A carcass layer 4 is mounted between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inner side to the outer side in the tire width direction around the bead cores 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead cores 5, and this bead filler 6 is wrapped by the main body and folded back parts of the carcass layer 4. On the other hand, a plurality of belt layers 7 (two layers in FIG. 1) are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so that they 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 to a range of, for example, 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.

The present invention relates to a tread pattern formed on the surface of the tread portion 1 of a tire, as described below, so the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. In addition, the following explanation will be based on the pneumatic tire shown in Figure 1, etc., but the present invention can be applied to various tires, including non-pneumatic tires, as long as they have a surface that contacts the road surface (a portion corresponding to the surface of the tread portion 1 in a pneumatic tire).

As shown in FIG. 2, the surface of the tread portion 1 of the tire of the present invention has four main grooves 11 that extend linearly along the tire circumferential direction. In the following description, a pair of the four main grooves 11 arranged on both sides of the tire equator CL may be referred to as the inner main groove 11i, and a pair arranged on the outer side of each inner main groove 11i in the tire width direction may be referred to as the outer main groove 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. Since the four main grooves 11 extend linearly in this way, the rigidity of the widthwise ends of the land portion 12 (blocks) described below can be ensured, and wear resistance and uneven wear resistance can be ensured.

These four main grooves 11 define five rows of land portions 12 extending along the tire circumferential direction. Specifically, a center land portion 12c is defined between a pair of inner main grooves 11i, an intermediate land portion 12m is defined between the inner main groove 11i and the outer main groove 11o, and a shoulder land portion 12s is 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 portion 12m is a land portion 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 portion 12s is a land portion located on the outermost side in the tire width direction including the ground contact edge E.

The center land portion 12c is divided into a plurality of center blocks 14c by center inclined grooves 13c formed at intervals in the tire circumferential direction. The intermediate land portion 12m is divided into a plurality of intermediate blocks 14m by intermediate inclined grooves 13m formed at intervals in the tire circumferential direction. The shoulder land portion 12s is divided into a plurality of shoulder blocks 14s by shoulder lateral grooves 13s formed at intervals in the tire circumferential direction. The center inclined groove 13c is a groove that extends at an incline with respect to the tire width direction, and both ends of the groove open into each of a pair of inner main grooves 11i arranged on both sides of the center land portion 12c. The intermediate inclined groove 13m is a groove that extends at an incline with respect to the tire width direction, and both ends of the groove open into each of the inner main groove 11i and the outer main groove 11o arranged on both sides of the intermediate land portion 12m. The shoulder lateral groove 13s is a groove that extends along the tire width direction, one end of which opens into the outer main groove 11o, and the other end of which opens outward in the tire width direction beyond the ground contact edge E. The center inclined groove 13c and the intermediate inclined groove 13m are inclined in opposite directions relative to the tire width direction. In the following description, the center inclined groove 13c and the intermediate inclined groove 13m may be collectively referred to as "inclined grooves." In this way, the center inclined groove 13c and the intermediate inclined groove 13m are inclined relative to the tire width direction, and further, the center inclined groove 13c and the intermediate inclined groove 13m are inclined in opposite directions, which effectively improves snow performance.

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°, when the inclination direction of the center inclined groove 13c is expressed as a positive (+) value. Unlike these inclined grooves, the shoulder lateral groove 13s may extend along the tire width direction, and the angle with respect to the tire width direction can be set to 0°±15°. The inclination angle θc and the inclination angle θm may be the same angle with the inclination direction (positive and negative) reversed, but it is preferable that the absolute value of the inclination angle θm is greater than the absolute value of the inclination angle θc. In this way, the intermediate inclined groove 13m is inclined more with respect to the tire width direction than the center inclined groove 13c, thereby effectively improving snow performance.

The inclination angles θc and θm are the angles formed by a straight line connecting the groove width centers at the opening ends of each inclined groove 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 straight 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.

The groove depth of each inclined 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.

At the extension position of the intermediate inclined groove 13m in the center block 14c, a shallow groove 15 is formed that extends in the same direction as the intermediate inclined groove 13m and terminates within the center block 14c without crossing the tire equator CL. The shallow groove 15 is a groove that has a smaller groove depth than the main groove 11 and the inclined grooves (particularly the intermediate inclined 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 inclined groove 13m is a position where at least a part of the opening end overlaps with the region (hatched part in FIG. 3) between the extension lines (dashed lines in FIG. 3) of the groove walls of the intermediate inclined groove 13m. By providing the shallow groove 15 in this way, the intermediate inclined groove 13m and the shallow groove 15 function as a series of grooves, and snow performance can be effectively improved. On the other hand, the shallow grooves 15 are smaller in depth than the main grooves 11 and terminate within the center block 14c without exceeding the tire equator CL, so the provision of the shallow grooves 15 prevents a decrease in block rigidity and ensures wear resistance.

The center block 14c, intermediate block 14m, and shoulder block 14s each have two or more, preferably two to four, sipes 16 extending along the tire width direction, spaced apart in the tire circumferential direction. There are no particular limitations on the shape of the sipes 16, but it is preferable that each block has a zigzag shape on its tread surface as shown. 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. In this way, snow performance can be effectively improved by providing an appropriate number of sipes 16 in each block.

The tire of the present invention has a tread pattern configured as described above, and as a result of the combined 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), it is possible to achieve a high level of both wear resistance and snow performance.

Of the sipes 16 formed in each block, the intermediate sipes 16m formed in the intermediate block 14m should have both ends open to the main groove. On the other hand, the center sipes 16c formed in the center block 14c should have both ends terminated within the center block 14c. In other words, for the center block 14c in which the shallow groove 15 is formed, the sipes 16 (center sipes 16c) should terminate within the block to ensure block rigidity, and for the intermediate block 14m in which the shallow groove 15 is not formed, the sipes 16 (intermediate sipes 16m) should open into the main groove 11 to obtain 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 that terminate within the block and the intermediate sipes 16m that open into the main groove 11) suppresses the rigidity difference between the center block 14c and the intermediate block 14m, and wear resistance can be effectively ensured. If the relationship between the opening and end of the sipes 16 deviates from the above combination, it becomes difficult to achieve a good balance between improving snow performance and ensuring block rigidity, making it difficult to fully achieve both of these performance characteristics.

The sipes 16 formed in each block preferably extend in the same direction as the grooves (center inclined groove 13c, intermediate inclined groove 13m, shoulder lateral groove 13s) that divide each block. In more detail, 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. In this way, the grooves extending in the width direction in each block and the sipes 16 extend approximately parallel to each other, thereby ensuring block rigidity and being 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. Furthermore, 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°.

The shape of the shallow grooves 15 is not particularly limited, but it is preferable that at least some of the shallow grooves 15 have a tapered shape in which the groove width narrows toward the end. The tapered shape may be a structure in which the groove width converges toward the tip of the groove (a V-shaped end), or, as in the illustrated example, a shape that has a narrow portion at the end and a connection portion in which the groove width gradually decreases from the main portion of the shallow groove toward the narrow portion. In the illustrated example, the shallow grooves 15 open on one side of the main groove 11 adjacent to the center land portion and are arranged at intervals in the tire circumferential direction, and every other shallow groove 15 has a tapered shape. In other words, the tapered shallow grooves 15 and the 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 a tapered shallow groove 15 in this way, 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.

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

The groove width of the center inclined groove 13c and the intermediate inclined groove 13m does 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 a part of the center inclined grooves 13c and at least a part of the intermediate inclined grooves 13m may be grooves with a narrow portion B at one end. In the illustrated example, all the intermediate inclined grooves 13m have a narrow portion B at one end. In the illustrated example, the intermediate inclined grooves 13m with a narrow portion B at the end opening to the inner main groove 11i and the intermediate inclined grooves 13m with 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 inclined groove 13c does not have a narrow portion B, but the center inclined groove 13c may have a narrow portion B at some or all of them. In this way, the block rigidity can be ensured by narrowing the groove width of the part of each inclined groove that communicates with the main groove 11. In this case, the groove width is secured in the center of each main groove 11 (other than the narrow portion B), so snow performance is also sufficiently secured, 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 portion) of the same groove. In addition, when providing the narrow portion, one groove wall of the groove in which the narrow portion is provided should be common to the narrow portion and the main portion (extending in a straight line). 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 so that the groove width gradually decreases from the main portion toward the narrow portion. In addition, since it is preferable to provide both the narrow portion B and the above-mentioned bottom-up portion A at the end opening into the main groove 11, they can also be provided in the same position.

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.

Eight types of pneumatic tires, namely, Conventional Example 1, Comparative Example 1, and Examples 1 to 6, were produced, 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 inclined groove, the inclination angle θm of the intermediate inclined 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 raised portion in each inclined groove (center inclined groove, intermediate inclined groove), the presence or absence of a narrow portion in each inclined groove (center inclined groove, intermediate inclined groove), and the angle difference between the grooves in each block (center inclined groove, intermediate inclined groove, shoulder lateral groove) and the sipes set as shown in Table 1 (Note that Examples 1 to 4 which do not have a narrow portion and a raised portion are reference examples) .

In Table 1, in the column "Shape of main groove", the case where the main groove extends in a straight line along the main direction is indicated as "straight line". In the columns "Center inclined groove angle θc" and "Intermediate inclined groove angle θm", the angle θc of the center inclined groove is indicated as a positive (+) value (negative (-) value means that it is inclined in the opposite direction to the center inclined groove). In the columns "Shape of center sipe" and "Shape of intermediate sipe", the case where both ends open to the main groove is indicated as "open", and the case where both ends terminate within the block is indicated as "terminating". In the column "Shape of shallow groove", the case where the shallow groove has a constant groove width is indicated as "constant width", and the case where the shallow groove has a tapered shape is indicated as "tapered". In the columns "Whether or not there is a bottom-raised portion" and "Whether or not there is a narrow width portion", the examples indicated as "Yes" mean that each groove has a bottom-raised portion or a narrow width portion as shown in Figure 2.

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

Snow Performance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire was set at an air pressure of 230kPa, and the rear tire was set at an air pressure of 230kPa. The test vehicle (four-wheel drive SUV) was then fitted with each test tire, and a sensory evaluation of the steering stability was carried out by a test driver on a test course consisting of a snowy road surface. The evaluation results were expressed as an index, with the value of Conventional Example 1 being 100. The higher the index value, the better the snow performance.

Wear resistance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire and rear tire were set at an air pressure of 230 kPa and 230 kPa, respectively, and mounted on a test vehicle (four-wheel drive SUV). A test driver performed a test run on a test course, and the running distance (unit: km) until complete wear was measured. 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 running distance until complete wear and the better the wear resistance.

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

The present disclosure includes the following inventions.
Invention [1] A tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape,
The tread portion includes four main grooves extending linearly along the tire circumferential direction and five rows of land portions defined by the four main grooves, the five rows of land portions including a center land portion disposed on the tire equator, intermediate land portions disposed on both sides of the center land portion in the tire width direction, and shoulder land portions positioned on the outermost sides in the tire width direction,
the center land portion is partitioned into a plurality of center blocks by center inclined grooves formed at intervals in the tire circumferential direction, the intermediate land portion is partitioned into a plurality of intermediate blocks by intermediate inclined grooves formed at intervals in the tire circumferential direction, the shoulder land portion is partitioned 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 are inclined in opposite directions with respect to the tire width direction,
a shallow groove extending in the same direction as the intermediate inclined groove and terminating within the center block without passing the tire equator, at an extension position of the intermediate inclined groove;
The center block, the intermediate block, and the shoulder block each have two or more sipes extending along the tire width direction formed at intervals in the tire circumferential direction ,
A tire characterized in that a bottom-raised portion is provided at the bottom of each of the center oblique groove and the intermediate oblique groove, and at least one end of the center oblique groove and/or the intermediate oblique groove has a narrow portion having a small groove width, and the narrow portion and the bottom-raised portion are both located at ends that open into the main groove .
Invention [2] The tire according to invention [1], characterized in that, of the sipes, the intermediate sipes formed in the intermediate block have both ends opening into the main groove, and the center sipes formed in the center block have both ends terminating within the center block.
Invention [3] The tire according to invention [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 an end portion.
Invention [ 4 ] The tire according to any one of inventions [1] to [3], 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 blocks extend in the same direction as the shoulder lateral groove.

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 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 (4)

A tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape,
The tread portion includes four main grooves extending linearly along the tire circumferential direction and five rows of land portions defined by the four main grooves, the five rows of land portions including a center land portion disposed on the tire equator, intermediate land portions disposed on both sides of the center land portion in the tire width direction, and shoulder land portions positioned on the outermost sides in the tire width direction,
the center land portion is partitioned into a plurality of center blocks by center inclined grooves formed at intervals in the tire circumferential direction, the intermediate land portion is partitioned into a plurality of intermediate blocks by intermediate inclined grooves formed at intervals in the tire circumferential direction, the shoulder land portion is partitioned 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 are inclined in opposite directions with respect to the tire width direction,
a shallow groove extending in the same direction as the intermediate inclined groove and terminating within the center block without passing the tire equator, at an extension position of the intermediate inclined groove in the center block;
The center block, the intermediate block, and the shoulder block each have two or more sipes extending along the tire width direction formed at intervals in the tire circumferential direction ,
A tire characterized in that a bottom-raised portion is provided at the bottom of each of the center oblique groove and the intermediate oblique groove, and at least one end of the center oblique groove and/or the intermediate oblique groove has a narrow portion having a small groove width, and the narrow portion and the bottom-raised portion are both located at ends that open into the main groove . The tire according to claim 1, characterized in that among the sipes, the intermediate sipes formed in the intermediate block have both ends open into the main groove, and the center sipes formed in the center block have both ends terminated within the center block. 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. The tire according to claim 1 or 2, characterized in that, of the sipes, the intermediate sipes formed in the intermediate block extend in the same direction as the intermediate inclined groove, the center sipes formed in the center block extend in the same direction as the center inclined groove, and the shoulder sipes formed in the shoulder block extend in the same direction as the shoulder lateral groove.

Images