WO2025057874A1 - Tire - Google Patents

Abstract

Provided is a tire with which snow performance can be improved without impairing wear resistance. A tread portion 1 is provided with a center land portion 12c, intermediate land portions 12m, and shoulder land portions 12s that are demarcated by four main grooves 11 extending linearly in the circumferential direction of the tire, wherein: the center land portion 12c is demarcated into a plurality of center blocks 14c by center inclined grooves 13c; each intermediate land portion 12m is demarcated into a plurality of intermediate blocks 14m by intermediate inclined grooves 13m; a shoulder circumferential narrow groove 20, first shoulder lateral grooves 21 that are connected to the shoulder circumferential narrow groove 20 and that do not reach the main groove 11, and second shoulder lateral grooves 22 that open in the main groove 11, intersect the shoulder circumferential narrow groove 20, and terminate in a land portion are provided in each shoulder land portion 12s; and two or more sipes 16 that extend in the width direction of the tire are provided in main parts of each of the center block 14c, the intermediate blocks 14m, and the shoulder land portions 12s.

Description

tire

The present invention relates to a tire with a block-based tread pattern, and more specifically, to a tire that allows for 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 a variety of road conditions (dry roads, wet roads, snowy roads) (see, for example, Patent Document 1). In recent years, there has been a particular 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. For this reason, measures are needed to improve snow performance without compromising wear resistance.

Japanese Patent Application Publication No. 2019-137218

The object of the present invention is to provide a tire that allows for improved snow performance without compromising wear resistance.

The tire of the present invention for achieving the above object is 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 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, the shoulder land portions being defined into a plurality of shoulder circumferential narrow grooves extending along the tire circumferential direction in parallel with the main grooves located on the outermost sides in the tire width direction, and a first shoulder lateral groove extending along the tire width direction. and a second shoulder lateral groove are formed, the first shoulder lateral groove has an outer end in the tire width direction that is open beyond the ground edge, and an inner end in the tire width direction that is connected to the shoulder circumferential narrow groove and does not reach the main groove, the second shoulder lateral groove has a groove width smaller than that of the first shoulder lateral groove, extends at an angle to the tire width direction, has an inner end in the tire width direction that is connected to the main groove, and has an outer end in the tire width direction that intersects with the shoulder circumferential narrow groove and terminates in the shoulder land portion, two or more sipes extending along the tire width direction are formed at intervals in the tire circumferential direction in the center block and the intermediate block, and two or more sipes extending along the tire width direction are formed at intervals in the tire circumferential direction in each of the areas surrounded by the shoulder circumferential narrow groove and a pair of the first shoulder lateral grooves adjacent in the tire circumferential direction in the shoulder land portion.

The tire of the present invention has a tread pattern configured as described above, which allows for improved snow performance without compromising wear resistance. Specifically, the four main grooves extend in a straight line, ensuring the rigidity of the widthwise ends of each block, and ensuring wear resistance and uneven wear resistance. The grooves (center inclined groove, middle inclined groove) that divide the center land portion and the intermediate land portion are inclined with respect to the tire width direction, which allows for improved snow performance. Furthermore, the shoulder land portion is formed with a shoulder circumferential narrow groove, a first shoulder lateral groove, and a second shoulder lateral groove, and the first shoulder lateral groove ensures snow performance, but the first shoulder lateral groove does not reach the main groove and is connected to the shoulder circumferential narrow groove and ends, so that a land portion that extends continuously around substantially the entire tire is formed between the outermost main groove in the tire width direction and the shoulder circumferential narrow groove, which allows for block rigidity to be ensured. Furthermore, the second shoulder lateral groove extends in the tire width direction from the main groove beyond the shoulder circumferential narrow groove, but because the second shoulder lateral groove has a smaller groove width than the first shoulder lateral groove, block rigidity is not compromised and the second shoulder lateral groove is expected to further improve snow performance. In addition, an appropriate amount of sipes extending along the tire width direction are provided in each block and land portion, improving snow performance. These cooperations allow a high level of both wear resistance and snow performance to be achieved.

In the present invention, it is preferable that the inner end of the first shoulder lateral groove in the tire width direction has a tapered shape in which the groove width narrows toward the shoulder circumferential narrow groove. By having the first shoulder lateral groove have such a tapered shape, it is possible to suppress the decrease in rigidity of the shoulder land portion (especially in the vicinity of the shoulder circumferential narrow groove) caused by forming the first shoulder lateral groove, which is advantageous in ensuring wear resistance.

In the present invention, it is preferable that the groove depth Dc of the shoulder circumferential narrow groove, the groove depth D1 of the first shoulder lateral groove, and the groove depth D2 of the second shoulder lateral groove satisfy the relationship Dc≦D2<D1. This provides a good balance between the snow performance provided by each groove and the block rigidity that is reduced by the formation of each groove, which is advantageous for achieving both snow performance and wear resistance.

In the present invention, it is preferable to have a center shallow groove at the extension position of the intermediate oblique groove in the center block, which extends in the same direction as the intermediate oblique groove and terminates within the center block without crossing the tire equator. When a center shallow groove is provided at the extension position of the intermediate oblique groove and extends in the same direction as the intermediate oblique groove, the intermediate oblique groove and the center shallow groove function as a continuous groove, and snow performance can be effectively improved. On the other hand, since the center shallow groove has a groove depth smaller than the main groove and terminates within the center block without crossing the tire equator, a decrease in block rigidity due to the provision of the center shallow groove can be suppressed and wear resistance can be ensured.

In the present invention, it is preferable to have an intermediate shallow groove between adjacent sipes in the tire circumferential direction in the intermediate block, which opens into the main groove located on the outermost side in the tire width direction, extends in the same direction as the intermediate oblique groove, and terminates within the intermediate block without passing the tire width center of the intermediate block. This adds an edge effect due to the intermediate shallow groove, further improving snow performance. On the other hand, since the intermediate shallow groove has a groove depth smaller than the main groove and terminates within the intermediate block without passing the center of the intermediate block, it is possible to suppress the decrease in block rigidity caused by the intermediate shallow groove and ensure wear resistance.

In the present invention, it is preferable to provide a bottom-raised portion at the bottom of each of the center inclined groove and the intermediate inclined groove. By providing the bottom-raised portion in this manner, block rigidity can be maintained without reducing the groove area, which is advantageous for achieving both snow performance and wear resistance.

In the present invention, it is preferable that among 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 land portion extend in the same direction as the first shoulder lateral groove. 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 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.

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 the tread surface of a tire according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing a part of FIG.

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 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 on the tire radial inside of the sidewall portions 2. In Figure 1, the symbol CL indicates the tire equator, and the symbol E indicates 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 in the tire circumferential direction to form an annular shape, which constitutes the basic toroidal structure of a pneumatic tire. The following explanation using Figure 1 is basically based on the meridian cross section shape shown in the figure, but each tire component extends in the tire circumferential direction to form an annular shape.

In addition, if the tire is a pneumatic tire, the contact edge E is the end in the tire width direction of the contact area formed when the tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load. A "standard rim" is a rim that is determined for each tire by the standard system that includes the standards on which the tire is based; for example, it is called the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. "Normal internal pressure" refers to the air pressure set for each tire by each standard in the system of standards on which the tire is based; for JATMA, it is the maximum air pressure; for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES; and for ETRTO, it is the "INFLATION PRESSURE," but if the tire is for a passenger car, it is 180 kPa. "Normal load" is the load determined for each tire by each standard, including the standard on which the tire is based. For JATMA, it is the maximum load capacity. For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "LOAD CAPACITY." However, if the tire is for passenger cars, it is a load equivalent to 88% of the above load.

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 is arranged so that the reinforcing cords 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, for example, a 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.

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 inner main grooves 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 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 way, the rigidity of the widthwise ends of the land portions 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, they 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 a shoulder land portion 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 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 center inclined groove 13c is a groove that extends at an incline with respect to the tire width direction and both ends of which 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 which open into each of the inner main grooves 11i and outer main grooves 11o arranged on both sides of the intermediate land portion 12m. It is preferable that the center inclined groove 13c and the intermediate inclined groove 13m are inclined in opposite directions with respect to the tire width direction. In addition, as shown in the example, the center inclined groove 13c extends linearly, while the middle inclined groove 13m is curved (in the example shown, the middle inclined groove 13m has a zigzag shape consisting of a first portion that opens into the inner main groove 11i and extends linearly at an incline with respect to the tire width direction, a second portion that extends linearly in the same direction as the first portion and opens into the outer main groove 11o, and a third portion that connects the first portion and the second portion and is inclined in the opposite direction to the first portion and the second portion). In the following description, the center inclined groove 13c and the middle inclined groove 13m may be collectively referred to as "inclined grooves". These inclined grooves can improve snow performance. In particular, if the center inclined groove 13c and the middle inclined groove 13m are inclined in opposite directions, or if the middle inclined groove 13m has the above-mentioned curved shape, an edge effect can be exerted in various directions, and snow performance can be effectively improved.

The inclination angle of each inclined groove can be set, for example, to 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 preferably to 10° to 50°, more preferably to 10° to 30°. The inclination angle θm of the intermediate inclined groove 13m with respect to the tire width direction can be set preferably to -10° to -50°, more preferably to -10° to -30°, when the inclination direction of the center inclined groove 13c described above is expressed as a positive (+) value. Note that 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 to make the absolute value of the inclination angle θm larger 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 that a straight line connecting the centers of the groove width at the opening ends of each inclined groove forms with the tire width direction, as shown in FIG.

The groove depth of each inclined groove is preferably set to 20% to 100% of the groove depth of the main groove 11, and more preferably 50% to 100%.

In the shoulder land portion 12s, a shoulder circumferential narrow groove 20 extending along the tire circumferential direction, and a first shoulder lateral groove 21 and a second shoulder lateral groove 21 extending along the tire width direction are formed. In detail, the shoulder circumferential narrow groove 20 extends along the tire circumferential direction in parallel with the main groove 11 (i.e., the outer main groove 11o) arranged on the outermost side in the tire width direction, and a continuous rib 23 extending continuously around substantially the entire tire circumference is formed between the outer main groove 11o and the shoulder circumferential narrow groove 20. The first shoulder lateral groove 21 has an outer end in the tire width direction that is open beyond the ground contact edge E, and an inner end in the tire width direction that is connected to the shoulder circumferential narrow groove 20. The first shoulder lateral groove 21 is interrupted by connecting to the shoulder circumferential narrow groove 20, and does not reach the continuous rib 23 or the outer main groove 11o. The second shoulder lateral groove 22 extends at an angle to the tire width direction so as to intersect with the shoulder circumferential narrow groove 20, with its inner end in the tire width direction connecting to the outer main groove 11o and its outer end in the tire width direction terminating within the shoulder land portion 12s. The shoulder circumferential narrow groove 20 and the second shoulder lateral groove 22 have a groove width smaller than that of the first shoulder lateral groove 21, so that the area defined by the shoulder circumferential narrow groove 20 and the second shoulder lateral groove 22 is not completely divided compared to the area defined by the first shoulder lateral groove 21, and the block rigidity is maintained. Snow performance is ensured by the edge effect of each groove formed in the shoulder land portion 12s, but as described above, the first shoulder lateral groove 21 does not reach the outer main groove 11o and forms a continuous rib 23, so that the block rigidity can be ensured. At this time, the shoulder circumferential narrow groove 20 and the second shoulder lateral groove 22 have a small groove width, so that even if the land portion is apparently defined by these grooves, the block rigidity is not significantly reduced, and wear resistance can be ensured.

As described above, the shoulder circumferential narrow groove 20 and the second shoulder lateral groove 22 have a smaller groove width than the first shoulder lateral groove 21, but when the groove width of the shoulder circumferential narrow groove 20 is Gc, the groove width of the first shoulder lateral groove 21 is G1, and the groove width of the second shoulder lateral groove 22 is G2, the groove width G1 of the first shoulder lateral groove 21 is preferably 1.5 to 3.0 times, and more preferably 1.8 to 2.7 times, the groove width Gc of the shoulder circumferential narrow groove 20 or the groove width G2 of the second shoulder lateral groove 22. Note that, in the case of a tapered shape described later, the groove width G1 of the first shoulder lateral groove is the groove width in the main portion excluding the narrow portion.

Furthermore, when the groove depth of the shoulder circumferential narrow groove 20 is Dc, the groove depth of the first shoulder lateral groove 21 is D1, and the groove depth of the second shoulder lateral groove 22 is D2, it is preferable that these groove depths satisfy the relationship Dc≦D2<D1. This provides a good balance between the snow performance added by each groove and the block rigidity reduced by the formation of each groove, which is advantageous for achieving both snow performance and wear resistance. Although the specific groove depth is not particularly limited, the groove depth D1 of the first shoulder lateral groove 21 is preferably 60% to 100%, more preferably 70% to 90%, of the groove depth of the main groove 11. The groove depth Dc of the shoulder circumferential narrow groove 20 and the groove depth D2 of the second shoulder lateral groove 22 are preferably 20% to 70%, more preferably 30% to 60% of the groove depth of the main groove 11.

The angle θ1 of the first shoulder lateral groove with respect to the tire width direction can be set preferably to 0°±15°, more preferably 0°±10°. The inclination angle θ2 of the second shoulder lateral groove with respect to the tire width direction can be set preferably to 10° to 50°, more preferably 10° to 30° (when the inclination direction of the center inclined groove 13c is expressed as a positive (+) value, it is preferably -10° to -50°, more preferably -10° to -30°). As with the inclination angles θc and θm, these angles θ1 and θ2 are measured as the angle formed with the tire width direction by a straight line connecting the groove width center at the opening end of the main groove 11 or shoulder circumferential narrow groove 20 to the groove width center at the ground contact edge E position or the terminal end.

The center block 14c and the intermediate block 14m each have two or more sipes 16 extending along the tire width direction, preferably two to four sipes 16 spaced apart in the tire circumferential direction. In the shoulder land portion 12s, two or more sipes extending along the tire width direction, preferably two to four sipes 16, are formed at intervals in the tire circumferential direction in each area surrounded by a pair of first shoulder lateral grooves 21 and shoulder circumferential narrow grooves 20 adjacent in the tire circumferential direction. The shape of each sipe 16 is not particularly limited, but it is preferable that each block or land portion has a zigzag shape on the tread surface as shown in the figure. In addition, 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, by providing sipes 16 appropriately in each block or land portion, snow performance can be effectively improved.

The tire of the present invention has a tread pattern configured as described above, and as a result of the cooperation of 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 groove 13m, maintaining wear resistance and improving snow performance with the shoulder circumferential narrow grooves 20, first shoulder lateral groove 21, and second shoulder lateral groove 22 provided in the shoulder land portion 12s, and improving snow performance with the sipes 16), it is possible to achieve a high level of both wear resistance and snow performance.

The groove width of the first shoulder lateral groove 21 does not need to be constant, and it is preferable that at least some, and preferably all, of the multiple first shoulder lateral grooves 21 have a tapered shape in which the groove width narrows toward the shoulder circumferential narrow groove 20 at the tire width inner end. The tapered shape may be a structure in which the groove width converges toward the tip of the groove (V-shaped end), or, as in the illustrated example, a shape having a narrow width portion where the groove width is narrow at the portion connecting with the shoulder circumferential narrow groove 20 and a connecting portion where the groove width gradually decreases from the main portion of the first shoulder lateral groove 21 toward the narrow portion. When the narrow width portion is present as in the illustrated example, the groove width at this narrow width portion is preferably 0.5 to 2.0 times the groove width of the shoulder circumferential groove 20. In addition, the length of the narrow width portion is preferably 0% to 30% of the tire width length from the shoulder circumferential groove 20 to the ground contact end E. By making the first shoulder lateral groove 21 tapered in this way, it is possible to suppress a decrease in rigidity of the shoulder land portion 12s (particularly in the vicinity of the shoulder circumferential narrow groove 20) caused by forming the first shoulder lateral groove 21, which is advantageous in ensuring wear resistance. The narrow portion of the first shoulder lateral groove 21 described above may be raised relative to the main portion of the first shoulder lateral groove 21.

At the extension position of the intermediate inclined groove 13m in the center block 14c, a center shallow groove 15c can be 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 center shallow groove 15c is a groove with 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 center shallow groove 15c in this way, the intermediate inclined groove 13m and the center shallow groove 15c function as a continuous groove, and snow performance can be effectively improved. On the other hand, the center shallow groove 15c has a smaller groove depth than the main groove 11 and terminates within the center block 14c without exceeding the tire equator CL, so the provision of the center shallow groove 15c suppresses a decrease in block rigidity and ensures wear resistance.

The shape of the center shallow groove 15c is not particularly limited, but it is preferable that at least some, and preferably all, of the multiple center shallow grooves 15c 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 tip of the groove (V-shaped end), or, as in the illustrated example, a shape that has a narrow portion at the terminal end and a connection portion where the groove width gradually decreases from the main portion of the center shallow groove 15c toward the narrow portion. By providing a tapered center shallow groove 15c in this way, it is possible to suppress the decrease in rigidity of the center block 14c caused by forming the center shallow groove 15c, which is advantageous for ensuring wear resistance.

A middle shallow groove 15m can be formed in the middle block 14m between the circumferentially adjacent sipes 16, opening into the main groove 11 (outer main groove 11o) arranged on the outermost side in the tire width direction, extending in the same direction as the middle inclined groove 13m, and terminating within the middle block 14m without passing the center of the middle block 14m in the tire width direction. The middle shallow groove 15m is a groove with a smaller groove depth than the main groove 11 and the inclined groove (particularly the middle inclined groove 13m), and the groove depth is preferably set to 10% to 80%, more preferably 30% to 60%, of the groove depth of the main groove 11. By providing the middle shallow groove 15m in this way, an edge effect due to the middle shallow groove 15m is added, and snow performance can be further improved. On the other hand, since the middle shallow groove 15m has a groove depth smaller than the main groove 11 and terminates within the middle block 14m without passing the center of the middle block 14m, the decrease in block rigidity due to the provision of the middle shallow groove 15m can be suppressed and wear resistance can be ensured.

The sipes 16 formed in each block (center block 14c, intermediate block 14m) and land portion (shoulder land portion 12s) preferably extend in the same direction as the grooves (center inclined groove 13c, intermediate inclined groove 13m, first shoulder lateral groove 21) that divide each block or land portion. In 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 land portion 12s preferably extend in the same direction as the first shoulder lateral groove 21. In this way, the grooves extending in the width direction in each block or land portion 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, first shoulder lateral groove 21) 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°.

In the present invention, the center inclined groove 13c, the intermediate inclined groove 13m, and the first shoulder lateral groove 21 may each have a bottom-raised portion A at their bottom. The bottom-raised portion A is a portion of each groove where the bottom is raised higher than other portions. The bottom-raised portion A may be provided at a position where each groove communicates with a groove (main groove 11 or shoulder circumferential narrow groove 20) that extends along the tire circumferential direction. When the bottom-raised portion A is provided at a position where it communicates with the main groove 11, the amount of bottom-raised portion A is preferably 20% to 80%, more preferably 40% to 60%, of the depth of the main groove 11. When the bottom-raised portion A is provided at a position where it communicates with the shoulder circumferential narrow groove 20, the groove depth at the bottom-raised portion A may be equal to or less than that of the shoulder circumferential narrow groove 20, and specifically, the amount of bottom-raised portion A is preferably 10% to 50%, more preferably 20% to 30%, of the depth of the main groove 11. The amount of bottom-raising is 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 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 amount of bottom-raising is below the above-mentioned range, there will be no substantial difference from when the raised portion A does not exist, and the effect of the raised portion A cannot be expected to be sufficient. If the amount of bottom-raising exceeds the above-mentioned range, the groove depth cannot be sufficiently secured in the area where the raised portion A is provided, making it difficult to ensure sufficient snow performance.

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, Conventional Example 1, Comparative Example 1, and Examples 1 to 6, were manufactured with a tire size of 265/70R17 115H, a basic structure (cross-sectional structure) as illustrated in FIG. 1, and the inclination angle θc of the center inclined groove, the inclination angle θm of the intermediate inclined groove, the presence or absence of shoulder circumferential narrow grooves, the presence or absence of first shoulder lateral grooves, the presence or absence of second shoulder lateral grooves, the number of sipes in each land portion (center block, intermediate block, shoulder land portion), the groove depth of each groove (shoulder circumferential narrow groove, first shoulder lateral groove, second shoulder lateral groove) formed in the shoulder land portion, the shape of the first shoulder lateral groove, the presence or absence of center shallow grooves, the presence or absence of intermediate shallow grooves, the presence or absence of bottom-up portions in each inclined groove (center inclined groove, intermediate inclined groove), and the angle difference between the grooves (center inclined groove, intermediate inclined groove, first shoulder lateral groove) and the sipes in each block or land portion, as shown in Table 1.

All examples had four straight main grooves. The angle of the first shoulder lateral groove was 0° relative to the tire width direction, and the angle of the second shoulder lateral groove, if provided, was the same as the angle θm of the intermediate inclined groove. The groove width of the shoulder circumferential narrow groove was 2 mm, the groove width of the first shoulder lateral groove was 5 mm, and the groove width of the second shoulder lateral groove was 2 mm. When the first shoulder lateral groove had a tapered shape, the groove width at its narrow portion was 2 mm. Note that Conventional Example 1 is a pattern in which the shoulder circumferential narrow groove and the second shoulder lateral groove are not provided, and therefore the shoulder land portion is divided into multiple blocks by the first shoulder lateral groove, and has a structure that does not include a "continuous rib" as shown in Figure 2.

In Table 1, in the columns "Center inclined groove angle θc" and "Middle inclined groove angle θm", the center inclined groove angle θc is shown as a positive (+) value (negative (-) value means that it is inclined in the opposite direction to the center inclined groove). In the column "Number of sipes in shoulder land portion", when the shoulder land portion is divided into multiple blocks (conventional example 1), the number of sipes in each block is recorded, and for Examples 1 to 6, the number of sipes included in the area surrounded by a pair of first shoulder lateral grooves and shoulder circumferential narrow grooves adjacent in the tire circumferential direction is recorded. Since Comparative Example 1 does not have a first shoulder lateral groove, it does not include a divided area like Examples 1 to 6, but since the sipe arrangement is the same as Examples 1 to 6 except for the lack of a first shoulder lateral groove, the same values as Examples 1 to 6 are recorded in parentheses for reference. In the column "Groove depth", the percentage relative to the depth of the main groove is shown. In the column "Shape of first shoulder lateral groove," a constant groove width is indicated as "constant width," and a tapered shape is indicated as "tapered." In the column "Whether or not there is a bottom-raised portion," examples marked "Yes" indicate that each groove has a bottom-raised portion or 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 shoulder circumferential narrow grooves and second shoulder lateral grooves in the shoulder land portion, but does not have first shoulder lateral grooves, so its snow performance is deteriorated.

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 14c center block 14m intermediate block 15 shallow groove 16 sipe 16c center sipe 16m intermediate sipe 16s shoulder sipe 20 shoulder circumferential narrow groove 21 first shoulder lateral groove 22 second shoulder lateral groove 23 continuous rib A bottom raised portion B narrow width portion CL tire equator E ground contact edge

Claims (7)

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 divided into a plurality of center blocks by center inclined grooves formed at intervals in the tire circumferential direction, and the intermediate land portion is divided into a plurality of intermediate blocks by intermediate inclined grooves formed at intervals in the tire circumferential direction,
In the shoulder land portion, a shoulder circumferential narrow groove extending along the tire circumferential direction in parallel with the main groove disposed on the outermost side in the tire width direction, and a first shoulder lateral groove and a second shoulder lateral groove extending along the tire width direction are formed,
The first shoulder lateral groove has an outer end in the tire width direction that is open beyond the ground contact edge, and an inner end in the tire width direction that is connected to the shoulder circumferential narrow groove and does not reach the main groove,
the second shoulder lateral groove has a groove width smaller than that of the first shoulder lateral groove, extends at an incline with respect to the tire width direction, an inner end in the tire width direction is connected to the main groove, and an outer end in the tire width direction intersects with the shoulder circumferential narrow groove and terminates within the shoulder land portion,
a pair of first shoulder lateral grooves adjacent to each other in the tire circumferential direction in each of the shoulder land portions, the pair of first shoulder lateral grooves adjacent to each other in the tire circumferential direction in each of the shoulder land portions, and the pair of first shoulder lateral grooves adjacent to each other in the tire circumferential direction in each of the shoulder land portions. The tire described in claim 1, characterized in that the inner end of the first shoulder lateral groove in the tire width direction has a tapered shape in which the groove width narrows toward the shoulder circumferential narrow groove. The tire according to claim 1 or 2, characterized in that the groove depth Dc of the shoulder circumferential narrow groove, the groove depth D1 of the first shoulder lateral groove, and the groove depth D2 of the second shoulder lateral groove satisfy the relationship Dc≦D2<D1. The tire according to any one of claims 1 to 3, characterized in that the center block has a shallow center groove at the extension position of the intermediate inclined groove, which extends in the same direction as the intermediate inclined groove and terminates within the center block without crossing the tire equator. A tire according to any one of claims 1 to 4, characterized in that the intermediate block has a shallow intermediate groove between adjacent sipes in the tire circumferential direction, which opens into the main groove located at the outermost side in the tire width direction, extends in the same direction as the intermediate inclined groove, and terminates within the intermediate block without passing the center of the intermediate block in the tire width direction. The tire according to any one of claims 1 to 5, characterized in that a bottom-raised portion is provided at the bottom of each of the center inclined groove and the intermediate inclined groove. A tire according to any one of claims 1 to 6, 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 land portion extend in the same direction as the first shoulder lateral groove.

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