Tire

Abstract

To provide a tire which achieves improvement of on-ice / snow performance while maintaining dry performance.SOLUTION: The invention relates to a tire. Grooves 3 provided at a tread part 2 include: a plurality of first inclined grooves 6; a plurality of second inclined grooves 7; a plurality of first shoulder vertical grooves 8; and a plurality of first crown vertical grooves 11. Each of the first inclined grooves 6 communicates with the second inclined grooves 7 and is terminated. Each of the second inclined grooves 7 communicates with the first inclined grooves 6 and is terminated. A plurality of blocks 4 includes a plurality of crown blocks 15, a plurality of first shoulder blocks 18, and a plurality of first middle blocks 16. A tread of each block 4 is formed with a plurality of sipes 10. As for a sipe density SDc of the crown block 15, a sipe density SDm of the first middle block 16, and a sipe density SDs of the first shoulder block 18, SDc>SDs and SDm>SDs are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] For example, Patent Document 1 below proposes a tire having a tread portion provided with a plurality of first oblique grooves, a plurality of second oblique grooves, and a plurality of first longitudinal grooves connecting two of the first oblique grooves. This tire is expected to maintain dry performance and improve performance on ice and snow by specifying the groove width of the first longitudinal grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-080118 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the improvement in vehicle performance, further improvements in snow and ice performance are required for all-season tires used on both dry and snowy roads. One method for improving snow and ice performance is to arrange many sipes in the land portion of the tread. However, depending on the arrangement of the sipes, this method may excessively reduce the rigidity of the land portion, impairing dry performance.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire that improves performance on ice and snow while maintaining dry performance. [Means for solving the problem]

[0006] The present invention is a tire having a tread portion with a designated rotation direction, the tread portion including a first tread edge and a second tread edge, a plurality of grooves provided between the first tread edge and the second tread edge, and a plurality of blocks divided into the plurality of grooves, the plurality of grooves including a plurality of first inclined grooves extending from at least the first tread edge toward the tire equator at an incline toward the leading side in the rotation direction, a plurality of second inclined grooves extending from at least the second tread edge toward the tire equator at an incline toward the leading side in the rotation direction, a plurality of first shoulder circumferential grooves extending in the tire circumferential direction and communicating with two of the first inclined grooves adjacent in the tire circumferential direction, and a plurality of first crown circumferential grooves disposed between the plurality of first shoulder circumferential grooves and the tire equator and communicating with the two first inclined grooves, Each of the first inclined grooves terminates in communication with one of the plurality of second inclined grooves, and each of the plurality of second inclined grooves terminates in communication with one of the plurality of first inclined grooves, and the plurality of blocks includes a plurality of crown blocks provided on the tire equator, the first tread edge, and a plurality of first shoulder blocks divided by the two first inclined grooves and the first shoulder longitudinal grooves, and a plurality of first middle blocks provided between the plurality of crown blocks and the plurality of first shoulder blocks, and a plurality of sipes are formed on the tread surfaces of the first shoulder blocks, the tread surfaces of the first middle blocks, and the tread surfaces of the crown blocks, respectively, and for each block, the total length (mm) of the plurality of sipes formed on the tread surface is expressed as the area (mm) of the tread surface. 2 ) divided by the sipe density (mm / mm 2 ), the sipe density SDc of the crown block, the sipe density SDm of the first middle block, and the sipe density SDs of the first shoulder block satisfy SDc>SDs and SDm>SDs. [Effects of the Invention]

[0007] By adopting the above-described configuration, the tire of the present invention can improve performance on ice and snow while maintaining dry performance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of a crown block, a first middle block, and a shoulder block shown in FIG. [Figure 3] FIG. 1 is a conceptual graph showing the rigidity distribution of the tread portion of various tires. [Figure 4] 3 is an enlarged cross-sectional view of the first shoulder sipe of FIG. 2 taken along the length direction. FIG. [Figure 5] 3 is an enlarged cross-sectional view of the second shoulder sipe of FIG. 2 taken along the length direction. FIG. [Figure 6] 3 is an enlarged cross-sectional view of the middle sipe of FIG. 2 taken along the length direction. [Figure 7] 3 is an enlarged cross-sectional view of the shallow sipe of FIG. 2 taken along the length direction. [Figure 8] 2 is an enlarged view of the contour of the first inclined groove of FIG. 1; [Figure 9] FIG. 2 is a development view of a tread portion of a tire of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. The drawings are intended to illustrate the features of the present invention, but may include exaggerated representations and representations that differ from the dimensional ratios of the actual structure to facilitate understanding of the present invention. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, well-known configurations may be appropriately adopted for configurations not described in this specification.

[0010] Fig. 1 shows a developed view of a tread portion 2 of a tire 1 of this embodiment. As shown in Fig. 1, the tire 1 of this embodiment is a pneumatic tire for passenger cars, and is used as a so-called all-season tire that combines sufficient dry performance with performance on snow and ice. However, the tire of the present invention is not limited to this embodiment.

[0011] The tire 1 of the present invention has a tread portion 2 in which a rotation direction R is specified. The rotation direction R is indicated, for example, by letters or symbols on a sidewall portion (not shown).

[0012] The tread portion 2 of the tire 1 of this embodiment includes a first tread edge T1 and a second tread edge T2. In each drawing in this specification, the tread edge on the left side of the tire equator C is referred to as the first tread edge T1, and the tread edge on the right side of the tire equator C is referred to as the second tread edge T2. The tread portion 2 includes a first tread portion 2A between the tire equator C and the first tread edge T1, and a second tread portion 2B between the tire equator C and the second tread edge T2. The first tread portion 2A and the second tread portion 2B are configured to be substantially line-symmetrical about the tire equator C, except that they are misaligned in the tire circumferential direction. Therefore, each configuration of the first tread portion 2A can be applied to the second tread portion 2B.

[0013] The first tread edge T1 and the second tread edge T2 correspond to the edges of the contact patch when 70% of the normal load is applied to the tire 1 in a normal state and the tread portion 2 is brought into contact with a flat surface at a camber angle of 0°.

[0014] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, a state in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal condition means a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0015] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0016] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard 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."

[0017] For pneumatic tires for which various standards are established, "normal load" refers to the load specified for each tire in the standard system including the standard on which the tire is based. For JATMA, this is "maximum load capacity," for TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, this is "LOAD CAPACITY." For tires for which various standards are not established, "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0018] The tread portion 2 includes a plurality of grooves 3 provided between a first tread edge T1 and a second tread edge T2, and a plurality of blocks 4 separated by the plurality of grooves 3.

[0019] The plurality of grooves 3 include a plurality of first inclined grooves 6, a plurality of second inclined grooves 7, a plurality of first shoulder circumferential grooves 8, and a plurality of first crown circumferential grooves 11. The first inclined grooves 6 extend from at least the first tread edge T1 toward the tire equator C, inclining toward the leading side in the rotational direction R. The second inclined grooves 7 extend from at least the second tread edge T2 toward the tire equator C, inclining toward the leading side in the rotational direction R. The first inclined grooves 6 and the second inclined grooves 7 each have a groove width W1 of 2 to 12 mm. The first inclined grooves 6 and the second inclined grooves 7 each have a depth of 5 to 12 mm.

[0020] In this specification, when the numerical ranges of various parameters are described, unless otherwise specified, the numerical ranges refer to the average values ​​of the parameters. Therefore, the numerical ranges of the groove width and depth of the inclined grooves described above refer to the average numerical ranges of the groove width and depth measured at various positions on the inclined grooves. The same applies to other parameters described below.

[0021] The first shoulder circumferential groove 8 extends in the tire circumferential direction and communicates with two circumferentially adjacent first oblique grooves 6. The first crown circumferential groove 11 is disposed between the first shoulder circumferential groove 8 and the tire equator C and communicates with the two first oblique grooves 6.

[0022] In this embodiment, the plurality of grooves 3 include a plurality of second shoulder longitudinal grooves 9 and a plurality of second crown longitudinal grooves 12 arranged in the second tread portion 2B. The second shoulder longitudinal grooves 9 have substantially the same characteristics as the first shoulder longitudinal grooves 8. The second crown longitudinal grooves 12 have substantially the same characteristics as the first crown longitudinal grooves 11. Therefore, the characteristics of the first shoulder longitudinal grooves 8 described below may also be applied to the second shoulder longitudinal grooves 9. The first crown longitudinal grooves 11 and the second crown longitudinal grooves 12 have the same relationship.

[0023] In the present invention, each of the plurality of first inclined grooves 6 terminates in communication with one of the plurality of second inclined grooves 7. Furthermore, each of the plurality of second inclined grooves 7 terminates in communication with one of the plurality of first inclined grooves 6.

[0024] The multiple blocks 4 include crown blocks 15, first shoulder blocks 18, and first middle blocks 16. In this embodiment, the crown blocks 15 include first crown blocks 15A and second crown blocks 15B that are alternately arranged in the tire circumferential direction. The first crown block 15A is divided into two first oblique grooves 6, one second oblique groove 7, and one first crown longitudinal groove 11. The second crown block 15B is divided into two second oblique grooves 7, one first oblique groove 6, and one second crown longitudinal groove 12.

[0025] The first shoulder block 18 includes the first tread edge T1 and is divided into two first oblique grooves 6 and a first shoulder longitudinal groove 8. The first middle block 16 is provided between the multiple crown blocks 15 and the multiple first shoulder blocks 18.

[0026] The block 4 of this embodiment further includes a second shoulder block 19 and a second middle block 17. The second shoulder block 19 has substantially the same characteristics as the first shoulder block 18. The second middle block 17 has substantially the same characteristics as the first middle block 16. Therefore, the characteristics of the first shoulder block 18 described below may also be applied to the second shoulder block 19. The first middle block 16 and the second middle block 17 have a similar relationship.

[0027] Fig. 2 shows an enlarged view of the crown block 15, the first middle block 16, and the first shoulder block 18. As shown in Fig. 2, a plurality of sipes 10 are formed on the tread surface 18s of the first shoulder block 18, the tread surface 16s of the first middle block 16, and the tread surface 15s of the crown block 15. Hereinafter, the sipes 10 provided on the crown block 15 may be referred to as crown sipes 21, the sipes 10 provided on the first middle block 16 may be referred to as middle sipes 23, and the sipes 10 provided on the first shoulder block 18 may be referred to as shoulder sipes 25.

[0028] In this specification, the term "sipe" refers to a small-width notch that, when a ground load acts on the tread portion 2, two sipe walls included in the sipe main body come into contact with each other, thereby maintaining the rigidity of the block. The sipe main body refers to a portion in which two sipe walls extend substantially parallel to each other (for example, at an angle of 10° or less) in the tire radial direction. From the viewpoint of achieving the above-described effect, the width between the two sipe walls in the sipe main body is, for example, 1.5 mm or less, preferably 0.4 to 1.2 mm, and more preferably 0.4 to 1.0 mm. The sipe of this embodiment extends with a constant width from its opening to its bottom. However, the sipe may have a chamfered edge. The sipe may also have a so-called flask bottom, which is wider at its bottom.

[0029] For each block, the total length (mm) of the plurality of sipes 10 formed on the tread surface is calculated based on the area (mm 2 ) divided by the sipe density (mm / mm 2 ), in the present invention, the sipe density SDc of the crown blocks 15, the sipe density SDm of the first middle blocks 16, and the sipe density SDs of the first shoulder blocks 18 satisfy the following formulas (1) and (2). As a result, the tire of the present invention can improve its performance on snow and ice while maintaining its dry performance. The reason for this is as follows. SDc>SDs…(1) SDm>SDs…(2)

[0030] As shown in FIG. 1, in the tire 1 of the present invention, each of the multiple first inclined grooves 6 terminates in communication with one of the multiple second inclined grooves 7. Furthermore, each of the multiple second inclined grooves 7 terminates in communication with one of the multiple first inclined grooves 6. Therefore, when the tire 1 of the present invention is driven on snow and ice, the communicating portions of these grooves strongly compact snow, exerting a large snow column shear force. Furthermore, because multiple sipes 10 are provided on the tread surface of each block, these edges provide a large frictional force even on snow and ice. This improves snow and ice performance.

[0031] Figure 3 shows a conceptual graph of the rigidity distribution of the tread portion of various tires. The horizontal axis P in Figure 3 indicates the axial position of the tread portion, with the center position corresponding to the tire equator C, the left side corresponding to the first tread edge T1 side, and the right side corresponding to the second tread edge T2 side. The vertical axis S in Figure 3 indicates the rigidity level of each portion. Graph GR1 in Figure 3 shows the rigidity distribution of a conventional studless tire. Graph GR2 shows the rigidity distribution of a conventional summer tire. Graph GR3 shows the rigidity distribution of tire 1 of this embodiment.

[0032] As can be seen from graphs GR1 and GR2 in Figure 3, studless tires that prioritize snow and ice performance have many sipes in the tread, which results in an overall low rigidity in the tread. On the other hand, conventional summer tires, which are not designed for driving on snow and ice and which prioritize dry performance, have a relatively high rigidity in the tread.

[0033] The inventors have conducted extensive research into the degree of contribution of each part of the tread when driving on dry roads and on snow and ice. As a result, they have discovered that to maintain dry performance, it is desirable to maintain the rigidity of the shoulder blocks, and to improve snow and ice performance, it is desirable to provide many sipes in the middle blocks and crown blocks to reduce their rigidity.

[0034] Based on this knowledge, in the present invention, the sipe density of each block satisfies the above-mentioned formulas (1) and (2). As a result, in the tread portion 2 of the tire 1 of the present invention, as shown in graph GR3 in Figure 3, the first shoulder blocks 18 exhibit high rigidity to maintain dry performance, while the first middle blocks 16 and crown blocks 15 provide high friction through the sipes 10, improving snow and ice performance. Due to this mechanism, the tire 1 of the present invention can improve snow and ice performance while maintaining dry performance, compared to conventional all-season tires.

[0035] As shown in FIG. 2, from the viewpoint of improving dry performance and snow and ice performance in a well-balanced manner, the sipe density SDs of the first shoulder block 18 is, for example, 0.10 to 0.15 (mm / mm 2 ), and preferably 0.12 to 0.14 (mm / mm 2 Similarly, the sipe density SDc of the crown block 15 and the sipe density SDm of the first middle block 16 are each, for example, 0.17 to 0.23 (mm / mm 2 ), and preferably 0.20 to 0.22 (mm / mm 2 )

[0036] The sipe density SDc of the crown blocks 15 and the sipe density SDm of the first middle blocks 16 are preferably 140% to 160% of the sipe density SDs, respectively, which suppresses uneven wear of the first middle blocks 16 and the crown blocks 15 and provides excellent performance on snow and ice.

[0037] The sipe density SDc of the crown block 15 is preferably 80% to 120% of the sipe density SDm of the first middle block 16. This further suppresses uneven wear of these blocks.

[0038] The following describes the configuration of this embodiment in more detail. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even if it does not include the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to the tire 1 of the present invention having the above-described characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, an improvement in combined performance corresponding to those configurations can be expected.

[0039] As shown in Fig. 1, the tread portion 2 includes tread rubber 2G that forms the tread surface of the blocks 4. From the viewpoint of improving dry performance and performance on snow and ice in a well-balanced manner, the rubber hardness of this tread rubber 2G is, for example, 50 to 65 degrees. In this specification, the rubber hardness refers to a durometer A hardness measured in an environment of 23°C in accordance with JIS-K6253.

[0040] From the same viewpoint, the land ratio of the tread portion 2 is 65% to 75%. In this specification, the "land ratio" corresponds to the ratio of the actual contact area to the hypothetical contact area in a state where all the grooves and sipes of the tread portion 2 are filled.

[0041] Conventional all-season tires often have a tread width of approximately 65% ​​to 70% of the tire's nominal width, placing some emphasis on wet performance. In contrast, the tread width TW of the tire 1 of this embodiment is 75% to 85% of the tire's nominal width, and more preferably 80% or more. This allows the tread portion 2 to have a sufficiently large contact area, enabling excellent grip on dry roads and icy and snowy roads. The above-mentioned nominal width of the tire corresponds to the nominal cross-sectional width of the tire. That is, if the tire size is, for example, "195 / 65R15," the nominal width is 195 mm.

[0042] The tread portion 2 is provided with a plurality of V-shaped block groups 5 arranged in the tire circumferential direction, each group including one crown block 15, one first middle block 16, one second middle block 17, one first shoulder block 18, and one second shoulder block 19. The tread portion 2 of this embodiment is composed of 55 to 78 of these block groups 5 around the entire tire circumference. However, the present invention is not limited to this configuration.

[0043] As shown in Figure 2, the multiple sipes 10 are each arranged at an angle of 15° or less with respect to the tire axial direction. This configuration means that the angle of an imaginary line connecting both ends of the sipes 10 with respect to the tire axial direction is 15° or less. In a desirable embodiment, all of the sipes 10 provided in the tread portion 2 are arranged in the above-mentioned manner. This configuration reliably improves traction performance and braking performance on icy and snowy roads, which are particularly important for all-season tires.

[0044] The sipes 10 of this embodiment include sipes 10A that extend in a zigzag pattern in a plan view of the tread and sipes 10B that extend linearly. The zigzag-extending sipes 10A also extend radially in a zigzag pattern in a cross section perpendicular to the longitudinal direction, and are configured as so-called 3D sipes. When ground pressure is applied, two sipe walls of the zigzag-extending sipes 10A come into contact with each other in a meshing manner, effectively maintaining the rigidity of the blocks.

[0045] The first shoulder block 18 is provided with a plurality of first shoulder sipes 26 and a plurality of second shoulder sipes 27. The first shoulder sipes 26 extend linearly from a circumferential narrow groove 30 (described later) to at least the first tread edge T1. The second shoulder sipes 27 extend in a zigzag pattern from the first shoulder circumferential groove 8 to the circumferential narrow groove 30. Two to four first shoulder sipes 26 are arranged in the circumferential direction of the tire per first shoulder block 18. The same is true for the second shoulder sipes 27. As a result, four to eight sipes 10 are arranged per first shoulder block 18.

[0046] FIG. 4 shows an enlarged cross-sectional view of the first shoulder sipe 26 along its length. As shown in FIG. 4, the depth of the first shoulder sipe 26 gradually increases from the end of the first shoulder sipe 26 on the tire equator C side toward the first tread edge T1 side. The first shoulder sipe 26 includes a first portion 26a, a second portion 26b, and a third portion 26c, each of which has a different depth from the end of the longitudinal narrow groove 30 side toward the end of the first tread edge T1 side. The first portion 26a has a depth d1, which is the maximum depth of the sipe. This depth d1 is, for example, 65% to 80% of the maximum depth (not shown) of the first oblique groove 6. The length of the first portion 26a in a tread plan view (the so-called periphery length along the longitudinal direction of the sipe; the same applies hereinafter) is, for example, 25% to 35% of the overall length of the first shoulder sipe 26 on the tread surface 18s of the first shoulder block 18.

[0047] The second portion 26b has a depth d2 that is smaller than the depth d1. The depth d2 is, for example, 60% to 75% of the depth d1. The length of the second portion 26b in a tread plan view is 25% to 35% of the overall length of the first shoulder sipe 26. The third portion 26c has a depth d3 that is smaller than the depth d2. The depth d3 is, for example, 25% to 40% of the depth d1. The length of the third portion 26c in a tread plan view is 25% to 35% of the overall length of the first shoulder sipe 26. The first shoulder sipe 26 having such a depth distribution helps to improve dry performance and icy and snowy performance in a well-balanced manner.

[0048] FIG. 5 shows an enlarged cross-sectional view of the second shoulder sipe 27 along its length. Because the second shoulder sipe 27 extends in a zigzag pattern, its sipe walls include irregularities and ridges that form their boundaries, but these are omitted in FIG. 5 . This also applies to other cross-sectional views of sipes in this specification. As shown in FIG. 5 , the second shoulder sipe 27 includes a first portion 27a, a second portion 27b, and a third portion 27c, each with a different depth, extending from the end on the first shoulder longitudinal groove 8 side toward the end on the longitudinal thin groove 30 side.

[0049] The first portion 27a of the second shoulder sipe 27 communicates with the first shoulder circumferential groove 8 and has the smallest depth. The second portion 27b has the largest depth d5 ​​of the second shoulder sipe 27. The depth d4 of the first portion 27a is 25% to 35% of the depth d5 ​​of the second portion 27b. The third portion 27c has a depth d6 that is greater than the depth d4 of the first portion 27a but less than the depth d5 ​​of the second portion 27b. The depth d6 of the third portion 27c is, for example, 60% to 70% of the depth d5 ​​of the second portion 27b. The second shoulder sipe 27 having such a depth distribution can prevent excessive opening at the end on the first shoulder circumferential groove 8 side, effectively maintaining dry performance.

[0050] The length of the first portion 27a in a tread plan view is 10% to 25% of the overall length of the second shoulder sipe 27. The length of the second portion 27b in a tread plan view is 25% to 35% of the overall length of the second shoulder sipe 27. The length of the third portion 27c in a tread plan view is 40% to 60% of the overall length of the second shoulder sipe 27.

[0051] FIG. 6 shows an enlarged cross-sectional view of the middle sipe 23 along its length. As shown in FIG. 6, the middle sipe 23 has shallow bottom portions 23a at both ends. The depth d8 of the shallow bottom portions 23a is, for example, 20% to 35% of the maximum depth d7 of the middle sipe 23. Such a middle sipe 23 can prevent opening at both ends, thereby improving performance on snow and ice while reliably maintaining dry performance. This cross-sectional shape may also be used for the crown sipe 21 (shown in FIG. 2).

[0052] As shown in FIG. 2, a plurality of axially extending sipes 10 are arranged in the circumferential direction of the tire on the first middle blocks 16 and the crown blocks 15. Of these sipes 10, the sipes 10 provided on the circumferential end sides of the blocks are preferably configured as shallow sipes 32. FIG. 7 shows an enlarged cross-sectional view of the shallow sipes 32 along their length. As shown in FIG. 7, the shallow sipes 32 have a depth d9 of, for example, 0.5 to 2.0 mm. By arranging such shallow sipes 32 at the ends of the blocks, damage to the blocks, such as chipping, can be suppressed.

[0053] Fig. 8 shows an enlarged view of the contour of the first inclined groove 6 in Fig. 1. Note that sipes arranged in the land portion are omitted in Fig. 8. As shown in Fig. 8, the plurality of first inclined grooves 6 include, for example, main first inclined grooves 6a that terminate closer to the second tread edge T2 (shown in Fig. 1) side of the tire equator C and sub-first inclined grooves 6b that terminate without crossing the tire equator C, alternately arranged in the tire circumferential direction.

[0054] For example, the angle of the first oblique grooves 6 with respect to the tire axial direction increases toward the tire equator C. Such first oblique grooves 6 provide snow column shear force in multiple directions, which helps to improve traction and cornering performance on snow.

[0055] The first inclined groove 6 includes, for example, a plurality of groove portions that extend linearly and are inclined with respect to the tire axial direction. In a preferred embodiment, the total length of the linearly extending groove edges of the first inclined groove 6 of this embodiment is 80% or more of the total length of the entire groove edges.

[0056] The first inclined groove 6 includes, for example, a first groove portion 36, a second groove portion 37, and a third groove portion 38. The first groove portion 36 extends linearly, for example, at an angle inclined toward the tire axial direction from at least the first tread edge T1. The second groove portion 37 is continuous with the first groove portion 36 and extends linearly at a larger angle relative to the tire axial direction than the first groove portion 36. The third groove portion 38 is continuous with the second groove portion 37 and extends at a larger angle relative to the tire axial direction than the second groove portion 37. In this embodiment, the third groove portion 38 of the main first inclined groove 6a communicates with the second inclined groove 7 across the tire equator C, and the third groove portion 38 of the sub-first inclined groove 6b communicates with the second inclined groove 7 without crossing the tire equator C.

[0057] The angle θ1 of the first groove portion 36 relative to the tire axial direction is, for example, 5 to 15 degrees. The angle θ2 of the second groove portion relative to the tire axial direction is, for example, 25 to 35 degrees. The angle θ3 of the third groove portion 38 relative to the tire axial direction is, for example, 45 to 60 degrees. This allows the edges of each groove portion to exert frictional forces in multiple directions when driving on icy and snowy roads, resulting in excellent performance on ice and snow.

[0058] It is desirable that the groove width W1 of the first inclined grooves 6 decreases from the first tread edge T1 side toward the tire equator C. This makes it easier for water in the first inclined grooves 6 to be guided toward the first tread edge T1 side during wet driving, improving wet performance.

[0059] For example, the first shoulder circumferential grooves 8 have their leading end portions in the rotational direction R connected to the groove edges of the first groove portions 36 and second groove portions 37 of the first oblique grooves 6. Also, their trailing end portions in the rotational direction R connected to the groove edges of the second groove portions 37 of the first oblique grooves 6. As a result, the first shoulder circumferential grooves 8 are inclined toward the first tread edge T1 toward the leading end in the rotational direction R. The angle θ4 of the first shoulder circumferential grooves 8 with respect to the tire circumferential direction is, for example, 5 to 15 degrees. Such first shoulder circumferential grooves 8 can provide large frictional force in the tire axial direction.

[0060] It is desirable that the groove width of the first shoulder longitudinal grooves 8 continuously increases toward the leading side in the direction of rotation R. Furthermore, it is desirable that the groove width W3 of the first shoulder longitudinal grooves 8 is 50% to 70% of the maximum groove width W2 of the first oblique grooves 6. Such first shoulder longitudinal grooves 8 can use the rotation of the tire to strongly compact snow inside, thereby exerting a large snow column shear force.

[0061] The first crown circumferential grooves 11 communicate with the third groove portions 38 of the two first oblique grooves 6. As a result, as shown in FIG. 2, the first crown circumferential grooves 11 separate the crown blocks 15 from the first middle blocks 16. The first crown circumferential grooves 11 are inclined toward the first tread edge T1 toward the leading side in the rotational direction R. As shown in FIG. 8, the angle θ5 of the first crown circumferential grooves 11 with respect to the tire circumferential direction is, for example, 25 to 35 degrees. Such first crown circumferential grooves 11 can exert a well-balanced frictional force in the axial and circumferential directions when traveling on snowy and icy roads.

[0062] In this embodiment, for example, one longitudinal narrow groove 30 is provided in the first shoulder block 18. The longitudinal narrow groove 30 communicates with the first groove portions 36 of the two first oblique grooves 6 and extends in the tire circumferential direction. The longitudinal narrow groove 30 is inclined toward the first tread edge T1 toward the leading side in the rotational direction R. The angle θ6 of the longitudinal narrow groove 30 with respect to the tire circumferential direction is desirably larger than the angle θ4 of the first shoulder longitudinal groove 8. Specifically, the angle θ6 of the longitudinal narrow groove 30 is 10 to 25°.

[0063] The longitudinal narrow groove 30 extends linearly with a constant groove width W4. The groove width W4 of the longitudinal narrow groove 30 is smaller than the groove width W3 of the first shoulder longitudinal groove 8 and is smaller than the groove width of the first crown longitudinal groove 11. In a preferred embodiment, the groove width W4 of the longitudinal narrow groove 30 is 10% to 20% of the groove width W3 of the first shoulder longitudinal groove 8. Such a longitudinal narrow groove 30 can reliably maintain dry performance.

[0064] 2, the longitudinal narrow groove 30 is connected to the first shoulder sipe 26 and the second shoulder sipe 27. However, the tire 1 of the present invention is not limited to this embodiment.

[0065] As shown in Figure 8, the first middle block 16 of this embodiment is provided with one short middle groove 40 that communicates with one first oblique groove 6 and has a closed end within the tread surface 16s. In a preferred embodiment, the short middle groove 40 that communicates with the secondary first oblique groove 6b overlaps with an extended region of the first crown longitudinal groove 11 that communicates with the secondary first oblique groove 6b. With this groove arrangement, the secondary first oblique groove 6b and the short middle groove 40 cooperate to form a solid snow column when driving on snowy and icy roads, further improving snow and ice performance.

[0066] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects. [Example]

[0067] A pneumatic tire of size 195 / 65R15 having the tread pattern shown in FIG. 1 was prototyped based on the specifications in Tables 1 and 2. A comparative tire having the tread pattern shown in FIG. 9 was prototyped. As shown in FIG. 9, in the comparative tire, the sipe density SDc of the crown block a and the sipe density SDm of the first middle block b are smaller than the sipe density SDs of the first shoulder block c. Except for the above-mentioned features, the comparative tire is substantially the same as the tire shown in FIG. 1. Each test tire was tested for dry performance and snow and ice performance. The common specifications and test methods for each test tire are as follows: Test vehicle: 1800cc, front-wheel drive Test tire mounting position: All wheels Rim: 15x6.0 Tire pressure: Front 230kPa, rear 240kPa

[0068] <Dry performance> The driving performance of the test vehicle when driven on a dry road surface was evaluated by the driver. The results were given as a rating indicating the driving performance, with a higher rating indicating better dry performance.

[0069] <Performance on ice and snow> The driving performance of the test vehicle when driven on snowy and icy roads was evaluated by the driver. The results were given as a rating indicating the driving performance, with a higher rating indicating better performance on snow and ice. The test results are shown in Table 1.

[0070] [Table 1]

[0071] As shown in Table 1, the comparative tire had dry performance and snow and ice performance of 6.0 points. In contrast, the example tire had dry performance of 5.8 points, which was only 0.2 points lower than the comparative tire. On the other hand, the example tire had snow and ice performance of 7.0 points, which was 1.0 point better than the comparative tire. As described above, it was confirmed that the example tire exhibited excellent snow and ice performance while maintaining dry performance.

[0072] [Note] The present invention includes the following aspects.

[0073] [Invention 1] A tire having a tread portion with a designated rotation direction, the tread portion includes a first tread edge and a second tread edge, a plurality of grooves provided between the first tread edge and the second tread edge, and a plurality of blocks separated by the plurality of grooves, The plurality of grooves are a plurality of first inclined grooves extending at least from the first tread edge toward the tire equator and inclining toward the leading side in the rotational direction; a plurality of second inclined grooves extending at least from the second tread edge toward the tire equator and inclined toward the leading side in the rotational direction; a plurality of first shoulder longitudinal grooves extending in the tire circumferential direction and communicating with two of the first oblique grooves adjacent in the tire circumferential direction; a plurality of first crown longitudinal grooves arranged between the plurality of first shoulder longitudinal grooves and the tire equator and communicating with the two first oblique grooves, each of the plurality of first inclined grooves communicates with and terminates in one of the plurality of second inclined grooves; each of the second inclined grooves communicates with any one of the first inclined grooves and terminates therein; The plurality of blocks are a plurality of crown blocks provided on the tire equator; a plurality of first shoulder blocks including the first tread edge and divided by the two first oblique grooves and the first shoulder longitudinal groove; a plurality of first middle blocks provided between the plurality of crown blocks and the plurality of first shoulder blocks, a plurality of sipes are formed on the tread surface of the first shoulder block, the tread surface of the first middle block, and the tread surface of the crown block, For each block, the total length (mm) of the plurality of sipes formed on the tread surface is multiplied by the area (mm 2 ) divided by the sipe density (mm / mm 2 ) and The sipe density SDc of the crown block, the sipe density SDm of the first middle block, and the sipe density SDs of the first shoulder block are SDc>SDs, and SDm>SDs, Satisfy your tires. [Invention 2] The sipe density SDs is 0.10 to 0.15 (mm / mm 2 ) The tire according to the present invention 1. [Invention 3] The sipe density SDc and the sipe density SDm are each 0.17 to 0.23 (mm / mm 2 3. The tire according to claim 1 or 2, wherein [Invention 4] 4. The tire according to any one of claims 1 to 3, wherein the sipe density SDc and the sipe density SDm are each 140% to 160% of the sipe density SDs. [Invention 5] 5. The tire according to any one of claims 1 to 4, wherein the sipe density SDc is 80% to 120% of the sipe density SDm. [Invention 6] The tire according to any one of claims 1 to 5, wherein a tread width, which is the distance in the tire axial direction from the first tread edge to the second tread edge, is 75% to 85% of the nominal width of the tire. [Invention 7] 7. The tire according to any one of claims 1 to 6, wherein the plurality of sipes are arranged at an angle of 15° or less with respect to the tire axial direction. [Invention 8] the plurality of blocks include a plurality of second middle blocks adjacent to the second tread edge sides of the plurality of crown blocks via the grooves, and a plurality of second shoulder blocks adjacent to the second tread edge sides of the plurality of second middle blocks via the grooves, The tire according to any one of the first to seventh aspects of the present invention, wherein the tread portion is provided with a plurality of V-shaped block groups arranged in the tire circumferential direction, each group including one crown block, one first middle block, one second middle block, one first shoulder block, and one second shoulder block. [Invention 9] A tire according to any one of claims 1 to 8, wherein the plurality of first inclined grooves include main first inclined grooves that terminate closer to the second tread edge than the tire equator and sub-first inclined grooves that terminate without crossing the tire equator, alternately arranged in the tire circumferential direction. [Invention 10] 10. The tire according to any one of claims 1 to 9, wherein the first shoulder circumferential groove has a groove width that continuously increases toward the leading side in the rotational direction. [Invention 11] The tire according to any one of claims 1 to 10, wherein the first shoulder block is provided with one longitudinal narrow groove that communicates with the two first oblique grooves and extends with a constant groove width. [Invention 12] 12. The tire according to any one of claims 11 to 19, wherein the longitudinal narrow grooves are inclined toward the first tread edge toward the leading side in the direction of rotation. [Invention 13] The tire according to claim 12, wherein the plurality of sipes provided on the tread surface of the first shoulder block include a plurality of first shoulder sipes extending linearly from the longitudinal narrow groove to at least the first tread edge. [Invention 14] The tire according to any one of claims 1 to 13, wherein the first middle block is provided with one middle short groove that is connected to one of the first oblique grooves and has a closed end within the tread surface. [Invention 15] The tread portion includes tread rubber that forms the tread surface, 15. The tire according to any one of claims 1 to 14, wherein the tread rubber has a rubber hardness of 50 to 65 degrees. [Explanation of symbols]

[0074] 2 Tread section 3 grooves 4 blocks 6 1st inclined groove 7 2nd inclined groove 8 First shoulder longitudinal groove 10 sipes 11 First crown longitudinal groove 15 Crown Block 16 First Middle Block 18 First Shoulder Block R Rotation direction T1 First tread edge T2 Second tread edge SDc Crown block sipe density SDm sipe density of first middle block SDs: Sipe density of first shoulder block

Claims

1. A tire having a tread portion with a designated rotation direction, the tread portion includes a first tread edge and a second tread edge, a plurality of grooves provided between the first tread edge and the second tread edge, and a plurality of blocks separated by the plurality of grooves, The plurality of grooves are a plurality of first inclined grooves extending from at least the first tread edge toward the tire equator and inclined toward the leading side in the rotational direction; a plurality of second inclined grooves extending from at least the second tread edge toward the tire equator and inclined toward the leading side in the rotational direction; a plurality of first shoulder longitudinal grooves extending in the tire circumferential direction and communicating with two of the first oblique grooves adjacent in the tire circumferential direction; a plurality of first crown longitudinal grooves arranged between the plurality of first shoulder longitudinal grooves and the tire equator and communicating with the two first oblique grooves, each of the plurality of first inclined grooves communicates with and terminates in one of the plurality of second inclined grooves; each of the second inclined grooves communicates with any one of the first inclined grooves and terminates therein; The plurality of blocks are a plurality of crown blocks provided on the tire equator; a plurality of first shoulder blocks including the first tread edge and divided by the two first oblique grooves and the first shoulder longitudinal groove; a plurality of first middle blocks disposed between the plurality of crown blocks and the plurality of first shoulder blocks, a plurality of sipes are formed on the tread surface of the first shoulder block, the tread surface of the first middle block, and the tread surface of the crown block, For each block, the total length (mm) of the plurality of sipes formed on the tread surface is multiplied by the area (mm 2 ) divided by the sipe density (mm / mm 2 ) and The sipe density SDc of the crown block, the sipe density SDm of the first middle block, and the sipe density SDs of the first shoulder block are SDc>SDs and SDm>SDs, Satisfy your tires.

2. The sipe density SDs is 0.10 to 0.15 (mm / mm 2 2. The tire of claim 1, wherein

3. The sipe density SDc and the sipe density SDm are each 0.17 to 0.23 (mm / mm 2 3. The tire of claim 2, wherein

4. The tire according to claim 3, wherein the sipe density SDc and the sipe density SDm are each 140% to 160% of the sipe density SDs.

5. The tire according to claim 4, wherein the sipe density SDc is 80% to 120% of the sipe density SDm.

6. The tire according to any one of claims 1 to 5, wherein a tread width, which is the distance in the tire axial direction from the first tread end to the second tread end, is 75% to 85% of a nominal width of the tire.

7. The tire according to claim 1 , wherein each of the plurality of sipes is arranged at an angle of 15° or less with respect to the tire axial direction.

8. the plurality of blocks include a plurality of second middle blocks adjacent to the plurality of crown blocks on the second tread edge side via the grooves, and a plurality of second shoulder blocks adjacent to the plurality of second middle blocks on the second tread edge side via the grooves, 6. The tire according to claim 1, wherein the tread portion includes a plurality of V-shaped block groups arranged in the tire circumferential direction, each V-shaped block group including one crown block, one first middle block, one second middle block, one first shoulder block, and one second shoulder block.

9. 6. The tire according to claim 1, wherein the plurality of first oblique grooves include main first oblique grooves that terminate closer to the second tread edge than the tire equator and sub-first oblique grooves that terminate without crossing the tire equator, alternately arranged in the tire circumferential direction.

10. The tire according to claim 1 , wherein the first shoulder circumferential groove has a groove width that continuously increases toward the leading side in the rotational direction.

11. The tire according to claim 1 , wherein the first shoulder block is provided with one narrow longitudinal groove that is connected to the two first oblique grooves and extends with a constant groove width.

12. The tire according to claim 11, wherein the longitudinal narrow groove is inclined toward the first tread edge toward the leading side in the rotational direction.

13. The tire according to claim 12, wherein the plurality of sipes provided on the tread surface of the first shoulder block include a plurality of first shoulder sipes extending linearly from the longitudinal narrow groove to at least the first tread edge.

14. 6. The tire according to claim 1, wherein the first middle block is provided with one middle short groove that is connected to one of the first oblique grooves and has a closed end within the tread surface.

15. The tread portion includes tread rubber that forms the tread surface, 6. The tire according to claim 1, wherein the tread rubber has a rubber hardness of 50 to 65 degrees.

Images