Tire

Abstract

To provide a tire that improves turning performance on a wet road, as well as, reduces noise outside the vehicle.SOLUTION: In a tire designated with a mounting direction onto a vehicle: an inner shoulder narrow groove 31 and multiple inner shoulder lug grooves 41 are formed in an inner shoulder land portion 21; a thin rib 61 is defined between the inner shoulder narrow groove 31 and a first main groove 11; a circumferential auxiliary groove 32 and multiple first sipes 51 are formed in an inner intermediate land portion 22; a thin rib 62 is defined between the circumferential auxiliary groove 32 and a second main groove 12; multiple second sipes 52 are formed in a center land portion 23; multiple third sipes 53 and multiple fourth sipes 54 are formed in an outer intermediate land portion 24; an outer shoulder narrow groove 35 and multiple outer shoulder lug grooves 45 are formed in an outer shoulder land portion 25; and a thin rib 65 is defined between the outer shoulder narrow groove 35 and a fourth main groove 14.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire having a specified mounting direction on a vehicle, and more particularly to a tire that improves cornering performance on wet roads and reduces noise outside the vehicle. [Background technology]

[0002] It has been proposed that in a tire for which the mounting direction on a vehicle is specified, four main grooves extending circumferentially in the tread portion are formed, and these main grooves divide five rows of land areas. In each land area located between the main grooves, multiple lug grooves are formed, extending in the tire width direction and connecting to the main groove on the inside of the vehicle, but terminating within the land area without connecting to the main groove on the outside of the vehicle (see, for example, Patent Document 1).

[0003] In a tire configured in this manner, the lug grooves formed in the land portions located between the main grooves each have a structure in which one end opens into the main groove and the other end terminates within the land portion, and therefore, it is expected that the tire will exhibit excellent steering stability on wet roads while maintaining sufficient rigidity of each land portion. Furthermore, because all of these lug grooves open toward the inside of the vehicle, pumping noise and pattern noise during driving are radiated toward the inside of the vehicle, and it is expected that this will reduce external noise. However, in recent years, with the increasing performance of vehicles, further improvements in performance on wet roads (particularly cornering performance) and noise performance have been required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2015 / 005194 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a tire that can improve cornering performance on wet road surfaces and reduce noise outside the vehicle. [Means for solving the problem]

[0006] In order to achieve the above object, the tire of the present invention has a tire in which a mounting direction on a vehicle is specified, and the tire has four main grooves formed in the tread portion extending in the tire circumferential direction, and five rows of land portions are defined by these main grooves, and the four main grooves include a first main groove, a second main groove, a third main groove, and a fourth main groove, which are arranged in succession from the inner side of the vehicle to the outer side of the vehicle, and the five rows of land portions include an inner shoulder land portion, an inner intermediate land portion, a center land portion, an outer intermediate land portion, and an outer shoulder land portion, which are arranged in succession from the inner side of the vehicle to the outer side of the vehicle, and the inner shoulder land portion has an inner shoulder narrow groove extending in the tire circumferential direction and multiple inner shoulder lug grooves extending in the tire width direction, and a thin rib that is continuous in the tire circumferential direction is defined between the inner shoulder narrow groove and the first main groove, and the inner intermediate land portion has a circumferential auxiliary groove extending in the tire circumferential direction, a plurality of first sipes are formed, one end of which opens into the first main groove and the other end of which connects to the circumferential auxiliary groove; a thin rib is defined between the circumferential auxiliary groove and the second main groove, the center land portion is formed with a plurality of second sipes, one end of which opens into the second main groove and the other end of which closes within the center land portion; the outer intermediate land portion is formed with a plurality of third sipes, one end of which opens into the third main groove and the other end of which closes within the outer intermediate land portion, and a plurality of fourth sipes, one end of which opens into the fourth main groove and the other end of which closes within the outer intermediate land portion; and the outer shoulder land portion is formed with an outer shoulder thin groove extending in the tire circumferential direction and a plurality of outer shoulder lug grooves extending in the tire width direction, and a thin rib is defined between the outer shoulder thin groove and the fourth main groove, [Effects of the Invention]

[0007] In the present invention, first to fourth sipes are formed in the inner intermediate land portion, center land portion, and outer intermediate land portion, respectively, thereby ensuring sufficient edge components in the tire width direction. Furthermore, by forming inner shoulder narrow grooves in the inner shoulder land portion, outer shoulder narrow grooves in the outer shoulder land portion, and circumferential auxiliary grooves in the inner intermediate land portion, sufficient edge components in the tire circumferential direction are ensured, thereby improving cornering performance on wet roads. While there is concern that forming inner shoulder narrow grooves in the inner shoulder land portion and outer shoulder narrow grooves in the outer shoulder land portion may worsen pattern noise, the inner intermediate land portion, center land portion, and outer intermediate land portion are provided with only sipes (first to fourth sipes) as elements extending in the tire width direction, and do not have lug grooves with large groove widths. This suppresses radiation of pattern noise to the outside of the vehicle, thereby reducing exterior noise. Furthermore, the narrow ribs defined in the inner shoulder land portion, inner intermediate land portion, and outer shoulder land portion are continuous and uninterrupted in the tire circumferential direction, thereby blocking pattern noise and reducing exterior noise. Furthermore, the second sipe formed in the center land portion is closed within the center land portion, which also blocks pattern noise and reduces exterior noise. The outer intermediate land portion is formed with third and fourth sipes, and the fourth sipe opens into the fourth main groove on the vehicle's outer side. However, because both the third and fourth sipes are closed within the outer intermediate land portion, they do not cause pattern noise to radiate to the outside of the vehicle, thereby reducing exterior noise. These cooperations improve cornering performance on wet roads and reduce exterior noise.

[0008] In the present invention, it is preferable that the inner shoulder narrow groove and the outer shoulder narrow groove are arranged within a region of the central 80% of the contact width of the tread portion, the ratio Wgi / Wsi of the groove width Wgi of the inner shoulder narrow groove to the width Wsi of the inner shoulder land portion is less than 0.30, and the ratio Wgo / Wso of the groove width Wgo of the outer shoulder narrow groove to the width Wso of the outer shoulder land portion is less than 0.30. This improves the drainage performance of the inner shoulder narrow groove and the outer shoulder narrow groove, and effectively improves cornering performance on wet roads.

[0009] In the present invention, it is preferable that the ratio Wgm / Wmi of the groove width Wgm of the circumferential auxiliary groove to the width Wmi of the inner intermediate land portion is less than 0.30, and the circumferential auxiliary groove is disposed on the outer side of the vehicle with respect to the widthwise center position of the inner intermediate land portion, thereby improving the drainage performance of the circumferential auxiliary groove and effectively improving cornering performance on wet roads.

[0010] In the present invention, it is preferable that the third sipes and the fourth sipes are arranged alternately in the tire circumferential direction, which makes it possible to prevent the generation of pattern noise caused by the repetition of multiple third sipes and the repetition of multiple fourth sipes, and is advantageous for reducing external noise.

[0011] In the present invention, the ratio L2 / Wc of the length L2 of the second sipe to the width Wc of the center land portion is preferably 0.30 or more and less than 0.70. Furthermore, the ratio L3 / Wmo of the length L3 of the third sipe to the width Wmo of the outer intermediate land portion is preferably 0.20 or more and less than 0.70, and the ratio L4 / Wmo of the length L4 of the fourth sipe to the width Wmo of the outer intermediate land portion is preferably 0.20 or more and less than 0.70. By setting each sipe to an appropriate length in this way, it is advantageous to achieve both improved cornering performance on wet roads and reduced exterior noise.

[0012] In the present invention, the inclination angle θ1 of the first sipe with respect to the tire circumferential direction is preferably 40° or more and 80° or less. The inclination angle θ2 of the second sipe with respect to the tire circumferential direction is preferably 40° or more and 80° or less. Furthermore, the inclination angle θ3 of the third sipe with respect to the tire circumferential direction is preferably 40° or more and 80° or less, and the inclination angle θ4 of the fourth sipe with respect to the tire circumferential direction is preferably 40° or more and 80° or less. By appropriately inclining each sipe with respect to the tire circumferential direction in this manner, each sipe can exert an appropriate edge effect in both the tire circumferential direction and the tire width direction, which is advantageous for improving cornering performance on wet roads.

[0013] In the present invention, it is preferable that the inclination angle θ1 of the first sipe with respect to the tire circumferential direction, the inclination angle θ2 of the second sipe with respect to the tire circumferential direction, the inclination angle θ3 of the third sipe with respect to the tire circumferential direction, and the inclination angle θ4 of the fourth sipe with respect to the tire circumferential direction satisfy the relationship θ1 ≥ θ3 ≈ θ4 ≥ θ2. This provides a good balance between the rigidity of each land portion and the edge effect based on each sipe, which is advantageous for achieving both improved cornering performance on wet roads and reduced exterior noise.

[0014] In the present invention, it is preferable to form chamfers at the acute angles formed by the first sipes and the first main groove, the acute angles formed by the first sipes and the circumferential auxiliary groove, the acute angles formed by the second sipes and the second main groove, the acute angles formed by the third sipes and the third main groove, and the acute angles formed by the fourth sipes and the fourth main groove, thereby improving drainage performance due to the chamfers, which is advantageous for improving cornering performance on wet roads.

[0015] The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, the interior thereof can be filled with air, an inert gas such as nitrogen, or other gases.

[0016] In this invention, the contact patch width of the tread portion is the axial contact patch width measured when a tire is mounted on a standard rim, inflated to the standard internal pressure (for pneumatic tires), placed vertically on a flat surface, and subjected to a standard load. The term "standard rim" refers to the rim specified for each tire by the standard system, including the standard on which the tire is based. For example, this refers to the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. The term "standard internal pressure" refers to the air pressure specified for each tire by the standard system, including the standard on which the tire is based. This refers to the maximum air pressure for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" table for TRA, and the "INFLATION PRESSURE" for ETRTO, but is 180 kPa for tires for passenger cars. "Normal load" is the load 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 load capacity, 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 "LOAD CAPACITY." However, if the tire is for a passenger car, it is a load equivalent to 88% of the above load. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a development view showing the tread pattern of the pneumatic tire of FIG. [Figure 3] FIG. 3 is an enlarged plan view showing the tread pattern of FIG. 2. [Figure 4] FIG. 10 is an explanatory diagram showing a conventional tread pattern. DETAILED DESCRIPTION OF THE INVENTION

[0018] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] In the case of a pneumatic tire as shown in Fig. 1, the tire of the present invention comprises a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. Although not depicted in Fig. 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, thereby constituting the basic toroidal structure of a pneumatic tire. The following explanation using Fig. 1 will be based basically on the meridian cross section shown, but each tire constituent member also extends in the tire circumferential direction to form an annular shape.

[0020] A carcass layer 4 is mounted between a pair of left and right bead portions 3. This 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 a bead core 5 disposed in each bead portion 3. A bead filler 6 is disposed on the outer periphery of the bead core 5, and this bead filler 6 is enclosed by the main body portion and folded back portion of the carcass layer 4. The bead filler 6 has a triangular cross section, for example, as shown in the figure, and is made of a rubber composition.

[0021] A plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords (belt cords) inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set, for example, in the range of 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layers 7. At least one belt cover layer 8 is provided on the outer peripheral side of the belt layer 7 for the purpose of improving high-speed durability. The belt cover layer 8 includes reinforcing cords (cover cords) oriented in the tire circumferential direction. In the belt cover layer 8, the angle of the reinforcing cords with respect to the tire circumferential direction is set, for example, to 0° to 5°. Organic fiber cords such as nylon and aramid cords are preferably used as the reinforcing cords of the belt cover layer 8.

[0022] The tire of the present invention is a tire in which the mounting direction of the front and back sides of the tire when mounted on a vehicle is specified. In Figs. 1 to 3, "IN" indicates the inside of the vehicle when mounted on the vehicle, and "OUT" indicates the outside of the vehicle when mounted on the vehicle. For example, as shown in Fig. 1, a mounting direction indicator 2A indicating the mounting direction relative to the vehicle is formed on at least the sidewall portion 2 on the outside of the vehicle. The mounting direction indicator 2A displays, for example, the character string "OUTSIDE" along the tire circumferential direction on the outside of the vehicle, and displays, for example, the character string "INSIDE" along the tire circumferential direction on the inside of the vehicle.

[0023] As described below, the present invention relates to a tread pattern formed on the surface of the tire tread portion 1, and therefore the basic structure (internal structure) of the tire is not limited to the general structure described above. Furthermore, the following description will be based on the pneumatic tire shown in Fig. 1 etc., but the present invention can be applied to various tires, including non-pneumatic tires, as long as they have a surface that comes into contact with the road surface (a portion corresponding to the surface of the tread portion 1 in a pneumatic tire).

[0024] As shown in FIG. 2, the tread portion 1 has four main grooves 10 extending in the tire circumferential direction, and these four main grooves 10 define five rows of land portions 20. The main grooves 10 are grooves that perform the primary drainage function, and their groove widths are set in the range of 6.0 mm to 12.0 mm, and their groove depths are set in the range of 6.0 mm to 10.0 mm. The main grooves 10 include a first main groove 11, a second main groove 12, a third main groove 13, and a fourth main groove 14, which are arranged in this order from the vehicle inner side to the vehicle outer side. The five rows of land portions 20 include an inner shoulder land portion 21, an inner intermediate land portion 22, a center land portion 23, an outer intermediate land portion 24, and an outer shoulder land portion 25, which are arranged in this order from the vehicle inner side to the vehicle outer side.

[0025] The inner shoulder land portion 21 is formed with one inner shoulder narrow groove 31 extending in the tire circumferential direction, and multiple inner shoulder lug grooves 41 extending in the tire width direction are formed at intervals in the tire circumferential direction. A narrow rib 61 continuing in the tire circumferential direction is defined between the inner shoulder narrow groove 31 and the first main groove 11. The inner shoulder narrow groove 31 has a groove width set in the range of 0.5 mm to 3.0 mm and a groove depth set in the range of 2.0 mm to 5.0 mm. The narrow rib 61 continues in the tire circumferential direction without being interrupted by groove components (lug grooves or sipes) extending along the tire width direction. In the illustrated example, the inner shoulder lug groove 41 crosses the inner shoulder narrow groove 31 and terminates within the narrow rib 61, and the narrow rib 61 continues in the tire circumferential direction without being interrupted by the inner shoulder lug groove 41.

[0026] The inner intermediate land portion 22 is formed with a circumferential auxiliary groove 32 extending in the tire circumferential direction, and with a plurality of first sipes 51 spaced apart in the tire circumferential direction, each of which has one end opening into the first main groove 11 on the vehicle inner side and the other end communicating with the circumferential auxiliary groove 32. A thin rib 62 is defined between the circumferential auxiliary groove 32 and the second main groove 12 and continues in the tire circumferential direction. The circumferential auxiliary groove 32 has a groove width set in the range of 0.5 mm to 3.0 mm and a groove depth set in the range of 2.0 mm to 5.0 mm. The first sipes 51 have a groove width set in the range of 0.5 mm to 1.2 mm and a groove depth set in the range of 0.5 mm to 6.0 mm. The thin rib 62 is continuous in the tire circumferential direction without being interrupted by groove components (lug grooves or sipes) extending along the tire width direction.

[0027] A plurality of second sipes 52 are formed at intervals in the tire circumferential direction in the center land portion 23. One end of each second sipe 52 opens into the second main groove 12 on the vehicle inner side and the other end closes within the center land portion 23. The second sipes 52 have a groove width set in the range of 0.5 mm to 1.2 mm and a groove depth set in the range of 0.5 mm to 6.0 mm.

[0028] In the outer intermediate land portion 24, a plurality of third sipes 53, one end of which opens into the third main groove 13 and the other end of which closes within the outer intermediate land portion 24, and a plurality of fourth sipes 54, one end of which opens into the fourth main groove 14 and the other end of which closes within the outer intermediate land portion 24, are formed at intervals in the tire circumferential direction. The third sipes 53 and the fourth sipes 54 each have a groove width set in the range of 0.5 mm to 1.2 mm, and each have a groove depth set in the range of 0.5 mm to 6.0 mm.

[0029] The outer shoulder land portion 25 is formed with one outer shoulder narrow groove 35 extending in the tire circumferential direction, and multiple outer shoulder lug grooves 45 extending in the tire width direction are formed at intervals in the tire circumferential direction. A narrow rib 65 continuing in the tire circumferential direction is defined between the outer shoulder narrow groove 35 and the fourth main groove 14. The outer shoulder narrow groove 35 has a groove width set in the range of 0.5 mm to 3.0 mm and a groove depth set in the range of 2.0 mm to 5.0 mm. The narrow rib 65 is continuous in the tire circumferential direction without being interrupted by groove components (lug grooves or sipes) extending along the tire width direction. In the illustrated example, the outer shoulder lug groove 45 crosses the outer shoulder narrow groove 35 and terminates within the narrow rib 65, and the narrow rib 65 is continuous in the tire circumferential direction without being interrupted by the outer shoulder lug groove 45.

[0030] The inner shoulder narrow groove 31, outer shoulder narrow groove 35, and circumferential auxiliary groove 32 are generally grooves with a larger groove width than the first to fourth sipes 51 to 54, but may have a groove width similar to that of the sipes depending on the tire size (see the groove width range of each narrow groove described above). However, even in this case, the inner shoulder narrow groove 31, outer shoulder narrow groove 35, and circumferential auxiliary groove 32 are grooves that extend continuously around the entire tire circumferential direction and are therefore distinguished from sipes.

[0031] In the above-described tire, sipes (first sipe 51, second sipe 52, third sipe 53, fourth sipe 54) are formed in each of the inner intermediate land portion 22, the center land portion 23, and the outer intermediate land portion 24, thereby ensuring sufficient edge components in the tire width direction, and also, by forming the inner shoulder narrow groove 31 in the inner shoulder land portion 21, the outer shoulder narrow groove 35 in the outer shoulder land portion 25, and the circumferential auxiliary groove 32 in the inner intermediate land portion 22, sufficient edge components in the tire circumferential direction can be improved, thereby enabling cornering performance on wet roads to be improved. On the other hand, there is concern that the formation of the inner shoulder narrow groove 31 in the inner shoulder land portion 21 and the outer shoulder narrow groove 35 in the outer shoulder land portion 25 may worsen pattern noise. However, the inner intermediate land portion 22, the center land portion 23, and the outer intermediate land portion 24 are provided with only sipes (first sipe 51, second sipe 52, third sipe 53, and fourth sipe 54) extending in the tire width direction, and do not have lug grooves with large groove widths. This suppresses radiation of pattern noise to the outside of the vehicle and reduces exterior noise. Furthermore, the narrow ribs 61, 62, and 65 defined in the inner shoulder land portion 21, the inner intermediate land portion 22, and the outer shoulder land portion 25 are continuous in the tire circumferential direction, thereby blocking pattern noise and reducing exterior noise. Furthermore, the second sipe 52 formed in the center land portion 23 is closed within the center land portion 23, which also blocks pattern noise and reduces exterior noise. The outer intermediate land portion 24 is formed with third sipes 53 and fourth sipes 54, and the fourth sipes 54 open to the fourth main groove 14 on the outer side of the vehicle, but because both the third sipes 53 and the fourth sipes 54 are closed within the outer intermediate land portion 24, they do not cause pattern noise to radiate outside the vehicle, thereby reducing exterior noise. These cooperation improves cornering performance on wet roads and reduces exterior noise.

[0032] In the above tire, it is preferable that the inner shoulder narrow groove 31 and the outer shoulder narrow groove 51 are disposed within a region that is 80% of the center of the contact width TCW of the tread portion 1. This improves the drainage performance of the inner shoulder narrow groove 31 and the outer shoulder narrow groove 51, and effectively improves cornering performance on wet roads. If the inner shoulder narrow groove 31 and the outer shoulder narrow groove 35 are disposed outside the above region (i.e., in a position where the contact length is short), the effect of improving cornering performance on wet roads will be limited.

[0033] As shown in FIG. 3 , the ratio Wgi / Wsi of the groove width Wgi of the inner shoulder narrow groove 31 to the width Wsi of the inner shoulder land portion 21 is preferably less than 0.30, more preferably 0.04 to 0.10. Similarly, the ratio Wgo / Wso of the groove width Wgo of the outer shoulder narrow groove 35 to the width Wso of the outer shoulder land portion 25 is less than 0.30, more preferably 0.04 to 0.10. Reducing the groove width in this way is advantageous for reducing external noise. If the ratio Wgi / Wsi or Wgo / Wso is 0.30 or greater, the groove width of the inner shoulder narrow groove 31 or the outer shoulder narrow groove 35 becomes too large, making it difficult to sufficiently suppress external noise. The width Wsi of the inner shoulder land portion 21 is the distance measured in the tire width direction from the vehicle-inner tread edge Ei to the first main groove 11, and the width Wso of the outer shoulder land portion 25 is the distance measured in the tire width direction from the vehicle-outer tread edge Eo to the fourth main groove 14.

[0034] The circumferential auxiliary grooves 32 are preferably positioned further outward from the widthwise center of the inner intermediate land portion 22. The ratio Wgm / Wmi of the groove width Wgm of the circumferential auxiliary grooves 32 to the width Wmi of the inner intermediate land portion 22 is preferably less than 0.30, more preferably 0.04 to 0.15. By setting the arrangement and dimensions of the circumferential auxiliary grooves 32 in this manner, the drainage performance of the circumferential auxiliary grooves 32 can be improved, effectively improving cornering performance on wet roads. If the circumferential auxiliary grooves 32 are positioned outside the above-mentioned range (i.e., in a position where the contact length is short), the effect of improving cornering performance on wet roads is limited. If the ratio Wgm / Wmi is 0.30 or more, the groove width of the circumferential auxiliary grooves 32 becomes large, making it difficult to sufficiently suppress external noise.

[0035] The third sipes 53 and the fourth sipes 54 are preferably arranged alternately in the tire circumferential direction. This makes it possible to prevent the generation of pattern noise caused by the repetition of multiple third sipes 53 and pattern noise caused by the repetition of multiple fourth sipes 54, which is advantageous for reducing exterior noise. If one of the third sipes 53 and the fourth sipes 54 is arranged repeatedly without the other being interposed, pattern noise may be generated, and exterior noise may not be sufficiently suppressed.

[0036] The ratio L2 / Wc of the length L2 of the second sipes 52 to the width Wc of the center land portion 23 is preferably 0.30 or more and less than 0.70, more preferably 0.40 or more and 0.60 or less. Setting the second sipes 52 to an appropriate length in this manner is advantageous for achieving both improved cornering performance on wet roads and reduced exterior noise. If the ratio L2 / Wc is less than 0.30, the drainage performance of the second sipes 52 cannot be sufficiently ensured, and the effect of improving cornering performance on wet roads is limited. If the ratio L2 / Wc is 0.70 or more, the length of the second sipes 52 is excessively large relative to the land portion width, and the effect of suppressing exterior noise is limited.

[0037] The ratio L3 / Wmo of the length L3 of the third sipes 53 to the width Wmo of the outer intermediate land portion 24 is preferably 0.20 or more and less than 0.70, more preferably 0.30 or more and 0.40 or less. Setting the third sipes 53 to an appropriate length in this manner is advantageous for achieving both improved cornering performance on wet roads and reduced exterior noise. If the ratio L3 / Wmo is less than 0.20, the drainage performance of the third sipes 53 cannot be sufficiently ensured, and the effect of improving cornering performance on wet roads is limited. If the ratio L3 / Wmo is 0.70 or more, the length of the fourth sipes 54 becomes excessively large relative to the land portion width, and the effect of suppressing exterior noise is limited.

[0038] The ratio L4 / Wmo of the length L4 of the fourth sipes 54 to the width Wmo of the outer intermediate land portion 24 is preferably 0.20 or more and less than 0.70, more preferably 0.30 or more and 0.40 or less. Setting the fourth sipes 54 to an appropriate length in this manner is advantageous for achieving both improved cornering performance on wet roads and reduced exterior noise. If the ratio L4 / Wmo is less than 0.20, the drainage performance of the fourth sipes 54 cannot be sufficiently ensured, and the effect of improving cornering performance on wet roads is limited. If the ratio L4 / Wmo is 0.70 or more, the length of the fourth sipes 54 is excessively large relative to the land portion width, and the effect of suppressing exterior noise is limited.

[0039] The outer intermediate land portion 24 is provided with third sipes 53 and fourth sipes 54, which may overlap each other near the center of the outer intermediate land portion 24 in the tire width direction. That is, an end of the fourth sipe 54 may be located between two third sipes 53 adjacent in the tire circumferential direction, or an end of the third sipe 53 may be located between two fourth sipes 54 adjacent in the tire circumferential direction. It is preferable that the length L3 of the third sipes 53 and the length L4 of the fourth sipes 54 satisfy the relationship L3≧L4.

[0040] As shown in Figure 3, the inclination angle θ1 of the first sipes 51 relative to the tire circumferential direction is preferably 40° to 80°, more preferably 50° to 70°. By appropriately inclining the first sipes 51 relative to the tire circumferential direction in this manner, the first sipes 51 can exhibit an appropriate edge effect in both the tire circumferential direction and the tire width direction, which is advantageous for improving cornering performance on wet roads. If the inclination angle θ1 is less than 40°, the land portion rigidity in the tire width direction decreases, making it difficult to achieve sufficient cornering performance. If the inclination angle θ1 exceeds 80°, the land portion rigidity increases, limiting the effect of reducing external noise.

[0041] The inclination angle θ2 of the second sipes 52 relative to the tire circumferential direction is preferably 40° or more and 80° or less, more preferably 50° or more and 70° or less. By appropriately inclining the second sipes 52 relative to the tire circumferential direction in this manner, the second sipes 52 can exert an appropriate edge effect in both the tire circumferential direction and the tire width direction, which is advantageous for improving cornering performance on wet roads. If the inclination angle θ2 is less than 40°, the land portion rigidity in the tire width direction decreases, making it difficult to achieve sufficient cornering performance. If the inclination angle θ2 exceeds 80°, the land portion rigidity increases, limiting the effect of reducing external noise.

[0042] The inclination angle θ3 of the third sipes 53 relative to the tire circumferential direction is preferably 40° or more and 80° or less, more preferably 50° or more and 70° or less. By appropriately inclining the third sipes 53 relative to the tire circumferential direction in this manner, the third sipes 53 can exert an appropriate edge effect in both the tire circumferential direction and the tire width direction, which is advantageous for improving cornering performance on wet roads. If the inclination angle θ3 is less than 40°, the land portion rigidity in the tire width direction decreases, making it difficult to achieve sufficient cornering performance. If the inclination angle θ3 exceeds 80°, the land portion rigidity increases, limiting the effect of reducing external noise.

[0043] The inclination angle θ4 of the fourth sipes 54 relative to the tire circumferential direction is preferably 40° to 80°, more preferably 50° to 70°. By appropriately inclining the fourth sipes 54 relative to the tire circumferential direction in this manner, the fourth sipes 54 can exert an appropriate edge effect in both the tire circumferential direction and the tire width direction, which is advantageous for improving cornering performance on wet roads. If the inclination angle θ4 is less than 40°, the land portion rigidity in the tire width direction decreases, making it difficult to achieve sufficient cornering performance. If the inclination angle θ4 exceeds 80°, the land portion rigidity increases, limiting the effect of reducing external noise.

[0044] The inclination angles θ1 to θ4 of the first to fourth sipes 51 to 54 are angles formed with respect to the tire circumferential direction by a line passing through the groove width center position at the open end and the groove width center position at the closed end of each of the first to fourth sipes 51 to 54. The first to third sipes 51 to 53 and the fourth sipe 54 open in opposite directions, but the inclination angles θ1 to θ4 are all acute angles.

[0045] The inclination angles θ1 to θ4 preferably satisfy the relationship θ1≧θ3≒θ4≧θ2. In other words, it is preferable that the relationships θ1≧θ3≧θ2 and θ1≧θ4≧θ2 are satisfied, and further that the relationship θ3≒θ4 is satisfied. The above relationship includes the case where the inclination angles θ1 to θ4 are all equal, but it is more preferable that the relationship θ1>θ3=θ4>θ2 is satisfied. This results in a good balance between the rigidity of each land portion and the edge effect based on each sipe, which is advantageous for achieving both improved cornering performance on wet roads and reduced exterior noise.

[0046] It is preferable to form chamfered portions 70 at the locations where the above-mentioned inclination angles θ1 to θ4 were measured, i.e., the acute angle formed by the first sipes 51 and the first main groove 11, the acute angle formed by the first sipes 51 and the circumferential auxiliary groove 32, the acute angle formed by the second sipes 52 and the second main groove 12, the acute angle formed by the third sipes 53 and the third main groove 13, and the acute angle formed by the fourth sipes 54 and the fourth main groove 14. By providing the chamfered portions 70 in this manner, it is expected that drainage performance will be improved, which is advantageous for improving cornering performance on wet roads.

[0047] 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. [Example]

[0048] In a pneumatic tire with a tire size of 235 / 65R17 and a specified mounting direction on a vehicle, four main grooves are formed in the tread portion extending in the tire circumferential direction, and five rows of land portions are defined by these main grooves, and the four main grooves include a first main groove, a second main groove, a third main groove, and a fourth main groove, which are arranged in sequence from the inside of the vehicle to the outside of the vehicle, and the five rows of land portions include an inner shoulder land portion, an inner intermediate land portion, a center land portion, an outer intermediate land portion, and an outer shoulder land portion, which are arranged in sequence from the inside of the vehicle to the outside of the vehicle, and one inner shoulder narrow groove and multiple inner shoulder lug grooves are formed in the inner shoulder land portion, and the inner shoulder Tires (test tires) of Examples 1 to 5 were manufactured having a structure in which a thin rib continuous in the tire circumferential direction is defined between the inner thin groove and the first main groove, one circumferential auxiliary groove and multiple first sipes are formed in the inner intermediate land portion, a thin rib continuous in the tire circumferential direction is defined between the circumferential auxiliary groove and the second main groove, multiple second sipes are formed in the center land portion, multiple third sipes and multiple fourth sipes are formed in the outer intermediate land portion, one outer shoulder thin groove and multiple outer shoulder lug grooves are formed in the outer shoulder land portion, and a thin rib continuous in the tire circumferential direction is defined between the outer shoulder thin groove and the fourth main groove.

[0049] For comparison, a conventional tire was prepared, which had the same structure as Example 1, except that all of the first to fourth sipes were replaced with lug grooves (reference numerals 42 to 44 in the figure) and no circumferential auxiliary groove was provided in the inner intermediate land portion, as shown in Figure 4. Note that, since the conventional tire does not have a circumferential auxiliary groove, one end of the lug groove that replaced the first sipe opens into the first main groove and the other end terminates within the inner intermediate land portion.

[0050] For the tires of the conventional example and Examples 1 to 5, the basic pattern, ratios Wgi / Wsi, Wgo / Wso, Wgm / Wmi, positions of the inner shoulder narrow groove, the outer shoulder narrow groove, the circumferential auxiliary groove, length ratios L2 / Wc, L3 / Wmo, L4 / Wmo, inclination angles θ1 to θ4, and presence or absence of chamfering are as shown in Table 1. The drawing numbers of the basic patterns for each example are shown. Regarding the positions of the inner shoulder narrow groove and the outer shoulder narrow groove, cases where these narrow grooves are located inside the central 80% region of the contact width of the tread portion are indicated as "inside the region," and cases where these narrow grooves are outside the central 80% region of the contact width of the tread portion are indicated as "outside the region." Regarding the position of the circumferential auxiliary groove, cases where the circumferential auxiliary groove is located on the vehicle outer side of the widthwise center position of the inner intermediate land portion are indicated as "outside," and cases where it is located on the vehicle inner side are indicated as "inside."

[0051] These test tires were evaluated for cornering performance on wet roads (wet cornering performance) and external noise using the following test methods. The results are also shown in Table 1.

[0052] Wet cornering performance Each test tire was mounted on a 17x7J rim wheel and mounted on a 2400cc SUV (front-wheel drive). After warming up, the tire pressure was set to 240kPa, and a test driver conducted a sensory evaluation of the tire's cornering performance while driving on a wet road. The evaluation results were expressed as an index, with the conventional tire being set at 100. The higher the index value, the better the cornering performance on wet roads.

[0053] exterior noise Each test tire was mounted on a 17x7J rim wheel and mounted on a 2400cc SUV (front-wheel drive). After warming up, the tire pressure was set to 240kPa, and tests were conducted in accordance with UN.R117 to measure external noise. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example being set at 100. The higher the index value, the lower the external noise.

[0054] [Table 1]

[0055] As can be seen from Table 1, the tires of Examples 1 to 5 had good cornering performance on wet roads and reduced external noise compared to the conventional tire.

[0056] The present disclosure includes the following inventions. Invention [1] A tire with a specified mounting direction on a vehicle, Four main grooves extending in the tire circumferential direction are formed in the tread portion, and five rows of land portions are defined by these main grooves, and the four main grooves include a first main groove, a second main groove, a third main groove, and a fourth main groove, which are arranged in sequence from the vehicle inner side to the vehicle outer side, and the five rows of land portions include an inner shoulder land portion, an inner intermediate land portion, a center land portion, an outer intermediate land portion, and an outer shoulder land portion, which are arranged in sequence from the vehicle inner side to the vehicle outer side, an inner shoulder land portion is formed with an inner shoulder narrow groove extending in the tire circumferential direction and a plurality of inner shoulder lug grooves extending in the tire width direction, and a narrow rib extending continuously in the tire circumferential direction is defined between the inner shoulder narrow groove and the first main groove, a circumferential auxiliary groove extending in the tire circumferential direction and a plurality of first sipes each having one end opening into the first main groove and the other end communicating with the circumferential auxiliary groove are formed in the inner intermediate land portion, and a thin rib extending continuously in the tire circumferential direction is defined between the circumferential auxiliary groove and the second main groove; A plurality of second sipes are formed in the center land portion, one end of which opens into the second main groove and the other end of which closes within the center land portion, a plurality of third sipes, one end of which opens into the third main groove and the other end of which closes within the outer intermediate land portion, and a plurality of fourth sipes, one end of which opens into the fourth main groove and the other end of which closes within the outer intermediate land portion, are formed in the outer intermediate land portion; a circumferentially extending outer shoulder narrow groove and a plurality of widthwise extending outer shoulder lug grooves are formed in the outer shoulder land portion, and a circumferentially continuous narrow rib is defined between the outer shoulder narrow groove and the fourth main groove. Invention [2] The tire according to invention [1], characterized in that the inner shoulder narrow groove and the outer shoulder narrow groove are arranged within a region of 80% of the center of the contact width of the tread portion, the ratio Wgi / Wsi of the groove width Wgi of the inner shoulder narrow groove to the width Wsi of the inner shoulder land portion is less than 0.30, and the ratio Wgo / Wso of the groove width Wgo of the outer shoulder narrow groove to the width Wso of the outer shoulder land portion is less than 0.30. Invention [3] The tire according to invention [1] or [2], characterized in that the ratio Wgm / Wmi of the groove width Wgm of the circumferential auxiliary groove to the width Wmi of the inner intermediate land portion is less than 0.30, and the circumferential auxiliary groove is positioned on the vehicle outer side with respect to the width direction center position of the inner intermediate land portion. Invention [4] The tire according to any one of inventions [1] to [3], wherein the third sipes and the fourth sipes are arranged alternately in the tire circumferential direction. Invention [5] The tire according to any one of inventions [1] to [4], characterized in that the ratio L2 / Wc of the length L2 of the second sipe to the width Wc of the center land portion is 0.30 or more and less than 0.70. Invention [6] A tire according to any one of inventions [1] to [5], characterized in that the ratio L3 / Wmo of the length L3 of the third sipe to the width Wmo of the outer intermediate land portion is 0.20 or more and less than 0.70, and the ratio L4 / Wmo of the length L4 of the fourth sipe to the width Wmo of the outer intermediate land portion is 0.20 or more and less than 0.70. Invention [7] The tire according to any one of inventions [1] to [6], characterized in that the inclination angle θ1 of the first sipe with respect to the tire circumferential direction is 40° or more and 80° or less. Invention [8] The tire according to any one of inventions [1] to [7], characterized in that the inclination angle θ2 of the second sipe with respect to the tire circumferential direction is 40° or more and 80° or less. Invention [9] A tire according to any one of inventions [1] to [8], characterized in that the inclination angle θ3 of the third sipe with respect to the tire circumferential direction is 40° or more and 80° or less, and the inclination angle θ4 of the fourth sipe with respect to the tire circumferential direction is 40° or more and 80° or less. Invention

[10] A tire according to any one of inventions [1] to [9], characterized in that the inclination angle θ1 of the first sipe with respect to the tire circumferential direction, the inclination angle θ2 of the second sipe with respect to the tire circumferential direction, the inclination angle θ3 of the third sipe with respect to the tire circumferential direction, and the inclination angle θ4 of the fourth sipe with respect to the tire circumferential direction satisfy the relationship θ1≧θ3≒θ4≧θ2. Invention

[11] A tire according to any one of inventions [1] to

[10] , characterized in that a chamfer is formed at each of the acute angle formed by the first sipe and the first main groove, the acute angle formed by the first sipe and the circumferential auxiliary groove, the acute angle formed by the second sipe and the second main groove, the acute angle formed by the third sipe and the third main groove, and the acute angle formed by the fourth sipe and the fourth main groove. [Explanation of symbols]

[0057] 1 Tread section 2 Sidewall 3 Bead section 10,11,12,13,14 Main groove 20,21,22,23,24,25 Land 31,35 narrow groove 32 Circumferential auxiliary groove 41,45 Lug groove 51, 52, 53, 54 Sipe 61,62,65 Thin rib

Claims

1. For tires with a specified mounting direction on a vehicle, Four main grooves extending in the tire circumferential direction are formed in the tread portion, and five rows of land portions are defined by these main grooves, and the four main grooves include a first main groove, a second main groove, a third main groove, and a fourth main groove, which are arranged in sequence from the vehicle inner side to the vehicle outer side, and the five rows of land portions include an inner shoulder land portion, an inner intermediate land portion, a center land portion, an outer intermediate land portion, and an outer shoulder land portion, which are arranged in sequence from the vehicle inner side to the vehicle outer side, an inner shoulder land portion is formed with an inner shoulder narrow groove extending in the tire circumferential direction and a plurality of inner shoulder lug grooves extending in the tire width direction, and a narrow rib extending continuously in the tire circumferential direction is defined between the inner shoulder narrow groove and the first main groove, a circumferential auxiliary groove extending in the tire circumferential direction and a plurality of first sipes each having one end opening into the first main groove and the other end communicating with the circumferential auxiliary groove are formed in the inner intermediate land portion, and a thin rib extending continuously in the tire circumferential direction is defined between the circumferential auxiliary groove and the second main groove; A plurality of second sipes are formed in the center land portion, one end of which opens into the second main groove and the other end of which closes within the center land portion, a plurality of third sipes, one end of which opens into the third main groove and the other end of which closes within the outer intermediate land portion, and a plurality of fourth sipes, one end of which opens into the fourth main groove and the other end of which closes within the outer intermediate land portion, are formed in the outer intermediate land portion; a circumferentially extending outer shoulder narrow groove and a plurality of widthwise extending outer shoulder lug grooves are formed in the outer shoulder land portion, and a circumferentially continuous narrow rib is defined between the outer shoulder narrow groove and the fourth main groove.

2. 2. The tire according to claim 1, wherein the inner shoulder narrow groove and the outer shoulder narrow groove are arranged within a region of 80% of the center of the contact width of the tread portion, a ratio Wgi / Wsi of a groove width Wgi of the inner shoulder narrow groove to a width Wsi of the inner shoulder land portion is less than 0.30, and a ratio Wgo / Wso of a groove width Wgo of the outer shoulder narrow groove to a width Wso of the outer shoulder land portion is less than 0.

30.

3. 3. The tire according to claim 1, wherein a ratio Wgm / Wmi of a groove width Wgm of the circumferential auxiliary groove to a width Wmi of the inner intermediate land portion is less than 0.30, and the circumferential auxiliary groove is positioned on a vehicle outer side with respect to a width direction center position of the inner intermediate land portion.

4. The tire according to claim 1 or 2, wherein the third sipes and the fourth sipes are arranged alternately in the tire circumferential direction.

5. 3. The tire according to claim 1, wherein a ratio L2 / Wc of a length L2 of the second sipe to a width Wc of the center land portion is equal to or greater than 0.30 and less than 0.

70.

6. 3. The tire according to claim 1, wherein a ratio L3 / Wmo of a length L3 of the third sipe to a width Wmo of the outer intermediate land portion is 0.20 or greater and less than 0.70, and a ratio L4 / Wmo of a length L4 of the fourth sipe to a width Wmo of the outer intermediate land portion is 0.20 or greater and less than 0.

70.

7. The tire according to claim 1 or 2, wherein an inclination angle θ1 of the first sipe with respect to the tire circumferential direction is equal to or greater than 40° and equal to or less than 80°.

8. The tire according to claim 1 or 2, wherein an inclination angle θ2 of the second sipe with respect to the tire circumferential direction is equal to or greater than 40° and equal to or less than 80°.

9. 3. The tire according to claim 1, wherein an inclination angle θ3 of the third sipe with respect to the tire circumferential direction is 40° or greater and 80° or less, and an inclination angle θ4 of the fourth sipe with respect to the tire circumferential direction is 40° or greater and 80° or less.

10. 3. The tire according to claim 1, wherein an inclination angle θ1 of the first sipe with respect to the tire circumferential direction, an inclination angle θ2 of the second sipe with respect to the tire circumferential direction, an inclination angle θ3 of the third sipe with respect to the tire circumferential direction, and an inclination angle θ4 of the fourth sipe with respect to the tire circumferential direction satisfy a relationship of θ1 ≧ θ3 ≒ θ4 ≧ θ2.

11. 3. The tire according to claim 1, wherein a chamfer is formed at each of an acute angle formed by the first sipe and the first main groove, an acute angle formed by the first sipe and the circumferential auxiliary groove, an acute angle formed by the second sipe and the second main groove, an acute angle formed by the third sipe and the third main groove, and an acute angle formed by the fourth sipe and the fourth main groove.

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