Tire

Abstract

To provide a tire capable of improving turning performance on a wet road surface and reducing noise outside a vehicle.SOLUTION: In a tire in which a mounting direction with respect to a vehicle is designated, a first circumferential auxiliary groove 31 and a plurality of inner shoulder lug grooves 41 are formed in an inner shoulder land portion 21, a plurality of second circumferential auxiliary grooves 32, a plurality of first lug grooves 42, and a plurality of first sipes 51 are formed in an inner intermediate land portion 22, a plurality of second sipes 52 are formed in a center land portion 23, a plurality of second lug grooves 43 and a plurality of third sipes 53 are formed in an outer intermediate land portion 24, and a plurality of outer shoulder lug grooves 44 are formed in an outer shoulder land portion 25.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire that is mounted in a specified 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 demanded. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 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 in which four main grooves extending in the tire circumferential direction are formed in the tread portion, and these main grooves define five rows of land portions, 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 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 sequence from the inner side of the vehicle to the outer side of the vehicle, and the inner shoulder land portion is formed with a first circumferential auxiliary groove extending in the tire circumferential direction and a plurality of inner shoulder lug grooves that terminate within the inner shoulder land portion and extend in the tire width direction, and the inner intermediate land portion is formed with a second circumferential auxiliary groove formed in the center land portion, a plurality of first lug grooves having one end opening into the first main groove and the other end terminating in the inner intermediate land portion, and a plurality of first sipes extending from the other ends of the first lug grooves and communicating with the second main groove; a plurality of second sipes having one end opening into the second main groove and the other end communicating with the third main groove are formed in the center land portion; a plurality of second lug grooves having one end opening into the fourth main groove and the other end terminating in the outer intermediate land portion, and a plurality of third sipes extending from the other ends of the second lug grooves and communicating with the third main groove are formed in the outer intermediate land portion; and a plurality of outer shoulder lug grooves terminating in the outer shoulder land portion and extending in the tire width direction are formed in the outer shoulder land portion. [Effects of the Invention]

[0007] In the present invention, circumferential auxiliary grooves are formed in the inner shoulder land portion and the inner intermediate land portion, thereby ensuring sufficient edge components in the tire circumferential direction. Furthermore, lug grooves and sipes are formed in the inner intermediate land portion, center land portion, and outer intermediate land portion, thereby ensuring sufficient edge components in the tire width direction. Furthermore, by dividing these land portions with the lug grooves and sipes, drainage can be improved. This improves cornering performance on wet roads. While there is concern that forming many grooves in the tread portion may increase exterior noise due to pattern noise, the lug grooves formed in the inner shoulder land portion and the outer shoulder land portion do not communicate with the main grooves, thereby reducing exterior noise. Furthermore, the center land portion, where ground pressure is highest, is provided with sipes instead of relatively wide grooves such as lug grooves (which are disadvantageous for suppressing exterior noise), thereby contributing to reducing exterior noise. This improves cornering performance on wet roads and reduces exterior noise.

[0008] In the tire of the present invention, the first circumferential auxiliary groove is preferably disposed within a region that occupies 80% of the center side of the contact width of the tread, and the groove width of the first circumferential auxiliary groove is preferably less than 30% of the distance from the inner contact edge of the tire to the first main groove, thereby effectively improving cornering performance on wet roads and effectively reducing external noise.

[0009] It is preferable that the groove width of the second circumferential auxiliary groove is less than 30% of the width of the inner intermediate land portion, and that the second circumferential auxiliary groove is disposed within a region that is 20% of the width of the inner intermediate land portion toward the center. This effectively improves cornering performance on wet roads and effectively reduces external noise.

[0010] The inclination angle θ1 of the first sipe with respect to the tire circumferential direction is preferably 30° or more and 70° or less, which effectively improves cornering performance on wet road surfaces and effectively reduces external noise.

[0011] The inclination angle θ2 of the second sipes with respect to the tire circumferential direction is preferably 30° or more and 70° or less, which effectively improves cornering performance on wet road surfaces and effectively reduces external noise.

[0012] The inclination angle θ3 of the third sipe with respect to the tire circumferential direction is preferably 30° or more and 70° or less, which effectively improves cornering performance on wet road surfaces and effectively reduces external noise.

[0013] 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, and the inclination angle θ3 of the third sipe with respect to the tire circumferential direction satisfy the relationship θ1≦θ2≦θ3. This relatively increases the rigidity of the land portion on the outer side of the vehicle, thereby effectively improving cornering performance on wet roads.

[0014] The third sipes are preferably curved so that the inclination angle of the third sipes relative to the tire circumferential direction decreases toward the inner side in the tire width direction, thereby effectively reducing external noise.

[0015] It is preferable that chamfers be formed at the acute angles formed by the first sipes and the second main groove, the acute angles formed by the second sipes and the second main groove, the acute angles formed by the second sipes and the third main groove, and the acute angles formed by the third sipes and the third main groove, respectively. The chamfers can effectively improve cornering performance on wet roads without impairing the effect of reducing external noise.

[0016] 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.

[0017] 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]

[0018] [Figure 1] 1 is a meridian cross-sectional view showing an example of 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. DETAILED DESCRIPTION OF THE INVENTION

[0019] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Figures 1 to 3 show a pneumatic tire according to an embodiment of the present invention. The tire shown in Figures 1 to 3 has a specified mounting direction relative to a vehicle, with IN indicating the region inside the tire center line CL with respect to the vehicle when the tire is mounted on the vehicle (hereinafter referred to as the vehicle inner side), and OUT indicating the region outside the tire center line CL with respect to the vehicle when the tire is mounted on the vehicle (hereinafter referred to as the vehicle outer side).

[0020] As shown in Fig. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending circumferentially in a ring shape, a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3, 3 disposed radially inward of the sidewall portions 2. For example, at least the sidewall portion 2 on the outer side of the vehicle is formed with a mounting direction indicator 2A indicating the mounting direction relative to the vehicle. The mounting direction indicator 2A displays, for example, "OUTSIDE" along the tire circumferential direction on the outer side of the vehicle, and displays, for example, "INSIDE" along the tire circumferential direction on the inner side of the vehicle.

[0021] A carcass layer 4 is mounted between the pair of bead portions 3, 3. This carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition and having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0022] On the other hand, multiple belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include multiple reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to a range of 10° to 40°, for example. Steel cords are preferably used as the reinforcing cords of the belt layers 7. At least one belt cover layer 8 is arranged on the outer peripheral side of the belt layer 7, with the aim of improving high-speed durability, and the reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction. As the reinforcing cords of the belt cover layer 8, organic fiber cords such as nylon and aramid are preferably used.

[0023] The above-described tire internal structure is a typical example of a pneumatic tire, but is not limited to this.

[0024] As shown in Figure 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 width is preferably set in the range of 6.0 mm to 12.0 mm, and their groove depth is preferably 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 sequence 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 sequence from the vehicle inner side to the vehicle outer side.

[0025] The inner shoulder land portion 21 is formed with a single first circumferential auxiliary 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. These inner shoulder lug grooves 41 terminate within the inner shoulder land portion 21. A thin rib 61 continuing in the tire circumferential direction is defined between the first circumferential auxiliary groove 31 and the first main groove 11. The first circumferential auxiliary groove 31 preferably 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 0.5 mm to 5.0 mm. The thin rib 61 continues in the tire circumferential direction without being interrupted by groove components including the inner shoulder lug groove 41 and sipes. Because this thin rib 61 continues uninterrupted in the tire circumferential direction, pattern noise is blocked, contributing to reducing exterior noise.

[0026] The inner intermediate land portion 22 is formed with one second circumferential auxiliary groove 32 extending in the tire circumferential direction, and is also formed with a plurality of first lug grooves 42 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 terminating within the inner intermediate land portion 22, and a plurality of first sipes 51 extending from the other ends of the first lug grooves 42 and communicating with the second main groove 12. The second circumferential auxiliary groove 32 preferably 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 0.5 mm to 5.0 mm.

[0027] In the center land portion 23, a plurality of second sipes 52 are formed at intervals in the tire circumferential direction, with one end opening to the second main groove 12 on the vehicle inner side and the other end communicating with the third main groove 13.

[0028] The outer intermediate land portion 24 is formed with a plurality of second lug grooves 43 spaced apart around the tire, one end of which opens into the fourth main groove 14 on the outer side of the vehicle and the other end of which terminates within the outer intermediate land portion 24, and a plurality of third sipes 53 which extend from the other ends of the second lug grooves 43 and communicate with the third main groove 13.

[0029] A plurality of outer shoulder lug grooves 44 extending in the tire width direction are formed at intervals in the tire circumferential direction in the outer shoulder land portion 25. These outer shoulder lug grooves 44 terminate within the outer shoulder land portion 25.

[0030] In the pneumatic tire described above, the circumferential auxiliary grooves 31, 32 are formed in the inboard shoulder land portion 21 and the inboard intermediate land portion 22, thereby ensuring sufficient edge components in the tire circumferential direction. The lug grooves 42, 43 and sipes 51-53 are formed in the inboard intermediate land portion 22, the center land portion 23, and the outboard intermediate land portion 24, thereby ensuring sufficient edge components in the tire width direction. Furthermore, the lug grooves 42, 43 and sipes 51-53 separate these land portions 22-24, thereby improving drainage. This improves cornering performance on wet roads. While there is concern that forming many grooves in the tread portion may increase external noise due to pattern noise, the lug grooves 41, 44 formed in the inboard shoulder land portion 21 and the outboard shoulder land portion 25 do not communicate with the main groove 10, thereby reducing external noise. Furthermore, the center land portion 23, where the ground pressure is highest, is provided with sipes 52 instead of lug grooves with a relatively large groove width (which are disadvantageous for suppressing external noise), which contributes to reducing external noise. This improves cornering performance on wet roads and reduces external noise.

[0031] In the pneumatic tire, the third sipes 53 are preferably curved. Specifically, the third sipes 53 are preferably curved so that the inclination angle of the third sipes 53 with respect to the tire circumferential direction decreases toward the inner side in the tire width direction (from the fourth main groove 14 side toward the third main groove 13 side). The inclination angle of the third sipes 53 here refers to the acute angle formed by the third sipes 53 and a line parallel to the tire circumferential direction at each portion in the extension direction of the third sipes 53. Furthermore, the radius of curvature of the curve constituting the third sipes 53 is preferably in the range of 50 mm to 200 mm. By having such a curved shape of the third sipes 53, the third sipes 53 do not coincide with the front end or rear end of the contact area (e.g., contact area A illustrated in FIG. 2 ) of the tread portion 1. The outer intermediate land portion 24 is located closer to the outer side of the vehicle than the inner intermediate land portion 22 and the center land portion 23, and therefore has a significant impact on external noise. Therefore, by configuring the third sipes 53 formed in the outer intermediate land portion 24 as described above, it is possible to effectively reduce external noise.

[0032] It is preferable that the first sipes 51, the second sipes 52, and the third sipes 53 are chamfered between each of them and the main groove 10. That is, it is preferable that a chamfered portion 70 is formed at each of the acute angles formed by the first sipes 51 and the second main groove 12, the acute angles formed by the second sipes 52 and the second main groove 12, the acute angles formed by the second sipes 52 and the third main groove 13, and the acute angles formed by the third sipes 53 and the third main groove 13. By providing such chamfered portions 70, it is possible to effectively improve cornering performance on wet roads without compromising the effect of reducing external noise.

[0033] In the above pneumatic tire, as shown in FIG. 3 , the first circumferential auxiliary groove 31 is preferably disposed within a region that is 80% of the center of the contact width TCW of the tread portion 1. Furthermore, the groove width w1 of the first circumferential auxiliary groove 31 is preferably less than 30% of the distance D in the tire width direction from the vehicle-inside contact edge Ei to the groove wall of the first main groove 11. The first circumferential auxiliary groove 31 is provided to improve drainage. However, if the first circumferential auxiliary groove 31 is disposed within a region that is 80% of the center of the contact width TCW of the tread portion 1, the first circumferential auxiliary groove 31 does not need to be disposed in a position where the contact length of the tread portion 1 is short, and therefore, a sufficient drainage effect can be obtained by the first circumferential auxiliary groove 31. Furthermore, if the groove width w1 of the first circumferential auxiliary groove 31 is less than 30% of the distance D, the generation of external noise can be effectively suppressed.

[0034] The groove width w2 of the second circumferential auxiliary groove 32 is preferably less than 30% of the width Rw of the inner intermediate land portion 22. Furthermore, the second circumferential auxiliary groove 32 is preferably disposed within a region that is 20% of the center of the width Rw of the inner intermediate land portion 22. When the groove width w2 of the second circumferential auxiliary groove 32 is less than 30% of the width Rw of the inner intermediate land portion 22, the groove width w2 is optimized relative to the width Rw, thereby effectively suppressing the generation of passing noise. Furthermore, if the contact lengths of the main grooves 11, 12 on both sides of the land portion 22 and the contact length of the second circumferential auxiliary groove 32 are substantially equal, resonance sounds of similar frequencies are generated from these grooves, which tends to worsen exterior noise. However, if the second circumferential auxiliary groove 32 is disposed in the central region of the land portion 22, sound pressure is suppressed without generating resonance sounds, thereby effectively reducing exterior noise.

[0035] In the pneumatic tire described above, as shown in FIG. 3 , the inclination angle θ1 of the first sipes 51 formed in the inner intermediate land portion 22 with respect to the tire circumferential direction is preferably 30° or more and 70° or less, and more preferably 40° or more and 60° or less. When the inclination angle θ1 of the first sipes 51 is 30° or more, the lateral block rigidity can be increased, and cornering performance on wet roads can be sufficiently ensured. On the other hand, when the inclination angle θ1 of the first sipes 51 is 70° or less, the block rigidity of the inner intermediate land portion 22 is not excessively high, and therefore the generation of external noise can be effectively suppressed. Note that the inclination angle θ1 of the first sipes 51 is the acute angle with respect to the tire circumferential direction measured at the end of the first sipe 51 on the first lug groove 42 side.

[0036] The inclination angle θ2 of the second sipes 52 formed in the center land portion 23 relative to the tire circumferential direction is preferably 30° or more and 70° or less, and more preferably 40° or more and 60° or less. When the inclination angle θ2 of the second sipes 52 is 30° or more, the lateral block rigidity can be increased, and cornering performance on wet roads can be sufficiently ensured. On the other hand, when the inclination angle θ2 of the second sipes 52 is 70° or less, the block rigidity of the center land portion 23 is not excessively high, and therefore the generation of external noise can be effectively suppressed. The inclination angle θ2 of the second sipes 52 is the acute angle relative to the tire circumferential direction measured at the end of the second sipes 52 on the second main groove 12 side.

[0037] The inclination angle θ3 of the third sipes 53 formed in the outer intermediate land portion 24 relative to the tire circumferential direction is preferably 30° or more and 70° or less, and more preferably 40° or more and 60° or less. When the inclination angle θ3 of the third sipes 53 is 30° or more, the lateral block rigidity can be increased, and cornering performance on wet roads can be sufficiently ensured. On the other hand, when the inclination angle θ3 of the third sipes 53 is 70° or less, the block rigidity of the outer intermediate land portion 24 is not excessively high, and the generation of external noise can be effectively suppressed. Note that the inclination angle θ3 of the third sipes 53 is an acute angle relative to the tire circumferential direction measured at the end of the third sipes 53 on the second lug groove 43 side, and is equivalent to the acute angle of the second lug groove 43 relative to the tire circumferential direction.

[0038] In the above pneumatic tire, the inclination angle θ1 of the first sipes 51 relative to the tire circumferential direction, the inclination angle θ2 of the second sipes 52 relative to the tire circumferential direction, and the inclination angle θ3 of the third sipes 53 relative to the tire circumferential direction preferably satisfy the relationship θ1≦θ2≦θ3, and more preferably satisfy the relationship θ1<θ2<θ3. By setting the inclination angles in this manner, the rigidity of the land portion on the outer side of the vehicle is relatively increased, thereby effectively improving cornering performance on wet roads.

[0039] In the above-described embodiment, an example has been shown in which the inner shoulder lug groove 41 terminates at the first circumferential auxiliary groove 31, but the present invention is not limited thereto. For example, the inner shoulder lug groove 41 may extend beyond the first circumferential auxiliary groove 31 and terminate within the inner shoulder land portion 21. Furthermore, an example has been shown in which the first lug groove 42 terminates without reaching the second circumferential auxiliary groove 32, but the present invention is not limited thereto. For example, the first lug groove 42 may extend beyond the second circumferential auxiliary groove 32. [Example]

[0040] The tire size was 235 / 60R18, and the mounting direction on the vehicle was specified. The pneumatic tire had four main grooves formed in the tread portion extending in the tire circumferential direction, and these main grooves partitioned five rows of land portions, and the four main grooves included a first main groove, a second main groove, a third main groove, and a fourth main groove, which were arranged sequentially from the inside of the vehicle to the outside of the vehicle. The five rows of land portions included 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 were arranged sequentially from the inside of the vehicle to the outside of the vehicle. The tires of Examples 1 to 9 had a structure in which one first circumferential auxiliary groove and multiple inner shoulder lug grooves were formed in the inner shoulder land portion, one second circumferential auxiliary groove, multiple first lug grooves, and multiple first sipes were formed in the inner intermediate land portion, multiple second sipes were formed in the center land portion, multiple second lug grooves and multiple third sipes were formed in the outer intermediate land portion, and multiple outer shoulder lug grooves were formed in the outer shoulder land portion.

[0041] For comparison, a conventional tire was prepared, which had the same structure as Example 1, except that the only lateral grooves formed in each of the inner intermediate land portion, the center land portion, and the outer intermediate land portion were lug grooves (i.e., non-through lug grooves) whose one end opens into the main groove and the other end terminates within the land portion. Also, a comparative tire was prepared, which had the same structure as Example 1, except that the only lateral grooves formed in each of the inner intermediate land portion, the center land portion, and the outer intermediate land portion were lug grooves (i.e., through lug grooves) whose both ends open into the main groove.

[0042] In the tires of the conventional example, comparative example, and Examples 1 to 9, the configuration of the lateral grooves, groove width of the first circumferential auxiliary groove, position of the first circumferential auxiliary groove, groove width of the second circumferential auxiliary groove, position of the second circumferential auxiliary groove, inclination angle θ1 of the first sipe, inclination angle θ2 of the second sipe, inclination angle θ3 of the third sipe, shape of the third sipe, and presence or absence of chamfering of the sipe ends are as shown in Table 1. Regarding the "lateral groove configuration," the first sipes, second sipes, and third sipes of Examples 1 to 9 are collectively referred to as "through sipes." The "groove width of the first circumferential auxiliary groove" is the ratio of the groove width of the first circumferential auxiliary groove to the distance from the vehicle inner contact edge to the first main groove. Regarding the "position of the first circumferential auxiliary groove," "85%" and "65%" mean that the widthwise center position of the first circumferential auxiliary groove is 85% or 65% toward the center of the contact width of the tread portion. The "groove width of the second circumferential auxiliary groove" is the ratio of the groove width of the second circumferential auxiliary groove to the width of the inner intermediate land portion. Regarding the "position of the second circumferential auxiliary groove," "0%" means that the widthwise center position of the second circumferential auxiliary groove coincides with the widthwise center position of the inner intermediate land portion, and "30%" means that the widthwise center position of the second circumferential auxiliary groove is located 30% of the width of the land portion from the widthwise center position of the inner intermediate land portion. Regarding the "inclination angle θ1 of the first sipe," "inclination angle θ2 of the second sipe," "inclination angle θ3 of the third sipe," and "shape of the third sipe," since there are no sipes in the conventional example and comparative example, they refer to the inclination angle and shape of the lug groove.

[0043] These test tires were evaluated for wet cornering performance and external noise using the following test methods, and the results are shown in Table 1.

[0044] Wet cornering performance: Each test tire was mounted on a rim size 18x7.0J wheel and mounted on a 2400cc SUV (front-wheel drive), with the air pressure at 240kPa. A sensory evaluation was carried out by a test driver on a test course on a wet road surface. The evaluation results were expressed as an index, with the conventional tire being set at 100. The higher the index value, the better the wet cornering performance.

[0045] Exterior noise: Each test tire was mounted on a rim size 18x7.0J wheel and mounted on a 2400cc SUV (front-wheel drive), with the tire pressure at 240kPa. Tests were conducted in accordance with UN. R117, and the vehicle exterior noise was measured. 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 vehicle exterior noise.

[0046] [Table 1]

[0047] As can be seen from Table 1, Examples 1 to 9 had better wet cornering performance and reduced external noise compared to the conventional example.

[0048] In the comparative example, lug grooves were formed in each of the inner intermediate land portion, center land portion, and outer intermediate land portion, penetrating each land portion. As a result, the increased groove area was able to improve wet cornering performance, but the increased groove area also significantly worsened external noise.

[0049] The present disclosure includes the following inventions [1] to [9]. Invention [1] is a tire for which a mounting direction on a vehicle is specified, in which four main grooves extending in the tire circumferential direction are formed in the tread portion, and five rows of land portions are partitioned 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 toward 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 toward the outside of the vehicle, and the inner shoulder land portion is formed with a first circumferential auxiliary groove extending in the tire circumferential direction and a plurality of inner shoulder lug grooves that terminate within the inner shoulder land portion and extend in the tire width direction, and the inner intermediate land portion is formed with a second circumferential auxiliary groove extending in the tire circumferential direction. The tire is characterized in that it is formed with an auxiliary groove, a plurality of first lug grooves, one end of which opens into the first main groove and the other end of which terminates within the inner intermediate land portion, and a plurality of first sipes extending from the other ends of the first lug grooves and communicating with 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 communicates with the third main groove; the outer intermediate land portion is formed with a plurality of second lug grooves, one end of which opens into the fourth main groove and the other end of which terminates within the outer intermediate land portion, and a plurality of third sipes extending from the other ends of the second lug grooves and communicating with the third main groove; and the outer shoulder land portion is formed with a plurality of outer shoulder lug grooves, which terminate within the outer shoulder land portion and extend in the tire width direction. Invention [2] is the tire according to invention [1], characterized in that the first circumferential auxiliary groove is arranged within a region of 80% of the center of the contact width of the tread portion, and the groove width of the first circumferential auxiliary groove is less than 30% of the distance from the contact edge on the vehicle inner side to the first main groove. Invention [3] is the tire according to invention [1] or [2], characterized in that the groove width of the second circumferential auxiliary groove is less than 30% of the width of the inner intermediate land portion, and the second circumferential auxiliary groove is arranged within an area of ​​the central 20% of the width of the inner intermediate land portion. Invention [4] is the tire according to any one of inventions [1] to [3], characterized in that the inclination angle θ1 of the first sipe with respect to the tire circumferential direction is 30° or more and 70° or less. Invention [5] is the tire according to any one of inventions [1] to [4], characterized in that the inclination angle θ2 of the second sipe with respect to the tire circumferential direction is 30° or more and 70° or less. Invention [6] is the tire according to any one of inventions [1] to [5], characterized in that the inclination angle θ3 of the third sipe with respect to the tire circumferential direction is 30° or more and 70° or less. Invention [7] is a 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, the inclination angle θ2 of the second sipe with respect to the tire circumferential direction, and the inclination angle θ3 of the third sipe with respect to the tire circumferential direction satisfy the relationship θ1≦θ2≦θ3. Invention [8] is a tire according to any one of inventions [1] to [7], characterized in that the third sipes are curved so that the inclination angle of the third sipes with respect to the tire circumferential direction becomes smaller as they move inward in the tire width direction. Invention [9] is a tire according to any one of inventions [1] to [8], characterized in that a chamfered portion is formed at each of the acute angle formed by the first sipe and the second main groove, the acute angle formed by the second sipe and the second main groove, the acute angle formed by the second sipe and the third main groove, and the acute angle formed by the third sipe and the third main groove. [Explanation of symbols]

[0050] 1 Tread section 2 Sidewall 3 Bead section 10,11,12,13,14 Main groove 20,21,22,23,24,25 Land 31,32 Circumferential auxiliary groove 41, 42, 43, 44 Lug grooves 51, 52, 53 Sipe CL Tire centerline

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 toward 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 toward the vehicle outer side, a first circumferential auxiliary groove extending in the tire circumferential direction and a plurality of inner shoulder lug grooves terminating within the inner shoulder land portion and extending in the tire width direction are formed in the inner shoulder land portion; The inner intermediate land portion is formed with a second circumferential auxiliary groove extending in the tire circumferential direction, a plurality of first lug grooves each having one end opening into the first main groove and the other end terminating within the inner intermediate land portion, and a plurality of first sipes extending from the other ends of the first lug grooves and communicating with 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 communicates with the third main groove; a plurality of second lug grooves, one end of which opens into the fourth main groove and the other end of which terminates within the outer intermediate land portion; and a plurality of third sipes, extending from the other ends of the second lug grooves and communicating with the third main groove, are formed in the outer intermediate land portion; A tire characterized in that a plurality of outer shoulder lug grooves are formed in the outer shoulder land portion, the outer shoulder lug grooves terminating within the outer shoulder land portion and extending in the tire width direction.

2. 2. The tire according to claim 1, wherein the first circumferential auxiliary groove is disposed within a region of 80% of the center side of the contact width of the tread portion, and the groove width of the first circumferential auxiliary groove is less than 30% of the distance from the vehicle inner contact edge to the first main groove.

3. 3. The tire according to claim 1, wherein a groove width of the second circumferential auxiliary groove is less than 30% of a width of the inner intermediate land portion, and the second circumferential auxiliary groove is disposed within a region that is 20% of a center side of a width of the inner intermediate land portion.

4. 3. The tire according to claim 1, wherein an inclination angle θ1 of the first sipe with respect to the tire circumferential direction is equal to or greater than 30° and equal to or less than 70°.

5. 3. The tire according to claim 1, wherein an inclination angle θ2 of the second sipe with respect to the tire circumferential direction is equal to or greater than 30° and equal to or less than 70°.

6. 3. The tire according to claim 1, wherein an inclination angle θ3 of the third sipe with respect to the tire circumferential direction is equal to or greater than 30° and equal to or less than 70°.

7. 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, and an inclination angle θ3 of the third sipe with respect to the tire circumferential direction satisfy a relationship of θ1≦θ2≦θ3.

8. 3. The tire according to claim 1, wherein the third sipes are curved such that an inclination angle of the third sipes with respect to the tire circumferential direction decreases toward the inner side in the tire width direction.

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

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