Tire

Abstract

Provided is a tire that can improve steering stability on snowy road surfaces and can reduce extravehicular noise. The present invention is a tire, having a designated direction for mounting onto a vehicle, wherein: an inner shoulder narrow groove 31 and a plurality of inner shoulder lug grooves 41 are formed in an inner shoulder land section 21; a narrow rib 61 is demarcated between the inner shoulder narrow groove 31 and a first main groove 11; a circumferential-direction auxiliary groove 31, a plurality of first lug grooves 42, and a plurality of first sipes 52 are formed in an inner intermediate land section 22; a narrow rib 62 is demarcated between the circumferential-direction auxiliary groove 32 and a second main groove 12; a plurality of second lug grooves 43 and a plurality of second sipes 53 are formed in a center land section 23; a plurality of third lug grooves 44 and a plurality of third sipes 54 are formed in an outer intermediate land section 24; an outer shoulder narrow groove 35 and a plurality of outer shoulder lug grooves 45 are formed in an outer shoulder land section 25; and a narrow rib 65 is demarcated between the outer shoulder narrow groove 35 and a fourth main groove 14.

Description

tire

[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 steering stability on snowy roads and reduces noise outside the vehicle.

[0002] In a tire for which the mounting direction on a vehicle is specified, it has been proposed to form four main grooves extending circumferentially in the tread portion, with these main grooves dividing five rows of land portions, and to form multiple lug grooves in each land portion located between the main grooves, which extend in the tire width direction and connect to the main groove on the inside of the vehicle, but terminate within the land portion without connecting to the main groove on the outside of the vehicle (see, for example, Patent Document 1).

[0003] In a tire configured as described above, the lug grooves formed in the land portions 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, thereby maintaining sufficient rigidity of each land portion and providing excellent driving stability on wet roads. Furthermore, since 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, which is expected to reduce external noise. However, in recent years, further improvement in noise performance has been required. Furthermore, such tires are required to provide excellent driving stability on snowy roads in case of snowfall.

[0004] International Publication No. WO2015 / 005194

[0005] An object of the present invention is to provide a tire that can improve steering stability on snowy road surfaces and reduce noise outside the vehicle.

[0006] In order to achieve the above object, the tire of the present invention is a tire for which a mounting direction on a vehicle is specified, in which 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 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 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 are formed in the inner shoulder land portion, and a thin rib continuing in the tire circumferential direction is defined between the inner shoulder narrow groove and the first main groove, the inner intermediate land portion is formed with a 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 closing within the inner intermediate land portion, and a plurality of first sipes extending from the closed ends of the first lug grooves to communicate with the circumferential auxiliary grooves, and 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 lug grooves each having one end opening into the second main groove and the other end closing within the center land portion, and a plurality of second sipes extending from the closed ends of the second lug grooves to communicate with the third main groove; the outer intermediate land portion is formed with a plurality of third lug grooves each having one end opening into the fourth main groove and the other end closing within the outer intermediate land portion, and a plurality of third sipes extending from the closed ends of the third lug grooves to communicate with the third main groove; The outer shoulder land portion is formed with an outer shoulder narrow groove extending in the tire circumferential direction and multiple outer shoulder lug grooves extending in the tire width direction, and a thin rib continuing in the tire circumferential direction is defined between the outer shoulder narrow groove and the fourth main groove.

[0007] The inventor conducted extensive research into the arrangement of lug grooves with closed ends for pneumatic tires with a specified mounting direction on a vehicle, and discovered that if all of these lug grooves were open toward the inside of the vehicle, the pattern noise generated by the lug grooves would be reflected inside the tire housing and emitted outside the vehicle, and the radiated sounds would add up, causing an increase in noise, which led to the invention of the present application.

[0008] That is, in the present invention, the first lug grooves formed in the inner intermediate land portion and the second lug grooves formed in the center land portion open toward the vehicle interior, and the third lug grooves formed in the outer intermediate land portion open toward the vehicle exterior, so that radiated sounds from these first lug grooves, second lug grooves, and third lug grooves are dispersed to the vehicle interior and vehicle exterior, thereby reducing exterior noise. Furthermore, because the first lug grooves, second lug grooves, and third lug grooves are closed within the inner intermediate land portion, center land portion, and outer intermediate land portion, respectively, an increase in groove area is suppressed, and the generation of pattern noise, which is a cause of exterior noise, can be reduced. Furthermore, the first sipes, second sipes, and third sipes are formed in the inner intermediate land portion, center land portion, and outer intermediate land portion, respectively, to ensure sufficient edge components in the tire width direction. The inner shoulder land portion has an inner shoulder narrow groove, the outer shoulder land portion has an outer shoulder narrow groove, and the inner intermediate land portion has a circumferential auxiliary groove, so that sufficient edge components in the tire circumferential direction can be ensured, thereby improving handling stability on snowy roads. In addition, the narrow ribs that define the inner shoulder land portion, inner intermediate land portion, and outer shoulder land portion are continuous in the circumferential direction of the tire, which contributes to blocking external noise, thereby improving handling stability on snowy roads and reducing external noise.

[0009] In the present invention, the ratio L3 / W3 of the length L3 of the third lug groove to the width W3 of the outer intermediate land portion is preferably 0.1 or more and 0.8 or less. The ratio L2 / W2 of the length L2 of the second lug groove to the width W2 of the center land portion is preferably 0.1 or more and 0.8 or less. The ratio L1 / W1 of the length L1 of the first lug groove to the width W1 of the inner intermediate land portion is preferably 0.1 or more and 0.8 or less. This makes it possible to improve handling stability on snowy roads while reducing external noise.

[0010] The inclination angle θ3 of the third lug groove with respect to the tire circumferential direction is preferably 40° or more and 80° or less. The inclination angle θ2 of the second lug groove with respect to the tire circumferential direction is preferably 40° or more and 80° or less. The inclination angle θ1 of the first lug groove with respect to the tire circumferential direction is preferably 40° or more and 80° or less. This makes it possible to reduce external noise while improving steering stability on snowy roads.

[0011] It is preferable that the inclination angle θ1 of the first lug groove relative to the tire circumferential direction, the inclination angle θ2 of the second lug groove relative to the tire circumferential direction, and the inclination angle θ3 of the third lug groove relative to the tire circumferential direction satisfy the relationship θ2≦θ3≦θ1, thereby effectively improving steering stability on snowy roads and effectively reducing external noise.

[0012] It is preferable that the ratio Wg / W1 of the groove width Wg of the circumferential auxiliary groove to the width W1 of the inner intermediate land portion be 0.3 or less, and that the circumferential auxiliary groove be positioned further outward from the widthwise center of the inner intermediate land portion, thereby effectively improving steering stability on snowy roads and effectively reducing exterior noise.

[0013] The inner shoulder narrow groove and the outer shoulder narrow groove are preferably disposed within a region of the center 80% of the contact width of the tread portion, thereby effectively improving steering stability on snowy roads and effectively reducing external noise.

[0014] 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.

[0015] In the present invention, the contact patch width of the tread portion is the axial contact patch width measured when the tire is mounted on a standard rim, inflated to the standard internal pressure (in the case of a pneumatic tire), placed vertically on a flat surface, and subjected to a standard load. A "standard rim" is a rim determined for each tire by the standard system that includes the standard on which the tire is based, and is, for example, a standard rim in the case of JATMA, a "Design Rim" in the case of TRA, or a "Measuring Rim" in the case of ETRTO. "Normal internal pressure" refers to the air pressure determined for each tire by the respective standards, including the standards on which the tire is based, and is the maximum air pressure in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO, but is set to 180 kPa when the tire is for a passenger car. The "normal load" is the load determined for each tire by the respective standards, including the standards on which the tire is based, and is the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO. However, if the tire is for a passenger car, it is a load equivalent to 88% of the above load.

[0016] Fig. 1 is a meridian cross-sectional view showing a pneumatic tire according to a first embodiment of the present invention. Fig. 2 is a developed view showing a tread pattern of the pneumatic tire of Fig. 1. Fig. 3 is an enlarged plan view showing the tread pattern of Fig. 2.

[0017] 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. This pneumatic tire is a tire in which the orientation of the front and back of the tire when mounted on a vehicle is specified. In Figures 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.

[0018] As shown in Figure 1, the pneumatic tire of this embodiment includes a tread portion 1 extending circumferentially in an annular 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 vehicle outer side 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 vehicle outer side, and displays, for example, "INSIDE" along the tire circumferential direction on the vehicle inner side.

[0019] 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.

[0020] Meanwhile, 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 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 layers 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. Organic fiber cords such as nylon and aramid cords are preferably used as the reinforcing cords of the belt cover layer 8.

[0021] The above-described tire internal structure is a typical example of a pneumatic tire, but is not limited to this.

[0022] 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 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 succession from the vehicle inner side to the vehicle outer side, and 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 succession from the vehicle inner side to the vehicle outer side.

[0023] 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 including the inner shoulder lug groove 41 and sipes.

[0024] The inner intermediate land portion 22 is formed with a circumferential auxiliary groove 32 extending in the tire circumferential direction, and is also formed with a plurality of first lug grooves 42, one end of which opens into the first main groove 11 on the vehicle inner side and the other end of which closes within the inner intermediate land portion 22, and a plurality of first sipes 52, which extend from the closed ends of the first lug grooves 42 and communicate with the circumferential auxiliary grooves 32, spaced apart in the tire circumferential direction. 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 thin rib 62 is continuous in the tire circumferential direction without being interrupted by groove components including the lug grooves 42 and the sipes 52.

[0025] The center land portion 23 is formed with a plurality of second lug grooves 43, one end of which opens into the second main groove 12 on the vehicle inner side and the other end of which closes within the center land portion 23, and a plurality of second sipes 53, which extend from the closed ends of the second lug grooves 43 and communicate with the third main groove 13, spaced apart around the tire circumference.

[0026] The outer intermediate land portion 24 is formed with a plurality of third lug grooves 44 spaced apart around the tire, each of which has one end opening into the fourth main groove 14 on the outer side of the vehicle and the other end closing within the outer intermediate land portion 24, and a plurality of third sipes 54 extending from the closed ends of the third lug grooves 44 and communicating with the third main groove 13.

[0027] 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 including the outer shoulder lug groove 45 and sipes.

[0028] In the pneumatic tire described above, the first lug grooves 42 formed in the inner intermediate land portion 22 and the second lug grooves 43 formed in the center land portion 23 open toward the inside of the vehicle, and the third lug grooves 44 formed in the outer intermediate land portion 24 open toward the outside of the vehicle, so that radiated sounds from these first lug grooves 42, second lug grooves 43, and third lug grooves 44 are dispersed to the inside and outside of the vehicle, thereby reducing exterior noise. Furthermore, because the first lug grooves 42, second lug grooves 43, and third lug grooves 44 are closed inside the inner intermediate land portion 22, center land portion 23, and outer intermediate land portion 24, respectively, an increase in groove area is suppressed, and the generation of pattern noise, which is a factor in exterior noise, can be reduced. Furthermore, the first sipes 52, second sipes 53, and third sipes 54 are formed in the inner intermediate land portion 22, center land portion 23, and outer intermediate land portion 24, respectively, thereby ensuring sufficient edge components in the tire width direction. The inner shoulder land portion 21 is formed with an inner shoulder narrow groove 31, the outer shoulder land portion 25 is formed with an outer shoulder narrow groove 35, and the inner intermediate land portion 22 is formed with a circumferential auxiliary groove 32, thereby ensuring sufficient edge components in the tire circumferential direction. This provides sufficient edge effect on snow, improving handling stability on snowy roads. Furthermore, the narrow ribs 61, 62, and 65 defined in the inner shoulder land portion 21, inner intermediate land portion 22, and outer shoulder land portion 24 are continuous in the tire circumferential direction, contributing to blocking external noise. This improves handling stability on snowy roads and reduces external noise.

[0029] In the pneumatic tire, as shown in Figure 3, the ratio L3 / W3 of the length L3 of the third lug groove 44 to the width W3 of the outer intermediate land portion 24 is preferably 0.1 or more and 0.8 or less. If the ratio L3 / W3 is less than 0.1, the steering stability on snowy roads cannot be effectively improved. Conversely, if the ratio L3 / W3 is greater than 0.8, the generation of pumping noise cannot be effectively suppressed, and the effect of reducing external noise is reduced. In particular, the ratio L3 / W3 is preferably 0.2 or more and 0.5 or less.

[0030] The ratio L2 / W2 of the length L2 of the second lug groove 43 to the width W2 of the center land portion 23 is preferably 0.1 or more and 0.8 or less. If the ratio L2 / W2 is less than 0.1, steering stability on snowy roads cannot be effectively improved. Conversely, if the ratio L2 / W2 is greater than 0.8, the generation of pumping noise cannot be effectively suppressed, and the effect of reducing external noise is reduced. In particular, the ratio L2 / W2 is preferably 0.2 or more and 0.5 or less.

[0031] The ratio L1 / W1 of the length L1 of the first lug groove 42 to the width W1 of the inner intermediate land portion 22 is preferably 0.1 or more and 0.8 or less. If the ratio L1 / W1 is less than 0.1, steering stability on snowy roads cannot be effectively improved. Conversely, if the ratio L1 / W1 is greater than 0.8, the generation of pumping noise cannot be effectively suppressed, and the effect of reducing external noise is reduced. In particular, the ratio L1 / W1 is preferably 0.2 or more and 0.5 or less.

[0032] In the above-described pneumatic tire, as shown in FIG. 3 , the inclination angle θ3 of the third lug grooves 44 formed in the outer intermediate land portion 24 with respect to the tire circumferential direction is preferably 40° or more and 80° or less. If the inclination angle θ3 of the third lug grooves 44 is less than 40°, sufficient snow column shear force cannot be obtained. Conversely, if the inclination angle θ3 of the third lug grooves 44 is greater than 80°, the rigidity of the outer intermediate land portion 24 becomes high, and deformation of the outer intermediate land portion 24 when ground pressure is applied becomes small, making it difficult to effectively suppress the generation of exterior noise. In particular, it is desirable that the inclination angle θ3 be 50° or more and 70° or less.

[0033] The inclination angle θ2 of the second lug grooves 43 formed in the center land portion 23 relative to the tire circumferential direction is preferably 40° or more and 80° or less. If the inclination angle θ2 of the second lug grooves 43 is less than 40°, sufficient snow column shear force cannot be obtained. Conversely, if the inclination angle θ2 of the second lug grooves 43 is greater than 80°, the rigidity of the center land portion 23 becomes high, and deformation of the center land portion 23 when ground pressure is applied becomes small, making it difficult to effectively suppress the generation of exterior noise. In particular, it is desirable that the inclination angle θ2 be 50° or more and 70° or less.

[0034] The inclination angle θ1 of the first lug grooves 42 formed in the inner intermediate land portion 22 relative to the tire circumferential direction is preferably 40° or more and 80° or less. If the inclination angle θ1 of the first lug grooves 42 is less than 40°, sufficient snow column shear force cannot be obtained. Conversely, if the inclination angle θ1 of the first lug grooves 42 is greater than 80°, the rigidity of the inner intermediate land portion 22 becomes high, and deformation of the inner intermediate land portion 22 when ground pressure is applied becomes small, making it difficult to effectively suppress the generation of exterior noise. In particular, the inclination angle θ1 is preferably 50° or more and 70° or less.

[0035] The inclination angles θ1 to θ3 of the lug grooves 42 to 44 are angles formed by a straight 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 lug grooves 42 to 44 relative to the tire circumferential direction.

[0036] In the above pneumatic tire, it is preferable that the inclination angle θ1 of the first lug grooves 42 relative to the tire circumferential direction, the inclination angle θ2 of the second lug grooves 43 relative to the tire circumferential direction, and the inclination angle θ3 of the third lug grooves 44 relative to the tire circumferential direction satisfy the relationship θ2≦θ3≦θ1. By satisfying such a relationship, the inclination angles θ1, θ2, and θ3 of the first lug grooves 42, the second lug grooves 43, and the third lug grooves 44 are optimized, effectively improving steering stability on snowy roads and effectively reducing external noise. In particular, it is preferable that the relationship θ2<θ3<θ1 be satisfied.

[0037] In the above pneumatic tire, it is preferable that the ratio Wg / W1 of the groove width Wg of the circumferential auxiliary groove 32 to the width W1 of the inner intermediate land portion 22 is 0.3 or less, and the circumferential auxiliary groove 32 is positioned further outward from the widthwise center of the inner intermediate land portion 22. This effectively improves steering stability on snowy roads while effectively reducing external noise. If the ratio Wg / W1 is greater than 0.3, the rigidity of the inner intermediate land portion 22 is excessively reduced, reducing the effect of improving steering stability on snowy roads. Furthermore, if the circumferential auxiliary groove 32 is positioned further inward from the widthwise center of the inner intermediate land portion 22, the arrangement area of ​​the first lug grooves 42 and the first sipes 52 is reduced, reducing the effect of improving steering stability on snowy roads.

[0038] In the above pneumatic tire, it is preferable that the inner shoulder narrow groove 31 and the outer shoulder narrow groove 35 are arranged within a region that is 80% of the center of the contact width TCW of the tread portion 1. This effectively improves steering stability on snowy roads while effectively reducing external noise. If the inner shoulder narrow groove 31 and the outer shoulder narrow groove 35 are located outside the above region, the effect of improving steering stability on snowy roads and the effect of reducing external noise are reduced.

[0039] In a pneumatic tire having a tire size of 265 / 45R21 and a specified mounting direction relative to 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 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. The tires of Examples 1 to 17 were manufactured with a structure in which a narrow rib was defined between the inner shoulder narrow groove and the first main groove, one circumferential auxiliary groove, multiple first lug grooves, and multiple first sipes were formed in the inner intermediate land portion, a narrow rib was defined between the circumferential auxiliary groove and the second main groove, multiple second lug grooves and multiple second sipes were formed in the center land portion, multiple third lug grooves and multiple third sipes were formed in the outer intermediate land portion, one shoulder narrow groove and multiple outer shoulder lug grooves were formed in the outer shoulder land portion, and a narrow rib was defined between the outer shoulder narrow groove and the fourth main groove.

[0040] For comparison, a conventional tire was prepared that had the same structure as Example 1, except that all of the lug grooves formed in the inner intermediate land portion, center land portion, and outer intermediate land portion were arranged to open toward the inside of the vehicle, and no circumferential auxiliary grooves were provided in the inner intermediate land portion.

[0041] In the tires of the conventional example and Examples 1 to 17, the lug groove opening direction, the ratios of the lug groove length to the land portion width L3 / W3, L2 / W2, and L1 / W1, the inclination angles θ3, θ2, and θ1 of the lug grooves with respect to the tire circumferential direction, the ratio Wg / W1 of the groove width Wg of the circumferential auxiliary groove to the width W1 of the inner intermediate land portion, and the position of the shoulder narrow groove are as shown in Tables 1 to 3. Regarding the lug groove opening direction, "IN" means a state in which the lug groove opens toward the inside of the vehicle, and "OUT" means a state in which the lug groove opens toward the outside of the vehicle. Regarding the position of the shoulder narrow groove, when the inner shoulder narrow groove and the outer shoulder narrow groove are located inside the central 80% region of the contact width of the tread portion, it is indicated as "within the 80% region," and when the inner shoulder narrow groove and the outer shoulder narrow groove are located outside the central 80% region of the contact width of the tread portion, it is indicated as "outside the 80% region." In the tires of Examples 1 to 6, the circumferential auxiliary grooves were arranged on the outer side of the vehicle from the widthwise center position of the inner intermediate land portion.

[0042] These test tires were evaluated for steering stability on snowy roads and external noise by the following test methods, and the results are shown in Tables 1 to 3.

[0043] Steering stability on snowy roads: Each test tire was mounted on a 21x9J rim size wheel and mounted on a 2400cc SUV (front-wheel drive vehicle). After warming up, the tire was inflated to a pressure of 230 kPa and driven on a snowy road. A sensory evaluation was conducted by a test driver. The evaluation results were expressed as an index, with the conventional tire being set at 100. The higher the index value, the better the steering stability on snowy roads.

[0044] External noise: Each test tire was mounted on a 21x9J rim size wheel and mounted on a 2400cc SUV (front-wheel drive). After warm-up, the tire was inflated to a pressure of 230 kPa and tested 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.

[0045]

[0046]

[0047]

[0048] As can be seen from Tables 1 to 3, the tires of Examples 1 to 17 had good driving stability on snowy roads and reduced external noise compared to the conventional tires.

[0049] REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 10, 11, 12, 13, 14 main groove 20, 21, 22, 23, 24, 25 land portion 31, 35 narrow groove 32 circumferential auxiliary groove 41, 42, 43, 44, 45 lug groove 52, 53, 54 sipe 61, 62, 65 narrow rib

Claims

1. In tires with a specified mounting direction for a vehicle, The tread portion has four main grooves extending in the circumferential direction of the tire, and these main grooves divide the land into five rows, 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 sequentially from the inside of the vehicle to the outside of the vehicle, and the five rows of land include an inner shoulder land, an inner intermediate land, a center land, an outer intermediate land, and an outer shoulder land, which are arranged sequentially from the inside of the vehicle to the outside of the vehicle. The 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 continuous in the tire circumferential direction is partitioned between the inner shoulder narrow groove and the first main groove. The inner intermediate land portion is formed with a circumferential auxiliary groove extending in the circumferential direction of the tire, a plurality of first lug grooves, one end of which opens into the first main groove and the other end which closes within the inner intermediate land portion, and a plurality of first sipes extending from the closed ends of the first lug grooves and communicating with the circumferential auxiliary groove, and a narrow rib continuous in the circumferential direction of the tire is partitioned between the circumferential auxiliary groove and the second main groove. The center land portion is formed with a plurality of second lug grooves, one end of which opens into the second main groove and the other end which closes within the center land portion, and a plurality of second sipes that extend from the closed ends of the second lug grooves and communicate with the third main groove. The outer intermediate land portion is formed with a plurality of third lug grooves, one end of which opens into the fourth main groove and the other end which closes within the outer intermediate land portion, and a plurality of third sipes that extend from the closed ends of the third lug grooves and communicate with the third main groove. A tire characterized in that the outer shoulder land portion has an outer shoulder narrow groove extending in the tire circumferential direction and a plurality of outer shoulder lug grooves extending in the tire width direction, and a narrow rib that is continuous in the tire circumferential direction is partitioned between the outer shoulder narrow groove and the fourth main groove.

2. The tire according to claim 1, characterized in that the ratio L3 / W3 of the length L3 of the third lug groove to the width W3 of the outer intermediate land portion is 0.1 or more and 0.8 or less.

3. The tire according to claim 2, characterized in that the ratio L2 / W2 of the length of the second lug groove to the width W2 of the center land portion is 0.1 or more and 0.8 or less.

4. The tire according to claim 3, characterized in that the ratio L1 / W1 of the length L1 of the first lug groove to the width W1 of the inner intermediate land portion is 0.1 or more and 0.8 or less.

5. The tire according to claim 1, characterized in that the inclination angle θ3 of the third lug groove with respect to the tire circumferential direction is 40° or more and 80° or less.

6. The tire according to claim 5, characterized in that the inclination angle θ2 of the second lug groove with respect to the tire circumferential direction is 40° or more and 80° or less.

7. The tire according to claim 6, characterized in that the inclination angle θ1 of the first lug groove with respect to the tire circumferential direction is 40° or more and 80° or less.

8. The tire according to any one of claims 1 to 7, characterized in that the inclination angle θ1 of the first lug groove with respect to the tire circumferential direction, the inclination angle θ2 of the second lug groove with respect to the tire circumferential direction, and the inclination angle θ3 of the third lug groove with respect to the tire circumferential direction satisfy the relationship θ2 ≤ θ3 ≤ θ1.

9. The tire according to any one of claims 1 to 7, characterized in that the ratio Wg / W1 of the groove width Wg of the circumferential auxiliary groove to the width W1 of the inner intermediate land portion is 0.3 or less, and the circumferential auxiliary groove is positioned outside the vehicle relative to the center position in the width direction of the inner intermediate land portion.

10. The tire according to any one of claims 1 to 7, characterized in that the inner shoulder groove and the outer shoulder groove are arranged within the central 80% area of ​​the contact width of the tread portion.