Pneumatic tire

Abstract

To provide a pneumatic tire capable of enhancing load durability while improving high speed durability and steering stability.SOLUTION: In a pneumatic tire whose mounting direction relative to a vehicle is designated, when the position of a ground contact end E on a contour of a tread part 1 is a point PA, the position away from the ground contact end E inward in a tire width direction by 5% of a tire nominal width W is a point PB, and the position away from the ground contact end E inward in the tire width direction by 10% of the tire nominal width W is a point PC, a curvature radius SRin of a circular arc passing through the three points PA, PB and PC inside the vehicle and a curvature radius SRout of a circular arc passing through the three points PA, PB and PC outside the vehicle satisfy a relationship of 1.1≤SRout / SRin≤2.0, and a rear angle θ formed by a linear line passing through a rim departure point P1 and the tire's maximum projection point P2 relative to the tire width direction within the vehicle and a rear angle θout outside the vehicle satisfy a relationship of 1.05≤θin / θout≤1.3.SELECTED DRAWING: Figure 1

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 pneumatic tire that enables improved load durability and high-speed durability. [Background technology]

[0002] Hybrid vehicles (HVs) and electric vehicles (EVs) have become increasingly popular in recent years, but because these vehicles require the installation of batteries, etc., they tend to be heavier than vehicles powered by conventional internal combustion engines. For this reason, tires are required to have excellent load durability.

[0003] Known methods for improving load durability include, for example, increasing the hardness of the sidewall portion or increasing the cross-sectional height of the bead filler (for example, Patent Document 1 sets the bead filler height high to improve handling stability, and such a high bead filler height is expected to improve load durability as well). However, while these measures can improve load durability, they increase the vertical spring of the sidewall portion, which increases the contact pressure in the shoulder area and may reduce high-speed durability. In addition, there is a risk that the vertical spring of the sidewall portion may affect handling stability. Therefore, there is a need for measures that improve high-speed durability and handling stability while improving load durability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2019-055651 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pneumatic tire that can improve high-speed durability and steering stability while improving load durability. [Means for solving the problem]

[0006] In order to achieve the above object, a pneumatic tire of the present invention comprises a tread portion extending in a tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the tire radially inward side of the sidewall portions, and the pneumatic tire has at least one carcass layer mounted between the pair of bead portions, a plurality of belt layers arranged on the outer peripheral side of the carcass layer in the tread portion, and a belt cover layer arranged on the outer peripheral side of the belt layer, and the tire is fitted in a specified direction to a vehicle. In the pneumatic tire, a plurality of main grooves extending in the tire circumferential direction are formed in the tread portion, and a pair of shoulder land portions are defined in the tire width direction of the pair of main grooves arranged on the outermost sides in the tire width direction, and in a tire meridian cross section, a contact edge position on the contour line of the tread portion is designated as point P A , the position 5% of the nominal tire width inward from the contact edge in the tire width direction is point P B , the position 10% of the nominal tire width inward from the contact edge in the tire width direction is point P C When the vehicle is mounted, the point P A , said point P B , and said point P C The radius of curvature of the arc passing through these three points is SRin, and the point P is the outer side of the vehicle when the vehicle is installed. A , said point P B , and said point P Cand the radius of curvature SRout of the arc passing through the three points satisfies the relationship 1.1≦SRout / SRin≦2.0, and when the point at which the outer surface of the bead portion separates from the rim flange in a rim-assembled state is defined as a rim separation point P1, the point at which the sidewall portion protrudes furthest outward in the tire width direction at the tire's widest position is defined as a tire maximum protrusion point P2, and the angle formed by a straight line passing through the rim separation point P1 and the tire maximum protrusion point P2 with respect to the tire width direction is defined as a rearward facing angle θin on the vehicle inner side and the rearward facing angle θout on the vehicle outer side satisfies 1.05≦θin / θout≦1.3. [Effects of the Invention]

[0007] As a result of extensive research into the cross-sectional shape (profile) of a pneumatic tire, the inventors of the present invention discovered that load durability can be improved by making the rearward facing angle θin on the vehicle's inner side larger than the rearward facing angle θout on the vehicle's outer side. Meanwhile, the vehicle's inner side of a pneumatic tire is at a disadvantage in terms of high-speed durability compared to the vehicle's outer side, which is more exposed to outside air and tends to cool naturally. However, the inventors discovered that by reducing the radius of curvature SRin on the vehicle's inner side, air flow on the vehicle's inner side can be improved when the tire is mounted on the vehicle, allowing the tire to be cooled by the air flow during driving, thereby improving high-speed durability. Furthermore, while pneumatic tires generally set with a negative camber tend to have a longer contact length on the vehicle's inner side, the inventors discovered that by increasing the radius of curvature SRout on the vehicle's outer side, the difference in contact length between the vehicle's inner and outer sides can be reduced, distributing the load on the vehicle's inner side during driving and improving high-speed durability. The present invention is based on these findings, and by satisfying the relationships 1.1≦SRout / SRin≦2.0 and 1.05≦θin / θout≦1.3 as described above, the above-mentioned effects can be exhibited in a balanced manner, and load durability, high-speed durability, and handling stability can all be improved, thereby achieving a high degree of compatibility between these performance characteristics.

[0008] In the present invention, the radius of curvature SRin on the vehicle inner side is preferably 30 mm to 200 mm, which is advantageous for improving the air flow inside the vehicle when mounted on the vehicle and improving high-speed durability.

[0009] In the present invention, it is preferable that the rearward angle θin on the vehicle inner side is 65° to 90°, which ensures sufficient vertical spring, and is advantageous for improving load durability.

[0010] In the present invention, it is preferable that the radius of curvature SRin and the rearward facing angle θin on the vehicle inner side satisfy the relationship 0.4≦SRin / θin≦1.2, which improves the overall cross-sectional shape of the tread portion from the vicinity of the shoulder to the sidewall, and is advantageous for achieving both load durability and high-speed durability.

[0011] In the present invention, it is preferable that the radius of curvature SRin and the rearward turning angle θin on the vehicle inner side and the radius of curvature SRout and the rearward turning angle θout on the vehicle outer side satisfy the relationship 0.3≦(SRout / θout) / (SRin / θin)≦2.3, which improves the balance of the cross-sectional shapes on the vehicle inner side and the vehicle outer side, and is advantageous for improving steering stability.

[0012] In the present invention, the tire section height is preferably 150 mm or less. Since a tire with a small section height (low aspect tire) is likely to have higher contact pressure in the shoulder region of the tread than a tire with a large section height (high aspect tire), application of the present invention makes it possible to effectively achieve both high-speed durability and load durability.

[0013] In the present invention, it is preferable that the groove area ratio Gin in the inner region of the tread portion, which is located on the inner side of the tire equator, and the groove area ratio Gout in the outer region of the tread portion, which is located on the outer side of the tire equator, satisfy the relationship Gin > Gout. By increasing the groove area ratio on the inner side of the vehicle in this way, it is possible to add a heat dissipation effect by the grooves on the inner side of the vehicle, which is advantageous for improving high-speed durability.

[0014] In the present invention, the cover cord constituting the belt cover layer is preferably a hybrid cord made of nylon fiber and aramid fiber. Since such hybrid cords tend to generate a high amount of heat, application of the present invention can effectively achieve both high-speed durability and load durability.

[0015] In the present invention, the carcass cords constituting the carcass layer are preferably rayon fiber cords. When the carcass layer is made of rayon fiber cords, it is desirable that the longitudinal spring characteristics are excellent, and therefore high-speed durability can be more effectively improved.

[0016] In this invention, the term "tread edge" refers to the axial end of the contact area formed when a tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load. 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, 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. For JATMA, the maximum air pressure is specified, for TRA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" table, and for ETRTO, the "INFLATION PRESSURE" is specified. However, if the tire is for a passenger car, the term is 180 kPa. "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.

[0017] In the present invention, the "rim-mounted state" when defining the "rim separation point" refers to a state in which the tire is mounted on the aforementioned "regular rim" and inflated to "regular internal pressure." The "tire maximum protrusion point" is the point at which the outer surface of the tire protrudes most outward in the tire width direction at the tire radial position (maximum tire width position) where the total tire width (tire cross-sectional width including patterns and lettering on the side of the tire) is at its maximum in the "rim-mounted state" similar to the "rim separation point." [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] As shown in Fig. 1, the pneumatic tire of the present invention includes a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on either side of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. In Fig. 1, the symbol CL indicates the tire equator, and the symbol E indicates the ground-contact edge. 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 and form an annular shape, thereby constituting the basic toroidal structure of the pneumatic tire. The following explanation using Fig. 1 will be based basically on the meridian cross-section shape shown, but each tire component also extends in the tire circumferential direction and forms an annular shape.

[0021] A carcass layer 4 is mounted between a pair of left and right bead portions 3. This carcass layer 4 includes multiple reinforcing cords (carcass cords) extending in the tire radial direction and folded back from the inner side to the outer side in the tire width direction around bead cores 5 arranged in each bead portion 3. The material of the carcass cords constituting the carcass layer 4 is not particularly limited, and various materials commonly used in pneumatic tires can be used. However, when the carcass cords are rayon fiber cords, it is preferable to supplement the vertical spring characteristics by the tire structure, so this can be suitably combined with the present invention described below. A bead filler 6 is arranged on the outer periphery of the bead core 5, and this bead filler 6 is enclosed by the main portion and folded back portion of the carcass layer 4. The bead filler 6 has a generally triangular cross section, for example, as shown in the figure, and is made of a rubber composition.

[0022] Multiple belt layers 7 are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes multiple 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 reinforcing cords have an inclination angle with respect to the tire circumferential direction, for example, set in the range of 10° to 40°. At least one belt cover layer 8 is provided on the outer periphery 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 reinforcing cords have an angle with respect to the tire circumferential direction, for example, set in the range of 0° to 5°. The material of the cover cords constituting the belt cover layer 8 is not particularly limited, and various organic fiber cords commonly used in pneumatic tires can be used. However, when the cover cords are hybrid cords made of nylon fiber and aramid fiber, such hybrid cords tend to generate a high amount of heat. Therefore, by applying the present invention described below, it is possible to effectively achieve both high-speed durability and load durability.

[0023] The pneumatic tire of the present invention is a tire for which the mounting direction of the front and back of the tire when mounted on a vehicle is specified. In Fig. 1, "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. A tire for which the mounting direction on a vehicle is specified has a mounting direction indicator (not shown) formed, for example, on at least the sidewall portion 2 on the outside of the vehicle, which indicates the mounting direction on the vehicle. The mounting direction indicator 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.

[0024] As shown in FIG. 1 , the tire of the present invention has a tread portion 1 formed with a plurality of (four in the illustrated example) main grooves 10 extending in the tire circumferential direction, and these main grooves 10 define a plurality of (five in the illustrated example) 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 5.0 mm to 20.0 mm, and their groove depths are set in the range of 5.0 mm to 10.0 mm. In particular, the land portions 20 defined in the tire width direction by a pair of main grooves 10 (outer main grooves 11) arranged on the outermost sides in the tire width direction are referred to as shoulder land portions 21. The present invention primarily relates to the cross-sectional shape (profile line) of the tire from the shoulder land portions 21 to the bead portions 3, and therefore the basic structure (internal structure) of the tire is not limited to the general structure described above.

[0025] In the present invention, as shown in FIG. 1, the position of the ground contact edge E on the contour line of the tread portion 1 in the tire meridian cross section is defined as point P A , point P at a position 5% of the nominal tire width W inward from the ground contact edge E in the tire width direction B , point P at a position 10% of the nominal tire width W inward from the ground contact edge E in the tire width direction C At this time, point P A , point P B , and point P C The radius of curvature of the arc passing through these three points is SRin, and point P A , point P B , and point P CThe radius of curvature of the arc passing through these three points is SRout, and the ratio SRout / SRin of the radius of curvature SRin to the radius of curvature SRout satisfies the relationship 1.1≦SRout / SRin≦2.0, preferably 1.1≦SRout / SRin≦1.5. A , point P B , and point P C It is the radius of curvature of the arc drawn based on these three points, and depending on the tire shape, it may not completely match the contour line of the actual tire meridian cross section of the tread portion 1. Note that the tire nominal width W is a value generally displayed as the tire size, and is a different value from the cross section width SW used when determining the back angle (rim separation point) described below.

[0026] 1, the point where the outer surface of the bead portion 3 separates from the rim flange of the rim R is defined as the rim separation point P1, the point where the sidewall portion 2 protrudes furthest outward in the tire width direction at the tire's widest position (the position in the tire radial direction where the tire cross-sectional width SW is greatest) is defined as the tire maximum protrusion point P2, and the angle formed by a line passing through the rim separation point P1 and the tire maximum protrusion point P2 with respect to the tire width direction is defined as the backlash angle. In this case, the backlash angle θin on the vehicle inner side and the backlash angle θout on the vehicle outer side satisfy the relationship 1.05≦θin / θout≦1.3, preferably 1.05≦θin / θout≦1.2.

[0027] As described above, load durability can be improved by making the rearward facing angle θin on the vehicle inner side larger than the rearward facing angle θout on the vehicle outer side. Meanwhile, by reducing the curvature radius SRin on the vehicle inner side, the tire contour from the shoulder land portion 21 to the sidewall portion 2 is appropriately curved, improving the airflow on the vehicle inner side when mounted on the vehicle. This airflow cools the tire during running, improving high-speed durability. Furthermore, by increasing the curvature radius SRout on the vehicle outer side, the difference in contact length between the vehicle inner and outer sides is reduced, distributing the load on the vehicle inner side during running and improving high-speed durability. In particular, by having the curvature radii SRout and SRin and the rearward facing angles θin and θout satisfy the above-mentioned ratios, the aforementioned effects are balanced, improving load durability, high-speed durability, and handling stability, and achieving a high level of compatibility among these performances.

[0028] If the ratio SRout / SRin is less than 1.1, the cooling effect described above is insufficient, and high-speed durability cannot be improved. If the ratio SRout / SRin exceeds 2.0, a sufficient contact length cannot be secured, resulting in reduced handling stability. If the ratio θin / θout is less than 1.05, the rearward angle θin on the vehicle inner side cannot be secured sufficiently, and load durability cannot be improved. If the ratio θin / θout exceeds 1.3, the difference in vertical spring strength of the sidewall portion 2 between the vehicle inner side and the vehicle outer side becomes large, resulting in reduced handling stability.

[0029] The radius of curvature SRin on the vehicle inner side is preferably 30 mm to 200 mm, more preferably 30 mm to 100 mm. This is advantageous for improving airflow inside the vehicle when installed on the vehicle and enhancing high-speed durability. If the radius of curvature SRin is less than 30 mm, the contact length on the vehicle inner side may not be sufficiently secured, which may result in a decrease in handling stability. If the radius of curvature SRin exceeds 200 mm, the tire contour from the shoulder land portion 21 to the sidewall portion 2 is not sufficiently curved, which limits the effect of improving airflow inside the vehicle and enhancing heat dissipation. The radius of curvature SRout on the vehicle outer side is not particularly limited, but may be set to, for example, 35 mm to 220 mm.

[0030] The rearward facing angle θin on the vehicle inner side is preferably 65° to 90°, and more preferably 70° to 80°. This ensures sufficient vertical spring in the sidewall portion 2 on the vehicle inner side, which is advantageous for improving load durability. If the rearward facing angle θin is less than 65°, sufficient vertical spring cannot be ensured, and the effect of improving load durability will be limited. The rearward facing angle θout on the vehicle outer side is not particularly limited, but can be set to, for example, 62° to 85°. Note that, due to the structure, the rearward facing angles θin and θout of a rim-mounted pneumatic tire will not exceed 90°.

[0031] The radius of curvature SRin and the backlash angle θin on the vehicle inner side each satisfy the above-mentioned ranges, and the ratio SRin / θin preferably satisfies the relationship 0.4≦SRin / θin≦1.2, more preferably 0.5≦SRin / θin≦1.0. This improves the overall cross-sectional shape from the shoulder land portion 21 on the vehicle inner side through the sidewall portion 2 to the bead portion 3, which is advantageous for achieving both load durability and high-speed durability. If the ratio SRin / θin is outside the above-mentioned range, it becomes difficult to achieve a good balance between the aforementioned effects achieved by setting the radius of curvature SRin and the aforementioned effects achieved by setting the backlash angle θin.

[0032] If the difference between the radius of curvature SRin and the rearward angle θin on the vehicle inner side and the radius of curvature SRout and the rearward angle θout on the vehicle outer side is large, the asymmetry between the vehicle inner side and the vehicle outer side becomes significant, which may affect handling stability. Therefore, the radius of curvature SRin and the rearward angle θin on the vehicle inner side and the radius of curvature SRout and the rearward angle θout on the vehicle outer side preferably satisfy the relationship 0.3≦(SRout / θout) / (SRin / θin)≦2.3, and more preferably the relationship 0.8≦(SRout / θout) / (SRin / θin)≦1.8. This improves the balance of the cross-sectional shapes on the vehicle inner side and the vehicle outer side, which is advantageous, particularly in terms of handling stability. If the ratio (SRout / θout) / (SRin / θin) is outside the above-mentioned range, the asymmetry between the vehicle inner side and the vehicle outer side becomes significant, limiting the effect of improving handling stability.

[0033] The present invention described above can be applied to various pneumatic tires, but since tires with small cross-sectional heights (low aspect tires) tend to have higher ground contact pressure in the shoulder regions (shoulder land portions 21) of the tread portion 1 compared to tires with large cross-sectional heights (high aspect tires), applying the present invention makes it possible to effectively achieve both high-speed durability and load durability. Specifically, the tire cross-sectional height of pneumatic tires to which the present invention is applied is preferably 150 mm or less.

[0034] While the tread pattern in the tread portion 1 of a pneumatic tire to which the present invention is applied is not particularly limited, it is preferable that the groove area ratio Gin in the vehicle-inner region, which is on the vehicle inner side of the tire equator CL, and the groove area ratio Gout in the vehicle-outer region, which is on the vehicle outer side of the tire equator CL, satisfy the relationship Gin > Gout. In particular, it is preferable that the difference (Gin - Gout) between the groove area ratio Gin in the vehicle-inner region and the groove area ratio Gout in the vehicle-outer region be 1% or more. In such a tread pattern with a large groove area ratio on the vehicle-inner side, the grooves can add a heat dissipation effect on the vehicle-inner side, and therefore, by combining it with the present invention described above, further improvement in high-speed durability can be expected.

[0035] 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]

[0036] The tire has the basic structure (internal structure) illustrated in FIG. 1, and the tire cross-sectional shape (profile line) in the tire meridian cross section is A ) and a point 5% of the nominal tire width inward from the contact edge E in the tire width direction (point P B ) and a position 10% of the nominal tire width inward from the contact edge E in the tire width direction (point P C ) are defined as SRin (inner side of the vehicle) and SRout (outer side of the vehicle), and the angle formed by a straight line passing through rim separation point P1 and tire maximum protrusion point P2 in the rim-assembled state with respect to the tire width direction is defined as back angle θin (inner side of the vehicle) and θout (outer side of the vehicle). The ratio SRout / SRin, radius of curvature ratio SRout, radius of curvature SRin, ratio θin / θout, back angle θin, back angle θout, ratio SRin / θin, ratio SRout / θout, and ratio (SRout / θout) / (SRin / θin) were set as shown in Table 1, and pneumatic tires (test tires) of Conventional Example 1, Comparative Examples 1 and 2, and Examples 1 to 9 were fabricated with the groove area ratio, cover cord material, and carcass cord material set as shown in Table 1. The tire sizes of the test tires were 275 / 45R21 110Y for the front and 315 / 40R21 115Y for the rear.

[0037] In the "Groove Area Ratio" column of Table 1, the relationship between the groove area ratio Gin in the inner region of the tread, which is on the inside of the tire equator, and the groove area ratio Gout in the outer region of the tread, which is on the outside of the tire equator, is shown using equal and inequality signs. In the "Cover Cord Material" and "Carcass Cord Material" columns of Table 1, the type of organic fiber that makes up each cord is listed. Note that hybrid cords made of nylon fiber and aramid fiber are listed as "nylon + aramid."

[0038] These test tires were evaluated for steering stability, high-speed durability, and load durability by the following test methods, and the results are shown in Table 1.

[0039] Steering stability Each test tire was mounted on a 21x9.5J rim wheel for the front tire and a 21x11.5J rim wheel for the rear tire, and mounted on a 4000cc SUV (4WD). Both the front and rear tires were inflated to an air pressure of 250kPa, and a test driver conducted a sensory evaluation of the handling stability on a test course consisting of a dry paved road. The evaluation results were expressed as an index, with the conventional example being 100. The higher the index value, the better the handling stability.

[0040] fast durability Each test tire was mounted on a wheel with a rim size of 21 x 9.5J for the front tires and a wheel with a rim size of 21 x 11.5J for the rear tires, and then attached to an indoor drum testing machine (drum diameter: 1707 mm). The tire was inflated to 360 kPa, subjected to 68% of the maximum load specified by the ETRTO standard, and at a camber angle of -3°. The speed was increased by 10 km / h every 10 minutes, and the maximum speed reached when the tire broke was measured. The evaluation results were expressed as an index, with Conventional Example 1's value being 100. A higher index value indicates a higher maximum speed reached when the tire broke, and therefore better high-speed durability.

[0041] Load durability Each test tire was mounted on a wheel with a rim size of 21 x 9.5J for the front tire and a wheel with a rim size of 21 x 11.5J for the rear tire, and then mounted on an indoor drum testing machine (drum diameter: 1707 mm). The tires were inflated to the normal internal pressure of the ETRTO standard, and the camber angle was -3°, the speed was 81 km / h, and the load was increased by 13% every two hours from the initial load (88% of the maximum load of the ETRTO standard), and the running distance until the tire broke was measured. The evaluation results were expressed as an index, with Conventional Example 1's value being 100. The higher the index value, the longer the running distance until the tire broke, indicating better load durability.

[0042] [Table 1]

[0043] As can be seen from Table 1, the tires of Examples 1 to 9 improved steering stability, high-speed durability, and load durability compared to the conventional tires, achieving all of these performance characteristics. On the other hand, in Comparative Example 1, the ratio of the back angle θin / θout did not satisfy the conditions of the present invention, so the effect of improving high-speed durability and load durability was not obtained. In Comparative Example 2, the ratio of the curvature radii SRout / SRin did not satisfy the conditions of the present invention, so the effect of improving high-speed durability was not obtained.

[0044] The present disclosure encompasses the following inventions. Invention [1] A pneumatic tire having a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the tire radially inward side of the sidewall portions, and having at least one carcass layer mounted between the pair of bead portions, a plurality of belt layers arranged on the outer peripheral side of the carcass layer in the tread portion, and a belt cover layer arranged on the outer peripheral side of the belt layer, and having a specified mounting direction on a vehicle, A plurality of main grooves extending in a tire circumferential direction are formed in the tread portion, and a pair of shoulder land portions are defined in the tire width direction by a pair of the main grooves arranged on the outermost sides in the tire width direction, In the tire meridian cross section, the contact edge position on the contour line of the tread portion is defined as point P A , the position 5% of the nominal tire width inward from the contact edge in the tire width direction is point P B , the position 10% of the nominal tire width inward from the contact edge in the tire width direction is point P C When the vehicle is mounted, the point P A , said point P B , and said point P C The radius of curvature of the arc passing through these three points is SRin, and the point P is the outer side of the vehicle when the vehicle is installed. A , said point P B , and said point P C The radius of curvature SRout of the arc passing through these three points satisfies the relationship 1.1≦SRout / SRin≦2.0, and A pneumatic tire characterized in that, when assembled to a rim, the point at which the outer surface of the bead portion separates from the rim flange is defined as a rim separation point P1, the point at which the sidewall portion protrudes furthest outward in the tire width direction at the tire's widest position is defined as a tire maximum protrusion point P2, and the angle formed by a line passing through the rim separation point P1 and the tire maximum protrusion point P2 with respect to the tire width direction is defined as a rearward facing angle θin on the vehicle inner side and the rearward facing angle θout on the vehicle outer side satisfy 1.05≦θin / θout≦1.3. Invention [2] The pneumatic tire according to invention [1], wherein the radius of curvature SRin on the inner side of the vehicle is 30 mm to 200 mm. Invention [3] The pneumatic tire according to invention [1] or [2], wherein the rearward facing angle θin on the vehicle inner side is 65° to 90°. Invention [4] The pneumatic tire according to any one of inventions [1] to [3], wherein the radius of curvature SRin and the rearward facing angle θin satisfy the relationship 0.4≦SRin / θin≦1.2 on the vehicle inner side. Invention [5] A pneumatic tire according to any one of inventions [1] to [4], characterized in that the radius of curvature SRin and the rearward turning angle θin on the inside of the vehicle and the radius of curvature SRout and the rearward turning angle θout on the outside of the vehicle satisfy the relationship 0.3≦(SRout / θout) / (SRin / θin)≦2.3. Invention [6] A pneumatic tire according to any one of inventions [1] to [5], characterized in that the tire cross-sectional height is 150 mm or less. Invention [7] A pneumatic tire according to any one of inventions [1] to [6], characterized in that in the tread portion, a groove area ratio Gin in a vehicle inner region that is on the vehicle inner side of the tire equator and a groove area ratio Gout in a vehicle outer region that is on the vehicle outer side of the tire equator satisfy the relationship Gin > Gout. Invention [8] The pneumatic tire according to any one of inventions [1] to [7], wherein the cover cord constituting the belt cover layer is a hybrid cord made of nylon fiber and aramid fiber. Invention [9] The pneumatic tire according to any one of inventions [1] to [8], wherein the carcass cords constituting the carcass layer are rayon fiber cords. [Explanation of symbols]

[0045] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt cover layer 10 Main groove 11 Outer main groove 20 Land 21 Shoulder Land Section CL Tire Equator E Ground end R rim

Claims

1. A pneumatic tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed radially inward of the sidewall portions, the pneumatic tire having at least one carcass layer mounted between the pair of bead portions, a plurality of belt layers disposed on the outer peripheral side of the carcass layer in the tread portion, and a belt cover layer disposed on the outer peripheral side of the belt layer, the pneumatic tire having a specified mounting direction on a vehicle, A plurality of main grooves extending in a tire circumferential direction are formed in the tread portion, and a pair of shoulder land portions are defined in the tire width direction by a pair of the main grooves arranged on the outermost sides in the tire width direction, In the tire meridian cross section, the contact edge position on the contour line of the tread portion is defined as point P A , the position 5% of the nominal tire width inward from the ground edge in the tire width direction is set to point P B , the position 10% of the nominal tire width inward from the ground edge in the tire width direction is set to point P C When the vehicle is mounted, the point P A , said point P B , and said point P C The radius of curvature SRin of the arc passing through these three points is the point P A , said point P B , and said point P C The radius of curvature SRout of the arc passing through these three points satisfies the relationship 1.1≦SRout / SRin≦2.0, and a rim separation point P1 is the point where the outer surface of the bead portion separates from the rim flange in a rim-mounted state; a tire maximum protrusion point P2 is the point where the sidewall portion protrudes furthest outward in the tire width direction at the tire's widest position; and a rearward facing angle θin on the vehicle's inner side and a rearward facing angle θout on the vehicle's outer side satisfy 1.05≦θin / θout≦1.

3.

2. 2. The pneumatic tire according to claim 1, wherein the radius of curvature SRin on the vehicle inner side is 30 mm to 200 mm.

3. 3. The pneumatic tire according to claim 1, wherein the rearward facing angle θin on the vehicle inner side is 65° to 90°.

4. 3. The pneumatic tire according to claim 1, wherein the radius of curvature SRin and the rearward facing angle θin satisfy the relationship 0.4≦SRin / θin≦1.2 on the inner side of the vehicle.

5. 3. The pneumatic tire according to claim 1, wherein the radius of curvature SRin and the rearward facing angle θin on the vehicle inner side and the radius of curvature SRout and the rearward facing angle θout on the vehicle outer side satisfy the relationship 0.3≦(SRout / θout) / (SRin / θin)≦2.

3.

6. 3. The pneumatic tire according to claim 1, wherein the tire cross section height is 150 mm or less.

7. 3. The pneumatic tire according to claim 1, wherein in the tread portion, a groove area ratio Gin in a vehicle inner region that is on the vehicle inner side of the tire equator and a groove area ratio Gout in a vehicle outer region that is on the vehicle outer side of the tire equator satisfy the relationship Gin > Gout.

8. 3. The pneumatic tire according to claim 1, wherein the cover cord constituting the belt cover layer is a hybrid cord made of nylon fiber and aramid fiber.

9. 3. The pneumatic tire according to claim 1, wherein the carcass cords constituting the carcass layer are rayon fiber cords.

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