Pneumatic tire

Abstract

To provide a pneumatic tire capable of easily achieving both of excellent drainage performance, excellent fuel consumption characteristics and excellent quietness.SOLUTION: A profile P constituting an outer edge in a cross section including a center in a width direction and a radial direction in a tire in a normal state where air to be normal internal pressure is filled inside and a normal rim is attached includes a plurality of different arcs 31, 32, and 33. An angle θ formed by a tangent C at an outer end 33a in the width direction of an outer arc 33 located on the outermost side in the width direction among the plurality of arcs 31, 32, and 33 and the widthwise direction is 40° or more and 47° or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires.

Background Art

[0002] It is known that increasing the groove volume improves drainage performance. For example, Patent Document 1 discloses that the area ratio of the grooves is preferably 10% or more and 30% or less, and that a tread pattern with an area ratio of 10% or more is disclosed to have excellent drainage performance. Further, from the viewpoint of drainage performance, it is disclosed that the area ratio is preferably 13% or more, and particularly preferably 15% or more.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Increasing the groove volume improves drainage performance. However, increasing the groove volume increases air resistance, resulting in increased fuel consumption and vehicle exterior noise. Therefore, an object of the present disclosure is to provide a pneumatic tire that can easily achieve both good drainage performance and good fuel consumption characteristics and good quietness, which are in a trade-off relationship with each other.

Means for Solving the Problems

[0005] To solve the above problems, a pneumatic tire according to the present disclosure has a profile that constitutes an outer edge in a cross section including the center in the width direction and the radial direction in a tire in a normal state in which air at a normal internal pressure is filled therein and a normal rim is attached, and includes a plurality of different arcs. An angle (shoulder angle) formed by a tangent line at the outer end in the width direction of the outermost arc in the width direction among the plurality of arcs and the width direction is 40° or more and 47° or less.

[0006] In addition, in this specification, the width direction is the width direction of the pneumatic tire, the radial direction is the radial direction of the pneumatic tire, and the circumferential direction is the circumferential direction of the pneumatic tire. Further, the tangent line may be defined as the line at the limit of the line including the moving point that has been moved on the profile so as to approach the outer end from the center side in the width direction and the outer end.

[0007] According to the present disclosure, since the angle formed by the tangent line at the outer end in the width direction of the outer arc and the width direction is 47° or less, which is smaller than the general angle, the shoulder can be rounded and the air resistance can be reduced. Therefore, even if a groove structure with excellent drainage performance is adopted, it is easy to achieve fuel consumption reduction and quietness improvement, and it is easy to achieve both good drainage performance and good fuel consumption characteristics and good quietness, which are in a trade-off relationship with each other. Further, since the angle formed by the tangent line at the outer end in the width direction of the outer arc and the width direction is 40° or more, the abrasion resistance is also easily made to be at a level without problems.

[0008] Further, the angle may be 40° or more and 45° or less.

[0009] According to this configuration, the shoulder can be further rounded and the air resistance can be further reduced. Therefore, it is easy to achieve further fuel consumption reduction and quietness improvement.

[0010] In the normal state, the contact width in the width direction may be 100% or more and 105% or less of the length in the width direction of the outer belt located most on the outer side in the radial direction.

[0011] According to this configuration, the contact width in the width direction is 105% or less of the length in the width direction of the outer belt located most on the outer side in the radial direction, and is smaller than the general length. Therefore, it is easy to achieve noise reduction, mass reduction, and rolling resistance reduction. Further, the contact width in the width direction is 100% or more of the length in the width direction of the outer belt located most on the outer side in the radial direction. Therefore, the abrasion resistance is also easily made to be at a level without problems.

[0012] Further, the value obtained by dividing the shoulder contact length in the footprint, which is the contact shape when the tire is filled with air at the normal internal pressure, a normal rim is attached to the tire, and a normal load is applied, by the center contact length may be 0.8 or more and 0.9 or less.

[0013] According to this configuration, since the value obtained by dividing the shoulder contact length in the footprint by the center contact length is 0.9 or less, which is smaller than a general value, the tire can be rounded, air resistance can be reduced, and it is easy to achieve fuel consumption reduction and quietness improvement. Further, since the value obtained by dividing the shoulder contact length in the footprint by the center contact length is 0.8 or more, the wear resistance is also likely to be at a level without problems.

[0014] Further, in the cross section, a straight line may be connected to the outer end.

[0015] According to this configuration, when wear progresses, the grounding width is less likely to decrease, and the wear resistance is likely to be good.

[0016] Further, the profile has a first portion with a first radius of curvature on the outer side in the width direction from the center in the width direction, a second portion with a second radius of curvature that is connected to the outer end in the width direction of the first portion and is smaller than the first radius of curvature, and a third portion with a third radius of curvature that is connected to the outer end in the width direction of the second portion and is smaller than the second radius of curvature, and the value obtained by dividing the third radius of curvature by the second radius of curvature may be 0.5 or more and 0.9 or less.

[0017] According to this configuration, since the value obtained by dividing the third radius of curvature by the second radius of curvature is 0.9 or less, the shoulder can be further rounded, so that the air resistance can be further reduced, and it is easy to achieve further fuel consumption reduction and quietness improvement. Further, since the value obtained by dividing the third radius of curvature by the second radius of curvature is 0.5 or more, the wear resistance is also likely to be at a level without problems.

[0018] Further, in the normal state, when the distance in the width direction between the outer end in the width direction of the outer belt and the tire equatorial plane is defined as a first distance, and the distance in the width direction between the outer end in the width direction of the main groove located most outward in the width direction and the tire equatorial plane is defined as a second distance, the value obtained by dividing the second distance by the first distance may be 0.5 or more and 0.8 or less.

[0019] According to this configuration, since the value obtained by dividing the second distance by the first distance is 0.5 or more and 0.8 or less, it is easy to realize good drainage performance.

Advantages of the Invention

[0020] According to the pneumatic tire according to the present disclosure, it is easy to achieve both good drainage performance, good fuel consumption characteristics, and good quietness.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In the following, when a plurality of embodiments, modification examples, etc. are included, it is assumed from the beginning that new embodiments can be constructed by appropriately combining their characteristic parts. Further, the plurality of drawings include schematic views, and the dimensional ratios such as the vertical, horizontal, and height of each member between different drawings do not necessarily match.

[0023] In the following description, the width direction is the width direction of the pneumatic tire 1, the radial direction is the radial direction of the pneumatic tire 1, and the circumferential direction is the circumferential direction of the pneumatic tire 1. Also, in the present disclosure, a state where the tire is mounted on a standard rim, the internal pressure of the tire is adjusted to the standard internal pressure, and no load is applied to this tire is defined as the standard state. In the present disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are those measured in the standard state.

[0024] The standard internal pressure means the internal pressure defined in the standard to which the tire conforms. For example, the "maximum air pressure" in the JATMA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and "INFLATION PRESSURE" in the ETRTO standard are the standard internal pressures.

[0025] The standard rim means the rim defined in the standard to which the tire conforms. For example, the "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are the standard rims.

[0026] Also, in the present disclosure, the standard load means the load defined in the standard to which the tire conforms. For example, the "maximum load capacity" in the JATMA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and "LOAD CAPACITY" in the ETRTO standard are the standard loads. For the standard rim and the like, the same definition as that described in Japanese Patent Application Laid-Open No. 2020-131965 may be used.

[0027] Among the components described below, components not described in the independent claims indicating the highest-level concept are arbitrary components and not essential components. Further, the present disclosure is not limited to the following embodiments and their modifications, and various improvements and changes can be made within the matters described in the claims of the present application and their equivalent scope.

[0028] FIG. 1 is a 1 / 4 cross-sectional view including the width direction (axial direction) and the radial direction in a pneumatic tire 1 according to an embodiment of the present disclosure, and is a cross-sectional view on one side in the width direction and one side in the radial direction. As shown in FIG. 1, the pneumatic tire (hereinafter simply referred to as the tire) 1 includes a tread 10, a pair of shoulders 11, a pair of sidewalls 12, and a pair of beads 13.

[0029] The tread 10 is disposed at the center in the width direction and includes a tread surface 10a that contacts the road surface. The tread 10 includes, for example, a central portion in the width direction of a tread rubber 36 made of crosslinked rubber or the like. One or more grooves 24 are provided on the outer peripheral surface of the tread 10. The one or more grooves 24 serve to drain rainwater that has entered between the road surface and the tire 1 and to secure the tread area between the road surface and the tire 1. The one or more grooves 24 include one central main groove 24a located at the center in the width direction and extending over the entire circumference in the circumferential direction, and two outer main grooves 24b located on the outermost side in the width direction and extending over the entire circumference in the circumferential direction.

[0030] The shoulders 11, the sidewalls 12, and the beads 13 are portions that form the side surface of the tire 1 and are provided on both sides in the width direction of the tire 1. The shoulders 11, the sidewalls 12, and the beads 13 extend radially inward from both ends in the width direction of the tread 10. The ground contact end E of the tire 1 may be defined as the boundary position between the tread 10 and the shoulder 11.

[0031] The tread surface 10a is a portion that contacts the road surface in a state where a normal rim is attached to the tire filled with air at a normal internal pressure and a normal load is applied. Further, the ground contact end E is both ends in the width direction of the portion that contacts the road surface when the tire 1 is mounted on a normal rim, the internal pressure is adjusted to the normal internal pressure, and the normal load is applied.

[0032] The shoulder 11 includes the outer end 36a in the width direction of the tread rubber 36. The shoulder 11 is the shoulder part of the tire 1, which protrudes outward in the width direction from both ends in the width direction of the tread 10 and extends radially inward. The shoulder 11 is a part that curves from the grounding end E to the radially outer end of the sidewall 12 in the tire radial direction. The shoulder 11 is provided annularly along the circumferential direction, similar to the tread 10.

[0033] The sidewall 12 is a rubber layer between the shoulder 11 and the bead 13, and is the part with the largest bending in the tire 1. The sidewall 12 extends radially inward from the shoulder 11 and is provided annularly along the circumferential direction. The sidewall 12 includes the part that protrudes most outward in the width direction of the tire 1 and is gently curved so as to be convex outward.

[0034] The sidewall 12 protects the carcass 15 and plays a role in preventing its elongation. The sidewall 12 includes the outer part in the width direction of the sidewall rubber 21 arranged on the radially outer side of the carcass 15. The sidewall rubber 21 is the part that bends most when the tire 1 acts as a cushion, and is usually composed of a flexible rubber with fatigue resistance. The radially outer end 21a of the sidewall rubber 21 is included in the shoulder 11. The tire 1 may have an annular rib on the side, and in that case, the annular rib may be defined as the boundary between the shoulder and the sidewall.

[0035] The bead 13 extends radially inward from the sidewall 12 and is formed annularly along the circumferential direction. The bead 13 is the part fixed to the rim of the wheel and constitutes the inner peripheral part of the tire 1. The bead 13 is gently curved so as to be convex inward and is located more radially inward than the sidewall 12.

[0036] The bead 13 is surrounded by the rim strip rubber 19 with the carcass 15 interposed therebetween. The rim strip rubber 19 is disposed on the inner side in the tire radial direction of the tire 1 in such a manner that it wraps around from the inner side in the width direction of the bead 13 through the inner end in the tire radial direction to the outer side in the width direction. The rim strip rubber 19 contacts the inner surface of the rim on which the tire 1 is mounted. On the outer surface on the outer side in the width direction of the rim strip rubber 19, a rim line along the tire circumferential direction is provided.

[0037] The bead 13 includes a bead core 26 and a bead filler 27. The bead core 26 and the bead filler 27 are provided on both sides in the width direction. The bead core 26 is a ring-shaped member in which bundled steel wires are coated with rubber. The bead core 26 is a member that serves to fix the air-filled tire 1 to the rim.

[0038] The bead filler 27 is disposed radially outside the bead core 26. The bead filler 27 has a tapered shape in which the thickness decreases as it extends from the inner side in the tire radial direction to the outer side in the tire radial direction. The bead filler 27 is provided to increase the rigidity of the peripheral portion of the bead 13 and ensure high maneuverability and stability. The bead filler 27 is composed of, for example, rubber having a higher hardness than the surrounding rubber members.

[0039] The tire 1 includes a carcass 15, a belt 16, a belt reinforcing member 17, and an inner liner 18. The carcass 15 is a cord layer coated with rubber. The carcass 15 includes a carcass ply and forms a tire skeleton that withstands loads, impacts, air pressure, etc. The carcass 15 has a radial structure in which carcass cords extending in a direction orthogonal to the circumferential direction are arranged. The rubber layer that covers and protects the carcass 15 is generally composed of a plurality of rubber materials such as tread rubber 36 and sidewall rubber 21.

[0040] The carcass ply constituting the carcass 15 is spanned from the inner side in the width direction to the bead core 26 and folded back toward the sidewall 12 so as to wrap the bead core 26 and the bead filler 27. In the example shown in FIG. 1, the ply end 15E, which is the end of the carcass ply, is located on the sidewall 12. When the carcass 15 includes two carcass plies, generally, the ply end of the other carcass ply is located on the bead 13.

[0041] The belt 16 is disposed between the tread 10 and the carcass 15. The belt 16 is installed over the entire area where the tread 10 radially overlaps in the width direction and a partial area of the shoulder 11. The belt 16 is a circumferentially tensioned reinforcing belt that tightly clamps the carcass 15 to increase the rigidity of the tread 10. The belt 16 is composed of, for example, a steel belt including steel cords and has a two-layer structure, and includes two steel belts 16a, 16b. The steel belt 16b constitutes the outer belt located most radially outside among all the belts 16a, 16b. The number of laminated belts is not limited to two, and instead of the steel belt, a belt including a tire cord using aramid fibers or the like may be used. Or, the belt may be composed of only one layer. By providing the belt 16, the rigidity of the tire 1 can be ensured and the grounding state between the tread 10 and the road surface can be improved.

[0042] The belt reinforcement 17 is disposed between the belt 16 and the tread 10. The belt reinforcement 17 has, for example, a two-layer structure and includes two cap plies 17a, 17b. The cap plies 17a, 17b are composed of, for example, an insulating organic fiber layer such as polyamide fiber and are covered with topping rubber. The belt reinforcement 17 is installed for purposes such as improving durability and reducing road noise during driving.

[0043] The number of laminated cap plies is not limited to two. The belt reinforcing member 17 is disposed over the entire area of the tread 10 in the radial direction and a partial area of the shoulder 11 in the width direction. The outer end 22 of the belt reinforcing member 17 in the width direction extends outward in the width direction from the belt 16. The center portions in the width direction of the belt 16 and the belt reinforcing member 17 are included in the tread 10, and the outer end portions in the width direction of the belt 16 and the belt reinforcing member 17 are included in the shoulder 11.

[0044] The inner liner 18 is a rubber layer for holding air pressure and is attached to the inner surface of the carcass 15 between a pair of beads 13 on both sides in the width direction. The inner liner 18 is made of, for example, air permeation resistant rubber to prevent air in the tire inner cavity from leaking to the outside. In the present embodiment, the inner liner 18 has a two-layer structure in which a first inner liner 18a and a second inner liner 18b are overlapped, and the first inner liner 18a is disposed on the tire inner cavity side of the second inner liner 18b. The inner liner 18 may be composed of a single layer.

[0045] FIG. 2 is a view showing a profile P which is the outer edge of the tire in a normal state in a cross section including the center in the width direction and the radial direction. As shown in FIG. 2, the profile P in the cross section includes a plurality of arcs 31, 32, 33, and in the present embodiment, includes three first to third arcs 31, 32, 33. The first arc 31 constitutes a first portion, the second arc 32 constitutes a second portion, and the third arc 33 constitutes a third portion. Further, the third arc 33 constitutes the outermost arc in the width direction among the plurality of arcs 31, 32, 33.

[0046] The shoulder angle θ, which is the angle formed by the tangent line C at the outer end 33a in the width direction of the third arc 33 and the width direction, is 40° or more and 47° or less. The shoulder angle θ is preferably 40° or more and 45° or less. Further, in the above cross-section, it is preferable that a straight line S is connected to the outer end 33a. Furthermore, the ground contact width in the width direction (the width direction distance between the ground contact ends E) L1 is preferably 100% or more and 105% or less of the width direction length L2 of the steel belt 16b constituting the outer belt.

[0047] In the present embodiment, the profile P has a first arc 31 with a first radius of curvature on the outer side in the width direction from the center in the width direction, a second arc 32 with a second radius of curvature that is connected to the outer end in the width direction of the first arc 31 and is smaller than the first radius of curvature, and a third arc 33 with a third radius of curvature that is connected to the outer end in the width direction of the second arc 32 and is smaller than the second radius of curvature. In this case, the value obtained by dividing the third radius of curvature by the second radius of curvature is preferably 0.5 or more and 0.95 or less.

[0048] Also, when the width direction distance between the outer end in the width direction of the steel belt 16b and the tire equatorial plane and CL is defined as the first distance L3 (= L1 / 2), and the width direction distance between the outer end in the width direction of the outermost main groove 24b and the tire equatorial plane CL is defined as the second distance L4, the value obtained by dividing the second distance L4 by the first distance L3 is preferably 0.5 or more and 0.8 or less.

[0049] FIG. 3 is a plan view showing a footprint F which is a ground contact shape in a state where a normal rim is attached to the tire 1 of the present embodiment filled with air at normal internal pressure and a normal load is applied. In the footprint F, when the length in the orthogonal direction passing through the center of the line segment 50 connecting the two ground contact ends E and orthogonal to the line segment 50 is defined as the center ground contact length CH, and the length in the orthogonal direction at a position where the line segment 50 is moved 10 mm from the ground contact end E toward the center in the width direction is defined as the shoulder ground contact length SH, the value of SH / CH, which is the value obtained by dividing the shoulder ground contact length SH by the center ground contact length CH, is preferably 0.8 or more and 0.9 or less. Next, the specific basis for the preferable ranges of the above various parameters will be described.

[0050] <Tires of the current product and tires of Study Items 1-5> The inventor of the present invention experimentally evaluated the drainage performance, exterior noise, and wear resistance of the tires of the current product and the tires of Study Items 1-5 in which the shoulder angle θ, SH / CH, and contact width were changed with respect to the tires of the current product. The shoulder angle θ, SH / CH, and contact width of the tires of the current product and Study Items 1-5 are shown in Table 1 below. In Table 1, the contact width is described as the increase or decrease length (mm) from the contact width of the tire of the current product.

[0051] (Evaluation method for drainage performance) With the front and rear wheels mounted on the vehicle, each tire was rotated on a wet road surface with a water depth of 8 mm, and the speed at which the hydroplaning phenomenon occurred was measured. The drainage performance evaluation test was conducted under the conditions that the air pressure of the front and rear wheels was 240 kPa, the load acting on the front wheel was 690 kg, and the load acting on the rear wheel was 470 kgf. The drainage performance was evaluated as a relative value with the drainage performance of the tire of the current product set to 100.

[0052] Regarding the drainage performance of the tire, if the drainage performance is poor, the removal of water from within the contact surface with the road surface during driving will not be in time, and the remaining water will form a water film between the road surface and the tread surface, resulting in a loss of ground contact with the road surface and causing the hydroplaning phenomenon. Therefore, the speed at which the hydroplaning phenomenon occurs was measured as an index of drainage performance, and it was evaluated that the slower the speed, the easier the hydroplaning phenomenon occurs, that is, the lower the drainage performance. The drainage performance of each tire is shown in Table 1.

[0053] (Evaluation method for exterior noise) The exterior noise was measured with a noise meter attached to the outer surface of the vehicle body for the noise level radiated from the tires during the coasting running of the vehicle. The engine was turned off, the vehicle speed was set at 50 km / h, the air pressures of the front and rear wheels were set at 240 kPa, the load acting on the front wheels was 655 kgf, and the load acting on the rear wheels was 440 kgf. The exterior noise was measured under these conditions. By conducting the test with the engine turned off, the noise from the engine is not measured, and the exterior noise can be evaluated with high precision. The exterior noise was evaluated as the increase or decrease value with respect to the exterior noise of the tires of the current product. The exterior noise of each tire is shown in Table 1.

[0054] (Evaluation method of wear resistance) With the front and rear wheels mounted on the vehicle, the wear resistance was simulated and evaluated by a method of obtaining the running distance Dmm until the tread contact surface wears by 1 mm in thickness from the following formula (1). The wear resistance was evaluated such that the larger the Dmm, the better. The simulation evaluation of the wear resistance evaluation was conducted under the conditions that the air pressures of the front and rear wheels were 240 kPa, the load acting on the front wheels was 690 kg, and the load acting on the rear wheels was 470 kgf. The wear resistance was evaluated as a relative value when the wear resistance of the tires of the current product was set to 100. In formula (1), D is the running distance, and Ceave is the average wear amount of the main groove. The wear resistance of each tire is shown in Table 1. Dmm = D / Ceave ···(1)

[0055] (Air resistance evaluation) The contact width in the tires of the current product was 110% of the width direction length of the outer belt. Without changing the width direction length of the outer belt 16b, a tire was manufactured with the contact width L1 being 105% of the width direction length of the outer belt 16b. For each of the current tires and the manufactured tires, the contact drag, which is a measure of the air resistance, was measured. As a result, while the contact drag of the tires of the current product was 0.494, the contact drag of the manufactured tires was 0.438, which was significantly smaller than the contact drag of the tires of the current product. Furthermore, as the contact width L1 was made smaller than 105% of the width direction length of the outer belt 16b, the contact drag became smaller.

[0056] Therefore, it was confirmed that when the grounding width L1 is made smaller than 105% of the widthwise length of the outer belt 16b, the air resistance can be significantly reduced compared to the current tire. Thus, when the grounding width L1 in the width direction is 105% or less of the widthwise length of the outer belt 16b located at the outermost in the radial direction, it is easy to achieve noise reduction. Furthermore, when the grounding width L1 is made smaller than 105% of the widthwise length of the outer belt 16b, it becomes easier to achieve mass reduction and rolling resistance reduction. However, when the grounding width L1 is made less than 100% of the widthwise length of the outer belt 16b, the abrasion resistance becomes 90% or less of the current abrasion resistance, and it was also confirmed that it is difficult to make the abrasion resistance at a level without problems.

[0057]

Table 1

[0058] For the study product 5 with a shoulder angle θ of 37°, it was confirmed that the abrasion resistance becomes 90% or less of the current abrasion resistance, and it is difficult to make the abrasion resistance at a level without problems. On the other hand, for the study products 1 - 4 with a shoulder angle θ of 40° or more and 47° or less, it was confirmed that the drainage performance and quietness are improved in comparison with the current product, and moreover, the abrasion resistance can also be made greater than 90% of the current product, and it was confirmed that it reaches a level without problems as a product. Furthermore, for the study products 1 - 4 with a shoulder angle θ of 42° or more and 47° or less, it was confirmed that not only the drainage performance and quietness are improved, but also the abrasion resistance can be made 94% or more of the current product and can be made good.

[0059] Also, as described in the air resistance evaluation section, when the ground contact width L1 is set to be 100% or more and 105% or less of the width direction length of the outer belt 16b, compared with the existing product, the air resistance can be greatly reduced, making it easier to achieve noise reduction, mass reduction, and rolling resistance reduction. Not only can it achieve excellent fuel efficiency and quietness, but it is also easy to ensure a wear resistance level without problems.

[0060] Therefore, as in the pneumatic tire 1 of the present disclosure, at the outer end 33a in the width direction of the third arc (outer arc) 33 included in the profile that constitutes the outer edge in the cross section including the center in the width direction and the radial direction in the tire in the normal state, if the shoulder angle θ formed by the tangent line C and the width direction is 47° or less, as is clear from the comparison between the profile K of the existing one tire shown by the dotted line in FIG. 2 and the profile P of the tire of one embodiment of the present disclosure, the shoulder 11 can be rounded, and it has been confirmed that the air resistance can be reduced. Therefore, even if a groove structure with excellent drainage performance is adopted, it is easy to achieve fuel consumption reduction and quietness improvement, and it is easy to achieve both good drainage performance and good fuel consumption characteristics and good quietness, which are in a trade-off relationship with each other. Further, since the angle formed by the tangent line C and the width direction at the outer end 33a in the width direction of the outer arc 33 is 40° or more, it is easy to ensure a wear resistance level without problems.

[0061] Also, when the shoulder angle θ is set to be 40° or more and 45° or less, the shoulder 11 can be further rounded, and the air resistance can be further reduced. Therefore, it is easy to achieve further fuel consumption reduction and quietness improvement.

[0062] Also, when the ground contact width L1 in the width direction is set to be 105% or less of the width direction length of the outer belt 16b located most radially outward, making it smaller than the general length, it is easy to achieve noise reduction, mass reduction, and rolling resistance reduction. Also, when the ground contact width in the width direction is 100% or more of the width direction length of the outer belt located most radially outward, it is easy to ensure a wear resistance level without problems.

[0063] Also, as shown in Table 1, when the value SH / CH obtained by dividing the shoulder ground contact length SH in the footprint F by the center ground contact length CH is 0.95 or less, which is smaller than the general value, the tire can be rounded, air resistance can be reduced, and it is easy to achieve fuel consumption reduction and quietness improvement. Further, when SH / CH is 0.8 or more, the wear resistance is also likely to be at a level without problems.

[0064] (Basis for specifying the preferred range of other parameters) The inventor of the present invention further performed simulations to specify the preferred ranges of other parameters. And it was confirmed that when the value obtained by dividing the above-mentioned third radius of curvature by the second radius of curvature is 0.9 or less, the shoulder 11 can be effectively rounded, air resistance can be further reduced, and it is easy to achieve further fuel consumption reduction and quietness improvement. Also, it was confirmed that when the value obtained by dividing the third radius of curvature by the second radius of curvature is 0.5 or more, the wear resistance is also likely to be at a level without problems. Further, it was confirmed that when the value obtained by dividing the above-mentioned second distance L4 by the first distance L3 is 0.5 or more and 0.8 or less, it is easy to achieve good drainage performance. Also, in a cross section including the center in the width direction and the radial direction, when a straight line S is connected to the outer end 33a in the width direction of the outer arc 33, the ground contact width is less likely to decrease when wear progresses, and the wear resistance is likely to be good.

Description of reference numerals

[0065] 1 Tubeless tire, 10 Tread, 10a Tread surface, 11 Shoulder, 12 Sidewall, 13 Bead, 15 Carcass, 15E Ply end, 16 Belt, 16b Outer belt, 17 Belt reinforcement, 17a Cap ply, 18 Inner liner, 18a First inner liner, 18b Second inner liner, 19 Rim strip rubber, 21 Sidewall rubber, 21a Radially outer end of the sidewall rubber, 22 Widthwise outer end of the belt reinforcement, 24 Groove, 24a Central main groove, 24b Outer main groove, 26 Bead core, 27 Bead filler, 31 First arc, 32 Second arc, 33 Third arc (outer arc), 33a Outer end of the outer arc, 36 Tread rubber, 36a Widthwise outer end of the tread rubber, 50 Line segment, C Tangent line, CH Center contact length, CL Tire equatorial plane, E Contact end, F Footprint, K Profile of the current single tire, L1 Contact width, L2 Widthwise length of the outer belt, L3 First distance, L4 Second distance, P Profile of the tire of the present embodiment, S Straight line, SH Shoulder contact length, θ Shoulder angle.

Claims

1. In a tire in a normal state filled with air at normal internal pressure and having a normal rim attached thereto, the profile forming the outer edge in a cross-section including the center in the width direction and the radial direction includes a plurality of different arcs, and the angle formed between the tangent at the outer end in the width direction of the outermost arc in the width direction among the plurality of arcs and the width direction is 40° or more and 47° or less. A pneumatic tire.

2. The pneumatic tire according to claim 1, wherein the angle is 40° or more and 45° or less.

3. The pneumatic tire according to claim 1, wherein in the normal state, the ground contact width in the width direction is 100% or more and 105% or less of the length in the width direction of the outermost belt located most on the outer side in the radial direction.

4. The pneumatic tire according to claim 1, wherein the value obtained by dividing the shoulder ground contact length by the center ground contact length in the footprint, which is the ground contact shape in a state where air at normal internal pressure is filled inside the tire, a normal rim is attached to the tire, and a normal load is applied, is 0.80 or more and 0.95 or less.

5. The pneumatic tire according to claim 1, wherein in the cross-section, a straight line is connected to the outer end.

6. The profile has a first portion with a first radius of curvature on the outer side in the width direction than the center in the width direction, a second portion with a second radius of curvature that is connected to the outer end in the width direction of the first portion and is smaller than the first radius of curvature, and a third portion with a third radius of curvature that is connected to the outer end in the width direction of the second portion and is smaller than the second radius of curvature, and the value obtained by dividing the third radius of curvature by the second radius of curvature is 0.5 or more and 0.9 or less. The pneumatic tire according to claim 1.

7. In the normal state, when the distance in the width direction between the outer end in the width direction of the outer belt and the tire equatorial plane is defined as a first distance, and the distance in the width direction between the outer end in the width direction of the main groove located most on the outer side in the width direction and the tire equatorial plane is defined as a second distance, the value obtained by dividing the second distance by the first distance is 0.5 or more and 0.8 or less. The pneumatic tire according to claim 3.

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