Run-flat tire

Abstract

To provide a run-flat tire that can make both reduction of rolling resistance due to weight reduction caused by volume reduction of a side reinforcement rubber layer and a run-flat function compatible.SOLUTION: The run-flat tire comprises: a pair of beads 10; a pair of side walls 20 extending from the pair of beads 10 respectively to outside in a tire radial direction; a tread 30 arranged between the pair of side walls 20; a carcass ply 40 hung across the pair of beads 10; and a reinforcement rubber layer 60 arranged at an inner cavity side of the tire of the carcass ply 40, in the side wall 20. A bent part 25 swelling out to outside in a tire width direction is formed in a region corresponding to 40% or more and 60% or less from the inside in the tire radial direction of a cross section height H of the tire in the side wall 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a run-flat tire.

Background Art

[0002] Conventionally, a side-reinforced type of run-flat tire in which a reinforcing rubber layer is disposed on the sidewall has been known. When the internal pressure of such a run-flat tire decreases, the reinforcing rubber layer suppresses the tire from being completely flattened, enabling run-flat driving for a certain distance (driving with the internal pressure of the tire decreased). For example, Patent Document 1 discloses a run-flat tire in which a side reinforcing layer corresponding to the above-described reinforcing rubber layer is disposed on the sidewall so as to extend from the tread to the bead, and side rubber is disposed outside the side reinforcing layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The reinforcing rubber layer that reinforces the side of the tire enables run-flat driving, but may increase the weight of the tire and cause an increase in rolling resistance. Therefore, there is a demand for a reinforcing structure that reduces the volume of the rubber for side reinforcement to achieve weight reduction while ensuring the run-flat function.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a run-flat tire in which both a reduction in rolling resistance due to weight reduction accompanying a reduction in the volume of the side reinforcing rubber layer and the run-flat function are achieved.

Means for Solving the Problems

[0006] The run-flat tire of the present invention includes a pair of beads, a pair of sidewalls extending radially outward in the tire diameter direction from each of the pair of beads, a tread disposed between the pair of sidewalls, a carcass ply spanned between the pair of beads, and in the sidewall, a reinforcing rubber layer disposed on the tire inner cavity side of the carcass ply, and has a bent portion bulging outward in the tire width direction in a region of more than 40% and within 60% from the inner side in the tire diameter direction of the tire cross-sectional height in the sidewall.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a run-flat tire in which both reduction of rolling resistance due to weight reduction accompanying reduction of the volume of the side reinforcing rubber layer and the run-flat function are achieved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a half cross section in the tire width direction of the tire 1 according to the present embodiment. FIG. 2 is an enlarged view of a part of FIG. 1. In FIG. 2, the hatching indicating the cross section is omitted. The tire 1 is a run-flat tire that can travel a certain distance even when the internal pressure has dropped to about atmospheric pressure.

[0010] Since the basic structure of the tire 1 is symmetric in the cross-section in the tire width direction, in FIG. 1, a cross-sectional view of the right half is shown. In FIG. 1, reference sign S1 is the tire equatorial plane. The tire equatorial plane S1 is a plane orthogonal to the tire rotation axis (tire meridian) and is located at the center in the tire width direction. Also, in FIG. 1, reference sign H indicates the tire cross-sectional height. The tire cross-sectional height H refers to the radial length between the inner end and the outer end in the tire radial direction.

[0011] Note that the cross-sectional view in FIG. 1 is a cross-sectional view in the tire width direction (tire meridian cross-sectional view) of the tire in the unloaded state where the tire is mounted on a specified rim and filled with a specified internal pressure. The specified rim refers to the standard rim defined by JATMA corresponding to the tire size. Also, the specified internal pressure is, for example, 180 kPa when the tire is for a passenger car. All of the configurations of the tire 1 including the numerical values described below refer to the configurations in the unloaded state filled with the specified internal pressure as described above.

[0012] Here, the tire width direction is a direction parallel to the tire rotation axis and is the left-right direction of the paper surface in the cross-sectional view of FIG. 1. In FIG. 1, it is illustrated as the tire width direction X. And the inner side in the tire width direction is the direction approaching the tire equatorial plane S1, which is the left side of the paper surface in FIG. 1. The outer side in the tire width direction is the direction away from the tire equatorial plane S1, which is the right side of the paper surface in FIG. 1. Also, the tire radial direction is a direction perpendicular to the tire rotation axis and is the up-down direction of the paper surface in FIG. 1. In FIG. 1, it is illustrated as the tire radial direction Y. And the outer side in the tire radial direction is the direction away from the tire rotation axis, which is the upper side of the paper surface in FIG. 1. The inner side in the tire radial direction is the direction approaching the tire rotation axis, which is the lower side of the paper surface in FIG. 1. The same applies to FIG. 2.

[0013] Note that "0 to 20%" shown in Fig. 2 indicates a region from 0% to 20% inclusive from the inner side in the tire radial direction of the tire cross-sectional height H, "20 to 40%" indicates a region from more than 20% to 40% inclusive from the inner side in the tire radial direction of the tire cross-sectional height H, "40 to 60%" indicates a region from more than 40% to 60% inclusive from the inner side in the tire radial direction of the tire cross-sectional height H, "60 to 80%" indicates a region from more than 60% to 80% inclusive from the inner side in the tire radial direction of the tire cross-sectional height H, and "80 to 100%" indicates a region from more than 80% to 100% inclusive from the inner side in the tire radial direction of the tire cross-sectional height H.

[0014] Tire 1 is, for example, a run-flat tire for a passenger car. As shown in Fig. 1, tire 1 includes a pair of beads 10 provided on both sides in the tire width direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a carcass ply 40 disposed between the pair of beads 10, and an inner liner 50 disposed on the inner cavity side of the carcass ply 40.

[0015] Bead 10 has a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a chafer 13, and a rim protector 15.

[0016] Bead core 11 is an annular member formed by winding a plurality of times a metal bead wire coated with rubber, and is a member that serves to fix the air-filled tire 1 to the rim. Bead filler 12 is a rubber member having a tapered shape as it extends radially outward. Bead filler 12 is a member provided to increase the rigidity of the peripheral portion of bead 10 and ensure high maneuverability and stability. Bead filler 12 is composed of, for example, rubber having a higher hardness than the surrounding rubber members.

[0017] Chafer 13 is provided on the inner side in the tire radial direction of the carcass ply 40 provided around the bead core 11. The rim protector 15 includes a rim strip rubber 14. The rim strip rubber 14 is disposed on the outer side in the tire width direction of the chafer 13 and the carcass ply 40. On the outer surface of the rim strip rubber 14, a top 14a is formed along the tire circumferential direction. The rim strip rubber 14 contacts the rim on which the tire 1 is mounted. The rim protector 15 is continuously annular in the tire circumferential direction. The rim protector 15 has a function of protecting the rim (not shown) from damage.

[0018] The sidewall 20 includes a sidewall rubber 21 disposed on the outer side in the tire width direction of the carcass ply 40, and a reinforcing rubber layer 60. The sidewall rubber 21 constitutes the outer wall surface of the tire 1. The sidewall rubber 21 is the portion that bends the most when the tire 1 performs a cushioning action, and usually, a flexible rubber having fatigue resistance is adopted. The sidewall rubber 21 is disposed on the outer side in the tire width direction of the reinforcing rubber layer 60.

[0019] The reinforcing rubber layer 60 is disposed in a state of being sandwiched between the carcass ply 40 and the inner liner 50. The reinforcing rubber layer 60 is a side reinforcing rubber having a substantially crescent shape in a cross-sectional view in the tire width direction (tire meridian cross-sectional view). The reinforcing rubber layer 60 is provided annularly over the entire circumference of the tire 1. The reinforcing rubber layer 60 has a function of suppressing buckling of the sidewall 20 and preventing the tire 1 from being completely flattened even when the internal pressure of the tire 1 drops to about atmospheric pressure, thereby enabling the vehicle to travel a certain distance.

[0020] The tread 30 includes an endless belt 31 and a cap ply 32 as a belt reinforcing layer, and a tread rubber 33.

[0021] The belt 31 is disposed on the outer side in the tire diameter direction of the carcass ply 40. The cap ply 32 is disposed on the outer side in the tire diameter direction of the belt 31. The belt 31 is a member that reinforces the tread 30. The belt 31 of the present embodiment has a two-layer structure including an inner belt 311 and an outer belt 312. Both the inner belt 311 and the outer belt 312 have a structure in which a plurality of cords such as steel cords are covered with rubber.

[0022] In the two-layer structure belt 31 of the present embodiment, the inner belt 311 is wider than the outer belt 312. Therefore, the outer end 31A of the belt 31 in the tire width direction is constituted by the outer end of the inner belt 311 in the tire width direction. By providing the belt 31, the rigidity of the tire 1 is ensured, and the grounding performance of the tread 30 with respect to the road surface is improved. Note that the belt 31 is not limited to a two-layer structure, and may have a single-layer or a three-layer or more structure.

[0023] The cap ply 32 is a member that reinforces the tread 30 together with the belt 31. The cap ply 32 has a structure in which a plurality of insulating organic fiber cords such as polyamide fibers are covered with rubber. In the present embodiment, the outer end 32A of the cap ply 32 in the tire width direction is disposed at substantially the same position as the outer end 31A of the belt 31 in the tire width direction. By providing the cap ply 32, it is possible to improve durability and reduce road noise during running.

[0024] Note that both ends of the cap ply 32 of the present embodiment in the tire width direction have a structure in which they are folded to the inner side of the tire cavity and overlapped twice, whereby both ends of the tread 30 in the tire width direction are more reinforced.

[0025] The tread rubber 33 is disposed outside the cap ply 32 in the tire radial direction. The tread rubber 33 is a member that constitutes the ground contact surface 331 that contacts the road surface during running. The ground contact surface 331 of the tread rubber 33 is provided with a tread pattern 34 composed of, for example, a plurality of grooves. The tread pattern 34 has a plurality of main grooves 341 arranged in the tire width direction. Each of the plurality of main grooves 341 extends along the tire circumferential direction.

[0026] The carcass ply 40 constitutes the ply that forms the framework of the tire 1. The carcass ply 40 is embedded in the tire 1 in a manner that passes between a pair of beads 10 through a pair of sidewalls 20 and a tread 30. The carcass ply 40 includes a plurality of carcass cords that form the framework of the tire 1. The plurality of carcass cords extend, for example, in the tire width direction and are arranged side by side in the tire circumferential direction. The carcass cords are composed of insulating organic fiber cords such as polyester or polyamide cords. The plurality of carcass cords are coated with rubber to form the carcass ply 40.

[0027] The carcass ply 40 has a ply main body portion 401 that extends from one bead core 11 to the other bead core 11 and extends between the tread 30 and the bead 10, a pair of bent portions 402 that are folded back by the bead core 11 from the ply main body portion 401, and a pair of folded-back portions 403 that extend radially outward of the tire from each of the bent portions 402. The ply main body portion 401, the bent portions 402, and the folded-back portions 403 are continuous.

[0028] The ply main body portion 401 is disposed inside the bead core 11 and inside the tire width direction of the bead filler 12 on the inner side in the tire radial direction. The folded-back portion 403 is disposed outside the bead core 11 and outside the tire width direction of the bead filler 12 on the inner side in the tire radial direction. In portions other than the bead core 11 and the bead filler 12, the folded-back portion 403 is overlapped with the ply main body portion 401. The bent portion 402 constitutes the innermost portion in the tire radial direction in the carcass ply 40.

[0029] Note that the carcass ply 40 of the present embodiment is constituted by a two-layer carcass ply in which a first carcass ply 410 disposed on the tire inner cavity side and a second carcass ply 420 disposed on the tire outer surface side are overlapped in the ply main body portion 401, but the carcass ply 40 may be a single layer or three or more layers.

[0030] In addition, in the present embodiment, in the folded-back portion 403 of the carcass ply 40, the folded-back end 410A of the first carcass ply 410 disposed on the outer surface side of the tire extends to the outside in the tire radial direction from the tire maximum width position 1A, and the folded-back end 420A of the second carcass ply 420 disposed on the inner cavity side of the tire is located on the inner side in the tire radial direction from the tire maximum width position 1A.

[0031] As in the present embodiment, it is preferable that a carcass ply 40 composed of at least two or more plies is sandwiched between the bead filler 12 and the reinforcing rubber layer 60. Thereby, local deformation in the vicinity of the rim mounting portion can be more effectively suppressed, and the run-flat durability can be further improved.

[0032] The chafer 13 of the bead 10 described above is provided so as to surround the end portion on the inner side in the tire radial direction of the carcass ply 40 including the bent portion 402. Further, the rim strip rubber 14 is disposed on the outer side in the tire width direction of the chafer 13 and the folded-back portion 403 of the carcass ply 40. The end portion on the outer side in the tire radial direction of the rim strip rubber 14 is covered with the sidewall rubber 21 described above.

[0033] The inner liner 50 covers the inner surface of the tire between the pair of beads 10 and constitutes the inner wall surface of the tire 1. The inner liner 50 covers the inner surface of the ply main body portion 401 of the carcass ply 40 in the region of the tread 30, covers the inner surface of the reinforcing rubber layer 60 in a part of the region on the bead 10 side of the pair of sidewalls 20, and covers the inner surfaces of the reinforcing rubber layer 60 and the chafer 13 in the region extending from the pair of sidewalls 20 to the pair of beads 10. The inner liner 50 is made of an air permeation resistant rubber and prevents the air in the tire inner cavity from leaking to the outside.

[0034] Here, as shown in FIG. 1, on the tire outer surface side of the carcass ply 40 in the transition region between the tread 30 and the sidewall 20, the sidewall rubber 21 extends toward the tread 30, the tread rubber 33 extends toward the sidewall 20, and the tread rubber 33 covers the outer surface side of the sidewall rubber 21.

[0035] Further, on the tire outer surface side of the carcass ply 40 in the transition region between the bead 10 and the sidewall 20, the sidewall rubber 21 extends toward the bead 10, the rim strip rubber 14 extends toward the sidewall 20, and the sidewall rubber 21 covers the outer surface side of the rim strip rubber 14.

[0036] Here, as the rubber to be used for the bead filler 12 and the reinforcing rubber layer 60, a rubber having a hardness higher than at least the sidewall rubber 21 and the inner liner 50 is used. The hardness of the rubber is a value (durometer hardness) measured with a Type A durometer in an atmosphere of 23°C in accordance with JIS K6253.

[0037] For example, when the hardness of the sidewall rubber 21 is used as a reference, it is more preferable to use a rubber having a hardness of about 1.2 times or more and 2.3 times or less the hardness of the sidewall rubber 21 for the bead filler 12. Also, for the reinforcing rubber layer 60, it is more preferable to use a rubber having a hardness of about 1.1 times or more and 1.9 times or less the hardness of the sidewall rubber 21. Furthermore, for the rim strip rubber 14, it is more preferable to use a rubber having a hardness of about 1 time or more and 1.6 times or less the hardness of the sidewall rubber 21. By setting the hardness in this way, it is possible to maintain the balance between the flexibility of the tire and the rigidity near the bead 10, and to ensure run-flat durability.

[0038] In the tire 1 according to the present embodiment having the above configuration, as shown in FIG. 1, the sidewall 20 has a bent portion 25. The bent portion 25 has the tire maximum width position 1A as its apex and curves and bulges outward in the tire width direction.

[0039] As shown in FIG. 2, the bent portion 25 is provided in a region more than 40% and within 60% from the inner side in the tire radial direction of the tire cross-sectional height H in the sidewall 20. In the cross-section in the tire width direction, the curvature of the outer surface 25a of the bent portion 25 is larger than the curvature of the inner cavity surface 25b of the tire. The outer surface 25a of the bent portion 25 is composed of sidewall rubber 21, and the inner cavity surface 25b of the bent portion 25 is composed of an inner liner 50.

[0040] As shown in FIG. 1, in the tire 1 of the present embodiment, a straight portion 26 that is linear in the cross-section in the tire width direction is provided on the outer surface of the tire in the region extending from the bent portion 25 to the tread 30. The straight portion 26 is inclined so as to approach the inner cavity side of the tire as it goes toward the outer side in the tire radial direction. As shown in FIG. 1, the inclination angle θ3 of the straight portion 26 with respect to the tire radial direction is, for example, 15° or more and 40° or less. Due to this straight portion 26, a conical flat surface is formed in the region on the outer side in the tire radial direction of the tire side surface.

[0041] As shown in FIG. 1, in the cross-section in the tire width direction, it is preferable that the length L1 in the tire radial direction of the straight portion 26 is 15% or more and 35% or less of the tire cross-sectional height H.

[0042] In FIG. 2, the angle θ1 is formed by a line G1 connecting the intersection point 2A (shown at the same position as 1A in FIG. 2) of a line CL along the tire width direction passing through the tire maximum width position 1A and the tire outer surface 25a, and a position 25a1 on the tire outer surface 25a that is 10% of the tire cross-sectional height H radially outward from the tire maximum width position 1A, and a line G2 connecting the intersection point 2A of the line CL along the tire width direction passing through the tire maximum width position 1A and the tire outer surface 25a, and a position 25a2 on the tire outer surface 25a that is 10% of the tire cross-sectional height H radially inward from the tire maximum width position 1A.

[0043] In FIG. 2, the angle θ2 is formed by a line F1 connecting the intersection point 3A of a line CL along the tire width direction passing through the tire maximum width position 1A and the tire inner cavity surface 25b, and a position 25b1 on the tire inner cavity surface 25b that is 10% of the tire cross-sectional height H radially outward from the tire maximum width position 1A, and a line F2 connecting the intersection point 3A of the line CL along the tire width direction passing through the tire maximum width position 1A and the tire inner cavity surface 25b, and a position 25b2 on the tire inner cavity surface 25b that is 10% of the tire cross-sectional height H radially inward from the tire maximum width position 1A.

[0044] In the present embodiment, it is preferable that the angle θ1 is smaller than the angle θ2. In the present embodiment, on the condition that the angle θ1 is smaller than the angle θ2, it is preferable that the angle θ1 and the angle θ2 are each greater than 140° and less than 170°.

[0045] Also, W1 shown in FIG. 2 is the tire width direction distance from the inner end 10B in the tire width direction of the bead 10 to the tire maximum width position 1A of the bent portion 25. Further, W2 is the tire width direction distance from the inner end in the tire width direction of the bead 10 to the most radially outward position of the tire inner cavity surface 25b of the bent portion 25. In the present embodiment, it is preferable that the ratio of W2 to W1 is greater than 60% and less than 80%. Also, it is preferable that the ratio of W2 to the tire cross-sectional height H is greater than 15% and less than 35%, and the ratio of W1 to the tire cross-sectional height H is greater than 20% and less than 40%.

[0046] In the present embodiment, it is preferable that the thickness of the sidewall rubber 21 in the bent portion 25 is 2.5 mm or more and 4.0 mm or less. As shown in FIG. 2, the sidewall rubber 21 of the present embodiment is disposed in a region of approximately 20 to 80% of the tire section height H. And the thickness of the region of more than 40% and within 60% from the inner side in the tire radial direction of the tire section height H in the sidewall rubber 21 is equal to or less than the thickness of the region of more than 20% and within 40% from the inner side in the tire radial direction of the tire section height H, and it is preferable that the thickness is equal to or less than the thickness of the region of more than 60% and within 80% from the inner side in the tire radial direction of the tire section height H. That is, the sidewall rubber 21 is thinnest in the central region in the tire section height direction.

[0047] In the present embodiment, as shown in FIG. 1, the outer end 60A in the tire radial direction of the reinforcing rubber layer 60 is located inside the outer end 31A in the tire width direction of the belt 31. And the distance L2 from the outer end 60A in the tire radial direction of the reinforcing rubber layer 60 to the outer end 31A in the tire width direction of the belt 31 is preferably 3 mm or more and 10 mm or less. Here, the distance L2 is the shortest distance from the outer end 60A in the tire radial direction of the reinforcing rubber layer 60 to the outer end 31A in the tire width direction of the belt 31.

[0048] Also, in the present embodiment, as shown in FIG. 1, the inner end 60B in the tire radial direction of the reinforcing rubber layer 60 is located inside the outer end 12A in the tire radial direction of the bead filler 12 in the tire radial direction. And the distance L3 from the inner end 60B in the tire radial direction of the reinforcing rubber layer 60 to the outer end 12A in the tire radial direction of the bead filler 12 is 5 mm or more and 20 mm or less. Here, the distance L3 is the shortest distance from the inner end 60B in the tire radial direction of the reinforcing rubber layer 60 to the outer end 12A in the tire radial direction of the bead filler 12.

[0049] In the tire 1 of the present embodiment, during run-flat driving, a stress is applied such that the bent portion 25 bends further. However, the reinforcing rubber layer 60 disposed inside the bent portion 25 resists the stress, thereby suppressing the bending of the bent portion 25. As a result, the flattening of the tire 1 is suppressed, and run-flat driving becomes possible.

[0050] According to the tire 1 of the present embodiment, the following effects are achieved.

[0051] (1) The tire 1 according to the present embodiment includes a pair of beads 10, a pair of sidewalls 20 extending radially outward in the tire diameter direction from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a carcass ply 40 spanned between the pair of beads 10, and a reinforcing rubber layer 60 disposed on the tire inner cavity side of the carcass ply 40 in the sidewall 20. The sidewall 20 has a bent portion 25 that bulges outward in the tire width direction in a region that is more than 40% and within 60% from the inner side in the tire diameter direction of the tire cross-sectional height H.

[0052] Since the bent portion 25 bends in a narrow region at the tire cross-sectional height H that is more than 40% and within 60% from the inner side in the tire diameter direction of the tire cross-sectional height H in the sidewall 20, the degree of bending, that is, the curvature is large. As a result, the reinforcing rubber layer 60 can be focused on being disposed inside the bent portion 25, so that the volume of the reinforcing rubber layer 60 can be reduced. For example, the thickness and the tire diameter direction length of the reinforcing rubber layer 60 can be reduced. As a result, both the reduction of rolling resistance due to weight reduction and the run-flat function can be achieved. In addition, the riding comfort is improved by reducing the volume of the reinforcing rubber layer 60 having a relatively high hardness.

[0053] (2) In the tire 1 according to the present embodiment, the outer surface of the tire between the bent portion 25 and the tread 30 has a straight portion 26 that is linear in the tire width direction cross-section.

[0054] This makes it easier to form the bent portion 25 with a large curvature on the outer surface of the tire, and the function of the bent portion 25 can be effectively obtained.

[0055] (3) The tire 1 according to the present embodiment includes a form in which, in a cross section in the tire width direction, the tire radial length of the straight portion 26 is 15% or more and 35% or less of the tire cross-sectional height H.

[0056] Thereby, the straight portion 26 has an appropriate length, and the bent portion 25 can be preferably arranged in a region of the sidewall 20 that is more than 40% and within 60% from the inner side in the tire radial direction of the tire cross-sectional height H.

[0057] (4) In the tire 1 according to the present embodiment, in a cross section in the tire width direction, a line G1 connecting the intersection of the line along the tire width direction passing through the tire maximum width position and the tire outer surface and the position on the tire outer surface that is 10% of the tire cross-sectional height H radially outside from the tire maximum width position, and a line G2 connecting the intersection of the line along the tire width direction passing through the tire maximum width position and the tire outer surface and the position on the tire outer surface that is 10% of the tire cross-sectional height H radially inside from the tire maximum width position, the angle θ1 formed by the lines G1 and G2 is smaller than the angle θ2 formed by a line F1 connecting the intersection of the line along the tire width direction passing through the tire maximum width position and the tire inner cavity surface and the position on the tire inner cavity surface that is 10% of the tire cross-sectional height H radially outside from the tire maximum width position, and a line F2 connecting the intersection of the line along the tire width direction passing through the tire maximum width position and the tire inner cavity surface and the position on the tire inner cavity surface that is 10% of the tire cross-sectional height H radially inside from the tire maximum width position.

[0058] Thereby, the curvature of the bent portion 25 can be increased, and it becomes easier to preferentially arrange the reinforcing rubber layer 60 inside the bent portion 25. Therefore, the weight reduction and the reduction effect of the rolling resistance associated with the volume reduction of the reinforcing rubber layer 60 can be obtained.

[0059] (5) In the tire 1 according to the present embodiment, it is preferable that the angle θ1 and the angle θ2 are each more than 140° and less than 170°.

[0060] As a result, the curvature of the bent portion 25 can be increased, and it becomes easier to focus on arranging the reinforcing rubber layer 60 inside the bent portion 25. Therefore, it is possible to surely and significantly obtain the weight reduction and the rolling resistance reduction effect associated with the volume reduction of the reinforcing rubber layer 60.

[0061] (6) In the tire 1 according to the present embodiment, when the tire width direction distance from the inner end 10B in the tire width direction of the bead 10 to the tire maximum width position 1A of the bent portion 25 is W1, and the tire width direction distance from the inner end 10B in the tire width direction of the bead 10 to the outermost position in the tire width direction of the tire inner cavity surface 25b of the bent portion 25 is W2, a form in which the ratio of W2 to W1 is more than 60% and less than 80% is included.

[0062] As a result, the bent portion 25 can be greatly bulged outward in the tire radial direction to increase the curvature, and it becomes easier to focus on arranging the reinforcing rubber layer 60 inside the bent portion 25. Therefore, it is possible to obtain the weight reduction and the rolling resistance reduction effect associated with the volume reduction of the reinforcing rubber layer 60.

[0063] (7) In the tire 1 according to the present embodiment, when the tire width direction distance from the inner end 10B in the tire width direction of the bead 10 to the tire maximum width position 1A of the bent portion 25 is W1, and the tire width direction distance from the inner end 10B in the tire width direction of the bead 10 to the outermost position in the tire width direction of the tire inner cavity surface 25b of the bent portion 25 is W2, a form in which the ratio of W2 to the tire cross-sectional height H is more than 15% and less than 35%, and the ratio of W1 to the tire cross-sectional height H is more than 20% and less than 40% is included.

[0064] As a result, the bent portion 25 can be greatly bulged outward in the tire radial direction to increase the curvature, and it becomes easier to focus on arranging the reinforcing rubber layer 60 inside the bent portion 25. Therefore, it is possible to obtain the weight reduction and the rolling resistance reduction effect associated with the volume reduction of the reinforcing rubber layer 60.

[0065] (8) In the tire 1 according to the present embodiment, the sidewall 20 has a sidewall rubber 21 on the outer side in the tire width direction of the reinforcing rubber layer 60, and the thickness of the sidewall rubber 21 in the bent portion 25 is in the range of 2.5 mm or more and 4.0 mm or less.

[0066] As a result, the sidewall rubber 21 is made thin and lightweight, and as a result, the weight of the tire 1 can be reduced and the rolling resistance can be decreased.

[0067] (9) In the tire 1 according to the present embodiment, the thickness of the sidewall rubber 21 in the region more than 40% and within 60% from the inner side in the tire radial direction of the tire cross-sectional height H is less than or equal to the thickness in the region more than 20% and within 40% from the inner side in the tire radial direction of the tire cross-sectional height H, and is also less than or equal to the thickness in the region more than 60% and within 80% from the inner side in the tire radial direction of the tire cross-sectional height H.

[0068] As a result, the sidewall rubber 21 in the bent portion 25 is made thin and lightweight, and as a result, the weight of the tire 1 can be reduced and the rolling resistance can be decreased.

[0069] (10) In the tire 1 according to the present embodiment, the tread 30 includes a belt 31 disposed on the outer side in the tire radial direction of the carcass ply 40, and the outer end 60A in the tire radial direction of the reinforcing rubber layer 60 is located inside the outer end 31A in the tire width direction of the belt 31, and the distance from the outer end 60A in the tire radial direction of the reinforcing rubber layer 60 to the outer end 31A in the tire width direction of the belt 31 is in the range of 3 mm or more and 10 mm or less.

[0070] As a result, since the outer end in the tire radial direction of the reinforcing rubber layer 60 and the outer end in the tire width direction of the belt 31 overlap, rigidity is ensured, and it is possible to suppress stress concentration and strain generation between the two.

[0071] (11) In the tire 1 according to this embodiment, the bead 10 includes a bead core 11 and a bead filler 12 extending radially outward of the bead core 11 in the tire radial direction. The radially inner end 60B of the reinforcing rubber layer 60 is located radially inward of the radially outer end 12A of the bead filler 12 in the tire radial direction, and the distance from the radially inner end 60B of the reinforcing rubber layer 60 to the radially outer end 12A of the bead filler 12 is preferably 5 mm or more and 20 mm or less.

[0072] As a result, since the radially inner end portion of the reinforcing rubber layer 60 and the radially outer end portion of the bead filler 12 overlap, rigidity is ensured, and it is possible to suppress stress from concentrating between the two and causing distortion.

[0073] Note that the tire of the present invention can be adopted as various tires such as passenger cars, light trucks, trucks, buses, etc.

[0074] Note that the present invention is not limited to the above embodiment, and even if deformation, improvement, etc. are performed within the range that can achieve the object of the present invention, it is included in the scope of the present invention. For example, the shape and hardness of the reinforcing rubber layer 60 disposed inside the bent portion 25 are not limited as long as it can suppress the flattening of the tire 1 as much as possible against further bending of the bent portion 25 during run-flat driving.

Explanation of reference numerals

[0075] 1 Tire (run-flat tire) 1A Tire maximum width position 10 Bead 10B Radially inner end of the bead in the tire width direction 11 Bead core 12 Bead filler 12A Radially outer end of the bead filler in the tire radial direction 20 Sidewall 21 Sidewall rubber 25 Bent portion 25a Tire outer surface 25b Tire inner cavity surface 26 Straight part 30 Tread 31 Belt 31A Outer end of the belt in the tire width direction 40 Carcass ply 60 Reinforcing rubber layer 60A Outer end of the reinforcing rubber layer in the tire diameter direction 60B Inner end of the reinforcing rubber layer in the tire diameter direction H Tire cross-sectional height

Claims

1. A pair of beads, A pair of sidewalls extending radially outward in the tire diameter direction from each of the pair of beads, A tread disposed between the pair of sidewalls, A carcass ply spanned between the pair of beads, In the sidewall, a reinforcing rubber layer disposed on the tire inner cavity side of the carcass ply, The sidewall extends radially outward in the tire diameter direction from each of the pair of beads and includes a pair of sidewall rubbers constituting the outer wall surface of the sidewall, The tread includes tread rubber, The sidewall rubber has a bent portion bulging outward in the tire width direction in a region exceeding 40% and within 60% from the inner side in the tire diameter direction of the tire cross-sectional height in the sidewall rubber, The carcass ply is disposed in a manner along the sidewall rubber between the sidewall rubber and the reinforcing rubber layer, On the outer surface of the tire between the bent portion and the tread, there is a straight portion inclined at a constant inclination angle with respect to the tire diameter direction and being linear in the tire width direction cross-section, In the tire width direction cross-section, the tire diameter direction length of the straight portion is 30% or more and 70% or less of half the length of the tire cross-sectional height, The straight portion has a straight portion formed on the outer surface of the sidewall rubber and a straight portion formed on the outer surface of the tread rubber, The straight portion inclined at a constant inclination angle with respect to the tire diameter direction and formed on the outer surface of the sidewall rubber forms a conical surface, a run-flat tire.

2. In the tire width direction cross-section, The angle θ1 formed by a line connecting the intersection of a line along the tire width direction passing through the tire maximum width position and the tire outer surface and a position on the tire outer surface 10% in the tire diameter direction outside the tire maximum width position, and a line connecting the intersection of a line along the tire width direction passing through the tire maximum width position and the tire outer surface and a position on the tire outer surface 10% in the tire diameter direction inside the tire maximum width position is, The run-flat tire according to claim 1, wherein an angle is smaller than an angle θ2 formed by a line connecting an intersection of a line along the tire width direction passing through the maximum tire width position and the tire inner cavity surface and a position on the tire inner cavity surface that is 10% of the tire cross-sectional height radially outward from the maximum tire width position, and a line connecting an intersection of a line along the tire width direction passing through the maximum tire width position and the tire inner cavity surface and a position on the tire inner cavity surface that is 10% of the tire cross-sectional height radially inward from the maximum tire width position.

3. The run-flat tire according to claim 2, wherein the angle θ1 and the angle θ2 are each greater than 140° and less than 170°.

4. Let the tire width direction distance from the inner end in the tire width direction of the bead to the maximum tire width position of the bent portion be W1. When the tire width direction distance from the inner end in the tire width direction of the bead to the outermost position in the tire width direction of the tire inner cavity surface of the bent portion is W2. The run-flat tire according to any one of claims 1 to 3, wherein the ratio of W2 to W1 is greater than 60% and less than 80%.

5. Let the tire width direction distance from the inner end in the tire width direction of the bead to the maximum tire width position of the bent portion be W1. When the tire width direction distance from the inner end in the tire width direction of the bead to the outermost position in the tire width direction of the tire inner cavity surface of the bent portion is W2. The ratio of W2 to the tire cross-sectional height is greater than 15% and less than 35%, The ratio of W1 to the tire cross-sectional height is greater than 20% and less than 40%, and the run-flat tire according to any one of claims 1 to 4.

6. The run-flat tire according to any one of claims 1 to 5, wherein the thickness of the sidewall rubber at the bent portion is 2.5 mm or more and 4.0 mm or less.

7. In the sidewall rubber, the thickness of the region that is more than 40% and within 60% radially inward from the tire cross-sectional height. The run-flat tire according to any one of claims 1 to 6, wherein the thickness is less than or equal to the thickness of the region that is more than 20% and within 40% radially inward from the tire cross-sectional height, and less than or equal to the thickness of the region that is more than 60% and within 80% radially inward from the tire cross-sectional height.

8. The tread includes a belt disposed radially outside the carcass ply. The radially outer end of the reinforcing rubber layer is located inside the radially outer end of the belt in the tire width direction. The distance from the outer end of the reinforcing rubber layer in the tire radial direction to the outer end of the belt in the tire width direction is 3 mm or more and 10 mm or less. The run-flat tire according to any one of claims 1 to 7.

9. The bead includes a bead core and a bead filler extending outward in the tire radial direction of the bead core. The inner end of the reinforcing rubber layer in the tire radial direction is located radially inward of the outer end of the bead filler in the tire radial direction. The distance from the inner end of the reinforcing rubber layer in the tire radial direction to the outer end of the bead filler in the tire radial direction is 5 mm or more and 20 mm or less. The run-flat tire according to any one of claims 1 to 8.

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