JP2017197152A - Run-flat radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a run-flat radial tire capable of suppressing asymmetrical deformation during run-flat traveling as well as enhancing durability during the run-flat traveling.SOLUTION: A tire 10 (run-flat radial tire) comprises: a carcass 14 straddling between a pair of bead parts 12; and a side reinforcing rubber 24 disposed in a tire side part 22, and extending in a tire radial direction along an inner surface of the carcass 14; cords disposed on an outer side of the carcass 14 in the tire radial direction, and extending in a direction inclined with respect to a tire circumferential direction; at least two belt layers 16, in which the cords intersect with each other in a tire radial direction view; and a tread 20 disposed on an outer side of the belt layer 16 in the tire radial direction. A tire cross section height SH is configured to be 145 mm or greater. When a distance between belt layer side ends 24B in the side reinforcing rubber 24 on both sides in a tire width direction is WA, and a ground contact width of the tread 20 is TW, their relation is configured to be WA≤0.9TW.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a run-flat radial tire.

  Patent Document 1 below discloses a side-reinforced run-flat radial tire in which a tire side portion is reinforced with a side-reinforcing rubber to ensure durability during run-flat running (during abnormal running with reduced air pressure). .

JP 2013-95369 A

As shown in Patent Document 1 described above, in recent years, a run flat radial tire having a relatively large tire cross-sectional height has been demanded. In such a run-flat radial tire, there are concerns about the following problems during run-flat running.
[1] Since the tire cross-section height is large, the absolute value of the vertical deflection with respect to the vertical load is large. This causes a large buckling on the tread surface.
[2] Due to the asymmetry of the buckling and the belt layer, the belt layer is twisted in the slip angle direction and a lateral force is generated to cause asymmetric deformation. In particular, in a run-flat radial tire having a large tire cross-section height, since the lateral rigidity in the run-flat running state is low, a larger asymmetric deformation occurs.
[3] Due to this asymmetric deformation, when the tread moves in the tire width direction with a large buckling (asymmetric deformation), the belt layer from the region where the belt layer exists on the lateral force input side (side where the lateral force enters) The outside in the width direction where there is no ground is grounded.
[4] By grounding in the region where the belt layer does not exist on the lateral force entry side, the lateral force generated on both sides of the contact surface on the lateral force entry side and the exit side is reduced. The imbalance of the outward force in the width direction on the entry side and the exit side increases. By increasing the imbalance, the movement of the tread surface in the tire width direction is further promoted, and the asymmetric deformation is further increased.
[5] When the movement of the tread surface in the tire width direction increases, the deflection of the side reinforcing rubber on the lateral force output side increases, and the run-flat durability deteriorates.
[6] The phenomenon in which the asymmetric deformation described in [3] and [4] is further increased occurs particularly in a run-flat radial tire having a tire cross-section height of 145 mm or more, and the run-flat having a tire cross-section height of less than 145 mm. Compared with radial tires, the deterioration of run-flat durability due to asymmetric deformation becomes a problem.

  In view of the above facts, the present invention has an object to suppress asymmetric deformation during run-flat running and to improve durability during run-flat running.

  The run-flat radial tire according to claim 1 includes a carcass straddling between a pair of bead portions, a side reinforcing rubber provided in a tire side portion and extending in a tire radial direction along an inner surface of the carcass, and a tire diameter of the carcass. At least two belt layers provided on the outer side in the direction and extending in a direction inclined with respect to the tire circumferential direction, the cords intersecting each other when viewed in the tire radial direction, and on the outer side in the tire radial direction of the belt layer A tire cross-section height of 145 mm or more, a distance between the belt layer side ends of the side reinforcing rubber on both sides in the tire width direction is WA, and a ground contact width of the tread is TW. WA ≦ 0.9TW.

  In this run-flat radial tire, by setting WA ≦ 0.9 TW, the overlapping range between the tread contact area and the side reinforcing rubber is increased. Thereby, the bending rigidity in the cross section in a grounding edge part becomes high, and the asymmetric deformation at the time of run flat driving | running | working is suppressed. For this reason, durability at the time of run-flat driving | running | working can be improved.

  According to a second aspect of the present invention, in the run flat radial tire according to the first aspect, B / TW ≧ 1.0, where B is the maximum width of the belt layer in the tire width direction.

  In this run-flat radial tire, by setting B / TW ≧ 1.0, the maximum width B of the belt layer in the tire width direction is made larger than the contact width TW of the tread. As a result, the contact portion on the side of the lateral force is asymmetrically deformed during run-flat travel, and does not go outside in the width direction where the belt layer does not exist, so that an increase in asymmetric deformation is suppressed. For this reason, the durability at the time of run-flat traveling can be further enhanced.

  According to a third aspect of the present invention, in the run flat radial tire according to the first or second aspect, TW / W ≧ 0.5, where W is the maximum tire width.

  In this run-flat radial tire, by setting TW / W ≧ 0.5, the angle change of the outer surface from the tread to the tire side portion as seen in the cross section in the tire width direction becomes large. It becomes difficult to move outward in the direction. As a result, the contact portion on the side of the lateral force is asymmetrically deformed during run-flat travel and does not go outside in the width direction where the belt layer does not exist, so that an increase in asymmetric deformation is suppressed.

  According to a fourth aspect of the present invention, in the run flat radial tire according to any one of the first to third aspects, TW / WR ≧ 0.7 when the rim width is WR.

  In this run-flat radial tire, by setting TW / WR ≧ 0.7, the change in the angle of the outer surface from the tread to the tire side portion as seen in the cross section in the tire width direction becomes large. It becomes difficult to move outward in the direction. Thereby, asymmetric deformation at the time of run-flat traveling is suppressed.

  The run-flat radial tire of the present invention can suppress asymmetric deformation during run-flat running, and can increase durability during run-flat running.

1 is a half sectional view showing one side of a cut surface obtained by cutting a run flat radial tire according to an embodiment of the present invention along a tire width direction and a tire radial direction in a state where the run flat radial tire is assembled to a rim. It is a partial expanded view which shows the structure of the tread surface. (A) is sectional drawing which shows the case where there is no asymmetric deformation in a run flat radial tire. (B) is a cross-sectional view showing a case where there is asymmetric deformation in a run-flat radial tire. (A) is a cross-sectional view showing a state in which the force toward the outer side in the width direction generated at both ends of the contact portion is substantially balanced in the run-flat radial tire without any asymmetric deformation. (B) is a cross-sectional view showing a state in which a run-flat radial tire has asymmetric deformation and an imbalance has occurred. It is a diagram which shows the relationship between a tire cross-sectional height and the amount of asymmetric deformation.

Hereinafter, an embodiment of a run flat radial tire of the present invention will be described with reference to the drawings.
FIG. 1 shows a cut surface cut along a tire width direction and a tire radial direction of a run-flat radial tire 10 (hereinafter referred to as “tire 10”) of the present embodiment (viewed from a direction along the tire circumferential direction). One side of the cross section) is shown. In the figure, an arrow AW indicates the width direction of the tire 10 (tire width direction), and an arrow AR indicates the radial direction of the tire 10 (tire radial direction). The tire width direction here refers to a direction parallel to the rotation axis of the tire 10. The tire radial direction refers to a direction orthogonal to the rotation axis of the tire 10. Reference sign CL indicates the equator plane of the tire 10 (tire equator plane).

  In the present embodiment, the side closer to the rotation axis of the tire 10 along the tire radial direction is “inner side in the tire radial direction”, and the side farther from the rotation axis of the tire 10 along the tire radial direction is “outer side in the tire radial direction”. It describes. On the other hand, the side close to the tire equator plane CL along the tire width direction is described as “inner side in the tire width direction”, and the side far from the tire equator plane CL along the tire width direction is described as “outer side in the tire width direction”.

(tire)
FIG. 1 shows the tire 10 when assembled to the rim 30 and filled with standard internal pressure. The rim 30 is a standard rim. The “standard rim” mentioned here is a standard rim (or “Applied Rim” or “Recommended Rim”) in the applicable size described in the Year Book 2015 edition of JATMA (Japan Automobile Tire Association). Yes, the rim width RW described later is also defined by this standard. The standard internal pressure is an air pressure corresponding to the maximum load (maximum load capacity) of a single wheel described in the Year Book. The standard load is the maximum load (maximum load capacity) of a single wheel at the applicable size described in the Year Book. The tire dimensions shall be measured in a state where the tire is assembled to a standard rim and a standard internal pressure is applied. The contact width TW of the tread 20 is a contact width in the tire width direction immediately below the load when a standard load is applied.

  The standards are determined by industry standards that are valid in the region where the tire is produced or used. For example, in the United States, “The Year Book of The Tire and Rim Association Inc.”. In Europe, it is “The Standards Manual of The European Tire and Rim Technical Organization”. In Japan, it is defined in the above-mentioned “JATMA Year Book” of the Japan Automobile Tire Association.

As shown in FIG. 1, the tire 10 includes a carcass 14 straddling a pair of bead portions 12, a side reinforcing rubber 24 provided on the tire side portion 22 and extending in the tire radial direction along the inner surface of the carcass 14, A belt layer 16 provided on the outer side in the tire radial direction of the carcass 14 and a tread 20 provided on the outer side in the tire radial direction of the belt layer 16 are provided. In FIG. 1, only the bead portion 12 on one side is shown.
A reinforcing cord layer 18 is provided outside the belt layer 16 in the tire radial direction. A tread 20 constituting the outer peripheral portion of the tire 10 is provided on the outer side in the tire radial direction than the reinforcing cord layer 18. The tire side portion 22 includes a sidewall portion 22A on the bead portion 12 side and a shoulder portion 22B on the tread 20 side, and connects the bead portion 12 and the tread 20.

  In the tire 10 of the present embodiment, the tire cross-section height (section height) SH shown in FIG. 1 is set to 145 mm or more and 500 mm or less. Further, it is more preferable that the thickness is 250 mm or less. The “tire cross-section height SH” here is 1/2 of the difference between the tire outer diameter and the rim diameter D when the tire 10 is assembled to the rim 30 (standard rim) and the internal pressure is the standard air pressure. Refers to the length. Further, the “tire outer diameter” is a distance from a point P on the tire equatorial plane CL of the tread 20 (see FIG. 1) to a similar point P that is arranged symmetrically with respect to the tire axis. “Rim diameter” is the rim diameter specified in the year 2015 version of JATMA (Japan Automobile Tire Association).

  In this embodiment, the tire size of the tire 10 is 235 / 65R17. However, the embodiment of the present invention is not limited to this, and for example, 245 / 60R18, 255 / 65R18, 235 / 65R18, 215 / 70R16, etc. Good.

(Bead part)
As shown in FIG. 1, a bead core 26 is embedded in each of the pair of bead portions 12. The carcass 14 straddles these bead cores 26. The bead core 26 can employ various structures in a pneumatic tire such as a circular cross section or a polygonal cross section. As the polygon, for example, a hexagon can be adopted. Further, the bead portion 12 may be further provided with a rubber layer, a cord layer, or the like for the purpose of reinforcement or the like, and such an additional member can be provided at various positions with respect to the carcass 14 and the bead filler 28.

(Carcass)
The carcass 14 is composed of two carcass plies 14A and 14B (a carcass ply 14A is a carcass ply disposed outside the tire radial direction on the tire equatorial plane CL, and a carcass ply 14B is a carcass ply disposed inside). Each of the carcass plies 14A and 14B is formed by coating a plurality of cords with a covering rubber.

  The carcass 14 formed in this manner extends from one bead core 26 to the other bead core 26 in a toroid form, thereby constituting a tire skeleton. Further, the end portion side of the carcass 14 is locked to the bead core 26. Specifically, the end portion of the carcass 14 is folded and locked around the bead core 26 from the inner side in the tire width direction to the outer side in the tire width direction. Further, the folded end portions (end portions 14AE, 14BE) of the carcass 14 are disposed on the tire side portion 22. The end portion 14AE of the carcass ply 14A is disposed on the inner side in the tire radial direction than the end portion 14BE of the carcass ply 14B.

  In the present embodiment, the end portion of the carcass 14 is arranged on the tire side portion 22, but the present invention is not limited to this configuration. For example, the end portion of the carcass 14 may be arranged on the tread 20. Good. Further, it is possible to adopt a structure in which the end portion side of the carcass 14 is not folded back and is sandwiched between a plurality of bead cores 26 or wound around the bead cores 26.

  The position of the tire maximum width W (the position of the straight line WL) is 0.6 SH or more on the outer side in the tire radial direction from the bead base portion 12B. That is, in FIG. 1, the height MH ≧ 0.6SH. The position in the tire radial direction (reference point O) at which the width of the carcass 14 is maximum substantially corresponds to the position of the tire maximum width W. Here, the straight line WL is a straight line drawn from the tire width direction end portion 22C of the tire side portion 22 along the tire width direction. The reference point O is a point where the straight line WL intersects the outer surface of the carcass 14 in the tire width direction.

  In the present embodiment, the carcass 14 is a radial carcass. The material of the carcass 14 is not particularly limited, and rayon, nylon, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), aramid, glass fiber, carbon fiber, steel, or the like can be used. From the viewpoint of weight reduction, an organic fiber cord is preferable. In addition, the number of carcass shots is in the range of 20 to 60 pieces / 50 mm, but is not limited to this range.

  A bead filler 28 extending from the bead core 26 to the outer side in the tire radial direction is embedded in a region surrounded by the carcass 14 of the bead portion 12. The bead filler 28 decreases in thickness toward the outer side in the tire radial direction. Note that a structure without the bead filler 28 may be employed.

(Belt layer)
At least two belt layers 16 are disposed outside the carcass 14 in the tire radial direction. The belt layer 16 is constituted by two belt plies 16A and 16B. The belt ply 16 </ b> A is disposed on the outer side in the tire radial direction in the belt layer 16. The belt ply 16B is disposed on the inner side in the tire radial direction of the belt ply 16A. Each of the belt plies 16A and 16B is formed by coating a plurality of cords (for example, an organic fiber cord or a metal cord) with a covering rubber. The cords constituting the belt plies 16A and 16B extend in a direction inclined with respect to the tire circumferential direction. The cords constituting the belt plies 16A and 16B intersect each other when viewed in the tire radial direction. The inclination angle of the cord is preferably 10 ° or more with respect to the tire circumferential direction. The belt ply 16A has a width (length) along the tire width direction narrower (shorter) than a width (length) along the tire width direction of the belt ply 16B.

  In addition, the belt layer 16 can also be made into the structure of only one layer. However, in the case of a radial tire for a passenger car having a narrow width and a large diameter, when there is only one belt layer, the shape of the ground contact surface at the time of turning tends to be distorted, so that the cords of two or more layers extend in the direction of crossing each other. A belt layer is preferred. As a pneumatic radial tire for passenger cars, a configuration in which two belt layers form an intersection layer is preferable.

  When a metal cord is used as the cord of the belt plies 16A and 16B, it is most common to use a steel cord. The steel cord is mainly composed of steel and can contain various trace contents such as carbon, manganese, silicon, phosphorus, sulfur, copper, and chromium.

  As the cord, a monofilament cord or a cord obtained by twisting a plurality of filaments can be used. Various designs can be adopted for the twist structure, and various cross-sectional structures, twist pitches, twist directions, and distances between adjacent filaments can be used. Furthermore, it is also possible to employ a cord in which filaments of different materials are wound together, and the cross-sectional structure is not particularly limited, and various twisted structures such as single twist, layer twist, and double twist can be taken.

(Reinforcement cord layer)
A reinforcing cord layer 18 is provided outside the belt layer 16 in the tire radial direction. The reinforcing cord layer 18 is composed of two reinforcing plies 18A and 18B (the reinforcing ply disposed on the outer side in the tire radial direction is the reinforcing ply 18A, and the reinforcing ply disposed on the inner side is the reinforcing ply 18B). . The reinforcement ply 18A is formed with a smaller width (length) in the tire width direction than the reinforcement ply 18B, and covers the entire belt layer 16. Each of the reinforcing plies 18A and 18B is formed by arranging a plurality of cords (for example, organic fiber cords, metal cords, etc.) whose angles are substantially parallel to the tire circumferential direction in parallel. Note that the reinforcement ply 18A may be formed to have a larger width (length) along the tire width direction than the reinforcement ply 18B. In any case, the rigidity change at the end of the tread 20 becomes gentle, and local breakage is suppressed.

  The reinforcing cord layer 18 may be a wavy cord in order to increase the breaking strength. Similarly, in order to increase the breaking strength, a high elongation cord (for example, an elongation at break of 4.5 to 5.5%) may be used.

  In the present embodiment, as an example, polyethylene terephthalate (PET) is used as a cord constituting the reinforcing cord layer 18, but various materials can be used for this cord, for example, rayon, nylon, polyethylene naphthalate. (PEN), aramid, glass fiber, carbon fiber, steel, etc. can be employed. From the viewpoint of weight reduction, an organic fiber cord is particularly preferable.

  Further, the cord may be a monofilament cord, a cord in which a plurality of filaments are combined, or a hybrid cord in which filaments of different materials are combined. The number of cords to be driven is in the range of 20 to 60/50 mm, but is not limited to this range.

  Further, the reinforcing cord layer 18 can have a distribution of rigidity, material, number of layers, driving density, and the like in the tire width direction according to the specifications of the tire 10. For example, in this embodiment, the reinforcing plies 18 </ b> A and 18 </ b> B are provided. Although the width (length) along the tire width direction is substantially the same, the present invention is not limited to this configuration. For example, the reinforcing ply 18A is narrower (shorter) or wider (longer) than the reinforcing ply 18B. May be. Further, the number of layers can be increased only at the end portion in the tire width direction, while the number of layers can be increased only at the center portion. Further, the reinforcing cord layer 18 may be omitted.

  Further, the reinforcing cord layer 18 can be designed to be wider or narrower than the belt layer 16. For example, the width may be 90% to 110% of the maximum width belt layer (belt ply 16B in the present embodiment) having the largest width among the belt layers 16.

(tread)
1 and 2, a tread 20 is provided on the outer side in the tire radial direction of the belt layer 16 and the reinforcing cord layer 18. The tread 20 is a part that contacts the road surface during traveling, and a plurality of circumferential grooves 51 extending in the tire circumferential direction are formed on the tread surface of the tread 20. The tread 20 is formed with a plurality of widthwise grooves (not shown) that communicate with the circumferential groove 51 and extend in the tire width direction. The shapes and the number of the circumferential grooves 51 and the width direction grooves are appropriately set according to performances such as drainage and steering stability required for the tire 10. For this reason, a width direction groove | channel can also be made into the horizontal groove | channel which terminates in a sipe or a rib-like land part, and can also be comprised combining these.

  Further, in the present embodiment, the negative rate is the same in the tire half on the inner side of the vehicle mounting direction and the outer side of the vehicle mounting direction with the equator plane CL as a boundary, but the embodiment of the present invention is not limited to this. . For example, in the case of a tire for which the mounting direction is specified, a difference may be provided in the negative rate between the tire half on the inner side in the vehicle mounting direction and the outer side in the vehicle mounting direction with the equator plane CL as a boundary.

  Among the rib-shaped land portions, various configurations are provided for the shoulder rib-shaped land portions that are divided by the outermost circumferential groove 51 in the tire width direction and the tire width direction end portion (tread outer end portion 20E) of the tread 20. Can be adopted. For example, in a tire in which the vehicle mounting direction is specified, the length in the tire width direction of the shoulder rib-shaped land portion on the outer side and the inner side in the mounting direction can be changed. In consideration of steering stability, it is preferable that the length in the tire width direction of the shoulder rib-shaped land portion on the outer side in the mounting direction is larger than the length in the tire width direction of the shoulder rib-shaped land portion on the inner side in the mounting direction.

  Further, in the tire 10, the distance in the tire radial direction between the tread 20 outer end portion 20E on the outer side in the tire width direction and the point P on the tire equatorial plane CL of the tread 20 on the tread 20 decreases, and the height TH [mm] It is preferable to set the drop height TH to be 4.5% or less of the tread width TW [mm]. By setting TH / TW within this range, the crown portion of the tire is flattened (flattened), the contact area increases, the input (pressure) from the road surface is relaxed, and the deflection rate in the tire radial direction is reduced. This can reduce the tire durability and wear resistance.

  In addition, although the tread rubber used for the tread 20 in this embodiment is made into the single layer structure, embodiment of this invention is not restricted to this. For example, the tread rubber may be formed of a plurality of rubber layers different in the tire radial direction. As the plurality of rubber layers, those having different tangent loss, modulus, hardness, glass transition temperature, material and the like can be used. Moreover, the ratio of the thickness of the plurality of rubber layers in the tire radial direction may be changed in the tire width direction, and only the circumferential groove bottom or the like may be a rubber layer different from the periphery thereof.

  Furthermore, the tread rubber may be formed of a plurality of rubber layers different in the tire width direction. As the plurality of rubber layers, those having different tangent loss, modulus, hardness, glass transition temperature, material and the like can be used. Moreover, the ratio of the length of the plurality of rubber layers in the tire width direction may be changed in the tire radial direction, and only in the vicinity of the circumferential groove, only in the vicinity of the tread, only in the shoulder land portion, only in the center land portion, etc. Only a limited part of the area may be a rubber layer different from the surrounding area.

(Tread pattern)
In FIG. 2, the configuration of the tread surface of the tread 20 is shown as a partial development view. The tire 10 is a so-called mounting direction designating pattern in which the mounting direction with respect to the vehicle is specified. In FIG. 2, the vehicle mounting outer side is indicated by an arrow OUT and the vehicle mounting inner side is indicated by an arrow IN.

  The tire 10 extends in the tire circumferential direction on the tread surface of at least one tread half-width region of the pair of tread half-width regions with the tire equator plane CL as a boundary, in the illustrated example, on the tread half-width region on the outer side of the vehicle. The outermost circumferential groove 51a (may be simply referred to as the circumferential groove 51a in the following description), the circumferential groove 51b, the shoulder portion circumferential sipe 52a extending in the tire circumferential direction, and the inner circumferential sipe 52b. Is provided.

  The shoulder portion circumferential sipe 52a is disposed in a shoulder land portion 53a defined by the tread ground end TE and the outermost circumferential groove 51a, and the inner circumferential sipe 52b is the inner side in the tire width direction of the outermost circumferential groove 51a. It is arrange | positioned at the inner side land part 53b adjacent to. In the present embodiment, sipe means a narrow groove having a width that can be closed when grounded, and has a width of 2 mm or less, for example.

  Thus, in this embodiment, the edge effect with respect to the input of a tire width direction is heightened by providing the circumferential sipe in each of the shoulder land portion 53a and the inner land portion 53b, and the turning performance on snow is improved. ing.

  In the present embodiment, the sipe width of the shoulder portion circumferential sipe 52a is larger than that of the inner circumferential sipe 52b, and the sipe depth of the shoulder portion circumferential sipe 52a is smaller than that of the inner circumferential sipe 52b. Is formed. That is, as shown in FIG. 2, when the sipe width of the shoulder portion circumferential sipe 52a is ws, the sipe depth is ds, the sipe width of the inner circumferential sipe 52b is wi, and the sipe depth is di, ws> wi and ds <di hold.

  The sipe width ws of the shoulder portion circumferential sipe 52a and the sipe width wi of the inner circumferential sipe 52b preferably satisfy 1.7 <ws / wi <2.1, and the sipe of the shoulder portion circumferential sipe 52a. It is preferable that the depth ds and the sipe depth di of the inner circumferential sipe 52b satisfy 1.6 <di / ds <1.9. By setting the ratio of the sipe width and the sipe depth within this range, it is possible to obtain a good balance between the performance on snow and the wear performance.

  Further, in the pattern shown in FIG. 2, four circumferential grooves 51 a to 51 d extending in the tire circumferential direction are disposed in the tread 20, and these four circumferential grooves 51 a to 51 d and the tread grounding end TE are arranged. The five land portions 53a to 53e are provided. In the illustrated pattern, there is no circumferential groove on the tire equatorial plane CL. From the circumferential groove 51b, lug grooves 54a, 54b extend on both sides in the tire width direction, and from the circumferential groove 51c, lug grooves 54c, 54d extend on both sides in the tire width direction. The outermost circumferential groove 51d communicates. Further, a lateral groove 55a extends from the outermost circumferential groove 51a to the outer side in the tire width direction, and a lateral groove 55b extends from the outermost circumferential groove 51d to the outer side in the tire width direction. Reference numerals 56a to 56e denote sipes arranged in communication with the circumferential grooves.

  Further, as shown in FIG. 1, the upper end portion 24B of the side reinforcing rubber layer 24 is positioned on the inner side in the tire width direction than the shoulder portion circumferential sipe 52a in the tire width direction cross section. In the region where the side reinforcing rubber layer 24 and the shoulder land portion 53a overlap each other in the tire width direction, the contact pressure tends to increase particularly. By providing the shoulder portion circumferential sipe 52a in this region, the edge effect is further increased. Can be obtained.

(Tire side)
The tire side portion 22 extends in the tire radial direction, connects the bead portion 12 and the tread 20, and is configured to be able to bear a load acting on the tire 10 during run-flat travel. Both end portions 22C in the tire width direction of the tire side portion 22 can be provided on the outer side in the tire radial direction from the bead base portion 12B in a range of 50% to 90% in comparison with the tire cross-section height SH.

  Note that the tire side portion 22 may be provided with a turbulent flow generation projection. In this case, the tire side portion 22 is cooled by the turbulent flow generated by the turbulent flow generation projection, and the run-flat running performance can be further improved. The turbulent flow generation projection can be provided on either the tire outer surface or the tire inner surface of the tire side portion. In addition, it can be provided on either the outer surface of the tire or the inner surface of the tire, and in the case of a tire for which the mounting direction is specified, a projection for generating turbulence is provided only on one side portion of the pair of tire side portions. Is also possible. Furthermore, run flat running performance can be further improved by providing dimples on the tire side portion to increase the surface area and increase heat dissipation.

(Side reinforcement rubber)
The tire side portion 22 is provided with a side reinforcing rubber 24 that reinforces the tire side portion 22 inside the carcass 14 in the tire width direction. The side reinforcing rubber 24 is a reinforcing rubber for traveling a predetermined distance while supporting the weight of the vehicle and the occupant when the internal pressure of the tire 10 decreases due to puncture or the like.

  In the present embodiment, the side reinforcing rubber 24 is formed of one type of rubber material, but the embodiment of the present invention is not limited to this, and may be formed of a plurality of rubber materials. The side reinforcing rubber 24 may include other materials such as fillers, short fibers, and resins as long as the rubber material is the main component. Further, a rubber material having a hardness of 70 to 85 may be included as a rubber material constituting the side reinforcing rubber 24 in order to enhance durability during run-flat running. Furthermore, the loss coefficient tan δ measured by using a viscoelastic spectrometer (for example, a spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ± 2%, and a temperature of 60 ° C. is 0.10 or less. A rubber material having physical properties may be included. In addition, the hardness of rubber | gum here refers to the hardness prescribed | regulated by JISK6253 (type A durometer).

  In this embodiment, as an example of the side reinforcing layer of the present invention, the side reinforcing rubber 24 mainly composed of rubber is used. However, the present invention is not limited to this, and other materials having rubber-like elasticity (for example, A side reinforcing layer mainly composed of a thermoplastic resin or the like may be used.

  The side reinforcing rubber 24 extends in the tire radial direction along the inner surface of the carcass 14 from the bead portion 12 side to the tread 20 side. Further, the side reinforcing rubber 24 has a shape whose thickness decreases from the center portion toward the bead portion 12 side and the tread 20 side, for example, a substantially crescent shape. Here, the thickness of the side reinforcing rubber 24 refers to a length along the normal line of the carcass 14 in a state where the tire 10 is assembled to the rim 30 and the internal pressure is a standard air pressure.

  In the side reinforcing rubber 24, the lower end portion 24 </ b> A on the bead portion 12 side overlaps the bead filler 28 with the carcass 14 interposed therebetween when viewed from the tire width direction, and the upper end portion 24 </ b> B on the tread 20 side sandwiches the carcass 14 with the belt layer 16. And overlapping from the tire radial direction. Specifically, the upper end portion 24B of the side reinforcing rubber 24 overlaps the belt ply 16B with the carcass 14 interposed therebetween. That is, the upper end portion 24B of the side reinforcing rubber 24 is located on the inner side in the tire width direction than the end portion 16BE of the belt ply 16B.

When the distance between the belt layer side ends 24B in the side reinforcing rubber 24 on both sides in the tire width direction is WA and the ground contact width of the tread 20 is TW, WA ≦ 0.9TW. More preferably, WA ≦ 0.8TW.
Further, assuming that the maximum width of the belt layer 16 in the tire width direction (the width of the belt ply 16B) is B, B / TW ≧ 1.0. More preferably, B / TW ≧ 1.05.
When the maximum tire width is W, TW / W ≧ 0.5. More preferably, TW / W ≧ 0.65.
When the rim width of the rim 30 is WR, TW / WR ≧ 0.7. More preferably, TW / WR ≧ 0.86.

  An inner liner 25 is disposed on the inner surface of the tire 10 from one bead portion 12 to the other bead portion 12. In the present embodiment, as an example, the inner liner 25 mainly composed of butyl rubber is disposed. However, the present invention is not limited to this, and another rubber material or an inner liner of a film layer mainly composed of a resin is disposed. May be. The inner liner 25 may not be provided because at least the inner side of the tire side portion 22 among the inner surfaces of the tire 10 is formed with the side reinforcing rubber 24 and has low air permeability.

  Furthermore, a porous member can be disposed on the inner surface of the tire 10 or electrostatic flocking can be performed in order to reduce cavity resonance noise. Moreover, the inner surface of the tire 10 can also be provided with a sealant member for preventing air leakage during puncture.

  In this embodiment, since the tire 10 having a high tire cross-section height SH is targeted, the rim guard (rim protection) is not provided, but the present invention is not limited to this configuration, and a rim guard may be provided.

(Function)
Next, functions and effects of the tire 10 of the present embodiment will be described. In the tire 10 of the present embodiment, the relationship between the distance WA in the tire width direction between the belt layer side ends 24B of the side reinforcing rubbers 24 on both sides in the tire width direction and the ground contact width TW of the tread 20 is WA ≦ 0.9TW. Yes. Thereby, the overlapping range of the ground contact area of the tread and the side reinforcing rubber is increased. The relationship between the maximum width B of the belt layer 16 (the width of the belt ply 16B) and the ground contact width TW of the tread 20 is set to B / TW ≧ 1.0. Thereby, the maximum width of the belt layer in the tire width direction is made larger than the contact width of the tread. With this setting, the bending rigidity in the cross section at the ground contact end portion is increased, so that asymmetric deformation during run flat traveling is suppressed. Further, since the contact portion on the side of the lateral force is asymmetrically deformed during run-flat running and does not go outside in the width direction where the belt layer 16 does not exist, an increase in asymmetric deformation is suppressed. For this reason, durability at the time of run-flat driving | running | working can be improved.

  In the tire 10 of the present embodiment, the relationship between the ground contact width TW of the tread 20 and the tire maximum width W is TW / W ≧ 0.5. Further, in the tire 10 of the present embodiment, the relationship between the ground contact width TW of the tread 20 and the rim width WR is TW / WR ≧ 0.7. As a result, the angle change of the outer surface from the tread 20 to the tire side portion 22 as seen in the cross section in the tire width direction is increased, so that the contact position of the tread 20 is difficult to move outward in the tire width direction. Accordingly, since the grounding portion on the side of the lateral force is asymmetrically deformed during run-flat running and does not go outside in the width direction where the belt layer 16 does not exist, an increase in asymmetric deformation is suppressed.

Here, the asymmetric deformation will be briefly described. FIG. 3A is a cross-sectional view showing a case where there is no asymmetric deformation in the run-flat radial tire. FIG. 3B is a cross-sectional view showing a case where there is asymmetric deformation in the run-flat radial tire.
In the run-flat radial tire shown in FIG. 4 (A), there is no asymmetric deformation, and the outward force in the width direction generated at both ends of the contact portion is almost balanced. On the other hand, in the run flat radial tire shown in FIG. 4B, there is asymmetric deformation, and there is no belt layer on the grounding portion on the lateral force input side (right side of the drawing), so the width generated at both ends of the grounding portion. The outward force is weakened and an imbalance occurs.
As shown in FIG. 5, the asymmetric deformation amount (index) is such that the tire cross-section height increases rapidly from around 140 mm.

DESCRIPTION OF SYMBOLS 10 ... Tire (run flat radial tire), 12 ... Bead part, 14 ... Carcass, 16 ... Belt layer, 20 ... Tread, 22 ... Tire side part, 24 ... Side reinforcement rubber, 24B ... Belt layer side edge, 30 rim

Claims (4)

A carcass straddling between a pair of bead parts;
A side reinforcing rubber provided at the tire side portion and extending in the tire radial direction along the inner surface of the carcass;
At least two belt layers provided on the outer side in the tire radial direction of the carcass and extending in a direction inclined with respect to the tire circumferential direction, the cords intersecting each other in the tire radial direction;
A tread provided on the outer side in the tire radial direction of the belt layer,
The tire cross-section height is 145 mm or more,
A run-flat radial tire in which WA ≦ 0.9TW, where WA is the distance between the belt layer side ends of the side reinforcing rubber on both sides in the tire width direction, and TW is the contact width of the tread.   2. The run-flat radial tire according to claim 1, wherein B / TW ≧ 1.0, where B is a maximum width of the belt layer in the tire width direction.   The run-flat radial tire according to claim 1 or 2, wherein TW / W≥0.5, where W is a maximum tire width.   The run-flat radial tire according to any one of claims 1 to 3, wherein TW / WR≥0.7, where rim width is WR.