JP6803150B2 - Run-flat radial tire - Google Patents

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 the tire side portion is reinforced with side reinforcing rubber to ensure durability during run-flat running (during abnormal running when the air pressure drops). ..

Japanese Unexamined Patent Publication No. 2013-95369

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 required. With such a run-flat radial tire, there are concerns about the following problems during run-flat running.
[1] Since the tire cross-sectional height is large, the absolute value of the vertical deflection with respect to the vertical load is large. Tread of this by Ri tread large buckling occurs.
[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-sectional height, a larger asymmetric deformation occurs because the lateral rigidity in the run-flat running state is low.
[3] Due to this asymmetrical deformation, when the tread moves in the tire width direction in a state where the buckling is large (asymmetrical deformation), the belt layer from the region where the belt layer exists on the lateral force input side (lateral force input side). The outside in the width direction where there is no ground is grounded.
[4] By grounding in a region where the belt layer does not exist on the lateral force input side, the lateral force generated at both ends of the lateral force input side and exit side of the ground contact surface is reduced, so that the lateral force The imbalance of forces outward in the width direction on the entry side and the exit side becomes large. By increasing this imbalance, the movement of the tread in the tire width direction is further promoted, and the asymmetric deformation is further increased.
[5] When the movement of the tread in the tire width direction becomes large, 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] becomes even larger occurs remarkably especially in a run-flat radial tire having a tire cross-sectional height of 145 mm or more, and a run-flat with a tire cross-sectional height of less than 145 mm. Compared to radial tires, the deterioration of run-flat durability due to asymmetric deformation becomes a problem.

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

The runflat radial tire according to claim 1 includes a carcass straddling between a pair of bead portions, a side reinforcing rubber provided on the tire side portion and extending in the tire radial direction along the inner surface of the carcus, and a tire diameter of the carcus. A cord provided on the outer side of the direction and extending in a direction inclined with respect to the tire circumferential direction, and at least two belt layers in which the cords intersect each other in the tire radial direction and on the tire radial outer side of the belt layer. It is assumed that the tread is provided, the tire cross-sectional height is 145 mm or more, the distance between the belt layer side ends of the side reinforcing rubbers on both sides in the tire width direction is WA, and the ground contact width of the tread is TW. , WA ≦ 0.9 TW.

In this run-flat radial tire, the overlapping range between the ground contact area of the tread and the side reinforcing rubber is increased by setting WA ≦ 0.9 TW. As a result, the flexural rigidity in the cross section at the ground contact end portion is increased, so that asymmetric deformation during run-flat running is suppressed. Therefore, the durability during run-flat running can be improved.

According to the 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, the maximum width B of the belt layer in the tire width direction is made larger than the ground contact width TW of the tread by setting B / TW ≧ 1.0. As a result, the ground contact portion on the lateral force input side is asymmetrically deformed during run-flat running, and does not come out to the outside in the width direction in which the belt layer does not exist, so that the increase in asymmetrical deformation is suppressed. Therefore, the durability during run-flat running can be further improved.

The invention of claim 3 is the run-flat radial tire according to claim 1 or 2, where 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 tire width direction cross section becomes large, so that the ground contact position of the tread is the tire width. It becomes difficult to move outward in the direction. As a result, the ground contact portion on the lateral force input side is asymmetrically deformed during run-flat running, and does not come out to the outside in the width direction in which the belt layer does not exist, so that the increase in asymmetrical deformation is suppressed.

The invention of claim 4 is the run-flat radial tire according to any one of claims 1 to 3, where TW / RW ≥ 0.7, where RW is the rim width.

In this run-flat radial tire, by setting TW / RW ≥ 0.7, the angle change of the outer surface from the tread to the tire side portion as seen in the tire width direction cross section becomes large, so that the ground contact position of the tread is the tire width. It becomes difficult to move outward in the direction. As a result, asymmetric deformation during run-flat running is suppressed.
The invention of claim 5 is the run-flat radial tire according to any one of claims 1 to 4, wherein at least one of the pair of tread half-width regions with the tire equatorial plane as a boundary is a tread half-width region. The tread is provided with an outermost circumferential groove and a circumferential groove extending in the tire circumferential direction, and a shoulder circumferential sipe and an inner circumferential sipe extending in the tire circumferential direction, and the shoulder circumferential sipe is tread-grounded. It is arranged in the shoulder land portion defined by the end and the outermost circumferential groove, and the inner circumferential sipe is arranged in the inner land portion adjacent to the inner side in the tire width direction of the outermost circumferential groove.
The invention of claim 6 is the run-flat radial tire according to claim 5, wherein the sipe width of the shoulder portion circumferential sipe is ws, the sipe depth is ds, the sipe width of the inner circumferential sipe is wi, and the sipe depth. When the value is di, ws> wi and ds <di.
According to the invention of claim 7, in the run-flat radial tire according to claim 6, the sipe width ws and the sipe width wi satisfy 1.7 <ws / wi <2.1, and the sipe depth ds. And the sipe depth di satisfy 1.6 <di / ds <1.9.
The invention of claim 8 is the run-flat radial tire according to any one of claims 5 to 7, wherein the upper end portion of the side reinforcing rubber layer is a shoulder portion circumferential sipe in the tire width direction cross section. It is located inside the tire width direction.

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

It is a half cross-sectional view which shows one side of the cut surface which cut along the tire width direction and the tire radial direction in the state which the run-flat radial tire which concerns on embodiment of this invention is assembled to a rim. It is a partial development view which shows the structure of the tread of a tread. (A) is a cross-sectional view showing a case where there is no asymmetric deformation in a run-flat radial tire. (B) is a cross-sectional view showing a case where a run-flat radial tire has asymmetric deformation. (A) is a cross-sectional view showing a state in which there is no asymmetric deformation in a run-flat radial tire and the outward forces in the width direction generated at both ends of the ground contact portion are substantially balanced. (B) is a cross-sectional view showing a state in which an asymmetrical deformation occurs and an imbalance occurs in a run-flat radial tire. It is a diagram which shows the relationship between the tire cross-sectional height and the asymmetric deformation amount.

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

Further, in the present embodiment, the side close to the rotation axis of the tire 10 along the tire radial direction is "inside in the tire radial direction", and the side far from the rotation axis of the tire 10 along the tire radial direction is "outside in the tire radial direction". It is described as. On the other hand, the side close to the tire equatorial plane CL along the tire width direction is described as "inside in the tire width direction", and the side far from the tire equatorial plane CL along the tire width direction is described as "outside in the tire width direction".

(tire)
FIG. 1 shows a tire 10 when assembled on a rim 30 and filled with a standard internal pressure. The rim 30 is a standard rim. The "standard rim" here means a standard rim (or "Approved Rim" or "Recommended Rim") in the applicable size described in the Year Book 2015 edition of JATTA (Japan Automobile Tire Association). Yes, the rim width RW, which will be described later, is also specified by this standard. Further, 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 in the applicable size described in the Year Book. The dimensions of the tire shall be measured with the tire assembled on the standard rim and standard internal pressure applied. The ground contact width TW of the tread 20 is the ground contact width in the tire width direction immediately under the load when a standard load is applied.

The standards are set by industrial standards that are valid in the area where the tire is produced or used. For example, in the United States, "The Tire and Rim Association Inc.'s Year Book". In Europe, it is "Standards Manual of The European Tire and Rim Technical Organization". In Japan, it is stipulated in the "JATMA Year Book" of the Japan Automobile Tire Association mentioned above.

As shown in FIG. 1, the tire 10 includes a carcass 14 straddling between 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 of the carcass 14 in the tire radial direction and a tread 20 provided on the outer side of the belt layer 16 in the tire radial direction are provided. In FIG. 1, only the bead portion 12 on one side is shown.
A reinforcing cord layer 18 is provided on the outer side of the belt layer 16 in the tire radial direction. A tread 20 forming an outer peripheral portion of the tire 10 is provided outside the reinforcing cord layer 18 in the tire radial direction. The tire side portion 22 is composed of 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.

Further, in the tire 10 of the present embodiment, the tire cross-sectional 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-sectional height SH" referred to 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 set to the standard air pressure. Refers to the length. Further, the "tire outer diameter" is the distance from the point P (see FIG. 1) on the tire equatorial plane CL of the tread of the tread 20 to a similar point P arranged line-symmetrically with respect to the tire axis. The "rim diameter" is the rim diameter specified by JATMA (Japan Automobile Tire Association) Year Book 2015 edition.

Further, in the present embodiment, the tire size of the tire 10 is 235 / 65R17, but 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. A carcass 14 straddles these bead cores 26. The bead core 26 can adopt 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 additional members 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 (the carcass ply arranged on the outer side in the tire radial direction on the tire equatorial plane CL is referred to as the carcass ply 14A, and the carcass ply arranged on the inner side is referred to as the carcass ply 14B). The carcass ply 14A and 14B are each formed by coating a plurality of cords with a coating rubber.

The carcass 14 formed in this way extends from one bead core 26 to the other bead core 26 in a toroid shape to form a tire skeleton. Further, the end side of the carcass 14 is locked to the bead core 26. Specifically, the carcass 14 is locked with its end side folded around the bead core 26 from the inside in the tire width direction to the outside in the tire width direction. Further, the folded ends (ends 14AE, 14BE) of the carcass 14 are arranged on the tire side portion 22. The end portion 14AE of the carcass ply 14A is arranged inside the end portion 14BE of the carcass ply 14B in the tire radial direction.

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 also possible to adopt a structure in which the end side of the carcass 14 is not folded back and is sandwiched between a plurality of bead cores 26 or wound around the bead core 26.

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

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 terephthalate (PEN), polyethylene terephthalate (PET), aramid, glass fiber, carbon fiber, steel and the like can be adopted. From the viewpoint of weight reduction, the organic fiber cord is preferable. In addition, the number of carcass driven is in the range of 20 to 60/50 mm, but the number is not limited to this range.

A bead filler 28 extending outward in the tire radial direction from the bead core 26 is embedded in the region of the bead portion 12 surrounded by the carcass 14. The thickness of the bead filler 28 decreases toward the outside in the tire radial direction. The structure may be such that the bead filler 28 is not provided.

(Belt layer)
At least two layers of belt layers 16 are arranged on the outer side of the carcass 14 in the tire radial direction. The belt layer 16 is composed of two belt plies 16A and 16B. The belt ply 16A is arranged outside the tire radial direction in the belt layer 16. The belt ply 16B is arranged inside the belt ply 16A in the tire radial direction. Each of the belt plies 16A and 16B is formed by coating a plurality of cords (for example, an organic fiber cord, a metal cord, etc.) with a coating 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 in the tire radial direction. The inclination angle of the cord is preferably 10 ° or more with respect to the tire circumferential direction. The width (length) of the belt ply 16A along the tire width direction is narrower (shorter) than the width (length) of the belt ply 16B along the tire width direction.

The belt layer 16 may be composed of only one layer. However, in a narrow-width, large-diameter passenger car radial tire, if there is only one belt layer, the shape of the ground contact surface during turning is easily distorted, so the two or more layers extend in the direction of intersection. It is preferably a belt layer. As a pneumatic radial tire for a passenger car, a configuration in which two belt layers form an interlaced 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 substances such as carbon, manganese, silicon, phosphorus, sulfur, copper and chromium.

Further, 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 designs can be used for the cross-sectional structure, the twist pitch, the twist direction, and the distance between adjacent filaments. Furthermore, by adopting a cord in which filaments of different materials are twisted, 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 on the outer side of 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 arranged on the outer side in the tire radial direction is referred to as the reinforcing ply 18A, and the reinforcing ply arranged on the inner side is referred to as the reinforcing ply 18B). .. The reinforcing ply 18A is formed to have a smaller width (length) along the tire width direction than the reinforcing ply 18B, and covers the entire belt layer 16. Further, each of the reinforcing plies 18A and 18B is formed by arranging a plurality of cords (for example, organic fiber cords, metal cords, etc.) having substantially parallel angles with respect to the tire circumferential direction in parallel. The reinforcing ply 18A may be formed to have a larger width (length) along the tire width direction than the reinforcing ply 18B. In either case, the change in rigidity at the end of the tread 20 becomes gentle and local destruction is suppressed.

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

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

Further, as the cord, a monofilament cord, a cord in which a plurality of filaments are twisted, or a hybrid cord in which filaments of different materials are twisted can be adopted. The number of cords driven is in the range of 20 to 60/50 mm, but it 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 the present embodiment, the reinforcing cords 18A and 18B The width (length) along the tire width direction is substantially the same, but the present invention is not limited to this configuration. For example, the reinforcing ply 18A is made narrower (shorter) or wider (longer) than the reinforcing ply 18B. You may. 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 can be 90% to 110% of the maximum width belt layer (belt ply 16B in this embodiment) having the largest width among the belt layers 16.

(tread)
In FIGS. 1 and 2, a tread 20 is provided on the outer side of the belt layer 16 and the reinforcing cord layer 18 in the tire radial direction. The tread 20 is a portion that comes into contact with 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. Further, the tread 20 is formed with a plurality of widthwise grooves (not shown) extending in the tire width direction through the circumferential groove 51. The shape and number of the circumferential groove 51 and the width direction groove are appropriately set according to the performance such as drainage property and steering stability required for the tire 10. Therefore, the width direction groove can be a lateral groove terminating in the sipe or rib-shaped land portion, or can be configured by combining these.

Further, in the present embodiment, the negative rate is the same in the tire half portion inside the vehicle mounting direction and outside the vehicle mounting direction with the equatorial plane CL as the boundary, but the embodiment of the present invention is not limited to this. .. For example, in the case of a tire with a designated mounting direction, a difference may be provided in the negative rate between the tire half portion inside the vehicle mounting direction and the outside of the vehicle mounting direction with the equator surface CL as a boundary.

Further, among the rib-shaped land portions, the shoulder rib-shaped land portion classified 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 has various configurations. Can be adopted. For example, in a tire in which the vehicle mounting direction is specified, the length of the shoulder rib-shaped land portion on the outside and inside of the mounting direction in the tire width 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 tire width direction length 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 outer end portion 20E of the tread 20 on the outer side of the tread 20 in the tire width direction and the point P on the tire equatorial plane CL of the tread 20 is reduced to a 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 in this range, the crown portion of the tire is flattened (flattened), the ground contact area is increased, the input (pressure) from the road surface is relaxed, and the deflection rate in the tire radial direction is increased. It can be reduced and the durability and wear resistance of the tire can be improved.

The tread rubber used for the tread 20 in the present embodiment has a single-layer structure, but the embodiment of the present invention is not limited 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. Further, the ratio of the thicknesses of the plurality of rubber layers in the tire radial direction may change in the tire width direction, and only the circumferential groove bottom or the like may be a rubber layer different from the periphery thereof.

Further, 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. Further, the ratio of the lengths of the plurality of rubber layers in the tire width direction may change in the tire radial direction, such as only in the vicinity of the circumferential groove, only in the vicinity of the tread end, only in the shoulder land portion, and only in the center land portion. It is also possible to make only a limited part of the area a rubber layer different from the surrounding area.

(Tread pattern)
FIG. 2 shows the structure of the tread surface of the tread 20 as a partially developed view. The tire 10 has a so-called mounting direction designation pattern in which the mounting direction is designated with respect to the vehicle, and in FIG. 2, the outside of the vehicle mounting is indicated by an arrow OUT and the inside of the vehicle mounting is indicated by an arrow IN.

The tire 10 extends in the tire circumferential direction to the tread of at least one tread half-width region of the pair of tread half-width regions bordered by the tire equatorial plane CL, or to the tread of the tread half-width region outside the vehicle mounting in the illustrated example. The outermost circumferential groove 51a (in the following description, it may be simply referred to as the circumferential groove 51a), the circumferential groove 51b, the shoulder portion circumferential sipe 52a extending in the tire circumferential direction, and the inner circumferential sipe 52b. It is provided.

The shoulder portion circumferential sipe 52a is arranged in the shoulder land portion 53a partitioned by the tread ground contact end TE and the outermost circumferential groove 51a, and the inner circumferential sipe 52b is inside the outermost circumferential groove 51a in the tire width direction. It is located on the inner land portion 53b adjacent to. In the present embodiment, the sipe means a narrow groove having a width that can be closed when it touches the ground, and is, for example, a width of 2 mm or less.

As described above, in the present embodiment, by providing the shoulder land portion 53a and the inner land portion 53b with circumferential sipes, the edge effect on the input in the tire width direction is enhanced, and the turning performance on snow is improved. ing.

Further, in the present embodiment, the sipe width of the shoulder portion circumferential sipe 52a is larger than the inner circumferential sipe 52b, and the sipe depth of the shoulder portion circumferential sipe 52a is smaller than the inner circumferential sipe 52b. It 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 are established.

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. The depth ds and the sipe depth di of the inner circumferential sipe 52b preferably satisfy 1.6 <di / ds <1.9. By setting the ratio of the sipe width to the sipe depth within this range, it is possible to obtain a good balance between snow performance and wear performance.

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

Further, as shown in FIG. 1, in the cross section in the tire width direction, the upper end portion 24B of the side reinforcing rubber 24 is located inside the tire width direction with respect to the shoulder portion circumferential direction sipe 52a. In the region where the side reinforcing rubber 24 and the shoulder land portion 53a overlap in the tire width direction, the contact pressure tends to be particularly large. Therefore, by providing the shoulder portion circumferential sipe 52a in this region, the edge effect can be further increased. be able to.

(Tire side part)
The tire side portion 22 extends in the tire radial direction to connect the bead portion 12 and the tread 20 so that the load acting on the tire 10 can be borne during run-flat running. Both end portions 22C of the tire side portion 22 in the tire width direction can be provided outside the bead base portion 12B in the tire radial direction in a range of 50% to 90% of the tire cross-sectional height SH.

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

(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 weights of the vehicle and the occupant when the internal pressure of the tire 10 is reduced due to a flat tire 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 contain other materials such as fillers, short fibers, and resins as long as the rubber material is the main component. Further, in order to enhance the durability during run-flat running, a rubber material having a hardness of 70 to 85 may be included as the rubber material constituting the side reinforcing rubber 24. Further, the loss coefficient tan δ measured using a viscoelastic spectrometer (for example, a spectrometer manufactured by Toyo Seiki Seisakusho) under the conditions of frequency 20 Hz, initial strain 10%, dynamic strain ± 2%, and temperature 60 ° C. is 0.10 or less. A rubber material having physical properties may be included. The hardness of rubber here refers to the hardness defined by JIS K6253 (Type A durometer).

Further, in the present embodiment, the side reinforcing rubber 24 containing rubber as a main component is used as an example of the side reinforcing layer of the present invention, but the present invention is not limited to this, and other materials having rubber-like elasticity (for example, A side reinforcing layer containing (such as a thermoplastic resin) as a main component may be used.

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

In the side reinforcing rubber 24, the lower end portion 24A on the bead portion 12 side overlaps with the bead filler 28 with the carcass 14 in between when viewed from the tire width direction, and the upper end portion 24B on the tread 20 side sandwiches the carcass 14 with the belt layer 16. And overlap when viewed 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 inside the end portion 16BE of the belt ply 16B in the tire width direction.

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

An inner liner 25 is arranged 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 containing butyl rubber as a main component is arranged, but the present invention is not limited to this, and another rubber material or an inner liner of a film layer containing resin as a main component is arranged. You may. It should be noted that the inner liner 25 may not be provided on the inner surface of the tire 10 because at least the inside of the tire side portion 22 is formed with low air permeability by the side reinforcing rubber 24.

Further, in order to reduce the cavity resonance sound, a porous member may be arranged on the inner surface of the tire 10 or electrostatic flocking may be performed. Further, the inner surface of the tire 10 may be provided with a sealant member for preventing air leakage during a puncture.

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

(Action)
Next, the operation and effect 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 set to WA ≦ 0.9 TW. There is. As a result, the overlapping range between the ground contact area of the tread and the side reinforcing rubber is increased. Further, the relationship between the maximum width B of the belt layer 16 (width of the belt ply 16B) and the ground contact width TW of the tread 20 is set to B / TW ≧ 1.0. As a result, the maximum width of the belt layer in the tire width direction is made larger than the ground contact width of the tread. With this setting, the flexural rigidity in the cross section at the ground contact end is increased, so that asymmetric deformation during run-flat running is suppressed. Further, since the ground contact portion on the lateral force input side is asymmetrically deformed during run-flat running and does not come out to the outside in the width direction in which the belt layer 16 does not exist, the increase in asymmetrical deformation is suppressed. Therefore, the durability during run-flat running can be improved.

Further, in the tire 10 of the present embodiment, the relationship between the contact width TW of the tread 20 and the maximum tire width W is set to 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 RW is set to TW / RW ≥ 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 becomes large, so that the ground contact position of the tread 20 becomes difficult to move to the outside in the tire width direction. Therefore, since the ground contact portion on the lateral force input side is asymmetrically deformed during run-flat running and does not come out to the outside in the width direction in which the belt layer 16 does not exist, the increase in asymmetrical deformation is suppressed.

Here, the asymmetric deformation will be briefly described. FIG. 3A is a cross-sectional view showing the case where there is no asymmetric deformation in the run-flat radial tire. Further, FIG. 3B is a cross-sectional view showing a case where the run-flat radial tire has asymmetric deformation.
In the run-flat radial tire shown in FIG. 4 (A), there is no asymmetric deformation, and the outward forces in the width direction generated at both ends of the ground contact portion are substantially balanced. On the other hand, in the run-flat radial tire shown in FIG. 4 (B), there is asymmetric deformation, and since there is no belt layer in the ground contact portion on the lateral force input side (right side of the paper surface), the width generated at both ends of the ground contact portion The force outward in the direction weakens, causing an imbalance.
As shown in FIG. 5, the asymmetric deformation amount (index) is such that the tire cross-sectional height sharply increases from around 140 mm.

10 ... Tire (run flat radial tire), 12 ... Bead part, 14 ... Carcass, 16 ... Belt layer, 20 ... Tread, 22 ... Tire side part, 24 ... Side reinforcing rubber, 24B ... Belt layer side end, 30 rims

Claims (8)

A carcass that straddles between a pair of bead parts,
A side reinforcing rubber provided on 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 of the carcass in the tire radial direction, having a cord extending in a direction inclined with respect to the tire circumferential direction, and the cords intersecting each other in the tire radial direction.
A tread provided on the outer side of the belt layer in the tire radial direction is provided.
The tire cross-sectional height is 145 mm or more,
A run-flat radial tire in which WA ≤ 0.9 TW, where WA is the distance between the belt layer side ends of the side reinforcing rubbers on both sides in the tire width direction and the ground contact width of the tread is TW. The run-flat radial tire according to claim 1, wherein the maximum width of the belt layer in the tire width direction is B, and B / TW ≧ 1.0. The run-flat radial tire according to claim 1 or 2, wherein the maximum tire width is W, and TW / W ≥ 0.5. The run-flat radial tire according to any one of claims 1 to 3, wherein the rim width is RW and TW / RW ≥ 0.7. Of the pair of tread half-width regions bordering the tire equatorial plane, the tread surface of at least one tread half-width region has an outermost circumferential groove and a circumferential groove extending in the tire circumferential direction, and a shoulder portion circumferential direction extending in the tire circumferential direction. Sipe and inner circumferential sipe are provided,
The shoulder peripheral sipe is arranged on the shoulder land portion defined by the tread ground contact end and the outermost circumferential groove.
The run-flat radial tire according to any one of claims 1 to 4, wherein the inner circumferential sipe is arranged in an inner land portion adjacent to the inner side of the outermost circumferential groove in the tire width direction. When the sipe width of the shoulder portion circumferential sipe is ws, the sipe depth is ds, the sipe width of the inner circumferential sipe is wi, and the sipe depth is di, ws> wi and ds <di. The run-flat radial tire according to claim 5. The sipe width ws and the sipe width wi satisfy 1.7 <ws / wi <2.1.
The run-flat radial tire according to claim 6, wherein the sipe depth ds and the sipe depth di satisfy 1.6 <di / ds <1.9. The run-flat according to any one of claims 5 to 7, wherein the upper end portion of the side reinforcing rubber is located inside the tire width direction with respect to the shoulder portion circumferential sipe in the tire width direction cross section. Radial tires.