JP2017210212A - Run-flat radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a run-flat radial tire with a relatively high tire cross section height, capable of enhancing run-flat durability while maintaining a riding comfort.SOLUTION: A run-flat radial tire comprises: a carcass 14 straddling between a pair of bead parts 12; a side reinforcing rubber 24 provided on a tire side part 22 extending in a tire radial direction along an internal surface of the carcass 14; and a belt layer 16 provided outside the carcass 14 in the tire radial direction. The run-flat radial tire has a tire cross section height SH of 145 mm or higher, and when assembled to a rim 30 (standard rim), applied with a standard air pressure, in no load state, a position where a thickness of the side reinforcing rubber 24 is greatest is arranged within a range between 0.1H and 0.7H from a reference point O along the carcass 14, where H is a length from the reference point, at which a line drawn from a maximum width position 22C of the tire in a tire width direction crosses the carcass 14, to an end of the tire width direction of the belt layer 16 along the carcass 14.SELECTED DRAWING: Figure 2

Description

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

  Patent Document 1 below discloses a side-reinforced run-flat tire in which a tire side portion is reinforced with 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 tire, in order to ensure durability during run flat running, it is conceivable to increase the thickness of the side reinforcing rubber. However, simply increasing the thickness of the side reinforcing rubber causes the ride comfort to deteriorate. In addition, the manufacturing cost increases.

  An object of the present invention is to improve run-flat durability while maintaining ride comfort in a run-flat radial tire having a relatively large tire cross-section height.

  A run-flat radial tire according to a first aspect of the present invention includes a carcass straddling 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, A belt layer provided on the outer side in the tire radial direction of the carcass, having a tire cross-section height of 145 mm or more, assembled to a standard rim, applied with standard air pressure, and in a no-load state, the tire from the tire maximum width position When the length along the carcass from the reference point where the straight line drawn along the width direction intersects the carcass to the tire width direction end of the belt layer is H, the thickness of the side reinforcing rubber is The maximum position is arranged in the range of 0.1H to 0.7H along the carcass from the reference point.

  When “longitudinal deflection / tire section height” is defined as “deflection rate” when there is no tire air pressure or when the run flat is low, this deflection rate is highly correlated with run flat durability.

  In this run-flat radial tire, the tire cross-section height is 145 mm or more, and the tire size is relatively large. Thus, in a tire having a high tire cross-section height, the tire maximum width position of the side reinforcing rubber greatly contributes to the longitudinal rigidity of the tire in a region where the absolute value of the vertical deflection is small (normal internal pressure). Therefore, by arranging the position where the thickness of the side reinforcing rubber becomes maximum in the range of 0.1H to 0.7H along the carcass from the reference point, the thickness of the side reinforcing rubber at the tire maximum width position is suppressed. In addition, the increase in longitudinal rigidity can be suppressed, and the riding comfort during normal internal pressure can be maintained.

  On the other hand, in the region where the absolute value of the vertical deflection is large (during run flat), the portion from the maximum tire width position to the end of the belt layer in the tire width direction of the side reinforcing rubber greatly contributes to the vertical rigidity of the tire. Therefore, by increasing the thickness of this portion to increase the longitudinal rigidity, it is possible to suppress the vertical deflection and the deflection rate, and to improve the run-flat durability.

  When the tire cross-section height is less than 145 mm, the absolute value of the vertical deflection becomes smaller even when the deflection rate necessary for run-flat durability is the same as compared with the case where the tire cross-section height is 145 mm or more. As a result, the contribution of the side reinforcing rubber in the vicinity of the maximum tire width position becomes large with respect to the longitudinal rigidity, regardless of whether it is a normal internal pressure or a run flat.

  According to a second aspect, in the run-flat radial tire according to the first aspect, the side reinforcing rubber extends to a position overlapping with the belt layer in a tire radial direction, and the side reinforcing rubber at the tire maximum width position. G1 ≦ 0.8G, where G is the gauge of the side reinforcing rubber in the normal direction to the carcass at the end of the belt layer in the tire width direction.

  In this run-flat radial tire, the side reinforcement rubber extends to a position where it overlaps the belt layer in the tire radial direction, so that the bending rigidity of the tire near the end of the belt layer in the tire width direction is increased and rim removal is less likely to occur. Can do. Moreover, run-flat durability can be improved by appropriately setting the thickness of the side reinforcing rubber at the tire width direction end of the belt layer. If G1> 0.8G, the durability of the side reinforcing rubber at the end of the belt layer in the tire width direction is lowered.

  A third aspect is the run flat radial tire according to the first aspect or the second aspect, wherein B is a length along the carcass from the reference point to a bead core provided in the bead part. When the gauge of the side reinforcing rubber in the normal direction to the carcass at a position 0.2B from the reference point is G2, 0.5G ≦ G2 ≦ 0.9G.

  In this run flat radial tire, run flat durability can be improved by appropriately setting the thickness of the side reinforcing rubber on the bead portion side from the tire maximum width position. Below the lower limit of this range, there is a concern about failure at the end of the bead filler extending from the bead core to the tire radial direction along the carcass. If the upper limit of this range is exceeded, the longitudinal rigidity increases and the riding comfort deteriorates.

  A fourth aspect is the run flat radial tire according to any one of the first to third aspects, wherein a bead interval along the tire width direction before being assembled to the standard rim is formed larger than the standard rim width, A value obtained by dividing a difference between the bead interval before being assembled to the standard rim and the bead interval after being assembled to the standard rim by the tire cross-sectional height is larger than 0.06 and smaller than 2.00.

  In this run-flat radial tire, the bead interval before assembling to the standard rim is formed larger than the bead interval after assembling to the standard rim, so that when the tire is assembled to the rim, the bead portions approach each other. Is deformed. At this time, the side reinforcing rubber provided along the inner surface of the carcass is compressed, and the compressive stress in the range from 0.1H to 0.7H from the reference point, that is, the portion from the shoulder of the tire side portion, is the other portion. Compared to The side reinforcing rubber is formed so that the thickness of the side reinforcing rubber is maximized in the portion where the compressive stress increases. For this reason, the position where the thickness of the side reinforcing rubber is maximized is the volume of the portion where the compressive stress is large as compared with the tire arranged outside the range of 0.1H to 0.7H along the carcass from the reference point. Is big. Accordingly, the support load is increased and the durability during run-flat traveling is improved. The standard rim width is a dimension that substantially matches the bead interval after being assembled to the standard rim.

  Comparing a tire to which the non-compressed side reinforcing rubber is applied with a tire to which the compressed side reinforcing rubber is applied, the tire to which the compressed side reinforcing rubber is applied is the non-compressed side reinforcing rubber. Longitudinal deflection for the same load is reduced in the absence of or low tire pressure than the applied tire. In other words, if the tire to which the compressed side reinforcing rubber is applied and the tire to which the uncompressed side reinforcing rubber is applied are bent by the same amount, the tire to which the compressed side reinforcing rubber is applied is The load which can be supported becomes larger than the tire to which the side reinforcing rubber in the compressed state is applied.

  For this reason, durability at the time of run-flat driving can be improved without increasing the tire weight by increasing the thickness of the side reinforcing rubber, for example. Therefore, it is possible to ensure durability during run-flat running while suppressing an increase in tire weight.

  In addition, since the ratio of the change in the bead interval before and after assembly to the standard rim with respect to the tire cross-section height is greater than 6%, the side reinforcement rubber after assembly of the rim is smaller than that of a tire having the ratio of 6% or less. , Receive greater compressive force. Therefore, durability during run flat traveling is improved. Note that the bead interval and the standard rim width after being assembled to the standard rim substantially coincide with each other.

  Also, since the rate of change in the bead interval before and after assembly to the standard rim with respect to the tire cross-section height is less than 200%, the required performance is maintained compared to tires with this rate of change of 200% or more. It is easy to ensure the shape at the time of internal pressure (shape when standard air pressure is applied).

  According to a fifth aspect, in the run flat radial tire according to any one of the first to fourth aspects, a bead interval along the tire width direction before being assembled to the standard rim is 105% or more of the standard rim width. Less than 270%.

  In this run-flat radial tire, the bead interval along the tire width direction before being assembled to the standard rim is 105% or more of the standard rim width. For this reason, compared with a tire whose ratio is less than 105%, the side reinforcing rubber after being assembled to the standard rim is subjected to a larger compressive force. Therefore, durability during run flat traveling is improved.

  Further, the bead interval before assembling to the standard rim is less than 270% of the standard rim width. For this reason, it is easy to ensure the shape at the time of internal pressure that maintains the required performance (the shape when the standard air pressure is applied) compared to a tire in which this ratio is 270% or more of the standard rim width.

  Further, when the tire is deformed in the direction in which the bead portion approaches when assembling the tire to the rim, the range from 0.1H to 0.7H from the reference point, that is, the portion from the shoulder of the tire side portion is different from the other portions. In comparison, the compressive stress increases.

  In the run flat radial tire, the side reinforcing rubber is formed so that the thickness of the side reinforcing rubber is maximized at a portion where the compressive stress is increased. For this reason, the position where the thickness of the side reinforcing rubber is maximized is the volume of the portion where the compressive stress is large as compared with the tire arranged outside the range of 0.1H to 0.7H along the carcass from the reference point. Is big. Accordingly, the support load is increased and the durability during run-flat traveling is improved.

  ADVANTAGE OF THE INVENTION According to this invention, run flat durability can be improved, maintaining riding comfort in the run flat radial tire with comparatively large tire cross-section height.

1 is a half cross-sectional view showing one side of a cut surface of a run flat radial tire according to an embodiment of the present invention cut along a tire width direction and a tire radial direction in a state before being assembled to a rim. 1 is a half cross-sectional view showing one side of a cut surface cut along a tire width direction and a tire radial direction in a state after a run-flat radial tire according to an embodiment of the present invention is assembled to a rim. It is a partial expanded view which shows the structure of the tread surface. It is a stress distribution figure showing an internal stress state after attaching a run flat radial tire concerning an embodiment of the present invention to a rim. It is the graph which showed the relationship between each vertical deflection | deviation and support load of the pre-compressed run-flat radial tire which concerns on embodiment of this invention, and the run-flat radial tire which is not pre-compressed. It is a density distribution figure showing contribution of the increment of the support load after attaching the run flat radial tire concerning the embodiment of the present invention to a rim. It is the graph which showed the change rate of the run flat durability of the run flat radial tire which concerns on embodiment of this invention, and the reduction rate of rolling resistance.

  Hereinafter, an embodiment of a run flat radial tire of the present invention will be described with reference to the drawings. 1 and 2, a cut surface (direction along the tire circumferential direction) cut along the tire width direction and the tire radial direction of the run-flat radial tire (hereinafter referred to as “tire 10”) of the present embodiment. One side of the cross section viewed from FIG. 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”.

  The dimensions of each part of the tire 10 are measured in an unloaded state by assembling the tire 10 to a standard rim (for example, the rim 30), applying a standard air pressure.

(tire)
FIG. 1 shows the tire 10 before being assembled (attached) to the rim 30, and FIG. 2 shows the tire 10 when being assembled to the rim 30 and filled with standard air pressure. The rim 30 is a standard rim. Here, the “standard rim” refers to a rim stipulated in the year 2015 version of JATMA (Japan Automobile Tire Association). The standard air pressure is an air pressure corresponding to the maximum load capacity of the Year Book 2015 version of JATMA (Japan Automobile Tire Association).

  In the following explanation, the load is the maximum load (maximum load capacity) of a single wheel at the applicable size described in the following standard, and the internal pressure is the maximum load of a single wheel described in the following standard. The rim refers to a standard rim (or “Applied Rim” or “Recommended Rim”) in an applicable size described in the following standard. 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 Tire and Rim Association Inc. Year Book”, in Europe “The European Tire and Rim Technical Standards Standards” in the Japan Automobile Association of Japan Has been.

  As shown in FIGS. 1 and 2, the tire 10 includes a carcass 14 straddling a pair of bead portions 12 and a tire side portion 22, and a side reinforcing rubber that extends in the tire radial direction along the inner surface of the carcass 14. 24 and a belt layer 16 provided outside the carcass 14 in the tire radial direction. 1 and 2, 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 lower portion 22A on the bead portion 12 side and a sidewall upper portion 22B on the tread 20 side, and connects the bead portion 12 and the tread 20.

  The tire cross-section height (section height) SH of the tire 10 is set to 145 mm or more and 500 mm or less. More preferably, the tire cross-section height SH is 250 mm or less. The “tire cross-section height SH” herein refers to a length that is ½ of the difference between the tire outer diameter and the rim diameter D2 when the tire 10 is assembled to the rim 30 and the internal pressure is set to the standard air pressure. . Further, the “tire outer diameter” is a distance from a point P on the tire equatorial plane CL of the tread 20 (see FIG. 2) to a similar point P 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).

  The tire size of the tire 10 is, for example, 235 / 65R17, but is not limited thereto, and may be, for example, 245 / 60R18, 255 / 65R18, 235 / 65R18, 215 / 70R16, or the like.

(Bead part)
As shown in FIG. 2, 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.

  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. 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.

  When viewed from the direction along the tire circumferential direction, the bead interval WB1 before being assembled to the rim 30 is formed larger than the bead interval WB2 after being assembled to the rim 30. A value obtained by dividing the difference between the bead interval WB1 and the bead interval WB2 by the tire cross-section height SH is larger than 0.06 and smaller than 2.00. That is, the following expression (1) is satisfied.

  0.06 <(WB1-WB2) / SH <2.00 (1)

  The bead interval WB2 after being assembled to the rim 30 is a straight portion (straight portion perpendicular to the tire width direction) extending in the tire radial direction in the rim flange portion 30F in a state where the tire 10 is assembled to the rim and filled with standard air pressure. ) Is the distance between the intermediate points BE facing each other across the tire equatorial plane CL, and substantially coincides with the standard rim width RW. Here, the rim flange portion 30F is a portion in which the width in the tire radial direction is indicated by D3 between the portion indicated by the flange diameter D1 and the portion indicated by the rim diameter D2 in FIG.

  Further, when a place where a point corresponding to the intermediate point BE is located before the rim assembly of the tire 10 is a point BE1, a bead interval WB1 before the assembly to the rim 30 is a point BE1 that faces the tire equatorial plane CL across the tire equator CL. Distance.

  Furthermore, WB1 is 105% or more and less than 270% of WB2. That is, the expression (2) is satisfied.

  1.05WB2 ≦ WB1 <2.70WB2 (2)

In addition, in this embodiment, it is set as the structure with which (1) Formula and (2) Formula hold | maintain. Specifically, WB1 = 218 mm, WB2 = 178, and SH = 152.4, and 0.06 <(WB1-WB2) /SH=0.26 <2.00, and the formula (1) is established. Further, 1.05WB2 = 186.9 ≦ WB1 = 218 <2.70WB2 = 480.6, and Equation (2) is established.

  In the present embodiment, as described above, the bead interval WB2 after being assembled to the rim 30 substantially matches the standard rim width RW. Therefore, the bead interval WB1 before the tire 10 is assembled to the rim 30 is formed larger than the standard rim width RW.

  The bead interval WB1 before assembling the tire 10 to the rim 30 is in a standard state (standard temperature 23 ± 2 ° C., standard humidity 50 ± 10%, standard air pressure) with the tire axial direction being the vertical direction after the tire is molded. 86-106 kPa) and is measured after standing for 3 days or more.

(Carcass)
The carcass 14 includes two carcass plies 14A and 14B. The carcass ply 14A is a carcass ply disposed on the outer side in the tire radial direction on the tire equatorial plane CL, and the carcass ply 14B is a carcass ply disposed on the inner side in the tire radial direction. Each of the carcass plies 14A and 14B is formed by covering a plurality of cords with a covering rubber.

  The carcass 14 formed in this way extends in a toroidal form from one bead core 26 to the other bead core 26 to constitute 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, the end portion side of the carcass 14 may not be folded back, and may be sandwiched between a plurality of bead cores 26, or a structure wound around the bead cores 26 may be employed.

  The tire radial direction position (reference point O) at which the width of the carcass 14 is maximum when the tire 10 is assembled to the rim 30 and the internal pressure is set to the standard air pressure may be formed near the bead portion 12 or the tread. It may be formed closer to 20. For example, the tire radial direction position where the width of the carcass 14 is maximum can be provided in the tire radial direction outer side from the bead base portion 12B shown in FIG. 2 in a range of 50% to 90% in comparison with the tire cross-section height SH. . The bead base portion 12B corresponds to the position of the rim diameter D2.

  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.

(Belt layer)
A belt layer 16 is 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 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, when the width (length) along the tire width direction of the largest width inclined belt layer, that is, the belt ply 16B, is BW, BW is 90% or more and 115% or less of the tread width TW. 100% or more and 105% or less is more preferable.

  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 inclined belt layer, the shape of the ground contact surface during turning tends to be distorted, so that the cords of two or more layers extend in the direction of crossing each other. It is preferable to use an inclined belt layer. 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 possible to adopt a cord in which filaments of different materials are twisted 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 adopted.

(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 constituted by two reinforcing plies 18A and 18B. The reinforcing ply 18A is disposed on the outer side in the tire radial direction in the reinforcing cord layer 18. The reinforcement ply 18B is disposed on the inner side in the tire radial direction of the reinforcement ply 18A. 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 of the reinforcing cord layer 18 can be 90% to 110% of the width B of the maximum width inclined belt layer (belt ply 16B in the present embodiment) having the largest width among the belt layers 16. The reinforcing cord layer 18 may be provided only at both ends of the belt layer 16 in the tire width direction (portions corresponding to the shoulder portions of the tread 20).

(tread)
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 a and 51 b 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) that communicate with the circumferential grooves 51a and 51b and extend in the tire width direction. The shape and the number of the circumferential grooves 51a and 51b 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 on the outer side of the vehicle mounting direction with the tire equatorial plane CL as a boundary, but the embodiment of the present invention is limited to this. Absent. 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 vehicle mounting direction inside and the vehicle mounting direction outside on the tire equator plane CL.

  Of the rib-shaped land portions, various configurations are provided for the shoulder rib-shaped land portions that are divided by the outermost circumferential groove 51a in the tire width direction and the tire width direction end portion (the 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, when the distance in the tire radial direction between the tread 20 outer tread 20 outer end portion 20E in the tire width direction and the point P on the tire equatorial plane CL of the tread 20 tread 20 is reduced to a high TH. The falling height TH is preferably set to 4.5% or less of the tread width TW. 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.

  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. 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. 3, 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. 3, 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. 3, 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 TE. 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.

  As shown in FIG. 2, the upper end portion 24 </ b> B of the side reinforcing rubber 24 is positioned on the inner side in the tire width direction than the shoulder portion circumferential sipe 52 a in the tire width direction cross section. 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.

  As shown in FIG. 2, the upper end portion 24 </ b> B of the side reinforcing rubber 24 is located on the outer side in the tire width direction with respect to the outermost circumferential groove 51 a in the cross section in the tire width direction. That is, the side reinforcing rubber 24 does not exist on the inner side in the tire radial direction of the groove bottom of the outermost circumferential groove 51a, so that the tread starts from the groove bottom of the outermost circumferential groove in the tire width direction during run flat running. Even if it bends in the cross section, it can suppress that the input accompanying the bending of this tread acts on the side reinforcement rubber 24. FIG. Thereby, durability of the side reinforcement rubber 24 at the time of run flat traveling is improved.

(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.

  The tire side portion 22 may be provided with a turbulent flow generation projection (not shown). In this case, since the tire side portion 22 is cooled by the turbulent flow generated by the turbulent flow generation projection, 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 22. Further, in the case of a tire with a mounting direction designated, it is possible to provide a turbulent flow generation projection only on one side of the pair of tire side portions 22. Further, by providing dimples (not shown) on the tire side portion 22 and increasing the surface area to increase heat dissipation, the run-flat running performance can be further improved.

(Side reinforcement rubber)
A side reinforcing rubber 24 for reinforcing the tire side portion 22 is provided on the inner side in the tire width direction of the carcass 14 in the tire side portion 22. The side reinforcing rubber 24 is a reinforcing rubber for running 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. The rubber hardness here refers to the hardness defined by JIS K6253 (type A durometer). 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 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. The thickness of the side reinforcing rubber 24 here refers to the length along the normal line of the carcass 14.

  In the tire 10, a straight line WL drawn along the tire width direction from the tire maximum width position (both end portions 22 </ b> C in the tire width direction of the tire side portion 22) is attached to the rim 30, applied with standard air pressure, and unloaded. The length along the carcass 14 from the reference point O where the carcass 14 intersects to the end of the belt layer 16 in the tire width direction is defined as H. In this case, the position where the thickness of the side reinforcing rubber 24 becomes maximum is arranged in a range (region A) from 0.1H to 0.7H along the carcass 14 from the reference point O.

  A lower end portion 24A of the side reinforcing rubber 24 on the bead portion 12 side overlaps the bead filler 28 as viewed from the tire width direction with the carcass 14 interposed therebetween. The upper end portion 24B on the tread 20 side of the side reinforcing rubber 24 extends to a position overlapping the belt layer 16 in 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. In other words, 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. In addition, when the width (length) along the tire width direction of the belt ply 16B is BW, the overlapping width in which the upper end portion 24B of the side reinforcing rubber 24 overlaps the belt ply 16B is an end in one tire width direction. It is set to 0.15 BW or more on the part side.

  The gauge of the side reinforcing rubber 24 at the tire maximum width position is G, and the gauge of the side reinforcing rubber 24 in the normal direction to the carcass 14 at the tire width direction end of the belt layer 16 (end portion 16BE of the belt ply 16B). Is G1, G1 ≦ 0.8G.

  Here, if G1> 0.8G, the durability of the side reinforcing rubber 24 at the position of the end of the belt layer 16 in the tire width direction is lowered.

  The length along the carcass 14 from the reference point O to the bead core 26 provided in the bead portion 12 is B, and the side reinforcing rubber 24 in the normal direction to the carcass 14 at a position 0.2B from the reference point O. When G2 is G2, 0.5G ≦ G2 ≦ 0.9G.

  If the lower limit of this range is not reached, there is a concern about failure at the end of the bead filler extending from the bead core to the tire radial direction along the carcass 14. If the upper limit of this range is exceeded, the longitudinal rigidity increases and the riding comfort deteriorates. “Up to the bead core 26” means up to the center of the bead core 26.

  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 this 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 the inner liner 25 of a film layer mainly composed of other rubber material or resin is disposed. You may set up. Of the inner surface of the tire 10, at least the inner side of the tire side portion 22 is formed with a low side air permeability by the side reinforcing rubber 24, and therefore the inner liner 25 may not be provided.

  Furthermore, a porous member can be arranged 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. However, the present invention is not limited to this, and a rim guard may be provided.

(Action / Effect)
Next, functions and effects of the tire 10 of the present embodiment will be described. When “longitudinal deflection / tire section height” at the time when the tire 10 has no air pressure or is low in flat run is defined as “deflection rate”, this deflection rate is highly correlated with run flat durability.

  In the tire 10, the tire cross-section height SH is 145 mm or more, and the tire size is relatively large. In such a tire having a high tire cross-section height SH, the tire maximum width position of the side reinforcing rubber 24 (the tire side portion) with respect to the longitudinal rigidity of the tire 10 in a region where the absolute value of the vertical deflection is small (normally at the internal pressure). The vicinity of 22 end portions 22C) in the tire width direction greatly contributes. Therefore, the position where the thickness of the side reinforcing rubber 24 is maximum is arranged in the range of 0.1H to 0.7H along the carcass 14 from the reference point O, and the thickness of the side reinforcing rubber 24 at the tire maximum width position is set. By suppressing, increase of the longitudinal rigidity at the time of normal internal pressure of the tire 10 is suppressed, and riding comfort at the time of normal internal pressure can be maintained.

  On the other hand, in the region where the absolute value of the vertical deflection is large (during run flat), the end of the belt layer 16 in the tire width direction (the belt ply 16B of the belt ply 16B) from the maximum tire width position of the side reinforcing rubber 24 with respect to the vertical rigidity of the tire 10. The space up to the end 16BE) greatly contributes. Therefore, by increasing the thickness of this portion to increase the longitudinal rigidity, it is possible to suppress the vertical deflection and the deflection rate, and to improve the run-flat durability.

  When the tire cross-section height SH is less than 145 mm, the absolute value of the vertical deflection becomes smaller even when the deflection rate necessary for the run-flat durability is the same as compared with the case where the tire cross-section height SH is 145 mm or more. As a result, the contribution of the side reinforcing rubber 24 in the vicinity of the maximum tire width position becomes large with respect to the longitudinal rigidity regardless of whether it is a normal internal pressure or a run flat.

  In the tire 10, since the side reinforcing rubber 24 extends to a position where it overlaps the belt layer 16 in the tire radial direction, the vicinity of the end of the belt layer 16 in the tire width direction, for example, 14 at the tire cross-section height SH from the end in the tire axial direction. It is possible to increase the bending rigidity of the tire 10 at a position on the inner side in the tire axial direction by% and to prevent the rim from coming off. Moreover, run-flat durability can be improved by appropriately setting the thickness (gauge G1) of the side reinforcing rubber 24 at the end in the tire width direction of the belt layer 16 (end 16BE of the belt ply 16B).

  Furthermore, in the tire 10, the run flat durability is achieved by appropriately setting the thickness (gauge G <b> 2) of the side reinforcing rubber 24 on the bead portion 12 side from the tire maximum width position (the tire width direction both ends 22 </ b> C of the tire side portion 22). Can be improved.

  Next, in the tire 10 of the present embodiment, the distance WB1 between the bead portions 12 (the distance between the points BE1 facing each other across the tire equatorial plane CL in FIG. 2) before the tire 10 is assembled to the rim 30 is assembled to the rim 30. Is formed larger than the bead interval WB2 (distance between the intermediate points BE). That is, the tire 10 is assembled to the rim 30 while being deformed in the tire width direction. At this time, as shown in FIG. 4, a compressive stress is generated in the tire side portion 22. The hatched density shown in FIG. 4 indicates the magnitude of the compressive stress, and the higher the density, the greater the compressive stress. In the following description, a state in which a compressive force is applied to the tire before the load is applied and a compressive stress is generated as an internal stress of the tire is referred to as “pre-compression”. Or, it is also referred to as “pre-compressed”.

  As shown in FIG. 4, in a state where the tire 10 is assembled to the rim 30, compressive stress is concentrated on the sidewall upper portion 22 </ b> B on the tread 20 side of the tire side portion 22. Specifically, in the region A (see FIG. 2) in which the length along the carcass 14 from the reference point O to the side reinforcing rubber 24 is 0.1H to 0.7H, a portion having a large compressive stress is concentrated. ing.

  Here, the support load Fz of the tire during the run-flat running is roughly expressed as the equation (3) in relation to the stress σ inside the tire.

  In the equation (3), (dε / dz) indicates a strain change per change in the vertical deflection of the tire, and V indicates a volume of the tire. Therefore, the right side of equation (3) disassembles the tire into minute parts, multiplies “stress” by “distortion change per unit vertical deflection” and “volume” for each part, and adds these to the whole tire. The combined value is shown. Note that vertical deflection is the amount of deformation that causes the tire to deform along the vertical direction when a load is applied along the vertical direction (the vertical direction when the tire is mounted on the rim and filled with standard air pressure). It shows that.

  As shown in the equation (3), when the absolute value of the compressive stress σ inside the tire increases, the support load Fz during run-flat traveling increases. The tire 10 of the present embodiment is deformed in the tire width direction in a state where it is assembled to the rim 30, so that a compressive force is preliminarily applied (precompressed) to the side reinforcing rubber and the absolute value of the internal compressive stress σ is large. It has become. For this reason, the support load Fz at the time of run-flat traveling is larger than the tire in which the compression force is not applied in advance (there is no pre-compression) in the compression stress and the compression strain of the side reinforcing rubber that greatly contributes to the support load. .

  In FIG. 5, the relationship between the vertical deflection of a tire to which a compression force has not been applied in advance (no pre-compression) and the support load is indicated by a dotted line. Further, the relationship between the vertical deflection of a tire to which a compression force has been applied in advance (there is pre-compression) and the support load is shown by a solid line.

  Comparing a tire without pre-compression with a tire with pre-compression, a tire with pre-compression has a greater support load for the same vertical deflection than a tire without pre-compression. In other words, comparing a tire without pre-compression with a tire with pre-compression, a tire with pre-compression has less vertical deflection for the same support load than a tire without pre-compression.

  In the present embodiment, the tire cross-section height SH of the tire 10 is 145 mm or more, the deformation amount (WB1-WB2) of the tire 10 in the tire width direction before and after the tire 10 is assembled to the rim 30, and the tire cross-section. Equation (1) holds between the height SH. Further, the formula (2) is established between the bead interval WB1 before the tire 10 is assembled to the rim 30 and the bead interval WB2 after the tire 10 is assembled to the rim 30.

  That is, in the tire 10 that is a run-flat radial tire having a tire cross-section height SH larger than that of a general run-flat radial tire, the amount of deformation in the tire width direction before and after assembly to the rim 30 is large. . For this reason, in a run-flat radial tire having a large tire cross-section height SH that particularly requires durability during run-flat running, durability during run-flat running is improved.

  Moreover, in a general run flat radial tire, when the deformation amount (WB1-WB2) of the tire 10 in the tire width direction before and after the tire 10 is assembled to the rim 30 is large, it may be difficult to assemble the rim. Since the tire cross-section height SH is 145 mm or more, the tire 10 is relatively easily deformed and can be easily assembled with a rim.

  In the present embodiment, the expression (1) is established between the deformation amount (WB1-WB2) of the tire 10 in the tire width direction before and after the tire 10 is assembled to the rim 30 and the tire cross-section height SH. Although equation (2) is established between WB1 and WB2, the embodiment of the present invention is not limited to this. For example, it can be configured such that only one of the formulas (1) and (2) is established. Or, the left side of the formula (1), that is, the configuration in which only the following formula (4) is satisfied, the left side of the formula (2), that is, the configuration in which only the following formula (4) is satisfied, and the formulas (5) and (4) It is possible to adopt a configuration in which both hold.

(WB1-WB2) / SH> 0.06 (4)

WB1 ≧ 1.05WB2 (5)

  Or when none of (1) Formula-(5) Formula is materialized, it can also comprise so that only (6) Formula may be satisfied according to the durability at the time of the required run flat driving | running | working.

0 <(WB1-WB2) (6)

  In this way, if the tire 10 is configured to satisfy the expression (6), the tire 10 is deformed in the tire width direction and assembled to the rim 30, so that a compressive stress is generated in the tire side portion 22, and run flat Durability during running is improved. Further, the tire 10 can be easily assembled to the rim 30.

Note that when the tire 10 is precompressed to change the bead interval, the curvature of the tire side portion 22 changes. The compressive stress generated in the tire side portion 22 changes according to the curvature change amount. Since the curvature change amount is proportional to (WB1-WB2) / (SH) ² , when the tire cross-section height SH increases, the curvature change amount decreases and the compressive stress also decreases (correlation 100).

  On the other hand, since the thickness of the side reinforcing rubber 24 is increased in a tire having a large tire cross-section height SH, a large compressive stress is generated with respect to the same curvature change. That is, as the tire cross-section height SH increases, the compressive stress increases (correlation 200).

  In the tire 10 of the present embodiment, the pre-compression effect is obtained as in the equations (1), (4), and (6) in consideration of the correlations 100 and 200 regarding the tire cross-section height SH and the compressive stress. (WB1-WB2) / SH or (WB1-WB2) is used as an index of.

  In FIG. 6, the contribution of incremental support load after the tire 10 is assembled to the rim 30 is shown. The hatched density shown in FIG. 6 indicates the magnitude of the increment of the support load, and the higher the density, the greater the increment of the support load. In the state where the tire 10 is assembled to the rim 30, the increment of the support load is large at the sidewall upper portion 22 </ b> B on the tread 20 side of the tire side portion 22. Specifically, in the region A (see FIG. 2) where the length along the carcass 14 from the reference point O of the side reinforcing rubber 24 is 0.1H to 0.7H (see FIG. 2), the increase in the support load becomes large. Yes.

  Furthermore, since the compressive force is applied to the side reinforcing rubber 24 in advance (there is pre-compression), the vertical deflection of the tire 10 when a load is applied is less than when there is no pre-compression. For this reason, the rolling resistance at the time of the normal running before the run-flat running is reduced. Further, since the vertical deflection is small, the heat generation of the side rubber is reduced during run flat running, and the durability during run flat running is improved.

  FIG. 7 shows a graph comparing the performance of a plurality of run-flat radial tires that have been pre-compressed in the same manner as the embodiment of the tire 10 described above, with a run-flat radial tire that has not been pre-compressed. As shown in FIG. 7, the pre-compressed run-flat radial tire has a run-flat durability of about 4% to 52% and an average of about 27% higher than that of the non-pre-compressed run-flat radial tire. ing. In addition, the pre-compressed run-flat radial tire has a rolling resistance of about 2% to 5.3% and an average of about 3.1% less than that of a non-pre-compressed run-flat radial tire. doing. For this reason, fuel efficiency during normal driving is improved. Thus, the tire 10 according to the embodiment of the present invention has improved durability during run-flat travel and improved travel performance during normal travel. The durability during run flat running is measured by the running distance of the run flat durable drum according to the ISO conditions. Further, the rolling resistance during normal running is measured by a smooth drum and force type in accordance with ISO18164.

[Other Embodiments]
In the above embodiment, the gauge G of the side reinforcing rubber 24 at the tire maximum width position and the gauge G1 of the side reinforcing rubber 24 at the end of the belt layer 16 in the tire width direction are such that G1 ≦ 0.8G. The size of the gauge G1 is not limited to this.
Further, the gauge G2 of the side reinforcing rubber 24 in the normal direction to the carcass 14 at a position 0.2B from the reference point O toward the bead portion 12 is assumed to be 0.5G ≦ G2 ≦ 0.9G. The size of the gauge G2 is not limited to this.

DESCRIPTION OF SYMBOLS 10 ... Tire (run flat radial tire), 12 ... Bead part, 14 ... Carcass, 16 ... Belt layer, 22 ... Tire side part, 22C ... Tire maximum width position, 24 ... Side reinforcement rubber, 30 ... Rim (standard rim) , O ... Reference point, WB1 ... Bead interval before assembling to standard rim, WB2 ... Bead interval after assembling to standard rim, RW ... Standard rim width

Claims (5)

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;
A belt layer provided on the outer side in the tire radial direction of the carcass;
With
The tire cross-section height is 145 mm or more,
At the end of the belt layer in the tire width direction from a reference point where the carcass intersects with a straight line drawn along the tire width direction from the tire maximum width position in a no-load state, assembled to a standard rim Until the length along the carcass is H,
A run-flat radial tire in which the position where the thickness of the side reinforcing rubber is maximum is disposed in a range of 0.1H to 0.7H along the carcass from the reference point. The side reinforcing rubber extends to a position overlapping the belt layer and the tire radial direction,
When the gauge of the side reinforcing rubber at the tire maximum width position is G, and the gauge of the side reinforcing rubber in the normal direction to the carcass at the end of the belt layer in the tire width direction is G1, G1 ≦ 0. The run-flat radial tire according to claim 1, wherein the run-flat radial tire is .8G.   The length along the carcass from the reference point to the bead core provided in the bead portion is B, and the side reinforcing rubber in the normal direction to the carcass at a position 0.2B from the reference point The run-flat radial tire according to claim 1 or 2, wherein 0.5G≤G2≤0.9G, where G2 is a gauge. The bead interval along the tire width direction before being assembled to the standard rim is formed larger than the standard rim width,
A value obtained by dividing a difference between the bead interval before being assembled to the standard rim and the bead interval after being assembled to the standard rim by the tire cross-sectional height is larger than 0.06 and smaller than 2.00. The run-flat radial tire according to any one of claims 1 to 3.   The run-flat radial tire according to any one of claims 1 to 4, wherein a bead interval along the tire width direction before being assembled to the standard rim is 105% or more and less than 270% of the standard rim width. .