JP2016097831A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compatibly attain run-flat durability performance and ride comfort performance.SOLUTION: In an unloaded state in which a tire is assembled into a normal rim at normal inner pressure, a sectional height from a tire maximum width section H to a tire outer diameter D is defined as a and a sectional height from the tire maximum width section to a bead toe 53 is defined as b. In a 65% loaded state of normal load in which the tire is assembled into the normal rim at inner pressure 0kPa, a sectional height from the tire maximum width section H to the tire outer diameter D is defined as a' and a sectional height from the tire maximum width section to the bead toe 53 is defined as b'. At the time, a deformation ratio of (1-a'/a) is larger than a deformation ratio of (1-b'/b) in the sectional height.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire capable of run-flat running.

  Pneumatic tires are mounted on a rim that is mounted on a rim and filled with air. The pneumatic tires receive the load when the vehicle travels, but the air inside the pneumatic tires leaks due to puncture etc. It becomes difficult to receive a load. That is, since the load supported by the air pressure is supported by the sidewall portion, the sidewall portion is greatly deformed, and traveling becomes difficult.

  Therefore, as a pneumatic tire capable of running in the state where air leaks due to puncture, so-called run-flat running, reinforcing rubber is provided inside the sidewall to improve the bending rigidity of the sidewall. It has been. That is, even when air filled in the pneumatic tire leaks and a large load acts on the sidewall, the vehicle can travel by suppressing the deformation of the sidewall.

  Conventionally, for example, the pneumatic tire described in Patent Document 1 aims to increase the safety of a vehicle while preventing a decrease in high-speed durability performance and steering stability in a run-flat state so as to be able to travel a relatively long distance. It is said. This pneumatic tire is provided with an inner reinforcing layer extending from the inner surface of the sidewall portion to the inner surface of the bead portion and the inner surface of the tread portion, and the total thickness TA of the sidewall upper region S of the sidewall portion is set between the bead portion and the rim. The total thickness TC of the contact position C where the upper end of the flange contacts is smaller than 17% and 26% or less of the tire cross-section height, and the total thickness of the region S on the sidewall The length TA is 15% or more and 22% or less of the tire cross-section height.

  In addition, for example, the run flat tire described in Patent Document 2 aims to ensure ride comfort while improving steering stability during run flat travel. This run-flat tire includes a reinforcing rubber layer having a crescent-shaped cross section along the tread width direction and the tire radial direction over a sidewall portion continuous with the tread portion, and the reinforcing rubber layer is provided on the outer side in the tire radial direction. An elastic reinforcing layer and a low elastic reinforcing layer having a lower elastic modulus than the high elastic reinforcing layer, and the length from the tire equator line to the end of the tread along the tread width direction is used as a reference in the tread width direction. When assuming a virtual line passing through a position corresponding to 1.2 times the length from the tire equator line to the end of the tread portion and perpendicular to the carcass, the highly elastic reinforcing layer is a reinforcing rubber layer. The low elastic reinforcement layer is provided in the entire region extending from the inner end of the tread width direction to the imaginary line. Provided on the inner side in the tire radial direction.

  In addition, for example, the run flat tire described in Patent Document 3 is intended to enhance the ride comfort during normal traveling without impairing the run flat durability. This run-flat tire is provided with side reinforcing rubber having a substantially crescent-shaped cross section disposed in the side wall region Y and in the tire axial direction of the carcass, is assembled to a normal rim, is filled with a normal internal pressure, and is unloaded. In the tire meridian cross section including the tire rotation axis in the normal state, the sidewall portion has the thickness W1 of the belt layer at the outer end position in the tire axial direction, the thickness W3 at the tire maximum width position, and the outer end position and the tire. A thickness W2 at an intermediate position with respect to the maximum width position satisfies 0.9 ≦ W3 / W1 ≦ 1.1, 0.8 ≦ W2 / W1 <1.0, and W2 <W3.

Japanese Patent No. 2579398 Japanese Patent No. 5385731 JP 2009-126409 A

  By the way, in a SUV (Sport Utility Vehicle) vehicle, a pneumatic tire having a size that is higher in cross-sectional height (referred to as a high section height) than a general pneumatic tire for passenger cars is applied. In such a high section height pneumatic tire, a pneumatic tire capable of run flat running generally increases the thickness of the reinforcing rubber layer in order to maintain run flat durability performance. However, there is a problem that riding performance is deteriorated due to an increase in the longitudinal spring due to an increase in the thickness of the reinforcing rubber layer. Conversely, if the thickness of the reinforcing rubber layer is decreased to maintain the riding comfort performance, the run-flat durability performance is deteriorated.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can make run-flat durability performance and riding comfort performance compatible.

  In order to solve the above-described problems and achieve the object, the pneumatic tire of the present invention is a pneumatic tire in which a reinforcing rubber layer having a substantially crescent-shaped meridional section is disposed on the sidewall portions on both sides of the tire width direction. Assembled on a regular rim, the cross-sectional height from the tire maximum width to the tire outer diameter in a no-load state at normal internal pressure is a, the cross-sectional height from the tire maximum width to the bead toe is b, and 65% of the normal load at an internal pressure of 0 kPa When the cross-sectional height from the tire maximum width part to the tire outer diameter in a loaded state is a ′ and the cross-sectional height from the tire maximum width part to the bead toe is b ′, the deformation rate of the cross-sectional height (1-b ′ (1-a ′ / a) is larger than / b).

  According to this pneumatic tire, the deformation rate from the tire maximum width portion to the tire outer diameter (buttress portion) is made larger than the deformation rate from the tire maximum width portion to the bead toe, so that the stress is applied to the entire sidewall portion. Can be distributed. For this reason, the loss energy of the buttress part used as the starting point of failure generation | occurrence | production in a run flat durability test can be reduced. In addition, since the stress can be distributed throughout the sidewall portion, an increase in the vertical spring at the buttress portion can be suppressed. As a result, the run-flat durability performance can be improved and compatibility with riding comfort performance can be achieved.

  In the pneumatic tire of the present invention, the relationship between the deformation ratio (1-a ′ / a) and (1-b ′ / b) of the cross-sectional height is (1−b ′ / b) × 1. 8 ≦ (1-a ′ / a) ≦ (1-b ′ / b) × 3.2 is satisfied.

  According to this pneumatic tire, with respect to the deformation rate from the tire maximum width part to the bead toe, by defining the range of the deformation rate from the tire maximum width part to the tire outer diameter, the stress is distributed over the entire sidewall part. And the effect of reducing the loss energy of a buttress part can be acquired notably. That is, if the rate of change of the part a is less than 1.8 times the rate of change of the part b, the rate of change of the part a tends to be insufficient, and the effect of dispersing stress throughout the sidewall portion 4 is reduced. On the other hand, if the rate of change of the a part exceeds 3.2 times the rate of change of the b part, the rate of change of the a part tends to be excessive, and the effect of dispersing stress throughout the sidewall part 4 is reduced.

  In the pneumatic tire of the present invention, the cross-sectional height deformation rate (1-a ′ / a) is 0.35 or more and 0.65 or less.

  If the deformation ratio from the tire maximum width part to the tire outer diameter is less than 0.35, the rate of change of part a tends to be insufficient, and it becomes difficult to disperse the stress throughout the sidewall part, and run flat durability performance is improved. The improvement effect is reduced. On the other hand, if the deformation ratio from the tire maximum width portion H to the tire outer diameter D exceeds 0.65, the rigidity tends to decrease and the steering stability tends to decrease.

  In the pneumatic tire of the present invention, the cross-sectional height deformation rate (1-b '/ b) is 0.1 or more and 0.35 or less.

  When the deformation ratio from the tire maximum width portion to the bead toe is less than 0.1, it becomes difficult to disperse the stress throughout the sidewall portion, and the effect of improving the run-flat durability performance becomes low. On the other hand, when the deformation ratio from the tire maximum width part to the bead toe exceeds 0.35, the rigidity tends to decrease and the steering stability tends to decrease. For this reason, it is preferable that the deformation ratio (1-b ′ / b) of the cross-sectional height is 0.1 or more and 0.35 or less.

  Further, the pneumatic tire of the present invention has a carcass layer spanned between the bead cores disposed on the bead portions on both sides in the tire width direction, and has a cross-sectional height between the tire maximum width portion and the tire outer diameter. Ga is the meridional section thickness on the perpendicular to the carcass layer at the tire side position of 1/2, and the carcass layer is at the tire side position of 1/2 the section height from the tire maximum width portion to the bead toe. Gb × 0.4 ≦ Ga ≦ Gb × 0.8 is satisfied when the meridional section thickness on the perpendicular is Gb.

  According to this pneumatic tire, by reducing the meridional section thickness Ga from the tire maximum width portion to the tire outer diameter with respect to the meridional section thickness Gb from the tire maximum width portion to the bead toe, stress is reduced. Can be dispersed throughout the sidewall portion 4.

  In the pneumatic tire of the present invention, in the meridional section thickness Ga, the meridional section thickness in the range inside the tire from the carcass layer is Gac, and the meridional section thickness in the range outside the tire from the carcass layer is Gad. Then, Gad × 1.2 ≦ Gac ≦ Gad × 2.8, and 3.0 mm ≦ Gac ≦ 10.0 mm.

  Since the carcass layer constitutes the skeleton of the tire, it greatly contributes to run-flat durability. The relationship between the meridional section thickness Gac in the range inside the tire from the carcass layer and the meridional section thickness Gad in the range outside the carcass layer from the carcass layer is Gad × 1.2 ≦ Gac ≦ Gad × 2.8. By keeping the meridional section thickness Gac in the range of the inside of the tire from the carcass layer, the meridional section thickness Ga is not increased as a whole, so that both run-flat durability performance and riding comfort performance can be achieved. Further, if the meridional section thickness Gac in the tire inner side range from the carcass layer is less than 3.0 mm, the rigidity is lowered and the run-flat durability performance tends to be lowered. On the other hand, when the meridional cross section thickness Gac in the range inside the tire from the carcass layer exceeds 10.0 mm, the rigidity becomes high and the riding performance tends to decrease. For this reason, it is preferable that the meridional section thickness Gac in the range inside the tire from the carcass layer is 3.0 mm ≦ Gac ≦ 10.0 mm.

  In the pneumatic tire of the present invention, in the meridional section thickness Gb, the meridional section thickness in the range inside the tire from the carcass layer is Gbe, and the meridional section thickness in the range outside the tire from the carcass layer is Gbf. Then, Gbf × 1.1 ≦ Gbe ≦ Gbf × 1.8 and 3.0 mm ≦ Gbe ≦ 10.0 mm.

  The position of the meridional section thickness Gb is close to the bead filler and contributes less to riding comfort performance. In this meridional section thickness Gb, the relationship between the meridional section thickness Gbe in the range inside the tire from the carcass layer and the meridional section thickness Gbf in the range outside the tire from the carcass layer is expressed as Gbf × 1.1 ≦ Gbe. ≦ Gbf × 1.8, and the meridional section thickness Gbf in the range outside the carcass layer from the carcass layer is increased with respect to the meridional section thickness Gae in the range from the carcass layer to improve the run-flat durability performance. Further, if the meridional section thickness Gae in the tire inner side from the carcass layer is less than 3.0 mm, the rigidity is lowered and the run-flat durability performance tends to be lowered. On the other hand, when the meridional section thickness Gae in the tire inner side of the carcass layer exceeds 10.0 mm, the rigidity becomes high and the riding comfort performance tends to decrease. For this reason, it is preferable that the meridional section thickness Gae in the range inside the tire from the carcass layer is 3.0 mm ≦ Gac ≦ 10.0 mm.

  The pneumatic tire of the present invention has a carcass layer spanned between the bead cores arranged on the bead portions on both sides in the tire width direction, and has a cross-sectional height between the tire maximum width and the tire outermost diameter. The meridional section thickness on the perpendicular to the carcass layer at position ½ is Ga, and the meridional section on the perpendicular to the carcass layer at position ½ of the sectional height from the maximum tire width to the bead toe. When the thickness is Gb, the type of rubber forming the reinforcing rubber layer including the meridional section thickness Ga portion and the meridional section thickness Gb portion is different. The Gb portion is larger than the portion in the range of 3 to 20, and the Ga portion is in the range of 60 to 85.

  According to this pneumatic tire, the run-flat durability performance and the riding comfort performance can be optimized by forming the reinforcing rubber layer with a plurality of types of rubber having different hardnesses. However, if the rubber hardness at 20 ° C. is a difference between the reinforcing rubber layer of the Gb portion and the reinforcing rubber layer of the Gb portion of less than 3, the effect of optimizing the run-flat durability performance and the riding comfort performance is obtained. It becomes difficult. On the other hand, if the rubber hardness at 20 ° C. is a difference in which the reinforcing rubber layer in the Gb portion exceeds 20 with respect to the reinforcing rubber layer in the Ga portion, the productivity tends to deteriorate. For this reason, it is preferable that the rubber hardness at 20 ° C. is larger in the range of 3 to 20 in the reinforcing rubber layer in the Gb portion than the reinforcing rubber layer in the Ga portion. In addition, when the rubber hardness at 20 ° C. of the reinforcing rubber layer of the Ga portion is less than 60, it tends to be too soft and the run-flat durability performance tends to deteriorate. On the other hand, if the rubber hardness at 20 ° C. of the reinforcing rubber layer of the Ga portion exceeds 85, the riding comfort performance tends to deteriorate because it is too hard. For this reason, it is preferable that the rubber hardness in 20 degreeC of the reinforcement rubber layer of the Ga part is the range of 60 or more and 85 or less.

  The pneumatic tire of the present invention has a carcass layer spanned between the bead cores arranged on the bead portions on both sides in the tire width direction, and has a cross-sectional height between the tire maximum width and the tire outermost diameter. The meridional section thickness on the perpendicular to the carcass layer at position ½ is Ga, and the meridional section on the perpendicular to the carcass layer at position ½ of the sectional height from the maximum tire width to the bead toe. When the thickness is Gb, the reinforcing rubber layer is provided inside the tire from the carcass layer, and has another reinforcing rubber layer outside the tire from the carcass layer of the meridional section thickness Gb, Regarding the rubber hardness at 20 ° C., the portion of the other reinforcing rubber layer is larger in the range of 3 to 20 than the Ga portion, and the Ga portion is in the range of 60 to 85, Wherein the portion of the other of the reinforcing rubber layer is in a range of 80 or more 105 or less.

  According to this pneumatic tire, there is another reinforcing rubber layer on the tire outer side than the carcass layer of the meridional section thickness Gb, and the run flat durability performance and the hardness are different from those of the Ga reinforcing rubber layer. The ride performance can be optimized. However, when the rubber hardness at 20 ° C. is a difference between the reinforcing rubber layer of the Ga portion and other reinforcing rubber layers of the Gb portion of less than 3, the effect of optimizing the run-flat durability performance and the riding comfort performance Is difficult to obtain. On the other hand, when the rubber hardness at 20 ° C. is a difference in which the other reinforcing rubber layer of the Gb portion exceeds 20 with respect to the reinforcing rubber layer of the Ga portion, the productivity tends to deteriorate. For this reason, it is preferable that other reinforcing rubber layers in the Gb portion are larger than the reinforcing rubber layer in the Ga portion in the range of 3 to 20 inclusive. In addition, when the rubber hardness at 20 ° C. of the reinforcing rubber layer of the Ga portion is less than 60, it tends to be too soft and the run-flat durability performance tends to deteriorate. On the other hand, if the rubber hardness at 20 ° C. of the reinforcing rubber layer of the Ga portion exceeds 85, the riding comfort performance tends to deteriorate because it is too hard. For this reason, it is preferable that the rubber hardness in 20 degreeC of the reinforcement rubber layer of the Ga part is the range of 60 or more and 85 or less. Further, if the rubber hardness at 20 ° C. of the other reinforcing rubber layer of the Gb portion is less than 80, it tends to be too soft and the run-flat durability performance tends to deteriorate. On the other hand, when the rubber hardness at 20 ° C. of the other reinforcing rubber layer of the Gb portion exceeds 105, the riding comfort performance tends to deteriorate because it is too hard. For this reason, the rubber hardness at 20 ° C. of the other reinforcing rubber layer of the Gb portion is preferably in the range of 80 to 105.

  In the pneumatic tire of the present invention, the tire cross-section height SH from the tire outer diameter to the bead toe is 120 mm or more, and the tire cross-section width SW and the tire cross-section height SH are 1.3 ≦ SW / SH ≦. It satisfies the range of 2.1.

  A pneumatic tire of the above size is particularly difficult to achieve both run-flat durability performance and riding comfort performance. For this reason, the effect which makes run-flat durability performance and riding comfort performance compatible can be acquired notably by applying the structure of the form mentioned above to the said size.

  The pneumatic tire according to the present invention can achieve both run-flat durability performance and riding comfort performance.

FIG. 1 is a meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a meridional sectional view of a deformed state in the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a meridional sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is a partially enlarged meridional sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is a partially enlarged meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 6 is a meridional sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 7 is a meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 8 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

  FIG. 1 is a meridional sectional view of a pneumatic tire according to this embodiment.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side, and Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction means the tire width direction. Is the side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane that is orthogonal to the rotation axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equator line is a line along the tire circumferential direction of the pneumatic tire 1 on the tire equator plane CL. In the present embodiment, the same sign “CL” as that of the tire equator plane is attached to the tire equator line. In addition, since the pneumatic tire 1 described below is configured to be substantially symmetric about the tire equator plane CL, the pneumatic tire 1 is cut along a plane passing through the rotation axis of the pneumatic tire 1. In the meridional sectional views (FIGS. 1, 3, 6, and 7), only one side (right side in FIG. 1) of the tire equatorial plane CL is illustrated, and only the one side is described. Description of (left side in FIG. 1) is omitted.

  As shown in FIG. 1, the pneumatic tire 1 according to the present embodiment includes a tread portion 2, shoulder portions 3 on both sides thereof, and a sidewall portion 4 and a bead portion 5 that are sequentially continuous from the shoulder portions 3. ing. The pneumatic tire 1 includes a carcass layer 6, a belt layer 7, a belt reinforcing layer 8, an inner liner layer 9, and a reinforcing rubber layer 10.

  The tread portion 2 is made of a tread rubber 2 </ b> A, exposed at the outermost side in the tire radial direction of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. A tread surface 21 is formed on the outer peripheral surface of the tread portion 2, that is, on the tread surface that contacts the road surface during traveling. The tread surface 21 is provided with a plurality of (four in this embodiment) main grooves 22 which are straight main grooves extending along the tire circumferential direction and parallel to the tire equator line CL. The tread surface 21 is formed with a plurality of rib-like land portions 23 extending along the tire circumferential direction by the plurality of main grooves 22. The main groove 22 may be formed to be bent or curved while extending along the tire circumferential direction. Further, the tread surface 21 is provided with a lug groove extending in a direction intersecting the tire circumferential direction in the land portion 23. The lug groove may intersect the main groove 22, or at least one end of the lug groove may not terminate the main groove 22 and terminate in the land portion 23. When both ends of the lug groove intersect with the main groove 22, a block-like land portion is formed in which the land portion 23 is divided into a plurality of portions in the tire circumferential direction. Note that the lug groove may be formed to be bent or curved while extending while being inclined with respect to the tire circumferential direction.

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. That is, the shoulder portion 3 is made of the tread rubber 2A. Further, the sidewall portion 4 is exposed at the outermost side in the tire width direction of the pneumatic tire 1. The sidewall portion 4 is made of a side rubber 4A. The bead unit 5 includes a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 52 is a rubber material disposed in a space formed by folding the end portion in the tire width direction of the carcass layer 6 at the position of the bead core 51. The bead portion 5 includes a rim cushion rubber 5A that is exposed to an outer portion in contact with a rim (not shown). The rim cushion rubber 5A forms the outer periphery of the bead portion 5 and is provided from the tire inner side of the bead portion 5 to the position (sidewall portion 4) that covers the bead filler 52 outside the tire through the lower end portion.

  The carcass layer 6 is configured such that each tire width direction end portion is folded back from the tire width direction inner side to the tire width direction outer side by a pair of bead cores 51 and is wound around in a toroidal shape in the tire circumferential direction. It is. The carcass layer 6 is formed by coating a plurality of carcass cords (not shown) arranged in parallel at an angle in the tire circumferential direction with an angle with respect to the tire circumferential direction along the tire meridian direction. The carcass cord is made of organic fibers (polyester, rayon, nylon, etc.). The carcass layer 6 is provided as at least one layer, and is provided as two layers in this embodiment. In FIG. 1, the carcass layer 6 is provided so that the inner side of the folded end portions of the two layers covers the entire bead filler 52 and extends to the sidewall portion 4, and the outer side covers the middle of the bead filler 52. Is provided.

  The belt layer 7 has a multilayer structure in which at least two belts 71 and 72 are laminated, and is disposed on the outer side in the tire radial direction which is the outer periphery of the carcass layer 6 in the tread portion 2 and covers the carcass layer 6 in the tire circumferential direction. It is. The belts 71 and 72 are made by coating a plurality of cords (not shown) arranged in parallel at a predetermined angle (for example, 20 degrees to 30 degrees) with a coat rubber with respect to the tire circumferential direction. The cord is made of steel or organic fiber (polyester, rayon, nylon, etc.). Further, the overlapping belts 71 and 72 are arranged so that the cords intersect each other.

  The belt reinforcing layer 8 is disposed on the outer side in the tire radial direction which is the outer periphery of the belt layer 7 and covers the belt layer 7 in the tire circumferential direction. The belt reinforcing layer 8 is formed by coating a plurality of cords (not shown) arranged substantially in parallel (± 5 degrees) in the tire circumferential direction and in the tire width direction with a coat rubber. The cord is made of steel or organic fiber (polyester, rayon, nylon, etc.). The belt reinforcing layer 8 shown in FIG. 1 has one layer that covers the entire belt layer 7 and one layer that covers the end of the belt layer 7 in the tire width direction. The configuration of the belt reinforcing layer 8 is not limited to the above, and is not clearly shown in the figure. For example, the belt reinforcing layer 8 is arranged so as to cover the entire belt layer 7 with two layers, or the end portion in the tire width direction of the belt layer 7 with two layers It may be arranged so as to cover only. Further, although the configuration of the belt reinforcing layer 8 is not clearly shown in the figure, for example, the belt reinforcing layer 8 is disposed so as to cover the entire belt layer 7 with one layer, or covers only the end in the tire width direction of the belt layer 7 with one layer. It may be arranged like this. That is, the belt reinforcing layer 8 overlaps at least the end portion in the tire width direction of the belt layer 7. The belt reinforcing layer 8 is provided by winding a strip-shaped strip material (for example, a width of 10 [mm]) in the tire circumferential direction.

  The inner liner layer 9 is the inner surface of the tire, that is, the inner peripheral surface of the carcass layer 6, and both end portions in the tire width direction reach the position of the bead core 51 of the pair of bead portions 5, and in a toroidal shape in the tire circumferential direction. It is hung around and pasted. The inner liner layer 9 is for suppressing the permeation of air molecules to the outside of the tire. As shown in FIG. 1, the inner liner layer 9 is provided to reach the inside of the tire of the bead portion 5, but may be provided to the lower portion of the bead core 51 (inner side in the tire radial direction).

  The reinforcing rubber layer 10 is provided inside the sidewall portion 4 and does not appear on the tire inner side or the tire outer side. The reinforcing rubber layer 10 is mainly provided inside the tire of the carcass layer 6 and between the carcass layer 6 and the inner liner layer 9, and the meridional section is formed in a crescent shape. The reinforcing rubber layer 10 is formed of a rubber material having higher strength than the side rubber 4A forming the sidewall portion 4 and the rim cushion rubber 5A forming the bead portion 5. The reinforcing rubber layer 10 may be formed of a different rubber material (see FIG. 6), or may be provided inside the tire of the carcass layer 6 and between the carcass layer 6 and the side rubber 4A or the bead portion 5 ( (See FIG. 7).

  Here, the pneumatic tire 1 is mounted on a vehicle (not shown) in a state where air is filled at a predetermined air pressure inside the bead portion 5 assembled to the rim. When the vehicle travels, the pneumatic tire 1 rotates while the tread surface 21 is in contact with the road surface. When the vehicle travels, the tread surface 21 comes into contact with the road surface in this way, so that a load due to the weight of the vehicle acts on the tread surface 21. When a load is applied to the tread surface 21, the pneumatic tire 1 is elastically deformed according to the manner in which the load is applied and the hardness of each part. However, the pneumatic tire 1 is pushed outward from the inside by the air filled inside. The power to be given. Thereby, even if a load acts on the tread surface 21, the pneumatic tire 1 is suppressed from excessive deformation by the urging force of air filled therein. For this reason, the pneumatic tire 1 can rotate while receiving a load, and enables the vehicle to travel.

  Further, the pneumatic tire 1 is hardly deformed by the air pressure of the air filled therein, but when the vehicle is running, for example, a foreign object is stuck in the tread surface 21 and is punctured. Air may leak out. When the air inside leaks out, the urging force of the pneumatic tire 1 from the inside toward the outside is reduced. In the pneumatic tire 1 in a state where internal air has leaked, when a load is applied to the tread surface 21, a load in the tire radial direction is applied to the sidewall portion 4. As a result, the sidewall portion 4 is easily elastically deformed in the tire radial direction, and the reinforcing rubber layer 10 is provided on the sidewall portion 4. As described above, the reinforcing rubber layer 10 is formed of a rubber material having higher strength than the side rubber 4 </ b> A that forms the sidewall portion 4. For this reason, the reinforcing rubber layer 10 suppresses deformation of the sidewall portion 4 in the tire radial direction even when a load in the tire radial direction acts on the sidewall portion 4. As a result, the pneumatic tire 1 can run the vehicle by suppressing deformation of the sidewall portion 4 in the tire radial direction by the reinforcing rubber layer 10, and the air inside the pneumatic tire 1 leaks out. It is possible to run in the so-called run-flat manner.

  FIG. 2 is a meridional sectional view of a deformed state of the pneumatic tire according to the present embodiment.

  As shown in FIG. 2 (a), when the pneumatic tire 1 described above is assembled to a regular rim and no load is applied at a regular internal pressure, the sectional height from the tire maximum width portion H to the tire outer diameter D is a, the tire maximum width. The cross-sectional height from the part to the bead toe 53 is b. On the other hand, as shown in FIG. 2B, when the pneumatic tire 1 described above is assembled to a normal rim and the internal pressure is 0 kPa and the load is 65% of the normal load, the cross-sectional height from the tire maximum width H to the tire outer diameter D A ′, and the cross-sectional height from the tire maximum width portion to the bead toe 53 is b ′. At this time, the pneumatic tire 1 of the present embodiment has a larger (1-a ′ / a) than the deformation ratio (1-b ′ / b) of the cross-sectional height.

  As shown in FIG. 1, the tire maximum width portion H is the end of the tire cross-sectional width SW and is the largest position in the tire width direction. The tire cross-section width SW excludes patterns and characters on the tire side surface from the tire total width that is the largest in the tire width direction when the pneumatic tire 1 is assembled on a regular rim and filled with regular internal pressure in an unloaded state. Width. In a tire provided with a rim protect bar that protects the rim (provided along the tire circumferential direction and protrudes outward in the tire width direction), the rim protect bar is the largest portion in the tire width direction. However, the tire cross-sectional width defined in the present embodiment excludes the rim protect bar. The range of the sidewall portion 4 from the tire maximum width portion H to the tire outer diameter D is also referred to as a buttress portion. The tire cross-section height SH is a half of the difference between the tire outer diameter and the rim diameter when the pneumatic tire 1 is assembled on a regular rim and is loaded with a regular internal pressure in an unloaded state. The bead toe 53 is the innermost portion in the tire radial direction that contacts the rim in the bead portion 5.

  Here, the regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  According to such a pneumatic tire 1, by making the deformation rate from the tire maximum width portion H to the tire outer diameter D (buttress portion) larger than the deformation rate from the tire maximum width portion H to the bead toe 53, Stress can be distributed throughout the sidewall portion 4. For this reason, the loss energy of the buttress part used as the starting point of failure generation | occurrence | production in a run flat durability test can be reduced. In addition, since the stress can be distributed throughout the sidewall portion 4, an increase in the vertical spring at the buttress portion can be suppressed. As a result, the run-flat durability performance can be improved and compatibility with riding comfort performance can be achieved.

  Further, in the pneumatic tire 1 of the present embodiment, the relationship between the deformation ratio (1-a ′ / a) and (1-b ′ / b) of the cross-sectional height is (1−b ′ / b) × 1. It is preferable that .8 ≦ (1-a ′ / a) ≦ (1-b ′ / b) × 3.2 is satisfied.

  According to this pneumatic tire 1, by defining the range of the deformation rate from the tire maximum width portion H to the tire outer diameter D (buttress portion) with respect to the deformation rate from the tire maximum width portion H to the bead toe 53, The effect of reducing the loss energy of the buttress portion by distributing stress over the entire sidewall portion 4 can be obtained. That is, if the rate of change of the part a is less than 1.8 times the rate of change of the part b, the rate of change of the part a tends to be insufficient, and the effect of dispersing stress throughout the sidewall portion 4 is reduced. On the other hand, if the rate of change of the a part exceeds 3.2 times the rate of change of the b part, the rate of change of the a part tends to be excessive, and the effect of dispersing stress throughout the sidewall part 4 is reduced. In order to achieve both run-flat durability performance and riding comfort performance, (1-b ′ / b) × 2.0 ≦ (1-a ′ / a) ≦ (1-b ′ / b) × 3. A range of 0 is more preferable, and a range of (1-b ′ / b) × 2.3 ≦ (1-a ′ / a) ≦ (1-b ′ / b) × 2.7 is preferable. Further preferred.

  Moreover, in the pneumatic tire 1 of this embodiment, it is preferable that the deformation ratio (1-a ′ / a) of the cross-sectional height is 0.35 or more and 0.65 or less.

  If the deformation ratio from the tire maximum width portion H to the tire outer diameter D is less than 0.35, the rate of change of the portion a tends to be insufficient, and it becomes difficult to disperse the stress in the entire sidewall portion 4, and the run flat The effect of improving durability is reduced. On the other hand, if the deformation ratio from the tire maximum width portion H to the tire outer diameter D exceeds 0.65, the rigidity tends to decrease and the steering stability tends to decrease. For this reason, it is preferable that the deformation ratio (1-a ′ / a) of the cross-sectional height is 0.35 or more and 0.65 or less. In order to achieve both run-flat durability performance and riding comfort performance, it is more preferable that (1-a ′ / a) be in the range of 0.4 to 0.55, and 0.45 to 0.5. The following range is more preferable.

  Moreover, in the pneumatic tire 1 of this embodiment, it is preferable that the deformation ratio (1-b ′ / b) of the cross-sectional height is 0.1 or more and 0.35 or less.

  When the deformation ratio from the tire maximum width portion H to the bead toe 53 is less than 0.1, it becomes difficult to disperse the stress throughout the sidewall portion 4, and the effect of improving the run-flat durability performance is reduced. On the other hand, if the deformation ratio from the tire maximum width portion H to the bead toe 53 exceeds 0.35, the rigidity tends to decrease and the steering stability tends to decrease. For this reason, it is preferable that the deformation ratio (1-b ′ / b) of the cross-sectional height is 0.1 or more and 0.35 or less. In order to achieve both run-flat durability performance and riding comfort performance, it is more preferable that (1-b ′ / b) be in the range of 0.15 or more and 0.3 or less, and 0.18 or more and 0.25. The following range is more preferable.

  FIG. 3 is a meridional sectional view of the pneumatic tire according to the present embodiment.

  As shown in FIG. 3, the meridional section thickness on the perpendicular to the carcass layer 6 is Ga at the tire side face position of ½ of the section height between the tire maximum width portion H and the tire outer diameter D. Further, the meridional section thickness on the perpendicular to the carcass layer 6 is defined as Gb at the tire side surface position of ½ of the section height between the tire maximum width portion H and the bead toe 53. At this time, it is preferable that the pneumatic tire 1 of the present embodiment satisfies Gb × 0.4 ≦ Ga ≦ Gb × 0.8.

  The tire side surface is a surface that forms the outer shape of the pneumatic tire 1 excluding patterns and characters. Moreover, the perpendicular to the carcass layer 6 is a perpendicular to the curve formed by the carcass cord in the carcass layer 6 located near the tire side surface in the meridional section. The meridional section thicknesses Ga and Gb are meridional section thicknesses from the tire side surface to the tire inner surface including the inner liner layer 9. Moreover, although not shown in the drawing, the bead filler 52 may be included in the range of the meridional section thickness Gb.

  According to this pneumatic tire 1, the meridional section thickness Ga between the tire maximum width portion H and the tire outer diameter D is made thinner than the meridional section thickness Gb between the tire maximum width portion H and the bead toe 53. By doing so, the stress can be dispersed throughout the sidewall portion 4. In order to obtain the effect of dispersing the stress throughout the sidewall portion 4, it is more preferable to set the range of Gb × 0.5 ≦ Ga ≦ Gb × 0.7.

  FIG. 4 is a partially enlarged meridional sectional view of the pneumatic tire according to the present embodiment.

  In the above-described meridional section thickness Ga, as shown in FIG. 4, when the meridional section thickness in the range inside the tire from the carcass layer 6 is Gac and the meridional section thickness in the range outside the tire from the carcass layer 6 is Gad Gad × 1.2 ≦ Gac ≦ Gad × 2.8 and 3.0 mm ≦ Gac ≦ 10.0 mm are preferable.

  The meridional section thickness Gac is the meridional section thickness up to the carcass cord in the carcass layer 6 located near the tire inner surface. The meridional section thickness Gad is the meridional section thickness up to the carcass cord in the carcass layer 6 located near the tire side surface.

  Since the carcass layer 6 constitutes the skeleton of the tire, it greatly contributes to run-flat durability. The relationship between the meridional section thickness Gac in the range inside the tire from the carcass layer 6 and the meridional section thickness Gad in the range outside the tire from the carcass layer 6 is expressed as Gad × 1.2 ≦ Gac ≦ Gad × 2. 8 and maintaining the meridional section thickness Gac corresponding to the reinforcing rubber layer 10 in the range of the inside of the tire from the carcass layer 6, while preventing the meridional section thickness Ga from becoming thick as a whole. Both performance and performance can be achieved. In order to obtain the effect of achieving both run-flat durability performance and riding comfort performance, it is more preferable that the range is Gad × 1.6 ≦ Gac ≦ Gad × 2.4. Further, if the meridional section thickness Gac in the range from the carcass layer 6 to the inside of the tire is less than 3.0 mm, the rigidity is lowered and the run-flat durability performance tends to be lowered. On the other hand, when the meridional cross section thickness Gac in the range inside the tire from the carcass layer 6 exceeds 10.0 mm, the rigidity becomes high and the riding performance tends to decrease. For this reason, it is preferable that the meridional section thickness Gac in the range from the carcass layer 6 to the inside of the tire satisfies 3.0 mm ≦ Gac ≦ 10.0 mm.

  FIG. 5 is a partially enlarged meridional sectional view of the pneumatic tire according to the present embodiment.

  In the meridional section thickness Gb described above, as shown in FIG. 5, when the meridional section thickness in the range inside the tire from the carcass layer 6 is Gbe and the meridional section thickness in the range outside the tire from the carcass layer 6 is Gbf Gbf × 1.1 ≦ Gbe ≦ Gbf × 1.8, and preferably 3.0 mm ≦ Gbe ≦ 10.0 mm.

  The meridional section thickness Gae is the meridional section thickness up to the carcass cord in the carcass layer 6 at a position close to the tire inner surface. The meridional section thickness Gaf is the meridional section thickness up to the carcass cord in the carcass layer 6 located near the tire side surface.

  The position of the meridional section thickness Gb is close to the bead filler 52 and contributes less to the riding performance. In this meridional section thickness Gb, the relationship between the meridional section thickness Gbe in the range inside the tire from the carcass layer 6 and the meridional section thickness Gbf in the range outside the tire from the carcass layer 6 is expressed as Gbf × 1.1. ≦ Gbe ≦ Gbf × 1.8, and the meridional section thickness Gbf in the range outside the tire from the carcass layer 6 is thicker than the meridional section thickness Gae corresponding to the reinforcing rubber layer 10 in the range inside the tire from the carcass layer 6. To improve the run-flat durability. In order to obtain the effect of achieving both run-flat durability performance and riding comfort performance, it is more preferable to set the range of Gbf × 1.3 ≦ Gbe ≦ Gbf × 1.6. Further, when the meridional section thickness Gae in the range inside the tire from the carcass layer 6 is less than 3.0 mm, the rigidity is lowered and the run-flat durability performance tends to be lowered. On the other hand, when the meridional cross section thickness Gae in the range inside the tire from the carcass layer 6 exceeds 10.0 mm, the rigidity becomes high and the riding performance tends to be lowered. For this reason, it is preferable that the meridional section thickness Gae in the range inside the tire from the carcass layer 6 is 3.0 mm ≦ Gac ≦ 10.0 mm. Although not clearly shown in the drawing, when the bead filler 52 is included in the range of the meridional section thickness Gb, the bead filler 52 is excluded from the meridional section thickness Gbe and the meridional section thickness Gbf.

  FIG. 6 is a meridional sectional view of the pneumatic tire according to the present embodiment.

  In the meridional section thicknesses Ga and Gb described above, as shown in FIG. 6, the types of rubber forming the reinforcing rubber layer 10 including the meridional section thickness Ga portion and the meridional section thickness Gb portion are different. Regarding the rubber hardness at 0 ° C., the reinforcing rubber layer 10B of the Gb portion is larger in the range of 3 to 20 than the reinforcing rubber layer 10A of the Ga portion, and the reinforcing rubber layer 10A of the Ga portion is 60 to 85 inclusive. A range is preferable.

  The reinforcing rubber layer 10 </ b> A and the reinforcing rubber layer 10 </ b> B here relate to the reinforcing rubber layer 10 provided inside the tire from the carcass layer 6 as shown in FIG. 6. Moreover, in FIG. 6, although the example in which the reinforcement rubber layer 10 is formed with two types is shown, two or more types may be sufficient.

  According to this pneumatic tire 1, the run-flat durability performance and the riding comfort performance can be optimized by forming the reinforcing rubber layer 10 with a plurality of types of rubber having different hardnesses. However, when the rubber hardness at 20 ° C. is less than 3 in the reinforcing rubber layer 10B in the Gb portion with respect to the reinforcing rubber layer 10A in the Ga portion, the effect of optimizing the run flat durability performance and the riding comfort performance is achieved. Is difficult to obtain. On the other hand, if the rubber hardness at 20 ° C. is a difference in which the reinforcing rubber layer 10B in the Gb portion exceeds 20 with respect to the reinforcing rubber layer 10A in the Ga portion, productivity tends to deteriorate. For this reason, the rubber hardness at 20 ° C. is preferably larger in the range of 3 to 20 in the reinforcing rubber layer 10B in the Gb portion than in the reinforcing rubber layer 10A in the Ga portion. In addition, if the rubber hardness at 20 ° C. of the reinforcing rubber layer 10A of the Ga portion is less than 60, it tends to be too soft and the run-flat durability performance tends to deteriorate. On the other hand, when the rubber hardness at 20 ° C. of the reinforcing rubber layer 10A of the Ga portion exceeds 85, the riding comfort performance tends to deteriorate because it is too hard. For this reason, it is preferable that the rubber hardness at 20 ° C. of the reinforcing rubber layer 10A in the Ga portion is in the range of 60 to 85. In order to obtain the effect of optimizing the run-flat durability performance and riding comfort performance, the rubber hardness at 20 ° C. is 5 to 15 in the reinforcing rubber layer 10B in the Gb portion with respect to the reinforcing rubber layer 10A in the Ga portion. It is more preferable that the reinforcing rubber layer 10A in the Ga portion is in the range of 70 to 80 in the following range.

  FIG. 7 is a meridional sectional view of the pneumatic tire according to the present embodiment.

  In the above-described meridional section thicknesses Ga and Gb, as shown in FIG. 7, the reinforcing rubber layer 10 is provided on the tire inner side from the carcass layer 6, and the portion of the meridional section thickness Gb on the tire outer side. It has another reinforcing rubber layer 10C, and the rubber hardness at 20 ° C. is larger in the range of 3 to 20 than the portion of other reinforcing rubber layer 10C relative to the Ga portion, and the Ga portion is 60 to 85 inclusive. It is preferable that the portion of the other reinforcing rubber layer 10C is in the range of 80 to 105.

  Here, the reinforcing rubber layer 10 provided inside the tire from the carcass layer 6 may be formed of one type of rubber as shown in FIG. 7, but different types of reinforcing rubber layers as shown in FIG. 10A and the reinforcing rubber layer 10B may be formed.

  According to the pneumatic tire 1, the other reinforcing rubber layer 10 </ b> C is provided on the outer side of the tire from the carcass layer 6 of the meridional section thickness Gb, and the hardness is different from that of the reinforcing rubber layer 10 of the Ga portion. The flat durability and ride performance can be optimized. However, if the rubber hardness at 20 ° C. is a difference between the reinforcing rubber layer 10 (10A) of the Ga portion and the other reinforcing rubber layer 10C of the Gb portion of less than 3, run-flat durability performance and riding comfort performance The effect of optimizing is difficult to obtain. On the other hand, if the rubber hardness at 20 ° C. is a difference in which the other reinforcing rubber layer 10C of the Gb portion exceeds 20 with respect to the reinforcing rubber layer 10 (10A) of the Ga portion, the productivity tends to deteriorate. . For this reason, it is preferable that the other reinforcing rubber layer 10C of the Gb portion is larger than the reinforcing rubber layer 10 (10A) of the Ga portion in the range of 3 to 20. In addition, if the rubber hardness at 20 ° C. of the reinforcing rubber layer 10 (10A) in the Ga portion is less than 60, it tends to be too soft and the run-flat durability performance tends to deteriorate. On the other hand, if the rubber hardness at 20 ° C. of the reinforcing rubber layer 10 (10A) in the Ga portion exceeds 85, the ride comfort performance tends to deteriorate because it is too hard. For this reason, it is preferable that the rubber hardness in 20 degreeC of the reinforcement rubber layer 10 (10A) of Ga part is the range of 60-85. Further, if the rubber hardness at 20 ° C. of the other reinforcing rubber layer 10C of the Gb portion is less than 80, it tends to be too soft and the run-flat durability performance tends to deteriorate. On the other hand, when the rubber hardness at 20 ° C. of the other reinforcing rubber layer 10C of the Gb portion exceeds 105, the ride comfort performance tends to deteriorate because it is too hard. For this reason, the rubber hardness at 20 ° C. of the other reinforcing rubber layer 10C of the Gb portion is preferably in the range of 80 to 105. In order to obtain the effect of optimizing the run-flat durability performance and the riding comfort performance, the rubber hardness at 20 ° C. is the other reinforcing rubber layer of the Gb portion with respect to the reinforcing rubber layer 10 (10A) of the Ga portion. 10C is large in the range of 5 to 15, and the reinforcing rubber layer 10A of the Ga portion is in the range of 70 to 80, and the other reinforcing rubber layer 10C portion of the Gb portion is in the range of 85 to 95. More preferably.

  In the pneumatic tire 1 of the present embodiment, as shown in FIG. 1, the tire cross-section height SH from the tire outer diameter D to the bead toe 53 is 120 mm or more, and the tire cross-section width SW and the tire cross-section height SH are It is preferable to satisfy the range of 1.3 ≦ SW / SH ≦ 2.1.

  The pneumatic tire 1 of the above size is particularly difficult to achieve both run-flat durability performance and riding comfort performance. For this reason, by applying the configuration of the present embodiment to the above-mentioned size, it is possible to obtain a remarkable effect of achieving both run-flat durability performance and riding comfort performance.

  In this example, performance tests regarding run-flat durability performance and riding comfort performance were performed for a plurality of types of pneumatic tires having different conditions (see FIG. 8).

  In this performance test, a pneumatic tire (test tire) having a tire size of 235 / 50R18 in Example 1 and Examples 1 to 9 was assembled to a regular rim of 18 × 7.5 J. In this performance test, a pneumatic tire (test tire) having a tire size of 225 / 60R17 was assembled to a regular rim of 17 × 6.5 J in Conventional Example 2 and Example 10.

  The run-flat durability evaluation method was carried out under the ECE 30 conditions on the test course with the test tire having an internal pressure of 0 kPa. This evaluation is performed by index evaluation with the conventional example 1 as a reference (100) for the travel distance, and the larger the value, the longer the travel distance and the better the run-flat durability performance.

  The evaluation method of the riding comfort performance was a sensory evaluation performed by a test driver running on a test course with a test vehicle equipped with the above test tire with a specified internal pressure. This evaluation is performed by index evaluation using Conventional Example 1 as a reference (100). The larger the value, the better the riding comfort performance.

  In FIG. 8, the pneumatic tires of Conventional Example 1 and Conventional Example 2 have a smaller (1-a ′ / a) than the deformation ratio (1-b ′ / b) of the cross-sectional height. On the other hand, in the tires with mouthpieces of Examples 1 to 10, (1-a '/ a) is larger than the deformation ratio (1-b' / b) of the cross-sectional height. The pneumatic tires of Example 2 and Examples 5 to 10 are (1-b ′ / b) × 1.8 ≦ (1-a ′ / a) ≦ (1-b ′ / b) × 3. 2 is satisfied. In the pneumatic tires of Examples 3 to 10, the surface height deformation rate (1-a ′ / a) is 0.35 or more and 0.65 or less. In the pneumatic tires of Examples 4 to 10, the deformation ratio (1-b ′ / b) of the cross-sectional height is 0.1 or more and 0.35 or less. The pneumatic tires of Examples 5 to 10 satisfy Gb × 0.4 ≦ Ga ≦ Gb × 0.8. In the pneumatic tires of Examples 6 to 10, Gad × 1.2 ≦ Gac ≦ Gad × 2.8 and 3.0 mm ≦ Gac ≦ 10.0 mm. The pneumatic tires of Examples 7 to 10 satisfy Gbf × 1.1 ≦ Gbe ≦ Gbf × 1.8 and 3.0 mm ≦ Gbe ≦ 10.0 mm. In the pneumatic tires of Examples 8 to 10, the rubber hardness at 20 ° C. is large in the range of 3 to 20 Gb with respect to the Ga portion, and the range of 60 to 85 in the Ga portion. It is. In the pneumatic tires of Example 9 and Example 10, the rubber hardness at 20 ° C. is large in the range of 3 to 20 in the other reinforcing rubber layer with respect to the Ga part, and the Ga part is 60 or more. The range is 85 or less, and the portion of the other reinforcing rubber layer is 80 or more and 105 or less. The pneumatic tires of Conventional Example 2 and Example 10 have a tire cross-section height SH of 120 mm or more, and the tire cross-section width SW and the tire cross-section height SH are within a range of 1.3 ≦ SW / SH ≦ 2.1. Fulfill.

  As shown in the test results of FIG. 8, it can be seen that the pneumatic tires of Examples 1 to 10 have both run-flat durability performance and riding comfort performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2A Tread rubber 3 Shoulder part 4 Side wall part 4A Side rubber 5 Bead part 5A Rim cushion rubber 53 Bead toe 6 Carcass layer 10 Reinforcement rubber layer 10A Reinforcement rubber layer 10B Reinforcement rubber layer 10C Other reinforcement rubber layers

Claims (10)

In a pneumatic tire in which a reinforcing rubber layer having a substantially crescent-shaped meridional section is disposed on the sidewall portions on both sides in the tire width direction,
Assembled on a regular rim, the cross-sectional height from the tire maximum width to the tire outer diameter in a no-load state at normal internal pressure is a, the cross-sectional height from the tire maximum width to the bead toe is b, and 65% of the normal load at an internal pressure of 0 kPa When the cross-sectional height from the tire maximum width part to the tire outer diameter in a loaded state is a ′ and the cross-sectional height from the tire maximum width part to the bead toe is b ′, the deformation rate of the cross-sectional height (1-b ′ A pneumatic tire characterized in that (1-a ′ / a) is larger than / b).   The relationship between the deformation ratio (1-a ′ / a) and (1-b ′ / b) of the cross-sectional height is (1−b ′ / b) × 1.8 ≦ (1−a ′ / a). The pneumatic tire according to claim 1, wherein ≦ (1-b ′ / b) × 3.2 is satisfied.   The pneumatic tire according to claim 1 or 2, wherein a deformation ratio (1-a '/ a) of the cross-sectional height is 0.35 or more and 0.65 or less.   The pneumatic tire according to any one of claims 1 to 3, wherein a deformation ratio (1-b '/ b) of the cross-sectional height is 0.1 or more and 0.35 or less.   A carcass layer that spans between the bead cores disposed on the bead portions on both sides in the tire width direction, and the carcass is located at a tire side surface position that is ½ of the cross-sectional height from the tire maximum width portion to the tire outer diameter. The meridional section thickness on the perpendicular to the layer is Ga, and the meridional section thickness on the perpendicular to the carcass layer is Gb at the tire side surface position of ½ of the section height between the tire maximum width part and the bead toe. The pneumatic tire according to claim 1, wherein Gb × 0.4 ≦ Ga ≦ Gb × 0.8 is satisfied.   In the meridional section thickness Ga, when Gac is a meridional section thickness in a range inside the tire from the carcass layer and Gad is a meridional section thickness in a range outside the tire from the carcass layer, Gad × 1.2 ≦ Gac The pneumatic tire according to claim 5, wherein ≦ Gad × 2.8 and 3.0 mm ≦ Gac ≦ 10.0 mm.   In the meridional section thickness Gb, when the meridional section thickness in the range inside the tire from the carcass layer is Gbe and the meridional section thickness in the range outside the tire from the carcass layer is Gbf, Gbf × 1.1 ≦ Gbe The pneumatic tire according to claim 5 or 6, wherein ≦ Gbf × 1.8 and 3.0 mm ≦ Gbe ≦ 10.0 mm. It has a carcass layer that spans between the bead cores arranged on the bead portions on both sides in the tire width direction, and is located at a position that is ½ of the cross-sectional height from the tire maximum width to the tire outermost diameter with respect to the carcass layer. When the meridional section thickness on the perpendicular is Ga, and the meridional section thickness on the perpendicular to the carcass layer is Gb at a position of 1/2 the section height between the tire maximum width and the bead toe,
The type of rubber forming the reinforcing rubber layer including the meridional section thickness Ga portion and the meridional section thickness Gb portion is different. With respect to rubber hardness at 20 ° C., the Gb portion is different from the Ga portion. The pneumatic tire according to any one of claims 1 to 7, wherein the pneumatic tire is large in a range of 3 to 20 and a Ga portion is in a range of 60 to 85. It has a carcass layer that spans between the bead cores arranged on the bead portions on both sides in the tire width direction, and is located at a position that is ½ of the cross-sectional height from the tire maximum width to the tire outermost diameter with respect to the carcass layer. When the meridional section thickness on the perpendicular is Ga, and the meridional section thickness on the perpendicular to the carcass layer is Gb at a position of 1/2 the section height between the tire maximum width and the bead toe,
The reinforcing rubber layer is provided inside the tire from the carcass layer, and has another reinforcing rubber layer outside the tire from the carcass layer in the meridional section thickness Gb. The portion of the other reinforcing rubber layer is large in the range of 3 to 20 and the portion of Ga is in the range of 60 to 85, and the portion of the other reinforcing rubber layer is 80 to 105. The pneumatic tire according to any one of claims 1 to 8, characterized in that   The tire cross-section height SH from the tire outer diameter to the bead toe is 120 mm or more, and the tire cross-section width SW and the tire cross-section height SH satisfy a range of 1.3 ≦ SW / SH ≦ 2.1. The pneumatic tire according to any one of claims 1 to 9.

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