阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 竹森谅平 于 2019-10-10 设计创作，主要内容包括：本发明提供一种能在改善泄气保用耐久性的同时减小滚动阻力,并且改善通常行驶时的乘坐舒适性的充气轮胎。在胎圈部(3)的各胎圈芯(5)的外周侧配置有胎边芯(6),在侧壁部(2)的胎体层(4)的轮胎宽度方向内侧配置有剖面月牙状的胎侧增强层(11),作为构成胎侧增强层(11)的橡胶和构成胎边芯(6)的橡胶的物性,100％伸长时的模量为8.4MPa～10.2MPa的范围,60℃下的tanδ为0.04～0.08的范围,20℃下的JIS硬度为75～79的范围。(The invention provides a pneumatic tire which can improve the run-flat durability, reduce the rolling resistance and improve the riding comfort during the normal running. A bead filler (6) is disposed on the outer periphery of each bead core (5) of a bead portion (3), a side reinforcing layer (11) having a crescent cross-section is disposed on the inner side of a carcass layer (4) of a sidewall portion (2) in the tire width direction, and as the physical properties of the rubber constituting the side reinforcing layer (11) and the rubber constituting the bead filler (6), the modulus at 100% elongation is in the range of 8.4MPa to 10.2MPa, the tan delta at 60 ℃ is in the range of 0.04 to 0.08, and the JIS hardness at 20 ℃ is in the range of 75 to 79.)

1. A pneumatic tire, comprising: a tread portion extending in a tire circumferential direction and formed in a ring shape; a pair of side wall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on inner sides of the sidewall portions in a tire radial direction, at least one carcass layer being interposed between the pair of bead portions, the carcass layer being turned up around a bead core of each bead portion from a tire inner side to an outer side, a bead filler being disposed on an outer peripheral side of each bead core of the bead portion, a plurality of belt layers being disposed on an outer peripheral side of the carcass layer of the tread portion, and a side reinforcing layer having a crescent-shaped cross section being disposed on an inner side of the carcass layer of the sidewall portion in a tire width direction,

the physical properties of the rubber constituting the side reinforcing layer and the rubber constituting the bead filler are such that the modulus at 100% elongation is in the range of 8.4MPa to 10.2MPa, the tan delta at 60 ℃ is in the range of 0.04 to 0.08, and the JIS hardness at 20 ℃ is in the range of 75 to 79.

2. A pneumatic tire according to claim 1,

an outer reinforcement layer that overlaps the bead filler and the sidewall reinforcement layer in the tire radial direction is provided on the tire width direction outer side of the carcass layer of the sidewall portion.

3. A pneumatic tire according to claim 2,

a height HW from the bead heel to a maximum thickness position of the side reinforcing layer and a height H1 from the bead heel to a tire radial direction outer side end portion of the outer reinforcing layer satisfy a relationship of 0.6 ≦ H1/HW ≦ 0.8.

4. A pneumatic tire according to claim 2 or 3,

the rubber constituting the outer reinforcing layer has a modulus at 100% elongation in the range of 5.2MPa to 6.4MPa and a JIS hardness at 20 ℃ in the range of 70 to 74 as physical properties.

5. A pneumatic tire according to any one of claims 1 to 4,

a height HW from the bead heel to a maximum thickness position of the side reinforcing layer and a height H2 from the bead heel to a tire radial direction outer side end portion of the bead core satisfy a relationship of 0.35 ≦ H2/HW ≦ 0.50.

6. A pneumatic tire according to any one of claims 1 to 5,

the ratio of the width of the belt layer located on the outermost side in the tire radial direction to the ground contact width is in the range of 101% to 110%, and the amount of overlap between the belt layer located on the innermost side in the tire radial direction and the side reinforcing layer is in the range of 15mm to 30 mm.

7. A pneumatic tire according to any one of claims 1 to 6,

the belt layer has a cord angle in the range of 25 DEG to 35 DEG with respect to the tire circumferential direction, and has at least one belt cover layer covering the entire width on the outer circumferential side of the belt layer.

Technical Field

The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire capable of improving ride comfort during normal running while reducing rolling resistance while improving run-flat durability.

Background

As a pneumatic tire capable of running in a deflated state, a side-reinforced run-flat tire in which a run-flat reinforcing layer having a crescent-shaped cross section is disposed on the inner surface side of a side wall portion has been proposed (for example, see patent documents 1 and 2). In such a run-flat tire, when the volume of rubber constituting the side reinforcing layer is increased to suppress deflection during run-flat running, there is a problem as follows: heat generation is promoted and rolling resistance increases, and ride comfort during normal running deteriorates due to an increase in the rigidity of the side wall.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 7-304312

Patent document 2: japanese laid-open patent publication No. 2009-61866

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a pneumatic tire which can reduce rolling resistance while improving run-flat durability and improve riding comfort during normal running.

Technical scheme

The pneumatic tire of the present invention for achieving the above object includes: a tread portion extending in a tire circumferential direction and formed in a ring shape; a pair of side wall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on the inner side of the sidewall portions in the tire radial direction, at least one carcass layer being interposed between the pair of bead portions, the carcass layer being turned up around the bead cores of the respective bead portions from the inner side to the outer side of the tire, bead cores being disposed on the outer peripheral sides of the bead cores of the bead portions, a plurality of belt layers being disposed on the outer peripheral sides of the carcass layer of the tread portion, and a side reinforcing layer having a crescent-shaped cross section being disposed on the inner side of the sidewall portions in the tire width direction of the carcass layer, wherein the pneumatic tire is characterized in that the modulus at 100% elongation is in a range of 8.4MPa to 10.2MPa, the tan δ at 60 ℃ is in a range of 0.04 to 0.08, and the JIS hardness at 20 ℃ is in a range of 75 to 79.

Advantageous effects

In the present invention, the physical properties of the rubber constituting the side reinforcing layer and the rubber constituting the bead filler are such that the modulus at 100% elongation is in the range of 8.4MPa to 10.2MPa, and therefore, the occurrence of separation of the carcass layer located between the side reinforcing layer and the bead filler can be prevented, and the run-flat durability can be improved. Further, since the rubber has a tan delta of 0.04 to 0.08 at 60 ℃ and is low in heat generation, heat generation during run-flat running can be suppressed and rolling resistance can be reduced. Further, the JIS hardness at 20 ℃ is in the range of 75 to 79, so that the run-flat durability and the riding comfort during normal running can be improved in a well-balanced manner. By setting the physical properties of the rubbers constituting the side reinforcing layer and the bead filler within the specific ranges as described above, the difference in physical properties between the rubbers can be reduced without increasing the cross-sectional area or thickness of the rubber constituting the side reinforcing layer. This improves the run-flat durability and reduces the rolling resistance, thereby improving the riding comfort during normal running.

In the present invention, it is preferable that an outer reinforcing layer overlapping the bead filler and the side reinforcing layer in the tire radial direction is provided on the outer side in the tire width direction of the carcass layer of the sidewall portion. This can effectively improve the tire casing (casting) rigidity, and suppress the shear stress applied to the carcass layer during run-flat running while avoiding adverse effects on the ride comfort during normal running.

In the present invention, it is preferable that a height HW from the bead heel of the bead portion to the maximum thickness position of the side reinforcing layer and a height H1 from the bead heel of the bead portion to the tire radial direction outer side end portion of the outer reinforcing layer satisfy a relationship of 0.6 ≦ H1/HW ≦ 0.8. This suppresses deformation around the bead portion, and the bending point of the sidewall portion during run-flat running can be moved toward the tread portion, thereby effectively improving run-flat durability.

In the present invention, it is preferable that the rubber constituting the outer reinforcing layer has a modulus at 100% elongation in the range of 5.2MPa to 6.4MPa and a JIS hardness at 20 ℃ in the range of 70 to 74 as physical properties. This improves the riding comfort during normal running while maintaining the run-flat durability.

In the present invention, it is preferable that a height HW from the bead heel of the bead portion to the maximum thickness position of the side reinforcing layer and a height H2 from the bead heel of the bead portion to the tire radial direction outer side end portion of the bead core satisfy a relationship of 0.35 ≦ H2/HW ≦ 0.50. Thus, the bending point of the sidewall portion during run-flat running can be moved toward the tread portion, and the tire weight can be reduced while maintaining run-flat durability even when the sidewall reinforcing layer is made thinner than in the conventional case.

In the present invention, it is preferable that the ratio of the width of the belt layer located on the outermost side in the tire radial direction to the ground contact width is in the range of 101% to 110%, and the amount of overlap between the belt layer located on the innermost side in the tire radial direction and the side reinforcing layer is in the range of 15mm to 30 mm. This effectively improves the run-flat durability.

In the present invention, it is preferable that the belt layer has a cord angle in the range of 25 ° to 35 ° with respect to the tire circumferential direction, and has at least one belt cover layer covering the entire width on the outer circumferential side of the belt layer. This can suppress the warp of the tread portion and effectively improve the run-flat durability.

In the present invention, the modulus at 100% elongation used for specifying the rubber properties is the measurement result of the modulus at 100% strain when a tensile test is performed at room temperature using a rubber sample having a shape based on No. 3 dumbbell in accordance with JIS-K6251. tan δ (60 ℃) is a measurement result of a viscoelastometer according to JIS-K6934 under the conditions of a frequency of 20Hz, an initial strain of 10%, a dynamic strain of. + -. 2%, and a temperature of 60 ℃. The JIS hardness (20 ℃ C.) is a durometer hardness measured at a temperature of 20 ℃ in accordance with JIS-K6253 using a type A durometer. In the present invention, the ground contact width is the maximum linear distance in the tire axial direction of the contact surface with the flat surface when the tire is placed perpendicular to the flat surface by assembling the tire rim to a JATMA standard rim, applying a load of 70% of the load capacity in a state filled with an internal pressure of 230kPa, and placing the tire on the flat surface.

Drawings

Fig. 1 is a meridian semi-sectional view showing an example of a pneumatic tire according to an embodiment of the present invention.

Detailed Description

Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings. Fig. 1 is a diagram showing an example of a pneumatic tire according to an embodiment of the present invention.

As shown in fig. 1, the pneumatic tire of the present embodiment includes: a tread portion 1 extending in a tire circumferential direction and formed in a ring shape; a pair of side wall portions 2 disposed on both sides of the tread portion 1; and a pair of bead portions 3 disposed on the inner side of the sidewall portions 2 in the tire radial direction. In fig. 1, only a half section of one side in the tire width direction with the tire center line CL as a boundary is depicted, and the pneumatic tire has a symmetrical configuration on both sides of the tire center line CL. Of course, an asymmetrical configuration may also be employed.

At least one carcass layer 4 (two layers in fig. 1) is mounted between a pair of left and right bead portions 3, 3. Each end of the carcass layer 4 is wound up around the bead core 5 disposed in each bead portion 3 from the inner side to the outer side of the tire. A bead filler 6 having a triangular cross section and made of rubber is disposed on the outer circumferential side of each bead core 5. The carcass layer 4 encases the bead filler 6 and extends to terminate adjacent the sidewall portion 2. An inner liner 7 is disposed in a region between the pair of left and right bead portions 3, 3 on the inner surface of the tire.

A plurality of (two in fig. 1) belt layers 8 are embedded in the tread portion 1 on the tire outer circumferential side of the carcass layer 4. The belt layer 8 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and is configured such that the reinforcing cords cross each other between layers. The reinforcing cords of the belt layer 8 are preferably steel cords. At least one (two in fig. 1) belt cover layer 9 arranged at an angle of 5 ° or less with respect to the tire circumferential direction is disposed on the tire outer circumferential side of the belt layer 8 for the purpose of improving high-speed durability. In the solution of fig. 1, the belt cover layer 9 located on the inner side in the tire radial direction constitutes a full cover covering the entire width of the belt layer 8, and the belt cover layer 9 located on the outer side in the tire radial direction constitutes an edge cover covering only the end portions of the belt layer 8. As the reinforcing cord of the belt cover layer 9, an organic fiber cord of nylon, aramid, or the like is preferably used.

A tread rubber layer 10 is disposed on the outer peripheral side of the belt layer 8 and the belt cover layer 9 of the tread portion 1. A side reinforcing layer 11 having a crescent-shaped cross section for enabling run-flat running is disposed between the carcass layer 4 and the inner liner 7 of the side wall portion 2. The sidewall reinforcing layer 11 overlaps with the bead filler 6 in the tire radial direction. The length of the portion where the side reinforcing layer 11 and the bead filler 6 overlap each other as measured in the tire radial direction is preferably in the range of 15mm to 30 mm. A side rubber layer 12 is disposed on the outer peripheral side (outer side in the tire width direction) of the carcass layer 4 of the sidewall 2. A rim cushion rubber layer 13 is disposed on the outer peripheral side (outer side in the tire width direction) of the carcass layer 4 of the bead portion 3.

In the pneumatic tire described above, the rubber constituting the side reinforcing layer 11 and the rubber constituting the bead filler 6 have the following physical properties. The modulus M100 at 100% elongation of the rubber constituting the side reinforcing layer 11 and the rubber constituting the bead filler 6 is in the range of 8.4MPa to 10.2 MPa. Particularly preferably, the modulus M100 of the rubber constituting the bead filler 6_BFGreater than the modulus M100 of the rubber constituting the side reinforcing layer 11_SLMore preferably, the difference between the moduli of the two (M100)_BF-M100_SL)/M100_BFIs 10% or less.

Further, the rubber constituting the side reinforcing layer 11 and the rubber constituting the bead filler 6 both have tan δ at 60 ℃ in the range of 0.04 to 0.08. Particularly preferably, the tan delta at 60 ℃ is in the range of 0.05 to 0.07. Further, it is more preferable that the rubber constituting the bead filler 6 has tan δ at 60 ℃_BFTan delta at 60 ℃ greater than that of the rubber constituting the side reinforcing layer 11_SLMost preferably, the difference between tan δ and tan δ (tan δ)_BF-tanδ_SL)/tanδ_BFIs 10% or less.

The rubber constituting the side reinforcing layer 11 and the rubber constituting the bead filler 6 both have a JIS hardness at 20 ℃ in the range of 75 to 79. It is particularly preferable that the JIS hardness at 20 ℃ of the rubber constituting the bead filler 6 is higher than that of the rubber constituting the side reinforcing layer 11.

In the side reinforcing layer 11 and the bead filler 6, the ratio (S/S) of the sectional area S of the bead filler 6 to the sectional area S of the side reinforcing layer 11 is preferably in the range of 0.15 to 0.35. Further, it is preferable that the maximum thickness Tm of the side reinforcing layer 11 is in the range of 8.5mm to 11.5 mm. The maximum thickness Tm of the side reinforcing layer 11 is the maximum value of the rubber thickness measured in the direction orthogonal to the inner circumferential surface of the carcass layer 4.

In the pneumatic tire described above, the modulus M100 at 100% elongation is in the range of 8.4MPa to 10.2MPa as the physical properties of the rubber constituting the side reinforcing layer 11 and the rubber constituting the bead filler 6, and therefore, the occurrence of separation of the carcass layer 4 located between the side reinforcing layer 11 and the bead filler 6 can be prevented, and the run-flat durability can be improved. Further, since the rubber has a tan delta of 0.04 to 0.08 at 60 ℃ and is low in heat generation, heat generation during run-flat running can be suppressed and rolling resistance can be reduced. Further, the JIS hardness at 20 ℃ is in the range of 75 to 79, so that the run-flat durability and the riding comfort during normal running can be improved in a well-balanced manner. By setting the physical properties of the rubbers constituting the side reinforcing layer 11 and the bead filler 6 to specific ranges in this way, the difference in physical properties between the rubbers can be reduced without increasing the cross-sectional area or thickness of the rubber constituting the side reinforcing layer 11. This improves the run-flat durability and reduces the rolling resistance, thereby improving the riding comfort during normal running.

On the other hand, when the modulus M100 is less than 8.4MPa or more than 10.2MPa, the separation of the carcass layer 4 tends to occur easily, and the run-flat durability tends to deteriorate. Further, although the smaller the tan δ at 60 ℃, the more suppressed the heat generation during run-flat running, it is difficult to make the tan δ at 60 ℃ less than 0.04, and when the tan δ at 60 ℃ is made greater than 0.08, the heat generation during run-flat running tends to occur more easily, and rolling resistance tends to deteriorate. Further, if the JIS hardness at 20 ℃ is less than 75, the run-flat durability becomes insufficient, and if the JIS hardness at 20 ℃ is more than 79, the riding comfort during normal running deteriorates.

In fig. 1, an outer reinforcing layer 14 that overlaps the bead filler 6 and the side reinforcing layer 11 in the tire radial direction is disposed on the outer side of the carcass layer 4 of the sidewall portion 2 in the tire width direction. In the embodiment of fig. 1, the outer reinforcing layer 14 extends in the tire radial direction so that one end thereof is located halfway through the bead filler 6 and the other end thereof is located halfway through the sidewall reinforcing layer 11. By disposing the outer reinforcing layer 14 on the tire width direction outer side of the carcass layer 4 of the side wall portion 2, the tire rigidity can be effectively improved, and the shear stress received by the carcass layer 4 during run-flat running can be suppressed while avoiding adverse effects on the riding comfort during normal running.

Preferably, the physical properties of the rubber constituting the outer reinforcing layer 14 include a modulus at 100% elongation in the range of 5.2MPa to 6.4MPa and a JIS hardness at 20 ℃ in the range of 70 to 74. Since the rubber constituting the outer reinforcing layer 14 has the above physical properties, the riding comfort during normal running can be improved while maintaining the run-flat durability.

In the pneumatic tire described above, the height from the bead heel 3A of the bead portion 3 to the position of the maximum thickness Tm of the side reinforcing layer 11 is defined as the height HW, and the height from the bead heel 3A of the bead portion 3 to the tire radial direction outer side end of the outer reinforcing layer 14 is defined as the height H1. At this time, it is preferable that the height HW of the side reinforcing layer 11 and the height H1 of the outer reinforcing layer 14 satisfy the relationship of 0.6. ltoreq.H 1/HW. ltoreq.0.8. Further, it is more preferable that the height H1 of the outer reinforcing layer 14 and the height H2 of the bead filler 6 described later satisfy the relationship of H1> H2. By appropriately setting the ratio of the height H1 of the outer reinforcing layer 14 to the height HW of the side reinforcing layer 11 in this way, deformation around the bead portion 3 can be suppressed, the bending point of the side wall portion 2 during run-flat running can be moved toward the tread portion 1 side, and run-flat durability can be effectively improved. Here, if the ratio of the height H1 of the outer reinforcing layer 14 to the height HW of the side reinforcing layer 11 is less than 0.6, the tire weight can be reduced, but the effect of improving the run-flat durability cannot be sufficiently obtained. On the other hand, if the ratio is more than 0.8, the run-flat durability can be improved, but the tire weight tends to increase and the rolling resistance tends to deteriorate.

Further, the height from the bead heel 3A of the bead portion 3 to the outer end of the bead core 6 in the tire radial direction is set to a height H2. At this time, it is preferable that the height HW of the side reinforcing layer 11 and the height H2 of the bead filler 6 satisfy the relationship of 0.35. ltoreq.H 2/HW. ltoreq.0.50. By appropriately setting the ratio of the height H2 of the bead core 6 to the height HW of the side reinforcing layer 11 in this way, the bending point of the side wall portion 2 during run-flat running can be moved toward the tread portion 1, and even when the side reinforcing layer 11 is made thinner than in the past, the tire weight can be reduced while maintaining run-flat durability. Here, when the ratio of the height H2 of the bead filler 6 to the height HW of the side reinforcing layer 11 is less than 0.35, ride comfort during normal running tends to be deteriorated, and when the ratio of the height H2 of the bead filler 6 to the height HW of the side reinforcing layer 11 is more than 0.50, rolling resistance tends to be deteriorated.

Further, it is preferable that the ratio of the width BW of the belt layer 8 located on the outermost side in the tire radial direction to the ground contact width W is in the range of 101% to 110%, and the overlap L of the belt layer 8 located on the innermost side in the tire radial direction and the side reinforcing layer 11 is in the range of 15mm to 30 mm. By appropriately setting the ratio of the width BW of the belt layer 8 to the ground contact width W and the overlap amount L of the belt layer 8 and the side reinforcing layer 11 in this way, respectively, the runflat durability can be effectively improved. Here, if the ratio of the width BW of the belt layer 8 to the ground contact width W is less than 101%, the reinforcing effect of the belt layer 8 cannot be sufficiently obtained, while if the ratio of the width BW of the belt layer 8 to the ground contact width W is more than 110%, the tire weight tends to increase and the rolling resistance tends to deteriorate. The overlap L between the belt layer 8 and the side reinforcing layer 11 is a length obtained by measuring the overlap portion along the extending direction of the belt layer 8.

In the present invention, it is preferable that the belt layer 8 has a cord angle in the range of 25 ° to 35 ° with respect to the tire circumferential direction, and at least one belt cover layer 9 covering the entire width on the outer circumferential side of the belt layer 8. By appropriately setting the cord angle of the belt layer 8 and providing the belt cover layer 9 constituting the full coverage in this way, the warp of the tread portion 1 can be suppressed, and the run-flat durability can be effectively improved. Here, if the cord angle is less than 25 °, the tire width direction component of the cord is insufficient, and therefore the warpage of the tread portion 1 cannot be sufficiently suppressed, whereas if the cord angle is greater than 35 °, the tire performance during normal running cannot be sufficiently obtained.

In the case of applying the present invention to a pneumatic tire having a high tire section height, the obtained effect is remarkable. The tire cross-sectional height of such a pneumatic tire having a high tire cross-sectional height is preferably in the range of 115mm to 145 mm.

Examples of the invention

Tires of the conventional examples, comparative examples 1 to 3, and examples 1 to 9 were produced in which the following parameters were set as shown in table 1 in pneumatic tires: m100, tan. delta. (60 ℃ C.) and JIS hardness (20 ℃ C.) of the rubber constituting the side reinforcing layer and the rubber constituting the bead filler; presence or absence of an outer reinforcement layer; m100 and JIS hardness (20 ℃ C.) of the rubber constituting the outer reinforcing layer; the ratio of the height H1 of the outer reinforcing layer relative to the height HW of the sidewall reinforcing layer (H1/HW); the ratio of the height H2 of the bead filler relative to the height HW of the sidewall reinforcement layer (H2/HW); the ratio of the belt layer width BW to the ground contact width W (BW/W × 100%); the overlap L of the belt layer and the sidewall reinforcing layer; cord angle of the belt; and the presence or absence of a fully covered belt cover layer. The pneumatic tire has a tire size of 235/60RF18, and includes: a tread portion extending in a tire circumferential direction and formed in a ring shape; a pair of side wall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on the inner side of the sidewall portions in the tire radial direction, at least one carcass layer is mounted between the pair of bead portions, the carcass layer is turned up around the bead core of each bead portion from the inner side to the outer side of the tire, a bead filler is disposed on the outer circumferential side of each bead core of the bead portion, a plurality of belt layers are disposed on the outer circumferential side of the carcass layer of the tread portion, and a side reinforcing layer having a crescent-shaped cross section is disposed on the inner side of the carcass layer of the sidewall portion in the tire width direction.

These test tires were evaluated for rolling resistance, riding comfort, and run-flat durability by the following test methods, and the results are shown in table 1.

Rolling resistance:

each test tire was assembled to a wheel having a rim size of 18 × 7.5J, and the rolling resistance was measured using a drum tester under the condition of an air pressure of 210 kPa. The evaluation results are expressed as an index with the conventional example set to 100. The smaller the index value, the smaller the rolling resistance is.

Riding comfort:

each test tire was assembled to a wheel having a rim size of 18 × 7.5J and attached to a vehicle having an air displacement of 2500cc, and subjected to sensory evaluation by a test driver under the condition of an air pressure of 250 kPa. The evaluation results are expressed by a 5-point full-scale method with the conventional example as a reference point of 3. The larger the evaluation value, the more excellent the riding comfort.

Run-flat durability:

each test tire was assembled to a wheel having a rim size of 18 × 7.5J, and a running test was performed using a drum tester under conditions of an air pressure of 0kPa and 65% of the maximum load capacity specified by JATMA or ETRTO as a load. Specifically, the running speed was set at 80km/h, and the running distance was measured until the tire failed. The evaluation results are expressed as an index with the conventional example set to 100. The larger the index value, the more excellent the runflat durability is.

As can be seen from table 1, the pneumatic tires of examples 1 to 9 have reduced rolling resistance and improved ride comfort while improving run-flat durability, as compared with the conventional examples.

On the other hand, in comparative example 1, M100 and tan δ (60 ℃) of the rubber constituting the side reinforcing layer were out of the ranges specified in the present invention, and in comparative example 2, M100 and tan δ (60 ℃) of the rubber constituting the bead filler were out of the ranges specified in the present invention, and therefore the effects of improving rolling resistance and runflat durability were insufficient. In comparative example 3, since M100 and tan δ (60 ℃) of the rubbers constituting the side reinforcing layer and the bead filler, respectively, are out of the ranges specified in the present invention, the effects of improving rolling resistance and runflat durability are insufficient.

Description of the symbols

1 tread part

2 side wall part

3 bead portion

4 carcass ply

5 bead core

6 bead filler

7 inner liner layer

8 belted layer

9 Belt overlay

10 Tread rubber layer

11 sidewall reinforcement layer

12 side wall rubber layer

13 rim cushion rubber layer

14 outer reinforcement layer