pneumatic tires

Abstract

Pneumatic tires, including: a tread section (1) which has a ring shape and extends in the circumferential direction of the tire; a pair of sidewall sections (2) arranged on both sides of the running surface section (1); and a pair of bead sections (3) arranged on inner surfaces in the tire radial direction of the pair of sidewall sections (2), wherein at least one carcass layer (4) is placed between the pair of bead sections (3), wherein the carcass layer (4) is turned upwards from an inner tire side to an outer tire side around a bead core (5) of each of the pair of bead sections (3), wherein a bead filler (6) is arranged on an outer circumferential side of the bead core (5) in each of the pair of bead sections (3), wherein a plurality of belt layers (8) are arranged on an outer circumferential side of the carcass layer (4) in the tread section (1), and wherein a side reinforcement layer (11) with a crescent-shaped cross-section is arranged on an inner side in the tire width direction of the carcass layer (4) in each of the pair of sidewall sections (2), and wherein the physical properties of a rubber forming the side reinforcement layer (11) and of a rubber forming the bead filler (6) are a modulus at 100% elongation in the range of 8.4 MPa to 10.2 MPa, a tan δ at 60 °C in the range of 0.04 to 0.08 and a JIS hardness at 20 °C in the range of 75 to 79, wherein an outer reinforcing layer (14) overlapping the bead filler (6) and the sidewall reinforcement layer (11) in the tire radial direction is arranged on an outer side in the tire width direction of the carcass layer (4) in each of the pair of sidewall sections (2), wherein the physical properties of a rubber forming the outer reinforcing layer (14) are a modulus at 100% elongation in the range of 5.2 MPa to 6.4 MPa and the JIS hardness at 20 °C in the range of 70 to 74.

Description

Technical field

[0001] The present invention relates to a pneumatic tire and more precisely to a pneumatic tire that can provide reduced rolling resistance while simultaneously improving run-flat durability and providing improved driving comfort under normal driving conditions. State of the art

[0002] Among pneumatic tires that can move while flat, a run-flat tire of the sidewall-reinforced type is known, which has a run-flat reinforcement layer with a crescent-shaped cross-section arranged on the inner surface of the sidewall section (see, for example, patent documents 1 and 2). With such a run-flat tire, increasing the volume of the rubber forming a sidewall reinforcement layer to suppress deflection under run-flat driving conditions promotes heat build-up and increases rolling resistance. Furthermore, a problem arises from the deterioration of ride comfort under normal driving conditions due to increased lateral stiffness. Patent document 3 describes a run-flat tire with a sidewall reinforcement layer made of a rubber.The rubber forming the sidewall reinforcement layer has a modulus at 100% elongation in the range of 8.4 MPa to 10.2 MPa, a tan δ at 60 °C in the range of 0.04 to 0.08, and a JIS hardness at 20 °C in the range of 75 to 79. Patent document 4 describes a run-flat tire in which a sidewall reinforcement rubber has a tan δ at 60 °C that is within the range of 0.01 or more and 0.08 or less, and a JIS hardness at 20 °C that is within the range of 72 or more and 82 or less. List of oppositions patent literature Patent Document 1: JP H07-304 312 A Patent document 2: JP 2009- 61 866 A Patent document 3: JP 2013- 95 369 A Patent document 4: DE 11 2018 005 545 T5 Brief description of the invention: Technical problem

[0003] One object of the present invention is to provide a pneumatic tire that can provide reduced rolling resistance while simultaneously improving run-flat durability and providing improved driving comfort under normal driving conditions. Solution to the problem

[0004] To solve the aforementioned problem, a pneumatic tire according to one embodiment of the present invention includes: a tread section having a ring shape and extending in the circumferential direction of the tire; a pair of sidewall sections arranged on both sides of the tread section; and a pair of bead sections arranged on the inner sides in the tire radial direction of the pair of sidewall sections, wherein at least one carcass layer is placed between the pair of bead sections, the carcass layer being turned upwards from an inner side of the tire to an outer side of the tire around a bead core of each of the bead sections, wherein a bead filler is arranged on an outer circumferential side of the bead core in each of the bead sections, and wherein a plurality of belt layers are arranged on an outer circumferential side of the carcass layer in the tread section.and wherein a sidewall reinforcement layer with a crescent-shaped cross-section is arranged on the inside in the tire width direction of the carcass layer in each of the pair of sidewall sections, wherein the physical properties of a rubber forming the sidewall reinforcement layer and of a rubber forming the bead filler are a modulus at 100% elongation in the range of 8.4 MPa to 10.2 MPa, a tan δ at 60 °C in the range of 0.04 to 0.08, and the JIS hardness at 20 °C in the range of 75 to 79. Advantageous effects of the invention

[0005] In embodiments of the present invention, the physical properties of the rubber forming the sidewall reinforcement layer and the rubber forming the bead filler, with their modulus at 100% extension ranging from 8.4 MPa to 10.2 MPa, prevent peeling of the carcass layer located between the sidewall reinforcement layer and the bead filler, and improve run-flat durability. Additionally, since the rubbers have a tan δ at 60 °C in the range of 0.04 to 0.08 and are low-heat-generating, heat build-up under run-flat driving conditions is suppressed, and rolling resistance can be reduced. Furthermore, since the JIS hardness at 20 °C is in the range of 75 to 79, run-flat durability and ride comfort under normal driving conditions can be improved in a well-balanced manner.By defining the physical properties of the rubbers forming the sidewall reinforcement layer and the bead filler within a specific range, the difference in physical properties between the rubber forming the sidewall reinforcement layer and the rubber forming the bead filler can be reduced without increasing the cross-sectional area or thickness of the rubber forming the sidewall reinforcement layer. This reduces rolling resistance while simultaneously improving run-flat durability and enhancing ride comfort under normal driving conditions.

[0006] According to the present invention, an outer reinforcing layer, which overlaps the bead filler and the sidewall reinforcement layer in the tire radial direction, is arranged on an outer surface in the tire width direction of the carcass layer in each of the pair of sidewall sections. In this way, the stiffness of the tire carcass can be effectively improved, and shear stress exerted on the carcass layer under run-flat driving conditions can be suppressed, while adverse effects on ride comfort under normal driving conditions are avoided.

[0007] In embodiments of the present invention, a height HW from a bead heel of each of the pair of bead sections to a position of maximum thickness of the sidewall reinforcement layer and a height H1 from the bead heel of each of the pair of bead sections to an outer end section in the tire radial direction of the outer reinforcement layer preferably satisfy the relationship 0.6 ≤ H1 / HW ≤ 0.8. In this way, deformation around the bead sections is suppressed, and a bending point of the sidewall section under run-flat driving conditions is moved to one side of the tread section, and the run-flat durability can be effectively improved.

[0008] According to the present invention, the physical properties of the rubber forming the outer reinforcement layer include a modulus at 100% elongation in the range of 5.2 MPa to 6.4 MPa, and a JIS hardness at 20 °C in the range of 70 to 74. In this way, driving comfort under normal driving conditions can be improved while maintaining run-flat durability.

[0009] In embodiments of the present invention, a height HW from a bead heel of each of the pair of bead sections to a position of maximum thickness of the sidewall reinforcement layer and a height H2 from the bead heel of each of the pair of bead sections to an outer end section in the tire radial direction of the bead filler preferably satisfy the relationship 0.35 ≤ H2 / HW ≤ 0.50. In this way, the bending point of the sidewall section is moved towards the side of the tread section under run-flat driving conditions, and thereby the tire weight can be reduced while maintaining run-flat durability even if the sidewall reinforcement layer is manufactured thinner than in the prior art.

[0010] In embodiments of the present invention, 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 sidewall reinforcement layer is preferably in the range of 15 mm to 30 mm. In this way, the run-flat durability can be effectively improved.

[0011] In embodiments of the present invention, the cord angle of the belt layers with respect to the tire's circumferential direction is preferably in a range of 25° to 35°, and preferably at least one belt cover layer, covering an entire width of the belt layer, is arranged on an outer circumferential side of the belt layers. In this way, yielding of the tread section is suppressed, and the run-flat durability can be effectively improved.

[0012] In embodiments of the present invention, the modulus at 100% elongation, used to specify physical rubber properties, refers to the modulus measurement at 100% deformation when a tensile test is performed at room temperature on a rubber specimen using a mold according to Dumbbell No. 3 in accordance with JIS-K 6251. The tan δ (60 °C) refers to the measurement under conditions of a frequency of 20 Hz, an initial stress of 10%, a dynamic stress of ±2%, and a temperature of 60 °C using a viscoelasticity spectrometer according to JIS-K 6934. The JIS hardness (20 °C) is the durometer hardness measured under conditions of a temperature of 20 °C using a type A durometer according to JIS-K 6253.Furthermore, in embodiments of the present invention, the ground contact width is the maximum linear distance in the tire axial direction at a contact surface with a flat surface when the tire is mounted on a JATMA standard rim, subjected to a load of 70% of a load capacity when inflated to an internal pressure of 230 kPa, and placed vertically on the flat surface. Brief description of the drawings Fig. Figure 1 is a meridian cross-sectional view illustrating an example of a pneumatic tire according to an embodiment of the present invention. Description of embodiments

[0013] Configurations of embodiments of the present invention are described in detail below with reference to the accompanying drawings. Fig. Figure 1 illustrates an example of a pneumatic tire according to an embodiment of the present invention.

[0014] As in Fig. As illustrated in Figure 1, the pneumatic tire according to the present embodiment includes an annular tread section 1 extending in the circumferential direction of the tire, a pair of sidewall sections 2 arranged on both sides of the tread section 1, and a pair of bead sections 3 arranged on an inner side of the pair of sidewall sections 2 in the radial direction of the tire. Fig. Figure 1 illustrates only half the cross-section on one side in the tire width direction, bounded by a tire centerline CL. However, the pneumatic tire has a symmetrical structure on both sides of the tire centerline CL. An asymmetrical structure can obviously be used.

[0015] At least one carcass layer 4 (two layers in Fig.1) is located between the pair of left and right bead sections 3, 3. Each end section of the carcass layer 4 is turned upwards around a bead core 5, which is located in each of the bead sections 3, from one tire inner surface to one tire outer surface. A rubber bead filler 6 with a triangular cross-sectional shape is located on one outer circumferential surface of each of the bead cores 5. The carcass layer 4 wraps around the bead filler 6, extends to near the sidewall sections 2, and terminates. An inner liner layer 7 is located in an area between the pair of left and right bead sections 3, 3 on one tire inner surface.

[0016] A plurality of belt layers 8 (two layers in Fig.1) are embedded on the outer circumference of the carcass layer 4 in the tread section 1. The belt layers 8 include a plurality of reinforcing cords inclined with respect to the tire's circumference, the reinforcing cords of the different layers being arranged crosswise. Steel cords are preferably used as the reinforcing cords of the belt layers 8. To improve high-speed durability, at least one belt cover layer 9 (two layers in Fig. 1), which is formed by arranging it at an angle of no more than 5° with respect to the tire's circumferential direction, is arranged on an outer circumferential side of the belt layers 8 of the tire. From one perspective of Fig.1. The belt cover layer 9, located on the inside in the tire radial direction, forms a complete cover that covers the entire width of the belt layers 8, and the belt cover layer 9, located on an outside in the tire radial direction, forms an edge cover layer that only covers end sections of the belt layers 8. Organic fiber cords such as nylon and aramid are preferably used as the reinforcing cords of the belt cover layer 9.

[0017] A tread rubber layer 10 is arranged on an outer circumferential side of the belt layers 8 and the belt cover layer 9 in the tread section 1. A sidewall reinforcement layer 11 with a crescent-shaped cross-section to enable run-flat driving is arranged between the carcass layer 4 and the inner liner layer 7 in the sidewall sections 2. The sidewall reinforcement layer 11 and the bead filler 6 overlap in the tire radial direction. The overlap section of the sidewall reinforcement layer 11 and the bead filler 6 has a length, preferably in the range of 15 mm to 30 mm, measured along the tire radial direction. A side rubber layer 12 is arranged on an outer circumferential side of the carcass layer 4 (an outer side in the tire width direction) in the sidewall sections 2. A rim padding rubber layer 13 is arranged on the outer circumferential side of the carcass layer 4 (the outside in the direction of tire width) in the bead sections 3.

[0018] In the pneumatic tire described above, the rubber forming the sidewall reinforcement layer 11 and the rubber forming the bead filler 6 exhibit the following physical properties. Both the rubber forming the sidewall reinforcement layer 11 and the rubber forming the bead filler 6 have a modulus of M100 at 100% elongation in the range of 8.4 MPa to 10.2 MPa. In particular, a modulus of M100 BF of the rubber forming the bead filler 6, preferably larger than a module M100 SL of the rubber that forms the side reinforcement layer 11, and the difference between the two modules (M100 BF - M100 SL ) / M100 BF is preferably not greater than 10%.

[0019] Furthermore, both the rubber forming the side reinforcement layer 11 and the rubber forming the bead filler 6 exhibit a tan δ at 60 °C in the range of 0.04 to 0.08. In particular, the tan δ at 60 °C is preferably in the range of 0.05 to 0.07. Furthermore, a tan δ BF at 60 °C of the rubber forming the bead filler 6, preferably larger than a tan δ SL at 60 °C of the rubber forming the side reinforcement layer 11, and the difference between the two tan δ (tan δ BF - tan δ SL ) / tan δ BF The most preferred size is not larger than 10%.

[0020] Furthermore, both the rubber forming the side reinforcement layer 11 and the rubber forming the bead filler 6 have a JIS hardness at 20 °C in the range of 75 to 79. In particular, the JIS hardness at 20 °C of the rubber forming the bead filler 6 is preferably greater than the JIS hardness at 20 °C of the rubber forming the side reinforcement layer 11.

[0021] In the side reinforcement layer 11 and the bead filler 6, the ratio (s / S) of the cross-sectional area s of the bead filler 6 to the cross-sectional area S of the side reinforcement layer 11 is preferably in the range of 0.15 to 0.35. Furthermore, the maximum thickness Tm of the side reinforcement layer 11 is preferably in the range of 8.5 mm to 11.5 mm. It should be noted that the maximum thickness Tm of the side reinforcement layer 11 is the maximum value of the rubber thickness, measured along a direction perpendicular to an inner circumferential surface of the carcass layer 4.

[0022] In the pneumatic tire described above, the physical properties of the rubber forming the sidewall reinforcement layer 11 and the rubber forming the bead filler 6 are such that the modulus M100 at 100% extension lies in the range of 8.4 MPa to 10.2 MPa. This prevents peeling of the carcass layer 4, located between the sidewall reinforcement layer 11 and the bead filler 6, and improves run-flat durability. Additionally, since the rubbers have a tan δ at 60 °C in the range of 0.04 to 0.08 and are low-heat-generating, heat build-up under run-flat driving conditions is suppressed, and rolling resistance is reduced. Furthermore, since the JIS hardness at 20 °C is in the range of 75 to 79, run-flat durability and driving comfort under normal driving conditions can be improved in a well-balanced way.By defining the physical properties of the rubbers forming the sidewall reinforcement layer 11 and the bead filler 6, respectively, within a specific range, the difference in physical properties between the rubber forming the sidewall reinforcement layer 11 and the rubber forming the bead filler 6 can be reduced without increasing the cross-sectional area or thickness of the rubber forming the sidewall reinforcement layer 11. In this way, rolling resistance can be reduced while simultaneously improving run-flat durability, and ride comfort under normal driving conditions can be enhanced.

[0023] On the other hand, if the modulus M100 is less than 8.4 MPa or greater than 10.2 MPa, peeling of carcass layer 4 is easily generated, and run-flat durability tends to deteriorate. Additionally, a smaller tan δ at 60 °C can suppress heat buildup under run-flat driving conditions; however, it is difficult to keep the tan δ below 0.04, and if the tan δ is greater than 0.08, heat buildup is easily generated under run-flat driving conditions, and rolling resistance tends to worsen. Furthermore, if the JIS hardness at 20 °C is less than 75, run-flat durability is insufficient, and if the JIS hardness is greater than 79, ride comfort deteriorates under normal driving conditions.

[0024] In Fig.1 is an outer reinforcement layer 14, which overlaps the bead filler 6 and the sidewall reinforcement layer 11 in the tire radial direction, arranged on an outer side in the tire width direction of the carcass layer 4 in the sidewall sections 2. In the embodiment in Fig. 1. One end of the outer reinforcement layer 14 is located on a central portion of the bead filler 6, while the other end is located on a central portion of the sidewall reinforcement layer 11, which extends along the tire's radial direction. By arranging the outer reinforcement layer 14 on the outside of the carcass layer 4 in the sidewall sections 2, in the tire width direction, the stiffness of the tire carcass can be effectively improved, and shear stress exerted on the carcass layer 4 under run-flat driving conditions can be suppressed, while avoiding adverse effects on ride comfort under normal driving conditions.

[0025] The physical properties of the rubber forming the outer reinforcement layer 14 are as follows: the modulus at 100% elongation is in the range of 5.2 MPa to 6.4 MPa, and the JIS hardness at 20 °C is in the range of 70 to 74. The rubber forming the outer reinforcement layer 14 exhibits the physical properties described above, and thus ride comfort under normal driving conditions can be improved while maintaining run-flat durability.

[0026] In the pneumatic tire described above, the height from a bead heel 3A of the bead section 3 to the position of the maximum thickness Tm of the sidewall reinforcement layer 11 is defined as height HW, and the height from the bead heel 3A of the bead section 3 to an outer end section in the tire radial direction of the outer reinforcement layer 14 is defined as height H1. At this point, the height HW of the sidewall reinforcement layer 11 and the height H1 of the outer reinforcement layer 14 preferably satisfy the relationship 0.6 ≤ H1 / HW ≤ 0.8. Furthermore, the height H1 of the outer reinforcement layer 14 and a subsequently described height H2 of the bead filler 6 more preferably satisfy the relationship H1 > H2.By appropriately defining the ratio of the height H1 of the outer reinforcement layer 14 to the height HW of the sidewall reinforcement layer 11, deformation around the bead sections 3 is suppressed, and a bending point of the sidewall sections 2 under run-flat driving conditions is shifted to one side of the tread section 1, thus effectively improving run-flat durability. If the ratio of the height H1 of the outer reinforcement layer 14 to the height HW of the sidewall reinforcement layer 11 is less than 0.6, the tire weight can be reduced, but the run-flat durability cannot be sufficiently improved. Conversely, if the ratio described above is greater than 0.8, the run-flat durability can be improved, but the tire weight increases and the rolling resistance tends to worsen.

[0027] The height H2 from the bead heel 3A of the bead section 3 to an end section on the outer side of the bead filler 6 in the tire radial direction is defined. At this point, the height HW of the sidewall reinforcement layer 11 and the height H2 of the bead filler 6 preferably satisfy the relationship 0.35 ≤ H2 / HW ≤ 0.50. By suitably defining a ratio of the height H2 of the bead filler 6 to the height HW of the sidewall reinforcement layer 11 in this way, the bending point of the sidewall sections 2 is moved towards the side of the tread section 1 under run-flat driving conditions, and thus the tire weight can be reduced while maintaining run-flat durability, even if the sidewall reinforcement layer 11 is manufactured thinner than in the prior art.Here, if the ratio of the height H2 of the bead filler 6 to the height HW of the side reinforcement layer 11 is less than 0.35, the ride comfort tends to worsen under normal driving conditions, and if the ratio is greater than 0.50, the rolling resistance tends to worsen.

[0028] Furthermore, the ratio of the width BW of the belt layers 8, located on the outermost side in the tire radial direction, to the ground contact width W is preferably in the range of 101% to 110%, and the amount of overlap L between the belt layers 8, located on the innermost side in the tire radial direction, and the side reinforcement layer 11 is preferably in the range of 15 mm to 30 mm. By appropriately determining the ratio of the width BW of the belt layers 8 to the ground contact width W and the amount of overlap L between the belt layers 8 and the side reinforcement layer 11 in this way, the run-flat durability can be effectively improved.Here, if the ratio of the width BW of the belt layers 8 to the ground contact width W is less than 101%, the reinforcing effect of the belt layers 8 cannot be sufficiently achieved; conversely, if the ratio is greater than 110%, the tire weight increases and the rolling resistance tends to worsen. It should be noted that the amount of overlap L between the belt layers 8 and the sidewall reinforcement layer 11 is a length obtained by measuring a section where the belt layers 8 and the sidewall reinforcement layer 11 overlap along the direction of the belt layers 8.

[0029] In embodiments of the present invention, the cord angle of the belt layers 8 with respect to the tire's circumferential direction is preferably in the range of 25° to 35°, and preferably at least one belt cover layer 9, which covers the entire width of the belt layers 8, is arranged on the outer circumferential side of the belt layers 8. By appropriately setting the cord angle of the belt layers 8 and providing the belt cover layer 9, which forms the complete coverage, in this way, yielding of the tread section 1 is suppressed, and the run-flat durability can be effectively improved. Here, if the cord angle is less than 25°, the portion of the cord in the tire's width direction is insufficient, and yielding of the tread section 1 cannot be adequately suppressed; and if the cord angle is greater than 35°, the tire performance under normal driving conditions cannot be sufficiently achieved.

[0030] When embodiments of the present invention are applied to a pneumatic tire with a high cross-sectional area, the effect achieved is significant. In such a pneumatic tire with a high cross-sectional area, the cross-sectional area is preferably in the range of 115 mm to 145 mm. Examples

[0031] Tires of a prior art example, of comparative examples 1 to 3 and of examples 1 to 9 are manufactured, wherein, in the case of pneumatic tires having a tire size of 235 / 60RF18, they comprise: a tread section having a ring shape and extending in the tire's circumferential direction, a pair of sidewall sections arranged on both sides of the tread section, and a pair of bead sections arranged on the inner sides in the tire's radial direction of the pair of sidewall sections, wherein at least one carcass layer is placed between the pair of bead sections, the carcass layer being turned upwards from an inner side of the tire to an outer side of the tire around a bead core of each of the bead sections, and wherein a bead filler is arranged on an outer circumferential side of the bead core in each of the bead sections.wherein a plurality of belt layers are arranged on an outer circumferential side of the carcass layer in the tread section, wherein a sidewall reinforcement layer with a crescent-shaped cross-section is arranged on the inner side in the tire width direction of the carcass layer in each of the pair of sidewall sections, the following is specified as shown in Table 1: an M100, a tan δ (60 °C) and a JIS hardness (20 °C) of a rubber forming the sidewall reinforcement layer and of a rubber forming the bead filler, the presence / absence of an outer reinforcement layer, an M100 and a JIS hardness (20 °C) of a rubber forming the outer reinforcement layer, a ratio (H1 / HW) of a height H1 of the outer reinforcement layer to a height HW of the sidewall reinforcement layer, a ratio (H2 / HW) of a height H2 of the bead filler to the height HW of the sidewall reinforcement layer,a ratio (BW / W × 100%) of a width BW of the belt layers to a soil contact width W, an amount of overlap L between the belt layers and the side reinforcement layer, a cord angle of the belt layers and the presence / absence of the fully covering belt cover layer.

[0032] The rolling resistance, ride comfort and run-flat durability of these test tires are evaluated according to the following test procedures, and the results of the evaluation are shown in Table 1. Rolling resistance:

[0033] Each test tire is mounted on a wheel with a rim size of 18 × 7.5 J, and the rolling resistance is measured using a drum tire testing machine at an air pressure of 210 kPa. Evaluation results are expressed as index values, where the state-of-the-art example value is defined as 100. Lower index values ​​indicate lower rolling resistance. Driving comfort:

[0034] Each of the test tires is mounted on a wheel with a rim size of 18 × 7.5 J, on a test vehicle with an engine displacement of 2500 cm³. 3 The system is installed, and sensory evaluations are performed by a test driver under an air pressure of 250 kPa. Evaluation results are expressed using a 5-point system, where the value of the state-of-the-art example is defined as the benchmark score of 3. Higher scores indicate greater ride comfort. Emergency running durability:

[0035] Each test tire is mounted on a wheel with a rim size of 18 × 7.5 J, and a road test is performed using a drum tire testing machine under conditions of 0 kPa air pressure and 65% of the maximum load capacity defined by JATMA or ETRTO. Specifically, a driving speed of 80 km / h is used, and the tires are driven until tire failure occurs, with the distances traveled being measured. Evaluation results are expressed as index values, with the state-of-the-art example value defined as 100. Higher index values ​​indicate greater run-flat durability. [Table 1-I] Table 1 State of the art example Comparative example 1 Comparative example 2 Comparative example 3 Example 1 Example 2 Example 3 M100 (MPa) 9,3 8,0 9,3 10,5 9,3 8,4 8,8 Side reinforcement layer tan δ(60 °C) 0,06 0,03 0,06 0,09 0,06 0,04 0,055 JIS hardness (20 °C) 77 77 77 77 77 77 77 Bead filler M100 (MPa) 10,1 9,3 8,0 10,5 9,3 10,2 9,5 tan δ(60 °C) 0,15 0,06 0,03 0,09 0,06 0,08 0,06 JIS hardness (20 °C) 91 77 77 77 77 79 79 Outer reinforcement layer Present / Not Present No No No No No No No M100 (MPa) - - - - - - - JIS hardness (20 °C) - - - - - - - Ratio (H1 / HW) of the height H1 of the outer reinforcement layer to the height HW of the side reinforcement layer - - - - - - - Ratio (H2 / HW) of the height H2 of the bead filler to the height HW of the side reinforcement layer 0,6 0,6 0,6 0,6 0,6 0,6 0,6 Ratio of the belt layer width BW to the soil contact width W (BW / W × 100%) 100 100 100 100 100 100 100 Amount of overlap L (mm) between belt layer and side reinforcement layer 10 10 10 10 10 10 10 Cord angle of the belt layer (degrees) 22 22 22 22 22 22 22 Presence / absence of the fully covering belt top layer No No No No No No No Rolling resistance 100 101 101 102 98 99 98 Driving comfort 3,0 3,5 3,5 3,5 3,5 3,25 3,5 Emergency running durability 100 99 99 98 101 101 101 [Table 1-II] Table 1 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Side reinforcement layer M100 (MPa) 9,3 9,3 9,3 9,3 9,3 9,3 tan δ(60 °C) 0,06 0,06 0,06 0,06 0,06 0,06 JIS hardness (20 °C) 77 77 77 77 77 77 Bead filler M100 (MPa) 9,3 9,3 9,3 9,3 9,3 9,3 tan δ(60 °C) 0,06 0,06 0,06 0,06 0,06 0,06 JIS hardness (20 °C) 77 77 77 77 77 77 Outer reinforcement layer Present / Not Present Yes Yes Yes Yes Yes Yes M100 (MPa) 10,1 10,1 5,8 5,8 5,8 5,8 JIS hardness (20 °C) 91 91 72 72 72 72 Ratio (H1 / HW) of the height H1 of the outer reinforcement layer to the height HW of the side reinforcement layer 0,5 0,7 0,7 0,7 0,7 0,7 Ratio (H2 / HW) of the height H2 of the bead filler to the height HW of the side reinforcement layer 0,6 0,6 0,6 0,4 0,4 0,4 Ratio of the belt layer width BW to the soil contact width W (BW / W × 100%) 100 100 100 100 103 103 Amount of overlap L (mm) 10 10 10 10 20 20 between belt layer and side reinforcement layer Cord angle of the belt layer (degrees) 22 22 22 22 22 29 Presence / absence of the fully covering belt top layer No No No No No Yes Rolling resistance 98 99 97 96 97 97 Driving comfort 3,5 3,5 4,0 4,5 4,5 4,5 Emergency running durability 103 104 104 104 105 106

[0036] As can be seen from Table 1, compared to the state of the art example for pneumatic tires according to examples 1 to 9, the rolling resistance is reduced while simultaneously improving run-flat durability, and driving comfort is improved.

[0037] On the other hand, in Comparative Example 1, the M100 and the tan δ (60 °C) of the rubber forming the sidewall reinforcement layer are outside the ranges specified in embodiments of the present invention, and in Comparative Example 2, the M100 and the tan δ (60 °C) of the rubber forming the bead filler are outside the ranges specified in embodiments of the present invention, and thus the effects of improving rolling resistance and run-flat durability are insufficient. Furthermore, in Comparative Example 3, the M100 and the tan δ (60 °C) of the rubbers forming the sidewall reinforcement layer and the bead filler, respectively, are outside the ranges specified in embodiments of the present invention, and thus the effects of improving rolling resistance and run-flat durability are insufficient. List of reference symbols 1 tread section 2 Side wall section 3 bead section 4 Carcass layer 5 bead core 6 bead fillers 7 Inner Soul Layer 8 belt layer 9 Belt cover layer 10 tread rubber layer 11 Side reinforcement layer 12 side rubber layer 13 Rim padding rubber layer 14 Outer reinforcement layer

Claims

[1] Pneumatic tires, including: a tread section (1) which has a ring shape and extends in the circumferential direction of the tire; a pair of sidewall sections (2) arranged on both sides of the running surface section (1); and a pair of bead sections (3) arranged on inner surfaces in the tire radial direction of the pair of sidewall sections (2), wherein at least one carcass layer (4) is placed between the pair of bead sections (3), wherein the carcass layer (4) is turned upwards from an inner tire side to an outer tire side around a bead core (5) of each of the pair of bead sections (3), wherein a bead filler (6) is arranged on an outer circumferential side of the bead core (5) in each of the pair of bead sections (3), wherein a plurality of belt layers (8) are arranged on an outer circumferential side of the carcass layer (4) in the tread section (1), and wherein a side reinforcement layer (11) with a crescent-shaped cross-section is arranged on an inner side in the tire width direction of the carcass layer (4) in each of the pair of sidewall sections (2), and wherein the physical properties of a rubber forming the side reinforcement layer (11) and of a rubber forming the bead filler (6) are a modulus at 100% elongation in the range of 8.4 MPa to 10.2 MPa, a tan δ at 60 °C in the range of 0.04 to 0.08 and a JIS hardness at 20 °C in the range of 75 to 79, wherein an outer reinforcing layer (14) overlapping the bead filler (6) and the sidewall reinforcement layer (11) in the tire radial direction is arranged on an outer side in the tire width direction of the carcass layer (4) in each of the pair of sidewall sections (2), wherein the physical properties of a rubber forming the outer reinforcing layer (14) are a modulus at 100% elongation in the range of 5.2 MPa to 6.4 MPa and the JIS hardness at 20 °C in the range of 70 to 74. [2] Pneumatic tire according to claim 1, wherein a height (HW) from a bead heel (3A) of each of the pair of bead sections (3) to a position of maximum thickness of the side reinforcement layer (11) and a height (H1) from the bead heel (3A) of each of the pair of bead sections (3) to an outer end section in tire radial direction of the outer reinforcement layer (14) satisfy the relationship 0.6 ≤ H1 / HW ≤ 0.

8. [3] Pneumatic tire according to one of claims 1 or 2, wherein a height (HW) from a bead heel (3A) of each of the pair of bead sections (3) to a position of maximum thickness (Tm) of the sidewall reinforcement layer (11) and a height (H2) from the bead heel (3A) of each of the pair of bead sections (3) to an outer end section in the tire radial direction of the bead filler (6) satisfy the relationship 0.35 ≤ H2 / HW ≤ 0.

50. [4] Pneumatic tire according to any one of claims 1 to 3, wherein the ratio of a width (BW) of the belt layer (8) located on an outermost side in the tire radial direction to a ground contact width (W) is in a range of 101% to 110% and the amount of overlap (L) between the belt layer (8) located on an innermost side in the tire radial direction and the side reinforcement layer (11) is in a range of 15 mm to 30 mm. [5] Pneumatic tire according to any one of claims 1 to 4, wherein a cord angle of the belt layer (8) with respect to the tire circumferential direction is in a range of 25° to 35° and at least one belt cover layer (9) covering an entire width of the belt layer (8) is arranged on an outer circumferential side of the belt layer (8).

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