pneumatic tires

Abstract

The present invention aims to provide a pneumatic tire that can suppress the reduction in cornering power. [Solution] The pneumatic tire of the present invention comprises a pair of bead cores embedded in a pair of bead portions, and a carcass consisting of one or more carcass plies that toroidally straddle the pair of bead cores, a bead filler is disposed on the radially outer side of the bead core, and a rubber chafer is provided on the widthwise outer side of the bead filler, and when the storage modulus of elasticity of the bead filler is E1' and the storage modulus of elasticity of the rubber chafer is E2', the ratio E2' / E1' satisfies 0.4 ≤ E2' / E1' ≤ 1.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire.

Background Art

[0002] Generally, in a pneumatic tire, it is desired to increase the cornering power.

[0003] Especially in recent years, there are cases where the fuel efficiency is improved by simplifying the tire structure and reducing the weight, such as thinning the rubber in the sidewall part or reducing the height of the bead filler (for example, Patent Document 1). In such cases, there is a risk that the cornering power will decrease particularly due to the reduction of the lateral spring constant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a pneumatic tire capable of suppressing a decrease in cornering power.

Means for Solving the Problems

[0006] The gist configuration of the present invention is as follows. (1) A pair of bead cores embedded in a pair of bead parts, and A carcass composed of one or more carcass plies straddling toroidally between the pair of bead cores, wherein A bead filler is disposed on the outer side in the tire radial direction of the bead core, A rubber chafer is provided on the outer side in the tire width direction of the bead filler, When the storage modulus of the bead filler is E1' and the storage modulus of the rubber chafer is E2', the ratio E2' / E1' is: 0.4 ≤ E2' / E1' ≤ 1 A pneumatic tire characterized by satisfying the following conditions.

[0007] Here, "storage modulus" refers to the value measured at a temperature of 25°C in accordance with JIS K7244.

[0008] (2) The ratio E2' / E1' is, 0.6 ≤ E2' / E1' ≤ 1 A pneumatic tire as described in (1) above, which further satisfies the above condition.

[0009] (3) The pneumatic tire described in (1) or (2) above, wherein the length of the rubber chafer in the tire radial direction is 30 to 60 mm.

[0010] (4) The pneumatic tire according to any one of (1) to (3) above, wherein the outer end of the rubber chafer in the tire radial direction is located radially outward from the rim separation point. Here, "rim separation point" refers to the point at which the outer surface of the tire separates from the rim flange under standard conditions, when a pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded.

[0011] Here, "applicable rim" refers to the standard rim for the applicable size (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) which is an industrial standard valid in the region where the tire is produced and used, and is listed or will be listed in the future in publications such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States. (That is, the above "rim" includes not only current sizes but also sizes that may be included in the above industrial standards in the future. An example of a "size to be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.) However, in the case of a size not listed in the above industrial standards, it refers to a rim with a width corresponding to the tire bead width. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in JATMA, etc., and in the case of sizes not listed in the above industrial standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0012] (5) The pneumatic tire according to any one of (1) to (4) above, wherein the inner end of the rubber chafer in the tire radial direction is located radially inward of the inner end of the bead core in the tire radial direction. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a pneumatic tire that can suppress the reduction in cornering power. [Brief explanation of the drawing]

[0014] [Figure 1]It is a partial cross-sectional view in the tire width direction of a pneumatic tire according to an embodiment of the present invention. [Figure 2] It is a diagram schematically showing out-of-plane bending acting on the bead portion.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be illustrated and described in detail with reference to the drawings.

[0016] FIG. 1 is a partial cross-sectional view in the tire width direction of a pneumatic tire (hereinafter, also simply referred to as a tire) according to an embodiment of the present invention. FIG. 1 shows a cross-section in the tire width direction in the above reference state.

[0017] This tire 1 includes a pair of bead cores 2a embedded in a pair of bead portions 2, and a carcass 3 composed of one or more carcass plies straddling toroidally between the pair of bead cores 2a.

[0018] In the bead portion 2, a bead filler 2b is disposed outside the bead core 2a in the tire radial direction. The bead core 2a includes, in this example, a plurality of bead wires whose peripheries are covered with rubber. The bead wire is formed of a steel cord in this example. The bead filler 2b is composed of rubber or the like in this example, and has a substantially triangular cross-sectional shape whose thickness decreases toward the outside in the tire radial direction.

[0019] Here, the height of the bead filler 2b (measured in the tire radial direction) is preferably 8 to 25 mm as in this example. By setting the height of the bead filler 2b to 8 mm or more, air intake during manufacturing can be suppressed. On the other hand, by setting the height of the bead filler 2b to 25 mm or less, weight reduction of the tire can be achieved. For the same reason, the height of the bead filler 2b is more preferably 10 to 15 mm.

[0020] In this example, the carcass 3 includes a carcass body portion 3a that extends toroidally between the pair of bead portions 2, and a carcass folded-back portion 3b that is folded back from the carcass body portion 3a around the bead core 2a from the inner side in the tire width direction to the outer side in the tire width direction. The carcass cord can be, for example, an organic fiber such as PET, or a hybrid cord formed by twisting two organic fiber cords (for example, nylon and aramid). Also, as described above, the carcass ply is a ply of radially arranged cords.

[0021] In this example, the outer end of the carcass folded-back portion 3b in the tire radial direction is located on the inner side in the tire radial direction from the maximum tire width position, and is located on the outer side in the tire radial direction from the outer end of the bead filler 2b in the tire radial direction. With such a configuration, further weight reduction of the tire can be achieved.

[0022] As shown in FIG. 1, on the outer side in the tire radial direction of the crown portion of the carcass 3, there is a belt 4 composed of one or more (two in the illustrated example) belt layers 4a, 4b. The belt cords of the belt layers 4a, 4b extend inclined at an inclination angle of 30° to 60° in the tire circumferential direction so as to cross each other between the layers. Steel cords can be used for the belt cords, but organic fiber cords can also be used for weight reduction. On the outer side in the tire radial direction of the belt 4, a tread portion 5 made of tread rubber is disposed.

[0023] As shown in FIG. 1, between the pair of bead portions 2 and the tread portion 5, a pair of sidewall portions 6 are continuous. Here, as in this example, the rubber gauge at the maximum tire width position (the thickness of the rubber measured in the direction orthogonal to the outer surface of the sidewall portion 6 in the cross section in the tire width direction in the reference state) is preferably 1 mm or more and 3 mm or less. By setting the rubber gauge at the maximum tire width position to 1 mm or more, a minimum level of side cut resistance can be ensured. On the other hand, by setting the rubber gauge at the maximum tire width position to 3 mm or less, weight reduction of the tire can be achieved.

[0024] Here, as shown in Figure 1, the tire 1 of this embodiment is provided with a reinforcing member 7 that extends inclined with respect to the tire radial direction on the outer side of the carcass 3 in the tire width direction, in the tire radial region including the tire maximum width position. In the illustrated example, the reinforcing member 7 has an arc shape along the carcass body 3a in this cross-section, but it can also have other shapes such as a straight line. Here, "tire maximum width position" refers to the position in the tire width direction cross-section in the above reference state where the width of the pneumatic tire in the tire width direction is the maximum.

[0025] In this example, the reinforcing member 7 is an organic fiber cord. As the organic fiber cord, an organic fiber such as PET, or a hybrid cord made by twisting together two types of organic fiber cords (for example, nylon cord and aramid cord) can be used. The Young's modulus of the cord of the reinforcing member 7 is tested according to JIS L1017 8.5 a) (2002) and determined in accordance with JIS L1017 8.8 (2002). The Young's modulus is not particularly limited but can be 3000 to 50000 GPa, the number of cords inserted into the reinforcing member 7 can be 20 to 70 cords / 50 mm, and the cord diameter of the cord of the reinforcing member 7 can be 0.3 to 0.9 mm. From the viewpoint of weight reduction, it is preferable to arrange one layer of reinforcing members, but it is also possible to arrange two or more layers. In that case, it is preferable to reduce the Young's modulus, the number of cords inserted, and the cord diameter so that they are similar to the case of one layer from the viewpoint of rigidity and weight reduction.

[0026] As in this example, the reinforcing member 7 is preferably inclined and extends at an angle of 30° to 60° with respect to the tire radial direction, and more preferably at an angle of 40° to 50° with respect to the tire radial direction.

[0027] Furthermore, the length of the reinforcing member 7 in the tire radial direction is preferably 10 to 40% of the tire cross-sectional height. This is because a length of 10% or more can improve cornering power, while a length of 40% or less can suppress weight increase.

[0028] Here, as shown in Figure 1, the tire 1 of this embodiment is equipped with a rubber chafer 8 on the outer side of the bead filler 2b in the tire width direction. The length of the rubber chafer 8 in the tire diameter direction is preferably 30 to 60 mm.

[0029] It is preferable that the outer end of the rubber chafer 8 in the tire radial direction is located radially outward from the rim separation point. It is also preferable that the inner end of the rubber chafer 8 in the tire radial direction is located radially inward from the inner end of the bead core 2a in the tire radial direction. In this example, as shown in Figure 1, the rubber chafer 8 extends in the tire radial region from near the bead baseline (an imaginary line passing through the bead base and parallel to the tire width direction) to radially outward from the apex of the rim guard.

[0030] In this embodiment, the rubber chafer 7 is made of highly elastic rubber. Specifically, when the storage modulus of the bead filler 2b is E1' and the storage modulus of the rubber chafer 7 is E2', the ratio E2' / E1' is: 0.4 ≤ E2' / E1' ≤ 1 It satisfies the condition. The following describes the effects and advantages of the pneumatic tire of this embodiment.

[0031] In the pneumatic tire of this embodiment, firstly, the height of the bead filler 2b is 25 mm or less (in this example, the outer end of the carcass folded portion 3b in the tire radial direction is positioned further inward in the tire radial direction than the tire's maximum width position, the rubber gauge at the tire's maximum width position is 3 mm or less, and the material of the carcass cord is an organic fiber such as PET or a hybrid cord of two types of organic fibers), which allows for weight reduction of the tire. As mentioned above, such a tire may reduce the lateral spring coefficient and decrease cornering power. In response to this, the inventors investigated and found that, as schematically shown in Figure 2, out-of-plane bending acts on the bead portion 2 (in particular, when the height of the bead filler 2b is 25 mm or less as described above, the rigidity of the bead portion decreases and the out-of-plane bending increases), and that the rotational component of the lateral displacement increases, among the translational, rotational, and bending components, is the cause of the decrease in the lateral spring coefficient. Furthermore, as schematically shown in Figure 2, the above out-of-plane bending acts as a tensile force on the inner side of the bead portion 2 and as a compressive force on the outer side of the bead portion 2. In particular, they found that the decrease in the lateral spring coefficient can be suppressed by counteracting the compressive force on the outer side of the bead portion 2 (inside the bend). Therefore, as described above, a highly rigid (0.4 ≤ E2' / E1' ≤ 1) rubber chafer 8 is placed on the outer side of the bead filler 2b in the tire width direction. As a result, even when a compressive force is applied to the outer surface of the bead portion 2 of the tire, the high-rigidity rubber chafer 8 can suppress the increase in the rotational component of the lateral displacement, thereby suppressing the decrease in the lateral spring coefficient and preventing a decrease in cornering power. If the ratio E2' / E1' is less than 0.4, the effect of suppressing the increase in the rotational component of lateral displacement cannot be sufficiently obtained. On the other hand, if the ratio E2' / E1' is greater than 1, the coefficient of friction at the contact point with the rim becomes small, raising concerns about the rim coming off. As described above, the pneumatic tire of this embodiment makes it possible to reduce the weight of the tire while suppressing a decrease in cornering power. While this is particularly effective in the lightweight configuration described above, as in this embodiment, even in configurations other than the lightweight one described above, the high-rigidity rubber chafer 8 can suppress the increase in the rotational component of lateral displacement due to the compressive force acting on the outer surface of the tire of the bead portion 2, thereby providing an effect that suppresses the decrease in cornering power.

[0032] Here, for the same reasons as above, the ratio E2' / E1' is, 0.6 ≤ E2' / E1' ≤ 1 It is preferable to further satisfy the following conditions.

[0033] The length of the rubber chafer in the tire diameter direction is preferably 30 to 60 mm. By setting it to 30 mm or more, the effect of suppressing the increase in the rotational component of lateral displacement can be more fully obtained, and by setting it to 60 mm or less, the weight increase due to the placement of the rubber chafer can be kept to a minimum.

[0034] It is preferable that the outer end of the rubber chafer in the tire's radial direction is located radially outward from the rim separation point. This is because it broadly covers the region where out-of-plane bending acts, thereby more effectively suppressing the increase in the rotational component of lateral displacement.

[0035] It is preferable that the inner end of the rubber chafer in the tire radial direction is located further inward than the inner end of the bead core in the tire radial direction. This is because it broadens the area where out-of-plane bending acts, thereby more effectively suppressing the increase in the rotational component of lateral displacement.

[0036] In this disclosure, the tire is preferably a pneumatic radial tire for passenger cars.

[0037] For example, this tire has a cross-sectional width SW of less than 165 mm, and the ratio SW / OD of the cross-sectional width SW to the outer diameter OD is 0.26 or less, resulting in a narrow width and large diameter shape. By making the cross-sectional width SW of the tire narrower than the outer diameter OD of the tire, air resistance can be reduced, and by making the outer diameter OD of the tire larger than the cross-sectional width SW of the tire, deformation of the tread rubber near the contact surface of the tire can be suppressed, thereby reducing rolling resistance, and thus improving the fuel efficiency of the tire. The SW / OD ratio is preferably 0.25 or less, and more preferably 0.24 or less. The above ratio is preferably met when the tire's internal pressure is 200 kPa or higher, more preferably when it is 220 kPa or higher, and even more preferably when it is 280 kPa or higher, because it can reduce rolling resistance. On the other hand, the above ratio is preferably met when the tire's internal pressure is 350 kPa or lower, because it can improve ride comfort. Here, from the viewpoint of securing contact area, the tire cross-sectional width SW is preferably 105 mm or more, more preferably 125 mm or more, even more preferably 135 mm or more, and particularly preferably 145 mm or more, within the range that satisfies the above ratio. On the other hand, from the viewpoint of reducing air resistance, the tire cross-sectional width SW is preferably 155 mm or less, within the range that satisfies the above ratio. Furthermore, from the viewpoint of reducing rolling resistance, the tire outer diameter OD is preferably 500 mm or more, more preferably 550 mm or more, and even more preferably 580 mm or more, within the range that satisfies the above ratio. On the other hand, from the viewpoint of reducing air resistance, the tire outer diameter OD is preferably 800 mm or less, more preferably 720 mm or less, even more preferably 650 mm or less, and particularly preferably 630 mm or less, within the range that satisfies the above ratio. Furthermore, from the viewpoint of reducing rolling resistance, the rim diameter is preferably 16 inches or larger, more preferably 17 inches or larger, and even more preferably 18 inches or larger, when the tire section width SW and outer diameter OD satisfy the above ratio. On the other hand, from the viewpoint of reducing air resistance, the rim diameter is preferably 22 inches or smaller, more preferably 21 inches or smaller, even more preferably 20 inches or smaller, and particularly preferably 19 inches or smaller, when the tire section width SW and outer diameter OD satisfy the above ratio. Furthermore, the aspect ratio of the tire is preferably 45 to 70, and even more preferably 45 to 65, when the tire section width SW and outer diameter OD satisfy the above ratio. While there are no specific limitations on tire sizes, some examples include 105 / 50R16, 115 / 50R17, 125 / 55R20, 125 / 60R18, 125 / 65R19, 135 / 45R21, 135 / 55R20, 135 / 60R17, 135 / 60R18, 135 / 60R19, 135 / 65R19, 145 / 45R21, and 145 / 5 The tire size can be any of the following: 5R20, 145 / 60R16, 145 / 60R17, 145 / 60R18, 145 / 60R19, 145 / 65R19, 155 / 45R18, 155 / 45R21, 155 / 55R18, 155 / 55R19, 155 / 55R21, 155 / 60R17, 155 / 65R18, 155 / 70R17, or 155 / 70R19.

[0038] As another example, the tire has a section width SW of 165 (mm) or more, and the tire's section width SW (mm) and outer diameter OD (mm) are related by the following formula: OD(mm)≧2.135×SW(mm)+282.3 It satisfies the requirements and has a narrow width and large diameter shape. By satisfying the above relationship, air resistance and rolling resistance can be reduced, thereby improving the fuel efficiency of the tire. In the second embodiment, the tire's cross-sectional width SW and outer diameter OD are preferably such that the ratio SW / OD satisfies the above relationship, is 0.26 or less, more preferably 0.25 or less, and even more preferably 0.24 or less. This is because it can further improve the tire's fuel efficiency. The above relationship and / or ratio is preferably satisfied when the tire internal pressure is 200 kPa or higher, more preferably 220 kPa or higher, and even more preferably 280 kPa or higher, because it can reduce rolling resistance. On the other hand, the above relationship and / or ratio is preferably satisfied when the tire internal pressure is 350 kPa or lower, because it can improve ride comfort. Here, from the viewpoint of securing contact area, the tire cross-sectional width SW is preferably 175 mm or more, and more preferably 185 mm or more, within the range that satisfies the above relationship. On the other hand, from the viewpoint of reducing air resistance, the tire cross-sectional width SW is preferably 230 mm or less, more preferably 215 mm or less, even more preferably 205 mm or less, and particularly preferably 195 mm or less, within the range that satisfies the above relationship. Furthermore, from the viewpoint of reducing rolling resistance, the tire outer diameter OD is preferably 630 mm or more, and more preferably 650 mm or more, within the range that satisfies the above relationship. On the other hand, from the viewpoint of reducing air resistance, the tire outer diameter OD is preferably 800 mm or less, more preferably 750 mm or less, and even more preferably 720 mm or less, within the range that satisfies the above relationship. Furthermore, from the viewpoint of reducing rolling resistance, the rim diameter is preferably 18 inches or larger, and more preferably 19 inches or larger, when the tire's section width SW and outer diameter OD satisfy the above relationship. On the other hand, from the viewpoint of reducing air resistance, the rim diameter is preferably 22 inches or smaller, and more preferably 21 inches or smaller, when the tire's section width SW and outer diameter OD satisfy the above relationship. Furthermore, when the tire's section width SW and outer diameter OD satisfy the above relationship, the tire's aspect ratio is preferably 45 to 70, and more preferably 45 to 65. While there are no specific limitations on tire sizes, some examples include: 165 / 45R22, 165 / 55R18, 165 / 55R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 45R23, 175 / 55R19, 175 / 55R20, 175 / 5 The tire size can be any of the following: 5R22, 175 / 60R18, 185 / 45R22, 185 / 50R20, 185 / 55R19, 185 / 55R20, 185 / 60R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, 195 / 60R19, 205 / 50R21, 205 / 55R20, or 215 / 50R21.

[0039] As another example, the tire's section width SW (mm) and outer diameter OD (mm) are related by the following formula: OD(mm)≧-0.0187×SW(mm)2+9.15×SW(mm)-380 It satisfies the requirements and has a narrow width and large diameter shape. By satisfying the above relationship, air resistance and rolling resistance can be reduced, thereby improving the fuel efficiency of the tire. In the third embodiment, the tire's cross-sectional width SW and outer diameter OD are preferably such that the ratio SW / OD satisfies the above relationship, is 0.26 or less, more preferably 0.25 or less, and even more preferably 0.24 or less. This is because it can further improve the tire's fuel efficiency. The above relationship and / or ratio is preferably satisfied when the tire internal pressure is 200 kPa or higher, more preferably 220 kPa or higher, and even more preferably 280 kPa or higher, because it can reduce rolling resistance. On the other hand, the above relationship and / or ratio is preferably satisfied when the tire internal pressure is 350 kPa or lower, because it can improve ride comfort. Here, from the viewpoint of securing contact area, the tire cross-sectional width SW is preferably 105 mm or more, more preferably 125 mm or more, even more preferably 135 mm or more, and particularly preferably 145 mm or more, within the range that satisfies the above relationship. On the other hand, from the viewpoint of reducing air resistance, the tire cross-sectional width SW is preferably 230 mm or less, more preferably 215 mm or less, even more preferably 205 mm or less, and particularly preferably 195 mm or less, within the range that satisfies the above relationship. Furthermore, from the viewpoint of reducing rolling resistance, the tire outer diameter OD is preferably 500 mm or more, more preferably 550 mm or more, and even more preferably 580 mm or more, within the range that satisfies the above relationship. On the other hand, from the viewpoint of reducing air resistance, the tire outer diameter OD is preferably 800 mm or less, more preferably 750 mm or less, and even more preferably 720 mm or less, within the range that satisfies the above relationship. Furthermore, from the viewpoint of reducing rolling resistance, the rim diameter is preferably 16 inches or larger, more preferably 17 inches or larger, and even more preferably 18 inches or larger, when the tire's cross-sectional width SW and outer diameter OD satisfy the above relationship. On the other hand, from the viewpoint of reducing air resistance, the rim diameter is preferably 22 inches or smaller, more preferably 21 inches or smaller, and even more preferably 20 inches or smaller, when the tire's cross-sectional width SW and outer diameter OD satisfy the above relationship. Furthermore, the aspect ratio of the tire is preferably 45 to 70, and even more preferably 45 to 65, when the tire's cross-sectional width SW and outer diameter OD satisfy the above ratio. While there are no specific limitations on tire sizes, some examples include 105 / 50R16, 115 / 50R17, 125 / 55R20, 125 / 60R18, 125 / 65R19, 135 / 45R21, 135 / 55R20, 135 / 60R17, 135 / 60R18, 135 / 60R19, 135 / 65R19, 1 45 / 45R21, 145 / 55R20, 145 / 60R16, 145 / 60R17, 145 / 60R18, 145 / 60R19, 145 / 65R19, 155 / 45R18, 155 / 45R21, 155 / 55R18, 155 / 55R19, 155 / 55R21, 155 / 60R17, 155 / 65R18, 155 / 7 0R17, 155 / 70R19, 165 / 45R22, 165 / 55R18, 165 / 55R19, 165 / 55R20, 165 / 55R21, 165 / 60R 19, 165 / 6R19, 165 / 70R18, 175 / 45R23, 175 / 55R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, The tire size can be any of the following: 175 / 60R18, 185 / 45R22, 185 / 50R20, 185 / 55R19, 185 / 55R20, 185 / 60R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, 195 / 60R19, 205 / 50R21, 205 / 55R20, or 215 / 50R21.

[0040] As mentioned above, with a lightweight tire configuration like the one described, there is a risk that the lateral spring coefficient will decrease, leading to a reduction in cornering power. The inventors investigated and found that the cause of the decrease in the lateral spring coefficient is that lateral displacement is concentrated directly under the load, and the surrounding area is pulled in the direction of the load, increasing shear deformation around the circumference. Therefore, in the tire of this embodiment, a reinforcing member 7 is provided on the outer side of the carcass 3 in the tire width direction, inclined with respect to the tire radial direction, in the tire radial region including the tire's maximum width position. This suppresses shear deformation by applying a force that pulls against the reinforcing member 7 in the opposite direction during shear deformation. This suppresses the decrease in the lateral spring coefficient and further suppresses the reduction in cornering power. Although this is particularly effective in lightweight configurations like the one described above, even in configurations that are not lightweight, the effect of further suppressing the reduction in cornering power can be obtained because a force that pulls against the reinforcing member 7 in the opposite direction acts during shear deformation.

[0041] In this case, the reinforcing member is preferably an organic fiber cord. This is because organic fibers are lightweight relative to their rigidity, thus minimizing the weight increase caused by the addition of the reinforcing member.

[0042] The reinforcing member is preferably inclined and extends at an angle of 30° to 60° with respect to the tire's radial direction, and more preferably at an angle of 40° to 50°. The effect of suppressing shear deformation, schematically shown in Figure 4, is most effective when the inclination angle of the reinforcing member with respect to the tire's radial direction is close to approximately 45°. Therefore, by setting it within the above range, the reduction in cornering power can be further suppressed.

[0043] The length of the reinforcing member in the tire radial direction is preferably 10-40% of the tire cross-sectional height. By setting it to 10% or more, the effect of suppressing the decrease in cornering power can be further obtained, while by setting it to 40% or less, the weight increase due to the addition of the reinforcing member can be kept to a minimum. For example, the outer end of the reinforcing member in the tire radial direction can be positioned at a tire radial position of 50-80% of the tire cross-sectional height from the bead baseline (an imaginary line parallel to the tire width direction passing through the bead base), and the inner end of the reinforcing member in the tire radial direction can be positioned at a tire radial position of 15-40% of the tire cross-sectional height from the bead baseline. Although not particularly limited, the length of the reinforcing member in the tire radial direction can be 15mm-40mm. [Examples]

[0044] To verify the effects of the present invention, prototype tires according to the inventive example, comparative example, and conventional example were manufactured and their performance was evaluated. Each tire comprises a pair of bead cores embedded in a pair of bead portions, and a carcass consisting of one or more carcass plies that toroidally straddle the pair of bead cores. A bead filler is positioned on the radially outer side of the bead core, and a rubber chafer is provided on the widthwise outer side of the bead filler. The specifications of each tire are summarized in Table 1 below. In Table 1, "side portion" means "sidewall portion," and "side portion gauge" means the rubber gauge at the tire's maximum width position. Also, "BF" is an abbreviation for bead filler, and "GC" is an abbreviation for rubber chafer. The lateral spring coefficient was determined by mounting each tire on a rim, measuring the amount of deflection using an indoor tester, and measuring the lateral spring coefficient from the tangential gradient at a load of 4kN. The weight of each tire before rim assembly was also measured. In Table 1, the evaluation results are shown as an index with the conventional example set to 100.

[0045] [Table 1] [Explanation of symbols]

[0046] 1: Pneumatic tire, 2: Bead section, 3: Carcass, 4: Belt, 5: Tread section, 6: Sidewall section, 7: Reinforcement member, 8: Rubber Chafa

Claims

1. A pair of bead cores embedded in a pair of bead sections, A pneumatic tire comprising a carcass consisting of one or more carcass plies that toroidally straddle the pair of bead cores, A bead filler is positioned on the radially outer side of the bead core. The bead filler is provided with a rubber chafer on the outer side in the tire width direction, When the storage modulus of the bead filler is E1' and the storage modulus of the rubber chafer is E2', the ratio E2' / E1' is: 0.4 ≤ E2' / E1' ≤ 1 Satisfying the conditions, A pneumatic tire characterized in that a reinforcing member is provided on the outer side of the carcass in the tire width direction, in a tire radial region including the tire's maximum width position, and is inclined with respect to the tire's radial direction.

2. The aforementioned ratio E2' / E1' is, 0.6 ≤ E2' / E1' ≤ 1 A pneumatic tire according to claim 1, further satisfying the above conditions.

3. The pneumatic tire according to claim 1 or 2, wherein the length of the rubber chafer in the tire radial direction is 30 to 60 mm.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the outer end of the rubber chafer in the tire radial direction is located radially outward from the rim separation point.

5. The pneumatic tire according to any one of claims 1 to 4, wherein the inner end of the rubber chafer in the tire radial direction is located radially inward of the inner end of the bead core in the tire radial direction.

6. A pneumatic tire according to any one of claims 1 to 5, wherein the rubber gauge at the maximum tire width position of the sidewall portion is 3 mm or less.

7. A pneumatic radial tire for passenger cars, as described in any one of claims 1 to 6.

Images