Pneumatic tire

Abstract

To provide a pneumatic tire whose cornering power can be suppressed from reducing.SOLUTION: A pneumatic tire according to the present invention comprises a pair of bead cores buried in a pair of bead parts and a carcass constituted of one or more carcass plies arranged in a toroidal shape across the pair of bead cores. Bead fillers are arranged outside in a tire radial direction of the bead cores, and rubber chafers are provided outside in a tire width direction of the bead fillers. When a storage elastic modulus of the bead filler is defined as E1' and a storage elastic modulus of the rubber chafer is defined as E2', a ratio E2' / E1' satisfies a relational expression of 0.4≤E2' / E1'≤1.SELECTED DRAWING: Figure 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 coefficient.

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 spanning toroidally between the pair of bead cores, and a pneumatic tire comprising: 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 elastic modulus of the bead filler is E1' and the storage elastic modulus of the rubber chafer is E2', the ratio E2' / E1' is 0.4 ≦ E2' / E1' ≦ 1 characterized by satisfying the above, a pneumatic tire.

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

[0008] (2) The ratio E2' / E1' 0.6 ≦ E2' / E1' ≦ 1 further satisfies the above, the pneumatic tire according to (1) above.

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

[0010] (4) The outer end of the rubber chafer in the tire radial direction is located outside the tire radial direction from the rim separation point, the pneumatic tire according to any one of (1) to (3) above. Here, the "rim separation point" refers to the point where the outer surface of the tire separates from the rim flange in the reference state where the pneumatic tire is mounted on the applicable rim, filled with the specified internal pressure, and made unloaded.

[0011] Here, the "applicable rim" refers to the industrial standard effective in the region where the tire is produced and used. In Japan, it is the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association); in Europe, it is the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation); in the United States, it is the YEAR BOOK of TRA (The Tire and Rim Association, Inc.), etc. It refers to the standard rim (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) in the applicable size described or to be described in the future (that is, the above "rim" includes sizes that may be included in the above industrial standards in the future in addition to the current sizes. Examples of "sizes to be described in the future" include the sizes described as "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO). In the case of a size not described in the above industrial standards, it refers to a rim with a width corresponding to the bead width of the tire). Also, the "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 described in the above JATMA, etc. In the case of a size not described in the above industrial standards, the "specified internal pressure" shall refer 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 radially inner end of the rubber chafer in the tire diameter direction is located radially inner in the tire diameter direction than the radially inner end of the bead core, and the pneumatic tire according to any one of (1) to (4) above).

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a pneumatic tire capable of suppressing a decrease in cornering power).

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be exemplified 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 circumferences 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 entry 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 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. As the carcass cord, for example, an organic fiber such as PET, or a hybrid cord formed by twisting two organic fiber cords (for example, nylon and aramid) can be used. 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 portion 3b in the tire radial direction is located on the inner side in the tire radial direction than the maximum tire width position, and is located on the outer side in the tire radial direction than the outer end of the bead filler 2b in the tire radial direction. According to 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 are inclined and extend at an inclination angle of 30° to 60° in this example with respect to the tire circumferential direction so as to cross each other between the layers. As the belt cord, a steel cord can be used, but an organic fiber cord 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 perpendicular 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 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 FIG. 1, the tire 1 of the present embodiment includes a reinforcing member 7 that is a tire radial direction region including the tire maximum width position and extends obliquely with respect to the tire radial direction on the outer side in the tire width direction of the carcass 3. In the illustrated example, the reinforcing member 7 has an arc shape along the carcass main body portion 3a in this cross section, but other shapes such as a straight line shape can also be used. Here, the "tire maximum width position" refers to the position where the width in the tire width direction of the pneumatic tire is maximum in the tire width direction cross section in the above reference state.

[0025] In this example, the reinforcing member 7 is an organic fiber cord. As the organic fiber cord, organic fibers such as PET or a hybrid cord formed by twisting two organic fiber cords (for example, a nylon cord and an aramid cord) can be used. The Young's modulus (JIS L1017 8.5 a) (2002) of the cord of the reinforcing member 7 is tested and obtained in accordance with JIS L1017 8.8 (2002). ) is not particularly limited, but can be 3000 to 50000 GPa, the number of cords of 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. Although it is preferable to arrange one layer of the reinforcing member from the viewpoint of weight reduction, two or more layers can also be arranged. In that case, it is preferable to reduce the Young's modulus, the number of driven cords, and the cord diameter so as to be comparable to the case of one layer from the viewpoints of rigidity and weight reduction.

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

[0027] Further, 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 the cornering power can be improved by setting it to 10% or more, while the weight increase can be suppressed by setting it to 40% or less.

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

[0029] The outer end of the rubber chafer 8 in the tire radial direction is preferably located on the outer side in the tire radial direction than the rim separation point. Further, the inner end of the rubber chafer 8 in the tire radial direction is preferably located on the inner side in the tire radial direction than the inner end of the bead core 2a in the tire radial direction. In this example, as shown in FIG. 1, the rubber chafer 8 extends from near the bead base line (a virtual line passing through the bead base and parallel to the tire width direction) to the outer side in the tire radial direction than the apex of the rim guard in the tire radial direction region.

[0030] In the present embodiment, the rubber chafer 7 is made of a high-elasticity rubber. Specifically, when the storage elastic modulus of the bead filler 2b is E1' and the storage elastic modulus of the rubber chafer 7 is E2', the ratio E2' / E1' is 0.4 ≦ E2' / E1' ≦ 1 is satisfied. Hereinafter, the operation and effect of the pneumatic tire of the present embodiment will be described.

[0031] In the pneumatic tire of the present embodiment, first, the height of the bead filler 2b is 25 mm or less (in this example, the outer end of the carcass turn-up portion 3b in the tire radial direction is further located on the inner side in the tire radial direction than the tire maximum width position, and the rubber gauge at the tire 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). Therefore, the tire can be weight-reduced. As described above, in such a tire, there is a possibility that the lateral spring constant decreases and the cornering power decreases. In contrast, as a result of investigations by the inventors, as schematically shown in FIG. 2, when out-of-plane bending acts on the bead portion 2 (particularly, 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), among the translational component, rotational component, and bending component of the lateral displacement, it was found that particularly the rotational component increases, which is the cause of the decrease in the lateral spring constant. Further, as schematically shown in FIG. 2, the above-described out-of-plane bending acts as a tensile force on the inner surface side of the tire of the bead portion 2 and as a compressive force on the outer surface side of the tire of the bead portion 2. In particular, it was found that the decrease in the lateral spring constant can be suppressed by countering the compressive force on the outer surface side (the inner side of the bending) of the bead portion 2. Therefore, as described above, a highly rigid rubber chafer 8 (where 0.4 ≦ E2' / E1' ≦ 1) is disposed on the outer side in the tire width direction of the bead filler 2b. Thereby, even when a compressive force acts on the outer surface side of the tire of the bead portion 2, the increase in the rotational component of the lateral displacement can be suppressed by the highly rigid rubber chafer 8, so that the decrease in the lateral spring constant can be suppressed and the decrease in the cornering power can be suppressed. If the ratio E2' / E1' is less than 0.4, the effect of suppressing the increase in the rotational component of the lateral displacement cannot be sufficiently obtained. On the other hand, if the ratio E2' / E1' exceeds 1, the friction coefficient at the contact portion with the rim becomes small, and there is a concern of rim detachment. As described above, according to the pneumatic tire of the present embodiment, it is possible to suppress a decrease in cornering power while reducing the weight of the tire. Although it is particularly effective in the above-described lightweight configuration as in the present embodiment, even when not in the above-described lightweight configuration, the highly rigid rubber chafer 8 can suppress the increase in the rotational component of the lateral displacement due to the compressive force acting on the outer surface side of the tire of the bead portion 2, so that the effect of suppressing the decrease in cornering power can be obtained.

[0032] Here, for the same reason as above, the ratio E2' / E1' is 0.6 ≦ E2' / E1' ≦ 1 and preferably further satisfies this.

[0033] The length of the rubber chafer in the tire radial 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 the lateral displacement can be obtained more sufficiently, and by setting it to 60 mm or less, the weight increase due to the arrangement of the rubber chafer can be suppressed as much as possible.

[0034] The outer end of the rubber chafer in the tire radial direction is preferably located outside the tire radial direction from the rim separation point. This is because a wider area where out-of-plane bending acts can be covered, and the effect of suppressing the increase in the rotational component of the lateral displacement can be obtained more sufficiently.

[0035] The inner end of the rubber chafer in the tire radial direction is preferably located inside the tire radial direction from the inner end of the bead core in the tire radial direction. This is because a wider area where out-of-plane bending acts can be covered, and the effect of suppressing the increase in the rotational component of the lateral displacement can be obtained more sufficiently.

[0036] Here, the tire in the present disclosure is preferably a pneumatic radial tire for a passenger car.

[0037] As an example, this tire has a tire cross-sectional width SW of less than 165 (mm), and the ratio SW / OD of the tire cross-sectional width SW to the outer diameter OD is 0.26 or less, having a narrow-width and large-diameter shape. By making the tire cross-sectional width SW narrower than the outer diameter OD of the tire, the air resistance can be reduced, and by making the outer diameter OD of the tire larger than the tire cross-sectional width SW, the deformation of the tread rubber near the ground contact surface of the tire can be suppressed, and the rolling resistance can be reduced. Thereby, the fuel efficiency of the tire can be improved. The above SW / OD is preferably 0.25 or less, and more preferably 0.24 or less. The above ratio is preferably satisfied when the internal pressure of the tire is 200 kPa or more, more preferably satisfied when it is 220 kPa or more, and even more preferably satisfied when it is 280 kPa or more. This is because the rolling resistance can be reduced. On the other hand, the above ratio is preferably satisfied when the internal pressure of the tire is 350 kPa or less. This is because the riding comfort can be improved. Here, from the viewpoint of ensuring the contact area, the cross-sectional width SW of the tire 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 satisfying the above ratio. On the other hand, from the viewpoint of reducing air resistance, the cross-sectional width SW of the tire is preferably 155 mm or less within the range satisfying the above ratio. Also, from the viewpoint of reducing the rolling resistance, the outer diameter OD of the tire is preferably 500 mm or more, more preferably 550 mm or more, and even more preferably 580 mm or more within the range satisfying the above ratio. On the other hand, from the viewpoint of reducing air resistance, the outer diameter OD of the tire 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 satisfying the above ratio. Further, from the viewpoint of reducing the rolling resistance, when the cross-sectional width SW and the outer diameter OD of the tire satisfy the above ratio, the rim diameter is preferably 16 inches or more, more preferably 17 inches or more, and even more preferably 18 inches or more. On the other hand, from the viewpoint of reducing air resistance, when the cross-sectional width SW and the outer diameter OD of the tire satisfy the above ratio, the rim diameter is preferably 22 inches or less, more preferably 21 inches or less, even more preferably 20 inches or less, and particularly preferably 19 inches or less. Also, when the cross-sectional width SW and the outer diameter OD of the tire satisfy the above ratio, the aspect ratio of the tire is more preferably 45 to 70, and even more preferably 45 to 65. The specific tire size is not particularly limited. As an example, it can be any one of 105 / 50R16, 115 / 50R17, 125 / 55R20, 125 / 60R18, 125 / 65R19, 135 / 45R21, 135 / 55R20, 135 / 60R17, 135 / 60R18, 135 / 60R19, 135 / 65R19, 145 / 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 / 70R17, 155 / 70R19.

[0038] Also, as another example, for the tire, the cross-sectional width SW of the tire is 165 (mm) or more, and the cross-sectional width SW (mm) and outer diameter OD (mm) of the tire satisfy the relational expression OD (mm) ≧ 2.135 × SW (mm) + 282.3 and have a narrow-width and large-diameter shape. By satisfying the above relational expression, air resistance can be reduced, and rolling resistance can be reduced. As a result, the fuel efficiency of the tire can be improved. In the second aspect, it is preferable that the cross-sectional width SW and outer diameter OD of the tire satisfy the above relational expression and the ratio SW / OD is 0.26 or less, more preferably 0.25 or less, and even more preferably 0.24 or less. This is because the fuel efficiency of the tire can be further improved. It is preferable that the above relational expression and / or ratio are satisfied when the internal pressure of the tire is 200 kPa or more, more preferably when the internal pressure is 220 kPa or more, and even more preferably when the internal pressure is 280 kPa or more. This is because rolling resistance can be reduced. On the other hand, it is preferable that the above relational expression and / or ratio are satisfied when the internal pressure of the tire is 350 kPa or less. This is because the riding comfort can be improved. Here, from the perspective of ensuring the contact area, the section width SW of the tire is preferably 175 mm or more, more preferably 185 mm or more, within the range satisfying the above relational expression. On the other hand, from the perspective of reducing air resistance, the section width SW of the tire is preferably 230 mm or less, more preferably 215 mm or less, still more preferably 205 mm or less, and particularly preferably 195 mm or less, within the range satisfying the above relational expression. Also, from the perspective of reducing rolling resistance, the outer diameter OD of the tire is preferably 630 mm or more, more preferably 650 mm or more, within the range satisfying the above relational expression. On the other hand, from the perspective of reducing air resistance, the outer diameter OD of the tire is preferably 800 mm or less, more preferably 750 mm or less, still more preferably 720 mm or less, within the range satisfying the above relational expression. Further, from the perspective of reducing rolling resistance, when the section width SW and the outer diameter OD of the tire satisfy the above relational expression, the rim diameter is preferably 18 inches or more, more preferably 19 inches or more. On the other hand, from the perspective of reducing air resistance, when the section width SW and the outer diameter OD of the tire satisfy the above relational expression, the rim diameter is preferably 22 inches or less, more preferably 21 inches or less. Also, when the section width SW and the outer diameter OD of the tire satisfy the above relational expression, the aspect ratio of the tire is preferably 45 to 70, more preferably 45 to 65. The specific tire size is not particularly limited. As an example, it can be any one of 165 / 45R22, 165 / 55R18, 165 / 55R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 45R23, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 45R22, 185 / 50R20, 185 / 55R19, 185 / 55R20, 185 / 60R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, 195 / 60R19, 205 / 50R21, 205 / 55R20, 215 / 50R21.

[0039] Also, as another example, for the tire, the cross-sectional width SW (mm) and the outer diameter OD (mm) of the tire satisfy the relational expression OD (mm) ≧ -0.0187 × SW (mm)2 + 9.15 × SW (mm) - 380 and have a narrow-width and large-diameter shape. By satisfying the above relational expression, air resistance can be reduced, and rolling resistance can be reduced. Thereby, the fuel efficiency of the tire can be improved. In the third aspect, it is preferable that the cross-sectional width SW and the outer diameter OD of the tire satisfy the above relational expression and the ratio SW / OD is 0.26 or less, more preferably 0.25 or less, and even more preferably 0.24 or less. This is because the fuel efficiency of the tire can be further improved. The above relational expression and / or ratio are preferably satisfied when the internal pressure of the tire is 200 kPa or more, more preferably satisfied when the internal pressure is 220 kPa or more, and even more preferably satisfied when the internal pressure is 280 kPa or more. This is because rolling resistance can be reduced. On the other hand, the above relational expression and / or ratio are preferably satisfied when the internal pressure of the tire is 350 kPa or less. This is because the riding comfort can be improved. Here, from the viewpoint of ensuring the contact area, the cross-sectional width SW of the tire is preferably 105 mm or more, more preferably 125 mm or more, still more preferably 135 mm or more, and particularly preferably 145 mm or more within the range satisfying the above relational expression. On the other hand, from the viewpoint of reducing air resistance, the cross-sectional width SW of the tire is preferably 230 mm or less, more preferably 215 mm or less, still more preferably 205 mm or less, and particularly preferably 195 mm or less within the range satisfying the above relational expression. Further, from the viewpoint of reducing rolling resistance, the outer diameter OD of the tire is preferably 500 mm or more, more preferably 550 mm or more, and still more preferably 580 mm or more within the range satisfying the above relational expression. On the other hand, from the viewpoint of reducing air resistance, the outer diameter OD of the tire is preferably 800 mm or less, more preferably 750 mm or less, and still more preferably 720 mm or less within the range satisfying the above relational expression. Also, from the viewpoint of reducing rolling resistance, when the cross-sectional width SW and the outer diameter OD of the tire satisfy the above relational expression, the rim diameter is preferably 16 inches or more, more preferably 17 inches or more, and still more preferably 18 inches or more. On the other hand, from the viewpoint of reducing air resistance, when the cross-sectional width SW and the outer diameter OD of the tire satisfy the above relational expression, the rim diameter is preferably 22 inches or less, more preferably 21 inches or less, and still more preferably 20 inches or less. Further, when the cross-sectional width SW and the outer diameter OD of the tire satisfy the above ratio, the aspect ratio of the tire is more preferably 45 to 70, and still more preferably 45 to 65. The specific tire size is not particularly limited. As an example, it can be any one of 105 / 50R16, 115 / 50R17, 125 / 55R20, 125 / 60R18, 125 / 65R19, 135 / 45R21, 135 / 55R20, 135 / 60R17, 135 / 60R18, 135 / 60R19, 135 / 65R19, 145 / 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 / 70R17, 155 / 70R19, 165 / 45R22, 165 / 55R18, 165 / 55R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 6R19, 165 / 70R18, 175 / 45R23, 175 / 55R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 45R22, 185 / 50R20, 185 / 55R19, 185 / 55R20, 185 / 60R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, 195 / 60R19, 205 / 50R21, 205 / 55R20, 215 / 50R21.

[0040] Here, as described above, in a tire having the above-described lightweight configuration, there is a risk that the lateral spring constant decreases and the cornering power deteriorates. As a result of investigations by the present inventors, it has been found that the concentration of lateral displacement directly under the load, with the periphery being pulled in the load direction and shear deformation increasing on the tire circumference, is the cause of the decrease in the lateral spring constant. Therefore, in the tire of the present embodiment, a reinforcing member 7 is provided in a tire radial direction region including the tire maximum width position, outside the tire width direction of the carcass 3, extending obliquely with respect to the tire radial direction. Thereby, a force that pulls in the opposite direction to the reinforcing member 7 acts during shear deformation, and thus the shear deformation can be suppressed. As a result, a decrease in the lateral spring constant can be suppressed, and a further decrease in cornering power can be suppressed. Although it is particularly effective in the lightweight configuration as described above, even when not in the lightweight configuration as described above, since a force that pulls in the opposite direction to the reinforcing member 7 acts during shear deformation, an effect of further suppressing a decrease in cornering power can be obtained.

[0041] Here, the reinforcing member is preferably an organic fiber cord. This is because organic fibers are lightweight compared to their rigidity, so an increase in weight due to the addition of the reinforcing member can be suppressed as much as possible.

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

[0043] The length of the reinforcing member in the tire radial direction is preferably 10 to 40% of the tire section height. By setting it to 10% or more, the effect of suppressing the decrease in cornering power can be further obtained. On the other hand, by setting it to 40% or less, the weight increase due to the addition of the reinforcing member can be suppressed as much as possible. As an example, the outer end of the reinforcing member in the tire radial direction can be set to a tire radial position of 50 to 80% of the tire section height from the bead base line (a virtual 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 set to a tire radial position of 15 to 40% of the tire section height from the bead base line. Although not particularly limited, the length of the reinforcing member in the tire radial direction can be 15 mm to 40 mm.

Example

[0044] To confirm the effects of the present invention, tires according to inventive examples, comparative examples, and conventional examples were prototyped and their performance was evaluated. Each tire includes a pair of bead cores embedded in a pair of bead portions, and a carcass composed of one or more carcass plies spanning toroidally between the pair of bead cores. A bead filler is disposed outside the bead core in the tire radial direction, and a rubber chafer is provided outside the bead filler in the tire width direction. 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 maximum width position of the tire. Also, "BF" is the bead filler, and "GC" is an abbreviation for the rubber chafer. The lateral spring coefficient was measured by mounting each tire on a rim, measuring the deflection amount using an indoor tester, and measuring the lateral spring coefficient from the tangent slope at a load of 4 kN. Also, the weight of each tire before rim assembly was measured. In Table 1, the evaluation results are shown in an index with the conventional example set to 100.

[0045]

Table 1

Explanation of Signs

[0046] 1: Pneumatic tire 2: Bead part, 3: Carcass, 4: Belt, 5: Tread part, 6: Sidewall part, 7: Reinforcing member, 8: Rubber chafer

Claims

1. A pair of bead cores embedded in the pair of bead portions; A carcass including one or more carcass plies extending in a toroidal shape between the pair of bead cores, A bead filler is disposed on the outer side of the bead core in the tire radial direction, A rubber chafer is provided on the outer side of the bead filler in the tire width direction, The rubber chafer extends radially outward in the tire radial direction beyond the apex of the rim guard, 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 above.

2. The ratio E2' / E1' is 0.6≦E2′ / E1′≦1 The pneumatic tire of claim 1 further comprising:

3. 3. The pneumatic tire according to claim 1, 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 an outer end in the tire radial direction of the rubber chafer is located outer in the tire radial direction than a rim separation point.

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

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

7. The pneumatic tire according to any one of claims 1 to 6, which is a pneumatic radial tire for passenger cars.

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