Pneumatic tire

Abstract

To provide a pneumatic tire which is reduced in weigh and furthermore is improved in driving force and steering stability.SOLUTION: A pneumatic tire 1 is provided, including a bead portion 4, a carcass 6, a bead reinforcing layer 9, and a bead apex rubber 8. The carcass 6 has a first carcass ply 6A including a plurality of carcass cords arranged at an angle of 60 to 90° with respect to a tire circumferential direction. The bead reinforcing layer 9 has a first reinforcing ply 9A including a plurality of bead reinforcing cords arranged at an angle of 60 to 90° with respect to the tire circumferential direction. The first carcass ply 6A includes a main body portion 6a and a turned-up portion 6b connected to the main body portion 6a. The first reinforcing ply 9A includes a first portion 9a and a second portion 9b connected to the first portion 9a. An outer end 9be of the second portion 9b is located outside the bead apex rubber 8 in a tire axial direction and inside an outer end 8e of the bead apex rubber 8 in a tire radial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Various pneumatic tires suitable for high-speed driving have been proposed. For example, Patent Document 1 below proposes a pneumatic tire that is lightweight and has improved durability by providing a bead reinforcing layer in the bead portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-172104 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the bead reinforcing layer of Patent Document 1, the first and second parts are in contact with each other, and the tension of the cords acts on each other, which may result in the desired effect not being achieved in terms of vertical rigidity, lateral rigidity, and longitudinal rigidity.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that is lightweight while improving driving force and steering stability. [Means for solving the problem]

[0006] The present invention provides a pneumatic tire including a pair of bead portions each having a bead core embedded therein, a carcass extending between the pair of bead portions, a bead reinforcing layer disposed in each of the pair of bead portions, and a bead apex rubber extending radially outward from the bead core, wherein the carcass has a first carcass ply including a plurality of carcass cords arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction, and the bead reinforcing layer has a first reinforcing ply including a plurality of bead reinforcing cords arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction, and the first carcass ply extends between the pair of bead portions. and a pair of turn-up portions connected to the main body portion and folded back around the bead core from the inside to the outside in the tire axial direction, in each of the pair of bead portions, the first reinforcing ply includes a first portion arranged along the main body portion and a second portion connected to the first portion and folded back around the bead core from the inside to the outside in the tire axial direction and arranged along the turn-up portion, and an outer end in the tire radial direction of the second portion is located outside the bead apex rubber in the tire axial direction and radially inward of the outer end in the tire radial direction of the bead apex rubber. [Effects of the Invention]

[0007] By having the above-described configuration, the pneumatic tire of the present invention can improve driving force and steering stability while achieving weight reduction. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing an embodiment of a pneumatic tire of the present invention. [Figure 2] FIG. 2 is an enlarged view of a sidewall portion and a bead portion. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 is a tire meridian cross-sectional view showing a pneumatic tire 1 of this embodiment in a normal state. Here, the "normal state" refers to a state in which the pneumatic tire 1 is mounted on a normal rim, adjusted to a normal internal pressure, and no load is applied. Unless otherwise specified below, the dimensions of each part of the pneumatic tire 1 are values ​​measured in this normal state.

[0010] If there is a standard system including the standard on which the pneumatic tire 1 is based, a "genuine rim" is a rim defined for each tire by that standard, for example, a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO. If there is no standard system including the standard on which the pneumatic tire 1 is based, a "genuine rim" is a rim with the smallest rim diameter and the smallest rim width among rims that can be assembled and do not cause air leakage.

[0011] "Normal internal pressure" is the air pressure set for each tire by a standard set by the JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for the TRA, and the "INFLATION PRESSURE" for the ETRTO. If there is no standard set that includes the standard set by the pneumatic tire 1, "normal internal pressure" is the air pressure set for each tire by the manufacturer, etc.

[0012] 1, the pneumatic tire 1 has a structure suitable for high-speed driving such as circuit driving. The pneumatic tire 1 is not limited to this embodiment, and can be applied to various pneumatic tires 1, such as tires for passenger cars, heavy-duty tires, and motorcycle tires.

[0013] The pneumatic tire 1 of this embodiment includes a tread portion 2 having a contact surface 2s, a pair of sidewall portions 3 extending radially inward from both sides of the tread portion 2 in the tire axial direction, and a pair of bead portions 4 in contact with the rim.

[0014] Each of the pair of bead portions 4 is located radially inward of each of the pair of sidewall portions 3. In this embodiment, an annular bead core 5 extending in the tire circumferential direction is embedded in each of the pair of bead portions 4. The bead core 5 is formed of, for example, steel wire.

[0015] The pneumatic tire 1 preferably includes a carcass 6 spanning the space between the pair of bead portions 4, and a belt layer 7 disposed radially outward of the carcass 6 in the tread portion 2. The belt layer 7 enables the pneumatic tire 1 to be lightweight and suppress distortion of the tread portion 2 under load.

[0016] The carcass 6 of this embodiment has a first carcass ply 6A including a plurality of carcass cords (not shown) arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction. The first carcass ply 6A preferably includes a main body portion 6a spanning a pair of bead portions 4, and a pair of turned-up portions 6b connected to the main body portion 6a and turned up around the bead cores 5 from the inside to the outside in the tire axial direction. Such a first carcass ply 6A helps to achieve both suppression of deformation under heavy load and weight reduction.

[0017] Fig. 2 is an enlarged view of the sidewall portion 3 and the bead portion 4. As shown in Fig. 1 and Fig. 2, the pneumatic tire 1 of this embodiment includes a bead apex rubber 8 extending radially outward from each of the pair of bead cores 5, and a bead reinforcing layer 9 disposed in each of the pair of bead portions 4. The bead reinforcing layer 9 enables the pneumatic tire 1 to improve the rigidity of the bead portion 4 while achieving a reduction in weight.

[0018] The bead reinforcing layer 9 of this embodiment has a first reinforcing ply 9A including a plurality of bead reinforcing cords (not shown) arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction. Such a bead reinforcing layer 9 can reduce longitudinal rigidity while maintaining good vertical and lateral rigidity, thereby improving the driving force of the pneumatic tire 1.

[0019] In each of the pair of bead portions 4, the first reinforcing ply 9A preferably includes a first portion 9a and a second portion 9b continuous with the first portion 9a. The first portion 9a is, for example, a portion disposed along the main body portion 6a of the first carcass ply 6A. The first portion 9a is preferably disposed adjacent to the outer side of the main body portion 6a in the tire axial direction.

[0020] The second portion 9b includes, for example, a portion that is folded back from the axially inner side to the axially outer side around the bead core 5 and disposed along the turned-up portion 6b of the first carcass ply 6A. The second portion 9b is preferably disposed adjacent to the axially inner side of the turned-up portion 6b.

[0021] In this embodiment, the radially outer end 9be of the second portion 9b is located axially outside the bead apex rubber 8 and radially inward of the radially outer end 8e of the bead apex rubber 8. Such a bead reinforcing layer 9 can generate tension in the bead reinforcing cords by deformation of the bead apex rubber 8, thereby improving lateral rigidity during cornering. Therefore, the pneumatic tire 1 of this embodiment can improve driving force and handling stability while achieving weight reduction.

[0022] In a more preferred embodiment, the outer end 9be of the second portion 9b is located radially inward of the outer end 9ae of the first portion 9a in the tire radial direction. Such a bead reinforcing layer 9 can suppress damage originating from the outer end 9be of the second portion 9b located axially outward, thereby improving the durability of the pneumatic tire 1.

[0023] The minimum distance L between the outer end 9be of the second portion 9b and the first portion 9a is preferably 0.5 mm or more. By making the minimum distance L 0.5 mm or more, tension in the bead reinforcing cord due to deformation of the bead apex rubber 8 can be reliably generated.

[0024] The height H of the first reinforcing ply 9A in the tire radial direction is preferably 10% or more of the tire cross-sectional height Sh. By making the height H 10% or more of the cross-sectional height Sh, the contact area between the first reinforcing ply 9A and the bead apex rubber 8 can be secured, and tension in the bead reinforcing cord due to deformation of the bead apex rubber 8 can be reliably generated.

[0025] From this viewpoint, the height H of the first reinforcing ply 9A is more preferably 20% or more of the cross-sectional height Sh. On the other hand, from the viewpoint of weight reduction, the upper limit of the height H of the first reinforcing ply 9A is preferably 80% or less. Thus, the height H of the first reinforcing ply 9A is preferably 10% to 80% of the cross-sectional height Sh, more preferably 20% to 80%. Note that the bead reinforcing layer 9 may further include, for example, another reinforcing ply (not shown) other than the first reinforcing ply 9A.

[0026] The complex elastic modulus of the bead apex rubber 8 at 70°C is preferably 55 to 70 MPa. When the complex elastic modulus of the bead apex rubber 8 is 55 MPa or more, the rigidity of the bead portion 4 can be improved. When the complex elastic modulus of the bead apex rubber 8 is 70 MPa or less, sufficient deformation for generating tension in the bead reinforcing layer 9 can be ensured.

[0027] Here, the complex modulus is a value measured by taking a rubber sample of 20 mm length × 4 mm width × 1 mm thickness and using a dynamic viscoelasticity measuring device (GARO Iplexar series) under the following conditions in accordance with the provisions of JIS-K6394. Initial strain: 5% Dynamic strain: 1% Frequency: 10Hz Deformation mode: Stretch Measurement temperature: 70℃

[0028] The outer end 6Ae of the turned-up portion 6b of the first carcass ply 6A is preferably located radially inward of the outer end 9be of the second portion 9b of the first reinforcing ply 9A. Such a first carcass ply 6A can suppress damage originating from the outer end 6Ae of the turned-up portion 6b, thereby improving the durability of the pneumatic tire 1.

[0029] The carcass 6 preferably has a second carcass ply 6B disposed radially outward of the first carcass ply 6A in the tread portion 2. The second carcass ply 6B extends, for example, from the tread portion 2 radially inward of the tire, outside the bead apex rubber 8 and the bead reinforcing layer 9 in the tire axial direction, and has an inner end 6Be in the bead portion 4. Such a second carcass ply 6B can achieve both suppression of deformation under heavy load and weight reduction.

[0030] The inner end 6Be of the second carcass ply 6B is desirably located radially inward of the outer end 6Ae of the turned-up portion 6b of the first carcass ply 6A. The inner end 6Be of the second carcass ply 6B is located, for example, axially outward of the bead core 5. Such a second carcass ply 6B can suppress damage originating from the outer end 6Ae of the turned-up portion 6b of the first carcass ply 6A, thereby improving the durability of the pneumatic tire 1.

[0031] The second carcass ply 6B includes, for example, a plurality of carcass cords (not shown) arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction, similar to the first carcass ply 6A. When the angle of the carcass cords of the first carcass ply 6A and the second carcass ply 6B is less than 90 degrees, it is desirable that the inclination directions of the respective carcass cords with respect to the tire circumferential direction are opposite to each other. Such a second carcass ply 6B can cooperate with the first carcass ply 6A to suppress deformation under high load.

[0032] The belt layer 7 has, for example, a first belt ply 7A, a second belt ply 7B disposed radially outward of the first belt ply 7A, and a third belt ply 7C disposed radially outward of the second belt ply 7B. Such a belt layer 7 can increase the rigidity of the tread portion 2, suppress distortion under load, and improve the steering stability of the pneumatic tire 1.

[0033] The first belt ply 7A of this embodiment is disposed radially outward of the second carcass ply 6B. The first belt ply 7A preferably includes a plurality of belt cords (not shown) arranged at an angle of 24 to 45 degrees relative to the tire circumferential direction. Such a first belt ply 7A, in cooperation with the bead reinforcing layer 9, can maintain appropriate lateral rigidity, which helps to improve the steering stability of the pneumatic tire 1.

[0034] The second belt ply 7B includes, for example, a plurality of belt cords (not shown) arranged at an angle of 24 to 45 degrees with respect to the tire circumferential direction, similar to the first belt ply 7A. The inclination directions of the belt cords of the first belt ply 7A and the second carcass ply 6B with respect to the tire circumferential direction are preferably opposite to each other. This second carcass ply 6B, in cooperation with the first belt ply 7A, can increase the rigidity of the tread portion 2, suppress distortion under load, and improve the steering stability of the pneumatic tire 1.

[0035] The third belt ply 7C may include, for example, a plurality of belt cords (not shown) arranged at an angle with respect to the tire circumferential direction, similar to the first belt ply 7A and the second carcass ply 6B, or may include belt cords arranged along the tire circumferential direction. Such a third belt ply 7C, in cooperation with the first belt ply 7A and the second carcass ply 6B, can increase the rigidity of the tread portion 2, suppress distortion under load, and improve the steering stability of the pneumatic tire 1.

[0036] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment and can be modified and practiced in various ways.

[0037] [Note] The present invention is as follows.

[0038] [Invention 1] A pneumatic tire, a pair of bead portions each having a bead core embedded therein; a carcass extending between the pair of bead portions; a bead reinforcing layer disposed in each of the pair of bead portions; a bead apex rubber extending from the bead core outward in the tire radial direction, The carcass has a first carcass ply including a plurality of carcass cords arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction, the bead reinforcing layer has a first reinforcing ply including a plurality of bead reinforcing cords arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction, the first carcass ply includes a main body portion spanning between the pair of bead portions, and a pair of turn-up portions connected to the main body portion and turned up around the bead core from the inside to the outside in the tire axial direction, In each of the pair of bead portions, the first reinforcing ply includes a first portion arranged along the main body portion, and a second portion that is continuous with the first portion, is folded back around the bead core from the inner side to the outer side in the tire axial direction, and is arranged along the turned-up portion, an outer end of the second portion in the tire radial direction is located outside the bead apex rubber in the tire axial direction and inside the outer end of the bead apex rubber in the tire radial direction; Pneumatic tires.

[0039] [Invention 2] The pneumatic tire according to aspect 1, wherein the outer end of the second portion is located radially inward of the outer end of the first portion in the tire radial direction.

[0040] [Invention 3] A pneumatic tire according to aspect 2, wherein the minimum distance between the outer end of the second portion and the first portion is 0.5 mm or more.

[0041] [Invention 4] 4. The pneumatic tire according to any one of claims 1 to 3, wherein the height of the first reinforcing ply in the tire radial direction is 10% or more of the cross-sectional height of the tire.

[0042] [Invention 5] 5. The pneumatic tire according to claim 4, wherein the height of the first reinforcing ply is 20% to 80% of the cross-sectional height.

[0043] [Invention 6] 6. The pneumatic tire according to any one of Inventions 1 to 5, wherein the bead apex rubber has a complex modulus of elasticity at 70° C. of 55 to 70%.

[0044] [Invention 7] a tread portion having a ground contact surface; a belt layer disposed radially outward of the carcass in the tread portion, 7. The pneumatic tire according to any one of Inventions 1 to 6, wherein the belt layer has a first belt ply including a plurality of belt cords arranged at an angle of 24 to 45° with respect to the circumferential direction of the tire. [Explanation of symbols]

[0045] 1 pneumatic tire 4 Bead section 6. Carcass 6A First carcass ply 6a Main body 6b Folded part 8 Bead apex rubber 8e outer edge 9 Bead reinforcement layer 9A First reinforcing ply 9a Part 1 9b Part 2 9be external end

Claims

1. A pneumatic tire, a pair of bead portions each having a bead core embedded therein; a carcass extending between the pair of bead portions; a bead reinforcing layer disposed in each of the pair of bead portions; a bead apex rubber extending from the bead core outward in the tire radial direction, the carcass has a first carcass ply including a plurality of carcass cords arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction, the bead reinforcing layer has a first reinforcing ply including a plurality of bead reinforcing cords arranged at an angle of 60 to 90 degrees with respect to the tire circumferential direction, the first carcass ply includes a main body portion spanning between the pair of bead portions, and a pair of turn-up portions connected to the main body portion and turned up around the bead core from the inside to the outside in the tire axial direction, In each of the pair of bead portions, the first reinforcing ply includes a first portion disposed axially outward of the main body portion, and a second portion connected to the first portion, folded back around the bead core from the axially inner side to the axially outer side, and disposed axially inward of the turned-up portion, an outer end of the second portion in the tire radial direction is located outside the bead apex rubber in the tire axial direction and inside the outer end of the bead apex rubber in the tire radial direction; Pneumatic tires.

2. The pneumatic tire according to claim 1 , wherein the outer end of the second portion is located radially inward of the outer end of the first portion in the tire radial direction.

3. The pneumatic tire according to claim 2 , wherein the minimum distance between the outer end of the second portion and the first portion is 0.5 mm or greater.

4. The pneumatic tire according to claim 1 , wherein the height of the first reinforcing ply in the tire radial direction is 10% or more of the cross-sectional height of the tire.

5. The pneumatic tire according to claim 4, wherein the height of the first reinforcing ply is 20% to 80% of the cross-sectional height.

6. The pneumatic tire according to claim 1, wherein the bead apex rubber has a complex modulus of elasticity at 70° C. of 55 to 70%.

7. a tread portion having a ground contact surface; a belt layer disposed radially outward of the carcass in the tread portion, The pneumatic tire according to any one of claims 1 to 6, wherein the belt layer has a first belt ply including a plurality of belt cords arranged at an angle of 24 to 45 degrees with respect to the tire circumferential direction.

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