JP6835541B2 - Pneumatic tires - Google Patents

Description

Embodiments of the present invention relate to pneumatic tires.

In order to improve the steering stability of a pneumatic tire, it is effective to increase the rigidity of the tire, and as a means for that purpose, it is known to incline the configuration code of the carcass ply with respect to the tire radial direction.

For example, as a tire having a structure in which a carcass ply configuration code is inclined, a racing tire such as a racing tire has a code that extends at an angle with respect to the tire circumferential direction, and the codes are opposite to each other. A semi-radial tire including two carcass plies laminated in this manner is known (see Patent Document 1).

JP 2015-063172

However, if the configuration cord of the carcass ply is tilted, the steering stability is improved, but there is a problem that the durability is impaired, and it is not easy to achieve both the steering stability and the durability.

It is an object of the present invention to provide a pneumatic tire capable of achieving both steering stability and durability.

The pneumatic tire according to the embodiment of the present invention has a first main body portion extending from the tread portion to the bead core of the bead portion via the sidewall portion, and extending from the first main body portion and surrounding the bead core from the inside to the outside in the tire width direction. A first carcass ply composed of a first folded portion folded toward the tire, and a tread portion arranged outside the tire radial direction of the first main body portion and from the tread portion to the bead core of the bead portion via the sidewall portion. A carcass layer including a second main body portion to reach, a second folded portion extending from the second main body portion and folded back from the inside to the outside in the tire width direction around the bead core, and a second carcass ply. Be prepared. The carcass layer has a four-layer portion in which the first main body portion, the second main body portion, the second folded portion, and the first folded portion are arranged in this order from the inner surface side of the tire. In the four-layer portion, the configuration cords of the first main body portion, the second main body portion, the second folded portion, and the first folded portion are inclined with respect to the tire circumferential direction and the directions of inclination are staggered. In addition to being arranged so as to be, the inclination angles of the first main body portion, the second main body portion, the second folded portion, and the first folded portion of the four-layer portion with respect to the tire circumferential direction are θ1 respectively. , Θ2, θ3 and θ4, satisfying θ1>θ2>θ3> θ4, 75 ° ≤ θ1 <90 °, 65 ° ≤ θ2 ≤ 85 °, 55 ° ≤ θ3 ≤ 75 °, and 45 ° ≤ θ4 ≤ 65 ° . To do.

In one embodiment, at least one of the first folded portion and the second folded portion may have a folded end located inside the outer end of the belt layer in the tire width direction in the tire width direction. Further, the folded end of the first folded portion is located inside the outer end of the belt layer in the tire width direction in the tire width direction, and the folded end of the second folded portion is provided outside the tire radial direction of the bead core. The first folded portion is located between the tip of the bead filler and the outer end of the belt layer in the tire width direction, and the first folded portion is a protruding portion protruding outward in the tire radial direction from the folded end of the second folded portion. A overlapping portion that overlaps with the second folded portion between the folded end of the second folded portion and the tip of the bead filler is included, and the configuration code of the protruding portion is relative to the tire circumferential direction with respect to the configuration code of the overlapping portion. It may be arranged with a larger inclination. Further, the difference in inclination angles of the constituent cords between the layers adjacent to each other in the tire thickness direction in the four-layer portion may be 10 ° or less.

According to the present embodiment, in the four-layer portion in which the first main body portion, the second main body portion, the second folded portion, and the first folded portion of the carcass layer are arranged, the inclination angle of the configuration code with respect to the tire circumferential direction is the tire inner surface. By setting the tires to become smaller from the side to the outer surface side, it is possible to achieve both steering stability and durability.

Semi-cross-sectional view of the pneumatic tire according to the embodiment Schematic cross-sectional view showing the internal structure of the pneumatic tire Explanatory drawing showing composition of carcass layer of the same pneumatic tire

Hereinafter, this embodiment will be described with reference to the drawings.

The pneumatic tire 10 according to the embodiment shown in FIGS. 1 and 2 includes a pair of left and right bead portions 12, a pair of left and right sidewall portions 14 extending outward in the tire radial direction from the bead portions 12, and a sidewall portion 14. It is provided with a tread portion 16 that connects the outer ends in the radial direction of the tire to form a ground contact surface. A ring-shaped bead core 18 is embedded in each of the pair of bead portions 12. A bead filler 20 made of hard rubber that tapers toward the outside in the tire radial direction is provided on the outer side of the bead core 18 in the tire radial direction.

In this example, the pneumatic tire 10 is symmetrical, and the left half is not shown. Further, the tire radial direction is a direction perpendicular to the tire rotation axis, and is indicated by reference numeral RD in FIG. The tire width direction is a direction parallel to the tire rotation axis, and is indicated by reference numeral WD in FIG. The tire circumferential direction is a direction on the circumference centered on the tire rotation axis, and is indicated by an arrow CD in FIG.

The pneumatic tire 10 includes a carcass layer 22 provided so as to be bridged between a pair of bead portions 12 in a toroidal shape. The carcass layer 22 has two carcass plies that have a constituent cord extending in an inclined direction with respect to the tire circumferential direction and are laminated so that the constituent cords are opposite to each other, that is, the first carcass ply 24 and the second carcus ply. It consists of a carcass ply 26. The carcass ply 24, 26 is a sheet-like material formed by rubber-coating a plurality of cords arranged in parallel, and the constituent cords thereof include, for example, organic fibers such as polyester fiber, rayon fiber, aramid fiber, and nylon fiber. Examples include fiber cords and steel cords.

The first carcass ply 24 has a first main body portion 24A extending from the tread portion 16 through the sidewall portion 14 to the bead core 18 of the bead portion 12, and extending from the first main body portion 24A around the bead core 18 from the inside in the tire width direction. It is composed of a first folded portion 24B that is folded toward the outside. The first main body portion 24A passes through the inside of the bead filler 20 in the tire width direction and reaches the inside of the bead core 18 in the tire radial direction. The first folded-back portion 24B is wound from the inside of the bead core 18 in the tire radial direction, through the outside of the bead filler 20 in the tire width direction, and to the outside in the tire radial direction.

The second carcass ply 26 has a second main body 26A extending from the tread portion 16 through the sidewall portion 14 to the bead core 18 of the bead portion 12, and extending from the second main body 26A from the inside in the tire width direction around the bead core 18. It is composed of a second folded portion 26B that is folded toward the outside. The second main body 26A is arranged on the outer side of the first main body 24A in the tire radial direction in the tread portion 16, extends toward the bead portion 12 along the outer surface of the first main body 24A, and is the first main body. It passes between 24A and the bead filler 20 and reaches the inside of the bead core 18 in the tire radial direction. The second folded-back portion 26B is wound up from the inside of the bead core 18 in the tire radial direction, passes between the bead filler 20 and the first folded-back portion 24B, and is wound outward in the tire radial direction.

A belt layer 30 is provided between the carcass layer 22 and the tread rubber 28 on the outer peripheral side of the carcass layer 22 in the tread portion 16. The belt layer 30 is composed of at least two crossed belt plies in which the belt cords are arranged at an inclination angle of 10 ° to 35 ° with respect to the tire circumferential direction. In this example, the first belt layer 30 is arranged inside the tire radial direction. It has a two-layer structure consisting of a belt ply 32 and a second belt ply 34 arranged on the outer peripheral side thereof. Of these, the first belt ply 32 is the widest maximum width belt, and the outer end in the tire width direction corresponds to the outer end 30A in the tire width direction of the belt layer 30. As the belt cord, a steel cord or an organic fiber cord having high tension is used.

In this example, the belt reinforcing layer 36 is provided on the outer side of the belt layer 30 in the tire radial direction, that is, between the belt layer 30 and the tread rubber 28. The belt reinforcing layer 36 is composed of a cap ply having a cord extending substantially parallel to the tire circumferential direction.

The first carcass ply 24 is a high turn-up ply in which the first folded portion 24B extends inward in the tire width direction from the outer end 30A of the belt layer 30 and terminates. That is, the folded end 24BE, which is the tip of the first folded portion 24B, is located inside the outer end 30A of the belt layer 30 in the tire width direction, and is located inside the second main body portion 26A of the second carcass ply 26 and the belt layer 30. It is sandwiched between. By adopting the high turn-up ply structure in this way, the rigidity of the tire can be increased and the steering stability can be improved.

The second folded portion 26B of the second carcass ply 26 extends outward in the tire radial direction from the tip (that is, the outer end in the tire radial direction) 20A of the bead filler 20 and is in front of the outer end 30A of the belt layer 30. It ends with. Therefore, the folded end 26BE, which is the tip of the second folded portion 26B, is located between the tip 20A of the bead filler 20 and the outer end 30A of the belt layer 30, and is the second main body portion 26A of the second carcass ply 26. It is sandwiched between the first carcass ply 24 and the first folding portion 24B of the first carcass ply 24.

In FIG. 1, reference numeral 38 is a side reinforcing layer provided between the bead filler 20 and the second folded-back portion 26B, and is made of a sheet-like material having a cord such as a steel cord coated with rubber.

The carcass layer 22 has a four-layer portion 40 having a four-layer structure in which the first main body portion 24A, the second main body portion 26A, the second folded portion 26B, and the first folded portion 24B are arranged in this order from the tire inner surface side. It is included in part 14. In the four-layer portion 40, the first main body portion 24A, the second main body portion 26A, the second folded portion 26B, and the first folded portion 24B need only be overlapped with each other when viewed from the tire thickness direction. The mating layers may be overlapped so as to be in contact with each other, or may be overlapped with the bead filler 20 and the side reinforcing layer 38 intervening. Preferably, the four-layer portion 40 is a portion located outside the tip 20A of the bead filler 20 in the tire radial direction. That is, the carcass layer 22 has a four-layer portion 40 on which the first main body portion 24A, the second main body portion 26A, the second folded portion 26B, and the first folded portion 24B overlap in order from the tire inner surface side, and the tip 20A of the bead filler 20. It is preferable to have the tire on the outer side in the radial direction of the tire.

In the present embodiment, in the four-layer portion 40, the inclination angle of the configuration code with respect to the tire circumferential direction is set to decrease from the tire inner surface side to the tire outer surface side. In detail, the inclination angle of each configuration code is set as schematically shown in FIG. Here, in FIG. 3, a part of the first folded-back portion 24B is cut out.

In the four-layer portion 40, the configuration codes of the first main body portion 24A, the second main body portion 26A, the second folded portion 26B, and the first folded portion 24B are inclined with respect to the tire circumferential direction CD and the directions of inclination are staggered. It is arranged so that it becomes. That is, the configuration code 24A1 of the first main body 24A is inclined at an angle of θ1 with respect to the tire circumferential direction CD, and the configuration code 26A1 of the second main body 26A is the direction of inclination at the first main body 24A. The configuration code 26B1 of the second folded-back portion 26B is inclined to the opposite side at an angle of θ2 with respect to the tire circumferential direction CD, and the configuration code 26B1 of the second folding portion 26B is on the tire circumferential direction CD on the opposite side of the inclination direction of the second main body portion 26A. On the other hand, the configuration code 24B1 of the first folding portion 24B is tilted at an angle of θ3, and is tilted at an angle of θ4 with respect to the tire circumferential direction CD on the opposite side of the tilting direction of the second folding portion 26B. There is.

The values of the inclination angles θ1, θ2, θ3, and θ4 are absolute values of the inclination angles without considering the direction of the inclination. The tilt angle of the configuration code is a value measured in a free state before assembling the pneumatic tire to the rim.

The configuration codes 24A1,26A1,26B1,24B1 of each layer in the four-layer portion 40 are set so that θ1 ≧ θ2 ≧ θ3 ≧ θ4 and θ1> θ4 is satisfied. That is, the inclination angle θ2 at the second main body 26A is the same as or smaller than the inclination angle θ1 at the first main body 24A inside the second main body 26A, and the inclination angle θ3 at the second folded-back portion 26B is inside the inclination angle θ1. The inclination angle θ2 at the second main body portion 26A is the same as or smaller than that, and the inclination angle θ4 at the first folding portion 24A is the same as or smaller than the inclination angle θ3 at the second folding portion 26B inside. Smaller than However, not all of them are the same, so that the inclination angle θ1 at the first main body portion 24A on the tire inner surface side is larger than the inclination angle θ4 at the first folding portion 24B on the tire outer surface side.

Preferably, in the four-layer portion 40, the inclination angle of the configuration code with respect to the tire circumferential direction is set to at least three steps, that is, θ1 ≧ θ2> θ3> θ4, θ1> θ2 ≧ θ3> θ4, or θ1>. It is preferable that θ2> θ3 ≧ θ4. More preferably, the inclination angle of the configuration code with respect to the tire circumferential direction is gradually set to be smaller from the tire inner surface side to the outer surface side, that is, θ1> θ2> θ3> θ4.

The inclination angle of each configuration code is not particularly limited, but is, for example, 75 ° ≤ θ1 <90 °, 65 ° ≤ θ2 ≤ 85 °, 55 ° ≤ θ3 ≤ 75 °, 45 ° ≤ θ4 ≤ 65 °. More preferably, there are 80 ° ≦ θ1 <90 °, 70 ° ≦ θ2 ≦ 80 °, 60 ° ≦ θ3 ≦ 70 °, and 50 ° ≦ θ4 ≦ 60 °.

The difference in the inclination angles of the constituent cords between the layers adjacent to each other in the tire thickness direction in the four-layer portion 40 is preferably 20 ° or less, more preferably 10 ° or less. Here, the difference in the inclination angle is the difference in the absolute value of the inclination angle without considering the direction of the inclination, as described above. Therefore, the difference between θ1 and θ2, the difference between θ2 and θ3, and the difference between θ3 and θ4, which are the differences in the inclination angles between adjacent layers, are all set to preferably 20 ° or less, more preferably 10 ° or less. To. In this way, by reducing the difference in inclination angle between adjacent layers, durability can be improved.

The first folded portion 24B of the first carcass ply 24 has a protruding portion 24BP protruding outward in the tire radial direction from the folded end 26BE of the second folded portion 26B, a folded end 26BE of the second folded portion 26B, and the tip of the bead filler 20. It includes a second folded portion 26B and an overlapping portion 24BQ that overlaps with 20A.

The configuration code 24BP1 of the protruding portion 24BP is arranged so as to be more inclined with respect to the tire circumferential direction CD than the configuration code 24B1 of the overlapping portion 24BQ. The overlapping portion 24BQ is a portion constituting the four-layer portion 40. Therefore, the inclination angle of the configuration code of the overlapping portion 24BQ is equal to the inclination angle θ4 of the configuration code 24B1 in the four-layer portion 40. Therefore, the inclination angle θ5 of the configuration code 24BP1 at the protruding portion 24BP with respect to the tire circumferential direction CD is set to be larger than the inclination angle θ4 (θ5> θ4). The configuration code 24BP1 of the protruding portion 24BP and the configuration code 24B1 of the overlapping portion 24BQ have the same inclination direction. The inclination angle θ5 at the protruding portion 24BP is not particularly limited, but may be, for example, 65 ° ≤ θ5 ≤ 85 ° or 70 ° ≤ θ5 ≤ 80 °.

In this embodiment, the inclination angle of the configuration code of the first main body portion 24A with respect to the tire circumferential direction is set to the inclination angle θ1 for the entire first main body portion 24A. Further, the inclination angle of the configuration code of the second main body 26A with respect to the tire circumferential direction is also set to the inclination angle θ2 for the entire second main body 26A, and further, the inclination angle of the configuration code of the second folding portion 26B with respect to the tire circumferential direction is set. The tilt angle is also set to the tilt angle θ3 for the entire second folding portion 26B. The inclination angle of the configuration code of the first folding portion 24B with respect to the tire circumferential direction is set to the inclination angle θ5 in the protruding portion 24BP and the inclination angle θ4 in the other parts.

As in the present embodiment, when the tires having different inclination angles of the constituent cords between the main body portions 24A and 26A and the folded portions 24B and 26B of the carcass ply 24 and 26, the carcass ply is placed around the bead core when the green tire is formed. When winding with, the angle may be changed.

The height of the bead filler 20 is not particularly limited, but it is preferable that the vertical height H1 from the bead heel BE to the tip 20A of the bead filler 20 is 30 to 60% of the tire cross-sectional height H0. When H1 is 30% or more of H0, the decrease in rigidity can be suppressed and the effect of improving steering stability can be enhanced, and when H1 is 60% or less of H0, the tire diameter is larger than that of the bead filler 20. Durability can be improved by ensuring flexibility in the outer portion in the direction.

Here, the tire cross-sectional height H0 is the vertical height from the bead heel BE to the tread tread on the equator of the tire, and is 1/2 of the difference between the tire outer diameter and the rim diameter. These heights are determined in a no-load state in which the tire is attached to the applicable rim and a predetermined internal pressure is applied. The applicable rim is a rim defined for each tire in a standard system including a standard on which the tire is based, and refers to a rim specified by, for example, JATTA, TRA, ETRTO, or the like. The predetermined internal pressure is the air pressure defined for each tire by each standard in the standard system. However, for tires that do not have standards such as racing tires, the rim and internal pressure may be selected according to the actual usage conditions according to these standards.

In the present embodiment as described above, in the four-layer portion 40 of the carcass layer 22 in which the first main body portion 24A, the second main body portion 26A, the second folding portion 26A and the first folding portion 24A are arranged, the tire circumferential direction By setting the inclination angles θ1, θ2, θ3, and θ4 of the configuration codes 24A1,26A1,26B1,24B1 to smaller from the inner surface side to the outer surface side of the tire, steering stability is improved while suppressing a decrease in durability. It can be improved, and both steering stability and durability can be achieved.

Specifically, when the sidewall portion 14 of the pneumatic tire 10 is flexed and deformed, the inner surface side of the tire is compressed and the outer surface side of the tire is pulled, so that the inner surface side of the tire contributes more to durability. Therefore, by setting the tilt angle of the configuration code to a high angle on the inner surface side of the tire and a lower angle toward the outer surface side of the tire, durability is maintained on the inner surface side of the tire, and rigidity is increased on the outer surface side of the tire to improve steering stability. Can be improved.

Further, after the first carcass ply 24 has a high turn-up ply structure, the cord inclination angle θ5 at the protruding portion 24BP of the first folding portion 24B is larger than the cord inclination angle θ4 at the overlapping portion 24BQ inside the tire radial direction. By increasing the size, the following effects are produced. That is, the buttress portion, which is a region close to the outer end 30A on the inner side of the outer end 30A of the belt layer 30 in the tire radial direction, contributes less to steering stability than the region on the inner diameter side. That is, the protruding portion 24BP located in the buttress portion contributes less to the steering stability than the overlapping portion 24BQ. Therefore, by setting the cord inclination angle at the protruding portion 24BP to a high angle, it is possible to improve durability while suppressing a decrease in steering stability.

In the above embodiment, the first folded portion 24B of the first carcass ply 24 is extended inward in the tire width direction from the outer end 30A of the belt layer 30, but the second folded portion 26B of the second carcass ply 26 is extended. May extend to the inside in the tire width direction from the outer end 30A of the belt layer 30.

The use of the pneumatic tire according to the present embodiment is not particularly limited, but it is preferably used as a competition pneumatic tire mounted on a competition vehicle such as a racing tire.

In order to show the effect of this embodiment, pneumatic tires for racing (size: 285 / 650R18, tread pattern: slick) of Examples 1 to 7 and Comparative Examples 1 to 4 were prototyped. Examples 1 to 6 are tires according to the above embodiment, and the inclination angles of the configuration codes of the plies are set as shown in Table 1. In the seventh embodiment, the cord inclination angle θ5 at the protruding portion 24BP of the first carcass ply 24 is set to the same value as the cord inclination angle θ4 at the four-layer portion 40 (overlapping portion 24BQ) on the inner diameter side thereof. For Comparative Examples 1 and 2, tires were produced in the same manner as in Examples except that the inclination angles of the configuration codes of the plies were set as shown in Table 1. The height H1 of the bead filler was set to 45% of the tire cross-sectional height H0. Regarding the tilt angles in Table 1, R and L indicate the tilt directions of the constituent codes, and R and L have opposite tilt directions.

Steering stability and durability were evaluated for each of these tires (internal pressure: 220 kPa). Each evaluation method is as follows.

-Maneuvering stability: About the average lap time when mounted on a competition vehicle (vehicle weight: 1300 kg, average speed: 150 km / h) suitable for circuit driving and traveling a circuit of 3.7 km per lap for 5 consecutive laps It is shown as an index with the reciprocal of the value of Comparative Example 1 as 100. The larger the index, the smaller the average lap time and the better the steering stability.

-Durability: The value of Comparative Example 1 was set to 100 for the mileage until a failure occurred by mounting a tire on a drum tester and running it with a load of 570 kg and a speed of 240 km / h equivalent to actual running. Shown as an index. The larger the index, the longer the mileage to failure and the better the durability.

The results are as shown in Table 1. In Comparative Example 2 in which the cord angle was made smaller than that in Comparative Example 1 which was the control, the steering stability was improved, but the durability was lowered. On the other hand, in Examples 1 to 7 in which the cord inclination angle is set to be smaller from the tire inner surface side to the outer surface side in the four-layer portion 40 of the sidewall portion 14, the cord inclination angle is constant as compared with Comparative Example 1. It was possible to improve the steering stability while suppressing the decrease in durability. In particular, in Examples 1 and 2 in which the cord inclination angle is gradually reduced for each layer from the inner surface side to the outer surface side of the tire, the effect of achieving both steering stability and durability is excellent. Further, by comparing the first and second embodiments with the seventh embodiment, the inclination angle of the first folded-back portion 24B at the protruding portion 24BP is set to be larger than the inclination angle of the four-layer portion 40 on the inner diameter side thereof. It can be seen that the durability can be improved while suppressing the decrease in steering stability.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

10 ... pneumatic tire, 12 ... bead part, 14 ... sidewall part, 16 ... tread part, 18 ... bead core, 20 ... bead filler, 22 ... carcass layer, 24 ... first carcass ply, 24A ... first body part, 24B ... 1st folded part, 24BE ... Folded end, 24BP ... Protruding part, 24BQ ... Overlapping part, 26 ... 2nd carcass ply, 26A ... 2nd main body part, 26B ... 2nd folded part, 26BE ... Folded end, 30 ... Belt layer, 30A ... Outer end of belt layer in tire width direction, 40 ... Four layers

Claims (4)

A first main body portion that extends from the tread portion through the sidewall portion to the bead core of the bead portion, and a first folded portion that extends from the first main body portion and is folded back from the inside to the outside in the tire width direction around the bead core. The first carcass ply consisting of
In the tread portion, a second main body portion that is arranged outside the tire radial direction of the first main body portion and extends from the tread portion to the bead core of the bead portion through the sidewall portion, and a tire extending from the second main body portion and around the bead core. A carcass layer including a second folded portion folded from the inside to the outside in the width direction and a second carcass ply composed of the second folded portion is provided.
The carcass layer has a four-layer portion in which the first main body portion, the second main body portion, the second folded portion, and the first folded portion are arranged in order from the inner surface side of the tire, and the sidewall portion has the same. In the four-layer portion, the configuration cords of the first main body portion, the second main body portion, the second folded portion, and the first folded portion are inclined with respect to the tire circumferential direction and the directions of inclination are staggered. In addition to being arranged in such a manner, the inclination angles of the first main body portion, the second main body portion, the second folded portion, and the first folded portion of the four-layer portion with respect to the tire circumferential direction are set to θ1, respectively. As θ2, θ3 and θ4, θ1>θ2>θ3> θ4, 75 ° ≤ θ1 <90 °, 65 ° ≤ θ2 ≤ 85 °, 55 ° ≤ θ3 ≤ 75 °, and 45 ° ≤ θ4 ≤ 65 ° are satisfied. ,
Pneumatic tires that feature that. The pneumatic tire according to claim 1, wherein at least one of the first folded portion and the second folded portion has a folded end located inside the outer end of the belt layer in the tire width direction in the tire width direction. The folded end of the first folded portion is located inside the outer end of the belt layer in the tire width direction in the tire width direction, and the folded end of the second folded portion is provided on the outer side of the bead core in the tire radial direction. Located between the tip of the filler and the outer end of the belt layer in the tire width direction,
The first folded portion is a protruding portion that protrudes outward in the tire radial direction from the folded end of the second folded portion, and the second folded portion between the folded end of the second folded portion and the tip of the bead filler. The configuration code of the protruding portion is arranged so as to be more inclined with respect to the tire circumferential direction than the configuration code of the overlapping portion, including the overlapping portion that overlaps with the tire.
The pneumatic tire according to claim 1. The pneumatic tire according to any one of claims 1 to 3, wherein the difference in the inclination angles of the constituent cords between the layers adjacent to each other in the tire thickness direction in the four-layer portion is 10 ° or less.

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