JP2023085817A - pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which can achieve improvement in operation stability in association with improvement in lateral rigidity while realizing weight saving by carcass ply of hollow structure.SOLUTION: A carcass ply 50 has: a first carcass ply 51 having a folding part 51e which extends to a tire width direction inner side of each of a pair of beads 10 from a tread 30, and is folded at a bead core 11 and extends to a tire radial direction outer side; and a second carcass ply 52 which is located on a tire outer surface side of the first carcass ply 51, and extends to a tire width direction outer side of a bead filler 12 from the tread 30. At least one of the first carcass ply 51 and the second carcass ply 52 is a split carcass ply including a pair of ply pieces 51A which are split in a tire width direction, the pair of ply pieces 51A are respectively arranged on the tread 30, and have inner ends 51a which are spaced from each other and face each other in the tire width direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to pneumatic tires.

2. Description of the Related Art Conventionally, in a pneumatic tire for a vehicle, an internal structure is known in which a carcass ply that forms the frame of the tire is bridged between a pair of beads. Patent Literature 1 discloses that, with regard to such a carcass ply, providing a discontinuous central portion in the width direction central portion of the tread of the tire reduces the weight and reduces the rolling resistance associated with the weight reduction. A pneumatic tire is disclosed.

The carcass ply disclosed in Patent Document 1 extends from the tread to the inner side in the tire width direction of each of a pair of beads, is folded back at the bead core, and extends to the outer side in the tire radial direction, and the folded end is in the middle of the sidewall. are placed in In such a structure, when the tire receives a lateral force, the carcass ply bends and compresses, and the resistance at that time exerts lateral rigidity.

Japanese Patent Application Laid-Open No. 2020-152380

Improving lateral rigidity contributes to improving steering stability. The number of carcass plies may be increased in order to further improve the lateral rigidity due to the compression resistance of the carcass plies, but this will result in an increase in weight.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire capable of improving steering stability due to an improvement in lateral rigidity while achieving weight reduction by means of a carcass ply having a hollow structure.

The pneumatic tire of the present invention comprises a pair of beads having a bead core and a bead filler extending radially outward from the bead core, a pair of sidewalls extending radially outward from each of the pair of beads, and the pair of A pneumatic tire comprising a tread disposed between sidewalls, a belt disposed on the tread, and a carcass ply extending from the tread to the pair of beads, wherein the carcass ply comprises at least the tread A first carcass ply having a folded portion extending inward in the tire width direction of each of the pair of beads and folded back at the bead core and extending outward in the tire radial direction; and the first carcass ply. a second carcass ply arranged on the tire outer surface side and extending from the tread to the outside in the tire width direction of the bead filler, wherein at least one of the first carcass ply and the second carcass ply is , a split carcass ply including a pair of ply pieces split in the tire width direction, each of the pair of ply pieces being disposed on the tread and having inner ends opposed to each other in the tire width direction.

ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can aim at the improvement of steering stability accompanying the improvement of lateral rigidity can be provided, realizing weight reduction by the carcass ply of hollow structure.

It is a tire width direction half section view of a pneumatic tire concerning an embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG. 1; FIG. 2 is a half cross-sectional view in the tire width direction showing the configuration of a tire of Comparative Example 1 as an evaluation target performed in Examples. FIG. 10 is a half cross-sectional view in the tire width direction showing the configuration of a tire of Comparative Example 2 as an evaluation target performed in Examples. FIG. 10 is a half cross-sectional view in the tire width direction showing the configuration of a tire of Comparative Example 3 as an evaluation target performed in Examples. It is a tire width direction half cross-sectional view which shows the structure of the tire of the comparative example 4 as evaluation object performed in the Example.

Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 shows a half section in the tire width direction of a tire 1, which is a pneumatic tire according to the embodiment. FIG. 2 is an enlarged view of a part of FIG. 1, and is a cross-sectional view showing a portion extending from a tread 30 to a bead 10, which will be described later.

A tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car. In addition, the tire 1 according to the embodiment can be used for various vehicles other than passenger cars, such as light trucks, trucks, and buses.

The structure of the tire 1 is bilaterally symmetrical in a cross section in the tire width direction. FIG. 1 shows a cross section of the right half of the tire 1, and the left half (not shown) has the same structure. In FIG. 1, symbol S1 is the tire equatorial plane. The tire equatorial plane S1 is a plane orthogonal to the tire rotation axis (tire meridian) and located at the center in the tire width direction.

The cross-sectional view of FIG. 1 shows a no-load state in which the tire 1 is mounted on a specified rim and filled with a specified internal pressure. In addition, the standard rim refers to a standard rim defined by JATMA corresponding to the tire size. Further, the specified internal pressure is 180 kPa, for example, when the tire 1 is for a passenger car.

Here, the tire width direction is a direction parallel to the tire rotation axis, and is the lateral direction on the paper surface of FIG. 1 . In FIG. 1, it is illustrated as the tire width direction X. The inner side in the tire width direction is the direction toward the tire equatorial plane S1, and is the left side of the paper surface in FIG. The outer side in the tire width direction is the direction away from the tire equatorial plane S1, and is the right side of the paper surface in FIG.

Moreover, the tire radial direction is a direction perpendicular to the tire rotation axis, which is the up-down direction on the paper surface of FIG. 1 . In FIG. 1, it is illustrated as the tire radial direction Y. The tire radial direction outer side is the direction away from the tire rotation axis, and is the upper side of the paper surface in FIG. 1 . The inner side in the tire radial direction is the direction toward the tire rotation axis, and is the lower side of the paper surface in FIG. 1 . The same applies to FIG. 2 and FIGS. 3 to 6, which will be described later.

As shown in FIG. 1, the tire 1 includes a pair of beads 10 provided on both sides in the tire width direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, and a pair of sidewalls 20. A tread 30 arranged between, a belt 40 arranged on the tread 30, a carcass ply 50 extending from the tread 30 to a pair of beads 10, an inner liner 60 arranged on the tire inner cavity side of the carcass ply 50, It has

The bead 10 includes a bead core 11 , a bead filler 12 extending outward in the tire radial direction from the bead core 11 , and a rim strip rubber 13 .

The bead core 11 is an annular member in which a metal bead wire coated with rubber is wound multiple times in the tire circumferential direction. The bead core 11 is a member that serves to fix the inflated tire 1 to the rim.

The bead filler 12 has an outer end 12a on the outside in the tire radial direction. The bead filler 12 has a tapered shape extending from the inner side in the tire radial direction to the outer end 12a.

The bead filler 12 is provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is made of, for example, rubber having a higher hardness than the surrounding rubber member.

The rim strip rubber 13 further surrounds the outside of the carcass ply 50 provided surrounding the bead core 11 and the bead filler 12 and constitutes most of the outer surface of the bead 10 . Rim strip rubber 13 contacts the inner portion of the rim on which tire 1 is mounted. A top portion 13a extending in the tire circumferential direction is formed on the outer surface of the rim strip rubber 13 on the outside in the tire width direction. The tire width direction outer portion of the rim strip rubber 13 including the top portion 13a constitutes a rim protector 14 that protects the rim from external damage. The rim protector 14 is annularly continuous in the tire circumferential direction.

The sidewall 20 includes a sidewall rubber 21 arranged outside the carcass ply 50 in the tire width direction. The sidewall rubber 21 constitutes the outer wall surface of the tire 1 . The sidewall rubber 21 is the portion that bends the most when the tire 1 acts as a cushion, and is generally made of flexible rubber having fatigue resistance. The radially inner end of the sidewall rubber 21 covers the radially outer end of the rim strip rubber 13 .

The tread 30 has tread rubber 31 . An endless belt 40 and a cap ply 45 are arranged on the tread 30 . The belt 40 is arranged outside the inner liner 60 in the tire radial direction. The cap ply 45 is arranged outside the belt 40 in the tire radial direction. The tread rubber 31 is arranged outside the cap ply 45 in the tire radial direction.

Belt 40 is a member that reinforces tread 30 . The belt 40 of the embodiment has a two-layer structure including an inner belt 41 arranged outside the inner liner 60 in the tire radial direction and an outer belt 42 arranged outside the inner belt 41 in the tire radial direction. Both the inner belt 41 and the outer belt 42 have a structure in which a plurality of cords such as steel cords are covered with rubber. The belt 40 has an outer end portion 40B formed by overlapping the inner belt 41 and the outer belt 42 on the outer side in the tire width direction.

In the belts 40, the inner belt 41 is wider than the outer belt 42. - 特許庁Therefore, the outer end 41A of the inner belt 41 on the outer side in the width direction of the tire is positioned further on the outer side in the width direction of the tire than the outer end 42A of the outer side belt 42 on the outer side in the width direction of the tire. By providing the belt 40, the rigidity of the tire 1 is ensured, and the ground contact of the tread 30 to the road surface is improved. In addition, the belt 40 is not limited to a two-layer structure, and may have a one-layer structure or a structure of three or more layers.

The cap ply 45 is a member that reinforces the tread 30 together with the belt 40 . The cap ply 45 has, for example, a structure in which a plurality of insulating organic fiber cords such as polyamide fibers are covered with rubber. An outer end portion 45B on the outer side in the tire width direction of the cap ply 45 is folded inward from the outer side in the tire radial direction to form a double layer. An outer end 45</b>A of the cap ply 45 on the outer side in the tire width direction is positioned further on the outer side in the tire width direction than the outer end 41</b>A of the inner belt 41 . The outer end portion 45B of the cap ply 45 covers and adheres to the outer end portion 41B of the inner belt 41 on the outer side in the tire width direction.

Although the cap ply 45 of the embodiment has a single layer, it may have a structure of two or more layers. By providing the cap ply 45, it is possible to improve durability and reduce road noise during running.

The tread rubber 31 is arranged outside the cap ply 45 in the tire radial direction. The tread rubber 31 is a member that forms a tread 31a that comes into contact with the road surface during running. The tread surface 31a of the tread rubber 31 is provided with a tread pattern 32 composed of, for example, a plurality of grooves. An outer end portion 31</b>B of the tread rubber 31 on the outer side in the tire width direction is bent radially inward beyond the outer end 45</b>A of the cap ply 45 on the outer side in the tire width direction and contacts the carcass ply 50 . The outer end portion 31B is covered with the outer end portion of the sidewall rubber 21 in the tire radial direction.

The carcass ply 50 constitutes a ply that forms the skeleton of the tire 1 . The carcass ply 50 of the embodiment includes a first carcass ply 51 and a second carcass ply 52 . The first carcass ply 51 is arranged on the tire outer surface side of the inner liner 60 , and the second carcass ply 52 is arranged on the tire outer surface side of the first carcass ply 51 . Each of the first carcass ply 51 and the second carcass ply 52 has a hollow portion that is discontinuous at the central portion in the tire width direction of the tread 30, and the hollow portion is sandwiched between them in the tire width direction. It has a configuration divided on both sides of the

The first carcass ply 51 extends from the tread 30 to the inner side in the tire width direction of each of the pair of beads 10, and has a folded portion 51e that is folded back at the bead core 11 and extends to the outer side in the tire radial direction.

The first carcass ply 51 includes a pair of first ply pieces 51A split in the tire width direction. That is, the first carcass ply 51 is a split carcass ply including a pair of first ply pieces 51A split in the tire width direction. The first carcass ply 51 has a hollow portion 51H that is discontinuous in the center portion of the tread 30 in the tire width direction. The pair of first ply pieces 51A are embedded in the tire 1 so as to be arranged on both sides in the tire width direction with the hollow portion 51H interposed therebetween.

As shown in FIG. 2, the first ply piece 51A has a first inner end 51a which is an end on the hollow portion 51H side and which is separated from each other in the tire width direction. The first inner end 51a is arranged at the outer end of the tread 30 in the tire width direction. The first ply piece 51A has a first inner end portion 51b including a first inner end 51a on the inner side in the tire width direction.

As shown in FIG. 2, the first ply piece 51A includes a first ply body portion 51c extending from the first inner end 51a to the sidewall 20 and further to the bead core 11, and a first ply body portion 51c. It has a bent portion 51d that bends around the bead core 11 from the portion 51c, a folded portion 51e that folds outward in the tire radial direction from the bent portion 51d, and a folded end 51f that is the outer end of the folded portion 51e in the tire radial direction.

The first ply body portion 51c, the bent portion 51d and the folded portion 51e are continuous. The inner end in the tire radial direction of the first ply main body portion 51c is disposed on the inner side of the bead core 11 and the bead filler 12 in the tire width direction. The folded portion 51e is arranged outside the bead core 11 and the bead filler 12 in the tire width direction. The bent portion 51d is arranged inside the bead core 11 in the tire radial direction, and constitutes the innermost portion of the first carcass ply 51 in the tire radial direction. The folded portion 51 e extends halfway through the bead filler 12 . The folded end 51f is arranged outside the bead filler 12 in the tire width direction.

In the first carcass ply 51, hollow portions 51H are formed between the first inner ends 51a of the pair of first ply pieces 51A facing each other in the tire width direction.

As shown in FIG. 1 , the second carcass ply 52 extends from the tread 30 to the outside of each of the pair of beads 10 in the tire width direction.

The second carcass ply 52 includes a pair of second ply pieces 52A split in the tire width direction. That is, the second carcass ply 52 is a split carcass ply including a pair of second ply pieces 52A split in the tire width direction. The second carcass ply 52 has a hollow portion 52H that is discontinuous at the central portion of the tread 30 in the tire width direction. The pair of second ply pieces 52A are embedded in the tire 1 so as to be arranged on both sides in the tire width direction with the hollow portion 52H interposed therebetween.

As shown in FIG. 2, the second ply piece 52A has second inner ends 52a which are ends on the hollow portion 52H side and which are separated from each other in the tire width direction. The second inner end 52a is arranged at the outer end of the tread 30 in the tire width direction. The second ply piece 52A has a second inner end 52b including a second inner end 52a on the inner side in the tire width direction. The second inner end 52b is sandwiched between the outer end 40B of the belt 40 and the first ply piece 51A in the tire radial direction.

The second inner end 52a of the second ply piece 52A is arranged outside the first inner end 51a of the first ply piece 51A in the tire width direction. As shown in FIG. 2, the distance L1 in the tire width direction between the second inner end 52a and the first inner end 51a is preferably 10 mm or more.

As shown in FIG. 2, the second ply piece 52A extends from the second inner end 52a to the sidewall 20, and further extends to the outside of the bead 10 in the tire width direction via the outer end 12a of the bead filler 12. It has a second ply main body portion 52c and a wrapping portion 52d that wraps around from the second ply main body portion 52c to the inner side of the bead core 11 in the tire radial direction. The second ply body portion 52c and the wrapping portion 52d are continuous.

In the tire radial direction, the second inner end 52b of the second ply piece 52A is sandwiched between the belt 40 and the first ply piece 51A.

A portion of the second ply body portion 52c from the second inner end 52a to the outer end 12a of the bead filler 12 is in close contact with the outer surface of the first ply body portion 51c of the first ply piece 51A. A portion of the second ply main body portion 52c on the inner side in the tire radial direction and on the inner side in the tire radial direction from the outer end 12a of the bead filler 12 is separated from the first ply piece 51A, and the bead filler 12 and the bead core 11 are separated from each other. It is arranged on the outside in the tire width direction. At the tire radially inner end portion of the second ply body portion 52c, the tire radially outer portion is in close contact with the outer surface of the bead filler 12, and the tire radially inner portion is folded back of the first ply piece 51A. It is in close contact with the outer surface of the portion 51e. That is, the folded portion 51e of the first ply piece 51A and the second carcass ply 52 overlap in the tire width direction.

The wrap-around portion 52d of the second ply piece 52A is arranged radially inward of the bent portion 51d of the first ply piece 51A. At least a portion of the wraparound portion 52d on the second ply body portion 52c side is in close contact with the bent portion 51d.

The rim strip rubber 13 of the bead 10 described above covers the outer portions of the bead core 11 and the bead filler 12 in the second ply main body portion 52c in the tire width direction and the wrapping portion 52d. In addition, the rim strip rubber 13 covers the radially inner end of the first ply body portion 51c. The wraparound portion 52d constitutes the innermost portion of the second carcass ply 52 in the tire radial direction.

In the second carcass ply 52, hollow portions 52H are formed between the second inner ends 52a of the pair of second ply pieces 52A facing each other in the tire width direction.

Each of the first ply piece 51A and the second ply piece 52A includes a plurality of unillustrated carcass cords that form the frame of the tire 1. As shown in FIG. The plurality of carcass cords extend, for example, along a plane along the tire width direction and are arranged side by side in the tire circumferential direction. This carcass cord is composed of an insulating organic fiber cord such as polyester or polyamide. The first ply piece 51A and the second ply piece 52A are formed by covering a plurality of carcass cords with rubber.

The inner liner 60 covers the tire inner surface between the pair of beads 10 . Therefore, the inner liner 60 constitutes the inner wall surface of the tire 1 . Inner liner 60 covers the inner surface of belt 40 and first ply piece 51A in the area of tread 30 . In addition, the inner liner 60 covers the inner surface of the first ply piece 51A in the sidewall 20 region. Further, the inner liner 60 covers the inner surface of the first ply piece 51A in the region outside the bead 10 in the tire radial direction, and covers the first ply piece 51A and the rim strip rubber in the region inside the bead 10 in the tire radial direction. It is sandwiched between 13.

The inner liner 60 is made of air permeable rubber and prevents the air inside the tire cavity from leaking to the outside.

Here, as the rubber used for the bead filler 12, a rubber having a higher hardness than at least the sidewall rubber 21 and the inner liner 60 is used. The hardness of rubber is a value (durometer hardness) measured with a type A durometer in an atmosphere of 23° C. in accordance with JIS K6253.

For example, when the hardness of the sidewall rubber 21 is used as a standard, the hardness of the bead filler 12 is preferably about 1.2 to 2.3 times the hardness of the sidewall rubber 21 . More preferably, the rim strip rubber 13 has a hardness of about 1 to 1.6 times the hardness of the sidewall rubber 21 . With such hardness, the balance between the flexibility of the tire and the rigidity around the bead 10 can be ensured.

The above is the overall configuration of the tire 1 of the embodiment. Next, the arrangement relationship between the first ply piece 51A and the second ply piece 52A in the tire 1 and the belt 40 will be described with reference to FIG.

The first inner end portion 51b of the first ply piece 51A and the outer end portion 40B of the belt 40 on the outer side in the tire width direction overlap in the tire radial direction.

The length in the tire width direction of the overlapping portion in the tire radial direction between the first inner end portion 51b of the first ply piece 51A and the outer end portion 40B on the outer side in the tire width direction of the belt 40 is expressed as a distance in FIG. It is indicated by L2. This distance L2 is between the first inner end 51a of the first ply piece 51A and the outer end of the belt 40 on the outer side in the tire width direction of the first inner end 51a. It is the distance in the tire width direction between the belt 41 and the outer end 41A. In embodiments, this distance L2 is preferably 20 mm or more.

A second inner end portion 52b on the inner side in the tire width direction of the second ply piece 52A including the second inner end 52a and an outer end portion 40B on the outer side in the tire width direction of the belt 40 overlap in the tire radial direction. there is

The length in the tire width direction of the overlapping portion in the tire radial direction between the second inner end 52b of the second ply piece 52A and the outer end 40B of the belt 40 on the outer side in the tire width direction is the distance in FIG. It is indicated by L3. This distance L3 is between the second inner end 52a of the second ply piece 52A and the outer end 41A on the outer side in the tire width direction of the inner belt 41 arranged on the outer side in the tire width direction from the second inner end 52a. is the distance in the tire width direction between In embodiments, this distance L3 is preferably 10 mm or more.

The carcass ply 50 included in the tire 1 of the embodiment detailed above includes a first carcass ply 51 and a second carcass ply 52 . The first carcass ply 51 and the second carcass ply 52 have hollow structures having hollow portions 51H and 52H, respectively. Therefore, the tire 1 of the embodiment can be lightened while having two carcass plies.

In the tire 1 of the embodiment, the two carcass plies, ie, the first carcass ply 51 and the second carcass ply 52, exhibit rigidity to withstand the load or impact received by the tire 1 during running, or the inflation air pressure. , suitable road contact and ride comfort are obtained.

When the tire 1 receives a lateral force due to cornering or the like, the sidewall 20 bends and the first carcass ply 51 is compressed to contract in the tire radial direction. On the other hand, since the second carcass ply 52 extends from the tread 30 to the outside of the bead filler 12 in the tire width direction, tension is generated so as to extend in the tire radial direction when subjected to a lateral force. The tension in the second carcass ply 52 increases the stiffness of the sidewall 20 and improves the lateral stiffness to withstand lateral forces. As a result, steering stability is improved.

The tire 1 of the embodiment described above has the following effects.

(1) The tire 1 according to the embodiment includes a pair of beads 10 having a bead core 11 and a bead filler 12 extending radially outward from the bead core 11, and a pair of sides extending radially outward from each of the pair of beads 10. A wall 20, a tread 30 arranged between a pair of sidewalls 20, a belt 40 arranged on the tread 30, and a carcass ply 50 extending from the tread 30 to a pair of beads 10, the carcass ply 50 comprising: At least a first carcass ply 51 extending from the tread 30 to the inner side in the tire width direction of each of the pair of beads 10 and having a folded portion 51e that is folded back at the bead core 11 and extends to the outer side in the tire radial direction; A second carcass ply 52 arranged on the tire outer surface side of one carcass ply 51 and extending from the tread 30 to the outside in the tire width direction of the bead filler 12, the first carcass ply 51 and the second carcass ply 52 At least one of the carcass plies 52, which in the embodiment is the first carcass ply 51, is a split carcass ply including a first ply piece 51A as a pair of ply pieces split in the tire width direction. Each of the first ply pieces 51A is arranged on the tread 30 and has a first inner end 51a as an inner end that is spaced apart and opposed to each other in the tire width direction.

As a result, the carcass ply 50 having the hollow structure can reduce the weight, and the second carcass ply 52 can improve the lateral rigidity, thereby improving the steering stability.

(2) In the tire 1 according to the embodiment, both the first carcass ply 51 and the second carcass ply 52 are split carcass plies split in the tire width direction, and the first carcass ply 51 is , has a first ply piece 51A as a ply piece and has a first inner end 51a as an inner end, and a second carcass ply 52 has a second ply piece 52A as a ply piece and an inner end as a second inner end 52a.

As a result, both the first carcass ply 51 and the second carcass ply 52 have hollow structures, so that the weight is further reduced, and the rolling resistance associated with the weight reduction is reduced.

(3) In the tire 1 according to the embodiment, the first inner end 51b on the inner side in the tire width direction of the first ply piece 51A including the first inner end 51a and the outer side on the outer side in the tire width direction of the belt 40 The end portion 40B overlaps with the tire radial direction.

As a result, the belt 40 and the first ply pieces 51A form a structure that is seamlessly continuous from the tire width direction to the tire radial direction, thereby dispersing stress and improving durability.

(4) In the tire 1 according to the embodiment, the first inner end 51a of the first ply piece 51A and the outer side in the tire width direction of the belt 40 arranged outside the first inner end 51a in the tire width direction It is preferable that the distance L2 in the width direction of the tire between the outer end 41A of and is 20 mm or more.

As a result, the length of the overlapping portion between the first inner end portion 51b of the first ply piece 51A and the outer end portion 40B of the belt 40 on the outer side in the tire width direction is ensured to be 20 mm or more. Therefore, continuity between the belt 40 and the first ply piece 51A is reliably maintained, and durability is further improved due to stress dispersion.

(5) In the tire 1 according to the embodiment, the second inner end 52b on the inner side in the tire width direction of the second ply piece 52A including the second inner end 52a and the outer side on the outer side in the tire width direction of the belt 40 The end portion 40B overlaps with the tire radial direction.

As a result, the belt 40 and the second ply pieces 52A have a structure in which they are seamlessly connected from the tire width direction to the tire radial direction, thereby dispersing stress and improving the durability of the tire.

(6) In the tire 1 according to the embodiment, the second inner end 52a of the second ply piece 52A and the outer side in the tire width direction of the belt 40 arranged outside the second inner end 52a in the tire width direction It is preferable that the distance in the tire width direction between the outer end 41A of and is 10 mm or more.

As a result, the length of the overlapping portion between the second inner end portion 52b of the second ply piece 52A and the outer end portion 40B of the belt 40 on the outer side in the tire width direction is ensured to be 10 mm or more. Therefore, continuity between the belt 40 and the second ply piece 52A is reliably maintained, and durability is further improved due to stress dispersion.

(7) In the tire 1 according to the embodiment, it is preferable that the second inner end 52a of the second ply piece 52A is arranged outside the first inner end 51a in the tire width direction.

As a result, the first inner end 51a and the second inner end 52a are displaced in the tire width direction, so that the thickness of the inner end of the carcass ply 50 in the tire width direction is displaced step by step. Therefore, concentration of stress is suppressed, and durability of the tire is improved. In the embodiment, as shown in FIG. 2, the distance L1 in the tire width direction between the second inner end 52a and the first inner end 51a is preferably 10 mm or more. By securing the distance L1 of 10 mm or more, the effect of suppressing stress concentration can be further obtained.

(8) In the tire 1 according to the embodiment, the second inner end 52b of the second ply piece 52A is arranged between the belt 40 and the first ply piece 51A in the tire radial direction. is preferred.

As a result, the second ply piece 52A is held by the belt 40 and the first ply piece 51A, increasing the binding force. As a result, the tension of the second ply piece 52A, ie, the second carcass ply 52, when receiving a lateral force can be kept large, and the lateral rigidity is further improved.

(9) In the tire 1 according to the embodiment, the second carcass ply 52 preferably has a wrapping portion 52d that wraps from the outside of the bead 10 in the tire width direction to the inside of the bead core 11 in the tire radial direction.

As a result, the wraparound portion 52 d is brought into a state of being engaged with the bead core 11 . Therefore, the tension of the second carcass ply 52 when subjected to lateral force can be kept large, and the lateral rigidity is further improved.

(10) In the tire 1 according to the embodiment, it is preferable that the folded portion 51e of the first carcass ply 51 and the second carcass ply 52 overlap each other in the tire width direction.

As a result, the folded portion 51e of the first carcass ply 51 and the second carcass ply 52 are continuously connected in the tire radial direction, so that stress is dispersed and durability is improved.

Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the scope of the present invention. be

For example, in the above-described embodiment, the second carcass ply 52 is also a hollow ply having a hollow portion 52H like the first carcass ply 51, but the second carcass ply 52 is not a hollow ply but a pair of may be a continuous ply between the beads 10 of the Conversely, the second carcass ply 52 may be a hollow ply, and the first carcass ply 51 may be a continuous ply between the pair of beads 10 .

The carcass ply 50 may be provided with three or more carcass plies, at least one of which has a hollow portion. At least one carcass ply among the three or more carcass plies has a folded portion 51 e like the first carcass ply 51 , and at least one carcass ply other than this has a second carcass ply 52 . , the bead filler 12 may extend from the tread 30 to the outside in the tire width direction.

As analysis models of a tire having a tire size of "225/55R19", an analysis model of an example having a structure similar to that of the above embodiment and analysis models of comparative examples 1 to 4, which do not have the configuration of the above embodiment, were prepared. , the stiffness of these analytical models was calculated and evaluated by simulation.

Tires of Comparative Examples 1 to 4 are shown in FIGS. 3 to 6, respectively. The tires of Comparative Examples 1 to 4 have the same basic configuration as the above embodiment except for the carcass ply 50 . Therefore, in FIGS. 3 to 6, the same reference numerals are assigned to the same components as in the above embodiment. In addition, the code|symbol is attached|subjected to the main component. The configurations of Comparative Examples 1 to 4 will be briefly described below.

(Comparative Example 1: FIG. 3 ) The two-ply carcass ply 100 has a configuration that does not have a hollow portion that spans between a pair of beads 10 . The carcass ply 100 has a two-layer structure (two-ply) having a first carcass ply 110 on the tire inner cavity side and a second carcass ply 120 on the tire outer surface side. It is folded back around the bead core 11 from the inner side in the width direction.

(Comparative Example 2: FIG. 4) A two-ply, hollow outer ply carcass ply 200 consists of an inner first carcass ply 210 that does not have a hollow portion that is bridged between the beads 10, and a first carcass ply 210. It has a two-layer structure (two plies) with a second carcass ply 220 that is arranged outside the ply 210 and has a hollow portion 220H. The second carcass ply 220 includes a pair of ply pieces 220A divided on both sides in the tire width direction of the hollow portion 220H. The radially inner end of the carcass ply 200 is folded back around the bead core 11 from the inner side in the tire width direction.

(Comparative Example 3: FIG. 5) One Ply, Ply Hollow Carcass ply 300 has a one-layer structure (one ply) having a hollow portion 300H. The carcass ply 300 includes a pair of ply pieces 300A that are split on both sides in the tire width direction of the hollow portion 300H. The radially inner end of the carcass ply 300 is folded back around the bead core 11 from the inner side in the tire width direction.

(Comparative Example 4: FIG. 6) 1-ply, hollow ply, with reinforcing layer A reinforcing layer 410 is added to the tire shown in FIG. The reinforcing layer 410 is arranged outside the bead core 11 and the bead filler 12 in the tire width direction. The reinforcing layer 410 is sandwiched between the bead core 11 and bead filler 12 and the rim strip rubber 13 . The tire radial direction outer end of the reinforcing layer 410 is sandwiched between the cavity side portion and the folded portion of the carcass ply 400 . The reinforcing layer 410 has a structure in which, for example, steel cords are covered with rubber.

The stiffness calculated by the simulation is the "horizontal stiffness" that resists the load from the lateral direction, and the "longitudinal stiffness" that resists the vertical load applied downward from above. In the simulation, the tire was mounted on a specified rim and the above stiffness was calculated with the specified internal pressure (180 kPa). In addition, the weight of the tire was calculated in order to verify the weight reduction achieved by the hollow portion. Table 1 shows the above results. In Table 1, each stiffness value of Comparative Example 1 is given an index of 100, and the other tires are indexed.

According to Table 1, the tire of Example having the structure of the present invention has higher lateral rigidity and longitudinal rigidity than the tires of Comparative Examples 1-4. Therefore, it is recognized that the configuration in which the second carcass ply extends from the tread to the outside of the bead filler in the tire width direction as in the embodiment improves the lateral rigidity and the longitudinal rigidity, and particularly contributes to the improvement of the lateral rigidity. was taken. In addition, the tires of Examples are lighter than Comparative Example 1, which has the same two-ply structure, demonstrating the reduction in weight due to the hollow portion. As a result, the tire of the example can realize an improvement in steering stability due to an improvement in lateral rigidity, while realizing a weight reduction due to the carcass ply of hollow structure.

1 tire (pneumatic tire)
Reference Signs List 10 bead 11 bead core 12 bead filler 20 sidewall 30 tread 40 belt 40B outer end portion of the belt on the outer side in the width direction of the tire 41A outer end of the belt on the outer side in the width direction of the tire 50 carcass ply 51 first carcass ply 51A first ply piece 51a first inner end (inner end)
51b First inner end 51e Folded portion 52 Second carcass ply 52A Second ply piece 52a Second inner end (inner end)
52b second inner end portion 52d wrapping portion

Claims (10)

a pair of beads having a bead core and a bead filler extending outward in the tire radial direction from the bead core;
a pair of sidewalls extending radially outward from each of the pair of beads;
a tread disposed between the pair of sidewalls;
a belt disposed on the tread;
a carcass ply extending from the tread to the pair of beads,
The carcass ply has at least
a first carcass ply extending from the tread to the inside in the tire width direction of the bead filler and having a folded portion that is folded back at the bead core and extends to the outside in the tire radial direction;
a second carcass ply arranged on the tire outer surface side of the first carcass ply and extending from the tread to the outside in the tire width direction of the bead filler;
At least one of the first carcass ply and the second carcass ply is a split carcass ply including a pair of ply pieces split in the tire width direction,
A pneumatic tire, wherein each of the pair of ply pieces is disposed on the tread and has inner ends facing each other in the tire width direction while being spaced apart from each other. Both the first carcass ply and the second carcass ply are the divided carcass plies,
The first carcass ply has a first ply piece as the ply piece and a first inner end as the inner end,
The pneumatic tire according to claim 1, wherein the second carcass ply has a second ply piece as the ply piece and a second inner end as the inner end. A first inner end portion on the inner side in the tire width direction of the first ply piece including the first inner end and an outer end portion on the outer side in the tire width direction of the belt overlap in the tire radial direction. The pneumatic tire according to claim 2. A distance in the tire width direction between the first inner end and an outer end of the belt located on the outer side in the tire width direction of the first inner end in the tire width direction is 20 mm or more. A pneumatic tire according to any one of claims 2 or 3. A second inner end portion on the inner side in the tire width direction of the second ply piece including the second inner end and an outer end portion on the outer side in the tire width direction of the belt overlap in the tire radial direction. The pneumatic tire according to claim 2. A distance in the tire width direction between the second inner end and an outer end of the belt located on the outer side in the tire width direction of the second inner end in the tire width direction is 10 mm or more. A pneumatic tire according to claim 5. The pneumatic tire according to claim 2, wherein the second inner end is arranged outside the first inner end in the tire width direction. The pneumatic tire according to claim 5, wherein the second inner end is arranged between the belt and the first ply piece in the tire radial direction. The pneumatic tire according to any one of claims 1 to 8, wherein the second carcass ply has a wrap portion that wraps from the outside of the bead in the tire width direction to the inside of the bead core in the tire radial direction. The pneumatic tire according to any one of claims 1 to 9, wherein the folded portion of the first carcass ply and the second carcass ply overlap in the tire width direction.

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