JP2024000880A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can reduce air resistance without increasing labor hours in manufacturing.

SOLUTION: The pneumatic tire is provided with: a pair of beads 10 having bead members 16 including a bead core 11 and a bead filler 12; a pair of side walls 20 extending from the pair of beads 10 respectively to outside in a tire radial direction; a tread 30 arranged between the pair of side walls 20; and a carcass ply 50 hung across the pair of beads 10. In a cross section in a tire width direction, in a state where tensile strength of the carcass ply 50 is 250 N or more and 420 N or less and the bead member is attached to a specified rim and specified inner pressure is applied to the member, a length in the tire radial direction of the bead member 16 is 20% or more and 25% or less of a height of the cross section of the tire.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to pneumatic tires.

Generally, a pneumatic tire has a structure in which a skeleton structure in which a carcass ply is bridged between a pair of beads arranged on the inner circumference of both ends in the width direction of the tire is covered with tread rubber, sidewall rubber, or the like. Conventionally, pneumatic tires are known in which air resistance is reduced by arranging a plurality of fin-shaped protrusions along the circumferential direction of the tire on the side surface of the tire made of sidewall rubber (Patent Document (See 1, 2 etc.)

JP2021-49954A Patent No. 6690642

Pneumatic tires are usually formed using a mold. Therefore, a new mold is required to form fin-like protrusions on the side surface of a conventionally shaped tire, but in that case, there is a risk of complicating the process and increasing manufacturing costs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pneumatic tire that can reduce air resistance without increasing the manufacturing effort.

The pneumatic tire of the present invention includes a pair of beads having a bead member including a bead core and a bead filler, a pair of sidewalls extending outward in the tire radial direction from each of the pair of beads, and a space between the pair of sidewalls. A pneumatic tire comprising a tread and a carcass ply spanning between the pair of beads, wherein the carcass ply has a tensile strength of 250N or more and 420N or less, and is mounted on a specified rim. , and the length of the bead member in the tire radial direction is 20% or more and 25% or less of the tire cross-sectional height in the cross-section in the tire width direction when a specified internal pressure is applied.

According to the present invention, it is possible to provide a pneumatic tire that can reduce air resistance without increasing the manufacturing effort.

FIG. 1 is a diagram showing a half cross section in the tire width direction of a pneumatic tire according to an embodiment. 2 is an enlarged view of part II in FIG. 1. FIG.

FIG. 1 shows a half cross section in the tire width direction of a tire 1, which is a pneumatic tire according to an embodiment. FIG. 2 is an enlarged view of a portion indicated by II in FIG. 1, and is a sectional view mainly showing a shoulder 40 portion to be described later. The cross-sectional view of FIG. 1 is a tire width direction cross-sectional view (tire meridian cross-sectional view) in an unloaded state in which the tire 1 is mounted on a specified rim (not shown) and filled with a specified internal pressure. Note that the standard rim refers to a standard rim defined by JATMA corresponding to the tire size. Further, the specified internal pressure is, for example, 180 kPa when the tire is for a passenger car.

The tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car. Note that the tire 1 according to the embodiment can be used for various vehicles such as light trucks, trucks, and buses in addition to passenger cars.

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

Here, the tire width direction is a direction parallel to the tire rotation axis, and is a left-right direction in the plane of the paper in FIG. In FIG. 1, the tire width direction X is shown. The inner side in the tire width direction is the direction approaching the tire equatorial plane S1, and is the left side in the drawing 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 in the drawing in FIG.

Further, the tire radial direction is a direction perpendicular to the tire rotation axis, and is a vertical direction in the plane of the paper in FIG. In FIG. 1, the tire radial direction Y is shown. The outer side in the tire radial direction is the direction away from the tire rotation axis, and is the upper side of the paper in FIG. The inner side in the tire radial direction is the direction approaching the tire rotation axis, and in FIG. 1 is the lower side of the page.

As shown in FIG. 1, the tire 1 includes a pair of beads 10, a pair of sidewalls 20 extending outward in the tire radial direction from each of the pair of beads 10, and a tread 30 disposed between the pair of sidewalls 20. a pair of shoulders 40 disposed between each of the pair of sidewalls 20 and the tread 30; a carcass ply 50 disposed across the pair of beads 10; An inner liner 60 disposed on the cavity side.

The pair of beads 10 are arranged on both sides in the tire width direction and at the inner end in the tire radial direction. The bead 10 includes a bead member 16, a Chehar 13, a rim strip rubber 14, and a rim protector 15.

The bead member 16 includes a bead core 11 and a bead filler 12 extending outward in the tire radial direction from the bead core 11. The bead core 11 is an annular member in which a metal bead wire coated with rubber is wound multiple times in the circumferential direction of the tire. The bead core 11 is a member that serves to fix the tire 1 filled with air to the rim. The bead filler 12 has a tapered shape whose thickness decreases as it extends from the inside in the tire radial direction to the outside in the tire radial direction. 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 that is harder than the surrounding rubber members. The bead member 16 is formed by joining the inner surface of the bead filler 12 in the tire radial direction to the outer surface of the bead core 11 in the tire radial direction using, for example, an adhesive.

Cheher 13 further surrounds the outside of carcass ply 50 provided surrounding bead core 11 and bead filler 12. The rim strip rubber 14 is arranged on the outside of the Chehar 13 and carcass ply 50 in the tire width direction. Chehar 13 and rim strip rubber 14 contact the inner surface of the rim on which tire 1 is mounted.

The sidewall 20 includes sidewall rubber 21 disposed on the outside of the carcass ply 50 in the tire width direction. The sidewall rubber 21 constitutes the outer side surface of the tire 1 in the tire circumferential direction. The inner end 21c of the sidewall rubber 21 in the tire radial direction covers the outer end 14b of the rim strip rubber 14 in the tire radial direction. The sidewall rubber 21 is the part that bends the most when the tire 1 acts as a cushion, and is usually made of flexible rubber with fatigue resistance.

The inner end of the sidewall rubber 21 in the tire radial direction includes a top portion 21a along the tire circumferential direction. This top portion 21a and the outer surface of the rim strip rubber 14 described above constitute a rim protector 15 that protects the rim from external damage. This rim protector 15 is annularly continuous in the tire circumferential direction.

The tread 30 includes an endless belt 31, a cap ply 35, and tread rubber 36. The belt 31 is arranged on the outer side of the inner liner 60 in the tire radial direction. The cap ply 35 is arranged on the outer side of the belt 31 in the tire radial direction. The tread rubber 36 is arranged on the outer side of the cap ply 35 in the tire radial direction.

The belt 31 is a member that reinforces the tread 30. The belt 31 of the embodiment has a two-layer structure including an inner belt 32 disposed on the outer side of the inner liner 60 in the tire radial direction, and an outer belt 33 disposed on the outer side of the inner belt 32 in the tire radial direction. Both the inner belt 32 and the outer belt 33 have a structure in which a plurality of cords such as steel cords are covered with rubber.

The inner belt 32 is wider than the outer belt 33. Therefore, the outer end 32a of the inner belt 32 in the tire width direction is located further outward in the tire width direction than the outer end 33a of the outer belt 33 in the tire width direction. By providing the belt 31, the rigidity of the tire 1 is ensured, and the ground contact of the tread 30 with respect to the road surface is improved. Note that the belt 31 is not limited to a two-layer structure, but may have a one-layer, three or more layer structure.

The cap ply 35 is a member that reinforces the tread 30 together with the belt 31. The cap ply 35 has a structure in which a plurality of insulating organic fiber cords such as polyamide fibers are covered with rubber, for example. The outer end 35a in the tire width direction of the cap ply 35 is folded inward from the outer side in the tire radial direction, so that it is doubled. The outer end 35b of the cap ply 35 in the tire width direction is located further outward in the tire width direction than the outer end 32a of the inner belt 32 in the tire width direction. The cap ply 35 is a wide member that covers the entire belt 31 with one piece.

Although the cap ply 35 in the embodiment has one layer, it may have a structure of two or more layers. By providing the cap ply 35, it is possible to improve durability and reduce road noise during driving.

The tread rubber 36 is arranged on the outer side of the cap ply 35 in the tire radial direction. The tread rubber 36 is a member that constitutes a tread surface 36a, which is the outer surface of the tread 30 that contacts the road surface during running. A tread pattern 37 is provided on the tread surface 36a of the tread rubber 36.

The tread pattern 37 includes a plurality of main grooves 38 and a plurality of slits 39. The plurality of main grooves 38 in the embodiment include two first main grooves 38A arranged on the inner side in the tire width direction, and two second main grooves 38A arranged on the outer side in the tire width direction than these first main grooves 38A. Main groove 38B. Both the first main groove 38A and the second main groove 38B are formed in an annular shape along the tire circumferential direction. The slit 39 is a narrow groove extending substantially along the tire width direction, and is disposed on the outer side of the tire width direction than the second main groove 38B. The slit 39 is formed from the outer end in the tire width direction of the tread surface 36a of the tread 30 to the outer surface of a shoulder 40, which will be described later.

The outer end 36b of the tread rubber 36 in the tire width direction extends inward in the tire radial direction beyond the outer end 35b of the cap ply 35 in the tire width direction, and covers the outer end 21b of the sidewall rubber 21 in the tire radial direction.

The shoulder 40 is located in the transition region from the sidewall 20 to the tread 30. The shoulder 40 includes shoulder rubber 41. The shoulder rubber 41 covers a part of the outer surface of the tire radial outer end 21b of the sidewall rubber 21 and the outer surface of the tire width outer end 36b of the tread rubber 36.

The carcass ply 50 constitutes a ply that serves as the frame of the tire 1. The carcass ply 50 is embedded in the tire 1 in such a manner that it passes between the pair of beads 10 on the tire inner cavity side of the pair of sidewalls 20 and the tread 30.

The carcass ply 50 includes a plurality of ply cords (not shown) that serve as the frame of the tire 1. The plurality of ply cords extend, for example, in a plane along the width direction of the tire, and are arranged side by side in the tire circumferential direction. This ply cord is made of an insulating organic fiber cord such as polyester or polyamide. A carcass ply 50 is constructed by covering a plurality of ply cords with rubber.

The carcass ply 50 has a ply main body portion 51, a ply folded portion 52, and a bent portion 53. The ply main body portion 51 is a portion that extends from the inner side of one bead core 11 in the tire width direction, through one sidewall 20, the tread 30, and the other sidewall 20, to the inner side of the other bead core 11 in the tire width direction. . The ply folded-back portion 52 is a portion extending outward in the tire width direction of the bead filler 12 on the outside in the tire width direction by being folded back around the bead core 11 from the inner end in the tire radial direction of the ply main body portion 51 . The bent portion 53 is a portion that is bent in a U-shape from the ply main body portion 51 around the bead core 11 and connected to the ply folded portion 52. The ply main body portion 51 and the ply folded portion 52 are continuous via the bent portion 53.

The ply main body portion 51 is arranged on the inner side in the tire width direction of the bead core 11 and the bead filler 12 on the inner side in the tire radial direction. The ply folded portion 52 is arranged on the outer side of the bead core 11 and the bead filler 12 in the tire width direction. The bent portion 53 includes the innermost portion of the carcass ply 50 in the tire radial direction.

The carcass ply 50 of the embodiment has a two-layer structure in which a first carcass ply 55 and a second carcass ply 56 are stacked. In the ply body portion 51, the first carcass ply 55 is arranged on the tire inner cavity side of the second carcass ply 56.

In the ply folded portion 52, the first carcass ply 55 is arranged on the outside of the second carcass ply 56 in the tire width direction. The first carcass ply 55 of the ply folded portion 52 extends from the bent portion 53 to near the tire maximum width position H on the outer surface of the sidewall 20. That is, the folded end 55a of the first carcass ply 55 is located near the tire maximum width position H. The second carcass ply 56 of the ply folded portion 52 extends from the bent portion 53 to the middle of the bead filler 12. That is, the folded end 56a of the second carcass ply 56 is located on the outside of the bead filler 12 in the tire width direction.

A side reinforcing layer 70, which is a reinforcing layer made of a steel member, is arranged outside the bead filler 12 in the tire radial direction. This side reinforcing layer 70 is sandwiched between the bead filler 12 and the ply folded portion 52 of the carcass ply 50, and further extends from the bead filler 12 outward in the tire radial direction. A portion of the side reinforcing layer 70 extending outward in the tire radial direction from the bead filler 12 is sandwiched between the second carcass ply 56 of the ply main body portion 51 and the first carcass ply 55 of the ply folded portion 52. The tire radial outer end portion 55b of the first carcass ply 55 of the ply folded portion 52 is overlapped with the second carcass ply 56 of the ply main body portion 51.

Although the carcass ply 50 of the embodiment has a two-layer structure, the carcass ply 50 may have one layer or three or more layers. It is preferable that the carcass ply 50 is composed of a ply having a two-layer or more layered structure, since local deformation of the tire 1 near the mounting portion of the rim is sufficiently suppressed.

The chafer 13 of the bead 10 described above is provided so as to surround the inner end in the tire radial direction of the carcass ply 50 including the bent portion 53. Further, the rim strip rubber 14 is arranged on the outside of the ply folded portion 52 of the carcass ply 50 and the Chehar 13 in the tire width direction. The outer end 14b of the rim strip rubber 14 in the tire radial direction is covered with the inner end 21c of the sidewall rubber 21 in the tire radial direction.

The inner liner 60 covers the inner surface of the tire between the pair of beads 10. The inner liner 60 covers the inner surface of the ply main body portion 51 in the tread 30 and the region extending from the tread 30 to the sidewall 20. Further, the inner liner 60 covers the inner surface of the ply main body portion 51 and the Chehar 13 in a region extending from the sidewall 20 to the bead 10. Therefore, the inner liner 60 constitutes the inner wall surface of the tire 1. The inner liner 60 is made of air-permeable rubber and prevents air within the tire cavity from leaking to the outside.

Here, as the rubber employed for the bead filler 12, a rubber whose hardness is higher than at least the sidewall rubber 21 and the inner liner 60 is used. The hardness of the rubber is a value measured with a type A durometer (durometer hardness) 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 reference, the hardness of the bead filler 12 is preferably about 1.2 times or more and 2.3 times or less the hardness of the sidewall rubber 21. The hardness of the rim strip rubber 14 is more preferably about 1 to 1.6 times the hardness of the sidewall rubber 21. With such hardness, a balance between flexibility as a tire and rigidity near the bead 10 can be ensured.

The above is the basic configuration of the tire 1 according to the embodiment. Next, the characteristic configurations of the carcass ply 50 and the bead member 16 will be explained.

The carcass ply 50 according to the embodiment having a two-layer structure including the first carcass ply 55 and the second carcass ply 56 has a tensile strength of 250N or more and 420N or less. That is, the tensile strength of the entire carcass ply 50 including the first carcass ply 55 and the second carcass ply 56 is 250N or more and 420N or less. For example, if the first carcass ply 55 and the second carcass ply 56 are of the same type and each has a tensile strength of 132N, the tensile strength of the carcass ply 50 will be 264N (132N x 2). . Since most of the tensile strength of the carcass ply 50 depends on the tensile strength of the ply cords, the tensile strength of the carcass ply 50 can be achieved by appropriately adjusting the tensile strength and number of the ply cords.

Compared to the case where the carcass ply has a one-layer structure consisting of one sheet, a two-layer structure consisting of two carcass plies (the first carcass ply 55 and the second carcass ply 56) like the carcass ply 50 of the embodiment , the carcass ply 50 can be made to have a desired tensile strength without increasing the tensile strength of the ply cord. Therefore, by using a two-layer structure, the carcass ply 50 can be easily configured to have the desired tensile strength, rather than using a single carcass ply using a ply cord with higher tensile strength. .

When the tensile strength of the carcass ply 50 is relatively high, for example, 250 N or more and 420 N or less, compared to a case where the tensile strength is about 200 N, the shoulder 40 expands outward due to the internal pressure due to the restraining action of the carcass ply 50. It is restrained from doing so.

As shown in FIG. 2, by suppressing the shoulder 40 from expanding outward due to internal pressure, the shoulder inclination angle θ becomes relatively large. This shoulder inclination angle θ is an angle formed by the outer surface 40a of the shoulder 40 with respect to the tire rotation axis parallel to the tire width direction, and is between a line L1 along the outer surface 40a of the shoulder 40 and a line along the tire width direction. This is the inner angle in the tire width direction formed by L2. Due to the cross-sectional shape of the tire in which expansion of the shoulder 40 is suppressed in this manner, retention of air flowing rearward from the shoulder 40 during driving is easily suppressed. Thereby, the Cd value (air resistance value) is reduced.

In the bead member 16, as shown in FIG. 1, the height of the bead member 16, that is, the tire diameter, in the cross section in the tire width direction when the tire 1 of the embodiment is mounted on a specified rim and a specified internal pressure is applied. The directional length H2 is 20% or more and 25% or less of the tire cross-sectional height H1. The tire radial direction length H2 of the bead member 16 is the distance in the tire radial direction between the tire radial direction inner end 11a of the bead core 11 and the tire radial direction outer end 12a of the bead filler 12.

Compared to a case where the tire radial direction length H2 of the bead member 16 is, for example, about 30% of the tire cross-sectional height H1, the weight of the bead member 16 is reduced by setting it to 20% or more and 25% or less. Reducing the weight of the bead member 16 leads to a reduction in the weight of the tire 1 as a whole, thereby reducing rolling resistance.

According to the tire 1 of the embodiment, the Cd value can be reduced by setting the tensile strength of the carcass ply 50 to 250 N or more and 420 N or less. Note that if the carcass ply 50 has improved tensile strength, the weight of the tire 1 will increase as the weight of the carcass ply 50 increases, which may lead to an increase in rolling resistance. However, in the tire 1 of the embodiment, the tire radial length H2 of the bead member 16 is made relatively small to 20% or more and 25% or less of the tire cross-sectional height H1 to reduce the weight, thereby suppressing the increase in rolling resistance. Can be suppressed. That is, it is possible to both reduce the Cd value and suppress rolling resistance. The Cd value can be reduced by increasing the tensile strength of the carcass ply 50, which requires less manufacturing effort than, for example, the conventional case of forming a plurality of fin-like protrusions on the tire side surface. Therefore, according to the tire 1 of the embodiment, air resistance can be reduced without increasing manufacturing effort and while suppressing rolling resistance. In addition, in order to obtain a tire having lateral rigidity to the extent that there is no problem in practical use, it is preferable that the ratio of the tire radial length H2 of the bead member 16 to the tire cross-sectional height H1 is maintained at 20% or more.

According to the tire 1 according to the embodiment described above, the following effects are achieved.

(1) The tire 1 according to the embodiment includes a pair of beads 10 having a bead member 16 including a bead core 11 and a bead filler 12, and a pair of sidewalls 20 extending outward in the tire radial direction from each of the pair of beads 10. A tread 30 disposed between a pair of sidewalls 20 and a carcass ply 50 spanned between a pair of beads 10, the tensile strength of the carcass ply 50 is 250N or more and 420N or less, and the specified rim In the cross section of the tire in the width direction when the tire is mounted on the tire and a specified internal pressure is applied, the tire radial length H2 of the bead member 16 is 20% or more and 25% or less of the tire cross-sectional height H1.

Thereby, the tire 1 according to the embodiment can reduce air resistance without increasing the manufacturing effort. The increase in rolling resistance that may occur due to the reduction in air resistance can be compensated for by reducing the weight of the bead member 16 by setting the length H2 of the bead member 16 in the tire radial direction to 20% or more and 25% or less of the tire cross-sectional height H1. Therefore, it is possible to reduce air resistance and suppress rolling resistance at the same time.

(2) In the tire 1 of the embodiment, it is preferable that the carcass ply 50 has a multilayer structure including at least two layers stacked on each other.

Thereby, the carcass ply 50 can be easily configured to have a desired tensile strength.

It should be noted that the present invention is not limited to the above-described embodiments, and even if modifications, improvements, etc. are made within the scope of achieving the object of the present invention, they are still within the scope of the present invention.

Examples will be described below. As shown in Table 1, the tensile strength of the carcass ply is 264N or 412N, and the height of the bead member (length in the tire radial direction) is 20.2%, 23.4%, or 25% of the tire cross-sectional height. The tires of Examples 1 to 4 were evaluated using a simulation model. The carcass ply strength in Table 1 is the tensile strength of the carcass ply. The carcass plies of Examples 1 to 4 all had a two-layer structure. On the other hand, although the tensile strength of the carcass ply is within the range of 250N or more and 420N or less, the tensile strength of the carcass ply is A conventional type tire of Comparative Example 1, in which the tire pressure was 132N and the height of the bead member was 28.3% of the tire cross-sectional height, was evaluated using a simulation model. The carcass plies of Comparative Example 2 and Comparative Example 3 had a two-layer structure. The carcass ply of Comparative Example 1 has a one-layer structure. Note that the tires of Examples 1 to 4 and Comparative Examples 1 to 3 all have a size of "225/55R19 99V" and have the same basic configuration as the above embodiment. Further, the height of the bead member is a value when the tire is mounted on a specified rim and the air pressure is 230 kPa.

For the tires of Examples 1 to 4 and Comparative Examples 1 to 3, lateral stiffness, Cd value, and rolling resistance coefficient were measured by simulation. In the measurement, a load of 69% of the maximum load according to the load index of the tire was applied.

These results are shown in Table 1. In Table 1, each value of the conventional type Comparative Example 1 is set as an index of 100, and the tires of Comparative Examples 2 and 3 and Examples 1 to 4 are evaluated by the index. The smaller the index evaluation, the lower the air resistance, and the Cd value is determined to be better. Further, regarding the rolling resistance coefficient, it is determined that the smaller the index evaluation is, the smaller the rolling resistance is, and the better the rolling resistance is. Further, the higher the index evaluation, the better the lateral stiffness is determined to be.

According to Table 1, in Comparative Examples 1 to 3 in which the tensile strength of the carcass ply was gradually increased, it was observed that the Cd value decreased as the tensile strength of the carcass ply increased. However, since the ratio of the height of the bead member to the tire cross-sectional height (bead member height ratio) is relatively large at 28.3%, it is recognized that the rolling resistance becomes large. Compared to these comparative examples, Examples 1 to 4 all have a reduced Cd value, and the tensile strength of the carcass ply is within the range of the present invention, thereby reducing air resistance. In addition, since the bead member height ratio is within the range of the present invention and is lower than Comparative Examples 2 and 3, the rolling resistance is lower than those of Comparative Examples 2 and 3, and the bead member height ratio is lower than Comparative Examples 2 and 3. It can be seen that the increase in rolling resistance can be suppressed by reducing . Note that reducing the bead member height ratio may lead to a reduction in lateral stiffness, but if the bead member height ratio can be maintained at 20% as in Example 1, the reduction will not be significant and will be practical. It is permissible.

1 Tire (pneumatic tire)
10 Bead 11 Bead core 12 Bead filler 16 Bead member 20 Sidewall 30 Tread 50 Carcass ply H1 Tire cross-sectional height H2 Length of bead member in tire radial direction

Claims (2)

a pair of beads having a bead member including a bead core and a bead filler;
a pair of sidewalls extending outward in the tire radial direction from each of the pair of beads;
a tread disposed between the pair of sidewalls;
A pneumatic tire comprising a carcass ply spanning between the pair of beads,
The tensile strength of the carcass ply is 250N or more and 420N or less,
A pneumatic tire, wherein the length of the bead member in the radial direction of the tire is 20% or more and 25% or less of the tire cross-sectional height in a cross-section in the tire width direction when mounted on a specified rim and with a specified internal pressure applied. . The pneumatic tire according to claim 1, wherein the carcass ply has a multilayer structure including at least two layers stacked on top of each other.

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